Varicella-zoster virus (VZV) causes a disseminated illness, varicella, and then becomes latent in sensory ganglia. Reactivation leads to zoster, an exanthem that is restricted to the innervated field of the ganglion in which reactivation occurs. We have developed a model that recapitulates the scenarios of latency and reactivation of VZV in human dorsal root ganglia. In latency, 6 of the 68 genes of VZV are expressed, all of which are either immediate early or early viral genes in the VZV cascade. In latent neuronal infection, the latency-associated proteins encoded by Orfs 4, 21, 29, 62, 63 and 66 are restricted to the cytoplasm, although they are regulatory proteins that are predominately nuclear during lytic infection. The model consists of neurons isolated from the guinea pig intestine or neural crest-derived cells from mice. When purified neurons are infected with cell free VZV, latent infection ensues with survival of neurons for weeks, despite the presence of cytoplasmic VZV proteins. Superinfection of latently infected neurons with an adenovirus encoding the ICP0 of herpes simplex virus (HSV) or a retrovirus encoding VZV Orf 61p reactivates VZV. Reactivation is evidenced by translocation of the VZV latency associated proteins to the nucleus, production of late gene products such as glycoproteins, and neuronal death. This model will be utilized to explore the hypothesis that a block in nuclear transport of specific proteins governs maintenance of latent VZV infection. We will use array technology to examine changes in gene expression in VZV latency and reactivation. Following mutagenesis, the potential roles of Orf 4p (the ortholog of HSV ICP 27) and Orf 29p, the major DNA-binding protein in reactivation will be examined. Finally we will identify the nuclear localization signal of Orf 29p and determine whether nuclear translocation is a prerequisite for reactivation from latency. ? ? ?
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