Multiple sclerosis (MS) is a debilitating autoimmune condition whereby neurons lose their myelin sheath leading to impaired neural transmission, neural degeneration and motor symptoms. Multiple factors have been considered to influence its development, like vitamin D, but now, a couple of studies have shown that the Epstein-Barr virus (EBV) is linked to multiple sclerosis.
You may have heard of this virus in relation to mononucleosis (aka “mono”), but it has also been related to a number of autoimmune diseases. Now, thanks to recently published research, we know that it is behind MS as well.
The first study 1 identified the link between EBV and MS in a huge sample of US military veterans, 10 million people, where they found that practically none of them developed MS without being infected by EBV first.
The second study 2 looked at the mechanism by which EBV leads to MS. To that end, they analysed the antibodies present in the blood and spinal fluid of nine MS patients and found that some antibodies in the spinal fluid reacted against EBV. Particularly, they found a high affinity for a viral protein called EBNA1 in 8 out of the 9 MS patients investigated.
After running some other tests, they found that those antibodies also targeted a glial protein, GlialCAM, which is located in the myelin sheaths that surround neuronal axons and allow for optimal nerve impulse transmission. This is the link between Epstein-Barr and multiple sclerosis.
To confirm this point, model mice for MS received an injection of EBNA1 proteins, after which they showed a strong immune reaction in their central nervous system, together with demyelination and accompanied by worsened physical symptoms like paralysis.
In conclusion, it appears that a previous infection with EBV would activate the host’s immune system to recognise EBNA1, and given the similarity between this antigen and GlialCAM, the antibodies created to fight against the EBV would instead target myelin leading to MS’ typical symptoms like muscle weakness, numbness, and fatigue.
Despite this link, it is still unclear why of all people infected with EBV –which are most people– only a few develop MS, but this discovery might help designing new treatments for MS or discover people at increased risk by testing for the presence of those autoantibodies.