PE17 protein from Mycobacterium tuberculosis enhances Mycobacterium smegmatis survival in macrophages and pathogenicity in mice

The capacity of Mycobacterium tuberculosis to survive and cause disease is strongly correlated with its ability to escape multiple defense strategies in hosts. In particular, M. tuberculosis has the remarkable capacity to survive within the hostile environment of macrophages. Here, we found that the PE17 (Rv1646) protein promoted intracellular survival of M. smegmatis in peritoneal macrophages from mice. Further experiments confirmed that the recombinant PE17 protein was localized in the cell wall of M. smegmatis. Results from the macrophage infection model showed that PE17 significantly downregulated pro-inflammatory cytokines (interleukin-6, interleukin-12, and tumer necrosis factor-α) secretion from macrophages induced by M. smegmatis and promoted macrophage necrosis. Furthermore, a C57BL/6 mouse infection model confirmed that PE17 significantly prolonged the survival of M. smegmatis in vivo and aggravated lesions in organs of infected mice. Moreover, persistent high levels of interferon-γ and interleukin-1β in infected mice indicated that the bacteria were not easily removed in vivo. Overall, our present results suggested that the PE17 may act as an important pathogenic factor in M. tuberculosis.