A potent vaccination strategy that circumvents lymphodepletion for effective antitumor adoptive T-cell therapy.

Adoptive cell therapy using tumor-reactive T lymphocytes is a promising approach for treating advanced cancer. Successful tumor eradication depends primarily on the expansion and survival of the adoptively transferred T cells. Lymphodepletion using total body irradiation (TBI) and administering high-dose interleukin (IL)-2 have been used with adoptive cell therapy to promote T-cell expansion and survival to achieve maximal therapeutic effects. However, TBI and high-dose IL-2 increase the risk for major complications that impact overall survival. Here we describe an alternative approach to TBI and high-dose IL-2 for optimizing adoptive cell therapy, resulting in dramatic therapeutic effects against established melanomas in mice. Administration of a potent, noninfectious peptide vaccine after adoptive cell therapy dramatically increased antigen-specific T-cell numbers leading to enhancement in the survival of melanoma-bearing mice. Furthermore, combinations of peptide vaccination with PD1 blockade or IL-2/anti-IL-2 antibody complexes led to complete disease eradication and long-term survival in mice with large tumors receiving adoptive cell therapy. Our results indicate that PD1 blockade and IL-2/anti-IL-2 complexes enhance both the quantitative and qualitative aspects of the T-cell responses induced by peptide vaccination after adoptive cell therapy. These findings could be useful for the optimization of adoptive cell therapy in cancer patients without the need of toxic adjunct procedures.