Mycobacterium tuberculosis antigen Wag31 induces expression of C-chemokine XCL2 in macrophages

Tuberculosis is still a major threat to human health. To date, only approximately half of the proteins encoded by Mycobacterium tuberculosis H37Rv have been assigned specific functions. Wag31 (Rv2145c) is one of the bacterial proteins whose function is mostly unknown. Using a modified split-ubiquitin membrane yeast two-hybrid system, we screened a macrophage cDNA library with Wag31 as bait and identified XCL2, a C-subfamily chemokine, as a binding partner for Wag31. More importantly, Wag31 was found to specifically stimulate XCL2 expression in macrophages. The results from this study demonstrate that expression of C-chemokine is not restricted to certain types of T cells and natural killer cells. Because C-chemokine is chemotactic for CD8+ and CD4+ T cells, our novel findings could provide a new mechanism by which the bacteria induce cell-mediated immunity and by which Wag31 could be a potential target for controlling M. tuberculosis infection.