Conjugation of CD8 + T cell determinants to lipid groups is known to enhance specific cell-mediated responses to target antigens in experimental animals and humans [25] [26] [27] [28] [29] , although mechanisms whereby immunity is achieved remains poorly understood. Lipopeptides hold several advantages over other conventional vaccine formulations; for instance, they are self-adjuvanting and display none of the toxicity-associated side effects of other Th1-inducing adjuvant systems. In our work, transgenic mice that were immunized with three short lipopeptide vaccines had T cells that produced IFN-γ. Among them the lipopeptide vaccine formulated with KS9 or AM9 In vivo protection demonstrated with imaging using Xenogen camera. HLA-A*1101 transgenic mice immunized with peptide pool and adjuvants were protected compared to control mice inoculated with PBS when they were challenged with 10,000 Prugneaud strain (Fluc)-T. gondii luciferase expressing parasites. There were a total of 5-9(usually 4-5 per group) mice tested in each control or immunization group. Differences between control and immunization groups were significant(p < 0.0064 using natural log transformed data and two-sample t test). Peptides derived from these proteins and the position within the proteins 2 Binding affinity was performed by MHC binding assay. 3 PBMC from four T. gondii-seropositive HLA-A03 supertype persons and four seronegative persons were stimulated with peptides, the T cell that produce IFN-γ were tested by ELISpot assay. 4 Splenic T cell were isolated from HLA-A*03 supertype(which includes the HLA-A*1101 haplotype) mice 10 to 14 days after peptide immunization and tested for their ability to generate IFN-γ in response to peptide. stimulated higher IFN-γ production than the lipopeptide vaccine formulated with RS9. Unexplained and variable responses have been observed to high affinity binding peptides in other models, e.g., studies of Livingstone, Alexander, Sette et al with Lassa fever virus. It will be of interest to better understand possible mechanisms for such lack of response in future studies. However, the lipopeptides with three epitope peptides linked together with alanine spacers did not stimulate an IFN-γ response by splenocytes from immunized mice when the splenocytes subsequently were exposed to each of the peptides in vitro. The reason why the lipopeptides with the three linked peptides did not work well in the transgenic mice might be related to a frame shift caused by the linkers that altered the response to the original peptides rather than the alanines functioning for the intended purpose of introducing a cleavage motif. The three linker "AAA" between the peptides had previously been demonstrated in other systems to result in sensitization to each linked peptide. However, surprisingly, it did not appear to work well herein. Because the three linked peptides in the lipopeptide formulation were not effective and we had found that a mixture of the components with a single peptide was as or more robust than the lipopeptide, we tried this approach with the three peptides that had been included in the linked lipopeptide with the universal helper CD4 + T cell peptide, PADRE, and adjuvants as described below. The response was robust both in vitro and in vivo (Figures 4 and 5) .