Shiga toxins and hemolytic uremic syndrome: pathogenesis, diagnosis, and therapy

Hemolytic Uremic Syndrome (HUS) is a severe thrombotic microangiopathy characterized by non-immune hemolytic anemia, thrombocytopenia, and acute renal failure. The most common form is caused by infections with Shiga toxin-producing Escherichia coli (STEC), which release potent Shiga toxins (Stx). This research addresses three objectives: elucidating mechanisms by which Stx subtypes contribute to HUS pathogenesis, developing a diagnostic platform for Stx detection, and evaluating novel therapeutic strategies. Patients infected with STEC co-producing Stx1 and Stx2 exhibit milder clinical manifestations than those infected with Stx2-producing strains. To investigate this, human blood was exposed to toxins, and extracellular vesicles (EV) were isolated and characterized. Co-exposure to both toxins produced a less toxic EV population, showing reduced number, size, and toxic cargo compared to EV generated by Stx2 alone, which are most strongly associated with HUS. Prompt STEC diagnosis is crucial for preventing HUS. A gold plasmonic biosensor was developed, coupling surface-enhanced Raman spectroscopy (SERS) with principal component analysis (PCA) for rapid Stx detection. The system recognizes Stx1a, Stx2a, and Stx2a-cleaved, enabling real-time analysis. Currently, no specific HUS therapy exists. NAB815, a polymyxin B derivative, emerged as a promising candidate. Previous studies showed sub-bactericidal NAB815 doses reduce Stx2a-containing EV formation in human blood. In vivo evaluation using CD1 mice demonstrated effective protection against kidney damage when NAB815 was co-administered with either free Stx2a or blood-derived Stx2a containing EV. Since antibiotics can trigger bacterial SOS response and increase Stx production, NAB815's safety was evaluated in both engineered and wildtype STEC strains. Results confirmed NAB815 as a safe strategy for HUS prevention and management. These findings provide new insights into HUS pathogenesis while offering innovative approaches for early diagnosis and targeted intervention in STEC infections.