Detection of hepatitis B surface gene mutation in carrier children with or without immunoprophylaxis at birth.

To investigate the clinical significance of mutation in hepatitis B virus (HBV) surface gene, DNA sequence analysis of the "a" determinant was performed on sera from 27 carrier children with immunoprophylaxis, their mothers, and 21 carriers without vaccination. A precore mutant (G to A) at nucleotide 1896 was detected in sera from 11 carriers without vaccination. Mutations in the "a" determinant were detected in 6 (22%) of the vaccinated children. Four HBV strains showed a Gly-to-Arg mutation at the 145th codon of the surface gene. Amino acid substitutions at amino acid 133 and 144 were noted in the other 2 children. Only 1 mother had the same predominant strain of mutant virus as her child. These observations indicate that immune pressure exerted by immunoprophylaxis at birth may select for a mutant virus.