Protein antigens of Theileria parva macroschizonts and immune precipitation studies.

The proteins of purified macroschizonts from Theileria parva, T. lawrencei, and T. taurotragi were analyzed by sodium dodecyl sulfate polyacrylamide gel electrophoresis. The major proteins of all species had molecular weights of 120,000, 70,000, 65,000, 62,000, 55,000, 44,000, and 35,000. All further experiments were carried out with T. parva. Using 125I surface labelling it was established that proteins with molecular weights of 70,000, 50,000, and 44,000 were membrane constituents. Staphylococcus aureus protein A-mediated immune precipitation studies with 125I-labelled lysates of macroschizonts and a rabbit anti-macroschizont serum specifically recognized proteins with molecular weights of 120,000, 91,000, 70,000, 62,000, and 35,000. A small proportion of sera recovered from Theileria immune cattle specifically recognized proteins with molecular weights of 180,000 and 70,000 in macroschizont-lysates.