Creutzfeldt-Jacob disease following cadaveric dura mater graft

Pathogenic mechanisms of prion protein, amyloid-β and α-synuclein misfolding: the prion concept and neurotoxicity of protein oligomers

Proteinopathies represent a group of diseases characterized by the unregulated misfolding and aggregation of proteins. Accumulation of misfolded protein in the central nervous system (CNS) is associated with neurodegenerative diseases, such as the transmissible spongiform encephalopathies (or prion diseases), Alzheimer's disease, and the synucleinopathies (the most common of which is Parkinson's disease). Of these, the pathogenic mechanisms of prion diseases are particularly striking where the transmissible, causative agent of disease is the prion, or proteinaceous infectious particle. Prions are composed almost exclusively of PrP^Sc ; a misfolded isoform of the normal cellular protein, PrP^C , which is found accumulated in the CNS in disease. Today, mounting evidence suggests other aggregating proteins, such as amyloid-β (Aβ) and α-synuclein (α-syn), proteins associated with Alzheimer's disease and synucleinopathies, respectively, share similar biophysical and biochemical properties with PrP^Sc that influences how they misfold, aggregate, and propagate in disease. In this regard, the definition of a 'prion' may ultimately expand to include other pathogenic proteins. Unifying knowledge of folded proteins may also reveal common mechanisms associated with other features of disease that are less understood, such as neurotoxicity. This review discusses the common features Aβ and α-syn share with PrP and neurotoxic mechanisms associated with these misfolded proteins. Several proteins are known to misfold and accumulate in the central nervous system causing a range of neurodegenerative diseases, such as Alzheimer's, Parkinson's, and the prion diseases. Prions are transmissible misfolded conformers of the prion protein, PrP, which seed further generation of infectious proteins. Similar effects have recently been observed in proteins associated with Alzheimer's disease and the synucleinopathies, leading to the proposition that the definition of a 'prion' may ultimately expand to include other pathogenic proteins. Unifying knowledge of misfolded proteins may also reveal common mechanisms associated with other features of disease that are less understood, such as neurotoxicity.

Iatrogenic Creutzfeldt-Jakob disease and its neurosurgical implications

Creutzfeldt-Jakob (CJD) disease has been reported after the insertion of dural homografts. Two Australian cases of CJD, both following posterior fossa craniotomies done in 1982, are reported; the incubation periods were 5 and 12 years. It seems highly probable that the association is causal. CJD infective agents (prions) are resistant to many previously accepted means of sterilisation and it is postulated that cadaver dural material was either derived from subjects with CID, or was contaminated during preparation. In Australia the use of dural homografts in neurosurgery was abandoned in 1987; as the mean incubation period (determined from a world-wide review) has been about 65 months, it is now hoped that this cause of CJD will not recur in the Australian population, although it is premature to state this with confidence. However, precautions against case-to-case transmission remain necessary, and guidelines for this purpose should be enforced in theatre practice and in organ donations.

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.

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.

Decreasing latitude and increasing regulation in transplantable tissue programs

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ADVANCED TECHNOLOGY and improved surgical techniques have led to new therapeutic uses for allografts.

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DISEASE TRANSMISSION via allograft tissue transplants has prompted federal intervention in the tissue banking industry and resulted in federal regulations.

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NEW STANDARDS from the Joint Commission on Accreditation of Healthcare Organizations became effective July 1,2005, and apply to all hospitals that store or implant allograft tissues. These standards include mandatory policies on all aspects of hospital transplantation programs, including tissue ordering, receipt, storage, issuance, and record keeping. AORN J 82 (November 2005) 806–814.

The public health impact of prion diseases

Several prion disease-related human health risks from an exogenous source can be identified in the United States, including the iatrogenic transmission of Creutzfeldt-Jakob disease (CJD), the possible occurrence of variant CJD (vCJD), and potential zoonotic transmission of chronic wasting disease (CWD). Although cross-species transmission of prion diseases seems to be limited by an apparent "species barrier," the occurrence of bovine spongiform encephalopathy (BSE) and its transmission to humans indicate that animal prion diseases can pose a significant public health risk. Recent reports of secondary person-to-person spread of vCJD via blood products and detection of vCJD transmission in a patient heterozygous at codon 129 further illustrate the potential public health impacts of BSE.

Epidemiological Study of Creutzfeldt-Jakob Disease Death Certificates in Canada, 1979–2001

INTRODUCTION

A descriptive epidemiological analysis to update trends of Creutzfeldt-Jakob disease (CJD) deaths, from 1979-2001, was undertaken.

METHODS

Cases with CJD as underlying cause were extracted. Age-adjusted death rates by age, sex, and province were calculated. Information on birthplace, autopsy indications and type of work were examined for death certificates from 1979 to 1997.

RESULTS

462 cases were identified between 1979 and 1997. The average annual age-standardized mortality rate was 0.93 deaths per million persons during this period and 1.03 for 1998-2001. Persons 60 years or older demonstrated the highest average annual mortality rate. Rates were slightly higher among males and increased with age. Persons born in Canada accounted for 72% of deaths. Cause of death was verified by autopsy for 9.1% of patients while 21% of deaths indicated that additional information relating to underlying cause was expected. The service industry occupation represented the largest mortality (Quebec does not capture these data).

CONCLUSIONS

Canadian rates are consistent with those of the United States and slightly higher than those of certain European countries. Approximately 44% of CJD cases had an autopsy record, though many were incomplete. We are unable to determine a relation with occupation. We recommend annual analysis of CJD death registrations for updated surveillance of trends, as mortality data are an efficient tool for monitoring incidence.

Prions and blood products

The transmission of Creutzfeldt-Jakob disease (CJD) by human pituitary-derived growth hormone has led to concerns that blood products might also provide a route for the iatrogenic transmission of CJD. A number of actions have been implemented by regulatory authorities to address such concerns, and numerous studies have been undertaken to determine whether or not there is a risk of CJD being transmitted in this manner. To date, no excess risk has been identified, leading to a growing consensus that there is little or no risk of long established forms of CJD being transmitted to recipients of blood products. This opinion does not extend to new variant CJD (vCJD) which is found predominantly in the UK and is believed to have resulted from the transmission of bovine spongiform encephalopathy (BSE) to humans. Unlike that of CJD, the prevalence of vCJD is not known. In addition, the detection of abnormal prion protein in the tonsils of vCJD-infected individuals has led to speculation that blood infectivity may be greater than in patients with CJD. A number of precautionary measures have been taken to address the possibility that vCJD may be transmissible by blood products; however, further scientific advances are needed to enable this risk to be defined. A suitable screening test is required to identify any infected blood donors, particularly where cellular blood components are being derived from populations believed to be at risk from BSE infection. Recent experimental data suggest that process operations used in the manufacture of plasma products may be capable of removing prion agents to a significant extent. However, further work is required to confirm these observations and to determine whether or not all potential vCJD infectivity would be removed by these means.

Creutzfeldt-Jakob disease and the eye. I. Background and patient management

This article attempts to summarise our current understanding of TSEs as they affect man. Specific aspects relevant to ophthalmological practice, in particular the management of patients in day-to-day clinical practice and with respect to corneal transplantation, have been discussed. In the companion article we discuss the specific ophthalmic and neuro-ophthalmic features of these diseases.

Transmissible spongiform encephalopathies in humans

Creutzfeldt-Jakob disease (CJD), the first transmissible spongiform encephalopathy (TSE) to be described in humans, occurs in a sporadic, familial, or iatrogenic form. Other TSEs in humans, shown to be associated with specific prion protein gene mutations, have been reported in different parts of the world. These TSEs compose a heterogeneous group of familial diseases that traditionally have been classified as familial CJD, Gerstmann-Sträussler-Scheinker syndrome, or fatal familial insomnia. In 1996, a newly recognized variant form of CJD among young patients (median age, 28 years) with unusual clinical features and a unique neuropathologic profile was reported in the United Kingdom. In the absence of known CJD risk factors or prion protein gene abnormalities, the UK government concluded that the clustering of these cases may represent transmission to humans of the agent causing bovine spongiform encephalopathy. Additional epidemiologic and recent laboratory data strongly support the UK government's conclusion.

The prion diseases: Creutzfeldt-Jakob, Gerstmann-Sträussler-Scheinker, and related disorders

The prion diseases are an interesting group of neurodegenerative disorders for a variety of reasons. The most obvious is their property of transmissibility, but beyond that they constitute a fascinating example of the diversity of disease expression possible from a common etiologic factor. Thought of as "strains" in animals and phenotypes in humans, these varied expressions of prion disease are most likely due to subtle conformational changes in the pathogenic form of the prion protein. These strain-like characteristics are best exemplified in the genetic varieties of human prion disease in which specific mutations are associated with specific phenotypic profiles. This review attempts to highlight the clinical and pathologic features of the prion diseases with a particular focus on the genetic determinants that define the various familial forms and that modify sporadic and iatrogenic forms of the disease.

Creutzfeldt-Jakob disease via dural and corneal transplants

A review of all published cases of iatrogenic Creutzfeldt-Jakob disease (CJD) via dural (N=71) and corneal (N=4) transplants is given. All but three of the dural cases were obviously due to a commercial product recalled in 1996. Two of the corneal grafts were taken from patients who had died of sporadic CJD. These cases differed from CJD due to human growth hormone injections and the new variant. Instead. they were akin to sporadic cases, but memory loss, disorders of higher cerebral functions and extrapyramidal signs were fewer, while cerebellar abnormalities were more frequent. Progressive dysarthria and gait disorder/gait ataxia were prominent signs during the early stages, myocloni the most salient feature later. A nonperiodic EEG did not contradict the diagnosis. Using current diagnostic criteria the disease was underdiagnosed ante mortem. Utmost care is needed in selecting, harvesting and handling dural and corneal grafts to avoid inadvertent transmission of CJD.

Etiology and pathogenesis of prion diseases

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Transmission of Creutzfeldt-Jakob disease from humans to transgenic mice expressing chimeric human-mouse prion protein

Transgenic (Tg) mice were constructed that express a chimeric prion protein (PrP) in which a segment of mouse (Mo) PrP was replaced with the corresponding human (Hu) PrP sequence. The chimeric PrP, designated MHu2MPrP, differs from MoPrP by 9 amino acids between residues 96 and 167. All of the Tg(MHu2M) mice developed neurologic disease approximately 200 days after inoculation with brain homogenates from three patients dying of Creutzfeldt-Jakob disease (CJD). Inoculation of Tg(MHu2M) mice with CJD prions produced MHu2MPrPSc (where PrPSc is the scrapie isoform of PrP); inoculation with Mo prions produced Mo-PrPSc. The patterns of MHu2MPrPSc and MoPrPSc accumulation in the brains of Tg(MHu2M) mice were different. About 10% of Tg(HuPrP) mice expressing HuPrP and non-Tg mice developed neurologic disease > 500 days after inoculation with CJD prions. The different susceptibilities of Tg(HuPrP) and Tg(MHu2M) mice to Hu prions indicate that additional species-specific factors are involved in prion replication. Diagnosis, prevention, and treatment of Hu prion diseases should be facilitated by Tg(MHu2M) mice.

Creutzfeld-Jakob disease: recommendations for infection control

Creutzfeld-Jakob disease, an infectious, progressive, degenerative neurologic disorder, has a presumably long incubation period but a rapid, fatal course. Brain tissue at autopsy resembles that seen in spongioform encephalopathies of other species. Creutzfeld-Jakob disease is transmitted by a proteinaceous infectious agent, or "prion." Epidemiologic patterns remain uncertain; various studies have reported conflicting risk factors in different populations, and genetic susceptibility may be involved. Although natural transmission routes are still unclear, both iatrogenic and nosocomial transmissions have been identified. Transmission has occurred through contaminated electrodes, contaminated biologic products from cadaveric brains, and infected donor tissues, including dura mater and corneas. Because the prion is difficult to eradicate, stringent sterilization precautions must be taken with all surgical instruments. Some tissues and body fluids (e.g., brain, ocular, central nervous system) from the patient with Creutzfeld-Jakob disease are highly infectious and must be contained or incinerated. Some body fluids, however, are not considered infectious. Persons with known or suspected Creutzfeld-Jakob disease, or with exposure to potential sources of iatrogenic infection, should not be considered as donors for any tissues or biologic products. Occupational transmission to health care and pathology workers is also possible. Therefore, specific preventive measures are necessary. Many questions remain regarding transmission and risk factors for Creutzfeld-Jakob syndrome, and the precautions presented here must be considered only preliminary.

Accidental transmission of Creutzfeldt-Jakob disease by dural cadaveric grafts

Four patients who received dural grafts of cadaveric origin in the course of posterior fossa procedures subsequently developed Creutzfeldt-Jakob disease (CJD). The interval from dural placement to clinical onset of CJD ranged from 16 months to nine years. Initial clinical presentation consisted of cerebellar symptoms, with dementia and myoclonus developing in later stages of the disease. EEGs showed diffuse slowing that evolved to a periodic activity pattern. CT and MRI were unremarkable in the early stages but pronounced cerebral and cerebellar atrophy with widened sulci and collections of fluid over the convexities were seen in the late stages of disease. The diagnosis was histologically proved by brain biopsy in all four cases. Molecular genetic analysis showed that the four patients were homozygous for methionine at codon 129 of the PrP gene. From this experience, and from six previous descriptions of this occurrence in the literature, it is manifest that awareness of the means of iatrogenic transmission of CJD, and the adoption of preventive measures, constitute the only effective way to stop the spread of CJD among patients who have neurosurgery.

Creutzfeldt-Jakob disease and lyophilised dura mater grafts: report of two cases

Two further cases of Creutzfeldt-Jakob disease (CJD) in association with cadaveric dura mater grafts are described. The clinical features of all such reported cases resemble more closely those of sporadic CJD, in contrast with kuru and the cases of CJD which have arisen after therapy with human pituitary-derived growth hormone. This observation may reflect the route of inoculation of the agent.

A new bioprosthesis in large abdominal wall defects

A collagen-coated Vicryl mesh bioprosthesis was used to repair a 4 x 4 cm full-thickness abdominal wall defect, created in experimental rats. The tensile strength of the repair at 6 months reached 70% of the original abdominal wall. Implant collagen could not be differentiated from host collagen after 2 weeks. The increase in collagen content of the repair was responsible for the increasing tensile strength of the wound with time. All histological sections showed good tolerance of the implant. These results support the use of collagen Vicryl membrane to repair large abdominal wall defects. Clinical trials are indicated.

Human prion diseases (spongiform encephalopathies)

Prion diseases (spongiform encephalopathies) in humans are Creutzfeldt-Jakob disease (CJD), Gerstmann-Sträussler-Scheinker syndrome (GSS), and kuru. Clinically, they are characterized by an inexorably progressing neurological illness with dementia and ataxia as the most prominent signs. The classical neuropathological changes are limited to the central nervous system and consist of spongiform degeneration, amyloid plaques, astrocytic gliosis, and nerve cell loss. The human spongiform encephalopathies, which for many years were considered neurodegenerative disorders of unknown etiology, were finally recognized as transmissible diseases similar to scrapie in sheep in the late 1960's. The infectious agent appears to consist of protein devoid of functional nucleic acid and has been termed prion to distinguish it from viruses. The prion hypothesis has gained wide acceptance through the finding that mutations of the prion protein gene are associated with heritable human prion disease. Different mutations appear to cause prion disease with a distinct pattern of clinical and pathological features in a great number of families. Certain mutations of the PrP gene have been shown to be associated with clinical and neuropathological changes not typical of any variant of human prion disease known to date. A new classification of prion diseases based on the molecular biology and biochemistry of the prion protein is likely to emerge.