RESUMO
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. METHODOLOGY: 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. SIGNIFICANCE: 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.
Assuntos
Genes Virais/genética , Vírus da Influenza A/crescimento & desenvolvimento , Vírus da Influenza A/genética , Vacinas contra Influenza/biossíntese , Vírus Reordenados/crescimento & desenvolvimento , Vírus Reordenados/genética , Glicoproteínas de Hemaglutininação de Vírus da Influenza/imunologia , Humanos , Vírus da Influenza A/imunologia , Fenótipo , Polimorfismo de Fragmento de Restrição , Vírus Reordenados/imunologia , Mapeamento por RestriçãoRESUMO
In May 2009, as the H1N1 swine flu outbreak was in the early stages, a conference was held at the New York Academy of Sciences to discuss what was known about the virus and what was being done to stop the outbreak. In May 2010, a follow-up conference was again held at the New York Academy of Sciences, but now to discuss the H1N1 outbreak retrospectively. The report presented here summarizes the 2010 conference proceedings.
