By Roberta Attanasio
For years, Epstein-Barr virus has been a prime suspect in the effort to identify the cause of multiple sclerosis, a progressive neurodegenerative disease that affects nearly 1 million people in the United States and an estimated 2.8 million people worldwide. A recently published study shows that, indeed, Epstein-Barr virus is the likely cause of multiple sclerosis—an inflammatory disease of the central nervous system. In people with multiple sclerosis, the immune system attacks the myelin sheaths protecting neurons in the brain and spinal cord, disrupting communication within the brain, and between the brain and body. The interruption of communication signals causes unpredictable symptoms such as numbness, tingling, mood changes, memory problems, pain, fatigue, blindness and/or paralysis.
Epstein-Barr virus (or EBV for short), is the common cause of infectious mononucleosis, also known as “mono.” Following infection, EBV is not eliminated but becomes latent (inactive) in the body throughout the life of the infected individual. In some cases, the virus may reactivate. Alberto Ascherio, senior author of the study, said that the hypothesis of causality between EBV and multiple sclerosis has been investigated by their group and others for several years, but this is the first time that research results provide compelling evidence for it. Causality implies that some individuals who developed multiple sclerosis after EBV infection would not have developed the disease if they had not been infected with EBV. He also said that the new study is a big step because it suggests that most multiple sclerosis cases could be prevented by stopping EBV infection, and that targeting EBV could lead to the discovery of a cure for multiple sclerosis.
For the study, published in the journal Science (January 2022), the researchers analyzed serum samples collected biennially—over a period of two decades—from more than 10 million young adults on active duty in the U.S. military. They identified 955 individuals who were diagnosed with multiple sclerosis. Then, they examined the relationship between EBV infection and the onset of multiple sclerosis during the time of active duty. The researcher found that the risk of multiple sclerosis increased 32-fold after infection with EBV but was unchanged after infection with other viruses, as for example cytomegalovirus. Furthermore, serum levels of neurofilament light chain, a protein that serves as biomarker for nerve degeneration typical of multiple sclerosis, increased only after EBV infection. All together, these findings strongly suggest that EBV is the leading cause of multiple sclerosis.
However, nearly everyone is infected with EBV—95 percent of adults carry it—but only a small fraction of infected individuals develops multiple sclerosis. Thus, other factors, such as genetic susceptibility, may contribute to the development of the disease.
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