Animal models of VZV infection are needed for studies of VZV vaccine strategies and to test newer antiviral agents against VZV. We propose to continue to investigate VZV infection in the strain 2 guinea pig model of VZV because of its value for the analysis of VZV immunity and its potential for studies using viremia as a biological marker in primary VZV infection. Our experiments will focus upon immunomodulation to enhance the response to two major VZV proteins, the glycoprotein I, and p 170, a non- glycosylated VZV phosphoprotein, in the strain 2 guinea pig. Methods of incorporating these proteins into polymeric adjuvants, biodegradable microspherules or liposomes to facilitate antigen presentation in vivo will also be evaluated. The guinea pig VZV system will be most valuable if biological markers can be identified which will correlate with the reduction of viral replication in animals that have been immunized before viral challenge or treated with antiviral agents during the acute phase of the infection. Our strategy has been to use VZV viremia as a marker of particular relevance in VZV pathogenesis since viremia is a critical event during primary VZV infection of human subjects. A VZV DNA probe consisting of the HindIII a, b, c, and d fragments has been developed to identify VZV in peripheral blood cells by in situ hybridization. The VZV DNA probe will also provide an important tool for analyzing issues in VZV pathogenesis that can be addressed only in the animal model, e.g., the investigation of VZV infection of nasopharyngeal mucosal cells. Our preliminary results indicate that VZV viremia can be potentiated by selective immunosuppression, which is analogous to the observation of persistent viremia associated with progressive disseminated varicella infection in immunocompromised children. Other likely target organs of primary VZV infection in the strain 2 guinea pig, e.g., lungs spleen and liver, will be examined for evidence of VZV infection particularly in animals in which VZV viremia has been potentiated by immunosuppressive regimens. Viral culture of tissue samples will be done by cocultivation with guinea pig embryo fibroblasts and tissue sections will be examined by immunofluorescence or immunoperoxidase staining with VZV monoclonal antibodies and by in situ hybridization with the VZV DNA probe. A new rationale for further work with VZV in the guinea pig system is the potential for the study of VZV pathogenesis using viral strains that have been modified by recombinant DNA techniques. Recombinant strains of VZV which express the E. coli lacZ gene will be developed; cells infected by these VZV recombinants in strain 2 guinea pigs will be identified by staining with a chromogenic substrate for beta-galactosidase. The guinea pig model of VZV infection as developed by using in situ hybridization to detect viremia, by immunosuppressive regimens and by the use of genetically altered strains of VZV will provide the basis for experiments to determine the efficacy of VZV immunization strategies and of antiviral agents that inhibit VZV.
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