title: Neuraminidase Activity and Resistance of 2009 Pandemic H1N1 Influenza Virus to Antiviral Activity in Bronchoalveolar Fluid.
abstract: Human bronchoalveolar fluid is known to have anti-influenza activity. It is believed to be a frontline innate defense against the virus. Several antiviral factors, including surfactant protein D, are believed to contribute to the activity. The 2009 pandemic H1N1 influenza virus was previously shown to be less sensitive to surfactant protein D. Nevertheless, whether different influenza virus strains have different sensitivities to the overall anti-influenza activity of human bronchoalveolar fluid was not known. We compared the sensitivities of 2009 pandemic H1N1, seasonal H1N1, and seasonal H3N2 influenza virus strains to inhibition by human bronchoalveolar lavage (BAL) fluid. The pandemic and seasonal H1N1 strains showed lower sensitivity to human BAL fluid than the H3N2 strains. The BAL fluid anti-influenza activity could be enhanced by oseltamivir, indicating that the viral neuraminidase (NA) activity could provide resistance to the antiviral defense. In accordance with this finding, the BAL fluid anti-influenza activity was found to be sensitive to sialidase. The oseltamivir resistance mutation H275Y rendered the pandemic H1N1 virus but not the seasonal H1N1 virus more sensitive to BAL fluid. Since only the seasonal H1N1 but not the pandemic H1N1 had compensatory mutations that allowed oseltamivir-resistant strains to maintain NA enzymatic activity and transmission fitness, the resistance to BAL fluid of the drug-resistant seasonal H1N1 virus might play a role in viral fitness.
  
  
  OBJECTIVE
  Human airway secretion contains anti-influenza activity. Different influenza strains may vary in their susceptibilities to this antiviral activity. Here we show that the 2009 pandemic and seasonal H1N1 influenza viruses were less sensitive to human bronchoalveolar lavage (BAL) fluid than H3N2 seasonal influenza virus. The resistance to the pulmonary innate antiviral activity of the pandemic virus was determined by its neuraminidase (NA) gene, and it was shown that the NA inhibitor resistance mutation H275Y abolished this resistance of the pandemic H1N1 but not the seasonal H1N1 virus, which had compensatory mutations that maintained the fitness of drug-resistant strains. Therefore, the innate respiratory tract defense may be a barrier against NA inhibitor-resistant mutants, and evasion of this defense may play a role in the emergence and spread of drug-resistant strains.
authors.affiliation: Department of Microbiology, Faculty of Medicine, Siriraj Hospital, Mahidol University, Bangkok, Thailand.
authors.forename: Kanyarat
authors.initials: K
authors.lastname: Ruangrung
authors.affiliation: Department of Microbiology, Faculty of Medicine, Siriraj Hospital, Mahidol University, Bangkok, Thailand.
authors.forename: Ornpreya
authors.initials: O
authors.lastname: Suptawiwat
authors.affiliation: Division of Respiratory Diseases and Tuberculosis, Department of Medicine, Faculty of Medicine, Siriraj Hospital, Mahidol University, Bangkok, Thailand.
authors.forename: Kittipong
authors.initials: K
authors.lastname: Maneechotesuwan
authors.affiliation: Department of Microbiology, Faculty of Medicine, Siriraj Hospital, Mahidol University, Bangkok, Thailand.
authors.forename: Chompunuch
authors.initials: C
authors.lastname: Boonarkart
authors.affiliation: Faculty of Veterinary Science, Mahidol University, Bangkok, Thailand.
authors.forename: Warunya
authors.initials: W
authors.lastname: Chakritbudsabong
authors.affiliation: Division of Respiratory Diseases and Tuberculosis, Department of Medicine, Faculty of Medicine, Siriraj Hospital, Mahidol University, Bangkok, Thailand.
authors.forename: Jirawatna
authors.initials: J
authors.lastname: Assawabhumi
authors.affiliation: Department of Microbiology, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand.
authors.forename: Parvapan
authors.initials: P
authors.lastname: Bhattarakosol
authors.affiliation: Department of Pathology, Faculty of Medicine, Siriraj Hospital, Mahidol University, Bangkok, Thailand.
authors.forename: Mongkol
authors.initials: M
authors.lastname: Uiprasertkul
authors.affiliation: Department of Microbiology, Faculty of Medicine, Siriraj Hospital, Mahidol University, Bangkok, Thailand.|Center of Research and Innovation, Faculty of Medical Technology, Mahidol University, Bangkok, Thailand.
authors.forename: Pilaipan
authors.initials: P
authors.lastname: Puthavathana
authors.affiliation: Faculty of Veterinary Science, Mahidol University, Bangkok, Thailand.
authors.forename: Witthawat
authors.initials: W
authors.lastname: Wiriyarat
authors.affiliation: Virology and Cell Technology Laboratory, National Center for Genetic Engineering and Biotechnology, Khlong Luang, Thailand.
authors.forename: Anan
authors.initials: A
authors.lastname: Jongkaewwattana
authors.affiliation: Department of Microbiology, Faculty of Medicine, Siriraj Hospital, Mahidol University, Bangkok, Thailand prasert.aue@mahidol.ac.th.|Institute of Molecular Biosciences, Mahidol University, Bangkok, Thailand.
authors.forename: Prasert
authors.initials: P
authors.lastname: Auewarakul
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000818:Animals; D000998:Antiviral Agents / Q000494:pharmacology; D001992:Bronchoalveolar Lavage Fluid / Q000276:immunology*; D004195:Disease Models, Animal; D060467:Disease Resistance / Q000276:immunology*; D024882:Drug Resistance, Viral; D005260:Female; D005289:Ferrets; D054884:Host-Pathogen Interactions; D006801:Humans; D007113:Immunity, Innate; D007070:Immunoglobulin A / Q000276:immunology; D007074:Immunoglobulin G / Q000276:immunology; D053118:Influenza A Virus, H1N1 Subtype / Q000187:drug effects / Q000502:physiology*; D007251:Influenza, Human / Q000276:immunology* / Q000821:virology*; D008297:Male; D008875:Middle Aged; D009439:Neuraminidase / Q000378:metabolism*; D053139:Oseltamivir / Q000494:pharmacology; D019562:Viral Load; D014764:Viral Proteins / Q000378:metabolism*
chemical_list: D000998:Antiviral Agents; D007070:Immunoglobulin A; D007074:Immunoglobulin G; D014764:Viral Proteins; D053139:Oseltamivir; C487630:NA protein, influenza A virus; D009439:Neuraminidase