Components of the cell surface membrane of amastigotes, trypomastigotes, and epimastigotes of 3 different strains of Trypanosoma cruzi were radioiodinated by the lactoperoxidase technique, and the solubilized membranes were analyzed by 1- and 2-dimensional Polyacrylamide gel electrophoresis with sodium dodecyl sulfate (1D and 2D SDS-PAGE). Significant differences were noted when the amastigotes, trypomastigotes, and epimastigotes of a single strain of T. cruzi were compared. A major band of m.w. >94 K was noted in the trypomastigote preparation but was barely discernible in the amastigote preparation. When amastigotes, trypomastigotes, and epimastigotes of the 3 different strains of the organism were compared, demonstrable differences were observed in the preparations from trypomastigotes but not in those from the amastigote or epimastigote stages. A conspicuous component of m.w. <30 K was noted in trypomastigotes of only 1 strain. Radioiodinated cell surface components were immunoprecipitated with serum from rabbits infected with trypomastigotes or epimastigotes and with a serum from a human chronically infected with T. cruzi. All 3 sera precipitated a significant amount of surface antigens of amastigotes. In contrast, considerably less surface antigens of epimastigotes and particularly of trypomastigotes were precipitated by these same sera. These results suggest that a greater number or a higher concentration of antigens recognized by immune sera are expressed on the cell surface of amastigotes than of epimastigotes or trypomastigotes. 2D SDS-PAGE revealed a complex pattern of radioiodinated surface components for all 3 stages of T. cruzi, particularly the epimastigote stage. This complex pattern was markedly simplified after immunoprecipitation, indicating that a large number of radioiodinated surface components were not recognized by the antisera.
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Araujo et al. (1981) studied this question.