<i>Cryptococcus gattii</i> evades CD11b‐mediated fungal recognition by coating itself with capsular polysaccharides

<jats:title>Abstract</jats:title><jats:p><jats:italic>Cryptococcus gattii</jats:italic> is a capsular pathogenic fungus causing life‐threatening cryptococcosis. Although the capsular polysaccharides (CPs) of <jats:italic>C. gattii</jats:italic> are considered as virulence factors, the physiological significance of CP biosynthesis and of CPs themselves is not fully understood, with many conflicting data reported. First, we demonstrated that <jats:italic>CAP</jats:italic> gene deletant of <jats:italic>C. gattii</jats:italic> completely lacked capsule layer and its virulence, and that the strain was susceptible to host‐related factors including oxidizing, hypoxic, and hypotrophic conditions in vitro. Extracellular CPs recovered from culture supernatant bound specifically to <jats:italic>C. gattii</jats:italic> acapsular strains, not to other fungi and immune cells, and rendered them the immune escape effects. In fact, dendritic cells (DCs) did not efficiently uptake the CP‐treated acapsular strains, which possessed no visible capsule layer, and a decreased amount of phosphorylated proteins and cytokine levels after the stimulation. DCs recognized <jats:italic>C. gattii</jats:italic> acapuslar cells via an immune receptor CD11b‐ and Syk‐related pathway; however, CD11b did not bind to CP‐treated acapsular cells. These results suggested that CPs support immune evasion by coating antigens on <jats:italic>C. gattii</jats:italic> and blocking the interaction between CD11b and <jats:italic>C. gattii</jats:italic> cells. Here, we describe the importance of CPs in pathogenicity and immune evasion mechanisms of <jats:italic>C. gattii</jats:italic>.</jats:p>