Platelet thrombus formation in eHUS is prevented by anti-MBL2

Area of Science:

• Immunology
• Nephrology
• Microbiology

Background:

• E. coli associated Hemolytic Uremic Syndrome (eHUS) involves Shiga toxin-producing bacteria, leading to thrombocytopenia, hemolytic anemia, and acute kidney injury.
• The mannose-binding lectin (MBL) pathway of complement activation is hypothesized to play a role in eHUS pathogenesis.
• Previous studies showed Shiga Toxin-2 (Stx-2) induced fibrin deposition in mouse glomeruli, which was blocked by an anti-MBL-2 antibody (3F8).

Purpose of the Study:

• To investigate the role of the MBL pathway in platelet thrombosis during eHUS.
• To delineate markers of platelet thrombosis in mouse glomeruli following Stx-2 injection.
• To evaluate the effect of the anti-MBL-2 antibody 3F8 on Stx-2-induced platelet thrombosis.

Main Methods:

• Utilized a mouse model (MBL-2+/+ Mbl-A/C-/-; MBL2 KI mouse) with control, Stx-2, and 3F8+Stx-2 treatment groups.
• Employed double immunofluorescence (IF) staining for fibrin(ogen), CD41 (platelets), von-Willebrand factor (endothelial cells/platelets), and podocin (podocytes).
• Conducted electron microscopy (EM) on kidney sections from mice and humans with HUS to confirm findings.

Main Results:

• Stx-2 injection significantly increased glomerular fibrin and platelets compared to controls.
• Co-administration of 3F8 with Stx-2 reduced both platelet and fibrin levels to control levels.
• EM confirmed that CD41-positive structures were indeed platelets, validating the IF findings.

Conclusions:

• Stx-2 induces platelet-fibrin thrombi formation in the glomeruli.
• Inhibition of the MBL pathway using the 3F8 antibody effectively prevents Stx-2-mediated platelet aggregation and fibrin deposition.
• These findings support the MBL pathway's critical role in eHUS and suggest 3F8 as a potential therapeutic agent.