Multiple Sites on Glycoprotein H (gH) Functionally Interact with the gB Fusion Protein to Promote Fusion during Herpes Simplex Virus (HSV) Entry

Leveraging biotin-based proximity labeling to identify cellular factors governing early alphaherpesvirus infection

Neurotropic alphaherpesviruses, including herpes simplex virus type 1 and pseudorabies virus, establish a lifelong presence within the peripheral nervous system of their mammalian hosts. Upon entering cells, two conserved tegument proteins, pUL36 and pUL37, traffic DNA-containing capsids to nuclei. These proteins support long-distance retrograde axonal transport and invasion of the nervous system in vivo. To better understand how pUL36 and pUL37 function, recombinant viral particles carrying BioID2 fused to these proteins were produced to biotinylate cellular proteins in their proximity (<10 nm) during infection. Eighty-six high-confidence host proteins were identified by mass spectrometry and subsequently targeted by CRISPR-Cas9 gene editing to assess their contributions to early infection. Proteins were identified that both supported and antagonized infection in immortalized human epithelial cells. The latter included zyxin, a protein that localizes to focal adhesions and regulates actin cytoskeletal dynamics. Zyxin knockout cells were hyper-permissive to infection and could be rescued with even modest expression of GFP-zyxin. These results provide a resource for studies of the virus-cell interface and identify zyxin as a novel deterrent to alphaherpesvirus infection.IMPORTANCENeuroinvasive alphaherpesviruses are highly prevalent with many members found across mammals [e.g., herpes simplex virus type 1 (HSV-1) in humans and pseudorabies virus in pigs]. HSV-1 causes a range of clinical manifestations from cold sores to blindness and encephalitis. There are no vaccines or curative therapies available for HSV-1. A fundamental feature of these viruses is their establishment of lifelong infection of the nervous system in their respective hosts. This outcome is possible due to a potent neuroinvasive property that is coordinated by two proteins: pUL36 and pUL37. In this study, we explore the cellular protein network in proximity to pUL36 and pUL37 during infection and examine the impact of knocking down the expression of these proteins upon infection.

Anti-HSV activity of nectin-1-derived peptides targeting HSV gD: an in-silico and in-vitro approach

Herpes simplex virus (HSV) infections affect a wide range of the global population. The emergence of resistance to the existing anti-HSV therapy highlights the necessity for an innovative strategy. The interaction of HSV gD with its main host receptor nectin-1 is a potential target for new antiviral drugs. The aim of this study was to develop a peptide derived from nectin-1 targeting HSV gD using the in-silico method and evaluate them for anti-HSV activity. Residues 59-133 of the Nectin-1 V-domain constitute the interaction interface with HSV gD. Bioinformatic tools viz., PEP-FOLD3, ClusPro 2.0, HawkDock and Desmond were used to model the peptide and confirm its binding specificity with HSV gD protein. The peptides with potential interactions were custom synthesized and anti-HSV activity was evaluated in vitro against HSV-1 and HSV-2 by CPE inhibition assay. Five peptide sequences were identified as exhibiting good interaction with HSV-gD proteins. Among them, peptide N1 (residues 76-90) offered maximum protection against HSV-1 (66.57%) and HSV-2 (71.12%) infections. Modification of the identified peptide through peptidomimetic approaches may further enhance the activity and stability of the identified peptide.Communicated by Ramaswamy H. Sarma.

Herpes Simplex Virus 1 Glycoprotein B from a Hyperfusogenic Virus Mediates Enhanced Cell-Cell Fusion

Herpes simplex virus 1 (HSV-1) causes significant morbidity and death in humans worldwide. Herpes simplex virus 1 has a complex fusion mechanism that is incompletely understood. The HSV-1 strain ANG has notable fusion and entry activities that distinguish it from wild type. HSV-1 ANG virions fused with the Vero cell surface at 4 °C and also entered cells more efficiently at 15 °C, relative to wild type HSV-1 strain KOS virions, consistent with a hyperfusogenic phenotype. Understanding the molecular basis for the unique entry and fusion activities of HSV-1 strain ANG will help decipher the HSV fusion reaction and entry process. Sequencing of HSV-1 ANG genes revealed multiple changes in gB, gC, gD, gH, and gL proteins relative to wild type HSV-1 strains. The ANG UL45 gene sequence, which codes for a non-essential envelope protein, was identical to wild type KOS. HSV-1 ANG gB, gD, and gH/gL were necessary and sufficient to mediate cell-cell fusion in a virus-free reporter assay. ANG gB, when expressed with wild type KOS gD and gH/gL, increased membrane fusion, suggesting that ANG gB has hyperfusogenic cell-cell fusion activity. Replacing the KOS gD, gH, or gL with the corresponding ANG alleles did not enhance cell-cell fusion. The novel mutations in the ANG fusion and entry glycoproteins provide a platform for dissecting the cascade of interactions that culminate in HSV fusion and entry.

Impact of actin polymerization and filopodia formation on herpes simplex virus entry in epithelial, neuronal, and T lymphocyte cells

Herpes simplex virus type 1 (HSV-1) has been known as a common viral pathogen that can infect several parts of the body, leading to various clinical manifestations. According to this diverse manifestation, HSV-1 infection in many cell types was demonstrated. Besides the HSV-1 cell tropism, e.g., fibroblast, epithelial, mucosal cells, and neurons, HSV-1 infections can occur in human T lymphocyte cells, especially in activated T cells. In addition, several studies found that actin polymerization and filopodia formation support HSV-1 infection in diverse cell types. Hence, the goal of this review is to explore the mechanism of HSV-1 infection in various types of cells involving filopodia formation and highlight potential future directions for HSV-1 entry-related research. Moreover, this review covers several strategies for possible anti-HSV drugs focused on the entry step, offering insights into potential therapeutic interventions.

Mechanism of herpesvirus UL24 protein regulating viral immune escape and virulence

Herpesviruses have evolved a series of abilities involved in the process of host infection that are conducive to virus survival and adaptation to the host, such as immune escape, latent infection, and induction of programmed cell death for sustainable infection. The herpesvirus gene UL24 encodes a highly conserved core protein that plays an important role in effective viral infection. The UL24 protein can inhibit the innate immune response of the host by acting on multiple immune signaling pathways during virus infection, and it also plays a key role in the proliferation and pathogenicity of the virus in the later stage of infection. This article reviews the mechanism by which the UL24 protein mediates herpesvirus immune escape and its effects on viral proliferation and virulence by influencing syncytial formation, DNA damage and the cell cycle. Reviewing these studies will enhance our understanding of the pathogenesis of herpesvirus infection and provide evidence for new strategies to combat against viral infection.