Therapies that target certain commensal fungi could provide a new way of treating inflammatory bowel disease (IBD), according to LA researchers.
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IBD is characterized by changes in the response of the immune system to bacteria in the gut. It is therefore unsurprising that most studies are focused on the intestinal microbiome.
Now, a team at Cedars-Sinai Medical Center have found that a dandruff-related fungus commonly found in human hair follicles also resides in the intestine.
For most people, the fungus is harmless, but in some people with a particular genetic make-up, it can worsen digestive diseases such as IBD.
The researchers had previously discovered that the fungus Malassezia restricta worsened the inflammatory disorder in a mouse model of colitis.
As reported in the journal Cell Host and Microbe, the team compared the intestinal fungi of healthy people and those with Crohn’s disease. They found that certain fungi were more abundant in those with Crohn’s than in healthy individuals.
Malassezia was significantly more abundant in Crohn’s patients that had a genetic variant referred to as the IBD CARD9 risk allele.
The presence of Malassezia was linked to a common variation in a gene known to be important for immunity to fungi—a genetic signature more common in patients with Crohn's disease than the healthy population.”
David Underhill, Co-author
This mutation increases the ability of immune cells to release inflammatory substances called cytokines in response to the presence of Malassezia.
"The data so far do not suggest that the presence of Malassezia in the gut is an inherently bad thing. We found it in some healthy people, and in mice, it does not seem to cause disease in the gut by itself," explains Underhill.
However, if there is some intestinal inflammation, Malassezia seems to worsen it, he adds.
The team says that taken together, their findings suggest that targeting specific commensal fungi may be a therapeutic strategy for IBD.
The next step will be to investigate whether removing Malassezia from the gut microbiome in this subset of patients relieves their symptoms.