Virus persistence in pig herds led to successive reassortment events between swine and human influenza A viruses, resulting in the emergence of a novel triple-reassortant swine influenza virus

Abstract

This report describes the detection of a triple reassortant swine influenza A virus of H1avN2 subtype. It evolved from an avian-like swine H1avN1 that first acquired the N2 segment from a seasonal H3N2, then the M segment from a 2009 pandemic H1N1, in two reassortments estimated to have occurred 10 years apart. This study illustrates how recurrent influenza infections increase the co-infection risk and facilitate evolutionary jumps by successive gene exchanges. It recalls the importance of appropriate biosecurity measures inside holdings to limit virus persistence and interspecies transmissions, which both contribute to the emergence of new potentially zoonotic viruses.

Influenza A virus vaccine research conducted in swine from 1990 to May 2018: A scoping review

“…In both vaccinated and non-vaccinated pigs, influenza A viruses can be diverse at the level of the population, within an individual pig, and even within a cell [ 72 – 75 ]. Investigation of virus characterization and of transmissibility is necessary to understand, at the individual animal level, vaccine induced cross-protection and duration of immunity, and at the population level, the impact of vaccination on the viral ecology of influenza in swine [ 1 , 21 , 56 , 76 – 82 ]. In poultry, vaccination has been associated with selective transmission of more virulent strains of IAV [ 83 ].…”

Genetic and Antigenic Evolution of European Swine Influenza A Viruses of HA-1C (Avian-Like) and HA-1B (Human-Like) Lineages in France from 2000 to 2018

“…Three reassortant H1 av N2 strains harbored a M segment from the H1N1pdm lineage (Mpdm). Two of these, with a N2 from human seasonal IAV, acquired only the M segment from the H1N1pdm, whereas the third one harbored all internal segments from the H1N1pdm lineage, as detailed in previous studies [ 44 , 46 ]. Finally, the majority of French swine H1Ny strains classified into two main genogroups we called the “M recent Eurasian avian-like swine” group (MswEA-‘recent’) and the “M European swine” group (MswEU), respectively, which showed no specific associations with HA or NA clades ( Figure 2 and Figure 4 ).…”

“…Within this lineage, French H1N2 strains had N2 genes closer to those described in Danish enzootic H1 av N2 viruses than to those of Eurasian swine H3N2 viruses ( Figure 6 ). Finally, three reassortant H1 av N2 strains shared a N2 gene derived from a human seasonal H3N2 lineage, as detailed in a previous study [ 44 ] ( Figure 6 ).…”

“…Indeed, swine H3N2 subtype is rare in France, with less than one isolate detected each year on average, and furthermore restricted to the north (data not shown), which limits reassortment opportunities. However, three H1 av N2 strains were shown to contain a N2 gene from a seasonal human H3N2 lineage, recalling the importance of implementing biosecurity measures in holdings to avoid inter-species transmissions that may lead to the emergence of new viruses in pigs [ 44 ].…”

Dynamic Propagation and Impact of Pandemic Influenza A (2009 H1N1) in Children: A Detailed Review

“…It was assumed that swine are a logical candidate and work as a "mixing vessel" for the novel genetic shift of avian, swine, and human viruses, since they share a common signaling receptor (epitopes) that classifies both strains equally. Thus, swine play a significant role in the occurrence of swine flu viruses as well as in the initiation of human pandemic outbreaks [ 5 ].…”