Construction, expression and identification of a recombinant BCG vaccine encoding human Mycobacterium tuberculosis heat shock protein 65.

Heat shock protein 65 (HSP65) is one of the most important protective immunogens against the tuberculosis infection. The signal sequence of antigen 85B and the whole HSP65 DNA sequence of human Mycobacterium tuberculosis (M. tuberculosis) were amplified from BCG genome and plasmid pCMV-MTHSP65 respectively by polymerase chain reactions (PCR). These two sequences were cloned into the plasmid pBCG-2100 under the control of the promoter of heat shock protein 70 (HSP70) from human M. tuberculosis, yielding the prokaryotic shuttle expression plasmid pBCG-SP-HSP65. Results of restriction endonuclease analysis, PCR detection and DNA sequencing analysis showed that the two cloned DNA sequences were consistent with those previously reported, and the direction of their inserting into the recombinant was correct and the reading frame had been maintained. The recombinants were electroporated into BCG to construct the recombinant BCG vaccine and induced by heating. The induced expression detected by SDS-PAGE showed that the content of 65 kD protein expressed in recombinant BCG was 35.69% in total bacterial protein and 74.09% in the cell lysate supernatants, suggesting that the recombinant HSP65 gene could express in BCG with high efficiency and the expressed proteins were mainly soluble. Western-blot showed that the secretive recombinant proteins could specifically combine with antibody against M. tuberculosis HSP65, indicating that the recombinant proteins possess the biological activity of HSP65.