Epstein-Barr virus: Could it be the cause of multiple sclerosis?

According to a large epidemiological study conducted in the United States and published in the Science journal on January 13, 2022, the association of Epstein-Barr virus and MS has finally been proved. The link between these two conditions has been the subject of the study for many years, and up until now, it was difficult to prove its existence.

What is Epstein-Barr virus (EBV)? 

Epstein-Barr virus (EBV) belongs to the herpes virus family. It is a very common virus, present in over 90% of the adult population. The initial transmission happens most often through saliva, in childhood or adolescence. The virus enters the oropharynx where it infects local epithelial cells and B lymphocytes, before spreading to the other B lymphocytes throughout the body.

This virus is responsible for mononucleosis, a disease that can be transmitted by direct contact between two people (through kissing) and through saliva (through coughing or spitting). Mononucleosis is usually benign and heals spontaneously. It can also be completely asymptomatic, but in all cases the virus will persist in the lymphocytes where its DNA genome is maintained as an episome, without integrating the cellular DNA. In this state, some viral genes continue to be expressed and contribute to the development of cancers, lymphomas (including Burkitt's lymphoma and some Hodgkin's lymphomas) and nasopharyngeal cancer.

What is the link between multiple sclerosis (MS) and Epstein-Barr virus (EBV)? 

Infection with Epstein-Barr virus (EBV) has long been suspected of being involved in the development of multiple sclerosis.

In MS, the myelin sheath that surrounds the thin extensions of our neurons (called axons) is attacked by the patient's own immune cells. The destruction of the myelin sheath causes "plaques" that spread throughout the brain and spinal cord. The symptoms of multiple sclerosis include tingling in the arms or legs, muscle weakness, visual impairments, etc. This condition affects nearly 1 million people in the US; almost 75% of patients are women. It is generally diagnosed in people aged between 25 and 35.

According to previous studies, blood antibodies against Epstein-Barr virus can be found in high quantities in about 99.5% of people affected with multiple sclerosis.

A renowned team from Harvard School of Public Health analyzed EBV antibodies in the serum of 955 people who had developed multiple sclerosis., among more than 10 million young adults on active duty in the US military (between 1993 and 2013).

All but one had EBV antibodies in their serum at the time of their MS diagnosis.

This study demonstrates that EBV plays an important role in the development of MS, even though a small number of people actually develop the disease.

According to Catherine Lubetzki, Professor of Neurology at the Pitié-Salpêtrière Hospital in Paris, scientists have been investigating a link between Epstein-Barr virus and multiple sclerosis for a very long time. The first studies on this subject were published 20 years ago.

Nevertheless, the study conducted by the Harvard researchers is the first one to include a chronological dimension. It made it possible to highlight the link between the appearance of antibodies and the onset of multiple sclerosis. Thus, EBV infection precedes the onset of MS.

However, the study shows that infection with Epstein-Barr virus is a necessary but not sufficient condition for the development of multiple sclerosis. Other factors, such as genetics, could play a role in whether or not the disease develops.

What will be the impact of this discovery on patient care? 

The discovery of the link between Epstein-Barr virus and multiple sclerosis is encouraging for scientists in search of treatments specific to Epstein-Barr virus.

The solution could lie in the development of a vaccine. On January 5th, the American pharmaceutical company Moderna announced that it had started clinical trials for a vaccine against Epstein-Barr virus.

This discovery will also pave the way for research into other autoimmune diseases, such as Crohn's disease or psoriasis, which are also suspected to be caused by a virus.

Improving our understanding of the causes of a disease opens up new therapeutic avenues.

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