Fig. 4 |. Neutralizing activity of anti-SARS-CoV-2 RBD monoclonal antibodies.

a, SARS-CoV-2 pseudovirus neutralization assay. IC₅₀ values for all antibodies measured at 1.3 months¹, and 122 selected antibodies measured at 6.2 months. Antibodies with IC₅₀ values above 1 μg ml⁻¹ were plotted at 1 μg ml⁻¹. Mean of two independent experiments. Red bar indicates geometric mean. Statistical significance was determined using two-tailed Mann–Whitney U-test. b, IC₅₀ values for 52 antibodies appearing at 1.3 and 6.2 months. Red bar indicates geometric mean. Statistical significance was determined using two-tailed Wilcoxon matched-pairs signed-rank test. c, IC₅₀ values for 5 pairs of monoclonal antibody clonal relatives obtained after 1.3 or 6.2 months for neutralization of wild-type and mutant SARS-CoV-2 pseudovirus. Antibody identifiers of the 1.3-month–6.2-month monoclonal antibody pairs as indicated. Bold styling denotes antibody pairs with substantial increase in neutralizing activity after 6.2 months. d, Graph shows the normalized relative luminescence units (RLU) for cell lysates of 293T cells expressing ACE2, 48 h after infection with SARS-CoV-2 pseudovirus containing wild-type RBD or one of three mutant RBDs (Q493R, E484G and R346S) in the presence of increasing concentrations of one of two monoclonal antibodies C144 (1.3 months) (dashed lines) or C051 (6.2 months) (solid lines). Experiments were performed at least twice. e, C051 binding model. Surface representation of two adjacent ‘down’ RBDs (RBD_A and RBD_B) on a spike trimer, with the C144 epitope on the RBDs highlighted in cyan and positions of amino acid mutations that accumulated in C051 compared to the parent antibody C144 highlighted as stick side chains on a Cα atom representation of C051 V_HV_L binding to adjacent RBDs. The C051 interaction with two RBDs was modelled on the basis of a cryo-electron microscopy structure of C144 Fab bound to spike trimer¹⁸. HC, heavy chain; LC, light chain.