The evidence that Epstein-Barr Virus can cause multiple sclerosis is mounting
It has been hypothesized that infection with Epstein-Barr Virus can result in the development of multiple sclerosis. We now have good evidence that this is true.
But you might be thinking to yourself, “Epstein-Barr? Isn’t that the virus that causes mono? WE’VE ALL BEEN INFECTED WITH THAT!”
While it’s true that 95% of people have been infected with Epstein-Barr (EBV), only about 1 in 300 people in the United States have multiple sclerosis (MS).
Recent research has shown that genetic risk for MS emerged in northern europe 5,000 years ago, providing some evidence for why MS affects predominantly people of northern european descent.
The hypothesis being that as humans switched from a nomadic to a pastoral lifestyle, MS associated variants, mostly in the HLA genes, conferred an evolutionary advantage to these people.
And because MS is a disease of later onset, ages 20-50, these variants did not negatively impact their ability to reproduce.
But the impact here on the HLA genes is important, because HLA helps our immune system detect and clear infections!
HLA is also implicated in autoimmune diseases like Lupus, Psoriatic Arthritis and MS where the immune system inappropriately identifies its own proteins as foreign.
In the case of MS, it attacks the proteins that make up the protective coating (myelin) of neuronal cells.
This de-mylelination is a hallmark of MS and results in many of the symptoms associated with the disease including muscle weakness, eye pain, and loss of coordination.
But, you’re probably asking yourself what this all has to do with EBV?
Well, large population studies in the early 2000’s identified that EBV infection appeared to be a risk factor for developing MS.
And more recent studies have shown that the antibodies that recognize the EBNA-1 protein from EBV also cross-react and recognize the ‘glue’ that holds neuronal cells together!
But this presents an interesting question: If antibodies to EBV also recognize a neuronal protein, why doesn’t everyone that’s infected with EBV develop MS?
To answer that question, the author’s of today’s paper looked at differences in the immune systems of people infected with EBV who did or did not display symptoms of MS.
What they found was super interesting.
It turns out that a number of factors are at play here and that the controls that are in place to prevent autoimmunity fail.
This failure also seems to be closely associated with HLA-E expression in immune cells.
And, people with elevated levels of HLA-E had up to a 260 fold increased risk of developing MS!
While EBV may not be the only contributing factor in the development of MS, its association with MS could provide new pathways for the treatment or prevention of the disease.