HLA-A01-, -A03-, and -A024-binding nanomeric epitopes in polyomavirus BK large T antigen

Polyomavirus BK (BKV) infections are increasingly recognized. The development of immune-monitoring strategies against BKV requires definition of antigenic epitopes. Bioinformatic algorithms were used to identify 60 BKV large T-antigen (LT-Ag) peptides predicted to bind HLA class I alleles. In vitro peptide binding was used to select a subset of 19 peptides for interferon (IFN)-γ ELISPOT assays in 13 healthy subjects and 12 kidney transplant recipients. Four A01-, nine A03-, and five A24-binding immunogenic peptides were identified in 1 to 3 (14-67%) tested subjects in each group. BKV epitope sequences were identical to homologous JC virus sequences for 3 of 19 peptides and homologous SV40 sequences for 5 of 19 peptides. Homology modeling localized these epitopes to the helicase, origin of DNA binding, or J domains, respectively. In conclusion, we have identified multiple 9-mer BKV LT-Ag-derived immunogenic epitopes that bind HLA-A01, -A03, or -A24 molecules. Sequence alignments indicate that two epitopes, FLICKGVNK and RYWLFKGPI, are common to BKV, JC virus, and SV40 virus.