AIM:To seek for an effective method to improve the immuneresponses induced by DNA vaccine expressing HBV surfaceantigen(pCR3.1-S)in Balb/c mice(H-2~d).METHODS:The pCR3.1-S plasmid and the eukaryoticexpression vectors expressing murine IL-2(pDOR-IL-2)orIL-12(pWRG3169)were injected into mice subcutaneously.The immune responses to pCR3.1-S and the adjuvant effectof the cytokines plasmid were studied.Meanwhile the effectof pCR3.1-S on anti-translated subcutaneous tumor of P815mastocytoma cells stably expressing HBsAg(P815-HBV-S)was also studied.Anti-HBs in serum was detected by enzyme-linked immunoadsordent assay(ELISA)and HBsAg specificcytotoxic T lymphocytes(CTLs)activity was measured by ~(51)Crrelease assay.After three weeks of DNA immunization,thecells of P815-HBV-S were inoculated into mice subcutaneouslyand the tumor growth was measured every five days.Thesurvival rate and living periods of mice were also calculated.RESULTS:After 8 wk DNA immunization,the A 450 nmvalues of sera in mice immunized with pCR3.1,pCR3.1-Sand pCR3.1-S codeliveried with IL-2 or IL-12 plasmids were0.03+0.01,1.24±0.10,1.98±0.17 and 1.67±0.12respectively.Data in mice codeliveried pCR3.1-S with IL-2or IL-12 plasmids were significantly higher than that of miceinjected pCR3.1 or pCR3.1-S only.The HBsAg specific CTLactivities 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 ofmice injected with pCR3.1(10.1±2.1)% or pCR3.1-S(50.5±6.4)%.The HBsAg specific CTL activities in mice injectedwith 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 significantchange to anti-CD4~+ monoclonal antibody or unrelated tomonoclonal antibody.The HBV-S DNA vaccine(pCR3.1-S)could evidently inhibit the tumor growth,prolong the survivalperiod of mice and improve the survival rate of mice andthese effects could be improved by IL-12 gene codeliveried.CONCLUSION:HBV DNA vaccine has a strong antigenicityin humoral and cellular immunities,which can be promotedby plasmid expressing IL-2 or IL-12.CD8+ cells executed the CTL activities.DNA vaccine may be useful for bothprophylaxis and treatment of HBV infection. AIM: To seek for an effective method to improve the immuneresponses 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 eukaryoticexpression 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 were studied. Meanwhile the effect of pCR3. Anti-HBs in serum was detected by enzyme-linked immunoadsordent assay (ELISA) and HBsAg specific cytotoxic T lymphocytes (CTLs) activity was measured by ~ (51) Crrelease 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. Tissue viral and living periods of mice were also calculated. RESULTS: After 8 wk DNA immunization, the A 450 nmvalues ​​of sera in mi ce immunized with pCR3.1, pCR3.1-Sand 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 ± 0.12respectively.Data in mice codeliveried pCR3.1-S with IL-2or IL-12 plasmids were significantly higher than that of mice injected with pCR3.1 or pCR3.1-S only. The HBsAg specific CTLactivities 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 mouse 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-12 eukaryotic expression vectors showed 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 no significant change to anti-CD4 ~ + monoclonal antibody or unrelated tomonoclonal antibody. HBV-S DNA vaccine (pCR3.1-S) could evidently inhibit the tumorgrowth, prolong the survival period of mice and improve the survival rate of mice and the effect of 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 plasmid load IL-2 or IL-12.CD8 + cells executed the CTL activities. DNA vaccine may be useful for bothprophylaxis and treatment of HBV infection.