Publicação
Translational research of regulatory T-cells within clinical studies
| Resumo: | Regulatory T cells (Tregs) are essential elements of a healthy immune system. They comprise 5-10% of the peripheral blood CD4 T cell compartment in healthy individuals and play a critical role in protecting their host against immunopathological damage following inflammatory or immunological challenges. Tregs are composed of heterogeneous subsets that together can suppress a wide range of effector cell types through several mechanisms. Humans have since birth Treg maturation and phenotypic heterogeneity, which increases during our childhood. The Treg capacity to suppress effector cells allows transplantation tolerance, and when this careful balance is disturbed, it can lead to graft-versus-host disease (GVHD). Treg heterogeneity also rapidly increases after hematopoietic stem cell transplantation (HSCT). However, a precise and coordinated balance between several immune cells is required to prevent transplant rejection. Patients with GVHD not only have fewer Treg cells but also fewer Treg subpopulations and higher activation of effector cells. Two newer possible ways to treat GVHD, are with low-dose interleukin 2 (IL-2) or with antibodies conjugated to an immunotoxin (CD3/CD7-ricin A). Low-dose IL-2 therapy selectively induces the expansion of Tregs, improving the clinical manifestations of chronic GVHD. It promotes Treg homeostasis without activating effector cells. The anti-CD3/CD7-ricin A therapy, which mostly depletes T and natural killer cells, has an overall response rate of 60%, with 50% achieving a complete response. The 6-month overall survival rate is 60%. After the profound depletion caused by the treatment, the immune system recovers with a diverse T cell repertoire leading to the transplant tolerance. The profound but highly selective immunologic effects of both therapies in promoting immune tolerance may be used in a wide variety of clinical settings. Furthermore, the translational research methodology developed can be reapplied in future clinical studies, unveiling the defects that contribute to other immune dysfunctions. Chapter 1 contains a general introduction. We start by defining Treg cells and explaining how these cells are essential for maintaining tolerance and preserving the immune system's homeostasis. Then, we analyzed the relationship between Treg cells and HSCT. Tregs have the ability to mediate transplant tolerance and, when this careful balance is disturbed, it can trigger GVHD. The imbalance between effector and regulatory T cells that occurs during GVHD is explored in detail. In addition, we highlight the relevance of low-dose IL-2 therapy for patients with GVHD and how the therapy positively recovers the Treg population. Finally, we briefly describe the main objectives of this thesis. In chapter 2 we specify the aims and outline of this thesis. In chapter 3, we investigated the diversity of the Treg cell compartment in newborns, healthy adults, during the 2-year period after HSCT and in patients suffering from chronic GVHD. We have shown that adults have significantly higher amounts of Tregs in their blood than those present in umbilical cord blood (CB), but they also have additional functional and memory subpopulations of Tregs that are not present in CB. The number of subpopulations of functional and memory Tregs expands from birth to adulthood. As for patients after HSCT, the memory Treg subpopulation repertoire is already present after transplantation, while the diversity of Treg cells still expands within the 2-year post-transplant. GVHD patients present significantly fewer distinct subpopulations of functional Tregs, proposing a correlation between the lack of heterogeneity of Tregs and chronic GVHD. In chapter 4, we demonstrated that low-dose IL-2 therapy selectively induces the expansion of CD4 Tregs and improves the clinical manifestations of chronic GVHD. Using mass cytometry, we demonstrated in chapter 4 that low concentrations of IL-2 selectively induce STAT5 phosphorylation in Helios CD4 Tregs cells and CD56bright CD16– NK cells in vitro and in vivo. The effects of low-dose IL-2 therapy on conventional CD4 T cells and CD8 T cells were limited to increased expression of PD-1 in memory effector T cells. The selective effects of low-dose IL-2 therapy on Helios CD4 Tregs cells and NK CD56bright cells induce the constitutive expression of high-affinity IL-2 receptors. Recognizing that we urgently need more effective therapies for the treatment of patients with steroid-refractory acute graft-versus-host-disease (SR-aGVHD), we describe, in chapter 5, a phase I / II clinical trial that examines the safety and effectiveness of a new biological therapy for (SR-aGVHD). A combination of anti-CD3 and anti-CD7 antibodies separately conjugated to recombinant ricin A (CD3/CD7–1T). This induces in vivo depletion of T cells and NK cells, and suppresses the activation of the cellular receptor in T cells. On the 28th day after the initiation of therapy with CD3/CD7-IT, the overall response rate was 60%, with 50% reaching a complete response. The overall 6-month survival rate was 60%. The treatment, which was administered for 1 week, caused profound but transient depletion of T cells and NK cells, followed by rapid recovery of the immune system with a diverse repertoire of T cells and preservation of specific T cells capable of identifying Epstein-Barr virus and cytomegalovirus. Treatment with CD3/CD7- IT was safe and well tolerated by patients, with a relatively low prevalence of adverse events, such as hypoalbuminemia, microangiopathy and thrombocytopenia, which were controllable and reversible. Finally, we were interested in testing the same mass cytometry panel used in chapter 3, to study Treg cells in other circumstances of immune disorder, unrelated to HSCT. In chapter 6, we evaluated idelalisib as a first-line therapy for the treatment of chronic lymphocytic leukemia (CLL) relapse. After a follow-up period of 14.7 months (on average), hepatotoxicity was considered a frequent and often serious adverse event. Several lines of evidence suggest that this hepatotoxicity was immune-mediated. A lymphocytic infiltrate was seen in liver biopsy samples taken from 2 individuals with transaminitis, and the levels of pro-inflammatory cytokines CCL-3 and CCL-4 were higher in individuals with hepatotoxicity. A decrease in peripheral blood regulatory T cells was observed in patients who suffered from hepatotoxicity during therapy, which is consistent with an imune-mediated mechanism. In chapter 7 we conclude this thesis by summarizing and discussing the results. |
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| Autores principais: | Matos, Tiago R. |
| Assunto: | Imunologia Células T Células T reguladoras Investigação translational Estudos clínicos Teses de doutoramento - 2021 |
| Ano: | 2021 |
| País: | Portugal |
| Tipo de documento: | tese de doutoramento |
| Tipo de acesso: | acesso aberto |
| Instituição associada: | Universidade de Lisboa |
| Idioma: | inglês |
| Origem: | Repositório da Universidade de Lisboa |
| Resumo: | Regulatory T cells (Tregs) are essential elements of a healthy immune system. They comprise 5-10% of the peripheral blood CD4 T cell compartment in healthy individuals and play a critical role in protecting their host against immunopathological damage following inflammatory or immunological challenges. Tregs are composed of heterogeneous subsets that together can suppress a wide range of effector cell types through several mechanisms. Humans have since birth Treg maturation and phenotypic heterogeneity, which increases during our childhood. The Treg capacity to suppress effector cells allows transplantation tolerance, and when this careful balance is disturbed, it can lead to graft-versus-host disease (GVHD). Treg heterogeneity also rapidly increases after hematopoietic stem cell transplantation (HSCT). However, a precise and coordinated balance between several immune cells is required to prevent transplant rejection. Patients with GVHD not only have fewer Treg cells but also fewer Treg subpopulations and higher activation of effector cells. Two newer possible ways to treat GVHD, are with low-dose interleukin 2 (IL-2) or with antibodies conjugated to an immunotoxin (CD3/CD7-ricin A). Low-dose IL-2 therapy selectively induces the expansion of Tregs, improving the clinical manifestations of chronic GVHD. It promotes Treg homeostasis without activating effector cells. The anti-CD3/CD7-ricin A therapy, which mostly depletes T and natural killer cells, has an overall response rate of 60%, with 50% achieving a complete response. The 6-month overall survival rate is 60%. After the profound depletion caused by the treatment, the immune system recovers with a diverse T cell repertoire leading to the transplant tolerance. The profound but highly selective immunologic effects of both therapies in promoting immune tolerance may be used in a wide variety of clinical settings. Furthermore, the translational research methodology developed can be reapplied in future clinical studies, unveiling the defects that contribute to other immune dysfunctions. Chapter 1 contains a general introduction. We start by defining Treg cells and explaining how these cells are essential for maintaining tolerance and preserving the immune system's homeostasis. Then, we analyzed the relationship between Treg cells and HSCT. Tregs have the ability to mediate transplant tolerance and, when this careful balance is disturbed, it can trigger GVHD. The imbalance between effector and regulatory T cells that occurs during GVHD is explored in detail. In addition, we highlight the relevance of low-dose IL-2 therapy for patients with GVHD and how the therapy positively recovers the Treg population. Finally, we briefly describe the main objectives of this thesis. In chapter 2 we specify the aims and outline of this thesis. In chapter 3, we investigated the diversity of the Treg cell compartment in newborns, healthy adults, during the 2-year period after HSCT and in patients suffering from chronic GVHD. We have shown that adults have significantly higher amounts of Tregs in their blood than those present in umbilical cord blood (CB), but they also have additional functional and memory subpopulations of Tregs that are not present in CB. The number of subpopulations of functional and memory Tregs expands from birth to adulthood. As for patients after HSCT, the memory Treg subpopulation repertoire is already present after transplantation, while the diversity of Treg cells still expands within the 2-year post-transplant. GVHD patients present significantly fewer distinct subpopulations of functional Tregs, proposing a correlation between the lack of heterogeneity of Tregs and chronic GVHD. In chapter 4, we demonstrated that low-dose IL-2 therapy selectively induces the expansion of CD4 Tregs and improves the clinical manifestations of chronic GVHD. Using mass cytometry, we demonstrated in chapter 4 that low concentrations of IL-2 selectively induce STAT5 phosphorylation in Helios CD4 Tregs cells and CD56bright CD16– NK cells in vitro and in vivo. The effects of low-dose IL-2 therapy on conventional CD4 T cells and CD8 T cells were limited to increased expression of PD-1 in memory effector T cells. The selective effects of low-dose IL-2 therapy on Helios CD4 Tregs cells and NK CD56bright cells induce the constitutive expression of high-affinity IL-2 receptors. Recognizing that we urgently need more effective therapies for the treatment of patients with steroid-refractory acute graft-versus-host-disease (SR-aGVHD), we describe, in chapter 5, a phase I / II clinical trial that examines the safety and effectiveness of a new biological therapy for (SR-aGVHD). A combination of anti-CD3 and anti-CD7 antibodies separately conjugated to recombinant ricin A (CD3/CD7–1T). This induces in vivo depletion of T cells and NK cells, and suppresses the activation of the cellular receptor in T cells. On the 28th day after the initiation of therapy with CD3/CD7-IT, the overall response rate was 60%, with 50% reaching a complete response. The overall 6-month survival rate was 60%. The treatment, which was administered for 1 week, caused profound but transient depletion of T cells and NK cells, followed by rapid recovery of the immune system with a diverse repertoire of T cells and preservation of specific T cells capable of identifying Epstein-Barr virus and cytomegalovirus. Treatment with CD3/CD7- IT was safe and well tolerated by patients, with a relatively low prevalence of adverse events, such as hypoalbuminemia, microangiopathy and thrombocytopenia, which were controllable and reversible. Finally, we were interested in testing the same mass cytometry panel used in chapter 3, to study Treg cells in other circumstances of immune disorder, unrelated to HSCT. In chapter 6, we evaluated idelalisib as a first-line therapy for the treatment of chronic lymphocytic leukemia (CLL) relapse. After a follow-up period of 14.7 months (on average), hepatotoxicity was considered a frequent and often serious adverse event. Several lines of evidence suggest that this hepatotoxicity was immune-mediated. A lymphocytic infiltrate was seen in liver biopsy samples taken from 2 individuals with transaminitis, and the levels of pro-inflammatory cytokines CCL-3 and CCL-4 were higher in individuals with hepatotoxicity. A decrease in peripheral blood regulatory T cells was observed in patients who suffered from hepatotoxicity during therapy, which is consistent with an imune-mediated mechanism. In chapter 7 we conclude this thesis by summarizing and discussing the results. |
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