OFFLU Animal Influenza Report: July 2020 to December 2020

Authors: ARENDSEE, ZEBULUN - Orise Fellow; YOUNG, KATHERINE - Orise Fellow; HUFNAGEL, DAVID - Orise Fellow; MARKIN, ALEXEY - Orise Fellow; KIMBLE, BRIAN - Orise Fellow; KUNZLER-SOUZA, CARINE - Orise Fellow; BROWN, IAN - Animal & Plant Health Agency Apha; LEWIS, NICOLA - Royal Veterinary College; Anderson, Tavis; Baker, Amy

Submitted to: Meeting Abstract
Publication Type: Government Publication
Publication Acceptance Date: 3/4/2021
Publication Date: 3/4/2021
Citation: Arendsee, Z., Young, K., Hufnagel, D.E., Markin, A., Kimble, B., Kunzler-Souza, C., Brown, I., Lewis, N., Anderson, T.K., Vincent, A.L. 2021. OFFLU Animal Influenza Report: July 2020 to December 2020 [Abstract]. Technical report generated for the World Health Organization (WHO) Vaccine Consultation Meeting (VCM).

Interpretive Summary:

Technical Abstract: Epidemiologic and phylogenetic analyses of influenza A viruses (IAV) provide rational criteria for vaccine strain selection, control strategies, and may identify viruses with pandemic potential. From the 1918 human influenza pandemic to date, human-to-swine interspecies influenza A virus (IAV) transmission events have repeatedly occurred, some leading to sustained transmission and increased IAV diversity in pig populations. These swine IAV have the potential to be introduced back into the human population if they are substantially different from current human seasonal strains. We quantified the global genetic diversity of swine IAV circulating from July 2020 to December 2020. We determined how similar the circulating swine IAV diversity was to human IAV vaccines and current candidate vaccine viruses (CVV) that are used in pandemic preparedness efforts. We also antigenically characterized a subset of viruses representing circulating swine IAV using a panel of monovalent anti-sera raised in ferrets against human vaccine strains or CVV strains in hemagglutination inhibition (HI) assays. These data demonstrated that the tested swine IAV was significantly different to the current H1 and H3 components of human IAV vaccines. Additionally, only 11 of the 32 distinct genetic clades detected in swine globally are covered by CVV or human vaccine strains; and the degree to which those vaccines provide protection is dubious given observed genetic differences. We present a comprehensive picture of IAVs infecting swine and how this diversity varies between regions. These analyses demonstrate the dynamic interplay of IAV transmission between humans and swine, and identify genetic groups that should be considered in vaccine strain selection for pandemic preparedness. Testing additional viruses in HI assays with human sera will provide an assessment of human population immunity and quantify the pandemic potential of these swine H1 and H3 viruses.