Although previous strategies were not very successful (4, –, 6), we have recently demonstrated that a calcium phosphate (CaP)-based nanoparticle vaccine (NPV) containing the Toll-like receptor 9 (TLR9) ligand CpG and a virus-specific CD8+ T cell epitope is highly efficient in activating CD8+ T cell immunity during chronic retroviral infection and cancer (7, –, 9). This evidence concerns the gene TLR9 and cancer.