Abstract: Objective To express the antigen gene Ts21 of Trichinella spiralis， purify the recombinant protein and test its antigenicity. Methods T. spiralis gene Ts21 was subcloned into the prokaryotic expression vector pMAL-c2X and the recombinant pMAL-c2X-Ts21 was constructed. The recombinant plasmid was transformed into E. coli TB1 strain and induced by IPTG. The expression products were purified by MBP-binding affinity chromatography. The antigenicity of the recombinant protein was examined by SDS-PAGE and Western blotting. Mice were immunized with the recombinant protein， the titer of the immune sera was detected by ELISA. The distribution of Ts21 protein in muscle larvae was observed by IFA. Results The molecular weight of the expressed fusion protein was about Mr 63 500 and the expression level peaked at 4 h post-incubation. The portion of the fusion protein accounted for 18.2% of all the protein by thin-layer gel optical scanning. Western blotting demonstrated that the recombinant protein was recognized by sera from mice infected by T. spiralis （T1） and T. nelsoni （T7） as well as sera of patients with trichinellosis， but not by sera from mice infected with T. nativa （T2）， T. britovi （T3） and T. pseudospiralis （T4）. The recombinant protein did not react with sera from patients with ancylostomiasis， cysticercosis and schistosomiasis， but cross-reacted with sera from patients with paragonimiasis， clonorchiasis and echinococcosis. High titers of antibodies were produced in mice immunized with the recombinant protein. IFA showed that the Ts21 protein was mainly distributed in the cuticle of muscle larvae. Conclusion The Ts21 antigen gene of T. spiralis has been expressed and the recombinant protein shows antigenicity.

Key words: Trichinella, Prokaryotic expression, Recombinant protein, Antigenicity, Identification