Copyright © 2019. Published by Elsevier B. V. The well-known immunosuppressive drug cyclosporin A inhibits replication of various viruses including coronaviruses by binding to cellular cyclophilins thus inactivating their cis-trans peptidyl-prolyl isomerase function. Viral nucleocapsid proteins are inevitable for genome encapsidation and replication. Here we demonstrate the interaction between the N protein of HCoV-229E and cyclophilin A, not cyclophilin B. Cyclophilin inhibitors abolish this interaction. Upon infection, cyclophilin A stays evenly distributed throughout the cell, whereas cyclophilin B concentrates at ER-bleb-like structures. We further show the inhibitory potential of non-immunosuppressive CsA derivatives Alisporivir, NIM811, compound 3 on HCoV-229E-GFP and -Luciferase replication in human Huh-7.5 hepatoma cells at 18 and 48 h time points post infection with EC50 s at low micromolar ranges. Thus, non-immunosuppressive CsA derivatives effectively inhibit HCoV-229E replication suggesting them as possible candidates for the treatment of HCoV infection. The interruption of interaction between CypA and N protein by CsA and its derivatives suggest a mechanism how CypA inhibitors suppress viral replication.
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