Mycobacterium bovis Mce4E protein may play a role in modulating cytokine expression profile in alveolar macrophage

A large body of research has confirmed that mammalian cell entry proteins (Mce) are related to tuberculosis virulence.

To obtain an insight into the effect of Mce family protein on the pathogenesis of Mycobacterium bovis, we expressed recombinant Mce4E protein in Escherichia coli, and investigated its effect on the expression of tumor necrosis factor alpha (TNF-alpha), inducible NO, interleukin 6 (IL-6) and interleukin 12 (IL-12) in alveolar macrophage by real-time reverse transcriptase polymerase chain reaction (RT-PCR).

Our study demonstrated that after stimulation of alveolar macrophages by Mce4E protein for 48 h, the expression of TNF-alpha was induced, with an enhanced IL-6 mRNA level (P < 0.05) and no changes in IL-12 expression in the macrophages. In addition to the changes in the cytokine expression profile in macrophages, the expression of inducible NO synthase was reduced (P < 0.05). Our MTT [3,(4,5 dimethylthiazol-2yl)-2,5 diphenyl-tetrazolium bromide] analysis of the macrophage also demonstrated that Mce4E protein could inhibit macrophage activity.

Our data suggest that Mce4E proteins can induce host inflammation response to M. bovis and may play an important role in host/pathogen interactions.