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United States Department of Agriculture

Agricultural Research Service

Research Project: INTERVENTION STRATEGIES TO CONTROL VIRAL DISEASES OF SWINE Title: Pathogenicity and transmission of the novel A (H3N2v) influenza virus isolated from humans in experimentally inoculated pigs

Authors
item Kitikoon, Pravina
item Gauger, Phillip -
item Schlink, Sarah
item Bayles, Darrell
item Culhane, Marie -
item Darnell, Daniel -
item Webby, Richard -
item Lager, Kelly
item Swenson, Sabrina -
item Klimov, Alexander -
item Vincent, Amy

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: February 15, 2013
Publication Date: N/A

Technical Abstract: Human cases with H3N2 (H3N2v) viruses closely related to swine H3N2 viruses were detected in 2011 and increased to >320 cases by the end of 2012. H3N2-TRIG was the H3N2 genotype endemically circulating in the U.S. swine population prior to the emergence of H1N1pdm09, and rH3N2p are novel H1N1pdm09/H3N2-TRIG reassortant genotypes. Whole genome analysis showed ten different rH3N2p genotypes present in the U.S. swine population since 2009. Genotype 1 (G1) acquired the pM gene alone from H1N1pdm09 similar to H3N2v, and was most frequently detected among rH3N2p in pigs. This indicates a genetic fitness of G1 in swine and possibly transmission to human. Hemagglutinin (HA) gene analysis indicated that rH3N2p and H3N2v are related to the contemporary H3N2-TRIG virus, but recent rH3N2p swine isolates formed separate clusters. We compared the pathogenic, transmission, genetic, and antigenic properties of a human H3N2v isolate with two swine H3N2 viruses, H3N2-TRIG and rH3N2p in the swine host. Groups were assigned as negative controls; H3N2v-infected; H3N2-TRIG-infected and rH3N2p-infected, with contact pigs in each group to study virus transmission. No differences in pathogenicity or transmissibility among the three H3N2 viruses were detected. Antibodies to H3N2-TRIG virus cross-reacted to H3N2v. However mutations at putative HA antigenic sites of contemporary swine H3N2 viruses were detected with reduced serologic cross-reactivity among the rH3N2p sub-clusters. The findings demonstrate antigenic drift of these new viruses concurrent with the genomic reassortment. As influenza A viruses continue to evolve and transmit between humans and animals, the role of pigs in generating reassortant influenza viruses cannot be overlooked. Continued genetic, antigenic, and in vivo studies in swine are essential to determine the phenotypes of these novel emerging viruses in their natural host.

Last Modified: 9/10/2014
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