Immune Pathway Stops Candida Albicans from Turning Deadly

Researchers at King’s College London have identified an immune pathway that stops a normally harmless fungus from turning into a fatal infection, offering the first potential explanation for why only certain immunocompromised patients, including those undergoing chemotherapy or living with HIV, face a risk of life-threatening Candida albicans disease. The study, published in Nature Microbiology, focused on Candida albicans, a fungus that usually lives without causing harm in places such as the mouth and gut but can sometimes spread through the body and become deadly. If the results hold up in humans, they could lead to a test for identifying at-risk patients and point to a possible therapeutic target.

Fungal infections cause more than 2.5 million deaths each year, with Candida albicans responsible for close to a million on its own, yet little has been understood about why the fungus escapes its usual location and causes severe illness in around 10% of patients with weakened immune systems. The research team examined IL-1, a signal the immune system produces to trigger a response against infection. Mice genetically altered to not produce IL-1 developed severe disease after exposure to Candida albicans, suggesting the pathway plays a critical role in keeping the fungus contained.

To confirm this, the researchers gave IL-1-deficient mice a drug that eliminates neutrophils, white blood cells that respond early to threats like bacteria and fungi, mimicking the weakened immune defenses seen in some patients. When Candida albicans was then introduced into the mice’s mouths, it spread throughout their bodies and caused fatal disease for the first time, confirming IL-1’s protective role. The team believes the pathway could be a broader defense mechanism relevant to other fungi found in healthy microbiomes, though further research is needed to confirm this.

The findings could eventually help identify immunocompromised patients with low IL-1 levels before Candida albicans spreads, and may support future studies testing IL-1-targeted drugs as a personalized therapy alongside existing treatments like antibiotics.

According to corresponding author James S. Griffiths, “Most people carry Candida albicans harmlessly as part of the body’s natural microbiome, but in immunocompromised patients it can spread throughout the body and become life-threatening. A major challenge has been understanding why a fungus that is normally harmless can suddenly spread beyond its natural niche and cause invasive disease. Our study identified the IL-1 family as a critical early immune defense system that helps prevent this fungus from escaping the mouth and gut and spreading to multiple organs. We hope these findings will help identify patients at greatest risk of invasive fungal disease and provide a foundation for developing new ways to strengthen protective antifungal immunity.”