Despite the immune-reconstitution with antiretroviral therapy (ART), HIV-infected individuals remain highly susceptible to tuberculosis (TB) and have an enrichment of oral anaerobes in the lung. Products of bacterial anaerobic metabolism, like butyrate and other short-chain fatty acids (SCFAs), induce regulatory T cells (Tregs). We tested whether SCFAs contribute to poor TB control in a longitudinal cohort of ART-treated HIV-infected South Africans. Increase in serum SCFAs was associated with increased TB susceptibility. SCFAs inhibited IFN-γ and IL-17A production in peripheral blood mononuclear cells from HIV-infected ART-treated individuals in response to M. tuberculosis antigen stimulation. Pulmonary SCFAs correlated with increased oral anaerobes, such as Prevotella in the lung, and with M. tuberculosis antigen-induced Tregs. Metabolites from anaerobic bacterial fermentation may, therefore, increase TB susceptibility by suppressing IFN-γ and IL-17A production during the cellular immune response to M. tuberculosis.
Keywords: FoxP1; FoxP3; HIV; dysbiosis; lung; short-chain fatty acids; tuberculosis.
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