van Moorsel MVA, Poolen GC, Koekman CA, Verhoef S, de Maat S, Barendrecht A, van Kleef ND, Meijers JCM, Schiffelers RM, Maas C, Urbanus RT. VhH anti-thrombomodulin clone 1 inhibits TAFI activation and enhances fibrinolysis in human whole blood under flow.
J Thromb Haemost 2022;
20:1213-1222. [PMID:
35170225 PMCID:
PMC9311061 DOI:
10.1111/jth.15674]
[Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2021] [Revised: 02/09/2022] [Accepted: 02/10/2022] [Indexed: 11/28/2022]
Abstract
BACKGROUND
Thrombomodulin on endothelial cells can form a complex with thrombin. This complex has both anticoagulant properties, by activating protein C, and clot-protective properties, by activating thrombin-activatable fibrinolysis inhibitor (TAFI). Activated TAFI (TAFIa) inhibits plasmin-mediated fibrinolysis.
OBJECTIVES
TAFIa inhibition is considered a potential antithrombotic strategy. So far, this goal has been pursued by developing compounds that directly inhibit TAFIa. In contrast, we here describe variable domain of heavy-chain-only antibody (VhH) clone 1 that inhibits TAFI activation by targeting human thrombomodulin.
METHODS
Two llamas (Lama Glama) were immunized, and phage display was used to select VhH anti-thrombomodulin (TM) clone 1. Affinity was determined with surface plasmon resonance and binding to native TM was confirmed with flow cytometry. Clone 1 was functionally assessed by competition, clot lysis, and thrombin generation assays. Last, the effect of clone 1 on tPA-mediated fibrinolysis in human whole blood was investigated in a microfluidic fibrinolysis model.
RESULTS
VhH anti-TM clone 1 bound recombinant TM with a binding affinity of 1.7 ± 0.4 nM and showed binding to native TM. Clone 1 competed with thrombin for binding to TM and attenuated TAFI activation in clot lysis assays and protein C activation in thrombin generation experiments. In a microfluidic fibrinolysis model, inhibition of TM with clone 1 fully prevented TAFI activation.
DISCUSSION
We have developed VhH anti-TM clone 1, which inhibits TAFI activation and enhances tPA-mediated fibrinolysis under flow. Different from agents that directly target TAFIa, our strategy should preserve direct TAFI activation via thrombin.
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