Type 17 CD8+ T cells display enhanced antitumor immunity

Abstract

Interleukin-17 (IL-17)-secreting CD8(+) T cells have been described, but they have not been thoroughly studied and they do not have a known role in cancer immunotherapy. We skewed CD8(+) T cells to secrete IL-17 through priming in Th17-polarizing conditions. IL-17-producing CD8(+) T cells demonstrated reduced expression of Eomes and diminished cytolytic differentiation in vitro. However, after adoptive transfer, these cells converted to interferon-gamma-producing effector cells and mediated regression of large, established tumors. This improved antitumor immunity was associated with increased expression of IL-7R-alpha, decreased expression of killer cell lectin-like receptor G1, and enhanced persistence of the transferred cells. This report is the first description of a cancer therapy with IL-17-secreting CD8(+) T cells. These findings have implications for the improvement of CD8(+) T cell-based adoptive immunotherapy.

Figure 1

Type 17–polarized CD8⁺ T cells produced IL-17 and were diverted from cytolytic differentiation. Pmel-1/Thy1.1 CD8⁺ T cells were primed in IL-17–polarizing conditions or in nonpolarizing conditions and then expanded with IL-2. (A-D) The cells were then cocultured overnight with target splenocytes pulsed with hgp100_25-33 peptide. Production of IL-17, CCL20, IFN-γ, and IL-2 was determined by enzyme-linked immunosorbent assay. (E) Four-hour ⁵¹Cr release cytolysis assays were performed. Target cells were pulsed with the peptide indicated in the figure legend. Error bars indicate the SEM. (F) Real-time reverse-transcribed polymerase chain reaction was performed to assess expression of the indicated transcription factors. Expression relative to β-actin is displayed. Error bars represent the SEM.

Figure 2

Type 17–polarized CD8⁺ T cells mediated enhanced antitumor immunity and demonstrated greater persistence. A total of 10⁶ pmel-1/Thy1.1 CD8⁺ T cells were adoptively transferred into mice bearing established, vascularized B16F10 melanomas. Recipient mice were pretreated with 5 Gy total body irradiation, and they received adjuvant vaccine and IL-2 in conjunction with cell therapy. (A) Serial tumor measurements were obtained and tumor areas were calculated. Error bars indicate the SEM (N = 5). The experiment shown is representative of 3 independent experiments. (B) Expansion and persistence of adoptively transferred cells. The spleens of 3 mice per condition were examined at each time point. Error bars represent the SEM. (C-D) Expression of killer cell lectin-like receptor G1 and IL-7Rα by transferred cells after infusion as determined by flow cytometry gated on Thy1.1⁺ cells. The data represent 3 spleens per condition at each time point. Error bars represent the SEM. (E) Flow cytometric determination of intracellular cytokines after infusion. The dot plots are gated on Thy1.1⁺ cells from a pool of 3 spleens per condition at each time point.