Hepatitis B virus replication in well differentiated mouse hepatocyte cell lines immortalized by plasmid DNA.

The primary hepatocytes cultured from adult BALB/c mice were readily transfected by plasmid DNA and could be immortalized at a frequency of approximately 0.1 to 0.6 x 10(-7) cells/micrograms of the transfected DNA. There was no detectable plasmid DNA at the tenth cell passages. A total of five mouse hepatocyte cell lines were established. Most of them were tumorigenic. Three of the established mouse hepatocyte cell lines were well differentiated, since they expressed liver-specific genes. Further transfection of these three well differentiated mouse hepatocyte cell lines with hepatitis B virus (HBV) DNA showed that the HBV-transfected cells had integrated HBV genomes, HBV-specific mRNA transcripts, and expression of hepatitis B surface and hepatitis B core antigens. One of the lines, ML-3Neo (HBV), even secreted HBV-like particles. Furthermore, circulating hepatitis B surface antigens were detected in the sera of BALB/c mice bearing ML-3Neo (HBV) tumors. These cell lines provide a convenient model for future studies on the host immune reaction against HBV and on the transformation of hepatocytes by HBV and other cellular oncogenes and the determination of their effects on hepatocellular differentiation.