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Dendritic cell-based genetic immunization in mice with a recombinant adenovirus encoding murine TRP2 induces
1Department of Dermatology, J. Gutenberg-University, Mainz, Germany. tueting@hautklinik.klinik.uni-mainz.de
Background:
The induction of cellular immune responses to melanocyte-specific enzymes such as the tyrosinase family of proteins is the goal of various clinical studies for the immunotherapy of melanoma. Tyrosinase-related protein-2 (TRP2) is an attractive model antigen for preclinical studies in C57BL/6 mice because it is naturally expressed by the murine B16 melanoma and can be recognized by self-reactive cytolytic T lymphocytes (CTL). Here we describe efforts to develop genetic immunization with dendritic cells (DC) for the immunotherapy of melanoma in this clinically relevant system.
Methods:
Recombinant adenoviruses encoding green fluorescent protein (Ad-EGFP) and murine TRP2 (Ad-mTRP2) were constructed using Cre-loxP-mediated recombination. DC were generated in vitro from precursors in bone marrow and transduced with Ad-EGFP or Ad-mTRP2. Mice were immunized by direct injection of adenovirus or by injection of Ad-transduced DC. Induction of tumor immunity was assessed by intravenous challenge with B16 melanoma cells and enumeration of experimentally induced lung metastases.
Results:
Flowcytometric analysis of DC transduced with Ad-EGFP demonstrated endogenous fluorescence due to cytoplasmatic expression of EGFP in 30-60% of cells. Ad-EGFP-transduced DC simultaneously displayed the DC-specific marker NLDC145 and high levels of MHC and costimulatory molecules on their cell surface. Transduction of DC with Ad-mTRP2 resulted in strong intracellular expression of TRP2 which could be readily detected by immunostaining. Importantly, immunization of mice with cultured Ad-mTRP2-transduced DC completely prevented the development of lung metastases following an intravenous challenge with B16 melanoma cells. This striking protective effect was observed with both the intravenous and the subcutaneous route of DC immunization. In vivo depletion of T-cell subsets suggested that the protective effect of an immunization with Ad-mTRP2-transduced DC involved both CD8+ and CD4+ T-cells.
Conclusions:
Our results demonstrate that DC-based genetic immunization of mice with TRP2, a clinically relevant melanocyte-specific self-antigen, induces effective cellular immunity and prevents metastatic growth of B16 melanoma cells in vivo.
Insights
Genetic immunization using dendritic cells (DC) carrying tyrosinase-related protein-2 (TRP2) effectively prevented melanoma metastasis in mice. This approach shows promise for melanoma immunotherapy by inducing cellular immunity against TRP2-expressing tumors.
Area of Science:
- Immunology
- Oncology
- Biotechnology
Background:
- Melanoma immunotherapy aims to induce cellular immune responses against melanocyte-specific antigens.
- Tyrosinase-related protein-2 (TRP2) is a key antigen for preclinical melanoma studies in C57BL/6 mice.
- Dendritic cell (DC)-based genetic immunization is explored for melanoma treatment.
Purpose of the Study:
- To develop a DC-based genetic immunization strategy for melanoma immunotherapy.
- To assess the efficacy of TRP2-transduced DC in preventing B16 melanoma metastasis in mice.
Main Methods:
- Recombinant adenoviruses encoding TRP2 (Ad-mTRP2) or GFP (Ad-EGFP) were constructed.
- Bone marrow-derived DC were generated and transduced with Ad-mTRP2 or Ad-EGFP.
- Mice were immunized with Ad-transduced DC and challenged with B16 melanoma cells.
Main Results:
- Ad-mTRP2-transduced DC expressed intracellular TRP2 and maintained DC surface markers.
- Immunization with Ad-mTRP2-transduced DC completely prevented lung metastases after B16 melanoma challenge.
- The protective effect involved both CD8+ and CD4+ T-cells.
Conclusions:
- DC-based genetic immunization with TRP2 induces effective cellular immunity against melanoma.
- This approach prevents metastatic growth of B16 melanoma in vivo.
- TRP2 is a viable target antigen for DC-based melanoma immunotherapy.