The development of effective vaccines against cancer and viruses still remains a challenge. Many immunotherapeutic strategies have been developed but without sufficient therapeutic success. Plasmacytoid dendritic cells (pDC) play a crucial role in antitumor and antiviral responses. Despite their outstanding functional properties, their therapeutic potential has not yet been worked out. We propose a new immunotherapeutic strategy based on a pDC cell line irradiated and pulsed with tumor or viral antigens. GENiusVac allows the induction of multispecific and highly functional cytotoxic cell responses directed against viral or tumor targets. We demonstrated the potential of this strategy in vitro, its therapeutic efficacy in vivo in a humanized mouse model, and its clinical relevance ex vivo from melanoma patients' cells. GENiusVac highlights pDCs as potent vector of immunotherapy and provide a way to exploit them in cell therapy to fight cancer or chronic viral infections.