CD8+ T cells are effective for tumor rejection. The presence of tumor infiltrating CD8+ T cells is associated with tumor regression and better prognosis. Cytomegalovirus (CMV) infection elicits a robust and long-lasting CD8+ T cell response, which makes CMV a potentially promising vaccine vector against cancer. In the current study, we used recombinant murine CMV (MCMV) strains as prophylactic and therapeutic vaccines in an aggressive B16 lung metastatic melanoma model. Immunization with MCMV expressing ovalbumin (OVA) induced a potent OVA-specific CD8+ T cell response and was effective in protecting mice from OVA-expressing B16 melanoma in an antigen-dependent manner. We further engineered MCMV to express a modified B16 melanoma antigen gp100 (MCMV-gp100KGP). Immunization with MCMV-gp100KGP was highly effective in overcoming immune tolerance to self-antigen and induced a strong, long-lasting gp100-specific CD8+ T cell response even in the presence of pre-existing CMV immunity. Furthermore, both prophylactic and therapeutic vaccination of mice with MCMV-gp100KGP effectively protected mice from highly aggressive lung B16-F10 melanoma and the protection was mediated by gp100-specific CD8+ T cells. Moreover, we demonstrated that MCMV is a superior vaccine vector compared to a commonly used vaccine vector vesicular stomatitis virus (VSV). Collectively, our studies demonstrated that CMV is a promising vaccine vector to prevent and treat tumors.
- Received March 17, 2014.
- Revision received January 6, 2015.
- Accepted January 20, 2015.
- Copyright © 2015, American Association for Cancer Research.