Figure 5
Interaction of NIH-CoVnb-112 with SARS-Cov-2 Spike Protein RBD variants. (a) Binding of NIH-CoVnb-112 to RBD “wild type” and 3 variant forms of the RBD had similar affinity, with half maximal binding at approximately 0.01 µg/mL (b) Competitive inhibition assay: RBD “wild type” and 3 variant forms of the RBD coated ELISA plates were blocked with non-specific protein and incubated with dilutions of the lead candidate anti-SARS-CoV-2 RBD nanobody NIH-CoVnb-112. Biotinylated-ACE2 was added to each well and allowed to bind to unoccupied RBD. The ELISA was then developed using a standard streptavidin-HRP and tetramethylbenzidine reaction. Unoccupied RBD allows for a positive reaction signal which is suppressed in the presence of bound competitive nanobody. NIH-CoVnb-112 inhibited ACE2 binding to each of the variants with a similar EC50 of 0.02 µg/mL (1.11 nM).
