Mutations of some critical amino acid residues in the hepatitis B virus surface antigen.

Amino acid substitutions at several positions in the surface antigen (HBsAg) of hepatitis B virus (HBV) in natural isolates and the products of recombinant DNA molecules have identified important residues for cross-reaction with specific antibodies (anti-HBs) and the induction of antibodies with certain serological specificities. In a further group of mutants described here, cysteine residues in a region believed to be significant of the a epitope have been changed to serines. Of the three adjacent cysteine residues at positions 137, 138 and 139, mutation of either of the flanking residues reduced cross-reactivity with polyclonal anti-HBs, while alteration of the central residue was relatively well-tolerated. Mutation of cysteine 149 to serine or of glycine 145 to arginine (imitating naturally occurring mutants), lysine, or glutamatic acid all led to loss of cross-reactivity with polyclonal antisera.