Figure 3

Competitive inhibition of RBD-ACE2 binding. (A) Schematic representation of the competitive inhibition of RBD-ACE2 interaction. The assay was performed based on the ELISA method. ELISA plates were coated with human ACE2. Binding between the RBD and ACE2 was measured in three different conditions: (i) RBD alone, (ii) RBD with monkey serum (diluted 1:500), and (iii) RBD with monkey serum and peptide. (B) Antibody response against each epitope observed in the three monkey sera used in the assay (left panel) and inhibition of RBD-ACE2 interaction by monkey antibodies in the presence and absence of peptide (right panel). * indicates a significant difference between the conditions with and without peptide (p < 0.05). (C) Effect of peptide concentration on antibody blocking and RBD-ACE2 interaction. The assay was performed with three different concentrations (0.1, 1, 5 nmole/100 uL reaction) of peptide and the study with serum from vaccinated monkey number 4 is shown as a representative. (D) Percent change in RBD-ACE2 interaction in the presence of peptide. Percent change was calculated based on the formula described in the materials and methods.