title: A cell culture-derived whole-virus H9N2 vaccine induces high titer antibodies against hemagglutinin and neuraminidase and protects mice from severe lung pathology and weight loss after challenge with a highly virulent H9N2 isolate.
abstract: BACKGROUND
  Influenza viruses of subtype A/H9N2 are enzootic in poultry across Asia and the Middle East and are considered to have pandemic potential. The development of new vaccine manufacturing technologies is a cornerstone of influenza pandemic preparedness.
  
  
  METHODS
  A non-adjuvanted whole-virus H9N2 vaccine was developed using Vero cell culture manufacturing technology. The induction of hemagglutination inhibition (HI) and virus-neutralizing antibodies was assessed in CD1 mice and guinea pigs. A highly sensitive enzyme-linked lectin assay was used to investigate the induction of antibodies capable of inhibiting the enzymatic activity of the H9N2 neuraminidase. Protective efficacy against virus replication in the lung after challenge with the homologous virus was evaluated in BALB/c mice by a TCID(50) assay, and prevention of virus replication in the lung and associated pathology were evaluated by histology and immunohistochemistry. To investigate the ability of the vaccine to prevent severe disease, BALB/c mice were challenged with a highly virulent mouse-adapted H9N2 isolate which was generated by multiple lung-to-lung passage of wild-type virus.
  
  
  RESULTS
  The vaccine elicited high titers of functional H9N2-specific HA antibodies in both mice and guinea pigs, as determined by HI and virus neutralization assays. High titer H9N2-specific neuraminidase inhibiting (NAi) antibodies were also induced in both species. Vaccinated mice were protected from lung virus replication in a dose-dependent manner after challenge with the homologous H9N2 virus. Immunohistochemical analyses confirmed the lack of virus replication in the lung and an associated substantial reduction in lung pathology. Dose-dependent protection from severe weight loss was also provided after challenge with the highly virulent mouse-adapted H9N2 virus.
  
  
  CONCLUSIONS
  The induction of high titers of H9N2-specific HI, virus-neutralizing and NAi antibodies and dose-dependent protection from virus replication and severe disease in animal models suggest that the Vero cell culture-derived whole-virus vaccine will provide an effective intervention in the event of a H9N2 pandemic situation.
authors.affiliation: Vaccine R&D, Baxter BioScience, Biomedical Research Centre, Orth/Donau, Austria.
authors.forename: Walter
authors.initials: W
authors.lastname: Wodal
authors.forename: Falko G
authors.initials: FG
authors.lastname: Falkner
authors.forename: Astrid
authors.initials: A
authors.lastname: Kerschbaum
authors.forename: Claudia
authors.initials: C
authors.lastname: Gaiswinkler
authors.forename: Richard
authors.initials: R
authors.lastname: Fritz
authors.forename: Stefan
authors.initials: S
authors.lastname: Kiermayr
authors.forename: Daniel
authors.initials: D
authors.lastname: Portsmouth
authors.forename: Helga
authors.initials: H
authors.lastname: Savidis-Dacho
authors.forename: Sogue
authors.initials: S
authors.lastname: Coulibaly
authors.forename: Christina
authors.initials: C
authors.lastname: Piskernik
authors.forename: Christine
authors.initials: C
authors.lastname: Hohenadl
authors.forename: M Keith
authors.initials: MK
authors.lastname: Howard
authors.forename: Otfried
authors.initials: O
authors.lastname: Kistner
authors.forename: P Noel
authors.initials: PN
authors.lastname: Barrett
authors.forename: Thomas R
authors.initials: TR
authors.lastname: Kreil
mesh_terms: D000818:Animals; D057134:Antibodies, Neutralizing / Q000097:blood; D000914:Antibodies, Viral / Q000097:blood; D004306:Dose-Response Relationship, Immunologic; D005260:Female; D006168:Guinea Pigs; D006385:Hemagglutination Inhibition Tests; D019267:Hemagglutinin Glycoproteins, Influenza Virus / Q000276:immunology*; D053127:Influenza A Virus, H9N2 Subtype / Q000276:immunology*; D007252:Influenza Vaccines / Q000276:immunology*; D008168:Lung / Q000473:pathology / Q000821:virology; D051379:Mice; D008807:Mice, Inbred BALB C; D009439:Neuraminidase / Q000276:immunology*; D009500:Neutralization Tests; D009976:Orthomyxoviridae Infections / Q000276:immunology / Q000517:prevention & control*; D015431:Weight Loss
chemical_list: D057134:Antibodies, Neutralizing; D000914:Antibodies, Viral; D019267:Hemagglutinin Glycoproteins, Influenza Virus; D007252:Influenza Vaccines; D009439:Neuraminidase