Objective:To construct recombinant Bb-EmⅡ/3 vaccine of Echinococcus multilocularis and to investigate the expression efficiency of EmⅡ/3 antigen encoding gene in Escherichia coli BL21(DE3). Methods:EmⅡ/3 antigen gene was amplified by PCR. Then the gene was cloned into Escherichia coli-Bifidobacteria shuttle plasmid pGEX-1λT containing gluathione-S-transferaze(GST) gene to construct pGEX-EmⅡ/3. The recombinant plasmid was electroporated into Bifidobacteria bifidum(Bb) to construct rBb-EmⅡ/3 vaccine. The vaccine was identified with PCR and restriction-endonuclease digestion. The expression of pGEX-EmⅡ/3 was induced with isopropyl-β-D-thiogalactopyranosid(IPTG)

and fusion protein EmⅡ/3/GST was examined by SDS-PAGE and Western blot techniques. Results:1 759bp gene of EmⅡ/3 was successfully amplified by PCR and cloned into pGEX-1λT by restriction analysis. rBb-EmⅡ/3 vaccine was successfully constructed according to PCR and restriction-endonuclease digestion.It was demonstrated with SDS-PAGE and Western blot that the fusion protein EmⅡ/3/GST were expressed in E.coli

BL21. Conclusions:rBb-EmⅡ/3 vaccine of Echinococcus multilocularis is successfully constructed. The plasmid pGEX-EmⅡ/3 was highly expressed in E.coli in fused form with GST and this kind of protein shows specific antigenicity according to western blot.