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Title: Limited antigenic diversity in contemporary H7 avian-origin influenza A viruses from North America

Author
item XU, YIFEI - Mississippi State University
item BAILEY, ELIZABETH - Mississippi State University
item Spackman, Erica
item LI, TAO - Walter Reed Army Institute
item WANG, HUI - Mississippi State University
item LONG, LI-PING - Mississippi State University
item BAROCH, JOHN - Animal And Plant Health Inspection Service (APHIS)
item CUNNINGHAM, FRED - Animal And Plant Health Inspection Service (APHIS)
item LIN, XIAOXU - Walter Reed Army Institute
item JARMAN, RICHARD - Walter Reed Army Institute
item DELIBERTO, THOMAS - Animal And Plant Health Inspection Service (APHIS)
item WAN, XIU-FENG - Mississippi State University

Submitted to: Scientific Reports
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/11/2016
Publication Date: 2/9/2016
Publication URL: http://handle.nal.usda.gov/10113/62726
Citation: Xu, Y., Bailey, E., Spackman, E., Li, T., Wang, H., Long, L., Baroch, J.A., Cunningham, F.L., Lin, X., Jarman, R.G., Deliberto, T.J., Wan, X. 2016. Limited antigenic diversity in contemporary H7 avian-origin influenza A viruses from North America. Scientific Reports. 6:20688. http://doi.org/10.1038/srep20688.
DOI: https://doi.org/10.1038/srep20688

Interpretive Summary: The surface of the influenza has a projection named the hemagglutinin (HA) protein. HA proteins are divided into groups based on their structure. Some types, such as H7, are more common and more important because of the animals they can infect. Because the fine structure of the HA protein can affect how well a vaccine works, we examined the relationships of the H7 HA protein among influenza viruses from North America from 1976 through 2012. It was found that most North American H7 proteins were somewhat related. In addition to providing information for vaccine development for H7 influenza, this shows that the ecology of the virus in natural hosts has not caused changes to occur. This is in contrast to many other influenza strains from non-natural hosts, where the surface proteins develop high levels of diversity over time.

Technical Abstract: Subtype H7 avian–origin influenza A viruses (AIVs) have caused at least 500 confirmed human infections since 2003 and culling of >75 million birds in recent years. Understanding the antigenic diversity and genetic evolution of H7 AIVs is critical for developing effective strategies for disease prevention and control. We antigenically and genetically characterized 93 AIV isolates from North America (85 from migratory waterfowl [1976–2010], 7 from domestic poultry [1971–2012], and 1 from a seal [1980]). Phylogenetic analyses identified 3 major genetically different clusters for the hemagglutinin gene of H7 viruses that have been circulating in North America, and they are clearly separated from those from Eurasia. Gradual accumulation of nucleotide and amino acid substitutions was observed in the hemagglutinin of H7 AIVs from waterfowl and domestic poultry. Genotype characterization suggested that H7 AIVs in wild birds form diverse and transient internal gene constellations. Serologic analyses showed that the 93 isolates cross-reacted with each other to different extents. Antigenic cartography showed that the average antigenic distance among them was 1.14 units (standard deviation [SD], 0.57 unit) and that antigenic diversity among the H7 isolates we tested was limited. No clear correspondence was seen between genetic diversity, host species, and antigenic properties. Our results suggest that the continuous genetic evolution has not led to significant antigenic diversity for H7 AIVs from North America. These findings add to our understanding of the natural history of influenza A viruses and will inform public health decision-making regarding the threat these viruses pose to humans and poultry.