Canine Influenza Virus is Mildly Restricted by Canine Tetherin Protein.

Tetherin (BST2/CD317/HM1.24) has emerged as a key host-cell ·defence molecule that acts by inhibiting the release and spread of diverse enveloped virions from infected cells. We analysed the biological features of canine tetherin and found it to be an unstable hydrophilic type I transmembrane protein with one transmembrane domain, no signal peptide, and multiple glycosylation and phosphorylation sites. Furthermore, the tissue expression profile of canine tetherin revealed that it was particularly abundant in immune organs. The canine tetherin gene contains an interferon response element sequence that can be regulated and expressed by canine IFN-α. A CCK-8 assay showed that canine tetherin was effective in helping mitigate cellular damage caused by canine influenza virus (CIV) infection. Additionally, we found that the overexpression of canine tetherin inhibited replication of the CIV and that interference with the canine tetherin gene enhanced CIV replication in cells. The impact of canine tetherin on CIV replication was mild. However, these results elucidate the role of the innate immune factor, canine tetherin, during CIV infection for the first time.