title: Enhanced growth of seed viruses for H5N1 influenza vaccines.
abstract: Seed viruses used to produce inactivated H5N1 influenza vaccines are recombinant viruses with modified avirulent-type hemagglutinin (HA) and intact neuraminidase (NA) genes, both derived from an H5N1 isolate, and all remaining genes from the PR8 strain, which grows well in eggs. However, some reassortants grow suboptimally in eggs, imposing obstacles to timely, cost-efficient vaccine production. Here, we demonstrate that our PR8 strain supports better in ovo growth than the PR8 strain used for the WHO-recommended seed virus, NIBRG-14. Moreover, inclusion of an alternative NA protein further enhanced viral growth in eggs. These findings suggest that our H5N1 vaccine candidates would increase the availability of H5N1 vaccine doses at the onset of a new pandemic.
authors.affiliation: Division of Virology, Department of Microbiology and Immunology, Institute of Medical Science, University of Tokyo, 4-6-1 Shirokaneda, Minato-ku, Tokyo 108-8639, Japan. horimoto@ims.u-tokyo.ac.jp
authors.forename: Taisuke
authors.initials: T
authors.lastname: Horimoto
authors.forename: Shin
authors.initials: S
authors.lastname: Murakami
authors.forename: Yukiko
authors.initials: Y
authors.lastname: Muramoto
authors.forename: Shinya
authors.initials: S
authors.lastname: Yamada
authors.forename: Ken
authors.initials: K
authors.lastname: Fujii
authors.forename: Maki
authors.initials: M
authors.lastname: Kiso
authors.forename: Kiyoko
authors.initials: K
authors.lastname: Iwatsuki-Horimoto
authors.forename: Yoichiro
authors.initials: Y
authors.lastname: Kino
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Kawaoka
mesh_terms: D000818:Animals; D002642:Chick Embryo / Q000276:immunology* / Q000821:virology*; D002645:Chickens; D005814:Genes, Viral; D006801:Humans; D053124:Influenza A Virus, H5N1 Subtype / Q000235:genetics / Q000254:growth & development* / Q000276:immunology*; D007252:Influenza Vaccines; D005585:Influenza in Birds / Q000276:immunology*; D007251:Influenza, Human / Q000276:immunology*; D015164:Vaccines, Inactivated
chemical_list: D007252:Influenza Vaccines; D015164:Vaccines, Inactivated