Expression and localization of an S100 protein-like molecule in Eimeria tenella

We investigated the expression of a calcium-binding protein, the S100 protein, in Eimeria tenella. Cecal paraffin sections from experimentally infected chickens were treated with anti-alpha-S100 (anti-alpha subunit of S100 protein) and anti-beta-S100 (anti-beta subunit of S100 protein) monoclonal antibodies and anti-S100 whole molecule polyclonal antibody. The avidin-biotin peroxidase method was used for immunocytochemical staining. Our results demonstrated a positive immunoreaction within the schizonts, macrogametes, and oocysts. These stages were all beta subunit and S100 whole-molecule positive. Immunoblot studies of the total proteins of E. tenella merozoites and sporozoites of the original strain and 2 precocious lines have demonstrated that precocious attenuation produced different S100 protein isotypes.