Abstract
In this paper, we show that the pattern of expression of the human hepatitis B surface antigen (HBs Ag) gene, transfected along with a dominant selectable marker into mammalian cells, is complex. In human hepatoma (HepG2) cells, late transient expression occurs and permanent expression takes place at high frequencies in the selected clones. In HeLa and human xeroderma pigmentosum (GM4312A)-derived cells, the late transient expression is barely seen or absent and permanent expression is only seen in a few selected clones. In monkey kidney Vero cells, late transient expression has been described and we show in this report that only 5% of the selected clones are capable of expressing HBs Ag in a permanent manner. In most of the Vero clones, the absence of HBs Ag expression is mainly due to HBs Ag gene rearrangements. We have selected and amplified more than 500 transfected Vero clones and have characterized in detail one clone (GAR1412) which is a permanent high- level HBs Ag expressor.