Highly specific monoclonal antibodies and epitope identification against SARS-CoV-2 nucleocapsid protein for antigen detection tests

Yamaoka, Yutaro; Miyakawa, Kei; Jeremiah, Sundararaj Stanleyraj; Funabashi, Rikako; Okudela, Koji; Kikuchi, Sayaka; Katada, Junichi; Wada, Atsuhiko; Takei, Toshiki; Nishi, Mayuko; Shimizu, Kohei; Ozawa, Hiroki; Usuku, Shuzo; Kawakami, Chiharu; Tanaka, Nobuko; Morita, Takeshi; Hayashi, Hiroyuki; Mitsui, Hideaki; Suzuki, Keita; Aizawa, Daisuke; Yoshimura, Yukihiro; Miyazaki, Tomoyuki; Yamazaki, Etsuko; Suzuki, Tadaki; Kimura, Hirokazu; Shimizu, Hideaki; Okabe, Nobuhiko; Hasegawa, Hideki; Ryo, Akihide

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 of the outbreak, the current antigen tests are less sensitive than nucleic acid testing. In our current study, we produce monoclonal antibodies (mAb) that exclusively react with SARS-CoV-2 and exhibit no cross-reactivity with other human coronaviruses including SARS-CoV. Molecular modeling suggest that the mAbs bind to epitopes present on the exterior surface of the nucleocapsid, making them suitable for detecting SARS-CoV-2 in clinical samples. We further select the optimal pair of anti-SARS-CoV-2 NP mAbs using ELISA, and then use this mAb pair to develop immunochromatographic assay augmented with silver amplification technology. Our mAbs recognize the variants of concern (501Y.V1-V3) that are currently in circulation. Due to their high performance, the mAbs of this study can serve as good candidates for developing antigen detection kits for COVID-19.