title: Evidence for sequence selection within the non-structural 5A gene of hepatitis C virus type 1b during unsuccessful treatment with interferon-alpha.
abstract: Resistance of the hepatitis C virus (HCV) to interferon-alpha (IFN-alpha) therapy in patients with hepatitis C may be genetically controlled by an IFN sensitivity-determining region (ISDR) within the non-structural 5A (NS5A) gene. To assess whether HCV 1b strains carrying a 'resistant' type of ISDR are selected during unsuccessful IFN therapy, we analysed the evolution of the NS5A quasispecies, as detected by the clonal frequency analysis technique, and of the ISDR sequence by nucleotide sequence determination, in 11 patients showing no virological response during two consecutive cycles of IFN-alpha therapy. IFN-resistant patients had a homogeneous ISDR quasispecies with sequences identical to those described as 'resistant-' or 'intermediate-' type ISDR. After retreatment with IFN, further selection towards a homogeneous viral population was observed and 10 out of 11 patients had only one variant of HCV with no or just one single amino acid mutation within the ISDR sequence. Treatment and retreatment with IFN was associated in our non-responder patients with evolution of the ISDR quasispecies towards a rather homogeneous viral population carrying a conserved or minimally mutated ISDR motif, supporting the idea that this motif may be relevant for IFN resistance in HCV 1b-infected individuals.
authors.affiliation: Department of Clinical and Experimental Medicine, University of Padua, Italy.
authors.forename: M
authors.initials: M
authors.lastname: Gerotto
authors.forename: F
authors.initials: F
authors.lastname: Dal Pero
authors.forename: D G
authors.initials: DG
authors.lastname: Sullivan
authors.forename: L
authors.initials: L
authors.lastname: Chemello
authors.forename: L
authors.initials: L
authors.lastname: Cavalletto
authors.forename: S J
authors.initials: SJ
authors.lastname: Polyak
authors.forename: P
authors.initials: P
authors.lastname: Pontisso
authors.forename: D R
authors.initials: DR
authors.lastname: Gretch
authors.forename: A
authors.initials: A
authors.lastname: Alberti
mesh_terms: D000328:Adult; D000595:Amino Acid Sequence; D000998:Antiviral Agents / Q000494:pharmacology* / Q000627:therapeutic use; D004352:Drug Resistance, Microbial / Q000235:genetics; D005260:Female; D016174:Hepacivirus / Q000145:classification / Q000187:drug effects* / Q000235:genetics; D006526:Hepatitis C / Q000188:drug therapy* / Q000821:virology; D006801:Humans; D016898:Interferon-alpha / Q000494:pharmacology* / Q000627:therapeutic use; D008297:Male; D008875:Middle Aged; D008969:Molecular Sequence Data; D017422:Sequence Analysis, DNA; D017361:Viral Nonstructural Proteins / Q000737:chemistry / Q000187:drug effects / Q000235:genetics*; D012324:RNA-Dependent RNA Polymerase
chemical_list: D000998:Antiviral Agents; D016898:Interferon-alpha; D017361:Viral Nonstructural Proteins; C087036:NS-5 protein, hepatitis C virus; D012324:RNA-Dependent RNA Polymerase