OBJECTIVE: The aim of this study was to predict breakthrough hepatitis and analyze the dynamics of lamivudine-resistant hepatitis B virus in patients treated with lamivudine. METHODS: Fifty-five chronic hepatitis B patients treated with lamivudine were included. The emergence of YMDD motif mutants was detected by peptide nucleic acid (PNA) mediated PCR clamping with a detection limit of 10(1) YMDD mutants. We then performed a semiquantitative PCR assay of subjects in whom YMDD mutants were detected. This assay detects 10(2.7)-10(7.7) copies of mutant virus per 1 ml of serum. RESULTS: YMDD mutants were detected in 28 (51%) of the 55 patients. Eight patients stopped medication before viral breakthrough. YMDD mutants appeared transiently despite the continuance of lamivudine therapy in 12 patients. In all 8 patients with breakthrough hepatitis, the quantities of YMDD mutants ranged from 10(2.7)-10(4.7) copies/ml in the two to three months before clinical breakthrough. In contrast, in 12 patients without viral breakthrough, there were always less than 10(2.7) copies/ml YMDD mutants. CONCLUSIONS: Lamivudine-resistant viruses sometimes disappear even during lamivudine administration. Our sensitive quantitative assay proved useful for early detection of YMDD mutants and a threshold of 10(2.7) copies/ml is suggested for predicting viral breakthrough.
OBJECTIVE: The aim of this study was to predict breakthrough hepatitis and analyze the dynamics of lamivudine-resistant hepatitis B virus in patients treated with lamivudine. METHODS: Fifty-five chronic hepatitis Bpatients treated with lamivudine were included. The emergence of YMDD motif mutants was detected by peptide nucleic acid (PNA) mediated PCR clamping with a detection limit of 10(1) YMDD mutants. We then performed a semiquantitative PCR assay of subjects in whom YMDD mutants were detected. This assay detects 10(2.7)-10(7.7) copies of mutant virus per 1 ml of serum. RESULTS: YMDD mutants were detected in 28 (51%) of the 55 patients. Eight patients stopped medication before viral breakthrough. YMDD mutants appeared transiently despite the continuance of lamivudine therapy in 12 patients. In all 8 patients with breakthrough hepatitis, the quantities of YMDD mutants ranged from 10(2.7)-10(4.7) copies/ml in the two to three months before clinical breakthrough. In contrast, in 12 patients without viral breakthrough, there were always less than 10(2.7) copies/ml YMDD mutants. CONCLUSIONS:Lamivudine-resistant viruses sometimes disappear even during lamivudine administration. Our sensitive quantitative assay proved useful for early detection of YMDD mutants and a threshold of 10(2.7) copies/ml is suggested for predicting viral breakthrough.