Abstract
The accumulation and propagation in the brain of misfolded proteins is a pathological hallmark shared by many neurodegenerative diseases such as Alzheimer’s disease (Aβ and tau), Parkinson’s disease (α-synuclein), and prion disease (prion protein). Currently, there is no epidemiological evidence to suggest that neurodegenerative disorders are infectious, apart from prion diseases. However, there is an increasing body of evidence from experimental models to suggest that other pathogenic proteins such as Aβ and tau can propagate in vivo and in vitro in a prion-like mechanism, inducing the formation of misfolded protein aggregates such as amyloid plaques and neurofibrillary tangles. Such similarities have raised concerns that misfolded proteins, other than the prion protein, could potentially transmit from person-to-person as rare events after lengthy incubation periods. Such concerns have been heightened following a number of recent reports of the possible inadvertent transmission of Aβ pathology via medical and surgical procedures. This review will provide a historical perspective on the unique transmissible nature of prion diseases, examining their impact on public health and the ongoing concerns raised by this rare group of disorders. Additionally, this review will provide an insight into current evidence supporting the potential transmissibility of other pathogenic proteins associated with more common neurodegenerative disorders and the potential implications for public health.
Highlights
Average life expectancy has shown a sustained increase over the last four decades
Brain isolates in wild-type mice resulted in transmission properties that were indistinguishable from those obtained with bovine spongiform encephalopathy (BSE) but that differed from those obtained with sporadic Creutzfeldt-Jakob disease (sCJD) [46]
Lessons learned from instances of acquired prion diseases have resulted in the implementation of a range of safety measures in order to prevent future iatrogenic transmission of Creutzfeldt-Jakob disease (CJD), further secondary transmission of variant CJD (vCJD), and the potential zoonotic spread from other animal prion diseases
Summary
Average life expectancy has shown a sustained increase over the last four decades. The vast majority of neurodegenerative diseases are associated with the intracellular or extracellular accumulation of misfolded protein within the brain [4] These abnormal protein deposits lead to the dysfunction and subsequent loss of the neuronal population, resulting in the progression of a wide range of clinical symptoms that may include cognitive decline, dementia, and a gradual loss of locomotor functions. With no large-scale epidemiological studies suggesting that other neurodegenerative disorders are infectious, apart from prion disease, the categorisation of disorders such as AD and PD as prion-like remains somewhat contentious Advocates of this categorisation point to an increasing body of evidence from experimental models demonstrating that protein aggregates such as Aβ and tau can propagate in vivo and in vitro in a prion-like mechanism generating misfolded protein aggregates such as amyloid plaques and neurofibrillary tangles. This review will provide an insight into current evidence supporting the potential transmissibility of other pathogenic proteins associated with more common neurodegenerative disorders and the possible implications for public health
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