Expression of hepatitis B antigens with a simian virus 40 vector.

Recombinant DNA molecules consisting of the simian virus 40 (SV40) early region and different subgenomic hepatitis B virus DNA fragments were constructed in vitro and packaged in vivo into SV40 capsids by using a complementing SV40 helper virus. Upon infection with these virus stocks the three known hepatitis B-specific antigens were expressed under SV40 control. The surface antigen was released into the medium, and the core antigen and its derivative hepatitis B e antigen were only detected intracellularly. Size analysis of the core gene product(s) by immunoblotting revealed the presence of a single protein species identical with the 21-kilodalton core antigen isolated from human liver. The hepatitis B core antigen expressing construct did not contain a putative precore sequence, indicating that such a sequence is not needed for hepatitis B core antigen synthesis in animal cells. S1 analysis demonstrated the use of SV40 signals for initiation and polyadenylation of the core gene transcripts. In addition, a processing-polyadenylation signal was identified within the core gene.