Thromb Haemost 2018; 118(10): 1729-1742
DOI: 10.1055/s-0038-1669459
Coagulation and Fibrinolysis
Georg Thieme Verlag KG Stuttgart · New York

Anti-ADAMTS13 Autoantibodies against Cryptic Epitopes in Immune-Mediated Thrombotic Thrombocytopenic Purpura

Elien Roose
1  Laboratory for Thrombosis Research, IRF Life Sciences, KU Leuven Campus Kulak Kortrijk, Kortrijk, Belgium
,
Gestur Vidarsson
2  Department of Experimental Immunohematology, Sanquin Research and Landsteiner Laboratory, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands
,
Kadri Kangro
1  Laboratory for Thrombosis Research, IRF Life Sciences, KU Leuven Campus Kulak Kortrijk, Kortrijk, Belgium
,
Onno J. H. M. Verhagen
2  Department of Experimental Immunohematology, Sanquin Research and Landsteiner Laboratory, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands
,
Ilaria Mancini
3  Department of Pathophysiology and Transplantation, Università degli Studi di Milano, and Fondazione Luigi Villa, Milan, Italy
,
Linda Desender
1  Laboratory for Thrombosis Research, IRF Life Sciences, KU Leuven Campus Kulak Kortrijk, Kortrijk, Belgium
,
Inge Pareyn
1  Laboratory for Thrombosis Research, IRF Life Sciences, KU Leuven Campus Kulak Kortrijk, Kortrijk, Belgium
,
Nele Vandeputte
1  Laboratory for Thrombosis Research, IRF Life Sciences, KU Leuven Campus Kulak Kortrijk, Kortrijk, Belgium
,
Aline Vandenbulcke
1  Laboratory for Thrombosis Research, IRF Life Sciences, KU Leuven Campus Kulak Kortrijk, Kortrijk, Belgium
,
Chiara Vendramin
4  Department of Haematology, University College London Hospital, London, United Kingdom
,
An-Sofie Schelpe
1  Laboratory for Thrombosis Research, IRF Life Sciences, KU Leuven Campus Kulak Kortrijk, Kortrijk, Belgium
,
Jan Voorberg
5  Department of Plasma Proteins, Sanquin Research and Landsteiner Laboratory, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands
,
Marie-Agnès Azerad
6  Department of Hematology, CHU Brugmann, Brussels, Belgium
7  Department of Hematology, CHU Liège, Liège, Belgium
,
Laurent Gilardin
8  Département de Médicine Interne et Immunologie Clinique, Hôpital Pitié-Salpêtrière, Assistance Publique-Hôpitaux de Paris, Paris, France
,
Marie Scully
4  Department of Haematology, University College London Hospital, London, United Kingdom
,
Daan Dierickx
9  Department of Hematology, University Hospitals Leuven, Leuven, Belgium
,
Hans Deckmyn
1  Laboratory for Thrombosis Research, IRF Life Sciences, KU Leuven Campus Kulak Kortrijk, Kortrijk, Belgium
,
Simon F. De Meyer
1  Laboratory for Thrombosis Research, IRF Life Sciences, KU Leuven Campus Kulak Kortrijk, Kortrijk, Belgium
,
Flora Peyvandi
3  Department of Pathophysiology and Transplantation, Università degli Studi di Milano, and Fondazione Luigi Villa, Milan, Italy
10  Angelo Bianchi Bonomi Hemophilia and Thrombosis Center, Fondazione IRCCS Ca'Granda Ospedale Maggiore Policlinico, Milan, Italy
,
Karen Vanhoorelbeke
1  Laboratory for Thrombosis Research, IRF Life Sciences, KU Leuven Campus Kulak Kortrijk, Kortrijk, Belgium
› Author Affiliations
Funding This work was supported by the European Framework Program for Research and Innovation (Horizon 2020 Marie Sklodowska Curie Innovative training network PROFILE grant 675746) and KU Leuven grants OT/14/071 and PF/10/014 awarded to K.V. A.S.S. is supported by a PhD grant from the Agency Innovation And Entrepreneurship (VLAIO, www.iwt.be), Flanders, Belgium (141136). Academische Stichting Leuven is acknowledged for providing a travel grant to E.R. to present this study at the ISTH 2017, Berlin, Germany.
Further Information

Publication History

11 May 2018

18 July 2018

Publication Date:
20 September 2018 (eFirst)

Abstract

Immune-mediated thrombotic thrombocytopenic purpura (iTTP) is characterized by severe ADAMTS13 (a disintegrin and metalloprotease with thrombospondin type 1 repeats, member 13) deficiency, the presence of anti-ADAMTS13 autoantibodies and an open ADAMTS13 conformation with a cryptic epitope in the spacer domain exposed. A detailed knowledge of anti-ADAMTS13 autoantibodies will help identifying pathogenic antibodies and elucidating the cause of ADAMTS13 deficiency. We aimed at cloning anti-ADAMTS13 autoantibodies from iTTP patients to study their epitopes and inhibitory characteristics. We sorted anti-ADAMTS13 autoantibody expressing B cells from peripheral blood mononuclear cells of 13 iTTP patients to isolate anti-ADAMTS13 autoantibody sequences. Ninety-six B cell clones producing anti-ADAMTS13 autoantibodies were identified from which 30 immunoglobulin M (IgM) and 5 IgG sequences were obtained. For this study, we only cloned, expressed and purified the five IgG antibodies. In vitro characterization revealed that three of the five cloned IgG antibodies, TTP73–1, ELH2–1 and TR8C11, indeed recognize ADAMTS13. Epitope mapping showed that antibodies TTP73–1 and TR8C11 bind to the cysteine–spacer domains, while the antibody ELH2–1 recognizes the T2–T3 domains in ADAMTS13. None of the antibodies inhibited ADAMTS13 activity. Given the recent findings regarding the open ADAMTS13 conformation during acute iTTP, we studied if the cloned antibodies could recognize cryptic epitopes in ADAMTS13. Interestingly, all three antibodies recognize cryptic epitopes. In conclusion, we cloned three anti-ADAMTS13 autoantibodies from iTTP patients that recognize cryptic epitopes. Hence, these data nicely fit our recent finding that the conformation of ADAMTS13 is open during acute iTTP.

Authors' Contributions

E.R., G.V., O.J.H.M.V., F.P. and K.V. designed the experiments. E.R., K.K., O.J.H.M.V., L.D., I.P., N.V. and A.V. performed the experiments. I.M., C.V., M.A.A., L.G., M.S., D.D. and F.P. provided clinical information and PBMCs from iTTP patients. A.S.S. developed the antibody 1C4 and J.V. provided the antibodies II-1 and I-9. E.R., G.V., K.K., O.J.H.M.V., I.M., H.D. and S.F.D.M. and K.V. interpreted the data. E.R. and K.V. wrote the manuscript, which was critically reviewed by G.V., K.K., O.J.H.M.V., I.M., A.S.S., J.V., M.A.A., L.G., M.S., D.D., H.D., S.F.D.M. and F.P. All authors approved the final version of the manuscript. K.V. provided funding.