- 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
- 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
- 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
- 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