title: Characterization of drug-resistant influenza A(H7N9) variants isolated from an oseltamivir-treated patient in Taiwan.
abstract: BACKGROUND
  Patients contracting influenza A(H7N9) infection often developed severe disease causing respiratory failure. Neuraminidase (NA) inhibitors (NAIs) are the primary option for treatment, but information on drug-resistance markers for influenza A(H7N9) is limited.
  
  
  METHODS
  Four NA variants of A/Taiwan/1/2013(H7N9) virus containing a single substitution (NA-E119V, NA-I222K, NA-I222R, or NA-R292K) recovered from an oseltamivir-treated patient were tested for NAI susceptibility in vitro; their replicative fitness was evaluated in cell culture, mice, and ferrets.
  
  
  RESULTS
  NA-R292K led to highly reduced inhibition by oseltamivir and peramivir, while NA-E119V, NA-I222K, and NA-I222R caused reduced inhibition by oseltamivir. Mice infected with any virus showed severe clinical signs with high mortality rates. NA-I222K virus was the most virulent in mice, whereas virus lacking NA change (NA-WT) and NA-R292K virus seemed the least virulent. Sequence analysis suggests that PB2-S714N increased virulence of NA-I222K virus in mice; NS1-K126R, alone or in combination with PB2-V227M, produced contrasting effects in NA-WT and NA-R292K viruses. In ferrets, all viruses replicated to high titers in the upper respiratory tract but produced only mild illness. NA-R292K virus, showed reduced replicative fitness in this animal model.
  
  
  CONCLUSIONS
  Our data highlight challenges in assessment of the replicative fitness of H7N9 NA variants that emerged in NAI-treated patients.
authors.affiliation: Influenza Division, National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention.
authors.forename: Henju
authors.initials: H
authors.lastname: Marjuki
authors.affiliation: Influenza Division, National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention.
authors.forename: Vasiliy P
authors.initials: VP
authors.lastname: Mishin
authors.affiliation: Influenza Division, National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention Battelle Memorial Institute, Atlanta, Georgia.
authors.forename: Anton P
authors.initials: AP
authors.lastname: Chesnokov
authors.affiliation: Influenza Division, National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention.
authors.forename: Joyce
authors.initials: J
authors.lastname: Jones
authors.affiliation: Influenza Division, National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention Battelle Memorial Institute, Atlanta, Georgia.
authors.forename: Juan A
authors.initials: JA
authors.lastname: De La Cruz
authors.affiliation: Influenza Division, National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention.
authors.forename: Katrina
authors.initials: K
authors.lastname: Sleeman
authors.affiliation: Influenza Division, National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention Oak Ridge Institute for Science and Education, Tennessee.
authors.forename: Daisuke
authors.initials: D
authors.lastname: Tamura
authors.affiliation: Influenza Division, National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention Battelle Memorial Institute, Atlanta, Georgia.
authors.forename: Ha T
authors.initials: HT
authors.lastname: Nguyen
authors.affiliation: Taiwan Centers for Disease Control, Taipei City.
authors.forename: Ho-Sheng
authors.initials: HS
authors.lastname: Wu
authors.affiliation: Taiwan Centers for Disease Control, Taipei City.
authors.forename: Feng-Yee
authors.initials: FY
authors.lastname: Chang
authors.affiliation: Taiwan Centers for Disease Control, Taipei City.
authors.forename: Ming-Tsan
authors.initials: MT
authors.lastname: Liu
authors.affiliation: Influenza Division, National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention.
authors.forename: Alicia M
authors.initials: AM
authors.lastname: Fry
authors.affiliation: Influenza Division, National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention.
authors.forename: Nancy J
authors.initials: NJ
authors.lastname: Cox
authors.affiliation: Influenza Division, National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention.
authors.forename: Julie M
authors.initials: JM
authors.lastname: Villanueva
authors.affiliation: Influenza Division, National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention.
authors.forename: Charles T
authors.initials: CT
authors.lastname: Davis
authors.affiliation: Influenza Division, National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention lgubareva@cdc.gov.
authors.forename: Larisa V
authors.initials: LV
authors.lastname: Gubareva
mesh_terms: D000818:Animals; D000998:Antiviral Agents / Q000627:therapeutic use*; D004195:Disease Models, Animal; D024882:Drug Resistance, Viral; D005289:Ferrets; D006801:Humans; D064766:Influenza A Virus, H7N9 Subtype / Q000187:drug effects* / Q000201:enzymology / Q000235:genetics / Q000302:isolation & purification; D007251:Influenza, Human / Q000188:drug therapy* / Q000821:virology*; D008807:Mice, Inbred BALB C; D008826:Microbial Sensitivity Tests; D050505:Mutant Proteins / Q000235:genetics; D020125:Mutation, Missense; D009439:Neuraminidase / Q000235:genetics; D009976:Orthomyxoviridae Infections / Q000473:pathology / Q000821:virology; D053139:Oseltamivir / Q000627:therapeutic use*; D014764:Viral Proteins / Q000235:genetics; D014776:Virus Cultivation; D014779:Virus Replication
chemical_list: D000998:Antiviral Agents; D050505:Mutant Proteins; D014764:Viral Proteins; D053139:Oseltamivir; C487630:NA protein, influenza A virus; D009439:Neuraminidase
keywords: E119V; H7N9; I222K; I222R; R292K; ferrets; influenza virus; mice; oseltamivir; peramivir