The nosology of Creutzfeldt-Jakob disease and conditions related to the accumulation of PrPCJD in the nervous system

Clarence J. Gibbs Effect and the "Creutzfeldt-Jakob Disease" Eponym

In 2014, American neurologist and Nobel laureate Stanley Prusiner reported that microbiologist Clarence Joseph Gibbs at the US NIH had intentionally, systematically, and mischievously used the eponym Creutzfeldt-Jakob disease, rather than Jakob-Creutzfeldt disease, because of the correspondence with Gibbs' own initials, to imply "Clarence Joseph disease." The present study examines temporal trends in the use of "Creutzfeldt-Jakob" and "Jakob-Creutzfeldt" in scientific articles and monographs from 1946 to 2019 to assess whether there was a "Clarence J. Gibbs effect" that influenced the general use of a specific eponym by the scientific community. During Gibbs' period of publication on Creutzfeldt-Jakob disease (CJD), there was an abrupt, dramatic, and steady increase in use of the CJD eponym while use of the Jakob-Creutzfeldt disease (JCD) eponym remained at a low level. In the period after Gibbs ceased to publish, there was a corresponding marked fall-off in use of the CJD eponym. Surviving collaborators thought Gibbs may have been joking, but in 1991 Gibbs had admitted what Prusiner reported. Regardless of motive, Gibbs strongly influenced the preferred eponym for this human prion disease by (1) publishing a seminal and highly referenced initial article in a high-profile journal; (2) sustained output of further important studies published in high-quality journals over more than 30 years; (3) professional affiliation with an esteemed national laboratory where he worked with a large number of high-profile colleagues; and (4) extensive collaborations with a large number of colleagues, who published multiple further articles using the eponym Gibbs preferred.

Exosomes and their role in the intercellular trafficking of normal and disease associated prion proteins

Over the past decade, small extracellular vesicles called exosomes have been observed to harbour protein and genetic cargo that can assist in health and also cause disease. Many groups are extensively investigating the mechanisms involved that regulate the trafficking and packaging of exosomal contents and how these processes may be deregulated in disease. Prion diseases are transmissible neurodegenerative disorders and are characterized by the presence of detectable misfolded prion proteins. The disease associated form of the prion protein can be found in exosomes and its transmissible properties have provided a reliable experimental read out that can be used to understand how exosomes and their cargo are involved in cell-cell communication and in the spread of prion diseases. This review reports on the current understanding of how exosomes are involved in the intercellular spread of infectious prions. Furthermore, we discuss how these principles are leading future investigations in developing new exosome based diagnostic tools and therapeutic drugs that could be applied to other neurodegenerative diseases.

X-ray structural and molecular dynamical studies of the globular domains of cow, deer, elk and Syrian hamster prion proteins

Misfolded prion proteins are the cause of neurodegenerative diseases that affect many mammalian species, including humans. Transmission of the prion diseases poses a considerable public-health risk as a specific prion disease such as bovine spongiform encephalopathy can be transferred to humans and other mammalian species upon contaminant exposure. The underlying mechanism of prion propagation and the species barriers that control cross species transmission has been investigated quite extensively. So far a number of prion strains have been characterized and those have been intimately linked to species-specific infectivity and other pathophysiological manifestations. These strains are encoded by a protein-only agent, and have a high degree of sequence identity across mammalian species. The molecular events that lead to strain differentiation remain elusive. In order to contribute to the understanding of strain differentiation, we have determined the crystal structures of the globular, folded domains of four prion proteins (cow, deer, elk and Syrian hamster) bound to the POM1 antibody fragment Fab. Although the overall structural folds of the mammalian prion proteins remains extremely similar, there are several local structural variations observed in the misfolding-initiator motifs. In additional molecular dynamics simulation studies on these several prion proteins reveal differences in the local fluctuations and imply that these differences have possible roles in the unfolding of the globular domains. These local variations in the structured domains perpetuate diverse patterns of prion misfolding and possibly facilitate the strain selection and adaptation.

Structural basis of prion inhibition by phenothiazine compounds

Conformational transitions of the cellular form of the prion protein, PrP(C), into an infectious isoform, PrP(Sc), are considered to be central events in the progression of fatal neurodegenerative diseases known as transmissible spongiform encephalopathies. Tricyclic phenothiazine compounds exhibit antiprion activity; however, the underlying molecular mechanism of PrP(Sc) inhibition remains elusive. We report the molecular structures of two phenothiazine compounds, promazine and chlorpromazine bound to a binding pocket formed at the intersection of the structured and the unstructured domains of the mouse prion protein. Promazine binding induces structural rearrangement of the unstructured region proximal to β1, through the formation of a "hydrophobic anchor." We demonstrate that these molecules, promazine in particular, allosterically stabilize the misfolding initiator-motifs such as the C terminus of α2, the α2-α3 loop, as well as the polymorphic β2-α2 loop. Hence, the stabilization effects of the phenothiazine derivatives on initiator-motifs induce a PrP(C) isoform that potentially resists oligomerization.

An overview of human prion diseases

Prion diseases are transmissible, progressive and invariably fatal neurodegenerative conditions associated with misfolding and aggregation of a host-encoded cellular prion protein, PrP^C. They have occurred in a wide range of mammalian species including human. Human prion diseases can arise sporadically, be hereditary or be acquired. Sporadic human prion diseases include Cruetzfeldt-Jacob disease (CJD), fatal insomnia and variably protease-sensitive prionopathy. Genetic or familial prion diseases are caused by autosomal dominantly inherited mutations in the gene encoding for PrP^C and include familial or genetic CJD, fatal familial insomnia and Gerstmann-Sträussler-Scheinker syndrome. Acquired human prion diseases account for only 5% of cases of human prion disease. They include kuru, iatrogenic CJD and a new variant form of CJD that was transmitted to humans from affected cattle via meat consumption especially brain. This review presents information on the epidemiology, etiology, clinical assessment, neuropathology and public health concerns of human prion diseases. The role of the PrP encoding gene (PRNP) in conferring susceptibility to human prion diseases is also discussed.

A case of dementia with PRNP D178Ncis-129M and no insomnia

OBJECTIVE

To describe a dementia case clinically diagnosed as Alzheimer disease with a PRNP genotype usually associated with familial fatal insomnia.

METHODS

Polymerase chain reaction amplification and subsequent direct sequencing of PGRN, MAPT, PSEN1, PSEN2, APP, and PRNP genes.

RESULTS

A point mutation (D178N) was found in the PRNP gene.

CONCLUSIONS

The mutation D178N in the PRNP gene associated with the M129 genotype is usually associated with familial fatal insomnia. However, a few cases have been reported with different clinical phenotypes. Here, we describe one of these cases and stress the importance of genetic screening of PRNP in early onset dementia cases.

Sporadic Creutzfeldt-Jakob disease--a review

The objective is to study a patient with sporadic Creutzfeldt-Jakob disease (CJD). The patient, a 70-year-old woman with a history spanning over 1 month, with acute onset, progressive abnormal behavior, and cognitive decline with generalized asymmetrical myoclonic jerking, startle phenomenon, and cortical blindness, was referred to the hospital. On observation of clinical symptoms, metabolic and hematological investigations, MRI (magnetic resonance imaging), and EEG (electroencephalogram) were done. The clinical symptoms, MRI, and diagnostic EEG were suggestive of sporadic CJD. Other metabolic encephalopathies were ruled out. With sodium valproate and clonezepam, her myoclonic jerks improved slightly. As CJD is an incurable disease, no definitive treatment could be given.

Disorder-to-order conformational transitions in protein structure and its relationship to disease

Function in proteins largely depends on the acquisition of specific structures through folding at physiological time scales. Under both equilibrium and non-equilibrium states, proteins develop partially structured molecules that being intermediates in the process, usually resemble the structure of the fully folded protein. These intermediates, known as molten globules, present the faculty of adopting a large variety of conformations mainly supported by changes in their side chains. Taking into account that the mechanism to obtain a fully packed structure is considered more difficult energetically than forming partially "disordered" folding intermediates, evolution might have conferred upon an important number of proteins the capability to first partially fold and-depending on the presence of specific partner ligands-switch on disorder-to-order transitions to adopt a highly ordered well-folded state and reach the lowest energy conformation possible. Disorder in this context can represent segments of proteins or complete proteins that might exist in the native state. Moreover, because this type of disorder-to-order transition in proteins has been found to be reversible, it has been frequently associated with important signaling events in the cell. Due to the central role of this phenomenon in cell biology, protein misfolding and aberrant disorder-to-order transitions have been at present associated with an important number of diseases.

Prion protein disease and neuropathology of prion disease

Human prion diseases, in common with other neurodegenerative diseases, may be sporadic or inherited and are characterized by the accumulation of cellular proteins accompanied by neuronal death and synaptic loss. Prion diseases are, however, unique in being transmissible. Central to the pathogenesis of all forms of prion disease is the prion protein. This article provides a brief overview of the biology of human prion diseases followed by a more in-depth discussion of the neuropathology of these diseases, including features of neuroradiologic relevance.

Prion disease

Prion diseases are a unique group of neurologic diseases caused by an abnormal protein conformation. Prion diseases encompass genetic, sporadic, iatrogenic, and acquired conditions in humans and other mammals. Although they are relatively rare, they produce a diverse array of symptoms, uniformly are fatal, and provide important information about proteins and degenerative neurobiology in addition to lessons about animal and human food chains.

Comparative neuropathology of Kuru with the new variant of Creutzfeldt-Jakob disease: evidence for strain of agent predominating over genotype of host

The three major influences on the phenotype of the transmissible spongiform encephalopathies are believed to be strain of agent, route of infection and host genotype. We have compared the pathologic profiles and genotypes of the new variant of Creutzfeldt-Jakob disease (vCJD) and kuru. The comparison reveals that there are distinct lesional differences particularly in the prion protein (PrP) load and distribution as seen by immunohistochemistry. The clinico-pathologic phenotypes and the genotypes of these two diseases are sufficiently different to suggest that the strain of agent may play a greater role than any presumptive common route of peripherally acquired infection.

Prion protein induced signaling cascades in monocytes

Prion proteins play a central role in transmission and pathogenesis of transmissible spongiform encephalopathies. The cellular prion protein (PrP(C)), whose physiological function remains elusive, is anchored to the surface of a variety of cell types including neurons and cells of the lymphoreticular system. In this study, we investigated the response of a mouse monocyte/macrophage cell line to exposure with PrP(C) fusion proteins synthesized with a human Fc-tag. PrP(C) fusion proteins showed an attachment to the surface of monocyte/macrophages in nanomolar concentrations. This was accompanied by an increase of cellular tyrosine phosphorylation as a result of activated signaling pathways. Detailed investigations exhibited activation of downstream pathways through a stimulation with PrP fusion proteins, which include phosphorylation of ERK(1,2) and Akt kinase. Macrophages opsonize and present antigenic structures, contact lymphocytes, and deliver cytokines. The findings reported here may become the basis of understanding the molecular function of PrP(C) in monocytes and macrophages.

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.

Species barriers in prion diseases--brief review

Transmissible spongiform encephalopathies (TSEs or prion diseases) are neurological disorders associated with the aggregation of a pathologic isoform of a host-encoded protein, termed prion protein (PrP). The pathologic isoform of PrP, termed PrP(Sc), is a major constituent of the infectious agent. TSE diseases are characterized by neurodegenerative failure and inevitable morbidity. Bovine spongiform encephalopathy (BSE) has been transmitted from cattle to humans to cause a new variant of Creutzfeldt-Jakob syndrome. The potential for chronic wasting disease to similarly cross the species barrier from cervids to humans is considered unlikely but possible. Thus, understanding how TSE agents overcome resistance to transmission between species is crucial if we are to prevent future epidemics. The species barrier usually can be abrogated to varying degrees in laboratory animals. Studies done with transgenic animals, tissue culture, and cell-free assays established PrP as being necessary for TSE pathogenesis and illustrated that certain amino acid residues are more influential than others for conferring resistance to TSE agent transmission. The essence of what constitutes a TSE agent's species compatibility is thought to be orchestrated by a complex interplay of contributions from its primary amino acid sequence, its glycoform patterns, and its three-dimensional structure.

Hearing Loss as the Initial Presentation of Creutzfeldt-Jakob Disease

Creutzfeldt-Jakob disease is a rare type of spongiform encephalopathy. Affected patients present with constitutional symptoms, which progress to severe mental deterioration and movement disorders. Dizziness is the most common early otologic symptom. Few reports in the literature describe patients with Creutzfeldt-Jakob disease who present with sudden-onset hearing loss as their primary symptom for seeking treatment. This paper discusses one such patient and reviews the clinical presentation, treatment options, and relevant literature.

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.

Creutzfeldt-Jakob disease: two case studies

Creutzfeldt-Jakob disease (CJD) is a rapidly progressive, neurodegenerative disorder causing dramatic neuromuscular symptoms, profound dementia, and death. In this article, the epidemiology, etiology, modes of transmission, clinical manifestations, determination of possible/probable CJD diagnosis in life, and the postmortem neuropathology of definite CJD are discussed in depth. Case studies of two individuals, each affected by different subtypes of sporadic Creutzfeldt-Jakob disease (sCJD), are presented, along with a discussion of the many challenging nursing and psychosocial issues surrounding the supportive care of these individuals and families in life and death.

Neuropathology of prion diseases

In prion diseases, neuropathology has remained the most important tool to give a definite diagnosis, and neuropathological research has contributed significantly to our current pathogenetic understanding. Immunohistochemistry for the disease-associated prion protein (PrP(Sc)) is indispensable for the neuropathological confirmation of prion diseases. The amount and distribution of PrP(Sc) deposits do not always correlate with type and severity of local tissue damage. PrP(Sc) deposition occurs only where neuronal parenchyma is present; in scarred infarctions with prominent gliosis, PrP(Sc) does not accumulate. Early, severe and selective loss affects a subset of inhibitory GABAergic neurons both in human and experimental prion diseases. The central pathogenetic cascade includes oxidative stress to neurons and their apoptosis. New patterns of PrP(Sc) immunoreactivity include granular ganglionic and tiny adaxonal PrP(Sc) deposits in peripheral nervous tissue, and dendritic cells and macrophages in vessel walls, suggesting that mobile haematogenous cells may be involved in spread of prions.

Introduction to the transmissible spongiform encephalopathies or prion diseases

Sheep scrapie has been known for at least 200 years and was described as a transmissible disease over 100 years ago. Since then, three groups of transmissible spongiform encephalopathies or TSE diseases have been identified in humans including familial, infectious and sporadic types. The discovery of the prion protein (PrP) in the 1980s greatly accelerated knowledge of the biology and pathogenesis of TSE diseases as this protein was found to play a critical role in disease susceptibility and the TSE species-barrier and may also be a component of the infectious agent itself. Nevertheless, the nature of the TSE agents remains an enigma. Proof of the protein-only hypothesis may require generation of biologically active transmissible agent in a cell-free environment where a virus cannot replicate. Conversely, proof of a viral aetiology will require identification and isolation of a candidate virus. Further understanding of the structure of the disease-associated protease-resistant PrP should help elucidate the mechanism of PrP conversion from the normal to the abnormal form. Such information should open up new approaches to both diagnosis and therapy.

Prion disease resembling frontotemporal dementia and parkinsonism linked to chromosome 17

OBJECTIVE

To compare the clinical features of a familial prion disease with those of frontotemporal dementia and parkinsonism linked to chromosome 17 (FTDP-17).

BACKGROUND

Prion diseases are not usually considered in the differential diagnosis of FTDP-17, since familial Creutzfeldt-Jakob disease (CJD), the most common inherited prion disease, often manifests as a rapidly progressive dementia. Conversely, FTDP-17 usually has an insidious onset in the fifth decade, with abnormal behavior and parkinsonian features.

METHOD

We present the clinical features of 12 patients from a family with CJD associated with a point mutation at codon 183 of the prion protein gene.

RESULTS

The mean age at onset was 44.0 +/- 3.7; the duration of the symptoms until death ranged from two to nine years. Behavioral disturbances were the predominant presenting symptoms. Nine patients were first seen by psychiatrists. Eight patients manifested parkinsonian signs.

CONCLUSION

These clinical features bear a considerable resemblance to those described in FTDP-17.

Diffusion-weighted MRI in two cases of familial Creutzfeldt--Jakob disease

Diffusion-weighted magnetic resonance imaging (DWI) has been described as a useful tool for the diagnosis of sporadic Creutzfeldt--Jakob disease (CJD). To our knowledge, DWI abnormalities have not previously been reported in familial CJD. In two patients with familial CJD associated with distinct mutations at codon 183 and at codon 210 of the prion protein gene, DWI showed a high signal in the basal ganglia and in the cerebral cortex. These abnormalities are similar to those described in sporadic CJD. This observation expands the value of DWI for the diagnosis of some forms of familial CJD. It remains to be investigated whether this finding also holds for CJD associated with other mutations of the prion protein gene.

Intracerebral distribution of the abnormal isoform of the prion protein in sporadic Creutzfeldt-Jakob disease and fatal insomnia

Molecular genetics and protein chemistry have led to major advances in our understanding of the molecular basis of phenotypic variability of prion diseases. A large body of evidence indicates that a common methionine/valine polymorphism at codon 129 in the prion protein gene (PRNP), alone or in conjunction with PRNP mutations, modulates both disease susceptibility and phenotypic expression of human prion diseases. In addition, there are physicochemical properties of the abnormal isoform of the prion protein (PrP(sc)), such as relative molecular mass and glycosylation, that correlate with distinct phenotypes even in subjects carrying the same PRNP genotype. Different PrP(sc) "type"-PRNP genotype combinations are found associated with pathological phenotypes that differ in the relative severity of lesions among distinct brain regions, the presence and morphology of certain lesions such as amyloid plaques, and the pattern of intracerebral and tissue deposition of PrP(sc). This review summarizes the currently available data on the molecular pathology of sporadic Creutzfeldt-Jakob disease, the most common human prion disease, and fatal insomnia, a more recently defined entity that has rapidly become one of the best characterized of the human prion diseases.

Creutzfeldt-Jakob disease and the eye. I. Background and patient management

This article attempts to summarise our current understanding of TSEs as they affect man. Specific aspects relevant to ophthalmological practice, in particular the management of patients in day-to-day clinical practice and with respect to corneal transplantation, have been discussed. In the companion article we discuss the specific ophthalmic and neuro-ophthalmic features of these diseases.

Transmissible spongiform encephalopathies in humans

Creutzfeldt-Jakob disease (CJD), the first transmissible spongiform encephalopathy (TSE) to be described in humans, occurs in a sporadic, familial, or iatrogenic form. Other TSEs in humans, shown to be associated with specific prion protein gene mutations, have been reported in different parts of the world. These TSEs compose a heterogeneous group of familial diseases that traditionally have been classified as familial CJD, Gerstmann-Sträussler-Scheinker syndrome, or fatal familial insomnia. In 1996, a newly recognized variant form of CJD among young patients (median age, 28 years) with unusual clinical features and a unique neuropathologic profile was reported in the United Kingdom. In the absence of known CJD risk factors or prion protein gene abnormalities, the UK government concluded that the clustering of these cases may represent transmission to humans of the agent causing bovine spongiform encephalopathy. Additional epidemiologic and recent laboratory data strongly support the UK government's conclusion.

Neuropathology of prion diseases

Prion diseases include sporadic forms such as Creutzfeldt-Jakob disease (CJD), familial forms (familial CJD), fatal familial insomnia, Gerstmann-Sträussler-Scheinker disease, and acquired forms (i.e., kuru, iatrogenic CJD). The most frequent of the latter include acquired forms secondary to injections of human cadaveric pituitary-derived growth hormone and the new variant of CJD--probably related to bovine spongiform encephalopathy. The communal lesions are neuronal loss, spongiosis and gliosis and, inconstantly, the presence of amyloid plaques and different kinds of small deposits immunolabeled with anti-prion (PrP) antibodies. Their number and topography are variable. Recent works have shown the role of the host genotype, especially of codon 129, in the susceptibility to these diseases. We have tried to correlate neuropathology with the genotype of codon 129 and the type of PrP to establish a molecular classification.

Expression of proteins linked to exocytosis and neurotransmission in patients with Creutzfeldt-Jakob disease

In order to characterize synaptic involvement in human spongiform encephalopathies, the expression of synaptic vesicle-associated proteins, synaptophysin and synapsin-I, and presynaptic plasma membrane proteins, synaptosomal-associated protein of 25 kDa (SNAP-25) and syntaxin-I, was examined in the brains of four patients who had suffered from sporadic Creutzfeldt-Jakob disease. Nerve cell loss, spongiform degeneration, astrocytosis, and deposition of prion protein (PrP) were observed in the cerebral cortex in every case. Decreased immunoreactivity for synaptophysin, synapsin-I, SNAP-25, and syntaxin-I was observed in the cerebral cortex in every case, thus showing generalized reduction of proteins involved in exocytosis of synaptic vesicles in the brains of patients with spongiform encephalopathy. Upregulation of synaptophysin and SNAP-25, a feature associated with beta A4 deposits in Alzheimer's disease (AD), was not observed in associated with PrP deposition. The present results indicate that synaptic pathology is a major event in spongiform encephalopathy, and suggest that synaptic loss, together with neuron loss and selective involvement of certain populations of local-circuit neurons, as shown in other studies, may account for the dramatic neurological decay and for the main neurological symptoms in patients with CJD.

Wernicke encephalopathy-like symptoms as an early manifestation of Creutzfeldt-Jakob disease in a chronic alcoholic

A case of Creutzfeldt-Jakob disease (CJD) with presenting Wernicke encephalopathy (WE)-like symptoms and severe insomnia is presented. An 80-year-old alcoholic man with a 6 month history of tremors, ataxia, memory loss and confabulation, developed profound insomnia, confusion, and delirium with vivid hallucinations. Polysomnography revealed a marked reduction of sleep time, with central-type sleep apnea. Neither myoclonus nor periodic synchronous discharge (PSD) was observed. An autopsy revealed diffuse spongiform changes and astrocytosis throughout the cerebral gray matter, with severe involvement of the mammillary bodies and thalamus. Prion protein (PrP) immunostaining was positive in kuru plaques in the cerebellum, PrP polymorphism at codon 129 was heterozygous Met/Val, and proteinase K resistant PrP (PrP(res)) was demonstrated by Western blotting. The lack of necrotizing lesions in the mammillary bodies, thalamus, and periaqueductal gray matter could rule out WE. The data suggest that the present case of CJD is consistent with PrP(res) type 2 (CJD M/V 2), but was unique in the lack of some typical CJD signs and the presence of signs of WE and sleep abnormalities.

Prion diseases in man

Prion diseases are uncommon fatal neurodegenerative disorders which have gained scientific and public importance as a result of major advances in the understanding of the nature of the causative agent, and the emergence of new forms of these diseases in both animals and man. The transmissible agent in prion diseases is unique and is closely associated with an abnormal isoform of a widely distributed cell-surface glycoprotein, prion protein. The precise mechanisms of conversion to the abnormal isoform are unknown; changes in protein folding are of major importance. The abnormal isoform of the protein accumulates in the central nervous system in all prion diseases, but the processes involved in protein accumulation and the pathogenesis of neuronal dysfunction and cell death are poorly understood. Human prion diseases occur as sporadic, familial, and acquired disorders, the most recently identified of which is new variant Creutzfeldt-Jakob disease, which has been aetiologically linked to exposure to the bovine spongiform encephalopathy agent through the food chain. Surveillance of human prion diseases will be crucial in the assessment of the impact of this new disease in the United Kingdom and elsewhere. Effective surveillance depends on accurate diagnosis, which in turn places a high priority on autopsy in suspected cases; neuropathology is essential for the diagnosis of human prion diseases. Phenotypic variation is prominent in all forms of human prion disease; future classifications of these disorders are likely to incorporate genetic and biochemical data in addition to clinical and pathological parameters.

Prion diseases: what will be next?

Images

Familial spongiform encephalopathy associated with a novel prion protein gene mutation

Human prion diseases include Creutzfeldt-Jakob disease, Gerstmann-Stráussler-Scheinker disease, fatal familial insomnia, and kuru. Each of these diseases has a specific clinical presentation while spongiform encephalopathy, neuronal loss, and gliosis are their neuropathological hallmarks. We studied a Brazilian family with an autosomal dominant form of dementia. Nine members of the family were affected by a dementia with frontotemporal clinical features, with a mean age at onset of 44.8 +/- 3.8 years and a mean duration of symptoms of 4.2 +/- 2.4 years. Neuropathological examination of 3 patients showed severe spongiform change and neuronal loss in the deep cortical layers and in the putamen, but minimal gliosis in the most severely affected areas. The putamen and cerebellum, but not other areas of the affected brain, displayed prion protein immunoreactivity. A novel prion protein gene mutation causing a nonconservative substitution at codon 183 was identified in 2 neuropathologically confirmed affected individuals (mother and son). The mutation was transmitted in a mendelian fashion to 12 members of the family. Therefore, we identified a novel prion disease variant characterized by an early onset and long duration of the symptoms, severe spongiform change with minimal gliosis, associated with a prion protein gene mutation at codon 183.

Prion diseases: transmission from mad cows?

Prion diseases in humans show considerable clinical and pathological heterogeneity. The identification of a new variant of Creutzfeldt-Jakob disease, and its interpretation as evidence of transmission of mad cow disease to man, rely critically on our understanding of the epidemiology of prion diseases.

Interactions between wild-type and mutant prion proteins modulate neurodegeneration in transgenic mice

Transgenic mice overexpressing approximately eightfold the mouse (Mo) prion protein (PrP) gene carrying the P102L mutation of GSS developed neurodegeneration between 150 and 300 days of age, while controls expressing the wild-type MoPrP-A transgene at the same level remained healthy. Mice overexpressing the wild-type MoPrP-A transgene were highly susceptible to inoculated mouse prions, exhibiting abbreviated scrapie incubation times of 45 days. After crossing the mutant transgene onto a null (Prnp 0/0) background, the resulting Tg(MoPrP-P101L)Prnp 0/0 mice displayed a highly synchronous onset of illness at 145 days of age, which was shortened to 85 days upon breeding to homozygosity for the transgene array. Besides occasional PrP plaques and modest spongiform degeneration, Tg(MoPrP-P101L) mice suffered from a myopathy and a peripheral neuropathy. Disruption of the wild-type MoPrP gene increased the number of PrP plaques and the severity of spongiform degeneration. Brain extracts prepared from spontaneously ill transgenic mice transmitted disease to Tg196/Prnp 0/0 mice, expressing low levels of the mutant transgene. Our results demonstrate that the presence of wild-type PrP genes, the level of PrP transgene expression, and the sequence of the transgene can profoundly modify experimental prion disease.

Molecular basis of phenotypic variability in sporadic Creutzfeldt-Jakob disease

We sequenced the prion protein gene and studied the biochemical characteristics and the intracerebral distribution of protease-resistant prion protein with Western blot and immunohistochemistry in 19 cases of sporadic Creutzfeldt-Jakob disease. We identified four groups of subjects defined by the genotype at codon 129 of the prion protein gene, the site of a common methionine/valine polymorphism, and two types of protease-resistant prion proteins that differed in size and glycosylation. The four Creutzfeldt-Jakob disease groups showed distinct clinicopathological features that corresponded to previously described variants. The typical Creutzfeldt-Jakob disease phenotype or myoclonic variant and the Heidenhain variant were linked to methionine homozygosity at codon 129 and to "type 1" protease-resistant prion protein. The atypical and rarer variants such as that with dementia of long duration, the ataxic variant, and the variant with kuru plaques were linked to different genotypes at codon 129 and shared the "type 2" protease-resistant prion protein. Our data indicate that the sporadic form of Creutzfeldt-Jakob disease comprises a limited number of variants. The methionine/valine polymorphism at codon 129 of the prion protein gene and two types of protease-resistant prion proteins are the major determinants of these variants. These findings suggest the existence of prion strains in humans and provide the molecular basis for a novel classification of sporadic Creutzfeldt-Jakob disease.

Classification of dementia and Alzheimer's disease

Classification of dementia involves the recognition of its presence, followed by the differential diagnosis of its cause. Informant-based methods for dementia detection can be highly sensitive, even when cognitive impairment is mild. Alzheimer's disease (AD) is by far the leading cause of dementia; standardized clinical criteria result in high diagnostic accuracy rates. Classification of other dementing disorders is less satisfactory, particularly because there is frequent clinical and pathological overlap with AD. After AD, the most common causes of dementia are vascular dementia and dementia in persons with Parkinson's disease. Less common dementias include progressive supranuclear palsy, Huntington's disease, Pick's disease, Creutzfeldt-Jakob disease, and inherited metabolic disorders, most of which are extremely rare. Identifying the cause of dementia is important because some forms can be treated with currently available therapies. In instances involving genetically transmitted disease, genetic testing and counseling of family members may be advisable.

Human prion diseases

The classical prion diseases in man comprise Creutzfeldt-Jakob disease (CJD), Kuru and Gerstmann-Sträussler-Scheinker syndrome (GSS). Recent advances in the biochemistry and the molecular biology of the transmissible agents responsible for these human spongiform encephalopathies have prompted renewed interest in their clinical and pathological features. A broadening spectrum of human prion diseases has now been identified including novel entities such as Fatal Familial Insomnia and variants of CJD and GSS characterised by specific abnormalities in the human prion protein (PrP) gene on chromosome 20. Accumulation of PrP in the central nervous system is a characteristic feature of all these disorders, although the relationship between PrP localisation, classical neuropathology, clinical features and genotype still requires clarification. A national surveillance project for CJD was established in 1990 in the United Kingdom in order to assess the possible implications of bovine spongiform encephalopathy for human health. The identification of an apparently new variant of CJD in young patients in UK raises the possibility of such a link; further studies are required to assess the significance of this observation.

Neuropathological diagnostic criteria for Creutzfeldt-Jakob disease (CJD) and other human spongiform encephalopathies (prion diseases)

Neuropathological diagnostic criteria for Creutzfeldt-Jakob disease (CJD) and other human transmissible spongiform encephalopathies (prion diseases) are proposed for the following disease entities: CJD--sporadic, iatrogenic (recognised risk) or familial (same disease in 1st degree relative): spongiform encephalopathy in cerebral and/or cerebellar cortex and/or subcortical grey matter; or encephalopathy with prion protein (PrP) immunoreactivity (plaque and/or diffuse synaptic and/or patchy/perivacuolar types). Gerstmann-Sträussler-Scheinker disease (GSS) (in family with dominantly inherited progressive ataxia and/or dementia): encephalo(myelo)pathy with multicentric PrP plaques. Familial fatal insomnia (FFI) (in member of a family with PRNP178 mutation): thalamic degeneration, variable spongiform change in cerebrum. Kuru (in the Fore population). Without PrP data, the crucial feature is the spongiform change accompanied by neuronal loss and gliosis. This spongiform change is characterised by diffuse or focally clustered small round or oval vacuoles in the neuropil of the deep cortical layers, cerebellar cortex or subcortical grey matter, which might become confluent. Spongiform change should not be confused with non-specific spongiosis. This includes status spongiosus ("spongiform state"), comprising irregular cavities in gliotic neuropil following extensive neuronal loss (including also lesions of "burnt-out" CJD), "spongy" changes in brain oedema and metabolic encephalopathies, and artefacts such as superficial cortical, perineuronal, or perivascular vacuolation; focal changes indistinguishable from spongiform change may occur in some cases of Alzheimer's and diffuse Lewy body diseases. Very rare cases might not be diagnosed by these criteria. Then confirmation must be sought by additional techniques such as PrP immunoblotting, preparations for electron microscopic examination of scrapie associated fibrils (SAF), molecular biologic studies, or experimental transmission.