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.