Acquired transmissibility of sheep-passaged L-type bovine spongiform encephalopathy prion to wild-type mice

Acquired transmissibility of sheep-passaged L-type bovine spongiform encephalopathy prion to wild-type mice

Short report Acquired transmissibility of sheep-passaged L-type bovine spongiform encephalopathy prion to wild-type mice Hiroyuki Okada*, Kentaro Masujin*, Kohtaro Miyazawa and Takashi Yokoyama

* Corresponding authors: Hiroyuki Okada okadahi@affrc.go.jp - Kentaro Masujin masujin@affrc.go.jp

Author Affiliations

National Institute of Animal Health, National Agriculture and Food Research Organization (NARO), Tsukuba, Ibaraki, Japan

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Veterinary Research 2015, 46:81 doi:10.1186/s13567-015-0211-2

The electronic version of this article is the complete one and can be found online at: http://www.veterinaryresearch.org/content/46/1/81

Received: 3 February 2015 Accepted: 8 June 2015 Published: 13 July 2015

© 2015 Okada et al.

This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly credited. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.

Abstract L-type bovine spongiform encephalopathy (L-BSE) is an atypical form of BSE that is transmissible to cattle and several lines of prion protein (PrP) transgenic mice, but not to wild-type mice. In this study, we examined the transmissibility of sheep-passaged L-BSE prions to wild-type mice. Disease-associated prion protein (PrP Sc ) was detected in the brain and/or lymphoid tissues during the lifespan of mice that were asymptomatic subclinical carriers, indicating that wild-type mice were susceptible to sheep-passaged L-BSE. The morphological characteristics of the PrP Sc of sheep-passaged L-BSE included florid plaques that were distributed mainly in the cerebral cortex and hippocampus of subsequent passaged mice. The PrP Sc glycoform profiles of wild-type mice infected with sheep-passaged L-BSE were similar to those of the original isolate. The data indicate that sheep-passaged L-BSE has an altered host range and acquired transmissibility to wild-type mice.

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Experimentally, L-BSE prions have shown transmissibility by intracerebral challenge to cattle [3]-[6]; bovinized [7]-[10], ovinized [7],[10],[11], and humanized prion protein (PrP) transgenic mice [12]; Syrian hamsters [13],[14], and non-human primates [15] with a shorter incubation period than C-BSE. In contrast, L-BSE was transmitted to sheep with a longer incubation period than C-BSE [10],[16]. L-BSE identified in Italy, also known as bovine amyloidotic spongiform encephalopathy (BASE), was transmissible to wild-type mice after subsequent passages, with an altered C-BSE-like phenotype [17]. In this study, we examine the biological and biochemical characteristics of ARQ/ARQ sheep-passaged L-BSE (L-BSE/sheep) to evaluate any alteration or consistency in the biological phenotypes during inter-species transmission.

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In the results of WB tests, a strain-specific molecular signature such as the glycoform pattern was conserved in the transmitted wild-type mice. The occurrence of size shifts in PK-digested PrP Sc has been reported in cross-species transmission of sporadic Creutzfeldt-Jakob disease (CJD) to humanized transgenic mice [34], variant CJD to wild-type mice [35], and hamster Sc237 to wild-type mice [36]. The transmission of L-BSE/sheep did not alter the glycoprofile of PrP Sc , but gained the transmissibility to wild-type mice. Although the key event that determines the shift in the size of PK-resistant PrP Sc remains unknown, it seems likely that the molecular characteristics may be influenced by the host-environment factors rather than the nature of the prion strain. The specific strain features of L-BSE observed in TgBoPrP mice affected with L-BSE/cattle [22],[37] or L-BSE/sheep were consistent after the passage transmission in sheep.

To the best of our knowledge, the transmission of L-BSE/cattle to wild-type mice has only been reported in one study, and even in this case the L-BSE prions were converted to a C-BSE-like prion using serial passages, and had indistinguishable phenotypic traits compared with mouse-passaged C-BSE [17]. A phenotypic change during the transmission of prions is a common phenomenon across a species barrier [33],[38],[39]. However, the reasons for the discrepancy between this study here and another, suggesting that BASE prion converts into C-BSE-like phenotypes during interspecies transmission in wild-type mice [17] are unknown. Several possible reasons are concisely considered: (1) cross contamination may occur during the inoculation procedure, (2) undetectable levels of C-BSE agent by WB analysis emerge in the brain of mice challenged with BASE at the first passage, thereafter inoculated mice develop the disease in subsequent passages [29], (3) L-BSE could generate at least 2 types of prions in wild-type mice: one showing L-BSE phenotypic properties and the other producing C-BSE-like signatures, (4) differences of unidentified prion-related host factors between outbred (ICR) and inbred (C57BL/6, SJL, or RIII) mice may have influenced the emergence of C-BSE-like prions during the cross-species transmission, and (5) differences of experimental procedures including prepared inocula and/or challenge routes of the infection may have influenced the propagation and/or generation of PrP Sc in the brain. The first two possibilities were completely ruled out by the authors [17]. The last possibility, is that mice were inoculated by a combination of intracerebral and intraperitoneal routes with a thalamic sample at first passage and with brain pools prepared from C57Bl/6 or SJL mice at second passage [17], should help address this issue [40]. No transmissibility including lymphotropism was found on the first passage in the Italian study. Although PrP Sc was undetectable in the brain of these mice, a faint positive signal was identified in one RIII mouse that showed biochemical characteristics of PrP Sc identical to those of C-BSE-infected mice by WB analyses.

Four L-BSE isolates from Japan [18], Germany [8], France [41], and Canada [42] were transmitted to TgBoPrP mice and no distinctive differences were detected in their pathological and molecular signatures [37]. These results suggest that the Japanese L-BSE isolates (BSE/JP24) used in this study may be identical to those from Canadian and European L-BSE cases examined. However, further studies regarding transmission to wild-type mice using these L-BSE isolates is now under consideration to address the issue that L-BSE prions from cattle are not transmitted to wild-type mice, which is a general phenomenon for L-BSE prions that is not restricted to the isolate used in this study. Furthermore, reverse transmission of L-BSE/sheep to TgBoPrP mice showed that L-BSE prions retained their pathological and biochemical signatures after passage in ARQ/ARQ sheep, which was in accordance with the findings of a previous study [10]. However, the mean incubation period of L-BSE/sheep affected TgBoPrP mice was much longer than that of L-BSE/cattle. Although the exact reason for the discrepancy that determines the incubation periods remains unknown, the environment in sheep as an intermediate host may influence the incubation periods.

Finally, the results indicate that L-BSE/sheep is transmissible to wild-type mice and it results in low virulence compared with C-BSE [23]. In contrast, experimental transmission of sheep-passaged C-BSE to bovine PrP transgenic mice induced a shorter incubation period and more severe neuropathological changes compared to cattle C-BSE, suggesting that the pathogenic properties of the C-BSE agent were altered during the inter-species transmission, making it more virulent in sheep [43]. Amino acid differences between the host PrP C and the PrP Sc of inocula result in species barriers to the cross-species transmission of prions [33]. In this context, the transmission of L-BSE to wild-type mice may be influenced by the ovine PrP amino-acid sequence. The biochemical nature of the protein in terms of its glycoform profile is identical in original L-BSE, L-BSE/sheep, and inoculated mice, even after the subsequent passage. Here, we have generated mouse-passaged L-BSE prions, which have the similar biochemical characteristics as the original cattle L-BSE. Therefore, this wild-type mouse model may be a useful experimental tool for elucidating BSE prion strains. The transmission experiment reported here shows that the host range of L-BSE prions can be extended by inter-species transmission. Further experimental transmission of L-BSE/sheep along with L-BSE into humanized PrP mice will be necessary to evaluate the potential risk for humans.

see full text ;

 http://www.veterinaryresearch.org/content/46/1/81

sporadic/spontaneous. might? might not too.

*** We describe the transmission of spongiform encephalopathy in a non-human primate inoculated 10 years earlier with a strain of sheep c-scrapie. Because of this extended incubation period in a facility in which other prion diseases are under study, we are obliged to consider two alternative possibilities that might explain its occurrence. We first considered the possibility of a sporadic origin (like CJD in humans). Such an event is extremely improbable because the inoculated animal was 14 years old when the clinical signs appeared, i.e. about 40% through the expected natural lifetime of this species, compared to a peak age incidence of 60–65 years in human sporadic CJD, or about 80% through their expected lifetimes.

***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.***

>>> 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. <<<

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

Emmanuel E. Comoy1 , Jacqueline Mikol1 , Sophie Luccantoni-Freire1 , Evelyne Correia1 , Nathalie Lescoutra-Etchegaray1 , Valérie Durand1 , Capucine Dehen1 , Olivier Andreoletti2 , Cristina Casalone3 , Juergen A. Richt4 n1 , Justin J. Greenlee4 , Thierry Baron5 , Sylvie L. Benestad6 , Paul Brown1 […] & Jean-Philippe Deslys1 - Show fewer authors Scientific Reports 5, Article number: 11573 (2015) doi:10.1038/srep11573 Download Citation

Epidemiology | Neurological manifestations | Prion diseases Received: 16 February 2015 Accepted: 28 May 2015 Published online: 30 June 2015 ABSTRACT 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.

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Discussion

We describe the transmission of spongiform encephalopathy in a non-human primate inoculated 10 years earlier with a strain of sheep c-scrapie. Because of this extended incubation period in a facility in which other prion diseases are under study, we are obliged to consider two alternative possibilities that might explain its occurrence. We first considered the possibility of a sporadic origin (like CJD in humans). Such an event is extremely improbable because the inoculated animal was 14 years old when the clinical signs appeared, i.e. about 40% through the expected natural lifetime of this species, compared to a peak age incidence of 60–65 years in human sporadic CJD, or about 80% through their expected lifetimes. 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.

The second possibility is a laboratory cross-contamination. Three facts make this possibility equally unlikely. First, handling of specimens in our laboratory is performed with fastidious attention to the avoidance of any such cross-contamination. Second, no laboratory cross-contamination has ever been documented in other primate laboratories, including the NIH, even between infected and uninfected animals housed in the same or adjacent cages with daily intimate contact (P. Brown, personal communication). Third, the cerebral lesion profile is different from all the other prion diseases we have studied in this model19, with a correlation between cerebellar lesions (massive spongiform change of Purkinje cells, intense PrPres staining and reactive gliosis26) and ataxia. The iron deposits present in the globus pallidus are a non specific finding that have been reported previously in neurodegenerative diseases and aging27. Conversely, the thalamic lesion was reminiscent of a metabolic disease due to thiamine deficiency28 but blood thiamine levels were within normal limits (data not shown). The preferential distribution of spongiform change in cortex associated with a limited distribution in the brainstem is reminiscent of the lesion profile in MM2c and VV1 sCJD patients29, but interspecies comparison of lesion profiles should be interpreted with caution. It is of note that the same classical scrapie isolate induced TSE in C57Bl/6 mice with similar incubation periods and lesional profiles as a sample derived from a MM1 sCJD patient30.

We are therefore confident that the illness in this cynomolgus macaque represents a true transmission of a sheep c-scrapie isolate directly to an old-world monkey, which taxonomically resides in the primate subdivision (parvorder of catarrhini) that includes humans. With an homology of its PrP protein with humans of 96.4%31, cynomolgus macaque constitutes a highly relevant model for assessing zoonotic risk of prion diseases. Since our initial aim was to show the absence of transmission of scrapie to macaques in the worst-case scenario, we obtained materials from a flock of naturally-infected sheep, affecting animals with different genotypes32. This c-scrapie isolate exhibited complete transmission in ARQ/ARQ sheep (332 ± 56 days) and Tg338 transgenic mice expressing ovine VRQ/VRQ prion protein (220 ± 5 days) (O. Andreoletti, personal communication). From the standpoint of zoonotic risk, it is important to note that sheep with c-scrapie (including the isolate used in our study) have demonstrable infectivity throughout their lymphoreticular system early in the incubation period of the disease (3 months-old for all the lymphoid organs, and as early as 2 months-old in gut-associated lymph nodes)33. In addition, scrapie infectivity has been identified in blood34, milk35 and skeletal muscle36 from asymptomatic but scrapie infected small ruminants which implies a potential dietary exposure for consumers.

Two earlier studies have reported the occurrence of clinical TSE in cynomolgus macaques after exposures to scrapie isolates. In the first study, the “Compton” scrapie isolate (derived from an English sheep) and serially propagated for 9 passages in goats did not transmit TSE in cynomolgus macaque, rhesus macaque or chimpanzee within 7 years following intracerebral challenge1; conversely, after 8 supplementary passages in conventional mice, this “Compton” isolate induced TSE in a cynomolgus macaque 5 years after intracerebral challenge, but rhesus macaques and chimpanzee remained asymptomatic 8.5 years post-exposure8. However, multiple successive passages that are classically used to select laboratory-adapted prion strains can significantly modify the initial properties of a scrapie isolate, thus questioning the relevance of zoonotic potential for the initial sheep-derived isolate. The same isolate had also induced disease into squirrel monkeys (new-world monkey)9. A second historical observation reported that a cynomolgus macaque developed TSE 6 years post-inoculation with brain homogenate from a scrapie-infected Suffolk ewe (derived from USA), whereas a rhesus macaque and a chimpanzee exposed to the same inoculum remained healthy 9 years post-exposure1. This inoculum also induced TSE in squirrel monkeys after 4 passages in mice. Other scrapie transmission attempts in macaque failed but had more shorter periods of observation in comparison to the current study. Further, it is possible that there are differences in the zoonotic potential of different scrapie strains.

The most striking observation in our study is the extended incubation period of scrapie in the macaque model, which has several implications. Firstly, our observations constitute experimental evidence in favor of the zoonotic potential of c-scrapie, at least for this isolate that has been extensively studied32,33,34,35,36. The cross-species zoonotic ability of this isolate should be confirmed by performing duplicate intracerebral exposures and assessing the transmissibility by the oral route (a successful transmission of prion strains through the intracerebral route may not necessarily indicate the potential for oral transmission37). However, such confirmatory experiments may require more than one decade, which is hardly compatible with current general management and support of scientific projects; thus this study should be rather considered as a case report.

Secondly, transmission of c-BSE to primates occurred within 8 years post exposure for the lowest doses able to transmit the disease (the survival period after inoculation is inversely proportional to the initial amount of infectious inoculum). The occurrence of scrapie 10 years after exposure to a high dose (25 mg) of scrapie-infected sheep brain suggests that the macaque has a higher species barrier for sheep c-scrapie than c-BSE, although it is notable that previous studies based on in vitro conversion of PrP suggested that BSE and scrapie prions would have a similar conversion potential for human PrP38.

Thirdly, prion diseases typically have longer incubation periods after oral exposure than after intracerebral inoculations: since humans can develop Kuru 47 years after oral exposure39, an incubation time of several decades after oral exposure to scrapie would therefore be expected, leading the disease to occur in older adults, i.e. the peak age for cases considered to be sporadic disease, and making a distinction between scrapie-associated and truly sporadic disease extremely difficult to appreciate.

Fourthly, epidemiologic evidence is necessary to confirm the zoonotic potential of an animal disease suggested by experimental studies. A relatively short incubation period and a peculiar epidemiological situation (e.g., all the first vCJD cases occurring in the country with the most important ongoing c-BSE epizootic) led to a high degree of suspicion that c-BSE was the cause of vCJD. Sporadic CJD are considered spontaneous diseases with an almost stable and constant worldwide prevalence (0.5–2 cases per million inhabitants per year), and previous epidemiological studies were unable to draw a link between sCJD and classical scrapie6,7,40,41, even though external causes were hypothesized to explain the occurrence of some sCJD clusters42,43,44. However, extended incubation periods exceeding several decades would impair the predictive values of epidemiological surveillance for prion diseases, already weakened by a limited prevalence of prion diseases and the multiplicity of isolates gathered under the phenotypes of “scrapie” and “sporadic CJD”.

Fifthly, considering this 10 year-long incubation period, together with both laboratory and epidemiological evidence of decade or longer intervals between infection and clinical onset of disease, no premature conclusions should be drawn from negative transmission studies in cynomolgus macaques with less than a decade of observation, as in the aforementioned historical transmission studies of scrapie to primates1,8,9. Our observations and those of others45,46 to date are unable to provide definitive evidence regarding the zoonotic potential of CWD, atypical/Nor98 scrapie or H-type BSE. The extended incubation period of the scrapie-affected macaque in the current study also underscores the limitations of rodent models expressing human PrP for assessing the zoonotic potential of some prion diseases since their lifespan remains limited to approximately two years21,47,48. This point is illustrated by the fact that the recently reported transmission of scrapie to humanized mice was not associated with clinical signs for up to 750 days and occurred in an extreme minority of mice with only a marginal increase in attack rate upon second passage13. The low attack rate in these studies is certainly linked to the limited lifespan of mice compared to the very long periods of observation necessary to demonstrate the development of scrapie. Alternatively, one could estimate that a successful second passage is the result of strain adaptation to the species barrier, thus poorly relevant of the real zoonotic potential of the original scrapie isolate of sheep origin49. The development of scrapie in this primate after an incubation period compatible with its lifespan complements the study conducted in transgenic (humanized) mice; taken together these studies suggest that some isolates of sheep scrapie can promote misfolding of the human prion protein and that scrapie can develop within the lifespan of some primate species.

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.

http://www.nature.com/articles/srep11573

spontaneous atypical BSE ???

if that's the case, then France is having one hell of an epidemic of atypical BSE, probably why they stopped testing for BSE, problem solved $$$

As of December 2011, around 60 atypical BSE cases have currently been reported in 13 countries, *** with over one third in France.

 http://www.biomedcentral.com/1746-6148/8/74

so 20 cases of atypical BSE in France, compared to the remaining 40 cases in the remaining 12 Countries, divided by the remaining 12 Countries, about 3+ cases per country, besides Frances 20 cases. you cannot explain this away with any spontaneous BSe. ...TSS

Sunday, October 5, 2014

France stops BSE testing for Mad Cow Disease

 http://transmissiblespongiformencephalopathy.blogspot.com/2014/10/france-stops-bse-testing-for-mad-cow.html

Thursday, July 24, 2014

*** Protocol for further laboratory investigations into the distribution of infectivity of Atypical BSE SCIENTIFIC REPORT OF EFSA New protocol for Atypical BSE investigations

 http://bse-atypical.blogspot.com/2014/07/protocol-for-further-laboratory.html

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IBNC Tauopathy or TSE Prion disease, it appears, no one is sure

Posted by flounder on 03 Jul 2015 at 16:53 GMT

http://www.plosone.org/annotation/listThread.action?root=86610

Wednesday, July 15, 2015

Additional BSE TSE prion testing detects pathologic lesion in unusual brain location and PrPsc by PMCA only, how many cases have we missed?

http://transmissiblespongiformencephalopathy.blogspot.com/2015/07/additional-bse-tse-prion-testing.html

HOUND STUDY

*** 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. ***

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http://web.archive.org/web/20010305222642/www.bseinquiry.gov.uk/files/yb/1991/01/04004001.pdf

full text ;

Saturday, July 18, 2015

SPONTANEOUS TRANSMISSIBLE SPONGIFORM ENCEPHALOPATHY TSE PRION AKA MAD COW TYPE DISEASE, DOES IT EXIST NATURALLY IN THE FIELD?

http://transmissiblespongiformencephalopathy.blogspot.com/2015/07/spontaneous-transmissible-spongiform.html

Article

Evaluation of the Zoonotic Potential of Transmissible Mink Encephalopathy

Emmanuel E. Comoy 1,*, Jacqueline Mikol 1, Marie-Madeleine Ruchoux 1, Valérie Durand 1, Sophie Luccantoni-Freire 1, Capucine Dehen 1, Evelyne Correia 1, Cristina Casalone 2, Juergen A. Richt 3, Justin J. Greenlee 4, Juan Maria Torres 5, Paul Brown 1 and Jean-Philippe Deslys 1

1 CEA, Institute of Emerging Diseases and Innovative Therapies (iMETI), Division of Prions and Related Diseases (SEPIA), Route du Panorama, BP6, 92265 Fontenay-aux-Roses, France; E-Mails: jacqueline.mikol@wanadoo.fr (J.M.); mruchoux@yahoo.fr (M.-M.R.); valerie.durand@cea.fr (V.D.); sophie.luccantoni@cea.fr (S.L.); capucine.dehen@cea.fr (C.D.); evelyne.correia@cea.fr (E.C.); paulwbrown@comcast.net (P.B.); jpdeslys@cea.fr (J-P.D.)

2 Istituto Zooprofilattico Sperimentale del Piemonte, Via Bologna 148, 10154 Torino, Italy; E-Mail: cristina.casalone@izsto.it (C.C.)

3 Kansas State University, College of Veterinary Medicine, K224B Mosier Hall, Manhattan, Kansas 66506-5601 USA; E-Mail: jricht@vet.k-state.edu

4 National Animal Disease Center, USDA, Agricultural Research Service, 1920 Dayton Ave, Ames, Iowa 50010 USA; E-Mail: justin.greenlee@ars.usda.gov (J.J.G.)

5 Instituto Nacional de Investigacion y Tecnologia Agraria y Alimentaria, Madrid, Spain; E-mail: jmtorres@inia.es

* Author to whom correspondence should be addressed; E-Mail: emmanuel.comoy@cea.fr (E.E.C.); Tel.: +33-46-54-90-05; Fax: +33-46-54-93-19.

Received: 27 June 2013; in revised form: 28 July 2013 / Accepted: 30 July 2013 / Published: 30 July 2013

Abstract: Successful transmission of Transmissible Mink Encephalopathy (TME) to cattle supports the bovine hypothesis for the still controversial origin of TME outbreaks. Human and primate susceptibility to classical Bovine Spongiform Encephalopathy (c-BSE) and the transmissibility of L-type BSE to macaques indicate a low cattle-to-primate species barrier. We therefore evaluated the zoonotic potential of cattle-adapted TME. In less than two years, this strain induced in cynomolgus macaques a neurological disease similar to L-BSE but distinct from c-BSE. TME derived from another donor species (raccoon) induced a similar disease with even shorter incubation periods. L-BSE and cattle-adapted TME were also transmissible to transgenic mice expressing human prion protein (PrP). Secondary transmissions to transgenic mice expressing bovine PrP maintained the features of the three tested bovine strains (cattle TME, c-BSE and L-BSE) regardless of intermediate host. Thus, TME is the third animal prion strain transmissible to both macaques and humanized transgenic mice, suggesting zoonotic potentials that should be considered in the risk analysis of animal prion diseases for human health. Moreover, the similarities between TME and L-BSE are highly suggestive of a link between these strains, and therefore the possible presence of L-BSE for many decades prior to its identification in USA and Europe.

OPEN ACCESS Pathogens 2013, 2 521

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4. Conclusions

We have shown that cattle-adapted TME is the third cattle prion strain (joining classical and L-type BSE) to be transmissible both to non-human primates and transgenic mice overexpressing human PrP. However, the successful transmission of raccoon TME to primate, inducing a disease with similar features as cattle TME, extends this notion to TME-related strains independent of host origin. Pathological, biochemical and bioassay investigations converged to demonstrate the similarity between cattle-adapted TME and L-BSE. Together with previous experiments performed in ovinized and bovinized transgenic mice and hamsters [8,9] indicating similarities between TME and L-BSE, the data support the hypothesis that L-BSE could be the origin of the TME outbreaks in North America and Europe during the mid-1900s. The corollary of this notion is the longstanding existence of atypical bovine prion cases in those countries during the same period, if not earlier. Although the risk of L-BSE for public health must be further assessed through studies using the oral route of exposure before drawing definitive conclusions, these data underline the importance of a potential zoonotic risk of L-BSE in the management of consumer protection, particularly in the context of the current relaxation of European policy with respect to BSE.

Pathogens 2013, 2 530

Keywords: primate; prion; transgenic mice; TME; cattle; raccoon; zoonotic potential

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4235697/pdf/pathogens-02-00520.pdf

Evidence That Transmissible Mink Encephalopathy Results from Feeding Infected Cattle

Over the next 8-10 weeks, approximately 40% of all the adult mink on the farm died from TME.

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The rancher was a ''dead stock'' feeder using mostly (>95%) downer or dead dairy cattle...

 http://collections.europarchive.org/tna/20090505194948/http://bseinquiry.gov.uk/files/mb/m09/tab05.pdf

http://collections.europarchive.org/tna/20090505194948/http://bseinquiry.gov.uk/files/mb/m09a/tab01.pdf

http://collections.europarchive.org/tna/20090505194948/http://bseinquiry.gov.uk/files/yb/1987/06/10004001.pdf



Terry S. Singeltary Sr.