title: Characterization of Clade 7.2 H5 Avian Influenza Viruses That Continue To Circulate in Chickens in China.
abstract: The H5N1 avian influenza viruses emerged in Southeast Asia in the late 20th century and have evolved into multiple phylogenetic clades based on their hemagglutinin (HA)-encoding genes. The clade 7.2 viruses were first detected in chickens in northern China in 2006, and vaccines specifically targeted to the clade were developed and have been used in poultry in China since 2006. During routine surveillance and disease diagnosis, we isolated seven H5 viruses between 2011 and 2014 that bear the clade 7.2 HA genes. Here, we performed extensive studies to understand how the clade 7.2 H5 viruses have evolved in chickens in China. Full genome sequence analysis revealed that the seven viruses formed two subtypes (four H5N1 viruses and three H5N2 viruses) and four genotypes by deriving genes from other influenza viruses. All of the viruses had antigenically drifted from the clade 7.2 viruses that were isolated in 2006. Pathogenicity studies of four viruses, one from each genotype, revealed that all of the viruses are highly pathogenic in chickens, but none of them could replicate in ducks. The four viruses exclusively bound to avian-type receptors and replicated only in the turbinates and/or lungs of mice; none of them were lethal to mice at a dosage of 10650% egg infective doses (EID50). Our study indicates that although the clade 7.2 viruses have not been eradicated from poultry through vaccination, they have not become more dangerous to other animals (e.g., ducks and mice) and humans.
  
  
  OBJECTIVE
  Animal influenza viruses can acquire the ability to infect and kill humans. The H5N1 viruses have been a concern in recent decades because of their clear pandemic potential. We sorted H5N1 influenza viruses into different phylogenetic clades based on their HA genes. The clade 7.2 viruses were detected in chickens in several provinces of northern China in 2006. Vaccines for these viruses were subsequently developed and have been used ever since to control infection of poultry. Here, we analyzed the genetic and biologic properties of seven clade 7.2 viruses that were isolated from chickens between 2011 and 2014. We found that after nearly 9 years of circulation in chickens, the clade 7.2 viruses still exclusively bind to avian-type receptors and are of low pathogenicity to mice, suggesting that these H5 viruses pose a low risk to human public health.
authors: State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin, People's Republic of China.
authors: Liling
authors: L
authors: Liu
authors: State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin, People's Republic of China.
authors: Xianying
authors: X
authors: Zeng
authors: State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin, People's Republic of China.
authors: Pucheng
authors: P
authors: Chen
authors: State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin, People's Republic of China.
authors: Guohua
authors: G
authors: Deng
authors: State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin, People's Republic of China.
authors: Yanbing
authors: Y
authors: Li
authors: State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin, People's Republic of China.
authors: Jianzhong
authors: J
authors: Shi
authors: State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin, People's Republic of China.
authors: Chunyang
authors: C
authors: Gu
authors: State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin, People's Republic of China.
authors: Huihui
authors: H
authors: Kong
authors: College of Life and Health Sciences, Chubu University, Aichi, Japan.
authors: Yasuo
authors: Y
authors: Suzuki
authors: State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin, People's Republic of China.
authors: Yongping
authors: Y
authors: Jiang
authors: State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin, People's Republic of China.
authors: Guobin
authors: G
authors: Tian
authors: State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin, People's Republic of China chenhualan@caas.cn.
authors: Hualan
authors: H
authors: Chen
mesh_terms: D000818:Animals; D002645:Chickens; D002681:China / Q000453:epidemiology; D004372:Ducks / Q000821:virology; D016679:Genome, Viral / Q000235:genetics; D005838:Genotype; D019267:Hemagglutinin Glycoproteins, Influenza Virus / Q000378:metabolism; D053124:Influenza A Virus, H5N1 Subtype / Q000235:genetics* / Q000276:immunology; D053125:Influenza A Virus, H5N2 Subtype / Q000235:genetics* / Q000276:immunology; D007252:Influenza Vaccines / Q000276:immunology; D005585:Influenza in Birds / Q000453:epidemiology* / Q000276:immunology / Q000821:virology*; D010802:Phylogeny; D011200:Poultry; D014611:Vaccination / Q000379:methods
chemical_list: D019267:Hemagglutinin Glycoproteins, Influenza Virus; D007252:Influenza Vaccines