Treatment follow-up. The reactivities of sera from chronic Chagas' disease patients with successful therapy (A), a decrease in titers after treatment (C), and resistance to treatment (E) determined before benznidazole treatment (○) and 1 year (□) and 2 years (▵) after benznidazole treatment are shown. The values are the ratio of the absorbance of each serum sample at 492 nm to the reaction cutoff. Values greater than 1.0 were considered reactive. The horizontal lines represent the arithmetic means. Immunoblots for serum samples from the three groups of patients before treatment (Pre) and after treatment (Post-T) are shown in panels B, D, and F, respectively.