Functional mapping of B-cell linear epitopes 1 of SARS-CoV-2 in COVID-19 convalescent population

ABSTRACT

Pandemic SARS-CoV-2 has infected over 10 million people and caused over 500,000 mortalities. Vaccine development is in urgent need to stop the pandemic. Despite great progresses on SARS-CoV-2 vaccine development, the efficacy of the vaccines remains to be determined. Deciphering the interactions of the viral epitopes with their elicited neutralizing antibodies in the convalescent COVID-19 population inspires the vaccine development. In this study, we devised a peptide array composed of 20-mer overlapped peptides of spike (S), membrane (M) and envelope (E) proteins, and performed a screening with 120 COVID-19 convalescent serums and 24 non-COVID-19 serums. We identified five SARS-CoV-2-specific dominant epitopes that reacted with above 40% COVID-19 convalescent serums. Epitopes in the receptor-binding domain (RBD) of S ill reacted with the convalescent serums. Of note, two peptides non-specifically interacted with most of the non-COVID-19 serums. Neutralization assay indicated that only five serums completely blocked viral infection at the dilution of 1200. By using a peptide-compete neutralizing assay, we found that three dominant epitopes partially competed the neutralization activity of several convalescent serums, suggesting antibodies elicited by these epitopes played an important role in neutralizing viral infection. The epitopes we identified in this study may serve as vaccine candidates to elicit neutralizing antibodies in most vaccinated people or specific antigens for SARS-CoV-2 diagnosis.