Modification of T cell responses by stem cell mobilization requires direct signaling of the T cell by G-CSF and IL-10

Regulatory T cells suppress myeloma-specific immunity during autologous stem cell mobilization and transplantation

ABSTRACT

Autologous stem cell transplantation (ASCT) is the standard of care consolidation therapy for eligible patients with myeloma but most patients eventually progress, an event associated with features of immune escape. Novel approaches to enhance antimyeloma immunity after ASCT represent a major unmet need. Here, we demonstrate that patient-mobilized stem cell grafts contain high numbers of effector CD8 T cells and immunosuppressive regulatory T cells (Tregs). We showed that bone marrow (BM)-residing T cells are efficiently mobilized during stem cell mobilization (SCM) and hypothesized that mobilized and highly suppressive BM-derived Tregs might limit antimyeloma immunity during SCM. Thus, we performed ASCT in a preclinical myeloma model with or without stringent Treg depletion during SCM. Treg depletion generated SCM grafts containing polyfunctional CD8 T effector memory cells, which dramatically enhanced myeloma control after ASCT. Thus, we explored clinically tractable translational approaches to mimic this scenario. Antibody-based approaches resulted in only partial Treg depletion and were inadequate to recapitulate this effect. In contrast, a synthetic interleukin-2 (IL-2)/IL-15 mimetic that stimulates the IL-2 receptor on CD8 T cells without binding to the high-affinity IL-2Ra used by Tregs efficiently expanded polyfunctional CD8 T cells in mobilized grafts and protected recipients from myeloma progression after ASCT. We confirmed that Treg depletion during stem cell mobilization can mitigate constraints on tumor immunity and result in profound myeloma control after ASCT. Direct and selective cytokine signaling of CD8 T cells can recapitulate this effect and represent a clinically testable strategy to improve responses after ASCT.

A cohort-based study of host gene expression: tumor suppressor and innate immune/inflammatory pathways associated with the HIV reservoir size

The major barrier to an HIV cure is the HIV reservoir: latently-infected cells that persist despite effective antiretroviral therapy (ART). There have been few cohort-based studies evaluating host genomic or transcriptomic predictors of the HIV reservoir. We performed host RNA sequencing and HIV reservoir quantification (total DNA [tDNA], unspliced RNA [usRNA], intact DNA) from peripheral CD4+ T cells from 191 ART-suppressed people with HIV (PWH). After adjusting for nadir CD4+ count, timing of ART initiation, and genetic ancestry, we identified two host genes for which higher expression was significantly associated with smaller total DNA viral reservoir size, P3H3 and NBL1, both known tumor suppressor genes. We then identified 17 host genes for which lower expression was associated with higher residual transcription (HIV usRNA). These included novel associations with membrane channel (KCNJ2, GJB2), inflammasome (IL1A, CSF3, TNFAIP5, TNFAIP6, TNFAIP9, CXCL3, CXCL10), and innate immunity (TLR7) genes (FDR-adjusted q<0.05). Gene set enrichment analyses further identified significant associations of HIV usRNA with TLR4/microbial translocation (q = 0.006), IL-1/NRLP3 inflammasome (q = 0.008), and IL-10 (q = 0.037) signaling. Protein validation assays using ELISA and multiplex cytokine assays supported these observed inverse host gene correlations, with P3H3, IL-10, and TNF-α protein associations achieving statistical significance (p<0.05). Plasma IL-10 was also significantly inversely associated with HIV DNA (p = 0.016). HIV intact DNA was not associated with differential host gene expression, although this may have been due to a large number of undetectable values in our study. To our knowledge, this is the largest host transcriptomic study of the HIV reservoir. Our findings suggest that host gene expression may vary in response to the transcriptionally active reservoir and that changes in cellular proliferation genes may influence the size of the HIV reservoir. These findings add important data to the limited host genetic HIV reservoir studies to date.

Multiomics Analysis Identifies SOCS1 as Restraining T Cell Activation and Preventing Graft-Versus-Host Disease

Graft-versus-host disease (GVHD) is a major life-threatening complication of allogeneic hematopoietic stem cell transplantation (allo-HSCT). Inflammatory signaling pathways promote T-cell activation and are involved in the pathogenesis of GVHD. Suppressor of cytokine signaling 1 (SOCS1) is a critical negative regulator for several inflammatory cytokines. However, its regulatory role in T-cell activation and GVHD has not been elucidated. Multiomics analysis of the transcriptome and chromatin structure of granulocyte-colony-stimulating-factor (G-CSF)-administered hyporesponsive T cells from healthy donors reveal that G-CSF upregulates SOCS1 by reorganizing the chromatin structure around the SOCS1 locus. Parallel in vitro and in vivo analyses demonstrate that SOCS1 is critical for restraining T cell activation. Loss of Socs1 in T cells exacerbates GVHD pathogenesis and diminishes the protective role of G-CSF in GVHD mouse models. Further analysis shows that SOCS1 inhibits T cell activation not only by inhibiting the colony-stimulating-factor 3 receptor (CSF3R)/Janus kinase 2 (JAK2)/signal transducer and activator of transcription 3 (STAT3) pathway, but also by restraining activation of the inflammasome signaling pathway. Moreover, high expression of SOCS1 in T cells from patients correlates with low acute GVHD occurrence after HSCT. Overall, these findings identify that SOCS1 is critical for inhibiting T cell activation and represents a potential target for the attenuation of GVHD.

An Overview of Autophagy in Hematopoietic Stem Cell Transplantation

Autophagy is a fundamental homeostatic process crucial for cellular adaptation in response to metabolic stress. Autophagy exerts its effect through degrading intracellular components and recycling them to produce macromolecular precursors and energy. This physiological process contributes to cellular development, maintenance of cellular/tissue homeostasis, immune system regulation, and human disease. Allogeneic hematopoietic stem cell transplantation (HSCT) is the only preferred therapy for most bone marrow-derived cancers. Unfortunately, HSCT can result in several serious and sometimes untreatable conditions due to graft-versus-host disease (GVHD), graft failure, and infection. These are the major cause of morbidity and mortality in patients receiving the transplant. During the last decade, autophagy has gained a considerable understanding of its role in various diseases and cellular processes. In light of recent research, it has been confirmed that autophagy plays a crucial role in the survival and function of hematopoietic stem cells (HSCs), T-cell differentiation, antigen presentation, and responsiveness to cytokine stimulation. Despite the importance of these events to HSCT, the role of autophagy in HSCT as a whole remains relatively ambiguous. As a result of the growing use of autophagy-modulating agents in the clinic, it is imperative to understand how autophagy functions in allogeneic HSCT. The purpose of this literature review is to elucidate the established and implicated roles of autophagy in HSCT, identifying this pathway as a potential therapeutic target for improving transplant outcomes.

Functional Role of AKNA: A Scoping Review

Human akna encodes an AT-hook transcription factor whose expression participates in various cellular processes. We conducted a scoping review on the literature regarding the functional role of AKNA according to the evidence found in human and in vivo and in vitro models, stringently following the “PRISMA-ScR” statement recommendations. Methods: We undertook an independent PubMed literature search using the following search terms, AKNA OR AKNA ADJ gene OR AKNA protein, human OR AKNA ADJ functions. Observational and experimental articles were considered. The selected studies were categorized using a pre-determined data extraction form. A narrative summary of the evidence was produced. Results: AKNA modulates the expression of CD40 and CD40L genes in immune system cells. It is a negative regulator of inflammatory processes as evidenced by knockout mouse models and observational studies for several autoimmune and inflammatory diseases. Furthermore, AKNA contributes to the de-regulation of the immune system in cancer, and it has been proposed as a susceptibility genetic factor and biomarker in CC, GC, and HNSCC. Finally, AKNA regulates neurogenesis by destabilizing the microtubules dynamics. Conclusion: Our results provide evidence for the role of AKNA in various cellular processes, including immune response, inflammation, development, cancer, autoimmunity, and neurogenesis.

Optimizing outcomes for haploidentical hematopoietic stem cell transplantation in severe aplastic anemia with intensive GVHD prophylaxis: a review of current findings

Introduction: Allogeneic hematopoietic stem cell transplantation (allo-HSCT) has resulted in increased levels of disease-free survival in severe aplastic anemia (SAA). Haploidentical transplantation (haplo-SCT) was previously not recommended due to unacceptable incidences of graft-versus-host disease (GvHD) and graft failures. With the advent of intensive GvHD prophylaxis strategies, the outcomes obtained with haplo-SCT for SAA have gradually improved.Areas covered: A comprehensive search considered PubMed reported articles before 1 February 2021, presented abstracts, and clinical trials pertaining to haplo-HSCT for SAA. This manuscript covers modern approaches with intensive GvHD prophylaxis in haplo-SCT for SAA. The representative methods consist of granulocyte colony stimulating factor (G-CSF) plus ATG-based and posttransplantation cyclophosphamide (PT-Cy)-based protocols.Expert opinion: Currently, haplo-SCT has become a feasible option for treating SAA. The G-CSF/ATG-based protocol included the largest sample size and reported comparable survival rates with identical siblings. The PT-Cy protocol resulted in a relatively lower incidence of GvHD and seemingly poorer but continuously improved engraftment with augmented conditioning. The optimized outcomes are constantly updated with the modification of the conditioning regimen, donor selection, graft source and GvHD prophylaxis. In the future, we should pay more attention to quality of life in addition to survival, and personalized haplo-SCT may improve outcomes.

Contrasting Immunopathogenic and Therapeutic Roles of Granulocyte Colony-Stimulating Factor in Cancer

Tumor cells are particularly adept at exploiting the immunosuppressive potential of neutrophils as a strategy to achieve uncontrolled proliferation and spread. Recruitment of neutrophils, particularly those of an immature phenotype, known as granulocytic myeloid-derived suppressor cells, is achieved via the production of tumor-derived granulocyte colony-stimulating factor (G-CSF) and neutrophil-selective chemokines. This is not the only mechanism by which G-CSF contributes to tumor-mediated immunosuppression. In this context, the G-CSF receptor is expressed on various cells of the adaptive and innate immune systems and is associated with induction of T cell polarization towards the Th2 and regulatory T cell (Treg) phenotypes. In contrast to the potentially adverse effects of sustained, endogenous production of G-CSF by tumor cells, stringently controlled prophylactic administration of recombinant (r) G-CSF is now a widely practiced strategy in medical oncology to prevent, and in some cases treat, chemotherapy-induced severe neutropenia. Following an overview of the synthesis, structure and function of G-CSF and its receptor, the remainder of this review is focused on: (i) effects of G-CSF on the cells of the adaptive and innate immune systems; (ii) mechanisms by which this cytokine promotes tumor progression and invasion; and (iii) current clinical applications and potential risks of the use of rG-CSF in medical oncology.

Effect of rhG-CSF Combined With Decitabine Prophylaxis on Relapse of Patients With High-Risk MRD-Negative AML After HSCT: An Open-Label, Multicenter, Randomized Controlled Trial

Relapse is a major cause of treatment failure after allogeneic hematopoietic stem-cell transplantation (allo-HSCT) for high-risk acute myeloid leukemia (HR-AML). The aim of this study was to explore the effect of recombinant human granulocyte colony-stimulating factor (rhG-CSF) combined with minimal-dose decitabine (Dec) on the prevention of HR-AML relapse after allo-HSCT.

Granulocyte Colony-Stimulating Factor-Primed Unmanipulated Haploidentical Blood and Marrow Transplantation

Granulocyte colony-stimulating factor (G-CSF), a growth factor for neutrophils, has been successfully used for stem cell mobilization and T cell immune tolerance induction. The establishment of G-CSF-primed unmanipulated haploidentical blood and marrow transplantation (The Beijing Protocol) has achieved outcomes for the treatment of acute leukemia, myelodysplastic syndrome, and severe aplastic anemia with haploidentical allografts comparable to those of human leukocyte antigen (HLA)-matched sibling donor transplantation. Currently, G-CSF-mobilized bone marrow and/or peripheral blood stem cell sources have been widely used in unmanipulated haploidentical transplant settings. In this review, we summarize the roles of G-CSF in inducing T cell immune tolerance. We discuss the recent advances in the Beijing Protocol, mainly focusing on strategies that have been used to improve transplant outcomes in cases of poor graft function, virus infections, and relapse. The application of G-CSF-primed allografts in other haploidentical modalities is also discussed.

Interleukin-10 mediated immune regulation after stem cell transplantation: Mechanisms and implications for therapeutic intervention

Interleukin-10 (IL-10) is a multi-faceted anti-inflammatory cytokine which plays an essential role in immune tolerance. Indeed, deficiency of IL-10 or its receptor results in aberrant immune responses that lead to immunopathology. Graft-versus-host disease (GVHD) is the limiting complication of allogeneic stem cell transplantation (SCT) and results from an imbalance in pathological versus regulatory immune networks. A number of immune cells exert their immunomodulatory role through secretion of IL-10 or induction of IL-10-secreting cells after SCT. Type-1 regulatory T cells (Tr1 cells) and FoxP3⁺ regulatory T cells (T_regs) are predominant sources of IL-10 after SCT and the critical role of this cytokine in preventing GVHD is now established. Recently, intriguing interactions among IL-10, immune cells, commensal microbes and host tissues in the gastrointestinal (GI) tract and other barrier surfaces have been uncovered. We now understand that IL-10 secretion is dynamically modulated by the availability of antigen, co-stimulatory signals, cytokines, commensal microbes and their metabolites in the microenvironment. In this review, we provide an overview of the control of IL-10 secretion and signaling after SCT and the therapeutic interventions, with a focus on Tr1 cells.

Granulocyte Colony-Stimulating Factor Treatment During Radiotherapy Is Associated With Survival Benefit in Patients With Lung Cancer

Objectives:

Granulocyte colony-stimulating factor, an agent commonly used for neutropenia treatment, plays an important role in cancer treatment. However, the effect of granulocyte colony-stimulating factor treatment on patient’s survival during radiation therapy in lung cancer remains unknown.

Materials and Methods:

A retrospective study of patients with lung cancer who underwent radiation therapy from 2012 to 2015 at Shandong Provincial Qianfoshan Hospital was performed. Granulocyte colony-stimulating factor was administered when grade 3 or 4 leukopenia and/or neutropenia occurred during radiation therapy, and no prophylactic granulocyte colony-stimulating factor was used in this study. Patients were classified into high and low granulocyte colony-stimulating factor group according the dosage of granulocyte colony-stimulating factor use during radiation therapy. The influence of granulocyte colony-stimulating factor on survival was investigated. In addition, the predict value of granulocyte colony-stimulating factor in concurrent chemoradiotherapy group and radiation therapy alone group was also evaluated, respectively.

Results:

A total of 231 patients were enrolled, with 56 in the high granulocyte colony-stimulating factor group and 175 in the low granulocyte colony-stimulating factor group. High dose of granulocyte colony-stimulating factor for the entire population group was associated with a favorable overall survival (hazard ratio [95% confidence interval] = 1.798 [1.260-2.568]; P = .001) and a longer progression-free survival (hazard ratio = 1.550 [1.127-2.132]; P = .002). However, compared with a lower granulocyte colony-stimulating factor, a higher granulocyte colony-stimulating factor was associated with significant better overall survival and progression-free survival in radiation therapy group, not in concurrent chemoradiotherapy group. Although there was no statistical significance in concurrent chemoradiotherapy group, the median overall survival and progression-free survival of patients in the higher granulocyte colony-stimulating factor group were longer than those in the lower group. Furthermore, the treatment strategy was also associated with the overall survival, not the progression-free survival.

Conclusion:

This study suggests that granulocyte colony-stimulating factor treatment during radiation therapy has favorable impact on outcome in patients with lung cancer. Besides, results showed that patients treated with concurrent chemoradiotherapy had better prognosis than those treated with radiation therapy alone.

Autophagy in regulatory T cells: A double-edged sword in disease settings

Autophagy is an evolutionarily conserved catabolic process that directs cytoplasmic proteins, organelles and microbes to lysosomes for degradation. It not only represents an essential cell-intrinsic mechanism to protect against internal and external stresses but also shapes both innate and adaptive immunity. Regulatory T cells (Tregs) are a developmentally and functionally distinct T cell subpopulation engaged in sustaining immunological self-tolerance and homeostasis. There is compelling evidence that autophagy is actively regulated in Tregs and serves as a central signal-dependent controller for Tregs by restraining excessive apoptotic and metabolic activities. In this review, we discuss how autophagy modulates the stability and functionality of Tregs in different disease settings, and provide a perspective on how manipulation of autophagy enables better control of immune response by targeting the generation of Tregs and the maintenance of their stability.

Regulatory γδ T cells induced by G-CSF participate in acute graft-versus-host disease regulation in G-CSF-mobilized allogeneic peripheral blood stem cell transplantation

Background

The immunomodulatory effects of granulocyte colony-stimulating factor (G-CSF) on T cells result in a low incidence of acute graft-versus-host disease (aGVHD) in G-CSF-mobilized allogeneic peripheral blood stem cell transplantation (G-PBSCT). However, the exact mechanism remains unclear. Regulatory γδ T cells (γδTregs), characterized by the presence of TCRγδ and Foxp3, have aroused great concern in the maintenance of immune tolerance. We hypothesized that γδTregs might involve in the immunomodulatory effects of G-CSF mobilization.

Methods

The expression and immunomodulatory function of γδTreg subsets in peripheral blood of donors before and after G-CSF treatment in vivo and in vitro were evaluated by flow cytometry and CFSE assays. To investigate the effects of γδTregs on aGVHD, the association between γδTreg subsets in grafts and aGVHD in recipients was estimated.

Results

The proportions of Vδ1Tregs, CD27⁺Vδ1Tregs and CD25⁺Vδ1Tregs were significantly increased in peripheral blood after G-CSF treatment in vivo. γδTregs could be generated in vitro by stimulating with anti-TCRγδ in the presence of G-CSF. The immune phenotype, proliferation suppression function, and cytokine secretion of G-CSF-induced γδTregs were similar to that of transforming growth factor-β (TGF-β)-induced γδTregs. The clinical data demonstrated that the proportion of CD27⁺Vδ1Tregs in grafts was significantly lower in the patients who experienced aGVHD than in those who did not develop aGVHD (P = 0.028), and the proportions of other γδTreg subsets in grafts did not differ significantly between the two groups. The best cutoff value for CD27⁺Vδ1Treg proportion in grafts in prediction of aGVHD was 0.33%, with an area under the curve value of 0.725 (P = 0.043). Eight patients (26.7%) were classified as the low-CD27⁺Vδ1Treg group (< 0.33%), and 22 patients (73.3%) as the high-CD27⁺Vδ1Treg group (≥ 0.33%). The incidence of aGVHD was higher in the low-CD27⁺Vδ1Treg group than in the high-CD27⁺Vδ1Treg group (75.0% versus 22.7%, P = 0.028).

Conclusions

G-CSF could induce the generation of γδTregs in vivo and in vitro, and γδTregs might participate in aGVHD regulation in G-PBSCT.

Harnessing Advances in T Regulatory Cell Biology for Cellular Therapy in Transplantation

Cellular therapy with CD4FOXP3 T regulatory (Treg) cells is a promising strategy to induce tolerance after solid-organ transplantation or prevent graft-versus-host disease after transfer of hematopoietic stem cells. Treg cells currently used in clinical trials are either polyclonal, donor- or antigen-specific. Aside from variations in isolation and expansion protocols, however, most therapeutic Treg cell-based products are much alike. Ongoing basic science work has provided considerable new insight into multiple facets of Treg cell biology, including their stability, homing, and functional specialization; integrating these basic science discoveries with clinical efforts will support the development of next-generation therapeutic Treg cells with enhanced efficacy. In this review, we summarize recent advances in knowledge of how Treg cells home to lymphoid and peripheral tissues, and control antibody production and tissue repair. We also discuss newly appreciated pathways that modulate context-specific Treg cell function and stability. Strategies to improve and tailor Treg cells for cell therapy to induce transplantation tolerance are highlighted.

Cytokine mediators of chronic graft-versus-host disease

Substantial preclinical and clinical research into chronic graft-versus-host disease (cGVHD) has come to fruition in the last five years, generating a clear understanding of a complex cytokine-driven cellular network. cGVHD is mediated by naive T cells differentiating within IL-17-secreting T cell and follicular Th cell paradigms to generate IL-21 and IL-17A, which drive pathogenic germinal center (GC) B cell reactions and monocyte-macrophage differentiation, respectively. cGVHD pathogenesis includes thymic damage, impaired antigen presentation, and a failure in IL-2-dependent Treg homeostasis. Pathogenic GC B cell and macrophage reactions culminate in antibody formation and TGF-β secretion, respectively, leading to fibrosis. This new understanding permits the design of rational cytokine and intracellular signaling pathway-targeted therapeutics, reviewed herein.

The efficacy of human placenta-derived mesenchymal stem cells on radiation enteropathy along with proteomic biomarkers predicting a favorable response

BACKGROUND

Radiation enteropathy is a common complication in patients with abdominopelvic cancer, but no treatment has yet been established. Stem cell therapy may be a viable therapeutic option because intestinal stem cells are highly vulnerable to ionizing radiation (IR) and stem cell loss explains its intractability to general treatment. Here, we investigated either prophylactic or therapeutic efficacy of human placenta-derived mesenchymal stem cells (hPDSCs) against radiation enteropathy and could identify biomarkers predicting a favorable response to stem cell therapy.

METHODS

We challenged a radiation-induced enteropathy model with hPDSCs. After sacrifice, we checked the gross anatomy of small intestine, histology gross, and analyzed that, accompanied with molecular changes implicated in this model.

RESULTS

hPDSCs significantly improved the outcome of mice induced with either radiation enteropathy or lethal radiation syndrome (P < 0.01). hPDSCs exerted inhibitory actions on inflammatory cytokines, the re-establishment of epithelium homeostasis was completed with increasing endogenous restorative processes as assessed with increased levels of proliferative markers in the hPDSCs group, and a significant inhibition of IR-induced apoptosis. The preservation of cells expressing lysozyme, and Musashi-1 were significantly increased in the hPDSC treatment group. Both preventive and therapeutic efficacies of hPDSCs were noted against IR-induced enteropathy. Label-free quantification was used to identify biomarkers which predict favorable responses after hPDSC treatment, and finally glutathione S-transferase-mu type, interleukin-10, and peroxiredoxin-2 were validated as proteomic biomarkers predicting a favorable response to hPDSCs in radiation enteropathy.

CONCLUSIONS

hPDSCs may be a useful prophylactic and therapeutic cell therapy for radiation enteropathy.

Harnessing bone marrow resident regulatory T cells to improve allogeneic stem cell transplant outcomes

Regulatory T cells (Treg) are a suppressive T cell population which play a crucial role in the establishment of tolerance after stem cell transplantation (SCT) by controlling the effector T cell responses that drive acute and chronic GVHD. The BM compartment is enriched in a highly suppressive, activated/memory autophagy-dependent Treg population, which contributes to the HSC engraftment and the control of GVHD. G-CSF administration releases Treg from the BM through disruption of the CXCR4/SDF-1 axis and further improves Treg survival following SCT through the induction of autophagy. However, AMD3100 is more efficacious in mobilizing these Treg highlighting the potential for optimized mobilization regimes to produce more tolerogenic grafts. Notably, the disruption of adhesive interaction between integrins and their ligands contributes to HSC mobilization and may be relevant for BM Treg. Importantly, the Tregs in the BM niche contribute to maintenance of the HSC niche and appear required for optimal control of GVHD post-transplant. Although poorly studied, the BM Treg appear phenotypically and functionally unique to Treg in the periphery. Understanding the requirements for maintaining the enrichment, function and survival of BM Treg needs to be further investigated to improve therapeutic strategies and promote tolerance after SCT.

Regulator Versus Effector Paradigm: Interleukin-10 as Indicator of the Switching Response

The interleukin-10 (IL-10) is generally considered as the most important cytokine with anti-inflammatory properties and one of the key cytokines preventing inflammation-mediated tissue damage. In this respect, IL-10 producing cells play a crucial role in the outcome of infections, allergy, autoimmune reactions, tumor development, and transplant tolerance. Based on recent findings with regard to the mentioned clinical conditions, this review attempts to shed some light on the IL-10 functions, considering this cytokine as inherent inducer of the switching immunity. While acute infections and vaccinations are associated by IL-10 enhanced during few weeks, chronic parasitoses, tumor diseases, allergen-specific immunotherapy, transplants, and use of immune-suppressor drugs show an increased IL-10 level along months or years. With regard to autoimmune pathologies, the IL-10 increase is prevalently observed during early stages, whereas the successive stages are characterized by reaching of immune equilibrium independently to disease's activity. Together, these findings indicate that IL-10 is mainly produced during transient immune conditions and the persistent IL-10-related effect is the indication/prediction (and maybe effectuation) of the switching immunity. Actual knowledge emphasizes that any manipulation of the IL-10 response for treatment purposes should be considered very cautiously due to its potential hazards to the immune system. Probably, the IL-10 as potential switcher of immunity response should be used in association with co-stimulatory immune effectors that are necessary to determine the appropriate deviation during treatment of respective pathologies. Hopefully, further findings would open new avenues to study the biology of this "master switch" cytokine and its therapeutic potential.

Autophagy-dependent regulatory T cells are critical for the control of graft-versus-host disease

Regulatory T cells (Tregs) play a crucial role in the maintenance of peripheral tolerance. Quantitative and/or qualitative defects in Tregs result in diseases such as autoimmunity, allergy, malignancy, and graft-versus-host disease (GVHD), a serious complication of allogeneic stem cell transplantation (SCT). We recently reported increased expression of autophagy-related genes (Atg) in association with enhanced survival of Tregs after SCT. Autophagy is a self-degradative process for cytosolic components that promotes cell homeostasis and survival. Here, we demonstrate that the disruption of autophagy within FoxP3⁺ Tregs (B6.Atg7^fl/fl-FoxP3cre⁺ ) resulted in a profound loss of Tregs, particularly within the bone marrow (BM). This resulted in dysregulated effector T cell activation and expansion, and the development of enterocolitis and scleroderma in aged mice. We show that the BM compartment is highly enriched in TIGIT⁺ Tregs and that this subset is differentially depleted in the absence of autophagy. Moreover, following allogeneic SCT, recipients of grafts from B6.Atg7^fl/fl-FoxP3cre⁺ donors exhibited reduced Treg reconstitution, exacerbated GVHD, and reduced survival compared with recipients of B6.WT-FoxP3cre⁺ grafts. Collectively, these data indicate that autophagy-dependent Tregs are critical for the maintenance of tolerance after SCT and that the promotion of autophagy represents an attractive immune-restorative therapeutic strategy after allogeneic SCT.

Continuous AMD3100 Treatment Worsens Renal Fibrosis through Regulation of Bone Marrow Derived Pro-Angiogenic Cells Homing and T-Cell-Related Inflammation

AMD3100 is a small molecule inhibitor of chemokine receptor type 4 (CXCR4), which is located in the cell membranes of CD34+ cells and a variety of inflammatory cells and has been reported to reduce organ fibrosis in the lung, liver and myocardium. However, the effect of AMD3100 on renal fibrosis is unknown. This study investigated the impact of AMD3100 on renal fibrosis. C57bl/6 mice were subjected to unilateral ureteral obstruction (UUO) surgery with or without AMD3100 administration. Tubular injury, collagen deposition and fibrosis were detected and analyzed by histological staining, immunocytochemistry and Western Blot. Bone marrow derived pro-angiogenic cells (CD45+, CD34+ and CD309+ cells) and capillary density (CD31+) were measured by flow cytometry (FACS) and immunofluorescence (IF). Inflammatory cells, chemotactic factors and T cell proliferation were characterized. We found that AMD3100 treatment did not alleviate renal fibrosis but, rather, increased tissue damage and renal fibrosis. Continuous AMD3100 administration did not improve bone marrow derived pro-angiogenic cells mobilization but, rather, inhibited the migration of bone marrow derived pro-angiogenic cells into the fibrotic kidney. Additionally, T cell infiltration was significantly increased in AMD3100-treated kidneys compared to un-treated kidneys. Thus, treatment of UUO mice with AMD3100 led to an increase in T cell infiltration, suggesting that AMD3100 aggravated renal fibrosis.

Mechanisms for T cell tolerance induced with granulocyte colony-stimulating factor

Granulocyte colony-stimulating factor (G-CSF) has been widely accepted as a mediator of T cell tolerance. The immune modulatory effect of G-CSF on T cells is believed to be mediated exclusively through other effector cells, such as monocytes, tolerogenic dendritic cells (DC), and myeloid-derived suppressor cells. Recent advances confirmed the direct effects of G-CSF in inducing immune tolerance of T cells through the G-CSF-G-CSF receptor pathway and related molecular mechanisms. This review aims to summarize the findings associated with the direct and indirect mechanisms for T cell tolerance induced with G-CSF. The role of G-CSF in preventing graft-versus-host disease (GVHD) and in treating autoimmune diseases (ADs) is also discussed. It is conceivable that G-CSF and immune cell compositions, such as tolerogenic DC and CD4(+)CD25(+)Foxp3(+) T cells, modulated by G-CSF could become an integral part of the immunomodulatory therapies against GVHD and ADs in the future.

Anti-G-CSF treatment induces protective tumor immunity in mouse colon cancer by promoting protective NK cell, macrophage and T cell responses

Granulocyte colony-stimulating factor (G-CSF) is a cytokine that is highly expressed in human and mouse colorectal cancers (CRC). We previously reported that G-CSF stimulated human CRC cell growth and migration, therefore in this study we sought to examine the therapeutic potential of anti-G-CSF treatment for CRC. G-CSF is known to mobilize neutrophils, however its impact on other immune cells has not been well examined. Here, we investigated the effects of therapeutic anti-G-CSF treatment on CRC growth and anti-tumor immune responses. C57BL/6 mice treated with azoxymethane/dextran sodium sulfate (AOM/DSS) to induce neoplasms were administered anti-G-CSF or isotype control antibodies three times a week for three weeks. Animals treated with anti-G-CSF antibodies had a marked decrease in neoplasm number and size compared to the isotype control group. Colon neutrophil and macrophage frequency were unchanged, but the number of macrophages producing IL-10 were decreased while IL-12 producing macrophages were increased. NK cells were substantially increased in colons of anti-G-CSF treated mice, along with IFNγ producing CD4(+) and CD8(+) T cells. These studies are the first to indicate a crucial role for G-CSF inhibition in promoting protective anti-tumor immunity, and suggest that anti-G-CSF treatment is a potential therapeutic approach for CRC.

Leukemia cell mobilization with G-CSF plus plerixafor during busulfan-fludarabine conditioning for allogeneic stem cell transplantation

We hypothesized that during conditioning chemotherapy for allogeneic stem cell transplant (allo-SCT), disruption of stromal-leukemia interactions using granulocyte-colony stimulating factor (G-CSF) in combination with the CXCR4-specific inhibitor plerixafor, may promote release of leukemic cells from the niche and increase tumor elimination. In a phase 1/2 investigation, we treated 45 AML/MDS/CML patients (34 AML, 7 MDS, and 4 CML) with G-CSF (10 μg/kg daily for 6 days starting on day −9) plus plerixafor (doses of 0, 80, 160 or 240 μg/kg daily for 4 days starting on day −7) along with the busulfan-fludarabine (Bu-Flu) conditioning regimen. In the phase 1 part, we determined that G-CSF plus plerixafor is safe in this setting. We compared clinical effects and outcomes of AML/MDS study patients (n = 40) to 164 patients from a historical data set who received Bu-Flu alone prior to allo-SCT by stratifying on cytogenetics and disease status to correct for bias. Study patients had increased myeloid chimerism and lower rates of GvHD. There was no significant difference in relapse free survival or overall survival. The G-CSF plus plerixafor combination increased circulating white blood cells, CD34+ cells, and CXCR4+ cells, and preferentially mobilized FISH+ leukemic cells. ClinicalTrials.gov identifier is NCT00822770.

Impact of donor hematopoietic cells mobilized with G-CSF and plerixafor on murine acute graft-versus-host-disease

BACKGROUND AIMS

This study aimed to characterize the immune effectors contained in the grafts from donor mice mobilized by granulocyte colony-stimulating factor (G-CSF) and plerixafor and to evaluate their impact on the development of acute graft-versus-host-disease (aGVHD).

METHODS

Mobilization was done with G-CSF alone or G-CSF plus plerixafor (G+P).

RESULTS

In grafts collected after G+P mobilization, we observed a significantly higher proportion of c-kit(+)Sca-1(+) hematopoietic stem cells compared with G-CSF. A significant increase in the percentage of plasmacytoid dendritic cells was detected in the G+P graft compared with G-CSF graft. We also studied the ability of stem cell grafts mobilized with G+P to induce GVHD in a mouse model. We observed higher mortality (P < 0.001) associated with increased aGVHD clinical score (P < 0.0001) as well as higher pathology score in the intestine of mice receiving G+P as compared with G-CSF grafts (P < 0.001). Moreover, the exacerbated aGVHD severity was associated with upregulation of CCR6 expression on both CD4(+) and CD8(+) T cells from the G+P grafts, as well as on T cells from mice transplanted with G+P grafts.

CONCLUSIONS

In conclusion, we showed that grafts mobilized with G+P exhibited functional features different from those mobilized with G-CSF alone, which increase the severity of aGVHD in the recipients.

Mobilized peripheral blood grafts include more than hematopoietic stem cells: the immunological perspective

Although stem cell mobilization has been performed for more than 20 years, little is known about the effects of mobilizing agents on apheresis composition and the impact of graft cell subsets on patients' outcome. With the increasing use of plerixafor and the inclusion of poor mobilizers in autologous transplant procedures, new parameters other than CD34(+) stem cell dose are emerging; plerixafor seems to mobilize more primitive CD34(+)/CD38(-) stem cells compared with G-CSF, but their correlation with stable hematopoietic engraftment is still obscure. Immune recovery is as crucial as hematopoietic reconstitution, and higher T and natural killer cells infused within the graft have been correlated with better outcome in autologous transplant; recent studies showed increased mobilization of immune effectors with plerixafor compared with G-CSF, but further data are needed to clarify the clinical impact of these findings. In the allogeneic setting, much evidence suggests that mobilized T-cell alloreactivity is tempered by G-CSF, probably with the mediation of dendritic cells, even though no clear correlation with GVL and GVHD has been found. Plerixafor is not approved in healthy donors yet; early data suggest it might mobilize a GVHD protective balance of immune effectors, but further studies are needed to define its role in allogeneic transplant.

Mobilization of healthy donors with plerixafor affects the cellular composition of T-cell receptor (TCR)-αβ/CD19-depleted haploidentical stem cell grafts

BACKGROUND

HLA-haploidentical hematopoietic stem cell transplantation (HSCT) is suitable for patients lacking related or unrelated HLA-matched donors. Herein, we investigated whether plerixafor (MZ), as an adjunct to G-CSF, facilitated the collection of mega-doses of hematopoietic stem cells (HSC) for TCR-αβ/CD19-depleted haploidentical HSCT, and how this agent affects the cellular graft composition.

METHODS

Ninety healthy donors were evaluated. Single-dose MZ was given to 30 'poor mobilizers' (PM) failing to attain ≥40 CD34+ HSCs/μL after 4 daily G-CSF doses and/or with predicted apheresis yields ≤12.0x106 CD34+ cells/kg recipient's body weight.

RESULTS

MZ significantly increased CD34+ counts in PM. Naïve/memory T and B cells, as well as natural killer (NK) cells, myeloid/plasmacytoid dendritic cells (DCs), were unchanged compared with baseline. MZ did not further promote the G-CSF-induced mobilization of CD16+ monocytes and the down-regulation of IFN-γ production by T cells. HSC grafts harvested after G-CSF + MZ were enriched in myeloid and plasmacytoid DCs, but contained low numbers of pro-inflammatory 6-sulfo-LacNAc+ (Slan)-DCs. Finally, children transplanted with G-CSF + MZ-mobilized grafts received greater numbers of monocytes, myeloid and plasmacytoid DCs, but lower numbers of NK cells, NK-like T cells and Slan-DCs.

CONCLUSIONS

MZ facilitates the collection of mega-doses of CD34+ HSCs for haploidentical HSCT, while affecting graft composition.