Fig. 4: SNV-42 neutralization is dependent on bivalency and occurs by combination of receptor blocking and fusion inhibition.

a, Representative neutralization curves of IgG1 and Fab forms of SNV-42 to VSV/SNV determined by RTCA using the Vero CCL-81 cell line. IC₅₀ values were calculated on the basis of a nonlinear regression and error bars denote mean ± s.d. The assay was performed three independent times with similar results. b, Representative affinity curves of the F(ab′)2 and F(ab) form of SNV-42 for binding to SNV Gn^H, measured by bio-layer interferometry. Representative curves and K_D values are shown for SNV-42 F(ab), while the K_D value for SNV-42 F(ab′)2 could not be determined because the K_off could not be measured. Dashed line indicates the dissociation step at 300 s. c, sEC1-EC2 blocking activity of neutralizing antibodies determined through a flow cytometric assay in which mAbs were added at saturating concentration before the addition of the soluble PCDH-1 domain labelled with Alexa Fluor 647 dye. High (50 µg ml⁻¹), medium (10 µg ml⁻¹) or low (0.5 µg ml⁻¹) mAb concentrations were tested. Two-way analysis of variance (ANOVA) with Dunnett’s multiple comparisons, ****P < 0.0001; NS, not significant. The data are shown as mean ± s.d., n = 9 technical replicates. The assay was performed two independent times with similar results. d, FFWO assay testing VSV/SNV post-attachment antibody neutralization in permissive (pH 5.5) conditions at 10 µg ml⁻¹. Vero CCL-81 cells were used and GFP expression was measured to determine relative infectivity. The data are shown as mean ± s.d. of technical replicates, n = 9. The assay was performed two independent times with similar results. One-way ANOVA with Dunnett’s multiple comparisons, ****P < 0.0001.