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Treatment of bleeding in von Willebrand's disease usually consists of the infusion of cryoprecipitate or plasma. DDAVP is effective in some patients. Commercial concentrates for the treatment of Hemophilia A are ineffective as a source of von Willebrand Factor (vWF) replacement in von Willibrand's disease presumedly because of the absence of higher molecular weight forms of vWF protein. A vWF concentrate obtained during the course of preparation of an affinity purified Factor VIII may provide an alternative therapeutic agent without impacting the available Factor VIII supplies. The process used for the preparation of a highly purified Factor VIII concentrate (MonoclateTM, Armour Pharmaceutical Co.) from cryoprecipitate includes an affinity chromatography step which separates vWF/Factor VIII complex from other proteins in cryoprecipitate using an anti-vWF monoclonal antibody (C. A. Fulcher & T. S. Zimmerman, 1982). Factor VIII is then dissociated from the vWF remaining on the column and is eluted immediately by 3M sodium thiocyanante (NaSCN) as a step in the regeneration of the column. Unless the NaSCN is rapidly removed from the elutriant, the vWF activity as measured by platelet agglutination is destroyed. We have taken the NaSCN eluate and processed it immediately over an in-line G-10 or G-25 Sephadex column which removes the NaSCN while the vWF is eluted with a buffered isotonic solution. Alternatively, the vWF has been precipitated from the NaSCN by ammonium sulfate or polyethylene glycol. VWF prepared by any of these methods retains platelet agglutinating activity and has a distribution of vWF multimers similar to those of vWF in normal plasma.The potency of vWF prepared from cryoprecipitate by this process is 20 units/ml and the specific activity is 20 units/mg. In several fractionations of kilogram amounts of cryoprecipitate, vWF was isolated and subjected to lyophilization and heating at 68° for 30 hours without loss of bioactivity. Drug development in progress suggest that the combined effect of affinity chromatography and exposure to NaSCN may negate the need for a heating procedure to reduce the risk of viral transmittance. |
