title: γ-H2AX+CD8+ T lymphocytes cannot respond to IFN-α, IL-2 or IL-6 in chronic hepatitis C virus infection.
abstract: OBJECTIVE
  Age is the dominant prognostic factor influencing the natural history of hepatitis C virus (HCV) infection and treatment response. Accelerated lymphocyte telomere shortening in HCV infection correlates with adverse clinical outcomes. Critical telomere shortening generates double-stranded DNA breaks (DSB) inducing the DNA damage response, leading to replicative senescence. The phenotype and function of CD8+ T lymphocytes and the in vitro response to IFN-α in relation to the DNA damage response were investigated in patients with chronic HCV infection.
  
  
  METHODS
  CD8+ T lymphocytes with DSB were identified by expression of γ-H2AX (Ser-139) in 134 HCV-exposed subjects and 27 controls. Telomere length was determined by flow-FISH; cytokine expression by intracellular cytokine staining; in vitro responses to IFN-α, IL-2 or IL-6 by phospho-STAT1 (Y701) or phospho-STAT5 (Y694) expression.
  
  
  RESULTS
  The proportion of circulating CD8+γ-H2AX+ T lymphocytes rose with increasing fibrosis stage (p=0.0023). CD8+γ-H2AX+ T lymphocytes were enriched in liver compared to blood (p=0.03). CD8+γ-H2AX+ T lymphocytes demonstrated increased IFN-γ (p=0.02) and reduced IL-2 expression (p=0.02). CD8+γ-H2AX+ T lymphocytes failed to phosphorylate STAT1 in response to IFN-α compared to unfractionated CD8+ T lymphocytes (p <0.0001). More widespread failure of Jak/Stat signalling in CD8+γ-H2AX+ T lymphocytes was suggested by impaired phosphorylation of STAT1 with IL-6 (p=0.002) and STAT5 with IL-2 (p=0.0039) compared to unfractionated CD8+ T-lymphocytes.
  
  
  CONCLUSIONS
  In chronic HCV infection, CD8+γ-H2AX+ T lymphocytes are highly differentiated with shortened telomeres, are more frequent within the liver, are associated with severe fibrosis and fail to activate Jak/Stat pathways in response to IFN-α, IL-2 or IL-6, perhaps explaining treatment failure in those with severe fibrosis.
authors.affiliation: Department of Medicine, School of Clinical Medicine, University of Cambridge, Cambridge, UK.
authors.forename: Matthew
authors.initials: M
authors.lastname: Hoare
authors.forename: Arun
authors.initials: A
authors.lastname: Shankar
authors.forename: Meera
authors.initials: M
authors.lastname: Shah
authors.forename: Simon
authors.initials: S
authors.lastname: Rushbrook
authors.forename: William
authors.initials: W
authors.lastname: Gelson
authors.forename: Susan
authors.initials: S
authors.lastname: Davies
authors.forename: Arne
authors.initials: A
authors.lastname: Akbar
authors.forename: Graeme J M
authors.initials: GJ
authors.lastname: Alexander
mesh_terms: D000328:Adult; D001706:Biopsy; D018414:CD8-Positive T-Lymphocytes / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D016022:Case-Control Studies; D002478:Cells, Cultured; D004247:DNA; D004249:DNA Damage; D005260:Female; D016174:Hepacivirus / Q000302:isolation & purification; D019698:Hepatitis C, Chronic / Q000378:metabolism* / Q000473:pathology; D006657:Histones / Q000378:metabolism*; D006801:Humans; D066298:In Vitro Techniques; D016898:Interferon-alpha / Q000494:pharmacology*; D007376:Interleukin-2 / Q000494:pharmacology*; D015850:Interleukin-6 / Q000494:pharmacology*; D008099:Liver / Q000378:metabolism* / Q000473:pathology / Q000821:virology; D008297:Male; D008875:Middle Aged; D050794:STAT1 Transcription Factor / Q000378:metabolism; D050799:STAT5 Transcription Factor / Q000378:metabolism; D059506:Telomere Shortening
chemical_list: C468783:H2AX protein, human; D006657:Histones; D016898:Interferon-alpha; D007376:Interleukin-2; D015850:Interleukin-6; D050794:STAT1 Transcription Factor; C494079:STAT1 protein, human; D050799:STAT5 Transcription Factor; D004247:DNA