Expression of Shiga toxin epitopes in E. coli immunological characterization.

Synthetic oligodeoxynucleotides encoding for two peptides corresponding to residues 9-21 and 19-31 in the amino acid sequence of the B subunit of Shiga toxin were prepared and inserted into pTOZ plasmid, in phase with the lacZ gene. The resultant vectors were used for transfection of E. coli. The bacteria containing the recombinant DNA expressed the respective peptides in the form of fusion proteins with beta-galactosidase. The N-terminal region of the Shiga toxin B subunit, containing the two peptides, was previously identified as a relevant epitope of the toxin, leading to the induction of neutralizing antibodies. The present study demonstrates that the bacterial extracts containing the fusion proteins as the products of the recombinant vectors, when used for immunization of rabbits, elicited a humoral immune response which was specific toward the respective peptides. Furthermore, the antibodies cross-reacted with the intact Shiga toxin.