Immunization by direct DNA inoculation induces rejection of tumor cell challenge.

Direct DNA inoculation is the basis for a new technology that has been successfully used for in vivo induction of both humoral and cellular immune responses. However, the immunological parameters of this new approach remain to be evaluated in detail. We report here that direct DNA inoculation can induce protection from malignant tumor cell challenge through the generation of specific immune responses directed against antigens displayed on the tumor cells. The protected mice remain tumor-free for more than 1 year post-challenge. Memory responses upon tumor rechallenge were observed for both humoral and cellular immunity. Inoculated animals were able to reject otherwise lethal tumors several months following the original DNA inoculation protocol. These in vivo protective responses suggest that further analysis of this technology for vaccine development or immune therapeutic strategies is warranted.