Iatrogenic Creutzfeldt-Jakob disease at the millennium

Intra-operative washing of morcellised bone allograft with pulse lavage: how effective is it in reducing blood and marrow content?

The use of unprocessed bone carries a risk of transmission of blood borne diseases. Although models of infectivity are unproven, a theoretical risk of transmission of variant Creutzfeld-Jakob Disease, a human prion disease, exists as probable blood borne transmission has been reported in three cases. The aim of our study was to determine the effectiveness of standard operating theatre pulse lavage in removing protein, fat and double stranded Deoxyribonucleic acid (dsDNA) from morcellised bone allograft. Twelve donated femoral heads were divided into halves and milled into bone chips. One half of the bone chips were washed with pulse lavage, whereas, the other half acted as control. In order to determine the amount of protein, fat and dsDNA present in the washed and unwashed samples, a validated multistep washing protocol was used. Using the validated technique, simple intra-operative washing of morcellised unprocessed bone allograft removed a significant amount of the protein (70.5%, range: 39.5-85%), fat (95.2%, range: 87.8-98.8%) and DNA (68.4%, range: 31.4-93.1%) content. Intra-operative washing of morcellised bone allograft with pulse lavage may thereby reduce the theoretical risk of prion and other blood borne disease transmission. Combined with the known improved mechanical characteristics of washed allograft, we would recommend pulse lavage as a routine part of bone allograft preparation.

Molecular pathology of human prion disease

Human prion diseases are associated with a range of clinical presentations and are classified by both clinicopathological syndrome and aetiology with sub-classification according to molecular criteria. Considerable experimental evidence suggests that phenotypic diversity in human prion disease relates in significant part to the existence of distinct human prion strains encoded by abnormal PrP isoforms with differing physicochemical properties. To date, however, the conformational repertoire of pathological isoforms of wild-type human PrP and the various forms of mutant human PrP has not been fully defined. Efforts to produce a unified international classification of human prion disease are still ongoing. The ability of genetic background to influence prion strain selection together with knowledge of numerous other factors that may influence clinical and neuropathological presentation strongly emphasises the requirement to identify distinct human prion strains in appropriate transgenic models, where host genetic variability and other modifiers of phenotype are removed. Defining how many human prion strains exist allied with transgenic modelling of potentially zoonotic prion strains will inform on how many human infections may have an animal origin. Understanding these relationships will have direct translation to protecting public health.

Tau, prions and Aβ: the triad of neurodegeneration

This article highlights the features that connect prion diseases with other cerebral amyloidoses and how these relate to neurodegeneration, with focus on tau phosphorylation. It also discusses similarities between prion disease and Alzheimer's disease: mechanisms of amyloid formation, neurotoxicity, pathways involved in triggering tau phosphorylation, links to cell cycle pathways and neuronal apoptosis. We review previous evidence of prion diseases triggering hyperphosphorylation of tau, and complement these findings with cases from our collection of genetic, sporadic and transmitted forms of prion diseases. This includes the novel finding that tau phosphorylation consistently occurs in sporadic CJD, in the absence of amyloid plaques.

PrioNet Canada: a network of centres of excellence for research on prion diseases--ongoing and future research directions

It is PrioNet's vision to build a network that shapes and sustains prion research in Canada, translating basic science into accessible socioeconomic benefits for global betterment. PrioNet's research is developing surveillance measures, diagnostic tools, vaccines, and potential therapies and determining the various impacts of prion diseases on people. PrioNet seeks to integrate scientifically informed risk management strategies and to use this knowledge to address ongoing problems posed by bovine spongiform encephalopathy (BSE), the gathering crisis of chronic wasting disease (CWD), emerging issues of human prion disease, and basic scientific understanding of the nature of prions. PrioNet is strategically responding to prion threats by focusing its network of highly accomplished researchers and trainees to implement integrated risk management strategies that could not be supported by other mechanisms.

Entzündliche Erkrankungen

Unter einer Meningitis versteht man eine Entzündung von Pia mater und Arachnoidea. Das Erregerspektrum ist weit und reicht von Bakterien, die hämatogen-metastatisch, fortgeleitet oder durch offene Hirnverletzung zur eitrigen Meningitis führen, über Viren zu Pilzen und Parasiten. Insbesondere bei den unbehandelt häufig letal verlaufenden eitrigen Meningitiden ist eine rasche Diagnose mit Erregernachweis notwendig. Unverzüglich ist daraufhin eine spezifische, der regionalen Resistenzentwicklung angepasste Therapie einzuleiten. Die meningeale Affektion im Rahmen einer Listeriose oder Tuberkulose verdient aufgrund des klinischen Bildes, des Verlaufs und der spezifischen Therapie besondere Beachtung. Die fungalen Infektionen werden, da klinisch häufig als Meningoenzephalitis imponierend, in Abschn. 33.3 abgehandelt.

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.

The prion diseases

The prion diseases are a family of rare neurodegenerative disorders that result from the accumulation of a misfolded isoform of the prion protein (PrP), a normal constituent of the neuronal membrane. Five subtypes constitute the known human prion diseases; kuru, Creutzfeldt-Jakob disease (CJD), Gerstmann-Sträussler-Scheinker syndrome (GSS), fatal insomnia (FI), and variant CJD (vCJD). These subtypes are distinguished, in part, by their clinical phenotype, but primarily by their associated brain histopathology. Evidence suggests these phenotypes are defined by differences in the pathogenic conformation of misfolded PrP. Although the vast majority of cases are sporadic, 10% to 15% result from an autosomal dominant mutation of the PrP gene (PRNP). General phenotype-genotype correlations can be made for the major subtypes of CJD, GSS, and FI. This paper will review some of the general background related to prion biology and detail the clinical and pathologic features of the major prion diseases, with a particular focus on the genetic aspects that result in prion disease or modification of its risk or phenotype.

Defining sporadic Creutzfeldt-Jakob disease strains and their transmission properties

The biological determinants of the phenotypic variation in sporadic Creutzfeldt-Jakob disease (sCJD) are unknown. To categorize sCJD cases, the prion protein (PrP) codon 129 genotype and the biochemical characteristics of the disease-associated form of PrP (PrP(Sc)) can be combined to form six subgroups (MM1, MM2, MV1, MV2, VV1, and VV2). This classification largely correlates with the known variation in the clinical and pathological features of sCJD, with the MM1 and MV1 cases representing the "classic" phenotype of sCJD. To address how this classification relates to different strains of sCJD we have inoculated each subgroup of sCJD to a panel of mice expressing different forms of the human PRNP gene (129MM, 129VV, and 129MV). We have established that all subtypes are transmissible to at least one genotype of mouse, and both agent and host factors determine transmission efficiency and the form of PrP(Sc) deposited in the brain. Moreover, we have identified four distinct strains of sCJD using our in vivo strain typing panel.

Growth hormone administration: is it safe and effective for athletic performance

Human growth hormone (GH) is widely abused by athletes; however, there is little evidence that GH improves physical performance. Replacement of GH in GH deficiency improves some aspects of exercise capacity. There is evidence for a protein anabolic effect of GH in healthy adults and for increased lean body mass following GH, although fluid retention likely contributes to this increase. The evidence suggests that muscle strength, power, and aerobic exercise capacity are not enhanced by GH administration, however GH may improve anaerobic exercise capacity. There are risks of adverse effects of long-term abuse of GH. Sustained abuse of GH may lead to a state mimicking acromegaly, a condition with increased morbidity and mortality.

Glycosylation of PrPC determines timing of neuroinvasion and targeting in the brain following transmissible spongiform encephalopathy infection by a peripheral route

Transmissible spongiform encephalopathy (TSE) infectivity naturally spreads from site of entry in the periphery to the central nervous system where pathological lesions are formed. Several routes and cells within the host have been identified as important for facilitating the infectious process. Expression of the glycoprotein cellular PrP (PrP(C)) is considered a key factor for replication of infectivity in the central nervous system (CNS) and its transport to the brain, and it has been suggested that the infectious agent propagates from cell to cell via a domino-like effect. However, precisely how this is achieved and what involvement the different glycoforms of PrP have in these processes remain to be determined. To address this issue, we have used our unique models of gene-targeted transgenic mice expressing different glycosylated forms of PrP. Two TSE strains were inoculated intraperitoneally into these mice to assess the contribution of diglycosylated, monoglycosylated, and unglycosylated PrP in spreading of infectivity to the brain. This study demonstrates that glycosylation of host PrP has a profound effect in determining the outcome of disease. Lack of diglycosylated PrP slowed or prevented disease onset after peripheral challenge, suggesting an important role for fully glycosylated PrP in either the replication of the infectious agent in the periphery or its transport to the CNS. Moreover, mice expressing unglycosylated PrP did not develop clinical disease, and mice expressing monoglycosylated PrP showed strikingly different neuropathologic features compared to those expressing diglycosylated PrP. This demonstrates that targeting in the brain following peripheral inoculation is profoundly influenced by the glycosylation status of host PrP.

Continuous intraventricular infusion of pentosan polysulfate: clinical trial against prion diseases

Prion diseases are progressive neurological disorders due to abnormal prion protein (PrP(Sc)) deposition in the central nervous system. At present, there is no effective treatment available for any form of prion disease. Pentosan polysulfate (PPS) has been shown to prolong significantly the incubation period in mice with PrP(Sc) infection when administered to the cerebral ventricles in preclinical trials. In human studies conducted in European countries and Japan, intraventricular PPS was administered to patients with different forms of prion disease and was well tolerated. We report 11 patients with prion disease treated with intraventricular PPS at Fukuoka University from 2004. Cases included three familial CJD (two with V180I mutation, one GSS with P102L mutation), two iatrogenic CJD, and six sporadic CJD cases. At present, average survival period after treatment was 24.2 months (range, 4-49). Seven cases died of sepsis and pneumonia. Subdural effusion with various degrees was seen on CT scan in most cases. Except for these, adverse effects did not occur in the treatment period. Although our preliminary study of the new treatment with PPS by continuous intraventricular infusion showed no apparent improvement of clinical features in patients with prion disease, the possibility of extended survival in some patients receiving long-term PPS was suggested.

Risk of Creutzfeldt-Jakob disease transmission by ocular surgery and tissue transplantation

Creutzfeldt-Jakob disease (CJD) is a rare, fatal neurodegenerative disease that occurs in sporadic, genetic, variant, and iatrogenic forms. The transformation of normal prion protein (PrP(C)) to the abnormal form (PrP(Sc)) is a key step in the pathogenesis of CJD and leads to the accumulation of amyloid and spongiform changes in the brain. The presence of PrP(Sc) in tissue is a surrogate marker for CJD infectivity. Sporadic CJD, whose cause is unknown, is by far the most frequent form with 1-2 cases per million population occurring every year-the genetic forms of CJD are rather rarer. The majority of variant CJD cases have occurred in the United Kingdom, where there have been four reports of transmission of vCJD by blood transfusion. The great majority of iatrogenic transmissions of CJD have resulted from the use of pituitary-derived hormones or dura mater with only a very few cases attributable to neurosurgical instruments or corneal transplants. In the absence of a validated test for CJD infectivity in eye donors, the application of appropriate donor selection criteria and the use of single-use instruments in eye banks are currently the most effective means of reducing the risk of CJD transmission. Onward transmission by reusable ophthalmic surgical instruments has not been reported, but the risk cannot be excluded. Use of appropriate cleaning and disinfection protocols and the ability to identify and quarantine instruments that may have been used on an infected patient are important safeguards.

A traceback phenomenon can reveal the origin of prion infection

The transmission of prions to animals with incongruent prion protein (PrP) gene (referred to as cross-sequence transmission) results in a relatively long incubation period and can generate a new prion strain with unique transmissibility designated as a traceback phenomenon. For example, cross-sequence transmission of bovine spongiform encephalopathy (BSE) prions to human generated variant Creutzfeldt-Jakob disease (vCJD) prions which retained the transmissibility to mice expressing bovine PrP. This finding suggests that traceback studies could enable us to identify the origin of prions. There are two distinct phenotypes in dura mater graft-associated Creutzfeldt-Jakob disease (dCJD), with the majority represented by a non-plaque-type of dCJD (np-dCJD) and the minority by a plaque-type of dCJD (p-dCJD). To identify the origin of p-dCJD, we performed a traceback study using mice expressing human PrP with methionine homozygosity (129M/M) or valine homozygosity (129V/V) at polymorphic codon 129. The characteristics of p-dCJD such as the accumulation of abnormal isoform of PrP (PrP(Sc)) intermediate in size between type 1 and type 2, and plaque-type PrP deposition in the brain were maintained after transmission to the 129M/M mice. Furthermore, the 129V/V mice were more susceptible to p-dCJD prions than the 129M/M mice and produced type 2 PrP(Sc) that were identical in size to those from the 129V/V mice inoculated with sporadic CJD prions from a patient with 129V/V and type 2 PrP(Sc) (sCJD-VV2). In addition, we performed intracerebral transmission of sCJD-VV2 prions to the 129M/M mice as an experimental model for p-dCJD. These 129M/M mice showed the accumulation of the intermediate type PrP(Sc) and plaque-type PrP deposition in the brain. These results suggest that p-dCJD could be caused by cross-sequence transmission of sCJD-VV2 prions to individuals with the 129M/M genotype.

The risk of iatrogenic Creutzfeldt-Jakob disease through medical and surgical procedures

There have been more than 400 patients who contracted Creutzfeldt-Jakob disease (CJD) via a medical procedure, that is, through the use of neurosurgical instruments, intracerebral electroencephalographic electrodes (EEG), human pituitary hormone, dura mater grafts, corneal transplant, and blood transfusion. The number of new patients with iatrogenic CJD has decreased; however, cases of variant CJD that was transmitted via blood transfusion have been reported since 2004. Clearly, iatrogenic transmission of CJD remains a serious problem. Recently, we investigated medical procedures (any surgery, neurosurgery, ophthalmic surgery, and blood transfusion) performed on patients registered by the CJD Surveillance Committee in Japan during a recent 9-year period. In a case-control study comprising 753 sporadic CJD (sCJD) patients and 210 control subjects, we found no evidence that prion disease was transmitted via the investigated medical procedures before onset of sCJD. In a review of previously reported case-control studies, blood transfusion was never shown to be a significant risk factor for CJD; our study yielded the same result. Some case-control studies reported that surgery was a significant risk factor for sCJD. However, when surgical procedures were categorized by type of surgery, the results were conflicting, which suggests that there is little possibility of prion transmission via surgical procedures. In our study, 4.5% of sCJD patients underwent surgery after onset of sCJD, including neurosurgeries in 0.8% and ophthalmic surgeries in 1.9%. The fact that some patients underwent surgery, including neurosurgery, even after the onset of sCJD indicates that we cannot exclude the possibility of prion transmission via medical procedures. We must remain vigilant against prion diseases to reduce the risk of iatrogenesis.

Ultraviolet-ozone treatment reduces levels of disease-associated prion protein and prion infectivity

Background

Transmissible spongiform encephalopathies (TSEs) are a group of fatal neurodegenerative diseases caused by novel infectious agents referred to as prions. Prions appear to be composed primarily, if not exclusively, of a misfolded isoform of the cellular prion protein. TSE infectivity is remarkably stable and can resist many aggressive decontamination procedures, increasing human, livestock and wildlife exposure to TSEs.

Findings

We tested the hypothesis that UV-ozone treatment reduces levels of the pathogenic prion protein and inactivates the infectious agent. We found that UV-ozone treatment decreased the carbon and prion protein content in infected brain homogenate to levels undetectable by dry-ashing carbon analysis or immunoblotting, respectively. After 8 weeks of ashing, UV-ozone treatment reduced the infectious titer of treated material by a factor of at least 10⁵. A small amount of infectivity, however, persisted despite UV-ozone treatment. When bound to either montmorillonite clay or quartz surfaces, PrP^TSE was still susceptible to degradation by UV-ozone.

Conclusion

Our findings strongly suggest that UV-ozone treatment can degrade pathogenic prion protein and inactivate prions, even when the agent is associated with surfaces. Using larger UV-ozone doses or combining UV-ozone treatment with other decontaminant methods may allow the sterilization of TSE-contaminated materials.

Creutzfeldt-Jakob disease--implications for anaesthetists in New Zealand

Since 1996 with the recognition of a variant form, Creutzfeldt-Jakob disease has become more prominent in the medical literature. Of particular interest to anaesthetists is the risk of iatrogenic spread of the disease. In this article, the relevant literature is reviewed and the experience within New Zealand examined. The presentation, pathology and incidence of the disease is reviewed and the current guidelines for the preoperative management of patients with known or suspected Creutzfeldt-Jakob disease are outlined.

[Epidemiological surveillance of Creutzfeldt-Jakob in France]

INTRODUCTION

Transmissible spongiform encephalopathies (TSE) have been under epidemiological surveillance in France and in Europe since the early 1990s. The observation of iatrogenic Creutzfeldt-Jakob disease (CJD), the outbreak of bovine spongiform encephalopathy (ESB) and its probable transmission to many species gave rise to the surveillance which remains warranted by the emergence of a variant of CJD (vCJD), in 1996.

STATE OF ART

In France, epidemiological surveillance is coordinated by the InVS which receives input from cases notifications addressed to INSERM Unit 708 directly by clinicians or more often following requests for 14-3-3 detection in CSF. All suspected cases are followed up until a final diagnosis is established. Thanks to the effectiveness of the French network of neuropathology, autopsies are performed in more than half of patients who die with a diagnosis of suspected CJD. Diagnostic criteria allow comparison of the incidence of the different forms of the disease in all countries with a system of surveillance. Sporadic CJD is the most frequent form of the disease with more than 80% of the cases. Its origin remains unknown. To date, cases of iatrogenic CJD referred to the French surveillance network have been caused by dura mater grafts or human growth hormone treatments administrated in the 1980s. Ten percent of TSE are of genetic origin with an autosomic dominant transmission of a mutation or an insertion located on the PRNP gene. The most recent form of the disease is vCJD which is a new form, first described in the United Kingdom in 1994.

PROSPECT AND CONCLUSION

Active epidemiological surveillance remains a timely issue, particularly in France, because of the development of new cases of iatrogenic CJD after human growth hormone treatment. It is of importance in France and worldwide because of the emergence of post-transfusional cases of vCJD and the possible appearance of vCJD in persons with valine-valine or methionine-valine genotypes at codon 129.

Bovine spongiform encephalopathy

Bovine spongiform encephalopathy is an infectious disease of cattle that is transmitted through the consumption of meat-and-bone meal from infected cattle. The etiologic agent is an aberrant isoform of the native cellular prion protein that is a normal component of neurologic tissue. There currently are no approved tests that can detect BSE in live cattle.

MRI and clinical syndrome in dura mater-related Creutzfeldt-Jakob disease

OBJECTIVE

Iatrogenic Creutzfeldt-Jakob disease (iCJD) is mainly associated with dura mater (DM) grafts and administration of human growth hormones (hGH). Data on disease course in DM-CJD are limited. We describe the clinical and diagnostic findings in this patient group with special emphasis on MRI signal alterations.

METHODS

Ten DM-CJD patients were studied for their clinical symptoms and diagnostic findings. The MRIs were evaluated for signal increase of the cortical and subcortical structures.

RESULTS

DM-CJD patients had a median incubation time of 18 years and median disease duration of 7 months. The majority of patients were MM homozygous at codon 129 of the prion protein gene (PRNP) and presented with gait ataxia and psychiatric symptoms. No correlation between the graft site and the initial disease course was found. The MRI showed cortical and basal ganglia signal increase each in eight out of ten patients and thalamic hyperintensity in five out of ten cases. Of interest, patients with thalamic signal increase were homozygous for methionine.

CONCLUSION

The MRI findings in DM-CJD largely resemble those seen in sporadic CJD, as the cortex and basal ganglia are mainly affected.

A case-control study of sporadic Creutzfeldt-Jakob disease in Switzerland: analysis of potential risk factors with regard to an increased CJD incidence in the years 2001-2004

Background

In 2001, the observed annual mortality from Creutzfeldt-Jakob disease (CJD) in Switzerland increased from less than 1.5 to 2.6 per million inhabitants. An underlying cause could not be identified.

Methods

To analyse potential risk factors for sCJD in Switzerland, close relatives of 69 sCJD-patients and 224 frequency age-matched controls were interviewed in a case-control study using a standardised questionnaire. 135 potential risk factors including socio-demographics, medical history, occupation and diet were analysed by logistic regression adjusting for age, sex and education.

Results

sCJD patients were more likely to have travelled abroad, worked at an animal laboratory, undergone invasive dental treatment, orthopaedic surgery, ophthalmologic surgery after 1980, regular GP visits, taken medication regularly, and consumed kidney. No differences between patients and controls were found for residency, family history, and exposure to environmental and other dietary factors.

Conclusion

Although some factors were significantly more frequent among sCJD-cases, this study did not reveal specific explanations for the increased incidence of deaths due to sporadic CJD observed in Switzerland since 2001. Results have to be interpreted with caution due to multiple testing and possible recall bias in association with a long incubation period. The most plausible reason for the increase in Swiss sCJD cases after 2000 is an improved case ascertainment. Therefore, underreporting of cases might well have occurred before the year 2001, and the "real" yearly incidence of sCJD might not be lower than, but rather above 2 per million inhabitants.

From mad cows to sensible blood transfusion: the risk of prion transmission by labile blood components in the United Kingdom and in France

Transfusion transmission of the prion, the agent of variant Creutzfeldt-Jakob disease (vCJD), is now established. Subjects infected through food may transmit the disease through blood donations. The two nations most affected to date by this threat are the United Kingdom (UK) and France. The first transfusion cases have been observed in the UK over the past 5 years. In France, a few individuals who developed vCJD had a history of blood donation, leading to a risk of transmission to recipients, some of whom could be incubating the disease. In the absence of a large-scale screening test, it is impossible to establish the prevalence of infection in the blood donor population and transfused patients. This lack of a test also prevents specific screening of blood donations. Thus, prevention of transfusion transmission essentially relies at present on deferral of "at-risk" individuals. Because prions are present in both white blood cells and plasma, leukoreduction is probably insufficient to totally eliminate the transfusion risk. In the absence of a screening test for blood donations, recently developed prion-specific filters could be a solution. Furthermore, while the dietary spread of vCJD seems efficiently controlled, uncertainty remains as to the extent of the spread of prions through blood transfusion and other secondary routes.

Review. The origin of the prion agent of kuru: molecular and biological strain typing

Kuru is an acquired human prion disease that primarily affected the Fore linguistic group of the Eastern Highlands of Papua New Guinea. The central clinical feature of kuru is progressive cerebellar ataxia and, in sharp contrast to most cases of sporadic Creutzfeldt-Jakob disease (CJD), dementia is a less prominent and usually late clinical feature. In this regard, kuru is more similar to variant CJD, which also has similar prodromal symptoms of sensory disturbance and joint pains in the legs and psychiatric and behavioural changes. Since a significant part of the clinicopathological diversity seen in human prion disease is likely to relate to the propagation of distinct human prion strains, we have compared the transmission properties of kuru prions with those isolated from patients with sporadic, iatrogenic and variant CJD in both transgenic and wild-type mice. These data have established that kuru prions have prion strain properties equivalent to those of classical (sporadic and iatrogenic) CJD prions but distinct from variant CJD prions. Here, we review these findings and discuss how peripheral routes of infection and other factors may be critical modifiers of the kuru phenotype.

A clinical study of kuru patients with long incubation periods at the end of the epidemic in Papua New Guinea

Kuru is so far the principal human epidemic prion disease. While its incidence has steadily declined since the cessation of its route of transmission, endocannibalism, in Papua New Guinea in the 1950s, the arrival of variant Creutzfeldt-Jakob disease (vCJD), also thought to be transmitted by dietary prion exposure, has given kuru a new global relevance. We investigated all suspected cases of kuru from July 1996 to June 2004 and identified 11 kuru patients. There were four females and seven males, with an age range of 46-63 years at the onset of disease, in marked contrast to the age and sex distribution when kuru was first investigated 50 years ago. We obtained detailed histories of residence and exposure to mortuary feasts and performed serial neurological examination and genetic studies where possible. All patients were born a significant period before the mortuary practice of transumption ceased and their estimated incubation periods in some cases exceeded 50 years. The principal clinical features of kuru in the studied patients showed the same progressive cerebellar syndrome that had been previously described. Two patients showed marked cognitive impairment well before preterminal stages, in contrast to earlier clinical descriptions. In these patients, the mean clinical duration of 17 months was longer than the overall average in kuru but similar to that previously reported for the same age group, and this may relate to the effects of both patient age and PRNP codon 129 genotype. Importantly, no evidence for lymphoreticular colonization with prions, seen uniformly in vCJD, was observed in a patient with kuru at tonsil biopsy.

Genetic susceptibility, evolution and the kuru epidemic

The acquired prion disease kuru was restricted to the Fore and neighbouring linguistic groups of the Papua New Guinea highlands and largely affected children and adult women. Oral history documents the onset of the epidemic in the early twentieth century, followed by a peak in the mid-twentieth century and subsequently a well-documented decline in frequency. In the context of these strong associations (gender, region and time), we have considered the genetic factors associated with susceptibility and resistance to kuru. Heterozygosity at codon 129 of the human prion protein gene (PRNP) is known to confer relative resistance to both sporadic and acquired prion diseases. In kuru, heterozygosity is associated with older patients and longer incubation times. Elderly survivors of the kuru epidemic, who had multiple exposures at mortuary feasts, are predominantly PRNP codon 129 heterozygotes and this group show marked Hardy-Weinberg disequilibrium. The deviation from Hardy-Weinberg equilibrium is most marked in elderly women, but is also significant in a slightly younger cohort of men, consistent with their exposure to kuru as boys. Young Fore and the elderly from populations with no history of kuru show Hardy-Weinberg equilibrium. An increasing cline in 129V allele frequency centres on the kuru region, consistent with the effect of selection in elevating the frequency of resistant genotypes in the exposed population. The genetic data are thus strikingly correlated with exposure. Considering the strong coding sequence conservation of primate prion protein genes, the number of global coding polymorphisms in man is surprising. By intronic resequencing in a European population, we have shown that haplotype diversity at PRNP comprises two major and divergent clades associated with 129M and 129V. Kuru may have imposed the strongest episode of recent human balancing selection, which may not have been an isolated episode in human history.

Central and peripheral pathology of kuru: pathological analysis of a recent case and comparison with other forms of human prion disease

While the neuropathology of kuru is well defined, there are few data concerning the distribution of disease-related prion protein in peripheral tissues. Here we report the investigation of brain and peripheral tissues from a kuru patient who died in 2003. Neuropathological findings were compared with those seen in classical (sporadic and iatrogenic) Creutzfeldt-Jakob disease (CJD) and variant CJD (vCJD). The neuropathological findings of the kuru patient showed all the stereotypical changes that define kuru, with the occurrence of prominent PrP plaques throughout the brain. Lymphoreticular tissue showed no evidence of prion colonization, suggesting that the peripheral pathogenesis of kuru is similar to that seen in classical CJD rather than vCJD. These findings now strongly suggest that the characteristic peripheral pathogenesis of vCJD is determined by prion strain type alone rather than route of infection.

Heightened incidence of sporadic Creutzfeldt-Jakob disease is associated with a shift in clinicopathological profiles

Incidences of human transmissible spongiform encephalopathies are monitored by national registries in the majority of countries in Western Europe. During the past 13 years incidences for Creutzfeldt-Jakob disease (CJD) in Switzerland fluctuated between 0.4 and 2.63 cases/10(6) inhabitants. We have compared clinicpathological patient profiles including geographic and gender distribution, age at disease onset, duration of disease, clinical symptoms, and recognized or hypothetical risk factors for CJD, genetic risk factors, biochemical and histopathological data for two cohorts of Swiss sporadic CJD patients from years of regular sporadic CJD incidence (1996-2000, mean incidence 1.3 cases/10(6) inhabitants, n = 47) to Swiss sporadic CJD patients from years of elevated sporadic CJD incidence (2001-2004, mean incidence 2.3 cases/10(6) inhabitants, n = 73). Sporadic CJD patients from the cohort with elevated sporadic CJD incidence presented with a higher frequency of rare sporadic CJD subtypes. Patients of these subtypes were significantly older and showed a skewed male/female ratio when compared to published patients of identical sporadic CJD-types or to patients from the 1996-2000 cohort and indicates that improved detection of rare sporadic CJD subtypes may have contributed to increased incidence.

Surgery and risk of sporadic Creutzfeldt-Jakob disease in Denmark and Sweden: registry-based case-control studies

BACKGROUND

Epidemiologic evidence of surgical transmission of sporadic Creutzfeldt-Jakob disease (sCJD) remains controversial.

METHODS

From Danish and Swedish registries we selected 167 definite and probable sCJD cases (with onset between 1987 and 2003) and 3,059 controls (835 age-, sex-, and residence-matched, and 2,224 unmatched). Independent of case/control status, surgical histories were obtained from National Hospital Discharge Registries. Surgical procedures were categorized by body system group and lag time to onset of sCJD. Exposure frequencies were compared using logistic regression.

RESULTS

A history of any major surgery, conducted >/=20 years before sCJD onset, was more common in cases than both matched (OR = 2.44, 95% CI = 1.46-4.07) and unmatched controls (OR = 2.25, 95% CI = 1.48-3.44). This observation was corroborated by a linear increase in risk per surgical discharge (OR = 1.57, 95% CI = 1.13-2.18; OR = 1.50, 95% CI = 1.18-1.91). Surgery of various body systems, including peripheral vessels, digestive system and spleen, and female genital organs, was significantly associated with increased sCJD risk.

CONCLUSIONS

A variety of major surgical procedures constitute a risk factor for sCJD following an incubation period of many years. A considerable number of sCJD cases may originate from health care-related accidental transmission.

First report of Creutzfeldt-Jakob disease occurring in 2 siblings unexplained by PRNP mutation

Sibling concurrence of pathologically confirmed prion disease has only been reported in association with pathogenic mutation of the prion protein gene (PRNP). Here, we report 2 siblings with classic neuropathologic features of sporadic Creutzfeldt-Jakob disease unexplained by PRNP mutation or known risk factors for iatrogenic transmission of prion infection. Possible explanations include coincidental occurrence, common exposure to an unidentified environmental source of prions, horizontal transmission of disease, or the presence of unknown shared genetic predisposition.

Lack of TAR-DNA binding protein-43 (TDP-43) pathology in human prion diseases

AIMS

TAR-DNA binding protein-43 (TDP-43) is the major ubiquitinated protein in the aggregates in frontotemporal dementia with ubiquitin-positive, tau-negative inclusions and motor neurone disease. Abnormal TDP-43 immunoreactivity has also been described in Alzheimer's disease, Lewy body diseases and Guam parkinsonism-dementia complex. We therefore aimed to determine whether there is TDP-43 pathology in human prion diseases, which are characterised by variable deposition of prion protein (PrP) aggregates in the brain as amyloid plaques or more diffuse deposits.

MATERIAL AND METHODS

TDP-43, ubiquitin and PrP were analysed by immunohistochemistry and double-labelling immunofluorescence, in sporadic, acquired and inherited forms of human prion disease.

RESULTS

Most PrP plaques contained ubiquitin, while synaptic PrP deposits were not associated with ubiquitin. No abnormal TDP-43 inclusions were identified in any type of prion disease case, and TDP-43 did not co-localize with ubiquitin-positive PrP plaques or with diffuse PrP aggregates.

CONCLUSIONS

These data do not support a role for TDP-43 in prion disease pathogenesis and argue that TDP-43 inclusions define a distinct group of neurodegenerative disorders.

Animal pharming, two decades on

Since its inception 20 years ago, the animal pharming industry has promoted transgenic animals as a cost-effective method of biopharmaceutical production. However, it took until 2006 for the first therapeutic product to gain regulatory approval. This was an important milestone, but scepticism still abounds. Can pharming regain investor confidence, and will society accept transgenic livestock as a production method? There is some cause for optimism, biopharmaceuticals are a large, expanding market and animal pharming has already made considerable strides. A novel production platform has been established, groundbreaking technologies developed, a necessary regulatory framework put in place. Nevertheless, despite cost advantages, pharming has become a niche production method and its long term success may depend on products unique to transgenic animals.

Effective gene therapy in a mouse model of prion diseases

Classical drug therapies against prion diseases have encountered serious difficulties. It has become urgent to develop radically different therapeutic strategies. Previously, we showed that VSV-G pseudotyped FIV derived vectors carrying dominant negative mutants of the PrP gene are efficient to inhibit prion replication in chronically prion-infected cells. Besides, they can transduce neurons and cells of the lymphoreticular system, highlighting their potential use in gene therapy approaches. Here, we used lentiviral gene transfer to deliver PrPQ167R virions possessing anti-prion properties to analyse their efficiency in vivo. Since treatment for prion diseases is initiated belatedly in human patients, we focused on the development of a curative therapeutic protocol targeting the late stage of the disease, either at 35 or 105 days post-infection (d.p.i.) with prions. We observed a prolongation in the lifespan of the treated mice that prompted us to develop a system of cannula implantation into the brain of prion-infected mice. Chronic injections of PrPQ167R virions were done at 80 and 95 d.p.i. After only two injections, survival of the treated mice was extended by 30 days (20%), accompanied by substantial improvement in behaviour. This delay was correlated with: (i) a strong reduction of spongiosis in the ipsilateral side of the brain by comparison with the contralateral side; and (ii) a remarkable decrease in astrocytic gliosis in the whole brain. These results suggest that chronic injections of dominant negative lentiviral vectors into the brain, may be a promising approach for a curative treatment of prion diseases.

Clinical features and diagnosis of human prion diseases

Human prion diseases are a group of progressive, fatal encephalopathies united by their similar neuropathological features, their potential transmissibility and a core molecular feature: a conformational change in prion protein. They exist in sporadic/idiopathic, genetic and acquired forms. The clinical features vary according to a number of factors, including cause and the prion protein genotype of the affected individual. Common features include dementia, cerebellar ataxia and involuntary movements. There is no absolute clinical diagnostic test; definitive diagnosis is neuropathological. However, MRI, electroencephalogram, cerebrospinal fluid protein tests, genetic tests and tonsil biopsy, can be very helpful in supporting a clinical diagnosis. The development of a noninvasive diagnostic test (e.g., on blood) would be very helpful in terms of easier, earlier clinical diagnosis, as well as having other applications (such as blood donor screening or population infection prevalence surveys). A relatively new technique (protein misfolding cyclic amplification) holds promise as such a test. Various therapeutic approaches have been suggested, but there is no current effective treatment and there are significant problems in the assessment of any candidate therapies.

Implications for Creutzfeldt-Jakob Disease (CJD) in Dentistry: a Review of Current Knowledge

This review explores our current understanding of the risks of (variant) Creutzfeldt-Jakob disease transmission via dental practice, and whether they merit the rigorous enforcement of improved standards of instrument cleaning and decontamination. The recognition of prions as novel infectious agents in humans has caused significant concern among the public and medical professionals alike. Creutzfeldt-Jakob disease (CJD) in humans has been shown to be transmissible via several routes, including transplantation, contaminated medical products, and via neurosurgery. While the likelihood of transmission via dentistry is undoubtedly very low, this may be amplified considerably by unknown risk factors, such as disease prevalence (particularly in the UK), altered tissue distribution of vCJD, and the failure of decontamination processes to address the inactivation of prions adequately. Since current diagnostic techniques are unable to detect PrPSc in human dental tissues, there is limited evidence for the presence of infectivity. Given these uncertainties, the control of risk by reinforced and improved decontamination practices seems the most appropriate response.

Clinicopathologic characteristics of five autopsied cases of dura mater-associated Creutzfeldt-Jakob disease

We present five cases of dura mater-associated Creutzfeldt-Jakob disease (dura-CJD) that were analyzed clinicopathologically and review previous reports. The average age at dura mater transplantation was 54.4 +/- 7.3 years, and the average age at CJD onset was 66.0 +/- 8.2 years, with an average latency period of 11.6 +/- 1.1 years. The average age at death was 67.6 +/- 8.7 years, with an average CJD disease duration of 16.8 +/- 10.4 months. Symptoms of CJD onset in four patients who received dura mater transplantation below the cerebellar tent reflected cerebellar or brainstem dysfunction, whereas symptoms of one patient who received transplantation above the cerebellar tent reflected cerebral cortical involvement. All patients showed rapidly progressive cognitive impairment, and both periodic sharp-wave complexes on electroencephalogram and myoclonus were observed in the early disease stage. Neuropathologic evaluation showed one case of subacute spongiform encephalopathy and four cases of panencephalopathic-type CJD. Widespread cerebral neocortical, subcortical gray matter and cerebellar cortical involvement were observed to varying degrees, and severity tended to be associated with CJD disease duration. There were no instances of kuru plaques or florid plaques. Prion protein (PrP) immunostaining showed widespread synaptic-type PrP deposition. No differences between our dura-CJD cases and typical cases of sporadic CJD were found with respect to clinicopathologic findings, except history of dura mater transplantation. Although a specific association between the dura mater graft site and neuropathologic observations was not evaluated in the present study, the initial symptoms appear to be closely related to the graft site, indicating a direct transmission of CJD from the graft site to the adjacent brain.

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.

Prion protein disease and neuropathology of prion disease

Human prion diseases, in common with other neurodegenerative diseases, may be sporadic or inherited and are characterized by the accumulation of cellular proteins accompanied by neuronal death and synaptic loss. Prion diseases are, however, unique in being transmissible. Central to the pathogenesis of all forms of prion disease is the prion protein. This article provides a brief overview of the biology of human prion diseases followed by a more in-depth discussion of the neuropathology of these diseases, including features of neuroradiologic relevance.

Cathepsin D SNP associated with increased risk of variant Creutzfeldt-Jakob disease

Background

Variant Creutzfeldt-Jakob disease (vCJD) originally resulted from the consumption of foodstuffs contaminated by bovine spongiform encephalopathy (BSE) material, with 163 confirmed cases in the UK to date. Many thousands are likely to have been exposed to dietary infection and so it is important (for surveillance, epidemic modelling, public health and understanding pathogenesis) to identify genetic factors that may affect individual susceptibility to infection. This study looked at a polymorphism in the cathepsin D gene (refSNP ID: rs17571) previously examined in Alzheimer's disease (AD).

Methods

Blood samples taken from 110 vCJD patients were tested for the C-T base change, and genotype data were compared with published frequencies for a control population using multiple logistic regression.

Results

There was a significant excess of the cathepsin D polymorphism TT genotype in the vCJD cohort compared to controls. The TT genotype was found to have a 9.75 fold increase in risk of vCJD compared to the CT genotype and a 10.92 fold increase compared to the CC genotype.

Conclusion

This mutation event has been observed to alter the protease activity of the cathepsin D protein and has been linked to an increase in amyloid beta plaque formation in AD. vCJD neuropathology is characterised by the presence of amyloid plaques, formed from the prion protein, and therefore alterations in the amyloid processing activity of cathepsin D may affect the neuropathogenesis of this disease.

Spatial clusters of Creutzfeldt-Jakob disease mortality in Japan between 1995 and 2004

BACKGROUND

There is suggested to be a geographical difference in Creutzfeldt-Jakob disease (CJD) mortality in Japan. We performed a study to detect localized clusters and hot-spot areas of deaths from CJD in Japan during the 10-year period from 1995 to 2004.

METHODS

The diagnosis of CJD was taken from the death certificate (coded as A81.0 in the ICD-10). A total number of 1,168 CJD deaths (500 males and 668 females) were used for analysis using empirical Bayes estimates of standardized mortality ratios and the flexible spatial scan statistic to detect clusters. To detect the most likely cluster, p values were obtained using Monte Carlo hypothesis testing (with p < 0.05 as statistical significance).

RESULTS

The most likely cluster of CJD mortality was located in the northwest region from the base of Mt. Fuji, stretching over the two neighboring prefectures of Yamanashi and Shizuoka (relative risk = 2.28, p = 0.021). Some other clusters were detected but were not significant.

CONCLUSIONS

The present study supports the evidence of geographical clustering of deaths from CJD at a specific location in Japan.