Lipid and Lipopolysaccharide-Like Antigens of Leishmania Promastigotes1

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Abstract
Extraction of whole promastigotes of L. tropica major and L. donovani with a mixture of hexane and isopropanol (3:2) yielded 3 fractions containing immunological activity: lipids, where the activity was determined by radioimmunoassay; a lipopolysaccharide-like (LPS-like), water soluble precipitate, where activity was determined both by radioimmunoassay and double gel diffusion, and the phenol: water extract of the lipid-free promastigotes, where activity was followed by double gel diffusion. The use of a solid state, lipid-based radioimmunoassay for detection of leishmanial antigens provided a sensitive measure of their activity with a considerable degree of species and serotype specificity. Antibodies were found to be leishmanial lipids in sera from immunized rabbits, convalescent mice, and human patients with confirmed cases of cutaneous leishmaniasis or kala azar. There was very little activity in normal human or animal sera. Analysis by Na dodecylsulfate (SDS)-polyacrylamide gel electrophoresis of fractions from promastigotes surface-labeled with galactose oxidase and Na borotritiate and preliminary immunochemical characterization of the LPS-like antigen showed that it contained galactose, but otherwise differed immunologically and chemically from excreted factor (EF), the best characterized leishmanial antigen.