NEWS: Possible Blood Test for Mad Cow Disease - Reuters 7/6/06

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Studies suggest blood test possible for mad cow

 

Thu Jul 6, 2006

 

By Maggie Fox, Health and Science Correspondent

 

WASHINGTON (Reuters) - Tests in hamsters suggest it may be possible to

develop a blood test for mad cow and related diseases in both humans and

animals before they develop symptoms, researchers reported on Thursday.

 

The study, published in the journal Science, also suggests that the

damaged brain cells may "leak" the infectious prions that cause the

diseases, offering a chance to detect the disease in blood.

 

Such a test would allow animals to be checked before they enter the food

supply. It could also screen people, including blood or organ donors,

for the rare but devastating Creutzfeldt-Jakob Disease or CJD, and its

close cousin, vCJD, the researchers said.

 

Current tests require brain or other tissue samples.

 

Mad cow disease, formally known as bovine spongiform encephalopathy or

BSE, is part of the family of prion diseases which also includes scrapie

in sheep, chronic wasting disease in deer and elk, and CJD in people.

 

BSE emerged in Britain in the 1980s and swept through dairy herds. Some

people who ate infected beef products developed a form of CJD called

variant or vCJD and at least 191 cases have been identified, mostly in

Britain.

 

People can have CJD before they know it and in a few suspected cases,

blood and organ donors may have unwittingly infected others.

 

'SILENT PHASE'

 

Claudio Soto of the University of Texas Medical Branch at Galveston and

colleagues infected hamsters with prions, the misfolded nerve proteins

believed to cause the diseases, and then tested blood at various times.

 

They invented a technique known as protein misfolding cyclic

amplification to accelerate the process by which prions convert normal

proteins to misshapen infectious forms.

 

"With this method, for the first time we have detected prions in what we

call the silent phase of infection, which in humans can last up to 40

years," Soto said in a statement.

 

Soto and his university have formed a company, called Amprion, to

commercially develop the test.

 

The test may need to be used at precise times, they said. It worked best

in hamsters 40 days after infection. It did not detect prions 80 days

after infection.

 

Then at 114 days, after the hamsters started showing symptoms, the blood

test again revealed prions. "It has been reported that large quantities

of (infectious prions) appear in the brain only a few weeks before the

onset of clinical signs," the researchers wrote.

 

A second study in Science showed that mice infected with prions

developed heart disease similar to a type known as amyloid heart disease

in people.

 

Dr. Bruce Chesebro of the National Institutes of Health and colleagues

said these diseases are marked by waxy protein deposits that stiffen the

heart, limit its pumping ability and typically lead to fatal heart stoppage.

 

"Although several types of protein are known to form heart amyloid, this

is the first time prion protein amyloid has been found in heart muscle

and also found to cause heart malfunction," Chesebro said.