Population structure and migration in the Eastern Highlands of Papua New Guinea, a region impacted by the kuru epidemic.

Populations of the Eastern Highlands of Papua New Guinea (EHPNG, area 11,157 km2) lived in relative isolation from the rest of the world until the mid-20th century, and the region contains a wealth of linguistic and cultural diversity. Notably, several populations of EHPNG were devastated by an epidemic prion disease, kuru, which at its peak in the mid-twentieth century led to some villages being almost depleted of adult women. Until now, population genetic analyses to learn about genetic diversity, migration, admixture, and the impact of the kuru epidemic have been restricted to a small number of variants or samples. Here, we present a population genetic analysis of the region based on genome-wide genotype data of 943 individuals from 21 linguistic groups and 68 villages in EHPNG, including 34 villages in the South Fore linguistic group, the group most affected by kuru. We find a striking degree of genetic population structure in the relatively small region (average FST between linguistic groups 0.024). The genetic population structure correlates well with linguistic grouping, with some noticeable exceptions that reflect the clan system of community organization that has historically existed in EHPNG. We also detect the presence of migrant individuals within the EHPNG region and observe a significant excess of females among migrants compared to among non-migrants in areas of high kuru exposure (p = 0.0145, chi-squared test). This likely reflects the continued practice of patrilocality despite documented fears and strains placed on communities as a result of kuru and its associated skew in female incidence.

Defining the phenotypic spectrum of sporadic Creutzfeldt-Jakob disease MV2K: the kuru plaque type.

The current classification of sporadic Creutzfeldt-Jakob disease identifies six major subtypes mainly defined by the combination of the genotype at polymorphic codon 129 (methionine/M or valine/V) of the prion protein gene and the type (1 or 2) of misfolded prion protein accumulating in the brain (e.g. MM1, MM2, MV1, MV2, etc.). Here, we systematically characterized the clinical and histo-molecular features associated with the third prevalent subtype, the MV2 subtype with kuru plaques (MV2K), in the most extensive series collected to date. We evaluated neurological histories, cerebrospinal biomarkers, brain MRI and EEG results in 126 patients. The histo-molecular assessment included misfolded prion protein typing, standard histologic staining and immunohistochemistry for prion protein in several brain areas. We also investigated the prevalence and topographic extent of coexisting MV2-cortical features, the number of cerebellar kuru plaques and their effect on clinical phenotype. Systematic regional typing revealed a western blot profile of misfolded prion protein comprising a doublet of 19 and 20 kDa unglycosylated fragments, with the former more prominent in neocortices and the latter in the deep grey nuclei. The 20/19 kDa fragment ratio positively correlated with the number of cerebellar kuru plaques. The mean disease duration was exceedingly longer than in the typical MM1 subtype (18.0 versus 3.4 months). Disease duration correlated positively with the severity of pathologic change and the number of cerebellar kuru plaques. At the onset and early stages, patients manifested prominent, often mixed, cerebellar symptoms and memory loss, variably associated with behavioural/psychiatric and sleep disturbances. The cerebrospinal fluid prion real-time quaking-induced conversion assay was positive in 97.3% of cases, while 14-3-3 protein and total-tau positive tests were 52.6 and 75.9%. Brain diffusion-weighted MRI showed hyperintensity of the striatum, cerebral cortex and thalamus in 81.4, 49.3 and 33.8% of cases, and a typical profile in 92.2%. Mixed histotypes (MV2K + MV2-cortical) showed an abnormal cortical signal more frequently than the pure MV2K (64.7 versus 16.7%, P = 0.007). EEG revealed periodic sharp-wave complexes in only 8.7% of participants. These results further establish MV2K as the most common 'atypical' subtype of sporadic Creutzfeldt-Jakob disease, showing a clinical course that often challenges the early diagnosis. The plaque-type aggregation of the misfolded prion protein accounts for most of the atypical clinical features. Nonetheless, our data strongly suggest that the consistent use of the real-time quaking-induced conversion assay and brain diffusion-weighted MRI allows an accurate early clinical diagnosis in most patients.

An autopsy case of MV2K-type sporadic Creutzfeldt-Jakob disease presenting with characteristic clinical, radiological, and neuropathological findings.

In Japan, because MV2-type sporadic Creutzfeldt-Jakob disease (CJD) is rare, little is known about its clinical and neuropathological characteristics. An autopsy case of MV2K-type sporadic CJD is presented, and the characteristic clinical, radiological, and neuropathological findings are discussed. The patient was a Japanese woman who died at the age of 72 years. Her initial symptom was rapidly progressive dementia. She then developed truncal ataxia and delusions. Approximately nine months after onset, she exhibited akinetic mutism. The total clinical course was 11 months. Magnetic resonance imaging revealed hyperintensity areas in the basal ganglia, thalamus, and hippocampus on diffusion-weighted images. In the cerebral cortex, this finding was slight and inconspicuous. Electroencephalography revealed no periodic sharp wave complexes. Prion protein (PrP) gene analysis revealed no mutations, and polymorphic codon 129 exhibited methionine and valine heterozygosity. In the cerebrospinal fluid, levels of both total tau and 14-3-3 proteins were elevated. Grossly, the brain weighed 1050 g before fixation and exhibited diffuse cortical atrophy. On histopathological examination, extensive fine vacuole-type spongiform degeneration was noted in the cerebral cortex. Numerous kuru plaques were observed in the cerebellum. PrP immunohistochemistry revealed extensive diffuse synaptic- and perineuronal-type PrP deposits in the cerebral cortex. Kuru plaques were strongly immunoreactive for PrP. Western blot analysis of brain tissue samples revealed mixed type 2 and intermediate type. Systematic and comprehensive investigations of both clinical and neuropathological aspects are required for accurate diagnosis.

A naturally occurring variant of the human prion protein completely prevents prion disease.

Mammalian prions, transmissible agents causing lethal neurodegenerative diseases, are composed of assemblies of misfolded cellular prion protein (PrP). A novel PrP variant, G127V, was under positive evolutionary selection during the epidemic of kuru--an acquired prion disease epidemic of the Fore population in Papua New Guinea--and appeared to provide strong protection against disease in the heterozygous state. Here we have investigated the protective role of this variant and its interaction with the common, worldwide M129V PrP polymorphism. V127 was seen exclusively on a M129 PRNP allele. We demonstrate that transgenic mice expressing both variant and wild-type human PrP are completely resistant to both kuru and classical Creutzfeldt-Jakob disease (CJD) prions (which are closely similar) but can be infected with variant CJD prions, a human prion strain resulting from exposure to bovine spongiform encephalopathy prions to which the Fore were not exposed. Notably, mice expressing only PrP V127 were completely resistant to all prion strains, demonstrating a different molecular mechanism to M129V, which provides its relative protection against classical CJD and kuru in the heterozygous state. Indeed, this single amino acid substitution (G→V) at a residue invariant in vertebrate evolution is as protective as deletion of the protein. Further study in transgenic mice expressing different ratios of variant and wild-type PrP indicates that not only is PrP V127 completely refractory to prion conversion but acts as a potent dose-dependent inhibitor of wild-type prion propagation.

Recent kuru-induced female gene flow disrupted the coevolution of genes and languages in the Papua New Guinea highlands.

OBJECTIVES: The island of New Guinea was settled by modern human over 50,000 years ago, and is currently characterized by a complex landscape and contains one-seventh of the world's languages. The Eastern Highlands of New Guinea were also the home to the devastating prion disease called kuru that primarily affected Fore-speaking populations, with some 68% of cases involving adult females. We characterized the mitochondrial DNA (mtDNA) diversity of highlanders from Papua New Guinea (PNG) to: (a) gain insight into the coevolution of genes and languages in situ over mountainous landscapes; and (b) evaluate the recent influence of kuru mortality on the pattern of female gene flow. MATERIALS AND METHODS: We sequenced the mtDNA hypervariable segment 1 of 870 individuals from the Eastern and Southern Highlands of PNG using serums collected in the 1950s to 1960s. These highlanders were selected from villages representing 15 linguistic groups within the Trans-New Guinea phylum. Genetic, linguistic, and geographic distances were calculated separately and correlations among those distance matrices were assessed using the Mantel test. RESULTS: Geographic, genetic, and linguistic patterns were independently correlated with each other (p < .05). Increased mtDNA diversity in kuru-affected populations and low Fst estimates between kuru-affected linguistic groups were observed. DISCUSSION: In general, the genetic structure among the Highland populations was shaped by both geography and language, and language is a good predictor of mtDNA affinity in the PNG Highlands. High kuru female mortality increased female gene flow locally, disrupting coevolutionary pattern among genes, languages, and geography.

An autopsied case of MV2K + C-type sporadic Creutzfeldt-Jakob disease presenting with widespread cerebral cortical involvement and Kuru plaques.

MV2-type sporadic Creutzfeldt-Jakob disease (sCJD), which was previously called "Kuru-plaque variant", was gradually revealed to have a wide spectrum and has been classified into three pathological subtypes: MV2K, MV2C and MV2K + C. We herein describe the detailed clinical findings and neuropathologic observations from an autopsied MV2K + C-type Japanese sCJD case with widespread cerebral cortical pathology and Kuru plaques. In the early stages of the disease, the patient exhibited gait disturbance with ataxia and dysarthria as well as gradual appearance of cognitive dysfunction. Diffusion-weighted images (DWI) on MRI revealed extensive cerebral cortical hyperintensity. Pathologic investigation revealed extensive spongiform change in the cerebral cortex, particularly in the deeper layers. Vacuole size varied, and some were confluent. Prion protein (PrP) immunostaining revealed extensive PrP deposition in the cerebral cortex, basal ganglia, thalamus, cerebellum, brainstem and spinal cord. In the cerebral cortex, synaptic-type, Kuru plaque-like, and coarse plaque-type PrP depositions were mainly observed, along with some perivacuolar-type PrP depositions. Kuru plaques and coarse plaque-type PrP depositions also were observed in the cerebellar cortex. PrP gene analysis revealed no mutations, and polymorphic codon 129 exhibited Met/Val heterozygosity. Western blot analysis revealed a mixture of intermediate-type PrPSc and type 2 PrPSc . Based on previous reports regarding MV2-type sCJD and the clinicopathologic findings of the present case, we speculated that it may be possible to clinically distinguish each MV2 subtype. Clinical presentation of the MV2K + C subtype includes predominant cerebral cortical involvement signs with ataxia and DWI hyperintensity of the cerebral cortex on MRI.

Atypical sporadic CJD-MM phenotype with white matter kuru plaques associated with intranuclear inclusion body and argyrophilic grain disease.

We describe an atypical neuropathological phenotype of sporadic Creutzfeldt-Jakob disease in a 76-year-old man. The clinical symptoms were characterized by progressive dementia, gait ataxia, rigidity and urinary incontinence. The disease duration was 6 weeks. MRI did not show prominent atrophy or hyperintensities in cortical areas, striatum or thalamus. Biomarker examination of the cerebrospinal fluid deviated from that seen in pure Alzheimer's disease. Triphasic waves in the EEG were detected only later in the disease course, while 14-3-3 assay was positive. PRNP genotyping revealed methionine homozygosity (MM) at codon 129. Neuropathology showed classical CJD changes corresponding to the MM type 1 cases. However, a striking feature was the presence of abundant kuru-type plaques in the white matter. This rare morphology was associated with neuropathological signs of intranuclear inclusion body disease and advanced stage of argyrophilic grain disease. These alterations did not show correlation with each other, thus seemed to develop independently. This case further highlights the complexity of neuropathological alterations in the ageing brain.

Genome-wide association study in multiple human prion diseases suggests genetic risk factors additional to PRNP.

Prion diseases are fatal neurodegenerative diseases of humans and animals caused by the misfolding and aggregation of prion protein (PrP). Mammalian prion diseases are under strong genetic control but few risk factors are known aside from the PrP gene locus (PRNP). No genome-wide association study (GWAS) has been done aside from a small sample of variant Creutzfeldt-Jakob disease (CJD). We conducted GWAS of sporadic CJD (sCJD), variant CJD (vCJD), iatrogenic CJD, inherited prion disease, kuru and resistance to kuru despite attendance at mortuary feasts. After quality control, we analysed 2000 samples and 6015 control individuals (provided by the Wellcome Trust Case Control Consortium and KORA-gen) for 491032-511862 SNPs in the European study. Association studies were done in each geographical and aetiological group followed by several combined analyses. The PRNP locus was highly associated with risk in all geographical and aetiological groups. This association was driven by the known coding variation at rs1799990 (PRNP codon 129). No non-PRNP loci achieved genome-wide significance in the meta-analysis of all human prion disease. SNPs at the ZBTB38-RASA2 locus were associated with CJD in the UK (rs295301, P = 3.13 × 10(-8); OR, 0.70) but these SNPs showed no replication evidence of association in German sCJD or in Papua New Guinea-based tests. A SNP in the CHN2 gene was associated with vCJD [P = 1.5 × 10(-7); odds ratio (OR), 2.36], but not in UK sCJD (P = 0.049; OR, 1.24), in German sCJD or in PNG groups. In the overall meta-analysis of CJD, 14 SNPs were associated (P < 10(-5); two at PRNP, three at ZBTB38-RASA2, nine at nine other independent non-PRNP loci), more than would be expected by chance. None of the loci recently identified as genome-wide significant in studies of other neurodegenerative diseases showed any clear evidence of association in prion diseases. Concerning common genetic variation, it is likely that the PRNP locus contains the only strong risk factors that act universally across human prion diseases. Our data are most consistent with several other risk loci of modest overall effects which will require further genetic association studies to provide definitive evidence.

Prion meeting 2023: implications of a growing field.

The history of human prion diseases began with the original description, by Hans Gerhard Creutzfeldt and by Alfons Maria Jakob, of patients with a severe brain disease that included speech abnormalities, confusion, and myoclonus, in a disease that was then named Creutzfeldt Jakob disease (CJD). Later, in Papua New Guinea, a disease characterized by trembling was identified, and given the name "Kuru". Neuropathological examination of the brains from CJD and Kuru patients, and of brains of sheep with scrapie disease revealed significant similarities and suggested a possible common mode of infection that, at the time, was thought to derive from an unknown virus that caused slow infections. John Stanley Griffith hypothesized that the agent causing these diseases was "probably a protein without nucleic acid" and, in 1982, Stanley Prusiner reported the identification of a proteinaceous infectious particle (coining the term prion) that was resistant to inactivation methods that were at the time standard for nucleic acids, and identified PrP as the major protein component of the infectious agent in scrapie and in Creutzfeldt-Jakob disease, classifying this also as a prion disease. Interestingly, the prion concept had been previously expanded to yeast proteins capable of replicating their conformation, seeding their own aggregation and transmitting phenotypic information. The prion concept has been more recently expanded to refer to misfolded proteins that are capable of converting a normal form of a protein into an abnormal form. The quest to understand and treat prion diseases has united a specific research community around the topic, and regular meetings (Prion Meetings) have taken place over the years to enable discussions, train junior researchers, and inspire research in the field.

Atypical neuropathological sCJD-MM phenotype with abundant white matter Kuru-type plaques sparing the cerebellar cortex.

We describe an atypical neuropatholgical phenotype of sporadic Creutzfeldt-Jakob disease (sCJD) in a 64-year-old man presenting with a 5-month history of rapidly progressive dementia, comprising behavioral disturbances, memory complaints, disorientation and language alterations. MRI showed diffuse atrophy and hyperintensities in parietal, occipital, temporal and frontal cortices and left caudate nucleus on T2-weighted and fluid-attenuated inversion recovery images. No typical EEG alterations were observed. Repeated 14-3-3 assay was positive after a first negative test. Neuropathology showed classical CJD changes with small cortical foci of large confluent vacuoles and relatively well-preserved cerebellar cortex. The most striking feature was the presence of abundant Kuru-type plaques in both cerebral cortex and subcortical white matter. Sparse Kuru-type plaques were also seen in cerebellum, although only in white matter. Immunohistochemistry showed, in addition to unicentric plaques, diffuse synaptic and patchy perivacuolar, as well as plaque-like and periaxonal pathological prion protein deposits (PrP(res) ). Western blot studies demonstrated the co-occurrence of PrP(res) types 1 and 2 in frontal cortex and a relatively weak type 2 signal in cerebellum. PRNP genotyping revealed methionine homozygosity at codon 129 and excluded mutations. This case shows a previously undescribed combination of histopathological features which preclude its classification according to the current phenotypic and molecular sCJD classification. The observation demonstrates that Kuru-type amyloid plaques mainly involving the cerebral white matter may also occur in sCJD cases with short clinical course and the co-existence of PrP(res) types 1 and 2. This case further highlights the complexity of the correlations between histopathological phenotype and PrP(res) isotype in prion diseases.

Human prion diseases: from Kuru to variant Creutzfeldt-Jakob disease.

Transmissible spongiform encephalopathies (TSEs) or prion diseases are the names given to the group of fatal neurodegenerative disorders that includes kuru, Creutzfeldt-Jakob disease (CJD), Gerstmann-Sträussler-Scheinker disease (GSS), fatal and sporadic familial insomnia and the novel prion disease variable protease-sensitive prionopathy (PSPr) in humans. Kuru was restricted to natives of the Foré linguistic group in Papua New Guinea and spread by ritualistic endocannibalism. CJD appears as sporadic, familial (genetic or hereditary) and infectious (iatrogenic) forms. Variant CJD is a zoonotic CJD type and of major public health importance, which resulted from transmission from bovine spongiform encephalopathy (BSE) through ingestion of contaminated meat products. GSS is a slowly progressive hereditary autosomal dominant disease and the first human TSE in which a mutation in a gene encoding for prion protein (PrP) was discovered. The rarest human prion disease is fatal insomnia, which may occur, in genetic and sporadic form. More recently a novel prion disease variable protease-sensitive prionopathy (PSPr) was described in humans.TSEs are caused by a still incompletely defined infectious agent known as a "prion" which is widely regarded to be an aggregate of a misfolded isoform (PrP(Sc)) of a normal cellular glycoprotein (PrP(c)). The conversion mechanism of PrP(c) into PrP(Sc) is still not certain.

Structural and functional neuroimaging in human prion diseases.

INTRODUCTION: Prion diseases are neurodegenerative disorders resulting from the accumulation of a misfolded isoform of the cellular prion protein (PrPc). They can occur as acquired, sporadic, or hereditary forms. Although prion diseases show a wide range of phenotypic variations, pathological features and clinical evolution, they are all characterised by a common unfavourable course and a fatal outcome. REVIEW SUMMARY: Some variants, such as kuru, have practically disappeared, while others, for example the variant Creutzfeldt-Jakob (vCJD) or those attributable to iatrogenic causes, are still in force and pose a challenge to current medicine. There are no definitive pre-mortem diagnostic tests, except for vCJD, where a tonsil biopsy detects 100% of the cases. For this reason, diagnostic criteria dependent on statistical probability have had to be created. These require complementary examinations, such as an electroencephalogram (EEG) or the detection of 14-3-3 protein in cerebrospinal fluid (CSF). Only the pulvinar sign in magnetic resonance imaging (MRI) has been included as a vCJD diagnostic criterion. The present review discusses neuroimaging findings for each type of prion disease in patients with a definitive histopathological diagnosis. CONCLUSIONS: The aim is to define the usefulness of these complementary examinations as a tool for the diagnosis of this family of neurodegenerative diseases.

Novel histotypes of sporadic Creutzfeldt-Jakob disease linked to 129MV genotype.

The MV1 and MV2 subtypes of sporadic Creutzfeldt-Jakob disease (sCJD) are linked to the heterozygous methionine (M)/valine (V) polymorphism at codon 129 of the prion protein (PrP) gene. MV2 is phenotypically heterogeneous, whereas MV1, due to its low prevalence, is one of the least well characterized subtypes. In this study, we investigated the biochemical properties of PrPSc and phenotypic expression of cases diagnosed as sCJD MV1 and MV2. We describe four MV2 histotypes: 2C, with cortical (C) coarse pathology; 2K, with kuru (K) plaque deposits; 2C-K, with co-existing C and K histotypic features; and the novel histotype 2C-PL that mimics 2C in the cerebral cortex and cerebellum, but exhibits plaque-like (PL) PrP deposits in subcortical regions (e.g., basal nuclei, thalamus and midbrain). Histotype prevalence is highest for 2C-K (55%), intermediate for 2C (31%), and lowest for 2C-PL and 2K (7%). Nearly every MV2 case expressed both PrPSc types, with T2 being the predominant type ("MV2-1"). MV1 cases typically show a rapid disease course (≤ 4 months), and feature the 1C histotype, phenotypically identical to sCJDMM1. Co-existing PrPSc types, with T1 significantly exceeding T2 ("MV1-2"), are detected in patients diagnosed as MV1 with longer disease courses. We observed four histotypes among MV1-2 cases, including two novel histotypes: 1V, reminiscent of sCJDVV1; 1C-2C, resembling sCJDMM1-2 with predominant MM1 histotypic component; and novel histotypes 1C-2PL and 1C-2K, overall mimicking 1C in the cerebral cortex, but harboring T2 and plaque-like PrP deposits in subcortical regions (1C-2PL), and T2 and kuru plaques in the cerebellum (1C-2K). Lesion profiles of 1C, 1V, and 1C-2C are similar, but differ from 1C-2PL and 1C-2K, as the latter two groups show prominent hippocampal and nigral degeneration. We believe that the novel "C-PL" histotypes are distinct entities rather than intermediate forms between "C" and "C-K" groups, and that 1C-2PL and 1C-2K histotypes may be characterized by different T1 variants of the same size.

A novel protective prion protein variant that colocalizes with kuru exposure.

BACKGROUND: Kuru is a devastating epidemic prion disease that affected a highly restricted geographic area of the Papua New Guinea highlands; at its peak, it predominantly affected adult women and children of both sexes. Its incidence has steadily declined since the cessation of its route of transmission, endocannibalism. METHODS: We performed genetic and selected clinical and genealogic assessments of more than 3000 persons from Eastern Highland populations, including 709 who participated in cannibalistic mortuary feasts, 152 of whom subsequently died of kuru. RESULTS: Persons who were exposed to kuru and survived the epidemic in Papua New Guinea are predominantly heterozygotes at the known resistance factor at codon 129 of the prion protein gene (PRNP). We now report a novel PRNP variant--G127V--that was found exclusively in people who lived in the region in which kuru was prevalent and that was present in half of the otherwise susceptible women from the region of highest exposure who were homozygous for methionine at PRNP codon 129. Although this allele is common in the area with the highest incidence of kuru, it is not found in patients with kuru and in unexposed population groups worldwide. Genealogic analysis reveals a significantly lower incidence of kuru in pedigrees that harbor the protective allele than in geographically matched control families. CONCLUSIONS: The 127V polymorphism is an acquired prion disease resistance factor selected during the kuru epidemic, rather than a pathogenic mutation that could have triggered the kuru epidemic. Variants at codons 127 and 129 of PRNP demonstrate the population genetic response to an epidemic of prion disease and represent a powerful episode of recent selection in humans.

Kuru: the first prion disease.

Kuru disease is linked with the name of D. Carleton Gajdusek and he was the first to show that this human neurodegenerative disease can be transmitted to chimpanzees and subsequently classified as a transmissible spongiform encephalopathy (TSE), or slow unconventional virus disease. It was first reported to Western world in 1957 by Gajdusek and Vincent Zigas,(1,2) and in 1975 a complete bibliography of kuru was published by Alpers et al.(3) "Kuru" in the Fore language in Papua New Guinea means to shiver from fever and cold. The disease has been found to spread through ritualistic cannibalism and is an invariably fatal cerebellar ataxia accompanied by tremor, choreiform and athetoid movements. Neuropathologically, kuru is characterized by the presence of amyloid "kuru" plaques.

The kuru infectious agent is a unique geographic isolate distinct from Creutzfeldt-Jakob disease and scrapie agents.

Human sporadic Creutzfeldt-Jakob disease (sCJD), endemic sheep scrapie, and epidemic bovine spongiform encephalopathy (BSE) are caused by a related group of infectious agents. The new U.K. BSE agent spread to many species, including humans, and clarifying the origin, specificity, virulence, and diversity of these agents is critical, particularly because infected humans do not develop disease for many years. As with viruses, transmissible spongiform encephalopathy (TSE) agents can adapt to new species and become more virulent yet maintain fundamentally unique and stable identities. To make agent differences manifest, one must keep the host genotype constant. Many TSE agents have revealed their independent identities in normal mice. We transmitted primate kuru, a TSE once epidemic in New Guinea, to mice expressing normal and approximately 8-fold higher levels of murine prion protein (PrP). High levels of murine PrP did not prevent infection but instead shortened incubation time, as would be expected for a viral receptor. Sporadic CJD and BSE agents and representative scrapie agents were clearly different from kuru in incubation time, brain neuropathology, and lymphoreticular involvement. Many TSE agents can infect monotypic cultured GT1 cells, and unlike sporadic CJD isolates, kuru rapidly and stably infected these cells. The geographic independence of the kuru agent provides additional reasons to explore causal environmental pathogens in these infectious neurodegenerative diseases.

[Prion diseases or transmissible spongiform encephalopathies]. / Les maladies à prions ou encéphalopathies spongiformes transmissibles.

Prion diseases or transmissible spongiform encephalopathies (TSEs) are human and animal diseases naturally or experimentally transmissible with a long incubation period and a fatal course without remission. The nature of the transmissible agent remains debated but the absence of a structure evoking a conventional microorganism led Stanley B. Prusiner to hypothesize that it could be an infectious protein (proteinaceous infectious particle or prion). The prion would be the abnormal form of a normal protein, cellular PrP (PrPc) which will change its spatial conformation and be converted into scrapie prion protein (PrPsc) with properties of partial resistance to proteases, aggregation and insolubility in detergents. No inflammatory or immune response are detected in TSEs which are characterized by brain damage combining spongiosis, neuronal loss, astrocytic gliosis, and deposits of PrPsc that may appear as amyloid plaques. Although the link between the accumulation of PrPsc and the appearance of lesions remains debated, the presence of PrPsc is constant during TSE and necessary for a definitive diagnosis. Even if they remain rare diseases (2 cases per million), the identification of kuru, at the end of the 1950s, of iatrogenic cases in the course of the 1970s and of the variant of Creutzfeldt-Jakob disease (CJD) in the mid-1990s explain the interest in these diseases but also the fears they can raise for public health. They remain an exciting research model because they belong both to the group of neurodegenerative diseases with protein accumulation (sporadic CJD), to the group of communicable diseases (iatrogenic CJD, variant of CJD) but also to the group of genetic diseases with a transmission Mendelian dominant (genetic CJD, Gerstmann-Straussler-Scheinker syndrome, fatal familial insomnia).

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.

Agent strain variation in human prion disease: insights from a molecular and pathological review of the National Institutes of Health series of experimentally transmitted disease.

Six clinico-pathological phenotypes of sporadic Creutzfeldt-Jakob disease have been characterized which correlate at the molecular level with the type (1 or 2) of the abnormal prion protein, PrP(TSE), present in the brain and with the genotype of polymorphic (methionine or valine) codon 129 of the prion protein gene. However, to what extent these phenotypes with their corresponding molecular combinations (i.e. MM1, MM2, VV1 etc.) encipher distinct prion strains upon transmission remains uncertain. We studied the PrP(TSE) type and the prion protein gene in archival brain tissues from the National Institutes of Health series of transmitted Creutzfeldt-Jakob disease and kuru cases, and characterized the molecular and pathological phenotype in the affected non-human primates, including squirrel, spider, capuchin and African green monkeys. We found that the transmission properties of prions from the common sporadic Creutzfeldt-Jakob disease MM1 phenotype are homogeneous and significantly differ from those of sporadic Creutzfeldt-Jakob disease VV2 or MV2 prions. Animals injected with iatrogenic Creutzfeldt-Jakob disease MM1 and genetic Creutzfeldt-Jakob disease MM1 linked to the E200K mutation showed the same phenotypic features as those infected with sporadic Creutzfeldt-Jakob disease MM1 prions, whereas kuru most closely resembled the sporadic Creutzfeldt-Jakob disease VV2 or MV2 prion signature and neuropathology. The findings indicate that two distinct prion strains are linked to the three most common Creutzfeldt-Jakob disease clinico-pathological and molecular subtypes and kuru, and suggest that kuru may have originated from cannibalistic transmission of a sporadic Creutzfeldt-Jakob disease of the VV2 or MV2 subtype.

Kuru prions and sporadic Creutzfeldt-Jakob disease prions have equivalent transmission properties in transgenic and wild-type mice.

Kuru provides our principal experience of an epidemic human prion disease and primarily affected the Fore linguistic group of the Eastern Highlands of Papua New Guinea. Kuru was transmitted by the practice of consuming dead relatives as a mark of respect and mourning (transumption). To date, detailed information of the prion strain type propagated in kuru has been lacking. Here, we directly compare the transmission properties of kuru prions with sporadic, iatrogenic, and variant Creutzfeldt-Jakob disease (CJD) prions in Prnp-null transgenic mice expressing human prion protein and in wild-type mice. Molecular and neuropathological data from these transmissions show that kuru prions are distinct from variant CJD and have transmission properties equivalent to those of classical (sporadic) CJD prions. These findings are consistent with the hypothesis that kuru originated from chance consumption of an individual with sporadic CJD.