THE REPETITIVE DOMAIN OF TRYPANOSOMA-CRUZI TRANS-SIALIDASE ENHANCES THE IMMUNE-RESPONSE AGAINST THE CATALYTIC DOMAIN

Trypanosoma cruzi trans-sialidase consists of a C-terminal domain comp osed essentially of immunodominant amino acid repeat units (SAPA-repea ts) and an amino region responsible for the enzymatic activity (cataly tic domain). To investigate the possible function(s) of SAPA-repeats, recombinant trans-sialidases either containing or lacking the C-termin al region were tested in mice. The presence of SAPA-repeats in the int ravenously injected protein has two consequences. First, they enhance the persistence of the trans-sialidase activity in blood. Second, SAPA -repeats promoted the production of antibodies directed to the catalyt ic domain that inhibit trans-sialidase activity. These results suggest that SAPA-repeats modulate the trans-sialidase activity in blood.