Molecular mechanisms of diversity of theileria parasite genes distributed in middle and South America

他们的大肠杆菌是一种蜱传播的牛原生动物。良性牛肠杆菌寄生虫分布在亚洲国家，被认为是T. sergenti / buffeli / orientalis群。该寄生虫具有主螺质表面蛋白（MPSP）基因，该基因是寄生虫逃避宿主免疫的手段之一。蜱是人类最重要的类群之一，并传播其寄生虫。为了比较分布在世界各地的蜱类唾液腺衍生分子，对唾液衍生分子钙网蛋白（calreticulin）进行了分子克隆。钙网蛋白是一种结合Ca<++>的多功能蛋白，具有抗补体和抗凝血酶的活性。本研究从引起非洲东海岸热的小t虫（T. parva）的主要媒介——尾尾棘头蜱（Rhipicephalus appendiculatus）蜱中分离出钙网蛋白基因。利用3′和5′RACE方法，从尾鱼cDNA文库中获得一个钙网蛋白cDNA克隆。钙网蛋白基因的核苷酸序列和推导出的氨基酸序列与其他已知蜱种、美洲钝瘤和微乳蜱的钙网蛋白基因具有高度的同源性。这个基因的表达目前正在研究中。接下来，我们研究了丝氨酸蛋白酶抑制剂（serpins）的分子克隆。蛇形蛋白在维持体内平衡方面具有重要的调节功能，如凝血级联、纤维蛋白溶解、食物消化和受精。从长角天牛cDNA文库和尾尾天牛cDNA文库中分别获得3个和4个蛇形蛋白cDNA。这些克隆与其他已知蜱类或哺乳动物的蛇形蛋白基因具有较高的同源性。目前正在研究这些基因在大肠杆菌中的表达及其生物活性。

Theileria sergenti is a tick-borne protozoa of cattle. Benign bovine theileria parasites, which are presumed to be of the T. sergenti / buffeli / orientalis group are distributed in Asian countries. The parasites have the major piroplasm surface protein (MPSP) gene which is one of the means of parasite evasion of host immunity.Ticks represent one of the most important groups of anthropods, and transmit theileria parasites. To compare the tick salivary gland derived molecules among ticks distributed all over the world, molecular cloning of saliva derived molecules, such as calreticulin, a Ca<++>-binding multifunctional protein showing anti-complement and anti-thrombin antivities. In this study, the calreticulin gene from a tick species Rhipicephalus appendiculatus, which is a major vector of T. parva causing East coast fever in Africa was clearified. A calreticulin cDNA clone was obtained from a R. appendiculatus cDNA library by the 3' and 5' RACE methods. The mucleotide and deduced amino acid sequences of the calreticulin genes showed high homology with those of known calreticulin genes of other tick species, Amblyoma americanum and Boopiylus microplus. The expression of this gene is now under investigation.Next, we examined the molecular cloning of serine proteinase inhibitors (serpins). Serpins are known to regulate important functions in maintenance of homeostasis, such as the blood coagulation cascade, fibrinolysis, food digestion and fertilization. Three and 4 serpin cDNAs were obtained from H. longicornis and R. appendiculatus cDNA libraries, respectively. These clones showed high homology with known serpin genes of other ticks or mammalian species. Expression of these genes in E. coli and examination of biological activities are now under investigation.