Objective.To study whether the abilities of hepatitis C virus(HCV)E2 gene immunization to induce humoral and cellular immune responses to E2 protein were affected by hepatitis B virus(HBV)preS gene when they were fused in DNA-immunized mice.Methods.Mice were immunized with E2,preS-E2(preS gene was upstream of E2 gene),and E2-preS(preS gene was downstream of E2 gene)gene by their eukaryotic expression vectors,respectively.The anti-E2 or anti-preS antibodies were detected using the E2 and preS antigens.The cellular immune response to E2 pro-tein in immunized mice was presented by its survival time after injecting SP2/O myeloma cells expressing HCV E2 protein into the abdominal cavity.Results. Chimeric E2 and preS gene immunization can induce mice to develop anti-preS and anti-E2 antibodies.The number of the mice developing anti-E2 antibody and the antibody titers in preS-E2 gene-injected group were higher than those in E2-preS gene-immunized group.However,the mice injected with E2 gene did not develop the detectable anti-E2 antibodies until 12 weeks after DNA immunization.After the mice was injected with target cells,the average survival time of the mice in the group immunized with E2 gene alone was longer than that of the group injected with E2 gene fused with HBV preS and was significantly longer than that of the control(P< 0.05).Conclusion.HBV preS might be a humoral enhancer that can affect the abilities of HCV E2 protein to in-duce immune responses in DNA-immunized mice.