A galactosyl(alpha 1-3)mannose epitope on phospholipids of Leishmania mexicana and L. braziliensis is recognized by trypanosomatid-infected human sera.

An immunoglobulin M antibody reactive with galactosyl(alpha 1-3)mannose [Gal(alpha 1-3)Man] residues present on phospholipids extracted from Leishmania mexicana and L. braziliensis was found to be present in high titer in the serum of every normal individual studied. Periodate oxidation, acid hydrolysis, or acetylation suppressed immunoreactivity, suggesting that an oligosaccharide chain was responsible for antibody binding. Interaction occurs only with alpha-Gal terminal residues, since treatment of purified glycophospholipids with alpha-galactosidase but not with beta-galactosidase abolished it. Antibody bound to galactosyl(alpha 1-3)galactose-linked synthetic antigens but did not bind to the same residues present in rabbit, rat, and guinea pig erythrocytes or in murine laminin. Antigen-antibody binding was strongly blocked with Gal(alpha 1-3)Man and Gal(beta 1-4)Man. These results plus inhibition studies with several oligosaccharides suggest that they are indeed different from antibodies against the galactosyl(alpha 1-3)galactose residue. Anti-Gal(alpha 1-3)Man antibody values were significantly elevated in 89% of patients with diffuse cutaneous leishmaniasis, 84% of patients with localized cutaneous leishmaniasis, 69% of patients with mucocutaneous leishmaniasis, and 44 and 62% of patients with Trypanosoma cruzi or T. rangeli infection, respectively, but not in patients with 15 other different infectious and inflammatory diseases. Anti-Gal(alpha 1-3)Man antibody readily absorbed to American Leishmania and Trypanosoma culture forms, suggesting a surface membrane localization of reactive epitope. Gal(alpha 1-3)Man-bearing glycophospholipid was easily extracted from American Leishmania promastigotes and T. cruzi trypomastigotes as well as from American Trypanosoma culture forms. The possibility that this antibody arises against parasitic glycophospholipid-linked Gal(alpha 1-3)Man terminal residues is proposed.