Abstract Title
Synergy between HA cleavage site sequence and NA-mediated plasminogen recruitment as a virulence mechanism for low pathogenic avian influenza
Abstract
An outbreak of H3N1 low pathogenic avian influenza viruses (IVPI=0.13) in Belgium in 2019 caused unexpected levels of mortality and morbidity. Schon and colleagues(a) proposed that HA cleavage mediated by NA-driven plasminogen recruitment contributed to the systemic spread and pathogenicity of this virus. Aligning HA sequences of the outbreak viruses with other H3 strains also showed an unusual sequence around the HA cleavage site, as well as the NA polymorphisms associated with plasminogen binding. We established a reverse genetics system for A/chicken/Belgium/460/2019 (Ck/Belgium) and created single mutations in HA (K345R), and NA (S122N) that restored the viruses to normal consensus, as well as an HA/NA double mutant. Confirming previous work(a), trypsin-independent spread and HA cleavage of wild type Ck/Belgium was observed in the presence of serum containing plasminogen in vitro. Dose-dependent HA cleavage and trypsin-independent spread was also observed in the presence of purified chicken plasminogen. Compared to the wild type, both HA cleavage and spread were lower in HA K345R mutant and further blocked by NA mutation S122N. This plasminogen-mediated HA cleavage was seen in various avian cell lines, excluding cell type-dependent effects. Similar observations were also found in chicken enteroids infected with the wild type or mutant viruses in the presence of plasminogen. Furthermore, in ovo tests showed that mutant viruses unable to recruit plasminogen had significantly lower titres and viral protein expression in embryos. We conclude that the unusual HA cleavage site and NA-mediated plasminogen recruitment work concertedly to increase the virulence of Ck/Belgium.
(a)Schon et al. 2021. PLoS Pathogens.
(a)Schon et al. 2021. PLoS Pathogens.
Co-Author(s)
Hui Min Lee1, Kate Sutton1, Rute Maria Pinto1, Lonneke Vervelde2, Sjaak de Wit2, Paul Digard1
1 The Roslin Institute, The University of Edinburgh, Easter Bush, Midlothian, UK
2 Royal GD, Deventer, The Netherlands
Abstract Category
Transmission pathways, pathobiology, immune responses