Genetic toxoids of Shiga toxin types 1 and 2 protect mice against homologous but not heterologous toxin challenge.

Shiga toxin type 1 (Stx1) and type 2 (Stx2) are produced by Escherichia coli O157:H7 and are responsible for the life-threatening sequela, the hemolytic uremic syndrome. Whether antisera to Stx1 or Stx2 are cross-neutralizing remains controversial, so we constructed genetic toxoids of Stx1 and Stx2 and evaluated them as vaccines. Antisera from mice immunized with a single toxoid type recognized and neutralized the homologous toxin but not the heterologous toxin. Furthermore, only mice immunized with Stx1 and Stx2 toxoids were protected against a lethal challenge of both toxins. We conclude that Stx1 and Stx2 are distinct antigens for mice.