DNA-based vaccination against hepatitis B virus

The prospects for world-wide control of hepatitis B virus (HBV) depend on the availability of safe, effective and affordable vaccines, Current protein-based vaccines contain HBV surface antigen (HBsAg) and are safe and generally efficacious. However they are expensive, do not induce adequate immunity in all individuals and are ineffective for treatment of chronic HBV carriers, DNA-based immunization of mice by injection of HBsAg-expressing plasmid DNA results in rapid induction of strong and long-lasting humoral and cell-mediated immune responses. For example, a single injection of DNA can induce anti-HBs IgG ELISA titers > 10(5), which persist for up to 17 months without boost. The DNA approach is also able to overcome H-2-restricted non-response to HBsAg and can break tolerance to HBsAg in HBsAg-transgenic mice, DNA-based vaccination of chimpanzees can induce anti-HBs titers as high as those induced by the commercial protein-based vaccines. Thus, results from animal models suggest that DNA vaccines against HBV may be useful for both prophylactic and therapeutic purposes.