Synthesis in yeast of hepatitis B virus surface antigen modified P31 particles by gene modification.

The pre-S2 portion of hepatitis B virus surface antigen P31 gene was modified to make gene products resistant to trypsin-like proteases in Saccharomyces cerevisiae. The coding sequence for 6 amino acids (Ser44 - Thr49) including Arg48 was removed, and the altered gene was inserted into an expression vector. The modified HBsAg P31 (M-P31c) gene products, consisting of GP37 and GP34, formed particles having both HBsAg antigenicity and polymerized-albumin receptor activity. Since the M-P31c particles can elicite two kinds of protective antibodies against hepatitis B virus, anti-S and anti-pre-S2 antibodies, the M-P31c particles are expected to be potentially effective to S-nonresponders.