title: Human and Murine IFIT1 Proteins Do Not Restrict Infection of Negative-Sense RNA Viruses of the Orthomyxoviridae, Bunyaviridae, and Filoviridae Families.
abstract: Interferon-induced protein with tetratricopeptide repeats 1 (IFIT1) is a host protein with reported cell-intrinsic antiviral activity against several RNA viruses. The proposed basis for the activity against negative-sense RNA viruses is the binding to exposed 5'-triphosphates (5'-ppp) on the genome of viral RNA. However, recent studies reported relatively low binding affinities of IFIT1 for 5'-ppp RNA, suggesting that IFIT1 may not interact efficiently with this moiety under physiological conditions. To evaluate the ability of IFIT1 to have an impact on negative-sense RNA viruses, we infected Ifit1(-/-) and wild-type control mice and primary cells with four negative-sense RNA viruses (influenza A virus [IAV], La Crosse virus [LACV], Oropouche virus [OROV], and Ebola virus) corresponding to three distinct families. Unexpectedly, a lack of Ifit1 gene expression did not result in increased infection by any of these viruses in cell culture. Analogously, morbidity, mortality, and viral burdens in tissues were identical between Ifit1(-/-) and control mice after infection with IAV, LACV, or OROV. Finally, deletion of the human IFIT1 protein in A549 cells did not affect IAV replication or infection, and reciprocally, ectopic expression of IFIT1 in HEK293T cells did not inhibit IAV infection. To explain the lack of antiviral activity against IAV, we measured the binding affinity of IFIT1 for RNA oligonucleotides resembling the 5' ends of IAV gene segments. The affinity for 5'-ppp RNA was approximately 10-fold lower than that for non-2'-O-methylated (cap 0) RNA oligonucleotides. Based on this analysis, we conclude that IFIT1 is not a dominant restriction factor against negative-sense RNA viruses.
  
  
  OBJECTIVE
  Negative-sense RNA viruses, including influenza virus and Ebola virus, have been responsible for some of the most deadly outbreaks in recent history. The host interferon response and induction of antiviral genes contribute to the control of infections by these viruses. IFIT1 is highly induced after virus infection and reportedly has antiviral activity against several RNA and DNA viruses. However, its role in restricting infection by negative-sense RNA viruses remains unclear. In this study, we evaluated the ability of IFIT1 to inhibit negative-sense RNA virus replication and pathogenesis both in vitro and in vivo. Detailed cell culture and animal studies demonstrated that IFIT1 is not a dominant restriction factor against three different families of negative-sense RNA viruses.
authors.affiliation: Department of Medicine, Washington University School of Medicine, St. Louis, Missouri, USA.
authors.forename: Amelia K
authors.initials: AK
authors.lastname: Pinto
authors.affiliation: Department of Medicine, Washington University School of Medicine, St. Louis, Missouri, USA.
authors.forename: Graham D
authors.initials: GD
authors.lastname: Williams
authors.affiliation: Department of Medicine, Washington University School of Medicine, St. Louis, Missouri, USA.
authors.forename: Kristy J
authors.initials: KJ
authors.lastname: Szretter
authors.affiliation: Department of Medicine, Washington University School of Medicine, St. Louis, Missouri, USA.
authors.forename: James P
authors.initials: JP
authors.lastname: White
authors.affiliation: Department of Medicine, Washington University School of Medicine, St. Louis, Missouri, USA Department of Genetics, Evolution and Bioagents, Institute of Biology, University of Campinas (UNICAMP), Campinas, SP, Brazil.
authors.forename: José Luiz
authors.initials: JL
authors.lastname: Proença-Módena
authors.affiliation: Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, Missouri, USA.
authors.forename: Gai
authors.initials: G
authors.lastname: Liu
authors.affiliation: Department of Microbiology, Boston University School of Medicine, Boston, Massachusetts, USA National Emerging Infectious Diseases Laboratories, Boston University School of Medicine, Boston, Massachusetts, USA.
authors.forename: Judith
authors.initials: J
authors.lastname: Olejnik
authors.affiliation: Department of Medicine, Washington University School of Medicine, St. Louis, Missouri, USA.
authors.forename: James D
authors.initials: JD
authors.lastname: Brien
authors.affiliation: Laboratory of Virology, Division of Intramural Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rocky Mountain Laboratories, Hamilton, Montana, USA.
authors.forename: Hideki
authors.initials: H
authors.lastname: Ebihara
authors.affiliation: Department of Microbiology, Boston University School of Medicine, Boston, Massachusetts, USA National Emerging Infectious Diseases Laboratories, Boston University School of Medicine, Boston, Massachusetts, USA.
authors.forename: Elke
authors.initials: E
authors.lastname: Mühlberger
authors.affiliation: Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, Missouri, USA.
authors.forename: Gaya
authors.initials: G
authors.lastname: Amarasinghe
authors.affiliation: Department of Medicine, Washington University School of Medicine, St. Louis, Missouri, USA Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, Missouri, USA Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, Missouri, USA.
authors.forename: Michael S
authors.initials: MS
authors.lastname: Diamond
authors.affiliation: Department of Medicine, Washington University School of Medicine, St. Louis, Missouri, USA Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, Missouri, USA Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, Missouri, USA jboon@dom.wustl.edu.
authors.forename: Adrianus C M
authors.initials: AC
authors.lastname: Boon
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D029043:Ebolavirus / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D009980:Influenza A virus / Q000235:genetics / Q000378:metabolism*; D018062:La Crosse virus / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D018345:Mice, Knockout; D012327:RNA Virus Infections / Q000235:genetics / Q000378:metabolism*; D016601:RNA-Binding Proteins
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; C484290:IFIT1 protein, human; C092573:Ifit1 protein, mouse; D016601:RNA-Binding Proteins