OBJECTIVETo gain some insights into the critical events relating to HBV transcriptional regulation by comparing HBV replicative characteristics in different cell lines.

METHODSHepatic cell lines QSG-7701 and HepG2 were transfected with plasmid PUC18-HBV 1.2 by standard calcium phosphate precipitation method, and 1.0 microg pSEAP2-control vector was included in the transfection procedures to serve as an internal control monitoring the transfection efficiency. Hepatitis B surface antigen (HBsAg) in the medium was detected by ELISA method and HBV DNA was quantitated using fluorescent quantitative PCR. The intracellular HBsAg and HBcAg were detected with immunofluorescent staining. The gene expression profiles of QSG-7701 and HepG2 were compared using oligonucleotide microarray; partial differentially expressed genes were verified with quantitative RT-PCR.

RESULTSIn the medium of the cultured HepG2 cells, HBsAg and HBV DNA could be detected 6 days after the transfection, whereas in QSG-7701 cells, the HBsAg and HBV DNA could be detected for 2 weeks. The HBV DNA in the culture medium of QSG-7701 was about 50 times more than that of the HepG2 cells which were kept in 1 x 10(7)copies/ml(-3) x 10(7)copies/ml for 0 to 10 days after the transfection. On the 4th day after the transfection, 20% to 30% of the QSG-7701 cells were positive with HBsAg and HBcAg immunofluorescent staining. The gene microarray analysis showed that most transcription factors involved with HBV life cycle in QSG-7701 and HepG2 cells had similar levels, whereas some factors involved with HBV transcriptional regulation and core particle disassembly, such as interleukin-6 (R=5.1340), retinoid X receptor, alpha (R=5.1268), hepatic leukemia factor (R=3.2538), serine protease PRRS23 (R=2.8356), hepatitis B virus x interacting protein (R=0.4939), serine protease inhibitor Kazal type 1 (R=0.0740) and matrix metalloproteinase 3 (negative in QSG-7701) were all differentially expressed by HepG2 cells.

CONCLUSIONDifferent than HepG2 cells, the QSG-7701 cells could support a high level and relatively stable HBV replication after HBV DNA transient transfection. The HBV core particles were probably recycled in the QSG-7701 cells. The differential gene expressions between QSG-7701 and HepG2 might explain the mechanism of the different HBV replication patterns. Hepatic cell line QSG-7701 might serve as a useful tool for HBV transcriptional regulation research.