Bayer Scientists Demonstrate Pathogenic Form of Human Prion Proteins Can Be Removed by Plasma Protein Purification Processes

RESEARCH TRIANGLE PARK, N.C. -- Bayer Biological Products scientists have demonstrated the ability of current purification processes to remove pathogenic forms of human prion proteins, including the prion protein associated with variant Creutzfeldt Jakob disease (vCJD), during simulations of the process for manufacturing plasma proteins. This industry-leading research, focusing on the safety of therapeutic proteins derived from human plasma, is featured in the November issue of Transfusion. Collaborating with the New York State Institute for Basic Research in Developmental Disabilities and the National Institute of Neurological Disorders and Stroke, Bayer BP scientists measured the removal of pathogenic prion proteins purposely added under experimental conditions to human plasma samples undergoing purification processes that simulate those used in the manufacture of blood protein products. The results confirm that these experimentally added prions, which cause vCJD and other related diseases, can be removed, thereby reducing the theoretical risk of transmission through use of these products.

This latest report, building on a series of studies conducted by Bayer BP scientists over the last several months, utilized the Bayer-developed prion-specific Western blot assay. Key to this work is the continued demonstration that the Western blot assay is valuable in estimating the removal of prions. This assay, quicker and less expensive than conven-tional bioassays for detecting infectivity, was licensed to BioReliance Corporation so that it could be made commercially available for other manufacturers of biological products to more quickly and efficiently assess manufacturing processes for prion protein removal.

The article's lead author, Chris Stenland, PhD, senior scientist, Bayer BP, spoke of the importance of this research. "Our research demonstrates that purification steps designed for the isolation of therapeutic plasma proteins can remove human forms of pathogenic prion proteins. Although no cases of variant CJD or related diseases have been reported from use of therapeutic plasma proteins, we remain diligent in our work to prevent this possibility."

"Because product safety is our No. 1 priority, Bayer remains committed to further increasing our ability to ensure all our biological products are safe from any theoretical threat posed by prions," said Dr. Gunnar Riemann, executive vice president, Bayer Corporation, and president, Bayer BP Division. "When patients receive a Bayer BP product, we want them to have peace of mind, knowing this is the safest product available."

The pathogenic form of prion proteins has been associated with fatal diseases, including mad cow disease in cattle, scrapie in sheep, and the human disorders Creutzfeldt-Jakob Disease (CJD), Gerstmann-Straussler-Scheinker syndrome, Kuru, and fatal familial insomnia. To date, no clinical evidence exists to support the transmission of human transmissible spongiform encephalopathies (TSE), such as CJD, by blood or blood-derived products. However, recent evidence from experimental animal models suggests that blood has the potential to contain TSE infectivity and cross-species transmission may occur. For these reasons, biopharmaceuticals, including human plasma derivatives, recombinant proteins grown in media containing fetal calf serum, and human-derived products containing bovine additives, have a hypothetical risk of containing TSE infec-tivity, increasing the importance of continuing advances in this field of research. Bayer scientists are working toward reducing this theoretical risk for transmission even further.

Regulatory agencies require manufacturers to demonstrate removal or inactivation of pathogen impurities, such as viruses, from biological products. Although agencies currently do not require documentation of prion protein or TSE removal, they continue to follow the science in this area closely. Moreover, because methods that effectively inactivate the infectious TSE agent also destroy most therapeutic proteins, the removal of prions remains the most viable strategy for addressing the hypothetical risk of TSE transmission. Assessing the ability of a particular manufacturing process to remove pathogenic prions is an important step in addressing this hypothetical risk. The methodology developed by Bayer allows researchers to quickly evaluate whether a particular manufacturing process is capable of removing TSE infectivity.

Best known for its flagship product, Bayer Aspirin, Bayer Corporation produces a broad range of health care, crop protection, polymer, and chemical products that help diagnose and treat diseases, purify water, preserve local landmarks, protect crops, advance automobile safety and durability, and improve people's lives.

Source: PRNewswire