A systematic review of the use of rituximab for the treatment of antibody-mediated renal transplant rejection

Current Scenario and Future Perspectives of Porcine Corneal Xenotransplantation

ABSTRACT

Corneal diseases represent a significant cause of blindness worldwide, with corneal transplantation being an effective treatment to prevent vision loss. Despite substantial advances in transplantation techniques, the demand for donor corneas exceeds the available supply, particularly in developing countries. Cornea xenotransplantation has emerged as a promising strategy to address the worldwide scarcity, notably using porcine corneas. In addition to the inherent immune privilege of the cornea, the low cost of porcine breeding and the anatomical and physiological similarities between humans and pigs have made porcine corneas a viable alternative. Nonetheless, ethical concerns, specifically the risk of xenozoonotic transmission and the necessity for stringent biosafety measures, remain significant obstacles. Moreover, the success of xenotransplantation is compromised by innate and adaptive immune responses, which requires meticulous consideration and further studies. Despite these challenges, recent breakthroughs have further contributed to reducing immunogenicity while preserving the corneal architecture. Advances in genetic engineering, such as the use of CRISPR-Cas9 to eliminate critical porcine antigens, have shown promise for mitigating immune reactions. Additionally, new immunosuppressive protocols, such as have techniques like decellularization and the use of porcine-derived acellular matrices, have greatly increased graft survival in preclinical models. Future research must focus on refining immunomodulatory strategies and improving graft preparation techniques to ensure the long-term survival and safety of porcine corneal xenotransplantation in clinical trials in humans.

Interchain disulfide engineering enables the efficient production of functional HLA-DQ-Fc fusion proteins

HLA-DQ molecules drive unwanted alloimmune responses after solid-organ transplants and several autoimmune diseases, including type 1 diabetes and celiac disease. Biologics with HLA molecules as part of the design are emerging therapeutic options for these allo- and autoimmune conditions. However, the soluble α and β chains of class II HLA molecules do not dimerize efficiently without their transmembrane domains, which hinders their production. In this study, we examined the feasibility of interchain disulfide engineering by introducing paired cysteines to juxtaposed positions in the α and β chains of HLA-DQ7, encoded by HLA-DQA1∗05:01 and HLA-DQB1∗03:01 respectively. We identified three variant peptide-HLA-DQ7-Fc fusion proteins (DQ7Fc) with increased expression and production yield, namely Y19C-D6C (YCDC), A83C-E5C (ACEC), and A84C-N33C (ACNC). The mutated residues were conserved across all HLA-DQ proteins and had limited solvent exposure. Further characterizations of the YCDC variant showed that the expression of the fusion protein is peptide-dependent; inclusion of a higher-affinity peptide correlated with increased protein expression. However, high-affinity peptide alone was insufficient for stabilizing the DQ7 complex without the engineered disulfide bond. Multiple DQ7Fc variants demonstrated expected binding characteristics with commercial anti-DQ antibodies in two immunoassays and by a cell-based assay. Lastly, DQ7Fc variants demonstrated dose-dependent killing of DQ7-specific B cell hybridomas in a flow cytometric, complement-dependent cytotoxicity assay. These data support inter-chain disulfide engineering as a novel approach to efficiently producing functional HLA-DQ molecules and potentially other class II HLA molecules as candidate therapeutic agents.

Pemphigoid diseases in patients with end-stage kidney diseases: pathogenesis and treatment

Background

Pemphigoid diseases constitute a group of autoimmune blistering disorders characterized by subepithelial blistering. The association between pemphigoid diseases and both end-stage kidney disease (ESKD) and its treatment is notable. However, there is limited evidence about the management of pemphigoid diseases in patients with ESKD. This systematic review compiled case reports and relevant studies, summarized the underlying mechanisms of pemphigoid diseases in patients with ESKD, and summarized the efficacy of various therapies.

Methods

A systematic search of PubMed and Embase was performed for articles published between 1982 to June 2, 2024.

Results

Fifty-three case reports and eight relevant studies were included. Triggers for pemphigoids in patients with ESKD included materials used to treat ESKD, immune dysregulation of patients with ESKD, and rejection of renal allograft. Treatment for these patients included removing triggers, as well as administering of corticosteroids, mycophenolate mofetil (MMF), tetracyclines, rituximab, methotrexate, dapsone, azathioprine, cyclosporine, intravenous immunoglobin (IVIG), plasmapheresis, and Janus kinase inhibitors.

Conclusion

Removing triggers is the most effective strategy. Despite their suboptimal efficacy, corticosteroids remain the most commonly used agents in this patient population. MMF, tetracyclines, and rituximab are less used but with benefits. There are significant adverse effects associated with methotrexate treatment. Other treatment may also be beneficial and require further investigation. These findings may enable clinicians to optimize the therapeutic approach for these patients.

Rituximab use in paediatric nephrology practice in Türkiye: TRTX

AIM

Rituximab (RTX) is a genetically engineered chimeric monoclonal antibody which binds directly to CD20 antigen and mediates inhibition of B cell development. Although RTX has been widely used in paediatric nephrology, there is no routine protocol for its use. In this study, paediatric nephrologists in Türkiye were asked to fill out a questionnaire to understand their practice in using RTX. This study aimed to determine common practices and clarify the uncertainties regarding the use of RTX in paediatric nephrology.

METHODS

This was a nationwide, multicenter, retrospective cohort study based on data evaluating the use of RTX in paediatric nephrology practice. An online questionnaire was sent to all paediatric nephrology centers in Türkiye. The questionnaire forms included information about how many patients in total applied RTX treatment, for which indications they use RTX, and whether they made any preparations before using RTX.

RESULTS

According to this survey on RTX use in Türkiye, paediatric nephrologists use it most commonly in SSNS and followed by SRNS, ABMR, SLE and AAV, respectively. Dosing was highly standard but there is significant heterogeneity in pre-exposure tests and patient monitoring in the clinical practice of RTX. Also, the rate of encountering RTX-related allergic and infectious side effects at least once during the professional experience of our physicians can be quite high.

CONCLUSION

There is an increasing need for the preparation of a guideline on the indications for RTX use for each diagnosis, posology, and the practices to be performed before and after infusion.

Tocilizumab in chronic active antibody-mediated rejection: rationale and protocol of an in-progress randomized controlled open-label multi-center trial (INTERCEPT study)

BACKGROUND

Chronic active antibody-mediated rejection (caAMR) in kidney transplants is associated with irreversible tissue damage and a leading cause of graft loss in the long-term. However, the treatment for caAMR remains a challenge to date. Recently, tocilizumab, a recombinant humanized monoclonal antibody directed against the human interleukin-6 (IL-6) receptor, has shown promise in the treatment of caAMR. However, it has not been systematically investigated so far underscoring the need for randomized controlled studies in this area.

METHODS

The INTERCEPT study is an investigator-driven randomized controlled open-label multi-center trial in kidney transplant recipients to assess the efficacy of tocilizumab in the treatment of biopsy-proven caAMR. A total of 50 recipients with biopsy-proven caAMR at least 12 months after transplantation will be randomized to receive either tocilizumab (n = 25) added to our standard of care (SOC) maintenance treatment or SOC alone (n = 25) for a period of 24 months. Patients will be followed for an additional 12 months after cessation of study medication. After the inclusion biopsies at baseline, protocol kidney graft biopsies will be performed at 12 and 24 months. The sample size calculation assumed a difference of 5 ml/year in slope of estimated glomerular filtration rate (eGFR) between the two groups for 80% power at an alpha of 0.05. The primary endpoint is the slope of eGFR at 24 months after start of treatment. The secondary endpoints include assessment of the following at 12, 24, and 36 months: composite risk score iBox, safety, evolution and characteristics of donor-specific antibodies (DSA), graft histology, proteinuria, kidney function assessed by measured GFR (mGFR), patient- and death-censored graft survival, and patient-reported outcomes that include transplant-specific well-being, adherence to immunosuppressive medications and perceived threat of the risk of graft rejection.

DISCUSSION

No effective treatment exists for caAMR at present. Based on the hypothesis that inhibition of IL-6 receptor by tocilizumab will reduce antibody production and reduce antibody-mediated damage, our randomized trial has a potential to provide evidence for a novel treatment strategy for caAMR, therewith slowing the decline in graft function in the long-term.

TRIAL REGISTRATION

ClinicalTrials.gov NCT04561986. Registered on September 24, 2020.

Repurposing of rituximab biosimilars to treat B cell mediated autoimmune diseases

Rituximab, the first monoclonal antibody approved for the treatment of lymphoma, eventually became one of the most popular and versatile drugs ever in terms of clinical application and revenue. Since its patent expiration, and consequently, the loss of exclusivity of the original biologic, its repurposing as an off-label drug has increased dramatically, propelled by the development and commercialization of its many biosimilars. Currently, rituximab is prescribed worldwide to treat a vast range of autoimmune diseases mediated by B cells. Here, we present a comprehensive overview of rituximab repurposing in 115 autoimmune diseases across 17 medical specialties, sourced from over 1530 publications. Our work highlights the extent of its off-label use and clinical benefits, underlining the success of rituximab repurposing for both common and orphan immune-related diseases. We discuss the scientific mechanism associated with its clinical efficacy and provide additional indications for which rituximab could be investigated. Our study presents rituximab as a flagship example of drug repurposing owing to its central role in targeting cluster of differentiate 20 positive (CD20) B cells in 115 autoimmune diseases.

Therapy in the Course of Kidney Graft Rejection-Implications for the Cardiovascular System-A Systematic Review

Kidney graft failure is not a homogenous disease and the Banff classification distinguishes several types of graft rejection. The maintenance of a transplant and the treatment of its failure require specific medications and differ due to the underlying molecular mechanism. As a consequence, patients suffering from different rejection types will experience distinct side-effects upon therapy. The review is focused on comparing treatment regimens as well as presenting the latest insights into innovative therapeutic approaches in patients with an ongoing active ABMR, chronic active ABMR, chronic ABMR, acute TCMR, chronic active TCMR, borderline and mixed rejection. Furthermore, the profile of cardiovascular adverse effects in relation to the applied therapy was subjected to scrutiny. Lastly, a detailed assessment and comparison of different approaches were conducted in order to identify those that are the most and least detrimental for patients suffering from kidney graft failure.

Trends in systematic reviews of kidney transplantation: A 10-year analysis of the evidence base

BACKGROUND

Systematic reviews (SRs) are the highest form of evidence for all types of clinical questions in evidence-based practice. For the first time in 2018, the number of SRs in transplantation outstripped those from randomised controlled trials (RCTs). This raises concerns of duplication or increased use of non-RCT evidence. We aimed to analyse the trends, strength and quality of SRs in kidney transplantation over a 10-year period.

METHODS

SRs in kidney transplantation were identified from the Transplant Library, without language restriction. All full-text citations were exported to a custom Research Electronic Data Capture (REDCap) database prior to evaluation. Quality of evidence in all included SRs was assessed using AMSTAR-2.

RESULTS

We included 454 SRs, of which, only three were scored as 'high quality'. We found that 96.70% of SRs were identified as 'critically low quality', which increased in number over time. We also found that inclusion of non-RCT data increased in the most recent 5 years. Only 14.12% of SRs had made a clear recommendation for practice.

CONCLUSIONS

This review highlights several concerning statistics that need to be addressed. In the last 10 years, only three SRs in kidney transplantation were 'high-quality'. The weaknesses identified in critical domains, alongside the increased use of non-RCT data and lack of conclusive recommendations undermines the confidence in the results of the SRs and purpose of publication. As these SRs are instrumental to clinical decision-making and patient care in kidney transplantation, we advocate for improved reporting quality among SRs in kidney transplantation.

Corticosteroids, Plasmapheresis, Argatroban, Rituximab, and Sirolimus Provided Clinical Benefit for Catastrophic Antiphospholipid Syndrome in a Patient with a History of Heparin-Induced Thrombocytopenia

We report a patient with catastrophic antiphospholipid syndrome who had significant improvement after corticosteroids, plasmapheresis, argatroban, rituximab, and sirolimus. Argatroban was used instead of heparin due to a history of heparin-induced thrombocytopenia.

Heterogeneity of antibody-secreting cells infiltrating autoimmune tissues

The humoral response is frequently dysfunctioning in autoimmunity with a frequent rise in total serum immunoglobulins, among which are found autoantibodies that may be pathogenic by themselves and/or propagate the inflammatory reaction. The infiltration of autoimmune tissues by antibody-secreting cells (ASCs) constitutes another dysfunction. The known high dependency of ASCs on the microenvironment to survive combined to the high diversity of infiltrated tissues implies that ASCs must adapt. Some tissues even within a single clinical autoimmune entity are devoid of infiltration. The latter means that either the tissue is not permissive or ASCs fail to adapt. The origin of infiltrated ASCs is also variable. Indeed, ASCs may be commonly generated in the secondary lymphoid organ draining the autoimmune tissue, and home at the inflammation site under the guidance of specific chemokines. Alternatively, ASCs may be generated locally, when ectopic germinal centers are formed in the autoimmune tissue. Alloimmune tissues with the example of kidney transplantation will also be discussed own to their high similarity with autoimmune tissues. It should also be noted that antibody production is not the only function of ASCs, since cells with regulatory functions have also been described. This article will review all the phenotypic variations indicative of tissue adaptation described so for at the level of ASC-infiltrating auto/alloimmune tissues. The aim is to potentially define tissue-specific molecular targets in ASCs to improve the specificity of future autoimmune treatments.

Rationale for the IMAGINE study for chronic active antibody-mediated rejection (caAMR) in kidney transplantation

Chronic active antibody-mediated rejection (caAMR) in kidney transplantation is a major cause of late graft loss and despite all efforts to date, there is no proven effective therapy. Indeed, the Transplant Society (TTS) consensus opinion called for a conservative approach optimizing baseline immunosuppression and supportive care focused on blood pressure, blood glucose, and lipid control. This review provides the rationale and early evidence in kidney transplant recipients with caAMR that supported the design of the IMAGINE study whose goal is to evaluate the potential impact of targeting the IL6/IL6R pathway.

Investigational drugs for the treatment of kidney transplant rejection

INTRODUCTION

Kidney transplant rejection remains an important clinical problem despite the development of effective immunosuppressive drug combination therapy. Two major types of rejection are recognized, namely T-cell-mediated rejection (TCMR) and antibody-mediated rejection (ABMR), which have a different pathophysiology and are treated differently. Unfortunately, long-term outcomes of both TCMR and ABMR remain unsatisfactory despite current therapy. Hence, alternative therapeutic drugs are urgently needed.

AREAS COVERED

This review covers novel and investigational drugs for the pharmacological treatment of kidney transplant rejection. Potential therapeutic strategies and future directions are discussed.

EXPERT OPINION

The development of alternative pharmacologic treatment of rejection has focused mostly on ABMR, since this is the leading cause of kidney allograft loss and currently lacks an effective, evidence-based therapy. At present, there is insufficient high-quality evidence for any of the covered investigational drugs to support their use in ABMR. However, with the emergence of targeted therapies, this potential arises for individualized treatment strategies. In order to generate more high-quality evidence for such strategies and overcome the obstacles of classic, randomized, controlled trials, we advocate the implementation of adaptive trial designs and surrogate clinical endpoints. We believe such adaptive trial designs could help to understand the risks and benefits of promising drugs such as tocilizumab, clazakizumab, belimumab, and imlifidase.

Role of the Immune System in Renal Transplantation, Types of Response, Technical Approaches and Current Challenges

Advances over the last decades have made renal transplantation an important therapy for patients with end-stage renal disease, as the incidences of acute rejection and short-term transplant loss have been significantly reduced. However, long-term transplant survival remains a challenge in the renal transplantation community. The main causes of long-term graft loss are acute and chronic rejection, as well as the complications related to immunosuppression therapy. In spite of the breakthroughs achieved in recent years, histology is the gold standard technique to confirm the activation of the immune system against the graft with all the ensuing problems that taking biopsies brings to immunosuppressed patients. For this reason, several assays have been developed to try to monitor the immune function, but they show serious constraints owing to the fact that they require substantial laboratory work, they are not clinically available and they provide controversial results, so the combination of multiple assays is often needed to obtain a reliable diagnosis. Thus, the aim of this review is to perform a retrospective study of the immune system in renal transplantation, with special emphasis on the cutting-edge technological developments for monitoring, classification and early detection of rejection episodes in order to contribute to a better adjustment of immunosuppressive therapies and, hence, to a more personalized medicine that improves the quality of life of patients.

In Vivo Kidney Allograft Endothelial Specific Scavengers for On-Site Inflammation Reduction under Antibody-Mediated Rejection

Kidney transplantation is the most effective therapy for patients with end-stage renal disease. However, antibody-mediated rejection (ABMR) threatens long-term survival of renal grafts. Although ABMR can be controlled by donor-specific antibody clearance and B- or (and) plasma-cells inhibition, the treatment often causes severe side effects in patients. Therefore, there is need to explore site-specific scavengers. In this study, a nanovehicle carrying an anti-inflammatory drug is developed with complement component 4d targeting, a specific biomarker expressed on allograft endothelium under ABMR. Moreover, the nanovehicle is endowed with photothermal properties to control drug release. Analysis through systematic in vitro and in vivo toxicity, non-invasive targeted imaging, and in situ remote controlled drug release show the nanovehicle specifically targets allograft kidney endothelium, releases an anti-inflammatory drug, methylprednisolone, locally upon laser irradiation, and promotes recovery of injured endothelium, without affecting systemic inflammation or innate immune responses. This strategy has the potential for future clinical application in ABMR treatment.

Current status of xenotransplantation research and the strategies for preventing xenograft rejection

Transplantation is often the last resort for end-stage organ failures, e.g., kidney, liver, heart, lung, and pancreas. The shortage of donor organs is the main limiting factor for successful transplantation in humans. Except living donations, other alternatives are needed, e.g., xenotransplantation of pig organs. However, immune rejection remains the major challenge to overcome in xenotransplantation. There are three different xenogeneic types of rejections, based on the responses and mechanisms involved. It includes hyperacute rejection (HAR), delayed xenograft rejection (DXR) and chronic rejection. DXR, sometimes involves acute humoral xenograft rejection (AHR) and cellular xenograft rejection (CXR), which cannot be strictly distinguished from each other in pathological process. In this review, we comprehensively discussed the mechanism of these immunological rejections and summarized the strategies for preventing them, such as generation of gene knock out donors by different genome editing tools and the use of immunosuppressive regimens. We also addressed organ-specific barriers and challenges needed to pave the way for clinical xenotransplantation. Taken together, this information will benefit the current immunological research in the field of xenotransplantation.

Use of rituximab in paediatric nephrology

Rituximab is a chimeric monoclonal antibody capable of depleting B cell populations by targeting the CD20 antigen expressed on the cell surface. Its use in oncology, initially in B cell lymphoma and post-transplant lymphoproliferative disorders, predates its current utility in various fields of medicine wherein it has become one of the safest and most effective antibody-based therapies. It was subsequently found to be effective for rheumatological conditions such as rheumatoid arthritis and antineutrophil cytoplasmic antibody-associated vasculitis. Over the past decade, rituximab has generated a lot of interest in nephrology and has become an emerging or accepted therapy for multiple renal conditions, including systemic lupus erythematosus, lupus nephritis, vasculitis, nephrotic syndrome and in different scenarios before and after kidney transplantation. This review outlines its current use in paediatric nephrology practice, focusing on the knowledge required for general paediatricians who may be caring for children prescribed this medication and reviewing them on a shared care basis.

On the road to eliminating long-lived plasma cells-"are we there yet?"

Central to protective humoral immunity is the activation of B cells and their terminal differentiation into antibody-secreting plasma cells. Long-lived plasma cells (LLPC) may survive for years to decades. Such long-lived plasma cells are also responsible for producing pathogenic antibodies that cause a variety of challenges such as autoimmunity, allograft rejection, and drug neutralization. Up to now, various therapeutic strategies aimed at durably eliminating pathogenic antibodies have failed, in large part due to their inability to efficiently target LLPCs. Several antibody-based therapies have recently gained regulatory approval or are in clinical phases of development for the treatment of multiple myeloma, a malignancy of plasma cells. We discuss the exciting potential of using these emerging cancer immunotherapies to solve the antibody problem.

Plasma cell biology: Foundations for targeted therapeutic development in transplantation

Solid organ transplantation is a life-saving procedure for patients with end-stage organ disease. Over the past 70 years, tremendous progress has been made in solid organ transplantation, particularly in T-cell-targeted immunosuppression and organ allocation systems. However, humoral alloimmune responses remain a major challenge to progress. Patients with preexisting antibodies to human leukocyte antigen (HLA) are at significant disadvantages in regard to receiving a well-matched organ, moreover, those who develop anti-HLA antibodies after transplantation face a significant foreshortening of renal allograft survival. Historical therapies to desensitize patients prior to transplantation or to treat posttransplant AMR have had limited effectiveness, likely because they do not significantly reduce antibody levels, as plasma cells, the source of antibody production, remain largely unaffected. Herein, we will discuss the significance of plasma cells in transplantation, aspects of their biology as potential therapeutic targets, clinical challenges in developing strategies to target plasma cells in transplantation, and lastly, novel approaches that have potential to advance the field.

Therapies for Chronic Allograft Rejection

Remarkable advances have been made in the pathophysiology, diagnosis, and treatment of antibody-mediated rejection (ABMR) over the past decades, leading to improved graft outcomes. However, long-term failure is still high and effective treatment for chronic ABMR, an important cause of graft failure, has not yet been identified. Chronic ABMR has a relatively different phenotype from active ABMR and is a slowly progressive disease in which graft injury is mainly caused by de novo donor specific antibodies (DSA). Since most trials of current immunosuppressive therapies for rejection have focused on active ABMR, treatment strategies based on those data might be less effective in chronic ABMR. A better understanding of chronic ABMR may serve as a bridge in establishing treatment strategies to improve graft outcomes. In this in-depth review, we focus on the pathophysiology and characteristics of chronic ABMR along with the newly revised Banff criteria in 2017. In addition, in terms of chronic ABMR, we identify the reasons for the resistance of current immunosuppressive therapies and look at ongoing research that could play a role in setting better treatment strategies in the future. Finally, we review non-invasive biomarkers as tools to monitor for rejection.

Regulatory B cells: TIM-1, transplant tolerance, and rejection

Regulatory B cells (Bregs) ameliorate autoimmune disease and prevent allograft rejection. Conversely, they hinder effective clearance of pathogens and malignancies. Breg activity is mainly attributed to IL-10 expression, but also utilizes additional regulatory mechanisms such as TGF-β, FasL, IL-35, and TIGIT. Although Bregs are present in various subsets defined by phenotypic markers (including canonical B cell subsets), our understanding of Bregs has been limited by the lack of a broadly inclusive and specific phenotypic or transcriptional marker. TIM-1, a broad marker for Bregs first identified in transplant models, plays a major role in Breg maintenance and induction. Here, we expand on the role of TIM-1⁺  Bregs in immune tolerance and propose TIM-1 as a unifying marker for Bregs that utilize various inhibitory mechanisms in addition to IL-10. Further, this review provides an in-depth assessment of our understanding of Bregs in transplantation as elucidated in murine models and clinical studies. These studies highlight the major contribution of Bregs in preventing allograft rejection, and their ability to serve as highly predictive biomarkers for clinical transplant outcomes.

Impact of rituximab on the T-cell flow cytometric crossmatch

Rituximab is frequently used in the setting of ABO-incompatible renal transplants, and highly sensitized patients. Its interference with B-cell flow cytometric crossmatch (B-FCXM) is well known. However, its effect on the T-cell flow cytometric crossmatch (T-FCXM) has not been described. We aimed to evaluate the effect of rituximab on the T-FCXM using non-pronase and pronase treated donor lymphocytes and compare results with the single antigen bead (SAB) assay. In this retrospective study, 28 patients on rituximab therapy were evaluated against 30 donors. Using non-pronase treated donor lymphocytes, all 30 FCXMs showed strong B-cell positivity {median (IQR) B-cell ratio: 184.65 (253.17)} which significantly reduced {1.0 (1.18); p < 0.00001} with pronase treatment. 'T-cell tailing' phenomenon was observed in 17/30 FCXMs in the non-pronase group as a 'tail of T-cells', indicating a rare sub-population. However, it disappeared in the pronase-treated group. SAB assay did not show donor-specific antibodies (DSA) in all 17 patients with 'T-cell tailing' phenomenon. Although, rituximab is described to impact only B-FCXM, we have consistently found 'T-cell tailing' in 57% of T-FCXMs, which clears with pronase treatment. The 'T-cell tailing' led to weak positive T-FCMX ratios due to increased MFI in the FL1 channel. However, the absence of DSA in all recipients reinforces the fact that this is a false positive finding and should not be misconstrued as a possible class I DSA. Structural homology of Fc receptors on activated T-cells to CD20 could be a possible explanation of the same and provide insight into a novel mechanism of action of rituximab.

Novel strategies to target the humoral alloimmune response

Antibody-mediated rejection (ABMR) represents a major cause of late allograft loss in solid organ transplantation worldwide. This process is driven by donor-specific antibodies (DSA), which develop either de-novo or, in sensitized patients, are preformed at the time of transplantation. Effective targeting of ABMR has been hampered by a lack of robust randomized controlled trials (RCT), required for the regulatory approval of new therapeutics. In this review, we discuss the evidence behind the present "standard" of care and recent progress in the development of novel strategies targeting different aspects of the alloimmune humoral response, including naïve and memory B-cell activation, the germinal centre reaction, plasma cell survival and antibody effector functions. In particular, we focus on co-stimulation blockade and its combination with next-generation proteasome inhibitors, new depleting monoclonal antibodies (anti-CD19, anti-BCMA, anti-CD38, anti-CD138), interleukin-6 blockade, complement inhibition and DSA degradation. These treatment modalities, when used in the appropriate clinical context and combination, have the potential to finally improve long-term allograft survival.

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.

Intravenous immunoglobulin significantly reduces exposure of concomitantly administered anti-C5 monoclonal antibody tesidolumab

Awareness of drug-drug interactions is critical in organ transplant recipient management. However, biologic agents interfering with monoclonal antibodies is not widely considered. We report the effect of high-dose intravenous immunoglobulin (IVIg) on safety, tolerability, pharmacokinetics (PK), and pharmacodynamics (PD) of the human anti-C5 monoclonal antibody tesidolumab (LFG316) in end-stage renal disease patients awaiting kidney transplant. In this single-center, phase 1, open-label, parallel-group study, 8 patients were assigned to receive either single-dose tesidolumab + IVIg or tesidolumab alone, with 56-day follow-up. Within-group PK parameters were consistent. Mean tesidolumab exposure decreased 34%, clearance increased 63%, and half-life decreased 41% comparing tesidolumab + IVIg to tesidolumab alone. IVIg influence on tesidolumab elimination was most evident in the first 3 weeks. Complete suppression of both total and alternative complement activities was maintained for 4 weeks in the tesidolumab alone group and for 2 weeks in the tesidolumab + IVIg group. Tesidolumab was well tolerated. IVIg infused before tesidolumab affected tesidolumab PK and PD, resulting in a shortened period of full complement activity inhibition. These findings suggest a clinically relevant impact of IVIg on monoclonal antibody clearance and indirectly hint at an IVIg mechanism of action in treating autoimmune diseases and allosensitization by accelerating pathogenic IgG antibody degradation. Trial registration number: NCT02878616.

What have we learned about how to prevent and treat antibody-mediated rejection in kidney transplantation?

Antibody-mediated rejection (ABMR) in kidney transplantation is a major cause of late graft loss, and despite all efforts to date the "standard of care" remains plasmapheresis, IVIg, and steroids, which itself is based on low quality evidence. This review focuses on the risk factors leading to memory and de novo donor-specific antibody (DSA)-associated ABMR, the optimal prevention strategies for ABMR, and advances in  adjunctive and emerging therapies for ABMR. Because new agents require regulatory approval via a Phase 3 randomized control trial (RCT), an overview of progress in innovative trial design for ABMR is provided. Finally, based on the insights gained in the biology of ABMR, current knowledge gaps are identified for future research that could significantly affect our understanding of how to optimally treat ABMR.

Successful Treatment of Antibody-Mediated Rejection by De Novo Donor Specific Antibody After Primary Renal Transplantation in a Recipient From a Cadaveric Donor: A Case Report

A 19-year-old Japanese male recipient, who received a living related kidney transplantation from his father at 5 years old, was hospitalized for second renal transplantation from a cadaveric donor. The recipient had had an antibody-mediated rejection (AMR) to the first transplanted kidney. HLA typing of A, B, and DRB showed 2 of 6 mismatches. Lymphocyte cytotoxicity test (LCT) and flow cytometry crossmatches (FCXM) were negative on T cells. Tacrolimus, mycophenolate mofetil, methylprednisolone, and basiliximab induction were used as the standard immunosuppressive therapy. After second renal transplantation, his serum creatinine level favorably decreased until postoperative day (POD) 7, but his serum creatinine level raised from POD 8. We performed steroid pulse and intravenous immunoglobulin (IVIG). The episode biopsy showed AMR although FCXM and LCT were still negative on T cell. To determine the cause of AMR, we examined LABScreen single antigen test (One Lambda, Canoga Park, Calif., United States), and there was a donor-specific antibody (DSA) that is DQB8 in pre- and post-second renal transplantation. The DSA was suspected de novo DSA for the first transplanted kidney. AMR was successfully treated with plasma exchange, IVIG, and rituximab.

Favorable Short-Term Outcome of Living Donor Kidney Transplantations in Flow Cytometry Crossmatch Positive Cases by Pretransplant Splenectomy: A Case Report

BACKGROUND

The introduction of rituximab has contributed to successful living donor kidney transplantations in ABO-incompatible recipients and has replaced splenectomy for desensitization. However, several reports still suggest that postoperative splenectomy may be effective in preventing graft failure in patients with acute antibody-mediated kidney transplant rejection (AAMR) in kidney transplantation. Therefore, we aim to assess if preoperative splenectomy also could be an alternative practical choice to avoid AAMR in high-risk rejection cases such as flow cytometry crossmatch (FCXM)-positive cases.

MATERIAL AND METHOD

We carried out 4 living donor kidney transplantations in FCXM-positive cases: 3 underwent pretransplant splenectomy, and 1 did not.

RESULTS

All 3 cases in whom pretransplant splenectomy was performed were discharged without rejection. On the contrary, in the case where pretransplant splenectomy was not performed, there was graft rejection and additional desensitization therapies were needed.

CONCLUSION

While larger clinical studies with longer observation periods are needed, our report suggested that pretransplant splenectomy may lead to successful short-term kidney transplantation outcomes in FCXM-positive cases.

Interferon-γ-induced HLA Class II expression on endothelial cells is decreased by inhibition of mTOR and HMG-CoA reductase

In organ transplantation, donor‐specific HLA antibody (DSA) is considered a major cause of graft rejection. Because DSA targets primarily donor‐specific human leukocyte antigen (HLA) expressed on graft endothelial cells, the prevention of its expression is a possible strategy for avoiding or salvaging DSA‐mediated graft rejection. We examined the effect of various clinically used drugs on HLA class II expression on endothelial cells. Interferon‐γ (IFN‐γ)‐induced HLA class II DR (HLA‐DR) was downregulated by everolimus (EVR, 49.1% ± 0.8%; P < 0.01) and fluvastatin (FLU, 33.8% ± 0.6%; P < 0.01). Moreover, the combination of EVR and FLU showed a greater suppressive effect on HLA‐DR expression. In contrast, cyclosporine, tacrolimus, mycophenolic acid, and prednisolone did not exhibit any significant suppressive effect. FLU, but not EVR, suppressed mRNA of HLA‐DR. Imaging analysis revealed that HLA‐DR expressed in cytosol or on the cell surface was repressed by EVR (cytosol: 58.6% ± 4.9%, P < 0.01; cell surface: 80.9% ± 4.0%, P < 0.01) and FLU (cytosol: 19.0% ± 3.4%, P < 0.01; cell surface: 48.3% ± 4.8%, P < 0.01). These data indicated that FLU and EVR suppressed IFN‐γ‐induced HLA‐DR expression at the transcriptional and post‐translational level, respectively, suggesting a potential approach for alleviating DSA‐related issues in organ transplantation.

Effect of Optimized Immunosuppression (Including Rituximab) on Anti-Donor Alloresponses in Patients With Chronically Rejecting Renal Allografts

RituxiCAN-C4 combined an open-labeled randomized controlled trial (RCT) in 7 UK centers to assess whether rituximab could stabilize kidney function in patients with chronic rejection, with an exploratory analysis of how B cell-depletion influenced T cell anti-donor responses relative to outcome. Between January 2007 and March 2015, 59 recruits were enrolled after screening, 23 of whom consented to the embedded RCT. Recruitment was halted when in a pre-specified per protocol interim analysis, the RCT was discovered to be significantly underpowered. This report therefore focuses on the exploratory analysis, in which we confirmed that when B cells promoted CD4+ anti-donor IFNγ production assessed by ELISPOT, this associated with inferior clinical outcome; these patterns were inhibited by optimized immunosuppression but not rituximab. B cell suppression of IFNγ production, which associated with number of transitional B cells and correlated with slower declines in kidney function was abolished by rituximab, which depleted transitional B cells for prolonged periods. We conclude that in this patient population, optimized immunosuppression but not rituximab promotes anti-donor alloresponses associated with favorable outcomes.

Clinical Trial Registration: Registered with EudraCT (2006-002330-38) and www.ClinicalTrials.gov, identifier: NCT00476164.

Management of Chronic Active Antibody-Mediated Rejection in Renal Transplant Recipients: Single-Center Experience

OBJECTIVES

Data on the management of chronic antibody-mediated rejection after kidney transplantation are limited. We aimed to assess the impact of treatment of biopsy-proven chronic active antibodymediated rejection with combined plasma exchange, intravenous immunoglobulin, and rituximab treatment versus intravenous immunoglobulin alone or conservative management on the evolution of renal function in renal transplant recipients.

MATERIALS AND METHODS

In this retrospective study, we compared patients diagnosed with chronic active antibody-mediated rejection who were treated with standard of care steroids, intravenous immunoglobulin, plasma exchange, and rituximab (n = 40) at our center versus those who received intravenous immunoglobulin only or just intensified maintenance immunosuppression (n = 28). All patients were followed for 12 months clinically and by laboratory tests for graft and patient outcomes.

RESULTS

The two groups were matched regarding mean recipient age (41.9 ± 15.4 vs 37.8 ± 15.5 y in patients with conservative versus combined treatment), recipient sex, mean body weight, and the cause of end-stage kidney disease. Most patients and their donors were males. Glomerulonephritis represented the most common cause of end-stage kidney disease in both groups followed by diabetic nephropathy. The type of induction and pretransplant comorbidities were not different between groups (P > .05) except for the significantly higher number of chronic hepatitis C infections in patients who received conservative treatment (P = .007). Mean serum creatinine values before and after treatment of chronic active antibodymediated rejection were comparable between groups (P > .05). Active treatment with heavier immunosuppression (rituximab and plasma exchange) was associated with posttreatment viral (cytomegalovirus and BK virus) and bacterial infections that necessitated more hospitalization (P > .05). However, graft and patient outcomes were significantly better in the active treatment group than in patients with conservative treatment (P = .002 and .028, respectively).

CONCLUSIONS

Combined treatment of chronic active antibody-mediated rejection with plasma exchange, intravenous immunoglobulin, and rituximab can significantly improve outcomes after renal transplant.

Rituximab in kidney disease and transplant

Rituximab is a chimeric monoclonal antibody that binds to CD20 antigen of B-cells. It depletes the level of mature B-cells by various mechanisms such as mediation of antibody-dependent cellular cytotoxicity, complement-dependent cytotoxicity, and B-cell apoptosis. Rituximab is a USFDA approved drug for clinical use in non-Hodgkin's B-cell lymphoma (NHL), rheumatoid arthritis, chronic lymphocytic leukemia (CLL), granulomatosis with polyangiitis and pemphigus vulgaris. It is also known for its "off label" use in renal disease and renal transplant worldwide. However, the exact mechanisms by which it exerts its effect in the aforementioned condition remain unclear but may be related to its long-term effects on plasma cell development and the impact on B-cell modulation of T cell responses. This review discusses the current use of rituximab in renal disease and renal transplantation, and its potential role in novel therapeutic protocols.

Comparative efficacy of anti-CD40 antibody-mediated costimulation blockade on long-term survival of full-thickness porcine corneal grafts in nonhuman primates

Porcine corneas may be good substitutes for human corneas in donor shortage. Therefore, we evaluated the efficacy and safety of an anti-CD40 antibody-based regimen compared with an anti-CD20 antibody-based regimen on the survival of full-thickness corneas in pig-to-rhesus xenotransplant. Thirteen Chinese rhesuses underwent full-thickness corneal xenotransplant. Six were administered anti-CD40 antibody, and the others were administered anti-CD20 antibody, basiliximab, and tacrolimus. Graft survival and changes in lymphocyte, donor-specific and anti-Galα1,3Galβ1,4GlcNAc-R (αGal) antibody, and aqueous complement levels were evaluated. Treatment with the anti-CD40 antibody (>511, >422, >273, >203, >196, 41 days) and anti-CD20 antibody (>470, 297, >260, >210, >184, 134, >97 days) resulted in long-term survival of grafts. In the anti-CD20 group, the number of activated B cells was significantly lower than that in the anti-CD40 group, and the level of aqueous complements at 6 months was significantly higher than the preoperative level. There were no differences in the levels of T cells or donor-specific and anti-αGal antibodies between the 2 groups. In the anti-CD20 group, 3 primates had adverse reactions. In conclusion, both the anti-CD40 antibody- and the anti-CD20 antibody-based protocols were effective for the long-term survival of full-thickness corneal xenografts, but the anti-CD40 antibody-based treatment had fewer adverse effects.

Endothelin A Receptors Expressed in Renal Blood Vessels of Renal Transplant Patients Are Connected With Acute Tubular Necrosis or Antibody-Mediated Rejection

BACKGROUND

The role of non-HLA antibodies named antiendothelin A receptor antibodies is potentially significant but not established. The significance of the endothelin A receptor (ETAR) and its expression in renal biopsy has not been defined. We decided to evaluate the presence and relevance of ETARs in renal transplant biopsy for cause. The aim of our study was to evaluate the immunoreactivity of the ETAR and its significance in patients who had a renal transplant biopsy due to deterioration of transplant function (biopsy for cause) with detailed characterization of staining in small and intermediate arteries of renal transplant biopsies.

METHODS

Immunohistochemical expression of ETARs was analyzed in 162 renal transplant biopsies. Microscopic evaluation of ETAR expression (polyclonal antibody) was performed on paraffin sections. ETAR expression was analyzed in renal blood vessels (small and intermediate arteries) based on three-step scale.

RESULTS

We analyzed 154 patients who had renal allograft biopsy between 6 days and 24 years (median 597 days) after transplantation. Positive staining of ETAR in small and intermediate arteries was noticed in 9 patients. Among these patients, 4 had early biopsies (<3 months after transplantation), all developed acute tubular necrosis, and 1 developed additionally acute humoral rejection. Further, 4 patients had late biopsy (1-8 years after transplantation) and all developed characteristics of antibody mediated rejection. Lastly, 1 patient had no characteristic changes in the biopsy 4 months after transplantation. Graft loss 1 year after biopsy was higher in patients who were ETAR-positive but statistical significance was not achieved.

CONCLUSIONS

The expression of endothelin receptors in renal blood vessels (small and intermediate arteries) seems to be important in diagnosis of damage during acute tubular necrosis and antibody-mediated rejection.

Treatment of chronic antibody mediated rejection with intravenous immunoglobulins and rituximab: A multicenter, prospective, randomized, double-blind clinical trial

There are no approved treatments for chronic antibody mediated rejection (ABMR). We conducted a multicenter, prospective, randomized, placebo-controlled, double-blind clinical trial to evaluate efficacy and safety of intravenous immunoglobulins (IVIG) combined with rituximab (RTX) (EudraCT 2010-023746-67). Patients with transplant glomerulopathy and anti-HLA donor-specific antibodies (DSA) were eligible. Patients with estimated glomerular filtration rate (eGFR) <20 mL/min per 1.73m² and/or severe interstitial fibrosis/tubular atrophy were excluded. Patients were randomized to receive IVIG (4 doses of 0.5 g/kg) and RTX (375 mg/m² ) or a wrapped isovolumetric saline infusion. Primary efficacy variable was the decline of eGFR at one year. Secondary efficacy variables included evolution of proteinuria, renal lesions, and DSA at 1 year. The planned sample size was 25 patients per group. During 2012-2015, 25 patients were randomized (13 to the treatment and 12 to the placebo group). The planned patient enrollment was not achieved because of budgetary constraints and slow patient recruitment. There were no differences between the treatment and placebo groups in eGFR decline (-4.2 ± 14.4 vs. -6.6 ± 12.0 mL/min per 1.73 m² , P-value = .475), increase of proteinuria (+0.9 ± 2.1 vs. +0.9 ± 2.1 g/day, P-value = .378), Banff scores at one year and MFI of the immunodominant DSA. Safety was similar between groups. These data suggest that the combination of IVIG and RTX is not useful in patients displaying transplant glomerulopathy and DSA.

Targeting B Cells and Plasma Cells in Glomerular Diseases: Translational Perspectives

The unique contributions of memory B cells and plasma cells in kidney diseases remain unclear. In this review, we evaluate the clinical experience with treatments directed at B cells, such as rituximab, and at plasma cells, such as proteasome inhibition, to shed light on the role of these two B lineage compartments in glomerular diseases. Specifically, analysis of these targeted interventions in diseases such as ANCA-associated vasculitis, SLE, and antibody-mediated transplant rejection permits insight into the pathogenetic effect of these cells. Notwithstanding the limitations of preclinical models and clinical studies (heterogeneous populations, among others), the data suggest that memory B and plasma cells represent two engines of autoimmunity, with variable involvement in these diseases. Whereas memory B cells and plasma cells appear to be key in ANCA-associated vasculitis and antibody-mediated transplant rejection, respectively, SLE seems likely to be driven by both autoimmune compartments. These conclusions have implications for the future development of targeted therapeutics in immune-mediated renal disease.