Immunogenicity and protective efficacy of a DNA vaccine encoding the fusion protein of mycobacterium heat shock protein 65(Hsp65) with human interleukin-2 against Mycobacterium tuberculosis in BALB/c mice

Developing a new generation of vaccines is important for preventing tuberculosis (TB). DNA vaccine is one promising candidate. In this study we evaluated the immunogenicity and protective efficacy of the DNA vaccine encoding the fusion protein of Mycobacterium tuberculosis heat shock protein 65 (Hsp65) with human interleukin-2 (hIL-2) in BALB/c mice. We showed that the DNA vaccine pcDNA-Hsp65-hIL-2 could induce high levels of antigen-specific antibody, IFN-gamma, CD4(+) and CD8(+) T cell production. When the immunized mice were infected with M. tuberculosis H37Rv, the organ bacterial loads in the DNA immunized group were significantly reduced compared to those of the saline control group, but the ability to reduce bacteria was not better than for BCG. The histopathology in lungs of the DNA vaccine immunized mice was similar to that of BCG immunized mice, which was obviously ameliorated compared to that of the saline control group. Overall, the DNA vaccine could afford protection against M. tuberculosis infection, though the protection efficacy was not as great as that of conventional BCG.