Long-term Cardiac Allograft Survival Research Articles

Simultaneous heart-kidney transplant compared with heart transplant alone in patients with borderline renal function who are not dialysis dependent

ObjectiveThis study assessed characteristics and outcomes of patients who are not dependent on dialysis receiving simultaneous heart kidney transplantation versus heart transplantation alone (HTA) to identify optimal eGFR threshold where combined transplant strategy may be superior. MethodsThis study retrospectively analyzed 7896 adult patients with estimated glomerular filtration rate (eGFR) <60 mL/minute from the United Network for Organ Sharing database who received HTA or simultaneous heart kidney transplant between 2005 and 2021, excluding those who received pretransplant dialysis. Subjects were further stratified into 3 groups based on chronic kidney disease stage at time of transplant: Stage 3A (eGFR 45-59 mL/minute; n = 5044), Stage 3B (eGFR 30-44 mL/minute; n = 2193), and Stage 4 or 5 (eGFR <30 mL/minute; n = 659). Outcomes of interest were all-cause mortality, cardiac allograft failure, and freedom from chronic dialysis or renal transplant following heart transplant. ResultsSimultaneous heart kidney transplant and HTA recipients differed in various baseline characteristics. Simultaneous heart kidney transplant recipients with eGFR <45 mL/minute had greater short- and long-term overall survival and cardiac allograft survival compared with HTA, as well as greater long-term freedom from chronic dialysis or renal transplant. These results were consistent with both propensity matched analyses and multivariable Cox regression analysis of 10 year outcomes. Optimal cutoff value for pretransplant eGFR in predicting elevated risk of renal failure in recipients of heart transplant alone was found to be eGFR ∼45 mL/minute. ConclusionsSimilar to patients with eGFR <30 mL/minute, patients with eGFR 30 to 44 mL/minute who underwent simultaneous heart kidney transplant had superior outcomes compared with HTA, suggesting possible benefit of combined transplant strategy for this subset of heart transplant candidates.

The dynamic cellular landscape of grafts with acute rejection after heart transplantation.

Acute cellular rejection (ACR) is a major barrier to the long-term survival of cardiac allografts. Although immune cells are well known to play critical roles in ACR, the dynamic cellular landscape of allografts with ACR remains obscure. Single-cell RNA sequencing (scRNA-seq) was carried out for mouse cardiac allografts with ACR. Bioinformatic analysis was performed, and subsequent transplant experiments were conducted to validate the findings. Despite an overall large depletion of cardiac fibroblasts (CFBs), highly expanded cytotoxic T lymphocytes and a CXCL10+Gbp2+ subcluster of CFBs were enriched within grafts at the late stage. CXCL10+Gbp2+ CFBs featured strong interferon responsiveness and high expression of chemokines and major histocompatibility complex molecules, implying their involvement in the recruitment and activation of immune cells. Cell‒cell communication analysis revealed that CXCL9/CXCL10-CXCR3 might contribute to regulating CXCL10+Gbp2+ CFB-induced chemotaxis and immune cell recruitment. In vivo transplant studies revealed the therapeutic potential of CXCR3 antagonism in transplant rejection. The findings of our study unveiled a novel CFB subcluster that might mediate acute cardiac rejection. Targeting CXCR3 could prolong allograft survival.

Chronic CD40L blockade is required for long-term cardiac allograft survival with a clinically relevant CTLA4-Ig dosing regimen.

In de-novo kidney transplantation, the CTLA4-Ig fusion protein belatacept is associated with improved graft function but also an increased risk of acute rejection compared to calcineurin inhibitor therapy. The combination with a second costimulation blocker could potentially improve outcome while avoiding calcineurin inhibitor toxicity. The aim of this study was to define the conditions under which the combination of CTLA4-Ig and CD40L blockade leads to rejection-free permanent graft survival in a stringent murine heart transplantation model. Naïve wild-type or CD40L (CD154) knock-out mice received a fully mismatched BALB/c cardiac allograft. Selected induction and maintenance protocols for CTLA4-Ig and blocking αCD40L monoclonal antibodies (mAB) were investigated. Graft survival, rejection severity and donor-specific antibody (DSA) formation were assessed during a 100-day follow-up period. Administering αCD40L mAb as monotherapy at the time of transplantation significantly prolonged heart allograft survival but did not further improve the outcome when given in addition to chronic CTLA4-Ig therapy (which prolongs graft survival to a median of 22 days). Likewise, chronic αCD40L mAb therapy (0.5mg) combined with perioperative CTLA4-Ig led to rejection in a proportion of mice and extensive histological damage, despite abrogating DSA formation. Only the permanent interruption of CD40-CD40L signaling by using CD40L-/- recipient mice or by chronic αCD40L administration synergized with chronic CTLA4-Ig to achieve long-term allograft survival with preserved histological graft integrity in all recipients without DSA formation. The combination of α-CD40L and CTLA4-Ig works most effectively when both therapeutics are administered chronically.

Successful Use of Anti-IL-6R Therapy to Achieve Cardiac Allograft Tolerance in Non-Human Primates

<h3>Purpose</h3> In contrast to kidney allografts, attempts to achieve tolerance of isolated cardiac allografts in non-human primates (NHPs) using a mixed chimerism strategy have been unsuccessful. IL-6 is a pro-inflammatory cytokine known to play an important role in allograft rejection. We investigated whether adding anti-IL-6R therapy to our mixed chimerism protocol would enable the induction of tolerance in NHP recipients of MHC mismatched heart allografts. <h3>Methods</h3> Ten cynomolgous NHPs underwent heart and bone marrow transplantation (BMTx) with non-myeloablative conditioning including total body and thymic irradiation, ATGAM, anti-CD154 mAb, and cyclosporine until post-operative day (POD) 28, with or without anti-IL-6R therapy (tocilizumab, 10 mg/kg IV on POD 0, 7, 14, 21, 28, 56, 84). Group A (n=2) received allogeneic BMTx without anti-IL-6R therapy, Group B (n=6) received allogeneic BMTx with anti-IL-6R therapy, and Group C (n=2) received autologous BMTx with anti-IL-6R therapy. <h3>Results</h3> In Group A, both recipients experienced allograft failure due to rejection on POD 104 and 132 [Table]. In Group B, 3 recipients achieved long-term cardiac allograft survival of >400 days off immunosuppression; one recipient is ongoing at POD 360. Two rejected on POD 169 and 383. For Groups A and B, peak lymphocyte chimerism was 10.1% and 18.1%, respectively and duration of lymphocyte chimerism was 57 and 178 days, respectively. In Group C, one recipient rejected on POD 131 and one is ongoing at POD 120. There was no significant difference in magnitude of peripheral T_reg expansion between groups (p=0.77). Compared to Group A, Groups B and C had lower CRP levels (mean 12.3 vs 54.3 μg/mL) and higher free serum IL-6 (mean 23.0 vs <7.7 pg/mL) while receiving anti-IL-6R therapy. <h3>Conclusion</h3> Tolerance of cardiac allografts has been achieved for the first time in NHPs using a combination of IL-6 signaling blockade and mixed chimerism. This approach represents significant progress towards clinical cardiac allograft tolerance.

Saireito (TJ-114) Suppressed Donor-Specific Antibody Through Immunomodulatory Effects and Regulatory T Cell Induction in a Murine Heart Transplant Model

Saireito (Tsumura Japan [TJ]-114) could induce long-term cardiac allograft survival through the generation of CD4+CD25+Foxp3+ cells (regulatory T cells, Tregs). However, little is known regarding the effects of TJ-114 on the suppression of donor-specific antibody (DSA). Therefore, we aimed to further investigate the suppressive properties of TJ-114 and its effects on DSA production in a murine cardiac allograft model. CBA mice underwent transplantation of C57BL/6 hearts and were subsequently administered TJ-114 (2g/kg/d) from the day of transplantation until 7 days afterward. TJ-114-treated recipients demonstrated upregulation of splenic Tregs and suppressed DSA production at postoperative day 10 relative to untreated controls. This effect was sustained at postoperative day 20 even when TJ-114 administration was stopped at day 7. To then investigate the involvement of Tregs in the suppression of DSA production, anti-interleukin-2 receptor alpha antibody (PC-61) was administered to deplete Treg populations in TJ-114-treated CBA recipients on postoperative days 0, 3, 6, and 9 or 20, 23, and 26. At day 10, CBA recipients that received PC-61 with TJ-114 demonstrated suppression of DSA production similar to those receiving only TJ-114. Nonetheless, when mice were treated with PC-61 at days 20, 23, and 26, DSA levels gradually increased to levels comparable to those of untreated mice by day 29, suggesting that Tregs are necessary to sustain the suppression of DSA once the effects of TJ-114 have subsided. Taken together, TJ-114 may be a promising therapeutic strategy to prolong allograft survival through its combined immunosuppressive effects in inducing Tregs and suppressing DSA production.

A short course of tofacitinib sustains the immunoregulatory effect of CTLA4-Ig in the presence of inflammatory cytokines and promotes long-term survival of murine cardiac allografts

Costimulation blockade-based regimens are a promising strategy for management of transplant recipients. However, maintenance immunosuppression via CTLA4-Ig monotherapy is characterized by high frequency of rejection episodes. Recent evidence suggests that inflammatory cytokines contribute to alloreactive T cell activation in a CD28-independent manner, a reasonable contributor to the limited efficacy of CTLA4-Ig. In this study, we investigated the possible synergism of a combined short-term inhibition of cytokine signaling and CD28 engagement on the modulation of rejection. Our results demonstrate that the JAK/STAT inhibitor tofacitinib restored the immunomodulatory effect of CTLA4-Ig on mouse alloreactive T cells in the presence of inflammatory cytokines. Tofacitinib exposure conferred dendritic cells with a tolerogenic phenotype reducing their cytokine secretion and costimulatory molecules expression. JAK inhibition also directly affected T cell activation. In vivo, the combination of CTLA4-Ig and tofacitinib induced long-term survival of heart allografts and, importantly, it was equally effective when using grafts subjected to prolonged ischemia. Transplant survival correlated with a reduction in effector T cells and intragraft accumulation of regulatory T cells. Collectively, our studies demonstrate a powerful synergism between CTLA4-Ig and tofacitinib and suggest their combined use is a promising strategy for improved management of transplanted patients.

Galectin-9 is required for endometrial regenerative cells to induce long-term cardiac allograft survival in mice

BackgroundEndometrial regenerative cells (ERCs), a novel type of mesenchymal-like stem cells, were identified as an attractive candidate for immunoregulation and induction of cardiac allograft tolerance. However, the underlying mechanisms of ERCs in immune regulation still remain largely unclear. The present study is designed to determine whether the expression of Galectin-9 (Gal-9), a soluble tandem-repeat member of the galectin family, is crucial for ERC-based immunomodulation.MethodsIn this study, we measured Gal-9 expression on ERCs and then co-cultured Gal-9-ERCs, ERCs, and ERCs+lactose (Gal-9 blocker) with activated C57BL/6-derived splenocytes. Furthermore, we performed mouse heart transplantation between BALB/c (H-2d) donor and C57BL/6 (H-2b) recipient. ERCs were administrated 24 h after the surgery, either alone or in combination with rapamycin.ResultsOur data demonstrate that ERCs express Gal-9, and this expression is increased by IFN-γ stimulation in a dose-dependent manner. Moreover, both in vitro and in vivo results show that Gal-9-ERC-mediated therapy significantly suppressed Th1 and Th17 cell response, inhibited CD8+ T cell proliferation, abrogated B cell activation, decreased donor-specific antibody production, and enhanced the Treg population. The therapeutic effect of ERCs was further verified by their roles in prolonging cardiac allograft survival and alleviating graft pathological changes.ConclusionsTaken together, these data indicate that Gal-9 is required for ERC-mediated immunomodulation and prevention of allograft rejection.

Dedicator of Cytokinesis 2 in Cell Signaling Regulation and Disease Development.

Dedicator of cytokinesis 2 (DOCK2) is a CDM family protein containing DOCK homology region (DHR)-1 and DHR-2, Src-homology 3 (SH3) domain, and C-terminal polybasic amino acid cluster. The CDM family consists of 11 mammalian members and is classified into four subfamilies, the DOCK-A, -B, -C, and -D. DOCK2 is a member of DOCK-A subfamily and an atypical guanine exchange factor regulating the loading of GTP to activate Rac. It is primarily found in peripheral blood, spleen, and thymus and mainly expressed in lymphocytes and macrophages of various organs. DOCK2 is also expressed in microglial in brain and is induced in neointima smooth muscle following vascular injury. Functionally, DOCK2 is involved in cell motility, polarity, adhesion, proliferation, and apoptosis. It is essential for lymphocyte migration and activation as well as neutrophil chemotaxis. DOCK2 also regulates the differentiation of natural killer T cells, type 2 T helper cells, and plasmacytoid dendritic cells. In addition, it is important for the growth of B cell lymphoma and prostate cancer cells. Deletion of DOCK2 enables long-term cardiac allograft survival. Moreover, DOCK2 is associated with the Alzheimer Disease, HIV development, and the early-onset of invasive infections. Recently, we found that DOCK2 plays a critical role in SMC phenotypic modulation and vascular remodeling. In this review, we will briefly summarize recent advancement of DOCK2 function. J. Cell. Physiol. 232: 1931-1940, 2017. © 2016 Wiley Periodicals, Inc.

Tanshinol suppresses cardiac allograft rejection in a murine model

Achieving long-term cardiac allograft survival without continuous immunosuppression is highly desired in organ transplantation. Studies have shown that Salvia miltiorrhiza, an herb also known as danshen, improves microcirculation and is highly effective in treating coronary heart disease. Our objective is to determine whether tanshinol, an ingredient of danshen, improves cardiac allograft survival. Fully vascularized heterotopic heart transplantation was performed using BALB/c mice as donors and C57BL/6 mice as recipients, which were then treated with tanshinol and rapamycin. CD4+FoxP3+ regulatory T cells (Tregs) were quantified by flow analyses, whereas CCL22 was measured by real-time polymerase chain reaction and Western blotting. We found that tanshinol significantly delayed cardiac allograft rejection. It promoted long-term allograft survival induced by rapamycin, a mammalian target-of-rapamycin (mTOR) inhibitor. Tanshinol increased CD4+FoxP3+ Treg numbers in cardiac allografts, but not spleens and lymph nodes, of recipient mice by enhancing chemokine CCL22 expression in cardiac allografts, especially cardiac dendritic cells. In contrast, rapamycin increased Treg numbers in both lymphoid organs and allografts, suggesting that it generally expands Tregs. Moreover, Tregs induced by rapamycin plus tanshinol were more potent in suppressing T-cell proliferation in vitro than those from untreated recipients. Neutralizing CCL22 hindered CD4+FoxP3+ Treg migration to cardiac allografts and reversed long-term allograft survival induced by tanshinol plus rapamycin. Tanshinol suppresses cardiac allograft rejection by recruiting CD4+FoxP3+ Tregs to the graft, whereas rapamycin does so via expanding the Tregs. Thus, tanshinol cooperates with rapamycin to further extend cardiac allograft survival.

Tracking of TCR-Transgenic T Cells Reveals That Multiple Mechanisms Maintain Cardiac Transplant Tolerance in Mice.

Solid organ transplantation tolerance can be achieved following select transient immunosuppressive regimens that result in long-lasting restraint of alloimmunity without affecting responses to other antigens. Transplantation tolerance has been observed in animal models following costimulation or coreceptor blockade therapies, and in a subset of patients through induction protocols that include donor bone marrow transplantation, or following withdrawal of immunosuppression. Previous data from our lab and others have shown that proinflammatory interventions that successfully prevent the induction of transplantation tolerance in mice often fail to break tolerance once it has been stably established. This suggests that established tolerance acquires resilience to proinflammatory insults, and prompted us to investigate the mechanisms that maintain a stable state of robust tolerance. Our results demonstrate that only a triple intervention of depleting CD25+ regulatory T cells (Tregs), blocking programmed death ligand-1 (PD-L1) signals, and transferring low numbers of alloreactive T cells was sufficient to break established tolerance. We infer from these observations that Tregs and PD-1/PD-L1 signals cooperate to preserve a low alloreactive T cell frequency to maintain tolerance. Thus, therapeutic protocols designed to induce multiple parallel mechanisms of peripheral tolerance may be necessary to achieve robust transplantation tolerance capable of maintaining one allograft for life in the clinic.

Abstract 15539: A Novel Compound Tanshinol Prolongs Cardiac Allograft Survival Induced by Rapamycin

Introduction: Cardiac transplantation provides a cure for end-stage heart diseases. Achieving long-term cardiac allograft survival without continuously global immunosuppression is a highly desirable goal because long-term immunosuppression causes serious side effects. This study is to induce long-term cardiac allograft survival without long-term conventional immunosuppression via treatments with Tanshinol, a major compound derived from traditional Chinese medicine, Danshen, which has been shown to improve tissue microcirculation and reduce inflammation. Hypothesis: Tanshinol alone, or in combination with mTOR inhibitor rapamycin, prolongs cardiac allograft survival. Methods: In this study, C57BL/6 mice were transplanted with a Balb/C heart and treated with Tanshinol (5mg/kg/day i.p. on days 0, 2, 4, 6, 8, 10 and 14) and/or rapamycin (1 mg/kg/day for 3 weeks). In vivo CD4+FoxP3+ Treg numbers from draining LNs and graft-infiltrating cells were quantified by FACS 3 weeks after transplantation. Results: We found that Tanshinol alone did not extend cardiac allograft survival compared to control group (MST = 8 vs. 7 days, n=7-8) while rapamycin delayed the rejection significantly (MST = 28 vs. 7 days, n=6-7, P&lt;0.05). Interestingly, treatments with both Tanshinol and rapamycin further prolonged allograft survival (MST = 63 versus 28 days, n=7-8, P&lt;0.05). Moreover, Tanshinol did not increase CD4+FoxP3+ Treg numbers in draining LN (DLN) (2.5±0.4 vs 2.2±0.3, x10000, P&gt;0.05) while rapamycin did so (3.9±0.5 vs 2.2±0.3, P&lt;0.05). In contrast, Tanshinol increased Treg number in grafts (13.5±0.9 vs 7.4±0.6, P&lt;0.05) while rapamycin did not (8.1±0.7 vs 7.4±0.6, P&gt;0.05). Tanshinol plus rapamycin augmented Treg numbers in both DLNs and grafts compared to untreated group. Thus, our studies reveal that Tanshinol and rapamycin synergistically prolong cardiac allograft survival without long-term immunosuppression by promoting Treg generation and migration to LNs and allografts. Conclusion: Our data, for the first time, demonstrate that Tanshinol synergizes with rapamycin to prolong cardiac allograft survival via enhancing both generation and migration of Tregs.

IL-34 is a Treg-specific cytokine and mediates transplant tolerance

Cytokines and metabolic pathway-controlling enzymes regulate immune responses and have potential as powerful tools to mediate immune tolerance. Blockade of the interaction between CD40 and CD40L induces long-term cardiac allograft survival in rats through a CD8+CD45RClo Treg potentiation. Here, we have shown that the cytokine IL-34, the immunoregulatory properties of which have not been previously studied in transplantation or T cell biology, is expressed by rodent CD8+CD45RClo Tregs and human FOXP3+CD45RCloCD8+ and CD4+ Tregs. IL-34 was involved in the suppressive function of both CD8+ and CD4+ Tregs and markedly inhibited alloreactive immune responses. Additionally, in a rat cardiac allograft model, IL-34 potently induced transplant tolerance that was associated with a total inhibition of alloantibody production. Treatment of rats with IL-34 promoted allograft tolerance that was mediated by induction of CD8+ and CD4+ Tregs. Moreover, these Tregs were capable of serial tolerance induction through modulation of macrophages that migrate early to the graft. Finally, we demonstrated that human macrophages cultured in the presence of IL-34 greatly expanded CD8+ and CD4+ FOXP3+ Tregs, with a superior suppressive potential of antidonor immune responses compared with non-IL-34-expanded Tregs. In conclusion, we reveal that IL-34 serves as a suppressive Treg-specific cytokine and as a tolerogenic cytokine that efficiently inhibits alloreactive immune responses and mediates transplant tolerance.

Inhibition of Histone Methylation Induces Long-Term Survival of Vascularized Cardiac Allografts and Preserves the Third-Party T Cell Immunity.

Inhibition of Histone Methylation Induces Long-Term Survival of Vascularized Cardiac Allografts and Preserves the Third-Party T Cell Immunity.

Immunomodulation Induced By a Novel Immunosuppressant, NK026680 Plus Donor Specific Transfusion Permits a Long-Term Cardiac Allograft Survival in Mice.

Background: We have recently demonstrated that a novel triazolopylimidine derivative, NK026680 (NK), inhibits T cell proliferation and prolongs rat cardiac allograft survival. In this study, we examined the immunomodulatory effect of NK in combination with donor specific transfusion (DST) in mice. Methods: A fully MHC incompatible BALB/c-to-C57BL/6 mouse heart transplantation was performed on day 0. DST, 20x106 donor-splenocytes, was given intravenously on day -7. NK (40 mg/kg/day) was orally administered from day -7 to day +6. Recipient-splenocytes were cocultured with irradiated donor-splenocytes, and T cell proliferation (3H-thymidine incorporation), IFN-g production (ELISPOT) and cell phenotypes (FACS) were assessed. Results: Untreated mice promptly rejected cardiac allograft at a graft median survival time (gMST) of 6.5 days. DST or NK monotherapy prolonged gMST to 24.5 and 25.5 days, respectively. In a sharp contrast, NK plus DST treatment (NK+DST) markedly prolonged gMST to 75.5 days. (A). In the NK+DST group, both proliferation and IFN-g production against donorantigens transiently increased on day 0, while they were both significantly suppressed on day 7 (p<0.05, vs. Untreated). Following in vivo antigen-challenge by infusing 20x106 donor-splenocytes on day 0, the splenic Foxp3+CD4+ T cells increased[Figure 1](B); however, CD69+ effector T cells were abolished.Figure: No Caption available.(C and D) in the NK+DST group. Conclusion:NK together with DST induces a potent immunomodulatory effect by shifting immune-balance towards a regulatory milieu, and markedly prolongs cardiac allograft survival in mice. DISCLOSURES:Saiga, K.: Employee, salary.

Anti-TCRβ mAb Induces Long-Term Allograft Survival by Reducing Antigen-Reactive T Cells and Sparing Regulatory T Cells

TCR specific antibodies may modulate the TCR engagement with antigen-MHC complexes, and in turn regulate in vivo T cell responses to alloantigens. Herein, we found that in vivo administration of mAbs specific for mouse TCRβ (H57-597), TCRα or CD3 promptly reduced the number of CD4(+) and CD8(+) T cells in normal mice, but H57-597 mAb most potently increased the frequency of CD4(+) Foxp3(+) Treg cells. When mice were injected with staphylococcal enterotoxin B (SEB) superantigen and H57-597 mAb, the expansion of SEB-reactive Vβ8(+) T cells was completely abrogated while SEB-nonreactive Vβ2(+) T cells remained unaffected. More importantly, transient H57-597 mAb treatment exerted long-lasting effect in preventing T cell responses to alloantigens, and produced long-term cardiac allograft survival (>100 days) in 10 out of 11 recipients. While Treg cells were involved in maintaining donor-specific long-term graft survival, T cell homeostasis recovered over time and immunity was retained against third party allografts. Moreover, transient H57-597 mAb treatment significantly prolonged survival of skin allografts in naïve recipients as well as heart allografts in skin-sensitized recipients. Thus, transient modulation of the TCRβ chain by H57-597 mAb exhibits potent, long-lasting therapeutic effects to control alloimmune responses.

Blockade of NKG2D Synergized With CTLA4-Ig in Promoting Long-Term Graft Survival in Murine Models of Cardiac Transplantation [RETRACTED

Blockade of B7-CD28 interaction with CTLA4-Ig could prolong allograft survival in cardiac transplantation. NKG2D is an activating or coactivating receptor on NK cells, γδ T, and CD8 T cells and played an important role in transplant immunity. C57BL/6 (wild type and γδ or interleukin (IL)-17) mice were transplanted with allogeneic BALB/c hearts and treated with CTLA4-Ig alone or in combination with anti-NKG2D monoclonal antibodies. The survival of grafts was monitored daily by abdominal palpation until the complete cessation of cardiac contractility. We found that wild type recipient treated with anti-NKG2D monoclonal antibodies plus CTLA4-Ig showed significantly prolonged survival cardiac allograft (>90 days, P<0.001). These in vivo results in combined therapy group correlated with low expression of interferon-γ whereas increased expression of IL-4 and alternatively activated macrophage markers. Furthermore, with blockade of NKG2D, the number of IL-17-producing γδ T cells was significantly reduced, which was demonstrated as the main source of IL-17 production. And in our γδ and IL-17 murine cardiac transplantation models, we found that γδ or IL-17 deficiency could significantly prolong cardiac allograft survival. Blockade of NKG2D is effective in synergizing with CTLA4-Ig to promote long-term cardiac allograft survival in mice, and this effect is associated with decreased infiltration of IL-17-producing γδ T cells.

Arsenic trioxide is a novel agent for combination therapy to prolong heart allograft survival in allo-primed T cells transferred mice

Alloreactive memory T cells are major barriers to transplantation acceptance due to their capacity to accelerate rejection. Here, we investigated the effects of combined treatment with arsenic trioxide (As2O3) and blocking monoclonal antibodies (mAb) against CD154 and LFA-1 (anti-CD154/LFA-1) on graft survival as well as changes in pathology and immunological responses in mice with adoptively transferred allo-primed T cells. The mean survival time (MST) for the cardiac allografts in recipient mice receiving the combination of As2O3 and anti-CD154/LFA-1 was significantly longer (>113.7days) compared to those receiving anti-CD154/LFA-1 (23.2days), As2O3 (12.5days) alone or no treatment (5.5days). This combined strategy distinctly inhibited lymphocyte infiltration in grafts, proliferation of splenic T cells and the generation of memory T cells in spleens. Moreover, the combined treatment caused the significant down-regulation of IL-2 and IFN-γ accompanied by increased expression of TGF-β and regulatory T cells (Tregs) in spleens, which led to long-term cardiac allograft survival in recipient mice. These results highlight the potential application of As2O3 and its contribution in combination therapy with antibody blockade to delay rejection by memory T cells.

Association of Pediatric Heart Transplant Coronary Vasculopathy with Abnormal Hemodynamic Measures

Transplant coronary artery disease (TCAD) is the limiting factor to long-term cardiac allograft survival; however, presymptomatic diagnosis remains challenging. To that concern, we evaluated the association of abnormal catheter-derived filling pressures with TCAD in pediatric heart transplant (HTx) recipients. DESIGN, PATIENTS, OUTCOME MEASURES: Data from 52 presymptomatic pediatric HTx patients were analyzed. Catheter-derived right ventricular end-diastolic pressure (RVEDP) and pulmonary capillary wedge pressure (PCWP) were recorded. Biopsies were collected to verify the absence of rejection. TCAD was diagnosed an average of 8.3 years post-HTx in 20 (38%) patients, six of whom died and four of whom underwent retransplantation. Catheter-derived pressure measurements showed that RVEDP was elevated in TCAD compared with non-TCAD patients (9.5 ± 6.0 vs. 5.4 ± 4.7; P= .005), as was the PCWP (12.9 ± 5.7 vs. 9.1 ± 5.7; P= .012). Results from logistic regression analysis showed RVEDP > 10 mm Hg or PCWP > 12 mm Hg was associated with TCAD (OR = 5.2; P= .010). In this series, elevated ventricular filling pressures measured during routine surveillance catheterizations were associated with angiographic TCAD. Recognizing the association between elevated RVEDP/PCWP and TCAD may prompt earlier diagnosis and treatment of this potentially lethal process.

Adoptive transfer of DNT cells induces long-term cardiac allograft survival and augments recipient CD4+Foxp3+ Treg cell accumulation

Regulatory T (Treg) cells play an important role in the regulation of immune responses but whether Treg will induce tolerance in transplant recipients in the clinic remains unknown. Our previous studies have shown that TCRαβ+CD3+CD4−CD8−NK1.1− (double negative, DN) T cells suppress T cell responses and prolong allograft survival in a single locus MHC-mismatched mouse model. In this study, we investigated the role of DNT cells in a more robust, fully MHC-mismatched BALB/c to C57BL/6 transplantation model, which may be more clinically relevant. Adoptive transfer of DNT cells in combination with short-term rapamycin treatment (days 1–9) induced long-term heart allograft survival (101±31 vs. 39±13days rapamycin alone, p<0.01). Furthermore adoptive transfer DNT cells augmented CD4+Foxp3+ Treg cells accumulation in transplant recipients while depletion of CD4+ Treg cells by anti-CD25 inhibited the effect of DNT cells on long-term graft survival (48±12days vs. 101±31days, p<0.001). In conclusion, DNT cells combined with short-term immunosuppression can prolong allograft survival, which may be through the accumulation of CD4+Foxp3+ Treg cells in the recipient. Our result suggests that allograft tolerance may require the co-existence of different type Treg cell phenotypes which are affected by current immunosuppression.

DN-Treg cells induce long-term cardiac allograft survival in fully MHC mismatched recipients but do not eliminate T memory cells (145.13)

Abstract Establishment of immune tolerance is a major goal in transplantation. Regulatory T (Treg) cells play an important role in the regulation of immune responses. Our previous studies have shown that TCRαβ+CD3+CD4-CD8-NK1.1- (double negative, DN) Treg cells suppress anti-donor T cell responses and prolong allograft survival in a single MHC-mismatched mouse model. In this study, we tested whether DN-Treg cells can induce long-term graft survival in the stringent BALB/c to C57BL/6 heart transplant model. Adoptive transfer of 107 DN-Treg cells in combination with rapamycin (RAPA) treatment (day 1- 9) induced long-term graft survival (101 vs. 39 days RAPA alone, p&amp;lt;0.01). DN-Treg treated recipients had few graft-infiltrating CD4+ and CD8+ T cells on day 40 compared to massive infiltration in RAPA treated controls. Memory T (Tm) cells (CD3+CD44+) were found to be resistant to DN-Treg cell-mediated suppression in vitro. The effect of DN-Treg on Tm in vivo was tested in B6-Rag1-/- mice. DN-Treg cells along with CD44+ Tm cells modestly prolonged BALB/c skin graft survival in contrast to DN-Treg with CD44- T cells (26 vs 43 days, P&amp;lt;0.001). In conclusion, DN-Treg cells combined with short term immunosuppression, can prolong allograft survival in the absence of tolerance. Furthermore, this may be related to the resistance of Tm cells to DN-Treg cell suppression, suggesting alternative strategies will be needed to control Tm cells and establish tolerance after transplantation.