Combined Recombinant DNA Vaccine Results in Significant
Protection against Mycobacterium Tuberculosis

( College of Life
Sciences, Peking University, Beijing 100871, China; ¹Xinjiang Academy
of Animal Science, Wulumuqi 830000, China )

Abstract
Three proteins secrected from Mycobacterium tuberculosis,
Ag85B, ESAT -6 and MPT63 were seclected as antigens for making combined DNA
vaccine by immunizing mice. The immune response induced by the vaccine and
its protective efficacy were studied. It was demonstrated that when mice were
immunized with the combined DNA vaccine, the titer of antibody for Ag85B in
serum increased to more than 10⁵, but the titers of ESAT-6 and
MPT63 specific antibodies were undetectable. After the final immunization,
the level of IFN-γ specific for Ag85B, ESAT-6 and MPT63 reached (17.0±7.0)
u/ml, (6.0±0.8) u/ml and (11.9±8.0) u/ml, respectively. Mice, that were inoculated
with the empty eukaryotic expression vector pJW4303 DNA, produced negligible
amounts of antigen-specific INF-γ. The combined DNA vaccine resulted also
in significantly reduced amount of bacteria in the lungs of experimental mice.
Microphotographs showed clearly that these lungs were better protected against
Mycobacterium tuberculosis challenge than control mice. The combined
DNA vaccine reported in this work shed new lights on the prophylactic protection
against tuberculosis.