Prevention Of Antibody-mediated Rejection Research Articles

404.5: The Role of LAG3 in Antibody Responses to Kidney Transplantation

The functions of coinhibitory receptor lymphocyte activation gene-3 (LAG3) in T cells are well studied, however its role in humoral immune responses remains poorly characterized. The goal of this study was to test the role of recipient LAG3 in a mouse model of renal allograft rejection. Murine kidney transplant surgeries were performed from C3H (H-2Dk) donors to B6 WT, LAG3-/-, CD4CreLAG3fl/fl & CD19CreLAG3fl/fl recipients (H-2Db) after bilateral nephrectomy. Grafts were evaluated by immunistochemistry. WT recipients were treated with anti-mCD20 or anti-CD8 mAbs to deplete B cells or CD8 T cells, respectively. Immune responses were assessed by flow cytometry, ELISPOT assay, and serum levels of MHC-I and MHC-II-reactive IgG donor specific antibody (DSA) were determined by ELISA. Compared to WT animals, naïve B6.LAG3-/- mice have elevated numbers of CD44hi memory T cells, CXCR5hi follicular T cells, and B220+CD138+ plasma cells, and increased frequencies of memory T cells reactive to H-2Dd, H-2Ds, H-2Dq and H-2Dk (Figure 1A) and increased levels of serum IgG antibodies against H-2Dd, H-2Dk, I-Ad and I-Ak alloantigens (Figure 1B). All C3H kidney allografts survived for > 60d (n=5) in WT recipients, whereas recipient LAG3 deficiency led to rapid allograft rejection (MST of 14d, n=5) (Figure 2A) and elevated serum creatinine levels at d14 posttransplant. Compared to WT, LAG3-/- recipients had elevated frequencies of anti-donor IFNγ producing T cells and increased levels of DSA against MHC-I and MHC-II (Figure 2B). Graft histology at rejection revealed minimal T cell infiltration, diffuse C4d staining, atrophic peritubular capillaries, endothelial swelling and edema characteristic of antibody mediated rejection (AMR) (Figure 2C). Recipient CD8 T cell depletion did not alter rejection kinetics in LAG3-/- recipients (MST of 16d) (Figure 3A&B), and graft histological findings (Figure 3C) mirrored those of unmanipulated LAG3 deficient recipients (Figure 2C), demonstrating hallmark characterstics of AMR. B cell depletion significantly extended C3H kidney allograft survival (MST of >30d) (Figure 3D&E), suggesting the predominant role of alloantibody rather than T cell mediated rejection in these mice. However, neither T nor B cell conditional knockout recipients rejected the allograft demonstrating LAG3 expression on both cell types is necessary to mediate rejection.These findings demonstrate that LAG3 regulates both T and B cell functions in response to kidney allografts, and is an attractive therapeutic target for the prevention of AMR.

The Role of LAG3 in Antibody Responses To Kidney Transplantation

Abstract The role of lymphocyte activation gene-3 (LAG3) in T cell functions is well studied, however its role in humoral immune responses remains poorly characterized. The goal of this study was to test the role of recipient LAG3 in a mouse model of renal allograft rejectionNaive B6.LAG3−/− mice have elevated numbers of follicular and memory T cells, and plasma cells compared to WT mice, as well as increased frequencies of memory T cells reactive to H-2Dd, H-2Ds, H-2Dq and H-2Dk alloantigens. When kidneys were transplanted from C3H donors to B6 WT and LAG3−/− mice, all C3H kidney allografts survived for > 60d in WT recipients, whereas LAG3−/− recipients rapidly reject allografts and have elevated serum creatinine levels at d14 posttransplant. Graft histology at rejection revealed minimal T cell infiltration, diffuse C4d staining, atrophic peritubular capillaries, endothelial swelling and edema characteristic of antibody mediated rejection (AMR). Compared to WT, LAG3−/− recipients had elevated frequencies of anti-donor IFNγ producing T cells and increased levels of donor specific antibody (DSA) against MHC-I and MHC-II. Depletion of CD8 T cells in LAG3−/− recipients did not alter rejection kinetics, while B cell depletion significantly extended C3H kidney allograft survival, suggesting the predominant role of alloantibody rather than T cell mediated rejection in these mice. However, neither T nor B cell conditional knockout recipients rejected the allograft demonstrating LAG3 expression on both cell types is necessary to mediate rejection. These findings demonstrate that LAG3 regulates both T and B cell functions in response to kidney allografts, and is an attractive therapeutic target for the prevention of AMR. Supported by grants from NIH (P01AI087586-10)

Recent progress and remaining hurdles toward clinical xenotransplantation.

Xenotransplantation has made tremendous progress over the last decade. We discuss kidney and heart xenotransplantation, which are nearing initial clinical trials. Life sustaining genetically modified kidney xenografts can now last for approximately 500days and orthotopic heart xenografts for 200days in non-human primates. Anti-swine specific antibody screening, preemptive desensitization protocols, complement inhibition and targeted immunosuppression are currently being adapted to xenotransplantation with the hope to achieve better control of antibody-mediated rejection (AMR) and improve xenograft longevity. These newest advances could probably facilitate future clinical trials, a significant step for the medical community, given that dialysis remains difficult for many patients and can have prohibitive costs. Performing a successful pig-to-human clinical kidney xenograft, that could last for more than a year after transplant, seems feasible but it still has significant potential hurdles to overcome. The risk/benefit balance is progressively reaching an acceptable equilibrium for future human recipients, e.g. those with a life expectancy inferior to two years. The ultimate question at this stage would be to determine if a "proof of concept" in humans is desirable, or whether further experimental/pre-clinical advances are still needed to demonstrate longer xenograft survival in non-human primates. In this review, we discuss the most recent advances in kidney and heart xenotransplantation, with a focus on the prevention and treatment of AMR and on the recipient's selection, two aspects that will likely be the major points of discussion in the first pig organ xenotransplantation clinical trials.

Update on Treatment and Prevention of Chronic Antibody Mediated Rejection in Renal Transplant Recipients

Chronic antibody mediated rejection (AMR) is a major cause of allograft failure1,2. Chronic AMR clinically presents with proteinuria and gradual decline in renal function. The underlying mechanisms of AMR include both antibody mediated complement-dependent cytotoxicity, complement-independent cellular cytotoxicity and other mechanisms. The purpose of this review is to appraise recent literature on diagnosis, treatment and prevention of chronic AMR.

New concepts in chronic antibody-mediated kidney allograft rejection: prevention and treatment.

Chronic antibody-mediated rejection (AMR) is a cardinal cause of transplant failure, with currently no proven effective prevention or treatment. The present review will focus on new therapeutic concepts currently under clinical evaluation. One interesting treatment approach may be interference with interleukin-6 (IL-6) signaling to modulate B-cell immunity and donor-specific antibody (DSA) production. Currently, a large phase III randomized controlled trial is underway to clarify the safety and efficacy of clazakizumab, a high-affinity anti-IL-6 antibody, in chronic AMR. A prevention/treatment strategy may be costimulation blockade using belatacept to interfere with germinal center responses and DSA formation. In a recent uncontrolled study, belatacept conversion was shown to stabilize renal function and dampen AMR activity. Moreover, preliminary clinical results suggest efficacy of CD38 antibodies to deplete plasma and natural killer cells to treat AMR, with anecdotal reports demonstrating at least transient resolution of active rejection. There are promising concepts on the horizon for the prevention and treatment of chronic AMR. The design of adequately powered placebo-controlled trials to clarify the safety and efficacy of such new therapies, however, remains a big challenge, and will rely on the definition of precise surrogate endpoints predicting long-term allograft survival. Mapping the natural history of AMR would greatly help the understanding of who would derive benefits from treatment.

The role of novel therapeutic approaches for prevention of allosensitization and antibody-mediated rejection.

Modification of pathogenic antibodies and their effector functions in autoimmune diseases or use of B cell/plasma cell-directed anticancer therapies have illuminated the biologic relevance of B cells, plasma cells (PCs), and pathogenic antibodies and complement in alloimmunity. They have also rejuvenated interest in how B cells mediate multiple effector functions that include antibody production, antigen presentation to T cells, costimulation, and the production of immune stimulating and immune modulatory cytokines that drive dysfunctional immune responses. Current methods to reduce alloantibodies are only modestly successful. Rituximab is used for desensitization and antibody-mediated rejection (AMR) treatment by targeting CD20 found on B-lymphocytes. However, PCs do not express CD20, likely explaining the limited success of this approach. Intravenous immunoglobulin and plasmapheresis (PLEX) have limited success due to antibody rebound. Despite attempts to develop tolerable therapeutics for management of AMR, none, to date, have been universally accepted or obtained Food and Drug Administration approval. Lack of approved therapeutics often results in patients having a much shorter graft survival due to AMR. Repurposing drugs from autoimmunity and cancer immunotherapy has rapidly yielded important advancements in the care of AMR patients. Here we discuss emerging therapeutics aimed at prevention and treatment of AMR.

Complement-Based Therapy in the Management of Antibody-Mediated Rejection.

Antibody-mediated rejection (AMR) is one of the leading causes of kidney allograft failure and is usually mediated by anti-human leukocyte antigen donor-specific antibodies (DSAs). Activation of classical pathway of the complement system is responsible for downstream effects of DSA and account for significant manifestations of AMR. Currently, the treatment of AMR is based on strategies to remove preformed antibodies or to prevent their production; however, these strategies are often unsuccessful. It is theoretically possible to inhibit complement activity to prevent the effect of DSA on kidney allograft function. Complement inhibitors such as eculizumab, a complement 5 monoclonal antibody, and complement 1 esterase inhibitors (C1 INHs) have been used in prevention and treatment of AMR with variable success. Eculizumab and C1 INH seem to reduce the incidence of early AMR and allow transplantation in highly sensitized kidney transplant recipients, but data on their long-term effect on kidney allograft function are limited. Several case reports described the successful use of eculizumab in the treatment of AMR, but there are no randomized controlled studies that showed efficacy. Treatment of AMR with C1 INH, in addition to standard of care, did not change short-term outcome but long-term studies are underway.

Summary of 2017 FDA Public Workshop: Antibody-mediated Rejection in Kidney Transplantation.

Despite major advances in understanding the pathophysiology of antibody-mediated rejection (AMR); prevention, diagnosis and treatment remain unmet medical needs. It appears that early T cell-mediated rejection, de novo donor-specific antibody (dnDSA) formation and AMR result from patient or physician initiated suboptimal immunosuppression, and represent landmarks in an ongoing process rather than separate events. On April 12 and 13, 2017, the Food and Drug Administration sponsored a public workshop on AMR in kidney transplantation to discuss new advances, importance of immunosuppressive medication nonadherence in dnDSA formation, associations between AMR, cellular rejection, changes in glomerular filtration rate, and challenges of clinical trial design for the prevention and treatment of AMR. Key messages from the workshop are included in this summary. Distinction between type 1 (due to preexisting DSA) and type 2 (due to dnDSA) phenotypes of AMR needs to be considered in patient management and clinical trial design. Standardization and more widespread adoption of routine posttransplant DSA monitoring may permit timely diagnosis and understanding of the natural course of type 2 and chronic AMR. Clinical trial design, especially as related to type 2 and chronic AMR, has specific challenges, including the high prevalence of nonadherence in the population at risk, indolent nature of the process until the appearance of graft dysfunction, and the absence of accepted surrogate endpoints. Other challenges include sample size and study duration, which could be mitigated by enrichment strategies.

Desensitization and Prevention of Antibody-Mediated Rejection in Vascularized Composite Allotransplantation by Syngeneic Hematopoietic Stem Cell Transplantation.

Candidates for vascularized composite allotransplantation (VCA) are frequently sensitized, putting them at risk for antibody-mediated rejection. Current desensitization strategies are imperfect and require a living-donor setting. Here we investigated the impact of sensitization on and the efficacy of a desensitization protocol utilizing syngeneic hematopoietic stem cell transplantation (HSCT) to prevent antibody-mediated rejection in VCA. Skin transplants from Dark Agouti to Lewis rats were performed for sensitization. Orthotopic hind limb transplants from Dark Agouti donors were performed to sensitized and nonsensitized recipients, and the animals were treated with either daily tacrolimus or no immunosuppression. A desensitization protocol consisting of total body irradiation, fludarabine, and syngeneic HSCT was applied to sensitized animals. Graft rejection was monitored by clinical assessment and histological analysis. Serum levels of donor-specific antibodies (DSA IgG) were measured using flow cytometry. Sensitized recipients exhibited accelerated rejection by 5.5 ± 1.2 days without immunosuppression and 10.2 ± 3.6 days with daily tacrolimus compared with 8.7 ± 1.2 days and longer than 30 days in nonsensitized recipients, respectively. Serum levels of DSA IgG were markedly elevated (37.3 ± 3.34-fold from baseline) in sensitized recipients after VCA and correlated with histologic evidence of rejection and C4d deposition. Desensitization significantly reduced DSA compared with sensitized controls (2.6 ± 0.5-fold vs 6.0 ± 1.2-fold, P < 0.01) and along with daily tacrolimus led to improved VCA survival longer than 30 days without evidence of C4d deposition (n = 6). In summary, sensitization leads to accelerated rejection of VCA, and syngeneic HSCT combined with conventional immunosuppression effectively reduces DSA and improves allograft survival in sensitized rats.

In Vivo Attenuation of Antibody-Mediated Acute Renal Allograft Rejection by Ex Vivo TGF-β-Induced CD4+Foxp3+ Regulatory T Cells.

Antibody-mediated rejection (AMR) has emerged as the major cause of renal allograft dysfunction, and more effective strategies need to be explored for improving transplant outcomes. Regulatory T cells (Tregs), consisting of at least natural and induced Treg subsets, suppress effector responses at multiple levels and play a key role in transplantation tolerance. In this study, we investigated the effect of induced Tregs (iTregs) on preventing antibody-mediated renal injury and rejection in a mouse model. We observed that infusion of iTregs markedly attenuated histological graft injury and rejection and significantly improved renal allograft survival. iTregs exhibited a comprehensive ability to regulate immunological disorders in AMR. First, iTreg treatment decreased the levels of circulating antidonor antibody and the antibody deposition within allografts. Second, iTregs significantly reduced cell infiltration including CD4+ T cells (including Th1, Th17, and Tfh), CD8+IFN-γ+ cells, natural killer cells, B cells, and plasma cells, which are involved in the process of AMR. Our results also highlight a predominance of M1 macrophage infiltration in grafts with acute AMR, and M1 macrophage could be reduced by iTreg treatment. Collectively, our data demonstrate, for the first time, that TGF-β-induced Tregs can attenuate antibody-mediated acute renal allograft injury through targeting multiple effectors. Thus, use of iTregs in prevention of AMR in clinical practice could be expected.

Impact of complement component 3/4/5 single nucleotide polymorphisms on renal transplant recipients with antibody-mediated rejection.

Antibody-mediated rejection (ABMR) is an important risk of allograft dysfunction in kidney transplantation. The complement system is considered to be associated with the generation of alloreative antibodies and donor-specific antibodies. However, the association of complement single nucleotide polymorphisms (SNPs) with ABMR still remained unclear. Blood samples of 199 renal transplant recipients containing 68 with ABMR and 131 with stable graft function were collected, and analyzed by next-generation sequencing with an established gene panel. High quality readout was obtained in 18 C3 SNPs, 9 C4 SNPs and 22 C5 SNPs. Concerning C3 gene polymorphisms, after being adjusted with age, sex and immunosuppressive protocols, rs10411506 and rs2230205 were found to be statistically associated with ABMR in dominant model (rs10411506: OR=2.73, 95% CIs: 1.16, 6.68, P=0.028; rs2230205: OR=2.52, 95% CIs: 1.07, 5.92, P=0.034); rs10411506, rs2230205 and rs2230201 were found different in HET model (rs10411506: OR=3.05, 95% CIs: 1.22, 7.64, P=0.017; rs2230205: OR=2.90, 95% CIs: 1.20, 7.00, P=0.018; rs2230201: OR=2.41, 95% CIs: 1.03, 5.64, P=0.042). The linkage analysis showed relatively high linkage disequilibrium among these SNPs. In addition, no significant correlation was found between C4 SNPs, or C5 SNPs, and the development of ABMR. Our study firstly identified the two SNPs (rs10411506 and rs2230205) in C3 gene were statistically correlated with ABMR in kidney transplantation. These findings may have implications for the diagnosis and prevention of ABMR.

Elimination of Anti-HLA Alloantibody Producing B Cells through the Use of a CAR-Like HLA Molecule in T Cells

Introduction: T cell immunotherapy using Chimeric Antigen Receptors (CARs) to generate tumor antigen-specific effector T cells has achieved excellent results in anti-leukemic clinical trials, and in a broader appraisal, promising immunotherapeutic results. A major problem in solid organ transplantation is the presence in the recipient of donor specific antibodies, which preclude the success of the transplant due to the associated high risk of antibody-mediated rejection. Methods: we hypothesize that a CAR (chimeric antigen receptor)-like molecule with a particular HLA molecule as the CAR extracellular domain will engineer T cells to kill alloimmune B cells with anti-HLA antibodies as BcR, completely eliminating alloantibodies in a specific manner. Results: first step was to create this chimeric receptor with the HLA-A2 antigen as the CAR-like extracellular domain: extracellular domains of the HLA-A*02:01 molecule were amplified by PCR from cDNA of an A*02:01 positive donor. A CAR comprising the extracellular domains of HLA-A2 and 4-1BB/CD3ζ signalling domain was constructed and delivered by lentiviral transduction into human T cells. The cytotoxic capacity of these transduced T cells was assessed by co-culturing them with EBV-transformed B cells which produce anti-HLA-A2 alloantibodies. Conclusion: specific T cells directed to kill anti-HLA alloantibody producing B cells can be generated by means of the use of an HLA CAR-like receptor. This technology could open new ways of treatment and prevention of antibody-mediated rejection in solid organ transplantation.

Complement Inhibition for Prevention and Treatment of Antibody-Mediated Rejection in Renal Allograft Recipients

Therapeutic interventions aimed at the human complement system are recognized as potentially important strategies for the treatment of inflammatory and autoimmune diseases because there is often evidence of complement-mediated injury according to pathologic assessments. In addition, there are a large number of potential targets, both soluble and cell bound, that might offer potential for new drug development, but progress in this area has met with significant challenges. Currently, 2 drugs are approved aimed at inhibition of complement activation. The first option is eculizumab (anti-C5), which is approved for the treatment of paroxysmal nocturnal hemoglobinuria and atypical hemolytic uremic syndrome. Eculizumab has also been studied in human transplantation for the treatment and prevention of antibody-mediated rejection (ABMR). Initial data from uncontrolled studies suggested a significant benefit of eculizumab for the prevention of ABMR in highly HLA-sensitized patients, but a subsequent randomized, placebo-controlled trial failed to meet its primary endpoint. Anecdotal data, primarily from case studies, showed benefits in treating complement-mediated ABMR. A second approved complement-inhibiting therapy is C1 esterase inhibitor (C1-INH), which is approved for use in patients with hereditary angioedema, a condition caused by mutations in the gene that codes for C1-INH. A recent placebo-controlled trial of C1-INH for prevention of ABMR in HLA-sensitized patients found that the drug was safe, with evidence for inhibition of systemic complement activation and complement-activating donor-specific antibodies. Other drugs are now under development.

Review of the Clinical and Economic Burden of Antibody-Mediated Rejection in Renal Transplant Recipients.

Antibody-mediated rejection (AbMR) is a leading cause of late graft loss in kidney transplant recipients, accounting for up to 60% of late graft failures. AbMR manifests as two distinct phenotypes: the first occurs in the immediate post-transplant period in sensitized patients; the second occurs in the late post-transplant period and has been associated with non-adherence to immunosuppression. The present review summarizes the current treatment options for AbMR, its clinical and economic burden, and approaches for reducing the risk of AbMR. While AbMR is typically refractory to treatment with corticosteroids, there are numerous other approaches focused on removal, inhibition or neutralization of donor-specific antibodies, or inhibition of complement-mediated allograft damage. AbMR treatment is generally expensive with one US study reporting costs of USD 49,000-155,000 per episode. However, leaving AbMR untreated puts patients at high risk of capillaritis, microangiopathy, necrosis and graft failure, which may ultimately result in much greater costs associated with a return to dialysis. Given the barriers to treatment, which include the high cost and the fact that pharmacologic treatments are currently used off-label, prevention of AbMR is important, with improvement in patient adherence to immunosuppression a key strategic approach that may be worthy of further evaluation. Astellas Pharma EMEA Limited.

Calcineurin Inhibitor Minimization With Ixazomib, an Investigational Proteasome Inhibitor, for the Prevention of Antibody Mediated Rejection in a Preclinical Model.

There is a need for new immunosuppression strategies to minimize calcineurin inhibitor (CNI) toxicity while effectively preventing antibody-mediated rejection (AMR). We tested the efficacy of an investigational proteasome inhibitor, ixazomib, alone and in a CNI minimization strategy in a rat kidney transplant model of transfusion-elicited acute AMR. Nonsensitized (naïve) and sensitized allograft recipients were randomized into 4 treatment groups (8 groups total, n = 3 to 6 in each group) and treated for 1 week. Groups included: no treatment, full dose cyclosporine (CsA, 10 mg/kg per day), ixazomib (0.25 mg/kg on days -5, -2 and +2) alone, and half dose CsA (5 mg/kg per day) + ixazomib. Compared to untreated animals, ixazomib alone or in combination with ½ dose CsA reduced donor-specific antibody, intragraft transcripts for chemokines CCL-21 and CXCL-13, and CD19 expression in both sensitized and naïve transplants. Compared to full dose CsA, the CNI minimization strategy with ixazomib inhibited AMR and allograft injury as evidenced by reduced C4d staining in peritubular capillaries, microcirculation inflammation, splenic plasma cells, circulating B cell activating factor, and intragraft transcripts for major histocompatibility complex class II, Toll-like receptors (TLR-1, TLR-10, and TLR-12) and CCL-21 and CXCL-13 in sensitized animals, indicating downregulation of B cell activation, antigen presentation and T-cell and B-cell signaling. These studies suggest that CNI minimization strategies including ixazomib are effective to prevent AMR including in sensitized kidney allograft recipients. Clinical studies are needed to determine the role of novel proteasome inhibitors for the prevention and treatment of AMR.

Antibody-mediated rejection: analyzing the risk, proposing solutions.

Antibody-mediated rejection: analyzing the risk, proposing solutions.

(384) - Intravenous Immunoglobulin and Plasmapheresis in Prevention of Antibody Mediated Rejection in Sensitized Recipients in Cardiac Allograft. “Before - After” Treatment Study

Plasmapheresis (PP) and intravenous immunoglobulin (IVIg) are used in renal allograft to prevent antibody mediated rejection (AMR) in sensitized recipients(DSA MFI>1000 UI). In cardiac allograft, the benefit of this prophylactic treatment is unknown. The aim of this study was to investigate the efficiency of this prophylactic therapy on the incidence of histologic AMR in cardiac allograft.

Regulation of Anti-HLA Antibody-Dependent Natural Killer Cell Activation by Immunosuppressive Agents

It was demonstrated that human natural killer (NK) cells, via antibody-dependent cellular cytotoxicity (ADCC)-like mechanism, increase IFNγ production after exposure to alloantigens. This finding was associated with an increased risk for antibody-mediated rejection (ABMR). Although the effects of various immunosuppressive drugs on T cells and B cells have been extensively studied, their effects on NK cells are less clear. This study reports the effect of immunosuppressive agents on antibody-mediated NK cell activation in vitro. Whole blood from normal individuals was incubated with irradiated peripheral blood mononuclear cells (PBMCs) pretreated with anti-HLA antibody+ sera (in vitro ADCC), with or without immunosuppressive agents. The %IFNγ+ and CD107a+ (degranulation marker) in CD56+ NK cells were enumerated by flow cytometry. Cyclosporine A and tacrolimus significantly reduced IFNγ production in a dose-dependent manner (53%-83%), but showed minimal effect on degranulation (20%). Prednisone significantly reduced both IFNγ production and degranulation (50%-66% reduction at maximum therapeutic levels). Calcineurin inhibitors (CNIs) in combination with prednisone additively suppressed IFNγ production and degranulation. The effect of sirolimus or mycophenolate mofetil on NK cells was minimal. These results suggest that potent suppressive effects of CNIs and prednisone on antibody-mediated NK cell activation may contribute to the reduction of ADCC in sensitized patients and possibly reduce the risk for ADCC-mediated ABMR. These further underscore the importance of medication compliance in prevention of ABMR and possibly chronic rejection, and suggest that ADCC-mediated injury may increase in strategies aimed at CNI or steroid minimization or avoidance.

Evaluating the Use of Bortezomib and Eculizumab in Desensitization of Transplant Patients.

Objective: To systematically review the existing literature concerning the utilization of bortezomib and eculizumab to determine if there is enough evidence to warrant their routine use in desensitization protocols for high-risk transplant candidates. Data Sources: PubMed, Google Scholar, and ClinicalTrials.gov were searched using the terms bortezomib, eculizumab, desensitization, transplant, highly-sensitized, pre-sensitized, and antibody-mediated rejection (AMR). The articles included were published between January 2009 and August 2012. Study Selection and Data Extraction: All English-language articles involving human subjects were assessed for inclusion. The search included articles evaluating the use of these agents in desensitization and the prevention of AMR, but excluded articles investigating these drugs in the treatment of established AMR. Data Synthesis: Highly sensitized transplant candidates are at an increased risk of developing AMR after transplant; desensitization potentially reduces this risk. The addition of bortezomib and eculizumab to current desensitization protocols may enhance outcomes. The bortezomib search produced 3 efficacy trials, 1 safety trial, 2 in-progress trials, 14 patient cases from 8 published case reports, and 3 efficacy study abstracts. Conclusions: Much of the available literature assessing the efficacy of bortezomib and eculizumab for use in desensitization exists as restricted clinical trials and incomplete case reports. Bortezomib and eculizumab appear to be potentially effective additions to current desensitization protocols. However, we are unable to determine at this time whether these agents improve the most clinically relevant outcome of successful transplantation. Further well-designed clinical trials are needed to determine their true clinical efficacy in highly sensitized transplant candidates.

SAHA, an HDAC Inhibitor, Attenuates Antibody-Mediated Allograft Rejection

Antibody-mediated rejection (AMR) is gaining increasing recognition as a critical causative factor contributing to graft loss in organ transplantation. However, current therapeutic options for prevention and treatment of AMR are very limited and ineffective. The impact of epigenetic modification in B-cell function and its involvement in AMR is still yet to be explored. The impacts of suberoylanilide hydroxamic acid (SAHA), a histone deacetylase inhibitor, on isolated murine B-cell viability, proliferation, apoptosis, expression of surface marker, and secretion of immunoglobulin and interleukin-10 were investigated. In vivo, a murine cardiac transplant model was used to evaluate the effect of SAHA on splenic B-cell subsets and on AMR in Rag1(-/-) recipient mice after reconstitution of allostimulated B cells. SAHA possesses capability to repress B-cell function. Specifically, SAHA is potent to decrease the viability of isolated B cells by inducing apoptosis. SAHA was also found capable of suppressing the expression of B-cell costimulatory molecules and, as a result, addition of SAHA into the cultures attenuated B-cell proliferation and immunoglobulin secretion. In line with these results, administration of SAHA significantly suppressed AMR in Rag1(-/-) recipient mice after reconstitution of allostimulated B cells along with enhanced cardiac allograft survival time. Mechanistic studies revealed that SAHA promotes B-cell secretion of interleukin-10. Our data support that SAHA could be a promising immunosuppressive agent with potential beneficial effect on prevention and treatment of AMR.