Differential chemokine response of human monocytes to yeast and hyphal forms ofCandida albicansand its relation to the β-1,6 glucan of the fungal cell wall

Hyphae formation from yeast cells is a virulence trait enabling the human opportunistic pathogen Candida albicans to invade host tissues. Hyphal cells proved to be much less efficient than yeast cells in stimulating production of macrophage inflammatory protein-1α (MIP-1α), MIP-1β, interleukin-8 (IL-8), and particularly, monocyte chemotactic protein-1 (MCP-1) by human monocyte. This different stimulation did not depend on the monocyte inability to ingest the hyphae nor did it imply hyphal resistance to the extracellular killing by the monocytes. Purified hyphal and yeast cell walls reproduced the differences shown by the intact cells, and chemical-enzymatic dissection of cell wall components suggested that cell wall β-1,6 rather than β-1,3 glucan was the main chemokine inducer. Coherently, immunofluorescence studies with an anti β-1,6 glucan serum showed that the surface expression of this polysaccharide was much lower on hyphae than on yeast cells. By minimizing chemokine induction, the formation of hyphal filaments might facilitate C. albicans escaping from host immunity.