Abstract
Mycobacterial proteins interact with host macrophages and modulate their functions and cytokine gene expression profile. The protein Rv0652 is abundant in culture filtrates of Mycobacterium tuberculosis K-strain, which belongs to the Beijing family, compared with levels in the H37Rv and CDC1551 strains. Rv0652 induces strong antibody responses in patients with active tuberculosis. We investigated pro-inflammatory cytokine production induced by Rv0652 in murine macrophages and the roles of signalling pathways. In RAW264.7 cells and bone marrow-derived macrophages, recombinant Rv0652 induced predominantly tumour necrosis factor (TNF) and monocyte chemoattractant protein (MCP)-1 production, which was dependent on mitogen-activated protein kinases and nuclear factor-κB. Specific signalling pathway inhibitors revealed that the extracellular signal-regulated kinase 1/2 (ERK1/2), p38 and phosphatidylinositol 3-kinase (PI3K) pathways were essential for Rv0652-induced TNF production, whereas the ERK1/2 and PI3K pathways, but not the p38 pathway, were critical for MCP-1 production in macrophages. Rv0652-stimulated TNF and MCP-1 secretion by macrophages occurred in a Toll-like receptor 4-dependent and MyD88-dependent manner. In addition, Rv0652 significantly up-regulated the expression of the mannose receptor, CD80, CD86 and MHC class II molecules. These results suggest that Rv0652 can induce a protective immunity against M. tuberculosis through the macrophage activation.