Figure 4.

RBD can bind to VERO E6 cells that express high levels of endogenous ACE2 but not to RT4 cells. VERO E6/TMPRSS2, A549 and RT4 cells were harvested by either trypsin/EDTA or non-enzymatic cell dissociation solution (CDS) and then incubated with 1000 nM RBD for 60 min, before staining with anti-His6 secondary antibody labelled with Dylight 488. The data are shown as a percentage of the binding of 100 nM wtS1S2 and are the means ± SEM from 5–6 independent experiments performed in duplicate. The significance of the difference from 0 was assessed by a one-sample t test; * p < 0.05; ** p < 0.001.