Properties of L-type bovine spongiform encephalopathy in intraspecies passages

The origin and transmission routes of atypical bovine spongiform encephalopathy (BSE) remain unclear. To assess whether the biological and biochemical characteristics of atypical L-type BSE detected in Japanese cattle (BSE/JP24) are conserved during serial passages within a single host, 3 calves were inoculated intracerebrally with a brain homogenate prepared from first-passaged BSE/JP24-affected cattle. Detailed immunohistochemical and neuropathologic analysis of the brains of second-passaged animals, which had developed the disease and survived for an average of 16 months after inoculation, revealed distribution of spongiform changes and disease-associated prion protein (PrP(Sc)) throughout the brain. Although immunolabeled PrP(Sc) obtained from brain tissue was characterized by the presence of PrP plaques and diffuse synaptic granular accumulations, no stellate-type deposits were detected. Western blot analysis suggested no obvious differences in PrP(Sc) molecular mass or glycoform pattern in the brains of first- and second-passaged cattle. These findings suggest failures to identify differences in mean incubation period and biochemical and neuropathologic properties of the BSE/JP24 prion between the first and second passages in cattle.     

Antibodies to prion and Acinetobacter peptide sequences in bovine spongiform encephalopathy

An amino acid sequence homology has been identified between the bovine prion sequence (RPVDQ) and the Acinetobacter calcoaceticus enzyme, uridine-diphosphate-N-acetyl glucosamine-1-carboxy-vinyl-transferase which also contains (RPVDQ). Class-specific IgA, IgG and IgM antibodies against synthetic peptides containing the structurally related sequences present in bovine prion and A. calcoaceticus were measured in 189 bovine spongiform encephalopathy (BSE) positive cattle, 127 BSE negative cattle and 87 healthy control animals using an ELISA technique. Class-specific IgA, IgG and IgM antibodies against the structurally related synthetic peptides were significantly elevated in BSE positive cattle when compared to BSE negative cattle (P < 0.001) and healthy control animals (P < 0.001). These autoantibodies may have a role in the pathogenesis of BSE.     

Experimental transmission of h-type bovine spongiform encephalopathy to bovinized transgenic mice

To characterize the biological and biochemical properties of H-type bovine spongiform encephalopathy (BSE), a transmission study with a Canadian H-type isolate was performed with bovinized transgenic mice (TgBoPrP), which were inoculated intracerebrally with brain homogenate from cattle with H-type BSE. All mice exhibited characteristic neurologic signs, and the subsequent passage showed a shortened incubation period. The distribution of disease-associated prion protein (PrP(Sc)) was determined by immunohistochemistry, Western blot, and paraffin-embedded tissue (PET) blot. Biochemical properties and higher molecular weight of the glycoform pattern were well conserved within mice. Immunolabeled granular PrP(Sc), aggregates, and/or plaque-like deposits were mainly detected in the following brain locations: septal nuclei, subcallosal regions, hypothalamus, paraventricular nucleus of the thalamus, interstitial nucleus of the stria terminalis, and the reticular formation of the midbrain. Weak reactivity was detected by immunohistochemistry and PET blot in the cerebral cortex, most thalamic nuclei, the hippocampus, medulla oblongata, and cerebellum. These findings indicate that the H-type BSE prion has biological and biochemical properties distinct from those of C-type and L-type BSE in TgBoPrP mice, which suggests that TgBoPrP mice constitute a useful animal model to distinguish isolates from BSE-infected cattle.     

Prion biology relevant to bovine spongiform encephalopathy

Bovine spongiform encephalopathy (BSE) and chronic wasting disease (CWD) of deer and elk are a threat to agriculture and natural resources, as well as a human health concern. Both diseases are transmissible spongiform encephalopathies (TSE), or prion diseases, caused by autocatalytic conversion of endogenously encoded prion protein (PrP) to an abnormal, neurotoxic conformation designated PrPsc. Most mammalian species are susceptible to TSE, which, despite a range of species-linked names, is caused by a single highly conserved protein, with no apparent normal function. In the simplest sense, TSE transmission can occur because PrPsc is resistant to both endogenous and environmental proteinases, although many details remain unclear. Questions about the transmission of TSE are central to practical issues such as livestock testing, access to international livestock markets, and wildlife management strategies, as well as intangible issues such as consumer confidence in the safety of the meat supply. The majority of BSE cases seem to have been transmitted by feed containing meat and bone meal from infected animals. In the United Kingdom, there was a dramatic decrease in BSE cases after neural tissue and, later, all ruminant tissues were banned from ruminant feed. However, probably because of heightened awareness and widespread testing, there is growing evidence that new variants of BSE are arising "spontaneously," suggesting ongoing surveillance will continue to find infected animals. Interspecies transmission is inefficient and depends on exposure, sequence homology, TSE donor strain, genetic polymorphism of the host, and architecture of the visceral nerves if exposure is by an oral route. Considering the low probability of interspecies transmission, the low efficiency of oral transmission, and the low prion levels in nonnervous tissues, consumption of conventional animal products represents minimal risk. However, detection of rare events is challenging, and TSE literature is characterized by subsequently unsupported claims of species barriers or absolute tissue safety. This review presents an overview of TSE and summarizes recent research on pathogenesis and transmission.     

Stability of bovine spongiform encephalopathy prions: absence of prion protein degradation by bovine gut microbiota

Bovine spongiform encephalopathy (BSE) is transmitted by the oral route. However, the impacts of anaerobic fermentation processes in cattle on the stability of BSE-associated prion protein (PrP(Sc)) are still unresolved. In this study, experiments were designed to assess the ability of complex ruminal and colonic contents of bovines to degrade BSE-derived PrP(Sc). No significant decrease in PrP(Sc) levels in BSE brain homogenates was detected by Western blotting after up to 66 h of co-incubation with intestinal fluids. These results indicate that BSE-associated PrP(Sc) survive gastrointestinal digestion processes in cattle and might be excreted via faeces.     

严防疯牛病传入中国

20世纪 80年代中期发生于英国的疯牛病 ,如今已搅得世界不安 ,特别是欧洲大陆。据在欧洲所作的一项调查表明 ,人们已达到谈牛色变的程度。在接受调查的人中 ,有一半人已停止吃牛肉。有的国家 ,已将牛肉从学生的食谱中撤消了 ,以杜绝疯牛病对人体的危害。由此可见 ,疯牛病已成为人类的新恶魔。1　疯牛病 ,医学上称为牛海绵样脑病 (bovinespongiform encephalopathy,BSE) ,是 1 985年 4月首次在英国发现的牛的致死性疾病 ,1 986年 1 1月定名为 BSE,并首次作了报道。此后 1 0余年中 ,英国已有 1 6万多头牛发生 BSE,英国政府为此付出了惨重…     

Experimental H-type bovine spongiform encephalopathy characterized by plaques and glial- and stellate-type prion protein deposits

ABSTRACT: Atypical bovine spongiform encephalopathy (BSE) has recently been identified in Europe, North America, and Japan. It is classified as H-type and L-type BSE according to the molecular mass of the disease-associated prion protein (PrPSc). To investigate the topographical distribution and deposition patterns of immunolabeled PrPSc, H-type BSE isolate was inoculated intracerebrally into cattle. H-type BSE was successfully transmitted to 3 calves, with incubation periods between 500 and 600 days. Moderate to severe spongiform changes were detected in the cerebral and cerebellar cortices, basal ganglia, thalamus, and brainstem. H-type BSE was characterized by the presence of PrP-immunopositive amyloid plaques in the white matter of the cerebrum, basal ganglia, and thalamus. Moreover, intraglial-type immunolabeled PrPSc was prominent throughout the brain. Stellate-type immunolabeled PrPSc was conspicuous in the gray matter of the cerebral cortex, basal ganglia, and thalamus, but not in the brainstem. In addition, PrPSc accumulation was detected in the peripheral nervous tissues, such as trigeminal ganglia, dorsal root ganglia, optic nerve, retina, and neurohypophysis. Cattle are susceptible to H-type BSE with a shorter incubation period, showing distinct and distinguishable phenotypes of PrPSc accumulation.     

The welfare problems associated with using transgenic mice to bioassay for bovine spongiform encephalopathy

Prion diseases are fatal neurodegenerative disorders, epitomized by the the recent bovine spongiform encephalopathy (BSE) epidemic in cattle and the emergence of a novel variant of Creutzfeldt-Jacob disease (vCJD) in humans. In prion disease, the agent of infection is believed to be composed of proteinaceous particles, termed prions, which are converted from a normal isoform into a pathogenic isoform during pathogenesis. A bioassay to detect pathogenic prions of BSE in bovine products consumed by humans was unattainable until the development of transgenic mice, due to the significantly lower susceptibility of wild-type mice to BSE. Transgenic mice have now been generated which express the bovine prion protein and are susceptible to BSE. Following an intracerebral injection with brain homogenate of BSE-infected cattle, transgenic mice develop numerous clinical signs of prion disease, including truncal ataxia (inability to coordinate the torso's muscular activity), increased tone of the tail, generalized tremor, and lack of a forelimb extensor response. In this study, the ethical score system devised by Porter (1992) was applied to the BSE bioassay as a tool for identifying welfare issues affecting animals used in the bioassay. We acknowledge that there are limitations to the use of the information arising from the application of the Porter scoring scheme for assessing the justification to proceed with any animal experiment; notwithstanding these problems, however, our application of the Porter model to the BSE bioassay enabled us to identify potential targets for refinement: pain involved, duration of distress and the duration of the experiment. This was despite lenient scoring for the duration of distress and pain experienced by the mice, and optimal scoring for the quality of animal care. The targets identified for refinement are discussed in relation to the method of inoculation, the duration of the bioassay, and the duration of the clinical phase, with the objective of exploring ways of reducing the severity of the bioassay.     

Polymorphisms of the prion gene promoter region that influence classical bovine spongiform encephalopathy susceptibility are not applicable to other transmissible spongiform encephalopathies in cattle

Two regulatory region polymorphisms in the prion gene of cattle have been reported to have an association with resistance to classical bovine spongiform encephalopathy (BSE). However, it is not known if this association also applies to other transmissible spongiform encephalopathies (TSE) in cattle. In this report, we compare the relationship between these 2 polymorphisms and resistance in cattle affected with naturally occurring atypical BSE as well as in cattle experimentally inoculated with either scrapie, chronic wasting disease, or transmissible mink encephalopathy. Our analysis revealed no association between genotype and resistance to atypical BSE or experimentally inoculated TSE. This indicates the promoter polymorphism correlation is specific to classical BSE and that atypical BSE and experimentally inoculated TSE are bypassing the site of influence of the polymorphisms. This genetic discrepancy demonstrates that atypical BSE progresses differently in the host relative to classical BSE. These results are consistent with the notion that atypical BSE originates spontaneously in cattle.     

牛海绵状脑病的检测方法

牛海绵状脑病 (BSE)是牛的一种致命性、进行性的神经退化病征 ,并与人的克雅氏病有关。本文列举了BSE常规检测技术 ,并介绍了德国等国家BSE的生前检测方法的研究进展和我国目前的检测现状。     

Diagnosis of bovine spongiform encephalopathy: a review

Cows affected with bovine spongiform encephalopathy (BSE) display chronic neurological signs consisting of behavioural changes, abnormalities of posture and movement, and/or hyperaesthesia. At present, there are no laboratory test available to diagnose BSE in the live animal. In this article, we describe the post-mortem diagnostic examination of brains from BSE-suspected cattle as currently performed at ID-Lelystad. The routine laboratory diagnosis of BSE consists of histopathological examination of the brain and detection of the modified prion protein, PrP(BSE), in brain tissue. These tests, however, have the disadvantage of being laborious and time consuming, so that results are available only after several days. Recently, at ID-Lelystad a new post-mortem test has been developed that enables screening of larger volumes of brain samples for PrP(BSE) within 1 day. This BSE test is especially suited for slaughterline monitoring. A preliminary validation study has shown that both sensitivity and specificity are 100% compared to the gold diagnostic standard of histopathology.     

Diagnosis of bovine spongiform encephalopathy: A review

Summary

Cows affected with bovine spongiform encephalopathy (BSE) display chronic neurological signs consisting of behavioural changes, abnormalities of posture and movement, and/or hyperaesthesia. At present, there are no laboratory test available to diagnose BSE in the live animal. In this article, we describe the post‐mortem diagnostic examination of brains from BSE‐suspected cattle as currently performed at ID‐Lelystad. The routine laboratory diagnosis of BSE consists of histopathological examination of the brain and detection of the modified prion protein, PrP^BSE, in brain tissue. These tests, however, have the disadvantage of being laborious and time consuming, so that results are available only after several days.

Recently, at ID‐Lelystad a new post‐mortem test has been developed that enables screening of larger volumes of brain samples for PrP^BSE within 1 day. This BSE test is especially suited for slaughterline monitoring. A preliminary validation study has shown that both sensitivity and specificity are 100% compared to the gold diagnostic standard of histopathology.