Enhancement of immune responses to hepatitis B DNA vaccine by heat shock protein 65 in mice

Objective:To observe the effect of eukaryotic expression vector pHSP65 coding heat shock protein 65 on immune responses induced by DNA immunization of HBV surface antigen(pHBVS2S) in BABL/c(H-2~(d)) mice.Methods:The immunization was performed by intra-muscular injection of empty vector pcDNA3,HBV DNA vaccine(pHBVS2S) with or without pHSP65 adjuvant plasmid.Anti-HBs in serum was detected by ELISA and HBsAg specific cytotoxic T lymphocytes(CTLs) activity was measured by ~(51)Chromium Release Assay.The number and affinity of HBs peptide antigen-specific IFNγ secreting T cells were detected by ELISPOT.Results: The CTLs activity of mice in pHBVS2S+pHSP65 group was significanly higher(P0.05) than that in mice intramuscular injected pHBVS2S DNA vaccine group.The anti-HBs titer of mouse serum in pHBVS2S+pHSP65 group was higher than that in mice intramuscularly injected pHBVS2S DNA vaccine group.The ratio of IgG1/IgG2a was different from the group immunized with peptide and was 0.395 and 10 in the(pHBVS2S+)pHSP65 group and the rHBsAg group respectively.The number of HBs peptide antigen-specific IFN-γ-secreting T cells in pHSP65 adjuvant group was 2-3 times higher than that in pHBVS2S DNA vaccine group.Conclusion:The DNA vaccine of HBV(pHBVS2S) has strong immunogenecity and the HSP65 adjuvant can enhance the immune response to hepatitis B DNA vaccine in mice.Thus the pHSP65 may be a promising adjuvant for DNA vaccine.