PBMCs from healthy controls (HC; n = 3) and kidney transplant patients (KT) (n = 6) were expanded with or without BKV-infected cell lysate/BKV LT-Ag PepMix for 13–15 days. Expanded T cells were harvested and tested in an IFN-γ ELISPOT assay. We used HLA-A03 binding individual BKV LT-Ag peptides as an antigen and HLA-matched allogeneic LCL as antigen-presenting cells. Positive results are expressed as the mean number of IFN-γ spots/105 cells. The numbers in brackets below every peptide represent the percentage relative to pass/fail control score obtained with in vitro peptide-binding assays. Bars without standard deviation indicate that a single positive result was obtained with some selected peptides. Of 3 HC subjects tested, all responded to peptides P208 and P506, 2 responded to peptides P159, P172, and P414, and only 1 responded to P156. In the KT patients group, 4 of 6 responded to peptide P506, 3 of 6 responded to peptide P156, 2 of 6 responded to peptides P159, 1 of 6 responded to peptide P414, and 1 of 4 responded to peptides P172, P208, P222, P227, and P394.