VP16‐HCF interaction is required for herpes simplex virus exit from latency in neurons in vivo

Abstract

A mechanistic understanding of viral and host functions regulating herpes simplex virus (HSV) latency and reactivation remains a major goal. We have shown that the interaction of VP16 and Oct‐1 is required very early during entry into the lytic cycle from the latent state and have proposed a VP16‐dependent model of reactivation in vivo. HCF‐1 has important roles in promoting HSV replication and a model has been proposed in which stress induces translocation of HCF‐1 into the neuronal nucleus and reactivation is regulated by direct recruitment of HCF to viral IE genes. To investigate whether HCF‐1 can precipitate viral gene expression in latently infected neurons in the absence of binding to VP16, a mutation in VP16 at Y364A, shown previously to disrupt VP16‐ HCF interaction (but not interaction with Oct‐1) was engineered into HSV‐1. Three independent isolates and a genomically restored virus were examined in vitro and in the mouse ocular model. Our findings demonstrate that the interaction of VP16 with HCF‐1 is required for efficient infection at low moi, efficient viral replication in vivo, and exit from latency/entry into the lytic cycle in trigeminal ganglion neurons in mice following hyperthermic stress. In the absence of VP16 binding, nuclear translocation of HCF is not sufficient to initiate the viral lytic cycle, demonstrating the key role of VP16 in regulating in vivo reactivation.