Fig. 3

Examination of RBD-binding abilities and epitope mapping of RBD-hAb-B22, -B23, -B25 and -B34 antibodies. A Binding activities of four RBD-hAbs were measured against RBD proteins of Alpha, Beta, Gamma, Delta, Omicron BA.5, BQ.1.1 and XBB.1.5 by ELISA. Abs were threefold serially diluted from 900 to 0.4 ng/mL. B Epitope mapping by mutagenesis assays. HEK293T cells transiently expressing exogenous wild-type (WT) or mutant RBD proteins with single or combinatorial alanine mutations. Binding of the four RBD-hAbs to RBD mutants was examined by cellular ELISA. The results were normalized and are presented as percentages. C The four RBD-hAbs were used as primary antibodies for detection of recombinant BA.5 RBD and spike protein-His in Western blots. Anti-6 × His mAb was used as a positive control. Normal human IgG (NhIgG) was used as a negative control