A buffer to CJD

An Australian company has developed a membrane filter to prevent the transmission of human variant Creutzfeldt-Jakob brain disease through blood products.

The technology promises to revolutionise testing for vCJD in humans and BSE in cattle, which until now can only be confirmed after death. By identifying contaminated blood products the test would also help to stop the spread of vCJD and BSE and lower the number of associated health scares.

Abnormal prions

The developers claim the Gradiflow system will separate out prions, or rogue proteins that can transmit vCJD from blood components including gamma globulin, an antibody found in blood that is used to make vaccines, and albumin, a protein used in treatments for blood-clotting disorders. Diseased prions circulate in the blood and congregate in the brain, destroying healthy tissue and eventually killing their host.However, the only reliable prion test available at present requires a sample of brain tissue. This means the diagnosis can only be carried out after death, which may allow the disease to spread in the meantime.

The filter, designed by biotech firm Gradipore of New South Wales, with the help of the Scottish National Blood Transfusion Service and Glasgow-based Q-One Biotech, comes in a unit the size of a television set.

As abnormal prions have a different size and electrical charge from normal prions they can be separated and then concentrated to allow them to be identified.The Gradiflow system works by adding a buffer substance with a pH value above or below that of the blood or plasma sample. The buffer causes a change in the electrical charge of the proteins, which allows them to be drawn through a polyacrylamide membrane using a positive or negatively charged terminal on the other side.

The membrane contains holes small enough to allow healthy prions across, but traps infected prions as they tend to clump together in large groups, leaving them behind. ‘We have proved that our technology can be used to isolate and concentrate prions, though we must carry out a little more investigation to see exactly how it does this,’ said Dr Hari Nair, chief operating officer of Gradipore’s US office in New York.

‘Our results mean that the system is suitable for use in a non-invasive diagnostic kit. We are now talking to manufacturers about integrating our system within one.’The kit would allow laboratories to identify contaminated blood products and prevent a health scare or vCJD transmission occurring.

Animal tests

‘The system is still at an early stage in its development and there is a lot of work to be done,’ said Dr Ian MacGregor, lead scientist for the research directorate at the Scottish National Blood Transfusion Service. ‘However, the initial results have been promising.’

The Gradiflow system could also be used to analyse blood samples from cattle, helping farmers to diagnose infected animals quickly and isolate them from their herds. This would lessen the need to cull large numbers of animals to prevent CJD transmission.

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