title: Amino acid changes in the influenza A virus PA protein that attenuate avian H5N1 viruses in mammals.
abstract: The influenza viral polymerase complex affects host tropism and pathogenicity. In particular, several amino acids in the PB2 polymerase subunit are essential for the efficient replication of avian influenza viruses in mammals. The PA polymerase subunit also contributes to host range and pathogenicity. Here, we report that the PA proteins of several highly pathogenic avian H5N1 viruses have attenuating properties in mammalian cells and that the attenuating phenotype is conferred by strain-specific amino acid changes. Specifically, lysine at position 185 of A/duck/Vietnam/TY165/2010 (TY165; H5N1) PA induced strongly attenuating effects in vitro and in vivo. More importantly, the introduction of the arginine residue commonly found at this position in PA significantly increased the viral polymerase activity of TY165 in mammalian cells and its virulence and pathogenicity in mice. These findings demonstrate that the PA protein plays an important role in influenza virulence and pathogenicity.
  
  
  OBJECTIVE
  Highly pathogenic influenza viruses of the H5N1 subtype cause severe respiratory infections in humans, which have resulted in death in nearly two-thirds of the patients with laboratory-confirmed cases. We found that the viral PA polymerase subunit of several H5N1 viruses possesses amino acid changes that attenuate virus replication in mammalian cells (yet the H5N1 viruses possessing these mutations are highly pathogenic in mice). Specifically, we found that an arginine-to-lysine substitution at position 185 of an H5N1 virus PA protein significantly affected that virus's virulence and pathogenicity in mice. The PA protein thus plays a role in the pathogenicity of highly pathogenic H5N1 influenza viruses.
authors.affiliation: Influenza Research Institute, School of Veterinary Medicine, University of Wisconsin-Madison, Madison, Wisconsin, USA.
authors.forename: Shufang
authors.initials: S
authors.lastname: Fan
authors.affiliation: Influenza Research Institute, School of Veterinary Medicine, University of Wisconsin-Madison, Madison, Wisconsin, USA.
authors.forename: Masato
authors.initials: M
authors.lastname: Hatta
authors.affiliation: Influenza Research Institute, School of Veterinary Medicine, University of Wisconsin-Madison, Madison, Wisconsin, USA.
authors.forename: Jin Hyun
authors.initials: JH
authors.lastname: Kim
authors.affiliation: National Institute of Hygiene and Epidemiology, Hanoi, Vietnam.
authors.forename: Mai Quynh
authors.initials: MQ
authors.lastname: Le
authors.affiliation: Influenza Research Institute, School of Veterinary Medicine, University of Wisconsin-Madison, Madison, Wisconsin, USA.
authors.forename: Gabriele
authors.initials: G
authors.lastname: Neumann
authors.affiliation: Influenza Research Institute, School of Veterinary Medicine, University of Wisconsin-Madison, Madison, Wisconsin, USA Division of Virology, Department of Microbiology and Immunology and International Research Center for Infectious Diseases, Institute of Medical Science, University of Tokyo, Tokyo, Japan Infection-Induced Host Responses Project, Exploratory Research for Advanced Technology, Saitama, Japan kawaokay@svm.vetmed.wisc.edu.
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Kawaoka
mesh_terms: D000220:Adaptation, Biological; D019943:Amino Acid Substitution; D000818:Animals; D002460:Cell Line; D002645:Chickens; D004195:Disease Models, Animal; D004285:Dogs; D004372:Ducks; D058507:Host Specificity; D006801:Humans; D053124:Influenza A Virus, H5N1 Subtype / Q000235:genetics* / Q000302:isolation & purification / Q000472:pathogenicity* / Q000502:physiology; D005585:Influenza in Birds / Q000821:virology; D051379:Mice; D050505:Mutant Proteins / Q000235:genetics / Q000378:metabolism; D020125:Mutation, Missense; D009976:Orthomyxoviridae Infections / Q000473:pathology / Q000821:virology; D012324:RNA-Dependent RNA Polymerase / Q000235:genetics* / Q000378:metabolism; D014764:Viral Proteins / Q000235:genetics* / Q000378:metabolism; D014774:Virulence
chemical_list: D050505:Mutant Proteins; C061290:PA protein, influenza viruses; D014764:Viral Proteins; D012324:RNA-Dependent RNA Polymerase