Immunochemical characterisation of Schistosoma mansoni glycolipid antigens

The aim of this study was to investigate the occurrence, distribution and i mmunochemical properties of antibody-defined carbohydrate epitopes in neutr al glycolipid fractions of Schistosoma mansoni eggs, cercariae and adults. The amount of extractable, antigenic, neutral glycolipids was lowest in adu lt worms, increasing consecutively in cercariae and eggs. The immunoreactiv ity of the glycolipids resided in the carbohydrate moiety in that it was pe riodate-sensitive. Serological reactivity, and monosaccharide component ana lysis, anomeric configuration and methylation-linkage analyses indicated th at there were two dominant epitopes, which could be partially defined immun ologically. The first epitope was detected on egg, cercarial and adult glyc olipids. It was strongly recognised by mouse chronic infection sera and rab bit hyperimmune sera raised against specific egg antigens, and was defined by the monoclonal antibody M2D3H (Bickle QD, Andrews BJ. Characterisation o f Schistosoma mansoni monoclonal antibodies which block in-vitro killing: f ailure to demonstrate blockage of immunity in vivo. Parasite Immunol 1988;1 0:151-168). M2D3H appeared to have the same epitope specificity as monoclon al antibody 128C3/3 (Weiss J, Magnani JL, Strand M. Identification of Schis tosoma mansoni glycolipids that share immunogenic carbohydrate epitopes wit h glycoproteins. J Immunol. 1986;136:4275-82). The internal epitope was def ined structurally by the presence of fucose 3-linked to 3,4-disubstituted N -acetylglucosamine, which was itself partially substituted by a second fuco se residue, to yield the determinant -4[Fuc alpha 1,2Fuc alpha 3]GlcNAc bet a 1-. The second epitope was defined by the anti-Lewis(x) monoclonal antibo dy 4D1 and was found primarily on cercarial glycolipids. It was chemically characterised as the Lewis(x) epitope of Ga1 beta 1,4[Fuc alpha 1,3]GlcNAc beta 1- in a terminal position. The removal of fucose greatly diminished th e binding of the anti-Lewis(x) and M2D3H monoclonal antibodies, as well as the polyclonal chronicinfection sera, to glycolipids of all three life-cycl e stages and thus revealed the epitopic importance of fucose. (C) 1999 Publ ished by Elsevier Science B.V. All rights reserved.