Cell surface antigens of Trypanosoma cruzi: possible correlation with the interiorization process in mammalian cells.

Differences were observed in the pattern of the cell surface proteins of evolutive stages of Trypanosoma cruzi after radioiodination of the cells and subsequent analysis by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Affinity chromatography revealed that surface glycoproteins also vary in the epimastigote and trypomastigote forms of the parasite. The cell surface antigens of the two forms were identified after radioiodination or biosynthetic labeling with [35S]methionine and incubation with different antisera. Both epimastigotes and trypomastigotes share two main antigens, possibly glycoproteins, of apparent molecular weight 95 000 and 80 000, respectively, which are recognized by all antisera tested. On the other hand, the trypomastigote form possesses somewhat more cell surface antigens recognized both by rabbit anti-trypomastigote and by human Chagasic sera. Sequential immunoprecipitations with heterologous and homologous antisera established that an 85 000 and some higher molecular weight antigens are specific to the trypomastigote form. Preincubation of the trypomastigotes with sera from Chagasic patients elicits a 60% inhibition of the parasite interiorization into mammalian cells in culture when compared with normal human serum or anti-epimastigote serum. This result suggests that the antigens specific to the trypomastigote form are involved in the interiorization process.