Outcome of patients with preformed donor-specific antibodies following alemtuzumab induction and tacrolimus monotherapy

Application of HLA molecular level mismatching in ethnically diverse kidney transplant recipients receiving a steroid-sparing immunosuppression protocol

Defining HLA mismatch at the molecular compared with the antigen level has been shown to be superior in predicting alloimmune responses, although data from across different patient populations are lacking. Using HLA-Matchmaker, HLA-EMMA and PIRCHE-II, this study reports on the association between molecular mismatch (MolMM) and de novo donor-specific antibody (dnDSA) in an ethnically diverse kidney transplant population receiving a steroid-sparing immunosuppression protocol. Of the 419 patients, 51 (12.2%) patients had dnDSA. De novo DSA were seen more frequently with males, primary transplants, patients receiving tacrolimus monotherapy, and unfavorably HLA-matched transplants. There was a strong correlation between MolMM load and antigen mismatch, although significant variation of MolMM load existed at each antigen mismatch. MolMM loads differed significantly by recipient ethnicity, although ethnicity alone was not associated with dnDSA. On multivariate analysis, increasing MolMM loads associated with dnDSA, whereas antigen mismatch did not. De novo DSA against 8 specific epitopes occurred at high frequency; of the 51 patients, 47 (92.1%) patients with dnDSA underwent a pretreatment biopsy, with 21 (44.7%) having evidence of alloimmune injury. MolMM has higher specificity than antigen mismatching at identifying recipients who are at low risk of dnDSA while receiving minimalist immunosuppression. Immunogenicity consideration is important, with more work needed on identification, especially across different ethnic groups.

Impact of Low-Level Donor-Specific Anti-HLA Antibody on Posttransplant Clinical Outcomes in Kidney Transplant Recipients

Background

The clinical significance of low-level donor-specific anti-HLA antibody (low-DSA) remains controversial. We investigated the impact of low-DSA on posttransplant clinical outcomes in kidney transplant (KT) recipients.

Methods

We retrospectively reviewed 1,027 KT recipients, namely, 629 living donor KT (LDKT) recipients and 398 deceased donor KT (DDKT) recipients, in Seoul St. Mary's Hospital (Seoul, Korea) between 2010 and 2018. Low-DSA was defined as a positive anti-HLA-DSA result in the Luminex single antigen assay (LABScreen single antigen HLA class I - combi and class II - group 1 kits; One Lambda, Canoga Park, CA, USA) but a negative result in a crossmatch test. We compared the incidence of biopsy-proven allograft rejection (BPAR), changes in allograft function, allograft survival, patient survival, and posttransplant infections between subgroups according to pretransplant low-DSA.

Results

The incidence of overall BPAR and T cell-mediated rejection did not differ between the subgroups. However, antibody-mediated rejection (ABMR) developed more frequently in patients with low-DSA than in those without low-DSA in the total cohort and the LDKT and DDKT subgroups. In multivariate analysis, low-DSA was identified as a risk factor for ABMR development. Its impact was more pronounced in DDKT (odds ratio [OR]: 9.60, 95% confidence interval [CI]: 1.79-51.56) than in LDKT (OR: 3.76, 95% CI: 0.99-14.26) recipients. There were no significant differences in other outcomes according to pretransplant low-DSA.

Conclusions

Pretransplant low-DSA has a significant impact on the development of ABMR, and more so in DDKT recipients than in LDKT recipients, but not on long-term outcomes.

Steroid Sparing Maintenance Immunosuppression in Highly Sensitised Patients Receiving Alemtuzumab Induction

This analysis reports on the outcomes of two different steroid sparing immunosuppression protocols used in the management of 120 highly sensitised patients (HSPs) with cRF>85% receiving Alemtuzumab induction, 53 maintained on tacrolimus (FK) monotherapy and 67 tacrolimus plus mycophenolate mofetil (FK + MMF). There was no difference in the median cRF or mode of sensitisation between the two groups, although the FK + MMF cohort received more poorly matched grafts. There was no difference in one-year patient or allograft survival, however rejection free survival was inferior with FK monotherapy compared with FK + MMF at 65.4% and 91.4% respectively, p < 0.01. DSA-free survival was comparable. Whilst there was no difference in rates of BK between the cohorts, CMV-free survival was inferior in the FK + MMF group at 86.0% compared with 98.1% in the FK group, p = 0.026. One-year post-transplant diabetes free survival was 89.6% and 100.0% in the FK and FK + MMF group respectively, p = 0.027, the difference attributed to the use of prednisolone to treat rejection in the FK cohort, p = 0.006. We report good outcomes in HSPs utilising a steroid sparing protocol with Alemtuzumab induction and FK + MMF maintenance and provide granular data on immunological and infectious complications to inform steroid avoidance in these patient groups.

Classic and Current Opinions in Human Organ and Tissue Transplantation

Graft tolerance is a pathophysiological condition heavily reliant on the dynamic interaction of the innate and adaptive immune systems. Genetic polymorphism determines immune responses to tissue/organ transplantation, and intricate humoral and cell-mediated mechanisms control these responses. In transplantation, the clinician's goal is to achieve a delicate equilibrium between the allogeneic immune response, undesired effects of the immunosuppressive drugs, and the existing morbidities that are potentially life-threatening. Transplant immunopathology involves sensitization, effector, and apoptosis phases which recruit and engages immunological cells like natural killer cells, lymphocytes, neutrophils, and monocytes. Similarly, these cells are involved in the transfer of normal or genetically engineered T cells. Advances in tissue transplantation would involve a profound knowledge of the molecular mechanisms that underpin the respective immunopathology involved and the design of precision medicines that are safe and effective.

Recommended Treatment for Antibody-mediated Rejection After Kidney Transplantation: The 2019 Expert Consensus From the Transplantion Society Working Group

With the development of modern solid-phase assays to detect anti-HLA antibodies and a more precise histological classification, the diagnosis of antibody-mediated rejection (AMR) has become more common and is a major cause of kidney graft loss. Currently, there are no approved therapies and treatment guidelines are based on low-level evidence. The number of prospective randomized trials for the treatment of AMR is small, and the lack of an accepted common standard for care has been an impediment to the development of new therapies. To help alleviate this, The Transplantation Society convened a meeting of international experts to develop a consensus as to what is appropriate treatment for active and chronic active AMR. The aim was to reach a consensus for standard of care treatment against which new therapies could be evaluated. At the meeting, the underlying biology of AMR, the criteria for diagnosis, the clinical phenotypes, and outcomes were discussed. The evidence for different treatments was reviewed, and a consensus for what is acceptable standard of care for the treatment of active and chronic active AMR was presented. While it was agreed that the aims of treatment are to preserve renal function, reduce histological injury, and reduce the titer of donor-specific antibody, there was no conclusive evidence to support any specific therapy. As a result, the treatment recommendations are largely based on expert opinion. It is acknowledged that properly conducted and powered clinical trials of biologically plausible agents are urgently needed to improve patient outcomes.

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 Kidney Donor Profile Index (KDPI) to predict graft survival in a South Brazilian Cohort

Introduction:

Kidney Donor Profile Index (KDPI) has been incorporated in the United States to improve the kidney transplant allocation system.

Objectives:

To evaluate deceased kidney donors’ profile using KDPI and compare to the previous United Network for Organ Sharing (UNOS) definition of expanded criteria donors (ECD) and assess the KDPI applicability to predict five-year graft survival and renal function in our sample.

Methods:

Retrospective cohort of 589 kidney transplants from deceased donors performed from January 2009 to May 2013 with follow-up until May 2018.

Results:

In 589 kidney transplants, 36.6% of donors were classified as ECD and 28.8% had KDPI ≥ 85%. Mean KDPI was 63.1 (95%CI: 60.8-65.3). There was an overlap of standard and ECD in KDPI between 60 and 95 and a significantly lower death-censored graft survival in KDPI ≥ 85% (78.6%); KDPI 0-20: 89.8%, KDPI 21-59: 91.6%, and KDPI 60-84: 83.0%; p = 0.006. The AUC-ROC was 0.577 (95%CI: 0.514-0.641; p = 0.027). Renal function at 5 years was significantly lower according to the incremental KDPI (p < 0.002). KDPI (HR 1.011; 95%CI 1.001-1.020; p = 0.008), donor-specific antibodies (HR 2.77; 95%CI 1.69-4.54; p < 0.001), acute rejection episode (HR 1.73; 95%CI 1.04-2.86; p = 0.034) were independent and significant risk factors for death-censored graft loss at 5 years.

Conclusion:

In our study, 36.6% were classified as ECD and 28.8% had KDPI ≥ 85%. KDPI score showed a moderate power to predict graft survival at 5 years. Renal function was significantly lower in patients with higher KDPI.

Donor-specific antibodies detected by single antigen beads alone can help risk stratify patients undergoing retransplantation across a repeat HLA mismatch

Whether reexposure to mismatched HLA antigens (RMM) in the setting of a negative crossmatch is associated with increased immunological risk remains an area of uncertainty. This is due to evidence derived predominantly from registry data, which lacks comprehensive information on alloantibody and rejection. In this study, we analyze the impact of low-level preformed donor-specific antibodies (DSA) against an RMM on transplant outcomes. From 1988 consecutive renal transplant recipients, we analyzed 179 patients undergoing retransplantation, of whom 55 had a RMM. All patients were crossmatch negative and preformed DSA were detected by single antigen beads alone. Multivariate analysis revealed that patients with preformed DSA against an RMM were independently at risk of antibody-mediated rejection (HR 8.70 [3.42-22.10], P < .0001) and death-censored allograft loss (HR 3.08 [1.17-8.14], P = .023). In addition, prior transplant nephrectomy (HR 2.04 [1.00-4.17], P = .0495) was also associated with allograft failure, whereas receiving a retransplant that was matched at HLA class II was associated with a favorable outcome (HR 0.37 [0.14-0.99], P = .047). In the absence of preformed DSA, an RMM was not associated with de novo DSA development, rejection, or allograft loss. In conclusion, an RMM portends increased immunological risk only in the presence of a preformed DSA in patients undergoing retransplantation.

Positive Luminex and negative flow cytometry in kidney transplantation: a systematic review and meta-analysis

The presence of pre-formed donor-specific antibodies (DSAs) in kidney transplantation is associated with worse overall outcomes compared with DSA-negative transplantation. A positive complement-dependant cytotoxic crossmatch presents a high immunological risk, while a negative flow cytometry crossmatch is at the lower end of the risk spectrum. Yet, the presence of low-level DSA detected by Luminex alone, that is, positive Luminex and negative flow (PLNF) cytometry crossmatch lacks robust scientific exploration. In this systematic review and pooled analysis, we investigate the glomerular filtration rate, acute rejection (AR), graft survival and patient survival of PLNF transplants compared with DSA-negative transplants. Our analysis identified seven retrospective studies consisting of 429 PLNF transplants and 10 677 DSA-negative transplants. Pooled analysis identified no significant difference in the incidence of AR at 1 year [relative risk (RR) = 1.35, 95% confidence interval (CI) 0.90–2.02, Z = 1.46, P = 0.14, I2 = 0%], graft failure at 1 year (RR = 1.66, 95% CI 0.94–2.94, Z = 1.75, P = 0.08, I2 = 23%), graft failure at 5 years (RR = 1.29, 95% CI 0.90–1.87, Z = 1.38, P = 0.17, I2 = 0%), patient mortality at 1 year (RR = 0.89, 95% CI 0.31–2.56, Z = 0.22, P = 0.82, I2 = 0%) and patient mortality at 5 years (RR = 1.76, 95% CI 0.48–6.48, Z = 0.85, P = 0.39, I2 = 61%). Pooled analysis of graft function was not possible due to insufficient data. Current evidence suggests that low-level DSA detected by Luminex alone does not pose significant risk at least in the short–medium term. Considering the shortage of kidney transplants and the ever-increasing waiting time, the avoidance of PLNF transplants may be unwarranted especially in patients who have been enlisted for a long time.

IL-21 Biased Alemtuzumab Induced Chronic Antibody-Mediated Rejection Is Reversed by LFA-1 Costimulation Blockade

Despite its excellent efficacy in controlling T cell mediated acute rejection, lymphocyte depletion may promote a humoral response. While T cell repopulation after depletion has been evaluated in many aspects, the B cell response has not been fully elucidated. We tested the hypothesis that the mechanisms also involve skewed T helper phenotype after lymphocytic depletion. Post-transplant immune response was measured from alemtuzumab treated hCD52Tg cardiac allograft recipients with or without anti-LFA-1 mAb. Alemtuzumab induction promoted serum DSA, allo-B cells, and CAV in humanized CD52 transgenic (hCD52Tg) mice after heterotopic heart transplantation. Additional anti-LFA-1 mAb treatment resulted in reduced DSA (Fold increase 4.75 ± 6.9 vs. 0.7 ± 0.5; p < 0.01), allo-specific B cells (0.07 ± 0.06 vs. 0.006 ± 0.002 %; p < 0.01), neo-intimal hyperplasia (56 ± 14% vs. 23 ± 13%; p < 0.05), arterial disease (77.8 ± 14.2 vs. 25.8 ± 20.1%; p < 0.05), and fibrosis (15 ± 23.3 vs. 4.3 ± 1.65%; p < 0.05) in this alemtuzumab-induced chronic antibody-mediated rejection (CAMR) model. Surprisingly, elevated serum IL-21 levels in alemtuzumab-treated mice was reduced with LFA-1 blockade. In accordance with the increased serum IL-21 level, alemtuzumab treated mice showed hyperplastic germinal center (GC) development, while the supplemental anti-LFA-1 mAb significantly reduced the GC frequency and size. We report that the incomplete T cell depletion inside of the GC leads to a systemic IL-21 dominant milieu with hyperplastic GC formation and CAMR. Conventional immunosuppression, such as tacrolimus and rapamycin, failed to reverse AMR, while co-stimulation blockade with LFA-1 corrected the GC hyperplastic response. The identification of IL-21 driven chronic AMR elucidates a novel mechanism that suggests a therapeutic approach with cytolytic induction.

Impact of persistent and cleared preformed HLA DSA on kidney transplant outcomes

Preformed HLA donor-specific antibodies (DSA) only detected with Luminex have been associated with increased risk of antibody-mediated rejection (ABMR) and graft failure after kidney transplantation (KT). Their evolution after KT may modify this risk. We analyzed postransplant evolution of preformed DSA identified retrospectively and their impact on outcomes of 370 KT performed 2006-2014. Antibodies were monitored prospectively at 1-3-5 years after KT and if any dysfunction. Early acute ABMR was more frequent among patients with preformed DSA class-I or I + II than isolated class-II (29.4% vs 4.5%, p = 0.02). One year post-KT, 20 of 34 patients with functioning KT had persistent DSA. Preformed DSA class-II persisted more frequently than class-I/I + II (66.7% vs 33.3%; p = 0.031). The only risk factor independently associated with persistence was pretransplant MFI. Patients with de novo DSA had the highest risk of ABMR (HR 22.2 [CI 6.1-81.2]). Although recipients with persisting preformed DSA had significantly increased ABMR risk (HR 14.7 [CI 6.5-33.0]), those with cleared preformed DSA also had a higher risk than those without DSA (HR 7.01 [CI 2.2-21.8]). Preformed DSA are a very important risk factor for ABMR and graft loss. Patients who clear preformed DSA still show an increased risk of ABMR and graft loss after KT.

Complement-dependent cytotoxicity and Luminex technology for human leucocyte antigen antibody detection in kidney transplant candidates exposed to different sensitizing events

Background

The aim of this study was to determine the frequency of exposure to different sensitizing events (SEs) and to assess their effects on human leucocyte antigen (HLA) alloimmunization in transplant candidates using two different HLA antibody screening techniques: complement-dependent cytotoxicity (CDC) and Luminex.

Methods

This retrospective study included HLA antibody screening results for 163 patients on the kidney transplant waiting list (WL) tested from March 2012 until the end of December 2015 at the Tissue Typing Laboratory, Rijeka, Croatia. All sera samples were tested using the CDC and Luminex techniques in parallel.

Results

Two-thirds of the patients [114 (70%)] on the WL were exposed to transfusions, pregnancies and/or kidney transplant. The pre-transplant sera of 104 (63.80%) patients were negative for antibodies. In the sera of 23 (14.11%) patients, HLA antibodies were detected by CDC and Luminex and in the sera of 36 (22.09%) patients by Luminex only.

Conclusion

In patients on kidney WL, previous organ transplantation represents the strongest immunogenic stimulus, followed by blood transfusions (the most frequent SE) and pregnancies. Although Luminex is more sensitive than CDC in HLA antibody detection, the decision on unacceptable HLA antigens in WL patients has to be based on the results of both assays and the patient's immunization history.

Pre-transplant infusion of donor-derived dendritic cells maintained at the immature stage by sinomenine increases splenic Foxp3+ Tregs in recipient rats after renal allotransplantation

OBJECTIVE

The immunosuppressive mechanism of sinomenine in organ allotransplantation was investigated, especially its effect of blocking dendritic cell (DC) maturation, which might influence the frequency of regulatory T cells (Tregs).

METHODS

Bone marrow cells from male donor Wistar rats were induced to differentiate into DCs in vitro in the presence or absence of sinomenine, and characterized by flow cytometry. These two groups of DCs were respectively injected into male recipient Sprague-Dawley rats via the tail vein, at both high and low doses. Sprague-Dawley rats receiving saline injection were used as controls. Seven days later, renal transplantation was performed from donor Wistar rats to the recipient Sprague-Dawley rats. Seven days after transplantation, spleens were collected from the recipients. The proportions of Tregs and Foxp3⁺ Tregs to CD4⁺ T cells were determined using flow cytometry.

RESULTS

With sinomenine treatment, the frequency of mature DCs was reduced, as indicated by lower expression of the surface markers CD80, CD86, and RT1B. In recipient Sprague-Dawley rats that received sinomenine-treated DCs before renal allotransplantation, the proportions of splenic Tregs and Foxp3⁺ Tregs were significantly higher than in control recipients receiving saline or DCs without sinomenine treatment (all p<0.05). A high dose of sinomenine-treated DCs (10⁶ cells) had a more obvious effect in increasing Tregs than the low dose (10⁵ cells) (p<0.05).

CONCLUSION

Pre-transplant infusion of donor-derived sinomenine-induced maturation arrested DCs could result in the increase of Foxp3⁺ Tregs in the spleens of recipients after renal allotransplantation.

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.

Crosstalk Between T and B Cells in the Germinal Center After Transplantation

Crosstalk between B and T cells in transplantation is increasingly recognized as being important in the alloimmune response. T cell activation of B cells occurs by a 3-stage pathway, culminating with costimulation signals. We review the distinct T cell subtypes required for B-cell activation and discuss the formation of the germinal center (GC) after transplantation, with particular reference to the repopulation of the GC after depletional induction, and the subsequent effect of immunosuppressive manipulation of T cell-B cell interactions. In addition, ectopic GCs are seen in transplantation, but their role is not fully understood. Therapeutic options to target T cell-B cell interactions are of considerable interest, both as immunosuppressive tools, and to aid in the further understanding of these important alloimmune mechanisms.

Peritubular Capillary Basement Membrane Multilayering in Renal Allograft Biopsies of Patients With De Novo Donor-Specific Antibodies

BACKGROUND

Severe peritubular capillary basement membrane multilayering (PTCBML) is part of the Banff definition of chronic antibody-mediated rejection. We retrospectively investigated whether assessment of the mean number of layers of basement membrane (BM) around peritubular capillaries (PTC) can be used in a cohort of patients with de novo donor-specific antibodies (dnDSA) as an early marker to predict long-term antibody-mediated injury.

METHODS

This is a retrospective cohort study with 151 electron microscopy samples from 54 patients with dnDSA, assessed at around 1 year after transplantation, for a mean number of BM layers around PTC and in serial biopsies. Graft survival and time to transplant glomerulopathy (TG) development were estimated in survival analyses.

RESULTS

We found that a mean PTCBML count greater than 2.5 layers assessed in a sample of 25 PTCs around 1 year after transplantation is indicative of the development of TG in patients with dnDSA (P = 0.001). In addition, in patients with serial biopsies available for electron microscopy analysis, we could distinguish 2 groups: patients with a mean PTCBML count of 2.5 or less on all biopsies, and patients who developed greater than 2.5 layers at any time after transplantation. The latter group reflected dnDSA patients at risk for TG development (P < 0.001). In patients with dnDSA, PTCBML score added significantly to the sensitivity and specificity of prediction of TG compared with microcirculation injury score alone.

CONCLUSIONS

Our results highlight the potential value of assessing the mean number of BM in PTC for early prediction of progression to chronic antibody-mediated injury.

Clinically-relevant threshold of preformed donor-specific anti-HLA antibodies in kidney transplantation

BACKGROUND

Pretransplant anti-HLA donor-specific antibodies (DSA) are recognized as a risk factor for acute antibody-mediated rejection (AMR) in kidney transplantation. The predictive value of C4d-fixing capability by DSA or of IgG DSA subclasses for acute AMR in the pretransplant setting has been recently studied. In addition DSA strength assessed by mean fluorescence intensity (MFI) may improve risk stratification. We aimed to analyze the relevance of preformed DSA and of DSA MFI values.

METHODS

280 consecutive patients with negative complement-dependent cytotoxicity crossmatches received a kidney transplant between 01/2008 and 03/2014. Sera were screened for the presence of DSA with a solid-phase assays on a Luminex flow analyzer, and the results were correlated with biopsy-proven acute AMR in the first year and survival.

RESULTS

Pretransplant anti-HLA antibodies were present in 72 patients (25.7%) and 24 (8.6%) had DSA. There were 46 (16.4%) acute rejection episodes, 32 (11.4%) being cellular and 14 (5.0%) AMR. The incidence of acute AMR was higher in patients with pretransplant DSA (41.7%) than in those without (1.6%) (p<0.001). The median cumulative MFI (cMFI) of the group DSA+/AMR+ was 5680 vs 2208 in DSA+/AMR- (p=0.058). With univariate logistic regression a threshold value of 5280 cMFI was predictive for acute AMR. DSA cMFI's ability to predict AMR was also explored by ROC analysis. AUC was 0.728 and the best threshold was a cMFI of 4340. Importantly pretransplant DSA>5280 cMFI had a detrimental effect on 5-year graft survival.

CONCLUSIONS

Preformed DSA cMFI values were clinically-relevant for the prediction of acute AMR and graft survival in kidney transplantation. A threshold of 4300-5300 cMFI was a significant outcome predictor.

Analysis of preformed donor-specific anti-HLA antibodies characteristics for prediction of antibody-mediated rejection in kidney transplantation

BACKGROUND

The relevance of preformed donor specific antibodies (DSA) detected by Luminex assays, with a negative complement-dependent cytotoxicity (CDC) crossmatch, remains unsettled in kidney transplantation (KT). We aimed to analyze the impact of preformed DSA characteristics on kidney graft outcomes.

METHODS

In 462 patients that received a kidney graft in our unit, between 2007 and 2012, pre-transplant sera were analyzed by Luminex screening assay to determine the presence of anti-human leukocyte antigen (HLA) antibodies and single-antigen bead assay [positive if mean fluorescence intensity (MFI) ≥ 1000] to assign anti-HLA specificities.

RESULTS

Anti-HLA antibodies were present in 95 patients (20.6%), but only 40 (8.7%) had DSA. Antibody-mediated rejection (AMR) at 1-year was higher in patients with DSA (35.0%) than in those without them (0.9%) (P < 0.001). Only DSA with a MFI of >3000 were significantly associated with AMR occurrence. Receiver operator curves revealed that a MFI of >4900 in the highest DSA bead had a high sensitivity (85.7%) and that the sum of all DSA beads MFI > 11,000 had a high specificity (92.3%) for AMR prediction. Anti-thymocyte globulin versus basiliximab induction was more frequent in DSA+ AMR- (65.4%) versus DSA+ AMR+ (34.6%) patients (P = 0.072). Five-year censored graft survival was lower in DSA+ than in DSA- patients (respectively, 84.8% versus 94.9%, P = 0.006), although survival was only reduced in DSA+ AMR+ (68.8%) versus DSA+ AMR- (96.0%) patients (P = 0.038).

CONCLUSIONS

Preformed DSA is associated with kidney graft loss, in relation with AMR occurrence. DSA strength may be used to improve immunological risk stratification of sensitized patients and their clinical management.

Antibody-incompatible kidney transplantation in 2015 and beyond

Rejection caused by donor-specific antibodies (principally ABO and HLA antibodies) has become one of the major barriers to successful long-term transplantation. This review focuses on clinical outcomes in antibody-incompatible transplantation, the current state of the science underpinning clinical observations, and how these may be translated into further novel therapies. The clinical outcomes for allografts facing donor-specific antibodies are at present determined largely by the use of agents developed in the 20th century for the treatment of T-lymphocyte-mediated cellular rejection, such as interleukin-2 agents and anti-thymocyte globulin. These treatments are partially effective, because acute antibody-mediated rejection is mediated to a considerable extent by T lymphocytes. However these treatments are essentially ineffective in chronic antibody-mediated rejection. Future therapies for the prevention and treatment of antibody-mediated rejection are likely to fall into the categories of those that reduce antibody production, extracorporeal antibody removal and disruption of the effector arms of antibody-mediated tissue damage.

HLA antibody detection with solid phase assays: great expectations or expectations too great?

Alloantibodies directed against HLA antigens, are a barrier to long-term solid organ allograft survival. The clinical impact of preformed, donor-directed HLA alloantibodies range from acceptable risk to unequivocal contraindication for organ transplantation. HLA antibodies are key factors that limit patient access to donor organs. Serological methods were once the only approach to identify HLA antigens and antibodies. Limitations in these technologies led to the development of solid phase approaches. In the early 1990s, the development of the polymerase chain reaction enabled DNA-based HLA antigen testing to be performed. By the mid-1990s, microparticle-based technology that utilized flow cytometry for analysis was developed to detect both classes I and II HLA antibodies. These methodologies revolutionized clinical histocompatibility testing. The strengths and weaknesses of these assays are described in detail in this review.

Outcome of kidney transplantations performed with preformed donor-specific antibodies of unknown etiology

The detection of preformed donor-specific alloantibodies (DSA) with multiplex-bead arrays has led to the common observation that individuals without a history of pregnancy, transfusion or transplantation can have circulating anti-HLA antibodies of unknown etiology. We retrospectively analyzed the risk of antibody-mediated rejection (AMR) and graft outcome in 41 kidney transplant recipients with DSA of unknown etiology (DSA cause-unk) at the time of transplantation. Twenty-one patients received a posttransplantation desensitization protocol, and 20 received standard immunosuppressive therapy. The mean number of DSA was 1.4 ± 0.8, ranging from 1 to 5. Complement-dependent cytotoxicity crossmatches were negative for all the patients. Flow cytometry crossmatches were positive in 47.6% of cases. The incidence of acute AMR was 14.6% at 1 year, regardless of the immunosuppressive regimen. No patients experienced graft loss following AMR. At month 12, across the entire population of patients with DSA cause-unk, the outcomes were favorable: the measured glomerular filtration rate was 63.8 ± 16.4 mL/min/1.73 m(2), the screening biopsies showed low frequencies of microvascular inflammation and no transplant glomerulopathy, and graft and patient survival were 100%. In conclusion, patients with DSA cause-unk are able to mount AMR but have favorable 1-year outcomes.

Postanastomotic transplant renal artery stenosis: association with de novo class II donor-specific antibodies

In this study, we analyze the outcomes of transplant renal artery stenosis (TRAS), determine the different anatomical positions of TRAS, and establish cardiovascular and immunological risk factors associated with its development. One hundred thirty-seven of 999 (13.7%) patients had TRAS diagnosed by angiography; 119/137 (86.9%) were treated with angioplasty, of which 113/137 (82.5%) were stented. Allograft survival in the TRAS+ intervention, TRAS+ nonintervention and TRAS- groups was 80.4%, 71.3% and 83.1%, respectively. There was no difference in allograft survival between the TRAS+ intervention and TRAS- groups, p = 0.12; there was a difference in allograft survival between the TRAS- and TRAS+ nonintervention groups, p < 0.001, and between the TRAS+ intervention and TRAS+ nonintervention groups, p = 0.037. TRAS developed at the anastomosis, within a bend/kink or distally. Anastomotic TRAS developed in living donor recipients; postanastomotic TRAS (TRAS-P) developed in diabetic and older patients who received grafts from deceased, older donors. Compared with the TRAS- group, patients with TRAS-P were more likely to have had rejection with arteritis, odds ratio (OR): 4.83 (1.47-15.87), p = 0.0095, and capillaritis, OR: 3.03 (1.10-8.36), p = 0.033. Patients with TRAS-P were more likely to have developed de novo class II DSA compared with TRAS- patients hazard ratio: 4.41 (2.0-9.73), p < 0.001. TRAS is a heterogeneous condition with TRAS-P having both alloimmune and traditional cardiovascular risk factors.

An update on the impact of pre-transplant transfusions and allosensitization on time to renal transplant and on allograft survival

Background

Blood transfusions have the potential to improve graft survival, induce sensitization, and transmit infections. Current clinical practice is to minimize transfusions in renal transplantation candidates, but it is unclear if the evidence continues to support pre-transplant transfusion avoidance. Changes in the Medicare prospective payment system may increase transfusion rates. Thus there is a need to re-evaluate the literature to improve the management options for renal transplant candidates.

Methods

A review applying a systematic approach and conducted using MEDLINE^®, Embase^®, and the Cochrane Library for English-language publications (timeframe: 01/1984–03/2011) captured 180 studies and data from publically available registries and assessed the impact of transfusions on allosensitization and graft survival, and the impact of allosensitization on graft survival and wait time.

Results

Blood transfusions continued to be a major cause of allosensitization, with allosensitization associated with increased rejection and graft loss, and longer wait times to transplantation. Although older studies showed a beneficial effect of transfusion on graft survival, this benefit has largely disappeared in the post-cyclosporine era due to improved graft outcomes with current practice. Recent data suggested that it may be the donor-specific antibody component of allosensitization that carried the risk to graft outcomes.

Conclusions

Results of this review indicated that avoiding transfusions whenever possible is a sound management option that could prevent detrimental effects in patients awaiting kidney transplantation.

Influence of test technique on sensitization status of patients on the kidney transplant waiting list

The exquisitely sensitive single antigen bead (SAB) technique was shown to detect human leukocyte antigen (HLA) antibodies in sera of healthy male blood donors. Such false reactions can have an impact on critical decisions, especially with respect to the determination of unacceptable HLA-antigen mismatches in patients awaiting a kidney transplant. We tested pretransplant sera of 534 patients on the kidney waiting list using complement-dependent cytotoxicity (CDC), enzyme-linked immunosorbent assay (ELISA) and SAB in parallel. Evidence of HLA antibodies was obtained in 5% of patients using CDC, 14% using ELISA, and 81% using SAB. Among patients without history of an immunizing event, 77% showed evidence of HLA antibodies in SAB. In contrast 98% of these patients were negative in ELISA and CDC. In patients without an immunizing event, SAB-detected antibodies reacted not always weakly but with mean fluorescence intensity (MFI) values as high as 14 440. High-MFI-value antibodies were found in some of these patients with HLA specificities that are rather common in general population, consideration of which would lead to unjustified exclusion of potential kidney donors. False SAB reactions can be unveiled by testing with additional antibody assays. Denial of donor kidneys to recipients based on HLA-antibody specificities detected exclusively in the SAB assay is not advisable.

HLA class I antibodies trigger increased adherence of monocytes to endothelial cells by eliciting an increase in endothelial P-selectin and, depending on subclass, by engaging FcγRs

Ab-mediated rejection (AMR) of solid organ transplants is characterized by intragraft macrophages. It is incompletely understood how donor-specific Ab binding to graft endothelium promotes monocyte adhesion, and what, if any, contribution is made by the Fc region of the Ab. We investigated the mechanisms underlying monocyte recruitment by HLA class I (HLA I) Ab-activated endothelium. We used a panel of murine mAbs of different subclasses to crosslink HLA I on human aortic, venous, and microvascular endothelial cells and measured the binding of human monocytic cell lines and peripheral blood monocytes. Both anti-HLA I murine (m)IgG1 and mIgG2a induced endothelial P-selectin, which was required for monocyte adhesion to endothelium irrespective of subclass. mIgG2a but not mIgG1 could bind human FcγRs. Accordingly, HLA I mIgG2a but not mIgG1 treatment of endothelial cells significantly augmented recruitment, predominantly through FcγRI, and, to a lesser extent, FcγRIIa. Moreover, HLA I mIgG2a promoted firm adhesion of monocytes to ICAM-1 through Mac-1, which may explain the prominence of monocytes during AMR. We confirmed these observations using human HLA allele-specific mAbs and IgG purified from transplant patient sera. HLA I Abs universally elicit endothelial exocytosis leading to monocyte adherence, implying that P-selectin is a putative therapeutic target to prevent macrophage infiltration during AMR. Importantly, the subclass of donor-specific Ab may influence its pathogenesis. These results imply that human IgG1 and human IgG3 should have a greater capacity to trigger monocyte infiltration into the graft than IgG2 or IgG4 due to enhancement by FcγR interactions.

Preformed complement-activating low-level donor-specific antibody predicts early antibody-mediated rejection in renal allografts

BACKGROUND.: Donor-specific anti-HLA antibodies (DSA) are a major cause of alloimmune injury. Transplant recipients with negative complement-dependent cytotoxic crossmatch (CDC-XM) and donor cell-based flow cytometric crossmatch (flow-XM) but low level DSA (i.e., by Luminex) have worse outcomes compared with nonsensitized patients. The aim of this study was to establish whether complement-activating ability in this low-level DSA, present before transplantation, as determined by this technique is important in dictating pathogenicity. METHODS.: We retrospectively studied 52 patients with preformed DSA detected by single-antigen flow cytometric fluorescent beads (SAFBs). Patients were transplanted using a steroid-sparing regimen consisting of alemtuzumab induction, 1 week of corticosteroids and tacrolimus monotherapy.Fifteen (29%) of 52 patients experienced antibody-mediated rejection (AMR), whereas 37 (71%) patients did not. There were no demographic differences between patients with AMR and those without. Pretransplant sera were retested using a modified (SAFB) assay, which detects the presence of the complement fragment C4d as a result of DSA-induced complement activation. RESULTS.: C4d+DSA were detected in 10 (19%) of 52 patients. Biopsy-proven AMR occurred in 7 (70%) of the 10 patients with C4d+DSA and in 8 (19%) of 42 patients with C4d-DSA. AMR-free survival was worse in patients with C4d+DSA (P<0.001). CONCLUSIONS.: The ability of preformed, low-level, DSA to trigger C4d fixation in vitro in patients with negative conventional crossmatch tests is predictive for AMR. C4d SAFB is potentially a powerful tool for risk stratification prior to transplantation and may allow identification of unacceptable donor antigens, or patients who may require enhanced immunosuppression.

Upper-extremity transplantation using a cell-based protocol to minimize immunosuppression

OBJECTIVE

To minimize maintenance immunosuppression in upper-extremity transplantation to favor the risk-benefit balance of this procedure.

BACKGROUND

Despite favorable outcomes, broad clinical application of reconstructive transplantation is limited by the risks and side effects of multidrug immunosuppression. We present our experience with upper-extremity transplantation under a novel, donor bone marrow (BM) cell-based treatment protocol ("Pittsburgh protocol").

METHODS

Between March 2009 and September 2010, 5 patients received a bilateral hand (n = 2), a bilateral hand/forearm (n = 1), or a unilateral (n = 2) hand transplant. Patients were treated with alemtuzumab and methylprednisolone for induction, followed by tacrolimus monotherapy. On day 14, patients received an infusion of donor BM cells isolated from 9 vertebral bodies. Comprehensive follow-up included functional evaluation, imaging, and immunomonitoring.

RESULTS

All patients are maintained on tacrolimus monotherapy with trough levels ranging between 4 and 12 ng/mL. Skin rejections were infrequent and reversible. Patients demonstrated sustained improvements in motor function and sensory return correlating with time after transplantation and level of amputation. Side effects included transient increase in serum creatinine, hyperglycemia managed with oral hypoglycemics, minor wound infection, and hyperuricemia but no infections. Immunomonitoring revealed transient moderate levels of donor-specific antibodies, adequate immunocompetence, and no peripheral blood chimerism. Imaging demonstrated patent vessels with only mild luminal narrowing/occlusion in 1 case. Protocol skin biopsies showed absent or minimal perivascular cellular infiltrates.

CONCLUSIONS

Our data suggest that this BM cell-based treatment protocol is safe, is well tolerated, and allows upper-extremity transplantation using low-dose tacrolimus monotherapy.

Microcirculation inflammation associates with outcome in renal transplant patients with de novo donor-specific antibodies

In renal transplant patients with de novo donor-specific antibodies (dnDSA) we studied the value of microcirculation inflammation (MI; defined by the addition of glomerulitis (g) and peritubular capillaritis (ptc) scores) to assess long-term graft survival in a retrospective cohort study. Out of all transplant patients with standard immunological risk (n = 638), 79 (12.4%) developed dnDSA and 58/79 (73%) had an indication biopsy at or after dnDSA development. Based on the MI score on that indication biopsy patients were categorized, MI0 (n = 26), MI1 + 2 (n = 21) and MI ≥ 3 (n = 11). The MI groups did not differ significantly pretransplantation, whereas posttransplantation higher MI scores developed more anti-HLA class I + II DSA (p = 0.011), showed more TCMR (p < 0.001) and showed a trend to C4d-positive staining (p = 0.059). Four-year graft survival estimates from time of indication biopsy were MI0 96.1%, MI1 + 2 76.1% and MI ≥ 3 17.1%; resulting in a 24-fold increased risk of graft failure in the MI ≥ 3 compared to the MI0 group (p = 0.003; 95% CI [3.0-196.0]). When adjusted for C4d, MI ≥ 3 still had a 21-fold increased risk of graft failure (p = 0.005; 95% CI [2.5-180.0]), while C4d positivity on indication biopsy lost significance. In renal transplant patients with de novo DSA, microcirculation inflammation, defined by g + ptc, associates with graft survival.

Donor-specific antibodies adversely affect kidney allograft outcomes

The effect of low titers of donor-specific antibodies (DSAs) detected only by sensitive solid-phase assays (SPAs) on renal transplant outcomes is unclear. We report the results of a systematic review and meta-analysis of rejection rates and graft outcomes for renal transplant recipients with such preformed DSAs, defined by positive results on SPA but negative complement-dependent cytotoxicity and flow cytometry crossmatch results. Our search identified seven retrospective cohort studies comprising a total of 1119 patients, including 145 with isolated DSA-SPA. Together, these studies suggest that the presence of DSA-SPA, despite a negative flow cytometry crossmatch result, nearly doubles the risk for antibody-mediated rejection (relative risk [RR], 1.98; 95% confidence interval [CI], 1.36-2.89; P<0.001) and increases the risk for graft failure by 76% (RR, 1.76; 95% CI, 1.13-2.74; P=0.01). These results suggest that donor selection should consider the presence of antibodies in the recipient, identified by the SPA, even in the presence of a negative flow cytometry crossmatch result.

Human leukocyte antigen antibody incompatible renal transplantation

Anti-human leukocyte antigen (HLA) antibodies are recognized as an important problem in organ transplant recipients. This is because antibodies formed against a graft months or years after implantations are the major cause of late allograft failure, and also because protocols allow the transplantation of some grafts across pre-formed HLA antibodies. Advances in our understanding of anti-HLA antibody- mediated rejection (AMR) have occurred because of a better understanding of the histological findings during AMR; more sensitive and specific methods to measure anti-HLA antibodies; and through clinical investigation of patients transplanted across an HLA barrier. Despite advances in therapy and investigation, AMR remains a major problem and treatment protocols often fail to treat it successfully. This review aims to describe the issues in each of these areas and to suggest how clinicians may be able to improve the management of patients with anti-HLA antibodies.

Preformed and de novo donor specific antibodies in visceral transplantation: long-term outcome with special reference to the liver

Despite improvement in early outcome, rejection particularly chronic allograft enteropathy continues to be a major barrier to long-term visceral engraftment. The potential role of donor specific antibodies (DSA) was examined in 194 primary adult recipients. All underwent complement-dependent lymphocytotoxic crossmatch (CDC-XM) with pre- and posttransplant solid phase HLA-DSA assay in 156 (80%). Grafts were ABO-identical with random HLA-match. Liver was included in 71 (37%) allografts. Immunosuppression was tacrolimus-based with antilymphocyte recipient pretreatment in 150 (77%). CDC-XM was positive in 55 (28%). HLA-DSA was detectable before transplant in 49 (31%) recipients with 19 continuing to have circulating antibodies. Another 19 (18%) developed de novo DSA. Ninety percent of patients with preformed DSA harbored HLA Class-I whereas 74% of recipients with de novo antibodies had Class-II. Gender, age, ABO blood-type, cold ischemia, splenectomy and allograft type were significant DSA predictors. Preformed DSA significantly (p < 0.05) increased risk of acute rejection. Persistent and de novo HLA-DSA significantly (p < 0.001) increased risk of chronic rejection and associated graft loss. Inclusion of the liver was a significant predictor of better outcome (p = 0.004, HR = 0.347) with significant clearance of preformed antibodies (p = 0.04, OR = 56) and lower induction of de novo DSA (p = 0.07, OR = 24). Innovative multifaceted anti-DSA strategies are required to further improve long-term survival particularly of liver-free allografts.

Human leukocyte antigen antibody-incompatible renal transplantation: excellent medium-term outcomes with negative cytotoxic crossmatch

BACKGROUND

Human leukocyte antigen (HLA) antibody-incompatible renal transplantation has been increasingly performed since 2000 but with few data on the medium-term outcomes.

METHODS

Between 2003 and 2011, 84 patients received renal transplants with a pretreatment donor-specific antibody (DSA) level of more than 500 in a microbead assay. Seventeen patients had positive complement-dependent cytotoxic (CDC) crossmatch (XM), 44 had negative CDC XM and positive flow cytometric XM, and 23 had DSA detectable by microbead only. We also reviewed 28 patients with HLA antibodies but no DSA at transplant. DSAs were removed with plasmapheresis pretransplant, and patients did not routinely receive antithymocyte globulin posttransplant.

RESULTS

Mean follow-up posttransplantation was 39.6 (range 2-91) months. Patient survival after the first year was 93.8%. Death-censored graft survival at 1, 3, and 5 years was 97.5%, 94.2%, and 80.4%, respectively, in all DSA+ve patients, worse at 5 years in the CDC+ve than in the CDC-ve/DSA+ve group at 45.6% and 88.6%, respectively (P<0.03). Five-year graft survival in the DSA-ve group was 82.1%. Rejection occurred in 53.1% of DSA+ve patients in the first year compared with 22% in the DSA-ve patients (P<0.003).

CONCLUSIONS

HLA antibody-incompatible renal transplantation had a high success rate if the CDC XM was negative. Further work is required to predict which CDC+ve XM grafts will be successful and to treat slowly progressive graft damage because of DSA in the first few years after transplantation.

Clinical relevance of HLA donor-specific antibodies detected by single antigen assay in kidney transplantation

BACKGROUND

Clinical relevance of donor-specific antibodies (DSAs) detected by a single antigen Luminex virtual crossmatch in pre-transplant serum samples from patients with a negative cytotoxicity-dependent complement crossmatch is controversial. The aim of this study was to analyse the influence of a pre-transplant positive virtual crossmatch in the outcome of kidney transplantation.

METHODS

A total of 892 patients who received a graft from deceased donors after a negative cytotoxicity crossmatch were included. Presence of anti-human leucocyte antigen (HLA) antibodies was investigated using a Luminex screening assay and anti-HLA specificities were assigned performing a Luminex single antigen assay.

RESULTS

Graft survival was significantly worse among patients with anti-HLA DSA compared to both patients with anti-HLA with no DSA (P = 0.001) and patients without HLA antibodies (P < 0.001) using a log-rank test. No graft survival differences between anti-HLA with no DSA and no HLA antibodies patient groups were observed (P = 0.595). Influence of both anti-Class I and anti-Class II DSA was detected (P < 0.0001 in both cases). When the fluorescence values were stratified in four groups, no significant differences in graft survival were observed among the groups with fluorescence levels >1500 (global P > 0.05).

CONCLUSIONS

The presence of preformed HLA DSA in transplanted patients with a negative cytotoxicity crossmatch is associated with a lower allograft survival. The detection of anti-HLA with no DSA has no influence in the graft outcome. Finally, there were no demonstrable effects of mean fluorescence intensity (MFI) values >1500 on graft survival.