The research focused on three approaches to evaluate the performance of the Pall prion reduction filter. In the exogenous (spiking) phase of the study, scrapie-infected brain homogenates were added to human red blood cells and then passed through a prion removal filter. The results showed that prions were removed below the level of detection by the Western blot assay.
In another phase of the exogenous study, scrapie-infected brain homogenates were diluted to obtain a variety of concentrations of infectious prion. These varying concentrations were divided into a test (filtered) group and a control (non-filtered) group and injected into the brains of healthy hamsters. (The hamster is a typical model used to determine prion removal efficiency.) The results of this phase of the study found that the prion reduction filter removed 3.7 logs (over 99.9%) of the infectious prion.
In the endogenous infectivity phase of the study, which is the most relevant to transfusion-transmitted TSEs, whole blood was collected from symptomatic scrapie-infected hamsters. It was processed into red blood cell samples that were designated either as test (filtered) or control (non-filtered) groups and then injected into healthy hamsters. Endogenously scrapie-infected red blood cells that were not filtered transmitted disease to six of the 43 animals, while the filtered red blood cells did not transmit disease to any of 35 animals.
The researchers concluded that the use of this type of filter should reduce the risk of vCJD transmission through blood transfusion. Dr. Coker explains, "Transmission of vCJD by blood transfusion is a serious threat and prion reduction by filtration is a realistic and practical approach to minimize the risk."
Concerns about vCJD are high on the radar screen of health authorities around the globe. There have been 179 human cases identified worldwide, with a majority in the United Kingdom (UK). There has been a recent increase in the number of cases outside the UK. The U.S. just reported its second case of vCJD. However, public health experts contend that the risk of vCJD should not be gauged by the number of actual clinical cases seen to date, but by the prevalence of people who may be carriers of the infectious prions.
Protecting the blood supply from prions is a top priority since vCJD can be asymptomatic for many years and no one knows how many transfusion recipients may be receiving infected blood. There is no reliable test available to determine the presence of vCJD in blood. This past month, the British Department of Health announced that it must track down another 50 people who received a blood transfusion to notify them of potential exposure to vCJD.
Many countries have taken measures to reduce transfusion transmission of prions, including donor deferral and leukocyte (white blood cell) reduction. Leukoreduction alone, however, is known to be only partially effective because not all prions are cell-associated. A report cited in the study suggests that the current generation of leukoreduction filters is effective in removing only 42 percent of the total TSE infectivity suggesting that a complementary strategy to reduce risk is required.
Study authors concluded, "The use of a filter that combines efficient leukoreduction with removal of infectious prions should help improve the safety of the blood supply by reducing, and perhaps even eliminating, the risk of transmission of vCJD and other forms of human prion disease through blood transfusion."
The Pall Leukotrap® Affinity Prion Reduction Filter System reduces both leukocytes and infectious prions. It was CE marked with 99.9 percent prion removal efficiency in May 2005 and is currently being evaluated by blood services in several European countries. It is the first technology that reduces infectious prions from red cells, the most widely transfused blood component. Pall developed the prion reduction technology as part of the Company's mission to help safeguard the global blood supply.
About Pall Corporation
Pall Corporation is the global leader in the rapidly growing field of filtration, separations and purification. Pall's business is organized around two broad markets: Life Sciences and Industrial. The Company provides leading-edge products to meet the demanding needs of customers in biotechnology, pharmaceutical, transfusion medicine, semiconductor, water purification, aerospace and broad industrial markets. Total revenues for fiscal 2005 were $1.9 billion. The Company headquarters is in East Hills, New York with extensive operations throughout the world. Visit Pall at http://www.
A study abstract is available online via a link from www.aabb.org.
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Photos and additional information about prion diseases and the Pall Leukotrap Affinity Prion Reduction Filter System can be found on http://www.