De novo donor‐specific anti‐HLA antibodies mediated rejection in liver‐transplant patients

The incidence and consequences of de novo donor‐specific anti‐HLA antibodies (DSAs) after liver transplantation (LT) are not well known. We investigated the incidence, risk factors, and complications associated with de novo DSAs in this setting. A total of 152 de novo liver‐transplant patients, without preformed anti‐HLA DSAs, were tested for anti‐HLA antibodies, with single‐antigen bead technology, before, at transplantation, at 1, 3, 6 and 12 months after transplantation, and thereafter annually and at each time they presented with increased liver‐enzyme levels until the last follow‐up, that is, 34 (1.5–77) months. Twenty‐one patients (14%) developed de novo DSAs. Of these, five patients had C1q‐binding DSAs (24%). Younger age, low exposure to calcineurin inhibitors, and noncompliance were predictive factors for de novo DSA formation. Nine of the 21 patients (43%) with de novo DSAs experienced an acute antibody‐mediated rejection (AMR). Positive C4d staining was more frequently observed in liver biopsies of patients with AMR (9/9 vs. 1/12, P < 0.0001). Eight patients received a B‐cell targeting therapy, and one patient received polyclonal antibodies. Only one patient required retransplantation. Patient‐ and graft‐survival rates did not differ between patients with and without DSAs. In conclusion, liver‐transplant patients with liver abnormalities should be screened for DSAs and AMR.     

Posttransplant donor‐specific antibody characterization and kidney graft survival

Abstract This study was designed to investigate the clinical relevance of donor‐specific antibodies (DS‐Abs) and their influence on graft survival. Among 106 patients who underwent cadaveric kidney donor transplantation and were monitored by flow cytometry crossmatch (FCXM) during the 1st posttransplantation year, 25 (23.6%) resulted positive for DS‐Ab production. During a 2‐year follow up only 12 of the 81 FCXM‐negative patients (14.8%) suffered rejection vs 17 of 25 FCXM‐positive patients (68%; P = 0.00001). Correlating graft loss to DS‐Ab production, 9 FCXM‐positive patients lost the graft vs only 1 among the FCXM‐negative patients. A worse graft function was evidenced in FCXM‐positive subjects who had also suffered rejection episodes than in those which had acute rejection but did not produce DS‐Abs. A high incidence of HLA‐AB mismatches was found in FCXM‐positive subjects which produced anti‐class I antibodies. FCXM appears useful in estimating post‐transplant alloimmune response. Moreover our findings confirm the harmful effects of anti‐class IDS‐Abs on long‐term graft survival.     

Determining donor‐specific antibody C1q‐binding ability improves the prediction of antibody‐mediated rejection in human leucocyte antigen‐incompatible kidney transplantation

Detrimental impact of preformed donor‐specific antibodies (DSAs) against human leucocyte antigens on outcomes after kidney transplantation are well documented, however, the value of their capacity to bind complement for predicting antibody‐mediated rejection (AMR) and graft survival still needs to be confirmed. We aimed to study DSA characteristics (strength and C1q binding) that might distinguish harmful DSA from clinically irrelevant ones. We retrospectively studied 60 kidney‐transplanted patients with preformed DSA detected by single antigen bead (SAB) assays (IgG and C1q kits), from a cohort of 517 kidney graft recipients (124 with detectable anti‐HLA antibodies). Patients were divided into DSA strength (MFI < vs. ≥ 15 000) and C1q‐binding ability. AMR frequency was high (30%) and it increased with DSA strength (P = 0.002) and C1q+ DSA (P < 0.001). The performance of DSA C1q‐binding ability as a predictor of AMR was better than DSA strength (diagnostic odds ratio 16.3 vs. 6.4, respectively). Furthermore, a multivariable logistic regression showed that C1q+ DSA was a risk factor for AMR (OR = 16.80, P = 0.001), while high MFI DSAs were not. Graft survival was lower in high MFI C1q+ DSA in comparison with patients with C1q? high or low MFI DSA (at 6 years, 38%, 83% and 80%, respectively; P = 0.001). Both DSA strength and C1q‐binding ability assessment seem valuable for improving pretransplant risk assessment. Since DSA C1q‐binding ability was a better predictor of AMR and correlated with graft survival, C1q‐SAB may be a particularly useful tool.     

Incidence of donor‐specific antibodies in kidney transplant patients following conversion to an everolimus‐based calcineurin inhibitor‐free regimen

Scarce data exist regarding the incidence of donor‐specific antibodies (DSAs) in kidney transplant patients receiving everolimus‐based immunosuppression without calcineurin inhibitors (CNIs). The aim of this retrospective case–control study was to compare the incidence of de novo DSAs in patients converted to an everolimus‐based regimen without CNIs with that seen in patients maintained on CNIs. Sixty‐one DSA‐free kidney transplant patients who had been converted to an everolimus‐based regimen (everolimus group) were compared to 61 other patients maintained on CNIs‐based regimen (control group). Patients were matched according to age, gender, induction therapy, date of transplantation, and being DSA‐free at baseline. At last follow‐up, the incidence of DSAs was 9.8% in the everolimus group and 5% in the control group (p = ns). In the everolimus group, the increased incidence of DSAs between baseline and last follow‐up was statistically significant. Antibody‐mediated rejection occurred in 6.5% in the everolimus group and 0% in the CNIs group. The incidence of DSAs is numerically increased in kidney transplant patients treated with an everolimus‐based without CNIs. A study including a larger number of patients is required to determine whether a CNI‐free everolimus‐based immunosuppression significantly increases DSAs formation.     

Ethylene carbodiimide‐fixed donor splenocytes combined with α‐1 antitrypsin induce indefinite donor‐specific protection to mice cardiac allografts

Peritransplant infusion of ethylene carbodiimide‐fixed donor splenocytes (ECDI‐SPs) induces protection of islet and cardiac allografts. However, pro‐inflammatory cytokine production during the peritransplantation period may negate the effect of ECDI‐SPs. Therefore, we hypothesized that blocking pro‐inflammatory cytokine secretion while increasing levels of anti‐inflammatory cytokines would enhance the tolerance‐induced efficacy of ECDI‐SPs. The objective of this study was to determine the effectiveness of using ECDI‐SPs combined with a short course of α1‐antitrypsin (AAT) for induction of tolerance. Using a mice cardiac transplant model, we demonstrated that ECDI‐SPs + AAT effectively induced indefinite mice cardiac allograft protection in a donor‐specific fashion. This effect was accompanied by modulation of cytokines through decreasing levels of pro‐inflammatory cytokines (including IFN‐γ, TNF‐α, IL‐1β, IL‐6, IL‐17, and IL‐23) and increasing levels of anti‐inflammatory cytokines (including IL‐10, IL‐13, and TGF‐β), and by inhibition of effector T cells (Teff) and expansion of regulatory T cells (Tregs). Therefore, we concluded that combined ECDI‐SPs and AAT appeared to modulate the expression of cytokines and regulate the Teff:Treg balance to create a support milieu for graft protection. Our strategy of combining ECDI‐SPs and AAT provides a promising approach for inducing donor‐specific transplant tolerance.     

Pre‐existing donor‐specific antibodies are detrimental to kidney allograft only when persistent after transplantation

Donor‐specific antibodies (DSA) increase the risk of allograft rejection and graft failure. They may be present before transplant or develop de novo after transplantation. Here, we studied the evolution of preformed DSA and their impact on graft outcome in kidney transplant recipients. Using the Luminex Single Antigen assay, we analyzed the sera on the day of transplantation of 239 patients who received a kidney transplant. Thirty‐seven patients (15.5%) had pre‐existing DSA detected the day of transplantation. After 5 years, the pre‐existing DSA disappeared in 22 patients whereas they persisted in 12. Variables associated with DSA persistence were age <50 years (P = 0.009), a history of previous transplantation (P = 0.039), the presence of class II DSA (P = 0.009), an MFI of preformed DSA >3500 (P < 0.001), and the presence of two or more DSA (P < 0.001). DSA persistence was associated with a higher risk of graft loss and antibody‐mediated rejection. Previously undetected preformed DSA are deleterious to graft survival only when they persist after transplantation.     

Outcome of the risk‐stratified desensitization protocol in donor‐specific antibody‐positive living kidney transplant recipients: a retrospective study

Acceptable outcomes of donor‐specific antibody (DSA)‐positive living kidney transplantation (LKT) have recently been reported. However, LKT in crossmatch (XM)‐positive patients remains at high‐risk and requires an optimal desensitization protocol. We report our intermediate‐term outcomes of XM‐positive LKT vs. XM‐negative LKT in patients who underwent LKT between January 2012 and June 2015 in our institution. The rate of acute antibody‐mediated rejection (ABMR) within 90 days postoperation, graft function, and patient, and graft survival rates at 4 years were investigated. Patients were divided into three groups: XM?DSA? (n = 229), XM?DSA+ (n = 36), and XM + DSA+ (n = 15). The XM + DSA+ group patients underwent desensitization with high‐dose intravenous immunoglobulin, plasmapheresis, and rituximab. The rates of ABMR within 90 days in the XM?DSA?, XM?DSA+, and XM + DSA+ groups were 1.3%, 9.4%, and 60.0%, respectively (P < 0.001). There were no significant differences in the graft function throughout the observational period, the 4‐year patient or graft survival rates among three groups. This study showed that intermediate‐term outcomes of XM‐positive LKT were comparable to XM‐negative LKT. However, our current desensitization protocol cannot avert ABMR within 90 days, and XM positivity is still a significant risk factor for ABMR. Further refinement of the current desensitization regimen is required.     

Beneficial effects of donor‐specific transfusion on renal allograft outcome

Jovi?i? S, Le?ai? V, Simonovi? R, Djukanovi? L. Beneficial effects of donor‐specific transfusion on renal allograft outcome.
Clin Transplant 2011: 25: 317–324. © 2010 John Wiley & Sons A/S. Abstract: Introduction: Donor‐specific transfusion (DST) is claimed to improve graft survival in living kidney transplantation. The aim of this study was to determine the influence of DST on the incidence of acute rejection (AR), graft function and survival in the early and late post‐transplantation period in transfusion‐naïve patients. Methods: Three patient groups were compared: group 1 received DST (n = 18), group 2 patients received no transfusion prior to surgery (n = 13) and group 3 consisted of 132 randomly transfused patients. The DST protocol consisted of infusion of fresh whole donor blood (3 × 150 mL) at two‐wk intervals accompanied by three d of azathioprine. All patients were grafted within one month after the third DST. Triple drug immunosuppression based on cyclosporine A was given to all patients. Results: DST and polytransfused patients experienced significantly less AR compared with group 2 patients. Two‐yr graft function was significantly better in patients in groups 1 and 3 compared with group 2. Although similar eight‐yr patient and graft survival was found in all the groups, delayed graft function patients had the longest graft half‐life. Conclusion: DST imposes a significant beneficial effect on the incidence of AR, DGF and graft function during the first post‐transplantation year in transfusion‐naïve patients receiving standard immunosuppression therapy.     

Conversion to mammalian target of rapamycin inhibitors increases risk of de novo donor‐specific antibodies

In kidney transplantation, conversion to mammalian target of rapamycin (mTOR) inhibitors may avoid calcineurin inhibitor (CNI) nephrotoxicity, but its impact on post‐transplant allo‐immunization remains largely unexplored. This retrospective cohort study analyzed the emergence of donor‐specific antibodies (DSA) in kidney transplant recipients relative to their immunosuppressive therapy. Among 270 recipients without pretransplant immunization who were screened regularly for de novo DSA, 56 were converted to mTOR inhibitors after CNI withdrawal. DSA emergence was increased in patients who were converted to mTOR inhibitors (HR 2.4; 95% CI 1.06–5.41, P = 0.036). DSA were mainly directed against donor HLA‐DQB1 antigens. The presence of one or two DQ mismatches was a major risk factor for DQ DSA (HR 5.32; 95% CI 1.58–17.89 and HR 10.43; 95% CI 2.29–47.56, respectively; P < 0.01). Rejection episodes were more likely in patients converted to mTOR inhibitors, but this difference did not reach significance (16% vs. 7.9%, P = 0.185). Concerning graft function, no significant change was observed one year after conversion (P = 0.31). In conclusion, conversion to mTOR inhibitors may increase the risk of developing class II DSA, especially in the presence of DQ mismatches: this strategy may favor chronic antibody‐mediated rejection and thus reduce graft survival.     

Failure to remove de novo donor‐specific HLA antibodies is influenced by antibody properties and identifies kidney recipients with late antibody‐mediated rejection destined to graft loss – a retrospective study

Current research is focusing on identifying bioclinical parameters for risk stratification of renal allograft loss, largely due to antibody‐mediated rejection (AMR). We retrospectively investigated graft outcome predictors in 24 unsensitized pediatric kidney recipients developing HLA de novo donor‐specific antibodies (dnDSAs), and treated for late AMR with plasmapheresis + low‐dose IVIG + Rituximab or high‐dose IVIG + Rituximab. Renal function and DSA properties were assessed before and longitudinally post treatment. The estimated GFR (eGFR) decline after treatment was dependent on a negative % eGFR variation in the year preceding treatment (P = 0.021) but not on eGFR at treatment (P = 0.74). At a median follow‐up of 36 months from AMR diagnosis, 10 patients lost their graft. Altered eGFR (P < 0.001) and presence of C3d‐binding DSAs (P = 0.005) at treatment, and failure to remove DSAs (P = 0.01) were negatively associated with graft survival in the univariable analysis. Given the relevance of DSA removal for therapeutic success, we analyzed antibody properties dictating resistance to anti‐humoral treatment. In the multivariable analysis, C3d‐binding ability (P < 0.05), but not C1q‐binding, and high mean fluorescence intensity (P < 0.05) were independent factors characterizing DSAs scarcely susceptible to removal. The poor prognosis of late AMR is related to deterioration of graft function prior to treatment and failure to remove C3d binding and/or high‐MFI DSAs.     

De novo donor‐specific HLA antibodies after combined intestinal and vascularized composite allotransplantation — a retrospective study

Combining vascularized composite allotransplantation (VCA) with intestinal transplantation to achieve primary abdominal closure has become a feasible procedure. Besides facilitating closure, the abdominal wall can be used to monitor intestinal rejection. As the inclusion of a VCA raises the possibility of an enhanced alloimmune response, we investigated the incidence and clinical effect of de novo donor‐specific HLA antibodies (dnDSA) in a cohort of patients receiving an intestinal transplant with or without a VCA. The sequential clinical study includes 32 recipients of deceased donor intestinal and VCA transplants performed between 2008 and 2015; eight (25%) modified multivisceral transplants and 24 (75%) isolated small bowel transplants. A VCA was used in 18 (56.3%) cases. There were no episodes of intestinal rejection without VCA rejection. Fourteen patients (14 of 29; 48.3%) developed dnDSA. In the VCA group, fewer patients developed dnDSA; six of 16 (37.5%) VCA vs. eight of 13 (61.5%) non‐VCA. There was no statistically significant difference in one‐ and 3‐year overall graft survival stratified for the presence of dnDSA; P = 0.286. In the study, there is no evidence that the addition of a VCA increases the incidence of dnDSA formation compared to transplantation of the intestine alone.     

De novo donor‐specific anti‐HLA antibodies after kidney transplantation are associated with impaired graft outcome independently of their C1q‐binding ability

Many aspects of post‐transplant monitoring of donor‐specific (DSA) and non‐donor‐specific (nDSA) anti‐HLA antibodies on renal allograft survival are still unclear. Differentiating them by their ability to bind C1q may offer a better risk assessment. We retrospectively investigated the clinical relevance of de novo C1q‐binding anti‐HLA antibodies on graft outcome in 611 renal transplant recipients. Acute rejection (AR), renal function, and graft survival were assessed within a mean follow‐up of 6.66 years. Post‐transplant 6.5% patients developed de novo DSA and 11.5% de novo nDSA. DSA (60.0%; P < 0.0001) but not nDSA (34.1%, P = 0.4788) increased rate of AR as compared with controls (27.4%). C1q‐binding anti‐HLA antibodies did not alter rate of AR in both groups. Renal function was only significantly diminished in patients with DSAC1q⁺. However, DSA significantly impaired 5‐year graft survival (65.2%; P < 0.0001) in comparison with nDSA (86.7%; P = 0.0054) and controls (90.7%). While graft survival did not differ between DSAC1q⁻ and DSAC1q⁺ recipients, 5‐year allograft survival was reduced in nDSAC1q⁺ (80.9%) versus nDSAC1q⁻ (90.7%, P = 0.0251). De novo DSA independently of their ability to bind C1q are associated with diminished graft survival.     

Donor‐specific HLA antibody‐mediated complement activation is a significant indicator of antibody‐mediated rejection and poor long‐term graft outcome during lung transplantation: a single center cohort study

Complement‐mediated allograft injury, elicited by donor‐specific HLA antibodies (DSA ), is a defining pathophysiological characteristic of allograft damage. We aimed to study DSA ‐induced complement activation as a diagnostic marker of antibody‐mediated rejection (AMR ) and a risk stratification tool for graft loss in the context of lung transplantation (LT ). We identified 38 DSA ‐positive patients whose serum samples were submitted for C3d deposition testing via the C3d assay. Among these 38 patients, 15 had AMR (DSA^{P os}AMR^{P os}). Results were reported for each patient as the C3d ratio for each DSA , the immunodominant DSA , and the C3d ratio for all DSA present in a sample (C3d ratio_SUM ). DSA^{P os}AMR^{P os} patients had higher C3d ratio_SUM values (58.66 (?1.32 to 118.6) vs. 1.52 (0.30 to 2.74), P  = 0.0016) and increased immunodominant C3d ratios (41.87 (1.72 to 82.02) vs. 0.69 (0.21 to 1.19), P  = 0.001) when compared with DSA^{P os}AMR^{N eg} patients. Specificity and calculated positive predictive value of the immunodominant C3d ratio and BCM sum tests for AMR diagnosis were both 100% (CI  = 17.4–100) in this cohort. Worst graft survival was associated with both immunodominant C3d ratio ≥4 or C3d ratio_SUM ≥10 or BCM sum >7000, suggesting that the antibody composition and/or strength are the principal determinants of an HLA DSA 's capacity to activate complement.     

Impact of de novo donor‐specific HLA antibodies detected by Luminex solid‐phase assay after transplantation in a group of 88 consecutive living‐donor renal transplantations

De novo donor‐specific HLA antibodies (DSA) after renal transplantation are known to be correlated with poor graft outcome and the development of acute and chronic rejection. Currently, data for the influence of de novo DSA in patient cohorts including only living‐donor renal transplantations (LDRT) are limited. A consecutive cohort of 88 LDRT was tested for the occurrence of de novo DSA by utilizing the highly sensitive Luminex solid‐phase assay for antibody detection. Data were analyzed for risk factors for de novo DSA development and correlated with acute rejection (AR) and graft function. Patients with de novo DSA [31 (35%)] showed a trend for inferior graft function [mean creatinine change (mg/dL/year) after the first year: 0.15 DSA (+) vs. 0.02 DSA (?) (P = 0.10)] and a higher rate of AR episodes, especially in case of de novo DSA of both class I and II [6 (55%), (P = 0.05)]. Antibody‐mediated rejection (AMR) appeared in five patients and was significantly correlated with de novo DSA (P = 0.05). Monitoring for de novo DSA after LDRT may help to identify patients at risk of declining renal function. Especially patients with simultaneous presence of de novo DSA class I and class II are at a high risk to suffer AR episodes.