ESAT-6 Abrogates IL-18 Mediated Phagosome Lysosome Fusion Via Microrna30a Upon Calcimycin Treatment in Mycobacteria Infected Macrophages

Abstract

The major immunodominant antigens of Mycobacterium tuberculosis (M. tb) confiscate the host immune system to give a survival advantage to this intracellular pathogen. But, the mechanism of action behind this control is not entirelyknown. Since we have previously reported the mechanism of autophagy inhibition by early secreted antigenic target 6 kDa (ESAT-6) through microRNA (miR)-30a-3p in Calcimycin-treated differentiated THP-1 (dTHP-1) cells, the presentstudy was undertaken to evaluate the effect of miR-30a on the immunomodulatory profile of ESAT-6 treated cells, and the mechanism involved thereof, if any. The effect of recombinant ESAT-6 (rESAT-6) on the immunomodulatory profilein Calcimycin-treated phorbol 12-myristate 13- acetate (PMA) dTHP-1 cells was checked. Later, transfection studies using miR-30a-3p inhibitor or -5p mimic highlighted the contrary roles of different arms of the same miRNA in regulatingIL-18 response by ESAT-6 in dTHP-1 cells upon Calcimycin treatment. By using either IL-18 neutralizing antibody or inhibitors of phosphoinositide 3-kinase (PI3K)/NF-κB/phagosome-lysosome fusion in the miRNA-30a transfectedbackground, IL-18 mediated signaling and intracellular killing of mycobacteria was reversed in the presence of ESAT-6. Overall, the results of this study conclusively prove the contrary roles of miR-30a-3p and miR-30a-5p in modulatingIL-18 signaling by ESAT-6 in dTHP-1 cells upon Calcimycin treatment that affected phagosome-lysosome fusion and intracellular viability of mycobacteria.