Surface membrane components of Theileria spp piroplasms and associated complement fixation activity

Area of Science:

• Veterinary immunology
• Parasitology
• Molecular biology

Background:

• Theileria parva causes significant cattleileriosis.
• Understanding Theileria antigens is crucial for developing effective control strategies.
• Complement fixation (CF) is a serological assay used in diagnosing parasitic infections.

Purpose of the Study:

• To identify and characterize Theileria parva antigens responsible for complement fixation (CF) activity.
• To investigate the localization of these antigens within the parasite.
• To assess the potential of these antigens for differentiating Theileria species.

Main Methods:

• Complement fixation (CF) assays with immune cattle sera.
• Fractionation of Theileria parva piroplasms.
• Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE).
• Surface labeling of intact piroplasms with iodine-125.

Main Results:

• Theileria parva (parva) piroplasms exhibited high CF activity.
• Antigens responsible for CF activity were insoluble in aqueous media.
• Active fractions contained two polypeptides (21,500 and 34,000 molecular weight).
• These polypeptides were heavily surface-labeled, indicating plasma membrane localization.
• Electrophoresis allowed differentiation between Theileria species (T. parva, T. mutans, T. taurotragi).
• Three stocks of T. parva (parva) were chemically indistinguishable.

Conclusions:

• The study identified two major plasma membrane-bound polypeptides of Theileria parva as key antigens for CF reactivity.
• These antigens hold potential for serological differentiation of Theileria species.
• Further research may lead to improved diagnostics for Theileria infections in cattle.