Expression and purification of Mycobacterium tuberculosis ESAT-6 and MPT64 fusion protein and its immunoprophylactic potential in mouse model

The completion of Mycobacterium tuberculosis genome sequence has opened a new way for the identification and characterization of bacterial antigens, such as ESAT-6, CFP10, MPT64, and Ag85 complex, which are helpful for tuberculosis control. In this work, genes of ESAT-6 and MPT64 were fused and expressed in Escherichia coli in form of inclusion bodies with a histidine tag. The expressed fusion protein was purified by nitrilotriacetic acid (Ni–NTA) affinity chromatography under denaturing conditions, and the yield was 18 mg/L of culture. In mice, the purified ESAT-6–MPT64 fusion protein elicited stronger humoral response, greater splenic lymphocyte stimulated index, and higher levels of IFN-γ and IL-12 production than that of the single MPT64 inoculation group, and rendered modest protection on the experimental tuberculosis mouse models. In short, the ESAT-6–MPT64 fusion protein might be a potential candidate vaccine for tuberculosis.