title: Development of a new candidate H5N1 avian influenza virus for pre-pandemic vaccine production.
abstract: BACKGROUND
  Highly pathogenic H5N1 avian influenza viruses currently circulating in birds have caused hundreds of human infections, and pose a significant pandemic threat. Vaccines are a major component of the public health preparedness for this likely event. The rapid evolution of H5N1 viruses has resulted in the emergence of multiple clades with distinct antigenic characteristics that require clade-specific vaccines. A variant H5N1 virus termed clade 2.3.4 emerged in 2005 and has caused multiple fatal infections. Vaccine candidates that match the antigenic properties of variant viruses are necessary because inactivated influenza vaccines elicit strain-specific protection.
  
  
  OBJECTIVE
  To address the need for a suitable seed for manufacturing a clade 2.3.4 vaccine, we developed a new H5N1 pre-pandemic candidate vaccine by reverse genetics and evaluated its safety and replication in vitro and in vivo.
  
  
  METHODS
  A reassortant virus termed, Anhui/PR8, was produced by reverse genetics in compliance with WHO pandemic vaccine development guidelines and contains six genes from A/Puerto Rico/8/34 as well as the neuraminidase and hemagglutinin (HA) genomic segments from the A/Anhui/01/2005 virus. The multi-basic cleavage site of HA was removed to reduce virulence.
  
  
  RESULTS
  The reassortant Anhui/PR8 grows well in eggs and is avirulent to chicken and ferrets but retains the antigenicity of the parental A/Anhui/01/2005 virus.
  
  
  CONCLUSIONS
  These results indicate that the Anhui/PR8 reassortant lost a major virulent determinant and it is suitable for its use in vaccine manufacturing and as a reference vaccine virus against the H5N1 clade 2.3.4 viruses circulating in eastern China, Vietnam, Thailand, and Laos.
authors.affiliation: Chinese National Influenza Center, State Key Laboratory for Infectious Disease Prevention and Control, National Institute for Viral Disease Control and Prevention, China CDC, Xuanwu District Beijing, China.
authors.forename: Jie
authors.initials: J
authors.lastname: Dong
authors.forename: Yumiko
authors.initials: Y
authors.lastname: Matsuoka
authors.forename: Taronna R
authors.initials: TR
authors.lastname: Maines
authors.forename: David E
authors.initials: DE
authors.lastname: Swayne
authors.forename: Eduardo
authors.initials: E
authors.lastname: O'Neill
authors.forename: C Todd
authors.initials: CT
authors.lastname: Davis
authors.forename: Neal
authors.initials: N
authors.lastname: Van-Hoven
authors.forename: Amanda
authors.initials: A
authors.lastname: Balish
authors.forename: Hong-jie
authors.initials: HJ
authors.lastname: Yu
authors.forename: Jacqueline M
authors.initials: JM
authors.lastname: Katz
authors.forename: Alexander
authors.initials: A
authors.lastname: Klimov
authors.forename: Nancy
authors.initials: N
authors.lastname: Cox
authors.forename: De-xin
authors.initials: DX
authors.lastname: Li
authors.forename: Yu
authors.initials: Y
authors.lastname: Wang
authors.forename: Yuan-ji
authors.initials: YJ
authors.lastname: Guo
authors.forename: Wei-zhong
authors.initials: WZ
authors.lastname: Yang
authors.forename: Ruben O
authors.initials: RO
authors.lastname: Donis
authors.forename: Yue-long
authors.initials: YL
authors.lastname: Shu
mesh_terms: D000818:Animals; D000914:Antibodies, Viral / Q000097:blood; D001717:Birds; D001921:Brain / Q000821:virology; D002642:Chick Embryo; D002645:Chickens; D016000:Cluster Analysis; D004196:Disease Outbreaks / Q000517:prevention & control*; D005260:Female; D005289:Ferrets; D006385:Hemagglutination Inhibition Tests; D006801:Humans; D053124:Influenza A Virus, H5N1 Subtype / Q000235:genetics / Q000276:immunology* / Q000302:isolation & purification; D007252:Influenza Vaccines / Q000235:genetics / Q000276:immunology*; D005585:Influenza in Birds / Q000473:pathology / Q000821:virology; D007251:Influenza, Human / Q000517:prevention & control*; D008168:Lung / Q000821:virology; D008297:Male; D009976:Orthomyxoviridae Infections / Q000473:pathology / Q000821:virology; D010802:Phylogeny; D011247:Pregnancy; D012367:RNA, Viral / Q000235:genetics; D016865:Reassortant Viruses / Q000235:genetics / Q000276:immunology*; D017422:Sequence Analysis, DNA; D013154:Spleen / Q000821:virology; D016019:Survival Analysis; D014613:Vaccines, Attenuated / Q000235:genetics / Q000276:immunology; D014614:Vaccines, Synthetic / Q000235:genetics / Q000276:immunology; D010948:Viral Plaque Assay; D014774:Virulence
chemical_list: D000914:Antibodies, Viral; D007252:Influenza Vaccines; D012367:RNA, Viral; D014613:Vaccines, Attenuated; D014614:Vaccines, Synthetic