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Abstract The SARS-CoV-2 nucleocapsid protein (NP) is an important indicator for the virus infection, highlighting the crucial role of NP-specific monoclonal antibodies (mAbs) used in multiple biochemical assays and clinical diagnosis for detecting the NP antigen. Here, we reported a pair of noncompeting human NP-specific mAbs, named P301-F7 and P301-H5, targeting two distinct linear epitopes on SARS-CoV-2 or SARS-CoV. We evaluated the application of P301-F7 in the analysis of enzyme linked immunosorbent assay, western blot, flow cytometry, immunofluorescence, and focus reduction neutralization test. We for the first time report a broad mAb effectively recognizing various live viruses of SARS-CoV-2 variants including Alpha, Beta, Delta, and Omicron, indicating a wide range of application prospects.

Abstract The current COVID-19 pandemic caused by constantly emerging SARS-CoV-2 variants still poses a threat to public health worldwide. Effective next-generation vaccines and optimized booster vaccination strategies are urgently needed. Here, we sequentially immunized mice with a SARS-CoV-2 wild-type inactivated vaccine and a heterologous mutant RBD vaccine, and then evaluated their neutralizing antibody responses against variants including Beta, Delta, Alpha, Iota, Kappa, and A.23.1. These data showed that a third booster dose of heterologous RBD vaccine especially after two doses of inactivated vaccines significantly enhanced the GMTs of nAbs against all SARS-CoV-2 variants we tested. In addition, the WT and variants all displayed good cross-immunogenicity and might be applied in the design of booster vaccines to induce broadly neutralizing antibodies.

Abstract The emergence and rapid spread of the B.1.1.7 lineage (VOC-202012/01) SARS-CoV-2 variant has aroused global concern. The N501Y substitution is the only mutation in the interface between the RBD of B.1.1.7 and ACE2, raising concerns that its recognition by neutralizing antibodies may be affected. Here, we assessed the neutralizing activity and binding affinity of a panel of 12 monoclonal antibodies against the wild type and N501Y mutant SARS-CoV-2 pseudovirus and RBD protein, respectively. We found that the neutralization activity and binding affinity of most detected antibodies (10 out of 12) were unaffected, although the N501Y substitution decreased the neutralizing and binding activities of CB6 and increased that of BD-23. These findings could be of value in the development of therapeutic antibodies.