No abstract

Autologous dendritic cells loaded with HPV E7 protein can induce T cell responses in healthy individuals by in vitro stimulation and evoke responses in TIL from cervical cancer biopsies. Since there are no limitations with respect to specific HLA-haplotypes, these findings may be a basis for the development of a therapeutic protein-based DC tumor vaccine against cervical cancer for HPV16- and HPV18-positive patients.

Immunotherapy of HPV-associated disease such as cervical cancer is moving from preclinical investigation to clinical trials. The viral oncoproteins E6 and E7 are ideal target antigens because their expression is mandatory in HPVtransformed tumor cells. T cells are the most important effector cells for therapeutic vaccination strategies. Therefore, the identification and characterization of HPV E6 and E7 T cell epitopes is necessary. Methods to date rely on screening for immunogenicity of peptides predicted by algorithms. Presentation of the identified peptides on tumor cells, however, needs to be confirmed. In our study, we have improved the method to identify peptide epitopes of HPV18 E7 that are actually presented by tumor cells. We induced allogeneic T-cell lines by stimulation with HPV18-positive, CD80 and HLA-A*0201 transfected cervical cancer cells. Sensitized T cells were probed against an array of a HPV18 E7 20mer peptide-library. We found specific reactivity to one of the 20mer peptides. This sequence was then screened via algorithms for putative epitopes. One putative HLA-A2 restricted epitope was confirmed to bind to HLA-A2, to be immunogenic and to induce IFN␥-release in ELISpot assays. Epitope-specific T cells were cytolytic toward autologous peptide pulsed targets and HPV18 transformed tumor cells. The identification of epitope-specific T cells in tumor infiltrating lymphocytes of a HPV18-positive HLA-matched cervical cancer patient suggests an in vivo relevance of the identified epitope. We suggest that our approach is advantageous over conventional methods, because it yields candidate peptides that are relevant CTL epitopes that are expressed, processed and presented by tumor cells.