A direct relationship between the partitioning of the pathogenic prion protein and transmissible spongiform encephalopathy infectivity during the purification of plasma proteins

Authors

  • Douglas C. Lee,

    1. From the Department of Pathogen Safety Research/Biological Products, Bayer Corporation, Research Triangle Park, North Carolina; and the New York State Institute for Basic Research, Staten Island, New York.
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  • Christopher J. Stenland,

    1. From the Department of Pathogen Safety Research/Biological Products, Bayer Corporation, Research Triangle Park, North Carolina; and the New York State Institute for Basic Research, Staten Island, New York.
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  • Jeanette L.C. Miller,

    1. From the Department of Pathogen Safety Research/Biological Products, Bayer Corporation, Research Triangle Park, North Carolina; and the New York State Institute for Basic Research, Staten Island, New York.
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  • Kang Cai,

    1. From the Department of Pathogen Safety Research/Biological Products, Bayer Corporation, Research Triangle Park, North Carolina; and the New York State Institute for Basic Research, Staten Island, New York.
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  • Elizabeth K. Ford,

    1. From the Department of Pathogen Safety Research/Biological Products, Bayer Corporation, Research Triangle Park, North Carolina; and the New York State Institute for Basic Research, Staten Island, New York.
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  • Kevin J. Gilligan,

    1. From the Department of Pathogen Safety Research/Biological Products, Bayer Corporation, Research Triangle Park, North Carolina; and the New York State Institute for Basic Research, Staten Island, New York.
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  • Randal C. Hartwell,

    1. From the Department of Pathogen Safety Research/Biological Products, Bayer Corporation, Research Triangle Park, North Carolina; and the New York State Institute for Basic Research, Staten Island, New York.
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  • Jarrett C. Terry,

    1. From the Department of Pathogen Safety Research/Biological Products, Bayer Corporation, Research Triangle Park, North Carolina; and the New York State Institute for Basic Research, Staten Island, New York.
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  • Richard Rubenstein,

    1. From the Department of Pathogen Safety Research/Biological Products, Bayer Corporation, Research Triangle Park, North Carolina; and the New York State Institute for Basic Research, Staten Island, New York.
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  • Michael Fournel,

    1. From the Department of Pathogen Safety Research/Biological Products, Bayer Corporation, Research Triangle Park, North Carolina; and the New York State Institute for Basic Research, Staten Island, New York.
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  • Stephen R. Petteway  Jr.

    1. From the Department of Pathogen Safety Research/Biological Products, Bayer Corporation, Research Triangle Park, North Carolina; and the New York State Institute for Basic Research, Staten Island, New York.
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  • Supported in part by the New York State Institute for Basic Research (RR), Grant No. 99-9136-0101-CA from the United States Department of Agriculture, Grant No. RO1-HL-63837-01 from the NIH, and funds from the New York State Office of Mental Retardation and Developmental Disabilities.

Address reprint requests to: Douglas C. Lee, PhD, Bayer Corporation, 85 TW Alexander Drive, Research Triangle Park, NC 27709; e-mail: doug.lee.b@bayer.com.

Abstract

BACKGROUND: Experimental evidence from rodent models indicates that blood can contain transmissible spongiform encephalopathy (TSE) infectivity, which suggests a potential risk for TSE transmission via proteins isolated from human plasma. Because methods that can reduce TSE infectivity typically are detrimental to protein function, infectivity must be removed to ensure the safety of these therapeutic proteins. Animal bioassays are conventionally used to detect infectivity, but the pathogenic form of the prion protein (PrPSc) can serve as a marker for TSE infectivity.

STUDY DESIGN AND METHODS: Seven plasma protein-purification steps were performed after the plasma intermediates were spiked with TSE-infected material. Resulting fractions were analyzed for PrPSc by using a Western blot assay and for TSE infectivity by using an animal bioassay. Western blots were quantitated by an endpoint dilution analysis, and infectivity titers were calculated by the Spearman-Kärber method.

RESULTS: PrPSc partitioning paralleled TSE infectivity partitioning, regardless of the nature of the protein-purification step. The detection ranges for PrPSc and infectivity were 0 to 5.3 log and 1.1 to 8.9 log median infectious dose per unit, respectively. Clearance of PrPSc and infectivity ranged from 1.0 to 6.0 log.

CONCLUSION: Purification steps for isolating therapeutic proteins from human plasma showed the removal of both PrPSc and TSE infectivity. PrPSc partitioning coincided with infectivity partitioning, which showed a close relationship between PrPSc and TSE infectivity. By exploiting this association, the in vitro Western blot assay for PrPSc was valuable for estimating the partitioning of TSE infectivity during plasma protein purification.

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