Abstract Number: PB0326
Meeting: ISTH 2020 Congress
Background: High Factor VIII (FVIII) content is a major contributing factor to deep-vein thrombosis (DVT). On the other hand, Von Willebrand Factor (VWF), the FVIII carrier protein, is not associated with this condition. In thrombosis patients with high FVIII levels, DVT recurrence rates are higher than in patients without this coagulation abnormality. Although VWF could theoretically bind FVIII, an unbound FVIII plasma fraction remains. In venous thromboembolism, an altered unbound FVIII fraction could be indicative of dysfunctional FVIII regulation. The evaluation of the unbound component could better characterize high plasma FVIII levels and provide insight into the pathophysiology of this thrombophilic state.
Aims: To develop a method to determine the FVIII fraction able to bind VWF.
Methods: Five purified FVIII samples from Kedrion have been used after determination of FVIII:Ag and VWF:Ag levels with Asserachrom®-VIII:Ag and STA®-Liatest®-VWF. These concentrated samples have been diluted at 1:100 in 0.9% saline solution.
Assay optimization was performed using Asserachrom®-VWF:FVIIIB. Calibrations were carried out with lyophilized human plasma containing, after reconstitution, a known quantity of recombinant FVIII provided by Stago.
· To dose the complex FVIII:VWF, the samples are immobilized directly in the wells, without dissociation of the complex.
· To estimate the unbound FVIII capacity to bind exogenous VWF, the wells are first saturated with exogenous VWF from STA®-Immunodef-VIII. Then, samples are immobilized without dissociation of the complex.
Results: The addition of both assays results allows to dose the part of total FVIII:Ag able to bind VWF.
| (%) | VWF:Ag | FVIII:Ag | FVIII:VWF complex | Unbound FVIII capacity to bind exogenous VWF | Total FVIII capacity to bind VWF |
| Sample n°1 | 5750 | 7541 | 1891 | 901 | 37.0% |
| Sample n°2 | 6650 | 9051 | 2861 | 1511 | 48.3% |
| Sample n°3 | 4050 | 10077 | 1656 | 1727 | 33.6% |
| Sample n°4 | 7550 | 12606 | 5384 | 1376 | 53.6% |
| Sample n°5 | 6150 | 15375 | 4935 | 1490 | 41.8% |
[Summary of Stago assay results with Kedrion samples]
Conclusions: These new methods give the possibility to dose both the complex of FVIII:VWF and FVIII ability to bind exogenous VWF. This approach could be useful in the understanding of mechanisms associated with FVIII stabilization in DVT, as well as more generally to the blood derivatives industry.
To cite this abstract in AMA style:
Mori F, Genuardo C, Caricasole A, Grimaux M, Kerleau O, Mathieu O, Natelli S, Hervé T, Depasse F, Fuligni P, Juif A. A New Test Set up to Dose Factor VIII Ability to Bind Exogenous VWF [abstract]. Res Pract Thromb Haemost. 2020; 4 (Suppl 1). https://abstracts.isth.org/abstract/a-new-test-set-up-to-dose-factor-viii-ability-to-bind-exogenous-vwf/. Accessed January 26, 2022.« Back to ISTH 2020 Congress
ISTH Congress Abstracts - https://abstracts.isth.org/abstract/a-new-test-set-up-to-dose-factor-viii-ability-to-bind-exogenous-vwf/