New Technique Swiftly Detects
Mad Cow Disease

By Jenny Duong
Contributing Writer
Daily Californian

UC San Francisco scientists have developed a new test to detect the diseased proteins behind mad cow disease that may prove more rapid, accurate and sensitive than current methods.
Known as the conformation-dependent immunoassay, the test can identify infected cattle before symptoms appear, helping to prevent the spread of the disease to humans.
"The (test) essentially lowers the threshold for detection of bovine spongiform encephalopathies (mad cow disease)," said Jiri Safar, the lead scientist involved in the test's development, in a press release.
Prions are a type of protein typically found in humans and animals. Deformed versions of these proteins are responsible for mad cow disease.
The new test involves genetically engineered mice that are extremely sensitive to infection by the deformed prions.
It uses high-affinity antibodies, molecules oftentimes used by the body to combat invaders, to identify abnormal prions in brain tissue by locking on to the exact shape of the molecules.
"Normal and infected prions only differ by shape," Safar said. "We must look directly at the shape of the molecule."
The test exposes an infected tissue extract in its natural state to the antibody, then monitors its reactivity.
The older, more conventional technique uses an enzyme to destroy normal brain tissue prions.
After they are destroyed, fluorescent antibodies that react with deformed prion proteins are added.
Some portions of abnormal prions are not affected by protease, and thus evade detection"limiting the effectiveness of the technique.
The new test will be able to identify smaller levels of malformed prions than previous methods, which only detect fragments of infected prions.
The new immunoassay test is also able to yield results faster, as it requires only six hours to complete.
Comparatively, the older technique typically takes almost 400 days.
The new test will be capable of matching the sensitivity of the traditional method while also rapidly detecting infectious prions.
For UCSF scientists, the concepts underpinning the new test can be applied widely to other neurodegenerative diseases.
The treatment of afflictions like Alzheimer's disease and Creutzfeldt-Jakob disease that also involve deformed prion proteins may be improved by this new research.
The test is a first step towards early detection of these other chronic wasting diseases in humans and animals.
Experiments thus far have been very accurate and effective at detecting diseased proteins in both infected and uninfected cattle.
The ultimate goal of the immunoassay test development effort would be to apply the technology to test infectious proteins while animals are still alive.
(c) 2002
Berkeley, California


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