Stable expression of hepatitis B virus genome in a primate kidney cell.

Transfection of Vero cells with cloned hepatitis B virus (HBV) DNA resulted in the secretion of hepatitis B surface protein (HBsAg) and core proteins (HBc/eAg). Syntheses of both viral antigens in the transformed Vero cells continued for at least 50 days after cultivation. HBsAg particles were composed of many spherical and some filamentous particles containing both pre-S1 and pre-S2 domains. Restriction analysis of the transfected cellular DNA showed that one copy of HBV DNA was integrated in the cells. Some species of HBV-specific RNA were detected by Northern blot, and among these a major transcript was found to migrate at 2.1 kb by S1-mapping analysis. Viral core proteins present in the culture medium were fractionated and characterized by cesium chloride gradient and found to form particles.