Fungi are our Friends: Immunity Conferred by Mycotic Probiotics

Published March 2019 | Cell Host & Microbe

Scientists have long known that large percentages of the population are colonized with pathogens such as Candida albicans and Staphylococcus aureus. However, invasive infections caused by these pathogens are relatively rare.

Now a study led by Tzu-Yu Jenny Shao and Sing Sing Way, MD, PhD, shows that persistent fungal colonization is needed to prevent commensal C. albicans from becoming dangerously invasive.

In the intestine, the team found that colonization with C. albicans drives a systemic expansion of protective CD4+ T cells with fungal specificity and IL-17 responsiveness by circulating neutrophils. This tonic immunological stimulation augments host defense to protect against invasive C. albicans. But it also protects against other pathogens such as S. aureus.

“Existence of this dynamic interplay between commensal C. albicans and systemic immune cells, which sense not only the presence of C. albicans colonization, but also transient shifts in colonization levels, opens up exciting new opportunities to target fungi with mycotic probiotics and/or antifungal agents for therapeutically fine-tuning systemic immunity,” the co-authors state.

However, this form of defense is not universally beneficial. Tonic neutrophil stimulation does not protect against influenza virus infection, for example. It also exacerbates risk of allergic airway inflammation.

This finding was recommended on F1000 by Lloyd Miller, MD, PhD, of Johns Hopkins Medicine in Baltimore. “This study is important because it provides the proof-of-concept for mycotic probiotics as novel therapeutics to enhance and modify systemic immune responses,” Miller wrote.