In vivo induction of regulatory T cells by anti-CD45RB antibody causes transferable tolerance to discordant human xenogenic islets

BACKGROUND

The treatment of diabetes by islet cell transplantation has become an accepted therapy, with transplantation of xenogeneic islet cells an attractive alternative to the problem. Previous studies in mice have demonstrated that anti-CD45RB induce immune tolerance in human pancreatic islet cells. The current study was to define the mechanism of action of anti-CD45RB induced nonspecific immune tolerance to heteroantigens.

METHODS

A total of 1500 IEQ human islets were transplanted to diabetic B6μMT-/- mice, B6 mice, and μMT-/- diabetic mice undergoing thymectomy. These mice were treated short-term with doses of anti-CD45RB. CD4+Foxp3+Tregs were detected in the blood, peripheral lymphatic organs by flow cytometry, and immunohistochemistry. In addition, anti-CD25 mAb was administered to tolerant human islet cells B6μMT-/-mice. Mice then were transplanted with other human islet cells and received CD4+CD25+Tregs isolated from tolerant human islets mice to observe islet destruction.

RESULTS

Anti-CD45RB treatment-induced tolerance to islets in both immunocompetent and B-cell-deficient mice (μMT-/- mice) by processes that were dependent on CD25+ Tregs, but not B cells. Anti-CD45RB treatment increased the number of CD4+Foxp3+Tregs cells. Anti-CD45RB treatment-induced immune tolerance that was antigen nonspecific, with Tregs playing an important role. Anti-CD45RB treatment-induced tolerance generated Tregs that could be transferred to another individual to manifest nonspecific immune tolerance.

CONCLUSION

The results of the experiment suggest that anti-CD45RB induced tolerance to human islet xenografts is mediated by the proliferation of Tregs. These tolerogenic Tregs can be transferred to other mice and induce nonspecific immune tolerance.

Feasibility, long-term safety, and immune monitoring of regulatory T cell therapy in living donor kidney transplant recipients

Short-term outcomes in kidney transplantation are marred by progressive transplant failure and mortality secondary to immunosuppression toxicity. Immune modulation with autologous polyclonal regulatory T cell (Treg) therapy may facilitate immunosuppression reduction promoting better long-term clinical outcomes. In a Phase I clinical trial, 12 kidney transplant recipients received 1-10 × 10⁶ Treg per kg at Day +5 posttransplantation in lieu of induction immunosuppression (Treg Therapy cohort). Nineteen patients received standard immunosuppression (Reference cohort). Primary outcomes were rejection-free and patient survival. Patient and transplant survival was 100%; acute rejection-free survival was 100% in the Treg Therapy versus 78.9% in the reference cohort at 48 months posttransplant. Treg therapy revealed no excess safety concerns. Four patients in the Treg Therapy cohort had mycophenolate mofetil withdrawn successfully and remain on tacrolimus monotherapy. Treg infusion resulted in a long-lasting dose-dependent increase in peripheral blood Tregs together with an increase in marginal zone B cell numbers. We identified a pretransplantation immune phenotype suggesting a high risk of unsuccessful ex-vivo Treg expansion. Autologous Treg therapy is feasible, safe, and is potentially associated with a lower rejection rate than standard immunosuppression. Treg therapy may provide an exciting opportunity to minimize immunosuppression therapy and improve long-term outcomes.

The efficacy of HBOC-201 in ex situ gradual rewarming kidney perfusion in a rat model

Gradual rewarming from hypothermic to normothermic is a novel perfusion modality with superior outcome to sudden rewarming to normothermic. However, the identification of an oxygen carrier that could function at a temperature range from 4 to 7°C or whether it is necessary to use oxygen carrier during kidney rewarming, remains unresolved. This study was designed to test the use of a hemoglobin‐based oxygen carrier (HBOC) during gradual kidney rewarming as an alternative to simple dissolved oxygen. In this study, 10 rat kidneys were randomly divided into the control and the HBOC group. In the control group, no oxygen carrier was used during rewarming perfusion and the perfusion solution was oxygenated only by applying diffused carbogen flow. The protocol mimicked a donor after circulatory death (DCD) kidney transplantation, where after 30 minutes warm ischemia and 120 minutes cold storage in University of Wisconsin solution, the DCD kidneys underwent gradual rewarming from 10 to 37°C during 90 minutes with or without HBOC. This was followed by 30 minutes of warm ischemia in room temperature to mimic the anastomosis time and 120 minutes of reperfusion at 37°C to mimic the early post‐transplant state of the graft. The HBOC group demonstrated superior kidney function which was highlighted by higher ultrafiltrate production, better glomerular filtration rate and improved sodium reabsorption. There was no significant difference between the 2 groups regarding the hemodynamics, tissue injury, and adenosine triphosphate levels. In conclusion, this study suggests better renal function recovery in DCD kidneys after rewarming with HBOC compared to rewarming without an oxygen carrier.

Pre-emptive pangenotypic direct acting antiviral therapy in donor HCV-positive to recipient HCV-negative heart transplantation: an open-label study

BACKGROUND

Low donor heart availability underscores the need to identify all potentially transplantable organs. We sought to determine whether pre-emptive administration of pangenotypic direct-acting antiviral therapy can safely prevent the development of chronic hepatitis C virus (HCV) infection in uninfected recipients of HCV-infected donor hearts.

METHODS

Patients were recruited for this an open-label, single-centre, proof-of-concept study from Nov 1, 2017, to Nov 30, 2018. Following enrolment, the recipient's status on the heart transplantation waiting list was updated to reflect a willingness to accept either an HCV-positive or HCV-negative heart donor. Patients who underwent transplantation with a viraemic donor heart, as determined by nucleic acid testing (NAT), received pre-emptive oral glecaprevir-pibrentasvir before transport to the operating room followed by an 8-week course of glecaprevir-pibrentasvir after transplantation. Patients receiving HCV antibody-positive donor hearts without detectable circulating HCV RNA were followed using a reactive approach and started glecaprevir-pibrentasvir only if they developed viraemia. The primary outcome was achievement of sustained virological response 12 weeks after completion of glecaprevir-pibrentasvir therapy (SVR12). Patients were followed from study enrolment to 1 year after transplantation. This is an interim analysis, initiated after all enrolled patients reached the primary outcome. Results reflect data from Nov 1, 2017, to May 30, 2019. This trial is registered with ClinicalTrials.gov, number NCT03208244.

FINDINGS

55 patients were assessed for eligibility and 52 consented to enrolment. 25 patients underwent heart transplantation with HCV-positive donor hearts (20 NAT-positive, five NAT-negative), three of whom underwent simultaneous heart-kidney transplantation. All 20 recipients of NAT-positive hearts tolerated glecaprevir-pibrentasvir and showed rapid viral suppression (median time to clearance 3·5 days, IQR 0·0-8·3), with the subsequent achievement of SVR12 by all 20. The five recipients of NAT-negative grafts did not become viraemic. Median pre-transplant waiting time for patients following enrolment in the HCV protocol was 20 days (IQR 8-57). Patient and allograft survival were 100% at a median follow-up of 10·7 months (range 6·5-18·0).

INTERPRETATION

Pre-emptive administration of glecaprevir-pibrentasvir therapy results in expedited organ transplantation, rapid HCV suppression, prevention of chronic HCV infection, and excellent early allograft function in patients receiving HCV-infected donor hearts. Long-term outcomes are not yet known.

FUNDING

American Association for the Study of Liver Diseases, National Institutes of Health, and the Massachusetts General Hospital.

Normothermic ex vivo liver perfusion: platform for liver graft assessment and therapeutic modification

Liver transplantation as a treatment for end stage liver failure remains limited in the United States by the number and quality of donor allografts. Static cold storage, the current standard of care for organ storage prior to transplantation, offers no method for assessment or therapeutic modification. Cold ischemia and its attendant hypoxia deplete cellular adenosine triphosphate (ATP) stores, promote cellular damage, and degrade overall organ quality. Normothermic ex vivo liver perfusion (NEVLP) offers the potential for assessment of allograft function and restoration of intracellular energy stores prior to transplantation. A completed phase III randomized trial demonstrated livers undergoing NEVLP prior to transplantation demonstrate superior early graft function and less early graft dysfunction. NEVLP offers a platform for modification of the allograft via the application of defatting or therapeutic cocktails, missense RNA technology, or gene editing modalities. The wide versatility of NEVLP appears to be a promising tool to expand the current pool of transplantable liver allografts.

PD-L1 genetic overexpression or pharmacological restoration in hematopoietic stem and progenitor cells reverses autoimmune diabetes

Immunologically based clinical trials performed thus far have failed to cure type 1 diabetes (T1D), in part because these approaches were nonspecific. Because the disease is driven by autoreactive CD4 T cells, which destroy β cells, transplantation of hematopoietic stem and progenitor cells (HSPCs) has been recently offered as a therapy for T1D. Our transcriptomic profiling of HSPCs revealed that these cells are deficient in programmed death ligand 1 (PD-L1), an important immune checkpoint, in the T1D nonobese diabetic (NOD) mouse model. Notably, the immunoregulatory molecule PD-L1 plays a determinant role in controlling/inhibiting activated T cells and thus maintains immune tolerance. Furthermore, our genome-wide and bioinformatic analysis revealed the existence of a network of microRNAs (miRNAs) controlling PD-L1 expression, and silencing one of key altered miRNAs restored PD-L1 expression in HSPCs. We therefore sought to determine whether restoration of this defect would cure T1D as an alternative to immunosuppression. Genetically engineered or pharmacologically modulated HSPCs overexpressing PD-L1 inhibited the autoimmune response in vitro, reverted diabetes in newly hyperglycemic NOD mice in vivo, and homed to the pancreas of hyperglycemic NOD mice. The PD-L1 expression defect was confirmed in human HSPCs in T1D patients as well, and pharmacologically modulated human HSPCs also inhibited the autoimmune response in vitro. Targeting a specific immune checkpoint defect in HSPCs thus may contribute to establishing a cure for T1D.

Heterogeneity of SOX9 and HNF1β in Pancreatic Ducts Is Dynamic

Pancreatic duct epithelial cells have been suggested as a source of progenitors for pancreatic growth and regeneration. However, genetic lineage-tracing experiments with pancreatic duct-specific Cre expression have given conflicting results. Using immunofluorescence and flow cytometry, we show heterogeneous expression of both HNF1β and SOX9 in adult human and murine ductal epithelium. Their expression was dynamic and diminished significantly after induced replication. Purified pancreatic duct cells formed organoid structures in 3D culture, and heterogeneity of expression of Hnf1β and Sox9 was maintained even after passaging. Using antibodies against a second cell surface molecule CD51 (human) or CD24 (mouse), we could isolate living subpopulations of duct cells enriched for high or low expression of HNF1β and SOX9. Only the CD24^high (Hnfβ^high/Sox9^high) subpopulation was able to form organoids.

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HNF1β and SOX9 are differentially expressed across the pancreatic ductal tree

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Their expression was dynamic and diminished significantly after replication

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Live subpopulations can be isolated using CD51 (human) and CD24 (mouse).

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Only the CD24^high (Hnfβ^high/Sox9^high) subpopulation was able to form organoids

Immunosuppression With CD40 Costimulatory Blockade Plus Rapamycin for Simultaneous Islet-Kidney Transplantation in Nonhuman Primates

The lack of a reliable immunosuppressive regimen that effectively suppresses both renal and islet allograft rejection without islet toxicity hampers a wider clinical application of simultaneous islet-kidney transplantation (SIK). Seven MHC-mismatched SIKs were performed in diabetic cynomolgus monkeys. Two recipients received rabbit antithymocyte globulin (ATG) induction followed by daily tacrolimus and rapamycin (ATG/Tac/Rapa), and five recipients were treated with anti-CD40 monoclonal antibody (mAb) and rapamycin (aCD40/Rapa). Anti-inflammatory therapy, including anti-interleukin-6 receptor mAb and anti-tumor necrosis factor-α mAb, was given in both groups. The ATG/Tac/Rapa recipients failed to achieve long-term islet allograft survival (19 and 26 days) due to poor islet engraftment and cytomegalovirus pneumonia. In contrast, the aCD40/Rapa regimen provided long-term islet and kidney allograft survival (90, 94, >120, >120, and >120 days), with only one recipient developing evidence of allograft rejection. The aCD40/Rapa regimen was also tested in four kidney-alone transplant recipients. All four recipients achieved long-term renal allograft survival (100% at day 120), which was superior to renal allograft survival (62.9% at day 120) with triple immunosuppressive regimen (tacrolimus, mycophenolate mofetil, and steroids). The combination of anti-CD40 mAb and rapamycin is an effective and nontoxic immunosuppressive regimen that uses only clinically available agents for kidney and islet recipients.

Dealloying-based interpenetrating-phase nanocomposites matching the elastic behavior of human bone

The long-term performance of orthopedic implants depends crucially on a close match between the mechanical behavior of bone and of the implant material. Yet, the present man-made materials with the required biocompatibility and strength are substantially stiffer than bone. This mismatch results in stress shielding, which can lead to the loss of bone mass and may even lead to a revision surgery. Here we report a new materials design strategy towards metal-polymer composites that are based on constituents with established biocompatibility and that can be matched to bone. Ti-based nanoporous alloys, prepared by liquid-metal dealloying, are infiltrated with epoxy to form interpenetrating-phase nanocomposites. At up to 260 MPa, their yield strength is technologically interesting for a deformable light-weight material. More importantly, Young’s modulus can be adjusted between 4.4 and 24 GPa, which affords matching to bone. As another parallel to bone, the strength of the composite materials is strain-rate dependent. These findings suggest that the novel composite materials may provide the basis for promising future implant materials.

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.

Co-transplantation of autologous MSCs delays islet allograft rejection and generates a local immunoprivileged site

AIMS

Mesenchymal stem cells (MSCs) are multipotent cells with immunomodulatory properties. We tested the ability of MSCs to delay islet allograft rejection.

METHODS

Mesenchymal stem cells were generated in vitro from C57BL/6 and BALB/c mice bone marrow, and their immunomodulatory properties were tested in vitro. We then tested the effect of a local or systemic administration of heterologous and autologous MSCs on graft survival in a fully allogeneic model of islet transplantation (BALB/c islets into C57BL/6 mice).

RESULTS

In vitro, autologous, but not heterologous, MSCs abrogated immune cell proliferation in response to alloantigens and skewed the immune response toward a Th2 profile. A single dose of autologous MSCs co-transplanted under the kidney capsule with allogeneic islets delayed islet rejection, reduced graft infiltration, and induced long-term graft function in 30 % of recipients. Based on ex vivo analysis of recipient splenocytes, the use of autologous MSCs did not appear to have any systemic effect on the immune response toward graft alloantigens. The systemic injection of autologous MSCs or the local injection of heterologous MSCs failed to delay islet graft rejection.

CONCLUSION

Autologous, but not heterologous, MSCs showed multiple immunoregulatory properties in vitro and delayed allograft rejection in vivo when co-transplanted with islets; however, they failed to prevent rejection when injected systemically. Autologous MSCs thus appear to produce a local immunoprivileged site, which promotes graft survival.

β-Cell differentiation of human pancreatic duct-derived cells after in vitro expansion

β-Cell replacement therapy is a promising field of research that is currently evaluating new sources of cells for clinical use. Pancreatic epithelial cells are potent candidates for β-cell engineering, but their large-scale expansion has not been evidenced yet. Here we describe the efficient expansion and β-cell differentiation of purified human pancreatic duct cells (DCs). When cultured in endothelial growth-promoting media, purified CA19-9(+) cells proliferated extensively and achieved up to 22 population doublings over nine passages. While proliferating, human pancreatic duct-derived cells (HDDCs) downregulated most DC markers, but they retained low CK19 and SOX9 gene expression. HDDCs acquired mesenchymal features but differed from fibroblasts or pancreatic stromal cells. Coexpression of duct and mesenchymal markers suggested that HDDCs were derived from DCs via a partial epithelial-to-mesenchymal transition (EMT). This was supported by the blockade of HDDC appearance in CA19-9(+) cell cultures after incubation with the EMT inhibitor A83-01. After a differentiation protocol mimicking pancreatic development, HDDC populations contained about 2% of immature insulin-producing cells and showed glucose-unresponsive insulin secretion. Downregulation of the mesenchymal phenotype improved β-cell gene expression profile of differentiated HDDCs without affecting insulin protein expression and secretion. We show that pancreatic ducts represent a new source for engineering large amounts of β-like-cells with potential for treating diabetes.

Alginate encapsulant incorporating CXCL12 supports long-term allo- and xenoislet transplantation without systemic immune suppression

Islet transplantation represents a potentially curative approach for individuals with Type I Diabetes. The requirement for systemic immune suppression to control immune-mediated rejection of transplanted islets and the limited human islet supply represent significant roadblocks to progress for this approach. Islet microencapsulation in alginate offers limited protection in the absence of systemic immunosuppression, but does not support long-term islet survival. The chemokine, CXCL12, can repel effector T cells while recruiting immune-suppressive regulatory T cells (Tregs) to an anatomic site while providing a prosurvival signal for beta-cells. We proposed that coating or encapsulating donor islets with CXCL12 would induce local immune-isolation and protect and support the function of an allo- or xenograft without systemic immune suppression. This study investigated the effect of alginate microcapsules incorporating CXCL12 on islet function. Islet transplantation was performed in murine models of insulin-dependent diabetes. Coating of islets with CXCL12 or microencapsulation of islets with alginate incorporating the chemokine, resulted in long-term allo- and xenoislet survival and function, as well as a selective increase in intragraft Tregs. These data support the use of CXCL12 as a coating or a component of an alginate encapsulant to induce sustained local immune-isolation for allo- or xenoislet transplantation without systemic immunosuppression.

Islet product characteristics and factors related to successful human islet transplantation from the Collaborative Islet Transplant Registry (CITR) 1999-2010

The Collaborative Islet Transplant Registry (CITR) collects data on clinical islet isolations and transplants. This retrospective report analyzed 1017 islet isolation procedures performed for 537 recipients of allogeneic clinical islet transplantation in 1999-2010. This study describes changes in donor and islet isolation variables by era and factors associated with quantity and quality of final islet products. Donor body weight and BMI increased significantly over the period (p<0.001). Islet yield measures have improved with time including islet equivalent (IEQ)/particle ratio and IEQs infused. The average dose of islets infused significantly increased in the era of 2007-2010 when compared to 1999-2002 (445.4±156.8 vs. 421.3±155.4×0(3) IEQ; p<0.05). Islet purity and total number of β cells significantly improved over the study period (p<0.01 and <0.05, respectively). Otherwise, the quality of clinical islets has remained consistently very high through this period, and differs substantially from nonclinical islets. In multivariate analysis of all recipient, donor and islet factors, and medical management factors, the only islet product characteristic that correlated with clinical outcomes was total IEQs infused. This analysis shows improvements in both quantity and some quality criteria of clinical islets produced over 1999-2010, and these parallel improvements in clinical outcomes over the same period.

Transplant tolerance depends on regulatory T cells induced by TGF-β-producing regulatory B cells (P2168)

Regulatory B cells (Bregs) have been shown to play a critical role in immune homeostasis and in autoimmunity models. We have recently demonstrated that combined anti-TIM-1 and anti-CD45RB antibody treatment results in tolerance to full MHC mismatch islet allografts in mice, generating Bregs that are necessary for tolerance, and capable of transferring tolerance to untreated animals. Herein, we demonstrate that adoptively transferred Bregs require the presence of Tregs to establish tolerance, and that adoptive transfer of Bregs increases the number of Tregs. Bregs induce significantly more Foxp3 expression in CD4+CD25- T cells, in vivo, compared to naive B cells. We also show that Bregs express the TGF-β associated latency-associated peptide (LAP). Furthermore, Breg-mediated graft prolongation post-adoptive transfer is abrogated by neutralization of TGF-β activity. Collectively, these findings suggest that in this model of antibody-induced transplantation tolerance, Bregs promote graft survival by promoting Treg development, possibly via TGF-β production.

Human monoclonal antibody MBL-HCV1 delays HCV viral rebound following liver transplantation: a randomized controlled study

Rapid allograft infection complicates liver transplantation (LT) in patients with hepatitis C virus (HCV). Pegylated interferon-α and ribavirin therapy after LT has significant toxicity and limited efficacy. The effect of a human monoclonal antibody targeting the HCV E2 glycoprotein (MBL-HCV1) on viral clearance was examined in a randomized, double-blind, placebo-controlled pilot study in patients infected with HCV genotype 1a undergoing LT. Subjects received 11 infusions of 50 mg/kg MBL-HCV1 (n=6) or placebo (n=5) intravenously with three infusions on day of transplant, a single infusion on days 1 through 7 and one infusion on day 14 after LT. MBL-HCV1 was well-tolerated and reduced viral load for a period ranging from 7 to 28 days. Median change in viral load (log10 IU/mL) from baseline was significantly greater (p=0.02) for the antibody-treated group (range -3.07 to -3.34) compared to placebo group (range -0.331 to -1.01) on days 3 through 6 posttransplant. MBL-HCV1 treatment significantly delayed median time to viral rebound compared to placebo treatment (18.7 days vs. 2.4 days, p<0.001). As with other HCV monotherapies, antibody-treated subjects had resistance-associated variants at the time of viral rebound. A combination study of MBL-HCV1 with a direct-acting antiviral is underway.

Birth and death of human β-cells in pancreases from cadaver donors, autopsies, surgical specimens, and islets transplanted into mice

There is great interest in the potential of the human endocrine pancreas for regeneration by β-cell replication or neogenesis. Our aim was to explore this potential in adult human pancreases and in both islet and exocrine tissue transplanted into mice. The design was to examine pancreases obtained from cadaver donors, autopsies, and fresh surgical specimens and compare these findings with those obtained from islet and duct tissue grafted into the kidney. Islets and exocrine tissue were transplanted into normoglycemic ICR-SCID mice and studied 4 and 14 weeks later. β-Cell replication, as assessed by double staining for insulin and Ki67, was 0.22 ± 0.03% at 4 weeks and 0.13 ± 0.03% at 14 weeks. In contrast, no evidence of β-cell replication could be found in 11 cadaver donor and 10 autopsy pancreases. However, Ki67 staining of β-cells in frozen sections obtained at surgery was comparable to that found in transplanted islets. Evidence for neogenesis in transplanted pancreatic exocrine tissue was supported by finding β-cells within the duct epithelium and the presence of cells double stained for insulin and cytokeratin 19 (CK19). However, β-cells within the ducts never constituted more than 1% of the CK19-positive cells. With confocal microscopy, 7 of 12 examined cells expressed both markers, consistent with a neogeneic process. Mice with grafts containing islet or exocrine tissue were treated with various combinations of exendin-4, gastrin, and epidermal growth factor; none increased β-cell replication or stimulated neogenesis. In summary, human β-cells replicate at a low level in islets transplanted into mice and in surgical pancreatic frozen sections, but rarely in cadaver donor or autopsy pancreases. The absence of β-cell replication in many adult cadaver or autopsy pancreases could, in part, be an artifact of the postmortem state. Thus, it appears that adult human β-cells maintain a low level of turnover through replication and neogenesis.

Mechanisms of xenogeneic baboon platelet aggregation and phagocytosis by porcine liver sinusoidal endothelial cells

Background

Baboons receiving xenogeneic livers from wild type and transgenic pigs survive less than 10 days. One of the major issues is the early development of profound thrombocytopenia that results in fatal hemorrhage. Histological examination of xenotransplanted livers has shown baboon platelet activation, phagocytosis and sequestration within the sinusoids. In order to study the mechanisms of platelet consumption in liver xenotransplantation, we have developed an in vitro system to examine the interaction between pig endothelial cells with baboon platelets and to thereby identify molecular mechanisms and therapies.

Methods

Fresh pig hepatocytes, liver sinusoidal and aortic endothelial cells were isolated by collagenase digestion of livers and processing of aortae from GTKO and Gal+ MGH-miniature swine. These primary cell cultures were then tested for the differential ability to induce baboon or pig platelet aggregation. Phagocytosis was evaluated by direct observation of CFSE labeled-platelets, which are incubated with endothelial cells under confocal light microscopy. Aurintricarboxylic acid (GpIb antagonist blocking interactions with von Willebrand factor/vWF), eptifibatide (Gp IIb/IIIa antagonist), and anti-Mac-1 Ab (anti-α_Mβ₂ integrin Ab) were tested for the ability to inhibit phagocytosis.

Results

None of the pig cells induced aggregation or phagocytosis of porcine platelets. However, pig hepatocytes, liver sinusoidal and aortic endothelial cells (GTKO and Gal+) all induced moderate aggregation of baboon platelets. Importantly, pig liver sinusoidal endothelial cells efficiently phagocytosed baboon platelets, while pig aortic endothelial cells and hepatocytes had minimal effects on platelet numbers. Anti-MAC-1 Ab, aurintricarboxylic acid or eptifibatide, significantly decreased baboon platelet phagocytosis by pig liver endothelial cells (P<0.01).

Conclusions

Although pig hepatocytes and aortic endothelial cells directly caused aggregation of baboon platelets, only pig liver endothelial cells efficiently phagocytosed baboon platelets. Blocking vWF and integrin adhesion pathways prevented both aggregation and phagocytosis.

Regulatory-B cell and regulatory-T cell collaborate to promote transplantation tolerance (126.2)

Backgrounds: The role of regulatory-B cells (Bregs) in transplant tolerance remains unclear. We found that the anti-CD45RB/anti-TIM1 induced tolerance depends on both Bregs and regulatory-T cells (Tregs). This finding offers a unique opportunity to explore the interplay of Bregs and Tregs in a transplant setting. Methods: Islet allograft were prepared from BALB/c donors and transplanted into B6. Recipients were treated with anti-CD45RB and anti-TIM1 antibodies for tolerance induction. Naive B cells or B cells isolated from mice that have been transplanted and treated in combination antibody therapy transferred into µMT-KO and assessed Treg expression by FACS. Anti-CD25 antibody, PC61, was used for Treg depletion. Anti-IL-10 or anti-TGF-β was used to neutralizing cytokine activity. Results: Treg numbers significantly increase following adoptive transfer of B cells purified from recipients bearing long-term surviving grafts (LTS). Moreover, adoptive transfer of LTS B cells suppressed allograft rejection upon transfer to untreated B cell-deficient secondary host, but this effect was not observed in Treg-deleted recipients. The absence of IL-10 by using anti-IL10 antibody did not affect on induction of long-term islet allograft by anti-CD45RB/anti-TIM1, however anti-TGF-β treatment abrogated the graft survival. Conclusions: B cell regulation induced by anti-CD45RB/anti-TIM1 is associated with Treg generation. This effect may be mediated by Treg promoting cytokines such as TGF-β.

A novel clinically relevant strategy to abrogate autoimmunity and regulate alloimmunity in NOD mice

OBJECTIVE

To investigate a new clinically relevant immunoregulatory strategy based on treatment with murine Thymoglobulin mATG Genzyme and CTLA4-Ig in NOD mice to prevent allo- and autoimmune activation using a stringent model of islet transplantation and diabetes reversal.

RESEARCH DESIGN AND METHODS

Using allogeneic islet transplantation models as well as NOD mice with recent onset type 1 diabetes, we addressed the therapeutic efficacy and immunomodulatory mechanisms associated with a new immunoregulatory protocol based on prolonged low-dose mATG plus CTLA4-Ig.

RESULTS

BALB/c islets transplanted into hyperglycemic NOD mice under prolonged mATG+CTLA4-Ig treatment showed a pronounced delay in allograft rejection compared with untreated mice (mean survival time: 54 vs. 8 days, P < 0.0001). Immunologic analysis of mice receiving transplants revealed a complete abrogation of autoimmune responses and severe downregulation of alloimmunity in response to treatment. The striking effect on autoimmunity was confirmed by 100% diabetes reversal in newly hyperglycemic NOD mice and 100% indefinite survival of syngeneic islet transplantation (NOD.SCID into NOD mice).

CONCLUSIONS

The capacity to regulate alloimmunity and to abrogate the autoimmune response in NOD mice in different settings confirmed that prolonged mATG+CTLA4-Ig treatment is a clinically relevant strategy to translate to humans with type 1 diabetes.

Suppressive regulatory T cell activity is potentiated by glycogen synthase kinase 3{beta} inhibition

The mechanism by which regulatory T (Treg) cells suppress the immune response is not well defined. A recent study has shown that β-catenin prolongs Treg cell survival. Because β-catenin is regulated by glycogen synthase kinase 3β (GSK-3β)-directed phosphorylation, we focused on GSK-3β and the role it plays in Treg cell function. Inhibition of GSK-3β led to increased suppression activity by Treg cells. Inhibitor-treated Treg cells exhibited prolonged FoxP3 expression and increased levels of β-catenin and of the antiapoptotic protein Bcl-xL. Systemic administration of GSK-3β inhibitor resulted in prolonged islet survival in an allotransplant mouse model. Our data suggest that GSK-3β could be a useful target in developing strategies designed to increase the stability and function of Treg cells for inducing allotransplant tolerance or treating autoimmune conditions.

Live donor partial hepatectomy for liver transplantation: is there a learning curve?

BACKGROUND

Donor safety is the first priority in living donor liver transplantation (LDLT).

OBJECTIVE

To determine the characteristics and outcome of live liver donors who underwent donor hepatectomy from January, 1997 to May, 2007 at Massachusetts General Hospital.

METHODS

30 patients underwent LDLT between January, 1997 and May, 2007 at our institution.

RESULTS

The type of graft was the right lobe (segments 5-8) in 14, left lobe (segments 2-4) in 4, and left lateral sector (segments 2 and 3) in 12 patients. The mean donor age was 36 (range: 26-57) years. The mean follow-up was 48 (range: 18-120) months. No deaths occurred. Overall, 8 (26.6%) patients experienced a total of 14 post-operative complications. Donor complications based on graft type were as follows: left lateral sector (16.7%), left lobe (25%), and right lobe (35.7%). The experience was divided into two periods 1997-2001 (n=15) and 2002-2007 (n=15). Overall complications during 2 periods were 40% and 13.3%, respectively (p<0.001). The incidence of grade III complication also significantly decreased; 66.7% vs 33.3% (p<0.01).

CONCLUSION

Partial hepatectomy in living donors has a learning curve which appears to be approximately 15 cases. This learning curve is not restricted to the surgeons performing the procedure but involves all aspects of patient care.

Biliary reconstruction and complications after living-donor liver transplantation

BACKGROUND

The technique of biliary reconstruction remains controversial in living-donor liver transplantation (LDLT). The objective of this study was to assess the incidence of biliary complications after LDLT based on the reconstruction technique.

METHODS

Between 1997 and 2007, 30 patients underwent LDLT. The type of allograft was the right lobe in 15, left lobe in 4 and left lateral sector in 11 patients. There were 18 adult and 12 paediatric recipients. The mean follow-up was 48 months (range 18-120 months). Biliary complications were defined as leak or stricture requiring intervention.

RESULTS

Biliary reconstruction was achieved with Roux-en-Y choledochojejunostomy (RYCJ) in 17 patients and duct-to-duct (DD) anastomosis in 13 patients. An external biliary stent was placed in all patients (except one) in the RYCJ group and reconstruction over a T-tube was done in 6 out of 13 patients in the DD Group. Twenty-five (83.3%) patients had one biliary anastomosis and the remaining five (16.7%) had multiple anastomoses (one in the RYCJ group and four in the DD group). The overall incidence of biliary complications was 30%.; 29.4% in the RYCJ group and 38.4% in the DD group (P = 0.6). Biliary complications occurred equally in patients with and without an external stent or T-tube stenting (12.5% vs. 18.8%). The incidence of biliary leakage was 23.5% for RYCJ and 15.3% for DD (P = 0.4). Although the incidence of biliary stricture was significantly higher in the DD (23.1%) compared with the RYCY group (5.9 %) (P < 0.01), all DDCC strictures were successfully managed endoscopically. Need for operative revision of biliary anastomoses was significantly higher in patients with RYCY compared with DD reconstruction; 17.7% vs. 7.7% (P < 0.01).

CONCLUSIONS

Although there was a higher rate of biliary stricture formation in the DDCC group, we feel that because of physiological bilioenteric continuity, comparable incidence of leakage and easy endoscopic access, DD reconstruction is the preferred approach for biliary drainage in LDLT. After LDLT, the endoscopic approach has been shown to provide effective treatment of most biliary complications.

Grain-boundary-induced spin disorder in nanocrystalline gadolinium

Based on experimental magnetic-field-dependent neutron scattering data, we have calculated the autocorrelation function of the spin misalignment of nanocrystalline (160)gadolinium. The analysis suggests the existence of two characteristic length scales in the spin system: the smaller one is about 5 nm and is attributed to the defect cores of the grain boundaries, whereas the larger length scale is of the order of the average crystallite size D = 21 nm and presumably describes the response of the magnetization to the magnetic anisotropy field of the individual crystallites.

Transplantation: impact of pretransplant renal insufficiency

Pre-liver transplant renal dysfunction is associated with decreased survival following transplantation and is also a prognostic indicator of posttransplant chronic kidney disease. Selection of patients for combined liver/kidney transplantation versus orthotopic liver transplantation alone (OLTa) is often difficult given the lack of a reliable method to predict which patients will have ongoing severe renal dysfunction in the absence of concomitant kidney transplantation. We hypothesized that most patients with pretransplant renal dysfunction (serum creatinine > or = 1.5 mg/dL for at least 2 weeks prior to and at time of transplant) will not experience a rapid decline in estimated glomerular filtration rates (eGF) post-OLTa to the point of necessitating consideration for kidney transplantation, even in the setting of calcineurin inhibitor-based immunosuppression. We performed a single-center retrospective study of 60 OLTa patients with pretransplant renal dysfunction transplanted between 2000 and 2005. Kaplan-Meier analysis was performed of the time interval to develop eGFR < 20 mL/minute post-OLTa. At OLTa, the mean patient age was 59 years, and median serum creatinine was 1.8 mg/dL; 42% patients were hepatitis C-positive, 32% were diabetic, 38% had kidney dysfunction > 12 weeks, and 5% were receiving hemodialysis. After 36 months median follow-up post-OLTa, only 8 patients (13%) with significant renal dysfunction pre-OLTa achieved eGFR < 20 mL/minute. Patients with pretransplant kidney dysfunction > 12 weeks were at increased risk for eGFR < 20 mL/minute (hazard ratio = 5.3, P = 0.04), a risk that escalated after adjustment for age and serum creatinine at transplant (hazard ratio = 8.9, P = 0.01). Significant predictors of eGFR < 20 mL/minute post-OLTa in this patient cohort were the presence of diabetes and the serum creatinine level at transplant. In conclusion, few patients with preexisting renal dysfunction, especially if <12 weeks duration, experience a significant drop in eGFR post-OLTa.

Posttransplant lymphoproliferative disorder in adult liver transplant recipients: a report of seventeen cases

Posttransplant lymphoproliferative disorder (PTLD) is a major complication of liver transplantation, but previous descriptions have been limited to case reports and small case series. We report a retrospective analysis of 17 consecutive cases of PTLD associated with liver transplantation. The median age at PTLD diagnosis was 47 years (range 19 - 63) with a median time of 25 months from liver transplantation to PTLD diagnosis (range 3 - 75). PTLD location was frequently extranodal (71%) and involved the transplanted liver (41%). PTLD histology consisted of nine (53%) monomorphic and eight (47%) polymorphic disease. EBV was present by in situ hybridization in 11 (79%) of 14 cases evaluated. Initial therapy included reduction in immunosuppression (RI) alone in 13 (76%) of 17 patients, resulting in 6 (46%) complete responses (CR) and 7 (54%) progressive disease (PD). Monoclonal CD20 antibody (rituximab) and CHOP chemotherapy were used as initial therapy or as second line after RI failure. Currently, five patients (29%) are alive in CR. Although detection and treatment of PTLD in liver transplant recipients remains problematic and upfront mortality is still high, long-term survival is possible. Further studies are necessary to better define treatment strategies.

Leucine regulation of glucokinase and ATP synthase sensitizes glucose-induced insulin secretion in pancreatic beta-cells

We have recently shown that leucine culture upregulates ATP synthase beta-subunit (ATPSbeta) and increases ATP level, cytosolic Ca(2+), and glucose-induced insulin secretion in rat islets. The aim is to test whether glucokinase expression is also affected in rat islets and its role in glucose sensitization during leucine culture. Leucine culture increased glucose-induced NAD(P)H level at 1 and 2 days but not at 1 week. The half-maximal effective concentration of the glucose response curve for NAD(P)H was left-shifted from 5-7 to 2-3 mmol/l. The effect was dose dependent and rapamycin insensitive. Leucine culture did not affect glyceraldehyde effects on NAD(P)H. Leucine pretreatment for 30 min had no effects on NAD(P)H levels. Leucine culture for 2 days also increased glucose-induced cytosolic Ca(2+) elevation, ATP level, and insulin secretion. Leucine increase of glucokinase mRNA levels occurred as early as day 1 and lasted through 1 week. That of ATPSbeta did not occur until day 2 and lasted through 1 week. Leucine effects on both mRNAs were dose dependent. The upregulation of both genes was confirmed by Western blotting. Leucine culture also increased glucose-induced insulin secretion, ATP level, glucokinase, and ATPSbeta levels of type 2 diabetic human islets. In conclusion, leucine culture upregulates glucokinase, which increases NAD(P)H level, and ATPSbeta, which increases oxidation of NADH and production of ATP. The combined upregulation of both genes increases glucose-induced cytosolic Ca(2+) and insulin secretion.

Development of anti-human leukocyte antigen class 1 antibodies following allogeneic islet cell transplantation

Currently there is minimal concern that islet allograft failure could result from the development of anti-human leukocyte antigen (HLA) antibodies reactive to the allograft. We report here a case of islet allograft failure where the recipient developed immunoglobulin G anti-HLA class I antibodies reactive to HLA antigens present in two of the three islet cell donors. The patient had no detectable anti-HLA antibodies prior to the transplant but these antibodies were detected approximately 4 months posttransplant. Of concern, these antibodies developed despite induction with anti-IL2R antibodies (Zenapex) prior to intraportal islet cell infusion, low-dose tacrolimus (12-hour troughs 3 to 5 ng/mL) and rapammune (target troughs 12 to 15 ng/mL). The patient was not presensitized with blood products or a previous allograft. Her husband, however, shared antigens present in one of the islet donors and the recipient could have been presensitized to her husband during her two pregnancies. This case clearly demonstrates that islet allografts can lead to development of anti-HLA antibodies, which can cause islet allograft failure, as is the case with solid organ transplants, and hence emphasizes the need to monitor for such antibodies pre- and posttransplant. Additionally it appears that currently recommended immunosuppression may not be sufficient to inhibit a humoral response to both alloantigens and autoantigens.

Endoscopic management of biliary complications after adult living donor liver transplantation

OBJECTIVES

Biliary complications and their treatment in adult cadaveric liver transplantation (CLT) are well described. However, biliary complications and their management in living donor liver transplantation (LDLT) are not well characterized. We assessed the role of endoscopic retrograde cholangiopancreatography (ERCP) in the diagnosis and management of biliary complications following LDLT.

METHODS

We performed a retrospective cohort analysis of all LDLT recipients with duct-to-duct anastomoses (n = 15). Specific data included referral for ERCP, diagnosis, and therapy. Comparisons were made to a 260 CLT recipient cohort.

RESULTS

Greater percentage of LDLT recipients underwent ERCP (73%) compared to CLT recipients (25%; p= 0.001). Biliary complications diagnosed by ERCP in LDLT recipients consisted of bile leaks and strictures, and were more frequent than in CLT recipients (leaks: 53%vs 12%; p= 0.001; strictures: 27%vs 5%; p= 0.01). Most leaks occurred at T-tube sites (LDLT: 87%; CLT: 65%). Diagnosis and therapy of leaks required a median of 2 ERCP procedures in both groups. Bile leaks were successfully treated endoscopically in 100% and 84% of LDLT and CLT recipients, respectively (p= 0.56). Most biliary strictures were anastomotic (LDLT: 100%; CLT: 64%). Strictures were diagnosed and treated with a median of 1.5 and 2 ERCP procedures in the LDLT and CLT groups, respectively. The duration of endoscopic therapy was a median of 10 and 14 wk, and success rates were 75% and 62% (p= 1.0) in LDLT and CLT groups, respectively.

CONCLUSIONS

LDLT is associated with increased biliary complications as compared to CLT. ERCP is useful for diagnosis, can successfully treat most LDLT-related biliary complications, and should be attempted prior to more invasive interventions.

Assessment of human pancreatic islets after long distance transportation

Pancreatic islet transplantation can replace functional insulin-secreting beta cells for patients with type 1 diabetes. More than 300 patients who have received islet transplantation have returned to a euglycemic condition without using insulin. Therefore, islet transplantation has gained public attention and interest. Unfortunately, shortages in organ donations, suboptional antirejection regimens, and difficulties in islet isolation limit clinical utilization of this therapy. Recently, successful islet transplantation has been reported using a centralized islet isolation facility. The advantage of this experience is that it avoids the high costs in building an isolation facility and maintaining an experienced technical team. However, a private airplane carrier was required for transporting islets back to the transplantation site in a remote hospital. The cost of this specialized transportation was still too high to be considered as a routine procedure. In this study, we report our experience using commercial carriers to deliver isolated human islets from an established isolation facility to a remote medical center.

Liver transplantation from controlled non-heart-beating donors: an increased incidence of biliary complications

BACKGROUND

Hepatic allografts from non-heart-beating donors (NHBD) have been cited as a means to expand the supply of donor livers. Concern exists that donor warm ischemic time in addition to subsequent cold ischemia-reperfusion injury may result in damage to sensitive cell populations within the liver. Because the biliary epithelium is sensitive to ischemia-reperfusion injury, the authors surmised that an increased incidence of biliary complications might occur among recipients of an NHBD allograft.

METHODS

This study was a retrospective evaluation of NHBD recipients compared to a group of heart-beating donor (HBD) recipients from a single institution.

RESULTS

Fifteen patients received a hepatic allograft from a controlled NHBD donor. NHBD and HBD (n=221) graft survival did not differ at 1 (71.8% vs. 85.4%, P=0.23) or 3 years (71.8% vs. 73.9%, P=0.68). Patient survival at 1 (79% vs. 90.9%, P=0.16) and 3 years (79.0% vs. 77.7%, P=0.8) was also similar. Major biliary complications occurred in five (33.3%) NHBD recipients; 66.6% of the NHBD biliary complications consisted of intrahepatic strictures versus 19.2% among HBD recipients (P<0.01). Major biliary complications in the NHBD recipients resulted in multiple interventional procedures, retransplantation, and death.

CONCLUSIONS

Donor warm ischemic time may predispose hepatic allografts to an increased incidence of ischemic type strictures. Although graft and patient survival was similar to a cohort of HBD recipients, caution is urged with the use of these organs.

Effect of prolonged monoclonal antibody administration on cardiac allograft survival in the rat

After heterotopic cardiac transplantation in the rat, monoclonal antibodies (MoAb) specific for rat T-cell subsets were administered until rejection. Across combined major histocompatibility complex (MHC) and non-MHC differences (WF to Lew) and isolated non-MHC differences (WF to Lew.1W) cardiac allografts were rapidly rejected in unmodified hosts (7.7 +/- 1.0 days and 12.2 +/- 0.8 days respectively). Across combined MHC and non-MHC differences, administration of MoAb OX-19 (pan T-cell) on days -1, 0, and 1 (where day 0 was the day of transplantation) and alternate days thereafter until rejection significantly prolonged allograft survival (28.5 +/- 10.2 days, P less than 0.01). Administration of MoAb W3/25 (helper T cell) and MoAb OX-39 (interleukin 2 (IL-2) receptor) prolonged allograft survival (11.3 +/- 2.6 days, P less than 0.05 and 13.3 +/- 2.0 days, P less than 0.01 respectively), whereas MoAb OX-8 (cytotoxic/suppressor T cell) administration had no effect on allograft survival. In contrast, across non-MHC differences (WF to Lew.1W) administration of MoAb OX-8 markedly prolonged allograft survival (85, greater than 100 x 3 days) whereas MoAb W3/25 administration had no effect. The effect of MoAb administration on lymphocyte subsets at rejection was assessed by flow cytometry. The relationship between depletion of targeted T-cell subsets and graft survival was variable. Across both combined MHC and non-MHC and isolated non-MHC differences MoAb OX-8 administration resulted in a marked reduction of OX-8+ cells at rejection with no prolongation of graft survival in the former and indefinite graft survival in the latter. In contrast, OX-19 administration resulted in prolonged graft survival but at rejection there were significant numbers of OX-19+ cells present. Administration of MoAb W3/25 failed to affect a significant reduction in W3/25+ cells, but allograft survival was nonetheless prolonged.

Antigen presenting function of class II MHC expressing pancreatic beta cells

Class II major histocompatibility complex (MHC) gene expression in the mouse is generally limited to thymic epithelium and bone marrow-derived cells such as B lymphocytes and cells of the macrophage/dendritic cell lineage (M phi/DC). Class II-bearing B lymphocytes and M phi/DC possess antigen presenting cell (APC) function; that is, they can stimulate T lymphocytes reactive to either antigen plus MHC or foreign MHC alone. To assess whether non-bone-marrow-derived cells can acquire APC function and elicit graft rejection through expression of class II, we studied transgenic pancreatic islet beta cells that express a foreign class II (I-E) molecule. In vivo, grafts of I-E+ transgenic islets into I-E- naive hosts are not rejected unless the host is primed by an injection of I-E+ spleen cells. In vitro, the I-E+ beta cells are unable to stimulate T lymphocytes reactive to I-E plus a peptide antigen. Paradoxically, they induce antigen specific unresponsiveness in the T cells. We propose that expression of class II on non-lymphoid cells may serve as an extrathymic mechanism for maintaining self tolerance.