title: Characterization of H1N1 swine influenza viruses circulating in Canadian pigs in 2009.
abstract: The 2009 pandemic H1N1 (pH1N1), of apparent swine origin, may have evolved in pigs unnoticed because of insufficient surveillance. Consequently, the need for surveillance of influenza viruses circulating in pigs has received added attention. In this study we characterized H1N1 viruses isolated from Canadian pigs in 2009. Isolates from May 2009 were comprised of hemagglutinin and neuraminidase (NA) genes of classical SIV origin in combination with the North American triple-reassortant internal gene (TRIG) cassette, here termed contemporary SIV (conSIV) H1N1. These conSIV H1N1 viruses were contiguous with the North American αH1 cluster, which was distinct from the pH1N1 isolates that were antigenically more related to the γH1 cluster. After the initial isolation of pH1N1 from an Alberta pig farm in early May 2009, pH1N1 was found several times in Canadian pigs. These pH1N1 isolates were genetically and antigenically homogeneous. In addition, H1N1 viruses bearing seasonal human H1 and N1 genes together with the TRIG cassette and an NA encoding an oseltamivir-resistance marker were isolated from pigs. The NS gene of one of these seasonal human-like SIV (shSIV) H1N1 isolates was homologous to pH1N1 NS, implicating reassortment between the two strains. Antigenic cross-reactivity was observed between pH1N1 and conSIV but not with shSIV H1N1. In summary, although there was cocirculation of pH1N1 with conSIV and shSIV H1N1 in Canadian pigs after May 2009, there was no evidence supporting the presence of pH1N1 in pigs prior to May 2009. The possibility for further reassortants being generated exists and should be closely monitored.
authors.affiliation: National Centres for Animal Disease, 1015 Arlington Street, Winnipeg, Manitoba R3E 3M4, Canada.
authors.forename: Charles K
authors.initials: CK
authors.lastname: Nfon
authors.forename: Yohannes
authors.initials: Y
authors.lastname: Berhane
authors.forename: Tamiko
authors.initials: T
authors.lastname: Hisanaga
authors.forename: Shunzhen
authors.initials: S
authors.lastname: Zhang
authors.forename: Katherine
authors.initials: K
authors.lastname: Handel
authors.forename: Helen
authors.initials: H
authors.lastname: Kehler
authors.forename: Olivia
authors.initials: O
authors.lastname: Labrecque
authors.forename: Nicola S
authors.initials: NS
authors.lastname: Lewis
authors.forename: Amy L
authors.initials: AL
authors.lastname: Vincent
authors.forename: John
authors.initials: J
authors.lastname: Copps
authors.forename: Soren
authors.initials: S
authors.lastname: Alexandersen
authors.forename: John
authors.initials: J
authors.lastname: Pasick
mesh_terms: D000818:Animals; D000956:Antigens, Viral / Q000276:immunology; D002170:Canada; D016000:Cluster Analysis; D003429:Cross Reactions; D005838:Genotype; D019267:Hemagglutinin Glycoproteins, Influenza Virus / Q000235:genetics*; D006801:Humans; D053118:Influenza A Virus, H1N1 Subtype / Q000145:classification* / Q000235:genetics* / Q000302:isolation & purification; D008969:Molecular Sequence Data; D009439:Neuraminidase / Q000235:genetics*; D018184:Paramyxoviridae Infections / Q000662:veterinary* / Q000821:virology; D010802:Phylogeny; D012367:RNA, Viral / Q000235:genetics; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D013552:Swine; D013553:Swine Diseases / Q000821:virology*; D014764:Viral Proteins / Q000235:genetics*
chemical_list: D000956:Antigens, Viral; D019267:Hemagglutinin Glycoproteins, Influenza Virus; D012367:RNA, Viral; D014764:Viral Proteins; C487630:NA protein, influenza A virus; D009439:Neuraminidase