Education & Certifications

  • Bachelor of Science, Westmont College, Biology, Chemistry, Music (2016)
  • Doctor of Philosophy, Stanford University, IMMUN-PHD (2022)

All Publications

  • Pro-inflammatory feedback loops define immune responses to pathogenic Lentivirus infection. Genome medicine Wilk, A. J., Marceau, J. O., Kazer, S. W., Fleming, I., Miao, V. N., Galvez-Reyes, J., Kimata, J. T., Shalek, A. K., Holmes, S., Overbaugh, J., Blish, C. A. 2024; 16 (1): 24


    BACKGROUND: The Lentivirus human immunodeficiency virus (HIV) causes chronic inflammation and AIDS in humans, with variable rates of disease progression between individuals driven by both host and viral factors. Similarly, simian lentiviruses vary in their pathogenicity based on characteristics of both the host species and the virus strain, yet the immune underpinnings that drive differential Lentivirus pathogenicity remain incompletely understood.METHODS: We profile immune responses in a unique model of differential lentiviral pathogenicity where pig-tailed macaques are infected with highly genetically similar variants of SIV that differ in virulence. We apply longitudinal single-cell transcriptomics to this cohort, along with single-cell resolution cell-cell communication techniques, to understand the immune mechanisms underlying lentiviral pathogenicity.RESULTS: Compared to a minimally pathogenic lentiviral variant, infection with a highly pathogenic variant results in a more delayed, broad, and sustained activation of inflammatory pathways, including an extensive global interferon signature. Conversely, individual cells infected with highly pathogenic Lentivirus upregulated fewer interferon-stimulated genes at a lower magnitude, indicating that highly pathogenic Lentivirus has evolved to partially escape from interferon responses. Further, we identify CXCL10 and CXCL16 as important molecular drivers of inflammatory pathways specifically in response to highly pathogenic Lentivirus infection. Immune responses to highly pathogenic Lentivirus infection are characterized by amplifying regulatory circuits of pro-inflammatory cytokines with dense longitudinal connectivity.CONCLUSIONS: Our work presents a model of lentiviral pathogenicity where failures in early viral control mechanisms lead to delayed, sustained, and amplifying pro-inflammatory circuits, which in turn drives disease progression.

    View details for DOI 10.1186/s13073-024-01290-y

    View details for PubMedID 38317183

  • Comparative analysis of cell-cell communication at single-cell resolution. Nature biotechnology Wilk, A. J., Shalek, A. K., Holmes, S., Blish, C. A. 2023


    Inference of cell-cell communication from single-cell RNA sequencing data is a powerful technique to uncover intercellular communication pathways, yet existing methods perform this analysis at the level of the cell type or cluster, discarding single-cell-level information. Here we present Scriabin, a flexible and scalable framework for comparative analysis of cell-cell communication at single-cell resolution that is performed without cell aggregation or downsampling. We use multiple published atlas-scale datasets, genetic perturbation screens and direct experimental validation to show that Scriabin accurately recovers expected cell-cell communication edges and identifies communication networks that can be obscured by agglomerative methods. Additionally, we use spatial transcriptomic data to show that Scriabin can uncover spatial features of interaction from dissociated data alone. Finally, we demonstrate applications to longitudinal datasets to follow communication pathways operating between timepoints. Our approach represents a broadly applicable strategy to reveal the full structure of niche-phenotype relationships in health and disease.

    View details for DOI 10.1038/s41587-023-01782-z

    View details for PubMedID 37169965

    View details for PubMedCentralID 8104132

  • Multi-omic profiling reveals widespread dysregulation of innate immunity and hematopoiesis in COVID-19. The Journal of experimental medicine Wilk, A. J., Lee, M. J., Wei, B., Parks, B., Pi, R., Martinez-Colon, G. J., Ranganath, T., Zhao, N. Q., Taylor, S., Becker, W., Stanford COVID-19 Biobank, Jimenez-Morales, D., Blomkalns, A. L., O'Hara, R., Ashley, E. A., Nadeau, K. C., Yang, S., Holmes, S., Rabinovitch, M., Rogers, A. J., Greenleaf, W. J., Blish, C. A. 2021; 218 (8)


    Our understanding of protective versus pathological immune responses to SARS-CoV-2, the virus that causes coronavirus disease 2019 (COVID-19), is limited by inadequate profiling of patients at the extremes of the disease severity spectrum. Here, we performed multi-omic single-cell immune profiling of 64 COVID-19 patients across the full range of disease severity, from outpatients with mild disease to fatal cases. Our transcriptomic, epigenomic, and proteomic analyses revealed widespread dysfunction of peripheral innate immunity in severe and fatal COVID-19, including prominent hyperactivation signatures in neutrophils and NK cells. We also identified chromatin accessibility changes at NF-kappaB binding sites within cytokine gene loci as a potential mechanism for the striking lack of pro-inflammatory cytokine production observed in monocytes in severe and fatal COVID-19. We further demonstrated that emergency myelopoiesis is a prominent feature of fatal COVID-19. Collectively, our results reveal disease severity-associated immune phenotypes in COVID-19 and identify pathogenesis-associated pathways that are potential targets for therapeutic intervention.

    View details for DOI 10.1084/jem.20210582

    View details for PubMedID 34128959

  • A single-cell atlas of the peripheral immune response in patients with severe COVID-19. Nature medicine Wilk, A. J., Rustagi, A., Zhao, N. Q., Roque, J., Martinez-Colon, G. J., McKechnie, J. L., Ivison, G. T., Ranganath, T., Vergara, R., Hollis, T., Simpson, L. J., Grant, P., Subramanian, A., Rogers, A. J., Blish, C. A. 2020


    There is an urgent need to better understand the pathophysiology of Coronavirus disease 2019 (COVID-19), the global pandemic caused by SARS-CoV-2, which has infected more than three million people worldwide1. Approximately 20% of patients with COVID-19 develop severe disease and 5% of patients require intensive care2. Severe disease has been associated with changes in peripheral immune activity, including increased levels of pro-inflammatory cytokines3,4 that may be produced by a subset of inflammatory monocytes5,6, lymphopenia7,8 and T cell exhaustion9,10. To elucidate pathways in peripheral immune cells that might lead to immunopathology or protective immunity in severe COVID-19, we applied single-cell RNA sequencing (scRNA-seq) to profile peripheral blood mononuclear cells (PBMCs) from seven patients hospitalized for COVID-19, four of whom had acute respiratory distress syndrome, and six healthy controls. We identify reconfiguration of peripheral immune cell phenotype in COVID-19, including a heterogeneous interferon-stimulated gene signature, HLA class II downregulation and a developing neutrophil population that appears closely related to plasmablasts appearing in patients with acute respiratory failure requiring mechanical ventilation. Importantly, we found that peripheral monocytes and lymphocytes do not express substantial amounts of pro-inflammatory cytokines. Collectively, we provide a cell atlas of the peripheral immune response to severe COVID-19.

    View details for DOI 10.1038/s41591-020-0944-y

    View details for PubMedID 32514174

  • Charge-altering releasable transporters enable phenotypic manipulation of natural killer cells for cancer immunotherapy. Blood advances Wilk, A. J., Weidenbacher, N. L., Vergara, R. n., Haabeth, O. A., Levy, R. n., Waymouth, R. M., Wender, P. A., Blish, C. A. 2020; 4 (17): 4244–55


    Chimeric antigen receptor (CAR) natural killer (NK) cells are an emerging cell therapy with promising results in oncology trials. However, primary human NK cells are difficult to transfect, hampering both mechanistic studies and clinical applications of NK cells. Currently, NK cell CAR modification relies on viral vectors or cell activation. The former raises cost and tolerability issues, while the latter alters NK cell biology. Here, we report that readily synthesized and inexpensive nonviral charge-altering releasable transporters (CARTs) efficiently transfect primary human NK cells with messenger RNA without relying on NK cell activation. Compared with electroporation, CARTs transfect NK cells more efficiently, better preserve cell viability, and cause minimal reconfiguration of NK cell phenotype and function. We use CARTs to generate cytotoxic primary anti-CD19 CAR NK cells, demonstrating this technology can drive clinical applications of NK cells. To our knowledge, CARTs represent the first efficacious transfection technique for resting primary human NK cells that preserves NK cell phenotype and can enable new biological discoveries and therapeutic applications of this understudied lymphocyte subset.

    View details for DOI 10.1182/bloodadvances.2020002355

    View details for PubMedID 32898247

  • NK Cell-Monocyte Cross-talk Underlies NK Cell Activation in Severe COVID-19. Journal of immunology (Baltimore, Md. : 1950) Lee, M. J., de Los Rios Kobara, I., Barnard, T. R., Vales Torres, X., Tobin, N. H., Ferbas, K. G., Rimoin, A. W., Yang, O. O., Aldrovandi, G. M., Wilk, A. J., Fulcher, J. A., Blish, C. A. 2024


    NK cells in the peripheral blood of severe COVID-19 patients exhibit a unique profile characterized by activation and dysfunction. Previous studies have identified soluble factors, including type I IFN and TGF-β, that underlie this dysregulation. However, the role of cell-cell interactions in modulating NK cell function during COVID-19 remains unclear. To address this question, we combined cell-cell communication analysis on existing single-cell RNA sequencing data with in vitro primary cell coculture experiments to dissect the mechanisms underlying NK cell dysfunction in COVID-19. We found that NK cells are predicted to interact most strongly with monocytes and that this occurs via both soluble factors and direct interactions. To validate these findings, we performed in vitro cocultures in which NK cells from healthy human donors were incubated with monocytes from COVID-19+ or healthy donors. Coculture of healthy NK cells with monocytes from COVID-19 patients recapitulated aspects of the NK cell phenotype observed in severe COVID-19, including decreased expression of NKG2D, increased expression of activation markers, and increased proliferation. When these experiments were performed in a Transwell setting, we found that only CD56bright CD16- NK cells were activated in the presence of severe COVID-19 patient monocytes. O-link analysis of supernatants from Transwell cocultures revealed that cultures containing severe COVID-19 patient monocytes had significantly elevated levels of proinflammatory cytokines and chemokines, as well as TGF-β. Collectively, these results demonstrate that interactions between NK cells and monocytes in the peripheral blood of COVID-19 patients contribute to NK cell activation and dysfunction in severe COVID-19.

    View details for DOI 10.4049/jimmunol.2300731

    View details for PubMedID 38578283

  • Inferring cell-cell communication at single-cell resolution NATURE BIOTECHNOLOGY Wilk, A. J., Blish, C. A. 2023

    View details for DOI 10.1038/s41587-023-01834-4

    View details for Web of Science ID 001000628300001

    View details for PubMedID 37264218

    View details for PubMedCentralID 7649713

  • Disrupted memory T cell expansion in HIV-exposed uninfected infants is preceded by premature skewing of T cell receptor clonality. bioRxiv : the preprint server for biology Dzanibe, S., Wilk, A. J., Canny, S., Ranganath, T., Alinde, B., Rubelt, F., Huang, H., Davis, M. M., Holmes, S., Jaspan, H. B., Blish, C. A., Gray, C. M. 2023


    While preventing vertical HIV transmission has been very successful, the increasing number of HIV-exposed uninfected infants (iHEU) experience an elevated risk to infections compared to HIV-unexposed and uninfected infants (iHUU). Immune developmental differences between iHEU and iHUU remains poorly understood and here we present a longitudinal multimodal analysis of infant immune ontogeny that highlights the impact of HIV/ARV exposure. Using mass cytometry, we show alterations and differences in the emergence of NK cell populations and T cell memory differentiation between iHEU and iHUU. Specific NK cells observed at birth were also predictive of acellular pertussis and rotavirus vaccine-induced IgG and IgA responses, respectively, at 3 and 9 months of life. T cell receptor Vβ clonotypic diversity was significantly and persistently lower in iHEU preceding the expansion of T cell memory. Our findings show that HIV/ARV exposure disrupts innate and adaptive immunity from birth which may underlie relative vulnerability to infections.

    View details for DOI 10.1101/2023.05.19.540713

    View details for PubMedID 37292866

    View details for PubMedCentralID PMC10245741

  • Single-cell RNA-seq methods to interrogate virus-host interactions. Seminars in immunopathology Ratnasiri, K., Wilk, A. J., Lee, M. J., Khatri, P., Blish, C. A. 2022


    The twenty-first century has seen the emergence of many epidemic and pandemic viruses, with the most recent being the SARS-CoV-2-driven COVID-19 pandemic. As obligate intracellular parasites, viruses rely on host cells to replicate and produce progeny, resulting in complex virus and host dynamics during an infection. Single-cell RNA sequencing (scRNA-seq), by enabling broad and simultaneous profiling of both host and virus transcripts, represents a powerful technology to unravel the delicate balance between host and virus. In this review, we summarize technological and methodological advances in scRNA-seq and their applications to antiviral immunity. We highlight key scRNA-seq applications that have enabled the understanding of viral genomic and host response heterogeneity, differential responses of infected versus bystander cells, and intercellular communication networks. We expect further development of scRNA-seq technologies and analytical methods, combined with measurements of additional multi-omic modalities and increased availability of publicly accessible scRNA-seq datasets, to enable a better understanding of viral pathogenesis and enhance the development of antiviral therapeutics strategies.

    View details for DOI 10.1007/s00281-022-00972-2

    View details for PubMedID 36414692

  • Integrated analysis of multimodal single-cell data. Cell Hao, Y., Hao, S., Andersen-Nissen, E., Mauck, W. M., Zheng, S., Butler, A., Lee, M. J., Wilk, A. J., Darby, C., Zager, M., Hoffman, P., Stoeckius, M., Papalexi, E., Mimitou, E. P., Jain, J., Srivastava, A., Stuart, T., Fleming, L. M., Yeung, B., Rogers, A. J., McElrath, J. M., Blish, C. A., Gottardo, R., Smibert, P., Satija, R. 2021


    The simultaneous measurement of multiple modalities represents an exciting frontier for single-cell genomics and necessitates computational methods that can define cellular states based on multimodal data. Here, we introduce "weighted-nearest neighbor" analysis, an unsupervised framework to learn the relative utility of each data type in each cell, enabling an integrative analysis of multiple modalities. We apply our procedure to a CITE-seq dataset of 211,000 human peripheral blood mononuclear cells (PBMCs) with panels extending to 228 antibodies to construct a multimodal reference atlas of the circulating immune system. Multimodal analysis substantially improves our ability to resolve cell states, allowing us to identify and validate previously unreported lymphoid subpopulations. Moreover, we demonstrate how to leverage this reference to rapidly map new datasets and to interpret immune responses to vaccination and coronavirus disease 2019 (COVID-19). Our approach represents a broadly applicable strategy to analyze single-cell multimodal datasets and to look beyond the transcriptome toward a unified and multimodal definition of cellular identity.

    View details for DOI 10.1016/j.cell.2021.04.048

    View details for PubMedID 34062119

  • Synthetic Siglec-9 Agonists Inhibit Neutrophil Activation Associated with COVID-19. ACS central science Delaveris, C. S., Wilk, A. J., Riley, N. M., Stark, J. C., Yang, S. S., Rogers, A. J., Ranganath, T., Nadeau, K. C., Blish, C. A., Bertozzi, C. R. 2021; 7 (4): 650-657


    Severe cases of coronavirus disease 2019 (COVID-19), caused by infection with SARS-CoV-2, are characterized by a hyperinflammatory immune response that leads to numerous complications. Production of proinflammatory neutrophil extracellular traps (NETs) has been suggested to be a key factor in inducing a hyperinflammatory signaling cascade, allegedly causing both pulmonary tissue damage and peripheral inflammation. Accordingly, therapeutic blockage of neutrophil activation and NETosis, the cell death pathway accompanying NET formation, could limit respiratory damage and death from severe COVID-19. Here, we demonstrate that synthetic glycopolymers that activate signaling of the neutrophil checkpoint receptor Siglec-9 suppress NETosis induced by agonists of viral toll-like receptors (TLRs) and plasma from patients with severe COVID-19. Thus, Siglec-9 agonism is a promising therapeutic strategy to curb neutrophilic hyperinflammation in COVID-19.

    View details for DOI 10.1021/acscentsci.0c01669

    View details for PubMedID 34056095

    View details for PubMedCentralID PMC8009098

  • SARS-CoV-2 RNAemia predicts clinical deterioration and extrapulmonary complications from COVID-19. Clinical infectious diseases : an official publication of the Infectious Diseases Society of America Ram-Mohan, N. n., Kim, D. n., Zudock, E. J., Hashemi, M. M., Tjandra, K. C., Rogers, A. J., Blish, C. A., Nadeau, K. C., Newberry, J. A., Quinn, J. V., O'Hara, R. n., Ashley, E. n., Nguyen, H. n., Jiang, L. n., Hung, P. n., Blomkalns, A. L., Yang, S. n. 2021


    The determinants of COVID-19 disease severity and extrapulmonary complications (EPCs) are poorly understood. We characterized relationships between SARS-CoV-2 RNAemia and disease severity, clinical deterioration, and specific EPCs.We used quantitative (qPCR) and digital (dPCR) PCR to quantify SARS-CoV-2 RNA from plasma in 191 patients presenting to the Emergency Department (ED) with COVID-19. We recorded patient symptoms, laboratory markers, and clinical outcomes, with a focus on oxygen requirements over time. We collected longitudinal plasma samples from a subset of patients. We characterized the role of RNAemia in predicting clinical severity and EPCs using elastic net regression.23.0% (44/191) of SARS-CoV-2 positive patients had viral RNA detected in plasma by dPCR, compared to 1.4% (2/147) by qPCR. Most patients with serial measurements had undetectable RNAemia within 10 days of symptom onset, reached maximum clinical severity within 16 days, and symptom resolution within 33 days. Initially RNAaemic patients were more likely to manifest severe disease (OR 6.72 [95% CI, 2.45 - 19.79]), worsening of disease severity (OR 2.43 [95% CI, 1.07 - 5.38]), and EPCs (OR 2.81 [95% CI, 1.26 - 6.36]). RNA load correlated with maximum severity (r = 0.47 [95% CI, 0.20 - 0.67]).dPCR is more sensitive than qPCR for the detection of SARS-CoV-2 RNAemia, which is a robust predictor of eventual COVID-19 severity and oxygen requirements, as well as EPCs. Since many COVID-19 therapies are initiated on the basis of oxygen requirements, RNAemia on presentation might serve to direct early initiation of appropriate therapies for the patients most likely to deteriorate.

    View details for DOI 10.1093/cid/ciab394

    View details for PubMedID 33949665

  • Diversification of human NK cells: Lessons from deep profiling. Journal of leukocyte biology Wilk, A. J., Blish, C. A. 2018


    NK cells are innate lymphocytes with important roles in immunoregulation, immunosurveillance, and cytokine production. Originally defined on the functional basis of their "natural" ability to lyse tumor targets and thought to be a relatively homogeneous group of lymphocytes, NK cells possess a remarkable degree of phenotypic and functional diversity due to the combinatorial expression of an array of activating and inhibitory receptors. Diversification of NK cells is multifaceted: mechanisms of NK cell education that promote self-tolerance result in a heterogeneous repertoire that further diversifies upon encounters with viral pathogens. Here, we review the genetic, developmental, and environmental sources of NK cell diversity with a particular focus on deep profiling and single-cell technologies that will enable a more thorough and accurate dissection of this intricate and poorly understood lymphocyte lineage.

    View details for PubMedID 29350874

  • Bordetella PlrSR regulatory system controls BvgAS activity and virulence in the lower respiratory tract. Proceedings of the National Academy of Sciences of the United States of America Bone, M. A., Wilk, A. J., Perault, A. I., Marlatt, S. A., Scheller, E. V., Anthouard, R., Chen, Q., Stibitz, S., Cotter, P. A., Julio, S. M. 2017; 114 (8): E1519-E1527


    Bacterial pathogens coordinate virulence using two-component regulatory systems (TCS). The Bordetella virulence gene (BvgAS) phosphorelay-type TCS controls expression of all known protein virulence factor-encoding genes and is considered the "master virulence regulator" in Bordetella pertussis, the causal agent of pertussis, and related organisms, including the broad host range pathogen Bordetella bronchiseptica We recently discovered an additional sensor kinase, PlrS [for persistence in the lower respiratory tract (LRT) sensor], which is required for B. bronchiseptica persistence in the LRT. Here, we show that PlrS is required for BvgAS to become and remain fully active in mouse lungs but not the nasal cavity, demonstrating that PlrS coordinates virulence specifically in the LRT. PlrS is required for LRT persistence even when BvgAS is rendered constitutively active, suggesting the presence of BvgAS-independent, PlrS-dependent virulence factors that are critical for bacterial survival in the LRT. We show that PlrS is also required for persistence of the human pathogen B. pertussis in the murine LRT and we provide evidence that PlrS most likely functions via the putative cognate response regulator PlrR. These data support a model in which PlrS senses conditions present in the LRT and activates PlrR, which controls expression of genes required for the maintenance of BvgAS activity and for essential BvgAS-independent functions. In addition to providing a major advance in our understanding of virulence regulation in Bordetella, which has served as a paradigm for several decades, these results indicate the existence of previously unknown virulence factors that may serve as new vaccine components and therapeutic or diagnostic targets.

    View details for DOI 10.1073/pnas.1609565114

    View details for PubMedID 28167784

    View details for PubMedCentralID PMC5338435