A Conformation-Dependent Neutralizing Monoclonal Antibody Specifically Targeting Receptor-Binding Domain in Middle East Respiratory Syndrome Coronavirus Spike Protein

Prophylactic and therapeutic strategies are urgently needed to combat infections caused by the newly emerged Middle East respiratory syndrome coronavirus (MERS-CoV). Here, we have developed a neutralizing monoclonal antibody (MAb), designated Mersmab1, which potently blocks MERS-CoV entry into human cells. Biochemical assays reveal that Mersmab1 specifically binds to the receptor-binding domain (RBD) of the MERS-CoV spike protein and thereby competitively blocks the binding of the RBD to its cellular receptor, dipeptidyl peptidase 4 (DPP4). Furthermore, alanine scanning of the RBD has identified several residues at the DPP4-binding surface that serve as neutralizing epitopes for Mersmab1. These results suggest that if humanized, Mersmab1 could potentially function as a therapeutic antibody for treating and preventing MERS-CoV infections. Additionally, Mersmab1 may facilitate studies of the conformation and antigenicity of MERS-CoV RBD and thus will guide rational design of MERS-CoV subunit vaccines.