Health: Scientists concerned as signs of CJD are discovered in white blood cells

Fears that the fatal brain-wasting illness CJD can be carried in blood are growing following new research which suggests that white blood cells carry the disease agent.

A Swiss team of scientists led by Adriano Aguzzi, an acknowledged leader in the field, found that B-lymphocyte cells, which produce antibodies, are vital to infection by scrapie, the sheep equivalent of Creutzfeldt- Jakob Disease (CJD) and "mad cow disease", or BSE.

The experiment, described today in the science journal Nature, found that removing B-lymphocytes blocked the scrapie agent from invading nerve cells. This implied that the white cells were carriers of the abnormal prion protein that is believed to cause the disease, and that they transport it around the body.

Although scrapie is a sheep disease, it resembles CJD. If scrapie is carried in the blood, CJD almost certainly is too.

Speaking last night on Channel 4 News, Professor Aguzzi said: "We do try to be pretty careful about [interpreting] this. This is one possibility ... If B-cells prove to be carriers of infectivity this would call for a critical re-evaluation of the safety of blood products." He praised the call by Frank Dobson, the Secretary of State for Health, to remove white blood cells from all blood products.

The emergence of "new variant" CJD, caused by eating BSE-infected food, has already raised new doubts about the infectivity of blood. In October, the Medicines Control Agency ordered all blood products made with donations from victims of new variant CJD to be recalled as a safety precaution.

But that came too late to prevent a blood product made from plasma taken from a donor who died from new variant CJD being given to 268 patients at nine Irish hospitals, and to scores of people in New Zealand.

Scientists have never found direct evidence that TSEs, or transmissible spongiform encephalopathies, can be transmitted by blood. But this could be because there is no test sensitive enough to find the disease agent in low concentrations. The standard test uses mice, but they may be immune below a certain concentration.