Abstract: In order to prevent and cure EHEC O157∶ H7，genetically engineering vaccine，especially subunit vaccine， has significant dominance over others. To construct tir-stx fusion gene，the DNA fragments encoding middle 295 amino acids(Tir295) of tir and 72 amino acids(stx72) of stx1b and stx2b were fused in turn in frame with the multiple cloning sites of pGEX and the recombinant plasmid of pGEX-stx2b-tir-stx1b was transferred to host cells E. coli BL21 strain (DE3) . Then，the protein was induced and expressed with induction of IPTG. The expression quantities and style of fusion protein were determined by SDS-PAGE and thin layer scanning results showed that amount of expressed fusion protein was 30% in total of bacteria protein. Purified recombinant Stx2B-Tir-Stx1B protein can elicit high titer IgG (10⁵) by subcutaneous immunization BALB / c mice，also，e licit high titer IgG (10⁴) and IgA (10²) by intra nasal immunization. Moreover， compared to non-immunized mice still shed EHEC O157∶ H7 on 14th day，immunized mice shed no bacteria in the fecal samples 8 day later after challenged with O157∶ H7. All results shows that stx2b-tir-stx1b protein has good antigenicity， and tir295 ，and stxb72 antigens can evoke immune responses against tir295 and stxb72， reseptively. The tir-stxb fusion protein expressed in E.coli could offer an important ingredient that should be consider in construction of recombinant EHEC O157 vaccine or preparation of experimental material for the monoclonal antibody.

Key words: EHEC O157∶ H7, Tir, Stx, Fusion gene, Immunogenicity

CLC Number: 

• S852.61