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Neurodegenerative diseases (NDs) are some of the most important health challenges modern medicine and advanced societies face. Indeed, the number of patients affected by one of these illnesses will increase in the following years at the same rate that human life expectancy allows us to live longer. Despite many years of research, NDs remain invariably fatal. A complete understanding of the exact mechanisms leading to neuronal death, which will ideally allow preclinical detection and the development of effective treatments, has not yet been achieved. However, a great deal of information about ND pathology and the search for possible therapies has been acquired using animal models and more precisely transgenic mouse models. In this review, the main contributions of these powerful research tools in NDs as well as their advantages and caveats are discussed.

Biomarkers are becoming increasingly important for the differential diagnosis of neurodegenerative diseases. Previous observations indicated neurofilament light chain (NfL) as a potential blood-based biomarker for sporadic Creutzfeldt-Jakob disease (sCJD). Here, we investigated the stability, inter-assay/intra-assay variation and the regulation of NfL levels in CSF and plasma in a large cohort of sCJD patients by using a single-molecule array (SIMOA). We defined cutoffs for an accurate diagnosis and measured plasma NfL level in prion-infected mice models at different time points to identify the potential dynamics throughout the disease. Our analyses confirmed CSF and plasma NfL as stable and consistent marker for sCJD. Receiver operating characteristic (ROC) curve analysis showed an AUC of 0.92-0.93 to distinguish sCJD from control groups. Newly defined cutoffs revealed good diagnostic accuracies of CSF and plasma NfL, indicated by a sensitivity of 80-83.5% and a specificity of 87.4-91%. Studies on two humanized prion-infected mice lines (Tg340-PRNP 129MM and Tg361-PRNP 129VV) revealed increased plasma NfL levels in a late pre-clinical or very early clinical stage between 120-150 days post-inoculation. In conclusion, our work supports the potential use of CSF and plasma NfL as a very early biomarker in sCJD diagnostic with good diagnostic accuracies.

Triggering receptor expressed on myeloid cells 2 (TREM2) is an innate immune cell surface receptor that regulates microglial function and is involved in the pathophysiology of several neurodegenerative diseases. Its soluble form (sTREM2) results from shedding of the TREM2 ectodomain. The role of TREM2 in prion diseases, a group of rapidly progressive dementias remains to be elucidated. In the present study, we analysed the expression of TREM2 and its main sheddase ADAM10 in the brain of sporadic Creutzfeldt-Jakob disease (sCJD) patients and evaluated the role of CSF and plasma sTREM2 as a potential diagnostic marker of prion disease. Our data indicate that, compared to controls, TREM2 is increased in sCJD patient brains at the mRNA and protein levels in a regional and subtype dependent fashion, and expressed in a subpopulation of microglia. In contrast, ADAM10 is increased at the protein, but not the mRNA level, with a restricted neuronal expression. Elevated CSF sTREM2 is found in sCJD, genetic CJD with mutations E200K and V210I in the prion protein gene (PRNP), and iatrogenic CJD, as compared to healthy controls (HC) (AUC = 0.78-0.90) and neurological controls (AUC = 0.73-0.85), while CSF sTREM2 is unchanged in fatal familial insomnia. sTREM2 in the CSF of cases with Alzheimer's disease, and multiple sclerosis was not significantly altered in our series. CSF sTREM2 concentrations in sCJD are PRNP codon 129 and subtype-related, correlate with CSF 14-3-3 positivity, total-tau and YKL-40, and increase with disease progression. In plasma, sTREM2 is increased in sCJD compared with HC (AUC = 0.80), displaying positive correlations with plasma total-tau, neurofilament light, and YKL-40. We conclude that comparative study of TREM2 in brain and biological fluids of prion diseases reveals TREM2 to be altered in human prion diseases with a potential value in target engagement, patient stratification, and disease monitoring.

Although experimental transmission of bovine spongiform encephalopathy (BSE) to pigs and transgenic mice expressing pig cellular prion protein (PrPC) (porcine PrP [PoPrP]-Tg001) has been described, no natural cases of prion diseases in pig were reported. This study analyzed pig-PrPC susceptibility to different prion strains using PoPrP-Tg001 mice either as animal bioassay or as substrate for protein misfolding cyclic amplification (PMCA). A panel of isolates representatives of different prion strains was selected, including classic and atypical/Nor98 scrapie, atypical-BSE, rodent scrapie, human Creutzfeldt-Jakob-disease and classic BSE from different species. Bioassay proved that PoPrP-Tg001-mice were susceptible only to the classic BSE agent, and PMCA results indicate that only classic BSE can convert pig-PrPC into scrapie-type PrP (PrPSc), independently of the species origin. Therefore, conformational flexibility constraints associated with pig-PrP would limit the number of permissible PrPSc conformations compatible with pig-PrPC, thus suggesting that pig-PrPC may constitute a paradigm of low conformational flexibility that could confer high resistance to the diversity of prion strains.

The diversity of goat scrapie strains in Europe has recently been studied using bioassays in a wide collection of rodent models, resulting in the classification of classical scrapie into four different categories. However, the sole use of the first passage does not lead to isolate adaptation and identification of the strains involved and might therefore lead to misclassification of some scrapie isolates. Therefore, this work reports the complete transmission study of a wide collection of goat transmissible spongiform encephalopathy (TSE) isolates by intracranial inoculation in two transgenic mouse lines overexpressing either small ruminant (TgGoat-ARQ) or bovine (TgBov) PrPC. To compare scrapie strains in sheep and goats, sheep scrapie isolates from different European countries were also included in the study. Once the species barrier phenomenon was overcome, an accurate classification of the isolates was attained. Thus, the use of just two rodent models allowed us to fully differentiate at least four different classical scrapie strains in small ruminants and to identify isolates containing mixtures of strains. This work reinforces the idea that classical scrapie in small ruminants is a prion disease caused by multiple different prion strains and not by a single strain, as is the case for epidemic classical bovine spongiform encephalopathy (BSE-C). In addition, the clear dissimilarity between the different scrapie strains and BSE-C does not support the idea that classical scrapie is the origin of epidemic BSE-C.

E/D163 polymorphism of dog prion protein (PrP) has been recently proposed as the variant responsible for canid prion resistance. To further investigate the protective role of this variant against prion replication, the transgenic mouse model OvPrP-Tg532 expressing sheep/goat PrP carrying the substitution D162 (equivalent to D163 position of dog PrP) was generated and intracranially inoculated with a broad collection of small ruminant prion strains. OvPrP-Tg532 mice showed resistance to classical bovine spongiform encephalopathy (BSE) from sheep and some classical scrapie isolates from sheep and goat but were susceptible to ovine atypical L-BSE and numerous classical scrapie isolates. Strikingly, some of these classical scrapie isolates showed a shift in their prion strain properties. These results suggest that other PrP residues apart from E/D163 variant of dog PrP or factors distinct than PrP may participate in prion resistance of canids and that different factors may be required for D162 sheep PrP to provide effective protection to sheep against ruminant prions.

More than 40 pathogenic heterozygous PRNP mutations causing inherited prion diseases have been identified to date. Recessive inherited prion disease has not been described to date.

Current classifications of sporadic Creutzfeldt-Jakob disease (sCJD) identify five subtypes associated with different disease phenotypes. Most of these histopathological phenotypes (histotypes) co-distribute with distinct pairings of methionine (M)/valine (V) genotypes at codon 129 of the prion protein (PrP) gene and the type (1 or 2) of the disease-associated PrP (PrPD). Types 1 and 2 are defined by the molecular mass (~ 21 kDa and ~ 19 kDa, respectively) of the unglycosylated isoform of the proteinase K-resistant PrPD (resPrPD). We recently reported that the sCJDVV1 subtype (129VV homozygosity paired with PrPD type 1, T1) shows an electrophoretic profile where the resPrPD unglycosylated isoform is characterized by either one of two single bands of ~ 20 kDa (T120) and ~ 21 kDa (T121), or a doublet of ~ 21-20 kDa (T121-20). We also showed that T120 and T121 in sCJDVV have different conformational features but are associated with indistinguishable histotypes. The presence of three distinct molecular profiles of T1 is unique and raises the issue as to whether T120 and T121 represent distinct prion strains. To answer this question, brain homogenates from sCJDVV cases harboring each of the three resPrPD profiles, were inoculated to transgenic (Tg) mice expressing the human PrP-129M or PrP-129V genotypes. We found that T120 and T121 were faithfully replicated in Tg129V mice. Electrophoretic profile and incubation period of mice challenged with T121-20 resembled those of mice inoculated with T121 and T120, respectively. As in sCJDVV1, Tg129V mice challenged with T121 and T120 generated virtually undistinguishable histotypes. In Tg129M mice, T121 was not replicated while T120 and T121-20 generated a ~ 21-20 kDa doublet after lengthier incubation periods. On second passage, Tg129M mice incubation periods and regional PrP accumulation significantly differed in T120 and T121-20 challenged mice. Combined, these data indicate that T121 and T120 resPrPD represent distinct human

Early studies in transgenic mouse lines have shown that the coexpression of endogenous murine prion protein (PrPC) and transgenic PrPC from another species either inhibits or allows the propagation of prions, depending on the infecting prion strain and interacting protein species. The way whereby this phenomenon, so-called "interference," is modulated remains to be determined. In this study, different transgenic mouse lines were crossbred to produce mice coexpressing bovine and porcine PrPC, bovine and murine PrPC, or murine and porcine PrPC These animals and their respective hemizygous controls were inoculated with several prion strains from different sources (cattle, mice, and pigs) to examine the effects of the simultaneous presence of PrPC from two different species. Our results indicate interference with the infection process, manifested as extended survival times and reduced attack rates. The interference with the infectious process was reduced or absent when the potentiality interfering PrPC species was efficiently converted by the inoculated agent. However, the propagation of the endogenous murine PrPSc was favored, allowing us to speculate that host-specific factors may disturb the interference caused by the coexpression of an exogenous second PrPC IMPORTANCE Prion propagation can be interfered with by the expression of a second prion protein in the host. In the present study, we investigated prion propagation in a host expressing two different prion protein genes. Our findings indicate that the ability of the second prion protein to interfere with prion propagation is related to the transmissibility of the prion in the host expressing only the interfering prion protein. The interference detected occurs in a prion strain-dependent manner. Interestingly, a bias favoring the propagation of the murine PrP allele has been observed. These results open the door to future studies in order to determine the role of host factors other than the PrP amino acid sequence

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.

Sporadic Creutzfeldt-Jakob disease (sCJD) cases are currently classified according to the methionine/valine polymorphism at codon 129 of the PRNP gene and the proteinase K-digested abnormal prion protein (PrPres) isoform identified by Western blotting (type 1 or type 2). Converging evidence led to the view that MM/MV1, VV/MV2, and VV1 and MM2 sCJD cases are caused by distinct prion strains. However, in a significant proportion of sCJD patients, both type 1 and type 2 PrPres were reported to accumulate in the brain, which raised questions about the diversity of sCJD prion strains and the coexistence of two prion strains in the same patient. In this study, a panel of sCJD brain isolates (n = 29) that displayed either a single or mixed type 1/type 2 PrPres were transmitted into human-PrP-expressing mice (tgHu). These bioassays demonstrated that two distinct prion strains (M1CJD and V2CJD) were associated with the development of sCJD in MM1/MV1 and VV2/MV2 patients. However, in about 35% of the investigated VV and MV cases, transmission results were consistent with the presence of both M1CJD and V2CJD strains, including in patients who displayed a "pure" type 1 or type 2 PrPres The use of a highly sensitive prion in vitro amplification technique that specifically probes the V2CJD strain revealed the presence of the V2CJD prion in more than 80% of the investigated isolates, including isolates that propagated as a pure M1CJD strain in tgHu. These results demonstrate that at least two sCJD prion strains can be present in a single patient.IMPORTANCE sCJD occurrence is currently assumed to result from spontaneous and stochastic formation of a misfolded PrP nucleus in the brains of affected patients. This original nucleus then recruits and converts nascent PrPC into PrPSc, leading to the propagation of prions in the patient's brain. Our study demonstrates the coexistence of two prion strains in the brains of a majority of the 23 sCJD patients investigated. The relative propor

MicroRNAs (miRNAs) may contribute to the development and pathology of many neurodegenerative diseases, including prion diseases. They are also promising biomarker candidates due to their stability in body fluids. We investigated miRNA alterations in a Tg501 mouse model of prion diseases that expresses a transgene encoding the goat prion protein (PRNP). Tg501 mice intracranially inoculated with mouse-adapted goat scrapie were compared with age-matched, mock inoculated controls in preclinical and clinical stages. Small RNA sequencing from the cervical spinal cord indicated that miR-223-3p, miR-151-3p, and miR-144-5p were dysregulated in scrapie-inoculated animals before the onset of symptoms. In clinical-stage animals, 23 significant miRNA alterations were found. These miRNAs were predicted to modify the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways including prion disease, extracellular matrix interactions, glutaminergic synapse, axon guidance, and transforming growth factor-beta signaling. MicroRNAs miR-146a-5p (up in cervical spinal cord) and miR-342-3p (down in cervical spinal cord, cerebellum and plasma), both indicated in neurodegenerative diseases earlier, were verified by quantitative real-time polymerase chain reaction (qRT-PCR). Minimal changes observed before the disease onset suggests that most miRNA alterations observed here are driven by advanced prion-associated pathology, possibly limiting their use as diagnostic markers. However, the results encourage further mechanistic studies on miRNA-regulated pathways involved in these neurodegenerative conditions.

Bovine Spongiform Encephalopathy (BSE) is the only animal prion which has been recognized as a zoonotic agent so far. The identification of BSE in two goats raised the need to reliably identify BSE in small ruminants. However, our understanding of scrapie strain diversity in small ruminants remains ill-defined, thus limiting the accuracy of BSE surveillance and spreading fear that BSE might lurk unrecognized in goats. We investigated prion strain diversity in a large panel of European goats by a novel experimental approach that, instead of assessing the neuropathological profile after serial transmissions in a single animal model, was based on the direct interaction of prion isolates with several recipient rodent models expressing small ruminants or heterologous prion proteins. The findings show that the biological properties of scrapie isolates display different patterns of geographical distribution in Europe and suggest that goat BSE could be reliably discriminated from a wide range of biologically and geographically diverse goat prion isolates. Finally, most field prion isolates showed composite strain features, with discrete strain components or sub-strains being present in different proportions in individual goats or tissues. This has important implications for understanding the nature and evolution of scrapie strains and their transmissibility to other species, including humans.

In "Porcine Prion Protein as a Paradigm of Limited Susceptibility to Prion Strain Propagation" by Espinosa et al. [J Infect Dis, doi:10.1093/infdis/jiz646], there was an error in Figure 2 and the footnote corresponding to Supplementary Figure 1 was missing. These have been corrected in the original article. (Figure Presented)., This is a correction to: The Journal of Infectious Diseases, Volume 223, Issue 6, 15 March 2021, Pages 1103–1112, https://doi.org/10.1093/infdis/jiz646

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

Bovine spongiform encephalopathy (BSE) is caused by different prion strains that are discriminated by the molecular characteristics of the pathological prion protein. In 2011, Switzerland reported two presumptive cases of BSE in cattle with a prion protein phenotype different from previously described strains, and it was unclear whether these findings were related to a transmissible disease and have implications on animal and public health. In this study, brain tissues of these cases were inoculated into transgenic mice expressing the bovine prion protein (BoPrP-Tg110) and into cattle. Clinical and pathological investigations as well as molecular testing did not provide evidence for the presence of BSE in the Swiss cases after two passages in BoPrP-Tg110 mice and a challenge period of 3.5 years in cattle. This lack of disease transmission suggests that the Swiss 2011 cases were not affected by a prion disease and were unrelated to the feed-born BSE epidemic.

Co-occurrence of different prion strains into the same host has been recognized as a natural phenomenon for several sporadic Creutzfeldt-Jakob disease (sCJD) patients and natural scrapie cases. The final outcome of prion coinfection is not easily predictable. In addition to the usual factors that influence prion conversion, the replication of one strain may entail positive or negative consequences to the other. The main aim of this study was to gain insights into the prion coinfection and interference concepts and their potential therapeutic implications. Here, different mouse models were challenged with several combinations of prion strains coupled on the basis of the lengths of their incubation periods and the existence/absence of a species barrier in the tested animal model. We found that nontransmissible strains can interfere the replication of fully transmissible strains when there is a species transmission barrier involved, as happened with the combination of a mouse (22L) and a human (sCJD) strain. However, this phenomenon seems to be strain dependent, since no interference was observed when the human strain coinoculated was vCJD. For the other combinations tested in this study, the results suggest that both strains replicate independently without effect on the replication of one over the other. It is common that the strain with more favorable conditions (e.g., a higher speed of disease development or the absence of a species barrier) ends being the only one detectable at the terminal stage of the disease. However, this does not exclude the replication of the least favored strain, leading to situations of the coexistence of prion strains.IMPORTANCE As a general conclusion, the outcome of prion coinfection is strongly dependent on the strain combination and the model utilized and is therefore difficult to predict. The coexistence of several prion strains may remain undetected if one of the strains has more favorable conditions to replicate in the host. The use

Bovine spongiform encephalopathy (BSE) is the only known zoonotic prion that causes variant Creutzfeldt-Jakob disease (vCJD) in humans. The major risk determinant for this disease is the polymorphic codon 129 of the human prion protein (Hu-PrP), where either methionine (Met129) or valine (Val129) can be encoded. To date, all clinical and neuropathologically confirmed vCJD cases have been Met129 homozygous, with the exception of 1 recently reported Met/Val heterozygous case. Here, we found that transgenic mice homozygous for Val129 Hu-PrP show severely restricted propagation of the BSE prion strain, but this constraint can be partially overcome by adaptation of the BSE agent to the Met129 Hu-PrP. In addition, the transmission of vCJD to transgenic mice homozygous for Val129 Hu-PrP resulted in a prion with distinct strain features. These observations may indicate increased risk for vCJD secondary transmission in Val129 Hu-PrP–positive humans with the emergence of new strain features.

Reelin is an extracellular glycoprotein involved in key cellular processes in developing and adult nervous system, including regulation of neuronal migration, synapse formation, and plasticity. Most of these roles are mediated by the intracellular phosphorylation of disabled-1 (Dab1), an intracellular adaptor molecule, in turn mediated by binding Reelin to its receptors. Altered expression and glycosylation patterns of Reelin in cerebrospinal and cortical extracts have been reported in Alzheimer’s disease. However, putative changes in Reelin are not described in natural prionopathies or experimental models of prion infection or toxicity. With this is mind, in the present study, we determined that Reelin protein and mRNA levels increased in CJD human samples and in mouse models of human prion disease in contrast to murine models of prion infection. However, changes in Reelin expression appeared only at late terminal stages of the disease, which prevent their use as an efficient diagnostic biomarker. In addition, increased Reelin in CJD and in in vitro models does not correlate with Dab1 phosphorylation, indicating failure in its intracellular signaling. Overall, these findings widen our understanding of the putative changes of Reelin in neurodegeneration.

Host prion (PrPC) genotype is a major determinant for the susceptibility to prion diseases. The Q/K222-PrPC polymorphic variant provides goats and mice with high resistance against classical scrapie and bovine spongiform encephalopathy (BSE); yet its effect against atypical scrapie is unknown. Here, transgenic mice expressing the goat wild-type (wt) or the K222-PrPC variant were intracerebrally inoculated with several natural cases of atypical scrapie from sheep and goat and their susceptibility to the prion disease was determined. Goat wt and K222-PrPC transgenic mice were 100% susceptible to all the atypical scrapie isolates, showing similar survival times and almost identical disease phenotypes. The capacity of the K222-PrPC variant to replicate specifically the atypical scrapie strain as efficiently as the goat wt PrPC, but not the classical scrapie or cattle-BSE as previously reported, further suggests the involvement of concrete areas of the host PrPC in the strain-dependent replication of prions. © 2016 The Author(s).

The environment plays a key role in horizontal transmission of prion diseases, since prions are extremely resistant to classical inactivation procedures. In prior work, we observed the high stability of bovine spongiform encephalopathy (BSE) infectivity when these prions were incubated in aqueous media such as phosphate-buffered saline (PBS) or wastewater for nearly nine months. As a continuation of this experiment, the same samples were maintained in PBS or wastewater for five additional years and residual BSE infectivity was assessed in bovine PrPC transgenic mice. Over this long time period (more than six years), BSE infectivity was reduced by three and one orders of magnitude in wastewater and PBS respectively. To rule out a possible agent specific effect, sheep scrapie prions were subjected to the same experimental protocol, using eight years as the experimental end-point. No significant reduction in scrapie infectivity was observed over the first nine months of wastewater incubation while PBS incubation for eight years only produced a two logarithmic unit reduction in infectivity. By contrast, the dynamics of PrPRes persistence was different, disappearing progressively over the first year. The long persistence of prion infectivity observed in this study for two different agents provides supporting evidence of the assumed high stability of these agents in aquatic environments and that environmental processes or conventional wastewater treatments with low retention times would have little impact on prion infectivity. These results could have great repercussions in terms of risk assessment and safety for animals and human populations. © 2016 Elsevier Inc.

Bank vole is a rodent species that shows differential susceptibility to the experimental transmission of different prion strains. In this work, the transmission features of a panel of diverse prions with distinct origins were assayed both in bank vole expressing methionine at codon 109 (Bv109M) and in transgenic mice expressing physiological levels of bank vole PrPC (the BvPrP-Tg407 mouse line). This work is the first systematic comparison of the transmission features of a collection of prion isolates, representing a panel of diverse prion strains, in a transgenic-mouse model and in its natural counterpart. The results showed very similar transmission properties in both the natural species and the transgenic-mouse model, demonstrating the key role of the PrP amino acid sequence in prion transmission susceptibility. However, differences in the PrPSc types propagated by Bv109M and BvPrP-Tg407 suggest that host factors other than PrPC modulate prion strain features. © 2016, American Society for Microbiology. All Rights Reserved.

Bovine spongiform encephalopathy (BSE) created a global European crisis in the 1980s and 90s, with very serious health and economic implications. Classical BSE now appears to be under control, to a great extent as a result of a global research effort that identified the sources of prions in meat and bone meal (MBM) and developed new animal-testing tools that guided policy. Priority (www.prionpriority.eu) was a European Union (EU) Framework Program 7 (FP7)-funded project through which 21 European research institutions and small and medium enterprises (SMEs) joined efforts between 2009 and 2014, to conduct coordinated basic and applied research on prions and prion diseases. At the end of the project, the Priority consortium drafted a position paper (www.prionpriority.eu/Priority position paper) with its main conclusions. In the present opinion paper, we summarize these conclusions. With respect to the issue of re-introducing ruminant protein into the feed-chain, our opinion is that sustaining an absolute ban on feeding ruminant protein to ruminants is essential. In particular, the spread and impact of non-classical forms of scrapie and BSE in ruminants is not fully understood and the risks cannot be estimated. Atypical prion agents will probably continue to represent the dominant form of prion diseases in the near future in Europe. Atypical L-type BSE has clear zoonotic potential, as demonstrated in experimental models. Similarly, there are now data indicating that the atypical scrapie agent can cross various species barriers. More epidemiological data from large cohorts are necessary to reach any conclusion on the impact of its transmissibility on public health. Re-evaluations of safety precautions may become necessary depending on the outcome of these studies. Intensified searching for molecular determinants of the species barrier is recommended, since this barrier is key for important policy areas and risk assessment. Understanding the structural basis for

Background The infectious agent responsible for the bovine spongiform encephalopathy (BSE) epidemic in Great Britain is a transmissible spongiform encephalopathy (TSE) strain with uniform properties but the origin of this strain remains unknown. Based on the hypothesis that classical BSE may have been caused by a TSE strain present in sheep, cattle were inoculated intracerebrally with two different pools of brains from scrapie-affected sheep sourced prior to and during the BSE epidemic to investigate resulting disease phenotypes and characterise their causal agents by transmission to rodents. Results As reported in 2006, intracerebral inoculation of cattle with pre-1975 and post-1990 scrapie brain pools produced two distinct disease phenotypes, which were unlike classical BSE. Subsequent to that report none of the remaining cattle, culled at 10 years post inoculation, developed a TSE. Retrospective Western immunoblot examination of the brains from TSE cases inoculated with the pre-1975 scrapie pool revealed a molecular profile similar to L-type BSE. The inoculation of transgenic mice expressing the bovine, ovine, porcine, murine or human prion protein gene and bank voles with brains from scrapie-affected cattle did not detect classical or atypical BSE strains but identified two previously characterised scrapie strains of sheep. Conclusions Characterisation of the causal agents of disease resulting from exposure of cattle to naturally occurring scrapie agents sourced in Great Britain did not reveal evidence of classical or atypical BSE, but did identify two distinct previously recognised strains of scrapie. Although scrapie was still recognizable upon cattle passage there were irreconcilable discrepancies between the results of biological strain typing approaches and molecular profiling methods, suggesting that the latter may not be appropriate for the identification and differentiation of atypical, particularly L-type, BSE agents from cattle experimentally infected

Background. The prion protein-encoding gene (PRNP) is one of the major determinants for scrapie occurrence in sheep and goats. However, its effect on bovine spongiform encephalopathy (BSE) transmission to goats is not clear. Methods. Goats harboring wild-type, R/Q211 or Q/K222 PRNP genotypes were orally inoculated with a goat-BSE isolate to assess their relative susceptibility to BSE infection. Goats were killed at different time points during the incubation period and after the onset of clinical signs, and their brains as well as several peripheral tissues were analyzed for the accumulation of pathological prion protein (PrPSc) and prion infectivity by mouse bioassay. Results. R/Q211 goats displayed delayed clinical signs compared with wild-type goats. Deposits of PrPSc were detected only in brain, whereas infectivity was present in peripheral tissues too. In contrast, none of the Q/K222 goats showed any evidence of clinical prion disease. No PrPSc accumulation was observed in their brains or peripheral tissues, but very low infectivity was detected in some tissues very long after inoculation (44-45 months). Conclusions. These results demonstrate that transmission of goat BSE is genotype dependent, and they highlight the pivotal protective effect of the K222 PRNP variant in the oral susceptibility of goats to BSE. © 2015 The Author.

The specific characteristics of Transmissible Spongiform Encephalopathy (TSE) strains may be altered during passage across a species barrier. In this study we investigated the biochemical and biological characteristics of Bovine Spongiform Encephalopathy (BSE) after transmission in both natural host species (cattle, sheep, pigs and mice) and in transgenic mice overexpressing the corresponding cellular prion protein (PrPC) in comparison with other non-BSE related prions from the same species. After these passages, most features of the BSE agent remained unchanged. BSE-derived agents only showed slight modifications in the biochemical properties of the accumulated PrPSc, which were demonstrated to be reversible upon re-inoculation into transgenic mice expressing bovine-PrPC. Transmission experiments in transgenic mice expressing bovine, porcine or human-PrP revealed that all BSE-derived agents were transmitted with no or a weak transmission barrier. In contrast, a high species barrier was observed for the non-BSE related prions that harboured an identical PrP amino acid sequence, supporting the theory that the prion transmission barrier is modulated by strain properties (presumably conformation-dependent) rather than by PrP amino acid sequence differences between host and donor. As identical results were observed with prions propagated either in natural hosts or in transgenic mouse models, we postulate that the species barrier and its passage consequences are uniquely governed by the host PrPC sequence and not influenced by other host genetic factors. The results presented herein reinforce the idea that the BSE agent is highly promiscuous, infecting other species, maintaining its properties in the new species, and even increasing its capabilities to jump to other species including humans. These data are essential for the development of an accurate risk assessment for BSE. © 2014 Torres et al.

The prion protein-encoding gene (prnp) strongly influences the susceptibility of small ruminants to transmissible spongiform encephalopathies (TSEs). Hence, selective breeding programs have been implemented to increase sheep resistance to scrapie. For goats, epidemiological and experimental studies have provided some association between certain polymorphisms of the cellular prion protein (PrPC) and resistance to TSEs. Among them, the Q/K polymorphism at PrPC codon 222 (Q/K222) yielded the most promising results. In this work, we investigated the individual effects of the K222-PrPC variant on the resistance/susceptibility of goats to TSEs. For that purpose, we generated two transgenic mouse lines, expressing either the Q222 (wild type) or K222 variant of goat PrPC. Both mouse lines were challenged intracerebrally with a panel of TSE isolates. Transgenic mice expressing the wildtype (Q222) allele were fully susceptible to infection with all tested isolates, whereas transgenic mice expressing similar levels of the K222 allele were resistant to all goat scrapie and cattle BSE isolates but not to goat BSE isolates. Finally, heterozygous K/Q222 mice displayed a reduced susceptibility to the tested panel of scrapie isolates. These results demonstrate a highly protective effect of the K222 variant against a broad panel of different prion isolates and further reinforce the argument supporting the use of this variant in breeding programs to control TSEs in goat herds. © 2014, American Society for Microbiology.

Using different prion strains, such as the variant Creutzfeldt-Jakob disease agent and the atypical bovine spongiform encephalopathy agents, and using transgenic mice expressing human or bovine prion protein, we assessed the reliability of protein misfolding cyclic amplification (PMCA) to model interspecies and genetic barriers to prion transmission. We compared our PMCA results with in vivo transmission data characterized by attack rates, i.e.;the percentage of inoculated mice that developed the disease. Using 19 seed/substrate combinations, we observed that a significant PMCA amplification was only obtained when the mouse line used as substrate is susceptible to the corresponding strain. Our results suggest that PMCA provides a useful tool to study genetic barriers to transmission and to study the zoonotic potential of emerging prion strains. © 2014 by the authors; licensee MDPI, Basel, Switzerland.

Variably protease-sensitive prionopathy (VPSPr), a recently identified and seemingly sporadic human prion disease, is distinct from Creutzfeldt-Jakob disease (CJD) but shares features of Gerstmann-Sträussler-Scheinker disease (GSS). However, contrary to exclusively inherited GSS, no prion protein (PrP) gene variations have been detected in VPSPr, suggesting that VPSPr might be the long-sought sporadic form of GSS. The VPSPr atypical features raised the issue of transmissibility, a prototypical property of prion diseases. We inoculated VPSPr brain homogenate into transgenic mice expressing various levels of human PrP (PrPC). On first passage, 54% of challenged mice showed histopathologic lesions, and 34% harbored abnormal PrP similar to that of VPSPr. Surprisingly, no prion disease was detected on second passage. We concluded that VPSPr is transmissible; thus, it is an authentic prion disease. However, we speculate that normal human PrPC is not an efficient conversion substrate (or mouse brain not a favorable environment) and therefore cannot sustain replication beyond the first passage. © 2014, Centers for Disease Control and Prevention (CDC). All rights reserved.

Although Bovine Spongiform Encephalopathy (BSE) is the cause of variant Creutzfeldt Jakob disease (vCJD) in humans, the zoonotic potential of scrapie prions remains unknown. Mice genetically engineered to overexpress the human prion protein (tgHu) have emerged as highly relevant models for gauging the capacity of prions to transmit to humans. These models can propagate human prions without any apparent transmission barrier and have been used used to confirm the zoonotic ability of BSE. Here we show that a panel of sheep scrapie prions transmit to several tgHu mice models with an efficiency comparable to that of cattle BSE. The serial transmission of different scrapie isolates in these mice led to the propagation of prions that are phenotypically identical to those causing sporadic CJD (sCJD) in humans. These results demonstrate that scrapie prions have a zoonotic potential and raise new questions about the possible link between animal and human prions. © 2014 Macmillan Publishers Limited. All rights reserved.

Objective. To determine whether the level of apoptosis induced by infectious pancreatic necrosis virus (IPNV) is related to the amino acid sequence of the BH2 domain of the VP5 protein and the level of infectivity. Materials and methods. Three IPNV strains were used, the VP2 protein gene was amplified for genotyping and the VP5 sequence was also obtained. The infectivity of the strains was calculated using the viral titer obtained at 12, 24, 36 and 45 hpi in CHSE-214 cells. The percentage of apoptosis in infected cells was visualized by TUNEL assay and immunohistochemistry (caspase 3 detection). Results. The V70/06 and V33/98 strains corresponded to genotype Sp, while V112/06 to VR-299; the amino acid analysis of the V70/06 strain allows its classification as middle virulent strain and V33/98 and V112/06 strains as low virulent ones; infection with the V112/06 strain produced a lower viral titer (p<0.05). The VP5 gene of the 3 strains showed four homologous domains to Bcl-2, however, the BH2 domain was truncated in V70/06 and V33/98 (12 kDa), being complete (15kDa) in V112/06, which also showed the Trp155 residue, equivalent to Trp188 considered as a critical factor for the function of Bcl-2. The average apoptosis was below 12%, showing no differences between strains (p>0.05). Conclusions. The results showed that the differences in the BH2 sequence of the VP5 protein, infectivity and the VP2 sequence are not associated with the modulation of apoptosis., Objetivo. Determinar si el nivel de apoptosis inducido por cepas del virus de la necrosis pancreática infecciosa (IPNV) tiene relación con la secuencia aminoacídica del dominio BH2 de la proteína VP5 y el nivel de infectividad. Materiales y métodos. Se utilizaron tres cepas de IPNV; el gen de la proteína VP2 fue amplificado para genotipificación y se obtuvo la secuencia de VP5. La infectividad de las cepas se calculó mediante el título viral obtenido a 12, 24, 36 y 45 hpi en células CHSE-214. Los porcentajes de apoptosis en células infectadas se visualizaron mediante ensayo TUNEL e inmuno-histoquímica (detección de caspasa 3). Resultados. Las cepas V70/06 y V33/98 correspondieron a genotipo Sp, mientras que V112/06 a VR-299; el análisis aminoacídico relacionó a V70/06 como cepa de mediana virulencia y a V33/98 y V112/06 de baja virulencia; la infección con V112/06 produjo menor título viral (p<0.05). El gen VP5 de las 3 cepas presentó los cuatro dominios homólogos a Bcl-2; sin embargo, el dominio BH2 fue truncado en V70/06 y V33/98 (12 kDa); siendo completo (15kDa) en V112/06, que además, presentó el residuo Trp155, equivalente a Trp188 considerado factor crítico para la función de Bcl-2. El promedio de apoptosis fue inferior a 12%, no se observaron diferencias entre cepas (p>0.05). Conclusiones. Los resultados mostraron que las diferencias en la secuencia de BH2 de la proteína VP5, la infectividad y en la secuencia de la proteína VP2 no están asociadas con la modulación de apoptosis.

We generated transgenic mice expressing bovine cellular prion protein (PrPC) with a leucine substitution at codon 113 (113L). This protein is homologous to human protein with mutation 102L, and its genetic link with Gerstmann- Sträussler-Scheinker syndrome has been established. This mutation in bovine PrPC causes a fully penetrant, lethal, spongiform encephalopathy. This genetic disease was transmitted by intracerebral inoculation of brain homogenate from ill mice expressing mutant bovine PrP to mice expressing wild-type bovine PrP, which indicated de novo generation of infectious prions. Our findings demonstrate that a single amino acid change in the PrPC sequence can induce spontaneous generation of an infectious prion disease that differs from all others identified in hosts expressing the same PrPC sequence. These observations support the view that a variety of infectious prion strains might spontaneously emerge in hosts displaying random genetic PrPC mutations.

Horizontal transmission of prion diseases through the environment represents a considerable concern. Prions are extremely resistant to inactivation and are thought to enter the environment after burial of animal mortalities or through biosolids from wastewater treatment plants. In addition, deposition of prions in the environment through biological fluids and/or faeces has been proved in the last years. Little is known about the behaviour of prion infectivity in the environment. In this study, the persistence of BSE infectious agent in sewage has been assessed by both PrP Res immunoblotting and mouse bioassay in a long-term incubation study. Results indicated that no PrP Res was detected after 150 day of incubation and consistent with this, a statistical regression model estimated 2-logs decay in 151 day. In contrast, no reduction in infectivity was observed during this period. Similarly, BSE infectivity remained unaltered after incubation in PBS for 265 day, whereas PrP Res levels dropped progressively over the length of the study. These results indicate that in sewage and PBS, prion infectivity persists longer and with different dynamics than its commonly used marker PrP Res. Thus, mathematical models computed on the basis of PrP Res detection were unable to predict inactivation of prion infectivity. It is also reasonable to assume that conventional wastewater treatments with low retention times could have a very limited impact on prion infectivity. This data is essential for the development of accurate risk assessment analysis for BSE and other prion diseases in the environment. © 2012 Elsevier Inc.

Bovine spongiform encephalopathy (BSE) and BSErelated disorders have been associated with a single major prion strain. Recently, 2 atypical, presumably sporadic forms of BSE have been associated with 2 distinct prion strains that are characterized mainly by distinct Western blot profi les of abnormal protease-resistant prion protein (PrPres), named high-type (BSE-H) and low-type (BSE-L), that also differed from classical BSE. We characterized 5 atypical BSE-H isolates by analyzing their molecular and neuropathologic properties during transmission in transgenic mice expressing homologous bovine prion protein. Unexpectedly, in several inoculated animals, strain features emerged that were highly similar to those of classical BSE agent. These fi ndings demonstrate the capability of an atypical bovine prion to acquire classical BSE-like properties during propagation in a homologous bovine prion protein context and support the view that the epidemic BSE agent could have originated from such a cattle prion.

A new variant of Creutzfeldt Jacob Disease (vCJD) was identified in humans and linked to the consumption of Bovine Spongiform Encephalopathy (BSE)-infected meat products. Recycling of ruminant tissue in meat and bone meal (MBM) has been proposed as origin of the BSE epidemic. During this epidemic, sheep and goats have been exposed to BSE-contaminated MBM. It is well known that sheep can be experimentally infected with BSE and two field BSE-like cases have been reported in goats. In this work we evaluated the human susceptibility to small ruminants-passaged BSE prions by inoculating two different transgenic mouse lines expressing the methionine (Met) allele of human PrP at codon 129 (tg650 and tg340) with several sheep and goat BSE isolates and compared their transmission characteristics with those of cattle BSE. While the molecular and neuropathological transmission features were undistinguishable and similar to those obtained after transmission of vCJD in both transgenic mouse lines, sheep and goat BSE isolates showed higher transmission efficiency on serial passaging compared to cattle BSE. We found that this higher transmission efficiency was strongly influenced by the ovine PrP sequence, rather than by other host species-specific factors. Although extrapolation of results from prion transmission studies by using transgenic mice has to be done very carefully, especially when human susceptibility to prions is analyzed, our results clearly indicate that Met129 homozygous individuals might be susceptible to a sheep or goat BSE agent at a higher degree than to cattle BSE, and that these agents might transmit with molecular and neuropathological properties indistinguishable from those of vCJD. Our results suggest that the possibility of a small ruminant BSE prion as vCJD causal agent could not be ruled out, and that the risk for humans of a potential goat and/or sheep BSE agent should not be underestimated. © 2011 Padilla et al.

How susceptible pigs are to infection with sheep prions is unknown. We show, through transmission experiments in transgenic mice expressing porcine prion protein (PrP), that the susceptibility of this mouse model to bovine spongiform encephalopathy (BSE) can be enhanced after its passage in ARQ sheep, indicating that the pathogenicity of the BSE agent is modified after passage in sheep. Transgenic mice expressing porcine PrP were, nevertheless, completely resistant to infection with a broad panel of classical scrapie isolates from different sheep PrP genotypes and with different biochemical characteristics. The atypical (Nor98 like) isolate (SC-PS152) was the only scrapie isolate capable of transmission in these mice, although with a marked transmission barrier. Unexpectedly, the atypical scrapie agent appeared to undergo a strain phenotype shift upon transmission to porcine-PrP transgenic mice and acquired new strain properties, suggesting that atypical scrapie agent may exhibit different phenotypes depending on the host cellular PrP or other genetic factors.

In the present report, the selective detection of sheep PrP haplotypes by monoclonal antibody 2A11 is described. It is showed that the substitution of glutamine by arginine but not by histidine at ovine PrP position 171 abolishes completely the recognition of either PrPc or PrPd by mAb 2A11, in such a way that the application of this antibody allows the unambiguous discrimination of R171 homozygotes. On the basis of the high resistance to classical scrapie and bovine spongiform encephalophaty (BSE) infection associated to the R171 PrP haplotype, animals bearing the ARR allele are currently selected within the scrapie national plan initiated in Great Britain. A 2A11-based immuno enzymatic test have been developed and evaluated using a panel of plasma and sera from sheep of different PrP genotypes and breeds. The test allows the efficient discrimination of R171 homozygotes, R171 heterozygotes and non-R171 carriers, therefore offering a rapid, cheap and easy to use alternative method to select sheep for their resistance to scrapie. © 2007 Elsevier B.V. All rights reserved.

In the past, natural scrapie and bovine spongiform encephalopathy (BSE) infections have essentially not been diagnosed in sheep homozygous for the A136R154R171 haplotype of the prion protein. This genotype was therefore assumed to confer resistance to BSE and classic scrapie under natural exposure conditions. Hence, to exclude prions from the human food chain, massive breeding efforts have been undertaken in the European Union to amplify this gene. We report the identification of 2 natural scrapie cases in ARR/ARR sheep that have biochemical and transmission characteristics similar to cases of classic scrapie, although the abnormally folded prion protein (PrPSc) was associated with a lower proteinase-K resistance. PrPSc was clearly distinct from BSE prions passaged in sheep and from atypical scrapie prions. These findings strongly support the idea that scrapie prions are a mosaic of agents, which harbor different biologic properties, rather than a unique entity.

The presence of BSE prion infectivity in asymptomatic cattle and its tissue distribution are important concerns for both human and veterinary health and food safety. In this work, a collection of tissues from asymptomatic cattle challenged orally with BSE and culled at 20, 24, 27, 30 and 33 months have been used to inoculate intracerebrally BoPrP-Tg110 mice expressing bovine PrP to assess their infectivity. Results demonstrate that BSE infectivity in asymptomatic cattle is essentially restricted to the nervous system, Peyer's patches and tonsils, as reported previously for terminally BSE-diseased cattle. BSE infectivity was detectable in Peyer's patches and tonsils at all time points analysed, but infectivity in nervous tissues (brainstem and sciatic nerve) was only detectable after 27 months from inoculation. Infectivity in brainstem increased markedly at 33 months after inoculation. All other investigated tissues or fluids (spleen, skeletal muscle, blood and urine) revealed no detectable infectivity throughout the time course studied. © 2007 SGM.

Oxidative stress and antioxidants play an important role in neurodegenerative diseases. However, the exact participation of antioxidants in the evolution of prion diseases is still largely unknown. The aim of this study was to assess brain levels of coenzyme Q (CoQ), an endogenous lipophilic antioxidant, and the antioxidant/pro-oxidant status by determining oxidative damage to proteins and lipids after intracerebral bovine spongiform encephalopathy (BSE) infection of transgenic mice expressing bovine prion protein (PrP). Our results indicate that, whereas the ratio between the two CoQ homologues present in mice (CoQ9 and CoQ10) is not altered by prion infection during the course of the disease, significant increases in total CoQ9 and CoQ10 were observed in BSE-infected mice 150 days after inoculation. This time point coincided with the first manifestation of PrPSc deposition in nervous tissue. In addition, CoQ9 and CoQ10 levels, neuropathological alterations, and PrPSc deposition in nervous tissues underwent further increases as the illness progressed. Lipid and protein oxidation were observed only at the final stage of the disease after clinical signs had appeared. These findings indicate upregulation of CoQ9- and CoQ10-dependent antioxidant systems in response to the increased oxidative stress induced by prion infection in nervous tissue. However, the induction of these endogenous antioxidant systems seems to be insufficient to prevent the development of the illness. © 2007 Elsevier Inc. All rights reserved.

Sheep can be experimentally infected with bovine spongiform encephalopathy (BSE), and the ensuing disease is similar to scrapie in terms of pathogenesis and clinical signs. BSE infection in sheep is an animal and human health concern. In this study, the transmission in BoPrP-Tg110 mice of prions from BSE-infected sheep was examined and compared to the transmission of original cattle BSE in cattle and sheep scrapie prions. Our results indicate no transmission barrier for sheep BSE prions to infect BoPrP-Tg110 mice, but the course of the disease is accelerated compared to the effects of the original BSE isolate. The shortened incubation period of sheep BSE in the model was conserved in subsequent passage in BoPrP-Tg110 mice, indicating that it is not related to infectious titer differences. Biochemical signature, lesion profile, and PrPSc deposition pattern of both cattle and sheep BSE were similar. In contrast, all three sheep scrapie isolates tested showed an evident transmission barrier and further adaptation in subsequent passage. Taken together, those data indicate that BSE agent can be altered by crossing a species barrier, raising concerns about the virulence of this new prion towards other species, including humans. The BoPrP-Tg110 mouse bioassay should be considered as a valuable tool for discriminating scrapie and BSE in sheep. Copyright © 2007, American Society for Microbiology. All Rights Reserved.

In this work, transgenic (Tg) mice were generated expressing a bovine prion protein containing five octarepeats (BoPrP5OR-Tg). After intracerebral inoculation of bovine spongiform encephalopathy (BSE) inoculum, these mice suffered a BSE-like neuropathology but survived longer compared with homologous Tg mice expressing similar levels of a six octarepeat BoPrP protein (BoPrp6OR-Tg). De novo-generated five octarepeat (50R) PrPSc showed no biochemical differences from 60R-PrPsc, and the proteinase K-resistant core (Prpres) was biochemically indistinguishable from the 60R counterpart. Lower susceptibility to BSE is suggested for BoPrp5OR-Tg mice, as they were not as efficient at replicating BSE prions from the same natural source inoculum as BoPrp60R-Tg mice expressing similar PrPC levels. These results raise the possibility of selecting cattle breeds bearing the 50R Prnp allele that are less susceptible to prion infection. © 2007 SGM.

Prion diseases are characterized by neuronal loss, astrocytic gliosis, spongiform change, and abnormal protease-resistant prion protein (PrP) deposition. Creutzfeldt-Jakob disease (CJD) is the most prevalent human prion disease, whereas scrapie and bovine spongiform encephalopathy (BSE) are the most common animal prion diseases. Several candidates have been proposed as mediators of degeneration in prion diseases, one of them glutamate. Recent studies have shown reduced metabotropic glutamate receptor/phospholipase C signaling in the cerebral cortex in CJD, suggesting that this important neuromodulator and neuroprotector pathway is attenuated in CJD. Adenosine is involved in the regulation of different metabolic processes under physiological and pathologic conditions. Adenosine function is mediated by adenosine receptors, which are categorized into 4 types A1, A2A, A2B, and A3. A1Rs are G-protein-coupled receptors that induce the inhibition of adenylyl cyclase activity. The most dramatic inhibitory actions of adenosine receptors are on the glutamatergic system. For these reasons, we examined the levels of A1Rs in the frontal cortex of 12 patients with CJD and 6 age-matched controls and in BSE-infected bovine-PrP transgenic mice (BoPrP-Tg110 mice) at different postincubation times to address modifications in A1Rs with disease progression. A significant increase in the protein levels of A1Rs was found in the cerebral cortex in CJD and in the murine BSE model at advanced stages of the disease and coincidental with the appearance of PrP expression. In addition, the activity of A1Rs was analyzed by in vitro assays with isolated membranes of the frontal cortex in CJD. Increased activity of the receptor, as revealed by the decreased forskolin-stimulated cAMP production in response to the A1R agonists cyclohexyl adenosine and cyclopentyl adenosine, was observed in CJD cases when compared with controls. Finally, mRNA A1R levels were similar in CJD and control cases, thus sugg

Oral contamination with bovine spongiform encephalopathy (BSE) agent in susceptible PRNP genotype sheep results in widespread distribution of prion in the host. Because ARR homozygous sheep are considered to be resistant to transmissible spongiform encephalopathies, they have been selected to eradicate scrapie from sheep flocks and to protect the human food chain from small ruminant BSE risk. However, results presented here show that several months after an oral challenge with BSE agent, healthy ARR/ARR sheep can accumulate significant amounts of PrPSc in the spleen. © 2006 SGM.

In transmissible spongiform encephalopathies (TSEs) the prion protein (PrP) plays a central role in pathogenesis. The PrP gene (Prnp) has been described in a number of mammalian and avian species and its expression product, the cellular prion protein (PrPC), has been mapped in brains of different laboratory animals (rodent and non-human primates). However, mapping of PrPC expression in mammalian species suffering from natural (bovine and ovine) and experimental (swine) TSE or in species in which prion disease has never been reported (equine and canine) deserves further attention. Thus, localising the cellular prion protein (PrPC) distribution in brain may be noteworthy for the understanding of prion disease pathogenesis since lesions seem to be restricted to particular brain areas. In the present work, we analysed the distribution of PrPC expression among several brain structures of the above species. Our results suggest that the expression of PrPC, within the same species, differs depending on the brain structure studied, but no essential differences between the PrPC distribution patterns among the studied species could be established. Positive immunoreaction was found mainly in the neuropil and to a lesser extent in neuronal bodies which occasionally appeared strongly stained in discrete regions. Overall, the expression of PrPC in the brain was significantly higher in grey matter areas than in white matter, where accumulation of PrPSc is first observed in prion diseases. Therefore, other factors besides the level of expression of cellular PrP may account for the pathogenesis of TSEs. © Springer-Verlag 2006.

RK13 cell lines generated to express bovine PrPC with a four extra octarepeat insertional mutation (Bo-10ORPrPC) show partially insoluble PrPC and lower rates of cell growth when compared to either the same cells expressing wild type Bo-6ORPrPC or the original RK13 cell line. The expression of Bo-10ORPrPC in cell cultures was also associated with changes in cell size and reorganization of the actin cytoskeleton. This last process was reversed by Clostridium difficile toxin-B, a specific inhibitor of small GTPase proteins. Further, in clones expressing Bo-10ORPrPC, increased proportions of cells at cell cycle stage G2/M were observed. Proteasome inhibitors caused a further expansion of G2/M-stage cells that was more marked in cell lines expressing Bo-10ORPrPC than those expressing Bo-6ORPrPC, while this effect was minimal or null in the original RK13 cell line. Hence, the presence of Bo-10ORPrPC in RK13 cells promotes cell cycle arrest at G2/M, and the effect is amplified by proteasome inhibition. These findings suggest a role for PrPC in cell morphology and cell cycle regulation, and open new avenues for understanding the mechanisms underlying PrP mutation-associated diseases. © 2006 Federation of European Biochemical Studies.

This report represents a case study of an outbreak of African swine fever(ASF) that took place in the autonomic region of Extramadura, Badajoz Province, during the month of August 1992, and aims to describe the Spanish ASF eradication programme as carried out in the field at producer level. Extensive husbandry methods used in the management of Iberian pigs in ASF endemic areas of Spain (about 4% of Spanish territory in 4/52 provinces) makes eradication particularly difficult. Since there is no vaccine available for ASF, the identification and slaughter of carrier animals is crucial to the control of the disease. A case of ASF, which caused one secondary outbreak, was diagnosed on 26 August 1992 and is described in terms of case history, laboratory examination, disease eradication measures and epidemiological observations. Additional evidence is presented in an attempt to evaluate and gain an understanding of the long-term risk of carrier animals, wild European pigs, vector ticks and biting flies as a cause of the persistence in endemic areas of recrudescence of ASF in areas from which the disease was previously eradicated. © 1995 Baillière Tindall.