Contruction of the Genetic Engineering Strain Expressed Nontoxic ST_1-LT_B Fusion Protein Against Enterotoxigenic Eschenichia coli

摘要

Thermostable enterotoxinⅠ (ST_1) mutant genes and thermolabile enterotoxin B subunit (LT_B) genes were amplified by PCR from plasmids of Eschenichia coli C83902. The recombinant expression plasmid pZST3LTB containing ST_1-LT_B fusion gene was constructed by recombinant DNA technique and then transformed into Escherichia coli BL21(DE3). The ST_1-LT_B fusion protein was highly expressed in recombinant strain BL21(DE3)(pZST3LTB) and the fusion protein was about 38.53% of total cellular protein by SDS-PAGE and thin-layer gel scanning analysis. More important, mice immunized with crude preparation containing the fusion protein inclusion bodies or inactivated recombinant strain produced antibodies that were able to recognize ST_l in vitro. These sera antibodies were able to neutralize the biological activity of native ST_1 in the suckling mouse assay. Hence the ST_1-LT_B fusion protein was nontoxic and immunogenic, the constructed recombinant strain BL21 (DE3)(pZST3LTB) could be used as a candidate of vaccine strain.