Immunoprophylactic potential of cloned shiga toxin 2 B subunit

The Shiga toxins Stx1 and Stx2 contribute to the development of enterohemor rhagic O157: H7 Escherichia coli-mediated colitis and hemolytic-uremic synd rome in humans. The Stx2 B subunit, which binds to globotriaosylceramide (G B3) receptors on target cells, was cloned. This involved replacing the Stx2 B subunit leader peptide nucleotide sequences with those from the Stx1 B s ubunit. The construct was expressed in the TOPP3 E. coli strain. The Stx2 B subunits from this strain assembled into a pentamer and bound to a GB3 rec eptor analogue. The cloned Stx2 B subunit was not cytotoxic to Vero cells o r apoptogenic in Burkitt's lymphoma cells. Although their immune response t o the Stx2 B subunit was variable, rabbits that developed Stx2 B subunit-sp ecific antibodies, as determined by immunoblot and in vitro cytotoxicity ne utralization assays, survived a challenge with Stx2 holotoxin. This is thou ght to be the first demonstration of the immunoprophylactic potential of th e Stx2 B subunit.