FIG 1.

MAb binding specificity and neutralization potency. (A) Binding specificity. MAbs isolated from immunized NHPs and a MERS survivor were assayed by ELISA for binding to soluble receptor-binding domain (RBD) or S1 protein. RBD-specific MAbs (in red) bound to both RBD and S1 proteins, while S1-specific MAbs (in blue) bound only to S1. (B) Neutralization potency. Neutralization activity was measured using a MERS-CoV EMC S-pseudotyped lentivirus neutralization assay. NHP MAbs are shown in the left graph and human MAbs in the right graph (two NHP RBD-specific MAbs in black were included for comparison). Percent neutralization at the different MAb concentrations is shown. Data points represent the means of triplicate replicates with standard errors. (C) IC₅₀, IC₈₀, and IC₉₀ neutralization titers. ^aIC values represent average results from two technical replicates of neutralization testing using a pseudovirion entry assay or plaque reduction neutralization testing (PRNT). ^bThe PRNT IC₅₀ for MAb JC57-13 was not available (N/A), as >50% neutralization was obtained at the lowest concentration of MAb tested, 0.0032 μg ml⁻¹.