title: Sensitivity of hepatitis C virus to cyclosporine A depends on nonstructural proteins NS5A and NS5B.
abstract: HCV re-occurs after liver transplantation and increases mortality. Cyclosporine, but not tacrolimus, has potent antiviral effects against HCV replication in cell culture. To determine the conditions, if any, under which HCV is susceptible to cyclosporine in vivo, we selected for cyclosporine-resistant mutant HCV in vitro. The resulting mutations were mapped to x-ray crystallographic structures and sequence databases. Mutations selected by cyclosporine were clustered in the nonstructural (NS) proteins NS5A and NS5B. Different sets of mutations in NS5A, paired with the same 2 NS5B mutations, conferred different levels of cyclosporine resistance when engineered back into the HCV replicon. Mutations in NS5B are structurally consistent with a proposed model of regulation of RNA binding by cyclophilin B (CyPB). These mutations also highlight a natural polymorphism between different HCV genotypes that correlates with the variation in response to cyclosporine A (CsA) noted in some clinical trials. Replicons engineered to have mutations in only NS5A (P < or = 0.0001) or only NS5B (P = 0.002) suggest that while both NS5A or NS5B variants alter cyclosporine susceptibility, NS5A has the largest effect.
  
  
  CONCLUSIONS
  Preexisting sequence variation could alter the effect of cyclosporine on HCV in vivo.
authors.affiliation: Department of Medicine, University of Wisconsin School of Medicine and Public Health, Madison, WI 53706, USA.
authors.forename: Fiona
authors.initials: F
authors.lastname: Fernandes
authors.forename: Daniel S
authors.initials: DS
authors.lastname: Poole
authors.forename: Spencer
authors.initials: S
authors.lastname: Hoover
authors.forename: Rannveig
authors.initials: R
authors.lastname: Middleton
authors.forename: Adin-Cristian
authors.initials: AC
authors.lastname: Andrei
authors.forename: Justin
authors.initials: J
authors.lastname: Gerstner
authors.forename: Rob
authors.initials: R
authors.lastname: Striker
mesh_terms: D000595:Amino Acid Sequence; D000998:Antiviral Agents / Q000494:pharmacology* / Q000627:therapeutic use; D045744:Cell Line, Tumor; D016572:Cyclosporine / Q000494:pharmacology* / Q000627:therapeutic use; D024882:Drug Resistance, Viral; D005838:Genotype; D016174:Hepacivirus / Q000187:drug effects* / Q000235:genetics; D006526:Hepatitis C / Q000188:drug therapy; D006801:Humans; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D011110:Polymorphism, Genetic; D012093:Replicon / Q000235:genetics; D017361:Viral Nonstructural Proteins / Q000187:drug effects* / Q000235:genetics; D012324:RNA-Dependent RNA Polymerase
chemical_list: D000998:Antiviral Agents; D016572:Cyclosporine; D017361:Viral Nonstructural Proteins; C087036:NS-5 protein, hepatitis C virus; D012324:RNA-Dependent RNA Polymerase