Genetic Characterisation of Swine Influenza Viruses Isolated from Minnesota

by 5m Editor
26 October 2011, at 12:00am

H3N2 influenza strains circulating in North America share the same genetic constellation, according to researchers in Virginia, who investigated viruses isolated from Minnesota in 2006-2007.

Triple-reassortant (TR) H3N2 swine influenza viruses (SIV) are a major cause of respiratory disease in swine worldwide, causing considerable morbidity and mortality, according to S.R. Kumar and colleagues at Virginia Polytechnic Institute and State University. In their paper in a recent issue of Virus Genes, they add that continuous surveillance of circulating SIV strains is imperative for effective control and prediction of new emerging strains with inter-species transmission potential.

Their study characterised SIV isolates from commercial swine population in USA (2006-2007). Nine isolates were completely sequenced, and the molecular evolution of all gene segments was analysed.

Phylogenetic analysis of the nine H3N2 viruses indicated that these strains belonged to cluster-IV of the human/swine/avian TR genotype, grouping with H3N2 viruses of turkey origin, while forming a separate sub-lineage from those of human and avian origin strains. Ten amino acid changes were observed at the major antigenic sites of HA1 region compared to the cluster-III reference strain, with differences in glycosylation sites.

All nine strains were antigenically related to the cluster-IV turkey strain than the cluster-III reference strain.

Kumar and co-authors conclude that the results of their study suggest that contemporary TR H3N2 strains circulating in North America share the same genetic constellation, thus maintaining the gene pool without any further event of genetic reassortment, unlike swine-origin pandemic strain A/California/04/2009/H1N1.

These findings strongly support the need for continuous surveillance and monitoring of genetic changes in SIV, to identify evolving strains that might pose a threat to human or animal health, added the Blacksburg-based researchers.


Kumar S.R., Deflube L., Biswas M., Shobana R. and Elankumaran S. 2011. Genetic characterization of swine influenza viruses (H3N2) isolated from Minnesota in 2006-2007. Virus Genes. 43(2):161-76. Epub 2011 May 21.

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Further Reading

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October 2011