Subject: BSE: The Prion Connection

From: Ed Blonz <[email-masked]>
Date: Wed, 03 Apr 1996 08:09:12 -0800

>From  today's San Francisco Chronicle:

           Chronicle Front Page
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           The Gate

 Wednesday, April 3, 1996 · Page A10 
  © 1996 San Francisco Chronicle 

`Mad Cow' Researcher Talks About the Link to Humans 

David Perlman, Chronicle Science Editor 

To the scientist who first linked Britain's mad cow disease and its counterpart in sheep to a mysterious organism
that causes deadly brain disorders in humans, the British crisis underscores all the unknowns that have plagued
researchers for more than 40 years. 

Dr. Stanley B. Prusiner, a neurologist and biochemist at the University of California at San Francisco, dubbed the
unknown disease agents ``prions'' when he discovered that they were neither viruses nor bacteria but rather a
new class of highly infectious proteins that somehow reproduced even though they carried no trace of genetic
material. 

Prusiner discovered the prions -- pronounced ``pree-ons'' -- in 1982, and it took years for other scientists to accept
their existence. In his first interview since the mad-cow crisis began, Prusiner described to The Chronicle yesterday
the long course the research has taken and how the animal brain diseases appear strongly related to obscure human
disorders of the central nervous system that can destroy muscle coordination and cause dementia and death. 

In New York after returning from Israel, where he had received the Israeli government's prestigious $100,000 Wolf
Prize for his prion research, Prusiner also urged that the U.S. Department of Agriculture urgently boost its support
for research into the prion diseases of animals and their possible relation to human disease. 

Although he followed accounts of the British crisis closely during his month in Israel, he still had no time to confer
with colleagues there and was not yet aware of Britain's decision to conduct a mass slaughter of its cattle. 

The disorder known as mad cow disease -- technically termed bovine spongiform encephalopathy, or BSE -- is
caused by infection by ``rogue prions,'' as Prusiner calls them. But the disease has appeared only among aging
cattle and no one knows how long those proteins may be latent in the bodies of cattle after infection. 

The big questions now are whether the same disease might emerge widely in the United States and just how the
``rogue prions'' can infect humans and ultimately cause disease. 

``I don't know the answer,'' Prusiner conceded, but he estimated that at least one person in a million worldwide is
dying of a rare prion- caused neurological illness called Creutzfeldt-Jakob Disease. 

That disorder rarely afflicts people before their 60s -- but British health officials have recently detected the disease
in at least 10 people who are far younger. Some, in fact, are teenagers, and the oldest is only 42. The
continentwide health scare flared March 20 when the British government acknowledged that there may be a link
between mad cow disease and the also incurable Creutzfeldt-Jakob Disease. 

Those unusual British cases should prove highly significant in the effort to understand how prion diseases are
transmitted, whether the prion proteins in BSE might infect humans and whether they exist in various strains that
are specific to certain diseases or certain animals, Prusiner said. 

``We still just don't know how prions cause disease,'' he said. The first unexplained brain disease that led to the
prion concept was an obscure one called kuru, which once afflicted members of the Fore tribe in the highlands of
Papua New Guinea. Kuru victims lost all muscular coordination and later succumbed to dementia. 

When Dr. D. Carleton Gajdusek of the National Institutes of Health studied kuru in 1955, he discovered that it was
caused by the tribe's custom of honoring the dead by eating their brains. Gajdusek later won the Nobel Prize for his
kuru work. 

In 1972, Prusiner was treating a patient with Creutzfeldt-Jakob Disease who died with symptoms strongly
resembling kuru. Prusiner learned that both diseases, as well as a fatal nervous system disorder in sheep called
scrapie, could all be transmitted by injecting extracts of their diseased brains into the brains of healthy animals. 

All are known as ``spongiform'' diseases because their brains at autopsy all have a spongy appearance filled with
holes and tangled deposits called amyloid plaque. Adding to the mystery is the fact that in certain other neurological
disorders of the elderly, such as Alzheimer's disease, brains also show similar characteristics at autopsy. 

Prusiner and colleagues have learned that Creutzfeldt-Jakob disease appears to develop in three distinctly different
ways: 

Some cases are inherited and run in families -- particularly among Libyan Jews who migrated to Israel and among
other Jews who left Tunisia and Algeria for France. Others, Prusiner believes, are caused by medical treatments
that somehow transmitted disease- causing prions. 

But by far most Creutzfeldt-Jakob disease cases -- at least 75 percent in Prusiner's estimation -- are ``sporadic,''
and no one knows how their normal prion proteins alter to become rogue proteins. 

Normal prion proteins, Prusiner said, are shaped like corkscrews with four twisted helical strands. But when, for
whatever reason, they turn into disease-causing agents, their shape changes and they transform neighboring normal
prion proteins into the same distorted shapes. 

In Britain, the mad cow disease came from the practice of supplementing their feed with ground bone and tissues
taken from sheep that had died of scrapie. And although that practice was banned in Britain in 1988, the disease
continues to fell British cattle. The government has decreed the slaughter of all the nation's older cows. 

In the U.S., Prusiner is concerned because the Department of Agriculture devotes very little money to research on
the role of prion proteins in scrapie, BSE and other animal forms of the fatal disease. 

His concern is shared by Dr. Richard Marsh, a University of Wisconsin specialist in the nervous system diseases of
animals. Marsh has studied a rare disorder called mink encephalopathy for 34 years and, although like many other
scientists he initially rejected Prusiner's concept of prions, he is now convinced that mink too can die of a prion
disease that is strikingly similar to scrapie and mad cow disease. 

Marsh said he has found at least three different strains of Prusiner's prion protein in mink encephalopathy, and in
Britain some 29 different strains of the disease agent have been detected. 

As a result, Marsh is joining Prusiner in urging the Department of Agriculture to greatly increase its support for
research into the prion diseases of animals. This is particularly important in cattle, he noted, because cows in the
Midwest still occasionally die with delayed symptoms of the brain disease resembling the cattle disorder that has so
alarmed Britain's public, its government and its livestock industry. 

© The Chronicle Publishing Company 

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