Most HIV seropositive persons show humoral and cell-mediated immune responses to HIv antigens and in particular to the env gene products of HIV, the external envelope glycoprotein gp120 (EEG). the overall goal of this proposal is to define the role of the carbohydrates of the external envelope glycoprotein in affecting the immune response to the virus. The simian immunodeficiency virus/rhesus macaque model system will be used to focus on a variety of humoral and cell-mediated immune responses to the wild-type EEG and selected mutant and variant EEGs of the cloned SIVmac239 strain of the rhesus macaque simian immunodeficiency virus. Variant and mutant EEGs will be produced using oligonucleotide-mediated site-directed mutagenesis of the EEg DNA sequence and B' mutations in the pathway of protein glycosylation (Objective 1). Purified EEGs will characterized based on their structural and functional properties (Objective 2), and after immunization of small animals with selected mutant and variant glycoproteins the specific immune responses will be assessed (Objective 3). The strength, nature and extent of the responses will be compared with those induced by the wild-type EEg and will be correlated with the carbohydrate structure of the immunogen. The ability of mutant and variant EEG to provide protection from SIV infection will be determined (Objective 4), by challenging immunized monkeys with infectious clones of SIVmac 239 and 251 and with extracts that produce AIDs-like symptoms to determine whether the immune responses are broadly protective. To enhance development of cell mediated immunity, genes specifying the appropriate EEGs will be used to construct replicating simian adenovirus.SIVenv expression vectors, as has been done previously for an HIV env-adenovirus vector. These recombinants will be evaluated as potential vaccine candidates.
