title: A novel approach for preparation of the antisera reagent for potency determination of inactivated H7N9 influenza vaccines.
abstract: BACKGROUND
  The potency of inactivated influenza vaccines is determined using a single-radial immunodiffusion (SRID) assay and requires standardized reagents consisting of a Reference Antigen and an influenza strain-specific antiserum. Timely availability of reagents is a critical step in influenza vaccine production, and the need for backup approaches for reagent preparation is an important component of pandemic preparedness.
  
  
  OBJECTIVE
  When novel H7N9 viruses emerged in China in 2013, candidate inactivated H7N9 influenza vaccines were developed for evaluation in clinical trials, and reagents were needed to measure vaccine potency.
  
  
  METHODS
  We previously described an alternative approach for generating strain-specific potency antisera, utilizing modified vaccinia virus Ankara vectors to produce influenza hemagglutinin (HA)-containing virus-like particles (VLPs) for immunization. Vector-produced HA antigen is not dependent upon the success of the traditional bromelain-digestion and HA purification.
  
  
  RESULTS
  Antiserum for H7N9 vaccines, produced after immunization of sheep with preparations of bromelain-HA (br-HA), was not optimal for the SRID assay, and the supply of antiserum was limited. However, antiserum obtained from sheep boosted with VLPs containing H7 HA greatly improved the ring quality in the SRID assay. Importantly, this antiserum worked well with both egg- and cell-derived antigen and was distributed to vaccine manufacturers.
  
  
  CONCLUSIONS
  Utilizing a previously developed approach for preparing vaccine potency antiserum, we have addressed a major bottleneck encountered in preparation of H7N9 vaccine reagents. The combination of br-HA and mammalian VLPs for sequential immunization represents the first use of an alternative approach for producing an influenza vaccine potency antiserum.
authors.affiliation: Laboratory of DNA Viruses, Division of Viral Products, Center for Biologics Evaluations and Research, Food and Drug Administration, Silver Spring, MD, USA.
authors.forename: Falko
authors.initials: F
authors.lastname: Schmeisser
authors.affiliation: Laboratory of Respiratory Viral Diseases, Division of Viral Products, Center for Biologics Evaluations and Research, Food and Drug Administration, Silver Spring, MD, USA.
authors.forename: Xianghong
authors.initials: X
authors.lastname: Jing
authors.affiliation: Division of Biological Standards and Quality Control, Center for Biologics Evaluations and Research, Food and Drug Administration, Silver Spring, MD, USA.
authors.forename: Manju
authors.initials: M
authors.lastname: Joshi
authors.affiliation: Laboratory of DNA Viruses, Division of Viral Products, Center for Biologics Evaluations and Research, Food and Drug Administration, Silver Spring, MD, USA.
authors.forename: Anupama
authors.initials: A
authors.lastname: Vasudevan
authors.affiliation: Laboratory of Respiratory Viral Diseases, Division of Viral Products, Center for Biologics Evaluations and Research, Food and Drug Administration, Silver Spring, MD, USA.
authors.forename: Jackeline
authors.initials: J
authors.lastname: Soto
authors.affiliation: Laboratory of Respiratory Viral Diseases, Division of Viral Products, Center for Biologics Evaluations and Research, Food and Drug Administration, Silver Spring, MD, USA.
authors.forename: Xing
authors.initials: X
authors.lastname: Li
authors.affiliation: Division of Biological Standards and Quality Control, Center for Biologics Evaluations and Research, Food and Drug Administration, Silver Spring, MD, USA.
authors.forename: Anil
authors.initials: A
authors.lastname: Choudhary
authors.affiliation: Division of Biological Standards and Quality Control, Center for Biologics Evaluations and Research, Food and Drug Administration, Silver Spring, MD, USA.
authors.forename: Noel
authors.initials: N
authors.lastname: Baichoo
authors.affiliation: Division of Biological Standards and Quality Control, Center for Biologics Evaluations and Research, Food and Drug Administration, Silver Spring, MD, USA.
authors.forename: Josephine
authors.initials: J
authors.lastname: Resnick
authors.affiliation: Laboratory of Respiratory Viral Diseases, Division of Viral Products, Center for Biologics Evaluations and Research, Food and Drug Administration, Silver Spring, MD, USA.
authors.forename: Zhiping
authors.initials: Z
authors.lastname: Ye
authors.affiliation: Division of Biological Standards and Quality Control, Center for Biologics Evaluations and Research, Food and Drug Administration, Silver Spring, MD, USA.
authors.forename: William
authors.initials: W
authors.lastname: McCormick
authors.affiliation: Laboratory of DNA Viruses, Division of Viral Products, Center for Biologics Evaluations and Research, Food and Drug Administration, Silver Spring, MD, USA.
authors.forename: Jerry P
authors.initials: JP
authors.lastname: Weir
mesh_terms: D000818:Animals; D000914:Antibodies, Viral / Q000096:biosynthesis*; D002681:China; D019267:Hemagglutinin Glycoproteins, Influenza Virus / Q000276:immunology; D006801:Humans; D007106:Immune Sera / Q000096:biosynthesis*; D005779:Immunodiffusion; D053118:Influenza A Virus, H1N1 Subtype / Q000276:immunology; D053124:Influenza A Virus, H5N1 Subtype / Q000276:immunology; D064766:Influenza A Virus, H7N9 Subtype / Q000254:growth & development / Q000276:immunology*; D007252:Influenza Vaccines / Q000276:immunology* / Q000592:standards; D007251:Influenza, Human / Q000517:prevention & control / Q000821:virology; D058873:Pandemics / Q000517:prevention & control; D012756:Sheep; D064166:Vaccine Potency; D015164:Vaccines, Inactivated / Q000276:immunology* / Q000592:standards; D058425:Vaccines, Virus-Like Particle / Q000276:immunology
chemical_list: D000914:Antibodies, Viral; D019267:Hemagglutinin Glycoproteins, Influenza Virus; D007106:Immune Sera; D007252:Influenza Vaccines; D015164:Vaccines, Inactivated; D058425:Vaccines, Virus-Like Particle; C109963:hemagglutinin, avian influenza A virus
keywords: Influenza vaccine reagents; influenza vaccines; single-radial immunodiffusion assay; vaccine potency assay