title: Genotype patterns of contemporary reassorted H3N2 virus in US swine.
abstract: To understand the evolution of swine-origin H3N2v influenza viruses that have infected 320 humans in the USA since August 2011, we performed a phylogenetic analysis at a whole genome scale of North American swine influenza viruses (n = 200). All viral isolates evolved from the prototypical North American H3 cluster 4 (c4), with evidence for further diversification into subclusters. At least ten distinct reassorted H3N2/pandemic H1N1 (rH3N2p) genotypes were identified in swine. Genotype 1 (G1) was most frequently detected in swine and all human H3N2v viruses clustered within a single G1 clade. These data suggest that the genetic requirements for transmission to humans may be restricted to a specific subset of swine viruses. Mutations at putative antigenic sites as well as reduced serological cross-reactivity among the H3 subclusters suggest antigenic drift of these contemporary viruses.
authors.affiliation: Virus and Prion Disease Research Unit, National Animal Disease Center, USDA-ARS, Ames, IA 50010, USA.
authors.forename: Pravina
authors.initials: P
authors.lastname: Kitikoon
authors.forename: Martha I
authors.initials: MI
authors.lastname: Nelson
authors.forename: Mary Lea
authors.initials: ML
authors.lastname: Killian
authors.forename: Tavis K
authors.initials: TK
authors.lastname: Anderson
authors.forename: Leo
authors.initials: L
authors.lastname: Koster
authors.forename: Marie R
authors.initials: MR
authors.lastname: Culhane
authors.forename: Amy L
authors.initials: AL
authors.lastname: Vincent
mesh_terms: D000818:Animals; D003429:Cross Reactions; D005838:Genotype; D006801:Humans; D053122:Influenza A Virus, H3N2 Subtype / Q000145:classification / Q000235:genetics* / Q000276:immunology / Q000302:isolation & purification; D007251:Influenza, Human / Q000276:immunology / Q000821:virology*; D008969:Molecular Sequence Data; D009976:Orthomyxoviridae Infections / Q000276:immunology / Q000662:veterinary* / Q000821:virology; D010802:Phylogeny; D016865:Reassortant Viruses / Q000145:classification / Q000235:genetics* / Q000276:immunology / Q000302:isolation & purification; D013552:Swine; D013553:Swine Diseases / Q000276:immunology / Q000821:virology*; D014481:United States