In vivo examination of antigen candidates that may block the transfer of Theileria annulata to ticks

Objective: In this study, it was aimed to investigate the potential of previously identified antigen candidates (TA17050, TA20855, TA03640, TA10955) to prevent the transmission of the T. annulata to Hyalomma excavatum ticks. Materials and Methods: TA17050, TA20855, TA03640 and TA10955 gene regions were cloned and the expressed proteins were produced recombinantly. Animals in four different the experimental groups were immunized by administering each recombinant protein and adjuvant mixture twice at a dose of 500 µg with an interval of 21 days. Animals in the control group were injected with PBS + adjuvant mixture. The immune response levels against recombinant proteins were evaluated by western blot method using serum samples collected from all immunised animals. Following immunization, animals in the experimental and control groups were infected with T. annulata Ankara 279 sporozoite stabilate. During the immunization and infection period, complete blood analyzes and parasitological examinations of the animals were performed. The effectiveness of antigen candidates in preventing the transmission of the parasite to ticks was investigated by counting the infected acini cells in the tick salivary glands of H. excavatum ticks that were feed on experimental animals. Results: Western blot analyzes showed that calves in the experimental group were successfully immunized with the relevant recombinant proteins. An enhanced immune response against recombinant proteins was not detected in the control group. Following immunization, no significant changes were detected in the body temperature and complete blood values of experimental animals, but local reactions developed and swelling occurred at the injection sites. Severe clinical reactions were observed in all animals following experimental infection. The average infection rate detected in tick salivary gland acini cells was determined as 78,12% in animals immunized with Tams1, and 82,72% in the control group. The average infection rates in salivary glands of ticks fed on animals immunized with TA03640_F1.3, TA10955_F1.2 and TA20855 recombinant proteins separately were 59,44%, 26,41% and 26,24%, respectively, while it was found to be 51,87%, 12,56% and 36,63%, respectively, in the control group animals Conclusion: Analyzes revealed no statistically significant difference in infection rates of tick salivary glands between the experimental and control groups. It was determined that the proteins encoded by the TA17050, TA03640, TA10955, and TA20855 gene regions did not exhibit the desired level of efficacy in blocking in vivo transmission.