A plasmid(DNA vaccine)pSC-IL12,coexpressing hepatitis B virus(HBV)envelope-core fusion antigen and murine IL-12,was constructed.After the plasmid was transfected into COS7 cells,HBsAg and HBcAg were detected in cytoplasm,murine IL-12 was detected in supernatant.BALB/c mice were vaccinated intramuscularly with this construct or HBV envelope-core fusion antigen DNA vaccine pSC.Following twice immunizations,humoral and cellular immune responses of the mice were detected.Results showed that pSC-IL12 induced weaker antibody but stronger T lymphocyte proliferative response and cytotoxic T lymphocyte response than pSC did,which indicated that HBV fusion antigen and IL-12 coexpressing DNA vaccine may be more useful for therapy of hepatitis B.