Correction of age-associated defects in dendritic cells enables CD4⁺ T cells to eradicate tumors

Defective host defenses later in life are associated with changes in immune cell activities, suggesting that age-specific considerations are needed in immunotherapy approaches. In this study, we found that PD-1 and CTLA4-based cancer immunotherapies are unable to eradicate tumors in elderly mice. This defect in anti-tumor activity correlated with two known age-associated immune defects: diminished abundance of systemic naive CD8⁺ T cells and weak migratory activities of dendritic cells (DCs). We identified a vaccine adjuvant, referred to as a DC hyperactivator, which corrects DC migratory defects in the elderly. Vaccines containing tumor antigens and DC hyperactivators induced T helper type 1 (TH1) CD4⁺ T cells with cytolytic activity that drive anti-tumor immunity in elderly mice. When administered early in life, DC hyperactivators were the only adjuvant identified that elicited anti-tumor CD4⁺ T cells that persisted into old age. These results raise the possibility of correcting age-associated immune defects through DC manipulation.