title: Meta-analysis of mutations in the NS5A gene and hepatitis C virus resistance to interferon therapy: uniting discordant conclusions.
abstract: BACKGROUND
  Hepatitis C virus genotype 1B responds poorly to treatment with interferon, in contrast to the more interferon-sensitive genotypes 2 and 3. Studies on combination therapy regimens with PEG-interferon and ribavirin report sustained response rates that generally do not exceed 50%, in contrast to sustained response rates of 80% for genotype 2 and 3. In Japan, a correlation was found between the number of mutations in an 'interferon sensitivity determining region' (ISDR) and outcome of interferon treatment in genotype 1B-infected patients. However, an ongoing controversy on the existence of an ISDR in non-Japanese isolates resulted, as non-Japanese studies failed to confirm this association. The present study approached this issue by carrying out a meta-analysis of ISDR sequences and response to interferon treatment.
  
  
  METHODS
  Twenty-seven studies were included, reporting 1351 ISDR sequence data of genotype 1B-infected patients and their virological response to interferon treatment. Both summary statistics and individual patient data were used systematically to explore the association between ISDR mutations and response to interferon.
  
  
  RESULTS
  The ISDR effect on response was universally present but appeared to be stronger in Japan, with a relative risk of 5.73 for mutant viruses as compared to 4.66 for non-Japanese isolates. High interferon dose, in Japan administered more frequently, was associated with an increase in response rate only among patients infected with mutant isolates. Interaction between dose and ISDR type was confirmed in a logistic regression model. After stratifying for dose, differences in response rate between Japanese and non-Japanese patients were no longer present.
  
  
  CONCLUSIONS
  This study puts an end to a longstanding controversy by confirming the universal existence of an ISDR in genotype 1B-infected patients. Apparent discrepant findings from Japanese and non-Japanese studies can be explained by differences in dosing regimens and a dose-dependent differential effect of ISDR mutations on response to treatment.
authors.affiliation: Department of Medical Microbiology, Leiden University Medical Center, Leiden, the Netherlands. c.j.schinkel@lumc.nl
authors.forename: Janke
authors.initials: J
authors.lastname: Schinkel
authors.forename: Willy J M
authors.initials: WJ
authors.lastname: Spaan
authors.forename: Aloys C M
authors.initials: AC
authors.lastname: Kroes
mesh_terms: D000998:Antiviral Agents / Q000008:administration & dosage* / Q000494:pharmacology; D016022:Case-Control Studies; D024882:Drug Resistance, Viral / Q000235:genetics*; D005060:Europe; D005500:Follow-Up Studies; D005838:Genotype; D016174:Hepacivirus / Q000187:drug effects* / Q000235:genetics; D006526:Hepatitis C / Q000188:drug therapy* / Q000821:virology; D006801:Humans; D007372:Interferons / Q000008:administration & dosage* / Q000494:pharmacology; D007564:Japan; D009154:Mutation; D016896:Treatment Outcome; D017361:Viral Nonstructural Proteins / Q000235:genetics*; D012324:RNA-Dependent RNA Polymerase
chemical_list: D000998:Antiviral Agents; D007372:Interferons; D017361:Viral Nonstructural Proteins; C087036:NS-5 protein, hepatitis C virus; D012324:RNA-Dependent RNA Polymerase