Much information regarding beneficial leishmania immune responses has been acquired by the investigation of murine infection models and human patient material. These studies indicate that the Th1 subset of CD4+ T cells is important for recovery from disease. Gp63, a leishmania antigen believed to be one target of these protective T cell responses, is an abundant, well-conserved cell surface metalloprotease of both infective promastigotes and replicative intracellular amastigotes. As with many subunit vaccine efforts, the production of gp63 in an appropriate recombinant/synthetic form followed by immunization in an immunogenic context which induces protective responses has been problematic. This issue needs to be systematically addressed not only with experimental models of leishmania infection but more importantly directly with naive human T cells. In this proposal recombinant gp63 (rgp63-B) produced in the baculovirus expression system, will be evaluated for the ability to induce protective T cell responses upon immunization, in both murine and human systems. Purified baculovirus derived rgp63-B will be used to sensitize naive human T cells in vitro. The sensitized T cell populations will be evaluated by proliferation, cell surface marker expression, cytokine production and cytotoxic effector activity in response to rgp63-B, leishmania lysate and leishmania infected macrophages. Sensitization of human T cells with rgp63-B in combination with immunomodulators will be used to drive gp63 specific T cells with selected beneficial phenotypes. These studies will define the parameters for the immunization of human T cells with rgp63-B necessary for the induction of protective Leishmania specific T cell responses. Based on these findings, the ability of rgp63-B in combination with selected adjuvants to immunize against challenge infection in vivo will be tested using murine models of leishmaniasis. Characterization of protective murine T cell responses will complement those involving human T cells sensitized in vitro.
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