Cyclophilin inhibitors restrict Middle East respiratory syndrome coronavirus via interferon-λ in vitro and in mice

Eur Respir J. 2020 Nov 26;56(5):1901826. doi: 10.1183/13993003.01826-2019. Print 2020 Nov.


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.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.Calu-3 cells and primary human alveolar epithelial cells (hAECs) were infected with MERS-CoV and treated with CsA or ALV or inhibitors targeting cyclophilin inhibitor-regulated molecules including calcineurin, nuclear factor of activated T-cells (NFATs) or mitogen-activated protein kinases. Novel CsA-induced pathways were identified by RNA sequencing and manipulated by gene knockdown or neutralising antibodies. Viral replication was quantified by quantitative real-time PCR and 50% tissue culture infective dose. Data were validated in a murine MERS-CoV infection model.Both CsA and ALV reduced MERS-CoV titres and viral RNA replication in Calu-3 cells and hAECs, 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. Downregulation of IRF1 or IFNλ increased MERS-CoV propagation in the presence of CsA. Importantly, oral application of CsA reduced MERS-CoV replication in vivo, correlating with elevated lung IFNλ levels and improved outcome.We provide evidence that cyclophilin inhibitors efficiently decrease MERS-CoV replication in vitro and in vivo via upregulation of inflammatory antiviral cell responses, in particular IFNλ. CsA might therefore represent a promising candidate for treating MERS-CoV infection.

MeSH terms

  • Alveolar Epithelial Cells / drug effects
  • Alveolar Epithelial Cells / metabolism
  • Alveolar Epithelial Cells / virology
  • Animals
  • Calcineurin Inhibitors / pharmacology
  • Cell Culture Techniques
  • Coronavirus Infections / metabolism
  • Coronavirus Infections / prevention & control*
  • Cyclophilins / antagonists & inhibitors*
  • Cyclosporine / pharmacology*
  • Disease Models, Animal
  • Humans
  • Interferon Lambda
  • Interferon Regulatory Factor-1 / drug effects
  • Interferon Regulatory Factor-1 / metabolism
  • Interferons / drug effects
  • Interferons / metabolism*
  • Mice
  • Middle East Respiratory Syndrome Coronavirus / drug effects*
  • Middle East Respiratory Syndrome Coronavirus / physiology
  • Virus Replication / drug effects


  • Calcineurin Inhibitors
  • IRF1 protein, human
  • Interferon Regulatory Factor-1
  • Cyclosporine
  • Interferons
  • Cyclophilins
  • alisporivir
  • Interferon Lambda