Enhanced Lymphodepletion Is Insufficient to Replace Exogenous IL2 or IL15 Therapy in Augmenting the Efficacy of Adoptively Transferred Effector CD8+ T Cells

Effector CD8⁺ T cells conditioned with IL12 during activation mediate enhanced antitumor efficacy after adoptive transfer into lymphodepleted hosts; this is due in part to improved IL7 responsiveness. Therefore, we hypothesized that increasing the intensity or type of lymphodepletion would deplete more IL7-consuming host cells and improve the persistence and antitumor activity of IL12-conditioned CD8⁺ T cells. Using cyclophosphamide, fludarabine, and total body irradiation (TBI, 6 Gy) either individually or in combination, we found that combined lymphodepletion best enhanced T-cell engraftment in mice. This improvement was strongly related to the extent of leukopenia, as posttransfer levels of donor T cells inversely correlated to host cell counts after lymphodepletion. Despite the improvement in engraftment seen with combination lymphodepletion, dual-agent lymphodepletion did not augment the antitumor efficacy of donor T cells compared with TBI alone. Similarly, IL7 supplementation after TBI and transfer of tumor-reactive T cells failed to improve persistence or antitumor immunity. However, IL15 or IL2 supplementation greatly augmented the persistence and antitumor efficacy of donor tumor-reactive T cells. Our results indicate that the amount of host IL7 induced after single agent lymphodepletion is sufficient to potentiate the expansion and antitumor activity of donor T cells, and that the efficacy of future regimens may be improved by providing posttransfer support with IL2 or IL15.Significance: The relationship between lymphodepletion and cytokine support plays a critical role in determining donor T-cell engraftment and antitumor efficacy. Cancer Res; 78(11); 3067-74. ©2018 AACR.

Effector CD8+ T-cell Engraftment and Antitumor Immunity in Lymphodepleted Hosts Is IL7Rα Dependent

Adoptive cellular therapy, in which activated tumor-reactive T cells are transferred into lymphodepleted recipients, is a promising cancer treatment option. Activation of T cells decreases IL7 responsiveness; therefore, IL15 is generally considered the main driver of effector T-cell responses in this setting. However, we found in lymphodepleted mice that CD8(+) T cells activated with IL12 showed enhanced engraftment that was initially dependent on host IL7, but not IL15. Mechanistically, enhanced IL7 responsiveness was conferred by elevated IL7Rα expression, which was critical for antitumor immunity. Elevated IL7Rα expression was achievable without IL12, as polyclonal CD8(+) T cells activated with high T-cell receptor (TCR) stimulation depended on T-cell IL7Rα expression and host IL7 for maximal engraftment. Finally, IL12 conditioning during the activation of human CD8(+) T cells, including TCR-modified T cells generated using a clinically relevant protocol, led to enhanced IL7Rα expression. Our results demonstrate the importance of the donor IL7Rα/host IL7 axis for effector CD8(+) T-cell engraftment and suggest novel strategies to improve adoptive cellular therapy as a cancer treatment.

Abstract A6: The synergy between IL-12 priming of CD8 T cells and lymphodepletion is mediated by host IL-7

Adoptive T-cell transfer therapy (ACT) is a promising approach for the treatment of metastatic melanoma. Using the pmel-1 transgenic mouse as a source of melanoma-reactive CD8 T-cells, our lab has shown that priming these tumor-specific cells ex vivo with IL-12 (pmelIL-12) prior to ACT results in significant anti-tumor synergy and enhanced persistence in combination with cyclophosphamide (CTX). Here we demonstrate that other currently accepted lymphodepletion approaches, total body irradiation (TBI) alone or in combination with CTX, are also capable of synergizing with ACT of pmelIL-12. Interestingly, all 3 regimens (CTX, TBI and CTX + TBI) showed a similar ability to synergize with pmelIL-12, suggesting a common underlying mechanism. To elucidate the mechanism(s) behind this observed synergy, we evaluated whether the persistence of pmelIL-12 cells transferred into a lymphopenic host required the cytokines IL-7 and IL-15, which are known to be increased in the host post lymphodepletion. We found that the early expansion of pmelIL-12 in an irradiated host was partially dependent on IL-7, but not IL-15, as both the percentage and total number of donor cells recovered from spleens of irradiated hosts 1-week after ACT were greatly diminished in mice treated with an antibody against the IL-7 receptor alpha, CD127, or with an IL-7 neutralizing antibody (clone M25). In vitro these pmelIL-12 cells were able to proliferate in response to IL-7 to a much greater extent than pmel CD8 T-cells activated without IL-12. Together, these findings demonstrate that activated CD8 T cells primed with IL-12 display enhanced responsiveness to IL-7, and that IL-7 is necessary for maximal persistence of these cells in an irradiated host. Therefore, we conclude that the observed synergy between IL-12 priming of CD8 T cells and lymphodepletion is due in part to increased availability of host IL-7 after lymphodepletion.

Citation Format: Christopher Bryce Johnson, Bennett R. May, Colleen A. Cloud, Mark P. Rubinstein, David J. Cole. The synergy between IL-12 priming of CD8 T cells and lymphodepletion is mediated by host IL-7. [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology: Multidisciplinary Science Driving Basic and Clinical Advances; Dec 2-5, 2012; Miami, FL. Philadelphia (PA): AACR; Cancer Res 2013;73(1 Suppl):Abstract nr A6.

A posterior pharyngeal web in sideropenic dysphagia

A case is presented in which a post-cricoid web was shown arising posteriorly instead of in the almost invariable anterior situation. The patient was not anaemic and some brief comments are made on the inconstant relationship between anaemia and the presence of a web.