Expression of hepatitis B surface antigen gene in yeast.

Abstract
The DNA sequence coding for hepatitis B virus surface antigen (HBsAg) was placed under control of the repressible acid phosphatase promoter of the yeast Saccharomyces cerevisiae in a plasmid capable of autonomous replication in both yeast and Escherichia coli. Yeast transformed by this plasmid synthesized up to 5 .times. 105 molecules/cell of immunologically active HBsAg polypeptide in phosphate-free medium. The HBsAg polypeptides produced in the yeast cells were assembled into 20-22 nm spherical or oval particles and were immunogenic.