Highly Specific Monoclonal Antibodies Against SARS-CoV-2 Nucleocapsid Antigen for Accurate Diagnosis of COVID-19

The ongoing COVID-19 pandemic is a major global public health concern.  Although rapid point of care testing for detecting viral antigen is important for management the outbreak, none of current antigen detection kits provide a reliable diagnosis due to the lack of a specific monoclonal antibody (mAb) against SARS-CoV-2. In our current study, we produced mAbs exclusively react with SARS-CoV-2 and exhibited no cross-reactivity with other human coronaviruses including SARS-CoV. Molecular modeling revealed that the mAbs bound to epitopes present on the exterior surface of the nucleocapsid, encompassing their scope for detecting SARS-CoV-2 in clinical samples. We further selected the optimal pair of anti-SARS-CoV-2 NP mAbs for designing ELISA and immunochromatographic assay. An integrated bioinformatics analysis revealed that our mAbs could comprehensively detect divergent strains of SARS-CoV-2. Due to the high redundancy and absence of cross-reactivity, our newly developed mAbs would be instrumental for developing reliable diagnosis kits for COVID-19. Funding: This work was supported in part by Japan Agency for Medical Research and Development (AMED, Grant number: JP19fk0108110 and JP20he0522001), and by Health Labour Sciences research grant from The Ministry of Health Labour and Welfare. Conflict of Interest: The authors have no conflicts of interest directly relevant to the content of this article. YY, SK, KS and DA is a current employee of Kanto Chemical Co., Inc. Ethical Approval: This study was approved by the Institutional Review Board of Yokohama City University (IRB No. B200800106), and the protocols used in the study were approved by the ethics committee.