ABSTRACT
Antibodies from Chagasic patients (Ch), bound to a column of immobilized purified glycoprotein 25-kDa antigen of Trypanosoma cruzi epimastigotes (gp25), were partially lytic (70% lysis at 50 microng/ml) to cultured metacyclic trypomastigotes (Y strain) in a complement-mediated reaction (alternative pathway). Antibodies (Ch) eluted with galactose from a melibiose-Agarose column reacted in ELISA titration plates with gp25, whole cells of metacyclic trypomastigotes (Y strain), and less intensely with aqueous extracts of either T. cruzi (CL- 14 strain) or Herpetomonas muscarum. Agglutination of rabbit erythrocytes by anti-Gal antibodies from Chagasic patients or normal human sera (NHS) was inhibited by galactose and alfa- but not ß- anomeric galactosides. Anti-Gal antibodies (Ch or NHS) were lytic to metacyclic trypomastigotes in complement-mediated reactions. Agglutination of rabbit red cells by a serum sample from a T. cruzi-infected Rhesus monkey was inhibited by laminin. This serum was also lytic to metacyclic forms of T. cruzi (Y strain) involving the alternative complement pathway (70% lysis at 1:20 final dilution). These results open the possibility of using anti-Gal antibodies for protection against infection by virulent T. cruzi