Partial or complete blocking of gD binding to HVEM affects primary and latent HSV-1 infection as well as eye disease in HSV-1 infected mice.

Herpes simplex virus type 1 (HSV-1) glycoprotein D (gD) engages herpesvirus entry mediator (HVEM) and other cellular receptors to mediate efficient viral attachment. We recently identified gD amino acids (aa) Q27-T29 as critical to completely block gD binding to HVEM, while the single Q27P mutation in gD reduced its binding to HVEM by approximately 80%. Thus, we constructed two mutant viruses: one with a single gD aa mutation (v27) and the other with three gD aa mutations (v27-29) in the HSV-1 strain GFP-McKrae background. These mutant viruses clearly demonstrated the consequences of disrupting gD binding to HVEM, which reduced HVEM expression and altered the expression of other receptors. To determine whether these mutations also affected viral replication, ocular disease severity, latency levels, and reactivation kinetics, mice were ocularly infected with WT, v27, or v27-29 viruses. Both mutant viruses exhibited significantly reduced viral replication in tears compared with the WT virus, even after corneal scarification. The v27-29 virus showed a greater reduction in viral replication than the v27 virus. Mice infected with both mutant viruses had significantly lower levels of eye disease, latency, and T cell exhaustion than in WT virus-infected mice. In the absence of scarification, significantly fewer trigeminal ganglia (TG) were reactivated by mutant viruses than by the WT virus. In contrast, after scarification, all TG from WT-, v27-, and v27-29-infected mice were reactivated, and the time to reactivate was similar between the two mutant viruses, but reactivation was significantly less delayed than in WT-infected mice. Together, these findings demonstrate that disrupting gD-HVEM binding reduces viral virulence and limits latency, reactivation, and T cell exhaustion. Thus, the Q27-T29 region of gD is a critical determinant of infection dynamics and a potential therapeutic or vaccine target.