Mycobacterium tuberculosis-specific (M. tuberculosis-specific) T cell responses associated with immune control during asymptomatic latent tuberculosis infection (LTBI) remain poorly understood. Using a nonhuman primate aerosol model, we studied the kinetics, phenotypes, and functions of M. tuberculosis antigen-specific T cells in peripheral and lung compartments of M. tuberculosis-infected asymptomatic rhesus macaques by longitudinally sampling blood and bronchoalveolar lavage, for up to 24 weeks postinfection. We found substantially higher frequencies of M. tuberculosis-specific effector and memory CD4+ and CD8+ T cells producing IFN-γ in the airways compared with peripheral blood, and these frequencies were maintained throughout the study period. Moreover, M. tuberculosis-specific IL-17+ and IL-17+IFN-γ+ double-positive T cells were present in the airways but were largely absent in the periphery, suggesting that balanced mucosal Th1/Th17 responses are associated with LTBI. The majority of M. tuberculosis-specific CD4+ T cells that homed to the airways expressed the chemokine receptor CXCR3 and coexpressed CCR6. Notably, CXCR3+CD4+ cells were found in granulomatous and nongranulomatous regions of the lung and inversely correlated with M. tuberculosis burden. Our findings provide insights into antigen-specific T cell responses associated with asymptomatic M. tuberculosis infection that are relevant for developing better strategies to control TB.
Keywords: Immunology; Infectious disease; Tuberculosis.