Clearing Hurdles: Prions Know How to Do It
Researchers have some answers on how these infectious proteins overcome
species barriers, yet investigators are still stymied on the issue of
reinfectivity
By Nicole Johnston

In the relative quiet following the outbreak of bovine spongiform
encephalopathy in the United Kingdom, BSE returned to the headlines recently
with a sole case found in the United States and new strains of BSE prion
protein identified in France, Italy, and Japan. And, in May, French
researchers said they found scrapie prion in sheep muscle, showing for the
first time that prions have a direct path to the grocery store.1

While these events made headlines, other discoveries in the prion world also
were occurring. Researchers have started, and only started, to get to the
core of some fundamental questions involving prions. One of these is whether
infectivity can be established in mammals using purified prion protein; the
answer appears to be no. Investigators can isolate the protein from diseased
animals, but they cannot reestablish infection in an uninfected animal.
Researchers aren't sure why, but theories abound: The purified prion protein
may not refold correctly, or perhaps other cellular factors act as
accomplices.

Answering the infectivity question would help confirm the role of prions in
neurodegenerative diseases associated with mammalian transmissible
spongiform encephalopathies (TSEs). "With mammals, the difficulty is that
nobody has been able to take normal prion protein [PrPC], convert it in a
test tube, and then infect animals," says biophysicist Witold Surewicz of
Case Western Reserve University, Cleveland, Ohio. And that crucial missing
link is what bothers prion skeptics such as Yale neurophysiologist Laura
Manuelidis. "Nobody has shown that the protein is infectious."

Read the rest at The Scientist.com
http://www.the-scientist.com/yr2004/jun/feature_040607.html

Comment:
Comprehensive article including illustrations and includes a description of
Prion basics eg:
THE BASICS The term prion describes unusual proteins widely believed to be
infectious and responsible for TSEs in mammals. Besides BSE, the various
strains include scrapie in sheep, chronic wasting disease in deer and elk,
and Creutzfeldt-Jakob disease in humans. CJD can be inherited, infectious,
or sporadic......

Posted by
Robert Karl Stonjek.
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