Gut microbes could help trigger multiple sclerosis

The trillions of bacteria that live in our intestines, known collectively as the gut microbiome, have been linked to maladies from eye disease to rheumatoid arthritis. Now, two new studies have added another disease: multiple sclerosis (MS), an autoimmune disorder that strips away nerve cells’ protective covers, leading to muscle weakness, blindness, and even death. What’s more, the studies suggest how our gut microbes make the immune system turn against nerve cells—a finding that could lead to treatments, like drugs based on microbial byproducts, that might improve the course of the disease.

MS affects 2.5 million people worldwide, but little is known about what causes the disease, which progressively disrupts information flow from and within the brain. Most researchers think it starts when genetically predisposed people encounter an as-yet-unknown environmental trigger. Previous studies have identified particular bacteria present in increased amounts in the guts of MS patients. But the new papers “took it to the next level” in trying to understand how these bacteria affect the immune system, says Francisco Quintana, a neuroimmunologist at Brigham and Women’s Hospital in Boston not involved with the work. “These are going to be landmark studies.”

In the first paper, a team of researchers led by Sergio Baranzini, a human geneticist at the University of California, San Francisco, analyzed the microbiomes of 71 people with MS and 71 healthy individuals, aged 19 to 71. They found that two bacterial groups, Acinetobacterand Akkermansia, were four times more abundant in MS patients than in individuals with no disease. Another group, Parabacteroides, was four times as abundant in healthy people.