Potent Neutralization of MERS-CoV by Human Neutralizing Monoclonal Antibodies to the Viral Spike Glycoprotein

Abstract

The recently identified Middle East respiratory syndrome coronavirus (MERS-CoV) causes severe and fatal acute respiratory illness in humans. However, no prophylactic and therapeutic agents specifically against MERS-CoV are currently available. Entry of MERS-CoV into target cells depends on binding of the receptor binding domain (RBD) of the viral envelope spike glycoprotein to the cellular receptor dipeptidyl peptidase 4 (DPP4). We report the isolation and characterization of two potent human RBD-specific neutralizing monoclonal antibodies (MERS-4 and MERS-27) derived from single-chain variable region fragments of a nonimmune human antibody library. MERS-4 and MERS-27 inhibited infection of both pseudotyped and live MERS-CoV with IC50 (half-maximal inhibitory concentration) at nanomolar concentrations. MERS-4 also showed inhibitory activity against syncytia formation mediated by interaction between MERS-CoV spike glycoprotein and DPP4. Combination of MERS-4 and MERS-27 demonstrated a synergistic effect in neutralization against pseudotyped MERS-CoV. Biochemical analysis indicated that MERS-4 and MERS-27 blocked RBD interaction with DPP4 on the cell surface. MERS-4, in particular, bound soluble RBD with an about 45-fold higher affinity than DPP4. Mutagenesis analysis suggested that MERS-4 and MERS-27 recognized distinct regions in RBD. These results suggest that MERS-4 and MERS-27 are RBD-specific potent inhibitors and could serve as promising candidates for prophylactic and therapeutic interventions against MERS-CoV infection.

Pre- and postexposure efficacy of fully human antibodies against Spike protein in a novel humanized mouse model of MERS-CoV infection

“…For our studies, we selected a panel of three antibodies with published variable domain sequences, which were reported to potently neutralize MERS-CoV and bind to diverse epitopes. The published sequences for antibodies 3B12, MERS-4, and MERS-27 (27,32) were cloned onto human IgG1 constant domains, then expressed and purified similarly to REGN3051 and REGN3048. We tested the three purified antibodies for binding to MERS S protein, blockade of the S protein-DPP4 interaction, and published neutralization properties (Fig.…”

Human Neutralizing Antibodies Against Mers Coronavirus: Implications for Future Immunotherapy

“…With a yeast displayed scFv library and purified RBD as panning target, Jiang et al identified two antibodies (MERS-4 and MERS-27) that can neutralize MERS-CoV infection as well as inhibit syncytia formation [13]. These two mAbs bind to RBD with nanomolar binding affinities.…”

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“…Human monoclonal neutralising antibodies and convalescent sera from recovered patients might be useful for treatment if delivered in a timely fashion 91,101,102 , an exploratory post-hoc meta-analysis of studies of SARS and severe influenza showed a significant reduction of mortality following antibody treatment compared with placebo or no treatment 103 . Systemic corticosteroids have been used empirically in some patients to dampen immune pathological host responses, although no survival benefit has been reported 95 .…”