We next observed the repertoire of the polyclonal antibodies raised in avian and mammalian models. Although p30 was evenly recognized by antibodies from the distinct species by onedimensional immunoblotts (WB1D), differential protein recognition pattern was noted (Fig. 5A ). Only chicken-derived antibodies recognized proteins with approximate molecular weights of 40 kDa, while IgG anti-STAg from mice reacted strongly to ,50 kDa antigen. These differences were maintained independently of the route used to immunize the mice (i.m. or s.c., Fig. 5A ). In order to further observe those differences in recognition, we performed 2D-immunoblots (WB2D) using the polyclonal antibodies obtained from immunized hens and mice. The differences in recognition were clearly noted in WB2D assay, with IgY antibodies recognizing a sequence of five antigenic spots at ,40 kDa, however with distinct isoelectric points -from neutral to basic pH (Fig. 5B ). On the other hand, mouse IgG reacted strongly to two acidic antigens at ,50 kDa ( Fig. 5C ), while IgY reacted faintly to the same spots and a basic protein with similar molecular weight (Fig. 5B ). Such differences were also noted in the distinct recognition patterns in antigens with 60-80 kDa, as well as the absence of immunodominant p22 antigen by chicken IgY. Additionally, STAg immobilized in nitrocellulose strips were probed to anti-Neospora caninum e anti-Eimeria spp. IgY in order to check the specificity of the antibodies. The assay revealed that IgY antibodies against the closely related protozoa did not cross-react with Toxoplasma antigens ( Figure 5D ).