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Towards the therapeutic use of regulatory T cells for the treatment of human autoimmune diseases

Publication . Mota, Catarina; Caramalho, Íris Maria Ferreira; Victorino, Rui M. M., 1949-

Regulatory T Cells (Treg), constitutively expressing the transcription factor Foxp3/FOXP3, play a crucial role in maintaining self-tolerance, assuming particular relevance in the context of autoimmunity. Adoptive transfer of Treg has been shown to be highly efficient in the prevention and treatment of autoimmunity in rodents and clinical trials exploring Treg-based adoptive therapy in Type I Diabetes (T1D) are currently ongoing. These therapies require large numbers of Treg, stressing the importance of a better knowledge of the molecular and cellular requirements for human thymic and peripheral Treg development. Moreover, widespread application of Treg-based therapy dealt with several limitations regarding the stability and function of in vitro expanded populations for in vivo use. The creation of efficient protocols enabling stable FOXP3 acquisition by human non-regulatory cells could overcome the limited availability of thymus-derived (t)Treg and would facilitate the generation of antigen-specific Treg, an ideal candidate in autoimmune diseases (AID) setting. The overall objective of this work was to provide new insights into the principles dictating human thymic and peripheral Treg development and homeostasis, thus facilitating the progress of Treg-based immunotherapy. First, we proposed to investigate the capacity of human non-regulatory memory CD4+ T cells to differentiate in vitro into bona-fide FOXP3-expressing cells and to assess the role of the Notch signaling pathway in modulating this conversion. We showed that stable and functional bona-fide Treg can be generated from memory CD4+ T cells and that Delta like (DL)1-mediated Notch signaling activation enhanced this conversion. We additionally showed that DL1 increased Treg proliferation, reinforcing the possible role of Notch in the homeostasis of the human peripheral Treg compartment. Importantly, we also demonstrated that DL1 enhanced the expression of function-related molecules within these cells, contributing to the maintenance of their regulatory phenotype. In order to better clarify the principles governing Treg development in the human thymus, we investigated the role of common gamma-chain (c) cytokines in human tTreg differentiation. We identified interleukin (IL)-2 and IL-15 as key molecular determinants in this process and excluded a major function for IL-4, IL-7 and IL-21. Moreover, we revealed that IL-2 and IL-15 are expressed in a non-overlapping pattern in the human thymus, with the former produced mainly by mature αβ and γδ thymocytes and the latter by monocyte/macrophages and B lymphocytes. Overall, this work has provided a better understading of the core mechanisms governing human Treg differentiation and homeostasis that should facilitate the further establishment of Treg-based therapies.

2016Doctoral thesis

Open access

Human regulatory T-cell development is dictated by Interleukin-2 and -15 expressed in a non-overlapping pattern in the thymus

Publication . Caramalho, I.; Nunes-Silva, V.; Pires, A. R.; Mota, C.; Pinto, A. I.; Nunes-Cabaço, H.; Foxall, R. B.; Sousa, A. E.

Thymus-derived FOXP3-expressing regulatory T-cells (tTregs) are master orchestrators of physiological and pathological immune responses, thus constituting ideal targets for the treatment of autoimmunity. Despite their clinical importance, the developmental program governing their differentiation in the human thymus remains poorly understood. Here, we investigated the role of common gamma-chain cytokines in human tTreg differentiation, by performing gain- and loss-of-function experiments in 3D and 2D postnatal thymic cultures. We identified IL-2 and IL-15 as key molecular determinants in this process and excluded a major function for IL-4, IL-7 and IL-21. Mechanistically, IL-2 and IL-15 were equally able to drive tTreg precursor differentiation into FOXP3(+) cells, and promote tTreg proliferation and survival. Both cytokines also increased the expression levels of molecules associated with effector function within FOXP3(+) subsets, supporting their involvement in tTreg functional maturation. Furthermore, we revealed that IL-2 and IL-15 are expressed in a non-overlapping pattern in the human thymus, with the former produced mainly by mature αβ and γδ thymocytes and the latter by monocyte/macrophages and B lymphocytes. Our results identify core mechanisms dictating human tTreg development, with IL-2 and IL-15 defining specific niches required for tTreg lineage stabilization and differentiation, with implications for their therapeutic targeting in autoimmune conditions.

2014Journal article

Restricted access

Recent thymic emigrants are the preferential precursors of regulatory T cells differentiated in the periphery

Publication . Paiva, Ricardo S.; Lino, Andreia C.; Bergman, Marie-Louise; Caramalho, Íris; Sousa, Ana E.; Zelenay, Santiago; Demengeot, Jocelyne

Most Forkhead box P3(+) (Foxp3(+)) CD4 regulatory T cell (Treg) precursors are newly formed thymocytes that acquire Foxp3 expression on antigen encounter in the thymus. Differentiation of Treg, however, can also occur in the periphery. What limits this second layer of self- and nonself-reactive Treg production in physiological conditions remains to be understood. In this work, we tested the hypothesis that, similarly to thymic Treg, the precursors of peripheral Treg are immature T cells. We show that CD4(+)CD8(-)Foxp3(-) thymocytes and recent thymic emigrants (RTEs), contrarily to peripheral naïve mature cells, efficiently differentiate into Treg on transfer into lymphopenic mice. By varying donor and recipient mice and conducting ex vivo assays, we document that the preferential conversion of newly formed T cells does not require intrathymic preactivation, is cell-intrinsic, and correlates with low and high sensitivity to natural inhibitors and inducers of Foxp3 expression, such as IL-6, T-cell receptor triggering, and TGF-β. Finally, ex vivo analysis of human thymocytes and peripheral blood T cells revealed that human RTE and newly developed T cells share an increased potential to acquire a FOXP3(bright)CD25(high) Treg phenotype. Our findings indicating that RTEs are the precursors of Tregs differentiated in the periphery should guide the design of Treg-based therapies.

2013Journal article

Open access

Delta-like 1–mediated notch signaling enhances the in vitro conversion of human memory CD4 T cells into FOXP3-expressing regulatory T cells

Publication . Mota, Catarina; Nunes-Silva, Vânia; Pires, Ana R.; Matoso, Paula; Victorino, Rui M. M.; Sousa, Ana E.; Caramalho, Íris

FOXP3-expressing regulatory T cells (Treg) are essential for the prevention of autoimmunity and were shown to be reduced and/or dysfunctional in several autoimmune diseases. Although Treg-based adoptive transfer represents a promising therapy, the large cell number required to achieve clinical efficacy constitutes an important limitation. Therefore, novel strategies to generate bona fide in vitro-induced Treg (iTreg) are critical. In this study, we report that human memory CD4 T cells can be efficiently converted into iTreg, and that Delta-like 1 (DL1)-mediated Notch signaling significantly enhances this process. The iTreg generated in the presence of DL1 featured higher levels of Treg function-associated molecules and were efficient suppressors. Importantly, these iTreg displayed a stable phenotype in long-term cultures, even in the presence of proinflammatory cytokines. Additionally, DL1 potentiated FOXP3 acquisition by memory CD4 cells through the modulation of the TGF-β signaling pathway and of Foxp3 transcription. Our data demonstrate that iTreg can be efficiently induced from memory CD4 cells, a subset enriched in relevant specificities for targeting in autoimmune diseases, and that DL1 enhances this process. DL1 also enhanced the proliferation and Treg function-associated marker expression of ex vivo-stimulated human circulating FOXP3(+) cells. Manipulation of the Notch signaling pathway constitutes a promising approach to boost the in vitro generation of iTreg and ex vivo Treg expansion, thus facilitating the establishment of effective Treg-based adoptive therapy in autoimmune diseases.

2014Journal article

Restricted access