Increased Infectivity of Anchorless Mouse Scrapie Prions in Transgenic Mice Overexpressing Human Prion Protein
Increased Infectivity of Anchorless Mouse Scrapie Prions in Transgenic Mice
Overexpressing Human Prion Protein
Brent Race1#, Katie Phillips1, Kimberly Meade-White2, James Striebel1 and
Bruce Chesebro1
+ Author Affiliations 1Laboratory of Persistent Viral Diseases, Rocky
Mountain Laboratories, National Institute of Allergy and Infectious Diseases,
National Institutes of Health, Hamilton, MT, 59840 USA 2Rocky Mountain
Veterinary Branch, Rocky Mountain Laboratories, National Instituteof Allergy and
Infectious Diseases, National Institutes of Health, Hamilton, MT, 59840 USA
ABSTRACT
Prion protein (PrP) is found in all mammals mostly as a glycoprotein
anchored to the plasma membrane by a C-terminal glycophosphatidylinositol (GPI)
linkage. Following prion infection, host protease-sensitive prion protein
(PrPsen or PrPC) is converted into an abnormal, disease-associated,
protease-resistant form (PrPres). Biochemical characteristics such as the PrP
amino acid sequence and post-translational modifications such as glycosylation
and GPI anchoring, can affect the transmissibility of prions as well as the
biochemical properties of the PrPres generated. Previous in vivo studies on the
effects of GPI anchoring on prion infectivity have not examined cross-species
transmission. Here we tested the effect of lack of GPI anchoring on a species
barrier model using mice expressing human PrP. In this model, anchorless 22L
prions derived from tg44 mice were more infectious than 22L prions derived from
C57BL/10 mice when tested in tg66 transgenic mice, which expressed wild-type
anchored human PrP at 8-16 fold above normal. Thus the lack of the GPI anchor on
the PrPres from tg44 mice appeared to reduce the effect of the mouse-human PrP
species barrier. In contrast, neither source of prions induced disease in tgRM
transgenic mice which expressed human PrP at 2-4 fold above normal.
Importance Prion protein (PrP) is found in all mammals, usually attached to
cells by an anchor molecule, called GPI. Following prion infection, PrP is
converted into a disease-associated form (PrPres). While most prion diseases are
species-specific, this finding is not consistent, and species barriers differ in
strength. The amino acid sequence of PrP varies among species, and this
variability affects prion species barriers. However, other PrP modifications,
including glycosylation and GPI-anchoring, may also influence cross-species
infectivity. We studied the effect of PrP GPI-anchoring using a mouse to human
species barrier model. Experiments showed that prions produced by mice
expressing only anchorless PrP were more infectious than prions produced in mice
expressing anchored PrP. Thus, the lack of the GPI anchor on prions reduced the
effect of the mouse-human species barrier. Our results suggest that prion
diseases that produce higher levels of anchorless PrP may pose an increased risk
for cross-species infection.
FOOTNOTES
↵#Corresponding author. Mailing address: Laboratory of Persistent Viral
Diseases, Rocky Mountain Laboratories, National Institute of Allergy and
Infectious Diseases, National Institutes of Health, 903 South Fourth Street,
Hamilton, MT, 59840 USA, Phone: 406-363-9360, Email: raceb@niaid.nih.gov
Copyright © 2015, American Society for Microbiology. All Rights Reserved.
Tuesday, December 16, 2014
Evidence for zoonotic potential of ovine scrapie prions
Hervé Cassard,1, n1 Juan-Maria Torres,2, n1 Caroline Lacroux,1, Jean-Yves
Douet,1, Sylvie L. Benestad,3, Frédéric Lantier,4, Séverine Lugan,1, Isabelle
Lantier,4, Pierrette Costes,1, Naima Aron,1, Fabienne Reine,5, Laetitia
Herzog,5, Juan-Carlos Espinosa,2, Vincent Beringue5, & Olivier Andréoletti1,
Affiliations Contributions Corresponding author Journal name: Nature
Communications Volume: 5, Article number: 5821 DOI: doi:10.1038/ncomms6821
Received 07 August 2014 Accepted 10 November 2014 Published 16 December 2014
Article tools Citation Reprints Rights & permissions Article metrics
Abstract
Although Bovine Spongiform Encephalopathy (BSE) is the cause of variant
Creutzfeldt Jakob disease (vCJD) in humans, the zoonotic potential of scrapie
prions remains unknown. Mice genetically engineered to overexpress the human
prion protein (tgHu) have emerged as highly relevant models for gauging the
capacity of prions to transmit to humans. These models can propagate human
prions without any apparent transmission barrier and have been used used to
confirm the zoonotic ability of BSE. Here we show that a panel of sheep scrapie
prions transmit to several tgHu mice models with an efficiency comparable to
that of cattle BSE. 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
why do we not want to do TSE transmission studies on chimpanzees $
5. A positive result from a chimpanzee challenged severly would likely
create alarm in some circles even if the result could not be interpreted for
man. I have a view that all these agents could be transmitted provided a large
enough dose by appropriate routes was given and the animals kept long enough.
Until the mechanisms of the species barrier are more clearly understood it might
be best to retain that hypothesis.
snip...
R. BRADLEY
Suspect symptoms
What if you can catch old-fashioned CJD by eating meat from a sheep
infected with scrapie?
28 Mar 01 Most doctors believe that sCJD is caused by a prion protein
deforming by chance into a killer. But Singeltary thinks otherwise. He is one of
a number of campaigners who say that some sCJD, like the variant CJD related to
BSE, is caused by eating meat from infected animals. Their suspicions have
focused on sheep carrying scrapie, a BSE-like disease that is widespread in
flocks across Europe and North America.
Now scientists in France have stumbled across new evidence that adds weight
to the campaigners' fears. To their complete surprise, the researchers found
that one strain of scrapie causes the same brain damage in mice as sCJD.
"This means we cannot rule out that at least some sCJD may be caused by
some strains of scrapie," says team member Jean-Philippe Deslys of the French
Atomic Energy Commission's medical research laboratory in Fontenay-aux-Roses,
south-west of Paris. Hans Kretschmar of the University of Göttingen, who
coordinates CJD surveillance in Germany, is so concerned by the findings that he
now wants to trawl back through past sCJD cases to see if any might have been
caused by eating infected mutton or lamb...
2001
Suspect symptoms
What if you can catch old-fashioned CJD by eating meat from a sheep
infected with scrapie?
28 Mar 01
Like lambs to the slaughter
31 March 2001
by Debora MacKenzie Magazine issue 2284.
FOUR years ago, Terry Singeltary watched his mother die horribly from a
degenerative brain disease. Doctors told him it was Alzheimer's, but Singeltary
was suspicious. The diagnosis didn't fit her violent symptoms, and he demanded
an autopsy. It showed she had died of sporadic Creutzfeldt-Jakob disease.
Most doctors believe that sCJD is caused by a prion protein deforming by
chance into a killer. But Singeltary thinks otherwise. He is one of a number of
campaigners who say that some sCJD, like the variant CJD related to BSE, is
caused by eating meat from infected animals. Their suspicions have focused on
sheep carrying scrapie, a BSE-like disease that is widespread in flocks across
Europe and North America.
Now scientists in France have stumbled across new evidence that adds weight
to the campaigners' fears. To their complete surprise, the researchers found
that one strain of scrapie causes the same brain damage in mice as sCJD.
"This means we cannot rule out that at least some sCJD may be caused by
some strains of scrapie," says team member Jean-Philippe Deslys of the French
Atomic Energy Commission's medical research laboratory in Fontenay-aux-Roses,
south-west of Paris. Hans Kretschmar of the University of Göttingen, who
coordinates CJD surveillance in Germany, is so concerned by the findings that he
now wants to trawl back through past sCJD cases to see if any might have been
caused by eating infected mutton or lamb.
Scrapie has been around for centuries and until now there has been no
evidence that it poses a risk to human health. But if the French finding means
that scrapie can cause sCJD in people, countries around the world may have
overlooked a CJD crisis to rival that caused by BSE.
Deslys and colleagues were originally studying vCJD, not sCJD. They
injected the brains of macaque monkeys with brain from BSE cattle, and from
French and British vCJD patients. The brain damage and clinical symptoms in the
monkeys were the same for all three. Mice injected with the original sets of
brain tissue or with infected monkey brain also developed the same
symptoms.
As a control experiment, the team also injected mice with brain tissue from
people and animals with other prion diseases: a French case of sCJD; a French
patient who caught sCJD from human-derived growth hormone; sheep with a French
strain of scrapie; and mice carrying a prion derived from an American scrapie
strain. As expected, they all affected the brain in a different way from BSE and
vCJD. But while the American strain of scrapie caused different damage from
sCJD, the French strain produced exactly the same pathology.
"The main evidence that scrapie does not affect humans has been
epidemiology," says Moira Bruce of the neuropathogenesis unit of the Institute
for Animal Health in Edinburgh, who was a member of the same team as Deslys.
"You see about the same incidence of the disease everywhere, whether or not
there are many sheep, and in countries such as New Zealand with no scrapie." In
the only previous comparisons of sCJD and scrapie in mice, Bruce found they were
dissimilar.
But there are more than 20 strains of scrapie, and six of sCJD. "You would
not necessarily see a relationship between the two with epidemiology if only
some strains affect only some people," says Deslys. Bruce is cautious about the
mouse results, but agrees they require further investigation. Other trials of
scrapie and sCJD in mice, she says, are in progress.
People can have three different genetic variations of the human prion
protein, and each type of protein can fold up two different ways. Kretschmar has
found that these six combinations correspond to six clinical types of sCJD: each
type of normal prion produces a particular pathology when it spontaneously
deforms to produce sCJD.
But if these proteins deform because of infection with a disease-causing
prion, the relationship between pathology and prion type should be different, as
it is in vCJD. "If we look at brain samples from sporadic CJD cases and find
some that do not fit the pattern," says Kretschmar, "that could mean they were
caused by infection."
There are 250 deaths per year from sCJD in the US, and a similar incidence
elsewhere. Singeltary and other US activists think that some of these people
died after eating contaminated meat or "nutritional" pills containing dried
animal brain. Governments will have a hard time facing activists like Singeltary
if it turns out that some sCJD isn't as spontaneous as doctors have
insisted.
Deslys's work on macaques also provides further proof that the human
disease vCJD is caused by BSE. And the experiments showed that vCJD is much more
virulent to primates than BSE, even when injected into the bloodstream rather
than the brain. This, says Deslys, means that there is an even bigger risk than
we thought that vCJD can be passed from one patient to another through
contaminated blood transfusions and surgical instruments.
Friday, January 30, 2015
*** Scrapie: a particularly persistent pathogen ***
TSS
posted by Terry S. Singeltary Sr. | 12:17 PM
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