Purification and characterization of a protective antigen from Eimeria tenella

Chickens were partially protected against coccidiosis induced by Eimeria tenella by using extracts prepared from sonicated sporulated oocysts or from sonicated sporozoites. Following gel filtration of either extract, most of the protective antigens were confined to a single pool of proteins in the molecular mass range between 20 and 30 kDa. Further purification of proteins from the protective pool of sporulated oocyst extract yielded a protective polypeptide with a molecular mass of 26 kDa. An antiserum raised to this pool identified a polypeptide with a molecular mass of 22 kDa in the protective pool from a similarly prepared extract of sporozoites of E. tenella. In subsequent studies, this antiserum was used as an aid in cloning protective polypeptides.