Fig. 6.

Identification of potentially important amino acids by site-directed mutagenesis for the binding of the mAbs with the RBD. ELISA was used to measure the binding activity of the mAbs with the RBD or with mutated RBD generated from supernatants of HEK293T cells transfected with RBD-Fc plasmid or mutated RBD-Fc plasmids. ‘+’: supernatant of RBD-Fc plasmid transfection, ‘RBD-Fc’: purified RBD-Fc protein dissolved in distilled water at a concentration of 20 μg/ml, ‘−’: supernatant of cells without transfection. ‘VAD’ etc.: five mutated RBD-Fc proteins (selected amino acids mutated to alanine) expressed in cell culture supernatants. (A) Reaction measured by mAb S-9-11. (B) Reaction measured by mAb N-176-15.