Send to

Choose Destination
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

Clinical Chemistry and Haematology, University Medical Center Utrecht, Netherlands.
Utrecht University Medical Center, Netherlands.
Institute of Clinical Chemistry and Laboratory Medicine, University Medical Center Hamburg-Eppendorf (UKE), Germany.
SERPINx B.V., Netherlands.
University Medical Center Utrecht, Netherlands.
Molecular and Cellular Hemostasis, Sanquin Research, Netherlands.
Institute for Clinical Chemistry, University Medical Center Hamburg (UKE), Germany.
Lab. for Clinical Chemistry and Haematology, Utrecht University Medical Center, Netherlands


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.


Supplemental Content

Full text links

Icon for HighWire
Loading ...
Support Center