Boosting Immune Response to Hepatitis B DNA Vaccine by Coadministration of Prothymosin α-Expressing Plasmid

DNA vaccines induce protective humoral and cell-mediated immune responses in several animal models. However, compared to conventional vaccines, DNA vaccines usually induce poor antibody responses. In this study, we report that coadministration of a hepatitis B virus (HBV) DNA vaccine with prothymosin α as an adjuvant improves antibody responses to HBV S antigen. We also observed higher seroconversion rates and higher antibody titers. Prothymosin α appears to increase the number and affinity of hepatitis B surface antigen-specific, gamma interferon-secreting T cells and to enhance cellular immune response to the PreS2S DNA vaccine. Interestingly, administering the DNA separately from the prothymosin α plasmid abrogated the enhancement of DNA vaccine potency. The results suggest that prothymosin α may be a promising adjuvant for DNA vaccines.