Emergence of YMDD motif mutant of hepatitis B virus during short-term lamivudine therapy in South Korea

Background/Aims: The emergence of a YMDD mutant resistant to lamivudine therapy has been reported in patients with hepatitis B treated with long-term lamivudine therapy, However, it is not well known whether the YMDD mutant could be detected early in lamivudine therapy in hepatitis B virus (HBV) endemic areas. The aim of this study was to investigate the emergence of the YMDD mutant during short-term lamivudine therapy in South Korea. Methods: We prospectively investigated the emergence of the YMDD mutant by the nested PCR assay using restriction fragment length polymorphism in 28 patients with chronic hepatitis B who were treated,vith 100 mg of lamivudine daily for 12 weeks. Results: The YMDD mutant was detected in 17 (60.7%) out of 28 patients at week 12, and the only type of mutation found was the YIDD mutation. When we carried out the nested PCR serially in five patients, YIDD mutants were detected as early as 2 weeks by the nested PCR assay. The nested PCR results were in concordance with DNA sequencing in one patient's serial samples. Conclusions: YMDD mutants in HBV were defected within a few weeks during lamivudine therapy in South Korea, which suggests that the YMDD mutant may exist even before lamivudine therapy in HBV endemic areas. (C) 2001 European Association for the Study of the Liver. Published by Elsevier Science B.V. All rights reserved.