Insights into CWD and BSE species barriers using real-time conversion
Kristen A. Davenport1, Davin M. Henderson1, Candace K. Mathiason1 and
Edward A. Hoover1#
+ Author Affiliations Prion Research Center, Department of Microbiology,
Immunology and Pathology, College of Veterinary Medicine and Biomedical
Sciences, Colorado State University, Fort Collins, CO 805231
ABSTRACT
The propensity for trans-species prion transmission is related to the
structural characteristics of the enciphering and new host PrP, although the
exact mechanism remains incompletely understood. The effects of variability in
prion protein on cross-species prion transmission have been studied with animal
bioassays, but the influence of prion protein structure vs. host co-factors
(e.g. cellular constituents, trafficking, and innate immune interactions)
remains difficult to dissect. To isolate the effects of protein:protein
interactions on trans-species conversion, we used recombinant PrPC and real-time
quaking-induced conversion (RT-QuIC) and compared chronic wasting disease (CWD)
and classical bovine spongiform encephalopathy (cBSE) prions. To assess the
impact of transmission to a new species, we studied feline CWD (fCWD) and feline
BSE (i.e. feline spongiform encephalopathy, FSE). We cross-seeded fCWD and FSE
into each species' full-length, recombinant PrPC and measured the time required
for conversion to the amyloid (PrPRes) form, which we describe here as the rate
of amyloid conversion. These studies revealed that:
(1) CWD and BSE seeded their homologous species' PrP best;
(2) fCWD was a more efficient seed for feline rPrP than for white-tailed
deer rPrP;
(3) conversely, FSE more efficiently converted bovine than feline rPrP;
(4) and CWD, fCWD, BSE, and FSE all converted human rPrP, although not as
efficiently as homologous sCJD prions.
These results suggest that:
(1) at the level of protein: protein interactions, CWD adapts to a new
species more readily than does BSE, and
(2) the barrier preventing transmission of CWD to humans may be less robust
than estimated.
IMPORTANCE We demonstrate that bovine spongiform encephalopathy prions
maintain their trans-species conversion characteristics upon passage to cats,
but that chronic wasting disease prions adapt to the cat and are distinguishable
from the original prion.
***Additionally, we showed that chronic wasting disease prions are
effective at seeding the conversion of normal human prion protein to an amyloid
conformation, perhaps the first step in crossing the species barrier.
FOOTNOTES
↵#Address correspondence to Edward A. Hoover, edward.hoover@colostate.edu
Copyright © 2015, American Society for Microbiology. All Rights Reserved.
*** We hypothesize that both BSE prions and CWD prions passaged through
felines will seed human recPrP more efficiently than BSE or CWD from the
original hosts, evidence that the new host will dampen the species barrier
between humans and BSE or CWD. The new host effect is particularly relevant as
we investigate potential means of trans-species transmission of prion disease.
*** PPo3-7: Prion Transmission from Cervids to Humans is Strain-dependent
*** Here we report that a human prion strain that had adopted the cervid
prion protein (PrP) sequence through passage in cervidized transgenic mice
efficiently infected transgenic mice expressing human PrP,
*** indicating that the species barrier from cervid to humans is prion
strain-dependent and humans can be vulnerable to novel cervid prion strains.
PPo2-27:
Generation of a Novel form of Human PrPSc by Inter-species Transmission of
Cervid Prions
*** Our findings suggest that CWD prions have the capability to infect
humans, and that this ability depends on CWD strain adaptation, implying that
the risk for human health progressively increases with the spread of CWD among
cervids.
PPo2-7:
Biochemical and Biophysical Characterization of Different CWD Isolates
*** The data presented here substantiate and expand previous reports on the
existence of different CWD strains.
Envt.07:
Pathological Prion Protein (PrPTSE) in Skeletal Muscles of Farmed and Free
Ranging White-Tailed Deer Infected with Chronic Wasting Disease
***The presence and seeding activity of PrPTSE in skeletal muscle from
CWD-infected cervids suggests prevention of such tissue in the human diet as a
precautionary measure for food safety, pending on further clarification of
whether CWD may be transmissible to humans.
>>>CHRONIC WASTING DISEASE , THERE WAS NO ABSOLUTE BARRIER TO
CONVERSION OF THE HUMAN PRION PROTEIN<<<
*** PRICE OF CWD TSE PRION POKER GOES UP 2014 ***
Transmissible Spongiform Encephalopathy TSE PRION update January 2, 2014
Wednesday, January 01, 2014
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.
PRION2013 CONGRESSIONAL ABSTRACTS CWD
Sunday, August 25, 2013
HD.13: CWD infection in the spleen of humanized transgenic mice
***These results indicate that the CWD prion may have the potential to
infect human peripheral lymphoid tissues.
Oral.15: Molecular barriers to zoonotic prion transmission: Comparison of
the ability of sheep, cattle and deer prion disease isolates to convert normal
human prion protein to its pathological isoform in a cell-free system
***However, they also show that there is no absolute barrier to conversion of
human prion protein in the case of chronic wasting disease.
PRION2013 CONGRESSIONAL ABSTRACTS CWD
Sunday, August 25, 2013
***Chronic Wasting Disease CWD risk factors, humans, domestic cats, blood,
and mother to offspring transmission
PPo3-7:
Prion Transmission from Cervids to Humans is Strain-dependent
Qingzhong Kong, Shenghai Huang,*Fusong Chen, Michael Payne, Pierluigi
Gambetti and Liuting Qing Department of Pathology; Case western Reserve
University; Cleveland, OH USA *Current address: Nursing Informatics; Memorial
Sloan-Kettering Cancer Center; New York, NY USA
Key words: CWD, strain, human transmission
Chronic wasting disease (CWD) is a widespread prion disease in cervids
(deer and elk) in North America where significant human exposure to CWD is
likely and zoonotic transmission of CWD is a concern. Current evidence indicates
a strong barrier for transmission of the classical CWD strain to humans with the
PrP-129MM genotype. A few recent reports suggest the presence of two or more CWD
strains. What remain unknown is whether individuals with the PrP-129VV/MV
genotypes are also resistant to the classical CWD strain and whether humans are
resistant to all natural or adapted cervid prion strains. Here we report that a
human prion strain that had adopted the cervid prion protein (PrP) sequence
through passage in cervidized transgenic mice efficiently infected transgenic
mice expressing human PrP, indicating that the species barrier from cervid to
humans is prion strain-dependent and humans can be vulnerable to novel cervid
prion strains. Preliminary results on CWD transmission in transgenic mice
expressing human PrP-129V will also be discussed.
Acknowledgement Supported by NINDS NS052319 and NIA AG14359.
PPo2-27:
Generation of a Novel form of Human PrPSc by Inter-species Transmission of
Cervid Prions
Marcelo A. Barria,1 Glenn C. Telling,2 Pierluigi Gambetti,3 James A.
Mastrianni4 and Claudio Soto1 1Mitchell Center for Alzheimer’s disease and
related Brain disorders; Dept of Neurology; University of Texas Houston Medical
School; Houston, TX USA; 2Dept of Microbiology, Immunology & Molecular
Genetics and Neurology; Sanders Brown Center on Aging; University of Kentucky
Medical Center; Lexington, KY USA; 3Institute of Pathology; Case western Reserve
University; Cleveland, OH USA; 4Dept of Neurology; University of Chicago;
Chicago, IL USA
Prion diseases are infectious neurodegenerative disorders affecting humans
and animals that result from the conversion of normal prion protein (PrPC) into
the misfolded and infectious prion (PrPSc). Chronic wasting disease (CWD) of
cervids is a prion disorder of increasing prevalence within the United States
that affects a large population of wild and captive deer and elk. CWD is highly
contagious and its origin, mechanism of transmission and exact prevalence are
currently unclear. The risk of transmission of CWD to humans is unknown.
Defining that risk is of utmost importance, considering that people have been
infected by animal prions, resulting in new fatal diseases. To study the
possibility that human PrPC can be converted into the infectious form by CWD
PrPSc we performed experiments using the Protein Misfolding Cyclic Amplification
(PMCA) technique, which mimic in vitro the process of prion replication. Our
results show that cervid PrPSc can induce the pathological conversion of human
PrPC, but only after the CWD prion strain has been stabilized by successive
passages in vitro or in vivo. Interestingly, this newly generated human PrPSc
exhibits a distinct biochemical pattern that differs from any of the currently
known forms of human PrPSc, indicating that it corresponds to a novel human
prion strain. Our findings suggest that CWD prions have the capability to infect
humans, and that this ability depends on CWD strain adaptation, implying that
the risk for human health progressively increases with the spread of CWD among
cervids.
PPo2-7:
Biochemical and Biophysical Characterization of Different CWD Isolates
Martin L. Daus and Michael Beekes Robert Koch Institute; Berlin, Germany
Key words: CWD, strains, FT-IR, AFM
Chronic wasting disease (CWD) is one of three naturally occurring forms of
prion disease. The other two are Creutzfeldt-Jakob disease in humans and scrapie
in sheep. CWD is contagious and affects captive as well as free ranging cervids.
As long as there is no definite answer of whether CWD can breach the species
barrier to humans precautionary measures especially for the protection of
consumers need to be considered. In principle, different strains of CWD may be
associated with different risks of transmission to humans. Sophisticated strain
differentiation as accomplished for other prion diseases has not yet been
established for CWD. However, several different findings indicate that there
exists more than one strain of CWD agent in cervids. We have analysed a set of
CWD isolates from white-tailed deer and could detect at least two biochemically
different forms of disease-associated prion protein PrPTSE. Limited proteolysis
with different concentrations of proteinase K and/or after exposure of PrPTSE to
different pH-values or concentrations of Guanidinium hydrochloride resulted in
distinct isolate-specific digestion patterns. Our CWD isolates were also
examined in protein misfolding cyclic amplification studies. This showed
different conversion activities for those isolates that had displayed
significantly different sensitivities to limited proteolysis by PK in the
biochemical experiments described above. We further applied Fourier transform
infrared spectroscopy in combination with atomic force microscopy. This
confirmed structural differences in the PrPTSE of at least two disinct CWD
isolates. The data presented here substantiate and expand previous reports on
the existence of different CWD strains.
2012
Envt.06:
Zoonotic Potential of CWD: Experimental Transmissions to Non-Human Primates
Emmanuel Comoy,1,† Valérie Durand,1 Evelyne Correia,1 Aru Balachandran,2
Jürgen Richt,3 Vincent Beringue,4 Juan-Maria Torres,5 Paul Brown,1 Bob Hills6
and Jean-Philippe Deslys1
1Atomic Energy Commission; Fontenay-aux-Roses, France; 2Canadian Food
Inspection Agency; Ottawa, ON Canada; 3Kansas State University; Manhattan, KS
USA; 4INRA; Jouy-en-Josas, France; 5INIA; Madrid, Spain; 6Health Canada; Ottawa,
ON Canada
†Presenting author; Email: emmanuel.comoy@cea.fr
The constant increase of chronic wasting disease (CWD) incidence in North
America raises a question about their zoonotic potential. A recent publication
showed their transmissibility to new-world monkeys, but no transmission to
old-world monkeys, which are phylogenetically closer to humans, has so far been
reported. Moreover, several studies have failed to transmit CWD to transgenic
mice overexpressing human PrP. Bovine spongiform encephalopathy (BSE) is the
only animal prion disease for which a zoonotic potential has been proven. We
described the transmission of the atypical BSE-L strain of BSE to cynomolgus
monkeys, suggesting a weak cattle-to-primate species barrier. We observed the
same phenomenon with a cattleadapted strain of TME (Transmissible Mink
Encephalopathy). Since cattle experimentally exposed to CWD strains have also
developed spongiform encephalopathies, we inoculated brain tissue from
CWD-infected cattle to three cynomolgus macaques as well as to transgenic mice
overexpressing bovine or human PrP. Since CWD prion strains are highly
lymphotropic, suggesting an adaptation of these agents after peripheral
exposure, a parallel set of four monkeys was inoculated with CWD-infected cervid
brains using the oral route. Nearly four years post-exposure, monkeys exposed to
CWD-related prion strains remain asymptomatic. In contrast, bovinized and
humanized transgenic mice showed signs of infection, suggesting that CWD-related
prion strains may be capable of crossing the cattle-to-primate species barrier.
Comparisons with transmission results and incubation periods obtained after
exposure to other cattle prion strains (c-BSE, BSE-L, BSE-H and cattle-adapted
TME) will also be presented, in order to evaluate the respective risks of each
strain.
Envt.07:
Pathological Prion Protein (PrPTSE) in Skeletal Muscles of Farmed and Free
Ranging White-Tailed Deer Infected with Chronic Wasting Disease
Martin L. Daus,1,† Johanna Breyer,2 Katjs Wagenfuehr,1 Wiebke Wemheuer,2
Achim Thomzig,1 Walter Schulz-Schaeffer2 and Michael Beekes1 1Robert Koch
Institut; P24 TSE; Berlin, Germany; 2Department of Neuropathology, Prion and
Dementia Research Unit, University Medical Center Göttingen; Göttingen, Germany
†Presenting author; Email: dausm@rki.de
Chronic wasting disease (CWD) is a contagious, rapidly spreading
transmissible spongiform encephalopathy (TSE) occurring in cervids in North
America. Despite efficient horizontal transmission of CWD among cervids natural
transmission of the disease to other species has not yet been observed. Here, we
report a direct biochemical demonstration of pathological prion protein PrPTSE
and of PrPTSE-associated seeding activity in skeletal muscles of CWD-infected
cervids. The presence of PrPTSE was detected by Western- and postfixed frozen
tissue blotting, while the seeding activity of PrPTSE was revealed by protein
misfolding cyclic amplification (PMCA). The concentration of PrPTSE in skeletal
muscles of CWD-infected WTD was estimated to be approximately 2000- to
10000-fold lower than in brain tissue. Tissue-blot-analyses revealed that PrPTSE
was located in muscle- associated nerve fascicles but not, in detectable
amounts, in myocytes. The presence and seeding activity of PrPTSE in skeletal
muscle from CWD-infected cervids suggests prevention of such tissue in the human
diet as a precautionary measure for food safety, pending on further
clarification of whether CWD may be transmissible to humans.
P.10.15
ADAPTATION OF CHRONIC WASTING DISEASE (CWD) INTO HAMSTERS, EVIDENCE OF A
WISCONSIN STRAIN OF CWD
Chad Johnson1, Judd Aiken2,3,4 and Debbie McKenzie4,5 1 Department of
Comparative Biosciences, University of Wisconsin, Madison WI, USA 53706 2
Department of Agriculture, Food and Nutritional Sciences, 3 Alberta Veterinary
Research Institute, 4.Center for Prions and Protein Folding Diseases, 5
Department of Biological Sciences, University of Alberta, Edmonton AB, Canada
T6G 2P5
The identification and characterization of prion strains is increasingly
important for the diagnosis and biological definition of these infectious
pathogens. Although well-established in scrapie and, more recently, in BSE,
comparatively little is known about the possibility of prion strains in chronic
wasting disease (CWD), a disease affecting free ranging and captive cervids,
primarily in North America. We have identified prion protein variants in the
white-tailed deer population and demonstrated that Prnp genotype affects the
susceptibility/disease progression of white-tailed deer to CWD agent. The
existence of cervid prion protein variants raises the likelihood of distinct CWD
strains. Small rodent models are a useful means of identifying prion strains. We
intracerebrally inoculated hamsters with brain homogenates and phosphotungstate
concentrated preparations from CWD positive hunter-harvested (Wisconsin CWD
endemic area) and experimentally infected deer of known Prnp genotypes. These
transmission studies resulted in clinical presentation in primary passage of
concentrated CWD prions. Subclinical infection was established with the other
primary passages based on the detection of PrPCWD in the brains of hamsters and
the successful disease transmission upon second passage. Second and third
passage data, when compared to transmission studies using different CWD inocula
(Raymond et al., 2007) indicate that the CWD agent present in the Wisconsin
white-tailed deer population is different than the strain(s) present in elk,
mule-deer and white-tailed deer from the western United States endemic region.
CHRONIC WASTING DISEASE CWD
Transmissibility to humans.
The current state of epidemiological research suggests a rather robust
barrier for the transmission of CWD to humans. Particularly, the surveillance of
human prion diseases in areas with a long history of endemic CWD such as
Colorado and Wyoming did not reveal evidence for zoonotic transmissions of the
disease to cervid hunters or consumers of meat from elk and deer.66. Belay ED,
Maddox RA, Williams ES, Miller MW, Gambetti P, Schonberger LB. Chronic wasting
disease and potential transmission to humans. Emerg Infect Dis 2004; 10:977 -
984; PMID: 15207045 [CrossRef] View all references,1111. Belay ED, Abrams J,
Kenfield J, Weidenbach K, Maddox RA, Lawaczeck E, et al. Monitoring the
potential transmission of chronic wasting disease to humans (Abstract Oral.40,
Prion 2011 Oral Presentations). Prion 2011; 5:17 Supplemental Issue
April/May/June 2011 View all references
However, as discussed by Belay et al.66. Belay ED, Maddox RA, Williams ES,
Miller MW, Gambetti P, Schonberger LB. Chronic wasting disease and potential
transmission to humans. Emerg Infect Dis 2004; 10:977 - 984; PMID: 15207045
[CrossRef] View all references
the intensity of human exposure to CWD prions may increase due to a further
spread and rising prevalence of the disease in cervids. Therefore, and with the
generally long latency periods of human prion diseases in mind, previous
epidemiological findings cannot be readily extrapolated. Until recently,
experimental studies that pursued biochemical approaches or used transgenic mice
to ascertain the susceptibility of humans to CWD infections consistently seemed
to corroborate current epidemiological findings: CWD-infected cervid brain
tissue did not seed the conversion of PrPC into PrPres in PMCA assays using
brain homogenate from macaques or transgenic mice expressing human PrPC as test
substrate,1212. Kurt TD, Telling GC, Zabel MD, Hoover EA. Trans-species
amplification of PrP(CWD) and correlation with rigid loop 170N. Virology 2009;
387:235 - 243; PMID: 19269662; http://dx.doi.org/10.1016/j.virol.2009.02.025
[CrossRef] View all references
and transgenic mice overexpressing human PrPC were resistant to infection
after intracerebral challenge with CWD prions from mule deer.1313. Sandberg MK,
Al-Doujaily H, Sigurdson CJ, Glatzel M, O'Malley C, Powell C, et al. Chronic
wasting disease prions are not transmissible to transgenic mice overexpressing
human prion protein. J Gen Virol 2010; 91:2651 - 2657; PMID: 20610667; http://dx.doi.org/10.1099/vir.0.024380-0
[CrossRef] View all references
However, a study published by Barria et al.1414. Barria MA, Telling GC,
Gambetti P, Mastrianni JA, Soto C. Generation of a new form of human PrPSc in
vitro by interspecies transmission from cervid prions. J Biol Chem 2011;
286:7490 - 7495; PMID: 21209079; http://dx.doi.org/10.1074/jbc.M110.198465
[CrossRef] View all references
in March 2011 found that cervid PrPTSE can seed the conversion of human
PrPC into PrPres by PMCA when the CWD agent has been previously passaged in
vitro or in vivo. Specifically, this was demonstrated for CWD prions from
naturally affected mule deer either passaged by serial PMCA using deer PrPC as
conversion substrate or in transgenic mice expressing cervid PrPC. The authors
of this study pointed out that CWD prions may undergo a gradual process of
change and adaptation via successive passages in the cervid population. They
concluded that the reported findings, if corroborated by infectivity assays, may
imply “that CWD prions have the potential to infect humans and that this ability
progressively increases with CWD spreading.” Cynomolgus macaques used as a
primate model for testing the susceptibility of humans to CWD as close to
reality as possible have not shown clinical signs of a prion disease at nearly 6
years after intracerebral or peroral inoculation of CWD agents from white-tailed
deer, Rocky Mountain elk or mule deer.1515. Race B, Meade-White KD, Miller MW,
Barbian KD, Rubenstein R, LaFauci G, et al. Susceptibilities of nonhuman
primates to chronic wasting disease. Emerg Infect Dis 2009; 15:1366 - 1376;
PMID: 19788803; http://dx.doi.org/10.3201/eid1509.090253
[CrossRef] View all references
In contrast to macaques, squirrel monkeys were susceptible to CWD infection
by the intracerebral route and showed even a low rate of disease transmission
after oral challenge.1515. Race B, Meade-White KD, Miller MW, Barbian KD,
Rubenstein R, LaFauci G, et al. Susceptibilities of nonhuman primates to chronic
wasting disease. Emerg Infect Dis 2009; 15:1366 - 1376; PMID: 19788803; http://dx.doi.org/10.3201/eid1509.090253
[CrossRef] View all references,1616. Marsh RF, Kincaid AE, Bessen RA, Bartz JC.
Interspecies transmission of chronic wasting disease prions to squirrel monkeys
(Saimiri sciureus). J Virol 2005; 79:13794 - 13796; PMID: 16227298; http://dx.doi.org/10.1128/JVI.79.21.13794-6.2005
[CrossRef] View all references
Since humans are phylogenetically closer related to macaques than to
squirrel monkeys, macaques are regarded as the more relevant primate model for
assessing the zoonotic transmissibility of CWD.1515. Race B, Meade-White KD,
Miller MW, Barbian KD, Rubenstein R, LaFauci G, et al. Susceptibilities of
nonhuman primates to chronic wasting disease. Emerg Infect Dis 2009; 15:1366 -
1376; PMID: 19788803; http://dx.doi.org/10.3201/eid1509.090253
[CrossRef] View all references
Ongoing transmission studies in macaques. In addition to the primate study
by Race et al.1515. Race B, Meade-White KD, Miller MW, Barbian KD, Rubenstein R,
LaFauci G, et al. Susceptibilities of nonhuman primates to chronic wasting
disease. Emerg Infect Dis 2009; 15:1366 - 1376; PMID: 19788803; http://dx.doi.org/10.3201/eid1509.090253
[CrossRef] View all references
two further studies in which macaques were challenged with tissue
homogenates from CWD-affected cervids by intracerebral inoculation or via the
oral route have been reported to be in progress.1717. Comoy E, Durand V, Correia
E, Balachandran A, Richt JA, Beringue V, et al. Zoonotic potential of CWD:
Experimental transmissions to non-human primates (Abstract Envt.06, Prion 2011
Poster Presentations). Prion 2011; 5:101 View all references,1818. Motzkus D,
Schulz-Schaeffer WJ, Beekes M, Schätzl HM, Jirik FR, Schmädicke AC, et al.
Transmission of CWD to non-human primates: Interim results of a comprehensive
study on the transmissibility to humans (Abstract Envt. 22, Prion 2011 Poster
Presentations). Prion 2011; 5:107 Supplemental Issue April/May/June 2011 View
all references
The purpose, research effort, financial investment and ethical aspects of
these studies demand an utmost experimental scrutiny, careful data analysis and
thorough exploitation of results. This has two immediate implications: (1) Since
the incubation period of CWD may be very long in case of primary (i.e.,
inter-species) transmission to macaques a sustained monitoring of the animals
appears mandatory for many years despite negative interim findings. (2)
Increasing evidence suggests the existence of different CWD agents (see below),
and theoretically, CWD prions may also change over time thereby possibly
altering their potential host range. Thus, CWD isolates used in individual or
pooled inocula for the challenge of macaques should be typed as precisely as
possible in terms of their strain characteristics and molecular identity. Other
field isolates could then be checked for their similarity or dissimilarity to
the macaque-tested CWD agents in order to ascertain whether or not they are
covered by the ongoing primate risk assessments. Evidence for Distinct CWD
Strains Jump to section Transmissible Spongiform... Exposure of Humans to CWD
Prions CWD Risk Assessments Evidence for Distinct CWD Strains Outlook Disclosure
of Potential Conflicts of Interest Funding Figures and Tables Biochemical
indications for isolate-dependent structural differences of PrPTSE. In 2002 it
was reported that glycoform patterns of PrPTSE showed differences among
individual CWD-affected cervids.1919. Race RE, Raines A, Baron TG, Miller MW,
Jenny A, Williams ES. Comparison of abnormal prion protein glycoform patterns
from transmissible spongiform encephalopathy agent-infected deer, elk, sheep and
cattle. J Virol 2002; 76:12365 - 12368; PMID: 12414979; http://dx.doi.org/10.1128/JVI.76.23.12365-8.2002
[CrossRef] View all references
In a variety of studies the glycosylation of PrPTSE had been previously
established as a biochemical feature that may differ between distinct TSE
agents.2020. Parchi P, Capellari S, Chen SG, Petersen RB, Gambetti P, Kopp N, et
al. Typing prion isoforms. Nature 1997; 386:232 - 234; PMID: 9069279; http://dx.doi.org/10.1038/386232a0
[CrossRef] View all references,2121. Aguzzi A, Heikenwalder M, Polymenidou M.
Insights into prion strains and neurotoxicity. Nat Rev Mol Cell Biol 2007; 8:552
- 561; PMID: 17585315; http://dx.doi.org/10.1038/nrm2204
[CrossRef] View all references
Accordingly, the finding by Race et al. possibly indicated CWD infections
with different or multiple strains of agent, although, alternatively, it could
also be explained by random selection from a heterogeneous population of
CWD-affected ruminants.1919. Race RE, Raines A, Baron TG, Miller MW, Jenny A,
Williams ES. Comparison of abnormal prion protein glycoform patterns from
transmissible spongiform encephalopathy agent-infected deer, elk, sheep and
cattle. J Virol 2002; 76:12365 - 12368; PMID: 12414979; http://dx.doi.org/10.1128/JVI.76.23.12365-8.2002
[CrossRef] View all references
Using a conformation-dependent immunoassay (CDI), Safar et al. found
evidence for different conformations of PrPTSE in elk CWD as compared with
white-tailed and mule deer CWD.2222. Safar JG, Scott M, Monaghan J, Deering C,
Didorenko S, Vergara J, et al. Measuring prions causing bovine spongiform
encephalopathy or chronic wasting disease by immunoassays and transgenic mice.
Nat Biotechnol 2002; 20:1147 - 1150; PMID: 12389035; http://dx.doi.org/10.1038/nbt748
[CrossRef] View all references
However, the amino acid sequences of elk and deer PrPC differ at residues
226 (glutamic acid in elk and glutamine in deer), and it remained to be
established whether the structural differences detected by CDI were related to
biologically distinct CWD strains. Isolation of CWD-associated agents causing
distinct phenotypes in laboratory rodents. Classically, prion strains are
differentiated based on their incubation periods in inbred mice with distinct
PrP genotypes and by lesion profiles of the vacuolation in selected brain areas
of reporter animals.2323. Bruce ME, Fraser H. Scrapie strain variation and its
implications. Curr Top Microbiol Immunol 1991; 172:125 - 138; PMID: 1810707
[CrossRef] View all references
When Raymond et al. serially passaged a CWD inoculum from mule deer either
in Syrian hamsters or first into transgenic mice expressing hamster PrPC, and
then further on in hamsters, they obtained two distinct isolates termed
SghaCWDmd-f and SghaCWDmd-s, respectively.2424. Raymond GJ, Raymond LD,
Meade-White KD, Hughson AG, Favara C, Gardner D, et al. Transmission and
adaptation of chronic wasting disease to hamsters and transgenic mice: evidence
for strains. J Virol 2007; 81:4305 - 4314; PMID: 17287284; http://dx.doi.org/10.1128/JVI.02474-06
[CrossRef] View all references
The first isolate showed an about 5-fold shorter incubation period in
Syrian hamsters than the latter, and the cerebral patterns of PrPTSE deposition
and gliosis in clinically affected hamsters were also different. Based on their
findings the authors concluded that the “cervid-derived inocula may have
contained or diverged into at least two distinct transmissible spongiform
encephalopathy strains.” Angers et al. transmitted CWD inocula from elk and deer
to transgenic mice expressing cervid PrP and found that these mice were affected
by one of two strains, referred to as CWD1 and CWD2, that caused different
incubation times and lesion profiles.2525. Angers RC, Kang HE, Napier D,
Browning S, Seward T, Mathiason C, et al. Prion strain mutation determined by
prion protein conformational compatibility and primary structure. Science 2010;
328:1154 - 1158; PMID: 20466881; http://dx.doi.org/10.1126/science.1187107
[CrossRef] View all references
The results of this study “appear to reflect strain constitutions in the
natural host, rather than adaptation and divergence of progenitor strains in
recipient mice,” according to the authors. Interestingly, CWD1 and CWD2 did not
show recognizably different biochemical properties of their PrPTSE. The
electrophoretic migration and glycosylation patterns as well as the stability
characteristics after treatment with guanidine hydrochloride were
indistinguishable for CWD1- and CWD2-associated PrPTSE. Consistent with these
findings it has been previously reported that biologically distinct prion
strains cannot always be differentiated by biochemical PrPTSE-typing or
characterization of the conformational stability of PrPTSE.2626. Thomzig A,
Spassov S, Friedrich M, Naumann D, Beekes M. Discriminating scrapie and bovine
spongiform encephalopathy isolates by infrared spectroscopy of pathological
prion protein. J Biol Chem 2004; 279:33847 - 33854; PMID: 15155741; http://dx.doi.org/10.1074/jbc.M403730200
[CrossRef] View all references,2727. Peretz D, Scott MR, Groth D, Williamson RA,
Burton DR, Cohen FE, et al. Strain-specified relative conformational stability
of the scrapie prion protein. Protein Sci 2001; 10:854 - 863; PMID: 11274476; http://dx.doi.org/10.1110/ps.39201
[CrossRef] View all references
UPDATED DATA ON 2ND CWD STRAIN Wednesday, September 08, 2010 CWD PRION
CONGRESS SEPTEMBER 8-11 2010
OR-12: Chronic wasting disease transmission and pathogenesis in cervid and
non-cervid Species
Edward A. Hoover, Candace K. Mathiason, Nicholas J. Haley, Timothy D. Kurt,
Davis M. Seelig, Nathaniel D. Denkers, Amy V. Nalls, Mark D. Zabel, and Glenn C.
Telling
Prion Research Program, Department of Microbiology, Immunology, and
Pathology; Colorado State University; Fort Collins, CO USA
Since its recognition as a TSE in the late 1970s, chronic wasting disease
(CWD) of cervids has been distinguished by its facile spread and is now
recognized in 18 states, 2 Canadian provinces, and South Korea. The efficient
horizontal spread of CWD reflects a prion/host relationship that facilitates
efficient mucosal uptake, peripheral lymphoid amplification, and dissemination
by exploiting excretory tissues and their products, helping to establish
indirect/environmental and well as direct (e.g., salivary) transmission. Recent
studies from our group also support the likelihood of early life mother to
offspring and aerosol CWD prion transmission. Studies of cervid CWD exposure by
natural routes indicate that incubation period for detection of overt infection,
while still uncertain, may be much longer than originally thought.
Several non-cervid species can be infected by CWD experimentally (e.g.,
ferrets, voles, cats) with consequent species-specific disease phenotypes. The
species-adapted prions so generated can be transmitted by mucosal, i.e., more
natural, routes. Whether non-cervid species sympatric with deer/elk can be
infected in nature, however, remains unknown. In vitro CWD prion amplification
studies, in particular sPMCA, can foreshadow in vivo susceptibility and suggest
the importance of the PrPC rigid loop region in species barrier permissiveness.
Trans-species CWD amplification appears to broaden the host range/strain
characteristics of the resultant prions. The origins of CWD remain unknown,
however, the existence of multiple CWD prion strains/ quasi-species, the
mechanisms of prion shedding/dissemination, and the relationship between sheep
scrapie and CWD merit further investigation.
Monday, May 23, 2011
CDC Assesses Potential Human Exposure to Prion Diseases Travel Warning
Public release date: 23-May-2011
Contact: Francesca Costanzo adajmedia@elsevier.com 215-239-3249 Elsevier
Health Sciences
CDC assesses potential human exposure to prion diseases Study results
reported in the Journal of the American Dietetic Association Philadelphia, PA,
May 23, 2011 – Researchers from the Centers for Disease Control and Prevention
(CDC) have examined the potential for human exposure to prion diseases, looking
at hunting, venison consumption, and travel to areas in which prion diseases
have been reported in animals. Three prion diseases in particular – bovine
spongiform encephalopathy (BSE or “Mad Cow Disease”), variant Creutzfeldt-Jakob
disease (vCJD), and chronic wasting disease (CWD) – were specified in the
investigation. The results of this investigation are published in the June issue
of the Journal of the American Dietetic Association.
“While prion diseases are rare, they are generally fatal for anyone who
becomes infected. More than anything else, the results of this study support the
need for continued surveillance of prion diseases,” commented lead investigator
Joseph Y. Abrams, MPH, National Center for Emerging and Zoonotic Infectious
Diseases, CDC, Atlanta.”But it’s also important that people know the facts about
these diseases, especially since this study shows that a good number of people
have participated in activities that may expose them to infection-causing
agents.”
Although rare, human prion diseases such as CJD may be related to BSE.
Prion (proteinaceous infectious particles) diseases are a group of rare brain
diseases that affect humans and animals. When a person gets a prion disease,
brain function is impaired. This causes memory and personality changes,
dementia, and problems with movement. All of these worsen over time. These
diseases are invariably fatal. Since these diseases may take years to manifest,
knowing the extent of human exposure to possible prion diseases could become
important in the event of an outbreak.
CDC investigators evaluated the results of the 2006-2007 population survey
conducted by the Foodborne Diseases Active Surveillance Network (FoodNet). This
survey collects information on food consumption practices, health outcomes, and
demographic characteristics of residents of the participating Emerging
Infections Program sites. The survey was conducted in Connecticut, Georgia,
Maryland, Minnesota, New Mexico, Oregon, and Tennessee, as well as five counties
in the San Francisco Bay area, seven counties in the Greater Denver area, and 34
counties in western and northeastern New York.
Survey participants were asked about behaviors that could be associated
with exposure to the agents causing BSE and CWD, including travel to the nine
countries considered to be BSE-endemic (United Kingdom, Republic of Ireland,
France, Portugal, Switzerland, Italy, the Netherlands, Germany, Spain) and the
cumulative length of stay in each of those countries. Respondents were asked if
they ever had hunted for deer or elk, and if that hunting had taken place in
areas considered to be CWD-endemic (northeastern Colorado, southeastern Wyoming
or southwestern Nebraska). They were also asked if they had ever consumed
venison, the frequency of consumption, and whether the meat came from the wild.
The proportion of survey respondents who reported travel to at least one of
the nine BSE endemic countries since 1980 was 29.5%. Travel to the United
Kingdom was reported by 19.4% of respondents, higher than to any other
BSE-endemic country. Among those who traveled, the median duration of travel to
the United Kingdom (14 days) was longer than that of any other BSE-endemic
country. Travelers to the UK were more likely to have spent at least 30 days in
the country (24.9%) compared to travelers to any other BSE endemic country. The
prevalence and extent of travel to the UK indicate that health concerns in the
UK may also become issues for US residents.
The proportion of survey respondents reporting having hunted for deer or
elk was 18.5% and 1.2% reported having hunted for deer or elk in CWD-endemic
areas. Venison consumption was reported by 67.4% of FoodNet respondents, and
88.6% of those reporting venison consumption had obtained all of their meat from
the wild. These findings reinforce the importance of CWD surveillance and
control programs for wild deer and elk to reduce human exposure to the CWD
agent. Hunters in CWD-endemic areas are advised to take simple precautions such
as: avoiding consuming meat from sickly deer or elk, avoiding consuming brain or
spinal cord tissues, minimizing the handling of brain and spinal cord tissues,
and wearing gloves when field-dressing carcasses.
According to Abrams, “The 2006-2007 FoodNet population survey provides
useful information should foodborne prion infection become an increasing public
health concern in the future. The data presented describe the prevalence of
important behaviors and their associations with demographic characteristics.
Surveillance of BSE, CWD, and human prion diseases are critical aspects of
addressing the burden of these diseases in animal populations and how that may
relate to human health.”
###
The article is “Travel history, hunting, and venison consumption related to
prion disease exposure, 2006-2007 FoodNet population survey” by Joseph Y.
Abrams, MPH; Ryan A. Maddox, MPH; Alexis R Harvey, MPH; Lawrence B. Schonberger,
MD; and Ermias D. Belay, MD. It appears in the Journal of the American Dietetic
Association, Volume 111, Issue 6 (June 2011) published by Elsevier.
In an accompanying podcast CDC’s Joseph Y. Abrams discusses travel,
hunting, and eating venison in relation to prion diseases. It is available at http://adajournal.org/content/podcast.
Thursday, May 26, 2011
Travel History, Hunting, and Venison Consumption Related to Prion Disease
Exposure, 2006-2007 FoodNet Population Survey
Journal of the American Dietetic Association Volume 111, Issue 6 , Pages
858-863, June 2011.
Travel History, Hunting, and Venison Consumption Related to Prion Disease
Exposure, 2006-2007 FoodNet Population Survey
Joseph Y. Abrams, MPH, Ryan A. Maddox, MPH , Alexis R. Harvey, MPH ,
Lawrence B. Schonberger, MD , Ermias D. Belay, MD
Accepted 15 November 2010. Abstract Full Text PDF References .
Abstract
The transmission of bovine spongiform encephalopathy (BSE) to human beings
and the spread of chronic wasting disease (CWD) among cervids have prompted
concerns about zoonotic transmission of prion diseases. Travel to the United
Kingdom and other European countries, hunting for deer or elk, and venison
consumption could result in the exposure of US residents to the agents that
cause BSE and CWD. The Foodborne Diseases Active Surveillance Network 2006-2007
population survey was used to assess the prevalence of these behaviors among
residents of 10 catchment areas across the United States. Of 17,372 survey
respondents, 19.4% reported travel to the United Kingdom since 1980, and 29.5%
reported travel to any of the nine European countries considered to be
BSE-endemic since 1980. The proportion of respondents who had ever hunted deer
or elk was 18.5%, and 1.2% had hunted deer or elk in a CWD–endemic area. More
than two thirds (67.4%) reported having ever eaten deer or elk meat. Respondents
who traveled spent more time in the United Kingdom (median 14 days) than in any
other BSE-endemic country. Of the 11,635 respondents who had consumed venison,
59.8% ate venison at most one to two times during their year of highest
consumption, and 88.6% had obtained all of their meat from the wild. The survey
results were useful in determining the prevalence and frequency of behaviors
that could be important factors for foodborne prion transmission.
CDC
Saturday, February 18, 2012
Occurrence, Transmission, and Zoonotic Potential of Chronic Wasting Disease
CDC Volume 18, Number 3—March 2012
SNIP…
Interspecies transmission of CWD to noncervids has not been observed under
natural conditions. CWD infection of carcass scavengers such as raccoons,
opossums, and coyotes was not observed in a recent study in Wisconsin (22). In
addition, natural transmission of CWD to cattle has not been observed in
experimentally controlled natural exposure studies or targeted surveillance (2).
However, CWD has been experimentally transmitted to cattle, sheep, goats, mink,
ferrets, voles, and mice by intracerebral inoculation (2,29,33).
CWD is likely transmitted among mule, white-tailed deer, and elk without a
major species barrier (1), and other members of the cervid family, including
reindeer, caribou, and other species of deer worldwide, may be vulnerable to CWD
infection. Black-tailed deer (a subspecies of mule deer) and European red deer
(Cervus elaphus) are susceptible to CWD by natural routes of infection (1,34).
Fallow deer (Dama dama) are susceptible to CWD by intracerebral inoculation
(35). Continued study of CWD susceptibility in other cervids is of considerable
interest.
Reasons for Caution There are several reasons for caution with respect to
zoonotic and interspecies CWD transmission. First, there is strong evidence that
distinct CWD strains exist (36). Prion strains are distinguished by varied
incubation periods, clinical symptoms, PrPSc conformations, and CNS PrPSc
depositions (3,32). Strains have been identified in other natural prion
diseases, including scrapie, BSE, and CJD (3). Intraspecies and interspecies
transmission of prions from CWD-positive deer and elk isolates resulted in
identification of >2 strains of CWD in rodent models (36), indicating that
CWD strains likely exist in cervids. However, nothing is currently known about
natural distribution and prevalence of CWD strains. Currently, host range and
pathogenicity vary with prion strain (28,37). Therefore, zoonotic potential of
CWD may also vary with CWD strain. In addition, diversity in host (cervid) and
target (e.g., human) genotypes further complicates definitive findings of
zoonotic and interspecies transmission potentials of CWD.
Intraspecies and interspecies passage of the CWD agent may also increase
the risk for zoonotic CWD transmission. The CWD prion agent is undergoing serial
passage naturally as the disease continues to emerge. In vitro and in vivo
intraspecies transmission of the CWD agent yields PrPSc with an increased
capacity to convert human PrPc to PrPSc (30). Interspecies prion transmission
can alter CWD host range (38) and yield multiple novel prion strains (3,28). The
potential for interspecies CWD transmission (by cohabitating mammals) will only
increase as the disease spreads and CWD prions continue to be shed into the
environment. This environmental passage itself may alter CWD prions or exert
selective pressures on CWD strain mixtures by interactions with soil, which are
known to vary with prion strain (25), or exposure to environmental or gut
degradation.
Given that prion disease in humans can be difficult to diagnose and the
asymptomatic incubation period can last decades, continued research,
epidemiologic surveillance, and caution in handling risky material remain
prudent as CWD continues to spread and the opportunity for interspecies
transmission increases. Otherwise, similar to what occurred in the United
Kingdom after detection of variant CJD and its subsequent link to BSE, years of
prevention could be lost if zoonotic transmission of CWD is subsequently
identified, CWD will likely continue to emerge in North America. …
SNIP…
Generation of a new form of human PrPSc in vitro by inter-species
transmission from cervids prions
Our results have far-reaching implications for human health, since they
indicate that cervid PrPSc can trigger the conversion of human PrPC into PrPSc,
suggesting that CWD might be infectious to humans. Interestingly our findings
suggest that unstable strains from CWD affected animals might not be a problem
for humans, but upon strain stabilization by successive passages in the wild,
this disease might become progressively more transmissible to man.
Our results also have profound implications for understanding the
mechanisms of the prion species barrier and indicate that the transmission
barrier is a dynamic process that depends on the strain and moreover the degree
of adaptation of the strain. If our findings are corroborated by infectivity
assays, they will imply that CWD prions have the potential to infect humans and
that this ability progressively increases with CWD spreading.
I thought your readers and hunters and those that consume the venison,
should have all the scientific facts, personally, I don’t care what you eat, but
if it effects me and my family down the road, it should then concern everyone,
and the potential of iatrogenic transmission of the TSE prion is real i.e.
‘friendly fire’, medical, surgical, dental, blood, tissue, and or products there
from...like deer antler velvet and TSE prions and nutritional supplements there
from, all a potential risk factor that should not be ignored or silenced. ...
the prion gods at the cdc state that there is ;
''no strong evidence''
but let's see exactly what the authors of this cwd to human at the cdc
state ;
now, let’s see what the authors said about this casual link, personal
communications years ago. see where it is stated NO STRONG evidence. so, does
this mean there IS casual evidence ????
“Our conclusion stating that we found no strong evidence of CWD
transmission to humans”
From: TSS (216-119-163-189.ipset45.wt.net)
Subject: CWD aka MAD DEER/ELK TO HUMANS ???
Date: September 30, 2002 at 7:06 am PST
From: "Belay, Ermias"
To:
Cc: "Race, Richard (NIH)" ; ; "Belay, Ermias"
Sent: Monday, September 30, 2002 9:22 AM
Subject: RE: TO CDC AND NIH - PUB MED- 3 MORE DEATHS - CWD - YOUNG HUNTERS
Dear Sir/Madam,
In the Archives of Neurology you quoted (the abstract of which was attached
to your email), we did not say CWD in humans will present like variant CJD.
That assumption would be wrong. I encourage you to read the whole article
and call me if you have questions or need more clarification (phone:
404-639-3091). Also, we do not claim that "no-one has ever been infected with
prion disease from eating venison." Our conclusion stating that we found no
strong evidence of CWD transmission to humans in the article you quoted or in
any other forum is limited to the patients we investigated.
Ermias Belay, M.D. Centers for Disease Control and Prevention
-----Original Message-----
From:
Sent: Sunday, September 29, 2002 10:15 AM
To: rr26k@nih.gov; rrace@niaid.nih.gov; ebb8@CDC.GOV
Subject: TO CDC AND NIH - PUB MED- 3 MORE DEATHS - CWD - YOUNG HUNTERS
Sunday, November 10, 2002 6:26 PM ......snip........end..............TSS
Thursday, April 03, 2008
A prion disease of cervids: Chronic wasting disease
2008 1: Vet Res. 2008 Apr 3;39(4):41
A prion disease of cervids: Chronic wasting disease
Sigurdson CJ.
snip...
*** twenty-seven CJD patients who regularly consumed venison were reported
to the Surveillance Center***,
snip...
full text ;
***********CJD REPORT 1994 increased risk for consumption of veal and
venison and lamb***********
CREUTZFELDT JAKOB DISEASE SURVEILLANCE IN THE UNITED KINGDOM THIRD ANNUAL
REPORT AUGUST 1994
Consumption of venison and veal was much less widespread among both cases
and controls. For both of these meats there was evidence of a trend with
increasing frequency of consumption being associated with increasing risk of
CJD. (not nvCJD, but sporadic CJD...tss)
These associations were largely unchanged when attention was restricted to
pairs with data obtained from relatives. ...
Table 9 presents the results of an analysis of these data.
There is STRONG evidence of an association between ‘’regular’’ veal eating
and risk of CJD (p = .0.01).
Individuals reported to eat veal on average at least once a year appear to
be at 13 TIMES THE RISK of individuals who have never eaten veal.
There is, however, a very wide confidence interval around this estimate.
There is no strong evidence that eating veal less than once per year is
associated with increased risk of CJD (p = 0.51).
The association between venison eating and risk of CJD shows similar
pattern, with regular venison eating associated with a 9 FOLD INCREASE IN RISK
OF CJD (p = 0.04).
There is some evidence that risk of CJD INCREASES WITH INCREASING FREQUENCY
OF LAMB EATING (p = 0.02).
The evidence for such an association between beef eating and CJD is weaker
(p = 0.14). When only controls for whom a relative was interviewed are included,
this evidence becomes a little STRONGER (p = 0.08).
snip...
It was found that when veal was included in the model with another
exposure, the association between veal and CJD remained statistically
significant (p = < 0.05 for all exposures), while the other exposures ceased
to be statistically significant (p = > 0.05).
snip...
In conclusion, an analysis of dietary histories revealed statistical
associations between various meats/animal products and INCREASED RISK OF CJD.
When some account was taken of possible confounding, the association between
VEAL EATING AND RISK OF CJD EMERGED AS THE STRONGEST OF THESE ASSOCIATIONS
STATISTICALLY. ...
snip...
In the study in the USA, a range of foodstuffs were associated with an
increased risk of CJD, including liver consumption which was associated with an
apparent SIX-FOLD INCREASE IN THE RISK OF CJD. By comparing the data from 3
studies in relation to this particular dietary factor, the risk of liver
consumption became non-significant with an odds ratio of 1.2 (PERSONAL
COMMUNICATION, PROFESSOR A. HOFMAN. ERASMUS UNIVERSITY, ROTTERDAM). (???...TSS)
snip...see full report ;
Thursday, October 10, 2013
*************CJD REPORT 1994 increased risk for consumption of veal and
venison and lamb**************
CJD9/10022
October 1994
Mr R.N. Elmhirst Chairman British Deer Farmers Association Holly Lodge
Spencers Lane BerksWell Coventry CV7 7BZ
Dear Mr Elmhirst,
CREUTZFELDT-JAKOB DISEASE (CJD) SURVEILLANCE UNIT REPORT
Thank you for your recent letter concerning the publication of the third
annual report from the CJD Surveillance Unit. I am sorry that you are
dissatisfied with the way in which this report was published.
The Surveillance Unit is a completely independant outside body and the
Department of Health is committed to publishing their reports as soon as they
become available. In the circumstances it is not the practice to circulate the
report for comment since the findings of the report would not be amended. In
future we can ensure that the British Deer Farmers Association receives a copy
of the report in advance of publication.
The Chief Medical Officer has undertaken to keep the public fully informed
of the results of any research in respect of CJD. This report was entirely the
work of the unit and was produced completely independantly of the the
Department.
The statistical results reqarding the consumption of venison was put into
perspective in the body of the report and was not mentioned at all in the press
release. Media attention regarding this report was low key but gave a realistic
presentation of the statistical findings of the Unit. This approach to
publication was successful in that consumption of venison was highlighted only
once by the media ie. in the News at one television proqramme.
I believe that a further statement about the report, or indeed statistical
links between CJD and consumption of venison, would increase, and quite possibly
give damaging credence, to the whole issue. From the low key media reports of
which I am aware it seems unlikely that venison consumption will suffer
adversely, if at all.
http://web.archive.org/web/20030511010117/http://www.bseinquiry.gov.uk/files/yb/1994/10/00003001.pdf
*** our results raise the possibility that CJD cases classified as VV1 may
include cases caused by iatrogenic transmission of sCJD-MM1 prions or food-borne
infection by type 1 prions from animals, e.g., chronic wasting disease prions in
cervid. In fact, two CJD-VV1 patients who hunted deer or consumed venison have
been reported (40, 41). The results of the present study emphasize the need for
traceback studies and careful re-examination of the biochemical properties of
sCJD-VV1 prions. ***
snip...see full text ;
Thursday, January 2, 2014
*** CWD TSE Prion in cervids to hTGmice, Heidenhain Variant
Creutzfeldt-Jacob Disease MM1 genotype, and iatrogenic CJD ??? ***
*** The potential impact of prion diseases on human health was greatly
magnified by the recognition that interspecies transfer of BSE to humans by beef
ingestion resulted in vCJD. While changes in animal feed constituents and
slaughter practices appear to have curtailed vCJD, there is concern that CWD of
free-ranging deer and elk in the U.S. might also cross the species barrier.
Thus, consuming venison could be a source of human prion disease. Whether BSE
and CWD represent interspecies scrapie transfer or are newly arisen prion
diseases is unknown. Therefore, the possibility of transmission of prion disease
through other food animals cannot be ruled out. There is evidence that vCJD can
be transmitted through blood transfusion. There is likely a pool of unknown size
of asymptomatic individuals infected with vCJD, and there may be asymptomatic
individuals infected with the CWD equivalent. These circumstances represent a
potential threat to blood, blood products, and plasma supplies.
Monday, August 8, 2011
*** Susceptibility of Domestic Cats to CWD Infection ***
Oral.29: Susceptibility of Domestic Cats to CWD Infection
Amy Nalls, Nicholas J. Haley, Jeanette Hayes-Klug, Kelly Anderson, Davis M.
Seelig, Dan S. Bucy, Susan L. Kraft, Edward A. Hoover and Candace K. Mathiason†
Colorado State University; Fort Collins, CO USA†Presenting author; Email:
ckm@lamar.colostate.edu
Domestic and non-domestic cats have been shown to be susceptible to one
prion disease, feline spongiform encephalopathy (FSE), thought to be transmitted
through consumption of bovine spongiform encephalopathy (BSE) contaminated meat.
Because domestic and free ranging felids scavenge cervid carcasses, including
those in CWD affected areas, we evaluated the susceptibility of domestic cats to
CWD infection experimentally. Groups of n = 5 cats each were inoculated either
intracerebrally (IC) or orally (PO) with CWD deer brain homogenate. Between
40–43 months following IC inoculation, two cats developed mild but progressive
symptoms including weight loss, anorexia, polydipsia, patterned motor behaviors
and ataxia—ultimately mandating euthanasia. Magnetic resonance imaging (MRI) on
the brain of one of these animals (vs. two age-matched controls) performed just
before euthanasia revealed increased ventricular system volume, more prominent
sulci, and T2 hyperintensity deep in the white matter of the frontal hemisphere
and in cortical grey distributed through the brain, likely representing
inflammation or gliosis. PrPRES and widely distributed peri-neuronal vacuoles
were demonstrated in the brains of both animals by immunodetection assays. No
clinical signs of TSE have been detected in the remaining primary passage cats
after 80 months pi. Feline-adapted CWD was sub-passaged into groups (n=4 or 5)
of cats by IC, PO, and IP/SQ routes. Currently, at 22 months pi, all five IC
inoculated cats are demonstrating abnormal behavior including increasing
aggressiveness, pacing, and hyper responsiveness.
*** Two of these cats have developed rear limb ataxia. Although the limited
data from this ongoing study must be considered preliminary, they raise the
potential for cervid-to-feline transmission in nature.
AD.63:
Susceptibility of domestic cats to chronic wasting disease
Amy V.Nalls,1 Candace Mathiason,1 Davis Seelig,2 Susan Kraft,1 Kevin
Carnes,1 Kelly Anderson,1 Jeanette Hayes-Klug1 and Edward A. Hoover1 1Colorado
State University; Fort Collins, CO USA; 2University of Minnesota; Saint Paul, MN
USA
Domestic and nondomestic cats have been shown to be susceptible to feline
spongiform encephalopathy (FSE), almost certainly caused by consumption of
bovine spongiform encephalopathy (BSE)-contaminated meat. Because domestic and
free-ranging nondomestic felids scavenge cervid carcasses, including those in
areas affected by chronic wasting disease (CWD), we evaluated the susceptibility
of the domestic cat (Felis catus) to CWD infection experimentally. Cohorts of 5
cats each were inoculated either intracerebrally (IC) or orally (PO) with
CWD-infected deer brain. At 40 and 42 mo post-inoculation, two IC-inoculated
cats developed signs consistent with prion disease, including a stilted gait,
weight loss, anorexia, polydipsia, patterned motor behaviors, head and tail
tremors, and ataxia, and progressed to terminal disease within 5 mo. Brains from
these two cats were pooled and inoculated into cohorts of cats by IC, PO, and
intraperitoneal and subcutaneous (IP/SC) routes. Upon subpassage, feline-adapted
CWD (FelCWD) was transmitted to all IC-inoculated cats with a decreased
incubation period of 23 to 27 mo. FelCWD was detected in the brains of all the
symptomatic cats by western blotting and immunohistochemistry and abnormalities
were seen in magnetic resonance imaging, including multifocal T2 fluid
attenuated inversion recovery (FLAIR) signal hyper-intensities, ventricular size
increases, prominent sulci, and white matter tract cavitation. Currently, 3 of 4
IP/SQ and 2 of 4 PO inoculared cats have developed abnormal behavior patterns
consistent with the early stage of feline CWD.
*** These results demonstrate that CWD can be transmitted and adapted to
the domestic cat, thus raising the issue of potential cervid-to- feline
transmission in nature.
Tuesday, November 04, 2014
*** Six-year follow-up of a point-source exposure to CWD contaminated
venison in an Upstate New York community: risk behaviours and health outcomes
2005–2011
PO-081: Chronic wasting disease in the cat— Similarities to feline
spongiform encephalopathy (FSE)
FELINE SPONGIFORM ENCEPHALOPATHY FSE
Thursday, July 03, 2014
*** How Chronic Wasting Disease is affecting deer population and what’s the
risk to humans and pets?
Saturday, January 31, 2015
European red deer (Cervus elaphus elaphus) are susceptible to Bovine
Spongiform Encephalopathy BSE by Oral Alimentary route
*** Singeltary reply ;
ruminant feed ban for cervids in the United States ?
31 Jan 2015 at 20:14 GMT
Friday, January 30, 2015
*** Scrapie: a particularly persistent pathogen ***
Wednesday, April 22, 2015
Circulation of prions within dust on a scrapie affected farm
Friday, May 22, 2015
Chronic Wasting Disease and Program Updates - 2014 NEUSAHA Annual Meeting
12-14 May 2014
Thursday, July 09, 2015
TEXAS Chronic Wasting Disease (CWD) Herd Plan for Trace-Forward Exposed
Herd with Testing of Exposed Animals
============
P.70: Experimental transmission of chronic wasting disease to sheep and
goats
Gordon Mitchell, Nishandan Yogasingam, Ines Walther, and Aru Balachandran
National and OIE Reference Laboratory for Scrapie and CWD; Canadian Food
Inspection Agency; Ottawa, ON, Canada
The persistence of chronic wasting disease (CWD) in North American cervids,
coupled with efforts to eradicate scrapie in sheep and goats, necessitates an
understanding of the transmission, clinical and diagnostic characteristics of
CWD in small ruminants. Oral and intracerebral transmission studies were
conducted in sheep and goats using tissues from CWD-infected elk. Four lambs and
4 goats were orally inoculated with a pooled brain and lymph node homogenate
from a group of farmed elk with clinical CWD. At study endpoint, there was no
evidence of primary CWD transmission in the sheep or goat tissues examined by
ELISA, western blot and immunohistochemistry (IHC). Two lambs which were
challenged intracerebrally with the same pooled elk inoculate displayed
neurological signs beginning at 27 months postinoculation (mpi) and were
euthanized within 10 d of each other at 28 mpi. Testing of tissues by ELISA and
IHC confirmed disease transmission and revealed differences in the distribution
and intensity of PrPd deposition between animals. Western immunoblot analysis
identified characteristics permitting the differentiation of CWD in sheep from
other prion diseases in small ruminants. CWD-infected tissue from the
intracerabrally-inoculated sheep has undergone secondary passage into sheep and
goats and currently shows no evidence of oral transmission in rectal mucosa
biopsies at 20 mpi. These findings corroborate evidence of a significant species
barrier preventing the oral transmission of CWD to sheep and goats, and identify
diagnostic characteristics to enable the differentiation of prion diseases
affecting small ruminants.
===========
P.97: Scrapie transmits to white-tailed deer by the oral route and has a
molecular profile similar to chronic wasting disease and distinct from the
scrapie inoculum
Justin Greenlee1, S Jo Moore1, Jodi Smith1, M Heather West Greenlee2, and
Robert Kunkle1 1National Animal Disease Center; Ames, IA USA; 2Iowa State
University; Ames, IA USA
The purpose of this work was to determine susceptibility of white-tailed
deer (WTD) to the agent of sheep scrapie and to compare the resultant PrPSc to
that of the original inoculum and chronic wasting disease (CWD). We inoculated
WTD by a natural route of exposure (concurrent oral and intranasal (IN); n D 5)
with a US scrapie isolate. All scrapie-inoculated deer had evidence of PrPSc
accumulation. PrPSc was detected in lymphoid tissues at preclinical time points,
and deer necropsied after 28 months post-inoculation had clinical signs,
spongiform encephalopathy, and widespread distribution of PrPSc in neural and
lymphoid tissues. Western blotting (WB) revealed PrPSc with 2 distinct molecular
profiles. WB on cerebral cortex had a profile similar to the original scrapie
inoculum, whereas WB of brainstem, cerebellum, or lymph nodes revealed PrPSc
with a higher profile resembling CWD. Homogenates with the 2 distinct profiles
from WTD with clinical scrapie were further passaged to mice expressing cervid
prion protein and intranasally to sheep and WTD. In cervidized mice, the 2
inocula have distinct incubation times. Sheep inoculated intranasally with WTD
derived scrapie developed disease, but only after inoculation with the inoculum
that had a scrapie-like profile. The WTD study is ongoing, but deer in both
inoculation groups are positive for PrPSc by rectal mucosal biopsy.*** In
summary, this work demonstrates that WTD are susceptible to the agent of
scrapie, 2 distinct molecular profiles of PrPSc are present in the tissues of
affected deer, and inoculum of either profile readily passes to deer.
=================
*** In summary, this work demonstrates that WTD are susceptible to the
agent of scrapie, 2 distinct molecular profiles of PrPSc are present in the
tissues of affected deer, and inoculum of either profile readily passes to deer.
***
================
P.128: Bioassay using ovine and cervid PrP transgenic mice for
discrimination of scrapie and CWD origins in sheep and goats
Sally Madsen-Bouterse1,*, Dongyue Zhuang2, David Schneider2, Rohana
Dassanayake1, Aru Balachandran3, Gordon Mitchell3, and Katherine O’Rourke1
1Department of Veterinary Microbiology and Pathology; College of Veterinary
Medicine; Washington State University; Pullman, WA USA; 2Animal Disease Research
Unit; Agricultural Research Service; US. Department of Agriculture; Pullman, WA
USA; 3National and OIE Reference Laboratory for Scrapie and CWD; Canadian Food
Inspection Agency; Ottawa Laboratory– Fallowfield; Ottawa, ON Canada
As the United States works toward the eradication of scrapie, identifying
TSE reservoirs that could lead to disease re-emergence is imperative.
Development of transgenic mice expressing either the ovine or cervid prion
protein has aided characterization of scrapie and CWD, respectively. We
hypothesize that transgenic mouse models will discern whether new incidents of
scrapie in sheep and goats with clinical disease originated from CWD exposure.
Two transgenic mouse lines (Tg338 and TgElk; minimum 5 mice/strain) were
inoculated with brain homogenate from clinically affected animals including
sheep or goats with naturally acquired classical scrapie, white-tailed deer with
naturally acquired CWD (WTD-CWD), or sheep experimentally inoculated with
elk-CWD (sheepelk- CWD). Transmission was assessed via survival analysis and
western blot characterization of brain PrPres. WTD-CWD transmitted efficiently
to TgElk with all mice culled due to clinical disease, whereas all Tg338
remained asymptomatic at endpoint with no PrPres detected in the brain. Ovine
and caprine scrapie transmitted poorly to TgElk with all mice asymptomatic at
endpoint and 6.8% brain-positive for PrPres, whereas all Tg338 were culled due
to clinical disease. Sheep elk-CWD yielded Tg338 that were all asymptomatic at
endpoint and were all brainpositive for PrPres. However, sheepelk-CWD yielded
TgElk with 5/22 displaying clinical disease near endpoint but 16/22
brain-positive for PrPres. Furthermore, TgElk-PrPres molecular mass appeared
lower when inoculated with caprine scrapie versus WTD-CWD and both molecular
masses were yielded when inoculated with sheepelk-CWD. ***These findings suggest
primary passage in Tg338 and TgElk could discern whether scrapie in sheep and
goats originated from CWD exposure.
===========
P.73: Oral challenge of goats with atypical scrapie
Silvia Colussi1, Maria Mazza1, Francesca Martucci1, Simone Peletto1,
Cristiano Corona1, Marina Gallo1, Cristina Bona1, Romolo Nonno2, Michele Di
Bari2, Claudia D’Agostino2, Nicola Martinelli3, Guerino Lombardi3, and Pier
Luigi Acutis1 1Istituto Zooprofilattico Sperimentale del Piemonte; Liguria e
Valle d’Aosta; Turin, Italy; 2Istituto Superiore di Sanit a; Rome, Italy;
3Istituto Zooprofilattico Sperimentale della Lombardia e dell’Emilia Romagna;
Brescia, Italy
Atypical scrapie transmission has been demonstrated in sheep by
intracerebral and oral route (Simmons et al., Andreoletti et al., 2011) but data
about goats are not available yet. In 2006 we orally challenged four goats, five
months old, with genotype R/H and R/R at codon 154. Animals died starting from
24 to 77 months p.i. without clinical signs. They all resulted negative for
scrapie in CNS and peripheral tissues using Western blot and
immunohistochemistry. Nevertheless these goats could still represent carriers.
This hypothesis was investigated through bioassay in tg338 mice, a sensitive
animal model for atypical scrapie infectivity. By end-point dilution titration,
the starting inoculum contained 106.8 ID50/g. In contrast, all tissues from
challenged goats were negative by bioassay. These negative results could be
explained with the low infectivity of the starting inoculum, which could have
been unable to induce disease or infectivity within our period of observation.
However the challenge conditions could have been a bias too: as the matter of
the fact, while the oral challenge of classical scrapie is still effective in
sheep 6–10 months old (Andreoletti et al., 2011), Simmons et al. (2011)
demonstrated a very short efficacy period for atypical scrapie (24 hours after
birth), hypothesizing that natural transmission could occur mainly via milk.
***Our work suggests that this could be true also for goats and it should be
taken into account in oral challenges. However a low susceptibility of goats to
atypical scrapie transmission via oral route cannot be excluded.
=============
P.74: Transmission of experimental CH1641 scrapie to wild-type mice
Lucien van Keulen1,*, Jan Langeveld1, Corry Dolstra1, Jorg Jacobs1, Alex
Bossers1, and Fred van Zijderveld2 1Department of Infection Biology; Central
Veterinary Institute of Wageningen UR, Lelystad, The Netherlands; 2Department of
Bacteriology and TSEs; Central Veterinary Institute of Wageningen UR, Lelystad,
The Netherlands
Introduction. CH1641 was isolated in the UK in 1970 from a natural case of
scrapie in a Cheviot sheep and was further passaged intracerebrally in sheep.
CH1641 has been the subject of extensive research because of the biochemical
similarities of PrPres from CH1641- and BSE-affected sheep brains. Previous
attempts to transmit CH1641 to wild type mice have been unsuccessful. We report
here for the first time, the positive transmission of experimental CH1641 to
RIII mice and compare the incubation period, PrPSc profile and PrPres Western
blot properties to those of known scrapie and BSE reference strains.
Methods. The CH1641 brain homogenate used in this study came from a pool a
5 sheep brains which had been challenged intracerebrally with brain material
from the third passage of CH1641 in sheep. Groups of 15–20 RIII mice were
inoculated intracerebrally with a 10% brain homogenate of CH1641. The brains of
the mice were examined by PrPSc profiling and triplex Western blot as reported
previously.
Results. Surprisingly CH1641 transmitted to RIII mice with a 100% attack
rate although with a long incubation period (794 § 149 d). The resulting PrPSc
profile was unlike any of the profiles of the scrapie and BSE reference strains
reported previously. Triplex Western blot pointed after first passage to a very
low PrPres level. We observed a reduction of molecular mass of the non-glycosyl
PrPres moiety and concomittant N-terminal 12B2 epitope signal. In comparison to
the original CH1641 inoculum there was a lack of a dual population of
PrPres.
===========
***The serial transmission of different scrapie isolates in these mice led
to the propagation of prions that are phenotypically identical to those causing
sporadic CJD (sCJD) in humans.
***These results demonstrate that scrapie prions have a zoonotic potential
and raise new questions about the possible link between animal and human
prions.
Subject terms: Biological sciences• Medical research At a glance
2015
Longitudinal Detection of Prion Shedding in Saliva and Urine by
CWD-Infected Deer by RT-QuIC
Davin M. Henderson1, Nathaniel D. Denkers1, Clare E. Hoover1, Nina
Garbino1, Candace K. Mathiason1 and Edward A. Hoover1# + Author
Affiliations
1Prion Research Center, Department of Microbiology, Immunology, and
Pathology, College of Veterinary Medicine and Biomedical Sciences, Colorado
State University, Fort Collins, CO 80523 ABSTRACT Chronic Wasting Disease (CWD)
is an emergent, rapidly spreading prion disease of cervids. Shedding of
infectious prions in saliva and urine is thought to be an important factor in
CWD transmission. To help elucidate this issue, we applied an in vitro
amplification assay to determine the onset, duration, and magnitude of prion
shedding in longitudinally collected saliva and urine samples from CWD-exposed
white-tailed deer. We detected prion shedding as early as 3 months after CWD
exposure and sustained shedding throughout the disease course. We estimated that
a 50% lethal dose (LD50) for cervidized transgenic mice would be contained in 1
ml of infected deer saliva or 10 ml or urine. Given the average course of
infection and daily production of these body fluids, an infected deer would shed
thousands of prion infectious dosesover the course of CWD infection. The direct
and indirect environmental impact of this magnitude of prion shedding for cervid
and non-cervid species is surely significant.
Importance: Chronic wasting disease (CWD) is an emerging and uniformly
fatal prion disease affecting free ranging deer and elk and now recognized in 22
United States and 2 C anadian Provinces. It is unique among prion diseases in
that it is transmitted naturally though wild populations. A major hypothesis for
CWD's florid spread is that prions are shed in excreta and transmitted via
direct or indirect environmental contact. Here we use a rapid in vitro assay to
show that infectious doses of CWD prions are in fact shed throughout the
multi-year disease course in deer. This finding is an important advance in
assessing the risks posed by shed CWD prions to animals as well as humans.
FOOTNOTES
↵#To whom correspondence should be addressed: Edward A. Hoover, Prion
Research Center, Department of Microbiology, Immunology and Pathology, Colorado
State University, Fort Collins, Colorado, US Email:
edward.hoover@colostate.edu
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.
snip...
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.
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, Val erie 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 longe 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...TSS
===============
Saturday, May 30, 2015
PRION 2015 ORAL AND POSTER CONGRESSIONAL ABSTRACTS
LATE-BREAKING ABSTRACTS
O18
Zoonotic Potential of CWD Prions
Liuting Qing1, Ignazio Cali1,2, Jue Yuan1, Shenghai Huang3, Diane Kofskey1,
Pierluigi Gambetti1, Wenquan Zou1, Qingzhong Kong1 1Case Western Reserve
University, Cleveland, Ohio, USA, 2Second University of Naples, Naples, Italy,
3Encore Health Resources, Houston, Texas, USA
Chronic wasting disease (CWD) is a widespread and expanding prion disease
in free-ranging and captive cervid species in North America. The zoonotic
potential of CWD prions is a serious public health concern. Current literature
generated with in vitro methods and in vivo animal models (transgenic mice,
macaques and squirrel monkeys) reports conflicting results. The susceptibility
of human CNS and peripheral organs to CWD prions remains largely unresolved. In
our earlier bioassay experiments using several humanized transgenic mouse lines,
we detected protease-resistant PrPSc in the spleen of two out of 140 mice that
were intracerebrally inoculated with natural CWD isolates, but PrPSc was not
detected in the brain of the same mice. Secondary passages with such
PrPSc-positive CWD-inoculated humanized mouse spleen tissues led to efficient
prion transmission with clear clinical and pathological signs in both humanized
and cervidized transgenic mice. Furthermore, a recent bioassay with natural CWD
isolates in a new humanized transgenic mouse line led to clinical prion
infection in 2 out of 20 mice. These results indicate that the CWD prion has the
potential to infect human CNS and peripheral lymphoid tissues and that there
might be asymptomatic human carriers of CWD infection.
==================
***These results indicate that the CWD prion has the potential to infect
human CNS and peripheral lymphoid tissues and that there might be asymptomatic
human carriers of CWD infection.***
==================
I strenuously once again urge the FDA and its industry constituents, to
make it MANDATORY that all ruminant feed be banned to all ruminants, and this
should include all cervids as soon as possible for the following
reasons...
======
In the USA, under the Food and Drug Administrations BSE Feed Regulation (21
CFR 589.2000) most material (exceptions include milk, tallow, and gelatin) from
deer and elk is prohibited for use in feed for ruminant animals. With regards to
feed for non-ruminant animals, under FDA law, CWD positive deer may not be used
for any animal feed or feed ingredients. For elk and deer considered at high
risk for CWD, the FDA recommends that these animals do not enter the animal feed
system.
***However, this recommendation is guidance and not a requirement by law.
======
31 Jan 2015 at 20:14 GMT
*** Ruminant feed ban for cervids in the United States? ***
31 Jan 2015 at 20:14 GMT
Terry S. Singeltary Sr.
