UK scientists have shown that symptoms of prion disease in mice similar to vCJD in humans can be reversed if treated early enough.
The study is published in the journal Neuron.
The biggest problem with getting the treatment to work on humans will be the early diagnosis of vCJD before it does permanent damage to the brain. Currently the only sure way to diagnose vCJD in the early stages is to take a sample of brain tissue, a dangerous procedure.
Dr Giovanna Mallucci of the UK’s Medical Research Council Prion Unit and her colleagues have used mice to show that if you halt the production of naturally occuring prions, then this can reverse the damage caused by the ones that cause brain damage.
vCJD in humans, BSE in cattle (mad cow disease) and scrapie in sheep are all forms of a brain degenerative disease where abnormal versions of proteins called “prions” clog up the brain synapses and stop messages passing between cells. The abnormal prions get into the brain and reproduce by making the natural prions change shape into the unnatural form. Eventually the brain develops a spongy-like form.
Humans get vCJD from eating BSE infected meat products and also from receiving the blood of someone who is infected.
The scientists in this study used genetically engineered mice and stopped normal prion production at 9 weeks of age using an enzyme that takes away the gene that codes for the protein in brain cells. They compared these prion-halted mice with others that had not had this procedure.
In an earlier study they had already established that removing the normal prion protein in infected mice reversed the brain sponginess caused by the abnormal prions.
What they had not investigated however was how this physiological reversal impacted on brain function and behaviour.
As expected, in the early stages of the disease, before the enzyme intervention at 9 weeks of age, in line with the development of sponginess in the brain tissue, all the mice developed behaviour and memory problems, for example they stopped burrowing .
But what had not been shown before was that the mice that had their normal prion production halted by the enzyme recovered their lost memory and behaviour abilities. For instance they were able to burrow again, a distinctive behavioural trait. And their ability to learn was also restored.
However, the mice that did not have their prion production switched off at 9 weeks did not show any signs of recovery. Their symptoms got worse and they died.
This result suggests that early treatment in human prion diseases could have a similar effect. That is, if the disease is caught at an early stage, before widespread brain damage, then brain cells affected by the abnormal prion invasion can be fully restored, not only physically but also in terms of their function in the brain.
Dr Malucci said that “Our results have shown that early problems with brain function can be rescued in mice.” And she added, “The challenge now is to be able to detect early disease in humans and to develop treatments that can remove normal prion protein.”
“Targeting Cellular Prion Protein Reverses Early Cognitive Deficits and Neurophysiological Dysfunction in Prion-Infected Mice.”
Giovanna R. Mallucci, Melanie D. White, Michael Farmer, Andrew Dickinson, Husna Khatun, Andrew D. Powell, Sebastian Brandner, John G.R. Jefferys, and John Collinge.
Neuron, Vol 53, 325-335, 01 February 2007
The National Creutzfeldt-Jakob Disease Surveillance Unit (UK)
Written by: Catharine Paddock
Writer: Medical News Today