Rense.com



Trying - Carefully - To Learn The Risk
Of Chronic Wasting Disease

By Maura Lerner
Minneapolis Star Tribune
10-27-2

The prion is a protein that somehow gets twisted into a deadly form. Once it does, it's nearly indestructible. It can withstand temperatures of 1,100 degrees Fahrenheit, and disinfectants are useless against it. . . . It's the only known infectious agent that has no DNA or genetic material of its own -- yet it can reproduce, in a sense.
 
 
CLEVELAND -- Tim Hnath, the Fed Ex man, doesn't seem worried as he places the packages on the lab doorstep.
 
Sure, he knows his cargo could be toxic. How could he forget? The warning signs are everywhere: Biohazard. Caution. No food or drink.
 
But he's learned how to negotiate his way down this hall. "If you ever see a room like this," Hnath warns a colleague, "never walk across the red tape."
 
Most people don't want to be anywhere near the infectious agent that causes mad cow disease and its family of brain-wasting illnesses. But at the medical school at Case Western Reserve University, they can't get enough of it.
 
Thanks to Hnath and his daily deliveries, scientists here are amassing the world's largest collection of human tissue infected by prions (pree-ons) -- the strangely misshapen proteins that are believed to be causing all the trouble. What is a prion?
 
As a result, they just may hold the key to a mystery that has baffled scientists and cast a pall over this year's hunting season -- whether humans are in any danger from deer and elk with chronic wasting disease.
 
If the animal disease ever does spread to humans, Dr. Pierluigi Gambetti and his team at Case Western may be the first to spot it.
 
Gambetti has created, in effect, a first-alert system for human prion disease in labs where the words "be careful" take on a whole new meaning. Once inside these labs, explains one of Gambetti's technicians, "everything that leaves here is incinerated -- except us."
 
Prion immersion
 
Gambetti, an Italian-born expert in brain disorders, has immersed himself for 18 years in prion diseases. So he has his own theory about the one in the news now: chronic wasting disease (CWD), which turned up in scattered deer and elk herds across the country (so far in Minnesota, in a single elk).
 
Like most scientists, he thinks it's unlikely to infect people. But the evidence that humans are safe from CWD is circumstantial, and no one is offering iron-clad guarantees, especially in the wake of Britain's mad cow debacle, where the experts turned out to be wrong.
 
So he and other scientists are trying to find out what makes prions dangerous. "In other words, we want to know the enemy," he says.
 
Long before mad cow and chronic wasting got their ghoulish names, these types of diseases roamed the earth in relative obscurity. In people, they would occur randomly at the rate of about one in a million; and in some unlucky families, prion diseases run in the bloodline. Invariably, these illnesses are gruesome and fatal, causing rapid dementia and death.
 
It was only in 1996, when British health officials noticed an unusual increase in people with one such illness -- Creutzfeldt-Jakob disease (CJD) -- that they realized they had an entirely new problem on their hands. Some people, they concluded, were getting sick from eating tainted beef.
 
Shortly after, Gambetti won a federal grant to set up the National Prion Disease Pathology Surveillance Center on the shores of Lake Erie. Now, he's asking doctors from all over the United States to send him samples of suspected CJD cases, on a strictly voluntary basis. This way, he hopes to be able to spot any suspicious trends -- as well as study the rogue proteins that seem to be wreaking havoc in both animals and humans.
 
Lots of gloves
 
Phyllis Scalzo, a lab technician, figures she may have seen the deadly CJD infection once in 17 years before she went to work for Gambetti. Now, it's all around her. It's in the freezers lining the hall, and in a half-dozen metal cabinets where brain tissue is preserved in white buckets. It's on the slides she prepares for testing. It's on the equipment.
 
And it's in the packages that greet her each morning. Or so she must assume.
 
"I'm going to be going through a lot of gloves," she explains.
 
The danger is unspoken, and in many ways unknown. There's no known case of anyone getting sick from handling the diseased tissue. But then again, she's dealing with something that seems to defy the laws of science.
 
The prion is a protein that somehow gets twisted into a deadly form. Once it does, it's nearly indestructible. It can withstand temperatures of 1,100 degrees Fahrenheit, and disinfectants are useless against it.
 
It's the only known infectious agent that has no DNA or genetic material of its own -- yet it can reproduce, in a sense. It apparently triggers a chain reaction in other proteins, turning normal ones astray. Eventually, they destroy cells in the brain, leaving it looking like a sponge, pocked with holes.
 
The whole thing once seemed so preposterous that Dr. Stanley Prusiner, the scientist who discovered and named prions, was ridiculed at first. In 1997, however, he won the Nobel Prize in medicine for his discovery.
 
The worst part is that the diseases have been uniformly fatal. No exceptions.
 
So Scalzo and her colleagues take no chances.
 
Before she opens the mail, she slips on a disposable lab coat, apron, booties and a splatter guard to cover her face. She'll add two more sets of gloves before she moves the tissue samples -- which arrive in special styrofoam coolers, packed in dry ice or preservative -- to the biohazard table for closer inspection.
 
She rips gloves on and off obsessively. No pair is worn for more than a few minutes. She doesn't want to contaminate anything accidentally. "That's the most important thing: Know where your hands are at all times," she says. Your feet, too. Nobody wears the same shoes home.
 
Gambetti's team is about to open an even more secure lab where everyone will be covered head to toe at all times, and the garbage will be steamed for hours in a device called an autoclave before it is incinerated.
 
Unusual obsession
 
Gambetti remembers when he would examine such tissue with his bare hands. It was in the early 1960s, when, as a young pathologist, he would stumble on a rare case of CJD. Back then, it was little more than a medical oddity.
 
But in 1984, a mentor from his old medical school in Bologna , Italy, sent him a curious brain sample. It came from a man who developed incurable insomnia, went mad and died. Gambetti, an expert in Alzheimer's disease, started looking for answers in the patient's brain tissue. Then a second member of the family died in similar fashion; and a second sample was sent to Gambetti. Ultimately, he discovered it was a type of prion disease that ran in the unfortunate family. He named it fatal familial insomnia.
 
Thus began his obsession with collecting human prion diseases. It was, he figured, the only way to see enough of these rare cases to study them properly.
 
Prion diseases have long been a mystery.
 
The earliest known form is scrapie, found in sheep more than 200 years ago. The story goes that it got its name when infected sheep would start acting erratically and scrape themselves endlessly against trees, as if scratching an itch.
 
In the 1950s, a human disease called kuru turned up in a tribe of cannibals in New Guinea, after women and children ate the brains of relatives in a funeral ritual. They called it "the laughing death."
 
Mad cow disease appeared suddenly in English cattle in the 1980s, and it spread in epidemic proportions through animal herds. It's believed that the disease started when cows ate feed that contained ground-up, scrapie-infested sheep.
 
Experts hastened to assure the British people that they had no reason to worry -- after all, people had been eating scrapie-infested sheep for hundreds of years and were none the worse for it. In an infamous publicity stunt, the agriculture minister, John Gummer, and his 4-year-old daughter chomped on burgers for the cameras in 1990. Six years later, the first human cases were tied to tainted beef.
 
So far, about 135 people have come down with the disease in England and several European countries. Its victims plunge into depression and dementia at an average age of 27, and die in about a year. The illness is distinct enough that doctors call it "variant CJD." Given the millions of people who ate beef, it's still exceptionally rare. Yet even though the animal epidemic has been stopped -- by mass destruction of Britain's cattle -- no one knows how many more human cases are incubating.
 
In more than 250 reported cases worldwide, doctors have inadvertently spread CJD from patient to patient through tainted surgical equipment, transplant tissue and human growth hormone. Health officials have warned brain surgeons and others to take extra precautions, but there is no widely available test to check equipment or tissue for prions.
 
The sobering experience in Britain prompted health officials in the United States to take a fresh look at chronic wasting disease, which first surfaced in Colorado deer 35 years ago. So far, animals in nine states and two Canadian provinces have tested positive, including wild deer in southwestern Wisconsin and a single captive elk in Minnesota. Yet CWD hasn't been linked to a single case of human illness.
 
Assessing risk
 
Dr. William Hueston, a University of Minnesota veterinarian, knows what a mad cow outbreak looks like. And this doesn't look like one to him.
 
As a scientist with the U.S. Department of Agriculture, he helped investigate the outbreak in England in the late 1980s and early 1990s.
 
By comparison, the threat of chronic wasting disease doesn't keep him up at night. "We put all [the] evidence together, and what it says is that there's no evidence that this is a disease that rapidly spreads to humans," he says.
 
Why not?
 
First, the differences. In England, he says, "there were tens of millions of people exposed" to tainted beef products; here, eating venison and elk meat is far less common. In England, people ate the most infected areas of sick cows, such as the brain and spinal cord. As the old joke goes, he says, they "used everything but the moo." U.S. hunters are being advised to take the prime cuts of venison -- where prions are not thought to accumulate -- and leave the rest behind.
 
Second, there's no sign that people get sick at higher rates if they hunt or live in areas where chronic wasting disease has been found for decades.
 
Government investigators have checked out about a dozen cases of CJD in hunters -- including two men who shared a cabin in Wisconsin (Gambetti's lab ruled out a third suspected case). So far, no link to venison has been found.
 
"There are two errors we can make," Hueston says. "One is to say something's safe when it's not. The other is to say something's dangerous when it's not."
 
A species barrier?
 
Is there, as Hueston and others believe, a species barrier protecting us?
 
The answer may well be yes and no.
 
For obvious reasons, no one's going to expose someone intentionally to find out.
 
But Byron Caughey, a scientist at the National Institutes of Health's Rocky Mountain lab in Hamilton, Mont., tried to approximate those conditions in a test tube. He and his colleagues took prions from deer and elk with chronic wasting disease and exposed them to normal human proteins.
 
No one's sure how they work, but prions somehow "convert" ordinary proteins and cause them to fold abnormally. Caughey and his colleagues wanted to see whether deer prions did that to human proteins in test tubes.
 
They found that some of the human proteins converted to an "apparently toxic" state -- but not many. It was, Caughey says, only about 1/10th to 1/20th the rate they see in deer-to-deer transmission. "It was barely detectable," he says.
 
To scientists, it was good news, suggesting a "molecular incompatibility" between the species. But skeptics saw it as proof of danger, and one mad cow Web site even posted the story with the headline: "Chronic Wasting Disease transmits to humans."
 
Says Caughey: "We got a borderline result. As such, people interpret it however they wish, I'm afraid."
 
To him, it's a mixed message. "We have to acknowledge that there is some risk of CWD going into humans. But it's likely to be relatively low."
 
Detecting unknowns
 
If it does transmit to humans, how will anyone know it when they see it?
 
"Very difficult, at this point, because you ask me to recognize an unknown," says Gambetti. But if it's anything like the mad cow experience, he says, a human form of CWD might look different under the microscope, and possibly act differently, than other human prion illnesses.
 
Those, he says, are the "kind of indirect clues" that they watch for. "So we will be ready to recognize these cases, even if we don't know what it's going to look like."
 
In the meantime, his lab and others are hoping animal studies will shed more light. In Gambetti's lab, a genetic specialist, Dr. Qingzhong Kong, has bred what he calls "humanized" lab mice that have human, rather than mouse, proteins. Researchers want to know whether these mice can acquire CWD.
 
But even those tests won't be the final word.
 
They may not know for sure unless they actually find a human case of chronic wasting disease. And that's where Gambetti's center, which reports to the U.S. Centers for Disease Control and Prevention, comes in.
 
If that day comes, he'll notify federal health officials "and then shut the door and run," he says with a laugh. "I'm the arm, but not the mouth, in this operation."
 
But he doesn't shy away from the possibility. "My loyalty is to the truth," he says. "The important thing is to be as well prepared as possible."
 
-- Maura Lerner is at mlerner@startribune.com.
 
© Copyright 2002 Star Tribune. All rights reserved.
 
http://startribune.com/stories/1556/3391355.html






MainPage
http://www.rense.com


This Site Served by TheHostPros