P16 Specific IFN-gamma Secreting T Cells in Tumor Infiltrating Populations of Cervical Intraepithelial Neoplasia (CIN) and Cervical Cancer

Infection by human papillomavirus (HPV) is a necessary event in development of cervical cancer. More than 18 different so called high-risk (hr) HPV types cause immortalization of cervical epithelial cells. In response to the action of the viral oncogene E7 a regulatory feed back loop leads to upregulation of the cyclin-dependent kinase inhibitor p16^INK4a. In turn, p16 ^INK4a is consistently over expressed in hr-HPV infected cells and is a tumor associated self antigen. Therefore, it represents a generic target antigen independently of the HPV type. We have investigated whether such strong over expression elicits a cellular immune response. P16 ^INK4a derived HLA-A2-restricted peptides were predicted by an algorithm for MHC ligands and peptide motives (SYFPEITHI). Seven peptides were identified. Four tumor-infiltrating lymphocyte lines from biopsies of CIN III lesions (2) and cervical cancers (2), all HPV16 and HLA-A2 positive, were established. T cells were tested for their response to synthetic peptide stimulation by IFN-γ ELISpot assays. T cells isolated from one of the CIN III and one of the cervical cancer biopsies reacted specifically with one of the peptide epitopes. None of the other peptides were recognized when compared to unpulsed or control epitope BMLF-1 loaded antigen presenting cells. In addition, such TIL displayed cytolytic function. The presence of p16 ^INK4a reactive TIL in cervical cancer indicates its potential as a target antigen for immunotherapy.