Influenza A viruses are important infectious agents for swine and human populations. Distinct HI influenza A viruses were recently identified and characterized in US swine herds. Genomic characterization demonstrated the viruses were triple reassortants with an internal gene constellation similar to contemporary US swine influenza virus (SIV) but hemagglutinin (HA) and neuraminidase (NA) most similar to human seasonal influenza virus lineages. The HA gene of these viruses form the 8-cluster in phylogenetic analyses of HA genes from North American SIV. PB1-F2 is an influenza A virus protein encoded on gene segment 2 and described to be a virulence factor in other host species, but its role in swine is currently unknown. The 8-cluster HI SIV were demonstrated to contain segment 2 encoding PB1-F2 proteins with and without premature truncations. The objective of this work was to study the pathogenesis and transmission of d-cluster HI SIV in swine, comparing three isolates from different locations (TX,MN and IL), periods (2008, 2007 and 2005) and presence or absence of full-length PB1-F2.
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