Inhibiting Immune Check Point Inhibitors Rescues T Cell Response in TB Patients: Impact on Drug Pump Expression and Clearance of M.tuberculosis

Abstract Background: Host T cell response, especially the Polyfunctional T cells (Ifn-γ+ TNF-α+) plays a critical role in containment of M. tuberculosis (Mtb) infection. We previously demonstrated that heightened PD1/PDL1 axis dampens the T cell response against Mtb and leads to active disease among PTB patients. However, the status of other Immune Checkpoint Inhibitors {ICIs,: (TIM3, TIGIT, PD1, CTLA4, LAG3)} in TB patients still remain inconclusive. Moreover, DR TB patients elicit weaker T cell response against M.tb, suggesting important role of immune suppression in active disease development, especially DR tuberculosis. Here, we evaluated the i) expression of immune checkpoint inhibitors in DSvsDR Tuberculosis patients, their impact on ii) Mtb specific T cell response, iii) rescue in TB patients and iv) impact on the drug pump expression of M.tb.Methods- PBMCs isolated from PTB patients were used for FACS based evaluation of i) ex vivo expression of ICIs (TIM3, TIGIT, PD1, CTLA4, LAG3) on helper T cells, ii) rescue of T cell response after blocking of ICIs & iii) drug pump expression on M tuberculosis in in vitro MDM infection model. Multicolour flowcytometry for immune profiling and in-vitro Monocyte derived Macrophages (MDMs) culture was performed for assessing bacillary clearance after in vitro M.tuberculosis infection. Results: DR-TB patients elicit weaker T cell response against M.tuberculosis and correlated with ICIs+ T cells. Inhibiting ICIs could rescue pro-inflammatory cytokine (IFN-γ & TNF-α) producing T cells. A definitive pattern of their impact emerged in the following order; PD1> TIM3> TIGIT > LAG3=CTLA4. These not only suppressed the poly-functional T cell response in active tuberculosis but also enhanced the suppressive functions of Treg cells. Blocking ICIs enhanced the bacillary clearance in in-vitro MDM model. Interestingly, Cytokine milieu of the MDM experiment influenced the drug pump expression; Ifn-γ/TNF-α suppressed and IL-10/TGF-β enhanced drug pump expression on M.tuberculosis. Conclusions: • Our findings demonstrate that in active PTB patients, expression of several Immune Checkpoint Inhibitors are heightened, especially on Treg cells and blocking them either alone or in combination restores Polyfunctional T cells response against M.tuberculosis. • We also demonstrate that such restored effector T cells response is capable of working synergistically with drugs to facilitating better bacillary clearance. Type of immune response can modulate the expression of drug pumps on M.tuberculosis and influence the efficacy of chemotherapy. • This implicates in i) improving the efficacy of anti-tubercular chemotherapy ii) reducing the dose of anti-tubercular drugs and their toxicity among patients.