title: Identification of PB2 mutations responsible for the efficient replication of H5N1 influenza viruses in human lung epithelial cells.
abstract: Highly pathogenic H5N1 avian influenza viruses have caused outbreaks among poultry worldwide, resulting in sporadic infections in humans with approximately 60% mortality. However, efficient transmission of H5N1 viruses among humans has yet to occur, suggesting that further adaptation of H5N1 viruses to humans is required for their efficient transmission among humans. The viral determinants for efficient replication in humans are currently poorly understood. Here, we report that the polymerase PB2 protein of an H5N1 influenza virus isolated from a human in Vietnam (A/Vietnam/UT36285/2010, virus 36285) increased the growth ability of an avian H5N1 virus (A/wild bird/Anhui/82/2005, virus Wb/AH82) in human lung epithelial A549 cells (however, the reassortant virus did not replicate more efficiently than human 36285 virus). Furthermore, we demonstrate that the amino acid residues at positions 249, 309, and 339 of the PB2 protein from this human isolate were responsible for its efficient replication in A549 cells. PB2 residues 249G and 339M, which are found in the human H5N1 virus, are rare in H5N1 viruses from both human and avian sources. Interestingly, PB2-249G is found in over 30% of human seasonal H3N2 viruses, which suggests that H5N1 viruses may replicate well in human cells when they acquire this mutation. Our data are of value to H5N1 virus surveillance.
  
  
  OBJECTIVE
  Highly pathogenic H5N1 avian influenza viruses must acquire mutations to overcome the species barrier between avian species and humans. When H5N1 viruses replicate in human respiratory cells, they can acquire amino acid mutations that allow them to adapt to humans through continuous selective pressure. Several amino acid mutations have been shown to be advantageous for virus adaptation to mammalian hosts. Here, we found that amino acid changes at positions 249, 309, and 339 of PB2 contribute to efficient replication of avian H5N1 viruses in human lung cells. These findings are beneficial for evaluating the pandemic risk of circulating avian viruses and for further functional analysis of PB2.
authors.affiliation: Division of Virology, Department of Microbiology and Immunology, Institute of Medical Science, University of Tokyo, Tokyo, Japan.
authors.forename: Reina
authors.initials: R
authors.lastname: Yamaji
authors.affiliation: Division of Virology, Department of Microbiology and Immunology, Institute of Medical Science, University of Tokyo, Tokyo, Japan shinya@ims.u-tokyo.ac.jp kawaoka@ims.u-tokyo.ac.jp.
authors.forename: Shinya
authors.initials: S
authors.lastname: Yamada
authors.affiliation: National Institute of Hygiene and Epidemiology, Hanoi, Vietnam.
authors.forename: Mai Q
authors.initials: MQ
authors.lastname: Le
authors.affiliation: State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin, China.
authors.forename: Chengjun
authors.initials: C
authors.lastname: Li
authors.affiliation: State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin, China.
authors.forename: Hualan
authors.initials: H
authors.lastname: Chen
authors.affiliation: Avian Influenza Research Center, Airlangga University, Surabaya, Indonesia.
authors.forename: Ema
authors.initials: E
authors.lastname: Qurnianingsih
authors.affiliation: Avian Influenza Research Center, Airlangga University, Surabaya, Indonesia.
authors.forename: Chairul A
authors.initials: CA
authors.lastname: Nidom
authors.affiliation: Division of Virology, Department of Microbiology and Immunology, Institute of Medical Science, University of Tokyo, Tokyo, Japan.
authors.forename: Mutsumi
authors.initials: M
authors.lastname: Ito
authors.affiliation: Division of Virology, Department of Microbiology and Immunology, Institute of Medical Science, University of Tokyo, Tokyo, Japan.
authors.forename: Yuko
authors.initials: Y
authors.lastname: Sakai-Tagawa
authors.affiliation: Division of Virology, Department of Microbiology and Immunology, Institute of Medical Science, University of Tokyo, Tokyo, Japan Department of Pathobiological Sciences, School of Veterinary Medicine, University of Wisconsin-Madison, Wisconsin, USA Department of Special Pathogens, International Research Center for Infectious Diseases, Institute of Medical Science, University of Tokyo, Tokyo, Japan shinya@ims.u-tokyo.ac.jp kawaoka@ims.u-tokyo.ac.jp.
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Kawaoka
mesh_terms: D000220:Adaptation, Biological; D002460:Cell Line; D004847:Epithelial Cells / Q000821:virology*; D006801:Humans; D053124:Influenza A Virus, H5N1 Subtype / Q000235:genetics / Q000502:physiology*; D050505:Mutant Proteins / Q000235:genetics / Q000378:metabolism; D020125:Mutation, Missense; D011995:Recombination, Genetic; D059386:Reverse Genetics; D014764:Viral Proteins / Q000235:genetics* / Q000378:metabolism; D014779:Virus Replication
chemical_list: D050505:Mutant Proteins; C502893:PB2 protein, influenza virus; D014764:Viral Proteins