Evaluation Of Its Immune Protective Effects Of Recombinant Surface Protein Against Theileria Luwenshuni In Sheep

Theileria luwenshuni is a protozoal parasite,which was transmitted by Haemaphysalis qinghaiensis and H.longicornis in China.It invades the lymphocytes,macrophages and erythrocytes of sheep,goats and some wild animals.The infected animals showed clinical manifestations,such as fever,anemia,enlarged lymph nodes,weakness,especially death.It caused huge economic losses to the sheep husbandry in China.The vaccine is the most promising measure for prevention and control the disease in view of the drug residues and resistance to this disease.TlSP is a membrane protein of T.luwenshuni,and it expresses in sporozoite and merozoite stages of this parasite.Its homologous genes were discovered in T.annulata,T.uilenbergi and T.ovis.It can become a candidate antigen for the development of antiTheileria vaccine.The major results were presented as following:1.The TlSP gene was successfully amplified by RT-PCR,and the epitopes and transmembrane regions of the TlSP were predicted by bioinformatics methods.The results showed that N-terminal of the TlSP showed good antigenicity effect,only TlSP without 3 transmembrane regions could be expressed,the recombinant TlSP had strong reactions with the positive sera of T.luwenshuni,T.uilenbergi,T.ovis and T.annulata,but no cross-reaction was found with positive sera of Babesia motasi and Anaplasma ovis.2.Experimental results showed that there were clinical symptoms,including raising the temperature twice,enlarged lymph nodes,morbidity(100%)and mortality(40%)with parasitemia ranges 2.23-3.5% in control sheep;but the sheep in experimental group I and II showed mild clinical symptoms,and the low parasitemia(1.23-1.89%).The highest titer of antibodies produced in experimental group I and II were1 ? 102 400 and 1 ? 25 600,respectively,with morbidity rate of 60% in both experimental groups.The recombinant Theileria luwenshuni surface protein(rTlSP)could partially protect sheep against Theileria infection and induced protective immune response at the dose rate of 150 ?g;the rTlSP could stimulate the proliferation of specific T lymphocytes,and significantly increases the secretion of IL-2,IL-4 and IFN-?.This study provided an experimental basis for the development of subunit vaccine of ovine and caprine theileriosis in the future study.