HIV-1 Infection Impairs the Bronchoalveolar T-Cell Response to Mycobacteria
The risk of developing active tuberculosis in persons with latent Mycobacterium tuberculosis infection is substantially increased shortly after HIV-1 seroconversion. Immune responses in the lung are important to restrict the growth of M. tuberculosis to prevent the development of disease.Objectives:
To investigate innate and adaptive immune responses to M. tuberculosis in bronchoalveolar lavage from HIV-1–infected persons without active tuberculosis.Methods:
Peripheral blood was drawn and bronchoalveolar lavage (BAL) performed on healthy, HIV-1–uninfected (n = 21) and HIV-1–infected (n = 15) adults. Growth of M. tuberculosis was assessed in monocytes and alveolar macrophages. Cytokine expression by mycobacteria-specific CD4 and CD8 T cells was measured by intracellular cytokine staining or IFN-γ ELISpot.Measurements and Main Results:
Mycobacterial growth in monocytes or alveolar macrophages from HIV-1–infected and –uninfected persons did not differ. Total CD4 T-cell frequencies in BAL were lower in HIV-1–infected than in HIV-1–uninfected persons (P < 0.001). Mycobacteria (bacillus Calmette-Guérin)-specific CD4 T-cell responses in BAL were severely impaired: Frequencies of cells expressing IFN-γ or tumor necrosis factor (TNF)-α, as well as polyfunctional cells, expressing IFN-γ, TNF-α, and IL-2 together, were lower in HIV-1–infected persons than in uninfected controls (P < 0.01 for all).Conclusions:
In addition to a total CD4 T-cell deficit, the function of mycobacteria-specific CD4 T cells is significantly impaired in the lung of HIV-1–infected persons, which may account for the HIV-1–associated elevated risk for developing tuberculosis.