Location: Virus and Prion ResearchTitle: Antigenic and genetic evolution of contemporary swine H1 influenza viruses in the United States
|RAJAO, DANIELA - UNIVERSITY OF GEORGIA|
|KITIKOON, PRAVINA - MERCK ANIMAL HEALTH|
|LEWIS, NICOLA - UNIVERSITY OF CAMBRIDGE|
Submitted to: Virology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/5/2018
Publication Date: 5/1/2018
Citation: Rajao, D.S., Anderson, T.K., Kitikoon, P., Stratton, J., Lewis, N.S., Vincent, A.L. 2018. Antigenic and genetic evolution of contemporary swine H1 influenza viruses in the United States. Virology. 518:45-54. https://doi.10.1016/j.virol.2018.02.006.
Interpretive Summary: Influenza A viruses (IAV) that circulate in North American pigs maintain a high degree of diversity, especially those of the H1 subtype, determined by the hemagglutinin (HA) gene. The HA protein is the primary target of protective immune responses and the major consideration for vaccine formulation. The way immune antibodies recognize and bind to the HA protein affect its antigenic properties. One process of virus evolution, called antigenic drift, may lead to potential mismatches between vaccines and circulating strains. We found that changes in H1 from IAV in the U.S. pig population resulted in seven distinct antigenic groups of the H1 subtype. We identified changes in the HA protein associated with the observed antigenic drift that may allow for prediction of antigenic changes bases on genetic sequence. The continued genetic and antigenic evolution of contemporary H1 viruses may lead to loss of vaccine protection, with significant economic impact to the swine industry. This also represents a challenge to public health initiatives to minimize human exposure to IAV from swine.
Technical Abstract: Several lineages of influenza A viruses (IAV) currently circulate in North American pigs. Genetic diversity is further increased by the bidirectional transmission of IAV between swine and humans and the subsequent processes of antigenic shift and drift. Such evolution can be the basis for changes in antigenic properties of IAV that lead to vaccine failure. Here, we characterized the genetic and antigenic evolution of contemporary swine H1N1 and H1N2 viruses representing clusters H1-alpha (1A.1), H1-beta (1A.2), H1pdm (1A.3.3.2), H1-gamma (1A.3.3.3), H1-delta1 (1B.2.2), and H1-delta2 (1B.2.1) currently circulating in pigs in the United States. While the classical swine H1 viruses evolved within established genetic clades, the delta1-viruses diversified into two new genetic sub-clades, H1-delta1a (1B.2.2.1) and H1-delta1b (1B.2.2.2), which were also antigenically distinct from the earlier H1-delta1-viruses. Further characterization revealed that few key amino acid changes were associated with antigenic divergence in these groups. The continued genetic and antigenic evolution of contemporary H1 viruses might lead to loss of vaccine cross-protection that could lead to significant economic impact to the swine industry, and represents a challenge to public health initiatives that attempt to minimize swine-to-human IAV transmission.