Acute myocardial infarction during treatment with an activated prothrombin complex concentrate in a patient with factor VIII deficiency and a factor VIII inhibitor.
Explore the source record for details and available documents.
Adolescent↗
SEARCH · Search PubMed
Results for “FACTOR VIII”
Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Detection of factor VIII von Willebrand factor in endothelial cells in first-trimester fetuses.
Factor VIII von Willebrand factor was studied by the immunoperoxidase method in 38 cases of first-trimester therapeutic abortion and two cases of early second-trimester therapeutic abortion. Positive immunostaining was observed in endothelial cells at all gestational ages studied. The findings demonstrate the presence of factor VIII von Willebrand factor in endothelial cells as early as four weeks' gestational age.
Blood Vessels↗
Suppression of factor VIII antibody by combined factor VIII and cyclophosphamide.
Explore the source record for details and available documents.
Administration, Oral↗
Factor VIII concentrate-responsive thrombocytopenia, hemolytic anemia, and nephropathy. Evidence that factor VIII:von Willebrand factor is involved in its pathogenesis.
A 4-year-old Japanese girl had a congenital disorder that was characterized by recurrent thrombocytopenia, hemolytic anemia, hematuria, and proteinuria, which were repeatedly improved by the infusion of factor VIII concentrate. She developed the similar symptoms within 1 h after 1-desamino-8-D-arginine vasopressin (DDAVP) administration. Coagulation studies 30 and 60 min after DDAVP infusion showed a disappearance of large factor VIII:von Willebrand factor (VIII:vWF) multimers, which was the same abnormality that was observed at acute episodes. There were no significant changes in the plasma levels of 6-keto-prostaglandin F1 alpha and thromboxane B2 before and after DDAVP infusion. These results provide further support that VIII:vWF is directly involved in the pathogenesis of this congenital disorder.
Anemia, Hemolytic↗
The effect of thrombin on human factor VIII. Cleavage of the factor VIII procoagulant protein during activation.
Human VIII: C has been partially purified by immunoabsorbent chromatography and agarose gel filtration in the presence of 2 mM DFP. The ratio of VIII:C to VIIIR:Ag in these preparations was greater than 1000:1, and the VIII:C procoagulant and immunologic (VIII:CAg) activities eluted together from Sephadex G-200 with a Kav of 0.05, a value consistent with a Stokes radius of 88 A. The molecular weight estimated from this measurement and sucrose density-gradient centrifugation studies (8.2S) is 285,000. VIII:C activation was detected when the purified procoagulant was incubated with 2 x 10(-5) to 10(-2) U/ml highly purified human alpha-thrombin. Although 2 mM DEP inhibits VIII:C activation by alpha-thrombin, DFP added after activation did not prevent subsequent loss of activity. When VIII:C was incubated for 4 hr with dilute alpha-thrombin, 2 x 10(-5) to 2 x 10(-3) U/ml, the activated procoagulant (VIII:C/VIII:CAg > 1) eluted from Sephadex G-200 with a Kav of about 0.2 This gel filtration pattern corresponds to a protein with a Stokes radius of 60 A and, taken together with a preliminary estimate of sedimentation properties (5S), suggests a molecular weight of about 116,000. Higher concentration of thrombin, 10(-3) to 10(-1) U/ml, inactivated VIII:C in these experiments, and the nonfunctional protein was identified by VIII:CAg immunoassay. The inactivated VIII:CAg eluted from Sephadex G-200 in a broad peak of Kav approximately 0.3. THese data suggest that alpha-thrombin activates and inactivates human VIII:C by proteolytic modification of VIII:C structure and that thrombin-activated VIII:C is smaller than the unactivated procoagulant.
Blood Coagulation↗
The use of a chromogenic assay for factor VIII in patients with factor VIII inhibitors or von Willebrand's disease.
Explore the source record for details and available documents.
Autoantibodies↗
Factor VIII von Willebrand factor antigen levels correlate with symptom severity in patients with Raynaud's phenomenon.
We have previously documented raised levels of factor VIII von Willebrand factor antigen (FVIII vWF Ag), an endothelial product, in patients with vascular diseases and suggested that levels of this relate to disease activity. No one has yet investigated patients with Raynaud's phenomenon (RP) alone to see if the severity of vasospastic attacks relates to FVIII vWF Ag. We studied 22 patients with RP. None of these patients fulfilled diagnostic criteria for a connective tissue disease but all had severe symptoms which warranted referral to hospital. We measured the FVIII vWF Ag and the procoagulant factor VIII (FVIII:c) levels in these patients. FVIII:c is not an endothelial product and is released by different mechanisms, thus it forms an active control to FVIII vWF Ag. FVIII vWF Ag measurements were carried out using the Laurell method and FVIII:c was assessed using the technique described by Nilsson. Patients were asked to complete diaries over a 2-week winter period. The frequency and duration of all Raynaud's attacks were recorded. There were significant positive correlations between FVIII vWF Ag and the total number and duration of RP attacks over the 2-week period (P less than 0.005, r = 0.67 and P less than 0.05, r = 0.40, respectively; Spearman's rank correlation). No correlation was found between levels of FVIII:c and the same clinical parameters. It has been suggested that patients with clinical evidence of vascular damage have elevated plasma levels of FVIII vWF Ag. Our present study has demonstrated correlations between FVIII vWF Ag levels and the clinical severity of vasospasm in patients with RP.(ABSTRACT TRUNCATED AT 250 WORDS)
Adolescent↗
Protein content and factor VIII complex in untreated, treated and monoclonal factor VIII concentrates.
Replacement therapy with clotting factor concentrates may expose the recipients not only to virus contamination but also to continuous stimulation of the immune system by repeated infusions of allogenic proteins. Concentrate purity is now a very important prerequisite to be taken into account in choosing what product can better meet the patient's needs. We compared protein content (albumin, fibrinogen, fibronectin, immunoglobulins) and factor VIII:C/vWF:Ag complex in untreated, treated and monoclonal factor VIII concentrates. Protein content is dramatically decreased in new treated ultrapure concentrates. Improved traditional fractionation methods allowed to obtain very high Factor VIII specific activity. New fractionation methods with immunoaffinity chromatography by means of monoclonal antibodies can give highly pure concentrates even if deliberately added albumin decreases factor VIII specific activity in final formulation. Otherwise monoclonal concentrates show a very high specific activity in terms of fibrinogen and immunoglobulin content, which, unlike albumin, are affecting the immune system in hemophiliacs.
Antibodies, Monoclonal↗
Long-term high dose factor VIII treatment of 3 haemophiliacs with factor VIII inhibitor.
3 patients with haemophilia A and inhibitor against Factor VIII were developing progressive haemophiliac arthropathy due to the non-feasibility of prophylactic treatment. In order to suppress inhibitor formation, long-term treatment with high-dose Factor VIII (100 units per kg body weight twice daily) was initiated. Prothrombin complex concentrate was given only for bleeding episodes. Though all 3 patients were high responders, they presented different treatment courses. 2 became low responders after 4 and 11 months' treatment, respectively. 1 patient had no demonstrable inhibitor after start of treatment. In all 3 patients, prophylactic treatment was established, in 1 case still with increased doses compared to non-inhibitor patients. The high-dose Factor VIII treatment makes in possible to provide prophylactic treatment for the high-responder inhibitor patients. However, the extremely high costs represent a serious obstacle to this treatment.
Adolescent↗
The subunit structure of normal and hemophilic factor VIII.
Human factor VIII from normals and hemophiliacs was partially purified by ethanol and polyethylene glycol precipitations. Final purification was achieved by gel filtration on 2 or 4% agarose or ion exchange chromatography on diethylaminoethyl cellulose. Comparable amounts of highly purified protein were obtained from normal and hemophilic plasma following the agarose chromatography step. Highly purified factor VIII was not dissociated by 6 M guanidine hydrochloride or 1% sodium dodecyl sulfate. However, when reduced by beta-mercaptoethanol and analyzed by sodium dodecyl sulfate polyacrylamide gel electrophoresis, a single subunit species with an estimated 195,000 molecular weight was found for both normal and hemophilic factor VIII. By sedimentation equilibrium analysis, the normal factor VIII subunit was homogeneous and had an estimated molecular weight of 202,000. The subunit polypeptides from normal or hemophilic factor VIII contained carbohydrate. Each was homogeneous by isoelectric focusing. Immunodiffusion of purified normal and hemophilic factor VIII against rabbit antiserum to purified normal human factor VIII showed a single line of precipitation. Very low concentrations of purified human thrombin initially increased the activity of normal factor VIII about threefold and then progressively destroyed activity by 3 h. Only minimal activation occurred with hemophilic factor VIII. Both the activation and inactivation of normal and hemophilic factor VIII were unaccompanied by detectable changes in subunit molecular weight. These findings may have implications for the definition of the molecular defect in hemophilic factor VIII.
Amino Acids↗
Reactivity of factor VIII inhibitors in a micro ELISA for factor VIII: CAg and in solid phase immunoisolation of VIII: CAg.
Factor VIII coagulant antigen (VIII: CAg) was measured in a sandwich-ELISA. Microplates were used as solid phase and peroxidase conjugated F(ab')2 fragments of IgG isolated from inhibitor plasma was used as label without affinity purification. The capacity of the assay was high and the sensitivity for VIII: CAg was 0.002 U/ml. Using this assay it was possible to measure coagulation inactive VIII: CAg in samples from purification studies. Below 0.05 VIII: CAg U/ml these samples responded in parallel with standard plasma. Seven of 7 inhibitor antibodies tested were able to inhibit binding of peroxidase-conjugate in the VIII: CAg assay, and the inhibitory capacity correlated with coagulation inhibition as measured by the Bethesda method. Using the highest titered antibodies bound to a solid phase, VIII: CAg was isolated and identified in SDS-PAGE as a doublet with a molecular weight of 77-80 kD.
Antigen-Antibody Complex↗
The use of polyelectrolyte-fractionated porcine factor VIII in the treatment of a spontaneously acquired inhibitor to factor VIII.
Polyelectrolyte-fractionated porcine factor VIII concentrate is a recent addition to the therapeutic choices for treatment of factor VIII inhibitor patients, but cross-reactivity of the inhibitor with porcine factor VIII limits its usefulness in some cases. Hemophilic patients with inhibitor titers greater than or equal to 50 Bethesda units/micromilligrams often demonstrate sufficient cross-reactivity (10-20%) to prevent the achievement of a satisfactory plasma factor VIII level and a therapeutic response with porcine factor VIII. We have studied plasma from five women with high-titer, spontaneously acquired factor VIII inhibitors to determine the degree of cross-reactivity with porcine factor VIII. Four of the five had little or no detectable inhibitor to porcine factor VIII despite high titers to human factor VIII (26-143 Bethesda units/micromilligrams). One of these patients, with a titer of 53 Bethesda units/micromilligrams against human factor VIII, was treated successfully with porcine factor VIII concentrate, given for serious hemorrhagic complications. These studies and other reports support the conclusion that the majority of high-titer spontaneous factor VIII inhibitors exhibit little cross-reactivity with porcine factor VIII and can be treated successfully with this product.
Adult↗
Validation of a procedure for potency assessing of a high purity factor VIII concentrate--comparison of different factor VIII coagulant assays and effect of prediluent.
The assessment of factor VIII coagulant activity (FVIII:C) in recently available highly purified and concentrated FVIII therapeutic products calls for careful evaluation of assay methodologies. We assayed more than 130 batches of a concentrate with a specific activity of about 150 FVIII:C units/mg protein, using one-stage and two-stage clotting and chromogenic methods. There was good agreement between the potency estimates obtained with the different methods. We also compared the FVIII:C potencies obtained after predilution in buffer or FVIII-deficient plasma using either calibrated plasma or FVIII concentrate as references. With the one-stage assay we found a marked discrepancy between the potency values obtained with buffer and with FVII-deficient plasma used as prediluents. In order to validate our "in vitro" data we performed 6 "in vivo" analyses in severe haemophilia A patients. On the basis of the overall data obtained we chose to label FVIII potency by using FVIII-deficient plasma as prediluent, reference plasma as standard and the chromogenic assay method.
Blood Coagulation Tests↗
Immunoblot analysis shows changes in factor VIII inhibitor chain specificity in factor VIII inhibitor patients over time.
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-Kd thrombin fragment of the 80-Kd FVIII light chain, showed no change in FVIII chain specificity. However, six of the inhibitors analyzed showed changes in FVIII fragment specificity. Four inhibitors (three hemophilic and one spontaneous) reactive with 72-Kd thrombin fragment also became reactive with the 44-Kd thrombin fragment after an anamnestic response to FVIII infusion. Another inhibitor with epitopes on both the 54-Kd and 44-Kd thrombin fragments lost most of its reactivity with the 44-Kd fragment but retained its reactivity with the 54-Kd fragment following a FVIII infusion. The inhibitor later regained its 44-Kd-fragment reactivity but lost its 54-Kd-fragment reactivity following treatment with FEIBA, FVIII inhibitor bypassing activity. The last inhibitor studied had an antibody to either the 44-Kd fragment or to both the 44-Kd and 72-Kd fragments during anamnestic responses to FVIII. These data indicate that a FVIII inhibitor patient can potentially produce antibody to multiple areas on the FVIII molecule and that this must be taken into account in the design of specific therapeutic products.
Epitopes↗
Mechanism of factor VIII inactivation by human antibodies. IV. Antibody binding prevents factor VIII proteolysis by thrombin.
Factor VIII activation by thrombin is the result of a proteolytic cleavage of the procoagulant component. These studies examine the effect of human antibody on this activation step in a solid phase immunoadsorbent assay system. Radiolabeled factor VIII antibody: factor VIII protein immune complexes were bound to agarose beads by mouse monoclonal antifactor VIII R:Ag antibody. The incubation of these bound labeled immune complexes with high ionic strength buffers (1 M NaCl, 0.24 M CaCl2), or with acidic buffers (0.01 M glycine-0.1 M NaCl, pH 3.0 or 3.5), or with trypsin (1, 5, and 20 mg per ml) dissociated 14 to 62 percent of the bound radiolabel. Thrombin at a concentration of 0.05 U per ml, however, only dissociated 2.9 percent of the label, an amount not significantly different than borate buffered saline control. It is concluded that inactivation of factor VIII is the result of human antibody inhibition of thrombin-induced proteolysis of factor VIII procoagulant protein.
Antigen-Antibody Complex↗
A synthetic factor VIII peptide of eight amino acid residues (1677-1684) contains the binding region of an anti-factor VIII antibody which inhibits the binding of factor VIII to von Willebrand factor.
The monoclonal anti-factor VIII (FVIII) antibody C4 has previously been reported to inhibit the binding of purified FVIII to immobilized von Willebrand factor (vWF). The binding area of C4 was identified to be within fifteen amino acid residues (1670-1684) based on the ability of a synthetic FVIII peptide consisting of amino acid residues 1670-1684 to completely inhibit the binding of C4 to FVIII. We now report the further localization of the binding region of C4 to within eight amino acid residues (1677-1684) of FVIII light chain. Nine new overlapping FVIII peptides were synthesized based on the amino acid sequence of the acidic region of FVIII light chain and tested, along with seven previously tested peptides, for the ability to inhibit C4 binding to FVIII in an ELISA assay. Three synthetic FVIII peptides 1670-1684, 1675-1690, and 1677-1684 demonstrated dose dependent inhibition of C4 binding to FVIII. The three reactive peptides contain residues 1677-1684 in common. Since C4 can completely inhibit the binding of FVIII to vWF, this report further localizes an eight amino acid residue region of FVIII which may be important in the mediation of vWF binding.
Amino Acid Sequence↗
In vitro reactivity of factor VIII inhibitors with von Willebrand factor in different commercial factor VIII concentrates.
A relevant aspect in the treatment of patients with hemophilia A (HA) presenting inhibitor against factor VIII (FVIII) is the different antigenicity of FVIII used for replacement therapy. The aim of the study was to assess the effect of different products, with variable von Willebrand factor (vWF) concentration, in preventing the binding of inhibitor to FVIII. The reactivity of inhibitors from plasma of 18 patients with HA versus three commercial concentrates containing different amounts of vWF was compared. The results show that increasing amounts of vWF might have a protective effect on the transfused FVIII inactivation.
Adult↗
Clinical experience with polyelectrolyte-fractionated porcine factor VIII concentrate in the treatment of hemophiliacs with antibodies to factor VIII.
Circulating antibodies to factor VIII (anti-VIII, "inhibitors") occurring in patients with hemophilia neutralize porcine factor VIII less readily than human factor VIII in vitro. Over an 18-mo period, 8 patients with anti-VIII were treated with 45 courses (297 infusions) of polyelectrolyte-fractionated porcine factor VIII concentrate (PE porcine VIII). Where no anti-PE porcine VIII was detectable, mean post-infusion rise in plasma factor VIII was 1.29 U/dl/units infused/kg. Above 13 Old Oxford units of anti-PE porcine VIII and 48 Bethesda units of anti-human VIII, there were no postinfusion rises in plasma factor VIII. Where postinfusion rises were detected, clinical responses were good and conventional methods could be used to guide dosage. Ten percent of infusions were followed by febrile reactions, but these were usually mild and decreased in frequency and severity with increasing exposure. Multiple and prolonged courses of therapy were given to some patients without evidence of loss of clinical or laboratory efficacy. PE porcine VIII could provoke anamnestic rises of anti-VIII in susceptible patients, but appeared to have a lower immunogenic potential than human VIII. PE porcine VIII is a rational and effective therapeutic alternative for patients with anti-VIII, particularly those with intermediate level inhibitors who cannot be managed effectively using human factor VIII.
Adolescent↗