Cross-reactive immune responses to Mycobacterium vaccae, Mycobacterium tuberculosis and Bacillus Calmette-Guerin

Objective To investigate the cross-reactive immune responses to Mycobacterium vaccae (M.vaccae), Mycobacterium tuberculosis (M.tuberculosis, H37Rv) and Mycobacterium bovis Bacillus Calmette-Guerin (BCG) for providing reference for the development of new vaccines with M. vaccae. Methods M. vaccae (ATCC95051), M. tuberculosis (H37Rv) and BCG (China strain) were cultured on L-J solid media and harvested. Total bacterial protein antigens prepared by ultrasonic disruption were used to immunize BALB/c mice. IgG antibodies in serum samples were detected with enzyme-linked immunosorbent assay (ELISA) to evaluate humoral immune responses. Cellular immunity was assessed by detecting various cytokines with cytokine release assay (CRA). Results The mice that were respectively immunized with the three mycobacterial antigens could produce high titers of antibodies (IgG) and high levels of IFN-γ and IL-2, but low levels of IL-4 and IL-10. Results of the cross reactivity tests showed that ATCC95051, H37Rv and BCG were able to cross-react with the immunized mice, and all of them induced high levels of IFN-γ, IL-2 and IgG antibodies. Conclusions The three Mycobacteria mainly elicited Th1 immune responses. There were cross-reactive immune responses to M. vaccae, M. tuberculosis and BCG, which might provide reference for using M. vaccae in the development of new anti-tuberculous vaccines. Key words: Mycobacterium vaccae; Mycobacterium tuberculosis; Bacillus Calmette-Guerin; Cross immunity; Vaccine