Rorc restrains the potency of ST2+ regulatory T cells in ameliorating intestinal graft-versus-host disease

Soluble stimulation-2 (ST2) is increased during graft-versus-host disease (GVHD), while Tregs that express ST2 prevent GVHD through unknown mechanisms. Transplantation of Foxp3- T cells and Tregs that were collected and sorted from different Foxp3 reporter mice indicated that in mice that developed GVHD, ST2+ Tregs were thymus derived and predominantly localized to the intestine. ST2-/- Treg transplantation was associated with reduced total intestinal Treg frequency and activation. ST2-/- versus WT intestinal Treg transcriptomes showed decreased Treg functional markers and, reciprocally, increased Rorc expression. Rorc-/- T cells transplantation enhanced the frequency and function of intestinal ST2+ Tregs and reduced GVHD through decreased gut-infiltrating soluble ST2-producing type 1 and increased IL-4/IL-10-producing type 2 T cells. Cotransfer of ST2+ Tregs sorted from Rorc-/- mice with WT CD25-depleted T cells decreased GVHD severity and mortality, increased intestinal ST2+KLRG1+ Tregs, and decreased type 1 T cells after transplantation, indicating an intrinsic mechanism. Ex vivo IL-33-stimulated Tregs (TregIL-33) expressed higher amphiregulin and displayed better immunosuppression, and adoptive transfer prevented GVHD better than control Tregs or TregIL-33 cultured with IL-23/IL-17. Amphiregulin blockade by neutralizing antibody in vivo abolished the protective effect of TregIL-33. Our data show that inverse expression of ST2 and RORγt in intestinal Tregs determines GVHD and that TregIL-33 has potential as a cellular therapy avenue for preventing GVHD

ST2/MyD88 deficiency protects mice against aGVHD and spares T-regulatory cells

Acute graft-versus-host disease (aGVHD) hinders the efficacy of allogeneic hematopoietic cell transplantation (HCT). Plasma levels of soluble membrane-bound ST2 (ST2) are elevated in human and murine aGVHD and correlated to type 1 T cells response. ST2 signals through the adapter protein MyD88. The role of MyD88 in T cells during aGVHD has yet to be elucidated. We found that knocking out MyD88 in the donor T cells protected against aGVHD independent of IL-1R and TLR4 signaling in two murine HCT models. This protection was entirely driven by MyD88-/- CD4 T cells. Transplanting donor MyD88-/- conventional T cells (Tcons) with wild-type (WT) or MyD88-/- regulatory T cells (Tregs) lowered aGVHD severity and mortality. Transcriptome analysis of sorted MyD88-/- CD4 T cells from the intestine 10 d post-HCT showed lower levels of Il1rl1 (gene of ST2), Ifng, Csf2, Stat5, Batf, and Jak2 Transplanting donor ST2-/- Tcons with WT or ST2-/- Tregs showed a similar phenotype with what we observed when using donor MyD88-/- Tcons. Decreased ST2 was confirmed at the protein level with less secretion of soluble ST2 and more expression of ST2 compared with WT T cells. Our data suggest that Treg suppression from lack of MyD88 signaling in donor Tcons during alloreactivity uses the ST2 but not the IL-1R or TLR4 pathways, and ST2 represents a potential aGVHD therapeutic target sparing Tregs

From proteomics to discovery of first-in-class ST2 inhibitors active in vivo

Soluble cytokine receptors function as decoy receptors to attenuate cytokine-mediated signaling and modulate downstream cellular responses. Dysregulated overproduction of soluble receptors can be pathological, such as soluble ST2 (sST2), a prognostic biomarker in cardiovascular diseases, ulcerative colitis, and graft-versus-host disease (GVHD). Although intervention using an ST2 antibody improves survival in murine GVHD models, sST2 is a challenging target for drug development because it binds to IL-33 via an extensive interaction interface. Here, we report the discovery of small-molecule ST2 inhibitors through a combination of high-throughput screening and computational analysis. After in vitro and in vivo toxicity assessment, 3 compounds were selected for evaluation in 2 experimental GVHD models. We show that the most effective compound, iST2-1, reduces plasma sST2 levels, alleviates disease symptoms, improves survival, and maintains graft-versus-leukemia activity. Our data suggest that iST2-1 warrants further optimization to develop treatment for inflammatory diseases mediated by sST2

Proteomics analysis reveals a Th17-prone cell population in presymptomatic graft-versus-host disease

Gastrointestinal graft-versus-host-disease (GI-GVHD) is a life-threatening complication occurring after allogeneic hematopoietic cell transplantation (HCT), and a blood biomarker that permits stratification of HCT patients according to their risk of developing GI-GVHD would greatly aid treatment planning. Through in-depth, large-scale proteomic profiling of presymptomatic samples, we identified a T cell population expressing both CD146, a cell adhesion molecule, and CCR5, a chemokine receptor that is upregulated as early as 14 days after transplantation in patients who develop GI-GVHD. The CD4+CD146+CCR5+ T cell population is Th17 prone and increased by ICOS stimulation. shRNA knockdown of CD146 in T cells reduced their transmigration through endothelial cells, and maraviroc, a CCR5 inhibitor, reduced chemotaxis of the CD4+CD146+CCR5+ T cell population toward CCL14. Mice that received CD146 shRNA-transduced human T cells did not lose weight, showed better survival, and had fewer CD4+CD146+CCR5+ T cells and less pathogenic Th17 infiltration in the intestine, even compared with mice receiving maraviroc with control shRNA- transduced human T cells. Furthermore, the frequency of CD4+CD146+CCR5+ Tregs was increased in GI-GVHD patients, and these cells showed increased plasticity toward Th17 upon ICOS stimulation. Our findings can be applied to early risk stratification, as well as specific preventative therapeutic strategies following HCT

ICOSL+ plasmacytoid dendritic cells as inducer of graft-versus-host disease, responsive to a dual ICOS/CD28 antagonist

Acute graft-versus-host disease (aGVHD) remains a major complication of allogeneic hematopoietic cell transplantation (HCT). CD146 and CCR5 are proteins that mark activated T helper 17 (Th17) cells. The Th17 cell phenotype is promoted by the interaction of the receptor ICOS on T cells with ICOS ligand (ICOSL) on dendritic cells (DCs). We performed multiparametric flow cytometry in a cohort of 156 HCT recipients and conducted experiments with aGVHD murine models to understand the role of ICOSL+ DCs. We observed an increased frequency of ICOSL+ plasmacytoid DCs, correlating with CD146+CCR5+ T cell frequencies, in the 64 HCT recipients with gastrointestinal aGVHD. In murine models, donor bone marrow cells from ICOSL-deficient mice compared to those from wild-type mice reduced aGVHD-related mortality. Reduced aGVHD resulted from lower intestinal infiltration of pDCs and pathogenic Th17 cells. We transplanted activated human ICOSL+ pDCs along with human peripheral blood mononuclear cells into immunocompromised mice and observed infiltration of intestinal CD146+CCR5+ T cells. We found that prophylactic administration of a dual human ICOS/CD28 antagonist (ALPN-101) prevented aGVHD in this model better than did the clinically approved belatacept (CTLA-4-Fc), which binds CD80 (B7-1) and CD86 (B7-2) and interferes with the CD28 T cell costimulatory pathway. When started at onset of aGVHD signs, ALPN-101 treatment alleviated symptoms of ongoing aGVHD and improved survival while preserving antitumoral cytotoxicity. Our data identified ICOSL+-pDCs as an aGVHD biomarker and suggest that coinhibition of the ICOSL/ICOS and B7/CD28 axes with one biologic drug may represent a therapeutic opportunity to prevent or treat aGVHD

Systemic Toll-Like Receptor Stimulation Suppresses Experimental Allergic Asthma and Autoimmune Diabetes in NOD Mice

BackgroundInfections may be associated with exacerbation of allergic and autoimmune diseases. Paradoxically, epidemiological and experimental data have shown that some microorganisms can also prevent these pathologies. This observation is at the origin of the hygiene hypothesis according to which the decline of infections in western countries is at the origin of the increased incidence of both Th1-mediated autoimmune diseases and Th2-mediated allergic diseases over the last decades. We have tested whether Toll-like receptor (TLR) stimulation can recapitulate the protective effect of infectious agents on allergy and autoimmunity. Methods and Findings Here, we performed a systematic study of the disease-modifying effects of a set of natural or synthetic TLR agonists using two experimental models, ovalbumin (OVA)-induced asthma and spontaneous autoimmune diabetes, presenting the same genetic background of the non obese diabetic mouse (NOD) that is highly susceptible to both pathologies. In the same models, we also investigated the effect of probiotics. Additionally, we examined the effect of the genetic invalidation of MyD88 on the development of allergic asthma and spontaneous diabetes. We demonstrate that multiple TLR agonists prevent from both allergy and autoimmunity when administered parenterally. Probiotics which stimulate TLRs also protect from these two diseases. The physiological relevance of these findings is further suggested by the major acceleration of OVA-induced asthma in MyD88 invalidated mice. Our results strongly indicate that the TLR-mediated effects involve immunoregulatory cytokines such as interleukin (IL)-10 and transforming growth factor (TGF)-β and different subsets of regulatory T cells, notably CD4+CD25+FoxP3+ T cells for TLR4 agonists and NKT cells for TLR3 agonists. Conclusions/Significance These observations demonstrate that systemic administration of TLR ligands can suppress both allergic and autoimmune responses. They provide a plausible explanation for the hygiene hypothesis. They also open new therapeutic perspectives for the prevention of these pathologies

Le rôle des basophiles et effets régulateurs induit par les probiotiques dans le modèle expérimental d'asthme allergique

Dans cette thèse, nous avons étudié le rôle ambivalent des microorganismes dans la pathologie de l'asthme allergique. Nous avons ainsi montré le rôle protecteur des probiotiques, bactéries non pathogènes dont la signalisation utilise la molécule MyD88, dans un modèle d'inflammation allergique induit par l'ovalbumine. Cette protection se caractérise par une diminution de l'hyperreactivité bronchique, de l'infiltration des eosinophiles et de la production de cytokines de type Th2 (IL-4, IL-5, IL-13) dans les poumons. Quant aux mécanismes responsables de cette protection, nous avons montré qu'elle était associée à une réduction des cytokines pro-inflammatoires (IL-17 et TNF-a) et à une augmentation des cellules T régulatrices CD4*CD25*FoxP3*. Cette protection est transférable par les cellules T CD4* et est dépendante de l'IL-10. Dans une étude indépendante, nous avons démontré l'implication des basophiles dans l'asthme allergique à la fois après transfert adoptif et après déplétion. Nous avons également testé la réponse des basophiles murins à différents agomstes TLR et identifié une molécule qui était capable d'activer cette cellule. Ainsi, nous avons démontré que l'ARN synthétique double brin, le poly(A:U), qui est décrit comme un ligand TLR3/TLR7, induit une production d'IL-4, d'IL-6, d'IL-13 et d'histamine par les basophiles in vitro. Cette stimulation dépend du senseur viral RIG-I et de l'adaptateur moléculaire CARDIF. Nous avons enfin démontré la pertinence de ces observations puisque Pactivation des basoplulcs in vivo par le poly(A:U) exacerbe tous les paramètres de l'asthme expérimental allergique. Nous suggérons que nos résultats sur le poly(A:U), considéré comme mimant l'effet d'un virus, pourraient constituer une approche du mécanisme responsable de l'aggravation de la pathologie bien connue chez les patients asthmatiques durant une infection virale.We have shown here that non-pathogenic microorganisms such as probiotics can protect mice from experimental allergic asthma. We have observed that oral administration of the preparation containing lactobacillus, bifidobacterium and spretococcus prevents from allergic asthma induced by ovalbumin as shown by the decreased broncho-hyperactivity, the eosmophilia in the bronchoalveolar liquid (BAL) and the production of Th2 type cytokines (IL-4, IL-5, IL-13) and chemokines (eotaxin) in the lungs. Probiotic administration also decreased the level of pro-inflammatory cytokines IL-6, IL-17 and TNFa in sera and increased the frequency of CD4+CD25+FoxP3+T cells in the spleen. In addition, we have shown that the asthma protection was MyD88- and IL-10-dependent. We have also analyzed the potential role and activation of basophils in experimental allergic asthma. We have demonstrated by adoptive transfer and by depletion of these cells the role of basophils in this model. We have further characterized the double-stranded RNA poly(A:U) as a potent agonist of purified murine basophils since it induced a strong IL-4, IL-6, IL-13 and histamine production in vitro. Poly(A:U). which is described as TLR3/TLR7 ligand, activated basophils through the RIG-I/CARDIF pathway. The relevance of this stimulation has been illustrated in the model of allergic asthma, since poly(A:U)-activated basophils exacerbated asthma responses by increasing TH2 cytokine and chemokine production in lungs as well as eosinophilia in the BAL. We suggest that this mechanism may account for the aggravating effect of respiratory viral infections well known in asthma patients.PARIS5-BU Méd.Cochin (751142101) / SudocSudocFranceF

Danger Signals Triggering Immune Response and Inflammation

The immune system detects "danger" through a series of what we call pathogen-associated molecular patterns (PAMPs) or damage-associated molecular pattern molecules (DAMPs), working in concert with both positive and negative signals derived from other tissues. PAMPs are molecules associated with groups of pathogens that are small molecular motifs conserved within a class of microbes. They are recognized by Toll-like receptors (TLRs) and other pattern recognition receptors. A vast array of different types of molecules can serve as PAMPs, including glycans and glycoconjugates. Bacterial lipopolysaccharides (LPSs), endotoxins found on the cell membranes of Gram-negative bacteria, are considered to be the prototypical class of PAMPs. LPSs are specifically recognized by TLR4, a recognition receptor of the innate immune system. Other PAMPs include bacterial flagellin (recognized by TLR5), lipoteichoic acid from Gram-positive bacteria, peptidoglycan, and nucleic acid variants normally associated with viruses, such as double-stranded RNA, recognized by TLR3 or unmethylated CpG motifs, recognized by TLR9. DAMPs, also known as alarmins, are molecules released by stressed cells undergoing necrosis that act as endogenous danger signals to promote and exacerbate the immune and inflammatory response. DAMPs vary greatly depending on the type of cell (epithelial, mesenchymal, etc.) and injured tissue. Some endogenous danger signals include heat-shock proteins, HMGB1 (high-mobility group box 1), reactive oxygen intermediates, extracellular matrix breakdown products such as hyaluronan fragments, neuromediators, and cytokines like the interferons (IFNs). Non-protein DAMPs include ATP, uric acid, heparin sulfate, and DNA. Furthermore, accumulating evidence supports correlation between alarmins and changes in the microbiome. Increased serum or plasma levels of these DAMPs have been associated with many inflammatory diseases, including gastric and intestinal inflammatory diseases, graft-versus-host disease (GVHD), sepsis and multiple organ failure, allergies particularly in the lungs, atherosclerosis, age-associated insulin resistance, arthritis, lupus, neuro-inflammation/degeneration and more recently in tumors, which is particularly interesting with the emergence of immunotherapies. Therapeutic strategies are being developed to modulate the expression of these DAMPs for the treatment of these diseases. A vast number of reviews have already been published in this area; thus, in an effort to not duplicate what has already been written, we will focus on recent discoveries particularly in disease models that are epidemic in Western society: intestinal chronic inflammatory diseases including GVHD and its relationship with the microbiome, chronic infectious diseases, allergies, autoimmune diseases, neuroinflammation and cancers. We will also focus on the basic cellular roles of macrophages, T cells and B cells. This research topic brings together sixteen articles that provide novel insights into the mechanisms of action of DAMPS/alarmins and their regulation and subsequent immunologically driven responses