Hepatitis B virus S gene mutants in infants infected despite immunoprophylaxis

Objective To assess the correlation between hepatitis B virus (HBV) surface gene mutant infection and hepatitis B (HB) vaccination failure. Methods Using sera from 106 infants who were born to HBV carrier mothers an d failed in HB immunoprophylaxis, HBV S gene was amplified by PCR, transfer red to nylon membranes for Southern blots, and then hybridized with oligonu cleotide probes. Eleven of non-hybridizing samples were used for DNA sequen cing. Results 93.4% (99/106) of the samples were HBV DNA positive, and 30.3% (30/ 99) failed to hybridize with at least one of the four probes. DNA sequencin g confirmed that 10 of the 11 samples had an S gene mutation with amino aci d (aa) change. The identified mutants included nucleotide (nt) 546T-->A (aa 131N-->T). nt531T-->C (aa126I-->T), nt491A-->C (aa113T-->P), nt491T-->A (aa 113S-->T), nt533C-->A (aa127P-->T), nt581T-->A (aa143S-->T), nt636A-->T (aa 161Y-->F), and nt679A-->C (aa175L-->F). The sequence in one mother-infant p air was completely the same, with mutations at aa131 and aa161. Conclusions The prevalence of HBV surface mutants is about 30% in the child ren failing in HB vaccination. HBV mutants can infect infants by maternal-i nfant transmission.