this was very interesting, Meir

--- Meir Weiss <[log in to unmask]> wrote:

> -----Original Message-----
> From: NIH news releases and news items
> [mailto:[log in to unmask]] On
> Behalf Of NIH OLIB (NIH/OD)
> Sent: Friday, June 03, 2005 10:19
> To: [log in to unmask]
> Subject: VARIANT PRION PROTEIN CAUSES INFECTION BUT
> NO SYMPTOM
>
>
> U.S. Department of Health and Human Services
>
> NATIONAL INSTITUTES OF HEALTH
>
> NIH News
>
> National Institute of
> Allergy and Infectious Diseases (NIAID)
> http://www.niaid.nih.gov/default.htm
>
> EMBARGOED FOR RELEASE
> Thursday, June 2, 2005
> 2:00 p.m. ET
>
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>
>
>
> VARIANT PRION PROTEIN CAUSES INFECTION BUT NO
> SYMPTOMS
> Finding Could Have Implications for Alzheimer's
> Disease
>
> Abnormal prion proteins are little understood
> disease agents involved in
> causing horrific brain-wasting diseases such as
> Creutzfeldt-Jacob
> disease in people, mad cow disease in cattle and
> chronic wasting disease
> in deer and elk. Now, new research suggests that a
> variant form of
> abnormal prion protein -- one lacking an "anchor"
> into the cell membrane
> -- may be unable to signal cells to start the lethal
> disease process,
> according to scientists at the Rocky Mountain
> Laboratories (RML), part
> of the National Institute of Allergy and Infectious
> Diseases (NIAID) of
> the National Institutes of Health.
>
> "This work provides novel insights into how prion
> and other
> neurodegenerative diseases develop and it provides
> tantalizing clues as
> to how we might delay or even prevent such diseases
> by preventing
> certain cellular interactions," notes NIAID Director
> Anthony S. Fauci,
> M.D.
>
> A paper describing the research was released online
> today by the journal
> "Science". RML virologist Bruce Chesebro, M.D.,
> directed the project.
> Other key co-authors from the Hamilton, MT, RML
> laboratory include
> Richard Race, D.V.M., and Gerald Baron, Ph.D. Their
> collaborators
> included Michael Oldstone, M.D., and Matthew
> Trifilo, Ph.D., of The
> Scripps Research Institute in La Jolla, CA, and
> Eliezer Masliah, M.D.,
> of the University of California, San Diego (UCSD).
>
> Drawing on experimental concepts first developed at
> RML a decade ago,
> the research team exposed two groups of 6-week-old
> mice to different
> strains of the agent that causes scrapie, a
> brain-wasting disease of
> sheep. Within 150 days of being inoculated with the
> natural form of
> scrapie prion protein, all 70 mice in the control
> group showed visible
> signs of infection: twitching, emaciation and poor
> coordination. In
> contrast, the scientists observed 128 transgenic
> mice -- those
> engineered to produce prion protein without a
> glycophosphoinositol (GPI)
> cell membrane anchor -- for 500 to 600 days and saw
> no signs of scrapie
> disease. Subsequent electron microscopic
> examinations at UCSD, however,
> confirmed that they produced amyloid fibrils, an
> abnormal form of prion
> protein, and that they even had brain lesions. More
> remarkably,
> according to Dr. Chesebro, the diseased brain tissue
> resembled that
> found in Alzheimer's disease rather than in scrapie.
>
> Chesebro mentions two theories as to why the
> transgenic mice did not
> show symptoms of illness despite being infected:
>
> The host cell might require the GPI anchor to
> receive the "toxic signal"
> from the abnormal prion protein The plaques might be
> less toxic than the
> non-plaque form of prion protein clumps In either
> case, more time might
> be required to produce disease due to the reduced
> toxicity, Dr. Chesebro
> says.
>
> "There was so much about this research that
> surprised us and gave us
> ideas to pursue," says Dr. Chesebro. "First, the
> mice didn't get sick.
> That's very significant. Second, the dense
> accumulations of scrapie
> plaque in the brain resembled the plaque seen in
> Alzheimer's, but it
> wasn't toxic," which might support more recent
> concepts about plaque in
> Alzheimer's patients. "Previously, most researchers
> thought plaques were
> the toxic component of Alzheimer's that kills
> neurons, and many
> treatments focus on removing the plaques. But what
> if the plaques are
> inert, as they were in this research? What if only
> small clumps are
> toxic?"
>
> If this hypothesis proves correct, Dr. Chesebro
> says, the ongoing
> research could eventually alter scientists' views on
> preventing prion
> diseases, shifting emphasis away from stopping the
> production of prion
> protein clumps and toward preventing interactions
> with prion protein
> anchored to cells, or learning to direct abnormal
> prion protein
> accumulations to specific parts of the brain where
> they will not produce
> symptoms.
>
> "Abnormal prion protein by itself may not be rapidly
> lethal -- in these
> mice it wasn't," Dr. Chesebro says.
>
> To view an image that shows how abnormal prion
> proteins also appear as
> plaques in the brains of scrapie-infected mice
> expressing anchorless
> prion proteins, please visit
> http://www.nih.gov/news/pr/jun2005/niaid-02.htm.
>
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> http://www.niaid.nih.gov.
>
>
-----------------------------------------------------------------------
> Reference: B Chesebro et al. Anchorless prion
> protein results in
> infectious amyloid disease without clinical scrapie.
> "Science". DOI:
> 10.1126/science.1110837.
>
-----------------------------------------------------------------------
>
> ##
>
> This NIH News Release is available online at:
> http://www.nih.gov/news/pr/jun2005/niaid-02.htm.
>
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