International Journal of Mycobacteriology (Jan 2015)
Cell wall-associated Mycobacterium tuberculosis rRv3083 protein stimulates macrophages through toll-like receptor-2 (TLR2)
Abstract
Aims and objectives: Characterization of proteins associated with the mycobacterial cell wall is critical to understanding bacterial survival and immune modulation in the host. A variety of mycobacterial products are able to recognize and activate mammalian toll-like receptors (TLRs) mediating the secretion of antibacterial effector molecules. Mycobacterium tuberculosis MymA Rv3083 protein is a cell wall-associated protein which is up-regulated upon infection of macrophages. The objective of the present study is to understand the role of Rv3083 protein as a TLR agonist and its contribution in activating macrophages. Methods: The MymA (Rv3083) gene was cloned and expressed. The purified 55.5kDa recombinant protein was used to stimulate phorbol myristate acetate (PMA) differentiated THP-1 macrophage cell line. Cell surface markers of Rv3083 stimulated THP-1 cells were done using flow cytometry for TLR2, TLR4, HLA-DR and co-stimulatory molecules CD40, CD64 and CD80. Cytokines TNF-α, IL-10 and IL-12 were assayed in the culture supernatant using ELISA. Results: Stimulation of THP-1 macrophages for 48 and 72 h with rRv3083 protein resulted in significantly increased expression of TLR2. A significant up-regulation was also seen in the expression of co-stimulatory molecules CD40, CD80 and antigen-presenting molecule HLA-DR on THP-1 cells. These macrophages also produced a significant quantity of proinflammatory TH1 cytokines TNF-α and IL-12, but not IL-10 at 48 and 72 h post-stimulation. Conclusion: The cell wall-associated M. tuberculosis rRv3083 protein acts as an agonist of TLR2 and thereby activates macrophages to produce a TH1 immune response. Acknowledgements: The financial support of OSDD-CSIR and the research fellowships of ICMR to I. Saraav and S. Singh is duly acknowledged.
