ACE2 and viral infectious disease: However, single-mutation H41Y or E42Q could dramatically increase the binding of marmoset (25.9% or 52.9%) or tufted capuchin (56.9% or 61.8%) ACE2 orthologs with S1-Fc; double-mutations YQ (H41Y and E42Q) further strengthen their binding with S1-Fc (87.3% or 87.6%, respectively) (Fig. 4C); in parallel to the authentic virus infection, at 48 h postinfection the complemented A549 cells were subjected to immunofluorescent staining for ACE2 ortholog protein and viral nucleocapsid for quantification of the infection efficiency by the Operetta High Content Imaging System.