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.