Rapid emergence of a viral resistant mutant in WHV chronically infected woodchucks treated with lamivudine and a pre-S/S CHO-derived hepatitis B virus vaccine.

To determine whether the addition of a pre-S/S human vaccine increases the antiviral activity of lamivudine, four woodchucks were treated with a daily dose of 100 mg/kg lamivudine and four 50 microg doses of CHO-derived pre-S/S human vaccine. WHV DNA titres decreased up to two logarithms in three woodchucks. At week 4, in three of the animals, the sequence analysis showed a predominant strain containing a nucleotide change from A to T at position 1696 of domain B of the WHV DNA polymerase. Vaccination did not further suppress WHV DNA, despite anti-HBs production in three animals. The woodchuck remains a useful model for characterising the biology and kinetics of the emergence of drug-resistant variants and could be used for pre-clinical studies of combinations of new antiviral drugs.