Clinical Focus


  • Transfusion Medicine
  • Anatomic and Clinical Pathology

Academic Appointments


Professional Education


  • Fellowship: Stanford University Pediatric Hematology Oncology Fellowship (1980) CA
  • Internship: Zuckerberg San Francisco General Hospital (1976) CA
  • Residency: Stanford University Pediatric Residency at Lucile Packard Children's Hospital (1980) CA
  • Fellowship: Stanford University Department of Pathology CA
  • Residency: Moffitt Hospital UCSF (1977) CA
  • Medical Education: University of California San Diego School of Medicine (1975) CA

Current Research and Scholarly Interests


The focus of the Foung Laboratory is to define immune correlates of protection against hepatitis C virus and other viral pathogens. More specifically, our goal is to define protective humoral immunity to viral pathogens through the isolation, biochemical and functional characterization of broadly neutralizing human or nonhuman primate monoclonal antibodies. Dependent on the pathogen, approaches to isolate these antibodies include yeast surface IgG display or single-cell cloning. These efforts will create high-resolution, functional maps of linear and nonlinear epitopes comprising the major binding sites of both isolate-specific and broadly neutralizing antibodies for rational vaccine design.

2023-24 Courses


All Publications


  • Induction of broadly neutralizing antibodies using a secreted form of the hepatitis C virus E1E2 heterodimer as a vaccine candidate. Proceedings of the National Academy of Sciences of the United States of America Wang, R., Suzuki, S., Guest, J. D., Heller, B., Almeda, M., Andrianov, A. K., Marin, A., Mariuzza, R. A., Keck, Z. Y., Foung, S. K., Yunus, A. S., Pierce, B. G., Toth, E. A., Ploss, A., Fuerst, T. R. 2022; 119 (11): e2112008119

    Abstract

    SignificanceHepatitis C virus chronically infects approximately 1% of the world's population, making an effective vaccine for hepatitis C virus a major unmet public health need. The membrane-associated E1E2 envelope glycoprotein has been used in clinical studies as a vaccine candidate. However, limited neutralization breadth and difficulty in producing large amounts of homogeneous membrane-associated E1E2 have hampered efforts to develop an E1E2-based vaccine. Our previous work described the design and biochemical validation of a native-like soluble secreted form of E1E2 (sE1E2). Here, we describe the immunogenic characterization of the sE1E2 complex. sE1E2 elicited broadly neutralizing antibodies in immunized mice, with increased neutralization breadth relative to the membrane-associated E1E2, thereby validating this platform as a promising model system for vaccine development.

    View details for DOI 10.1073/pnas.2112008119

    View details for PubMedID 35263223

  • Editorial overview: Engineering elimination of chronic viral hepatitis. Current opinion in virology Walker, C., Ou, J., Foung, S. 2021; 52: 57-59

    View details for DOI 10.1016/j.coviro.2021.10.008

    View details for PubMedID 34861638

  • An antigenically diverse, representative panel of envelope glycoproteins for HCV vaccine development. Gastroenterology Salas, J. H., Urbanowicz, R. A., Guest, J. D., Frumento, N., Figueroa, A., Clark, K. E., Keck, Z., Cowton, V. M., Cole, S. J., Patel, A. H., Fuerst, T. R., Drummer, H. E., Major, M., Tarr, A. W., Ball, J. K., Law, M., Pierce, B. G., Foung, S. K., Bailey, J. R. 2021

    Abstract

    BACKGROUND AND AIMS: Development of a prophylactic hepatitis C virus (HCV) vaccine will require accurate and reproducible measurement of neutralizing breadth of vaccine-induced antibodies. Currently available HCV panels may not adequately represent the genetic and antigenic diversity of circulating HCV strains, and the lack of standardization of these panels makes it difficult to compare neutralization results obtained in different studies. Here, we describe the selection and validation of a genetically and antigenically diverse reference panel of 15 HCV pseudoparticles (HCVpp) for neutralization assays.METHODS: We chose 75 envelope (E1E2) clones to maximize representation of natural polymorphisms observed in circulating HCV isolates, and 65 of these clones generated functional HCVpp. Neutralization sensitivity of these HCVpp varied widely. HCVpp clustered into 15 distinct groups based on patterns of relative sensitivity to seven broadly neutralizing monoclonal antibodies (bNAbs). We used these data to select a final panel of 15 antigenically representative HCVpp.RESULTS: Both the 65 and 15 HCVpp panels span four tiers of neutralization sensitivity, and neutralizing breadth measurements for seven bNAbs were nearly equivalent using either panel. Differences in neutralization sensitivity between HCVpp were independent of genetic distances between E1E2 clones.CONCLUSIONS: Neutralizing breadth of HCV antibodies should be defined using viruses spanning multiple tiers of neutralization sensitivity, rather than panels selected solely for genetic diversity. We propose that this multi-tier reference panel could be adopted as a standard for the measurement of neutralizing antibody potency and breadth, facilitating meaningful comparisons of neutralization results from vaccine studies in different laboratories.

    View details for DOI 10.1053/j.gastro.2021.10.005

    View details for PubMedID 34655573

  • Structural perspectives on HCV humoral immune evasion mechanisms. Current opinion in virology Sevvana, M., Keck, Z., Foung, S. K., Kuhn, R. J. 2021; 49: 92-101

    Abstract

    The molecular mechanisms of hepatitis C virus (HCV) persistence and pathogenesis are poorly understood. The design of an effective HCV vaccine is challenging despite a robust humoral immune response against closely related strains of HCV. This is primarily because of the huge genetic diversity of HCV and the molecular evolution of various virus escape mechanisms. These mechanisms are steered by the presence of a high mutational rate in HCV, structural plasticity of the immunodominant regions on the virion surface of diverse HCV genotypes, and constant amino acid substitutions on key structural components of HCV envelope glycoproteins. Here, we review the molecular basis of neutralizing antibody (nAb)-mediated immune response against diverse HCV variants, HCV-steered humoral immune evasion strategies and explore the essential structural elements to consider for designing a universal HCV vaccine. Structural perspectives on key escape pathways mediated by a point mutation within the epitope, allosteric modulation of the epitope by distant mutations and glycan shift on envelope glycoproteins will be highlighted (abstract graphic).

    View details for DOI 10.1016/j.coviro.2021.05.002

    View details for PubMedID 34091143

  • Design of a native-like secreted form of the hepatitis C virus E1E2 heterodimer. Proceedings of the National Academy of Sciences of the United States of America Guest, J. D., Wang, R. n., Elkholy, K. H., Chagas, A. n., Chao, K. L., Cleveland, T. E., Kim, Y. C., Keck, Z. Y., Marin, A. n., Yunus, A. S., Mariuzza, R. A., Andrianov, A. K., Toth, E. A., Foung, S. K., Pierce, B. G., Fuerst, T. R. 2021; 118 (3)

    Abstract

    Hepatitis C virus (HCV) is a major worldwide health burden, and a preventive vaccine is needed for global control or eradication of this virus. A substantial hurdle to an effective HCV vaccine is the high variability of the virus, leading to immune escape. The E1E2 glycoprotein complex contains conserved epitopes and elicits neutralizing antibody responses, making it a primary target for HCV vaccine development. However, the E1E2 transmembrane domains that are critical for native assembly make it challenging to produce this complex in a homogenous soluble form that is reflective of its state on the viral envelope. To enable rational design of an E1E2 vaccine, as well as structural characterization efforts, we have designed a soluble, secreted form of E1E2 (sE1E2). As with soluble glycoprotein designs for other viruses, it incorporates a scaffold to enforce assembly in the absence of the transmembrane domains, along with a furin cleavage site to permit native-like heterodimerization. This sE1E2 was found to assemble into a form closer to its expected size than full-length E1E2. Preservation of native structural elements was confirmed by high-affinity binding to a panel of conformationally specific monoclonal antibodies, including two neutralizing antibodies specific to native E1E2 and to its primary receptor, CD81. Finally, sE1E2 was found to elicit robust neutralizing antibodies in vivo. This designed sE1E2 can both provide insights into the determinants of native E1E2 assembly and serve as a platform for production of E1E2 for future structural and vaccine studies, enabling rational optimization of an E1E2-based antigen.

    View details for DOI 10.1073/pnas.2015149118

    View details for PubMedID 33431677

  • Crystal Structure of a Bivalent Antibody Fab Fragment. Journal of molecular biology Shahid, S., Gao, M., Travis Gallagher, D., Pozharski, E., Brinson, R. G., Keck, Z., Foung, S. K., Fuerst, T. R., Mariuzza, R. A. 2020

    Abstract

    We determined the crystal structure to 1.8 A resolution of the Fab fragment of an affinity-matured human monoclonal antibody (HC84.26.5D) that recognizes the E2 envelope glycoprotein of hepatitis C virus (HCV). Unlike conventional Fabs, which are monovalent monomers, Fab HC84.26.5D assembles into a bivalent domain-swapped dimer in which the two VL/VH modules are separated by 25 A. In solution, Fab HC84.26.5D exists predominantly as a dimer (80%) in equilibrium with the monomeric form of the Fab (20%). Dimerization is mediated entirely by deletion of a single residue, VHSer113 (Kabat numbering), in the elbow region linking the VH and CH1 domains. In agreement with the crystal structure, dimeric Fab HC84.26.5D is able to bind two HCV E2 molecules in solution. This is only the second example of a domain-swapped Fab dimer from among >3,000 Fab crystal structures determined to date. Moreover, the architecture of the doughnut-shaped Fab HC84.26.5D dimer is completely different from that of the previously reported Fab 2G12 dimer. We demonstrate that the highly identifiable shape of dimeric Fab HC84.26.5D makes it useful as a fiducial marker for single-particle cryoEM analysis of HCV E2. Bivalent domain-swapped Fab dimers engineered on the basis of HC84.26.5D may also serve as a means of doubling the effective size of conventional Fab-protein complexes for cryoEM.

    View details for DOI 10.1016/j.jmb.2020.11.013

    View details for PubMedID 33220264

  • Structure-based design of hepatitis C virus E2 glycoprotein improves serum binding and cross-neutralization. Journal of virology Pierce, B. G., Keck, Z., Wang, R., Lau, P., Garagusi, K., Elkholy, K., Toth, E. A., Urbanowicz, R. A., Guest, J. D., Agnihotri, P., Kerzic, M. C., Marin, A., Andrianov, A. K., Ball, J. K., Mariuzza, R. A., Fuerst, T. R., Foung, S. K. 2020

    Abstract

    An effective vaccine for hepatitis C virus (HCV) is a major unmet need, and it requires an antigen that elicits immune responses to key conserved epitopes. Based on structures of antibodies targeting HCV envelope glycoprotein E2, we designed immunogens to modulate the structure and dynamics of E2 and favor induction of bNAbs in the context of a vaccine. These designs include a point mutation in a key conserved antigenic site to stabilize its conformation, as well as redesigns of an immunogenic region to add a new N-glycosylation site and mask it from antibody binding. Designs were experimentally characterized for binding to a panel of human monoclonal antibodies (HMAbs) and the coreceptor CD81 to confirm preservation of epitope structure and preferred antigenicity profile. Selected E2 designs were tested for immunogenicity in mice, with and without hypervariable region 1, which is an immunogenic region associated with viral escape. One of these designs showed improvement in polyclonal immune serum binding to HCV pseudoparticles and neutralization of isolates associated with antibody resistance. These results indicate that antigen optimization through structure-based design of the envelope glycoproteins is a promising route to an effective vaccine for HCV.IMPORTANCE Hepatitis C virus infects approximately 1% of the world's population, and no vaccine is currently available. Due to the high variability of HCV and its ability to actively escape the immune response, a goal of HCV vaccine design is to induce neutralizing antibodies that target conserved epitopes. Here we performed structure-based design of several epitopes of the HCV E2 envelope glycoprotein to engineer its antigenic properties. Designs were tested in vitro and in vivo, demonstrating alteration of the E2 antigenic profile in several cases, and one design led to improvement of cross-neutralization of heterologous viruses. This represents a proof of concept that rational engineering of HCV envelope glycoproteins can be used to modulate E2 antigenicity and optimize a vaccine for this challenging viral target.

    View details for DOI 10.1128/JVI.00704-20

    View details for PubMedID 32878891

  • An alternate conformation of HCV E2 neutralizing face as an additional vaccine target SCIENCE ADVANCES Tzarum, N., Giang, E., Kadam, R. U., Chen, F., Nagy, K., Augestad, E. H., Velazquez-Moctezuma, R., Keck, Z., Hua, Y., Stanfield, R. L., Dreux, M., Prentoe, J., Foung, S. H., Bukh, J., Wilson, I. A., Law, M. 2020; 6 (30): eabb5642

    Abstract

    To achieve global elimination of hepatitis C virus (HCV), an effective cross-genotype vaccine is needed. The HCV envelope glycoprotein E2 is the main target for neutralizing antibodies (nAbs), which aid in HCV clearance and protection. E2 is structurally flexible and functions in engaging host receptors. Many nAbs bind to the "neutralizing face" on E2, including several broadly nAbs encoded by the VH1-69 germline gene family that bind to a similar conformation (A) of this face. Here, a previously unknown conformation (B) of the neutralizing face is revealed in crystal structures of two of four additional E2-VH1-69 nAb complexes. In this conformation, the E2 front-layer region is displaced upon antibody binding, exposing residues in the back layer for direct antibody interaction. This E2 B structure may represent another conformational state in the viral entry process that is susceptible to antibody neutralization and thus provide a new target for rational vaccine development.

    View details for DOI 10.1126/sciadv.abb5642

    View details for Web of Science ID 000552228100039

    View details for PubMedID 32754640

    View details for PubMedCentralID PMC7380959

  • SARS-CoV-2 RNAemia in a Healthy Blood Donor 40 Days After Respiratory Illness Resolution. Annals of internal medicine Pham, T. D., Huang, C. n., Wirz, O. F., Röltgen, K. n., Sahoo, M. K., Layon, A. n., Pandey, S. n., Foung, S. K., Boyd, S. D., Pinsky, B. A. 2020

    View details for DOI 10.7326/L20-0725

    View details for PubMedID 32678685

  • Interferon-Induced Transmembrane Proteins Mediate Viral Evasion in Acute and Chronic Hepatitis C Virus Infection HEPATOLOGY Wrensch, F., Ligat, G., Heydmann, L., Schuster, C., Zeisel, M. B., Pessaux, P., Habersetzer, F., King, B. J., Tarr, A. W., Ball, J. K., Winkler, M., Poehlmann, S., Keck, Z., Foung, S. H., Baumert, T. F. 2019; 70 (5): 1506–20

    View details for DOI 10.1002/hep.30699

    View details for Web of Science ID 000493023400003

  • Learning from a clinical cohort for HCV vaccine development JOURNAL OF HEPATOLOGY Wrensch, F., Keck, Z., Foung, S. H., Baumert, T. F. 2019; 71 (1): 9–11
  • Broadly neutralizing antibodies from an individual that naturally cleared multiple hepatitis C virus infections uncover molecular determinants for E2 targeting and vaccine design. PLoS pathogens Keck, Z., Pierce, B. G., Lau, P., Lu, J., Wang, Y., Underwood, A., Bull, R. A., Prentoe, J., Velazquez-Moctezuma, R., Walker, M. R., Luciani, F., Guest, J. D., Fauvelle, C., Baumert, T. F., Bukh, J., Lloyd, A. R., Foung, S. K. 2019; 15 (5): e1007772

    Abstract

    Cumulative evidence supports a role for neutralizing antibodies contributing to spontaneous viral clearance during acute hepatitis C virus (HCV) infection. Information on the timing and specificity of the B cell response associated with clearance is crucial to inform vaccine design. From an individual who cleared three sequential HCV infections with genotypes 1b, 1a and 3a strains, respectively, we employed peripheral B cells to isolate and characterize neutralizing human monoclonal antibodies (HMAbs) to HCV after the genotype 1 infections. The majority of isolated antibodies, designated as HMAbs 212, target conformational epitopes on the envelope glycoprotein E2 and bound broadly to genotype 1-6 E1E2 proteins. Further, some of these antibodies showed neutralization potential against cultured genotype 1-6 viruses. Competition studies with defined broadly neutralizing HCV HMAbs to epitopes in distinct clusters, designated antigenic domains B, C, D and E, revealed that the selected HMAbs compete with B, C and D HMAbs, previously isolated from subjects with chronic HCV infections. Epitope mapping studies revealed domain B and C specificity of these HMAbs 212. Sequential serum samples from the studied subject inhibited the binding of HMAbs 212 to autologous E2 and blocked a representative domain D HMAb. The specificity of this antibody response appears similar to that observed during chronic infection, suggesting that the timing and affinity maturation of the antibody response are the critical determinants in successful and repeated viral clearance. While additional studies should be performed for individuals with clearance or persistence of HCV, our results define epitope determinants for antibody E2 targeting with important implications for the development of a B cell vaccine.

    View details for DOI 10.1371/journal.ppat.1007772

    View details for PubMedID 31100098

  • IFITMs mediate viral evasion in acute and chronic hepatitis C virus infection. Hepatology (Baltimore, Md.) Wrensch, F., Ligat, G., Heydmann, L., Schuster, C., Zeisel, M. B., Pessaux, P., Habersetzer, F., King, B. J., Tarr, A. W., Ball, J. K., Winkler, M., Pohlmann, S., Keck, Z., Foung, S. K., Baumert, T. F. 2019

    Abstract

    While adaptive immune responses against hepatitis C virus (HCV) infection have been studied in great detail, the role of innate immunity in protection against HCV infection and immune evasion is only partially understood. Interferon-induced transmembrane proteins (IFITMs) are innate effector proteins restricting host cell entry of many enveloped viruses, including HCV. However, the clinical impact of IFITMs on HCV immune escape remains to be determined. Here, we show that IFITMs promote viral escape from the neutralizing antibody response in clinical cohorts of HCV-infected patients. Using pseudoparticles bearing HCV envelope proteins from acutely infected patients, we show that HCV variants isolated pre-seroconversion are more sensitive to the antiviral activity of IFITMs than variants from patients isolated during chronic infection post-seroconversion. Furthermore, HCV variants escaping neutralizing antibody responses during liver transplantation exhibited a significantly higher resistance to IFITMs than variants that were eliminated post-transplantation. Gain-of-function and mechanistic studies revealed that IFITMs markedly enhance the antiviral activity of neutralizing antibodies and suggest a cooperative effect of human monoclonal antibodies and IFITMs for antibody-mediated neutralization driving the selection pressure in viral evasion. Perturbation studies with the IFITM antagonist amphotericin B revealed that modulation of membrane properties by IFITM proteins is responsible for the IFITM-mediated blockade of viral entry and enhancement of antibody-mediated neutralization. CONCLUSION: Our results identify IFITM proteins as a previously unknown driver of viral immune escape and antibody-mediated HCV neutralization in acute and chronic HCV infection. These findings are of clinical relevance for the design of urgently needed HCV B cell vaccines and might help to increase the efficacy of future vaccine candidates. This article is protected by copyright. All rights reserved.

    View details for PubMedID 31062385

  • Learning from a clinical cohort for HCV vaccine development. Journal of hepatology Wrensch, F., Keck, Z., Foung, S. K., Baumert, T. F. 2019

    View details for PubMedID 30992137

  • Antigenicity and Immunogenicity of Differentially Glycosylated Hepatitis C Virus E2 Envelope Proteins Expressed in Mammalian and Insect Cells JOURNAL OF VIROLOGY Urbanowicz, R. A., Wang, R., Schiel, J. E., Keck, Z., Kerzic, M. C., Lau, P., Rangarajan, S., Garagusi, K. J., Tan, L., Guest, J. D., Ball, J. K., Pierce, B. G., Mariuzza, R. A., Foung, S. H., Fuerst, T. R. 2019; 93 (7)
  • In vivo combination of human anti-envelope glycoprotein E2 and -Claudin-1 monoclonal antibodies for prevention of hepatitis C virus infection ANTIVIRAL RESEARCH Mailly, L., Wrensch, F., Heydmann, L., Fauvelle, C., Brignon, N., Zeisel, M. B., Pessaux, P., Keck, Z., Schuster, C., Fuerst, T. R., Foung, S. H., Baumert, T. F. 2019; 162: 136–41
  • Antigenicity and Immunogenicity of Differentially Glycosylated HCV E2 Envelope Proteins Expressed in Mammalian and Insect Cells. Journal of virology Urbanowicz, R. A., Wang, R., Schiel, J. E., Keck, Z., Kerzic, M. C., Lau, P., Rangarajan, S., Garagusi, K. J., Tan, L., Guest, J. D., Ball, J. K., Pierce, B. G., Mariuzza, R. A., Foung, S. K., Fuerst, T. R. 2019

    Abstract

    Development of a prophylactic vaccine for hepatitis C virus (HCV) remains a global health challenge. Cumulative evidence supports the importance of antibodies targeting the HCV E2 envelope glycoprotein to facilitate viral clearance. However, a significant challenge for a B cell-based vaccine is focusing the immune response on conserved E2 epitopes capable of eliciting neutralizing antibodies not associated with viral escape. We hypothesized that glycosylation might influence the antigenicity and immunogenicity of E2. Accordingly, we performed head-to-head molecular, antigenic and immunogenic comparisons of soluble E2 (sE2) produced in (i) mammalian (HEK293) cells, which confer mostly complex and high mannose type glycans; and (ii) insect (Sf9) cells, which impart mainly paucimannose type glycans. Mass spectrometry demonstrated that all 11 predicted N-glycosylation sites were utilized in both HEK293- and Sf9-derived sE2, but that N-glycans in insect sE2 were on average smaller and less complex. Both proteins bound CD81 and were recognized by conformation-dependent antibodies. Mouse immunogenicity studies revealed that similar polyclonal antibody responses were generated against antigenic domains A-E of E2. Although neutralizing antibody titers showed that Sf9-derived sE2 induced moderately stronger responses than HEK293-derived sE2 against the homologous HCV H77c isolate, the two proteins elicited comparable neutralization titers against heterologous isolates. Given that global alteration of HCV E2 glycosylation by expression in different hosts did not appreciably affect antigenicity or overall immunogenicity, a more productive approach to increasing the antibody response to neutralizing epitopes may be complete deletion, rather than just modification, of specific N-glycans proximal to these epitopes.IMPORTANCE Development of a vaccine for hepatitis C virus (HCV) remains a global health challenge. A major challenge for vaccine development is focusing the immune response on conserved regions of the HCV envelope protein, E2, capable of eliciting neutralizing antibodies. Modification of E2 by glycosylation might influence the immunogenicity of E2. Accordingly, we performed molecular and immunogenic comparisons of E2 produced in mammalian and insect cells. Mass spectrometry demonstrated that the predicted glycosylation sites were utilized in both mammalian and insect cell E2, although the glycan types in insect cell E2 were smaller and less complex. Mouse immunogenicity studies revealed similar polyclonal antibody responses. However, insect cell E2 induced stronger neutralizing antibody responses against the homologous isolate used in the vaccine, albeit the two proteins elicited comparable neutralization titers against heterologous isolates. A more productive approach for vaccine development may be complete deletion of specific glycans in the E2 protein.

    View details for PubMedID 30651366

  • Isolation of HCV Neutralizing Antibodies by Yeast Display. Methods in molecular biology (Clifton, N.J.) Keck, Z., Wang, Y., Lau, P., Foung, S. K. 2019; 1911: 395–419

    Abstract

    Yeast surface display (YSD) enables efficient screening and selection of single chain variable fragments (scFvs) of heavy (VH) and light (VL) chains that bind to target antigen with different affinities. Assembly of a scFv library from cDNA usually involves adding different primers and linkers (Gly4/Ser)3 through multiple rounds of PCR amplification and purification. We describe here a simplified scFv assembly method by creating a modified YSD vector with a built-in linker that reduces the time of assembly and decreases accumulated base exchanges due to PCR errors. In addition, we describe a bias screening strategy toward maximizing novel antibodies of interest by a combination of memory B cell selection and depletion by binding to mutant antigens that do not bind to previously identified monoclonal antibodies.

    View details for PubMedID 30593641

  • Standardized Method for the Study of Antibody Neutralization of HCV Pseudoparticles (HCVpp) HEPATITIS C VIRUS PROTOCOLS Bailey, J. R., Urbanowicz, R. A., Ball, J. K., Law, M., Foung, S. H., Law, M. 2019; 1911: 441-450
  • Isolation of HCV Neutralizing Antibodies by Yeast Display HEPATITIS C VIRUS PROTOCOLS Keck, Z., Wang, Y., Lau, P., Foung, S. H., Law, M. 2019; 1911: 395-419
  • Standardized Method for the Study of Antibody Neutralization of HCV Pseudoparticles (HCVpp). Methods in molecular biology (Clifton, N.J.) Bailey, J. R., Urbanowicz, R. A., Ball, J. K., Law, M., Foung, S. K. 2019; 1911: 441–50

    Abstract

    Hepatitis C virus (HCV) pseudoparticles (HCVpp) are generated by cotransfection of HCV envelope (E1 and E2) genes along with a retroviral packaging/reporter construct into HEK293T cells. Enveloped particles bearing HCV E1E2 proteins on their surface are released through a retroviral budding process into the supernatant. Viral E1E2 glycoproteins facilitate a single round of receptor-mediated entry of HCVpp into hepatoma cells, which can be quantified by reporter gene expression. These HCVpp have been employed to study mechanisms of HCV entry into hepatoma cells, as well as HCV neutralization by immune sera or HCV-specific monoclonal antibodies.

    View details for PubMedID 30593644

  • In vivo combination of human anti-envelope glycoprotein E2 and -Claudin-1 monoclonal antibodies for prevention of hepatitis C virus infection. Antiviral research Mailly, L., Wrensch, F., Heydmann, L., Fauvelle, C., Brignon, N., Zeisel, M. B., Pessaux, P., Keck, Z., Schuster, C., Fuerst, T. R., Foung, S. K., Baumert, T. F. 2018

    Abstract

    Despite the development of direct-acting antivirals (DAAs), hepatitis C virus (HCV) infection remains a major cause for liver disease and cancer worldwide. Entry inhibitors block virus host cell entry and, therefore, prevent establishment of chronic infection and liver disease. Due to their unique mechanism of action, entry inhibitors provide an attractive antiviral strategy in organ transplantation. In this study, we developed an innovative approach in preventing HCV infection using a synergistic combination of a broadly neutralizing human monoclonal antibody (HMAb) targeting the HCV E2 protein and a host-targeting anti-claudin 1 (CLDN1) humanized monoclonal antibody. An in vivo proof-of-concept study in human liver-chimeric FRG-NOD mice proved the efficacy of the combination therapy at preventing infection by an HCV genotype 1b infectious serum. While administration of individual antibodies at lower doses only showed a delay in HCV infection, the combination therapy was highly protective. Furthermore, the combination proved to be effective in preventing infection of primary human hepatocytes by neutralization-resistant HCV escape variants selected during liver transplantation, suggesting that a combination therapy is suited for the neutralization of difficult-to-treat variants. In conclusion, our findings suggest that the combination of two HMAbs targeting different steps of virus entry improves treatment efficacy while simultaneously reducing treatment duration and costs. Our approach not only provides a clinical perspective to employ HMAb combination therapies to prevent graft re-infection and its associated liver disease but may also help to alleviate the urgent demand for organ transplants by allowing the transplantation of organs from HCV-positive donors.

    View details for PubMedID 30599173

  • Editorial: Current Progress and Challenges in the Development of a B Cell Based Hepatitis C Virus Vaccine. Frontiers in immunology Foung, S. K., Baumert, T. F. 2018; 9: 2577

    View details for DOI 10.3389/fimmu.2018.02577

    View details for PubMedID 30473699

    View details for PubMedCentralID PMC6237980

  • Current Progress and Challenges in the Development of a B Cell Based Hepatitis C Virus Vaccine FRONTIERS IN IMMUNOLOGY Foung, S. H., Baumert, T. F. 2018; 9
  • Ifitm-Mediated Viral Immune Evasion in Acute and Chronic Hepatitis C Virus Infection Wrensch, F., Heydmann, L., Ligat, G., Zeisel, M. B., Pessaux, P., Habersetzer, F., King, B. J., Tarr, A. W., Ball, J. K., Keck, Z., Schuster, C., Foung, S., Baumert, T. F. WILEY. 2018: 126A
  • Hepatitis C virus (HCv)-Apolipoprotein interactions and immune evasion and Their impact on HCv vaccine Design FRONTIERS IN IMMUNOLOGY Wrensch, F., Crouchet, E., Ligat, G., Zeisel, M. B., Keck, Z., Foung, S. H., Schuster, C., Baumert, T. F. 2018; 9
  • Hepatitis C Virus (HCV)-Apolipoprotein Interactions and Immune Evasion and Their Impact on HCV Vaccine Design. Frontiers in immunology Wrensch, F., Crouchet, E., Ligat, G., Zeisel, M. B., Keck, Z. Y., Foung, S. K., Schuster, C., Baumert, T. F. 2018; 9: 1436

    Abstract

    With more than 71 million people chronically infected, hepatitis C virus (HCV) is one of the leading causes of liver disease and hepatocellular carcinoma. While efficient antiviral therapies have entered clinical standard of care, the development of a protective vaccine is still elusive. Recent studies have shown that the HCV life cycle is closely linked to lipid metabolism. HCV virions associate with hepatocyte-derived lipoproteins to form infectious hybrid particles that have been termed lipo-viro-particles. The close association with lipoproteins is not only critical for virus entry and assembly but also plays an important role during viral pathogenesis and for viral evasion from neutralizing antibodies. In this review, we summarize recent findings on the functional role of apolipoproteins for HCV entry and assembly. Furthermore, we highlight the impact of HCV-apolipoprotein interactions for evasion from neutralizing antibodies and discuss the consequences for antiviral therapy and vaccine design. Understanding these interactions offers novel strategies for the development of an urgently needed protective vaccine.

    View details for DOI 10.3389/fimmu.2018.01436

    View details for PubMedID 29977246

    View details for PubMedCentralID PMC6021501

  • Mapping Determinants of Virus Neutralization and Viral Escape for Rational Design of a Hepatitis C Virus Vaccine FRONTIERS IN IMMUNOLOGY Keck, M., Wrensch, F., Pierce, B. G., Baumert, T. F., Foung, S. H. 2018; 9: 1194

    Abstract

    Hepatitis C virus (HCV) continues to spread worldwide with an annual increase of 1.75 million new infections. The number of HCV cases in the U.S. is now greater than the number of HIV cases and is increasing in young adults because of the opioid epidemic sweeping the country. HCV-related liver disease is the leading indication of liver transplantation. An effective vaccine is of paramount importance to control and prevent HCV infection. While this vaccine will need to induce both cellular and humoral immunity, this review is focused on the required antibody responses. For highly variable viruses, such as HCV, isolation and characterization of monoclonal antibodies mediating broad virus neutralization are an important guide for vaccine design. The viral envelope glycoproteins, E1 and E2, are the main targets of these antibodies. Epitopes on the E2 protein have been studied more extensively than epitopes on E1, due to higher antibody targeting that reflects these epitopes having higher degrees of immunogenicity. E2 epitopes are overall organized in discrete clusters of overlapping epitopes that ranged from high conservation to high variability. Other epitopes on E1 and E1E2 also are targets of neutralizing antibodies. Taken together, these regions are important for vaccine design. Another element in vaccine design is based on information on how the virus escapes from broadly neutralizing antibodies. Escape mutations can occur within the epitopes that are involved in antibody binding and in regions that are not involved in their epitopes, but nonetheless reduce the efficiency of neutralizing antibodies. An understanding on the specificities of a protective B cell response, the molecular locations of these epitopes on E1, E2, and E1E2, and the mechanisms, which enable the virus to negatively modulate neutralizing antibody responses to these regions will provide the necessary guidance for vaccine design.

    View details for PubMedID 29904384

  • Immunological responses following administration of a genotype 1a/1b/2/3a quadrivalent HCV VLP vaccine SCIENTIFIC REPORTS Christiansen, D., Earnest-Silveira, L., Chua, B., Meuleman, P., Boo, I., Grubor-Bauk, B., Jackson, D. C., Keck, Z. Y., Foung, S. H., Drummer, H. E., Gowans, E. J., Torresi, J. 2018; 8: 6483

    Abstract

    The significant public health problem of Hepatitis C virus (HCV) has been partially addressed with the advent of directly acting antiviral agents (DAAs). However, the development of an effective preventative vaccine would have a significant impact on HCV incidence and would represent a major advance towards controlling and possibly eradicating HCV globally. We previously reported a genotype 1a HCV viral-like particle (VLP) vaccine that produced neutralizing antibodies (NAb) and T cell responses to HCV. To advance this approach, we produced a quadrivalent genotype 1a/1b/2a/3a HCV VLP vaccine to produce broader immune responses. We show that this quadrivalent vaccine produces antibody and NAb responses together with strong T and B cell responses in vaccinated mice. Moreover, selective neutralizing human monoclonal antibodies (HuMAbs) targeting conserved antigenic domain B and D epitopes of the E2 protein bound strongly to the HCV VLPs, suggesting that these critical epitopes are expressed on the surface of the particles. Our findings demonstrate that a quadrivalent HCV VLP based vaccine induces broad humoral and cellular immune responses that will be necessary for protection against HCV. Such a vaccine could provide a substantial addition to highly active antiviral drugs in eliminating HCV.

    View details for PubMedID 29691437

  • Designing a B Cell-Based Vaccine against a Highly Variable Hepatitis C Virus FRONTIERS IN MICROBIOLOGY Fuerst, T. R., Pierce, B. G., Keck, Z., Foung, S. H. 2018; 8
  • Development and characterization of a human monoclonal antibody targeting the N-terminal region of hepatitis C virus envelope glycoprotein E1 VIROLOGY Mesalam, A., Desombere, I., Farhoudi, A., Van Houtte, F., Verhoye, L., Ball, J., Dubuisson, J., Foung, S. H., Patel, A. H., Persson, M. A., Leroux-Roels, G., Meuleman, P. 2018; 514: 30–41

    Abstract

    Monoclonal antibodies (mAbs) targeting the hepatitis C virus (HCV) envelope have been raised mainly against envelope protein 2 (E2), while the antigenic epitopes of envelope protein 1 (E1) are not fully identified. Here we describe the detailed characterization of a human mAb, designated A6, generated from an HCV genotype 1b infected patient. ELISA results showed reactivity of mAb A6 to full-length HCV E1E2 of genotypes 1a, 1b and 2a. Epitope mapping identified a region spanning amino acids 230-239 within the N-terminal region of E1 as critical for binding. Antibody binding to this epitope was not conformation dependent. Neutralization assays showed that mAb A6 lacks neutralizing capacity and does not interfere with the activity of known neutralizing antibodies. In summary, mAb A6 is an important tool to study the structure and function of E1 within the viral envelope, a crucial step in the development of an effective prophylactic HCV vaccine.

    View details for PubMedID 29128754

  • A novel neutralizing human monoclonal antibody broadly abrogates hepatitis C virus infection in vitro and in vivo ANTIVIRAL RESEARCH Desombere, I., Mesalam, A., Urbanowicz, R. A., Van Houtte, F., Verhoye, L., Keck, Z., Farhoudi, A., Vercauteren, K., Weening, K. E., Baumert, T. F., Patel, A. H., Foung, S. H., Ball, J., Leroux-Roels, G., Meuleman, P. 2017; 148: 53–64

    Abstract

    Infections with hepatitis C virus (HCV) represent a worldwide health burden and a prophylactic vaccine is still not available. Liver transplantation (LT) is often the only option for patients with HCV-induced end-stage liver disease. However, immediately after transplantation, the liver graft becomes infected by circulating virus, resulting in accelerated progression of liver disease. Although the efficacy of HCV treatment using direct-acting antivirals has improved significantly, immune compromised LT-patients and patients with advanced liver disease remain difficult to treat. As an alternative approach, interfering with viral entry could prevent infection of the donor liver. We generated a human monoclonal antibody (mAb), designated 2A5, which targets the HCV envelope. The neutralizing activity of mAb 2A5 was assessed using multiple prototype and patient-derived HCV pseudoparticles (HCVpp), cell culture produced HCV (HCVcc), and a human-liver chimeric mouse model. Neutralization levels observed for mAb 2A5 were generally high and mostly superior to those obtained with AP33, a well-characterized HCV-neutralizing monoclonal antibody. Using humanized mice, complete protection was observed after genotype 1a and 4a HCV challenge, while only partial protection was achieved using gt1b and 6a isolates. Epitope mapping revealed that mAb 2A5 binding is conformation-dependent and identified the E2-region spanning amino acids 434 to 446 (epitope II) as the predominant contact domain.mAb 2A5 shows potent anti-HCV neutralizing activity both in vitro and in vivo and could hence represent a valuable candidate to prevent HCV recurrence in LT-patients. In addition, the detailed identification of the neutralizing epitope can be applied for the design of prophylactic HCV vaccines.

    View details for PubMedID 29074219

    View details for PubMedCentralID PMC5785094

  • Conformational Flexibility in the Immunoglobulin-Like Domain of the Hepatitis C Virus Glycoprotein E2. mBio Vasiliauskaite, I., Owsianka, A., England, P., Khan, A. G., Cole, S., Bankwitz, D., Foung, S. K., Pietschmann, T., Marcotrigiano, J., Rey, F. A., Patel, A. H., Krey, T. 2017; 8 (3)

    Abstract

    The hepatitis C virus (HCV) glycoprotein E2 is the major target of neutralizing antibodies and is therefore highly relevant for vaccine design. Its structure features a central immunoglobulin (Ig)-like β-sandwich that contributes to the binding site for the cellular receptor CD81. We show that a synthetic peptide corresponding to a β-strand of this Ig-like domain forms an α-helix in complex with the anti-E2 antibody DAO5, demonstrating an inside-out flip of hydrophobic residues and a secondary structure change in the composite CD81 binding site. A detailed interaction analysis of DAO5 and cross-competing neutralizing antibodies with soluble E2 revealed that the Ig-like domain is trapped by different antibodies in at least two distinct conformations. DAO5 specifically captures retrovirus particles bearing HCV glycoproteins (HCVpp) and infectious cell culture-derived HCV particles (HCVcc). Infection of cells by DAO5-captured HCVpp can be blocked by a cross-competing neutralizing antibody, indicating that a single virus particle simultaneously displays E2 molecules in more than one conformation on its surface. Such conformational plasticity of the HCV E2 receptor binding site has important implications for immunogen design.IMPORTANCE Recent advances in the treatment of hepatitis C virus (HCV) infection with direct-acting antiviral drugs have enabled the control of this major human pathogen. However, due to their high costs and limited accessibility in combination with the lack of awareness of the mostly asymptomatic infection, there is an unchanged urgent need for an effective vaccine. The viral glycoprotein E2 contains regions that are crucial for virus entry into the host cell, and antibodies that bind to these regions can neutralize infection. One of the major targets of neutralizing antibodies is the central immunoglobulin (Ig)-like domain within E2. We show here that this Ig-like domain is conformationally flexible at the surface of infectious HCV particles and pseudoparticles. Our study provides novel insights into the interactions of HCV E2 with the humoral immune system that should aid future vaccine development.

    View details for DOI 10.1128/mBio.00382-17

    View details for PubMedID 28512091

  • Designing a B Cell-Based Vaccine against a Highly Variable Hepatitis C Virus. Frontiers in microbiology Fuerst, T. R., Pierce, B. G., Keck, Z. Y., Foung, S. K. 2017; 8: 2692

    Abstract

    The ability to use structure-based design and engineering to control the molecular shape and reactivity of an immunogen to induce protective responses shows great promise, along with corresponding advancements in vaccine testing and evaluation systems. We describe in this review new paradigms for the development of a B cell-based HCV vaccine. Advances in test systems to measure in vitro and in vivo antibody-mediated virus neutralization include retroviral pseudotype particles expressing HCV E1E2 glycoproteins (HCVpp), infectious cell culture-derived HCV virions (HCVcc), and surrogate animal models mimicking acute HCV infection. Their applications have established the role of broadly neutralizing antibodies to control HCV infection. However, the virus has immunogenic regions in the viral envelope glycoproteins that are associated with viral escape or non-neutralizing antibodies. These regions serve as immunologic decoys that divert the antibody response from less prominent conserved regions mediating virus neutralization. This review outlines the immunogenic regions on E2, which are roughly segregated into the hypervariable region 1 (HVR1), and five clusters of overlapping epitopes designated as antigenic domains A-E. Understanding the molecular architecture of conserved neutralizing epitopes within these antigenic domains, and how other antigenic regions or decoys deflect the immune response from these conserved regions will provide a roadmap for the rational design of an HCV vaccine.

    View details for DOI 10.3389/fmicb.2017.02692

    View details for PubMedID 29379486

    View details for PubMedCentralID PMC5775222

  • Native Folding of a Recombinant gpE1/gpE2 Heterodimer Vaccine Antigen from a Precursor Protein Fused with Fc IgG JOURNAL OF VIROLOGY Logan, M., Law, J., Wong, J. A., Hockman, D., Landi, A., Chen, C., Crawford, K., Kundu, J., Baldwin, L., Johnson, J., Dahiya, A., Lachance, G., Marcotrigiano, J., Law, M., Foung, S., Tyrrell, L., Houghton, M. 2017; 91 (1)
  • Native Folding of a Recombinant gpE1/gpE2 Heterodimer Vaccine Antigen from a Precursor Protein Fused with Fc IgG. Journal of virology Logan, M., Law, J., Wong, J. A., Hockman, D., Landi, A., Chen, C., Crawford, K., Kundu, J., Baldwin, L., Johnson, J., Dahiya, A., LaChance, G., Marcotrigiano, J., Law, M., Foung, S., Tyrrell, L., Houghton, M. 2017; 91 (1)

    Abstract

    A recombinant strain HCV1 (hepatitis C virus [HCV] genotype 1a) gpE1/gpE2 (E1E2) vaccine candidate was previously shown by our group to protect chimpanzees and generate broad cross-neutralizing antibodies in animals and humans. In addition, recent independent studies have highlighted the importance of conserved neutralizing epitopes in HCV vaccine development that map to antigenic clusters in E2 or the E1E2 heterodimer. E1E2 can be purified using Galanthis nivalis lectin agarose (GNA), but this technique is suboptimal for global production. Our goal was to investigate a high-affinity and scalable method for isolating E1E2. We generated an Fc tag-derived (Fc-d) E1E2 that was selectively captured by protein G Sepharose, with the tag being removed subsequently using PreScission protease. Surprisingly, despite the presence of the large Fc tag, Fc-d E1E2 formed heterodimers similar to those formed by GNA-purified wild-type (WT) E1E2 and exhibited nearly identical binding profiles to HCV monoclonal antibodies that target conserved neutralizing epitopes in E2 (HC33.4, HC84.26, and AR3B) and the E1E2 heterodimer (AR4A and AR5A). Antisera from immunized mice showed that Fc-d E1E2 elicited anti-E2 antibody titers and neutralization of HCV pseudotype viruses similar to those with WT E1E2. Competition enzyme-linked immunosorbent assays (ELISAs) showed that antisera from immunized mice inhibited monoclonal antibody binding to neutralizing epitopes. Antisera from Fc-d E1E2-immunized mice exhibited stronger competition for AR3B and AR5A than the WT, whereas the levels of competition for HC84.26 and AR4A were similar. We anticipate that Fc-d E1E2 will provide a scalable purification and manufacturing process using protein A/G-based chromatography.IMPORTANCE: A prophylactic HCV vaccine is still needed to control this global disease despite the availability of direct-acting antivirals. Previously, we demonstrated that a recombinant envelope glycoprotein (E1E2) vaccine (genotype 1a) elicited cross-neutralizing antibodies from human volunteers. A challenge for isolating the E1E2 antigen is the reliance on GNA, which is unsuitable for large scale-up and global vaccine delivery. We have generated a novel Fc domain-tagged E1E2 antigen that forms functional heterodimers similar to those with native E1E2. Affinity purification and removal of the Fc tag from E1E2 resulted in an antigen with a nearly identical profile of cross-neutralizing epitopes. This antigen elicited anti-HCV antibodies that targeted conserved neutralizing epitopes of E1E2. Owing to the high selectivity and cost-effective binding capacity of affinity resins for capture of the Fc-tagged rE1E2, we anticipate that our method will provide a means for large-scale production of this HCV vaccine candidate.

    View details for PubMedID 27795422

  • Hepatitis C virus vaccine candidates inducing protective neutralizing antibodies EXPERT REVIEW OF VACCINES Fauvelle, C., Colpitts, C. C., Keck, Z., Pierce, B. G., Foung, S. K., Baumert, T. F. 2016; 15 (12): 1535-1544

    Abstract

    With more than 150 million chronically infected people, hepatitis C virus (HCV) remains a substantial global health burden. Direct-acting antivirals have dramatically improved viral cure. However, limited access to therapy, late stage detection of infection and re-infection following cure illustrate the need for a vaccine for global control of infection. Vaccines with induction of neutralizing antibodies (nAbs) have been shown to protect successfully against infections by multiple viruses and are currently developed for HCV. Areas covered: Here we review the progress towards the development of vaccines aiming to confer protection against chronic HCV infection by inducing broadly nAbs. The understanding or viral immune evasion in infected patients, the development of novel model systems and the recent structural characterization of viral envelope glycoprotein E2 has markedly advanced our understanding of the molecular mechanisms of virus neutralization with the concomitant development of several vaccine candidates. Expert commentary: While HCV vaccine development remains challenged by the high viral diversity and immune evasion, marked progress in HCV research has advanced vaccine design. Several vaccine candidates have shown robust induction of nAbs in animal models and humans. Randomized clinical trials are the next step to assess their clinical efficacy for protection against chronic infection.

    View details for DOI 10.1080/14760584.2016.1194759

    View details for Web of Science ID 000388964400007

    View details for PubMedID 27267297

    View details for PubMedCentralID PMC5156833

  • Affinity Maturation of a Broadly Neutralizing Human Monoclonal Antibody That Prevents Acute Hepatitis C Virus Infection in Mice HEPATOLOGY Keck, Z., Wang, Y., Lau, P., Lund, G., Rangarajan, S., Fauvelle, C., Liao, G. C., Holtsberg, F. W., Warfield, K. L., Javad Aman, M., Pierce, B. G., Fuerst, T. R., Bailey, J. R., Baumert, T. F., Mariuzza, R. A., Kneteman, N. M., Foung, S. K. 2016; 64 (6): 1922-1933

    Abstract

    Direct-acting antivirals (DAAs) have led to a high cure rate in treated patients with chronic hepatitis C virus (HCV) infection, but this still leaves a large number of treatment failures secondary to the emergence of resistance-associated variants (RAVs). To increase the barrier to resistance, a complementary strategy is to use neutralizing human monoclonal antibodies (HMAbs) to prevent acute infection. However, earlier efforts with the selected antibodies led to RAVs in animal and clinical studies. Therefore, we identified an HMAb that is less likely to elicit RAVs for affinity maturation to increase potency and, more important, breadth of protection. Selected matured antibodies show improved affinity and neutralization against a panel of diverse HCV isolates. Structural and modeling studies reveal that the affinity-matured HMAb mediates virus neutralization, in part, by inducing conformational change to the targeted epitope, and that the maturated light chain is responsible for the improved affinity and breadth of protection. A matured HMAb protected humanized mice when challenged with an infectious HCV human serum inoculum for a prolonged period. However, a single mouse experienced breakthrough infection after 63 days when the serum HMAb concentration dropped by several logs; sequence analysis revealed no viral escape mutation.The findings suggest that a single broadly neutralizing antibody can prevent acute HCV infection without inducing RAVs and may complement DAAs to reduce the emergence of RAVs. (Hepatology 2016;64:1922-1933).

    View details for DOI 10.1002/hep.28850

    View details for Web of Science ID 000393900200051

    View details for PubMedCentralID PMC5115987

  • Global mapping of antibody recognition of the hepatitis C virus E2 glycoprotein: Implications for vaccine design PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Pierce, B. G., Keck, Z., Lau, P., Fauvelle, C., Gowthaman, R., Baumert, T. F., Fuerst, T. R., Mariuzza, R. A., Foung, S. H. 2016; 113 (45): E6946–E6954
  • Anti-envelope antibody responses in individuals at high risk of hepatitis C virus who resist infection. Journal of viral hepatitis Swann, R. E., Mandalou, P., Robinson, M. W., Ow, M. M., Foung, S. K., McLauchlan, J., Patel, A. H., Cramp, M. E. 2016; 23 (11): 873-880

    Abstract

    Injection drug users uninfected by hepatitis C virus (HCV) despite likely repeated exposure through high-risk behaviour are well documented. Factors preventing infection in these individuals are incompletely understood. Here, we looked for anti-HCV-envelope antibody responses in a cohort of repeatedly exposed but uninfected subjects. Forty-two hepatitis C diagnostic antibody- and RNA-negative injection drug users at high risk of exposure were studied and findings compared to healthy controls and cases with chronic HCV infection. Purified IgGs from sera were tested by ELISA for binding to genotype 1a and 3a envelope glycoproteins E1E2 with further testing for IgG and IgM reactivity against soluble E2. Virus-neutralizing activity was assessed using an HCV pseudoparticle system. Uninfected subjects demonstrated significantly greater IgG and IgM reactivities to envelope glycoproteins than healthy controls with IgG from 6 individuals additionally showing significant neutralization. This study is the first to describe humoral immunological responses targeting the HCV envelope, important for viral neutralization, in exposed uninfected individuals. A subset of these cases also had evidence of viral neutralization via anti-envelope antibodies. In addition to confirming viral exposure, the presence of specific anti-envelope antibodies may be a factor that helps these individuals resist HCV infection.

    View details for DOI 10.1111/jvh.12568

    View details for PubMedID 27405885

  • Global mapping of antibody recognition of the hepatitis C virus E2 glycoprotein: Implications for vaccine design. Proceedings of the National Academy of Sciences of the United States of America Pierce, B. G., Keck, Z., Lau, P., Fauvelle, C., Gowthaman, R., Baumert, T. F., Fuerst, T. R., Mariuzza, R. A., Foung, S. K. 2016

    Abstract

    The E2 envelope glycoprotein is the primary target of human neutralizing antibody response against hepatitis C virus (HCV), and is thus a major focus of vaccine and immunotherapeutics efforts. There is emerging evidence that E2 is a highly complex, dynamic protein with residues across the protein that are modulating antibody recognition, local and global E2 stability, and viral escape. To comprehensively map these determinants, we performed global E2 alanine scanning with a panel of 16 human monoclonal antibodies (hmAbs), resulting in an unprecedented dataset of the effects of individual alanine substitutions across the E2 protein (355 positions) on antibody recognition. Analysis of shared energetic effects across the antibody panel identified networks of E2 residues involved in antibody recognition and local and global E2 stability, as well as predicted contacts between residues across the entire E2 protein. Further analysis of antibody binding hotspot residues defined groups of residues essential for E2 conformation and recognition for all 14 conformationally dependent E2 antibodies and subsets thereof, as well as residues that enhance antibody recognition when mutated to alanine, providing a potential route to engineer E2 vaccine immunogens. By incorporating E2 sequence variability, we found a number of E2 polymorphic sites that are responsible for loss of neutralizing antibody binding. These data and analyses provide fundamental insights into antibody recognition of E2, highlighting the dynamic and complex nature of this viral envelope glycoprotein, and can serve as a reference for development and rational design of E2-targeting vaccines and immunotherapeutics.

    View details for PubMedID 27791171

  • Viral evasion and challenges of hepatitis C virus vaccine development. Current opinion in virology Pierce, B. G., Keck, Z., Foung, S. K. 2016; 20: 55-63

    Abstract

    Hepatitis C virus (HCV) is a major global disease burden, often leading to chronic liver diseases, cirrhosis, cancer, and death in those infected. Despite the recent approval of antiviral therapeutics, a preventative vaccine is recognized as the most effective means to control HCV globally, particularly in at-risk and developing country populations. Here we describe the efforts and challenges related to the development of an HCV vaccine, which after decades of research have not been successful. Viral sequence variability poses a major challenge, yet recent research has provided unprecedented views of the atomic structure of HCV epitopes and immune recognition by antibodies and T cell receptors. This, coupled with insights from deep sequencing, robust neutralization assays, and other technological advances, is spurring research toward rationally HCV designed vaccines that preferentially elicit responses toward conserved epitopes of interest that are associated with viral neutralization and clearance.

    View details for DOI 10.1016/j.coviro.2016.09.004

    View details for PubMedID 27657659

    View details for PubMedCentralID PMC5102773

  • Affinity maturation of a broadly neutralizing human monoclonal antibody that prevents acute hepatitis C virus infection in mice. Hepatology Keck, Z., Wang, Y., Lau, P., Lund, G., Rangarajan, S., Fauvelle, C., Liao, G. C., Holtsberg, F. W., Warfield, K. L., Aman, M. J., Pierce, B. G., Fuerst, T. R., Bailey, J. R., Baumert, T. F., Mariuzza, R. A., Kneteman, N. M., Foung, S. K. 2016

    Abstract

    Direct-acting antivirals (DAAs) have led to a high cure rate in treated patients with chronic hepatitis C virus (HCV) infection, but this still leaves a large number of treatment failures secondary to the emergence of resistance-associated variants (RAVs). To increase the barrier to resistance, a complementary strategy is to use neutralizing human monoclonal antibodies (HMAbs) to prevent acute infection. However, earlier efforts with the selected antibodies led to RAVs in animal and clinical studies. Therefore, we identified an HMAb that is less likely to elicit RAVs for affinity maturation to increase potency and, more important, breadth of protection. Selected matured antibodies show improved affinity and neutralization against a panel of diverse HCV isolates. Structural and modeling studies reveal that the affinity-matured HMAb mediates virus neutralization, in part, by inducing conformational change to the targeted epitope, and that the maturated light chain is responsible for the improved affinity and breadth of protection. A matured HMAb protected humanized mice when challenged with an infectious HCV human serum inoculum for a prolonged period. However, a single mouse experienced breakthrough infection after 63 days when the serum HMAb concentration dropped by several logs; sequence analysis revealed no viral escape mutation.The findings suggest that a single broadly neutralizing antibody can prevent acute HCV infection without inducing RAVs and may complement DAAs to reduce the emergence of RAVs. (Hepatology 2016;64:1922-1933).

    View details for DOI 10.1002/hep.28850

    View details for PubMedID 27641232

    View details for PubMedCentralID PMC5115987

  • Hypervariable region 1 shielding of hepatitis C virus is a main contributor to genotypic differences in neutralization sensitivity. Hepatology Prentoe, J., Velázquez-Moctezuma, R., Foung, S. K., Law, M., Bukh, J. 2016

    Abstract

    There are 3-4 million new hepatitis C virus (HCV) infections yearly. The extensive intergenotypic sequence diversity of envelope proteins E1 and E2 of HCV and shielding of important epitopes by hypervariable region 1 (HVR1) of E2 are believed to be major hindrances to developing universally protective HCV vaccines. Using cultured viruses expressing the E1/E2 complex of isolates H77 (genotype 1a), J6 (2a), or S52 (3a), with and without HVR1, we tested HVR1-mediated neutralization occlusion in vitro against a panel of 12 well-characterized human monoclonal antibodies (HMAbs) targeting diverse E1, E2, and E1/E2 epitopes. Surprisingly, HVR1-mediated protection was greatest for S52, followed by J6 and then H77. HCV pulldown experiments showed that this phenomenon was caused by epitope shielding. Moreover, by regression analysis of HMAb binding and neutralization titer of HCV we found a strong correlation for HVR1-deleted viruses but not for parental viruses retaining HVR1. The intergenotype neutralization sensitivity of the parental viruses to HMAb antigenic region (AR) 2A, AR3A, AR4A, AR5A, HC84.26, and HC33.4 varied greatly (>24-fold to >130-fold differences in 50% inhibitory concentration values). However, except for AR5A, these differences decreased to less than 6.0-fold when comparing the corresponding HVR1-deleted viruses. Importantly, this simplified pattern of neutralization sensitivity in the absence of HVR1 was also demonstrated in a panel of HVR1-deleted viruses of genotypes 1a, 2a, 2b, 3a, 5a, and 6a, although for all HMAbs, except AR4A, an outlier was observed. Finally, unique amino acid residues in HCV E2 could explain these outliers in the tested cases of AR5A and HC84.26.HVR1 adds complexity to HCV neutralization by shielding a diverse array of unexpectedly cross-genotype-conserved E1/E2 epitopes. Thus, an HVR1-deleted antigen could be a better HCV vaccine immunogen. (Hepatology 2016;64:1881-1892).

    View details for DOI 10.1002/hep.28705

    View details for PubMedID 27351277

    View details for PubMedCentralID PMC5115964

  • Antibody Treatment of Ebola and Sudan Virus Infection via a Uniquely Exposed Epitope within the Glycoprotein Receptor-Binding Site CELL REPORTS Howell, K. A., Qiu, X., Brannan, J. M., Bryan, C., Davidson, E., Holtsberg, F. W., Wec, A. Z., Shulenin, S., Biggins, J. E., Douglas, R., Enterlein, S. G., Turner, H. L., Pallesen, J., Murin, C. D., He, S., Kroeker, A., Vu, H., Herbert, A. S., Fusco, M. L., Nyakatura, E. K., Lai, J. R., Keck, Z., Foung, S. K., Saphire, E. O., Zeitlin, L., Ward, A. B., Chandran, K., Doranz, B. J., Kobinger, G. P., Dye, J. M., Aman, M. J. 2016; 15 (7): 1514-1526

    Abstract

    Previous efforts to identify cross-neutralizing antibodies to the receptor-binding site (RBS) of ebolavirus glycoproteins have been unsuccessful, largely because the RBS is occluded on the viral surface. We report a monoclonal antibody (FVM04) that targets a uniquely exposed epitope within the RBS; cross-neutralizes Ebola (EBOV), Sudan (SUDV), and, to a lesser extent, Bundibugyo viruses; and shows protection against EBOV and SUDV in mice and guinea pigs. The antibody cocktail ZMapp™ is remarkably effective against EBOV (Zaire) but does not cross-neutralize other ebolaviruses. By replacing one of the ZMapp™ components with FVM04, we retained the anti-EBOV efficacy while extending the breadth of protection to SUDV, thereby generating a cross-protective antibody cocktail. In addition, we report several mutations at the base of the ebolavirus glycoprotein that enhance the binding of FVM04 and other cross-reactive antibodies. These findings have important implications for pan-ebolavirus vaccine development and defining broadly protective antibody cocktails.

    View details for DOI 10.1016/j.celrep.2016.04.026

    View details for Web of Science ID 000376165300015

    View details for PubMedID 27160900

    View details for PubMedCentralID PMC4871745

  • Macaque Monoclonal Antibodies Targeting Novel Conserved Epitopes within Filovirus Glycoprotein JOURNAL OF VIROLOGY Keck, Z., Enterlein, S. G., Howell, K. A., Hong Vu, H., Shulenin, S., Warfield, K. L., Froude, J. W., Araghi, N., Douglas, R., Biggins, J., Lear-Rooney, C. M., Wirchnianski, A. S., Lau, P., Wang, Y., Herbert, A. S., Dye, J. M., Glass, P. J., Holtsberg, F. W., Foung, S. K., Aman, M. J. 2016; 90 (1): 279-291

    Abstract

    Filoviruses cause highly lethal viral hemorrhagic fever in humans and nonhuman primates. Current immunotherapeutic options for filoviruses are mostly specific to Ebola virus (EBOV), although other members of Filoviridae such as Sudan virus (SUDV), Bundibugyo virus (BDBV), and Marburg virus (MARV) have also caused sizeable human outbreaks. Here we report a set of pan-ebolavirus and pan-filovirus monoclonal antibodies (MAbs) derived from cynomolgus macaques immunized repeatedly with a mixture of engineered glycoproteins (GPs) and virus-like particles (VLPs) for three different filovirus species. The antibodies recognize novel neutralizing and nonneutralizing epitopes on the filovirus glycoprotein, including conserved conformational epitopes within the core regions of the GP1 subunit and a novel linear epitope within the glycan cap. We further report the first filovirus antibody binding to a highly conserved epitope within the fusion loop of ebolavirus and marburgvirus species. One of the antibodies binding to the core GP1 region of all ebolavirus species and with lower affinity to MARV GP cross neutralized both SUDV and EBOV, the most divergent ebolavirus species. In a mouse model of EBOV infection, this antibody provided 100% protection when administered in two doses and partial, but significant, protection when given once at the peak of viremia 3 days postinfection. Furthermore, we describe novel cocktails of antibodies with enhanced protective efficacy compared to individual MAbs. In summary, the present work describes multiple novel, cross-reactive filovirus epitopes and innovative combination concepts that challenge the current therapeutic models.Filoviruses are among the most deadly human pathogens. The 2014-2015 outbreak of Ebola virus disease (EVD) led to more than 27,000 cases and 11,000 fatalities. While there are five species of Ebolavirus and several strains of marburgvirus, the current immunotherapeutics primarily target Ebola virus. Since the nature of future outbreaks cannot be predicted, there is an urgent need for therapeutics with broad protective efficacy against multiple filoviruses. Here we describe a set of monoclonal antibodies cross-reactive with multiple filovirus species. These antibodies target novel conserved epitopes within the envelope glycoprotein and exhibit protective efficacy in mice. We further present novel concepts for combination of cross-reactive antibodies against multiple epitopes that show enhanced efficacy compared to monotherapy and provide complete protection in mice. These findings set the stage for further evaluation of these antibodies in nonhuman primates and development of effective pan-filovirus immunotherapeutics for use in future outbreaks.

    View details for DOI 10.1128/JVI.02172-15

    View details for Web of Science ID 000366899000025

    View details for PubMedCentralID PMC4702572

  • Antibody Response to Hypervariable Region 1 Interferes with Broadly Neutralizing Antibodies to Hepatitis C Virus. Journal of virology Keck, Z., Girard-Blanc, C., Wang, W., Lau, P., Zuiani, A., Rey, F. A., Krey, T., Diamond, M. S., Foung, S. K. 2016; 90 (6): 3112-3122

    Abstract

    Hypervariable region 1 (HVR1) (amino acids [aa] 384 to 410) on the E2 glycoprotein of hepatitis C virus contributes to persistent infection by evolving escape mutations that attenuate binding of inhibitory antibodies and by blocking access of broadly neutralizing antibodies to their epitopes. A third proposed mechanism of immune antagonism is that poorly neutralizing antibodies binding to HVR1 interfere with binding of other superior neutralizing antibodies. Epitope mapping of human monoclonal antibodies (HMAbs) that bind to an adjacent, conserved domain on E2 encompassing aa 412 to 423 revealed two subsets, designated HC33 HMAbs. While both subsets have contact residues within aa 412 to 423, alanine-scanning mutagenesis suggested that one subset, which includes HC33.8, has an additional contact residue within HVR1. To test for interference of anti-HVR1 antibodies with binding of antibodies to aa 412 to 423 and other E2 determinants recognized by broadly neutralizing HMAbs, two murine MAbs against HVR1 (H77.16) and aa 412 to 423 (H77.39) were studied. As expected, H77.39 inhibited the binding of all HC33 HMAbs. Unexpectedly, H77.16 also inhibited the binding of both subsets of HC33 HMAbs. This inhibition also was observed against other broadly neutralizing HMAbs to epitopes outside aa 412 to 423. Combination antibody neutralization studies by the median-effect analysis method with H77.16 and broadly reactive HMAbs revealed antagonism between these antibodies. Structural studies demonstrated conformational flexibility in this antigenic region, which supports the possibility of anti-HVR1 antibodies hindering the binding of broadly neutralizing MAbs. These findings support the hypothesis that anti-HVR1 antibodies can interfere with a protective humoral response against HCV infection.HVR1 contributes to persistent infection by evolving mutations that escape from neutralizing antibodies to HVR1 and by shielding broadly neutralizing antibodies from their epitopes. This study provides insight into a new immune antagonism mechanism by which the binding of antibodies to HVR1 blocks the binding and activity of broadly neutralizing antibodies to HCV. Immunization strategies that avoid the induction of HVR1 antibodies should increase the inhibitory activity of broadly neutralizing anti-HCV antibodies elicited by candidate vaccines.

    View details for DOI 10.1128/JVI.02458-15

    View details for PubMedID 26739044

    View details for PubMedCentralID PMC4810650

  • Apolipoprotein E Mediates Evasion From Hepatitis C Virus Neutralizing Antibodies GASTROENTEROLOGY Fauvelle, C., Felmlee, D. J., Crouchet, E., Lee, J., Heydmann, L., Lefevre, M., Magri, A., Hiet, M., Fofana, I., Habersetzer, F., Foung, S. K., Milne, R., Patel, A. H., Vercauteren, K., Meuleman, P., Zeisel, M. B., Bartenschlager, R., Schuster, C., Baumert, T. F. 2016; 150 (1): 206-?

    Abstract

    Efforts to develop an effective vaccine against hepatitis C virus (HCV) have been hindered by the propensity of the virus to evade host immune responses. HCV particles in serum and in cell culture associate with lipoproteins, which contribute to viral entry. Lipoprotein association has also been proposed to mediate viral evasion of the humoral immune response, though the mechanisms are poorly defined.We used small interfering RNAs to reduce levels of apolipoprotein E (apoE) in cell culture-derived HCV-producing Huh7.5-derived hepatoma cells and confirmed its depletion by immunoblot analyses of purified viral particles. Before infection of naïve hepatoma cells, we exposed cell culture-derived HCV strains of different genotypes, subtypes, and variants to serum and polyclonal and monoclonal antibodies isolated from patients with chronic HCV infection. We analyzed the interaction of apoE with viral envelope glycoprotein E2 and HCV virions by immunoprecipitation.Through loss-of-function studies on patient-derived HCV variants of several genotypes and subtypes, we found that the HCV particle apoE allows the virus to avoid neutralization by patient-derived antibodies. Functional studies with human monoclonal antiviral antibodies showed that conformational epitopes of envelope glycoprotein E2 domains B and C were exposed after depletion of apoE. The level and conformation of virion-associated apoE affected the ability of the virus to escape neutralization by antibodies.In cell-infection studies, we found that HCV-associated apoE helps the virus avoid neutralization by antibodies against HCV isolated from chronically infected patients. This method of immune evasion poses a challenge for the development of HCV vaccines.

    View details for DOI 10.1053/j.gastro.2015.09.014

    View details for Web of Science ID 000366832800037

    View details for PubMedID 26404951

  • Structural basis for penetration of the glycan shield of hepatitis C virus e2 glycoprotein by a broadly neutralizing human antibody. journal of biological chemistry Li, Y., Pierce, B. G., Wang, Q., Keck, Z., Fuerst, T. R., Foung, S. K., Mariuzza, R. A. 2015; 290 (16): 10117-10125

    Abstract

    Hepatitis C virus (HCV) is a major cause of liver cirrhosis and hepatocellular carcinoma. A challenge for HCV vaccine development is to identify conserved epitopes able to elicit protective antibodies against this highly diverse virus. Glycan shielding is a mechanism by which HCV masks such epitopes on its E2 envelope glycoprotein. Antibodies to the E2 region comprising residues 412-423 (E2412-423) have broadly neutralizing activities. However, an adaptive mutation in this linear epitope, N417S, is associated with a glycosylation shift from Asn-417 to Asn-415 that enables HCV to escape neutralization by mAbs such as HCV1 and AP33. By contrast, the human mAb HC33.1 can neutralize virus bearing the N417S mutation. To understand how HC33.1 penetrates the glycan shield created by the glycosylation shift to Asn-415, we determined the structure of this broadly neutralizing mAb in complex with its E2412-423 epitope to 2.0 Å resolution. The conformation of E2412-423 bound to HC33.1 is distinct from the β-hairpin conformation of this peptide bound to HCV1 or AP33, because of disruption of the β-hairpin through interactions with the unusually long complementarity-determining region 3 of the HC33.1 heavy chain. Whereas Asn-415 is buried by HCV1 and AP33, it is solvent-exposed in the HC33.1-E2412-423 complex, such that glycosylation of Asn-415 would not prevent antibody binding. Furthermore, our results highlight the structural flexibility of the E2412-423 epitope, which may serve as an immune evasion strategy to impede induction of antibodies targeting this site by reducing its antigenicity.

    View details for DOI 10.1074/jbc.M115.643528

    View details for PubMedID 25737449

    View details for PubMedCentralID PMC4400327

  • An Anti-H5N1 Influenza Virus FcDART Antibody Is a Highly Efficacious Therapeutic Agent and Prophylactic against H5N1 Influenza Virus Infection JOURNAL OF VIROLOGY Zanin, M., Keck, Z., Rainey, G. J., Lam, C. K., Boon, A. C., Rubrum, A., Darnell, D., Wong, S., Griffin, Y., Xia, J., Webster, R. G., Webby, R., Johnson, S., Foung, S. 2015; 89 (8): 4549-4561

    Abstract

    Highly pathogenic H5N1 avian influenza viruses are associated with severe disease in humans and continue to be a pandemic threat. While vaccines are available, other approaches are required for patients that typically respond poorly to vaccination, such as the elderly and the immunocompromised. To produce a therapeutic agent that is highly efficacious at low doses and is broadly specific against antigenically drifted H5N1 influenza viruses, we developed two neutralizing monoclonal antibodies and combined them into a single bispecific Fc fusion protein (the Fc dual-affinity retargeting [FcDART] molecule). In mice, a single therapeutic or prophylactic dose of either monoclonal antibody at 2.5 mg/kg of body weight provided 100% protection against challenge with A/Vietnam/1203/04 (H5N1) or the antigenically drifted strain A/Whooper swan/Mongolia/244/05 (H5N1). In ferrets, a single 1-mg/kg prophylactic dose provided 100% protection against A/Vietnam/1203/04 challenge. FcDART was also effective, as a single 2.5-mg/kg therapeutic or prophylactic dose in mice provided 100% protection against A/Vietnam/1203/04 challenge. Antibodies bound to conformational epitopes in antigenic sites on the globular head of the hemagglutinin protein, on the basis of analysis of mutants with antibody escape mutations. While it was possible to generate escape mutants in vitro, they were neutralized by the antibodies in vivo, as mice infected with escape mutants were 100% protected after only a single therapeutic dose of the antibody used to generate the escape mutant in vitro. In summary, we have combined the antigen specificities of two highly efficacious anti-H5N1 influenza virus antibodies into a bispecific FcDART molecule, which represents a strategy to produce broadly neutralizing antibodies that are effective against antigenically diverse influenza viruses.Highly pathogenic H5N1 avian influenza viruses are associated with severe disease in humans and are a pandemic threat. A vaccine is available, but other approaches are required for patients that typically respond poorly to vaccination, such as the elderly and the immunocompromised. The variability of the virus means that such an approach must be broad spectrum. To achieve this, we developed two antibodies that neutralize H5N1 influenza viruses. In mice, these antibodies provided complete protection against a spectrum of H5N1 influenza viruses at a single low dose. We then combined the two antibodies into a single molecule, FcDART, which combined the broad-spectrum activity and protective efficacy of both antibodies. This treatment provides a novel and effective therapeutic agent or prophylactic with activity against highly pathogenic H5N1 avian influenza viruses.

    View details for DOI 10.1128/JVI.00078-15

    View details for Web of Science ID 000352218400043

    View details for PubMedID 25673719

    View details for PubMedCentralID PMC4442345

  • Structural flexibility of a conserved antigenic region in hepatitis C virus glycoprotein e2 recognized by broadly neutralizing antibodies. Journal of virology Meola, A., Tarr, A. W., England, P., Meredith, L. W., McClure, C. P., Foung, S. K., McKeating, J. A., Ball, J. K., Rey, F. A., Krey, T. 2015; 89 (4): 2170-2181

    Abstract

    Neutralizing antibodies (NAbs) targeting glycoprotein E2 are important for the control of hepatitis C virus (HCV) infection. One conserved antigenic site (amino acids 412 to 423) is disordered in the reported E2 structure, but a synthetic peptide mimicking this site forms a β-hairpin in complex with three independent NAbs. Our structure of the same peptide in complex with NAb 3/11 demonstrates a strikingly different extended conformation. We also show that residues 412 to 423 are essential for virus entry but not for E2 folding. Together with the neutralizing capacity of the 3/11 Fab fragment, this indicates an unexpected structural flexibility within this epitope. NAbs 3/11 and AP33 (recognizing the extended and β-hairpin conformations, respectively) display similar neutralizing activities despite converse binding kinetics. Our results suggest that HCV utilizes conformational flexibility as an immune evasion strategy, contributing to the limited immunogenicity of this epitope in patients, similar to the conformational flexibility described for other enveloped and nonenveloped viruses.Approximately 180 million people worldwide are infected with hepatitis C virus (HCV), and neutralizing antibodies play an important role in controlling the replication of this major human pathogen. We show here that one of the most conserved antigenic sites within the major glycoprotein E2 (amino acids 412 to 423), which is disordered in the recently reported crystal structure of an E2 core fragment, can adopt different conformations in the context of the infectious virus particle. Recombinant Fab fragments recognizing different conformations of this antigenic site have similar neutralization activities in spite of converse kinetic binding parameters. Of note, an antibody response targeting this antigenic region is less frequent than those targeting other more immunogenic regions in E2. Our results suggest that the observed conformational flexibility in this conserved antigenic region contributes to the evasion of the humoral host immune response, facilitating chronicity and the viral spread of HCV within an infected individual.

    View details for DOI 10.1128/JVI.02190-14

    View details for PubMedID 25473061

  • Naturally selected hepatitis C virus polymorphisms confer broad neutralizing antibody resistance JOURNAL OF CLINICAL INVESTIGATION Bailey, J. R., Wasilewski, L. N., Snider, A. E., El-Diwany, R., Osburn, W. O., Keck, Z., Foung, S. K., Ray, S. C. 2015; 125 (1): 437-447

    Abstract

    For hepatitis C virus (HCV) and other highly variable viruses, broadly neutralizing mAbs are an important guide for vaccine development. The development of resistance to anti-HCV mAbs is poorly understood, in part due to a lack of neutralization testing against diverse, representative panels of HCV variants. Here, we developed a neutralization panel expressing diverse, naturally occurring HCV envelopes (E1E2s) and used this panel to characterize neutralizing breadth and resistance mechanisms of 18 previously described broadly neutralizing anti-HCV human mAbs. The observed mAb resistance could not be attributed to polymorphisms in E1E2 at known mAb-binding residues. Additionally, hierarchical clustering analysis of neutralization resistance patterns revealed relationships between mAbs that were not predicted by prior epitope mapping, identifying 3 distinct neutralization clusters. Using this clustering analysis and envelope sequence data, we identified polymorphisms in E2 that confer resistance to multiple broadly neutralizing mAbs. These polymorphisms, which are not at mAb contact residues, also conferred resistance to neutralization by plasma from HCV-infected subjects. Together, our method of neutralization clustering with sequence analysis reveals that polymorphisms at noncontact residues may be a major immune evasion mechanism for HCV, facilitating viral persistence and presenting a challenge for HCV vaccine development.

    View details for DOI 10.1172/JCI78794

    View details for Web of Science ID 000347747300044

    View details for PubMedID 25500884

    View details for PubMedCentralID PMC4382262

  • Macaque Monoclonal Antibodies Targeting Novel Conserved Epitopes within Filovirus Glycoprotein. Journal of virology Keck, Z., Enterlein, S. G., Howell, K. A., Vu, H., Shulenin, S., Warfield, K. L., Froude, J. W., Araghi, N., Douglas, R., Biggins, J., Lear-Rooney, C. M., Wirchnianski, A. S., Lau, P., Wang, Y., Herbert, A. S., Dye, J. M., Glass, P. J., Holtsberg, F. W., Foung, S. K., Aman, M. J. 2015; 90 (1): 279-291

    Abstract

    Filoviruses cause highly lethal viral hemorrhagic fever in humans and nonhuman primates. Current immunotherapeutic options for filoviruses are mostly specific to Ebola virus (EBOV), although other members of Filoviridae such as Sudan virus (SUDV), Bundibugyo virus (BDBV), and Marburg virus (MARV) have also caused sizeable human outbreaks. Here we report a set of pan-ebolavirus and pan-filovirus monoclonal antibodies (MAbs) derived from cynomolgus macaques immunized repeatedly with a mixture of engineered glycoproteins (GPs) and virus-like particles (VLPs) for three different filovirus species. The antibodies recognize novel neutralizing and nonneutralizing epitopes on the filovirus glycoprotein, including conserved conformational epitopes within the core regions of the GP1 subunit and a novel linear epitope within the glycan cap. We further report the first filovirus antibody binding to a highly conserved epitope within the fusion loop of ebolavirus and marburgvirus species. One of the antibodies binding to the core GP1 region of all ebolavirus species and with lower affinity to MARV GP cross neutralized both SUDV and EBOV, the most divergent ebolavirus species. In a mouse model of EBOV infection, this antibody provided 100% protection when administered in two doses and partial, but significant, protection when given once at the peak of viremia 3 days postinfection. Furthermore, we describe novel cocktails of antibodies with enhanced protective efficacy compared to individual MAbs. In summary, the present work describes multiple novel, cross-reactive filovirus epitopes and innovative combination concepts that challenge the current therapeutic models.Filoviruses are among the most deadly human pathogens. The 2014-2015 outbreak of Ebola virus disease (EVD) led to more than 27,000 cases and 11,000 fatalities. While there are five species of Ebolavirus and several strains of marburgvirus, the current immunotherapeutics primarily target Ebola virus. Since the nature of future outbreaks cannot be predicted, there is an urgent need for therapeutics with broad protective efficacy against multiple filoviruses. Here we describe a set of monoclonal antibodies cross-reactive with multiple filovirus species. These antibodies target novel conserved epitopes within the envelope glycoprotein and exhibit protective efficacy in mice. We further present novel concepts for combination of cross-reactive antibodies against multiple epitopes that show enhanced efficacy compared to monotherapy and provide complete protection in mice. These findings set the stage for further evaluation of these antibodies in nonhuman primates and development of effective pan-filovirus immunotherapeutics for use in future outbreaks.

    View details for DOI 10.1128/JVI.02172-15

    View details for PubMedID 26468532

    View details for PubMedCentralID PMC4702572

  • Breadth of Neutralization and Synergy of Clinically Relevant Human Monoclonal Antibodies Against HCV Genotypes 1a, 1b, 2a, 2b, 2c, and 3a HEPATOLOGY Carlsen, T. H., Pedersen, J., Prentoe, J. C., Giang, E., Keck, Z., Mikkelsen, L. S., Law, M., Foung, S. K., Bukh, J. 2014; 60 (5): 1551-1562

    Abstract

    Human monoclonal antibodies (HMAbs) with neutralizing capabilities constitute potential immune-based treatments or prophylaxis against hepatitis C virus (HCV). However, lack of cell culture-derived HCV (HCVcc) harboring authentic envelope proteins (E1/E2) has hindered neutralization investigations across genotypes, subtypes, and isolates. We investigated the breadth of neutralization of 10 HMAbs with therapeutic potential against a panel of 16 JFH1-based HCVcc-expressing patient-derived Core-NS2 from genotypes 1a (strains H77, TN, and DH6), 1b (J4, DH1, and DH5), 2a (J6, JFH1, and T9), 2b (J8, DH8, and DH10), 2c (S83), and 3a (S52, DBN, and DH11). Virus stocks used for in vitro neutralization analysis contained authentic E1/E2, with the exception of full-length JFH1 that acquired the N417S substitution in E2. The 50% inhibition concentration (IC50) for each HMAb against the HCVcc panel was determined by dose-response neutralization assays in Huh7.5 cells with antibody concentrations ranging from 0.0012 to 100 μg/mL. Interestingly, IC50 values against the different HCVcc's exhibited large variations among the HMAbs, and only three HMAbs (HC-1AM, HC84.24, and AR4A) neutralized all 16 HCVcc recombinants. Furthermore, the IC50 values for a given HMAb varied greatly with the HCVcc strain, which supports the use of a diverse virus panel. In cooperation analyses, HMAbs HC84.24, AR3A, and, especially HC84.26, demonstrated synergistic effects towards the majority of the HCVcc's when combined individually with AR4A.Through a neutralization analysis of 10 clinically relevant HMAbs against 16 JFH1-based Core-NS2 recombinants from genotypes 1a, 1b, 2a, 2b, 2c, and 3a, we identified at least three HMAbs with potent and broad neutralization potential. The neutralization synergism obtained when pooling the most potent HMAbs could have significant implications for developing novel strategies to treat and control HCV.

    View details for DOI 10.1002/hep.27298

    View details for Web of Science ID 000344352400015

    View details for PubMedCentralID PMC4415877

  • Breadth of neutralization and synergy of clinically relevant human monoclonal antibodies against HCV genotypes 1a, 1b, 2a, 2b, 2c, and 3a. Hepatology Carlsen, T. H., Pedersen, J., Prentoe, J. C., Giang, E., Keck, Z., Mikkelsen, L. S., Law, M., Foung, S. K., Bukh, J. 2014; 60 (5): 1551-1562

    Abstract

    Human monoclonal antibodies (HMAbs) with neutralizing capabilities constitute potential immune-based treatments or prophylaxis against hepatitis C virus (HCV). However, lack of cell culture-derived HCV (HCVcc) harboring authentic envelope proteins (E1/E2) has hindered neutralization investigations across genotypes, subtypes, and isolates. We investigated the breadth of neutralization of 10 HMAbs with therapeutic potential against a panel of 16 JFH1-based HCVcc-expressing patient-derived Core-NS2 from genotypes 1a (strains H77, TN, and DH6), 1b (J4, DH1, and DH5), 2a (J6, JFH1, and T9), 2b (J8, DH8, and DH10), 2c (S83), and 3a (S52, DBN, and DH11). Virus stocks used for in vitro neutralization analysis contained authentic E1/E2, with the exception of full-length JFH1 that acquired the N417S substitution in E2. The 50% inhibition concentration (IC50) for each HMAb against the HCVcc panel was determined by dose-response neutralization assays in Huh7.5 cells with antibody concentrations ranging from 0.0012 to 100 μg/mL. Interestingly, IC50 values against the different HCVcc's exhibited large variations among the HMAbs, and only three HMAbs (HC-1AM, HC84.24, and AR4A) neutralized all 16 HCVcc recombinants. Furthermore, the IC50 values for a given HMAb varied greatly with the HCVcc strain, which supports the use of a diverse virus panel. In cooperation analyses, HMAbs HC84.24, AR3A, and, especially HC84.26, demonstrated synergistic effects towards the majority of the HCVcc's when combined individually with AR4A.Through a neutralization analysis of 10 clinically relevant HMAbs against 16 JFH1-based Core-NS2 recombinants from genotypes 1a, 1b, 2a, 2b, 2c, and 3a, we identified at least three HMAbs with potent and broad neutralization potential. The neutralization synergism obtained when pooling the most potent HMAbs could have significant implications for developing novel strategies to treat and control HCV.

    View details for DOI 10.1002/hep.27298

    View details for PubMedID 25043937

  • Non-random Escape Pathways from a Broadly Neutralizing Human Monoclonal Antibody Map to a Highly Conserved Region on the Hepatitis C Virus E2 Glycoprotein Encompassing Amino Acids 412-423. PLoS pathogens Keck, Z., Angus, A. G., Wang, W., Lau, P., Wang, Y., Gatherer, D., Patel, A. H., Foung, S. K. 2014; 10 (8)

    Abstract

    A challenge for hepatitis C virus (HCV) vaccine development is to define epitopes that are able to elicit protective antibodies against this highly diverse virus. The E2 glycoprotein region located at residues 412-423 is conserved and antibodies to 412-423 have broadly neutralizing activities. However, an adaptive mutation, N417S, is associated with a glycan shift in a variant that cannot be neutralized by a murine but by human monoclonal antibodies (HMAbs) against 412-423. To determine whether HCV escapes from these antibodies, we analyzed variants that emerged when cell culture infectious HCV virions (HCVcc) were passaged under increasing concentrations of a specific HMAb, HC33.1. Multiple nonrandom escape pathways were identified. Two pathways occurred in the context of an N-glycan shift mutation at N417T. At low antibody concentrations, substitutions of two residues outside of the epitope, N434D and K610R, led to variants having improved in vitro viral fitness and reduced sensitivity to HC33.1 binding and neutralization. At moderate concentrations, a S419N mutation occurred within 412-423 in escape variants that have greatly reduced sensitivity to HC33.1 but compromised viral fitness. Importantly, the variants generated from these pathways differed in their stability. N434D and K610R-associated variants were stable and became dominant as the virions were passaged. The S419N mutation reverted back to N419S when immune pressure was reduced by removing HC33.1. At high antibody concentrations, a mutation at L413I was observed in variants that were resistant to HC33.1 neutralization. Collectively, the combination of multiple escape pathways enabled the virus to persist under a wide range of antibody concentrations. Moreover, these findings pose a different challenge to vaccine development beyond the identification of highly conserved epitopes. It will be necessary for a vaccine to induce high potency antibodies that prevent the formation of escape variants, which can co-exist with lower potency or levels of neutralizing activities.

    View details for DOI 10.1371/journal.ppat.1004297

    View details for PubMedID 25122476

    View details for PubMedCentralID PMC4133389

  • Neutralization Resistance of Hepatitis C Virus Can Be Overcome by Recombinant Human Monoclonal Antibodies HEPATOLOGY Pedersen, J., Carlsen, T. H., Prentoe, J., Ramirez, S., Jensen, T. B., Forns, X., Alter, H., Foung, S. K., Law, M., Gottwein, J., Weis, N., Bukh, J. 2013; 58 (5): 1587-1597

    Abstract

    Immunotherapy and vaccine development for hepatitis C virus (HCV) will depend on broadly reactive neutralizing antibodies. However, studies in infectious JFH1-based culture systems expressing patient derived Core-NS2 proteins have suggested neutralization resistance for specific HCV strains, in particular of genotype 2. To further examine this phenomenon, we developed a panel of HCV genotype 2 recombinants for testing of sensitivity to neutralization by chronic-phase patient sera and lead human monoclonal antibodies. The novel Core-NS2 recombinants, with patient derived genotype 2a (strain T9), 2b (strains DH8 and DH10), and 2c (strain S83) consensus sequences, were viable in Huh7.5 hepatoma cells without requirement for adaptive mutations, reaching HCV infectivity titers of 3.9-4.5 log10 focus-forming units per mL. In in vitro neutralization assays, we demonstrated that the novel genotype 2 viruses as well as prototype strains J6(2a) and J8(2b), all with authentic envelope proteins, were resistant to neutralization by genotype 2a, 2b, 2c, 2j, 2i, and 2q patient sera. These patient sera, however, had high titers of HCV-specific neutralizing antibodies, since they efficiently reduced the infectivity of J6(2a) and J8(2b) with deleted hypervariable region 1. The genotype 2a, 2b, and 2c viruses, found resistant to polyclonal patient sera neutralization, were efficiently neutralized by two lead human monoclonal antibodies, AR4A and HC84.26. Conclusion: Using novel 2a, 2b, and 2c cell culture systems, expressing authentic envelope proteins, we demonstrated resistance of HCV to patient-derived polyclonal high-titer neutralizing antibodies. However, the same genotype 2 culture viruses were all sensitive to human monoclonal HCV antibodies recognizing conformational epitopes, indicating that neutralization resistance of HCV can be overcome by applying recombinant antibodies. These findings have important implications for HCV immunotherapy and vaccine development. (HEPATOLOGY 2013.).

    View details for DOI 10.1002/hep.26524

    View details for Web of Science ID 000326327600010

  • Neutralization resistance of hepatitis C virus can be overcome by recombinant human monoclonal antibodies. Hepatology (Baltimore, Md.) Pedersen, J., Carlsen, T. H., Prentoe, J., Ramirez, S., Jensen, T. B., Forns, X., Alter, H., Foung, S. K., Law, M., Gottwein, J., Weis, N., Bukh, J. 2013

    Abstract

    Immunotherapy and vaccine development for hepatitis C virus (HCV) will depend on broadly reactive neutralizing antibodies. However, studies in infectious JFH1-based culture systems expressing patient derived Core-NS2 proteins have suggested neutralization resistance for specific HCV strains, in particular of genotype 2. To further examine this phenomenon, we developed a panel of HCV genotype 2 recombinants for testing of sensitivity to neutralization by chronic-phase patient sera and lead human monoclonal antibodies. The novel Core-NS2 recombinants, with patient derived genotype 2a (strain T9), 2b (strains DH8 and DH10), and 2c (strain S83) consensus sequences, were viable in Huh7.5 hepatoma cells without requirement for adaptive mutations, reaching HCV infectivity titers of 3.9-4.5 log10 focus-forming units per mL. In in vitro neutralization assays, we demonstrated that the novel genotype 2 viruses as well as prototype strains J6(2a) and J8(2b), all with authentic envelope proteins, were resistant to neutralization by genotype 2a, 2b, 2c, 2j, 2i, and 2q patient sera. These patient sera, however, had high titers of HCV-specific neutralizing antibodies, since they efficiently reduced the infectivity of J6(2a) and J8(2b) with deleted hypervariable region 1. The genotype 2a, 2b, and 2c viruses, found resistant to polyclonal patient sera neutralization, were efficiently neutralized by two lead human monoclonal antibodies, AR4A and HC84.26. Conclusion: Using novel 2a, 2b, and 2c cell culture systems, expressing authentic envelope proteins, we demonstrated resistance of HCV to patient-derived polyclonal high-titer neutralizing antibodies. However, the same genotype 2 culture viruses were all sensitive to human monoclonal HCV antibodies recognizing conformational epitopes, indicating that neutralization resistance of HCV can be overcome by applying recombinant antibodies. These findings have important implications for HCV immunotherapy and vaccine development. (HEPATOLOGY 2013.).

    View details for DOI 10.1002/hep.26524

    View details for PubMedID 23729237

  • Structural basis of HCV neutralization by human monoclonal antibodies resistant to viral neutralization escape. PLoS pathogens Krey, T., Meola, A., Keck, Z., Damier-Piolle, L., Foung, S. K., Rey, F. A. 2013; 9 (5)

    Abstract

    The high mutation rate of hepatitis C virus allows it to rapidly evade the humoral immune response. However, certain epitopes in the envelope glycoproteins cannot vary without compromising virus viability. Antibodies targeting these epitopes are resistant to viral escape from neutralization and understanding their binding-mode is important for vaccine design. Human monoclonal antibodies HC84-1 and HC84-27 target conformational epitopes overlapping the CD81 receptor-binding site, formed by segments aa434-446 and aa610-619 within the major HCV glycoprotein E2. No neutralization escape was yet observed for these antibodies. We report here the crystal structures of their Fab fragments in complex with a synthetic peptide comprising aa434-446. The structures show that the peptide adopts an α-helical conformation with the main contact residues F(442) and Y(443) forming a hydrophobic protrusion. The peptide retained its conformation in both complexes, independently of crystal packing, indicating that it reflects a surface feature of the folded glycoprotein that is exposed similarly on the virion. The same residues of E2 are also involved in interaction with CD81, suggesting that the cellular receptor binds the same surface feature and potential escape mutants critically compromise receptor binding. In summary, our results identify a critical structural motif at the E2 surface, which is essential for virus propagation and therefore represents an ideal candidate for structure-based immunogen design for vaccine development.

    View details for DOI 10.1371/journal.ppat.1003364

    View details for PubMedID 23696737

    View details for PubMedCentralID PMC3656090

  • Contrasting Roles of Mitogen-Activated Protein Kinases in Cellular Entry and Replication of Hepatitis C Virus: MKNK1 Facilitates Cell Entry JOURNAL OF VIROLOGY Kim, S., Ishida, H., Yamane, D., Yi, M., Swinney, D. C., Foung, S., Lemon, S. M. 2013; 87 (8): 4214-4224

    Abstract

    The human kinome comprises over 800 individual kinases. These contribute in multiple ways to regulation of cellular metabolism and may have direct and indirect effects on virus replication. Kinases are tempting therapeutic targets for drug development, but achieving sufficient specificity is often a challenge for chemical inhibitors. While using inhibitors to assess whether c-Jun N-terminal (JNK) kinases regulate hepatitis C virus (HCV) replication, we encountered unexpected off-target effects that led us to discover a role for a mitogen-activated protein kinase (MAPK)-related kinase, MAPK interacting serine/threonine kinase 1 (MKNK1), in viral entry. Two JNK inhibitors, AS601245 and SP600125, as well as RNA interference (RNAi)-mediated knockdown of JNK1 and JNK2, enhanced replication of HCV replicon RNAs as well as infectious genome-length RNA transfected into Huh-7 cells. JNK knockdown also enhanced replication following infection with cell-free virus, suggesting that JNK actively restricts HCV replication. Despite this, AS601245 and SP600125 both inhibited viral entry. Screening of a panel of inhibitors targeting kinases that may be modulated by off-target effects of AS601245 and SP600125 led us to identify MKNK1 as a host factor involved in HCV entry. Chemical inhibition or siRNA knockdown of MKNK1 significantly impaired entry of genotype 1a HCV and HCV-pseudotyped lentiviral particles (HCVpp) in Huh-7 cells but had only minimal impact on viral RNA replication or cell proliferation and viability. We propose a model by which MKNK1 acts to facilitate viral entry downstream of the epidermal growth factor receptor (EGFR) and extracellular signal-regulated kinase (ERK), both of which have been implicated in the entry process.

    View details for DOI 10.1128/JVI.00954-12

    View details for Web of Science ID 000316671000008

    View details for PubMedID 23365451

    View details for PubMedCentralID PMC3624358

  • Characterization of Hepatitis C Virus Recombinants with Chimeric E1/E2 Envelope Proteins and Identification of Single Amino Acids in the E2 Stem Region Important for Entry JOURNAL OF VIROLOGY Carlsen, T. H., Scheel, T. K., Ramirez, S., Foung, S. K., Bukh, J. 2013; 87 (3): 1385-1399

    Abstract

    The hepatitis C virus (HCV) envelope proteins E1 and E2 play a key role in host cell entry and represent important targets for vaccine and drug development. Here, we characterized HCV recombinants with chimeric E1/E2 complexes in vitro. Using genotype 1a/2a JFH1-based recombinants expressing 1a core-NS2, we exchanged E2 with functional isolate sequences of genotypes 1a (alternative isolate), 1b, and 2a. While the 1a-E2 exchange did not impact virus viability, the 2a-E2 recombinant was nonviable. After E2 exchange from three 1b isolates, long delays were observed before spread of infection. For recovered 1b-E2 recombinants, single E2 stem region amino acid changes were identified at residues 706, 707, and 710. In reverse genetic studies, these mutations increased infectivity titers by ~100-fold, apparently without influencing particle stability or cell binding although introducing slight decrease in particle density. In addition, the 1b-E2 exchange led to a decrease in secreted core protein of 25 to 50%, which was further reduced by the E2 stem region mutations. These findings indicated that compensatory mutations permitted robust infectious virus production, without increasing assembly/release. Studies of E1/E2 heterodimerization showed no differences in intracellular E1/E2 interaction for chimeric constructs with or without E2 stem region mutations. Interestingly, the E2 stem region mutations allowed efficient entry, which was verified in 1a-E1/1b-E2 HCV pseudoparticle assays. A CD81 inhibition assay indicated that the mutations influenced a late step of the HCV entry pathway. Overall, this study identified specific amino acids in the E2 stem region of importance for HCV entry and for production of infectious virus particles.

    View details for DOI 10.1128/JVI.00684-12

    View details for Web of Science ID 000313558100009

    View details for PubMedID 23152512

    View details for PubMedCentralID PMC3554168

  • Cooperativity in Virus Neutralization by Human Monoclonal Antibodies to Two Adjacent Regions Located at the Amino Terminus of Hepatitis C Virus E2 Glycoprotein JOURNAL OF VIROLOGY Keck, Z., Wang, W., Wang, Y., Lau, P., Carlsen, T. H., Prentoe, J., Xia, J., Patel, A. H., Bukh, J., Foung, S. K. 2013; 87 (1): 37-51

    Abstract

    A challenge for hepatitis C virus (HCV) vaccine development is defining conserved epitopes that induce protective antibodies against this highly diverse virus. An envelope glycoprotein (E2) segment located at amino acids (aa) 412 to 423 contains highly conserved neutralizing epitopes. While polyclonal antibodies to aa 412 to 423 from HCV-infected individuals confirmed broad neutralization, conflicting findings have been reported on polyclonal antibodies to an adjacent region, aa 434 to 446, that may or may not interfere with neutralization by antibodies to aa 412 to 423. To define the interplay between these antibodies, we isolated human monoclonal antibodies (HMAbs) to aa 412 to 423, designated HC33-related HMAbs (HC33 HMAbs), and characterized their interactions with other HMAbs to aa 434 to 446. A subset of the HC33 HMAbs neutralized genotype 1 to 6 infectious cell culture-derived HCV virions (HCVcc) with various activities. Although nonneutralizing HC33 HMAbs were isolated, they had lower binding affinities than neutralizing HC33 HMAbs. These antibodies could be converted to neutralizing antibodies by affinity maturation. Unidirectional competition for binding to E2 was observed between HC33 HMAbs and HMAbs to aa 434 to 446. When HMAbs to aa 434 to 446, which mediated neutralization, were combined with neutralizing HC33 HMAbs, biphasic patterns in neutralization were observed. A modest degree of antagonism was observed at lower concentrations, and a modest degree of synergism was observed at higher concentrations. However, the overall effect was additive neutralization. A similar pattern was observed when these antibodies were combined to block E2 binding to the HCV coreceptor, CD81. These findings demonstrate that both of these E2 regions participate in epitopes mediating virus neutralization and that the antibodies to aa 412 to 423 and aa 434 to 446 do not hinder their respective virus-neutralizing activities.

    View details for DOI 10.1128/JVI.01941-12

    View details for Web of Science ID 000312455500004

    View details for PubMedID 23097455

    View details for PubMedCentralID PMC3536422

  • Transient Activation of the PI3K-AKT Pathway by Hepatitis C Virus to Enhance Viral Entry JOURNAL OF BIOLOGICAL CHEMISTRY Liu, Z., Tian, Y., Machida, K., Lai, M. M., Luo, G., Foung, S. K., Ou, J. J. 2012; 287 (50): 41922-41930

    Abstract

    The PI3K-AKT signaling pathway plays an important role in cell growth and metabolism. Here we report that hepatitis C virus (HCV) transiently activates the PI3K-AKT pathway. This activation was observed as early as 15 min postinfection, peaked by 30 min, and became undetectable at 24 h postinfection. The activation of AKT could also be mediated by UV-inactivated HCV, HCV pseudoparticle, and the ectodomain of the HCV E2 envelope protein. Because antibodies directed against CD81 and claudin-1, but not antibodies directed against scavenger receptor class B type I or occludin, could also activate AKT, the interaction between HCV E2 and its two co-receptors CD81 and claudin-1 probably triggered the activation of AKT. This activation of AKT by HCV was important for HCV infectivity, because the silencing of AKT by siRNA or the treatment of cells with its inhibitors or with the inhibitor of its upstream regulator PI3K significantly inhibited HCV infection, whereas the expression of constitutively active AKT enhanced HCV infection. The PI3K-AKT pathway is probably involved in HCV entry, because the inhibition of this pathway could inhibit the entry of HCV pseudoparticle but not the VSV pseudoparticle into cells. Furthermore, the treatment of cells with the AKT inhibitor AKT-V prior to HCV infection inhibited HCV infection, whereas the treatment after HCV infection had no obvious effect. Taken together, our studies indicated that HCV transiently activates the PI3K-AKT pathway to facilitate its entry. These results provide important information for understanding HCV replication and pathogenesis and raised the possibility of targeting this cellular pathway to treat HCV patients.

    View details for DOI 10.1074/jbc.M112.414789

    View details for Web of Science ID 000312103000032

    View details for PubMedID 23095753

    View details for PubMedCentralID PMC3516739

  • Toward a Hepatitis C Virus Vaccine: the Structural Basis of Hepatitis C Virus Neutralization by AP33, a Broadly Neutralizing Antibody JOURNAL OF VIROLOGY Potter, J. A., Owsianka, A. M., Jeffery, N., Matthews, D. J., Keck, Z., Lau, P., Foung, S. K., Taylor, G. L., Patel, A. H. 2012; 86 (23): 12923-12932

    Abstract

    The E2 envelope glycoprotein of hepatitis C virus (HCV) binds to the host entry factor CD81 and is the principal target for neutralizing antibodies (NAbs). Most NAbs recognize hypervariable region 1 on E2, which undergoes frequent mutation, thereby allowing the virus to evade neutralization. Consequently, there is great interest in NAbs that target conserved epitopes. One such NAb is AP33, a mouse monoclonal antibody that recognizes a conserved, linear epitope on E2 and potently neutralizes a broad range of HCV genotypes. In this study, the X-ray structure of AP33 Fab in complex with an epitope peptide spanning residues 412 to 423 of HCV E2 was determined to 1.8 Å. In the complex, the peptide adopts a β-hairpin conformation and docks into a deep binding pocket on the antibody. The major determinants of antibody recognition are E2 residues L413, N415, G418, and W420. The structure is compared to the recently described HCV1 Fab in complex with the same epitope. Interestingly, the antigen-binding sites of HCV1 and AP33 are completely different, whereas the peptide conformation is very similar in the two structures. Mutagenesis of the peptide-binding residues on AP33 confirmed that these residues are also critical for AP33 recognition of whole E2, confirming that the peptide-bound structure truly represents AP33 interaction with the intact glycoprotein. The slightly conformation-sensitive character of the AP33-E2 interaction was explored by cross-competition analysis and alanine-scanning mutagenesis. The structural details of this neutralizing epitope provide a starting point for the design of an immunogen capable of eliciting AP33-like antibodies.

    View details for DOI 10.1128/JVI.02052-12

    View details for Web of Science ID 000310585300042

    View details for PubMedID 22993159

    View details for PubMedCentralID PMC3497650

  • Mutations That Alter Use of Hepatitis C Virus Cell Entry Factors Mediate Escape From Neutralizing Antibodies GASTROENTEROLOGY Fofana, I., Fafi-Kremer, S., Carolla, P., Fauvelle, C., Zahid, M. N., Turek, M., Heydmann, L., Cury, K., Hayer, J., Combet, C., Cosset, F., Pietschmann, T., Hiet, M., Bartenschlager, R., Habersetzer, F., Doffoel, M., Keck, Z., Foung, S. K., Zeisel, M. B., Stoll-Keller, F., Baumert, T. F. 2012; 143 (1): 223-U429

    Abstract

    The development of vaccines and other strategies to prevent hepatitis C virus (HCV) infection is limited by rapid viral evasion. HCV entry is the first step of infection; this process involves several viral and host factors and is targeted by host-neutralizing responses. Although the roles of host factors in HCV entry have been well characterized, their involvement in evasion of immune responses is poorly understood. We used acute infection of liver graft as a model to investigate the molecular mechanisms of viral evasion.We studied factors that contribute to evasion of host immune responses using patient-derived antibodies, HCV pseudoparticles, and cell culture-derived HCV that express viral envelopes from patients who have undergone liver transplantation. These viruses were used to infect hepatoma cell lines that express different levels of HCV entry factors.By using reverse genetic analyses, we identified altered use of host-cell entry factors as a mechanism by which HCV evades host immune responses. Mutations that alter use of the CD81 receptor also allowed the virus to escape neutralizing antibodies. Kinetic studies showed that these mutations affect virus-antibody interactions during postbinding steps of the HCV entry process. Functional studies with a large panel of patient-derived antibodies showed that this mechanism mediates viral escape, leading to persistent infection in general.We identified a mechanism by which HCV evades host immune responses, in which use of cell entry factors evolves with escape from neutralizing antibodies. These findings advance our understanding of the pathogenesis of HCV infection and might be used to develop antiviral strategies and vaccines.

    View details for DOI 10.1053/j.gastro.2012.04.006

    View details for Web of Science ID 000305781500044

    View details for PubMedID 22503792

  • Human Monoclonal Antibodies to a Novel Cluster of Conformational Epitopes on HCV E2 with Resistance to Neutralization Escape in a Genotype 2a Isolate PLOS PATHOGENS Keck, Z., Xia, J., Wang, Y., Wang, W., Krey, T., Prentoe, J., Carlsen, T., Li, A. Y., Patel, A. H., Lemon, S. M., Bukh, J., Rey, F. A., Foung, S. K. 2012; 8 (4)

    Abstract

    The majority of broadly neutralizing antibodies to hepatitis C virus (HCV) are against conformational epitopes on the E2 glycoprotein. Many of them recognize overlapping epitopes in a cluster, designated as antigenic domain B, that contains residues G530 and D535. To gain information on other regions that will be relevant for vaccine design, we employed yeast surface display of antibodies that bound to genotype 1a H77C E2 mutant proteins containing a substitution either at Y632A (to avoid selecting non-neutralizing antibodies) or D535A. A panel of nine human monoclonal antibodies (HMAbs) was isolated and designated as HC-84-related antibodies. Each HMAb neutralized cell culture infectious HCV (HCVcc) with genotypes 1-6 envelope proteins with varying profiles, and each inhibited E2 binding to the viral receptor CD81. Five of these antibodies neutralized representative genotypes 1-6 HCVcc. Epitope mapping identified a cluster of overlapping epitopes that included nine contact residues in two E2 regions encompassing aa418-446 and aa611-616. Effect on virus entry was measured using H77C HCV retroviral pseudoparticles, HCVpp, bearing an alanine substitution at each of the contact residues. Seven of ten mutant HCVpp showed over 90% reduction compared to wild-type HCVpp and two others showed approximately 80% reduction. Interestingly, four of these antibodies bound to a linear E2 synthetic peptide encompassing aa434-446. This region on E2 has been proposed to elicit non-neutralizing antibodies in humans that interfere with neutralizing antibodies directed at an adjacent E2 region from aa410-425. The isolation of four HC-84 HMAbs binding to the peptide, aa434-446, proves that some antibodies to this region are to highly conserved epitopes mediating broad virus neutralization. Indeed, when HCVcc were passaged in the presence of each of these antibodies, virus escape was not observed. Thus, the cluster of HC-84 epitopes, designated as antigenic domain D, is relevant for vaccine design for this highly diverse virus.

    View details for DOI 10.1371/journal.ppat.1002653

    View details for Web of Science ID 000303444200043

    View details for PubMedID 22511875

    View details for PubMedCentralID PMC3325216

  • IMMUNE RESPONSES AGAINST FOUNDER HEPATITIS C VIRUSES IN ACUTE ASYMPTOMATIC SUBJECTS 47th Annual Meeting of the European-Association-for-the-Study-of-the-Liver (EASL) Luciani, F., Bull, R. A., Cameron, B., Gaudieri, S., Nguyen, N., Yuen, D., White, P. A., Purcell, D. F., Foung, S., Lloyd, A. R. ELSEVIER SCIENCE BV. 2012: S312–S312
  • Affinity Maturation to Improve Human Monoclonal Antibody Neutralization Potency and Breadth against Hepatitis C Virus JOURNAL OF BIOLOGICAL CHEMISTRY Wang, Y., Keck, Z., Saha, A., Xia, J., Conrad, F., Lou, J., Eckart, M., Marks, J. D., Foung, S. K. 2011; 286 (51): 44218-44233

    Abstract

    A potent neutralizing antibody to a conserved hepatitis C virus (HCV) epitope might overcome its extreme variability, allowing immunotherapy. The human monoclonal antibody HC-1 recognizes a conformational epitope on the HCV E2 glycoprotein. Previous studies showed that HC-1 neutralizes most HCV genotypes but has modest potency. To improve neutralization, we affinity-matured HC-1 by constructing a library of yeast-displayed HC-1 single chain Fv (scFv) mutants, using for selection an E2 antigen from one of the poorly neutralized HCVpp. We developed an approach by parallel mutagenesis of the heavy chain variable (VH) and κ-chain variable (Vk) genes separately, then combining the optimized VH and Vk mutants. This resulted in the generation of HC-1-related scFv variants exhibiting improved affinities. The best scFv variant had a 92-fold improved affinity. After conversion to IgG1, some of the antibodies exhibited a 30-fold improvement in neutralization activity. Both surface plasmon resonance and solution kinetic exclusion analysis showed that the increase in affinity was largely due to a lowering of the dissociation rate constant, Koff. Neutralization against a panel of HCV pseudoparticles and infectious 2a HCV virus improved with the affinity-matured IgG1 antibodies. Interestingly, some of these antibodies neutralized a viral isolate that was not neutralized by wild-type HC-1. Moreover, propagating 2a HCVcc under the selective pressure of WT HC-1 or affinity-matured HC-1 antibodies yielded no viral escape mutants and, with the affinity-matured IgG1, needed 100-fold less antibody to achieve complete virus elimination. Taken together, these findings suggest that affinity-matured HC-1 antibodies are excellent candidates for therapeutic development.

    View details for DOI 10.1074/jbc.M111.290783

    View details for Web of Science ID 000298402300062

    View details for PubMedID 22002064

    View details for PubMedCentralID PMC3243554

  • Neutralizing Antibody Response to Hepatitis C Virus VIRUSES-BASEL Wang, Y., Keck, Z., Foung, S. K. 2011; 3 (11): 2127-2145

    Abstract

    A critical first step in a "rational vaccine design" approach for hepatitis C virus (HCV) is to identify the most relevant mechanisms of immune protection. Emerging evidence provides support for a protective role of virus neutralizing antibodies, and the ability of the B cell response to modify the course of acute HCV infection. This has been made possible by the development of in vitro cell culture models, based on HCV retroviral pseudotype particles expressing E1E2 and infectious cell culture-derived HCV virions, and small animal models that are robust tools in studies of antibody-mediated virus neutralization. This review is focused on the immunogenic determinants on the E2 glycoprotein mediating virus neutralization and the pathways in which the virus is able to escape from immune containment. Encouraging findings from recent studies provide support for the existence of broadly neutralization antibodies that are not associated with virus escape. The identification of conserved epitopes mediating virus neutralization that are not associated with virus escape will facilitate the design of a vaccine immunogen capable of eliciting broadly neutralizing antibodies against this highly diverse virus.

    View details for DOI 10.3390/v3112127

    View details for Web of Science ID 000297699200005

    View details for PubMedID 22163337

    View details for PubMedCentralID PMC3230844

  • Mapping a Region of Hepatitis C Virus E2 That Is Responsible for Escape from Neutralizing Antibodies and a Core CD81-Binding Region That Does Not Tolerate Neutralization Escape Mutations JOURNAL OF VIROLOGY Keck, Z., Saha, A., Xia, J., Wang, Y., Lau, P., Krey, T., Rey, F. A., Foung, S. K. 2011; 85 (20): 10451-10463

    Abstract

    Understanding the interaction between broadly neutralizing antibodies and their epitopes provides a basis for the rational design of a preventive hepatitis C virus (HCV) vaccine. CBH-2, HC-11, and HC-1 are representatives of antibodies to overlapping epitopes on E2 that mediate neutralization by blocking virus binding to CD81. To obtain insights into escape mechanisms, infectious cell culture virus, 2a HCVcc, was propagated under increasing concentrations of a neutralizing antibody to isolate escape mutants. Three escape patterns were observed with these antibodies. First, CBH-2 escape mutants that contained mutations at D431G or A439E, which did not compromise viral fitness, were isolated. Second, under the selective pressure of HC-11, escape mutations progressed from a single L438F substitution at a low antibody concentration to double substitutions, L438F and N434D or L438F and T435A, at higher antibody concentrations. Escape from HC-11 was associated with a loss of viral fitness. An HCV pseudoparticle (HCVpp) containing the L438F mutation bound to CD81 half as efficiently as did wild-type (wt) HCVpp. Third, for HC-1, the antibody at a critical concentration completely suppressed viral replication and generated no escape mutants. Epitope mapping revealed contact residues for CBH-2 and HC-11 in two regions of the E2 glycoprotein, amino acids (aa) 425 to 443 and aa 529 to 535. Interestingly, contact residues for HC-1 were identified only in the region encompassing aa 529 to 535 and not in aa 425 to 443. Taken together, these findings point to a region of variability, aa 425 to 443, that is responsible primarily for viral escape from neutralization, with or without compromising viral fitness. Moreover, the region aa 529 to 535 is a core CD81 binding region that does not tolerate neutralization escape mutations.

    View details for DOI 10.1128/JVI.05259-11

    View details for Web of Science ID 000296254100003

    View details for PubMedID 21813602

    View details for PubMedCentralID PMC3187491

  • Comprehensive linker-scanning mutagenesis of the hepatitis C virus E1 and E2 envelope glycoproteins reveals new structure-function relationships JOURNAL OF GENERAL VIROLOGY Rychlowska, M., Owsianka, A. M., Foung, S. K., Dubuisson, J., Bienkowska-Szewczyk, K., Patel, A. H. 2011; 92: 2249-2261

    Abstract

    Despite extensive research, many details about the structure and functions of hepatitis C virus (HCV) glycoproteins E1 and E2 are not fully understood, and their crystal structure remains to be determined. We applied linker-scanning mutagenesis to generate a panel of 34 mutants, each containing an insertion of 5 aa at a random position within the E1E2 sequence. The mutated glycoproteins were analysed by using a range of assays to identify regions critical for maintaining protein conformation, E1E2 complex assembly, CD81 receptor binding, membrane fusion and infectivity. The results, while supporting previously published data, provide several interesting new findings. Firstly, insertion at amino acid 587 or 596 reduced E1E2 heterodimerization without affecting reactivity with some conformation-sensitive mAbs or with CD81, thus implicating these residues in glycoprotein assembly. Secondly, insertions within a conserved region of E2, between amino acid residues 611 and 631, severely disrupted protein conformation and abrogated binding of all conformation-sensitive antibodies, suggesting that the structural integrity of this region is critical for the correct folding of E2. Thirdly, an insertion at Leu-682 specifically affected membrane fusion, providing direct evidence that the membrane-proximal 'stem' of E2 is involved in the fusion mechanism. Overall, our results show that the HCV glycoproteins generally do not tolerate insertions and that there are a very limited number of sites that can be changed without dramatic loss of function. Nevertheless, we identified two E2 insertion mutants, at amino acid residues 408 and 577, that were infectious in the murine leukemia virus-based HCV pseudoparticle system.

    View details for DOI 10.1099/vir.0.034314-0

    View details for Web of Science ID 000295856000003

    View details for PubMedID 21697343

    View details for PubMedCentralID PMC3347801

  • The Hepatitis C Virus E1 Glycoprotein Undergoes Productive Folding but Accelerated Degradation When Expressed as an Individual Subunit in CHO Cells PLOS ONE Botti, V., Bianchi, A., Foung, S. K., Merola, M. 2011; 6 (8)

    Abstract

    Hepatitis C Virus E1E2 heterodimers are components of the viral spike. Although there is a general agreement on the necessity of the co-expression of both E1 and E2 on a single coding unit for their productive folding and assembly, in a previous study using an in vitro system we obtained strong indications that E1 can achieve folding in absence of E2. Here, we have studied the folding pathway of unescorted E1 from stably expressing CHO cells, compared to the folding observed in presence of the E2 protein. A DTT-resistant conformation is achieved by E1 in both situations, consistent with the presence of an E2-independent oxidative pathway. However, while the E1E2 heterodimer is stable inside cells, E1 expressed alone is degraded within a few hours. On the other hand, the oxidation and stability of individually expressed E2 subunits is dependent on E1 co-expression. These data are consistent with E1 and E2 assisting each other for correct folding via different mechanisms: E2 assists E1 by stabilizing a semi-native conformation meanwhile E1 drives E2 towards a productive folding pathway.

    View details for DOI 10.1371/journal.pone.0023838

    View details for Web of Science ID 000294121300100

    View details for PubMedID 21858229

    View details for PubMedCentralID PMC3157478

  • CELL ENTRY FACTOR USAGE AND VIRAL EVASION IN HEPATITIS C VIRUS INFECTION IN VIVO Carolla, P., Fofana, I., Fafi-Kremer, S., Zahid, M. N., Cury, K., Turek, M., Bastien-Valle, M., Cosset, F., Pietschmann, T., Hayer, J., Combet, C., Habersetzer, F., Doffoeel, M., Keck, Z., Foung, S. H., Zeisel, M. B., Stoll-Keller, F., Baumert, T. F. ELSEVIER SCIENCE BV. 2011: S315
  • The GB viruses: a review and proposed classification of GBV-A, GBV-C (HGV), and GBV-D in genus Pegivirus within the family Flaviviridae JOURNAL OF GENERAL VIROLOGY Stapleton, J. T., Foung, S., Muerhoff, A. S., Bukh, J., Simmonds, P. 2011; 92: 233-246

    Abstract

    In 1967, it was reported that experimental inoculation of serum from a surgeon (G.B.) with acute hepatitis into tamarins resulted in hepatitis. In 1995, two new members of the family Flaviviridae, named GBV-A and GBV-B, were identified in tamarins that developed hepatitis following inoculation with the 11th GB passage. Neither virus infects humans, and a number of GBV-A variants were identified in wild New World monkeys that were captured. Subsequently, a related human virus was identified [named GBV-C or hepatitis G virus (HGV)], and recently a more distantly related virus (named GBV-D) was discovered in bats. Only GBV-B, a second species within the genus Hepacivirus (type species hepatitis C virus), has been shown to cause hepatitis; it causes acute hepatitis in experimentally infected tamarins. The other GB viruses have however not been assigned to a genus within the family Flaviviridae. Based on phylogenetic relationships, genome organization and pathogenic features of the GB viruses, we propose to classify GBV-A-like viruses, GBV-C and GBV-D as members of a fourth genus in the family Flaviviridae, named Pegivirus (pe, persistent; g, GB or G). We also propose renaming 'GB' viruses within the tentative genus Pegivirus to reflect their host origin.

    View details for DOI 10.1099/vir.0.027490-0

    View details for Web of Science ID 000287638800001

    View details for PubMedID 21084497

    View details for PubMedCentralID PMC3081076

  • Hepatitis C virus e2 protein ectodomain is essential for assembly of infectious virions. International journal of hepatology Bianchi, A., Crotta, S., Brazzoli, M., Foung, S. K., Merola, M. 2011; 2011: 968161-?

    Abstract

    The Hepatitis C virus E1 and E2 envelope proteins are the major players in all events required for virus entry into target cells. In addition, the recently developed HCV cell culture system has indicated that E1E2 heterodimer formation is a prerequisite for viral particle production. In this paper, we explored a new genetic approach to construct intergenotypic 2a/1b chimeras, maintaining the structural region of the infectious strain JFH1 and substituting the soluble portion of E1 and/or E2 proteins. This strategy provides useful information on the role of the surface-exposed domain of the envelope proteins in virus morphogenesis and allows comparative analysis of different HCV genotypes. We found that substituting the E2 protein ectodomain region abolishes the production of chimeric infectious particles. Our data indicate that the soluble part of the E2 protein is involved in a genotype-specific interplay with remaining viral proteins that affect the HCV assembly process.

    View details for DOI 10.4061/2011/968161

    View details for PubMedID 22007314

    View details for PubMedCentralID PMC3172978

  • IDENTIFICATION OF RESIDUES IN HCV E2 GLYCOPROTEIN THAT AFFECT NEUTRALIZATION BY HUMAN ANTIBODIES IN SERA OF INFECTED PATIENTS-IMPLICATIONS FOR ANTI-HCV VACCINE DEVELOPMENT 61st Annual Meeting of the American-Association-for-the-Study-of-Liver-Diseases Gal-Tanamy, M., Zemel, R., Yi, M., Foung, S., Lemon, S. M., Tur-Kaspa, R. WILEY-BLACKWELL. 2010: 820A–820A
  • MOLECULAR MECHANISMS OF VIRAL EVASION IN ACUTE HEPATITIS C VIRUS LIVER GRAFT INFECTION Carolla, P., Fofana, I., Fafi-Kremer, S., Cury, K., Zahid, M., Turek, M., Bastien-Valle, M., Grunert, F., Cosset, F., Pietschmann, T., Habersetzer, F. T., Wolf, P., Keck, Z., Foung, S., Zeisel, M. B., Stoll-Keller, F., Baumert, T. F. WILEY-BLACKWELL. 2010: 739A
  • Hepatitis C Virus Hypervariable Region 1 Modulates Receptor Interactions, Conceals the CD81 Binding Site, and Protects Conserved Neutralizing Epitopes JOURNAL OF VIROLOGY Bankwitz, D., Steinmann, E., Bitzegeio, J., Ciesek, S., Friesland, M., Herrmann, E., Zeisel, M. B., Baumert, T. F., Keck, Z., Foung, S. K., Pecheur, E., Pietschmann, T. 2010; 84 (11): 5751-5763

    Abstract

    The variability of the hepatitis C virus (HCV), which likely contributes to immune escape, is most pronounced in hypervariable region 1 (HVR1) of viral envelope protein 2. This domain is the target for neutralizing antibodies, and its deletion attenuates replication in vivo. Here we characterized the relevance of HVR1 for virus replication in vitro using cell culture-derived HCV. We show that HVR1 is dispensable for RNA replication. However, viruses lacking HVR1 (Delta HVR1) are less infectious, and separation by density gradients revealed that the population of Delta HVR1 virions comprises fewer particles with low density. Strikingly, Delta HVR1 particles with intermediate density (1.12 g/ml) are as infectious as wild-type virions, while those with low density (1.02 to 1.08 g/ml) are poorly infectious, despite quantities of RNA and core similar to those in wild-type particles. Moreover, Delta HVR1 particles exhibited impaired fusion, a defect that was partially restored by an E1 mutation (I347L), which also rescues infectivity and which was selected during long-term culture. Finally, Delta HVR1 particles were no longer neutralized by SR-B1-specific immunoglobulins but were more prone to neutralization and precipitation by soluble CD81, E2-specific monoclonal antibodies, and patient sera. These results suggest that HVR1 influences the biophysical properties of released viruses and that this domain is particularly important for infectivity of low-density particles. Moreover, they indicate that HVR1 obstructs the viral CD81 binding site and conserved neutralizing epitopes. These functions likely optimize virus replication, facilitate immune escape, and thus foster establishment and maintenance of a chronic infection.

    View details for DOI 10.1128/JVI.02200-09

    View details for Web of Science ID 000277386700029

    View details for PubMedID 20357091

    View details for PubMedCentralID PMC2876602

  • Mutations within a Conserved Region of the Hepatitis C Virus E2 Glycoprotein That Influence Virus-Receptor Interactions and Sensitivity to Neutralizing Antibodies JOURNAL OF VIROLOGY Dhillon, S., Witteveldt, J., Gatherer, D., Owsianka, A. M., Zeisel, M. B., Zahid, M. N., Rychlowska, M., Foung, S. K., Baumert, T. F., Angus, A. G., Patel, A. H. 2010; 84 (11): 5494-5507

    Abstract

    Cell culture-adaptive mutations within the hepatitis C virus (HCV) E2 glycoprotein have been widely reported. We identify here a single mutation (N415D) in E2 that arose during long-term passaging of HCV strain JFH1-infected cells. This mutation was located within E2 residues 412 to 423, a highly conserved region that is recognized by several broadly neutralizing antibodies, including the mouse monoclonal antibody (MAb) AP33. Introduction of N415D into the wild-type (WT) JFH1 genome increased the affinity of E2 to the CD81 receptor and made the virus less sensitive to neutralization by an antiserum to another essential entry factor, SR-BI. Unlike JFH1(WT), the JFH1(N415D) was not neutralized by AP33. In contrast, it was highly sensitive to neutralization by patient-derived antibodies, suggesting an increased availability of other neutralizing epitopes on the virus particle. We included in this analysis viruses carrying four other single mutations located within this conserved E2 region: T416A, N417S, and I422L were cell culture-adaptive mutations reported previously, while G418D was generated here by growing JFH1(WT) under MAb AP33 selective pressure. MAb AP33 neutralized JFH1(T416A) and JFH1(I422L) more efficiently than the WT virus, while neutralization of JFH1(N417S) and JFH1(G418D) was abrogated. The properties of all of these viruses in terms of receptor reactivity and neutralization by human antibodies were similar to JFH1(N415D), highlighting the importance of the E2 412-423 region in virus entry.

    View details for DOI 10.1128/JVI.02153-09

    View details for Web of Science ID 000277386700005

    View details for PubMedID 20237087

    View details for PubMedCentralID PMC2876616

  • TWO MUTATIONS IN HEPATITIS C VIRUS ENVELOPE GLYCOPROTEIN DOMAIN E2(424-482) MEDIATE ENHANCED INFECTIVITY OF A VIRAL VARIANT SELECTED DURING RE-INFECTION OF THE LIVER GRAFT Carolla, P., Fofana, I., Fafi-Kremer, S., Soulier, E., Bastien-Valle, M., Cosset, F., Foung, S., Doffoel, M., Wolf, P., Stoll-Keller, F., Baumert, T. F. JOHN WILEY & SONS INC. 2009: 544A
  • Antigen-specific Proteolysis by Hybrid Antibodies Containing Promiscuous Proteolytic Light Chains Paired with an Antigen-binding Heavy Chain JOURNAL OF BIOLOGICAL CHEMISTRY Sapparapu, G., Planque, S. A., Nishiyama, Y., Foung, S. K., Paul, S. 2009; 284 (36): 24622-24633

    Abstract

    The antigen recognition site of antibodies consists of the heavy and light chain variable domains (V(L) and V(H) domains). V(L) domains catalyze peptide bond hydrolysis independent of V(H) domains (Mei, S., Mody, B., Eklund, S. H., and Paul, S. (1991) J. Biol. Chem. 266, 15571-15574). V(H) domains bind antigens noncovalently independent of V(L) domains (Ward, E. S., Güssow, D., Griffiths, A. D., Jones, P. T., and Winter, G. (1989) Nature 341, 544-546). We describe specific hydrolysis of fusion proteins of the hepatitis C virus E2 protein with glutathione S-transferase (GST-E2) or FLAG peptide (FLAG-E2) by antibodies containing the V(H) domain of an anti-E2 IgG paired with promiscuously catalytic V(L) domains. The hybrid IgG hydrolyzed the E2 fusion proteins more rapidly than the unpaired light chain. An active site-directed inhibitor of serine proteases inhibited the proteolytic activity of the hybrid IgG, indicating a serine protease mechanism. The hybrid IgG displayed noncovalent E2 binding in enzyme-linked immunosorbent assay tests. Immunoblotting studies suggested hydrolysis of FLAG-E2 at a bond within E2 located approximately 11 kDa from the N terminus. GST-E2 was hydrolyzed by the hybrid IgG at bonds in the GST tag. The differing cleavage pattern of FLAG-E2 and GST-E2 can be explained by the split-site model of catalysis, in which conformational differences in the E2 fusion protein substrates position alternate peptide bonds in register with the antibody catalytic subsite despite a common noncovalent binding mechanism. These studies provide proof-of-principle that the catalytic activity of a light chain can be rendered antigen-specific by pairing with a noncovalently binding heavy chain subunit.

    View details for DOI 10.1074/jbc.M109.011858

    View details for Web of Science ID 000269380200071

    View details for PubMedID 19542217

    View details for PubMedCentralID PMC2782051

  • CD81 is dispensable for hepatitis C virus cell-to-cell transmission in hepatoma cells JOURNAL OF GENERAL VIROLOGY Witteveldt, J., Evans, M. J., Bitzegeio, J., Koutsoudakis, G., Owsianka, A. M., Angus, A. G., Keck, Z., Foung, S. K., Pietschmann, T., Rice, C. M., Patel, A. H. 2009; 90: 48-58

    Abstract

    Hepatitis C virus (HCV) infects cells by the direct uptake of cell-free virus following virus engagement with specific cell receptors such as CD81. Recent data have shown that HCV is also capable of direct cell-to-cell transmission, although the role of CD81 in this process is disputed. Here, we generated cell culture infectious strain JFH1 HCV (HCVcc) genomes carrying an alanine substitution of E2 residues W529 or D535 that are critical for binding to CD81 and infectivity. Co-cultivation of these cells with naïve cells expressing enhanced green fluorescent protein (EGFP) resulted in a small number of cells co-expressing both EGFP and HCV NS5A, showing that the HCVcc mutants are capable of cell-to-cell spread. In contrast, no cell-to-cell transmission from JFH1(DeltaE1E2)-transfected cells occurred, indicating that the HCV glycoproteins are essential for this process. The frequency of cell-to-cell transmission of JFH1(W529A) was unaffected by the presence of neutralizing antibodies that inhibit E2-CD81 interactions. By using cell lines that expressed little or no CD81 and that were refractive to infection with cell-free virus, we showed that the occurrence of viral cell-to-cell transmission is not influenced by the levels of CD81 on either donor or recipient cells. Thus, our results show that CD81 plays no role in the cell-to-cell spread of HCVcc and that this mode of transmission is shielded from neutralizing antibodies. These data suggest that therapeutic interventions targeting the entry of cell-free HCV may not be sufficient in controlling an ongoing chronic infection, but need to be complemented by additional strategies aimed at disrupting direct cell-to-cell viral transmission.

    View details for DOI 10.1099/vir.0.2008/006700-0

    View details for Web of Science ID 000262263000005

    View details for PubMedID 19088272

    View details for PubMedCentralID PMC2885024

  • Hepatitis C VACCINES FOR BIODEFENSE AND EMERGING AND NEGLECTED DISEASES Gal-Tanamy, M., Walker, C., Foung, S., Lemon, S. M., Barrett, A. D., Stanberry, L. R. 2009: 413–40
  • In vitro selection of a neutralization-resistant hepatitis C virus escape mutant PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Gal-Tanamy, M., Keck, Z., Yi, M., McKeating, J. A., Patel, A. H., Foung, S. K., Lemon, S. M. 2008; 105 (49): 19450-19455

    Abstract

    Effective immunization against hepatitis C virus (HCV) infections is likely to require the induction of both robust T and B cell immunity. Although neutralizing antibodies may play an important role in control of infection, there is little understanding of the structure of the HCV envelope glycoproteins and how they interact with such antibodies. An additional challenge for vaccine design is the genetic diversity of HCV and the rapid evolution of viral quasispecies that escape antibody-mediated neutralization. We used a cell culture-infectious, chimeric HCV with the structural proteins of genotype 1a virus to identify envelope residues contributing to the epitope recognized by a broadly neutralizing, murine monoclonal antibody, AP33. By repetitive rounds of neutralization followed by amplification, we selected a population of viral escape mutants that resist stringent neutralization with AP33 and no longer bind the antibody. Two amino acid substitutions, widely separated in the linear sequence of the E2 envelope protein (N415Y and E655G), were identified by sequencing of cloned cDNA and shown by reverse genetics analysis to contribute jointly to the AP33 resistance phenotype. The N415Y mutation substantially lowered virus fitness, most likely because of a defect in viral entry, but did not reduce binding of soluble CD81 to immobilized HCV-pseudotyped retrovirus particles. The in vitro selection of an HCV escape mutant recapitulates the ongoing evolution of antigenic variants that contributes to viral persistence in humans and reveals information concerning the conformational structure of the AP33 epitope, its role in viral replication, and constraints on its molecular evolution.

    View details for DOI 10.1073/pnas.0809879105

    View details for Web of Science ID 000261706600076

    View details for PubMedID 19052239

    View details for PubMedCentralID PMC2614781

  • Hepatitis C virus (HCV)-induced immunoglobulin hypermutation reduces the affinity and neutralizing activities of antibodies against HCV envelope protein JOURNAL OF VIROLOGY Machida, K., Kondo, Y., Huang, J. Y., Chen, Y., Cheng, K. T., Keck, Z., Foung, S., Dubuisson, J., Sung, V. M., Lai, M. M. 2008; 82 (13): 6711-6720

    Abstract

    Hepatitis C virus (HCV) often causes persistent infection despite the presence of neutralizing antibodies against the virus in the sera of hepatitis C patients. HCV infects both hepatocytes and B cells through the binding of its envelope glycoprotein E2 to CD81, the putative viral receptor. Previously, we have shown that E2-CD81 interaction induces hypermutation of heavy-chain immunoglobulin (V(H)) in B cells. We hypothesize that if HCV infects antibody-producing B cells, the resultant hypermutation of V(H) may lower the affinity and specificity of the HCV-specific antibodies, enabling HCV to escape from immune surveillance. To test this hypothesis, we infected human hybridoma clones producing either neutralizing or non-neutralizing anti-E2 or anti-E1 antibodies with a lymphotropic HCV (SB strain). All of the hybridoma clones, except for a neutralizing antibody-producing hybridoma, could be infected with HCV and support virus replication for at least 8 weeks after infection. The V(H) sequences in the infected hybridomas had a significantly higher mutation frequency than those in the uninfected hybridomas, with mutations concentrating in complementarity-determining region 3. These mutations lowered the antibody affinity against the targeting protein and also lowered the virus-neutralizing activity of anti-E2 antibodies. Furthermore, antibody-mediated complement-dependent cytotoxicity with the antibodies secreted from the HCV-infected hybridomas was impaired. These results suggest that HCV infection could cause some anti-HCV-antibody-producing hybridoma B cells to make less-protective antibodies.

    View details for DOI 10.1128/JVI.02582-07

    View details for Web of Science ID 000256947300058

    View details for PubMedID 18417597

    View details for PubMedCentralID PMC2447061

  • A point mutation leading to hepatitis C virus escape from neutralization by a monoclonal antibody to a conserved conformational epitope JOURNAL OF VIROLOGY Keck, Z., Olson, O., Gal-Tanamy, M., Xia, J., Patel, A. H., Dreux, M., Cosset, F., Lemon, S. M., Foung, S. K. 2008; 82 (12): 6067-6072

    Abstract

    A challenge in hepatitis C virus (HCV) vaccine development is defining conserved protective epitopes. A cluster of these epitopes comprises an immunodominant domain on the E2 glycoprotein, designated domain B. CBH-2 is a neutralizing human monoclonal antibody to a domain B epitope that is highly conserved. Alanine scanning demonstrated that the epitope involves residues G523, G530, and D535 that are also contact residues for E2 binding to CD81, a coreceptor required for virus entry into cells. However, another residue, located at position 431 and thus at a considerable distance in the linear sequence of E2, also contributes to the CBH-2 epitope. A single amino acid substitution at this residue results in escape from CBH-2-mediated neutralization in a genotype 1a virus. These results highlight the challenges inherent in developing HCV vaccines and show that an effective vaccine must induce antibodies to both conserved and more invariant epitopes to minimize virus escape.

    View details for DOI 10.1128/JVI.00252-08

    View details for Web of Science ID 000256453600041

    View details for PubMedID 18385242

    View details for PubMedCentralID PMC2395135

  • Definition of a conserved immunodominant domain on hepatitis C virus E2 glycoprotein by neutralizing human monoclonal antibodies JOURNAL OF VIROLOGY Keck, Z., Li, T., Xia, J., Gal-Tanamy, M., Olson, O., Li, S. H., Patel, A. H., Ball, J. K., Lemon, S. M., Foung, S. K. 2008; 82 (12): 6061-6066

    Abstract

    Development of a successful hepatitis C virus (HCV) vaccine requires the definition of neutralization epitopes that are conserved among different HCV genotypes. Five human monoclonal antibodies (HMAbs) are described that cross-compete with other antibodies to a cluster of overlapping epitopes, previously designated domain B. Each HMAb broadly neutralizes retroviral pseudotype particles expressing HCV E1 and E2 glycoproteins, as well as the infectious chimeric genotype 1a and genotype 2a viruses. Alanine substitutions of residues within a region of E2 involved in binding to CD81 showed that critical E2 contact residues involved in the binding of representative antibodies are identical to those involved in the binding of E2 to CD81.

    View details for DOI 10.1128/JVI.02475-07

    View details for Web of Science ID 000256453600040

    View details for PubMedID 18400849

    View details for PubMedCentralID PMC2395155

  • Antibody-dependent enhancement of hepatitis C virus infection JOURNAL OF VIROLOGY Meyer, K., Ait-Goughoulte, M., Keck, Z., Foung, S., Ray, R. 2008; 82 (5): 2140-2149

    Abstract

    Hepatitis C virus (HCV) often causes a persistent infection associated with hypergammaglobulinemia, high levels of antiviral antibody and circulating immune complexes, and immune complex disease. We previously reported that only a limited neutralizing activity to vesicular stomatitis virus or HCV pseudotype is generated in animals immunized with recombinant HCV envelope proteins and chronically infected HCV patient sera. Interestingly, when some of these neutralizing sera were diluted into a range of concentrations below those that reduced virus plaque number, an increase in pseudotype plaque formation was observed. Purified HCV E2-specific human monoclonal antibodies were used to further verify the specificity of this enhancement, and one- to twofold increases were apparent on permissive Huh-7 cells. The enhancement of HCV pseudotype titer could be inhibited by the addition of a Fc-specific anti-human immunoglobulin G Fab fragment to the virus-antibody mixture prior to infection. Treatment of cells with antibody to Fc receptor I (FcRI) or FcRII, but not FcRIII, also led to an inhibition of pseudotype titer enhancement in an additive manner. Human lymphoblastoid cell line (Raji), a poor host for HCV pseudotype infection, exhibited a four- to sixfold enhancement of pseudotype-mediated cell death upon incubation with antibody at nonneutralizing concentrations. A similar enhancement of cell culture-grown HCV infectivity by a human monoclonal antibody was also observed. Taken together, antibodies to viral epitopes enhancing HCV infection need to be taken into consideration for pathogenesis and in the development of an effective vaccine.

    View details for DOI 10.1128/JVI.01867-07

    View details for Web of Science ID 000253481000010

    View details for PubMedID 18094180

    View details for PubMedCentralID PMC2258956

  • Broadly neutralizing human monoclonal antibodies to the hepatitis C virus E2 glycoprotein JOURNAL OF GENERAL VIROLOGY Owsianka, A. M., Tarr, A. W., Keck, Z., Li, T., Witteveldt, J., Adair, R., Foung, S. K., Ball, J. K., Patel, A. H. 2008; 89: 653-659

    Abstract

    The humoral response to hepatitis C virus (HCV) may contribute to controlling infection. We previously isolated human monoclonal antibodies to conformational epitopes on the HCV E2 glycoprotein. Here, we report on their ability to inhibit infection by retroviral pseudoparticles incorporating a panel of full-length E1E2 clones representing the full spectrum of genotypes 1-6. We identified one antibody, CBH-5, that was capable of neutralizing every genotype tested. It also potently inhibited chimeric cell culture-infectious HCV, which had genotype 2b envelope proteins in a genotype 2a (JFH-1) background. Analysis using a panel of alanine-substitution mutants of HCV E2 revealed that the epitope of CBH-5 includes amino acid residues that are required for binding of E2 to CD81, a cellular receptor essential for virus entry. This suggests that CBH-5 inhibits HCV infection by competing directly with CD81 for a binding site on E2.

    View details for DOI 10.1099/vir.0.83386-0

    View details for Web of Science ID 000253998700005

    View details for PubMedID 18272755

    View details for PubMedCentralID PMC2885755

  • Structural elucidation of critical residues involved in binding of human monoclonal antibodies to hepatitis C virus E2 envelope glycoprotein BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS Iacob, R. E., Keck, Z., Olson, O., Foung, S. K., Tomer, K. B. 2008; 1784 (3): 530-542

    Abstract

    Human monoclonal antibodies derived from B cells of HCV-infected individuals provide information on the immune response to native HCV envelope proteins as they are recognized during infection. Monoclonal antibodies have been useful in the determination of the function and structure of specific immunogenic domains of proteins and should also be useful for the structure/function characterization of HCV E1 and E2 envelope glycoproteins. The HCV E2 envelope glycoprotein has at least three immunodistinctive conformation domains, designated A, B, and C. Conformational epitopes within domain B and C are neutralizing antibody targets on HCV pseudoparticles as well as from infectious cell culture virus. In this study, a combination of differential surface modification and mass spectrometric limited proteolysis followed by alanine mutagenesis was used to provide insight into potential conformational changes within the E2 protein upon antibody binding. The arginine guanidine groups in the E2 protein were modified with CHD in both the affinity bound and free states followed by mass spectrometric analysis, and the regions showing protection upon antibody binding were identified. This protection can arise by direct contact between the residues and the monoclonal antibody, or by antibody-induced conformational changes. Based on the mass spectrometric data, site-directed mutagenesis experiments were performed which clearly identified additional amino acid residues on E2 distant from the site of antibody interaction, whose change to alanine inhibited antibody recognition by inducing conformational changes within the E2 protein.

    View details for DOI 10.1016/j.bbapap.2007.12.015

    View details for Web of Science ID 000254780200012

    View details for PubMedID 18230369

    View details for PubMedCentralID PMC2277214

  • Therapeutic control of hepatitis C virus: The role of neutralizing monoclonal antibodies HUMAN ANTIBODY THERAPEUTICS FOR VIRAL DISEASE Keck, Z. Y., Machida, K., Lai, M. M., Ball, J. K., Patel, A. H., Foung, S. K. 2008; 317: 1-38

    Abstract

    Liver failure associated with hepatitis C virus (HCV) accounts for a substantial portion of liver transplantation. Although current therapy helps some patients with chronic HCV infection, adverse side effects and a high relapse rate are major problems. These problems are compounded in liver transplant recipients as reinfection occurs shortly after transplantation. One approach to control reinfection is the combined use of specific antivirals together with HCV-specific antibodies. Indeed, a number of human and mouse monoclonal antibodies to conformational and linear epitopes on HCV envelope proteins are potential candidates, since they have high virus neutralization potency and are directed to epitopes conserved across diverse HCV genotypes. However, a greater understanding of the factors contributing to virus escape and the role of lipoproteins in masking virion surface domains involved in virus entry will be required to help define those protective determinants most likely to give broad protection. An approach to immune escape is potentially caused by viral infection of immune cells leading to the induction hypermutation of the immunoglobulin gene in B cells. These effects may contribute to HCV persistence and B cell lymphoproliferative diseases.

    View details for Web of Science ID 000251960900001

    View details for PubMedID 17990788

  • The neutralizing activity of anti-hepatitis C virus antibodies is modulated by specific glycans on the E2 envelope protein JOURNAL OF VIROLOGY Helle, F., Goffard, A., Morel, V., Duverlie, G., McKeating, J., Keck, Z., Foung, S., Penin, F., Dubuisson, J., Voisset, C. 2007; 81 (15): 8101-8111

    Abstract

    Hepatitis C virus (HCV) envelope glycoproteins are highly glycosylated, with up to 5 and 11 N-linked glycans on E1 and E2, respectively. Most of the glycosylation sites on HCV envelope glycoproteins are conserved, and some of the glycans associated with these proteins have been shown to play an essential role in protein folding and HCV entry. Such a high level of glycosylation suggests that these glycans can limit the immunogenicity of HCV envelope proteins and restrict the binding of some antibodies to their epitopes. Here, we investigated whether these glycans can modulate the neutralizing activity of anti-HCV antibodies. HCV pseudoparticles (HCVpp) bearing wild-type glycoproteins or mutants at individual glycosylation sites were evaluated for their sensitivity to neutralization by antibodies from the sera of infected patients and anti-E2 monoclonal antibodies. While we did not find any evidence that N-linked glycans of E1 contribute to the masking of neutralizing epitopes, our data demonstrate that at least three glycans on E2 (denoted E2N1, E2N6, and E2N11) reduce the sensitivity of HCVpp to antibody neutralization. Importantly, these three glycans also reduced the access of CD81 to its E2 binding site, as shown by using a soluble form of the extracellular loop of CD81 in inhibition of entry. These data suggest that glycans E2N1, E2N6, and E2N11 are close to the binding site of CD81 and modulate both CD81 and neutralizing antibody binding to E2. In conclusion, this work indicates that HCV glycans contribute to the evasion of HCV from the humoral immune response.

    View details for DOI 10.1128/JVI.00127-07

    View details for Web of Science ID 000248027400029

    View details for PubMedID 17522218

    View details for PubMedCentralID PMC1951279

  • Directing the natural catalytic activity of antibodies to hepatitis C virus E2 protein Sapparapu, G., Planque, S. A., Wang, R., Nishiyama, Y., Keck, Z., Foung, S., Paul, S. AMER ASSOC IMMUNOLOGISTS. 2007
  • Immunogenic and functional organization of hepatitis C virus (HCV) glycoprotein E2 on infectious HCV virions JOURNAL OF VIROLOGY Keck, Z., Xia, J., Cai, Z., Li, T., Owsianka, A. M., Patel, A. H., Luo, G., Foung, S. K. 2007; 81 (2): 1043-1047

    Abstract

    Development of full-length hepatitis C virus (HCV) RNAs replicating efficiently and producing infectious cell-cultured virions, HCVcc, in hepatoma cells provides an opportunity to characterize immunogenic domains on viral envelope proteins involved in entry into target cells. A panel of immunoglobulin G1 human monoclonal antibodies (HMAbs) to three immunogenic conformational domains (designated A, B, and C) on HCV E2 glycoprotein showed that epitopes within two domains, B and C, mediated HCVcc neutralization, whereas HMAbs to domain A were all nonneutralizing. For the neutralizing antibodies to domain B (with some to conserved epitopes among different HCV genotypes), the inhibitory antibody concentration reducing HCVcc infection by 90%, IC90, ranged from 0.1 to 4 microg/ml. For some neutralizing HMAbs, HCVcc neutralization displayed a linear correlation with an antibody concentration between the IC50 and the IC90 while others showed a nonlinear correlation. The differences between IC50/IC90 ratios and earlier findings that neutralizing HMAbs block E2 interaction with CD81 suggest that these antibodies block different facets of virus-receptor interaction. Collectively, these findings support an immunogenic model of HCV E2 having three immunogenic domains with distinct structures and functions and provide added support for the idea that CD81 is required for virus entry.

    View details for DOI 10.1128/JVI.01710-06

    View details for Web of Science ID 000243350100061

    View details for PubMedID 17079294

    View details for PubMedCentralID PMC1797433

  • High density lipoprotein inhibits hepatitis C virus-neutralizing antibodies by stimulating cell entry via activation of the scavenger receptor BI JOURNAL OF BIOLOGICAL CHEMISTRY Dreux, M., Pietschmann, T., Granier, C., Voisset, C., Ricard-Blum, S., Mangeot, P., Keck, Z., Foung, S., Vu-Dac, N., Dubuisson, J., Bartenschlager, R., Lavillette, D., Cosset, F. 2006; 281 (27): 18285-18295

    Abstract

    Hepatitis C virus (HCV) exploits serum-dependent mechanisms that inhibit neutralizing antibodies. Here we demonstrate that high density lipoprotein (HDL) is a key serum factor that attenuates neutralization by monoclonal and HCV patient-derived polyclonal antibodies of infectious pseudo-particles (HCVpp) harboring authentic E1E2 glycoproteins and cell culture-grown genuine HCV (HCVcc). Over 10-fold higher antibody concentrations are required to neutralize either HCV-enveloped particles in the presence of HDL or human serum, and less than 3-5-fold reduction of infectious titers are obtained at saturating antibody concentrations, in contrast to complete inhibition in serum-free conditions. We show that HDL interaction with the scavenger receptor BI (SR-BI), a proposed cell entry co-factor of HCV and a receptor mediating lipid transfer with HDL, strongly reduces neutralization of HCVpp and HCVcc. We found that HDL activation of target cells strongly stimulates cell entry of viral particles by accelerating their endocytosis, thereby suppressing a 1-h time lag during which cell-bound virions are not internalized and can be targeted by antibodies. Compounds that inhibit lipid transfer functions of SR-BI fully restore neutralization by antibodies in human serum. We demonstrate that this functional HDL/SR-BI interaction only interferes with antibodies blocking HCV-E2 binding to CD81, a major HCV receptor, reflecting its prominent role during the cell entry process. Moreover, we identify monoclonal antibodies targeted to epitopes in the E1E2 complex that are not inhibited by HDL. Consistently, we show that antibodies targeted to HCV-E1 efficiently neutralize HCVpp and HCVcc in the presence of human serum.

    View details for DOI 10.1074/jbc.M602706200

    View details for Web of Science ID 000238687300005

    View details for PubMedID 16675450

  • HDL inhibits HCV neutralisation by CD81-NOB antibodies by stimulating cell entry through activation of the scavenger receptor Bl Dreux, M., Pietschmann, T., Granier, C., Voisset, C., Ricard-Blum, S., Mangeot, P., Keck, Z., Foung, S., Vu-Dac, N., Dubuisson, J., Bartenschlager, R., Lavillette, D., Cosset, F. ELSEVIER SCIENCE BV. 2006: S52–S53
  • HDL inhibits neutralisation by HCV antibodies via a ternary interaction with the scavenger receptor Bl Dreux, M., Pietschmann, T., Granier, C., Voisset, C., Ricard-Blum, S., Mangeot, P. E., Keck, Z., Foung, S., Vu-Dac, N., Dubuisson, J., Bartenschlager, R., Lavillette, D., Cosset, F. L. ELSEVIER SCIENCE BV. 2006: S42
  • Preclinical evaluation of two neutralizing human monoclonal antibodies against hepatitis C virus (HCV): A potential treatment to prevent HCV reinfection in liver transplant patients JOURNAL OF VIROLOGY Eren, R., Landstein, D., Terkieltaub, D., Nussbaum, O., Zauberman, A., Ben-Porath, J., Gopher, J., Buchnick, R., Kovjazin, R., Rosenthal-Galili, Z., Aviel, S., Ilan, E., Shoshany, Y., Neville, L., Waisman, T., Ben-Moshe, O., Kischitsky, A., Foung, S. K., Keck, Z. Y., Pappo, O., Eid, A., Jurim, O., Zamir, G., Galun, E., Dagan, S. 2006; 80 (6): 2654-2664

    Abstract

    Passive immunotherapy is potentially effective in preventing reinfection of liver grafts in hepatitis C virus (HCV)-associated liver transplant patients. A combination of monoclonal antibodies directed against different epitopes may be advantageous against a highly mutating virus such as HCV. Two human monoclonal antibodies (HumAbs) against the E2 envelope protein of HCV were developed and tested for the ability to neutralize the virus and prevent human liver infection. These antibodies, designated HCV-AB 68 and HCV-AB 65, recognize different conformational epitopes on E2. They were characterized in vitro biochemically and functionally. Both HumAbs are immunoglobulin G1 and have affinity constants to recombinant E2 constructs in the range of 10(-10) M. They are able to immunoprecipitate HCV particles from infected patients' sera from diverse genotypes and to stain HCV-infected human liver tissue. Both antibodies can fix complement and form immune complexes, but they do not activate complement-dependent or antibody-dependent cytotoxicity. Upon complement fixation, the monoclonal antibodies induce phagocytosis of the immune complexes by neutrophils, suggesting that the mechanism of viral clearance includes endocytosis. In vivo, in the HCV-Trimera model, both HumAbs were capable of inhibiting HCV infection of human liver fragments and of reducing the mean viral load in HCV-positive animals. The demonstrated neutralizing activities of HCV-AB 68 and HCV-AB 65 suggest that they have the potential to prevent reinfection in liver transplant patients and to serve as prophylactic treatment in postexposure events.

    View details for DOI 10.1128/JVI.80.6.2654-2664.2006

    View details for Web of Science ID 000236131400007

    View details for PubMedID 16501075

    View details for PubMedCentralID PMC1395448

  • Hepatitis C virus induces toll-like receptor 4 expression, leading to enhanced production of beta interferon and interleukin-6 JOURNAL OF VIROLOGY Machida, K., Cheng, K. T., Sung, V. M., Levine, A. M., Foung, S., Lai, M. M. 2006; 80 (2): 866-874

    Abstract

    Hepatitis C virus (HCV) induces inflammatory signals, leading to hepatitis, hepatocellular carcinomas, and lymphomas. The mechanism of HCV involvement in the host's innate immune responses has not been well characterized. In this study, we analyzed expression and regulation of the entire panel of toll-like receptors (TLRs) in human B cells following HCV infection in vitro. Among all of the TLRs (TLRs 1 to 10) examined, only TLR4 showed an altered expression (a three- to sevenfold up-regulation) after HCV infection. Peripheral blood mononuclear cells from HCV-infected individuals also showed a higher expression level of TLR4 compared with those of healthy individuals. HCV infection significantly increased beta interferon (IFN-beta) and interleukin-6 (IL-6) secretion from B cells, particularly after lipopolysaccharide stimulation. The increased IFN-beta and IL-6 production was mediated by TLR4 induction, since the introduction of the small interfering RNA against TLR4 specifically inhibited the HCV-induced cytokine production. Among all of the viral proteins, only NS5A caused TLR4 induction in hepatocytes and B cells. NS5A specifically activated the promoter of the TLR4 gene in both hepatocytes and B cells. In conclusion, HCV infection directly induces TLR4 expression and thereby activates B cells, which may contribute to the host's innate immune responses.

    View details for DOI 10.1128/JVI.80.2.866-874.2006

    View details for Web of Science ID 000234382900032

    View details for PubMedID 16378988

    View details for PubMedCentralID PMC1346849

  • Analysis of a highly flexible conformational immunogenic domain a in hepatitis C virus E2 JOURNAL OF VIROLOGY Keck, Z. Y., LI, T. K., Xia, J. M., Bartosch, B., Cosset, F. L., Dubuisson, J., Foung, S. K. 2005; 79 (21): 13199-13208

    Abstract

    Hepatitis C (HCV) E2 glycoprotein is involved in virus attachment and entry, and its structural organization is largely unknown. Characterization of a panel of human monoclonal antibodies (HMAbs) to HCV by competition studies has led to an immunogenic organization model of E2 with three domains designated A, B, and C and epitopes in each domain having similar structural and functional properties. Domain A contains nonneutralizing epitopes, and domains B and C contain neutralizing epitopes. The isolation and characterization of three new HMAbs within domain A for a total of six provide support for this model. All six domain A HMAbs do not neutralize HCV retroviral pseudotype particle (HCVpp) infection on Huh-7 cells, and all six HMAbs have similar binding affinity and maximum binding, B(max), a relative indicator of epitope density, as other neutralizing HMAbs, suggesting that neutralization is epitope specific and not by binding to any surface epitope. The dose-dependent neutralizing activity of CBH-7, an HMAb to a domain C epitope in spatial proximity to domain A, and of CBH-5, a domain B HMAb to a more distant epitope, were tested in the presence and absence of each domain A HMAb. No enhancement or reduction in CBH-7 or CBH-5 neutralizing activity was observed, indicating that the potential induction of nonneutralizing antibodies should not be a central issue for HCV vaccine design. To assess whether domain A is involved in the structural changes as part of a pH-dependent virus envelope fusion process, changes in antibody binding patterns to normal pH and acid pH-treated HCVpp were measured. Antibody binding affinity of HMAbs to HCVpp was not affected by low pH. However, the B(max) values for low-pH-treated HCVpp with antibodies to domain A increased 46%, for domain C (CBH-7) they increased 23%, and for domain B (CBH-5) there was a decrease of 12%. Collectively, the organization and function of HCV E2 antigenic domains are roughly analogous to the large envelope glycoprotein E organizational structure for other flaviviruses with three distinct structural and functional domains.

    View details for DOI 10.1128/JVI.79.21.13199-13208.2005

    View details for Web of Science ID 000232666300001

    View details for PubMedID 16227243

    View details for PubMedCentralID PMC1262592

  • Preclinical evaluation of two neutralizing human monoclonal antibodies against HCV: A potential treatment to prevent HCV re-infection in liver transplant patients Eren, R., Landstein, D., Kovjazin, R., Rosenthal-Galili, Z., Waisman, T., Aviel, S., Terkieltaub, D., Gopher, J., Ilan, E., Zauberman, A., Keck, Z. Y., Foung, S., Dagan, S. ELSEVIER SCIENCE BV. 2005: 204
  • Preclinical evaluation of two neutralizing human monoclonal antibodies against HCV: A potential treatment to prevent HCV re-infection in liver transplant patients Ilan, E., Eren, R., Landstein, D., Kovjazin, R., Galili, Z., Waisman, T., Aviel, S., Terkieltaub, D., Gopher, J., Zauberman, A., Keck, Z. Y., Foung, S., Dagan, S. ELSEVIER SCIENCE BV. 2005: A58
  • Folding and dimerization of hepatitis C virus E1 and E2 glycoproteins in stably transfected CHO cells VIROLOGY Brazzoli, M., HELENIUS, A., Foung, S. K., Houghton, M., Abrignani, S., Merola, M. 2005; 332 (1): 438-453

    Abstract

    The recombinant E1E2 heterodimer of the hepatitis C virus is a candidate for a subunit vaccine. Folding analysis of E1 and E2 glycoproteins, stably expressed in CHO cells, showed that E1 folding was faster and more efficient than E2. The oxidized DTT-resistant conformation of E1 was completed within 2 h post-synthesis, while E2 not only required up to 6 h but also generated non-native species. Calnexin was found to assist E1 folding, whereas no chaperone association was found with E2. The assembly of E1 and E2 was assessed by co-immunoprecipitation and sedimentation velocity analysis. We found that the formation of native E1E2 heterodimers paralleled E2 oxidation kinetics, suggesting that E2 completed its folding process after association with E1. Once formed, sedimentation of the native E1E2 heterodimers was consistent with the absence of additional associated factors. Taken together, our data strongly suggest that productive folding of the major HCV spike protein E2 is assisted by E1.

    View details for DOI 10.1016/j.virol.2004.11.034

    View details for Web of Science ID 000226688500041

    View details for PubMedID 15661174

  • Preclinical evaluation of two neutralizing human monoclonal antibodies against HCV: A potential treatment to prevent HCV reinfection in liver transplant patients Eren, R., Landstein, D., Kovjazin, R., Aviel, S., Terkieltaub, D., Buchnick, R., Gopher, J., Ilan, E., Zauberman, A., Keck, Z. Y., Foung, S., Galun, E., Dagan, S. JOHN WILEY & SONS INC. 2004: 281A
  • Antibody light chain-catalyzed hydrolysis of a hepatitis C virus peptide BIOORGANIC & MEDICINAL CHEMISTRY LETTERS Taguchi, H., Keck, Z. Y., Foung, S. K., Paul, S., Nishiyama, Y. 2004; 14 (17): 4529-4532

    Abstract

    A panel of human monoclonal and recombinant antibody light chains was screened for cleavage of the synthetic peptide corresponding to a neutralizing epitope of hepatitis C virus (residues 192-205 of envelope glycoprotein E1). One of the 39 light chains studied hydrolyzed the Val197-Ser198 bond of the peptide with Km and kcat values of 223 +/- 7 microM and 0.087 +/- 0.001 min(-1).

    View details for DOI 10.1016/j.bmcl.2004.06.044

    View details for Web of Science ID 000223382000032

    View details for PubMedID 15357986

  • Hepatitis C virus E2 has three immunogenic domains containing conformational epitopes with distinct properties and biological functions JOURNAL OF VIROLOGY Keck, Z. Y., Op de Beeck, A., Hadlock, K. G., Xia, J. M., LI, T. K., Dubuisson, J., Foung, S. K. 2004; 78 (17): 9224-9232

    Abstract

    Mechanisms of virion attachment, interaction with its receptor, and cell entry are poorly understood for hepatitis C virus (HCV) because of a lack of an efficient and reliable in vitro system for virus propagation. Infectious HCV retroviral pseudotype particles (HCVpp) were recently shown to express native E1E2 glycoproteins, as defined in part by HCV human monoclonal antibodies (HMAbs) to conformational epitopes on E2, and some of these antibodies block HCVpp infection (A. Op De Beeck, C. Voisset, B. Bartosch, Y. Ciczora, L. Cocquerel, Z. Y. Keck, S. Foung, F. L. Cosset, and J. Dubuisson, J. Virol. 78:2994-3002, 2004). Why some HMAbs are neutralizing and others are nonneutralizing is looked at in this report by a series of studies to determine the expression of their epitopes on E2 associated with HCVpp and the role of antibody binding affinity. Antibody cross-competition defined three E2 immunogenic domains with neutralizing HMAbs restricted to two domains that were also able to block E2 interaction with CD81, a putative receptor for HCV. HCVpp immunoprecipitation showed that neutralizing and nonneutralizing domains are expressed on E2 associated with HCVpp, and affinity studies found moderate-to-high-affinity antibodies in all domains. These findings support the perspective that HCV-specific epitopes are responsible for functional steps in virus infection, with specific antibodies blocking distinct steps of virus attachment and entry, rather than the perspective that virus neutralization correlates with increased antibody binding to any virion surface site, independent of the epitope recognized by the antibody. Segregation of virus neutralization and sensitivity to low pH to specific regions supports a model of HCV E2 immunogenic domains similar to the antigenic structural and functional domains of other flavivirus envelope E glycoproteins.

    View details for DOI 10.1128/JVI.78.17.9224-9232.2004

    View details for Web of Science ID 000223386600026

    View details for PubMedID 15308717

    View details for PubMedCentralID PMC506923

  • Human monoclonal antibody to hepatitis C virus El glycoprotein that blocks virus attachment and viral infectivity JOURNAL OF VIROLOGY Keck, Z. Y., Sung, V. M., Perkins, S., Rowe, J., Paul, S., Liang, T. J., Lai, M. M., Foung, S. K. 2004; 78 (13): 7257-7263

    Abstract

    Human antibodies elicited in response to hepatitis C virus (HCV) infection are anticipated to react with the native conformation of the viral envelope structure. Isolation of these antibodies as human monoclonal antibodies that block virus binding and entry will be useful in providing potential therapeutic reagents and for vaccine development. H-111, an antibody to HCV envelope 1 protein (E1) that maps to the YEVRNVSGVYH sequence and is located near the N terminus of E1 and is able to immunoprecipitate E1E2 heterodimers, is described. Binding of H-111 to HCV E1 genotypes 1a, 1b, 2b, and 3a indicates that the H-111 epitope is highly conserved. Sequence analysis of antibody V regions showed evidence of somatic and affinity maturation of H-111. Finally, H-111 blocks HCV-like particle binding to and HCV virion infection of target cells, suggesting the involvement of this epitope in virus binding and entry.

    View details for DOI 10.1128/JVI.78.13.7257-7263.2004

    View details for PubMedID 15194801

  • Incomplete humoral immunity against hepatitis C virus is linked with distinct recognition of putative multiple receptors by E2 envelope glycoprotein JOURNAL OF IMMUNOLOGY Heo, T. H., Chang, J. H., Lee, J. W., Foung, S. K., Dubuisson, J., Kang, C. Y. 2004; 173 (1): 446-455

    Abstract

    Little is known about the role of the humoral immune response to hepatitis C virus (HCV). This study provides molecular evidence for the mechanism by which neutralizing Abs from the sera of chronic HCV patients have lower inhibitory activities against the binding of HCV E2 envelope protein to human hepatoma cell lines than to a lymphoma cell line. E2 binds to several putative receptors, specifically human CD81; human scavenger receptor, class B, type 1; and heparan sulfate. We have shown that E2 binds to target cells via these receptors in a noncompetitive manner. Thus, incomplete inhibition of one of the receptors leads to only a partial E2 blockade and, possibly, evasion of the host immune response. We demonstrated that the difference in and reduction of inhibition was closely related to impaired blockade of E2 binding to scavenger receptor, class B, type 1, and heparan sulfate. We have also shown that soluble E2 protein binds to multiple soluble receptors via separate binding domains on E2, providing further evidence for the distinct recognition of multiple cellular receptors by E2. This report suggests a novel finding that biased humoral immune responses to HCV E2 might provide an alternative mechanism for viral escape without the involvement of mutation. Additionally, our data give crucial consideration to the development of HCV vaccines that stimulate protective humoral immune responses.

    View details for Web of Science ID 000222170900057

    View details for PubMedID 15210804

  • Characterization of functional hepatitis C virus envelope glycoproteins JOURNAL OF VIROLOGY De Beeck, A. O., Voisset, C., Bartosch, B., Ciczora, Y., Cocquerel, L., Keck, Z., Foung, S., Cosset, F. L., Dubuisson, J. 2004; 78 (6): 2994-3002

    Abstract

    Hepatitis C virus (HCV) encodes two envelope glycoproteins, E1 and E2, that assemble as a noncovalent heterodimer which is mainly retained in the endoplasmic reticulum. Because assembly into particles and secretion from the cell lead to structural changes in viral envelope proteins, characterization of the proteins associated with the virion is necessary in order to better understand how they mature to be functional in virus entry. There is currently no efficient and reliable cell culture system to amplify HCV, and the envelope glycoproteins associated with the virion have therefore not been characterized yet. Recently, infectious pseudotype particles that are assembled by displaying unmodified HCV envelope glycoproteins on retroviral core particles have been successfully generated. Because HCV pseudotype particles contain fully functional envelope glycoproteins, these envelope proteins, or at least a fraction of them, should be in a mature conformation similar to that on the native HCV particles. In this study, we used conformation-dependent monoclonal antibodies to characterize the envelope glycoproteins associated with HCV pseudotype particles. We showed that the functional unit is a noncovalent E1E2 heterodimer containing complex or hybrid type glycans. We did not observe any evidence of maturation by a cellular endoprotease during the transport of these envelope glycoproteins through the secretory pathway. These envelope glycoproteins were recognized by a panel of conformation-dependent monoclonal antibodies as well as by CD81, a molecule involved in HCV entry. The functional envelope glycoproteins associated with HCV pseudotype particles were also shown to be sensitive to low-pH treatment. Such conformational changes are likely necessary to initiate fusion.

    View details for DOI 10.1128/JVI.78.6.2994-3002.2004

    View details for Web of Science ID 000220043100034

    View details for PubMedID 14990718

    View details for PubMedCentralID PMC353750

  • DC-SIGN and L-SIGN are high affinity binding receptors for hepatitis C virus glycoprotein E2 JOURNAL OF BIOLOGICAL CHEMISTRY Lozach, P. Y., Lortat-Jacob, H., de Lavalette, A. D., Staropoli, I., Foung, S., Amara, A., Houles, C., Fieschi, F., Schwartz, O., Virelizier, J. L., Arenzana-Seisdedos, F., Altmeyer, R. 2003; 278 (22): 20358-20366

    Abstract

    The hepatitis C virus (HCV) genome codes for highly mannosylated envelope proteins, which are naturally retained in the endoplasmic reticulum. We found that the HCV envelope glycoprotein E2 binds the dendritic cell-specific intercellular adhesion molecule 3-grabbing nonintegrin (DC-SIGN) and the related liver endothelial cell lectin L-SIGN through high-mannose N-glycans. Competing ligands such as mannan and an antibody directed against the carbohydrate recognition domains (CRD) abrogated binding. While no E2 interaction with distant monomeric CRDs on biosensor chips could be detected, binding is observed if CRDs are closely seeded (Kd = 48 nm) and if the CRD is part of the oligomeric-soluble extracellular domain of DC-SIGN (Kd = 30 nm). The highest affinity is seen for plasma membrane-expressed DC-SIGN and L-SIGN (Kd = 3 and 6 nm, respectively). These results indicate that several high-mannose N-glycans in a structurally defined cluster on E2 bind to several subunits of the oligomeric lectin CRD. High affinity interaction of viral glycoproteins with oligomeric lectins might represent a strategy by which HCV targets to and concentrates in the liver and infects dendritic cells.

    View details for DOI 10.1074/jbc.M301284200

    View details for Web of Science ID 000183078000100

    View details for PubMedID 12609975

  • Recognition of native hepatitis C virus E1E2 heterodimers by a human monoclonal antibody JOURNAL OF VIROLOGY Cocquerel, L., Quinn, E. R., Flint, M., Hadlock, K. G., Foung, S. K., Levy, S. 2003; 77 (2): 1604-1609

    Abstract

    The majority of hepatitis C virus (HCV)-infected individuals progress from acute to chronic disease, despite the presence of a strong humoral immune response to the envelope glycoproteins E1 and E2. When expressed in mammalian cells, E1 and E2 form both noncovalently linked E1E2 heterodimers, believed to be properly folded, and disulfide-linked, high-molecular-weight aggregates that are misfolded. Previously, we identified 10 human monoclonal antibodies (HMAbs) that bind E2 glycoproteins from different genotypes. Here we demonstrate that one of these HMAbs, CBH-2, is unique in its ability to distinguish between properly folded and misfolded envelope proteins. This HMAb recognizes HCV-E2 only when complexed with E1. The E1E2 complexes recognized by CBH-2 are noncovalently linked heterodimers and not misfolded disulfide-linked, high-molecular-weight aggregates. The E1E2 heterodimers seen by CBH-2 no longer associate with the endoplasmic reticulum chaperone calnexin and are likely to represent the prebudding form of the HCV virion.

    View details for DOI 10.1128/JVI.77.2.1604-1609.2003

    View details for Web of Science ID 000180166600080

    View details for PubMedID 12502876

    View details for PubMedCentralID PMC140849

  • Structural features of envelope proteins on hepatitis C virus-like particles as determined by anti-envelope monoclonal antibodies and CD81 binding VIROLOGY Triyatni, M., Vergalla, J., Davis, A. R., Hadlock, K. G., Foung, S. K., Liang, T. J. 2002; 298 (1): 124-132

    Abstract

    The envelope glycoprotein E2 of hepatitis C virus (HCV) is a major component of the viral envelope. Knowledge of its topologic features and antigenic determinants in virions is crucial in understanding the viral binding sites to cellular receptor(s) and the induction of neutralizing antibodies. The lack of a robust cell culture system for virus propagation has hampered the characterization of E2 presented on the virion. Here we report the structural features of hepatitis C virus-like particles (HCV-LPs) of the 1a and 1b genotypes as determined by various mouse and human monoclonal anti-envelope antibodies. Our results show that the E2 protein of HCV-LPs reacts with human monoclonal antibodies recognizing conformational determinants. Monoclonal antibodies (mAbs) specific for the hypervariable region 1 (HVR-1) sequence reacted strongly with HCV-LPs, suggesting that the HVR-1 is exposed on the viral surface. Several mAbs recognized both HCV-LPs with equally high affinity, indicating that the corresponding epitopes [amino acids (aa) 192-217 of E1 and aa 412-423, aa 522-531, and aa 640-653 of E2] are conserved in both genotypes and exposed on the surface of the HCV-LP. The E2 and E1/E2 dimers of 1a bound strongly to the recombinant large extracellular loop (LEL) of CD81 (CD81-LEL) of human and African green monkey, while the HCV-LP of 1a bound weakly to human CD81-LEL. E1/E2 dimers and the HCV-LPs of 1b did not bind CD81-LEL, consistent with the notion that CD81 recognition by E2 is strain-specific and does not correlate with permissiveness of infection. A model of the topology and exposed antigenic determinants of the envelope proteins of HCV is proposed.

    View details for DOI 10.1006/viro.2002.1463

    View details for Web of Science ID 000176822900014

    View details for PubMedID 12093180

  • Epitope mapping of human monoclonal antibodies recognizing conformational epitopes within HTLV type 1 gp46, employing HTLV type 1/2 envelope chimeras AIDS RESEARCH AND HUMAN RETROVIRUSES Hadlock, K. G., Yang, Q., Rowe, J., Foung, S. K. 2002; 18 (1): 57-70

    Abstract

    The majority of the antibody response to HTLV-1 surface glycoprotein, gp46, is directed at conformational epitopes. However, the regions of HTLV-1 gp46 that contain conformational epitopes are poorly defined. We previously reported on human monoclonal antibodies (hMAbs) to conformational epitopes within the HTLV-1 surface glycoprotein (gp46) that inhibit HTLV-1-mediated syncytium formation (Hadlock KG, Rowe J, Perkins S, et al.: J Virol 1997;71:5828-5840). To localize the conformational epitopes recognized by these antibodies, chimeric envelope proteins were constructed in which selected regions of the HTLV-1 envelope were replaced with the corresponding sequences from other members of the HTLV family of retroviruses. The chimeras were tested for reactivity with three hMAbs to conformational epitopes in HTLV-1 gp46, PRH-7A, PRH-3, and PRH-4, and one hMAb to a linear epitope, 0.5alpha. hMAb PRH-3 was specifically nonreactive with a chimera that replaced amino acids 32-36 of HTLV-1 gp46 and exhibited sharply reduced reactivity with a chimera that replaced amino acids 224-251 of HTLV-1 with the corresponding HTLV-2 sequence. hMAb PRH-4 was specifically nonreactive with a construct replacing amino acids 1-162 of HTLV-1 gp46 with the corresponding HTLV-2 sequence. Thus, HTLV-1 gp46 contains multiple conformational epitopes located in the amino-terminal portion of the protein.

    View details for Web of Science ID 000173367400007

    View details for PubMedID 11804557

  • The B-cell receptor of a hepatitis C virus (HCV)-associated non-Hodgkin lymphoma binds the viral E2 envelope protein, implicating HCV in lymphomagenesis BLOOD Quinn, E. R., Chan, C. H., Hadlock, K. G., Foung, S. K., Flint, M., Levy, S. 2001; 98 (13): 3745-3749

    Abstract

    Hepatitis C virus (HCV) infection is associated with extrahepatic B-cell lymphoproliferative disorders. To determine whether a viral antigen drives this B-cell expansion, the B-cell receptors were cloned from HCV-associated lymphomas and were expressed as soluble immunoglobulins. The rescued immunoglobulins were then tested for their ability to bind the HCV-E2 envelope glycoprotein, an antigen that was previously implicated in the pathogenesis of HCV-associated B-cell diseases. One of 2 lymphoma immunoglobulin test cases bound the E2 protein in a manner identical to a bona fide human anti-E2 antibody. Moreover, it bound E2 from multiple viral genotypes, suggesting reactivity with a conserved E2 epitope. These findings support the hypothesis that some HCV-associated lymphomas originate from B cells that were initially activated by the HCV-E2 protein and might explain the association between HCV infection and some B-cell lymphoproliferative disorders.

    View details for Web of Science ID 000172604700032

    View details for PubMedID 11739181

  • Cross-reactivity and clinical impact of the antibody response to hepatitis C virus second envelope glycoprotein (E2) JOURNAL OF MEDICAL VIROLOGY Hadlock, K. G., Gish, R., Rowe, J., Rajyaguru, S. S., Newsom, M., Warford, A., Foung, S. K. 2001; 65 (1): 23-29

    Abstract

    The genotype of hepatitis C virus (HCV) can profoundly affect the success of antiviral therapy for HCV infection. A possible contributing factor is a varied immune response elicited by infection with different HCV genotypes. In this study, full-length E2 proteins of HCV genotypes 1a, 1b, 2a, and 2b were used to determine the fraction of the humoral immune response to HCV E2 that is genotype specific. Greater than 90% of all infected individuals had serum antibodies to the four E2 proteins. Overall, individuals infected with genotype 1a or 1b were characterized by variable immune responses to HCV E2 with relatively high amounts of cross-reactivity with other E2 proteins. Individuals infected with genotype 2a or 2b exhibited a strong preferential reactivity to genotype 2a and 2b E2 proteins. Individuals with elevated titers to HCV E2 were more likely to be infected with genotype 2a and had a significantly lower median viral load. These findings indicate that the antibody response to HCV E2 is affected by the genotype of the virus and that induction of a strong humoral immune response to HCV E2 may contribute to a decreased viral load.

    View details for Web of Science ID 000170257200004

    View details for PubMedID 11505439

  • Evaluation of human monoclonal antibodies to HCV in the HCV-Trimera model: A mouse model for HCV infection Nussbaum, O., Ilan, E., Eren, R., Zauberman, A., Porat, Y., Neville, L., Arazi, Y., Livneh, G., Shavit, S., Hadlock, K., Foung, S., Dagan, S. ELSEVIER SCIENCE BV. 2001: 26
  • V(H)1-69 gene is preferentially used by hepatitis C virus-associated B cell lymphomas and by normal B cells responding to the E2 viral antigen BLOOD Chan, C. H., Hadlock, K. G., Foung, S. K., Levy, S. 2001; 97 (4): 1023-1026

    Abstract

    Hepatitis C virus (HCV)-associated B cell lymphomas were previously shown to express a restricted repertoire of immunoglobulin V(H) and V(L) genes, V(H)1-69 and VkappaA27, respectively. Although this suggests a role for antigen selection in the pathogenesis of these lymphomas, the driving antigen involved in the clonal expansion has not been identified. B cell response to a viral antigen, the HCV envelope glycoprotein 2 (E2), was analyzed in an asymptomatic HCV-infected patient. Single B cells, immortalized as hybridomas and selected for binding E2, were analyzed for their V gene usage. Sequences of these V region genes demonstrated that each hybridoma expressed unique V(H) and V(L) genes. Remarkably, these anti-E2 hybridomas preferentially used the V(H)1-69 gene. Analysis of replacement to silent mutation ratios indicated that the genes underwent somatic mutation and antigenic selection. In a separate report, human anti-E2 antibodies were also shown to express the same V(H) gene. These data strengthen the hypothesis that the HCV-associated lymphomas are derived from clonally expanded B cells stimulated by HCV.

    View details for Web of Science ID 000166867200032

    View details for PubMedID 11159532

  • Human monoclonal antibodies that inhibit binding of hepatitis C virus E2 protein to CD81 and recognize conserved conformational epitopes JOURNAL OF VIROLOGY Hadlock, K. G., Lanford, R. E., Perkins, S., Rowe, J., Yang, Q., Levy, S., Pileri, P., Abrignani, S., Foung, S. K. 2000; 74 (22): 10407-10416

    Abstract

    The intrinsic variability of hepatitis C virus (HCV) envelope proteins E1 and E2 complicates the identification of protective antibodies. In an attempt to identify antibodies to E2 proteins from divergent HCV isolates, we produced HCV E2 recombinant proteins from individuals infected with HCV genotypes 1a, 1b, 2a, and 2b. These proteins were then used to characterize 10 human monoclonal antibodies (HMAbs) produced from peripheral B cells isolated from an individual infected with HCV genotype 1b. Nine of the antibodies recognize conformational epitopes within HCV E2. Six HMAbs identify epitopes shared among HCV genotypes 1a, 1b, 2a, and 2b. Six, including five broadly reactive HMAbs, could inhibit binding of HCV E2 of genotypes 1a, 1b, 2a, and 2b to human CD81 when E2 and the antibody were simultaneously exposed to CD81. Surprisingly, all of the antibodies that inhibited the binding of E2 to CD81 retained the ability to recognize preformed CD81-E2 complexes generated with some of the same recombinant E2 proteins. Two antibodies that did not recognize preformed complexes of HCV 1a E2 and CD81 also inhibited binding of HCV 1a virions to CD81. Thus, HCV-infected individuals can produce antibodies that recognize conserved conformational epitopes and inhibit the binding of HCV to CD81. The inhibition is mediated via antibody binding to epitopes outside of the CD81 binding site in E2, possibly by preventing conformational changes in E2 that are required for CD81 binding.

    View details for Web of Science ID 000090083800016

    View details for PubMedID 11044085

  • Preferential expression of the VH1-69 gene in an anti-hepatitis C virus (HCV) immune response in an HCV-infected individual Chan, C. H., Hadlock, K. G., Perkins, S. L., Foung, S. K., Levy, S. FEDERATION AMER SOC EXP BIOL. 2000: A1122–A1122
  • The humoral immune response to human T-cell lymphotropic virus type 1 envelope glycoprotein gp46 is directed primarily against conformational epitopes JOURNAL OF VIROLOGY Hadlock, K. G., Rowe, J., Foung, S. K. 1999; 73 (2): 1205-1212

    Abstract

    Individuals infected with human T-cell lymphotropic virus type 1 (HTLV-1) develop a robust immune response to the surface envelope glycoprotein gp46 that is partially protective. The relative contribution of antibodies to conformation-dependent epitopes, including those mediating virus neutralization as part of the humoral immune response, is not well defined. We assess in this report the relationship between defined linear and conformational epitopes and the antibodies elicited to these domains. First, five monoclonal antibodies to linear epitopes within gp46 were evaluated for their ability to abrogate binding of three human monoclonal antibodies that inhibit HTLV-1-mediated syncytia formation and recognize conformational epitopes. Binding of antibodies to conformational epitopes was unaffected by antibodies to linear epitopes throughout the carboxy-terminal half and central domain of HTLV-1 gp46. Second, an enzyme-linked immunoadsorbent assay was developed and used to measure serum antibodies to native and denatured gp46 from HTLV-1-infected individuals. In sera from infected individuals, reactivity to denatured gp46 had an average of 15% of the reactivity observed to native gp46. Third, serum antibodies from 24 of 25 of HTLV-1-infected individuals inhibited binding of a neutralizing human monoclonal antibody, PRH-7A, to a conformational epitope on gp46 that is common to HTLV-1 and -2. Thus, antibodies to conformational epitopes comprise the majority of the immune response to HTLV-1 gp46, and the epitopes recognized by these antibodies do not appear to involve sequences in previously described immunodominant linear epitopes.

    View details for Web of Science ID 000078017500037

    View details for PubMedID 9882322

  • Human monoclonal antibodies to conserved conformational epitopes within hepatitis C virus E2 protein. Hadlock, K. G., Yang, Q., Rowe, J., Perkins, S., Lanford, R., Foung, S. K. WILEY-BLACKWELL. 1998: 275A–275A
  • Large granular lymphocyte leukaemia occurring after renal transplantation BRITISH JOURNAL OF HAEMATOLOGY Gentile, T. C., Hadlock, K. G., Uner, A. H., Delal, B., Squiers, E., CROWLEY, S., Woodman, R. C., Foung, S. K., Poiesz, B. J., Loughran, T. P. 1998; 101 (3): 507-512

    Abstract

    Post-transplantation lymphoproliferative disorders (PTLD) are a clinicopathologically heterogeneous group of lymphoid proliferations. The majority are of B-cell origin and associated with Epstein-Barr virus (EBV) infection. In contrast, the development of T-cell PTLD is much less common and EBV does not appear to be involved in pathogenesis. In this report we describe three patients who developed large granular lymphocyte (LGL) leukaemia after renal transplantation. These patients had clonal expansion of CD3+, CD8+, CD57+, CD56- LGL. We were unable to detect CMV antigen or find evidence for EBV or human T-cell leukaemia/lymphoma virus genome in the LGL from these patients. These data show that LGL leukaemia should be included as one of the types of T-cell proliferations which can occur post transplant.

    View details for Web of Science ID 000074236100019

    View details for PubMedID 9633895

  • Epitope mapping of HTLV envelope seroreactivity in LGL leukaemia BRITISH JOURNAL OF HAEMATOLOGY Loughran, T. P., Hadlock, K. G., Perzova, R., Gentile, T. C., Yang, Q., Foung, S. K., Poiesz, B. J. 1998; 101 (2): 318-324

    Abstract

    Sera from approximately 50% of patients with large granular lymphocyte (LGL) leukaemia react with a recombinant human T-cell leukaemia/lymphoma virus (HTLV) transmembrane envelope protein, p21e. Two immunodominant epitopes within env p21e have been defined by reactivity against recombinant proteins GD21 and BA21. In this study sera from 41 patients with LGL leukaemia were examined for reactivity against these recombinant HTLV env proteins. Overall, 21/41 (51%) sera reacted to p21e. Only two sera reacted to GD21. The predominant immunoreactivity against p21e was directed against the BA21 epitope, with 19/41 (46%) sera being BA21 positive. Seroconversion to BA21 protein was also documented. PCR analyses confirmed the low incidence of protypical HTLV sequences (2/41, 5%). These data document an association between BA21 seroreactivity and LGL leukaemia. This finding raises the possibility that such BA21 seroreactivity could be due to cross-reactivity to a cellular or retroviral antigen sharing some amino acid homology with the transmembrane glycoprotein of HTLV.

    View details for Web of Science ID 000073738200016

    View details for PubMedID 9609528

  • GBV-C/HGV: A new virus within the Flaviviridae and its clinical implications TRANSFUSION MEDICINE REVIEWS Hadlock, K. G., Foung, S. K. 1998; 12 (2): 94-108

    View details for Web of Science ID 000073086100003

    View details for PubMedID 9566077

  • Experimental infection of chimpanzees with hepatitis G virus and genetic analysis of the virus 16th Annual Meeting of the American-Society-for-Virology Bukh, J., Kim, J. P., Govindarajan, S., Apgar, C. L., Foung, S. K., Wages, J., Yun, A. J., Shapiro, M., Emerson, S. U., Purcell, R. H. OXFORD UNIV PRESS INC. 1998: 855–62

    Abstract

    Hepatitis G virus (HGV) was transmitted to 2 chimpanzees by inoculation with human plasma containing approximately 10(8) genome equivalents (GE) of HGV. The infection was characterized by the late appearance (weeks 10 and 11 after inoculation [pi]) of viremia that persisted throughout the 120-week follow-up. Serum HGV titer increased steadily until it plateaued at 10(6)-10(7) GE/mL. However, despite this relatively high titer, neither of the chimpanzees developed hepatitis. The sequence of the viral genome, recovered from each chimpanzee at week 77 pi, differed from that of the inoculum by 5 nt (2 aa) and 27 nt (2 aa). Two more chimpanzees were inoculated with a first-passage plasma pool. The chimpanzee inoculated with approximately 10(6.7) GE of HGV had viremia at week 1 pi. However, the viral titer increased with the same kinetics as observed in the first passage. The second chimpanzee inoculated with approximately 10(4.7) GE of HGV had late appearance (week 7 pi) of viremia.

    View details for Web of Science ID 000072719400004

    View details for PubMedID 9534956

  • Seroreactivity to an envelope protein of human T-cell leukemia/lymphoma virus in patients with CD3(-) (natural killer) lymphoproliferative disease of granular lymphocytes BLOOD Loughran, T. P., Hadlock, K. G., Yang, Q., Perzova, R., Zambello, R., Semenzato, G., Foung, S. K., Poiesz, B. J. 1997; 90 (5): 1977-1981

    Abstract

    Natural killer (NK) cells are CD3- large granular lymphocytes (LGL) responsible for immunity against viral infections. A chronic lymphoproliferative disorder of NK cells has been described in which the expanded NK cells display a restricted phenotype and cytotoxic activity. These data raise the hypothesis that proliferating LGL in these patients result from discrete expansions of NK cells responding to an unknown, perhaps viral, antigen. Recently, it was found that mice transgenic for the tax gene of human T-cell leukemia/lymphoma virus (HTLV) develop NK leukemia. Therefore, we studied 15 patients with chronic NK lymphoproliferative disorder for evidence of HTLV infection. Sera were tested using an HTLV-I/II-enzyme linked immunosorbent assay and a modified Western blot assay containing recombinant env proteins. None of the sera met conventional criteria for HTLV seroreactivity. However, sera from 11 patients (73%) reacted with the recombinant HTLV env protein p21E. The anti-p21E reactivity of these sera was then mapped employing the recombinant proteins GD21 and BA21. No reactivity to the immunodominant HTLV epitope GD21 was observed, suggesting that prototypical HTLV infection is unlikely in these patients. This was confirmed by finding no evidence for HTLV nucleic acids by PCR analyses employing primers specific for conserved regions in the env, pol, and pX genes. In contrast, 10 of the 15 sera reacted with the epitope BA21, documenting for the first time an association between a unique seroreactivity and disease. The high incidence of BA21 seroreactivity in these patients suggests that exposure to a protein containing homology to BA21 may be important in the pathogenesis of this lymphoproliferative disorder.

    View details for Web of Science ID A1997XX16600028

    View details for PubMedID 9292532

  • Neutralizing human monoclonal antibodies to conformational epitopes of human T-cell lymphotropic virus type 1 and 2 gp46 JOURNAL OF VIROLOGY Hadlock, K. G., Rowe, J., Perkins, S., Bradshaw, P., Song, G. Y., Cheng, C., Yang, J., Gascon, R., HALMOS, J., REHMAN, S. M., McGrath, M. S., Foung, S. K. 1997; 71 (8): 5828-5840

    Abstract

    Ten human monoclonal antibodies derived from peripheral B cells of a patient with human T-cell lymphotropic virus (HTLV)-associated myelopathy are described. One monoclonal antibody recognized a linear epitope within the carboxy-terminal 43 amino acids of HTLV gp21, and two monoclonal antibodies recognized linear epitopes within HTLV type 1 (HTLV-1) gp46. The remaining seven monoclonal antibodies recognized denaturation-sensitive epitopes within HTLV-1 gp46 that were expressed on the surfaces of infected cells. Two of these antibodies also bound to viable HTLV-2 infected cells and immunoprecipitated HTLV-2 gp46. Virus neutralization was determined by syncytium inhibition assays. Eight monoclonal antibodies, including all seven that recognized denaturation-sensitive epitopes within HTLV-1 gp46, possessed significant virus neutralization activity. By competitive inhibition analysis it was determined that these antibodies recognized at least four distinct conformational epitopes within HTLV-1 gp46. These findings indicate the importance of conformational epitopes within HTLV-1 gp46 in mediating a neutralizing antibody response to HTLV infection.

    View details for Web of Science ID A1997XK15300016

    View details for PubMedID 9223472

  • A source of glycosylated human T-cell lymphotropic virus type 1 envelope protein: Expression of gp46 by the vaccinia virus T7 polymerase system JOURNAL OF VIROLOGY Arp, J., LEVATTE, M., Rowe, J., Perkins, S., King, E., LEYSTRALANTZ, C., Foung, S. K., Dekaban, G. K. 1996; 70 (11): 7349-7359

    Abstract

    Heterologous expression of the human T-cell lymphotropic virus type 1 (HTLV-1) envelope surface glycoprotein (gp46) in a vaccinia virus/T7 polymerase system resulted in the production of authentic recombinant gp46. Five differentially glycosylated forms of the surface envelope protein were produced by this mammalian system, as demonstrated by tunicamycin inhibition of N-glycosylation and N-glycan removal with endoglycosidase H and glycopeptidase F. These studies revealed that all four potential N-glycosylation sites in gp46 were used for oligosaccharide modification and that the oligosaccharides were mannose-rich and/or hybrid in composition. Conformational integrity of the recombinant HTLV-1 envelope protein was determined by the ability to bind to various HTLV-1-infected human sera and a panel of conformational-dependent human monoclonal antibodies under nondenaturing conditions. Furthermore, this recombinant gp46 was recognized by a series of HTLV-2-infected human sera and sera from a Pan paniscus chimpanzee infected with the distantly related simian T-cell lymphotropic virus STLVpan-p. Maintenance of highly conserved conformational epitopes in the recombinant HTLV-1 envelope protein structure suggests that it may serve as a useful diagnostic reagent and an effective vaccine candidate.

    View details for Web of Science ID A1996VL79200001

    View details for PubMedID 8892853

    View details for PubMedCentralID PMC190802

  • Molecular cloning and disease association of hepatitis G virus: A transfusion-transmissible agent SCIENCE Linnen, J., Wages, J., ZHANGKECK, Z. Y., Fry, K. E., KRAWCZYNSKI, K. Z., Alter, H., Koonin, E., Gallagher, M., Alter, M., Hadziyannis, S., Karayiannis, P., Fung, K., Nakatsuji, Y., SHIH, J. W., Young, L., Piatak, M., Hoover, C., Fernandez, J., Chen, S., Zou, J. C., Morris, T., Hyams, K. C., Ismay, S., Lifson, J. D., Hess, G., Foung, S. K., Thomas, H., Bradley, D., Margolis, H., Kim, J. P. 1996; 271 (5248): 505-508

    Abstract

    An RNA virus, designated hepatitis G virus (HGV), was identified from the plasma of a patient with chronic hepatitis. Extension from an immunoreactive complementary DNA clone yielded the entire genome (9392 nucleotides) encoding a polyprotein of 2873 amino acids. The virus is closely related to GB virus C (GBV-C) and distantly related to hepatitis C virus, GBV-A, and GBV-B. HGV was associated with acute and chronic hepatitis. Persistent viremia was detected for up to 9 years in patients with hepatitis. The virus is transfusion-transmissible. It has a global distribution and is present within the volunteer blood donor population in the United States.

    View details for Web of Science ID A1996TR32200042

    View details for PubMedID 8560265

  • ENHANCED SPECIFICITY OF TRUNCATED TRANSMEMBRANE PROTEIN FOR SEROLOGIC CONFIRMATION OF HUMAN T-CELL LYMPHOTROPIC VIRUS TYPE-1 (HTLV-1) AND HTLV-2 INFECTIONS BY WESTERN-BLOT (IMMUNOBLOT) ASSAY CONTAINING RECOMBINANT ENVELOPE GLYCOPROTEINS JOURNAL OF CLINICAL MICROBIOLOGY Varma, M., Rudolph, D. L., KNUCHEL, M., Switzer, W. M., Hadlock, K. G., Velligan, M., Chan, L., Foung, S. K., Lal, R. B. 1995; 33 (12): 3239-3244

    Abstract

    Immunoassays based on the highly immunogenic transmembrane protein of human T-cell lymphotropic virus type 1 (HTLV-1) (protein 21c) are capable of detecting antibodies in all individuals infected with HTLV-1 and HTLV-2. However, because of antigenic mimicry with other cellular and viral proteins, such assays also have a large proportion of false-positive reactions. We have recently identified an immunodominant epitope, designated GD21-I located within amino acids 361 to 404 of the transmembrane protein, that appears to eliminate such false positivity. This recombinant GD21-I protein was used in conjunction with additional recombinant HTLV type-specific proteins and a whole virus lysate to develop a modified Western blot (immunoblot) assay (HTLV WB 2.4). The sensitivity and specificity of this assay were evaluated with 352 specimens whose infection status was determined by PCR assay for the presence or absence of HTLV-1/2 proviral sequences. All HTLV-1-positive (n = 102) and HTLV-2-positive (n = 107) specimens reacted with GD21-1 in the HTLV WB 2.4 assay, yielding a test sensitivity of 100%. Furthermore, all specimens derived from individuals infected with different viral subtypes of HTLV-1 (Cosmopolitan, Japanese, and Melanesian) and HTLV-2 (IIa0, a3, a4, IIb1, b4, and b5) reacted with GD21-I in the HTLV WB 2.4 assay. More importantly, HTLV WB 2.4 analysis of 81 PCR-negative specimens, all of which reacted to recombinant protein 21e in the presence or absence of p24 and p19 reactivity in the standard WB assay, showed that only two specimens retained reactivity to GD21-I, yielding an improved test specificity for the transmembrane protein of 97.5%. None of 41 specimens with gag reactivity only or 21 HTLV-negative specimens demonstrated reactivity to GD21-I. In an analysis of additional specimens (n = 169) from different geographic areas for which PCR results were not available, a substantial increase in the specificity of GD21-I detection was demonstrated, with no effect on the sensitivity of GD21-I detection among specimens from seropositive donors. Thus, the highly sensitive, GD21-I-based HTLV WB 2.4 assay eliminates the majority of false-positive transmembrane results, thereby increasing the specificity for serologic confirmation of HTLV-1 and HTLV-2 infections.

    View details for Web of Science ID A1995TF01500033

    View details for PubMedID 8586709

  • DELINEATION OF IMMUNOGENIC REGIONS WITHIN HTLV-I AND HTLV-II P24 Hadlock, K. G., Cheng, C., Yang, Q., Perkins, S., Rowe, J., Foung, S. K. LIPPINCOTT WILLIAMS & WILKINS. 1995: 136–36
  • BIOCHEMICAL AND CONFORMATIONAL INTEGRITY OF RECOMBINANT HTLV-I GP46 ENVELOPE PROTEIN EXPRESSED IN A VACCINIA/T7 POLYMERASE SYSTEM ARP, J., LEVATTE, M., FOUNG, S., ROWE, J., DEKABAN, G. A. LIPPINCOTT-RAVEN PUBL. 1995: 41
  • DELINEATION OF AN IMMUNODOMINANT AND HUMAN T-CELL LYMPHOTROPIC VIRUS (HTLV)-SPECIFIC EPITOPE WITHIN THE HTLV-I TRANSMEMBRANE GLYCOPROTEIN BLOOD Hadlock, K. G., Goh, C. J., BRADSHAW, P. A., Perkins, S., Lo, J., Kaplan, J. E., Khabbaz, R., Foung, S. K. 1995; 86 (4): 1392-1399

    Abstract

    Antibody reactivity to the transmembrane region of human T-cell lymphotropic virus type I (HTLV-I) envelope, gp21, is observed in virtually all individuals infected with HTLV-I or HTLV-II. Recombinant proteins encoding selected portions of gp21 are described and used to define two immunogenic regions. The first epitope (designated GD21-I) contains amino acids 361 to 404 of the HTLV-I envelope and reacted with all of 54 sera from HTLV-I- and HTLV-II-infected individuals. The second epitope (designated BA21) expresses amino acids 397 to 430 of the HTLV-I envelope and was recognized by 33 of 54 HTLV antisera. To determine the specificity of GD21-I and BA21, sera from 17 HTLV-negative individuals with nonspecific reactivity to p21E were tested. None of these sera reacted with GD21-I, but 16 of 17 sera reacted with BA21. With virtually complete reactivity to sera from HTLV-infected individuals and no reactivity to sera from p21E-reactive uninfected individuals, GD21-I will be useful in immunoassays for the detection of HTLV infection.

    View details for Web of Science ID A1995RN46700022

    View details for PubMedID 7632947

  • Stabilizing antibody secretion of human Epstein Barr virus-activated B-lymphocytes with hybridoma formation by electrofusion. Methods in molecular biology (Clifton, N.J.) Perkins, S., FOUNG, S. K. 1995; 48: 295-307

    View details for PubMedID 8528401

  • LOCALIZATION OF ANTIGENIC SITES ON HUMAN CYTOMEGALOVIRUS VIRION STRUCTURAL PROTEINS ENCODED BY UL48 AND UL56 VIROLOGY BRADSHAW, P. A., DURANGUARINO, M. R., Perkins, S., ROWE, J. I., Fernandez, J., Fry, K. E., Reyes, G. R., Young, L., Foung, S. K. 1994; 205 (1): 321-328

    Abstract

    Two human cytomegalovirus (HCMV) virion structural proteins and their associated reading frames have been identified with two human-derived monoclonal antibodies (HMAbs), X2-16 and X-16. HMAb X2-16 identified recombinant protein expressing molecular clones that mapped to the open reading frame (ORF) of the UL48 gene of HCMV, between amino acids 584 and 646 (nucleotides 65,084 and 65,272, Chee et al., 1990, "Current Topics in Microbiology and Immunology," Vol. 154, pp. 125-169). The UL48 gene product has an apparent molecular weight of 216 kDa. HMAb X-16 identified clones derived from the UL56 ORF between amino acids 380 and 425 (nucleotides 84,733 and 84,870). On immunoblots, HMAb X-16 detected two HCMV proteins of 96 and 60 kDa. Both UL48 and UL56 are highly conserved among the human herpesviruses and their products have been predicted to have essential functions for virus production and maturation. These results confirm that UL48 and UL56 are functional genes encoding essential viral proteins which also generate an immune response in the immunocompetent host.

    View details for Web of Science ID A1994PQ62300036

    View details for PubMedID 7975228

  • DELINEATION OF AN IMMUNODOMINANT AND HIGHLY HTLV SPECIFIC EPITOPE WITHIN HTLV-I GP21 Hadlock, K. G., Goh, C. J., BRADSHAW, P. A., Perkins, S., Lo, J., Khabbaz, R., Kaplan, J., Foung, S. K. MARY ANN LIEBERT INC. 1994: 499–99
  • MOLECULAR BIOLOGICAL EVIDENCE FOR HTLV-1 PROVIRAL INTEGRATION IN SOME CASES OF MYCOSIS-FUNGOIDES SEZARY-SYNDROME (MF/SS) WOOD, G. S., SALVEKAR, A., CROOKS, C. F., BONI, R., HENGHOLD, W., SCHWANDT, A., FOUNG, S., WARNKE, R. A., BURG, G. BLACKWELL SCIENCE INC. 1994: 543
  • IMPROVED DETECTION OF HTLV USING RECOMBINANT PROTEIN-DERIVED FROM GP21 REGION Varma, M., Chan, L., Walsh, A., Song, G. Y., TOSTADO, M., Hadlock, K., Foung, S., Lal, R. MARY ANN LIEBERT INC. 1994: 495–95
  • NEUTRALIZING HTLV-I HUMAN MONOCLONAL-ANTIBODIES (HMABS) TO CONFORMATIONAL EPITOPES Rowe, J., Perkins, S., Bradshaw, P., Song, G. Y., Foung, S. MARY ANN LIEBERT INC. 1994: 509–
  • IMMUNOGLOBULIN PROPHYLAXIS AGAINST HUMAN T-CELL LYMPHOTROPIC VIRUS TYPE-II IN RABBITS JOURNAL OF INFECTIOUS DISEASES Morishita, N., Ishii, K., Tanaka, Y., Sawada, T., Hoshino, H., Foung, S. K., Miyoshi, I. 1994; 169 (3): 620-623

    Abstract

    Hyperimmune globulins, I-IgG and II-IgG, prepared from healthy persons seropositive for human T cell lymphotropic virus (HTLV) types I and II, respectively, were tested for their prophylactic effect against HTLV-II infection in rabbits. Three groups (A, B, and C) of 3 female rabbits each were used. Group A rabbits were inoculated intravenously with HTLV-II-carrying rabbit lymphoid cell line RII. Group B and C rabbits were immunized, respectively, with II-IgG and I-IgG and challenged with RII cells 24 h later. All group A and C rabbits seroconverted for HTLV-II after 2 weeks, but all group B rabbits were protected from HTLV-II infection. Gene amplification by polymerase chain reaction revealed the presence of HTLV-II provirus sequences in all group A and C rabbits but in none of the group B rabbits. These findings indicate that passive immunization with II-IgG is effective in preventing HTLV-II infection and that there is no cross-neutralization between HTLV-I and -II.

    View details for Web of Science ID A1994NP10900023

    View details for PubMedID 8158037

  • AMPLIFICATION AND DETECTION OF A SINGLE-MOLECULE OF HUMAN-IMMUNODEFICIENCY-VIRUS RNA VIRUS GENES Nakamura, S., Katamine, S., Yamamoto, T., Foung, S. K., Kurata, T., HIRABAYASHI, Y., Shimada, K., Hino, S., Miyamoto, T. 1993; 7 (4): 325-338

    Abstract

    Detection of plasma viremia in human immunodeficiency virus type 1 (HIV-1)-infected people is indispensable for the diagnosis of seronegative infection as well as for the evaluation of virus activities in vivo. The direct detection of HIV-1 RNA in circulation has been performed by means of reverse transcription followed by polymerase chain reaction (RT-PCR). As an attempt to establish a highly sensitive assay, we evaluated the effects of two-step amplification with nested primers and double priming of reverse transcription on the sensitivity of RT-PCR. The sensitivity of two-step amplification was 100 times higher than that of one-step amplification. The double priming of reverse transcription further increased the sensitivity of the following two-step amplification 100 times, which appeared to be enough to detect HIV-1 RNA from as little as a 2.2 x 10(-4) TCID50 unit equivalent of culture supernatant of HIV-1-infected cells and a single molecule of HIV-1 gag complementary RNA synthesized by in vitro transcription. By use of this most sensitive assay, we successfully detected HIV-1 RNA in serum or plasma from all 22 patients with acquired immune deficiency syndrome (AIDS) or AIDS-related complex (ARC) and 13 out of 14 untreated asymptomatic carriers. Of 43 asymptomatic carriers under the treatment with interferon-alpha or azidothymidine, 17 cases showed negative results, indicating that the virus activity was suppressed by the therapeutics. We also noted the inhibitory effect of heparin on RT-PCR.

    View details for Web of Science ID A1993MP63100002

    View details for PubMedID 8122393

  • HUMAN T-LYMPHOTROPIC VIRUS TYPE-I/II IN LAKE LINDU VALLEY, CENTRAL SULAWESI, INDONESIA JOURNAL OF ACQUIRED IMMUNE DEFICIENCY SYNDROMES AND HUMAN RETROVIROLOGY Lal, R. B., LIPKA, J. J., Foung, S. K., Hadlock, K. G., Reyes, G. R., Carney, W. P. 1993; 6 (9): 1067-1068

    View details for Web of Science ID A1993MC82800016

    View details for PubMedID 8340898

  • DETERMINATION OF IMMUNODOMINANT EPITOPE WITHIN HTLV-I GP21 BRADSHAW, P. A., Lo, J., Perkins, S., Foung, S. K., Hadlock, K. G., Goh, C. J., Chan, L., Ruda, M. WILEY-BLACKWELL. 1993: S39–S39
  • ASSOCIATION OF (TROPICAL) ATAXIC NEUROPATHY WITH HTLV-II VIRUS RESEARCH Sheremata, W. A., Harrington, W. J., BRADSHAW, P. A., Foung, S. K., Raffanti, S. P., Berger, J. R., Snodgrass, S., Resnick, L., Poiesz, B. J. 1993; 29 (1): 71-77

    Abstract

    Jamaican Neuropathy of the ataxic type (tropical ataxic neuropathy [TAN] and spastic type (tropical spastic paraparesis [TSP]) have been recognized for over a century in Jamaica. The recent association of TSP with HTLV-I (TSP/HAM) is now well established. We now present evidence for a possible association between a TAN-like illness with HTLV-II in four females aged 34-49. All presented with ataxic gait and all four have prominent mental changes. Three of the four also have minor motor deficits with urinary frequency and two have nocturnal leg cramps. All have serum antibody and all had PCR evidence of HTLV-II infection. Antibody to HTLV-II is present in CSF from two subjects. The distinctive picture of prominent ataxia and altered mental status in these subjects contrasts with a predominantly myelopathic picture seen in TSP/HAM.

    View details for Web of Science ID A1993LQ24000006

    View details for PubMedID 8212851

  • ISOTYPIC AND IGG SUBCLASS RESTRICTION OF THE HUMORAL IMMUNE-RESPONSES TO HUMAN T-LYMPHOTROPIC VIRUS TYPE-I CLINICAL IMMUNOLOGY AND IMMUNOPATHOLOGY Lal, R. B., Buckner, C., Khabbaz, R. F., Kaplan, J. E., Reyes, G., Hadlock, K., Lipka, J., Foung, S. K., Chan, L., Coligan, J. E. 1993; 67 (1): 40-49

    Abstract

    We have investigated the isotypic and IgG subclass profile of the antibody response to HTLV-I structural proteins (gag and env) in patients with HTLV-I-associated myelopathy (HAM; n = 20), adult T-cell leukemia (ATL; n = 15), and HTLV-I-positive asymptomatic carriers (ASY; n = 21). IgG, IgM, and IgA were the predominant antibody responses in all HTLV-I-infected individuals; minimal IgE response was detectable in the HAM and ATL groups. Among the IgG subclasses, IgG1 was the most predominant antibody detected in responses to HTLV-I antigens, followed by IgG3 and IgG2; IgG4 could not be detected in any patient group. Levels of both IgG1 and IgG3 were significantly higher in patients with HAM, when compared to ATL and ASY (P < 0.01 for both comparisons). In addition, Ig isotypes and IgG subclass antibody in patient sera reactive with purified viral proteins and several immunodominant epitopes, represented by synthetic peptides, Gag-1a102-117, Env-1(191-214), Env-5(242-257), and recombinant proteins, MTA-1(162-209) and r21e303-440, were examined to delineate specific epitopes responsible for inducing the host immune responses of each isotype and subclass to the structural proteins of HTLV-I. IgG, IgM, and IgA responses were directed against both the gag and env gene products. Among IgG subclasses, the IgG1 and IgG3 responses were directed against both the gag (p53, p24, p19, and Gag-1a) and env (recombinant MTA-1, r21e, and synthetic Env-1, Env-5) proteins; IgG2 responses were mainly restricted to gag proteins. The frequency profile of HTLV-I-specific antigen recognition in all four IgG subclasses were similar in all of the clinical groups. These results further define the fine specificity of anti-HTLV-I immune reaction for understanding the mechanism of pathogenesis in these individuals and suggest that factors other than the humoral immune responses may be associated with the clinical manifestation of the disease.

    View details for Web of Science ID A1993KT71700006

    View details for PubMedID 7680300

  • SPASTIC ATAXIA ASSOCIATED WITH HUMAN T-CELL LYMPHOTROPIC VIRUS TYPE-II INFECTION ANNALS OF NEUROLOGY Harrington, W. J., Sheremata, W., Hjelle, B., Dube, D. K., Bradshaw, P., Foung, S. K., Snodgrass, S., TOEDTER, G., Cabral, L., Poiesz, B. 1993; 33 (4): 411-414

    Abstract

    Human T-cell lymphotropic virus type one (HTLV-1) is associated with tropical spastic paraparesis or HTLV-I--associated myelopathy. We report 2 women with a spastic ataxic illness similar to HTLV-I--associated myelopathy infected solely with HTLV-II. Identification of HTLV-II infection was made serologically, by polymerase chain reaction, and by viral culture (in 1 woman). One woman, treated with 200 mg of danazol orally, three times daily, had pronounced improvement in ambulation, nocturnal spasticity, and nighttime urinary frequency. It appears that infection with HTLV-II may cause an illness similar to HTLV-I--associated myelopathy, but distinguished by the presence of ataxia.

    View details for Web of Science ID A1993KW78100015

    View details for PubMedID 8489213

  • EVALUATION OF AN IMMUNOBLOT ASSAY FOR SEROLOGICAL CONFIRMATION AND DIFFERENTIATION OF HUMAN T-CELL LYMPHOTROPIC VIRUS TYPE-I AND TYPE-II JOURNAL OF CLINICAL MICROBIOLOGY Roberts, B. D., Foung, S. K., LIPKA, J. J., Kaplan, J. E., Hadlock, K. G., Reyes, G. R., Chan, L., Heneine, W., Khabbaz, R. F. 1993; 31 (2): 260-264

    Abstract

    The confirmation of infection with human T-cell lymphotropic virus type I (HTLV-I) and type II (HTLV-II) currently involves multiple assays. These include Western blot (immunoblot) (WB) and/or radioimmunoprecipitation assay for detection of antibodies to HTLV-specific viral proteins and polymerase chain reaction and/or peptide-based enzyme immunoassays for differentiating between the two viruses. We undertook an evaluation of a modified WB assay that includes native HTLV-I viral proteins from MT-2 cells spiked with an HTLV-I transmembrane glycoprotein (recombinant p21e) and the HTLV-I- and HTLV-II-specific recombinant proteins MTA-1 and K55. The test panel consisted of well-characterized sera from U.S. blood donors, American Indians, intravenous drug users, and patients seen in sexually transmitted disease clinics. Of 158 HTLV-I/II-seropositive serum specimens tested, 156 (98.7%) were confirmed and typed as HTLV-I or HTLV-II. Of 82 HTLV-I/II-seroindeterminate or -seronegative serum specimens, only 1 was classified as HTLV-II positive: the sample had weak gag p19 and strong gag p24 and env p21e reactivity and was radioimmunoprecipitation assay negative for env gp61/68 but polymerase chain reaction positive for HTLV-II. The specificity of the modified WB for confirming and typing serum samples was therefore 100%. We conclude that this WB assay is useful for confirming and typing HTLV infection and can help simplify HTLV-I/II testing algorithms.

    View details for Web of Science ID A1993KH75100017

    View details for PubMedID 8432811

    View details for PubMedCentralID PMC262746

  • NEUTRALIZING ANTIBODY TO VESICULAR STOMATITIS-VIRUS (HTLV-I) PSEUDOTYPE IN INFANTS BORN TO SEROPOSITIVE MOTHERS JAPANESE JOURNAL OF CANCER RESEARCH Iwahara, Y., Sawada, T., Taguchi, H., Hoshino, H., Umemoto, M., Take, H., Foung, S., Miyoshi, I. 1993; 84 (2): 114-116

    Abstract

    Breast feeding is the major route of mother-to-child transmission of human T-cell leukemia virus type I (HTLV-I). Our experiments with rabbits have shown that passive immunization is capable of blocking cell-to-cell infection of HTLV-I by blood transfusion or breast feeding. In this study, sera were collected serially from 3 infants born to seropositive mothers and were tested for the presence of neutralizing antibody to vesicular stomatitis virus (HTLV-I) pseudotype as well as antibodies to viral structural proteins. There was a good correlation between neutralizing and viral antibody titers, both of which were detectable until 3-6 months after birth. Whether maternally transmitted neutralizing antibody is protective against perinatal infection of HTLV-I remains to be studied.

    View details for Web of Science ID A1993KN14300003

    View details for PubMedID 8385083

  • IMMUNE RESPONSIVENESS TO THE IMMUNODOMINANT RECOMBINANT ENVELOPE EPITOPES OF HUMAN T-LYMPHOTROPIC VIRUS TYPE-1 AND TYPE-2 IN DIVERSE GEOGRAPHIC POPULATIONS JOURNAL OF INFECTIOUS DISEASES Buckner, C., ROBERTS, C. R., Foung, S. K., Lipka, J., Reyes, G. R., Hadlock, K., Chan, L., GONGORABIACHI, A., Hjelle, B., Lal, R. B. 1992; 166 (5): 1160-1163

    Abstract

    The heterogeneity of immune responsiveness to the immunodominant epitopes of human T lymphotropic virus (HTLV) types I (MTA-1(162-209)) and II (K-55(162-205)) were determined in natural infections with HTLV-I and -II from diverse geographic areas (n = 285). Of the HTLV-I specimens confirmed by polymerase chain reaction (PCR), all North American (n = 37) and Peruvian (n = 19) specimens reacted with MTA-1. Of HTLV-II specimens confirmed by PCR, 44 (96%) of 46 from North American blood donors, 28 (97%) of 29 from native Americans, and all from intravenous drug users (n = 29) reacted with K-55. Specimens from other geographic areas (Peru, 30; Brazil, 4; Mexico, 10; Italy, 5; Somalia, 13; Ethiopia, 17; Japan, 32; and Jamaica, 15) all reacted either with MTA-1 or K-55. By synthetic peptide-based serologic typing, all of these specimens could be typed as HTLV-I or -II. In addition to the direct implications of these findings for diagnostic purposes, these data provide indirect evidence for the conservation of immunodominant HTLVenv epitopes in diverse geographic populations.

    View details for Web of Science ID A1992JV01500031

    View details for PubMedID 1383353

  • EPITOPE MAPPING OF THE HTLV-I SPECIFIC AND IMMUNODOMINANT RECOMBINANT PROTEIN MTA-1 Mishra, A., LIPKA, J. J., Foung, S. K., Guan, M., Reyes, G. R., Hadlock, K. G. AMER ASSOC BLOOD BANKS. 1992: S34–S34
  • DIAGNOSIS OF HTLV-I AND HTLV-II INFECTIONS AMONG UNITED-STATES BLOOD-DONORS SVOBODA, S., LIPKA, J. J., FOUNG, S. K., CHAN, L., BUSCH, M., FANG, C. T. AMER ASSOC BLOOD BANKS. 1992: S34
  • EVALUATION OF AN IMMUNOBLOT ASSAY FOR SEROLOGICAL CONFIRMATION AND DIFFERENTIATION OF HUMAN T-CELL LYMPHOTROPHIC VIRUS TYPE-I AND TYPE-II ROBERTS, B. D., FOUNG, S. K., LIPKA, J. J., KAPLAN, J. E., HADLOCK, K. G., REYES, G. R., CHAN, L., HENEINE, W., KHABBAZ, R. F. AMER ASSOC BLOOD BANKS. 1992: S58
  • CLONING AND ANALYSIS OF A RECOMBINANT ANTIGEN CONTAINING AN EPITOPE SPECIFIC FOR HUMAN T-CELL LYMPHOTROPIC VIRUS TYPE-II BLOOD Hadlock, K. G., LIPKA, J. J., Chow, T. P., Foung, S. K., Reyes, G. R. 1992; 79 (10): 2789-2796

    Abstract

    An immunodominant HTLV-I-specific epitope in the HTLV-I envelope glycoprotein (GP) 46 has been described. To determine if the analogous region of HTLV-II contains a similarly immunogenic and specific epitope, the polymerase chain reaction (PCR) was used to amplify HTLV-II DNA fragments encoding various portions of the putative epitope. The synthesized DNAs were cloned into lambda-phage gt11 and screened for production of immunoreactive fusion protein using sera from HTLV-II- or HTLV-I-infected individuals. Antisera from HTLV-II-infected individuals identified three of four recombinant clones when tested in a plaque immunoassay. Fusion protein from one of the clones, GH2-K15, was purified and analyzed by Western blot against a panel of HTLV-I and HTLV-II antisera. Twenty-one of 22 HTLV-II-infected sera were reactive with the GH2-K15 epitope. Sera from HTLV-I-infected and HTLV-I-uninfected individuals did not cross-react with GH2-K15. Western blot analysis of recombinant proteins encoding portions of the HTLV-II sequences in the Gh2-K15 antigen localized the HTLV-II-specific epitope to a 17-amino acid sequence. Recombinant antigens containing this epitope should be useful for type-specific serologic diagnosis of HTLV-II infection.

    View details for Web of Science ID A1992HW61800041

    View details for PubMedID 1375112

  • SEROLOGIC CONFIRMATION OF SIMIAN T-LYMPHOTROPIC VIRUS TYPE-I INFECTION BY USING IMMUNOASSAYS DEVELOPED FOR HUMAN T-LYMPHOTROPIC VIRUS-ANTIBODY DETECTION JOURNAL OF CLINICAL MICROBIOLOGY Rudolph, D. L., Yee, J., Mone, J., Foung, S. K., LIPKA, J. J., Reyes, G. R., Hadlock, K., Chan, L., Villinger, F., Lairmore, M. D., Sinha, S., Lal, R. B. 1992; 30 (4): 858-861

    Abstract

    Serum specimens from diverse species of Old World monkeys, categorized as seropositive (n = 97) or seronegative (n = 23) for human T-lymphotropic virus (HTLV) infection, were tested by using recombinant env-spiked Western immunoblot assays and synthetic peptide assays for simultaneous detection and discrimination of simian T-lymphotropic virus (STLV) infection. Of the 97 seropositive specimens, 93 reacted with the recombinant transmembrane (r21env) protein and 90 reacted with a recombinant, MTA-1, derived from the central region of the external glycoprotein of HTLV-I (rgp46env), thus yielding test sensitivities of 96 and 93%, respectively. While 1 of the 23 negative monkey specimens reacted with r21env, none reacted with rgp46env, for overall specificities of 96 and 100%, respectively. Analysis of synthetic peptide-based immunoassays demonstrated that while 85 of 97 (88%) seropositive specimens reacted with HTLV-I-specific epitope (p19gag), none of the specimens reacted with HTLV-II-specific epitope (gp52env). These results show that recombinant envelope-spiked Western blots provide a simple means for serologic confirmation of STLV-I infection and that type-specific synthetic peptides can be used to confirm the virus type in seropositive monkey specimens.

    View details for Web of Science ID A1992HJ48700018

    View details for PubMedID 1349306

    View details for PubMedCentralID PMC265174

  • SEGREGATION OF HUMAN T-CELL LYMPHOTROPIC VIRUS TYPE-I AND TYPE-II INFECTIONS BY ANTIBODY REACTIVITY TO UNIQUE VIRAL EPITOPES JOURNAL OF INFECTIOUS DISEASES LIPKA, J. J., Miyoshi, I., Hadlock, K. G., Reyes, G. R., Chow, T. P., Blattner, W. A., Shaw, G. M., Hanson, C. V., Gallo, D., Chan, L., Foung, S. K. 1992; 165 (2): 268-272

    Abstract

    A recombinant protein of the human T cell lymphotropic virus type I (HTLV-I) gp46 outer membrane envelope, MTA-4 (residues 129-203), reacted by Western blot with sera from HTLV-I-infected individuals from the United States and Jamaica but not with 24 (10%) of 242 Japanese sera. A related gp46 recombinant protein, MTA-1 (residues 162-209), reacted with all 58 sera from HTLV-I-infected US and Jamaican individuals and 238 of 242 sera from infected Japanese (combined sensitivity of 99%). Neither recombinant showed reactivity to sera from HTLV-II-infected individuals or uninfected controls. The reactivity of recombinant proteins containing the region of HTLV-II gp46 analogous to MTA-1 was also evaluated by Western blot: GH2-K15 (residues 157-205) and GH2-K55 (residues 162-205) reacted with 88 (98%) and 89 (99%), respectively, of 90 sera from HTLV-II-infected individuals but not with sera from HTLV-I-infected individuals or uninfected controls. These recombinant proteins should permit the development of assays to unambiguously confirm and differentiate HTLV-I and HTLV-II infections.

    View details for Web of Science ID A1992HF38700011

  • PRODUCTION OF HTLV-I HUMAN MONOCLONAL-ANTIBODIES REHMAN, S. M., Perkins, S., Rowe, J., Foung, S. K. MOSBY-ELSEVIER. 1992: 264–64
  • ANTIBODIES TO HEPATITIS-C VIRUS IN LOW-RISK BLOOD-DONORS - IMPLICATIONS FOR COUNSELING POSITIVE DONORS GASTROENTEROLOGY Hsu, H. H., Gonzalez, M., Foung, S. K., Feinstone, S. M., Greenberg, H. B. 1991; 101 (6): 1724-1727

    Abstract

    The significance of antibodies to hepatitis C virus (HCV) found by screening enzyme-linked immunoassay testing in a low-risk blood donor population is unclear. The rate of false positivity in this group as well as the usefulness of supplemental testing were examined by correlating the results of two screening enzyme-linked immunoassays (Ortho Diagnostics, Raritan, NJ, and Abbott Laboratories, North Chicago, IL) with supplemental antibody testing by the recombinant immunoblot assays (1 and 2) (Ortho) and neutralization assay (Abbott). Polymerase chain reaction was used to detect HCV genomic RNA to confirm viremia. Among 11.243 volunteer donors who were screened for the presence of antibodies to HCV by enzyme-linked immunoassay, 60 (0.53%) sera were repeatedly reactive. Twenty-five of these 60 sera were available for further testing. Seven sera were reactive by both screening enzyme-linked immunoassays, as well as by both recombinant immunoblot and neutralization assays. Six of these seven sera had detectable HCV genomic RNA by polymerase chain reaction. Among the remaining 18 sera, none were reactive by either recombinant immunoblot assays, whereas two sera were reactive by the neutralization assay only. None of the 18 samples had detectable HCV genomic RNA. Five of the six sera with elevated aminotransferase levels were among the seven sera reactive by all immunoassays. It is concluded that there is a significant false positivity rate associated with screening enzyme-linked immunoassay testing in a low-risk blood donor population. Supplemental testing correlates well with detection of hepatitis C genomic material by polymerase chain reaction and identifies donors who are truly infected.

    View details for Web of Science ID A1991GT00700035

    View details for PubMedID 1720106

  • MODIFIED WESTERN-BLOT ASSAY FOR CONFIRMATION AND DIFFERENTIATION OF HUMAN T-CELL LYMPHOTROPIC VIRUS TYPE-I AND TYPE-II JOURNAL OF INFECTIOUS DISEASES LIPKA, J. J., Santiago, P., Chan, L., Reyes, G. R., Samuel, K. P., Blattner, W. A., Shaw, G. M., Hanson, C. V., Sninsky, J. J., Foung, S. K. 1991; 164 (2): 400-403

    Abstract

    Disease association studies of human T cell lymphotropic virus (HTLV) types I and II are hindered by the need for multiple assays to confirm and differentiate between the viruses. A modified Western blot assay has been developed using HTLV-I viral lysate and unique (MTA-4) and shared (p21E) HTLV recombinant proteins. By defining confirmation of infection as the presence of antibodies to p24 gag protein and to p21E, all 56 HTLV-I and 49 HTLV-II antisera were confirmed by this modified Western blot alone. Differentiation was determined by reactivity to MTA-4. All HTLV-I antisera reacted with MTA-4 and all HTLV-II antisera did not react with MTA-4. These findings indicate the utility of selected HTLV-I recombinant proteins in a single assay format to confirm and differentiate infections with HTLV-I and HTLV-II.

    View details for PubMedID 1856487

  • Parameters to enhance human hybridoma formation with hypoosmolar electrofusion. Human antibodies and hybridomas Perkins, S., Zimmermann, U., FOUNG, S. K. 1991; 2 (3): 155-159

    Abstract

    Hypoosmolar conditions have permitted the development of electrofusion techniques capable of producing human hybridomas from as few as 10(5) B cells. A hybridoma formation efficiency of one hybrid for each 125 input B cells has been achieved with Epstein-Barr virus--activated B cells and mouse-human heteromyelomas. This is at least 100-fold higher in efficiency than with polyethylene glycol-induced cell fusion, as well as a 50- to 100-fold decrease in the required number of human B cells. The ability to fuse a small number of input B cells should lead to a greater success rate in immortalizing the rare antigen-specific B cells. The critical parameters include fusion voltages, the composition and number of wash steps used in cell preparation, the composition and duration of exposure to hypoosmolar fusion medium, fusion ratio, plating density, the use of growth medium without pH indicator, and the use of an irradiated human fibroblast feeder layer. By manipulating these parameters, a high hybrid yield can be achieved with different mouse-human heteromyelomas and Epstein-Barr virus-activated B cells.

    View details for PubMedID 1651789

  • HTLV-I-ASSOCIATED MYELOPATHY IN A CALIFORNIAN - DIAGNOSIS BY REACTIVITY TO A VIRAL RECOMBINANT ANTIGEN NEUROLOGY Honig, L. S., LIPKA, J. J., Young, K. Y., Weiss, J. H., Foung, S. K. 1991; 41 (3): 448-450

    Abstract

    A male patient developed leg numbness and weakness, and bowel, bladder, and erectile dysfunction. Examination revealed an isolated thoracic myelopathy, with lower-extremity spasticity, decreased vibration and position sense, hyperreflexia, and Babinski's signs. Serum and CSF showed antibody reactivity to human T-cell lymphotropic virus type I or II (HTLV-I/II), suggesting HTLV-I-associated myelopathy. Antibody reactivity to a unique HTLV-I recombinant protein provided definitive diagnosis of HTLV-I infection.

    View details for Web of Science ID A1991FD56600028

    View details for PubMedID 1706492

  • SIGNIFICANCE OF HUMAN T-LYMPHOTROPIC VIRUS TYPE-I INDETERMINANT SEROLOGICAL FINDINGS AMONG HEALTHY-INDIVIDUALS VOX SANGUINIS LIPKA, J. J., Young, K. K., Kwok, S. Y., Reyes, G. R., Sninsky, J. J., Foung, S. K. 1991; 61 (3): 171-176

    Abstract

    Follow-up studies on 67 blood donors with indeterminant serological findings for human T-lymphotropic virus (HTLV) type I by standard immunoassays showed no evidence of infection by polymerase chain reaction analysis for HTLV-I or HTLV-II nucleic acids or by antibody reactivity to a unique HTLV-I recombinant envelope protein, MTA-4. Among HTLV-I- or -II-infected individuals, a history of blood transfusion, past residence in established HTLV-I endemic areas or some association with intravenous drug use were common. In contrast, 85% of indeterminant cases had none of these risk factors. These observations suggest that healthy individuals with indeterminant serology for HTLV-I should not require additional studies.

    View details for Web of Science ID A1991GR19300003

    View details for PubMedID 1725466

  • DEVELOPMENT OF MICROFUSION TECHNIQUES TO GENERATE HUMAN HYBRIDOMAS JOURNAL OF IMMUNOLOGICAL METHODS Foung, S., Perkins, S., Kafadar, K., Gessner, P., Zimmermann, U. 1990; 134 (1): 35-42

    Abstract

    The rarity of antigen-specific B cells in peripheral blood and lymphoid tissues is a major limitation in the production of human monoclonal antibodies. This has led to a requirement for techniques capable of fusing small numbers of cells and achieving a higher hybridoma formation efficiency than currently is possible. The approach used in these studies to generate human hybridomas is based on the observation that under hypo-osmolar conditions electric field induced cell fusion or electrofusion is facilitated. Electrofusion parameters have been defined in strongly hypo-osmolar solutions which have resulted in a hybridoma formation efficiency greater than 5 X 10(-3) under optimal conditions. Furthermore, this has been accomplished with total input B cells of 1-2 X 10(5). This is a ten-fold reduction in the required number of input B cells and is associated with a hybridoma formation efficiency at least equal to that achieved with a higher input B cell number. An important factor in the development of this microfusion technique appears to be the duration of exposure to the hypo-osmolar solution by B cells to be immortalized. Other parameters which may affect hybridoma yield include the electrical field strength used for cell alignment and membrane breakdown, ratio of human B cells to fusion partner, washing procedure, post-fusion incubation time, and the elimination of toxic molecules.

    View details for Web of Science ID A1990EG52200003

    View details for PubMedID 2172386

  • EFFICIENT HYBRIDIZATION OF MOUSE-HUMAN CELL-LINES BY MEANS OF HYPOOSMOLAR ELECTROFUSION JOURNAL OF IMMUNOLOGICAL METHODS Zimmermann, U., Gessner, P., Schnettler, R., Perkins, S., Foung, S. K. 1990; 134 (1): 43-50

    Abstract

    The fusion of a mouse-human heteromyeloma with a mouse hybridoma is used as a model to define parameters to generate human hybridomas. Electrofusion of these cells in 300 mosM and 75 mosM solutions showed that strong hypo-osmolar conditions resulted in a dramatic increase in the efficiency of hybridoma formation. In contrast to iso-osmolar electrofusion, a high hybrid yield could be obtained by injection of only a single field pulse. The field strength was adjusted in proportion to the increased size of the cells in hypo-osmolar solutions. Hypo-osmolar electrofusion allowed the generation of approximately 0.45% hybrids at a suspension density of 1.75 X 10(5) mouse-human cells/ml corresponding to an input number of 3.5 X 10(4) mouse-human cells. A further increase in the efficiency of hybridoma formation to about 0.6% was achieved by cell alignment in an alternating field of modulated field strength. Experiments in which the total cell number per fusion chamber was decreased at constant optimum suspension density showed that a further increase in the efficiency of hybridoma formation in hypo-osmolar solution was not possible because of the increasing influence of the heterogeneity of the cell lines with decreasing cell number. The results allow the conclusion that hypo-osmolar electrofusion is a potential tool to enhance successful immortalisation of human B lymphocytes.

    View details for Web of Science ID A1990EG52200004

    View details for PubMedID 2230148

  • DETERMINATION OF A UNIQUE AND IMMUNODOMINANT EPITOPE OF HUMAN T-CELL LYMPHOTROPIC VIRUS TYPE-I JOURNAL OF INFECTIOUS DISEASES LIPKA, J. J., Bui, K., Reyes, G. R., Moeckli, R., Wiktor, S. Z., Blattner, W. A., Murphy, E. L., Shaw, G. M., Hanson, C. V., Sninsky, J. J., Foung, S. K. 1990; 162 (2): 353-357

    Abstract

    The identification and isolation of unique and immunogenic recombinant epitopes for human T cell lymphotrophic virus (HTLV) type I might allow the development of an antibody-based assay to differentiate between HTLV-I and HTLV-II infections. To test the feasibility of this approach, an HTLV-I envelope epitope was isolated by immunoscreening of a lambda gt11 recombinant HTLV-I DNA library with a human monoclonal antibody to HTLV-I. This recombinant epitope. MTA-4, when tested with sera from HTLV-I- or HTLV-II-infected individuals, was reactive with all HTLV-I and nonreactive with all HTLV-II antisera. These results indicate that MTA-4 is a unique and immunodominant epitope on HTLV-I and confirm the usefulness of human-derived monoclonal antibodies in an experimental approach to dissect the human humoral response to a viral pathogen.

    View details for Web of Science ID A1990DQ92600009

    View details for PubMedID 1695653

  • LOW INCIDENCE OF HTLV INFECTIONS IN RANDOM BLOOD-DONORS WITH INDETERMINATE WESTERN-BLOT PATTERNS TRANSFUSION Kwok, S., LIPKA, J. J., McKinney, N., KELLOGG, D. E., Poiesz, B., Foung, S. K., Sninsky, J. J. 1990; 30 (6): 491-494

    Abstract

    Peripheral blood mononuclear cells (PBMCs) were recovered from platelet units of 61 blood donors who were HTLV-I positive and 3 blood donors who were HTLV-I negative on enzyme-linked immunosorbent assay (ELISA). Western blot analyses were performed on the sera and DNA was prepared from the PBMCs and analyzed by the polymerase chain reaction (PCR). Of the 61 repeatably reactive samples, 2 were positive, 26 were negative, and 33 were interpreted as indeterminate on Western blot. HTLV-II sequences were detected by PCR in one of the Western blot-positive samples, as well as in one Western blot-indeterminate sample that showed reactivity to p24 only. HTLV-I sequences were detected in the second Western blot-positive sample. HTLV sequences were not detected in the remaining samples, which suggested that the majority of individuals with indeterminate results on Western blots that used one set of commercially available reagents are not infected with HTLV. It is demonstrated in this study that PCR can be used not only to resolve the infection status of individuals with indeterminate Western blots but also to distinguish between HTLV-I and HTLV-II.

    View details for Web of Science ID A1990DR32700004

    View details for PubMedID 1974089

  • GENERATION OF A HUMAN HYBRIDOMA PRODUCING A PURE ANTI-HLA-A2 MONOCLONAL-ANTIBODY HUMAN IMMUNOLOGY WALLACE, E. F., Foung, S. K., Bradbury, K., PASK, S. L., GRUMET, F. C. 1990; 28 (1): 65-69

    Abstract

    We report the production and characterization of a human monoclonal IgM hybridoma antibody recognizing antigen HLA-A2. B lymphocytes obtained from the peripheral blood of a multiparous volunteer 1 week postpartum were transformed in vitro by Epstein-Barr virus, screened by a microlymphocytotoxicity assay, and electrofused with the heterohybridoma fusion partner, K6H6/B5. A specifically anti-A2 secreting hybridoma cell line. MBW1, was then identified and cloned. The cytotoxic IgM antibody produced showed complete correlation (r = 1.00) with the A2 antigen on a large panel of unrelated donors' lymphocytes, and no cross-reactivity with A28, Aw68, or Aw69 antigens was observed.

    View details for Web of Science ID A1990CZ82300007

    View details for PubMedID 2160447

  • ENHANCING THE SENSITIVITY OF HTLV-I IMMUNOASSAYS CONF ON HUMAN RETROVIROLOGY : HTLV ( HUMAN T-CELL LYMPHOTROPHIC VIRUS ) LIPKA, J. J., Parker, J. L., Foung, S. K. RAVEN PRESS. 1990: 409–417
  • HUMAN MONOCLONAL-ANTIBODIES TO HUMAN CYTOMEGALO-VIRUS JOURNAL OF INFECTIOUS DISEASES Foung, S. K., Perkins, S., Bradshaw, P., Rowe, J., RABIN, L. B., Reyes, G. R., Lennette, E. T. 1989; 159 (3): 436-443

    Abstract

    Human monoclonal antibodies (HMAbs) to human cytomegalovirus (HCMV) have been developed by using electric field-induced cell fusion of human B lymphocytes to the human-mouse cell line SBC-H20. By this procedure, multiple hybridomas have been produced that secrete IgG 1 HMAbs with distinct patterns of indirect immunofluorescence on HCMV-infected cells. HMAbs Z01 and X20 immunoprecipitated a major protein at 64 kDa. HMAb Z02 immunoprecipitated a major protein of 48-50 kDa. HMAb Z10 identified a single protein at 65 kDa and HMAb X16 identified proteins at 100, 65, and 36-38 kDa. The HMAbs demonstrated varying degrees of virus-neutralizing activity. The production of HMAbs to HCMV provides an important approach to studying the human host response to HCMV by elucidating biologically relevant antigens and epitopes. In addition, HMAbs are a potentially unlimited source of relevant human antibodies for treating life-threatening HCMV infection.

    View details for Web of Science ID A1989T266800011

    View details for PubMedID 2536787

  • ELECTRIC FIELD-INDUCED CELL-FUSION AND HUMAN MONOCLONAL-ANTIBODIES JOURNAL OF IMMUNOLOGICAL METHODS Foung, S. K., Perkins, S. 1989; 116 (1): 117-122

    Abstract

    A persistent problem in the generation of antigen-specific human monoclonal antibodies is the rarity of appropriate B cells in human blood or splenic tissues. In order to immortalize the rare antigen-specific cells that are available, an electric field-induced cell fusion technique has been shown to markedly increase the fusion efficiency in comparison to polyethylene glycol-induced cell fusion using Epstein-Barr virus (EBV) or pokeweed mitogen activated B cells. Fusion efficiency of 10(-3)-10(-4) has been achieved by this process with as low as 1 X 10(6) input EBV-activated B cells. A panel of human monoclonal antibodies to human cytomegalovirus has subsequently been produced using this technique. This improvement should enable wider therapeutic and diagnostic applications of human monoclonal antibodies.

    View details for Web of Science ID A1989R695200014

    View details for PubMedID 2536773

  • INITIAL IDENTIFICATION AND MAPPING OF DISTINCT RH0 (D) EPITOPES REVUE FRANCAISE DE TRANSFUSION ET IMMUNO-HEMATOLOGIE Rodriguez, L., WINN, L., Foung, S. K. 1988; 31 (2): 223-231

    View details for Web of Science ID A1988T651900013

    View details for PubMedID 2463657

  • THE EFFICACY OF PLA1-NEGATIVE PLATELET TRANSFUSION THERAPY IN POSTTRANSFUSION PURPURA WESTERN JOURNAL OF MEDICINE Lippman, S. M., LIZAK, G. E., Foung, S. K., GRUMET, F. C. 1988; 148 (1): 86-88

    View details for Web of Science ID A1988L724600026

    View details for PubMedID 3341139

    View details for PubMedCentralID PMC1026031

  • CYTOMEGALO-VIRUS ANTIGENS IDENTIFIED BY HUMAN MONOCLONAL-ANTIBODIES BRADSHAW, P. A., Perkins, S., Lennette, E., HAYES, C. F., Foung, S. K. ELSEVIER SCIENCE BV. 1988: 158–58
  • HUMAN MONOCLONAL-ANTIBODIES TO RH0(D) VOX SANGUINIS Foung, S. K., Blunt, J. A., Wu, P. S., AHEARN, P., WINN, L. C., Engleman, E. G., GRUMET, F. C. 1987; 53 (1): 44-47

    Abstract

    B lymphocytes from Rh negative donors with serum anti-D antibodies were isolated and fused with the mouse-human heteromyeloma, SBC-H20, to produce hybridomas secreting IgM or IgG1 human monoclonal antibodies to D antigen. The IgM antibody in hybridoma supernatant agglutinates all normal D positive cells at the immediate spin phase of reactivity. Using concentrated IgM hybridoma supernatant of approximately 50 micrograms/ml, Du cells were also agglutinated. The IgG1 antibody reacts by indirect hemagglutination with all D and Du cells. Against Rh mosaics, different reactivity was noted for each antibody. Furthermore, D positive cells precoated with the IgG1 antibody inhibit the IgM direct hemagglutination, suggesting that the antibodies identify closely associated epitopes. These human monoclonal antibodies will be useful diagnostic reagents and, ultimately, should be useful in the prevention of Rh hemolytic disease of the newborn.

    View details for Web of Science ID A1987J436100009

    View details for PubMedID 3116771

  • HUMAN MONOCLONAL ANTI-T-CELL ANTIBODY FROM A PATIENT WITH JUVENILE RHEUMATOID-ARTHRITIS JOURNAL OF IMMUNOLOGY ALPERT, S. D., Turek, P. J., Foung, S. K., Engleman, E. G. 1987; 138 (1): 104-108

    Abstract

    Antibody JRAI is a human monoclonal IgM antibody derived from a patient with juvenile rheumatoid arthritis that is cytotoxic to a subpopulation of normal T lymphocytes. JRAI recognizes approximately 80% of normal peripheral blood T cells, 90% of CD4+ cells, and 75% of CD8+ cells, as determined by complement-mediated cytotoxicity. Within the CD8+ population, JRAI preferentially spares OKM1+ and Leu-11+ cells. These CD8+ cells retain suppressor-effector potential and show enriched natural killer cell activity. Within the CD4+ population, JRAI preferentially kills cells within the Leu-8+ subset, which contains suppressor-inducer cells, and spares the Leu-8- subset, which contains the helpers for immunoglobulin synthesis. JRAI appears to recognize a previously undefined human lymphocyte surface molecule expressed differentially on phenotypically and functionally distinct subsets of human T cells.

    View details for Web of Science ID A1987F377900018

    View details for PubMedID 3097140

  • EARLY IMMUNE-RESPONSE IN HEALTHY AND IMMUNOCOMPROMISED SUBJECTS WITH PRIMARY VARICELLA-ZOSTER VIRUS-INFECTION JOURNAL OF INFECTIOUS DISEASES Arvin, A. M., Koropchak, C. M., Williams, B. R., GRUMET, F. C., Foung, S. K. 1986; 154 (3): 422-429

    Abstract

    Events in pathogenesis and immunity during primary varicella-zoster virus (VZV) infection were examined in 64 healthy subjects and 21 immunocompromised patients. Activation of the interferon system and activation of circulating T lymphocytes were early immune responses that occurred during the incubation period in some healthy subjects. Elevated levels of 2-5A synthetase in peripheral blood mononuclear cells and detection of serum alpha interferon (IFN-alpha) and gamma interferon (IFN-gamma) were present in the majority of healthy subjects who had acute primary VZV infection. Expression of HLA-DR antigen occurred on circulating T lymphocytes from subjects with acute VZV infection. The early production of VZV-specific IgG or IgM antibodies did not correlate with the severity of the clinical infection, but the detection of T lymphocyte proliferation to VZV antigen within three days after the appearance of the varicella exanthem was associated with milder illness. The mean VZV-specific lymphocyte transformation for subjects with less than 100 lesions/m2 was 7.5 +/- 10.43 SD compared with 1.4 +/- 1.85 SD for those with greater than 400 lesions/m2 (P less than .05). Only one (7.7%) of 13 immunocompromised patients had early VZV-specific lymphocyte transformation compared with 19 (42%) of 45 healthy subjects (P less than .05). The rapid host response to primary VZV infection was associated with rapid termination of viremia in healthy subjects; VZV was isolated from only 11% of peripheral blood mononuclear cell samples cultured within 48 hr after the appearance of the exanthem.

    View details for Web of Science ID A1986D760000006

    View details for PubMedID 3016110

  • A MONOCLONAL-ANTIBODY AGAINST HLA-A11 AND A24 HUMAN IMMUNOLOGY Foung, S. K., Taidi, B., Ness, D., GRUMET, F. C. 1986; 15 (3): 316-319

    Abstract

    A monoclonal IgG antibody was produced from a mouse immunized with an A11, A24; B27, B44 Epstein-Barr virus transformed B lymphoblastoid cell line. The antibody, A11.1M, by standard lymphocytotoxicity assay, reacts with all cells expressing HLA-A11 and -A24. Absorption studies with both A11+, A24- and A11-, A24+ platelets removed antibody reactivity against A11 and A24 lymphocytes. The shared antigenic determinant between A11 and A24, as defined by this antibody, A11.1M, represents a new "supertypic" determinant.

    View details for Web of Science ID A1986A381800006

    View details for PubMedID 2420768

  • A HUMAN MONOCLONAL-ANTIBODY TO RHG VOX SANGUINIS Foung, S. K., Blunt, J., Perkins, S., WINN, L., GRUMET, F. C. 1986; 50 (3): 160-163

    Abstract

    Hybridomas secreting a human monoclonal IgG1 antibody against a variant of the rhG antigen were produced from B lymphocytes of an Rh-negative donor with serum antibodies to D and G [correction of C] antigens. The antibody reacts by indirect hemagglutination with nearly all C- or D-positive cells, confirming the strong association in the expression of G with D or C antigens. The lack of antibody reactivity to C-negative Du cells suggests a particular epitope on the D complex associated with the G antigen.

    View details for Web of Science ID A1986A969300008

    View details for PubMedID 2424176

  • GENERATION OF HUMAN MONOCLONAL-ANTIBODIES BY FUSION OF EBV-ACTIVATED B-CELLS TO A HUMAN MOUSE HYBRIDOMA METHODS IN ENZYMOLOGY Foung, S. K., Engleman, E. G., GRUMET, F. C. 1986; 121: 168-174

    View details for Web of Science ID A1986D161200013

    View details for PubMedID 3014266

  • PRODUCTION OF HUMAN-ANTIBODIES TO MYCOBACTERIUM-LEPRAE Mohagheghpour, N., Cho, S. N., Gelber, R. H., Foung, S. K., Engleman, E. G. AMER LEPROSY MISSION. 1985: 717–18
  • HUMAN MONOCLONAL-ANTIBODIES NEUTRALIZING VARICELLA-ZOSTER VIRUS JOURNAL OF INFECTIOUS DISEASES Foung, S. K., Perkins, S., KOROPCHAK, C., Fishwild, D. M., Wittek, A. E., Engleman, E. G., GRUMET, F. C., Arvin, A. M. 1985; 152 (2): 280-285

    Abstract

    Hybridomas secreting human monoclonal antibodies to varicella-zoster virus were produced by fusing B cells of a patient recovering from acute varicella infection with a human-mouse cell line. Two hybrid lines have continued to secrete IgG1, one with kappa and the other with lambda chains, for at least 12 months. Each antibody neutralizes virus infectivity between 1-5 micrograms of partially purified immunoglobulin/ml, each shows a different pattern of immunofluorescent staining of virus-infected cells, and one identifies three viral proteins with molecular weights of 60,000, 95,000, and 97,000.

    View details for Web of Science ID A1985AQZ7900006

    View details for PubMedID 2993433

  • PRODUCTION OF HUMAN MONOCLONAL-ANTIBODIES TO MYCOBACTERIUM-LEPRAE MOHAGHEGHPOUR, N., FOUNG, S. K., GELBER, R. H., BRENNAN, P. J., ENGLEMAN, E. G. AMER LEPROSY MISSION. 1985: 178
  • CONSTITUTIVE PRODUCTION OF B-CELL GROWTH-FACTOR BY HUMAN T-T HYBRIDS DERIVED FROM HELPER T-CELL CLONES Trail, P. A., Foung, S. K., Choi, Y. S. FEDERATION AMER SOC EXP BIOL. 1985: 1288–88
  • HUMAN MONOCLONAL-ANTIBODIES AGAINST GROUP-A RED BLOOD-CELLS VOX SANGUINIS Raubitschek, A., SENYK, G., LARRICK, J., LIZAK, G., Foung, S. 1985; 48 (5): 305-308

    Abstract

    A human monoclonal antibody with anti-A specificity was generated by Epstein-Barr virus transformation of lymphocytes isolated from splenic tissue after in vitro stimulation with group A red blood cells. This antibody is of the IgM class and directly agglutinates group A red blood cells. Type A1, A2, Aint, A3, AX, Aend and A5 cells were agglutinated by the reagent indicating a single determinant is shared by these A subgroups.

    View details for Web of Science ID A1985AFM5900006

    View details for PubMedID 2986353

  • A NEW APPROACH TO THE DIAGNOSIS OF ACTIVE RH0(D) IMMUNIZATION IN PASSIVELY IMMUNIZED PREGNANT-WOMEN VOX SANGUINIS Foung, S. K., Perkins, S., MCCALLUM, W. D., Tom, S., Engleman, E. G., GRUMET, F. C. 1985; 49 (3): 206-210

    Abstract

    An assay has been developed to distinguish active from passive Rh0(D) immunization in a patient who had recently received hyperimmune anti-Rh0(D) immunoglobulin therapy. Isolated peripheral B lymphocytes from a pregnant woman at 32 weeks gestation were co-cultured with Epstein-Barr virus in a liquid growth medium. After 7 days, anti-Rh0(D) antibodies produced in vitro by the transformed lymphocytes were detected in culture supernatants, thereby proving active immunization and indicating the potential of hemolytic disease of the newborn in the current pregnancy. This assay was also performed with peripheral B lymphocytes from three groups of individuals: mothers known to be Rh0(D) immunized and who recently delivered Rh-positive infants, women with longstanding Rh0(D) immunization, and women who were treated with anti-Rh0(D) globulin. In the first group, anti-Rh0(D) antibodies were again detected after in vitro viral stimulation. In the latter two groups, essentially no anti-Rh0(D) activity was detected.

    View details for Web of Science ID A1985APS1800005

    View details for PubMedID 2996227

  • RESCUE OF HUMAN MONOCLONAL-ANTIBODY PRODUCTION FROM AN EBV-TRANSFORMED B-CELL LINE BY FUSION TO A HUMAN-MOUSE HYBRIDOMA JOURNAL OF IMMUNOLOGICAL METHODS Foung, S. K., Perkins, S., Raubitschek, A., LARRICK, J., LIZAK, G., Fishwild, D., Engleman, E. G., GRUMET, F. C. 1984; 70 (1): 83-90

    Abstract

    A human-mouse cell line that is hypoxanthine-aminopterin-thymidine sensitive and ouabain resistant was derived from a fusion between human B lymphocytes and a mouse myeloma line. This new mutant, when fused to a relatively unstable EBV-transformed B cell secreting a human monoclonal anti-A (red blood cell antigen) antibody, resulted in stable hybridomas capable of long term production of the specific human monoclonal antibody. Furthermore, some of the hybrid clones secreted antibody in far greater titer than the original EBV cell line. We conclude that fusion to this human-mouse line is an efficient approach to the production of human monoclonal alloantibodies and an effective method of 'rescuing' secretion of desired antibody from EBV cell lines.

    View details for Web of Science ID A1984SR32200010

    View details for PubMedID 6201562

  • GRANULOCYTE DIFFERENTIATION FACTOR PRODUCTION BY HUMAN MARROW AND BLOOD-CELLS GREENBERG, P. L., BAKER, S. J., FOK, W. Y., FOUNG, S. K., ENGLEMAN, E. G. CARDEN JENNINGS PUBL CO LTD. 1984: 370
  • ANALYSIS OF VARICELLA-ZOSTER VIRUS WITH HUMAN MONOCLONAL-ANTIBODIES Foung, S. K., Engleman, E. G., Perkins, S., KORAPCHAK, C., GRUMET, F. C., Arvin, A. SLACK INC. 1984: A513–A513
  • MONOCLONAL-ANTIBODY (B27M2) SUBDIVIDING HLA-B27 HUMAN IMMUNOLOGY GRUMET, F. C., Fendly, B. M., Fish, L., Foung, S., Engleman, E. G. 1982; 5 (1): 61-72

    View details for Web of Science ID A1982PH53300005

    View details for PubMedID 6981637

  • PRODUCTION AND CHARACTERIZATION OF HUMAN T-CELL HYBRIDS PRODUCING INTELEUKIN-2 AND INTERFERON FOUNG, S. K., SASAKI, D., ENGLEMAN, E. G. SLACK INC. 1982: A348
  • SUBDIVISION OF B27 BY USE OF A LYMPHOCYTOTOXIC MONOCLONAL-ANTIBODY, B27M2 GRUMET, F. C., FISH, L., FENDLY, B. M., FOUNG, S., ENGLEMAN, E. G. ELSEVIER SCIENCE INC. 1982: 153
  • PRODUCTION OF FUNCTIONAL HUMAN T-T-HYBRIDOMAS IN SELECTION MEDIUM LACKING AMINOPTERIN AND THYMIDINE PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA-BIOLOGICAL SCIENCES Foung, S. K., Sasaki, D. T., GRUMET, F. C., Engleman, E. G. 1982; 79 (23): 7484-7488

    Abstract

    The production of hybridomas between immunologically activated T cells and malignant T-cell lines offers a potentially unlimited source of soluble T-cell-derived products. Recently, human T-T hybrids have been described; however, their use has been hampered by slow growth and chromosomal instability due at least in part to the presence of thymidine in the traditional hypoxanthine/aminopterin/thymidine (HAT) selection medium. In this report, we describe the development of a rapidly growing hypoxanthine phosphoribosyltransferase-deficient human T-cell line designated J3R7, the use of azaserine/hypoxanthine (AH) medium as an alternative selection medium to HAT medium, and the production of functional T-T hybrids by using the J3R7 line and the AH selection technique. Hybrids selected in AH medium were 4-fold greater in number and 3-fold faster in growth rate than hybrids grown in HAT medium. No stable clones were obtained from HAT cultures whereas AH-derived hybrids could be readily cloned by the method of limiting dilution. Evidence for hybridization included (i) the presence of approximately twice the number of chromosomes in hybrids than in J3R7 cells; (ii) the presence on hybrid cells of the Leu-3a surface antigen, present on normal helper T cells but not on J3R7 cells; (iii) the expression of HLA antigens of both the normal T-cell partner and the J3R7 line; and (iv) the constitutive secretion of interleukin 2 from multiple hybrid clones but not from the J3R7 cell line. Thus far, these clones have maintained their rapid growth, chromosome number, surface phenotype, and constitutive secretion of interleukin 2 for 4 months.

    View details for Web of Science ID A1982PT40700084

    View details for PubMedID 6984190

    View details for PubMedCentralID PMC347364

  • EOSINOPHILIA IN CHILDREN PEDIATRIC ANNALS Foung, S., Glader, B. E. 1979; 8 (6): 39-?

    View details for Web of Science ID A1979GY10400003

    View details for PubMedID 471550

  • EFFECTS OF STARVATION AND REFEEDING ON MUSCLE PROTEIN-SYNTHESIS AND CATABOLISM IN YOUNG RAT JOURNAL OF NUTRITION Ogata, E. S., Foung, S. K., Holliday, M. A. 1978; 108 (5): 759-765

    Abstract

    We studied the effects of acute starvation and refeeding on muscle protein synthesis and degradation in young rats. As measures of synthesis, we determined muscle RNA concentration and the rate of incorporation of [14C]leucine into skeletal muscle protein (Sm). As an estimate of nitrogen retention we measured urea production (UrP). Starvation reduced these variables significantly. One refeeding period returned Sm to control values, only partially restored RNA concentration, and increased UrP. We determined the urinary excretion rate of 3-methylhistidine (3-MH) as a measure of the rate of myofibrillar protein degradation. Excretion of 3-MH was lowest in control and highest in starved rats. Refeeding decreased 3-MH excretion to a level midway between control and starved animals. Growth was attended by high rates of synthesis and low rates of degradation. Starvation depressed synthesis and increased degradation. With refeeding, synthesis increased and degradation decreased, compared with the starved state.

    View details for Web of Science ID A1978EZ25200005

    View details for PubMedID 641592