There’s growing evidence that one of the world’s most common viruses can cause some people to develop multiple sclerosis.
Multiple sclerosis is a potentially debilitating disease that occurs when cells of the immune system mistakenly attack the protective covering of nerve fibers, gradually eroding them.
The Epstein-Barr virus has long been suspected of playing a role in the development of MS. It’s a hard link to prove because almost everyone is infected with Epstein-Barr, usually as children or young adults – but only a tiny fraction develop MS.
On Thursday, Harvard researchers reported one of the largest studies to date to support the Epstein-Barr theory.
They tracked stored blood samples from more than 10 million people in the US military and found the risk of MS increased 32-fold after an Epstein-Barr infection.
The military routinely administers blood tests to its members, and researchers checked samples stored from 1993 to 2013, hunting for antibodies signaling viral infection.
Only 5.3% of recruits showed no signs of Epstein-Barr when they joined the military. The researchers compared 801 subsequently diagnosed MS cases over a 20-year period with 1,566 military personnel who never had MS.
Only one of the multiple sclerosis patients had no evidence of Epstein-Barr virus before diagnosis. And despite intensive searches, researchers found no evidence that other viral infections played a role.
The results “strongly suggest” that Epstein-Barr infection is “a cause and not a consequence of MS”, reported study author Dr. Alberto Ascherio of Harvard TH Chan School of Public. Health and colleagues in the journal Science.
It’s clearly not the only factor, given that around 90% of adults have antibodies showing they’ve had Epstein-Barr – while nearly a million people in the US live with MS, according to the National Multiple Sclerosis Society.
The virus appears to be “the initial trigger,” Drs. William H. Robinson and Lawrence Steinman of Stanford University wrote in an editorial accompanying Thursday’s study. But they warned that “additional fuses need to be switched on”, such as genes that can make people more vulnerable.
Epstein-Barr is best known for causing “mono” or infectious mononucleosis in adolescents and young adults, but often occurs without symptoms. A virus that remains inactive in the body after initial infection, it has also been linked to the later development of certain autoimmune diseases and rare cancers.
We do not know why. Among the possibilities is something called “molecular mimicry,” which means that viral proteins can look so similar to certain proteins in the nervous system that they induce a mistaken immune attack.
Either way, the new study is “the strongest evidence yet that Epstein-Barr helps cause MS,” said Mark Allegretta, vice president of research at the National Multiple Sclerosis Society.
And that, he added, “opens the door to the potential prevention of MS by preventing Epstein-Barr infection.”
Attempts are underway to develop Epstein-Barr vaccines, including a small study just started by Moderna Inc., best known for its COVID-19 vaccine.