POINT MUTATIONS IN THE S AND PRE-S2 GENES OBSERVED IN 2 HEPATITIS-B VIRUS CARRIERS POSITIVE FOR ANTIBODY TO HEPATITIS-B SURFACE-ANTIGEN

Two hepatitis B virus (HBV) carriers who had antibodies to HBV surface antigen (anti-HBs) were studied. Case 1 was a 47 year old woman posit ive for hepatitis B e antigen (HBeAg), and case 2 was a 61 year old ma n positive for antibody to HBeAg (anti-HBe) and DNA-polymerase (DNA-p) . Neither case had received the HBV vaccine. The nucleotide sequences of the HBV-DNA extracted from the patients' sera were determined withi n the pre-S2 and S genes. Seven out of nine S gene clones from case I and six out of nine S gene clones from case 2 had an amino acid replac ement from Thr or lie to Ser at codon 126 in the alpha-determinant of the S gene. Amino acid substitution of codon 145 of the S gene previou sly reported was not observed. Although two previous reports on HBV es cape mutant carriers with both anti-HBs and HBeAg described some delet ions in the pre-Sa gene, our cases did not show these deletions. Our a nalysis indicated that carriers with the HBV escape mutant did not alw ays have pre-Sa gene deletions. We found two HBV escape mutant carrier s who had amino acid substitutions at codon 126 in the S gene due to p oint mutation without any deletions in the pre-S2 gene.