Antibodies to T. cruzi cytosol acidic antigens (FIV) in Chagas' disease recognize parasite cell surface and human heart epitopes.

The expression of T. cruzi electronegative antigens (FIV) on the parasite surface and their cross-reactivity with heart tissue antigens was studied. For the former purpose epimastigotes (EPI) treated with glutaraldehyde were used to absorb antibodies against surface antigens. Glutaraldehyde fixed heart tissue was used for absorption of antibodies in sera from two groups of chagasic patients with normal and altered electrocardiogram. The absorption of sera from normal electrocardiogram group with EPI significantly reduced the anti FIV activity by ELISA (p less than 0.001). The decreased reactivity was observed with the antigenic bands focused at pI about 4.5. Thus, the results indicate that chagasic patients without electrocardiographic alterations have a high percentage of antibodies reactive with T. cruzi cell surface antigens. Serum absorption with glutaraldehyde fixed heart tissue reduced the anti FIV activity from both groups of patients by ELISA and diminished the intensity of several bands focused at pI 4-6.