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

Abstract number: 1733_1275

D'Ugo E., Kondili L., Canitano A., Catone S., Giuseppetti R., Gallinella B., Palmieri G., Orobello S., Argentini C., Rapicetta M.

Objectives: The woodchuck hepatitis virus (WHV) and its host, the Eastern woodchuck (Marmota monax) are predictive models for evaluating HBV antiviral therapy. To determine whether the addition of a pre-S/S human vaccine, previously shown to protect woodchucks from productive WHV infection, could increase the antiviral activity of a high-dosage of lamivudine in the woodchuck model.

Methods: The 4 woodchucks were administered a daily dose of 100 mg/kg body weight of lamivudine for 40 weeks and were vaccinated with four doses (50mg each) of CHO–HBsAg vaccine at 14, 18, 22, and 34 weeks after starting lamivudine. WHV-DNA were determined using a TaqMan Real-Time PCR (sensitivity of 10 genome equivalents/mL); the positive samples were considered for the sequence analysis. The A, B, C and D domains of the WHV polymerase region were amplified by specific primers. Serial liver biopsies were performed and numerical score according to the Ishak system was used.

Results: WHV DNA titres decreased up to two logarithms in 3 woodchucks. Since week 4 the sequence analysis in 3 of the 4 animals showed a heterogeneous viral population, with the predominant strain containing a single nucleotide change at position 1696 (from A to T) in the sequence coding of FLLA motif (domain B). In 2 of the last 3 woodchucks, the increase in WHV DNA titres was observed, though not immediately after the FLLT mutation appearance. No mutations in the other domains were observed. Vaccination did not further suppress WHV DNA, despite anti-HBs production in three animals. In one animal WHV DNA levels increased immediately after the first dose of pre-S/S vaccine and the grading score increased from 2 to 10.

Conclusions: The emergence of the lamivudine-resistant mutation in the B domain was observed within 4 weeks of starting lamivudine, which is much earlier than previously reported. Vaccination could trigger the immune system and liver inflammation in the context of high WHV DNA levels resistant to lamivudine. Under the conditions used, a transient effect of combination lamivudine and anti HBs vaccine therapy was observed.

Session Details

Date: 31/03/2007
Time: 00:00-00:00
Session name: European Society of Clinical Microbiology and Infectious Diseases
Location: ICC, Munich, Germany
Presentation type:
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