Epstein-Barr infection found to increase risk of multiple sclerosis
The underlying cause of multiple sclerosis is not yet known, but Epstein-Barr virus is a possible culprit, Harvard researchers say.
Multiple sclerosis (MS) is an incurable autoimmune disease that afflicts 2.8 million people worldwide. People diagnosed with MS experience progressive damage to their central nervous system and can lose about seven years of their life expectancy, according to the National Multiple Sclerosis Society.
Now, using data from more than 10 million U.S. military recruits monitored over a 20-year period, researchers at the Harvard T.H. Chan School of Public Health determined that the biggest risk factor for contracting the disease may be previous infection with the Epstein-Barr virus (EBV). The team published its findings on January 13 in the journal Science.
While there are nearly 1,000 genetic precursors for MS, including sex, “no risk factor stands out like Epstein-Barr infections,” epidemiologist and Principal Investigator of the study Alberto Ascherio told The New York Times. In fact, nearly every case of MS observed by Ascherio and his team was preceded by infection with EBV, a common strain of herpes spread through saliva and other bodily fluids. Of the 10 million military personnel involved in the study, 955 were diagnosed with MS during their service. Risk of MS increased 32-fold after infection with EBV, researchers found, a correlation not seen with any other viruses that the subjects contracted during their service. Additionally, other clinical biomarkers of MS increased only after EBV antibodies were detected in the patients' blood.
Researchers say the findings suggest that EBV is the leading contributor to the development of MS. But how EBV leads to MS remains “unknown and elusive,” two Stanford University immunologists who were not involved in the study told Scientific American.
According to the CDC, most people will be infected with EBV at some point in their lives. The virus also causes mononucleosis, commonly called “mono,” which more than 3 million people fall ill with every year in the U.S. Initial EBV infections cause few symptoms, but once EBV gets into the body’s immune cells, “it lurks in them permanently,” Michael Le Page writes for New Scientist.
But contracting EBV will not necessarily lead someone to develop MS, the study authors caution. “Most people infected with this common virus do not develop multiple sclerosis,” the team reports in its paper. Still, like many other common viruses, EBV’s potential to wreak havoc on the body through reactivation is cause for investigation. There is currently no vaccine for EBV. Its status as a "non life-threatening" illness has led to a “lack of investment” in creating a vaccine, Michael Wilson, a neurologist at the University of California San Francisco told STAT News. A preventative vaccine against EBV—much like the one launched for human papillomavirus (HPV), a common virus that in rare cases can cause cancer—may reduce the incidence of MS. “Studies like this suggest we should be pushing harder on developing a vaccine against EBV,” Wilson told STAT News.
MS is diagnosed with an MRI of a person’s brain, usually between the ages of 20 and 50. In MS patients, a brain scan reveals small lesions, which are dead networks of thousands or millions of neurons. People who develop MS tend to have overactive immune systems, Gina Kolata writes for The New York Times. Patients may report “never getting a cold,” because their immune systems so quickly fight off viruses.
Neurons are insulated by myelin sheaths, which not only protect the cells but also facilitate communication from the brain to the rest of the body. In MS patients, the immune system eats away at these myelin sheaths. Without the ability to send messages from the brain to the body, a person in the first stages of MS may have trouble gripping objects or experience dizziness, fatigue, and vision problems. As a patient’s immune system continues to attack their myelin sheaths, their symptoms may get progressively worse. “But what triggers the immune system to turn on itself,” Megan Molteni writes for STAT News, “is still a mystery.”
The connection between EBV and MS is helping demystify some of the questions around the debilitating chronic disease and accelerating vaccine development. Both Moderna, one of the first companies to produce an mRNA COVID-19 vaccine, and the National Institute of Allergy and Infectious Diseases are looking into manufacturing an EBV vaccine. This month, Moderna launched its first phase trial for an mRNA vaccine against EBV. If successful, Lydia Denworth reports for Scientific American, the vaccines could reduce the incidence of mono, some EBV-associated cancers, and potentially MS.