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Blood. 2019 Jul 31. pii: blood.2019000481. doi: 10.1182/blood.2019000481. [Epub ahead of print]

Design and characterization of α1-antitrypsin variants for treatment of contact system-driven thromboinflammation.

Author information

1
Clinical Chemistry and Haematology, University Medical Center Utrecht, Netherlands.
2
Utrecht University Medical Center, Netherlands.
3
Institute of Clinical Chemistry and Laboratory Medicine, University Medical Center Hamburg-Eppendorf (UKE), Germany.
4
SERPINx B.V., Netherlands.
5
University Medical Center Utrecht, Netherlands.
6
Molecular and Cellular Hemostasis, Sanquin Research, Netherlands.
7
Institute for Clinical Chemistry, University Medical Center Hamburg (UKE), Germany.
8
Lab. for Clinical Chemistry and Haematology, Utrecht University Medical Center, Netherlands cmaas4@umcutrecht.nl.

Abstract

The contact system produces the inflammatory peptide bradykinin and contributes to experimental thrombosis. C1 esterase-inhibitor (C1INH) deficiency or gain-of-function mutations in Factor XII (FXII) cause hereditary angioedema, a life-threatening tissue swelling disease. C1INH is a relatively weak contact system enzyme inhibitor. Although α1-antitrypsin (α1AT) does not naturally inhibit contact system enzymes, a human mutation (M358R; α1AT-Pittsburgh) changes it into a powerful broad-spectrum enzyme inhibitor. It blocks the contact system, but also thrombin and activated protein C (APC), making it an unattractive candidate for therapeutic contact system blockade. We adapted the reactive center loop of α1AT-Pittsburgh (AIPR/S) to overcome these obstacles. Two α1AT variants (SMTR/S and SLLR/S) strongly inhibit plasma kallikrein, activated FXII and plasmin. α1AT-SMTR/S no longer inhibits thrombin, but residually inhibits APC. In contrast, α1AT-SLLR/S residually inhibits thrombin, but no longer APC. Additional modification at the P1' position (S→V) eliminates residual inhibition of thrombin and APC for both variants, while retaining their properties as contact system inhibitors. Both α1AT-SMTR/V and -SLLR/V are superior to C1INH in reducing bradykinin production in plasma. Owing to their capacity to selectively block contact system-driven coagulation, both variants block vascular occlusion in an in vivo model for arterial thrombosis. Furthermore, both variants block acute carrageenan-induced tissue edema in mice. Finally, α1AT-SLLR/V, our most powerful candidate, suppresses epithelial leakage of the gut in a mouse model of colitis. Our findings confirm that redesign of α1AT strongly alters its inhibitory behavior and can be used for the treatment of contact system-mediated thrombosis and inflammation.

PMID:
31366623
DOI:
10.1182/blood.2019000481

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