It is “the first study providing convincing evidence of causation”, welcomed Alberto Ascherio. With his team, Professor of Epidemiology at Harvard University School of Public Health showed, in a study published in the journal Science (paid article in English), Thursday, January 13, that the development of multiple sclerosis is most likely caused by the Epstein-Barr virus. The possible link between the disease and the virus had been studied for several years, but it remained difficult to prove.
To better understand how this study represents a turning point for specialists in this disease and constitutes hope for patients, franceinfo answers five questions raised by this publication.
1What is the Epstein-Barr virus?
The Epstein-Barr virus (EBV) belongs to the herpes virus family. It is notably responsible for mononucleosis: this “fiancé’s disease” is transmissible by direct contact between two people (a kiss) and by saliva (via projections such as coughs or sputters).
In the vast majority of cases, the first contact with this virus takes place at an early age and it goes unnoticed, because the child does not show any symptoms. However, this does not mean that it does not have consequences on the body, which “develops antibodies that protect him against this virus”, specifies the Medicare, which “estimates that 90% of adults have already been in contact with the Epstein-Barr virus.”
2What is multiple sclerosis?
Multiple sclerosis (MS) is an autoimmune, neurological and degenerative disease that affects the central nervous system (brain and spinal cord). It causes a disruption of the immune system, which attacks myelin, the sheath used to protect nerve fibers. Evolving by “relapses”, the disease is very variable from one patient to another, but it can lead to serious sequelae and it is one of the frequent causes of disability in young adults.
This disease affects around 2.8 million people worldwide, including 1 million in Europe, according to the Multiple Sclerosis Research Aid Foundation. SAccording to Public Health France, 100,000 people are affected in France, three quarters of whom are women. The disease is most often diagnosed in people between the ages of 25 and 35.
3What does this new study show?
The study shows that the Epstein-Barr virus is a necessary factor in the development of multiple sclerosis, even though only a tiny minority of those infected develop this disease. “It has been known for a very long time that there is probably a link between EBV and MS., specifies Catherine Lubetzki, professor of neurology at Pitié-Salpêtrière in Paris, contacted by franceinfo. The first works in this direction were published twenty years ago.”
On the other hand, it is the first time that researchers have highlighted this link by including a chronological dimension. “What we missed was the temporal link between the appearance of antibodies and the fact of having multiple sclerosis”, exposes Patrick Vermersch, professor of neurology at the University and at the University Hospital of Lille. The authors of the study showed that infection with the Epstein-Barr virus precedes the onset of multiple sclerosis.
Using blood samples, the researchers measured the rate of neurofilaments in the blood, explains Patrick Vermersch. These neurofilaments are fibers present in the neurons and which testify to their suffering. The American researchers found that the level of neurofilaments increased in certain rare patients: young people who had never been exposed to the Epstein-Barr virus before, who were then infected with this virus, and who subsequently developed multiple sclerosis. “This means that when some people get this virus, they will develop mild central nervous system damage.” observes Patrick Vermersch.
“It’s a very interesting temporal connection that has been brought to light.”
Patrick Vermersch, professor of neurology at the University and at the University Hospital of Lilleat franceinfo
4Why is this study important?
The study is particularly interesting with regard to the number of patients observed and the duration of the observation period. “It covered a very large population of patients”, explains Catherine Lubetzki. The researchers followed for twenty years more than 10 million young adults engaged in the American army, of which 955 were diagnosed with multiple sclerosis during their service.
This follow-up makes it possible to provide additional precision on the link between the Epstein-Barr virus and multiple sclerosis: “Until now, it was said that having contracted EBV multiplied by 20 the risk of having multiple sclerosis (this is the figure I taught my students twenty years ago), but this new study proves that this risk is actually multiplied by 32”, details the neurologist.
The work of American researchers, however, shows that infection with the Epstein-Barr virus “is a necessary but not sufficient condition” to explain the onset of multiple sclerosis, emphasizes Catherine Lubetzki, because “not everyone with a symptomatic form of EBV will necessarily develop multiple sclerosis”. According to researchers at Stanford University, who published a commentary on the study in the journal Science (paid link in English), other factors, for example genetic, could play a role in the fact of developing or not developing the disease.
5Why is this a hope?
This discovery is encouraging for the search for treatments. “It is a hope for the research and the discovery of antivirals specific to Epstein-Barr, says Patrick Vermersch. This virus is one of the herpes viruses, for which there are treatments (such as acyclovir, for example). But the problem is that very few patients who contract this virus show clinical signs. So we can’t treat them all.”
The solution would therefore go through the development of a vaccine. The American company Moderna announced on January 5 (document in English), have started clinical trials on humans of a vaccine against the Epstein-Barr virus. “You should vaccinate young people, very early in childhood, and see over ten, twenty or thirty years whether these young people develop multiple sclerosis compared to other non-vaccinated people”, underlines the Lille professor.
This discovery will also pave the way for research on other autoimmune diseases, which have many similarities, such as Crohn’s disease or psoriasis, believes Patrick Vermersch. “It has been a long time since, for this kind of disease, we strongly suspect a virus to be the cause. So if we prove this correlation for one disease, we will move forward for the others”, he concludes.