Immune responses to coagulation factors VIII (FVIII) and IX (FIX) represent primary obstacles to hemophilia treatment. Previously, we showed that hematopoietic stem cell (HSC) retroviral gene therapy induces immune nonresponsiveness to FVIII in both naive and preimmunized murine hemophilia A settings. Liver-directed adeno-associated viral (AAV)-FIX vector gene transfer achieved similar results ...

Neutralizing autoantibodies against factor VIII (FVIII), also called FVIII inhibitors, are the cause of acquired hemophilia A (AHA). They are quantified in the Bethesda assay or Nijmegen-modified Bethesda assay by their ability to neutralize FVIII in normal human plasma. However, FVIII inhibitors do not represent the whole spectrum of anti-FVIII autoantibodies. Here, we studied isotypes, immuno...

Gene therapy for hemophilia A would be facilitated by development of smaller expression cassettes encoding factor VIII (FVIII), which demonstrate improved biosynthesis and/or enhanced biologic properties. B domain deleted (BDD) FVIII retains full procoagulant function and is expressed at higher levels than wild-type FVIII. However, a partial BDD FVIII, leaving an N-terminal 226 amino acid stret...

Haemophilia A patients treated with human factor VIII (fVIII) may develop antibody (Ab) inhibitors to fVIII. FVIII-specific CD4(+) T cells are common in haemophilia A patients, but also in healthy subjects who do not have a sustained anti-fVIII Ab response. Here, we examined the fVIII-induced IFN gamma-, IL-4- and TGF-beta1-producing CD4(+) T blasts by culturing peripheral blood mononuclear cel...

The formation of inhibitory antibodies directed against coagulation factor VIII (FVIII) is a severe complication in the treatment of hemophilia A patients. The induction of anti-FVIII antibodies is a CD4(+) T cell-dependent process. Activation of FVIII-specific CD4(+) T cells is dependent on the presentation of FVIII-derived peptides on MHC class II by antigen-presenting cells. Previously, we h...

We have used immunoblotting of purified factor VIII (FVIII) to determine whether or not changes in FVIII chain specificity occur during the course of an inhibitor. Serial plasma samples from 15 inhibitor patients (13 hemophilic and two spontaneous) were analyzed. Nine of the 15 antibodies, all with epitopes on the 44-kilodalton (Kd) thrombin fragment of the 92-Kd FVIII heavy chain and/or the 72...

ABO blood groups are known to influence the plasma level of von Willebrand factor (VWF), but little is known about the relationship between ABO and coagulation factor VIII (FVIII). We analyzed the influence of ABO genotypes on VWF antigen, FVIII activity, and their quantitative relationship in 11,673 participants in the Atherosclerosis Risk in Communities (ARIC) study. VWF, FVIII, and FVIII/VWF...

A factor VIII-deficient knockout mouse was used as a model for severe hemophilia A to characterize the immune response to recombinant human factor VIII (fVIII) and to study new approaches for induction of immune tolerance to fVIII. Mice initially received periodic injections of fVIII in doses similar to those used for the treatment of human hemophilia A. To induce immune tolerance, a hamster mo...

BACKGROUND Recombinant factor VIII (FVIII), used for haemophilia A therapy, is one of the most challenging among the therapeutic proteins produced in heterologous expression systems. Deletion variant of FVIII, in which the entire domain B is replaced by a short linker peptide, was approved for medical use. Efficacy and safety of this FVIII deletion variant are similar to full-length FVIII prepa...

When Factor VIII/von Willebrand factor (FVIII/vWF) protein is rechromatographed on 4% agarose in 0.25 M CaCl(2), the protein and vWF activity appear in the void volume, but most of the FVIII procoagulant activity elutes later. Recent evidence suggests that the delayed FVIII procoagulant activity is a proteolytically modified form of FVIII/vWF protein that filters anomalously from agarose in 0.2...