Scientific Publications by FDA Staff

J Virol 2013 Nov;87(22):12349-56

Dissociation of prion protein amyloid seeding from transmission of a spongiform encephalopathy.

Piccardo P, King D, Telling G, Manson JC, Barron RM

Misfolding and aggregation of proteins is a common pathogenic mechanism of a group of diseases called proteinopathies. The formation and spread of proteinaceous lesions within and between individuals was first described in prion diseases and proposed as the basis of its infectious nature. Recently a similar "prion-like" mechanism of transmission has been proposed in other neurodegenerative diseases such as Alzheimer's disease. We investigated if misfolding and aggregation of corrupted prion protein (PrPTSE) is always associated with horizontal transmission of disease. Knock-in transgenic mice (101LL) expressing mutant PrP (PrP-101L) that are susceptible to disease but do not develop any spontaneous neurological phenotype were inoculated with (i) brain extracts containing PrPTSE from healthy 101LL mice with PrP plaques in the corpus callosum or (ii) mice overexpressing PrP-101L with neurological disease, severe spongiform encephalopathy and formation of proteinase-K-resistant PrPTSE. In all instances, 101LL mice developed PrP plaques in the area of inoculation and vicinity in the absence of clinical disease or spongiform degeneration of the brain. Importantly 101LL mice did not transmit disease on serial passage ruling out the presence of subclinical infection. Thus, in both experimental models formation of PrPTSE is not infectious. These results have implications for the interpretation of tests based on the detection of protein aggregates and suggest that de novo formation of PrPTSE in the host does not always result in a transmissible prion disease. In addition, these results question the validity of assuming that all diseases due to protein misfolding can be transmitted between individuals.