Trypanosoma cruzi: immunobiological studies on epimastigotes of several strains.

Epimastigotes from six Trypanosoma cruzi strains showed similar growth pattern and duplication time in a biphasic culture medium as well as similar capability to differentiate into metacyclic forms when grown in the special GM-TIIH culture; interactions of epimastigotes and Concanavalin A, Soy bean agglutinin or Wheat germ agglutinin were also similar for all the strains. On the other hand, differences in the antigenic patterns were detected by double diffusion tests. At least one precipitogen, undetectable in the other strains, was shared by the Y and RA strains. In the RA a second precipitogen was shared with Tul strain. The three strains mentioned, as identified by their IEPh pattern belonged to the C group described by Nussenzweig and Goble in 1966. However, the differences between Y and Tul precipitogens proved that the C group originally described might be made up by several subgroups. As Tul strain had been previously classified twice in the A group and once in the C group, the classic A, B and C antigenic groups seem to be relatively unstable. Due to this, and because of the differences in shape, infective capability surface saccharides, etc. already established for the trypomastigote stage, which correlate making strain grouping feasible, we consider the latter might prove a better stage to search for a strain marker.