Diagnosis in Scrapie: Conventional Methods and New Biomarkers.

Scrapie, a naturally occurring prion disease affecting goats and sheep, comprises classical and atypical forms, with classical scrapie being the archetype of transmissible spongiform encephalopathies. This review explores the challenges of scrapie diagnosis and the utility of various biomarkers and their potential implications for human prion diseases. Understanding these biomarkers in the context of scrapie may enable earlier prion disease diagnosis in humans, which is crucial for effective intervention. Research on scrapie biomarkers bridges the gap between veterinary and human medicine, offering hope for the early detection and improved management of prion diseases.

Detection of classical BSE prions in asymptomatic cows after inoculation with atypical/Nor98 scrapie.

The emergence of bovine spongiform encephalopathy (BSE) prions from atypical scrapie has been recently observed upon experimental transmission to rodent and swine models. This study aimed to assess whether the inoculation of atypical scrapie could induce BSE-like disease in cattle. Four calves were intracerebrally challenged with atypical scrapie. Animals were euthanized without clinical signs of prion disease and tested negative for PrPSc accumulation by immunohistochemistry and western blotting. However, an emergence of BSE-like prion seeding activity was detected during in vitro propagation of brain samples from the inoculated animals. These findings suggest that atypical scrapie may represent a potential source of BSE infection in cattle.

Endoplasmic reticulum stress and ubiquitin-proteasome system impairment in natural scrapie.

Chronic accumulation of misfolded proteins such as PrPSc can alter the endoplasmic reticulum homeostasis triggering the unfolded protein response (UPR). In this pathogenic event, the molecular chaperones play an important role. Several reports in humans and animals have suggested that neurodegeneration is related to endoplasmic reticulum stress in diseases caused by the accumulation of misfolded proteins. In this study, we investigated the expression of three endoplasmic reticulum stress markers: PERK (protein kinase R-like endoplasmic reticulum kinase), BiP (binding immunoglobulin protein), and PDI (Protein Disulfide Isomerase). In addition, we evaluated the accumulation of ubiquitin as a marker for protein degradation mediated by the proteasome. These proteins were studied in brain tissues of sheep affected by scrapie in clinical and preclinical stages of the disease. Results were compared with those observed in healthy controls. Scrapie-infected sheep showed significant higher levels of PERK, BiP/Grp78 and PDI than healthy animals. As we observed before in models of spontaneous prion disease, PDI was the most altered ER stress marker between scrapie-infected and healthy sheep. Significantly increased intraneuronal and neuropil ubiquitinated deposits were observed in certain brain areas in scrapie-affected animals compared to controls. Our results suggest that the neuropathological and neuroinflammatory phenomena that develop in prion diseases cause endoplasmic reticulum stress in brain cells triggering the UPR. In addition, the significantly higher accumulation of ubiquitin aggregates in scrapie-affected animals suggests an impairment of the ubiquitin-proteasome system in natural scrapie. Therefore, these proteins may contribute as biomarkers and/or therapeutic targets for prion diseases.

Peripheral neuropathy caused by fenugreek (Trigonella foenum-graecum) straw intoxication in cattle and experimental reproduction in sheep and goats.

Trigonella foenum-graecum (fenugreek) is a legume widely used as a food supplement in humans and less frequently in ruminants. Toxicity has been described sporadically in ruminants grazing mature fenugreek plants or stubble; however, the pathological features are unclear. This report describes a natural outbreak of intoxication in cattle fed fenugreek straw and the experimental reproduction using 8 sheep and 8 goats. Affected cattle presented clinical signs approximately 1 month after consuming the straw and 100 of 400 cattle (25%) were affected, of which 60 of 100 (60%) died or were euthanized. Clinical signs were characterized by proprioceptive positioning defects with abnormal postures and weakness of hindlimbs. Forelimbs were also affected in severely affected animals, and cattle became recumbent. Locomotion was characterized by trembling, and some cattle showed high-stepping movements of their forelimbs and knuckled over in their fetlocks. Experimental intoxication induced clinical signs only in sheep and were similar to cattle, although with signs starting in the forelegs. Gross and microscopic lesions were similar in spontaneous and experimental intoxications. Macroscopic changes corresponded with muscular hemorrhages and edema, mainly surrounding the peripheral nerves. Microscopic examination only demonstrated lesions in the distal peripheral nerves, which included edema, hemorrhages, and Wallerian degeneration. Neurofilament immunohistochemistry revealed altered axon labeling and S100 showed a decrease in myelin intensity and loss of its typical compact arrangement around axons. Biochemical and hematological abnormalities included elevated levels of muscle and liver enzymes and thrombocytopenia. These findings indicate that fenugreek straw induces peripheral neuropathy in cattle and sheep, but not in goats.

Emergence of CWD strains.

Chronic wasting disease (CWD) strains present a novel challenge to defining and mitigating this contagious prion disease of deer, elk, moose, and reindeer. Similar to strains of other prion diseases (bovine spongiform encephalopathy, sheep scrapie), CWD strains can affect biochemical and neuropathological properties of the infectious agent, and importantly interspecies transmission. To date, ten CWD strains have been characterized. The expanding range of CWD in North America and its presence in South Korea as well as Scandinavian countries will potentially result in millions of cervids infected with CWD; thus, novel strains will continue to emerge. In this review, we will summarize the characteristics of known CWD strains and describe the impact of prion protein gene polymorphisms on the generation of strains. We will also discuss the evidence that individual cervids can harbor more than one CWD strain, complicating strain analysis, and affecting selection and adaptation of strains in new hosts.

Bona fide atypical scrapie faithfully reproduced for the first time in a rodent model.

Atypical Scrapie, which is not linked to epidemics, is assumed to be an idiopathic spontaneous prion disease in small ruminants. Therefore, its occurrence is unlikely to be controlled through selective breeding or other strategies as it is done for classical scrapie outbreaks. Its spontaneous nature and its sporadic incidence worldwide is reminiscent of the incidence of idiopathic spontaneous prion diseases in humans, which account for more than 85% of the cases in humans. Hence, developing animal models that consistently reproduce this phenomenon of spontaneous PrP misfolding, is of importance to study the pathobiology of idiopathic spontaneous prion disorders. Transgenic mice overexpressing sheep PrPC with I112 polymorphism (TgShI112, 1-2 × PrP levels compared to sheep brain) manifest clinical signs of a spongiform encephalopathy spontaneously as early as 380 days of age. The brains of these animals show the neuropathological hallmarks of prion disease and biochemical analyses of the misfolded prion protein show a ladder-like PrPres pattern with a predominant 7-10 kDa band. Brain homogenates from spontaneously diseased transgenic mice were inoculated in several models to assess their transmissibility and characterize the prion strain generated: TgShI112 (ovine I112 ARQ PrPC), Tg338 (ovine VRQ PrPC), Tg501 (ovine ARQ PrPC), Tg340 (human M129 PrPC), Tg361 (human V129 PrPC), TgVole (bank vole I109 PrPC), bank vole (I109I PrPC), and sheep (AHQ/ARR and AHQ/AHQ churra-tensina breeds). Our analysis of the results of these bioassays concludes that the strain generated in this model is indistinguishable to that causing atypical scrapie (Nor98). Thus, we present the first faithful model for a bona fide, transmissible, ovine, atypical scrapie prion disease.

Chronic wasting disease prions in mule deer interdigital glands.

Chronic wasting disease (CWD) is a geographically expanding, fatal neurodegenerative disease in cervids. The disease can be transmitted directly (animal-animal) or indirectly via infectious prions shed into the environment. The precise mechanisms of indirect CWD transmission are unclear but known sources of the infectious prions that contaminate the environment include saliva, urine and feces. We have previously identified PrPC expression in deer interdigital glands, sac-like exocrine structures located between the digits of the hooves. In this study, we assayed for CWD prions within the interdigital glands of CWD infected deer to determine if they could serve as a source of prion shedding and potentially contribute to CWD transmission. Immunohistochemical analysis of interdigital glands from a CWD-infected female mule deer identified disease-associated PrPCWD within clusters of infiltrating leukocytes adjacent to sudoriferous and sebaceous glands, and within the acrosyringeal epidermis of a sudoriferous gland tubule. Proteinase K-resistant PrPCWD material was amplified by serial protein misfolding cyclic amplification (sPMCA) from soil retrieved from between the hoof digits of a clinically affected mule deer. Blinded testing of interdigital glands from 11 mule deer by real-time quake-induced conversion (RT-QuIC) accurately identified CWD-infected animals. The data described suggests that interdigital glands may play a role in the dissemination of CWD prions into the environment, warranting future investigation.

Glycans are not necessary to maintain the pathobiological features of bovine spongiform encephalopathy.

The role of the glycosylation status of PrPC in the conversion to its pathological counterpart and on cross-species transmission of prion strains has been widely discussed. Here, we assessed the effect on strain characteristics of bovine spongiform encephalopathy (BSE) isolates with different transmission histories upon propagation on a model expressing a non-glycosylated human PrPC. Bovine, ovine and porcine-passaged BSE, and variant Creutzfeldt-Jakob disease (vCJD) isolates were used as seeds/inocula in both in vitro and in vivo propagation assays using the non-glycosylated human PrPC-expressing mouse model (TgNN6h). After protein misfolding cyclic amplification (PMCA), all isolates maintained the biochemical characteristics of BSE. On bioassay, all PMCA-propagated BSE prions were readily transmitted to TgNN6h mice, in agreement with our previous in vitro results. TgNN6h mice reproduced the characteristic neuropathological and biochemical hallmarks of BSE, suggesting that the absence of glycans did not alter the pathobiological features of BSE prions. Moreover, back-passage of TgNN6h-adapted BSE prions to BoTg110 mice recovered the full BSE phenotype, confirming that the glycosylation of human PrPC is not essential for the preservation of the human transmission barrier for BSE prions or for the maintenance of BSE strain properties.

Neurogranin and Neurofilament Light Chain as Preclinical Biomarkers in Scrapie.

Prion diseases are diagnosed in the symptomatic stage, when the neuronal damage is spread throughout the central nervous system (CNS). The assessment of biological features that allow the detection of asymptomatic cases is needed, and, in this context, scrapie, where pre-symptomatic infected animals can be detected through rectal biopsy, becomes a good study model. Neurogranin (Ng) and neurofilament light chain (NfL) are proteins that reflect synaptic and axonal damage and have been studied as cerebrospinal fluid (CSF) biomarkers in different neurodegenerative disorders. In this study, we evaluated Ng and NfL both at the protein and transcript levels in the CNS of preclinical and clinical scrapie-affected sheep compared with healthy controls and assessed their levels in ovine CSF. The correlation between these proteins and the main neuropathological events in prion diseases, PrPSc deposition and spongiosis, was also assessed. The results show a decrease in Ng and NfL at the protein and gene expression levels as the disease progresses, and significant changes between the control and preclinical animals. On the contrary, the CSF levels of NfL increased throughout the progression of the disease. Negative correlations between neuropathological markers of prion disease and the concentration of the studied proteins were also found. Although further research is needed, these results suggest that Ng and NfL could act as biomarkers for neurodegeneration onset and intensity in preclinical cases of scrapie.

Susceptibility of Beavers to Chronic Wasting Disease.

Chronic wasting disease (CWD) is a contagious, fatal, neurodegenerative prion disease of cervids. The expanding geographical range and rising prevalence of CWD are increasing the risk of pathogen transfer and spillover of CWD to non-cervid sympatric species. As beavers have close contact with environmental and food sources of CWD infectivity, we hypothesized that they may be susceptible to CWD prions. We evaluated the susceptibility of beavers to prion diseases by challenging transgenic mice expressing beaver prion protein (tgBeaver) with five strains of CWD, four isolates of rodent-adapted prions and one strain of Creutzfeldt-Jakob disease. All CWD strains transmitted to the tgBeaver mice, with attack rates highest from moose CWD and the 116AG and H95+ strains of deer CWD. Mouse-, rat-, and especially hamster-adapted prions were also transmitted with complete attack rates and short incubation periods. We conclude that the beaver prion protein is an excellent substrate for sustaining prion replication and that beavers are at risk for CWD pathogen transfer and spillover.

Cellular prion protein distribution in the vomeronasal organ, parotid, and scent glands of white-tailed deer and mule deer.

Chronic wasting disease (CWD) is a contagious and fatal transmissible spongiform encephalopathy affecting species of the cervidae family. CWD has an expanding geographic range and complex, poorly understood transmission mechanics. CWD is disproportionately prevalent in wild male mule deer and male white-tailed deer. Sex and species influences on CWD prevalence have been hypothesized to be related to animal behaviours that involve deer facial and body exocrine glands. Understanding CWD transmission potential requires a foundational knowledge of the cellular prion protein (PrPC) in glands associated with cervid behaviours. In this study, we characterized the presence and distribution of PrPC in six integumentary and two non-integumentary tissues of hunter-harvested mule deer (Odocoileus hemionus) and white-tailed deer (O. virginianus). We report that white-tailed deer expressed significantly more PrPC than their mule deer in the parotid, metatarsal, and interdigital glands. Females expressed more PrPC than males in the forehead and preorbital glands. The distribution of PrPC within the integumentary exocrine glands of the face and legs were localized to glandular cells, hair follicles, epidermis, and immune cell infiltrates. All tissues examined expressed sufficient quantities of PrPC to serve as possible sites of prion initial infection, propagation, and shedding.

Distinctive Toll-like Receptors Gene Expression and Glial Response in Different Brain Regions of Natural Scrapie.

Prion diseases are chronic and fatal neurodegenerative diseases characterized by the accumulation of disease-specific prion protein (PrPSc), spongiform changes, neuronal loss, and gliosis. Growing evidence shows that the neuroinflammatory response is a key component of prion diseases and contributes to neurodegeneration. Toll-like receptors (TLRs) have been proposed as important mediators of innate immune responses triggered in the central nervous system in other human neurodegenerative diseases, including Alzheimer's disease, Parkinson's disease, and amyotrophic lateral sclerosis. However, little is known about the role of TLRs in prion diseases, and their involvement in the neuropathology of natural scrapie has not been studied. We assessed the gene expression of ovine TLRs in four anatomically distinct brain regions in natural scrapie-infected sheep and evaluated the possible correlations between gene expression and the pathological hallmarks of prion disease. We observed significant changes in TLR expression in scrapie-infected sheep that correlate with the degree of spongiosis, PrPSc deposition, and gliosis in each of the regions studied. Remarkably, TLR4 was the only gene upregulated in all regions, regardless of the severity of neuropathology. In the hippocampus, we observed milder neuropathology associated with a distinct TLR gene expression profile and the presence of a peculiar microglial morphology, called rod microglia, described here for the first time in the brain of scrapie-infected sheep. The concurrence of these features suggests partial neuroprotection of the hippocampus. Finally, a comparison of the findings in naturallyinfected sheep versus an ovinized mouse model (tg338 mice) revealed distinct patterns of TLRgene expression.

Condiciones de alojamiento de los terneros en crianzas artificiales de tambo y su relación con el estrés por frío / Housing conditions of dairy calves and its relationship with cold stress

Resumen El estrés por frío en los terneros puede ser muy perjudicial para su salud y rendimiento futuro. El objetivo del presente trabajo fue evaluar el efecto de las condiciones de manejo de la crianza artificial y su relación con estrés por frío en terneros de tambo. Se evaluaron 160 terneros durante las primeras horas de la mañana, y se registró si los animales poseían capa o no y si disponían o no de cama. Se observó si contaban con reparo para limitantes climáticas. También se registró la temperatura rectal y si temblaban o no. Se consideró que terneros con temperatura rectal igual o inferior a 37,2 °C se encontraban en estrés por frio. El análisis estadístico de los datos se hizo mediante la prueba no paramétrica de Chi cuadrado y se calculó la probabilidad de ocurrencia mediante Odds Ratio. Encontrándose que los terneros en condiciones de estrés presentaron 4,93 veces mayor probabilidad de temblar; que disponer de cama fue favorable para prevenir el estrés (0,027), que las capas plásticas incrementaron la probabilidad de sufrir de estrés (0,006) y que proveer reparo a los animales tiene un efecto positivo en la prevención del estrés por frío (p = 0,027) en los terneros de tambo.

Abstract Cold stress in calves can be very detrimental to their health and performance. The aim of this work was to evaluate the effect of artificial rearing management conditions and their relationship to cold stress in dairy calves. A total of 160 calves were evaluated during the early morning hours and it was recorded whether or not the animals had cape and whether or not they had bed in pens. Also, it was observed if they had protection for climatic limitations. Rectal temperature and whether or not they were shivering were also recorded. Calves with rectal temperature equal to or lower than 37.2 °C were considered to be in cold stress. The statistical analysis of the data was performed using the non-parametric Chi-square test and the probability of occurrence was calculated using Odds Ratio. It was found that calves under stress conditions were 4.93 times more likely to shiver; that having bed in pens was favorable for preventing stress (0.027), that plastic cape increased the probability of suffering from stress (0.006) and that providing shelter to animals had a positive effect on the prevention of cold stress (p = 0.027) in dairy calves.

Chronic wasting disease: a cervid prion infection looming to spillover.

The spread of chronic wasting disease (CWD) during the last six decades has resulted in cervid populations of North America where CWD has become enzootic. This insidious disease has also been reported in wild and captive cervids from other continents, threatening ecosystems, livestock and public health. These CWD "hot zones" are particularly complex given the interplay between cervid PRNP genetics, the infection biology, the strain diversity of infectious prions and the long-term environmental persistence of infectivity, which hinder eradication efforts. Here, we review different aspects of CWD including transmission mechanisms, pathogenesis, epidemiology and assessment of interspecies infection. Further understanding of these aspects could help identify "control points" that could help reduce exposure for humans and livestock and decrease CWD spread between cervids.

Classical BSE prions emerge from asymptomatic pigs challenged with atypical/Nor98 scrapie.

Pigs are susceptible to infection with the classical bovine spongiform encephalopathy (C-BSE) agent following experimental inoculation, and PrPSc accumulation was detected in porcine tissues after the inoculation of certain scrapie and chronic wasting disease isolates. However, a robust transmission barrier has been described in this species and, although they were exposed to C-BSE agent in many European countries, no cases of natural transmissible spongiform encephalopathies (TSE) infections have been reported in pigs. Transmission of atypical scrapie to bovinized mice resulted in the emergence of C-BSE prions. Here, we conducted a study to determine if pigs are susceptible to atypical scrapie. To this end, 12, 8-9-month-old minipigs were intracerebrally inoculated with two atypical scrapie sources. Animals were euthanized between 22- and 72-months post inoculation without clinical signs of TSE. All pigs tested negative for PrPSc accumulation by enzyme immunoassay, immunohistochemistry, western blotting and bioassay in porcine PrP mice. Surprisingly, in vitro protein misfolding cyclic amplification demonstrated the presence of C-BSE prions in different brain areas from seven pigs inoculated with both atypical scrapie isolates. Our results suggest that pigs exposed to atypical scrapie prions could become a reservoir for C-BSE and corroborate that C-BSE prions emerge during interspecies passage of atypical scrapie.

Cerebrospinal Fluid and Plasma Small Extracellular Vesicles and miRNAs as Biomarkers for Prion Diseases.

Diagnosis of transmissible spongiform encephalopathies (TSEs), or prion diseases, is based on the detection of proteinase K (PK)-resistant PrPSc in post-mortem tissues as indication of infection and disease. Since PrPSc detection is not considered a reliable method for in vivo diagnosis in most TSEs, it is of crucial importance to identify an alternative source of biomarkers to provide useful alternatives for current diagnostic methodology. Ovine scrapie is the prototype of TSEs and has been known for a long time. Using this natural model of TSE, we investigated the presence of PrPSc in exosomes derived from plasma and cerebrospinal fluid (CSF) by protein misfolding cyclic amplification (PMCA) and the levels of candidate microRNAs (miRNAs) by quantitative PCR (qPCR). Significant scrapie-associated increase was found for miR-21-5p in plasma-derived but not in CSF-derived exosomes. However, miR-342-3p, miR-146a-5p, miR-128-3p and miR-21-5p displayed higher levels in total CSF from scrapie-infected sheep. The analysis of overexpressed miRNAs in this biofluid, together with plasma exosomal miR-21-5p, could help in scrapie diagnosis once the presence of the disease is suspected. In addition, we found the presence of PrPSc in most CSF-derived exosomes from clinically affected sheep, which may facilitate in vivo diagnosis of prion diseases, at least during the clinical stage.

Therapeutic Assay with the Non-toxic C-Terminal Fragment of Tetanus Toxin (TTC) in Transgenic Murine Models of Prion Disease.

The non-toxic C-terminal fragment of the tetanus toxin (TTC) has been described as a neuroprotective molecule since it binds to Trk receptors and activates Trk-dependent signaling, activating neuronal survival pathways and inhibiting apoptosis. Previous in vivo studies have demonstrated the ability of this molecule to increase mice survival, inhibit apoptosis and regulate autophagy in murine models of neurodegenerative diseases such as amyotrophic lateral sclerosis and spinal muscular atrophy. Prion diseases are fatal neurodegenerative disorders in which the main pathogenic event is the conversion of the cellular prion protein (PrPC) into an abnormal and misfolded isoform known as PrPSc. These diseases share different pathological features with other neurodegenerative diseases, such as amyotrophic lateral sclerosis, Parkinson's disease or Alzheimer's disease. Hitherto, there are no effective therapies to treat prion diseases. Here, we present a pilot study to test the therapeutic potential of TTC to treat prion diseases. C57BL6 wild-type mice and the transgenic mice Tg338, which overexpress PrPC, were intracerebrally inoculated with scrapie prions and then subjected to a treatment consisting of repeated intramuscular injections of TTC. Our results indicate that TTC displays neuroprotective effects in the murine models of prion disease reducing apoptosis, regulating autophagy and therefore increasing neuronal survival, although TTC did not increase survival time in these models.

White-tailed deer S96 prion protein does not support stable in vitro propagation of most common CWD strains.

PrPC variation at residue 96 (G/S) plays an important role in the epidemiology of chronic wasting disease (CWD) in exposed white-tailed deer populations. In vivo studies have demonstrated the protective effect of serine at codon 96, which hinders the propagation of common CWD strains when expressed in homozygosis and increases the survival period of S96/wt heterozygous deer after challenge with CWD. Previous in vitro studies of the transmission barrier suggested that following a single amplification step, wt and S96 PrPC were equally susceptible to misfolding when seeded with various CWD prions. When we performed serial prion amplification in vitro using S96-PrPC, we observed a reduction in the efficiency of propagation with the Wisc-1 or CWD2 strains, suggesting these strains cannot stably template their conformations on this PrPC once the primary sequence has changed after the first round of replication. Our data shows the S96-PrPC polymorphism is detrimental to prion conversion of some CWD strains. These data suggests that deer homozygous for S96-PrPC may not sustain prion transmission as compared to a deer expressing G96-PrPC.

Evidence of p75 Neurotrophin Receptor Involvement in the Central Nervous System Pathogenesis of Classical Scrapie in Sheep and a Transgenic Mouse Model.

Neurotrophins constitute a group of growth factor that exerts important functions in the nervous system of vertebrates. They act through two classes of transmembrane receptors: tyrosine-kinase receptors and the p75 neurotrophin receptor (p75NTR). The activation of p75NTR can favor cell survival or apoptosis depending on diverse factors. Several studies evidenced a link between p75NTR and the pathogenesis of prion diseases. In this study, we investigated the distribution of several neurotrophins and their receptors, including p75NTR, in the brain of naturally scrapie-affected sheep and experimentally infected ovinized transgenic mice and its correlation with other markers of prion disease. No evident changes in infected mice or sheep were observed regarding neurotrophins and their receptors except for the immunohistochemistry against p75NTR. Infected mice showed higher abundance of p75NTR immunostained cells than their non-infected counterparts. The astrocytic labeling correlated with other neuropathological alterations of prion disease. Confocal microscopy demonstrated the co-localization of p75NTR and the astrocytic marker GFAP, suggesting an involvement of astrocytes in p75NTR-mediated neurodegeneration. In contrast, p75NTR staining in sheep lacked astrocytic labeling. However, digital image analyses revealed increased labeling intensities in preclinical sheep compared with non-infected and terminal sheep in several brain nuclei. This suggests that this receptor is overexpressed in early stages of prion-related neurodegeneration in sheep. Our results confirm a role of p75NTR in the pathogenesis of classical ovine scrapie in both the natural host and in an experimental transgenic mouse model.

Effect of Scrapie Prion Infection in Ovine Bone Marrow-Derived Mesenchymal Stem Cells and Ovine Mesenchymal Stem Cell-Derived Neurons.

Scrapie is a prion disease affecting sheep and goats and it is considered a prototype of transmissible spongiform encephalopathies (TSEs). Mesenchymal stem cells (MSCs) have been proposed as candidates for developing in vitro models of prion diseases. Murine MSCs are able to propagate prions after previous mouse-adaptation of prion strains and, although ovine MSCs express the cellular prion protein (PrPC), their susceptibility to prion infection has never been investigated. Here, we analyze the potential of ovine bone marrow-derived MSCs (oBM-MSCs), in growth and neurogenic conditions, to be infected by natural scrapie and propagate prion particles (PrPSc) in vitro, as well as the effect of this infection on cell viability and proliferation. Cultures were kept for 48-72 h in contact with homogenates of central nervous system (CNS) samples from scrapie or control sheep. In growth conditions, oBM-MSCs initially maintained detectable levels of PrPSc post-inoculation, as determined by Western blotting and ELISA. However, the PrPSc signal weakened and was lost over time. oBM-MSCs infected with scrapie displayed lower cell doubling and higher doubling times than those infected with control inocula. On the other hand, in neurogenic conditions, oBM-MSCs not only maintained detectable levels of PrPSc post-inoculation, as determined by ELISA, but this PrPSc signal also increased progressively over time. Finally, inoculation with CNS extracts seems to induce the proliferation of oBM-MSCs in both growth and neurogenic conditions. Our results suggest that oBM-MSCs respond to prion infection by decreasing their proliferation capacity and thus might not be permissive to prion replication, whereas ovine MSC-derived neuron-like cells seem to maintain and replicate PrPSc.