SummaryTypical haemolytic uraemic syndrome (HUS) is caused by Shiga toxin (Stx)-producing Escherichia coli infections and is characterized by thrombotic microangiopathy that leads to haemolytic anaemia, thrombocytopenia and acute renal failure. Renal or neurological sequelae are consequences of irreversible tissue damage during the acute phase. Stx toxicity and the acute inflammatory response raised by the host determine the development of HUS. At present there is no specific therapy to control Stx damage. The pathogenic role of reactive oxygen species (ROS) on endothelial injury has been largely documented. In this study, we investigated the in-vivo effects of Stx on the oxidative balance and its contribution to the development of HUS in mice. In addition, we analysed the effect of anti-oxidant agents as therapeutic tools to counteract Stx toxicity. We demonstrated that Stx induced an oxidative imbalance, evidenced by renal glutathione depletion and increased lipid membrane peroxidation. The increased ROS production by neutrophils may be one of the major sources of oxidative stress during Stx intoxication. All these parameters were ameliorated by anti-oxidants reducing platelet activation, renal damage and increasing survival. To conclude, Stx generates a pro-oxidative state that contributes to kidney failure, and exogenous antioxidants could be beneficial to counteract this pathogenic pathway.

Circulating monocytes (Mos) may continuously repopulate macrophage (MAC) or dendritic cell (DC) populations to maintain homeostasis. MACs and DCs are specialized cells that play different and complementary immunological functions. Accordingly, they present distinct migratory properties. Specifically, whereas MACs largely remain in tissues, DCs are capable of migrating from peripheral tissues to lymphoid organs. The aim of this work was to analyze the expression of the fractalkine receptor (CX 3 CR1) during the monocytic differentiation process. Freshly isolated Mos express high levels of both CX 3 CR1 mRNA and protein. During the Mo differentiation process, CX 3 CR1 is downregulated in both DCs and MACs. However, MACs showed significantly higher CX 3 CR1 expression levels than did DC. We also observed an antagonistic CX 3 CR1 regulation by interferon (IFN)-c and interleukin (IL)-4 during MAC activation through the classical and alternative MAC pathways, respectively. IFN-c inhibited the loss of CX 3 CR1, but IL-4 induced it. Additionally, we demonstrated an association between CX 3 CR1 expression and apoptosis prevention by soluble fractalkine (sCX 3 CL1) in Mos, DCs and MACs. This is the first report demonstrating sequential and differential CX 3 CR1 modulation during Mo differentiation. Most importantly, we demonstrated a functional link between CX 3 CR1 expression and cell survival in the presence of sCX 3 CL1.

Moreover, pups were totally protected against a lethal dose of systemic Stx2 injection up to 2 to 3 months postpartum. In addition, pups were resistant to an oral challenge with an Stx2-producing EHEC strain at weaning and did not develop any symptomatology associated with Stx2 toxicity. Fostering experiments demonstrated that anti-Stx2B neutralizing IgG antibodies were transmitted through breast-feeding. Pups that survived the EHEC infection due to maternally transferred immunity prolonged an active and specific immune response that protected them against a subsequent challenge with intravenous Stx2. Our study shows that maternal immunization with BLS-Stx2B was very effective at promoting the transfer of specific antibodies, and suggests that preexposure of adult females to this immunogen could protect their offspring during the early phase of life.