010629 Mad Cow Testing Methods Improved

Scientists have developed a method to rapidly culture large amounts of the infectious agent blamed for mad cow disease, a development they say could improve testing and research into the malady that has threatened European livestock and consumers.

Mad cow disease and a related disease in humans are caused by abnormally shaped proteins, known as prions, that prompt healthy brain proteins to assume their shape. The misshapen proteins eventually form sponge-like holes in the brain, killing those infected.

Researchers at the Serono Pharmaceutical Research Institute in Switzerland said they placed prions from infected hamster brains in a dish with normal hamster brain proteins. More than 97% of the normal proteins were converted to prion-shaped proteins using an ultrasound technique, the researchers said.

The technique, which the institute hopes to license, could lead to simple blood tests by raising the number of prions to detectable levels, the researchers report in Thursday's issue of the journal Nature.

Blood tests currently are not sensitive enough to detect the extremely small number of prions that may be in the blood streams of those infected. Developing tests to detect prions if they are in the blood will be a daunting task, said one scientists not connected with the research.

Cows suspected of having the disease have to be killed so samples of their brains can be tested. The human form of mad cow disease, variant Creutzfeldt- Jakob Disease (news - web sites), can only be confirmed by a brain biopsy, usually after death.

The ultrasound vibrations break up clumps of protein, bringing healthy proteins into contact with newly converted proteins and speeding the conversion process, accomplishing in hours in the laboratory what happens over years in the brain, said researcher Claudio Soto.

“We wanted to mimic what happens during the disease,” Soto said. “We thought, `There must be a way to amplify the infectious agent.”'

Randy Johnson, a Johns Hopkins University professor and a consultant to the National Institutes of Health on prion-related diseases, said the culturing of prions might be commercially useful to test livestock, but may not lead to a blood test for humans.

Scientists still have not proven if prions are in the bloodstream of those infected. If they are, the Swiss researchers still have not boosted prion levels enough to make a blood test effective, Johnson said.

“I like the idea, I'm just not sure they can get the kind of sensitivity that would be needed for a practical blood test,” Johnson said. “This is a really tough problem, it's not going to be solved easily.”

Cows and humans are believed to contract the disease by eating other animals infected with prions.

A form of CJD has been linked to eating meat from cattle infected with mad cow disease. Cows are believed to have become infected with the disease through feed containing bone-meal from infected sheep.

Nearly 100 people in Europe have died of mad-cow related CJD since 1995.

The outbreak has led to drastic measures in Europe. Animals suspected of being infected have been killed and some countries have banned cuts of beef, such as the T-bone steak, which are thought to more easily transmit the disease.

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