We initially identified 3 epitopes that provided protection against parasite challenge. As a next generation vaccine that might be even more robust, elicit CD8 + T cells that would be effective against all three life cycle stages and Type I and II genetic types of the parasite, we sought to identify additional HLA-A11 epitopes to be used for vaccine development. In order to identify additional peptides from T. gondii that were present in tachyzoites, bradyzoites, and sporozoites of Type II strains for HLA-A03 supertype restricted CD8 + T cells, we screened candidate peptides from tachyzoite, bradyzoite and sporozoite proteins (GRA15, GRA10, SAG2C, SAG2X, SAG3, SRS9, SPA and MIC) of the Type II T. gondii strain (Tables 1 and 2 ). For parsimony in numbers of peptides utilized, we attempted to include peptides present in Type I as well as Type II parasite genetic types. Peripheral blood mononuclear cells from seropositive T. gondii donors were tested for response to these peptides by using the IFN-γ ELISpot assay. Pooled peptides were tested initially. Pools 2 and 5 were significantly different (p < 0.05) from the control (data not shown). Then the individual peptides were tested ( Figure 6 ). Three out of 34 epitopes elicited responses greater than 50 IFN-γ SFC from seropositive donors PBMC, but not from seronegative donors PBMC ( Figure 6 ). These peptides and the proteins from which they are derived are: STFWPCLLR (SAG2C 13-21 ); SSAYVFSVK (SPA 250-258 ); and AVVSLLRLLK (SPA 89-98 ) adding proteins expressed in sporozoites and bradyzoites to the peptides selected. All peptides identified herein then were found to show high binding affinity to three to five HLA-A03 supertype alleles in the MHC-peptide binding assay ( Table 3 ). The numbers in Table 3 which indicate high binding affinity are those less than 500 IC 50 nM. They are indicated by bolded font numbers in Table 3 .