T Cells Modified with CD70 as an Alternative Cellular Vaccine for Antitumor Immunity

Successful tumor eradication primarily depends on generation and maintenance of a large population of tumor-reactive CD8 T cells. Dendritic cells (DCs) are well-known potent antigen-presenting cells and have applied to clinics as potent antitumor therapeutic agents. However, high cost and difficulty in obtaining sufficient amounts for clinical use are the crucial drawbacks of DC-based vaccines. Here, we aimed to develop T cell-based vaccine capable of eliciting potent antitumor therapeutic effects by providing effective costimulatory signals.

Antigenic peptide-loaded T cells transfected with retrovirus encoding costimulatory ligands CD70, CD80, OX40L, or 4-1BBL were assessed for antigen-specific CD8 T-cell responses and evaluated antitumor effects along with immunization of a mixture of synthetic peptides, poly-IC and anti-CD40 antibodies (TriVax).

T cells expressing CD70 (CD70-T) exhibited similar level of stimulatory functionality and therapeutic efficacy as DCs. Moreover, CD70-T prime followed by TriVax booster heterologous vaccination elicited therapeutic antitumor effect against B16 melanoma where mediated by CD8 T cells but not CD4 T cells or natural killer cells. The combination with programmed death-ligand 1 blockade led to potent therapeutic efficacy which exhibited increased tumor-infiltrating CD8 T cells. CD70-T pulsed with multi-antigenic peptide generated multiple antigen-specific polyvalent CD8 T cells that were capable of inhibiting tumor growth effectively. Moreover, CD70-T vaccination resulted in higher expansion and migration of adoptively transferred T cells into tumor sites and elicits enhanced therapeutic effects with peptide-based booster immu-nization.

These results imply that T cells endowed with CD70 enable the design of effective vaccination strategies against solid cancer, which may overcome current limitations of DC-based vaccines.