Elicitation of efficient, protective immune responses by using DNA vaccines against tuberculosis

DNA vaccination is an effective method for elicitation of strong humoral as well as cellular immune responses. DNA vaccines expressing mycobacterial antigens ESAT-6 (Rv3875), α-crystallin (Rv2031c) and superoxide dismutase A (Rv3846) were evaluated for their immune responses in Balb/c mice and protective efficacy in guinea pigs. Immunization of mice with the DNA vaccines expressing superoxide dismutase A and α-crystallin resulted in markedly higher levels of IFN-γ as compared to the levels of IL-10. The DNA vaccine expressing ESAT-6 elicited a mixed Th1/Th2 response. Immunization of guinea pigs with these DNA vaccines and subsequent challenge of animals with Mycobacterium tuberculosis H37Rv, showed that DNA vaccine expressing superoxide dismutase imparted the maximum protection as observed by a 50 and 10 folds reduction in bacillary load in spleens and lungs, respectively, in comparison to immunization with vector control.