Development and evaluation of an enzyme-linked immunosorbent assay for detection of antibodies against the spike protein of SARS-coronavirus

BACKGROUND: Severe acute respiratory syndrome (SARS) is caused by infection with SARS-associated coronavirus (CoV). Amino acid residues 450–650 of the spike (S) glycoprotein of SARS-CoV (S450-650) contains dominant epitopes for anti-viral antibodies (Abs) in patient sera. OBJECTIVES: To develop and evaluate an ELISA system for detection of anti-S Abs in patient sera. STUDY DESIGN: Express recombinant S450-650 in E. Coli and evaluate the sensitivity and specificity of an ELISA system based on the S450-650 polypeptide. RESULTS: The S450-650-based ELISA detected IgG Abs in 41 out of 51 serum samples from 22 hospitalized patients with probable SARS, a result closely correlated with that obtained with a virus-based ELISA (r = 0.75, k = 0.8). Differential anti-S IgG responses were observed amongst SARS patients. Some of them produced anti-S Abs early during their infection, while others failed to make IgG Abs against the S450-650 polypeptide. None of the serum samples from 100 healthy blood donors was positive in the S450-650-based assay. CONCLUSION: The S450-650-based ELISA can detect anti-S IgG Abs with high sensitivity and specificity.