Heat-regulated expression of the hepatitis B virus surface antigen in the human Wish cell line

The DNA fragment coding for the hepatitis B virus surface antigen (HBsAg) was placed under the control of a human 70 kDa heat-shock protein (hsp70) promotor sequence. This plasmid construct has been used in transfection experiments to establish a stable amnion cell line of human origin (Wish), expressing an HBsAg in a heat-regulated fashion. Post-translational modifications, such as assembly, glycosylation, secretion and production of both major and middle S proteins appear to function normally. In addition, production of HBsAg under various protocols of heat induction is described. After inoculation into nude mice, development of tumours has been observed at the site of injection. Tumour cells, dispersed by means of collagenase or trypsin treatment from excised tumours, and subsequently seeded into Petri dishes, were able to secrete the same quantities of HBsAg after heat induction as were cells of the original cell line.