Project Summary Mycobacterium tuberculosis (M.tb) causes tuberculosis (TB), a serious lung disease that affects over one third of the global population and results in ~1.5 million deaths every year. TB treatment includes a combination of three or more anti-TB drugs over a prolonged period (6–9 months). In the last few decades, multidrug-resistant TB and extensively drug resistant TB strains have emerged due to mismanaged use of anti-TB drugs, (e.g., not completing the full course of the TB regimen, using the wrong dose or length of administration time, and/or the use of poor-quality drugs). We propose that shortening the treatment period for clearance of M.tb would assist to eradicate TB and preventing the development of drug resistance in active and latent TB. We discovered that, the need for long treatment period is partly due to suppression of the host innate immune response by M.tb, which involves the efflux of endogenous anti-microbial substances and administered TB drugs from host macrophages. Specifically, when macrophages are infected with M.tb, expression of the macrophage drug efflux pump MDR1 increases, resulting in various endogenous and exogenous chemical substances, including TB drugs, being expelled from macrophages to benefit the survival of the bacteria. Thus, M.tb co-opts these host pathways. Overall, the mission of my laboratory is to identify molecules in the host that will enable us to create a novel host-directed therapy for TB. Toward that end, we were the first to discover the link between M.tb pathogenesis and macrophage MDR1 expression and function during infection. Elevated MDR1 alters the macrophage innate immune response and subsequent efflux of antimicrobials reduces the effectiveness of macrophages M.tb killing. We hypothesize that M.tb-dependent upregulation of MDR1 expression in human macrophages is mediated by heat shock factor protein 1 (HSF1). The aims of the proposed research are to 1) Define the role of MDR1 in M.tb survival in macrophages; 2) Determine whether HSF1 activation or MDR1 inhibition shortens the sterilization period of M.tb by TB drugs; and 3) Identification of endogenous antimicrobials produced by macrophages in response to M.tb infection. We will use human monocyte-derived macrophages, biochemical and genetic techniques, and a mouse model to accomplish our aims. Our basic research discoveries will jump-start the development of new drugs to treat tuberculosis.