Levodopa pharmacodynamics.

Abstract

<h3>Rationale</h3> While severe coronavirus infections, including Middle East respiratory syndrome coronavirus (MERS-CoV) cause lung injury with high mortality rates, protective treatment strategies are not approved for clinical use. <h3>Objectives</h3> We elucidated the molecular mechanisms by which the cyclophilin inhibitors Cyclosporin A (CsA) and Alisporivir (ALV) restrict MERS-CoV to validate their suitability as readily-available therapy in MERS-CoV infection. <h3>Methods</h3> Calu-3 cells and primary human alveolar epithelial cells (hAEC) were infected with MERS-CoV and treated with CsA or ALV or inhibitors targeting cyclophilin inhibitor-regulated molecules including Calcineurin, NFAT, or MAP kinases. Novel CsA-induced pathways were identified by RNA sequencing and manipulated by gene knockdown or neutralising antibodies. Viral replication was quantified by qRT-PCR and TCID₅₀. Data were validated in a murine MERS-CoV infection model. <h3>Results</h3> CsA and ALV both reduced MERS-CoV titers and viral RNA replication in Calu-3 and hAEC improving epithelial integrity. While neither Calcineurin nor NFAT inhibition reduced MERS-CoV propagation, blockade of c-Jun N-terminal kinase diminished infectious viral particle release but not RNA accumulation. Importantly, CsA induced interferon regulatory factor 1 (IRF1), a pronounced type-III-interferon (IFNλ) response and expression of antiviral genes. Down-regulation of IRF1 or IFNλ increased MERS-CoV propagation in presence of CsA. Importantly, oral application of CsA reduced MERS-CoV replication <i>in vivo</i>, correlating with elevated lung IFNλ levels and improved outcome. <h3>Conclusions</h3> We provide evidence that cyclophilin inhibitors efficiently decrease MERS-CoV replication <i>in vitro</i> and <i>in vivo via</i> upregulation of inflammatory, antiviral cell responses, in particular IFNλ. CsA might therefore represent a promising candidate to treat MERS-CoV infection.