ANTIGENIC ALTERATION IN MAJOR PIROPLASM SURFACE-PROTEINS OF THEILERIA-SERGENTI DURING INFECTION

Theileria sergenti piroplasms were purified from different parasitemia peaks of cattle infected with parasitized erythrocytes or sporozoites during persistent infection. Their reactivities with monoclonal antib odies 13F5 and C9, which recognize 23 kDa and 32 kDa piroplasm surface proteins, respectively, were analyzed. Antigenic differences were obs erved among parasites from different parasitemia peaks during persiste nt infection when cattle were infected with sporozoites. Results of tw o-dimensional polyacrylamide gel electrophoresis showed that the 23 an d 32 kDa proteins were expressed in all samples tested, regardless of their reactivities with the monoclonal antibodies. In contrast, parasi tes obtained from cattle inoculated with parasitized erythrocytes show ed no antigenic alteration over a 2 month observation period. The resu lts suggest that antigenic alteration of T. sergenti during persistent infection is related to whether the parasites proliferate through ext raerythrocytic schizont stage in cattle or sporozoite and other sexual stages in tick vector.