Scrapie removal using Planova virus removal filters.

As a possible method for reducing the risk of transmissible spongiform encephalopathy (TSE) infection, Planova virus removal filters were tested for their ability to remove scrapie agent ME7. Albumin solution was spiked with high-titre ME7 and filtered through three different pore sizes of Planova filters. Infectivity of the pre- and post-filtration samples was assayed in log dilutions by intracerebral inoculation into C57B1/6 mice. Filtration of albumin solution in the absence or presence of a detergent (Sarkosyl) with Planova 35N (35+/-2 nm mean pore size) removed the contaminating scrapie agent with reduction factors of 4.93 log10 and 1.61 log10, respectively. Filtration, both in the absence and presence of detergent with Planova 15N (15+/-2 nm mean pore size), and in the presence of detergent with Planova 10N (9+/-2 nm mean pore size), showed high levels of scrapie reduction of >5.87 log10, >4.21 log10, and >3.80 log10, respectively, with no residual infectively detected in any of the filtrate samples. The effectiveness of Planova 35N filtration for the removal of infectivity of this TSE agent is greatly reduced in the presence of a strong detergent, but Planova filters with 15 nm or smaller pore size membranes can remove such infectivity at high reduction rates.