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.