Prions and the Oral Cavity

Prion diseases have recently emerged as a significant challenge to health-care workers, including those involved in dentistry. Abnormal prion proteins are resistant to complete inactivation by conventional sterilization techniques. In the last decade, a new form of prion disease emerged in the UK, termed "variant CJD", thought to be acquired by consumption of bovine spongiform encephalopathy-contaminated food products. At present, CJD is an invariably fatal disease with no immediate prospect of treatment or vaccination. Of concern with the variant form of CJD, unlike the more classic forms of the disease, is the appearance of significant levels of infectivity outside the central nervous system. This raises concerns for the potential transmission of prion proteins via surgical procedures from individuals in the asymptomatic stage of the disease. This article reviews the existing knowledge base on the nature of prions, their distribution in oral tissues, and the implications for dental treatment.

Postmortem findings in a case of variant Creutzfeldt-Jakob disease treated with intraventricular pentosan polysulfate

BACKGROUND

A small number of patients with variant Creutzfeldt-Jakob disease (vCJD) have been treated with intraventicular pentosan polysulfate (iPPS) and extended survival has been reported in some cases. To date, there have been no reports on the findings of postmortem examination of the brain in treated patients and the reasons for the extended survival are uncertain. We report on the neuropathological findings in a case of vCJD treated with PPS.

METHODS

Data on survival in vCJD is available from information held at the National CJD Research and Surveillance Unit and includes the duration of illness in 176 cases of vCJD, five of which were treated with iPPS. One of these individuals, who received iPPS for 8 years and lived for 105 months, underwent postmortem examination, including neuropathological examination of the brain.

RESULTS

The mean survival in vCJD is 17 months, with 40 months the maximum survival in patients not treated with PPS. In the 5 patients treated with PPS survival was 16 months, 45 months, 84 months, 105 months and 114 months. The patient who survived 105 months underwent postmortem examination which confirmed the diagnosis of vCJD and showed severe, but typical, changes, including neuronal loss, astrocytic gliosis and extensive prion protein (PrP) deposition in the brain. The patient was also given PPS for a short period by peripheral infusion and there was limited PrP immunostaining in lymphoreticular tissues such as spleen and appendix.

CONCLUSIONS

Treatment with iPPS did not reduce the overall neuropathological changes in the brain. The reduced peripheral immunostaining for PrP may reflect atrophy of these tissues in relation to chronic illness rather than a treatment effect. The reason for the long survival in patients treated with iPPS is unclear, but a treatment effect on the disease process cannot be excluded.

Review: Creutzfeldt-Jakob disease: prion protein type, disease phenotype and agent strain

The human transmissible spongiform encephalopathies or human prion diseases are one of the most intensively investigated groups of rare human neurodegenerative conditions. They are generally held to be unique in terms of their complex epidemiology and phenotypic variability, but they may also serve as a paradigm with which other more common protein misfolding disorders might be compared and contrasted. The clinico-pathological phenotype of human prion diseases appears to depend on a complex interaction between the prion protein genotype of the affected individual and the physico-chemical properties of the neurotoxic and transmissible agent, thought to comprise of misfolded prion protein. A major focus of research in recent years has been to define the phenotypic heterogeneity of the recognized human prion diseases, correlate this with molecular-genetic features and then determine whether this molecular-genetic classification of human prion disease defines the biological properties of the agent as determined by animal transmission studies. This review seeks to survey the field as it currently stands, summarize what has been learned, and explore what remains to be investigated in order to obtain a more complete scientific understanding of prion diseases and to protect public health.

Variant Creutzfeldt-Jakob disease

SUMMARY

Variant Creutzfeldt-Jakob disease (CJD) is an emerging form of human prion disease caused by oral exposure to the bovine spongiform encephalopathy agent. Most cases have occurred in the UK, but smaller numbers of cases have been identified in 10 other countries worldwide. All confirmed cases belong to a single genetic subgroup defined by methionine homozygosity at codon 129 in the prion protein gene. Variant CJD has a widespread distribution of infectivity in the body, involving lymphoid tissues during at least the latter part of the incubation period. This is unlike other forms of human prion disease, and raised concerns that the transmissible agent might also be present in blood. To date, four probable cases of variant CJD infection have been identified following transfusion of packed red blood cells from asymptomatic donors who subsequently died from variant CJD. Recently, one case of likely transmission of variant CJD infection by UK factor VIII (FVIII) concentrates has been reported in an elderly haemophilic patient in the UK, who had been treated with FVIII produced from pooled plasma to which a donor who subsequently died from variant CJD had contributed. The recipient showed no signs or symptoms of variant CJD during life, but evidence of variant CJD infection was detected in his spleen following a postmortem examination. Continued surveillance is required to investigate the prevalence of secondary variant CJD infection in other patients with bleeding disorders who have been treated with UK-sourced pooled plasma products.

The first case of protease-sensitive prionopathy (PSPr) in The Netherlands: a patient with an unusual GSS-like clinical phenotype

An atypical case of prion disease is described in a 54-year-old Dutch man, homozygous for valine at codon 129 of the prion protein gene (PRNP). The clinical phenotype was characterised by progressive dementia, spastic paraplegia and sensorimotor polyneuropathy. The disease duration was 20 months. Genetic analysis of PRNP did not reveal any abnormalities. Neuropathologically, only mild spongiform change and a coarse granular immunohistochemical staining for the abnormal prion protein, PrP(Sc), was observed, with poorly formed plaques in the molecular layer of the cerebellar cortex. However, Western blotting showed low but detectable levels of proteinase K(PK)-resistant PrP(Sc) occurring in an unusual ladder-like profile. These features define a phenotype that corresponds to the recently described protease-sensitive prionopathy (PSPr). Our report on the first Dutch patient with PSPr further expands the spectrum of prionopathies and exemplifies the need to re-evaluate cases of atypical prion disease.

Primary postoperative chemotherapy without radiotherapy for treatment of brain tumours other than ependymoma in children under 3 years: results of the first UKCCSG/SIOP CNS 9204 trial

BACKGROUND

Radiotherapy is an effective adjuvant treatment for brain tumours arising in very young children, but it has the potential to damage the child's developing nervous system at a crucial time - with a resultant reduction in IQ leading to cognitive impairment, associated endocrinopathy and risk of second malignancy. We aimed to assess the role of a primary chemotherapy strategy in avoiding or delaying radiotherapy in children younger than 3 years with malignant brain tumours other than ependymoma, the results of which have already been published.

METHODS

Ninety-seven children were enrolled between March 1993 and July 2003 and, following diagnostic review, comprised: medulloblastoma (n=31), astrocytoma (26), choroid plexus carcinoma [CPC] (15), CNS PNET (11), atypical teratoid/rhabdoid tumours [AT/RT] (6) and ineligible (6). Following maximal surgical resection, chemotherapy was delivered every 14 d for 1 year or until disease progression. Radiotherapy was withheld in the absence of progression.

FINDINGS

Over all diagnostic groups the cumulative progression rate was 80.9% at 5 years while the corresponding need-for-radiotherapy rate for progression was 54.6%, but both rates varied by tumour type. There was no clear relationship between chemotherapy dose intensity and outcome. Patients with medulloblastoma presented as a high-risk group, 83.9% having residual disease and/or metastases at diagnosis. For these patients, outcome was related to histology. The 5-year OS for desmoplastic/nodular medulloblastoma was 52.9% (95% confidence interval (CI): 27.6-73.0) and for classic medulloblastoma 33.3% (CI: 4.6-67.6); the 5-year EFS were 35.3% (CI: 14.5-57.0) and 33.3% (CI: 4.6-67.6), respectively. All children with large cell or anaplastic variants of medulloblastoma died within 2 years of diagnosis. The 5-year EFS for non-brainstem high-grade gliomas [HGGs] was 13.0% (CI: 2.2-33.4) and the OS was 30.9% (CI: 11.5-52.8). For CPC the 5-year OS was 26.67% (CI: 8.3-49.6) without RT. This treatment strategy was less effective for AT/RT with 3-year OS of 16.7% (CI: 0.8-51.7) and CNS PNET with 1-year OS of 9.1% (CI: 0.5-33.3).

INTERPRETATION

The outcome for very young children with brain tumours is dictated by degree of surgical resection and histological tumour type and underlying biology as an indicator of treatment sensitivity. Overall, the median age at radiotherapy was 3 years and radiotherapy was avoided in 45% of patients. Desmoplastic/nodular sub-type of medulloblastoma has a better prognosis than classic histology, despite traditional adverse clinical features of metastatic disease and incomplete surgical resection. A subgroup with HGG and CPC are long-term survivors without RT. This study highlights the differing therapeutic challenges presented by the malignant brain tumours of early childhood, the importance of surgical approaches and the need to explore individualised brain sparing approaches to the range of malignant brain tumours that present in early childhood.

Variant CJD infection in the spleen of a neurologically asymptomatic UK adult patient with haemophilia

SUMMARY

All UK patients with bleeding disorders treated with any UK-sourced pooled factor concentrates between 1980 and 2001 have been informed that they may be at an increased risk of infection with variant Creutzfeldt-Jakob disease (vCJD). We describe a study to detect disease-associated, protease-resistant prion protein (PrP(res)) in 17 neurologically aymptomatic patients with haemophilia considered to be at increased risk of vCJD. Materials from 11 autopsy and seven biopsy cases were analysed for PrP(res). The tissues available from each case were variable, ranging from a single biopsy sample to a wide range of autopsy tissues. A single specimen from the spleen of one autopsy case gave a strong positive result on repeated testing for PrP(res) by Western blot analysis. This tissue came from a 73-year-old male patient with no history of neurological disease, who was heterozygous (methionine/valine) at codon 129 in the prion protein gene. He had received over 9000 units of factor VIII concentrate prepared from plasma pools known to include donations from a vCJD-infected donor, and some 400,000 units not known to include donations from vCJD-infected donors. He had also received 14 units of red blood cells and had undergone several surgical and invasive endoscopic procedures. Estimates of the relative risks of exposure through diet, surgery, endoscopy, blood transfusion and receipt of UK-sourced plasma products suggest that by far the most likely route of infection in this patient was receipt of UK plasma products.

Panencephalopathic Creutzfeldt-Jakob disease in the Netherlands and the UK: clinical and pathological characteristics of nine patients

AIMS

The panencephalopathic type of Creutzfeldt-Jakob disease (PECJD) has extensive abnormalities in cerebral white matter as well as the cortex. PECJD has rarely been described in Caucasians and debate continues on its classification and pathogenesis. We describe our experience of PECJD over a 14-year period of surveillance for CJD in the Netherlands and the UK.

METHODS

Between 1993 and 2006, nine cases of PECJD were identified. Clinical, histological and biochemical characteristics of all patients were analysed and compared; all cases were classified clinically as sporadic CJD.

RESULTS

The median age at onset was 57.8 years and median disease duration was 22 months. The average brain weight was 887 g. Most patients showed a two-stage clinical course with initial rapid deterioration to a state of akinetic mutism, which then persisted over a longer time scale. Neuropathological findings were characterized by severe global atrophy with status spongiosus. Cerebral white matter involvement tended to be associated with either disease duration or severity of cerebral cortical lesions. Five patients could be classified into the MM1 subtype of sporadic CJD, one patient into the MM2 subgroup and another into the MV2 subgroup. Two patients were heterozygous at codon 129 in the prion protein gene and contained both type 1 and type 2 PrP(res) isoforms in the brain.

CONCLUSIONS

We believe that white matter pathology in PECJD represents an end-stage pattern that reflects secondary degeneration due to widespread cortical neuronal loss that occurs in the early part of the disease, rather than representing a primary lesion.

Isolated cervical intramedullary sarcoidosis--a histological surprise

We present a case of cervical intramedullary sarcoidosis. A 56 year old woman presented with progressive paraesthesia affecting the lower limbs. MRI revealed an intramedullar lesion from C4-C7. A laminectomy and subtotal resection was carried out for this presumed intramedullary tumour. Pathology revealed this to be a granulomatous lesion with features indicative of sarcoidosis. Postoperatively, there was no change in her neurological function and her symptoms improved with steroid therapy.

A quantitative study of the pathological changes in the cerebellum in 15 cases of variant Creutzfeldt-Jakob disease (vCJD)

AIMS

To determine in the cerebellum in variant Creutzfeldt-Jakob disease (vCJD): (i) whether the pathology affected all laminae; (ii) the spatial topography of the pathology along the folia; (iii) spatial correlations between the pathological changes; and (iv) whether the pathology was similar to that of the common methionine/methionine Type 1 subtype of sporadic CJD.

METHODS

Sequential cerebellar sections of 15 cases of vCJD were stained with haematoxylin and eosin, or immunolabelled with monoclonal antibody 12F10 against prion protein (PrP) and studied using spatial pattern analysis.

RESULTS

Loss of Purkinje cells was evident compared with control cases. Densities of the vacuolation and the protease-resistant form of prion protein (PrP(Sc)) (diffuse and florid plaques) were greater in the granule cell layer (GL) than the molecular layer (ML). In the ML, vacuoles and PrP(Sc) plaques occurred in clusters regularly distributed along the folia with larger clusters of vacuoles and diffuse plaques in the GL. There was a negative spatial correlation between the vacuoles and the surviving Purkinje cells in the ML. There was a positive spatial correlation between the vacuoles and diffuse PrP(Sc) plaques in the ML and GL.

CONCLUSIONS

(i) all laminae were affected by the pathology, the GL more severely than the ML; (ii) the pathology was topographically distributed along the folia especially in the Purkinje cell layer and ML; (iii) pathological spread may occur in relation to the loop of anatomical connections involving the cerebellum, thalamus, cerebral cortex and pons; and (iv) there were pathological differences compared with methionine/methionine Type 1 sporadic CJD.

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.

Ultrastructural study of florid plaques in variant Creutzfeldt-Jakob disease: a comparison with amyloid plaques in kuru, sporadic Creutzfeldt-Jakob disease and Gerstmann-Sträussler-Scheinker disease

BACKGROUND

Although the histological features of the amyloid plaques in variant Creutzfeldt-Jakob disease (vCJD) are distinct from those in other forms of prion disease [kuru, sporadic Creutzfeldt-Jakob disease (sCJD) and Gerstmann-Sträussler-Scheinker disease (GSS)], their ultrastructural features have only been described in a single case report.

AIMS

To study vCJD plaques systematically and compare them with plaques in kuru, sCJD, GSS and Alzheimer disease (AD).

METHODS

Amyloid plaques were studied by transmission electron microscopy and image analysis in five cases of vCJD, three cases of GSS, two cases of sCJD, one case of kuru and five cases of AD. Immunohistochemistry was performed on paraffin sections from one case of vCJD, two cases of GSS, one case of kuru and two cases of sCJD.

RESULTS

The florid plaques in vCJD were either compact or more diffuse; in both forms, the radiating fibrils were organized into thick 'tongues', in contrast to kuru plaques. Dystrophic neurites (DNs) containing lysosomal electron-dense bodies or vesicles surrounded florid plaques. Microglial cells were found within florid plaques; occasional amyloid fibrils were identified in membrane-bound pockets of microglial cells. In vCJD, there was significant tau immunoreactivity in DNs around florid plaques while, in sCJD, GSS and kuru, minimal tau immunoreactivity was observed around plaques.

CONCLUSIONS

The ultrastructure of the florid plaques and DNs in vCJD is more reminiscent of neuritic plaques in AD than kuru or multicentric plaques. These findings may reflect differences both in the strains of the transmissible agents responsible for these disorders and in host factors.

Tissue and organ donation for research in forensic pathology: the MRC Sudden Death Brain and Tissue Bank

Novel methodological approaches to the investigation of brain and non-central nervous system disorders have led to increased demand for well-characterized, high quality human tissue samples, particularly from control cases. In the setting of the new Human Tissue legislation, we sought to determine whether relatives who have been suddenly bereaved are willing to grant authorization for research use of post mortem tissue samples and organs in sufficient numbers to support the establishment of a brain and tissue bank based in the forensic service. Research authorization was sought from families on the day prior to forensic post mortem examination followed up by written confirmation. We have to date selected individuals who have died suddenly (age range 1-89 years) and who were likely to have normal brains or who had displayed symptoms of a CNS disorder of interest to researchers, including psychiatric disorders. One hundred and eleven families have been approached during the first 2 years of this project. Research use of tissue samples was authorized by 96% of families and 17% agreed to whole brain donation. Audit of families' experience does not suggest that they are further distressed by being approached. Respondents expressed a clear view that the opportunity for research donation should be open to all bereaved families. Despite the sometimes long post mortem intervals, the quality of tissue samples is good, as assessed by a range of markers including Agilent BioAnalyzer quantification of RNA integrity (mean value 6.4). We conclude that the vast majority of families are willing to support research use of post mortem tissues even in the context of sudden bereavement and despite previous adverse publicity. The potential for acquisition of normal CNS and non-CNS tissues and of various hard-to-get CNS disorders suggests that efforts to access the forensic post mortem service for research material are eminently worthwhile.

Sporadic Creutzfeldt-Jakob disease in two adolescents

BACKGROUND

Sporadic Creutzfeldt-Jakob disease (CJD) is a condition predominantly affecting older age groups, with cases aged less than 45 years rare and an age at onset or death of less than 20 years exceptional.

METHODS

Data from the systematic study of sporadic CJD in the UK are available from 1970 onwards. Clinical and pathological data are reviewed in order to identify atypical cases, including those at the extremes of the age range of sporadic CJD. Detailed analysis of atypical cases is undertaken, and in selected cases laboratory transmission studies are carried out in order to provide information on the characteristics of the infectious agent.

RESULTS

In the UK, two cases of sporadic CJD in adolescents have been identified, dying at ages 16 and 20 years. The first case predated the epidemic of bovine spongiform encephalopathy and the characteristics of the second case, including laboratory transmission studies, are consistent with a diagnosis of sporadic rather than variant CJD.

CONCLUSION

The cases in this report indicate that sporadic CJD can develop at a very young age, that variant CJD is not the only form of CJD occurring in this age group and that neuropathological examination is essential for accurate diagnosis of human prion disease.

Infective dementias

A wide range of infectious diseases can result in dementia, although the identity and nature of these diseases has changed over time. Two of the most significant current groups in terms of scientific complexity are HIV/AIDS and prion diseases. In these disorders, dementia occurs either as a consequence of targeting the brain and selectively damaging neurones, or by an indirect effect of neuroinflammation. In prion diseases, both direct neurotoxicity and neuroinflammation may act to result in neuronal damage. In HIV encephalitis, the progression of the dementia is slower, perhaps reflecting indirect damage that appears to result from neuroinflammation as a main cause of neuronal death. An ever-increasing range of model systems is now available to study the neuronal damage in infectious dementias, ranging from cell culture systems to animal models, some of which, particularly in the case of prion diseases, are very well characterised and amenable to controlled manipulation in terms of both host and agent parameters. As valuable as these experimental models are, they do not allow a direct approach to an understanding of dementia, the complexities of which cannot readily be studied in vitro or in animal models, but they do allow studies of interventions and therapeutic strategies. This review summarises the current state of knowledge regarding the major infective dementias.

Disease-associated prion protein is not detectable in human systemic amyloid deposits

Cerebral and cardiac amyloid deposits have been reported after scrapie infection in transgenic mice expressing variant prion protein (PrP(C)) lacking the glycophosphatidylinositol anchor. The amyloid fibril protein in the systemic amyloid deposits was not characterized, and there is no clinical or pathological association between prion diseases and systemic amyloidosis in humans. Nevertheless, in view of the potential clinical significance of these murine observations, we tested both human amyloidotic tissues and isolated amyloid fibrils for the presence of PrP(Sc), the prion protein conformation associated with transmissible spongiform encephalopathy (TSE). We also sequenced the complete prion protein gene, PRNP, in amyloidosis patients. No specific immunohistochemical staining for PrP(Sc) was obtained in the amyloidotic cardiac and other visceral tissues of patients with different types of systemic amyloidosis. No protease-resistant prion protein, PrP(res), was detectable by Western blotting of amyloid fibrils isolated from cardiac and other systemic amyloid deposits. Only the complete normal wild-type PRNP gene sequence was identified, including the usual distribution of codon 129 polymorphisms. These reassuringly negative results do not support the idea that there is any relationship of prions or TSE with human systemic amyloidosis, including cardiac amyloid deposition.

In vitro amplification and detection of variant Creutzfeldt–Jakob disease PrPSc

Variant Creutzfeldt-Jakob disease (vCJD) poses a serious risk of secondary transmission and the need to detect infectivity in asymptomatic individuals is therefore of major importance. Following infection, it is assumed that minute amounts of disease-associated prion protein (PrP(Sc)) replicate by conversion of the host cellular prion protein (PrP(C)). Therefore, methods of rapidly reproducing this conversion process in vitro would be valuable tools in the development of such tests. We show that one such technique, protein misfolding cyclic amplification (PMCA), can amplify vCJD PrP(Sc) from human brain tissue, and that the degree of amplification is dependent upon the substrate PRNP codon 129 polymorphism. Both human platelets and transgenic mouse brain are shown to be suitable alternative substrate sources, and amplified PrP(Sc) can be detected using a conformation-dependent immunoassay (CDI), allowing the detection of putative proteinase K sensitive forms of PrP(Sc).

vCJD and the gut: implications for endoscopy

Surveillance for infection by endoscopy for variant CJD and other human prion diseases

Dura mater-associated Creutzfeldt-Jakob disease: experience from surveillance in the UK

Between 1970 and 2003, seven cases of human dura mater-associated Creutzfeldt-Jakob disease (CJD) were identified in the UK. Furthermore, we identified a case of CJD in a porcine dura graft recipient. The mean incubation period of the human dura mater cases was 93 (range 45-177) months. The clinico-pathological features of the cases are described and compared with cases previously reported in the world literature.

Size frequency distributions of the florid prion protein aggregates in variant Creutzfeldt-Jakob disease follow a power-law function

The objective was to test the hypothesis that the size frequency distributions of the prion protein (PrP) plaques in cases of variant Creutzfeldt-Jakob disease (vCJD) follow a power-law function. The design was a retrospective neuropathological study. The patients were 11 cases of clinically and neuropathologically verified vCJD. Size distributions of the diffuse and florid-type plaques were measured in several areas of the cerebral cortex and hippocampus from each case and a power-law function fitted to each distribution. The size distributions of the florid and diffuse plaques were fitted successfully by a powerlaw function in 100% and 42% of brain areas investigated respectively. Processes of aggregation/disaggregation may be more important than surface diffusion in the pathogenesis of the florid plaques. By contrast, surface diffusion may be a more significant factor in the development of the diffuse plaques.

Predicting susceptibility and incubation time of human-to-human transmission of vCJD

BACKGROUND

Identification of possible transmission of variant Creutzfeldt-Jakob disease (vCJD) via blood transfusion has caused concern over spread of the disease within the human population. We aimed to model iatrogenic spread to enable a comparison of transmission efficiencies of vCJD and bovine spongiform encephalopathy (BSE) and an assessment of the effect of the codon-129 polymorphism on human susceptibility.

METHODS

Mice were produced to express human or bovine prion protein (PrP) by direct replacement of the mouse PrP gene. Since the human PrP gene has variation at codon 129, with MM, VV, and MV genotypes, three inbred lines with an identical genetic background were produced to express human PrP with the codon-129 MM, MV, and VV genotypes. Mice were inoculated with BSE or vCJD and assessed for clinical and pathological signs of disease.

FINDINGS

BSE was transmitted to the bovine line but did not transmit to the human lines. By contrast, vCJD was transmitted to all three human lines with different pathological characteristics for each genotype and a gradation of transmission efficiency from MM to MV to VV.

INTERPRETATION

Transmission of BSE to human beings is probably restricted by the presence of a significant species barrier. However, there seems to be a substantially reduced barrier for human-to-human transmission of vCJD. Moreover, all individuals, irrespective of codon-129 genotype, could be susceptible to secondary transmission of vCJD through routes such as blood transfusion. A lengthy preclinical disease is predicted by these models, which may represent a risk for further disease transmission and thus a significant public-health issue.

Comparative neuropathology of Kuru with the new variant of Creutzfeldt-Jakob disease: evidence for strain of agent predominating over genotype of host

The three major influences on the phenotype of the transmissible spongiform encephalopathies are believed to be strain of agent, route of infection and host genotype. We have compared the pathologic profiles and genotypes of the new variant of Creutzfeldt-Jakob disease (vCJD) and kuru. The comparison reveals that there are distinct lesional differences particularly in the prion protein (PrP) load and distribution as seen by immunohistochemistry. The clinico-pathologic phenotypes and the genotypes of these two diseases are sufficiently different to suggest that the strain of agent may play a greater role than any presumptive common route of peripherally acquired infection.

Variant Creutzfeldt-Jakob disease: risk of transmission by blood transfusion and blood therapies

In the last decade, a new variant of the human prion disease Creutzfeldt-Jakob disease (now known as variant CJD or vCJD) was identified and causally linked to dietary exposure to bovine spongiform encephalopathy (BSE) during the 1980s and early 1990s. Preliminary studies in animal models suggest that prions can be transmitted by blood. Based on two recent reports of iatrogenic vCJD transmission by blood transfusion in humans, a Department of Health-sponsored risk assessment warned that recipients of plasma therapies are now at risk of contracting vCJD from potentially infected donors. It is believed that all the population may be susceptible to vCJD infection, although clinical cases have so far occurred only in methionine homozygotes at codon 129 in the human prion protein gene. A non-invasive blood-based diagnostic assay is urgently needed. Because the incubation period may be upwards of 40 years and there is no reliable screening test, it is currently unknown how many people may be in an asymptomatic phase of vCJD infection in the UK. However, there remains a distinct possibility that some infected patients may never develop clinical symptoms but will remain asymptomatic carriers who can potentially transmit the disease to other individuals. Therefore, screening of infectious individuals will be a critical component for individuals who rely on blood transfusions and/or blood therapies. In the absence of screening tests or effective therapies to treat this disease, a formidable worldwide public health challenge lies ahead to prevent new infections, accurately assess infection rates and treat infected patients.

Phenotypic variability in human prion diseases

Human prion diseases are rare neurodegenerative disorders that can occur as sporadic, familial or acquired disorders. Within each of these categories there is a wide range of phenotypic variation that is not encountered in other neurodegenerative disorders. The identification of the prion protein and its key role in the pathogenesis of this diverse group of diseases has allowed a fuller understanding of factors that influence disease phenotype. In particular, the naturally occurring polymorphism at codon 129 in the prion protein gene has a major influence on the disease phenotype in sporadic, familial and acquired prion diseases, although the underlying mechanisms remain unclear. Recent technical advances have improved our ability to study the isoforms of the abnormal prion protein in the brain and in other tissues. This has lead to the concept of molecular strain typing, in which different isoforms of the prion protein are proposed to correspond to individual strains of the transmissible agent, each with specific biological properties. In sporadic Creutzfeldt-Jakob disease there are at least six major combinations of codon 129 genotype and prion protein isotype, which appear to relate to distinctive clinical subgroups of this disease. However, these relationships are proving to be more complex than first considered, particularly in cases with more than a single prion protein isotype in the brain. Further work is required to clarify these relationships and to explain the mechanism of neuropathological targeting of specific brain regions, which accounts for the diversity of clinical features within human prion diseases.

Raised CSF phospho-tau concentrations in variant Creutzfeldt-Jakob disease: diagnostic and pathological implications

OBJECTIVE

To investigate whether phosphorylated tau protein (tau-pT181) is increased in variant Creutzfeldt-Jakob disease (vCJD) and if the tau-pT181/tau protein ratio is useful for distinguishing between patients with and without CJD.

METHODS

CSF tau protein and tau-pT181 were measured in 50 patients with sporadic CJD (sCJD), 51 patients with vCJD, 46 sCJD controls, and 37 vCJD controls, using Innotest hTau and Innotest P-Thr181, Innogenetics.

RESULTS

Concentrations of CSF tau protein were increased in sCJD (5120 v 367 pg/ml in controls, p < 0.001) and vCJD (952 v 106 pg/ml, p < 0.001); tau-pT181 was also raised in sCJD (61 v 35 pg/ml in controls, p = 0.002) and vCJD (114 v 33 pg/ml, p < 0.001). Median concentrations of tau-pT181 were higher in vCJD than in sCJD (p < 0.001). The tau-pT181/tau protein ratio was lower than in controls in both sCJD (12 v 128 (p < 0.001)) and vCJD (119 v 279 (p < 0.001)). Mean tau-pT181/tau protein ratio was 10-fold higher in vCJD than in sCJD. Raised CSF tau protein had the highest efficiency for distinguishing sCJD and vCJD from controls.

CONCLUSIONS

CSF tau-pT181 concentrations are raised in vCJD and are higher than in sCJD. Measurement of CSF tau-pT181/tau protein ratio does not improve the diagnostic efficiency of CSF tau protein alone for either vCJD or sCJD. The higher concentration of CSF tau-pT181 found in vCJD suggests that unexplained pathogenic factors influence the phosphorylation of tau protein in vCJD patients.

Variant Creutzfeldt-Jakob disease transmission by plasma products: assessing and communicating risk in an era of scientific uncertainty

A substantial body of animal data indicates that transmissible spongiform encephalopathies (TSEs) are transmitted through blood. These data have been augmented in the past year by reports that two recipients of red cells from donors with variant Creutzfeldt-Jakob disease (vCJD) in the United Kingdom have acquired this infection. Most of the blood donations collected in countries affected by bovine spongiform encephalopathy (BSE) and vCJD also contribute plasma to fractionation pools. Thus, a number of batches of fractionated products have included plasma from donors who developed vCJD. On the basis of public health strategies influenced, in part, by risk assessments, the UK and the French authorities have instituted measures for recalling products and informing patients of the estimated risks. It is therefore relevant to review the principles used by authorities in generating risk assessments for the transmission of TSEs by blood and blood products. While the general principles are fairly straightforward, the final assessments are very dependent on the magnitude of several key parameters, which are, largely, still unknown. A critical determinant of final product risk is the extent to which the plasma fractionation process will contribute to eliminating the infectious prion agent. Therefore, regulatory and industry measures to characterize fractionation processes for their capacity to eliminate prions are to be strongly encouraged. In the interim, an understanding of the principles used to generate risk assessments should contribute to an enhanced ability to address this threat to patient safety. Authorities should recognize that adequate communication is an integral part of good risk-management practices.

Abnormal prion protein in the retina of the most commonly occurring subtype of sporadic Creutzfeldt-Jakob disease

BACKGROUND

Involvement of the eye has been reported in patients with variant Creutzfeldt-Jakob disease (vCJD), but there is disagreement on whether retinal involvement occurs in sporadic Creutzfeldt-Jakob disease (sCJD).

METHODS

Western blotting, paraffin embedded tissue blotting, and immunohistochemistry were used to test whether the abnormal form of the prion protein (PrPSc) accumulates to detectable levels in the eye in a case of the most common subtype of sCJD (MM1).

RESULTS

Low levels of PrPSc were detectable in the retina, localised to the plexiform layers of the central retina. PrPSc was not detectable in other ocular tissues.

CONCLUSIONS

The abnormal form of the prion protein is present in the retina in the most common sCJD subtype (MM1), albeit at levels lower than those found previously in vCJD and in sCJD of the VV2 subtype.

Third ventricular chordoid glioma: clinicopathological study of two cases with evidence for a poor clinical outcome despite low grade histological features

Chordoid glioma of the third ventricle is a rare glial tumour whose precise histogenesis remains uncertain. We describe two cases that presented recently to our department and review the background literature. The neoplasm tends to occur in women and its clinical presentation is variable, resulting from acute hydrocephalus or impingement upon local structures. However, the radiological appearance is distinct, with an ovoid shape, hyperdensity and uniform contrast enhancement on computerized tomography and magnetic resonance imaging. Intraoperative smear diagnosis is difficult because of the lack of specific features, although the presence of metachromatic extracellular mucin may be useful. The characteristic histological appearance is that of cords and clusters of cohesive, oval-to-polygonal epithelioid cells with abundant eosinophilic cytoplasm and a mucinous background. There is often a mixed chronic inflammatory infiltrate with lymphocytes and plasma cells with Russell bodies. The main differentials for histological diagnosis include chordoid meningiomas, pilocytic astrocytomas and ependymomas. An immunohistochemical panel including antibodies to glial fibrillary acidic protein, CD 34, epithelial membrane antigen, pan cytokeratin, S100 and vimentin can be used to distinguish between these possibilities. Ultrastructurally the tumour cells have basal lamina and microvilli, reminiscent of ependymomas. The clinical outcome in our cases was poor because of the location of the lesion and its close relation to the hypothalamus. Limited follow-up after surgery with or without radiotherapy suggests that as-full-as-possible resection favours a better outcome, although surgery in this area carries significant operative risks.

The accuracy of meningioma grading: a 10-year retrospective audit

Although descriptive classifications of meningioma subtypes are well established, there has been inconsistency in the categorization of meningiomas into benign, atypical and anaplastic groups. The aim of this study was to reassess the incidence of atypical (grade II) meningiomas over a 10-year period by applying the World Health Organization (WHO) 2000 classification system. A secondary aim was to determine if grade II and III tumours were becoming more common. Sections of 314 meningiomas resected between 1994 and 2003 were retrieved from the archives of the Western General Hospital's neuropathology unit in Edinburgh. They were reassessed and graded by using the WHO 2000 classification system. The reviewers were blind to the original classification and grading. There was a gradual increase in the numbers of meningiomas being resected annually over the 10-year period. On reclassification, 78% of the meningiomas were classified as grade I, 20.4% as grade II and 1.6% as grade III. With regard to grade II meningiomas classified by using the WHO 2000 classification system, 38.1% had originally been classified as grade I prior to 2000, whereas 13.6% had originally been classified as grade I after 2000. In most cases, reclassification was due to formal counts of mitotic figures. Atypical meningiomas are diagnosed more frequently under the current WHO classification system than they were under the previous classification systems. Although the current WHO (2000) classification is more prescriptive than its predecessors, interobserver variability is likely to remain because of the subjective nature of some of the criteria.

Size frequency distribution of prion protein (PrP) aggregates in variant Creutzfeldt-Jakob disease (vCJD)

The frequency distribution of aggregate size of the diffuse and florid-type prion protein (PrP) plaques was studied in various brain regions in cases of variant Creutzfeldt-Jakob disease (vCJD). The size distributions were unimodal and positively skewed and resembled those of beta-amyloid (A beta) deposits in Alzheimer's disease (AD) and Down's syndrome (DS). The frequency distributions of the PrP aggregates were log-normal in shape, but there were deviations from the expected number of plaques in specific size classes. More diffuse plaques were observed in the modal size class and fewer in the larger size classes than expected and more florid plaques were present in the larger size classes compared with the log-normal model. It was concluded that the growth of the PrP aggregates in vCJD does not strictly follow a log-normal model, diffuse plaques growing to within a more restricted size range and florid plaques to larger sizes than predicted.

Advances in the detection of prion protein in peripheral tissues of variant Creutzfeldt-Jakob disease patients using paraffin-embedded tissue blotting

The accumulation of PrP(Sc), an abnormal and disease-associated form of the normal prion protein (PrP(c)), within the central nervous system (CNS) is a key pathological feature of Creutzfeldt-Jakob disease (CJD). Following limited proteolytic digestion of PrP(Sc), the detection of PrP(res) within lymphoid tissues is a unique characteristic of variant CJD in comparison with other human prion diseases, raising fears of an increased risk of iatrogenic spread. Because levels of PrP(res) in lymphoid tissues are lower than those found in CNS tissue, there is concern that other peripheral tissues may harbour infectivity at levels that current detection systems cannot demonstrate PrP(res). We have modified the paraffin-embedded tissue blot (PET blot), a technique combining immunohistochemistry (IHC), histoblot and Western blotting, for the detection of PrP(res) in paraffin sections in peripheral tissues in variant CJD. Five cases of variant CJD were examined, using a panel of anti-PrP antibodies. In each of these five cases, spleen, tonsil, lymph nodes and dorsal root ganglia showed an increase in the sensitivity and specificity of labelling using the PET blot when compared with optimized PrP(res) IHC methods. Control cases showed no evidence of PrP accumulation in either peripheral or CNS tissues. Autopsy and biopsy brain material from sporadic CJD cases also showed an increased sensitivity of PrP(res) detection with the PET blot, confirming its value as an important diagnostic and research tool in human prion diseases.

Variant Creutzfeldt-Jakob disease: risk of transmission by blood and blood products

Variant Creutzfeldt-Jakob disease (CJD) is a novel acquired human prion disease apparently resulting from exposure to the bovine spongiform encephalopathy (BSE) agent. Variant CJD differs from other human prion diseases in that the disease-associated form of the prion protein and infectivity are readily detectable in lymphoid tissues throughout the body. Lymphoid tissues and lymphocytes are implicated in the peripheral pathogenesis of prion diseases (where infectivity may be detected during the preclinical phase of the illness), giving rise to concerns that blood and blood products may also contain infectious particles, representing a possible source of iatrogenic spread of variant CJD. This concern has been reinforced following the experimental transmission of BSE in a sheep model by transfusion of blood and buffy coat from animals in the preclinical phase of the illness, and the recent identification of a UK case of variant CJD in a patient who had received packed red blood cells that had been donated by an individual who subsequently died from variant CJD. Studies in animal models suggest that most prion infectivity in blood may be cell-associated, with lower levels in the plasma, and there is evidence to suggest that any infectivity present may be reduced during the process of plasma fractionation. However, the possibility that plasma or blood products could transmit the disease cannot be excluded. Further studies are required to develop more sensitive means to detect disease-associated prion protein in blood; such techniques could be employed for screening purposes to reduce exposure to contaminated products and to assist with risk management in potentially exposed individuals.

Presentation of a case of variant CJD in general dental practice

This case report describes the initial presentation of variant CJD to a general dental practitioner. The case highlights the importance of prompt referral of patients presenting with a history of atypical facial symptoms.

Spatial correlation between the vacuolation, prion protein, deposition and surviving neurons in patients with Creutzfeldt-Jakob disease (vCJD)

The histological features of cases of variant Creutzfeldt-Jakob disease (vCJD) are often distributed in the brain in clusters. This study investigated the spatial associations between the clusters of the vacuoles, surviving neurons, and prion protein (PrP) deposits in various brain areas in 11 cases of vCJD. Clusters of vacuoles and surviving neurons were positively correlated in the cerebral cortex but negatively correlated in dentate gyrus. Clusters of the florid and diffuse type of PrP deposit were not positively correlated with those of either the vacuoles or the surviving neurons although a negative correlation was observed between the florid plaques and surviving neurons in some cortical areas. Clusters of florid and diffuse deposits were either negatively correlated or uncorrelated. These data suggest: 10 that clusters of vacuoles in the cerebral cortex are associated with the presence of surviving neuronal cell bodies, 2) that clusters of vacuoles are not spatially related to those of the PrP deposits, and 3) different factors are involved in the pathogenesis of the florid and diffuse PrP deposits.

Specificity of lymphoreticular accumulation of prion protein for variant Creutzfeldt-Jakob disease

BACKGROUND

Immunocytochemical accumulation of prion protein (PrP) in lymphoid tissues is a feature of variant Creutzfeldt-Jakob disease (vCJD) that has been used both to aid in the diagnosis of patients and as a basis of large scale screening studies to assess the prevalence of preclinical disease in the UK. However, the specificity of this approach is unknown.

AIM

To assess the specificity of lymphoreticular accumulation of PrP for vCJD by examining a range of human diseases.

METHODS

Paraffin wax embedded lymphoreticular tissues from patients with several reactive conditions (58 cases), tumours (27 cases), vCJD (54 cases), and other human prion diseases (56 cases) were assessed. PrP accumulation was assessed by immunocytochemistry using two different monoclonal anti-PrP antibodies and a sensitive detection system.

RESULTS

All cases of vCJD showed widespread lymphoreticular accumulation of PrP; however, this was not seen in the other conditions examined.

CONCLUSION

Lymphoreticular accumulation of PrP, as assessed by immunocytochemistry, appears to be a highly specific feature of vCJD.

Neuropathology and molecular biology of variant Creutzfeldt-Jakob disease

The neuropathological features of human prion diseases are spongiform change, neuronal loss, astrocytic proliferation and the accumulation of PrP(Sc), the abnormal isoform of prion protein (PrP). The pattern of brain involvement is remarkably variable and is substantially influenced by the host PrP genotype and PrP(Sc) isotype. Variant Creutzfeldt-Jakob disease (vCJD) is a novel human prion disease which results from exposure to the bovine spongiform encephalopathy (BSE) agent. The neuropathology of vCJD shows consistent characteristics, with abundant florid and cluster plaques in the cerebrum and cerebellum, and widespread accumulation of PrP(res) on immunocytochemistry. These features are distinct from all other types of human prion disease. Spongiform change is most marked in the basal ganglia, while the thalamus exhibits severe neuronal loss and gliosis in the posterior nuclei. These areas of thalamic pathology correlate with the areas of high signal seen in the thalamus on magnetic resonance imaging (MRI) examination of the brain. Western blot analysis of PrP(Sc) in the brain in vCJD tissue shows a uniform isotype, with a glycoform ratio characterized by predominance of the diglycosylated band, distinct from sporadic CJD. PrP(Sc) accumulation in vCJD is readily detectable outside the brain, in contrast with other forms of human prion disease, particularly in the lymphoid system and in parts of the peripheral nervous system. This has raised concern about the possible iatrogenic transmission of vCJD by contaminated surgical instruments, or blood. All cases of vCJD are methionine homozygotes at codon 129 of the prion protein gene (PRNP). Continued surveillance is required to investigate cases of vCJD in the UK and other countries where BSE has been reported, particularly as cases of 'human BSE' in individuals who are MV or VV at codon 129 of the PrP gene have not yet been identified. Histological, genetic and biochemical techniques are essential tools for the adequate diagnosis and investigation of human prion diseases.

Investigation of PrPres in dental tissues in variant CJD

OBJECTIVES

To study the distribution of disease-associated prion protein (PrP) in oral and dental tissues in variant CJD.

DESIGN

Prospective single centre autopsy based study.

SETTING

Within the National CJD Surveillance Unit, UK, 2000-2002.

MATERIALS AND METHODS

Patients with suspected variant CJD undergoing autopsy where permission to remove tissues for research purposes had been obtained from the relatives. Fixed and frozen autopsy tissues from the brain, trigeminal ganglion, alveolar nerve, dental pulp, gingiva, salivary gland, tongue and tonsils were studied by Western blot, PET blot and immunocytochemistry to detect disease-associated PrP.

RESULTS

Disease-associated PrP was only detected in the brain, trigeminal ganglia and tonsils.

CONCLUSIONS

The failure to detect disease-associated PrP in most dental and oral tissues will help inform ongoing risk assessments for dental surgery in relation to the possible iatrogenic transmission of variant CJD via dental instruments.

Neuronal and astrocytic responses involving the serotonergic system in human spongiform encephalopathies

The relationships between the degree of cortical prion protein (PrP) deposition, tissue vacuolation and astrocytosis were studied in the frontal cortex of 27 cases of human spongiform encephalopathy, encompassing 13 cases of sporadic Creutzfeldt-Jakob disease (sCJD), four cases of familial CJD (fCJD) (one owing to E200K mutation, one owing to 144 bp insertion, one owing to P102L mutation and one owing to A117V mutation), five cases of iatrogenic CJD (iCJD) owing to growth hormone therapy and five cases of variant CJD (vCJD). The size and number of tryptophan hydroxylase (TPH) positive cells in the dorsal raphe were determined as an index of the function of the brain's serotonergic system. The amount of PrP deposited in frontal cortex in vCJD was significantly greater than that in both sCJD and iCJD, which did not differ significantly from each other. The extent of grey matter deposition of PrP correlated with that of white matter deposition. Deposition of PrP as plaques was greater in cases of sCJD bearing valine at codon 129 of PrP gene, especially when homozygous. However, all cases of vCJD displayed florid plaque formation yet these were homozygous for methionine at codon 129. Prion protein deposition as plaques was greater in cases of sCJD with 2A PrP isotype than those with 1 PrP isotype, similar to that seen in cases of vCJD all of which are 2B PrP isotype. There were no significant differences in the extent of astrocytosis between the different aetiological groups, in either grey or white matter, as visualized with glial fibrillary acidic protein (GFAP) or 5HT-2A receptor (5HT-2AR) immunostaining, although there was a strong correlation between the severity of 5HT-2AR and GFAP reactions within both grey and white matter. The extent of PrP deposition within the grey, but not white, matter correlated with the degree of astrocytosis for both GFAP and 5HT-2AR and the extent of tissue vacuolation in grey and white matter, although the latter did not correlate with degree of astrocytosis for either GFAP or 5HT-2AR. Astrocytes may be responding directly to the presence of PrP within the tissue, rather than the vacuolar damage to neurones. Although S100beta immunoreactivity was present in astrocytes in control cases, no S100beta staining was seen in astrocytes in either grey or white matter in most CJD cases. There were no differences in the number of TPH-positive cells between CJD and control cases, although the mean TPH-positive cell size was significantly greater, and cells were more intensely stained, in CJD compared to controls, suggesting a pathological overactivity of the brain's serotonergic system in CJD. This may result in excessive release of 5HT within the brain triggering increased 5HT-2AR expression within activated astrocytes leading to release and depletion of S100beta protein from such cells. The clinical symptoms of fluctuating attention and arousal could be mediated, at least in part, by such alterations in function of the serotonergic system.