Antigenic polymorphism of Trypanosoma cruzi: clonal analysis of trypomastigote surface antigens.

The surface membrane antigens of infectious Trypanosoma cruzi trypomastigotes were studied at the levels of the strain and of individual trypomastigote clones. Blood trypomastigotes from three T. cruzi strains, Y, CL and Tehuantepec ("Teh"), were grown in vitro by weekly infection of J774 mouse macrophage tumor cells. Each T. cruzi strain was subsequently cloned by infection of J774 cells at limited trypomastigote dilution, and antisera were produced in mice against a selection of trypomastigote clones. Criss-cross panel analyses indicated the existence of a large degree of polymorphism among trypomastigote surface antigens. Various trypomastigote surface antigens were cross-reactive, appeared to be highly conserved, and were common to the three strains considered and to all the clones derived from each strain. Analysis by sodium dodecyl sulfate polyacrylamide gel electrophoresis showed that numerous trypomastigote antigenic proteins were precipitated by mouse antisera generated against cloned trypomastigotes. Some of these proteins were commonly distributed, while others were polymorphic. Finally, a state of cross-reactive immunity could be induced in C3H/He mice by infection with a cloned T. cruzi trypomastigote population. Immune mice resisted subsequent infections with lethal doses of wild-type bloodstream trypomastigotes from any one of the three T. cruzi strains.