Rebecca Cardigan, BSc, PhD; Sheila Maclennan , MBBS, FRCP, FrCPath

Disclosures

Transfusion Alter Transfusion Med. 2008;10(3):92-101. 

In This Article

Prion Removal

At the time of writing, there have been four cases of possible transmission of vCJD by transfusion,[11] all from non-leukocyte-depleted red cells. Recently, studies using hamster scrapie models have shown that LD reduces infectivity by 42%.[12] As LD alone is unlikely to render units non-infectious, there is considerable interest in alternative methods to reduce infectivity. Several companies are developing technology to remove prion protein from blood. PRDT/Macopharma has developed a filter that removes prion protein from LD red-cell concentrates. As this is an additional filtration step to LD, it is associated with a further loss of hemoglobin. Based on current Spongiform Encephalopathy Advisory Committee (SEAC) working assumptions on levels of infectivity, it is predicted that at least 3 log removal of infectivity (in addition to LD) would be needed to provide clinical benefit in terms of preventing transmission of vCJD. The PRDT device removes 3-4 logs of infectivity from red cells spiked with scrapie infected hamster brain[13] and > 1.2 log (to below the limit of detection) of infectivity from the blood of hamsters infected with scrapie.[14]

The PRDT/Macopharma P-CaptTM Prion Capture filter (Pathogen Removal and Diagnostic Technologies, Inc., New York, NY, USA, and Macopharma Tourcoring, France) has been shown in vitro to have negligible effect on the quality of red cells or on the expression of common red cell antigens. Studies in healthy volunteers examining the recovery of red cells filtered using P-Capt have been completed with satisfactory results, and a clinical study in patients designed to detect increased rates of adverse events or red-cell alloimmunization has commenced. Furthermore, the UK transfusion services have commissioned an independent assessment of the efficacy of prion reduction which is being performed by the Health Protection Agency.

Combined LD and prion removal filters are being developed by Fenwal/Asahi (Glendale, CA, USA/Tokyo, Japan) and Pall (Ann Arbor, MI, USA). As yet, there are no prion removal filters for whole blood, platelets or plasma.

Prion removal technologies would therefore appear to offer great promise in reducing the risk of vCJD by transfusion; however, their implementation will require careful consideration of the costs and benefits involved and what role they will play if and when it becomes possible to test donors for vCJD.

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