Vaccine development against Theileria parasites using liposome as adjuvant

细胞介导免疫（CMI）被认为是一种有效的控制感染的细胞内病原体，如原生动物。为了研制能诱导CMI的肽基疫苗，构建了包封牛白血病病毒包膜糖蛋白gp51合成肽的甘露聚糖包被脂质体。脂质体诱导小鼠特异性延迟型超敏反应、淋巴细胞增殖反应和细胞毒性淋巴细胞反应。通过这种肽的刺激，免疫小鼠的脾脏细胞产生大量的ifn - γ和IL2，而它们既不释放IL4也不释放IL10。这些结果表明合成肽脂质体增强小鼠Th-1型免疫。在日本，由梭形虫引起的牛螺旋体病是造成放牧牛经济损失的一个主要原因。日本的寄生虫种群和分离株由基因混合种群组成。piroplasm主要表面蛋白p32的氨基酸序列含有疟原虫入侵红细胞所需的三肽基序之一Lys-Glu-Lys （KEK）基序。我们合成了含有KEK序列的肽，由于肽对CMI的诱导作用，这些肽被包裹在甘露聚糖包被的脂质体中作为佐剂。用脂质体免疫含有KEK基序的合成肽，与未接种疫苗的对照犊牛相比，降低了寄生虫率，减轻了临床症状。有趣的是，具有与用作免疫原的p32等位基因形式相对应的寄生虫被抑制。因此，需要一种含有从C型和I型寄生虫中提取的KEK肽的鸡尾酒疫苗来控制日本血吸虫感染。

Cell-mediated immunity (CMI) is considered to be an effective in controlling infection with intracellular pathogenes, such as protozoa. To develope apeptide-based vaccine capable inducing CMI,mannan-coated liposome encapsulating 20-mer synthetic peptide of bovine leukemia virus envelope glycoprotein, gp51 was constructed. The liposome induced specific delayd-type hypersensitivity, lymphocyte proliferative responses and a cytotoxic lymphocyte response in mice.By stimnlation with the peptide, the spleen cells from the immunized mice produced a large amount of IFN-gamma and IL2, whereas they released neither IL4 or IL10. These results indicate the augmentation of Th-1 type immunity in mice by the synthetic peptide-liposome. Bovine piroplasmosis caused by T.sergenti is a major cause of economical loss in grazing cattle in Japan. Parasite stocks and isolates in Japan consist of genetically mixed population. Amino acid sequence of major piroplasm surface protein, p32 contains Lys-Glu-Lys (KEK) motif which is one of tripeptide motif necessary for Malaria parasite to invade erythrocytes. We produced synthetic peptides containing KEK sequences and encapsulated in mannan-coated liposome as adjuvant bacause of the induction of CMI by peptide. Immunization of synthetic peptides containing KEK motifs with liposome resulted in low parasitemia and reduced the clinical symptoms compared to that of control non-vaccinated calves. Interestingly, parasites with a p32 allelic form corresponding to one used as immunogen were suppressed.Therefore, a cocktail vaccine containing KEK peptides derived from C and I type parasites is desired for control Theileria parasite infection in Japan.