Neutralizing antibodies and combinations recognize the conserved epitope of SARS-CoV-2 S protein

Objective Identify the recognition epitopes of antibodies and detect their neutralizing activity to explore possible antibody combinations.Methods The binding epitope of the antibody and whether the epitope overlaps were determined by capturing ELISA and Bio-Layer Interferometry(BLI). The neutralizing activity of antibodies and combinations against XBB.1.16 was detected using a pseudovirus neutralization assay and to explore their changes in neutralizing activity.Results 2F8, 808 and 846 were obtained from the previous study. 2F8 and 808 targeted the receptor-binding domain (RBD) of SARS-CoV-2 with EC50s of 0.01654 μg/ml and 0.01871 μg/ml. 846 targeted the N-terminal domain (NTD) with EC50 of 0.02944 μg/ml. It was clear that the binding epitopes of three antibodies did not overlap with each other at all. 2F8 can potently neutralize SARS-CoV-2 wild type (WT) with an IC50 of 0.0037 μg/ml. However, it maintained a high level of neutralization against Omicron BA4/5, BF7 and XBB.1.16 with IC50s ranging from 0.0028 μg/ml-0.0048 μg/ml. 2F8, 808 and 846, which had weaker neutralizing activity, formed the combinations of 2F8/808 and 2F8/808/846. Respectively, their IC50s against XBB.1.16 were 0.0079 and 0.0107 μg/ml, which potently neutralized XBB.1.16.Conclusion In this study, we successfully obtained 2F8, which can recognize the conserved epitope of SARS-CoV-2 S protein. And it could effectively neutralize WT and three Omicron subvariants detected. 2F8, 808 and 846 can synergistically and potently neutralize the XBB.1.16. The antibody combinations (2F8/808 and 2F8/808/846) provide a means of coping with immune evasion of new variants.