Improved Outcomes after ABO-Incompatible Living-Donor Kidney Transplantation after 4 Weeks of Treatment with Mycophenolate Mofetil

Strategies to overcome the ABO barrier in kidney transplantation

Kidney transplantation across the ABO blood group barrier was long considered a contraindication for transplantation, but in an effort to increase donor pools, specific regimens for ABO-incompatible (ABOi) transplantation have been developed. These regimens are now widely used as an integral part of the available treatment options. Various desensitization protocols, commonly based on transient depletion of preformed anti-A and/or anti-B antibodies and modulation of B-cell immunity, enable excellent transplant outcomes, even in the long-term. Nevertheless, the molecular mechanisms behind transplant acceptance facilitated by a short course of anti-humoral treatment are still incompletely understood. With the evolution of efficient clinical programmes, tailoring of recipient preconditioning based on individual donor-recipient blood type combinations and the levels of pretransplant anti-A/B antibodies has become possible. In the context of low antibody titres and/or donor A2 phenotype, immunomodulation and/or apheresis might be dispensable. A concern still exists, however, that ABOi kidney transplantation is associated with an increased risk of surgical and infectious complications, partly owing to the effects of extracorporeal treatment and intensified immunosuppression. Nevertheless, a continuous improvement in desensitization strategies, with the aim of minimizing the immunosuppressive burden, might pave the way to clinical outcomes that are comparable to those achieved in ABO-compatible transplantation.

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.

Conversion of stable ABO-incompatible kidney transplant recipients from mycophenolate mofetil with standard exposure calcineurin inhibitors (CNIs) to everolimus with very low exposure CNIs-a short-term pilot study

BACKGROUND

A recent report has demonstrated that as with mycophenolate mofetil (MMF), everolimus is capable of inhibiting human B-lymphocyte function and activation including B-lymphocyte proliferation, apoptosis, and immunoglobulin production in vitro. Everolimus may therefore be used as an immunosuppressant in ABO-incompatible kidney transplantation.

METHODS

A three-month pilot study was performed to examine the efficacy and safety of conversion of stable ABO-incompatible kidney transplant recipients from MMF with standard exposure calcineurin inhibitors (CNIs) to everolimus with very low exposure CNIs. Sixteen recipients were enrolled in the study. The patients without acute rejection by graft biopsy were switched from MMF to everolimus with CNI minimization. At three months after conversion, graft biopsies were performed to check for acute rejection and C4d deposition.

RESULTS

Conversion to everolimus with CNI minimization for three months did not induce acute rejection and C4d deposition in all of the ABO-incompatible kidney transplant recipients. A slight elevation of anti-A/B antibody titer occurred in our present study. Everolimus was associated with hyperlipidemia and edema.

CONCLUSIONS

These results demonstrated that short-term conversion from MMF to everolimus after one yr post-transplant may be a safe and effective alternate for ABO-incompatible kidney transplant recipients requiring temporary discontinuation of MMF.

In vitro and in vivo characterization of AS2643361, a novel and highly potent inosine 5'-monophosphate dehydrogenase inhibitor

Inosine 5'-monophosphate (IMP) dehydrogenase is a critical target in solid organ transplantation. To this end, the development of mycophenolate mofetil (MMF) represents a major advance in transplant medicine. Here, we investigated the in vitro and in vivo pharmacological effects of a novel IMP dehydrogenase inhibitor, AS2643361, in several immunological and non-immunological models. The in vitro inhibitory activity of AS2643361 on immune cell and endothelial cell proliferation and on antibody production from lipopolysaccharide-stimulated B cells, was significantly more potent than that of mycophenolic acid, the active form of MMF, despite the similar potency of these compounds on IMP dehydrogenase. In a rat heterotopic cardiac transplant model, monotherapy using orally administered AS2643361 at 10 or 20mg/kg/day prolonged the median graft survival time from 6 to 16 and 19days, respectively. In dinitrophenol-lipopolysaccharide stimulated rats, oral administration of AS2643361 at 2.5, 5 or 10mg/kg/day resulted in suppression of antibody production. In vivo antibody production against alloantigen was also suppressed by AS2643361 treatment at 5 or 10mg/kg/day. Furthermore, treatment with AS2543361 effectively inhibited balloon injury induced-intimal thickening, which is a major cause of late allograft loss. Overall, the in vivo activity of AS2643361 was over two-fold more potent than that of MMF. In addition, gastrointestinal toxicity, considered a dose-limiting factor for MMF, was reduced with AS2643361 treatment. These results suggest AS2643361 has higher potency and less toxicity than MMF, making it a potential candidate for treatment of acute and chronic rejection in transplant medicine.

ABO blood group incompatibility: a diminishing barrier to successful kidney transplantation?

Blood type-incompatible transplantation has gained wide acceptance over the last decade. This is largely the result of B-cell-directed therapies aimed at modulating anti-blood group antibodies, which were the cause of the poor outcomes originally seen. Now rituximab (anti-CD20 and anti-B cell) has largely replaced splenectomy in preconditioning protocols, allowing for the wider implementation of ABO-incompatible transplants. Plasma exchange followed by intravenous immunoglobulin is also critical for the success of ABO-incompatible transplants. In this article, we describe the important contributions immunomodulatory drugs and antibody reduction therapies have made in achieving excellent outcomes in what was once an impenetrable barrier to transplantation.

Adult Living Donor Liver Transplantation with ABO-Incompatible Grafts: A German Single Center Experience

Adult living donor liver transplantations (ALDLTs) across the ABO blood group barrier have been reported in Asia, North Americas, and Europe, but not yet in Germany. Several strategies have been established to overcome the detrimental effects that are attached with such a disparity between donor and host, but no gold standard has yet emerged. Here, we present the first experiences with three ABO-incompatible adult living donor liver transplantations in Germany applying different immunosuppressive strategies. Four patient-donor couples were considered for ABO-incompatible ALDLT. In these patients, resident ABO blood group antibodies (isoagglutinins) were depleted by plasmapheresis or immunoadsorption and replenishment was inhibited by splenectomy and/or B-cell-targeted immunosuppression. Despite different treatments ALDLT could safely be performed in three patients and all patients had good initial graft function without signs for antibody-mediated rejection (AMR). Two patients had long-term graft survival with stable graft function. We thus propose the feasibility of ABO-incompatible ALDLT with these protocols and advocate further expansion of ABO incompatible ALDLT in multicenter trials to improve efficacy and safety.

Effect of the inosine 5'-monophosphate dehydrogenase inhibitor BMS-566419 on rat cardiac allograft rejection

Inosine 5'-monophosphate dehydrogenase (IMPDH) inhibition is a critical target in solid organ transplantation, and the development of mycophenolate mofetil (MMF) represents a major advance in transplant medicine. In this study, the in vitro and in vivo pharmacological effects of BMS-566419, a novel chemically synthesized IMPDH inhibitor, were compared to those of mycophenolic acid (MPA) and MMF based on results from several immunological experiments. The in vitro inhibitory activity of BMS-566419 on IMPDH type I/II, immune cell proliferation and antibody production from lipopolysaccharide (LPS)-stimulated B cells was similar, albeit slightly less potent than that of MPA. In a rat heterotopic cardiac transplant model, monotherapy using orally administered BMS-566419 60mg/kg or MMF 40mg/kg prolonged the median survival time (MST) of transplanted grafts in the vehicle group from 5 to 18 and 18.5 days, respectively. In the presence of a sub-therapeutic dose of FK506, BMS-566419 30mg/kg and MMF 20mg/kg showed identical efficacy with an MST of 21.5 days. In dinitrophenol-LPS-stimulated rats in which calcineurin inhibitors failed to inhibit antibody production, in vivo oral administration of BMS-566419 resulted in antibody production suppression with similar efficacy to MMF. The in vivo antibody production against alloantigen was also suppressed by MMF or BMS-566419 treatment. In addition, gastrointestinal toxicity, considered a dose-limiting factor of MMF, was reduced in BMS-566419 treatment. These results suggest that BMS-566419 and other chemically synthesized IMPDH inhibitors have beneficial pharmacological effects similar to those of MMF, and are potential pharmaceutical candidates in transplant indications.

Preapheresis immunosuppressive induction: necessary or harmful?

In ABO-incompatible kidney transplantation, only a few studies have addressed the necessity, duration, and content of immunosuppressive induction therapy. At our center (Karolinska Institute, Stockholm, Sweden), using a preconditioning regimen consisting of 13 days of tacrolimus, mycophenolate mofetil, and prednisolone, we have investigated both short- and long-term renal allograft function (up to 28 days and 1 year after transplantation, respectively) and correlated them to tacrolimus 12-hr trough levels. In summary, during the first 28 days after transplantation, renal allograft function in the ABO-incompatible group was impaired when compared with that observed in the ABO-compatible group. One possible explanation for this finding is the prolonged pretransplantation exposure to tacrolimus in the ABO-incompatible group, resulting in tacrolimus-associated renal toxicity, which slows the reduction in plasma creatinine. In fact, the day before, and also immediately after, the transplantation (for the first 3-4 postoperative days), the tacrolimus 12-hr trough levels in the ABO-incompatible group were greater than in the ABO-compatible group. Possibly, a shorter pretreatment period with tacrolimus or a reduced target tacrolimus trough level could eliminate this difference in postoperative renal allograft function. However, 1 year after transplantation, kidney allograft function in the two study groups was similar.

Live donor nephrectomy for kidney transplantation

The number of patients with end-stage renal disease is increasing substantially every year around the world. Renal transplantation is the best treatment option to improve survival and quality of life. Although the numbers of living, related and deceased transplant donors has also increased, this growth is insufficient to keep up with the expansion rate of the renal failure population. The introduction of laparoscopic donor nephrectomy has gained widespread acceptance by physicians and patients, and seems to be better than open donor nephrectomy in terms of reduced postoperative pain, quick recovery and improved cosmetic outcomes. Evidence strongly suggests that graft survival is similar in recipients of kidneys from living related and unrelated donors. Fortunately, this information has raised awareness of the suitability of potential live, unrelated donors, including spouses, friends, or even anonymous donors. In this Review we touch on sociological aspects of living related kidney transplantation and review the available and proposed methods of increasing the live donor pool, including organ exchange and desensitization protocols for ABO-incompatible and cross-match-positive donor pairs.

ABO incompatible kidney transplantation

PURPOSE OF REVIEW

Although ABO incompatible kidney transplantation is increasingly recognized as effective, the procedure is still evolving. The purpose of this review is to summarize recent advances in this area.

RECENT FINDINGS

Short to intermediate-term outcome appears good, although long-term results are still preliminary. Pretransplant risk stratification based on antidonor antibody titer may be of limited value. Splenectomy, previously reported to be an important component of ABO incompatible transplantation, appears to be avoidable under many circumstances. The wider implementation of A2 blood group incompatible transplantation shortens waiting time for deceased donor transplantation of blood group B recipients without significantly disadvantaging others. The diagnosis of acute humoral rejection has become clearer following the recognition that C4d deposition commonly occurs in well functioning ABO incompatible allografts. The long-term implications of acute humoral rejection appear substantial even following successful acute therapy, with a significant percentage of patients developing chronic humoral rejection manifested as transplant glomerulopathy. Finally, although ABO incompatible transplantation entails increased expense, when compared with maintenance dialysis and taking into account the health related quality of life benefits of a successful transplant, it is clearly cost effective.

SUMMARY

ABO incompatible kidney transplantation is an effective therapy, and will become more widely implemented in the future.

Implementation of a Protocol for ABO-incompatible kidney transplantation--a three-center experience with 60 consecutive transplantations

BACKGROUND

A new protocol for ABO-incompatible kidney transplantation has recently been introduced. We report here on the joint experience of the implementation in Stockholm and Uppsala, Sweden and Freiburg, Germany.

METHODS

The new protocol utilizes antigen-specific immunoadsorption to remove existing ABO-antibodies, rituximab, and intravenous immunoglobulin to prevent the rebound of antibodies, and conventional tacrolimus, mycophenolate-mofetil, and prednisolone immunosuppression. Sixty consecutive ABO-incompatible kidney transplantations were included in the study. The outcome is compared with the results of 274 ABO-compatible live donor transplantations performed during the same period.

RESULTS

Two of the ABO-incompatible grafts have been lost (non-compliance and death with functioning graft). All the remaining 58 grafts had good renal function at a follow-up of up to 61 months. We did not observe any late rebound of antibodies and there were no humoral rejections. Graft survival was 97% for the ABO-incompatible compared with 95% for the ABO-compatible. Patient survival was 98% in both groups. There was a significant variation in preoperative A/B-antibody titer between the centers, with a median 1:8 in Uppsala, median 1:32 in Stockholm and median 1:128 in Freiburg. More preoperative antibody adsorptions were therefore needed in Freiburg than in Stockholm and Uppsala.

CONCLUSIONS

The new protocol was easily implemented and there were no graft losses that could be related to ABO-incompatibility. A significant inter-institutional variation in the measurement of anti-AB-antibodies was found, having a substantial impact on the number of immunoadsorptions and consequently on the total cost for the procedure. A standardized fluorescence-activated cell sorting technique for antibody quantification is much needed.

Pinpoint targeted immunosuppression: anti-CD20/MMF desensitization with anti-CD25 in successful ABO-incompatible kidney transplantation without splenectomy

BACKGROUND

In Japan, ABO-incompatible (ABO-I) kidney transplantation began in 1989; these transplantations have flourished because of the lack of cadaveric donors, and more than 600 cases were performed up to 2004. Splenectomy has been considered to be necessary for successful ABO-I kidney transplantation, and the majority of pre-conditioning protocols include splenectomy in Japan. However, we have lost some grafts due to antibody-mediated rejection (AMR) accompanying explosive elevation of anti-A/B antibody (Ab) titer even though the patients had a low pre-operative Ab titer.

PATIENTS AND METHODS

We utilized two doses of anti-CD20, rituximab, simply combined with mycophenolate mofetil (MMF)/low-dose steroid desensitization started 1 month before surgery in ABO-I kidney transplantation. Two sessions of pre-operative Ab removal by double filtration plasmapheresis or plasma exchange were carried out. We performed six ABO-I kidney transplantations without splenectomy. Anti-A/B Ab titers were more than 16 to 32 times before treatment. We did not plan any post-operative repeated Ab removal or intravenous immunoglobulin G (IVIG).

RESULTS

Pre-operative anti-A/B Ab titers were successfully reduced to less than eight times in all cases. Except for one case in which we had to remove the graft due to aspiration pneumonia and methicillin-resistant staphylococcus epidermidis (MRSE) sepsis, the other five cases did not experience antibody-mediated rejection (AMR). An additional session of post-operative Ab removal and/or IVIG was not necessary. In all patients, B cells (CD19+, CD20+, CD21+) and activated T cells (CD25+) were selectively suppressed, although CD3+, CD4+ and CD8+ cell populations remained stable, thus we call our protocol "pinpoint targeted immunosuppression." Plasma immunoglobulin level was also successfully suppressed, especially after 6 weeks of surgery.

CONCLUSION

Anti-CD20/MMF desensitization is safe and allows successful ABO-I kidney transplantation without splenectomy.

Present status of ABO-incompatible kidney transplantation in Japan

BACKGROUND

We have been making continuous efforts in ABO-incompatible kidney transplantation since 1989 to expand the opportunities for kidney transplantation from living donors in Japan.

PATIENTS AND METHOD

From the Japanese registry, we reviewed the long-term patient and graft survival of ABO-incompatible kidney transplantation. This survey focused on 564 patients who received ABO-incompatible kidney grafts from January 1989 to December 2003 in whom monitoring follow-up could be achieved in 60 institutions all over Japan. The mean age of 367 (65%) male and 197 (35%) female patients at surgery was 34.5 yr. Pre-operative anti-A/B antibody (Ab) removal and splenectomy (n = 553, 98%) were routinely performed combined with triple or quadruple immunosuppression using calcinurine inhibitor (CNI), anti-metabolites and steroids with or without deoxyspurgualin (DSG) or anti-lymphocyte Abs.

RESULTS

The overall patient survival rate at 1, 3, 5 and 10 yr after transplantation was 94, 91, 88 and 81%, with overall graft survival rates of 86, 82, 74 and 53%, respectively. The graft survival rate was significantly higher in patients aged 29 and younger compared with those aged 30 and older. Children aged 15 or younger in particular have shown excellent graft survival rates at 1, 3, 5 and 10 yr of 90, 90, 86 and 76%, respectively. Patients with anticoagulation therapy (n = 285) showed a significantly higher graft survival rate than those without anticoagulation (n = 213), with 10-yr graft survival rates of 59 vs. 48%. There were no significant differences between A and B incompatibility with respect to clinical outcomes. There were also no significant difference in numbers of human leukocyte antigen mismatches, induction and maintenance CNI (cyclosporin A (CYA) vs. tacrolimus) and donor/recipient relationships with respect to the outcomes. We divided the patients into five groups according to the transplanted year periods. The outcome of the most recent 124 cases since 2001 had dramatically improved, with 2-yr graft survival of 94%, and there is a significant difference between the groups in 2001 onwards and the other four groups.

CONCLUSION

This study confirms that the long-term outcome of ABO-incompatible living kidney transplantation is excellent and is similar to that of ABO-compatible cases. Recent data show that short-term graft survival has also improved. ABO-incompatible kidney transplantation is a radical, but safe and effective, treatment choice for end-stage renal disease.

Umfrage zur Überkreuznierentransplantation in Deutschland

Due to increasingly better long-term survival rates with dialysis the number of patients with renal failure constantly increases by 4% annually worldwide. Despite great progress in operative and perioperative management as well as improved immunosuppressive drugs, kidney transplantation still faces two major problems. First of all there is a huge deficit of donor organs and secondly the long-term results of the kidney grafts must be improved. One way to relieve this tense situation may be live kidney donation. In many countries not participating in Eurotransplant, especially the United States and Scandinavia, live kidney donation is performed more often than kidney transplantation from deceased donors. Germany implemented a transplantation law in December 1997. This law also regulates living donation, with exclusion of crossover transplantations. Cross-over transplantation is a special variation of live donation for couples who cannot donate/receive in their respective couple constellation. Therefore, the donor of the one couple donates his/her kidney to the recipient of the other couple and vice versa. According to German legislation this is illegal. We performed a study in order to evaluate the opinions of the German kidney transplant centers on crossover kidney transplantations. The majority of the German transplantation centers believe that crossover transplantation is acceptable with regard to ethical and medical concerns. To enable this kind of kidney transplantation the transplantation law would have to be changed. Nevertheless, nationwide polls show that live kidney donation represents only a very small portion of all transplantations taking place. Live kidney donation should be granted higher priority as dialysis triggers psychological and physical damage, especially in children. For many patients live kidney donation is the only chance for early transplantation with an excellent long-lasting kidney graft function.