Scientists debate the role of a virus in multiple sclerosis

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Ryan Grant was in his twenties and serving in the military when he learned that numbness and tingling in his hands and feet, as well as unrelenting fatigue, were symptoms of multiple sclerosis in plates. Like nearly a million other people with MS in the United States, Grant had felt his immune system attack his central nervous system. The insulation around his nerves was breaking down, weakening the signals between his brain and his body.

The disease can have a wide range of symptoms and outcomes. Now 43, Grant has lost the ability to walk and has moved into a veterans' home in Oregon so his wife and children won't have to be his caretakers. He knows the course of the disease all too well and can name the risk factors he has shared and has not shared with other MS patients, three-quarters of whom are women. But until recently, he hadn't heard that many scientists now believe the most important factor behind MS is a virus.

For decades, researchers suspected that Epstein-Barr virus, a common childhood infection, was linked to multiple sclerosis. In January, the journal Science made headlines when it published the results of a two-decade study of people who, like Grant, served in the military. The study researchers concluded that EBV infection is "the primary cause" of MS.

Bruce Bebo, executive vice president of research at the nonprofit National Multiple Sclerosis Society, which helped fund the study, said he thought the results fell far short of proving causation. However, they provide "probably the strongest evidence yet for this link between EBV and MS," he said.

The Epstein-Barr virus has infected approximately 95% of adults. Yet only a tiny fraction of them will develop multiple sclerosis. Other factors are also known to affect a person's risk of MS, including genetics, low vitamin D, smoking, and childhood obesity. If this virus that infects almost everyone on Earth causes multiple sclerosis, it does so in concert with other players in a choreography that scientists don't yet understand.

Amid this lingering uncertainty, scientists are discussing how to proceed from here. Antivirals or drugs that target infected cells, some of which are already in development, could help MS patients. EBV vaccines are also under development. The authors of the scientific paper claim that widespread vaccination could prevent most cases of MS. But other researchers aren't sure the case is closed and suggest putting more emphasis on understanding how the virus might interact with social factors such as stress.

"Patients often want to know why this disease happened to them," said Lindsey Wooliscroft, neurologist and associate director of research for the VA's Multiple Sclerosis Center of Excellence in Portland, Oregon. "It's frustrating when I can't tell them."

Epstein-Barr strikes most often in early childhood, with few or no noticeable symptoms. After the initial infection, the virus hides inside certain immune cells for the rest of a person's life.

If someone avoids EBV until adolescence or adulthood, the virus is more likely to cause mononucleosis, a condition characterized by fever and fatigue. Mono is more common in Western countries, where children encounter fewer germs early in life, said Alberto Ascherio, professor of epidemiology and nutrition at the Harvard T.H. Chan School of Public Health and lead author of the paper. scientist.

Like mono, multiple sclerosis is more common in the United States and parts of Europe. Scientists first suggested more than four decades ago that the two conditions might be linked. Over the next several years, the evidence piled up: almost everyone with multiple sclerosis has EBV latent in their cells. People who remember having mono have an increased risk of MS. Immune cells harboring the virus are more present in the brains of MS patients.

“We have long suspected that the Epstein-Barr virus played a role” in the development of MS, Wooliscroft said. "But it's just very hard to prove."

The surest way to prove causation would be to start with a group of healthy, uninfected adults and various...