title: Gene constellation of influenza A virus reassortants with high growth phenotype prepared as seed candidates for vaccine production.
abstract: BACKGROUND
  Influenza A virus vaccines undergo yearly reformulations due to the antigenic variability of the virus caused by antigenic drift and shift. It is critical to the vaccine manufacturing process to obtain influenza A seed virus that is antigenically identical to circulating wild type (wt) virus and grows to high titers in embryonated chicken eggs. Inactivated influenza A seasonal vaccines are generated by classical reassortment. The classical method takes advantage of the ability of the influenza virus to reassort based on the segmented nature of its genome. In ovo co-inoculation of a high growth or yield (hy) donor virus and a low yield wt virus with antibody selection against the donor surface antigens results in progeny viruses that grow to high titers in ovo with wt origin hemagglutinin (HA) and neuraminidase (NA) glycoproteins. In this report we determined the parental origin of the remaining six genes encoding the internal proteins that contribute to the hy phenotype in ovo.
  
  
  METHODS
  The genetic analysis was conducted using reverse transcription-polymerase chain reaction (RT-PCR) and restriction fragment length polymorphism (RFLP). The characterization was conducted to determine the parental origin of the gene segments (hy donor virus or wt virus), gene segment ratios and constellations. Fold increase in growth of reassortant viruses compared to respective parent wt viruses was determined by hemagglutination assay titers.
  
  
  CONCLUSIONS
  In this study fifty-seven influenza A vaccine candidate reassortants were analyzed for the presence or absence of correlations between specific gene segment ratios, gene constellations and hy reassortant phenotype. We found two gene ratios, 6:2 and 5:3, to be the most prevalent among the hy reassortants analyzed, although other gene ratios also conferred hy in certain reassortants.
authors.affiliation: Department of Microbiology and Immunology, New York Medical College, Valhalla, New York, United States of America.
authors.forename: Andrew A
authors.initials: AA
authors.lastname: Fulvini
authors.forename: Manojkumar
authors.initials: M
authors.lastname: Ramanunninair
authors.forename: Jianhua
authors.initials: J
authors.lastname: Le
authors.forename: Barbara A
authors.initials: BA
authors.lastname: Pokorny
authors.forename: Jennifer Minieri
authors.initials: JM
authors.lastname: Arroyo
authors.forename: Jeanmarie
authors.initials: J
authors.lastname: Silverman
authors.forename: Rene
authors.initials: R
authors.lastname: Devis
authors.forename: Doris
authors.initials: D
authors.lastname: Bucher
mesh_terms: D005814:Genes, Viral / Q000235:genetics*; D019267:Hemagglutinin Glycoproteins, Influenza Virus / Q000276:immunology; D006801:Humans; D009980:Influenza A virus / Q000235:genetics* / Q000254:growth & development* / Q000276:immunology; D007252:Influenza Vaccines / Q000096:biosynthesis*; D010641:Phenotype; D012150:Polymorphism, Restriction Fragment Length; D016865:Reassortant Viruses / Q000235:genetics* / Q000254:growth & development* / Q000276:immunology; D015183:Restriction Mapping
chemical_list: D019267:Hemagglutinin Glycoproteins, Influenza Virus; D007252:Influenza Vaccines