OBJECTIVESTo study antibody response to a hepatitis B DNA vaccine by formulation with aluminum phosphate in mice.

METHODSAn eukaryotic expression plasmid inserted HBsAg gene (pcDNA3.1-S) was constructed by cloning technique and the accuracy of the construct was confirmed by restriction enzyme digestion and DNA sequencing, then hepatitis B DNA vaccine formulations were prepared by mixing pcDNA3.1-S with various concentration of aluminum phosphate in 0.9% NaCl. HBsAg expressions were assayed by ELISA in vivo five days after intramuscular injection of pcDNA3.1-S with or without aluminum phosphate. And serum samples were obtained from individual immunized or control mice 6 weeks post injection. Then anti-HBs were assayed in mice sera by ELISA.

RESULTSFive days after intramuscular immunization, the levels of HBsAg expression of groups with aluminum phosphate showed no difference from those of control group in tibialis arterials muscles. In sera, HBsAg could not be detectable in all groups. Intramuscular immunization of BABL/C mice with pcDNA3.1-S mixed aluminum phosphate (0microg, 1microg, 10microg, 50microg, 100microg) 6 weeks later, the P/N values of anti-HBs in sera were 11.54+/-5.60, 11.00+/-6.62, 20.30+/-10.20, 49.18+/-24.40 and 48.68+/-27.78, respectively. It showed that pcDNA3.1-S mixing with aluminum phosphate could increase anti-HBs titers in mice.

CONCLUSIONNo increase of HBsAg expression was observed by mixing plasmid pcDNA3.1-S with various concentration of aluminum phosphate in vivo. But Intramuscular immunization of BALB/C mice with pcDNA3.1-S mixing aluminum phosphate adjuvant can increase anti -HBs titers. It seemed that aluminum phosphate would be valuable for further investigation as a potential adjuvant of hepatitis B DNA vaccines.