Seroconversion after the addition of famciclovir therapy in a child with hepatitis B virus infection after liver transplantation who developed lamivudine resistance

YMDD variants of HBV DNA polymerase gene: Rapid detection and clinicopathological analysis with long-term lamivudine therapy after liver transplantation

AIM: To look for a rapid low-cost technique for the detection of HBV variants.

METHODS: Two patients who underwent orthotopic liver transplantation (OLT) for HBV infection were treated with lamivudine (100 mg daily) and HBV infection recurred in the grafted livers. The patients were monitored intensively for liver enzymes, hepatitis B surface antigen (HBsAg) and HBV DNA in serum. Liver biopsy was performed regularly. HBV DNA in a conserved polymerase domain (the YMDD locus) was amplified from serum of each patient by PCR and sequenced. HBV genotypes were analyzed by restriction fragment length polymorphism (RFLP) of the PCR products generated from a fragment of the polymerase gene.

RESULTS: YMDD wild-type HBV was detected in one patient by PCR-RFLP and DNA sequencing 19 mo after OLT, and YIDD mutant-type HBV in the other patient, 16 mo after OLT.

CONCLUSION: PCR-RFLP assay is an accurate and simple method for genotyping lamivudine-resistant HBV variants.

Pediatric issues in new therapies for hepatitis B and C

Two antiviral treatments have been approved for hepatitis B virus (HBV) infection by the US Food and Drug Administration (FDA) for use in children: interferon (IFN)-alpha, 6 MU/m(2) three times a week subcutaneously for 6 months, and lamivudine, 3 mg/kg/d orally for 12 months. Twenty-six percent to 58% of children treated with IFN become HBV DNA negative, and up to 38% become negative to hepatitis B e antigen (HBeAg). Lamivudine, a nucleoside analogue that blocks viral replication by inhibition of the HBV polymerase, has been associated with comparable rates of seroconversion of HBeAg to anti-HBe. Loss of surface antigen occurs in less than 5% of patients treated with lamivudine, compared with 3% to 33% in those treated with IFN-alpha. Fifty percent to 65% of children treated with lamivudine clear HBV DNA after 12 months of therapy, but relapse rates have not been clarified. Patients treated with lamivudine develop drug-resistant (YMDD) mutants in the HBV polymerase at the rate of 16% to 32% per year. No treatments for children with hepatitis C virus (HCV) have been approved by the FDA. However, published reports describe treatment with IFN monotherapy and combination therapy with IFN and ribavirin. Trials of PEG-IFN alone or in combination with ribavirin are in progress. Given the lack of data regarding treatment of HCV in children, it is generally agreed among pediatric hepatologists that the optimal treatment is within the context of randomized, controlled trials.

Hepatitis B virus resistance to lamivudine and its clinical implications

Lamivudine is the first orally available drug approved for treatment of chronic hepatitis B, but hepatitis B virus (HBV) resistance to lamivudine appears to be a sine qua non in the therapy of HBV. The mutations at the FLLA and YMDD motif in the domains B and C of HBV polymerase contribute to this resistance. These mutations are found at codon (or AA) rtL180M and rtM204V/I in the reverse transcriptase (RT) domain of the HBV polymerase for all genotypes according to a new standardized RT domain numbering system. The resistant HBV may be less replication-competent in vitro and in vivo, and it is rarely associated with markedly increased HBV replication or liver injury. Therefore, certain physicians favour continuing lamivudine therapy even after emergence of HBV resistance with the expectation of maintaining lower-than baseline HBV DNA, alanine amino-transferase, and histological improvement, and avoiding reversion to wild-type HBV until additional antiviral strategies are developed. Ultimately, once several antiviral agents are approved, combination strategy is likely to be incorporated in antiviral treatment for chronic HBV to suppress, prevent or minimize the emergence of resistant virus.