Daily Times

Livestock is an integral part of our country’s gross domestic products (GDP), and it plays an important role in reshaping the life of many poor and middle-income families in Pakistan. Good management practices keep the livestock healthy, and safe from extreme environmental factors. At the same time, this sector faces many challenges that reduce its performance and productivity. One such problem is the presence of ticks which not only cause direct losses by sucking blood and causing damage to the skin, but also transmit many infectious diseases such as Babesiosis, Theileriosis, and Crimean Congo Hemorrhagic Fever (Congo fever). Theileriosis, also known as Tropical theileriosis, is caused by an intra-cellular protozoan parasite, Theileria annulata, that primarily affect the cattle population. This parasite is transmitted through the bite of an infected hard tick of genus Hyalomma.

Theileria annulata has a very complicated life cycle that involves a tick vector for its transmission to next host. One form of this parasite, known as sporozoite, is transferred to the cattle through the bite of infected tick. These sporozoites reaches the lymph nodes of cow where they enter the white blood cells (lymphocytes) and cause uncontrolled division of these cells that lead to localized swelling of lymph nodes. In lymphocytes, the nucleus of these sporozoites divide continuously to form a so-called structure known as schizont having many nuclei. Schizonts when disrupt, release many merozoites, that is another form of this parasite which is capable to invade the circulating red blood cells (RBCs). In the RBCs, this parasite transforms into a pear-shaped structure that is known as piroplasm. These RBCs infected with piroplasm stage of this parasite are ingested by another tick of the same species, where the sexual phase of this parasite takes place. These piroplasms are converted into male and female gametocytes inside the gut of infected tick. The male and female gametes fuse together to form a zygote, which transforms into motile form (kinetes), that penetrate the tissues and reach the salivary glands of infected tick. In the salivary glands, these are again transformed to sporozoites, that are ready to be transmitted to the naïve cattle.

Researchers are finding new treatment and vaccine strategies to control this parasite. Buparvaquone is the only drug that is effective against Theileriosis but it has very high cost and environmental safety concerns. Secondly, there is only one vaccine available that targets the schizont stage of this parasite. It takes long time for its production, and does not provide complete protection in cattle, and more importantly it is not commercially available in Pakistan. To keep in view the challenges posed by this parasite, we have successfully prepared a vaccine that targets the development of parasite at all of its stages. This vaccine is cost-effective, takes less time for its production, and has no environmental safety concerns.

We have selected five different proteins of T. annulata, that are released from different stages of its development for the production of this vaccine; as our purpose was to target the parasite at every stage of its development. We took the amino acid sequence from the potential target sites of these proteins and unite them to form a single vaccine construct. We then checked its properties such as stability and non-allergic nature using different computer aided software packages; and expressed this protein in E. coli bacteria to get its production at large scale. We injected this protein in animal model and cow; and obtain a good response in both hosts. We verified the immune response using state of the art techniques i.e. ELISA and Flow cytometry, available at the Department of Parasitology, UVAS, Lahore. Our results show a successful preparation and evaluation of vaccine against Theileriosis. Furthermore, this is a molecular vaccine that is based on selected immunogenic regions of the protein; therefore, it is safe to use in animals without the need of cold-chain and has a potential for mass-scale production. We also expect that this model will be followed for the preparation of future vaccines against different pathogens.