PRNP and prion disease: During prion disease, aggregations of PrPSc, an abnormally folded isoform of the host cellular prion glycoprotein (PrPC) accumulate in affected tissues.1 Prion infectivity co-purifies with PrPSc and is considered to constitute the major component of the infectious agent.2,3 The accumulation of PrPSc within the central nervous system (CNS) of prion-infected hosts, coincident with neuronal loss, vacuolation (spongiosis) and reactive glial responses in both astrocytes and microglia, are the major neuropathological hallmarks of prion disease.