Control of Immune Response to Allogeneic Embryonic Stem Cells by CD3 Antibody–Mediated Operational Tolerance Induction

Implantation of embryonic stem cells (ESCs) and their differentiated derivatives into allogeneic hosts triggers an immune response that represents a hurdle to clinical application. We established in autoimmunity and in transplantation that CD3 antibody therapy induces a state of immune tolerance. Promising results have been obtained with CD3 antibodies in the clinic. In this study, we tested whether this strategy can prolong the survival of undifferentiated ESCs and their differentiated derivatives in histoincompatible hosts. Recipients of either mouse ESC–derived embryoid bodies (EBs) or cardiac progenitors received a single short tolerogenic regimen of CD3 antibody. In immunocompetent mice, allogeneic EBs and cardiac progenitors were rejected within 20–25 days. Recipients treated with CD3 antibody showed long‐term survival of implanted cardiac progenitors or EBs. In due course, EBs became teratomas, the growth of which was self‐limited. Regulatory CD4⁺FoxP3⁺ T cells and signaling through the PD1/PDL1 pathway played key roles in the CD3 antibody therapeutic effect. Gene profiling emphasized the importance of TGF‐β and the inhibitory T cell coreceptor Tim3 to the observed effect. These results demonstrate that CD3 antibody administered alone promotes prolonged survival of allogeneic ESC derivatives and thus could prove useful for enhancing cell engraftment in the absence of chronic immunosuppression.     

Cell Therapy for Parkinson's Disease: A Translational Approach to Assess the Role of Local and Systemic Immunosuppression

Neural transplantation is a promising therapeutic approach for neurodegenerative diseases; however, many patients receiving intracerebral fetal allografts exhibit signs of immunization to donor antigens that could compromise the graft. In this context, we intracerebrally transplanted mesencephalic pig xenografts into primates to identify a suitable strategy to enable long‐term cell survival, maturation, and differentiation. Parkinsonian primates received WT or CTLA4‐Ig transgenic porcine xenografts and different durations of peripheral immunosuppression to test whether systemic plus graft‐mediated local immunosuppression might avoid rejection. A striking recovery of spontaneous locomotion was observed in primates receiving systemic plus local immunosuppression for 6 mo. Recovery was associated with restoration of dopaminergic activity detected both by positron emission tomography imaging and histological examination. Local infiltration by T cells and CD80/86+ microglial cells expressing indoleamine 2,3‐dioxigenase were observed only in CTLA4‐Ig recipients. Results suggest that in this primate neurotransplantation model, peripheral immunosuppression is indispensable to achieve the long‐term survival of porcine neuronal xenografts that is required to study the beneficial immunomodulatory effect of local blockade of T cell costimulation.     

Ex Vivo Costimulatory Blockade to Generate Regulatory T Cells From Patients Awaiting Kidney Transplantation

Short‐term outcomes of kidney transplantation have improved dramatically, but chronic rejection and regimen‐related toxicity continue to compromise overall patient outcomes. Development of regulatory T cells (Tregs) as a means to decrease alloresponsiveness and limit the need for pharmacologic immunosuppression is an active area of preclinical and clinical investigation. Nevertheless, the immunomodulatory effects of end‐stage renal disease on the efficacy of various strategies to generate and expand recipient Tregs for kidney transplantation are incompletely characterized. In this study, we show that Tregs can be successfully generated from either freshly isolated or previously cryopreserved uremic recipient (responder) and healthy donor (stimulator) peripheral blood mononuclear cells using the strategy of ex vivo costimulatory blockade with belatacept during mixed lymphocyte culture. Moreover, these Tregs maintain a CD3⁺CD4⁺CD25⁺CD127^lo surface phenotype, high levels of intracellular FOXP3 and significant demethylation of the FOXP3 Treg‐specific demethylation region on allorestimulation with donor stimulator cells. These data support evaluation of this simple, brief Treg production strategy in clinical trials of mismatched kidney transplantation.     

Protecting the Kidney in Liver Transplant Recipients: Practice‐Based Recommendations From the American Society of Transplantation Liver and Intestine Community of Practice

Both acute and chronic kidney disease are common after liver transplantation and result in significant morbidity and mortality. The introduction of the Model for End‐stage Liver Disease score has directly correlated with an increased prevalence of perioperative renal dysfunction and the number of simultaneous liver–kidney transplantations performed. Kidney dysfunction in this population is typically multifactorial and related to preexisting conditions, pretransplantation renal injury, perioperative events, and posttransplantation nephrotoxic immunosuppressive therapies. The management of kidney disease after liver transplantation is challenging, as by the time the serum creatinine level is significantly elevated, few interventions affect the course of progression. Also, immunological factors such as antibody‐mediated kidney rejection have become of greater interest given the rising liver–kidney transplant population. Therefore, this review, assembled by experts in the field and endorsed by the American Society of Transplantation Liver and Intestine Community of Practice, provides a critical assessment of measures of renal function and interventions aimed at preserving renal function early and late after liver and simultaneous liver–kidney transplantation. Key points and practice‐based recommendations for the prevention and management of kidney injury in this population are provided to offer guidance for clinicians and identify gaps in knowledge for future investigations.     

Chimeric Allografts Induced by Short‐Term Treatment With Stem Cell–Mobilizing Agents Result in Long‐Term Kidney Transplant Survival Without Immunosuppression: A Study in Rats

Transplant tolerance allowing the elimination of lifelong immunosuppression has been the goal of research for 60 years. The induction of mixed chimerism has shown promise and has been extended successfully to large animals and to the clinic; however, it remains cumbersome and requires heavy early immunosuppression. In this study, we reported that four injections of AMD3100, a CXCR4 antagonist, plus eight injections of low‐dose FK506 (0.05 mg/kg per day) in the first week after kidney transplantation extended survival, but death from renal failure occurred at 30–90 days. Repeating the same course of AMD3100 and FK506 at 1, 2 and 3 mo after transplant resulted in 92% allograft acceptance (n = 12) at 7 mo, normal kidney function and histology with no further treatment. Transplant acceptance was associated with the influx of host stem cells, resulting in a hybrid kidney and a modulated host immune response. Confirmation of these results could initiate a paradigm shift in posttransplant therapy.     

Human islets and dendritic cells generate post‐translationally modified islet autoantigens

The initiation of type 1 diabetes (T1D) requires a break in peripheral tolerance. New insights into neoepitope formation indicate that post‐translational modification of islet autoantigens, for example via deamidation, may be an important component of disease initiation or exacerbation. Indeed, deamidation of islet autoantigens increases their binding affinity to the T1D highest‐risk human leucocyte antigen (HLA) haplotypes HLA‐DR3/DQ2 and ‐DR4/DQ8, increasing the chance that T cells reactive to deamidated autoantigens can be activated upon T cell receptor ligation. Here we investigated human pancreatic islets and inflammatory and tolerogenic human dendritic cells (DC and tolDC) as potential sources of deamidated islet autoantigens and examined whether deamidation is altered in an inflammatory environment. Islets, DC and tolDC contained tissue transglutaminase, the key enzyme responsible for peptide deamidation, and enzyme activity increased following an inflammatory insult. Islets treated with inflammatory cytokines were found to contain deamidated insulin C‐peptide. DC, heterozygous for the T1D highest‐risk DQ2/8, pulsed with native islet autoantigens could present naturally processed deamidated neoepitopes. HLA‐DQ2 or ‐DQ8 homozygous DC did not present deamidated islet peptides. This study identifies both human islets and DC as sources of deamidated islet autoantigens and implicates inflammatory activation of tissue transglutaminase as a potential mechanism for islet and DC deamidation.     

细胞色素P450 3A4表达调控机制的研究进展

细胞色素P450 3A4(CYP3A4)的表达具有很强的个体间特异性,会引起复杂的药物相互作用。故明确CYP3A4的表达调控机制,对于指导临床合理用药意义重大。本文从转录前、转录后、翻译后修饰3个阶段对CYP3A4的调控机制进行综述。     

Shielding islets with human amniotic epithelial cells enhances islet engraftment and revascularization in a murine diabetes model

Hypoxia is a major cause of considerable islet loss during the early posttransplant period. Here, we investigate whether shielding islets with human amniotic epithelial cells (hAECs), which possess anti‐inflammatory and regenerative properties, improves islet engraftment and survival. Shielded islets were generated on agarose microwells by mixing rat islets (RIs) or human islets (HI) and hAECs (100 hAECs/IEQ). Islet secretory function and viability were assessed after culture in hypoxia (1% O₂) or normoxia (21% O₂) in vitro. In vivo function was evaluated after transplant under the kidney capsule of diabetic immunodeficient mice. Graft morphology and vascularization were evaluated by immunohistochemistry. Both shielded RIs and HIs show higher viability and increased glucose‐stimulated insulin secretion after exposure to hypoxia in vitro compared with control islets. Transplant of shielded islets results in considerably earlier normoglycemia and vascularization, an enhanced glucose tolerance, and a higher β cell mass. Our results show that hAECs have a clear cytoprotective effect against hypoxic damages in vitro. This strategy improves β cell mass engraftment and islet revascularization, leading to an improved capacity of islets to reverse hyperglycemia, and could be rapidly applicable in the clinical situation seeing that the modification to HIs are minor.     

Multicenter evaluation of parametric response mapping as an indicator of bronchiolitis obliterans syndrome after hematopoietic stem cell transplantation

Parametric response mapping (PRM) is a novel computed tomography (CT) technology that has shown potential for assessment of bronchiolitis obliterans syndrome (BOS) after hematopoietic stem cell transplantation (HCT). The primary aim of this study was to evaluate whether variations in image acquisition under real‐world conditions affect the PRM measurements of clinically diagnosed BOS. CT scans were obtained retrospectively from 72 HCT recipients with BOS and graft‐versus‐host disease from Fred Hutchinson Cancer Research Center, Karolinska Institute, and the University of Michigan. Whole lung volumetric scans were performed at inspiration and expiration using site‐specific acquisition and reconstruction protocols. PRM and pulmonary function measurements were assessed. Patients with moderately severe BOS at diagnosis (median forced expiratory volume at 1 second [FEV1] 53.5% predicted) had similar characteristics between sites. Variations in site‐specific CT acquisition protocols had a negligible effect on the PRM‐derived small airways disease (SAD), that is, BOS measurements. PRM‐derived SAD was found to correlate with FEV1% predicted and FEV1/ forced vital capacity (R = ?0.236, P = .046; and R = ?0.689, P < .0001, respectively), which suggests that elevated levels in the PRM measurements are primarily affected by BOS airflow obstruction and not CT scan acquisition parameters. Based on these results, PRM may be applied broadly for post‐HCT diagnosis and monitoring of BOS.     

Reversing donor‐specific antibody responses and antibody‐mediated rejection with bortezomib and belatacept in mice and kidney transplant recipients

Active antibody‐mediated rejection (AMR) is a potentially devastating complication and consistently effective treatment remains elusive. We hypothesized that the reversal of acute AMR requires rapid elimination of antibody‐secreting plasma cells (PC) with a proteasome inhibitor, bortezomib, followed by the sustained inhibition of PC generation with CTLA4‐Ig or belatacept (B/B). We show in mice that B/B therapy selectively depleted mature PC producing donor‐specific antibodies (DSA) and reduced DSA, when administered after primary and secondary DSA responses had been established. A pilot investigation was initiated to treat six consecutive patients with active AMR with B/B. Compassionate use of this regimen was initiated for the first patient who developed early, severe acute AMR that did not respond to steroids, plasmapheresis, and intravenous immunoglobulin after his third kidney transplant. B/B treatment resulted in a rapid reversal of AMR, leading us to treat five additional patients who also resolved their acute AMR episode and had sustained disappearance of circulating DSA for ≤30 months. This study provides a proof‐of‐principle demonstration that mouse models can identify mechanistically rational therapies for the clinic. Follow‐up investigations with a more stringent clinical design are warranted to test whether B/B improves on the standard of care for the treatment of acute AMR.