Early detection of viral resistance by determination of hepatitis B virus polymerase mutations in patients treated by lamivudine for chronic hepatitis B

We have analyzed the molecular dynamics of emergence of drug-resistant stra ins in patients receiving lamivudine therapy for chronic hepatitis B. Twent y consecutive patients with lamivudine resistance were studied (13 hepatiti s 8 e antigen [HBeAg]-positive patients and 7 HBe antibody [anti-HBe]-posit ive patients). Determination of viral genotype, precore mutants, and polyme rase gene mutants (L528M, M552V, M552I) was performed using the research ve rsion of Lipa-HBV. Quantitative analysis of HBV DNA was performed using bot h branched DNA (bDNA) and polymerase chain reaction (PCR) assays. Polymeras e mutants (genotypic resistance) were found in 16 of 20 patients. Genotypic resistance was detected earlier than the phenotypic resistance (P = .004). Quantitative PCR allowed detection of viral DNA throughout the entire stud y period in 16 of 20 patients. Analysis of pretreatment variables showed th at high alanine transaminase (ALT) levels (>3 x the upper limit of normal [ ULN]) was associated with a more rapid selection of drug-resistant mutants (P = .027) and a high hepatitis B virus (HBV) DNA level (>1,497 Meq/mL, bDN A) with a more rapid occurrence of phenotypic resistance (P = .04), At the time of viral breakthrough, the mean serum HBV-DNA values were not differen t from the pretreatment values (P = .37). ALT levels were higher in anti-HB e-positive patients compared with pretreatment values and to HBeAg-positive patients (P = .01). In 8 patients, antiviral therapy was modified after vi ral breakthrough, with the introduction of famciclovir and/or interferon al fa. Viral DNA became undetectable by bDNA in 3 patients who received interf eron. Our results suggest that genotypic assays for polymerase mutant detec tion and quantitative determination of viremia with highly sensitive assay are warranted for an optimal monitoring of antiviral therapy of chronic hep atitis B.