Sanna Herwald received her M.D. and Ph.D. degrees from Tufts University. Her Ph.D. research in the field of Microbiology focused on the opportunistic fungal pathogen Candida albicans. During her time in the M.D.-Ph.D. program she discovered her interest in Radiology, and the possibilities for visualizing the interaction between microorganisms and the human body.

Professional Education

  • Internship, California Pacific Medical Center, Internal Medicine (2020)
  • MD, Tufts University School of Medicine (2019)
  • PhD, Tufts University, Department of Molecular Biology and Microbiology, Molecular Microbiology (2019)
  • BA, Pomona College, Molecular Biology (2010)

All Publications

  • Radiofrequency Ablation, Cryoablation, and Microwave Ablation for T1a Renal Cell Carcinoma: A Comparative Evaluation of Therapeutic and Renal Function Outcomes JOURNAL OF VASCULAR AND INTERVENTIONAL RADIOLOGY Zhou, W., Herwald, S. E., McCarthy, C., Uppot, R. N., Arellano, R. S. 2019; 30 (7): 1035–42


    To compare the therapeutic and renal function outcomes of radiofrequency (RF) ablation, cryoablation, and microwave (MW) ablation for treatment of T1a renal cell carcinoma (RCC).A retrospective assessment of 297 patients (mean age 72 years range 24-90 years) with biopsy-proven RCC treated with image-guided percutaneous thermal ablation was performed between October 2006 and December 2016. Mean tumor size was 2.4 cm; mean radius, exophytic/endophytic properties, nearness of tumor to collecting system or sinus, anterior/posterior, hilar tumor touching the main renal artery or vein, and location relative to polar lines; Preoperative Aspects and Dimensions Used for an Anatomical; and c-centrality scores were 6.0, 7.0, and 2.8, respectively. Assessments of adverse events, treatment efficacy, and therapeutic outcomes were performed among RF ablation, cryoablation, and MW ablation. The 2-year disease-free, metastatic-free, and cancer-specific survival rates were tabulated. Estimated glomerular filtration rate was used to assess for treatment related changes in renal function.A total of 297 T1aN0M0 biopsy-proven RCCs measuring 1.2-3.9 cm were treated with computed tomography-guided RF ablation (n = 244, 82%), cryoablation (n = 26, 9%), and MW ablation (n = 27, 9%). There were no significant differences in patient demographics among the 3 groups (P = .09). Technical success rates were similar among the 3 treatments (P = .33). Primary efficacy at 1 month postablation was more likely to be achieved with RF ablation and MW ablation than with cryoablation. At 2 years' follow-up, there was no local recurrence, metastatic progression, or RCC-related death observed in the 3 groups. There was no significant change in estimated glomerular filtration rate among the 3 ablation groups compared with baseline at 2-year follow-up (P = .71).RF ablation, cryoablation, and MW ablation are equivalent at 2 years for treatment of T1a RCC for therapeutic outcome, stability of renal function, and low adverse event rate.

    View details for DOI 10.1016/j.jvir.2018.12.013

    View details for Web of Science ID 000475412000009

    View details for PubMedID 30956075

  • Risk Assessment of Chronic Kidney Disease following Microwave Ablation for Stage T1 Renal Cell Carcinoma JOURNAL OF VASCULAR AND INTERVENTIONAL RADIOLOGY Zhou, W., Herwald, S. E., Uppot, R. N., Arellano, R. S. 2018; 29 (12): 1685–91


    To assess safety and renal-function outcomes after microwave (MW) ablation of localized stage T1 renal cell carcinoma (RCC).A retrospective review was conducted of 38 patients (28 men; mean age, 69 y; range, 51-88 y) who underwent computed tomography (CT)-guided MW ablation for stage T1N0M0 RCC. Baseline and follow-up renal function surrogates including creatinine level and estimated glomerular filtration rate (eGFR) were statistically compared. Peri- and postoperative complication rates, technical success, and treatment response were also assessed.A total of 44 biopsy-proven stage T1N0M0 RCCs measuring 1.2-6.9 cm (mean, 2.5 cm) were treated, and renal function was measured 1 mo after treatment. Mean eGFRs were 60 mL/min/1.73 m2 at baseline and 59 mL/min/1.73 m2 at 1 month after ablation. At 1-year and last follow-ups, the means of difference were 3.3% (95% confidence interval, -4.4 to 4.3; P = .99) and 3.3% (95% confidence interval, -4.3 to 4.8; P = .91), respectively. The 2-years freedom from eGFR decrease to < 60 mL/min/1.73 m2 was 2% (P = .91). Among the 5 patients (13%) with preexisting stage 4 chronic kidney disease (CKD; eGFR < 30 mL/min/1.73 m2) before ablation, there was no significant postablative onset of decline or CKD upstaging (P = .001). There were no major complications, and 5 patients (13%) had small asymptomatic perinephric hematomas (Society of Interventional Radiology minor complication, class A/B) that were managed conservatively.At 2-year follow-up, CT-guided percutaneous MW ablation is safe and well-tolerated and achieves nephron preservation similar to existing ablative modalities.

    View details for DOI 10.1016/j.jvir.2018.06.021

    View details for Web of Science ID 000453341200009

    View details for PubMedID 30297311

  • Image-Guided Thermal Ablation for Non-resectable Recurrence of Renal Cell Cancer Following Nephrectomy: Clinical Experience with Eleven Patients CARDIOVASCULAR AND INTERVENTIONAL RADIOLOGY Zhou, W., Herwald, S. E., Uppot, R. N., Arellano, R. S. 2018; 41 (11): 1743–50


    To assess the feasibility, safety and clinical outcomes of image-guided percutaneous thermal ablation as salvage therapy for local recurrence of renal cell carcinoma (RCC) in patients initially treated surgically with curative intent.A retrospective review of 11 consecutive patients (M/F = 8:3, mean age = 76 years) who underwent computed tomography (CT)-guided thermal ablation for locally recurrent RCC after partial (72%, 8/11) or radical nephrectomy (28%, 3/11) with a mean time to recurrence of 48 months (range 2-156). Assessment of technical success, complication (peri- and post-procedural), oncological outcome and survival analysis were performed. Patient baseline and follow-up renal function surrogates including creatinine level (Cr) and estimated glomerular filtration rate (eGFR) were statistically compared.Eleven biopsy-proven recurrent RCC measuring 1.4-3.9 cm (mean = 2.8 cm) were treated with CT-guided thermal ablation. Technical success was achieved in 100% (11/11) of the cases. There were no major complications except for one (9%) asymptomatic hemorrhage (Clavien-Dindo grade I complication). Complete response, local progression-free and overall survival rate were 91, 91 and 82% during the mean follow-up time of 2.5 years (range 0.1-7.1). Renal function was overall stable without significant change at 1 month and last follow-up (p = 0.21; GFR, p = 0.10; creatinine).Image-guided percutaneous thermal ablation is a feasible, safe and effective for local recurrence after nephrectomy, representing a non-surgical alternative for unresectable disease.

    View details for DOI 10.1007/s00270-018-1976-2

    View details for Web of Science ID 000451930300013

    View details for PubMedID 29721615

  • The two transmembrane regions of Candida albicans Dfi1 contribute to its biogenesis BIOCHEMICAL AND BIOPHYSICAL RESEARCH COMMUNICATIONS Herwald, S. E., Zucchi, P. C., Tan, S., Kumamoto, C. A. 2017; 488 (1): 153–58


    The opportunistic pathogen Candida albicans forms invasive filaments that grow into host tissues during disease. The glycosylated, integral plasma membrane protein Dfi1 is important for invasive filamentation in a laboratory model, and for lethality in murine disseminated candidiasis. However, Dfi1 topology and essential domains for Dfi1 biogenesis were undefined. Sequence analysis predicted that Dfi1 contains two transmembrane regions, located near the N- and C-termini. In this communication, we show that Dfi1 remains an integral membrane protein despite deletion of either predicted transmembrane region, whereas deletion of both regions results in a soluble protein. Additionally, Dfi1 that was properly oriented in the membrane, as indicated by N-linked glycosylation, was observed when either transmembrane region was deleted, but was absent when both transmembrane regions were deleted. Interestingly, deletion of the N-terminal transmembrane region resulted in production of two forms of Dfi1. Most of the protein molecules acquired normal N-linked glycosylation and a smaller population failed to become normally N-linked glycosylated. This defect was reversed by replacement of the N-terminal hydrophobic sequence with one synthetic transmembrane sequence but not another. Finally, microscopy studies revealed that Dfi1 lacking the N-terminal transmembrane region was observed at the cell periphery, where full-length Dfi1 normally localizes, whereas the double-truncation mutant was diffusely intracellular. Therefore, mature Dfi1 protein contains two transmembrane domains which contribute to its biogenesis.

    View details for DOI 10.1016/j.bbrc.2017.04.158

    View details for Web of Science ID 000402587000024

    View details for PubMedID 28483525

    View details for PubMedCentralID PMC5521179

  • Anticipated Supply and Demand for Independent Interventional Radiology Residency Positions: A Survey of Department Chairs JOURNAL OF THE AMERICAN COLLEGE OF RADIOLOGY Herwald, S. E., Spies, J. B., Yucel, E. 2017; 14 (2): 242–46


    The first participants in the independent interventional radiology (IR) residency match will begin prerequisite diagnostic radiology (DR) residencies before the anticipated launch of the independent IR programs in 2020. The aim of this study was to estimate the competitiveness level of the first independent IR residency matches before these applicants have already committed to DR residencies and possibly early specialization in IR (ESIR) programs.The Society of Chairs of Academic Radiology Departments (SCARD) Task Force on the IR Residency distributed a survey to all active SCARD members using SurveyMonkey. The survey requested the number of planned IR residency and ESIR positions. The average, minimum, and maximum of the range of planned independent IR residency positions were compared with the average, maximum, and minimum, respectively, of the range of planned ESIR positions, to model matches of average, high, and low competitiveness.Seventy-four active SCARD members (56%) answered at least one survey question. The respondents' programs planned to fill, in total, 98 to 102 positions in integrated IR residency programs, 61 to 76 positions in independent IR residency programs, and 50 to 77 positions in ESIR DR residency programs each year. The ranges indicate the uncertainty of some programs regarding the number of positions.The survey suggests that participating programs will fill sufficient independent IR residency positions to accommodate all ESIR applicants in a match year of average or low competitiveness, but not in a match year of high competitiveness. This suggestion does not account for certain difficult-to-predict factors that may affect the independent IR residency match.

    View details for DOI 10.1016/j.jacr.2016.08.036

    View details for Web of Science ID 000394478300021

    View details for PubMedID 28161025

  • Irreversible Electroporation for Treatment of Hepatocellular Carcinoma Adjacent to the Gallbladder JOURNAL OF VASCULAR AND INTERVENTIONAL RADIOLOGY Herwald, S. E., Chen, J. H., Arellano, R. S. 2016; 27 (7): 1093–94

    View details for DOI 10.1016/j.jvir.2016.03.008

    View details for Web of Science ID 000379796500023

    View details for PubMedID 27338501

  • The game theory of Candida albicans colonization dynamics reveals host status-responsive gene expression BMC SYSTEMS BIOLOGY Tyc, K. M., Herwald, S. E., Hogan, J. A., Pierce, J. V., Klipp, E., Kumamoto, C. A. 2016; 10: 20


    The fungal pathogen Candida albicans colonizes the gastrointestinal (GI) tract of mammalian hosts as a benign commensal. However, in an immunocompromised host, the fungus is capable of causing life-threatening infection. We previously showed that the major transcription factor Efg1p is differentially expressed in GI-colonizing C. albicans cells dependent on the host immune status. To understand the mechanisms that underlie this host-dependent differential gene expression, we utilized mathematical modeling to dissect host-pathogen interactions. Specifically, we used principles of evolutionary game theory to study the mechanism that governs dynamics of EFG1 expression during C. albicans colonization.Mathematical modeling predicted that down-regulation of EFG1 expression within individual fungal cells occurred at different average rates in different hosts. Rather than using relatively transient signaling pathways to adapt to a new environment, we demonstrate that C. albicans overcomes the host defense strategy by modulating the activity of diverse fungal histone modifying enzymes that control EFG1 expression.Based on our modeling and experimental results we conclude that C. albicans cells sense the local environment of the GI tract and respond to differences by altering EFG1 expression to establish optimal survival strategies. We show that the overall process is governed via modulation of epigenetic regulators of chromatin structure.

    View details for DOI 10.1186/s12918-016-0268-1

    View details for Web of Science ID 000370950700001

    View details for PubMedID 26927448

    View details for PubMedCentralID PMC4772284

  • Candida albicans Niche Specialization: Features That Distinguish Biofilm Cells from Commensal Cells CURRENT FUNGAL INFECTION REPORTS Herwald, S. E., Kumamoto, C. A. 2014; 8 (2): 179–84


    The fungus Candida albicans is a frequent commensal colonizer of the human gastrointestinal (GI) tract, but is also an opportunistic pathogen. This review explores features that distinguish the colonizing and pathogenic forms of C. albicans. Candida albicans in a biofilm is used as an example of a pathogenic form of the organism, because biofilms are a common feature of device-associated C. albicans infections. Biofilms (complex, sessile communities of cells) have been the subject of several large-scale gene expression studies. Biofilms and commensal C. albicans colonizing the murine GI tract show a variety of differentially expressed genes. Cell surface proteins encoded by these differentially expressed genes are especially attractive as targets for new clinical prevention, diagnosis, or treatment tools that are specific for C. albicans in its pathogenic biofilm state.

    View details for DOI 10.1007/s12281-014-0178-x

    View details for Web of Science ID 000219664900008

    View details for PubMedID 24839528

    View details for PubMedCentralID PMC4019406

  • Structure and Substrate Specificity of the Pyrococcal Coenzyme A Disulfide Reductases/Polysulfide Reductases (CoADR/Psr): Implications for S-0-Based Respiration and a Sulfur-Dependent Antioxidant System in Pyrococcus BIOCHEMISTRY Herwald, S., Liu, A. Y., Zhu, B. E., Sea, K. W., Lopez, K. M., Sazinsky, M. H., Crane, E. J. 2013; 52 (16): 2764–73


    FAD and NAD(P)H-dependent coenzyme A disulfide reductases/polysulfide reductases (CoADR/Psr) have been proposed to be important for the reduction of sulfur and disulfides in the sulfur-reducing anaerobic hyperthermophiles Pyrococcus horikoshii and Pyrococcus furiosus; however, the form(s) of sulfur that the enzyme actually reduces are not clear. Here we determined the structure for the FAD- and coenzyme A-containing holoenzyme from P. horikoshii to 2.7 Å resolution and characterized its substrate specificity. The enzyme is relatively promiscuous and reduces a range of disulfide, persulfide, and polysulfide compounds. These results indicate that the likely in vivo substrates are NAD(P)H and di-, poly-, and persulfide derivatives of coenzyme A, although polysulfide itself is also efficiently reduced. The role of the enzyme in the reduction of elemental sulfur (S(8)) in situ is not, however, ruled out by these results, and the possible roles of this substrate are discussed. During aerobic persulfide reduction, rapid recycling of the persulfide substrate was observed, which is proposed to occur via sulfide oxidation by O(2) and/or H(2)O(2). As expected, this reaction disappears under anaerobic conditions and may explain observations by others that CoADR is not essential for S(0) respiration in Pyrococcus or Thermococcus but appears to participate in oxidative defense in the presence of S(0). When compared to the homologous Npsr enzyme from Shewanella loihica PV-4 and homologous enzymes known to reduce CoA disulfide, the phCoADR structure shows a relatively restricted substrate channel leading into the sulfur-reducing side of the FAD isoalloxazine ring, suggesting how this enzyme class may select for specific disulfide substrates.

    View details for DOI 10.1021/bi3014399

    View details for Web of Science ID 000318143700006

    View details for PubMedID 23530771

  • Purification of high yields of catalytically active lysyl oxidase directly from Escherichia coli cell culture PROTEIN EXPRESSION AND PURIFICATION Herwald, S. E., Greenaway, F. T., Lopez, K. M. 2010; 74 (1): 116–21


    Lysyl oxidase is a highly insoluble enzyme requiring high concentrations of urea to solubilize. A method to obtain lysyl oxidase in high yields directly from an Escherichia coli culture without the need for refolding of inclusion bodies has been developed using nutrient rich media. pET21b was used to overexpress the lysyl oxidase enzyme and to introduce a C-terminal 6X histidine tag for purification. Lysyl oxidase yields of 10 mg of active and properly folded enzyme per liter of media have been obtained. Purification was achieved via affinity chromatography using a Ni-NTA column. Copper content was found to be 19%. LTQ cofactor formation in LOX is a self-processing event in the presence of copper. LTQ content was determined to be 24% based on reaction with phenylhydrazine to form a phenylhydrazone adduct. Quantification of this adduct was attained using the previously reported extinction coefficient of 15.4 mM(-1)cm(-1). LTQ presence was also verified by redox cycling. Specific enzymatic activity was measured to be 0.31 U/mg, one of the highest activities reported.

    View details for DOI 10.1016/j.pep.2010.06.013

    View details for Web of Science ID 000281495100015

    View details for PubMedID 20600936