title: Virus-specific CD4+ T cell responses in chronic HCV infection in blood and liver identified by antigen-specific upregulation of CD154.
abstract: OBJECTIVE
  Virus-specific CD4+ T cells play a major role in hepatitis C virus (HCV) infection. Viral clearance is associated with vigorous and multispecific CD4+ T cell responses, while chronic infection has been shown to be associated with weak or absent T cell responses. Most of these studies, however, have used functional assays to analyse virus-specific CD4+ T cell responses. Therefore, the important question, of whether virus-specific CD4+ T cells are completely absent or primarily impaired in specific effector functions during chronic infection, has yet to be analysed in detail.
  
  
  METHODS
  To address this issue, a novel assay, where CD4+ T cell frequencies can be determined by de novo CD154 (CD40 ligand) expression in response to HCV antigens, was used in a cohort of chronically infected HCV patients and patients who spontaneously resolved HCV infection. These responses were compared to functional assays, such as the IFN-gamma ELISpot and flow cytometry-based proliferative assays.
  
  
  RESULTS
  Our results reveal that using the CD154 assay, virus-specific CD4+ T cells are readily detectable during chronic HCV infection albeit at a lower frequency when compared to patients who spontaneously resolved the infection. Importantly, no CD4+ T cell responses were detectable from these patients when using functional assays. Finally, these cell populations were enriched in the intrahepatic compartment.
  
  
  CONCLUSIONS
  Our findings suggest that HCV-specific CD4+ T cell responses are readily detectable in chronic HCV infection and enriched in the infected liver.
authors.affiliation: Department of Medicine II, University Hospital Freiburg, Freiburg, Germany.
authors.forename: Mareike
authors.initials: M
authors.lastname: Mueller
authors.forename: Hans Christian
authors.initials: HC
authors.lastname: Spangenberg
authors.forename: Nadine
authors.initials: N
authors.lastname: Kersting
authors.forename: Tayibe
authors.initials: T
authors.lastname: Altay
authors.forename: Hubert E
authors.initials: HE
authors.lastname: Blum
authors.forename: Paul
authors.initials: P
authors.lastname: Klenerman
authors.forename: Robert
authors.initials: R
authors.lastname: Thimme
authors.forename: Nasser
authors.initials: N
authors.lastname: Semmo
mesh_terms: D000328:Adult; D000368:Aged; D000595:Amino Acid Sequence; D019138:Antibodies, Blocking / Q000494:pharmacology; D001706:Biopsy; D015496:CD4-Positive T-Lymphocytes / Q000166:cytology / Q000378:metabolism / Q000821:virology; D023201:CD40 Ligand / Q000276:immunology / Q000378:metabolism*; D002455:Cell Division / Q000276:immunology; D002478:Cells, Cultured; D003289:Convalescence; D005260:Female; D005434:Flow Cytometry / Q000379:methods*; D018936:Hepatitis C Antigens / Q000235:genetics / Q000276:immunology / Q000494:pharmacology; D019698:Hepatitis C, Chronic / Q000097:blood / Q000276:immunology / Q000473:pathology; D000949:Histocompatibility Antigens Class II / Q000276:immunology; D006801:Humans; D018189:Immunomagnetic Separation / Q000379:methods; D007371:Interferon-gamma / Q000378:metabolism; D008099:Liver / Q000276:immunology / Q000473:pathology / Q000821:virology; D008297:Male; D008875:Middle Aged; D008969:Molecular Sequence Data; D011994:Recombinant Proteins / Q000235:genetics / Q000276:immunology / Q000494:pharmacology; D015854:Up-Regulation / Q000276:immunology
chemical_list: D019138:Antibodies, Blocking; D018936:Hepatitis C Antigens; D000949:Histocompatibility Antigens Class II; D011994:Recombinant Proteins; D023201:CD40 Ligand; D007371:Interferon-gamma