The spike (S) glycoprotein is thought to play a complex and central role in the biology and athogenesis of SARS coronavirus infection. In this study, a fragment (amino acid 268-1255) of SARS-CoV S protein was cloned into the prokaryotic expression vector, pET101/D-TOPO, and the recombinant protein (rS268) was expressed and purified to near homogeneity. After immunization with rS268, S protein-specific rabbit antisera and BALB/c monoclonal antibodies were induced and confirmed using ELISA, Western blot and IFA. Both rabbit antiserum and BALB/c monoclonal antibodies were found to be effectively neutralizing the infection of Vero E6 cells by SARS CoV in a dose-dependent manner. Further studies revealed the mode of action of these neutralizing monoclonal antibodies that inhibited the entry of SARS-CoV into Vero E6 cells. Systematic epitope mapping showed that all these neutralizing monoclonal antibodies recognized a 15-residues peptide (CB-119) corresponding to residues 143-1157 (SPDVDLGDISGINAS) that was located to the second heptad repeat (HR2) region near to the C-terminal end of the SARS-CoV spike protein. The current results implicated that the second heptad repeat region of spike protein could be a good target for vaccine development against SARS CoV.
