Cytomegalovirus vector expressing RAE-1γ induces enhanced anti-tumor capacity of murine CD8+ T cells.

Designing CD8+ T-cell vaccines, which would provide protection against tumors is still considered a great challenge in immunotherapy. Here we show the robust potential of cytomegalovirus (CMV) vector expressing the NKG2D ligand RAE-1γ as CD8+ T cell-based vaccine against malignant tumors. Immunization with the CMV vector expressing RAE-1γ, delayed tumor growth or even provided complete protection against tumor challenge in both prophylactic and therapeutic settings. Moreover, a potent tumor control in mice vaccinated with this vector can be further enhanced by blocking the immune checkpoints TIGIT and PD-1. CMV vector expressing RAE-1γ potentiated expansion of KLRG1+ CD8+ T cells with enhanced effector properties. This vaccination was even more efficient in neonatal mice, resulting in the expansion and long-term maintenance of epitope-specific CD8+ T cells conferring robust resistance against tumor challenge. Our data show that immunomodulation of CD8+ T-cell responses promoted by herpesvirus expressing a ligand for NKG2D receptor can provide a powerful platform for the prevention and treatment of CD8+ T-cell sensitive tumors.