WASHINGTON – Multiple sclerosis, a neurodegenerative disease that has not improved and affects about 2.8 million people worldwide, is largely due to an infection with the Epstein-Barr virus, according to a new study by researchers at Harvard University.
Their findings, published in Science this week, seem crucial to a long-standing but hard-to-prove hypothesis, and were welcomed by outside experts because they felt the focus should now turn to prevention and cure.
“This is the first study to provide convincing evidence of a causal relationship,” said Alberto Ascherio, professor of epidemiology and nutrition at Harvard TH Chan School of Public Health, and senior author of the study in a statement.
“This is a big step because it suggests that most cases of MS could be prevented by stopping EBV infection, and that targeting EBV could lead to a cure for MS.”
EBV is a herpes virus that can cause infectious mononucleosis – sometimes called kiss disease – and stays in the host for the rest of its life.
MS is a chronic inflammatory disease that destroys the myelin sheaths that protect the nerve cells in the brain and spinal cord and causes vision problems, balance and mobility.
The idea of a link between the two had been studied for years, but it was difficult to definitively establish, due in part to the fact that EBV is very common, reaches about 95 percent of adults, and symptoms of MS begin to develop ten years after infection.
To investigate the issue, the researchers looked at more than 10 million young adults who had been in active service in the U.S. military for 20 years and identified 955 people who were diagnosed with MS during their service.
They analyzed blood serum samples taken every two years to determine the EBV status of the soldiers at the time of the first sample and the relationship between EBV infection and the onset of MS.
They found that the risk of MS increased 32-fold after EBV infection, but there was no increase in other viral infections.
Levels of a protein called neurofilament light chain, a well-known biomarker of MS, only rose after MS – and the authors were able to show that their finding could not be explained by other risk factors.
William Robinson and Lawrence Steinman of Stanford University write in a comment in the same journal because because everyone is infected with EBV but few get MS, genetic factors are “additional shadows” to MS after the first trigger.
They also noted some hypotheses about how EBV causes MS. These include the fact that some of the viral proteins may “mimic” the myelin sheath, causing the immune system to attack it.
Another idea is that EBV may turn certain immune cells, called B cells, against host cells.
Ascherio, author of a new study, said, “There is currently no way to effectively prevent or treat EBV infection, but targeting an EBV vaccine or virus with EBV-specific antiviral drugs can ultimately prevent or cure MS.”
Moderna began a clinical trial of the mRNA EBV vaccine this month. Development is even more important because of the new discovery.