After purification of an enriched IgY fraction, kinetics and avidity of the purified antibodies were evaluated by indirect ELISA. We verified that immunized hens presented detectable levels of specific IgY starting on day 21 after the first immunization (p.i.). The production of IgY anti-STAg increased significantly along the next weeks, and developed a progressive and sustained response, reaching its peak on day 42 p.i. ( Fig. 2A) . High avidity of IgY anti-STAg antibodies was already observed in the first reactive samples, at 21 days p.i., as demonstrated by the lack of significant differences in EI values between 6 M urea-treated and untreated samples (Fig. 2B) . The antigen recognition repertoire and avidity maturation of IgY anti-STAg were also verified by immunoblot. Similar to ELISA, reactivity was first observed on day 21 after immunization, with strong staining of a 30 kDa protein (Fig. 2C) . From the 35 th day onwards, IgY anti-STAg antibodies recognized a broad range of T. gondii antigens. The 6 M urea treatment presented a reduction in staining intensity of the described antigens between the 21 st and 35 th days p.i., with normal reactivity being observed after that period (Fig. 2C) .