Molecular Barriers to Zoonotic Transmission of Prions
Molecular Barriers to Zoonotic Transmission of Prions
*** chronic wasting disease, there was no absolute barrier to conversion of
the human prion protein.
Volume 20, Number 1—January 2014
Research
Molecular Barriers to Zoonotic Transmission of Prions
Suggested Citation
Marcelo A. Barria, Aru Balachandran, Masanori Morita, Tetsuyuki Kitamoto,
Rona Barron, Jean Manson, Richard Knight, James W. Ironside, and Mark W.
HeadComments to Author
Author affiliations: The University of Edinburgh, Edinburgh, Scotland, UK
(M.A. Barria, R. Knight, J.W. Ironside, M.W Head); Canadian Food Inspection
Agency, Ottawa, Ontario, Canada (A. Balachandran); Japan Blood Products
Organization, Kobe, Japan (M. Morita); Tohoku University Graduate School of
Medicine, Sendai, Japan (T. Kitamoto); University of Edinburgh, Easter Bush,
Scotland, UK (R. Barron, J. Manson)
Abstract
The risks posed to human health by individual animal prion diseases cannot
be determined a priori and are difficult to address empirically. The fundamental
event in prion disease pathogenesis is thought to be the seeded conversion of
normal prion protein to its pathologic isoform. We used a rapid molecular
conversion assay (protein misfolding cyclic amplification) to test whether brain
homogenates from specimens of classical bovine spongiform encephalopathy (BSE),
atypical BSE (H-type BSE and L-type BSE), classical scrapie, atypical scrapie,
and chronic wasting disease can convert normal human prion protein to the
abnormal disease-associated form. None of the tested prion isolates from
diseased animals were as efficient as classical BSE in converting human prion
protein. However, in the case of chronic wasting disease, there was no absolute
barrier to conversion of the human prion protein.
snip...
Discussion
Multiple factors govern the transmission of prions in experimental
settings. In addition to infectious dose and route, a species or transmission
barrier phenomenon is well recognized. Within the theoretical confines of the
prion hypothesis, the most obvious basis of a species barrier effect would be
dissimilarity in PRNP sequence between the infectious source and the exposed
individual. However, PRNP sequence similarity alone does not seem to accurately
predict whether prions are transmissible between species, perhaps because
interactions between PrPC and PrPSc occur as native PrPC and misfolded and
aggregated PrPSc conformers. The possible effects of species-specific sequence
difference on PrPC folding are not well understood. Neither is the secondary and
higher order structure of PrPSc, except for clear evidence that different prion
strains are associated with different PrPSc conformers and glycotypes (reviewed
in 4,18) and that these might exist as a quasispecies or molecular cloud (19).
Under such a scenario molecular compatibility might be difficult to
predict.
To isolate and study molecular effects, we have previously conducted
cell-free PrP conversion experiments by PMCA using homogenates of bovine and
ovine prion disease brain samples to seed brain homogenates containing human
PrP, assessing the extent of conversion by detection of human PrPres. These
studies showed that samples of C-type BSE (which is a known human pathogen and
the cause of vCJD) efficiently converted human PrP, with a codon 129 preference
similar to that of vCJD (MM>MV>VV), whereas samples of classical scrapie
(which is not thought to be a human pathogen) failed to convert human PrP to a
measurable extent. Equally importantly, a sheep BSE isolate resembled C-type BSE
and vCJD in its ability to convert human PrP, thus underscoring influence of
strain over sequence similarity in determining what might be termed a molecular
transmission barrier (10).
Here we applied the same approach to a series of animal prion diseases
whose risk to human health is poorly characterized. Our results show that under
the PMCA conditions used, L-type BSE, H-type BSE, and atypical scrapie isolates
fail to produce detectable human PrPres. The CWD isolate used converted human
PrPC, albeit less efficiently than C-type BSE. This observation remained true
whether the input animal prion disease brain homogenate was normalized by tissue
weight or by PrPres abundance and whether the PMCA substrate was from human
brain, PRNP humanized murine brain, or a human-derived and human PrPC
overexpressing cell line. The conversion of human PrPC by CWD brain homogenate
in PMCA reactions was less efficient when the amino acid at position 129 was
valine rather than methionine. 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.
Previous attempts to determine the transmissibility of these prion diseases
to humans and thus assess their zoonotic potential have used experimental
challenge of nonhuman primates, humanized PrP transgenic mice, and cell-free
assays with sometimes conflicting results. Successful transmission of CWD and
L-BSE to certain nonhuman primates has been reported: L-type BSE showing a
different pathologic profile and a shorter incubation period than C-type BSE
(20–23). However, Kong et al. (24) reported that CWD failed to transmit to
humanized PrP 129M overexpressing mice inoculated with an elk brain homogenate.
In contrast, Beringue et al. (25) reported that humanized PrP 129M
overexpressing mice were susceptible to L-type BSE and suggested that L-type BSE
was more virulent than C-type BSE and presented a zoonotic risk. H-type BSE
reportedly failed to transmit to these same mice. Sandberg et al. (26) and
Tamgüney et al. (27) confirmed the previous report of Kong et al. that CWD fails
to transmit to transgenic mice, irrespective of whether 1) the mice expressed
bovine, ovine, or human PrP; 2) the mice expressed the human 129M or 129V PrP
allelic variants; or 3) the CWD isolates were from mule deer, elk, or
white-tailed deer.
Cell-free approaches to modeling human susceptibility to animal prion prion
diseases also have been published (8,10,28–31). Raymond et al. (28) compared the
ability of CWD, C-type BSE, sheep scrapie, and CJD brain homogenates to convert
human PrPC metabolically labeled and purified from transfected cells. These
experiments obtained limited conversion of human PrPC by CWD, C-type BSE, and
scrapie. In contrast to our study, this early cell-free system failed to
distinguish between scrapie and C-type BSE in their ability to convert human
PrPC; however, it indicated a substantial molecular barrier to conversion of
human PrPC by CWD PrPSc (28,29), which agrees with this report. Kurt et al. (31)
reported that PMCA using human PrPC overexpressing transgenic mice brain (both
129M and 129V lines) as substrate failed to support amplification when seeded
with CWD cervine brain homogenate. Cervidized Prnp transgenic mouse brain
homogenate can support CWD prion replication (32), and extensive in vitro
conditioning of a CWD isolate by PMCA in a cervidized substrate (or passage in
cervidized mice) was sufficient to overcome the barrier and enable efficient in
vitro amplification in a humanized transgenic mouse substrate (33). Direct
comparison of these studies is made difficult by the differences in approach (in
vivo vs. in vitro), the different transgenic constructs used, and the technical
details of the cell-free conversion assays undertaken (Table). An additional
possibly significant difference between these studies is the nature of the CWD
isolate used. CWD affects different deer species (some of which show allelic
variation in their Prnp sequence), but CWD also occurs as different biologic
strains of agent (34–36). Different strains of CWD may have a role in
determining transmissibility and conversion efficiency. Recently, Meyerett et
al. (37) reported the in vitro strain adaptation of a CWD isolate by serial
PMCA, similar to that produced by in vivo subpassage.
The most directly comparable in vivo study to that reported here is Wilson
et al. (11), in which a similar series of atypical animal prion diseases were
used to challenge transgenic mice expressing physiologic levels of human PrPC.
Atypical scrapie; C-, H-, and L-type BSE; and CWD all failed to produce disease
(or signs of infection) on first passage in these mice (11). The use of
different animal prion disease isolates (and possibly differing species and
strains of CWD) might explain this discrepancy; however, a more fundamental
difference might be that the in vivo and in vitro model systems assess different
aspects of the agent and its replication. The in vivo model is undoubtedly more
complex and arguably more physiologically relevant, and the readout is disease;
however, it remains disease in a mouse, in which the PRNP sequence alone is
human. The in vitro cell-free model does not assess disease as such, only the
compatibility of particular combinations of seed and substrate homogenates (some
of which, in these examples, were entirely of human origin) to produce PrPres.
Differences between the in vivo and in vitro models are exemplified by the
comparison of C-type BSE, and vCJD. Both amplify well in PMCA using humanized
(129MM) brain homogenate as a substrate (10), whereas intracranial inoculation
of C-type BSE into humanized (129MM) mice fails to produce disease (12), unless
first experimentally transmitted to sheep or goats (13,38,39).
The interpretation of different amplification efficiencies as a
semiquantitative measure of relative risk is tempting but is probably premature
and almost certainly an oversimplification. The testing of more isolates,
especially of CWD in deer and elk, is advisable before any firm conclusions can
be drawn. Additionally, possible strain-specific effects on amplification
efficiency by the precise PMCA experimental conditions are difficult to discount
and might complicate interpretation. The relative amplification efficiencies of
C-, H-, and L-type BSE might differ intrinsically because certain strains of
sheep scrapie appear to, even when amplified in homologous sheep substrates
(40). However, we can say with confidence that under the conditions used here,
none of the animal isolates tested were as efficient as C-type BSE in converting
human PrPC, which is reassuring. Less reassuring is the finding that there is no
absolute barrier to the conversion of human PrPC by CWD prions in a protocol
using a single round of PMCA and an entirely human substrate prepared from the
target organ of prion diseases, the brain.
Mr Barria is a PhD student at the National CJD Research and Surveillance
Unit, University of Edinburgh (UK). His main research interest is the molecular
basis of human prion diseases.
snip...
*** chronic wasting disease, there was no absolute barrier to conversion of
the human prion protein.
*** 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.
http://cdmrp.army.mil/prevfunded/nprp/NPRP_Summit_Final_Report.pdf
PRION2013 CONGRESSIONAL ABSTRACTS CWD
Sunday, August 25, 2013
***Chronic Wasting Disease CWD risk factors, *humans*, domestic cats,
blood, and mother to offspring transmission
Sunday, July 21, 2013
*** As Chronic Wasting Disease CWD rises in deer herd, what about risk for
humans?
Thursday, October 10, 2013
*** CJD REPORT 1994 increased risk for consumption of veal and venison and lamb
http://creutzfeldt-jakob-disease.blogspot.com/2013/10/cjd-report-1994-increased-risk-for.html
*** CWD TSE Prion in cervids to hTGmice, Heidenhain Variant Creutzfeldt-Jacob Disease MM1 genotype, and iatrogenic CJD ???
http://transmissiblespongiformencephalopathy.blogspot.com/2014/01/cwd-tse-prion-in-cervids-to-htgmice.html
Wednesday, January 01, 2014
APHIS-2006-0118-0100 Chronic Wasting Disease Herd Certification Program and
Interstate Movement of Farmed or Captive Deer, Elk, and Moose
Friday, November 22, 2013
*** Wasting disease is threat to the entire UK deer population CWD TSE
PRION DISEASE Singeltary submission to Scottish Parliament
Sunday, December 29, 2013
Impacts of wildlife baiting and supplemental feeding on infectious disease
transmission risk: A synthesis of knowledge
Sunday, November 3, 2013
*** Environmental Impact Statements; Availability, etc.: Animal Carcass
Management [Docket No. APHIS-2013-0044]
Wednesday, September 04, 2013
***cwd - cervid captive livestock escapes, loose and on the run in the
wild...
Saturday, February 04, 2012
Wisconsin 16 MONTH age limit on testing dead deer Game Farm CWD Testing
Protocol Needs To Be Revised
PRION2013 CONGRESSIONAL ABSTRACTS CWD
Thursday, August 08, 2013
Characterization of the first case of naturally occurring chronic wasting
disease in a captive red deer (Cervus elaphus) in North America
Friday, August 09, 2013
***CWD TSE prion, plants, vegetables, and the potential for environmental
contamination
Sunday, September 01, 2013
hunting over gut piles and CWD TSE prion disease
Monday, October 07, 2013
The importance of localized culling in stabilizing chronic wasting disease
prevalence in white-tailed deer populations
Friday, December 14, 2012
DEFRA U.K. What is the risk of Chronic Wasting Disease CWD being introduced
into Great Britain? A Qualitative Risk Assessment October 2012
Saturday, March 10, 2012
CWD, GAME FARMS, urine, feces, soil, lichens, and banned mad cow protein
feed CUSTOM MADE for deer and elk
----- Original Message -----
From: "Terry S. Singeltary Sr."
To: "INFORMATION DEPT"
Sent: Friday, July 12, 2002 8:43 PM
Subject: Re: CWD AMERICA ???
hello Dr. Jebara,
many thanks for your swift and kind reply.
if i am not mistaken, it was the same email address. it was 3 or 4 weeks
ago i wrote, as it is, i don't save 'sent' emails anymore, unless very
important.
my main concern (besides the fact that a potential TSE has been in the USA
cattle for some time, but the APHIS do not test to find), is that the CWD could
very well be transmitting to humans, and i just did not see to much posted about
it on OIE site.
Coming back to your question, Chronic Wasting Disease is not an OIE
listed disease. Please see OIE disease lists at
why is this TSE (CWD) not listed and followed as with BSE ?'
Article 1.1.3.2. 1. Countries shall make available to other countries,
through the OIE, whatever information is necessary to minimise the spread of
important animal diseases and to assist in achieving better worldwide control of
these diseases.
The USA CWD is an important animal disease.
why is it not followed?
The decision to add or delete a disease from the OIE lists, come through
proposals made by Member Countries and it has to be adopted by the International
Committee.
i _urgently_ suggest a proposal to the OIE to follow this disease very
closely, and to propose _more_ testing in the USA for TSEs in the USA cattle...
kindest regards, terry
Tuesday, July 17, 2012
O.I.E. BSE, CWD, SCRAPIE, TSE PRION DISEASE Final Report of the 80th
General Session, 20 - 25 May 2012
IN A NUT SHELL ;
(Adopted by the International Committee of the OIE on 23 May 2006)
11. Information published by the OIE is derived from appropriate
declarations made by the official Veterinary Services of Member Countries. The
OIE is not responsible for inaccurate publication of country disease status
based on inaccurate information or changes in epidemiological status or other
significant events that were not promptly reported to the Central Bureau,
Sunday, December 15, 2013
*** FDA PART 589 -- SUBSTANCES PROHIBITED FROM USE IN ANIMAL FOOD OR FEED
VIOLATIONS OFFICIAL ACTION INDICATED OAI UPDATE DECEMBER 2013 UPDATE
Saturday, December 21, 2013
**** Complementary studies detecting classical bovine spongiform
encephalopathy infectivity in jejunum, ileum and ileocaecal junction in
incubating cattle ****
Wednesday, December 4, 2013
*** Bovine Spongiform Encephalopathy; Importation of Bovines and Bovine
Products; Final Rule Federal Register / Vol. 78 , No. 233 / Wednesday, December
4, 2013
Saturday, November 2, 2013
*** APHIS Finalizes Bovine Import Regulations in Line with International
Animal Health Standards while enhancing the spread of BSE TSE prion mad cow type
disease around the Globe
Thursday, December 05, 2013
National Scrapie Eradication Program October 2013 Monthly Report Fiscal
Year 2014 TSE PRION REPORT
Tuesday, October 29, 2013
VARIANT CJD PRESENTS DIFFERENTLY IN OLDER PATIENTS
Wednesday, October 09, 2013
*** WHY THE UKBSEnvCJD ONLY THEORY IS SO POPULAR IN IT'S FALLACY,
£41,078,281 in compensation REVISED
Thursday, October 10, 2013
CJD REPORT 1994 increased risk for consumption of veal and venison and lamb
Friday, August 16, 2013
*** Creutzfeldt-Jakob disease (CJD) biannual update August 2013 U.K. and
Contaminated blood products induce a highly atypical prion disease devoid of
PrPres in primates
WHAT about the sporadic CJD TSE proteins ?
WE now know that some cases of sporadic CJD are linked to atypical BSE and
atypical Scrapie, so why are not MORE concerned about the sporadic CJD, and all
it’s sub-types $$$
Creutzfeldt-Jakob Disease CJD cases rising North America updated report
August 2013
*** Creutzfeldt-Jakob Disease CJD cases rising North America with Canada
seeing an extreme increase of 48% between 2008 and 2010 ***
Sunday, October 13, 2013
*** CJD TSE Prion Disease Cases in Texas by Year, 2003-2012
From: noreply@parliament.uk
Sent:
Tuesday, December 03, 2013 4:49 AM
To: Terry Singeltary Sr
Subject: Written submission to House of Commons Science and Technology
Committee inquiry
Parliament UK
Thank you for your written submission to the House of Commons Science and
Technology Committee inquiry on Blood, tissue and organ screening.
We will be in touch if we have any further questions.
From: Terry S. Singeltary Sr.
Sent: Monday, December 02, 2013 9:18 PM
To: CJDVOICE CJDVOICE Cc: bloodcjd bloodcjd
Subject: [BLOODCJD] A parliamentary inquiry has been launched today into
the safety of blood, tissue and organ screening following fears that vCJD – the
human form of ‘mad cow’ disease – may be being spread by medical procedures
Monday, December 02, 2013
*** A parliamentary inquiry has been launched today into the safety of
blood, tissue and organ screening following fears that vCJD – the human form of
‘mad cow’ disease – may be being spread by medical procedures
Wednesday, December 11, 2013
Detection of Infectivity in Blood of Persons with Variant and Sporadic
Creutzfeldt-Jakob Disease
TSS
posted by Terry S. Singeltary Sr. at
10:41 PM
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