title: Molecular signature of high yield (growth) influenza a virus reassortants prepared as candidate vaccine seeds.
abstract: BACKGROUND
  Human influenza virus isolates generally grow poorly in embryonated chicken eggs. Hence, gene reassortment of influenza A wild type (wt) viruses is performed with a highly egg adapted donor virus, A/Puerto Rico/8/1934 (PR8), to provide the high yield reassortant (HYR) viral 'seeds' for vaccine production. HYR must contain the hemagglutinin (HA) and neuraminidase (NA) genes of wt virus and one to six 'internal' genes from PR8. Most studies of influenza wt and HYRs have focused on the HA gene. The main objective of this study is the identification of the molecular signature in all eight gene segments of influenza A HYR candidate vaccine seeds associated with high growth in ovo.
  
  
  METHODS
  The genomes of 14 wt parental viruses, 23 HYRs (5 H1N1; 2, 1976 H1N1-SOIV; 2, 2009 H1N1pdm; 2 H2N2 and 12 H3N2) and PR8 were sequenced using the high-throughput sequencing pipeline with big dye terminator chemistry.
  
  
  RESULTS
  Silent and coding mutations were found in all internal genes derived from PR8 with the exception of the M gene. The M gene derived from PR8 was invariant in all 23 HYRs underlining the critical role of PR8 M in high yield phenotype. None of the wt virus derived internal genes had any silent change(s) except the PB1 gene in X-157. The highest number of recurrent silent and coding mutations was found in NS. With respect to the surface antigens, the majority of HYRs had coding mutations in HA; only 2 HYRs had coding mutations in NA.
  
  
  CONCLUSIONS
  In the era of application of reverse genetics to alter influenza A virus genomes, the mutations identified in the HYR gene segments associated with high growth in ovo may be of great practical benefit to modify PR8 and/or wt virus gene sequences for improved growth of vaccine 'seed' viruses.
authors.affiliation: Department of Microbiology and Immunology, New York Medical College, Valhalla, New York, United States of America.
authors.forename: Manojkumar
authors.initials: M
authors.lastname: Ramanunninair
authors.forename: Jianhua
authors.initials: J
authors.lastname: Le
authors.forename: Shiroh
authors.initials: S
authors.lastname: Onodera
authors.forename: Andrew A
authors.initials: AA
authors.lastname: Fulvini
authors.forename: Barbara A
authors.initials: BA
authors.lastname: Pokorny
authors.forename: Jeanmarie
authors.initials: J
authors.lastname: Silverman
authors.forename: Rene
authors.initials: R
authors.lastname: Devis
authors.forename: Jennifer M
authors.initials: JM
authors.lastname: Arroyo
authors.forename: Yu
authors.initials: Y
authors.lastname: He
authors.forename: Alex
authors.initials: A
authors.lastname: Boyne
authors.forename: Jayati
authors.initials: J
authors.lastname: Bera
authors.forename: Rebecca
authors.initials: R
authors.lastname: Halpin
authors.forename: Erin
authors.initials: E
authors.lastname: Hine
authors.forename: David J
authors.initials: DJ
authors.lastname: Spiro
authors.forename: Doris
authors.initials: D
authors.lastname: Bucher
mesh_terms: D016679:Genome, Viral / Q000235:genetics*; D006388:Hemagglutinins / Q000235:genetics; D006801:Humans; D053118:Influenza A Virus, H1N1 Subtype / Q000235:genetics / Q000276:immunology; D053122:Influenza A Virus, H3N2 Subtype / Q000235:genetics / Q000276:immunology; D053124:Influenza A Virus, H5N1 Subtype / Q000235:genetics / Q000276:immunology; D009980:Influenza A virus / Q000235:genetics* / Q000276:immunology; D007252:Influenza Vaccines / Q000235:genetics / Q000276:immunology; D009154:Mutation; D009439:Neuraminidase / Q000235:genetics
chemical_list: D006388:Hemagglutinins; D007252:Influenza Vaccines; D009439:Neuraminidase