Fig. 3: Design and characterization of bispecific antibodies (bsAbs).
a Schematic of four bispecific antibodies in IgG-ScFv format. The parental monoclonal antibodies that form the bispecific antibodies are color-coded: purple, 6-2C; orange, 10-5B; blue, 13-1C. b Binding affinity of bsAbs to RBDs of WT and Omicron BA.4/BA.5. Biotinylated SARS-CoV-2 RBDs were loaded onto the surface of SA biosensors. Individual antibodies were at a series of concentrations. The association and dissociation of response curves of the antibodies are shown. The gray lines represent the fitted curves based on the experimental data. Apparent dissociation constants (KD,app) are shown above each plot. c, d Competitive binding of parental monoclonal antibodies and bispecific antibodies. In c, the immobilized RBD complexed with parental monoclonal antibodies (first antibody) binds to bispecific antibodies (second antibody). In d, RBD–bsAbs prevent binding by their parental monoclonal antibodies. e Neutralization profile of SARS-CoV-2 pseudoviruses for the two bispecific antibodies. The number in the box indicates IC50 values. The color gradient indicates IC50 values ranging from 0 (white) to 10,000 ng/ml. The experiments were performed at least twice. Neutralization curves are shown in Supplementary Fig. 12. f Neutralizing activity of bispecific antibodies against live SARS-CoV-2 wild type, Beta, Delta, Omicron BA.1, and Omicron BA.2 variants. Authentic SARS-CoV-2 neutralization was performed using a cytopathic effect (CPE) assay. The curves were fitted by nonlinear regression (log [inhibitor] vs. normalized response, variable slope). The dashed line indicates a 50% reduction in viral infectivity. Data for each bsAb were obtained from a representative neutralization experiment. Mean ± s.d. of triplicates (BI-2C5B, BI-5B2C) or mean of duplicates (BI-2C1C, BI-1C2C) is shown. The experiment was replicated twice with similar results.
