Reactivity of stage-specific monoclonal antibody 1G7 with metacyclic trypomastigotes of Trypanosoma cruzi strains: lytic property and 90,000 mol. wt surface antigen polymorphism.

Eleven strains of Trypanosoma cruzi, originating from a variety of vertebrate and invertebrate hosts in distinct geographical regions, were examined for the reactivity of metacyclic stages with the monoclonal antibody 1G7. Trypomastigotes of five strains were susceptible to complement-dependent 1G7-mediated lysis. Higher levels of 1G7 bound to metacyclics of lysis-susceptible strains as compared to lysis-resistant isolates. Excluding Y and CL strains, 1G7 reacted with metacyclics of all T. cruzi isolates by binding to a 90,000 mol. wt surface polypeptide. A 90,000 mol. wt protein lacking the 1G7-specific epitope but immunologically related to the 90,000 mol. wt antigen of other T. cruzi isolates is present in Y and CL strains. The intensity of the 90,000 mol. wt band, detected by surface iodination of metacyclics or in immunoblots using the monoclonal antibody 1G7 or the monospecific antiserum to 90,000 mol. wt protein, varied among different strains and also a discrete variation was observed in its molecular weight. The overall analysis reveals a polymorphism of the 90,000 mol. wt protein, which is ubiquitous among the different T. cruzi isolates.