Transmission of Creutzfeldt-Jakob disease from human blood and urine into mice

Harnessing the Physiological Functions of Cellular Prion Protein in the Kidneys: Applications for Treating Renal Diseases

A cellular prion protein (PrP^C) is a ubiquitous cell surface glycoprotein, and its physiological functions have been receiving increased attention. Endogenous PrP^C is present in various kidney tissues and undergoes glomerular filtration. In prion diseases, abnormal prion proteins are found to accumulate in renal tissues and filtered into urine. Urinary prion protein could serve as a diagnostic biomarker. PrP^C plays a role in cellular signaling pathways, reno-protective effects, and kidney iron uptake. PrP^C signaling affects mitochondrial function via the ERK pathway and is affected by the regulatory influence of microRNAs, small molecules, and signaling proteins. Targeting PrP^C in acute and chronic kidney disease could help improve iron homeostasis, ameliorate damage from ischemia/reperfusion injury, and enhance the efficacy of mesenchymal stem/stromal cell or extracellular vesicle-based therapeutic strategies. PrP^C may also be under the influence of BMP/Smad signaling and affect the progression of TGF-β-related renal fibrosis. PrP^C conveys TNF-α resistance in some renal cancers, and therefore, the coadministration of anti-PrP^C antibodies improves chemotherapy. PrP^C can be used to design antibody-drug conjugates, aptamer-drug conjugates, and customized tissue inhibitors of metalloproteinases to suppress cancer. With preclinical studies demonstrating promising results, further research on PrP^C in the kidney may lead to innovative PrP^C-based therapeutic strategies for renal disease.

Prion Seeds Distribute throughout the Eyes of Sporadic Creutzfeldt-Jakob Disease Patients

Sporadic Creutzfeldt-Jakob disease (sCJD) is the most common prion disease in humans and has been iatrogenically transmitted through corneal graft transplantation. Approximately 40% of sCJD patients develop visual or oculomotor symptoms and may seek ophthalmological consultation. Here we used the highly sensitive real-time quaking-induced conversion (RT-QuIC) assay to measure postmortem prion seeding activities in cornea, lens, ocular fluid, retina, choroid, sclera, optic nerve, and extraocular muscle in the largest series of sCJD patient eyes studied by any assay to date. We detected prion seeding activity in 100% of sCJD eyes, representing three common sCJD subtypes, with levels varying by up to 4 log-fold among individuals. The retina consistently showed the highest seed levels, which in some cases were only slightly lower than brain. Within the retina, prion deposits were detected by immunohistochemistry (IHC) in the retinal outer plexiform layer in most sCJD cases, and in some eyes the inner plexiform layer, consistent with synaptic prion deposition. Prions were not detected by IHC in any other eye region. With RT-QuIC, prion seed levels generally declined in eye tissues with increased distance from the brain, and yet all corneas had prion seeds detectable. Prion seeds were also present in the optic nerve, extraocular muscle, choroid, lens, vitreous, and sclera. Collectively, these results reveal that sCJD patients accumulate prion seeds throughout the eye, indicating the potential diagnostic utility as well as a possible biohazard.IMPORTANCE Cases of iatrogenic prion disease have been reported from corneal transplants, yet the distribution and levels of prions throughout the eye remain unknown. This study probes the occurrence, level, and distribution of prions in the eyes of patients with sporadic Creutzfeldt-Jakob disease (sCJD). We tested the largest series of prion-infected eyes reported to date using an ultrasensitive technique to establish the prion seed levels in eight regions of the eye. All 11 cases had detectable prion seeds in the eye, and in some cases, the seed levels in the retina approached those in brain. In most cases, prion deposits could also be seen by immunohistochemical staining of retinal tissue; other ocular tissues were negative. Our results have implications for estimating the risk for iatrogenic transmission of sCJD as well as for the development of antemortem diagnostic tests for prion diseases.

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.

Experience with preventive genetic testing of corneal donors in slovakia

PURPOSE

The purpose of this study was (1) to detect asymptomatic carriers of the prion protein gene mutation E200K, which is associated with Creutzfeldt-Jakob disease (CJD), in corneal donors and in the general population of Slovakia and (2) to assess the genetic testing of corneal donors as an effective preventive measure against iatrogenic infection in a country with an unusually high incidence of genetic CJD.

METHODS

The prion protein gene (PRNP) was analyzed in 1133 corneal donors and 970 control subjects to search for E200K mutation and to determine the genotype at codon 129.

RESULTS

Mutation E200K was found in 2 of the 1133 donors and in 4 of the 970 control subjects. The most frequent genotype at the codon 129 polymorphic region was methionine homozygous (48% of donors and controls).

CONCLUSIONS

An E200K mutation, which confers a risk of developing genetic CJD, was detected in corneal donors and in the general population. The majority of subjects were codon 129 methionine homozygous that increases susceptibility to CJD. Genetic testing of corneal donors in Slovakia is a useful and effective preventive measure against iatrogenic CJD through human corneal transplantation in the investigated population.

Bone marrow stroma cells are susceptible to prion infection

Abnormal protease-resistant prion protein (PrP-res) is the only surrogate biochemical marker for prion diseases, and a sensitive technique to detect PrP-res in blood or tissues is urgently needed. Primary cultured bone marrow stromal cells (MSCs) expressed PrP and were capable of supporting stable human prion infection. Using a mouse-adapted BSE strain, we demonstrated that PrP-res can be detected in expanded MSCs. We then analyzed the bone marrow cells collected at autopsy from two individuals with sporadic Creutzfeldt-Jakob disease (CJD), and, in both cases, cultured MSCs were positive for PrP-res. These data would suggest that ex vivo MSC expansion accompanied by PrP-res analysis could be a helpful tool in the definitive diagnosis of prion disease at an earlier stage in the disease process than is currently possible, and with considerably less distress to the patient.

A 25 nm virion is the likely cause of transmissible spongiform encephalopathies

The transmissible spongiform encephalopathies (TSEs) such as endemic sheep scrapie, sporadic human Creutzfeldt-Jakob disease (CJD), and epidemic bovine spongiform encephalopathy (BSE) may all be caused by a unique class of "slow" viruses. This concept remains the most parsimonious explanation of the evidence to date, and correctly predicted the spread of the BSE agent to vastly divergent species. With the popularization of the prion (infectious protein) hypothesis, substantial data pointing to a TSE virus have been largely ignored. Yet no form of prion protein (PrP) fulfills Koch's postulates for infection. Pathologic PrP is not proportional to, or necessary for infection, and recombinant and "amplified" prions have failed to produce significant infectivity. Moreover, the "wealth of data" claimed to support the existence of infectious PrP are increasingly contradicted by experimental observations, and cumbersome speculative notions, such as spontaneous PrP mutations and invisible strain-specific forms of "infectious PrP" are proposed to explain the incompatible data. The ability of many "slow" viruses to survive harsh environmental conditions and enzymatic assaults, their stealth invasion through protective host-immune defenses, and their ability to hide in the host and persist for many years, all fit nicely with the characteristics of TSE agents. Highly infectious preparations with negligible PrP contain nucleic acids of 1-5 kb, even after exhaustive nuclease digestion. Sedimentation as well as electron microscopic data also reveal spherical infectious particles of 25-35 nm in diameter. This particle size can accommodate a viral genome of 1-4 kb, sufficient to encode a protective nucleocapsid and/or an enzyme required for its replication. Host PrP acts as a cellular facilitator for infectious particles, and ultimately accrues pathological amyloid features. A most significant advance has been the development of tissue culture models that support the replication of many different strains of agent and can produce high levels of infectivity. These models provide new ways to rapidly identify intrinsic viral and strain-specific molecules so important for diagnosis, prevention, and fundamental understanding.

Urine from scrapie-infected hamsters comprises low levels of prion infectivity

The question of whether prion diseases can be transmitted by body fluids has important epidemiological, environmental and economical implications. In this work, we set to investigate whether urine collected from scrapie-infected hamsters can transmit fatal or subclinical infectivity to normal hamsters. After prolonged incubation times ranging from 300 to 700 days, a small number of animals inoculated with scrapie urine succumbed to scrapie disease, and several asymptomatic hamsters presented low levels of PrP(Sc) in their brains. In addition, most of the asymptomatic hamsters inoculated with scrapie urine, as opposed to those inoculated with normal urine, presented extensive gliosis as well as protease-resistant light chain IgG in their urine, a molecule shown by us and others to be a surrogate marker for prion infection. Our results suggest that urine from scrapie-infected hamsters can transmit a widespread subclinical disease that in some cases develops into fatal scrapie.

New molecular markers of early and progressive CJD brain infection

Transmissible spongiform encephalopathies (TSEs), including human Creutzfeldt-Jakob disease (CJD), are caused by a related group of infectious agents that can be transmitted to many mammalian species. Because the infectious component of TSE agents has not been identified, we examined myeloid cell linked inflammatory pathways to find if they were activated early in CJD infection. We here identify a specific set of transcripts in CJD infected mouse brains that define early and later stages of progressive disease. Serum amyloid A3 and L-selectin mRNAs were elevated as early as 20 days after intracerebral inoculation. Transcripts of myeloid cell recruitment factors such as MIP-1alpha, MIP-1beta, and MCP1, as well as IL1alpha and TNFalpha were upregulated > 10 fold between 30 and 40 days, well before prion protein (PrP) abnormalities that begin only after 80 days. At later stages of symptomatic neurodegenerative disease (100-110 days), a selected set of transcripts rose by as much as 100 fold. In contrast, normal brain inoculated controls showed no similar sequential changes. In sum, rapid and simple PCR tests defined progressive stages of CJD brain infection. These markers may also facilitate early diagnosis of CJD in accessible peripheral tissues such as spleen and blood. Because some TSE strains can differentially target particular cell types such as microglia, several of these molecular changes may also distinguish specific agent strains. The many host responses to the CJD agent challenge the assumption that the immune system does not recognize TSE infections because these agents are composed only of the host's own PrP.

Consensus statement on the bio-safety of urinary-derived gonadotrophins with respect to Creutzfeldt–Jakob disease

Human transmissible spongiform encephalopathies (TSE) encompass a group of rare neurodegenerative diseases. In April 2004, a group of international experts and regulators met in Buenos Aires, Argentina, to review the safety and to reach consensus on the use of urinary-derived gonadotrophins with respect to TSE. Iatrogenic transmission of Creutzfeldt-Jakob Disease (CJD) from pituitary-derived gonadotrophins has been reported, no infectivity in urine has been demonstrated, and no definite cases of transmission via urine have been reported. It is currently not possible to monitor donor urine or finished product for the presence of prions. Therefore the assessment of risk has to be based on the likelihood of infection in urine, the source of the urine, and the capacity of the manufacturing process to remove any adventitious infection. Urine for the production of medicinal products should be obtained from sources that minimize the possible presence of materials derived from subjects suffering from human TSE. As no strong evidence for TSE infectivity in urine exists, it can be concluded that the risk of disease-generating prions and TSE infectivity being present in donor urine is low. Current evidence indicates that, with respect to the risk of TSE infection, urinary-derived gonadotrophins appear to be safe.

Variant Creutzfeldt-Jakob disease and its transmission by blood

Variant Creutzfeldt-Jakob disease (vCJD) is a novel acquired human prion disease resulting from human exposure to the agent causing bovine spongiform encephalopathy (BSE). vCJD differs from all other human prion diseases in that the disease-associated form of the prion protein and infectivity are present in lymphoid tissues throughout the body. Lymphoid tissues and lymphocytes are implicated in the peripheral pathogenesis of prion diseases (where infectivity may be detected during the preclinical phase of the illness), giving rise to concerns that blood and blood products may also contain infectivity, thus representing a possible source of iatrogenic spread of vCJD. These concerns have been reinforced by the recent transmission of BSE in an experimental sheep model by blood transfusion from an infected animal in the preclinical phase of the illness. Studies in other animal models suggest that most infectivity in blood may be cell-associated, with lower levels in the plasma, and there is evidence to indicate that any infectivity present may be reduced during the process of plasma fractionation. At present, the attempts to detect disease-associated prion protein and infectivity in buffy coat from vCJD patients have been negative, but these studies have been limited in size and in the sensitivity of the detection systems employed. Further studies are required to develop more sensitive means of detection of disease-associated prion protein in blood; such techniques could also be employed for screening purposes, both individually and to help ascertain more precisely the likely numbers of future cases of vCJD.

Diagnosis and prevention of bovine spongiform encephalopathy and variant Creutzfeldt-Jakob disease

An outbreak of bovine spongiform encephalopathy (BSE) arose in the United Kingdom as a result of prions entering and being recycled through the ruminant food chain. Humans have since developed a variant form of Creutzfeldt-Jakob disease (vCJD), also mostly in the United Kingdom, that occurs in younger individuals and causes prominent psychiatric and/or behavioral manifestations early in disease. Laboratory studies now provide strong evidence that the causative agent of BSE in cattle and vCJD in humans share a common origin. Because of a lack of information regarding the incubation period of vCJD and the number of people who may have been exposed, the future scope of this disease remains unknown. Control of the current and any future outbreaks in cattle requires strict measures to prevent contamination of the animal food chain with prions of any species. Prevention of human exposure mandates the avoidance of neural tissue in all human foods.

Retention of corneal epithelial cells following Goldmann tonometry: implications for CJD risk

AIMS

To assess the adequacy of current decontamination methods for the Goldmann tonometer in the context of variant Creutzfeldt-Jakob disease (vCJD).

METHODS

Reusable Goldmann tonometer prisms were used to perform applanation tonometry on different groups of patients. Following tonometry, retained materials were collected from the tonometer prism head and examined using cytological methods. The used tonometers were subjected to a series of conditions to evaluate their effect on the residual cell numbers found on the tonometer heads. These included wiping alone and wiping or washing followed by disinfection of the tonometer prism. The effect on cell counts of drying the prism overnight was studied, as well as drying overnight and then wiping and disinfecting. All disinfections were performed with sodium hypochlorite (0.05% w/v).

RESULTS

The cytology specimens of 69 patients were studied. Patients using eye drops regularly desquamated significantly more corneal epithelial cells with Goldmann tonometry than patients not using regular eye drops. The mean number of cells was 156 (range 0-470) for patients using eye drops and 14 (4-57) for patients not using eye drops (p = 0.004). Wiping or washing the tonometer head reduced the cell number significantly but neither method completely eliminated cells. The two methods were not significantly different (p=0.3). Drying left a large number of cells (23-320 cells).

CONCLUSIONS

Retained corneal epithelial cells, following the standard decontamination routine of tonometer prisms, may represent potential prion infectivity. Manual cleaning was the most important step in reducing epithelial cell retention.

Virus-like interference in the latency and prevention of Creutzfeldt-Jakob disease

We previously showed that intracerebral (ic) inoculation of the attenuated SY strain of Creutzfeld-Jakob disease in mice could delay clinical signs and widespread neuropathology evoked by subsequent ic challenge with the more virulent FU strain. Using lower doses of SY and FU ic, we here demonstrate that mice can be protected well into old age without demonstrable neuropathology or pathologic prion protein (PrP-res). In contrast, parallel FU only controls became terminally diseased 1 year earlier. To determine whether factors elaborated in response to SY might be part of this effect, we evaluated brain and serum samples from additional parallel mice at 90 days after SY infection and just before FU challenge. The infectivity of FU preparations was significantly reduced by mixing with these fresh SY brain homogenates but not by mixing with SY serum samples, suggesting that brain cells were elaborating labile inhibitory factors that were part of the protective response. SY infectivity was too low to be detected in these brain homogenates. Although suppression could be overcome by higher FU doses ic, strong protection against maximal doses of FU was observed by using i.v. inoculations. Because myeloid microglia are infectious and also elaborate many factors in response to the foreign Creutzfeld-Jakob disease agent, it is likely that innate immunity underlies the profound protection shown here. In principle, it should be possible to artificially stimulate relevant myeloid pathways to better prevent and/or delay the clinical and pathological sequelae of these infections.

Organ distribution of prion proteins in variant Creutzfeldt-Jakob disease

In this article we give an overview of the transmissible spongiform encephalopathies, with emphasis on the evidence for the distribution of abnormal prions in tissues. The normal prion protein is distributed ubiquitously throughout human body tissues. Endogenous expression of the normal prion protein, as well as auxiliary proteins, plays a part in accumulation of the abnormal prion protein. As exemplified by variant Creutzfeldt-Jakob disease (vCJD) the abnormal prion protein can accumulate in the host lymphoid system, in particular the follicular dendritic cells. The route for the disease-related prion neuroinvasion is likely to involve the peripheral nervous system. An alternative route may involve blood constituents. Both animal studies and studies on vCJD patients suggest a potential for abnormal prion distribution in several peripheral tissues other than the lymphoreticular system. In human beings the abnormal prion has been reported in the brain, tonsils, spleen, lymph node, retina, and proximal optic nerve. Infectivity, although present in peripheral tissues, is at lower levels than in the central nervous system (CNS). Animal models suggest that the growth of infectivity in the CNS is likely to be gradual with maximum values during the clinical phase of disease. That tissues may harbour the abnormal prion, at different levels of infectivity, during the incubation period of the disease raises concerns of iatrogenic transmission of the disease either after surgery, blood transfusion, or accidental organ transplantation from donors in the preclinical phase of the disease.

The risk of transmission of variant Creutzfeldt–Jakob disease via contact lenses and ophthalmic devices

This review collated the available information regarding the risk of transmission of variant Creutzfeldt-Jakob disease (vCJD) via contact lenses and other ophthalmic devices. The topics examined include: the emerging background science of the unconventional infective agent, the prion, particularly those factors affecting transmission; the estimates of the number of undiagnosed infective individuals; and evidence of infectivity in the external eye. Despite many uncertainties in the literature, we conclude that cross-infection is theoretically possible. An assessment of the extensive search for a complete inactivation procedure resulted in the recommendation of the use of sodium hypochlorite (NaOCl), which does not appear to distort rigid lenses. Further tests are required for other devices.

Improved flow cytometric method to enumerate residual cells: minimal linear detection limits for platelets, erythrocytes, and leukocytes

Increasing demand for quality control of blood products requires more sensitive methods to enumerate residual cells. Presently, the reported threshold (in cells per microliter) is 400 for red blood cells, 30-500 for platelets, and 1 for leukocytes. To examine precision and linearity in enumerating residual platelets and red blood cells, EDTA-anticoagulated blood from healthy donors was serially diluted with serum, stained in TruCount tubes using a no-lyse/no-wash procedure and a monoclonal antibody cocktail against the CD42a (FL1) and glycophorin-A (FL2) epitopes, and analyzed by flow cytometry. Leukocyte counts were determined in separate tubes. Cell preparation and analysis were performed once for 20 blood samples each and 20 times using the same specimen. Acquisition from the same tube was performed separately for platelets (threshold on FL1) and red blood cells (threshold on FL2). Multiparameter analysis was used for data evaluation. Linear results were obtained for platelets per microliter between 3,410 and 5 and for red blood cells per microliter between 54,000 and 3. For the lower cell concentrations, the coefficient of variation was 16.7% for platelets and 10.9% for red blood cells. The presented method allows the distinction between physiologically intact and ghost red blood cells. The method represents a reliable, sensitive, and accurate approach to quantify platelets and red blood cells in diluted blood. It can be applied to enumerate residual cells in plasma products and meets the increasing demand for quality control in blood components.

[Prions--clinical significance, epidemiology and possibilities of transmission through blood and blood products]

INTRODUCTION

Prions play a leading role in development of transmissible spongiform encephalopathies (TSE). These infectious particles, smaller than viruses and viroids, consist of special kind of proteins and don't contain nucleic acids. Due to that, they are named defective viruses.

BIOCHEMICAL CHARACTERISTICS

Prion protein determined as PrPcs was isolated in infective material of all known prion diseases. This represents an abnormal conformer of PrPc prion protein, normally synthesized in all cells, predominantly in neurons of vertebrates.

PATHOGENESIS OF TSE

Transmissible spongiform encephalopathies are neurodegenarative diseases whose pathogenesis includes modification of secondary structure of normal glycoprotein--prion protein. In human peripheral blood, PrP are expressed in T and B lymphocytes, NK cells, monocytes, dendritic cells, platelets and plasma.

EPIDEMIOLOGICAL STUDIES

Investigations of transmission of prions to experimental animals, showed that lymphoid tissues are infectious in the earliest phase of the disease. Experimental transmission of sporadic Creutzfeldt-Jakob disease (CJD) by intracerebral inoculation of experimental animals with whole blood, buffy coat, platelet concentrates, plasma, early cohn fractions and albumin preparations, has been reported. A small number of clinical studies reported transmission of CJD by human blood, urine and lymphoid tissues and the role of B lymphocytes in neuroinvasion and transmission of prions.

CONCLUSION

Thus, importance of prion diseases in blood transfusion is obvious, latrogenic transmission of prion diseases by blood and blood products, can't be neglected. Moreover, it is necessary to find markers in prion diseases as well as new technologies and methodologies in blood transfusion practice to minimize the theoretical risk of transmission of prion diseases by blood and blood products.

The sclera, the prion, and the ophthalmologist

Prions have emerged in the past 5 years as serious transmissible infective agents. Ocular tissue transplantation has come under scrutiny after potential infected tissue was transplanted into healthy patients. In this review we examine the evidence for the risk of transmission of prions after scleral transplantation and explore alternative materials that may be used in ocular surgery.

Factor VIII and transmissible spongiform encephalopathy: the case for safety

Haemophilia A is the most common inherited bleeding disorder, caused by a deficiency in coagulation factor VIII (FVIII). Current treatment of haemophilia A is based on repeated infusions of plasma-derived FVIII concentrate or of recombinant FVIII, which may be exposed to plasma-derived material of human or animal origin used in its tissue culture production process. We review epidemiological and experimental studies relevant to blood infectivity in the transmissible spongiform encephalopathies (TSEs, or 'prion' diseases), and evaluate the hypothetical risk of TSE transmission through treatment with plasma-derived or recombinant FVIII.

Evaluation of performance of white blood cell reduction filters: an original flow cytometric method for detection and quantification of cell-derived membrane fragments

BACKGROUND

Contamination of blood products by white blood cells leads to a risk of transmission of infectious agents, particularly abnormal prion protein, the probable causative agent of new-variant Creutzfeldt-Jakob disease. Blood product filtration could reduce this risk, but the filtration systems might generate potentially infectious membrane fragments. We developed an original flow cytometric method that allows the detection and quantification of membrane fragments in filtered products and the evaluation of the quantity of destroyed cells.

METHODS

This method has four technical requirements: cytofluorometric acquisition of forward scatter parameters on a log scale, use of a fluorescent aliphatic reporter molecule (PKH26-GL) to identify membrane fragments, quantification with fluorescent beads, and the drawing up of a standard curve on the basis of cells destroyed by freezing/thawing to generate cell debris (i.e., quantity of membrane fragments measured versus quantity of destroyed cells).

RESULTS AND CONCLUSIONS

This original method can be used to test new filtration devices and it allows optimization of the filtration process or comparison of different filtration systems. We tested the method with three commercial white cell removal filters. We demonstrated that it is possible to evaluate the filter quality, particularly the likelihood of fragment removal during the filtration process.

Neuroinvasion by a Creutzfeldt-Jakob disease agent in the absence of B cells and follicular dendritic cells

With the potential spread of bovine spongiform encephalopathy to people as a variant Creutzfeldt-Jakob disease (CJD), it becomes critical to identify cells in the periphery that carry infection. Initial work with scrapie agents suggested that B cells were central vectors for neuroinvasion. Subsequent studies indicated that B cells played an indirect role by promoting the development of follicular dendritic cells (FDCs) that accumulate abnormal prion protein (PrP). The mechanism for the role of FDCs, however, has not been clear. To further dissect potential B cell functions that contribute to neuroinvasion, we inoculated a CJD agent into mutant mice that (i) lacked B cells, (ii) had B cells unable to secrete Ig, or (iii) could secrete only IgM. Remarkably, all these mice developed disease with practically indistinguishable incubation times. The demonstration that neither immune complexes nor B cells were required for neuroinvasion from the periphery mandates a reanalysis of the accepted view of the essential role of B cells and FDC in these infections. Moreover, immune complexes were not required for the accumulation of pathologic PrP on the surface of FDCs, suggesting that PrP can bind to FDCs autonomously or by means of another factor. Wild-type mice had incubation times approximately 50 days less than all mutant mice at the same peripheral doses, indicating that an intact immune system may increase agent uptake and delivery, but this condition is not essential. Specifically, the evidence to date suggests that IgG may enhance pivotal agent interactions with migratory myeloid cells.

A critical review of atypical cerebellum-type Creutzfeldt-Jakob disease: its relationship to "new variant" CJD and bovine spongiform encephalopathy

Shortly after the appearance of bovine spongiform encephalopathy (BSE), Creutzfeldt-Jakob disease (CJD) was identified in young patients with nonclassical presentation such as difficulty in balancing and ataxia. The classical CJD in older patients starts with dementia. To distinguish between the two types, CJD in young persons has been termed "new variant" (nvCJD). The distinguishing features of classical CJD include initial presentation with dementia, confluent spongiform changes are very unusual in the cerebellum, and PrP plaques are rarely observed. For nvCJD, initially, difficulty with balancing and ataxia occurs, confluent spongiform changes are seen in the cerebellum, and a large number of PrP plaques are seen. The icelandic observation of sheep scrapie revealed a predominantly ataxic form of scrapie, termed Type II, rather than the itchy form termed Type I. Both types have been known to exist in Europe. Since the clinical signs of Type II scrapie in sheep with trembling and ataxia are similar to those seen in BSE and nvCJD, this suggests that Type II is the cause of BSE and nvCJD. Over 8 years, from 1989 to 1996, I examined the clinical histories of 33 CJD cases aged between the ages of 18 and 84. Six under the age of 40 and 15 over the age of 40 had leading clinical features such as difficulty in balancing and ataxia similar to those seen in the young cases classified as "nvCJD." Brains were examined from the six of 15 cases over the age of 40, which revealed similar pathology to that seen in young patients classified as "nvCJD." These findings suggest that all age groups are susceptible to the strain of the agent derived from BSE cattle.

Lingering doubts about spongiform encephalopathy and Creutzfeldt-Jakob disease

Bovine spongiform encephalopathy (BSE) is an infectious disease and has been transmitted orally to many other animals, including humans. There is clear evidence of maternal transmission, although disagreement on the source of the BSE agent remains. The current theories link the origin of BSE to common scrapie in sheep. Twenty different strains of the scrapie agent have been isolated from sheep. A search of the literature indicates two distinct clinical syndromes in sheep, both of which have been called scrapie. I have designated these Type I (the common type), which exhibits itchiness and lose their wool, and Type II, which exhibits trembling and ataxia. Sheep inoculated with BSE develop Type II scrapie and they exhibit trembling. When cattle or mink are injected with the Type I strain, only a few will develop a clinical disease. By contrast, no clinical disease has so far been shown in cattle or mink by feeding them with Type I-infected sheep brains. However, either by injecting or feeding with the BSE strain, 100% of calves and mink develop the clinical disease. Evidence suggests that Type II is the cause of BSE. Identical clinical signs of Type II trembling are found in kuru and many of the recent cases of Creutzfeldt-Jakob disease. The BSE agent has caused spongiform encephalopathies (SEs) in domestic cats, tigers, and in some species of ruminants in zoos. The nature of the BSE agent remains unchanged when passaged through a range of species, irrespective of their genetic make up, demonstrating that variations in the host PrP gene are not a major factor in the susceptibility to the BSE agent. Since more than 85 zoo animals of many species have been diagnosed with SEs, from these studies it seems reasonable to conclude that the BSE agent can infect almost all mammalian species, including humans. For eradication of BSE and to reduce the risk of infection to humans, the development of a vaccine against BSE is suggested. Such a possibility should be fully explored.

Creutzfeldt-Jakob disease: recommendations for disinfection and sterilization

Prion diseases constitute a unique infection control problem because prions exhibit unusual resistance to conventional chemical and physical decontamination methods. Recommendations to prevent cross-transmission of infection from medical devices contaminated by Creutzfeldt-Jakob disease (CJD) have been based primarily on prion inactivation studies. The recommendations in this article consider inactivation data but also use epidemiological studies of prion transmission, infectivity of human tissues, and efficacy of removing microbes by cleaning. On the basis of the scientific data, only critical (e.g., surgical instruments) and semicritical devices contaminated with high-risk tissue (i.e., brain, spinal cord, and eye tissue) from high-risk patients--those with known or suspected infection with CJD--require special treatment.

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.

Follicular dendritic cells and dissemination of Creutzfeldt-Jakob disease

The contribution of immune system cells to the propagation of transmissible encephalopathies is not well understood. To determine how follicular dendritic cells (FDC) may act, we challenged lymphotoxin beta null and wild-type (wt) controls with a Creutzfeldt-Jakob disease (CJD) agent. There was only a small difference in incubation time to clinical disease even after peripheral challenge with low infectious doses (31 in a total of 410 days). Brain pathology with extensive microglial infiltration, identified by keratan sulfate, as well as astrocytic hypertrophy, was also equivalent in all groups despite the fact that null mice had neither FDC nor splenic metallophilic macrophages that filter particulate antigen. Because FDC accumulate pathologic prion protein (PrP) in infected but not wt mice, we studied the cellular distribution of PrP by confocal microscopy. The majority of pathologic PrP collected on the plasma membrane of FDC, as identified by the Ca(+2)-binding protein S100A. This surface distribution suggested that agent aggregated with pathologic PrP might spread by cell-to-cell contacts. While several types of leukocytes may be involved in agent dissemination, cells of myeloid lineage were found to be infectious. Moreover, perivascular tracks of microglia and abnormal PrP after intraperitoneal inoculation were consistent with hematogenous spread. In summary, FDC are not required for CJD agent spread from the periphery, although FDC may enhance spread through surface accumulation of pathologic PrP. While it is still not clear where the infectious agent replicates, macrophages can sequester appreciable levels of infectivity and hence act as reservoirs for prolonged latent infection.

European surveillance on Creutzfeldt-Jakob disease: a case-control study for medical risk factors

Medical risk factors for Creutzfeldt-Jakob disease (CJD) were analyzed in a prospective ongoing case-control study based on European CJD surveillance. Detailed data on past and recent medical history were analyzed in 405 cases and controls matched by sex, age, and hospital. Data were correlated with polymorphism at codon 129 of the prion protein gene. Our analysis did not support a number of previously reported associations and failed to identify any common medical risk factor for CJD. Although not statistically significant, brain surgery was associated with an increased risk of CJD. A detailed medical history should be obtained in every suspected CJD case in order to identify iatrogenic sources of CJD.

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.

Risk of transmission of Creutzfeldt-Jakob disease by transfusion of blood, plasma, and plasma derivatives

Studies in experimental animals and case-reports of transmission of Creutzfeldt-Jakob Disease (CJD) by blood transfusion or by albumin products have raised the possibility that CJD may be transmitted by transfusion. The risk of transmission of CJD by transfusion remains theoretical, since no confirmed case of CJD has ever been causally attributed to the receipt of a blood transfusion, no confirmed case of CJD has developed in recipients of clotting factor concentrates, and no cluster of CJD cases has been reported following the administration of a pooled plasma derivative to which a donor who subsequently developed CJD had contributed. However, based on a review of the hitherto available data, it is impossible to conclude at this time that CJD is not transmitted by blood or plasma transfusion or by the administration of pooled plasma derivatives. This review discusses the findings of the animal experiments and the human studies that investigated the potential for transmission of CJD among humans by transfusion, and explains the statistical difficulties associated with proving the negative hypothesis that CJD is not transmitted by transfusion.

Distribution of cell-associated prion protein in normal adult blood determined by flow cytometry

Leucocyte subpopulations from normally healthy individuals were identified by recognized combinations of fluorochrome-conjugated antibodies to CD markers and stained by different monoclonal antibodies (MAb) to normal cellular prion protein (PrPC), including the 3F4 MAb. Cell preparations were examined by three-colour flow cytometry. All mononuclear leucocyte subpopulations and platelets expressed PrPC, but polymorphonuclear leucocytes and red blood cells expressed little or no PrPC. The amounts of PrPC expressed by the different cells were calculated by comparison to bead standards. Mononuclear leucocytes expressed 3000-4000 molecules of antibody-reactive PrPC per cell. Resting platelets expressed around 1400 molecules of PrPC per cell, whereas activated platelets expressed around 4800 molecules of PrPC per cell. Extrapolation of these values to the amounts of the various cells in whole blood showed that platelet PrPC accounted for at least 96% of cell-expressed PrPC in blood. The PrPC on mononuclear cells and platelets was sensitive to enzymatic treatment of cells by proteinase k and phosphatidylinositol-specific phospholipase C. Certain anti-PrPC MAbs which showed equivalent intensity of staining to MAb 3F4 on fresh cells showed relative reductions of staining compared to MAb 3F4 on stored cells, indicating possible structural alterations of PrPC under these conditions.

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.

[Prion diseases and blood transfusion]

Prion diseases are lethal disorders, some of which are transmissible by infectious route. Experimental data concerning neuroinvasion indicate that there is a viremia during the migration of the prion agent to the central nervous system. The possibility of accidental transmission via blood products and therefore potential transfusion risk thus arises. The analysis of experimental and epidemiological data available at present contributes to the following conclusion: the potential and theoretical risk for contamination from blood products is not null but mathematically very low, there is no indisputable experimental proof for that risk via systemic route and no case is definite and the risk is probably linked to leukocytes, and especially B lymphocytes. These conclusions are reassuring but nevertheless justify strict epidemiological survey and a reasonable discussion for each transfusion. Some groups of people have to be excluded from blood donors.

Prions and haemophilia: assessment of risk

Based on information accumulated to date, it is still difficult to assess the risk of Creutzfeldt-Jakob disease (CJD) and blood transfusion with any degree of confidence. However, it is reasonable to conclude that CJD is produced by a transmittable agent which is probably contained in low titer in the blood of infected people and animals. From the present clinical and epidemiological studies, transmission by blood or blood products appears to be a rare or non-existent cause of current and past cases of CJD in humans. Since blood products are necessary to prevent the immediate risk of death or significant morbidity in many clinical conditions, therapeutic decisions should be made after consideration of the known risk in these situations vs the theoretical long-term risk of the rare occurrence of CJD.

Case-control study of risk factors of Creutzfeldt-Jakob disease in Europe during 1993-95. European Union (EU) Collaborative Study Group of Creutzfeldt-Jakob disease (CJD)

BACKGROUND

Creutzfeldt-Jakob disease (CJD) is a transmissible spongiform encephalopathy. Genetic and iatrogenic forms have been recognised but most are sporadic and of unknown cause. We have studied risk factors for CJD as part of the 1993-95 European Union collaborative studies of CJD in Europe.

METHODS

The 405 patients with definite or probable CJD who took part in our study had taken part in population-based studies done between 1993 and 1995 in Belgium, France, Germany, Italy, the Netherlands, and the UK. Data on putative risk factors from these patients were compared with data from 405 controls.

FINDINGS

We found evidence for familial aggregation of CJD with dementia due to causes other than CJD (relative risk [RR] 2.26, 95% CI 1.31-3.90). No significant increased risk of CJD in relation to a history of surgery and blood transfusion was shown. There was no evidence for an association between the risk of CJD and the consumption of beef, veal, lamb, cheese, or milk. No association was found with occupational exposure to animals or leather. The few positive findings of the study include increased risk in relation to consumption of raw meat (RR 1.63 [95% CI 1.18-2.23]) and brain (1.68 [1.18-2.39]), frequent exposure to leather products (1.94 [1.13-3.33]), and exposure to fertiliser consisting of hoofs and horns (2.32 [1.38-2.91]). Additional analyses, for example stratification by country and of exposures pre-1985 and post-1985, suggest that these results should be interpreted with great caution.

INTERPRETATION

Within the limits of the retrospective design of the study, our findings suggest that genetic factors other than the known CJD mutations may play an important part in CJD. Iatrogenic transmission of disease seems rare in this large population-based sample of patients with CJD. There is little evidence for an association between the risk of CJD and either animal exposure, or consumption of processed bovine meat or milk products for the period studied.

Emerging issues in blood safety

Improvements in donor selection, testing of donors for markers of infection, and viral inactivation of plasma-derived products have helped reduce the risk of transfusion-associated infections, including hepatitis B (HBV), hepatitis C (HCV), and human immunodeficiency viruses (HIV). The potential for transmission of emerging infections is illustrated by current concerns about group O strains of HIV, nonenveloped viruses, newly discovered microbial agents, prions, Chagas' disease, tick-borne infections, and the need to assess the frequency of transfusion reactions associated with bacterial contamination.

Understanding Creutzfeldt-Jakob disease

The "mad cow disease" that decimated cattle in England has brought wide-spread attention to a similar disease in humans, Creutzfeldt-Jakob disease (CJD). This has led to concerns about the transmissibility and contagiousness of the infectious agent from possible CJD patients to health care workers and family members. Despite these worries, the occurrence of CJD in the human population has remained stable over the years at an incidence of about one person per million in the United States population, and increasing to six individuals per million for the older-than-60 age group. This article will review the etiology, clinical manifestations, and potential for transmission of this unusual infectious agent.

Is Creutzfeldt-Jakob disease transmitted in blood?

Creutzfeldt-Jakob disease (CJD) has been considered infectious since the mid-1960s, but its transmissibility through the transfusion of blood or blood products is controversial. The causative agent's novel undefined nature and resistance to standard decontamination, the absence of a screening test, and the recognition that even rare cases of transmission may be unacceptable have led to the revision of policies and procedures worldwide affecting all facets of blood product manufacturing from blood collection to transfusion. We reviewed current evidence that CJD is transmitted through blood.

A matter for debate: the risk of bovine spongiform encephalopathy to humans posed by blood transfusion in the UK

If human infection with bovine spongiform encephalopathy (BSE) were to occur, donated peripheral blood from humans that might have become infected from eating adequate quantities of food containing BSE should, until evidence is available to the contrary, be assumed to contain the human form of the disease. The chance of disease transfer to a blood recipient in 1995, which might in turn cause clinical disease with an incubation period of 20 years, is calculated. Transfusion is calculated to be a potential cause of a maximum of only 0.2% of clinical cases of Creutzfeldt-Jakob disease (CJD) in the UK population if the BSE epidemic were to spread to humans. Prospective epidemiological techniques would be unlikely to demonstrate any such minor contribution that blood transfusion might make to CJD incidence.