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Updated: Jul 12, 2026
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Automated Measurement of Cryptococcal Species Polysaccharide Capsule and Cell Body
Published on: January 11, 2018
Calcium triggers Cryptococcus neoformans aggregation by forming coordination bonds with capsular glucuronoxylomannan
Gracen Gerbig1, Arturo Casadevall1, Sindhoora Raja2
1Johns Hopkins Bloomberg School of Public Health, Baltimore, MD.
Biorxiv : the Preprint Server for Biology
|July 10, 2026
Summary
Calcium ions uniquely scaffold the cryptococcal polysaccharide capsule, influencing aggregation and host interactions. This calcium phosphate precipitation mechanism impacts virulence and antibody binding, offering new therapeutic targets for Cryptococcus neoformans infections.
Area of Science:
- Microbiology
- Biochemistry
- Immunology
Background:
- The cryptococcal polysaccharide capsule is a key virulence factor.
- Its architecture and metal ion interactions are not fully understood.
- Metal dications are suggested to play a role in capsule structure.
Purpose of the Study:
- To investigate calcium's role in cryptococcal aggregation and capsule structure.
- To characterize the biophysical properties of calcium interaction with glucuronoxylomannan (GXM).
- To determine the impact of calcium on cryptococcal-host interactions.
Main Methods:
- Calcium phosphate precipitation assays
- Size exclusion chromatography
- Circular dichroism
- Diffusion ordered spectroscopy NMR
- Ab-initio calculations
Main Results:
- Calcium dications induce pH-dependent, dose-dependent cell aggregation.
- Calcium uniquely interacts with glucuronic acid (GlcA) residues of GXM.
- Calcium acts as a scaffold, binding up to four GlcA monomers.
- Calcium phosphate treatment reduces capsule's anti-phagocytic properties and alters antibody interactions.
Conclusions:
- Calcium ions are critical for cryptococcal capsule structure and aggregation.
- Calcium-GXM interactions modulate host immune responses.
- This reveals a novel mechanism impacting Cryptococcus neoformans pathogenesis.
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