Molecules involved in ligand-receptor interactions required for trypanosome entry into mammalian cells are prime targets for molecular intervention. A novel Trypanosoma cruzi gene, Tc-1, that codes for a 62 kDa protein has been identified and may be involved in parasite attachment and entry. The gene was recognized by a neutralizing monoclonal antibody, mAb 4A4 that recognizes epitopes on T. cruzi trypomastigote surface proteins. Our hypothesis is that Tc-1 codes for a novel 62 kDa protein that cardes an epitope required for trypanosome binding to mammalian cells. To test this hypothesis, the following specific aims were developed: (1) to characterize the Tc-1 gene coding for the 62 kDa protein, and (2) to determine the role of the 62 kDa protein in T. cruzi infection. Computer analysis, Northern, and Southern blots will be performed to obtain information about the possible function and developmental expression of Tc-l. The gene will be expressed and the 62 kDa protein pudfied; binding assays, immunoblots, and immunofluorescence studies will be done to try to localize the protein and determine its role in infection. The proposed studies will aid in the discovery of a novel T. cruzi ligand and advance our knowledge of the mechanisms involved in the eady molecular pathogenesis of T. cruzi infection.