Assessment of mucosal integrity by quantifying neutrophil granulocyte influx in murine models of acute intestinal injury

Chemotherapy-induced intestinal epithelial damage directly promotes galectin-9-driven modulation of T cell behavior

The intestine is vulnerable to chemotherapy-induced damage due to the high rate of intestinal epithelial cell (IEC) proliferation. We have developed a human intestinal organoid-based 3D model system to study the direct effect of chemotherapy-induced IEC damage on T cell behavior. Exposure of intestinal organoids to busulfan, fludarabine, and clofarabine induced damage-related responses affecting both the capacity to regenerate and transcriptional reprogramming. In ex vivo co-culture assays, prior intestinal organoid damage resulted in increased T cell activation, proliferation, and migration. We identified galectin-9 (Gal-9) as a key molecule released by damaged organoids. The use of anti-Gal-9 blocking antibodies or CRISPR/Cas9-mediated Gal-9 knock-out prevented intestinal organoid damage-induced T cell proliferation, interferon-gamma release, and migration. Increased levels of Gal-9 were found early after HSCT chemotherapeutic conditioning in the plasma of patients who later developed acute GVHD. Taken together, chemotherapy-induced intestinal damage can influence T cell behavior in a Gal-9-dependent manner which may provide novel strategies for therapeutic intervention.

Influence of intestinal microbial metabolites on the abscopal effect after radiation therapy combined with immune checkpoint inhibitors

Background

Most clinical studies failed to elicit a strong antitumor immune response and subsequent systemic tumor regression after radiation therapy (RT), even in combination with the immune checkpoint inhibitors (ICI) anti-CTLA4 or anti-PD1. Mechanistically, type I interferon (IFN-I) activation is essential for the development of such abscopal effects (AE); however, mechanisms driving or limiting IFN-I activation are ill defined. Groundbreaking discoveries have shown that antibiotics (ABx) can affect oncological outcomes and that microbiota-derived metabolites can modulate systemic antitumor immunity. Recent studies have demonstrated that the bacterial metabolites desaminotyrosine (DAT) and indole-3-carboxaldehyde (ICA) can enhance IFN-I activation in models of inflammatory diseases.

Materials and Methods

The subcutaneous bilateral MC38 tumor model is a widely used experimental tool to study the AE in mice. We applied it to explore the influence of broad-spectrum ABx, DAT and ICA on the AE after radioimmunotherapy (RIT). We performed 1x8 Gy of the primary tumor ± anti-CTLA4 or anti-PD1, and ± daily oral application of ABx or metabolites.

Result

Combinatory ABx had neither a significant effect on tumor growth of the irradiated tumor nor on tumor progression of the abscopal tumor after RIT with anti-CTLA4. Furthermore, DAT and ICA did not significantly impact on the AE after RIT with anti-CTLA4 or anti-PD1. Surprisingly, ICA even appears to reduce outcomes after RIT with anti-CTLA4.

Conclusion

We did not find a significant impact of combinatory ABx on the AE. Experimental application of the IFN-I-inducing metabolites DAT or ICA did not boost the AE after combined RIT. Additional studies are important to further investigate whether the intestinal microbiota or specific microbiota-derived metabolites modulate the AE.

ROCK1/2 signaling contributes to corticosteroid-refractory acute graft-versus-host disease

Patients with corticosteroid-refractory acute graft-versus-host disease (aGVHD) have a low one-year survival rate. Identification and validation of novel targetable kinases in patients who experience corticosteroid-refractory-aGVHD may help improve outcomes. Kinase-specific proteomics of leukocytes from patients with corticosteroid-refractory-GVHD identified rho kinase type 1 (ROCK1) as the most significantly upregulated kinase. ROCK1/2 inhibition improved survival and histological GVHD severity in mice and was synergistic with JAK1/2 inhibition, without compromising graft-versus-leukemia-effects. ROCK1/2-inhibition in macrophages or dendritic cells prior to transfer reduced GVHD severity. Mechanistically, ROCK1/2 inhibition or ROCK1 knockdown interfered with CD80, CD86, MHC-II expression and IL-6, IL-1β, iNOS and TNF production in myeloid cells. This was accompanied by impaired T cell activation by dendritic cells and inhibition of cytoskeletal rearrangements, thereby reducing macrophage and DC migration. NF-κB signaling was reduced in myeloid cells following ROCK1/2 inhibition. In conclusion, ROCK1/2 inhibition interferes with immune activation at multiple levels and reduces acute GVHD while maintaining GVL-effects, including in corticosteroid-refractory settings.

The microbial metabolite desaminotyrosine enhances T-cell priming and cancer immunotherapy with immune checkpoint inhibitors

BACKGROUND

Inter-individual differences in response to immune checkpoint inhibitors (ICI) remain a major challenge in cancer treatment. The composition of the gut microbiome has been associated with differential ICI outcome, but the underlying molecular mechanisms remain unclear, and therapeutic modulation challenging.

METHODS

We established an in vivo model to treat C57Bl/6j mice with the type-I interferon (IFN-I)-modulating, bacterial-derived metabolite desaminotyrosine (DAT) to improve ICI therapy. Broad spectrum antibiotics were used to mimic gut microbial dysbiosis and associated ICI resistance. We utilized genetic mouse models to address the role of host IFN-I in DAT-modulated antitumour immunity. Changes in gut microbiota were assessed using 16S-rRNA sequencing analyses.

FINDINGS

We found that oral supplementation of mice with the microbial metabolite DAT delays tumour growth and promotes ICI immunotherapy with anti-CTLA-4 or anti-PD-1. DAT-enhanced antitumour immunity was associated with more activated T cells and natural killer cells in the tumour microenvironment and was dependent on host IFN-I signalling. Consistent with this, DAT potently enhanced expansion of antigen-specific T cells following vaccination with an IFN-I-inducing adjuvant. DAT supplementation in mice compensated for the negative effects of broad-spectrum antibiotic-induced dysbiosis on anti-CTLA-4-mediated antitumour immunity. Oral administration of DAT altered the gut microbial composition in mice with increased abundance of bacterial taxa that are associated with beneficial response to ICI immunotherapy.

INTERPRETATION

We introduce the therapeutic use of an IFN-I-modulating bacterial-derived metabolite to overcome resistance to ICI. This approach is a promising strategy particularly for patients with a history of broad-spectrum antibiotic use and associated loss of gut microbial diversity.

FUNDING

Melanoma Research Alliance, Deutsche Forschungsgemeinschaft, German Cancer Aid, Wilhelm Sander Foundation, Novartis Foundation.

Chemotherapy-induced intestinal injury promotes Galectin-9-driven modulation of T cell function

The intestine is vulnerable to chemotherapy-induced toxicity due to its high epithelial proliferative rate, making gut toxicity an off-target effect in several cancer treatments, including conditioning regimens for allogeneic hematopoietic cell transplantation (allo-HCT). In allo-HCT, intestinal damage is an important factor in the development of Graft-versus-Host Disease (GVHD), an immune complication in which donor immune cells attack the recipient's tissues. Here, we developed a novel human intestinal organoid-based 3D model system to study the direct effect of chemotherapy-induced intestinal epithelial damage on T cell behavior. Chemotherapy treatment using busulfan, fludarabine, and clofarabine led to damage responses in organoids resulting in increased T cell migration, activation, and proliferation in ex- vivo co-culture assays. We identified galectin-9 (Gal-9), a beta-galactoside-binding lectin released by damaged organoids, as a key molecule mediating T cell responses to damage. Increased levels of Gal-9 were also found in the plasma of allo-HCT patients who later developed acute GVHD, supporting the predictive value of the model system in the clinical setting. This study highlights the potential contribution of chemotherapy-induced epithelial damage to the pathogenesis of intestinal GVHD through direct effects on T cell activation and trafficking promoted by galectin-9.

Challenges and opportunities targeting mechanisms of epithelial injury and recovery in acute intestinal graft-versus-host disease

Despite advances in immunosuppressive prophylaxis and overall supportive care, gastrointestinal (GI) graft-versus-host disease (GVHD) remains a major, lethal side effect after allogeneic hematopoietic stem cell transplantation (allo-HSCT). It has become increasingly clear that the intestinal epithelium, in addition to being a target of transplant-related toxicity and GVHD, plays an important role in the onset of GVHD. Over the last two decades, increased understanding of the epithelial constituents and their microenvironment has led to the development of novel prophylactic and therapeutic interventions, with the potential to protect the intestinal epithelium from GVHD-associated damage and promote its recovery following insult. In this review, we will discuss intestinal epithelial injury and the role of the intestinal epithelium in GVHD pathogenesis. In addition, we will highlight possible approaches to protect the GI tract from damage posttransplant and to stimulate epithelial regeneration, in order to promote intestinal recovery. Combined treatment modalities integrating immunomodulation, epithelial protection, and induction of regeneration may hold the key to unlocking mucosal recovery and optimizing therapy for acute intestinal GVHD.

STING and transplantation: can targeting this pathway improve outcomes?

Stimulator of interferon genes (STING) is an innate immune sensor of cytoplasmic dsDNA originating from microorganisms and host cells. STING plays an important role in the regulation of murine graft-versus-host disease (GVHD) after allogeneic hematopoietic stem cell transplantation (allo-HSCT) and may be similarly activated during other transplantation modalities. In this review, we discuss STING in allo-HSCT and its prospective involvement in autologous HSCT (auto-HSCT) and solid organ transplantation (SOT), highlighting its unique role in nonhematopoietic, hematopoietic, and malignant cell types.

Type I interferon signaling before hematopoietic stem cell transplantation lowers donor T cell activation via reduced allogenicity of recipient cells

Recent studies highlight immunoregulatory functions of type I interferons (IFN-I) during the pathogenesis of graft-versus-host disease (GVHD) after allogeneic hematopoietic stem cell transplantation (allo-HSCT). We demonstrated that selective activation of IFN-I pathways including RIG-I/MAVS and cGAS/STING prior to allo-HSCT conditioning therapy can ameliorate the course of GVHD. However, direct effects of IFN-Is on immune cells remain ill characterized. We applied RIG-I agonists (3pRNA) to stimulate IFN-I production in murine models of conditioning therapy with total body irradiation (TBI) and GVHD. Using IFN-I receptor-deficient donor T cells and hematopoietic cells, we found that endogenous and RIG-I-induced IFN-Is do not reduce GVHD by acting on these cell types. However, 3pRNA applied before conditioning therapy reduced the ability of CD11c⁺ recipient cells to stimulate proliferation and interferon gamma expression of allogeneic T cells. Consistently, RIG-I activation before TBI reduced the proliferation of transplanted allogeneic T-cells. The reduced allogenicity of CD11c⁺ recipient cells was dependent on IFN-I signaling. Notably, this immunosuppressive function of DCs was restricted to a scenario where tissue damage occurs. Our findings uncover a context (damage by TBI) and IFN-I dependent modulation of T cells by DCs and extend the understanding about the cellular targets of IFN-I during allo-HSCT and GVHD.

Regeneration After Radiation- and Immune-Mediated Tissue Injury Is Not Enhanced by Type III Interferon Signaling

PURPOSE

Type I interferon (IFN-I) and interleukin (IL)-22 modulate regeneration of the thymus and intestinal epithelial cells (IECs) after cytotoxic stress such as irradiation. Radiation-induced damage to thymic tissues and IECs is a crucial aspect during the pathogenesis of inadequate immune reconstitution and acute graft-versus-host disease (GVHD) after allogeneic hematopoietic stem cell transplantation (allo-HSCT) with myeloablative total body irradiation (TBI), respectively. IL-22 and IFN-I reduce the severity of acute GVHD after allo-HSCT with myeloablative TBI. However, the role of biologically related type III interferon (IFN-III), also known as interferon lambda (IFN-λ) or IL-28, in this context is unclear. We therefore studied the role of the IFN-III pathway in thymic regeneration and GVHD after TBI and allo-HSCT.

METHODS AND MATERIALS

Cohoused wild-type (WT) and IFN-III receptor-deficient (IL-28 receptor alpha subunit-deficient/IL-28Ra^-/-) mice were analyzed in models of TBI-induced thymus damage and a model of GVHD after allo-HSCT with myeloablative TBI. PASylated IFN-III (PASylated IL-28A, XL-protein GmbH) was generated to prolong the plasma half-life of IFN-III. Pharmacologic activity and the effects of PASylated IL-28A on radiation-induced thymus damage and the course of GVHD after allo-HSCT with myeloablative TBI were tested.

RESULTS

The course and severity of GVHD after myeloablative TBI and allo-HSCT in IL-28Ra^-/- mice was comparable to those in WT mice. Activation of the IFN-III pathway by PASylated IL-28A did not significantly modulate GVHD after allo-HSCT with TBI. Furthermore, IL28Ra^-/- mice and WT mice showed similar thymus regeneration after radiation, which could also not be significantly modulated by IFN-III receptor engagement using PASylated IL-28A.

CONCLUSIONS

We analyzed the role of IFN-III signaling during radiation-mediated acute tissue injury. Despite molecular and biologic homologies with IFN-I and IL-22, IFN-III signaling did not improve thymus regeneration after radiation or the course of GVHD after myeloablative TBI and allo-HSCT.

The interplay between neutrophils and microbiota in cancer

The role of the microbiota in many diseases including cancer has gained increasing attention. Paired with this is our expanding appreciation for the heterogeneity of the neutrophil compartment regarding surface marker expression and functionality. In this review, we will discuss the influence of the microbiota on granulopoiesis and consequent activity of neutrophils in cancer. As evidence for this microbiota-neutrophil-cancer axis builds, it exposes new therapeutic targets to improve a cancer patient's outcome.

Biomarkers for monitoring intestinal health in poultry: present status and future perspectives

Intestinal health is determined by host (immunity, mucosal barrier), nutritional, microbial and environmental factors. Deficiencies in intestinal health are associated with shifts in the composition of the intestinal microbiome (dysbiosis), leakage of the mucosal barrier and/or inflammation. Since the ban on growth promoting antimicrobials in animal feed, these dysbiosis-related problems have become a major issue, especially in intensive animal farming. The economical and animal welfare consequences are considerable. Consequently, there is a need for continuous monitoring of the intestinal health status, particularly in intensively reared animals, where the intestinal function is often pushed to the limit. In the current review, the recent advances in the field of intestinal health biomarkers, both in human and veterinary medicine are discussed, trying to identify present and future markers of intestinal health in poultry. The most promising new biomarkers will be stable molecules ending up in the feces and litter that can be quantified, preferably using rapid and simple pen-side tests. It is unlikely, however, that a single biomarker will be sufficient to follow up all aspects of intestinal health. Combinations of multiple biomarkers and/or metabarcoding, metagenomic, metatranscriptomic, metaproteomic and metabolomic approaches will be the way to go in the future. Candidate biomarkers currently are being investigated by many research groups, but the validation will be a major challenge, due to the complexity of intestinal health in the field.

Neutrophils provide cellular communication between ileum and mesenteric lymph nodes at graft-versus-host disease onset

Conditioning-induced damage of the intestinal tract plays a critical role during the onset of acute graft-versus-host disease (GVHD). Therapeutic interference with these early events of GVHD is difficult, and currently used immunosuppressive drugs mainly target donor T cells. However, not donor T cells but neutrophils reach the sites of tissue injury first, and therefore could be a potential target for GVHD prevention. A detailed analysis of neutrophil fate during acute GVHD and the effect on T cells is difficult because of the short lifespan of this cell type. By using a novel photoconverter reporter system, we show that neutrophils that had been photoconverted in the ileum postconditioning later migrated to mesenteric lymph nodes (mLN). This neutrophil migration was dependent on the intestinal microflora. In the mLN, neutrophils colocalized with T cells and presented antigen on major histocompatibility complex (MHC)-II, thereby affecting T cell expansion. Pharmacological JAK1/JAK2 inhibition reduced neutrophil influx into the mLN and MHC-II expression, thereby interfering with an early event in acute GVHD pathogenesis. In agreement with this finding, neutrophil depletion reduced acute GVHD. We conclude that neutrophils are attracted to the ileum, where the intestinal barrier is disrupted, and then migrate to the mLN, where they participate in alloantigen presentation. JAK1/JAK2-inhibition can interfere with this process, which provides a potential therapeutic strategy to prevent early events of tissue damage-related innate immune cell activation and, ultimately, GVHD.

Dynamics of M1 macrophages in oral mucosal lesions during the development of acute graft-versus-host disease in rats

The role of macrophage infiltrates in oral mucosal acute graft-versus-host disease (AGVHD) remains unclear, although clinical studies suggest that macrophage infiltration correlates directly with the severity of AGVHD. In this study, we investigated the role of M1 macrophage infiltration in the oral mucosa of rats with AGVHD. Lewis rat spleen cells were injected into (Lewis × Brown Norway) F₁ rats to induce systemic GVHD. Tongue samples were evaluated using histology, immunohistochemistry, dual immunofluorescence, real-time reverse transcription-polymerase chain reaction, Transwell migration assays and Stamper-Woodruff binding assays. At the onset of oral mucosal AGVHD, dual immunofluorescence and migration assays revealed that M1 macrophages had accumulated in the basement membrane (BM) region via the laminin/CD29 β1 integrin pathway. Macrophage-secreted matrix metalloproteinase-2 was related to BM degradation. The adhesion of macrophages to the oral epithelium could be inhibited by pretreating macrophages with a CC chemokine receptor 2 (CCR2) antibody and/or pretreating lesion sections with monocyte chemoattractant protein-1 (MCP-1) antibody. Our data show that the migration and adhesion of M1 macrophages are associated with oral mucosal AGVHD, which is mediated in part by both laminin/CD29 β 1 intern and MCP-1/CCR2 pathways. Therefore, our study provides additional support for the contribution of macrophage infiltrate to the development of oral mucosal AGVHD.

A20 deletion in T cells modulates acute graft-versus-host disease in mice

The NF-κB regulator A20 limits inflammation by providing negative feedback in myeloid cells and B cells. Functional lack of A20 has been linked to several inflammatory and autoimmune diseases. To define how A20 affects the functionality of T effector cells in a highly inflammatory environment, we performed conventional allogeneic hematopoietic stem cell transplantation (allo-HSCT) with A20-deficient CD4⁺ and CD8⁺ donor T cells in mice. Severity and mortality of graft-versus-host disease (GVHD) after allo-HSCT was drastically reduced in recipients transplanted with conventional doses of A20-deficient T cells. Consistently, we found that the A20-deficient donor T-cell compartment was strongly diminished at various timepoints after allo-HSCT. However, proportionally more A20-deficient donor T cells produced IFN-γ and systemic inflammation was elevated early after allo-HSCT. Consequently, increasing the dose of transplanted A20-deficient T cells reversed the original phenotype and resulted in enhanced GVHD mortality compared to recipients that received A20^+/+ T cells. Still, A20-deficient T cells, activated either through T cell receptor-dependent or -independent mechanisms, were less viable than control A20^+/+ T cells, highlighting that A20 balances both, T-cell activation and survival. Thus, our findings suggest that targeting A20 in T cells may allow to modulate T-cell-mediated inflammatory diseases like GVHD.

A20 Restrains Thymic Regulatory T Cell Development

Maintaining immune tolerance requires the production of Foxp3-expressing regulatory T (T_reg) cells in the thymus. Activation of NF-κB transcription factors is critically required for T_reg cell development, partly via initiating Foxp3 expression. NF-κB activation is controlled by a negative feedback regulation through the ubiquitin editing enzyme A20, which reduces proinflammatory signaling in myeloid cells and B cells. In naive CD4⁺ T cells, A20 prevents kinase RIPK3-dependent necroptosis. Using mice deficient for A20 in T lineage cells, we show that thymic and peripheral T_reg cell compartments are quantitatively enlarged because of a cell-intrinsic developmental advantage of A20-deficient thymic T_reg differentiation. A20-deficient thymic T_reg cells exhibit reduced dependence on IL-2 but unchanged rates of proliferation and apoptosis. Activation of the NF-κB transcription factor RelA was enhanced, whereas nuclear translocation of c-Rel was decreased in A20-deficient thymic T_reg cells. Furthermore, we found that the increase in T_reg cells in T cell–specific A20-deficient mice was already observed in CD4⁺ single-positive CD25⁺ GITR⁺ Foxp3⁻ thymic T_reg cell progenitors. T_reg cell precursors expressed high levels of the tumor necrosis factor receptor superfamily molecule GITR, whose stimulation is closely linked to thymic T_reg cell development. A20-deficient T_reg cells efficiently suppressed effector T cell–mediated graft-versus-host disease after allogeneic hematopoietic stem cell transplantation, suggesting normal suppressive function. Holding thymic production of natural T_reg cells in check, A20 thus integrates T_reg cell activity and increased effector T cell survival into an efficient CD4⁺ T cell response.