New concern about CJD in blood has been raised by publication of research strongly suggesting white blood cells carry the infectious agent that causes the disease.
Swiss scientists have found that one white cell form - B lymphocyte, which produces antibodies - is vital to infection by scrapie, the CJD equivalent that affects sheep.
Meanwhile the EU's Committee for Proprietary Medicinal Products is expected this week to consider the latest difficulties with the British blood product which carried a risk of CJD. The committee includes representatives from all member-states, including the Irish Medicines Board.
The product, Amerscam Pulmonate II, has been exported to more than 40 countries. A decision on British products, where donations from two people with new-variant-CJD (nv-CJD) entered the blood pool, would be made on a Europe-wide basis, according to the IMB chief executive, Dr John Kelly.
"We are likely to agree with our European partners on this and reflect the consensus," he said.
The nine Irish hospitals where the product was used are due to receive information packs from the Department of Health today, and begin the process of notifying the 467 people involved.
The CJD study in the science journal Nature says the scrapie agent is transported among organs of the body through the blood stream by B lymphocytes. Once the agent reaches the brain and spinal cord, it causes damage typical of CJD and BSE.
No evidence has shown that CJD can be transmitted from person to person through blood. But the emergence of nv-CJD, thought to be caused by BSE-infected beef, raised new doubts. Most attention focused on white blood cells, components in many blood products.
In October the British Medicines Control Agency ordered all blood products made with donations from nv-CJD victims to be recalled as a precaution. It came too late for the Irish patients, but risk to them is said to be minuscule as the Amerscam product is albumen-based.
The findings by the Swiss team, led by Dr Adriano Aguzzi, will strengthen calls for white cells to be removed from blood products. The Blood Transfusion Service Board is already examining the case for their removal.
Dr Aguzzi's team found that removing B lymphocytes blocked the scrapie agent from invading nerve cells after it had been injected into peripheral organs. This suggests white cells were carriers of the abnormal prion protein believed to cause the disease. If scrapie is carried in the blood, it is believed CJD almost certainly is, too.
Dr Aguzzi said: "Suspicion that B cells may be the physical carriers of prions may eventually call for a re-evaluation of the safety of blood products."
Dr Paul Brown, of the US National Institute of Health, said the findings "add another reason to consider a step that will deplete white blood cells during the commercial processing of blood, to reduce the possibility of transmitting CJD through blood products".
The BTSB said this "important new research appears to strengthen the hypothesis that white cell removal from blood for transfusion may help to reduce any theoretical risk" of spreading nv-CJD agent via blood. It would evaluate it in consultation with international CJD experts, and ensure the appropriate measures were introduced.