Isoagglutinin adsorption in ABO-incompatible transplantation

Sex, T Cells, and the Microbiome in Natural ABO Antibody Production in Mice

BACKGROUND

"Natural" ABO antibodies (Abs) are produced without known exposure to A/B carbohydrate antigens, posing significant risks for hyperacute rejection during ABO-incompatible transplantation. We investigated anti-A "natural" ABO antibodies versus intentionally induced Abs with regard to the need for T-cell help, the impact of sex, and stimulation by the microbiome.

METHODS

Anti-A was measured by hemagglutination assay of sera from untreated C57BL/6 wild-type (WT) or T cell-deficient mice of both sexes. Human ABO-A reagent blood cell membranes were injected intraperitoneally to induce anti-A Abs. The gut microbiome was eliminated by maintenance of mice in germ-free housing.

RESULTS

Compared with WT mice, CD4 + T-cell knockout (KO), major histocompability complex-II KO, and αβ/γδ T-cell receptor KO mice produced much higher levels of anti-A nAbs; females produced dramatically more anti-A nAbs than males, rising substantially with puberty. Sensitization with human ABO-A reagent blood cell membranes did not induce additional anti-A in KO mice, unlike WT. Sex-matched CD4 + T-cell transfer significantly suppressed anti-A nAbs in KO mice and rendered mice responsive to A-sensitization. Even under germ-free conditions, WT mice of several strains produced anti-A nAbs, with significantly higher anti-A nAbs levels in females than males.

CONCLUSIONS

Anti-A nAbs were produced without T-cell help, without microbiome stimulation, in a sex- and age-dependent manner, suggestive of a role for sex hormones in regulating anti-A nAbs. Although CD4 + T cells were not required for anti-A nAbs, our findings indicate that T cells regulate anti-A nAb production. In contrast to anti-A nAbs, induced anti-A production was T-cell dependent without a sex bias.

Plasmapheresis in ABO incompatible kidney transplant

In patients with an end-stage renal disease, dialysis a or kidney transplant are required to prolong live. For survival of the transplanted kidney, besides the HLA-system, the ABO blood type of donor and patient is also of importance. When the donor organ is derived from a living donor, time can be available prior to the transplant to reduce blood type AB antibodies in case of ABO major incompatibility between organ donor and recipient by double filtration apheresis.

Current Perspectives in ABO-Incompatible Kidney Transplant

For a long time, ABO incompatible living donor kidney transplantation has been considered contraindicated, due to the presence of isohemagglutinins, natural antibodies reacting with non-self ABO antigens. However, as the demand for kidney transplantation is constantly growing, methods to expand the donor pool have become increasingly important. Thus, in the last decades, specific desensitization strategies for ABOi transplantation have been developed. Nowadays, these regimens consist of transient removal of preformed anti-A or anti-B antibodies by using plasmapheresis or immunoadsorption and B-cell immunity modulation by CD20+ cells depletion with rituximab, in association with maintenance immunosuppression including corticosteroids, tacrolimus and mycophenolate mofetil. The outcome in ABOi kidney transplantation have markedly improved over the years. In fact, although randomized trials are still lacking, recent meta analysis has revealed that there is no difference in terms of graft and patient's survival between ABOi and ABO compatible kidney transplant, even in the long term. However, many concerns still exist, because ABOi kidney transplantation is associated with an increased risk of bleeding and infectious complications, partly related to the effects of extracorporeal treatments and the strong immunosuppression. Thus, a continuous improvement in desensitization strategies, with the aim of minimize the immunosuppressive burden, on the basis of immune pathogenesis, antibodies titers and/or ABO blood group, is warranted. In this review, we discuss the main immune mechanisms involved in ABOi kidney transplantation, the pathogenesis of tolerance and the desensitization regimens, including immunoadsorption and plasmapheresis and the immunosuppressive protocol. Finally, we provide an overview on outcome and future perspectives in ABOi kidney transplant.

The First North American Experience Using Glycosorb Immunoadsorption Columns for Blood Group-Incompatible Kidney Transplantation

Background:

Blood group incompatibility (ABOi) is the most common barrier to living donor kidney transplantation. Options for such recipients include kidney paired donation (KPD) or desensitization methodology to reduce blood antibody response.

Objective:

The objective of this study is to report on the first North America experience in ABOi living donor kidney transplantation using Glycosorb ABO immunoadsorption columns.

Design:

Retrospective observational cohort study.

Setting:

Renal transplant program at St. Michael’s Hospital, Unity Health Toronto, University of Toronto.

Patients:

Twenty-six ABOi living donor transplants from August 2011 through February 2020 were undertaken at our center.

Measurements:

Renal allograft and patient survival postdesensitization for ABOi living donor transplants and isohemagglutinin titer reduction.

Methods:

Preoperative immunosuppressive regimen consisted of a single dose of Rituximab 375 mg/m² IV on day −28; tacrolimus, mycophenolic acid, and prednisone to start on day −7. Immunoadsorption treatments with Glycosorb A or B columns were performed on day −7 through day −1 based on anti-A or anti-B titers on Spectra Optia Apheresis System. Immunosuppression included basiliximab, solumedrol followed by oral prednisone, once-daily tacrolimus, and mycophenolic acid. The mean follow-up was 53 months (3-96 months).

Results:

A total of 26 individuals underwent an attempt at desensitization of whom 24 patients underwent immediate transplant. One patient had a rebound in titers and subsequently was transplanted from a blood group compatible living donor. A second patient had an unrelated medical issue and desensitization was discontinued. Five-year patient survival was 96% and death censored allograft survival was 92%. Posttransplant anti-A or anti-B titers were monitored daily for the first 7 days posttransplant and every 2 days from days 7 to 14. There were no acute rejections seen in this cohort of transplant recipients.

Limitations:

As our protocol was first initiated as proof of concept, a few recipients had low initial isohemagglutinin titers. This may have contributed to improved clinical outcomes.

Conclusions:

ABO column immunoadsorption with specific columns is a safe and effective method for ABOi living donor kidney transplantation, and an option when KPD is less than ideal.

Trial not registered as this was a retrospective cohort review.

Current protocols and outcomes of ABO-incompatible kidney transplantation

One of the principal obstacles in transplantation from living donors is that approximately 30% are immunologically incompatible because of the presence in the recipient of antibodies directed against the human leukocyte antigen system of the donor or because of the incompatibility of the ABO system. The aim of this review is to describe the more recent data from the literature on the different protocols used and the clinical outcomes of ABO-incompatible kidney transplantation. Two different strategies are used to overcome these barriers: desensitization of the recipient to remove the antibodies and to prevent their rebound after transplantation and the exchange of organs between two or more pairs. The largest part of this review is dedicated to describing the techniques of desensitization. Even if the first reports of successful renal transplantation between ABO-incompatible pairs have been published by 1980, the number of ABO-incompatible transplants increased substantially in this century because of our improved knowledge of the immune system and the availability of new drugs. Rituximab has substantially replaced splenectomy. The technique of apheresis has improved and more recently a tailored desensitization proved to be the more efficient strategy avoiding an excess of immunosuppression with the related side effects. Recent reports document outcomes for such transplantation similar to the outcomes of standard transplantation.

Current protocols and outcomes of ABO-incompatible kidney transplantation based on a single-center experience

ABO-incompatible living kidney transplantation (ABO-ILKT) is an effective option for increasing living kidney transplant opportunities. ABO-ILKT has been conducted in our institution since 1989 to widen the indication for living kidney transplantation. ABO-ILKT is considered to require extra treatment, and it has increased risks compared with ABO-compatible living kidney transplantation (ABO-CLKT). In the past two decades, some protocols have removed anti-blood-type antibodies to prevent the production of antibodies. Additionally, we have made considerable changes to our ABO-ILKT protocol as new immunosuppressive agents have been developed. Consequently, increased immunosuppression and immunological understanding have helped shape recent desensitization protocols. Herein, we review the history, therapeutic strategy, pathology, and future directions of ABO-ILKT. Our standard immunosuppressive regimen and desensitization protocol for ABO-ILKT recipients consist of low doses of tacrolimus (TAC), mycophenolate mofetil (MMF), and rituximab; several sessions of double filtration plasmapheresis; and basiliximab induction. We do not use thymoglobulin induction, intravenous immunoglobulin, or prophylactic post-transplant plasmapheresis. Recently, ABO-ILKT has been recognized as a useful alternative therapy for end-stage kidney disease with ABO-incompatibility, and its outcome is comparable to that of ABO-CLKT.

Preconditioning Therapy in ABO-Incompatible Living Kidney Transplantation: A Systematic Review and Meta-Analysis

BACKGROUND

ABO-incompatible (ABOi) kidney transplantation is now an established form of renal replacement therapy, but the efficacy and safety of the different types of preconditioning therapies are unclear. We aimed to synthesize the totality of the published evidence about the effects of any form of preconditioning therapies in living donor ABOi kidney transplantation on graft and patient outcomes.

METHODS

We searched MEDLINE, Embase, and Clinicaltrial.gov databases (inception through June 2015) to identify all studies that described the outcomes of adult living donor ABOi kidney transplantations using any form of preconditioning therapies. Two independent reviewers identified studies, extracted data, and assessed the risk of bias. Data were summarized using the random effects model, and heterogeneity was explored using subgroup analyses. We assessed confidence in the evidence using the Grading of Recommendations Assessment, Development, and Evaluation framework.

RESULTS

Eighty-three studies (54 case reports and case series, 25 cohort, 2 case-control, and 2 registry studies) involving 4810 ABOi transplant recipients were identified. Overall, confidence in the available evidence was low. During a mean follow-up time of 28 (standard deviation [SD], 26.6) months, the overall graft survival for recipients who received immunoadsorption or apheresis was 94.1% (95% confidence interval [95%CI], 88.2%-97.1%) and 88.0% (95% CI, 82.6%-91.8%), respectively. For those who received rituximab or underwent splenectomy, the overall graft survival was 94.5% (95% CI, 91.6%-96.5%) and 79.7% (95% CI, 72.9%-85.1%), respectively. Data on other longer-term outcomes, including malignancy, were sparse.

CONCLUSIONS

Rituximab or immunoadsorption appeared to be promising preconditioning strategies before ABOi kidney transplantation. However, the overall quality of evidence and the confidence in the observed treatment effects are low. The increased use of ABOi kidney transplantation needs to be matched with randomized trials of different types, dosing, and frequency of preconditioning therapies so that this scarce resource can be used most effectively and efficiently.

Desensitization in ABO-Incompatible Kidney Transplantation With Low ABO Iso-Agglutinin Titers

BACKGROUND

In ABO-incompatible (ABOi) kidney transplantation (KT) with low iso-agglutinin (IG) titers (IGT), standard pre-conditioning treatment might be excessive. To try to answer this question, we evaluated the pre-conditioning requirements of a group of ABOi KT with low ABO IGT in our center. Our main objective was to assess desensitization requirements for ABOi KT with low IGT (<16) at Hospital Clinic of Barcelona from 2006 to 2014.

METHODS

A retrospective study of desensitization (rituximab and plasma exchange [PE]) requirements for ABOi KT with IGT <16 was conducted.

RESULTS

One and 5 years after KT, patient survival was 100%. Renal graft survival was 90% at 1 and 5 years after KT. Mean PE performed before KT was 1.7 (standard deviation [SD], 1.703); 50% of the patients did not receive PE after transplantation, 30% received 2 sessions of PE, and 20% received only 1. The average is 0.8 (SD, 0.91).Follow-up IG determinations remained with low titers (≤8/8). No rebounds of titers were observed during the first 4 to 6 months after transplantation.

CONCLUSIONS

Recipients with IGT ≤8 required none or only 1 PE session to reach acceptable titers (titers ≤4) to perform ABOi KT safely. This information is useful to assess the possibility of a minimized desensitization protocol in ABOi KT donors with low titers of IG to reduce adverse effects, reduce cost, and simplify pre-transplant logistics.

ABO-Incompatible Living Kidney Transplants: Evolution of Outcomes and Immunosuppressive Management

ABO-incompatible living kidney transplantation (ABO-ILKT) has steadily become more widespread. However, the optimal immunosuppressive regimen for ABO-ILKT remains uncertain. We aimed to determine the longitudinal changes in the outcomes from ABO-ILKT compared with those from ABO-compatible living kidney transplantation (ABO-CLKT) over the last 25 years. Of 1195 patients who underwent living kidney transplantations (LKT) at our institute between 1989 and 2013, 1032-including 247 ABO-ILKT and 785 ABO-CLKT cases-were evaluated for graft survival, patient survival, infectious adverse events, and renal function. The patients were divided into four groups according to the transplantation era and ABO-compatibility. In the past decade, ABO-ILKT and ABO-CLKT recipients yielded almost equivalent outcomes with respect to the 9-year graft survival rates, which were 86.9% and 92.0%, respectively (hazard ratio [HR] 1.38, 95% confidence interval [CI] 0.59-3.22, p = 0.455). The graft survival rate for ABO-ILKT conducted between 2005 and 2013 was better than that for ABO-ILKT conducted between 1998 and 2004 (HR 0.30, 95% CI 0.13-0.72, p = 0.007). ABO-ILKT recipients showed substantial improvements in the graft survival rate over time. Graft survival was almost identical over the past decade, regardless of ABO-incompatibility. Currently, ABO-ILKT is an acceptable treatment for patients with end-stage renal disease.

Advances in pharmacotherapy to treat kidney transplant rejection

INTRODUCTION

Current immunosuppressive combination therapy provides excellent prevention of T-cell-mediated rejection following renal transplantation; however, antibody-mediated rejection remains of high concern and accounts for a large number of long-term allograft losses. The recent development of protocol biopsies resulted in the definition of subclinical rejection (SCR), showing histologic evidence for rejection but unremarkable clinical course.

AREAS COVERED

This review describes the current knowledge and evidence of pharmacotherapy to treat kidney allograft rejections and covers SCR treatment options. Each substance is analyzed with regard to its classical indication and further discussed for the treatment of other forms of rejection.

EXPERT OPINION

Despite a lack of randomized trials, early acute T-cell-mediated rejection can be treated effectively in most cases without graft loss. The necessity to treat SCR is currently unclear. Due to a lack of effective therapies, new treatment approaches for antibody-mediated rejection are an urgent medical need to improve long-term outcomes. Future research should aim to better define pathophysiology and histology, stratify risk, and develop rational treatment strategies from randomized controlled trials, in order to establish the value of novel therapies in the arsenal of rejection pharmacotherapy. However, the effective prevention of rejection with minimal side effects still remains the goal in immunosuppression.

An update on ABO-incompatible kidney transplantation

ABO-incompatible kidney transplantation is nowadays a well-established procedure to expand living donor transplantation to blood group incompatible donor/recipient constellations. In the last two decades, transplantation protocols evolved to more specific isohaemagglutinin elimination techniques and established competent antirejection protection protocols without the need of splenectomy. ABOi kidney transplantation associated accommodation despite isohaemagglutinin reappearance, C4d positivity of peritubular capillaries as well as the increased incidence of bleeding complications is currently under intense investigation. However, most recent data show excellent graft survival rates equivalent to ABO-compatible kidney transplantation outcome.

Desensitization with plasmapheresis and anti-Cd20 for ABO incompatible kidney transplantation from living donor: experience of a single center in Italy

OBJECTIVE

Blood group incompatibility in kidney transplants from a living donor can be successfully overcome by using various desensitization protocols: intravenous immunoglobulin, plasmapheresis (PP), immunoadsorption, and double filtration PP.

PATIENTS AND METHODS

From July 2010 to October 2013, we performed 10 ABO incompatible kidney transplantation (KT) procedures from a living donor. The desensitization protocol was based on rituximab and PP+cytomegalovirus immune globulin. All patients received induction with basiliximab, except 1 case treated with Thymoglobuline® (ATG) for the simultaneous presence of donor-specific antibody. Tacrolimus and mycophenolate mofetil were initiated at the time of desensitization and continued after the transplant.

RESULTS

After a mean follow-up of 11.6±10.4 months, all patients are alive with a functioning graft. The mean serum creatinine concentration at 1 month, 3 months, 6 months, and 1 year was 1.48±0.29, 1.47±0.18, 1.47±0.27, and 1.5±0.27 mg/dl. Three episodes of acute cellular rejection occurred in 2 patients. There was only 1 case of BK virus infection, treated with reduction of immunosuppressive therapy. The protocol biopsy specimens at 1, 3, and 6 months were C4d positive in the absence of acute rejection.

CONCLUSIONS

Desensitization with rituximab, PP, and anti-cytomegalovirus immune globulin allowed us to perform transplants from living donors to ABO incompatible recipients with excellent results and reduced costs.

Desensitization for solid organ and hematopoietic stem cell transplantation

Desensitization protocols are being used worldwide to enable kidney transplantation across immunologic barriers, i.e. antibody to donor HLA or ABO antigens, which were once thought to be absolute contraindications to transplantation. Desensitization protocols are also being applied to permit transplantation of HLA mismatched hematopoietic stem cells to patients with antibody to donor HLA, to enhance the opportunity for transplantation of non-renal organs, and to treat antibody-mediated rejection. Although desensitization for organ transplantation carries an increased risk of antibody-mediated rejection, ultimately these transplants extend and enhance the quality of life for solid organ recipients, and desensitization that permits transplantation of hematopoietic stem cells is life saving for patients with limited donor options. Complex patient factors and variability in treatment protocols have made it difficult to identify, precisely, the mechanisms underlying the downregulation of donor-specific antibodies. The mechanisms underlying desensitization may differ among the various protocols in use, although there are likely to be some common features. However, it is likely that desensitization achieves a sort of immune detente by first reducing the immunologic barrier and then by creating an environment in which an autoregulatory process restricts the immune response to the allograft.

Molecular deciphering of the ABO system as a basis for novel diagnostics and therapeutics in ABO incompatible transplantation

In recent years ABO incompatible kidney transplantation (KTx) has become a more or less clinical routine procedure with graft and patient survival similar to those of ABO compatible transplants. Antigen-specific immunoadsorption (IA) for anti-A and anti-B antibody removal constitutes in many centers an important part of the treatment protocol. ABO antibody titration by hemagglutination is guiding the treatment; both if the recipient can be transplanted as well as in cases of suspected rejections if antibody removal should be performed. Despite the overall success of ABO incompatible KTx, there is still room for improvements and an extension of the technology to include other solid organs. Based on an increased understanding of the structural complexity and tissue distribution of ABH antigens and the fine epitope specificity of the ABO antibody repertoire, improved IA matrices and ABO antibody diagnostics should be developed. Furthermore, understanding the molecular mechanisms behind accommodation of ABO incompatible renal allografts could make it possible to induce long-term allograft acceptance also in human leukocyte antigen (HLA) sensitized recipients and, perhaps, also make clinical xenotransplantation possible.

Impact of the baseline anti-A/B antibody titer on the clinical outcome in ABO-incompatible kidney transplantation

BACKGROUND/AIMS

We investigated the impact of the baseline anti-A/B antibody titer on the clinical outcome in ABO-incompatible kidney transplantation (IKT).

METHODS

We included 183 patients who had undergone KT (40 ABO IKT and 143 ABO-compatible KT). Eight patients with a baseline titer of ≥1:512 were assigned to the high-titer group and 32 patients with a baseline titer of ≤1:256 were assigned to the low-titer group. Patients who underwent ABO-compatible KT were used as the control group. We compared the clinical outcomes of the three groups.

RESULTS

Before transplantation, the high-titer group displayed more frequent antibody rebound, as shown in a lower titer reduction rate, and more difficulty reaching the target titer (1:16) than the low-titer group. During the postoperative period and out-clinic follow-up, antibody rebound was more frequent, and the rate of acute rejection and infection were significantly higher and allograft function was lower in the high-titer group than in the low-titer and control groups. Multivariate analysis showed that high baseline antibody titer was an independent risk factor for acute rejection.

CONCLUSION

ABO IKT in the high-titer group (baseline titer ≥1:512) required greater caution compared to the low-titer group because of the higher tendency of antibody rebound and the risk for acute rejection.

Renal transplantation across ABO barrier

In India, patients without a compatible blood group donor are usually excluded from renal transplantation. For young patients, it is a difficult therapeutic choice to stay on long-term dialysis. We describe the case of a 19-year-old male patient who had blood group O +ve and had no compatible donor in the family. His mother was B +ve and was willing to donate. The patient had an initial anti-B antibody titer of 1:512 and underwent antibody depletion with plasmapheresis (11 sessions) and intravenous immunoglobulin (IVIG) 100 mg/kg after every plasmapheresis. He also received rituximab 500 mg for 3 days prior to transplant and was induced with basiliximab. At the time of transplant, his anti-B titers were <1:8. Post-operatively, he required four sessions of plasmapheresis and IVIG as his titers rebounded to 1:64. The titers then spontaneously subsided to <1:16 and have stayed at the same level for 6 months post-transplant. The patient continues to have normal renal function with a creatinine of 1.4 mg/dl% and has had no episodes of rejection.

ABO Incompatible Kidney Transplantation-Current Status and Uncertainties

In the past, ABO blood group incompatibility was considered an absolute contraindication for kidney transplantation. Progress in defined desensitization practice and immunologic understanding has allowed increasingly successful ABO incompatible transplantation during recent years. This paper focused on the history, disserted outcomes, desensitization modalities and protocols, posttransplant immunologic surveillance, and antibody-mediated rejection in transplantation with an ABO incompatible kidney allograft. The mechanism underlying accommodation and antibody-mediated injury was also described.