A pig kidney supporting human physiology

Because of the global shortage of donor kidneys, xenotransplantation emerges as a potential solution for individuals with kidney failure who face challenges in securing a suitable donor kidney. A study featured in this month's issue of Kidney International assesses the kidney physiology of a porcine kidney transplanted into a brain-dead human with kidney failure, demonstrating life-sustaining physiological function for 7 days. Together with preclinical nonhuman primate studies, decedent models provide complementary data for development of clinical kidney xenotransplantation.

Banff 2022 Liver Group Meeting report: Monitoring long-term allograft health

The Banff Working Group on Liver Allograft Pathology met in September 2022. Participants included hepatologists, surgeons, pathologists, immunologists, and histocompatibility specialists. Presentations and discussions focused on the evaluation of long-term allograft health, including noninvasive and tissue monitoring, immunosuppression optimization, and long-term structural changes. Potential revision of the rejection classification scheme to better accommodate and communicate late T cell-mediated rejection patterns and related structural changes, such as nodular regenerative hyperplasia, were discussed. Improved stratification of long-term maintenance immunosuppression to match the heterogeneity of patient settings will be central to improving long-term patient survival. Such personalized therapeutics are in turn contingent on a better understanding and monitoring of allograft status within a rational decision-making approach, likely to be facilitated in implementation with emerging decision-support tools. Proposed revisions to rejection classification emerging from the meeting include the incorporation of interface hepatitis and fibrosis staging. These will be opened to online testing, modified accordingly, and subject to consensus discussion leading up to the next Banff conference.

The impact of IdeS (imlifidase) on allo-specific, xeno-reactive, and protective antibodies in a sensitized rhesus macaque model

BACKGROUND

Highly sensitized patients face many barriers to kidney transplantation, including higher rates of antibody-mediated rejection after HLA-incompatible transplant. IdeS, an endopeptidase that cleaves IgG nonspecifically, has been trialed as desensitization prior to kidney transplant, and successfully cleaves donor-specific antibody (DSA), albeit with rebound.

METHODS

IdeS was generated and tested (2 mg/kg, IV) in two naïve and four allosensitized nonhuman primates (NHP). Peripheral blood samples were collected at regular intervals following IdeS administration. Total IgG, total IgM, and anti-CMV antibodies were quantified with ELISA, and donor-specific antibody (DSA) and anti-pig antibodies were evaluated using flow cytometric crossmatch. B cell populations were assessed using flow cytometry.

RESULTS

IdeS successfully cleaved rhesus IgG in vitro. In allosensitized NHP, robust reduction of total, DSA, anti-pig, and anti-CMV IgG was observed within one day following IdeS administration. Rapid rebound of all IgG antibody populations was observed, with antibody levels returning to baseline around day 14 post-infusion. Total IgM level was not affected by IdeS. Interestingly, a comparable reduction in antibody populations was observed after the second dose of IdeS. However, we have not observed any significant modulation of B cell subpopulations after IdeS.

CONCLUSIONS

This study evaluated efficacy of IdeS in the allosensitized NHP in IgG with various specificities, mirroring antibody kinetics in human patients. The efficacy of IdeS on preexisting anti-pig antibodies may be useful in clinical xenotransplantation. However, given the limitation of IdeS on its durability as a monotherapy, optimization of IdeS with other agents targeting the humoral response is further needed.

HRSA's Patient-Centric Approach to Modernizing the US Transplant System

This Viewpoint discusses the benefits of modernization efforts for the US transplant system.

Normothermic Machine Perfusion of Donor Livers for Transplantation in the United States: A Randomized Controlled Trial

OBJECTIVE

To compare conventional low-temperature storage of transplant donor livers [static cold storage (SCS)] with storage of the organs at physiological body temperature [normothermic machine perfusion (NMP)].

BACKGROUND

The high success rate of liver transplantation is constrained by the shortage of transplantable organs (eg, waiting list mortality >20% in many centers). NMP maintains the liver in a functioning state to improve preservation quality and enable testing of the organ before transplantation. This is of greatest potential value with organs from brain-dead donor organs (DBD) with risk factors (age and comorbidities), and those from donors declared dead by cardiovascular criteria (donation after circulatory death).

METHODS

Three hundred eighty-three donor organs were randomized by 15 US liver transplant centers to undergo NMP (n = 192) or SCS (n = 191). Two hundred sixty-six donor livers proceeded to transplantation (NMP: n = 136; SCS: n = 130). The primary endpoint of the study was "early allograft dysfunction" (EAD), a marker of early posttransplant liver injury and function.

RESULTS

The difference in the incidence of EAD did not achieve significance, with 20.6% (NMP) versus 23.7% (SCS). Using exploratory, "as-treated" rather than "intent-to-treat," subgroup analyses, there was a greater effect size in donation after circulatory death donor livers (22.8% NMP vs 44.6% SCS) and in organs in the highest risk quartile by donor risk (19.2% NMP vs 33.3% SCS). The incidence of acute cardiovascular decompensation at organ reperfusion, "postreperfusion syndrome," as a secondary outcome was reduced in the NMP arm (5.9% vs 14.6%).

CONCLUSIONS

NMP did not lower EAD, perhaps related to the inclusion of lower-risk liver donors, as higher-risk donor livers seemed to benefit more. The technology is safe in standard organ recovery and seems to have the greatest benefit for marginal donors.

Design and testing of a humanized porcine donor for xenotransplantation

Recent human decedent model studies1,2 and compassionate xenograft use3 have explored the promise of porcine organs for human transplantation. To proceed to human studies, a clinically ready porcine donor must be engineered and its xenograft successfully tested in nonhuman primates. Here we describe the design, creation and long-term life-supporting function of kidney grafts from a genetically engineered porcine donor transplanted into a cynomolgus monkey model. The porcine donor was engineered to carry 69 genomic edits, eliminating glycan antigens, overexpressing human transgenes and inactivating porcine endogenous retroviruses. In vitro functional analyses showed that the edited kidney endothelial cells modulated inflammation to an extent that was indistinguishable from that of human endothelial cells, suggesting that these edited cells acquired a high level of human immune compatibility. When transplanted into cynomolgus monkeys, the kidneys with three glycan antigen knockouts alone experienced poor graft survival, whereas those with glycan antigen knockouts and human transgene expression demonstrated significantly longer survival time, suggesting the benefit of human transgene expression in vivo. These results show that preclinical studies of renal xenotransplantation could be successfully conducted in nonhuman primates and bring us closer to clinical trials of genetically engineered porcine renal grafts.

Detailed Analysis of Simultaneous Renal and Liver Allografts in the Presence of DSA

Liver allografts protect renal allografts from the same donor from some, but not all, preformed donor specific alloantibodies (DSA). However, the precise mechanisms of protection and the potential for more subtle alterations/injuries within the grafts resulting from DSA interactions require further study.

Methods

We reevaluated allograft biopsies from simultaneous liver-kidney transplant recipients who had both allografts biopsied within 60 d of one another and within 30 d of DSA being positive in serum (positive: mean florescence intensity ≥5000). Routine histology, C4d staining, and specialized immunohistochemistry for Kupffer cells (KCs; CD163) and a C4d receptor immunoglobulin-like transcript-4 were carried out in 4 patients with 6 paired biopsies.

Results

Overt antibody-mediated rejection was found in 3 of 4 renal and liver allografts. One patient had biopsy-confirmed renal and liver allograft antibody-mediated rejection despite serum clearance of DSA. All biopsies showed KC hypertrophy (minimal: 1; mild: 2; moderate: 1; severe: 2) and cytoplasmic C4d KC staining was easily detected in 2 biopsies from 2 patients; minimal and negative in 2 biopsies each. Implications of which are discussed. Control 1-y protocol liver allograft biopsies from DSA- recipients showed neither KC hypertrophy nor KC C4d staining (n = 6).

Conclusions

Partial renal allograft protection by a liver allograft from the same donor may be partially mediated by phagocytosis/elimination of antibody and complement split products by KCs, as shown decades ago in controlled sensitized experimental animal experiments.

Doing it right: Caring for and protecting patient information for US organ donors and transplant recipients

In the current US organ transplantation system, there are no regulations defining how organ procurement organizations must manage personal data and protect the privacy of donors and recipients. In response to the recent announcement of a major overhaul of the US transplantation system, we describe a practical approach to improving transplant data quality and protecting the autonomy of patients interacting with the system.

Daratumumab Use Prior to Kidney Transplant and T Cell-Mediated Rejection: A Case Report

There is growing interest in daratumumab in the solid organ transplant realm owing to the potential immunomodulatory effects on CD38-expressing cells, primarily plasma cells, as they have a key role in antibody production. In particular there is interest in use of daratumumab for desensitization and potential treatment for antibody-mediated rejection. However, ongoing investigation with daratumumab has shown potential immunologic concerns in vitro, with a significant increase in populations of CD4-positive cytotoxic T cells and CD8-positive helper T cells in both peripheral blood and bone marrow that could lead to acute T cell-mediated rejection in the solid organ transplant patient. To date, there are no published reports of an association with daratumumab use and T cell-mediated rejection in vivo. In this case report we present what is to our knowledge the first documented case of an early severe T cell-mediated rejection in a low-immunologic-risk living-donor kidney transplant recipient who received daratumumab for multiple myeloma maintenance prior to transplant.

Information design to support growth, quality, and equity of the US transplant system

The Organ Procurement and Transplantation Network, an arm of the Health Resources and Services Administration, has a contract with the United Network for Organ Sharing since 1986 to provide central oversight of organ donation and transplants in the United States. The United Network for Organ Sharing has recently come under scrutiny, prompting a review by the National Academies of Sciences, Engineering, and Medicine as summarized in its recent report and also by the US Senate Finance Committee. The national news services have opined about organ donation ethics, access to transplantation particularly for medically underserved populations, and management of organ transplantation data. These critiques raise important concerns that deserve our best response as a transplant community. Broadly, we suggest that the data management approach of the Organ Procurement and Transplantation Network be replaced with a patient-centric omnichannel network in which all donor and recipient data exist in a single longitudinal record that can be used by all applications. A more comprehensive and standardized approach to donor data collection would drive quality improvement across organ procurement organizations and help address inequities in transplantation. Finally, a substantial increase in organ donation would be prompted by considering organ donors as a public health resource, meriting transparent publicly available data collection with respect to organ donor referral, screening, and management.

A novel method for in vitro culture and expansion of nonhuman primate B cells

BACKGROUND

Given the role of B cells in sensitization and antibody-mediated rejection pathogenesis, the ability to identify, isolate, and study B cells in vitro is critical for understanding these processes and developing novel therapeutics. While in vivo nonhuman primate models have been used to this end, an in vitro nonhuman primate model of B cell activation and proliferation has not been developed.

METHODS

CD20+ B cells and CD3+ T cells were isolated using magnetic bead separation from the peripheral blood of naive and skin allograft sensitized nonhuman primates. Allogeneic B and T cells were co-cultured in plates pre-coated with murine stromal cells engineered to express human CD40L and stimulated with cytokines. Cells and supernatants were harvested every 2 days for immune phenotyping and donor specific antibody quantification by flow cytometry.

RESULTS

The optimized culture system consisted of MS40L cells co-cultured with B and allogenic T cells and stimulated with cytokines. This culture system resulted in increased memory cells and plasmablasts over time compared to other culture systems. Comparison of culture of naïve and sensitized nonhuman primate samples revealed faster B cell exhaustion and marginally increased plasmablast differentiation in sensitized culture. Donor-specific antibody production was not observed in either culture group.

CONCLUSIONS

This study describes the first in vitro nonhuman primate model of B cell activation and proliferation using both naïve and allosensitized samples. This model provides an opportunity for exploration of B cell mechanisms and novel therapeutics and is a preliminary step in the development of an in vitro germinal center model.

Addition of interleukin-6 receptor blockade to carfilzomib-based desensitization in a highly sensitized nonhuman primate model

Sensitized patients, those who had prior exposure to foreign human leukocyte antigens, are transplanted at lower rates due to challenges in finding suitable organs. Desensitization strategies have permitted highly sensitized patients to undergo kidney transplantation, albeit with higher rates of rejection. This study assesses targeting plasma cell and interleukin (IL)-6 receptor for desensitization in a sensitized nonhuman primate kidney transplantation model. All animals were sensitized using two sequential skin transplants from maximally major histocompatibility complex-mismatched donors. Carfilzomib (CFZ)/tocilizumab (TCZ) desensitization (N = 6) successfully decreased donor-specific antibody (DSA) titers and prevented the expansion of B cells compared to CFZ monotherapy (N = 3). Dual desensitization further delayed, but did not prevent humoral rebound, as evidenced by a delayed increase in post-kidney transplant DSA titers. Accordingly, CFZ/TCZ desensitization conferred a significant survival advantage over CFZ monotherapy. A trend toward increased T follicular helper cells was also observed in the dual therapy group along the same timeline as an increase in DSA and subsequent graft loss. Cytomegalovirus reactivation also occurred in the CFZ/TCZ group but was prevented with ganciclovir prophylaxis. In accordance with prior studies of CFZ-based dual desensitization strategies, the addition of IL-6 receptor blockade resulted in desensitization with further suppression of posttransplant humoral response compared to CFZ monotherapy.

Complement-targeted therapies in kidney transplantation-insights from preclinical studies

Aberrant activation of the complement system contributes to solid-organ graft dysfunction and failure. In kidney transplantation, the complement system is implicated in the pathogenesis of antibody- and cell-mediated rejection, ischemia-reperfusion injury, and vascular injury. This has led to the evaluation of select complement inhibitors (e.g., C1 and C5 inhibitors) in clinical trials with mixed results. However, the complement system is highly complex: it is composed of more than 50 fluid-phase and surface-bound elements, including several complement-activated receptors-all potential therapeutic targets in kidney transplantation. Generation of targeted pharmaceuticals and use of gene editing tools have led to an improved understanding of the intricacies of the complement system in allo- and xeno-transplantation. This review summarizes our current knowledge of the role of the complement system as it relates to rejection in kidney transplantation, specifically reviewing evidence gained from pre-clinical models (rodent and nonhuman primate) that may potentially be translated to clinical trials.

Belatacept-Based Maintenance Immunosuppression Controls the Post-Transplant Humoral Immune Response in Highly Sensitized Nonhuman Primates

Preexisting donor-specific antibodies (DSA) to MHC antigens increase the risk of antibody-mediated rejection (AMR) in sensitized transplant recipients and reduces graft survival. Pretransplant desensitization with costimulation blockade and proteasome inhibition has facilitated transplantation in our preclinical nonhuman primate (NHP) model. However, long-term graft survival is limited by rebound of DSA after transplantation. In this study, we performed kidney transplants between highly sensitized, maximally MHC-mismatched NHPs (n=14). At kidney transplantation, primates received T cell depletion with rhesus-specific anti-thymocyte globulin (rhATG; n=10) or monoclonal anti-CD4 and anti-CD8 antibodies (n=4). Maintenance immunosuppression consisted of belatacept and tacrolimus (n=5) or belatacept and rapamycin (n=9) with steroids. Rebound of DSA post-kidney transplantation was significantly reduced compared with maintenance immunosuppression with tacrolimus, mycophenolate, and steroids. Protocol lymph node biopsy specimens showed a decrease in germinal center activity, with low frequencies of T follicular helper cells and class-switched B cells after kidney transplantation. Combined belatacept and rapamycin was superior in controlling viral reactivation, enabling weaning of ganciclovir prophylaxis. Tacrolimus was associated with increased morbidity that included cytomegalovirus and parvovirus viremia and post-transplant lymphoproliferative disorder. All primates in the tacrolimus/belatacept group failed discontinuation of antiviral therapy. Overall, belatacept-based immunosuppression increased AMR-free graft survival by controlling post-transplant humoral responses in highly sensitized NHP recipients and should be further investigated in a human clinical trial.

Shifting Clinical Trial Endpoints in Kidney Transplantation: The Rise of Composite Endpoints and Machine Learning to Refine Prognostication

The measurement of outcomes in kidney transplantation has been more accurately documented than almost any other surgical procedure result in recent decades. With significant improvements in short- and long-term outcomes related to optimized immunosuppression, outcomes have gradually shifted away from conventional clinical endpoints (ie, patient and graft survival) to surrogate and composite endpoints. This article reviews how outcomes measurements have evolved in the past 2 decades in the setting of increased data collection and summarizes recent advances in outcomes measurements pertaining to clinical, histopathological, and immune outcomes. Finally, we discuss the use of composite endpoints and Bayesian concepts, specifically focusing on the integrative box risk prediction score, in conjunction with machine learning to refine prognostication.

Harnessing the B Cell Response in Kidney Transplantation - Current State and Future Directions

Despite dramatic improvement in kidney transplantation outcomes over the last decades due to advent of modern immunosuppressive agents, long-term outcomes remain poor. Antibody-mediated rejection (ABMR), a B cell driven process, accounts for the majority of chronic graft failures. There are currently no FDA-approved regimens for ABMR; however, several clinical trials are currently on-going. In this review, we present current mechanisms of B cell response in kidney transplantation, the clinical impact of sensitization and ABMR, the B cell response under current immunosuppressive regimens, and ongoing clinical trials for ABMR and desensitization treatment.

Introducing thymus for promoting transplantation tolerance

Establishing tolerance remains a central, if elusive, goal of transplantation. In solid-organ transplantation, one strategy for inducing tolerance has been cotransplantation of various forms of thymic tissue along with another organ. As one of the biological foundations of central tolerance, thymic tissue carries with it the ability to induce tolerance to any other organ or tissue from the same donor (or another donor tissue-matched to the thymic tissue) if successfully transplanted. In this review, we outline the history of this approach as well as work to date on its application in organ transplantation, concluding with future directions. We also review our experience with allogeneic processed thymus tissue for the treatment of congenital athymia, encompassing complete DiGeorge syndrome and other rare genetic disorders, and consider whether allogeneic processed thymic tissue implantation may offer a novel method for future experimentation with tolerance induction in organ transplantation.

Optical coherence tomography of small intestine allograft biopsies using a handheld surgical probe

SIGNIFICANCE

The current gold standard for monitoring small intestinal transplant (IT) rejection is endoscopic visual assessment and biopsy of suspicious lesions; however, these lesions are only superficially visualized by endoscopy. Invasive biopsies provide a coarse sampling of tissue health without depicting the true presence and extent of any pathology. Optical coherence tomography (OCT) presents a potential alternative approach with significant advantages over traditional white-light endoscopy.

AIM

The aim of our investigation was to evaluate OCT performance in distinguishing clinically relevant morphological features associated with IT graft failure.

APPROACH

OCT was applied to evaluate the small bowel tissues of two rhesus macaques that had undergone IT of the ileum. The traditional assessment from routine histological observation was compared with OCT captured using a handheld surgical probe during the days post-transplant and subsequently was compared with histophaology.

RESULTS

The reported OCT system was capable of identifying major biological landmarks in healthy intestinal tissue. Following IT, one nonhuman primate (NHP) model suffered a severe graft ischemia, and the second NHP graft failed due to acute cellular rejection. OCT images show visual evidence of correspondence with histological signs of IT rejection.

CONCLUSIONS

Results suggest that OCT imaging has significant potential to reveal morphological changes associated with IT rejection and to improve patient outcomes overall.

Allo-Specific Humoral Responses: New Methods for Screening Donor-Specific Antibody and Characterization of HLA-Specific Memory B Cells

Antibody-mediated allograft rejection (AMR) causes more kidney transplant failure than any other single cause. AMR is mediated by antibodies recognizing antigens expressed by the graft, and antibodies generated against major histocompatibility complex (MHC) mismatches are especially problematic. Most research directed towards the management of clinical AMR has focused on identifying and characterizing circulating donor-specific HLA antibody (DSA) and optimizing therapies that reduce B-cell activation and/or block antibody secretion by inhibiting plasmacyte survival. Here we describe a novel set of reagents and techniques to allow more specific measurements of MHC sensitization across different animal transplant models. Additionally, we have used these approaches to isolate and clone individual HLA-specific B cells from patients sensitized by pregnancy or transplantation. We have identified and characterized the phenotypes of individual HLA-specific B cells, determined the V(D)J rearrangements of their paired H and L chains, and generated recombinant antibodies to determine affinity and specificity. Knowledge of the BCR genes of individual HLA-specific B cells will allow identification of clonally related B cells by high-throughput sequence analysis of peripheral blood mononuclear cells and permit us to re-construct the origins of HLA-specific B cells and follow their somatic evolution by mutation and selection.

B cells in transplant tolerance and rejection: friends or foes?

Our understanding of the role of B cells in organ transplantation remains incomplete and continues to grow. The majority of research has focused on the detrimental role of antibodies that drive the development of pathogenesis of the transplanted organ. However, it has been shown that not all donor-specific antibodies are harmful and in some circumstances can even promote tolerance through the mechanism of accommodation. Furthermore, B cells can have effects on transplanted organs through their interaction with T cells, namely antigen presentation, cytokine production, and costimulation. More recently, the role and importance of Bregs was introduced to the field of transplantation. Due to this functional and ontogenetic heterogeneity, targeting B cells in transplantation may bring undesired immunologic side effects including increased rejection. Therefore, the selective control of B cells that contribute to the humoral response against donor antigens will continue to be an important and challenging area of research and potentially lead to improved long-term transplant outcomes.

Definition and Analysis of Textbook Outcome: A Novel Quality Measure in Kidney Transplantation

BACKGROUND

"Textbook outcome" (TO) is a novel composite quality measure that encompasses multiple postoperative endpoints, representing the ideal "textbook" hospitalization for complex surgical procedures. We defined TO for kidney transplantation using a cohort from a high-volume institution.

METHODS

Adult patients who underwent isolated kidney transplantation at our institution between 2016 and 2019 were included. TO was defined by clinician consensus at our institution to include freedom from intraoperative complication, postoperative reintervention, 30-day intensive care unit or hospital readmission, length of stay > 75th percentile of kidney transplant patients, 90-day mortality, 30-day acute rejection, delayed graft function, and discharge with a Foley catheter. Recipient, operative, financial characteristics, and post-transplant patient, graft, and rejection-free survival were compared between patients who achieved and failed to achieve TO.

RESULTS

A total of 557 kidney transplant patients were included. Of those, 245 (44%) achieved TO. The most common reasons for TO failure were delayed graft function (N = 157, 50%) and hospital readmission within 30 days (N = 155, 50%); the least common was mortality within 90 days (N = 6, 2%). Patient, graft, and rejection-free survival were significantly improved among patients who achieved TO. On average, patients who achieved TO incurred approximately $50,000 less in total inpatient charges compared to those who failed TO.

CONCLUSIONS

TO in kidney transplantation was associated with favorable post-transplant outcomes and significant cost-savings. TO may offer transplant centers a detailed performance breakdown to identify aspects of perioperative care in need of process improvement.

Textbook Outcomes in Liver Transplantation

BACKGROUND

Textbook outcome (TO) is an emerging concept within multiple surgical domains, which represents a novel effort to define a standardized, composite quality benchmark based on multiple postoperative endpoints that represent the ideal "textbook" hospitalization. We sought to define TO for liver transplantation (LT) using a cohort from a high procedural volume center.

METHODS

Patients who underwent LT at our institution between 2014 and 2017 were eligible for the study. The definition of TO was determined by clinician consensus at our institution to include freedom from: mortality within 90 days, primary allograft non-function, early allograft dysfunction (EAD), rejection within 30 days, readmission with 30 days, readmission to the ICU during index hospitalization, hospital length of stay > 75th percentile of all liver transplant patients, red blood cell (RBC) transfusion requirement greater than the 75th percentile for all liver transplant patients, Clavien-Dindo Grade III complication (re-intervention), and major intraoperative complication.

RESULTS

Two hundred and thirty-one liver transplants with complete data were performed within the study period. Of those, 71 (31%) achieved a TO. Overall, the most likely event to lead to failure to achieve TO was readmission within 30 days (n = 57, 37%) or reoperation (n = 49, 32%). Overall and rejection-free survival did not differ significantly between the 2 groups. Interestingly, patients who achieved TO incurred approximately $60,000 less in total charges than those who did not. When we limit this to charges specifically attributable to the transplant episode, the difference was approximately $50,000 and remained significantly less for those that achieved TO.

CONCLUSIONS

Here, we present the first definition of TO in LT. Though not associated with long-term outcomes, TO in LT is associated with a significantly lower charges and costs of the initial hospitalization. A multi-institutional study to validate this definition of TO is warranted.

Preoperative carfilzomib and lulizumab based desensitization prolongs graft survival in a sensitized non-human primate model

Sensitized patients are difficult to transplant due to pre-formed anti-donor immunity. We have previously reported successful desensitization using carfilzomib and belatacept in a non-human primate (NHP) model. Here we evaluated selective blockade of the co-stimulatory signal (CD28-B7) with Lulizumab, which preserves the co-inhibitory signal (CTLA4-B7). Five maximally MHC-mismatched pairs of NHPs were sensitized to each other with two sequential skin transplants. Individuals from each pair were randomized to either desensitization with once-weekly Carfilzomib (27mg/m² IV) and Lulizumab (12.5mg/kg SC) over four weeks, or no desensitization (Control). NHPs then underwent life-sustaining kidney transplantation from their previous skin donor. Rhesus-specific anti-thymocyte globulin was used as induction therapy and immunosuppression maintained with tacrolimus, mycophenolate, and methylprednisolone. Desensitized subjects demonstrated a significant reduction in donor-specific antibody, follicular helper T cells (CD4⁺PD-1⁺ICOS⁺), and proliferating B cells (CD20⁺Ki67⁺) in the lymph nodes. Interestingly, regulatory T cell (CD4⁺CD25⁺CD127^lo) frequency was maintained after desensitization in addition to increased frequency of naïve CD4 T cells (CCR7⁺CD45RA⁺) and naïve B cells (IgD⁺CD27^-CD20⁺) in circulation. This was associated with significant prolongation in graft survival (MST = 5.8 ± 4.0 vs. 64.8 ± 36.3; p<0.05) and lower antibody-mediated rejection scores compared to control animals. However, all desensitized animals eventually developed AMR and graft failure. Desensitization with CFZ and Lulizumab improves allograft survival in allosensitized NHPs, by transient control of the germinal center and shifting of the immune system to a more naive phenotype. This regimen may translate into clinical practice to improve outcomes of highly sensitized transplant patients.

Translational impact of NIH-funded nonhuman primate research in transplantation

The National Institutes of Health (NIH) has long supported using nonhuman primate (NHP) models for research on kidney, pancreatic islet, heart, and lung transplantation. The primary purpose of this research has been to develop new treatments for down-modulating or preventing deleterious immune responses after transplantation in human patients. Here, we discuss NIH-funded NHP studies of immune cell depletion, costimulation blockade, regulatory cell therapy, desensitization, and mixed hematopoietic chimerism that either preceded clinical trials or prevented the human application of therapies that were toxic or ineffective.

Cultured thymus tissue implantation promotes donor-specific tolerance to allogeneic heart transplants

Eighty-six infants born without a thymus have been treated with allogeneic cultured thymus tissue implantation (CTTI). These infants, who lack T cells and are profoundly immunodeficient at birth, after CTTI from an unmatched donor develop T cells similar to those of recipient that are tolerant to both their own major histocompatibility antigens and those of the donor. We tested use of CTTI with the goal of inducing tolerance to unmatched heart transplants in immunocompetent rats. We thymectomized and T cell-depleted Lewis rats. The rats were then given cultured thymus tissue from F1 (Lewis × Dark Agouti ) under the kidney capsule and vascularized Dark Agouti (DA) heart transplants in the abdomen. Cyclosporine was administered for 4 months. The control group did not receive CTTI. Recipients with CTTI showed repopulation of naive and recent thymic emigrant CD4 T cells; controls had none. Recipients of CTTI did not reject DA cardiac allografts. Control animals did not reject DA grafts, due to lack of functional T cells. To confirm donor-specific unresponsiveness, MHC-mismatched Brown Norway (BN) hearts were transplanted 6 months after the initial DA heart transplant. LW rats with LWxDA CTTI rejected the third-party BN hearts (mean survival time 10 days); controls did not. CTTI recipients produced antibody against third-party BN donor but not against the DA thymus donor, demonstrating humoral donor-specific tolerance. Taken together, F1(LWxDA) CTTI given to Lewis rats resulted in specific tolerance to the allogeneic DA MHC expressed in the donor thymus, with resulting long-term survival of DA heart transplants after withdrawal of all immunosuppression.

Regulatory cell therapy in kidney transplantation (The ONE Study): a harmonised design and analysis of seven non-randomised, single-arm, phase 1/2A trials

BACKGROUND

Use of cell-based medicinal products (CBMPs) represents a state-of-the-art approach for reducing general immunosuppression in organ transplantation. We tested multiple regulatory CBMPs in kidney transplant trials to establish the safety of regulatory CBMPs when combined with reduced immunosuppressive treatment.

METHODS

The ONE Study consisted of seven investigator-led, single-arm trials done internationally at eight hospitals in France, Germany, Italy, the UK, and the USA (60 week follow-up). Included patients were living-donor kidney transplant recipients aged 18 years and older. The reference group trial (RGT) was a standard-of-care group given basiliximab, tapered steroids, mycophenolate mofetil, and tacrolimus. Six non-randomised phase 1/2A cell therapy group (CTG) trials were pooled and analysed, in which patients received one of six CBMPs containing regulatory T cells, dendritic cells, or macrophages; patient selection and immunosuppression mirrored the RGT, except basiliximab induction was substituted with CBMPs and mycophenolate mofetil tapering was allowed. None of the trials were randomised and none of the individuals involved were masked. The primary endpoint was biopsy-confirmed acute rejection (BCAR) within 60 weeks after transplantation; adverse event coding was centralised. The RTG and CTG trials are registered with ClinicalTrials.gov, NCT01656135, NCT02252055, NCT02085629, NCT02244801, NCT02371434, NCT02129881, and NCT02091232.

FINDINGS

The seven trials took place between Dec 11, 2012, and Nov 14, 2018. Of 782 patients assessed for eligibility, 130 (17%) patients were enrolled and 104 were treated and included in the analysis. The 66 patients who were treated in the RGT were 73% male and had a median age of 47 years. The 38 patients who were treated across six CTG trials were 71% male and had a median age of 45 years. Standard-of-care immunosuppression in the recipients in the RGT resulted in a 12% BCAR rate (expected range 3·2-18·0). The overall BCAR rate for the six parallel CTG trials was 16%. 15 (40%) patients given CBMPs were successfully weaned from mycophenolate mofetil and maintained on tacrolimus monotherapy. Combined adverse event data and BCAR episodes from all six CTG trials revealed no safety concerns when compared with the RGT. Fewer episodes of infections were registered in CTG trials versus the RGT.

INTERPRETATION

Regulatory cell therapy is achievable and safe in living-donor kidney transplant recipients, and is associated with fewer infectious complications, but similar rejection rates in the first year. Therefore, immune cell therapy is a potentially useful therapeutic approach in recipients of kidney transplant to minimise the burden of general immunosuppression.

FUNDING

The 7th EU Framework Programme.

Pretransplant Desensitization with Costimulation Blockade and Proteasome Inhibitor Reduces DSA and Delays Antibody-Mediated Rejection in Highly Sensitized Nonhuman Primate Kidney Transplant Recipients

BACKGROUND

Patients with broad HLA sensitization have poor access to donor organs, high mortality while waiting for kidney transplant, and inferior graft survival. Although desensitization strategies permit transplantation via lowering of donor-specific antibodies, the B cell-response axis from germinal center activation to plasma cell differentiation remains intact.

METHODS

To investigate targeting the germinal center response and plasma cells as a desensitization strategy, we sensitized maximally MHC-mismatched rhesus pairs with two sequential skin transplants. We administered a proteasome inhibitor (carfilzomib) and costimulation blockade agent (belatacept) to six animals weekly for 1 month; four controls received no treatment. We analyzed blood, lymph node, bone marrow cells, and serum before desensitization, after desensitization, and after kidney transplantation.

RESULTS

The group receiving carfilzomib and belatacept exhibited significantly reduced levels of donor-specific antibodies (P=0.05) and bone marrow plasma cells (P=0.02) compared with controls, with a trend toward reduced lymph node T follicular helper cells (P=0.06). Compared with controls, carfilzomib- and belatacept-treated animals had significantly prolonged graft survival (P=0.02), and renal biopsy at 1 month showed significantly reduced antibody-mediated rejection scores (P=0.02). However, four of five animals with long-term graft survival showed gradual rebound of donor-specific antibodies and antibody-mediated rejection.

CONCLUSIONS

Desensitization using proteasome inhibition and costimulation blockade reduces bone marrow plasma cells, disorganizes germinal center responses, reduces donor-specific antibody levels, and prolongs allograft survival in highly sensitized nonhuman primates. Most animals experienced antibody-mediated rejection with humoral-response rebound, suggesting desensitization must be maintained after transplantation using ongoing suppression of the B cell response.

Comparison between liver transplantation and resection for hilar cholangiocarcinoma: A systematic review and meta-analysis

BACKGROUND

Hilar cholangiocarcinoma (hCCA) is a rare and aggressive malignancy with R0 resection being currently the only option for long-term survival. With the improvement in the outcomes of liver transplantation (LT), the indications for LT have expanded to include other malignant tumors, such as hCCA. The aim of the present analysis is to demonstrate and critically evaluate the outcomes of LT compared to resection with curative intent in patients with hCCA.

METHODS

We systematically searched the literature for articles published up to May 2018. The following algorithm was applied ((hilar cholangiocarcinoma) OR (perihilar cholangiocarcinoma) OR klatskin$ OR (bile duct neoplasm) OR cholangiocarcinoma) AND (transplant$ OR graft$).

RESULTS

Neoadjuvant treatment with chemotherapy and radiation therapy was far more common in the LT group, with very few patients having received preoperative therapy in the resection group (p = 0.0005). Moreover, length of hospital stay was shorter after LT than after resection (p<0.00001). In contrast, no difference was found between the two treatment methods concerning postoperative mortality (p = 0.57). There was a trend towards longer overall survival after LT in comparison with resection. This was not obvious in the first year postoperatively, however, the advantage of LT over resection became obvious at 3 years after the operation (p = 0.02).

CONCLUSIONS

In non-disseminated unresectable tumors, LT seems to have a non-inferior survival. In the same patients, neoadjuvant chemoradiotherapy and/or strict selection criteria may contribute to superior survival outcomes compared to curative-intent resection. Due to the scarcity of level 1 evidence, it remains unclear whether LT should be increasingly considered for technically resectable early stage hCCA.

Transplant research in nonhuman primates to evaluate clinically relevant immune strategies in organ transplantation

Research in transplant immunology using non-human primate (NHP) species to evaluate immunologic strategies to prevent rejection and prolong allograft survival has yielded results that have translated successfully into human organ transplant patient management. Other therapies have not proceeded to human translation due to failure in NHP testing, arguably sparing humans the futility and risk of such testing. The NHP transplant models are ethically necessary for drug development in this field and provide the closest analogue to human transplant patients available. The refinement of this resource with respect to colony MHC typing, reagent and assay development, and availability to the research community has greatly enhanced knowledge about transplant immunology and drug development.

Dual targeting: Combining costimulation blockade and bortezomib to permit kidney transplantation in sensitized recipients

Previous evidence suggests that a homeostatic germinal center (GC) response may limit bortezomib desensitization therapy. We evaluated the combination of costimulation blockade with bortezomib in a sensitized non-human primate kidney transplant model. Sensitized animals were treated with bortezomib, belatacept, and anti-CD40 mAb twice weekly for a month (n = 6) and compared to control animals (n = 7). Desensitization therapy-mediated DSA reductions approached statistical significance (P = .07) and significantly diminished bone marrow PCs, lymph node follicular helper T cells, and memory B cell proliferation. Graft survival was prolonged in the desensitization group (P = .073). All control animals (n = 6) experienced graft loss due to antibody-mediated rejection (AMR) after kidney transplantation, compared to one desensitized animal (1/5). Overall, histological AMR scores were significantly lower in the treatment group (n = 5) compared to control (P = .020). However, CMV disease was common in the desensitized group (3/5). Desensitized animals were sacrificed after long-term follow-up with functioning grafts. Dual targeting of both plasma cells and upstream GC responses successfully prolongs graft survival in a sensitized NHP model despite significant infectious complications and drug toxicity. Further work is planned to dissect underlying mechanisms, and explore safety concerns.

Improved contemporary outcomes of liver transplantation for pediatric hepatoblastoma and hepatocellular carcinoma

PURPOSE

Improvement in outcomes of LT for pediatric HB and HCC has been reported in small series. We analyzed national outcomes and changes in donor, recipient, and perioperative factors over time that may contribute to survival differences.

METHODS

The UNOS database was queried for patients age <21 years that underwent LT for a primary diagnosis of HB or HCC (1987-2017). Subjects were divided into historic (transplant before 2010) and contemporary (transplant after 2010) cohorts. Baseline characteristics were compiled and examined. Survival was estimated using the Kaplan-Meier method and compared using the log-rank test.

RESULTS

In total, 599 children with HB received LT (320 historic vs 279 contemporary). Concurrently, 141 children with HCC received LT (92 historic vs 49 contemporary). For both tumors, waitlist time decreased (HB 56.2 days historic vs 33.2 days contemporary, P = 0.017; HCC 189.3 days historic vs 71.7 days contemporary, P = 0.012). In the historic cohorts, patients with HB had a 1-year and 5-year OS of 84.6% and 75.1%, respectively. Survival for HCC was 84.4% and 59.9%, respectively. Outcomes improved in the contemporary era to 89.1% and 82.6% for HB, and 94.7% and 80.8% for HCC, respectively (both log-rank test P < 0.0001).

CONCLUSION

Outcomes of LT have improved significantly, with contemporary survival now equivalent between these tumors and exceeding 80% 5-year OS. Future studies are needed to explore whether offering LT in patients that are resectable is justifiable.

IL-21 Biased Alemtuzumab Induced Chronic Antibody-Mediated Rejection Is Reversed by LFA-1 Costimulation Blockade

Despite its excellent efficacy in controlling T cell mediated acute rejection, lymphocyte depletion may promote a humoral response. While T cell repopulation after depletion has been evaluated in many aspects, the B cell response has not been fully elucidated. We tested the hypothesis that the mechanisms also involve skewed T helper phenotype after lymphocytic depletion. Post-transplant immune response was measured from alemtuzumab treated hCD52Tg cardiac allograft recipients with or without anti-LFA-1 mAb. Alemtuzumab induction promoted serum DSA, allo-B cells, and CAV in humanized CD52 transgenic (hCD52Tg) mice after heterotopic heart transplantation. Additional anti-LFA-1 mAb treatment resulted in reduced DSA (Fold increase 4.75 ± 6.9 vs. 0.7 ± 0.5; p < 0.01), allo-specific B cells (0.07 ± 0.06 vs. 0.006 ± 0.002 %; p < 0.01), neo-intimal hyperplasia (56 ± 14% vs. 23 ± 13%; p < 0.05), arterial disease (77.8 ± 14.2 vs. 25.8 ± 20.1%; p < 0.05), and fibrosis (15 ± 23.3 vs. 4.3 ± 1.65%; p < 0.05) in this alemtuzumab-induced chronic antibody-mediated rejection (CAMR) model. Surprisingly, elevated serum IL-21 levels in alemtuzumab-treated mice was reduced with LFA-1 blockade. In accordance with the increased serum IL-21 level, alemtuzumab treated mice showed hyperplastic germinal center (GC) development, while the supplemental anti-LFA-1 mAb significantly reduced the GC frequency and size. We report that the incomplete T cell depletion inside of the GC leads to a systemic IL-21 dominant milieu with hyperplastic GC formation and CAMR. Conventional immunosuppression, such as tacrolimus and rapamycin, failed to reverse AMR, while co-stimulation blockade with LFA-1 corrected the GC hyperplastic response. The identification of IL-21 driven chronic AMR elucidates a novel mechanism that suggests a therapeutic approach with cytolytic induction.

The impact of human leukocyte antigen donor and recipient serotyping and matching on liver transplant graft failure in primary sclerosing cholangitis, autoimmune hepatitis, and primary biliary cholangitis

Human leukocyte antigen (HLA) serotyping is not considered to have significant impact on liver graft survival and does not factor into U.S. organ allocation. Immune-related liver diseases such as primary sclerosing cholangitis (PSC), autoimmune hepatitis (AIH), and primary biliary cholangitis (PBC) have been speculated to represent a disease subgroup that may have significantly different graft outcomes depending on HLA donor/recipient characterization. The aim of this study was to investigate whether HLA serotyping/matching influenced post-transplant graft failure for immune-related liver diseases using the United Network for Organ Sharing database. From 1994 to 2015, 5665 patients underwent first-time liver-only transplants for PSC, AIH, and PBC with complete graft survival and donor/recipient HLA data. Graft failure was noted in 38.6% (2188/5665), and all groups had comparable 5-year graft survival (75.1%-78.8%, P = 0.069). The overall degree of, and loci-specific mismatch level, did not influence outcomes. Multivariable Cox proportional hazards regression noted increased graft failure risk for recipient HLA-B7, HLA-B57, HLA-B75, HLA-DR13 and donor HLA-B55, HLA-B58, and HLA-DR8 for PSC patients, protective effects for recipient HLA-DR1 and HLA-DR3 for AIH patients, and increased risk for HLA-DR7 for AIH patients. These findings warrant further investigation to evaluate the impact of HLA serotyping on post-transplant outcomes.

Contemporary Strategies and Barriers to Transplantation Tolerance

The purpose of this review is to discuss immunologic tolerance as it applies to solid organ transplantation and to identify barriers that hinder the achievement of this long-term goal. First, the definition of tolerance and an introduction of mechanisms by which tolerance exists or can be achieved will be discussed. Next, a review of contemporary attempts at achieving transplant tolerance will be described. Finally, a discussion of the humoral barriers to transplantation tolerance and potential ways to overcome these barriers will be presented.

Elevated HbA1c in donor organs from patients without a diagnosis of diabetes portends worse liver allograft survival

Recipients of liver allografts from diabetic donors have decreased graft survival. However, limited data exist on the effects of donor HbA1c. We hypothesized that allografts from nondiabetic donors with elevated HbA1c would be associated with decreased survival. Liver transplant recipients from the UNOS database from nondiabetic donors were stratified into two groups: euglycemic (HbA1c<6.5) and hyperglycemic (HbA1c≥6.5). Propensity score matching (10:1) was used to adjust for donor and recipient characteristics. Kaplan-Meier analysis was used to assess survival. Donors of hyperglycemic allografts were older (49 vs 36, P<.001), were more likely to be non-white, had a higher BMI (29.8 vs 26.2, P<.001), were more likely to engage in heavy cigarette use (1.5% vs 1.3%, P=.004), had higher serum creatinine levels (1.3 vs 1.0, P=.002), and were more likely to be an expanded-criteria donor (35.8% vs 14.4%, P<.001). After propensity matching to account for these differences, allograft survival was significantly decreased in the recipients of hyperglycemic allografts (P=.049), and patient survival showed a trend toward reduction (P=.082). These findings suggest that HbA1c may be a simple and inexpensive test with potential utility for better organ risk stratification.

Bridging Locoregional Therapy Prolongs Survival in Patients Listed for Liver Transplant with Hepatocellular Carcinoma

BACKGROUND AND AIMS

To evaluate the long-term survival benefit of bridging locoregional therapy (LRT) prior to orthotopic liver transplantation (OLT) in patients with hepatocellular carcinoma (HCC) within Milan criteria.

METHODS

Our transplant center registry was studied for all HCC patients within the Milan criteria who were listed for OLT from 1998 to 2013. Baseline clinical characteristics and median overall survival (OS) were calculated and stratified by LRT, OLT status, and wait times. Survival analysis was conducted using Kaplan-Meier estimation and log-rank test.

RESULTS

Of 265 listed, 205 underwent OLT (mean follow-up 7.6 years). Of 205, 111 received bridging LRT (A), and 94 did not (B). Both were similar in demographics and tumor characteristics (p > 0.05). Median OS from HCC for A/B were 86.4 vs. 68.9 months (p = 0.01). Median OS from OLT for A/B were 74.6 vs. 63.6 months (p = 0.03). On multivariate analysis, independent predictors for survival from HCC were bridging LRT (p = 0.002) and high wait time (p = 0.008); independent predictors for survival from OLT were bridging LRT (p = 0.005) and high wait time (p = 0.005). Of 60 who were listed but did not undergo transplant, 44 received LRT (C) and 16 received best supportive care (D). Median OS from HCC for C/D were 37.1 vs. 24.8 months (p = 0.03).

CONCLUSIONS

Bridging LRT and high wait times were independent positive prognostic factors for survival from HCC diagnosis and OLT.

Antibody-Mediated Rejection in Sensitized Nonhuman Primates: Modeling Human Biology

We have established a model of sensitization in nonhuman primates and tested two immunosuppressive regimens. Animals underwent fully mismatched skin transplantation, and donor-specific antibody (DSA) response was monitored by flow cross-match. Sensitized animals subsequently underwent kidney transplantation from their skin donor. Immunosuppression included tacrolimus, mycophenolate, and methylprednisolone. Three animals received basiliximab induction; compared with nonsensitized animals, they showed a shorter mean survival time (4.7 ± 3.1 vs. 187 ± 88 days). Six animals were treated with T cell depletion (anti-CD4/CD8 mAbs), which prolonged survival (mean survival time 21.6 ± 19.0 days). All presensitized animals showed antibody-mediated rejection (AMR). In two of three basiliximab-injected animals, cellular rejection (ACR) was prominent. After T cell depletion, three of six monkeys experienced early acute rejection within 8 days with histological evidence of thrombotic microangiopathy and AMR. The remaining three monkeys survived 27-44 days, with mixed AMR and ACR. Most T cell-depleted animals experienced a rebound of DSA that correlated with deteriorating kidney function. We also found an increase in proliferating memory B cells (CD20(+) CD27(+) IgD(-) Ki67(+) ), lymph node follicular helper T cells (ICOS(+) PD-1(hi) CXCR5(+) CD4(+) ), and germinal center (GC) response. Depletion controlled cell-mediated rejection in sensitized nonhuman primates better than basiliximab, yet grafts were rejected with concomitant DSA rise. This model provides an opportunity to test novel desensitization strategies.

One Size Does Not Fit All--Regional Variation in the Impact of the Share 35 Liver Allocation Policy

Allocation policies for liver transplantation underwent significant changes in June 2013 with the introduction of Share 35. We aimed to examine the effect of Share 35 on regional variation in posttransplant outcomes. We examined two patient groups from the United Network for Organ Sharing dataset; a pre-Share 35 group composed of patients transplanted between June 17, 2012, and June 17, 2013 (n = 5523), and a post-Share group composed of patients transplanted between June 18, 2013, and June 18, 2014 (n = 5815). We used Kaplan-Meier and Cox multivariable analyses to compare survival. There were significant increases in allocation Model for End-stage Liver Disease (MELD) scores, laboratory MELD scores, and proportions of patients in the intensive care unit and on mechanical, ventilated, or organ-perfusion support at transplant post-Share 35. We also observed a significant increase in donor risk index in this group. We found no difference on a national level in survival between patients transplanted pre-Share 35 and post-Share 35 (p = 0.987). Regionally, however, posttransplantation survival was significantly worse in the post-Share 35 patients in regions 4 and 10 (p = 0.008 and p = 0.04), with no significant differences in the remaining regions. These results suggest that Share 35 has been associated with transplanting "sicker patients" with higher MELD scores, and although no difference in survival is observed on a national level, outcomes appear to be concerning in some regions.