IL-6 dysregulation originates in dendritic cells and mediates graft-versus-host disease via classical signaling

IL-6-mediated endothelial injury impairs antiviral humoral immunity after bone marrow transplantation

Endothelial function and integrity are compromised after allogeneic bone marrow transplantation (BMT), but how this affects immune responses broadly remains unknown. Using a preclinical model of CMV reactivation after BMT, we found compromised antiviral humoral responses induced by IL-6 signaling. IL-6 signaling in T cells maintained Th1 cells, resulting in sustained IFN-γ secretion, which promoted endothelial cell (EC) injury, loss of the neonatal Fc receptor (FcRn) responsible for IgG recycling, and rapid IgG loss. T cell-specific deletion of IL-6R led to persistence of recipient-derived, CMV-specific IgG and inhibited CMV reactivation. Deletion of IFN-γ in donor T cells also eliminated EC injury and FcRn loss. In a phase III clinical trial, blockade of IL-6R with tocilizumab promoted CMV-specific IgG persistence and significantly attenuated early HCMV reactivation. In sum, IL-6 invoked IFN-γ-dependent EC injury and consequent IgG loss, leading to CMV reactivation. Hence, cytokine inhibition represents a logical strategy to prevent endothelial injury, thereby preserving humoral immunity after immunotherapy.

A randomized phase 2 trial of oral vitamin A for graft-versus-host disease in children and young adults

ABSTRACT

Vitamin A plays a key role in the maintenance of gastrointestinal homeostasis and promotes a tolerogenic phenotype in tissue resident macrophages. We conducted a prospective randomized double-blinded placebo-controlled clinical trial in which 80 recipients of hematopoietic stem cell transplantation (HSCT) were randomized 1:1 to receive pretransplant high-dose vitamin A or placebo. A single oral dose of vitamin A of 4000 IU/kg, maximum 250 000 IU was given before conditioning. The primary end point was incidence of acute graft-versus-host disease (GVHD) at day +100. In an intent-to-treat analysis, incidence of acute GVHD was 12.5% in the vitamin A arm and 20% in the placebo arm (P = .5). Incidence of acute gastrointestinal (GI) GVHD was 2.5% in the vitamin A arm (P = .09) and 12.5% in the placebo arm at day +180. Incidence of chronic GVHD was 5% in the vitamin A arm and 15% in the placebo arm (P = .02) at 1 year. In an "as treated" analysis, cumulative incidence of acute GI GVHD at day +180 was 0% and 12.5% in recipients of vitamin A and placebo, respectively (P = .02), and cumulative incidence of chronic GVHD was 2.7% and 15% in recipients of vitamin A and placebo, respectively (P = .01). The only possibly attributable toxicity was asymptomatic grade 3 hyperbilirubinemia in 1 recipient of vitamin A at day +30, which self-resolved. Absolute CCR9+ CD8+ effector memory T cells, reflecting gut T-cell trafficking, were lower in the vitamin A arm at day +30 after HSCT (P = .01). Levels of serum amyloid A-1, a vitamin A transport protein with proinflammatory effects, were lower in the vitamin A arm. The vitamin A arm had lower interleukin-6 (IL-6), IL-8, and suppressor of tumorigenicity 2 levels and likely a more favorable gut microbiome and short chain fatty acids. Pre-HSCT oral vitamin A is inexpensive, has low toxicity, and reduces GVHD. This trial was registered at www.ClinicalTrials.gov as NCT03202849.

Treatment of steroid-refractory graft versus host disease in children

Systemic steroids are still the first-line approach in acute graft-versus-host disease (aGvHD), and the backbone of chronic GvHD management. Refractoriness to steroid represent a major cause of morbidity and non-relapse mortality after hematopoietic stem cell transplantation (HSCT). In both backgrounds, several second-line immunosuppressive agents have been tested with variable results in terms of efficacy and toxicity. Solid evidence regarding these approaches is still lacking in the pediatric setting where results are mainly derived from adult experiences. Furthermore, the number of treated patients is limited and the incidence of acute and chronic GvHD is lower, resulting in a very heterogeneous approach to this complication by pediatric hematologists. Some conventional therapies and anti-cytokine monoclonal antibodies used in the adult setting have been evaluated in children. In recent years, the increasing understanding of the biological mechanisms underpinning the pathogenesis of GvHD justified the efforts toward the adoption of targeted therapies and non-pharmacologic approaches, with higher response rates and lower immunosuppressive effects. Moreover, many questions regarding the precise timing and setting in which to integrate these new approaches remain unanswered. This Review aims to critically explore the current evidence regarding novel approaches to treat SR-GvHD in pediatric HSCT recipients.

Tocilizumab for Cytokine Release Syndrome Management After Haploidentical Hematopoietic Cell Transplantation With Post-Transplantation Cyclophosphamide-Based Graft-Versus-Host Disease Prophylaxis

Cytokine release syndrome (CRS) is a common complication after haploidentical hematopoietic cell transplantation (HaploHCT). Severe CRS after haploHCT leads to higher risk of non-relapse mortality (NRM) and worse overall survival (OS). Tocilizumab (TOCI) is an interleukin-6 receptor inhibitor and is commonly used as first-line for CRS management after chimeric antigen receptor T cell therapy, but the impact of TOCI administration for CRS management on Haplo HCT outcomes is not known. In this single center retrospective analysis, we compared HCT outcomes in patients treated with or without TOCI for CRS management after HaploHCT with post-transplantation cyclophosphamide- (PTCy-) based graft-versus-host disease (GvHD) prophylaxis. Of the 115 patients eligible patients who underwent HaploHCT at City of Hope between 2019 to 2021 and developed CRS, we identified 11 patients who received tocilizumab for CRS management (TOCI). These patients were matched with 21 patients who developed CRS but did not receive tocilizumab (NO-TOCI) based on age at the time of HCT (≤64 years or >65 years or older), conditioning intensity (myeloablative versus reduced-intensity/nonmyeloablative), and CRS grading (1, 2, versus 3-4). Instead of 22 controls, we chose 21 patients because there was only 1 control matched with 1 TOCI treatment patient in 1 stratum. With only 11 patients in receiving tocilizumab for CRS treatment, matching with 21 patients who developed CRS but did not receive tocilizumab, we had 80% power to detect big differences (hazard ratio [HR] = 3.4 or higher) in transplantation outcomes using a 2-sided 0.05 test. The power would be reduced to about 20% to 30% if the difference was moderate (HR = 2.0) using the same test. No CRS-related deaths were recorded in either group. Median time to neutrophil engraftment was 21 days (range 16-43) in TOCI and 18 days (range 14-23) in NO-TOCI group (HR = 0.55; 95% confidence interval [CI] = 0.28-1.06, P = .08). Median time to platelet engraftment was 34 days (range 20-81) in TOCI and 28 days (range 12-94) in NO-TOCI group (HR = 0.56; 95% CI = 0.25-1.22, P = .19). Cumulative incidences of day 100 acute GvHD grades II-IV (P = .97) and grades III-IV (P = .47) were similar between the 2 groups. However, cumulative incidence of chronic GvHD at 1 year was significantly higher in patients receiving TOCI (64% versus 24%; P = .05). Rates of NRM (P = .66), relapse (P = .83), disease-free survival (P = .86), and overall survival (P = .73) were similar at 1 year after HCT between the 2 groups. Tocilizumab administration for CRS management after HaploHCT appears to be safe with no short-term adverse effect and no effect on relapse rate. However, the significantly higher cumulative incidence of chronic GvHD, negates the high efficacy of PTCy on GvHD prophylaxis in this patient population. Therefore using tocilizumab for CRS management in the HaploHCT population with PTCy maybe kept only for patients with severe CRS. The impact on such approach on long term outcome in HaploHCT with PTCy will need to be evaluated in a larger retrospective study or a prospective manner.

[Clinical study of 19 cases of steroid-refractory gastrointestinal acute graft-versus-host disease after allogeneic hematopoietic stem cell transplantation with fecal microbiota transplantation]

Objective: To investigate the clinical efficacy of fecal microbiota transplantation (FMT) for treating steroid-refractory gastrointestinal acute graft-versus-host disease (GI-aGVHD) . Methods: This analysis included 29 patients with hematology who developed steroid-refractory GI-aGVHD after allogeneic hematopoietic stem cell transplantation (allo-HSCT) in Huaian Hospital Affiliated to Xuzhou Medical University from March 2017 to March 2022. Among them, 19 patients underwent FMT treatment (the FMT group) and 10 patients did not (the control group). The efficacy and safety of FMT were assessed, as well as the changes in intestinal microbiota abundance, lymphocyte subpopulation ratio, peripheral blood inflammatory cytokines, and GVHD biomarkers before and after FMT treatment. Results: ① Complete remission of clinical symptoms after FMT was achieved by 13 (68.4%) patients and 2 (20.0%) controls, with a statistically significant difference (P<0.05). Intestinal microbiota diversity increased and gradually recovered to normal levels after FMT and FMT-related infections did not occur. ②The proportion of CD3(+) and CD8(+) cells in the FMT group after treatment decreased compared with the control group, and the ratio of CD4(+), regulatory T cells (Treg), and CD4(+)/CD8(+) cells increased (all P< 0.05). The interleukin (IL) -6 concentration in the FMT group was lower than that in the control group [4.15 (1.91-5.71) ng/L vs 6.82 (2.40-8.91) ng/L, P=0.040], and the IL-10 concentration in the FMT group was higher than that in the control group [12.11 (5.69-20.36) ng/L vs 7.51 (4.10-9.58) ng/L, P=0.024]. Islet-derived protein 3α (REG3α) was significantly increased in patients with GI-aGVHD, and the REG3α level in the FMT group was lower than that in the control group after treatment [30.70 (10.50-105.00) μg/L vs 74.35 (33.50-139.50) μg/L, P=0.021]. Conclusion: FMT is a safe and effective method for the treatment of steroid-refractory GI-aGVHD by restoring intestinal microbiota diversity, regulating inflammatory cytokines, and upregulating Treg cells.

Erythrocyte membrane-camouflaged DNA-functionalized upconversion nanoparticles for tumor-targeted chemotherapy and immunotherapy

A synergistic combination of treatment with immunogenic cell death (ICD) inducers and immunoadjuvants may be a practical way to boost the anticancer response and successfully induce an immune response. The use of HR@UCNPs/CpG-Apt/DOX, new biomimetic drug delivery nanoparticles generated to combat breast cancer, is reported here as a unique strategy to produce immunogenicity and boost cancer immunotherapy. HR@UCNPs/CpG-Apt/DOX (HR-UCAD) consists of two parts. The core is composed of an immunoadjuvant CpG (a toll-like receptor 9 agonist) fused with a dendritic cell-specific aptamer sequence (CpG-Apt) to decorate upconversion nanoparticles (UCNPs) with the successful intercalation of doxorubicin (DOX) into the consecutive base pairs of Apt-CpG to construct an immune nanodrug UCNPs@CpG-Apt/DOX. The targeting molecule hyaluronic acid (HA) was inserted into a red blood cell membrane (RBCm) to form the shell (HR). HR-UCAD possessed a strong capacity to specifically induce ICD. Following DOX-induced ICD of cancer cells, sufficient exposure to tumor antigens and UCNPs@CpG-Apt (UCA) activated the tumor-specific immune response and reversed the immunosuppressive tumor microenvironment. In addition, HR-UCAD has good biocompatibility and increases the active tumor-targeting effect. Furthermore, HR-UCAD exhibits excellent near-infrared upconversion luminescence emission at 804 nm under irradiation with a 980 nm laser, which has great potential in biomedical imaging. Thus, the RBCm-camouflaged drug delivery system is a promising targeted chemotherapy and immunotherapy nanocomplex that could be used for effective targeted breast cancer treatment.

USP11 plays a critical role in the onset and progression of acute graft-versus-host disease：Novel target for precision therapeutics

Acute graft-versus-host disease (aGvHD) is considered a result of "cytokine storm." Targeted therapeutic interventions on cytokines via ubiquitination regulatory pathways may provide a potential approach for aGvHD treatment. Ubiquitin-specific peptidase 11 (USP11) has been reported to play key roles in a variety of physiopathological processes by regulating the stability and function of several vital protein molecules. However, its role in aGvHD remains unclear. In this study, we identified USP11 was associated with aGvHD in patients. In the aGvHD mouse model, the colon and liver were more seriously affected in recipient mice who received USP11 wt bone marrow (BM) cells and eased after the donor was treated with a USP11 inhibitor or received USP11 ko BM cells. In mouse models, IL-6 was identified as a major effecter in accelerating aGvHD induced by USP11. In the cell model, IL-6 mRNA transcript was affected by USP11. In addition, USP11 also inhibited IL-6 degradation by affecting IL-6 ubiquitination. Furthermore, the positive correlation between USP11 and IL-6 was confirmed in the GvHD patients' samples. Collectively, all results indicated that USP11 played a critical role in the onset and progression of aGvHD. USP11 might be a potential target for aGvHD treatment.

Putrescine accelerates the differentiation of bone marrow derived dendritic cells via inhibiting phosphorylation of STAT3 at Tyr705

Dendritic cells (DCs) play pivotal roles in immune responses. The differentiation and function of DCs are regulated by environmental metabolites. Putrescine is ubiquitous in various metabolic microenvironments and its immunoregulation has been of increasing interest. However, the mechanisms associated with its DC-induced immunoregulation remain unclear. In this study, we found putrescine promoted induction of immature bone marrow derived DCs (BMDCs), along with the increased phagocytosis and migration, and altered cytokine secretion in immature BMDCs. Transcriptomic profiles indicated significantly impaired inflammatory-related pathways, elevated oxidative phosphorylation, and decreased p-STAT3 (Tyr705) expression. Additionally, putrescine performed minor influence on the lipopolysaccharide (LPS)-induced maturation of BMDCs but significantly impaired LPS-induced DC-elicited allogeneic T-cell proliferation as well as the cytokine secretion. Furthermore, molecular docking and dynamics on the conjugation between putrescine and STAT3 revealed that putrescine could be stably bound to the hydrophilic cavity in STAT3 and performed significant influence on the Tyr705 phosphorylation. CUT&Tag analysis uncovered altered motifs, downregulated IFN-γ response, and upregulated p53 pathway in Putrescine group compared with Control group. In summary, our results demonstrated for the first time that putrescine might accelerate the differentiation of BMDCs by inhibiting the phosphorylation of STAT3 at Tyr705. Given that both DCs and putrescine have ubiquitous and distinct roles in various immune responses and pathogeneses, our findings may provide more insights into polyamine immunoregulation on DCs, as well as distinct strategies in the clinical utilization of DCs by targeting polyamines.

Effects of Lycium Barbarum Polysaccharides on the Metabolism of Dendritic Cells: An In Vitro Study

Targeting dendritic cells (DCs) metabolism-related pathways and in-situ activation of DCs have become a new trend in DC-based immunotherapy. Studies have shown that Lycium barbarum polysaccharide can promote DCs function. This study is aimed at exploring the mechanism of LBP affecting DCs function from the perspective of metabolomics. MTT method was used to detect the activity of DC2.4 cells. ELISA kit method was used to detect the contents of IL-6, IL-12, and TNF-α in the supernatant of cells. Ultra-performance liquid chromatography-quadrupole-time-of-flight mass spectrometry (UPLC-Q-TOF/MS) was used to detect general changes in DC2.4 cell metabolism. And then multidistance covariates and bioinformatics, partial least squares-discriminant analysis (PLS-DA) were used to analyze differential metabolites. Finally, metabolic pathway analysis was performed by MetaboAnalyst v5.0. The results showed that LBP had no significant inhibitory effect on the activity of DC2.4 cells at the experimental dose of 50-200 μg/ml. LBP (100 μg/ml) could significantly stimulate DC2.4 cells to secrete IL-6, TNF-α, and IL-12. Moreover, 20 differential metabolites could be identified, including betaine, hypoxanthine, L-carnitine, 5'-methylthioadenosine, orotic acid, sphingomyelin, and L-glutamine. These metabolites were involved 28 metabolic pathways and the top 5 metabolic pathways were aspartate metabolism, pyrimidine metabolism, phenylacetate metabolism, methionine metabolism, and fatty acid metabolism. These results suggest that the effect of LBP on DCs function is related to the regulation of cell metabolism.

The Role of T Helper 22 Cells in Dermatological Disorders

T helper 22 (Th22) cells are a newly identified subset of CD4+ T cells that secrete the effector cytokine interleukin 22 (IL-22) upon specific antigen stimulation, barely with IFN-γ or IL-17. Increasing studies have demonstrated that Th22 cells and IL-22 play essential roles in skin barrier defense and skin disease pathogenesis since the IL-22 receptor is widely expressed in the skin, especially in keratinocytes. Herein, we reviewed the characterization, differentiation, and biological activities of Th22 cells and elucidated their roles in skin health and disease. We mainly focused on the intricate crosstalk between Th22 cells and keratinocytes and provided potential therapeutic strategies targeting the Th22/IL-22 signaling pathway.

Retention of Donor T Cells in Lymphohematopoietic Tissue and Augmentation of Tissue PD-L1 Protection for Prevention of GVHD While Preserving GVL Activity

Allogeneic hematopoietic cell transplantation (Allo-HCT) is a curative therapy for hematological malignancies (i.e., leukemia and lymphoma) due to the graft-versus-leukemia (GVL) activity mediated by alloreactive T cells that can eliminate residual malignant cells and prevent relapse. However, the same alloreactive T cells can cause a serious side effect, known as graft-versus-host disease (GVHD). GVHD and GVL occur in distinct organ and tissues, with GVHD occurring in target organs (e.g., the gut, liver, lung, skin, etc.) and GVL in lympho-hematopoietic tissues where hematological cancer cells primarily reside. Currently used immunosuppressive drugs for the treatment of GVHD inhibit donor T cell activation and expansion, resulting in a decrease in both GVHD and GVL activity that is associated with cancer relapse. To prevent GVHD, it is important to allow full activation and expansion of alloreactive T cells in the lympho-hematopoietic tissues, as well as prevent donor T cells from migrating into the GVHD target tissues, and tolerize infiltrating T cells via protective mechanisms, such as PD-L1 interacting with PD-1, in the target tissues. In this review, we will summarize major approaches that prevent donor T cell migration into GVHD target tissues and approaches that augment tolerization of the infiltrating T cells in the GVHD target tissues while preserving strong GVL activity in the lympho-hematopoietic tissues.

Posaconazole oral suspension for secondary antifungal prophylaxis in allogeneic stem cell transplantation recipients: a retrospective study

Background

There is no consensus on the optimal secondary antifungal prophylaxis (SAP) regimen in patients receiving allogeneic hematopoietic stem cell transplantation (allo-HSCT). The purpose of this study was to evaluate the efficacy and safety of posaconazole oral suspension as secondary prophylaxis of invasive fungal disease (IFD) for allo-HSCT patients.

Methods

We retrospectively reviewed clinical data from prior IFD patients who received posaconazole oral suspension as systemic antifungal prophylaxis between June 2016 and January 2021 and have a follow-up period of 1 year after HSCT. The clinical outcomes of patients with a prior history of IFD (n = 30) and those without (n = 93) were compared.

Results

The 1-year cumulative incidence of prophylaxis failure was 58.3% in the group with prior history of IFD and 41.6% in the group without a prior history of IFD (p = 0.459). The cumulative incidence of proven, probable or possible IFD within 1 year after allo-HSCT was 23.1% in the group with prior history of IFD and 14.1% in the group without prior history of IFD (p = 0.230). There was no significant difference between the cumulative incidence of proven or probable IFD within 1-year after allo-HSCT in the group with a prior history of IFD and the group without (p = 0.807). Multivariate logistic regression revealed cytomegalovirus disease as risk factor for post-transplantation IFD occurrence in posaconazole oral suspension prophylaxis. There was not a significant difference in overall survival between the patients with IFD history and those without (P = 0.559).

Conclusions

Our study support that allo-HSCT recipients with a prior history of IFD and normal GI absorption can choose posaconazole oral suspension as a safe and effective SAP option.

A Promising Insight: The Potential Influence and Therapeutic Value of the Gut Microbiota in GI GVHD

Allogeneic hematopoietic cell transplantation (allo-HSCT) is a reconstruction process of hematopoietic and immune functions that can be curative in patients with hematologic malignancies, but it carries risks of graft-versus-host disease (GVHD), thrombotic microangiopathy (TMA), Epstein–Barr virus (EBV) infection, cytomegalovirus infection, secondary hemophagocytic lymphohistiocytosis (sHLH), macrophage activation syndrome (MAS), bronchiolitis obliterans, and posterior reversible encephalopathy syndrome (PRES). Gastrointestinal graft-versus-host disease (GI GVHD), a common complication of allo-HSCT, is one of the leading causes of transplant-related death because of its high treatment difficulty, which is affected by preimplantation, antibiotic use, dietary changes, and intestinal inflammation. At present, human trials and animal studies have proven that a decrease in intestinal bacterial diversity is associated with the occurrence of GI GVHD. Metabolites produced by intestinal bacteria, such as lipopolysaccharides, short-chain fatty acids, and secondary bile acids, can affect the development of GVHD through direct or indirect interactions with immune cells. The targeted damage of GVHD on intestinal stem cells (ISCs) and Paneth cells results in intestinal dysbiosis or dysbacteriosis. Based on the effect of microbiota metabolites on the gastrointestinal tract, the clinical treatment of GI GVHD can be further optimized. In this review, we describe the mechanisms of GI GVHD and the damage it causes to intestinal cells and we summarize recent studies on the relationship between intestinal microbiota and GVHD in the gastrointestinal tract, highlighting the role of intestinal microbiota metabolites in GI GVHD. We hope to elucidate strategies for immunomodulatory combined microbiota targeting in the clinical treatment of GI GVHD.

CCL8 deficiency in the host abrogates early mortality of acute graft-versus-host disease in mice with dysregulated IL-6 expression

Although allogeneic hematopoietic stem cell transplantation (HSCT) is a curative treatment for diverse malignant and nonmalignant diseases, acute graft-versus-host disease (aGVHD) is strongly linked to mortality caused by HSCT. We previously reported that CC chemokine ligand 8 (CCL8) is closely correlated to aGVHD mortality in both humans and mice. To study the role of CCL8 in aGVHD, CCL8 knockout (CCL8-/-) mice were transplanted with fully allogeneic marrow grafts. These mice exhibited a significant reduction in mortality (90.0% vs. 23.4% survival for CCL8-/- vs. wild-type recipients at day 28, p < 0.0001). As a result, apparent prolonged median survival from 9 days in wild-type mice to 45 days in CCL8-/- mice was observed. Acute GVHD pathology and liver dysfunction in CCL8-/- mice were significantly attenuated compared with those in wild-type mice. In association with the reduced mortality, a surge of plasma interleukin (IL)-6 was observed in CCL8-/- recipients with allogeneic marrow, which was significantly increased compared with wild-type mice that received allografts. Donor T-cell expansion and plasma levels of interferon-γ and TNF-α during aGVHD were similar in both types of mice. Collectively, these findings indicate that CCL8 plays a major role in aGVHD pathogenesis with possible involvement of an IL-6 signaling cascade.

Translational Clinical Strategies for the Prevention of Gastrointestinal Tract Graft Versus Host Disease

Graft versus host disease (GVHD) is the major non-relapse complication associated with allogeneic hematopoietic stem cell transplantation (HSCT). Unfortunately, GVHD occurs in roughly half of patients following this therapy and can induce severe life-threatening side effects and premature mortality. The pathophysiology of GVHD is driven by alloreactive donor T cells that induce a proinflammatory environment to cause pathological damage in the skin, gastrointestinal (GI) tract, lung, and liver during the acute phase of this disease. Recent work has demonstrated that the GI tract is a pivotal target organ and a primary driver of morbidity and mortality in patients. Prevention of this complication has therefore emerged as an important goal of prophylaxis strategies given the primacy of this tissue site in GVHD pathophysiology. In this review, we summarize foundational pre-clinical studies that have been conducted in animal models to prevent GI tract GVHD and examine the efficacy of these approaches upon subsequent translation into the clinic. Specifically, we focus on therapies designed to block inflammatory cytokine pathways, inhibit cellular trafficking of alloreactive donor T cells to the GI tract, and reconstitute impaired regulatory networks for the prevention of GVHD in the GI tract.

The Pathophysiology and Treatment of Graft-Versus-Host Disease: Lessons Learnt From Animal Models

Allogeneic hematopoietic cell transplantation (HCT) is a curative treatment for hematologic malignancies, bone marrow failure syndromes, and inherited immunodeficiencies and metabolic diseases. Graft-versus-host disease (GVHD) is the major life-threatening complication after allogeneic HCT. New insights into the pathophysiology of GVHD garnered from our understanding of the immunological pathways within animal models have been pivotal in driving new therapeutic paradigms in the clinic. Successful clinical translations include histocompatibility matching, GVHD prophylaxis using cyclosporine and methotrexate, posttransplant cyclophosphamide, and the use of broad kinase inhibitors that inhibit cytokine signaling (e.g. ruxolitinib). New approaches focus on naïve T cell depletion, targeted cytokine modulation and the inhibition of co-stimulation. This review highlights the use of animal transplantation models to guide new therapeutic principles.

National Institutes of Health Consensus Development Project on Criteria for Clinical Trials in Chronic Graft-versus-Host Disease: IIb. The 2020 Preemptive Therapy Working Group Report

Chronic graft-versus-host disease (GVHD) commonly occurs after allogeneic hematopoietic cell transplantation (HCT) despite standard prophylactic immune suppression. Intensified universal prophylaxis approaches are effective but risk possible overtreatment and may interfere with the graft-versus-malignancy immune response. Here we summarize conceptual and practical considerations regarding preemptive therapy of chronic GVHD, namely interventions applied after HCT based on evidence that the risk of developing chronic GVHD is higher than previously appreciated. This risk may be anticipated by clinical factors or risk assignment biomarkers or may be indicated by early signs and symptoms of chronic GVHD that do not fully meet National Institutes of Health diagnostic criteria. However, truly preemptive, individualized, and targeted chronic GVHD therapies currently do not exist. In this report, we (1) review current knowledge regarding clinical risk factors for chronic GVHD, (2) review what is known about chronic GVHD risk assignment biomarkers, (3) examine how chronic GVHD pathogenesis intersects with available targeted therapeutic agents, and (4) summarize considerations for preemptive therapy for chronic GVHD, emphasizing trial development, including trial design and statistical considerations. We conclude that robust risk assignment models that accurately predict chronic GVHD after HCT and early-phase preemptive therapy trials represent the most urgent priorities for advancing this novel area of research.

Inflammatory monocytes promote pre-engraftment syndrome and tocilizumab can therapeutically limit pathology in patients

Unrelated cord blood transplantation (UCBT) is an effective treatment for hematopoietic disorders. However, this attractive approach is frequently accompanied by pre-engraftment syndrome (PES), severe cases of PES are associated with enhanced mortality and morbidity, but the pathogenesis of PES remains unclear. Here we show that GM-CSF produced by cord blood-derived inflammatory monocytes drives PES pathology, and that monocytes are the main source of IL-6 during PES. Further, we report the outcome of a single arm, single-center clinical study of tocilizumab in the treatment of steroid-refractory severe PES patients (www.chictr.org.cn ChiCTR1800015472). The study met the primary outcome measure since none of the patients was nonrelapse death during the 100 days follow-up. The study also met key secondary outcomes measures of neutrophil engraftment and hematopoiesis. These findings offer a therapeutic strategy with which to tackle PES and improve nonrelapse mortality.

Pre-engraftment syndrome is a major consideration during clinical application of unrelated cord blood transfusion and monocytes represent a critical cell type in immune-pathogenesis. Here the authors further establish the role of monocytes and GM-CSF in pre-engraftment syndrome and show clinical administration of tocilizumab limits pathology in pre-engraftment syndrome pathology in patients.

Immune control of cytomegalovirus reactivation in stem cell transplantation

The reactivation of viruses from latency after allogeneic stem cell transplantation (SCT) continues to represent a major clinical challenge requiring sophisticated monitoring strategies in the context of prophylactic and/or pre-emptive antiviral drugs that are associated with significant expense, toxicity, and rates of failure. Accumulating evidence has demonstrated the association of polyfunctional virus-specific T-cells with protection from viral reactivation, affirmed by the ability of adoptively transferred virus-specific T-cells to prevent and treat reactivation and disease. The roles of innate cells (NK cells) in early viral surveillance, and dendritic cells in priming of T-cells have also been delineated. Most recently, a role for strain-specific humoral responses in preventing early cytomegalovirus (CMV) reactivation has been demonstrated in preclinical models. Despite these advances, many unknowns remain: what are the critical innate and adaptive responses over time, is the origin (e.g. recipient versus donor) and localization (e.g. in parenchymal tissue versus lymphoid organs) of these responses important, how does GVHD and the prevention/treatment thereof (e.g. high dose steroids) impact the functionality and relevance of a particular immune axis, do the immune parameters that control latency, reactivation and dissemination differ, and what is the impact of new antiviral drugs on the development of enduring antiviral immunity. Thus, whilst antiviral drugs have provided major improvements over the last two decades, understanding the immunological paradigms underpinning protective antiviral immunity after SCT offers the potential to generate non-toxic immune-based therapeutic approaches for lasting protection from viral reactivation.

Methods to Assess Disease Activity and Severity in Cutaneous Chronic Graft-versus-Host Disease: A Critical Literature Review

Chronic graft-versus-host disease (cGVHD), a potentially debilitating complication of hematopoietic cell transplantation, confers increased risk for mortality. Whereas treatment decisions rely on an accurate assessment of disease activity/severity, validated methods of assessing cutaneous cGVHD activity/severity appear to be limited. In this study, we aimed to identify and evaluate current data on the assessment of disease activity/severity in cutaneous cGVHD. Using modified PRISMA methods, we performed a critical literature review for relevant articles. Our literature search identified 1741 articles, of which 1635 were excluded as duplicates or failure to meet inclusion criteria. Of the included studies (n = 106), 39 (37%) addressed clinical and/or histopathologic parameters, 53 (50%) addressed serologic parameters, 8 (7.5%) addressed imaging parameters, and 6 (5.5%) addressed computer-based technologies. The only formally validated metric of disease activity/severity assessment in cutaneous cGVHD is the National Institutes of Health consensus scoring system, which is founded on clinical assessment alone. The lack of an objective marker for cGVHD necessitates further studies. An evaluation of the potential contributions of serologic, imaging, and/or computer-based technologies is warranted.

A phase 3 double-blind study of the addition of tocilizumab vs placebo to cyclosporin/methotrexate GVHD prophylaxis

We determined the efficacy of tocilizumab (TCZ) in preventing grade 2-4 acute graft-versus-host disease (aGVHD) in patients with acute leukemia or myelodysplasia undergoing matched sibling donor (MSD) or volunteer unrelated donor (VUD) allogeneic stem cell transplantation after myeloablative or reduced-intensity conditioning across 5 Australian centers. A total of 145 patients (50 MSD, 95 VUD) were randomly assigned to placebo or TCZ on day -1. All patients received T-cell-replete peripheral blood stem cell grafts and graft-versus-host disease (GVHD) prophylaxis with cyclosporin/methotrexate. A planned substudy analyzed the VUD cohort. With a median follow-up of 746 days, the incidence of grade 2-4 aGVHD at day 100 for the entire cohort was 36% for placebo vs 27% for TCZ (hazard ratio [HR], 0.69; 95% confidence interval [CI], 0.38-1.26; P = .23) and 45% vs 32% (HR, 0.61; 95% CI, 0.31-1.22; P = .16) for the VUD subgroup. The incidence of grade 2-4 aGVHD at day 180 for the entire cohort was 40% for placebo vs 29% for TCZ (HR, 0.68; 95% CI, 0.38-1.22; P = .19) and 48% vs 32% (HR, 0.59; 95% CI, 0.30-1.16; P = .13) for the VUD subgroup. Reductions in aGVHD were predominantly in grade 2 disease. For the entire cohort, transplant-related mortality occurred in 8% vs 11% of placebo-treated vs TCZ-treated patients, respectively (P = .56), and overall survival was 79% vs 71% (P = .27). Median day to neutrophil and platelet engraftment was delayed by 2 to 3 days in TCZ-treated patients, whereas liver toxicity and infectious complications were similar between groups. In this phase 3 randomized double-blind trial, TCZ showed nonsignificant trends toward reduced incidence of grade 2-4 aGVHD in recipients from HLA-matched VUDs but no improvements in long term-survival.

Positive Effects of Oral Antibiotic Administration in Murine Chronic Graft-Versus-Host Disease

Chronic graft-versus-host disease (cGVHD) is one of the most frequent complications experienced after allogeneic hematopoietic stem cell transplantation. Reportedly, dysbiosis and severe damage to the microbiome are also closely associated with GVHD. Herein, we aimed to elucidate the positive and negative effects of the administration of various antibiotics in a murine model of cGVHD. For allogeneic bone marrow transplantation (allo-BMT), bone marrow from B10.D2 mice were transplanted in BALB/c mice to induce cGVHD. The cGVHD mice were orally administered ampicillin, gentamicin (GM), fradiomycin, vancomycin, or the solvent vehicle (control group). Among the antibiotic-treated mice, the systemic cGVHD phenotypes and ocular cGVHD manifestations were suppressed significantly in GM-treated mice compared to that in control mice. Inflammatory cell infiltration and fibrosis in cGVHD-targeted organs were significantly attenuated in GM-treated mice. Although regulatory T cells were retained at greater levels in GM-treated mice, there were significantly fewer Th17 cells and interleukin (IL)-6-producing macrophages in cGVHD-targeted organs in these mice. Collectively, our results revealed that orally administered GM may exert positive effects in a cGVHD mouse model.

Highly pathogenic porcine reproductive and respiratory syndrome virus (HP-PRRSV) induces IL-6 production through TAK-1/JNK/AP-1 and TAK-1/NF-κB signaling pathways

Porcine reproductive and respiratory syndrome virus (PRRSV) mainly infects monocyte/macrophage lineage and regulates the production of cytokines to influence host immune responses. Interleukin-6 (IL-6) is originally identified as a B-cell stimulatory factor and has important functions in regulating immune response, hemopoiesis, and inflammation. In this study, we verified that highly pathogenic PRRSV (HP-PRRSV) infection up-regulated IL-6 production in vivo and in vitro. Subsequently, we demonstrated that HP-PRRSV infection activated JNK and NF-κB signaling pathways to enhance IL-6 expression. We further showed that TAK-1 was important in the activation of JNK and NF-κB pathways following HP-PRRSV infection. Moreover, AP-1 and NF-κB binding motifs were found in the cloned porcine IL-6 (pIL-6) promoter, and deletion of these motifs abrogated the activation of pIL-6 promoter by HP-PRRSV, suggesting that IL-6 expression is dependent on AP-1 and NF-κB activation. These findings imply that IL-6 induced by HP-PRRSV infection is dependent on the activation of TAK-1/JNK/AP-1 and TAK-1/NF-κB signaling pathways.

Cytokines that Modulate the Differentiation of Th17 Cells in Autoimmune Uveitis

Increasing evidence has suggested that T helper 17 (Th17) cells play a central role in the pathogenesis of ocular immune disease. The association between pathogenic Th17 cells and the development of uveitis has been confirmed in experimental and clinical studies. Several cytokines affect the initiation and stabilization of the differentiation of Th17 cells. Therefore, understanding the mechanism of related cytokines in the differentiation of Th17 cells is important for exploring the pathogenesis and the potential therapeutic targets of uveitis. This article briefly describes the structures, mechanisms, and targeted drugs of cytokines-including interleukin (IL)-6, transforming growth factor-β1 (TGF-β1), IL-1β, IL-23, IL-27, IL-35, IL-2, IL-4, IL-21, and interferon (IFN)-γ-which have an important influence on the differentiation of Th17 cells and discusses their potential as therapeutic targets for treating autoimmune uveitis.

How to Make an Immune System and a Foreign Host Quickly Cohabit in Peace? The Challenge of Acute Graft-Versus-Host Disease Prevention After Allogeneic Hematopoietic Cell Transplantation

Allogeneic hematopoietic cell transplantation (alloHCT) has been used as cellular immunotherapy against hematological cancers for more than six decades. Its therapeutic efficacy relies on the cytoreductive effects of the conditioning regimen but also on potent graft-versus-tumor (GVT) reactions mediated by donor-derived immune cells. However, beneficial GVT effects may be counterbalanced by acute GVHD (aGVHD), a systemic syndrome in which donor immune cells attack healthy tissues of the recipient, resulting in severe inflammatory lesions mainly of the skin, gut, and liver. Despite standard prophylaxis regimens, aGVHD still occurs in approximately 20–50% of alloHCT recipients and remains a leading cause of transplant-related mortality. Over the past two decades, advances in the understanding its pathophysiology have helped to redefine aGVHD reactions and clinical presentations as well as developing novel strategies to optimize its prevention. In this review, we provide a brief overview of current knowledge on aGVHD immunopathology and discuss current approaches and novel strategies being developed and evaluated in clinical trials for aGVHD prevention. Optimal prophylaxis of aGVHD would prevent the development of clinically significant aGVHD, while preserving sufficient immune responsiveness to maintain beneficial GVT effects and immune defenses against pathogens.

Cytokines and costimulation in acute graft-versus-host disease

Allogeneic hematopoietic stem cell transplantation (alloSCT) is an important curative therapy for high-risk hematological malignancies, but the development of severe and/or steroid-refractory acute graft-versus-host disease (aGVHD) remains a significant limitation to optimal outcomes. New approaches to prevent and treat aGVHD remain an unmet need that can be best addressed by understanding the complex disease pathophysiology. It is now clear that chemoradiotherapy used prior to alloSCT induces the release of endogenous alarmins (eg, HMGB-1, ATP, IL-1α, IL-33) from recipient tissue. Exogenous pathogen-derived molecules (eg, lipopolysaccharide, nucleic acids) also translocate from the gastrointestinal tract lumen. Together, these danger signals activate antigen-presenting cells (APCs) to efficiently present alloantigen to donor T cells while releasing cytokines (eg, interleukin-12 [IL-12], IL-23, IL-6, IL-27, IL-10, transforming growth factor-β) that expand and differentiate both pathogenic and regulatory donor T cells. Concurrent costimulatory signals at the APC-T-cell interface (eg, CD80/CD86-CD28, CD40-CD40L, OX40L-OX40, CD155/CD112-DNAM-1) and subsequent coinhibitory signals (eg, CD80/CD86-CTLA4, PDL1/2-PD1, CD155/CD112-TIGIT) are critical to the acquisition of effector T-cell function and ensuing secretion of pathogenic cytokines (eg, IL-17, interferon-γ, tissue necrosis factor, granulocyte-macrophage colony-stimulating factor) and cytolytic degranulation pathway effectors (eg, perforin/granzyme). This review focuses on the combination of cytokine and costimulatory networks at the T-cell surface that culminates in effector function and subsequent aGVHD in target tissue. Together, these pathways now represent robust and clinically tractable targets for preventing the initiation of deleterious immunity after alloSCT.

Bendamustine with total body irradiation conditioning yields tolerant T-cells while preserving T-cell-dependent graft-versus-leukemia

Graft-versus-host disease (GvHD) remains a significant impediment to allogeneic hematopoietic cell transplantation (HCT) success, necessitating studies focused on alleviating GvHD, while preserving the graft-versus-leukemia (GvL) effect. Based on our previous studies showing bendamustine with total body irradiation (BEN-TBI) conditioning reduces GvHD compared to the current clinical standard of care cyclophosphamide (CY)-TBI in a murine MHC-mismatched bone marrow transplantation (BMT) model, this study aimed to evaluate the role and fate of donor T-cells following BEN-TBI conditioning. We demonstrate that BEN-TBI reduces GvHD compared to CY-TBI independently of T regulatory cells (Tregs). BEN-TBI conditioned mice have a smaller proportion and less activated donor T-cells, with lower CD47 expression, early post-transplant, but no sustained phenotypic differences in T-cells. In BEN-TBI conditioned mice, donor T-cells gain tolerance specific to host MHC antigens. Though these T-cells are tolerant to host antigens, we demonstrate that BEN-TBI preserves a T-cell-dependent GvL effect. These findings indicate that BEN-TBI conditioning reduces GvHD without compromising GvL, warranting its further investigation as a potentially safer and more efficacious clinical alternative to CY-TBI.

Immune Monitoring After Allogeneic Hematopoietic Cell Transplantation: Toward Practical Guidelines and Standardization

Hematopoietic cell transplantation (HCT) is often a last resort, but potentially curative treatment option for children suffering from hematological malignancies and a variety of non-malignant disorders, such as bone marrow failure, inborn metabolic disease or immune deficiencies. Although efficacy and safety of the HCT procedure has increased significantly over the last decades, the majority of the patients still suffer from severe acute toxicity, viral reactivation, acute or chronic graft-versus-host disease (GvHD) and/or, in case of malignant disease, relapses. Factors influencing HCT outcomes are numerous and versatile. For example, there is variation in the selected graft sources, type of infused cell subsets, cell doses, and the protocols used for conditioning, as well as immune suppression and treatment of adverse events. Moreover, recent pharmacokinetic studies show that medications used in the conditioning regimen (e.g., busulphan, fludarabine, anti-thymocyte globulin) should be dosed patient-specific to achieve optimal exposure in every individual patient. Due to this multitude of variables and site-specific policies/preferences, harmonization between HCT centers is still difficult to achieve. Literature shows that adequate immune recovery post-HCT limits both relapse and non-relapse mortality (death due to viral reactivations and GvHD). Monitoring immune parameters post-HCT may facilitate a timely prediction of outcome. The use of standardized assays to measure immune parameters would facilitate a fast comparison between different strategies tested in different centers or between different clinical trials. We here discuss immune cell markers that may contribute to clinical decision making and may be worth to standardize in multicenter collaborations for future trials.