New Process May Lead to Mad Cow Diagnosis

Monday, August 29th 2005, 12:54 pm

By: News On 6

WASHINGTON (AP) _ One of the biggest hurdles in fighting ailments such as mad cow disease and its human version has been the lack of a way to diagnose the illness. A new process may point the way to a useful blood test.

Transfusions can spread the disease among people, but there is no practical test to detect it. That is why blood donors are carefully screened to weed out people who have lived or visited in certain areas where they might have become infected.

Until now, dissecting the brains of victims has offered the only way to detect such brain-wasting diseases in humans.

These diseases are caused by agents called prions. Researchers led by neurology professor Claudio Soto at the University of Texas Medical Branch at Galveston report they have developed a method of multiplying the number prions in a blood sample so a blood test then can detect them.

Such a test could help prevent the spread of the disease through transfusions and could detect the illness in people or animals before it can be spread to others.

The findings, to appear in the September issue of the journal Nature Medicine, were released online Sunday.

The first known prion disease was scrapie, which has infected sheep for many years. In the 1980s, Britain had an outbreak of bovine spongiform encephalopathy, better known as mad cow disease, which spread to Europe and other areas. Two cows have been found with the illness in the United States.

The human form of the illness is called variant Creutzfeld-Jakob disease and is believed to have originated from eating infected beef.

The extent of the vCJD epidemic is not known, but it has killed about 180 people worldwide. Symptoms can take years to develop.

In addition to improving the safety of the blood supply, a practical test could help find infected people and animals before they show symptoms.

``It is very important because we could have an idea of the magnitude of the problem. We might be sitting on a time bomb and 20 years from now it could be too late,'' Soto said in a telephone interview. ``If we know today there are many people infected, companies will start to look for therapies.''

Soto's research team infected 18 hamsters with prions. Scientists used their process to amplify the prions in blood samples from the hamsters. Also, blood from 12 uninfected hamsters went through the same process.

Blood tests then were able to detect the prions in 16 of the 18 infected animals. Not one of the uninfected ones indicated an infection.

Now, Soto said, he is seeking to test animals that have been infected naturally, rather than one injected with the disease. Eventually, he would like to try it on humans to see if the process makes prions subject to detection.

``We have shown here we can detect (prions) in the blood of experimental animals, the next step is to demonstrate we can do the same with humans and cattle,'' he said.

He said researchers need to see if they can find prions not only in already sick animals but also in those without visible symptoms.

Robert B. Petersen, a professor of neuropathology at Case Western Reserve University in Cleveland, said the work is an impressive improvement of a technique for amplifying prions so they can be detected.

But Petersen, who was not part of Soto's research team, added: ``I would be more convinced if they had used samples from naturally infected animals.''

Past studies of sheep with scrapie have shown prions in the blood of six-month-old sheep, but not in older sheep, he said. ``This suggests that the natural course of the disease may involve the transient presence of (prions),''

The research was supported by the National Institutes of Health and the Intramural John Sealy Endowed Fund for Biomedical Research. Soto has patented the process.