Resistance mutations define specific antiviral effects for inhibitors of the hepatitis C virus p7 ion channel

Authors

  • Toshana L. Foster,

    1. Section of Oncology and Clinical Research, Leeds Institute of Molecular Medicine, St. James's University Hospital, Leeds, United Kingdom
    2. Institute of Molecular & Cellular Biology and Astbury Centre for Structural & Molecular Biology, Faculty of Biological Sciences
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    • These authors contributed equally to this work.

  • Mark Verow,

    1. Institute of Molecular & Cellular Biology and Astbury Centre for Structural & Molecular Biology, Faculty of Biological Sciences
    2. School of Chemistry, University of Leeds, Leeds, United Kingdom
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    • These authors contributed equally to this work.

  • Ann L. Wozniak,

    1. Department of Internal Medicine, University of Kansas Medical Center, Kansas City, KS
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  • Matthew J. Bentham,

    1. Section of Oncology and Clinical Research, Leeds Institute of Molecular Medicine, St. James's University Hospital, Leeds, United Kingdom
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  • Joseph Thompson,

    1. School of Chemistry, University of Leeds, Leeds, United Kingdom
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  • Elizabeth Atkins,

    1. Institute of Molecular & Cellular Biology and Astbury Centre for Structural & Molecular Biology, Faculty of Biological Sciences
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  • Steven A. Weinman,

    1. Department of Internal Medicine, University of Kansas Medical Center, Kansas City, KS
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  • Colin Fishwick,

    1. School of Chemistry, University of Leeds, Leeds, United Kingdom
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  • Richard Foster,

    1. School of Chemistry, University of Leeds, Leeds, United Kingdom
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  • Mark Harris,

    1. Institute of Molecular & Cellular Biology and Astbury Centre for Structural & Molecular Biology, Faculty of Biological Sciences
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  • Stephen Griffin

    Corresponding author
    1. Section of Oncology and Clinical Research, Leeds Institute of Molecular Medicine, St. James's University Hospital, Leeds, United Kingdom
    2. Institute of Molecular & Cellular Biology and Astbury Centre for Structural & Molecular Biology, Faculty of Biological Sciences
    • Section of Oncology and Clinical Research, Leeds Institute of Molecular Medicine, Wellcome Trust Brenner Building, St. James's University Hospital, University of Leeds, LS9 7TF, United Kingdom
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    • fax: (44)-113-343-8501


  • Potential conflict of interest: Nothing to report.

  • Supported by the University of Leeds Biomedical Health Research Centre; a Medical Research Council New Investigator Research Grant (G0700124) and Yorkshire Cancer Research Grant (PP025) (to S. G.); a Wellcome Trust Ph.D. studentship (to T. L. F.); a Cooperative Awards in Science and Engineering Ph.D. studentship from the Biotechnology and Biological Sciences Research Council (BBSRC) and Pfizer (to E. A.); and a BBSRC studentship (to M. V.).

Abstract

The hepatitis C virus (HCV) p7 ion channel plays a critical role during infectious virus production and represents an important new therapeutic target. Its activity is blocked by structurally distinct classes of small molecules, with sensitivity varying between isolate p7 sequences. Although this is indicative of specific protein–drug interactions, a lack of high-resolution structural information has precluded the identification of inhibitor binding sites, and their modes of action remain undefined. Furthermore, a lack of clinical efficacy for existing p7 inhibitors has cast doubt over their specific antiviral effects. We identified specific resistance mutations that define the mode of action for two classes of p7 inhibitor: adamantanes and alkylated imino sugars (IS). Adamantane resistance was mediated by an L20F mutation, which has been documented in clinical trials. Molecular modeling revealed that L20 resided within a membrane-exposed binding pocket, where drug binding prevented low pH-mediated channel opening. The peripheral binding pocket was further validated by a panel of adamantane derivatives as well as a bespoke molecule designed to bind the region with high affinity. By contrast, an F25A polymorphism found in genotype 3a HCV conferred IS resistance and confirmed that these compounds intercalate between p7 protomers, preventing channel oligomerization. Neither resistance mutation significantly reduced viral fitness in culture, consistent with a low genetic barrier to resistance occurring in vivo. Furthermore, no cross-resistance was observed for the mutant phenotypes, and the two inhibitor classes showed additive effects against wild-type HCV. Conclusion: These observations support the notion that p7 inhibitor combinations could be a useful addition to future HCV-specific therapies. (HEPATOLOGY 2011;)

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