Therapeutic Strategy for YMDD Mutants of Hepatitis B Virus / 대한간학회지

No abstract available.

Viral Breakthrough in HBeAg-Negative Chronic Hepatitis B Patients Receiving Lamivudine Therapy / 대한간학회지

BACKGROUND/AIMS: Long-term efficacy and the rate of viral breakthrough in patients with HBeAg- negative chronic hepatitis B receiving lamivudine therapy is uncertain. This study was conducted to determine the rate of viral breakthrough according to the HBeAg status and the relation of viral breakthrough with YMDD mutants. METHODS: Two hundred and five patients with HBeAg-positive and 49 patients with HBeAg-negative chronic hepatitis B, who had received lamivudine for at least 9 months, were included. The mean durations of the lamivudine treatment were 176 months and 155 months in HBeAg-positive and negative patients, respectively. Analysis of HBV genome for YMDD mutations was performed by restriction-fragment-length polymorphism assay and direct sequencing. RESULTS: While the cumulative rates of viral breakthrough at 12th and 24th months of the lamivudine therapy were 0% and 7% in the HBeAg-negative group, they were 12% and 39% in the HBeAg-positive group. The cumulative rate of viral breakthrough in the HBeAg-negative group was significantly lower than in the HBeAg-positive group (p<0.01). In multivariate analysis, the only significant factor related to viral breakthrough was the HBeAg status (p<0.05). The YMDD mutants were detected in all patients with viral breakthrough irrespective of HBeAg status. However, in patients without viral breakthrough, the rate of YMDD mutants was significantly higher in the HBeAg-negative group than in the HBeAg-positive group (13.3% vs 5.1%; p<0.01). CONCLUSIONS: Lamivudine is expected to be more persistently effective in HBeAg-negative chronic hepatitis B because of a lower viral breakthrough rate than in HBeAg-positive chronic hepatitis B in spite of the emergence of YMDD mutants.

Clinical and Virologic Characteristics of Lamivudine Resistance in HBV-associated Chronic Liver Disease / 대한간학회지

BACKGROUND/AIMS: Lamivudine therapy in chronic hepatitis B has been shown to be effective in inhibiting HBV replication. However, lamivudine resistance has been developed with prolonged use. We studied to determine the prevalence, predictive factors, and clinical outcomes of lamivudine resistance. Mutations in YMDD motif of HBV polymerase, which have been associated with lamivudine resistance, were also assessed. METHODS: 170 patients with HBV-associated chronic liver disease who have received lamivudine for at least one year, were studied. The clinical, biochemical, and virologic characteristics were analyzed and compared according to presence (resistance group) or absence (non-resistance group) of DNA breakthrough. Their clinical outcomes were regularly followed. Stored sera before treatment and after DNA breakthrough were examined for detection of HBV polymerase mutation by direct sequencing and/or RFLP. RESULTS: Cumulative rates of lamivudine resistance after one and two years of treatment were 11% and 34%, respectively. In the resistance group, as compared to the non-resistance group, age, the presence of HBeAg before treatment, and disappearance of HBeAg during treatment, were significantly different. The predictive factors associated with lamivudine resistance were not found. ALT and HBV-DNA level after lamivudine resistance was variable, but jaundice or hepatic failure was absent. Mutation in YMDD motif was detected in 73% and other variable mutations were detected before treatment and after DNA breakthrough. CONCLUSIONS: Lamivudine resistance increases the longer the duration of treatment and clinical outcomes are variable. The mutation in YMDD motif was found in about 2/3 of cases. Other causes for lamivudine resistance may be considered.

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

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.