THE FLAGELLAR FRACTION OF TRYPANOSOMA-CRUZI DEPLETED OF AN IMMUNOSUPPRESSIVE ANTIGEN ENHANCES PROTECTION TO INFECTION AND ELICITS SPONTANEOUS T-CELL RESPONSES

The flagellar fraction (FF) of Trypanosoma cruzi can be separated by i mmunoaffinity chromatography in two fractions with balanced but opposi te immunological effects. The immunoaffinity purified fraction has imm unosuppressive activity mediated at least partially by TGF-beta (Hanse n et al., submitted). Here we report that the fr action depleted of im munosuppresive antigens (FT) administered with iscom-matrix as adjuvan t provides enhanced protection to an infection challenge in immunized mice. In vitro, the FT but not the FF stimulated resident peritoneal c ells to produce IL-1 and IL-6. In immunized mice, the FT elicited high er levels of antigen-specific IgG(2a) than the FF as well as broader r ecognition of T. cruzi antigens. Splenocytes from mice immunized with FT proliferated spontaneously in vitro and secreted T-H1 and T-H2 cyto kines. and T The protection provided by FT correlates with its capacit y to enhance the secretion of IFN-gamma. We postulate that immunosuppr essive antigens present in the FF prevent the development of memory ce lls secreting IFN-gamma through a TGF-beta dependent mechanism.