Characterization of a newly emerged genetic cluster of H1N1 and H1N2 swine influenza virus in the United States

Virus and Prion Diseases of Livestock Research Unit, National Animal Disease Center, USDA-ARS, 2300 Dayton Road, Ames, IA 50010, USA.
Virus Genes (Impact Factor: 1.84). 08/2009; 39(2):176-85. DOI: 10.1007/s11262-009-0386-6
Source: PubMed

ABSTRACT H1 influenza A viruses that were distinct from the classical swine H1 lineage were identified in pigs in Canada in 2003–2004; antigenic and genetic characterization identified the hemagglutinin (HA) as human H1 lineage. The viruses identified in Canadian pigs were human lineage in entirety or double (human–swine) reassortants. Here, we report the whole genome sequence analysis of four human-like H1 viruses isolated from U.S. swine in 2005 and 2007. All four isolates were characterized as triple reassortants with an internal gene constellation similar to contemporary U.S. swine influenza virus (SIV), with HA and neuraminidase (NA) most similar to human influenza virus lineages. A 2007 human-like H1N1 was evaluated in a pathogenesis and transmission model and compared to a 2004 reassortant H1N1 SIV isolate with swine lineage HA and NA. The 2007 isolate induced disease typical of influenza virus and was transmitted to contact pigs; however, the kinetics and magnitude differed from the 2004 H1N1 SIV. This study indicates that the human-like H1 SIV can efficiently replicate and transmit in the swine host and now co-circulates with contemporary SIVs as a distinct genetic cluster of H1 SIV.

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Available from: Wenjun ma, Jul 08, 2014
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    • "The starting tree was generated under parsimony methods, with the best-scoring tree and statistical support values obtained with the rapid bootstrap algorithm (1000 replications). Using the H1 phylogeny, H1N1 and H1N2 isolates were assigned to one of six previously described H1 clusters: H1␣, H1␤, H1␥, H1␦1, H1␦2, H1pdm09 (Vincent et al., 2009a, 2009b; Lorusso et al., 2011). Similarly, H3N2 isolates were assigned to one of four main clusters based upon the H3 phylogeny, and H3 Cluster IV isolates to one of 6 putative clades (Kitikoon et al., 2013). "
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    • "To represent the evolution of the currently circulating North American H1 viruses, a cluster classification was established. Viruses with the HA gene of the classical H1N1 viruses that have circulated in swine since 1918 evolved into the contemporary a-, b-and c-clusters, whereas H1 subtype isolates with HA genes most similar to those of human seasonal H1 viruses circulating in the early 2000s evolved into the d-cluster (Vincent et al., 2009b). All four HA gene cluster types (a, b, c, and d) can be found with NA genes of either the N1 or N2 subtype. "
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    • "The main subtypes of IAV circulating in North American swine are H1N1, H1N2 and H3N2 Cluster IV (Richt et al., 2003; Vincent et al., 2009; Kumar et al., 2011). According to the data from 2001 to 2007 from the University of Minnesota Veterinary Diagnostic Laboratory , among H1 subtypes, cluster a has been replaced with clusters b, d and g , and among H3N2 subtypes, cluster IV became dominant (Rapp-Gabrielson et al., 2008). "
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