Varicella-zoster virus (VZV) is the etiologic agent of both the common childhood illness chickenpox and, upon reactivation, the dermatomal exanthem shingles (herpes zoster). Although only moderately distressful in healthy people, both diseases are important causes of morbidity and mortality in children and adults with cancer or other chronic immunocompromising illnesses, including AIDS. The goal of the research is to define and characterize the major antigenic determinants of this herpesvirus. Glycoproteins encoded by VZV will be given the highest priority because they play a prominent role in the induction of protective immune responses; the same glycoproteins mediate important interactions between virus and cell, and also function as cell surface receptors. VZV is unique among the human herpesviruses in having the fewest glycoproteins; the focus of this proposal will be restricted to the two glycoproteins encoded within the Us segment of the VZV genome: VZV gpI and gpIV.
The Specific Aims i nclude the following: (1) Analyze the cell surface expression of a VZV induced Fc receptor and prepare glycoprotein gene constructs which mimic its biologic activity; (2) Investigate the cellular protein kinases which catalyze phosphorylation of VZV gpI and gpIV; (3) Clone and express the two putative VZV protein kinases and determine whether they phosphorylate the two glycoproteins; and (4) Define the functions of the VZV Fc receptor and this constituent glycoproteins. Epitopes of gpI and gpIV are involved in antibody dependent cellular toxicity and antibody plus complement lysis of VZV-infected cells, activities which may be inhibited after engagement of the viral Fc receptor by nonimmune IgG or bipolar antibody bridging. Methods include subcloning of VZV glycoprotein genes for transcription/translation and transfection experiments; protein kinase assays with cellular phosphotransferases; site- directed mutagenesis of serine/threonine residues; analyses of cloned putative viral kinases; hybridoma production and flow cytometry, as well as functional assays to characterize antigenic sites. Results from these studies should define major structure-function relationships of the two VZV Us glycoproteins, and at the same time, provide at least a partial explanation why VZV can be a competent alpha/herpesvirus with a limited number of glycoproteins.
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