'Tests possible soon' for human 'mad cow' disease

'Tests possible soon' for human 'mad cow' disease

July 6, 2001 Press Association by John von Radowitz

Routine screening for the human form of mad cow disease could be possible in little more than a year, it has been claimed.

A British biotechnology company believes it will soon have the ability to spot minute signs of the disease in blood or urine.

If so, it may not be long before anyone will be able to get a test for variant CJD. Blood banks could also be tested to ensure they are safe, amid fears the test could cut the amount of blood held in banks by half.

The National Blood Service said it was worried there could be a drop of around 50% as people fear being subjected to the test and the positive samples have to be discarded.

When the screening for HIV was introduced, there was a 5% fall in donations.

The service's medical director Dr Angela Robinson told BBC2's Newsnight: "We do not know how much (of the disease) is out there in the population, so one of the 'what ifs' is if we lose some of our donors because we have a positive test."

The test also raises serious ethical issues as there is no cure for the disease at present.

People who find they have the faulty prion protein associated with variant CJD would face the prospect of a horrific death.

The situation is not unlike the one that existed when tests for the Aids virus, HIV, first became available.

People undergoing HIV tests are now given counselling to help prepare them for the worst. This may also have to be introduced for vCJD tests.

The new technology developed by the London company Microsens Biophage uses multiplying bacteria as a "magnifying glass" to detect tiny levels of prion.

At present, nothing is sensitive enough to spot prions - which are harder to detect than viruses - in blood or urine.

The Microsens Biophage system binds antibodies onto the prions, which are themselves "tagged" by a kind of virus that infects bacteria.

Viruses attached to prions via the antibodies inject their DNA into E.coli bugs. The DNA does not kill the bacterium, but some of it inserts itself into the bug's own genetic material. It also contains a fluorescent element that makes the bacteria glow so they can easily be detected.

When the infected bugs multiply they produce more glowing bacteria, whose numbers are directly proportional to the number of prion molecules originally present.

Tests on artificial molecules designed to mimic prions indicate that incredibly low detection levels of around 100 molecules might be achievable - well within the limits for screening blood or urine.

Biochemist Dr Chris Stanley, chief executive of Microsens Biophage, said: "A year from now we should have a prototype. These tests will be expensive, but HIV tests were expensive when they came out.

"I think we're looking at both kinds of test, blood and urine. The main market is going to be in blood banking, but urine is a really good sample type if you want to carry out non-invasive screening."

In practice vCJD testing is likely to combine different technologies, to lessen the risk of false results.

A number of front-line scientific groups are looking at various methods of detecting prions.

One Swiss team from the Serono Pharmaceutical Research Institute in Geneva has developed an "amplification" technique that uses small numbers of abnormal prions to convert large numbers of normal prions into rogue molecules in the laboratory.

A second group in Ireland is working on a DNA-based technique, and Israeli scientists are investigating a centrifuge method of finding prions in urine.

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