Dendritic cell-derived interleukin-15 is crucial for therapeutic cancer vaccine potency

Abstract

IL-15 supports improved antitumor immunity. How to best incorporate IL-15 into vaccine formulations for superior cancer immunotherapy remains a challenge. DC-derived IL-15 (DCIL-15) notably has the capacity to activate DC, to substitute for CD4 C Th and to potentiate vaccine efficacy making IL-15-based therapies attractive treatment options. We observed in transplantable melanoma, glioma and metastatic breast carcinoma models that DCIL-15-based DNA vaccines in which DC specifically express IL-15 and simultaneously produce tumor Aghsp70 were able to mediate potent therapeutic efficacy that required both host Batf3C DC and CD8 C T cells. In an inducible Braf V600E /Pten-driven murine melanoma model, DCIL-15 (not rIL-15)-based DNA vaccines elicited durable therapeutic CD8C T cell-dependent antitumor immunity. DCIL-15 was found to be superior to rIL-15 in "licensing" both mouse and human DC, and for activating CD8 C T cells. Such activation occurred even in the presence of Treg, without a need for CD4 C Th, but was IL-15/IL-15Ra-dependent. A single low-dose of DCIL-15 (not rIL-15)-based DC vaccines induced therapeutic antitumor immunity. CD14C DC emigrating from human skin explants genetically-immunized by IL-15 and Aghsp70 were more effective than similar DC emigrating from the explants genetically-immunized by Aghsp70 in the presence of rIL-15 in expressing membrane-bound IL-15/IL-15Ra and activating CD8 C T cells. These results support future clinical use of DCIL-15 as a therapeutic agent in battling cancer.

Genetic Vaccines To Potentiate the Effective CD103+ Dendritic Cell–Mediated Cross-Priming of Antitumor Immunity

“…All animal procedures were performed according to IACUC-approved protocols and in accordance with recommendations for the proper use and care of laboratory animals. Murine melanoma B16 (ATCC, Manassas, VA) and glioma GL26 cells were maintained in DMEM (IRVINE Scientific, Santa Ana, CA) supplemented with 10% fetal bovine serum (FBS) (Hyclone, Logan, UT), 2 mmol/l glutamine (Invitrogen, Carlsbad, CA) and 1xantibiotic/antimycotic solution (Sigma, St Louis, MO), and murine breast carcinoma 4T1.2-Neu cells were cultured in the aforementioned medium including G-418 (500 μg/ml) (Invitrogen) (23–24). …”

“…Day 5–6, DC were purified using anti-mouse CD11c microbeads (Miltenyi Biotec, Auburn, CA). Purified DC (2–3x10 6 ) were untreated or transfected with 7 μg endotoxin-free DNA using Amaxa mouse DC Nucleofector kit (Lonza, Cologne, Germany) following the vendor’s instruction, and continually cultured in 1 ml DC culture medium for 2–3 days before analysis or immunization (24). …”

“…Immature human moDC were generated from peripheral blood mononuclear cells (PBMC) obtained from adult healthy donors with written consent under an IRB-approved protocol in DC culture medium [AIM V medium (invitrogen) supplemented with rhuIL-4 (20ng/ml) (PeproTech) and clinical-grade rhuGM-CSF (Leukine®) (1,000 U/ml) (Bayer)] (24). Day 5–6, moDC (3x10 6 ) were untreated or transfected with 7μg endotoxin-free DNA using Amaxa Human DC Nucleofector kit (Lonza) following the vendor’s instruction, and continually cultured in 1 ml DC culture medium for 2 days before use.…”

“…Human skin epidermal/dermal explants were prepared from abdominal skins with a skin graft knife, and subsequently untreated or immunized by 0.6μm gold particles (BioRad) conjugated with DNA using a gene gun (GG) under sterile conditions (24). After vaccination, skins were cultured on a sterile steel mesh with the epidermal side up in AIM V medium supplemented with 1xantibiotic/antimycotic solution at 37°C in 5% CO 2 .…”

“…Untreated or DNA-transfected moDC (2x10 4 ) were co-cultured with autologous human T cells (1x10 5 ) isolated from peripherl blood using a human T cell isolation kit (Miltenyi) in a total volume of 200 μl human T cell culture medium [IMDM supplemented with L-glutamine, penicillin, streptomycin, and nonessential amino acids (Invitrogen) and 10% (v/v) human AB serum (Cellgro)] (24). On day 6 of DC-T cell co-culture, T cells were then re-stimulated with MAGEA3hsp70-transfected autogolous moDC (2x10 4 ) for 6 days.…”