3.4.3 The peptidyl/prolyl isomerases (PPIases)
The 18-kDa cytosolic cyclophilin A is an essential cellular molecule required for replication of RNA viruses including HIV (Luban et al., 1993), HCV (Watashi et al., 2005), influenza A (Liu et al., 2012) and also coronavirus. Cyclophilins (Cyps), belonging to the family of peptidyl-prolyl isomerases (PPIases), catalyze the rate-limiting cis/trans isomerization step of proline-preceding peptide bonds during the protein folding. The PPIase activity is blocked by cyclosporin A and its different non-immunosuppressive analogs (de Wilde et al., 2018) such as Alisporivir (ALV; or Debio-025) (Landrieu et al., 2010), NIM811 (Ciechomska et al., 2005) and SCY-635 (Hopkins et al., 2010).
There are various reports indicating the effect of Cyps (de Wilde et al., 2011; Pfefferle et al., 2011) and its derivatives (Carbajo-Lozoya et al., 2014; de Wilde et al., 2017) on different genera of coronaviruses mainly MERS-CoV, HCoV-229E, HCoV-NL63 and SARS-CoV in cell culture.