tetano
Editor, Senior Moderator
PLoS Pathog
. 2021 Apr 23;17(4):e1009490.
doi: 10.1371/journal.ppat.1009490. Online ahead of print.
Neuraminidase-associated plasminogen recruitment enables systemic spread of natural avian Influenza viruses H3N1
Jacob Sch?n[SUP] 1 [/SUP], Angele Breithaupt[SUP] 2 [/SUP], Dirk H?per[SUP] 1 [/SUP], Jacqueline King[SUP] 1 [/SUP], Anne Pohlmann[SUP] 1 [/SUP], Rokshana Parvin[SUP] 3 [/SUP], Klaus-Peter Behr[SUP] 4 [/SUP], Bernd-Andreas Schwarz[SUP] 5 [/SUP], Martin Beer[SUP] 1 [/SUP], J?rgen Stech[SUP] 6 [/SUP], Timm Harder[SUP] 1 [/SUP], Christian Grund[SUP] 1 [/SUP]
Affiliations
Abstract
Repeated outbreaks due to H3N1 low pathogenicity avian influenza viruses (LPAIV) in Belgium were associated with unusually high mortality in chicken in 2019. Those events caused considerable economic losses and prompted restriction measures normally implemented for eradicating high pathogenicity avian influenza viruses (HPAIV). Initial pathology investigations and infection studies suggested this virus to be able to replicate systemically, being very atypical for H3 LPAIV. Here, we investigate the pathogenesis of this H3N1 virus and propose a mechanism explaining its unusual systemic replication capability. By intravenous and intracerebral inoculation in chicken, we demonstrate systemic spread of this virus, extending to the central nervous system. Endoproteolytic viral hemagglutinin (HA) protein activation by either tissue-restricted serine peptidases or ubiquitous subtilisin-like proteases is the functional hallmark distinguishing (H5 or H7) LPAIV from HPAIV. However, luciferase reporter assays show that HA cleavage in case of the H3N1 strain in contrast to the HPAIV is not processed by intracellular proteases. Yet the H3N1 virus replicates efficiently in cell culture without trypsin, unlike LPAIVs. Moreover, this trypsin-independent virus replication is inhibited by 6-aminohexanoic acid, a plasmin inhibitor. Correspondingly, in silico analysis indicates that plasminogen is recruitable by the viral neuraminidase for proteolytic activation due to the loss of a strongly conserved N-glycosylation site at position 130. This mutation was shown responsible for plasminogen recruitment and neurovirulence of the mouse brain-passaged laboratory strain A/WSN/33 (H1N1). In conclusion, our findings provide good evidence in natural chicken strains for N1 neuraminidase-operated recruitment of plasminogen, enabling systemic replication leading to an unusual high pathogenicity phenotype. Such a gain of function in naturally occurring AIVs representing an established human influenza HA-subtype raises concerns over potential zoonotic threats.
. 2021 Apr 23;17(4):e1009490.
doi: 10.1371/journal.ppat.1009490. Online ahead of print.
Neuraminidase-associated plasminogen recruitment enables systemic spread of natural avian Influenza viruses H3N1
Jacob Sch?n[SUP] 1 [/SUP], Angele Breithaupt[SUP] 2 [/SUP], Dirk H?per[SUP] 1 [/SUP], Jacqueline King[SUP] 1 [/SUP], Anne Pohlmann[SUP] 1 [/SUP], Rokshana Parvin[SUP] 3 [/SUP], Klaus-Peter Behr[SUP] 4 [/SUP], Bernd-Andreas Schwarz[SUP] 5 [/SUP], Martin Beer[SUP] 1 [/SUP], J?rgen Stech[SUP] 6 [/SUP], Timm Harder[SUP] 1 [/SUP], Christian Grund[SUP] 1 [/SUP]
Affiliations
- PMID: 33891662
- DOI: 10.1371/journal.ppat.1009490
Abstract
Repeated outbreaks due to H3N1 low pathogenicity avian influenza viruses (LPAIV) in Belgium were associated with unusually high mortality in chicken in 2019. Those events caused considerable economic losses and prompted restriction measures normally implemented for eradicating high pathogenicity avian influenza viruses (HPAIV). Initial pathology investigations and infection studies suggested this virus to be able to replicate systemically, being very atypical for H3 LPAIV. Here, we investigate the pathogenesis of this H3N1 virus and propose a mechanism explaining its unusual systemic replication capability. By intravenous and intracerebral inoculation in chicken, we demonstrate systemic spread of this virus, extending to the central nervous system. Endoproteolytic viral hemagglutinin (HA) protein activation by either tissue-restricted serine peptidases or ubiquitous subtilisin-like proteases is the functional hallmark distinguishing (H5 or H7) LPAIV from HPAIV. However, luciferase reporter assays show that HA cleavage in case of the H3N1 strain in contrast to the HPAIV is not processed by intracellular proteases. Yet the H3N1 virus replicates efficiently in cell culture without trypsin, unlike LPAIVs. Moreover, this trypsin-independent virus replication is inhibited by 6-aminohexanoic acid, a plasmin inhibitor. Correspondingly, in silico analysis indicates that plasminogen is recruitable by the viral neuraminidase for proteolytic activation due to the loss of a strongly conserved N-glycosylation site at position 130. This mutation was shown responsible for plasminogen recruitment and neurovirulence of the mouse brain-passaged laboratory strain A/WSN/33 (H1N1). In conclusion, our findings provide good evidence in natural chicken strains for N1 neuraminidase-operated recruitment of plasminogen, enabling systemic replication leading to an unusual high pathogenicity phenotype. Such a gain of function in naturally occurring AIVs representing an established human influenza HA-subtype raises concerns over potential zoonotic threats.