Identification of the new T-cell-stimulating antigens from Mycobacterium tuberculosis culture filtrate

The proteins secreted by Mycobacterium tuberculosis are an important target for vaccine development. To identify the antigens from M. tuberculosis culture filtrate (CF) that strongly stimulate T-cells, the CF was fractionated by ion-exchange chromatography and then non-reducing sodium dodecyl sulfate-polyacrylamide gel electrophoresis with mini-whole gel elution. Each fraction was screened for its ability to induce interferon-gamma (IFN-gamma) production in peripheral blood mononuclear cells isolated from healthy tuberculin reactors. The protein bands that strongly induced IFN-gamma production were subjected to N-terminal sequencing. Two new proteins, a 17-kDa protein (Rv0164, MTSP17) and an 11-kDa (Rv3204, MTSP11) protein, were identified. The recombinant MTSP17 (rMTSP17) and rMTSP11 induced significant production of IFN-gamma and interleukin (IL)-12p40 in peripheral blood mononuclear cells from healthy tuberculin reactors. Interestingly, IL-12p40 production in response to rMTSP11 was significantly higher than that in response to rMTSP17 or the three components of the antigen 85 complex. These results suggest that MTSP11 antigen should be further evaluated as a component of a subunit vaccine.