Fig. 1: Screen and identify RBD-specific nanobodies.
From: A broad neutralizing nanobody against SARS-CoV-2 engineered from an approved drug
a Schematic of nanobody engineering. Sequence of the framework for caplacizumab are fixed (gray); the CDR1, CDR and CDR3, shown in pink, yellow and orange, respectively, are engineered for RBD specificity. The amino acid diversity of each position in the CDRs are indicated by one letter codes, that of highly variable loop in CDR3 is indicated by “X” representing the amino acid composition in the box. The residue numbers indicate the length diversity of highly variable loop in CDR3. b The scheme of screening. The caplacizumab engineering phage library was subjected to 3 rounds of solid phase biopanning against RBD-Fc, the RBD-specific VHHs were recombinantly expressed by PCR-based gene expression cassette strategy in high-throughput format. c Blocking ELISA to select nanobodies that can block hACE2 binding to RBD, smaller value reflects stronger blockage. Orange bar: hACE2-Fc as an internal control; Red bar: VHH72 as a positive control; Black bar: Non-reactive nanobody as a negative control. d EC50 from ELISA-based binding assay in (c). e chart of SPR results from Fig. S2a.
