Trypanosoma simiae and Trypanosoma congolense: surface glycoconjugates of procyclic forms—the same coats on different hangers?

Abstract

Organic solvent extraction, reverse-phase high performance liquid chromatography and enzyme-linked immunosorbent assay with surface binding monoclonal antibodies were used to isolate membrane molecules of procyclic culture forms of Trypanosoma simiae and Trypanosoma congolense. Gel electrophoresis of the purified molecules revealed two predominant molecular species from each parasite that were broadly similar yet showed different apparent molecular masses and staining characteristics. The molecules were shown to be glycosylphosphatidylinositol-lipid anchored glycoconjugates, rich in carbohydrates. Each moiety displayed surface-disposed carbohydrate epitopes that were recognized on the surface of both species of trypanosomes by monoclonal antibodies specific for procyclic parasites of the subgenus Nannomonas. The epitopes were previously shown to be displayed on the glutamic acid-alanine rich protein of T. congolense yet neither this protein, nor its encoding gene is present in T. simiae. The results indicate that although T. congolense and T. simiae share common carbohydrate surface epitopes, these are displayed on biochemically different molecules. We speculate that the surface disposed carbohydrate structures are involved in parasite–tsetse interactions since these species have the same developmental cycles in the insect vector. Index Descriptors and Abbreviations: African trypanosomes; procyclics, Trypanosoma simiae, Trypanosoma congolense, BSF, bloodstream forms; VSG, variant surface glycoprotein; GPI, glycosylphosphatidylinositol; GARP, glutamic acid alanine rich protein; mAb, monoclonal antibodies; PCF, procyclic culture forms; FBS, fetal bovine serum; KMP-11, kinetoplastid membrane protein-11; ELISA, enzyme-linked immunosorbent assay; SDS–PAGE, sodium dodecyl sulfate polyacrylamide gel electrophoresis; CBB, Coomassie brilliant blue; HPLC, high performance liquid chromatography; PVDF, polyvinylidene difluoride; MALDI-TOF MS, matrix-assisted laser desorption ionization time-of-flight mass spectrometry. ESI, electrospray ionization.