Histological and Extended Clinical Outcomes After ABO-Incompatible Renal Transplantation Without Splenectomy or Rituximab

A Multicenter Retrospective Cohort Study on Management Protocols and Clinical Outcomes After ABO-incompatible Kidney Transplantation in India

BACKGROUND

There is no robust evidence-based data for ABO-incompatible kidney transplantation (ABOiKT) from emerging countries.

METHODS

Data from 1759 living donor ABOiKT and 33 157 ABO-compatible kidney transplantations (ABOcKT) performed in India between March 5, 2011, and July 2, 2022, were included in this retrospective, multicenter (n = 25) study. The primary outcomes included management protocols, mortality, graft loss, and biopsy-proven acute rejection (BPAR).

RESULTS

Protocol included rituximab 100 (232 [13.18%]), 200 (877 [49.85%]), and 500 mg (569 [32.34%]); immunoadsorption (IA) (145 [8.24%]), IVIG (663 [37.69%]), and no induction 200 (11.37%). Mortality, graft loss, and BPAR were reported in 167 (9.49%), 136 (7.73%), and 228 (12.96%) patients, respectively, over a median follow-up of 36.3 mo. In cox proportional hazard model, mortality was higher with IA (hazard ratio [HR]: 2.53 [1.62-3.97]; P  < 0.001), BPAR (HR: 1.83 [1.25-2.69]; P  = 0.0020), and graft loss (HR: 1.66 [1.05-2.64]; P  = 0.0310); improved graft survival was associated with IVIG (HR: 0.44 [0.26-0.72]; P  = 0.0010); higher BPAR was reported with conventional tube method (HR: 3.22 [1.9-5.46]; P  < 0.0001) and IA use (HR: 2 [1.37-2.92]; P  < 0.0001), whereas lower BPAR was reported in the prepandemic era (HR: 0.61 [0.43-0.88]; P  = 0.008). Primary outcomes were not associated with rituximab dosing or high preconditioning/presurgery anti-A/anti-B titers. Incidence of overall infection 306 (17.39%), cytomegalovirus 66 (3.75%), and BK virus polyoma virus 20 (1.13%) was low. In unmatched univariate analysis, the outcomes between ABOiKT and ABOcKT were comparable.

CONCLUSIONS

Our largest multicenter study on ABOiKT provides insights into various protocols and management strategies with results comparable to those of ABOcKT.

Advancement in preoperative desensitization therapy for ABO incompatible kidney transplantation recipients

ABO incompatibility has long been considered an absolute contraindication for kidney transplantation. However, with the increasing number of patients with ESRD in recent years, ABO-incompatible kidney transplantation (ABOi-KT) has expanded the types of donors by crossing the blood group barrier through preoperative desensitization therapy. At present, the desensitization protocols consist of removal of preexisting ABO blood group antibody titers and prevention of ABO blood group antibody return. Studies have suggested similar patient and graft survival among ABOi-KT and ABOc-KT recipients. In this review, we will summarize the effective desensitization regimens of ABOi-KT, aiming to explore effective ways to improve the success rate and the long-term survival rate of ABOi-KT recipients.

ABO Incompatible Kidney Transplantation Without B-cell Depletion is Associated With Increased Early Acute Rejection: A Single-Center Australian Experience

We performed a single-center retrospective cohort study of 66 consecutive ABO incompatible kidney transplants (ABOiKT) performed without B-cell depleting therapy. Outcomes were compared to an earlier era performed with rituximab (n = 18) and a contemporaneous cohort of ABO compatible live donor transplants (ABOcKT). Acute rejection within 3 months of transplant was significantly more common after rituximab-free ABOiKT compared to ABOiKT with rituximab (OR 8.8, p = 0.04) and ABOcKT (OR 2.9, p = 0.005) in adjusted analyses. Six recipients of rituximab-free ABOiKT experienced refractory antibody mediated rejection requiring splenectomy, and a further two incurred early graft loss with no such episodes amongst ABOiKT with rituximab or ABOcKT cohorts. Patient and graft survival were similar between groups over a median follow-up of 3.1 years. This observational evidence lends strong support to the continued inclusion of rituximab in desensitization protocols for ABOiKT.

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.

Renal Biopsy and Clinical Outcomes in Patients With ABO-Incompatible Renal Transplant: Experience From a Tertiary Care Hospital

OBJECTIVES

Renal transplant with ABO-incompatible donors expands the donor pool. Earlier studies have focused the use of protocol biopsies in ABO-incompatible transplant patients. Our study described outcomes of indication (for cause) renal biopsies and clinical outcomes in patients with ABO-incompatible renal transplant.

MATERIALS AND METHODS

This retrospective study included 164 patients from January 2012 to June 2019. Biochemical parameters, serial immunoglobulin G anti-ABO titers, and class I and II donor-specific antibody findings were obtained from hospital records, and renal graft biopsies were reviewed according to the Banff 2017 update.

RESULTS

We analyzed the results of 65 biopsies from 54 patients. Biopsy-proven acute antibody-mediated rejection (12.8%) was found to be more prevalent than acute cellular rejection (1.8%). Patients with antibodymediated rejection all had microvascular inflammation (g+ptc score of 2 or more, where g+ptc is the sum of the glomerulitis and peritubular capillaritis scores) and were positive for C4d. Acute tubular injury per se was seen in 10.3% of patients; 65% of these patients had C4d positivity in peritubular capillaries, and only 1 patient developed chronic active antibody-mediated rejection on follow-up. Patient and death-censored graft survival rates were 92% and 98% at 1 year after transplant and 88% and 91% at 3 years, respectively. Patients with an episode of antibody-mediated rejection had lower rates of patient (76.5%) and deathcensored graft survival (84.6%) at 1 year.

CONCLUSIONS

The microvascular inflammation score (g+ptc score of 2 or higher) is more reliable than diffuse C4d positivity to determine antibody-mediated rejection in ABO-incompatible transplants because diffuse C4d positivity may also be seen in etiologies unrelated to antibody-mediated rejection. Acute tubular injury with C4d positivity without microvascular injury does not confirm antibody-mediated rejection. We suggest that Banff classification be updated in ABO-incompatible transplants to include diagnostic criteria for the diagnosis of antibody-mediated rejection.

A Safe Anti-A2 Titer for a Successful A2 Incompatible Kidney Transplantation: A Single-center Experience and Review of the Literature

Background.

Kidney allocation system allows blood type B candidates accept kidneys from A2/A2B donors. There is no mandate by UNOS on which the anti-A2 level is acceptable. We aimed to investigate the safety of kidney transplant in blood group B patients with anti-A2 titers ≤16.

Methods.

We performed 41 A2-incompatible kidney transplants in blood group B recipients between May 2015 and September 2019. Clinical outcomes were compared with a control group of 75 blood group B recipients who received blood group compatible kidney transplantation at the same period.

Results.

Of the 41 recipients, 85% were male, 48% African American, with a median age of 53 (20–73) y. Thirty-eight (93%) were deceased-donor and 3 (7%) were living-donor kidney transplant recipients. Pretransplant anti-A2 IgG titers were 2 in 16, 4 in 9, 8 in 6, and 16 in 5 and too weak to titer in 5 recipients. Eight patients had pretransplant donor-specific antibodies. During a median follow-up of 32.6 mo (6–57.3) patient and graft survival were 100% and 92% in the A2-incompatible kidney transplant group, and 91% and 92% in the blood group compatible group, respectively. Twelve A2-incompatible recipients underwent a 21 clinically indicated kidney biopsies at a median 28 d (6–390) after transplantation. None of the patients developed acute antibody-mediated rejection and 2 patients (5%) had acute T-cell–mediated rejection. Interestingly, peritubular capillary C4d positivity was seen in 7 biopsies which did not have any findings of acute rejection or microvascular inflammation but not in any of the rejection-free biopsies in the control group. C4d positivity was persistent in 5 of those patients who had follow-up biopsies.

Conclusions.

A2-incompatible transplantation is safe in patients with anti-A2 titers ≤16 with excellent short-term kidney allograft outcomes. C4d positivity is frequent in allograft biopsies without acute rejection.

Characteristics of Immunoglobulin M Type Antibodies of Different Origins from the Immunologic and Clinical Viewpoints and Their Application in Controlling Antibody-Mediated Allograft Rejection

Antibody-mediated allograft rejection (AMR) hinders patient prognosis after organ transplantation. Current studies concerning AMR have mainly focused on the diagnostic value of immunoglobulin G (IgG)-type donor-specific antihuman leukocyte antigen antibodies (DSAs), primarily because of their antigen specificity, whereas the clinical significance of immunoglobulin M (IgM)-type DSAs has not been thoroughly investigated in the context of organ transplantation because of their nonspecificity against antigens. Although consensus regarding the clinical significance and role of IgM antibodies is not clear, as discussed in this review, recent findings strongly suggest that they also have a huge potential in novel diagnostic as well as therapeutic application for the prevention of AMR. Most serum IgM antibodies are known to comprise natural antibodies with low affinity toward antigens, and this is derived from B-1 cells (innate B cells). However, some of the serum IgM-type antibodies reportedly also produced by B-2 cells (conventional B cells). The latter are known to have a high affinity for donor-specific antigens. In this review, we initially discuss how IgM-type antibodies of different origins participate in the pathology of various diseases, directly or through cell surface receptors, complement activation, or cytokine production. Then, we discuss the clinical applicability of B-1 and B-2 cell-derived IgM-type antibodies for controlling AMR with reference to the involvement of IgM antibodies in various pathological conditions.

Everolimus Initiation With Early Calcineurin Inhibitor Withdrawal in De Novo Heart Transplant Recipients: Long-term Follow-up From the Randomized SCHEDULE Study

BACKGROUND

A calcineurin inhibitor (CNI)-free immunosuppressive regimen has been demonstrated to improve renal function early after heart transplantation, but long-term outcome of such a strategy has not been well described.

METHODS

In the randomized SCHEDULE trial, de novo heart transplant recipients received (1) everolimus with reduced-exposure CNI (cyclosporine) followed by CNI withdrawal at week 7-11 posttransplant or (2) standard-exposure cyclosporine, both with mycophenolate mofetil and corticosteroids; 95/115 randomized patients were followed up at 5-7 years posttransplant.

RESULTS

Mean measured glomerular filtration rate was 74.7 mL/min and 62.4 mL/min with everolimus and CNI, respectively. The mean difference was in favor of everolimus by 11.8 mL/min in the intent-to-treat population (P = 0.004) and 17.2 mL/min in the per protocol population (n = 75; P < 0.001). From transplantation to last follow-up, the incidence of biopsy-proven acute rejection (BPAR) was 77% (37/48) and 66% (31/47) (P = 0.23) with treated BPAR in 50% and 23% (P < 0.01) in the everolimus and CNI groups, respectively; no episode led to hemodynamic compromise. Coronary allograft vasculopathy (CAV) assessed by coronary intravascular ultrasound was present in 53% (19/36) and 74% (26/35) of everolimus- and CNI-treated patients, respectively (P = 0.037). Graft dimensions and function were similar between the groups. Late adverse events were comparable.

CONCLUSIONS

These results suggest that de novo heart transplant patients randomized to everolimus and low-dose CNI followed by CNI-free therapy maintain significantly better long-term renal function as well as significantly reduced CAV than patients randomized to standard CNI treatment. Increased BPAR in the everolimus group during year 1 did not impair long-term graft function.

ABO-incompatible living kidney transplantation

ABO-incompatible living kidney transplantation is nowadays a routine procedure to expand living donor pool. The past decades have seen the evolution of desensitization protocol and immunosuppression regimen. Despite increased bleeding events, infectious complications, and rejection episodes reported in some studies, favorable graft and patient survival rate are now achieved, regardless of various protocols among transplant centers. Several issues such as the usage of rituximab and standardization of blood group antibody titration remain to be settled. The deposition of C4d is no longer the histopathologic hallmark of antibody-mediated rejection, which have inspired innovative strategies of peripheral molecular screening and the improvement of histological diagnosis of AMR (antibody-mediated rejection). The better understanding of the underlying mechanism might facilitate the distinction and therapeutic schemes of AMR.

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 outcomes after ABO-incompatible renal transplantation: a systematic review and meta-analysis

BACKGROUND

ABO-incompatible renal transplantation (ABOi-rTx) is increasingly used to overcome organ shortage. Evidence about its non-inferiority in comparison with ABO-compatible renal transplantation (ABOc-rTx) needs to be analysed at early and late timepoints. We aimed to investigate differences in outcome after ABOi-rTX and ABOc-rTX.

METHODS

We did a systematic review and meta-analysis of observational studies published up until Dec 31, 2017, that reported outcome data (≥1 year of follow-up) after ABOi-rTx and included an ABO-compatible control group, by searching the Cochrane Central Register of Controlled Trials (CENTRAL), Embase Ovid, MEDLINE Ovid, and PubMed. Trials on recipients of ABOi-rTx were assessed, if an ABO-compatible control group was included and if outcome data on at least graft or recipient survival with 1 year or more of follow-up were available. Exclusion criteria included case reports, editorials, reviews and letters, animal studies, meeting papers, studies unable to extract data, non-renal solid organ and bone-marrow transplant studies, and deceased donor ABOc-rTx. Data were extracted from published reports. Primary endpoints were all-cause mortality and graft survival at 1, 3, 5, and more than 8 years after transplantation. In the meta-analysis, we used a fixed-effects model if the I² value was 0, and both a fixed-effects and random-effects model if I² was more than 0. This study is registered with PROSPERO, number CRD42018094550.

FINDINGS

1264 studies were screened and 40 studies including 49 patient groups were identified. 65 063 patients were eligible for analysis, 7098 of whom had undergone ABOi-rTx. Compared with ABOc-rTx, ABOi-rTx was associated with significantly higher 1-year mortality (odds ratio [OR] 2·17 [95% CI 1·63-2·90], p<0·0001; I²=37%), 3 years (OR 1·89 [1·46-2·45], p<0·0001; I²=29%), and 5 years (OR 1·47 [1·08-2·00], p=0·010; I²=68%) following transplantation. Death-censored graft survival was lower with ABOi-rTx than with ABOc-rTx at 1 year (OR 2·52 [1·80-3·54], p<0·0001; I²=61%) and 3 years (OR 1·59 [1·15-2·18], p=0·0040; I²=58%) only. Graft losses were equivalent to that of ABOc-rTx after 5 years and patient survival after 8 years. No publication bias was detected and the results were robust to trial sequential analysis until 5 years after transplantation; thereafter, data became futile or inconclusive.

INTERPRETATION

Despite progress in desensitisation protocols and optimisation of ABOi-rTx procedures, excess mortality and loss of kidney grafts was found compared with ABOc-rTx within the first 3 years after transplantation. Only long-term outcomes after 5 years yielded equivalent survival rates and organ function. Awareness of the increased risks of infection, organ rejection, and bleeding could improve care of patients and promote efforts towards paired kidney exchange programmes.

FUNDING

None.

ABO-incompatible kidney transplantation as a renal replacement therapy-A single low-volume center experience in Japan

INTRODUCTION

Living donor kidney transplantation is preferable to deceased donor transplantation due to its superior long-term patient and graft survivals. However, ABO blood group incompatibility is a major barrier to living donor kidney transplantation. ABO-incompatible kidney transplantation has been performed in Japan since the late 1980's, but it is still globally uncommon. The objective of this study is to compare the clinical outcomes of ABO-incompatible kidney transplantation (ABO-IKT) with that of ABO-compatible kidney transplantation (ABO-CKT) at an institution where only about two kidney transplants are performed a month on average.

DESIGN

A single center propensity score-matched cohort study.

PATIENTS AND METHODS

We retrospectively collected and analyzed the data of 240 patients with end-stage kidney disease (ESKD) who underwent living donor kidney transplantation at Osaka City University Hospital from January 1999 to December 2016, of which 66 patients were ABO-IKT. The remaining 174 patients who underwent ABO-CKT were studied as the control group, and the clinical outcomes of ABO-IKT and ABO-CKT recipients were compared based on propensity score matching.

RESULTS

After propensity score matching, there were no significant differences in both patient survival and death-censored graft survival rates between the ABO-IKT and ABO-CKT groups. Moreover, there were no significant differences in estimated glomerular filtration rate as well as frequency of acute cellular rejection, antibody-mediated rejection, infectious adverse events, malignancies, and post-operative bleeding between the two groups.

CONCLUSION

Currently, ABO-IKT may be an acceptable treatment for patients with ESKD even at a low-volume transplant center.

Five-year outcomes in kidney transplant patients randomized to everolimus with cyclosporine withdrawal or low-exposure cyclosporine versus standard therapy

HERAKLES was a 1-year randomized, multicenter trial. Patients were randomized at 3 months after kidney transplantation to remain on cyclosporine-based therapy, switch to everolimus without a calcineurin inhibitor (CNI), or switch to everolimus with low-exposure cyclosporine. Overall, 417 of 497 (83.9%) patients from the core study entered a 4-year extension study. The randomized regimen was continued to year 5 in 75.9%, 41.9% and 24.6% of patients in the standard-CNI, CNI-free and low-CNI groups, respectively. Adjusted estimated GFR at year 5 was significantly higher in the CNI-free group versus standard CNI (difference 7.2 mL/min/1.73 m² , P < .001) or low CNI (difference 7.6 mL/min/1.73 m² , P < .001). For patients who continued randomized therapy for 5 years, differences were 14.4 mL/min/1.73 m²  and 10.1 mL/min/1.73 m² , respectively. Biopsy-proven acute rejection occurred during the 4-year extension study in 7.6%, 8.6%, and 9.0% of patients in the standard-CNI, CNI-free and low-CNI groups, respectively (P = .927). In conclusion, conversion to a CNI-free everolimus regimen 3 months after kidney transplantation improved long-term graft function, particularly in patients who continued the CNI-free regimen. Low CNI with everolimus did not improve renal function. Efficacy was comparable between groups but frequent immunosuppression changes should be taken into account.

Favorable results in ABO-incompatible renal transplantation without B cell-targeted therapy: Advantages and disadvantages of rituximab pretreatment

The effectiveness of desensitization with rituximab in ABO-incompatible renal transplantation (ABO-I) has been widely reported. However, ABO-I outcomes are still worse than those of ABO-identical or ABO-compatible renal transplantation (ABO-Id/C). We retrospectively examined the outcomes in consecutive living donor ABO-Id/C (n = 412) and ABO-I (n = 205) cases to elucidate the causes of inferiority in ABO-I. ABO-I cases included recipients treated with rituximab (RIT, n = 131), splenectomy (SPX, n = 21), or neither because of low anti-A/B antibody titers (NoR/S, n = 53). Graft survival, infection, and de novo HLA antibody production were compared for ABO-I and ABO-Id/C, followed by stratification into RIT and NoR/S groups. Propensity score-based methods were employed to limit selection bias and potential confounders. Overall graft survival for ABO-I was significantly lower than that for ABO-Id/C (92.8% vs 97.2% after 5 years, P = .0037). Graft loss due to infection with ABO-I was significantly more frequent than that with ABO-Id/C, whereas acute antibody-mediated rejection (AMR) caused no graft failure in ABO-I recipients. Stratified analysis demonstrated significantly higher infection risk with RIT than with NoR/S. Safe reduction or avoidance of rituximab in desensitization protocols might contribute to further improvement of ABO-I outcome.

The UK National Registry of ABO and HLA Antibody Incompatible Renal Transplantation: Pretransplant Factors Associated With Outcome in 879 Transplants

BACKGROUND

ABO and HLA antibody incompatible (HLAi) renal transplants (AIT) now comprise around 10% of living donor kidney transplants. However, the relationship between pretransplant factors and medium-term outcomes are not fully understood, especially in relation to factors that may vary between centers.

METHODS

The comprehensive national registry of AIT in the United Kingdom was investigated to describe the donor, recipient and transplant characteristics of AIT. Kaplan-Meier analysis was used to compare survival of AIT to all other compatible kidney transplants performed in the United Kingdom. Cox proportional hazards regression modeling was used to determine which pretransplant factors were associated with transplant survival in HLAi and ABOi separately. The primary outcome was transplant survival, taking account of death and graft failure.

RESULTS

For 522 HLAi and 357 ABO incompatible (ABOi) transplants, 5-year transplant survival rates were 71% (95% confidence interval [CI], 66-75%) for HLAi and 83% (95% CI, 78-87%) for ABOi, compared with 88% (95% CI, 87-89%) for 7290 standard living donor transplants, and 78% (95% CI, 77-79%) for 15 322 standard deceased donor transplants (P < 0.0001). Increased chance of transplant loss in HLAi was associated with increasing number of donor specific HLA antibodies, center performing the transplant, antibody level at the time of transplant, and an interaction between donor age and dialysis status. In ABOi, transplant loss was associated with no use of IVIg, cytomegalovirus seronegative recipient, 000 HLA donor-recipient mismatch; and increasing recipient age.

CONCLUSIONS

Results of AIT were acceptable, certainly in the context of a choice between living donor AIT and an antibody compatible deceased donor transplant. Several factors were associated with increased chance of transplant loss, and these can lead to testable hypotheses for further improving therapy.