Fig. 2: Neutralization of first-wave and 501Y.V2 variants by convalescent plasma elicited by first-wave and 501Y.V2 infections.

a, Focus formation by first-wave and 501Y.V2 virus variants. To obtain similar focus sizes, the incubation time with 501Y.V2 was reduced to 18 h. Scale bar, 2 mm. b, c, A representative focus-forming assay using plasma from participant 039-13-0015, who was infected with a first-wave variant (b), and participant 039-02-0033, who was infected with 501Y.V2 (c). Columns are plasma dilutions—which range from 1:25 to 1:1,600—a plasma pool from three uninfected individuals (control) and a no-plasma control (no plasma). d, Quantified neutralization per participant for the first-wave virus variants (left two plots) and 501Y.V2 (right two plots). Red points are neutralization by the A02051 neutralizing antibody (NAb), grey points show neutralization by the plasma pool from uninfected individuals (control), green points indicate neutralization by plasma from the participant who was infected with the S(E484K)-mutant virus, orange points are neutralization by plasma from participants who were infected by first-wave variants, and blue points are neutralization by plasma from participants who were infected with 501Y.V2. Data are mean and s.e.m. of 3–4 independent experiments per plasma sample of participants convalescing from infection with the first-wave (n = 14) or 501Y.V2 (n = 6) virus variants or 10 independent experiments for A02051 and uninfected plasma controls. Solid lines of the corresponding colour are fitted values using a sigmoidal equation. From left to right, the plots show the following analyses. First plot, neutralization of the first-wave virus by the neutralizing antibody A02051 (PRNT₅₀ = 6.5 ng ml⁻¹; 95% confidence intervals, 3.9–9.1 ng ml⁻¹) and control plasma. Second plot, neutralization of first-wave virus by plasma from participants convalescing from infection with first-wave or 501Y.V2 viruses. Third plot, neutralization of the 501Y.V2 variant by the neutralizing antibody A02051 (PRNT₅₀ = 3.5 ng ml⁻¹ (2.9–4.1 ng ml⁻¹)) and control plasma. Fourth plot, neutralization of the 501Y.V2 variant by plasma from participants convalescing from infection with first-wave or 501Y.V2 viruses. e, Decrease in PRNT₅₀ in cross-neutralization. Left, neutralization of first-wave or 501Y.V2 virus variants by first-wave plasma. Right, neutralization of 501Y.V2 or first-wave virus variants by second-wave plasma. The fold change was calculated as PRNT₅₀ of the homologous virus/PRNT₅₀ of the heterologous virus and ranged from 3.2 to 41.9 for first-wave plasma, and from 1.6 to 7.2 for second-wave plasma. The fold change in PRNT₅₀ elicited by the S(E484K)-mutant virus was excluded.