Scientist develops supertest for CJD

THE GOVERNMENT is funding development of a test for CJD which could detect the presence of just a few hundred infectious molecules in a drop of blood.

The pounds 500,000 project is the brainchild of the independent scientist Stephen Dealler who, in the past, has been a continual critic of Government policies over "mad cow disease" (BSE) and Creutzfeldt-Jakob Disease (CJD).

But now, backed by the Department of Health, his idea could produce preliminary results by next spring, if successful. If it meets expectations, blood donors could eventually be screened to see whether they are carrying the infectious "prions" reckoned to cause all forms of CJD, in the same way that donors are currently screened for illnesses such as HIV and hepatitis.

Such a technique is urgently needed. Last month the Government announced that it will have to spend a total of pounds 100m annually safeguarding the nation's blood supply against the possibility that British donors are incubating forms of CJD, including "new variant" CJD, caused by exposure to BSE.

While no case of CJD has ever been shown to be caused by a transfusion, laboratory experiments with infected human blood injected into animals show it could happen. The Health Secretary, Frank Dobson, said last month: "Although the risks are theoretical, it is better to be safe than sorry."

It can take 20 years or more to show symptoms after infection with CJD, and the research shows that blood is very infective almost immediately after infection.

The pounds 100m cost of blood treatment includes pounds 70m for removing white cells from blood, because they are thought to harbour prions, and another pounds 30m importing plasma, the liquid left when the red and white cells are removed.

A simple overnight test that could detect the presence of prions could cut that cost radically. But developing it poses huge scientific problems. "You can detect 10 molecules of DNA from one millilitre using existing scientific techniques," said Dr Dealler. "One of the problems in a test like this for CJD is that you are looking for a protein, not DNA, and for tiny amounts of protein at that."

DNA has a tendency to replicate itself, so tests for it try to "amplify" any pieces in a sample. Proteins, however, do not have those properties. Yet in BSE and CJD, where the protein becomes misshapen, the effect can be drastic. "A thousand prion molecules might not sound like much, but it could be deadly," said Dr Dealler.

The project uses technologies developed by Proteus International, a biotechnology company. It is devising a test to detect the misshapen prion molecules using a combination of antibodies - the cells that our bodies produce as a reaction to foreign objects.

The funding award is a victory both for Dr Dealler and for Proteus, which approached the Ministry of Agriculture, Fisheries and Food in 1992 offering to develop an antibody test for BSE. "They said that they already had an equivalent technology," said Arthur Rushton, Proteus's development director. "We have never seen it. However, there's been a sea change in the Government's attitude."