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Evolution of the immune humoral response against experimentally induced Chagas disease was followed in three groups of white mice CD-1; one group without any previous treatment; a second group that had been immunized with membranes from cultured epimastigotes, and a third group treated only with Freund's adjuvant. The response was observed through immunotransference (Western Blot) against membrane antigens from cultured epimastigotes. As early as 11 days after inoculation, the sera of animals previously immunized showed a great number of recognition bands between 22 and 115 kDa; on the other hand, the animals treated only with adjuvant or those inoculated without any previous treatment, showed antibodies on the 18th day. These reacted against 52 and 62 kDa proteins. Antibodies against 68 and 72 kDa proteins were found on the 32nd day in mice treated with adjuvant and on the 39th day, in mice with no treatment. The antibodies could be relevant in the healing of the animals because they appear at the same time that parasites start disappearing from the blood.

Mice were immunized with whole membranes of cultured epimastigotes and then inoculated with cultured trypomastigotes. The blood parasite count was lower than in the control. No changes could be detected however, in the length of the prepatent period nor in the extent and duration of the tissue damage observed in the chronic phase of the infection. Damage was evident in the tissues of both immunized and naive animals up to 171 days post inoculum. Blood parasites could be demonstrated neither by direct observation nor by culture, as soon as 117 days after infection. The presence of mast cells a few hours after infection and throughout the study suggests a role of these cells in both the specific and nonspecific components of host response.