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Identification of three conserved linear B cell epitopes on the SARS-CoV-2 spike protein

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posted on 05.08.2022, 16:41 authored by Aiping Wang, Yuanyuan Tian, Hongliang Liu, Peiyang Ding, Yumei Chen, Chao Liang, Yongkun Du, Dawei Jiang, Xifang Zhu, Jiajia Yin, Gaiping Zhang

Spike (S) glycoproteins is the most significant structural protein of SARS-CoV-2 and a key target for neutralizing antibodies. In light of the ongoing SARS-CoV-2 pandemic, identification and screening of epitopes of spike glycoproteins will provide vital progress in the development of sensitive and specific diagnostic tools. In the present study, NTD, RBD and S2 gene were inserted to the pcDNA3.1(+) vector and designed with N-terminal 6×His-tag for fusion expression in HEK293F cells by transient transfection. Six monoclonal antibodies (4G, 9E, 4B, 7D, 8F, 3D) were prepared using the expressed proteins by cell fusion technique. The characterization of mAbs were performed by indirect -ELISA, western blot and IFA. We designed 49 overlapping synthetized peptides cover the extracellular region of S protein which 6 amino acid residues were offset between adjacent (S1-S49). Peptides S12, S19 and S49 were identified as the immunodominant epitopes regions by the mAbs. These regions were further truncated and the peptides S12.2 286TDAVDCALDPLS297, S19.2 464FERDISTEIYQA475 and S49.4 1202ELGKYEQYIKWP1213 were identified as B- cell linear epitopes for the first time. Alanine scans showed that, the D467, I468, E471, Q474, A475 of the epitope S19.2 and K1205, Q1208, Y1209 of the epitope S49.4 were the core sites involved in the mAbs binding. Multiple sequence alignment analysis showed that these three epitopes were highly conserved among the variants of concern (VOCs) and variants of interest (VOIs). Taken together, the findings provide a potential material for rapid diagnosis methods of COVID-19.