Eculizumab Salvage Therapy for Antibody-Mediated Rejection in a Desensitization-Resistant Intestinal Re-Transplant Patient

Intestinal transplantation: Significance of immune responses

Intestinal allografts, with many resident immune cells and as a destination for circulating lymphocytes of the recipient, appear to be the most challenging solid organ transplants. The high incidence of acute rejection and frequent reports of fatal graft-versus-host disease (GvHD) after intestinal transplantation call for more research to describe the molecular mechanisms involved in the immunopathogenesis of post-transplant complications to define new therapeutic targets. In addition, according to the rapid development of immunosuppressive agents, it is time to consider novel therapeutic approaches in managing treatment-refractory patients with rejection or severe GvHD. Herein, the main immunological challenges before and after intestinal transplant including, brain-dead donor inflammation, acute rejection, antibody-mediated, and chronic rejections, as well as GvHD have been described. Besides, the new immune-based therapies used in experimental and clinical settings to improve tolerance toward intestinal allograft, and cases of operational tolerance have been reviewed.

A Complement to Traditional Treatments for Antibody-Mediated Rejection? Use of Eculizumab in Lung Transplantation: A Review and Early Center Experience

OBJECTIVE

To review the efficacy and safety of eculizumab for prevention and treatment of antibody-mediated rejection (AMR) in lung transplant recipients (LTRs).

DATA SOURCES

A literature search of PubMed and the Cochrane Controlled Trials Register (2007 to mid-October 2023) was performed using the following search terms: eculizumab, complement inhibitor, solid organ transplant, lung transplant, and AMR.

STUDY SELECTION AND DATA EXTRACTION

All relevant English-language studies were reviewed and considered.

DATA SYNTHESIS

Eculizumab, a monoclonal antibody that binds complement protein C5 to inhibit its cleavage and subsequent generation of the membrane attack complex, is currently approved to treat paroxysmal nocturnal hemoglobinuria, atypical hemolytic uremic syndrome, generalized myasthenia and neuromyelitis optica spectrum disorder. Given the role of antibodies directed against donor antigens that are produced by allospecific B-cells and plasma cells in AMR, eculizumab is being investigated for use within this indication. Three case reports have described the successful use of eculizumab for the prevention and treatment of AMR in LTRs. Given this lack of robust data, evidence for the use of eculizumab in other solid organ transplant recipients is of increased value. Early experiences from a single center's use of eculizumab in LTRs are also described.

RELEVANCE TO PATIENT CARE AND CLINICAL PRACTICE

Lung transplant is a recognized treatment for end-stage lung disease, though complications posttransplant can be associated with significant morbidity and mortality. While prevention and management of AMR remains a substantial challenge without comprehensive guidance from societal guidelines, recently published literature may be helpful to guide clinical practice using alternative treatment options. However, this remains an area of great clinical importance, given the impact of AMR on long-term allograft function.

CONCLUSIONS

Optimizing use of current therapies, as well as identifying and advancing novel therapeutic modalities such as eculizumab, are vital for the improvement of AMR prevention and treatment in LTRs to extend long-term allograft function and survival.

New insights in immunomodulation for intestinal transplantation

Tolerance is the Holy Grail of solid organ transplantation (SOT) and remains its primary challenge since its inception. In this topic, the seminal contributions of Thomas Starzl at Pittsburgh University outlined foundational principles of graft acceptance and tolerance, with chimerism emerging as a pivotal factor. Immunologically, intestinal transplantation (ITx) poses a unique hurdle due to the inherent characteristics and functions of the small bowel, resulting in increased immunogenicity. This necessitates heavy immunosuppression (IS) while IS drugs side effects cause significant morbidity. In addition, current IS therapies fall short of inducing clinical tolerance and their discontinuation has been proven unattainable in most cases. This underscores the unfulfilled need for immunological modulation to safely reduce IS-related burdens. To address this challenge, the Leuven Immunomodulatory Protocol (LIP), introduced in 2000, incorporates various pro-tolerogenic interventions in both the donor to the recipient, with the aim of facilitating graft acceptance and improving outcome. This review seeks to provide an overview of the current understanding of tolerance in ITx and outline recent advances in this domain.

Small bowel transplant - novel indications and recent progress

INTRODUCTION

Advances in the management of intestinal failure have led to a reduction in the number of intestinal transplants. The number of bowel transplants has been mainly stable even though a slight increase has been observed in the last 5 years.

AREAS COVERED

Standard indication includes patients with a reasonable life expectancy. Recent progress can be deduced by the increased number of intestine transplants in adults: this is due to the continuous improvement of 1-year graft survival worldwide (without differences in 3- and 5-year) associated with better abdominal wall closure techniques. This review aims to provide an update on new indications and changes in trends of pediatric and adult intestine transplantation. This analysis, which stretches through the past 5 years, is based on a collection of related manuscripts from PubMed.

EXPERT COMMENTARY

Intestinal transplants should be solely intended for a group of individuals for whom indications for transplantation are clear and both medical and surgical rehabilitations have failed. Nevertheless, many protocols developed over the years have not yet solved the key question represented by the over-immunosuppression. Novel indications and recent progress in the bowel transplant field, minimal yet consistent, represent a pathway to be followed.

Pediatric intestinal transplantation

Advancements in donor management, organ preservation and operative techniques, as well as immunosuppressive therapies, have provided children with intestinal failure and its complications a chance not only for enteral autonomy but also long-term survival through intestinal transplantation (ITx). First described in the 1960's, experience has grown in managing these complex patients both pre- and post-transplant. The goals of this review are to provide a brief history of intestinal transplantation and intestinal rehabilitation in pediatric patients, followed by focused discussions of the indications for ITx, induction and maintenance immunosuppression therapies, common post-operative complications, and outcomes/quality of life post-transplant.

Update on immunosuppressive strategies in intestinal transplantation

PURPOSE OF REVIEW

The intestine is the most immunologically complex solid organ allograft with the greatest risk of both rejection and graft-versus-host disease (GVHD). High levels of immunosuppression are required, further increasing morbidity. Due to low volume of transplants and few centers with experience, there is paucity of evidence-based, standardized, and effective therapeutic regimens. We herein review the most recent data about immunosuppression, focusing on novel and emerging therapies.

RECENT FINDINGS

Recent data are moving the field toward increasing use of basilixumab and consideration of alemtuzumab for induction and inclusion of mammalian target of rapamycin inhibitors and antimetabolites for maintenance. For rejection, we highlight novel roles for tumor necrosis factor-α inhibition, α4β7 integrin inhibition, microbiome modulation, desensitization protocols, and tolerance induction strategies. We also highlight emerging novel therapies for GVHD, especially the promising role of Janus kinase inhibition.

SUMMARY

New insights into immune pathways associated with rejection and GVHD in intestinal allografts have led to an evolution of therapies from broad-based immunosuppression to more targeted strategies that hold promise for reducing morbidity from infection, rejection, and GVHD. These should be the focus of further study to facilitate their widespread use.

C3 complement inhibition prevents antibody-mediated rejection and prolongs renal allograft survival in sensitized non-human primates

Sensitized kidney transplant recipients experience high rates of antibody-mediated rejection due to the presence of donor-specific antibodies and immunologic memory. Here we show that transient peri-transplant treatment with the central complement component C3 inhibitor Cp40 significantly prolongs median allograft survival in a sensitized nonhuman primate model. Despite donor-specific antibody levels remaining high, fifty percent of Cp40-treated primates maintain normal kidney function beyond the last day of treatment. Interestingly, presence of antibodies of the IgM class associates with reduced median graft survival (8 vs. 40 days; p = 0.02). Cp40 does not alter lymphocyte depletion by rhesus-specific anti-thymocyte globulin, but inhibits lymphocyte activation and proliferation, resulting in reduced antibody-mediated injury and complement deposition. In summary, Cp40 prevents acute antibody-mediated rejection and prolongs graft survival in primates, and inhibits T and B cell activation and proliferation, suggesting an immunomodulatory effect beyond its direct impact on antibody-mediated injury.

Donor-specific antibodies in sensitized recipients may cause kidney transplant rejection. Here the authors show that complement component C3 inhibition prolongs graft survival by inhibiting T and B cell proliferation/activation and hence tissue injury, despite antibody levels remaining unaffected.

Immunosuppressive Agents and Infectious Risk in Transplantation: Managing the "Net State of Immunosuppression"

Successful solid organ transplantation reflects meticulous attention to the details of immunosuppression, balancing risks for graft rejection against risks for infection. The 'net state of immune suppression' is a conceptual framework of all factors contributing to infectious risk. Assays which measure immune function in the immunosuppressed transplant recipient relative to infectious risk and allograft function are lacking. The best measures of integrated immune function may be quantitative viral loads to assess the individual's ability to control latent viral infections. Few studies address adjustment of immunosuppression during active infections. Thus, confronted with infection in solid organ recipients, the management of immunosuppression is based largely on clinical experience. This review examines known measures of immune function and the immunologic effects of common immunosuppressive drugs and available studies reporting modification of drug regimens for specific infections. These data provide a conceptual framework for the management of immunosuppression during infection in organ 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.

The complex functioning of the complement system in xenotransplantation

The role of complement in xenotransplantation is well-known and is a topic that has been reviewed previously. However, our understanding of the immense complexity of its interaction with other constituents of the innate immune response and of the coagulation, adaptive immune, and inflammatory responses to a xenograft is steadily increasing. In addition, the complement system plays a function in metabolism and homeostasis. New reviews at intervals are therefore clearly warranted. The pathways of complement activation, the function of the complement system, and the interaction between complement and coagulation, inflammation, and the adaptive immune system in relation to xenotransplantation are reviewed. Through several different mechanisms, complement activation is a major factor in contributing to xenograft failure. In the organ-source pig, the detrimental influence of the complement system is seen during organ harvest and preservation, for example, in ischemia-reperfusion injury. In the recipient, the effect of complement can be seen through its interaction with the immune, coagulation, and inflammatory responses. Genetic-engineering and other therapeutic methods by which the xenograft can be protected from the effects of complement activation are discussed. The review provides an updated source of reference to this increasingly complex subject.

Improvements in intestine transplantation

Transplantation of the intestine in children has presented significant challenges even as it has become a standard to treat nutritional failure due to short gut syndrome. These challenges have been addressed in part by significant improvements in short and long-term care. Noteworthy enhancements include reduced need for intestine transplantation, drug-sparing immunosuppressive regimens, immune monitoring, and improved surveillance and management of PTLD and non-adherence.

Efficacy of eculizumab in an adult patient with HIV-associated hemolytic uremic syndrome: A case report

INTRODUCTION

Hemolytic uremic syndrome (HUS) in Human Immunodeficiency Virus (HIV)-positive patients has become a rare cause of kidney injury since the era of highly active antiretroviral therapy (HAART). Plasma exchange and antiretroviral therapy were previously recommended but often failed to achieve remission. We report a case of HUS in a HIV-positive patient treated successfully with eculizumab.

CASE SUMMARY

A 52-year-old woman presented to hospital with acute renal failure, thrombocytopenia, anemia, and hypoxemia. She had been diagnosed with HIV infection in 1997. Kidney biopsy showed several fibrinous microthrombi in the glomerular capillaries, formation of thrombi in arterioles, moderate parietal and mesangial deposits of C3 and Immunoglobulin M, and intense glomerular and arterial deposits of Complement component 5b9 complement component. Serum HIV viral load was 227,848 copies/mL, and CD4 lymphocyte count was 120 cells/μL. A diagnosis of HIV-associated HUS was made. The patient had no confounding cause of HUS. Initiation of eculizumab and HAART resulted in complete hematological remission on day 32 and dialysis withdrawal on day 110. The patient has not relapsed during long-term follow-up (M17).

CONCLUSION

This observation suggests that eculizumab can achieve remission in HIV patients with HUS.

Antibody-mediated rejection across solid organ transplants: manifestations, mechanisms, and therapies

Solid organ transplantation is a curative therapy for hundreds of thousands of patients with end-stage organ failure. However, long-term outcomes have not improved, and nearly half of transplant recipients will lose their allografts by 10 years after transplant. One of the major challenges facing clinical transplantation is antibody-mediated rejection (AMR) caused by anti-donor HLA antibodies. AMR is highly associated with graft loss, but unfortunately there are few efficacious therapies to prevent and reverse AMR. This Review describes the clinical and histological manifestations of AMR, and discusses the immunopathological mechanisms contributing to antibody-mediated allograft injury as well as current and emerging therapies.

Intestinal transplantation: a review

PURPOSE OF REVIEW

The purpose of this article is to review the existing literature on the current indications, surgical techniques, immunosuppressive therapy and outcomes following intestinal transplantation (ITx).

RECENT FINDINGS

Over recent years, ITx has become a more common operation with approximately 2500 procedures carried out worldwide by 2014. It is reserved for patients with intestinal failure and who have developed complications of home parenteral nutrition or who have a high risk of dying from their underlying disease. Recent advances such as the improvement in survival rates, not only for isolated small bowel transplants but also following inclusion of a liver graft in combined liver-small bowel transplant, and the utility of citrulline as a noninvasive biomarker to appreciate acute rejection herald an exciting shift in the field of ITx.

SUMMARY

With advancements in immunosuppressive drugs, induction regimens, standardization of surgical techniques and improved postoperative care, survival is increasing. In due course, it will most likely become as good as remaining on home parenteral nutrition and as such could become a viable first-line option.

Acute antibody-mediated rejection in ABO-compatible pediatric liver transplant recipients: case series and review of the literature

Acute AMR is well reported following ABO-incompatible LTx. However, it remains uncommon in ABO-compatible LTx. It typically presents with graft dysfunction ≤2 weeks post-LTx and is often associated with graft loss. We report the clinical presentation, treatment regimen, and outcome of six pediatric LTx recipients diagnosed with early acute AMR based on (i) clinical signs of graft dysfunction, (ii) histopathology indicative of acute injury ± C4d staining, and (iii) presence of HLA DSA. All patients developed elevated ALT and GGT ≤ 45 days post-LTx. All showed HLA class I (n=4) and/or II (n=6) DSA (peak MFI 6153-11 910). Four had de novo DSA, and two had preformed DSA. Five were initially diagnosed with ACR refractory to steroid therapy. Four exhibited resolution of graft dysfunction with AMR therapy. Two had refractory AMR-one was re-transplanted; the other was treated with eculizumab and showed improvement in graft function but later died due to a tracheostomy complication. Our case series suggests that AMR following ABO-compatible LTx may be under-diagnosed. The presentation can be variable, and treatment should be individualized. Eculizumab may be an option for refractory AMR. Ultimately, future multicenter studies are needed to better define diagnostic criteria, characterize optimal treatment, and assess long-term outcomes following liver AMR.

Intestinal Transplant Inflammation: the Third Inflammatory Bowel Disease

Intestinal transplantation is the most immunologically complex of all abdominal organ transplants. Understanding the role both humoral and innate and adaptive cellular immunity play in intestinal transplantation is critical to improving outcomes and increasing indications for patients suffering from intestinal failure. Recent findings highlighting the impact of donor-specific antibodies on intestinal allografts, the role of NOD2 as a key regulator of intestinal immunity, the protective effects of innate lymphoid cells, and the role of Th17 in acute cellular rejection are reviewed here.

Updates on antibody-mediated rejection in intestinal transplantation

Antibody-mediated rejection (ABMR) has increasingly emerged as an important cause of allograft loss after intestinal transplantation (ITx). Compelling evidence indicates that donor-specific antibodies can mediate and promote acute and chronic rejection after ITx. However, diagnostic criteria for ABMR after ITx have not been established yet and the mechanisms of antibody-mediated graft injury are not well-known. Effective approaches to prevent and treat ABMR are required to improve long-term outcomes of intestine recipients. Clearly, ABMR after ITx has become an important area for research and clinical investigation.

The role of biologicals in intestinal transplantation

PURPOSE OF REVIEW

This article reviews the role of biologicals in intestinal transplantation.

RECENT FINDINGS

Several biologicals have been used in intestinal and multivisceral transplantation for various indications, such as induction therapy, prevention and treatment of antibody-mediated rejection, desensitization, anti-inflammatory treatment, as well as treatment of Epstein-Barr virus-associated posttransplant lymphoproliferative disease. Particularly, the administration of biologicals in induction therapy such as T-cell depleting antibodies and interleukin-2 receptor antagonists have significantly contributed to the great improvement of patient and allograft outcome. Novel biologicals, such as B-cell, plasma-cell, and complement-directed agents have been successfully applied to treat antibody and complement-driven alloimmune processes to stabilize long-term outcome. Several other inflammatory allotransplant conditions have been addressed with anti-TNF-α antibodies, such as infliximab.

SUMMARY

Biologicals have contributed significantly to the recent success of intestinal transplantation. Novel developments in this field are supposed to aid in addressing various urgent needs in intestinal transplantation, such as preimmunization, antibody and complement-induced graft injury, as well as pathologies originating from innate immune responses.

The Complement System and Antibody-Mediated Transplant Rejection

Complement activation is an important cause of tissue injury in patients with Ab-mediated rejection (AMR) of transplanted organs. Complement activation triggers a strong inflammatory response, and it also generates tissue-bound and soluble fragments that are clinically useful markers of inflammation. The detection of complement proteins deposited within transplanted tissues has become an indispensible biomarker of AMR, and several assays have recently been developed to measure complement activation by Abs reactive to specific donor HLA expressed within the transplant. Complement inhibitors have entered clinical use and have shown efficacy for the treatment of AMR. New methods of detecting complement activation within transplanted organs will improve our ability to diagnose and monitor AMR, and they will also help guide the use of complement inhibitory drugs.

The importance of non-HLA antibodies in transplantation

The development of post-transplantation antibodies against non-HLA autoantigens is associated with rejection and decreased long-term graft survival. Although our knowledge of non-HLA antibodies is incomplete, compelling experimental and clinical findings demonstrate that antibodies directed against autoantigens such as angiotensin type 1 receptor, perlecan and collagen, contribute to the process of antibody-mediated acute and chronic rejection. The mechanisms that underlie the production of autoantibodies in the setting of organ transplantation is an important area of ongoing investigation. Ischaemia-reperfusion injury, surgical trauma and/or alloimmune responses can result in the release of organ-derived autoantigens (such as soluble antigens, extracellular vesicles or apoptotic bodies) that are presented to B cells in the context of the transplant recipient's antigen presenting cells and stimulate autoantibody production. Type 17 T helper cells orchestrate autoantibody production by supporting the proliferation and maturation of autoreactive B cells within ectopic tertiary lymphoid tissue. Conversely, autoantibody-mediated graft damage can trigger alloimmunity and the development of donor-specific HLA antibodies that can act in synergy to promote allograft rejection. Identification of the immunologic phenotypes of transplant recipients at risk of non-HLA antibody-mediated rejection, and the development of targeted therapies to treat such rejection, are sorely needed to improve both graft and patient survival.

Intestinal transplantation in children: current status

Intestinal transplantation (IT) is the least common form of organ transplantation; however, it has shown exceptional growth and improvement in graft survival rates over the past two decades mainly due to better outcomes achieved during the first year of transplantation (76 % at 1 year), due to improvement in surgical techniques and the development of better immunosupressive therapies as we understand more about the relationship between the recipient and host immune system. There are still ongoing issues with chronic rejection and long-term survival. Intestinal transplantation is still an acceptable therapy for patients with intestinal failure (IF), but it is generally reserved for patients who develop severe and life-threatening complications despite standard therapies, or those who are not able to maintain a good quality of life. The purpose of this review is to describe the current status, indications, outcomes and advances in the field of intestinal transplantation.

The alternative pathway of complement and the thrombotic microangiopathies

Thrombotic microangiopathies (TMA) are disorders defined by microangiopathic hemolytic anemia, non-immune thrombocytopenia and have multi-organ involvement including the kidneys, brain, gastrointestinal, respiratory tract and skin. Emerging evidence points to the central role of complement dysregulation in leading to microvascular endothelial injury which is crucial for the development of TMAs. This key insight has led to the development of complement-targeted therapy. Eculizumab is an anti-C5 monoclonal antibody, which has revolutionized the treatment of atypical hemolytic uremic syndrome. Several other anti-complement therapeutic agents are currently in development, offering a potential armamentarium of therapies available to treat complement-mediated TMAs. The development of sensitive, reliable and easy to perform assays to monitor complement activity and therapeutic efficacy will be key to devising an individualized treatment regime with the potential of safely weaning or discontinuing treatment in the appropriate clinical setting.