Altered decamer and nonamer from an HLA-A0201-restricted epitope of Survivin differentially stimulate T-cell responses in different individuals

Survivin is a universal tumor antigen that is being currently targeted in vaccine approaches against cancer. Our study here examined the immunogenicity of a novel variant of an HLA-A0201-binding decamer peptide from region 95 to 104 of Survivin (ELMLGEFLKL) with a T→M modification at position 3 in the peptide. We found that this new modified 10-mer peptide had enhanced HLA-A0201 binding and induced a stronger T-cell response over its wild type counterpart peptide (ELTLGEFLKL) in select HLA-A0201(+) normal donors. In addition, when compared to the previously characterized altered 96-104 peptide (LMLGEFLKL) from the same region of Survivin currently used in vaccine trials, we found that both peptides had similar immunogenicity, but donor T cells preferentially reacted strongly to either one or the other, but not strongly to both. These results suggest that these two closely related Survivin peptides yield distinct T-cell responses and that most individuals dominantly respond to one or the other altered peptide. We also found a novel association between positive reactivity to the new altered decamer Survivin peptide in some individuals and their expression of the HLA-C0701 allele along with HLA-A0201. Thus, vaccinating with both the 10-mer and 9-mer peptides would be required to immunize a maximum number of individuals in the HLA-A0201(+) population and could lead to more consistent T-cell responses against this region of Survivin.