Objective    To clone lexA gene from enterohemorrhagic Escherichia coli (EHEC) O157∶H7

and express and purify it

and measure its immunogenicity.      Methods    The objective fragment was amplified from standard EHEC O157∶H7 cells by PCR

and then linked with the vector pET22b(+). The objective protein was induced to express in the BL21(DE3) cells after transfection. The expressed protein was purified by 2 steps of Heparin Agrose chelate affinity chromatography and gel filtration chromatography respectively. The purified lexA protein was used to immune the rabbits to prepare the polyclonal antibody. ELISA and Western blotting was used to detect the obtained serum.      Results    The expressed protein was found in insoluble form

accounted for 40% of the total bacteria protein. The final purity was 98%

which was determined by HPLC. The obtained protein was confirmed to have sound immunogenicity.     Conclusion    Our obtained recombinant LexA protein expressed in E. coli BL21(DE3) has good immunological activity.