Clinical and pathologic features of H-type bovine spongiform encephalopathy associated with E211K prion protein polymorphism

Sporadic cases of chronic wasting disease in old moose - an epidemiological study

Transmissible spongiform encephalopathies or prion diseases comprise diseases with different levels of contagiousness under natural conditions. The hypothesis has been raised that the chronic wasting disease (CWD) cases detected in Nordic moose (Alces alces) may be less contagious, or not contagious between live animals under field conditions. This study aims to investigate the epidemiology of CWD cases detected in moose in Norway, Sweden and Finland using surveillance data from 2016 to 2022.In total, 18 CWD cases were detected in Nordic moose. All moose were positive for prion (PrPres) detection in the brain, but negative in lymph nodes, all were old (mean 16 years; range 12-20) and all except one, were female. Age appeared to be a strong risk factor, and the sex difference may be explained by few males reaching high age due to hunting targeting calves, yearlings and males.The cases were geographically scattered, distributed over 15 municipalities. However, three cases were detected in each of two areas, Selbu in Norway and Arjeplog-Arvidsjaur in Sweden. A Monte Carlo simulation approach was applied to investigate the likelihood of such clustering occurring by chance, given the assumption of a non-contagious disease. The empirical P-value for obtaining three cases in one Norwegian municipality was less than 0.05, indicating clustering. However, the moose in Selbu were affected by different CWD strains, and over a 6 year period with intensive surveillance, the apparent prevalence decreased, which would not be expected for an ongoing outbreak of CWD. Likewise, the three cases in Arjeplog-Arvidsjaur could also indicate clustering, but management practices promotes a larger proportion of old females and the detection of the first CWD case contributed to increased awareness and sampling.The results of our study show that the CWD cases detected so far in Nordic moose have a different epidemiology compared to CWD cases reported from North America and in Norwegian reindeer (Rangifer tarandus tarandus). The results support the hypothesis that these cases are less contagious or not contagious between live animals under field conditions. To enable differentiation from other types of CWD, we support the use of sporadic CWD (sCWD) among the names already in use.

Short incubation periods of atypical H-type BSE in cattle with EK211 and KK211 prion protein genotypes after intracranial inoculation

In 2006, a case of atypical H-type BSE (H-BSE) was found to be associated with a germline mutation in the PRNP gene that resulted in a lysine substitution for glutamic acid at codon 211 (E211K). The E211K amino acid substitution in cattle is analogous to E200K in humans, which is associated with the development of genetic Creutzfeldt-Jakob disease (CJD). In the present study, we aimed to determine the effect of the EK211 prion protein genotype on incubation time in cattle inoculated with the agent of H-BSE; to characterize the molecular profile of H-BSE in KK211 and EK211 genotype cattle; and to assess the influence of serial passage on BSE strain. Eight cattle, representing three PRNP genotype groups (EE211, EK211, and KK211), were intracranially inoculated with the agent of H-BSE originating from either a case in a cow with the EE211 prion protein genotype or a case in a cow with E211K amino acid substitution. All inoculated animals developed clinical disease; post-mortem samples were collected, and prion disease was confirmed through enzyme immunoassay, anti-PrPSc immunohistochemistry, and western blot. Western blot molecular analysis revealed distinct patterns in a steer with KK211 H-BSE compared to EK211 and EE211 cattle. Incubation periods were significantly shorter in cattle with the EK211 and KK211 genotypes compared to the EE211 genotype. Inoculum type did not significantly influence the incubation period. This study demonstrates a shorter incubation period for H-BSE in cattle with the K211 genotype in both the homozygous and heterozygous forms.

Discrimination of Classical and Atypical BSE by a Distinct Immunohistochemical PrPSc Profile

Bovine spongiform encephalopathy (BSE) belongs to the group of transmissible spongiform encephalopathies and is associated with the accumulation of a pathological isoform of the host-encoded glycoprotein, designated prion protein (PrP^Sc). Classical BSE (C-type) and two atypical BSE forms (L- and H-type) are known, and can be discriminated by biochemical characteristics. The goal of our study was to identify type-specific PrP^Sc profiles by using Immunohistochemistry. In our study, brain samples from 21 cattle, intracerebrally inoculated with C-, H-, and L-type BSE, were used. In addition, the corresponding samples from three orally C-type BSE infected animals were also included. From all animals, a lesion and PrP^Sc-profiles of six brain regions were determined. The lesion profile and the neuroanatomical distribution of PrP^Sc was highly consistent between the groups, but the immunohistochemical analysis revealed a distinct PrP^Sc profile for the different BSE-types, which included both the topographic and cellular pattern of PrP^Sc. This qualitative and quantitative analysis of PrP^Sc affected structures sheds new light into the pathogenesis of the different BSE types. Furthermore, immunohistochemical characterization is supported as an additional diagnostic tool in BSE surveillance programs, especially when only formalin-fixed tissue samples are available.

Differential Accumulation of Misfolded Prion Strains in Natural Hosts of Prion Diseases

Prion diseases, also known as transmissible spongiform encephalopathies (TSEs), are a group of neurodegenerative protein misfolding diseases that invariably cause death. TSEs occur when the endogenous cellular prion protein (PrP^C) misfolds to form the pathological prion protein (PrP^Sc), which templates further conversion of PrP^C to PrP^Sc, accumulates, and initiates a cascade of pathologic processes in cells and tissues. Different strains of prion disease within a species are thought to arise from the differential misfolding of the prion protein and have different clinical phenotypes. Different strains of prion disease may also result in differential accumulation of PrP^Sc in brain regions and tissues of natural hosts. Here, we review differential accumulation that occurs in the retinal ganglion cells, cerebellar cortex and white matter, and plexuses of the enteric nervous system in cattle with bovine spongiform encephalopathy, sheep and goats with scrapie, cervids with chronic wasting disease, and humans with prion diseases. By characterizing TSEs in their natural host, we can better understand the pathogenesis of different prion strains. This information is valuable in the pursuit of evaluating and discovering potential biomarkers and therapeutics for prion diseases.

In-depth examination of PrPSc in Holstein cattle carrying the E211K somatic mutation of the bovine prion protein gene (PRNP)

Prion diseases are transmissible spongiform encephalopathies caused by deleterious prion protein (PrP^Sc ) derived from normal prion protein (PrP^C ), which is encoded by the prion protein gene (PRNP). We performed an in-depth examination to detect PrP^Sc by using enzyme immunoassay (EIA), real-time quaking-induced conversion reactions (RT-QuIC) and protein misfolding cyclic amplification (PMCA) in nine brain tissues derived from three Holstein cattle carrying the E211K somatic mutation of the bovine PRNP gene. The EIA, RT-QuIC and PMCA analyses were not able to detect the PrP^Sc band in any tested samples. To the best of our knowledge, this report is the first to describe an in-depth examination of PrP^Sc in cattle carrying the E211K somatic mutation of the bovine PRNP gene.

Absence of proteinase K-resistant PrP in Korean Holstein cattle carrying potential bovine spongiform encephalopathy-related E211K somatic mutation

Bovine spongiform encephalopathy (BSE) is a kind of prion disease caused by proteinase K-resistant prion protein (PrP^Sc ) in cattle. Although BSE has been reported worldwide, BSE-infected cases have never been reported in Korea. In a previous study, we identified BSE-related somatic mutation E211K in 3 Korean Holstein cattle. In Korea, the BSE surveillance system has been established. However, several genetic factors have not been controlled simultaneously thus far. In the present study, we performed enhanced surveillance of prion disease-related factors in Korean cattle, including Holstein cattle and Hanwoo (Korean native cattle), which is widely raised for meat. We investigated the germline mutation E211K at codon 211 of the PRNP gene and analysed genotype, allele and haplotype frequencies of the 23- and 12-bp insertion/deletion polymorphisms of the PRNP gene using direct DNA sequencing. In addition, we investigated linkage disequilibrium (LD) and compared haplotype distributions of polymorphisms among cattle breeds. Furthermore, we carried out BSE diagnosis in the medulla oblongata (MO) of Korean cattle including 3 Korean Holstein cattle carrying somatic mutation E211K using Western blotting analysis. We did not find the E211K mutation in the PRNP gene in any of the Korean cattle and found significantly different genotype, allele and haplotype distributions of the 23- and 12-bp insertion/deletion polymorphisms of the PRNP gene in male Holstein compared with male Hanwoo, female Hanwoo and total Hanwoo. In addition, only male Holstein showed weak LD between 23- and 12-bp insertion/deletion polymorphisms. Furthermore, the PrP^Sc bands were not detected in all Korean cattle tested. To the best of our knowledge, the enhanced surveillance system of BSE was conducted for the first time in Korean cattle.

First Report of the Potential Bovine Spongiform Encephalopathy (BSE)-Related Somatic Mutation E211K of the Prion Protein Gene (PRNP) in Cattle

Bovine spongiform encephalopathy (BSE) is a prion disease characterized by spongiform degeneration and astrocytosis in the brain. Unlike classical BSE, which is caused by prion-disease-contaminated meat and bone meal, the cause of atypical BSE has not been determined. Since previous studies have reported that the somatic mutation in the human prion protein gene (PRNP) has been linked to human prion disease, the somatic mutation of the PRNP gene was presumed to be one cause of prion disease. However, to the best of our knowledge, the somatic mutation of this gene in cattle has not been investigated to date. We investigated somatic mutations in a total of 58 samples, including peripheral blood; brain tissue including the medulla oblongata, cerebellum, cortex, and thalamus; and skin tissue in 20 individuals from each breed using pyrosequencing. In addition, we estimated the deleterious effect of the K211 somatic mutation on bovine prion protein by in silico evaluation tools, including PolyPhen-2 and PANTHER. We found a high rate of K211 somatic mutations of the bovine PRNP gene in the medulla oblongata of three Holsteins (10% ± 4.4%, 28% ± 2%, and 19.55% ± 3.1%). In addition, in silico programs showed that the K211 somatic mutation was damaging. To the best of our knowledge, this study is the first to investigate K211 somatic mutations of the bovine PRNP gene that are associated with potential BSE progression.

Deciphering the BSE-type specific cell and tissue tropisms of atypical (H and L) and classical BSE

After the discovery of two atypical bovine spongiform encephalopathy (BSE) forms in France and Italy designated H- and L-BSE, the question arose whether these new forms differed from classical BSE (C-BSE) in their pathogenesis. Samples collected from cattle in the clinical stage of BSE during an intracranial challenge study with L- and H-BSE were analysed using biochemical and histological methods as well as in a transgenic mouse bioassay. Our results generally confirmed what had been described for C-BSE to be true also for both atypical BSE forms, namely the restriction of the pathological prion protein (PrP^Sc) and BSE infectivity to the nervous system. However, analysis of samples collected under identical conditions from both atypical H- and L-BSE forms allowed us a more precise assessment of the grade of involvement of different tissues during the clinical end stage of disease as compared to C-BSE. One important feature is the involvement of the peripheral nervous and musculoskeletal tissues in both L-BSE and H-BSE affected cattle. We were, however, able to show that in H-BSE cases, the PrP^Sc depositions in the central and peripheral nervous system are dominated by a glial pattern, whereas a neuronal deposition pattern dominates in L-BSE cases, indicating differences in the cellular and topical tropism of both atypical BSE forms. As a consequence of this cell tropism, H-BSE seems to spread more rapidly from the CNS into the periphery via the glial cell system such as Schwann cells, as opposed to L-BSE which is mostly propagated via neuronal cells.

Experimental Study Using Multiple Strains of Prion Disease in Cattle Reveals an Inverse Relationship between Incubation Time and Misfolded Prion Accumulation, Neuroinflammation, and Autophagy

Proteinopathies result from aberrant folding and accumulation of specific proteins. Currently, there is a lack of knowledge about the factors that influence disease progression, making this a key challenge for the development of therapies for proteinopathies. Because of the similarities between transmissible spongiform encephalopathies (TSEs) and other protein misfolding diseases, TSEs can be used to understand other proteinopathies. Bovine spongiform encephalopathy (BSE) is a TSE that occurs in cattle and can be subdivided into three strains: classic BSE and atypical BSEs (H and L types) that have shorter incubation periods. The NACHT, LRR, and PYD domains-containing protein 3 inflammasome is a critical component of the innate immune system that leads to release of IL-1β. Macroautophagy is an intracellular mechanism that plays an essential role in protein clearance. In this study, the retina was used as a model to investigate the relationship between disease incubation period, prion protein accumulation, neuroinflammation, and changes in macroautophagy. We demonstrate that atypical BSEs present with increased prion protein accumulation, neuroinflammation, and decreased autophagy. This work suggests a relationship between disease time course, neuroinflammation, and the autophagic stress response, and may help identify novel therapeutic biomarkers that can delay or prevent the progression of proteinopathies.

Raccoons accumulate PrPSc after intracranial inoculation of the agents of chronic wasting disease or transmissible mink encephalopathy but not atypical scrapie

Prion diseases are neurodegenerative diseases characterized by the accumulation of misfolded prion protein (PrP^Sc) in the brain and other tissues. Animal prion diseases include scrapie in sheep, chronic wasting disease (CWD) in cervids, and transmissible mink encephalopathy (TME) in ranch-raised mink. We investigated the susceptibility of raccoons to various prion disease agents and compared the clinicopathologic features of the resulting disease. Raccoon kits were inoculated intracranially with the agents of raccoon-passaged TME (TME^Rac), bovine-passaged TME (TME^Bov), hamster-adapted drowsy (TME^DY) or hyper TME (TME^HY), CWD from white-tailed deer (CWD^Wtd) or elk (CWD^Elk), or atypical (Nor98) scrapie. Raccoons were euthanized when they developed clinical signs of prion disease or at study endpoint (<82 mo post-inoculation). Brain was examined for the presence of spongiform change, and disease-associated PrP^Sc was detected using an enzyme immunoassay, western blot, and immunohistochemistry. All raccoons inoculated with the agents of TME^Rac and TME^Bov developed clinical disease at ~6.6 mo post-inoculation, with widespread PrP^Sc accumulation in central nervous system tissues. PrP^Sc was detected in the brain of 1 of 4 raccoons in each of the CWD^Wtd-, CWD^Elk-, and TME^HY-inoculated groups. None of the raccoons inoculated with TME^DY or atypical scrapie agents developed clinical disease or detectable PrP^Sc accumulation. Our results indicate that raccoons are highly susceptible to infection with raccoon- and bovine-passaged TME agents, whereas CWD isolates from white-tailed deer or elk and hamster-adapted TME^HY transmit poorly. Raccoons appear to be resistant to infection with hamster-adapted TME^DY and atypical scrapie agents.

Pathologic and biochemical characterization of PrPSc from elk with PRNP polymorphisms at codon 132 after experimental infection with the chronic wasting disease agent

BACKGROUND

The Rocky Mountain elk (Cervus elaphus nelsoni) prion protein gene (PRNP) is polymorphic at codon 132, with leucine (L132) and methionine (M132) allelic variants present in the population. In elk experimentally inoculated with the chronic wasting disease (CWD) agent, different incubation periods are associated with PRNP genotype: LL132 elk survive the longest, LM132 elk are intermediate, and MM132 elk the shortest. The purpose of this study was to investigate potential mechanisms underlying variations in incubation period in elk of different prion protein genotypes. Elk calves of three PRNP genotypes (n = 2 MM132, n = 2 LM132, n = 4 LL132) were orally inoculated with brain homogenate from elk clinically affected with CWD.

RESULTS

Elk with longer incubation periods accumulated relatively less PrP^Sc in the brain than elk with shorter incubation periods. PrP^Sc accumulation in LM132 and MM132 elk was primarily neuropil-associated while glial-associated immunoreactivity was prominent in LL132 elk. The fibril stability of PrP^Sc from MM132 and LM132 elk were similar to each other and less stable than that from LL132 elk. Real-time quaking induced conversion assays (RT-QuIC) revealed differences in the ability of PrP^Sc seed from elk of different genotypes to convert recombinant 132 M or 132 L substrate.

CONCLUSIONS

This study provides further evidence of the importance of PRNP genotype in the pathogenesis of CWD of elk. The longer incubation periods observed in LL132 elk are associated with PrP^Sc that is more stable and relatively less abundant at the time of clinical disease. The biochemical properties of PrP^Sc from MM132 and LM132 elk are similar to each other and different to PrP^Sc from LL132 elk. The shorter incubation periods in MM132 compared to LM132 elk may be the result of genotype-dependent differences in the efficiency of propagation of PrP^Sc moieties present in the inoculum. A better understanding of the mechanisms by which the polymorphisms at codon 132 in elk PRNP influence disease pathogenesis will help to improve control of CWD in captive and free-ranging elk populations.

Real-Time Quaking-Induced Conversion Detection of Bovine Spongiform Encephalopathy Prions in a Subclinical Steer

Bovine spongiform encephalopathy (BSE) belongs to a group of fatal prion diseases that result from the misfolding of the cellular prion protein (PrP^C) into a pathogenic form (PrP^Sc) that accumulates in the brain. In vitro assays such as serial protein misfolding amplification and real-time quaking-induced conversion (RT-QuIC) allow assessment of the conversion of PrP^C to PrP^Sc. RT-QuIC can be used for the detection of prions in a variety of biological tissues from humans and animals. However, there is no such comparison of RT-QuIC data between BSE positive and presymptomatic cattle. Further, the current study assesses prion distribution in multiple brain regions of clinically ill or subclinical animals. Here, we compare RT-QuIC reactions seeded with brain samples collected from experimentally inoculated cattle that were clinically ill or subclinically affected with BSE. The results demonstrate RT-QuIC seeding in various brain regions of an animal with subclinical BSE despite being determined negative by immunohistochemistry. Bioassay of the subclinical animal and RT-QuIC of brainstem from inoculated knockout (PRNP^-/-) cattle were used to confirm infectivity in the subclinical animal and determine that RT-QuIC reactions were not the result of residual inoculum, respectively. These results confirm that RT-QuIC is a highly sensitive prion detection assay that can detect prions in a steer prior to the onset of clinical signs of BSE.

Experimental Transmission of the Chronic Wasting Disease Agent to Swine after Oral or Intracranial Inoculation

Chronic wasting disease (CWD) is a naturally occurring, fatal neurodegenerative disease of cervids. The potential for swine to serve as hosts for the agent of CWD is unknown. The purpose of this study was to investigate the susceptibility of swine to the CWD agent following experimental oral or intracranial inoculation. Crossbred piglets were assigned to three groups, intracranially inoculated (n = 20), orally inoculated (n = 19), and noninoculated (n = 9). At approximately the age at which commercial pigs reach market weight, half of the pigs in each group were culled ("market weight" groups). The remaining pigs ("aged" groups) were allowed to incubate for up to 73 months postinoculation (mpi). Tissues collected at necropsy were examined for disease-associated prion protein (PrPSc) by Western blotting (WB), antigen capture enzyme immunoassay (EIA), immunohistochemistry (IHC), and in vitro real-time quaking-induced conversion (RT-QuIC). Brain samples from selected pigs were also bioassayed in mice expressing porcine prion protein. Four intracranially inoculated aged pigs and one orally inoculated aged pig were positive by EIA, IHC, and/or WB. By RT-QuIC, PrPSc was detected in lymphoid and/or brain tissue from one or more pigs in each inoculated group. The bioassay was positive in four out of five pigs assayed. This study demonstrates that pigs can support low-level amplification of CWD prions, although the species barrier to CWD infection is relatively high. However, detection of infectivity in orally inoculated pigs with a mouse bioassay raises the possibility that naturally exposed pigs could act as a reservoir of CWD infectivity.IMPORTANCE We challenged domestic swine with the chronic wasting disease agent by inoculation directly into the brain (intracranially) or by oral gavage (orally). Disease-associated prion protein (PrPSc) was detected in brain and lymphoid tissues from intracranially and orally inoculated pigs as early as 8 months of age (6 months postinoculation). Only one pig developed clinical neurologic signs suggestive of prion disease. The amount of PrPSc in the brains and lymphoid tissues of positive pigs was small, especially in orally inoculated pigs. Regardless, positive results obtained with orally inoculated pigs suggest that it may be possible for swine to serve as a reservoir for prion disease under natural conditions.

Experimental Infection of Cattle With a Novel Prion Derived From Atypical H-Type Bovine Spongiform Encephalopathy

H-type bovine spongiform encephalopathy (H-BSE) is an atypical form of BSE in cattle. During passaging of H-BSE in transgenic bovinized (TgBoPrP) mice, a novel phenotype of BSE, termed BSE-SW emerged and was characterized by a short incubation time and host weight loss. To investigate the biological and biochemical properties of the BSE-SW prion, a transmission study was conducted in cattle, which were inoculated intracerebrally with brain homogenate from BSE-SW-infected TgBoPrP mice. The disease incubation period was approximately 15 months. The animals showed characteristic neurological signs of dullness, and severe spongiform changes and a widespread, uniform distribution of disease-associated prion protein (PrP^Sc) were observed throughout the brain of infected cattle. Immunohistochemical PrP^Sc staining of the brain revealed the presence of intraglial accumulations and plaque-like deposits. No remarkable differences were identified in vacuolar lesion scores, topographical distribution patterns, and staining types of PrP^Sc in the brains of BSE-SW- vs H-BSE-infected cattle. PrP^Sc deposition was detected in the ganglia, vagus nerve, spinal nerve, cauda equina, adrenal medulla, and ocular muscle. Western blot analysis revealed that the specific biochemical properties of the BSE-SW prion, with an additional 10- to 12-kDa fragment, were well maintained after transmission. These findings indicated that the BSE-SW prion has biochemical properties distinct from those of H-BSE in cattle, although clinical and pathologic features of BSW-SW in cattle are indistinguishable from those of H-BSE. The results suggest that the 2 infectious agents, BSE-SW and H-BSE, are closely related strains.

Use of bovine recombinant prion protein and real-time quaking-induced conversion to detect cattle transmissible mink encephalopathy prions and discriminate classical and atypical L- and H-Type bovine spongiform encephalopathy

Prions are amyloid-forming proteins that cause transmissible spongiform encephalopathies through a process involving conversion from the normal cellular prion protein to the pathogenic misfolded conformation (PrP^Sc). This conversion has been used for in vitro assays including serial protein misfolding amplification and real-time quaking induced conversion (RT-QuIC). RT-QuIC can be used for the detection of prions in a variety of biological tissues from humans and animals. Extensive work has been done to demonstrate that RT-QuIC is a rapid, specific, and highly sensitive prion detection assay. RT-QuIC uses recombinant prion protein to detect minute amounts of PrP^Sc. RT-QuIC has been successfully used to detect PrP^Sc from different prion diseases with a variety of substrates including hamster, human, sheep, bank vole, bovine and chimeric forms of prion protein. However, recombinant bovine prion protein has not been used to detect transmissible mink encephalopathy (TME) or to differentiate types of bovine spongiform encephalopathy (BSE) in samples from cattle. We evaluated whether PrP^Sc from TME and BSE infected cattle can be detected with RT-QuIC using recombinant bovine prion proteins, and optimized the reaction conditions to specifically detect cattle TME and to discriminate between classical and atypical BSE by conversion efficiency. We also found that substrate composed of the disease associated E211K mutant protein can be effective for the detection of TME in cattle and that wild type prion protein appears to be a practical substrate to discriminate between the different types of BSEs.

A Review of Selected Genes with Known Effects on Performance and Health of Cattle

There are genetic conditions that influence production in dairy and beef cattle. The objective of this review was to describe relevant genetic conditions that have been associated with productivity and health in cattle. Genes or genomic regions that have been identified as a candidate for the condition will be included, and the genetic basis of the condition will be defined. Genes and genetic conditions included in this review are bovine leukocyte adhesion deficiency, deficiency of the uridine monophosphate synthase, bovine chronic interstitial nephritis, horn development, myostatin, complex vertebral malformation, leptin, osteopetrosis, apoptosis peptide activating factor 1, chondrodysplastic dwarfism, caseins, calpastatin, umbilical hernia, lactoglobulin, citrullinemia, cholesterol deficiency, prions, thyroglobulin, diacylglycerol acyltransferase, syndactyly, maple syrup urine disease, slick hair, Factor XI deficiency, and μ-Calpain. This review is not meant to be comprehensive, and relevant information is provided to ascertain genetic markers associated with the conditions.

A Comparison of Classical and H-Type Bovine Spongiform Encephalopathy Associated with E211K Prion Protein Polymorphism in Wild-Type and EK211 Cattle Following Intracranial Inoculation

In 2006, a case of H-type bovine spongiform encephalopathy (BSE-H) was diagnosed in a cow that was associated with a heritable polymorphism in the bovine prion protein gene (PRNP) resulting in a lysine for glutamate amino acid substitution at codon 211 (called E211K) of the prion protein. Although the prevalence of this polymorphism is low, cattle carrying the K211 allele may be predisposed to rapid onset of BSE-H when exposed or to the potential development of a genetic BSE. This study was conducted to better understand the relationship between the K211 polymorphism and its effect on BSE phenotype. BSE-H from the US 2006 case was inoculated intracranially (IC) in one PRNP wild-type (EE211) calf and one EK211 calf. In addition, one wild-type calf and one EK211 calf were inoculated IC with brain homogenate from a US 2003 classical BSE case. All cattle developed clinical disease. The survival time of the E211K BSE-H inoculated EK211 calf (10 months) was shorter than the wild-type calf (18 months). This genotype effect was not observed in classical BSE inoculated cattle (both 26 months). Significant changes in retinal function were observed in H-type BSE challenged cattle only. Cattle challenged with the same inoculum showed similar severity and neuroanatomical distribution of vacuolation and disease-associated prion protein deposition in the brain, though differences in neuropathology were observed between E211K BSE-H and classical BSE inoculated animals. Western blot results for brain tissue from challenged animals were consistent with the inoculum strains. This study demonstrates that the phenotype of E211K BSE-H remains stable when transmitted to cattle without the K211 polymorphism, and exhibits a number of features that differ from classical BSE in both wild-type and heterozygous EK211 animals.

Temporal Resolution of Misfolded Prion Protein Transport, Accumulation, Glial Activation, and Neuronal Death in the Retinas of Mice Inoculated with Scrapie

Currently, there is a lack of pathological landmarks to describe the progression of prion disease in vivo. Our goal was to use an experimental model to determine the temporal relationship between the transport of misfolded prion protein (PrP(Sc)) from the brain to the retina, the accumulation of PrP(Sc) in the retina, the response of the surrounding retinal tissue, and loss of neurons. Retinal samples from mice inoculated with RML scrapie were collected at 30, 60, 90, 105, and 120 days post inoculation (dpi) or at the onset of clinical signs of disease (153 dpi). Retinal homogenates were tested for prion seeding activity. Antibody staining was used to assess accumulation of PrP(Sc) and the resulting response of retinal tissue. Loss of photoreceptors was used as a measure of neuronal death. PrP(Sc) seeding activity was first detected in all samples at 60 dpi. Accumulation of PrP(Sc) and coincident activation of retinal glia were first detected at 90 dpi. Activation of microglia was first detected at 105 dpi, but neuronal death was not detectable until 120 dpi. Our results demonstrate that by using the retina we can resolve the temporal separation between several key events in the pathogenesis of prion disease.

Use of canonical discriminant analysis to study signatures of selection in cattle

BACKGROUND

Cattle include a large number of breeds that are characterized by marked phenotypic differences and thus constitute a valuable model to study genome evolution in response to processes such as selection and domestication. Detection of "signatures of selection" is a useful approach to study the evolutionary pressures experienced throughout history. In the present study, signatures of selection were investigated in five cattle breeds farmed in Italy using a multivariate approach.

METHODS

A total of 4094 bulls from five breeds with different production aptitudes (two dairy breeds: Italian Holstein and Italian Brown Swiss; two beef breeds: Piemontese and Marchigiana; and one dual purpose breed: Italian Simmental) were genotyped using the Illumina BovineSNP50 v.1 beadchip. Canonical discriminant analysis was carried out on the matrix of single nucleotide polymorphisms (SNP) genotyping data, separately for each chromosome. Scores for each canonical variable were calculated and then plotted in the canonical space to quantify the distance between breeds. SNPs for which the correlation with the canonical variable was in the 99th percentile for a specific chromosome were considered to be significantly associated with that variable. Results were compared with those obtained using an FST-based approach.

RESULTS

Based on the results of the canonical discriminant analysis, a large number of signatures of selection were detected, among which several had strong signals in genomic regions that harbour genes known to have an impact on production and morphological bovine traits, including MSTN, LCT, GHR, SCD, NCAPG, KIT, and ASIP. Moreover, new putative candidate genes were identified, such as GCK, B3GALNT1, MGAT1, GALNTL1, PRNP, and PRND. Similar results were obtained with the FST-based approach.

CONCLUSIONS

The use of canonical discriminant analysis on 50 K SNP genotypes allowed the extraction of new variables that maximize the separation between breeds. This approach is quite straightforward, it can compare more than two groups simultaneously, and relative distances between breeds can be visualized. The genes that were highlighted in the canonical discriminant analysis were in concordance with those obtained using the FST index.

Coexistence of two forms of disease-associated prion protein in extracerebral tissues of cattle infected with H-type bovine spongiform encephalopathy

H-type bovine spongiform encephalopathy (H-BSE) is an atypical form of BSE in aged cattle. H-BSE is characterized by the presence of two proteinase K-resistant forms of disease-associated prion protein (PrP^Sc), identified as PrP^Sc #1 and PrP^Sc #2, in the brain. To investigate the coexistence of different PrP^Sc forms in the extracerebral tissues of cattle experimentally infected with H-BSE, immunohistochemical and molecular analyses were performed by using N-terminal-, core-region- and C-terminal-specific anti-prion protein antibodies. Our results demonstrated that two distinct forms of PrP^Sc coexisted in the various extracerebral tissues.

The transmissible spongiform encephalopathies of livestock

Prion diseases or transmissible spongiform encephalopathies (TSEs) are fatal protein-misfolding neurodegenerative diseases. TSEs have been described in several species, including bovine spongiform encephalopathy (BSE) in cattle, scrapie in sheep and goats, chronic wasting disease (CWD) in cervids, transmissible mink encephalopathy (TME) in mink, and Kuru and Creutzfeldt-Jakob disease (CJD) in humans. These diseases are associated with the accumulation of a protease-resistant, disease-associated isoform of the prion protein (called PrP(Sc)) in the central nervous system and other tissues, depending on the host species. Typically, TSEs are acquired through exposure to infectious material, but inherited and spontaneous TSEs also occur. All TSEs share pathologic features and infectious mechanisms but have distinct differences in transmission and epidemiology due to host factors and strain differences encoded within the structure of the misfolded prion protein. The possibility that BSE can be transmitted to humans as the cause of variant Creutzfeldt-Jakob disease has brought attention to this family of diseases. This review is focused on the TSEs of livestock: bovine spongiform encephalopathy in cattle and scrapie in sheep and goats.

Fluorescence Spectroscopy of the Retina for the Screening of Bovine Spongiform Encephalopathy

Transmissible spongiform encephalopathies (TSE) are progressive, neurodegenerative disorders, of which bovine spongiform encephalopathy (BSE) is of special concern because it is infectious and debilitating to humans. The possibility of using fluorescence spectroscopy to screen for BSE in cattle was explored. Fluorescence spectra from the retinas of experimentally infected BSE-positive cattle with clinical disease were compared with those from both sham-inoculated and non-inoculated BSE-negative cattle. The distinct intensity difference of about 4-10-fold between the spectra of the BSE-positive and the BSE-negative (sham-inoculated and non-inoculated) eyes suggests the basis for a means of developing a rapid, noninvasive examination of BSE in particular and TSEs in general.

Transmissibility of H-Type Bovine Spongiform Encephalopathy to Hamster PrP Transgenic Mice

Two distinct forms of atypical bovine spongiform encephalopathies (H-BSE and L-BSE) can be distinguished from classical (C-) BSE found in cattle based on biochemical signatures of disease-associated prion protein (PrP^Sc). H-BSE is transmissible to wild-type mice—with infected mice showing a long survival period that is close to their normal lifespan—but not to hamsters. Therefore, rodent-adapted H-BSE with a short survival period would be useful for analyzing H-BSE characteristics. In this study, we investigated the transmissibility of H-BSE to hamster prion protein transgenic (TgHaNSE) mice with long survival periods. Although none of the TgHaNSE mice manifested the disease during their lifespan, PrP^Sc accumulation was observed in some areas of the brain after the first passage. With subsequent passages, TgHaNSE mice developed the disease with a mean survival period of 220 days. The molecular characteristics of proteinase K-resistant PrP^Sc (PrP^res) in the brain were identical to those observed in first-passage mice. The distribution of immunolabeled PrP^Sc in the brains of TgHaNSE mice differed between those infected with H-BSE as compared to C-BSE or L-BSE, and the molecular properties of PrP^res in TgHaNSE mice infected with H-BSE differed from those of the original isolate. The strain-specific electromobility, glycoform profiles, and proteolytic cleavage sites of H-BSE in TgHaNSE mice were indistinguishable from those of C-BSE, in which the diglycosylated form was predominant. These findings indicate that strain-specific pathogenic characteristics and molecular features of PrP^res in the brain are altered during cross-species transmission. Typical H-BSE features were restored after back passage from TgHaNSE to bovinized transgenic mice, indicating that the H-BSE strain was propagated in TgHaNSE mice. This could result from the overexpression of the hamster prion protein.

Changes in retinal function and morphology are early clinical signs of disease in cattle with bovine spongiform encephalopathy

Bovine spongiform encephalopathy (BSE) belongs to a group of fatal, transmissible protein misfolding diseases known as transmissible spongiform encephalopathies (TSEs). All TSEs are caused by accumulation of misfolded prion protein (PrPSc) throughout the central nervous system (CNS), which results in neuronal loss and ultimately death. Like other protein misfolding diseases including Parkinson's disease and Alzheimer's disease, TSEs are generally not diagnosed until the onset of disease after the appearance of unequivocal clinical signs. As such, identification of the earliest clinical signs of disease may facilitate diagnosis. The retina is the most accessible part of the central nervous system, and retinal pathology in TSE affected animals has been previously reported. Here we describe antemortem changes in retinal function and morphology that are detectable in BSE inoculated animals several months (up to 11 months) prior to the appearance of any other signs of clinical disease. We also demonstrate that differences in the severity of these clinical signs reflect the amount of PrPSc accumulation in the retina and the resulting inflammatory response of the tissue. These results are the earliest reported clinical signs associated with TSE infection and provide a basis for understanding the pathology and evaluating therapeutic interventions.

Detection of the disease-associated form of the prion protein in biological samples

Transmissible spongiform encephalopathies (TSEs) are neurodegenerative diseases that occur in a variety of mammals. In TSEs, a chromosomally encoded protein (PrPC) undergoes a conformational change to the disease-associated form (PrPd). PrPd is capable of inducing a change in additional molecules of PrPC to the PrPd conformation. TSEs are inevitably fatal and cross-species transmission is known to occur, and there is potential for transmission via blood transfusion and organ transplantation in humans. Thus, there is interest in high-quality diagnostics for both humans and animals. This review summarizes methods of TSE detection currently in use in diagnostic settings and discusses recent advances in PrPd detection that afford substantial enhancements in sensitivity over currently approved methods for use in clinical settings.

Stability properties of PrP(Sc) from cattle with experimental transmissible spongiform encephalopathies: use of a rapid whole homogenate, protease-free assay

Background

Transmissible Spongiform Encephalopathies (TSEs), including scrapie in sheep, chronic wasting disease (CWD) in cervids, transmissible mink encephalopathy (TME), and bovine spongiform encephalopathy (BSE), are fatal diseases of the nervous system associated with accumulation of misfolded prion protein (PrP^Sc). Different strains of TSEs exist, associated with different PrP^Sc conformations that can be probed by the stability assay, in which PrP^Sc is treated with increasing concentrations of the denaturant guanidine hydrochloride (GdnHCl).

Results

Here, we provide the first comprehensive application of a rapid, protease-free version of the GdnHCl stability assay to brain tissue from cattle experimentally infected with various TSE isolates. Consistent with previous findings from a single Japanese isolate, the L-type isolates of BSE are not distinguishable from classical BSE in this assay. In contrast, H-type isolates of BSE, including our unique isolate of E211K BSE, exhibit higher stability than classical BSE, suggesting that its increased protection against protease digestion at the BSE N-terminus is associated with a higher stability in GdnHCl. While the difference in stability in our version of the assay is likely not large enough for effective use in a diagnostic laboratory setting, the use of alternative experimental conditions may enhance this effect. TSEs from other natural host species that have been passaged in cattle, including CWD and TME, were not distinguishable from classical BSE, while isolates of cattle passaged scrapie exhibited a slight increase in stability as compared to classical BSE.

Conclusions

These results suggest that the core of PrP^Sc, as probed in this assay, has similar stability properties among cattle-passaged TSE isolates and that the conformational differences that lead to changes in the proteinase K cleavage site do not cause large changes in the stability of PrP^Sc from TSE-affected cattle. However, the stability differences observed here will provide a basis of comparison for new isolates of atypical BSE observed in the future and in other geographic locations, especially in the case of H-type BSE.

Susceptibility of cattle to the agent of chronic wasting disease from elk after intracranial inoculation

Cattle could be exposed to the agent of chronic wasting disease (CWD) through contact with infected farmed or free-ranging cervids or exposure to contaminated premises. The purpose of the current study was to assess the potential for CWD derived from elk to transmit to cattle after intracranial inoculation. Calves ( n = 14) were inoculated with brain homogenate derived from elk with CWD to determine the potential for transmission and to define the clinicopathologic features of disease. Cattle were necropsied if clinical signs occurred or at the end of the study (49 months postinoculation; MPI). Clinical signs of poor appetite, weight loss, circling, and bruxism occurred in 2 cattle (14%) at 16 and 17 MPI, respectively. Accumulation of abnormal prion protein (PrPSc) occurred in only the 2 clinically affected cattle and was confined to the central nervous system, with the most prominent immunoreactivity in midbrain, brainstem, and hippocampus with lesser immunoreactivity in the cervical spinal cord. The rate of transmission was lower than in cattle inoculated with CWD derived from mule deer (38%) or white-tailed deer (86%). Additional studies are required to fully assess the potential for cattle to develop CWD through a more natural route of exposure, but a low rate of transmission after intracranial inoculation suggests that risk of transmission through other routes is low. A critical finding is that if CWD did transmit to exposed cattle, currently used diagnostic techniques would detect and differentiate it from other prion diseases in cattle based on absence of spongiform change, distinct pattern of PrPSc deposition, and unique molecular profile.