Reactivation of varicella zoster virus decades after infection leads to the common and painful disease shingles. VZV latency in neurons is difficult to study, and experimental reactivation is has not been demonstrated because of the human-specificity of the virus. A simple culture model of neuronal latency that can be reactivated could have enormous impact on our understanding of these important processes. Here we report that hESC derived neurons infected with GFP-expressing recombinant VZV in the presence of acyclovir results in a non-productive persistent infection of human neurons that can be “reactivated”. When hESC-derived neurons were exposed to cell free VZV-GFP66 in the presence of acyclovir at low PFU, 80% of wells did not show GFP fluorescence after one week. qPCR analysis of these non-fluorescing neurons 2, 4 and 7 weeks after VZV introduction revealed both VZV DNA and transcripts for VZV genes at all time points, with the level of DNA and transcripts decreasing with time. Addition of an HDAC inhibitor or growth factor withdrawal 2-4 weeks after initial VZV exposure resulted in 30% of the previously GFP-negative wells displaying GFP-fluorescence. RNA of two VZV genes, one IE and one L, showed a large increase after experimental "reactivation", and a large increase in viral genomes were found using Taqman qPCR. These results establish a simple model for latency and reactivation based on hESC neurons that could shed light on these clinically important phenomena.
