DNA VACCINE FOR HEPATITIS-B - EVIDENCE FOR IMMUNOGENICITY IN CHIMPANZEES AND COMPARISON WITH OTHER VACCINES

Vaccination of two chimpanzees against hepatitis B virus (HBV) by intr amuscular injection of plasmid DNA encoding the major and middle HBV e nvelope proteins induced group-, subtype- and preS2-specific antibodie s. These were initially of IgM isotype, and then they were of IgG (pre dominantly IgG1) isotype, The chimpanzee injected with 2 mg of DNA att ained >100 milli-international units/ml of anti-HBs antibody after one injection and 14,000 milli-international units/ml after four injectio ns. A smaller dose (400 mu g) induced lower and transient titers, but a strong anamnestic response occurred 1 year later. Comparison with re sponses in 23 chimpanzees receiving various antigen-based HBV vaccines suggests that the DNA approach is promising for prophylactic immuniza tion against HBV.