Shiga toxin 2a binds antithrombin and heparin, but does not directly activate platelets

Int J Med Microbiol. 2018 Oct;308(7):969-976. doi: 10.1016/j.ijmm.2018.07.008. Epub 2018 Jul 23.


Escherichia coli-induced hemolytic uremic syndrome (eHUS) is a life-threatening complication of infection with Shiga toxin (Stx), in particular Stx2a-producing Escherichia coli. Enhanced coagulation activation with formation of microthrombi seems to be a key event in development of eHUS. Platelet activation has been postulated as a possible, but controversially debated mechanism. The present study investigated the effect of Stx2a on plasmatic coagulation and platelets. Binding studies were initially performed with ELISA and co-immunoprecipitation and supported by quartz crystal microbalance with dissipation monitoring (QCM-D). Antithrombin (AT) activity was measured using the automated BCS XP® system. ROTEM® was used for functional coagulation testing. Platelet binding and activation was studied with FACS and light-transmission aggregometry. We found binding of Stx2a to AT, an important inhibitor of blood coagulation, but only a mild albeit significant reduction of AT activity against FXa in the presence of Stx2a. QCM-D analysis also showed binding of Stx2a to heparin and an impaired binding of AT to Stx2a-bound heparin. ROTEM® using Stx2a-treated platelet-poor plasma revealed a significant, but only moderate shortening of clotting time. Neither binding nor activation of platelets by Stx2a could be demonstrated. In summary, data of this study suggest that Stx2a binds to AT, but does not induce major effects on plasmatic coagulation. In addition, no interaction with platelets occurred. The well-known non-beneficial administration of heparin in eHUS patients could be explained by the interaction of Stx2a with heparin.

Keywords: Antithrombin; Hemolytic uremic syndrome; Plasmatic coagulation; Stx2a.

MeSH terms

  • Antithrombins / metabolism*
  • Blood Coagulation / physiology*
  • Blood Platelets / immunology
  • Hemolytic-Uremic Syndrome / microbiology
  • Heparin / metabolism*
  • Humans
  • Platelet Aggregation / immunology*
  • Protein Binding / physiology
  • Shiga Toxin 2 / metabolism*
  • Shiga-Toxigenic Escherichia coli / pathogenicity


  • Antithrombins
  • Shiga Toxin 2
  • Heparin