Objective: To describe application of a new method for the evaluation of anti-Trypanosoma cruzi activity against intracellular forms.
Method: Vero fibroblasts in 96-well tissue culture plates were infected with trypomastigote forms of T. cruzi. Amastigotes growth was estimated after 24 and 96 h both by microscopic counts of Giemsa-stained monolayers and enzyme-linked immunoIsorbent assay (ELISA). ELISA was performed directly on the fixed cultures using a rabbit anti-T. cruzi immunoIglobulin as the first antibody and a peroxidase-labelled antirabbit immunoglobulin as the second antibody. Three chemical series of structural analogous of gentian violet, thiadiazines and derivatives of 5-nitrothiophene-2-carbaldehyde as well as three reference compounds (nifurtimox, benznidazole and gentian violet) were then assayed. The anti-T. cruzi activity of all of them had been determined previously by microscopic counting of Giemsa-stained infected cultures.
Results: None of the assayed compounds showed better activity than the reference ones, but the application of the enzyme immunoassay to quantify the inhibition of growth amastigotes is of great interest, as it yielded results comparable with microscopic counts.
Conclusion: ELISA can be applied to pharmacological screening, with some advantages over the microscopic examination, including possible automation, rapidity and objectivity in assessment.