title: Suppression of interferon-α signaling by hepatitis E virus.
abstract: The interferon (IFN) system is integral to the host response against viruses, and many viruses have developed strategies to overcome its antiviral effects. The effects of hepatitis E virus (HEV), the causative agent of hepatitis E, on IFN signaling have not been investigated primarily because of the nonavailability of an efficient in vitro culture system or small animal models of infection. We report here the generation of A549 cell lines persistently infected with genotype 3 HEV, designated as HEV-A549 cells and the effects HEV has on IFN-α-mediated Janus kinase-signal transducer and activator of transcription (JAK-STAT) signaling. Treatment of HEV-A549 cells with 250, 500, and 1000 U/mL of IFN-α for 72 hours showed a dose-dependent reduction in HEV RNA levels by 10%, 20%, and 50%, respectively. IFN-α-stimulated genes coding for the antiviral proteins dsRNA-activated protein kinase (PKR) and 2',5'-oligoadenylate synthetase (2',5'-OAS) were down-regulated in IFN-α-treated HEV-A549 cells. HEV infection also prevented IFN-α-induced phosphorylation of STAT1. Regulation of STAT1 by HEV was specific, as phosphorylation of STAT2, tyrosine kinase (Tyk) 2, and Jak1 by IFN-α was unaltered. Additionally, STAT1 levels were markedly increased in HEV-A549 cells compared with naive A549 cells. Furthermore, binding of HEV open reading frame (ORF)3 protein to STAT1 in HEV-A549 cells was observed. HEV ORF3 protein alone inhibited IFN-α-induced phosphorylation of STAT1 and down-regulated the IFN-α-stimulated genes encoding PKR, 2',5'-OAS, and myxovirus resistance A.
  
  
  CONCLUSIONS
  HEV inhibits IFN-α signaling through the regulation of STAT1 phosphorylation in A549 cells. These findings have implications for the development of new strategies against hepatitis E.
authors.affiliation: Division of Viral Hepatitis, Centers for Disease Control and Prevention, Atlanta, GA, USA.
authors.forename: Chen
authors.initials: C
authors.lastname: Dong
authors.forename: Mohammad
authors.initials: M
authors.lastname: Zafrullah
authors.forename: Tonya
authors.initials: T
authors.lastname: Mixson-Hayden
authors.forename: Xing
authors.initials: X
authors.lastname: Dai
authors.forename: Jiuhong
authors.initials: J
authors.lastname: Liang
authors.forename: Jihong
authors.initials: J
authors.lastname: Meng
authors.forename: Saleem
authors.initials: S
authors.lastname: Kamili
mesh_terms: D002478:Cells, Cultured / Q000187:drug effects; D015536:Down-Regulation; D005455:Fluorescent Antibody Technique; D015967:Gene Expression Regulation, Viral; D016751:Hepatitis E / Q000235:genetics / Q000503:physiopathology; D016752:Hepatitis E virus / Q000235:genetics* / Q000502:physiology; D022781:Hepatocytes / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D015151:Immunoblotting; D016898:Interferon-alpha / Q000378:metabolism / Q000494:pharmacology*; D053613:Janus Kinase 1 / Q000235:genetics / Q000378:metabolism; D010766:Phosphorylation; D012367:RNA, Viral / Q000032:analysis; D060888:Real-Time Polymerase Chain Reaction / Q000379:methods; D050794:STAT1 Transcription Factor / Q000235:genetics / Q000378:metabolism*; D012680:Sensitivity and Specificity; D015398:Signal Transduction / Q000235:genetics / Q000502:physiology*; D014162:Transfection; D014779:Virus Replication / Q000235:genetics / Q000502:physiology
chemical_list: D016898:Interferon-alpha; D012367:RNA, Viral; D050794:STAT1 Transcription Factor; D053613:Janus Kinase 1