Quantitative real-time RT-PCR as a method for monitoring T lymphocyte reactivity to full-length tyrosinase protein in vaccinated melanoma patients.

The major goal of therapeutic cancer vaccine trials is to mediate tumor regression. However, it is critically important to devise in vitro immunological assays that correlate with clinical outcome, for use as surrogate markers of vaccine efficacy. To date, clinical emphasis has been placed on peptide vaccines, but trends towards the use of more complex immunogens such as whole proteins require the development of efficient and sensitive methods for monitoring their immunological effects. In the context of a vaccination trial using full-length tyrosinase (Ty) to immunize patients with metastatic melanoma, a monitoring technique was developed in which autologous dendritic cells (DC) infected with a recombinant adenovirus encoding the Ty protein were used to assess the Ty-specific reactivity of fresh peripheral blood lymphocytes (PBL) collected from patients at different intervals during therapy. Quantitative real-time RT-PCR (qRT-PCR) was used to measure the production of cytokine mRNA by T cells following a 2.5-h incubation with Ty-expressing DC. Two out of ten patients studied demonstrated Ty protein-specific reactivity that increased during and after the period of vaccination. While one of these patients also reacted to an HLA-A1-compatible Ty peptide, the second did not recognize any of the known Ty epitopes, highlighting the importance of this technique for monitoring the effects of complex vaccines.

Tumor-specific CD8+ T lymphocytes derived from the peripheral blood of prostate cancer patients by in vitro stimulation with autologous tumor cell lines.

To identify tumor-associated antigens as putative targets for developing immunotherapies against prostate cancer, we investigated the ability of T cells derived from the peripheral blood lymphocytes of prostate cancer patients to recognize autologous tumor cells. The technical challenge of growing in vitro carcinoma cell lines from small prostate cancer samples was previously addressed by immortalization of early epithelial cell cultures with the HPV16 transforming proteins E6 and E7 and by genetic characterization of the carcinoma and normal prostate cell lines. In our study, peripheral blood lymphocytes were stimulated in vitro using autologous IFNgamma-treated prostate carcinoma cells transduced with the B7.1 molecule as a source of T-cell costimulation. Tumor-specific CD8+ T lymphocytes were obtained from 3 of 6 prostate cancer patients tested and included T cells restricted by classical and nonclassical HLA molecules. In 1 case, we demonstrated that the prostate cancer-reactive T cells were TCRalpha/beta+ and recognized autologous tumor cells but not autologous normal cells in the context of HLA-B or -C molecules. These results validate the approach of in vitro stimulation of peripheral blood lymphocytes from prostate cancer patients with autologous tumor cell lines to isolate prostate cancer-specific T cells and demonstrate the existence of a functionally diverse immune response against prostate cancer.