Addition of interleukin-6 inhibition with tocilizumab to standard graft-versus-host disease prophylaxis after allogeneic stem-cell transplantation: a phase 1/2 trial

Possible involvement of IL-6-producing tissue-resident macrophages in early-onset pericardial effusion pathogenesis after hematopoietic stem cell transplantation

PURPOSE

Pericardial effusion (PE) is a potentially life-threatening complication following hematopoietic stem cell transplantation (HCT). A higher incidence of early-onset PE, unrelated to graft-versus-host disease, before day 100 after HCT has been reported in pediatric patients, but the pathogenic mechanism is poorly understood. Aiming to determine the pathogenesis of early-onset PE in pediatric patients, we analyzed the cytokine concentration and cell population in the pericardial fluid of four pediatric patients with PE.

METHODS

Between January 2009 and December 2015, four patients requiring pericardiocentesis for clinically significant PE were identified in 60 patients. We evaluated the interleukin-6 (IL-6), interferon-γ, IL-1β, and tumor necrosis factor-α levels in PE. Two patients were available for analysis with intracellular cytokine flow cytometry and a chimerism assay.

RESULTS

All patients showed the accumulation of pericardial macrophages and high concentrations of IL-6 in PE. Notably, the accumulated pericardial macrophages were CD163⁺ CD15⁺ CD14⁺ cells of host origin that produced IL-6.

CONCLUSION

These IL-6-producing tissue-resident macrophages may be key players in the pathogenesis of early-onset PE.

Tocilizumab for the treatment of severe steroid-refractory acute graft-versus-host disease of the lower gastrointestinal tract

Steroid-refractory (SR) acute gastrointestinal (GI) graft-versus-host disease (GVHD) is associated with significant mortality in allogeneic hematopoietic cell transplantation recipients. We retrospectively evaluated the efficacy of tocilizumab for the treatment of SR biopsy-proven acute lower GI GVHD in 16 consecutive adult transplant recipients between October 2015 and July 2016. Tocilizumab 8 mg/kg was administered every 2 weeks until achievement of complete response, defined as resolution of all manifestations of GI GVHD, or until patients had progression or initiation of other therapy. Ten of 16 patients (62.5%; 95% CI, 0.39-82) achieved a complete response after a median time of 11 days (range, 2-28 days) from tocilizumab initiation. The median time to response onset (improvement in stage by at least 1) was 1 day (range, 1-4 days). Tocilizumab was administered at a median of 9 days (range, 3-75 days) from GVHD diagnosis and 10 days (range, 3-75 days) from initiation of high-dose steroids. At a median follow-up of 7.6 months (range, 0.8-27.7 months) from initiation of tocilizumab, 6/16 (37.5%) patients are alive and free of their underlying hematologic malignancy. Tocilizumab appears to be a highly active agent for the treatment of severe SR lower GI acute GVHD.

Immune regulatory cell infusion for graft-versus-host disease prevention and therapy

Current approaches to prevent and treat graft-versus-host disease (GVHD) after stem cell transplantation rely principally on pharmacological immune suppression. Such approaches are limited by drug toxicity, nonspecific immune suppression, and a requirement for long-term therapy. Our increased understanding of the regulatory cells and molecular pathways involved in limiting pathogenic immune responses opens the opportunity for the use of these cell subsets to prevent and/or GVHD. The theoretical advantages of this approach is permanency of effect, potential for facilitating tissue repair, and induction of tolerance that obviates a need for ongoing drug therapy. To date, a number of potential cell subsets have been identified, including FoxP3⁺ regulatory T (Treg) and FoxP3^negIL-10⁺ (FoxP3-negative) regulatory T (Tr1), natural killer (NK) and natural killer T (NKT) cells, innate lymphoid cells, and various myeloid suppressor populations of hematopoietic (eg, myeloid derived suppressor cells) and stromal origin (eg, mesenchymal stem cells). Despite initial technical challenges relating to large-scale selection and expansion, these regulatory lineages are now undergoing early phase clinical testing. To date, Treg therapies have shown promising results in preventing clinical GVHD when infused early after transplant. Results from ongoing studies over the next 5 years will delineate the most appropriate cell lineage, source (donor, host, third party), timing, and potential exogenous cytokine support needed to achieve the goal of clinical transplant tolerance.

Biomarkers for posttransplantation outcomes

During the last decade, the development of biomarkers for the complications seen after allogeneic hematopoietic stem cell transplantation has expanded tremendously, with the most progress having been made for acute graft-versus-host disease (aGVHD), a common and often fatal complication. Although many factors are known to determine transplant outcome (including the age of the recipient, comorbidity, conditioning intensity, donor source, donor-recipient HLA compatibility, conditioning regimen, posttransplant GVHD prophylaxis), they are incomplete guides for predicting outcomes. Thanks to the advances in genomics, transcriptomics, proteomics, and cytomics technologies, blood biomarkers have been identified and validated for us in promising diagnostic tests, prognostic tests stratifying for future occurrence of aGVHD, and predictive tests for responsiveness to GVHD therapy and nonrelapse mortality. These biomarkers may facilitate timely and selective therapeutic intervention. However, such blood tests are not yet available for routine clinical care. This article provides an overview of the candidate biomarkers for clinical evaluation and outlines a path from biomarker discovery to first clinical correlation, to validation in independent cohorts, to a biomarker-based clinical trial, and finally to general clinical application. This article focuses on biomarkers discovered with a large-scale proteomics platform and validated with the same reproducible assay in at least 2 independent cohorts with sufficient sample size according to the 2014 National Institutes of Health consensus on biomarker criteria, as well as on biomarkers as tests for risk stratification of outcomes, but not on their pathophysiologic contributions, which have been reviewed recently.

A critical role for donor-derived IL-22 in cutaneous chronic GVHD

Graft-versus-host disease (GVHD) is the major cause of nonrelapse morbidity and mortality after allogeneic stem cell transplantation (allo-SCT). Prevention and treatment of GVHD remain inadequate and commonly lead to end-organ dysfunction and opportunistic infection. The role of interleukin (IL)-17 and IL-22 in GVHD remains uncertain, due to an apparent lack of lineage fidelity and variable and contextually determined protective and pathogenic effects. We demonstrate that donor T cell-derived IL-22 significantly exacerbates cutaneous chronic GVHD and that IL-22 is produced by highly inflammatory donor CD4+ T cells posttransplantation. IL-22 and IL-17A derive from both independent and overlapping lineages, defined as T helper (Th)22 and IL-22+ Th17 cells. Donor Th22 and IL-22+ Th17 cells share a similar IL-6-dependent developmental pathway, and while Th22 cells arise independently of the IL-22+ Th17 lineage, IL-17 signaling to donor Th22 directly promotes their development in allo-SCT. Importantly, while both IL-22 and IL-17 mediate skin GVHD, Th17-induced chronic GVHD can be attenuated by IL-22 inhibition in preclinical systems. In the clinic, high levels of both IL-17A and IL-22 expression are present in the skin of patients with GVHD after allo-SCT. Together, these data demonstrate a key role for donor-derived IL-22 in patients with chronic skin GVHD and confirm parallel but symbiotic developmental pathways of Th22 and Th17 differentiation.

A pilot study of single nucleotide polymorphisms in the interleukin-6 receptor and their effects on pre- and post-transplant serum mediator level and outcome after allogeneic stem cell transplantation

Interleukin (IL)-6 is an important regulator of immunity and inflammation in many diseases. Single nucleotide polymorphisms (SNPs) in the IL-6 gene influence outcome after allogeneic stem cell transplantation (ASCT), but the possible importance of SNPs in the IL-6 receptor has not been examined. We therefore investigated whether SNPs in the IL-6R gene influenced biochemical characteristics and clinical outcomes after ASCT. We examined the IL-6 promoter variant rs1800975 and the IL-6R SNPs rs4453032, rs2228145, rs4129267, rs4845374, rs4329505, rs4845617, rs12083537, rs4845618, rs6698040 and rs4379670 in a 101 population-based cohort of allotransplant recipients and their family donors. Patients being homozygous for the major alleles of the IL-6R SNPs rs2228145 and rs4845618 showed high pretransplant CRP serum levels together with decreased sIL-6R levels; the decreased IL-6R levels persisted 6 months post-transplant. In contrast, patients being homozygous for the minor allele of the IL-6R SNP rs4379670 showed decreased pretransplant CRP levels. Furthermore, the IL-6R rs4845618 donor genotype showed an association with severe acute graft-versus-host disease (GVHD), whereas the donor genotype of the IL-6 SNP rs1800795 was associated with decreased survival 100 days post-transplant. Finally, the recipient genotype of the IL-6R SNP rs4329505 showed a strong association with 2-years non-relapse mortality, and this effect was also highly significant in multivariate analysis. IL-6 and IL-6R SNPs influence the clinical outcome after allogeneic stem cell transplantation.

In vivo IL-12/IL-23p40 neutralization blocks Th1/Th17 response after allogeneic hematopoietic cell transplantation

T-helper 1 and T-helper 17 lymphocytes mediate acute graft-versus-host disease (GvHD). Interleukin 12 is critical for T-helper 1 differentiation and interleukin 23 for T-helper 17 maintenance. Interleukin 12 and 23 are heterodimeric cytokines that share the p40 subunit (IL-12/IL-23p40). In a randomized, blinded, placebo-controlled trial, we examined the biological impact and clinical outcomes following IL-12/IL-23p40 neutralization using ustekinumab. Thirty patients received peripheral blood mobilized hematopoietic cell transplantation (HCT) from HLA-matched sibling or unrelated donors, received sirolimus plus tacrolimus as GvHD prophylaxis, and were randomized to ustekinumab versus placebo with 1:1 allocation after stratification by donor type. The primary end point of the trial was the mean percentage (%) T-regulatory (Treg) cells on day 30 post HCT. Ustekinumab was delivered by subcutaneous injection on day -1 and day +20 after transplantation. On day 30 post transplant, no significant difference in % Treg was observed. Ustekinumab suppressed serum IL-12/IL-23p40 levels. Host-reactive donor alloresponse at days 30 and 90 after transplantation was polarized with significant reduction in IL-17 and IFN-α production and increase in IL-4. No toxicity attributed to ustekinumab was observed. Overall survival and National Institute of Health moderate/severe chronic GvHD-free, relapse-free survival were significantly improved among ustekinumab-treated patients. No significant improvements were observed in acute or chronic GvHD, relapse, or non-relapse mortality. These data provide first evidence that IL-12/IL-23p40 neutralization can polarize donor anti-host alloresponse in vivo and provide initial clinical efficacy evidence to be tested in subsequent trials. (Trial registered at clinicaltrials.gov identifier: 01713400).

The microRNA miR-33a suppresses IL-6-induced tumor progression by binding Twist in gallbladder cancer

Cytokine is a key molecular link between chronic inflammation and gallbladder cancer (GBC) progression. The potential mechanism of cytokine-associated modulation of microRNAs (miRNAs) expression in GBC progression is not fully understood. In this study, we investigated the biological effects and prognostic significance of interleukin-6 (IL-6) -induced miRNAs in the development of GBC. We identify that inflammatory cytokine, IL-6 promotes proliferation, migration, invasion and epithelial-mesenchymal transition (EMT) of GBC both in vitro and in vivo. Among all the changed miRNAs in miRNA profiling, miR-33a expression was significantly decreased in IL-6 treated GBC cell lines, as well as in GBC tissues compared with case-matched normal tissues and cholecystitis tissues. In turn, miR-33a suppresses IL-6-induced tumor metastasis by directly binding Twist which was identified as an EMT marker. High expression of miR-33a suppressed xenograft tumor growth and dissemination in nude mice. The downregulation of miR-33a was closely associated with advanced clinical stage, lymph node metastasis, and poor clinical outcomes in patients with GBC. miR-33a acts as a tumor suppressor miRNA in GBC progression and may be considered for the development of potential therapeutics against GBC.

Effects of MicroRNA on Regulatory T Cells and Implications for Adoptive Cellular Therapy to Ameliorate Graft-versus-Host Disease

Regulatory T cells (Tregs) are key mediators of the immune system. MicroRNAs (miRNAs) are a family of ~22 nucleotide non-coding RNAs that are processed from longer precursors by the RNases Drosha and Dicer. miRNA regulates protein expression posttranscriptionally through mRNA destabilization or translational silencing. A critical role for miRNA in Treg function was initially discovered when both Dicer and Drosha knockout (KO) mice were found to develop a fatal autoimmune disease phenotypically similar to Foxp3 KO mice.

Targeting JAK2 reduces GVHD and xenograft rejection through regulation of T cell differentiation

Janus kinase 2 (JAK2) signal transduction is a critical mediator of the immune response. JAK2 is implicated in the onset of graft-versus-host disease (GVHD), which is a significant cause of transplant-related mortality after allogeneic hematopoietic cell transplantation (allo-HCT). Transfer of JAK2^-/- donor T cells to allogeneic recipients leads to attenuated GVHD yet maintains graft-versus-leukemia. Th1 differentiation among JAK2^-/- T cells is significantly decreased compared with wild-type controls. Conversely, iTreg and Th2 polarization is significantly increased among JAK2^-/- T cells. Pacritinib is a multikinase inhibitor with potent activity against JAK2. Pacritinib significantly reduces GVHD and xenogeneic skin graft rejection in distinct rodent models and maintains donor antitumor immunity. Moreover, pacritinib spares iTregs and polarizes Th2 responses as observed among JAK2^-/- T cells. Collectively, these data clearly identify JAK2 as a therapeutic target to control donor alloreactivity and promote iTreg responses after allo-HCT or solid organ transplantation. As such, a phase I/II acute GVHD prevention trial combining pacritinib with standard immune suppression after allo-HCT is actively being investigated (https://clinicaltrials.gov/ct2/show/NCT02891603).

Tocilizumab, tacrolimus and methotrexate for the prevention of acute graft-versus-host disease: low incidence of lower gastrointestinal tract disease

We conducted a phase 2 study in which patients undergoing allogeneic hematopoietic stem cell transplantation received tocilizumab in addition to standard immune suppression with tacrolimus and methotrexate for graft-versus-host disease prophylaxis. Thirty-five patients were enrolled between January 2015 and June 2016. The median age of the cohort was 66 (range: 22-76). All patients received busulfan-based conditioning, and were transplanted with human leukocyte antigen-matched related or matched unrelated bone marrow or peripheral stem cell grafts. The cumulative incidences of grades II-IV and III-IV acute graft-versus-host disease were 14% (95% CI 5-30) and 3% (95% CI 0-11) at day 100, and 17% (95% CI 7-31) and 6% (95% CI 1-16) at day 180, respectively. Notably, there were no cases of graft-versus-host disease of the lower gastrointestinal tract within the first 100 days. A comparison to 130 matched controls who only received tacrolimus and methotrexate demonstrated a lower cumulative incidence of grades II-IV acute graft-versus-host disease (17% versus 45%, P=0.003) and a significant increase in grades II-IV acute graft-versus-host disease-free survival at six months (69% versus 42%, P=0.001) with tocilizumab, tacrolimus and methotrexate, which was the primary endpoint of the study. Immune reconstitution was preserved in patients treated with tocilizumab, tacrolimus and methotrexate, as T-cell and B-cell subsets recovered to near normal levels by 6-12 months post-transplantation. We conclude that tocilizumab has promising activity in preventing acute graft-versus-host disease, particularly in the lower gastrointestinal tract, and warrants examination in a randomized setting.

Targeting Aurora kinase A and JAK2 prevents GVHD while maintaining Treg and antitumor CTL function

Graft-versus-host disease (GVHD) is a leading cause of nonrelapse mortality after allogeneic hematopoietic cell transplantation. T cell costimulation by CD28 contributes to GVHD, but prevention is incomplete when targeting CD28, downstream mammalian target of rapamycin (mTOR), or Aurora A. Likewise, interleukin-6 (IL-6)-mediated Janus kinase 2 (JAK2) signaling promotes alloreactivity, yet JAK2 inhibition does not eliminate GVHD. We provide evidence that blocking Aurora A and JAK2 in human T cells is synergistic in vitro, prevents xenogeneic GVHD, and maintains antitumor responses by cytotoxic T lymphocytes (CTLs). Aurora A/JAK2 inhibition is immunosuppressive but permits the differentiation of inducible regulatory T cells (iT_regs) that are hyperfunctional and CD39 bright and efficiently scavenge adenosine triphosphate (ATP). Increased iT_reg potency is primarily a function of Aurora A blockade, whereas JAK2 inhibition suppresses T helper 17 (T_H17) differentiation. Inhibiting either Aurora A or JAK2 significantly suppresses T_H1 T cells. However, CTL generated in vivo retains tumor-specific killing despite Aurora A/JAK2 blockade. Thus, inhibiting CD28 and IL-6 signal transduction pathways in donor T cells can increase the T_reg/T_conv ratio, prevent GVHD, and preserve antitumor CTL.

Transplantation Tolerance through Hematopoietic Chimerism: Progress and Challenges for Clinical Translation

The perception that transplantation of hematopoietic stem cells can confer tolerance to any tissue or organ from the same donor is widely accepted but it has not yet become a treatment option in clinical routine. The reasons for this are multifaceted but can generally be classified into safety and efficacy concerns that also became evident from the results of the first clinical pilot trials. In comparison to standard immunosuppressive therapies, the infection risk associated with the cytotoxic pre-conditioning necessary to allow allogeneic bone marrow engraftment and the risk of developing graft-vs.-host disease (GVHD) constitute the most prohibitive hurdles. However, several approaches have recently been developed at the experimental level to reduce or even overcome the necessity for cytoreductive conditioning, such as costimulation blockade, pro-apoptotic drugs, or Treg therapy. But even in the absence of any hazardous pretreatment, the recipients are exposed to the risk of developing GVHD as long as non-tolerant donor T cells are present. Total lymphoid irradiation and enriching the stem cell graft with facilitating cells emerged as potential strategies to reduce this peril. On the other hand, the long-lasting survival of kidney allografts, seen with transient chimerism in some clinical series, questions the need for durable chimerism for robust tolerance. From a safety point of view, loss of chimerism would indeed be favorable as it eliminates the risk of GVHD, but also complicates the assessment of tolerance. Therefore, other biomarkers are warranted to monitor tolerance and to identify those patients who can safely be weaned off immunosuppression. In addition to these safety concerns, the limited efficacy of the current pilot trials with approximately 40-60% patients becoming tolerant remains an important issue that needs to be resolved. Overall, the road ahead to clinical routine may still be rocky but the first successful long-term patients and progress in pre-clinical research provide encouraging evidence that deliberately inducing tolerance through hematopoietic chimerism might eventually make it from dream to reality.

Interleukin-6 Inhibition in Inflammatory Diseases: Results Achieved and Tasks to Accomplish

Interleukin-6 (IL-6) is a prototypical cytokine featuring functional pleiotropy and redundancy. Under situations of stress, such as infection or tissue injury, IL-6 is rapidly synthesized and plays a major role in host defense. However, uncontrolled excessive or persistent production of IL-6 has a pathological effect in various diseases. Thus, IL-6 blockade was expected to become a novel therapeutic strategy for IL-6–mediated inflammatory diseases, and the first-in-class IL-6 inhibitor tocilizumab, which blocks IL-6 activity by inhibiting IL-6 binding to its receptor, was developed. Clinical trials of tocilizumab have verified its efficacy and tolerable safety profile in several diseases, and it has been approved for the treatment of patients with rheumatoid arthritis, Castleman's disease, systemic and polyarticular juvenile idiopathic arthritis, and giant cell arteritis. Off-label use and clinical trials strongly indicate that tocilizumab will be applicable for a wide variety of acute and chronic inflammatory diseases.

Vorinostat plus tacrolimus/methotrexate to prevent GVHD after myeloablative conditioning, unrelated donor HCT

The oral histone deacetylase (HDAC) inhibitor (vorinostat) is safe and results in low incidence of acute graft-versus-host disease (GVHD) after reduced-intensity conditioning, related donor hematopoietic cell transplantation (HCT). However, its safety and efficacy in preventing acute GVHD in settings of heightened clinical risk that use myeloablative conditioning, unrelated donor (URD), and methotrexate are not known. We conducted a prospective, phase 2 study in this higher-risk setting. We enrolled 37 patients to provide 80% power to detect a significant difference in grade 2 to 4 acute GVHD of 50% compared with a reduction in target to 28%. Eligibility included adults with a hematological malignancy to receive myeloablative HCT from an available 8/8-HLA matched URD. Patients received GVHD prophylaxis with tacrolimus and methotrexate. Vorinostat (100 mg twice daily) was started on day -10 and continued through day +100 post-HCT. Median age was 56 years (range, 18-69 years), and 95% had acute myelogenous leukemia or high-risk myelodysplastic syndrome. Vorinostat was safe and tolerable. The cumulative incidence of grade 2 to 4 acute GVHD at day 100 was 22%, and for grade 3 to 4 it was 8%. The cumulative incidence of chronic GVHD was 29%; relapse, nonrelapse mortality, GVHD-free relapse-free survival, and overall survival at 1 year were 19%, 16%, 47%, and 76%, respectively. Correlative analyses showed enhanced histone (H3) acetylation in peripheral blood mononuclear cells and reduced interleukin 6 (P = .028) and GVHD biomarkers (Reg3, P = .041; ST2, P = .002) at day 30 post-HCT in vorinostat-treated subjects compared with similarly treated patients who did not receive vorinostat. Vorinostat for GVHD prevention is an effective strategy that should be confirmed in a randomized phase 3 study. This trial was registered at www.clinicaltrials.gov as #NCT01790568.

Role of the intestinal mucosa in acute gastrointestinal GVHD

Intestinal graft-versus-host disease (GVHD) remains a significant obstacle to the success of allogeneic hematopoietic cell transplantation. The intestinal mucosa comprises the inner lining of the intestinal tract and maintains close proximity with commensal microbes that reside within the intestinal lumen. Recent advances have significantly improved our understanding of the interactions between the intestinal mucosa and the enteric microbiota. Changes in host mucosal tissue and commensals posttransplant have been actively investigated, and provocative insights into mucosal immunity and the enteric microbiota are now being translated into clinical trials of novel approaches for preventing and treating acute GVHD. In this review, we summarize recent findings related to aspects of the intestinal mucosa during acute GVHD.

Host interleukin 6 production regulates inflammation but not tryptophan metabolism in the brain during murine GVHD

Graft-versus-host disease (GVHD) induces pathological damage in peripheral target organs leading to well-characterized, organ-specific clinical manifestations. Patients with GVHD, however, can also have behavioral alterations that affect overall cognitive function, but the extent to which GVHD alters inflammatory and biochemical pathways in the brain remain poorly understood. In the current study, we employed complementary murine GVHD models to demonstrate that alloreactive donor T cells accumulate in the brain and affect a proinflammatory cytokine milieu that is associated with specific behavioral abnormalities. Host IL-6 was identified as a pivotal cytokine mediator, as was host indoleamine 2,3-dioxygenase (IDO-1), which was upregulated in GVHD in an IL-6-dependent manner in microglial cells and was accompanied by dysregulated tryptophan metabolism in the dorsal raphe nucleus and prefrontal cortex. Blockade of the IL-6 signaling pathway significantly reduced donor T cell accumulation, inflammatory cytokine gene expression, and host microglial cell expansion, but did not reverse GVHD-induced tryptophan metabolite dysregulation. Thus, these results indicate that inhibition of IL-6 signaling attenuates neuroinflammation, but does not reverse all of the metabolic abnormalities in the brain during GVHD, which may also have implications for the treatment of neurotoxicity occurring after other T cell-based immune therapies with IL-6-directed approaches.

Anti-Interleukin-6 Promotes Allogeneic Bone Marrow Engraftment and Prolonged Graft Survival in an Irradiation-Free Murine Transplant Model

Transfer of recipient regulatory T cells (Tregs) induces mixed chimerism and tolerance in an irradiation-free bone marrow (BM) transplantation (BMT) model involving short-course co-stimulation blockade and mTOR inhibition. Boosting endogenous Tregs pharmacologically in vivo would be an attractive alternative avoiding the current limitations of performing adoptive cell therapy in the routine clinical setting. Interleukin-6 (IL-6) potently inhibits Treg differentiation and its blockade was shown to increase Treg numbers in vivo. Therefore, we investigated whether IL-6 blockade can replace adoptive Treg transfer in irradiation-free allogeneic BMT. Treatment with anti-IL-6 instead of Treg transfer led to multi-lineage chimerism (persisting for ~12 weeks) in recipients of fully mismatched BM and significantly prolonged donor skin (MST 58 days) and heart (MST > 100 days) graft survival. Endogenous Foxp3⁺ Tregs expanded in anti-IL-6-treated BMT recipients, while dendritic cell (DC) activation and memory CD8⁺ T cell development were inhibited. Adding anti-IL-17 to anti-IL-6 treatment increased Treg frequencies, but did not further prolong donor skin graft survival significantly. These results demonstrate that IL-6 blockade promotes BM engraftment and donor graft survival in non-irradiated recipients and might provide an alternative to Treg cell therapy in the clinical setting.

Infectious pathogens may trigger specific allo-HLA reactivity via multiple mechanisms

Transplant recipients can be sensitized against allo-HLA antigens by previous transplantation, blood transfusion, or pregnancy. While there is growing awareness that multiple components of the immune system can act as effectors of the alloresponse, the role of infectious pathogen exposure in triggering sensitization and allograft rejection has remained a matter of much debate. Here, we describe that exposure to pathogens may enhance the immune response to allogeneic HLA antigens via different pathways. The potential role of allo-HLA cross-reactivity of virus-specific memory T cells, activation of innate immunity leading to a more efficient induction of the adaptive alloimmune response by antigen-presenting cells, and bystander activation of existing memory B cell activation will be discussed in this review.

Psoriasiform graft-versus-host disease distributed along Blaschko's lines

This case presents an unusual manifestation of cutaneous chronic graft-vs-host disease (cGVHD) mimicking psoriasis along Blaschko's lines. Such a presentation may pose a particular challenge to providers as it is quite rarely reported, and, therefore, it is possibly misdiagnosed. cGVHD may mimic psoriasis and should be considered in any patient previously transplanted even with a previous history of psoriasis. A Blaschkoid pattern of cGVHD is unusual and may be the manifestation of an immune reaction unveiling a previously masked mosaicism.

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.

Interleukin-6 in Allogeneic Stem Cell Transplantation: Its Possible Importance for Immunoregulation and As a Therapeutic Target

Allogeneic stem cell transplantation is associated with a high risk of treatment-related mortality mainly caused by infections and graft-versus-host disease (GVHD). GVHD is characterized by severe immune dysregulation and impaired regeneration of different tissues, i.e., epithelial barriers and the liver. The balance between pro- and anti-inflammatory cytokine influences the risk of GVHD. Interleukin-6 (IL-6) is a cytokine that previously has been associated with pro-inflammatory effects. However, more recent evidence from various autoimmune diseases (e.g., inflammatory bowel disease, rheumatoid arthritis) has shown that the IL-6 activity is more complex with important effects also on tissue homeostasis, regeneration, and metabolism. This review summarizes the current understanding of how pro-inflammatory IL-6 effects exerted during the peritransplant period shapes T-cell polarization with enhancement of Th17 differentiation and suppression of regulatory T cells, and in addition we also review and discuss the results from trials exploring non-selective IL-6 inhibition in prophylaxis and treatment of GVHD. Emerging evidence suggests that the molecular strategy for targeting of IL-6-initiated intracellular signaling is important for the effect on GVHD. It will therefore be important to further characterize the role of IL-6 in the pathogenesis of GVHD to clarify whether combined IL-6 inhibition of both trans- (i.e., binding of the soluble IL-6/IL-6 receptor complex to cell surface gp130) and cis-signaling (i.e., IL-6 ligation of the IL-6 receptor/gp130 complex) or selective inhibition of trans-signaling should be tried in the prophylaxis and/or treatment of GVHD in allotransplant patients.

Altered homeostatic regulation of innate and adaptive immunity in lower gastrointestinal tract GVHD pathogenesis

Lower gastrointestinal (GI) tract graft-versus-host disease (GVHD) is the predominant cause of morbidity and mortality from GVHD after allogeneic stem cell transplantation. Recent data indicate that lower GI tract GVHD is a complicated process mediated by donor/host antigenic disparities. This process is exacerbated by significant changes to the microbiome, and innate and adaptive immune responses that are critical to the induction of disease, persistence of inflammation, and a lack of response to therapy. Here, we discuss new insights into the biology of lower GI tract GVHD and focus on intrinsic pathways and regulatory mechanisms crucial to normal intestinal function. We then describe multiple instances in which these homeostatic mechanisms are altered by donor T cells or conditioning therapy, resulting in exacerbation of GVHD. We also discuss data suggesting that some of these mechanisms produce biomarkers that could be informative as to the severity of GVHD and its response to therapy. Finally, novel therapies that might restore homeostasis in the GI tract during GVHD are highlighted.

Interleukin-6, A Cytokine Critical to Mediation of Inflammation, Autoimmunity and Allograft Rejection: Therapeutic Implications of IL-6 Receptor Blockade

The success of kidney transplants is limited by the lack of robust improvements in long-term survival. It is now recognized that alloimmune responses are responsible for the majority of allograft failures. Development of novel therapies to decrease allosensitization is critical. The lack of new drug development in kidney transplantation necessitated repurposing drugs initially developed in oncology and autoimmunity. Among these is tocilizumab (anti-IL-6 receptor [IL-6R]) which holds promise for modulating multiple immune pathways responsible for allograft injury and loss. Interleukin-6 is a cytokine critical to proinflammatory and immune regulatory cascades. Emerging data have identified important roles for IL-6 in innate immune responses and adaptive immunity. Excessive IL-6 production is associated with activation of T-helper 17 cell and inhibition of regulatory T cell with attendant inflammation. Plasmablast production of IL-6 is critical for initiation of T follicular helper cells and production of high-affinity IgG. Tocilizumab is the first-in-class drug developed to treat diseases mediated by IL-6. Data are emerging from animal and human studies indicating a critical role for IL-6 in mediation of cell-mediated rejection, antibody-mediated rejection, and chronic allograft vasculopathy. This suggests that anti-IL-6/IL-6R blockade could be effective in modifying T- and B-cell responses to allografts. Initial data from our group suggest anti-IL-6R therapy is of value in desensitization and prevention and treatment of antibody-mediated rejection. In addition, human trials have shown benefits in treatment of graft versus host disease in matched or mismatched stem cell transplants. Here, we explore the biology of IL-6/IL-6R interactions and the evidence for an important role of IL-6 in mediating allograft rejection.

Eomesodermin promotes the development of type 1 regulatory T (TR1) cells

Type 1 regulatory T (T_R1) cells are Foxp3^- interleukin-10 (IL-10)-producing CD4⁺ T cells with potent immunosuppressive properties, but their requirements for lineage development have remained elusive. We show that T_R1 cells constitute the most abundant regulatory population after allogeneic bone marrow transplantation (BMT), express the transcription factor Eomesodermin (Eomes), and are critical for the prevention of graft-versus-host disease. We demonstrate that Eomes is required for T_R1 cell differentiation, during which it acts in concert with the transcription factor B lymphocyte-induced maturation protein-1 (Blimp-1) by transcriptionally activating IL-10 expression and repressing differentiation into other T helper cell lineages. We further show that Eomes induction in T_R1 cells requires T-bet and donor macrophage-derived IL-27. Thus, we define the cellular and transcriptional control of T_R1 cell differentiation during BMT, opening new avenues to therapeutic manipulation.

Citrulline and Monocyte-Derived Macrophage Reactivity before Conditioning Predict Acute Graft-versus-Host Disease

During conditioning, intestinal damage induces microbial translocation which primes macrophage reactivity and leads to donor-derived T cell stimulation. Little is known about the role of intestinal health and macrophage reactivity before conditioning in the development of acute graft-versus-host disease (aGVHD) in patients undergoing allogeneic hematopoietic cell transplantation (allo-HCT). We assessed (1) citrulline, a surrogate marker of functional enterocyte mass and (2) circulating monocyte-derived macrophage reactivity, before allo-HCT. Forty-seven consecutive patients were prospectively included. Citrulline levels from blood samples withdrawn 30 days before transplantation were assessed using liquid chromatography combined with mass spectrometry. Monocyte-derived macrophages were isolated and incubated with 5 pathogen-associated molecular patterns: lipopolysaccharide, PamCSK4, flagellin, muramyl dipeptide, and curdlan. Multiplex fluorescent immunoassay on culture supernatant assessed levels of TNF-α, IL-1β, IL-6, and IL-10 in each condition. Citrulline and cytokine levels were analyzed relatively to aGVHD onset within 100 days after transplantation. Citrulline levels were lower in the aGVHD group (n = 20) than in the no-aGVHD group (n = 27) (P = .005). Conversely, IL-6 and IL-10 were greater in aGVHD group, especially after curdlan stimulation (P = .005 and P = .012). Citrulline levels ≤20 µmol/L, IL-6 ≥ 332 pg/mL, and IL-10 ≥ 90 pg/mL were associated with aGVHD development (log-rank test, P = .002, P = .041, and P < .0001, respectively). In multivariate analysis, IL-10 ≥ 90 pg/mL, myeloablative conditioning, and citrulline ≤20 µmol/L remained independent factors of aGVHD development (hazard ratio [HR],  8.18, P = .0003; HR, 4.28, P = .006; and HR, 4.43, P = .01, respectively). Preconditioning citrulline and monocyte-derived macrophage reactivity are objective surrogate markers suitable to identify patients at risk of developing aGVHD. This work highlights the influence of preconditioning status in aGVHD development.

The Biology of Chronic Graft-versus-Host Disease: A Task Force Report from the National Institutes of Health Consensus Development Project on Criteria for Clinical Trials in Chronic Graft-versus-Host Disease

Chronic graft-versus-host disease (GVHD) is the leading cause of late, nonrelapse mortality and disability in allogeneic hematopoietic cell transplantation recipients and a major obstacle to improving outcomes. The biology of chronic GVHD remains enigmatic, but understanding the underpinnings of the immunologic mechanisms responsible for the initiation and progression of disease is fundamental to developing effective prevention and treatment strategies. The goals of this task force review are as follows: This document is intended as a review of our understanding of chronic GVHD biology and therapies resulting from preclinical studies, and as a platform for developing innovative clinical strategies to prevent and treat chronic GVHD.

Th17 plasticity and transition toward a pathogenic cytokine signature are regulated by cyclosporine after allogeneic SCT

T-helper 17 (Th17) cells have been widely implicated as drivers of autoimmune disease. In particular, Th17 cytokine plasticity and acquisition of an interleukin-17A⁺(IL-17A⁺)interferon γ(IFNγ)⁺ cytokine profile is associated with increased pathogenic capacity. Donor Th17 polarization is known to exacerbate graft-versus-host disease (GVHD) after allogeneic stem cell transplantation (allo-SCT); however, donor Th17 cytokine coexpression and plasticity have not been fully characterized. Using IL-17 "fate-mapping" mice, we identified IL-6-dependent Th17 cells early after allo-SCT, characterized by elevated expression of proinflammatory cytokines, IL-17A, IL-22, granulocyte-macrophage colony-stimulating factor, and tumor necrosis factor. This population did not maintain lineage fidelity, with a marked loss of IL-17A and IL-22 expression late posttransplant. Th17 cells were further segregated based on IFNγ coexpression, and IL-17A⁺IFNγ⁺ Th17 displayed an enhanced proinflammatory phenotype. Th17 cytokine plasticity and IFNγ production were critically dependent upon donor-derived IL-12p40, and cyclosporine (CsA) treatment regulated this differentiation pathway. This observation was highly concordant with clinical samples from allo-SCT recipients receiving CsA-based immune suppression where although the IFNγ-negative-Th17 subset predominated, IFNγ⁺-Th17 cells were also present. In sum, Th17 polarization and ensuing differentiation are mediated by sequential inflammatory signals, which are modulated by immunosuppressive therapy, leading to distinct phenotypes within this lineage.

Desensitization: Overcoming the Immunologic Barriers to Transplantation

HLA (Human Leucocyte Antigen) sensitization is a significant barrier to successful kidney transplantation. It often translates into difficult crossmatch before transplant and increased risk of acute and chronic antibody mediated rejection after transplant. Over the last decade, several immunomodulatory therapies have emerged allowing for increased access to kidney transplantation for the immunologically disadvantaged group of HLA sensitized end stage kidney disease patients. These include IgG inactivating agents, anti-cytokine antibodies, costimulatory molecule blockers, complement inhibitors, and agents targeting plasma cells. In this review, we discuss currently available agents for desensitization and provide a brief analysis of data on novel biologics, which will likely improve desensitization outcomes, and have potential implications in treatment of antibody mediated rejection.

Ex Vivo CD34+-Selected T Cell-Depleted Peripheral Blood Stem Cell Grafts for Allogeneic Hematopoietic Stem Cell Transplantation in Acute Leukemia and Myelodysplastic Syndrome Is Associated with Low Incidence of Acute and Chronic Graft-versus-Host Disease and High Treatment Response

Ex vivo CD34⁺-selected T cell depletion (TCD) has been developed as a strategy to reduce the incidence of graft-versus-host disease (GVHD) after allogeneic (allo) hematopoietic stem cell transplantation (HSCT). Clinical characteristics, treatment responses, and outcomes of patients developing acute (aGVHD) and chronic GVHD (cGVHD) after TCD allo-HSCT have not been well established. We evaluated 241 consecutive patients (median age, 57 years) with acute leukemia (n = 191, 79%) or myelodysplastic syndrome (MDS) (n = 50, 21%) undergoing CD34⁺-selected TCD allo-HSCT without post-HCST immunosuppression in a single institution. Cumulative incidences of grades II-IV and III-IV aGVHD at 180 days were 16% (95% confidence interval [CI], 12 to 21) and 5% (95% CI, 3 to 9), respectively. The skin was the most frequent organ involved, followed by the gastrointestinal tract. Patients were treated with topical corticosteroids, poorly absorbed corticosteroids (budesonide), and/or systemic corticosteroids. The overall day 28 treatment response was high at 82%. The cumulative incidence of any cGVHD at 3 years was 5% (95% CI, 3 to 9), with a median time of onset of 256 days (range, 95 to 1645). The 3-year transplant-related mortality, relapse, overall survival, and disease-free survival were 24% (95% CI, 18 to 30), 22% (95% CI, 17 to 27), 57% (95% CI, 50 to 64), and 54% (95% CI, 47 to 61), respectively. The 1-year and 3-year probabilities of cGVHD-free/relapse-free survival were 65% (95% CI, 59 to 71) and 52% (95% CI, 45 to 59), respectively. Our findings support the use of ex vivo CD34⁺-selected TCD allograft as a calcineurin inhibitor-free intervention for the prevention of GVHD in patients with acute leukemia and MDS.

Role of the intestinal mucosa in acute gastrointestinal GVHD

Intestinal graft-versus-host disease (GVHD) remains a significant obstacle to the success of allogeneic hematopoietic cell transplantation. The intestinal mucosa comprises the inner lining of the intestinal tract and maintains close proximity with commensal microbes that reside within the intestinal lumen. Recent advances have significantly improved our understanding of the interactions between the intestinal mucosa and the enteric microbiota. Changes in host mucosal tissue and commensals posttransplant have been actively investigated, and provocative insights into mucosal immunity and the enteric microbiota are now being translated into clinical trials of novel approaches for preventing and treating acute GVHD. In this review, we summarize recent findings related to aspects of the intestinal mucosa during acute GVHD.

Plasma biomarkers of risk for death in a multicenter phase 3 trial with uniform transplant characteristics post-allogeneic HCT

A phase 3 clinical trial (BMT CTN 0402) comparing tacrolimus/sirolimus (Tac/Sir) vs tacrolimus/methotrexate (Tac/Mtx) as graft-versus-host disease (GVHD) prophylaxis after matched-related allogeneic hematopoietic cell transplantation (HCT) recently showed no difference between study arms in acute GVHD-free survival. Within this setting of a prospective, multicenter study with uniform GVHD prophylaxis, conditioning regimen, and donor source, we explored the correlation of 10 previously identified biomarkers with clinical outcomes after allogeneic HCT. We measured biomarkers from plasma samples collected in 211 patients using enzyme-linked immunosorbent assay (Tac/Sir = 104, Tac/Mtx = 107). High suppression of tumorigenicity-2 (ST2) and T-cell immunoglobulin mucin-3 (TIM3) at day 28 correlated with 2-year nonrelapse mortality in multivariate analysis (P = .0050, P = .0075, respectively) and in a proportional hazards model with time-dependent covariates (adjusted hazard ratio: 2.43 [1.49-3.95], P = .0038 and 4.87 [2.53-9.34], P < .0001, respectively). High ST2 and TIM3 correlated with overall survival. Chemokine (C-X-C motif) ligand 9 (CXCL9) levels above the median were associated with chronic GVHD compared with levels below the median in a time-dependent proportional hazard analysis (P = .0069). Low L-Ficolin was associated with hepatic veno-occlusive disease (P = .0053, AUC = 0.80). We confirmed the correlation of plasma-derived proteins, previously assessed in single-center cohorts, with clinical outcomes after allogeneic HCT within this prospective, multicenter study.

Chronic graft-versus-host disease: biological insights from preclinical and clinical studies

With the increasing use of mismatched, unrelated, and granulocyte colony-stimulating factor-mobilized peripheral blood stem cell donor grafts and successful treatment of older recipients, chronic graft-versus-host disease (cGVHD) has emerged as the major cause of nonrelapse mortality and morbidity. cGVHD is characterized by lichenoid changes and fibrosis that affects a multitude of tissues, compromising organ function. Beyond steroids, effective treatment options are limited. Thus, new strategies to both prevent and treat disease are urgently required. Over the last 5 years, our understanding of cGVHD pathogenesis and basic biology, born out of a combination of mouse models and correlative clinical studies, has radically improved. We now understand that cGVHD is initiated by naive T cells, differentiating predominantly within highly inflammatory T-helper 17/T-cytotoxic 17 and T-follicular helper paradigms with consequent thymic damage and impaired donor antigen presentation in the periphery. This leads to aberrant T- and B-cell activation and differentiation, which cooperate to generate antibody-secreting cells that cause the deposition of antibodies to polymorphic recipient antigens (ie, alloantibody) or nonpolymorphic antigens common to both recipient and donor (ie, autoantibody). It is now clear that alloantibody can, in concert with colony-stimulating factor 1 (CSF-1)-dependent donor macrophages, induce a transforming growth factor β-high environment locally within target tissue that results in scleroderma and bronchiolitis obliterans, diagnostic features of cGVHD. These findings have yielded a raft of potential new therapeutics, centered on naive T-cell depletion, interleukin-17/21 inhibition, kinase inhibition, regulatory T-cell restoration, and CSF-1 inhibition. This new understanding of cGVHD finally gives hope that effective therapies are imminent for this devastating transplant complication.

Pretransplant Levels of CRP and Interleukin-6 Family Cytokines; Effects on Outcome after Allogeneic Stem Cell Transplantation

Several pretransplant factors, including CRP (C-reactive protein) levels, reflect the risk of complications after allogeneic stem cell transplantation. IL-6 induces CRP increase, and we therefore investigated the effects of pretransplant IL-6, soluble IL-6 receptors, IL-6 family cytokines and CRP serum levels on outcome for 100 consecutive allotransplant recipients. All patients had related donors, none had active infections and 99 patients were in complete remission before conditioning. The incidence of acute graft versus host disease (aGVHD) requiring treatment was 40%, survival at Day +100 82%, and overall survival 48%. Despite a significant correlation between pretransplant CRP and IL-6 levels, only CRP levels significantly influenced transplant-related mortality (TRM). However, CRP did not influence overall survival (OS). Pretransplant IL-31 influenced late TRM. Finally, there was a significant association between pretransplant IL-6 and early postconditioning weight gain (i.e., fluid retention), and this fluid retention was a risk factor for aGVHD, TRM and OS. To conclude, pretransplant CRP, IL-31 and early posttransplant fluid retention were independent risk factors for TRM and survival after allotransplantation.

Pathogenesis of acute graft-versus-host disease: from intestinal microbiota alterations to donor T cell activation

Acute graft-versus-host disease (aGVHD) is a major life-threatening complication of allogeneic haematopoietic cell transplantation (allo-HCT). Here we discuss the aGVHD pathophysiology initiated by multiple signals that cause alloreactive T-cell activation. The outcome of such donor T-cell activation is influenced by T-cell receptor-signal strength, anatomical location, co-stimulatory/co-inhibitory signals and differentiation stage (naive, effector/memory) of T-cells. Additionally, cross-priming of T cells to antigens expressed by pathogens can contribute to aGVHD-mediated tissue injury. In addition to the properties of donor T-cell activation, highly specialized tissue resident cell types, such as innate lymphoid cells, antigen-presenting cells, immune regulatory cells and various intestinal cell populations are critically involved in aGVHD pathogenesis. The role of the thymus and secondary lymphoid tissue injury, non-haematopoietic cells, intestinal microflora, cytokines, chemokines, microRNAs, metabolites and kinases in aGVHD pathophysiology will be highlighted. Acute GVHD pathogenic mechanisms will be connected to novel therapeutic approaches under development for, and tested in, the clinic.

Blockade of interleukin-27 signaling reduces GVHD in mice by augmenting Treg reconstitution and stabilizing Foxp3 expression

Reestablishment of competent regulatory pathways has emerged as a strategy to reduce the severity of graft-versus-host disease (GVHD), and recalibrate the effector and regulatory arms of the immune system. However, clinically feasible, cost-effective strategies that do not require extensive ex vivo cellular manipulation have remained elusive. In the current study, we demonstrate that inhibition of the interleukin-27p28 (IL-27p28) signaling pathway through antibody blockade or genetic ablation prevented lethal GVHD in multiple murine transplant models. Moreover, protection from GVHD was attributable to augmented global reconstitution of CD4⁺ natural regulatory T cells (nTregs), CD4⁺ induced Tregs (iTregs), and CD8⁺ iTregs, and was more potent than temporally concordant blockade of IL-6 signaling. Inhibition of IL-27p28 also enhanced the suppressive capacity of adoptively transferred CD4⁺ nTregs by increasing the stability of Foxp3 expression. Notably, blockade of IL-27p28 signaling reduced T-cell-derived-IL-10 production in conventional T cells; however, there was no corresponding effect in CD4⁺ or CD8⁺ Tregs, indicating that IL-27 inhibition had differential effects on IL-10 production and preserved a mechanistic pathway by which Tregs are known to suppress GVHD. Targeting of IL-27 therefore represents a novel strategy for the in vivo expansion of Tregs and subsequent prevention of GVHD without the requirement for ex vivo cellular manipulation, and provides additional support for the critical proinflammatory role that members of the IL-6 and IL-12 cytokine families play in GVHD biology.

Reprint of: Acute Graft-versus-Host Disease: Novel Biological Insights

Graft-versus-host disease (GVHD) continues to be a leading cause of morbidity and mortality after allogeneic hematopoietic stem cell transplantation. Recent insights into intestinal homeostasis and uncovering of new pathways and targets have greatly reconciled our understanding of GVHD pathophysiology and will reshape contemporary GVHD prophylaxis and treatment. Gastrointestinal (GI) GVHD is the major cause of mortality. Emerging data indicate that intestinal stem cells (ISCs) and their niche Paneth cells are targeted, resulting in dysregulation of the intestinal homeostasis and microbial ecology. The microbiota and their metabolites shape the immune system and intestinal homeostasis, and they may alter host susceptibility to GVHD. Protection of the ISC niche system and modification of the intestinal microbiota and metabolome to restore intestinal homeostasis may, thus, represent a novel approach to modulate GVHD and infection. Damage to the intestine plays a central role in amplifying systemic GVHD by propagating a proinflammatory cytokine milieu. Molecular targeting to inhibit kinase signaling may be a promising approach to treat GVHD, ideally via targeting the redundant effect of multiple cytokines on immune cells and enterocytes. In this review, we discuss insights on the biology of GI GVHD, interaction of microflora and metabolome with the hosts, identification of potential new target organs, and identification and targeting of novel T cell-signaling pathways. Better understanding of GVHD biology will, thus, pave a way to develop novel treatment strategies with great clinical benefits.

Severe Cytokine-Release Syndrome after T Cell-Replete Peripheral Blood Haploidentical Donor Transplantation Is Associated with Poor Survival and Anti-IL-6 Therapy Is Safe and Well Tolerated

Use of high-dose post-transplantation cyclophosphamide for graft-versus-host disease prophylaxis has expanded the use of unmanipulated haploidentical hematopoietic cell transplantation. The immediate post-transplantation course in T cell-replete peripheral blood haploidentical hematopoietic cell transplantation (haplo-HCT) is often complicated by symptoms resembling cytokine-release syndrome (CRS), previously described in recipients of targeted cellular therapeutics. However, we know little about the incidence and impact of CRS on outcomes in these patients. To understand this syndrome in haplo-HCT patients, we reviewed data from 75 consecutive patients who received granulocyte colony-stimulating factor-mobilized T cell-replete peripheral blood haplo-HCT at a single center. Using CRS criteria described in recipients of chimeric antigen receptor T cell therapies, we found 65 of 75 (87%) met criteria for CRS, although most cases were only mild (grades 1 or 2). However, 9 patients (12%) experienced severe (grades 3 or 4) CRS. Median survival was 2.6 months (95% confidence interval [CI], .43 to 5.8) in patients with severe CRS, compared with 13.1 months (95% CI, 8.1 to not reached) in patients with mild CRS. Transplantation-related mortality was worse in the severe CRS cohort with a hazard ratio of 4.59 (95% CI, 1.43 to 14.67) compared with that in the mild CRS cohort. Severe CRS patients had a significant delay in median time for neutrophil engraftment. Serum IL-6 levels were measured in 10 haplo-HCT patients and were elevated in the early post-transplantation setting. Seven patients with CRS were treated with tocilizumab, resulting in a complete resolution of their CRS symptoms. Severe CRS represents a potential complication of peripheral blood haplo-HCT and is associated with worse outcomes. Anti-IL-6 receptor therapy is associated with rapid resolution of the CRS symptoms.

IL-6 pathway in the liver: From physiopathology to therapy

Interleukin 6 (IL-6) is a pleiotropic four-helix-bundle cytokine that exerts multiple functions in the body. In the liver, IL-6 is an important inducer of the acute phase response and infection defense. IL-6 is furthermore crucial for hepatocyte homeostasis and is a potent hepatocyte mitogen. It is not only implicated in liver regeneration, but also in metabolic function of the liver. However, persistent activation of the IL-6 signaling pathway is detrimental to the liver and might ultimately result in the development of liver tumors. On target cells IL-6 can bind to the signal transducing subunit gp130 either in complex with the membrane-bound or with the soluble IL-6 receptor to induce intracellular signaling. In this review we describe how these different pathways are involved in the physiology and pathophyiology of the liver. We furthermore discuss how IL-6 pathways can be selectively inhibited and therapeutically exploited for the treatment of liver pathologies.

Platelet-released growth factors induce the antimicrobial peptide human beta-defensin-2 in primary keratinocytes

Platelet-released growth factors (PRGF) and its related clinically used formulations [e.g. Vivostat platelet-rich fibrin (PRF(®) )] are thrombocyte concentrate lysates that support healing of chronic, hard-to-heal and infected wounds. Human beta-defensin-2 (hBD-2) is an antimicrobial peptide expressed in human keratinocytes exhibiting potent antimicrobial activity against wound-related bacteria. In this study, we analysed the influence of PRGF on hBD-2 expression in human primary keratinocytes and the influence of Vivostat PRF(®) on hBD-2 expression in experimentally generated skin wounds in vivo. Treatment of primary keratinocytes with PRGF caused a significant increase in hBD-2 gene and protein expressions in a concentration- and time-dependent manner. The use of blocking antibodies revealed that the PRGF-mediated hBD-2 induction was partially mediated by the epidermal growth factor receptor and the interleukin-6 receptor (IL-6R). Luciferase gene reporter assays indicated that the hBD-2 induction through PRGF required activation of the transcription factor activator protein 1 (AP-1), but not of NF-kappaB. In concordance with these cell culture data, Vivostat PRF(®) induced hBD-2 expression when applied to experimentally generated skin wounds. Together, our results indicate that the induction of hBD-2 by thrombocyte concentrate lysates can contribute to the observed beneficial effects in the treatment of chronic and infected wounds.

Novel approaches for preventing acute graft-versus-host disease after allogeneic hematopoietic stem cell transplantation

INTRODUCTION

Allogeneic hematopoietic stem cell transplantation (alloHSCT) offers potential curative treatment for a wide range of malignant and nonmalignant hematological disorders. However, its success may be limited by post-transplant acute graft-versus-host disease (aGVHD), a systemic syndrome in which donor's immune cells attack healthy tissues in the immunocompromised host. aGVHD is one of the main causes of morbidity and mortality after alloHSCT. Despite standard GVHD prophylaxis regimens, aGVHD still develops in approximately 40-60% of alloHSCT recipients.

AREAS COVERED

In this review, after a brief summary of current knowledge on the pathogenesis of aGVHD, the authors review the current combination of a calcineurin inhibitor with an antimetabolite with or without added anti-thymocyte globulin (ATG) and emerging strategies for GVHD prevention.

EXPERT OPINION

A new understanding of the involvement of cytokines, intracellular signaling pathways, epigenetics and immunoregulatory cells in GVHD pathogenesis will lead to new standards for aGVHD prophylaxis allowing better prevention of severe aGVHD without affecting graft-versus-tumor effects.