Despite the significant reduction in HIV burden associated with HAART, reservoirs of latent virus remain in treated individuals. These reservoirs serve to provide a source for new virus when treatment is interrupted, and a site for creating drug resistant variants. In some individuals, discontinuation of HAART stimulates virus-specific T cell responses that appear to control virus. This phenomenon suggests that immunization with an effective vaccine during therapy may augment the effect of HAART. Two criteria are critical in the design of such a strategy: 1. Identification of the reservoir(s) so that immunization can be specifically targeted to it, and 2. The vaccine must induce responses that clear virus infected cells in the reservoir. We hypothesize that the intestinal lamina propria serve as a major reservoir of virus during HAART. Thus a mucosal vaccine is needed. An additional advantage is served by this approach because the GALT serves as an extrathymic site for T cell maturation, therapy overcoming the thymic destruction induced by chronic HIV infection. We propose to use a novel vaccine utilizing skin immunization with viral DNA co-delivered with vectors expressing genes for potent mucosal adjuvants, bacterial enterotoxin genes (CT or LT). Using the SIV: macaque model for AIDS this project will implement in vivo primate studies designed to compare the immunogenicity of SIV DNA with or Without vectors encoding CT or LT (project 1). Test vaccines encoding DC-specific chemokines and chemokine receptors (projects 3 and 4), and evaluate the ability of the optimized vaccine adjuvant formulation to serve as an effective adjunct to HAART in monkeys treated with PMPA (projects 1-4). Monkeys will be immunized, infected with titered stocks of SIV/DeltaB670 to determine the efficacy of treatment. The role of the GALT as a reservoir, and the ability of DNA immunization+/- PMPA to stimulate recovery (HAART +/- vaccine therapy) of immune responses in the GALT will be determined by analysis of antibody in mucosal secretions, function of CD4+ and CD8+ T cells, and quantitation of SIV-specific CD8+ cells by tetramer staining. T cells from the GALT will also be phenotyped to determine changes in lymphocyte subpopulations, the source of repopulating cells (naive versus memory subsets) and functional capability. The presence of SIV tetramer- binding CD8+ cells expressing alpha4beta7, the receptor mechanism whereby priming in the skin can induce effect responses in the mucosa, an ddetermine the relative magnitude of these responsres induced in the GALT by the different vaccine adjuvant formulations. The demonstration of this approach in identify the induction of mucosal immune response in the periphery of monkeys immunized during therapy will encourage similar studies in the analogous human trials described in project 5.
