title: Rescue of influenza B virus from eight plasmids.
abstract: Influenza B virus causes a significant amount of morbidity and mortality, yet the systems to produce high yield inactivated vaccines for these viruses have lagged behind the development of those for influenza A virus. We have established a plasmid-only reverse genetics system for the generation of recombinant influenza B virus that facilitates the generation of vaccine viruses without the need for time consuming coinfection and selection procedures currently required to produce reassortants. We cloned the eight viral cDNAs of influenza B/Yamanashi/166/98, which yields relatively high titers in embryonated chicken eggs, between RNA polymerase I and RNA polymerase II transcription units. Virus was detected as early as 3 days after transfection of cocultured COS7 and Madin-Darby canine kidney cells and achieved levels of 10(6)-10(7) plaque-forming units per ml of cell supernatant 6 days after transfection. The full-length sequence of the recombinant virus after passage into embryonated chicken eggs was identical to that of the input plasmids. To improve the utility of the eight-plasmid system for generating 6 + 2 reassortants from recently circulating influenza B strains, we optimized the reverse transcriptase-PCR for cloning of the hemagglutinin (HA) and neuraminidase (NA) segments. The six internal genes of B/Yamanashi/166/98 were used as the backbone to generate 6 + 2 reassortants including the HA and NA gene segments from B/Victoria/504/2000, B/Hong Kong/330/2001, and B/Hawaii/10/2001. Our results demonstrate that the eight-plasmid system can be used for the generation of high yields of influenza B virus vaccines expressing current HA and NA glycoproteins from either of the two lineages of influenza B virus.
authors.affiliation: MedImmune Vaccines, 297 North Bernardo Avenue, Mountain View, CA 94043, USA. hoffmane@medimmune.com
authors.forename: Erich
authors.initials: E
authors.lastname: Hoffmann
authors.forename: Kutubuddin
authors.initials: K
authors.lastname: Mahmood
authors.forename: Chin-Fen
authors.initials: CF
authors.lastname: Yang
authors.forename: Robert G
authors.initials: RG
authors.lastname: Webster
authors.forename: Harry B
authors.initials: HB
authors.lastname: Greenberg
authors.forename: George
authors.initials: G
authors.lastname: Kemble
mesh_terms: D000818:Animals; D001483:Base Sequence; D019556:COS Cells; D002522:Chlorocebus aethiops; D003001:Cloning, Molecular; D018920:Coculture Techniques; D017931:DNA Primers; D018076:DNA, Complementary / Q000235:genetics; D006801:Humans; D009981:Influenza B virus / Q000235:genetics* / Q000254:growth & development / Q000472:pathogenicity; D007252:Influenza Vaccines; D007251:Influenza, Human / Q000453:epidemiology; D007700:Kinetics; D008954:Models, Biological; D010957:Plasmids; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013997:Time Factors; D014162:Transfection; D010948:Viral Plaque Assay; D014765:Viral Vaccines
chemical_list: D017931:DNA Primers; D018076:DNA, Complementary; D007252:Influenza Vaccines; D014765:Viral Vaccines