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Prion test will identify victims of tainted beef

作者:阙墩    发布时间:2019-02-27 10:14:06    

By Peter Aldhous FAMILIES of people who appear to be suffering from the new form of Creutzfeldt-Jakob disease that has been linked to BSE may in future be spared at least one additional misery: not being given a firm diagnosis until after their relative is dead. At postmortem, new variant CJD can be distinguished from other forms of the disease by the distinctive pattern of spongy holes and clusters of protein fibrils which form in its victims’ brains. And last October, researchers led by John Collinge of St Mary’s Hospital in London produced a simple biochemical test to distinguish normal from new variant CJD (This Week, 2 November 1996, p 4). Collinge’s test relied on extracting the prion, a rogue form of a protein called PrP, that is thought to cause CJD. After the purified protein was treated with an enzyme called proteinase K, an electric current separated the protein into bands on a gel. The bands correspond to varieties of the rogue PrP that differ in the sugars attached to them, and Collinge’s team found that new variant CJD cases showed a distinctive banding pattern. In his initial experiments, Collinge had to extract the PrP from the brains of patients—which means that it is unlikely to be used before postmortem. But in last week’s issue of The Lancet, the researchers reported that PrP isolated from the tonsils of the one new variant CJD victim they have tested so far shows the same characteristic banding pattern. The team needs to confirm this result in other victims of new variant CJD, and test tonsils from patients with other forms of CJD to check that they produce different banding patterns. But if these experiments are successful, the tonsil test should allow earlier diagnosis for patients with suspected new variant CJD. Samples of tonsil tissue can be taken under a local anaesthetic. Such a test would be invaluable to scientists at the National CJD Surveillance Unit in Edinburgh, who are under pressure to spot new variant CJD cases as soon as they arise. But it is unlikely to be of much use in testing the general population—apart from the need for minor surgery, no one knows whether rogue PrP shows up in the tonsils before symptoms appear. “It’s difficult to envisage how it could be used for a screening procedure,” says James Ironside of the surveillance unit,

 

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