Dynamic Analysis Of Hepatitis B Virus Polymerase Gene In Lamivudine-treated Patients With Chronic Hepatitis B

Objective:The approval of lamivudine has revolutionized the treatment of chronic hepatitis B (CHB). Lamivudine is an orally administered nucleoside analog with an excellent safety profile. It can markedly reduce serum HBV DNA levels and normalize alanine aminotransferase (ALT) levels. However, more and more questions are found during anti-HBV treatment. Of these questions, the greatest drawback is the appearance of drug resistant HBV mutants. The most common mutation is YMDD variant in the catalytic domain of the HBV reverse transcriptase (P gene). With the emergence of YMDD mutation, virological and biochemical breakthroughmay occur. Furthermore, fatal hepatic failure after the emergence of the YMDD mutants during lamivudine therapy has been reported. In this study, we followed-up fourteen patients with CHB and examined dynamic changes of HBV polymerase gene, and grounded for investigating the way predicting the effect of lamivudine.Materials and Methods:Fourteen patients for long-term lamivudine antiviral therapy were included in the study. From the serum samples of patients before and after lamivudine treatment, HBV polymerase gene was amplificated by real-time PCR and PCR products were purified with a UNIQ-10 kit, and sequenced by Sanger method. The nucleotide sequences of HBV P gene before and after lamivudine therapy were analyzed with Mclone software to examine dynamic features of HBV polymerase gene.Results:After long-term lamivudine therapy, the variants with YMDD mutation in 14 patients with HBV DNA rebounding were detected. Mutation patterns detected in these patients included 11 YVDD and 3 YIDD. With the development of course of treatment,alanine aminotransferase rebounding occurred in a part of patients. The new mutations were detected in the second DNA sequencing. These mutational sites were A181VT184S, A181T S202I, A181TS202I, A181TV214, T184S V214A, A181VT184S, T184S S202I, A181VQ215S, A181VT184S , V214A , A181T, A181S V214A, S202T S239C C304S, focused on 181 and 204 amino acid sites.Conclusions:Lamivudine-resistant HBV mutants are based on the YMDD motif variants. During lamivudine treatment the resistant variants are selected and become resistant virus replicaton strains. The resistant pathogenic virus strains with the mutations of 181 and 204 amino acid sites occur through the second selection. The affinity of lamivudine for the transcriptase can be expected to correlate with these amino acid sites.