title: Novel genetic reassortants in H9N2 influenza A viruses and their diverse pathogenicity to mice.
abstract: BACKGROUND
  H9N2 influenza A viruses have undergone extensive reassortments in different host species, and could lead to the epidemics or pandemics with the potential emergence of novel viruses.
  
  
  METHODS
  To understand the genetic and pathogenic features of early and current circulating H9N2 viruses, 15 representative H9N2 viruses isolated from diseased chickens in northern China between 1998 and 2010 were characterized and compared with all Chinese H9N2 viruses available in the NCBI database. Then, the representative viruses of different genotypes were selected to study the pathogenicity in mice with the aim to investigate the adaptation and the potential pathogenicity of the novel H9N2 reassortants to mammals.
  
  
  RESULTS
  Our results demonstrated that most of the 15 isolates were reassortants and generated four novel genotypes (B62-B65), which incorporated the gene segments from Eurasian H9N2 lineage, North American H9N2 branch, and H5N1 viruses. It was noteworthy that the newly identified genotype B65 has been prevalent in China since 2007, and more importantly, different H9N2 influenza viruses displayed a diverse pathogenicity to mice. The isolates of the 2008-2010 epidemic (genotypes B55 and B65) were lowly infectious, while two representative viruses of genotypes B0 and G2 isolated from the late 1990s were highly pathogenic to mice. In addition, Ck/SD/LY-1/08 (genotype 63, containing H5N1-like NP and PA genes) was able to replicate well in mouse lungs with high virus titers but caused mild clinical signs.
  
  
  CONCLUSIONS
  Several lines of evidence indicated that the H9N2 influenza viruses constantly change their genetics and pathogenicity. Thus, the genetic evolution of H9N2 viruses and their pathogenicity to mammals should be closely monitored to prevent the emergence of novel pandemic viruses.
authors: Center for Molecular Virology, Key Laboratory of Pathogenic Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing 100101, China.
authors: Yuhai
authors: Y
authors: Bi
authors: Lu
authors: L
authors: Lu
authors: Jing
authors: J
authors: Li
authors: Yanbo
authors: Y
authors: Yin
authors: Yi
authors: Y
authors: Zhang
authors: Huijie
authors: H
authors: Gao
authors: Zhuoming
authors: Z
authors: Qin
authors: Basit
authors: B
authors: Zeshan
authors: Jinhua
authors: J
authors: Liu
authors: Lei
authors: L
authors: Sun
authors: Wenjun
authors: W
authors: Liu
mesh_terms: D000818:Animals; D002645:Chickens; D002681:China; D016000:Cluster Analysis; D004195:Disease Models, Animal; D019143:Evolution, Molecular; D005260:Female; D053127:Influenza A Virus, H9N2 Subtype / Q000235:genetics* / Q000302:isolation & purification / Q000472:pathogenicity*; D005585:Influenza in Birds / Q000821:virology*; D051379:Mice; D008807:Mice, Inbred BALB C; D008969:Molecular Sequence Data; D009976:Orthomyxoviridae Infections / Q000473:pathology / Q000821:virology; D010802:Phylogeny; D012367:RNA, Viral / Q000235:genetics; D016865:Reassortant Viruses / Q000235:genetics* / Q000302:isolation & purification / Q000472:pathogenicity*; D017422:Sequence Analysis, DNA
chemical_list: D012367:RNA, Viral