Pro-Resolving Factors Released by Macrophages After Efferocytosis Promote Mucosal Wound Healing in Inflammatory Bowel Disease

Nonresolving inflammation is a critical driver of several chronic inflammatory diseases, including inflammatory bowel diseases (IBD). This unresolved inflammation may result from the persistence of an initiating stimulus or from the alteration of the resolution phase of inflammation. Elimination of apoptotic cells by macrophages (a process called efferocytosis) is a critical step in the resolution phase of inflammation. Efferocytosis participates in macrophage reprogramming and favors the release of numerous pro-resolving factors. These pro-resolving factors exert therapeutic effects in experimental autoimmune arthritis. Here, we propose to evaluate the efficacy of pro-resolving factors produced by macrophages after efferocytosis, a secretome called SuperMApo, in two IBD models, namely dextran sodium sulfate (DSS)-induced and T cell transfer-induced colitis. Reintroducing these pro-resolving factors was sufficient to decrease clinical, endoscopic and histological colitis scores in ongoing naive T cell-transfer-induced colitis and in DSS-induced colitis. Mouse primary fibroblasts isolated from the colon demonstrated enhanced healing properties in the presence of SuperMApo, as attested by their increased migratory, proliferative and contractive properties. This was confirmed by the use of human fibroblasts isolated from patients with IBD. Exposure of an intestinal epithelial cell (IEC) line to these pro-resolving factors increased their proliferative properties and IEC acquired the capacity to capture apoptotic cells. The improvement of wound healing properties induced by SuperMApo was confirmed in vivo in a biopsy forceps-wound colonic mucosa model. Further in vivo analysis in naive T cell transfer-induced colitis model demonstrated an improvement of intestinal barrier permeability after administration of SuperMApo, an intestinal cell proliferation and an increase of α-SMA expression by fibroblasts, as well as a reduction of the transcript coding for fibronectin (Fn1). Finally, we identified TGF-β, IGF-I and VEGF among SuperMApo as necessary to favor mucosal healing and confirmed their role both in vitro (using neutralizing antibodies) and in vivo by depleting these factors from efferocytic macrophage secretome using antibody-coated microbeads. These growth factors only explained some of the beneficial effects induced by factors released by efferocytic macrophages. Overall, the administration of pro-resolving factors released by efferocytic macrophages limits intestinal inflammation and enhance tissue repair, which represents an innovative treatment of IBD.

Drug and Chemical Allergy: A Role for a Specific Naive T-Cell Repertoire?

Allergic reactions to drugs and chemicals are mediated by an adaptive immune response involving specific T cells. During thymic selection, T cells that have not yet encountered their cognate antigen are considered naive T cells. Due to the artificial nature of drug/chemical-T-cell epitopes, it is not clear whether thymic selection of drug/chemical-specific T cells is a common phenomenon or remains limited to few donors or simply does not exist, suggesting T-cell receptor (TCR) cross-reactivity with other antigens. Selection of drug/chemical-specific T cells could be a relatively rare event accounting for the low occurrence of drug allergy. On the other hand, a large T-cell repertoire found in multiple donors would underline the potential of a drug/chemical to be recognized by many donors. Recent observations raise the hypothesis that not only the drug/chemical, but also parts of the haptenated protein or peptides may constitute the important structural determinants for antigen recognition by the TCR. These observations may also suggest that in the case of drug/chemical allergy, the T-cell repertoire results from particular properties of certain TCR to recognize hapten-modified peptides without need for previous thymic selection. The aim of this review is to address the existence and the role of a naive T-cell repertoire in drug and chemical allergy. Understanding this role has the potential to reveal efficient strategies not only for allergy diagnosis but also for prediction of the immunogenic potential of new chemicals.

A DL-4- and TNFα-based culture system to generate high numbers of nonmodified or genetically modified immunotherapeutic human T-lymphoid progenitors

Several obstacles to the production, expansion and genetic modification of immunotherapeutic T cells in vitro have restricted the widespread use of T-cell immunotherapy. In the context of HSCT, delayed naïve T-cell recovery contributes to poor outcomes. A novel approach to overcome the major limitations of both T-cell immunotherapy and HSCT would be to transplant human T-lymphoid progenitors (HTLPs), allowing reconstitution of a fully functional naïve T-cell pool in the patient thymus. However, it is challenging to produce HTLPs in the high numbers required to meet clinical needs. Here, we found that adding tumor necrosis factor alpha (TNFα) to a DL-4-based culture system led to the generation of a large number of nonmodified or genetically modified HTLPs possessing highly efficient in vitro and in vivo T-cell potential from either CB HSPCs or mPB HSPCs through accelerated T-cell differentiation and enhanced HTLP cell cycling and survival. This study provides a clinically suitable cell culture platform to generate high numbers of clinically potent nonmodified or genetically modified HTLPs for accelerating immune recovery after HSCT and for T-cell-based immunotherapy (including CAR T-cell therapy).

Decreased Peripheral Naïve T Cell Number and Its Role in Predicting Cardiovascular and Infection Events in Hemodialysis Patients

Patients with end-stage renal disease (ESRD) are at high risk of morbidity and mortality from cardiovascular and infectious diseases, which have been found to be associated with a disturbed immune response. Accelerated T-cell senescence is prevalent in these patients and considered a significant factor contributing to increased risk of various morbidities. Nevertheless, few studies have explicated the relevance of T-cell senescence to these fatal morbidities in ESRD patients. In this study, we designed a longitudinal prospective study to evaluate the influence of T-cell senescence on cardiovascular events (CVEs) and infections in hemodialysis (HD) patients. Clinical outcomes of 404 patients who had been on HD treatment for at least 6 months were evaluated with respect to T-cell senescence determined using flow cytometry. We found that T-cell senescence was associated with systemic inflammation. High-sensitivity C-reactive protein was positively associated with decreased naïve T cell levels. Elevated tumor necrosis factor-α and interleukin 6 levels were significantly associated with lower central memory T cell and higher T effector memory CD45RA cell levels. Decreased CD4+ naïve T cell count was independently associated with CVEs, whereas decreased CD8+ naïve T cell count was independently associated with infection episodes in HD patients. In conclusion, HD patients exhibited accelerated T-cell senescence, which was positively related to inflammation. A reduction of naïve T cell could be a strong predictor of CVEs and infection episodes in HD patients.

A7 AN INULIN-TYPE FRUCTAN ENRICHED EXCLUSIVE ENTERAL NUTRITION FORMULA MODULATES THE GUT MICROBIOME AND PROMOTES EXPANSION OF ANTI-INFLAMMATORY T CELL SUBSETS TO SUPPRESS COLITIS

Background Exclusive enteral nutrition (EEN), a nutritionally complete fiber-free enteral formula, is the gold standard therapy for newly diagnosed children with Crohn’s disease (CD) but this therapy is not routinely used in pediatric ulcerative colitis patients due to lower efficacy in this subgroup. EEN therapy leads to high remission rates, however it also leads to a dysbiotic gut microbiota profile and disease relapse occurs in 60–80% of CD patients within 12 months of EEN discontinuation. Little is known about the mechanisms underlying the actions of EEN. Notably, previous studies have demonstrated that prebiotics, such as inulin-type fructans (IN), can beneficially modulate the gut microbiome, increase butyrate production and reduce inflammation by leading to anti-inflammatory T cell (i.e. FOXP3+IL10+ CD4+) expansion. To date, the effects of an IN enriched EEN (EEN IN) have not been studied. Aims To examine the effects of EEN vs EEN IN on colitis development, the gut microbiome and CD4+ T cell subsets using an adoptive T cell transfer model of colitis. Methods Mice were split into four groups: 1) Control – normal chow + PBS (n=13; negative control), 2) Chow – normal chow + naive T cell transfer (n=13; positive control), 3) EEN – Ensure Plus® + naive T cell transfer (n=13) and 4) EEN IN – Ensure Plus® with 3% IN + naive T cell transfer (n=13). Naïve T cells (or PBS) were transferred into TCR-b deficient mice and each group was started on their subsequent diets. The naïve T cells will expand into anti- or pro-inflammatory T cells subsets to either cause or suppress colitis in a gut microbiome dependent manner. Body weight and disease activity were monitored for 5-weeks. At the end of the experiment, spleen weights and colon lengths were recorded. Spleen and mesenteric/colonic lymph nodes (MLN) were collected for T cell subset analysis using flow cytometry. Gut microbiota differences were assessed using ddPCR. Short-chain fatty acid levels were analyzed using gas chromatography. The histopathology of the distal colon was scored. Results Mice fed EEN IN showed a reduction in colonic shortening (p<0.001) and histology scores (p=0.0088) compared to EEN mice, and reduced disease activity (p=0.0046) compared to Chow mice. Moreover, EEN IN mice showed a higher expansion of FOXP3+IL10+ CD4+ T cells in the MLN (p=0.0424) and spleen (p=0.0088). EEN IN also led to higher butyrate, Bifidobacterium and Bacteroides concentrations compared to EEN (p=0.0113, p=0.0063, p=0.0224; respectively) and Chow (p=0.0252, p=0.0042, p=0.0416; respectively). Conclusions EEN IN lead to superior outcomes compared to EEN and Chow. These results provide evidence to support undertaking a clinical trial utilizing EEN IN in pediatric inflammatory bowel disease patients. Funding Agencies Michael Smith Foundation for Health Research