Wednesday, July 8, 2009

Transgenic Mice Expressing Porcine Prion Protein Resistant to Classical Scrapie but Susceptible to Sheep BSE and Atypical Scrapie

DOI: 10.3201/eid1508.081218

Suggested citation for this article: Espinosa J-C, Herva M-E, Andréoletti O, Padilla D, Lacroux C, Cassard H, et al. Transgenic mice expressing porcine prion protein resistant to classical scrapie but susceptible to sheep bovine spongiform encephalopathy and atypical scrapie. Emerg Infect Dis. 2009 Aug; [Epub ahead of print]

Transgenic Mice Expressing Porcine Prion Protein Resistant to Classical Scrapie but Susceptible to Sheep Bovine Spongiform Encephalopathy and Atypical Scrapie

Juan-Carlos Espinosa,1 María-Eugenia Herva,1 Olivier Andréoletti, Danielle Padilla, Caroline Lacroux, Hervé Cassard, Isabelle Lantier, Joaquin Castilla, and Juan-María Torres

Author affiliations: Centro de Investigación en Sanidad Animal, Madrid, Spain (J.-C. Espinosa, M.-E. Herva, D. Padilla, J. Castilla, J.-M. Torres); École Nationale Vétérinaire de Toulouse, Toulouse, France (O. Andréoletti, C. Lacroux, H. Cassard); and Centre Institut National de la Recherche Agronomique de Tours, Nouzilly, France (I. Lantier)

1These authors contributed equally to this article.

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



In this study, transgenic mice expressing porcine PrP (8) were used to assess the transmission capacity of a wide range of TSE agents from sheep. Our results indicated that none of the classical scrapie isolates tested was transmitted to our porcine PrP mouse model after intracerebral inoculation (Table), suggesting a highly (if not completely) resistance to the classical scrapie strains tested independently of their origin and biochemical signature. The absence of successful transmission of the SC-PS48 isolates with an unglycosylated bands of 19 kDa-like BSE suggests a BSE-unrelated origin for these BSE-like scrapie strains.

The atypical isolate SC-PS152 was the only scrapie isolate able to infect the Po-PrP mouse model after intracerebral inoculation (Table), albeit with a low efficiency of infection in the first passage (attack rate 16%). These results suggest the potential ability of atypical scrapie prions to infect pigs, although with a strong transmission barrier. Given the increasing number of atypical scrapie cases found in Europe and in North America, the potential ability of atypical scrapie to adapt to the pig becoming more easily transmitted could raise concerns about the potential danger of feeding ruminant meat and bone meal to swine.

In our transmission experiments, an obviously shorter survival period (458 ± 11 dpi) and an increased attack rate (100%) were observed in PoPrP-Tg001 mice inoculated with sheep BSE (Table) compared with those inoculated with the original cattle BSE (>650 dpi, 19%). These last figures correlate well with those reported for other cattle BSE isolates (Table). Differences in survival times were maintained after subsequent passages in this mouse model (Table), suggesting that the increased infectivity of sheep BSE cannot be linked to a higher infectious titer in the initial inoculum but must be the outcome of a modification in the pathogenicity of the agent. We can also rule out that the primary amino acid sequence of the ovine PrPSC leads to more efficient conversion of porcine PrPC because scrapie isolates from sheep with the same ARQ-PrP genotype were not able to infect these mice (Table). Taken together, the increased infectivity of sheep BSE in the porcine PrP mouse model must be considered as increased pathogenicity of the agent attributable to its passage in sheep. These features support previous results indicating that the BSE agent modifies its biological properties after passage in sheep, with the result that its pathogenicity increases in transgenic mice expressing bovine PrP (24). An increased pathogenicity of ovine BSE was also reported in conventional RIII mice when compared with retrospective cattle BSE experiments (36). In other prion strains, passage through an intermediate species has also been noted to alter host susceptibility (37).

The enhanced infectivity of the BSE agent after its passage in ARQ sheep raises concern about its potential danger for other species, including humans. This question, as well as others related to the infectivity of the new porcine prion generated in this study, is currently being addressed in transmission experiments using transgenic mice expressing human PrP.

Upon passages in porcine PrP transgenic mice, the BSE agent retained most of its biochemical properties, except for its PrPres glycoprofile in which some differences were appreciable. Our comparative analysis of cattle BSE and sheep BSE upon transmission in porcine PrP transgenic mice showed that both agents exhibit similar molecular (Figure 2) and neuropathologic properties (Figure 4). These features were preserved after subsequent passages. These results suggest that, despite their modified pathogenicity, the 2 porcine prions generated share the same biochemical and neuropathologic properties, regardless of whether the BSE agent used to inoculate the mice was obtained from ARQ sheep or cows. In agreement with these results, the increased infectivity of sheep BSE previously observed upon transmission in bovine PrP transgenic mice was not reflected in its molecular or neuropathologic properties (24).

The atypical scrapie (SC-PS152) agent appeared to undergo a strain phenotype shift upon transmission to porcine PrP transgenic mice. Surprisingly, this novel strain phenotype was similar to that of sheep BSE propagated in the same mice in terms of several features: 1) survival times observed after stabilization in PoPrP-Tg001 mice (second passages) were similar (Table); 2) PrPres molecular profiles of the 2 agents in porcine PrP mice were indistinguishable (Figure 3); and 3) vacuolation profiles observed in second passages largely overlapped (Figure 4).

These findings could reflect the evolutionary potential of prion agents upon transmission to a foreign host able to promote strain shift and emergence of new properties (38,39). The converging molecular, neuropathologic, and biological properties of atypical scrapie and sheep BSE upon propagation in porcine transgenic mice could be the consequence of a restriction imposed by the porcine PrPC, which might only admit a few options as it changes its conformation to PrPSC.

Our results could also suggest a common origin for sheep BSE and atypical scrapie agents, which may exhibit different phenotypes depending on the host PrPC or other host factors.

Although this last explanation seems to be less likely, so far we cannot draw any definitive conclusion on this issue. Whichever the case, the ability of an atypical scrapie to infect other species and its potential capacity to undergo a strain phenotype shift in the new host prompts new concerns about the possible spread of this uncommon TSE in other species as a masked prion undistinguishable from other strains.

snip... see full text ;

Saturday, May 2, 2009


1: J Infect Dis 1980 Aug;142(2):205-8

Oral transmission of kuru, Creutzfeldt-Jakob disease, and scrapie to nonhuman primates.

Gibbs CJ Jr, Amyx HL, Bacote A, Masters CL, Gajdusek DC.

Kuru and Creutzfeldt-Jakob disease of humans and scrapie disease of sheep and goats were transmitted to squirrel monkeys (Saimiri sciureus) that were exposed to the infectious agents only by their nonforced consumption of known infectious tissues. The asymptomatic incubation period in the one monkey exposed to the virus of kuru was 36 months; that in the two monkeys exposed to the virus of Creutzfeldt-Jakob disease was 23 and 27 months, respectively; and that in the two monkeys exposed to the virus of scrapie was 25 and 32 months, respectively. Careful physical examination of the buccal cavities of all of the monkeys failed to reveal signs or oral lesions. One additional monkey similarly exposed to kuru has remained asymptomatic during the 39 months that it has been under observation.

PMID: 6997404



A The Present Position with respect to Scrapie

A1 The Problem

Scrapie is a natural disease of sheep and goats. It is a slow and inexorably progressive degenerative disorder of the nervous system and it ia fatal. It is enzootic in the United Kingdom but not in all countries.

The field problem has been reviewed by a MAFF working group (ARC 35/77). It is difficult to assess the incidence in Britain for a variety of reasons but the disease causes serious financial loss; it is estimated that it cost Swaledale breeders alone $l.7 M during the five years 1971-1975. A further inestimable loss arises from the closure of certain export markets, in particular those of the United States, to British sheep.

It is clear that scrapie in sheep is important commercially and for that reason alone effective measures to control it should be devised as quickly as possible.

Recently the question has again been brought up as to whether scrapie is transmissible to man. This has followed reports that the disease has been transmitted to primates. One particularly lurid speculation (Gajdusek 1977) conjectures that the agents of scrapie, kuru, Creutzfeldt-Jakob disease and transmissible encephalopathy of mink are varieties of a single "virus". The U.S. Department of Agriculture concluded that it could "no longer justify or permit scrapie-blood line and scrapie-exposed sheep and goats to be processed for human or animal food at slaughter or rendering plants" (ARC 84/77)" The problem is emphasised by the finding that some strains of scrapie produce lesions identical to the once which characterise the human dementias"

Whether true or not. the hypothesis that these agents might be transmissible to man raises two considerations. First, the safety of laboratory personnel requires prompt attention. Second, action such as the "scorched meat" policy of USDA makes the solution of the acrapie problem urgent if the sheep industry is not to suffer grievously.



Epidemiology of Scrapie in the United States 1977

Like lambs to the slaughter 31 March 2001 by Debora MacKenzie Magazine issue 2284

FOUR years ago, Terry Singeltary watched his mother die horribly from a degenerative brain disease. Doctors told him it was Alzheimer's, but Singeltary was suspicious. The diagnosis didn't fit her violent symptoms, and he demanded an autopsy. It showed she had died of sporadic Creutzfeldt-Jakob disease.

Most doctors believe that sCJD is caused by a prion protein deforming by chance into a killer. But Singeltary thinks otherwise. He is one of a number of campaigners who say that some sCJD, like the variant CJD related to BSE, is caused by eating meat from infected animals. Their suspicions have focused on sheep carrying scrapie, a BSE-like disease that is widespread in flocks across Europe and North America.

Now scientists in France have stumbled across new evidence that adds weight to the campaigners' fears. To their complete surprise, the researchers found that one strain of scrapie causes the same brain damage in ...

see full text ;

Wednesday, July 1, 2009

Nor98 scrapie identified in the United States J Vet Diagn Invest 21:454-463 (2009)

4.296 On 20 August 1990, a positive result was recorded in the CVL's experiment to transmit BSE to pigs. One pig had been diagnosed by post-mortem pathology as having developed a spongiform encephalopathy. A confidential pathology report submitted by Mr Gerald Wells, Head of the CVL's Neuropathology Section, to his colleague Mr Michael Dawson in the Virology Department, included the following remark:

The result, albeit confined to one animal in the experimental challenge group is incontrovertible evidence of the transmissibility of BSE to the pig by simultaneous intracerebral, intravenous and intraperitoneal inoculation routes. 11

4.303 The minutes of the meeting record that:

It was very difficult to draw conclusions from one experimental result for what may happen in the field. However it would be prudent to exclude specified bovine offals from the pig diet. Although any relationship between BSE and the finding of a spongiform encephalopathy in cats had yet to be demonstrated, the fact that this had occurred suggested that a cautious view should be taken of those species which might be susceptible. The 'specified offals' of bovines should therefore be excluded from the feed of all species. 17

4.308 SEAC issued formal advice on 20 September 1990, following its meeting on the previous day. The advice stated:

Since this result shows that pigs can get spongiform encephalopathy, even though there is no evidence that they have done so in the field, we believe that pigs should no longer be fed with protein derived from bovine tissues which might contain the BSE agent, ie, those 'specified' bovine offals that are already excluded from human consumption. It would make sense to extend this prohibition to feed for all species, including household pets, as other species have now developed spongiform encephalopathies. We are aware that many animal feed compounders and pet food manufacturers are already applying such a ban on a voluntary basis. 22

4.309 In a statement to the Inquiry, Dr Tyrrell said:

It was the rapid increase in the BSE epidemic, the occurrence of more cases of FSE and the results of the pig transmission experiment which led SEAC to give the advice we did on the extension of the SBO ban. Before then (September 1990), we were not asked to advise on the extension of the SBO ban. It was important to consider humans before other animals. It should be remembered that prior to the test results of the pig transmission experiment, pigs and poultry were not known to be susceptible to TSEs. Breeding pigs, in particular, were thought to have received a very high exposure to the same type of contaminated MBM as cattle but without any evidence of the occurrence of TSE. The issue of symptom-less hosts was considered very carefully because it could apply to all domestic and farmed animal species. 23

3.57 The experiment which might have determined whether BSE and scrapie were caused by the same agent (ie, the feeding of natural scrapie to cattle) was never undertaken in the UK. It was, however, performed in the USA in 1979, when it was shown that cattle inoculated with the scrapie agent endemic in the flock of Suffolk sheep at the United States Department of Agriculture in Mission, Texas, developed a TSE quite unlike BSE.339 The findings of the initial transmission, though not of the clinical or neurohistological examination, were communicated in October 1988 to Dr Watson, Director of the CVL, following a visit by Dr Wrathall, one of the project leaders in the Pathology Department of the CVL, to the United States Department of Agriculture.340 The results were not published at this point, since the attempted transmission to mice from the experimental cow brain had been inconclusive. The results of the clinical and histological differences between scrapie-affected sheep and cattle were published in 1995. Similar studies in which cattle were inoculated intracerebrally with scrapie inocula derived from a number of scrapie-affected sheep of different breeds and from different States, were carried out at the US National Animal Disease Centre.341 The results, published in 1994, showed that this source of scrapie agent, though pathogenic for cattle,

*** did not produce the same clinical signs of brain lesions characteristic of BSE. ***

3.58 There are several possible reasons why the experiment was not performed in the UK. It had been recommended by Sir Richard Southwood (Chairman of the Working Party on Bovine Spongiform Encephalopathy) in his letter to the Permanent Secretary of MAFF, Mr (now Sir) Derek Andrews, on 21 June 1988,342 though it was not specifically recommended in the Working Party Report or indeed in the Tyrrell Committee Report (details of the Southwood Working Party and the Tyrell Committee can be found in vol. 4: The Southwood Working Party, 1988–89 and vol. 11: Scientists after Southwood respectively). The direct inoculation of scrapie into calves was given low priority, because of its high cost and because it was known that it had already taken place in the USA.343 It was also felt that the results of such an experiment would be hard to interpret. While a negative result 337 Fraser, H., Bruce, M., Chree, A., McConnell, I. and Wells, G. (1992) Transmission of Bovine Spongiform Encephalopathy and Scrapie to Mice, Journal of General Virology, 73, 1891–7; Bruce, M., Chree, A., McConnell, I., Foster, J., Pearson, G. and Fraser, H. (1994) Transmission of Bovine Spongiform Encephalopathy and Scrapie to Mice: Strain Variation and the Species Barrier, Philosophical Transactions of the Royal Society of London, Series B, Biological Sciences, 343, 405–11 338 Bruce, M., Will, R., Ironside, J., McConell, I., Drummond, D., Suttie, A., McCordie, L., Chree, A., Hope, J., Birkett, C., Cousens, S., Fraser, H. and Bostock, C. (1997) Transmissions to Mice Indicate that ‘New Variant’ CJD is Caused by the BSE Agent, Nature, 389, 498–501 339 Clark, W., Hourrigan, J. and Hadlow, W. (1995) Encephalopathy in Cattle Experimentally Infected with the Scrapie Agent, American Journal of Veterinary Research, 56, 606–12 340 YB88/10.00/1.1 341 Cutlip, R., Miller, J., Race, R., Jenny, A., Katz, J., Lehmkuhl, H., Debey, B. and Robinson, M. (1994) Intracerebral Transmission of Scrapie to Cattle, Journal of Infectious Diseases, 169, 814–20 342 YB88/6.21/1.2 343 YB88/11.17/2.4 SCIENCE 84 would be informative, a positive result would need to demonstrate that when scrapie was transmitted to cattle, the disease which developed in cattle was the same as BSE.344 Given the large number of strains of scrapie and the possibility that BSE was one of them, it would be necessary to transmit every scrapie strain to cattle separately, to test the hypothesis properly. Such an experiment would be expensive. Secondly, as measures to control the epidemic took hold, the need for the experiment from the policy viewpoint was not considered so urgent. It was felt that the results would be mainly of academic interest.345 3.59 Nevertheless, from the first demonstration of transmissibility of BSE in 1988, the possibility of differences in the transmission properties of BSE and scrapie was clear. Scrapie was transmissible to hamsters, but by 1988 attempts to transmit BSE to hamsters had failed. Subsequent findings increased that possibility.

Monday, June 01, 2009

Biochemical typing of pathological prion protein in aging cattle with BSE

Sunday, June 07, 2009


Sunday, May 10, 2009

Identification and characterization of bovine spongiform encephalopathy cases diagnosed and NOT diagnosed in the United States

Sunday, December 28, 2008

MAD COW DISEASE USA DECEMBER 28, 2008 an 8 year review of a failed and flawed policy

Wednesday, August 20, 2008

Bovine Spongiform Encephalopathy Mad Cow Disease typical and atypical strains, was there a cover-up ?

Saturday, February 28, 2009

NEW RESULTS ON IDIOPATHIC BRAINSTEM NEURONAL CHROMATOLYSIS "All of the 15 cattle tested showed that the brains had abnormally accumulated PrP" 2009 SEAC 102/2

Saturday, June 13, 2009

BSE FEED VIOLATIONS USA UPDATE From 01/01/2009 To 06/10/2009

Thursday, March 19, 2009



Saturday, May 2, 2009


Sunday, April 12, 2009 BSE MAD COW TESTING USA 2009 FIGURES Month Number of Tests

Feb 2009 -- 1,891

Jan 2009 -- 4,620


Monday, May 4, 2009

Back to the Past With New TSE Testing Agricultural Research/May-June 2009

Thursday, April 9, 2009

Docket No. FDA2002N0031 (formerly Docket No. 2002N0273) RIN 0910AF46 Substances Prohibited From Use in Animal Food or Feed; Final Rule: Proposed

Sunday, April 12, 2009 r-calf and the USA mad cow problem, don't look, don't find, and then blame Canada

Sunday, May 10, 2009

Meeting of the Transmissible Spongiform Encephalopathies Committee On June 12, 2009 (Singeltary submission)

Saturday, June 13, 2009

Monitoring the occurrence of emerging forms of Creutzfeldt-Jakob disease in the United States 2003 revisited 2009


Terry S. Singeltary Sr.

P.O. Box 42

Bacliff, Texas USA 77518

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