Fig. 6. IgA dimers bind to RBD and neutralize authentic SARS-CoV-2 more potently than monomers in vitro.

(A) Graphs depict binding affinity measurements of individual IgA monomers and corresponding dimers. (B) The dissociation constant (K_D) values of monomers and dimers were compared. Horizontal lines indicate mean (n = 7). (C and D) Normalized relative luminescence values (RLU) for cell lysates of 293T_ACE2 cells after infection with SARS-CoV-2 pseudovirus (C) or normalized percentage of SARS-CoV-2–positive Vero E6 cells 48 hours after infection with SARS-CoV-2 authentic virus (D). Values obtained in the absence of antibody are plotted at x = 0.1 to be visible on a log scale in the presence of increasing concentrations of indicated monoclonal antibodies in their monomeric or dimeric form. Four-parameter nonlinear regression curve fits of normalized data are shown. (E) IC₉₀ values were compared between monomer to dimers after normalization to number of antibody binding sites. For (B), Student’s t test was used.