Tuesday, November 14, 2017

Unraveling the key to the resistance of canids to prion diseases

Unraveling the key to the resistance of canids to prion diseases

This is an uncorrected proof.


One of the characteristics of prions is their ability to infect some species but not others and prion resistant species have been of special interest because of their potential in deciphering the determinants for susceptibility. Previously, we developed different in vitro and in vivo models to assess the susceptibility of species that were erroneously considered resistant to prion infection, such as members of the Leporidae and Equidae families. Here we undertake in vitroand in vivo approaches to understand the unresolved low prion susceptibility of canids. Studies based on the amino acid sequence of the canine prion protein (PrP), together with a structural analysis in silico, identified unique key amino acids whose characteristics could orchestrate its high resistance to prion disease. Cell- and brain-based PMCA studies were performed highlighting the relevance of the D163 amino acid in proneness to protein misfolding. This was also investigated by the generation of a novel transgenic mouse model carrying this substitution and these mice showed complete resistance to disease despite intracerebral challenge with three different mouse prion strains (RML, 22L and 301C) known to cause disease in wild-type mice. These findings suggest that dog D163 amino acid is primarily, if not totally, responsible for the prion resistance of canids.

Author summary

Detection of individuals or whole species resistant to any infectious disease is vital to understand the determinants of susceptibility and to develop appropriate therapeutic and preventative strategies. Canids have long been considered resistant to prion infection given the absence of clinical disease despite exposure to the causal agent. Through extensive analysis of the canine prion protein we have detected a key amino acid that might be responsible for their universal resistance to prion disease. Using in vitro and in vivo models we demonstrated that the presence of this residue confers resistance to prion infection when introduced to susceptible animals, opening the way to develop a new therapeutic approach against these, at present, untreatable disorders.



To establish TSE resistance in any given species requires that several features are examined before a definitive conclusion can be reached. Since TSEs are a group of neurodegenerative disorders, sometimes with extremely low prevalence, the absence of TSE cases reported for certain species may be due to reduced size populations or because sporadic deaths in wildlife species are rarely investigated. For example, sporadic BSE cases in cattle affect around 2–5 individuals per million per year and were only detected when millions of animals were analyzed as a consequence of the “mad cow” crisis [51]. Therefore, to determine the susceptibility of certain species to TSEs experimental inoculations in a statistically representative number of individuals are required. Performing experimental infections in some mammalian species is relatively easy but for others difficult or even impossible due to a number of technical and ethical/cultural hindrances, and the latter is the reason of the absence of literature reporting prion inoculations in dogs. Although there are reports of suspected TSE cases in canids [3537], none of the results were conclusive and there is no definitive proof of prion disease in this genus. BSE contaminated feed was undoubtedly fed to several wild canine species in UK zoos and domestic dogs during the BSE epidemic which suggests that, if not completely resistant, canids have a very low susceptibility to prion infection, as many other mammals in zoological collections fed contaminated food succumbed to the disease [7].
Given the lack of rigorous experimental challenge studies in dogs, the definitive proof of their TSE resistance may be derived by inoculation of experimental transgenic mice models expressing dog PrP (ongoing experiments). However, based on the in vitro results presented here, including several attempts to misfold dog PrP by PMCA, it is reasonable to assume that dog PrP is highly resistant to misfolding as the same in vitro methodology misfolds the PrP of species previously considered to be TSE resistant such as the rabbit [13].
Dog PrP could eventually be misfolded in vitro but using only BSE and BSE-derived strains, which retained their ability to infect bovine PrP expressing transgenic mice [42]. This is strong evidence of the powerful misfolding capacity of PMCA and endorses the use of this system to evaluate the misfolding ability of different species’ PrPs. However, regarding the evaluation of the degree of transmission barrier, PMCA is qualitative or semi-quantitative at best. In order to semi-quantify the strength of an interspecies transmission barrier, the in vitro process should be done in a controlled manner since ultimately PMCA might convert any mammalian PrP through the seeding with any kind of prion inocula if enough rounds during the in vitro process are performed. The number of cycles in each round and the number of rounds are empirical data and should be established by comparison with an standard [52]. In this case, the degree of canine PrP resistance to misfolding was not specifically evaluated in comparison to other species. Nonetheless, a low susceptibility to misfolding was concluded due to the requirement of modified PMCA conditions which increased the possibility of misfolding and because from the seeds tested just BSE and derived strains were able to induce misfolding. These issues were not observed when rabbit PrP was misfolded in vitro, although its low susceptibility to prion infection in vivo is well known [13].
Assuming a high but not complete resistance of dog PrP to misfolding, we focused on the identification of the amino acids and their positions in the prion protein that could be responsible. A PrP sequence alignment with species phylogenetically close to canids showed that feline PrP was the most similar in terms of primary structure. Cats are highly susceptible to three distinct prion strains (BSE, CWD and CJD) [4347] and this led to the comparison of a small number of differing residues with PrPs from other species. From these comparisons, three specific amino acids were identified, although one of them was readily discarded due to its presence in PrPs of TSE susceptible animals. Of the other two identified residues detected in canine PrP, the Asp/Glu in position 163 was chosen as the most relevant for canine resistance. The presence of an Asn in that position is a highly conserved residue in mammalian PrP sequences from different species and located in the loop of residues linking helix-α1 and strand-β2. Therefore, from all the PrPC structures described (i.e. human, mouse, rabbit, sheep, cow, horse, hamster, cat, bank vole, pig and elk [23245360]), only the structural model of canine wild-type PrP [24] allows studying the role of Asp/Glu polymorphism in the overall structure of PrP. When N158 is replaced by D158 in the mouse PrP, no structural changes in the Cα backbone at the mutated position are observed in our in silico models except those stabilizing the backbone. This is probably due to D158 (D163 in dog PrP numbering) being highly exposed to the solvent and like most charged residues in proteins, it could play a role in the folding of the protein. A hydrogen bond present between N158 and R135 is not present in canine PrP (between residues D163 and R140 in dog PrP numbering). Nevertheless, a salt bridge could be established between D158 and R135 as observed in Model01 due to the high mobility of the R135 side chain present in mouse prion structures. Both non-covalent interactions are relatively weak but the presumptive salt bridge R135-D158 could contribute to D158-mouse PrP and canine-PrP overall increased structural stability.
The definitive selection of this substitution as a candidate for prion resistance came from its role on the surface of the PrP molecule and its influence over the basic area comprised of R135, R150, R155 and K119. Assuming these residues participate in the PrP conversion to the disease associated isoform, D158 probably disturbs that PrP region as well as establishing a salt bridge with R135 limiting the latter’s role in conversion. This is supported by recent findings in transgenic Drosophila expressing mouse PrP with N158D substitution where it impairs the locomotor dysfunction developed when wild-type mouse PrP is expressed [61].
Taking advantage of the PMCA system that allowed examining if this amino acid could cause a significant change in the misfolding and propagation ability of known prion strains, two assays were performed. Based on the expression of mouse PrP with the desired N158D or N158E substitutions (equivalent to position 163 in dog PrP numbering) in cell cultures from neuronal origin, cell-PMCAs were performed to test their misfolding ability. Both studies showed clearly that the presence of an Asp or a Glu in position 158 of the PrP significantly hindered its misfolding propagation ability. Therefore, as predicted by surface charge distribution analysis, the presence of a negatively charged amino acid (Asp or Glu) is needed for a significant alteration in misfolding ability. As well as being unable to misfold, these mutants were able to block the propagation over wild-type mouse protein. This data highlights the potential for using these proteins as dominant negatives, blocking the propagation of prions, which has been a successful strategy for other dominant negative PrPs in cell cultures [62], and becoming an efficient anti-prion therapy. Although the mechanism by which this proteins block prion propagation over wild-type proteins is unknown, our data suggests that dominant negative proteins may act by binding prion seeds or misfolded proteins and out-competing the PrP that can be misfolded.
The results obtained in cell-PMCA experiments did not clearly distinguish which of the substitutions, N158D or N158E, gave rise to the PrP with lowest misfolding capacity as they showed almost identical behaviour. However, there was a faint PrPres signal when 22L was used to seed N158E PrP propagation, suggesting that at least for certain strains, N158D substitution may exert a major blocking effect than N158E. Both are negatively charged residues with similar molecular weights, so a similar effect would be expected in PMCA for N158D and N158E mutants. Nonetheless, a classification based on the environment at protein structures for the 20 amino acids [6364] sets several groups for residues, in which both negatively charged residues show distinct features regarding their propensity to be involved on protein surfaces or in binding regions. Asp (D) shows similar tendency to both while Glu (E) shows a strong preference to be exposed to solvent on protein surfaces [65]. Analysis of electrostatic potentials on the surface for N158D PrP shows that it is located in a region surrounded by positively charged residues. Although the negative charge of both Asp (D) and Glu (E) suggests they could play a similar role in terms of surface charge distribution, the shorter side-chain of Asp (D) makes it more rigid within protein structures than Glu (E), with a larger and more flexible side-chain. Alterations in surface electrostatic potential due to the negatively charged residues could reduce PrPc to PrPSc conversion efficiency, but also could affect the structure of the fibrils decreasing their formation. The rigidity of Asp (D) compared to Glu (E), could therefore explain the slight differences observed in the PMCA results with N158D and N158E PrPs. The replacement of N158 by Asp (D), with its restricted mobility, would possibly lead to a major disturbance of the surrounding area in order to accommodate the negative charge. In contrast, the larger side-chain of Glu (E) could allow the adoption of a wider range of conformers, possibly reducing the effect observed for 158D and allowing some conversion of N158E PrP in PMCA. Thus, we decided to choose Asp (D) instead of Glu (E) for the substitution in the PrP of the transgenic mouse model presented herein. Also taking into account that all the dog brain homogenates used in previous PMCA studies contained the D163 polymorphism. Thus, our results on the effect of D163 on the high resistance of canines to prion disorders would be applicable to some breeds of domestic dogs, although the similarities of Asp (D) and Glu (E) and the results obtained in brain-cell PMCA studies (Fig 5) indicate that it might be applicable also to the domestic dog breeds bearing E163 polymorphism (S2 Fig).
The expression levels of the canine PrP transgene in both mouse lines was close to PrPCexpression in the brain of wild-type animals, thus, the results obtained from their experimental challenges are unlikely to be affected due to over expression, which is known to accelerate prion disease development [66]. The three different mouse-adapted prion strains used (RML, 22L and 301C) did not cause clinical disease nor histological brain lesions in any of the challenged transgenic animals, indicating that this specific amino acid substitution prevented mouse PrP from misfolding in vivo, in agreement with the in vitro results. Additionally, the complete absence of PK resistant PrP, by Western blotting (WB) and immunohistochemistry (IHC), compared to the extensive PrPres accumulation in wild-type mice inoculated with the same prion strains further supports the protective properties of this specific amino acid substitution. Despite the possible existence of subclinical carriers with minimal amounts of PrPSc, undetectable by conventional methods (WB and IHC) among the inoculated transgenic mice, a significant delay in the disease development was clearly demonstrated.
Although the possibility of overcoming this polymorphic transmission barrier through serial in vivo passages cannot be ruled out from the results shown here, the high resistance observed to misfolding both in vivo and in vitro shows the significant effect of this substitution on reducing the misfolding proneness of the protein. Although performed in transgenic mice, these results probably explain the purported resistance canids have to TSEs despite having been exposed to infectious prions by consuming TSE affected animals such as sheep, cattle or cervids. Definitive proof of their resistance will require the generation of transgenic mice expressing whole dog PrP to allow the appropriate bioassays.
The potential dominant negative effect of the mutated protein presented in this work over the wild-type protein (ongoing study) may determine their future as anti-prion therapies.

EP-021 Canine Prions: A New Form of Prion Disease
Mourad Tayebi1, Monique A David2, Brian Summers3
1 University of Melbourne, Veterinary Sciences, Australia; 2Ausbiologics, Sydney, Australia; 3Royal Veterinary College, London, UK
The origin of bovine spongiform encephalopathy (BSE), which rapidly evolved into a major epidemic remains unresolved and was initially widely attributed to transmission of sheep scrapie to cattle with contaminated feed prepared from rendered sheep carcasses. Alternative transmission hypotheses also include feed contaminated with unrecognized subclinical case(s) of bovine prion disease or with prion-infected human remains. However, following the demonstration of a BSE case exhibiting the novel mutation E211 K, similar to the E200K mutation associated with most genetic CJD in humans, support for a genetic origin of prion disease in cattle is gaining momentum. In contrast to other animal species such as feline, the canine species seems to be resistant to prion disease as no canine prion cases were previously reported.
We describe here three cases of Rottweiler puppy (called RWD cases) with neurological deficits and spongiform change. We used animal bioassays and in vitro studies to show efficient interspecies transmission of this novel canidae prion isolate to other species.
Biochemical studies revealed the presence of partially proteinase K (PK)-resistant fragment and immunohistochemistry displayed staining for PrPSc in the cerebral cortex. Importantly, interspecies transmission of canine PrPSc derived from RWD3 brain homogenates following inoculation of hamsters led to signs of prion disease and replication of PrPSc in brains, spinal cords and spleens of these animals.
These findings if confirmed by further cases of prion disease in canidae and regardless of the origin of the disease would have a major impact on animal and public health.

OR-09: Canine spongiform encephalopathy—A new form of animal prion disease 

Monique David, Mourad Tayebi UT Health; Houston, TX USA 

It was also hypothesized that BSE might have originated from an unrecognized sporadic or genetic case of bovine prion disease incorporated into cattle feed or even cattle feed contaminated with prion-infected human remains.1 However, strong support for a genetic origin of BSE has recently been demonstrated in an H-type BSE case exhibiting the novel mutation E211K.2 Furthermore, a specific prion protein strain causing BSE in cattle is believed to be the etiological agent responsible for the novel human prion disease, variant Creutzfeldt-Jakob disease (vCJD).3 Cases of vCJD have been identified in a number countries, including France, Italy, Ireland, the Netherlands, Canada, Japan, US and the UK with the largest number of cases. Naturally occurring feline spongiform encephalopathy of domestic cats4 and spongiform encephalopathies of a number of zoo animals so-called exotic ungulate encephalopathies5,6 are also recognized as animal prion diseases, and are thought to have resulted from the same BSE-contaminated food given to cattle and humans, although and at least in some of these cases, a sporadic and/or genetic etiology cannot be ruled out. The canine species seems to display resistance to prion disease and no single case has so far been reported.7,8 

Here, we describe a case of a 9 week old male Rottweiler puppy presenting neurological deficits; and histological examination revealed spongiform vacuolation characteristic of those associated with prion diseases.9 Initial biochemical studies using anti-PrP antibodies revealed the presence of partially proteinase K-resistant fragment by western blotting. Furthermore, immunohistochemistry revealed spongiform degeneration consistent with those found in prion disease and displayed staining for PrPSc in the cortex. 

Of major importance, PrPSc isolated from the Rottweiler was able to cross the species barrier transmitted to hamster in vitro with PMCA and in vivo (one hamster out of 5). Futhermore, second in vivo passage to hamsters, led to 100% attack rate (n = 4) and animals displayed untypical lesional profile and shorter incubation period. 

In this study, we show that the canine species might be sensitive to prion disease and that PrPSc isolated from a dog can be transmitted to dogs and hamsters in vitro using PMCA and in vivo to hamsters. 

If our preliminary results are confirmed, the proposal will have a major impact on animal and public health and would certainly lead to implementing new control measures for ‘canine spongiform encephalopathy’ (CSE). 


1. Colchester AC, Colchester NT. The origin of bovine spongiform encephalopathy: the human prion disease hypothesis. Lancet 2005; 366:856-61; PMID:16139661; http:// dx.doi.org/10.1016/S0140-6736(05)67218-2. 

2. Richt JA, Hall SM. BSE case associated with prion protein gene mutation. PLoS Pathog 2008; 4:e1000156; PMID:18787697; http://dx.doi.org/10.1371/journal. ppat.1000156. 

3. Collinge J. Human prion diseases and bovine spongiform encephalopathy (BSE). Hum Mol Genet 1997; 6:1699-705; PMID:9300662; http://dx.doi.org/10.1093/ hmg/6.10.1699. 

4. Wyatt JM, Pearson GR, Smerdon TN, Gruffydd-Jones TJ, Wells GA, Wilesmith JW. Naturally occurring scrapie-like spongiform encephalopathy in five domestic cats. Vet Rec 1991; 129:233-6; PMID:1957458; http://dx.doi.org/10.1136/vr.129.11.233. 

5. Jeffrey M, Wells GA. Spongiform encephalopathy in a nyala (Tragelaphus angasi). Vet Pathol 1988; 25:398-9; PMID:3232315; http://dx.doi.org/10.1177/030098588802500514. 

6. Kirkwood JK, Wells GA, Wilesmith JW, Cunningham AA, Jackson SI. Spongiform encephalopathy in an arabian oryx (Oryx leucoryx) and a greater kudu (Tragelaphus strepsiceros). Vet Rec 1990; 127:418-20; PMID:2264242. 

7. Bartz JC, McKenzie DI, Bessen RA, Marsh RF, Aiken JM. Transmissible mink encephalopathy species barrier effect between ferret and mink: PrP gene and protein analysis. J Gen Virol 1994; 75:2947-53; PMID:7964604; http://dx.doi.org/10.1099/0022-1317- 75-11-2947. 

8. Lysek DA, Schorn C, Nivon LG, Esteve-Moya V, Christen B, Calzolai L, et al. Prion protein NMR structures of cats, dogs, pigs, and sheep. Proc Natl Acad Sci U S A 2005; 102:640-5; PMID:15647367; http://dx.doi.org/10.1073/pnas.0408937102. 

9. Budka H. Neuropathology of prion diseases. Br Med Bull 2003; 66:121-30; PMID:14522854; http://dx.doi.org/10.1093/bmb/66.1.121. 

Strain characteristics of the in vitro-adapted rabbit and dog BSE agent remained invariable with respect to the original cattle BSE prion, suggesting that the naturally low susceptibility of rabbits and dogs to prion infections should not alter their zoonotic potential if these animals became infected with BSE.
Neurobiology of Disease
Bovine Spongiform Encephalopathy Induces Misfolding of Alleged Prion-Resistant Species Cellular Prion Protein without Altering Its Pathobiological Features
Enric Vidal3, Natalia Fernández-Borges1, Belén Pintado4, Montserrat Ordóñez3, Mercedes Márquez6, Dolors Fondevila5,6, Juan María Torres7, Martí Pumarola5,6, and Joaquín Castilla1,2 + Author Affiliations
1CIC bioGUNE, 48160 Derio, Bizkaia, Spain,
2IKERBASQUE, Basque Foundation for Science, 48011 Bilbao, Bizkaia, Spain,
3Centre de Recerca en Sanitat Animal, Campus de la Universitat Autònoma de Barcelona (UAB)-IRTA, 08193 Bellaterra, Barcelona, Spain,
4Centro Nacional de Biotecnología, Campus de Cantoblanco, 28049 Cantoblanco, Madrid, Spain,
5Department of Animal Medicine and Surgery, Veterinary Faculty, UAB, 08193 Bellaterra (Cerdanyola del Vallès), Barcelona, Spain,
6Murine Pathology Unit, Centre de Biotecnologia Animal i Teràpia Gènica, UAB, 08193 Bellaterra (Cerdanyola del Vallès), Barcelona, Spain, and
7Centro de Investigación en Sanidad Animal-Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria, 28130 Valdeolmos, Madrid, Spain
Author contributions: E.V., N.F.-B., and J.C. designed research; E.V., N.F.-B., B.P., M.O., M.M., D.F., and J.C. performed research; E.V., N.F.-B., B.P., and J.C. contributed unpublished reagents/analytic tools; E.V., N.F.-B., B.P., M.O., M.M., D.F., J.M.T., M.P., and J.C. analyzed data; E.V. and J.C. wrote the paper.
Bovine spongiform encephalopathy (BSE) prions were responsible for an unforeseen epizootic in cattle which had a vast social, economic, and public health impact. This was primarily because BSE prions were found to be transmissible to humans. Other species were also susceptible to BSE either by natural infection (e.g., felids, caprids) or in experimental settings (e.g., sheep, mice). However, certain species closely related to humans, such as canids and leporids, were apparently resistant to BSE. In vitro prion amplification techniques (saPMCA) were used to successfully misfold the cellular prion protein (PrPc) of these allegedly resistant species into a BSE-type prion protein. The biochemical and biological properties of the new prions generated in vitro after seeding rabbit and dog brain homogenates with classical BSE were studied. Pathobiological features of the resultant prion strains were determined after their inoculation into transgenic mice expressing bovine and human PrPC. Strain characteristics of the in vitro-adapted rabbit and dog BSE agent remained invariable with respect to the original cattle BSE prion, suggesting that the naturally low susceptibility of rabbits and dogs to prion infections should not alter their zoonotic potential if these animals became infected with BSE. This study provides a sound basis for risk assessment regarding prion diseases in purportedly resistant species.
Received January 18, 2013. Revision received March 7, 2013. Accepted March 23, 2013. Copyright © 2013 the authors 0270-6474/13/337778-09$15.00/0
Friday, March 8, 2013
Dogs may have been used to make Petfood and animal feed
Monday, March 26, 2012
Monday, February 14, 2011
Journal of Wildlife Diseases, 47(1), 2011, pp. 78-93 © Wildlife Disease Association 2011
Monday, March 8, 2010
Canine Spongiform Encephalopathy aka MAD DOG DISEASE

DEFRA Department for Environment, Food & Rural Affairs
Area 307, London, SW1P 4PQ Telephone: 0207 904 6000 Direct line: 0207 904 6287 E-mail: h.mcdonagh.defra.gsi.gov.uk
Mr T S Singeltary P.O. Box 42 Bacliff Texas USA 77518
21 November 2001
Dear Mr Singeltary
Thank you for e-mail regarding the hounds survey. I am sorry for the long delay in responding.
As you note, the hound survey remains unpublished. However the Spongiform Encephalopathy Advisory Committee (SEAC), the UK Government's independent Advisory Committee on all aspects related to BSE-like disease, gave the hound study detailed consideration at their meeting in January 1994. As a summary of this meeting published in the BSE inquiry noted, the Committee were clearly concerned about the work that had been carried out, concluding that there had clearly been problems with it, particularly the control on the histology, and that it was more or less inconclusive. However was agreed that there should be a re-evaluation of the pathological material in the study.
Later, at their meeting in June 95, The Committee re-evaluated the hound study to see if any useful results could be gained from it. The Chairman concluded that there were varying opinions within the Committee on further work. It did not suggest any further transmission studies and thought that the lack of clinical data was a major weakness.
Overall, it is clear that SEAC had major concerns about the survey as conducted. As a result it is likely that the authors felt that it would not stand up to r~eer review and hence it was never published. As noted above, and in the detailed minutes of the SEAC meeting in June 95, SEAC considered whether additional work should be performed to examine dogs for evidence of TSE infection. Although the Committee had mixed views about the merits of conducting further work, the Chairman noted that when the Southwood Committee made their recommendation to complete an assessment of possible spongiform disease in dogs, no TSEs had been identified in other species and hence dogs were perceived as a high risk population and worthy of study. However subsequent to the original recommendation, made in 1990, a number of other species had been identified with TSE ( e.g. cats) so a study in hounds was less

new url;

As this study remains unpublished, my understanding is that the ownership of the data essentially remains with the original researchers. Thus unfortunately, I am unable to help with your request to supply information on the hound survey directly. My only suggestion is that you contact one of the researchers originally involved in the project, such as Gerald Wells. He can be contacted at the following address.
Dr Gerald Wells, Veterinary Laboratories Agency, New Haw, Addlestone, Surrey, KT 15 3NB, UK
You may also wish to be aware that since November 1994 all suspected cases of spongiform encephalopathy in animals and poultry were made notifiable. Hence since that date there has been a requirement for vets to report any suspect SE in dogs for further investigation. To date there has never been positive identification of a TSE in a dog.
I hope this is helpful
Yours sincerely 4
I am sorry, but I really could have been a co-signatory of Gerald's minute.
I do NOT think that we can justify devoting any resources to this study, especially as larger and more important projects such as the pathogenesis study will be quite demanding.
If there is a POLITICAL need to continue with the examination of hound brains then it should be passed entirely to the VI Service.
J W WILESMITH Epidemiology Unit 18 October 1991
Mr. R Bradley
cc: Mr. G A H Wells

see new url;

3.3. Mr R J Higgins in conjunction with Mr G A Wells and Mr A C Scott would by the end of the year, indentify the three brains that were from the ''POSITIVE'' end of the lesion spectrum.

see new url;

TSE in dogs have not been documented simply because OF THE ONLY STUDY, those brain tissue samples were screwed up too. see my investigation of this here, and to follow, later follow up, a letter from defra, AND SEE SUSPICIOUS BRAIN TISSUE SAF's. ...TSS
GAH WELLS (very important statement here...TSS)
AS implied in the Inset 25 we must not _ASSUME_ that transmission of BSE to other species will invariably present pathology typical of a scrapie-like disease.
76 pages on hound study;
The spongiform changes were not pathognomonic (ie. conclusive proof) for prion disease, as they were atypical, being largely present in white matter rather than grey matter in the brain and spinal cord. However, Tony Scott, then head of electron microscopy work on TSEs, had no doubt that these SAFs were genuine and that these hounds therefore must have had a scrapie-like disease. I reviewed all the sections myself (original notes appended) and although the pathology was not typical, I could not exclude the possibility that this was a scrapie-like disorder, as white matter vacuolation is seen in TSEs and Wallerian degeneration was also present in the white matter of the hounds, another feature of scrapie.
38.I reviewed the literature on hound neuropathology, and discovered that micrographs and descriptive neuropathology from papers on 'hound ataxia' mirrored those in material from Robert Higgins' hound survey. Dr Tony Palmer (Cambridge) had done much of this work, and I obtained original sections from hound ataxia cases from him. This enabled me provisionally to conclude that Robert Higgins had in all probability detected hound ataxia, but also that hound ataxia itself was possibly a TSE. Gerald Wells confirmed in 'blind' examination of single restricted microscopic fields that there was no distinction between the white matter vacuolation present in BSE and scrapie cases, and that occurring in hound ataxia and the hound survey cases.
39.Hound ataxia had reportedly been occurring since the 1930's, and a known risk factor for its development was the feeding to hounds of downer cows, and particularly bovine offal. Circumstantial evidence suggests that bovine offal may also be causal in FSE, and TME in mink. Despite the inconclusive nature of the neuropathology, it was clearly evident that this putative canine spongiform encephalopathy merited further investigation.
40.The inconclusive results in hounds were never confirmed, nor was the link with hound ataxia pursued. I telephoned Robert Higgins six years after he first sent the slides to CVL. I was informed that despite his submitting a yearly report to the CVO including the suggestion that the hound work be continued, no further work had been done since 1991. This was surprising, to say the very least.
41.The hound work could have provided valuable evidence that a scrapie-like agent may have been present in cattle offal long before the BSE epidemic was recognised. The MAFF hound survey remains unpublished.
Histopathological support to various other published MAFF experiments
42.These included neuropathological examination of material from experiments studying the attempted transmission of BSE to chickens and pigs (CVL 1991) and to mice (RVC 1994).

It was thought likely that at least some, and probably all, of the cases in zoo animals were caused by the BSE agent. Strong support for this hypothesis came from the findings of Bruce and others (1994) ( Bruce, M.E., Chree, A., McConnell, I., Foster, J., Pearson, G. & Fraser, H. (1994) Transmission of bovine spongiform encephalopathy and scrapie to mice: strain variation and species barrier. Philosophical Transactions of the Royal Society B 343, 405-411: J/PTRSL/343/405 ), who demonstrated that the pattern of variation in incubation period and lesion profile in six strains of mice inoculated with brain homogenates from an affected kudu and the nyala, was similar to that seen when this panel of mouse strains was inoculated with brain from cattle with BSE. The affected zoo bovids were all from herds that were exposed to feeds that were likely to have contained contaminated ruminant-derived protein and the zoo felids had been exposed, if only occasionally in some cases, to tissues from cattle unfit for human consumption.

10. The case of SE in a cheetah that occurred during the period, involved a 7 year-old female which had been born and lived all her life at Whipsnade (except for the final stages when she was moved to the Animal Hospital at Regent’s Park for diagnosis and treatment). This animal, which died in December 1993, had been fed on cuts of meat and bone from carcases of cattle unfit for human consumption and it was thought likely that she had been exposed to spinal cord (Kirkwood, J.K., Cunningham, A.A., Flach, E.J., Thornton, S.M. & Wells, G.A.H. (1995) Spongiform encephalopathy in another captive cheetah (Acinonyx jubatus): evidence for variation in susceptibility or incubation periods between species. Journal of Zoo and Wildlife Medicine 26, 577-582: J/ZWM/26/577). 

11. During the period we also collated information on cases of SE that occurred in wild animals at or from other zoos in the British Isles. The total number of cases of which I was aware in June 1996, when I presented a review on occurrence of spongiform encephalopathies in zoo animals (at the Royal College of Pathologists’ Symposium on Transmitting prions: BSE, CJD, and other TSEs, The Royal Society, London, 4th July 1996), was 25, involving 10 species. The animals involved were all from the families Bovidae and Felidae, and comprised: 1 Nyala Tragelaphus angasi, 5 Eland Taurotragus oryx, 6 greater kudu Tragelaphus strepsiceros, 1 Gemsbok Oryx gazella, 1 Arabian oryx Oryx leucoryx, 1 Scimitar-horned oryx Oryx dammah, 4 Cheetah Acinonyx jubatus, 3 Puma Felis concolor 2 Ocelot Felis pardalis, and 1 Tiger Panthera tigris. (A spongiform encephalopathy, which was thought probably to have a different aetiology, had also been reported in 3 ostriches Struthio camelus in Germany). This list did not include cases of BSE in domesticated species in zoos (ie BSE in Ankole or other cattle, or SEs, assumed to be scrapie, in mouflon sheep Ovis musimon). 



Experimental transfusion of variant CJD-infected blood reveals previously uncharacterised prion disorder in mice and macaque

''On secondary and tertiary transmissions, however, the proportion of PrPres positive animals gradually increased to almost 100%. 

''Recent communications suggest that a similar situation might exist in other models of experimental exposure to prions involving swine32 and cattle33.'' 

''Experimental transfusion of variant CJD-infected blood reveals previously uncharacterised prion disorder in mice and macaque''

Holy Mad Cow Batman, i am thinking of that 10,000,000 POUNDS OF BLOOD LACED MEAT AND BONE MEAL IN COMMERCE WARNING LETTER back in 2007, see;



''I have a neighbor who is a dairy farmer. He tells me that he knows of several farmers who feed their cattle expired dog food. These farmers are unaware of any dangers posed to their cattle from the pet food contents. For these farmers, the pet food is just another source of protein.''



FDA 589.2000, Section 21 C.F.R. Animal Proteins Prohibited in Ruminant Feed WARNING Letters and FEED MILL VIOLATIONS OBSERVATIONS 2017 to 2006


What is the risk of chronic wasting disease being introduced into Great Britain? A Qualitative Risk Assessment October 2012

Several different animal feed products are imported into GB from North America. These include processed pet foods and consignments of unfinished feed ingredients for use in animal feed. The amount of imported feed, including pet food, that contains cervid protein is unknown and identified as a significant data gap. As non-ruminant animal feed may be produced with cervid protein (but not from positive CWD animals) in the United States (US), there is a greater than negligible risk that feed with cervid protein is imported from North America into GB. There is, however, uncertainty associated with this estimate.


In summary, given the volume of tourists, hunters and servicemen moving between GB and North America, the probability of at least one person travelling to/from a CWD affected area and, in doing so, contaminating their clothing, footwear and/or equipment prior to arriving in GB is greater than negligible. For deer hunters, specifically, the risk is likely to be greater given the increased contact with deer and their environment. However, there is significant uncertainty associated with these estimates.


Therefore, it is considered that farmed and park deer may have a higher probability of exposure to CWD transferred to the environment than wild deer given the restricted habitat range and higher frequency of contact with tourists and returning GB residents.


What is the risk of chronic wasting disease being introduced into Great Britain? A Qualitative Risk Assessment October 2012

Thursday, April 07, 2016

What is the risk of chronic wasting disease being introduced into Great Britain? An updated Qualitative Risk Assessment March 2016


cwd to pig, orally ;


Location: Virus and Prion Research

Title: Disease-associated prion protein detected in lymphoid tissues from pigs challenged with the agent of chronic wasting disease

Author item Moore, Sarah item Kunkle, Robert item Kondru, Naveen item Manne, Sireesha item Smith, Jodi item Kanthasamy, Anumantha item West Greenlee, M item Greenlee, Justin

Submitted to: Prion Publication Type: Abstract Only Publication Acceptance Date: 3/15/2017 Publication Date: N/A Citation: N/A Interpretive Summary:

Technical Abstract: Aims: Chronic wasting disease (CWD) is a naturally-occurring, fatal neurodegenerative disease of cervids. We previously demonstrated that disease-associated prion protein (PrPSc) can be detected in the brain and retina from pigs challenged intracranially or orally with the CWD agent. In that study, neurological signs consistent with prion disease were observed only in one pig: an intracranially challenged pig that was euthanized at 64 months post-challenge. The purpose of this study was to use an antigen-capture immunoassay (EIA) and real-time quaking-induced conversion (QuIC) to determine whether PrPSc is present in lymphoid tissues from pigs challenged with the CWD agent.

Methods: At two months of age, crossbred pigs were challenged by the intracranial route (n=20), oral route (n=19), or were left unchallenged (n=9). At approximately 6 months of age, the time at which commercial pigs reach market weight, half of the pigs in each group were culled (<6 challenge="" groups="" month="" pigs="" remaining="" the="">6 month challenge groups) were allowed to incubate for up to 73 months post challenge (mpc). The retropharyngeal lymph node (RPLN) was screened for the presence of PrPSc by EIA and immunohistochemistry (IHC). The RPLN, palatine tonsil, and mesenteric lymph node (MLN) from 6-7 pigs per challenge group were also tested using EIA and QuIC.

Results: PrPSc was not detected by EIA and IHC in any RPLNs. All tonsils and MLNs were negative by IHC, though the MLN from one pig in the oral <6 5="" 6="" at="" by="" detected="" eia.="" examined="" group="" in="" intracranial="" least="" lymphoid="" month="" months="" of="" one="" pigs="" positive="" prpsc="" quic="" the="" tissues="" was="">6 months group, 5/6 pigs in the oral <6 4="" and="" group="" months="" oral="">6 months group. Overall, the MLN was positive in 14/19 (74%) of samples examined, the RPLN in 8/18 (44%), and the tonsil in 10/25 (40%). Conclusions:

This study demonstrates that PrPSc accumulates in lymphoid tissues from pigs challenged intracranially or orally with the CWD agent, and can be detected as early as 4 months after challenge.

CWD-infected pigs rarely develop clinical disease and if they do, they do so after a long incubation period. This raises the possibility that CWD-infected pigs could shed prions into their environment long before they develop clinical disease.

Furthermore, lymphoid tissues from CWD-infected pigs could present a potential source of CWD infectivity in the animal and human food chains.



While this clearly is a cause for concern we should not jump to the conclusion that this means that pigs will necessarily be infected by bone and meat meal fed by the oral route as is the case with cattle. ...

we cannot rule out the possibility that unrecognised subclinical spongiform encephalopathy could be present in British pigs though there is no evidence for this: only with parenteral/implantable pharmaceuticals/devices is the theoretical risk to humans of sufficient concern to consider any action.

 Our records show that while some use is made of porcine materials in medicinal products, the only products which would appear to be in a hypothetically ''higher risk'' area are the adrenocorticotrophic hormone for which the source material comes from outside the United Kingdom, namely America China Sweden France and Germany. The products are manufactured by Ferring and Armour. A further product, ''Zenoderm Corium implant'' manufactured by Ethicon, makes use of porcine skin - which is not considered to be a ''high risk'' tissue, but one of its uses is described in the data sheet as ''in dural replacement''. This product is sourced from the United Kingdom.....

 snip...see much more here ;


Disease-associated prion protein detected in lymphoid tissues from pigs challenged with the agent of chronic wasting disease

MONDAY, AUGUST 14, 2017 

Experimental transmission of the chronic wasting disease agent to swine after oral or intracranial inoculation

TUESDAY, APRIL 18, 2017 




Subject: ***CDC Now Recommends Strongly consider having the deer or elk tested for CWD before you eat the meat

CDC Now Recommends Strongly consider having the deer or elk tested for CWD before you eat the meat 

Chronic Wasting Disease (CWD) 


If CWD could spread to people, it would most likely be through eating of infected deer and elk. In a 2006-2007 CDC survey of U.S. residents, nearly 20 percent of those surveyed said they had hunted deer or elk and more than two-thirds said they had eaten venison or elk meat. However, to date, no CWD infections have been reported in people. 

Hunters must consider many factors when determining whether to eat meat from deer and elk harvested from areas with CWD, including the level of risk they are willing to accept. Hunters harvesting wild deer and elk from areas with reported CWD should check state wildlife and public health guidance to see whether testing of animals is recommended or required in a given state or region. In areas where CWD is known to be present, CDC recommends that hunters strongly consider having those animals tested before eating the meat. 

Tests for CWD are monitoring tools that some state wildlife officials use to look at the rates of CWD in certain animal populations. Testing may not be available in every state, and states may use these tests in different ways. A negative test result does not guarantee that an individual animal is not infected with CWD, but it does make it considerably less likely and may reduce your risk of exposure to CWD. 

To be as safe as possible and decrease their potential risk of exposure to CWD, hunters should take the following steps when hunting in areas with CWD: 

Do not shoot, handle or eat meat from deer and elk that look sick or are acting strangely or are found dead (road-kill). When field-dressing a deer: Wear latex or rubber gloves when dressing the animal or handling the meat. Minimize how much you handle the organs of the animal, particularly the brain or spinal cord tissues. Do not use household knives or other kitchen utensils for field dressing. Check state wildlife and public health guidance to see whether testing of animals is recommended or required. Recommendations vary by state, but information about testing is available from many state wildlife agencies. Strongly consider having the deer or elk tested for CWD before you eat the meat. If you have your deer or elk commercially processed, consider asking that your animal be processed individually to avoid mixing meat from multiple animals. If your animal tests positive for CWD, do not eat meat from that animal. The U.S. Department of Agriculture’s Animal and Plant Health Inspection Service regulates commercially farmed deer and elk. The agency operates a national CWD herd certification program. As part of the voluntary program, states and individual herd owners agree to meet requirements meant to decrease the risk of CWD in their herds. Privately owned herds that do not participate in the herd certification program may be at increased risk for CWD. 

Page last reviewed: August 17, 2017 Page last updated: August 17, 2017 Content source: Centers for Disease Control and Prevention National Center for Emerging and Zoonotic Infectious Diseases (NCEZID) Division of High-Consequence Pathogens and Pathology (DHCPP) 

 > However, to date, no CWD infections have been reported in people. 

key word here is 'reported'. science has shown that CWD in humans will look like sporadic CJD. SO, how can one assume that CWD has not already transmitted to humans? they can't, and it's as simple as that. from all recorded science to date, CWD has already transmitted to humans, and it's being misdiagnosed as sporadic CJD. ...terry 


*** These results would seem to suggest that CWD does indeed have zoonotic potential, at least as judged by the compatibility of CWD prions and their human PrPC target. Furthermore, extrapolation from this simple in vitro assay suggests that if zoonotic CWD occurred, it would most likely effect those of the PRNP codon 129-MM genotype and that the PrPres type would be similar to that found in the most common subtype of sCJD (MM1).*** 

Molecular Barriers to Zoonotic Transmission of Prions 

*** chronic wasting disease, there was no absolute barrier to conversion of the human prion protein. 

*** Furthermore, the form of human PrPres produced in this in vitro assay when seeded with CWD, resembles that found in the most common human prion disease, namely sCJD of the MM1 subtype. 


CDC Now Recommends Strongly consider having the deer or elk tested for CWD before you eat the meat 

Prion 2017 Conference Abstracts CWD


First evidence of intracranial and peroral transmission of Chronic Wasting Disease (CWD) into Cynomolgus macaques: a work in progress 

Stefanie Czub1, Walter Schulz-Schaeffer2, Christiane Stahl-Hennig3, Michael Beekes4, Hermann Schaetzl5 and Dirk Motzkus6 1 

University of Calgary Faculty of Veterinary Medicine/Canadian Food Inspection Agency; 2Universitatsklinikum des Saarlandes und Medizinische Fakultat der Universitat des Saarlandes; 3 Deutsches Primaten Zentrum/Goettingen; 4 Robert-Koch-Institut Berlin; 5 University of Calgary Faculty of Veterinary Medicine; 6 presently: Boehringer Ingelheim Veterinary Research Center; previously: Deutsches Primaten Zentrum/Goettingen 

This is a progress report of a project which started in 2009. 21 cynomolgus macaques were challenged with characterized CWD material from white-tailed deer (WTD) or elk by intracerebral (ic), oral, and skin exposure routes. Additional blood transfusion experiments are supposed to assess the CWD contamination risk of human blood product. Challenge materials originated from symptomatic cervids for ic, skin scarification and partially per oral routes (WTD brain). Challenge material for feeding of muscle derived from preclinical WTD and from preclinical macaques for blood transfusion experiments. We have confirmed that the CWD challenge material contained at least two different CWD agents (brain material) as well as CWD prions in muscle-associated nerves. 

Here we present first data on a group of animals either challenged ic with steel wires or per orally and sacrificed with incubation times ranging from 4.5 to 6.9 years at postmortem. Three animals displayed signs of mild clinical disease, including anxiety, apathy, ataxia and/or tremor. In four animals wasting was observed, two of those had confirmed diabetes. All animals have variable signs of prion neuropathology in spinal cords and brains and by supersensitive IHC, reaction was detected in spinal cord segments of all animals. Protein misfolding cyclic amplification (PMCA), real-time quaking-induced conversion (RT-QuiC) and PET-blot assays to further substantiate these findings are on the way, as well as bioassays in bank voles and transgenic mice. 

At present, a total of 10 animals are sacrificed and read-outs are ongoing. Preclinical incubation of the remaining macaques covers a range from 6.4 to 7.10 years. Based on the species barrier and an incubation time of > 5 years for BSE in macaques and about 10 years for scrapie in macaques, we expected an onset of clinical disease beyond 6 years post inoculation. 





 TUESDAY, JUNE 13, 2017


First evidence of intracranial and peroral transmission of Chronic Wasting Disease (CWD) into Cynomolgus macaques: a work in progress

TUESDAY, JULY 04, 2017


TUESDAY, JUNE 13, 2017

PRION 2017 CONFERENCE ABSTRACT Chronic Wasting Disease in European moose is associated with PrPSc features different from North American CWD

Wednesday, May 24, 2017 

PRION2017 CONFERENCE VIDEO UPDATE 23 – 26 May 2017 Edinburgh UPDATE 1 

SATURDAY, JULY 29, 2017 

Risk Advisory Opinion: Potential Human Health Risks from Chronic Wasting Disease CFIA, PHAC, HC (HPFB and FNIHB), INAC, Parks Canada, ECCC and AAFC 

Transmission of scrapie prions to primate after an extended silent incubation period

Emmanuel E. Comoy, Jacqueline Mikol, Sophie Luccantoni-Freire, Evelyne Correia, Nathalie Lescoutra-Etchegaray, Valérie Durand, Capucine Dehen, Olivier Andreoletti, Cristina Casalone, Juergen A. Richt, Justin J. Greenlee, Thierry Baron, Sylvie L. Benestad, Paul Brown & Jean-Philippe Deslys Scientific Reports 5, Article number: 11573 (2015)


Download Citation

EpidemiologyNeurological manifestationsPrion diseases

Received: 16 February 2015

Accepted: 28 May 2015

Published online: 30 June 2015


Classical bovine spongiform encephalopathy (c-BSE) is the only animal prion disease reputed to be zoonotic, causing variant Creutzfeldt-Jakob disease (vCJD) in humans and having guided protective measures for animal and human health against animal prion diseases. Recently, partial transmissions to humanized mice showed that the zoonotic potential of scrapie might be similar to c-BSE. We here report the direct transmission of a natural classical scrapie isolate to cynomolgus macaque, a highly relevant model for human prion diseases, after a 10-year silent incubation period, with features similar to those reported for human cases of sporadic CJD. Scrapie is thus actually transmissible to primates with incubation periods compatible with their life expectancy, although fourfold longer than BSE. Long-term experimental transmission studies are necessary to better assess the zoonotic potential of other prion diseases with high prevalence, notably Chronic Wasting Disease of deer and elk and atypical/Nor98 scrapie.


In addition to previous studies on scrapie transmission to primate1,8,9 and the recently published study on transgenic humanized mice13, our results constitute new evidence for recommending that the potential risk of scrapie for human health should not be dismissed. Indeed, human PrP transgenic mice and primates are the most relevant models for investigating the human transmission barrier. To what extent such models are informative for measuring the zoonotic potential of an animal TSE under field exposure conditions is unknown. During the past decades, many protective measures have been successfully implemented to protect cattle from the spread of c-BSE, and some of these measures have been extended to sheep and goats to protect from scrapie according to the principle of precaution. Since cases of c-BSE have greatly reduced in number, those protective measures are currently being challenged and relaxed in the absence of other known zoonotic animal prion disease. We recommend that risk managers should be aware of the long term potential risk to human health of at least certain scrapie isolates, notably for lymphotropic strains like the classical scrapie strain used in the current study. Relatively high amounts of infectivity in peripheral lymphoid organs in animals infected with these strains could lead to contamination of food products produced for human consumption. Efforts should also be maintained to further assess the zoonotic potential of other animal prion strains in long-term studies, notably lymphotropic strains with high prevalence like CWD, which is spreading across North America, and atypical/Nor98 scrapie (Nor98)50 that was first detected in the past two decades and now represents approximately half of all reported cases of prion diseases in small ruminants worldwide, including territories previously considered as scrapie free. Even if the prevailing view is that sporadic CJD is due to the spontaneous formation of CJD prions, it remains possible that its apparent sporadic nature may, at least in part, result from our limited capacity to identify an environmental origin.


***Moreover, sporadic disease has never been observed in breeding colonies or primate research laboratories, most notably among hundreds of animals over several decades of study at the National Institutes of Health25, and in nearly twenty older animals continuously housed in our own facility.***

O.05: Transmission of prions to primates after extended silent incubation periods: Implications for BSE and scrapie risk assessment in human populations Emmanuel Comoy, Jacqueline Mikol, Valerie Durand, Sophie Luccantoni, Evelyne Correia, Nathalie Lescoutra, Capucine Dehen, and Jean-Philippe Deslys Atomic Energy Commission; Fontenay-aux-Roses, France Prion diseases (PD) are the unique neurodegenerative proteinopathies reputed to be transmissible under field conditions since decades. The transmission of Bovine Spongiform Encephalopathy (BSE) to humans evidenced that an animal PD might be zoonotic under appropriate conditions. Contrarily, in the absence of obvious (epidemiological or experimental) elements supporting a transmission or genetic predispositions, PD, like the other proteinopathies, are reputed to occur spontaneously (atpical animal prion strains, sporadic CJD summing 80% of human prion cases). Non-human primate models provided the first evidences supporting the transmissibiity of human prion strains and the zoonotic potential of BSE. Among them, cynomolgus macaques brought major information for BSE risk assessment for human health (Chen, 2014), according to their phylogenetic proximity to humans and extended lifetime. We used this model to assess the zoonotic potential of other animal PD from bovine, ovine and cervid origins even after very long silent incubation periods. 

*** We recently observed the direct transmission of a natural classical scrapie isolate to macaque after a 10-year silent incubation period, 

***with features similar to some reported for human cases of sporadic CJD, albeit requiring fourfold long incubation than BSE. Scrapie, as recently evoked in humanized mice (Cassard, 2014), 

***is the third potentially zoonotic PD (with BSE and L-type BSE), 

***thus questioning the origin of human sporadic cases. 

We will present an updated panorama of our different transmission studies and discuss the implications of such extended incubation periods on risk assessment of animal PD for human health. 


***thus questioning the origin of human sporadic cases*** 


***our findings suggest that possible transmission risk of H-type BSE to sheep and human. Bioassay will be required to determine whether the PMCA products are infectious to these animals. 


Transmission data also revealed that several scrapie prions propagate in HuPrP-Tg mice with efficiency comparable to that of cattle BSE. While the efficiency of transmission at primary passage was low, subsequent passages resulted in a highly virulent prion disease in both Met129 and Val129 mice. Transmission of the different scrapie isolates in these mice leads to the emergence of prion strain phenotypes that showed similar characteristics to those displayed by MM1 or VV2 sCJD prion. These results demonstrate that scrapie prions have a zoonotic potential and raise new questions about the possible link between animal and human prions. 

Saturday, April 23, 2016 


*** SCRAPIE WS-01: Prion diseases in animals and zoonotic potential 2016 

*** Prion. 10:S15-S21. 2016 ISSN: 1933-6896 printl 1933-690X 

SCRAPIE WS-01: Prion diseases in animals and zoonotic potential 2016 Prion. 10:S15-S21. 2016 ISSN: 1933-6896 printl 1933-690X online

Taylor & Francis

Prion 2016 Animal Prion Disease Workshop Abstracts

WS-01: Prion diseases in animals and zoonotic potential

Juan Maria Torres a, Olivier Andreoletti b, J uan-Carlos Espinosa a. Vincent Beringue c. Patricia Aguilar a,

Natalia Fernandez-Borges a. and Alba Marin-Moreno a

"Centro de Investigacion en Sanidad Animal ( CISA-INIA ). Valdeolmos, Madrid. Spain; b UMR INRA -ENVT 1225 Interactions Holes Agents Pathogenes. ENVT. Toulouse. France: "UR892. Virologie lmmunologie MolécuIaires, Jouy-en-Josas. France

Dietary exposure to bovine spongiform encephalopathy (BSE) contaminated bovine tissues is considered as the origin of variant Creutzfeldt Jakob (vCJD) disease in human. To date, BSE agent is the only recognized zoonotic prion. Despite the variety of Transmissible Spongiform Encephalopathy (TSE) agents that have been circulating for centuries in farmed ruminants there is no apparent epidemiological link between exposure to ruminant products and the occurrence of other form of TSE in human like sporadic Creutzfeldt Jakob Disease (sCJD). However, the zoonotic potential of the diversity of circulating TSE agents has never been systematically assessed. The major issue in experimental assessment of TSEs zoonotic potential lies in the modeling of the ‘species barrier‘, the biological phenomenon that limits TSE agents’ propagation from a species to another. In the last decade, mice genetically engineered to express normal forms of the human prion protein has proved essential in studying human prions pathogenesis and modeling the capacity of TSEs to cross the human species barrier.

To assess the zoonotic potential of prions circulating in farmed ruminants, we study their transmission ability in transgenic mice expressing human PrPC (HuPrP-Tg). Two lines of mice expressing different forms of the human PrPC (129Met or 129Val) are used to determine the role of the Met129Val dimorphism in susceptibility/resistance to the different agents.

These transmission experiments confirm the ability of BSE prions to propagate in 129M- HuPrP-Tg mice and demonstrate that Met129 homozygotes may be susceptible to BSE in sheep or goat to a greater degree than the BSE agent in cattle and that these agents can convey molecular properties and neuropathological indistinguishable from vCJD. However homozygous 129V mice are resistant to all tested BSE derived prions independently of the originating species suggesting a higher transmission barrier for 129V-PrP variant.

Transmission data also revealed that several scrapie prions propagate in HuPrP-Tg mice with efficiency comparable to that of cattle BSE. While the efficiency of transmission at primary passage was low, subsequent passages resulted in a highly virulent prion disease in both Met129 and Val129 mice. Transmission of the different scrapie isolates in these mice leads to the emergence of prion strain phenotypes that showed similar characteristics to those displayed by MM1 or VV2 sCJD prion. These results demonstrate that scrapie prions have a zoonotic potential and raise new questions about the possible link between animal and human prions.

Terry S. Singeltary Sr.