Gamma delta T-cell reconstitution after allogeneic HCT: A platform for cell therapy

Allogeneic Hematopoietic stem cell transplantation (allo-HCT) is a curative platform for several hematological diseases. Despite its therapeutic benefits, the profound immunodeficiency associated with the transplant procedure remains a major challenge that renders patients vulnerable to several complications. Today, It is well established that a rapid and efficient immune reconstitution, particularly of the T cell compartment is pivotal to both a short-term and a long-term favorable outcome. T cells expressing a TCR heterodimer comprised of gamma (γ) and delta (δ) chains have received particular attention in allo-HCT setting, as a large body of evidence has indicated that γδ T cells can exert favorable potent anti-tumor effects without inducing severe graft versus host disease (GVHD). However, despite their potential role in allo-HCT, studies investigating their detailed reconstitution in patients after allo-HCT are scarce. In this review we aim to shed lights on the current literature and understanding of γδ T cell reconstitution kinetics as well as the different transplant-related factors that may influence γδ reconstitution in allo-HCT. Furthermore, we will present data from available reports supporting a role of γδ cells and their subsets in patient outcome. Finally, we discuss the current and future strategies to develop γδ cell-based therapies to exploit the full immunotherapeutic potential of γδ cells in HCT setting.

SARS-CoV-2 (COVID-19)-specific T cell and B cell responses in convalescent rheumatoid arthritis: Monozygotic twins pair case observation

Rheumatoid arthritis (RA) patients present higher risk of SARS-CoV-2 infection (COVID-19), and proper management of the disease in this population requires a better understanding of how the immune system controls the virus. We analyzed the T cell and B cell phenotypes, and their repertoire in a pair of monozygotic twins with RA mismatched for COVID-19 infection. Twin- was not infected, while Twin+ was infected and effectively controlled the infection. We found no significant changes on the αβ T cell composition, while γδ T cells and B cells presented considerable expansion of memory population in Twin+ and robust T/B cell responses to several SARS-CoV-2 peptides. T cell receptor β/γ-chain and immunoglobulin heavy chain next-generation sequencing depicted a remarkable higher diversity in Twin+ compared with Twin-, despite no significant changes being found in variable/joining family usage. Repertoire overlap analyses showed that, although being identical twins, very few clones were shared between them, indicating that COVID-19 may lead to deep changes on the immune cell repertoire in RA patients. Altogether, our results indicate that RA patients may develop robust and persistent COVID-19-specific T/B cell responses; γδ T cells and B cells may play a key role in the management of COVID-19 in RA, and the infection may lead to a profound reshaping of immune cell receptor specificities.

A novel CD34-specific T-cell engager efficiently depletes acute myeloid leukemia and leukemic stem cells in vitro and in vivo

Less than a third of patients with acute myeloid leukemia (AML) are cured by chemotherapy and/or hematopoietic stem cell transplantation, highlighting the need to develop more efficient drugs. The low efficacy of standard treatments is associated with inadequate depletion of CD34⁺ blasts and leukemic stem cells, the latter a drug-resistant subpopulation of leukemia cells characterized by the CD34⁺CD38^- phenotype. To target these drug-resistant primitive leukemic cells better, we have designed a CD34/CD3 bi-specific T-cell engager (BTE) and characterized its anti-leukemia potential in vitro, ex vivo and in vivo. Our results show that this CD34-specific BTE induces CD34-dependent T-cell activation and subsequent leukemia cell killing in a dose-dependent manner, further corroborated by enhanced T-cell-mediated killing at the singlecell level. Additionally, the BTE triggered efficient T-cell-mediated depletion of CD34⁺ hematopoietic stem cells from peripheral blood stem cell grafts and CD34⁺ blasts from AML patients. Using a humanized AML xenograft model, we confirmed that the CD34-specific BTE had in vivo efficacy by depleting CD34⁺ blasts and leukemic stem cells without side effects. Taken together, these data demonstrate that the CD34-specific BTE has robust antitumor effects, supporting development of a novel treatment modality with the aim of improving outcomes of patients with AML and myelodysplastic syndromes.

Characterization of ascites- and tumor-infiltrating γδ T cells reveals distinct repertoires and a beneficial role in ovarian cancer

The role of γδ T cells in antitumor immunity has been under investigation for the past two decades, but little is known about their contribution to clinical outcomes in patients. Here, we set out to define the clonotypic, phenotypic, and functional features of γδ T cells in peripheral blood, ascites, and metastatic tumor tissue from patients with advanced epithelial ovarian cancer. T cell receptor (TCR) sequencing of the γ chain revealed that tumor-infiltrating γδ T cells have a unique and skewed repertoire with high TCR diversity and low clonality. In contrast, ascites-derived γδ T cells presented a lower TCR diversity and higher clonality, suggesting a TCR-dependent clonal focusing at this site. Further investigation showed that tumor samples had abundant γδ T cells with a tissue-resident, activation-associated phenotype, less usage of Vγ9 and an impaired response to adaptive-associated stimuli, implying an innate-like activation pathway, rather than an adaptive TCR-engaging pathway, at these tumor sites. Furthermore, high γδ T cell cytokine responsiveness upon stimulation was associated with a favorable outcome for patients in terms of both overall survival and reduced residual tumor burden after primary surgery. Last, the functionality of γδ T cells and patient survival were negatively affected by the proportions of CD39-expressing T cells, highlighting the potential of CD39 as a target to improve γδ T cell responses and unleash their antitumor capabilities.

Autologous hematopoietic stem cell transplantation restores the suppressive capacity of regulatory B cells in systemic sclerosis patients

OBJECTIVES

The rationale of autologous hematopoietic stem cell transplantation (AHSCT) for autoimmune diseases is that high-dose immunosuppression eradicates autoreactive T and B cells, and the infused autologous hematopoietic stem cells promote reconstitution of a naive and self-tolerant immune system. The aim of this study was to evaluate the reconstitution of different B cell subsets, both quantitatively and functionally, in systemic sclerosis (SSc) patients treated with AHSCT.

METHODS

Peripheral blood was harvested from twenty-two SSc patients before transplantation and at 30, 60, 120, 180 and 360 days post-AHSCT. Immunophenotyping of B cell subsets, B cell cytokine production, signaling pathways, and suppressive capacity of regulatory B cells (Bregs) were assessed by flow cytometry.

RESULTS

Naïve B cell frequencies increased from 60 to 360 days post-AHSCT, compared to pre-transplantation. Conversely, memory B cell frequencies decreased during the same period. Plasma cell frequencies transiently decreased at 60 days post-AHSCT. IL-10-producing Bregs CD19+CD24hiCD38hi and CD19+CD24hiCD27+ frequencies increased at 180 days. Moreover, the phosphorylation of ERK1/2 and p38MAPK proteins increased in B cells reconstituted post-AHSCT. Notably, CD19+CD24hiCD38hi Bregs recovered their ability to suppress production of Th1 cytokines by CD4+ T cells at 360 days post-AHSCT. Finally, IL-6 and TGF-β1-producing B cells decreased following AHSCT.

CONCLUSION

Taken together, these results suggest improvements in immunoregulatory and anti-fibrotic mechanisms after AHSCT for SSc, which may contribute to reestablishment of self-tolerance and clinical remission.

The role of the thymus in allogeneic bone marrow transplantation and the recovery of the peripheral T-cell compartment

As the thymus represents the primary site of T-cell development, optimal thymic function is of paramount importance for the successful reconstitution of the adaptive immunity after allogeneic hematopoietic stem cell transplantation. Thymus involutes as part of the aging process and several factors, including previous chemotherapy treatments, conditioning regimen used in preparation to the allograft, occurrence of graft-versus-host disease, and steroid therapy that impair the integrity of the thymus, thus affecting its role in supporting T-cell neogenesis. Although the pathways governing its regeneration are still poorly understood, the thymus has a remarkable capacity to recover its function after damage. Measurement of both recent thymic emigrants and T-cell receptor excision circles is valuable tools to assess thymic output and gain insights on its function. In this review, we will extensively discuss available data on factors regulating thymic function after allogeneic hematopoietic stem cell transplantation, as well as the strategies and therapeutic approaches under investigation to promote thymic reconstitution and accelerate immune recovery in transplanted patients, including the use of cytokines, sex-steroid ablation, precursor T-cells, and thymus bioengineering. Although none of them is routinely used in the clinic, these approaches have the potential to enhance thymic function and immune recovery, not only in patients given an allograft but also in other conditions characterized by immune deficiencies related to a defective function of the thymus.

Evaluating Thymic Function After Human Hematopoietic Stem Cell Transplantation in the Personalized Medicine Era

Hematopoietic stem cell transplantation (HSCT) is an effective treatment option for several malignant and non-malignant hematological diseases. The clinical outcome of this procedure relies to a large extent on optimal recovery of adaptive immunity. In this regard, the thymus plays a central role as the primary site for de novo generation of functional, diverse, and immunocompetent T-lymphocytes. The thymus is exquisitely sensitive to several insults during HSCT, including conditioning drugs, corticosteroids, infections, and graft-vs.-host disease. Impaired thymic recovery has been clearly associated with increased risk of opportunistic infections and poor clinical outcomes in HSCT recipients. Therefore, better understanding of thymic function can provide valuable information for improving HSCT outcomes. Recent data have shown that, besides gender and age, a specific single-nucleotide polymorphism affects thymopoiesis and may also influence thymic output post-HSCT, suggesting that the time of precision medicine of thymic function has arrived. Here, we review the current knowledge about thymic role in HSCT and the recent work of genetic control of human thymopoiesis. We also discuss different transplant-related factors that have been associated with impaired thymic recovery and the use of T-cell receptor excision circles (TREC) to assess thymic output, including its clinical significance. Finally, we present therapeutic strategies that could boost thymic recovery post-HSCT.

Homeostatic proliferation leads to telomere attrition and increased PD-1 expression after autologous hematopoietic SCT for systemic sclerosis

In the months that follow autologous hematopoietic stem cell transplantation (AHSCT), lymphopenia drives homeostatic proliferation, leading to oligoclonal expansion of residual cells. Here we evaluated how replicative senescent and exhausted cells associated with clinical outcomes of 25 systemic sclerosis (SSc) patients who underwent AHSCT. Patients were clinically monitored for skin (modified Rodnan's skin score, mRSS) and internal organ involvement and had blood samples collected before and semiannually, until 3 years post-AHSCT, for quantification of telomere length, CD8⁺CD28^- and PD-1⁺ cells, and serum cytokines. Patients were retrospectively classified as responders (n = 19) and non-responders (n = 6), according to clinical outcomes. At 6 months post-AHSCT, mRSS decreased (P < 0.001) and the pulmonary function stabilized, when compared with pre-transplant measures. In parallel, inflammatory cytokine (IL-6 and IL-1β) levels and telomere lengths decreased, whereas PD-1 expression on T-cells and the number of CD8⁺CD28^- cells expressing CD57 and FoxP3 increased. After AHSCT, responder patients presented higher PD-1 expression on T- (P < 0.05) and B- (P < 0.01) cells, and lower TGF-β, IL-6, G-CSF (P < 0.01), and IL-1β, IL-17A, MIP-1α, and IL-12 (P < 0.05) levels than non-responders. Homeostatic proliferation after AHSCT results in transient telomere attrition and increased numbers of senescent and exhausted cells. High PD-1 expression is associated with better clinical outcomes after AHSCT.

Immunological Balance Is Associated with Clinical Outcome after Autologous Hematopoietic Stem Cell Transplantation in Type 1 Diabetes

Autologous hematopoietic stem cell transplantation (AHSCT) increases C-peptide levels and induces insulin independence in patients with type 1 diabetes. This study aimed to investigate how clinical outcomes may associate with the immunological status, especially concerning the balance between immunoregulation and autoreactivity. Twenty-one type 1 diabetes patients were monitored after AHSCT and assessed every 6 months for duration of insulin independence, C-peptide levels, frequencies of islet-specific autoreactive CD8⁺ T cells (CTL), regulatory lymphocyte subsets, thymic function, and T-cell repertoire diversity. In median follow-up of 78 (range 15–106) months, all patients became insulin-independent, resuming insulin after median of 43 (range 6–100) months. Patients were retrospectively divided into short- or prolonged-remission groups, according to duration of insulin independence. For the entire follow-up, CD3⁺CD4⁺ T-cell numbers remained lower than baseline in both groups, whereas CD3⁺CD8⁺ T-cell levels did not change, resulting in a CD4/CD8 ratio inversion. Memory CTL comprehended most of T cells detected on long-term follow-up of patients after AHSCT. B cells reconstituted to baseline levels at 2–3 months post-AHSCT in both patient groups. In the prolonged-remission-group, baseline islet-specific T-cell autoreactivity persisted after transplantation, but regulatory T cell counts increased. Patients with lower frequencies of autoreactive islet-specific T cells remained insulin-free longer and presented greater C-peptide levels than those with lower frequencies of these cells. Therefore, immune monitoring identified a subgroup of patients with superior clinical outcome of AHSCT. Our study shows that improved immunoregulation may balance autoreactivity endorsing better metabolic outcomes in patients with lower frequencies of islet-specific T cells. Development of new strategies of AHSCT is necessary to increase frequency and function of T and B regulatory cells and decrease efficiently autoreactive islet-specific T and B memory cells in type 1 diabetes patients undergoing transplantation.

Long-term immune reconstitution and T cell repertoire analysis after autologous hematopoietic stem cell transplantation in systemic sclerosis patients

The determinants of clinical responses after autologous hematopoietic stem cell transplantation (aHSCT) in systemic sclerosis (SSc) are still unraveled. We analyzed long-term immune reconstitution (IR) and T cell receptor (TCR) repertoire diversity in 10 SSc patients, with at least 6 years simultaneous clinical and immunological follow-up after aHSCT. Patients were retrospectively classified as long-term responders (A, n = 5) or non-responders (B, n = 5), using modified Rodnan’s skin score (mRSS) and forced vital capacity (FVC%). All patients had similar severe SSc before aHSCT. Number of reinjected CD34⁺ cells was higher in group B versus A (P = 0.02). Long-term mRSS fall >25% was more pronounced in group A (P = 0.004), the only to improve long-term FVC% >10% (P = 0.026). There was an overall trend toward increased of T cell reconstitution in group B versus A. B cells had a positive linear regression slope in group A (LRS = 11.1) and negative in group B (LRS = −11.6). TCR repertoire was disturbed before aHSCT and the percentage of polyclonal families significantly increased at long-term (P = 0.046), with no difference between groups. Despite improved skin score after aHSCT in all SSc patients, pretransplant B cell clonal expansion and faster post-transplant T cell IR in long-term non-responder/relapsing patients call for new therapeutic protocols guided by IR analysis to improve their outcome.

Immunological correlates of favorable long-term clinical outcome in multiple sclerosis patients after autologous hematopoietic stem cell transplantation

High dose immunosuppression followed by autologous hematopoietic stem cell transplantation (AHSCT) induces prolonged clinical remission in multiple sclerosis (MS) patients. However, how patient immune profiles are associated with clinical outcomes has not yet been completely elucidated. In this study, 37 MS patients were assessed for neurological outcomes, thymic function and long-term immune reconstitution after AHSCT. Patients were followed for a mean (SD) of 68.5 (13.9) months post-transplantation and were retrospectively clustered into progression- and non-progression groups, based on Expanded Disease Status Scale (EDSS) outcomes at last visit. After AHSCT, both patient groups presented increased regulatory T-cell subset counts, early expansion of central- and effector-memory CD8(+)T-cells and late thymic reactivation. However, the non-progression group presented early expansion of PD-1(+)CD8(+)T-cells and of PD-1-expressing CD19(+) B-cells. Here, we suggest that along with increased numbers of regulatory T-cell subsets, PD-1 inhibitory signaling is one possible immunoregulatory mechanism by which AHSCT restores immune tolerance in MS patients.

Resetting the immune response after autologous hematopoietic stem cell transplantation for autoimmune diseases

Autologous hematopoietic stem cell transplantation (AHSCT) is currently investigated as treatment for severe and refractory autoimmune diseases, such as multiple sclerosis (MS), systemic sclerosis (SSc), Crohn's disease (CD) and systemic lupus erythematosus. Randomized clinical trials in MS, SSc and CD have shown the efficacy of AHSCT to promote control of disease activity and progression, when compared to conventional treatment. The use of high dose immunosuppressive conditioning is essential to eliminate the autoimmune repertoire, and the re-infusion of autologous hematopoietic stem cells avoids long-term leucopenia by reconstitution of both immune and hematological systems. Recent studies showed that AHSCT is able to deplete the autoimmune compartment and further promote the formation of a new auto-tolerant immune repertoire, reducing the inflammatory milieu and leading to long-term clinical remission without any complementary post-graft treatment. Deep knowledge about the mechanisms of action related to AHSCT-induced remission is required for the management of possible post-AHSCT relapse and improvement of clinical protocols. This paper will review the mechanisms enrolled in the immune response resetting promoted by AHSCT in patients with autoimmune diseases.

Cytokine profile and lymphocyte subsets in type 2 diabetes

Type 2 diabetes mellitus (T2D) is a metabolic disease with inflammation as an important pathogenic background. However, the pattern of immune cell subsets and the cytokine profile associated with development of T2D are unclear. The objective of this study was to evaluate different components of the immune system in T2D patients' peripheral blood by quantifying the frequency of lymphocyte subsets and intracellular pro- and anti-inflammatory cytokine production by T cells. Clinical data and blood samples were collected from 22 men (51.6±6.3 years old) with T2D and 20 nonsmoking men (49.4±7.6 years old) who were matched for age and sex as control subjects. Glycated hemoglobin, high-sensitivity C-reactive protein concentrations, and the lipid profile were measured by a commercially available automated system. Frequencies of lymphocyte subsets in peripheral blood and intracellular production of interleukin (IL)-4, IL-10, IL-17, tumor necrosis factor-α, and interferon-γ cytokines by CD3+ T cells were assessed by flow cytometry. No differences were observed in the frequency of CD19+ B cells, CD3+CD8+ and CD3+CD4+ T cells, CD16+56+ NK cells, and CD4+CD25+Foxp3+ T regulatory cells in patients with T2D compared with controls. The numbers of IL-10- and IL-17-producing CD3+ T cells were significantly higher in patients with T2D than in controls (P<0.05). The frequency of interferon-γ-producing CD3+ T cells was positively correlated with body mass index (r=0.59; P=0.01). In conclusion, this study shows increased numbers of circulating IL-10- and IL-17-producing CD3+ T cells in patients with T2D, suggesting that these cytokines are involved in the immune pathology of this disease.

Transforming growth factor-β increases interleukin-13 synthesis via GATA-3 transcription factor in T-lymphocytes from patients with systemic sclerosis

Introduction

Transforming growth factor (TGF)-β and interleukin (IL)-13 play a crucial role in the pathogenesis of systemic sclerosis (SSc), partly through activation of collagen production that leads to fibrosis. The aim of the present study was to determine whether TFG-β alters IL-13 production in T lymphocytes from patients with SSc from that seen in those of healthy donors.

Methods

IL-13 mRNA and protein synthesis under TFG-β exposure was measured in circulating T lymphocytes from healthy donors and patients with SSc and also in the Jurkat Th2 T-cell line, using quantitative real-time PCR and fluorescence-activated cell sorting analysis, respectively. The involvement of Smad and GATA-3 transcription factors was assessed by using specific inhibitors and small interfering RNA, and the binding capacity of GATA-3 to the IL-13 gene promoter was evaluated by chromatin immunoprecipitation assay.

Results

TGF-β induced a significant decrease in IL-13 mRNA and protein levels in lymphocytes from healthy donors (mean [±SD] inhibition of 30 % ± 10 % and 20 % ± 7 %, respectively; p < 0.05). In contrast, TGF-β promoted a significant increase in IL-13 mRNA levels and IL-13 synthesis by CD4⁺ and CD8⁺ T-cell subtypes from patients with SSc, with respective increases of 2.4 ± 0.3-fold, 1.6 ± 0.05-fold and 2.7 ± 0.02-fold. The involvement of the Smad signaling pathway and upregulation of GATA-3 binding capacity on the IL-13 promoter in lymphocytes from patients with SSc contributed to the effect of TGF-β on IL-13 production.

Conclusions

These results demonstrate that TGF-β upregulates IL-13 synthesis through GATA-3 expression in the T lymphocytes of patients with SSc, confirming that the GATA-3 transcription factor can be regarded as a novel therapeutic target in patients with SSc.

Autologous hematopoietic SCT normalizes miR-16, -155 and -142-3p expression in multiple sclerosis patients

Autologous hematopoietic SCT (AHSCT) has been investigated in the past as a therapeutic alternative for multiple sclerosis (MS). Despite advances in clinical management, knowledge about mechanisms involved with clinical remission post transplantation is still limited. Abnormal microRNA and gene expression patterns were described in MS and have been suggested as disease biomarkers and potential therapeutic targets. Here we assessed T- and B-cell reconstitution, microRNAs and immunoregulatory gene expression after AHSCT. Early immune reconstitution was mainly driven by peripheral homeostatic proliferation. AHSCT increased CD4(+)CD25(hi)FoxP3(+) regulatory T-cell counts and expression of CTLA-4 and GITR (glucocorticoid-induced TNFR) on CD4(+)CD25(hi) T cells. We found transient increase in exhausted PD-1(+) T cells and of suppressive CD8(+)CD28(-)CD57(+) T cells. At baseline, CD4(+) and CD8(+) T cells from MS patients presented upregulated miR-16, miR-155 and miR-142-3p and downregulated FOXP3, FOXO1, PDCD1 and IRF2BP2. After transplantation, the expression of FOXP3, FOXO1, PDCD1 and IRF2BP2 increased, reaching control levels at 2 years. Expression of miR-16, miR-155 and miR-142-3p decreased towards normal levels at 6 months post therapy, remaining downregulated until the end of follow-up. These data strongly suggest that AHSCT normalizes microRNA and gene expression, thereby improving the immunoregulatory network. These mechanisms may be important for disease control in the early periods after AHSCT.