Molecular aspects of antigenic variation in Trypanosoma brucei gambiense

Abstract

The variant specific antigens of Trypanosoma brucei gambiense were purified to homogeneity by a novel surface elution technique followed by lectin-agarose affinity chromatography and ion exchange chromatography. These antigens were characterized by isoelectric focusing, sodium dodecyl sulfate polyacrylamide electrophoresis, tryptic peptide mapping and immunological analyses. Similar to the antigens of related trypanosomes, these antigens from T. b. gambiense were about 60,000 MW, glycosylated, different in isoelectric points for each protein, and immunologically non-cross-reactive. Monospecific antisera were raised to different variant antigens and the surface orientation of the antigens was investigated by fluorescently labeled antibodies and antibody-linked surface markers for scanning electron microscopy. In addition, the relationship of the antigens to the outer membrane of the cells was probed on live trypanosomes with antibody and cytoskeletal-disruptive agents. The antigens were found to be mobile within the outer surface coat of the cell and they were found to be under cellular control in a capping phenomenon. Alternatively, the antigens could be shed without cap formation in a process which rendered the cells insusceptible to the lytic action of antibody and complement. ...