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 the-the-Open ↗
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.