Figure 3. Identification of immunodominant pentadecamer peptides.

To identify immunodominant T cell epitopes, 31 HLA-A*02⁺ healthy donors were stimulated with selected peptides. A. Two pentadecamer peptides (black bars) were found to be positive in more than 30% of all tested donors. B. IFN-γ production by CD8⁺ T cells in response to individual neighboring overlapping peptides confirmed the presence of immunogenic sequences within OP-29 and OP-72. Triplicates for each peptide were analyzed in ELISPOT assays. Mean and standard derivations were calculated. Antigen-specific responses were characterized by a stimulation index (S.I.). S. I. representing the ratio of the number of IFN-γ secreting cells after antigen stimulation to that without stimulation (negative control). Responses were considered as positive when the S.I. was equal or above the cut-off of two (dashed grey line).