Dendritic Cells in Irradiated Mice Trigger the Functional Plasticity and Antitumor Activity of Adoptively Transferred Tc17 Cells via IL12 Signaling.

PURPOSE: The adoptive cell transfer (ACT) of CD8(+) T cells is a promising treatment for advanced malignancies. Lymphodepletion before ACT enhances IFNγ(+)CD8(+) T cell (Tc0)-mediated tumor regression. Yet, how lymphodepletion regulates the function and antitumor activity of IL17A(+)CD8(+) T cells (Tc17) is unknown. EXPERIMENTAL DESIGN: To address this question, pmel-1 CD8(+) T cells were polarized to secrete either IL17A or IFNγ. These subsets were then infused into mice with B16F10 melanoma that were lymphoreplete [no total body irradiation (TBI)], or lymphodepleted with nonmyeloablative (5 Gy) or myeloablative (9 Gy with hematopoietic stem cell transplantation) TBI. The activation of innate immune cells and function of donor T-cell subsets were monitored in recipient mice. RESULTS: Tc17 cells regress melanoma in myeloablated mice to a greater extent than in lymphoreplete or nonmyeloablated mice. TBI induced functional plasticity in Tc17 cells, causing conversion from IL17A to IFNγ producers. Additional investigation revealed that Tc17 plasticity and antitumor activity were mediated by IL12 secreted by irradiated host dendritic cells (DC). Neutralization of endogenous IL12 reduced the antitumor activity of Tc17 cells in myeloablated mice, whereas ex vivo priming with IL12 enhanced their capacity to regress melanoma in nonmyeloablated animals. This, coupled with exogenous administration of low-dose IL12, obviated the need for host preconditioning, creating curative responses in nonirradiated mice. CONCLUSIONS: Our findings indicate that TBI-induced IL12 augments Tc17 cell-mediated tumor immunity and underline the substantial implications of in vitro preparation of antitumor Tc17 cells with IL12 in the design of T-cell immunotherapies.

Interleukin-12 enhances the function and anti-tumor activity in murine and human CD8(+) T cells.

Mouse CD8(+) T cells conditioned with interleukin (IL)-12 ex vivo mediate the potent regression of established melanoma when transferred into lymphodepleted mice. However, the quantitative and qualitative changes induced by IL-12 in the responding mouse CD8(+) T cells have not been well defined. Moreover, the mechanisms by which IL-12-conditioning impacts human CD8(+) T cells, and how such cells might be expanded prior to infusion into patients is not known. We found that ex vivo IL-12-conditioning of mouse CD8(+) T cells led to a tenfold-100-fold increase in persistence and anti-tumor efficacy upon adoptive transfer into lymphodepleted mice. The enhancing effect of IL-12 was associated with maintenance of functional avidity. Importantly, in the context of ongoing ACT clinical trials, human CD8(+) T cells genetically modified with a tyrosinase-specific T cell receptor (TCR) exhibited significantly enhanced functional activity when conditioned with IL-12 as indicated by heightened granzyme B expression and elevated peptide-specific CD107a degranulation. This effect was sustainable despite the 20 days of in vitro cellular expansion required to expand cells over 1,000-fold allowing adequate cell numbers for administration to cancer patients. Overall, these findings support the efficacy and feasibility of ex vivo IL-12-conditioning of TCR-modified human CD8(+) T cells for adoptive transfer and cancer therapy.

The inducible costimulator augments Tc17 cell responses to self and tumor tissue.

The inducible costimulator (ICOS) plays a key role in the development of Th17 cells, but its role in the development and antitumor activity of IL-17-producing CD8(+) T cells (Tc17) remains unknown. We found that ICOS costimulation was important for the functional maintenance, but not differentiation, of Tc17 cells in vitro. Blocking the ICOS pathway using an antagonist mAb or by using recipient mice genetically deficient in the ICOS ligand reduced the antitumor activity of adoptively transferred Tc17 cells. Conversely, activating Tc17 cells with an ICOS agonist in vitro enhanced their capacity to eradicate melanoma and induce autoimmune vitiligo when infused into mice. However, ICOS stimulation did not augment the antitumor activity of IL-2 expanded T cells. Additional investigation revealed that ICOS stimulation not only increased IL-2Rα, CXCR3, and IL-23R expression on Tc17 cells, but also dampened their expression of suppressive molecule CD39. Although Tc17 cells activated with an ICOS agonist cosecreted heightened IL-17A, IL-9, and IFN-γ, their therapeutic effectiveness was critically dependent on IFN-γ production. Depletion of IL-17A and IL-9 had little impact on antitumor Tc17 cells activated with an ICOS agonist. Collectively, our work reveals that the ICOS pathway potentiates the antitumor activity of adoptively transferred Tc17 cells. This work has major implications for the design of vaccine, Ab and cell-based therapies for autoimmunity, infectious disease, and cancer.

Ex vivo interleukin-12-priming during CD8(+) T cell activation dramatically improves adoptive T cell transfer antitumor efficacy in a lymphodepleted host.

BACKGROUND: Clinical application of adoptive T cell therapy has been hindered by an inability to generate adequate numbers of nontolerized, functionally active, tumor-specific T cells, which can persist in vivo. In order to address this, we evaluated the impact of interleukin (IL)-12 signaling during tumor-specific CD8(+) T cell priming in terms of persistence and antitumor efficacy using an established B16 melanoma tumor adoptive therapy model. STUDY DESIGN: B6 mice were injected subcutaneously with B16 melanoma tumor cells. On day 12 of tumor growth, mice were preconditioned with cyclophosphamide (4mg dose, intraperitoneally), and 1 day later were treated by adoptive transfer of tumor-specific pmel-1 CD8(+) T cells primed ex vivo 3 days earlier with both IL-12 and antigen (hGP100(25-33) peptide) or antigen only. Tumors were measured biweekly, and infused donor T cells were analyzed for persistence, localization to the tumor, phenotype, and effector function. RESULTS: Adoptive transfer of tumor-specific CD8(+) T cells primed with IL-12 was significantly more effective in reducing tumor burden in mice preconditioned with cyclophosphamide compared with transfer of T cells primed without IL-12. This enhanced antitumor response was associated with increased frequencies of infused T cells in the periphery and tumor as well as elevated expression of effector molecules including granzyme B and interferon-γ (IFNγ). CONCLUSIONS: Our findings demonstrate that ex vivo priming of tumor-specific CD8(+) T cells with IL-12 dramatically improves their in vivo persistence and therapeutic ability on transfer to tumor-bearing mice. These findings can be directly applied as novel clinical trial strategies.