Neuropathologic variants of sporadic Creutzfeldt-Jakob disease and codon 129 of PrP gene

The definition of precision medicine in neurodegenerative disorders and the one disease-many diseases tension

Precision medicine is a patient-centered approach that aims to translate new knowledge to optimize the type and timing of interventions for the greatest benefit to individual patients. There is considerable interest in applying this approach to treatments designed to slow or halt the progression of neurodegenerative diseases. Indeed, effective disease-modifying treatment (DMT) remains the greatest unmet therapeutic need in this field. In contrast to the enormous progress in oncology, precision medicine in the field of neurodegeneration faces multiple challenges. These are related to major limitations in our understanding of many aspects of the diseases. A critical barrier to advances in this field is the question of whether the common sporadic neurodegenerative diseases (of the elderly) are single uniform disorders (particularly related to their pathogenesis) or whether they represent a collection of related but still very distinct disease states. In this chapter, we briefly touch on lessons from other fields of medicine that might be applied to the development of precision medicine for DMT in neurodegenerative diseases. We discuss why DMT trials may have failed to date, and particularly the importance of appreciating the multifaceted nature of disease heterogeneity and how this has and will impact on these efforts. We conclude with comments on how we can move from this complex disease heterogeneity to the successful application of precision medicine principles in DMT for neurodegenerative diseases.

Amino Acid Substitution within Seven-Octapeptide Repeat Insertions in the Prion Protein Gene Associated with Short-Term Course

The majority of seven-octapeptide repeat insertion (7-OPRI) carriers exhibit relatively early onset and a slowly progressive course. We have presented three cases of 7-OPRI, including two that are rapidly progressing, and compared the clinical and ancillary characteristics of the short-term and long-term disease course, as well as factors that influence disease course. The clinical and ancillary features of three new 7-OPRI patients in a Chinese pedigree were analyzed. Global data on 7-OPRI cases were then collected by reviewing the literature, and the cases were grouped according to clinical duration as per the WHO sCJD criteria, with a two-year cut-off. A Chinese pedigree has a glycine-to-glutamate substitution within the 7-OPRI insertion, which enhances the hydrophilicity of the prion protein. Two cases in this pedigree had a short disease course (consistent with the typical clinical and ancillary features of sCJD). In addition, the members of this pedigree had a later onset (p < 0.001) and shorter disease course (p < 0.001) compared to previously reported 7-OPRI cases with 129 cis-M and a similar age of onset and disease course to that of cases with 129 cis-V. The 7-OPRI cases with a shorter clinical course (n = 4) had a later onset (p = 0.021), higher rate of hyperintensity on MRI (p = 0.029) and higher frequency of 129 cis-V (p = 0.066) compared to those with a longer clinical course (n = 13). The clinical presentation of 7-OPRI is significantly heterogeneous. Codon 129 cis-V and amino acid substitution within repeat insertions are possible contributors to the short-term disease course of 7-OPRI.

A clinicopathological study of selected cognitive impairment cases in Lothian, Scotland: enhanced CJD surveillance in the 65 + population group

Background

Variant Creutzfeldt-Jakob Disease (vCJD) is primarily associated with dietary exposure to bovine-spongiform-encephalopathy. Cases may be missed in the elderly population where dementia is common with less frequent referral to specialist neurological services. This study’s twin aims were to determine the feasibility of a method to detect possible missed cases in the elderly population and to identify any such cases.

Methods

A multi-site study was set-up in Lothian in 2016, to determine the feasibility of enhanced CJD-surveillance in the 65 + population-group, and undertake a clinicopathological investigation of patients with features of ‘atypical’ dementia.

Results

Thirty patients are included; 63% male, 37% female. They were referred because of at least one neurological feature regarded as ‘atypical’ (for the common dementing illnesses): cerebellar ataxia, rapid progression, or somato-sensory features. Mean-age at symptom-onset (66 years, range 53–82 years), the time between onset-of-symptoms and referral to the study (7 years, range 1–13 years), and duration-of-illness from onset-of-symptoms until death or the censor-date (9.5 years, range 1.1–17.4 years) were determined. By the censor-date, 9 cases were alive and 21 had died. Neuropathological investigations were performed on 10 cases, confirming: Alzheimer’s disease only (2 cases), mixed Alzheimer’s disease with Lewy bodies (2 cases), mixed Alzheimer’s disease with amyloid angiopathy (1 case), moderate non-amyloid small vessel angiopathy (1 case), a non-specific neurodegenerative disorder (1 case), Parkinson's disease with Lewy body dementia (1 case), and Lewy body dementia (2 cases). No prion disease cases of any type were detected.

Conclusion

The surveillance approach used was well received by the local clinicians and patients, though there were challenges in recruiting sufficient cases; far fewer than expected were identified, referred, and recruited. Further research is required to determine how such difficulties might be overcome. No missed cases of vCJD were found. However, there remains uncertainty whether this is because missed cases are very uncommon or because the study had insufficient power to detect them.

Accuracy of diagnosis criteria in patients with suspected diagnosis of sporadic Creutzfeldt-Jakob disease and detection of 14-3-3 protein, France, 1992 to 2009

Diagnostic criteria of Creutzfeldt–Jakob disease (CJD), a rare and fatal transmissible nervous system disease with public health implications, are determined by clinical data, electroencephalogram (EEG), detection of 14-3-3 protein in cerebrospinal fluid (CSF), brain magnetic resonance imaging and prion protein gene examination. The specificity of protein 14-3-3 has been questioned. We reviewed data from 1,572 autopsied patients collected over an 18-year period (1992–2009) and assessed whether and how 14-3-3 detection impacted the diagnosis of sporadic CJD in France, and whether this led to the misdiagnosis of treatable disorders. 14-3-3 detection was introduced into diagnostic criteria for CJD in 1998. Diagnostic accuracy decreased from 92% for the 1992–1997 period to 85% for the 1998–2009 period. This was associated with positive detections of 14-3-3 in cases with negative EEG and alternative diagnosis at autopsy. Potentially treatable diseases were found in 163 patients (10.5%). This study confirms the usefulness of the recent modification of diagnosis criteria by the addition of the results of CSF real-time quaking-induced conversion, a method based on prion seed-induced misfolding and aggregation of recombinant prion protein substrate that has proven to be a highly specific test for diagnosis of sporadic CJD.

Prion Diagnosis: Application of Real-Time Quaking-Induced Conversion

Prions composed of pathogenic scrapie prion protein (PrP^Sc) are infectious pathogens that cause progressive neurological conditions known as prion diseases or transmissible spongiform encephalopathies. Although these diseases pose considerable risk to public health, procedures for early diagnosis have not been established. One of the most recent attempts at sensitive and specific detection of prions is the real-time quaking-induced conversion (RT-QuIC) method, which measures the activity of PrP^Sc aggregates or amyloid formation triggered by PrP^Sc seeds in the presence of recombinant PrP. In this review, we summarize prions, prion diseases, and current approaches to diagnosis, including the principle, conditions for assay performance, and current diagnostic applications of RT-QuIC.

The Distribution of Prion Protein Allotypes Differs Between Sporadic and Iatrogenic Creutzfeldt-Jakob Disease Patients

Sporadic Creutzfeldt-Jakob disease (sCJD) is the most prevalent of the human prion diseases, which are fatal and transmissible neurodegenerative diseases caused by the infectious prion protein (PrP^Sc). The origin of sCJD is unknown, although the initiating event is thought to be the stochastic misfolding of endogenous prion protein (PrP^C) into infectious PrP^Sc. By contrast, human growth hormone-associated cases of iatrogenic CJD (iCJD) in the United Kingdom (UK) are associated with exposure to an exogenous source of PrP^Sc. In both forms of CJD, heterozygosity at residue 129 for methionine (M) or valine (V) in the prion protein gene may affect disease phenotype, onset and progression. However, the relative contribution of each PrP^C allotype to PrP^Sc in heterozygous cases of CJD is unknown. Using mass spectrometry, we determined that the relative abundance of PrP^Sc with M or V at residue 129 in brain specimens from MV cases of sCJD was highly variable. This result is consistent with PrP^C containing an M or V at residue 129 having a similar propensity to misfold into PrP^Sc thus causing sCJD. By contrast, PrP^Sc with V at residue 129 predominated in the majority of the UK human growth hormone associated iCJD cases, consistent with exposure to infectious PrP^Sc containing V at residue 129. In both types of CJD, the PrP^Sc allotype ratio had no correlation with CJD type, age at clinical onset, or disease duration. Therefore, factors other than PrP^Sc allotype abundance must influence the clinical progression and phenotype of heterozygous cases of CJD.

In Creutzfeldt-Jakob disease (CJD), heterozygosity at residue 129 for methionine or valine in normal prion protein may affect disease phenotype, onset and progression. However, the relative contribution of each prion protein allotype to the infectious, disease associated form of prion protein (PrP^Sc) is unknown. Here we report the novel observation that in heterozygous cases of sporadic CJD the PrP^Sc allotype ratio is highly variable. This case-by-case variability is consistent with the origin of sporadic CJD being the spontaneous, but random, misfolding of either host prion protein allotype into infectious PrP^Sc. By contrast, in heterozygous cases of iatrogenic CJD in the United Kingdom resulting from exposure to contaminated human growth hormone, the PrP^Sc allotype ratio is much more homogeneous and consistent with exposure to infectious PrP^Sc containing valine at residue 129. Surprisingly, the PrP^Sc allotype ratio did not correlate with disease onset or duration in either disease type. Thus, factors other than PrP^Sc allotype ratio likely influence the clinical progression of heterozygous cases of CJD. Moreover, our results suggest that the ratio of methionine to valine in PrP^Sc may be a means of determining the origin of prion infection.

[Perioperative considerations for performing a brain biopsy on a patient with subtype VV2 sporadic Creutzfeldt-Jakob disease]

Creutzfeldt-Jakob disease (CJD) is the most common transmissible spongiform encephalopathy. It is an infectious, progressive, degenerative neurological disorder, with a presumably long incubation period, but a rapid fatal course. CJD is transmitted by a proteinaceous infectious agent, or «prion». Because the prions are difficult to eradicate and are resistant to the currently used sterilization methods, special precautions must be taken with all surgical instruments. It is recommended the single-use equipment, destruction of contaminated equipment, decontamination of reusable instruments, use of protective clothing, and storing and quarantining surgical instruments. The single-use equipment and some tissues and body fluids from the patient with CJD are highly infectious and must be incinerated. We report a case of a patient who had undergone brain biopsy for suspected of CJD, being confirmed to have sporadic CJD. Specific preventive measures were taken to reduce the risk of transmission to healthcare workers.

Quantification of surviving cerebellar granule neurones and abnormal prion protein (PrPSc) deposition in sporadic Creutzfeldt-Jakob disease supports a pathogenic role for small PrPSc deposits common to the various molecular subtypes

AIMS

Neuronal death is a major neuropathological hallmark in prion diseases. The association between the accumulation of the disease-related prion protein (PrP(Sc) ) and neuronal loss varies within the wide spectrum of prion diseases and their experimental models. In this study, we investigated the relationships between neuronal loss and PrP(Sc) deposition in the cerebellum from cases of the six subtypes of sporadic Creutzfeldt-Jakob disease (sCJD; n=100) that can be determined according to the M129V polymorphism of the human prion protein gene (PRNP) and PrP(Sc) molecular types.

METHODS

The numerical density of neurones was estimated with a computer-assisted image analysis system and the accumulation of PrP(Sc) deposits was scored.

RESULTS

The scores of PrP(Sc) immunoreactive deposits of the punctate type (synaptic type) were correlated with neurone counts - the higher the score the higher the neuronal loss - in all sCJD subtypes. Large 5- to 50-µm-wide deposits (focal type) were found in sCJD-MV2 and sCJD-VV2 subtypes, and occasionally in a few cases of the other studied groups. By contrast, the highest scores for 5- to 50-µm-wide deposits observed in sCJD-MV2 subtype were not associated with higher neuronal loss. In addition, these scores were inversely correlated with neuronal counts in the sCJD-VV2 subtype.

CONCLUSIONS

These results support a putative pathogenic role for small PrP(Sc) deposits common to the various sCJD subtypes. Furthermore, the observation of a lower loss of neurones associated with PrP(Sc) type-2 large deposits is consistent with a possible 'protective' role of aggregated deposits in both sCJD-MV2 and sCJD-VV2 subtypes.

Biochemical and strain properties of CJD prions: complexity versus simplicity

Prions, the agents responsible for transmissible spongiform encephalopathies, are infectious proteins consisting primarily of scrapie prion protein (PrP(Sc)), a misfolded, β-sheet enriched and aggregated form of the host-encoded cellular prion protein (PrP(C)). Their propagation is based on an autocatalytic PrP conversion process. Despite the lack of a nucleic acid genome, different prion strains have been isolated from animal diseases. Increasing evidence supports the view that strain-specific properties may be enciphered within conformational variations of PrP(Sc). In humans, sporadic Creutzfeldt-Jakob disease (sCJD) is the most frequent form of prion diseases and has demonstrated a wide phenotypic and molecular spectrum. In contrast, variant Creutzfeldt-Jakob disease (vCJD), which results from oral exposure to the agent of bovine spongiform encephalopathy, is a highly stereotyped disease, that, until now, has only occurred in patients who are methionine homozygous at codon 129 of the PrP gene. Recent research has provided consistent evidence of strain diversity in sCJD and also, unexpectedly enough, in vCJD. Here, we discuss the puzzling biochemical/pathological diversity of human prion disorders and the relationship of that diversity to the biological properties of the agent as demonstrated by strain typing in experimental models.

Pathogenic mutations in the hydrophobic core of the human prion protein can promote structural instability and misfolding

Transmissible spongiform encephalopathies, or prion diseases, are caused by misfolding and aggregation of the prion protein PrP. These diseases can be hereditary in humans and four of the many disease-associated missense mutants of PrP are in the hydrophobic core: V180I, F198S, V203I and V210I. The T183A mutation is related to the hydrophobic core mutants as it is close to the hydrophobic core and known to cause instability. We used extensive molecular dynamics simulations of these five PrP mutants to compare their dynamics and conformations to those of the wild type PrP. The simulations highlight the changes that occur upon introduction of mutations and help to rationalize experimental findings. Changes can occur around the mutation site, but they can also be propagated over long distances. In particular, the F198S and T183A mutations lead to increased flexibility in parts of the structure that are normally stable, and the short β-sheet moves away from the rest of the protein. Mutations V180I, V210I and, to a lesser extent, V203I cause changes similar to those observed upon lowering the pH, which has been linked to misfolding. Early misfolding is observed in one V180I simulation. Overall, mutations in the hydrophobic core have a significant effect on the dynamics and stability of PrP, including the propensity to misfold, which helps to explain their role in the development of familial prion diseases.

Loss of cerebellar granule neurons is associated with punctate but not with large focal deposits of prion protein in Creutzfeldt-Jakob disease

Whether aggregates of prion protein (PrP) reflect neurotoxicity or are neuroprotective in prion diseases is unclear. To address this question, we performed a clinicopathologic study of cerebellar granular neurons in 100 patients affected with sporadic Creutzfeldt-Jakob disease (CJD). There was significant loss of these neurons in the subset of cases with Val/Val genotype at PRNP Codon 129 and Molecular Isotype 2 of abnormal PrP (sporadic CJD-VV2) (n=32) compared with both the other CJD subtypes and to controls. Pathological PrP deposits of the punctate-type (synaptic-type) in this subgroup correlated with neuronal loss and proliferation of astrocytes and microglia. By contrast, the numbers of large deposits (5- to 50-microm-diameter) and numbers of amyloid plaques did not correlate with neuronal loss. These findings are consistent with the view that large aggregates may protect neurons by sequestering neurotoxic PrP oligomers, whereas punctate deposits may indicate the location of neuronal death processes in CJD.

Variant Creutzfeldt-Jakob disease in France and the United Kingdom: Evidence for the same agent strain

OBJECTIVE

Variant Creutzfeldt-Jakob disease (vCJD) was first reported in the United Kingdom in 1996. Since then, the majority of cases have been observed in the United Kingdom where there was a major epidemic of bovine spongiform encephalopathy. France was the second country affected. To address the hypothesis of the involvement of a common strain of agent, we have compared clinical, neuropathological, and biochemical data on vCJD patients from both countries.

METHODS

In France and the United Kingdom, epidemiological and clinical data were obtained from analysis of medical records and direct interview of the family of the patients using the same standardized questionnaire in both countries. When brain material was available, we performed with similar methods a comparative study of brain lesions and PrP(res) glycoform ratios in both vCJD populations.

RESULTS

Clinical data, genetic background, neuropathological finding, and biochemical findings in the 185 patients observed in France (n = 23) and the United Kingdom (n = 162) were similar except for age at death. Currently, blood transfusion is a risk factor identified only in the United Kingdom.

INTERPRETATION

The close similarity between the cases of vCJD in France and the United Kingdom supports the hypothesis that a common strain of infectious agent is involved in both countries. The 5-year delay in the peak that we observed in France compared with the United Kingdom fits well with the increase in the importation of beef products to France from the United Kingdom between 1985 and 1995.

Inter-laboratory assessment of PrPSc typing in creutzfeldt-jakob disease: a Western blot study within the NeuroPrion Consortium

Molecular typing is of considerable importance for the surveillance and epidemiology of human transmissible spongiform encephalopathies (TSEs). It relies on the detection of distinct protease-resistant prion protein (PrP(Sc)) core fragments that differ in molecular mass and/or glycoform ratio. In this collaborative study, we tested the inter-laboratory agreement in TSE molecular typing. Sixteen characterized brain specimens from sporadic TSEs and variant Creutzfeldt-Jakob disease (vCJD) cases were distributed blindly to seven laboratories for molecular characterization by a defined protocol and classification. Agreement between laboratories in the classification of samples was excellent. In particular, there were no differences in the distinction between PrP(Sc) type 1, type 2A, and type 2B with one exception, which eventually was identified as a case with types 1 and 2 co-occurrence. This shows that the general technique and particular classification system used here are robust and represent a reliable basis for diagnostic and epidemiologic purposes. The subtle further distinction of subtypes among type 1 and type 2 groups requires high-sensitivity gel electrophoresis protocols that are unsuitable for routine diagnostic needs and must be reserved for research investigations. Further research is necessary on the identification and significance of co-occurrence of PrP(Sc) types 1 and 2 within one brain.

Human prion diseases: from antibody screening to a standardized fast immunodiagnosis using automation

Demonstration of pathological prion protein accumulation in the central nervous system is required to establish the diagnosis of transmissible subacute encephalopathies. In humans, this is frequently achieved using prion protein immunohistochemistry in paraffin-embedded tissue, a technique that requires multiple epitope retrieval and denaturing pretreatments. In addition to being time-consuming, this procedure induces tissue alterations that preclude accurate morphological examination. The aim of this study was to simplify prion protein immunohistochemistry procedure in human tissue, together with increased sensitivity and specificity. We screened a panel of 50 monoclonal antibodies produced using various immunogens (human and ovine recombinant prion protein, prion protein peptides, denatured scrapie-associated fibrils from 263K-infected Syrian hamsters) and directed against different epitopes along the human prion protein sequence. A panel of different forms of genetic, infectious and sporadic transmissible subacute encephalopathies was assessed. The monoclonal 12F10 antibody provided a high specificity and fast immunodiagnosis with very limited denaturing pretreatments. A standardized and reliable fast immunostaining procedure was established using an automated diagnostic system (Nexes, Ventana Medical Systems) and allowed prion protein detection in the central nervous system and in tonsil biopsies. It was evaluated in a series of 300 patients with a suspected diagnosis of transmissible subacute encephalopathies and showed high sensitivity and specificity.

Prominent and persistent extraneural infection in human PrP transgenic mice infected with variant CJD

BACKGROUND

The evolution of the variant Creutzfeldt-Jakob disease (vCJD) epidemic is hazardous to predict due to uncertainty in ascertaining the prevalence of infection and because the disease might remain asymptomatic or produce an alternate, sporadic-like phenotype.

METHODOLOGY/PRINCIPAL FINDINGS

Transgenic mice were produced that overexpress human prion protein with methionine at codon 129, the only allele found so far in vCJD-affected patients. These mice were infected with prions derived from variant and sporadic CJD (sCJD) cases by intracerebral or intraperitoneal route, and transmission efficiency and strain phenotype were analyzed in brain and spleen. We showed that i) the main features of vCJD infection in humans, including a prominent involvement of the lymphoid tissues compared to that in sCJD infection were faithfully reproduced in such mice; ii) transmission of vCJD agent by intracerebral route could lead to the propagation of either vCJD or sCJD-like prion in the brain, whereas vCJD prion was invariably propagated in the spleen, iii) after peripheral exposure, inefficient neuroinvasion was observed, resulting in an asymptomatic infection with life-long persistence of vCJD prion in the spleen at stable and elevated levels.

CONCLUSION/SIGNIFICANCE

Our findings emphasize the possibility that human-to-human transmission of vCJD might produce alternative neuropathological phenotypes and that lymphoid tissue examination of CJD cases classified as sporadic might reveal an infection by vCJD-type prions. They also provide evidence for the strong propensity of this agent to establish long-lasting, subclinical vCJD infection of lymphoreticular tissues, thus amplifying the risk for iatrogenic transmission.

The prion strain phenomenon: molecular basis and unprecedented features

Prions are unconventional infectious agents responsible for transmissible spongiform encephalopathies. Compelling evidences indicate that prions are composed exclusively by a misfolded form of the prion protein (PrP(Sc)) that replicates in the absence of nucleic acids. One of the most challenging problems for the prion hypothesis is the existence of different strains of the infectious agent. Prion strains have been characterized in most of the species. Biochemical characteristics of PrP(Sc) used to identify each strain include glycosylation profile, electrophoretic mobility, protease resistance, and sedimentation. In vivo, prion strains can be differentiated by the clinical signs, incubation period after inoculation and the lesion profiles in the brain of affected animals. Sources of prion strain diversity are the inherent conformational flexibility of the prion protein, the presence of PrP polymorphisms and inter-species transmissibility. The existence of the strain phenomenon is not only a scientific challenge, but it also represents a serious risk for public health. The dynamic nature and inter-relations between strains and the potential for the generation of a large number of new prion strains is the perfect recipe for the emergence of extremely dangerous new infectious agents.

Increased incidence of sporadic Creutzfeldt-Jakob disease in the age groups between 70 and 90 years in Belgium

From 1998 a prospective surveillance study of Creutzfeldt-Jakob disease (CJD) has been initiated in Belgium. In addition to epidemiological data, information on cerebrospinal fluid biomarkers, prion protein gene and brain neuropathology was collected. From 1-1-1998 to 31-12-2004, 188 patients were referred to the surveillance system. In 85 patients a 'definite' diagnosis of sporadic CJD (sCJD) could be made, whereas 26 patients remained 'probable'. We further identified two unrelated patients with an E200K mutation, and two patients with a seven octapeptide repeat insertion in one family. In one patient a familial history was noted but genetic analysis was not performed. In 72 patients different final diagnoses were made, Alzheimer's disease being the most frequent (N = 20). The demographic parameters of the Belgian population were similar to those observed in the rest of Europe. We did notice a significantly increased age-specific incidence (> 6/10(6)/year) of sCJD patients between 70 and 90 years old in the period 2002-2004 compared to 1998-2001 and retrospectively obtained data (1990-1997, p < 0.01). We undertook a detailed clinical and biochemical analysis to investigate this increase but could not identify any reason other than an increased vigilance for the diagnosis. In conclusion, our study identified that in the past sCJD may have been underestimated in patients over age 70 although these patients are both clinically and neurobiochemically similar to the general sCJD phenotype.

Is M129V of PRNP gene associated with Alzheimer's disease? A case-control study and a meta-analysis

The methionine/valine (M/V) polymorphism at codon 129 within the prion protein gene (PRNP) represents a known risk factor for Creutzfeldt-Jakob disease (CJD). Few authors reported also the effects of this polymorphism on the risk of Alzheimer's disease (AD), although with controversial results. To better clarify this issue, we performed a novel case-control study and a meta-analysis of published association studies between PRNP and AD. Our findings argue against PRNP as a susceptibility gene for developing AD in the Italian population but support the hypothesis that the V allele influences cognitive performances. The meta-analysis, revealed that Caucasian subjects homozygous at codon 129 had a 1.3-fold increased risk [95% CI: 1.0-1.6, p = 0.05] of developing AD compared to heterozygous individuals. We also observed that MM genotype and M allele represent a risk factor for AD, independently from the ethnic background, providing a significant but modest association between this polymorphism and AD.

The N-terminal cleavage of cellular prion protein in the human brain

Human brain cellular prion protein (PrP(c)) is cleaved within its highly conserved domain at amino acid 110/111/112. This cleavage generates a highly stable C-terminal fragment (C1). We examined the relative abundance of holo- and truncated PrP(c) in human cerebral cortex and we found important inter-individual variations in the proportion of C1. Neither age nor postmortem interval explain the large variability observed in C1 amount. Interestingly, our results show that high levels of C1 are associated with the presence of the active ADAM 10 suggesting this zinc metalloprotease as a candidate for the cleavage of PrP(c) in the human brain.

Analysis of the polymorphic prion protein gene codon 129 in idiopathic Parkinson's disease

Idiopathic Parkinson's disease (IPD) is a neurodegenerative disorder of unknown aetiology. Histopathological similarities between IPD and Creutzfeldt-Jakob prion disease (CJD) have been suggested. Homozygosity at polymorphic prion protein gene codon 129 (PRNP129) is a risk factor for developing CJD. Therefore we investigated a putative genetic link between CJD and IPD by studying PRNP129 genotype segregation in 81 patients with IPD. We did not ascertain a different PRNP129 genotype distribution in IPD patients compared to healthy Germans. We found a significant difference in PRNP129 genotype in dependence of the clinical predominance type of IPD. Patients with tremor-dominant IPD presented less frequent a methionine homozygosis at PRNP129 than hypokinetic-rigid IPD patients (30% versus 62.5%; p<0.033). In conclusion, genotype distribution at codon 129 is obviously not essential in determining IPD. But our results may provide first evidence of an association between certain PRNP129 polymorphisms and the clinical presentation of IPD.

Diffusion-weighted MRI in familial Creutzfeldt–Jakob disease with the codon 200 mutation in the prion protein gene

Magnetic resonance imaging (MRI) with diffusion-weighted imaging (DWI) has been reported to be a useful tool for early diagnosis of sporadic Creutzfeldt-Jakob disease (CJD). We report MRI findings with DWI, as well as with fluid-attenuated inversion recovery (FLAIR) and T1-weighted imaging (T1WI), in a case of familial CJD with a mutation at codon 200 of the prion protein gene. DWI in this patient showed high signal intensity in the basal ganglia and the cerebral cortex, similar to findings in sporadic CJD. In addition, T1WI showed areas of high signal intensity bilaterally in the globus pallidus. Despite the clinical diversity and atypical laboratory findings seen in familial CJD with the codon 200 mutation, these neuroimaging studies suggest that common regional distributions and a common pathogenesis might underlie the clinical progression both in sporadic CJD and in familial CJD with the codon 200 mutation in the prion protein gene. DWI abnormalities may be characteristic features that should be considered in the diagnosis of familial as well as of sporadic CJD.

The presence of valine at residue 129 in human prion protein accelerates amyloid formation

The polymorphism at residue 129 of the human PRNP gene modulates disease susceptibility and the clinico-pathological phenotypes in human transmissible spongiform encephalopathies. The molecular mechanisms by which the effect of this polymorphism are mediated remain unclear. It has been shown that the folding, dynamics and stability of the physiological, alpha-helix-rich form of recombinant PrP are not affected by codon 129 polymorphism. Consistent with this, we have recently shown that the kinetics of amyloid formation do not differ between protein containing methionine at codon 129 and valine at codon 129 when the reaction is initiated from the alpha-monomeric PrP(C)-like state. In contrast, we have shown that the misfolding pathway leading to the formation of beta-sheet-rich, soluble oligomer was favoured by the presence of methionine, compared with valine, at position 129. In the present work, we examine the effect of this polymorphism on the kinetics of an alternative misfolding pathway, that of amyloid formation using partially folded PrP allelomorphs. We show that the valine 129 allelomorph forms amyloids with a considerably shorter lag phase than the methionine 129 allelomorph both under spontaneous conditions and when seeded with pre-formed amyloid fibres. Taken together, our studies demonstrate that the effect of the codon 129 polymorphism depends on the specific misfolding pathway and on the initial conformation of the protein. The inverse propensities of the two allelomorphs to misfold in vitro through the alternative oligomeric and amyloidogenic pathways could explain some aspects of prion diseases linked to this polymorphism such as age at onset and disease incubation time.

Compassionate use of quinacrine in Creutzfeldt–Jakob disease fails to show significant effects

Quinacrine has been reported as an antiprion agent and proposed as an immediately applicable treatment for Creutzfeldt–Jakob disease (CJD). The authors report the results of an open compassionate procedure to which 32 CJD patients had access. In some genotypic subgroups, a slight but nonsignificant increase in survival was observed, likely due to biased inclusion of long-term surviving patients. There was no pathologic evidence of a beneficial effect of quinacrine treatment.

Methionine 129 Variant of Human Prion Protein Oligomerizes More Rapidly than the Valine 129 Variant

The human PrP gene (PRNP) has two common alleles that encode either methionine or valine at codon 129. This polymorphism modulates disease susceptibility and phenotype of human transmissible spongiform encyphalopathies, but the molecular mechanism by which these effects are mediated remains unclear. Here, we compared the misfolding pathway that leads to the formation of beta-sheet-rich oligomeric isoforms of the methionine 129 variant of PrP to that of the valine 129 variant. We provide evidence for differences in the folding behavior between the two variants at the early stages of oligomer formation. We show that Met(129) has a higher propensity to form beta-sheet-rich oligomers, whereas Val(129) has a higher tendency to fold into alpha-helical-rich monomers. An equimolar mixture of both variants displayed an intermidate folding behavior. We show that the oligomers of both variants are initially a mixture of alpha- and beta-rich conformers that evolve with time to an increasingly homogeneous beta-rich form. This maturation process, which involves no further change in proteinase K resistance, occurs more rapidly in the Met(129) form than the Val(129) form. Although the involvement of such beta-rich oligomers in prion pathogenesis is speculative, the misfolding behavior could, in part, explain the higher susceptibility of individuals that are methionine homozygote to both sporadic and variant Creutzfeldt-Jakob disease.

Coexistence of CJD and Alzheimer's disease: An autopsy case showing typical clinical features of CJD

The present report concerns an autopsy case of CJD showing typical clinical features of CJD. The patient was a Japanese woman without hereditary burden or dementing disorder anamnesis who was 70-years-old at the time of death. She developed gait disturbance at age 68, followed by memory impairment, visual disturbance, and myoclonus. A neurological examination approximately 2 months after the disease onset revealed akinetic mutism, in addition to periodic synchronous discharges on electroencephalogram. Serial neuroradiological examinations disclosed progressive atrophy of the brain. She died of bronchopneumonia 25 months after the disease onset. The brain weighed 560 g (cerebrum 490 g, brainstem with cerebellum 70 g). Macroscopically, neuropathological examination showed prominent atrophy of the cerebrum, caudate nucleus, and cerebellum, in addition to necrosis of the cerebral white matter, compatible with panencephalopathic CJD. Histologically, there was neuronal loss with or without spongiform change in the cerebral cortex, parahippocampal gyrus, amygdala, striatum, pallidum, thalamus, pontine nucleus, and cerebellar granule cells, in addition to diffuse synaptic-type prion staining in the cerebrum and cerebellum. Furthermore, senile plaques, compatible with definite Consortium to establish a registry for Alzheimer's disease rank Alzheimer's disease, and neurofibrillary changes of the limbic system, consistent with stage IV of Braak's classification, were found. Based on these clinicopathological findings and a review of the published literature, it is concluded that there were two forms of coexistence of CJD and Alzheimer's disease in the same patient.

Neuronal and astrocytic responses involving the serotonergic system in human spongiform encephalopathies

The relationships between the degree of cortical prion protein (PrP) deposition, tissue vacuolation and astrocytosis were studied in the frontal cortex of 27 cases of human spongiform encephalopathy, encompassing 13 cases of sporadic Creutzfeldt-Jakob disease (sCJD), four cases of familial CJD (fCJD) (one owing to E200K mutation, one owing to 144 bp insertion, one owing to P102L mutation and one owing to A117V mutation), five cases of iatrogenic CJD (iCJD) owing to growth hormone therapy and five cases of variant CJD (vCJD). The size and number of tryptophan hydroxylase (TPH) positive cells in the dorsal raphe were determined as an index of the function of the brain's serotonergic system. The amount of PrP deposited in frontal cortex in vCJD was significantly greater than that in both sCJD and iCJD, which did not differ significantly from each other. The extent of grey matter deposition of PrP correlated with that of white matter deposition. Deposition of PrP as plaques was greater in cases of sCJD bearing valine at codon 129 of PrP gene, especially when homozygous. However, all cases of vCJD displayed florid plaque formation yet these were homozygous for methionine at codon 129. Prion protein deposition as plaques was greater in cases of sCJD with 2A PrP isotype than those with 1 PrP isotype, similar to that seen in cases of vCJD all of which are 2B PrP isotype. There were no significant differences in the extent of astrocytosis between the different aetiological groups, in either grey or white matter, as visualized with glial fibrillary acidic protein (GFAP) or 5HT-2A receptor (5HT-2AR) immunostaining, although there was a strong correlation between the severity of 5HT-2AR and GFAP reactions within both grey and white matter. The extent of PrP deposition within the grey, but not white, matter correlated with the degree of astrocytosis for both GFAP and 5HT-2AR and the extent of tissue vacuolation in grey and white matter, although the latter did not correlate with degree of astrocytosis for either GFAP or 5HT-2AR. Astrocytes may be responding directly to the presence of PrP within the tissue, rather than the vacuolar damage to neurones. Although S100beta immunoreactivity was present in astrocytes in control cases, no S100beta staining was seen in astrocytes in either grey or white matter in most CJD cases. There were no differences in the number of TPH-positive cells between CJD and control cases, although the mean TPH-positive cell size was significantly greater, and cells were more intensely stained, in CJD compared to controls, suggesting a pathological overactivity of the brain's serotonergic system in CJD. This may result in excessive release of 5HT within the brain triggering increased 5HT-2AR expression within activated astrocytes leading to release and depletion of S100beta protein from such cells. The clinical symptoms of fluctuating attention and arousal could be mediated, at least in part, by such alterations in function of the serotonergic system.

Polymorphism of the codon 129 of the prion protein (PrP) gene and neuropathology of cerebral ageing

We studied whether codon 129 polymorphism of the PrP gene modulates the presence of tau- and Abeta-associated lesions among 188 patients over 70 years of age without evidence of dementia. Val allele carriers, either heterozygotes or homozygotes, were more frequently affected by Abeta-associated lesions than non Val allele carriers, whereas there were no differences for tau-positive neurones. Val allele carriers also had more focal and diffuse Abeta deposits. This association was most significant in the highest Braak's stages for neurofibrillary tangles (>/=III). In this group, cases with at least one Val allele had nearly twice as many Abeta-associated lesions. The most affected areas were the entorhinal cortex, TF-TH and the superior temporal cortex, where odds ratios for focal Abeta deposits ranged from 3.5 to 4.6.

Different chromogranin immunoreactivity between prion and a-beta amyloid plaque

Brain lesions in Creutzfeldt-Jakob disease (CJD) include spongiform change, neuronal loss, amyloid plaques, astrogliosis and microglial activation. Microglia are thought to play a key role in prion-induced neurodegeneration. However, the intermediate molecules supporting relationships between neurons and microglia are still unknown. Chromogranins (Cg) are soluble glycophosphoproteins that can activate microglial cells leading to a neurotoxic phenotype. The immunoreactive patterns of CgA and CgB were investigated in CJD and compared to those observed in Alzheimer's disease. We found that CgB, but not CgA, immunoreactivity was selectively associated with prion protein deposits, whereas CgA was only seen in Abeta plaques. This suggests a specific influence of the constitutive amyloid protein on chromogranin secretion and a role of CgB in the CJD neurodegenerative process.

Familial and sporadic fatal insomnia

Familial fatal insomnia (FFI)--a hereditary prion disease caused by a mutation at codon 178 of the prion-protein (PrP) gene (PRNP) that leads to a D178N substitution in the protein--and its sporadic form, sporadic fatal insomnia (SFI), have similar disease phenotypes. Both disorders have clinical features of disrupted sleep (loss of sleep spindles and slow-wave sleep and enacted dreams during rapid-eye-movement sleep), autonomic hyperactivation, and motor abnormalities (myoclonus, ataxia, dysarthria, dysphagia, and pyramidal signs). PET shows pronounced thalamic and limbic hypometabolism that becomes more widespread in later stages. Neuropathological assessment reveals severe neuronal loss and astrogliosis of the anterior medial thalamus and inferior olives, with later cerebral cortical and cerebellar involvement. Accumulation of an isoform of protease-resistant PrP fragment in FFI distinct from that found in a familial form of Creutzfeldt-Jakob disease with the same D178N mutation, shows the effect of the polymorphism at codon 129 of PRNP on phenotypic expression and the possibility of distinct prion "strains" with diverse pathological potential. Intriguing clinicopathological correlations in FFI and SFI suggest a role for the thalamolimbic system in the regulation of sleep and other circadian functions.

Dementia, the fate of brain? Neuropathological point of view

The prevalence of dementia dramatically increases during ageing, and this puts a serious strain on the optimism brought by the continuous increase in life expectancy observed in most industrialised countries. Diseases that produce dementia are numerous, and the cognitive deficit results from lesions of various regions and from different mechanisms. This modulates the possible prediction, prevention and cure of dementia. Emphasis is put on the necessity of, and prerequisite for, efficient research in the field of dementia. Three paradigmatic dementing disorders are reviewed. Subacute spongiform encephalopathies (prion diseases) constitute a biological enigma and a public health concern. In Alzheimer's disease and vascular or mixed dementia, the clinical diagnosis is still imperfect, and this hinders research. Distinguishing and accurately identifying the various types of dementia is essential for understanding their mechanism and for developing efficient therapeutic strategies, preventive and curative. For such objectives, the study of human brain tissue will remain mandatory until non-invasive markers and additional models are available. Ethical reasons banish the use of cerebral biopsy and favour the promotion of autopsy.

Two-dimensional mapping of three phenotype-associated isoforms of the prion protein in sporadic Creutzfeldt-Jakob disease

Transmissible spongiform encephalopathies (TSE), or prion diseases, are mammalian neurodegenerative disorders characterized by a conformational modification of the host-encoded prion protein (PrP(C)) into an isoform which is detergent-insoluble and partially resistant to protease treatment (PrP(Sc)). Distinct types of PrP(Sc), differing in conformation and variation in the relative amount of their glycoforms, have been associated with different phenotypes of TSE. In sporadic Creutzfeldt-Jakob disease (sCJD), two major types of PrP(Sc), with proteinase K (PK)-resistant fragments of 21 and 19 kDa, have been described. No consensus exists, however, on the molecular classification of PrP(Sc) in sCJD, since further heterogeneity within PrPSc conformers has been reported. We studied 19 subjects with dementia or dementia/ataxia at onset and 12 subjects with ataxia at onset. Following two-dimensional gel electrophoresis, we characterized PrP(C) and PrP(Sc) species in normal and sCJD brains by immunoblotting with antibodies recognizing N-terminal and C-terminal PrP regions. Three types of PrP(Sc) were detected in detergent-insoluble fractions from sCJD brains, mainly consisting of full-length PrP(Sc) in subjects with rapidly progressive dementia, and two different sets of amino-truncated PrP(Sc) glycoforms in subjects with dementia/ataxia and ataxia at onset. Examination of the PrP(Sc) core fragment, following PK treatment and deglycosylation, confirmed the existence of three distinctive patterns. These findings have immediate implications for the molecular classification of sCJD.

Biochemical and structural studies of the prion protein polymorphism

A hallmark event in transmissible spongiform encephalopathies is the conversion of the physiological prion protein into the disease-associated isoform. A natural polymorphism at codon 129 of the human prion gene, resulting in either methionine or valine, has profound influence on susceptibility and phenotypic expression of the disease in humans. In this study, we investigated the local propensity of synthetic peptides, corresponding to the region of the polymorphism and containing either methionine or valine, to adopt a beta-sheet-rich structure similar to the pathological protein. Circular dichroism studies showed that the methionine-containing peptide has a greater propensity to adopt a beta-sheet conformation in a variety of experimental conditions. The higher beta-sheet tendency of this peptide was also associated with an increased ability to aggregate into amyloid-like fibrils. These results suggest that methionine at position 129 of the prion protein increases its susceptibility to switch to the abnormal conformation, in comparison with the presence of valine at the same position.

PrP immunohistochemistry: different protocols, including a procedure for long formalin fixation, and a proposed schematic classification for deposits in sporadic Creutzfeldt-Jakob disease

The use of immunohistochemistry on formalin-fixed and paraffin-embedded tissue has greatly improved the neuropathological diagnosis of Creutzfeldt-Jakob disease and the other subacute spongiform encephalopathies in human and animals. Two pitfalls of this technique, however, currently exist: low sensitivity after long formalin fixation and difficulties in interpreting some images. Here we review the protocols currently in use for the pretreatment of sections allowing PrP detection by immunohistochemistry. In addition, a technique useful after long formalin fixation is reported: enzymatic digestion with proteinase K (24 degrees C, 1/100 for 8 minutes) was employed in addition to the usual autoclaving (121 degrees C for 10 minutes) followed by formic acid (99% for 5 minutes) and 4M guanidine thiocyanate (4 degrees C for 2 hours). This allowed a substantial increase in the sensitivity of 3F4 immunohistochemistry on paraffin-embedded tissue, especially after prolonged formalin fixation. In addition, we suggest a simple method for classification of PrP immunolabelling in sporadic Creutzfeldt-Jakob disease that would allow easy comparisons.