Effect of HIV on the frequency and number of Mycobacterium tuberculosis-specific CD4+ T cells in blood and the airways during latent M. tuberculosis infection

Human immunodeficiency virus type 1 (HIV) infection substantially increases the risk of developing tuberculosis. There is extensive depletion of Mycobacterium tuberculosis-specific CD4+ T cells in blood during early HIV infection, but little is known about responses in the lungs at this stage. Given that mucosal organs are a principal target for HIV-mediated CD4+ T-cell destruction, we investigated M. tuberculosis-specific responses in bronchoalveolar lavage (BAL) from persons with latent M. tuberculosis infection and untreated HIV coinfection with preserved CD4+ T-cell counts. M. tuberculosis-specific CD4+ T-cell cytokine (interferon γ, tumor necrosis factor α, and interleukin 2) responses were discordant in frequency and function between BAL and blood. Responses in BAL were 15-fold lower in HIV-infected persons as compared to uninfected persons (P = .048), whereas blood responses were 2-fold lower (P = .006). However, an increase in T cells in the airways in HIV-infected persons resulted in the overall number of M. tuberculosis-specific CD4+ T cells in BAL being similar. Our study highlights the important insights gained from studying M. tuberculosis immunity at the site of disease during HIV infection.