The prion diseases

The human prion diseases are fatal neurodegenerative maladies that may present as sporadic, genetic, or infectious illnesses. The sporadic form is called Creutzfeldt-Jakob disease (CJD) while the inherited disorders are called familial (f) CJD, Gerstmann-Straussler-Scheinker (GSS) disease and fatal familial insomnia (FFI). Prions are transmissible particles that are devoid of nucleic acid and seem to be composed exclusively of a modified protein (PrPSc). The normal, cellular PrP (PrPC) is converted into PrPSc through a posttranslational process during which it acquires a high beta-sheet content. In fCJD, GSS, and FFI, mutations in the PrP gene located on the short arm of chromosome 20 are the cause of disease. Considerable evidence argues that the prion diseases are disorders of protein conformation.     

Stimulated gracilis neosphincter: a new procedure for anal incontinence

Creutzfeldt-Jakob disease (CJD) is a transmissible neurodegenerative disorder characterized by the accumulation of proteinase-resistant prion protein (PrP) in the brain. Pathological changes in the cerebellum are common and include atrophy of the granular layer, spongiform change in the molecular layer, and astrocytic gliosis of the cerebellar cortex and white matter. In most cases of sporadic CJD immunohistochemistry for PrP shows widespread granular deposits of the scrapie isoform of the prion protein (PrPSc) in the cerebellar cortex. In a minority of cases plaque-like deposits of PrPSc are detectable. The genetic background of this phenomenon was investigated in 47 cases of sporadic CJD. Immunohistochemistry using antibodies against PrP was performed in brain autopsy specimens. A genetic analysis of the prion protein gene (PRNP) showed overrepresentation of homozygosity for either methionine (M/M) or valine (V/V) at the polymorphic codon 129 in CJD patients as compared to 74 controls. No significant difference in allele frequency between the 2 groups was found. Plaques or plaque-like PrPSc deposits were found in 9 cases of CJD and were associated with the presence of valine at codon 129 on at least 1 allele of PRNP. CJD patients homozygous for valine (V/V) were on an average more than 5 years younger than patients with M/M or M/V at codon 129.     

Differential allelic expression of PrP mRNA in carriers of the E200K mutation

Creutzfeldt-Jakob disease (CJD) linked to the E200K mutation of the prion protein (PrP) gene presents with a wide range of age at disease onset. Since most patients are heterozygous for the mutation, we tested whether differential expression of mutant versus wild-type (wt) PrP may affect the age at disease onset in carriers of the mutation. We measured wt and mutant PrP protein and mRNA in Epstein-Barr virus (EBV)-transformed B cells of either E200K CJD patients or healthy E200K carriers. Our results suggests that while in most healthy carriers the expression of wt PrP was higher than that of E200K PrP, most of the E200K CJD patients express equal levels of both PrP proteins. Similar results were obtained for either PrP protein or PrP mRNA. These results suggest that preferential expression of PrP from the wt allele may modulate the outbreak of the disease in carriers of prion mutations. This notion is consistent with the results obtained in transgenic mice carrying a human PrP gene, which suggest that endogenous PrP protects mice from contracting scrapie after inoculation with human CJD brain. Similar mechanisms may prevail in other inherited diseases with variable phenotypes.     

Abnormal properties of prion protein with insertional mutations in different cell types

Inherited forms of the human transmissible spongiform encephalopathy Creutzfeldt-Jakob disease (CJD) have been associated with mutations in the normal soluble, protease-sensitive form of the host prion protein (PrP-sen). Normal PrP protein contains five copies of a repeating eight-amino acid region, and PrP molecules with six or more copies of this region are associated with disease in familial CJD. It has been hypothesized that these mutations might facilitate spontaneous formation of the abnormal, aggregated protease-resistant PrP isoform, PrP-res, associated with clinical CJD and other transmissible spongiform encephalopathies (TSE). In the present experiments, hamster PrP molecules with 5 (wild-type), 7, 9, or 11 copies of this repeat region were generated and expressed in mouse fibroblast cells or mouse neuroblastoma cells. In mouse fibroblast cells, mutant hamster PrP molecules expressing 7, 9, and 11 copies of the octapeptide repeat sequence showed altered cell surface expression, but both mutant and wild-type hamster PrP-sen molecules demonstrated abnormal properties of aggregation and increased protease resistance. By contrast in mouse neuroblastoma cells, hamster PrP-sen with 5, 9, and 11 octapeptide repeats were expressed normally on the cell surface, but only PrP-sen molecules with 9 or 11 copies of the repeat motif had abnormal properties of aggregation and increased protease resistance. Overall, regardless of cell type, hamster PrP molecules with greater than 7 octapeptide repeats were more aggregated and more protease-resistant than molecules with 7 repeats or less. However, these abnormal molecules were at least 1000-fold less protease-resistant than bona fide PrP-res derived from TSE-infected brain tissue, and they showed no increased ability to form PrP-res in a cell-free system.     

New variant Creutzfeldt-Jakob disease: neurological features and diagnostic tests

BACKGROUND: In April, 1996, ten cases of Creutzfeldt-Jakob disease (CJD) with an apparently new clinicopathological phenotype were published and it was suggested that these new variant cases (nvCJD) might be causally linked to bovine spongiform encephalopathy (BSE). There have now been 21 cases of nvCJD in the UK and one case in France. We report clinical features and diagnostic test results of the first 14 cases of nvCJD in the UK. METHODS: Case ascertainment of CJD was mainly by direct referral from neurologists and neuropathologists. Clinical and investigate details were obtained by interview with patients' relatives and by examination of case notes. Ten cases in this report were examined while alive. Prion protein (PrP) gene analysis was carried out with informed consent from the patient or from a relative. The diagnosis of nvCJD was established histologically. FINDINGS: Eight cases were women. Mean age at onset of symptoms was 29 (16-48) years and the median duration of illness was 14 (9-35) months. All patients had early psychiatric symptoms, most often depression, and 13 were seen by a psychiatrist early in the clinical course. Eight patients developed early sensory symptoms which were persistent and often painful. Neurological signs, including ataxia and involuntary movements, developed in all cases and towards the end of the illness, most had akinetic mutism. The electroencephalogram was abnormal in most patients but typical periodic complexes of CJD were not seen in any case. Cerebral imaging was usually normal or showed non-specific abnormalities; in two cases magnetic-resonance imaging scans showed high signal in the thalamus. INTERPRETATION: Clinical features in these cases are similar and relatively distinct from other forms of CJD, suggesting that this is a new clinical phenotype consistent with a single strain of infectious agent. There is, however, some overlap with atypical cases of sporadic CJD, and the diagnosis of nvCJD remains dependent on neuropathological confirmation.     

Complete penetrance of Creutzfeldt-Jakob disease in Libyan Jews carrying the E200K mutation in the prion protein gene

BACKGROUND: Creutzfeldt-Jakob disease (CJD) is a prion disease which is manifest as a sporadic, inherited, and transmissible neurodegenerative disorder. The mean age at onset of CJD is approximately 60 years, and as such, many people destined to succumb undoubtedly die of other illnesses first. The delayed onset of CJD has complicated the analysis of inherited forms of the illness and led to the suggestion that mutations in the prion protein (PrP) gene are necessary but not sufficient for prion disease despite genetic linkage; indeed, an environmental factor such as a ubiquitous virus has been proposed as a second necessary factor. MATERIALS AND METHODS: To examine what appeared to be incomplete penetrance, we applied a life-table analysis to clinical and pedigree data from a cluster population of Libyan Jews in which the E200K mutation is prevalent. The study population included 42 affected and 44 unaffected members of 13 Libyan Jewish families, all of whom possessed the E200K mutation. RESULTS: The calculated value using life table analysis is 0.77 at age 70 which increases to 0.89 if a mutation carrier survives to age 80 and 0.96 if age 80 is surpassed. CONCLUSIONS: These data argue that the E200K mutation alone is sufficient to cause prion disease and does so in an age-dependent manner.     

Effect of the D178N mutation and the codon 129 polymorphism on the metabolism of the prion protein

Prion diseases are thought to be caused by the conversion of the normal, or cellular, prion protein (PrPC)(PrPres). There are three familial forms of human prion disease, Creutzfeldt-Jakob disease (CJD), Gerstmann-Straussler-Scheinker syndrome, and fatal familial insomnia (FFI) which are all expressed at advanced age despite the congenital presence of the mutant prion protein (PrPM). The cellular mechanisms that result in the age-dependent conversion of PrPM into PrPres and the unique phenotypes associated with each PrPM are unknown. FFI and a familial type of Creutzfeldt-Jakob disease (CJD178), share the D178N mutation in the PrP gene but have distinct phenotypes linked to codon 129, the site of a methionine/valine polymorphism (129M/V). We analyzed PrP processing in cells transfected with constructs reproducing the FFI and CJD178 genotypes. The D178N mutation results in instability of the mutant PrP which is partially corrected by N-glycosylation. Hence, only the glycosylated forms of PrPM reach the cell surface whereas the unglycosylated PrPM is also under-represented in the brain of FFI patients validating the cell model. These results offer new insight into the effect of the D178N mutation on the metabolism of the prion protein.     

An unusual case of Creutzfeldt-Jakob disease

A patient with histopathologically verified sporadic Creutzfeldt-Jakob disease (CJD) presented initially with diplopia, sleep disturbances, and L-dopa-responsive parkinsonism. After more than a year of slow progression, he did not become demented, and failed to fulfill the clinical criteria for possible CJD. No clinical examinations currently proposed to detect CJD showed the disease. CJD should be in the differential diagnosis of "parkinson plus" syndromes until a different etiology has been found or a histopathologic examination performed.     

Prions

Prions are unprecedented infectious pathogens that cause a group of invariably fatal neurodegenerative diseases by an entirely novel mechanism. Prion diseases may present as genetic, infectious, or sporadic disorders, all of which involve modification of the prion protein (PrP). Bovine spongiform encephalopathy (BSE), scrapie of sheep, and Creutzfeldt-Jakob disease (CJD) of humans are among the most notable prion diseases. Prions are transmissible particles that are devoid of nucleic acid and seem to be composed exclusively of a modified protein (PrPSc). The normal, cellular PrP (PrPC) is converted into PrPSc through a posttranslational process during which it acquires a high beta-sheet content. The species of a particular prion is encoded by the sequence of the chromosomal PrP gene of the mammals in which it last replicated. In contrast to pathogens carrying a nucleic acid genome, prions appear to encipher strain-specific properties in the tertiary structure of PrPSc. Transgenetic studies argue that PrPSc acts as a template upon which PrPC is refolded into a nascent PrPSc molecule through a process facilitated by another protein. Miniprions generated in transgenic mice expressing PrP, in which nearly half of the residues were deleted, exhibit unique biological properties and should facilitate structural studies of PrPSc. While knowledge about prions has profound implications for studies of the structural plasticity of proteins, investigations of prion diseases suggest that new strategies for the prevention and treatment of these disorders may also find application in the more common degenerative diseases.     

PET imaging using dual-headed gamma cameras: an update

The method of in situ end-labeling of nuclear DNA fragmentation was used in the study of ten patients (two biopsies, eight autopsies) with sporadic Creutzfeldt-Jakob disease (CJD). All the patients had the typical morphological lesions including neuron loss, spongiform change and astrocytosis. Four of them also showed prion protein (PrP) deposits in the cerebral cortex, and two of them kuru-like plaques in the cerebellum. A few cells with DNA breaks were found in the two biopsy cases; one of them, suffering from a panencephalopathic form of the disease, showed positive nuclei not only in the cerebral cortex but also in the subcortical white matter. Variable numbers of positive nuclei were observed in the gray and white matter in the eight autopsy cases, in which, although the distribution of positive cells roughly correlated with the distribution of neuron loss, no clear relationship was found as regards the distribution and degree of cell labeling and the degree of neuron loss. Furthermore, large numbers of positive cells were concentrated in a particular area, whereas a few cells were seen in a neighboring equally affected area. Positive glial cells in the plexiform layer of the CA1 area of the hippocampus, and in the frontal white matter were frequently encountered. Staining of the cytoplasm in a minority of cells was interpreted as the result of nuclear DNA leakage. None of the stained cells had the typical morphology of apoptosis; most particularly, peripheral chromatin condensation and formation of apoptotic bodies were not seen in any case. PrP deposits did not result in an increase of nuclear DNA breaks either within the area or in adjacent regions. Although positive cells were also observed in autopsy cases of controls which were processed in the same way, positive labeling as a whole was higher in CJD than in age-matched controls. These results show that brain nuclear DNA is vulnerable in CJD, and suggest that increased DNA vulnerability has a role in cell death and neuron loss. Since nuclear shrinkage and positive nuclear staining with the method of in situ end-labeling of nuclear DNA fragmentation are not exclusive to apoptosis, further information is needed to categorize cell death in CJD as apoptosis. Necrosis or other forms of cell death, as well as increased DNA vulnerability to agonal changes of the individuals, and to postmortem delay in the fixation of the tissues, may account for additional positive staining in cases examined at autopsy.     

BSE: can we predict the future?

Prion diseases are transmissible neurodegenerative disorders of humans and animals. The prion protein (PrPc) gene is expressed to some extent in many cell types but principally in neurons. Normal PrPc may contribute in the protection of neurons and are protease sensitive. Abnormal prions consist of a post-translationally modified form of PrP, PrPsc, which is partly protease resistant. PrPsc is a protein with high resistance to inactivation by irradiation, heat and harsh chemical treatments. It is currently proposed that PrPsc is an infectious protein that propagates by inducing the normal PrPc to become the abnormal PrPsc. PrPsc cause transmissible spongiform encephalopathies (TSE), an unusual group of degenerative brain diseases that can be transmitted by inoculation or ingestion of diseased brain or other tissues. The human diseases occur in an inherited, acquired and sporadic forms. Transmission of prion diseases between species is limited by a species barrier, determined in part by the degree of sequence homology between the host PrP and inoculated PrPsc. The epidemic of bovine spongiform encephalopathy (BSE) in the United Kingdom is a new disease that has affected over 160,000 cattle and has presumably arisen from dietary exposure to PrPsc from sheep with scrapie. Until shown otherwise we must assume that oral consumption of infectious BSE protein is a new factor for Creutzfeldt-Jakob (CJD) disease in man. This disease is a new variant of CJD (nvCJD) and has a different clinical picture. Early diagnostic markers to facilitate the diagnosis and screen blood and organ donors are not available. The control of the disease relies on the measures to eradicate the spread of BSE by banning the use of ruminant tissues in ruminant feed and slaughter and rendering procedures to ensure inactivation of prions of all infected animals. The control of nvCJD is based on reduction of exposure to BSE by banning a variety of tissues for consumption. A surveillance worldwide is increased for both BSE and nv-CJD and the WHO update regularly recommendations to limit the risk of transmitting the disease. The extent and size of the nvCJD will depend on different factors among others the dose of infectious material, the route of infection, the genetic susceptibility of the person. Therefore is not possible to predict how important the disease will be.     

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-Str?ussler-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.     

A trend of molecular genetics on prion diseases and prion protein

Infectious amyloid filaments designated as prion rods or scrapie associated fibrils (SAF) present in brain tissues affected by transmissible spongiform encephalopathies such as Creutzfeldt-Jakob disease (CJD), Gerstmann-Str?ussler-Scheinker disease (GSS) and kuru of humans, and scrapie of sheep. A hydrophobic glycoprotein, PrPSc is a major component of SAF, and is known to be associated with the infectivity of these diseases. Both PrPSc and the normal isoform of this glycoprotein, PrPC are encoded by a single host gene, PrP gene, and the conversion of PrPC to PrPSc is a posttranslational event. Several mutations on the PrP gene are associated with variations of the phenotype and the occurrence in familial CJD and GSS.     

A prion disease with a novel 96-base pair insertional mutation in the prion protein gene

There are coding mutations in the prion protein gene in familial Creutzfeldt-Jakob disease (CJD), Gerstmann-Straussler-Scheinker disease, and other phenotypes that make up the inherited prion diseases. Insertional mutations consisting of two, five, six, seven, eight, and nine additional octapeptide repeat elements are seen in the inherited prion diseases and usually present as atypical dementias with considerable intrafamilial phenotypic variability. A four-octarepeat insertion was reported previously in an individual without neurodegenerative disease who died of hepatic cirrhosis. Here we report a novel four-octarepeat insertional mutation in a case with classical clinical, electroencephalographic and histopathologic features of CJD with the unusual finding of pronounced prion protein immunoreactivity of the molecular layer of the cerebellum.     

Prions and the prion disorders

One of us remembers sitting in a high school biology class in 1977 being taught about scrapie, a naturally occurring disorder of sheep. The teacher had no particular interest in agriculture, but was pointing out some peculiar characteristics of this disease as a biological curiosity on a wet Friday afternoon. The prion disorders captured the imagination of a range of biologists (including that teacher) well before the epidemic of bovine spongiform encephalopathy (BSE) and the appearance of a new variant of the human prion disease, Creutzfeldt Jakob disease (CJD), in the UK, because of their extraordinary biology and the unique properties of the infectious agent. We review the results of studies leading to a convergence of evidence that the causative infectious agent, the 'prion', is devoid of nucleic acid and is composed of an abnormal isoform of a host-encoded protein, the prion protein (PrP).     

Experimental transmission of Creutzfeldt-Jakob disease and related diseases to rodents

Sporadic Creutzfeldt-Jakob disease (CJD) with 129M/M, and iatrogenic and familial CJD with E200K and M232R, showed similar clinicopathologic features, a synaptic type deposition of PrPCJD, and high transmission frequencies to mice. Sporadic patients with 129M/V or 129V/V, and mutation cases with V180I, showed slightly different features and low or null transmission frequencies to mice. Hereditary cases with P102L, P105L, A117V, Y145stop, and insertions had different features but all demonstrated a long clinical duration and the presence of PrP plaques. The experimental transmission to mice of these mutant forms was difficult, except for one-third of the cases with P102L. CJD and related diseases, even those that are hereditary, may thus be divided into two different groups, those that are easily transmissible and those that are either difficult to transmit or nontransmissible.     

Japanese Creutzfeldt-Jakob disease patients exhibiting high incidence of the E200K PRNP mutation and located in the basin of a river

Seven cases with Creutzfeldt-Jakob disease (CJD) located in the basin of the Fuji river (Fuji area) in Japan were examined genetically and clinicopathologically. The onset of the disease was between 1989 and 1995. All cases were from different families, although 3 cases were family members of previously reported CJD patients. They had clinical and/or neuropathological features, corresponding to subacute spongiform encephalopathy. Five of the 7 cases, including the 3 familial cases, had the E200K mutation in the gene encoding prion protein (PRNP). It is suggested that there is a small cluster of CJD patients with a founder effect of the E200K mutation in the Fuji area, because the incidence of CJD with the E200K mutation appears to be much higher in this area than other areas in Japan. The disease penetrance of the 5 cases with the E200K mutation seems to be low, and they may have an age-related incidence in the Fuji area. These findings support the hypothesis that the phenotypes of CJD patients with the PRNP mutations are linked to the position of the mutation, but not related to ethnic or environmental factors.     

Prion protein amyloidosis

The prion protein (PrP) plays an essential role in the pathogenesis of a group of sporadic, genetically determined and infectious fatal degenerative diseases, referred to as "prion diseases", affecting the central nervous system of humans and other mammals. The cellular PrP is encoded by a single copy gene, highly conserved across mammalian species. In prion diseases, PrP undergoes conformational changes involving a shift from alpha-helix to beta-sheet structure. This conversion is important for PrP amyloidogenesis, which occurs to the highest degree in the genetically determined Gerstmann-Str?ussler-Scheinker disease (GSS) and prion protein cerebral amyloid angiopathy (PrP-CAA), while it is less frequently seen in other prion diseases. GSS and PrP-CAA are associated with point mutations of the prion protein gene (PRNP); these conditions show a broad spectrum of clinical presentation, the main signs being ataxia, spastic paraparesis, extrapyramidal signs and dementia. In GSS, parenchymal amyloid may be associated with spongiform changes or neurofibrillary lesions; in PrP-CAA, vascular amyloid is associated with neurofibrillary lesions. A major component of the amyloid fibrils in the two diseases is a 7 kDa peptide, spanning residues 81-150 of PrP.     

A target for intervention in Plasmodium falciparum infections

After the occurrence of bovine spongiform encephalopathy (BSE), there has been concern that transmission of BSE to the human population might result in a change in the epidemiological characteristics of Creutzfeldt-Jakob disease (CJD). A collaborative study of CJD in the European Union was performed from 1993 to 1995, to compare data from national registries for CJD in France, Germany, Italy, The Netherlands, Slovakia, and the United Kingdom. Five hundred seventy-five patients with definite or probable CJD died in the study period with an overall annual mortality rate of 0.71 cases per million. The incidence rates for CJD were similar in all participating countries despite variations in postmortem rates, and age-specific incidence rates were also relatively consistent, with the exception of an increased incidence of CJD in patients younger than 39 years of age in the United Kingdom. In relation to etiological subtypes of CJD, 87% of cases were sporadic, 8% genetic, and 5% iatrogenic. Genetic forms of CJD comprised 80% of all cases in Slovakia, and iatrogenic forms of CJD occurred most frequently in France and the United Kingdom. The statistical data reported here do not provide evidence of a causal link between BSE and CJD in Europe as a whole. However, the study has established baseline epidemiological parameters for CJD in participating European countries, which may be important in the assessment of any future change in the characteristics of CJD as a result of the epidemic of BSE.     

Diffusion-weighted MRI in sporadic Creutzfeldt-Jakob disease

Diffusion-weighted MRI (DWI) was used in three patients with autopsy-proven sporadic Creutzfeldt-Jakob disease (CJD) to provide a rapid noninvasive way to make this sometimes confusing diagnosis. DWI prompted the diagnosis of CJD at an early stage and appears to be particularly useful for monitoring the progression of the disease. We suggest that patients with suspected CJD and no abnormalities on T2- and proton density-weighted images may have cortical involvement on DWI.