Enhancement of vaccine-mediated antitumor immunity in cancer patients after depletion of regulatory T cells
Jens Dannull, … , Eli Gilboa, Johannes Vieweg
Jens Dannull, … , Eli Gilboa, Johannes Vieweg
Published December 1, 2005
Citation Information: J Clin Invest. 2005;115(12):3623-3633. https://doi.org/10.1172/JCI25947.
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Enhancement of vaccine-mediated antitumor immunity in cancer patients after depletion of regulatory T cells

Abstract

In this study, we investigated whether elimination of CD4+/CD25+ Tregs using the recombinant IL-2 diphtheria toxin conjugate DAB389IL-2 (also known as denileukin diftitox and ONTAK) is capable of enhancing the immunostimulatory efficacy of tumor RNA-transfected DC vaccines. We show that DAB389IL-2 is capable of selectively eliminating CD25-expressing Tregs from the PBMCs of cancer patients without inducing toxicity on other cellular subsets with intermediate or low expression of CD25. DAB389IL-2–mediated Treg depletion resulted in enhanced stimulation of proliferative and cytotoxic T cell responses in vitro but only when DAB389IL-2 was omitted during T cell priming. DAB389IL-2 significantly reduced the number of Tregs present in the peripheral blood of metastatic renal cell carcinoma (RCC) patients and abrogated Treg-mediated immunosuppressive activity in vivo. Moreover, DAB389IL-2–mediated elimination of Tregs followed by vaccination with RNA-transfected DCs significantly improved the stimulation of tumor-specific T cell responses in RCC patients when compared with vaccination alone. Our findings may have implications in the design of immune-based strategies that may incorporate the Treg depletion strategy to achieve potent antitumor immunity with therapeutic impact.

Authors

Jens Dannull, Zhen Su, David Rizzieri, Benjamin K. Yang, Doris Coleman, Donna Yancey, Aijing Zhang, Philipp Dahm, Nelson Chao, Eli Gilboa, Johannes Vieweg

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Specificity of Treg depletion. (A) Calculated CD4+/CD25high Treg frequen...
Specificity of Treg depletion. (A) Calculated CD4+/CD25high Treg frequencies in 2 study subjects (01-RCC-DAB; 03-RCC-DAB) prior to, 4 days after, and 2 weeks after final vaccination (study week 8; d 56). (B) IFN-γ ELISPOT were performed on sorted CD4+CD25neg, CD4+CD25int, and CD4+CD25high T cell subsets using tetanus toxoid and CMV lysate–pulsed DCs as stimulators. (C–E) In separate experiments, IFN-γ ELISPOT and antigen-specific proliferation analyses were performed on T cells isolated prior to vaccination and 4 and 28 days after DAB389IL-2 treatment (results from patient RCC-01-DAB). For ELISPOT assays, 1 × 105 purified CD4+ T cells (C) or 1 × 105 purified CD8+ T cells (D) were stimulated with 1 × 104 DCs that were transfected with fluM1 mRNA, autologous PBMC RNA, CMV lysate (20 μg/ml), or tetanus toxoid (0.5 μg/ml). After 18 hours, visible spots were enumerated using an automated ELISPOT reader. The same stimulators and RCC RNA-transfected DCs were used in proliferation assays (E). For proliferation assays, isolated CD3+ T cells were used as responders. Assays were performed at a stimulator/responder ratio of 1:10. After 4 days, cells were pulsed with 1 μCi of 3H-thymidine, and incorporated radioactivity was determined after 16 hours by liquid scintillation counting.