Reconstitution of Th17, Tc17 and Treg cells after paediatric haematopoietic stem cell transplantation: Impact of interleukin-7

Reduced mitochondrial respiration in peripheral T cells after paediatric heamatopoietic stem cell transplantation

Background

Recovery and functional differentiation of T-cell subsets are central for the development of immune function and complications after allogeneic hematopoietic stem cell transplantation (HSCT), but little is known about the cellular respiration and factors influencing T-cell metabolic fitness during immune maturation after HSCT.

Method

We included 20 HSCT patients and analysed mitochondrial oxidative phosphorylation and mitochondrial fitness in peripheral blood mononuclear cell samples collected at days +90 and +180 after HSCT.

Results

Phenotypic analysis revealed lower overall T-cell counts, lower CD4+/CD8+ ratio and a skewed distribution of early T-cell subsets at day +90, gradually recovering by day +180. Although ATP turnover in HSCT patients was similar to healthy controls, the spare respiratory capacity (SRC) of T cells, reflecting the available energy reserve, was significantly reduced at day +90 and +180 compared to healthy controls. This reduction in SRC was not correlated with the occurrence of acute graft-versus-host disease (aGVHD), the intensity of conditioning regimens and markers of T-cell exhaustion.

Conclusion

We found significantly depressed SRC until six months post-HSCT, but we were not able to identify transplant-related risk factors or associations with the clinical outcome.

Defibrotide impact on the acute GVHD disease incidence in pediatric hematopoietic stem cell transplant recipients

Despite advances in acute graft-versus-host disease (aGVHD) prophylaxis, current pharmacological approaches fail to prevent aGVHD. The protective effect of defibrotide on GVHD incidence and GVHD-free survival has not been sufficiently studied. 91 pediatric patients included in this retrospective study were divided into two groups based on defibrotide use. We compared the incidence of aGVHD and chronic GVHD-free survival between the defibrotide and control groups. The incidence and severity of aGVHD were significantly lower in patients who received defibrotide prophylactic administration than in the control group. This improvement was observed in the liver and intestinal aGVHD. No defibrotide prophylaxis benefit was observed in the prevention of chronic GVHD. The pro-inflammatory cytokine levels were significantly higher in the control group. Our findings suggest that prophylactic administration of defibrotide in pediatric patients significantly reduces the incidence and severity of aGVHD, with a modification of cytokine pattern, both strongly coherent with the protective drug's action. This evidence adds to pediatric retrospective studies and preclinical data suggesting a possible defibrotide role in this setting.

T helper 17 and regulatory T-cell profile and graft-versus-host disease after allogeneic hematopoietic stem cell transplantation in pediatric patients with beta-thalassemia

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is an effective treatment option for hereditary hemoglobin disorders, such as beta-thalassemia; However, this procedure is not without constraints, mainly engendering complications such as acute graft-versus-host disease (aGvHD), chronic GvHD (cGvHD), and susceptibility to infections. The clinical outcomes of allo-HSCT are highly dependant on the quality and quantity of T-cell subsets reconstitution. Following the allo-HSCT of six pediatric patients afflicted with beta-thalassemia, their mononuclear cells were isolated, and then cultured with a combination of phorbol myristate acetate (PMA)/ionomycin and Brefeldin A. The content of CD4 T-cell subsets, including T helper 17 (Th17) cells and regulatory T cells (Tregs), were determined by specific conjugated-monoclonal antibodies three and six months post-HSCT. An increased frequency of total CD4 T-cells, Tregs and Th17 cells was observed at day 90 and 180 after allo-HSCT, albeit the numbers were still lower than that of our healthy controls. In patients who developed cGvHD, a lower Th17/Treg ratio was observed, owing it to a decreased proportion of Th17 cells. In conclusion, creating balance between Th17 and Treg subsets may prevent acute and chronic GvHD in patients after allo-HSCT.

Plasma Levels of MRP-8/14 Associate With Neutrophil Recovery, Bacterial Bloodstream Infections, and Engraftment Syndrome Following Pediatric Allogeneic Hematopoietic Stem Cell Transplantation

Neutrophil engraftment is essential for the successful outcome after allogeneic hematopoietic stem cell transplantation (HSCT), but neutrophil activation may also induce transplant-related complications. Myeloid-related protein (MRP)-8/14 is expressed in granulocytes during inflammatory conditions and secreted in response to tissue damage along with the release of pro-inflammatory cytokines together with leukocyte recruitment and activation. In this study, we investigated associations between levels of the neutrophil activition marker MRP-8/14, neutrophil recovery and toxicities after pediatric HSCT. We included 73 children undergoing allogeneic HSCT using bone marrow or peripheral blood stem cell grafts from matched sibling or unrelated donors. Plasma levels of MRP-8/14 were measured by enzyme-linked immunosorbent assay from preconditioning until 6 months after transplantation. Overall, MRP-8/14 levels decreased from pre-conditioning to a nadir at day 7 and then rose again until day 28, preceding the reappearance of neutrophils. MRP-8/14 levels were significantly reduced at day 14 in patients with delayed neutrophil engraftment compared with patients who engrafted by day 21 (0.20 versus 0.48 μg/mL, P = .0012) and in patients who developed bacterial bloodstream infections compared to patients without this complication (0.2 versus 0.36 μg/mL, P = .048). Patients developing engraftment syndrome had significantly elevated MRP-8/14 levels at day 7 and 21 compared to patients without engraftment syndrome (0.32 versus 0.2 μg/mL, P = .042 and 1.9 versus 0.80 μg/mL, P = .039, respectively), as well as increased neutrophil counts from day 9 to 25 (P ≤ .016). Similarly, neutrophil counts were increased at day 13 to 17 in patients with acute graft-versus-host disease grade III-IV compared with grade 0-II. This study is the first to monitor neutrophil activation by MRP-8/14 in HSCT patients in relation to infectious, as well as noninfectious post-transplantation complications. Our results provide increased insights into the pathophysiology of these complications, and further studies should explore the potential use of MRP-8/14 as a clinically useful biomarker.

Regulatory factors involved in Th17/Treg cell balance of immune thrombocytopenia

Immune thrombocytopenia is a common heterogeneous autoimmune disease that is characterized by decreasing peripheral blood platelet counts and increasing risk of bleeding. Studies have shown that an imbalance between T helper 17 (Th17) and Regulatory T (Treg) cells differentiated from CD4+T-cells is a key factor influencing the development and pathogenesis of immune thrombocytopenia. Th17 cells promote the development of chronic inflammatory disorders and induce autoimmune diseases, whereas Treg cells regulate immune homeostasis and prevent autoimmune diseases. Several regulators affecting the production and maintenance of these cells are also essential for proper regulation of Th17/Treg balance; these regulatory factors include cell surface proteins, miRNAs, and cytokine signaling. In this review, we focus on the function and role of balance between Th17 and Treg cells in immune thrombocytopenia, the regulatory factors, and therapeutic goals of this balance in immune thrombocytopenia.

Thymic stromal lymphopoietin levels after allogeneic hematopoietic stem cell transplantation

BACKGROUND

Thymic stromal lymphopoietin (TSLP) is an immunoregulatory, Th2-polarizing cytokine produced by epithelial cells. We hypothesized that TSLP affects immune reconstitution after hematopoietic stem cell transplantation (HSCT) leading to increased alloreactivity.

METHODS

We measured plasma TSLP by ELISA in 38 patients and assessed the immune reconstitution by flow cytometry.

RESULTS

TSLP levels rose after initiation of the conditioning to peak at day +21 after HSCT (p = .03), where TSLP levels correlated with counts of neutrophils (rho = 0.36, p = .04), monocytes (rho = 0.58, p = .006), and lymphocytes (rho = 0.59, p = .02). Overall absolute TSLP levels were not associated with acute or chronic graft-vs-host disease (a/cGvHD). However, patients mounting a sustained increase in TSLP levels at day +90 had a higher risk of cGvHD compared to patients who had returned to pre-conditioning levels at that stage (cumulative incidence: 77% vs. 38%, p = .01).

CONCLUSION

In conclusion, this study suggests a role of TSLP in immune reconstitution and alloreactivity post-HSCT. lymphopoietin (TSLP) is an immunoregulatory, Th2-polarizing cytokine produced by epithelial cells. We hypothesized that TSLP affects immune reconstitution after hematopoietic stem cell transplantation (HSCT) leading to increased alloreactivity. We measured plasma TSLP by ELISA in 38 patients and assessed the immune reconstitution by flow cytometry.

Microbiota long-term dynamics and prediction of acute graft-versus-host disease in pediatric allogeneic stem cell transplantation

BACKGROUND

Patients undergoing allogeneic hematopoietic stem cell transplantation (HSCT) exhibit changes in their gut microbiota and are experiencing a range of complications, including acute graft-versus-host disease (aGvHD). It is unknown if, when, and under which conditions a re-establishment of microbial and immunological homeostasis occurs. It is also unclear whether microbiota long-term dynamics occur at other body sites than the gut such as the mouth or nose. Moreover, it is not known whether the patients' microbiota prior to HSCT holds clues to whether the patient would suffer from severe complications subsequent to HSCT. Here, we take a holobiont perspective and performed an integrated host-microbiota analysis of the gut, oral, and nasal microbiota in 29 children undergoing allo-HSCT.

RESULTS

The bacterial diversity decreased in the gut, nose, and mouth during the first month and reconstituted again 1-3 months after allo-HSCT. The microbial community composition traversed three phases over 1 year. Distinct taxa discriminated the microbiota temporally at all three body sides, including Enterococcus spp., Lactobacillus spp., and Blautia spp. in the gut. Of note, certain microbial taxa appeared already changed in the patients prior to allo-HSCT as compared with healthy children. Acute GvHD occurring after allo-HSCT could be predicted from the microbiota composition at all three body sites prior to HSCT. The reconstitution of CD4⁺ T cells, T_H17, and B cells was associated with distinct taxa of the gut, oral, and nasal microbiota.

CONCLUSIONS

This study reveals for the first time bacteria in the mouth and nose that may predict aGvHD. Monitoring of the microbiota at different body sites in HSCT patients and particularly through involvement of samples prior to transplantation may be of prognostic value and could assist in guiding personalized treatment strategies. The identification of distinct bacteria that have a potential to predict post-transplant aGvHD might provide opportunities for an improved preventive clinical management, including a modulation of microbiomes. The host-microbiota associations shared between several body sites might also support an implementation of more feasible oral and nasal swab sampling-based analyses. Altogether, the findings suggest that the microbiota and host factors together could provide actionable information to guiding precision medicine. Video Abstract.

IL-7 and IL-15 Levels Reflect the Degree of T Cell Depletion during Lymphopenia and Are Associated with an Expansion of Effector Memory T Cells after Pediatric Hematopoietic Stem Cell Transplantation

Differentially and functionally distinct T cell subsets are involved in the development of complications after allogeneic hematopoietic stem cell transplantation (HSCT), but little is known about factors regulating their recovery after HSCT. In this study, we investigated associations between immune-regulating cytokines, T cell differentiation, and clinical outcomes. We included 80 children undergoing allogeneic HSCT for acute leukemia using bone marrow or peripheral blood stem cells grafted from a matched sibling or unrelated donor. Cytokines (IL-7, IL-15, IL-18, SCF, IL-6, IL-2, and TNF-α) and active anti-thymocyte globulin (ATG) levels were longitudinally measured along with extended T cell phenotyping. The cytokine profiles showed a temporary rise in IL-7 and IL-15 during lymphopenia, which was strongly dependent on exposure to active ATG. High levels of IL-7 and IL-15 from graft infusion to day +30 were predictive of slower T cell recovery during the first 2 mo post-HSCT; however, because of a major expansion of memory T cell stages, only naive T cells remained decreased after 3 mo (p < 0.05). No differential effect was seen on polarization of CD4⁺ T cells into Th1, Th2, or Th17 cells or regulatory T cells. Low levels of IL-7 and IL-15 at day +14 were associated with acute graft-versus-host disease grades II-IV in ATG-treated patients (p = 0.0004 and p = 0.0002, respectively). Children with IL-7 levels comparable to healthy controls at day +14 post-HSCT were less likely to develop EBV reactivation posttransplant. These findings suggest that quantification of IL-7 and IL-15 may be useful as biomarkers in assessing the overall T cell depletion and suggest a potential for predicting complications after HSCT.

Netrin-1 reduces lung ischemia-reperfusion injury by increasing the proportion of regulatory T cells

Objective

Inflammation is the primary mechanism of lung ischemia-reperfusion injury (LIRI) and neurologic factors can regulate inflammatory immune responses. Netrin-1 is an axonal guidance molecule, but whether Netrin-1 plays a role in LIRI remains unclear.

Methods

A mouse model of LIRI was established. Immunohistochemistry was used to detect expression of Netrin-1 and to enumerate macrophages and T cells in lung tissue. The proportion of regulatory T cells (Tregs) was assessed by flow cytometry. Levels of apoptosis were assessed by terminal deoxynucleotidyl transferase dUTP nick end staining.

Results

Numbers of macrophages and T cells in the lung tissues of mice with LIRI were elevated, while expression of netrin-1 was significantly decreased. Flow cytometry showed that the proportion of Tregs in mice with LIRI was significantly decreased. The proportion of Tregs among lymphocytes was positively correlated with netrin-1 expression. In vitro experiments showed that netrin-1 promoted an increase in Treg proportion through the A2b receptor. Animal experiments showed that netrin-1 could inhibit apoptosis and reduce T cell and macrophage infiltration by increasing the proportion of Tregs, ultimately reducing LIRI. Treg depletion using an anti-CD25 monoclonal antibody blocked the effects of netrin-1.

Conclusion

Netrin-1 reduced LIRI by increasing the proportion of Tregs.

Regulation of CD4+CD25+FOXP3+ cells in Pediatric Acute Lymphoblastic Leukemia (ALL): Implication of cytokines and miRNAs

Regulatory T cells (Tregs) is one of the immunosuppressive subsets of CD4⁺ T cells characterized by transcription factor forkhead box protein P3 (FOXP3) expression which are involved in tumor development and progression. Identification of the factors that influence Treg cell function is extremely important. Our current study aimed to evaluate the frequency of Treg cells, cytokine secretion and the expression of microRNAs (miRNAs) in pediatric acute lymphoblastic leukemia (ALL) patients. The frequency of CD3⁺, CD4⁺ and CD4⁺CD25⁺FOXP3⁺ Treg was assessed by flow cytometry in 43 ALL patients versus 42 controls. Plasma levels of IL-10, transcription factor β (TGF-β), IL-6, IL-17, IL-23 and tumor necrosis factor (TNF-α) were measured by Enzyme-linked immunosorbent assay (ELISA). miR-21, miR-24, miR-26a, miR133b, miR-148a and miR-155 expression were analyzed using quantitative real-time polymerase chain reaction (qRT-PCR). A slight insignificant increase in Treg cells in ALL patients compared to controls was observed. There was a significant elevation in IL-10 (p < 0.05), IL-6 (p < 0.01), IL-23 (p < 0.05) and TNF-α (p < 0.01) in ALL patients compared with controls. Meanwhile, a significant reduction in TGF-β (p < 0.001) was recorded. A slight insignificant decrease in IL-17 in ALL patients was observed.ALL patients showed a significant increase in miR-21 (p < 0.05), miR-148a (p < 0.01), miR-24 (p < 0.05) and a significant reduction in miR-155 (p < 0.01). In conclusion, the slight change in Treg cells frequency and alteration in related cytokines could possibly involve in the pathogenesis of ALL. Dysregulated miRNAs, as a regulatory mechanism of epigenetics, might contribute to these observed results. Further researches are required to confirm our interesting findings.

A Unique Role of T Helper 17 Cells in Different Treatment Stages of Multiple Myeloma

BACKGROUND

T helper 17 (Th17) cells are a subset of CD4-positive T cells, which secrete interleukin 17 and specifically express the retinoic acid receptor-related orphan receptors γt gene. Recently, Studies have shown that the level of Th17 cells in peripheral blood of newly diagnosed multiple myeloma (MM) patients is significantly higher than that of healthy persons. Th17 cells play an important role in the immune microenvironment of MM and interact with tumor cells, osteoclasts, and osteoblasts. Th17 cells might be a potential therapeutic target for MM patients.

PATIENTS AND METHODS

In this study, we further tracked the levels of Th17 cells in peripheral blood of 56 patients with MM from newly diagnosed to partial remission to complete remission to relapse and 11 healthy donors.

RESULTS

The level of Th17 cells increased further when the disease reached partial remission, decreased to normal level when it reached complete remission, and increased again when the disease recurred. In addition, we also found that in newly diagnosed MM patients, Th17 cell levels fluctuated greatly; not all patients were upregulated, and patients with normal Th17 cell levels had the highest chance of complete remission.

CONCLUSION

Th17 cells contribute to the stratification of different treatment stages of MM patients. The level of Th17 cells in patients with newly diagnosed MM is associated with the treatment outcome of complete remission.

Specific gut microbiome members are associated with distinct immune markers in pediatric allogeneic hematopoietic stem cell transplantation

BACKGROUND

Increasing evidence reveals the importance of the microbiome in health and disease and inseparable host-microbial dependencies. Host-microbe interactions are highly relevant in patients receiving allogeneic hematopoietic stem cell transplantation (HSCT), i.e., a replacement of the cellular components of the patients' immune system with that of a foreign donor. HSCT is employed as curative immunotherapy for a number of non-malignant and malignant hematologic conditions, including cancers such as acute lymphoblastic leukemia. The procedure can be accompanied by severe side effects such as infections, acute graft-versus-host disease (aGvHD), and death. Here, we performed a longitudinal analysis of immunological markers, immune reconstitution and gut microbiota composition in relation to clinical outcomes in children undergoing HSCT. Such an analysis could reveal biomarkers, e.g., at the time point prior to HSCT, that in the future could be used to predict which patients are of high risk in relation to side effects and clinical outcomes and guide treatment strategies accordingly.

RESULTS

In two multivariate analyses (sparse partial least squares regression and canonical correspondence analysis), we identified three consistent clusters: (1) high concentrations of the antimicrobial peptide human beta-defensin 2 (hBD2) prior to the transplantation in patients with high abundances of Lactobacillaceae, who later developed moderate or severe aGvHD and exhibited high mortality. (2) Rapid reconstitution of NK and B cells in patients with high abundances of obligate anaerobes such as Ruminococcaceae, who developed no or mild aGvHD and exhibited low mortality. (3) High inflammation, indicated by high levels of C-reactive protein, in patients with high abundances of facultative anaerobic bacteria such as Enterobacteriaceae. Furthermore, we observed that antibiotic treatment influenced the bacterial community state.

CONCLUSIONS

We identify multivariate associations between specific microbial taxa, host immune markers, immune cell reconstitution, and clinical outcomes in relation to HSCT. Our findings encourage further investigations into establishing longitudinal surveillance of the intestinal microbiome and relevant immune markers, such as hBD2, in HSCT patients. Profiling of the microbiome may prove useful as a prognostic tool that could help identify patients at risk of poor immune reconstitution and adverse outcomes, such as aGvHD and death, upon HSCT, providing actionable information in guiding precision medicine.

Assessment of the proposed EBMT pediatric criteria for diagnosis and severity grading of sinusoidal obstruction syndrome

Sinusoidal obstruction syndrome (SOS) is a potentially life-threatening complication of allogeneic hematopoietic stem cell transplantation (HSCT). We assessed the proposed pediatric EBMT criteria along with the Baltimore and modified Seattle criteria in a population-based cohort. Eighty-seven children (1.1–17.3 years) undergoing myeloablative HSCT from 2010 to 2017 were consecutively included at the Danish National Transplantation Center. In total, 39 (44.8%) patients fulfilled the EBMT criteria and 30 patients (35%) fulfilled the criteria for severe or very severe SOS. Nine (10.3%) patients fulfilled the modified Seattle criteria while none met the Baltimore criteria. Patients fulfilling the EBMT criteria for SOS had longer primary admission (31 days (23–183) vs. 27 days (17–61), p = 0.001), were treated more intensively with diuretics within the first 3 months (29 days (0–90) vs. 3.5 days (0–90), p < 0.0001), and had a longer time to stable platelet counts >50 × 10⁹/L (32 days (16–183) vs. 23 days (14–101), p < 0.0001). Two patients, fulfilling neither Baltimore nor Seattle criteria, but selectively fulfilling EBMT criteria, died of treatment-related acute inflammatory complications within 1 year post-HSCT. In conclusion, application of the pediatric EBMT diagnostic and severity criteria may be helpful in identifying patients at increased risk of severe treatment-related complications and mortality, although with a risk of over-diagnosing SOS.