Autophagy has recently been demonstrated in both cultured cells infected with varicella-zoster virus (VZV) as well as in a human zoster vesicle. The presence of punctate autophagosomesin a zoster skin vesicle firmly established that autophagy (macroautophagy) is a relevant biologicalprocess during the natural history of disease caused by this herpesvirus. Of importance, we havecarried out sufficient preliminary studies to document that autophagy induced by VZV infectiondoes not resemble HSV-induced autophagy. First of all, the VZV genome lacks a homolog of theHSV ICP 34.5 gene. Secondly, we have now shown by two different methods that VZV infectionquickly induces marked ER stress, an event not known to occur in the HSV system. Therefore, there-stated central hypothesis for this proposal is that ER stress is a critical component of VZVinfection, that ER stress is related to an over abundance of misfolded VZV glycoproteins in the ER,and that ER-associated degradation and autophagy are consequences that relieve ER stress. Theseevents allow the infected cell to survive longer, to avoid apoptosis, and in that sense can beconsidered pro-viral. The Research Plan to test this hypothesis involves three Specific Aims.
Aim1 is called Induction of autophagy as a consequence of VZV induced ER stress.
Aim 2 is calledActivation of the unfolded protein response (UPR) by VZV induced ER stress.
Aim 3, whichinvolves the A. Arvin laboratory, includes Studies of autophagy and ER stress in the SCID-humouse model, following infection with various recombinant mutated VZV genomes. In ourResearch Plan, we will continue prior investigations with an expanded experimental approachdirected toward the three sensor pathways that lead from ER stress to the UPR (IRE1, ATF6 andPERK). We have already detected four proteins associated with the UPR in VZV infected cells,including BiP (HSPA5), HSPA8, HSPD1 and PPIA: peptidyl-propyl-cis-trans-isomerase). Morerecently we have detected the spliced form of XBP1 (X-Box binding protein) in VZV infected cells,another marker of the UPR. The final approach will include animal experiments with alreadyprepared recombinant viruses containing numerous gE mutations. The phenotypes of these mutantviruses have already been determined in both cell culture and the SCID mouse model. Thus theabove experimental plan will determine the relative importance of ER stress and autophagy in thecellular response to VZV infection. The results are relevant not only to our understanding ofvaricella vaccination but also the debilitating zoster-related illness called post-herpetic neuralgia.
Varicella zoster virus is the first human herpesvirus to be attenuated for a vaccine to prevent chickenpox and also herpes zoster. Questions remain about the mechanisms of protection, especially for older adults who receive the vaccine to prevent shingles.
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