Multiple sclerosis, a neurodegenerative disease that affects around 50,000 people in Spain, is a consequence of infection with the Epstein-Barr virus, according to research that has analyzed all the cases diagnosed over twenty years in a sample of more than of ten million people in the United States. The results, presented today in the journal Science, open the way to preventing multiple sclerosis with vaccines and improving its treatment with antiviral drugs.
“It is a very important advance that will provide energy to research in multiple sclerosis to improve patient care and to avoid cases of the disease in the future,” highlights Xavier Montalban, neurologist at the Vall d’Hebron hospital and director of the Center d’Hebron. ‘Multiple Sclerosity of Catalonia (Cemcat).
The disease, which usually begins between 25 and 35 years of age, is characterized by the destruction of myelin, an insulating sheath that covers the axons of neurons. As myelin degrades, neurons lose their ability to transmit nerve signals. Hence, the most common symptoms of multiple sclerosis include balance and coordination problems, tingling and numbness in the extremities, vision problems, speech disorders or urinary incontinence.
Previous research has shown that myelin is destroyed by an autoimmune reaction in which the immune system attacks neurons by mistake. But the cause of this autoimmune attack had not yet been identified.
The Epstein-Barr virus was the number one suspect. This virus, which is transmitted mainly through saliva and is one of the most common in humans, infects B lymphocytes, a type of immune cells that produce antibodies. Some of the antibodies produced as a result of the infection appear to attack myelin. The new research, carried out at the Harvard School of Public Health (USA), now provides evidence that demonstrates the guilt of the virus.
Researchers have reviewed data from more than ten million young men enlisted in the US Army, who have their blood drawn every two years. 955 of them were diagnosed with multiple sclerosis while they were active between 1993 and 2013.
Most had contracted the Epstein-Barr virus before enlisting. But 34 cases were identified of people who had not contracted the infection at the time of enlistment, became infected later, and later developed multiple sclerosis. The average time between infection and diagnosis was seven and a half years.
Since only a minority of people infected with the Epstein-Barr virus develop multiple sclerosis, there must be other factors that influence the origin of the disease, observes Xavier Montalban. The risk factors identified so far include genetic predisposition, smoking, obesity and vitamin D deficiency. Hormonal factors may also play a role, since women have three times the risk of suffering from multiple sclerosis than men. But new data indicate that if an Epstein-Barr virus infection does not occur, the risk of developing multiple sclerosis is practically zero.
“The vast majority of cases of multiple sclerosis are caused by the Epstein-Barr virus and could potentially be prevented with an appropriate vaccine,” researchers from the Harvard School of Public Health write in Science.
The Moderna company announced on December 20 the start of a clinical trial of a first vaccine against the Epstein-Barr virus based on messenger RNA technology. The clinical trial, which will be carried out in the United States with 272 volunteers between 18 and 30 years old, will last until June 2023. If the results are positive, the vaccine could be effective not only in preventing multiple sclerosis but also other diseases. that the Epstein-Barr virus can cause: mononucleosis (popularly known as the kissing disease), Burkitt lymphoma or Hodgkin lymphoma, among others.
The Epstein-Barr virus is not only involved in the origin but probably also in the progression of multiple sclerosis, say researchers at Harvard Medical School. They remember that this virus has been found in damaged neurons of some patients and that the drugs currently used to treat the disease (anti-CD20 antibodies) attack the immune cells in which the virus is found. An antiviral drug that directly attacks the Epstein-Barr virus, the researchers say, could be more effective with fewer side effects.
“It can create new opportunities for therapy,” highlight William Robinson and Lawrence Steinman, from Stanford University (USA), in an analysis article in Science. “Now that the initial trigger of multiple sclerosis has been identified, perhaps multiple sclerosis could be eradicated.”