Phase 1 safety and immune response studies of a DNA vaccine encoding hepatitis B surface antigen delivered by a gene...

This study was designed to determine the safety and immunogenicity in volunteers of a DNA vaccine consisting of a plasmid encoding hepatitis B surface antigen delivered by the PowderJect XR1 gene delivery system into human skin. Seven healthy adult volunteers received two immunizations at one of three forces of delivery on day 0 and 56. The vaccine was well tolerated. One of six seronegative volunteers developed high titers of persistent HBsAb after a single immunization. In retrospect, this volunteer may have had previous exposure to hepatitis B. Our study suggests that the hepatitis B DNA vaccine given by this gene delivery system may induce a booster response, but the vaccine at the extremely low DNA dose used (0.25 microg) did not induce primary immune responses.