Herpes simplex virus 1 glycoprotein B from a hyperfusogenic virus mediates enhanced cell–cell fusion.

Authors: GIANOPULOS, KATRINA - Washington State University; MAKIO, ALBINA - Washington State University; PRITCHARD, SUZANNE - Washington State University; Cunha, Cristina; HULL, MCKENNA - Washington State University; NICOLA, ANTHONY - Washington State University

Submitted to: Viruses
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/30/2024
Publication Date: 2/4/2024
Citation: Gianopulos, K.A., Makio, A.O., Pritchard, S.M., Cunha, C.W., Hull, M.A., Nicola, A.V. 2024. Herpes simplex virus 1 glycoprotein B from a hyperfusogenic virus mediates enhanced cell–cell fusion.. Viruses. 16(2). Article 251. https://doi.org/10.3390/v16020251.
DOI: https://doi.org/10.3390/v16020251

Interpretive Summary: Herpes simplex virus 1 (HSV-1) causes severe diseases and death in humans worldwide. For HSV infection to occur, fusion between the virus envelope and the host cell membrane must occur, allowing the virus to penetrate the cell. This is a complex mechanism that is not fully elucidated. To better understand the molecular basis of the virus entry process, in this work we investigated viral envelope glycoproteins of a hyperfusogenic HSV, the HSV-1 strain ANG. We demonstrated that the genes encoding glycoproteins involved in virus entry, gB, gC, gD, gH, and gL, have multiple changes in HSV-1 ANG relative to wild type HSV-1 strains. Using a virus-free reporter assay we confirmed that HSV-1 ANG gB, gD, and gH/gL are necessary and sufficient to mediate cell-cell fusion. When wild type gB, gD, gH, or gL were replaced with the corresponding ANG gene, only ANG gB increased membrane fusion, suggesting that this protein determines the hyperfusogenic activity observed in the ANG strain. The study adds novel information that helps to dissect the cascade of HSV fusion and entry interactions that culminate in virus infection.

Technical Abstract: 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 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. 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 gD and gH/gL, increased membrane fusion, suggesting that ANG gB has hyperfusogenic cell-cell fusion activity. Replacing the wild type gD, gH, or gL with the corresponding ANG alleles did not enhance cell-cell fusion. Wild type gC is proposed to facilitate fusion and entry into epithelial cells by optimizing conformational changes in the fusion protein gB. ANG gC substitution or addition also had no effect on 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.