title: Matriptase, HAT, and TMPRSS2 activate the hemagglutinin of H9N2 influenza A viruses.
abstract: Influenza A viruses of the subtype H9N2 circulate worldwide and have become highly prevalent in poultry in many countries. Moreover, they are occasionally transmitted to humans, raising concern about their pandemic potential. Influenza virus infectivity requires cleavage of the surface glycoprotein hemagglutinin (HA) at a distinct cleavage site by host cell proteases. H9N2 viruses vary remarkably in the amino acid sequence at the cleavage site, and many isolates from Asia and the Middle East possess the multibasic motifs R-S-S-R and R-S-R-R, but are not activated by furin. Here, we investigated proteolytic activation of the early H9N2 isolate A/turkey/Wisconsin/1/66 (H9-Wisc) and two recent Asian isolates, A/quail/Shantou/782/00 (H9-782) and A/quail/Shantou/2061/00 (H9-2061), containing mono-, di-, and tribasic HA cleavage sites, respectively. All H9N2 isolates were activated by human proteases TMPRSS2 (transmembrane protease, serine S1 member 2) and HAT (human airway trypsin-like protease). Interestingly, H9-782 and H9-2061 were also activated by matriptase, a protease widely expressed in most epithelia with high expression levels in the kidney. Nephrotropism of H9N2 viruses has been observed in chickens, and here we found that H9-782 and H9-2061 were proteolytically activated in canine kidney (MDCK-II) and chicken embryo kidney (CEK) cells, whereas H9-Wisc was not. Virus activation was inhibited by peptide-mimetic inhibitors of matriptase, strongly suggesting that matriptase is responsible for HA cleavage in these kidney cells. Our data demonstrate that H9N2 viruses with R-S-S-R or R-S-R-R cleavage sites are activated by matriptase in addition to HAT and TMPRSS2 and, therefore, can be activated in a wide range of tissues what may affect virus spread, tissue tropism and pathogenicity.
authors.affiliation: Institute of Virology, Philipps University Marburg, Marburg, Germany.
authors.forename: Joanna
authors.initials: J
authors.lastname: Baron
authors.forename: Carolin
authors.initials: C
authors.lastname: Tarnow
authors.forename: Deborah
authors.initials: D
authors.lastname: Mayoli-Nüssle
authors.forename: Eva
authors.initials: E
authors.lastname: Schilling
authors.forename: Daniela
authors.initials: D
authors.lastname: Meyer
authors.forename: Maya
authors.initials: M
authors.lastname: Hammami
authors.forename: Folker
authors.initials: F
authors.lastname: Schwalm
authors.forename: Torsten
authors.initials: T
authors.lastname: Steinmetzer
authors.forename: Yi
authors.initials: Y
authors.lastname: Guan
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Garten
authors.forename: Hans-Dieter
authors.initials: HD
authors.lastname: Klenk
authors.forename: Eva
authors.initials: E
authors.lastname: Böttcher-Friebertshäuser
mesh_terms: D000818:Animals; D002460:Cell Line; D002645:Chickens; D004285:Dogs; D019267:Hemagglutinin Glycoproteins, Influenza Virus / Q000378:metabolism*; D054884:Host-Pathogen Interactions; D006801:Humans; D053127:Influenza A Virus, H9N2 Subtype / Q000502:physiology*; D012697:Serine Endopeptidases / Q000378:metabolism*; D053586:Virus Internalization
chemical_list: D019267:Hemagglutinin Glycoproteins, Influenza Virus; D012697:Serine Endopeptidases; C421305:TMPRSS2 protein, human; C112256:human airway trypsin-like protease; C485596:ST14 protein, human