title: ISG15 Is Upregulated in Respiratory Syncytial Virus Infection and Reduces Virus Growth through Protein ISGylation.
abstract: Human respiratory syncytial virus (RSV), for which neither a vaccine nor an effective therapeutic treatment is currently available, is the leading cause of severe lower respiratory tract infections in children. Interferon-stimulated gene 15 (ISG15) is a ubiquitin-like protein that is highly increased during viral infections and has been reported to have an antiviral or a proviral activity, depending on the virus. Previous studies from our laboratory demonstrated strong ISG15 upregulation during RSV infection in vitro. In this study, an in-depth analysis of the role of ISG15 in RSV infection is presented. ISG15 overexpression and small interfering RNA (siRNA)-silencing experiments, along with ISG15 knockout (ISG15(-/-)) cells, revealed an anti-RSV effect of the molecule. Conjugation inhibition assays demonstrated that ISG15 exerts its antiviral activity via protein ISGylation. This antiviral activity requires high levels of ISG15 to be present in the cells before RSV infection. Finally, ISG15 is also upregulated in human respiratory pseudostratified epithelia and in nasopharyngeal washes from infants infected with RSV, pointing to a possible antiviral role of the molecule in vivo. These results advance our understanding of the innate immune response elicited by RSV and open new possibilities to control infections by the virus.
  
  
  OBJECTIVE
  At present, no vaccine or effective treatment for human respiratory syncytial virus (RSV) is available. This study shows that interferon-stimulated gene 15 (ISG15) lowers RSV growth through protein ISGylation. In addition, ISG15 accumulation highly correlates with the RSV load in nasopharyngeal washes from children, indicating that ISG15 may also have an antiviral role in vivo. These results improve our understanding of the innate immune response to RSV and identify ISG15 as a potential target for virus control.
authors.affiliation: Unidad de Infección Viral e Inmunidad, Centro Nacional de Microbiología, Instituto de Salud Carlos III, Madrid, Spain Centro de Investigación Biomédica en Red, Enfermedades Respiratorias (CIBERES), Instituto de Salud Carlos III, Madrid, Spain.
authors.forename: Rubén
authors.initials: R
authors.lastname: González-Sanz
authors.affiliation: Centro de Investigación Biomédica en Red, Enfermedades Respiratorias (CIBERES), Instituto de Salud Carlos III, Madrid, Spain Fundación Investigación Hospital General Universitario de Valencia, Valencia, Spain.
authors.forename: Manuel
authors.initials: M
authors.lastname: Mata
authors.affiliation: Hospital Clínico Universitario de Valladolid, Valladolid, Spain.
authors.forename: Jesús
authors.initials: J
authors.lastname: Bermejo-Martín
authors.affiliation: Unidad de Infección Viral e Inmunidad, Centro Nacional de Microbiología, Instituto de Salud Carlos III, Madrid, Spain.
authors.forename: Amparo
authors.initials: A
authors.lastname: Álvarez
authors.affiliation: Centro de Investigación Biomédica en Red, Enfermedades Respiratorias (CIBERES), Instituto de Salud Carlos III, Madrid, Spain Fundación Investigación Hospital General Universitario de Valencia, Valencia, Spain.
authors.forename: Julio
authors.initials: J
authors.lastname: Cortijo
authors.affiliation: Centro de Investigación Biomédica en Red, Enfermedades Respiratorias (CIBERES), Instituto de Salud Carlos III, Madrid, Spain Unidad de Biología Viral, Centro Nacional de Microbiología, Instituto de Salud Carlos III, Madrid, Spain.
authors.forename: José A
authors.initials: JA
authors.lastname: Melero
authors.affiliation: Unidad de Infección Viral e Inmunidad, Centro Nacional de Microbiología, Instituto de Salud Carlos III, Madrid, Spain Centro de Investigación Biomédica en Red, Enfermedades Respiratorias (CIBERES), Instituto de Salud Carlos III, Madrid, Spain imago@isciii.es.
authors.forename: Isidoro
authors.identifier: http://orcid.org/0000-0002-9949-9264
authors.initials: I
authors.lastname: Martínez
mesh_terms: D045744:Cell Line, Tumor; D016207:Cytokines / Q000235:genetics / Q000378:metabolism*; D010450:Endopeptidases / Q000235:genetics; D004847:Epithelial Cells / Q000378:metabolism / Q000821:virology; D006367:HeLa Cells; D006801:Humans; D007113:Immunity, Innate; D007223:Infant; D011499:Protein Processing, Post-Translational; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000235:genetics; D018357:Respiratory Syncytial Virus Infections / Q000276:immunology* / Q000821:virology; D018113:Respiratory Syncytial Virus, Human / Q000235:genetics / Q000378:metabolism*; D012141:Respiratory Tract Infections / Q000276:immunology* / Q000821:virology; D043222:Ubiquitin Thiolesterase; D044764:Ubiquitin-Activating Enzymes / Q000235:genetics; D014452:Ubiquitins / Q000235:genetics / Q000378:metabolism*
chemical_list: D016207:Cytokines; D034741:RNA, Small Interfering; D014452:Ubiquitins; C074034:ISG15 protein, human; D010450:Endopeptidases; C485560:USP18 protein, human; D043222:Ubiquitin Thiolesterase; C534879:UBA7 protein, human; D044764:Ubiquitin-Activating Enzymes