Specificity and Epitope Mapping of Four Monoclonal Antibodies against SARS-CoV Nucleocapsid Protein
Abstract: In order to characterize the specificity of the monoclonal antibodies (McAbs) against SARS- associated coronavirus (SARS-CoV) nucleocapsid protein and to identify the epitopes recognized by the McAbs，the nucleocapsid proteins of human coronavirus OC43 (HCoV-OC43) and 229E (HCoV-229E) was expressed in E.coli. The specificities of four McAbs (1-1C2, 2-2E5, 1-1D6, and 2-8F11) were examined by Western blotting as well as indirect fluorescence assay. Twelve different recombinant truncated N proteins were then used to identify the epitopes recognized by the McAbs by Western blotting. The results showed that: (1) McAbs 1-1C2, 2-2E5, and 1-1D6 recognized neither human coronviruses HCoV-OC43 and HCoV-229E nor their nucleocapsid proteins, implying a possible specificity of these 3 McAbs to SARS-CoV; (2)The epitopes recognized by McAbs 2-8F11, 2-2E5, and 1-1D6 were located between the 30th and 60th amino acid (a.a.) residues of the SARS-CoV N protein, while the epitopes recognized by the McAb1-1C2 were located between 170th and 184 th a.a. residues. The identification of the specific epitopes of SARS-CoV N protein is paramount for the immunological characterization, the development of accurate immunological assay as well as for exploring the pathogenesis of SARS-CoV.