The removal of the abnormal form of prion protein i.e. PrP(SC) by filtration steps in the plasma fractionation process has been investigated by immuno-Western blotting. Depth filtration has been shown to be capable of removing scrapie by 2-3 log from certain plasma product intermediates. These include cryoprecipitate supernatant, used for the manufacture of immunoglobulin and albumin, and albumin fraction V, by filtration using Pall Seitz or 3m Cuno depth filters respectively. However no significant removal occurred with immunoglobulin Fraction II after Cuno depth filtration. When 0.2 microm PVDF and Nylon membrane filters were tested, the removal of TSEs from 20% albumin was limited i.e. 0.6-1.3 log. However under protein free conditions using phosphate buffered saline, filtration was not effective in the case of a PVDF filter but very effective i.e. >2.9 log in the case of a Nylon filter.
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