By Amy Norton
FRIDAY, Jan. 14, 2022 (HealthDay News) — For years, researchers have suspected that the Epstein-Barr virus, best known for causing mononucleois, could also play a role in causing multiple sclerosis. Now, a new study bolsters the case.
The study, involving more than 10 million U.S. servicemen, found that the risk of developing multiple sclerosis (MS) increased 32-fold after Epstein-Barr infection.
The Epstein-Barr virus (EBV) is ubiquitous and about 95% of the population becomes infected at some point. Many people get it as children, when it usually causes no symptoms. When people become infected as teenagers or young adults, it can cause mononucleosis.
Over the years, a number of studies have suggested that EBV may help increase the risk of multiple sclerosis in a small number of people. MS is a neurological disorder caused by a misguided attack by the immune system on the body’s own nervous tissue.
For example, people who have had mononucleosis are at a higher risk of developing MS than people who have never had symptoms of an EBV infection. Meanwhile, people with MS may show high levels of antibodies to EBV several years before their symptoms surface. Researchers have also found EBV-infected B cells in the brains of MS patients.
It all points to something in the immune response to EBV infection that can trigger the development of MS in certain people.
But proving that the virus is a cause of MS, and not just a bystander, has been challenging. That’s partly because almost everyone is infected with EBV, while MS is relatively rare.
A large-scale, long-term study is needed to identify people who are initially EBV negative, and then see if a new EBV infection increases their risk of subsequently developing MS.
The new study, published in the journal Science, did just that.
“This is the strongest evidence we have to date that EBV contributes to MS,” said Mark Allegretta, vice president of research for the nonprofit National MS Society.
Allegretta, who was not involved in the study, said the virus is likely “necessary, but not sufficient” to cause MS. That is, it interacts with other factors that make people more vulnerable to developing MS.
Currently, studies have identified some other factors associated with higher MS risk, said lead researcher Dr. Alberto Asherio.
Those include certain genes, as well as smoking, vitamin D deficiency and childhood obesity, said Ascherio, a professor of epidemiology at Harvard Medical School.
However, none of those factors approach the 32-fold increase in risk associated with EBV infection, Ascherio said.
He called the latest findings “compelling evidence” of the virus’ role in causing MS.
The study followed US military personnel for more than 20 years. All of them had blood samples taken on entry into service and every two years thereafter.
Ascherio’s team found that about 5% were EBV negative at the time of the first test.
A total of 955 military personnel were diagnosed with MS while on active duty. Among them, 35 were initially EBV negative. All but one of the individuals were infected with EBV before their MS diagnosis — usually five years earlier.
Compared to their counterparts who remained EBV negative, those recently infected with the virus had a 32 times higher risk of developing MS during the study period.
One question is whether people in the pre-symptomatic stages of MS have dysfunctional immune systems that make them more susceptible to viral infections in general.
So Ascherio’s team looked at whether MS risk was associated with other viral infections in military personnel, including cytomegalovirus — another common virus that lies dormant in the body for life. They found no similar association between those viruses and MS.
Ascherio said it’s likely that something about the immune response to EBV in particular helps trigger MS. What exactly remains unclear.
An editorial published with the study echoed the idea that EBV is necessary, but not enough on its own, to cause MS.
Infection is the first step, but other “fuses have to be blown” to cause MS, Drs. William Robinson and Lawrence Steinman, of Stanford University in California.
They question whether vaccines against EBV can help prevent MS. Such vaccines are under development: Moderna, maker of one of the messenger RNA COVID vaccines, has just begun an early trial of an mRNA vaccine against EBV.
Another possibility, Ascherio said, is that antivirals that target EBV-infected cells could be tested for the treatment of MS.
Some newer medications for MS slow the progression of the disease by depleting certain B cells in the body. Allegretta said it’s “reasonable” to speculate that one of the reasons the drugs work is by reducing EBV-infected B cells.
The National MS Society has more about the causes of MS.
SOURCES: Alberto Ascherio, MD, Dr.Ph., professor, medicine, Harvard Medical School, professor, epidemiology and nutrition, Harvard TH Chan School of Public Health, Boston; Mark Allegretta, Ph.D., vice president of research, National MS Society, New York City; January 13, 2022 Science, online
This post Can the ‘Mono’ Virus Help Cause Multiple Sclerosis?
was original published at “https://www.webmd.com/multiple-sclerosis/news/20220114/could-the-mono-virus-help-trigger-multiple-sclerosis?src=RSS_PUBLIC”