Localization of pp65-derived CTL epitopes estimated by ELISPOT assay using various pp65-deletion mutants. Amino acids (aa's) are numbered from the initial methionine. Each deletion mutant was transfected into 293T cells together with restricting HLA cDNA and was tested for the recognition by corresponding pp65-specific CTL line by ELISPOT assay. The number of spots over that of full-length pp65 or Δpp65(1-482) (only in Cw*1202) is indicated as follows: greater than 70% (large-sized circles), 20% to 70% (semicircles), less than 20% (small-sized circles). “—” indicates the absence of spots.