By destroying virus-infected cells, CD8+ cytotoxic T lymphocytes (CTL) contribute to the termination of viral infections and play an important role in immune defenses against many viruses. Although CTL are found in substantial numbers in individuals infected with human immunodeficiency virus type 1 (HIV-1) and may help lower the viral burden in these individuals, these cells do not succeed in eliminating HIV-1 infection. To help understand why these cells are not more effective in HIV-1 infections and to help lay the groundwork for a more rational development of vaccines aimed at enhancing the production and effectiveness of these cells, we will identify and analyze the naturally occurring peptides of HIV-1 origin in HIV-1 infected cells. The peptides analyzed will be principally those that are recognized in association with class I MHC class proteins by CD8+ CTL clones or lines from HIV-1 infected individuals. We will also analyze the most abundant HIV-1 peptides associated with class I MHC proteins from infected cells. All of these peptides will be characterized in terms of their a) amino acid sequence, b) abundance as adducts of class I MHC proteins isolated from cells that are producing HIV-1, and c) their affinity (intrinsic equilibrium association constant) for MHC-I proteins. To achieve these goals we will use specially constructed stable, cultured cell lines in which every cell produces HIV virus and expresses a class I MHC protein chosen to represent one of the more common ones in human populations and that restrict recognition of HIV-1 peptides by human cytotoxic T cell clones. These specially constructed HIV-1 producing cell lines and antigen-processing mutant cells (such as T2) that can be loaded exogenously with synthetic peptides will be used as stimulator cells to elicit new CD8+ CTL cell lines and clones from HIV-1 infected individuals of appropriate HLA type (e.g. HLA-H2); the cytolytic effectiveness of the new clones will be evaluated and the peptides they recognize (in association with MHC-1) will also be analyzed as described.