title: Recombinant Receptor-Binding Domains of Multiple Middle East Respiratory Syndrome Coronaviruses (MERS-CoVs) Induce Cross-Neutralizing Antibodies against Divergent Human and Camel MERS-CoVs and Antibody Escape Mutants.
abstract: Middle East respiratory syndrome coronavirus (MERS-CoV) binds to cellular receptor dipeptidyl peptidase 4 (DPP4) via the spike (S) protein receptor-binding domain (RBD). The RBD contains critical neutralizing epitopes and serves as an important vaccine target. Since RBD mutations occur in different MERS-CoV isolates and antibody escape mutants, cross-neutralization of divergent MERS-CoV strains by RBD-induced antibodies remains unknown. Here, we constructed four recombinant RBD (rRBD) proteins with single or multiple mutations detected in representative human MERS-CoV strains from the 2012, 2013, 2014, and 2015 outbreaks, respectively, and one rRBD protein with multiple changes derived from camel MERS-CoV strains. Like the RBD of prototype EMC2012 (EMC-RBD), all five RBDs maintained good antigenicity and functionality, the ability to bind RBD-specific neutralizing monoclonal antibodies (MAbs) and the DPP4 receptor, and high immunogenicity, able to elicit S-specific antibodies. They induced potent neutralizing antibodies cross-neutralizing 17 MERS pseudoviruses expressing S proteins of representative human and camel MERS-CoV strains identified during the 2012-2015 outbreaks, 5 MAb escape MERS-CoV mutants, and 2 live human MERS-CoV strains. We then constructed two RBDs mutated in multiple key residues in the receptor-binding motif (RBM) of RBD and demonstrated their strong cross-reactivity with anti-EMC-RBD antibodies. These RBD mutants with diminished DPP4 binding also led to virus attenuation, suggesting that immunoevasion after RBD immunization is accompanied by loss of viral fitness. Therefore, this study demonstrates that MERS-CoV RBD is an important vaccine target able to induce highly potent and broad-spectrum neutralizing antibodies against infection by divergent circulating human and camel MERS-CoV strains.
  
  
  OBJECTIVE
  MERS-CoV was first identified in June 2012 and has since spread in humans and camels. Mutations in its spike (S) protein receptor-binding domain (RBD), a key vaccine target, have been identified, raising concerns over the efficacy of RBD-based MERS vaccines against circulating human and camel MERS-CoV strains. Here, we constructed five vaccine candidates, designated 2012-RBD, 2013-RBD, 2014-RBD, 2015-RBD, and Camel-RBD, containing single or multiple mutations in the RBD of representative human and camel MERS-CoV strains during the 2012-2015 outbreaks. These RBD-based vaccine candidates maintained good functionality, antigenicity, and immunogenicity, and they induced strong cross-neutralizing antibodies against infection by divergent pseudotyped and live MERS-CoV strains, as well as antibody escape MERS-CoV mutants. This study provides impetus for further development of a safe, highly effective, and broad-spectrum RBD-based subunit vaccine to prevent MERS-CoV infection.
authors: Lindsley F. Kimball Research Institute, New York Blood Center, New York, New York, USA.|State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing, China.
authors: Wanbo
authors: W
authors: Tai
authors: Lindsley F. Kimball Research Institute, New York Blood Center, New York, New York, USA.|State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing, China.
authors: Yufei
authors: Y
authors: Wang
authors: Department of Microbiology, University of Iowa, Iowa City, Iowa, USA.
authors: Craig A
authors: CA
authors: Fett
authors: State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing, China.
authors: Guangyu
authors: G
authors: Zhao
authors: Department of Pharmacology, University of Minnesota Medical School, Minneapolis, Minnesota, USA.
authors: Fang
authors: F
authors: Li
authors: Department of Microbiology, University of Iowa, Iowa City, Iowa, USA.
authors: Stanley
authors: S
authors: Perlman
authors: Lindsley F. Kimball Research Institute, New York Blood Center, New York, New York, USA.|Key Laboratory of Medical Molecular Virology of Ministries of Education and Health, Basic Medical College and Institute of Medical Microbiology, Fudan University, Shanghai, China.
authors: Shibo
authors: S
authors: Jiang
authors: State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing, China yszhou@bmi.ac.cn ldu@nybc.org.
authors: Yusen
authors: Y
authors: Zhou
authors: Lindsley F. Kimball Research Institute, New York Blood Center, New York, New York, USA yszhou@bmi.ac.cn ldu@nybc.org.
authors: Lanying
authors: L
authors: Du
mesh_terms: D000818:Animals; D057134:Antibodies, Neutralizing / Q000096:biosynthesis* / Q000737:chemistry; D000914:Antibodies, Viral / Q000096:biosynthesis* / Q000737:chemistry; D001665:Binding Sites; D002162:Camelus; D018352:Coronavirus Infections / Q000276:immunology / Q000517:prevention & control* / Q000821:virology; D003429:Cross Reactions; D018819:Dipeptidyl Peptidase 4 / Q000737:chemistry / Q000235:genetics / Q000276:immunology*; D005260:Female; D015870:Gene Expression; D006801:Humans; D057131:Immune Evasion; D051379:Mice; D008807:Mice, Inbred BALB C; D065207:Middle East Respiratory Syndrome Coronavirus / Q000235:genetics / Q000276:immunology; D008958:Models, Molecular; D009154:Mutation; D009500:Neutralization Tests; D010957:Plasmids / Q000737:chemistry / Q000378:metabolism; D011485:Protein Binding; D054730:Protein Interaction Domains and Motifs; D017433:Protein Structure, Secondary; D011991:Receptors, Virus / Q000737:chemistry / Q000235:genetics / Q000276:immunology; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000276:immunology; D064370:Spike Glycoprotein, Coronavirus / Q000737:chemistry / Q000235:genetics / Q000276:immunology*; D014611:Vaccination; D014765:Viral Vaccines / Q000008:administration & dosage* / Q000096:biosynthesis
chemical_list: D057134:Antibodies, Neutralizing; D000914:Antibodies, Viral; D011991:Receptors, Virus; D011994:Recombinant Proteins; D064370:Spike Glycoprotein, Coronavirus; D014765:Viral Vaccines; C042807:DPP4 protein, human; D018819:Dipeptidyl Peptidase 4
keywords: MERS; MERS-CoV; antibody escape mutants; cross-neutralization; multiple strains; receptor-binding domain; spike protein