ARS | Publication request: Genetic and Antigenic Characterization of H1 Influenza Viruses from United States Swine Prior to the Emergence of the 2009 Pandemic H1N1

Submitted to: Research Workers in Animal Diseases Conference Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: September 30, 2010
Publication Date: December 7, 2010
Citation: Lorusso, A., Vincent, A., Harland, M., Alt, D., Bayles, D., Swenson, S., Gramer, M., Russell, C., Smith, D., Lager, K., Lewis, N. 2010. Genetic and antigenic characterization of H1 Influenza Viruses from United States swine prior to the emergence of the 2009 pandemic H1N1 [abstract]. Conference of Research Workers in Animal Diseases. Paper No. 194.

Technical Abstract: Swine play a role for the evolution of influenza A viruses. Prior to the introduction of the 2009 pandemic H1N1 virus from humans into pigs, four phylogenetic clusters of the hemagglutinin (HA) gene from H1 influenza viruses could be found in U.S. swine. Viruses from the classical H1N1 swine lineage evolved to form alpha-, beta-, and gamma-clusters whereas viruses with HA genes most similar to human seasonal H1 viruses emerged in 2003 to form the delta-cluster. Limited sequence information was available regarding the six genes that make up the triple reassortant internal gene (TRIG) cassette in contemporary H1 influenza viruses of swine. In addition, information regarding the antigenic relatedness of the H1 viruses was lacking due to the dynamic and variable nature of swine lineage H1. We characterized twelve H1 isolates from 2008 by sequencing and phylogenetic analysis of all eight gene segments and by serologic cross-reactivity in the hemagglutination inhibition (HI) assay. Based on genetic analysis, each of the four previously described phylogenetic clusters of H1 influenza viruses of swine were represented in the 2008 panel. Additionally, it was demonstrated that the delta-cluster HA were sub-divided into sub-clusters delta1 and delta2. Genetic diversity was demonstrated in all gene segments, but most notably in the HA gene. The genetic evolution of the NA gene was comparable to that of the HA gene. The gene segments from the 2009 pandemic H1N1 formed clusters separate from North American swine lineage viruses, suggesting progenitors of the pandemic virus were not present in U.S. pigs immediately prior to 2009. Serologic cross-reactivity paired with antigenic cartography demonstrated that the viruses in the different phylogenetic clusters are also antigenically divergent. Increased surveillance and monitoring of enzootic influenza viruses of swine as well as the 2009 pandemic H1N1 in the swine population worldwide are critical to understand the dynamic ecology of influenza A viruses in this susceptible host population.