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Rôle des cyclophilines dans la réplication des Coronavirus

Abstract : Coronaviruses (CoVs) are viruses leading to fatal diseases in humans and animals for which there is no specific treatment. In cats, one of the feline coronaviruses, the feline infectious peritonitis virus (FIPV) causes a systematically lethal pathology in cats. Because of their genomic plasticity and their ability to infect multiple animal species, mammals or birds, CoVs represent a constant risk of emergence. The latest human emergences of SARS-CoV, MERS-CoV and more recently SARS-CoV-2 are the result of interspecific transmissions between wildlife and humans. Recent studies have shown that cyclophilins (CyP), which are highly conserved cellular proteins, are required for the replicative cycle of CoVs but the specific modes of action of these proteins are undetermined.To investigate the role of cyclophilins in coronavirus replication, we used newly developed small molecule cyclophilin inhibitors (SM-CypI), which are non-immunosuppressive. We screened 21 SM-CypIs as well as Cyclosporin A (CsA) as a reference inhibitor. Nine SM-CypIs had a greater FIPV replication inhibitory activity than CsA. Of the nine molecules, three were selected: the molecule named 83233, which was shown to be the best FIPV inhibitor and the molecules 832 and 833 from which 83233 was developed. Using these cyclophilin inhibitors and performing experiments where these antiviral compounds were applied at different times post-infection (1h, 3h, 6h, 9h and 12h) or before infection, we showed that the antiviral effect of these compounds was maximal when they were administered at the time of infection or 1h after. In all other experimental conditions, their antiviral effect was reduced. We thus determined that cyclophilins were essential at an early step of feline coronavirus replication. This step(s) would correspond to the decapsidation and/or the establishment of the viral replication complex.To complement our study on the mechanisms of action of cyclophilins, we aimed to determine which viral proteins could interact with cellular cyclophilins, especially cyclophilin A. We identified that the N protein of the feline coronavirus interacts with feline cyclophilin A using a Proximity Ligation Assay (PLA). This interaction had so far only been shown in human models of coronavirus and cyclophilins. Thus, the mechanisms of interaction of cyclophilins with coronavirus proteins might be conserved. However, during inhibition tests with SM-CypI against the avian infectious bronchitis virus, a gammacoronavirus, the inhibitory effect of the molecules was moderate.This work has provided new insights into the role of cyclophilins in coronavirus replication and suggests that this role may be conserved at least in mammalian coronaviruses. Our data also enabled us to identify an interesting therapeutic target, as well as molecules presenting a major antiviral effect against various coronaviruses, which could lead to new therapeutic strategies.
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Submitted on : Tuesday, March 8, 2022 - 10:33:22 AM
Last modification on : Friday, August 19, 2022 - 1:40:05 PM
Long-term archiving on: : Thursday, June 9, 2022 - 7:06:20 PM

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Manon Delaplace. Rôle des cyclophilines dans la réplication des Coronavirus. Biologie moléculaire. AgroParisTech, 2021. Français. ⟨NNT : 2021AGPT0023⟩. ⟨tel-03601237⟩

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