IMMUNE RESPONSES TO CLYCOSYLATION-MODIFIED SIV VACCINES

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Human and simian immunodeficiency viruses (HIV and SIV, respectively) contain heavily glycosylated, surface and transmembrane envelope glycoproteins. The carbohydrate moieties of glycoproteins from other sources are known to play significant roles in immunogenicity. However, little is known regarding the role of HIV and SIV carbohydrate moieties in the immune response to these viruses. Information regarding this role could be important to the design of a safe and effective AIDS vaccine. Therefore, the objectives of this proposal are to elicit in rhesus macaques (Macaca mulatta) immune responses to glycosylation-modified, whole SIV vaccines, and to compare the effectiveness of these responses against naturally glycosylated SIV. Emphasis will be placed on humoral responses. Virus will be synthesized in H9 cells infected with SIVmac251. N- glycosylation will be modified using the glycoprotein processing inhibitors, castanospermine (glucosidase I inhibitor), 1- deoxymannojirimycin (mannosidase I inhibitor) and swainsonine (mannosidase II inhibitor) or by enzymatic removal of sialic acids using neuraminidase. Three different molecular species of high mannose-type, non-sialylated, non-fucosylated carbohydrate moieties should arise in the presence of these inhibitors, while neuraminidase treatment of naturally synthesized virus should yield complex-type, desialylated carbohydrate moieties. SIV, naturally synthesized in cell culture and untreated, will be used as control. Virions will be examined for biological activity, and the viral proteins analyzed for SDS-PAGE mobility, immunoblot reactivity, and carbohydrate content. Psoralen/UV-inactivated whole virus vaccines will be administered in adjuvent to macaques. General immune responses will be monitored by ELISA and Western immunoblot. Specific functional immune responses to be monitored are: 1). neutralizing antibody titers, 2). complement-mediated, antibody-dependent enhancing activity, 3). antisyncytial antibody titers, and 4). T cell proliferative responses. Finally, the macaques will be challenged with live SIV to determine vaccine efficacy. These studies are viewed as the first phase of a larger effort aimed at adequately addressing potential hazards and benefits that may be created by modifying normal glycosylation of potential SIV and HIV vaccines.