The in vitro interaction of Cryptococcus neoformans with human lung epithelial cells

The interaction of Cryptococcus neoformans with a human lung epithelial cell line (A549) is described. Encapsulated and acapsular strains adhered to epithelial cells in a time-dependent manner, with the acapsular strain being the most adherent under all conditions tested. Internalized cryptococci were additionally observed. The expression of the adhesins responsible for adherence to the epithelial cells was induced by growth at 37 degrees C. Adhesin expression was repressed in all strains by growth with sucrose as the sole carbon source. A strain-specific repression of adhesin expression was observed after growth with galactose and xylose. A variety of carbohydrates included in the assay suspensions blocked adherence, implicating certain carbohydrate moieties that might serve as ligands for the yeast adhesin. Finally, a monoclonal antibody is described that inhibited cryptococcal adherence to the epithelial cells. Collectively, the results demonstrate a specific interaction between C. neoformans and lung epithelial cells mediated by yeast adhesins whose expression is regulated by environmental factors.