Could Multiple Sclerosis Begin in the Gut?

“Research reveals striking differences in the gut microbiomes of people with newly diagnosed MS and healthy control subjects.”

Multiple sclerosis (MS) is widely considered a brain-centered disease, but a new study by a team of investigators from Yale University suggests that the underlying disease process may be connected to the gut microbiome. Published in Neurology: Neuroimmunology & Neuroinflammation, this research reveals striking differences in the gut microbiomes of people with newly diagnosed MS compared to non-affected controls, pointing to a disruption in how their immune system interacts with gut bacteria.

The researchers studied how the immune system’s regulation of gut bacteria differs in people recently diagnosed with MS. The study included 43 newly diagnosed MS patients who had not yet begun treatment, and 42 age- and sex-matched healthy controls. Stool and blood samples were collected from all participants. A subset of 19 MS patients also provided samples six months after starting B-cell depletion therapy (a common MS treatment).

“Reduced IgA coating of gut microbes suggests a disruption in the normal communication between the gut and the immune system.”

MS patients differed from healthy controls in two diversity measures, and had significantly fewer bacteria coated with immunoglobulin A (IgA). IgA is an antibody secreted by intestinal cells that helps maintain immune balance by selectively binding to specific bacteria. This coating not only tags bacteria for immune regulation, but also limits their ability to move across the intestinal barrier and modulates their behavior. Typically, IgA helps the immune system tolerate beneficial microbes and identify those that might trigger inflammation. A drop in IgA-bound bacteria, as seen in MS patients, suggests a breakdown in this communication system that may allow inflammatory microbes to persist.

Compared to healthy individuals, MS patients had significant differences in which bacterial strains were present. Faecalibacterium prausnitzii, a bacterium with well-known anti-inflammatory effects, was less prevalent in MS patients. At the same time, Monoglobus pectinilyticus was found to have increased relative abundance and prevalence in patients with untreated MS compared to healthy controls. According to the authors, this was a novel finding not reported in previous MS microbiome studies and the functional implications of this increase remain unclear.

What makes this finding even more compelling is the fact that Faecalibacterium prausnitzii produces short chain fatty acids (SCFAs) like butyrate, compounds that are essential for maintaining the gut lining and attenuating immune responses in the gut and the nervous system. A reduced prevalence of this microorganism could therefore lead to increased intestinal permeability (often referred to as “leaky gut”) and systemic inflammation, both of which are being considered as contributors to autoimmune diseases like MS.

“After six months of B-cell–depleting therapy, some gut microbiome features in MS patients began to reflect those of healthy controls.”

After six months of B-cell–depleting therapy, some gut microbiome features detected in MS patients began to reflect those of healthy controls. The immune system also showed more typical IgA-coating patterns for certain bacteria, including Akkermansia muciniphila, a microbe playing a key role in the regulation of the intestinal mucus layer, which has been implicated in MS development. These findings suggest that immune-targeted therapy may help restore balance in the gut-immune connection.

The results also raise intriguing possibilities for future MS treatments. If immune regulation can partly restore gut-immune homeostasis, could gut-targeted interventions, such as specific diets, probiotics, or prebiotics, be used alongside standard therapies to improve outcomes? While this remains hypothetical, the study opens the door for exploring gut microbiome-targeted therapies as a potential adjunct therapy in MS care.

While the study was observational and cannot prove causation, it highlights a potential role for the gut microbiome immune system interactions in the early stages of MS. If confirmed, the gut microbiome could one day serve as a biomarker for diagnosis and prediction of treatment response.

“The gut isn’t just a digestive organ, it’s a central player in immune and brain health.”

This study affirms a core belief of Dr. Mayer’s work: the gut isn’t just a digestive organ, it’s a central player in metabolic, immune and brain health. For MS and other autoimmune disorders, understanding the gut microbiome’s role in pathophysiology may help to change the course of treatment, prediction and prevention.