The immunogenicity of fusion protein linking the carboxyl terminus of the B subunit of Shiga toxin 2 to the B subunit of E-coli heat-labile enterotoxin

To augment the immunogenicity of the subunit B of Shiga toxin (Stx2e B) produced by Escherichia coli and protect piglets from edema disease in china, a fusion gene was constructed consisting of Stx2e B genetically linked at the N-terminus of the B subunit of heat-labile enterotoxin (LTB) in a translational fusion. After being induced with IPTG, the expressed fusion protein of Stx2e B-LTB was about 8.8% of total proteins, approximately 13 mu g/ml of the bacteria culture. The Stx2e B-LTB fusion protein was found to be nontoxic to Vero cells at the dose higher than 1 mu g/ml and to mice less than 100 mu g/ml. Antibody titer against the fusion protein Stx2e B-LTB was 1:76,800, much higher than that of the recombinant Stx2e B protein (1: 12,800) alone. All of the mice immunized with the Stx2e B-LTB fusion protein survived when challenged with a lethal dose (LD) of Stx2e toxin. The results showed that the poor irnmunogenicity of Stx2e B was overcome by conjugating the stx2e B to ltB. The immunogenicity of the constructed fusion protein Stx2e B-LTB in the present study was highly qualified to protect animals against Shiga toxin produced from Shiga toxin-producing Escherichia coli (STEC). The fusion protein of Stx2e B-LTB could be a candidate for a vaccine against edema disease and post-weaning diarrhea simultaneously in piglets. (c) 2007 Elsevier B.V. All rights reserved.