Clinical relevance of shiga toxin concentrations in the blood of patients with hemolytic uremic syndrome.

BACKGROUND: Intestinal infections with Shiga toxin-producing Escherichia coli (STEC) in children can lead to the hemolytic uremic syndrome (HUS). Shiga toxins (Stx) released in the gut by bacteria enter the blood stream and target the kidney causing endothelial injury. Free toxins have never been detected in the blood of HUS patients, but they have been found on the surface of polymorphonuclear leukocytes (PMN). METHODS: With respect to their clinical features, the clinical relevance of the amounts of serum Stx (cytotoxicity assay with human endothelial cells) and PMN-bound Stx (cytofluorimetric assay) in 46 patients with STEC-associated HUS was evaluated. RESULTS: Stx-positive PMN were found in 60% of patients, whereas negligible amounts of free Stx were detected in the sera. Patients with high amounts of Stx on PMN showed preserved or slightly impaired renal function (incomplete form of HUS), whereas cases with low amounts of Stx usually presented evidence of acute renal failure. CONCLUSIONS: These observations suggest that the extent of renal damage in children with STEC-associated HUS could depend on the concentration of Stx present on their PMN and presumably delivered by them to the kidney. As previously shown by experimental models from our laboratory, high amounts of Stx could induce a reduced release of cytokines by the renal endothelium, with a consequent lower degree of inflammation. Conversely, low toxin amounts can trigger the cytokine cascade, provoking inflammation, thereby leading to tissue damage.

Genetic risk factors in typical haemolytic uraemic syndrome.

BACKGROUND: Haemolytic uraemic syndrome (HUS) is a disorder characterized by thrombotic microangiopathy, which is caused in 'typical forms' by gastrointestinal infections with Escherichia Coli species that produce verotoxins. Several studies have identified negative prognostic factors of the disease, among which prolonged oliguria, neurological involvement and increased leukocytosis have been more consistently reported. We have hypothesized that the genetic background may also predispose to the development of typical forms of HUS and may influence the clinical course of the disease. METHODS: Fourteen polymorphisms, known to influence the coagulation pathway or the activity of the renin-angiotensin system, have been selected and studied in 150 Italian children with typical forms of HUS. Two hundred healthy Italian children were used as controls. RESULTS: The risk of developing HUS was strongly associated with the platelet glycoprotein 1balpha 145M allele (OR 3.08; CI: 1.62-5.85) (P < 0.001). A significant association was also found with polymorphisms located in the adipocyte-derived leucine aminopeptidase and factor V genes. A longer duration of dialysis was moderately associated with increased leukocytosis and with the 807T allele of the platelet glycoprotein 1a gene. High white blood cell count was also strongly associated with the risk of long-term sequelae (OR 2.91, CI: 1.21-6.98) (P < 0.02), whereas the 1166C allele of the angiotensin II type 1 receptor had a significant protective effect (OR 0.28, CI: 0.09-0.83) (P < 0.02). CONCLUSIONS: These results highlight the role of glycoprotein 1balpha in the physiopathology of typical forms of HUS and show that the genetic background plays a role in the susceptibility and severity of the disease.

Shiga toxins present in the gut and in the polymorphonuclear leukocytes circulating in the blood of children with hemolytic-uremic syndrome.

Hemolytic-uremic syndrome, the main cause of acute renal failure in early childhood, is caused primarily by intestinal infections from some Escherichia coli strains that produce Shiga toxins. The toxins released in the gut are targeted to renal endothelium after binding to polymorphonuclear leukocytes. The presence of Shiga toxins in the feces and the circulating neutrophils of 20 children with hemolytic uremic syndrome was evaluated by the Vero cell cytotoxicity assay and flow cytometric analysis, respectively. The latter showed the presence of Shiga toxins on the polymorphonuclear leukocytes of 13 patients, 5 of whom had no other microbiologic or serologic evidence of infection by Shiga toxin-producing Escherichia coli. A positive relationship was observed between the amounts of Shiga toxins released in the intestinal lumen and those released in the bloodstream. The toxins were detectable on the neutrophils for a median period of 5 days after they were no longer detectable in stools. This investigation confirms that the immunodetection of Shiga toxins on neutrophils is a valuable tool for laboratory diagnosis of Shiga toxin-producing Escherichia coli infection in hemolytic-uremic syndrome and provides clues for further studies on the role of neutrophils in the pathogenesis of this syndrome.