Dendritic Cell-Specific Antigen Delivery by Coronavirus Vaccine Vectors Induces Long-Lasting Protective Antiviral and Antitumor Immunity

Efficient vaccination against infectious agents and tumors depends on specific antigen targeting to dendritic cells (DCs). We report here that biosafe coronavirus-based vaccine vectors facilitate delivery of multiple antigens and immunostimulatory cytokines to professional antigen-presenting cells in vitro and in vivo. Vaccine vectors based on heavily attenuated murine coronavirus genomes were generated to express epitopes from the lymphocytic choriomeningitis virus glycoprotein, or human Melan-A, in combination with the immunostimulatory cytokine granulocyte-macrophage colony-stimulating factor (GMCSF). These vectors selectively targeted DCs in vitro and in vivo resulting in vector-mediated antigen expression and efficient maturation of DCs. Single application of only low vector doses elicited strong and long-lasting cytotoxic T-cell responses, providing protective antiviral and antitumor immunity. Furthermore, human DCs transduced with Melan-A-recombinant human coronavirus 229E efficiently activated tumor-specific CD8(+) T cells. Taken together, this novel vaccine platform is well suited to deliver antigens and immunostimulatory cytokines to DCs and to initiate and maintain protective immunity. IMPORTANCE Vaccination against infectious agents has protected many individuals from severe disease. In addition, prophylactic and, most likely, also therapeutic vaccination against tumors will save millions from metastatic disease. This study describes a novel vaccine approach that facilitates delivery of viral or tumor antigens to dendritic cells in vivo. Concomitant immunostimulation via the cytokine granulocyte-macrophage colony-stimulating factor (GM-CSF) was achieved through delivery by the same viral vector. Single immunization with only low doses of coronavirus-based vaccine vectors was sufficient to elicit (i) vigorous expansion and optimal differentiation of CD8(+) T cells, (ii) protective and long-lasting antiviral immunity, and (iii) prophylactic and therapeutic tumor immunity. Moreover, highly efficient antigen delivery to human DCs with recombinant human coronavirus 229E and specific stimulation of human CD8(+) T cells revealed that this approach is exceptionally well suited for translation into human vaccine studies.