Allogeneic Transplantation Model Research Articles

Dll1 and Dll4 Notch Ligands Prime T Cell Alloimmunity and Are Expressed in Non-Overlapping Populations of Fibroblastic Stromal Cells in Spleen and Lymph Nodes at the Onset of Gvhd

Notch signaling drives graft-versus-host-disease (GVHD) pathogenesis in preclinical models of allogeneic hematopoietic cell transplantation (allo-HCT). Short-term systemic blockade of the Notch ligands Delta-like1 (Dll1) and Delta-like4 (Dll4) within two days of allo-HCT conferred long-term protection from acute GVHD lethality in mice, with a dominant impact of Dll4. Surprisingly, critical Notch ligands in GVHD were provided by radioresistant non-hematopoietic fibroblastic stromal cells lineage traced by a Ccl19-Cre transgene in secondary lymphoid organs (SLO) (Chung, JCI 2017). Our discovery revises prevailing GVHD models and identifies a pathogenic role for a stromal cell niche expressing Notch ligands in SLOs. However, little is known about the distribution and regulation of Dll1/Dll4-expressing cells among SLO stromal cells. To address this question, we deployed genetic and biochemical tools to map expression of Notch ligands in SLO stromal cells, characterize the transcriptional landscape of these cells, and identify putative regulators of Notch ligand expression. To map Dll1 and Dll4 expression, we combined a Ccl19-Cre transgene with a ROSA26-YFP Cre-activated allele and Dll1-mCherry or Dll4-mCherry BAC reporters. Using this model, we fluorescently traced all cells derived from Ccl19-Cre+ cells which contain the essential Dll1/Dll4 source in GVHD, while detecting Dll1 vs. Dll4 expression with high sensitivity. Within the lymph node (LN) Ccl19-Cre+ROSA26-YFP+ compartment, Dll4-mCherry was present predominantly among CD157hi CD45-Ter119-CD31-gp38+ fibroblastic stromal cells, including fibroblastic reticular cells (FRCs), marginal reticular cells (MRCs) and follicular dendritic cells (FDCs). In the spleen, Dll4-mCherry was detected among both CD157+ cells (predominant in the T-zone) and CD157- cells. In contrast, Dll1-mCherry was abundant among spleen CD157+ and CD157- cells, but not detected in the corresponding LN compartments. Thus, Dll1 and Dll4 are expressed with a non-overlapping distribution pattern in different SLOs and stromal cell subsets. Next, we studied expression of the dominant Dll4 ligand after MHC-mismatched allo-HCT (BALB/c into C57BL/6). Although Dll4-mCherry fluorescence did not increase, we detected a rise in surface Dll4 protein, peaking 12 hrs after allo-HCT in LN Ccl19-Cre+ CD157hi FRCs, MRCs and FDCs. Increased Dll4 abundance coincided with the critical timing of pathogenic Notch signals within days after allo-HCT and required irradiation conditioning as well as infusion of allogeneic T cells, suggesting a crosstalk between alloreactive T cells and Dll4+ stromal cells. The mechanisms underlying increased surface Dll4 abundance are under investigation, but could involve post-transcriptional effects as the Dll4-mCherry transcriptional reporter did not change. We next characterized transcriptomic features of Dll4+ fibroblastic stromal cells. We performed RNA-Seq on rare SLO stromal cells sort-purified from LNs at baseline and 12 hrs after allo-HCT. We compared CD157hi FRCs that do or do not express Dll4-mCherry, while including CD157lo FRCs that do not express Dll4-mCherry and lymphatic endothelial cells that express Dll4 at high levels as controls. These populations were sort-purified for RNA-Seq analysis, using the data to produce a comprehensive picture of gene expression and regulatory machinery in the SLO niche in alloimmunity, as well as identify new putative regulators of Notch ligand expression. Interestingly, we found only 13 differentially expressed genes between Ccl19-Cre-expressing CD157hi fibroblastic stromal cells that do and do not express the Dll4-mCherry reporter 12 hrs after transplant (log-fold change ≥ 1, corrected p ≤ 0.01). The list of up-regulated transcripts included Cxcl13, encoding a chemokine produced by FDCs, and Rankl, encoding a TNF-family member important in LN development and homeostasis. In summary, our data uncover key new features of the specialized fibroblastic stromal cells expressing Delta-like Notch ligands in SLOs. Ongoing work is testing how qualitative and quantitative differences in Dll1 and Dll4's effects during GVHD may relate to their distribution, regulated expression, or biochemical properties as they interact with Notch receptors in T cells. Our ultimate goal is to design strategies that target Notch ligand expression in SLOs as new prophylactic approaches in GVHD. Disclosures Blazar: Magenta Therapeutics and BlueRock Therapeuetics: Membership on an entity's Board of Directors or advisory committees; Fate Therapeutics, Inc.: Research Funding; Tmunity: Other: Co-Founder; KidsFirst Fund: Research Funding; Childrens' Cancer Research Fund: Research Funding; Leukemia and Lymphoma Society: Research Funding; Abbvie Inc: Research Funding; Alpine Immune Sciences, Inc.: Research Funding; RXi Pharmaceuticals: Research Funding; Regeneron Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees; Five Prime Therapeutics Inc: Co-Founder, Membership on an entity's Board of Directors or advisory committees; Kamon Pharmaceuticals, Inc: Membership on an entity's Board of Directors or advisory committees; BlueRock Therapeutics: Membership on an entity's Board of Directors or advisory committees. Maillard:Genentech: Consultancy; Regeneron: Consultancy.

Results of a Phase III Double-Blind Study of the Addition of Tocilizumab Vs. Placebo to Cyclosporin/Methotrexate Gvhd Prophylaxis after HLA-Matched Allogeneic Stem Cell Transplantation

Results of a Phase III Double-Blind Study of the Addition of Tocilizumab Vs. Placebo to Cyclosporin/Methotrexate Gvhd Prophylaxis after HLA-Matched Allogeneic Stem Cell Transplantation

Graft Versus Host Disease-Associated Dry Eye: Role of Ocular Surface Mucins and the Effect of Rebamipide, a Mucin Secretagogue

The present study was designed to investigate the role of ocular surface glycocalyx and mucins in graft versus host disease (GVHD)-associated dry eye. The ameliorative effect of topical rebamipide, a mucin secretagogue, on GVHD-associated dry eye was also tested. A mouse model of allogeneic transplantation was used to induce ocular GVHD with C57BL/6 as donors and B6D2F1 as recipient mice. Phenol red thread method and fluorescein staining was used to quantify tear secretion and corneal keratopathy. At 8 weeks after the allogeneic transplantation, corneas were harvested to perform glycocalyx staining and confocal microscopy. Goblet cell staining was performed using periodic acid Schiff's staining. Corneal and tear film levels of Mucin 1, 4, 16, 19, and 5AC were quantified using ELISA and real-time PCR. Rebamipide was applied topically twice daily to mice eyes. Allogeneic transplantation resulted in ocular GVHD-associated dry eye characterized by a significant decrease in tear film volume and the onset of corneal keratopathy. Ocular GVHD caused a significant decrease in the area and thickness of corneal glycocalyx. A significant decrease in the goblet cells was also noted. A significant decrease in mucin 4 and 5AC levels was also observed. Topical treatment with rebamipide partially attenuated ocular GVHD-mediated decrease in tear film volume and significantly reduced the severity of corneal keratopathy. Ocular GVHD has detrimental impact on ocular surface glycocalyx and mucins. Rebamipide, a mucin secretagogue, partially prevents ocular GVHD-associated decrease in tear film and reduces the severity of corneal keratopathy.

Regulatory T cells promote corneal endothelial cell survival following transplantation via interleukin-10.

The functional competence of corneal endothelial cells (CEnCs) is critical for survival of corneal allografts, but these cells are often targets of the immune response mediated by graft-attacking effector T cells. Although regulatory T cells (Tregs) have been studied for their role in regulating the host's alloimmune response towards the graft, the cytoprotective function of these cells on CEnCs has not been investigated. The aim of this study was to determine whether Tregs suppress effector T cell-mediated and inflammatory cytokine-induced CEnC death, and to elucidate the mechanism by which this cytoprotection occurs. Using 2 well-established models of corneal transplantation (low-risk and high-risk models), we show that Tregs derived from low-risk graft recipients have a superior capacity in protecting CEnCs against effector T cell-mediated and interferon-γ and tumor necrosis factor-α-induced cell death compared to Tregs derived from high-risk hosts. We further demonstrate that the cytoprotective function of Tregs derived from low-risk hosts occurs independently of direct cell-cell contact and is mediated by the immunoregulatory cytokine IL-10. Our study is the first to report that Tregs provide cytoprotection for CEnCs through secretion of IL-10, indicating potentially novel therapeutic targets for enhancing CEnC survival following corneal transplantation.

A combination regimen of low-dose bortezomib and rapamycin prolonged the graft survival in a murine allogeneic islet transplantation model

As the first FDA-approved proteasome inhibitor drug, bortezomib has been used for the treatment of multiple myeloma and lymphoma. However, its effects alone or in combination with other immunosuppressants on allogeneic islet transplantation have not been reported so far. In this study, we showed that the short-term combination treatment of low-dose bortezomib and rapamycin significantly prolonged the survival of islet allografts. Short-term treatment of low-dose (0.05 mg/kg or 0.1 mg/kg) bortezomib reduced the MHC class II expression in dendritic cells (DCs) of alloantigen-sensitized mice, and prolonged the islet allograft survival for up to 50 days in diabetic mice. Notably, when bortezomib was combined with rapamycin, it induced islet-specific immunological tolerance which allowed the acceptance of a second graft without additional immunosuppression. This regimen dramatically reduced the alloantigen-specific IFN-γ-producing T cells in the spleen, and increased regulatory T cells both at the graft site and in the spleen. Therefore, we propose that short-term treatment of low-dose bortezomib and rapamycin could be a new tolerance-promoting immunosuppressive regimen for allogeneic islet transplantation.

Natural Killer Cells Promote Kidney Graft Rejection Independently of Cyclosporine A Therapy.

Natural Killer (NK) cells have recently been recognized as key players in antibody-mediated chronic allograft failure, thus requiring a comprehensive understanding whether NK cells can escape conventional immunosuppressive regimens. Influence of cyclosporine A (CyA) on NK cell function was studied in a mouse model of allogeneic kidney transplantation (KTX, BALB/c to C57BL/6). Recipients were treated daily with CyA (10 mg/kg) for seven or 14 days for long term survival (day 56). Administration of CyA in recipients resulted in significantly reduced frequencies of intragraft and splenic CD8+ T cells, whereas the latter illustrated reduced IFNγ production. In contrast, intragraft and splenic NK cell frequencies remained unaffected in CyA recipients and IFNγ production and degranulation of NK cells were not reduced as compared with controls. Depletion of NK cells in combination with CyA resulted in an improvement in kidney function until day 7 and prolonged graft survival until day 56 as compared to untreated controls. Surviving animals demonstrated higher intragraft frequencies of proliferating CD4+FoxP3+Ki67+ regulatory T (TREG) cells as well as higher frequencies of CD8+CD122+ TREG. We here demonstrate that NK cell depletion combined with CyA synergistically improves graft function and prolongs graft survival, suggesting that NK cell targeting constitutes a novel approach for improving KTX outcomes.

Stimulation of P2Y11 receptor protects human cardiomyocytes against Hypoxia/Reoxygenation injury and involves PKC\u03b5 signaling pathway

Sterile inflammation is a key determinant of myocardial reperfusion injuries. It participates in infarct size determination in acute myocardial infarction and graft rejection following heart transplantation. We previously showed that P2Y11 exerted an immunosuppressive role in human dendritic cells, modulated cardiofibroblasts’ response to ischemia/reperfusion in vitro and delayed graft rejection in an allogeneic heterotopic heart transplantation model. We sought to investigate a possible role of P2Y11 in the cellular response of cardiomyocytes to ischemia/reperfusion. We subjected human AC16 cardiomyocytes to 5 h hypoxia/1 h reoxygenation (H/R). P2Y11R (P2Y11 receptor) selective agonist NF546 and/or antagonist NF340 were added at the onset of reoxygenation. Cellular damages were assessed by LDH release, MTT assay and intracellular ATP level; intracellular signaling pathways were explored. The role of P2Y11R in mitochondria-derived ROS production and mitochondrial respiration was investigated. In vitro H/R injuries were significantly reduced by P2Y11R stimulation at reoxygenation. This protection was suppressed with P2Y11R antagonism. P2Y11R stimulation following H2O2-induced oxidative stress reduced mitochondria-derived ROS production and damages through PKCε signaling pathway activation. Our results suggest a novel protective role of P2Y11 in cardiomyocytes against reperfusion injuries. Pharmacological post-conditioning targeting P2Y11R could therefore contribute to improve myocardial ischemia/reperfusion outcomes in acute myocardial infarction and cardiac transplantation.

Correction to Simultaneous Diagnosis and Gene Therapy of Immuno-Rejection in Rat Allogeneic Heart Transplantation Model Using a T-Cell-Targeted Theranostic Nanosystem.

Correction to Simultaneous Diagnosis and Gene Therapy of Immuno-Rejection in Rat Allogeneic Heart Transplantation Model Using a T-Cell-Targeted Theranostic Nanosystem.

Differential Expression of Prostaglandin E2 Receptors in Porcine Kidney Transplants

BackgroundAcute rejection of a kidney allograft results from adaptive immune responses and marked inflammation. The eicosanoid prostaglandin E2 (PGE2) modulates the inflammatory response, is generated by cyclooxygenase 2 (COX-2), and binds to 1 of the 4 G protein-coupled E prostanoid cell surface receptors (EP1-4). Receptor activation results in in proinflammatory (EP1 and EP3) or anti-inflammatory (EP2 and EP4) responses. We theorized that expression of the components of the COX-PGE2-EP signaling pathway correlates with acute rejection in a porcine model of allogeneic renal transplantation. MethodCOX-2 enzyme and EP receptor protein expression were quantitated with western blotting and immunohistochemistry from allotransplants (n = 18) and autotransplants (n = 5). Linear regression analysis was used to correlate EP receptor expression with the Banff category of rejection. ResultsPigs with advanced rejection demonstrated significant increases in serum PGE2 metabolites, while pigs with less rejection demonstrated higher tissue concentrations of PGE2 metabolites. A significant negative correlation between COX-2 expression and Banff category of rejection (R = −0.877) was shown. Rejection decreased expression of EP2 and EP4. For both receptors, there was a significant negative correlation with the extent of rejection (R = −0.760 and R = −0.891 for EP2 and EP4, respectively). Rejection had no effect on the proinflammatory receptors EP1 and EP3. ConclusionDownregulation of COX-2 and the anti-inflammatory EP2 and EP4 receptors is associated with acute rejection in unmatched pig kidney transplants, suggesting that the COX-2-PGE2-EP pathway may modulate inflammation in this model. Enhancing EP2 and/or EP4 activity may offer novel therapeutic approaches to controlling the inflammation of acute allograft rejection.

FcγRIIIb Inhibits Renal Transplant Rejection by Inducing Neutrophils Apoptosis

Fcγ receptors (FcI³R) have been proposed to be involved in the pathogenesis of acute rejection (AR) after organ transplantation. However, the mechanisms by which FcγRIIIB mediate this process are still unclear. Previous studies suggested that the FCGR3B gene copy number variation (CNV) is associated with the risk of autoimmune diseases. In this study, we delineated the association of FCGR3B-CNV with end-stage renal disease (ESRD) and risk of rejection post kidney transplantation in 414 kidney transplant recipients and 219 healthy subjects. Our data showed that the percentage of kidney transplant recipients with high copy number of FCGR3B gene was significantly lower than that of healthy controls, suggesting that individuals with low copy of FCGR3B gene are more prone to develop ESRD. Besides, patients with low copy of the FCGR3B gene are associated with susceptibility to AR following kidney transplantation. In mice, transgenic expression of human FcγRIIIB effectively inhibited the AR and improved the function of the transplanted kidney in a model of allogeneic kidney transplantation. This protective effect was associated with an inhibition of T lymphocytes infiltration and Th1 cell immune response. Finally, we showed that FcγRIIIB cross-linking combined with TNF-α treatment in vitro promoted neutrophil apoptosis and was associated with increased activation of cleaved caspase-8 and caspase-3. The combined treatment also increased the arginase-1 expression in neutrophils, which may explain FcγRIIIB-mediated immunosuppression. Funding: This work was supported by the National Fund Committee of China (2012CB517603, 2012AA02A512). Declaration of Interest: No conflicts of interest exist for any authors. Ethical Approval: The study was performed in adherence with the Declaration of Helsinki, and was approved by the Ethics Committee of the First Affiliated Hospital of College of Medicine of Zhejiang University. All patients and healthy controls provided written informed consent.

The purinergic receptor antagonist oxidized adenosine triphosphate suppresses immune-mediated corneal allograft rejection

Adenosine triphosphate (ATP) is released into the extracellular environment during transplantation, and acts via purinergic receptors to amplify the alloimmune response. Here, using a well-established murine model of allogeneic corneal transplantation, we investigated the immunomodulatory mechanisms of the purinergic receptor antagonist oxidized ATP (oATP). Corneal transplantation was performed using C57BL/6 donors and BALB/c hosts. oATP or sterile saline was administered via intraperitoneal injection for 2 weeks postoperatively. Frequencies of CD45+ leukocytes, CD11b+MHCII+ antigen presenting cells (APCs), CD4+IFN-γ+ effector Th1 cells and CD4+Foxp3+ regulatory T cells (Tregs) were evaluated by flow cytometry. Slit-lamp microscopy was performed weekly for 8 weeks to evaluate graft opacity and determine transplant rejection. Treatment with oATP was shown to significantly reduce graft infiltration of CD45+ leukocytes, decrease APC maturation and suppress effector Th1 cell generation relative to saline-treated control. No difference in Treg frequencies or Foxp3 expression was observed between the oATP-treated and control groups. Finally, oATP treatment was shown to reduce graft opacity and increase graft survival. This report demonstrates that oATP limits the alloimmune response by regulating APC maturation and suppressing the generation of alloreactive Th1 immunity.

Thioredoxin-1 confines T cell alloresponse and pathogenicity in graft-versus-host disease.

Oxidative stress is elevated in the recipients of allogeneic hematopoietic transplantation (allo-HCT) and likely contributes to the development of graft-versus-host disease (GVHD). GVHD is characterized by activation, expansion, cytokine production and migration of alloreactive donor T cells, and remains a major cause of morbidity and mortality after allo-HCT. Hence, strategies to limit oxidative stress in GVHD are highly desirable. Thioredoxin1 (Trx1) counteracts oxidative stress by scavenging reactive oxygen species (ROS) and regulating other enzymes that metabolize H2O2. The present study sought to elucidate the role of Trx1 in the pathophysiology of GVHD. Using murine and xenograft models of allogeneic bone marrow transplantation (allo-BMT) and genetic (human Trx1-transgenic, Trx1-Tg) as well as pharmacologic (human recombinant Trx1, RTrx1) strategies; we found that Trx1-Tg donor T cells or administration of the recipients with RTrx1 significantly reduced GVHD severity. Mechanistically, we observed RTrx1 reduced ROS accumulation and cytokine production of mouse and human T cells in response to alloantigen stimulation in vitro. In allo-BMT settings, we found that Trx1-Tg or RTrx1 decreased downstream signaling molecules including NFκB activation and T-bet expression, and reduced proliferation, IFN-γ production and ROS accumulation in donor T cells within GVHD target organs. More importantly, administration of RTrx1 did not impair the graft-versus-leukemia (GVL) effect. Taken together, the current work provides a strong rationale and demonstrates feasibility to target the ROS pathway, which can be readily translated into clinic.

Dickkopf-1 Treatment Stimulates Hematopoietic Regenerative Function in Infused Endothelial Progenitor Cells.

Acute high-dose radiation injury damages the bone marrow hematopoietic stem and progenitor cell compartment. This damage compromises the functional ability of the bone marrow to produce mature blood cells and results in an increased risk of death due to hematopoietic complications. Past work has shown that the bone marrow endothelium provides critical cues, which promote hematopoietic stem cell regeneration after injury. Additionally, transfusion of endothelial cells after radiation injury has been shown to promote recovery of both the bone marrow vasculature and hematopoietic systems. In this work, we examined the regenerative capacity of intravenous infusion of umbilical cord-blood derived endothelial progenitor cells (EPCs) since this is a cell source which is easy to obtain, expand and cryopreserve. We show that pre-treatment with the Wnt-antagonist Dickkopf1 (Dkk1) augments EPC regenerative function in an allogeneic mouse transplant model. Here, hematopoietic recovery was assessed in Balb/c mice after 5 Gy total-body irradiation and transplantation with C57/BL6-derived EPCs either with or without Dkk1 pre-treatment. The Dkk1-treated EPC group had significantly faster recovery of peripheral white blood cells, total bone marrow cellularity, bone marrow progenitors and BM endothelial cells compared to EPC treatment alone or saline controls. Importantly, after an LD50/30 dose of 8 Gy in the Balb/c mouse, Dkk1-treated EPCs were able to rescue 100% of irradiated mice versus 80% in the EPC control group and only 33% in the saline-treated group. To understand how Dkk1 induces regenerative function in the EPCs, we screened for pro-regenerative factors secreted by the EPC in response to Dkk1. Dkk1-treated EPCs were observed to secrete high levels of the anti-fibrotic protein follistatin as well as several proteins known to promote regeneration including EGF, VEGF and G-CSF. This work demonstrates the potential for Dkk1-treated EPCs as a rescue therapeutic for victims of acute radiation injury.

The mechanism of CD8+ CD45RClow regulatory T cell in rat liver transplantation nature tolerance model

Objective To explore the mechanism of CD8+ CD45RClow regulatory T cells and its related cytokines function during the tolerance process of orthotopic liver transplantation in rats. Methods The male Brown Norway rats were selected as the donor, the Lewis rats were the recipients, the allogenic orthotopic liver transplantation model was established by the double cuff method. Experiment animals were divided into early transplantation group (10 rats), tolerance group (10 rats), sham group. Liver function were detected. The tolerance recipients were detected by hematoxylin and eosin (HE) staining. The Luminex used to detect of cytokine and the flow cytometry were used to analyze the changes of subsets of lymphocytes in the peripheral blood/graft and draining lymph node. Results 70% of recipients in operation group could be induced natural immune tolerance. The levels of aspartate aminotransferase (AST) in tolerance group were [(456±54) U/ml] vs. those of sham group [(460±151) U/ml], (P>0.05); the levels of alanine aminotransferase (ALT) in tolerance group were [(122±35) U/ml] vs. those of sham group [(121±46) U/ml, P>0.05]. The expression of CD8+ CD45RClow T cells in tolerance group were increased than in short term group; in grafts it was up regulated in tolerance group than in sham group, and it was no significance between sham group and tolerance group in lymph node around graft. The expression of pDC in short term group are significantly increased compared with sham group. The interferon (IFN)-γ was increased in short term group, return to normal level in tolerance group. interleukin (IL)-10 in grafts milieu were dramatically increased, keep in high level in tolerance group. Conclusion In the tolerance recipients of rat orthotopic liver transplantation model, CD8+ CD45RClow regulatory T cells were significantly increased and aggregated in the peripheral blood and liver. The inhibitory cytokines IL-10 was important to maintain the long-term graft tolerance. Key words: Regulatory T cell; Liver transplantation; Immune tolerance; Interleukin-10; Dendritic cell

Myeloid differentiation factor 88 signaling in donor T cells accelerates graft-versus-host disease.

Myeloid differentiation factor 88 (MyD88) signaling has a crucial role in activation of both innate and adoptive immunity. MyD88 transduces signals via Toll-like receptor and interleukin-1 receptor superfamily to the NFκB pathway and inflammasome by forming a molecular complex with interleukin-1 receptor-associated kinase 4. The MyD88/interleukin-1 receptor-associated kinase 4 pathway plays an important role, not only in innate immunity, but also T-cell immunity; however, its role in donor T cells on the pathophysiology of graft-versus-host disease (GvHD) remains to be elucidated. We addressed this issue by using MyD88-deficient T cells in a mouse model of allogeneic hematopoietic stem cell transplantation (allo-SCT). While MyD88-deficient and wild-type T cells proliferated equivalently after transplantation, MyD88-deficient T cells demonstrated impaired survival and differentiation toward Th1, Tc1, and Th17, and induced less severe GvHD compared to wild-type T cells. Administration of interleukin-1 receptor-associated kinase 4 inhibitor PF-06650833 significantly ameliorated GvHD after allo-SCT. These results thus demonstrate that donor T-cell MyD88/interleukin-1 receptor-associated kinase 4 pathway is a novel therapeutic target against GvHD after allo-SCT.

A Novel Injury Site-Targeted Complement Inhibitor Which Protects against Lung Transplant Ischemia Reperfusion Injury

Purpose Self-reactive natural Abs initiate complement activation and injury following ischemia and reperfusion of certain tissues, but their role in post-ischemic lung injury is unknown. Here, we investigated the expression of two previously identified post-ischemic neoepitopes, namely a modified annexin IV epitope recognized by B4 IgM mAb, and an epitope consisting of a subset of phospholipids recognized by C2 IgM mAb, and additionally determined their role in lung transplant ischemia reperfusion injury (IRI). Methods Lungs from C57Bl/6 mice were orthotopically transplanted into Rag1-/- (antibody-deficient) mice reconstituted with either B4 and C2 mAbs. Results Rag1-/- mice were protected from lung IRI, but reconstitution with either B4 or C2 natural IgM mAbs restored lung IRI. The C2 mAb was more effective than the B4 mAb at restoring injury, as determined by histological and micro-CT analysis. Based on this information, we developed and characterized a therapeutic strategy that exploited the post-ischemia recognition system of natural antibodies. We constructed a single-chain antibody (scFv) derived from C2 mAb and linked it to Crry, an inhibitor of C3 activation (C2scFv-Crry). In models of syngeneic (B6-B6) and allogeneic (Balb/c-B6) lung transplant models in which recipients contain a full natural antibody repertoire, a single post-transplant injection of C2scFv-Crry blocked the binding of endogenous IgM to the graft, inhibited complement activation, and significantly reduced graft inflammation and injury as determined by histology, μCT, and immunhistochemical analysis. The severity of IRI is associated with the onset of acute rejection. Conclusion We identified pathophysiologically important epitopes expressed within the lung after lung ischemia and reperfusion post transplantation. We further describe a novel translatable strategy for complement inhibition that is specifically targeted to the transplanted lung, and that has several advantages over currently available approaches that rely on systemic complement inhibition. Significantly, the C2 epitope has been identified in both mouse and man, increasing the translational relevance of the approach.

Leukotriene B4 Contributes to Development of Cardiac Allograft Vasculopathy

Purpose Cardiac allograft vasculopathy (CAV) is a highly prevalent vaso-occlusive disease that is a leading cause of graft failure and mortality after heart transplantation. While the pathogenesis of CAV remains incompletely understood, histologic evidence suggests that macrophages, which constitute an important part of the innate immune response, may play an important role. Prior studies in pulmonary hypertension have shown that macrophage-derived leukotriene B4 (LTB4) induces proliferation and hypertrophy of human pulmonary artery smooth muscle cells. We hypothesized that LTB4 plays a similar role in the development of CAV. Methods Human studies: We performed immunofluorescence staining of sections from human CAV+ and CAV- coronary arteries with CD68 (macrophage marker) and 5-LO (5-lipoxygenase, LTB4-producing enzyme), and measured serial LTB4 plasma levels in 14 patients with angiographic CAV and 14 matched CAV- controls. Rat model: We performed aortic transplants in a rat CAV model (Fischer into Lewis orthotopic aortic transplants, n=11) with allogeneic transplants as controls (n=6), and performed CD68 and 5-LO staining of aortic cross-sections of mice with and without aortic intimal hyperplasia. We then treated rat allogeneic transplants with bestatin (protease inhibitor that blocks LTB4 production) to determine whether LTB4 inhibition can prevent the intimal proliferation seen in this rat CAV model. Results Immunofluorescence staining showed that 5-LO co-localized with CD68+ macrophages in the intimal layer of CAV+ human arterioles and in allogeneic rat aortic transplant models. Plasma LTB4 levels were higher in CAV+ cases compared to CAV- controls (n=14 per group, p Conclusion Macrophage-derived leukotriene B4 may contribute to development of CAV. Blockade of LTB4 synthesis has the potential to prevent CAV development after heart transplantation.

Host NLRP6 exacerbates graft-versus-host disease independent of gut microbial composition.

Host NOD-like receptor family pyrin domain-containing 6 (NLRP6) regulates innate immune responses and gastrointestinal homeostasis. Its protective role in intestinal colitis and tumorigenesis is dependent on the host microbiome. Host innate immunity and microbial diversity also play a role in the severity of allogeneic immune-mediated gastrointestinal graft-versus-host disease (GVHD), the principal toxicity after allogeneic haematopoietic cell transplantation. Here, we examined the role of host NLRP6 in multiple murine models of allogeneic bone marrow transplantation. In contrast to its role in intestinal colitis, host NLRP6 aggravated gastrointestinal GVHD. The impact of host NLRP6 deficiency in mitigating GVHD was observed regardless of co-housing, antibiotic treatment or colonizing littermate germ-free wild-type and NLRP6-deficient hosts with faecal microbial transplantation from specific pathogen-free wild-type and Nlrp6-/- animals. Chimaera studies were performed to assess the role of NLRP6 expression on host haematopoietic and non-haematopoietic cells. The allogeneic [B6Ly5.2 → Nlrp6-/-] animals demonstrated significantly improved survival compared to the allogeneic [B6Ly5.2 → B6] animals, but did not alter the therapeutic graft-versus-tumour effects after haematopoietic cell transplantation. Our results unveil an unexpected, pathogenic role for host NLRP6 in gastrointestinal GVHD that is independent of variations in the intestinal microbiome and in contrast to its well-appreciated microbiome-dependent protective role in intestinal colitis and tumorigenesis.

Inhibition of cardiac allograft rejection in mice using interleukin-35-modified mesenchymal stem cells.

Interleukin-35 (IL-35) is a cytokine recently discovered to play a potent immunosuppressive role by intensifying the functions of regulatory T cells and inhibiting the proliferation and functions of T helper 1 and T helper 17 cells. Mesenchymal stem cells (MSCs) have recently emerged as promising candidates for cell-based immune therapy, and our previous study showed that IL-35 gene modification can effectively enhance the therapeutic effect of MSCs in vitro. In this study, we isolated adipose tissue-derived MSCs in vitro and infected them with lentiviral vectors overexpressing the IL-35 gene, thereby creating IL-35-MSCs. Subsequently, IL-35-MSCs were then injected into mice of the allogeneic heterotopic abdominal heart transplant model to determine their effect on allograft rejection. The results showed that IL-35-MSCs could continuously secrete IL-35 in vivo and in vitro, successfully alleviate allograft rejection and prolong graft survival. In addition, compared to MSCs, IL-35-MSCs showed a stronger immunosuppressive ability and further reduced the percentage of Th17 cells, increased the proportion of CD4+ Foxp3+ T cells, and regulated Th1/Th2 balance in heart transplant mice. These findings suggest that IL-35-MSCs have more advantages than MSCs in inhibiting graft rejection and may thus provide a new approach for inducing immune tolerance during transplantation.

CD45-Targeted Antibody Drug Conjugate Plus Post Transplant Cytoxan Is Sufficient to Enable Allogeneic Bone Marrow Transplant in a Minor Mismatch Mouse Model

Bone Marrow Transplant (BMT) is a potentially curative treatment for malignant and non-malignant blood disorders. Current regimens for patient preparation, or conditioning, prior to BMT limit the use of this curative procedure due to regimen-related mortality and morbidities, including risks of organ toxicity, infertility and secondary malignancies. Targeted preparation using antibody drug conjugates (ADCs) to mouse CD45 has previously been shown to be sufficient to enable bone marrow transplant (BMT) in syngeneic immune competent mice (Palchaudhuri et al. Nature Biotech 2016 34:738–745), and this approach to preparation has the potential to expand the utility of BMT if it can be successfully translated to patients. To further investigate the utility of this tool ADC in murine transplant models, we explored anti-CD45-saporin (CD45-SAP) in an allogeneic minor mismatch transplant model (Balb/c donor into DBA/2 recipients). The goal of the work was to identify the level of immune suppression, if any, that needs to be used in combination with CD45-SAP to enable high donor chimerism in the allogeneic setting. CD45-SAP (1.9 mg/kg, iv) was evaluated alone or in combination with additional immune modulating agents: clone 30F11 (25 mg/kg, IP), a naked anti-CD45 antibody that mimics ATG by relying on effector function to enable potent peripheral B- and T -cell depletion; pre-transplant Cytoxan (PreTCy, 200 mg/kg, IP), 2 Gy total body irradiation (TBI), and post-transplant Cytoxan (PTCy, 200 mg/kg, IP) to prevent graft versus host disease as well as block host versus graft rejection. 9 Gy TBI was used as the conventional conditioning positive control. Conditioned mice were transplanted with 2 × 107 whole bone marrow cells, and chimerism assessed over 12 weeks. CD45-SAP in combination with PTCy achieved comparable peripheral myeloid chimerism, a readout of stem cell engraftment, to 9 Gy TBI (>90%) at 8 weeks post-transplantation (Fig 1). The addition of 30F11 to the CD45-SAP/PTCy protocol had no effect on peripheral donor chimerism (59% vs 61%), suggesting additional lymphodepletion is not required. In contrast, the single agents alone, 2 Gy TBI in combination with 30F11 and PTCy resulted in These results indicate CD45-SAP in combination with PTCy is sufficient to enable high levels of donor chimerism in the minor mismatched setting without the need for additional immune suppression. CD45-SAP was more effective at conditioning than 2Gy TBI or PreTCy. Future experiments will investigate the CD45-SAP/PTCy protocol in haploidentical and fully mismatched allogeneic mouse models.