prions. cheese. mad cow disease. milk.

a. Theoretically, could the prions of mad cow disease get into cheese?...


b. Or why not?...

What is it about making cheese that takes care of any prions of mad cow
disease?...



c. How about milk ?...

On 06 Jan 2004 16:59:21 -0500, Don Saklad <[Only registered users see links. ].mit.edu>
wrote:


So far as I know, the prions do not seem to be in milk. (They are
primarily in the brain and nervous system.)

bob

In article <[Only registered users see links. ]>,
Bob <[Only registered users see links. ]> wrote:

They primarily *affect* the brain and nervous system, but at least
some of the evidence suggests that the lymphatic system is involved in
transit of the prions and establishing the infection. Can't comment
on the validity/seriousness of the implications of these results, but
it makes me at least a little nervous/squeamish.
--
__________________________________________________ ____________________________
Lou Hom >K'93
[Only registered users see links. ]
[Only registered users see links. ]

Louis Hom wrote:
I admit that I''m not up to date on the prion field, but the answers to two
questions are not clear to me:

1. Is there any evidence that eating contaminated meat can transfer the
disease to humans?

2. Considering that our digestive systems are efficient at digesting
protein, and our intestinal epithelia take up peptide fragments and not
whole proteins, how is it possible that the disease-causing form of PrP can
make it into our bodies and incorporate into nerve tissue membranes intact?

Call me skeptical, but I'm not convinced that BSE is worth the fear.

On Wed, 7 Jan 2004 15:08:45 +0000 (UTC), [Only registered users see links. ] (Louis
Hom) wrote:


Thanks for adding that. That info is probably relevant to the other Q
posted about how the prion gets in.



But again, isn't that tissue pretty much removed? One part of the news
story is that the relevant intestinal region is removed.

bob

On Wed, 07 Jan 2004 16:16:57 GMT, "Kyle Legate" <[Only registered users see links. ]>
wrote:


For transmission between humans, definitely. The biggest epidemic of
prion disease in humans was due to cannibalism, specifically eating
the brains.

For transmission from cow to human, the circumstantial evidence from
Britain is rather strong.



This was discussed in another thread recently. I do not recall the
details, but there are plausible pathways. Maybe not efficient, but
enough to be a potential problem. The disease prion is a difficult
protein.



What (kind/level of) fear? In the US, there is probably a very low
level of BSE, and there are substantial precautions to prevent
diseased tissue from getting into our food supply. I don't think an
American should worry much about getting BSE. But that is because we
are stopping it -- and are instituting even more stringent procedures
to control it further.

UK got caught without the knowledge we have, and 150 or so people have
died from it. The big concern is whether many many more are to come;
this type of disease often seems to have a very long incubation
period, so it is hard to know.

bob

In article <[Only registered users see links. ]>,
Bob <[Only registered users see links. ]> wrote:

The lymphatic system is pretty pervasive. It's not just a few
nodes plus the spleen -- it's a whole vascular system that feeds antigens
from tissues all over the body to the nodes. There are some diagrams on
google images.
As far as the other person's comments on digestion of proteins,
I think the level of digestibility of proteins varies greatly from protein
to protein, and that prion protein appears to be fairly stable toward
cleavage. Even casein can remain intact enough to serve as a transgut
transporter (if I recall my rBGH discussions correctly). [I guess IgG
transport in nursing babies is a receptor-mediated process though.]
--
__________________________________________________ ____________________________
Lou Hom >K'93
[Only registered users see links. ]
[Only registered users see links. ]

Here's an article by Robert Cooke


By Robert Cooke
[Only registered users see links. ]
boston.com Your Life your connection to The Boston Globe

Home > Your Life > Health & Fitness > Diseases & Treatments
The Boston Globe

We all have prions, the cause of mad cow, but why?

By Robert Cooke, Globe Correspondent, 1/6/2004

The early-morning news from Stockholm in October 1997 was a shocker:
Neurobiologist Stanley Prusiner had received the Nobel Prize in
medicine for his pioneering work on prions, the mysterious misshapen
proteins that cause mad cow disease. The prize was immediately
controversial because many researchers still thought the idea was
nuts.

After all, as infectious disease agents, prions break all the rules.
They seem to have no genetic material of their own. They are not
subject to immune attack. And they can't be "denatured" by heating,
digesting them with enzymes or hitting them with chemicals. Many of
the important answers were still missing.

Almost seven years later, the first case of mad cow disease has been
confirmed on US soil, and many important answers are still missing.
Nonetheless, Prusiner's work -- and similar work by dozens of other
research teams -- is looking better and better.

"We do have some understanding of this agent" and how a simple
protein can wreak such havoc in the brain, said Susan Lindquist,
director of the Whitehead Institute for Biomedical Research in
Cambridge, who has spent years studying prions.

It's now clear that a prion protein -- in its dangerous, abnormal
form -- has a sort of "Midas touch" that ruins normal prion
molecules that it contacts. When a bad prion meets its normal
neighbor, normal becomes abnormal, and then goes on to convert other
normals into bad guys.

Also, it's just a change in shape, not a change in chemistry, that
makes everything go haywire. The normal prion protein seems to twist
into a new, more stable abnormal form that persists in damaging
brain cells. As each abnormal prion kicks others into abnormal
shape, it's rather like an atomic chain reaction, only slower. The
disease progresses as bad prions accumulate, kill nerve cells and
eventually leave the brain in tatters.

Research has shown that the normal prion protein, in its
nonpoisonous form, must be playing some important role in the body,
especially in the nervous system. It is found in all tissues, but is
particularly abundant in cells of the spinal cord and brain. This
tells scientists the protein is there for an important reason.

"It is a natural protein with a natural function, something specific
for neural function," said neuroscientist Huntington Potter,
formerly at Harvard, now interim director of the Alzheimer's Center
and Research Institute in Tampa, Fla. "But it also has a natural
tendency to flip into an alternate shape, and it forms long fibers
that accumulate and kill brain cells."

Additionally, scientists at the Whitehead Institute, an affiliate of
MIT, and at Columbia University in New York City, have uncovered
hints that the abnormal prion protein may not really be a villain.
The new work, published last month in the journal, Cell, suggests
that the "normal" folding of the protein might actually be a resting
or dormant phase, while the supposedly toxic form is the active
version, perhaps playing some role that helps with memory.

Lindquist collaborated in this work with a team led by Nobel
laureate Eric Kandel at Columbia. And their findings suggest that
the poisoning effect may be derived from something else, perhaps a
toxin of some sort that is produced in response to accumulating
prions.

"We don't know what protein is the toxic species," Lindquist
explained.

Lindquist also said there is some evidence that the victim's own
immune system somehow helps infectious prion particles -- those that
arrive in the gut from eating an infected animal -- get into a new
host's tissues. First, she said, the entering prions somehow avoid
being chewed up by acids and enzymes in the gut.

Then "the immune system is what does us in," she said. Rather than
attack the prion as a foreign invader, or just ignore it, "the
immune system carries it in," apparently through small areas in the
gut called Peyer's patches. How that occurs is also not known.

Researchers hope that by focusing intensively on understanding the
disease, they can find ways to stop it, or repair the damage. So
far, nothing really works, although there are hints of potential
drug treatments that may yet emerge.

"It is a deadly disease, invariably fatal, and we don't know how to
attack it therapeutically," said Giuseppe Legname, a member of
Prusiner's team at the University of California at San Francisco.
"But we have a [potential] treatment -- an antimalaria drug -- that
is working in laboratory animals and is very promising."

No tests have been done in patients there, however, in part because
there are so few patients who can be studied.

Other researchers, such as Lindquist, have been focusing in part on
using truly modern weapons, called monoclonal antibodies, against
prions. These molecules, made by the immune system, can now be
tailored in the laboratory to recognize almost any protein and then
stir the immune system to attack it. The problem has been that
because a prion protein is inborn -- a part of the body rather than
a foreign microbe -- the immune systems tends to view it as "self,"
something to be ignored.

"You can't imagine how hard we've worked to get antibodies that will
recognize only the abnormal form" of the prion protein, she said. If
that can be done, it may be possible to alert a patient's immune
system to destroy only the bad prions, leaving the good proteins
undamaged. Antibodies could also provide a basis for quick and
accurate tests for diagnosing animals and people.

Tests also might become available to spotting prion contamination of
donated human blood. At present, according to the American Red
Cross, the blood supply is being protected by abstinence; donors are
asked not to give blood if they've lived six months or more in
Europe, or three months in the United Kingdom, where mad cow disease
hit hardest.

The human prion diseases known so far are Creutzfeld-Jakob disease,
Gerstmann-Straussler-Scheinker syndrome, Fatal Familial Insomnia,
Kuru, and Alpers syndrome. To some degree they seem to be inherited
-- a mutant gene may be involved -- yet Kuru and mad cow disease
proved that prions can be infectious, transmitted via nervous system
tissues included in foods.

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