Characterization of antitumor immunization to a defined melanoma antigen using genetically engineered murine dendritic cells

A murine model of dendritic cell (DC)-based genetic immunization to a defin ed human melanoma antigen (Ag), MART-1/Melan-A (MART-1), was developed. The MART-I gene was stably transfected into the nonimmunogenic mouse fibrosarc oma cell line NFSA that is syngeneic in C3Hf/Sem/Kam (C3H, H-2(k)) mice to generate the NFSA(MART1) cell line. In vivo protection from a lethal NFSA(M ART1) tumor challenge could be generated by DCs transduced with a recombina nt adenovirus (AdV) vector expressing MART-1 (AdVMART1). This model has the following characteristics: (a) immunological specificity and memory, (b) c omparable protection for varying transduction multiplicities of infection, cell doses, and sites of DC inoculation but interestingly, worse protection with increasing numbers of vaccinations, (c) the ability to treat small es tablished tumors, (d) an absolute requirement for CD8 and CD4 T cells, (e) generation of MART-1-specific splenic cytotoxic T lymphocytes, and (f) up-r egulation of both T helper type 1 and T helper type 2 cytokines. Geneticall y engineered DCs presenting defined tumor Ags represent an attractive metho d to generate effective immune responses.