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ARS Home » Midwest Area » Ames, Iowa » National Animal Disease Center » Virus and Prion Research » Research » Publications at this Location » Publication #364281

Research Project: Intervention Strategies to Control Influenza A Virus Infection in Swine

Location: Virus and Prion Research

Title: Characterization of a novel human seasonal H3 influenza A virus spillover that is now endemic in US swine

item SHARMA, ADITI - Iowa State University
item ZELLER, MICHAEL - Iowa State University
item Anderson, Tavis
item Baker, Amy
item HARMON, KAREN - Iowa State University
item LI, GANWU - Iowa State University
item ZHANG, JIANQIANG - Iowa State University
item GAUGER, PHILLIP - Iowa State University

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 5/24/2019
Publication Date: 10/26/2019
Citation: Sharma, A., Zeller, M., Anderson, T.K., Vincent, A.L., Harmon, K., Li, G., Zhang, J., Gauger, P.C. 2019. Characterization of a novel human seasonal H3 influenza A virus spillover that is now endemic in US swine [abstract]. American Association of Veterinary Laboratory Diagnosticians Annual Meeting. p. 13.

Interpretive Summary:

Technical Abstract: A reverse-zoonosis transmission of human-seasonal H3 subtype IAV from humans into swine was first detected in Oklahoma in March, 2017 and demonstrated sustained circulation within the U.S. swine population between 2017 to the present. To understand the origin of this virus and its evolution in the swine host, we genetically characterized the hemagglutinin (HA) and neuraminidase (NA) genes of 46 viruses, and whole genome sequenced 13 strains. A time-scaled Bayesian approach for the HA gene, demonstrated that the time to the most recent common human H3 ancestor was August, 2016 to September, 2016. Spatial dissemination of genetically similar H3 HA across the central U.S. was observed, with 1 detection in Ohio, 3 in Illinois, 5 in Iowa, 11 in Arkansas, 12 in Indiana and Oklahoma each and 2 from unknown states. Whole genome sequencing of 13 strains revealed that the N2 neuraminidase (NA) was of human-seasonal origin, with the matrix gene of H1N1pdm09 origin and all other internal genes of triple reassortant (TRIG) origin. Pairwise comparison between the first detected swine HA gene and the most similar human seasonal H3 revealed 99.9% similarity. Evaluation of glycosylation sites in HA gene revealed that after 2017, the HA protein lost a predicted glycosylation at position 133 (H3 numbering) within the antigenic site A and the 130-loop of the receptor binding site. Following spillover, early swine viruses had an antigenic motif of STHNYK (amino acid position 145, 155, 156, 158, 159 and 189) which was identical with the closest human seasonal virus. STHNYK was the primary motif post introduction whereas STHNYN was predominant after April, 2017. Changes in the antigenic motif and glycosylation patterns of the virus may be a consequence of antigenic drift and/or adaptation to the swine host. We report the second emergence of a sustained human seasonal H3 IAV spillover into swine in the 2010 decade (named “2010.2”). These data suggest human IAV continue to spillover into swine and become established in the population, contributing to the genetic and antigenic diversity of IAV circulating in swine. Continued monitoring for novel IAV will assist vaccine antigen selection and vaccine updates to improve the ability to prevent this costly disease.