Antibodies to Trypanosoma cruzi express idiotypic patterns that can differentiate between patients with asymptomatic or severe Chagas' disease.

Immunization of rabbits with pools of immunoaffinity-purified anti-Trypanosoma cruzi epimastigote antibodies derived from patients with different clinical forms of Chagas' disease induces antiidiotypic sera that can distinguish between anti-epimastigote antibodies from patients with asymptomatic (indeterminate (IND)) or severe (cardiac (CARD)) Chagas' disease. These idiotypically different anti-EPI antibodies from patients with the different clinical forms do not differ in their anti-epimastigote activities or isotypes. Analysis of immunoaffinity purified antibodies from individual chagasic patients by specific competitive ELISA generally confirms that Id-specific rabbit antisera can differentiate the clinical forms of the source of the antibodies. Based on these data, immunoaffinity-purified antibodies from patients share many Id with those from IND patients, although antibodies from IND patients express much lower levels of the distinctive Id characteristic of CARD patients. Reduction and alkylation of antibodies from IND patients reduces somewhat, but does not abolish, the ability of their Id to be recognized idiotypically, and to effectively inhibit in competitive ELISA. In contrast, reduction and alkylation of antibodies from CARD patients almost completely eliminates the ability of their predominant Id to be either recognized by, or inhibit, the appropriate systems. These data imply that the expression of the major Id that define CARD patients by these serologic anti-Id systems is largely dependent on the tertiary conformation of the Ig molecule. This agrees with our earlier studies on the respective differential abilities of CARD vs IND Id to stimulate anti-Id T cells by direct stimulation vs processing and presentation mechanisms.