Specificity of human cytotoxic T lymphocytes induced by a human papillomavirus type 16 E7-derived peptide

In order to establish tumour-specific cytotoxic T lymphocyte (CTL) cell lines, T cells from a human papillomavirus (HPV) type 16-positive patient with a cervical carcinoma in situ and from a healthy volunteer were stimulated in vitro with autologous dendritic cells loaded with peptides derived from the viral transforming proteins E6 and E7 and corresponding to potential HLA-A*0201-restricted T cell epitopes. From each donor a small number of low-affinity CTL lines against the peptide E7/86-93 was obtained, which specifically lysed HLA-A*0201-expressing B-lymphocytes (cell line 721) loaded with this peptide. Cytotoxicity was also observed against two HLA-A*0201-E7-positive epithelial cell lines, the cervical carcinoma cell line CaSki and the HPV-16-immortalized foreskin-keratinocyte cell line HPK IA. However, since none of the CTL recognized both cell lines, and E7-expressing 721 transfectants were never lysed, it was concluded that the reactivity against CaSki and HPK IA cells was due to cross-reactivity on allogeneic HLA molecules rather than to E7 recognition, which emphasizes that the specificity of tumour cell lysis by peptide-induced CTL has to be interpreted with caution.