1152 TRANSFUSION Volume 46, July 2006 Blackwell Publishing IncMalden, USATRFTransfusion0041-11322006 American Association of Blood BanksJuly 200646711521161Original Article PRION INFECTIVITY REDUCTION WITH LIGANDSGREGORI ET AL. ABBREVIATIONS: PK = proteinase K; PrP = prion protein; PrP c = normal prion protein; PrP res = protease-resistant prion protein; PrP TSE = infectious specific forms of PrP; TSE(s) = transmissible spongiform encephalopathy(-ies); vCJD = variant Creutzfeldt- Jakob disease. From the Veterans Affairs Maryland Health Care System, VA Medical Center, University of Maryland, Baltimore, Maryland; ProMetic BioSciences Ltd, Cambridge, United Kingdom; the Plasma Derivatives Department, American Red Cross Biomedical R&D, Rockville, Maryland; and the Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, North Carolina. Address reprint requests to: Robert G. Rohwer, PhD, 10 North Greene Street, Medical Research Services 151, VA Medical Center, University of Maryland, Baltimore, MD 21201; e-mail: rrohwer@ umaryland.edu. Financial support for this work was provided by Pathogen Removal and Diagnostic Technologies (a joint venture between the American Red Cross and ProMetic BioSciences) with a contract to the Baltimore Research and Education Foundation. LGr, BCL, CM, and RGR were in part funded by this contract. RC and PVG were in part funded by a contract between the American Red Cross and the NCSU. LGh, JL, and DH are employees of the American Red Cross. PE and SB are employees of ProMetic BioSciences. Declaration of potential conflicts of interest: Pathogen Removal and Diagnostic Technologies is a joint venture of the American Red Cross and ProMetic BioSciences established in part to develop reduction devices for TSE infectivity. DH, RGC, and RGR are founders of PRDT, have equity in the company, and sit on its scientific and executive boards with SJB. Thus, American Red Cross and ProMetic BioSciences have direct financial interest in the work presented. LGr is PI on a contract from PRDT to conduct the infectivity studies required for the device development. All other authors are employees either of the American Red Cross or ProMetic Biosciences or members of the Rohwer or Carbonell laboratories. Received for publication October 4, 2005; revision received November 23, 2005, and accepted November 28, 2005. doi: 10.1111/j.1537-2995.2006.00865.x TRANSFUSION 2006;46:1152-1161. TRANSFUSION COMPLICATIONS Reduction of transmissible spongiform encephalopathy infectivity from human red blood cells with prion protein affinity ligands Luisa Gregori, Brian C. Lambert, Patrick V. Gurgel, Liliana Gheorghiu, Peter Edwardson, Julia T. Lathrop, Claudia MacAuley, Ruben G. Carbonell, Steven J. Burton, David Hammond, and Robert G. Rohwer BACKGROUND: There is a demonstrated risk of infection by transmissible spongiform encephalopathies (TSEs) through transfusion from asymptomatic donors. Currently, blood-borne TSE infectivity cannot be detected with a diagnostic test, nor is it likely to be amenable to inactivation; however, its depletion with specific adsorp- tive ligand resins is possible. STUDY DESIGN AND METHODS: Six ligands that bind the prion protein, PrP, were selected by screening large solid-phase combinatorial chemical libraries. The selected resins were placed in columns and challenged with a unit of leukoreduced human red blood cells (RBCs) spiked with hamster brain–derived scrapie infectivity. The performance of each ligand was assessed by comparing the TSE infectivity titer in the RBCs before and after passage through each of five resin columns in series. RESULTS: Four resins were able to reduce infectivity titer by 3 to more than 4 log ID 50 per mL. The reduction was not due to nonspecific matrix interactions since a chemical modification of the most effective ligand completely abolished its ability to bind infectivity (negative control). A small subfraction of the infectivity, 0.01 percent, could not be removed, even upon repeated passage through successive columns. CONCLUSION: If endogenous TSE infectivity in RBCs binds to the ligands in the same proportion as brain- derived infectivity spiked into RBCs, the four most effective ligands would remove 3 to 4 log ID 50 per mL. A follow-up experiment is in progress to test whether endogenous blood-borne infectivity is also reduced.