Untreated Recipients Research Articles

Therapeutic role of interferon-γ in experimental autoimmune encephalomyelitis is mediated through a tolerogenic subset of splenic CD11b+ myeloid cells

Cumulative evidence has established that Interferon (IFN)-γ has both pathogenic and protective roles in Multiple Sclerosis and the animal model, Experimental Autoimmune Encephalomyelitis (EAE). However, the underlying mechanisms to the beneficial effects of IFN-γ are not well understood. In this study, we found that IFN-γ exerts therapeutic effects on chronic, relapsing-remitting, and chronic progressive EAE models. The frequency of regulatory T (Treg) cells in spinal cords from chronic EAE mice treated with IFN-γ was significantly increased with no effect on Th1 and Th17 cells. Consistently, depletion of FOXP3-expressing cells blocked the protective effects of IFN-γ, indicating that the therapeutic effect of IFN-γ depends on the presence of Treg cells. However, IFN-γ did not trigger direct in vitro differentiation of Treg cells. In vivo administration of blocking antibodies against either interleukin (IL)-10, transforming growth factor (TGF)-β or program death (PD)-1, revealed that the protective effects of IFN-γ in EAE were also dependent on TGF-β and PD-1, but not on IL-10, suggesting that IFN-γ might have an indirect role on Treg cells acting through antigen-presenting cells. Indeed, IFN-γ treatment increased the frequency of a subset of splenic CD11b+ myeloid cells expressing TGF-β-Latency Associated Peptide (LAP) and program death ligand 1 (PD-L1) in a signal transducer and activator of transcription (STAT)-1-dependent manner. Furthermore, splenic CD11b+ cells from EAE mice preconditioned in vitro with IFN-γ and myelin oligodendrocyte glycoprotein (MOG) peptide exhibited a tolerogenic phenotype with the capability to induce conversion of naïve CD4+ T cells mediated by secretion of TGF-β. Remarkably, adoptive transfer of splenic CD11b+ cells from IFN-γ-treated EAE mice into untreated recipient mice ameliorated clinical symptoms of EAE and limited central nervous system infiltration of mononuclear cells and effector helper T cells. These results reveal a novel cellular and molecular mechanism whereby IFN-γ promotes beneficial effects in EAE by endowing splenic CD11b+ myeloid cells with tolerogenic and therapeutic activities.

Catch and release: controlling eastern yellowjacket Vespula maculifrons colonies using horizontal insecticide transfer.

Horizontal insecticide transfer is thought to play an important role in controlling a wide range of urban pests including ants, bed bugs, cockroaches and termites. Trap-treat-release is an effective experimental approach that has been used to successfully manage populations of invasive ants in field applications. Trap-treat-release is based on the principles of horizontal transfer. Individuals are captured, treated with the toxicant and released back into the environment. The treated individuals then return to the colony and transfer the toxicant to other members of the population resulting in secondary mortality. The goal of the current study was to evaluate the efficacy of the trap-treat-release technique for controlling field populations of the eastern yellowjacket, Vespula maculifrons. Laboratory experiments demonstrated that fipronil was highly toxic against V. maculifrons across a wide range of concentrations. Furthermore, fipronil was efficiently transferred from treated donors to untreated recipients and caused significant secondary mortality. A field experiment utilized trap-treat-release and demonstrated that fipronil was effectively transferred when foraging worker wasps are trapped, treated, released and allowed to return to their respective colonies. The trap-treat-release method may be an effective alternative to direct nest treatments and could help alleviate problems such as insecticide runoff, environmental contamination, and non-target effects. This method has the potential to provide effective management of social wasps. © 2024 The Author(s). Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Interleukin-37 contributes to endometrial regenerative cell–mediated immunotherapeutic effect on chronic allograft vasculopathy

Background aimsChronic allograft vasculopathy (CAV) remains a predominant contributor to late allograft failure after organ transplantation. Several factors have already been shown to facilitate the progression of CAV, and there is still an urgent need for effective and specific therapeutic approaches to inhibit CAV. Human mesenchymal-like endometrial regenerative cells (ERCs) are free from the deficiencies of traditional invasive acquisition methods and possess many advantages. Nevertheless, the exact immunomodulation mechanism of ERCs remains to be elucidated. MethodsC57BL/6 (B6) mouse recipients receiving BALB/c mouse donor abdominal aorta transplantation were treated with ERCs, negative control (NC)-ERCs and interleukin (IL)-37−/−ERCs (ERCs with IL-37 ablation), respectively. Pathologic lesions and inflammatory cell infiltration in the grafts, splenic immune cell populations, circulating donor-specific antibody levels and cytokine profiles were analyzed on postoperative day (POD) 40. The proliferative capacities of Th1, Th17 and Treg subpopulations were assessed in vitro. ResultsAllografts from untreated recipients developed typical pathology features of CAV, namely endothelial thickening, on POD 40. Compared with untreated and IL-37−/−ERC-treated groups, IL-37–secreting ERCs (ERCs and NC-ERCs) significantly reduced vascular stenosis, the intimal hyperplasia and collagen deposition. IL-37–secreting ERCs significantly inhibited the proliferation of CD4+T cells, reduced the proportions of Th1 and Th17 cells, but increased the proportion of Tregs in vitro. Furthermore, in vitro results also showed that IL-37–secreting ERCs significantly inhibited Th1 and Th17 cell responses, abolished B-cell activation, diminished donor-specific antibody production and increased Treg proportions. Notably, IL-37–secreting ERCs remarkably downregulated the levels of pro-inflammatory cytokines (interferon-γ, tumor necrosis factor-α, IL-1β, IL-6 and IL-17A) and increased IL-10 levels in transplant recipients. ConclusionsThe knockdown of IL-37 dramatically abrogates the therapeutic ability of ERCs for CAV. Thus, this study highlights that IL-37 is indispensable for ERC-mediated immunomodulation for CAV and improves the long-term allograft acceptance.

Age and treatment on the day of embryo transfer in recipient mares affect likelihood of pregnancy.

This retrospective evaluation of data from a large commercial embryo transfer facility aimed to determine the extent to which age and treatment on the day of embryo transfer in recipient mares influence the likelihood of pregnancy. Embryo recovery was carried out on days 8-10 post-ovulation using transcervical uterine flushing. Recipient mares grouped according to their age were treated once on the day of embryo transfer (Day 3-8 post ovulation) and were assigned randomly to 1 of 3 groups: Mares in Group A (n=101) received antispasmodic, antimicrobial, and anti-inflammatory drugs. Mares in Group B (n=100) received gentamicin and flunixin meglumine. Group C (control) (n=103) did not receive any treatment. Detomidine (0.008 mg/kg bwt i.v.) was administered to all recipients before transfer of the embryo. The influence of treatment and recipient´s age was calculated using binary logistic regression. Day 16 post-transfer pregnancy rates were highest in Group A (74/101, 73.3a%), when compared to Group B (60/100, 60%), and Group C (57/103, 55.3b%) (a vs b, p<0.05). Pregnancy loss rates at D45 were not different between groups, A (8/74, 10.8%), B (5/60, 8.3%), and C (6/57, 10.5%), respectively (p>0.05). Pregnancy losses were increased in recipient mares 17-22 years (33.3a%) compared to younger recipient mares (2-6 years 7b%, 7-11 years 10%, 12-16 years 8b%) (a:b p<0.05). The regression model showed that the predicted probability for pregnancy after embryo transfer decreased as the age of the recipient mare increased for treated recipients in Group A (p=0.012), there was no effect of treatment and recipient´s age in Group B, and a decreased likelihood of pregnancy in recipients of advanced age (≥12 years of age) in untreated recipients (group C). Likelihood of pregnancy increased following single administration of antispasmodic, antimicrobial, and anti-inflammatory drugs at the time of embryo transfer in recipients 2-12 years of age. Likelihood of pregnancy in recipients decreased in recipients≥12 years of age. These results, obtained under the conditions of a large commercial embryo transfer program, offer an opportunity to improve pregnancy rates in recipient mares≤12 years of age.

Allograft TLR9 is required for endogenous donor-reactive memory CD8 T cell activation to mediate CTLA-4Ig resistant rejection of high-risk cardiac allografts

Abstract Organ cold ischemic storage (CIS) is inherent to deceased-donor solid organ transplantation and CIS time correlates with poorer transplant outcomes. Prolonged CIS enhances ischemia-reperfusion injury (IRI) following graft revascularization, generating an inflammatory environment that promotes endogenous donor-reactive memory T cell activation leading to CTLA-4Ig costimulatory blockade-resistant rejection. Using a murine heterotopic heart transplant model, we tested the impact of prolonged (8hr) versus minimal (0.5hr) CIS on cell-free mitochondrial DNA (cf-mtDNA) release and activation of the cf-mtDNA sensor TLR9 to understand their contributions to early post-transplant donor-reactive endogenous memory T cell activation and CTLA-4Ig resistant rejection. Plasma cf-mtDNA was significantly elevated in 8hr versus 0.5hr CIS allograft recipients as early as 12hr post-transplant. Flow cytometry analysis of graft infiltrating leukocytes showed reduced memory CD4 and CD8 T cell proliferation on D2 following 8hr CIS in TLR9KO compared to WT allografts. In contrast, graft TLR9KO did not impact the de novo donor-reactive T cell response. 8hr CIS TLR9KO and WT allografts had similar survival in untreated recipients (MST 7.5 vs 7 days) and there was no difference in IFN-γ producing donor-reactive T cells in recipient spleens on D7. When recipients of allografts subjected to 8hr CIS were conditioned with CTLA-4Ig to inhibit de novo T cell priming, graft TLR9KO significantly prolonged graft survival compared to WT (MST 59 vs 28 days). These findings indicate that IRI-induced cf-mtDNA release and TLR9 activation are novel targets for abrogating CTLA-4Ig resistant donor-reactive memory T cell activation within high-risk allografts. This work was supported by NIH grants R01AI40459, T32AI089474, and T32GM007250.

Systemic Cancer Immunostimulatory Therapies and Acute Viral Infection Induce Corticosteroid-Mediated Thymic Involution and Naïve T cell Output in Mice and Humans

Abstract Thymic involution (TI) occurs with aging and during stress responses, decreasing naïve T cell output. Thymic progenitor apoptosis can occur directly by corticosteroids (CS) leading to transient involution followed by recovery. The effects of systemic immunotherapies (IT) used in cancer or immune stimulation via acute viral infection on the thymus has not been well-characterized and was the primary goal of this study. IT treatment of mice with high dose IL-2 (HD IL-2) or models of acute viral infection (mouse cytomegalovirus, MCMV) all resulted in rapid TI due to apoptosis of CD4/CD8 double-positive progenitors followed with a reduction in naïve T cell content. Interestingly, cessation of therapy or resolution of viral infection resulted in greater thymic size compared to untreated recipients, indicating a rebound effect. In both models, increased CS levels in the serum of mice preceded TI. Clinically, patients receiving HD IL-2 for cancer had significantly reduced T cell receptor excision circles, a marker for naïve T cell output, also correlating with increased cortisol levels. Using a model of sub-lethal MCMV infection that did not increase systemic pro-inflammatory cytokines, we observed a similar correlation of TI and increased CS levels. To further analyze the effects of CS on TI, mice were adrenalectomized and then given HD IL-2, where significantly reduced CS levels correlated with partial protection from TI. These results indicate that strong systemic immunostimulation by either IT or acute viral infections markedly induce transient CS-mediated TI, leading to a decrease in naïve T cells. Therefore, targeting CS responses in preventing TI and, especially with the aged, allow for naïve T cell populations to be maintained.

Congenic hematopoietic stem cell transplantation promotes survival of heart allografts in murine models of acute and chronic rejection.

The ability to induce tolerance would be a major advance in the field of solid organ transplantation. Here, we investigated whether autologous (congenic) hematopoietic stem cell transplantation (HSCT) could promote tolerance to heart allografts in mice. In an acute rejection model, fully MHC-mismatched BALB/c hearts were heterotopically transplanted into C57BL/6 (CD45.2) mice. One week later, recipient mice were lethally irradiated and reconstituted with congenic B6 CD45.1 Lin-Sca1+ckit+ cells. Recipient mice received a 14-day course of rapamycin both to prevent rejection and to expand regulatory T cells (Tregs). Heart allografts in both untreated and rapamycin-treated recipients that did not undergo HSCT were rejected within 33 days (median survival time = 8 days for untreated recipients, median survival time = 32 days for rapamycin-treated recipients), whereas allografts in HSCT-treated recipients had a median survival time of 55 days (P < 0.001 vs. both untreated and rapamycin-treated recipients). Enhanced allograft survival following HSCT was associated with increased intragraft Foxp3+ Tregs, reduced intragraft B cells, and reduced serum donor-specific antibodies. In a chronic rejection model, Bm12 hearts were transplanted into C57BL/6 (CD45.2) mice, and congenic HSCT was performed two weeks following heart transplantation. HSCT led to enhanced survival of allografts (median survival time = 70 days vs. median survival time = 28 days in untreated recipients, P < 0.01). Increased allograft survival post-HSCT was associated with prevention of autoantibody development and absence of vasculopathy. These data support the concept that autologous HSCT can promote immune tolerance in the setting of allotransplantation. Further studies to optimize HSCT protocols should be performed before this procedure is adopted clinically.

Electrospun polymer fibers modified with FK506 for the long-term treatment of acute cardiac allograft rejection in a heart transplantation model.

FK506, a first-line immunosuppressant, is routinely administered orally and intravenously following heart transplantation. However, frequent administration can result in a substantial psychological burden to patients, resulting in non-adherence to medication. The purpose of our study is to overcome the disadvantages of systemic drug administration by developing a polymer-based delivery system that is tunable and biodegradable and that can release highly hydrophobic FK506 over extended periods to treat or prevent acute cardiac allograft rejection. Using an electrospinning method, long-acting microfibers were prepared, and FK506 appeared to be continuously released for up to 14 days based on the in vitro release profiles. After implanting the microfiber subcutaneously into the abdominals of transplanted rats, it was found that the infiltration of T cells and macrophages and the secretion of interleukin-2 (IL-2) and IL-1β were significantly reduced compared with those of the free FK506 groups. More importantly, the mean survival time (MST) of the PCL-FK506 group was significantly extended in comparison with that of untreated control recipients and free FK506 (MST of untreated control recipients, free FK506, and PCL-FK506 was 8, 26.1, and 37, respectively). In conclusion, we propose that this drug delivery approach would be suitable for developing long-lasting immunomodulatory agents that prolong cardiac graft survival safely and effectively.

A Novel Role for PLK1 in Leukemia Stem Cell Function in Acute Myeloid Leukemia

Acute myeloid leukemia (AML) is an aggressive hematologic malignancy with poor prognosis. While most patients achieve initial remission following standard chemotherapy, the majority will relapse and ultimately die. Poor outcomes in AML are tied to the properties of leukemia stem cells (LSC), which drive therapy resistance and relapse. For successful therapeutic targeting, it is critical to understand the pathways that operate in LSC function and survival and how they are impacted by drug activity. We carried out an innovative stemness-focused high-throughput drug screen employing a hierarchical AML cell model and a Nanostring-based LSC signature assay to probe for genes and pathways that impact LSC function. All 4 small molecule inhibitors of Polo-like Kinase 1 (PLK1) included in the compound library were among the top hits. PLK1 inhibitor treatment selectively targeted the CD34⁺CD38⁻ fraction of OCI-AML-8227 cells, which is enriched for quiescent LSCs. PLK1 is an important cell cycle regulator; although there are reports for cell cycle-independent roles, they have not been systematically characterized. Importantly, the role of PLK1 has not been previously studied in the context of cancer stem cells. To investigate the role of PLK1 in LSCs, we performed single-cell (sc) multi-omics incorporating both scRNAseq and scATACseq on the CD34⁺CD38⁻ compartment of OCI-AML-8227 cells. Enrichment analysis of previously-identified chromatin accessibility signatures of primitive long-term hematopoietic stem cells (LT-HSC) and progenitors was used to identify cell clusters with distinct stemness and differentiation properties. Interestingly, PLK1 mRNA expression in OCI-AML-8227 was restricted to cells enriched for the LT-HSC epigenetic signature (Fig 1A). In healthy human bone marrow, PLK1 expression was restricted to committed progenitors and not detected in HSCs (Fig 1B). These data strongly suggest a previously unexplored role of PLK1 in regulating stemness that may be specific LSCs and not normal HSCs. To determine the effects of PLK1 against LSCs in vivo, we carried out PLK1 inhibitor treatment using the specific PLK1 inhibitor volasertib in a cohort of 9 primary AML samples in PDX models. Volasertib treatment significantly reduced leukemic burden in 7 of 9 samples, all of which had a high LSC17 score (associated with poor prognosis and standard chemotherapy response). To quantify effects on LSCs, we serially transplanted 2 samples at limiting doses into untreated secondary recipients and demonstrated a 5- to 25-fold reduction in LSC frequency following volasertib treatment, indicating that functional LSCs were targeted by PLK1 inhibition. Together, these data strongly suggest that PLK1 impacts LSC function and stemness, and that PLK1 inhibitors are acting through an uncharacterized cell-cycle independent mechanism to target quiescent LSCs. To discover novel PLK1 signaling pathways, we carried out proximity-dependent biotinylation (PDB) to characterize the PLK1 interactome in serum-starved cells. Preliminary analysis has revealed a number of previously uncharacterized PLK1 interactors, including components of autophagy and apoptosis machinery, that are currently being validated in the hematopoietic cell context. Our study highlights PLK1 as a specific vulnerability of LSCs, and furthers the understanding of malignant PLK1 signaling in non-cell cycle related processes. Further insights into the underlying mechanisms will enable the development of effective therapies to target these pathways and improve patient outcomes in AML. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Reprogramming alveolar macrophage responses to TGF-β reveals CCR2+ monocyte activity that promotes bronchiolitis obliterans syndrome.

Bronchiolitis obliterans syndrome (BOS) is a major impediment to lung transplant survival and is generally resistant to medical therapy. Extracorporeal photophoresis (ECP) is an immunomodulatory therapy that shows promise in stabilizing BOS patients, but its mechanisms of action are unclear. In a mouse lung transplant model, we show that ECP blunts alloimmune responses and inhibits BOS through lowering airway TGF-β bioavailability without altering its expression. Surprisingly, ECP-treated leukocytes were primarily engulfed by alveolar macrophages (AMs), which were reprogrammed to become less responsive to TGF-β and reduce TGF-β bioavailability through secretion of the TGF-β antagonist decorin. In untreated recipients, high airway TGF-β activity stimulated AMs to express CCL2, leading to CCR2+ monocyte-driven BOS development. Moreover, we found TGF-β receptor 2–dependent differentiation of CCR2+ monocytes was required for the generation of monocyte-derived AMs, which in turn promoted BOS by expanding tissue-resident memory CD8+ T cells that inflicted airway injury through Blimp-1–mediated granzyme B expression. Thus, through studying the effects of ECP, we have identified an AM functional plasticity that controls a TGF-β–dependent network that couples CCR2+ monocyte recruitment and differentiation to alloimmunity and BOS.

Synergistic effect of CXCR5+CD8+TAb-supp cell therapy and mTOR inhibition (but not calcineurin inhibition) in suppressing alloantibody following kidney transplant in mice

Abstract CXCR5+CD8+TAb-supp cells inhibit alloantibody (alloAb) production, AMR, and prolong graft survival in mouse models. To determine if this cell therapy is compatible with standard immunosuppression (IS) strategies, we investigate the interaction of CD8+ TAb-supp adoptive cell therapy (ACT) and IS [mTOR inhibitors (mTORi) or CNi] in a mouse model of kidney transplant (KTx). CXCR5+CD8+ T cell ACT to CCR5 KO recipients on day 1 after KTx (D1) significantly suppresses D14 alloAb titer (1259±114) versus untreated controls (5951±630; p=0.0001). Administration of mTORi significantly inhibits alloAb titer (495±77; p&amp;lt;0.0001), while CNi does not (6473±434; p=ns). ACT combined with mTORi significantly reduces alloAb titer compared to ACT alone (387±63 vs 1259±114; p=0.0007). Conversely, CNi treatment partially negates the beneficial effects of ACT on alloAb titer (2385±114; p=0.03). Similarly, ACT reduced the quantity of D14 splenic germinal center (GC; GL-7+Fas+B220+) B cells compared to untreated KO recipients (4037±515 vs 5815±655 cells/mm3; p=0.03). Addition of mTORi to ACT preserves ACT-mediated suppression of GC B cells (4498±940 cells/mm3) while CNi negates ACT-mediated GC B cell suppression (6130±834 cells/mm3; p=0.04). Analysis of persisting GFP+CXCR5+CD8+ T cells D14 after ACT shows that concurrent mTORi treatment is associated with comparable quantity (1671±139 cells/mm3; p=ns), while CNi is associated with reduced quantity (900±83 cells/mm3; p=0.01)of transferred GFP+CXCR5+CD8+ T cells detected in the spleen compared to ACT alone (1601±116 cells/mm3). ACT with CXCR5+CD8+TAb-supp cells is optimal when combined with mTORi, not CNi, to significantly inhibit alloAb production and reduce quantity of splenic GC B cells. Supported by NIH R01 AI083456 (to GLB), T32 AI106704-07 and F32 AI161844 (to JLH), CA016058, UL1TR002733, the OSU Division of Transplant Surgery, and the OSU College of Medicine.

Vγ2+ γδ T Cells in the Presence of Anti-CD40L Control Surgical Inflammation and Promote Skin Allograft Survival

γδ T cells represent a small fraction of total T cells in the body and do not use classical polymorphic major histocompatibility complex‒loaded peptides for mounting an immune response. The importance of the effector and regulatory function of γδ T cells in infections, autoimmunity, and tumor models are well characterized. In this study, we investigated the mechanistic role of γδ T cells in costimulatory blockade‒induced transplantation tolerance. We used donor-specific transfusion and anti-CD40L treatment in C57BL/6 mice to induce tolerance to BALB/c skin allografts. We show that depletion of γδ T cells, specifically Vγ2+ γδ T cells, led to the acute rejection of skin allografts despite tolerogen treatment. Tolerogen treatment promoted CD39+Vγ2+ γδ T cells and suppressed IFN-γ‒producing Vγ2+ γδ T cells in the spleen and allografts. Vγ2+ γδ T cells isolated from tolerized mice suppress T helper type 1 cell differentiation. Adoptive transfer of these regulatory Vγ2+ γδ T cells prolonged the survival of allografts in an untreated recipient and Tcrδ‒/‒ mice. Together, our data show that the Vγ2+ subset promotes costimulatory blockade‒induced survival of skin allografts and that tolerogenic Vγ2+ T cells can be used as an adoptive cellular therapy to promote the survival of allografts.

Improved NK Cell Recovery Following Use of PTCy or Treg Expanded Donors in Experimental MHC-Matched Allogeneic HSCT

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is complicated by graft- versus-host disease (GVHD), which causes immune dysfunction and further delays immune reconstitution through its effects on primary and secondary lymphoid organs. Treatments to prevent GVHD and improve immune recovery following allo-HSCT are needed. Post-transplantation cyclophosphamide (PTCy) is a well-established and clinically widely used method for GVHD prophylaxis after HLA-matched as well as haploidentical allo-HSCT, as well as a promising strategy in the setting of mismatched unrelated donor allo-HSCT. Recently, regulatory T cells (Tregs), a critical subset for immune homeostasis and tolerance induction, have been evaluated for use as GVHD prophylaxis in experimental models and clinical trials. Natural killer (NK) cells are one of the first lymphoid populations to reconstitute following allo-HSCT and are important mediators of protective immunity against pathogens, and are also critical for limiting post-transplantation relapse of hematologic cancers. Several reports have noted that a delay in NK cell recovery may occur following experimental mouse allo-HSCT as well as after clinical allo-HSCT. Here we examined how 2 treatment strategies, PTCy and donor expanded Tregs (TrED), in experimental MHC-matched allo-HSCT affect NK recovery. Our experiments show that both strategies improved NK cell numbers, with PTCy slightly better than TrED, early after allo-HSCT (1 month) compared with untreated allo-HSCT recipients. Importantly, NK cell IFN-γ production and cytotoxic function, as reflected by CD107 expression as well as in vivo killing of NK-sensitive tumor cells, were improved using either PTCy or TrED versus control allo-HSCT recipients. In conclusion, both prophylactic treatments were found to be beneficial for NK recovery and NK cell function following MHC-matched minor antigen-mismatched experimental allo-HSCT. Improved NK recovery could help provide early immunity toward tumors and pathogens in these transplant recipients.

Effects of Glycyrrhizic Acid in Licorice on Prolongation of Murine Cardiac Allograft Survival

Recent evidence has pointed to the promising benefits of using specific immunosuppressive herbal compounds to prolong transplant allograft survival. In this study, we investigated the effects of glycyrrhizic acid (GA), a major component of licorice, in a model of murine heart transplantation. CBA (H2k) mice were transplanted with a fully-MHC mismatched C57BL/6 (H2b) heart allograft and subsequently received daily intraperitoneal administration of normal saline or 0.02, 0.2, or 2.0 mg/d of GA for 7 consecutive days. Untreated CBA recipients, with a median survival time (MST) of 7 days, and groups receiving 0.02mg/d (MST, 8 days) or 0.2mg/d (MST, 9 days) of GA acutely rejected C57BL/6 cardiac allografts. But mice treated with 2.0 mg/d of GA demonstrated significant prolongation of allografts (MST, 23 days). Histologic studies showed that cardiac allografts from GA-treated CBA recipients had preserved graft and vessel structure. Moreover, flow cytometric study showed that the percentage of CD4+CD25+Foxp3+ cell (regulatory T cell [Treg]) populations were increased in GA-treated CBA recipients. In a mixed leukocyte culture, splenocytes from GA-treated mice demonstrated suppressed allo-proliferation, in which interleukin (IL)-2 and interferon gamma production were downregulated and IL-10 secretion was upregulated. In conclusion, GA may be a novel promising therapeutic agent to prolong cardiac allograft survival through direct anti-inflammatory effects and induction of Treg populations.

Effects of Each Domain in Recombinant Human Soluble Thrombomodulin on Prolongation of Murine Cardiac Allograft Survival

Thrombomodulin is used to manage disseminated intravascular coagulation. In our murine heart transplantation model, the administration of recombinant human soluble thrombomodulin (rTM) could induce the prolongation of cardiac allograft survival. However, there are limited data on the graft protective effects of each r domain (D1, D2, and D3). In this study, we investigated the effects of each domain of rTM on alloimmune responses in a murine model of cardiac allograft transplantation. Fully vascularized heterotopic hearts from C57BL/6 donors were transplanted into CBA recipients using microsurgical techniques. CBA mice that underwent transplantation of C57BL/6 cardiac allografts were assigned to 4 groups: no treatment and each domain-exposed group. The dosage of each domain was determined based on our previous experiments. Flow cytometry and histologic studies were performed to determine whether Foxp3+ regulatory T cells were generated. Untreated and D2-exposed CBA recipients acutely rejected C57BL/6 cardiac allografts within 9 days. Administration of D3 resulted in modest prolongation of allograft survival, and administration of D1 significantly prolonged allograft survival. Histologic studies showed that myocardial damage of allografts from D1- and D3-exposed CBA recipients was controlled compared with that of untreated recipients. In particular, the CD4+CD25+Foxp3+ cell population in the splenocytes of D1-exposed CBA recipients was increased. In conclusion, D1 in rTM could help prolong cardiac allograft survival through regulatory T cell induction and graft protective effects.

Mathematical Modeling of Within-Host, Untreated, Cytomegalovirus Infection Dynamics after Allogeneic Transplantation.

Cytomegalovirus (CMV) causes significant morbidity and mortality in recipients of allogeneic hematopoietic cell transplantation (HCT). Whereas insights gained from mathematical modeling of other chronic viral infections such as HIV, hepatitis C, and herpes simplex virus-2 have aided in optimizing therapy, previous CMV modeling has been hindered by a lack of comprehensive quantitative PCR viral load data from untreated episodes of viremia in HCT recipients. We performed quantitative CMV DNA PCR on stored, frozen serum samples from the placebo group of participants in a historic randomized controlled trial of ganciclovir for the early treatment of CMV infection in bone marrow transplant recipients. We developed four main ordinary differential Equation mathematical models and used model selection theory to choose between 38 competing versions of these models. Models were fit using a population, nonlinear, mixed-effects approach. We found that CMV kinetics from untreated HCT recipients are highly variable. The models that recapitulated the observed patterns most parsimoniously included explicit, dynamic immune cell compartments and did not include dynamic target cell compartments, consistent with the large number of tissue and cell types that CMV infects. In addition, in our best-fitting models, viral clearance was extremely slow, suggesting severe impairment of the immune response after HCT. Parameters from our best model correlated well with participants’ clinical risk factors and outcomes from the trial, further validating our model. Our models suggest that CMV dynamics in HCT recipients are determined by host immune response rather than target cell limitation in the absence of antiviral treatment.

Nutritional Support from the Intestinal Microbiota Improves Hematopoietic Reconstitution after Bone-Marrow Transplantation in Mice

Bone-marrow transplantation (BMT) offers curative potential for patients with high-risk hematologic malignancies, but the post-transplantation period is characterized by profound immunodeficiency. Delayed immune reconstitution is an important contributor to transplant-related morbidity and mortality (Maury et al., Br J Haematol, 2001; Small et al., Blood, 1999). Thus, understanding the mechanisms by which the immune system reconstitutes and how environmental exposures might influence this process is an important objective in improving outcomes after BMT.The intestinal microbiota shapes both mucosal and systemic immunity and contributes to steady-state hematopoiesis (Belkaid and Hand, Cell, 2014). To determine the role of the intestinal flora in hematopoietic reconstitution following BMT, we performed syngeneic BMT after lethal irradiation in mice with an intact intestinal flora (control, C/No abx) and in mice treated with two different antibiotic (abx) regimens administered in the drinking water: ampicillin + enrofloxacin (AmpEnro/AE) or vancomycin + amikacin (VancAmik/VA). While both regimens depleted the intestinal flora 1000-fold, ampicillin and enrofloxacin are both relatively well absorbed in the intestine while vancomycin and amikacin both have poor oral bioavailability with negligible systemic effects. BMT recipients treated with either of the abx regimens had lower white blood cell (WBC) counts and, in particular, lower lymphocyte counts compared to untreated BMT recipients (Fig 1A). Fecal microbiota transfer (FMT) with an abx-resistant intestinal flora (Caballero et al., Cell Host Microbe, 2017) rescued the impaired hematopoietic reconstitution in AE-treated mice (Fig 1B). These data rule out a direct inhibitory effect of abx on hematopoietic recovery. When we examined multiple compartments of the hematopoietic cascade we observed that flora depletion significantly impaired hematopoiesis specifically in the lymphoid and myeloid compartments of the bone marrow, thymus, and peripheral blood, while the hematopoietic stem and progenitor compartment and erythroid lineage were largely unaffected. These data are summarized in a radial plot (Fig 1C) in which each compartment of the hematopoietic cascade is a spoke and the distance from the center is proportional the cell count.Treatment of mice with AmpEnro or VancAmik also reduced dietary energy uptake (Fig 1D), resulting in reduction of visceral adipose tissue (Fig 1E). The mice are normally fed a standard chow diet based on complex plant carbohydrates. To test if reduced uptake of calories in flora-depleted animals contributed to impaired hematopoiesis post-BMT, we supplemented the drinking water with 5% sucrose, a carbohydrate source that can be directly utilized by the host in the absence of microbiota metabolism. Sucrose supplementation increased peripheral WBC counts and lymphocyte counts in AE-treated mice (Fig 1F), indicating that a critical function of the intestinal microbiota in supporting hematopoiesis post-BMT is to improve dietary energy uptake.We conclude that apart from specific and direct effects of the microbiota on immuno-hematopoiesis as previously described (Balmer et al., J Immunol, 2014; Clarke et al., Nat Med, 2010; Mazmanian et al., Cell, 2005), the intestinal flora can contribute to post-transplant hematopoietic reconstitution through improved dietary energy uptake. [Display omitted] DisclosuresPeled:Seres: Research Funding. Jenq:Seres: Research Funding. van den Brink:Therakos Institute: Other: Speaking engagement; Jazz Pharmaceuticals: Consultancy; PureTech Health: Consultancy; Seres: Research Funding.

Melatonin Synergizes With Mesenchymal Stromal Cells Attenuates Chronic Allograft Vasculopathy.

BackgroundChronic rejection characterized by chronic allograft vasculopathy (CAV) remains a major obstacle to long-term graft survival. Due to multiple complicated mechanisms involved, a novel therapy for CAV remains exploration. Although mesenchymal stromal cells (MSCs) have been ubiquitously applied to various refractory immune-related diseases, rare research makes a thorough inquiry in CAV. Meanwhile, melatonin (MT), a wide spectrum of immunomodulator, plays a non-negligible role in transplantation immunity. Here, we have investigated the synergistic effects of MT in combination with MSCs in attenuation of CAV.MethodsC57BL/6 (B6) mouse recipients receiving BALB/c mouse donor aorta transplantation have been treated with MT and/or adipose-derived MSCs. Graft pathological changes, intragraft immunocyte infiltration, splenic immune cell populations, circulating donor-specific antibodies levels, cytokine profiles were detected on post-operative day 40. The proliferation capacity of CD4+ and CD8+ T cells, populations of Th1, Th17, and Tregs were also assessed in vitro.ResultsGrafts in untreated recipients developed a typical pathological feature of CAV characterized by intimal thickening 40 days after transplantation. Compared to untreated and monotherapy groups, MT in combination with MSCs effectively ameliorated pathological changes of aorta grafts indicated by markedly decreased levels of intimal hyperplasia and the infiltration of CD4+ cells, CD8+ cells, and macrophages, but elevated infiltration of Foxp3+ cells. MT either alone or in combination with MSCs effectively inhibited the proliferation of T cells, decreased populations of Th1 and Th17 cells, but increased the proportion of Tregs in vitro. MT synergized with MSCs displayed much fewer splenic populations of CD4+ and CD8+ T cells, Th1 cells, Th17 cells, CD4+ central memory T cells (Tcm), as well as effector memory T cells (Tem) in aorta transplant recipients. In addition, the percentage of splenic Tregs was substantially increased in the combination therapy group. Furthermore, MT combined with MSCs markedly reduced serum levels of circulating allospecific IgG and IgM, as well as decreased the levels of pro-inflammatory IFN-γ, TNF-α, IL-1β, IL-6, IL-17A, and MCP-1, but increased the level of IL-10 in the recipients.ConclusionsThese data suggest that MT has synergy with MSCs to markedly attenuate CAV and provide a novel therapeutic strategy to improve the long-term allograft acceptance in transplant recipients.

Pretransplant Hepatitis C Virus Treatment Decreases Access to High-quality Livers.

Background.Despite the revolutionary role of direct-acting antivirals for hepatitis C virus (HCV), the treatment timing for liver transplant candidates remains controversial. We hypothesize that deferring treatment until after liver transplantation improves access to a larger and higher-quality donor pool without a detrimental impact on post-liver transplantation outcomes.Methods.This single-center study includes recipients that underwent deceased-donor liver transplant with HCV as the primary indication January 1, 2014, to December 31, 2018. For recipients that were untreated (n = 87) versus treated (n = 42) pre-LT, we compared post-LT mortality using Cox regression with inverse probability of treatment-weighted data.Results.Among pre-LT untreated recipients, 95% were willing to accept an HCV+ donor, and 44.8% received a positive HCV antibody and nucleic acid amplification test (NAT) liver. Among pre-LT treated recipients, 5% were willing to accept an HCV+ donor, and 100% received a negative HCV antibody and NAT liver. The median calculated model for end-stage liver disease at transplant was similar between pre-LT untreated (13, IQR = 9–22) and treated recipients (11, IQR = 8–14) (P = 0.1). Pre-LT treated recipients received livers from older (47 y old versus 37, P < 0.01) and higher body mass index donors (30.2 versus 26.6; P = 0.04) and spent longer on the waiting list (319 d 180, P < 0.001). Unadjusted post-LT mortality at 1 year was higher in the pre-LT treated recipients (14.6% versus 3.5%, P = 0.02). After adjusting for recipient factors, pre-LT treated recipients trended toward a 3.9 times higher risk of mortality compared with the pre-LT untreated recipients (adjusted hazard ratio = 0.973.8615.4) (P = 0.06).Conclusions.Deferring HCV treatment improves access to higher-quality donors and may improve post-LT survival.

Phenotypic plasticity of invasive Carpobrotus edulis modulates tolerance against herbivores

The anthropogenic movement of species has favoured the introduction of invasive plants worldwide. Invasive plants are frequently released from their natural enemies; however, new associations with generalist herbivores may induce defence mechanisms of non-native plants. Defensive traits are often directly related to the highly competitive ability, but also to potential antagonisms and mutualisms that they can establish with soil microorganisms. Here, we examined whether the intraspecific competition and soil microorganisms influence the morphological and physiological traits of Carpobrotus edulis when is being attacked by the native generalist snail Theba pisana. To achieve this, we grew two C. edulis individuals in separate and same pots filled with live or sterile sand, and with or without T. pisana. Our results indicated that herbivory induced an increase of shoot biomass in attacked C. edulis individuals (i.e., treated donor plants), as well as in un-attacked neighbouring individuals co-growing in the same pot (i.e., untreated recipient plants). Nevertheless, intraspecific competition nor soil microorganisms did not affect the growth of C. edulis despite reduced physiological activity and damage caused by the herbivore. Overall, our findings revealed that C. edulis individuals tolerate snail attack by inducing a compensatory growth response. We conclude that phenotypic plasticity of invasive C. edulis favours tolerance against herbivores, but we also suggest that plant-plant interactions probably determine the plant growth of un-attacked neighbouring C. edulis individuals, thus favouring their invasion mechanisms.