New research from scientists at the American National Institute of Neurological Disorders and Stroke in Bethesda suggest that they might. In a research paper published in Science Translational Medicine yesterday, Li, Nath and colleagues proposed that sporadic MND may be linked to an endogenous retrovirus called ‘HERV-K’. So they conducted a series of experiments to investigate their ideas further.
What are endogenous retroviruses?
These are viruses that are our body’s equivalent of fossil – a left over from our evolution many thousands of years ago. Everyone has them but they are normally in an inactive state.
They are a bit like a family heirloom, lets say a vase. You might walk past the vase every day without really noticing it until one day the cat knocks it off and it smashes onto the floor in front of you.
What did the researchers do?
First, they compared brain tissue of 10 people who died from the sporadic form of MND to brain tissue of 10 people who died from Alzheimer’s Disease. They found proteins made by the virus in MND brain tissue but not in Alzheimer’s Disease brain tissue. Next, studying one of these proteins (called ‘env’) in more detail, they found it was toxic to motor neurones.
Li and colleagues then took a step back and asked ‘what triggered HERV-K to become active in the first place?’. (In other words, going back to my analogy, what caused the vase to fall on to the floor?). They found that the trigger was activation by a protein called ‘TDP-43’ – and this protein is already linked MND.
So what does this really mean?
In a comment article giving a wider perspective on the research study, Professors Bob Brown and MND Association grantee Ammar Al-Chalabi concluded:
“The exciting observations of Li, Nath and colleagues will provoke further follow up studies that will illuminate the interplay between the biology of endogenous retroviruses and seemingly impenetrable neurodegenerative disorders like ALS”.
So while this study in itself might not give us the answer, its an exciting step forward in understanding the most common form of MND, that other researchers around the world will build on.
Brown and Al-Chalabi Endogeneous retroviruses in ALS: a reawakening? Sci Transl Med 7 307fs40 (2015)
‘Dormant viruses may cause MND when awoken’ article in The Guardian
