Identifying Mycobacterium tuberculosis-derived MR1 ligands and the MAIT cell response 2826

Description Tuberculosis caused by Mycobacterium tuberculosis (Mtb) is the leading cause of infectious disease-related deaths. Mtb has evolved resistance to antimicrobials necessitating new approaches to anti-TB therapy. Our study focuses on mucosal-associated invariant T (MAIT) cells that have been identified as responsive to Mtb infection and may contribute to innate resistance against TB. MAIT cells are innate-like T cells that recognize non-peptide riboflavin intermediates derived from microbes and are presented by MHC I-related protein (MR1). Our objective is to define Mtb-specific MR1 ligands and target them for immune-directed therapy against Mtb. To identify these ligands, we extracted virulent Mtb culture and identified MR1 ligand 5-OE-RU using LC-MS. To test if this extract could activate MAIT cells, we incubated it with healthy human peripheral blood mononuclear cells. Mtb extract did not significantly induce MAIT cell activation, suggesting the dominant effect of inhibitory MR1 ligands. To interrogate how targeted disruption of Mtb riboflavin biosynthesis changes the MR1 ligand composition, we generated CRISPRi tetracycline-inducible knockdowns of Mtb Erdman riboflavin genes ribA2, ribC, and ribH. We identified significant changes in metabolites 5-A-RU and riboflavin in knockdown strains that are expected to predict MR1-mediated control of Mtb infection. Identification of Mtb-specific MR1 ligands will inform the design of novel antimicrobials/host-directed therapies against TB. Funding Sources Supported by NIH/NIAID R21 AI171578, Stony Brook University’s Scholars in Biomedical Sciences Topic Categories Microbial, Parasitic, and Fungal Immunology (MPF)