title: A promoter mutation in the haemagglutinin segment of influenza A virus generates an effective candidate live attenuated vaccine.
abstract: BACKGROUND
  Annual seasonal and pandemic influenza vaccines need to be produced in a very tight time frame. Haemagglutinin (HA) is the major immunogenic component of influenza vaccines, and there is a lot of interest in improving candidate vaccine viruses.
  
  
  OBJECTIVE
  It has been shown elsewhere that mutations introduced in the non-coding region of influenza genome segments can upregulate protein expression. Our objective was to assess a virus based on the laboratory strain A/PR/8/34 (PR8) containing a modified 3' non-coding region of RNA segment 4 (haemagglutinin).
  
  
  METHODS
  NIBRG-93 was generated using reverse genetics. HA protein expression and growth properties were assessed. The virus phenotype suggested that it could be a candidate for use as a live attenuated vaccine, so in vivo studies were performed to assess its suitability.
  
  
  RESULTS
  NIBRG-93 virus has enhanced haemagglutinin production and is significantly attenuated. Electron microscopy (EM) shows that the modified virus produces a large proportion of 'virus-like particles' that consist of budded cell membrane covered in HA but lacking M1 protein. The virus was shown to be attenuated in mice and offered complete protection against lethal challenge.
  
  
  CONCLUSIONS
  We demonstrate that NIBRG-93 is an effective live attenuated vaccine virus protecting mice against lethal challenge and reducing virus shedding.
authors.affiliation: National Institute for Biological Standards and Control, Medicines and Healthcare products Regulatory Agency, Potters Bar, UK.
authors.forename: Ruth
authors.initials: R
authors.lastname: Harvey
authors.forename: Rachel E
authors.initials: RE
authors.lastname: Johnson
authors.forename: Kirsty
authors.initials: K
authors.lastname: MacLellan-Gibson
authors.forename: James S
authors.initials: JS
authors.lastname: Robertson
authors.forename: Othmar G
authors.initials: OG
authors.lastname: Engelhardt
mesh_terms: D000818:Animals; D004195:Disease Models, Animal; D005260:Female; D019267:Hemagglutinin Glycoproteins, Influenza Virus / Q000235:genetics / Q000276:immunology*; D009980:Influenza A virus / Q000235:genetics / Q000276:immunology* / Q000648:ultrastructure; D007252:Influenza Vaccines / Q000008:administration & dosage / Q000235:genetics / Q000276:immunology*; D008807:Mice, Inbred BALB C; D046529:Microscopy, Electron, Transmission; D009154:Mutation; D009976:Orthomyxoviridae Infections / Q000473:pathology / Q000517:prevention & control / Q000821:virology; D011401:Promoter Regions, Genetic; D059386:Reverse Genetics; D014613:Vaccines, Attenuated / Q000008:administration & dosage / Q000235:genetics / Q000276:immunology; D022701:Virosomes / Q000648:ultrastructure; D017201:Virus Shedding
chemical_list: D019267:Hemagglutinin Glycoproteins, Influenza Virus; D007252:Influenza Vaccines; D014613:Vaccines, Attenuated; D022701:Virosomes
keywords: Candidate vaccine virus; haemagglutinin; influenza; live attenuated; promoter mutation; vaccine
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