Fig. 3: Fu2 cross-neutralizes SARS-CoV and SARS-CoV-2 variants of concern.

a SARS-CoV S pseudotyped lentivirus (PSV) was incubated with the indicated constructs before infecting HEK293T-ACE2 cells, and neutralization is shown compared to untreated PSV. Error bars indicated means values + SD. b, c Structural basis of SARS-CoV cross-neutralization by Fu2. Structural alignment of SARS-CoV-2 Spike (RBD bound Fu2) with SARS-CoV RBD (PDB:6ACD). Residues of interface-major and interface-minor shown as sticks, divergent residues are labelled. d, e Comparison of Fu2 neutralization of founder PSV with delta (d) or beta (e) PSV. Error bars indicated means values + SD. f Assessment of Fu2-RBD interaction in RBD variants. In silico mutational analyses of RBD residues and probable impact on Fu2 binding. Fu2 is shown in red and variant residues are indicated. g, h PRNTs with clinical isolates of SARS-CoV-2. 100 plaque-forming units (PFU) of SARS-CoV-2²⁷ or the beta variant¹ were incubated with dilution series of the indicated nanobody constructs for 1 h at 37 °C before infecting monolayers of Vero E6 cells. Plaques were quantified 72 h post infection. Neutralization representing the reduction of plaques relative to the control wells is shown. Error bars represent mean + SD across three replicate experiments. Source data are provided as a Source Data file for a, d, e, g, and h.