Fig. 4: IgA isotype switch enhances MAb362 neutralization of SARS-CoV-2.

MAb362 antibody-mediated neutralization of luciferase-encoding pseudovirions with spike proteins of SARS-CoV a and SARS-CoV-2 b. SARS-CoV and SARS-CoV-2 pseudovirions pre-incubated with serial dilutions of MAb362 were used to infect 293 cells expressing ACE2 receptor. Pseudoviral transduction was measured by luciferase activities in cell lysates 48 h post transduction to calculate neutralization (%) relative to non-antibody-treated controls. IC₅₀ values were calculated by nonlinear regression analysis using Prism version 8.1.1. Isotype switching improved SARS-CoV-2 IC50. Data are plotted as the mean ± s.d. from n = 3 independent experiments a, b. c Dose–response curve for PRNT with MAb362 at a starting concentration of 50 µg mL⁻¹ titrated 1:2. MAb362 sIgA had a 50% endpoint titer of 9.54 ± 5.88 µg mL⁻¹ calculated by Spearman–Kärber method, from n = 2 biologically independent experiments. Representative data are plotted with a Probit mid-point analysis curve ± 95% CI from one experiment with n = 2 technical replicates, using R programming language v3.5.3 and Library ggplot2 v3.3.0 for statistical computing and graphics^47,48. Source data are provided as a Source Data file a–c.