NR ASNK
AU Wise,J.
TI New variant CJD and BSE are linked
QU British Medical Journal 1996 Nov 2; 313(7065): 1100
IA http://bmj.bmjjournals.com/cgi/content/full/313/7065/1100/a
PT Article
VT
The first direct evidence that bovine spongiform encephalopathy (BSE) seems to have been transmitted to humans has been reported. The announcement has increased European pressure on the British government to accelerate the cull of cows.
Professor John Collinge and his colleagues from the Prion Disease Group at the Imperial College School of Medicine in London identified a molecular marker present in cases of new variant Creutzfeldt-Jakob disease (CJD) (Nature 1996;383:685-90). New variant CJD has so far been identified in 14 patients in the United Kingdom-two of them still alive-who developed the disease at a comparatively young age.
The characteristic molecular signature seen in the new variant form was not found in other strains of CJD but was seen in BSE in cattle and in BSE transmitted to mice, cats, and macaque monkeys. Professor Collinge said that this was consistent with the idea that this new human disease is caused by transmission of BSE. "However, we can't get direct proof because we cannot inject BSE into humans," he said.
The British government's spongiform encephalopathy advisory committee suggested in March that the new variant of CJD was probably caused by eating beef contaminated with the BSE agent. But it was impossible to be more definitive until the time consuming experiments in mice were complete
A spokeswoman for the Department of Health said: "This doesn't really change anything as we have been working on the assumption that there is a link since March. The new evidence is not totally conclusive but is persuasive, and it is important to replicate the work."
The discovery of this new molecular marker means that strain typing of CJD can be performed in days rather than the 1-2 years needed for conventional studies in mice. The technique at the moment is possible only using brain tissue, but within 4-6 months the team hopes to be able to use it on lymph node or tonsil tissue and eventually to develop a blood test.
Professor Collinge said that the new technique may help to identify more cases of the new variant CJD. "There appears to be no reason why new variant CJD doesn't affect the elderly. It may be that it just hasn't been spotted because it has different clinical features."
He also called for the test to be used to find out whether scrapie, a similar disease in sheep, originated from BSE in cattle. "There are large public health implications if we find BSE in sheep," he said.
Professor Collinge also hopes that understanding the molecular basis of the infectious agent or prion may help in the development of new treatments. "We cannot predict how many future cases there may be. We need to start talking very seriously about developing therapeutic drugs in case the worst case scenario arises," he said.
The molecular marker was detected by studying modifications of the prion protein thought to be the principal, and perhaps the only, component of the infective agents of the spongiform encephalopathies, which are known as prions. Differences in this protein are thought to correspond to variations in the strains of prions and may be the basis for producing varying patterns of disease.
There are four forms of CJD: a familial form linked to mutations in the PrP gene; an acquired form due to exposure to material contaminated with CJD, notably through use of human growth hormone from cadavers; new variant CJD, which is attributed to eating beef products made from cattle with BSE; and sporadic CJD, which is the most common form and is of unknown aetiology.
The typical age of onset of the disease for the new variant form of CJD is 19-39 years compared with 55-70 years for the sporadic form.
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SP englisch