A well-known complication of factor VIII replacement therapy in patients with hemophilia A is the development of inhibitory antibodies. Several studies have demonstrated the presence of a binding site for factor VIII inhibitors in the A3 domain. Six different human monoclonal single-chain variable domain antibody fragments (scFv) directed toward the A3-C1 domains of factor VIII have been isolat...

Thrombin treatment of the coagulation factor VIII results in a rapid activation of procoagulant activity with a subsequent first order decay. The structural requirements for thrombin-activated factor VIII were characterized using recombinant-derived human factor VIII and site-directed DNA-mediated mutagenesis. Thrombin-activated human recombinant-derived factor VIII was isolated in an active fo...

Apparently quiescent, nonapoptotic endothelial cells mediate the activation of factor X by activated factor IX in the presence of its cofactor, activated factor VIII. In a previous study, we reported that during the activation of factor X, the interaction of the cofactor with the endothelial cell membrane clearly differs from the interaction of the cofactor with artificial lipid membranes. In t...

With the aim of the production of human factor VIII antigen and its corresponding antibody an epitope coding fragment of the light-chain of hFVIII, fused to a His6-tag, was isolated and over-expressed in Escherichia coli. The over-expressed hFVIII-epitope containing peptide was confirmed by its reaction with a rabbit serum directed against native hFVIII as well as antiHis6-tag antibody. An expr...

Coagulation factor V is a high molecular weight plasma glycoprotein that participates as a cofactor in the conversion of prothrombin to thrombin by factor Xa. A phage lambda gt11 Hep G2 cell cDNA expression library was screened by using an affinity-purified antibody to human factor V, and 11 positive clones were isolated and plaque-purified. The clone containing the largest cDNA insert containe...

An immunoadsorbent method has been developed for the direct analysis of normal and variant plasma factor VIII. Using this method, the molecular defect responsible for mild hemophilia A has been identified for a patient whose plasma factor VIII activity is 0.05 unit/ml, even though the factor VIII antigen content is 3.25 units/ml. Although the variant factor VIII has an apparently normal molecul...

The heterogeneity of human circulating anticoagulants against antihemophilic factor (AHF, factor VIII) observed in seven patients, both with and without classic hemophilia, was investigated by neutralization of their activity with antiserums directed to whole IgG and to lambda and kappa light chains. All seven anticoagulants were immunoglobulins. Six appeared to contain both kinds of light chai...

Factor IXa was shown to inactivate both factor Vlll and factor Vllla in a phospholipid-dependent reaction that could be blocked by an antifactor IX antibody. Factor IXa-catalyzed inactivation correlated with proteolytic cleavages within the A1 subunit of factor Vllla and within the heavy chain (contiguous AI-A2-6 domains) of factor VIII. Furthermore, a relatively slow conversion of factor Vlll ...