Von Willebrand Factor Modulates Factor VIII Immunogenicity: Comparative Study of Different Factor VIII Concentrates in a Haemophilia A Mouse Model

Abstract

SummaryThe development of an immune response towards factor VIII (FVIII) remains the major complication of haemophilia A replacement therapy. Product-related risk factors have recently been identified on the basis of epidemiological studies, but the mechanism is not understood. To this end, various commercially available FVIII concentrates were administered by the IV route to FVIII-knockout mice and the resulting immune response was characterised. Significantly higher inhibitor titres (Bethesda assay) were observed for one recombinant FVIII and one plasma-derived FVIII product depleted in von Willebrand factor (VWF). Inhibitor titres were reduced upon pre-incubation of FVIII with purified VWF. Epitope specificity of anti-FVIII IgG was characterised using FVIII-fragments produced in E. coli. Concentrates with no or reduced VWF-level elicited antibodies recognising predominantly the acidic a1 and a3 regions. Addition of VWF prior to injection also modified the epitope specificity. FVIII concentrates, therefore, show qualitative and quantitative variations in immunogenicity, which are at least partly modulated by VWF.

Comparison of the immunogenicity of different therapeutic preparations of human factor VIII in the murine model of hemophilia A

“…This observation reflects previous findings in FVIII-deficient mice. 6 The VWF used in our studies is a plasma-derived preparation that contains trace amounts 9 Our results demonstrate that the in vitro pre-incubation of rFVIII with VWF reduced its immunogenicity to the level achieved with pdFVIII. These data suggest that the immunogenicity of rFVIII is not due exclusively to the reduced ability of rFVIII to bind to VWF, but that other mechanisms must be implicated.…”

“…5 In fact, studies in a murine model of hemophilia A have indicated that the immunogenicity of FVIII is reduced in the presence of VWF. 6 We used the well-established model of FVIII-deficient mice to compare the immunogenicity of therapeutic preparations of pdFVIII and recombinant FVIII (rFVIII) that were commercially available in France at the time of the study. …”

Optimizing management of immune tolerance induction in patients with severe haemophilia A and inhibitors: towards evidence‐based approaches

“…However, in this uncontrolled retrospective series, patient characteristics were not described and the duration of ITI courses with rFVIII was often shorter than that carried out with pdFVIII (Kreuz et al, 2001), therefore the influence of several confounding factors could not be ruled out. Due to the key roles of von Willebrand Factor (VWF) in FVIII function, stabilization and, possibly, immunogenicity (Suzuki et al, 1996;Behrmann et al, 2002), its presence in pdFVIII has been proposed for contributing to these findings. Binding of VWF to the C2 domain of FVIII, one of the most common inhibitor reactive sites, may result in epitope masking and decreased inhibitor reactivity to the FVIII/VWF complex.…”

Immune tolerance induction with a high purity von Willebrand factor/VIII complex concentrate in haemophilia A patients with inhibitors at high risk of a poor response

“…VWF, beyond being the physiological FVIII-stabilizing protein [12,13] was shown to protect FVIII from neutralizing antibodies in vitro [14][15][16][17][18][19][20]. Accordingly, a better response to ITI was observed in two case series when ITI carried out with FVIII concentrates rich in VWF [21,22] was compared with ITI carried out with VWF-free FVIII concentrates either plasmaderived monoclonally purified or recombinant.…”