Objective: To study the immunological characteristics of the spike (S) protein of SARS coronavirus (SARS-CoV) and analyze the feasibility of using this protein as the component for SARS vaccine development.
Methods: The two truncated fragments of S gene were separately cloned into the prokaryotic expression vector pET-15b and expressed in E.coli. The resulting recombinant proteins, rS(a) and rS(b), were purified by affinity chromatography. The full-length S gene was cloned into the eukaryotic expression plasmid pSecTagB to prepare recombinant plasmid pSecS as the DNA vaccine to immunize BALB/c mice for inducing the secretion of anti-SARS-CoV protein. The immunological effect of anti-SARS-CoV antibody was tested with purified rS(a) and rS(b) proteins by enzyme-linked immunosorbent assay (ELISA).
Results: Both the truncated recombinant proteins were expressed in soluble forms and reacted specifically with the sera from immunized pSecS mice and clinically diagnosed SARS patients. The prokaryotically expressed recombinant truncated S protein had similar antigenicity with SARS-CoV S protein.
Conclusion: The recombinant protein could be used as an antigen for detecting the serum of SARS CoV-infected patients. The SARS-CoV S gene vaccine could induce the production of specific antibody, which offers clues for the research of SARS DNA vaccine.