Prospects for early diagnosis, treatment of human mad cow disease encouraging

Prospects for early diagnosis, treatment of human mad cow disease encouraging

June 21, 2001 The Associated Press by Emma Ross

Research aimed at finding a treatment for the human form of mad cow disease is showing promise and could lead to a drug within about five years, a British scientist said.

The fatal illness, called variant Creutzfeldt-Jakob disease, occurs when normal proteins found in the brain, known as prions, change shape and prompt healthy prions to do the same. When enough prions have done so, they deposit a plaque on the brain and surround the mark with spongy holes, killing the victim.

Scientists believe people get it by eating beef infected with a similar disease, bovine spongiform encephalopathy, or BSE. So far, 102 people in Britain, three in France, one in Ireland and one in Hong Kong have died from the disease.

British researchers reported Wednesday at the World Congress of Neurology in London that they are working with the pharmaceutical company, GlaxoSmithKline, to screen hundreds of thousands of chemicals for one that could prevent the healthy prions from changing shape when they come across their rogue counterparts.

"The work we've been doing with Glaxo has been very encouraging," said Dr. John Collinge, director of the prion unit at Imperial College School of Medicine in London. "We think it's possible, although one can't make any promises, that in the next five years we may be able to produce something that blocks prion replication and provides a treatment for this disease."

Collinge's group has found the brain is capable of getting rid of the unhealthy prions, if there aren't too many of them. If scientists can stop the conversion of normal proteins, the brain should be able to eliminate the rest, he said.

Collinge said there is evidence of several strains of the unhealthy protein, which raises the possibility of it becoming resistant to drugs.

He said recent research also indicates the prion protein itself does not appear to be toxic to the brain and that a byproduct created when it changes shape is more likely to be to blame.

Therefore, he said, the aim is to find drugs that will help the healthy prions stay normal.

"It's very encouraging, but, of course, we'd need to have a diagnostic test first" so the disease can be identified in its early stages, said Robert Will, head of Britain's national Creutzfeldt-Jakob Disease surveillance unit.

Currently, the only way to confirm infection with variant CJD is by examining brain or tonsil tissue after death.

Recently, brain scans have been shown to pick up the damage, but it would probably be too late to do anything about it by then, experts say.

Collinge also reported progress with a potential tonsil biopsy test. He tested the tonsils of 28 people suspected of having variant CJD. Thirteen tested positive and the malady was confirmed in all 13 by subsequent examination of brain tissue. The test came up negative on 15 people, and post-mortem brain analysis confirmed none of those people had the disease.

Collinge said the test could allow a diagnosis of probable variant CJD.

The disease concentrates in the brain, but has also been found in the tonsils, spleen, lymph nodes, spinal cord, the retina of the eye and the rectum. It has not been detected in blood.

"If it is present in blood it's less than 1 in 50,000th of the concentration that it is in the brain," Collinge said.

Will said one of the most promising developments in the quest for a blood test is that Swiss scientists have devised a method to rapidly multiply a tiny amount of the bad prion in a test tube. Such amplification made its concentration high enough to be theoretically detectable with standard tests.

Scientists don't know how many people have been infected with the disease. They estimate that anywhere between a few hundred to 100,000 people could eventually be struck.

One of the main problems is scientists don't know how long the incubation period is.

"We shouldn't be surprised at all if the (average) incubation period is more than 30 years. We are looking at the beginning of the epidemic, not the end," Collinge said.

So far, the number of cases is doubling every three years, Will said.

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