Study advances vCJD prion detection

July 05, 2007

Scientists have made significant advances towards the development of a technique that could be used to confirm whether someone is infected with variant CJD.

The technique, which has so far been used mainly in animal models, works by mimicking and accelerating the replication of prions - abnormal proteins that progressively kill off brain tissue and are thought to cause the disease.

The method, known as known as Protein Misfolding Cyclic Amplification (PMCA), enables the level of prions to be increased so that they can be recognised by existing detection methods.

Researchers have shown for the first time that the number of vCJD prions can be amplified from infected human brain tissue extracts prepared from normal human platelets - a type of blood cell essential for clotting.

The sample is incubated and exposed to repeated rounds of ultrasound, which break the prions up into more numerous smaller particles.

The research was carried out by the University of Edinburgh National CJD Surveillance Unit working with the Scottish National Blood Transfusion Service, the Neuropathogenis Unit at the Roslin Institute and CSL Behring,

However, more research is urgently needed to ensure that the technique, which has been applied to brain tissue, can be applied to other tissues, such as blood, that might be used in tests for vCJD.

Professor James Ironside, of the National CJD Surveillance Unit at the University of Edinburgh, said: "While this method, due to the length of time it takes to carry out, is unlikely to produce a rapid screening test that could be implemented in blood donation centres it may well be suitable as a confirmatory test that could be conducted at a national centre.

"Work is currently ongoing to develop a screening test for vCJD but one of the issues common to various screening tests is that of "false" positive results. By developing a reliable confirmatory test, such as this one, the impact of these false positives can be minimised. However, the ethical dilemma remains over screening and testing for a disease for which there is no cure."

A total of 161 people have died from variant CJD since the disease emerged in early 1990, including three people who received blood transfusions from donors who later developed the disease. There is therefore an urgent need to develop tests that may be used to screen blood donations for vCJD infectivity, backed up with confirmatory tests, to prevent further examples of disease spread through infected blood.
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University of Edinburgh

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