Prion and Prion Disease: Immunobiology, Pathogenesis and Potential Threat to Mankind

ABSTRACT

Prion diseases, also known as Transmissible Spongiform Encephalopathies (TSEs), are fatal neurodegenerative disorders with characteristic sponge-like microscopic appearance in the infected brain. They are caused by a protein-only particle consisting of an abnormal isoform (PrPSc) of the normal ubiquitous cellular prion protein PrPc. Prion diseases affect both human and animals, and can cause interspecies transmission. In humans, there are six different phonotypes of prion diseases, including kuru disease, Creutzfeldt-Jakob disease (CJD), Gerstmann- Sträussler-Scheinker (GSS) syndrome, Fatal Familial Insomnia (FFI), variant Creutzfeldt-Jakob disease (vCJD) and variably protease sensitive prionopathy (VPSPr). In herbivorous animals and carnivorous animals, there are five well-studied prion diseases including scrapie, Bovine Spongiform Encephalopathy (BSE), Chronic Wasting Disease (CWD), Transmissible Mink Encephalopathy (TME), and Feline Spongiform Encephalopathy (FSE). As the pathogen of the diseases, PrPSc accumulates in tissues and body fluids of affected individuals, and serves as the most reliable marker for diagnosis of priondiseases. A variety of bioassays, including immunoblotting, immunohistochemistry (IHC), and enzyme-linked immunosorbent assay (ELISA) have been used in prion disease diagnosis and surveillance; however, none of them is sufficient for preclinical diagnosis. Recently improved in vitro PrPSc amplification methods, such as protein misfolding cyclic amplification (PMCA), amyloid seeding assay (ASA), and real-time quaking-induced conversion (RT-QUIC), showed greatly increased sensitivity. In particular, RT-QUIC and PMCA have been applied to noninvasive detection of PrPSc in urine or nasal swab recently, shedding light on the uses of

the two methods in early diagnosis and surveillance of prion diseases.