Strategies to overcome the ABO barrier in kidney transplantation

Kidney Paired Donation-European Transnational Experience in Adults and Opportunities for Pediatric Kidney Transplantation

BACKGROUND

Live donor kidney transplantation is considered the optimal choice for renal replacement therapy, providing established benefits, such as superior patient survival and improved quality of life. However, immunological challenges, including ABO blood group incompatibility and, particularly, donor-specific HLA antibodies, may impact long-term outcomes considerably or even prevent safe direct transplantation with the intended donor.

METHODS

In this review, the authors discuss kidney paired donation (KPD) as a viable strategy to overcome immunological barriers to living donation through organ exchanges. We thereby lay special focus on the Czech-Austrian transnational KPD program.

RESULTS

While the benefits of KPD programs are well established for adult recipients, recent data suggest that this may hold true also for pediatric patients. Complex algorithms, considering factors like the intricate patterns of HLA sensitization, play a pivotal role in predicting suitable matches, but for pediatric patients also non-immunological factors including age and weight match may play a role. As pool size proves crucial for program efficacy, several countries in Europe have now initiated transnational collaborations to maximize match rates. Among those, the Czech-Austrian transnational joint program, established in 2015 and now expanded to a cooperation with the Israel transplant program to further increase transplant rates, represents a successful example.

CONCLUSION

KPD programs, with their innovative approaches and international partnerships, hold promise for enhancing outcomes and addressing the increasing demand for kidney transplantation.

Enzymatic conversion of human blood group A kidneys to universal blood group O

ABO blood group compatibility restrictions present the first barrier to donor-recipient matching in kidney transplantation. Here, we present the use of two enzymes, FpGalNAc deacetylase and FpGalactosaminidase, from the bacterium Flavonifractor plautii to enzymatically convert blood group A antigens from the renal vasculature of human kidneys to 'universal' O-type. Using normothermic machine perfusion (NMP) and hypothermic machine perfusion (HMP) strategies, we demonstrate blood group A antigen loss of approximately 80% in as little as 2 h NMP and HMP. Furthermore, we show that treated kidneys do not bind circulating anti-A antibodies in an ex vivo model of ABO-incompatible transplantation and do not activate the classical complement pathway. This strategy presents a solution to the donor organ shortage crisis with the potential for direct clinical translation to reduce waiting times for patients with end stage renal disease.

Decreased rate of blood donors with high ABO antibody titers in Japan and the underlying factors: Comparisons between 2010 and 2021

BACKGROUND AND OBJECTIVES

Previously (2007), it was reported that ABO antibody titers in Japanese blood donors had decreased significantly compared to 20 years before. Here we evaluated whether further decrease of antibody titers had occurred in recent years, and the potential factors associated with changes in antibody titers.

MATERIALS AND METHODS

Serum/plasma from random blood donors in 2010 and 2021 (2010: 3369, 2021: 5796 donors) was classified into low, middle, and high ABO antibody titers according to the reactivity of diluted serum/plasma (2.5-fold and 20-fold) by an automated microplate system. The rates of low/high titer in the two periods were compared. Logistic regression and age-gender-BMI subgroup analyses were conducted to identify the factors that contributed to changes in antibody titers.

RESULTS

Compared to 2010, the rate of donors with high ABO antibody titers was　decreased in 2021 for both anti-A and anti-B (anti-A, 2010: 23.8%, 2021: 19.3%; anti-B, 2010: 23.8%, 2021: 16.4%). In logistic regression analysis, age was found to significantly affect both anti-A and anti-B antibody titers (anti-A, adjusted odds ratio 0.36, 95% CI 0.31-0.41; anti-B, 0.42, 0.37-0.47), and BMI (0.82, 0.73-0.92) and other time-related factors (0.79, 0.71-0.88) significantly affect anti-B antibody titers. Subgroup analysis revealed decreased rate of high anti-B titers in the higher age group in 2021.

CONCLUSION

The rate of high ABO antibody titers, especially high anti-B titers, was significantly decreased in 2021, and our results suggested an association with aging and obesity of blood donors as well as other time-related factors.

Outcomes of ABO-incompatible liver transplantation in end-stage liver disease patients co-infected with hepatitis B and human immunodeficiency virus

BACKGROUND

Human immunodeficiency virus (HIV)-positive patients coinfected with hepatitis B virus (HBV) are eligible for liver transplantation (LT) in Africa and Southeast Asia, particularly China. However, the outcome of HIV-HBV coinfected patients referred for ABO-incompatible LT (ABOi-LT) is unknown.

AIM

To clarify the outcome of ABOi-LT for HIV-HBV coinfected patients with end-stage liver disease (ESLD).

METHODS

We report on two Chinese HIV-HBV coinfected patients with ESLD who underwent A to O brain-dead donor LT and reviewed the literature on HIV-HBV coinfected patients treated with ABO-compatible LT. The pretransplantation HIV viral load was undetectable, with no active opportunistic infections. Induction therapy consisted of two sessions of plasmapheresis and a single dose of rituximab in two split doses, followed by an intraoperative regimen of intravenous immunoglobulin, methylprednisolone, and basiliximab. Post-transplant maintenance immunosuppressive agents consisted of tacrolimus and mycophenolate mofetil, and prednisone.

RESULTS

At the intermediate-term follow-up, patients showed undetectable HIV viral load, CD4(+) T cell counts greater than 150 cells/μL, no HBV recurrence, and stable liver function. A liver allograft biopsy showed no evidence of acute cellular rejection. Both patients survived at 36-42 mo of follow-up.

CONCLUSION

This is the first report of ABOi-LT in HIV-HBV recipients with good intermediate-term outcomes, suggesting that ABOi-LT may be feasible and safe for HIV-HBV coinfected patients with ESLD.

Enzymatic blood group conversion of human kidneys during ex vivo normothermic machine perfusion

A major restriction to transplantation is the requirement for ABO blood group compatibility between donor and recipient. In this study, an α-galactosidase enzyme from Bacteroides fragilis was used successfully to remove type B blood group antigens enzymatically from human kidneys using ex vivo normothermic machine perfusion. This provides the first step for a strategy to overcome the ABO barrier in kidney transplantation.

Recommendations for living donor kidney transplantation

This Guide for Living Donor Kidney Transplantation (LDKT) has been prepared with the sponsorship of the Spanish Society of Nephrology (SEN), the Spanish Transplant Society (SET), and the Spanish National Transplant Organization (ONT). It updates evidence to offer the best chronic renal failure treatment when a potential living donor is available. The core aim of this Guide is to supply clinicians who evaluate living donors and transplant recipients with the best decision-making tools, to optimise their outcomes. Moreover, the role of living donors in the current KT context should recover the level of importance it had until recently. To this end the new forms of incompatible HLA and/or ABO donation, as well as the paired donation which is possible in several hospitals with experience in LDKT, offer additional ways to treat renal patients with an incompatible donor. Good results in terms of patient and graft survival have expanded the range of circumstances under which living renal donors are accepted. Older donors are now accepted, as are others with factors that affect the decision, such as a borderline clinical history or alterations, which when evaluated may lead to an additional number of transplantations. This Guide does not forget that LDKT may lead to risk for the donor. Pre-donation evaluation has to centre on the problems which may arise over the short or long-term, and these have to be described to the potential donor so that they are able take them into account. Experience over recent years has led to progress in risk analysis, to protect donors' health. This aspect always has to be taken into account by LDKT programmes when evaluating potential donors. Finally, this Guide has been designed to aid decision-making, with recommendations and suggestions when uncertainties arise in pre-donation studies. Its overarching aim is to ensure that informed consent is based on high quality studies and information supplied to donors and recipients, offering the strongest possible guarantees.

Progression of histological lesions after ABO incompatible kidney transplantation

Recent large meta-analyses suggested a poorer long-term patients’ and grafts’ outcomes after ABO incompatible (ABOi) living-donor kidney transplantation (LDKT) compared to ABO compatible LDKT. However, little is known about the long-term histological pattern after ABOi LDKT. We compared the histological features observed on protocol biopsies from 03/11 to 11/19 in 94 ABOi LDKT (including 14 with preformed Donor Specific Antibodies, pDSAs), 27 LDKT ABO compatible (ABOc) with pDSAs, and 21 ABOc without pDSAs) during the first five years post transplantation. During the first 5 years post-transplantation, a progression of chronic lesions (patients with a ci >0 raised from 11% to 65%, p<0.0001, patients with a ct >0 raised from 29% to 78%, p<0.0001) was observed in ABOi LDKT without pDSAs. Histological patterns of evolution were comparable to those observed in ABOc kidney transplant patients. Microvascular inflammation was lower in ABOi LDKT without pDSAs compared to those with pDSAs (ABOi or ABOc). At last follow-up, 28 months, IQR (15-48) post-transplantation, 29 patients (36%) had a severe graft dysfunction (defined by a CKD-epi eGFR < 30 mL/min/1.73m²). The donor age was a predictive factor for the development of severe kidney allograft dysfunction at last follow-up (HR= 1.05, 95% CI [1.05-1.10], p= 0.03).

Hence, long-term histological analysis of ABOi LDKT shows only an increase of chronic interstitial and tubular atrophy changes, without active lesions. These data confirm that ABOi LDKT programs can be securely developed.

Protection of transplants against antibody-mediated injuries: from xenotransplantation to allogeneic transplantation, mechanisms and therapeutic insights

Long-term allograft survival in allotransplantation, especially in kidney and heart transplantation, is mainly limited by the occurrence of antibody-mediated rejection due to anti-Human Leukocyte Antigen antibodies. These types of rejection are difficult to handle and chronic endothelial damages are often irreversible. In the settings of ABO-incompatible transplantation and xenotransplantation, the presence of antibodies targeting graft antigens is not always associated with rejection. This resistance to antibodies toxicity seems to associate changes in endothelial cells phenotype and modification of the immune response. We describe here these mechanisms with a special focus on endothelial cells resistance to antibodies. Endothelial protection against anti-HLA antibodies has been described in vitro and in animal models, but do not seem to be a common feature in immunized allograft recipients. Complement regulation and anti-apoptotic molecules expression appear to be common features in all these settings. Lastly, pharmacological interventions that may promote endothelial cell protection against donor specific antibodies will be described.

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.

Laboratory support of ABO antibody monitoring for ABO-incompatible solid organ transplantation

The accurate measurement of ABO antibodies is essential for successful ABO-incompatible solid organ transplantation. Titration using two-fold dilution is considered a standard method and is applied in most laboratories. However, this titration method has inherent limitations, including differences in methods between laboratories, a lack of standardization, its semiquantitative nature, and the difficulty of considering the results to be representative of the in vivo activity of ABO antibodies. Various measurement methods other than titration have been developed, and new methods continue to be introduced. Physicians and laboratory specialists who are involved in ABO-incompatible solid organ transplantation need to fully understand these methods for optimal patient management.

Ex vivo enzymatic treatment converts blood type A donor lungs into universal blood type lungs

Donor organ allocation is dependent on ABO matching, restricting the opportunity for some patients to receive a life-saving transplant. The enzymes FpGalNAc deacetylase and FpGalactosaminidase, used in combination, have been described to effectively convert group A (ABO-A) red blood cells (RBCs) to group O (ABO-O). Here, we study the safety and preclinical efficacy of using these enzymes to remove A antigen (A-Ag) from human donor lungs using ex vivo lung perfusion (EVLP). First, the ability of these enzymes to remove A-Ag in organ perfusate solutions was examined on five human ABO-A1 RBC samples and three human aortae after static incubation. The enzymes removed greater than 99 and 90% A-Ag from RBCs and aortae, respectively, at concentrations as low as 1 μg/ml. Eight ABO-A1 human lungs were then treated by EVLP. Baseline analyses of A-Ag in lungs revealed expression predominantly in the endothelial and epithelial cells. EVLP of lungs with enzyme-containing perfusate removed over 97% of endothelial A-Ag within 4 hours. No treatment-related acute lung toxicity was observed. An ABO-incompatible transplant was then simulated with an ex vivo model of antibody-mediated rejection using ABO-O plasma as the surrogate for the recipient circulation using three donor lungs. The treatment of donor lungs minimized antibody binding, complement deposition, and antibody-mediated injury as compared with control lungs. These results show that depletion of donor lung A-Ag can be achieved with EVLP treatment. This strategy has the potential to expand ABO-incompatible lung transplantation and lead to improvements in fairness of organ allocation.

Hyperacute rejection in ABO-incompatible kidney transplantation: Significance of isoagglutinin subclass

INTRODUCTION

ABO-incompatible transplantation has expanded the limited donor pool for kidney transplantation. Despite the successful desensitization protocols and immunosuppression, undesirable cases of hyperacute rejection occurs.

OBJECTIVE

Flow cytometry was used to measure isoagglutinin titer and its IgG subclasses in assessment of the cause of hyperacute rejection in ABO-incompatible kidney transplantation.

MATERIALS AND METHODS

The recipient was admitted for kidney transplantation due to end-stage renal disease. Pre-transplantation work-up for ABO-incompatible kidney transplantation included blood group typing, HLA DNA typing and HLA antibody analyses. HLA crossmatch analysis was conducted using donor lymphocytes and anti-HLA antibody assay using Luminex panel reactive antibody test (One Lambda, Inc., Canoga Park, CA). Desensitization protocol was composed of therapeutic plasma exchange sessions and rituximab.

RESULTS

Despite negative HLA crossmatch results, a case of hyperacute rejection occurred after living donor kidney transplantation. Rejection resulted in immediate removal of graft, and the patient later received a second kidney transplantation. Retrospective evaluation of isoagglutinin titer and its subclasses using flow cytometry identified the cause of rejection to increased IgG1 subclass. Desensitization protocol for ABO-incompatible kidney transplantation now implements further caution for blood group O recipients.

DISCUSSION

Hyperacute rejection resulting from increased IgG1 isoagglutinin subclass has not been previously confirmed using flow cytometry. Unfortunate outcome of this rejection case provides insight to how we should approach and ensure successful ABO-incompatible kidney transplantation.

ABO-incompatible kidney transplantation in perspective of deceased donor transplantation and induction strategies: a propensity-matched analysis

Kidney transplant candidates are blood group incompatible with roughly one out of three potential living donors. We compared outcomes after ABO‐incompatible (ABOi) kidney transplantation with matched ABO‐compatible (ABOc) living and deceased donor transplantation and analyzed different induction regimens. We performed a retrospective study with propensity matching and compared patient and death‐censored graft survival after ABOi versus ABOc living donor and deceased donor kidney transplantation in a nationwide registry from 2006 till 2019. 296 ABOi were compared with 1184 center and propensity‐matched ABOc living donor and 1184 deceased donor recipients (matching: recipient age, sex, blood group, and PRA). Patient survival was better compared with deceased donor [hazard ratio (HR) for death of HR 0.69 (0.49–0.96)] and non‐significantly different from ABOc living donor recipients [HR 1.28 (0.90–1.81)]. Rate of graft failure was higher compared with ABOc living donor transplantation [HR 2.63 (1.72–4.01)]. Rejection occurred in 47% of 140 rituximab versus 22% of 50 rituximab/basiliximab, and 4% of 92 alemtuzumab‐treated recipients (P < 0.001). ABOi kidney transplantation is superior to deceased donor transplantation. Rejection rate and graft failure are higher compared with matched ABOc living donor transplantation, underscoring the need for further studies into risk stratification and induction therapy [NTR7587, www.trialregister.nl].

Kidney Transplantation with ABO-Incompatible Donors: A Comparison with Matched ABO Compatible Donor Transplants

Introduction:

ABO-incompatible kidney transplantation (ABOiKTx) expands the living donor pool. There is limited long-term outcome data from India especially in comparison with ABO-compatible kidney transplantation (ABOcKTx). Here we report outcomes of the first 100 ABOiKTx compared to ABOcKTx from our center.

Methods:

Between August 2013 and December 2019, 100 consecutive ABOiKTx were compared with 100 ABOcKTx done during the same period.Controls were matched for age, donor characteristics, HLA mismatches, and date of transplantation.

Results:

Mean (SD) follow up period was 25.9 ± 20.5 and 27.2 ± 20.6 months in ABOi and ABOcKTx respectively. Patient survival at 1 and 5 years post-transplant was 93.3 and 73.5% vs. 95.4 and 93% (P = 0.03), while graft survival rates were 85 and 60% vs. 93.1 and 83% in ABOi and ABOcKTx respectively (P = 0.03). The incidence of antibody-mediated rejections was 15% vs. 4%, and that of T-cell-mediated rejections was 10 vs. 12% respectively. Infections, malignancies, and surgical complications were similar. Level of anti ABO titers, HLA mismatches, recipient age, donor age, and presence of diabetes did not impact graft survival amongst ABOiKTx. The predicted survival and incidence of acute rejections and infections in the later 50 ABOiKTx transplants were better than the first 50 ABOiKTx when compared to their respective controls.

Conclusion:

Outcomes of ABOiKTx were inferior to ABOcKTx but tends to improve as more experience is gained. Incidence of ABMR was higher but infections and surgical complications were comparable. This data provides evidence that ABOiKTx is viable option for those without a ABO compatible donor.

Evaluation of Erythrocytes Magnetized Technology for Measurement of ABO Isoagglutinin Titers

Background  A variation in the measurement of ABO antibody titer has been seen among different laboratories due to lack of standardization. In our study, we aim to evaluate automated ABO isoagglutinin titer measurements by erythrocytes magnetized technology (EMT) and compare with conventional tube technique (TT).

Methods  We performed ABO isoagglutinin titration on samples received in a reference laboratory during a period of 2 months. A total of 134 tests for immunoglobulin G (IgG) titer and 116 for immunoglobulin M (IgM) for anti-A or anti-B were included in the study. Samples were processed for ABO isoagglutination titers by both TT and EMT by QWALYS-3 (DIAGAST, France). Microsoft Excel was used to compile data, for all calculations, and to draw graphs and plots. The number and percentage of cases within ±1, ±2, or ±3 titer difference (TT-EMT) were calculated.

Results  Median titers and their ranges obtained by EMT were higher or equal to those by TT for all IgM and IgG ABO-antibodies in all blood group (BGs), except anti-A IgM in (BG) O that was lower by EMT (32 [4:128]) than TT (48 [8:256]). One twenty one (121/134, 90.3%) cases of IgG titer showed an agreement by both methods (within ± one titer difference). One hundred seven cases (107/116, 92.2%) for IgM titer were within one titer difference by both the methods.

Conclusion  Results of titration by EMT-based automated instrument QWALYS-3 and conventional TT may vary by one titer dilution in the majority of cases. Use of consistent method for patient management is, therefore, advised.

Umbilical Cord Blood Units Cryopreserved in the Public Cord Blood Bank: A Breakthrough in iPSC Haplobanking?

The use of induced pluripotent stem cells (iPSCs) is an emerging therapeutic option for precision medicine. Cord blood (CB) cells with lower immunogenicity, fewer genomic changes, and persistent epigenetic memory might be ideal candidates for iPSC production. Based on the human leukocyte antigen (HLA) distribution of cord blood units (CBUs) in the public CB bank, we estimated the coverage of the Korean population with HLA-homozygous iPSCs to repurpose cryopreserved CBUs. We analyzed a total of 27,904 Korean CBUs donated to the public CB bank. Low-to-intermediate resolution typing was performed for HLA-A, -B, and -DRB1 alleles, and individuals possessing homozygous HLA haplotypes were identified by direct counting. Moreover, the matching probabilities for zero-mismatch transplantation were calculated for 27,904 CBUs and 50,000,000 potential Korean patients. Among the preserved CBUs, 15 HLA-A, 40 HLA-B, and 13 HLA-DRB1 alleles as well as 48 homozygous HLA-A-B-DRB1 haplotypes were identified at serological equivalents (2 digits). The 48 identified homozygous haplotypes cumulatively matched 78.18% of the 27,904 Korean CB donors as zero HLA-mismatch iPSC sources. Among the combinations of 1,699 haplotypes with frequencies greater than 0.001%, assuming a population of 50 million, those 48 haplotypes can provide a match for 78.37% of potential Korean recipients. A practicable number of HLA-A, -B, and -DRB1 homozygous iPSC lines derived from CBUs may be an efficient option in allogeneic iPSC therapy because this type of haplobanking may provide cell lines with optimal HLA matching for up to three-quarters of the Korean population.

Association between ABO and Duffy blood types and circulating chemokines and cytokines

Blood group antigens are inherited traits that may play a role in immune and inflammatory processes. We investigated associations between blood groups and circulating inflammation-related molecules in 3537 non-Hispanic white participants selected from the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial. Whole-genome scans were used to infer blood types for 12 common antigen systems based on well-characterized single-nucleotide polymorphisms. Serum levels of 96 biomarkers were measured on multiplex fluorescent bead-based panels. We estimated marker associations with blood type using weighted linear or logistic regression models adjusted for age, sex, smoking status, and principal components of population substructure. Bonferroni correction was used to control for multiple comparisons, with two-sided p values < 0.05 considered statistically significant. Among the 1152 associations tested, 10 were statistically significant. Duffy blood type was associated with levels of CXCL6/GCP2, CXCL5/ENA78, CCL11/EOTAXIN, CXCL1/GRO, CCL2/MCP1, CCL13/MCP4, and CCL17/TARC, whereas ABO blood type was associated with levels of sVEGFR2, sVEGFR3, and sGP130. Post hoc pairwise t-tests showed that individuals with type Fy(a+b−) had the lowest mean levels of all Duffy-associated markers, while individuals with type A blood had the lowest mean levels of all ABO-associated markers. Additional work is warranted to explore potential clinical implications of these differences.

Acute Rejection and Infectious Complications in ABO- and HLA-Incompatible Kidney Transplantations

Background

Patients receiving ABO-incompatible (ABOi) or human leukocyte antigen (HLA)-incompatible (HLAi) kidney transplantation (KT) require potent immunosuppression and are thus at a higher risk of infectious complications. We evaluated the clinical outcomes of KT stratified by ABO and HLA incompatibilities and identified the factors associated with the clinical outcomes.

Material/Methods

Recipients who underwent living-related KT between 2012 and 2017 were included and classified into 4 groups: ABO-compatible and HLA-compatible (ABOc/HLAc), HLA-incompatible (ABOc/HLAi), ABO-incompatible (ABOi/HLAc), and ABO-incompatible and HLA-incompatible (ABOi/HLAi). Cox proportional hazards regression analyses were carried out to evaluate the risk factors of acute rejection. Out of the 1732 patients who underwent KT, 1190, 131, 358, and 53 were in the ABOc/HLAc, ABOi/HLAc, ABOc/HLAi, and ABOi/HLAi groups, respectively.

Results

The ABO/HLAi group showed the lowest 5-year graft survival rate (91.7%). Death-censored graft survival was not significantly different among the groups. The mortality rate from infections was significantly higher in the ABOi/HLAi group (7.5%) than the other groups. Antibody-mediated rejection-free graft survival was the lowest in the ABOi/HLAi group, with significant differences compared with the ABOi/HLAc group (P=0.02) and the ABOc/HLAi group (P=0.03). ABOi/HLAi (hazard ratio [HR], 2.63; 95% confidence interval [CI], 1.04–6.65; P<0.01) and combined infection (HR, 1.91; 95% CI, 1.45–2.51; P<0.01) were significant risk factors for acute rejection.

Conclusions

Patients with both ABO and HLA incompatibilities showed inferior rates of overall patient and graft survival due to infectious complications. Infection was a prominent risk factor of acute rejection following KT after adjusting for possible confounders including ABO and HLA incompatibility.

Usefulness of the Hematopoietic Stem Cell Donor Pool as a Source of HLA-Homozygous Induced Pluripotent Stem Cells for Haplobanking: Combined Analysis of the Cord Blood Inventory and Bone Marrow Donor Registry

Induced pluripotent stem cells (iPSCs) have opened up unprecedented opportunities for novel therapeutic options for precision medicine. Hematopoietic stem cell (HSC) donor pools with previously determined HLA types may be ideal sources for iPSC production. Based on the HLA distribution of cryopreserved cord blood units (CBUs) and registered bone marrow (BM) donors, we estimated how much of the Korean population could be covered by HLA-homozygous iPSCs. We analyzed a total of 143,866 Korean HSC donors (27,904 CBUs and 115,962 BM donors). Each donor sample was typed for the HLA-A, -B, and -DRB1 alleles at low to intermediate resolution by DNA-based molecular techniques: PCR sequence-specific oligonucleotide (PCR-SSOP), PCR with sequence-specific primers (PCR-SSP) and PCR with sequence-based typing (PCR-SBT). We also identified individuals possessing homozygous HLA haplotypes by direct counting. The matching probabilities for zero-mismatch transplantation were calculated for 143,866 Koreans and 50 million potential Korean patients. Among the HSC donor pool, 17 HLA-A alleles, 41 HLA-B alleles, and 13 HLA-DRB1 alleles, as well as 128 homozygous HLA-A-B-DRB1 haplotypes, were identified at serologic equivalents, and those haplotypes cumulatively matched 93.20% of the 143,866 Korean donors as zero HLA-mismatch iPSC sources. Among the combinations of 2,056 haplotypes with frequencies ≥ 0.001% in a population of 50 million, those 128 homozygous haplotypes can provide 93.65% coverage for potential Korean recipients. Haplobanking of a reasonable number of HLA-A, -B, and -DRB1 homozygous iPSC lines derived from CBUs and cells of registered BM donors may be an efficient option for allogenic iPSC therapy.

Individualized Preconditioning for ABO-Incompatible Living-Donor Kidney Transplantation: An Initial Report of 48 Cases from China

Background

ABO-incompatible (ABOi) living-donor kidney transplantation (KTx) is well established in developed countries, but not yet in China.

Material/Methods

We developed individualized preconditioning protocols for ABOi KTx based on initial ABO antibody titers. After propensity score matching of ABOi with ABO-compatible (ABOc) KTx, post-transplant outcomes were compared.

Results

Between September 2014 and June 2018, 48 ABOi living-donor KTx candidates received individualized preconditioning, and all underwent subsequent KTx (median initial ABO titers: 16 for IgM and 16 for IgG). Thirty-one recipients (64.6%) were preconditioned with rituximab (median dose: 200 mg, range: 100–500 mg). Among 37 patients (77.1%) who received pre-transplant antibody removal, the median number of sessions of antibody removal required to achieve ABOi KTx was 2 (range: 1–5), which was conducted between days −10 and −1. Eleven ABOi recipients (22.9%) were preconditioned with oral immunosuppressants alone. Hyperacute rejection led to the loss of 2 grafts in the ABOi group. After a median follow-up of 27.6 months (ABOi group) and 29.8 months (ABOc group), there were no significant differences in graft/recipient survival, rejection, and infection. There were marginally higher rates of severe thrombocytopenia (<50×10⁹/L) (P=0.073) and delayed wound healing (P=0.096) in ABOi recipients.

Conclusions

Our individualized preconditioning protocol evolved as our experience grew, and the short-term clinical outcomes of ABOi KTx did not differ from those of matched ABOc patients. ABOi KTx may be a major step forward in expanding the kidney living-donor pool in China.

T cell reconstitution after lymphocyte depletion features a different pattern of inhibitory receptor expression in ABO- versus HLA-incompatible kidney transplant recipients

Chronic antigen stimulation can lead to immune exhaustion (a state of T cell dysfunction). Several phenotypical signatures of T cell exhaustion have been described in various pathological situations, characterized by aberrant expression of multiple inhibitory receptors (IR). This signature has been barely studied in the context of allogenic organ transplantation. We undertook a cross-sectional analysis of the expression of IR [CD244, CD279, T cell immunoreceptor with immunoglobulin (Ig) and immunoreceptor tyrosine-based inhibition motif (ITIM) domains (TIGIT) and CD57] and their correlation with cytokine-producing functions in T cells reconstituting after lymphocyte depletion in patients transplanted from living donors, with preformed donor-specific antibodies. After ABO incompatible transplantation, T cells progressively acquired a phenotype similar to healthy donors and the expression of several IR marked cells with increased functions, with the exception of TIGIT, which was associated with decreased cytokine production. In stark contrast, T cell reconstitution in patients with anti-human leukocyte antigen (HLA) antibodies was characterized with an increased co-expression of IR by T cells, and specifically by an increased expression of TIGIT. Furthermore, expression of these receptors was no longer directly correlated to cytokine production. These results suggest that T cell alloreactivity in HLA-incompatible kidney transplantation drives an aberrant T cell reconstitution with respect to IR profile, which could have an impact on the transplantation outcome.

Therapeutic apheresis in kidney transplantation: An updated review

Therapeutic apheresis is a cornerstone of therapy for several conditions in transplantation medicine and is available in different technical variants. In the setting of kidney transplantation, immunological barriers such as ABO blood group incompatibility and preformed donor-specific antibodies can complicate the outcome of deceased- or living- donor transplantation. Postoperatively, additional problems such as antibody-mediated rejection and a recurrence of primary focal segmental glomerulosclerosis can limit therapeutic success and decrease graft survival. Therapeutic apheresis techniques find application in these issues by separating and selectively removing exchanging or modifying pathogenic material from the patient by an extracorporeal aphaeresis system. The purpose of this review is to describe the available techniques of therapeutic aphaeresis with their specific advantages and disadvantages and examine the evidence supporting the application of therapeutic aphaeresis as an adjunctive therapeutic option to immunosuppressive agents in protocols before and after kidney transplantation.

Latest insights on ABO-incompatible living-donor renal transplantation

This review summarizes the latest insights on ABO‐incompatible living‐donor renal transplantation. Desensitization protocols and clinical outcomes were investigated, and a comparison was made with kidney‐paired donation, which is not permitted in Japan for ethical reasons. Although renal transplantation is greatly beneficial for most patients with end‐stage kidney disease, many of these patients must remain on dialysis therapy for extended periods due to the scarcity of organs from deceased donors. ABO blood type incompatibility was once believed to be a contraindication to renal transplantation due to the increased risk for antibody‐mediated rejection and early graft loss attributable to isoagglutinins. Recently, pretransplant desensitization strategies, such as removal of isoagglutinins and antibody‐producing cells, have achieved successful outcomes, although it remains unclear whether graft survival and patient morbidity are equivalent to those for ABO‐compatible renal transplantation. The present review suggested that ABO‐incompatible living‐donor renal transplantation might be a favorable radical renal replacement therapy for patients with end‐stage kidney disease.

Clinical significance of isoagglutinin titre with the current desensitization protocol in ABO-incompatible kidney transplantation

AIM

ABO-incompatible (ABOi) kidney transplantation (KT) has become a routine procedure with graft survival rates comparable to those of ABO-compatible KT. However, the clinical significance of the isoagglutinin titre in ABOi KT remains uncertain. Therefore, in this study, we analysed the clinical outcomes of ABOi KT according to the baseline and post-operative isoagglutinin titre.

METHODS

All patients who received ABOi KT between 2009 and 2013 were reviewed and followed up until December 2016. The patients were classified according to baseline (<1:128 or ≥1:128) and post-operative rebound isoagglutinin titre (<1:16 or ≥1:16), and the clinical outcomes of KT were compared.

RESULTS

Patients with a high baseline isoagglutinin titre showed a poor titre reduction rate (1.48 ± 0.41 vs 1.32 ± 0.34, P = 0.008), and more patients experienced titre rebound ≥1:16 after KT (15.0% vs 35.8%, P = 0.002). The occurrence of both T-cell-mediated rejection and antibody-mediated rejection did not show a significant difference (P = 0.805 and 0.714, respectively). The rate of rejection-free survival was not different among groups (P = 0.680, log-rank test). Furthermore, the rate of death-censored graft survival was not different among groups (P = 0.701, log-rank test). Urinary tract infection was the most frequently reported infectious complication overall. The incidence of urinary tract infection, pneumonia and viral infections (BK virus and cytomegalovirus) was not different among groups.

CONCLUSION

In conclusion, high baseline isoagglutinin titre was associated with a high rebound isoagglutinin titre, low titre reduction rates and more sessions of plasmapheresis. However, the isoagglutinin titre may not be as important as it was in the past in ABOi KT if appropriate desensitization is performed.

Clinical Outcomes of ABO-Incompatible Kidney Transplantation in Patients with End-Stage Kidney Disease due to Diabetes Nephropathy

BACKGROUND

Diabetes nephropathy is one of the most common causes of end-stage kidney disease (ESKD) worldwide. The data are clear that kidney transplantation is superior to remaining on dialysis for patients with diabetes. However, there have been no reports on ABO-incompatible kidney transplantation in patients with ESKD due to diabetes nephropathy.

PATIENTS AND METHODS

We conducted a retrospective, observational study to investigate the clinical outcomes of ABO-incompatible kidney transplantation for patients with pre-existing diabetes nephropathy at our institution from April 2011 to October 2017. A total of 14 recipients were enrolled in this study.

RESULTS

All 14 patients underwent successful kidney transplantation. Both overall patient and graft survival rates were 100, 89.9, and 89.9% at 1, 3, and 5 years, respectively. One patient died 20 months after transplantation with a functioning graft due to pancreas cancer. Two of the 14 patients (14.3%) developed biopsy-proven acute cellular rejection during the follow-up period. The median observation period was 32.0 months (range 5-83 months).

CONCLUSION

ABO-incompatible kidney transplantation may be an acceptable renal replacement therapy for ESKD patients with diabetes.

Steroid Withdrawal Using Everolimus in ABO-Incompatible Kidney Transplant Recipients With Post-Transplant Diabetes Mellitus

BACKGROUND

The effectiveness of everolimus (EVR) for ABO-incompatible (ABOi) kidney transplantation is unknown. We evaluated outcomes of conversion from steroid to EVR in ABOi kidney transplant recipients.

METHODS

We performed a retrospective observational cohort study of 33 de novo consecutive adult ABOi living donor kidney transplant recipients. Desensitization was performed using 0 to 4 sessions of plasmapheresis and 1 to 2 doses of 100 mg rituximab according to the anti-A/B antibody titer. ABOi recipients were administered a combination of tacrolimus, mycophenolate mofetil, and methylprednisolone. Diabetic patients were converted from methylprednisolone to EVR at 1 to 15 months post-transplantation to prevent diabetes progression. Graft outcomes, hemoglobin A1c (HbA1c) levels, and cytomegalovirus infection rates were compared between the EVR (n = 11) and steroid (n = 22) groups.

RESULTS

Mean postoperative duration was 814 and 727 days in the EVR and steroid groups, respectively (P = .65). Between the 2 groups, graft survival rate (100% vs 95.5%, P > .99), acute rejection rate (9.1% vs 18.2%, P = .64), and serum creatinine levels (1.46 mg/dL vs 1.68 mg/dL, P = .66) were comparable. Although HbA1c levels were elevated in the steroid group (5.47%, 5.87%; P = .003), no significant deterioration was observed in the EVR group without additional insulin administration (6.10%, 6.47%; P = .21). Cytomegalovirus infection rate was significantly lower in the EVR group than in the steroid group (18.2% vs 63.6%, P = .026).

CONCLUSION

Conversion from steroid to EVR in ABOi kidney transplant recipients maintained excellent graft outcomes and avoided diabetes progression and cytomegalovirus infection.

Glycosphingolipids of human embryonic stem cells

The application of human stem cell technology offers theoretically a great potential to treat various human diseases. However, to achieve this goal a large number of scientific issues remain to be solved. Cell surface carbohydrate antigens are involved in a number of biomedical phenomena that are important in clinical applications of stem cells, such as cell differentiation and immune reactivity. Due to their cell surface localization, carbohydrate epitopes are ideally suited for characterization of human pluripotent stem cells. Amongst the most commonly used markers to identify human pluripotent stem cells are the globo-series glycosphingolipids SSEA-3 and SSEA-4. However, our knowledge regarding human pluripotent stem cell glycosphingolipid expression was until recently mainly based on immunological assays of intact cells due to the very limited amounts of cell material available. In recent years the knowledge regarding glycosphingolipids in human embryonic stem cells has been extended by biochemical studies, which is the focus of this review. In addition, the distribution of the human pluripotent stem cell glycosphingolipids in human tissues, and glycosphingolipid changes during human stem cell differentiation, are discussed.

Biomimetic Principles to Develop Blood Compatible Surfaces

Functionalized biomaterial surface patterns capable of resisting nonspecific adsorption while retaining their bioactivity are crucial in the advancement of biomedical technologies, but currently available biomaterials intended for use in whole blood frequently suffer from nonspecific adsorption of proteins and cells, leading to a loss of activity over time. In this review, we address two concepts for the design and modification of blood compatible biomaterial surfaces, zwitterionic modification and surface functionalization with glycans – both of which are inspired by the membrane structure of mammalian cells – and discuss their potential for biomedical applications.

Endothelial Cells in Antibody-Mediated Rejection of Kidney Transplantation: Pathogenesis Mechanisms and Therapeutic Implications

Antibody-mediated rejection (AMR) has been identified as a main obstacle for stable immune tolerance and long survival of kidney allografts. In spite of new insights into the underlying mechanisms of AMR, accurate diagnosis and efficient treatment are still challenges in clinical practice. Endothelium is the first barrier between recipients' immune systems and grafts in vascularized organ transplants. Considering that endothelial cells express a number of antigens that can be attacked by various allo- and autoantibodies, endothelial cells act as main targets for the recipients' humoral immune responses. Importantly, emerging evidence has shown that endothelial cells in transplants could also initiate protective mechanisms in response to immune injuries. A better understanding of the role of endothelial cells during the pathogenesis of AMR might provide novel therapeutic targets. In the present review, we summarize the antigens expressed by endothelial cells and also discuss the activation and accommodation of endothelial cells as well as their clinical implications. Collectively, the progress discussed in this review indicates endothelial cells as promising targets to improve current diagnosis and therapeutic regimens for AMR.

Histone deacetylase inhibitors suppress ABO transcription in vitro, leading to reduced expression of the antigens

BACKGROUND

The ABO system is of fundamental importance in the fields of transfusion and transplantation and has apparent associations with certain diseases, including cardiovascular disorders. ABO expression is reduced in the late phase of erythroid differentiation in vitro, whereas histone deacetylase inhibitors (HDACIs) are known to promote cell differentiation. Therefore, whether or not HDACIs could reduce the amount of ABO transcripts and A or B antigens is an intriguing issue.

STUDY DESIGN AND METHODS

Quantitative polymerase chain reactions were carried out for the ABO transcripts in erythroid-lineage K562 and epithelial-lineage KATOIII cells after incubation with HDACIs, such as sodium butyrate, panobinostat, vorinostat, and sodium valproate. Flow cytometric analysis was conducted to evaluate the amounts of antigen in KATOIII cells treated with panobinostat. Quantitative chromatin immunoprecipitation (ChIP) assays and luciferase assays were performed on both cell types to examine the mechanisms of ABO suppression.

RESULTS

HDACIs reduced the ABO transcripts in both K562 and KATOIII cells, with panobinostat exerting the most significant effect. Flow cytometric analysis demonstrated a decrease in B-antigen expression on panobinostat-treated KATOIII cells. ChIP assays indicated that panobinostat altered the modification of histones in the transcriptional regulatory regions of ABO, and luciferase assays demonstrated reduced activity of these elements.

CONCLUSION

ABO transcription seems to be regulated by an epigenetic mechanism. Panobinostat appears to suppress ABO transcription, reducing the amount of antigens on the surface of cultured cells.

Treatment of large plasma volumes using specific immunoadsorption to desensitize ABO-incompatible kidney-transplant candidates

Background

ABO-incompatible (ABOi) kidney-transplantation has very good long-term results, i.e. similar to those observed for living-kidney ABO-compatible transplantation. This is because patients are desensitized at pretransplant using apheresis and rituximab therapy, with tacrolimus-based immunosuppression.

Objectives

To assess the efficacy of a single, pretransplant (Day –1), specific immunoadsorption session using Glycosorb® columns (anti-A or anti-B; Glycorex Sweden) to treat large volumes of plasma (up to 18 L).

Patients and Methods

Prospective single-center study evaluating 12 consecutive patients (6 males), aged 40 (23–59) years. Incompatibilities were A into 0 (8), B into 0 (3), and AB into 0 (1). Pretransplant desensitization relied on rituximab (D–30), tacrolimus, mycophenolic acid, and steroids (all started on D–13), and a single session of specific immunoadsorption on D–1. Immunoadsorption was coupled in tandem with a hemodialysis session.

Results

Overall, 15 L (11–18) of plasma were treated per patient, i.e., 0.2 (0.11–0.36 L/kg). Isoagglutinin titers were 1/16 (1/5–1/64) before the procedure, decreasing after 6 hours to 1/5 (1/1–1/16 P = 0.008), and to 1/2 (1/1–1/8; P = 0.05) at completion of the session. The next day, i.e., the day of transplantation, there was no rebound of isoagglutinins [1/4 (1/1–1/5); P = ns]. The procedure was well tolerated with no side-effects and no significant changes in hemoglobin level, platelet counts, fibrinogen, or albumin levels.

Conclusions

For ABOi kidney-transplantation, a single, longer, specific immunoadsorption session was very efficient at 1-day pre-transplantation with no rebound. These results should be confirmed when isoagglutinin titers are higher (≥120).