Evaluation Of The Humour-mediated Immunity Induced By Recombinant Antigen TuIP Against Ovine And Caprine Theileriosis

Theileria uilenbergi is one of the most important pathogen of ovine and caprine theileriosis inChina. The pathogen, which is transmitted by Haemaphysalis qinghaiensis and H. longicornis,parasitizes in lymphblast and eryhrocytes of a variety of goats and sheep and causes pyrexia, anemiaand choleplania, etc, and even leads to the animal death. The disease costs vast economic losses insheep husbandry in China. At present, the control strategy of the disease is mainly based on the use oftraditionally chemicals, but with the emergence of drug residue, drug tolerance, animal products andenvironment pollution, and the disease burst frequently because of the repeated biting by ticks, it isnecessary to search for an alternative biological method for theileriosis control.In this study, the TuIp gene, which had been immuno-screened from a merozoite cDNAlibrary of T.uilenbergi was successful expressed as recombinant protein in the Escherichia coli BL21(DE3)pLysE.The recombinant protein was used as antigen to immunize sheep while the His tagged protein was usedas control. Then, the sheep were challenged with H. qinghaiensis or blood infected with T. uilenbergi.The experimental results showed that,1. In the tick challenge experiment, the sheep in the immunized group produced specific antibody7thday after the initial immunization and reached a peak on14thday post boost immunization and remainedsuch high titer antibody through the period of experiment. The sheep in the control group were notdetected specific antibody at the beginning, until the30thday post tick challenge, viz the stage of manymerozoites involved in eryhrocytes, produced significantly increased antibody and up to the level ofimmunized group’s. By counting the numbers of parasites in the red blood cells, we find theparasitaemia in the immunized group (2.24%) was significant lower (p＜0.05) than that in the controlgroup (12.8%) and the emerging of the peak of piroplasms was delayed in the immunized group. Thedegrees of anemia of sheep in the immunized group were lighter than the control group and the bodytemperature restored to normal earlier.2. In the blood challenge experiment, the antibody level in the immunized group and the control groupwas similar to the tick challenge experiment, the difference is the specific antibody detected in thecontrol group increased gradually until near to the immunized group’s. The mean maximumpercentage of erythocytic parasitaemia of sheep in the immunized group (0.21%) and control group(0.37%) were both much lower than tick challenge groups’. The anemia levels were much lighter and nofever was observed.Now, there was no report about development of a vaccine in the control of ovine and caprinetheileriosis. T. uilenbergi is a high pathogenic parasite and seriously hazards the sheep industry, so it is aneed to develop vaccine to prevent this disease. However, the culture system of this parasite in vitro isnot established up to now, thus it is impossible to get adequate parasite materials for producing livevaccine. This experiment, through evaluation of immunoprotection of the recombinant antigen TuIP, itindicated that the TuIP antigen produced specific antibody, and therefore reduced the parasitaemia. These results laid the foundation for the further development of new type vaccine for control of ovineand caprine theileriosis in China.