Abstract Number: LPB0031
Meeting: ISTH 2021 Congress
Theme: Platelet Disorders, von Willebrand Disease and Thrombotic Microangiopathies » VWF and von Willebrand Factor Disorders - Clinical Conditions
Background: Von Willebrand disease (VWD) is the most common hereditary bleeding disorder. Subtype 2B (VWD2B) is caused by gain-of-function (GOF) mutations in the VWF-A1-domain inducing increased binding to platelet glycoprotein (GP)Ibα, inducing spontaneous platelet binding leading to thrombocytopenia. Further, variable reduction of von Willebrand factor (VWF) high molecular weight multimers (HMWM) and increased ADAMTS13 cleavage can occur.
Aims: Aim of this study was the identification of underlying mutations in 113 patients with suspected VWD2B and functional characterization of the identified variants with respect to GPIbα binding, multimer status and ADAMTS13 cleavage.
Methods: VWF exon 28 was sequenced in patient DNA samples for diagnostic purpose. VWF:GPIbα binding was measured by an ELISA employing a recombinant GPIbα peptide as capture component at multiple Ristocetin concentrations. Degradation of the variants by ADAMTS13 was measured employing a modified light transmission aggregometry (LTA) assay. Washed, recalcified platelets were mixed with the recombinant 2B proteins. After complex formation, their degradation by ADAMTS13 was detected by increase in turbidty.
Results: Genetic analysis revealed 15 different mutations in our patient cohort, two of which were previously associated with VWD2M (p.Arg1315Cys, p.Val1279Ile). Increased GPIbα binding was confirmed for the remaining 13 variants. Degradation of 2BVWF-platelet-complexes by ADAMTS13, counterintuitively, revealed that some variants exhibit decreased sensitivity for proteolytic cleavage in simulated circulation.
Conclusions: Summarizing, we characterized VWD2B variants found in a cohort of 113 patients. The used ELISA proved to be applicable to differentiate 2B variants from other types of VWD and the absence of patient platelets prevents false positive results due to platelet type-VWD. Additionally, our data indicate that increased proteolysis of some variants does not arise from enhanced degradation of circulating 2BVWF-platelet-complexes but more likely occurs at the surface of endothelial cells during secretion. Our data could increase understanding of VWD2B disease phenotypes.
To cite this abstract in AMA style:
Brehm M, Yildiz Y, Obser T, Mojzisch A, Peine S, Schneppenheim S, Budde U, Schneppenheim R. Activity and Cleavage of von Willebrand Disease Type 2B Variants [abstract]. Res Pract Thromb Haemost. 2021; 5 (Suppl 2). https://abstracts.isth.org/abstract/activity-and-cleavage-of-von-willebrand-disease-type-2b-variants/. Accessed September 21, 2023.« Back to ISTH 2021 Congress
ISTH Congress Abstracts - https://abstracts.isth.org/abstract/activity-and-cleavage-of-von-willebrand-disease-type-2b-variants/