Modulation of reactivation of latent herpes simplex virus 1 in ganglionic organ cultures by p300/CBP and STAT3

A key property of herpes simplex viruses (HSVs) is their ability to establish latent infection in sensory or autonomic ganglia and to reactivate on physical, hormonal, or emotional stress. In latently infected ganglia, HSV expresses a long noncoding RNA and a set of microRNAs, but viral proteins are not expressed. The mechanism by which latent HSV reactivates is unknown. A key question is, what is the mechanism of reactivation in the absence of tegument proteins that enable gene expression in productive infection? Elsewhere we have reported the use of ganglionic organ cultures that enable rapid reactivation in medium containing antibody to NGF or delayed reactivation in medium containing NGF and EGF. We also reported that in the ganglionic organ cultures incubated in medium containing antibody to NGF, all viral genes are derepressed at once without requiring de novo protein synthesis within the time frame of a single replicative cycle. Here we report that latent HSV in ganglia immersed in medium containing NGF and EGF is reactivated by (i) broad spectrum as well as specific histone deacetylase 1 or histone deacetylase 4 inhibitors, (ii) activation of p300/CBP, and (iii) either STAT3 carrying the substitution of tyrosine 705 to phenylalanine or an inhibitor of STAT3. Conversely, reactivation of latent HSV was blocked by p300/CBP inhibitor in medium containing antibody to NGF. The results suggest that (i) STAT3 is required for the maintenance of the latent state and interference with its functions leads to reactivation and (ii) p300/CBP is essential for HSV reactivation.