Presence of antibodies to the major surface glycoprotein of Trypanosoma cruzi amastigotes in sera from Chagasic patients.

The surface of amastigote forms of Trypanosoma cruzi is covered by a stage-specific glycoprotein, Ssp-4. We show that Y strain-derived Ssp-4 is recognized by antibodies in sera from Chagasic patients. All 51 sera reacted with the surface of amastigotes by indirect immunofluorescence assays and immunoprecipitated Ssp-4. The human antibodies inhibited the binding of monoclonal antibodies to Ssp-4 in immunoradiometric assays, suggesting that the corresponding region of the molecule may be conserved among distinct strains of the parasite.