Heme as a source of iron to Leishmania infantum amastigotes.

Amastigotes, the mammalian stage of Leishmania, must acquire iron from molecules accessing the macrophage parasitophorous vacuole (PV) where they inhabit. These molecules likely include non-heme and heme-bound forms of iron. Here we demonstrate that, in addition to the previously documented use of ferrous iron, Leishmania amastigotes are also capable of exploiting iron from hemin and hemoglobin for nutritional purposes. Moreover, evidence is presented that a ligand at the surface of amastigotes binds hemin with high-affinity (Kd=0.044nM). This ligand may function in intracellular transport of heme while hemoglobin internalization occurs through a different molecule. The co-existence in Leishmania amastigotes of different processes to acquire iron could constitute an infective strategy, ensuring parasites a substantial advantage in situations of iron limitation.