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University of Basel

07 June 2022

Mucus molecules can thwart fungal infection

Microscopy images of the yeast Candida albicans in round yeast form and as infectious filaments.
Candida albicans in its harmless (left) and its infectious (right) form. The white bar corresponds to 20 micrometers. (Image: Julie Takagi et al., Nat. Chem. Biol. 2022, Coloring: Daniel Mathys, University of Basel).

Candida albicans is a yeast that colonizes the mucosal surfaces of most healthy humans. Under certain conditions, it can switch to a harmful form and cause infection. Researchers have now identified components of mucus that keep the pathogen from turning destructive, thus laying the foundation for a new class of drugs.

Most people don’t ever notice that they carry potentially harmful pathogens. The fact that they remain ignorant of Candida albicans is in part thanks to a substance usually not very highly regarded: mucus. The slimy liquid covering all mucosal surfaces of the body keeps this yeast in check. However, which components of mucus are responsible for its pathogen-thwarting properties has remained unclear.

An international team of researchers including Dr. Rachel Hevey from the University of Basel and Katharina Ribbeck from the Massachusetts Institute of Technology (MIT) has now identified these components: complex sugar molecules referred to as glycans. As the scientists report in Nature Chemical Biology, specific glycans can suppress so-called filamentation of Candida albicans and other virulence-related traits, which are a hallmark of infection.

The sugar in mucus

Glycans are a major constituent of mucins, the gel-forming polymers that make up mucus. Mucins contain hundreds of different glycans, and a growing body of research suggests that these specialized sugar molecules can help tame specific pathogens.

To test which of the several hundred glycans found in mucus interact with Candida albicans, the team of researchers analyzed and compared the molecular composition of different mucus samples that suppressed filamentation. Among the glycans most abundant in all samples, Hevey and her team at the Department of Pharmaceutical Sciences synthesized six for further analysis.

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