PrPTSE distribution in a primate model of variant, sporadic, and iatrogenic Creutzfeldt-Jakob disease

Prion diseases disrupt glutamate/glutamine metabolism in skeletal muscle

In prion diseases (PrDs), aggregates of misfolded prion protein (PrPSc) accumulate not only in the brain but also in extraneural organs. This raises the question whether prion-specific pathologies arise also extraneurally. Here we sequenced mRNA transcripts in skeletal muscle, spleen and blood of prion-inoculated mice at eight timepoints during disease progression. We detected gene-expression changes in all three organs, with skeletal muscle showing the most consistent alterations. The glutamate-ammonia ligase (GLUL) gene exhibited uniform upregulation in skeletal muscles of mice infected with three distinct scrapie prion strains (RML, ME7, and 22L) and in victims of human sporadic Creutzfeldt-Jakob disease. GLUL dysregulation was accompanied by changes in glutamate/glutamine metabolism, leading to reduced glutamate levels in skeletal muscle. None of these changes were observed in skeletal muscle of humans with amyotrophic lateral sclerosis, Alzheimer's disease, or dementia with Lewy bodies, suggesting that they are specific to prion diseases. These findings reveal an unexpected metabolic dimension of prion infections and point to a potential role for GLUL dysregulation in the glutamate/glutamine metabolism in prion-affected skeletal muscle.

In Vitro and In Vivo Evidence towards Fibronectin's Protective Effects against Prion Infection

A distinctive signature of the prion diseases is the accumulation of the pathogenic isoform of the prion protein, PrPSc, in the central nervous system of prion-affected humans and animals. PrPSc is also found in peripheral tissues, raising concerns about the potential transmission of pathogenic prions through human food supplies and posing a significant risk to public health. Although muscle tissues are considered to contain levels of low prion infectivity, it has been shown that myotubes in culture efficiently propagate PrPSc. Given the high consumption of muscle tissue, it is important to understand what factors could influence the establishment of a prion infection in muscle tissue. Here we used in vitro myotube cultures, differentiated from the C2C12 myoblast cell line (dC2C12), to identify factors affecting prion replication. A range of experimental conditions revealed that PrPSc is tightly associated with proteins found in the systemic extracellular matrix, mostly fibronectin (FN). The interaction of PrPSc with FN decreased prion infectivity, as determined by standard scrapie cell assay. Interestingly, the prion-resistant reserve cells in dC2C12 cultures displayed a FN-rich extracellular matrix while the prion-susceptible myotubes expressed FN at a low level. In agreement with the in vitro results, immunohistopathological analyses of tissues from sheep infected with natural scrapie demonstrated a prion susceptibility phenotype linked to an extracellular matrix with undetectable levels of FN. Conversely, PrPSc deposits were not observed in tissues expressing FN. These data indicate that extracellular FN may act as a natural barrier against prion replication and that the extracellular matrix composition may be a crucial feature determining prion tropism in different tissues.

Unexpected decrease of full-length prion protein in macaques inoculated with prion-contaminated blood products

The presence of prion infectivity in the blood of patients affected by variant Creutzfeldt-Jakob disease (v-CJD), the human prion disease linked to the bovine spongiform encephalopathy (BSE), poses the risk of inter-human transmission of this fatal prion disease through transfusion. In the frame of various experiments, we have previously described that several cynomolgus macaques experimentally exposed to prion-contaminated blood products developed c-BSE/v-CJD, but the vast majority of them developed an unexpected, fatal disease phenotype focused on spinal cord involvement, which does not fulfill the classical diagnostic criteria of v-CJD. Here, we show that extensive analyses with current conventional techniques failed to detect any accumulation of abnormal prion protein (PrP^v-CJD) in the CNS of these myelopathic animals, i.e., the biomarker considered responsible for neuronal death and subsequent clinical signs in prion diseases. Conversely, in the spinal cord of these myelopathic primates, we observed an alteration of their physiological cellular PrP pattern: PrP was not detectable under its full-length classical expression but mainly under its physiological terminal-truncated C1 fragment. This observed disappearance of the N-terminal fragment of cellular PrP at the level of the lesions may provide the first experimental evidence of a link between loss of function of the cellular prion protein and disease onset. This original prion-induced myelopathic syndrome suggests an unexpected wide extension in the field of prion diseases that is so far limited to pathologies associated with abnormal changes of the cellular PrP to highly structured conformations.

Non-human primates in prion diseases

The fascinating history of prion diseases is intimately linked to the use of nonhuman primates as experimental models, which brought so fundamental and founding information about transmissibility, pathogenesis, and resistance of prions. These models are still of crucial need for risk assessment of human health and may contribute to pave a new way towards the moving field of prion-like entities which now includes the main human neurodegenerative diseases (especially Alzheimer's and Parkinson's diseases).

Experimental inoculation of CD11c+ B1 lymphocytes, CD68+ macrophages, or platelet-rich plasma from scrapie-infected sheep into susceptible sheep results in variable infectivity

Many studies have demonstrated prion infectivity in whole blood and blood components in a variety of transmissible spongiform encephalopathies of livestock and rodents, and variant Creutzfeldt–Jakob disease in humans, as well as an association between pathogenic prion protein (PrP^Sc) and different immune cells (e.g. follicular dendritic cells, T and B lymphocytes, monocytes and tingible body macrophages). To further investigate the role of various blood components in prion disease transmission, we intracranially inoculated genetically susceptible VRQ/ARQ and ARQ/ARQ sheep with inocula composed of CD11c⁺ B1 lymphocytes, CD68 +macrophages, or platelet-rich plasma derived from clinically ill sheep infected with the US no. 13–7 scrapie agent. At the completion of the study, we found that VRQ/ARQ and ARQ/ARQ sheep inoculated with CD11c⁺ B1 lymphocytes and CD68⁺ macrophages developed scrapie with detectable levels of PrP^Sc in the central nervous system and lymphoreticular system, while those inoculated with platelet-rich plasma did not develop disease and did not have detectable PrP^Sc by immunohistochemistry or enzyme immunoassay. This study complements and expands on earlier findings that white blood cells harbour prion infectivity, and reports CD11c⁺ B1 lymphocytes and CD68⁺ macrophages as additional targets for possible preclinical detection of prion infection in blood.

Transgenic mouse models for the study of prion diseases

Prions are unique agents that challenge the molecular biology dogma by transmitting information on the protein level. They cause neurodegenerative diseases that lack of any cure or treatment called transmissible spongiform encephalopathies. The function of the normal form of the prion protein, the exact mechanism of prion propagation between species as well as at the cellular level and neuron degeneration remains elusive. However, great amount of information known for all these aspects has been achieved thanks to the use of animal models and more precisely to transgenic mouse models. In this chapter, the main contributions of these powerful research tools in the prion field are revised.

Detection of Pathognomonic Biomarker PrPSc and the Contribution of Cell Free-Amplification Techniques to the Diagnosis of Prion Diseases

Transmissible spongiform encephalopathies or prion diseases are rapidly progressive neurodegenerative diseases, the clinical manifestation of which can resemble other promptly evolving neurological maladies. Therefore, the unequivocal ante-mortem diagnosis is highly challenging and was only possible by histopathological and immunohistochemical analysis of the brain at necropsy. Although surrogate biomarkers of neurological damage have become invaluable to complement clinical data and provide more accurate diagnostics at early stages, other neurodegenerative diseases show similar alterations hindering the differential diagnosis. To solve that, the detection of the pathognomonic biomarker of disease, PrP^Sc, the aberrantly folded isoform of the prion protein, could be used. However, the amounts in easily accessible tissues or body fluids at pre-clinical or early clinical stages are extremely low for the standard detection methods. The solution comes from the recent development of in vitro prion propagation techniques, such as Protein Misfolding Cyclic Amplification (PMCA) and Real Time-Quaking Induced Conversion (RT-QuIC), which have been already applied to detect minute amounts of PrP^Sc in different matrixes and make early diagnosis of prion diseases feasible in a near future. Herein, the most relevant tissues and body fluids in which PrP^Sc has been detected in animals and humans are being reviewed, especially those in which cell-free prion propagation systems have been used with diagnostic purposes.

Cardiomyopathy associated with Ceutzfeld-Jakob disease: a diagnosis of exclusion: a case report

Background

Creutzfeldt–Jakob disease (CJD), the most common prion disease in humans, is primarily known for its adverse neurological impact and inevitable mortality. Data regarding myocardial involvement in CJD are scarce.

Case summary

A 54-year-old female patient, presented with progressive effort dyspnoea, was diagnosed with unexplained non-ischaemic cardiomyopathy. An extensive cardiac work-up including cardiac magnetic resonance imaging (MRI) did not reveal any underlying aetiology. Simultaneously, the patient developed involuntary limb movements and progressive cognitive decline. Thalamic high-signal abnormalities on diffusion-weighted images were apparent on brain MRI. Based on these findings, she was subsequently referred to a neurology department, where she suddenly died the day after her admission. Brain autopsy demonstrated spongiform encephalopathy. A genetic analysis performed to her son revealed a mutation in the PRNP gene; all of these were consistent with CJD.

Discussion

This case describes the clinical association of CJD and cardiomyopathy and the diagnosis prion-induced cardiomyopathy by exclusion. It is not inconceivable that the coexistence of these two clinical entities may be related to genetic expression and contemporaneously deposition of infectious prions in myocardial muscle and brain tissue. Awareness of this possible association could be of important public-safety concern, and merits further collaborative cardiac-neurological work-up to elucidate this phenotype among patients with unexplained cardiomyopathy with neurological symptoms that resemble CJD.

Update on chronic wasting disease (CWD) III

The European Commission asked EFSA for a Scientific Opinion: to revise the state of knowledge about the differences between the chronic wasting disease (CWD) strains found in North America (NA) and Europe and within Europe; to review new scientific evidence on the zoonotic potential of CWD and to provide recommendations to address the potential risks and to identify risk factors for the spread of CWD in the European Union. Full characterisation of European isolates is being pursued, whereas most NA CWD isolates have not been characterised in this way. The differing surveillance programmes in these continents result in biases in the types of cases that can be detected. Preliminary data support the contention that the CWD strains identified in Europe and NA are different and suggest the presence of strain diversity in European cervids. Current data do not allow any conclusion on the implications of strain diversity on transmissibility, pathogenesis or prevalence. Available data do not allow any conclusion on the zoonotic potential of NA or European CWD isolates. The risk of CWD to humans through consumption of meat cannot be directly assessed. At individual level, consumers of meat, meat products and offal derived from CWD-infected cervids will be exposed to the CWD agent(s). Measures to reduce human dietary exposure could be applied, but exclusion from the food chain of whole carcasses of infected animals would be required to eliminate exposure. Based on NA experiences, all the risk factors identified for the spread of CWD may be associated with animals accumulating infectivity in both the peripheral tissues and the central nervous system. A subset of risk factors is relevant for infected animals without involvement of peripheral tissues. All the risk factors should be taken into account due to the potential co-localisation of animals presenting with different disease phenotypes.

Transgenic mouse models expressing human and macaque prion protein exhibit similar prion susceptibility on a strain-dependent manner

Cynomolgus macaque has been used for the evaluation of the zoonotic potential of prion diseases, especially for classical-Bovine Spongiform Encephalopathy (classical-BSE) infectious agent. PrP amino acid sequence is considered to play a key role in the susceptibility to prion strains and only one amino acid change may alter this susceptibility. Macaque and human-PrP sequences have only nine amino acid differences, but the effect of these amino acid changes in the susceptibility to dissimilar prion strains is unknown. In this work, the transmissibility of a panel of different prions from several species was compared in transgenic mice expressing either macaque-PrP^C (TgMac) or human-PrP^C (Hu-Tg340). Similarities in the transmissibility of most prion strains were observed suggesting that macaque is an adequate model for the evaluation of human susceptibility to most of the prion strains tested. Interestingly, TgMac were more susceptible to classical-BSE strain infection than Hu-Tg340. This differential susceptibility to classical-BSE transmission should be taken into account for the interpretation of the results obtained in macaques. It could notably explain why the macaque model turned out to be so efficient (worst case model) until now to model human situation towards classical-BSE despite the limited number of animals inoculated in the laboratory experiments.

Animal prion diseases: the risks to human health

Transmissible spongiform encephalopathies (TSEs) or prion diseases of animals notably include scrapie in small ruminants, chronic wasting disease (CWD) in cervids and classical bovine spongiform encephalopathy (C-BSE). As the transmission barrier phenomenon naturally limits the propagation of prions from one species to another, and the lack of epidemiological evidence for an association with human prion diseases, the zoonotic potential of these diseases was for a long time considered negligible. However, in 1996, C-BSE was recognized as the cause of a new human prion disease, variant Creutzfeldt-Jakob disease (vCJD), which triggered an unprecedented public health crisis in Europe. Large-scale epidemio-surveillance programs for scrapie and C-BSE that were implemented in the EU after the BSE crisis revealed that the distribution and prevalence of prion diseases in the ruminant population had previously been underestimated. They also led to the recognition of new forms of TSEs (named atypical) in cattle and small ruminants and to the recent identification of CWD in Europe. At this stage, the characterization of the strain diversity and zoonotic abilities associated with animal prion diseases remains largely incomplete. However, transmission experiments in nonhuman primates and transgenic mice expressing human PrP clearly indicate that classical scrapie, and certain forms of atypical BSE (L-BSE) or CWD may have the potential to infect humans. The remaining uncertainties about the origins and relationships between animal prion diseases emphasize the importance of the measures implemented to limit human exposure to these potentially zoonotic agents, and of continued surveillance for both animal and human prion diseases.

Lack of Transmission of Chronic Wasting Disease to Cynomolgus Macaques

Chronic wasting disease (CWD) is a fatal prion disease that can infect deer, elk, and moose. CWD was first recognized in captive deer kept in wildlife facilities in Colorado from 1967 to 1979. CWD has now been detected in 25 U.S. states, 2 Canadian provinces, South Korea, Norway, and Finland. It is currently unknown if humans are susceptible to CWD infection. Understanding the health risk from consuming meat and/or products from CWD-infected cervids is a critical human health concern. Previous research using transgenic mouse models and in vitro conversion assays suggests that a significant species barrier exists between CWD and humans. To date, reported epidemiologic studies of humans consuming cervids in areas where CWD is endemic have found no evidence to confirm CWD transmission to humans. Previously, we reported data from ongoing cross-species CWD transmission studies using two species of nonhuman primates as models. Squirrel monkeys (SM) and cynomolgus macaques (CM) were inoculated by either the intracerebral or oral route with brain homogenates from CWD-infected deer and elk containing high levels of infectivity. SM were highly susceptible to CWD infection, while CM were not. In the present study, we present new data for seven CWD-inoculated CM euthanized 11 to 13 years after CWD inoculation and eight additional uninoculated control CM. New and archival CM tissues were screened for prion infection by using the ultrasensitive real-time quaking-induced conversion (RT-QuIC) assay, immunohistochemistry, and immunoblotting. In this study, there was no clinical, pathological, or biochemical evidence suggesting that CWD was transmitted from cervids to CM.IMPORTANCE Chronic wasting disease (CWD) is a fatal prion disease found in deer, elk, and moose. Since it was first discovered in the late 1960s, CWD has now spread to at least 25 U.S. states, 2 Canadian provinces, South Korea, Norway, and Finland. Eradication of CWD from areas of endemicity is very unlikely, and additional spread will occur. As the range and prevalence of CWD increase, so will the potential for human exposure to CWD prions. It is currently unknown if CWD poses a risk to human health. However, determining this risk is critical to preventing a scenario similar to that which occurred when mad cow disease was found to be transmissible to humans. In the present study, we used cynomolgus macaque monkeys as a surrogate model for CWD transmission to humans. After 13 years, no evidence for CWD transmission to macaques was detected clinically or by using highly sensitive prion disease-screening assays.

Modeling Variant Creutzfeldt-Jakob Disease and Its Pathogenesis in Non-human Primates

In the early 90s', Europe was shaken by the fear that the prions from "mad cow disease" (bovine spongiform encephalopathy) would transmit the disease to humans via beef products. In 1996, the first variant Creutzfeldt-Jakob (vCJD) patients were described, and the same year our Bovine Spongiform Encephalopathy (BSE) transmission studies to cynomolgus macaques demonstrated that the BSE prion was highly infectious for primates, inducing brain lesions identical to those observed in vCJD patients. These studies provided the first experimental evidence that vCJD was BSE in humans. Subsequent studies established the BSE/vCJD-infected cynomolgus macaque as a robust model to study the pathogenesis of vCJD. We showed rapid adaptation of BSE prions to primates upon subsequent passage, and their distribution in peripheral tissues and blood. Some key studies are summarized in the present paper.

Preparation and Immunostaining of the Myenteric Plexus of Prion-Infected Mice

Intracerebral inoculation of mice with the M1000 strain of mouse-adapted human prions results in the consistent accumulation of PrP^Sc in the ileum of the gastrointestinal tract (GIT) of mice with clinical signs of prion disease. The accumulation of PrP^Sc in the ileum is accompanied by caspase activation and loss of immunoreactivity in subpopulations of neurons in the enteric nervous system. This suggests that like neurons in the central nervous system, cells in the enteric nervous system are also susceptible to prion-induced toxicity. In this chapter we describe the immunostaining of cells in myenteric plexus preparations of whole mounts prepared from the gastrointestinal tract of prion-infected mice.

Prion-Seeding Activity Is widely Distributed in Tissues of Sporadic Creutzfeldt-Jakob Disease Patients

Human prion diseases are neurodegenerative disorders caused by abnormally folded prion proteins in the central nervous system. These proteins can be detected using the quaking-induced conversion assay. Compared with other bioassays, this assay is extremely sensitive and was used in the present study to determine prion distribution in sporadic Creutzfeldt-Jakob disease patients at autopsy. Although infectivity of the sporadic form is thought to be restricted within the central nervous system, results showed that prion-seeding activities reach 10⁶/g from a 50% seeding dose in non-neuronal tissues, suggesting that prion-seeding activity exists in non-neural organs, and we suggested that non-neural tissues of 10⁶/g SD50 did not exist the infectivity.

Blood transmission studies of prion infectivity in the squirrel monkey (Saimiri sciureus): the Baxter study

BACKGROUND

Four secondary transmissions of variant Creutzfeldt-Jakob disease (vCJD) infectivity have been associated with the transfusion of nonleukoreduced red blood cells collected from vCJD patients during the asymptomatic phase of the disease. Establishing efficient experimental models for assessing the risk of future transmissions of vCJD infectivity via blood transfusion is of paramount importance in view of a study of archived appendix samples in which the prevalence of asymptomatic vCJD infection in the United Kingdom was estimated at approximately 1 in 2000 of the population. In this study, we investigated transmission of vCJD and sporadic CJD (sCJD) infectivity from blood using the squirrel monkey, which is highly susceptible to experimental challenge with human prion disease.

STUDY DESIGN AND METHODS

Whole blood collected from vCJD- and sCJD-infected squirrel monkeys was transfused at multiple time points into recipient squirrel monkeys. Blood recipients were euthanized approximately 7 years after their first blood transfusion.

RESULTS

No clinical or pathologic signs of a prion disease were observed in either the sCJD- or the vCJD-transfused monkeys, and immunohistochemistry and biochemical investigations showed no PrP(TSE) in central nervous system or lymphoreticular tissues. Similarly, monkeys inoculated intracerebrally (IC) and intravenously (IV) with either buffy coat or plasma from vCJD and sCJD patients failed to develop disease. However, white blood cells from a chimpanzee-passaged strain of human Gerstmann-Sträussler-Scheinker (GSS) disease transmitted autopsy-proven disease to two IC-inoculated monkeys after incubation periods of 34 and 39 months.

CONCLUSION

Blood transmits GSS but not sCJD or vCJD infectivity to IC- or IV-inoculated squirrel monkeys within a 7-year observation period.

Transmission of scrapie prions to primate after an extended silent incubation period

Classical bovine spongiform encephalopathy (c-BSE) is the only animal prion disease reputed to be zoonotic, causing variant Creutzfeldt-Jakob disease (vCJD) in humans and having guided protective measures for animal and human health against animal prion diseases. Recently, partial transmissions to humanized mice showed that the zoonotic potential of scrapie might be similar to c-BSE. We here report the direct transmission of a natural classical scrapie isolate to cynomolgus macaque, a highly relevant model for human prion diseases, after a 10-year silent incubation period, with features similar to those reported for human cases of sporadic CJD. Scrapie is thus actually transmissible to primates with incubation periods compatible with their life expectancy, although fourfold longer than BSE. Long-term experimental transmission studies are necessary to better assess the zoonotic potential of other prion diseases with high prevalence, notably Chronic Wasting Disease of deer and elk and atypical/Nor98 scrapie.

Prion protein aggregation assays in the diagnosis of human prion diseases

ABSTRACT 

Sporadic Creutzfeldt–Jakob disease (sCJD) is the most common form of human prion disease and is associated with a progressive cognitive decline and death usually occurs within 6 months. Neuropathologically these diseases are characterized by the deposition of an abnormal form (PrPSc) of a normally expressed protein PrPC. At present there are no disease-specific diagnostic tests for prion diseases. Therefore, a test that will enable accurate and earlier diagnosis is needed. The ability of PrPSc to convert native PrPC into PrPSc has been exploited in a variety of protein aggregation assays such as protein misfolding cyclic amplification (PMCA), and real-time QuIC (RT-QuIC). Cerebrospinal fluid RT-QuIC is rapidly growing in acceptance as a reliable and accurate diagnostic test for sCJD.

Evaluation of the protection of primates transfused with variant Creutzfeldt-Jakob disease-infected blood products filtered with prion removal devices: a 5-year update

BACKGROUND

Analysis of archived appendix samples reveals that one in 2000 individuals in the United Kingdom may carry the infectious prion protein associated with variant Creutzfeldt-Jakob disease (vCJD), raising questions about the risk of transfusion transmission from apparently healthy carriers. Blood leukoreduction shows limited efficiency against prions. Therefore, in absence of antemortem diagnostic tests, prion removal filters, including the P-Capt filter were designed to improve blood transfusion safety.

STUDY DESIGN AND METHODS

We evaluated the performances of two filters, the P-Capt and one prototype (PMC#005), with blood-borne infectivity in two independent experiments. Blood was drawn twice from prion-infected macaques. Corresponding RBCCs were prepared according to two different procedures: in Study A, the leukoreduction step was followed by the filtration through the P-Capt. In Study B, the leukoreduction and prion removal were performed simultaneously through the PMC#005. For each study, two groups of three animals were transfused twice with samples before or after filtration.

RESULTS

Among the six macaques transfused with nonfiltered samples, five developed neurologic signs but only four exhibited peripheral detectable protease-resistant prion protein (PrPres) accumulation. In Study A, the three animals transfused with P-Capt-filtered samples remain asymptomatic and devoid of PrPres in lymph node biopsies 6 years after the transfusion. In Study B, one animal transfused with PMC#005-filtered samples developed vCJD.

CONCLUSION

After 5 to 6 years of progress, this ongoing study provides encouraging results on the prion blood removal performances of the P-Capt filter in macaques, an utmost relevant model for human prion diseases.

Blood reference materials from macaques infected with variant Creutzfeldt-Jakob disease agent

BACKGROUND

Variant Creutzfeldt-Jakob disease (vCJD) is a fatal neurodegenerative infection that can be transmitted by blood and blood products from donors in the latent phase of the disease. Currently, there is no validated antemortem vCJD blood screening test. Several blood tests are under development. Any useful test must be validated with disease-relevant blood reference panels.

STUDY DESIGN AND METHODS

To generate blood reference materials, we infected four cynomolgus macaques with macaque-adapted vCJD brain homogenates. Blood was collected throughout the preclinical and clinical phases of infection. In parallel, equivalent blood was collected from one uninfected macaque. For each blood collection, an aliquot was stored as whole blood and the remainder was separated into components. Aliquots of plasma from terminally ill macaques were assayed for the presence of PrP(TSE) with the protein misfolding cyclic amplification (PMCA) method. Infectivity of the macaque brain homogenate used to infect macaques was titrated in C57BL/6 and RIII J/S inbred wild-type mice.

RESULTS

We sampled blood 19 times from the inoculated monkeys at various stages of the disease over a period of 29 months, generating liters of vCJD-infected macaque blood. vCJD was confirmed in all inoculated macaques. After PMCA, PrP(TSE) was detected in plasma from infected monkeys, but not from uninfected animals. Both mouse models were more sensitive to infection with macaque-adapted vCJD agent than to primary human vCJD agent.

CONCLUSION

The macaque vCJD blood panels generated in this study provide a unique resource to support vCJD assay development and to characterize vCJD infectivity in blood.

Chronic wasting disease agents in nonhuman primates

Chronic wasting disease is a prion disease of cervids. Assessment of its zoonotic potential is critical. To evaluate primate susceptibility, we tested monkeys from 2 genera. We found that 100% of intracerebrally inoculated and 92% of orally inoculated squirrel monkeys were susceptible, but cynomolgus macaques were not, suggesting possible low risk for humans.

Genetic prion disease: no role for the immune system in disease pathogenesis?

Prion diseases, which can manifest by transmissible, sporadic or genetic etiologies, share several common features, such as a fatal neurodegenerative outcome and the aberrant accumulation of proteinase K (PK)-resistant PrP forms in the CNS. In infectious prion diseases, such as scrapie in mice, prions first replicate in immune organs, then invade the CNS via ascending peripheral tracts, finally causing death. Accelerated neuroinvasion and death occurs when activated prion-infected immune cells infiltrate into the CNS, as is the case for scrapie-infected mice induced for experimental autoimmune encephalomyelitis (EAE), a CNS inflammatory insult. To establish whether the immune system plays such a central role also in genetic prion diseases, we induced EAE in TgMHu2ME199K mice, a line mimicking for late onset genetic Creutzfeldt Jacob disease (gCJD), a human prion disease. We show here that EAE induction of TgMHu2ME199K mice neither accelerated nor aggravated prion disease manifestation. Concomitantly, we present evidence that PK-resistant PrP forms were absent from CNS immune infiltrates, and most surprisingly also from lymph nodes and spleens of TgMHu2ME199K mice at all ages and stages of disease. These results imply that the mechanism of genetic prion disease differs widely from that of the infectious presentation, and that the conversion of mutant PrPs into PK resistant forms occurs mostly/only in the CNS. If the absence of pathogenic PrP forms form immune organs is also true for gCJD patients, it may suggest their blood is devoid of prion infectivity.

Preclinical detection of variant CJD and BSE prions in blood

The emergence of variant Creutzfeldt Jakob Disease (vCJD) is considered a likely consequence of human dietary exposure to Bovine Spongiform Encephalopathy (BSE) agent. More recently, secondary vCJD cases were identified in patients transfused with blood products prepared from apparently healthy donors who later went on to develop the disease. As there is no validated assay for detection of vCJD/BSE infected individuals the prevalence of the disease in the population remains uncertain. In that context, the risk of vCJD blood borne transmission is considered as a serious concern by health authorities. In this study, appropriate conditions and substrates for highly efficient and specific in vitro amplification of vCJD/BSE agent using Protein Misfolding Cyclic Amplification (PMCA) were first identified. This showed that whatever the origin (species) of the vCJD/BSE agent, the ovine Q171 PrP substrates provided the best amplification performances. These results indicate that the homology of PrP amino-acid sequence between the seed and the substrate is not the crucial determinant of the vCJD agent propagation in vitro. The ability of this method to detect endogenous vCJD/BSE agent in the blood was then defined. In both sheep and primate models of the disease, the assay enabled the identification of infected individuals in the early preclinical stage of the incubation period. Finally, sample panels that included buffy coat from vCJD affected patients and healthy controls were tested blind. The assay identified three out of the four tested vCJD affected patients and no false positive was observed in 141 healthy controls. The negative results observed in one of the tested vCJD cases concurs with results reported by others using a different vCJD agent blood detection assay and raises the question of the potential absence of prionemia in certain patients.

Gene expression profiling of brains from bovine spongiform encephalopathy (BSE)-infected cynomolgus macaques

BACKGROUND

Prion diseases are fatal neurodegenerative disorders whose pathogenesis mechanisms are not fully understood. In this context, the analysis of gene expression alterations occurring in prion-infected animals represents a powerful tool that may contribute to unravel the molecular basis of prion diseases and therefore discover novel potential targets for diagnosis and therapeutics. Here we present the first large-scale transcriptional profiling of brains from BSE-infected cynomolgus macaques, which are an excellent model for human prion disorders.

RESULTS

The study was conducted using the GeneChip® Rhesus Macaque Genome Array and revealed 300 transcripts with expression changes greater than twofold. Among these, the bioinformatics analysis identified 86 genes with known functions, most of which are involved in cellular development, cell death and survival, lipid homeostasis, and acute phase response signaling. RT-qPCR was performed on selected gene transcripts in order to validate the differential expression in infected animals versus controls. The results obtained with the microarray technology were confirmed and a gene signature was identified. In brief, HBB and HBA2 were down-regulated in infected macaques, whereas TTR, APOC1 and SERPINA3 were up-regulated.

CONCLUSIONS

Some genes involved in oxygen or lipid transport and in innate immunity were found to be dysregulated in prion infected macaques. These genes are known to be involved in other neurodegenerative disorders such as Alzheimer's and Parkinson's diseases. Our results may facilitate the identification of potential disease biomarkers for many neurodegenerative diseases.

De novo prion aggregates trigger autophagy in skeletal muscle

In certain sporadic, familial, and infectious prion diseases, the prion protein misfolds and aggregates in skeletal muscle in addition to the brain and spinal cord. In myocytes, prion aggregates accumulate intracellularly, yet little is known about clearance pathways. Here we investigated the clearance of prion aggregates in muscle of transgenic mice that develop prion disease de novo. In addition to neurodegeneration, aged mice developed a degenerative myopathy, with scattered myocytes containing ubiquitinated, intracellular prion inclusions that were adjacent to myocytes lacking inclusions. Myocytes also showed elevated levels of the endoplasmic reticulum chaperone Grp78/BiP, suggestive of impaired protein degradation and endoplasmic reticulum stress. Additionally, autophagy was induced, as indicated by increased levels of beclin-1 and LC3-II. In C2C12 myoblasts, inhibition of autophagosome maturation or lysosomal degradation led to enhanced prion aggregation, consistent with a role for autophagy in prion aggregate clearance. Taken together, these findings suggest that the induction of autophagy may be a central strategy for prion aggregate clearance in myocytes. IMPORTANCE In prion diseases, the prion protein misfolds and aggregates in the central nervous system and sometimes in other organs, including muscle, yet the cellular pathways of prion aggregate clearance are unclear. Here we investigated the clearance of prion aggregates in the muscle of a transgenic mouse model that develops profound muscle degeneration. We found that endoplasmic reticulum stress pathways were activated and that autophagy was induced. Blocking of autophagic degradation in cell culture models led to an accumulation of aggregated prion protein. Collectively, these findings suggest that autophagy has an instrumental role in prion protein clearance.

BSE-associated prion-amyloid cardiomyopathy in primates

Prion amyloidosis occurred in the heart of 1 of 3 macaques intraperitoneally inoculated with bovine spongiform encephalopathy prions. This macaque had a remarkably long duration of disease and signs of cardiac distress. Variant Creutzfeldt-Jakob disease, caused by transmission of bovine spongiform encephalopathy to humans, may manifest with cardiac symptoms from prion-amyloid cardiomyopathy.

The presence of disease-associated prion protein in skeletal muscle of cattle infected with classical bovine spongiform encephalopathy

The aim of this study was to investigate the presence of disease-associated prion protein (PrP(Sc)) in the skeletal muscle of cattle infected with classical bovine spongiform encephalopathy (C-BSE). The study was carried out systematically in 12 different muscle samples from 43 (3 field and 40 experimental) cases of C-BSE; however, muscle spindles were not available in many of these cases. Therefore, analysis became restricted to a total of 31 muscles in 23 cattle. Even after this restriction, low levels of PrP(Sc) were detected in the muscle spindles of the masseter, intercostal, triceps brachii, psoas major, quadriceps femoris and semitendinosus muscles from 3 field and 6 experimental clinical-stage cases. The present data indicate that small amounts of PrP(Sc) are detectable by immunohistochemistry in the skeletal muscles of animals terminally affected with C-BSE.

Re-assessment of PrP(Sc) distribution in sporadic and variant CJD

Human prion diseases are fatal neurodegenerative disorders associated with an accumulation of PrP^Sc in the central nervous system (CNS). Of the human prion diseases, sporadic Creutzfeldt-Jakob disease (sCJD), which has no known origin, is the most common form while variant CJD (vCJD) is an acquired human prion disease reported to differ from other human prion diseases in its neurological, neuropathological, and biochemical phenotype. Peripheral tissue involvement in prion disease, as judged by PrP^Sc accumulation in the tonsil, spleen, and lymph node has been reported in vCJD as well as several animal models of prion diseases. However, this distribution of PrP^Sc has not been consistently reported for sCJD. We reexamined CNS and non-CNS tissue distribution and levels of PrP^Sc in both sCJD and vCJD. Using a sensitive immunoassay, termed SOFIA, we also assessed PrP^Sc levels in human body fluids from sCJD as well as in vCJD-infected humanized transgenic mice (Tg666). Unexpectedly, the levels of PrP^Sc in non-CNS human tissues (spleens, lymph nodes, tonsils) from both sCJD and vCJD did not differ significantly and, as expected, were several logs lower than in the brain. Using protein misfolding cyclic amplification (PMCA) followed by SOFIA, PrP^Sc was detected in cerebrospinal fluid (CSF), but not in urine or blood, in sCJD patients. In addition, using PMCA and SOFIA, we demonstrated that blood from vCJD-infected Tg666 mice showing clinical disease contained prion disease-associated seeding activity although the data was not statistically significant likely due to the limited number of samples examined. These studies provide a comparison of PrP^Sc in sCJD vs. vCJD as well as analysis of body fluids. Further, these studies also provide circumstantial evidence that in human prion diseases, as in the animal prion diseases, a direct comparison and intraspecies correlation cannot be made between the levels of PrP^Sc and infectivity.

Lack of prion infectivity in fixed heart tissue from patients with Creutzfeldt-Jakob disease or amyloid heart disease

In most forms of prion disease, infectivity is present primarily in the central nervous system or immune system organs such as spleen and lymph node. However, a transgenic mouse model of prion disease has demonstrated that prion infectivity can also be present as amyloid deposits in heart tissue. Deposition of infectious prions as amyloid in human heart tissue would be a significant public health concern. Although abnormal disease-associated prion protein (PrP(Sc)) has not been detected in heart tissue from several amyloid heart disease patients, it has been observed in the heart tissue of a patient with sporadic Creutzfeldt-Jakob Disease (sCJD), the most common form of human prion disease. In order to determine whether prion infectivity can be found in heart tissue, we have inoculated formaldehyde fixed brain and heart tissue from two sCJD patients, as well as prion protein positive fixed heart tissue from two amyloid heart disease patients, into transgenic mice overexpressing the human prion protein. Although the sCJD brain samples led to clinical or subclinical prion infection and deposition of PrP(Sc) in the brain, none of the inoculated heart samples resulted in disease or the accumulation of PrP(Sc). Thus, our results suggest that prion infectivity is not likely present in cardiac tissue from sCJD or amyloid heart disease patients.

Infectivity in skeletal muscle of cattle with atypical bovine spongiform encephalopathy

The amyloidotic form of bovine spongiform encephalopathy (BSE) termed BASE is caused by a prion strain whose biological properties differ from those of typical BSE, resulting in a clinically and pathologically distinct phenotype. Whether peripheral tissues of BASE-affected cattle contain infectivity is unknown. This is a critical issue since the BASE prion is readily transmissible to a variety of hosts including primates, suggesting that humans may be susceptible. We carried out bioassays in transgenic mice overexpressing bovine PrP (Tgbov XV) and found infectivity in a variety of skeletal muscles from cattle with natural and experimental BASE. Noteworthy, all BASE muscles used for inoculation transmitted disease, although the attack rate differed between experimental and natural cases (∼70% versus ∼10%, respectively). This difference was likely related to different prion titers, possibly due to different stages of disease in the two conditions, i.e. terminal stage in experimental BASE and pre-symptomatic stage in natural BASE. The neuropathological phenotype and PrP^res type were consistent in all affected mice and matched those of Tgbov XV mice infected with brain homogenate from natural BASE. The immunohistochemical analysis of skeletal muscles from cattle with natural and experimental BASE showed the presence of abnormal prion protein deposits within muscle fibers. Conversely, Tgbov XV mice challenged with lymphoid tissue and kidney from natural and experimental BASE did not develop disease. The novel information on the neuromuscular tropism of the BASE strain, efficiently overcoming species barriers, underlines the relevance of maintaining an active surveillance.

Detection of disease-associated prion protein in the optic nerve and the adrenal gland of cattle with bovine spongiform encephalopathy by using highly sensitive immunolabeling procedures

A sensitive immunohistochemical procedure, the tyramide signal amplification (TSA) system, was applied to detect the localization of immunolabeled disease-associated prion protein (PrP(Sc)) in cattle affected with bovine spongiform encephalopathy (BSE). In this procedure, immunolabeling could be visualized in the optic nerve and the adrenal medulla. In the optic nerve, the dual immunofluorescent technique showed that the granular PrP(Sc) was occasionally detected in the astrocytes, microglia, and myelin sheath adjacent to the axon. Clustered PrP(Sc) was also scattered in association with microglial cells and astrocytes of the optic nerve. In the adrenal gland, PrP(Sc) immunolabeling was confined within the sympathetic nerve fibers and endings. The results suggest that (1) PrP(Sc) might centrifugally spread within and between glial cells and/or the non-axonal (also known as ad-axonal) region of nerve fibers, rather than the axonal and/or extracellular space pathway in the optic nerve, and (2) the sympathetic innervations might be important for the trafficking of BSE agent in the adrenal glands of cattle. This study also suggests that tyramide-based immunochemical analysis should be performed to detect immunolabeled PrP(Sc) in the extracerebral tissues of BSE-affected cattle.

Uptake dynamics of scrapie agent in the intestinal villous epithelium of suckling and weanling Syrian hamsters

In mice, the number of intestinal villous columnar epithelium cells that incorporate abnormal prion protein (PrP(Sc) ) decreases significantly after weaning. In this study, the dynamics of PrP(Sc) uptake during the growth of hamsters were investigated by inoculating scrapie 263K agent orally into suckling and weanling Syrian hamsters and estimating the number of PrP(Sc) -positive villous epithelium cells immunohistochemically. The number of PrP(Sc) -positive cells declined significantly as the hamsters aged. The present results suggest that a tendency toward decline of PrP(Sc) -positive cells with increasing age might be a common phenomenon among the superfamily Muridae.

Comparison of nanofiltration efficacy in reducing infectivity of centrifuged versus ultracentrifuged 263K scrapie-infected brain homogenates in "spiked" albumin solutions

BACKGROUND

The safety of plasma-derived products is of concern for possible transmission of variant Creutzfeldt-Jakob disease. The absence of validated screening tests requires the use of procedures to remove or inactivate prions during the manufacture of plasma-derived products to minimize the risk of transmission. These procedures need proper validation studies based on spiking human plasma or intermediate fractions of plasma fractionation with prions in a form as close as possible to that present in blood.

STUDY DESIGN AND METHODS

Human albumin was spiked with low-speed or high-speed supernatants of 263K scrapie-infected hamster brain homogenates. Spiked albumin was then passed through a cascade of filters from 100 nm down to 20 to 15 nm. Residual infectivity was measured by bioassay.

RESULTS

The overall removal of infectivity spiked into albumin through serial nanofiltration steps was 4 to 5 logs using low-speed supernatant and 2 to 3 logs with high-speed supernatant.

CONCLUSION

These findings confirm the utility of nanofiltration in removing infectivity from plasma (or other products) spiked with scrapie brain homogenate supernatants. However, efficiency is diminished using supernatants that have been ultracentrifuged to reduce aggregated forms of the infectious agent. Thus, filtration removal data based on experiments using "standard" low-speed centrifugation supernatants might overestimate the amount of prion removal in plasma or urine-derived therapeutic products.

Presence and seeding activity of pathological prion protein (PrP(TSE)) in skeletal muscles of white-tailed deer infected with chronic wasting disease

Chronic wasting disease (CWD) is a contagious, rapidly spreading transmissible spongiform encephalopathy (TSE), or prion disease, occurring in cervids such as white tailed-deer (WTD), mule deer or elk in North America. Despite efficient horizontal transmission of CWD among cervids natural transmission of the disease to other species has not yet been observed. Here, we report for the first time a direct biochemical demonstration of pathological prion protein PrP^TSE and of PrP^TSE-associated seeding activity, the static and dynamic biochemical markers for biological prion infectivity, respectively, in skeletal muscles of CWD-infected cervids, i. e. WTD for which no clinical signs of CWD had been recognized. The presence of PrP^TSE was detected by Western- and postfixed frozen tissue blotting, while the seeding activity of PrP^TSE was revealed by protein misfolding cyclic amplification (PMCA). Semi-quantitative Western blotting indicated that the concentration of PrP^TSE in skeletal muscles of CWD-infected WTD was approximately 2000-10000 -fold lower than in brain tissue. Tissue-blot-analyses revealed that PrP^TSE was located in muscle-associated nerve fascicles but not, in detectable amounts, in myocytes. The presence and seeding activity of PrP^TSE in skeletal muscle from CWD-infected cervids suggests prevention of such tissue in the human diet as a precautionary measure for food safety, pending on further clarification of whether CWD may be transmissible to humans.

Preclinical deposition of pathological prion protein in muscle of experimentally infected primates

Prion diseases are transmissible fatal neurodegenerative disorders affecting humans and animals. A central step in disease progression is the accumulation of a misfolded form (PrP^Sc) of the host encoded prion protein (PrP^C) in neuronal and non-neuronal tissues. The involvement of peripheral tissues in preclinical states increases the risk of accidental transmission. On the other hand, detection of PrP^Sc in non-neuronal easy-accessible compartments such as muscle may offer a novel diagnostic tool. Primate models have proven invaluable to investigate prion diseases. We have studied the deposition of PrP^Sc in muscle and central nervous system of rhesus monkeys challenged with sporadic Creutzfeldt-Jakob disease (sCJD), variant CJD (vCJD) and bovine spongiform encephalopathy (BSE) in preclinical and clinical stage using biochemical and morphological methods. Here, we show the preclinical presence of PrP^Sc in muscle and central nervous system of rhesus monkeys experimentally infected with vCJD.

BSE infectivity in the absence of detectable PrP(Sc) accumulation in the tongue and nasal mucosa of terminally diseased cattle

The pathogenesis of bovine spongiform encephalopathy (BSE) infections in cattle has been studied in recent years by using highly sensitive transgenic-mouse bioassays. It has been shown that in this species, the BSE agent amplifies almost exclusively in the central and peripheral nervous system. Even in animals that were killed in the clinical end stage of the disease, the lymphoreticular system was shown to be free of the infectious agent. No other animal species investigated to date exhibits such a restricted BSE-infectivity distribution pattern. However, there is growing evidence for a radial spread of infection from the central nervous system (CNS) into the periphery during the late stages of the disease. In this study, we challenged transgenic mice overexpressing the bovine prion protein with homogenates prepared from a wide variety of tissue samples collected from BSE-infected cattle. As prion infections involve the conversion of the cellular prion protein into its abnormally folded isoform (PrP(Sc)), we applied various detection methods, such as the purification of scrapie-associated fibrils, immunohistochemistry, and the protein misfolding cyclic amplification technique. Despite negative results using these highly sensitive biochemical methods, we were, for the first time, able to detect BSE infectivity in the tongue and in the nasal mucosa of terminally diseased BSE field cases as well as experimentally challenged cattle by transgenic-mouse bioassay. This shows that BSE infectivity can be present in the peripheral tissues of terminally diseased cattle, including tissues used for human consumption.

B cells and platelets harbor prion infectivity in the blood of deer infected with chronic wasting disease

Substantial evidence for prion transmission via blood transfusion exists for many transmissible spongiform encephalopathy (TSE) diseases. Determining which cell phenotype(s) is responsible for trafficking infectivity has important implications for our understanding of the dissemination of prions, as well as their detection and elimination from blood products. We used bioassay studies of native white-tailed deer and transgenic cervidized mice to determine (i) if chronic wasting disease (CWD) blood infectivity is associated with the cellular versus the cell-free/plasma fraction of blood and (ii) in particular if B-cell (MAb 2-104(+)), platelet (CD41/61(+)), or CD14(+) monocyte blood cell phenotypes harbor infectious prions. All four deer transfused with the blood mononuclear cell fraction from CWD(+) donor deer became PrP(CWD) positive by 19 months postinoculation, whereas none of the four deer inoculated with cell-free plasma from the same source developed prion infection. All four of the deer injected with B cells and three of four deer receiving platelets from CWD(+) donor deer became PrP(CWD) positive in as little as 6 months postinoculation, whereas none of the four deer receiving blood CD14(+) monocytes developed evidence of CWD infection (immunohistochemistry and Western blot analysis) after 19 months of observation. Results of the Tg(CerPrP) mouse bioassays mirrored those of the native cervid host. These results indicate that CWD blood infectivity is cell associated and suggest a significant role for B cells and platelets in trafficking CWD infectivity in vivo and support earlier tissue-based studies associating putative follicular B cells with PrP(CWD). Localization of CWD infectivity with leukocyte subpopulations may aid in enhancing the sensitivity of blood-based diagnostic assays for CWD and other TSEs.

Susceptibilities of nonhuman primates to chronic wasting disease

A species barrier may protect humans from this disease.

Chronic wasting disease (CWD) is a transmissible spongiform encephalopathy, or prion disease, that affects deer, elk, and moose. Human susceptibility to CWD remains unproven despite likely exposure to CWD-infected cervids. We used 2 nonhuman primate species, cynomolgus macaques and squirrel monkeys, as human models for CWD susceptibility. CWD was inoculated into these 2 species by intracerebral and oral routes. After intracerebral inoculation of squirrel monkeys, 7 of 8 CWD isolates induced a clinical wasting syndrome within 33–53 months. The monkeys’ brains showed spongiform encephalopathy and protease-resistant prion protein (PrPres) diagnostic of prion disease. After oral exposure, 2 squirrel monkeys had PrPres in brain, spleen, and lymph nodes at 69 months postinfection. In contrast, cynomolgus macaques have not shown evidence of clinical disease as of 70 months postinfection. Thus, these 2 species differed in susceptibility to CWD. Because humans are evolutionarily closer to macaques than to squirrel monkeys, they may also be resistant to CWD.

PrPTSE in muscle-associated lymphatic tissue during the preclinical stage of mice infected orally with bovine spongiform encephalopathy

The involvement of muscles in the pathogenesis of transmissible spongiform encephalopathies (TSEs) is irregular and unpredictable. We show that the TSE-specific protein (PrP(TSE)) is present in muscles of mice fed with a mouse-adapted strain of bovine spongiform encephalopathy as early as 100 days post-infection, corresponding to about one-third of the incubation period. The proportion of mice with PrP(TSE)-positive muscles and the number of muscles involved increased as infection progressed, but never attained more than a limited distribution, even at the clinical stage of disease. The appearance of PrP(TSE) in muscles during the preclinical stage of disease was probably due to the haematogenous/lymphatic spread of infectivity from the gastrointestinal tract to lymphatic tissues associated with muscles, whereas in symptomatic animals, the presence of PrP(TSE) in the nervous system, in neuromuscular junctions and in muscle fibres suggests a centrifugal spread from the central nervous system, as already observed in other TSE models.

Can protein contamination be removed from hand endodontic instruments?

AIM

The aim of this study was to quantify total protein adhering to hand endodontic files and to measure and compare the efficacy of ultrasonic cleaning and washer-disinfectors, with and without presoaking, in protein removal from clinically contaminated endodontic files.

METHOD

Total protein contamination of the endodontic files was quantified using an assay reagent colorimetric method. Twelve general dental practitioners were recruited to collect clinically contaminated files. One hundred and fifty clinically contaminated files were allowed to air-dry in sterile plastic containers and a further 60 files were immersed, working end down, in enzymatic detergent immediately following clinical use. Thirty clinically contaminated files were tested for total protein contamination as a positive control. Sixty files were subjected to ultrasonic cleaning and 30 to processing in each of the washer-disinfectors. The presoaked files were divided into two groups of 30 for processing in the washer-disinfectors. A further group of brand-new, unused files were tested for protein contamination as a negative control.

RESULTS

Protein was present on 29 of the 30 new files tested. The median total mass of protein recovered from clinically contaminated hand endodontic instruments was 2.046 microg. The most effective method of presterilisation cleaning tested was a presoak in Alkazyme followed by processing in the Miele G7881 washer-disinfector.

CONCLUSION

The most effective method of presterilisation cleaning for hand endodontic files is a presoak in Alkazyme, an alkaline enzymatic detergent, followed by processing in a Miele G7881 washer-disinfector. This study provides up-to-date evidence that newer methods of presterilisation cleaning may fail to remove protein from endodontic hand instruments totally. This may have implications for all reusable dental instruments.

Lack of evidence of transfusion transmission of Creutzfeldt-Jakob disease in a US surveillance study

BACKGROUND

Since 2004, several reported transfusion transmissions of variant Creutzfeldt-Jakob disease (vCJD) in the United Kingdom have reawakened concerns about the possible risk of similar transmissions of nonvariant or classic forms of CJD.

STUDY DESIGN AND METHODS

Patients with a CJD diagnosis and a history of donating blood were reported to the study coordinator. Through review of blood distribution and hospital records, the recipients of blood components from these donors were identified. We then determined each recipient's vital status and, if deceased, the cause(s) of death identified by matching the recipient's personal identifiers with the Centers for Disease Control and Prevention's National Death Index database. We conducted such searches after recipients were enrolled in this study and annually thereafter for those who remained alive.

RESULTS

The study included a total of 36 blood donors who subsequently developed CJD and 436 recipients. Through 2006, 91 of these recipients were still alive, 329 were deceased, and 16 were lost to follow-up. After transfusion, these three groups had survived a total of 2096.0 person-years. A total of 144 recipients survived 5 years or longer after transfusion and 68 of them had received blood donated 60 or fewer months before the onset of CJD in the donor. We identified no recipient with CJD.

CONCLUSIONS

The current results of this large, ongoing lookback study show no evidence of transfusion transmission of CJD. They reinforce the conclusion that the risk, if any, of transfusion transmission of prion disease by CJD donors is significantly lower than the comparable risk of such transmission by vCJD donors.

Detection of prion infectivity in fat tissues of scrapie-infected mice

Distribution of prion infectivity in organs and tissues is important in understanding prion disease pathogenesis and designing strategies to prevent prion infection in animals and humans. Transmission of prion disease from cattle to humans resulted in banning human consumption of ruminant nervous system and certain other tissues. In the present study, we surveyed tissue distribution of prion infectivity in mice with prion disease. We show for the first time detection of infectivity in white and brown fat. Since high amounts of ruminant fat are consumed by humans and also incorporated into animal feed, fat-containing tissues may pose a previously unappreciated hazard for spread of prion infection.

Prion diseases, also known as transmissible spongiform encephalopathies, are infectious progressive fatal neurodegenerative diseases which affect humans as well as wild and domestic animals. Distribution of prion infectivity in organs and tissues is important in understanding prion disease pathogenesis and designing strategies to prevent prion infection in animals and humans. We show for the first time the presence of prion infectivity in white fat and brown fat tissues of mice with prion disease. Our results suggest that fat tissues of domestic or wild animals infected with prions may pose an unappreciated hazard for spread of infection to humans or domestic animals. The presence of prion infectivity in fat suggests that additional consideration may be required to eliminate from the food chain any fat from ruminants suspected of exposure to or infection with prions. Thus, this finding has implications for public health, food safety, and prion disease prevention strategies.

Atypical BSE (BASE) transmitted from asymptomatic aging cattle to a primate

Background

Human variant Creutzfeldt-Jakob Disease (vCJD) results from foodborne transmission of prions from slaughtered cattle with classical Bovine Spongiform Encephalopathy (cBSE). Atypical forms of BSE, which remain mostly asymptomatic in aging cattle, were recently identified at slaughterhouses throughout Europe and North America, raising a question about human susceptibility to these new prion strains.

Methodology/Principal Findings

Brain homogenates from cattle with classical BSE and atypical (BASE) infections were inoculated intracerebrally into cynomolgus monkeys (Macacca fascicularis), a non-human primate model previously demonstrated to be susceptible to the original strain of cBSE. The resulting diseases were compared in terms of clinical signs, histology and biochemistry of the abnormal prion protein (PrPres). The single monkey infected with BASE had a shorter survival, and a different clinical evolution, histopathology, and prion protein (PrPres) pattern than was observed for either classical BSE or vCJD-inoculated animals. Also, the biochemical signature of PrPres in the BASE-inoculated animal was found to have a higher proteinase K sensitivity of the octa-repeat region. We found the same biochemical signature in three of four human patients with sporadic CJD and an MM type 2 PrP genotype who lived in the same country as the infected bovine.

Conclusion/Significance

Our results point to a possibly higher degree of pathogenicity of BASE than classical BSE in primates and also raise a question about a possible link to one uncommon subset of cases of apparently sporadic CJD. Thus, despite the waning epidemic of classical BSE, the occurrence of atypical strains should temper the urge to relax measures currently in place to protect public health from accidental contamination by BSE-contaminated products.

Macaque models of human infectious disease

Macaques have served as models for more than 70 human infectious diseases of diverse etiologies, including a multitude of agents—bacteria, viruses, fungi, parasites, prions. The remarkable diversity of human infectious diseases that have been modeled in the macaque includes global, childhood, and tropical diseases as well as newly emergent, sexually transmitted, oncogenic, degenerative neurologic, potential bioterrorism, and miscellaneous other diseases. Historically, macaques played a major role in establishing the etiology of yellow fever, polio, and prion diseases. With rare exceptions (Chagas disease, bartonellosis), all of the infectious diseases in this review are of Old World origin. Perhaps most surprising is the large number of tropical (16), newly emergent (7), and bioterrorism diseases (9) that have been modeled in macaques. Many of these human diseases (e.g., AIDS, hepatitis E, bartonellosis) are a consequence of zoonotic infection. However, infectious agents of certain diseases, including measles and tuberculosis, can sometimes go both ways, and thus several human pathogens are threats to nonhuman primates including macaques. Through experimental studies in macaques, researchers have gained insight into pathogenic mechanisms and novel treatment and vaccine approaches for many human infectious diseases, most notably acquired immunodeficiency syndrome (AIDS), which is caused by infection with human immunodeficiency virus (HIV). Other infectious agents for which macaques have been a uniquely valuable resource for biomedical research, and particularly vaccinology, include influenza virus, paramyxoviruses, flaviviruses, arenaviruses, hepatitis E virus, papillomavirus, smallpox virus, Mycobacteria, Bacillus anthracis, Helicobacter pylori, Yersinia pestis, and Plasmodium species. This review summarizes the extensive past and present research on macaque models of human infectious disease.