Antibody response and antigen recognition in human infection with Trypanosoma cruzi

Sequential serum samples of an individual accidentally infected with Trypanosoma cruzi were examined to study the evolution of the antibody response, particularly of those with the capacity to lyse trypanosomes, and to determine the antigens of each of the 3 stages of the life cycle of T. cruzi, recognized by antibodies formed as the infection progresses. T. cruzi specific IgM and subclasses of IgG antibodies were detected and reached peak levels at the same period of time. Lytic antibodies were detected 2 weeks before demonstration of parasitemia and of antibodies reacting in the ELISA and IFA tests. Western blots used to examine antigen recognition revealed a complex array of antigens of epimastigotes and amastigotes, but not of blood trypomastigotes, recognized by antibodies in the various serum samples. Most of the antigens recognized by antibodies were common to all 3 stages of T. cruzi, although a few were specific for each of the stages. Certain antigens were only recognized by antibodies in serum collected at distinct periods of time during the course of the infection. The pattern noted after immunoprecipitation of 125I labeled cell membrane surface antigens was simple. Antigens of molecular weight of 90, 72, 50, and 30 K were immunoprecipitated in higher quantities. Antibodies in serum collected early and late in the infection recognized similar antigens in epimastigotes of the infecting strain and in epimastigotes of 3 other strains of T. cruzi from widely separated geographic areas.