OBJECTIVES: To construct a DNA vaccine capable of expressing the S gene of hepatitis B virus (HBV) and evaluate the expression of the recombinant S gene in vitro and in vivo.
METHODS: A cloned S-X gene fragment was inserted into an eukaryote expression vector to construct a recombinant expressing plasmid pCMV-SX. The recombinant plasmid was transcribed in vitro with a T7 promoter transcription system and transfected into a human hepatoblastoma cell line HepG2. The expression of the S gene was detected by Northern blot hybridization, Western blot hybridization, and enzyme-linked immunosorbent assay (ELISA), respectively. BALB/c mice were inoculated with the recombinant plasmid, and the efficiency of DNA-based immunization in eliciting anti-HBs was evaluated by ELISA.
RESULTS: In vitro transcription of the subcloned HBV S gene was confirmed by Northern blot hybridization. The results of Western blot hybridization and ELISA showed that the S gene was expressed exactly in HepG2. In immune experiment, 2 of 10 immunized mice were shown to induce antibody against HBsAg.
CONCLUSION: The recombination and expression of the S gene can be achieved successfully in vitro. And the recombinant plasmid is able to elicit humoral immune response in mice.