von Willebrand factor characterization of a severe dry-heat treated factor VIII concentrate, AHF (high purity)

Eight batches of a severe dry-heat treated (80 degrees C for 72 hours) Factor VIII concentrate manufactured by the Commonwealth Serum Laboratories (CSL Ltd.) were analysed for the following von Willebrand factor-related (vWf) activities: ristocetin cofactor activity (vWf:RCof), collagen binding activity (CBA), vWf antigen levels (vWf:Ag), vWf multimeric analysis and 2-stage FVIII clotting activity (VIII:C). The average potency per vial of vWf:Ag was 440 +/- 80 units, vWf:RCof 500 +/- 60 units, CBA 350 +/- 50 units and VIII:C 242 +/- 36 International Units. Multimeric analysis indicated the presence of high molecular weight multimers and a triplet structure slightly different to normal plasma. Viral inactivation studies using a marker virus, Sindbis, demonstrated that the terminal severe dry- heating step reduced the viral load in the product by greater than 6 log10TCID50/ml. This CSL Ltd. FVIII concentrate may thus provide a safer, purer and more convenient source of vWf than cryoprecipitate. Clinical studies to establish product efficacy in patients with von Willebrand's disease are underway.

Improved in-vitro quality of platelet concentrates stored in a dextrose-free synthetic medium

The licensed balanced salt solution Plasma-Lyte, buffered with a clinical solution of sodium bicarbonate, was evaluated as a suspending fluid for platelet concentrates. Platelets suspended in this medium showed better pH maintenance over 5 days of storage compared to platelets stored in plasma (7.0 vs 6.45, P < 0.001). This was reflected in improvements in in-vitro indicators of platelet viability-hypotonic shock response (79 vs 48%, P < 0.05), aggregation to paired agonists (86 vs 62%, P < 0.05); and platelet size distribution (104 vs 119%, P < 0.001). Dissolved bicarbonate measurement showed less depletion of bicarbonate in the synthetic medium compared to plasma, which suggests a lower rate of lactate formation. A synthetic medium containing dextrose showed inferior platelet storage characteristics when compared to the plasma-lyte/bicarbonate medium in a paired study (Day 5, pH 6.53 vs 6.9, P < 0.05). The results suggest that utilization of substrates other than dextrose allows platelets to metabolize without the accumulation of lactate that leads to pH drops during storage in plasma, and continue to support the feasibility of storing platelets in a non-plasma environment.

Use of plasma with high levels of ionised calcium in the production of model scale coagulation factor concentrates

We have attempted to exploit the Ca2(+)-dependent stability of factor VIII in producing factor VIII concentrates of higher yield. Plasma levels of ionised calcium were increased in two ways: (a) whole blood collection into half-strength citrate CPD anticoagulant, leading to free Ca2+ levels of ca 120 microM and (b) apheresis collection of plasma which was then recalcified to free Ca2+ levels of ca 300 microM under heparin cover. Coagulation factor concentrates were prepared using model versions of our industrial scale manufacturing methods. Factor VIII yield was increased through low citrate collection. This did not compromise factor IX yield or thrombogenic potential. Use of recalcified heparinised plasma did not lead to any improvement in factor VIII yield and resulted in a marked drop in factor IX recovery, possibly from interference by heparin of factor IX binding in ion-exchange chromatography. The benefits accruable through the use of half-strength citrate CPD anticoagulant support the continued evaluation of this preservative in large scale blood collection and fractionation. The deleterious effects of heparin in charge-mediated plasma fractionations may pose serious difficulties in harvesting vitamin K dependent factors.

Microtitre plate measurement of platelet response to hypotonic stress

The conventional method of assessing the platelet response to hypotonic stress (HSR) was adapted to allow microtitre plate technology to be used. After water is added to a platelet suspension two sequential readings are taken at 414 nM on a vertical microplate reader. The difference between the second (three minutes) and the first (one minute) was defined as the HSR. This method allowed the relation between platelet concentrate pH and viability to be confirmed, and an HSR value for use in quality control was established. The method correlated well with the conventional technique and permitted measurement of undiluted samples as well as of products with a high free haemoglobin concentration.

Effects of plasma collection systems and processing parameters on the quality of factor IX concentrate

Using pilot-scale production of our present factor IX (II and X) concentrate, we have studied the effects of starting plasma source and processing parameter on two in-vitro indicators of product quality - yield and thrombogenic potential. Plasma source did not affect factor IX yield but had a marked effect on thrombogenic potential. Factor IX concentrates produced from plasma derived through centrifugation-based technology showed significantly higher thrombogenic potential than products derived from plasma derived through a filtration-based system. Removal of Cohn fraction I prior to ion-exchange chromatography resulted in a drop in factor IX yield and thrombogenic potential, as did heat treatment to 80 degrees C for 72 h. We conclude that a membrane-filtration-based plasmapheresis system may be the preferred method of plasma procurement for factor IX concentrate production.

Studies on the procurement of blood coagulation factor VIII in vitro studies on blood components prepared in half-strength citrate anticoagulant

The effect of replacing a standard citrate anticoagulant with one containing half the amount of citrate on the in vitro properties of components prepared from blood donations was investigated. This resulted in a significant improvement in factor VIII stability such that there was little loss during overnight storage, and this was reflected in the factor VIII yield in cryoprecipitate. The quality of cellular components in red cell units stored up to 35 days or platelet concentrates stored up to 7 days was not adversely affected. Although initial levels were similar to those in standard anticoagulant, the extent of fibrinopeptide A generation and complement C3 breakdown in red cell units stored for 35 days in half-strength citrate was somewhat increased.

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.

Studies on the procurement of coagulation factor VIII: selective precipitation of factor VIII with hydrophilic polymers

Early work on the purification of factor VIII using polyethylene glycol (PEG) indicated that other polymers might also be used to precipitate factor VIII leaving fibrinogen in solution. Recently polyvinylpyrrolidone (PVP) has also been advocated for this purpose. In this study, different concentrations and molecular weights of hydroxyethyl starch, dextran, PEG, PVP, Ficoll, Percoll and albumin were examined for their ability to precipitate the factor VIII complex from cooled (not frozen) fresh CPD plasma. At optimal concentrations near quantitative recovery of VIIIR:Ag and VIII:CAg was achieved in 2 hr with minimal precipitation of fibrinogen or total protein. The best separations were observed with hydroxyethyl starch, albumin or Ficoll. PVP and PEG gave inferior purifications. Results for cryoprecipitate and intermediate-purity factor VIII concentrate were inferior to those obtained with plasma. Simple pre-concentration of plasma prior to chilling is an attractive alternative for large scale continuous production.

A comparative study using immunological and biological assay of the haemostatic responses to DDAVP infusion venous occlusion and exercise in normal men

In a group of six normal male volunteers, infusion of DDAVP, venous occlusion and exercise were shown to increase plasma levels of factor VIII and plasminogen activator, activity and antigen, to different extents and at differing rates. Any mechanisms suggested to explain release of these proteins by various stimuli should account for such differences. All three stimuli could also increase plasma levels of prostacyclin metabolites, although this was only significant for high doses of DDAVP. Other potential endothelial markers, such as fibronectin and thrombospondin, showed no specific increase after any of the stimuli.