Verbesserung der immunstimulatorischen Wirkung von Tumorantigenen durch liposomale Vektoren
Introduction: Immunodominant epitopes from tumor associated antigens (TAA) are currently used as soluble peptides (SP) in clinical trials in spite of an acknowledged low immunogenicity. We asked whether encapsulation into liposomes (LP) could improve their immunogenic capacity. Materials and Methods: The HLA-A2 restricted melanoma associated epitope Mart26–35 was synthesized and included into sterically stabilized liposomes, characterized by prolonged bio-availability in biological fluids in comparison with conventional reagents. Proliferation, cytokine production and cytotoxicity induced by either LP or SP in Mart26-35 specific CTL clones were evaluated by 3H-thymidine incorporation, ELISA and 51Cr release assays. To assess the induction of specific CTL, peripheral blood mononuclear cells (PBMC) from healthy donors were stimulated with autologous antigen presenting cells and LP or SP. Cytotoxic activity was evaluated by 51Cr release. Results: Proliferation of CTL clones could be comparably stimulated by saturating doses (> 100 ng/ml) of either SP or LP. At limiting concentrations (< 50 ng/ml), however, only LP were effective. IFN-γ production by specific CTL was also enhanced by LP as compared to SP stimulation. Furthermore, LP displayed a significantly higher capacity of sensitizing target cells to the cytotoxic effects of specific CTL clones as compared to SP. Most importantly, LP were able to induce specific cytotoxic activity in healthy donors PBMC, following a limited number of restimulation courses (n = 2). In the same conditions SP was totally ineffective. Conclusion: These data indicate that the specific immunostimulatory capacity of Mart26-35 melanoma associated epitope can be significantly improved by encapsulation into sterically stabilized liposomes.
Unable to display preview. Download preview PDF.
- 3.Harrington KJ, Lewanski CR, Stewart JS (2000) Liposomes as vehicles for targeted therapy of cancer: clinical development. Clin. Oncol 12 (1): 16–24Google Scholar