Behind the picture: Proving the link between BSE and vCJD
Sometimes the most unremarkable-looking images turn out to tell remarkable stories. Katherine Nightingale spoke to Dr Jon Wadsworth at the MRC Prion Unit to find out how this humble picture of proteins contains one of the most high-profile health discoveries of the 1990s.
Even for those schooled in the art of the western blot, this image might not look like much. In fact, at first glance, it may seem even less remarkable to a trained eye – just another piece of film with its ladders of proteins.
In fact, this image, taken in 1996, represents the first clear evidence that bovine spongiform encephalopathy (BSE) had passed from cows to humans in the food chain to cause a type of Creutzfeldt-Jakob disease (CJD) never seen before.
The year was 1996 and a handful of young people had died from a new variant of the degenerative brain disease CJD. Previously there were three known types of CJD: sporadic, which has no known cause; familial, which is caused by a genetic mutation; and iatrogenic, caused by medical procedures. They are all caused by prions, rogue misfolded versions of the body’s own prion proteins which encourage normal prion proteins to misfold, thus spreading through the brain.
Researchers have used western blots to study proteins for decades. Invented in the late 1970s, the technique, when combined with enzymes to chop up proteins, allows differently sized fragments to be observed. Proteins can then be identified by the particular pattern that they make.
The different forms of the disease are caused by different shapes of the misfolded prion protein, which produce different fragment patterns that can be recognised on Western blots.
This blot was produced by Andrew Hill in Professor John Collinge’s research group at St Mary’s Hospital London (which subsequently expanded to form the MRC Prion Unit).
The eye is immediately drawn to the dark patches in the two bottom rows – those which are brain samples from patients labelled I345 and I343. These dark splodges indicate that a lot of particular protein fragments are present. Crucially, none of the samples marked ‘sporadic’, ‘s’ or ‘i’ have the same pattern – we’re looking at an entirely new form of CJD, which came to be known as variant CJD (vCJD).
All the young CJD patients analysed had the same pattern. And what’s not shown here is that this pattern is very similar to the one you get from brain tissue from a cow which has had BSE, or animals infected with BSE prions.
“Taken together, they provided the first definitive evidence that the cattle disease had passed to humans. Until that point it was theoretical that disease might be transmitted. While measures had been put in place to prevent this theoretical transmission, the urgency of addressing the situation in humans became clear,” says Dr Jon Wadsworth, a Programme Leader at the MRC Prion Unit.
Since 1996, researchers at the MRC Prion Unit have developed the world’s first prototype blood test for vCJD, and, if they are willing, involve vCJD patients in research via the National Prion Clinic at University College London (UCL) Hospitals NHS Foundation Trust. They are also working on potential treatments for all types of CJD.
So, not such an unremarkable picture after all.
The photo is included in the History is Now exhibition at the Hayward Gallery in London which runs until 26 April. The exhibition is the work of seven artists, each looking at an idea or topic that has shaped the nation from the post-war period. The MRC Prion Unit contributed objects and documents to the topic on the BSE crisis. The artist behind the BSE topic, Roger Hiorns, is supported by a Wellcome Trust People Award.