Shiga Toxin 2–Specific but Not Shiga Toxin 1–Specific Human Monoclonal Antibody Protects Piglets Challenged with EnterohemorrhagicEscherichia coliProducing Shiga Toxin 1 and Shiga Toxin 2

Escherichia coli strains that produce Shiga toxin 2 (Stx2) are isolated from hemolytic-uremic syndrome (HUS) cases more frequently than are strains that produce both Shiga toxin 1 (Stx1) and Stx2, whereas strains that produce only Stx1 are rarely isolated from HUS cases. Studies have implicated Stx2 as the sole contributor to acute kidney failure and other systemic complications in humans. The aim of the present study was to determine whether Stx2-specific antibody would be as effective against Shiga toxin-producing Escherichia coli (STEC) strains that produce both Stx1 and Stx2 as it is against strains that produce only Stx2, compared with Stx1-specific antibody. We found that Stx2-specific and Stx1-specific antibodies protected 100% and 0% of piglets, respectively, against oral challenge with a Stx1- and Stx2-producing STEC strain. We conclude that Stx2-specific antibody is sufficient to protect piglets, and possibly humans, against STEC strains that produce both toxins.