[Variability of Reverse Transcriptase Gene and S Gene in Lamivudine-treated Chronic Hepatitis B Patients].

We wished to undertake molecular characterization of the reverse transcriptase (RT) gene and overlapping surface (S) gene in lamivudine-treated patients with chronic infection with the hepatitis B virus (HBV). Sequencing analyses of the HBV RT/S gene of isolates from 25 chronic hepatitis B (CHB) patients with the YMDD mutation and 30 treatment-naïve CHB patients were undertaken. In patients with the YMDD mutation, rtM2041 was the major type of mutation (20/25, 80%). rtL80I was present in most of the patients with rtM204I (14/20, 70%). rtL180M coexisted with rtM204V (5/5, 100%). Patients with the YMDD mutation had a significantly higher prevalence of mutation of the RT gene than treatment-naïve CHB patients (P < 0.05). Classical primary resistance and secondary/compensatory mutations were detected at only five sites (rtL80, rtV173, rtL180, rtM204, rtM250) in CHB patients with the YMDD mutation. The frequency of nucleos(t)ide analog resistance (NAr) mutation within the RT gene in patients with the YMDD mutation was significantly higher than that in treatment-naïve patients (P < 0.05). Amino-acid mutations within the RT gene were also associated with other types of NAr in patients with the YMDD mutation. The rate of amino-acid variants within the S gene region was significantly higher in patients with the YMDD mutation than that in treatment-naïve patients (P < 0.05). sM133L and sG145R variants were also present in patients with the YMDD mutation. These observations suggest that CHB patients with the YMDD mutation also have NAr mutations related to other NA drugs, which might lead to cross-resistance in CHB patients. Variants present in the S gene region could cause changes in the antigenicity of HBsAg, which could result in a false-negative diagnosis of HBsAg and immune in escape of the HBV.