Persistent DNA Hyper-Methylation of the IFN-γ Signaling Pathway During Tuberculosis

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PROJECT SUMMARY: Tuberculosis (TB) is the world’s leading infectious disease cause of mortality and suffering. Existing “short-course” therapy lasts six grueling months and has case fatality rates of 3% that increase to >20% in TB hyper-endemic countries and > 30% in the setting of multi-drug resistant TB. The Mendelian Susceptibility to Mycobacterial Disease (MSMDs) are rare genetic mutations that perturb the immune system either up or down-stream of the IFN-γ signaling pathway. It is well known that TB subverts host immune control, however the multiple mechanisms it does so remain to be fully elucidated. Our preliminary data demonstrate that TB epigenetically subverts host immunity by inducing DNA hyper-methylation both up and down-stream of the IFN-γ signaling pathway, akin to the MSMD mutations. Further, our preliminary data demonstrates that immune cells from study participants with TB have decreased up-regulate of IFN-γ-inducible gene expression, thereby mimicking the functional defect seen in the down-stream MSMD mutations in IFNGR, STAT1, and IRF1. Our preliminary bioinformatics analysis demonstrates that the inhibition of IFN-γ-inducible gene expression occurs through epigenetic inhibition of a) the canonical IFN-γ signaling pathway, b) transcription factors and c) non-canonical signaling pathways. Using an existing biorepository, we will evaluate the DNA methylation of the canonical IFN-γ signaling pathway as well as overlapping and intertwined non-canonical signaling pathways. We will functionally validate these results by evaluating if de-methylating agents are able to reverse DNA hyper-methylation of the IFN-γ signaling pathway and restore IFN-γ inducible gene expression. We will longitudinally perform these analyses on adults with 1) asymptomatic household contacts, 2) pulmonary TB with treatment success and 3) pulmonary TB with treatment failure. The elucidation of epigenetic mechanisms by which TB subverts host immunity is a necessary step in developing improved treatment monitoring tools and the development of adjunct host directed immunotherapy to improve clinical outcomes. The proposed science and mentorship will have the applicant poised for successful transition to an independent researcher.