Chemistry: natural resins or derivatives; peptides or proteins; – Proteins – i.e. – more than 100 amino acid residues – Blood proteins or globulins – e.g. – proteoglycans – platelet...
Patent
1986-11-17
1988-12-06
Schain, Howard E.
Chemistry: natural resins or derivatives; peptides or proteins;
Proteins, i.e., more than 100 amino acid residues
Blood proteins or globulins, e.g., proteoglycans, platelet...
424101, 514 8, A61K 3514, A61K 3516, C07K 328
Patent
active
047897333
DESCRIPTION:
BRIEF SUMMARY
This invention relates to the purification of factor VIII (Antihaemophilic Factor, AHF) from blood plasma concentrates, especially cryoprecipitate.
Blood clotting factor VIII (which is also referred to in this specification as FVIII), is a protein component of blood which has for many years been used to treat individuals suffering from classical haemophilia (haemophilia A), a congenital disease caused by a deficiency or absence of factor VIII in the blood. Until the 1960s treatment of haemophiliacs consisted of transfusing the patient with whole blood or blood plasma. However, in the last 10 to 20 years, factor VIII--enriched plasma protein concentrates have increasingly replaced these whole plasma transfusions and have increased the effectiveness of anti-haemophilia treatment.
The most commercially important of the plasma concentrates currently used are the blood plasma fraction commonly known as cryoprecipitate and purified concentrates prepared from cryoprecipitate. Conventionally, cryoprecipitate is defined as a precipitate, rich in factor VIII, fibrinogen (blood coagulation Factor I) and fibronectin (cold-insoluble globulin, CIg), which is prepared from frozen freshly-prepared human plasma by a low temperature plasma fractionation technique. Typically, deep-frozen plasma is softened to -5.degree. C. to -15.degree. C., and then warmed slowly under efficient manual or mechanical stirring to a temperature of not more than about 3.degree. C. Under these conditions the frozen plasma partially thaws to yield a liquid phase and a solid phase, and it is this solid phase which is recovered by centrifugation as commercially valuable cryoprecipitate. Cryoprecipitate prepared in this way typically contains concentrated within it from 40 to 60% of the total amount of factor VIII contained in the whole blood from which the plasma is derived.
There have been numerous studies to improve the yield of factor VIII from cryoprecipitate and other blood plasma fractions, and to stabilise and further purify it. For example, a minimum purification step is the treatment of cryoprecipitate with Al(OH).sub.3 gels which have been found to eliminate some of the other blood clotting factors, stabilise the activity of factor VIII, and facilitate the subsequent sterile filtration of factor VIII. Usually, however, multi-stage processing of cryoprecipitate is required to produce sufficiently pure FVIII preparations.
The major shortcoming of present technology is that for the most part multi-stage processing of plasma results in rather costly losses of factor VIII activity. In addition, it has long been accepted that commercial preparations of factor VIII vary greatly in terms of anti-haemophilic activity, total protein content, and contamination by other proteins particularly fibrinogen and fibronectin. The presence of high concentrations of fibrinogen and fibronectin in FVIII preparations is undesirable because they have been found to give rise to unacceptable losses of FVII during some of the processing steps. Fibrinogen is of particular concerned because it is normally present in much greater concentrations than fibronectin in blood plasma and cryoprecipitate, and is usually more difficult to remove than fibronectin. Thus, all presently known methods for the purification of factor VIII preparations involve partial separation of fibrinogen at least from factor VIII in order to increase the ratio of factor VIII to total protein content in the preparations.
It has long been accepted that the presence of the proteins fibronectin and especially fibrinogen in blood plasma fractions tend to make those fractions sticky and viscous. This makes purification of these fractions difficult, especially if filtering is used. This problem can to a certain extent be overcome by diluting the fractions in (for example) buffer solutions, though at the expense of loss of plasma fraction concentration. Another serious problem with these proteins arises from the increased need to ensure that all possible blood born viruses, especially the hepatits B virus
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Schain Howard E.
The Central Blood Laboratories Authority
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