title: Hepatitis C virus core protein induces homotolerance and cross-tolerance to Toll-like receptor ligands by activation of Toll-like receptor 2.
abstract: BACKGROUND
  Hepatitis C virus (HCV) activates host innate immune responses mediated by retinoic acid inducing gene-I (RIG-I) and Toll-like receptors (TLRs). Although the nonstructural protein 3/4A (NS3/4A) of HCV disrupts interferon responses by inhibiting RIG-I signaling, the effects of TLR activation by HCV-associated proteins on host innate immune responses are poorly understood.
  
  
  METHODS
  Proinflammatory cytokine responses to various TLR ligands in human antigen-presenting cells (APCs) were examined either with or without prestimulation by HCV core protein.
  
  
  RESULTS
  TLR2 activation by the HCV core protein leads to a decrease in interleukin 6 (IL-6) production by human APCs after subsequent stimulation with TLR2 (homotolerance) ligands and TLR4 (cross-tolerance) ligands. This hyporesponsiveness induced by preexposure to the HCV core protein was partially mediated by the negative regulation of nuclear factor-kappaB activation by the induction of IRAK-M. TLR ligand-induced IL-6 production was significantly reduced in peripheral blood monocytes isolated from HCV-infected patients, compared with those of healthy control subjects. Alloantigen presentation by monocytes isolated from HCV-infected patients results in impaired production of interleukin 17 by naive CD4(+) T cells in the presence of TLR ligands.
  
  
  CONCLUSIONS
  Chronic stimulation of APCs with HCV core protein is associated with hyporesponsiveness in TLR-mediated innate immunity.
authors.affiliation: Department of Gastroenterology and Hepatology, Kinki University School of Medicine, Osaka-Sayama, Osaka, Japan.
authors.forename: Hobyung
authors.initials: H
authors.lastname: Chung
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Watanabe
authors.forename: Masatoshi
authors.initials: M
authors.lastname: Kudo
authors.forename: Tsutomu
authors.initials: T
authors.lastname: Chiba
mesh_terms: D000938:Antigen-Presenting Cells / Q000276:immunology / Q000821:virology; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology; D002478:Cells, Cultured; D016174:Hepacivirus / Q000276:immunology* / Q000472:pathogenicity*; D019698:Hepatitis C, Chronic / Q000276:immunology; D006801:Humans; D007108:Immune Tolerance; D053592:Interleukin-1 Receptor-Associated Kinases / Q000276:immunology; D020381:Interleukin-17 / Q000378:metabolism; D015850:Interleukin-6 / Q000378:metabolism; D007963:Leukocytes, Mononuclear / Q000276:immunology; D016328:NF-kappa B / Q000276:immunology; D051195:Toll-Like Receptor 2 / Q000276:immunology*; D014758:Viral Core Proteins / Q000276:immunology*
chemical_list: D020381:Interleukin-17; D015850:Interleukin-6; D016328:NF-kappa B; C495342:TLR2 protein, human; D051195:Toll-Like Receptor 2; D014758:Viral Core Proteins; C069130:nucleocapsid protein, Hepatitis C virus; C507771:IRAK3 protein, human; D053592:Interleukin-1 Receptor-Associated Kinases