Figure 4. Vaccine-elicited neutralizing antibodies target the RBD.

RBD-binding antibodies were adsorbed from sera from previously infected donors after receiving a single vaccine dose, or from uninfected donors after receiving two vaccine doses using Wuhan-Hu-1 RBD immobilized to magnetic beads. Antibody binding in undepleted or RBD-depleted serum from previously infected donors was measured to RBD at a 1:500 dilution (A), and S2P at a 1:4500 dilution (B) by ELISA as indicated. (C) The serum dilution resulting in 50% neutralization (ID₅₀) of the Wuhan-Hu-1 pseudovirus was measured in undepleted or RBD-depleted of serum from the previously SARS-CoV-2 infected donors in A and B. Antibody binding in undepleted and RBD-depleted and sera from uninfected vaccinated donors was measured to RBD at a 1:500 dilution (D), and S2P at a 1:500 dilution (E) by ELISA. (F) The percent neutralization of a 1:120 dilution of undepleted or RBD-depleted of serum from the donors in D and E was measured against the Wuhan-Hu-1 pseudovirus. Experiments were performed once.