Fig. 3: Homotypic and heterotypic neutralization of key SARS-CoV-2 lineages by antibody.

The potency of neutralization was determined by a focus-forming unit microneutralization assay against authentic virus of prototype B lineage and isolates of B.1.1.7 and B.1.351. a A cartoon of a ‘squirrel’ illustrating the receptor-binding domain (RBD). Markings on the squirrel show the epitopes of the RBD antibodies used in this study (classes 1–4⁴⁷). Neutralization by the panel of monoclonal antibodies binding to four distinct epitopes of RBD (upper left). A space-filling model of prototype RBD (PDB 6YZ5) created in PyMOL, shows the residue of the mutations present in the B.1.1.7 and B.1.351 lineages in blue (upper middle and upper right; same aspect and reverse aspect as the space-filling model, respectively). b Neutralization by the international reference plasma NIBSC 20/130³⁸, nominally NT50 = 1/1000. The mean number of foci ± SD relative to a no-antibody control is plotted against the reciprocal of the respective serum dilution. Data were fitted by non-linear regression in GraphPad Prism 9 to the Hill Equation, with TOP and BOTTOM constrained to 100 and 0%, respectively. Where a significant fit was obtained, it is represented by a trend line on the respective plot, and NT50 values used in Supplementary Fig. 1 and main results. NT50 against B established in our assay indicated by the vertical dashed line with grey bars indicating the 95% confidence interval. c Neutralization by convalescent sera from asymptomatic participants (left) and those with mild symptoms (right) against B, B.1.1.7 and B.1.351 isolates. A Tukey’s multiple comparison test was performed for each serum group, comparing mean NT50 response to each virus isolate. P values of all comparisons are displayed in the figures. d Neutralization by sera from recipients of a single dose (left) and both prime and boost doses (right) of BNT162b2 vaccine. e Homotypic and heterotypic neutralization potencies of the three sources of antibody against the three isolates, shown by individual (dots) and sub-population mean and SD of NT50 values shown with error bars (upper panel). For each isolate, pairwise comparisons of average NT50 estimates were made between groups of serum using the Kolmogorov–Smirnov non-parametric test. P values for the r statistic are shown (lower panel), both numerically and symbolically. P > 0.05 in green and ‘ns’. No results for 0.05 > P > 0.01. 0.01 > P > 0.001 in yellow and **P < 0.001 in red and ****. Vaccinees post-prime n = 11; vaccinees post-boost n = 25; asymptomatic COVID-19 convalescents n = 12; mild COVID-19 convalescents n = 13. MNA tests were performed in quadruplicate for all samples. Each plate contained serum-free controls for normalization of results.