Phosphocholine-containing, zwitterionic glycosphingolipids of adult Onchocerca volvulus as highly conserved antigenic structures of parasitic nematodes

Human Onchocerca volvulus infection sera were found to recognize zwitterion ic glycolipids of O. volvulus and to cross-react with those of other parasi tic nematodes (Ascaris suum, Setaria digitata and Litomosoides sigmodontis) . By the use of an epitope-specific monoclonal antibody, zwitterionic glyco lipids of all these nematode species were observed to contain the antigenic determinant phosphocholine. A hyperimmune serum specific for arthro-series glycolipid structures reacted with the various neutral glycolipids of all these nematodes, which demonstrated that their oligosaccharide moieties bel onged to the arthro-series of protostomial glycolipids. These results indic ated that arthro-series glycosphingolipids carrying, in part, phosphocholin e substituents, represent highly conserved, antigenic glycolipid markers of parasitic nematodes. Three glycolipid components of the O. volvulus zwitte rionic fraction were structurally characterized by matrix-assisted laser-de sorption/ionization time-of-flight MS, methylation analysis and exoglycosid ase treatment. Their chemical structures were elucidated to be phosphocholi ne-6GlcNAc(beta 1-3)Man(beta 1-4)Glc(1-1)ceramide, GalNAc(beta 1-4)-[phosph ocholine-6] GlcNAc(beta 1-3)Man(beta 1-4)Glc(l-l)ceramide and Gal(alpha 1-3 )GalNAc(beta 1-4)[phosphocholine-6]GlcNAc(beta 1-3)-Man(beta 1-4)Glc(1-1)ce ramide for the zwitterionic ceramide tri-, tetra- and penta-hexosides respe ctively. The ceramide composition was found to be dominated by 2-hydroxylat ed docosanoic (C-22h:0), tricosanoic (C-23h:0) and tetracosanoic (C-24h:0) acids, and C-17 sphingosine (C-d17:1) (where (h) is hydroxylated and (d) is dihydroxylated).