Monoclonal antibodies targeting the antifibrinolytic activity of activated thrombin-activatable fibrinolysis inhibitor but not the anti-inflammatory activity on osteopontin and C5a

Authors

  • F. Semeraro,

    Corresponding author
    1. Department of Biomedical Sciences and Human Oncology, Section of General and Experimental Pathology, Aldo Moro University, Bari, Italy
    • Correspondence: Fabrizio Semeraro, Department of Biomedical Sciences and Human Oncology, Section of General and Experimental Pathology, Aldo Moro University, Piazza G. Cesare 11, 70124 Bari, Italy.

      Tel.: +39 080 547 8497; fax: +39 080 547 8524.

      E-mail: brizioraro@hotmail.com

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  • C. T. Ammollo,

    1. Department of Biomedical Sciences and Human Oncology, Section of General and Experimental Pathology, Aldo Moro University, Bari, Italy
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  • A. Gils,

    1. Laboratory for Therapeutic and Diagnostic Antibodies, Department of Pharmaceutical and Pharmacological Sciences, KU Leuven, Leuven, Belgium
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  • P. J. Declerck,

    1. Laboratory for Therapeutic and Diagnostic Antibodies, Department of Pharmaceutical and Pharmacological Sciences, KU Leuven, Leuven, Belgium
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  • M. Colucci

    1. Department of Biomedical Sciences and Human Oncology, Section of General and Experimental Pathology, Aldo Moro University, Bari, Italy
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  • Manuscript handled by: R. Medcalf
  • Final decision: P. H. Reitsma, 4 October 2013

Summary

Background

Recently, anti-thrombin-activatable fibrinolysis inhibitor (TAFI) mAbs selectively inhibiting plasmin-mediated TAFI activation were shown to stimulate fibrinolysis in vitro and in vivo, suggesting, in contrast to other findings, that plasmin-mediated TAFI activation plays an important role in fibrinolysis regulation.

Objective

To further characterize the effects of two plasmin-specific anti-TAFI mAbs (MA-TCK11A9 and MA-TCK26D6) on TAFI-dependent inhibition of fibrinolysis.

Methods and Results

Both mAbs inhibited plasmin-mediated but not thrombin/thrombomodulin-mediated TAFI activation, whereas neither inhibited the cleavage of hippuryl-arginine by activated TAFI (TAFIa). They stimulated tissue-type plasminogen activator-induced fibrinolysis in different clot lysis models through a TAFI-dependent mechanism, especially in the presence of thrombomodulin (TM), a condition in which TAFI is largely activated by the thrombin–TM complex. In a fibrinolysis-based TAFIa activity assay, both mAbs inhibited TAFIa, whereas other mAbs targeting thrombin–TM-mediated TAFI activation did not. The inhibition of TAFIa activity, however, was substrate-specific, because neither mAb inhibited the cleavage of thrombin-activated osteopontin and C5a by TAFIa, thus sparing the anti-inflammatory activity of TAFIa.

Conclusions

Our anti-TAFI mAbs, by selectively inhibiting TAFIa activity on fibrin, may represent the prototype of a new class of TAFI inhibitors with improved pharmacologic activity.

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