DNA vaccines for prophylactic or therapeutic immunization against hepatitis B virus.

DNA vaccines, with which the antigen is synthesized in vivo after direct introduction of its encoding sequences, offer a unique method of immunization that may overcome many of the deficits of traditional antigen-based vaccines. By virtue of the sustained in vivo antigen synthesis and the comprised stimulatory CpG motifs, plasmid DNA vaccines appear to induce strong and long-lasting humoral (anti-bodies) and cell-mediated (T-help, other cytokine functions and cytotoxic T-cells) immune responses. In animal models, DNA vaccines against hepatitis B virus (HBV) give humoral and cell-mediated immunity superior to that of the current traditional antigen-based vaccines, indicating the possibility of a more effective prophylactic vaccine against HBV. Furthermore, DNA vaccines can overcome tolerance to and expression of HBV proteins in a transgenic mouse model of the HBV chronic carrier, opening up the possibility of an effective therapeutic DNA vaccine to treat chronic carriers of HBV.