ABSTRACT
Dormancy-associated antigens encoded by the dormancy survival regulon (DosR) genes are required for survival of Mycobacterium tuberculosis (Mtb) in macrophages. However, mechanisms underlying survival of Mtb in macrophages remains to be elucidated. A recombinant Mycobacterium smegmatis strain (rMs) expressing a fusion protein of two dormancyassociated antigens Rv2031c and Rv2626c from Mtb was constructed in the present study. In an in vitro culture, growth rate of rMs was lower compared with Ms. A total of 24 h following infection of murine macrophages with rMs or Ms, percentage of viable cells decreased and the number of bacteria in viable cells increased compared with Ms, demonstrating that virulence and intracellular survival of rMs were enhanced. Compared with macrophages infected with Ms, necrosis of macrophages infected with rMs was increased, while apoptosis was inhibited. Macrophages infected with rMs secreted more interferonγ and interleukin6, but fewer nitric oxide and tumor necrosis factorα, compared with macrophages infected with Ms. The present study demonstrated that the fusion protein composed of dormancyassociated antigens Rv2031c and Rv2626c in Ms serves a physiological function of a dormancyassociated antigen and modulates innate immunity of host macrophages, therefore favoring intracellular bacillary survival.