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From: TSS (216-119-144-80.ipset24.wt.net)
Subject: Humans may get different forms of BSE [NEW SCIENTIST]
Date: November 11, 2004 at 11:31 am PST

-------- Original Message --------
Subject: Humans may get different forms of BSE
Date: Thu, 11 Nov 2004 13:26:44 -0600
From: "Terry S. Singeltary Sr."
Reply-To: Bovine Spongiform Encephalopathy
To: BSE-L@UNI-KARLSRUHE.DE


The World's No.1 Science & Technology News Service

Humans may get different forms of BSE

19:00 11 November 04
NewScientist.com news service

Humans are likely to catch more than one form of mad cow disease,
experiments in mice suggest. But the good news is that some people may
have a genetic make-up that protects them against the disease.

So far, all 146 patients in the UK who have died of the human form of
mad cow disease had a distinctive type called variant Creutzfeldt-Jakob
Disease, or vCJD. And they all have a similar genetic background for the
prion protein implicated in the disease - called an MM genotype.
This is present in 36% of the UK population.

The results from the mice experiments now suggest that at least one, and
possibly two, other forms of the disease might exist in people. And the
new forms may affect people with the remaining two genetic backgrounds:
MV, which is in half the population; and VV, in about 14% of the
population. The new research is published in Science.

It means that the human population wont have just one form of disease
associated with BSE infection, says Jonathan Wadsworth of the UK
Medical Research Councils Prion Unit in London, who is an author of the
paper with team leader John Collinge.


Abnormal proteins

In their most recent experiments, Collinges team infected mice by
injecting their brains with the abnormal prion proteins that cause BSE
in cows and vCJD in people.

The injected mice had been genetically engineered to have either the
human MM genetic background or the VV background.

As expected, all MM mice developed the usual form of vCJD, as seen in
humans. But only half the VV mice developed any disease at all. And the
half that did develop disease had unusual damage to their brains.
Instead of the usual daisy-like patterns of plaque formation seen in
vCJD, the plaques were overlapping circles, like scales on a fish.

The big question is whether humans with the VV background have been
developing similar plaques without anyone knowing. But the experiments
suggest that if they are, the disease will either be asymptomatic,
milder or too slow-developing to harm anyone.


Protected status

The other surprise came when brain material from the mice with VV
disease was injected into the brains of healthy VV or MM mice.
Encouragingly, VV recipients seemed immune. None of the VV mice had
clinical disease, and died of old age or other symptoms, says Wadsworth.

But as well as developing vCJD, the MM mice injected with the infected
material also developed a form similar to that seen in humans with
sporadic CJD - the most common type that is not linked with mad cow
disease.

This could happen in humans only if an MM individual was accidentally
infected with material from someone with the VV background, perhaps
through inadequate sterilisation of surgical instruments used in brain
operations. But the implication is that if this form is in humans, it
would have been mistaken for classical, sporadic CJD.

The results also leave unanswered the question of how BSE and vCJD
manifest themselves in MV individuals, who make up half the population.

Wadsworth says that while experiments on MV mice have been completed,
the data is still being analysed. However, he says that MV individuals
are the most protected against all other uman forms of CJD. This
so-called heterozygote genotype is most resistant even in human diseases
closely related to vCJD such as Kuru.

James Ironside, head of the Medical Research Councils CJD Surveillance
Unit in Edinburgh, says that care should be taken in extrapolating the
results to humans. But he believes it makes sense that BSE might cause
more than one form of CJD in people. We already know that there are at
least six different types of sporadic CJD, he says.

Journal reference: Science (DOI: 10.1126/science.1103932)

Andy Coghlanhttp://www.newscientist.com/news/news.jsp?id=ns99996660tss


TSS



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