AN ENZYME-LINKED-IMMUNOSORBENT-ASSAY FOR DETECTION OF THEILERIA-PARVAANTIBODIES IN CATTLE USING A RECOMBINANT POLYMORPHIC IMMUNODOMINANT MOLECULE

Field and experimental bovine infection sera were used in immunoblots of sporozoite and schizont lysates of Theileria parva to identify cand idate diagnostic antigens. Four parasite antigens of Mr 67,000 (p67), 85,000 (the polymorphic immunodominant molecule, PIM), 104,000 (p104), and 150,000 (p150) were selected for a more detailed analysis. The p6 7 and p104 antigens were present only in the sporozoite lysates, where as PIM and p150 were found in both sporozoite and schizont lysates. Th e four antigens were expressed as recombinant fusion proteins and were compared with each other in an enzyme-linked immunosorbent assay (ELI SA) and in the whole-schizont-based indirect fluorescent antibody test (IFAT) in terms of their ability to detect antibodies in sera of expe rimentally infected cattle. The PIM-based ELISA provided a higher degr ee of sensitivity and specificity than did the ELISA using the other t hree recombinant antigens or the IFAT. Further evaluation of the PIM-E LISA using experimental sera derived from cattle infected with differe nt hemoparasites and field sera from endemic and nonendemic T. parva a reas showed that the assay had a sensitivity of > 99% and a specificit y of between 94% and 98%.