An effective vaccine against HIV infection remains an elusive goal, especially as the sequence diversity of the virus continues to expand. We developed a model system that relies on the recognition of T cell epitopes from immunodominant antigens of HIV to explore novel uses of oligodeoxynucleotides (ODN) as adjuvants, with the purpose of developing an improved strategy for vaccine delivery. We increased the sensitivity of our approach, by developing a novel synthetic chemical strategy of covalently modifying T-help/CTL epitope fusion peptides with CpG-ODN motifs. In this revised application, specific concerns of the Study Section have been addressed in preliminary data including the necessity for a T-help epitope, the fate of epitopes in the middle of peptide strings, and the evaluation of human-specific CpG-ODN. Immunogenicity, in vitro recognition of HIV-infected T cells, and protection against viral infection using a surrogate virus (poxvirus) will be criteria to measure efficacy of newly derived CpG-ODN:peptide conjugates in HLA transgenic murine models. The focus of the experimental section will be on strategies that yield greater sensitivity of immune stimulation by the conjugate vaccines, as well as broadness and strength of immune responses to epitopes from multiple antigens. The methodology for conjugating peptide to CpG-ODN will be intensively investigated in Specific Aim 1, with the purpose of disclosing new chemical structures that will heighten the sensitivity of immune response to the vaccine. A more focused ranking formula that distinguishes vaccines targeting acute and chronic HIV infection will be instituted. Since HIV has immense capacity for escape from cellular immunity, we will seek to combine epitopes from multiple antigens to prevent escape from immune recognition by HIV.
In Specific Aim 2, we will explore protection models to assess whether the synthetic vaccine strategies that are most immunogenic in Specific Aim 1, also are more efficient at providing protection against an HIV-antigen recombinant poxvirus challenge. These will include more virulent forms of vaccinia virus, whose clearance may closely model outcomes of human viral infection with un-attenuated viruses. In addition, we will explore whether increased efficiency of immune recognition by CpG-ODN:peptide conjugates will also apply to HIV strains including clades A-D in direct lytic assays of HIV-infected Jurkat T cells. These studies will establish feasibility and provide impetus to extend these observations into primate models of HIV infection, and will justify the intensive studies proposed in this application.
