A virus that infects 90% of humanity seems to be the trigger for multiple sclerosis, an autoimmune disease that affects the brain. This is the conclusion of a recent study published in Science, the first to provide strong evidence of causality between a viral infection and multiple sclerosis.
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For years, scientists have been collecting clues that suggest that a virus very common, Epstein-Barr (EBV) is believed to be the underlying cause of multiple sclerosis, an autoimmune disease that affects the nervous system. About 90% of the world’s population is infected with EBV, most often during thechildhood or theadolescence. On the other hand, the sclerosis en plaque concerns only 100,000 young adults in France with approximately 5,000 new cases each year.
An article published on January 13, 2022 in Science is the first to provide evidence solid of a causal link between an infection by EBV and the appearance of multiple sclerosis. ” This is a big step forward as it suggests that most cases of multiple sclerosis could be prevented by blocking EBV infection, and targeting EBV could lead to the discovery of a cure for sclerosis. in plate “, explains Alberto Ascherio, scientist at Harvard University and director of the work published in Science.
New results added to old ones
This study was made possible by the rich collection of blood samples from the US military. Thus, the researchers had access to blood samples from ten million young soldiers in service, taken between 1993 and 2013. Among them, 955 cases of multiple sclerosis were diagnosed. All but one had antibody anti-EBV in the serum at the time of their diagnostic.
From these data, the researchers calculated that individuals infected with EBV are 32 times more likely to develop multiple sclerosis. EBV is not the only virus that has been tested for in blood samples, but it is the only one that increases the risk of multiple sclerosis. The sheath debris myelin, which is destroyed by lymphocytes B in multiple sclerosis, appear in serum only after seroconversion to EBV.
These new results are in the same direction as others obtained previously. In October 2021, an Anglo-Swedish team studied the mononucleosis infectious, caused by EBV, such as risk factor multiple sclerosis in siblings. They conclude that having infectious mononucleosis during childhood or adolescence (between 11 and 19 years old) increases the risk of being diagnosed with multiple sclerosis from the age of 20 years. The risk appears to be greatest during the puberty (11-15 years) and disappears completely after 25 years.
A mechanism yet to be explored
How can a virus trigger a autoimmune disease of the nervous system? In people with multiple sclerosis, active B cells circulating in the blood travel through blood vessels to attack the insulating sheath, myelin, that surrounds the axons from neurons. However, the latter is essential for the proper transmission of thenerve impulses. The gradual disappearance of the myelin sheath induces motor, cognitive, visual and balance disorders which vary greatly between patients.
Several hypotheses are being studied to explain how EBV could trigger these symptoms – none are confirmed yet. EBV is a virus of the family herpes which infects B cells in the oropharynx using their surface receptor CD21 as gate of entry. the genome at DNA of the virus remains in the nucleus of the cells, alongside our own genome, so that an infected person remains infected throughout his life.
EBV causes diseases other than mononucleosis in healthy people, including lymphomas, from cancer characterized by abnormal lymphocyte proliferation, such as Burkitt’s lymphoma or Hodgkin’s disease. In the case of multiple sclerosis, some believe that EBV-infected B cells may be responsible for the symptoms.
Treat EBV to prevent multiple sclerosis?
Although EBV seems to be the trigger for multiple sclerosis, it is not enough for the disease to break out. Other environmental factors come into the equation. Scientists know that tobacco,obesity during adolescence, a deficiency in vitamin D or even the night work are factors favoring the onset of multiple sclerosis.
With these results, a tremendous hope emerges: that of treating multiple sclerosis. Current treatments can slow the progression of the disease, but do not prevent its long-term progression. Preventing EBV infections with a vaccine or antivirals seems like a natural solution. ” Currently, there is no effective way to prevent or treat EBV infection, but an EBV vaccine or medications antivirals may prevent or treat multiple sclerosis concludes Alberto Ascherio. coincidence of the calendar, Moderna announced on January 5, 2022 the start of clinical trials for an EBV vaccine using the technology mRNA.
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