Vaccine development against Theileria parasites using liposome as adjuvant

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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.