Recombinant canine B-domain deleted (BDD) factor VIII (FVIII) is predominantly expressed as a single-chain protein and exhibits greater stability after activation compared with human FVIII-BDD. We generated a novel BDD-FVIII variant (FVIII-RH) with an amino acid change at the furin cleavage site within the B domain (position R1645H) that mimics the canine sequence (HHQR vs human RHQR). Compared...

Acquired hemophilia is a rare hemorrhagic disorder caused by the spontaneous appearance of inhibitory autoantibodies directed against endogenous coagulation factor VIII (FVIII). Inhibitory Abs also arise in patients with congenital hemophilia A as alloantibodies directed to therapeutic FVIII. Both autoimmune and alloimmune inhibitors neutralize FVIII by steric hindrance. We have described FVIII...

Development of neutralizing Abs to blood coagulation factor VIII (FVIII) provides a major complication in hemophilia care. In this study we explored whether modulation of the uptake of FVIII by APCs can reduce its intrinsic immunogenicity. Endocytosis of FVIII by professional APCs is significantly blocked by mAb KM33, directed toward the C1 domain of FVIII. We created a C1 domain variant (FVIII...

Inhibitory antibodies to factor VIII (FVIII inhibitors) are the most significant complication in the management of haemophilia A. The immunogenicity of FVIII may be driven in part by structural determinants within the FVIII molecule itself. Regions of nonidentity between human and porcine FVIII possibly could drive differential immune responses. The goal of this study was to compare the overall...

The development of neutralizing anti-factor VIII (FVIII) antibodies complicates the treatment of many hemophilia A patients. The C-terminal C2 domain is a particularly antigenic FVIII region. A crystal structure of recombinant FVIII-C2 bound to an Fab fragment of the patient-derived monoclonal antibody BO2C11, which recognizes an immunodominant inhibitor epitope on FVIII and blocks its ability ...

The development of an immune response towards factor VIII (fVIII) remains a major complication for hemophilia A patients receiving fVIII infusions. The design of a specific therapy to restore unresponsiveness to fVIII has been hampered by the diversity of the anti-fVIII antibody. Molecular analysis of the specific immune response is therefore required. To this end, we have characterized an fVII...

A large fraction of FVIII in blood originates from liver sinusoidal endothelial cells although extrahepatic sources also contribute to plasma FVIII levels. Identification of cell-types other than endothelial cells with capacity to synthesize and release FVIII will be helpful for therapeutic approaches in hemophilia A. Recent cell therapy and bone marrow transplantation studies indicated that Ku...

Canine factor VIII (FVIII) preparations isolated from cryoprecipitates by gel chromatography were pooled to provide one batch of antigen for simultaneous immunization of two rabbits and a goat. The goat and rabbit antisera had similar FVIII-neutralizing titers, but the latter had seven to ten times more precipitating titer for FVIII-related antigen (FVIII-RA). Absorption with material low in FV...

Development of neutralizing antibodies against therapeutic Factor VIII (FVIII) is the most serious complication of the treatment of hemophilia A. There is growing evidence to show the multifactorial origin of the anti-FVIII immune response, combining both genetic and environmental factors. While a role for the complement system on innate as well as adaptive immunity has been documented, the imp...

Von Willebrand factor (VWF) is a chaperone molecule for procoagulant factor VIII (FVIII). Its role in the reduction of the immunogenicity of therapeutic FVIII in patients with hemophilia A has been evoked but lacks clear cellular and molecular rationale. Here, we demonstrate that VWF protects FVIII from being endocytosed by human dendritic cells (DCs) and subsequently presented to FVIII-specifi...