Use of intravenous immune globulin and rituximab for desensitization of highly HLA-sensitized patients awaiting kidney transplantation. Transplantation. 2010;89:1095-1102. [PMID: 20110854 DOI: 10.1097/tp.0b013e3181d21e7f]

Challenges and opportunities for designing clinical trials for antibody mediated rejection

Significant progress has been made in kidney transplantation, with 1-year graft survival nearing 95%. However, long-term allograft survival remains suboptimal, with a 10-year overall graft survival rate of only 53.6% for deceased donor transplant recipients. Chronic active antibody-mediated rejection (ABMR) is a leading cause of death-censored graft loss, yet no therapy has demonstrated efficacy in large, randomized trials, despite substantial investment from pharmaceutical companies. Several clinical trials aimed to treat chronic ABMR in the past decade have yielded disappointing results or were prematurely terminated, attributed to factors including incomplete understanding of disease mechanisms, heterogeneous patient populations with comorbidities, slow disease progression, and limited patient numbers. This review aims to discuss opportunities for improving retrospective and prospective studies of ABMR, focusing on addressing heterogeneity, outcome measurement, and strategies to enhance patient enrollment to inform study design, data collection, and reporting.

Management of the sensitized pediatric renal transplant candidate

Kidney transplantation is the treatment of choice for patients with ESRD as it is associated with improved patient survival and better quality of life, especially in children. There are several barriers to a successful transplant including organ shortage, anatomic barriers, and immunologic barriers. One of the biggest immunologic barriers that precludes transplantation is sensitization, when patients have antibodies prior to transplantation, resulting in positive crossmatches with donor. 30%-40% of adult patients on the wait list are sensitized. There is a growing number of pediatric patients on the wait list who are sensitized. This poses a unique challenge to the pediatric transplant community. Therefore, attempts to perform desensitization to remove or suppress pathogenic HLA antibodies resulting in acceptable crossmatches, and ultimately a successful transplant, while reducing the risk of acute rejection, are much needed in these children. This review article aims to address the management of such patients both prior to transplantation, with strategies to overcome sensitization, and after transplantation with monitoring for allograft rejection and other complications.

Novel Approaches to Immunomodulation for Solid Organ Transplantation

Despite significant advances in the field of transplantation in the past two decades, current clinically available therapeutic options for immunomodulation remain fairly limited. The advent of calcineurin inhibitor-based immunosuppression has led to significant success in improving short-term graft survival; however, improvements in long-term graft survival have stalled. Solid organ transplantation provides a unique opportunity for immunomodulation of both the donor organ prior to implantation and the recipient post transplantation. Furthermore, therapies beyond targeting the adaptive immune system have the potential to ameliorate ischemic injury to the allograft and halt its aging process, augment its repair, and promote recipient immune tolerance. Other recent advances include expanding the donor pool by reducing organ discard, and bioengineering and genetically modifying organs from other species to generate transplantable organs. Therapies discussed here will likely be most impactful if individualized on the basis of specific donor and recipient considerations.

Therapeutic tactics for targeting B lymphocytes in autoimmunity and cancer

B lymphocytes have become a very popular therapeutic target in a number of autoimmune indications due to their newly appreciated roles, and approachability, in these diseases. Many of the therapies now applied in autoimmunity were initially developed to deplete malignant B cells. These strategies have also been found to benefit patients suffering from such autoimmune diseases as multiple sclerosis, type I diabetes, systemic lupus erythematosus, and rheumatoid arthritis, to name a few. These observations have supported the expansion of research addressing the mechanistic contributions of B cells in these diseases, as well as blossoming of therapeutics that target them. This review seeks to summarize cutting-edge modalities for targeting B cells, including monoclonal antibodies, bispecific antibodies, antibody-drug conjugates, chimeric antigen receptor-T cells, and small molecule inhibitors. Efforts to refine B-cell targeted therapy to eliminate only pathogenic autoreactive cells will be addressed as well as the potential for future B-cell-based cellular therapeutics. Finally, we also address approaches that seek to silence B-cell function without depletion.

Modern advances in heart transplantation

Heart transplantation (HTx) is the only definitive therapy for patients with end stage heart disease. With the increasing global prevalence of heart failure, the demand for HTx has continued to grow and outpace supply. In this paper, we will review advances in the field of HTx along the clinical journey of a HTx recipient. Starting with the sensitized patient, we discuss current methods to define sensitization, and assays to help identify clinically relevant anti-HLA antibodies. Desensitization strategies targeting all levels of the adaptive immune system are discussed with emphasis on novel techniques such as anti-CD 38 blockade and use of the Immunoglobulin G-Degrading Enzyme of Streptococcus Pyogenes. We next discuss donor procurement and the resurgence of donation after circulatory death as a viable strategy to significantly and safely increase the donor pool. Post-transplant, we evaluate non-invasive surveillance techniques including gene expression profiling and donor-derived cell-free DNA. Last, we discuss the ground-breaking developments in the field of xenotransplantation.

Immune landscape of the kidney allograft in response to rejection

Preventing kidney graft dysfunction and rejection is a critical step in addressing the nationwide organ shortage and improving patient outcomes. While kidney transplants (KT) are performed more frequently, the overall number of patients on the waitlist consistently exceeds organ availability. Despite improved short-term outcomes in KT, comparable progress in long-term allograft survival has not been achieved. Major cause of graft loss at 5 years post-KT is chronic allograft dysfunction (CAD) characterized by interstitial fibrosis and tubular atrophy (IFTA). Accordingly, proactive prevention of CAD requires a comprehensive understanding of the immune mechanisms associated with either further dysfunction or impaired repair. Allograft rejection is primed by innate immune cells and carried out by adaptive immune cells. The rejection process is primarily facilitated by antibody-mediated rejection (ABMR) and T cell-mediated rejection (TCMR). It is essential to better elucidate the actions of individual immune cell subclasses (e.g. B memory, Tregs, Macrophage type 1 and 2) throughout the rejection process, rather than limiting our understanding to broad classes of immune cells. Embracing multi-omic approaches may be the solution in acknowledging these intricacies and decoding these enigmatic pathways. A transition alongside advancing technology will better allow organ biology to find its place in this era of precision and personalized medicine.

Desensitization in Crossmatch-positive Kidney Transplant Candidates

Access to kidney transplantation is limited by HLA-specific sensitization. Desensitization strategies enable crossmatch-positive kidney transplantation. In this review, we describe clinical experience gained over the last 20 y using desensitization strategies before kidney transplantation and describe the different tools used (both drugs and apheresis options), including IVIg, rituximab, apheresis techniques, interleukin-6 interference, proteasome inhibition, enzymatic degradation of HLA antibodies, complement inhibition, and B cytokine interference. Although access to transplantation for highly sensitized kidney transplantation candidates has been vastly improved by desensitization strategies, it remains, however, limited by the recurrence of HLA antibodies after transplantation and the occurrence of antibody-mediated rejection.

Seeking Standardized Definitions for HLA-incompatible Kidney Transplants: A Systematic Review

BACKGROUND

There is no standard definition for "HLA incompatible" transplants. For the first time, we systematically assessed how HLA incompatibility was defined in contemporary peer-reviewed publications and its prognostic implication to transplant outcomes.

METHODS

We combined 2 independent searches of MEDLINE, EMBASE, and the Cochrane Library from 2015 to 2019. Content-expert reviewers screened for original research on outcomes of HLA-incompatible transplants (defined as allele or molecular mismatch and solid-phase or cell-based assays). We ascertained the completeness of reporting on a predefined set of variables assessing HLA incompatibility, therapies, and outcomes. Given significant heterogeneity, we conducted narrative synthesis and assessed risk of bias in studies examining the association between death-censored graft failure and HLA incompatibility.

RESULTS

Of 6656 screened articles, 163 evaluated transplant outcomes by HLA incompatibility. Most articles reported on cytotoxic/flow T-cell crossmatches (n = 98). Molecular genotypes were reported for selected loci at the allele-group level. Sixteen articles reported on epitope compatibility. Pretransplant donor-specific HLA antibodies were often considered (n = 143); yet there was heterogeneity in sample handling, assay procedure, and incomplete reporting on donor-specific HLA antibodies assignment. Induction (n = 129) and maintenance immunosuppression (n = 140) were frequently mentioned but less so rejection treatment (n = 72) and desensitization (n = 70). Studies assessing death-censored graft failure risk by HLA incompatibility were vulnerable to bias in the participant, predictor, and analysis domains.

CONCLUSIONS

Optimization of transplant outcomes and personalized care depends on accurate HLA compatibility assessment. Reporting on a standard set of variables will help assess generalizability of research, allow knowledge synthesis, and facilitate international collaboration in clinical trials.

Splenic Vessels as a Rescue for Pediatric Kidney Retransplantation in Children With Iliac-caval Agenesis or Thrombosis

BACKGROUND

Unavailability of the iliac-caval system due to thrombosis or aberrant anatomy may preclude kidney transplantation (KT) in small infants, exposing them to the complications of long-term dialysis. A tailored approach may enable KT also in these difficult patients.

METHODS

We report the cases of 2 pediatric patients with a history of long-term hemodialysis, a previously failed KT, pending exhaustion of vascular accesses for dialysis, and unsuitability of the iliac-caval axis as a site for KT. Both patients were successfully managed by using splenic vessels as a source of arterial inflow or venous drainage during KT. Notably, one patient also had a previous liver transplant.

RESULTS

Both kidney grafts showed primary function. Posttransplant courses were uneventful, and no rejection episode was observed. At 64- and 10-mo follow-ups, both children had optimal renal function and excellent quality of life.

CONCLUSIONS

When the iliac-caval system is unavailable, kidney graft implantation on splenic vessels represents a safe and effective option for pediatric KT.

Clinical application of immune repertoire sequencing in solid organ transplant

Background

Measurement of T cell receptor (TCR) or B cell receptor (BCR) gene utilization may be valuable in monitoring the dynamic changes in donor-reactive clonal populations following transplantation and enabling adjustment in therapy to avoid the consequences of excess immune suppression or to prevent rejection with contingent graft damage and to indicate the development of tolerance.

Objective

We performed a review of current literature to examine research in immune repertoire sequencing in organ transplantation and to assess the feasibility of this technology for clinical application in immune monitoring.

Methods

We searched MEDLINE and PubMed Central for English-language studies published between 2010 and 2021 that examined T cell/B cell repertoire dynamics upon immune activation. Manual filtering of the search results was performed based on relevancy and predefined inclusion criteria. Data were extracted based on study and methodology characteristics.

Results

Our initial search yielded 1933 articles of which 37 met the inclusion criteria; 16 of these were kidney transplant studies (43%) and 21 were other or general transplantation studies (57%). The predominant method for repertoire characterization was sequencing the CDR3 region of the TCR β chain. Repertoires of transplant recipients were found to have decreased diversity in both rejectors and non-rejectors when compared to healthy controls. Rejectors and those with opportunistic infections were more likely to have clonal expansion in T or B cell populations. Mixed lymphocyte culture followed by TCR sequencing was used in 6 studies to define an alloreactive repertoire and in specialized transplant settings to track tolerance.

Conclusion

Methodological approaches to immune repertoire sequencing are becoming established and offer considerable potential as a novel clinical tool for pre- and post-transplant immune monitoring.

Strategies to Overcome HLA Sensitization and Improve Access to Retransplantation after Kidney Graft Loss

An increasing number of patients waitlisted for kidney transplantation have a previously failed graft. Retransplantation provides a significant improvement in morbidity, mortality, and quality of life when compared to dialysis. However, HLA sensitization is a major barrier to kidney retransplantation and the majority of the highly sensitized patients are waiting for a subsequent kidney transplant. A multidisciplinary team that includes immunogeneticists, transplant nephrologists and surgeons, and adequate allocation policies is fundamental to increase access to a kidney retransplant. A review of Pubmed, ScienceDirect, and the Cochrane Library was performed on the challenges of kidney retransplantation after graft loss, focusing on the HLA barrier and new strategies to overcome sensitization. Conclusion: Technical advances in immunogenetics, new desensitization protocols, and complex allocation programs have emerged in recent years to provide a new hope to kidney recipients with a previously failed graft.

HLA Desensitization Based on Results of the Luminex Technique in Kidney Transplant - A Single-center Experience

Background:

There is little experience of human leucocyte antigen (HLA) desensitization in India based on the Luminex single-antigen bead (SAB) testing. We retrospectively analyzed our patients, who underwent HLA desensitization based on Luminex SAB results.

Method:

Between 2014 and 2018, patients with complement-dependent cytotoxicity cross-match (CDC-XM) negativity but flow cytometry crossmatch (FC-XM) positivity were further analyzed with Luminex SAB for donor-specific antibodies (DSAs). A total of 12 patients who had DSA mean fluorescent intensity (MFI) of >1000 and <10,000 were included in the study. Our protocol for desensitization consisted of plasmapheresis (PP) followed by low dose intravenous immunoglobulin (IV IG) 100 mg/kg and induction with antithymocyte globulin (ATG). Patients were taken for transplant when either MFI was <1000 and/or FC-XM was negative.

Results:

All 12 patients were first transplant and 10 had a history of some sensitizing event; pregnancy in 4, blood transfusions in 4, and both in 2 patients. FC-XM was positive for T-cell in 4, B-cell in 6, and both in 2 patients. On evaluation by Luminex SAB, 6 patients had MFI from 1000 to 2000, and 6 had MFI of >2000. All underwent desensitization successfully. Two patients had an increase in posttransplant DSA titers requiring posttransplant PP. The mean follow-up was 26.6 ± 13.9 months. On follow-up, only one patient developed acute T cell-mediated rejection 1 year after transplant, which responded to pulse steroids. There was no graft or patient loss until the last follow-up.

Conclusion:

This study shows that HLA desensitization is feasible and successful in the Indian setting if patients are properly selected.

Therapeutic Potential of HLA-I Polyreactive mAbs Mimicking the HLA-I Polyreactivity and Immunoregulatory Functions of IVIg

HLA class-I (HLA-I) polyreactive monoclonal antibodies (mAbs) reacting to all HLA-I alleles were developed by immunizing mice with HLA-E monomeric, α-heavy chain (αHC) open conformers (OCs). Two mAbs (TFL-006 and TFL-007) were bound to the αHC’s coated on a solid matrix. The binding was inhibited by the peptide ¹¹⁷AYDGKDY¹²³, present in all alleles of the six HLA-I isoforms but masked by β2-microglobulin (β2-m) in intact HLA-I trimers (closed conformers, CCs). IVIg preparations administered to lower anti-HLA Abs in pre-and post-transplant patients have also shown HLA-I polyreactivity. We hypothesized that the mAbs that mimic IVIg HLA-I polyreactivity might also possess the immunomodulatory capabilities of IVIg. We tested the relative binding affinities of the mAbs and IVIg for both OCs and CCs and compared their effects on (a) the phytohemagglutinin (PHA)-activation T-cells; (b) the production of anti-HLA-II antibody (Ab) by B-memory cells and anti-HLA-I Ab by immortalized B-cells; and (c) the upregulation of CD4+, CD25+, and Fox P³+ T-regs. The mAbs bound only to OC, whereas IVIg bound to both CC and OC. The mAbs suppressed blastogenesis and proliferation of PHA-activated T-cells and anti-HLA Ab production by B-cells and expanded T-regs better than IVIg. We conclude that a humanized version of the TFL-mAbs could be an ideal, therapeutic IVIg-mimetic.

Emerging New Approaches in Desensitization: Targeted Therapies for HLA Sensitization

There is an urgent need for therapeutic interventions for desensitization and antibody-mediated rejection (AMR) in sensitized patients with preformed or de novo donor-specific HLA antibodies (DSA). The risk of AMR and allograft loss in sensitized patients is increased due to preformed DSA detected at time of transplant or the reactivation of HLA memory after transplantation, causing acute and chronic AMR. Alternatively, de novo DSA that develops post-transplant due to inadequate immunosuppression and again may lead to acute and chronic AMR or even allograft loss. Circulating antibody, the final product of the humoral immune response, has been the primary target of desensitization and AMR treatment. However, in many cases these protocols fail to achieve efficient removal of all DSA and long-term outcomes of patients with persistent DSA are far worse when compared to non-sensitized patients. We believe that targeting multiple components of humoral immunity will lead to improved outcomes for such patients. In this review, we will briefly discuss conventional desensitization methods targeting antibody or B cell removal and then present a mechanistically designed desensitization regimen targeting plasma cells and the humoral response.

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.

HLA Desensitization in Solid Organ Transplantation: Anti-CD38 to Across the Immunological Barriers

The presence of anti-human leucocyte antigen (HLA) antibodies in the potential solid organ transplant recipient's blood is one of the main barriers to access to a transplantation. The HLA sensitization is associated with longer waitlist time, antibody mediated rejection and transplant lost leading to increased recipient's morbidity and mortality. However, solid organ transplantation across the HLA immunological barriers have been reported in recipients who were highly sensitized to HLA using desensitization protocols. These desensitization regimens are focused on the reduction of circulating HLA antibodies. Despite those strategies improve rates of transplantation, it remains several limitations including persistent high rejection rate and worse long-term outcomes when compare with non-sensitized recipient population. Currently, interest is growing in the development of new desensitization approaches which, beyond targeting antibodies, would be based on the modulation of alloimmune pathways. Plasma cells appears as an interesting target given their critical role in antibody production. In the last decade, CD38-targeting immunotherapies, such as daratumumab, have been recognized as a key component in the treatment of myeloma by inducing an important plasma cell depletion. This review focuses on an emerging concept based on targeting CD38 to desensitize in the field of transplantation.

Current Approaches to Desensitization in Solid Organ Transplantation

Major advancements in the development of HLA antibody detection techniques and our understanding of the outcomes of solid organ transplant in the context of HLA antibody have occurred since the relevance of sensitization was first recognized nearly 50 years ago. Additionally, kidney paired donation programs (KPD) have become widespread, deceased donor allocation policies have changed, and several new therapeutic options have become available with promise to reduce HLA antibody. In this overview we aim to provide thoughtful guidance about when desensitization in kidney transplantation should be considered taking into account the outcomes of HLA incompatible transplantation. Novel therapeutics, desensitization endpoints, and strategies for future study will also be discussed. While most of our understanding about desensitization comes from studying kidney transplant candidates and recipients, many of the concepts discussed can be easily applied to desensitization in all of solid organ transplantation.

Recommended Treatment for Antibody-mediated Rejection After Kidney Transplantation: The 2019 Expert Consensus From the Transplantion Society Working Group

With the development of modern solid-phase assays to detect anti-HLA antibodies and a more precise histological classification, the diagnosis of antibody-mediated rejection (AMR) has become more common and is a major cause of kidney graft loss. Currently, there are no approved therapies and treatment guidelines are based on low-level evidence. The number of prospective randomized trials for the treatment of AMR is small, and the lack of an accepted common standard for care has been an impediment to the development of new therapies. To help alleviate this, The Transplantation Society convened a meeting of international experts to develop a consensus as to what is appropriate treatment for active and chronic active AMR. The aim was to reach a consensus for standard of care treatment against which new therapies could be evaluated. At the meeting, the underlying biology of AMR, the criteria for diagnosis, the clinical phenotypes, and outcomes were discussed. The evidence for different treatments was reviewed, and a consensus for what is acceptable standard of care for the treatment of active and chronic active AMR was presented. While it was agreed that the aims of treatment are to preserve renal function, reduce histological injury, and reduce the titer of donor-specific antibody, there was no conclusive evidence to support any specific therapy. As a result, the treatment recommendations are largely based on expert opinion. It is acknowledged that properly conducted and powered clinical trials of biologically plausible agents are urgently needed to improve patient outcomes.

Desensitization strategies: is it worth it?

Preformed donor-specific antibodies (DSAs) limit access to transplantation for thousands of renal transplant patients. While kidney paired donation offers the best strategy for patients with a living donor, for very highly sensitized patients and those without living donors, a strategy of desensitization offers the best hope of transplantation. Removal of DSAs with plasmapheresis, intravenous immunoglobulin and anti-CD20 antibodies can permit successful transplantation. While the clinical outcomes remain inferior to compatible transplant and the costs are significantly greater, when compared with long-term dialysis treatment, these strategies are offer improved survival and are cost-effective given nationally accepted benchmarks.

Renal transplantation in HLA sensitized patients: Traversing the immunological barrier

Successful renal transplantation across HLA barrier in sensitized individuals has been on the rise during the past decade, primarily due to improved desensitization regimes. The aim of this study was to share outcome of desensitization in renal transplant recipients with donor-specific anti-HLA antibodies (DSA). This was a retrospective analysis of all HLA immunized individuals who were prospective renal transplant recipients. All such patients underwent preconditioning as per the institutional desensitization protocol. Complement-dependent cytoxicity-based crossmatch (CDC-XM), luminex-based crossmatch (LM-XM) and flowcytometry-based crossmatch (FC-XM) were done in all cases. If any of these tests turned out positive, single antigen bead assay (SAB) was performed. Desensitization for DSA was performed in 55 patients and all patients were followed-up for 1 year to assess graft function and patient outcome. CDC-XM being a less sensitive assay, could not detect incompatibility in 29 (52.73%) cases. After desensitization, even though SAB and LM-XM results revealed an MFI within acceptable range, FC-XM being an extremely sensitive assay, continued to give a positive result in eight (14.55%) cases. The mean ± SD number of pretransplant TPE were 3.44 ± 0.98 (2-11). Out of 55, there were 10 patients who were lost to follow up. Patient and graft survival of 45 patients at 1 year was found to be 100%. Preconditioning for renal transplants in the form of immunosuppression with TPE is an extremely useful auxiliary for transplantation in HLA sensitized renal transplant recipients.

Use of Eculizumab for Active Antibody-mediated Rejection That Occurs Early Post-kidney Transplantation: A Consecutive Series of 15 Cases

BACKGROUND

Active antibody-mediated rejection (AMR) that occurs during the amnestic response within the first month posttransplant is a rare but devastating cause of early allograft loss after kidney transplant. Prior reports of eculizumab treatment for AMR have been in heterogeneous patient groups needing salvage therapy or presenting at varied time points. We investigated the role of eculizumab as primary therapy for active AMR early posttransplant.

METHODS

We performed a retrospective observational study of a consecutive cohort of solitary kidney transplant recipients who were transplanted between January 1, 2014, and January 31, 2018, and had AMR within the first 30 days posttransplant and treated with eculizumab ± plasmapheresis.

RESULTS

Fifteen patients had early active AMR at a median (interquartile range [IQR]) of 10 (7-11) days posttransplant and were treated with eculizumab ± plasmapheresis. Thirteen cases were biopsy proven, and 2 cases were presumed on the basis of donor-specific antibody trends and allograft function. Within 1 week of treatment, the median estimated glomerular filtration rate increased from 21 to 34 mL/min (P = 0.001); and persistent active AMR was only found in 16.7% (2/12) of biopsied patients within 4-6 months. No graft losses occurred, and at last follow-up (median [IQR] of 13 [12-19] mo), the median IQR estimated glomerular filtration rate increased to 52 (46-60) mL/min.

CONCLUSIONS

Prompt eculizumab treatment as primary therapy is safe and effective for early active AMR after kidney transplant or abrupt increases in donor-specific antibodies when biopsy cannot be performed for diagnosis confirmation.

Safety and efficacy of eculizumab in the prevention of antibody-mediated rejection in living-donor kidney transplant recipients requiring desensitization therapy: A randomized trial

We report results of a phase 2, randomized, multicenter, open-label, two-arm study evaluating the safety and efficacy of eculizumab in preventing acute antibody-mediated rejection (AMR) in sensitized recipients of living-donor kidney transplants requiring pretransplant desensitization (NCT01399593). In total, 102 patients underwent desensitization. Posttransplant, 51 patients received standard of care (SOC) and 51 received eculizumab. The primary end point was week 9 posttransplant treatment failure rate, a composite of: biopsy-proven acute AMR (Banff 2007 grade II or III; assessed by blinded central pathology); graft loss; death; or loss to follow-up. Eculizumab was well tolerated with no new safety concerns. No significant difference in treatment failure rate was observed between eculizumab (9.8%) and SOC (13.7%; P = .760). To determine whether data assessment assumptions affected study outcome, biopsies were reanalyzed by central pathologists using clinical information. The resulting treatment failure rates were 11.8% and 21.6% for the eculizumab and SOC groups, respectively (nominal P = .288). When reassessment included grade I AMR, the treatment failure rates were 11.8% (eculizumab) and 29.4% (SOC; nominal P = .048). This finding suggests a potential benefit for eculizumab compared with SOC in preventing acute AMR in recipients sensitized to their living-donor kidney transplants (EudraCT 2010-019630-28).

Safety and efficacy of eculizumab for the prevention of antibody-mediated rejection after deceased-donor kidney transplantation in patients with preformed donor-specific antibodies

The presence of preformed donor-specific antibodies in transplant recipients increases the risk of acute antibody-mediated rejection (AMR). Results of an open-label single-arm trial to evaluate the safety and efficacy of eculizumab in preventing acute AMR in recipients of deceased-donor kidney transplants with preformed donor-specific antibodies are reported. Participants received eculizumab as follows: 1200 mg immediately before reperfusion; 900 mg on posttransplant days 1, 7, 14, 21, and 28; and 1200 mg at weeks 5, 7, and 9. All patients received thymoglobulin induction therapy and standard maintenance immunosuppression including steroids. The primary end point was treatment failure rate, a composite of biopsy-proved grade II/III AMR (Banff 2007 criteria), graft loss, death, or loss to follow-up, within 9 weeks posttransplant. Eighty patients received transplants (48 women); the median age was 52 years (range 24-70 years). Observed treatment failure rate (8.8%) was significantly lower than expected for standard care (40%; P < .001). By 9 weeks, 3 of 80 patients had experienced AMR, and 4 of 80 had experienced graft loss. At 36 months, graft and patient survival rates were 83.4% and 91.5%, respectively. Eculizumab was well tolerated and no new safety concerns were identified. Eculizumab has the potential to provide prophylaxis against injury caused by acute AMR in such patients (EudraCT 2010-019631-35).

Renal Transplantation in High Immunological Risk Patients: A Single-Center Experience

BACKGROUND

Renal transplantation (RT) in high-risk patients is increasingly performed due to an inadequate organ pool and increased rate of RT after a failed transplantation. Safety and prognosis of RT in such patients with high risk is an ongoing debate. Herein we aimed to present our single-center experience on RT of high-risk patients.

METHODS

A total of 89 consecutive RT patients were included into this study in a 10-month period. Patients were divided into 3 groups: the low-risk group (n = 47) with negative panel reactive antibody (PRA), medium-risk group (n = 18) with positive PRA but mean fluorescence intensity (MFI) < 2000, and high-risk group (n = 24) with positive PRA and MFI >2000 or donor specific antibody (DSA) positivity. Groups were compared in terms of demographic features, serum creatinine levels, acute rejection rates, delayed graft function (DGF), and patient or graft loss.

RESULTS

Age of the recipients were similar between the groups. Desensitization (7% vs 11% vs 42%, respectively, in low-, medium-, and high-risk groups; P = .001), plasmapheresis (6% vs 11% vs 46%, respectively, P < .001), and rituximab treatments (0% vs 0% vs 25%, respectively, P < .001) were significantly more frequently performed in high-risk patients. Serum creatinine levels at 1 month and 6 months after RT were similar between the groups (P = .43 and P = .71, respectively). Rates of acute rejection (6% vs 6% vs 16%, respectively, P = .52) and DGF (9% vs 11% vs 29%, respectively, P = .15) were similar between the groups. Frequencies of loss of patient or graft were also similar (0% vs 6% vs 4%, P = .15).

CONCLUSION

RT may be successfully performed in high-risk patients without an increase in the risk of acute rejection, DGF, or patient/graft loss.

Effect of Calculated Panel Reactive Antibody Value on Waitlist Outcomes for Lung Transplant Candidates

Background

We conducted a retrospective cohort study using United Network of Organ Sharing (UNOS) data to determine the effect of the calculated panel reactive antibody (cPRA) value on waitlist outcomes for lung transplant candidates.

Material/Methods

We divided lung transplant candidates into groups based on their cPRA value at the time of waitlist activation (0–25%, 25.1–50%, 50.1–75%, and 75.1–100%) and compared each group’s waitlist outcomes to the lowest quartile (“minimally sensitized”) group. The primary outcome was lung transplantation and the secondary outcome was waitlist mortality (a composite of death on the waitlist/delisting for clinical deterioration).

Results

Compared to the minimally sensitized group, candidates with a cPRA value of 25.1–50% did not have a significantly different likelihood of undergoing lung transplant or waitlist mortality, candidates with a cPRA value of 50.1–75% were 25% less likely to undergo lung transplant and 44% more likely to die on the waitlist, and candidates with a cPRA value of 75.1–100% were 52% less likely to undergo lung transplant and 92% more likely to die on the waitlist.

Conclusions

CPRA values of greater than 50% are associated with significantly lower rates of transplantation and higher waitlist mortality.

Is There a Role for Desensitization in Intestinal Transplantation?

Human leukocyte antigen allosensitization prior to transplant can increase the risk of early graft loss and prolong waitlist times for intestinal transplant candidates. Desensitization offers a potential therapeutic option to reduce the quantity of preformed antibodies prior to organ allocation and facilitate transplantation with a more immunologically compatible donor allograft. However, there remains a paucity of data to guide the use of desensitization in the setting of intestinal transplantation. As a result, in this review we evaluate the existing literature supporting the role of desensitization therapy in intestinal transplant, describe our own experience with the implementation of a risk-stratified desensitization protocol, and finally explore barriers and unanswered questions that continue to limit the widespread adoption of desensitization as a management strategy for highly sensitized intestinal transplant candidates.

The results of HLA-incompatible kidney transplantation according to pre-transplant crossmatch tests: Donor-specific antibody as a prominent predictor of acute rejection

BACKGROUND

Crossmatching (XM) between organ donors and recipients is correlated with clinical outcomes. This study evaluates the results of HLA-incompatible kidney transplant (HLA-i KT) according to pre-transplant XM modalities.

METHODS

This study included 731 consecutive patients. HLA-i KT was defined as a transplant under conditions of complement-dependent cytotoxicity (CDC) XM positivity, flow-cytometric XM (FCXM) positivity, and/or maximal donor-specific antibody (DSA) mean fluorescence intensity (MFI) ≥5000.

RESULTS

The incidence of antibody-mediated rejection (AMR) within 1 year after transplant was significantly higher in the HLA-i group than in the HLA compatible (HLA-c) group (15 vs 9 patients, 14.2% vs 1.4%; P < 0.01). Multivariate analysis indicated that a DSA MFI ≥5000 (odds ratio [OR] = 2.63; 95% confidence interval [CI], 1.00-6.98; P = 0.05) was significantly associated with acute rejection (AR), whereas CDC (OR = 2.09; 95% CI, 0.55-7.99; P = 0.28) and FCXM positivity (OR = 2.07; 95% CI, 0.73-5.87; P = 0.17) were not. Similarly, DSA MFI ≥ 5000 (OR = 4.14; P = 0.02) was the only significant factor affecting the risk of AMR.

CONCLUSIONS

Of the various XM tests, DSA MFI ≥5000 was the most prominent predictor of AR in patients undergoing HLA-i KT.

Sensitization in Heart Transplantation: Emerging Knowledge: A Scientific Statement From the American Heart Association

Sensitization, defined as the presence of circulating antibodies, presents challenges for heart transplant recipients and physicians. When present, sensitization can limit a transplantation candidate’s access to organs, prolong wait time, and, in some cases, exclude the candidate from heart transplantation altogether. The management of sensitization is not yet standardized, and current therapies have not yielded consistent results. Although current strategies involve antibody suppression and removal with intravenous immunoglobulin, plasmapheresis, and antibody therapy, newer strategies with more specific targets are being investigated.

Impact of reduced exposure to calcineurin inhibitors on the development of de novo DSA: a cohort of non-immunized first kidney graft recipients between 2007 and 2014

Background

In low-immunological risk kidney transplant recipients (KTRs), reduced exposure to calcineurin inhibitor (CNI) appears particularly attractive for avoiding adverse events, but may increase the risk of developing de novo Donor Specific Antibodies (dnDSA).

Methods

CNI exposure was retrospectively analyzed in 247 non-HLA immunized first KTRs by taking into account trough levels (C0) collected during follow-up. Reduced exposure to CNI was defined as follows: C0 less than the lower limit of the international targets for ≥50% of follow-up.

Results

During a mean follow-up of 5.0 ± 2.0 years, 39 patients (15.8%) developed dnDSA (MFI ≥1000). Patients with DSA were significantly younger (46.6 ± 13.8 vs. 51.7 ± 14.0 years, p = 0.039), received more frequently poorly-matched grafts (59% with 6–8 A-B-DR-DQ HLA mismatches vs. 34.6%, p = 0.016) and had more frequently a reduced exposure to CNI (92.3% vs. 62.0%, p = 0.0002). Reduced exposure to CNI was associated with an increased risk of dnDSA (multivariable HR = 9.77, p = 0.002). Reduced exposure to CNI had no effect on patient survival, graft loss from any cause including death, or post-transplant cancer.

Conclusions

Even in a low-immunological risk population, reduced exposure to CNI is associated with increased risk of dnDSA. Benefits and risks of under-immunosuppression must be carefully evaluated before deciding on CNI minimization.

Successful Desensitization of T cell Flow Cytometry Crossmatch Positive Renal Transplant Recipients Using Plasmapheresis and Super High-Dose Intravenous Immunoglobulin

Background

High-dose IVIG (2 g/kg) alone or low-dose IVIG (100 mg/kg) in conjunction with plasma exchange is typically administered as a renal transplantation desensitization therapy. Herein, we monitored changes in T cell and B cell flow cytometry crossmatch (FCXM) to assess the effects of short-term super high-dose IVIG (4 g/kg) administration with plasmapheresis before living-donor renal transplantation.

Methods

Seventeen patients, each showing positive T cell FCXM (median ratio, ≥ 1.4) after 2 rounds of double-filtration plasmapheresis, received 4-day regimens of IVIG (1 g/kg per day) over 1-week periods. T cell and B cell FCXM determinations were obtained after every IVIG dose and again up to 4 weeks after initiating IVIG to ascertain negative conversion of T cell FCXM (median ratio < 1.4). The primary study endpoint was the percentage of patients achieving T cell FCXM-negative status after the 4-dose IVIG regimen.

Results

Upon completion (4 g/kg total) or discontinuation of IVIG administration, 8 (47.1%) of 17 patients displayed negative T cell FCXM. Based on Kaplan-Meier estimates, the cumulative T cell FCXM-negative conversion rate 4 weeks after IVIG administration initiation was 60.3%. The T cell FCXM-negative conversion rates after cumulative doses of 1, 2, 3, and 4 g/kg IVIG were 29.4%, 35.3%, 56.3%, and 46.7%, respectively.

Conclusions

Desensitization of donor-specific antibody-positive renal transplant recipients seems achievable in only a subset of recipients through IVIG dosing (1 g/kg × 4) within 1 week after double-filtration plasmapheresis. The T cell FCXM-negative conversion rate resulting from a cumulative IVIG dose of 3 g/kg or greater surpassed that attained via conventional single-dose IVIG (2 g/kg) protocol. This short-term high-dose IVIG desensitization protocol may be an alternative to conventional protocols for recipients with donor-specific antibody.

Regulatory B cells: the cutting edge of immune tolerance in kidney transplantation

Kidney transplantation is the optimal treatment for end-stage renal diseases. Although great improvement has been achieved, immune tolerance is still the Holy Grail that every organ transplant practitioner pursues. The role of B cells in transplantation has long been considered simply to serve as precursors of plasma cells, which produce alloantibodies and induce antibody-mediated rejection. Recent research indicates that a specialized subset of B cells plays an important role in immune regulation, which has been well demonstrated in autoimmune diseases, infections, and cancers. This category of regulatory B cells (Bregs) differs from conventional B cells, and they may help develop a novel immunomodulatory therapeutic strategy to achieve immune tolerance in transplantation. Here, we review the latest evidence regarding phenotypes, functions, and effectors of Bregs and discuss their diverse effects on kidney transplantation.

Risk factors for the development of antibody-mediated rejection in highly sensitized pediatric kidney transplant recipients

ABMR remains a significant concern for early graft loss, especially for those who are HS against HLA antigens. We sought to determine the risk factors leading to ABMR in HS pediatric kidney transplant recipients. From January 2009 to December 2015, 16 HS pediatric kidney transplant patients at our center (age range 2-21) were retrospectively reviewed for outcomes and risk factors for ABMR. All HS patients received desensitization with high-dose IVIG/rituximab prior to transplant. Two groups were examined: ABMR⁺ (n = 7) and ABMR^- (n = 9). Patient survival was 100%; however, one patient in the ABMR⁺ group suffered graft loss from ABMR 16 months post-transplant. ABMR⁺ patients had higher Class I PRA at the time of transplant (Class I: 73.1 ± 19.1 vs 49.1 ± 28.3, P = .075), although not statistically significant. ABMR⁺ patients were more likely to have a history of transplant nephrectomy (P = .013). The characteristic that most strongly correlated with ABMR was the DSA-RIS (P = .045), a scoring system used to quantify cumulative intensity of all DSA. In conclusion, DSA, as quantified by the RIS at the time of transplant, should be considered as part of the initial allocation strategy and patients with high RIS monitored closely for ABMR post-transplant.

Clinical and histopathologic features of antibody-mediated rejection among pediatric renal transplant recipients with preformed vs de novo donor-specific antibodies

Preformed and de novo donor specific antibodies (pDSA and dnDSA) are risk factors for ABMR. This study compares the effects of pDSA vs dnDSA in pediatric kidney transplant recipients. Sixteen pediatric patients with biopsy-proven ABMR were evaluated. Strong DSA (MFI >10 000) was recorded at transplant, rejection, and follow-up. DSAs with the highest MFI were termed iDSAs. Allograft biopsies were scored according to Banff 2013 criteria. Seven of 16 (44%) patients had pDSA at transplant; 9 (56%) developed dnDSA. Patients with pDSA developed ABMR earlier (median = 63 vs 1344 days, P = .017), while patients with dnDSA were more likely to have strong Class II iDSA (100% vs 28%, P = .009). Viral infection or non-adherence was more common in patients developing dnDSA (88.8% vs 28.6%, P < .01). Pathology in those with pDSAs demonstrated worse transplant glomerulitis (g score 1.57 ± 0.98 vs 0.56 ± 0.73, P = .031); however, those with dnDSAs exhibited higher C4d+ ABMR (P = .013). Patients developing dnDSAs showed ABMR later post-transplant with predominance of HLA-Class II iDSAs. Inadequate immunosuppression likely contributes to dnDSA formation. Patients with no DSA who have unprotocolized decreases in immunosuppression should be screened for dnDSA as it could lead to early intervention and potentially better outcomes.

Human Leukocyte Antigen Sensitization in Solid Organ Transplantation: A Primer on Terminology, Testing, and Clinical Significance for the Apheresis Practitioner

The human leukocyte antigen (HLA) system is an important immunologic barrier that must be considered for successful solid organ transplantation. Formation of donor-specific HLA antibodies in solid organ transplantation is an important cause of allograft injury and may contribute to recipient morbidity and mortality. Therapeutic plasma exchange is often requested to lower HLA antibody levels prior to or after transplantation and for management of HLA antibodies in the context of organ rejection. In this review, we summarize the current terminology, laboratory testing, and clinical significance of HLA sensitization in the solid organ transplant population. Furthermore, to illustrate applications of HLA testing in clinical practice, we summarize our own lung and kidney institutional protocols for managing HLA antibodies in the peri-transplant setting.

32 Doses of Bortezomib for Desensitization Is Not Well Tolerated and Is Associated With Only Modest Reductions in Anti-HLA Antibody

BACKGROUND

We previously showed that bortezomib (BTZ) partially depletes plasma cells, yet has limited efficacy for desensitization in kidney transplant candidates when up to 16 doses is given.

METHODS

This study aimed to determine the safety and efficacy of 32 doses of BTZ (1.3 mg/m of body surface area) in 10 highly sensitized kidney transplant candidates with alloantibodies against their intended living donor.

RESULTS

Dose reduction was needed in 2 patients and 2 others completely discontinued therapy for adverse events. Anti-HLA antibodies mean fluorescence intensity (MFI) values were stable prior to BTZ (P = 0.96) but decreased after therapy (mean decrease of 1916 [SE, 425] MFI, P < 0.01). No patient developed a negative crossmatch against their original intended donor, and the calculated panel-reactive antibodies based on MFI of 2000, 4000, and 8000 was unchanged in all patients.

CONCLUSIONS

These data suggest that 32 doses of BTZ monotherapy was not well tolerated and resulted in only a modest reduction in anti-HLA antibodies.

Safety and Efficacy of Alemtuzumab Induction in Highly Sensitized Pediatric Renal Transplant Recipients

BACKGROUND

Studies show that alemtuzumab, a potent lymphocyte-depleting agent, is well tolerated in pediatric renal transplantation. We report on the use of alemtuzumab induction in highly HLA sensitized (HS) pediatric kidney transplant patients.

METHODS

Fifty pediatric renal transplants were performed from 1/2009-12/2014. 15 HS patients received IVIG (2 g/kg ×2 doses)/rituximab (375 mg/m ×1) for desensitization with alemtuzumab induction (15-30 mg, 1 dose, subcutaneous), whereas 35 nonsensitized patients received anti-IL-2R. Graft survival and infections were compared between 2 groups.

RESULTS

All HS patients had received a prior transplant and were older with lower risk for viral infections due to serostatus. Patient survival was 100%, and graft outcomes were similar with mean 1-year creatinine of 1.03 ± 0.45 versus 0.99 ± 0.6 (P = 0.48). Although a higher incidence of acute cellular rejection was seen in HS patients receiving alemtuzumab (P = 0.001), there was a nonsignificant difference in antibody-mediated rejection. White blood cell and absolute lymphocyte count were significantly lower in alemtuzumab group at 30 days (P < 0.0001) and at 1 year (P = 0.026 and P = 0.001), respectively. There was no significant difference in bacterial, viral, or fungal infections after transplant.

CONCLUSIONS

Alemtuzumab induction with desensitization led to nearly equivalent graft survival and functional outcomes in HS pediatric patients as nonsensitized patients receiving anti-IL-2R induction. With this small sample size, we observed significant reduction of white blood cell and absolute lymphocyte count up to 1 year posttransplant. The risk of infection was comparable between the 2 groups; however, patients who received alemtuzumab were older and at lower risk of viral infection due to serostatus.

Implementation of a National Priority Allocation System for Hypersensitized Patients in Spain, Based on Virtual Crossmatch: Initial Results

Access to kidney transplantation for patients with high levels of antibodies against HLA is a major challenge. This issue makes it difficult to detect compatible donors for those patients in a certain geographical area. Consequently, hypersensitized patients remain on the waiting list for long periods and their quality of life deteriorates. Our purpose was to increase access to transplantation for highly sensitized patients by developing a national priority allocation system based on virtual crossmatch. Between June 15, 2015, and May 15, 2016, 675 patients on the kidney transplant waiting list with calculated panel-reactive antibodies ≥98% and undergoing dialysis for at least 12 months were included in the study; 86.1% of the patients had previously received at least one transplant. Solid-phase immunoassays were used to identify class I and II HLA antibodies in all patients. Participating hospitals assigned to the program one of the kidneys of every identified brain-dead real donor between 18 and 70 years old. Survival data were collected for the recipients transplanted between June 15, 2015, and December 31, 2015. In all, 475 (290 male and 185 female) brain-dead donors were assigned to the program. Virtual crossmatch was negative for 191 (41%) donors, 149 offers were accepted, and 102 (21.8%) kidneys were transplanted. At the end of the study, patient and graft survival were both 93.4%. The implementation of a national prioritization system based on virtual crossmatch increased access to transplantation for highly sensitized patients, with excellent results in terms of patient and graft survival.