Pathogenesis and prevalence of variant Creutzfeldt-Jakob disease

RT-QuIC as ultrasensitive method for prion detection

Real-time quaking-induced conversion (RT-QuIC) is a cell-free abnormal form of prion protein (PrP^Sc) amplification method using recombinant prion protein from Escherichia coli that can measure prion seeding activity in samples with high sensitivity. The advantages of this method are that it is much more sensitive than Western blotting, which is usually used to detect PrP^Sc, and that prion seeding activity can be easily quantified by combining it with endpoint dilution of the sample, and that it can be amplified in most species and prion strains. A decade has passed since the development of RT-QuIC, and many studies have been reported that take advantage of its characteristics. In particular, its usefulness in the diagnosis of sporadic CJD has been clarified, and it is recommended to be one of the diagnostic criteria. Future challenges include the establishment of a method to differentiate prion strains and application of RT-QuIC to early diagnosis of prion diseases and determination of treatment efficacy.

Human Prion Disorders: Review of the Current Literature and a Twenty-Year Experience of the National Surveillance Center in the Czech Republic

Human prion disorders (transmissible spongiform encephalopathies, TSEs) are unique, progressive, and fatal neurodegenerative diseases caused by aggregation of misfolded prion protein in neuronal tissue. Due to the potential transmission, human TSEs are under active surveillance in a majority of countries; in the Czech Republic data are centralized at the National surveillance center (NRL) which has a clinical and a neuropathological subdivision. The aim of our article is to review current knowledge about human TSEs and summarize the experience of active surveillance of human prion diseases in the Czech Republic during the last 20 years. Possible or probable TSEs undergo a mandatory autopsy using a standardized protocol. From 2001 to 2020, 305 cases of sporadic and genetic TSEs including 8 rare cases of Gerstmann-Sträussler-Scheinker syndrome (GSS) were confirmed. Additionally, in the Czech Republic, brain samples from all corneal donors have been tested by the NRL immunology laboratory to increase the safety of corneal transplants since January 2007. All tested 6590 corneal donor brain tissue samples were negative for prion protein deposits. Moreover, the routine use of diagnostic criteria including biomarkers are robust enough, and not even the COVID-19 pandemic has negatively impacted TSEs surveillance in the Czech Republic.

Processing and Handling Cost of Single-use Versus Traditional Instrumentation for 1 Level Lumbar Fusions

STUDY DESIGN

A single center, observational prospective clinical study.

OBJECTIVE

The aim of this study was to compare the instrumentation-related cost and efficiency of single-use instrumentation versus traditional reusable instrument trays.

SUMMARY OF BACKGROUND DATA

Single-use instrumentation provides the opportunity to reduce costs associated with cleaning and sterilizing instrumentation after surgery. Although previous studies have shown single-use instrumentation is effective in other orthopedic specialties, it is unclear if single-use instrumentation could provide economic advantages in spine surgery.

MATERIALS AND METHODS

A total of 40 (20 reusable instrumentation and 20 single-use instrumentation) lumbar decompression (1-3 level) and fusion (1 level) spine surgeries were collected. Instrument handling, opening, setup, re-stocking, cleaning, sterilization, inspection, packaging, and storage were recorded by direct observation for both reusable and single-use instrumentation. The rate of infection was noted for each group.

RESULTS

Mean time of handling instruments by the scrub nurse was 11.6 (±3.9) minutes for reusable instrumentation and 2.1 (±0.5) minutes for single-use instrumentation. Mean cost of handling reusable instruments was estimated to be $8.52 (±$2.96) per case, and the average cost to reprocess a single tray by Sterilization Processing Department (SPD) was $58. Thus, the median cost for sterilizing 2 reusable trays per case was $116, resulting in an average total Costresuable of $124.52 (±$2.96). Mean cost of handling single-use instrumentation was estimated to be $1.57 ($0.38) per case.

CONCLUSION

Single-use instrumentation provided greater cost savings and reduced time from the opening of instrumentation to use in surgery when compared with reusable instrumentation.

The importance of ongoing international surveillance for Creutzfeldt-Jakob disease

Creutzfeldt-Jakob disease (CJD) is a rapidly progressive, fatal and transmissible neurodegenerative disease associated with the accumulation of misfolded prion protein in the CNS. International CJD surveillance programmes have been active since the emergence, in the mid-1990s, of variant CJD (vCJD), a disease linked to bovine spongiform encephalopathy. Control measures have now successfully contained bovine spongiform encephalopathy and the incidence of vCJD has declined, leading to questions about the requirement for ongoing surveillance. However, several lines of evidence have raised concerns that further cases of vCJD could emerge as a result of prolonged incubation and/or secondary transmission. Emerging evidence from peripheral tissue distribution studies employing high-sensitivity assays suggests that all forms of human prion disease carry a theoretical risk of iatrogenic transmission. Finally, emerging diseases, such as chronic wasting disease and camel prion disease, pose further risks to public health. In this Review, we provide an up-to-date overview of the transmission of prion diseases in human populations and argue that CJD surveillance remains vital both from a public health perspective and to support essential research into disease pathophysiology, enhanced diagnostic tests and much-needed treatments.

Characteristics of Microbes Most Likely to Cause Pandemics and Global Catastrophes

Predicting which pathogen will confer the highest global catastrophic biological risk (GCBR) of a pandemic is a difficult task. Many approaches are retrospective and premised on prior pandemics; however, such an approach may fail to appreciate novel threats that do not have exact historical precedent. In this paper, based on a study and project we undertook, a new paradigm for pandemic preparedness is presented. This paradigm seeks to root pandemic risk in actual attributes possessed by specific classes of microbial organisms and leads to specific recommendations to augment preparedness activities.

Distribution and Quantitative Estimates of Variant Creutzfeldt-Jakob Disease Prions in Tissues of Clinical and Asymptomatic Patients

In the United-Kingdom, ≈1 of 2,000 persons could be infected with variant Creutzfeldt-Jakob disease (vCJD). Therefore, risk of transmission of vCJD by medical procedures remains a major concern for public health authorities. In this study, we used in vitro amplification of prions by protein misfolding cyclic amplification (PMCA) to estimate distribution and level of the vCJD agent in 21 tissues from 4 patients who died of clinical vCJD and from 1 asymptomatic person with vCJD. PMCA identified major levels of vCJD prions in a range of tissues, including liver, salivary gland, kidney, lung, and bone marrow. Bioassays confirmed that the quantitative estimate of levels of vCJD prion accumulation provided by PMCA are indicative of vCJD infectivity levels in tissues. Findings provide critical data for the design of measures to minimize risk for iatrogenic transmission of vCJD.

Recombinant PrP and Its Contribution to Research on Transmissible Spongiform Encephalopathies

The misfolding of the cellular prion protein (PrPC) into the disease-associated isoform (PrPSc) and its accumulation as amyloid fibrils in the central nervous system is one of the central events in transmissible spongiform encephalopathies (TSEs). Due to the proteinaceous nature of the causal agent the molecular mechanisms of misfolding, interspecies transmission, neurotoxicity and strain phenomenon remain mostly ill-defined or unknown. Significant advances were made using in vivo and in cellula models, but the limitations of these, primarily due to their inherent complexity and the small amounts of PrPSc that can be obtained, gave rise to the necessity of new model systems. The production of recombinant PrP using E. coli and subsequent induction of misfolding to the aberrant isoform using different techniques paved the way for the development of cell-free systems that complement the previous models. The generation of the first infectious recombinant prion proteins with identical properties of brain-derived PrPSc increased the value of cell-free systems for research on TSEs. The versatility and ease of implementation of these models have made them invaluable for the study of the molecular mechanisms of prion formation and propagation, and have enabled improvements in diagnosis, high-throughput screening of putative anti-prion compounds and the design of novel therapeutic strategies. Here, we provide an overview of the resultant advances in the prion field due to the development of recombinant PrP and its use in cell-free systems.

Transmission and Replication of Prions

Transmissible spongiform encephalopathies (TSEs) are a group of progressive, invariably fatal diseases that affect the nervous system of many mammals including humans. The key molecular event in the pathogenesis of TSEs is the conversion of the cellular prion protein PrP^C into a disease-associated isoform PrP^Sc. The "protein-only hypothesis" argues that PrP^Sc itself is the infectious agent. In effect, PrP^Sc can adopt several structures that represent different prion strains. The interspecies transmission of TSEs is difficult because of differences between the host and donor primary PrP sequence. However, transmission is not impossible as this occurred when bovine spongiform encephalopathy spread to humans causing variant Creutzfeldt-Jakob disease (vCJD). This event determined a need for a thorough understanding of prion replication and transmission so that we could be one step ahead of further threats for human health. This chapter focuses on these concepts and on new insights gained into prion propagation mechanisms.

Creutzfeldt-Jakob disease: updated diagnostic criteria, treatment algorithm, and the utility of brain biopsy

Creutzfeldt-Jakob disease (CJD) is a rare neurodegenerative condition with a rapid disease course and a mortality rate of 100%. Several forms of the disease have been described, and the most common is the sporadic type. The most challenging aspect of this disease is its diagnosis—the gold standard for definitive diagnosis is considered to be histopatho-logical confirmation—but newer tests are providing means for an antemortem diagnosis in ways less invasive than brain biopsy. Imaging studies, electroencephalography, and biomarkers are used in conjunction with the clinical picture to try to make the diagnosis of CJD without brain tissue samples, and all of these are reviewed in this article. The current diagnostic criteria are limited; test sensitivity and specificity varies with the genetics of the disease as well as the clinical stage. Physicians may be unsure of all diagnostic testing available, and may order outdated tests or prematurely request a brain biopsy when the diagnostic workup is incomplete. The authors review CJD, discuss the role of brain biopsy in this patient population, provide a diagnostic pathway for the patient presenting with rapidly progressive dementia, and propose newer diagnostic criteria.

Peripherally administrated prions reach the brain at sub-infectious quantities in experimental hamsters

The mechanisms implicated in prion infection and tissue distribution are not completely understood. In this study we investigated the levels of 263K prions in brain and spleen of Syrian hamsters few days after intra-peritoneal challenge. For this purpose we utilized the PMCA technology which permits to detect as little as few PrP(Sc) molecules. Our results show that peripherally administered prions directly reach the brain, although at levels below the minimum necessary to produce disease. PrP(Sc) remains in the brain several days after administration suggesting inefficient clearance or early replication. Understanding the fate of the infectious agent after administration and its uptake in different organs and fluids may provide useful information to develop strategies to minimize further spreading of prion diseases.

Human tonsil-derived follicular dendritic-like cells are refractory to human prion infection in vitro and traffic disease-associated prion protein to lysosomes

The molecular mechanisms involved in human cellular susceptibility to prion infection remain poorly defined. This is due, in part, to the absence of any well characterized and relevant cultured human cells susceptible to infection with human prions, such as those involved in Creutzfeldt-Jakob disease. In variant Creutzfeldt-Jakob disease, prion replication is thought to occur first in the lymphoreticular system and then spread into the brain. We have, therefore, examined the susceptibility of a human tonsil-derived follicular dendritic cell-like cell line (HK) to prion infection. HK cells were found to display a readily detectable, time-dependent increase in cell-associated abnormal prion protein (PrP(TSE)) when exposed to medium spiked with Creutzfeldt-Jakob disease brain homogenate, resulting in a coarse granular perinuclear PrP(TSE) staining pattern. Despite their high level of cellular prion protein expression, HK cells failed to support infection, as judged by longer term maintenance of PrP(TSE) accumulation. Colocalization studies revealed that exposure of HK cells to brain homogenate resulted in increased numbers of detectable lysosomes and that these structures immunostained intensely for PrP(TSE) after exposure to Creutzfeldt-Jakob disease brain homogenate. Our data suggest that human follicular dendritic-like cells and perhaps other human cell types are able to avoid prion infection by efficient lysosomal degradation of PrP(TSE).

Could immunomodulation be used to prevent prion diseases?

All prion diseases are currently without effective treatment and are universally fatal. The underlying pathogenesis of prion diseases (prionoses) is related to an autocatalytic conformational conversion of PrP(C) (C for cellular) to a pathological and infectious conformer known as PrP(Sc) (Sc for scrapie) or PrP(Res) (Res for proteinase K resistant). The past experience with variant Creutzfeldt-Jakob disease, which originated from bovine spongiform encephalopathy, as well as the ongoing epidemic of chronic wasting disease has highlighted the necessity for effective prophylactic and/or therapeutic approaches. Human prionoses are most commonly sporadic, and hence therapy is primarily directed to stop progression; however, in animals the majority of prionoses are infectious and, as a result, the emphasis is on prevention of transmission. These infectious prionoses are most commonly acquired via the alimentary tract as a major portal of infectious agent entry, making mucosal immunization a potentially attractive method to produce a local immune response that can partially or completely prevent prion entry across the gut barrier, while at the same time producing a modulated systemic immunity that is unlikely to be associated with toxicity. A critical factor in any immunomodulatory methodology that targets a self-antigen is the need to delicately balance an effective humoral immune response with potential autoimmune inflammatory toxicity. The ongoing epidemic of chronic wasting disease affecting the USA and Korea, with the potential to spread to human populations, highlights the need for such immunomodulatory approaches.

Sensitive and specific detection of sporadic Creutzfeldt-Jakob disease brain prion protein using real-time quaking-induced conversion

Real-time quaking-induced conversion (RT-QuIC) is an assay in which disease-associated prion protein (PrP) initiates a rapid conformational transition in recombinant PrP (recPrP), resulting in the formation of amyloid that can be monitored in real time using the dye thioflavin T. It therefore has potential advantages over analogous cell-free PrP conversion assays such as protein misfolding cyclic amplification (PMCA). The QuIC assay and the related amyloid seeding assay have been developed largely using rodent-passaged sheep scrapie strains. Given the potential RT-QuIC has for Creutzfeldt-Jakob disease (CJD) research and human prion test development, this study characterized the behaviour of a range of CJD brain specimens with hamster and human recPrP in the RT-QuIC assay. The results showed that RT-QuIC is a rapid, sensitive and specific test for the form of abnormal PrP found in the most commonly occurring forms of sporadic CJD. The assay appeared to be largely independent of species-related sequence differences between human and hamster recPrP and of the methionine/valine polymorphism at codon 129 of the human PrP gene. However, with the same conditions and substrate, the assay was less efficient in detecting the abnormal PrP that characterizes variant CJD brain. Comparison of these QuIC results with those previously obtained using PMCA suggested that these two seemingly similar assays differ in important respects.

Atomic structures suggest determinants of transmission barriers in mammalian prion disease

Prion represents a unique class of pathogens devoid of nucleic acid. The deadly diseases transmitted by it between members of one species and, in certain instances, to members of other species present a public health concern. Transmissibility and the barriers to transmission between species have been suggested to arise from the degree to which a pathological protein conformation from an individual of one species can seed a pathological conformation in another species. However, this hypothesis has never been illustrated at an atomic level. Here we present three X-ray atomic structures of the same segment from human, mouse, and hamster PrP, which is critical for forming amyloid and confers species specificity in PrP seeding experiments. The structures reveal that different sequences encode different steric zippers and suggest that the degree of dissimilarity of these zipper structures gives rise to transmission barriers in prion disease, such as those that protect humans from acquiring bovine spongiform encephalopathy (BSE) and chronic wasting disease (CWD).

A Chinese Creutzfeldt-Jakob disease patient with E196K mutation in PRNP

Genetic Creutzfeldt-Jakob disease (gCJD) is caused by a range of mutations in the prion protein gene (PRNP) and account for approximately 10-15% of overall human prion diseases worldwide. They are different with disease onset, disease duration, clinical signs and diagnostic findings. Here we reported a 71 year-old female with an E196K mutation in one PRNP allele, while the codon 129 was a methionine homozygous genotype. The patient started with non-specific symptoms, but displayed rapidly progressive disturbances of speech, memory, cognitive and physical movement. No periodic activity was recorded at electroencephalography (EEG) during the entire disease course. Retrospective investigation of her family members did not reveal similar neurological disorders. Total clinical course was about seven months.

Immunomodulation for prion and prion-related diseases

Prion diseases are a unique category of illness, affecting both animals and humans, where the underlying pathogenesis is related to a conformational change of a normal self protein called cellular prion protein to a pathological and infectious conformer known as scrapie prion protein (PrP(Sc)). Currently, all prion diseases lack effective treatment and are universally fatal. Past experiences with bovine spongiform encephalopathy and variant Creutzfeldt-Jakob disease mainly in Europe, as well as the current epidemic of chronic wasting disease in North America, have highlighted the need to develop prophylactic and/or therapeutic approaches. In Alzheimer's disease that, like prion disease, is a conformational neurodegenerative disorder, both passive and active immunization has been shown to be highly effective in model animals at preventing disease and cognitive deficits, with emerging data from human trials suggesting that this approach is able to reduce amyloid-related pathology. However, any immunomodulatory approach aimed at a self-antigen has to finely balance an effective humoral immune response with potential autoimmune toxicity. The prion diseases most commonly acquired by infection typically have the alimentary tract as a portal of infectious agent entry. This makes mucosal immunization a potentially attractive method to produce a local immune response that partially or completely prevents prion entry across the gut barrier, while at the same time producing modulated systemic immunity that is unlikely to be associated with toxicity. Our results using an attenuated Salmonella vaccine strain expressing the prion protein showed that mucosal vaccination can protect against prion infection from a peripheral source, suggesting the feasibility of this approach. It is also possible to develop active and/or passive immunomodulatory approaches that more specifically target PrP(Sc) or target the shared pathological conformer found in numerous conformational disorders. Such approaches could have a significant impact on many of the common age-associated dementias.

Probable variant Creutzfeldt–Jakob disease in Asia: a case report from Taiwan and review of two prior cases

New variant Creutzfeldt–Jakob disease (vCJD) was first identified in the UK in 1996, and was causally linked to bovine spongiform encephalopathy. Herein we report the first case of vCJD in Taiwan: a 34-year-old man who had lived in the UK between 1989 and 1997. The patient presented with depression, irritability, personality change, painful feet and allodynia, followed by gait ataxia and cognitive impairment. Electroencephalograms did not show the typical appearance of sporadic CJD. The cerebrospinal fluid 14-3-3 protein immunoassay was negative. Brain magnetic resonance imaging revealed high signal lesions involving bilateral caudate nuclei, left lentiform nucleus, bilateral dorsomedial thalami and pulvinar on fluid-attenuation inversion recovery, T2- and diffusion-weighted imaging. Prion protein gene analysis showed homozygous for methionine at codon 129. The patient developed akinetic mutism at 16 months and died at 28 months after onset. The clinical presentation and neuroimaging findings were compatible with the vCJD cases reported since 1996, and met the World Health Organization Case Definition for probable vCJD. In this communication, we also review two other cases of vCJD in Asia. All three cases were assumed as imported cases from the UK because of the residential or travel history of the patients.

Review: contribution of transgenic models to understanding human prion disease

Transgenic mice expressing human prion protein in the absence of endogenous mouse prion protein faithfully replicate human prions. These models reproduce all of the key features of human disease, including long clinically silent incubation periods prior to fatal neurodegeneration with neuropathological phenotypes that mirror human prion strain diversity. Critical contributions to our understanding of human prion disease pathogenesis and aetiology have only been possible through the use of transgenic mice. These models have provided the basis for the conformational selection model of prion transmission barriers and have causally linked bovine spongiform encephalopathy with variant Creutzfeldt-Jakob disease. In the future these models will be essential for evaluating newly identified potentially zoonotic prion strains, for validating effective methods of prion decontamination and for developing effective therapeutic treatments for human prion disease.

Immunotherapy for prion diseases: opportunities and obstacles

Transmissible spongiform encephalopathies (TSEs) represent a unique form of infectious disease based on the misfolding of a self-protein into a pathological conformation. While other human diseases are also attributed to protein misfolding, the TSEs are unique in their zoonotic potential and iatrogenic infectivity. These characteristics are of particular importance in the aftermath of the UK bovine spongiform encephalopathy (BSE) outbreak due to the dual concerns that a subpopulation of individuals exposed to the infectious agent may be serving as asymptomatic carriers, and that TSEs of other food animals may also threaten human health. These potentials, in addition to the ongoing baseline of familial and sporadic human prion diseases, necessitate development of effective treatment options. While TSEs represent a novel paradigm of infection, there is nevertheless the opportunity to apply traditional approaches of medicine for disease treatment and prevention, including vaccines for immunotherapy and immunoprophylaxis. However, vaccine development for TSEs is complicated by the challenges and potential dangers associated with induction of immune responses to a self-epitope, as well as the obstacles to treatment of a chronic infection through immunotherapy. The ongoing threat of TSEs to human health, together with the opportunity to apply information emerging from these investigations to other protein misfolding disorders, justifies the efforts required to overcome these obstacles.

[Prion diseases: what is the role of dendritic cells in the pathogenesis of transmissible prion diseases?]

Prion diseases are caused by the transconformation of a normal cellular protein, PrPc, into an infectious isoform, PrPsc, which ultimately triggers neuronal death. They are always fatal and, after transmission, they feature long incubation periods, during which prions accumulate in lymphoid tissues, infect nerves and progress to the central nervous system. In lymphoid organs, prions replicate and accumulate in follicular dendritic cells. Suppressing these cells slows down the neuro-invasion but does not totally abrogate it. This review examines the current knowledge in the roles of hematopoietic dendritic cells at different steps of the pathogenesis of prion diseases. Dendritic cells endocytose inoculated prions, permit their crossing of the intestinal epithelium and then migrate and transport them to lymphoid organs. They can carry prions to sites of neuroinvasion, and establish contacts with axons in peripheral lymph nodes or even after passage of the blood-brain barrier. However, results in the literature on the role of dendritic cells differ according to the host or the prion strain.

Similarities between forms of sheep scrapie and Creutzfeldt-Jakob disease are encoded by distinct prion types

Transmissible spongiform encephalopathies such as scrapie in sheep, Creutzfeldt-Jakob disease (CJD) in humans, and bovine sporadic encephalopathy in cattle are characterized by the accumulation of a misfolded protein: the pathological prion protein. Ever since bovine sporadic encephalopathy was discovered as the likely cause of the new variant of CJD in humans, parallels between human and animal transmissible spongiform encephalopathies must be viewed under the aspect of a disease risk for humans. In our study we have compared prion characteristics of different forms of sheep scrapie with those of different phenotypes of sporadic CJD. The disease characteristics of sporadic CJD depend considerably on the prion type 1 or 2. Our results show that there are obvious parallels between sporadic CJD type 1 and the so-called atypical/Nor98 scrapie. These parelleles apply to the deposition form of pathological prion protein in the brain, detected by the paraffin-embedded-tissue blot and the prion aggregate stability with regard to denaturation by the chaotropic salt guanidine hydrochloride. The same applies to sporadic CJD type 2 and classical scrapie. The observed parallels between types of sporadic CJD and types of sheep scrapie demonstrate that distinct groups of prion disease exist in different species. This should be taken into consideration when discussing interspecies transmission.

Prions: Protein Aggregation and Infectious Diseases

Transmissible spongiform encephalopathies (TSEs) are inevitably lethal neurodegenerative diseases that affect humans and a large variety of animals. The infectious agent responsible for TSEs is the prion, an abnormally folded and aggregated protein that propagates itself by imposing its conformation onto the cellular prion protein (PrPC) of the host. PrPCis necessary for prion replication and for prion-induced neurodegeneration, yet the proximal causes of neuronal injury and death are still poorly understood. Prion toxicity may arise from the interference with the normal function of PrPC, and therefore, understanding the physiological role of PrPCmay help to clarify the mechanism underlying prion diseases. Here we discuss the evolution of the prion concept and how prion-like mechanisms may apply to other protein aggregation diseases. We describe the clinical and the pathological features of the prion diseases in human and animals, the events occurring during neuroinvasion, and the possible scenarios underlying brain damage. Finally, we discuss potential antiprion therapies and current developments in the realm of prion diagnostics.

Detection of PrPsc in blood from sheep infected with the scrapie and bovine spongiform encephalopathy agents

The role of blood in the iatrogenic transmission of transmissible spongiform encephalopathy (TSE) or prion disease has become an increasing concern since the reports of variant Creutzfeldt-Jakob disease (vCJD) transmission through blood transfusion from humans with subclinical infection. The development of highly sensitive rapid assays to screen for prion infection in blood is of high priority in order to facilitate the prevention of transmission via blood and blood products. In the present study we show that PrP(sc), a surrogate marker for TSE infection, can be detected in cells isolated from the blood from naturally and experimentally infected sheep by using a rapid ligand-based immunoassay. In sheep with clinical disease, PrP(sc) was detected in the blood of 55% of scrapie agent-infected animals (n = 80) and 71% of animals with bovine spongiform encephalopathy (n = 7). PrP(sc) was also detected several months before the onset of clinical signs in a subset of scrapie agent-infected sheep, followed from 3 months of age to clinical disease. This study confirms that PrP(sc) is associated with the cellular component of blood and can be detected in preclinical sheep by an immunoassay in the absence of in vitro or in vivo amplification.

Transcriptional changes in the brains of cattle orally infected with the bovine spongiform encephalopathy agent precede detection of infectivity

Bovine spongiform encephalopathy (BSE) is a fatal, transmissible, neurodegenerative disease of cattle. BSE can be transmitted experimentally between cattle through the oral route, and in this study, brain tissue samples from animals at different time points postinoculation were analyzed for changes in gene expression. The aims of this study were to identify differentially regulated genes during the progression of BSE using microarray-based gene expression profiling and to understand the effect of prion pathogenesis on gene expression. A total of 114 genes were found to be differentially regulated over the time course of the infection, and many of these 114 genes encode proteins involved in immune response, apoptosis, cell adhesion, stress response, and transcription. This study also revealed a broad correlation between gene expression profiles and the progression of BSE in cattle. At 21 months postinoculation, the largest number of differentially regulated genes was detected, suggesting that there are many pathogenic processes in the animal brain even prior to the detection of infectivity in the central nervous systems of these orally infected cattle. Moreover, evidence is presented to suggest that it is possible to predict the infectious status of animals using the expression profiles from this study.

New hospital disinfection processes for both conventional and prion infectious agents compatible with thermosensitive medical equipment

With the detection of prions in specific tissues in variant and sporadic Creutzfeldt-Jakob diseases, efficient decontamination for human transmissible spongiform encephalopathy (TSE) agents, that is compatible with medical equipment, has become a major issue. We previously described the cleavage of prions on exposure to copper (Cu) and hydrogen peroxide (H(2)O(2)) and have used this property to develop efficient prion decontamination processes. To validate this approach, in-vitro assays on genuine human and animal prions using both brain homogenates and steel wires to mimic contamination of medical equipment were conducted. In-vivo experiments using steel wire in the hamster 263 K model were then used to evaluate the effect on prion infectivity. Assays on classical pathogens following international norms completed these prion experiments. In-vitro data confirmed the full decontamination efficacy of H(2)O(2)/Cu on different TSE strains. Combination of Cu with peracetic acid, used for endoscope disinfection, also revealed improved prion decontamination. Animal assay demonstrated efficacy on TSE infectivity of H(2)O(2)/Cu alone or in combination with detergents (reduction factor > or =5.25 log(10)). Assays on classical pathogens confirmed the disinfection properties of the different processes. Taken together, these new disinfection processes are efficient for both conventional and prion infectious agents and are, compatible with thermosensitive medical equipment. They can be adapted to hospitals' and practitioners' routine use, and they present reduced risks for the environment and for healthcare professionals.

Anti-PrP Mab 6D11 suppresses PrP(Sc) replication in prion infected myeloid precursor line FDC-P1/22L and in the lymphoreticular system in vivo

The pathogenesis of prion diseases is related to conformational transformation of cellular prion protein (PrP(C)) into a toxic, infectious, and self-replicating conformer termed PrP(Sc). Following extracerebral inoculation, the replication of PrP(Sc) is confined for months to years to the lymporeticular system (LRS) before the secondary CNS involvement results in occurrence of neurological symptoms. Therefore, replication of PrP(Sc), in the early stage of infection can be targeted by therapeutic approaches, which like passive immunization have limited blood-brain-barrier penetration. In this study, we show that 6D11 anti-PrP monoclonal antibody (Mab) prevents infection on a FDC-P1 myeloid precursor cell line stably infected with 22L mouse adapted scrapie strain. Passive immunization of extracerebrally infected CD-1 mice with Mab 6D11 resulted in effective suppression of PrP(Sc) replication in the LRS. Although, a rebound of PrP(Sc) presence occurred when the Mab 6D11 treatment was stopped, passively immunized mice showed a prolongation of the incubation period by 36.9% (pb0.0001) and a significant decrease in CNS pathology compared to control groups receiving vehicle or murine IgG. Our results indicate that antibody-based therapeutic strategies can be used, even on a short-term basis, to delay or prevent disease in subjects accidentally exposed to prions.

Bacterial colitis increases susceptibility to oral prion disease

Dietary exposure to prion-contaminated materials has caused kuru and variant Creutzfeldt-Jakob disease in humans and transmissible spongiform encephalopathies (TSEs) in cattle, mink, and felines. The epidemiology of dietary prion infections suggests that host genetic modifiers and possibly exogenous cofactors may play a decisive role in determining disease susceptibility. However, few cofactors influencing susceptibility to prion infection have been identified. In the present study, we investigated whether colitis might represent one such cofactor. We report that moderate colitis caused by an attenuated Salmonella strain more than doubles the susceptibility of mice to oral prion infection and modestly accelerates the development of disease after prion challenge. The prion protein was up-regulated in intestines and mesenteric lymph nodes of mice with colitis, providing a possible mechanism for the effect of colitis on the pathogenesis of prion disease. Therefore, moderate intestinal inflammation at the time of prion exposure may constitute one of the elusive risk factors underlying the development of TSE.

Monitoring the accumulation of lipofuscin in aging murine eyes by fluorescence spectroscopy

The integrated fluorescence of murine eyes is collected as a function of age. This fluorescence is attributed to pigments generally referred to as lipofuscin and is observed to increase with age. No difference in fluorescence intensity is observed between the eyes of males or females. This work provides a benchmark for further studies that are planned in order to use such signatures as markers of central nervous system (CNS) tissue or even of diseased CNS tissue and provides a basis for determining the age of a healthy animal.

Molecular mechanisms of prion pathogenesis

Prion diseases are infectious neurodegenerative diseases occurring in humans and animals with an invariably lethal outcome. One fundamental mechanistic event in prion diseases is the aggregation of aberrantly folded prion protein into large amyloid plaques and fibrous structures associated with neurodegeneration. The cellular prion protein (PrPC) is absolutely required for disease development, and prion knockout mice are not susceptible to prion disease. Prions accumulate not only in the central nervous system but also in lymphoid organs, as shown for new variant and sporadic Creutzfeldt-Jakob patients and for some animals. To date it is largely accepted that prions consist primarily of PrPSc, a misfolded and aggregated beta-sheet-rich isoform of PrPC. However, PrPSc may or may not be completely congruent with the infectious moiety. Here, we discuss the molecular mechanisms leading to neurodegeneration, the role of the immune system in prion pathogenesis, and the existence of prion strains that appear to have different tropisms and biochemical characteristics.

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.

A multicentre audit of single-use surgical instruments (SUSI) for tonsillectomy and adenoidectomy

INTRODUCTION

Prions are resistant to conventional sterilisation procedures and, therefore, could be transmitted iatrogenically through re-usable adenoid and tonsil surgical instruments. Using disposable instruments would avoid the risk of transmission. We present the results of a complete audit loop using BBraun single-use surgical instruments (SUSI).

PATIENTS AND METHODS

This was a prospective multicentre audit. Surgeons were asked to fill in a standardised questionnaire recording details including postoperative complications, and evaluation of each piece of equipment compared with their own experience of conventional re-usable instruments. In the first cycle, constructive criticisms of the instruments were noted and the manufacturers modified the instruments accordingly. A second cycle of audit was subsequently undertaken.

RESULTS

A total of 86 patients were audited in the first cycle and 97 in the second cycle. Postoperative haemorrhage rate for both cycles was well within acceptable range. In the first audit cycle, surgeons generally found the Draffin rods, Boyle-Davis gag and bipolar diathermy forceps of poor quality and difficult to use. These were redesigned and, on repeat evaluation during the second audit cycle, were found to be just as good, if not better, than the re-usable instruments.

CONCLUSIONS

This study suggests that SUSI may be just as good as re-usable instruments. Furthermore, they may be more cost effective.

Molecular diagnosis of human prion disease

Human prion diseases are associated with a range of clinical presentations, and they are classified by both clinicopathological syndrome and etiology, with subclassification according to molecular criteria. Here, we describe procedures that are used within the MRC Prion Unit to determine a molecular diagnosis of human prion disease. Sequencing of the PRNP open reading frame to establish the presence of pathogenic mutations is described, together with detailed methods for immunoblot or immunohistochemical determination of the presence of abnormal prion protein in brain or peripheral tissues.

Vacuolar degeneration affecting brain macrophages/microglia in variant CJD: a report on two cases

We present the neuropathology of two cases of variant Creutzfeldt-Jakob disease (vCJD) showing significant vacuolar degenerative alterations specifically affecting brain macrophages/microglia within the thalamus and, to a lesser extent, within the neocortical grey matter. Vacuolar degeneration in these cells was extensive, and likely to be associated with the development of a uniform sub-type of 'spongiform' vacuole seen in vCJD. The extensive morphological alterations described here closely resemble those very recently reported by Zucconi and colleagues, in response to experimental copper deficiency induced through dietary restriction, but could not be detected in cases of sporadic CJD examined. The significance of these novel findings are discussed in relation to copper homeostasis, loss of function of cellular prion protein and aberrant lysosomal catabolism within brain macrophages/microglia. This type of vacuolation may constitute a component of the overall profile of spongiform changes associated with vCJD.

Is there the potential for an epidemic of variant Creutzfeldt-Jakob disease via blood transfusion in the UK?

The discovery of three individuals suspected to have contracted variant Creutzfeldt-Jakob disease (vCJD) through blood transfusions has heightened concerns that a secondary epidemic via human-to-human transmission could occur in the UK. The Department of Health responded immediately to this threat by banning those who had received blood transfusions since 1980 from donating blood. In this paper, we conduct a sensitivity analysis to explore the potential size of a blood-borne vCJD epidemic and investigate the effectiveness of public health interventions. A mathematical model was developed together with an expression for the basic reproduction number (R0). The sensitivity of model predictions to unknown parameters determining the transmission of vCJD via infected blood was assessed under pessimistic modelling assumptions. We found that the size of the epidemic (up until 2080) was bounded above by 900 cases, with self-sustaining epidemics (R0>1) also possible; but the scenarios under which such epidemics could arise were found to be biologically implausible. Under optimistic assumptions, public health interventions reduced the upper bound to 250 and further still when only biologically plausible scenarios were considered. Our results support the belief that scenarios leading to large or self-sustaining epidemics are possible but unlikely, and that public health interventions were effective.

Therapeutic approaches for prion and Alzheimer's diseases

Alzheimer's and prion diseases belong to a category of conformational neurodegenerative disorders [Prusiner SB (2001) N Eng J Med344, 1516-1526; Sadowski M & Wisniewski T (2007) Curr Pharm Des 13, 1943-1954; Beekes M (2007) FEBS J 274, 575]. Treatments capable of arresting or at least effectively modifying the course of disease do not yet exist for either one of these diseases. Alzheimer's disease is the major cause of dementia in the elderly and has become an ever greater problem with the aging of Western societies. Unlike Alzheimer's disease, prion diseases are relatively rare. Each year only approximately 300 people in the USA and approximately 100 people in the UK succumb to various forms of prion diseases [Beekes M (2007) FEBS J 274, 575; Sigurdsson EM & Wisniewski T (2005) Exp Rev Vaccines 4, 607-610]. Nevertheless, these disorders have received great scientific and public interest due to the fact that they can be transmissible among humans and in certain conditions from animals to humans. The emergence of variant Creutzfeld-Jakob disease demonstrated the transmissibility of the bovine spongiform encephalopathy to humans [Beekes M (2007) FEBS J 274, 575]. Therefore, the spread of bovine spongiform encephalopathy across Europe and the recently identified cases in North America have put a large human population at risk of prion infection. It is estimated that at least several thousand Britons are asymptomatic carriers of prion infections and may develop variant Creutzfeld-Jakob disease in the future [Hilton DA (2006) J Pathol 208, 134-141]. This delayed emergence of human cases following the near elimination of bovine spongiform encephalopathy in the UK may occur because prion disease have a very prolonged incubation period, ranging from months to decades, which depends on the amount of inoculum, the route of infection and the genetic predisposition of the infected subject [Hilton DA (2006) J Pathol 208, 134-141]. Therefore, there is a great need for effective therapies for both Alzheimer's disease and prion diseases.

Update on human prion disease

The recognition that variant Creutzfeldt-Jakob disease (vCJD) is caused by the same prion strain as bovine spongiform encephalopathy in cattle has dramatically highlighted the need for a precise understanding of the molecular biology of human prion diseases. Detailed clinical, pathological and molecular data from a large number of human prion disease patients indicate that phenotypic diversity in human prion disease relates in part to the propagation of disease-related PrP isoforms with distinct physicochemical properties. Incubation periods of prion infection in humans can exceed 50 years and therefore it will be some years before the extent of any human vCJD epidemic can be predicted with confidence.

Electro-elution, a novel method to remove transmissible spongiform encephalopathy-associated PrPSc from stainless steel surgical instruments

Iatrogenic transmission of transmissible spongiform encephalopathies (TSEs) has been demonstrated via surgical instruments and there is concern over the efficacy of conventional decontamination techniques used to reprocess reusable instruments. This paper describes the development of a novel cleaning method, 'electro-elution', to remove TSE disease-specific abnormal protein PrP(Sc) from the surface of stainless steel surgical instruments. The electro-elution process subjects the stainless steel instrument to an electrical current in the presence of an electrolytic buffer to remove protein deposits. Stainless steel discs were contaminated with infectious brain homogenate and subjected to a range of conditions to determine the ability of electro-elution to remove the deposits. To determine whether there was any residual PrP(Sc) remaining on the disc after electro-elution, a novel detection method, 'direct blotting', was also developed. Direct blotting utilizes a process of passive transfer of proteins directly from the surface of the instrument to a proteophilic membrane for detection. Our study shows that electro-elution has the ability to effectively remove, and possibly degrade, disease-associated PrP(Sc) from the surface of stainless steel surgical instruments.

Is there a real risk of transmitting variant Creutzfeldt-Jakob disease by donor sperm insemination?

Although >99% of cases of Creutzfeldt-Jakob disease (CJD) are caused by spontaneous or inherited mutations in the prion protein, 'variant' CJD (vCJD) arose from dietary exposure to meat products infected with the bovine spongiform encephalopathy prion. While European and Canadian sperm donor candidates are rejected for significant CJD risk factors, American sperm donors are managed like blood donors (excluding all men who spent > or =3 months in the UK during 1980-1996 or > or =5 years in Europe since 1980), even though no evidence exists for sexual transmission of prion disease. This study surveyed international experts on either prions/prion disease or donor sperm/cryobanking as to the risk of vCJD transmission via semen/donor spermatozoa (45/104 replied). Consensus expert opinion was that the risk of transmission was <1:10,000,000, even for UK men, hence ultra-conservative risk avoidance would have minimal impact on public safety. Defining 'high vCJD risk' should be based on knowledge rather than fear, and due caution founded upon quantifying real risks rather than avoiding theoretical risks. Women seeking treatment using donor spermatozoa should be allowed to judge the negligible risk of vCJD infection in comparison with acceptable everyday risks, and given the choice of accepting spermatozoa from donors screened according to European-style criteria.

Current and future molecular diagnostics for prion diseases

It is now widely held that the infectious agents underlying the transmissible spongiform encephalopathies are prions, which are primarily composed of a misfolded, protease-resistant isoform of the host prion protein. Untreatable prion disorders include some human diseases, such as Creutzfeldt-Jakob disease, and diseases of economically important animals, such as bovine spongiform encephalopathy (cattle) and chronic wasting disease (deer and elk). Detection and diagnosis of prion disease (and presymptomatic incubation) is contingent upon developing novel assays, which exploit properties uniquely possessed by this misfolded protein complex, rather than targeting an agent-specific nucleic acid. This review highlights some of the conventional and disruptive technologies developed to respond to this challenge.

Infection and disease: cause and cure

Much can be learnt about the mechanisms by which micro‐organisms cause disease from the ways that they interact with cells and tissues. This issue of The Journal of Pathology contains articles that address the roles that cell and tissue biology and pathology are playing in the elucidation of these mechanisms. A review of variant Creutzfeldt–Jakob disease is followed by a discussion of severe acute respiratory syndrome (SARS). Two articles on human papillomavirus (HPV) infection address the association between viral infection and neoplasia, as do reviews on viruses and lymphoma/leukaemia, and Kaposi's sarcoma‐associated herpesvirus (human herpesvirus 8, HHV8). The section on viral disease concludes with an article on morbilliviruses. The intracellular effects of bacteria are addressed in a review of Listeria infection and a further review outlines recent advances in our knowledge of syphilis. Reviews on Helicobacter and gastric neoplasia, innate defences against methicillin‐resistant Staphylococcus aureus (MRSA) infection, and the function of granulomas in tuberculosis also address aspects of tissue responses to bacterial infection. Following a review of the function of immunoglobulin A in defence against infection, a group of articles considers vaccination and gene therapy approaches, the latter involving consideration of both viral and bacterial strategies. The reviews assembled here bridge several gaps: between microbiology and cellular pathology; between host and infecting organism; and between disease and therapy. It is clear that cell and tissue pathology approaches are of value in all of these spheres, providing cell and tissue relevance to microbiological and immunological observations. Copyright © 2006 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.