Association of an 11–12 kDa protease-resistant prion protein fragment with subtypes of dura graft-associated Creutzfeldt–Jakob disease and other prion diseases

Altered properties of amyloidogenic prion protein in genetic Creutzfeldt-Jakob disease with PRNP V180I mutation in response to pentosan polysulfate

Genetic Creutzfeldt-Jakob disease (gCJD) with V180I prion protein gene (PRNP) mutation shows weaker prion protein (PrP) deposition histologically compared with sporadic CJD, and it is more difficult to detect protease-resistant prion protein in immunoblotting. However, we previously reported the autopsy case of a patient with V180I gCJD who was treated with pentosan polysulfate sodium (PPS); this case had increased protease-resistant PrP deposition. It has been suggested that PPS might reduce protease-resistant PrP; however, the detailed pharmacological and histopathological effects of PPS in humans remain unknown. We examined autopsied human brain tissue from four cases with V180I gCJD that were added to our archives between 2011 and 2021: two cases treated with PPS and two cases without PPS. We conducted a neuropathological assessment, including immunohistochemistry for PrP. We also performed immunoblotting for PrP on homogenate samples from each brain to detect protease-resistant PrP using both a conventional procedure and size-exclusion gel chromatography for the purification of oligomeric PrP. Both PPS-treated cases showed long survival time over 5 years from onset and increased PrP deposition with a characteristic pattern of coarse granular depositions and congophilic PrP microspheres, whereas the cases without PPS showed around 1-year survival from onset and relatively mild neuronal loss and synaptic PrP deposition. Although cortical gliosis seemed similar among all cases, aquaporin 4-expression as a hallmark of astrocytic function was increased predominantly in PPS cases. Immunoblotting of non-PPS cases revealed protease-resistant PrP in the oligomeric fraction only, whereas the PPS-treated cases showed clear signals using conventional procedures and in the oligomeric fraction. These unique biochemical and histopathological changes may reflect the progression of V180I gCJD and its modification by PPS, suggesting the possible existence of toxic PrP-oligomer in the pathophysiology of V180I gCJD and beneficial effects of PPS toward the aggregation and detoxication of toxic PrP-oligomer.

Systematic Review of Clinical and Pathophysiological Features of Genetic Creutzfeldt-Jakob Disease Caused by a Val-to-Ile Mutation at Codon 180 in the Prion Protein Gene

Genetic Creutzfeldt-Jakob disease (gCJD) is a subtype of genetic prion diseases (gPrDs) caused by the accumulation of mutated pathological prion proteins (PrPSc). gCJD has a phenotypic similarity with sporadic CJD (sCJD). In Japan, gCJD with a Val to Ile substitution at codon 180 (V180I-gCJD) is the most frequent gPrD, while the mutation is extremely rare in countries other than Japan and Korea. In this article, we aim to review previously elucidated clinical and biochemical features of V180I-gCJD, expecting to advance the understanding of this unique subtype in gCJD. Compared to classical sCJD, specific clinical features of V180I-gCJD include older age at onset, a relatively slow progression of dementia, and a lower positivity for developing myoclonus, cerebellar, pyramidal signs, and visual disturbance. Diffuse edematous ribboning hyperintensity of the cerebral cortex, without occipital lobes in diffusion-weighted magnetic resonance imaging, is also specific. Laboratory data reveal the low positivity of PrPSc in the cerebrospinal fluid and periodic sharp wave complexes on an electroencephalogram. Most patients with V180I-gCJD have been reported to have no family history, probably due to the older age at onset, and clinical and biochemical features indicate the specific phenotype associated with the prion protein gene mutation.

The cellular prion protein and its derived fragments in human prion diseases and their role as potential biomarkers

Introduction: Human prion diseases are a heterogeneous group of incurable and debilitating conditions characterized by a progressive degeneration of the central nervous system. The conformational changes of the cellular prion protein and its formation into an abnormal isoform, spongiform degeneration, neuronal loss, and neuroinflammation are central to prion disease pathogenesis. It has been postulated that truncated variants of aggregation-prone proteins are implicated in neurodegenerative mechanisms. An increasing body of evidence indicates that proteolytic fragments and truncated variants of the prion protein are formed and accumulated in the brain of prion disease patients. These prion protein variants provide a high degree of relevance to disease pathology and diagnosis. Areas covered: In the present review, we summarize the current knowledge on the occurrence of truncated prion protein species and their potential roles in pathophysiological states during prion diseases progression. In addition, we discuss their usability as a diagnostic biomarker in prion diseases. Expert opinion: Either as a primary factor in the formation of prion diseases or as a consequence from neuropathological affection, abnormal prion protein variants and fragments may provide independent information about mechanisms of prion conversion, pathological states, or disease progression.

Understanding Prion Strains: Evidence from Studies of the Disease Forms Affecting Humans

Prion diseases are a unique group of rare neurodegenerative disorders characterized by tissue deposition of heterogeneous aggregates of abnormally folded protease-resistant prion protein (PrPSc), a broad spectrum of disease phenotypes and a variable efficiency of disease propagation in vivo. The dominant clinicopathological phenotypes of human prion disease include Creutzfeldt⁻Jakob disease, fatal insomnia, variably protease-sensitive prionopathy, and Gerstmann⁻Sträussler⁻Scheinker disease. Prion disease propagation into susceptible hosts led to the isolation and characterization of prion strains, initially operatively defined as "isolates" causing diseases with distinctive characteristics, such as the incubation period, the pattern of PrPSc distribution, and the regional severity of neuropathological changes after injection into syngeneic hosts. More recently, the structural basis of prion strains has been linked to amyloid polymorphs (i.e., variant amyloid protein conformations) and the concept extended to all protein amyloids showing polymorphic structures and some evidence of in vivo or in vitro propagation by seeding. Despite the significant advances, however, the link between amyloid structure and disease is not understood in many instances. Here we reviewed the most significant contributions of human prion disease studies to current knowledge of the molecular basis of phenotypic variability and the prion strain phenomenon and underlined the unsolved issues from the human disease perspective.

Mechanisms of Strain Diversity of Disease-Associated in-Register Parallel β-Sheet Amyloids and Implications About Prion Strains

The mechanism of prion strain diversity remains unsolved. Investigation of inheritance and diversification of protein-based pathogenic information demands the identification of the detailed structures of abnormal isoforms of the prion protein (PrPSc); however, achieving purification is difficult without affecting infectivity. Similar prion-like properties are recognized also in other disease-associated in-register parallel β-sheet amyloids including Tau and α-synuclein (αSyn) amyloids. Investigations into structures of those amyloids via solid-state nuclear magnetic resonance spectroscopy and cryo-electron microscopy recently made remarkable advances due to their relatively small sizes and lack of post-translational modifications. Herein, we review advances regarding pathogenic amyloids, particularly Tau and αSyn, and discuss implications about strain diversity mechanisms of prion/PrPSc from the perspective that PrPSc is an in-register parallel β-sheet amyloid. Additionally, we present our recent data of molecular dynamics simulations of αSyn amyloid, which suggest significance of compatibility between β-sheet propensities of the substrate and local structures of the template for stability of amyloid structures. Detailed structures of αSyn and Tau amyloids are excellent models of pathogenic amyloids, including PrPSc, to elucidate strain diversity and pathogenic mechanisms.

Biochemical features of genetic Creutzfeldt-Jakob disease with valine-to-isoleucine substitution at codon 180 on the prion protein gene

Valine-to-isoleucine substitution at codon 180 of the prion protein gene is only observed in patients with Creutzfeldt-Jakob disease and accounts for approximately half of all cases of genetic prion disease in Japan. In the present study, we investigated the biochemical characteristics of valine-to-isoleucine substitution at codon 180 in the prion protein gene, using samples obtained from the autopsied brains of seven patients with genetic Creutzfeldt-Jakob disease exhibiting this mutation (diagnoses confirmed via neuropathological examination). Among these patients, we observed an absence of diglycosylated and monoglycosylated forms of PrP^res at codon 181. Our findings further indicated that the abnormal prion proteins were composed of at least three components, although smaller carboxyl-terminal fragments were predominant. Western blot analyses revealed large amounts of PrP^res in the cerebral neocortices, where neuropathological examination revealed marked spongiosis. Relatively smaller amounts of PrP^res were detected in the hippocampus, where milder spongiosis was observed, than in the cerebral neocortex. These findings indicate that abnormal prion proteins in the neocortex are associated with severe toxicity, resulting in severe spongiosis. Our findings further indicate that the valine-to-isoleucine substitution is not a polymorphism, but rather an authentic pathogenic mutation associated with specific biochemical characteristics that differ from those observed in sporadic Creutzfeldt-Jakob disease.

Iatrogenic Creutzfeldt-Jakob disease

Iatrogenic transmission of Creutzfeldt-Jakob disease (CJD) has occurred through particular medical procedures. Among them, dura mater grafts and pituitary-derived growth hormone obtained from human cadavers undiagnosed as CJD are the most frequent sources of infection. Recent advances in our knowledge about dura mater graft- and human pituitary-derived growth hormone-associated CJD patients have revealed that the combination of the infected CJD strain and the PRNP genotype of the patient determines their clinical, neuropathologic, and biochemical features. In this chapter, we summarize the clinical, neuropathologic, biochemical, and diagnostic features of dura mater graft- and human pituitary-derived growth hormone-associated CJD patients for the appropriate diagnosis of iatrogenic CJD.

Dura mater graft-associated Creutzfeldt-Jakob disease with 30-year incubation period

Over 60% of all patients with dura mater graft-associated Creutzfeldt-Jakob disease (dCJD) have been diagnosed in Japan. The incubation period has ranged from 1 to 30 years and the age at onset from 15 to 80 years. Here, we report a 77-year-old male Japanese autopsied dCJD case with the longest incubation period so far in Japan. He received a cadaveric dural graft at the right cranial convexity following a craniotomy for meningioma at the age of 46. At 30 years post-dural graft placement, disorientation was observed as an initial symptom of dCJD. He rapidly began to present with inconsistent speech, cognitive impairment and tremor of the left upper extremity. Occasional myoclonic jerks were predominantly observed on the left side. Brain MRI presented hyperintense signals on diffusion-weighted and T2-weighted images, at the right cerebral cortex. The most hyperintense lesion was located at the right parietal lobe, where the dura mater graft had been transplanted. Single-photon emission CT scan showed markedly decreased cerebral blood flow at the right parietal lobe. EEG revealed diffuse and slow activities with periodic sharp-wave complex discharges seen in the right parietal, temporal and occipital lobes. He died of pneumonia 9 months after onset. Brain pathology revealed non-plaque-type dCJD. Laterality of neuropathological changes, including spongiform change, neuronal loss, gliosis or PrP deposits, was not evident. Western blot analysis showed type 1 PrP^CJD . Alzheimer-type pathology and PSP-like pathology were also observed.

Coexistence of two forms of disease-associated prion protein in extracerebral tissues of cattle infected with H-type bovine spongiform encephalopathy

H-type bovine spongiform encephalopathy (H-BSE) is an atypical form of BSE in aged cattle. H-BSE is characterized by the presence of two proteinase K-resistant forms of disease-associated prion protein (PrP^Sc), identified as PrP^Sc #1 and PrP^Sc #2, in the brain. To investigate the coexistence of different PrP^Sc forms in the extracerebral tissues of cattle experimentally infected with H-BSE, immunohistochemical and molecular analyses were performed by using N-terminal-, core-region- and C-terminal-specific anti-prion protein antibodies. Our results demonstrated that two distinct forms of PrP^Sc coexisted in the various extracerebral tissues.

New Molecular Insight into Mechanism of Evolution of Mammalian Synthetic Prions

Previous studies established that transmissible prion diseases could be induced by in vitro-produced recombinant prion protein (PrP) fibrils with structures that are fundamentally different from that of authentic PrP scrapie isoform (PrP(Sc)). To explain evolution of synthetic prions, a new mechanism referred to as deformed templating was introduced. Here, we asked whether an increase in expression level of the cellular form of PrP (PrP(C)) speeds up the evolution of synthetic strains in vivo. We found that in transgenic mice that overexpress hamster PrP(C), PrP(C) overexpression accelerated recombinant PrP fibril-induced conversion of PrP(C) to the abnormal proteinase K-resistant state, referred to as atypical PrPres, which was the first product of PrP(C) misfolding in vivo. However, overexpression of PrP(C) did not facilitate the second step of synthetic strain evolution-transition from atypical PrPres to PrP(Sc), which is attributed to the stochastic nature of rare deformed templating events. In addition, the potential of atypical PrPres to interfere with replication of a short-incubation time prion strain was investigated. Atypical PrPres was found to interfere strongly with replication of 263K in vitro; however, it did not delay prion disease in animals. The rate of deformed templating does not depend on the concentration of substrate and is hence more likely to be controlled by the intrinsic rate of conformational errors in templating alternative self-propagating states.

Two alternative pathways for generating transmissible prion disease de novo

Introduction

Previous studies established that prion disease with unique strain-specific phenotypes could be induced by in vitro-formed recombinant PrP (rPrP) fibrils with structures different from that of authentic prions, or PrP^Sc. To explain the etiology of prion diseases, new mechanism proposed that in animals the transition from rPrP fibrils to PrP^Sc consists of two main steps: the first involves fibril-induced formation of atypical PrPres, a self-replicating but clinically silent state, and the second consists of atypical PrPres-dependent formation of PrP^Sc via rare deformed templating events.

Results

In the current study, atypical PrPres with characteristics similar to those of brain-derived atypical PrPres was generated in vitro. Upon inoculation into animals, in vitro-generated atypical PrPres gave rise to PrP^Sc and prion disease with a phenotype similar to those induced by rPrP fibrils. Significant differences in the sialylation pattern between atypical PrPres and PrP^Sc suggested that only a small sub-fraction of the PrP^C that is acceptable as a substrate for PrP^Sc could be also recruited by atypical PrPres. This can explain why atypical PrPres replicates slower than PrP^Sc and why PrP^Sc outcompetes atypical PrPres.

Conclusions

This study illustrates that transmissible prion diseases with very similar disease phenotypes could be produced via two alternative procedures: direct inoculation of recombinant PrP amyloid fibrils or in vitro-produced atypical PrPres. Moreover, this work showed that preparations of atypical PrPres free of PrP^Sc can give rise to transmissible diseases in wild type animals and that atypical PrPres generated in vitro is an adequate model for brain-derived atypical PrPres.

Electronic supplementary material

The online version of this article (doi:10.1186/s40478-015-0248-5) contains supplementary material, which is available to authorized users.

Distinct pathological phenotypes of Creutzfeldt-Jakob disease in recipients of prion-contaminated growth hormone

Introduction

The present study compares the clinical, pathological and molecular features of a United States (US) case of growth hormone (GH)-associated Creutzfeldt-Jakob disease (GH-CJD) (index case) to those of two earlier referred US cases of GH-CJD and one case of dura mater (d)-associated CJD (dCJD). All iatrogenic CJD (iCJD) subjects were methionine (M) homozygous at codon 129 (129MM) of the prion protein (PrP) gene and had scrapie prion protein (PrP^Sc) type 1 (iCJDMM1).

Results

The index subject presented with ataxia, weight loss and changes in the sleep pattern about 38 years after the midpoint of GH treatment. Autopsy examination revealed a neuropathological phenotype reminiscent of both sCJDMV2-K (a sporadic CJD subtype in subjects methionine/valine heterozygous at codon 129 with PrP^Sc type 2 and the presence of kuru plaques) and variant CJD (vCJD). The two earlier cases of GH-CJDMM1 and the one of dCJDMM1 were associated with neuropathological phenotypes that differed from that of the index case mainly because they lacked PrP plaques. The phenotype of the earlier GH-CJDMM1 cases shared several, but not all, characteristics with sCJDMM1, whereas dCJDMM1 was phenotypically indistinguishable from sCJDMM1. Two distinct groups of dCJDMM1 have also been described in Japan based on clinical features, the presence or absence of PrP plaques and distinct PK-resistant PrP^Sc (resPrP^Sc) electrophoretic mobilities. The resPrP^Sc electrophoretic mobility was, however, identical in our GH-CJDMM1 and dCJDMM1 cases, and matched that of sCJDMM1.

Conclusions

Our study shows that receipt of prion-contaminated GH can lead to a prion disease with molecular features (129MM and PrP^Sc type 2) and phenotypic characteristics that differ from those of sporadic prion disease (sCJDMM1), a difference that may reflect adaptation of “heterologous” prion strains to the 129MM background.

The diversity and relationship of prion protein self-replicating states

It has become evident that the prion protein (PrP) can form a diverse range of self-replicating structures in addition to bona fide PrP(Sc) or strain-specific PrP(Sc) variants. Some self-replicating states can be only produced in vitro, whereas others can be formed in vivo and in vitro. While transmissible, not all states that replicate in vivo are truly pathogenic. Some of them can replicate silently without causing symptoms or clinical diseases. In the current article we discuss the data on PK-digestion patterns of different self-replicating PrP states in connection with other structural data available to date and assess possible relationships between different self-replicating states. Even though different self-replicating PrP states appear to have significantly different global folding patterns, it seems that the C-terminal region exhibits a cross-β-sheet structure in all self-replicating states, as this region acquires the proteolytically most stable conformation. We also discuss the possibility of the transformation of self-replicating states and triggering of PrP(Sc) formation within the frame of the deformed templating model. The spread of silent self-replicating states is of a particular concern because they can lead to transmissible prion disease. Moreover, examples on how different replication requirements favor different states are discussed. This knowledge can help in designing conditions for selective amplification of a particular PrP state in vitro.

Comparative Study of Prions in Iatrogenic and Sporadic Creutzfeldt-Jakob Disease

Differentiating iatrogenic Creutzfeldt-Jakob disease (iCJD) from sporadic CJD (sCJD) would be useful for the identification and prevention of human-to-human prion transmission. Currently, the diagnosis of iCJD depends on identification of a recognized source of contamination to which patients have been exposed, in addition to fulfilling basic requirements for the establishment of diagnosis of CJD. Attempts to identify differences in clinical manifestations, neuropathological changes and pathological prion protein (PrPSc) between iCJD and sCJD have been unsuccessful. In the present study, using a variety of more sophisticated methods including sucrose step gradient sedimentation, conformational stability immunoassay, protein misfolding cyclic amplification (PMCA), fragment-mapping, and transmission study, we show no significant differences in gel profiles, oligomeric state, conformational stability and infectivity of PrPSc between iCJD and sCJD. However, using PMCA, we find that convertibility and amplification efficiency of PrPSc is greater in iCJD than in sCJD in a polymorphism-dependent manner. Moreover, two protease-resistant PrP C-terminal fragments (termed PrP-CTF12/13) were detected in all 9 cases of sCJD but not in 6 of 8 cases of iCJD tested in this study. The use of fragment mapping- and PMCA-based assays thus provides a means to distinguish most cases of iCJD from sCJD.

Distinct origins of dura mater graft-associated Creutzfeldt-Jakob disease: past and future problems

Dura mater graft-associated Creutzfeldt-Jakob disease (dCJD) can be divided into two subgroups that exhibit distinct clinical and neuropathological features, with the majority represented by a non-plaque-type of dCJD (np-dCJD) and the minority by a plaque-type of dCJD (p-dCJD). The two distinct phenotypes of dCJD had been considered to be unrelated to the genotype (methionine, M or valine, V) at polymorphic codon 129 of the PRNP gene or type (type 1 or type 2) of abnormal isoform of prion protein (PrPSc) in the brain, while these are major determinants of clinicopathological phenotypes of sporadic CJD (sCJD). The reason for the existence of two distinct subgroups in dCJD had remained elusive. Recent progress in research of the pathogenesis of dCJD has revealed that two distinct subgroups of dCJD are caused by infection with different PrPSc strains from sCJD, i.e., np-dCJD caused by infection with sCJD-MM1/MV1, and p-dCJD caused by infection with sCJD-VV2 or -MV2. These studies have also revealed previously unrecognized problems as follows: (i) the numbers of p-dCJD patients may increase in the future, (ii) the potential risks of secondary infection from dCJD, particularly from p-dCJD, may be considerable, and (iii) the effectiveness of the current PrPSc decontamination procedures against the PrPSc from p-dCJD is uncertain. To prevent secondary infection from p-dCJD, the establishment of effective decontamination procedures is an urgent issue. In this review, we summarize the past and future problems surrounding dCJD.

Deciphering the pathogenesis of sporadic Creutzfeldt-Jakob disease with codon 129 M/V and type 2 abnormal prion protein

Background

Sporadic Creutzfeldt-Jakob disease is classified according to the genotype at polymorphic codon 129 (M or V) of the prion protein (PrP) gene and the type (1 or 2) of abnormal isoform of PrP (PrP^Sc) in the brain. The most complicated entity in the current classification system is MV2, since it shows wide phenotypic variations, i.e., MV2 cortical form (MV2C), MV2 with kuru plaques (MV2K), or a mixed form (MV2K + C). To resolve their complicated pathogenesis, we performed a comprehensive analysis of the three MV2 subgroups based on histopathological, molecular, and transmission properties.

Results

In histopathological and molecular analyses, MV2C showed close similarity to MM2 cortical form (MM2C) and could be easily discriminated from the other MV2 subgroups. By contrast, MV2K and MV2K + C showed the same molecular type and the same transmission type, and the sole difference between MV2K and MV2K + C was the presence of cortical pathology characteristic of MV2C/MM2C. The remarkable molecular feature of MV2K or MV2K + C was a mixture of type 2 PrP^Sc and intermediate type PrP^Sc, which shows intermediate electrophoretic mobility between types 1 and 2 PrP^Sc. Modeling experiments using PrP-humanized mice indicated that MV2K contains a mixture of intermediate type PrP^Sc with the 129M genotype (Mi PrP^Sc) and type 2 PrP^Sc with the 129V genotype (V2 PrP^Sc) that originated from V2 PrP^Sc, whereas MV2C + K may also contain type 2 PrP^Sc with the 129M genotype and cortical pathology (M2C PrP^Sc) that lacks infectivity to the PrP-humanized mice in addition to Mi and V2 PrP^Sc.

Conclusions

Taken together, the present study suggests that the phenotypic heterogeneity of MV2 stems from their different PrP^Sc origin(s).

Recombinant prion protein refolded with lipid and RNA has the biochemical hallmarks of a prion but lacks in vivo infectivity

During prion infection, the normal, protease-sensitive conformation of prion protein (PrP^C) is converted via seeded polymerization to an abnormal, infectious conformation with greatly increased protease-resistance (PrP^Sc). In vitro, protein misfolding cyclic amplification (PMCA) uses PrP^Sc in prion-infected brain homogenates as an initiating seed to convert PrP^C and trigger the self-propagation of PrP^Sc over many cycles of amplification. While PMCA reactions produce high levels of protease-resistant PrP, the infectious titer is often lower than that of brain-derived PrP^Sc. More recently, PMCA techniques using bacterially derived recombinant PrP (rPrP) in the presence of lipid and RNA but in the absence of any starting PrP^Sc seed have been used to generate infectious prions that cause disease in wild-type mice with relatively short incubation times. These data suggest that lipid and/or RNA act as cofactors to facilitate the de novo formation of high levels of prion infectivity. Using rPrP purified by two different techniques, we generated a self-propagating protease-resistant rPrP molecule that, regardless of the amount of RNA and lipid used, had a molecular mass, protease resistance and insolubility similar to that of PrP^Sc. However, we were unable to detect prion infectivity in any of our reactions using either cell-culture or animal bioassays. These results demonstrate that the ability to self-propagate into a protease-resistant insoluble conformer is not unique to infectious PrP molecules. They suggest that the presence of RNA and lipid cofactors may facilitate the spontaneous refolding of PrP into an infectious form while also allowing the de novo formation of self-propagating, but non-infectious, rPrP-res.

Kosmotropic anions promote conversion of recombinant prion protein into a PrPSc-like misfolded form

Prions are self-propagating proteins involved in transmissible spongiform encephalopaties in mammals. An aberrant conformation with amyloid-like features of a cell surface protein, termed prion protein (PrP), is thought to be the essential component of the infectious particle, though accessory co-factor molecules such as lipids and nucleotides may be involved. The cellular co-factors and environmental conditions implicated in PrP misfolding are not completely understood. To address this issue, several studies have been done inducing misfolding of recombinant PrP (recPrP) into classical amyloid structures using partially denaturing conditions. In this work, we report that misfolding of recPrP into PrP(Sc)-like aggregates can be induced by simply incubating the protein in the presence of kosmotropic salts at concentrations that are known to retain or increase the stability of the protein. We used a simple experimental reaction (protein, buffer and salts) submitted to agitation/incubation cycles at physiological temperature and pH. The formation of protease resistant-recPrP was time and salt-concentration dependent and required the presence of kosmotropic anions such as F(-) or SO(4)(-2). The molecular weights of the protease resistant recPrP fragments are reminiscent of those found in degradation assays of bona fide PrP(Sc). The aggregates also exhibited PrP(Sc)-like ultrastructural features including rod-shape morphology under electron microscope, high beta-sheet content and thioflavin-T positive signal. The formation of recPrP aggregates with PrP(Sc) biochemical features under conditions closer to physiological in the absence of organic co-factor molecules provides a simple setup that may prove helpful to understand the molecular mechanism of PrP misfolding.

Creutzfeldt-Jakob disease with the M232R mutation in the prion protein gene in two cases showing different disease courses: a clinicopathological study

We report two autopsy cases of Creutzfeldt-Jakob disease (CJD) with the M232R mutation of the prion protein (PrP) gene that exhibited different clinicopathological features (age at death, 64/54 years; disease duration, 13/26 months). Both cases showed myoclonus, hyperintensity on diffusion-weighted MRI, and increased 14-3-3 protein in the cerebrospinal fluid. The initial sign in each case was memory disturbance and abnormal pharyngeal sensation, respectively. In the first case, the disease progressed rapidly with akinetic mutism developing 6 months after onset, while it occurred 23 months after onset in the second case. Pathologically, both cases had severe neuronal loss with gliosis and spongiform change in the cerebral cortex, basal ganglia, and cerebellum. PrP deposition was the diffuse synaptic type in the first case, but the second case had both diffuse synaptic and perivacuolar types. PrP(sc) immunoblotting revealed a type 1 band pattern in the first case, but both types 1 and 2 in the second case. Based on these findings, together with the results in previous CJD cases with M232R, we noted the possibility that the presence of type 2 PrP(sc) may be associated with both morphological features of PrP deposition and slow disease progression in this genetic prion disease.

Co-occurrence of types 1 and 2 PrP(res) in sporadic Creutzfeldt-Jakob disease MM1

The genotype (M/M, M/V, or V/V) at polymorphic codon 129 of the human prion protein (PrP) gene and the type (1 or 2) of protease-resistant PrP (PrP(res)) in the brain are major determinants of the clinicopathological phenotypes of sporadic Creutzfeldt-Jakob disease (sCJD). According to this molecular typing system, sCJD has been classified into six subgroups (MM1, MM2, MV1, MV2, VV1, and VV2). Besides these pure subgroups, mixed cases presenting mixed neuropathological phenotypes and more than one PrP(res) type have been found in sCJD. To investigate the frequency of the co-occurrence of types 1 and 2 PrP(res) in sCJD patients classified as MM1, we produced type 2 PrP(res)-specific antibody Tohoku 2 (T2) that can specifically detect the N-terminal cleavage site of type 2 PrP(res) after protease treatment and examined brain samples from 23 patients with sCJD-MM1. Western blot analysis using the T2 antibody revealed that the minority type 2 PrP(res) could be detected in all sCJD-MM1 brain samples including those of the cerebellum where sCJD-MM2 prions rarely accumulate. These results show that the co-occurrence of types 1 and 2 PrP(res) within a single sCJD-MM1 patient is a universal phenomenon. The general co-occurrence of multiple PrP(res) fragments within a single prion strain questions the validity of the conventional molecular typing system.

Establishment of a standard 14-3-3 protein assay of cerebrospinal fluid as a diagnostic tool for Creutzfeldt-Jakob disease

Periodic sharp wave complexes observed on an electroencephalographic recording and the presence of a 14-3-3 protein in the cerebrospinal fluid (CSF) are both included in the diagnostic criteria for the Creutzfeldt-Jakob disease (CJD) supplied by the World Health Organization; however, the presence or absence of the 14-3-3 protein in the CSF is sometimes difficult to discern on a western blot because of equivocal bands. The goal of this study was to establish a standard 14-3-3 protein assay and to determine the threshold level of a 14-3-3 protein that can be assayed by western blot. We searched for the most suitable isoform of the 14-3-3 protein to test for in protein assays, and the most sensitive antibody among four antibodies with an affinity for 14-3-3. We measured the levels of all 14-3-3 isoforms in 112 patients with CJD and in 100 patients with other diseases. We compared the performances of four different antibodies. We carried out a semi-quantitative analysis of γ-isoform levels using the LAS 3000 system, which was capable of producing a digital image from the luminescence on a western blot. We determined that the most suitable isoform of the 14-3-3 protein for conducting a standardized assay was the γ-isoform. Among the four commercially available antibodies for this protein, the most sensitive and specific was 18647 (IBL, Japan). We report the high repeatability of the detection of the 14-3-3 protein by this antibody to the γ-isoform, showing that western blot can be used for semi-quantitative analysis.

Codon 129 polymorphism and the E200K mutation do not affect the cellular prion protein isoform composition in the cerebrospinal fluid from patients with Creutzfeldt-Jakob disease

The cellular prion protein (PrP(c)) is a multifunctional, highly conserved and ubiquitously expressed protein. It undergoes a number of modifications during its post-translational processing, resulting in different PrP(c) glycoforms and truncated PrP(c) fragments. Limited data are available in humans on the expression and cleavage of PrP(c). In this study we investigated the PrP(c) isoform composition in the cerebrospinal fluid from patients with different human prion diseases. The first group of patients was affected by sporadic Creutzfeldt-Jakob disease exhibiting different PrP codon 129 genotypes. The second group contained patients with a genetic form of Creutzfeldt-Jakob disease (E200K). The third group consisted of patients with fatal familial insomnia and the last group comprised cases with the Gerstmann-Sträussler-Scheinker syndrome. We examined whether the PrP codon 129 polymorphism in sporadic Creutzfeldt-Jakob disease as well as the type of prion disease in human patients has an impact on the glycosylation and processing of PrP(c). Immunoblotting analyses using different monoclonal PrP(c) antibodies directed against various epitopes of PrP(c) revealed, for all examined groups of patients, a consistent predominance of the glycosylated PrP(c) isoforms as compared with the unglycosylated form. In addition, the antibody SAF70 recognized a variety of PrP(c) fragments with sizes of 21, 18, 13 and 12 kDa. Our findings indicate that the polymorphisms at PrP codon 129, the E200K mutation at codon 200 or the examined types of human transmissible spongiform encephalopathies do not exert a measurable effect on the glycosylation and processing of PrP(c) in human prion diseases.

A traceback phenomenon can reveal the origin of prion infection

The transmission of prions to animals with incongruent prion protein (PrP) gene (referred to as cross-sequence transmission) results in a relatively long incubation period and can generate a new prion strain with unique transmissibility designated as a traceback phenomenon. For example, cross-sequence transmission of bovine spongiform encephalopathy (BSE) prions to human generated variant Creutzfeldt-Jakob disease (vCJD) prions which retained the transmissibility to mice expressing bovine PrP. This finding suggests that traceback studies could enable us to identify the origin of prions. There are two distinct phenotypes in dura mater graft-associated Creutzfeldt-Jakob disease (dCJD), with the majority represented by a non-plaque-type of dCJD (np-dCJD) and the minority by a plaque-type of dCJD (p-dCJD). To identify the origin of p-dCJD, we performed a traceback study using mice expressing human PrP with methionine homozygosity (129M/M) or valine homozygosity (129V/V) at polymorphic codon 129. The characteristics of p-dCJD such as the accumulation of abnormal isoform of PrP (PrP(Sc)) intermediate in size between type 1 and type 2, and plaque-type PrP deposition in the brain were maintained after transmission to the 129M/M mice. Furthermore, the 129V/V mice were more susceptible to p-dCJD prions than the 129M/M mice and produced type 2 PrP(Sc) that were identical in size to those from the 129V/V mice inoculated with sporadic CJD prions from a patient with 129V/V and type 2 PrP(Sc) (sCJD-VV2). In addition, we performed intracerebral transmission of sCJD-VV2 prions to the 129M/M mice as an experimental model for p-dCJD. These 129M/M mice showed the accumulation of the intermediate type PrP(Sc) and plaque-type PrP deposition in the brain. These results suggest that p-dCJD could be caused by cross-sequence transmission of sCJD-VV2 prions to individuals with the 129M/M genotype.

Dura mater graft-associated Creutzfeldt-Jakob disease in Japan: clinicopathological and molecular characterization of the two distinct subtypes

Up to February 2008, a total of 132 patients with dura mater graft-associated Creutzfeldt-Jakob disease (dCJD) have been identified in Japan, accounting for a majority of the world's patients with dCJD. The patients received dura mater grafts from 1978 to 1993. Lyodura (B. Braun, Melsungen, Germany) was used for all the patients in whom the brand name of the dura mater could be identified. After the incubation period of 1 to 25 years (mean, 11.8 years), CJD appeared from 1985 through to 2006. We analyzed clinical, pathological, and molecular features in 74 patients with dCJD who had been prospectively registered by the CJD Surveillance Committee. The cases of dCJD could be classified into two distinct clinicopathological phenotypes: a non-plaque type, showing typical features identical with those of classic CJD, and a plaque type, characterized by atypical features, including slow progression, lack of or late occurrence of periodic sharp wave complexes on EEG, and plaque formation in the brain. The plaque type accounted for one-third of the pathologically confirmed or clinically diagnosed cases of dCJD. The non-plaque type was associated with methionine homozygosity at codon 129 (129M/M) of the PrP gene in all patients, except for in one patient with the 129M/valine (V) genotype and type 1 protease-resistant PrP (PrP(res)), whereas the plaque type was always associated with the 129M/M genotype and the intermediate type between types 1 and 2 of PrP(res) in all cases. Thus, the clinicopathological and molecular features of the plaque type are distinct from those of the non-plaque type, suggesting contamination of the dura mater grafts with different prion strains.

An autopsied case of panencephalopathic-type Creutzfeldt-Jakob disease with mutation in the prion protein gene at codon 232 and type 1 prion protein

In this study, we describe the clinicopathologic findings in a 68-year-old man with panencephalopathic-type CJD with a substitution from methionine to arginine at codon 232 (M232R) in the prion protein (PrP) gene and type 1 PrP. Initial symptoms of the patient were a rapidly progressive memory disturbance and disorientation. The patient showed myoclonus and periodic sharp-wave complexes on electroencephalogram in the early stages of disease. Diffusion-weighted MRI along with the presence of both neuron-specific enolase and 14-3-3 protein in the CSF showed similarities to classic-type sporadic CJD. The patient reached the akinetic mutism state 2 months following the onset of symptoms and died after 13 months. Neuropathologic examination revealed panencephalopathic-type CJD pathology including widespread neuron loss with severe hypertrophic astrocytosis and status spongiosus in the cerebral gray matter, particularly in the neocortex. Cerebral white matter and the cerebellum also showed severe involvement. Immunohistochemical staining for PrP showed diffuse gray matter staining, indicating synaptic-type PrP deposition without plaque-type. Two different clinical phenotypes of M232R CJD were recognized despite the presence of the same PrP genotype, and the present case is speculated to correspond to the rapid-type.

Plaque-type deposition of prion protein in the damaged white matter of sporadic Creutzfeldt-Jakob disease MM1 patients

Plaque-type deposition of prion protein (PrP) in the brain has been extremely rare in sporadic Creutzfeldt-Jakob disease patients with methionine homozygosity at polymorphic codon 129 of the PrP gene and type 1 abnormal isoform of PrP (sCJD-MM1). Here we report three sCJD-MM1 patients who showed prominent PrP-positive amyloid plaques in the cerebral and cerebellar white matter. All three patients showed clinical courses of long duration (2 years < or =), particularly at the end-stage. The white matter of these patients was severely damaged because of the prolonged disease duration. Furthermore, Alzheimer's amyloid precursor protein, which accumulates within the axonal swellings under pathological conditions, co-accumulated with the PrP-amyloid plaques. These findings suggest that the axonal damage reflecting the prolonged disease duration causes the deposition of PrP-amyloid plaques in the white matter. The present study shows that PrP-amyloid plaques can occur in the white matter of sCJD-MM1 cases.

Characterization of truncated forms of abnormal prion protein in Creutzfeldt-Jakob disease

In prion disease, the abnormal conformer of the cellular prion protein, PrP(Sc), deposits in fibrillar protein aggregates in brain and other organs. Limited exposure of PrP(Sc) to proteolytic digestion in vitro generates a core fragment of 19-21 kDa, named PrP27-30, which is also found in vivo. Recent evidence indicates that abnormal truncated fragments other than PrP27-30 may form in prion disease either in vivo or in vitro. We characterized a novel protease-resistant PrP fragment migrating 2-3 kDa faster than PrP27-30 in Creutzfeldt-Jakob disease (CJD) brains. The fragment has a size of about 18.5 kDa when associated with PrP27-30 type 1 (21 kDa) and of 17 kDa when associated with type 2 (19 kDa). Molecular mass and epitope mapping showed that the two fragments share the primary N-terminal sequence with PrP27-30 types 1 and 2, respectively, but lack a few amino acids at the very end of C terminus together with the glycosylphosphatidylinositol anchor. The amounts of the 18.5- or 17-kDa fragments and the previously described 13-kDa PrP(Sc) C-terminal fragment relatively to the PrP27-30 signal significantly differed among CJD subtypes. Furthermore, protease digestion of PrP(Sc) or PrP27-30 in partially denaturing conditions generated an additional truncated fragment of about 16 kDa only in typical sporadic CJD (i.e. MM1). These results show that the physicochemical heterogeneity of PrP(Sc) in CJD extends to abnormal truncated forms of the protein. The findings support the notion of distinct structural "conformers" of PrP(Sc) and indicate that the characterization of truncated PrP(Sc) forms may further improve molecular typing in CJD.

Clinicopathologic characteristics of five autopsied cases of dura mater-associated Creutzfeldt-Jakob disease

We present five cases of dura mater-associated Creutzfeldt-Jakob disease (dura-CJD) that were analyzed clinicopathologically and review previous reports. The average age at dura mater transplantation was 54.4 +/- 7.3 years, and the average age at CJD onset was 66.0 +/- 8.2 years, with an average latency period of 11.6 +/- 1.1 years. The average age at death was 67.6 +/- 8.7 years, with an average CJD disease duration of 16.8 +/- 10.4 months. Symptoms of CJD onset in four patients who received dura mater transplantation below the cerebellar tent reflected cerebellar or brainstem dysfunction, whereas symptoms of one patient who received transplantation above the cerebellar tent reflected cerebral cortical involvement. All patients showed rapidly progressive cognitive impairment, and both periodic sharp-wave complexes on electroencephalogram and myoclonus were observed in the early disease stage. Neuropathologic evaluation showed one case of subacute spongiform encephalopathy and four cases of panencephalopathic-type CJD. Widespread cerebral neocortical, subcortical gray matter and cerebellar cortical involvement were observed to varying degrees, and severity tended to be associated with CJD disease duration. There were no instances of kuru plaques or florid plaques. Prion protein (PrP) immunostaining showed widespread synaptic-type PrP deposition. No differences between our dura-CJD cases and typical cases of sporadic CJD were found with respect to clinicopathologic findings, except history of dura mater transplantation. Although a specific association between the dura mater graft site and neuropathologic observations was not evaluated in the present study, the initial symptoms appear to be closely related to the graft site, indicating a direct transmission of CJD from the graft site to the adjacent brain.

Evidence for a pathogenic role of different mutations at codon 188 of PRNP

Clinical and pathological changes in familial Creutzfeldt-Jakob disease (CJD) cases may be similar or indistinguishable from sporadic CJD. Therefore determination of novel mutations in PRNP remains of major importance.

We identified two different rare mutations in codon 188 of the prion protein gene (PRNP) in four patients suffering from a disease clinically very similar to the major subtype of sporadic CJD. Both mutations result in an exchange of the amino acid residue threonine for a highly basic residue, either arginine (T188R) or lysine (T188K). The T188R mutation was found in one patient and the T188K mutation in three patients. The prevalence of mutations at codon 188 of PRNP was tested in 593 sporadic CJD cases and 735 healthy individuals. Neither mutation was found. The data presented here argue in favor of T188K being a pathogenic mutation causing genetic CJD. Since one individual with this mutation, who is the father of a clinically affected patient with T188K mutation, is now 79 years old and shows no signs of disease, this mutation is likely associated with a penetrance under 100%. Further observations will have to show whether T188R is a pathogenic mutation.

Two different clinical phenotypes of Creutzfeldt-Jakob disease with a M232R substitution

OBJECTIVE

To describe the clinical features of Creutzfeldt-Jakob disease with a substitution of arginine for methionine (M232R substitution) at codon 232 (CJD232) of the prion protein gene (PRNP).

PATIENTS AND METHODS

We evaluated the clinical and laboratory features of 20 CJD232 patients: age of onset, initial symptoms, duration until becoming akinetic and mute, duration until occurrence of periodic sharp and wave complexes on EEG (PSWC), MRI findings, and the presence of CSF 14-3-3 protein. Immunohistochemically, prion protein (PrP) deposition was studied.

RESULTS

None of the patients had a family history of CJD. We recognized two clinical phenotypes: a rapidly progressive type (rapidtype) and a slowly progressive type (slow-type). Out of 20 patients, 15 became akinetic and mute, demonstrated myoclonus, and showed PSWC within a mean duration of 3.1, 2.4, and 2.8 months, respectively (rapid-type). Five showed slowly progressive clinical courses (slow-type). Five became akinetic and mute and four demonstrated myoclonus within a mean duration of 20.6 and 15.3 months, respectively, which were significantly longer than those in the rapid-type. Only one demonstrated PSWC 13 months after the onset. Diffuse synaptic-type deposition was demonstrated in four rapidtype patients, and perivacuolar and diffuse synaptic-type deposition in two, and diffuse synaptic-type deposition in one slow-type patient. Three of 50 suspected but non-CJD patients had the M232R substitution.

CONCLUSIONS

Patients with CJD232 had no family history like patients with sCJD, and showed two different clinical phenotypes in spite of having the same PRNP genotype. More studies are needed to determine whether M232R substitution causes the disease and influences the disease progression.

Intracellular accumulation of a mild-denatured monomer of the human PrP fragment 90-231, as possible mechanism of its neurotoxic effects

Because of high tendency of the prion protein (PrP) to aggregate, the exact PrP isoform responsible for prion diseases as well as the pathological mechanism that it activates remains still controversial. In this study, we show that a pre-fibrillar, monomeric or small oligomeric conformation of the human PrP fragment 90-231 (hPrP90-231), rather than soluble or fibrillar large aggregates, represents the neurotoxic species. In particular, we demonstrate that monomeric mild-denatured hPrP90-231 (incubated for 1 h at 53 degrees C) induces SH-SY5Y neuroblastoma cell death, while, when structured in large aggregates, it is ineffective. Using spectroscopic and cellular techniques we demonstrate that this toxic conformer is characterized by a high exposure of hydrophobic regions that favors the intracellular accumulation of the protein. Inside the cells hPrP90-231 is mainly compartmentalized into the lysosomes where it may trigger pro-apoptotic 'cell death' signals. The PrP toxic conformation, which we have obtained inducing a controlled in vitro conformational change of the protein, might mimic mild-unfolding events occurring in vivo, in the presence of specific mutations, oxidative reactions or proteolysis. Thus, in light of this model, we propose that novel therapeutic strategies, designed to inhibit the interaction of the toxic PrP with the plasmamembrane, could be beneficial to prevent the formation of intracellular neurotoxic aggregates and ultimately the neuronal death.

Cross-sequence transmission of sporadic Creutzfeldt-Jakob disease creates a new prion strain

The genotype (methionine or valine) at polymorphic codon 129 of the human prion protein (PrP) gene and the type (type 1 or type 2) of abnormal isoform of PrP (PrP(Sc)) are major determinants of the clinicopathological phenotypes of sporadic Creutzfeldt-Jakob disease (sCJD). Here we found that the transmission of sCJD prions from a patient with valine homozygosity (129V/V) and type 2 PrP(Sc) (sCJD-VV2 prions) to mice expressing human PrP with methionine homozygosity (129M/M) generated unusual PrP(Sc) intermediate in size between type 1 and type 2. The intermediate type PrP(Sc) was seen in all examined dura mater graft-associated CJD cases with 129M/M and plaque-type PrP deposits (p-dCJD). p-dCJD prions and sCJD-VV2 prions exhibited similar transmissibility and neuropathology, and the identical type of PrP(Sc) when inoculated into PrP-humanized mice with 129M/M or 129V/V. These findings suggest that p-dCJD could be caused by cross-sequence transmission of sCJD-VV2 prions.

H-type bovine spongiform encephalopathy: complex molecular features and similarities with human prion diseases

We previously reported that some cattle affected by bovine spongiform encephalopathy (BSE) showed distinct molecular features of the protease-resistant prion protein (PrP(res)) in Western blot, with a 1-2 kDa higher apparent molecular mass of the unglycosylated PrP(res) associated with labelling by antibodies against the 86-107 region of the bovine PrP protein (H-type BSE). By Western blot analyses of PrP(res), we now showed that the essential features initially described in cattle were observed with a panel of different antibodies and were maintained after transmission of the disease in C57Bl/6 mice. In addition, antibodies against the C-terminal region of PrP revealed a second, more C-terminally cleaved, form of PrP(res) (PrP(res) #2), which, in unglycosylated form, migrated as a approximately 14 kDa fragment. Furthermore, a PrP(res) fragment of approximately 7 kDa, which was not labelled by C-terminus-specific antibodies and was thus presumed to be a product of cleavage at both N- and C-terminal sides of PrP protein, was also detected. Both PrP(res) #2 and approximately 7 kDa PrP(res) were detected in cattle and in C57Bl/6 infected mice. These complex molecular features are reminiscent of findings reported in human prion diseases. This raises questions regarding the respective origins and pathogenic mechanisms in prion diseases of animals and humans.

Gerstmann-Sträussler-Scheinker

Gerstmann-Sträussler-Scheinker (GSS) is a hereditary prion disease typically associated with prion protein (PrP)-containing plaques. The protease-resistant, scrapie PrP (PrPSc) is represented by internal fragments, whereas the C-terminal fragments associated with the other prion diseases are generally underrepresented. Different histopathologic and PrPSc features associated with at least 13 PrP gene (PRNP) mutations have been described in GSS. We report the histopathology and PrP characteristics in a father and son carrying a mutation at PRNP codon 187 that substitutes histidine (H) with arginine (R) and is coupled with valine (V) at position 129 (H187R-129V). The PrP plaques were present in both cases but with different structure and topography and minimal spongiform degeneration. A distinctive, "curly" PrP immunostaining was prominent in one case. The protease-resistant PrPSc differed in amount in the 2 cases, possibly depending on whether plaques or the curly immunostain was present. Two protease-resistant PrP fragments of 14 kDa and 7 kDa with, in at least one case, N-terminus between residues 90-99 and 82-90, respectively, codistributed with the plaques, whereas only very small amounts of the PK-resistant PrP were present in the curly staining regions. PK-resistant PrP recovered from the plaque and curly staining regions appeared to be full length.

Increased asymmetric pulvinar magnetic resonance imaging signals in Creutzfeldt-Jakob disease with florid plaques following a cadaveric dura mater graft

A 9-year-old Japanese girl received a cadaveric dura mater graft during surgery following a head injury with brain contusion. She continued to do well, but when she became 19-years-old, she gradually showed a violent character and was treated in a psychiatric hospital. Another 6 years later, 200 months after the procedure, she developed a progressive gait ataxia, which subsequently led to her death within 10 months of onset. An autopsy showed she had CJD. This patient represents an atypical case of dura-associated CJD (dCJD) with unusual clinicopathological features including the late occurrence of myoclonus, an absence of periodic synchronous discharges in the electroencephalogram, and the presence of widespread florid plaques. However, our detection of an asymmetrical increase in the MRI-derived images of pulvinar nuclei has not been previously observed in other atypical cases of dCJD. Because atypical dCJD cases share several clinicopathological features with those of vCJD, and because asymmetrical hyperintense signals in the pulvinar have been observed in some neuropathologically confirmed vCJD cases, we had some difficulty in a differential diagnosis between atypical dCJD and vCJD. This is the first atypical dCJD case showing a pulvinar high signal compared with all other basal ganglia on MRI.

Phenotypic variability in human prion diseases

Human prion diseases are rare neurodegenerative disorders that can occur as sporadic, familial or acquired disorders. Within each of these categories there is a wide range of phenotypic variation that is not encountered in other neurodegenerative disorders. The identification of the prion protein and its key role in the pathogenesis of this diverse group of diseases has allowed a fuller understanding of factors that influence disease phenotype. In particular, the naturally occurring polymorphism at codon 129 in the prion protein gene has a major influence on the disease phenotype in sporadic, familial and acquired prion diseases, although the underlying mechanisms remain unclear. Recent technical advances have improved our ability to study the isoforms of the abnormal prion protein in the brain and in other tissues. This has lead to the concept of molecular strain typing, in which different isoforms of the prion protein are proposed to correspond to individual strains of the transmissible agent, each with specific biological properties. In sporadic Creutzfeldt-Jakob disease there are at least six major combinations of codon 129 genotype and prion protein isotype, which appear to relate to distinctive clinical subgroups of this disease. However, these relationships are proving to be more complex than first considered, particularly in cases with more than a single prion protein isotype in the brain. Further work is required to clarify these relationships and to explain the mechanism of neuropathological targeting of specific brain regions, which accounts for the diversity of clinical features within human prion diseases.

Neuropathologic characteristics of spinal cord lesions in sporadic Creutzfeldt-Jakob disease

We investigated the neuropathologic features of spinal cord lesions in 23 patients with sporadic Creutzfeldt-Jakob disease (sCJD), paying particular attention to neuronal loss and gliosis, pyramidal tract degeneration and prion protein (PrP) deposition. The study included 9 cases of subacute spongiform encephalopathy, 13 cases of panencephalopathic-type sCJD and 1 case of sporadic fatal insomnia (sFI). In the spinal gray matter, although gliosis was present in some patients with disease of relatively long duration, the number of neurons, including large motor neurons, was well preserved regardless of disease duration. Pyramidal tract degeneration was observed in some patients with disease lasting more than 14 months but not in the patient with sFI. PrP deposition was present in the spinal cord of all sCJD patients, and was identified predominantly in the posterior horn, particularly in the substantia gelatinosa, regardless of disease duration or disease classification based on cerebral pathology. Relatively prominent PrP deposition was also observed in Clarke's column. The density of PrP deposition in the sCJD spinal cord was not associated with disease duration or neuronal degeneration. Our results indicate that PrP deposition in the spinal cord is an early pathologic event in sCJD and may remain to the end stage. Although no VV1, VV2 or MV2 cases were included in our study, we suggest that stereotypic accumulation of PrP is a consistent pathologic feature of sCJD and that the spinal cord remains relatively resistant to the pathologic process of sCJD, at least in patients with MM1 sCJD.

Neuropathologic characteristics of brainstem lesions in sporadic Creutzfeldt-Jakob disease

We investigated whether the brainstem is affected by the pathologic process of sporadic Creutzfeldt-Jakob disease (sCJD), with particular attention to brainstem atrophy, neuronal loss, pyramidal tract degeneration, and prion protein (PrP) deposition, in 33 patients with sCJD. Brainstem atrophy, particularly in the pontine base, was relatively prominent in patients with disease of unusually prolonged duration. Neuronal loss and pyramidal tract degeneration were also identified in some but not all patients with prolonged disease. Neuronal loss was relatively prominent in the pontine nucleus and less so in the substantia nigra and inferior olivary nucleus; motor nuclei of the brainstem tegmentum were well preserved. PrP deposition was present in the brainstem in all patients, and was identified predominantly in the substantia nigra, quadrigeminal body, pontine nucleus, and inferior olivary nucleus. PrP deposition was less prominent in the red nucleus and tegmentum of the pons and medulla oblongata. PrP deposition occurred least or not at all in the pyramidal tract. The density of PrP deposition in the sCJD brainstem was not associated with disease duration or neuronal degeneration until the late stage. Our results show that atrophy, neuronal loss, and pyramidal tract degeneration occur in the sCJD brainstem, particularly in patients with an unusually prolonged disease course. These findings are not associated directly with PrP deposition and may reflect end-stage sCJD. No VV1, VV2, or MV2 cases were included in our study; however, we suggest that widespread and relatively stereotypic PrP deposition is a consistent pathologic feature of sCJD, at least in MM1 sCJD patients. Although accumulation of PrP in the brainstem appears to be an early pathologic event in sCJD, and may remain into the late disease stage, the brainstem remains relatively resistant to the pathologic process of sCJD.

A new momentum in the field of transmissible spongiform encephalopathies (TSEs)

The present work is a critical survey answering a recent paper published by Stanley Prusiner's team in Science magazine. The authors claim that they used synthetic prions, instead of which they have tailored a particular recombinant protein, produced in E. coli, and devoid of its N-terminal part, therefore mimicking a truncated protein described by another team who isolated it from an iatrogenic TSE patient. This recombinant prion was lethal in normal mice, perhaps partly because, contrarily to what happens with the whole-length normal protein, these proteins are both neurotoxic, fibrillogenic and insensitive to proteolysis. Moreover, an accompanying nucleic acid could explain the infection, because, since 1982 and until now, the protein-only hypothesis has never been supported by any positive mechanism and experimental proof, and is becoming inadequate. Therefore, we have tried to elaborate an alternative hypothesis for the specific mechanism of infection in TSE. The transfer of at least a piece of nucleic acid from the infecting subject, perhaps the mRNA coding for the truncated protein described in human patients, could then reach the corresponding gene in the infected subject, where an endogenous reverse transcriptase would be able to integrate it. Once altered and stimulated, this last gene could, in turn, participate in the generation of nucleic acids able to code the generation of the truncated forms of the prion protein.

Creutzfeldt-Jakob disease in a patient with an R208H mutation of the prion protein gene (PRNP) and a 17-kDa prion protein fragment

A case of Creutzfeldt-Jakob disease (CJD) with a rare mutation of the prion protein (PrP) gene (PRNP) at codon 208 (R208H) is described. By comparison with two preceding reports, the case described here displayed two distinct biochemical and neuropathological features. Western blot analysis of brain homogenates showed, in addition to the commonly observed three bands of abnormal protease-resistant PrP isoform (PrP(Sc)), an additional band of about 17 kDa. Neuropathological examination of the post mortem brain revealed tau pathology in the hippocampus and entorhinal cortex, as well as ballooned neurons in the cortex, hippocampus and subcortical gray matter.

Synthetic prions generated in vitro are similar to a newly identified subpopulation of PrPSc from sporadic Creutzfeldt-Jakob Disease

In recent studies, the amyloid form of recombinant prion protein (PrP) encompassing residues 89-230 (rPrP 89-230) produced in vitro induced transmissible prion disease in mice. These studies showed that unlike "classical" PrP(Sc) produced in vivo, the amyloid fibrils generated in vitro were more proteinase-K sensitive. Here we demonstrate that the amyloid form contains a proteinase K-resistant core composed only of residues 152/153-230 and 162-230. The PK-resistant fragments of the amyloid form are similar to those observed upon PK digestion of a minor subpopulation of PrP(Sc) recently identified in patients with sporadic Creutzfeldt-Jakob disease (CJD). Remarkably, this core is sufficient for self-propagating activity in vitro and preserves a beta-sheet-rich fibrillar structure. Full-length recombinant PrP 23-230, however, generates two subpopulations of amyloid in vitro: One is similar to the minor subpopulation of PrP(Sc), and the other to classical PrP(Sc). Since no cellular factors or templates were used for generation of the amyloid fibrils in vitro, we speculate that formation of the subpopulation of PrP(Sc) with a short PK-resistant C-terminal region reflects an intrinsic property of PrP rather than the influence of cellular environments and/or cofactors. Our work significantly increases our understanding of the biochemical nature of prion infectious agents and provides a fundamental insight into the mechanisms of prions biogenesis.

Type 1 and type 2 human PrPSc have different aggregation sizes in methionine homozygotes with sporadic, iatrogenic and variant Creutzfeldt-Jakob disease

In Creutzfeldt-Jakob disease (CJD), the type (type 1 or 2) of abnormal isoform of the prion protein (PrP(Sc)) in the brain and the genotype at codon 129 of the PrP gene are major determinants of clinicopathological phenotype. Little is known about the difference in biochemical properties between the two types of PrP(Sc), except for the different proteinase K cleavage sites. To investigate the size of aggregates formed by PrP(Sc) types 1 and 2, brain homogenates from various cases of CJD with the same genotype (homozygous for methionine at codon 129) were passed through filters with a mean pore size of 72+/-4 nm. Type 2 PrP(Sc) was efficiently removed from the filtrates by the filters, in contrast to type 1. Even type 2 PrP(Sc) from a patient without amyloid plaques was removed more efficiently than type 1 from patients with amyloid plaques. These results indicate that type 2 PrP(Sc) has a larger aggregation size than type 1, irrespective of the existence of amyloid plaques.

Identification of distinct N-terminal truncated forms of prion protein in different Creutzfeldt-Jakob disease subtypes

In prion diseases, the cellular prion protein (PrP(C)) is converted to an insoluble and protease-resistant abnormal isoform termed PrP(Sc). In different prion strains, PrP(Sc) shows distinct sites of endogenous or exogenous proteolysis generating a core fragment named PrP27-30. Sporadic Creutzfeldt-Jakob disease (sCJD), the most frequent human prion disease, clinically presents with a variety of neurological signs. As yet, the clinical variability observed in sCJD has not been fully explained by molecular studies relating two major types of PrP27-30 with unglycosylated peptides of 21 (type 1) and 19 kDa (type 2) and the amino acid methionine or valine at position 129. Recently, smaller C-terminal fragments migrating at 12 and 13 kDa have been detected in different sCJD phenotypes, but their significance remains unclear. By using two-dimensional immunoblot with anti-PrP antibodies, we identified two novel groups of protease-resistant PrP fragments in sCJD brain tissues. All sCJD cases with type 1 PrP27-30, in addition to MM subjects with type 2 PrP27-30, were characterized by the presence of unglycosylated PrP fragments of 16-17 kDa. Conversely, brain homogenates from patients VV and MV with type 2 PrP27-30 contained fully glycosylated PrP fragments, which after deglycosylation migrated at 17.5-18 kDa. Interestingly, PrP species of 17.5-18 kDa matched deglycosylated forms of the C1 PrP(C) fragment and were associated with tissue PrP deposition as plaque-like aggregates or amyloid plaques. These data show the presence of multiple PrP(Sc) conformations in sCJD and, in addition, shed new light on the correlation between sCJD phenotypes and disease-associated PrP molecules.