Comparison of immune responses induced in mice by vaccination with DNA vaccine constructs expressing mycobacterial antigen 85A and interleukin-21 and Bacillus Galmette-Guérin.

In this paper, we addressed the immune adjuvant effects of interleukin(IL)-21 on DNA vaccine constructs expressing mycobacterium tuberculosis (TB) Ag85A and compared immune responses induced in mice inoculated DNA vaccine constructs expressing Ag85A and IL-21 with mice inoculated DNA vaccine constructs expressing Ag85A alone or Bacillus Galmette-Guérin(BCG.). In this experiment, the gene of IL-21 was firstly amplified from plasmid pcDNA3.1-mIL21 by PCR and cloned into the plasmid pRSC, forming recombinant plasmid pRSC-IL21. Then, the gene of Ag85A was amplified from the plasmid pIRES-Ag85A by PCR and cloned into the recombinant pRSC-IL21 again, finally forming co-expression DNA vaccine constructs pRSC-IL21-Ag85A. It was identified by the analysis of endonuclease digestion, DNA sequencing, the IL-21 and Ag85A expression in SP2/0 cells. Mice were i.m. immunized with BCG, DNA vaccine constructs pRSC-Ag85A or pRSC-IL21-Ag85A respectively, and the immune responses induced in mice was compared with other vaccines. The results showed that the DNA vaccine constructs pRSC-IL21-Ag85A was successfully constructed since the Ag85A and IL-21 was correctly expressed in SP2/0 cells respectively, and it elicited stronger immune responses in Balb/c mice than that of mice immunized with pRSC-Ag85A and the efficiency was as BCG did. We concluded that the IL-21 was a promising immune adjunctive modality to enhance immunigenicity of DNA vaccine containing Ag85A and the study provided the possibility of further development of immune accessory effect of IL-21 on DNA vaccine against TB.