A Mr 90 000 surface polypeptide of Trypanosoma cruzi as a candidate for a Chagas' disease diagnostic antigen

Abstract

Trypanosoma cruzi (Peru strain) trypomastigotes and epimastigotes were biosynthetically labeled with [ 35S]methionine, and the proteins were analyzed by two dimensional polyacrylamide gel electrophoresis (2D-PAGE). 2D-PAGE analysis of the trypomastigotes showed a complex array of polypeptides with distinct clusters at M r 88 000–92 000, isoelectric point (p I) 5.6–6.0, and M r 72 000–76 000, p I 5.6–5.8. 2D-PAGE analysis of the epimastigotes did not show the cluster of polypeptides at M r 90 000. When the trypomastigote lysate was reacted with sera from either mice or humans chronically infected with T. cruzi, 10–50 polypeptides were immunoprecipitated. Five of these polypeptides were recognized by all sera tested. However, of these polypeptides, only three, two of M r 90 000 and one of M r 150 000, can be identified by immunoreaction of [ 35S]methionine-labeled live parasites as surface proteins of T. cruzi trypomastigotes. 125I-iminobiotinylated surface proteins isolated from T. cruzi trypomastigotes were immunoprecipitated with the same series of sera as described above. Chagasic sera immunoprecipitated an antigen of M r 90 000. The [ 35S]methionine and 125I-labeled M r 90 000 polypeptides were not immunoprecipitated with sera from individuals infected with Leishmania donovani, Leishmania braziliensis, Leishmania tropica or Leishmania mexicana. These data indicate that a surface polypeptide of M r 90 000, p I 5.8–5.9 is a viable candidate for a Chagas' disease diagnostic antigen.