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From: TSS (216-119-143-29.ipset23.wt.net)
Subject: How vCJD proteins reach the blood
Date: December 14, 2004 at 5:34 pm PST

-------- Original Message --------
Subject: How vCJD proteins reach the blood
Date: Tue, 14 Dec 2004 19:33:57 -0600
From: "Terry S. Singeltary Sr."
Reply-To: Bovine Spongiform Encephalopathy
To: BSE-L@LISTSERV.KALIV.UNI-KARLSRUHE.DE


##################### Bovine Spongiform Encephalopathy #####################

Last Updated: Wednesday, 15 December, 2004, 00:42 GMT


How vCJD proteins reach the blood
Prion tissue
Prions damage brain tissue

Scientists say they have discovered how the proteins that cause vCJD are
able to side-step the body's defences and enter the bloodstream.

They found the rogue prions are able to cross the intestinal barrier
which blocks the path of potential toxins, by hitching a ride on another
protein.

It is hoped the finding could lead to new ways to block the disease.

The research, by Case Western Reserve University, is published in the
Journal of Neuroscience.

We may be able to prevent animals from getting this disease through
feed, and stop the transmission to humans.
Dr Neena Singh

It is now widely accepted that vCJD - a progressive brain disease -
results from eating infectious prion proteins contained in beef products
from cattle infected with BSE.

These prions accumulate in the tissue of the nervous system, where they
cause damage that is ultimately fatal.

To date 155 cases of confirmed and probable vCJD have been reported
worldwide. It is unclear how many other people may be harbouring the
disease.

The prions are tough enough to survive attack by the digestive enzymes
found in the stomach.

And the new study shows that they are able to pass across the intestinal
barrier by riding piggyback on ferritin.

This is another protein found in meat that plays a key role in mopping
up excess iron in the digestive tract, and which is normally absorbed by
the intestine.

Simulated digestion

Lead researcher Dr Neena Singh said: "The mad cow epidemic is far from
over. It is therefore essential to understand how this disease is
transmitted from one species to another, especially in the case of
humans where the infectious prions survive through stages of cooking and
digestion."

The researchers used brain tissues infected with the spontaneously
occurring version of CJD, which is also caused by prions.

They simulated the human digestive process by subjecting the tissue to
treatment with the same digestive fluids they would encounter in the
intestinal tract.

Dr Singh said ferritin was found in a similar form in different species.

Thus it may be the key which explains how prions are able to jump so
effectively across the species barrier.

She said: "If we can develop a method of blocking the binding of prions
to ferritin, we may be able to prevent animals from getting this disease
through feed, and stop the transmission to humans."

Professor James Ironside, of the CJD Surveillance Unit at Edinburgh
University, told the BBC News website the study seemed like "an
interesting piece of work".

But he added: "It might well be possible that there are other routes for
the abnormal prion protein to cross the gut wall, perhaps via
immunologically active cells known as M cells, or perhaps through
defects in the wall of the gut (including the mouth and gums).

"I would agree that blocking the entry of the abnormal prion to the
bloodstream would be desirable as a prophylaxis to oral exposure to
prions, but there will probably be a long way to go before this can be
achieved."

http://news.bbc.co.uk/1/hi/health/4094431.stm

TSS

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