Accelerated CD8+ T-cell memory and prime-boost response after dendritic-cell vaccination

Efficient boosting of memory T- cell numbers to protective levels generally requires a relatively long interval between immunizations. Decreasing this interval could be crucial in biodefense and cancer immunotherapy, in which rapid protective responses are essential. Here, we show that vaccination with peptide- coated dendritic cells (DCs) generated CD8(+) T cells with the phenotype and function of memory cells within 4 - 6 d. These early memory CD8(+) T cells underwent vigorous secondary expansion in response to a variety of booster immunizations, leading to elevated numbers of effector and memory T cells and enhanced protective immunity. Coinjection of CpG oligodeoxynucleotides, potent inducers of inflammation that did not alter the duration of DC antigen display, prevented the rapid generation of memory T cells in wild- type mice but not in mice lacking the interferon (IFN)-gamma receptor. These data show that DC vaccination stimulates a pathway of accelerated generation of memory T cells, and suggest that events of inflammation, including the action of IFN-gamma on the responding T cells, control the rate of development of memory CD8(+) T cells.