Preparation and characterization of monoclonal antibodies against S1 domain at N-terminal residues 249 to 667 of SARS-associated coronavirus S1 protein.

OBJECTIVE: To prepare and characterize monoclonal antibodies (mAbs) against S1 protein of severe acute respiratory syndrome (SARS)-associated coronavirus (SARS-CoV). METHODS: 6-His-tagged recombinant fragment at N-terminal residues 249 to 667 of SARS-CoV S1 protein including S-protein receptor-binding domain was expressed in E.coli. The immunogenicity of this S1 domain was identified and used to immunize BALB/c mice for the production of hybridomas. The identification of the mAbs against this S1 domain was performed using indirect enzyme-linked immunosorbent assay (ELISA), indirect immunofluorescence assay (IFA) and Western blotting, respectively. RESULTS: Three hybridomas producing mAbs specific to the S1 domain was obtained, with a relative molecular mass of 48,500. None of the 3 mAbs were reactive with human coronaviruses 229E and OC43. Two of the mAbs were IgG2a isotype, and the other was IgG1. CONCLUSIONS: This is the first report of mAbs produced against S-protein receptor-binding domain of SARS-CoV. The 3 S1-specific mAbs may be useful for further study of the function of the S protein and for diagnosis of SARS-CoV infection.