HBV DNA vaccine with adjuvant cytokines induced specific immune responses against HBV infection

AIM:To seek for an effective method to improve the immune responses induced by DNA vaccine expressing HBV surface antigen(pCR3.1-S)in Balb/c mice(H-2~d). METHODS:The pCR3.1-S plasmid and the eukaryotic expression vectors expressing murine IL-2(pDOR-IL-2)or IL-12(pWRG3169)were injected into mice subcutaneously. The immune responses to pCR3.1-S and the adjuvant effect of the cytokines plasmid were studied.Meanwhile the effect of pCR3.1-S on anti-translated subcutaneous tumor of P815 mastocytoma cells stably expressing HBsAg(P815-HBV-S) was also studied.Anti-HBs in serum was detected by enzyme- linked immunoadsordent assay(ELISA)and HBsAg specific cytotoxic T lymphocytes(CTLs)activity was measured by ^(51)Cr release assay.After three weeks of DNA immunization,the cells of P815-HBV-S were inoculated into mice subcutaneously and the tumor growth was measured every five days.The survival rate and living periods of mice were also calculated. RESULTS:After 8 wk DNA immunization,the A 450 nm values of sera in mice immunized with pCR3.1,pCR3.1-S and pCR3.1-S codeliveried with IL-2 or IL-12 plasmids were 0.03+0.01,1.24±0.10,1.98±0.17 and 1.67±0.12 respectively.Data in mice codeliveried pCR3.1-S with IL-2 or IL-12 plasmids were significantly higher than that of mice injected pCR3.1 or pCR3.1-S only.The HBsAg specific CTL activities in mice coinjected with pCR3.1-S and IL-2 or IL- l2 eukaryotic expression vectors were(61.9±7.1)% and (73.3±8.8)%,which were significantly higher than that of mice injected with pCR3.1(10.1±2.1)% or pCR3.1-S(50.5 ±6.4)%.The HBsAg specific CTL activities in mice injected with pCR3.1,pCR3.1-S,pCR3.1-S combined with IL-2 or IL- l2 eukaryotic expression vectors decreased significantly to (3.2±0.8)%,(10.6±1.4)%,(13.6±1.3)% and(16.9±2.3) % respectively after the spleen cells were treated by anti- CD8^+ monoclonal antibody,but presented no significant change to anti-CD4^+ monoclonal antibody or unrelated to monoclonal antibody.The HBV-S DNA vaccine(pCR3.1-S) could evidently inhibit the tumor growth,prolong the survival period of mice and improve the survival rate of mice and these effects could be improved by IL-12 gene codeliveried. CONCLUSION:HBV DNA vaccine has a strong antigenicity in humoral and cellular immunities,which can be promoted by plasmid expressing IL-2 or IL-12.CD8+ cells executed the CTL activities.DNA vaccine may be useful for both prophylaxis and treatment of HBV infection.