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Mad Cow, Human Disease Linked

23 October 1996 8:00 pm
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LONDON--A team of British scientists today announced new evidence linking a fatal degenerative brain disease that has killed 10 people in Britain since 1994 with bovine spongiform encephalopathy (BSE), a neurological condition popularly known as ``mad cow disease'' that has infected more than 150,000 British cattle.

The researchers have developed a test that reveals strong similarities between proteins thought to be responsible for the human disease--a new variant of Creutzfeldt-Jakob Disease (vCJD)--and those connected with BSE. ``This is the most suggestive evidence so far that the new variant of CJD came from BSE,'' says Byron Caughey, a biochemist at the National Institutes of Health's (NIH's) Rocky Mountain Laboratory in Montana. Not all experts agree, however.

At a press conference this morning, John Collinge of Imperial College School of Medicine at St. Mary's Hospital, London, explained that the simple test distinguishes differences between the infectious proteins, or prions, isolated from the brains of infected humans or animals. The researchers break down prions with an enzyme and separate them according to the number of sugar groups attached to them. The relative abundances of proteins with different numbers of sugar groups produce patterns characteristic of BSE, classical CJD, and the new vCJD strain. Collinge's report will appear in tomorrow's Nature.

Collinge's team found that the prion pattern of vCJD--which has stricken victims up to age 45--resembles the BSE pattern far more closely than that of people suffering from classical CJD, a more common, albeit rare, condition that tends to strike older people. But because the new test requires brain tissue, it is normally only possible to run after a patient has died. The team is now hoping to detect the proteins in another body tissue that could be sampled while a patient is still alive. They are analyzing lymph nodes and tonsils, where prions replicate. Collinge hopes to have results on such a test in a matter of months. With a test potentially able to detect the disease early on, ``we should think seriously about developing therapeutics,'' says Collinge.

But some experts are greeting the findings with caution. ``It's an interesting idea but not persuasive,'' says Paul Brown, a neuroscientist at NIH's main campus in Bethesda, Maryland. Brown says he's skeptical that differences between prion forms revealed in the new test account for variations in CJD, and he's waiting for results of experiments in transgenic mice. The mice produce the human prion that, when altered, is linked to vCJD. The mice were injected with brain tissue from vCJD victims, but so far, none have contracted CJD. Final results are due next year.

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