title: Cold adaptation generates mutations associated with the growth of influenza B vaccine viruses.
abstract: Seasonal inactivated influenza vaccines are usually trivalent or quadrivalent and are prepared from accredited seed viruses. Yields of influenza A seed viruses can be enhanced by gene reassortment with high-yielding donor strains, but similar approaches for influenza B seed viruses have been largely unsuccessful. For vaccine manufacture influenza B seed viruses are usually adapted for high-growth by serial passage. Influenza B antigen yields so obtained are often unpredictable and selection of influenza B seed viruses by this method can be a rate-limiting step in seasonal influenza vaccine manufacture. We recently have shown that selection of stable cold-adapted mutants from seasonal epidemic influenza B viruses is associated with improved growth. In this study, specific mutations were identified that were responsible for growth enhancement as a consequence of adaptation to growth at lower temperatures. Molecular analysis revealed that the following mutations in the HA, NP and NA genes are required for enhanced viral growth: G156/N160 in the HA, E253, G375 in the NP and T146 in the NA genes. These results demonstrate that the growth of seasonal influenza B viruses can be optimized or improved significantly by specific gene modifications.
authors.affiliation: Centre for Biomedical Research, Burnet Institute, Melbourne 3004, Victoria, Australia; School of Applied Sciences, RMIT University, Bundoora 3083, Victoria, Australia.
authors.forename: Hyunsuh
authors.initials: H
authors.lastname: Kim
authors.affiliation: Monash Institute of Pharmaceutical Sciences, Monash University, Parkville 3052, Victoria, Australia.
authors.forename: Tony
authors.initials: T
authors.lastname: Velkov
authors.affiliation: Influenza Research and Development, bioCSL Limited, Parkville 3052, Victoria, Australia.
authors.forename: Sarina
authors.initials: S
authors.lastname: Camuglia
authors.affiliation: Influenza Research and Development, bioCSL Limited, Parkville 3052, Victoria, Australia; Department of Microbiology and Immunology, The University of Melbourne, Parkville 3010, Victoria, Australia. Electronic address: Steve.Rockman@biocsl.com.au.
authors.forename: Steven P
authors.initials: SP
authors.lastname: Rockman
authors.affiliation: Centre for Biomedical Research, Burnet Institute, Melbourne 3004, Victoria, Australia; School of Applied Sciences, RMIT University, Bundoora 3083, Victoria, Australia. Electronic address: tannock@burnet.edu.au.
authors.forename: Gregory A
authors.initials: GA
authors.lastname: Tannock
mesh_terms: D000220:Adaptation, Biological; D000818:Animals; D003080:Cold Temperature; D004285:Dogs; D019267:Hemagglutinin Glycoproteins, Influenza Virus / Q000235:genetics; D009981:Influenza B virus / Q000235:genetics / Q000254:growth & development* / Q000528:radiation effects*; D061985:Madin Darby Canine Kidney Cells; D020125:Mutation, Missense; D009439:Neuraminidase / Q000235:genetics; D019590:Nucleocapsid Proteins; D017354:Point Mutation; D014758:Viral Core Proteins / Q000235:genetics; D014764:Viral Proteins / Q000235:genetics; D014776:Virus Cultivation / Q000379:methods
chemical_list: D019267:Hemagglutinin Glycoproteins, Influenza Virus; D019590:Nucleocapsid Proteins; D014758:Viral Core Proteins; D014764:Viral Proteins; C588186:nucleoprotein, influenza B virus; C541223:NA protein, influenza B virus; D009439:Neuraminidase
keywords: Cold adaptation; Growth; Influenza B virus; Mutations; Vaccine