Phenotypic variation and intracellular parasitism by Histoplasma capsulatum

The success of Histoplasma capsulatum as an intracellular pathogen depends completely on successful conversion of the saprophytic mycelial (mold) form of this fungus to a parasitic yeast form. It is therefore not surprising t hat yeast phase-specific genes and gene products are proving to be importan t for survival and proliferation of H. capsulatum within macrophages. In th is study, we have focused on the role and regulation of two yeast-specific characteristics: alpha-(1,3)-glucan, a cell wall polysaccharide modulated b y cell-density (quorum) sensing, and a secreted calcium-binding protein (CB P) that is essential for pathogenicity.