New alternative vaccine component against mycobacterium tuberculosis--heat shock protein 16.3 or its T-cell epitope

Heat shock protein 16.3 (Hsp16.3) of Mycobacterium tuberculosis (MTB) containing T-cell and B-cell epitopes not only plays an important role in the survival of MTB against macrophages, but also has great potential to be used to develop new TB vaccines. In order to study whether Hsp16.3 can be replaced with its T-cell epitope for producing a vaccine against TB, we expressed and purified Hsp16.3 protein of MTB H37Rv strain and confirmed by immunoblotting. The immune responses and protection against the H37Rv induced by Hsp16.3 protein were compared with its T-cell epitope synthetic peptide in mice. The results showed that both Hsp16.3 and its synthetic peptide induced significantly stronger specific antibodies than the classical TB vaccine-BCG (bacillus Calmette-Guérin). Compared with BCG, the stimulation index in the splenolymphocyte proliferation of both recombinant protein and its synthetic peptide were remarkably enhanced, but the levels of IFN-gamma release were lower. Dramatic reduction in the numbers of MTB colony forming units (CFU) in the spleens and lungs was observed in the mice immunized with Hsp16.3 or its synthetic peptide. The protection provided by Hsp16.3 or its synthetic peptide in the lungs was equivalent to that provided by BCG. Both Hsp16.3 and its T-cell epitope are effective components and Hsp16.3 can be replaced with its T-cell epitope while developing the vaccine against TB, without requiring the complicated procedure of expressing and purifying Hsp16.3.