IN-VITRO INFECTION OF HUMAN HEPATOMA-CELLS (HEPG2) WITH HEPATITIS-B VIRUS (HBV) - SPONTANEOUS SELECTION OF A STABLE HBV SURFACE ANTIGEN-PRODUCING HEPG2 CELL-LINE CONTAINING INTEGRATED HBV DNA-SEQUENCES

The degree of susceptibility of human hepatoma (HepG2) cells to direct hepatitis B virus (HBV) infection remains unknown. We previously obse rved a low level of Dane particle production and viral DNA replication after in vitro infection of HepG2 cells with serum-derived HBV. Howev er, this culture system appeared to be affected by variations as human hepatocyte cultures. In the present study, HBV infection of HepG2 cel ls led to a significant increase in the secretion of three envelope an tigens (HBsAg, preS2Ag and preS1Ag) at 4 days post-infection, and Nort hern blot analysis revealed the presence of both preS1 (2.6 kb) and pr eS2/S (2.2 kb) transcripts. Expression of preS1Ag and the correspondin g viral RNA became undetectable on 21 days post-infection whereas the 2.2 kb RNA species persisted and was associated with secretion of subv iral HBs particles expressing preS2-epitopes and banding between 30 an d 35% sucrose. At 35 days post-infection (fifth passage), a sudden hig h level production of HBsAg and preS1Ag was observed, followed by a ma ssive cell death (90%). A stable HBsAg-producing HepG2 cell line, desi gnated HepG2-BV3, grew out of the surviving cells. HepG2-BV3 cells cou ld integrate HBV DNA sequences and produce the three HBV surface antig ens. Treatment with dexamethasone increased the HBsAg and preS1Ag secr etion. Such a HBsAg-producing HepG2 cell line obtained by in vitro HBV infection seems to mimick events that occur in the naturally occurrin g persistent chronic infection, and therefore may be an efficient in v itro model for studying the contribution of viral integration in the d ysregulation of HBV and liver-specific genes expression.