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Introduction Sporadic Creutzfeldt-Jakob disease (sCJD) is a rapidly progressive neurodegenerative disease with public health implications. Mean age of onset is 68 years. Age-specific incidence declines after 80 years. This may arise from under-ascertainment or other biological features of the disease. Accurate characterisation of late-onset sCJD is important for early diagnosis, avoiding unnecessary investigations and improving ascertainment for public health purposes. Objective To phenotype the clinical features and investigation profile of sCJD in adults >80 years. Methods We analysed all probable and definite sCJD cases identified by the UK National CJD Research & Surveillance Unit over a 10-year period (2011–2021). Individuals were grouped by age of onset. Clinical features and investigation profiles were compared. Results 10.3% (123/1196) had an age of onset over 80. Median survival was shorter (3.2 vs 4.3 months; P  < 0.001). Pyramidal signs (48.3% vs 34.2%; P  = 0.008) and akinetic mutism (55.1% vs 33.2%; P  < 0.001) were more frequent. Psychiatric symptoms (26.3% vs 39.6%; P  = 0.01) and cerebellar signs (65.4% vs 78.6%, P  = 0.007) were less frequent. Cognitive impairment and myoclonus were highly prevalent regardless of age. Between age groups, the diagnostic sensitivity of cerebrospinal fluid real-time quaking-induced conversion (CSF RT-QuIC) (92.9% vs 91.9%, P  = 0.74) was comparable, electroencephalography was superior (41.5% vs 25.4%; P  = 0.006) and MRI was inferior (67.8% vs 91.4%; P  < 0.001). Conclusions Late-onset sCJD has distinct clinical features, shorter survival and a different profile of investigation sensitivity. CSF RT-QuIC, MRI brain and specialist CJD review is recommended in older adults with a rapidly progressive neurological disorder. Autopsy is valuable when the cause remains elusive. [ABSTRACT FROM AUTHOR]

Human prion diseases, including Creutzfeldt‐Jakob disease (CJD), occur in sporadic, genetic, and acquired forms. Variant Creutzfeldt‐Jakob disease (vCJD) first reported in 1996 in the United Kingdom (UK), resulted from contamination of food with bovine spongiform encephalopathy. There is a concern that UK national surveillance mechanisms might miss some CJD cases (including vCJD), particularly in the older population where other neurodegenerative disorders are more prevalent. We developed a highly sensitive protocol for analysing autopsy brain tissue for the misfolded prion protein (PrPSc) associated with prion disease, which could be used to screen for prion disease in the elderly. Brain tissue samples from 331 donors to the Edinburgh Brain and Tissue Bank (EBTB), from 2005 to 2022, were analysed, using immunohistochemical analysis on fixed tissue, and five biochemical tests on frozen specimens from six brain regions, based on different principles for detecting PrPSc. An algorithm was established for classifying the biochemical results. To test the effectiveness of the protocol, several neuropathologically confirmed prion disease controls, including vCJD, were included and blinded in the study cohort. On unblinding, all the positive control cases had been correctly identified. No other cases tested positive; our analysis uncovered no overlooked prion disease cases. Our algorithm for classifying cases was effective for handling anomalous biochemical results. An overall analysis suggested that a reduced biochemical protocol employing only three of the five tests on only two brain tissue regions gave sufficient sensitivity and specificity. We conclude that this protocol may be useful as a UK‐wide screening programme for human prion disease in selected brains from autopsies in the elderly. Further improvements to the protocol were suggested by enhancements of the in vitro conversion assays made during the course of this study. [ABSTRACT FROM AUTHOR]

Three retrospective lymphoreticular tissue studies (Appendix I, II, and III) aimed to estimate the UK prevalence of variant Creutzfeldt-Jakob disease (vCJD), following exposure of the population to the bovine spongiform encephalopathy (BSE) agent, in the late 1980s and 1990s. These studies evaluated the presence of abnormal prion protein aggregates, in archived formalin-fixed paraffin-embedded (FFPE) appendectomy samples, by immunohistochemical detection. Although there was concordance in the estimated prevalence of vCJD from these studies, the identification of positive specimens from pre- and post-BSE-exposure periods in Appendix III study has raised questions regarding the nature and origin of the detected abnormal prion protein. We applied a robust and novel approach in the extraction of disease-associated prion protein (PrPSc) present in frozen and FFPE samples of brain and appendix from a patient with pathologically confirmed vCJD. The extracted material was used to seed the highly sensitive protein misfolding cyclic amplification assay (hsPMCA) to investigate the in vitro and in vivo propagation properties of the extracted abnormal prion protein. We demonstrate that PrPSc can be successfully extracted from FFPE appendix tissue and propagated in vitro. Bioassay in wild-type and gene-targeted mouse models confirmed that the extracted and amplified product is infectious and retains strain properties consistent with vCJD. This provides a highly sensitive and reliable platform for subsequent analysis of the archived FFPE appendix tissue derived from the Appendix II and III surveys, to further evaluate the nature of the abnormal PrP detected in the positive samples. [ABSTRACT FROM AUTHOR]

Chronic wasting disease (CWD) is a fatal contagious prion disease of cervids that is found in the United States, Canada, South Korea, and most recently in Europe (1,2). The species [...]

Prion diseases are rare fatal neurodegenerative conditions that affect humans and animals. The human diseases include Creutzfeldt-Jakob disease (CJD), Gerstmann-Straussler-Scheinker disease, and fatal familial insomnia. Most cases of human prion [...]

Prion diseases are fatal neurodegenerative disorders that affect humans and animals, and can also be transmitted from animals to humans. A fundamental event in prion disease pathogenesis is the conversion of normal host prion protein (PrPC) to a disease-associated misfolded form (PrPSc). Whether or not an animal prion disease can infect humans cannot be determined a priori. There is a consensus that classical bovine spongiform encephalopathy (C-type BSE) in cattle transmits to humans, and that classical sheep scrapie is of little or no risk to human health. However, the zoonotic potential of more recently identified animal prion diseases, such as atypical scrapie, H-type and L-type BSE and chronic wasting disease (CWD) in cervids, remains an open question. Important components of the zoonotic barrier are (i) physiological differences between humans and the animal in question, (ii) amino acid sequence differences of the animal and human PrPC, and (iii) the animal prion strain, enciphered in the conformation of PrPSc. Historically, the direct inoculation of experimental animals has provided essential information on the transmissibility and compatibility of prion strains. More recently, cell-free molecular conversion assays have been used to examine the molecular compatibility on prion replication and zoonotic potential. One such assay is Protein Misfolding Cyclic Amplification (PMCA), in which a small amount of infected tissue homogenate, containing PrPSc, is added as a seed to an excess of normal tissue homogenate containing PrPC, and prion conversion is accelerated by cycles of incubation and ultrasonication. PMCA has been used to measure the molecular feasibility of prion transmission in a range of scenarios using genotypically homologous and heterologous combinations of PrPSc seed and PrPC substrate. Furthermore, this method can be used to speculate on the molecular profile of PrPSc that might arise from a zoonotic transmission. We discuss the experimental approaches that have been used to model both the intra- and inter-species molecular compatibility of prions, and the factors affecting PrPc to PrPSc conversion and zoonotic potential. We conclude that cell-free prion protein conversion assays, especially PMCA, are useful, rapid and low-cost approaches for elucidating the mechanisms of prion propagation and assessing the risk of animal prions to humans. [ABSTRACT FROM AUTHOR]

A previously well 54-year-old woman presented with a short history of diplopia, cognitive decline, hallucinations and hypersomnolence. The patient had progressive deterioration in short-term memory, ocular convergence spasm, tremor, myoclonus, gait apraxia, central fever, dream enactment and seizures. Results of investigations were normal including MRI brain, electroencephalogram, cerebrospinal fluid (CSF, including CSF prion protein markers) and brain biopsy. The patient died from pneumonia and pulmonary embolus. Brain postmortem analysis revealed neuropathological changes in keeping with Fatal familial insomnia (FFI); the diagnosis was confirmed on genetic testing. FFI is caused by an autosomal dominant and highly penetrant pathogenic Prion Protein gene PRNP. Although usually familial, fatal insomnia (FI) also occurs in a rare sporadic form. FI is a rare human prion disease with prominent sleep disturbance, autonomic, motor, cognitive and behavioural involvement. Patient management is with best supportive care and early suspected diagnosis allows for timely palliation. [ABSTRACT FROM AUTHOR]

Sporadic Creutzfeldt-Jakob disease (sCJD) is a transmissible, rapidly progressive and fatal neurodegenerative disease. The transmissible agent linked to sCJD is composed of the misfolded form of the host-encoded prion protein. The combination of histopathological and biochemical analyses has allowed the identification and sub-classification of six sCJD subtypes. This classification depends on the polymorphic variability of codon 129 of the prion protein gene and the PrPres isotype, and appears to be associated with neuropathological and clinical features. Currently, sCJD subtyping is only fully achievable post mortem. However, a rapid and non-invasive method for discriminating sCJD subtypes in vita would be invaluable for the clinical management of affected individuals, and for the selection of participants for clinical trials. The CSF analysis by Real Time Quaking Induced Conversion (RT-QuIC) reaction is the most sensitive and specific ante mortem sCJD diagnostic test available to date, and it is used by a number of laboratories internationally. RT-QuIC takes advantage of the natural replication mechanisms of prions by template-induced misfolding, employing recombinant prion protein as reaction substrate. We asked whether epitope mapping, of the RT-QuIC reaction products obtained from seeding RT-QuIC with brain and CSF samples from each of the six molecular subtypes of sCJD could be employed to distinguish them and therefore achieve in vita sCJD molecular subtyping. We found that it is possible to distinguish the RT-QuIC products generated by sCJD biological samples from the ones generated by spontaneous conversion in the negative controls, but that different sCJD subtypes generate very similar, if not identical RT-QuIC reaction products. We concluded that whilst RT-QuIC has demonstrable diagnostic value it has limited prognostic value at this point in time. [ABSTRACT FROM AUTHOR]

Abstract: Human prion diseases constitute a group of infectious and invariably fatal neurodegenerative disorders associated with misfolding of the prion protein. Variant Creutzfeldt–Jakob disease (vCJD) is a zoonotic prion disease linked to oral exposure to the infectious agent that causes bovine spongiform encephalopathy (BSE) in cattle. The most recent case of definite vCJD was heterozygous (MV) at polymorphic codon 129 of the prion protein gene PRNP while all of the previous 177 definite or probable vCJD cases who underwent genetic analysis were methionine homozygous (MM). Retrospective prevalence studies conducted on lympho‐reticular tissue suggest that the number of asymptomatic vCJD carriers in the United Kingdom might be around 1 in 2000 people. In addition, there have been four known cases of the transmission of vCJD infection via blood transfusion. For these reasons, a sensitive, reliable, and fast diagnostic test is currently needed. We describe a rapid and highly sensitive seeding conversion assay that detects disease‐associated prion protein in the brain and cerebrospinal fluid in vCJD after 48–96 h of amplification, with 100% sensitivity and specificity. This method can amplify prions from definite, probable, and possible vCJD cases from patients who are either MM or MV at PRNP‐codon 129. [ABSTRACT FROM AUTHOR]

Protein misfolding is common across many neurodegenerative diseases, with misfolded proteins acting as seeds for "prion-like" conversion of normally folded protein to abnormal conformations. A central hypothesis is that misfolded protein accumulation, spread, and distribution are restricted to specific neuronal populations of the central nervous system and thus predict regions of neurodegeneration. We examined this hypothesis using a highly sensitive assay system for detection of misfolded protein seeds in a murine model of prion disease. Misfolded prion protein (PrP) seeds were observed widespread throughout the brain, accumulating in all brain regions examined irrespective of neurodegeneration. Importantly, neither time of exposure nor amount of misfolded protein seeds present determined regions of neurodegeneration. We further demonstrate two distinct microglia responses in prion-infected brains: a novel homeostatic response in all regions and an innate immune response restricted to sites of neurodegeneration. Therefore, accumulation of misfolded prion protein alone does not define targeting of neurodegeneration, which instead results only when misfolded prion protein accompanies a specific innate immune response. [ABSTRACT FROM AUTHOR]

Prion diseases are rare fatal neurological conditions of humans and animals, one of which (variant Creutzfeldt-Jakob disease) is known to be a zoonotic form of the cattle disease bovine spongiform encephalopathy (BSE). What makes one animal prion disease zoonotic and others not is poorly understood, but it appears to involve compatibility between the prion strain and the host prion protein sequence. Concerns have been raised that the United Kingdom sheep flock may have been exposed to BSE early in the cattle BSE epidemic and that serial BSE transmission in sheep might have resulted in adaptation of the agent, which may have come to phenotypically resemble scrapie while maintaining its pathogenicity for humans. We have modeled this scenario in vitro. Extrapolation from our results suggests that if BSE were to infect sheep in the field it may, with time and in some sheep genotypes, become scrapie-like at the molecular level. However, the results also suggest that if BSE in sheep were to come to resemble scrapie it would lose its ability to affect humans. [ABSTRACT FROM AUTHOR]

Prion diseases are infectious neurodegenerative disorders that affect humans and animals and that result from the conversion of normal prion protein (PrPC) into the misfolded prion protein (PrPSc). Chronic wasting disease (CWD) is a prion disorder of increasing prevalence within the United States that affects a large population of wild and captive deer and elk. Determining the risk of transmission of CWD to humans is of utmost importance, considering that people can be infected by animal prions, resulting in new fatal diseases. To study the possibility that human PrPC can be converted into the misfolded form by CWD PrPSc, we performed experiments using the protein misfolding cyclic amplification technique, which mimics in vitro the process of prion replication. Our results show that cervid PrPSc can induce the conversion of human PrPC but only after the CWD prion strain has been stabilized by successive passages in vitro or in vivo. Interestingly, the newly generated human PrPSc exhibits a distinct biochemical pattern that differs from that of any of the currently known forms of human PrPSc. Our results also have profound implications for understanding the mechanisms of the prion species barrier and indicate that the transmission barrier is a dynamic process that depends on the strain and moreover the degree of adaptation of the strain. If our findings are corroborated by infectivity assays, they will imply that CWD prions have the potential to infect humans and that this ability progressively increases with CWD spreading. [ABSTRACT FROM AUTHOR]

Prions are the proteinaceous infectious agents responsible for Transmissible Spongiform Encephalopathies. Compelling evidence supports the hypothesis that prions are composed exclusively of a misfolded version of the prion protein (PrPSc) that replicates in the body in the absence of nucleic acids by inducing the misfolding of the cellular prion protein (PrPC). The most common form of human prion disease is sporadic, which appears to have its origin in a low frequency event of spontaneous misfolding to generate the first PrPSc particle that then propagates as in the infectious form of the disease. The main goal of this study was to mimic an early event in the etiology of sporadic disease by attempting de novo generation of infectious PrPSc in vitro. For this purpose we analyzed in detail the possibility of spontaneous generation of PrPSc by the protein misfolding cyclic amplification (PMCA) procedure. Under standard PMCA conditions, and taking precautions to avoid cross-contamination, de novo generation of PrPSc was never observed, supporting the use of the technology for diagnostic applications. However, we report that PMCA can be modified to generate PrPSc in the absence of pre-existing PrPSc in different animal species at a low and variable rate. De novo generated PrPSc was infectious when inoculated into wild type hamsters, producing a new disease phenotype with unique clinical, neuropathological and biochemical features. Our results represent additional evidence in support of the prion hypothesis and provide a simple model to study the mechanism of sporadic prion disease. The findings also suggest that prion diversity is not restricted to those currently known, and that likely new forms of infectious protein foldings may be produced, resulting in novel disease phenotypes. [ABSTRACT FROM AUTHOR]

Twenty-five years has now passed since variant Creutzfeldt-Jakob disease (vCJD) was first described in the United Kingdom (UK). Early epidemiological, neuropathological and biochemical investigations suggested that vCJD represented a new zoonotic form of human prion disease resulting from dietary exposure to the bovine spongiform encephalopathy (BSE) agent. This hypothesis has since been confirmed though a large body of experimental evidence, predominantly using animal models of the disease. Today, the clinical, pathological and biochemical phenotype of vCJD is well characterized and demonstrates a unique and remarkably consistent pattern between individual cases when compared to other human prion diseases. While the numbers of vCJD cases remain reassuringly low, with 178 primary vCJD cases reported in the UK and a further 54 reported worldwide, concerns remain over the possible appearance of new vCJD cases in other genetic cohorts and the numbers of asymptomatic individuals in the population harboring vCJD infectivity. This review will provide a historical perspective on vCJD, examining the origins of this acquired prion disease and its association with BSE. We will investigate the epidemiology of the disease along with the unique clinicopathological and biochemical phenotype associated with vCJD cases. Additionally, this review will examine the impact vCJD has had on public health in the UK and the ongoing concerns raised by this rare group of disorders. [ABSTRACT FROM AUTHOR]

Prions are the infectious agents responsible for prion diseases, which appear to be composed exclusively by the misfolded prion protein (PrPSc). Disease is transmitted by the autocatalytic propagation of PrPSc misfolding at the expense of the normal prion protein. The biggest challenge of the prion hypothesis has been to explain the molecular mechanism by which prions can exist as different strains, producing diseases with distinguishable characteristics. Here, we show that PrPSc generated in vitro by protein misfolding cyclic amplification from five different mouse prion strains maintains the strain-specific properties. Inoculation of wild-type mice with in vitro-generated PrPSc caused a disease with indistinguishable incubation times as well as neuropathological and biochemical characteristics as the parental strains. Biochemical features were also maintained upon replication of four human prion strains. These results provide additional support for the prion hypothesis and indicate that strain characteristics can be faithfully propagated in the absence of living cells, suggesting that strain variation is dependent on PrPSc properties. [ABSTRACT FROM AUTHOR]

Objective To report a novel prion disease characterized by distinct histopathological and immunostaining features, and associated with an abnormal isoform of the prion protein (PrP) that, contrary to the common prion diseases, is predominantly sensitive to protease digestion. Methods Eleven subjects were investigated at the National Prion Disease Pathology Surveillance Center for clinical, histopathological, immunohistochemical, genotypical, and PrP characteristics. Results Patients presented with behavioral and psychiatric manifestations on average at 62 years, whereas mean disease duration was 20 months. The type of spongiform degeneration, the PrP immunostaining pattern, and the presence of microplaques distinguished these cases from those with known prion diseases. Typical protease-resistant PrP was undetectable in the cerebral neocortex with standard diagnostic procedures. After enrichment, abnormal PrP was detected at concentrations 16 times lower than common prion diseases; it included nearly 4 times less protease-resistant PrP, which formed a distinct electrophoretic profile. The subjects examined comprised about 3% of sporadic cases evaluated by the National Prion Disease Pathology Surveillance Center. Although several subjects had family histories of dementia, no mutations were found in the PrP gene open reading frame. Interpretation The distinct histopathological, PrP immunohistochemical, and physicochemical features, together with the homogeneous genotype, indicate that this is a previously unidentified type of disease involving the PrP, which we designated 'protease-sensitive prionopathy' (or PSPr). Protease-sensitive prionopathy is not rare among prion diseases, and it may be even more prevalent than our data indicate because protease-sensitive prionopathy cases are likely also to be classified within the group of non-Alzheimer's dementias. Ann Neurol 2008;63:697-708 [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Introduction: Variably protease sensitive prionopathy (VPSPr) is a recently described, sporadic human prion disease that is pathologically and biochemically distinct from the currently recognised sporadic Creutzfeldt-Jakob disease (sCJD) subtypes. The defining biochemical features of the abnormal form of the prion protein (PrPSc) in VPSPr are increased sensitivity to proteolysis and the presence of an N- and C-terminally cleaved ~8 kDa protease resistant PrPSc (PrPres) fragment. The biochemical and neuropathological profile of VPSPr has been proposed to resemble either Gerstmann-Sträussler-Scheinker syndrome (GSS) or familial CJD with the PRNP-V180I mutation. However, in some cases of VPSPr two protease resistant bands have been observed in Western blots that co-migrate with those of type 2 PrPres, suggesting that a proportion of the PrPSc present in VPSPr has properties similar to those of sCJD., Results: Here, we have used conformation dependent immunoassay to confirm the presence of PrPSc in VPSPr that is more protease sensitive compared with sCJD. However, CDI also shows that a proportion of PrPSc in VPSPr resists PK digestion of its C-terminus, distinguishing it from GSS associated with ~8 kDa PrPres, and showing similarity to sCJD. Intensive investigation of a single VPSPr case with frozen tissue from multiple brain regions shows a broad, region-specific spectrum of protease sensitivity and differential stability of PrPSc in the absence of PK treatment. Finally, using protein misfolding cyclic amplification and real-time quaking induced conversion, we show that VPSPr PrPSc has the potential to seed conversion in vitro and that seeding activity is dispersed through a broad range of aggregate sizes. We further propose that seeding activity is associated with the ~19 and ~23 kDa PrPres rather than the ~8 kDa fragment., Conclusions: Therefore, PrPSc in VPSPr is heterogeneous in terms of protease sensitivity and stability to denaturation with the chaotrope GdnHCl and includes a proportion with similar properties to that found in sCJD.

Protein misfolding cyclic amplification (PMCA) is a technique that takes advantage of the nucleation-dependent prion replication process to accelerate the conversion of PrP(C) into PrP(Sc) in the test tube. PMCA uses ultrasound waves to fragment the PrP(Sc) polymers, increasing the amount of seeds present in the infected sample without affecting their ability to act as conversion nuclei. Over the past 5 years, PMCA has become an invaluable technique to study diverse aspects of prions. The PMCA technology has been used by several groups to understand the molecular mechanism of prion replication, the cellular factors involved in prion propagation, the intriguing phenomena of prion strains and species barriers, to detect PrP(Sc) in tissues and biological fluids, and to screen for inhibitors against prion replication. In this chapter, we describe a detailed protocol of the PMCA technique, highlighting some of the important technical aspects to obtain a successful and reproducible application of the technology.

Prion diseases are infectious neurodegenerative disorders that affect humans and animals and that result from the conversion of normal prion protein (PrP(C)) into the misfolded prion protein (PrP(Sc)). Chronic wasting disease (CWD) is a prion disorder of increasing prevalence within the United States that affects a large population of wild and captive deer and elk. Determining the risk of transmission of CWD to humans is of utmost importance, considering that people can be infected by animal prions, resulting in new fatal diseases. To study the possibility that human PrP(C) can be converted into the misfolded form by CWD PrP(Sc), we performed experiments using the protein misfolding cyclic amplification technique, which mimics in vitro the process of prion replication. Our results show that cervid PrP(Sc) can induce the conversion of human PrP(C) but only after the CWD prion strain has been stabilized by successive passages in vitro or in vivo. Interestingly, the newly generated human PrP(Sc) exhibits a distinct biochemical pattern that differs from that of any of the currently known forms of human PrP(Sc). Our results also have profound implications for understanding the mechanisms of the prion species barrier and indicate that the transmission barrier is a dynamic process that depends on the strain and moreover the degree of adaptation of the strain. If our findings are corroborated by infectivity assays, they will imply that CWD prions have the potential to infect humans and that this ability progressively increases with CWD spreading.