The enormous public health problem posed by tuberculosis in HIV-1- infected individuals, particularly the marked increase in highly lethal drug-resistant disease, has created an urgent need to develop new approaches to treat and prevent tuberculosis. We propose to devise novel immunotherapeutic approaches to augment cell-mediated immune responses to M. tuberculosis in HIV-1-infected persons. First, we will characterize the T-cell cytokine profiles in PBMC from HIV-infected tuberculin reactors and TB patients, using RT-PCR to quantify cytokine mRNA and measuring cytokine concentrations in supernatants of PBMC stimulated with M. tuberculosis antigens. We will determine the individual effects of HIV and TB infection on the cytokine profile, and verify whether some patients coinfected with TB and HIV mount weak Th1 responses, as suggested by our preliminary data. We will attempt to correlate the level of Th1 and Th2 cytokines with the manifestations of TB and the stages of HIV infection. Four approaches then will be taken to augment Th1 T-cell responses which are required for protective immunity: (1) stimulation with mycobacterial antigens shown above to be stimulatory of Th1 responses; (2) addition of exogenous IL-12, of particular interest because IL-12 augments Th1 responses; (3) activation of gammadelta-T-cells, a population spared by HIV-1 infection and therefore an ideal target for immunotherapy; and (4) if Th2 responses are found to be prominent in individuals with HIV and tuberculosis, we will utilize neutralizing antibodies to Th2 cytokines, well-established as favoring Th1 responses in experimental models. The effect of these immunotherapeutic modalities on macrophage killing of M. tuberculosis in vitro will also be investigated. Activation of CD4 cells and macrophages, or alterations in cytokine profiles, could promote HIV-1 replication. Therefore, it will be critical to establish whether therapies that augment anti-tuberculous responses have a similar effect on antiviral mechanisms or paradoxically enhance viral replication. We will evaluate the effects of the immunotherapeutic modalities on expression of latent HIV infection and de novo infectability of PBMC with HIV. We believe that the studies proposed here will provide a rationale for designing new immunotherapy protocols for HIV-1-infected individuals with opportunistic infection.
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