Abstract
The ongoing COVID-19 pandemic caused by SARS-CoV-2 is a huge public health crisis for the globe. The receptor-binding domain (RBD) of SARS-CoV-2 spike (S) protein plays a vital role in viral infection and serves as a major target for developing neutralizing antibodies. In this study, the antibody response to the RBD of SARS-CoV-2 S protein was analyzed by a panel of sera from animals immunized with RBD-based antigens and four linear B-cell epitope peptides (R345, R405, R450 and R465) were revealed. The immunogenicity of three immunodominant peptides (R345, R405, R465) was further accessed by peptide immunization in mice, and all of them could induced potent antibody response to SARS-CoV-2 S protein, indicating that the three determinants in the RBD were immunogenic. We further generated and characterized monoclonal antibodies (15G9, 12C10 and 10D2) binding to these epitope peptides, and finely mapped the three immunodominant epitopes using the corresponding antibodies. Neutralization assays showed that all three monoclonal antibodies had neutralization activity. Results from IFA and western blotting showed that 12C10 was a cross-reactive antibody against both of SARS-CoV-2 and SARS-CoV. Results from conservative and structural analysis showed that 350VYAWN354 was a highly conserved epitope and exposed on the surface of SARS-CoV-2 S trimer, whereas 473YQAGSTP479 located in the receptor binding motif (RBM) was variable among different SARS-CoV-2 strains. 407VRQIAP412 was a highly conserved, but cryptic epitope shared between SARS-CoV-2 and SARS-CoV. These findings provide important information for understanding the humoral antibody response to the RBD of SARS-CoV-2 S protein and may facilitate further efforts to design SARS-CoV-2 vaccines and the target of COVID-19 diagnostic.
Highlights
Common coronaviruses (CoVs) have been circulating in humans for a long time, which usually cause mild to moderate diseases, like the common cold
Analysis of B-Cell Epitope Peptides of Antibodies in the Sera From Animals Immunized With receptor-binding domain (RBD)-Based Antigens
The linear B-cell epitope peptides recognized by sera from animals immunized with RBD-based antigens were screened using 22 overlapping peptides with 5 amino acids offsets spanning the RBD of SARS-CoV-2 S protein (GenBank: YP_009724390) (Figure 1A and Table 1)
Summary
Common coronaviruses (CoVs) have been circulating in humans for a long time, which usually cause mild to moderate diseases, like the common cold. SARS-CoV-2 has caused a global pandemic, namely the coronavirus disease in 2019. According to real-time data from Worldometer (updated on August 12, 2021), 220 countries and territories around the world have reported a total of 205,512,912 confirmed cases of the coronavirus COVID-19 and a death toll of 4,337,588 deaths (https://www.worldometers.info/coronavirus/countrieswhere-coronavirus-has-spread/). The first COVID-19 wave has never really ended in some countries, and a new COVID-19 surge is on track this fall and winter, meaning more severe COVID-19 cases and potentially higher mortality (https://www.cdc.gov/coronavirus/2019-ncov/covid-data/ covidview/index.html). Various modalities of vaccines against SARS-CoV-2, based on different routes and immunization procedures, have been approved for marketing worldwide [5]. The antigen epitopes in these vaccines are poorly understood
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
