title: Activation of influenza A viruses by host proteases from swine airway epithelium.
abstract: Pigs are important natural hosts of influenza A viruses, and due to their susceptibility to swine, avian, and human viruses, they may serve as intermediate hosts supporting adaptation and genetic reassortment. Cleavage of the influenza virus surface glycoprotein hemagglutinin (HA) by host cell proteases is essential for viral infectivity. Most influenza viruses, including human and swine viruses, are activated at a monobasic HA cleavage site, and we previously identified TMPRSS2 and HAT to be relevant proteases present in human airways. We investigated the proteolytic activation of influenza viruses in primary porcine tracheal and bronchial epithelial cells (PTEC and PBEC, respectively). Human H1N1 and H3N2 viruses replicated efficiently in PTECs and PBECs, and viruses containing cleaved HA were released from infected cells. Moreover, the cells supported the proteolytic activation of HA at the stage of entry. We found that swine proteases homologous to TMPRSS2 and HAT, designated swTMPRSS2 and swAT, respectively, were expressed in several parts of the porcine respiratory tract. Both proteases cloned from primary PBECs were shown to activate HA with a monobasic cleavage site upon coexpression and support multicycle replication of influenza viruses. swAT was predominantly localized at the plasma membrane, where it was present as an active protease that mediated activation of incoming virus. In contrast, swTMPRSS2 accumulated in the trans-Golgi network, suggesting that it cleaves HA in this compartment. In conclusion, our data show that HA activation in porcine airways may occur by similar proteases and at similar stages of the viral life cycle as in human airways.
authors.affiliation: Institute of Virology, Philipps University Marburg, Marburg, Germany.
authors.forename: Catharina
authors.initials: C
authors.lastname: Peitsch
authors.forename: Hans-Dieter
authors.initials: HD
authors.lastname: Klenk
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Garten
authors.forename: Eva
authors.initials: E
authors.lastname: Böttcher-Friebertshäuser
mesh_terms: D000818:Animals; D001483:Base Sequence; D001980:Bronchi / Q000166:cytology / Q000821:virology*; D017931:DNA Primers; D006801:Humans; D053118:Influenza A Virus, H1N1 Subtype / Q000502:physiology*; D053122:Influenza A Virus, H3N2 Subtype / Q000502:physiology*; D010447:Peptide Hydrolases / Q000378:metabolism*; D059748:Proteolysis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013552:Swine; D014132:Trachea / Q000166:cytology / Q000821:virology*; D014779:Virus Replication
chemical_list: D017931:DNA Primers; D010447:Peptide Hydrolases