SURFACE-ANTIGENS OF LEISHMANIA-MEXICANA AMASTIGOTES - CHARACTERIZATION OF GLYCOINOSITOL PHOSPHOLIPIDS AND A MACROPHAGE-DERIVED GLYCOSPHINGOLIPID

Amastigotes of the protozoan parasite Leishmania proliferate in phagol ysosomes of macrophages. They abundantly express glycoinositol phospho lipids (GIPLs), which are considered necessary for parasite survival b y providing a shield at the surface against lysosomal hydrolases and b y serving as receptors for the interaction with host cells. The struct ures of four GIPLs of L. mexicana amastigotes were characterized by a combination of gas-liquid chromatography-mass spectrometry, methylatio n linkage analysis and enzymatic treatments. They contain the glycan s tructures Man alpha 1-3Man alpha 1-4GlcN (iM2), Man alpha 1-6(Man alph a 1-3)Man alpha 1-4GlcN (iM3), Man alpha 1-2Man alpha 1-6(Man alpha 1- 3)Man alpha 1-4GlcN (iM4) and (NH2-CH2CH2-PO4)Man alpha 1-6(Man alpha 1-3)Man alpha 1-4GlcN (EPiM3), which are linked to alkylacyl-phosphati dylinositol. The predominant amastigote GLPL, EPiM3 (similar to 2x10(7 ) molecules/cell), is located at the parasite cell surface, in the fla gellar pocket and in lysosomal membranes, but not on host cell structu res as shown by immunofluorescence and immunoelectron microscopy. In a ddition, amastigotes in infected Balb/c mice contain a glycolipid with similar distribution as EPiM3, which has the same characteristics as the Forssman antigen of mammalian cells. In contrast to EPiM3, there i s strong evidence that this glycosphingolipid is not synthesized by am astigotes but by macrophages in the lesion. This suggests a mechanism of lipid transfer from the macrophage to the parasite.