Prion Pathogenesis Revealed in a Series of the Special Issues "Prions and Prion Diseases".

Prion diseases are a group of devastating neurodegenerative disorders, which include Creutzfeldt-Jakob disease (CJD) in humans, and scrapie and bovine spongiform encephalopathy (BSE) in animals [...].

Risk of variant Creutzfeldt-Jakob disease transmission by blood transfusion in Australia.

BACKGROUND AND OBJECTIVES: Most of the 233 worldwide cases of variant Creutzfeldt-Jakob disease (vCJD) have been reported in the United Kingdom and 3 have been associated with transfusion-transmission. To mitigate the potential vCJD risk to blood safety, Australian Red Cross Lifeblood imposes restrictions on blood donation from people with prior residency in, or extended travel to, the United Kingdom during the risk period 1980-1996. We have modified a previously published methodology to estimate the transfusion-transmission risk of vCJD associated with fresh component transfusion in Australia if the UK residence deferral was removed. MATERIALS AND METHODS: The prevalence of current pre-symptomatic vCJD infection in the United Kingdom by age at infection and genotype was estimated based on risk of exposure to the bovine spongiform encephalopathy agent for the period 1980-1996. These results were used to estimate the age-specific prevalence of undiagnosed, pre-symptomatic vCJD in the Australian population in the current year due to prior UK residency or travel. The primary model outputs were the 2020 vCJD risks/unit of vCJD contamination, transfusion-transmission (infections) and clinical cases. RESULTS: The overall (prior UK residency in and travel to United Kingdom, 1980-1996) mean risk of contamination per unit was 1 in 29,900,000. The risks of resulting vCJD transmission (infection) and clinical case were 1 in 389,000,000 and 1 in 1,450,000,000, respectively. CONCLUSION: Our modelling suggests that removing the Lifeblood donation deferral for travel to, or UK residence, would result in virtually no increased risk of vCJD transfusion-transmission and would be a safe and effective strategy for increasing the donor base.

How an Infection of Sheep Revealed Prion Mechanisms in Alzheimer's Disease and Other Neurodegenerative Disorders.

Although it is not yet universally accepted that all neurodegenerative diseases (NDs) are prion disorders, there is little disagreement that Alzheimer's disease (AD), Parkinson's disease, frontotemporal dementia (FTD), and other NDs are a consequence of protein misfolding, aggregation, and spread. This widely accepted perspective arose from the prion hypothesis, which resulted from investigations on scrapie, a common transmissible disease of sheep and goats. The prion hypothesis argued that the causative infectious agent of scrapie was a novel proteinaceous pathogen devoid of functional nucleic acids and distinct from viruses, viroids, and bacteria. At the time, it seemed impossible that an infectious agent like the one causing scrapie could replicate and exist as diverse microbiological strains without nucleic acids. However, aggregates of a misfolded host-encoded protein, designated the prion protein (PrP), were shown to be the cause of scrapie as well as Creutzfeldt-Jakob disease (CJD) and Gerstmann-Sträussler-Scheinker syndrome (GSS), which are similar NDs in humans. This review discusses historical research on diseases caused by PrP misfolding, emphasizing principles of pathogenesis that were later found to be core features of other NDs. For example, the discovery that familial prion diseases can be caused by mutations in PrP was important for understanding prion replication and disease susceptibility not only for rare PrP diseases but also for far more common NDs involving other proteins. We compare diseases caused by misfolding and aggregation of APP-derived Aß peptides, tau, and α-synuclein with PrP prion disorders and argue for the classification of NDs caused by misfolding of these proteins as prion diseases. Deciphering the molecular pathogenesis of NDs as prion-mediated has provided new approaches for finding therapies for these intractable, invariably fatal disorders and has revolutionized the field.

Distribution of microRNA profiles in pre-clinical and clinical forms of murine and human prion disease.

Prion diseases are distinguished by long pre-clinical incubation periods during which prions actively propagate in the brain and cause neurodegeneration. In the pre-clinical stage, we hypothesize that upon prion infection, transcriptional changes occur that can lead to early neurodegeneration. A longitudinal analysis of miRNAs in pre-clinical and clinical forms of murine prion disease demonstrated dynamic expression changes during disease progression in the affected thalamus region and serum. Serum samples at each timepoint were collected whereby extracellular vesicles (EVs) were isolated and used to identify blood-based biomarkers reflective of pathology in the brain. Differentially expressed EV miRNAs were validated in human clinical samples from patients with human sporadic Creutzfeldt-Jakob disease (sCJD), with the molecular subtype at codon 129 either methionine-methionine (MM, n = 14) or valine-valine (VV, n = 12) compared to controls (n = 20). EV miRNA biomarkers associated with prion infection predicted sCJD with an AUC of 0.800 (85% sensitivity and 66.7% specificity) in a second independent validation cohort (n = 26) of sCJD and control patients with MM or VV subtype. This study discovered clinically relevant miRNAs that benefit diagnostic development to detect prion-related diseases and therapeutic development to inhibit prion infectivity.

Regional Differences in Neuroinflammation-Associated Gene Expression in the Brain of Sporadic Creutzfeldt-Jakob Disease Patients.

Neuroinflammation is an essential part of neurodegeneration. Yet, the current understanding of neuroinflammation-associated molecular events in distinct brain regions of prion disease patients is insufficient to lay the ground for effective treatment strategies targeting this complex neuropathological process. To address this problem, we analyzed the expression of 800 neuroinflammation-associated genes to create a profile of biological processes taking place in the frontal cortex and cerebellum of patients who suffered from sporadic Creutzfeldt-Jakob disease. The analysis was performed using NanoString nCounter technology with human neuroinflammation panel+. The observed gene expression patterns were regionally and sub-regionally distinct, suggesting a variable neuroinflammatory response. Interestingly, the observed differences could not be explained by the molecular subtypes of sporadic Creutzfeldt-Jakob disease. Furthermore, analyses of canonical pathways and upstream regulators based on differentially expressed genes indicated an overlap between biological processes taking place in different brain regions. This suggests that even smaller-scale spatial data reflecting subtle changes in brain cells' functional heterogeneity and their immediate pathologic microenvironments are needed to explain the observed differential gene expression in a greater detail.

Creutzfeldt-Jakob Disease with a Five-Year Clinical Course, Multicentric Cerebellar Prion Plaques and Prior History of Biopsy-Proven Primary Angiitis of the Central Nervous System: A Case for Iatrogenic Exposure?

Creutzfeldt-Jakob disease (CJD) is a rapidly progressive neurodegenerative disease that can arise spontaneously, genetically, or be acquired through iatrogenic exposure. Most patients die within a year of symptom onset. It is rare, affecting 1-2 per million per year, and the majority of cases are sporadic. Primary angiitis of the central nervous system (PACNS) is also rare, affecting 2.4 per million per year. We present a case of an unusually long clinical course of CJD, almost five years, which began with symptoms of apraxia. The patient had biopsy-proven PACNS 16 years prior to clinical presentation, and the site of biopsy was the left parietal lobe. Autopsy revealed multicentric prion plaques in the cerebellum, in the setting of normal genetic testing. The presence of plaques in the cerebellum, and prior neurosurgery, raises the possibility of iatrogenic exposure. We present the details of this case, including pathology from the original biopsy and final autopsy, as well as a review of relevant cases in the literature.

Characterization of Sporadic Creutzfeldt-Jakob Disease and History of Neurosurgery to Identify Potential Iatrogenic Cases.

We previously reported a phenotype of Creutzfeldt-Jakob disease (CJD), CJD-MMiK, that could help identify iatrogenic CJD. To find cases mimicking CJD-MMiK, we investigated clinical features and pathology of 1,155 patients with diagnosed sporadic CJD or unclassified CJD with and without history of neurosurgery. Patients with history of neurosurgery more frequently had an absence of periodic sharp-wave complexes on electroencephalogram than patients without a history of neurosurgery. Among 27 patients with history of neurosurgery, 5 had no periodic sharp-wave complexes on electroencephalogram. We confirmed 1 case of CJD-MMiK and suspected another. Both had methionine homozygosity at codon 129 of the prion protein gene and hyperintensity lesions in the thalamus on magnetic resonance images of the brain, which might be a clinical marker of CJD-MMiK. A subgroup with a history of neurosurgery and clinical features mimicking dura mater graft-associated CJD might have been infected during neurosurgery and had symptoms develop after many years.

[Update on Iatrogenic Creutzfeldt-Jakob Disease].

Recent progress in understanding of iatrogenic Creutzfeldt-Jakob disease (CJD) has revealed pathological and biochemical features specific to patients with iatrogenic CJD Based on the pathological and biochemical characteristics, we have identified iatrogenic CJD cases among presumed sporadic cases; in a neurosurgeon and in a patient with a medical history of neurosurgery. In addition, incidents of suspected CJD exposure via contaminated neurosurgical instruments are occasionally noted. Therefore, improvement of CJD case recognition and tracking of neurosurgical instruments are necessary to prevent iatrogenic CJD transmission via neurosurgical instruments. Further, accumulating evidence suggests that certain misfolded proteins and amyloid proteins, as well as prion proteins, are transmissible between individuals. Evaluation of the potential risks of iatrogenic transmission and the development of preventative strategies for these infectious proteins are our future tasks.

Assessment of risk of variant creutzfeldt-Jakob disease (vCJD) from use of bovine heparin.

PURPOSE: In the late1990s, reacting to the outbreak of bovine spongiform encephalopathy (BSE) in the United Kingdom that caused a new variant of Creutzfeldt-Jakob disease (vCJD) in humans, manufacturers withdrew bovine heparin from the market in the United States. There have been growing concerns about the adequate supply and safety of porcine heparin. Since the BSE epidemic has been declining markedly, the US Food and Drug Administration reevaluates the vCJD risk via use of bovine heparin. METHODS: We developed a computational model to estimate the vCJD risk to patients receiving bovine heparin injections. The model incorporated information including BSE prevalence, infectivity levels in the intestines, manufacturing batch size, yield of heparin, reduction in infectivity by manufacturing process, and the dose-response relationship. RESULTS: The model estimates a median risk of vCJD infection from a single intravenous dose (10 000 USP units) of heparin made from US-sourced bovine intestines to be 6.9 × 10-9 (2.5-97.fifth percentile: 1.5 × 10-9 -4.3 × 10-8 ), a risk of 1 in 145 million, and 4.6 × 10-8 (2.5-97.fifth percentile: 1.1 × 10-8 -2.6 × 10-7 ), a risk of 1 in 22 million for Canada-sourced products. The model estimates a median risk of 1.4 × 10-7 (2.5-97.fifth percentile: 2.9 × 10-8 -9.3 × 10-7 ) and 9.6 × 10-7 (2.5-97.fifth percentile: 2.1 × 10-7 -5.6 × 10-6 ) for a typical treatment for venous thromboembolism (infusion of 2-4 doses daily per week) using US-sourced and Canada-sourced bovine heparin, respectively. CONCLUSIONS: The model estimates the vCJD risk from use of heparin when appropriately manufactured from US or Canadian cattle is likely small. The model and conclusions should not be applied to other medicinal products manufactured using bovine-derived materials.

Informing patient contacts about iatrogenic Creutzfeldt-Jakob disease.

The unanticipated diagnosis of sporadic Creutzfeldt-Jakob disease (sCJD) in a patient after previous neurosurgery can lead to difficult decisions regarding informing contacts. A patient developed sCJD 3 years after neurosurgery. There were 29 potential contacts and 26 were contacted. Twelve completed a questionnaire. The majority of patients wished to know about the contact and to be seen face-to-face, and their main concern was developing the disease despite verbal and written reassurance that this was unlikely. Informing patients of sCJD contact is difficult and can lead to significant patient anxiety. Face-to-face meetings, a helpline and follow-up can help.

Correlation between Bioassay and Protein Misfolding Cyclic Amplification for Variant Creutzfeldt-Jakob Disease Decontamination Studies.

To date, approximately 500 iatrogenic Creutzfeldt-Jakob disease cases have been reported worldwide, most of them resulting from cadaveric dura mater graft and from the administration of prion-contaminated human growth hormone. The unusual resistance of prions to decontamination processes, their large tissue distribution, and the uncertainty about the prevalence of variant Creutzfeldt-Jakob disease (vCJD) in the general population lead to specific recommendations regarding identification of tissue at risk and reprocessing of reusable medical devices, including the use of dedicated treatment for prion inactivation. We previously described an in vitro assay, called Surf-PMCA, which allowed us to classify prion decontamination treatments according to their efficacy on vCJD prions by monitoring residual seeding activity (RSA). Here, we used a transgenic mouse line permissive to vCJD prions to study the correlation between the RSA measured in vitro and the in vivo infectivity. Implantation in mouse brains of prion-contaminated steel wires subjected to different decontamination procedures allows us to demonstrate a good concordance between RSA measured by Surf-PMCA (in vitro) and residual infectivity (in vivo). These experiments emphasize the strength of the Surf-PMCA method as a rapid and sensitive assay for the evaluation of prion decontamination procedures and also confirm the lack of efficacy of several marketed reagents on vCJD prion decontamination.IMPORTANCE Creutzfeldt-Jakob diseases are neurodegenerative disorders for which transmission linked to medical procedures have been reported in hundreds of patients. As prion diseases, they are characterized by an unusual resistance to conventional decontamination processes. Moreover, their large tissue distribution and the ability of prions to attach to many surfaces raised the risk of transmission in health care facilities. It is therefore of major importance that decontamination procedures applied to medical devices before their reprocessing are thoroughly validated for prion inactivation. We previously described an in vitro assay, which allowed us to classify accurately prion decontamination treatments according to their efficacy on variant Creutzfeldt-Jakob disease. The significance of this study is in demonstrating the concordance between previous in vitro results and infectivity studies in transgenic mice. Furthermore, commercial reagents currently used in hospitals were tested by both protocols, and we observed that most of them were ineffective on human prions.

Epitope mapping of the protease resistant products of RT-QuIC does not allow the discrimination of sCJD subtypes.

Sporadic Creutzfeldt-Jakob disease (sCJD) is a transmissible, rapidly progressive and fatal neurodegenerative disease. The transmissible agent linked to sCJD is composed of the misfolded form of the host-encoded prion protein. The combination of histopathological and biochemical analyses has allowed the identification and sub-classification of six sCJD subtypes. This classification depends on the polymorphic variability of codon 129 of the prion protein gene and the PrPres isotype, and appears to be associated with neuropathological and clinical features. Currently, sCJD subtyping is only fully achievable post mortem. However, a rapid and non-invasive method for discriminating sCJD subtypes in vita would be invaluable for the clinical management of affected individuals, and for the selection of participants for clinical trials. The CSF analysis by Real Time Quaking Induced Conversion (RT-QuIC) reaction is the most sensitive and specific ante mortem sCJD diagnostic test available to date, and it is used by a number of laboratories internationally. RT-QuIC takes advantage of the natural replication mechanisms of prions by template-induced misfolding, employing recombinant prion protein as reaction substrate. We asked whether epitope mapping, of the RT-QuIC reaction products obtained from seeding RT-QuIC with brain and CSF samples from each of the six molecular subtypes of sCJD could be employed to distinguish them and therefore achieve in vita sCJD molecular subtyping. We found that it is possible to distinguish the RT-QuIC products generated by sCJD biological samples from the ones generated by spontaneous conversion in the negative controls, but that different sCJD subtypes generate very similar, if not identical RT-QuIC reaction products. We concluded that whilst RT-QuIC has demonstrable diagnostic value it has limited prognostic value at this point in time.

Transmission of amyloid-ß protein pathology from cadaveric pituitary growth hormone.

We previously reported1 the presence of amyloid-ß protein (Aß) deposits in individuals with Creutzfeldt-Jakob disease (CJD) who had been treated during childhood with human cadaveric pituitary-derived growth hormone (c-hGH) contaminated with prions. The marked deposition of parenchymal and vascular Aß in these relatively young individuals with treatment-induced (iatrogenic) CJD (iCJD), in contrast to other prion-disease patients and population controls, allied with the ability of Alzheimer's disease brain homogenates to seed Aß deposition in laboratory animals, led us to argue that the implicated c-hGH batches might have been contaminated with Aß seeds as well as with prions. However, this was necessarily an association, and not an experimental, study in humans and causality could not be concluded. Given the public health importance of our hypothesis, we proceeded to identify and biochemically analyse archived vials of c-hGH. Here we show that certain c-hGH batches to which patients with iCJD and Aß pathology were exposed have substantial levels of Aß40, Aß42 and tau proteins, and that this material can seed the formation of Aß plaques and cerebral Aß-amyloid angiopathy in intracerebrally inoculated mice expressing a mutant, humanized amyloid precursor protein. These results confirm the presence of Aß seeds in archived c-hGH vials and are consistent with the hypothesized iatrogenic human transmission of Aß pathology. This experimental confirmation has implications for both the prevention and the treatment of Alzheimer's disease, and should prompt a review of the risk of iatrogenic transmission of Aß seeds by medical and surgical procedures long recognized to pose a risk of accidental prion transmission2,3.

Autopsied case of non-plaque-type dura mater graft-associated Creutzfeldt-Jakob disease presenting with extensive amyloid-ß deposition.

We present an autopsied case of non-plaque-type dura mater graft-associated Creutzfeldt-Jakob disease (dCJD) with extensive amyloid-ß (Aß) deposition in the brain. A 39-year-old Japanese woman presented with memory disturbance and abnormal behavior. The patient had a history of craniotomy with dura matter-graft transplant for a head injury which occurred when she was 19 years old. Magnetic resonance imaging (MRI) showed hyperintensities in the cerebral cortex and striatum on diffusion-weighted images, particularly on the dura mater-grafted right side. Her clinical symptoms, including rapidly progressing cognitive impairment, myoclonus, and periodic sharp wave complexes on electroencephalogram, could not be distinguished from typical sporadic CJD cases. The patient died 11 months after symptom onset, and pathological investigations showed extensive spongiform degeneration with prion protein (PrP) deposition without Kuru plaques; these observations were essentially the same as those of typical sporadic CJD cases. Furthermore, Aß immunohistochemistry showed extensive diffuse staining in the cerebral neocortex, plaque-type deposition, positive staining in the pia mater, and cerebral amyloid angiopathy. Although the MRI findings suggested that the pathological involvement originated from the dura mater-grafted right side, the PrP and Aß depositions showed no apparent regionalization and laterality. Tau-pathology including neurofibrillary tangles was hardly identified. The proteins phosphorylated α-synuclein and phosphorylated transactivation response DNA-binding protein 43 kDa were not detected on immunostaining. Although this report describes only one case, various speculations were made based on detailed clinical and pathological observations in conjunction with previous reports of dCJD. In particular, this report provides significant insight into the characteristics and progression of dCJD pathology and its relationship with Aß pathology.

Variant Creutzfeldt-Jakob disease.

Variant CJD (vCJD) was described first in the United Kingdom in 1996. It is a zoonotic form of human prion disease, originating from dietary contamination of human food with material from bovine spongiform encephalopathy (BSE)-affected cattle. It has important epidemiologic, clinical, and neuropathogic differences from other forms of human prion disease. Cases have occurred in several countries but the United Kingdom and France have been most affected. Following the decline in BSE in cattle and the dietary protective measures adopted, vCJD has become an extremely rare disease. However, important concerns remain about asymptomatic infection in human populations (especially the United Kingdom) and the possibility of human-to-human transmission via medical and surgical interventions. Definitive diagnosis depends on neuropathology, usually undertaken at autopsy, but sometimes on brain biopsy. Clinical diagnosis with a reasonable degree of likelihood is, however, possible based on the clinical features and the finding of the pulvinar sign on cerebral magnetic resonance. There are also emerging tests (including blood tests) that have promising sensitivity and specificity for vCJD. It is a progressive illness, inevitably fatal with no curative treatment.