title: A novel unsupervised method to identify genes important in the anti-viral response: application to interferon/ribavirin in hepatitis C patients.
abstract: BACKGROUND
  Treating hepatitis C with interferon/ribavirin results in a varied response in terms of decrease in viral titer and ultimate outcome. Marked responders have a sharp decline in viral titer within a few days of treatment initiation, whereas in other patients there is no effect on the virus (poor responders). Previous studies have shown that combination therapy modifies expression of hundreds of genes in vitro and in vivo. However, identifying which, if any, of these genes have a role in viral clearance remains challenging.
  
  
  OBJECTIVE
  The goal of this paper is to link viral levels with gene expression and thereby identify genes that may be responsible for early decrease in viral titer.
  
  
  METHODS
  Microarrays were performed on RNA isolated from PBMC of patients undergoing interferon/ribavirin therapy. Samples were collected at pre-treatment (day 0), and 1, 2, 7, 14 and 28 days after initiating treatment. A novel method was applied to identify genes that are linked to a decrease in viral titer during interferon/ribavirin treatment. The method uses the relationship between inter-patient gene expression based proximities and inter-patient viral titer based proximities to define the association between microarray gene expression measurements of each gene and viral-titer measurements.
  
  
  RESULTS
  We detected 36 unique genes whose expressions provide a clustering of patients that resembles viral titer based clustering of patients. These genes include IRF7, MX1, OASL and OAS2, viperin and many ISG's of unknown function.
  
  
  CONCLUSIONS
  The genes identified by this method appear to play a major role in the reduction of hepatitis C virus during the early phase of treatment. The method has broad utility and can be used to analyze response to any group of factors influencing biological outcome such as antiviral drugs or anti-cancer agents where microarray data are available.
authors.affiliation: Institute of Evolution, University of Haifa, Haifa, Israel.
authors.forename: Leonid I
authors.initials: LI
authors.lastname: Brodsky
authors.forename: Abdus S
authors.initials: AS
authors.lastname: Wahed
authors.forename: Jia
authors.initials: J
authors.lastname: Li
authors.forename: John E
authors.initials: JE
authors.lastname: Tavis
authors.forename: Takuma
authors.initials: T
authors.lastname: Tsukahara
authors.forename: Milton W
authors.initials: MW
authors.lastname: Taylor
mesh_terms: D000998:Antiviral Agents / Q000627:therapeutic use; D005786:Gene Expression Regulation; D016174:Hepacivirus / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism; D006526:Hepatitis C / Q000188:drug therapy* / Q000235:genetics*; D006801:Humans; D050839:Interferon Regulatory Factor-7 / Q000235:genetics; D007372:Interferons / Q000627:therapeutic use*; D020411:Oligonucleotide Array Sequence Analysis; D018579:Patient Selection; D012313:RNA / Q000097:blood / Q000235:genetics; D012254:Ribavirin / Q000627:therapeutic use*; D014764:Viral Proteins / Q000235:genetics
chemical_list: D000998:Antiviral Agents; D050839:Interferon Regulatory Factor-7; D014764:Viral Proteins; D012254:Ribavirin; D012313:RNA; D007372:Interferons