OBJECTIVESTo transfer 1.3-fold-overlength genome of HBV expression plasmid into HepG2 cells, and observe the dynamic changes of viral replication as well as expression in the transfected cells.

METHODS4.1 kb fragment of HBV genome, derived from pGEM-HBV, was cloned into Hind III site of the eukaryotic expression vector pCDNA3.1 to construct the recombinant plasmid pHBV. Then HepG2 hepatoma, cells were transfected with pHBV, using Lipofectamine2000 transfection reagent. After 24, 48, 72 hours, the levels of HBsAg and HBeAg in the supernatant of HepG2 cells were determined with Abbott MEIA Kit. Intracellular viral DNA and RNA were analyzed by Southern and northern blot hybridization. In addition, viral-specific proteins (HBsAg and HBcAg) were assayed by immunofluorescence staining.

RESULTSThe expression vector pCDNA3.1 was constructed successfully. The levels of HBsAg were 5.36+-0.25, 13.42+-1.24, 7.52+-0.43, and the values of HBeAg were 9.16+-0.32, 22.75+-1.49, 15.96+-1.03 after 24, 48, 72 hours, respectively. All expected HBV replicative intermediates and specific transcripts were verified by Southern and northern blot analysis. The HBsAg-positive cells peaked after 24 hours, and then dropped slowly. HBsAg positive staining scattered in the cytoplasm, whereas HBcAg lied maily in the cytoplasm apart from nuclears.

CONCLUSIONSThis recombinant plasmid, which initiates viral replication efficiently in infected cells, is expected as a novel tool for investigating HBV replication in vitro.