The newly emerged Middle East respiratory syndrome coronavirus (MERSCoV) continues to infect humans and camels, calling for efficient, cost-effective, and broad-spectrum strategies to control its spread. Nanobodies (Nbs) are single-domain antibodies derived from camelids and sharks and are potentially cost-effective antivirals with small size and great expression yield. In this study, we developed a novel neutralizing Nb (NbMS10) and its human-Fc-fused version (NbMS10-Fc), both of which target the MERS-CoV spike protein receptor-binding domain (RBD). We further tested their receptor-binding affinity, recognizing epitopes, cross-neutralizing activity, half-life, and efficacy against MERS-CoV infection. Both Nbs can be expressed in yeasts with high yield, bind to MERS-CoV RBD with high affinity, and block the binding of MERS-CoV RBD to the MERS-CoV receptor. The binding site of the Nbs on the RBD was mapped to be around residue Asp539, which is part of a conserved conformational epitope at the receptor-binding interface. NbMS10 and NbMS10-Fc maintained strong cross-neutralizing activity against divergent MERS-CoV strains isolated from humans and camels. Particularly, NbMS10-Fc had significantly extended half-life in vivo; a single-dose treatment of NbMS10-Fc exhibited high prophylactic and therapeutic efficacy by completely protecting humanized mice from lethal MERS-CoV challenge. Overall, this study proves the feasibility of producing cost-effective, potent, and broad-spectrum Nbs against MERS-CoV and has produced Nbs with great potentials as anti-MERS-CoV therapeutics.
Bibliographical noteFunding Information:
This study was supported by the National Key Plan for Scientific Research and Development of China (2016YFD0500306, NSFC81571983); the Technology Innovation Fund in China (grant 3407049), the State Key Laboratory of Pathogen and Biosecurity (grant SKLPBS1704 [to G.Z. and Y.Z.]); NIH grants R01AI137472, R21AI109094, and R21AI128311 (to S.J. and L.D.); NIH grants R01AI089728 and R01AI110700 (to F.L.); and NIH grant R01AI139092 (to S.J., F.L., and L.D.). The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication. The authors declare no competing interests.
© 2018 American Society for Microbiology. All Rights Reserved.
- Protective efficacy
- Receptor-binding domain
- Spike protein