Using knockout and bone marrow chimera mouse models, Oba, Hoki, and Yamauchi et al. showed that CD40 and CD70, but not CD80/86, signaling on Batf3-dependent host cDC1s was essential for the expansion and antitumor efficacy of adoptively transferred gp100-specific CD8+ T cells (ACT) in mice bearing B16 tumors and treated with a vaccine (hgp100 peptide, TLR7 agonist, agonistic (ag) anti-CD40 Ab) and systemic IL-2. Administration of Flt3L prior to ACT with TLR3/agCD40-based vaccination induced and activated host cDC1s and enhanced the expansion of transferred T cells, which could be useful in a clinical setting.

Contributed by Lauren Hitchings

ABSTRACT: In vivo expansion of adoptively transferred CD8(+) T cells is a critical determinant of successful adoptive T cell therapy. Emerging evidence indicates Batf3-dependent conventional type 1 dendritic cells (cDC1s) rarely found within the tumor myeloid compartment are crucial for effector T cell recruitment to the tumor microenvironment. However, the role of cDC1s in expansion of tumor-specific CD8(+) T cells remains unclear. In this article, we addressed the role of cDC1s and their costimulatory molecules, CD40, CD70, and CD80/CD86, in expansion and antitumor efficacy of adoptively transferred in vitro-primed CD8(+) T cells recognizing nonmutated tumor-associated self-antigens. We found that TLR/CD40-mediated expansion and antitumor efficacy of adoptively transferred tumor-specific CD8(+) T cells were abrogated in Batf3(-/-) mice. Further mechanistic studies using mixed bone marrow chimeric mice identified that CD40 and CD70 but not CD80/CD86 signaling in cDC1s played a critical role in expansion and antitumor efficacy of adoptively transferred CD8(+) T cells. Moreover, induction and activation of cDC1s by administration of FMS-like tyrosine kinase 3 ligand (Flt3L) and TLR/CD40 agonists augmented expansion of adoptively transferred CD8(+) T cells, delayed tumor growth, and improved survival. These findings reveal a key role for CD40 and CD70 signaling in cDC1s and have major implications for the design of new vaccination strategies with adoptive T cell therapy.

Author Info: (1) Center for Immunotherapy, Roswell Park Comprehensive Cancer Center, Buffalo, NY (2) Center for Immunotherapy, Roswell Park Comprehensive Cancer Center, Buffalo, NY (3) Center f

Author Info: (1) Center for Immunotherapy, Roswell Park Comprehensive Cancer Center, Buffalo, NY (2) Center for Immunotherapy, Roswell Park Comprehensive Cancer Center, Buffalo, NY (3) Center for Immunotherapy, Roswell Park Comprehensive Cancer Center, Buffalo, NY (4) Celldex Therapeutics, Inc., Hampton, NJ 08827. (5) Celldex Therapeutics, Inc., Hampton, NJ 08827. (6) Department of Microbiology and Immunology, University of Maryland School of Medicine, Baltimore, MD 21201. (7) Center for Immunotherapy, Roswell Park Comprehensive Cancer Center, Buffalo, NY 14263; fumito.ito@roswellpark.org. Department of Surgical Oncology, Roswell Park Comprehensive Cancer Center, Buffalo, NY 14263; and. Department of Surgery, Jacobs School of Medicine and Biomedical Sciences, State University of New York at Buffalo, Buffalo, NY 14263.