Production of high-potency concentrates of antihemophilic globulin in a closed-bag system

Direct capture of plasma factor VIII:C by ion exchange chromatography

An ion exchange medium, DEAE-Fractogel 650M, can be used to capture factor VIII (FVIII) directly from plasma. Previous reports have focussed on the use of this medium to capture FVIII from cryoprecipitate. In this report, citrate phosphate dextrose plasma was batch-stirred with DEAE-Sephadex A50, filtered, diluted, loaded onto a column packed with DEAE-Fractogel TSK 650M, and chromatographed. Most of the unwanted proteins flowed through the gel unadsorbed. Bound FVIII was eluted by increasing the ionic strength of the buffer. A citrate-based buffer gave an overall FVIII:C yield of 670 IU/kg plasma with a specific activity of 0.68 IU FVIII:C/mg protein. This process gave a higher yield of FVIII:C but significantly more prothrombin complex factors than cryoprecipitation. This method is a promising alternative to cryoprecipitation of FVIII.

Development and small-scale production of a severely heated factor VIII concentrate

The small-scale production of a severely heated factor VIII concentrate is described. As starting material for the production 48 units of fresh frozen plasma from whole-blood donations or 24 units of plasma from apheresis are used. During a glycine and sodium chloride fractionation, contaminating proteins are removed from a pooled extract of single-donor cryoprecipitates. The resulting factor VIII-rich precipitate is redissolved in freeze-drying buffer and this solution is desalted by diafiltration. After filtration, this solution is dispensed into 10 vials and frozen. The product is freeze dried, and heat treated at 80 degrees C for 72 h. The mean yield of the heat-treated product improved from 160 IU factor VIII per liter plasma at the start of the production to 215 IU per liter plasma after a modification of the purification process. The validation of the virus inactivation during freeze-drying and 80 degrees C heat treatment for 72 h showed a reduction of > or = 7.6 log PFU/ml for Sindbis and a reduction of > or = 6.4 log TCID50/ml for HIV-1. The factor VIII concentrate was clinically tested in 6 patients. It possessed a normal half-life, showed a high recovery and no side effects. A Dutch license was granted in June 1991 and since then this product has been routinely manufactured in three Dutch blood banks.

Some complications of the therapy of hemorrhagic disorders

The principal mode for treating disorders of hemostasis is correction of the patient's functional defect by transfusions of appropriate fractions of normal plasma or transfusions of platelets. Two major complications of such therapy are the transmission of infectious diseases, particularly hepatitis and the acquired immune deficiency syndrome (AIDS), and the development of antibodies against clotting factors that are deficient in the patient's plasma. Measures that reduce the occurrence of infection include careful selection of donors, fractionation of plasma with the help of monoclonal antibodies, and treatment of plasma or its fractions with heat or with virus-inactivating organic solvents. No technique of preparing or administering blood or its components can prevent the emergence of antibodies against clotting factors. Desensitization by repeated infusions of antigen, for example, antihemophilic factor, however, appears to result in remission in some patients.

Effectiveness of cryosupernatant therapy in refractory and chronic relapsing thrombotic thrombocytopenic purpura

This report describes objective improvement in two patients with poorly responsive thrombotic thrombocytopenic purpura (TTP) syndromes (with cryosupernatant). The first had a partial response to plasma exchange with whole plasma (fresh frozen plasma; FFP) and responded dramatically when switched to plasma exchange with cryosupernatant replacement. The second had chronic TTP (three relapses in 9 months) that required prolonged courses of exchange with FFP (approximately 1 month each) to achieve remission. Attempts to manage her recurrent TTP with infusion of two units of FFP had been unsuccessful. The latter patient was tried on cryosupernatant infusions (2 units daily) and responded within 4 days. Moreover, she has been in continuous remission for 12 months while receiving 2 units (one to three times per week). These results suggest that cryoprecipitate-poor plasma may offer advantages over whole plasma in the management of both acute and chronic forms of TTP.

Factor VIII:c concentrate virus inactivated: progress in purification by using classic chromatographic methods

This study was carried out with the aim of developing a production process for the manufacture of a highly purified factor VIII concentrate which is virus inactivated by pasteurization in liquid phase. Beside standard plasma protein separation techniques, the procedure uses a chromatographic step on anion exchanger, whose selectivity is increased by using high, but not destabilizing salt concentrations. The final product before stabilization has a specific activity higher than 300 IU/mg of protein, namely the highest specific activity reported for human factor VIII concentrates purified without the use of immunoadsorbents.

Circumcision in hemophilia: the use of fibrin glue for local hemostasis

Circumcision can be fatal in hemophilia patients unless they are treated with the missing coagulation factor. We describe 10 severe hemophilia patients in whom circumcision was performed with local fibrin glue instead of infusion of factor concentrate. Of the 10 patients 3 had postoperative bleeding and only 2 of them required infusion of factor VIII concentrate. Fibrin glue is a useful treatment modality for circumcision in patients with bleeding diathesis, and it is safer and cheaper than the infusion of factor concentrate.

Replacement therapy with virus-inactivated plasma concentrates in von Willebrand disease

In von Willebrand disease, the goal of treatment is to correct the two laboratory hallmarks of abnormal hemostasis, i.e. the deficiency of factor VIII (FVIII) and the prolonged bleeding time (BT). Since desmopressin (DDAVP) is able to achieve both these goals in the majority of patients, it is the treatment of choice. Some patients, however, are not responsive or become refractory to DDAVP. In these, blood products maintain an important therapeutic role, and there is a need to assess the efficacy of the recently available virus-inactivated plasma concentrates, which contain both FVIII and von Willebrand factor and carry a low risk of transmitting blood-borne viruses. Our survey of the data reported in the literature indicates that all available concentrates are similarly effective in attaining high and sustained levels of FVIII after infusion. Although they often shorten or normalize the prolonged BT, that effect is less uniform. Since concentrates appear efficacious in the majority of clinical situations that require the use of blood products, they should be preferred, because of their greater safety, to cryoprecipitate produced by blood banks, which cannot be virus inactivated.

Oliver Memorial Lecture 1989. The evolution and future of haemophilia therapy

Lane (1840) first noted the beneficial effect of blood transfusion in controlling haemophilic bleeding following ophthalmic surgery. The appreciation that haemophilia is due to a plasma defect, at first thought to be prothrombin, coincided with the discovery of blood groups. This led in due course to the discovery of citrate anti-coagulant and the ability to store blood. The beneficial effect of citrated plasma in haemophilia led to the exploitation of stored blood, fresh frozen plasma, and the subsequent development of cryoprecipitate and factor concentrates. All this would not have been possible, however, without the selfless contribution of blood donors and the development of an organized blood transfusion service. In the United Kingdom, P. L. Oliver pioneered the development of blood donor panels, the London Blood Transfusion Service and the British Red Cross Society Blood Transfusion Service leading directly to the National Blood Transfusion Service; recognized as the World's senior service. The development of haemophilia therapy owes much, therefore, to Oliver's energetic and pioneering work and it is entirely appropriate that the first Oliver Memorial Lecture be directed to the evolution and future of haemophilia therapy. It is indeed an honour to be invited to deliver this Oliver Memorial Lecture at the combined meeting of the British Blood Transfusion Society and the British Society for Haematology here in Wembley.

Modern haemophilia treatment: medical improvements and quality of life

Adequate replacement therapy in haemophilia has been available for two decades. This has led to considerable improvements in the life expectancy and physical status of haemophilia patients. A study was conducted to investigate whether this has also led to improvements in quality of life. With this aim, information was obtained from 935 Dutch haemophiliacs by mailed questionnaires on relationships, marriage, family life and employment. Haemophilia patients were less often married than men in the general population (13% fewer) and had a lower total number of children (30% lower, 17% for those who were married). Twenty-two per cent of the patients were not employed and received an income from the disability funds. While severity of haemophilia, joint damage and age increased the risk of disability, it was noted that home treatment was associated with a 50% reduction in this risk. Remarkably, haemophilia patients did not differ from the general population in their view of the quality of their own health. The results of this study show a positive influence of modern haemophilia treatment on quality of life. At present, AIDS overshadows all optimistic feelings one may have about this field. However, the results described here demonstrate the benefits that can be achieved with adequate replacement therapy, and justify the expectation of further improvements in the near future.

Effectiveness of the cryosupernatant fraction of plasma in the treatment of refractory thrombotic thrombocytopenic purpura

Many patients with thrombotic thrombocytopenic purpura (TTP) satisfactorily respond to plasma therapy (plasmapheresis and/or plasma infusion). Some, however, respond either not at all or only transiently and incompletely. Evidence indicates that platelets and endothelial cell-derived unusually large von Willebrand factor (ULvWF) multimers, as well as the largest vWF multimers in plasma, form thrombi which are deposited in the microvascular circulation. Accordingly, platelet transfusions are avoided unless there is intra-cranial or other life-threatening hemorrhage. The largest plasma multimers of vWF are, however, replenished by the infusion of large volumes of whole plasma. We postulated that under conditions of massive plasma replacement, plasma depleted of the largest multimers of vWF might be preferable for the treatment of TTP episodes. The largest vWF multimers sediment in the cryoprecipitate, and the cryoprecipitate-poor fraction of plasma (cryosupernatant) is depleted of these forms. Seven patients responding inadequately to intensive plasma therapy were switched to receive cryosupernatant in place of whole plasma. All patients improved quickly following this change in therapy, and the TTP syndrome resolved in all seven.

Large-scale purification of factor VIII by affinity chromatography: optimization of process parameters

The optimization of a new process for the extraction of human coagulation factor VIII (FVIII) from plasma with the tailor-made affinity matrix dimethylamino-propylcarbamylpentyl-Sepharose CL-4B (C3-C5 matrix) is described. First, plasma is applied to DEAE-Sephadex A-50 anion exchanger in order to separate a number of proteins, including coagulation factors II, IX and X (prothrombin complex), from FVIII. Subsequently, the unbound fraction of the ion exchanger, containing FVIII, is contacted with the C3-C5 affinity matrix. Optimization of the FVIII affinity chromatographic procedure is accomplished in terms of the ligand density of the matrix, adsorption mode (batch-wise versus column-wise adsorption and matrix to plasma ratio), and conditions of pH and conductivity to be applied on washing and desorption. In scale-up experiments, by processing 20 l of plasma, the recovery (340 U VIII:C/kg plasma) and the specific activity (s.a.) (1.2 U VIII:C/mg protein) are better than those obtained by cryoprecipitation (recovery 300 U VIII:C/kg plasma, s.a. 0.3 U VIII:C/mg protein). The newly developed process using the specially designed C3-C5 affinity matrix has potential application in the process-scale purification of FVIII.

HIV-1 infection in haemophilia

Guidelines have been prepared by the National Hemophilia Foundation, USA, for treating patients with haemophilia, these are: 1. General recommendations. The risks of withholding treatment far outweigh risks of treatment. Patients should however be educated to use appropriate clotting factor doses to minimize overuse and contain costs. 2. Factor VIIIC-deficient patients. DDAVP should be used whenever possible by patients with mild or moderate factor VIIIC deficiency. When feasible, an alternative to concentrates may be the use of cryo-precipitate prepared from one well-screened donor or from a small number of such donors. (a) Prevention of hepatitis. Hepatitis B vaccination is essential for uninfected patients. Preliminary data suggest that products that are pasteurized, solvent/detergent-treated or monoclonal antibody-purified are at a reduced risk of transmitting hepatitis viruses. (b) Prevention of HIV-1. Concentrates pasteurized, treated with solvent/detergent, purified with monoclonal antibody, heated in suspension with organic solvents, or dry heat-treated for long periods are preferred. These products carry a substantially reduced risk of transmitting HIV-1. 3. Factor IX deficiency. For patients with severe deficiency the use of virus-inactivated Factor IX concentrate is recommended. For mild to moderate patients when feasible an alternative would be fresh, frozen plasma prepared from one well-screened and repeatedly-tested donor or from a small number of such donors. In the past few years, significant progress has been made in understanding the nature of the defect in haemophilia both at the molecular and structural levels, such a foundation is necessary for definitive treatments in the future. For now, however, the dark side of replacement therapy must be accepted along with its benefits.

Enzyme-replacement therapy: problems and prospects

Several diseases can, at least in theory, be treated by the administration of an enzyme, the deficiency of which is the cause of the disease. Various attempts have been made to correct enzymatic deficiencies responsible for the clinical manifestation of diseases for which prevention cannot be achieved by modification of the diet or by supportive therapy with drugs. Except for treating certain digestive disorders, enzyme-replacement therapy has not yet found a broad application. In this review article a compilation is given of the problems and prospects of enzyme-replacement therapy in diseases caused by the deficiency of an enzyme.

Some factors affecting properties of elastin-fibrin biomaterial

The elasticity, mechanical strength and permeability of a new biomaterial made of elastin and fibrin were investigated. It was shown that gamma-irradiation to sterilize the product, and sulphur derivatives (Merceptyl, thiourea, cystein) working as reticulating agents modified these properties. Depending on whether or not the biomaterial needs to be stiff, strong or elastic both physical processes could intervene separately or together. The good permeability of this material allows it to be used in several surgical fields as a true artificial connective matrix.

Progressive loss of fibronectin-mediated opsonic activity in plasma cryoprecipitate with storage. Role of fibronectin fragmentation

Septic injured patients often manifest a deficiency of plasma fibronectin. Several studies have shown improvements in organ function in such patients following infusion of fibronectin-rich plasma cryoprecipitate, while other studies found no improvement. One explanation for these differences may be the use of plasma cryoprecipitate which has been stored for various time intervals prior to its use as a source of fibronectin. This investigation tested the hypothesis that the opsonic activity of fibronectin in cryoprecipitate may decline with increased storage duration. Using a bioassay of opsonic activity, we evaluated human plasma cryoprecipitate that was stored at either -20 or -80 degrees C for various intervals (2 weeks to 12 months) after its preparation from fresh donor plasma. Our findings demonstrated that the opsonic activity of fibronectin in cryoprecipitate declined with increasing time of storage. Significant loss (p less than 0.05) of opsonic activity was first evident after 2 months of storage. Storage at -80 degrees C did not prevent this decline in opsonic activity as compared to storage at -20 degrees C. Immunoblot analysis revealed extensive fragmentation of the dimeric fibronectin (440 kdaltons) and the presence of lower molecular weight fragments in 4- to 12-month-old plasma cryoprecipitate. Therefore, plasma cryoprecipitate of varying ages (storage time) when used as a source of fibronectin for replacement therapy to support phagocytic function in septic injured patients may result in different fibronectin-mediated responses. The decline in activity may be due, in part, to fragmentation of the fibronectin molecule.

A new reconstituted connective tissue matrix: preparation, biochemical, structural and mechanical studies

A fibrinogen derivative generated by thrombin was reacted with elastin to yield a new addition product or adduct between the two proteins. Addition of fibronectin, and then of collagen, did not interfere with the basic elastin-fibrinogen reaction and conferred the qualities of an artificial connective tissue to the product. Biochemical, structural and biomechanical aspects of the new matrix were studied. Aprotinin, heparin, thiomersal, and thiourea did not inhibit the main reaction; indeed, some of these ingredients improved the matrix cohesion. Scanning electron microscopy showed the genesis of a true network whose meshes were more reticulated by the addition of thiourea. Biomechanical studies, i.e., strength and elasticity showed the thiourea matrix to be the strongest. These intrinsic properties suggest the product could have biological and clinical applications.

Adduct formation between soluble fibrin monomers and elastin

Monomers of fibrin generated from fibrinogen by thrombin reacted with elastin to give a new addition product or adduct. The adduct formation results from a covalent bond between both proteins, formation of which is dependent on elastin, fibrinogen and Ca2+ concentrations; but, Factor XIIIa did not intervene. Addition of fibronectin, together with fibrinogen, as cold insoluble proteins from human plasma, and of soluble collagen from rat tail tendon did not inhibit the first reaction. This enabled us to elaborate a new artificial connective matrix.

Characteristics of a heat treated antihaemophilic cryoprecipitate

In order to evaluate the influence of heat treatment (68 degrees C for 24 or 72 hours) on the essential components of antihaemophilic cryoprecipitate, i.e. factor VIII coagulant activity (VIII:C), von Willebrand factor (VIIIR:Ag and VIIIR:RCF) and fibrinogen, ordinary lyophilized cryoprecipitate was compared to heat treated, aminoacid-enriched specimens. The median reduction in factors VIII:C, VIIIR:Ag, VIIIR:RCF and fibrinogen during lyophilization of ordinary cryoprecipitate was 26 per cent, 11 per cent, 1 per cent and 8.5 per cent, respectively. Heat treatment of such cryoprecipitate resulted in 85 to 98.5 per cent reduction in these parameters, while the reduction following lyophilization and heat treatment (24 hours) of aminoacid-containing preparations was not significantly different from non-heated, ordinary cryoprecipitate. Following heating of aminoacid-enriched cryoprecipitate for 72 hours, only factor VIIIR:RCF was significantly reduced (32.5 per cent) compared to non-heated samples. Ordinary cryoprecipitate was almost insoluble following heat treatment. Enrichment with aminoacids, however, made the heat treated cryoprecipitate fully soluble, but the content of these vials were slightly slower in dissolving than non-heated preparations. Ultracentrifugation prior to lyophilization and heating did not improve the solubility. If heat treatment proves to be efficient in inactivating viral agents, we conclude that heated (68 degrees C for 24 hours), aminoacid-enriched cryoprecipitate may be a convenient product for treating haemophilia A, von Willebrand's disease and hypofibrinogenemia.

Technical aspects of different donor plasmapheresis systems and biological results obtained in collected plasma

Four plasmapheresis systems were comparatively studied: a centrifugation system (Haemonetics Model 50) and three filtration ones (Dideco BT 810, Organon Teknika PLASMAPUR and HemaScience Autopheresis Plasmacell). For each separator we studied the technical conditions for plasma separation, the biological characteristics of the collected plasma and the in vitro recovery of factor VIIc after preparation of cryoprecipitates. Concerning the plasma extraction rate, the HemaScience apparatus was the most efficient but values were quite similar to those obtained with the Organon Teknika machine. Contaminating cells were only found in plasma separated with the Haemonetics. Total protein and immunoglobulin levels were higher in plasma collected with the Haemonetics and HaemaScience systems. Factor VIIIc activity was comparable in plasma separated by filtration or by centrifugation while fibrinopeptide A levels were higher in plasma collected by Haemonetics. Whatever the machine, no statistical difference was observed when in vitro recovery of factor VIII was studied.

Fibrin generation during production of freeze dried antihaemophilic cryoprecipitate

Thrombin activity during separation and cryoprecipitation of CPD-blood was monitored by fibrinopeptide A (FPA) determinations. After pooling and lyophilization of cryoprecipitate, the total amount of contaminating fibrin was estimated by N-terminal amino acid analyses. In addition, retention of fibrin in standard transfusion filters (170 micron) was examined by gamma counting of 125I des-AA fibrin monomer enriched cryoprecipitate prior and subsequent to filtration. Prior to pooling of cryoprecipitate, thrombin activity, as estimated by FPA levels, was most pronounced during collection of blood from the blood donors and during cryoprecipitation and thawing of the plasma bags. Comparison of these FPA concentrations to the total amount of fibrin in pooled, freeze dried cryoprecipitate, as estimated by N-terminal analyses, revealed a considerable generation of fibrin during the process of lyophilization. In freeze dried cryoprecipitate, 5.3 per cent (range 3.0-7.5 per cent) of the fibrinogen had been converted to fibrin, implying a fibrin content of 20.3-60.3 mg per bottle of 500 U factor VIII. The amount of fibrin in two bottles of a commercially available factor VIII concentrate, also containing 500 U of factor VIII, was 14.1 and 19.8 mg, respectively. Sham transfusions of 125I des-AA fibrin monomer enriched cryoprecipitate revealed that only 1.0 per cent (range 0-2.5 per cent) of the fibrin was retained in the standard transfusion filters. Thus, substantial amounts of fibrin may be transfused to patients upon treatment with freeze dried cryoprecipitate.

Small-pool high-yield factor VIII production

Hemophilia care depends on several factors for the production of purified FVIII: plasma procurement, plasma logistics, production method, and efficacy. The latter two are restrictive factors, both for the supply and the safety of FVIII preparations. Conventional production methodology unavoidably recovers only 10 to 20% of usable protein, therefore requiring large pools of source plasma. Related to pool size is the transmission of diseases, which poses unnecessary risks for patients. The development of new technologies to better recover FVIII allows reduction of the pool size: crush-thaw, controlled pore-glass chromatography, and heparin double-cold precipitation techniques. This review will reflect on current production methods, pool size concept, small-pool approaches in FVIII production, and future developments.

The physiology and pathophysiology of the factor VIII complex

The factor VIII complex consists of two noncovalently linked proteins: von Willebrand factor (VWF) and factor VIII (FVIII). VWF plays an important role in primary hemostasis by mediating the adherence of blood platelets to the damaged vessel wall. A review of the literature on VWF is given with regard to its physicochemical properties and mode of action. FVIII acts as a cofactor in the factor Xa-generating enzyme complex of the intrinsic coagulation cascade. Starting with the recently published primary structure of FVIII, the literature is reviewed for structural information on FVIII. Also, an effort is made to characterize the interaction of FVIII with VWF and to discuss the possible physiological significance of FVIII-VWF complex formation. Interaction of FVIII with the clotting factors of the intrinsic pathway of coagulation is described in detail. Hemophilia and von Willebrand's disease (VWD) are both congenital bleeding disorders affecting a great many people. The different variants of these diseases are described with some reference to therapy and detection.

Studies on the procurement of blood coagulation factor VIII: effects of plasma freezing rate and storage conditions on cryoprecipitate quality

Plasma was frozen and stored in different ways before processing to cryoprecipitate by a standard thawing technique. Freezing rate was found to be important with slow freezing having a deleterious effect on cryoprecipitate quality. Storage of frozen plasma at constant temperatures for periods up to six months had no effect on the quality of cryoprecipitate, with no difference being found for plasma stored at -20 degrees C or -40 degrees C. Subjecting frozen plasma to deliberate temperature fluctuations resulted in a considerable increase in the amount of fibrinogen recovered in cryoprecipitate, with the factor VIII yield being relatively unaffected.

Microwave-thawed plasma for cryoprecipitate production

A microwave oven has been used to obtain rapid and controlled thawing of frozen plasma packs for cryoprecipitate production. The resulting factor VIII yields were higher than the average of 77.8 IU (in a volume of 17.2 ml) obtained by the slow overnight thaw procedures in routine use. Assays on 10 individual packs showed mean results of 142 +/- 24.5 IU factor VIII procoagulant activity, 188.6 +/- 51.68 IU factor VIII-related antigen, 0.152 +/- 0.05 g fibrinogen and 218.9 +/- 66.5 IU fibronectin in a volume of 23.2 +/- 6.6 ml. The results of this preliminary study indicate that microwave thawing of plasma is worthy of further investigation and should be reconsidered for routine production of cryoprecipitate and high yield fibronectin.

Kinetic evaluation of four Factor VIII concentrates by model-independent methods

Single-dose kinetics of 4 Factor VIII concentrates (Kryobulin, Hemofil T, Koate, cryoprecipitate) were studied in 41 patients with haemophilia-A. Model-independent methods were adopted for calculating the kinetic parameters (area under the curve, clearance, area under the moment curve, mean residence time, volume of distribution at steady-state). No substantial difference was observed in the kinetic characteristics of the 4 Factor VIII concentrates. A considerable interindividual variability of the calculated kinetic parameters was demonstrated for all concentrates. Our findings support the need to individualize Factor VIII dosage.

Cryoprecipitate and Factor VIII commercial concentrates: in vitro characteristics and in vivo compartmental analysis

In vitro and in vivo characteristics of cryoprecipitates and three commercial factor VIII concentrates (Kryobulin, Hemofil and Koate) were comparatively studied. Factor VIII:C/VIIIR:Ag ratio was very low in all commercial concentrates without differences among them. Conversely, the decrease of factor VIIIR:WFRCof was proportional to the degree of purity. Factor VIII:C/VIIIR:WFRCof ratio was shown to be a reliable index of factor VIII complex denaturation. Crossed electroimmunoassay showed a faster migration of factor VIIIR:Ag only in commercial concentrates. Using a two-compartmental open model that accounts for endogenous synthesis of factor VIII:C, single-dose kinetics of factor VIII:C were studied in 23 patients with classic hemophilia. Good agreement between measured and fitted values of factor VIII:C plasma concentration was observed. beta half-life was shorter in high purity concentrates and longer in intermediate purity concentrates and cryoprecipitates.

An in vivo study of a new factor VIII high purity preparation

The efficacy of high purity preparations of factor VIII complex are usually lacking effect on the bleeding time in von Willebrand's disease. In this report we have studied the efficacy of a new high purity factor VIII preparation in two von Willebrand and two hemophilia A patients. The prolonged bleeding time in the patients with von Willebrand's disease was corrected after infusion of the preparation and a secondary rise in factor VIII procoagulant activity (VIII:C) demonstrated. The biological half-life time of VIII:C, in the two hemophilia A patients, was about 15 hrs. The investigation shows that this particular preparation is capable of correcting the prolonged bleeding time in von Willebrand's disease.

Freeze dried cryoprecipitate: a clinical evaluation

Freeze dried cryoprecipitate was used in the treatment of 14 patients with haemophilia A. The in vivo recovery was 91.2% which is comparable to that reported from other parts of Europe. The product was efficacious and no adverse effects were reported. Freeze dried cryoprecipitate is the high yield product of a low technology process and as such may be of value in reducing any possible shortfall in the factor VIII requirements of the haemophiliac population of the UK.

Response to infusions of polyelectrolyte fractionated human factor VIII concentrate in human haemophilia A and von Willebrand's disease

Factor VIII was purified from cryoprecipitate by ion exchange chromatography on solid phase polyelectrolyte E-5 (PE-E5). The product was highly purified (3.5 u VIII:C/mg protein) compared to conventional concentrate (0.3 u VIII:C/mg protein) with low fibrinogen, low isoagglutinin titre, and a ratio of factor VIII coagulant activity (VIII:C) to factor VII related antigen (VIIIR:Ag) of 16:1. Trial infusions of this material (PE VIII) were given to three patients with severe haemophilia A and one patient with homozygous von Willebrand's disease. These patients also each received separate infusions of intermediate purity concentrate (IPC) for comparison. There were no adverse effects. The mean half life of VIII:C after PE VIII infusion in the haemophiliacs was 10.9 h and after IPC was 12.1 h, a statistically insignificant difference. The survival of factor VIII coagulant antigen (VIII:CAg) was similar to that of VIII:C. In contrast, the half life of VIII:C and of VIII:CAg was very short after infusion of PE VIII in the patient wih von Willebrand's disease (2.4 h). IPC when infused in this patient produced a typical secondary rise of VIII:C. Two bleeding episodes in severe haemophiliacs were satisfactorily treated with PE VIII. PE-E5 deserves further study as a means of preparing clinical concentrates of factor VIII.

Production of freeze-dried human antihaemophilic cryoprecipitate

Concentration of factor VIII from fresh plasma by cryoprecipitation remains the basis for preparation of products used to treat haemophilia A. This paper describes the preparation of a factor VIII concentrate from small plasma pools in transfusion centres with drying facilities. The dried concentrate from one litre of plasma dissolves very well in 50 or 100 ml of distilled water and contains around 500 IU per bottle. The specific activity per mg protein is 0.19 IU and the fibrinogen concentration is half that in frozen cryoprecipitate. This method of drying causes no appreciable loss in the factor VIIIC activity and little denaturation as shown by the factor-VIII-related antigen/factor VIIIC ratio of 1.7.

Quantitation of binding of factor VIII antigen to concanavalin A

This study establishes a convenient method for screening plasma samples for abnormalities of the carbohydrate content of the factor VIII (FVIII) molecule. A radioimmuno-electrophoretic technique has been developed to quantitate the percentage binding of FVIII-related antigen (VIII-Ag) to the lectin concanavalin A (Con A). Plasma samples were electrophoresed through a strip of agarose containing Con A into agarose containing a mixture of unlabelled anti-FVIII and 125I-anti-FVIII where precipitant lines formed, the height of which was dependent upon the degree of VIII-Ag binding to Con A in the first gel. Using this system reduced binding of VIII-Ag to Con A was found in the plasma of 12 patients with moderate classical von Willebrand's disease (vWd), while the Con A binding of six haemophilia A patients fell within the normal range. The VIII-Ag in normal cryoprecipitate showed increased % binding to Con A while the VIII-Ag remaining in the cryo-supernate demonstrated reduced Con A % binding.

Studies on ultrafiltration of antihemophilic factor

Ultrafiltration as an alternative approach to reprecipitation was studied in the production of an intermediate-purity antihemophilic factor concentrate suitable for clinical use. Almost complete recoveries of factor-VIII-related activities have been demonstrated across the processing step resulting in increased net yield of the product. Several important processing parameters are discussed. The product thus prepared is stable and has improved VIII:C/mg fibrinogen ratio.