About

The overall goal of Dr. Gary H. Cohen’s research is to understand the molecular events that mediate the entry of herpes simplex virus (HSV) into mammalian cells and promote its pathogenesis in its human host. A major focus of this research has been on cellular receptors and the glycoproteins, which are found in the virus envelope and act as mediators of virus entry and as targets of the host’s immune response. A major goal is to develop a subunit vaccine against smallpox using proteins from vaccinia virus or from variola virus (smallpox). A second goal is to ask more fundamental questions about poxvirus entry into susceptible cells. A variety of experimental approaches are being taken, modeled on the herpesvirus work.

Research topics

• Biology
• Virology
• Molecular biology
• Cell biology
• Mathematics

Selected publications

• BPS2025 - Allosteric mechanism of membrane fusion activation in herpes viruses

  Biophysical Journal · 2025-02-01

  article
  PublisherDOI

• Antibody Binding and Neutralizing Targets within the Predicted Structure of the Poxvirus Multiprotein Entry-Fusion Complex

  bioRxiv (Cold Spring Harbor Laboratory) · 2025-05-07 · 3 citations

  preprintOpen access

  The increased incidence of mpox emphasizes a need for new and improved vaccines. Poxviruses rely on a highly conserved but poorly characterized 11-protein entry-fusion complex (EFC), providing numerous potential targets. Here, we demonstrate that antibodies induced by six of 10 EFC proteins are neutralizing. Protein targets of the neutralizing and non-neutralizing antibodies are located within discrete regions of a model of the EFC predicted by AlphaFold3. Two newly identified targets, A16 and G9, at the apex of the EFC induced cross-neutralizing orthopoxvirus antibodies and protected female mice against a lethal VACV infection. Unexpectedly, antibodies to A16 and G9 were not detected following infection by attenuated or pathogenic VACV, likely due to physical sequestration of the proteins in the viral membrane. Our findings provide a model for the physical, immunogenic and antigenic structure of the EFC, new immunogens for incorporation into recombinant vaccines and suggest a novel poxvirus immune evasion strategy.

  PublisherOA PDFDOI

• Unveiling the unique interaction mechanism of herpes simplex virus 2 glycoprotein C with C3b

  bioRxiv (Cold Spring Harbor Laboratory) · 2025-10-04

  preprintOpen access

  The complement cascade is part of the first line of defence against viral infections, and many viruses have evolved to block it. For example, glycoprotein C (gC) from Herpes Simplex Virus 1 and 2 (gC1 and gC2) facilitates infection by modulating the complement cascade through an interaction with C3b. gC is also involved in attachment and other viral processes. However, our understanding of the molecular mechanisms of gC have been limited due to the absence of a structure. AlphaFold predicts that gC contains a disordered N-terminus and three immunoglobulin-like domains. Here, we generated various gC2 constructs and demonstrated that gC2 domains 1 and 2 are necessary and sufficient to interact with C3b and block the alternative pathway. A gC2 construct lacking the N-terminus in complex with C3b was characterised by cryo-EM at 3.6 Å, providing the first structure for gC2, and revealing that the interaction is predominantly driven by gC2 domain 2 and the MG8 domain of C3b. This structure was confirmed by cross-linking mass spectrometry and by using C3b-blocking antibodies that recognised gC2 linear epitopes at the interface with C3b. Overall, the gC-C3b interaction is different from other C3b-interacting partners, providing a novel mechanism to regulate the complement cascade.

  PublisherOA PDFDOI

• Seroconversion Is Misleading as a Test for HSV-2 Infection in Prophylactic Genital Herpes Vaccine Trials: Results of Vaccine Studies in Guinea Pigs

  Viruses · 2025-05-29 · 1 citations

  articleOpen access

  Seroconversion is defined as a four-fold or greater rise in antibody titers. This assay is used in human prophylactic vaccine trials to confirm HSV as the cause of genital lesions and detect subclinical latent infection. We evaluated the accuracy of seroconversion in detecting infection using a guinea pig model of genital infection. Not all animals intravaginally inoculated with HSV-2 become infected, particularly if vaccinated; therefore, we need to establish criteria to determine whether an animal is infected. Our primary analysis involved considering animals to be infected if they had any of the following: (a) genital lesions; (b) HSV-2 DNA in vaginal secretions four or more weeks after HSV-2 inoculation as a marker of reactivation from latency; or (c) HSV-2 DNA in dorsal root ganglia, the site of latency. In the second analysis, we considered animals to be infected if they had positive virus cultures from vaginal swabs obtained on day two or four post HSV-2 inoculation. In the third analysis, we considered animals to be infected if they had any condition included in the first two analyses. We collected sera prior to HSV-2 inoculation and two months later and tested the first 57 animals for seroconversion using Western blotting and gG2 IgG ELISA. The results were concordant in 54 of 57 animals (95%), and when discordant, the gG2 ELISA matched infection results as defined by the primary analysis. The remaining animals were evaluated by gG2 IgG ELISA only. A total of 43 animals were inoculated with HSV-2 but not vaccinated (No vaccine group), and 224 were vaccinated with glycoprotein or mRNA vaccines prior to HSV-2 inoculation (Vaccine group). In the No vaccine group, we detected no false positives (seroconversion without infection) but 24% to 29% false negatives (no seroconversion despite infection) depending on the criteria used to define infection. In the Vaccine group, we detected 8% to 22% false positives and 31% to 37% false negatives. The accuracy of seroconversion was 74% to 79% in the No vaccine group and 71% to 76% in the Vaccine group. These results raise concerns about using seroconversion as a diagnostic test in human vaccine trials. Alternate approaches, such as subject home swabbing for HSV DNA, should be considered as a possible replacement.

  PublisherOA PDFDOI

• BPS2025 - Allosteric mechanism of membrane fusion activation in a herpes virus

  Biophysical Journal · 2025-02-01

  article
  PublisherDOI

• Debulking influenza and herpes simplex virus strains by a wide-spectrum anti-viral protein formulated in clinical grade chewing gum

  Molecular Therapy · 2024-12-10 · 9 citations

  articleOpen accessSenior author
  PublisherOA PDFDOI

• Cellugyrin (synaptogyrin-2) dependent pathways are used by bacterial cytolethal distending toxin and SARS-CoV-2 virus to gain cell entry

  Frontiers in Cellular and Infection Microbiology · 2024-04-18 · 2 citations

  articleOpen access

  Aggregatibacter actinomycetemcomitans cytolethal distending toxin (Cdt) is capable of intoxicating lymphocytes macrophages, mast cells and epithelial cells. Following Cdt binding to cholesterol, in the region of membrane lipid rafts, the CdtB and CdtC subunits are internalized and traffic to intracellular compartments. These events are dependent upon, cellugyrin, a critical component of synaptic like microvesicles (SLMV Cg+ ). Target cells, such as Jurkat cells, rendered unable to express cellugyrin are resistant to Cdt-induced toxicity. Similar to Cdt, SARS-CoV-2 entry into host cells is initiated by binding to cell surface receptors, ACE-2, also associated with cholesterol-rich lipid rafts; this association leads to fusion and/or endocytosis of viral and host cell membranes and intracellular trafficking. The similarity in internalization pathways for both Cdt and SARS-CoV-2 led us to consider the possibility that cellugyrin was a critical component in both processes. Cellugyrin deficient Calu-3 cells (Calu-3 Cg- ) were prepared using Lentiviral particles containing shRNA; these cells were resistant to infection by VSV/SARS-CoV-2-spike pseudotype virus and partially resistant to VSV/VSV-G pseudotype virus. Synthetic peptides representing various regions of the cellugyrin protein were prepared and assessed for their ability to bind to Cdt subunits using surface plasmon resonance. Cdt was capable of binding to a region designated the middle outer loop (MOL) which corresponds to a region extending into the cytoplasmic surface of the SLMV Cg+ . SARS-CoV-2 spike proteins were assessed for their ability to bind to cellugyrin peptides; SARS-CoV-2 full length spike protein preferentially binds to a region within the SLMV Cg+ lumen, designated intraluminal loop 1A. SARS-CoV-2-spike protein domain S1, which contains the receptor binding domains, binds to cellugyrin N-terminus which extends out from the cytoplasmic surface of SLMV. Binding specificity was further analyzed using cellugyrin scrambled peptide mutants. We propose that SLMV Cg+ represent a component of a common pathway that facilitates pathogen and/or pathogen-derived toxins to gain host cell entry.

  PublisherOA PDFDOI

• Allosteric mechanism of membrane fusion activation in a herpesvirus

  bioRxiv (Cold Spring Harbor Laboratory) · 2024-09-21 · 1 citations

  preprintOpen access

  ABSTRACT/SUMMARY Herpesviridae infect nearly all humans for life, causing diseases that range from painful to life-threatening 1 . These viruses penetrate cells by employing a complex apparatus composed of separate receptor-binding, signal-transmitting, and membrane-fusing components 2 . But how these components coordinate their functions is unknown. Here, we determined the 4.19-angstrom cryoEM reconstruction of the central signal-transmitting component from herpes simplex virus 2, the gH/gL complex, in its elusive pre-activation state. Analysis of the continuum of conformational ensembles observed in cryoEM data revealed a series of structural rearrangements in gH/gL that allosterically transmit the fusion-triggering signal from the receptor-binding glycoprotein gD to the membrane fusogen gB. Furthermore, we identified a structural “switch” element in gH/gL that refolds and flips 180 degrees during the transition from pre-activation to activated form. Conservation of this “switch” in gH/gL homologs suggests that the proposed fusion triggering mechanism may apply to all Herpesviridae and points to a new target for subunit-based vaccines and treatment efforts.

  PublisherDOI

• Boosting of vaginal HSV-2-specific B and T cell responses by intravaginal therapeutic immunization results in diminished recurrent HSV-2 disease

  Journal of Virology · 2023-09-01 · 1 citations

  articleOpen access

  Boosting herpes simplex virus (HSV)-specific immunity in the genital tissues of HSV-positive individuals to increase control of HSV-2 recurrent disease and virus shedding is an important goal of therapeutic immunization and would impact HSV-2 transmission. Experimental therapeutic HSV-2 vaccines delivered by a parenteral route have resulted in decreased recurrent disease in experimental animals. We used a guinea pig model of HSV-2 infection to test if HSV-specific antibody and cell-mediated responses in the vaginal mucosa would be more effectively increased by intravaginal (Ivag) therapeutic immunization compared to parenteral immunization. Therapeutic immunization with HSV glycoproteins and CpG adjuvant increased glycoprotein-specific IgG titers in vaginal secretions and serum to comparable levels in Ivag- and intramuscular (IM)-immunized animals. However, the mean numbers of HSV glycoprotein-specific antibody secreting cells (ASCs) and IFN-γ SCs were greater in Ivag-immunized animals demonstrating superior boosting of immunity in the vaginal mucosa compared to parenteral immunization. Therapeutic Ivag immunization also resulted in a significant decrease in the cumulative mean lesion days compared to IM immunization. There was no difference in the incidence or magnitude of HSV-2 shedding in either therapeutic immunization group compared to control-treated animals. Collectively, these data demonstrated that Ivag therapeutic immunization was superior compared to parenteral immunization to boost HSV-2 antigen-specific ASC and IFN-γ SC responses in the vagina and control recurrent HSV-2 disease. These results suggest that novel antigen delivery methods providing controlled release of optimized antigen/adjuvant combinations in the vaginal mucosa would be an effective approach for therapeutic HSV vaccines. IMPORTANCE HSV-2 replicates in skin cells before it infects sensory nerve cells where it establishes a lifelong but mostly silent infection. HSV-2 occasionally reactivates, producing new virus which is released back at the skin surface and may be transmitted to new individuals. Some HSV-specific immune cells reside at the skin site of the HSV-2 infection that can quickly activate and clear new virus. Immunizing people already infected with HSV-2 to boost their skin-resident immune cells and rapidly control the new HSV-2 infection is logical, but we do not know the best way to administer the vaccine to achieve this goal. In this study, a therapeutic vaccine given intravaginally resulted in significantly better protection against HSV-2 disease than immunization with the same vaccine by a conventional route. Immunization by the intravaginal route resulted in greater stimulation of vaginal-resident, virus-specific cells that produced antibody and produced immune molecules to rapidly clear virus.

  PublisherOA PDFDOI

• Receptor Binding-Induced Conformational Changes in Herpes Simplex Virus Glycoprotein D Permit Interaction with the gH/gL Complex to Activate Fusion

  Viruses · 2023-03-30 · 10 citations

  articleOpen accessSenior author

  Herpes simplex virus (HSV) requires four essential virion glycoproteins-gD, gH, gL, and gB-for virus entry and cell fusion. To initiate fusion, the receptor binding protein gD interacts with one of two major cell receptors, HVEM or nectin-1. Once gD binds to a receptor, fusion is carried out by the gH/gL heterodimer and gB. A comparison of free and receptor-bound gD crystal structures revealed that receptor binding domains are located within residues in the N-terminus and core of gD. Problematically, the C-terminus lies across and occludes these binding sites. Consequentially, the C-terminus must relocate to allow for both receptor binding and the subsequent gD interaction with the regulatory complex gH/gL. We previously constructed a disulfide bonded (K190C/A277C) protein that locked the C-terminus to the gD core. Importantly, this mutant protein bound receptor but failed to trigger fusion, effectively separating receptor binding and gH/gL interaction. Here, we show that "unlocking" gD by reducing the disulfide bond restored not only gH/gL interaction but fusion activity as well, confirming the importance of C-terminal movement in triggering the fusion cascade. We characterize these changes, showing that the C-terminus region exposed by unlocking is: (1) a gH/gL binding site; (2) contains epitopes for a group (competition community) of monoclonal antibodies (Mabs) that block gH/gL binding to gD and cell-cell fusion. Here, we generated 14 mutations within the gD C-terminus to identify residues important for the interaction with gH/gL and the key conformational changes involved in fusion. As one example, we found that gD L268N was antigenically correct in that it bound most Mabs but was impaired in fusion, exhibited compromised binding of MC14 (a Mab that blocks both gD-gH/gL interaction and fusion), and failed to bind truncated gH/gL, all events that are associated with the inhibition of C-terminus movement. We conclude that, within the C-terminus, residue 268 is essential for gH/gL binding and induction of conformational changes and serves as a flexible inflection point in the critical movement of the gD C-terminus.

  PublisherOA PDFDOI

Recent grants

• NIH Grant P01NS030606

  NIH · $14.6M · 2004

• Improving HSV-2 vaccine efficacy by focusing antibody epitope coverage.

  NIH · $285k · 2019–2021

• NIH Grant R43AI13207501

  NIH · $300k · 2019

• NIH Grant R37AI018289

  NIH · $3.9M · 2015

• NIH Grant R21AI053404

  NIH · $476k · 2004

Frequent coauthors

• Roselyn J. Eisenberg

  University of Pennsylvania

  221 shared

• R Bartnik

  University of Łódź

  121 shared

• J Hempel

  117 shared

• Robert Anderssen

  Kinokuniya

  117 shared

• J Rubinstein

  Macquarie University

  117 shared

• G Lehrer

  Australian Mathematical Sciences Institute

  117 shared

• Neil S. Trudinger

  117 shared

• G Ivanov

  New York University Press

  116 shared