title: Feasibility of reconstructed ancestral H5N1 influenza viruses for cross-clade protective vaccine development.
abstract: Since the reemergence of highly pathogenic H5N1 influenza viruses in humans in 2003, these viruses have spread throughout avian species in Asia, Europe, and Africa. Their sustained circulation has resulted in the evolution of phylogenetically diverse lineages. Viruses from these lineages show considerable antigenic variation, which has confounded vaccine planning efforts. We reconstructed ancestral protein sequences at several nodes of the hemagglutinin (HA) and neuraminidase (NA) gene phylogenies that represent ancestors to diverse H5N1 virus clades. By using the same methods that have been used to generate currently licensed inactivated H5N1 vaccines, we were able to produce a panel of replication competent influenza viruses containing synthesized HA and NA genes representing the reconstructed ancestral proteins. We identified two of these viruses that showed promising in vitro cross-reactivity with clade 1, 2.1, 2.2, 2.3.4, and 4 viruses. To confirm that vaccine antigens derived from these viruses were able to elicit functional antibodies following immunization, we created whole-virus vaccines and compared their protective efficacy versus that of antigens from positive control, naturally occurring, and broadly reactive H5N1 viruses. The ancestral viruses' vaccines provided robust protection against morbidity and mortality in ferrets challenged with H5N1 strains from clades 1, 2.1, and 2.2 in a manner similar to those based on the control strains. These findings provide proof of principle that viable, computationally derived vaccine seed viruses can be constructed within the context of currently licensed vaccine platforms. Such technologies should be explored to enhance the cross reactivity and availability of H5N1 influenza vaccines.
authors.affiliation: Department of Infectious Diseases, St. Jude Children's Research Hospital, Memphis, TN 38105-3678, USA.
authors.forename: Mariette F
authors.initials: MF
authors.lastname: Ducatez
authors.forename: Justin
authors.initials: J
authors.lastname: Bahl
authors.forename: Yolanda
authors.initials: Y
authors.lastname: Griffin
authors.forename: Evelyn
authors.initials: E
authors.lastname: Stigger-Rosser
authors.forename: John
authors.initials: J
authors.lastname: Franks
authors.forename: Subrata
authors.initials: S
authors.lastname: Barman
authors.forename: Dhanasekaran
authors.initials: D
authors.lastname: Vijaykrishna
authors.forename: Ashley
authors.initials: A
authors.lastname: Webb
authors.forename: Yi
authors.initials: Y
authors.lastname: Guan
authors.forename: Robert G
authors.initials: RG
authors.lastname: Webster
authors.forename: Gavin J D
authors.initials: GJ
authors.lastname: Smith
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Webby
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000940:Antigenic Variation / Q000235:genetics*; D019295:Computational Biology / Q000379:methods*; D003429:Cross Reactions / Q000235:genetics*; D019143:Evolution, Molecular; D005289:Ferrets; D006388:Hemagglutinins / Q000235:genetics; D053124:Influenza A Virus, H5N1 Subtype / Q000235:genetics / Q000276:immunology*; D007252:Influenza Vaccines / Q000276:immunology*; D016013:Likelihood Functions; D008969:Molecular Sequence Data; D009439:Neuraminidase / Q000235:genetics; D010802:Phylogeny; D016415:Sequence Alignment; D013045:Species Specificity; D016019:Survival Analysis
chemical_list: D006388:Hemagglutinins; D007252:Influenza Vaccines; D009439:Neuraminidase