Polymeric Ligands with Specificity for Aggregated Prion Proteins

Abstract

The misfolding of normal proteins and their subsequent aggregation in the brain is characteristic of a group of related neurologic diseases, the “protein conformational disorders”, including Parkinson disease, Alzheimer disease, and the transmissible spongiform encephalopathies (TSEs) (1). The development of highly sensitive and specific diagnostic assays for these diseases is a high priority as effective therapies become available or as food safety regulations mandate the removal of infected animals from the food chain. Current test development effort in the TSE field has been focused mainly on designing screening tests for the aggregated prion proteins in bovine, ovine, and cervid brain tissue. Several immunoassays for bovine spongiform encephalopathy (BSE) have been evaluated by the European Union (EU) (2), and three are now approved for routine use in testing laboratories. Those approved include two ELISAs in the microplate format and reagents for a Western blot analysis. The abnormal, or rogue, prion protein detected by these tests is considered to be the best indicator of TSE infection (2), but the anti-prion protein antibodies used in these assays cannot distinguish the normal, globular, proteinase K-sensitive (α-helix-rich) form of the prion protein (PrPsen) from the abnormal, aggregated, and relatively proteinase K-resistant form (PrPres), in which the secondary structure is dominated by β-sheet. Thus, a complex sample preparation procedure is required to eliminate the normal prion protein in the brain homogenate before immunoassay, usually involving a proteinase K digestion step …