LpqT improves mycobacteria survival in macrophages by inhibiting TLR2 mediated inflammatory cytokine expression and cell apoptosis.

Tuberculosis is a severe infectious disease caused by Mycobacterium tuberculosis (Mtb). LpqT is a lipoprotein of Mtb identified as a candidate virulence factor by a high-throughput screen searching for genes important for mycobacteria intracellular survival. To investigate its function, we constructed M. smegmatis strains deficient of LpqT or overexpressing LpqT. Wildtype or LpqT modified M. smegmatis strains were used to infect macrophages and mice, and intracellular survival of mycobacteria was measured. We found that LpqT can improve M. smegmatis survival in macrophage cell line, bone marrow derived macrophages (BMDMs), and murine lungs. This survival promoting effect is dependent on TLR2 and Myd88. Western blot analysis of M. smegmatis infected macrophages showed that LpqT suppressed M. smegmatis induced NF-κB and MAPK phosphorylation, indicating that LpqT hampered TLR2 signal activation. In consistent with this, LpqT inhibited M. smegmatis induced inflammatory cytokine expression and cell apoptosis in macrophages, thus supported mycobacteria intracellular survival.