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Objective: Comprehensively describe the phenotypic spectrum of sporadic fatal insomnia (sFI) to facilitate diagnosis and management of this rare and peculiar prion disorder., Methods: A survey among major prion disease reference centers in Europe identified 13 patients diagnosed with sFI in the past 20 years. We undertook a detailed analysis of clinical and histopathological features and the results of diagnostic investigations., Results: Mean age at onset was 43 years, and mean disease duration 30 months. Early clinical findings included psychiatric, sleep, and oculomotor disturbances, followed by cognitive decline and postural instability. In all tested patients, video-polysomnography demonstrated a severe reduction of total sleep time and/or a disorganized sleep. Cerebrospinal fluid (CSF) levels of proteins 14-3-3 and t-tau were unrevealing, the concentration of neurofilament light protein (NfL) was more consistently increased, and the real-time quaking-induced conversion assay (RT-QuIC) revealed a positive prion seeding activity in 60% of cases. Electroencephalography and magnetic resonance imaging showed nonspecific findings, whereas fluorodeoxyglucose positron emission tomography (FDG-PET) demonstrated a profound bilateral thalamic hypometabolism in 71% of cases. Molecular analyses revealed PrP Sc type 2 and methionine homozygosity at PRNP codon 129 in all cases., Interpretation: sFI is a disease of young or middle-aged adults, which is difficult to reconcile with the hypothesis of a spontaneous etiology related to stochastic, age-related PrP misfolding. The combination of psychiatric and/or sleep-related symptoms with oculomotor abnormalities represents an early peculiar clinical feature of sFI to be valued in the differential diagnosis. Video-polysomnography, FDG-PET, and especially CSF prion RT-QuIC and NfL constitute the most promising supportive diagnostic tests in vivo. Ann Neurol 2018;84:347-360., (© 2018 American Neurological Association.)

Development of transgenic mouse models expressing heterologous prion protein (PrP) has facilitated and advanced in vivo studies of prion diseases affecting humans and animals. Here, novel transgenic mouse lines expressing a chimaeric murine/ovine (Mu/Ov) PrP transgene, including amino acid residues alanine, histidine and glutamine at ovine polymorphic codons 136, 154 and 171 (A136H154Q171), were generated to provide a means of assessing the susceptibility of the ovine AHQ allele to ruminant prion diseases in an in vivo model. Transmission studies showed that the highest level of transgene overexpression, in Tg(Mu/OvPrP(AHQ))EM16 (EM16) mice, conferred high susceptibility to ruminant prions. Highly efficient primary transmission of atypical scrapie from sheep was shown, irrespective of donor sheep PrP genotype, with mean incubation periods (IPs) of 154–178 days post-inoculation (p.i.), 100% disease penetrance and early Western blot detection of protease-resistant fragments (PrP(res)) of the disease-associated isoform, PrP(Sc), in EM16 brain from 110 days p.i. onwards. EM16 mice were also highly susceptible to classical scrapie and bovine spongiform encephalopathy (BSE), with mean IPs 320 and 246 days faster, respectively, than WT mice. Primary passage of atypical scrapie, classical scrapie and BSE showed that the PrP(res) profiles associated with disease in the natural host were faithfully maintained in EM16 mice, and were distinguishable based on molecular masses, antibody reactivities and glycoform percentages. Immunohistochemistry was used to confirm PrP(Sc) deposition in brain sections from terminal phase transmissible spongiform encephalopathy-challenged EM16 mice. The findings indicate that EM16 mice represent a suitable bioassay model for detection of atypical scrapie infectivity and offer the prospect of differentiation of ruminant prions.

We discuss relevant aspects in two siblings with a neurodegenerative process of unclear aetiology who developed progressive dementia with global aphasia and hyperoral behaviour at the ages of 39 and 46 years and who died 6 and 5 years after disease onset. The cases were reported to the National Reference Center for TSE Surveillance in Göttingen, Germany. Detailed clinical examinations, CSF, blood samples, and copies of the important diagnostic tests (magnetic resonance imaging, electroencephalogram, laboratory tests) were obtained. Further neuropathological and genetic analyses were performed. Cerebral magnetic resonance imaging of both siblings showed prominent changes in signal intensity, especially in the left medial temporal cortex, but also the hippocampal formation. Neuropathological examination revealed spongiform changes, neuronal loss, and astrocytic gliosis, which are typical in Creutzfeldt-Jakob disease. However, no prion protein deposits were detectable by immunohistochemical analysis, Western blot, or PET blot, though abundant tau protein deposits were observed. A mutation in the coding region of the prion protein genes of both siblings was excluded. A detailed search of the literature revealed no other cases with a similar clinical and neuropathological appearance. While the disease aetiology remains unclear, the findings point to a neurodegenerative process and most likely a genetic disease.

A heterozygous T183A mutation in the prion protein (PrP) gene, PRNP, was identified in a patient with histopathologically confirmed spongiform encephalopathy. Clinically, this form of prion disease was characterized by early-onset dementia as the predominant sign, along with global cerebral atrophy and hypometabolism. The age at onset was 40 years and the disease duration was 4 years. Additional neurological signs including cerebellar ataxia and EEG abnormalities were absent until late stages of the disease. The T183A mutation was not found in non-affected family members. This mutation results in the removal of one of the two consensus sites for glycosylation of PrP. Neuropathological examination revealed severe spongiform degeneration and neuronal loss in the neocortex, putamen and claustrum, small plaque-like PrP-immunoreactive deposits in the molecular layer of the cerebellum, and faint intracellular cytoplasmic PrP immunoreactivity. Western blot analysis of the patient's brain tissue showed protease K-resistant PrP with a definite preponderance of the monoglycosylated form. The additional appearance of a band representing diglycosylated PrPSc strongly suggests that non-mutated PrP also acquires protease resistance in the present setting. Cell culture experiments confirmed previous reports on intracellular retention of the mutant protein in vitro. This is the second report of a disease-causing T183A mutation of PrP, and the clinical, histological and genetic observations strongly suggest that T183A is a disease-causing mutation.

The pathogenic mechanisms leading from mutations in the prion protein (PrP) gene to infectious disease are not understood. To investigate the possibility that cellular processing of mutant prion protein may contribute to the formation of infectious particles, a mouse PrP model system has been established using the green fluorescent protein. Three novel PrP mutants were examined employing this model system and compared with wild type as well as known mutant PrPs. Two Creutzfeldt-Jakob disease-associated PrP mutants, PrP T188K and PrP T188R, revealed a secretory pathway to the cell membrane and PrP(Sc)-like properties, i.e. enhanced proteinase K resistance and detergent insolubility similar to other mutant PrPs associated with familial prion diseases. Moreover, a recently described disease-related truncated PrP mutant, PrP Q160(Stop), showed an almost exclusive localization in the nucleus and a catabolism along the proteasomal pathway. Therefore, various distinct pathological mechanisms may cause prion diseases, and aberrant cellular processing may be included in the pathogenesis of prion diseases.

The document published in Acta Neuropathologica discusses the unsuccessful transmissions of atypical genetic Creutzfeldt–Jakob disease (PRNP p.T183A-129M) in transgenic mice. This specific genetic mutation is associated with early onset of the disease and a unique immunoblot profile. The study aimed to evaluate the transmission properties of this genetic prion disease in various animal recipients but found no evidence of transmission in any inoculated mice, highlighting the distinct features of this particular genetic form of the disease. The study suggests that abnormal glycosylation may play a role in the reduced transmission efficiency associated with this genetic variant. [Extracted from the article]

Prion diseases have been linked to impaired copper homeostasis and copper induced-oxidative damage to the brain. Divalent metal ions, such as Cu2+ and Zn2+, bind to cellular prion protein (PrPC) at octapeptide repeat (OR) and non-OR sites within the N-terminal half of the protein but information on the impact of such binding on conversion to the misfolded isoform often derives from studies using either OR and non-OR peptides or bacterially-expressed recombinant PrP. Here we created new transgenic mouse lines expressing PrP with disrupted copper binding sites within all four histidine-containing OR's (sites 1–4, H60G, H68G, H76G, H84G, "TetraH>G" allele) or at site 5 (composed of residues His-95 and His-110; "H95G" allele) and monitored the formation of misfolded PrP in vivo. Novel transgenic mice expressing PrP(TetraH>G) at levels comparable to wild-type (wt) controls were susceptible to mouse-adapted scrapie strain RML but showed significantly prolonged incubation times. In contrast, amino acid replacement at residue 95 accelerated disease progression in corresponding PrP(H95G) mice. Neuropathological lesions in terminally ill transgenic mice were similar to scrapie-infected wt controls, but less severe. The pattern of PrPSc deposition, however, was not synaptic as seen in wt animals, but instead dense globular plaque-like accumulations of PrPSc in TgPrP(TetraH>G) mice and diffuse PrPSc deposition in (TgPrP(H95G) mice), were observed throughout all brain sections. We conclude that OR and site 5 histidine substitutions have divergent phenotypic impacts and that cis interactions between the OR region and the site 5 region modulate pathogenic outcomes by affecting the PrP globular domain. [ABSTRACT FROM AUTHOR]

Bovine spongiform encephalopathy (BSE) is a zoonotic transmissible spongiform encephalopathy (TSE) thought to be caused by the same prion strain as variant Creutzfeldt-Jakob disease (vCJD). Unlike scrapie and chronic wasting disease there is no cell culture model allowing the replication of proteinase K resistant BSE (PrPBSE) and the further in vitro study of this disease. We have generated a cell line based on the Madin-Darby Bovine Kidney (MDBK) cell line over-expressing the bovine prion protein. After exposure to naturally BSE-infected bovine brain homogenate this cell line has shown to replicate and accumulate PrPBSE and maintain infection up to passage 83 after initial challenge. Collectively, we demonstrate, for the first time, that the BSE agent can infect cell lines over-expressing the bovine prion protein similar to other prion diseases. These BSE infected cells will provide a useful tool to facilitate the study of potential therapeutic agents and the diagnosis of BSE. [ABSTRACT FROM AUTHOR]

The prion agent is notoriously resistant to common proteases and conventional sterilisation procedures. The current methods known to destroy prion infectivity such as incineration, alkaline and thermal hydrolysis are harsh, destructive, environmentally polluting and potentially hazardous, thus limit their applications for decontamination of delicate medical and laboratory devices, remediation of prion contaminated environment and for processing animal by-products including specified risk materials and carcases. Therefore, an environmentally friendly, non-destructive enzymatic degradation approach is highly desirable. A feather-degrading Bacillus licheniformis N22 keratinase has been isolated which degraded scrapie prion to undetectable level of PrPSc signals as determined by Western Blot analysis. Prion infectivity was verified by ex vivo cell-based assay. An enzymatic formulation combining N22 keratinase and biosurfactant derived from Pseudomonas aeruginosa degraded PrPSc at 65°C in 10 min to undetectable level -. A time-course degradation analysis carried out at 50°C over 2 h revealed the progressive attenuation of PrPSc intensity. Test of residual infectivity by standard cell culture assay confirmed that the enzymatic formulation reduced PrPSc infectivity to undetectable levels as compared to cells challenged with untreated standard scrapie sheep prion (SSBP/1) (p-value = 0.008 at 95% confidence interval). This novel enzymatic formulation has significant potential application for prion decontamination in various environmentally friendly systems under mild treatment conditions. [ABSTRACT FROM AUTHOR]

To identify the dynamic transcriptional alterations in CNS during the development of prion disease, brains of scrapie-infected mice and age-matched, mock-inoculated controls were analyzed immediately before inoculation and at different time points post-inoculation using Affymetrix microarray technique. A total of 449 probe sets, representing 430 genes, showed differential expression between scrapie- and mock-inoculated mice over the time course. These genes could be separated into two clusters according to expression patterns: the genes in cluster 1 demonstrated lower mRNA levels in scrapie-infected brains when compared with mock-inoculated brains, whereas genes in cluster 2 showed higher mRNA levels in scrapie-infected brains. Functional analysis of differentially expressed genes revealed the most severely affected biological process: cholesterol metabolism. The expression patterns of the cholesterol-related genes indicated an inhibited cholesterol synthesis in the diseased brains. Conspicuously, a number of cluster 1 genes, including some of cholesterol-related genes, showed not only decreasing mRNA levels in scrapie-infected brains but also increasing mRNA levels in mock-inoculated brains with increasing age. Quantitative RT-PCR analysis of some cholesterol-related genes in untreated mice suggested that changes of the examined genes observed in mock-inoculated brains are mainly age related. This finding indicated a link between age-related genes and scrapie-associated neurodegeneration. [ABSTRACT FROM AUTHOR]

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

The pathogenesis of prion diseases, a class of transmissible fatal neurodegenerative diseases in humans and animals, is still unclear. The aim of this study was to identify the differentially regulated genes that correlate with the development of prion diseases for a better understanding of their pathological mechanisms. We employed Affymetrix Mouse Expression Arrays 430A containing >22,000 transcripts and compared the global gene expression profiles from brains of mice who were intracerebrally inoculated with scrapie strains ME7 and RML with those from brains of uninfected and mock-infected mice. The microarray data were analyzed by Significance Analysis of Microarrays, revealing 121 genes whose expression increased at least twofold in both ME7- and RML-infected mouse brains, with an estimated false discovery rate of ≤5%. These genes encode proteins involved in proteolysis, protease inhibition, cell growth and maintenance, the immune response, signal transduction, cell adhesion, and molecular metabolism. The time course of expression generally showed up-regulation of these genes from 120 days postinoculation (dpi) for ME7-inoculated mouse brains and from 90 dpi for RML-inoculated mouse brains. The onset of elevated expression correlated temporally with the onset of PrPSc accumulation and the activation of glia, which may have contributed to neuronal cell death. Among the differentially regulated genes reported in the present study, the emergence of genes for several cathepsins and S100 calcium binding proteins was conspicuous. These and other genes reported here may represent novel potential diagnostic and therapeutic targets for prion disease. [ABSTRACT FROM AUTHOR]