title: Hepatitis C virus non-structural 3/4A protein interferes with intrahepatic interferon-γ production.
abstract: BACKGROUND
  The non-structural (NS) 3/4A protease/helicase of the hepatitis C virus is known to modulate signalling pathways in the infected hepatocyte by cleaving CARD adaptor inducing IFNβ (Cardif), T-cell protein tyrosine phosphatase (TC-PTP) and TIR domain-containing adaptor inducing IFNβ (TRIF), but the effects of NS3/4A in vivo still remain unclear.
  
  
  OBJECTIVE
  To investigate the influence of NS3/4A on intracellular and intercellular signalling in vivo by analysing the intrahepatic inflammatory response of naïve, lipopolysaccharide (LPS)/D-galactosamine (D-galN) or tumour necrosis factor-α (TNFα)/D-galN-treated NS3/4A-transgenic (Tg) mice.
  
  
  METHODS
  The intrahepatic immunity of naïve and LPS/D-galN- or TNFα/D-galN-treated NS3/4A-Tg mice was determined using western blot, ELISA, real-time PCR, flow cytometry and survival monitoring. The injection of cytokines or antibodies against signalling components was performed to analyse the relevance of the respective pathways for the investigated issues. A Tg mouse lineage expressing an inactivated NS3/4A protease (NS3/4A(Ile1073Ala)-Tgs) was generated to examine if protective effects were NS3/4A protease dependent.
  
  
  RESULTS
  The activation of hepatic signal transducer and activator of transcription 1 and 2 was impaired in NS3/4A-Tg mice after treatment with LPS/D-galN or TNFα/D-galN. This was paralleled by a reduction in hepatic interferon-γ (IFNγ). Reconstitution of IFNγ reverted the resistance to LPS/TNFα in NS3/4A-Tg mice. Subsequently, blocking IFNγ in vivo rendered wild-type mice resistant against treatment with LPS/TNFα. A new Tg mouse expressing an inactivated NS3/4A protease had the same phenotype as wild-type mice with respect to hepatic IFNγ levels and sensitivity to LPS/d-galN. Finally, the chemokine profile was altered in the NS3/4A-Tg mice towards an anti-inflammatory state, which helps to explain the altered immune cell subsets and reduction in hepatic IFNγ production.
  
  
  CONCLUSIONS
  Our data demonstrate that the NS3/4A protease reduces the intrahepatic production of IFNγ and alters TNFα-mediated effects, thereby impairing the hepatic inflammatory response. This may contribute to viral persistence.
authors.affiliation: Division of Clinical Microbiology F68, Department of Laboratory Medicine, Karolinska Institutet, Karolinska University Hospital Huddinge, Stockholm, Sweden. erwin.brenndorfer@ki.se
authors.forename: Erwin Daniel
authors.initials: ED
authors.lastname: Brenndörfer
authors.forename: Anette
authors.initials: A
authors.lastname: Brass
authors.forename: Jonas
authors.initials: J
authors.lastname: Söderholm
authors.forename: Lars
authors.initials: L
authors.lastname: Frelin
authors.forename: Soo
authors.initials: S
authors.lastname: Aleman
authors.forename: Johannes Georg
authors.initials: JG
authors.lastname: Bode
authors.forename: Matti
authors.initials: M
authors.lastname: Sällberg
mesh_terms: D000818:Animals; D002352:Carrier Proteins / Q000502:physiology*; D016022:Case-Control Studies; D005260:Female; D016174:Hepacivirus / Q000378:metabolism*; D006526:Hepatitis C / Q000276:immunology; D006801:Humans; D016898:Interferon-alpha / Q000378:metabolism; D007371:Interferon-gamma / Q000096:biosynthesis* / Q000494:pharmacology; D047908:Intracellular Signaling Peptides and Proteins; D008070:Lipopolysaccharides / Q000494:pharmacology; D008099:Liver / Q000276:immunology*; D016131:Lymphocyte Subsets / Q000276:immunology; D008297:Male; D051379:Mice; D008822:Mice, Transgenic; D008875:Middle Aged; D050794:STAT1 Transcription Factor / Q000378:metabolism; D015398:Signal Transduction; D017361:Viral Nonstructural Proteins / Q000502:physiology*; D012697:Serine Endopeptidases; D043583:Nucleoside-Triphosphatase; D053487:DEAD-box RNA Helicases; D000085242:Viral Proteases
chemical_list: D002352:Carrier Proteins; D016898:Interferon-alpha; D007371:Interferon-gamma; D047908:Intracellular Signaling Peptides and Proteins; D008070:Lipopolysaccharides; D050794:STAT1 Transcription Factor; D017361:Viral Nonstructural Proteins; C084422:NS3 protein, hepatitis C virus; D012697:Serine Endopeptidases; D043583:Nucleoside-Triphosphatase; D053487:DEAD-box RNA Helicases; D000085242:Viral Proteases; C455041:NS4A cofactor peptide, Hepatitis C virus