Emergence of YMDD Motif Mutant Hepatitis B Virus during Short-erm Lamivudine Therapy

Paik, Yong Han; Han, Kwang Hyub; Chung, Hyo Young; Chun, Chae Yoon; Moon, Young Myoung

Abstract

BACKGROUND/AIMS: The emergence of lamivudine-resistant mutant hepatitis B virus (HBV), with aminoacid substitution in the YMDD motif of DNA polymerase, has been reported in the long-term lamivudine use group. However there is no report about the emergence of mutant viruses during the short-term lamivudine therapy. The objective of this study was to investigate the emergence of YMDD mutant HBV during short-term lamivudine therapy.
METHODS
We evaluated twenty-eight chronic hepatitis B patients who were HBeAg and HBV DNA positive and treated with lamivudine 100mg p.o. daily for 12 weeks. First, we investigated the emergence of YMDD mutants by nested polymerase chain reaction (PCR) method developed by Chayama et al in 19 patients who lost HBV DNA during lamivudine therapy but showed HBV DNA re-emergence 2 weeks after the end of therapy. Second, DNA subcloning and sequencing of HBV DNA polymerase including YMDD motif was undertaken in one patient's serial blood samples at 0, 8, 12 weeks to confirm the results of nested PCR.
RESULTS
YMDD motif mutation was detected in 17(90%) out of 19 patients at the end of therapy and the type of mutations were YIDD only. At the end of therapy, mutant was predominant in 5 patients, both mutant and wild type were similar in proportion in 3 patients, and wild type was predominant in 9 patients. When we carried out nested PCR serially with samples of 0, 2, 4, 8, 12, 14 weeks after initiation of therapy in 5 patients who were mutant predominant at 12 weeks, YIDD mutant began to be detected from 2 weeks in 4 patients and from 4 weeks in one patient. However, rapid turnover from mutant to wild type happened after the end of therapy, so only wild type was detected in 3 patients and wild type became predominant in 2 patients at 2 weeks after the end of therapy. All the sequencing results of serial blood samples in one patient were consistent with nested PCR data.
CONCLUSIONS
The presence of YMDD motif HBV polymerase mutant may be possible before administration of lamivudine in Korean chronic hepatitis B patients. Nested PCR assay would be an useful method to detect YMDD mutant.