Preclinical Detection of Prions in Blood of Nonhuman Primates Infected with Variant Creutzfeldt-Jakob Disease.

Variant Creutzfeldt-Jakob disease (vCJD) is caused by prion infection with bovine spongiform encephalopathy and can be transmitted by blood transfusion. Protein misfolding cyclic amplification (PMCA) can detect prions in blood from vCJD patients with 100% sensitivity and specificity. To determine whether PMCA enables prion detection in blood during the preclinical stage of infection, we performed a blind study using blood samples longitudinally collected from 28 control macaques and 3 macaques peripherally infected with vCJD. Our results demonstrate that PMCA consistently detected prions in blood during the entire preclinical stage in all infected macaques, without false positives from noninfected animals, when using the optimized conditions for amplification of macaque prions. Strikingly, prions were detected as early as 2 months postinoculation (>750 days before disease onset). These findings suggest that PMCA has the potential to detect vCJD prions in blood from asymptomatic carriers during the preclinical phase of the disease.

Detection and partial discrimination of atypical and classical bovine spongiform encephalopathies in cattle and primates using real-time quaking-induced conversion assay.

The transmission of classical bovine spongiform encephalopathy (C-BSE) through contaminated meat product consumption is responsible for variant Creutzfeldt-Jakob disease (vCJD) in humans. More recent and atypical forms of BSE (L-BSE and H-BSE) have been identified in cattle since the C-BSE epidemic. Their low incidence and advanced age of onset are compatible with a sporadic origin, as are most cases of Creutzfeldt-Jakob disease (CJD) in humans. Transmissions studies in primates and transgenic mice expressing a human prion protein (PrP) indicated that atypical forms of BSE may be associated with a higher zoonotic potential than classical BSE, and require particular attention for public health. Recently, methods designed to amplify misfolded forms of PrP have emerged as promising tools to detect prion strains and to study their diversity. Here, we validated real-time quaking-induced conversion assay for the discrimination of atypical and classical BSE strains using a large series of bovine samples encompassing all the atypical BSE cases detected by the French Centre of Reference during 10 years of exhaustive active surveillance. We obtained a 100% sensitivity and specificity for atypical BSE detection. In addition, the assay was able to discriminate atypical and classical BSE in non-human primates, and also sporadic CJD and vCJD in humans. The RT-QuIC assay appears as a practical means for a reliable detection of atypical BSE strains in a homologous or heterologous PrP context.

Foodborne-Transmitted Prions From the Brain of Cows With Bovine Spongiform Encephalopathy Ascend in Afferent Neurons to the Simian Central Nervous System and Spread to Tonsils and Spleen at a Late Stage of the Incubation Period.

BACKGROUND: Protease-resistant prion protein (PrP(res)) accumulation in lymphoreticular tissues indicates prion infection. To date, tonsillectomy and appendectomy samples have been used in population prevalence surveys to detect clinically silent carriers of variant Creutzfeldt-Jakob disease (vCJD). However, the temporal sequence of prion spread in the human body is still not known. We therefore traced the temporal-spatial pattern of PrP(res) accumulation in the body of a simian vCJD model. METHODS: Cynomolgus monkeys were fed brain of (eleven) cows with bovine spongiform encephalopathy, and some were euthanized before and some after onset of neurological signs. PrP(res) was detected in tissues by a paraffin-embedded tissue blot technique and a semiquantitative Western immunoblot assay. RESULTS: Bovine spongiform encephalopathy (BSE)-associated prions were preferentially transported from the gut to the central nervous system (CNS) along sensory nerve fibers and initially entered the simian CNS at lumbar spinal cord levels. In asymptomatic animals, we found BSE in 50% and 12% of gut- and tonsil-derived samples, respectively. CONCLUSIONS: Unlike in rodents and ruminants, foodborne BSE-associated prions entered the simian CNS via afferent neurons. From sites of initial CNS invasion, prions spread centrifugally to tonsils and spleen at an advanced stage of the incubation period, thus explaining why tonsil specimens were not reliable for detection of simian disease carriers before onset of clinical signs.

Experimental interspecies transmission studies of the transmissible spongiform encephalopathies to cattle: comparison to bovine spongiform encephalopathy in cattle.

Prion diseases or transmissible spongiform encephalopathies (TSEs) of animals include scrapie of sheep and goats; transmissible mink encephalopathy (TME); chronic wasting disease (CWD) of deer, elk and moose; and bovine spongiform encephalopathy (BSE) of cattle. The emergence of BSE and its spread to human beings in the form of variant Creutzfeldt-Jakob disease (vCJD) resulted in interest in susceptibility of cattle to CWD, TME and scrapie. Experimental cross-species transmission of TSE agents provides valuable information for potential host ranges of known TSEs. Some interspecies transmission studies have been conducted by inoculating disease-causing prions intracerebrally (IC) rather than orally; the latter is generally effective in intraspecies transmission studies and is considered a natural route by which animals acquire TSEs. The "species barrier" concept for TSEs resulted from unsuccessful interspecies oral transmission attempts. Oral inoculation of prions mimics the natural disease pathogenesis route whereas IC inoculation is rather artificial; however, it is very efficient since it requires smaller dosage of inoculum, and typically results in higher attack rates and reduces incubation time compared to oral transmission. A species resistant to a TSE by IC inoculation would have negligible potential for successful oral transmission. To date, results indicate that cattle are susceptible to IC inoculation of scrapie, TME, and CWD but it is only when inoculated with TME do they develop spongiform lesions or clinical disease similar to BSE. Importantly, cattle are resistant to oral transmission of scrapie or CWD; susceptibility of cattle to oral transmission of TME is not yet determined.

Universal white blood cell reduction in Europe: has transmission of variant Creutzfeldt-Jakob disease been prevented?

Universal white blood cell (WBC) reduction was introduced in Europe to prevent transmission of variant Creutzfeldt-Jakob disease (vCJD) by transfusion. Findings from rodent models indicate that WBC reduction should not prevent vCJD transmission because the residual plasma infectivity suffices to infect transfusion recipients even under optimistic infectivity assumptions. Although infectivity in human blood may not partition in the manner in which it is distributed in rodents, prion-reduction filters remove the residual plasma infectivity in rodent models. Precautionary introduction of prion filtration in the UK--for patients without dietary exposure to bovine spongiform encephalopathy and in the absence of a reported case of vCJD transmission attributable to infectivity residing in plasma--is consistent with the (already in place for such subjects) precautionary importation to the UK of fresh frozen plasma from low-risk countries. Thus, implementation of prion filtration in the UK does not imply that universal WBC reduction--as currently practiced in Europe--does not abrogate transmission of vCJD. Because neither a human case of vCJD transmission through transfusion of WBC-reduced red blood cells nor a case of experimental bovine spongiform encephalopathy transmission by WBC-reduced transfusion to sheep has been reported, it cannot be concluded that ordinary WBC reduction is ineffective in preventing transfusion transmission in humans. Accordingly, universal WBC reduction for the prevention of vCJD in Europe should continue.

Is vaccination against transmissible spongiform encephalopathy feasible?

Prion diseases are a unique category of illness, affecting both animals and humans, where the underlying pathogenesis is related to a conformation change of the cellular form of a normal, self-protein called a prion protein (PrP(c) [C for cellular]) to a pathological and infectious conformation known as scrapie form (PrPsc [Sc for scrapie]). Currently, all prion diseases are without effective treatment and are universally fatal. The emergence of bovine spongiform encephalopathy and variant Creutzfeldt-Jakob disease has highlighted the need to develop possible therapies. In Alzheimer's disease (AD), which has similarities to prion diseases, both passive and active immunisation have been shown to be highly effective at preventing disease and cognitive deficits in model animals. In a human trial of active vaccination in AD, despite indications of cognitive benefits in patients with an adequate humoral response, 6% of patients developed significant complications related to excessive cell-mediated immunity. This experience highlights that immunotherapies designed to be directed against a self-antigen have to finely balance an effective humoral immune response with potential autoimmune toxicity. Many prion diseases have the gut as a portal of infectious agent entry. This makes mucosal immunisation a potentially very attractive method to partially or completely prevent prion entry across the gut barrier and to also produce a modulated immune response that is unlikely to be associated with any toxicity. The authors' recent results using an attenuated Salmonella vaccine strain expressing the prion protein show that mucosal vaccination can partially protect against prion infection from a peripheral source, suggesting the feasibility of this approach.

Prion diseases of humans and farm animals: epidemiology, genetics, and pathogenesis.

Neuronal vacuolation (spongiosis), neuronal death, and pronounced glial reactions are the hallmarks of transmissible spongiform encephalopathies (TSEs), or prion diseases. A wealth of physical, biochemical, and immunological evidence indicates that the TSE agent, termed prion, does not contain agent-specific nucleic acid encoding its own constituents, as is the case for all other infectious pathogens. Also, no adaptive immune responses are elicited upon infection. A defining feature of TSEs is the deposition, mainly in the brain and lymphoreticular tissues, of an aggregated and structurally abnormal protein, designated PrP(Sc) or PrP-res, which represents a conformational isomer of the ubiquitous surface protein PrP(C). Biochemical and genetic evidence link PrP and its gene to the disease. Although TSEs are by definition transmissible, a growing number of Prnp-associated non-infectious neurodegenerative proteinopathies are now being recognized.

[Herbivore or carnivore? History of prions]. / Herbivore ou carnivore? Histoire de prions.

Transmissible subacute spongiform encephalopathies have been known for some times in man and in animals, but were considered of minor importance up to the development of the mad cow crisis. Bovine spongiform encephalopathy raises questions about nowadays farming and brings up the issue of cannibalism as a whole and imposed upon an herbivore. Even if the word cannibalism may seem excessive in the case of cattle, it is however true that BSE spreads from cow to cow through their feeding with meat and bone meal contaminated with infected bovine material. More generally this points out the problem of cannibalism among animal species.

First cases of animal diseases published since 2000. 1. Dogs.

In this first article of a series of papers listing first case reports of animal diseases published since 2000, the following 19 cases of dog diseases are discussed: Blastomycotic granuloma involving the cranial vena cava. Congenital myocardial hamartoma. Discospondylitis: three cases caused respectively by Pseudomonas aeruginosa, Enterococcus faecalis and Staphylococcus epidermidis. Dystrophin deficient muscular dystrophy in a Labrador Retriever. Emphysematous prostatitis. Erythema multiforme major caused by a Parvovirus infection of keratinocytes. Hemochromatosis due to repeated blood transfusions. Intraspinal synovial cyst. Juvenile nephropathy in the Collie and the Irish Wolfhound. Primary cerebellar cortical degeneration (abiotrophy) in a Scottish terrier. Primary pulmonary artery chondrosarcoma. Renal dysplasia in a Bull Mastiff. Rhabdomyosarcoma (botryoid sarcoma) of the urinary bladder in a Maltese. Spinal mast cell tumor. Spongiform degeneration of the white matter in the central nervous system of Australian Cattle dog. Systemic pasteurellosis caused by Pasteurella canis. Thymic hemorrhage caused by dicumarol intoxication. Undimerized biclonal gammopathy with a single heavy chain class IgA in a dog with multiple myeloma. After a short introduction, the bibliographical data and the abstract of the author(s) and mostly some additional information derived from the article are given. The article will be regularly updated adding overlooked as well as new first reports.

First cases of animal diseases published since 2000. 2. Cats.

In this second article of a series of papers listing first case reports of animal diseases published since 2000, the following nine cases of cat diseases are discussed: Congenital spongiform change in the brain stem nuclei. Enterococcus hirae enteropathy. Focal cerebral angiomatosis. Glomus tumor. Intraocular extramedullary plasmacytoma. Lens epithelial neoplasias. Phaeohyphomycosis due to Fonsecaea pedrosoi. Pulmonary lymphomatoid granulomatosis. Systemic amyloidosis in a Devon rex. After a short introduction, the bibliographical data, the abstract of the author(s) and some additional information derived from the article are given. The article will be regularly updated adding overlooked as well as new first reports.

Prion-induced neuronal damage--the mechanisms of neuronal destruction in the subacute spongiform encephalopathies.

Prion diseases are characterized by the accumulation of a specific disease-associated isoform of the prion protein (PrP), termed PrPSc, which is the main, if not the only, component of the infectious agent termed prion. PrPSc is derived by an autocatalytic post-translational process involving conformational changes from the normal host-encoded isoform of the prion protein, termed PrPC. PrPC is a copper-binding glycoprotein attached to the cell membrane of neurons and other cells by means of a GPI anchor. The pattern of neurodegeneration differs between variants of prion disease and is related to the pattern of PrPSc deposition and differences in susceptibility of different cell types to the disease process. The pattern of PrPSc deposition depends on the strain of the agent and the PrP genotype of the host. Strain properties of prions appear to be related to different pathological conformations of PrPSc. Neuronal cell death is a salient feature in the pathology of prion diseases. Histological and electron microscopical studies have shown that cell death in prion disease occurs by apoptosis. Apoptosis of neuronal cells can also be induced in vitro by exposure to PrPSc or a neurotoxic peptide fragment corresponding to amino acids 106-126 of human prion protein (PrP106-126). Both in vitro and in vivo, the toxicity of PrPSc and PrP fragments appears to depend on neuronal expression of PrPC and on microglial activation. Activated microglial cells release pro-inflammatory cytokines and reactive oxygen species. Cell culture experiments suggest an important role of microglia-mediated oxidative stress in the induction of neuronal cell death. Only limited data are available on direct effects of PrPSc on neuronal cells. Potential effects include increased formation of an aberrant transmembrane form of PrP, termed CtmPrP, and changes in plasma membrane properties. In addition to direct and indirect toxic effects of PrPSc, a loss of function of PrPC may contribute to neuronal cell death. Potential mechanisms include disturbances in cerebral copper metabolism and antioxidative defense mechanisms. A better understanding of the pathogenesis of neuronal cell death in prion diseases may also have important therapeutic implications in the future.

Mad cow disease--the OR connection.

Creutzfeldt-Jakob disease (CJD) is one of the transmissible spongiform encephalopathies, a group of fatal, neurodegenerative disorders affecting both humans and animals. The causative agent is the prion, which is still being researched and is controversial. In the 1980s, bovine spongiform encephalopathy brought much media attention to these diseases. Bovine spongiform encephalopathy is the result of faulty industrial practices that produced cattle feed contaminated by prions. In the 1990s, a new variant of CJD (i.e., nvCJD) appeared in Britain. Researchers believe that nvCJD was passed to humans through oral consumption of contaminated beef. This article describes the history, causative agent, mode of transmission, clinical features and course, diagnosis, treatment, and decontamination and sterilization guidelines for this baffling disease.

[Transmissible subacute spongiform encephalopathies in animals]. / Encéphalopathies spongiformes subaiguës transmissibles animales.

Transmissible subacute spongiform encephalopathies are a group of neurodegenerative diseases of man and of several species of domestic mammals. Scrapie has been recognised in sheep and goats for more than 250 years. Descriptions in 1986 of the first cases of bovine spongiform encephalopathy (BSE) in United Kingdom, its expansion with an enzootic pattern, and in 1996 of a new variant of Creutzfeldt-Jakob disease, probably related to the same agent, focused the attention of scientists, medias and public on what seems to be a new zoonosis. The biopathological study of BSE and scrapie is useful for evaluating what risk these animal diseases represent for human health.

Transmission of Creutzfeldt-Jakob disease to a chimpanzee by electrodes contaminated during neurosurgery.

Stereotactic multicontact electrodes used to probe the cerebral cortex of a middle aged woman with progressive dementia were previously implicated in the accidental transmission of Creutzfeldt-Jakob disease (CJD) to two younger patients. The diagnoses of CJD have been confirmed for all three cases. More than two years after their last use in humans, after three cleanings and repeated sterilisation in ethanol and formaldehyde vapour, the electrodes were implanted in the cortex of a chimpanzee. Eighteen months later the animal became ill with CJD. This finding serves to re-emphasise the potential danger posed by reuse of instruments contaminated with the agents of spongiform encephalopathies, even after scrupulous attempts to clean them.

Comparative ultrastructural neuropathology of naturally occurring bovine spongiform encephalopathy and experimentally induced scrapie and Creutzfeldt-Jakob disease.

We report the ultrastructural neuropathology of bovine spongiform encephalopathy (BSE), a recently described slow virus disease first recognized in Friesian/Holstein cattle, and compare it to that of experimental scrapie and Creutzfeldt-Jakob disease. The spongiform change, which was most pronounced in the central grey matter of the midbrain, consisted of membrane-bound vacuoles within neuronal processes, containing curled membrane fragments, secondary chambers and vesicles. Axons and dendrites accumulated whorls of neurofilaments and other subcellular organelles, such as mitochondria and dense bodies, which were entrapped within the filamentous masses. Other neurites accumulated electron-dense bodies, and still others electron-lucent cisterns and branching tubules. Membrane-bound neuronal inclusions, composed of tubules measuring 10 nm in diameter, were found in axonal terminals. Tubulovesicular structures were loosely packed and were occasionally surrounded by a common membrane, a finding previously described only in natural scrapie in sheep. Except for the intraneuronal inclusions, all of the ultrastructural features of BSE resembled those found in scrapie and Creutzfeldt-Jakob disease.