Intracellular Survival of <i>Leishmania major</i> Depends on Uptake and Degradation of Extracellular Matrix Glycosaminoglycans by Macrophages

<div><p>Abstract</p><p><i>Leishmania</i> parasites replicate within the phagolysosome compartment of mammalian macrophages. Although <i>Leishmania</i> depend on sugars as a major carbon source during infections, the nutrient composition of the phagolysosome remains poorly described. To determine the origin of the sugar carbon source in macrophage phagolysosomes, we have generated a N-acetylglucosamine acetyltransferase (GNAT) deficient <i>Leishmania major</i> mutant (<i>∆gnat</i>) that is auxotrophic for the amino sugar, N-acetylglucosamine (GlcNAc). This mutant was unable to grow or survive in <i>ex vivo</i> infected macrophages even when macrophages were cultivated in presence of exogenous GlcNAc. In contrast, the <i>L</i>. <i>major ∆gnat</i> mutant induced normal skin lesions in mice, suggesting that these parasites have access to GlcNAc in tissue macrophages. Intracellular growth of the mutant in <i>ex vivo</i> infected macrophages was restored by supplementation of the macrophage medium with hyaluronan, a GlcNAc-rich extracellular matrix glycosaminoglycan. Hyaluronan is present and constitutively turned-over in <i>Leishmania</i>-induced skin lesions and is efficiently internalized into <i>Leishmania</i> containing phagolysosomes. These findings suggest that the constitutive internalization and degradation of host glycosaminoglycans by macrophages provides <i>Leishmania</i> with essential carbon sources, creating a uniquely favorable niche for these parasites.</p>