Immunological evaluation of a novel Mycobacterium tuberculosis antigen, Rv3117, absent in Mycobacterium bovis BCG.

Tuberculosis (TB) remains a global infectious disease. To investigate the value of a novel Mycobacterium tuberculosis (M. tuberculosis) region of difference 5 (RD5)-encoded antigen, Rv3117, in the development of effective immuno-diagnostics and vaccines against TB, the immune responses to the antigen were examined in human subjects, as well as in C57BL/6 mice. The results showed that Rv3117 was able to evoke specific humoral and cellular immune responses. Consistent with the results from the RD1-encoded antigens, culture filtrate protein 10 kDa (CFP-10) and early secreted antigenic target 6 kDa (ESAT-6), the immunoglobulin G (IgG), IgM and IgA antibody responses to Rv3117 were able to statistically distinguish between the 65 patients with active pulmonary TB and the 59 healthy controls (P<0.01, respectively). In addition, higher levels of Rv3117‑specific interferon-γ (IFN-γ) were observed in immunized C57BL/6 mice than in the negative control mice (P<0.05). Furthermore, high titers of total IgG, IgG1 and IgG2a antibodies were present in the sera from immunized mice, even six weeks subsequent to the immunization. In conclusion, the present results suggested that Rv3117 may be used as a candidate for the development of TB immunodiagnostics and vaccine design.