A novel hepatitis B virus mutation with resistance to adefovir but not to tenofovir in an HIV-hepatitis B virus-co-infected patient
ABSTRACT A molecular virology analysis performed in an HIV-hepatitis B virus (HBV) co-infected patient showed the emergence of an unusual HBV polymerase gene mutation (rt A181T) under adefovir therapy, conferring resistance to adefovir but not to tenofovir, as proved by in-vitro phenotypic analysis. This observation suggests that careful monitoring of co-infected patients is required to diagnose HBV resistance to nucleos(t)ide analogues, and that tenofovir may be active at least against some of the adefovir-resistant strains.
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ABSTRACT: Impact of hepatitis B virus genetic barrier, defined as the number and type of nucleotide substitutions required to overcome drug/immune selective pressure, on drug-resistance/immune-escape development is unknown. Genetic barrier was calculated according to Van de Vijver (2006) in 3482 hepatitis B virus-reverse transcriptase/HBV surface antigen sequences from 555 drug-naïve patients and 2927 antiviral-treated patients infected with hepatitis B virus genotypes A-G. Despite high natural variability, genetic barrier for drug-resistance development is identical amongst hepatitis B virus genotypes, but varies according to drug-resistance mutation type. Highest genetic barrier is found for secondary/compensatory mutations (e.g. rtL80I/V-rtL180M-rtV173L), whilst most primary mutations (including rtM204V-rtA181T/V-rtI169T-rtA194T) are associated with low genetic barrier. An exception is rtM204I, which can derive from a transition or a transversion. Genotypes A and G are more prone to develop immune/diagnostic-escape mutations sT114R and sG130N. Vaccine-escape associated sT131N-mutation is a natural polymorphism in both A and G genotypes. Genetic barrier and reverse transcriptase/HBV surface antigen overlapping can synergistically influence hepatitis B virus drug-resistance/immune-escape development. The different immune-escape potential of specific hepatitis B virus genotypes could have important clinical consequences in terms of disease progression, vaccine strategies and correct HBV surface antigen detection.Digestive and Liver Disease 08/2011; 43(12):975-83. DOI:10.1016/j.dld.2011.07.002 · 2.89 Impact Factor
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ABSTRACT: Early detection of antiviral drug-resistant mutations enables prompt initiation of rescue therapy. The aim of this study was to determine the accuracy and sensitivity of a new line probe assay in the detection of antiviral drug-resistant HBV mutations. One-hundred samples from 54 patients with virologic breakthrough during entecavir, lamivudine or adefovir treatment and 21 samples from 21 nucleoside-naïve patients were tested by direct sequencing and an updated line probe assay (Innogenetics, HBV DR v.3) which incorporates probes that can detect mutations at 11 positions of the reverse transcriptase region of the HBV polymerase gene. Complete concordance between line probe and sequencing results was observed for 90/121 samples (74.3%) and 1291/1331 amino acid positions (96.9%). Testing of follow-up samples and clonal analysis of discordant samples confirmed the presence of mutations where line probe assay but not direct sequencing detected mutations. HBV DR v.3 assay consistently detected mutations present in > or = 5% of the virus population when HBV DNA concentration was > or = 4 log10copies/mL. The updated version of the line probe assay (HBV DR v.3) has high concordance with direct sequencing in detecting antiviral drug-resistant mutations but its sensitivity in detecting mutations at some positions needs to be improved.Journal of Hepatology 12/2008; 50(1):42-8. DOI:10.1016/j.jhep.2008.08.020 · 10.40 Impact Factor
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ABSTRACT: Molecular assays are instrumental in the clinical management of viral hepatitis. During the past years, a wide variety of molecular assays have been developed and implemented. This considerably improved the understanding of the natural history and pathogenesis of Hepatitis B virus (HBV), Hepatitis C virus (HCV) or Hepatitis delta virus (HDV) hepatitis, but also caused uncertainties in the selection of the most appropriate assays for clinical requirements. Indeed, a rational choice and application of these assays requires adequate knowledge of the performance of the single test. Moreover, the choice of the most accurate assay for patients' needs and physicians' objectives, needs to be oriented to specific contexts, such as diagnosis, management or treatment. In the past, a hurdle in the routine use of assays for hepatitis viruses nucleic acid quantification was represented by the availability of only "home brew" methods which lacked standardization. Major improvement in addressing the use of molecular assays for viral hepatitis has been derived from recent standardization procedures that allowed a comparison between different tests after results were given as International Units. In addition, it should be reminded that, before getting into the market, molecular assays should be approved by European regulation authorities and validated using internationally recognized standards. A subsequent clinical validation should address the diagnostic accuracy of the assay. These proceedings have the aim of identifying which molecular tests, among those currently available, meet clinical requirements for each specific application.Digestive and Liver Disease 07/2008; 40(6):395-404. DOI:10.1016/j.dld.2007.12.016 · 2.89 Impact Factor