Immune Responses of Mice Immunized with Active Recombinant Shiga Toxin and Its Derivatives

Bacterial protein toxins have been exploited as therapeutic agents and as vaccines. An issue of deserving interest is development of new generations of vaccines and immune adjuvants. In this study an active assembled recombinant Shiga toxin of Escherichia coli (rStx1) and its derivatives, recombinant A and B subunits (Stx1-A and Stx1-B), were used to immunize mice. The elicited antibody responses were compared with and without using adjuvant. Protection against intraperitoneal lethal dose of rStx challenge was observed by immunization with sublethal dose of rStx1, rStx-A and rStx-B subunits. The immunological studies on toxin subunits can be used for immunization against systemic shiga toxin mediated disease and also subunits as a vector for antigen presentation in immunotherapeutic approaches. In our experiment, while stimulation of the immune system by A and B subunits were different, both subunits produced neutralizing antibodies. Regarding B subunit the amount of specific IgG1/IgG2a antibody ratio was higher than A subunit. In addition B subunit stimulated proliferation of immune cells with IFN production the same as rStx1, suggesting that B subunit can be used as an immunomodulator to stimulate the immune response in conjunction with other recombinant proteins.