Neutralizing antibodies in the intestinal mucosa are essential to control gastrointestinal infection by Shiga toxin-producing Escherichia coli.

Infections with Shiga toxin (Stx)-producing Escherichia coli (STEC) strains can result in a wide range of clinical presentations. Despite STEC O157:H7 being the serotype most frequently associated with hemolytic uremic syndrome (HUS), in some patients, a self-limited gastrointestinal infection is observed. We have previously demonstrated that genetic differences between BALB/c and C57BL/6 mice account for a different outcome after an experimental gastrointestinal STEC O157:H7 infection, in which the better outcome observed in BALB/c mice was associated with a Th-2 biased immune response. The objective of this study was to determine the role of anti-STEC antibodies during STEC O157:H7 infections. We first demonstrated that the B-cell-dependent response triggered upon STEC O157:H7 infection is necessary to keep BALB/c mice healthy and reciprocally C57BL/6 mice pre-challenged with an Stx2-deficient STEC O157:H7 strain were able to survive, remaining healthy after a subsequent STEC O157:H7 infection. We further proved that anti-STEC O157:H7 antibodies raised after infection have binding specificity against STEC O157:H7 bacteria, recognize H7, and have neutralizing capacitiy, by interfering with important pathogenic mechanisms such as motility and adhesion to intestinal epithelial cells. We conclude that local and/or systemic specific antibodies against STEC mediate prevention of lethal complications during STEC O157:H7 infections.