- Prions are a class of poorly understood
proteins implicated in a number of exotic human neurological diseases and
in some common animal diseases such as sheep scrapie and bovine spongiform
encephalopathy in cattle ("mad cow disease"). One human disease
in which prions have been strongly implicated is Creutzfeldt- Jakob disease,
which appears to have a genetic basis in about 15% of the cases. What is
remarkable about prions is that they behave as infectious agents, but they
are 100 times smaller than viruses and their mechanism of replication is
unclear. All the prion diseases are apparently associated with the accumulation
in the brain of an abnormal protease-resistant isoform of the prion protein
PrP. In other words, an abnormal variant of the normal PrP is somehow copied
or produced by the disease process, which can be initiated by introducing
infectious prion into the system. B. Chesebro (Rocky Mountain Labs., US),
in a review of current research in prion diseases, points out that although
the idea of prions as self-sufficient infectious proteins has received
a great deal of publicity because of the recent award of the Nobel Prize
in Medicine and Physiology to S. Prusiner for the discovery of prions,
"at the present time the fact remains that there are no definitive
data on the nature of prions." The author suggests it would be tragic
if the recent Nobel Prize award were to lead to complacency regarding the
obstacles still remaining in prion research, and that "it is not mere
detail, but rather the central core of the problem, that remains to be
solved." QY: Bruce Chesebro <bchesebro@nih.gov (Science 2 Jan 98)
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