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Objective: To compare the diagnostic accuracy and the prognostic value of blood and cerebrospinal fluid (CSF) tests across prion disease subtypes., Methods: We used a single-molecule immunoassay to measure tau and neurofilament light chain (NfL) protein levels in the plasma and assessed CSF total(t)-tau, NfL and protein 14-3-3 levels in patients with prion disease (n=336), non-prion rapidly progressive dementias (n=106) and non-neurodegenerative controls (n=37). We then evaluated each plasma and CSF marker for diagnosis and their association with survival, taking into account the disease subtype, which is a strong independent prognostic factor in prion disease., Results: Plasma tau and NfL concentrations were higher in patients with prion disease than in non-neurodegenerative controls and non-prion rapidly progressive dementias. Plasma tau showed higher diagnostic value than plasma NfL, but a lower accuracy than the CSF proteins t-tau and 14-3-3. In the whole prion cohort, both plasma (tau and NfL) and CSF (t-tau, 14-3-3 and NfL) markers were significantly associated with survival and showed similar prognostic values. However, the intrasubtype analysis revealed that only CSF t-tau in sporadic Creutzfeldt-Jakob disease (sCJD) MM(V)1, plasma tau and CSF t-tau in sCJD VV2, and plasma NfL in slowly progressive prion diseases were significantly associated with survival after accounting for covariates., Conclusions: Plasma markers have lower diagnostic accuracy than CSF biomarkers. Plasma tau and NfL and CSF t-tau are significantly associated with survival in prion disease in a subtype-specific manner and can be used to improve clinical trial stratification and clinical care., Competing Interests: Competing interests: None declared., (© Author(s) (or their employer(s)) 2020. No commercial re-use. See rights and permissions. Published by BMJ.)

Chronic wasting disease (CWD) is a relatively new and burgeoning prion epidemic of deer, elk, reindeer, and moose, which are members of the cervid family. While the disease was first described in captive deer, its subsequent discovery in various species of free-ranging animals makes it the only currently recognized prion disorder of both wild and farmed animals. In addition to its expanding range of host species, CWD continues to spread from North America to new geographic areas, including South Korea, and most recently Norway, marking the first time this disease was detected in Europe. Its unparalleled efficiency of contagious transmission, combined with high densities of deer in certain areas, complicates strategies for controlling CWD, raising concerns about its potential for spread to new species. Because there is a high prevalence of CWD in deer and elk, which are commonly hunted and consumed by humans, and since prions from cattle with bovine spongiform encephalopathy have been transmitted to humans causing variant Creutzfeldt-Jakob disease, the possibility of zoonotic transmission of CWD is particularly concerning. Here we review the clinical and pathologic features of CWD and its disturbing epidemiology, and discuss features that affect its transmission, including genetic susceptibility, pathogenesis, and agent strain variability. Finally, we discuss evidence that speaks to the potential for zoonotic transmission of this emerging disease., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Genetic prion diseases (gPrDs) are caused by autosomal-dominant mutations in the prion protein gene (PRNP). Although the first PRNP mutations identified, and most since, are PRNP missense, octapeptide repeat insertions, deletion and nonsense mutations have now also been shown to cause gPrD. Based on clinicopathologic features of familial disease, gPrDs historically have been classified into three forms: familial Jakob-Creutzfeldt disease, Gerstmann-Sträussler-Scheinker disease, and fatal familial insomnia. This classification, however, occurred prior to the identification of PRNP, and although these forms are still recognized, classification now is somewhat more complex. Clinical manifestations, and even pathology, are known to be more heterogeneous and varied than the historic three phenotypic classifications. Most gPrDs either present rapidly with progression of dementia, ataxia, myoclonus, and other motor features leading to death in few months or present more slowly, declining over a few years with mild cognitive impairment, ataxia, or parkinsonism and later dementia; a few very rare mutations, however, present over years to decades with neuropsychiatric disorders and systemic symptoms (gastrointestinal disorders and neuropathy). In this chapter, we review the broad phenotypic spectrum of PRNP mutations causing gPrDs., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Prion diseases are fatal neurodegenerative disorders with sporadic, genetic or acquired etiologies. The molecular alterations leading to the onset and the spreading of these diseases are still unknown. In a previous work we identified a five-gene signature able to distinguish intracranially BSE-infected macaques from healthy ones, with SERPINA3 showing the most prominent dysregulation. We analyzed 128 suitable frontal cortex samples, from prion-affected patients (variant Creutzfeldt-Jakob disease (vCJD) n = 20, iatrogenic CJD (iCJD) n = 11, sporadic CJD (sCJD) n = 23, familial CJD (gCJD) n = 17, fatal familial insomnia (FFI) n = 9, Gerstmann-Sträussler-Scheinker syndrome (GSS)) n = 4), patients with Alzheimer disease (AD, n = 14) and age-matched controls (n = 30). Real Time-quantitative PCR was performed for SERPINA3 transcript, and ACTB, RPL19, GAPDH and B2M were used as reference genes. We report SERPINA3 to be strongly up-regulated in the brain of all human prion diseases, with only a mild up-regulation in AD. We show that this striking up-regulation, both at the mRNA and at the protein level, is present in all types of human prion diseases analyzed, although to a different extent for each specific disorder. Our data suggest that SERPINA3 may be involved in the pathogenesis and the progression of prion diseases, representing a valid tool for distinguishing different forms of these disorders in humans.

Exposure of human populations to bovine spongiform encephalopathy through contaminated food has resulted in <250 cases of variant Creutzfeldt-Jakob disease (vCJD). However, more than 99% of vCJD infections could have remained silent suggesting a long-term risk of secondary transmission particularly through blood. Here, we present experimental evidence that transfusion in mice and non-human primates of blood products from symptomatic and non-symptomatic infected donors induces not only vCJD, but also a different class of neurological impairments. These impairments can all be retransmitted to mice with a pathognomonic accumulation of abnormal prion protein, thus expanding the spectrum of known prion diseases. Our findings suggest that the intravenous route promotes propagation of masked prion variants according to different mechanisms involved in peripheral replication.

The most definitive classification systems for dementia are based on the underlying pathology which, in turn, is categorized largely according to the observed accumulation of abnormal protein aggregates in neurons and glia. These aggregates perturb molecular processes, cellular functions and, ultimately, cell survival, with ensuing disruption of large-scale neural networks subserving cognitive, behavioural and sensorimotor functions. The functional domains affected and the evolution of deficits in these domains over time serve as footprints that the clinician can trace back with various levels of certainty to the underlying neuropathology. The process of phenotyping and syndromic classification has substantially improved over decades of careful clinicopathological correlation, and through the discovery of in vivo biomarkers of disease. Here, we present an overview of the salient features of the most common dementia subtypes - Alzheimer disease, vascular dementia, frontotemporal dementia and related syndromes, Lewy body dementias, and prion diseases - with an emphasis on neuropathology, relevant epidemiology, risk factors, and signature signs and symptoms.

In most human sporadic prion diseases the phenotype is consistently associated with specific pairings of the genotype at codon 129 of the prion protein gene and conformational properties of the scrapie PrP (PrP Sc ) grossly identified types 1 and 2. This association suggests that the 129 genotype favours the selection of a distinct strain that in turn determines the phenotype. However, this mechanism cannot play a role in the phenotype determination of sporadic fatal insomnia (sFI) and a subtype of sporadic Creutzfeldt-Jakob disease (sCJD) identified as sCJDMM2, which share 129 MM genotype and PrP Sc type 2 but are associated with quite distinct phenotypes. Our detailed comparative study of the PrP Sc conformers has revealed major differences between the two diseases, which preferentially involve the PrP Sc component that is sensitive to digestion with proteases (senPrP Sc ) and to a lesser extent the resistant component (resPrP Sc ). We conclude that these variations are consistent with two distinct strains in sFI and sCJDMM2, and that the rarer sFI is the result of a variant strain selection pathway that might be favoured by a different brain site of initial PrP Sc formation in the two diseases.

Human prion diseases are rare neurodegenerative diseases that have become the subject of public and scientific interest because of concerns about interspecies transmission and the unusual biological properties of the causal agents: prions. These diseases are unique in that they occur in sporadic, hereditary, and infectious forms that are characterized by an extended incubation period between exposure to infection and the development of clinical illness. Silent infection can be present in peripheral tissues during the incubation period, which poses a challenge to public health, especially because prions are relatively resistant to standard decontamination procedures. Despite intense research efforts, no effective treatment has been developed for human prion diseases, which remain uniformly fatal., (Copyright © 2017 Cold Spring Harbor Laboratory Press; all rights reserved.)

The human prion diseases comprise sporadic, genetic, and acquired disorders. These are rare conditions with a heterogeneous clinicopathologic phenotype, which can make diagnosis challenging. A combined clinical, genetic, neuropathologic and biochemical approach to diagnosis is therefore essential. Since prion infectivity is the highest in tissues from the central nervous system, special laboratory precautions are required for the safe handling of these tissues. Neuropathologic assessment is generally performed following autopsy, when the fixed brain should be adequately sampled and studied by conventional stains and immunohistochemistry for the abnormal form of the prion protein. Frozen brain tissue is also required for DNA extraction for prion protein gene sequencing and for Western blot analysis of protease-resistant prion protein. The microscopic assessment of the nature and degree of spongiform change, neuronal loss, gliosis, and abnormal prion protein deposition in the brain can be used to determine the major categories of human prion disease. This information can be combined with clinical, genetic data, and biochemical data to allow an accurate diagnosis of a human prion disease and facilitates subclassification into recognized disease subtypes, for example in sporadic Creutzfeldt-Jakob disease. The spectrum of human prion diseases continues to expand and neuropathology will play a key role in the recognition and understanding of any further novel entities or disease variants that may emerge in the future., (© 2017 Elsevier Inc. All rights reserved.)

Prion diseases affect a wide range of mammal species and are caused by a misfolded self-propagating isoform (PrP Sc ) of the normal prion protein (PrP C ). Distinct strains of prions exist and are operationally defined by differences in a heritable phenotype under controlled experimental transmission conditions. Prion strains can differ in incubation period, clinical signs of disease, tissue tropism, and host range. The mechanism by which a protein-only pathogen can encode strain diversity is only beginning to be understood. The prevailing hypothesis is that prion strain diversity is encoded by strain-specific conformations of PrP Sc ; however, strain-specific cellular cofactors have been identified in vitro that may also contribute to prion strain diversity. Although much progress has been made on understanding the etiological agent of prion disease, the relationship between the strain-specific properties of PrP Sc and the resulting phenotype of disease in animals is poorly understood., (Copyright © 2016 Cold Spring Harbor Laboratory Press; all rights reserved.)

Prion diseases are typically recognized as rapidly progressive dementing illnesses that also feature myoclonus and cerebellar ataxia. Several families have now been described with a late-onset hereditary sensory and autonomic neuropathy caused by truncation of prion protein (PrP), and associated with systemic amyloidosis, which was a profoundly unexpected phenotype. The chronic symptoms of this disorder, termed PrP systemic amyloidosis, can be very disabling, and are comparable to familial amyloid polyneuropathy (FAP) caused by transthyretin mutations. Patients require symptomatic therapies directed towards control of nausea, diarrhoea, incontinence, neuropathic pain and postural hypotension. Although the potential transmissibility of this new prion disease is probably extremely low, we advocate PrP gene analysis before biopsy in the investigation of peripheral and autonomic neuropathies, or for patients with unexplained diarrhoea and neuropathy. Prion diseases and the FAPs both display prominent effects of mutation type on clinical presentation and patterns of pathology-a fascinating but unexplained observation. Several neurodegenerative diseases associated with central protein misfolding, such as Huntington and Parkinson diseases, also have under-recognized peripheral components. Most of the familial amyloidoses can be explained by known gene mutations, but amino acid variants in proteins involved in other central neurodegenerative diseases might direct the initial pathology to the periphery.

Prion diseases, or transmissible spongiform encephalopathies, are neurodegenerative diseases, which affect human and many species of animals with 100% fatality rate. The most accepted etiology for prion disease is 'prion', which arises from the conversion from cellular PrP(C) to the pathological PrP(Sc). This review discussed the characteristic structure of PrP, including PRNP gene, PrP(C), PrP(Sc), PrP amyloid, and prion strains.

Variably protease-sensitive prionopathy is a newly described human prion disease of unknown aetiology lying out with the hitherto recognized phenotypic spectrum of Creutzfeldt-Jakob disease. Two cases that conform to the variably protease-sensitive prionopathy phenotype have been identified prospectively in the U.K. since the first description of the condition in 2008 in the U.S.A. To determine the incidence and phenotype of variably protease-sensitive prionopathy within a single well-defined cohort, we have conducted a retrospective review of patients referred to the National Creutzfeldt-Jakob Disease Research & Surveillance Unit during the period 1991-2008. The approach taken was to screen frozen brain tissue by western blotting for the form of protease-resistant prion protein that characterizes variably protease-sensitive prionopathy, followed by neuropathological and clinical review of candidate cases. Cases diagnosed as sporadic Creutzfeldt-Jakob disease with atypical neuropathology were also reviewed. Four hundred and sixty-five cases were screened biochemically, yielding four candidate cases of variably protease-sensitive prionopathy. One was discounted on pathological and clinical grounds, and one was a known case of variably protease-sensitive prionopathy previously reported, leaving two new cases, which were confirmed biochemically and neuropathologically as variably protease-sensitive prionopathy. A third new case that lacked frozen tissue was recognized retrospectively on neuropathological grounds alone. This means that five cases of variably protease-sensitive prionopathy have been identified (prospectively and retrospectively) during the surveillance period 1991-2011 in the U.K. Assuming ascertainment levels equivalent to that of other human prion diseases, these data indicate that variably protease-sensitive prionopathy is a rare phenotype within human prion diseases, which are themselves rare. Biochemical investigation indicates that the abnormal protease-resistant prion protein fragment that characterizes variably protease-sensitive prionopathy is detectable at low levels in some cases of sporadic Creutzfeldt-Jakob disease and conversely, that the form of abnormal prion protein that characterizes sporadic Creutzfeldt-Jakob disease can be found in certain brain regions of cases of variably protease-sensitive prionopathy, indicating molecular overlaps between these two disorders.

The current classification of human sporadic prion diseases recognizes six major phenotypic subtypes with distinctive clinicopathological features, which largely correlate at the molecular level with the genotype at the polymorphic codon 129 (methionine, M, or valine, V) in the prion protein gene and with the size of the protease-resistant core of the abnormal prion protein, PrP(Sc) (i.e. type 1 migrating at 21 kDa and type 2 at 19 kDa). We previously demonstrated that PrP(Sc) typing by Western blotting is a reliable means of strain typing and disease classification. Limitations of this approach, however, particularly in the interlaboratory setting, are the association of PrP(Sc) types 1 or 2 with more than one clinicopathological phenotype, which precludes definitive case classification if not supported by further analysis, and the difficulty of fully recognizing cases with mixed phenotypic features. In this study, we tested the inter-rater reliability of disease classification based only on histopathological criteria. Slides from 21 cases covering the whole phenotypic spectrum of human sporadic prion diseases, and also including two cases of variant Creutzfeldt-Jakob disease (CJD), were distributed blindly to 13 assessors for classification according to given instructions. The results showed good-to-excellent agreement between assessors in the classification of cases. In particular, there was full agreement (100 %) for the two most common sporadic CJD subtypes and variant CJD, and very high concordance in general for all pure phenotypes and the most common subtype with mixed phenotypic features. The present data fully support the basis for the current classification of sporadic human prion diseases and indicate that, besides molecular PrP(Sc) typing, histopathological analysis permits reliable disease classification with high interlaboratory accuracy.

General problems of classification and nomenclature of human diseases caused by agents of biological nature are reviewed. From biological and epidemiological position, prion diseases that belong to non-infectious human pathology are analyzed. Directions of improvement of ecologic-etiologic and ecologic-epidemiologic classifications and nomenclature of human diseases caused by infectious, invasive and prion agents are determined.

Human prion diseases are a unique group of transmissible neurodegenerative diseases that occur as sporadic, familial or acquired disorders and show a wide range of phenotypic variation. The latter has been attributed to the existence of distinct strains of the agent or prion, and the genetic background of the host, namely the primary sequence of the gene encoding the prion protein, which is the site of mutations and polymorphisms. The characterization of distinct isoforms of the abnormal prion protein in the brain of affected patients, which has been shown to correlate with the disease phenotype, has recently led to the concept of molecular strain typing, in which the different prion protein isoforms or "types", possibly enciphering the strain variability in their conformation, may serve as surrogate markers for individual prion strains. In sporadic Creutzfeldt-Jakob disease, the most common human prion disease, there are at least six distinct clinico-pathological disease phenotypes that largely correlate at a molecular level with two prion protein types with distinctive physicochemical properties and the genotype at the methionine/valine polymorphic codon 129 in the prion protein gene. Recent results of transmission studies indicate that five prion strains with distinctive biological properties can be isolated from these six disease variants. It has also been shown that about a third of sporadic cases show a mixed phenotype and the co-occurrence of prion protein types. The origin of prion strains and their co-occurrence as well as the mechanisms underlying the strain-specific neuronal targeting remain largely unexplained and their understanding constitute, together with the development of successful therapies and more sensitive and specific clinical biomarkers, the major challenges that this disease poses for the future.

Transmissible spongiform encephalopathies (TSEs) or prion diseases are unique disorders that are not caused by infectious micro-organisms (bacteria or fungi), viruses or parasites, but rather seem to be the result of an infectious protein. TSEs are comprised of fatal neurodegenerative disorders affecting both human and animals. Prion diseases cause sponge-like degeneration of neuronal tissue and include (among others) Creutzfeldt-Jacob disease in humans, bovine spongiform encephalopathy (BSE) in cattle and scrapie in sheep. TSEs are characterized by the formation and accumulation of transmissible (infectious) disease-associated protease-resistant prion protein (PrP(Sc)), mainly in tissues of the central nervous system. The exact molecular processes behind the conversion of PrP(C) into PrP(Sc) are not clearly understood. Correlations between prion protein polymorphisms and disease have been found, however in what way these polymorphisms influence the conversion processes remains an enigma; is stabilization or destabilization of the prion protein the basis for a higher conversion propensity? Apart from the disease-associated polymorphisms of the prion protein, the molecular processes underlying conversion are not understood. There are some notions as to which regions of the prion protein are involved in refolding of PrP(C) into PrP(Sc) and where the most drastic structural changes take place. Direct interactions between PrP(C) molecules and/or PrP(Sc) are likely at the basis of conversion, however which specific amino acid domains are involved and to what extent these domains contribute to conversion resistance/sensitivity of the prion protein or the species barrier is still unknown.

The prion diseases are a family of rare neurodegenerative disorders that result from the accumulation of a misfolded isoform of the prion protein (PrP), a normal constituent of the neuronal membrane. Five subtypes constitute the known human prion diseases; kuru, Creutzfeldt-Jakob disease (CJD), Gerstmann-Sträussler-Scheinker syndrome (GSS), fatal insomnia (FI), and variant CJD (vCJD). These subtypes are distinguished, in part, by their clinical phenotype, but primarily by their associated brain histopathology. Evidence suggests these phenotypes are defined by differences in the pathogenic conformation of misfolded PrP. Although the vast majority of cases are sporadic, 10% to 15% result from an autosomal dominant mutation of the PrP gene (PRNP). General phenotype-genotype correlations can be made for the major subtypes of CJD, GSS, and FI. This paper will review some of the general background related to prion biology and detail the clinical and pathologic features of the major prion diseases, with a particular focus on the genetic aspects that result in prion disease or modification of its risk or phenotype.

Human prion diseases are classified into 3 categories according to etiologies: idiopathic of unknown cause, acquired of infectious origin, and genetic by PRNP mutation. The surveillance committee have analyzed 2,494 cases and identified 1,402 as prion diseases. Most of them are idiopathic, namely sporadic CJD (77%) with less genetic and acquired prion diseases (17% and 5%, respectively). The number of patients identified by the surveillance committee in these years is about 120 which are less than the number of annual death of prion disease. The difference might be due to partly the fact our surveillance need the consent from patients' family and is not complete. The mean age at onset of prion disease is late 60s while the range is fairly wide. Brain MRIs and increase of CSF 14-3-3 and tau protein levels are very characteristic. Classical sporadic CJD could show completely normal T1WI with patchy high signals in the cerebral cortex and basal ganglia on DWI. In Japan, classical sporadic CJD (MM1) is most popular but there are some rare atypical subtypes. Among them, MM2-thalamic CJD is hardest to diagnose because it shows no high intensity signals on DWI, in addition to frequent absence of CSF and EEG characteristics. In this case, CBF decrease in the thalamus on SPECT is very helpful. Genetic prion diseases in Japan are quite distinct from those in Europe. V180I and M232R mutations are unique to Japan and show sporadic CJD phenotype. Dura graft-associated CJD (dCJD) are composed of 67% of classical sporadic CJD phenotype and 33% of atypical phenotype showing slower progression with amyloid plaques. Trace-back experiments suggested the PrP(sc) of the atypical dCJD was likely to be modified from infection of abnormal VV2 protein. Although there are some atypical forms of prion diseases as mentioned above, almost all prion cases could be diagnosed with EEG, MRI, genetic test, CSF test and SPECT. We also have some incidents in which brain surgery was done before the diagnosis of prion disease and many other patients were operated using the same operating instruments before their sterilization against prion disease had been done. The explanation of possibility of prion disease infection to the patients and their follow-up was started by the incident committee. It is very important for all the nations to cooperate with each other in order to overcome this intractable disease.

Since 1987, when bovine spongiform encephalopathy (BSE) emerged as a novel disease in cattle, enormous efforts were undertaken to monitor and control the disease in ruminants worldwide. The driving force was its high economic impact, which resulted from trade restrictions and the loss of consumer confidence in beef products, the latter because BSE turned out to be a fatal zoonosis, causing variant Creutzfeldt-Jakob disease in human beings. The ban on meat and bone meal in livestock feed and the removal of specified risk materials from the food chain were the main measures to successfully prevent infection in cattle and to protect human beings from BSE exposure. However, although BSE is now under control, previously unknown, so-called atypical transmissible spongiform encephalopathies (TSEs) in cattle and small ruminants have been identified by enhanced disease surveillance. This report briefly reviews and summarizes the current level of knowledge on the spectrum of TSEs in cattle and small ruminants and addresses the question of the extent to which such atypical TSEs have an effect on disease surveillance and control strategies.

Summary: Variant Creutzfeldt-Jakob disease (CJD) is an emerging form of human prion disease caused by oral exposure to the bovine spongiform encephalopathy agent. Most cases have occurred in the UK, but smaller numbers of cases have been identified in 10 other countries worldwide. All confirmed cases belong to a single genetic subgroup defined by methionine homozygosity at codon 129 in the prion protein gene. Variant CJD has a widespread distribution of infectivity in the body, involving lymphoid tissues during at least the latter part of the incubation period. This is unlike other forms of human prion disease, and raised concerns that the transmissible agent might also be present in blood. To date, four probable cases of variant CJD infection have been identified following transfusion of packed red blood cells from asymptomatic donors who subsequently died from variant CJD. Recently, one case of likely transmission of variant CJD infection by UK factor VIII (FVIII) concentrates has been reported in an elderly haemophilic patient in the UK, who had been treated with FVIII produced from pooled plasma to which a donor who subsequently died from variant CJD had contributed. The recipient showed no signs or symptoms of variant CJD during life, but evidence of variant CJD infection was detected in his spleen following a postmortem examination. Continued surveillance is required to investigate the prevalence of secondary variant CJD infection in other patients with bleeding disorders who have been treated with UK-sourced pooled plasma products.

Prion diseases are a rare group of fatal neurodegenerative disorders of humans and animals that manifest primarily as progressive dementia and ataxia. Unique to these diseases is the prion, a misfolded isoform of the prion protein that can transmit disease from cell to cell or host to host by associating with, and transforming, normal prion protein into the misfolded isoform (the pathogenic scrapie-inducing form). Although the majority of cases occur on a sporadic basis, and rarely result from exposure to prions, such as mad cow disease, 10-15% are attributable to the presence of an autosomal dominant mutation of the prion protein gene (PRNP). Single base pair changes, or the insertion of one or more multiples of a 24 base pair repeat segment, make up the known sequence alterations of PRNP associated with genetic prion disease. The common polymorphic codon 129 of PRNP also plays an important and complex role in risk and phenotype of sporadic and genetic prion disease. This review will focus on the clinical and histopathologic features of the genetic prion diseases. Selected mutations will be highlighted as a way to illustrate general phenotype-genotype correlations.

The Creutzfeldt-Jakob Disease (CJD) Surveillance Committee has identified 1,241 patients with prion diseases during 1999-2009, including 953 with sporadic CJD (sCJD) (76.8%), 207 with genetic prion diseases (16.7%), 78 with environmentally acquired prion diseases (6.3%), and 3 with unclassified CJD. Among atypical cases of sCJD, most common was MM2 type including the cortical and thalamic forms. The genetic cases included 84 with a PrP V180I mutation (40.6%), 37 with a P102L mutation (17.9%), 34 with a E200K mutation (16.4%), 32 with a M232R mutation (15.5%), 4 with a P105L mutation (1.9%), and so on. The environmentally acquired cases included 77 with dura mater graft-associated CJD (dCJD) and one with variant CJD (vCJD). Combined with the results by the previous surveillance systems, a total number of dCJD in Japan was 135. The vCJD patient had a history of short stay in the UK and presented with periodic electroencephalogram in the late stage. Although there was no evidence of association of surgical procedures or blood transfusion with sCJD, 4.5% of the sCJD patients underwent operations after the onset of sCJD, including neurosurgical for 0.8% and ophthalmic for 1.9%, requiring more attention on prion diseases to reduce the iatrogenic risk.

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 (PrP(Sc)) that replicates in the body in the absence of nucleic acids by inducing the misfolding of the cellular prion protein (PrP(C)). 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 PrP(Sc) 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 PrP(Sc)in vitro. For this purpose we analyzed in detail the possibility of spontaneous generation of PrP(Sc) by the protein misfolding cyclic amplification (PMCA) procedure. Under standard PMCA conditions, and taking precautions to avoid cross-contamination, de novo generation of PrP(Sc) was never observed, supporting the use of the technology for diagnostic applications. However, we report that PMCA can be modified to generate PrP(Sc) in the absence of pre-existing PrP(Sc) in different animal species at a low and variable rate. De novo generated PrP(Sc) 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.

New forms of transmissible spongiform encephalopathy (TSE) continue to be identified, and consequently sensitive differential diagnosis is increasingly important both for the management of disease in humans and livestock and in providing confidence in the safety of the food chain. TSE diseases are associated with accumulation of protease-resistant prion protein (PrP(Sc)) and detection of this marker protein is central to diagnosis. Proteolysis by proteinase K (PK) generates protease-resistant products (PrP(res)) with partially variable N-termini. The conformation(s) of PrP(Sc) and thus the points of PK cleavage are thought to be dependent on the strain of prion disease. Western blot (WB) analysis of PrP(res) gives characteristic migration patterns that can be used to diagnose TSEs, but the relatively low resolution of this technique limits its ability to differentiate certain disease strains. Mass spectrometry (MS) has the capability to resolve these various PK cleavage sites to the level of individual amino acid residues. In the present study multiple selected reaction monitoring (mSRM) was used to detect and quantify PrP(res) N-terminal tryptic peptides by MS and thus to define the N-terminal amino acid profiles (N-TAAPs) of PrP(res) characteristic for various TSEs in sheep. The fragmentation behaviour of the N-terminal tryptic peptides was studied to allow selection of the transitions specific for each peptide. Different PrP(res) preparation methods were evaluated and the most effective approach applied to differentiate the N-TAAPs corresponding to various sheep TSE isolates. Marked differences were identified between the N-TAAPs of bovine spongiform encephalopathy (BSE) and classical scrapie, and between classical scrapie and the experimental strains SSBP/1 and CH1641, thereby validating this approach as a means of TSE-strain specific diagnosis., (Copyright (c) 2009 John Wiley & Sons, Ltd.)

There have been identified 1051 cases of prion dsease in Japan since 1999 by the surveillance committee, of which idiopathic prion disease held 77.8%, hereditary 15.9% and infectious 6.6%. Idiopathic prion disease is sporadic Creutzfeldt-Jakob disease (sCJD) and most sCJD cases were classified into MM1 presenting with classical clinical features. MM2, MV2, VV1 and VV2 sCJD cases were rare and showed atypical features including prolonged course, lack of myoclonus and absence of PSD. In such occasions, high signal intensities on DW-MRI as well as increased 14-3-3 and tau proteins in CSF were very helpful. MM2 tharamic sCJD may lack all these laboratory findings but reduction of tharamic CBF in SPECT or PET would support the diagnosis. Hereditary prion disease are classified into 3 major phenotypes such as familial CJD, Gerstmann-Straeussler-Scheinker disease (GSS) mainly showing spinocerebellar ataxia, and fatal familial insomunia. While there have been known many mutations of prion protein gene, only V180I (fCJD), E200K (fCJD), M232R (fCJD) and P102L (GSS) mutations were common. Because most cases did not have family history, genetic test is mandatory in all the cases of prion disease including seemingly "sporadic" CJD. All the cases but 1 case of variant CJD were dura-grafted CJD in infectious prion disease.

The aim of this article was to provide the dental community with a brief overview of the characteristics, risk of transmission, and the infection-control implications of prions in dentistry. MEDLINE, EMBASE, CINAHL, The Cochrane Library, and relevant databases were searched, and a targeted internet search was conducted up to July 2007. Transmissible spongiform encephalopathies (TSEs) are a group of fatal neurodegenerative diseases that are rapidly progressive and always fatal, with no approved cure, and their definite diagnosis can only be obtained at post mortem autopsy. The causative agent, prion protein, resists conventional sterilization methods especially when infected tissue becomes dried onto glass or metal surfaces. To date, there are no reported definite or suspected cases of disease transmission arising from dental procedures, and there seems to be no correlation between dental treatment and TSEs. Because there is a theoretical but real risk of transmission of prion disease from dental instruments (although it is extremely low, especially in North America), as a general rule, appropriate family and medical history (including the risk for prion diseases) should be obtained from all patients, before all dental procedures. TSE research regarding diagnosis, transmission, treatment, and inactivation of prions and other transmissible amyloidoses are ongoing, and, thus, dental professionals should maintain optimal and up-to-date standards of knowledge, infection control, and decontamination.

Prions are normal proteins present in all mammals, especially in the central nervous system (CNS) and lymphoreticular tissue. Their transformation into a highly infectious molecule gives rise to a group of diseases known as transmissible spongiform encephalopathies (TSEs), which cause vacuolar degeneration of gray matter and produce a fatal neurodegenerative disorder. Prion diseases have attracted considerable attention in recent years, and this review of the literature was designed to determine their implications for dentistry, studying the possibility of cross-transmission in the dental office and describing their oral manifestations. The main oral manifestations are dysphagia, dysarthria, paresthesias, dysesthesias, and dysgeusia. The most frequently involved oral tissues are the trigeminal ganglion, posterior third of the tongue, tonsils, and, much less commonly, alveolar nerves, gingiva, and salivary glands. Although no contagion has been reported in the dental setting to date, prions resist the usual dental sterilization systems and transmission of this type of disease remains a potential risk. It is therefore important for dentists to be aware of these diseases, to identify high-risk patients by obtaining an adequate clinical history, and to know the appropriate procedures to be followed.

Tubulovesicular structures (particles - TVS) are the only ultrastructural marker for all prion diseases as seen by thin-section electron microscopy as opposed to "negative-staining" techniques. TVS are spheres or short rods of approximately 27 nm in diameter. That size of TVS is also the size of filter cut-off of infectivity as judged from the ultrafiltration studies and the size of the smallest infectious unit as recently estimated. TVS have been found in all naturally occurring and experimentally induced prion diseases, including variant Creutzfeldt-Jakob disease and human familial TSEs - fatal familial insomnia and Gerstmann-Sträussler-Scheinker disease. In longitudinal studies, the number of neuronal processes containing TVS correlates roughly with the incubation period and with infectivity. Hence, they are readily found in hamsters infected with the 263K strain of scrapie but it is very difficult to find them in human TSEs where titer is lower. The composition of TVS is unknown but they are not composed of PrP. Their consistent presence in all TSEs suggests the unexplained role at least of TSE pathogenesis.

The Creutzfeldt-Jakob Disease (CJD) Surveillance Committee, Japan, started in April 1999, and has identified 918 patients with prion diseases until March 2007, including 716 with sporadic CJD (78.0%), 128 with genetic prion diseases (14.0%), and 72 with environmentally acquired prion diseases (7.8%). Among atypical cases of sporadic CJD, most common was MM2 type including thalamic and cortical forms. The 128 genetic cases were classified to 42 with CJD with a PrP V180I mutation (32.9%), 26 with CJD with a E200K mutation (20.4%), 25 with GSS with a P102L mutation (19.6%), 17 with CJD with a M232R mutation (13.3%), 4 with a insertion mutation in the octapeptide repeat region (3.1%), 3 with GSS with a P105L mutation (2.5%), 2 with fatal familial insomnia with a D178N mutation (1.8%), and so on. The 72 patients with environmentally acquired prion diseases included 71 with dural graft-associated CJD (dCJD) and one with variant CJD (vCJD). Taken together with the results by the previous surveillance systems, a total number of dCJD in Japan was 129. The vCJD patient had a history of short stay in the UK and presented with periodic electroencephalogram in the late stage, requiring revision of the vCJD case definition (WHO 2001).

Neuropathological diagnosis of prion disease consists of sequence analysis of PRNP (prion protein gene), located on chromosome 20 and characterization and visualization of deposited proteinase K-resistant prion protein (PrP(Sc)). SNP at 129 locus (M/V) and Type 1 and Type 2 difference in Western blot analysis of PrP(Sc) from the postmortem brain influence the clinical and pathological presentations. Prion disease is classified into sporadic, hereditary and infectious subtypes, but PrP(Sc) from almost all the subtypes can transmit the disease to transgenic mice expressing human PRNP. Variant CJD, apparently derived from bovine spongiformic encephalopathy, requires shift in disease control strategy, in that PrP(Sc) is present in peripheral lymphatic organs.

The history of prion diseases is derived from descriptions of scrapie of sheep and goats in the eighteenth century. In 1920, Creutzfeldt-Jakob disease was reported as the first case of human prion diseases, which was recognized as subacute spongiform encephalopathy, one of neurodegenerative diseases. Afterwards, many transmission experiments were performed, which lead to the establishment of the fundamental concept, transmissible spongiform encephalopathy(TSE). The infectious agent was supposed to be a novel virus, so TSE was classified into slow virus infection. In 1982, Prusiner investigated the infectious fraction of scrapie-infected brain homogenate, defined the infectious agent as proteinaceous infectious particles that resist inactivation by procedures that modify nucleic acid and newly designated as prion after virion in viral infection.

Transmissible spongiform encephalopathies (TSEs) are neurodegenerative diseases that are caused by prions and affect humans and many animal species. It is now widely accepted that the infectious agent that causes TSEs is PrP(Sc), an aggregated moiety of the host-derived membrane glycolipoprotein PrP(C). Although PrP(C) is encoded by the host genome, prions themselves encipher many phenotypic TSE variants, known as prion strains. Prion strains are TSE isolates that, after inoculation into distinct hosts, cause disease with consistent characteristics, such as incubation period, distinct patterns of PrP(Sc) distribution and spongiosis and relative severity of the spongiform changes in the brain. The existence of such strains poses a fascinating challenge to prion research.

In the 1700's a strange new disease affecting sheep was recognized in Europe. The disease later became known as "Scrapie" and was the first of a family of similar diseases affecting a number of species that are now known as the Transmissible Spongiform Encephalopathies (TSEs). The appearance of a new disease in humans linked to the consumption of meat products from infected cattle has stimulated widespread public concern and scientific interest in the prion protein and related diseases. Nearly 300 years after the first report, these diseases still merit the descriptor "strange". This family of diseases is characterized by a unique profile of histological changes, can be transmitted as inherited or acquired diseases, as well as apparent sporadic spontaneous generation of the disease. These diseases are believed by many, to be caused by a unique protein only infectious agent. The "prion protein" (PrPC), a term first coined by Stanley Prusiner in 1982 is crucial to the development of these diseases, apparently by acting as a substrate for an abnormal disease associated form. However, aside from being critical to the pathogenesis of the disease, the function of PrPC, which is expressed in all mammals, has defied definitive description. Several roles have been proposed on the basis of in vitro studies, however, thus far, in vivo confirmation has not been forthcoming. The biological features of PrPC also seem to be unusual. Numerous mouse models have been generated in an attempt to understand the pathogenesis of these diseases. This review summarizes the current state of histological features, the etiologic agent, the normal metabolism and the function of the prion protein, as well as the limitations of the mouse models.

TSEs (transmissible spongiform encephalopathies) are neurodegenerative diseases of various mammalian species, the best known of which include BSE (bovine spongiform encephalopathies) in cattle, CJD (Creutzfeldt-Jakob disease) in humans, scrapie in sheep and CWD (chronic wasting disease) in deer. This review examines the emergence of various TSE strains and their transmission, and discusses disease surveillance and control.

Background: The purpose of this study is to analyse the trends in scientific research on transmissible spongiform encephalopathies by applying bibliometric tools to the scientific literature published between 1973 and 2002., Methods: The data for the study were obtained from Medline database, in order to determine the volume of scientific output in the above period, the countries involved, the type of document and the trends in the subject matters addressed. The period 1973-2002 was divided in three sub-periods., Results: We observed a significant growth in scientific production. The percentage of increase is 871.7 from 1973 to 2002. This is more evident since 1991 and particularly in the 1996-2001 period. The countries found to have the highest output were the United States, the United Kingdom, Japan, France and Germany. The evolution in the subject matters was almost constant in the three sub-periods in which the study was divided. In the first and second sub-periods, the subject matters of greatest interest were more general, i.e Nervous system or Nervous system diseases, Creutzfeldt-Jakob disease, Scrapie, and Chemicals and Drugs, but in the last sub-period, some changes were observed because the Prion-related matters had the greatest presence. Collaboration among authors is small from 1973 to 1992, but increases notably in the third sub-period, and also the number of authors and clusters formed. Some of the authors, like Gajdusek or Prusiner, appear in the whole period., Conclusion: The study reveals a very high increase in scientific production. It is related also with the beginnings of research on bovine spongiform encephalopathy and variant Creutzfeldt-Jakob disease, with the establishment of progressive collaboration relationships and a reflection of public health concerns about this problem.

After the finding that anti-prion antibodies stain sensory and sympathetic ganglia in variant Creutzfeldt-Jakob disease (vCJD), it was suggested that this localization supported the oral route of entry. However, prion accumulation subsequently also appeared in the peripheral nervous system (PNS) in sporadic cases. This study aims at evaluating the extent of prion protein accumulation in the PNS in all clinicopathologic subgroups of the disorder, with the exception of the familial and sporadic forms of fatal insomnia. Patients included 2 vCJD cases, 2 Gerstmann-Sträussler-Scheinker (GSS), 2 iatrogenic (iCJD), and 16 sporadic CJD (sCJD) cases. Gasserian (17) and spinal (9), celiac (2) and thoracic sympathetic (one) ganglia, spinal cord and medulla of one vCJD, 2 GSS, one iCJD, and 5 sCJD cases were examined. Immunostained sensory ganglia were seen in both vCJD, both iCJD, one GSS, and 10 sCJD cases; the celiac ganglion was positive in one of two sCJD cases, and the spinal dorsal horn and the medullary sensory nuclei were positive in one patient with vCJD, one with iCJD, and 3 with sCJD. Western blot demonstrated presence of PrP in the gasserian ganglion of one patient with sCJD. Accumulation of prion in ganglia (including autonomic) of the PNS, shared by all subgroups of spongiform encephalopathy, and in the dorsal horns and medullary sensory nuclei, shows that the sensory route is involved in the trafficking of this protein.

Prions are infectious pathogens principally composed of abnormal forms of a protein encoded in the host genome. They cause lethal neurodegenerative conditions including CJD, GSS, and kuru in humans and scrapie and bovine spongiform encephalopathy in domestic animals. Remarkably, distinct strains of prions occur despite absence of an agent-specific genome: misfolded proteins themselves may encode strain diversity--with wide implications in biology. The arrival of variant CJD, and the experimental confirmation that it is caused by infection with BSE-like prions, has focussed research on early diagnosis and treatment. Recent advances lead to considerable optimism that effective human therapies may now be developed. While several drugs have been tried in small numbers of patients, there is no clear evidence of efficacy of any agent and controlled clinical trials are urgently needed. Importantly, there is increasing recognition that fundamental processes involved in prion propagation--seeded aggregation of misfolded host proteins--are of far wider significance, not least in understanding the commoner neurodegenerative diseases that pose such a major and increasing challenge for healthcare in an ageing population.

Fatal familial insomnia (FFI) and Creutzfeldt-Jakob disease (CJD) are associated to the same mutation at codon 178 but differentiate into clinicopathologically distinct diseases determined by this mutation and a naturally occurring methionine-valine polymorphism at codon 129 of the prion protein gene. It has been suggested that the clinical and pathological difference between FFI and CJD is caused by different conformations of the prion protein. Using molecular dynamics (MD), we investigated the effect of the mutation at codon 178 and the polymorphism at codon 129 on prion protein dynamics and conformation at normal and elevated temperatures. Four model structures were examined with a focus on their dynamics and conformational changes. The results showed differences in stability and dynamics between polymorphic variants. Methionine variants demonstrated a higher stability than valine variants. Elongation of existing beta-sheets and formation of new beta-sheets was found to occur more readily in valine polymorphic variants. We also discovered the inhibitory effect of proline residue on existing beta-sheet elongation.

Compared with that of other human pathogens, the proposed replicative cycle of prions is disarmingly simple. It encompasses misfolding of a single protein, the cellular prion protein (PrPC), into a disease-associated form called PrPSc. This is followed by PrPSc aggregation and possibly fragmentation of aggregates, which may augment the number of replicative units. Although there is no formal proof of the correctness of this model, a wealth of evidence indicates that pathogen-encoded informational nucleic acids are dispensable for prion replication. Despite the simplicity of the replicative process, the human phenotypic range of prion diseases is extremely variable and includes the sporadic, inherited, and acquired forms of Creutzfeldt-Jakob disease. In addition, prion diseases occur in a wide range of animals and can be propagated within and between animal species. The present review article discusses current concepts and controversies surrounding the basic biological features of prions.

Creutzfeldt-Jakob Disease (CJD) is a rare pathology (about 1 case per million) but it has a great importance for Public Health; the Italian National CJD register has been established in the Istituto Superiore di Sanita (ISS) since 1993, and epidemiological studies on CJD have been carried out as well. This paper reports a mortality study carried out comparing and integrating data from the two available sources: the National CJD Register and the Italian Data Base on Mortality, processed by the ISS Statistics Unit, on the data collected by the Italian Census Bureau (ISTAT). The study allowed to estimate: the underreporting of CJD mortality to both sources, the misclassification of ISTAT data and the integrated mortality rates from CJD in Italy: 1.58 per million persons aged 25 or more, average rate during the period 1993-1999.

To evaluate the ability of the Italian Creutzfeldt-Jakob (CJD) register to detect human transmissible spongiform encephalopathy (TSE) cases we compared mortality data from the CJD register with those obtained from death certificates collected by the Italian National Census Bureau (ISTAT) between 1993 and 1999. We used the method of record linkage to compare and integrate data from these two sources. The integrated estimate of TSE deaths was 457: 183 deaths recorded by the CJD register and ISTAT, 210 cases only by the CJD register, and 64 cases only by ISTAT. The average integrated estimated mortality rate was 1.58 deaths per million people per year over the study period and peaked in 1999 at 2.13. This figure is similar to that obtained from data from the CJD register alone in the years 2000-2002. The increase in mortality rates is likely due to an improvement in case ascertainment. The misclassification of cases by ISTAT was above 50% from 1996 onward, suggesting that using only death certificates is not a reliable way to monitor TSE cases in Italy.

Variant Creutzfeldt-Jakob disease (CJD) is a novel acquired human prion disease apparently resulting from exposure to the bovine spongiform encephalopathy (BSE) agent. Variant CJD differs from other human prion diseases in that the disease-associated form of the prion protein and infectivity are readily detectable in lymphoid tissues throughout the body. Lymphoid tissues and lymphocytes are implicated in the peripheral pathogenesis of prion diseases (where infectivity may be detected during the preclinical phase of the illness), giving rise to concerns that blood and blood products may also contain infectious particles, representing a possible source of iatrogenic spread of variant CJD. This concern has been reinforced following the experimental transmission of BSE in a sheep model by transfusion of blood and buffy coat from animals in the preclinical phase of the illness, and the recent identification of a UK case of variant CJD in a patient who had received packed red blood cells that had been donated by an individual who subsequently died from variant CJD. Studies in animal models suggest that most prion infectivity in blood may be cell-associated, with lower levels in the plasma, and there is evidence to suggest that any infectivity present may be reduced during the process of plasma fractionation. However, the possibility that plasma or blood products could transmit the disease cannot be excluded. Further studies are required to develop more sensitive means to detect disease-associated prion protein in blood; such techniques could be employed for screening purposes to reduce exposure to contaminated products and to assist with risk management in potentially exposed individuals.

We describe the clinical and genetic characteristics of the 85 definite or probable human prion diseases cases died between January 1993 and December 2002 in Catalonia (an autonomous community of Spain, 6 million population). Seventy-three (86%) cases were sporadic Creutzfeld-Jakob diseases (sCJD) (49 definite, 24 probable), with a median age at onset of 66 years. The clinical presentation was dementia in 29 cases, ataxia in 14 and visual symptoms in five. The median survival was 3 months. The 14-3-3 assay was positive in 93% cases, 62% presented periodic sharp wave complexes (PSWC) in EEG but only 18% the typical signs on MRI. Forty-eight sCJD were studied for codon 129 PRNP polymorphism: 69% were methionine/methionine (M/M), 14.5% valine/valine (V/V) and 16.5% M/V. Six out of seven V/V cases did not present PSWC and in two survival was longer than 20 months. Eleven cases (13%) were genetic: five familial fatal insomnia and six familial CJD (fCJD). Up to four (67%) fCJD lacked family history of disease, two presented seizures early at onset and one neurosensorial deafness. The only iatrogenic case was related to a dura mater graft. No case of variant CJD was registered. The study confirms in our population the consistent pattern reported worldwide on human prion diseases. Atypical features were seen more frequently in sporadic 129 V/V CJD and fCJD cases.