Despite the presence of a vigorous, broadly reactive HIV-1-specific immune response in infected individuals, progression to AIDS almost inevitably occurs. It has been postulated that mutations within critical epitopes may allow HIV-1 to escape immune recognition by cytotoxic T lymphocytes. A corollary to this hypothesis is that the ability of the host to generate new CTL responses may be a critical factor in containing viral replication. We propose to evaluate the CTL response a cohort of subjects with documented HIV-1 infection of over 10 years and with no evidence of disease progression (LTNP) to assess whether it is qualitatively or quantitatively different from the response in rapid progressors. In project 1 of this proposal, scientists at Cytel Corp. will identify high affinity HLA-A2.1 binding peptides that correspond to conserved regions of the HIV-1 genome. The ability of these peptides to induce primary and memory CTL responses in seropositive subjects will be evaluated in project 2. Peptides preferentially recognized by LTNP will be incorporated into a lipopeptide based immunotherapeutic agent designed to augment and broaden existing CTL responses in subjects with CD4 counts greater than 500. Specifically we propose to 1) Determine the ability of synthetic HIV-1 peptides with high binding affinity to the HLA A2 molecule to elicit in vitro memory Cit responses in infected long term nonprogressors, in recent seroconverters with normal CD4 counts, and rapid progressors. 2) Determine the ability of synthetic HIV-1 peptides with high binding affinity to HLA A2 to induce primary CTL responses in seronegative and seropositive subjects. 3) Sequence autologous virus in areas of Cit epitopes and assess the ability of variant peptides to elicit Cit activity. 4) Based on the above studies a lipopeptide based vaccine will be tested in humans in project 3 of this proposal. Pre and post vaccination studies will determine the immunogenicity of the vaccine by measuring the number of circulating epitope-specific CTL precursors, and Cit data will be correlated with virologic parameters. CTL generated after primary in vitro stimulation or after vaccination with the lipopeptide will be tested for the ability to recognize peptides representing HIV-1 variants as well as HLA matched HIV-1-infected cells. The T cell receptors of these Cit clones will be sequenced after anchored polymerase chain reaction. TCR cDNA libraries will be made from the PBMC of study subjects pre and post vaccination to follow the emergence and longevity of CTL clones generated as a result of this vaccination protocol. The results of this research will further our understanding of the HIV-1-specific Cit response. The generation of new HIV-1-specific CTL populations with broadened epitope specificity may lead to a practical strategy for HIV-l immunotherapy.

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