Construction of genetic engineering strain expressing nontoxic E coli heat-stable enterotoxin I and heat-labile enterotoxin B subunit fusion protein

With gene mutation technology, the mutated ST1 gene was acquired. Then the fusion gene ST1-LTB was constructed and inserted into an expression pET-28b(+).The recombinant plasmid pXST3LTB carried fusion gene ST1-LTB was transformed into E coli BL21(DE3)and the recombinant strain BL21(DE3)(pXST3LTB) was abtained. The recombinant strain BL21(DE3)(pXST3LTB) could produce ST1-LTB fusion protein after recombinant strain was inducted by IPTG and the fusion protein lost its activity as a toxin completely. The expressed ST1-LTB fusion protein could produce antibodies that were able to neutralize the biological activity of the native ST1 enterotoxin in the suckling mouse assay. Hence the recombinant strain BL21(DE3)(pXST3LTB) can be used as vaccine candidate strain.