Described herein are compositions and methods for treating a disease, particularly a melanoma, with a Dengue Virus and, optionally, primed dendritic cells recognizing a tumor antigen. Lysis protocols are described where the lysis does not result in complete or less than complete lysis of cells in order to provide cell surface molecules maintained in a cell surface-embedded state. Non-lethal Dengue virus strains are also provided for therapeutic purposes.