Trypanosoma cruzi: Monoclonal antibodies to the surface glycoprotein superfamily differentiate subsets of the 85-kDa surface glycoproteins and confirm simultaneous expression of variant 85-kDa surface glycoproteins

Most surface glycoproteins expressed by mammalian-stage forms of Trypanosom a cruzi are homologous to the parasite's trans-sialidase and therefore are members of the parasite's trans-sialidase superfamily. Few members of this superfamily have trans-sialidase activity. The SA85-1 family is a subfamily of the trans-sialidase superfamily whose members lack trans-sialidase acti vity. The function of these non-trans-sialidase members remains unknown. In this report a series of monoclonal and polyclonal antibodies to the SA85-1 glycoproteins is presented. The mAbs define distinct subgroups of SA85-1 g lycoproteins, and these distinct subgroups are simultaneously expressed by individual trypomastigotes, supporting previous studies indicating that mul tiple SA85-1 glycoproteins and trans-sialidase superfamily glycoproteins ar e simultaneously expressed by each trypomastigote. In addition, the antibod ies define two major subsets of the SA85-1 family (subset I and subset 2) b ased on differences in migration in SDS-PAGE; the subsets do not appear to be created by differences in glycosylation. Subset 1 migrates slower and is spontaneously released or shed preferentially from the parasite surface co mpared to subset 2. In addition, subset 1 is attached to the trypomastigote surface by a GPI linkage. Since these glycoprotein subsets are differentia lly expressed, they may have different functions. (C) 1999 Academic Press.