title: Identification and characterization of novel neutralizing epitopes in the receptor-binding domain of SARS-CoV spike protein: revealing the critical antigenic determinants in inactivated SARS-CoV vaccine.
abstract: The spike (S) protein of severe acute respiratory syndrome coronavirus (SARS-CoV) is considered as a major antigen for vaccine design. We previously demonstrated that the receptor-binding domain (RBD: residues 318-510) of S protein contains multiple conformation-dependent neutralizing epitopes (Conf I to VI) and serves as a major target of SARS-CoV neutralization. Here, we further characterized the antigenic structure in the RBD by a panel of novel mAbs isolated from the mice immunized with an inactivated SARS-CoV vaccine. Ten of the RBD-specific mAbs were mapped to four distinct groups of conformational epitopes (designated Group A to D), and all of which had potent neutralizing activity against S protein-pseudotyped SARS viruses. Group A, B, C mAbs target the epitopes that may overlap with the previously characterized Conf I, III, and VI respectively, but they display different capacity to block the receptor binding. Group D mAb (S25) was directed against a unique epitope by its competitive binding. Two anti-RBD mAbs recognizing the linear epitopes (Group E) were mapped to the RBD residues 335-352 and 442-458, respectively, and none of them inhibited the receptor binding and virus entry. Surprisingly, most neutralizing epitopes (Groups A to C) could be completely disrupted by single amino acid substitutions (e.g., D429A, R441A or D454A) or by deletions of several amino acids at the N-terminal or C-terminal region of the RBD; however, the Group D epitope was not sensitive to the mutations, highlighting its importance for vaccine development. These data provide important information for understanding the antigenicity and immunogenicity of SARS-CoV, and this panel of novel mAbs can be used as tools for studying the structure of S protein and for guiding SARS vaccine design.
authors.affiliation: Lindsley F. Kimball Research Institute, New York Blood Center, 310 East 67th Street, New York, NY 10021, USA. yhe@nybloodcenter.org
authors.forename: Yuxian
authors.initials: Y
authors.lastname: He
authors.forename: Jingjing
authors.initials: J
authors.lastname: Li
authors.forename: Lanying
authors.initials: L
authors.lastname: Du
authors.forename: Xuxia
authors.initials: X
authors.lastname: Yan
authors.forename: Guangan
authors.initials: G
authors.lastname: Hu
authors.forename: Yusen
authors.initials: Y
authors.lastname: Zhou
authors.forename: Shibo
authors.initials: S
authors.lastname: Jiang
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology; D000914:Antibodies, Viral / Q000097:blood; D000956:Antigens, Viral / Q000737:chemistry / Q000276:immunology; D000939:Epitopes / Q000737:chemistry* / Q000276:immunology*; D008562:Membrane Glycoproteins / Q000737:chemistry* / Q000276:immunology*; D051379:Mice; D009500:Neutralization Tests; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D045473:Severe acute respiratory syndrome-related coronavirus / Q000737:chemistry* / Q000276:immunology*; D064370:Spike Glycoprotein, Coronavirus; D014759:Viral Envelope Proteins / Q000737:chemistry* / Q000276:immunology*; D014765:Viral Vaccines / Q000276:immunology*
chemical_list: D000911:Antibodies, Monoclonal; D000914:Antibodies, Viral; D000956:Antigens, Viral; D000939:Epitopes; D008562:Membrane Glycoproteins; D064370:Spike Glycoprotein, Coronavirus; D014759:Viral Envelope Proteins; D014765:Viral Vaccines; C578557:spike glycoprotein, SARS-CoV; C578553:spike protein, mouse hepatitis virus