Strains and clones of Trypanosoma cruzi differ in their expression of a surface antigen identified by a monoclonal antibody.

Four Trypanosoma cruzi strains and 50 clones derived from a total of 10 strains were assayed with a monoclonal antibody, WIC 29.26 Ab, for expression of an epitope previously demonstrated to be on the carbohydrate portion of a 72 000 Da surface glycoprotein of Y strain epimastigotes. WIC 29.26 Ab bound to only 2 of the 4 strains and 23 of the 50 clones tested. A group of 10 cloned isolates from one strain contained both reactive and non-reactive clones. Competitive inhibition studies with soluble extracts of the reactive and non-reactive isolates suggested that in addition to being absent from the surface membrane, the antigenic determinant is not synthesized by the non-reactive parasites. These data indicate that the epitope recognized by WIC 29.26 Ab is not present on all T. cruzi epimastigotes, and provide the first demonstration of clone-specific differences in a parasite antigen detected by a monoclonal antibody. No correlation was found between the reactivity of isolates with WIC 29.26 Ab and the previously investigated parameters of growth rate and modal volume.