Noninvasive detection of graft injury after heart transplant using donor‐derived cell‐free DNA: A prospective multicenter study

Standardized donor‐derived cell‐free DNA (dd‐cfDNA) testing has been introduced into clinical use to monitor kidney transplant recipients for rejection. This report describes the performance of this dd‐cfDNA assay to detect allograft rejection in samples from heart transplant (HT) recipients undergoing surveillance monitoring across the United States. Venous blood was longitudinally sampled from 740 HT recipients from 26 centers and in a single‐center cohort of 33 patients at high risk for antibody‐mediated rejection (AMR). Plasma dd‐cfDNA was quantified by using targeted amplification and sequencing of a single nucleotide polymorphism panel. The dd‐cfDNA levels were correlated to paired events of biopsy‐based diagnosis of rejection. The median dd‐cfDNA was 0.07% in reference HT recipients (2164 samples) and 0.17% in samples classified as acute rejection (35 samples; P = .005). At a 0.2% threshold, dd‐cfDNA had a 44% sensitivity to detect rejection and a 97% negative predictive value. In the cohort at risk for AMR (11 samples), dd‐cfDNA levels were elevated 3‐fold in AMR compared with patients without AMR (99 samples, P = .004). The standardized dd‐cfDNA test identified acute rejection in samples from a broad population of HT recipients. The reported test performance characteristics will guide the next stage of clinical utility studies of the dd‐cfDNA assay.     

High levels of dd‐cfDNA identify patients with TCMR 1A and borderline allograft rejection at elevated risk of graft injury

The clinical importance of subclinical, early T cell–mediated rejection (Banff TCMR 1A and borderline lesions) remains unclear, due, in part to the fact that histologic lesions used to characterize early TCMR can be nonspecific. Donor‐derived cell‐free DNA (dd‐cfDNA) is an important molecular marker of active graft injury. Over a study period from June 2017 to May 2019, we assessed clinical outcomes in 79 patients diagnosed with TCMR 1A/borderline rejection across 11 US centers with a simultaneous measurement of dd‐cfDNA. Forty‐two patients had elevated dd‐cfDNA (≥0.5%) and 37 patients had low levels (<0.5%). Elevated levels of dd‐cfDNA predicted adverse clinical outcomes: among patients with elevated cfDNA, estimated glomerular filtration rate declined by 8.5% (interquartile rate [IQR] ?16.22% to ?1.39%) (?3.50 mL/min/1.73 m² IQR ?8.00 to ?1.00) vs 0% (?4.92%, 4.76%) in low dd‐cfDNA patients (P = .004), de novo donor‐specific antibody formation was seen in 40% (17/42) vs 2.7% (P < .0001), and future or persistent rejection occurred in 9 of 42 patients (21.4%) vs 0% (P = .003). The use of dd‐cfDNA may complement the Banff classification and to risk stratify patients with borderline/TCMR 1A identified on biopsy.     

Absolute quantification of donor‐derived cell‐free DNA as a marker of rejection and graft injury in kidney transplantation: Results from a prospective observational study

Donor‐derived cell‐free DNA (dd‐cfDNA) is a noninvasive biomarker for comprehensive monitoring of allograft injury and rejection in kidney transplantation (KTx). dd‐cfDNA quantification of copies/mL plasma (dd‐cfDNA[cp/mL]) was compared to dd‐cfDNA fraction (dd‐cfDNA[%]) at prespecified visits in 189 patients over 1 year post KTx. In patients (N = 15, n = 22 samples) with biopsy‐proven rejection (BPR), median dd‐cfDNA(cp/mL) was 3.3‐fold and median dd‐cfDNA(%) 2.0‐fold higher (82 cp/mL; 0.57%, respectively) than medians in Stable Phase patients (N = 83, n = 408) without rejection (25 cp/mL; 0.29%). Results for acute tubular necrosis (ATN) were not significantly different from those with biopsy‐proven rejection (BPR). dd‐cfDNA identified unnecessary biopsies triggered by a rise in plasma creatinine. Receiver operating characteristic (ROC) analysis showed superior performance (P = .02) of measuring dd‐cfDNA(cp/mL) (AUC = 0.83) compared to dd‐cfDNA(%) (area under the curve [AUC] = 0.73). Diagnostic odds ratios were 7.31 for dd‐cfDNA(cp/mL), and 6.02 for dd‐cfDNA(%) at thresholds of 52 cp/mL and 0.43%, respectively. Plasma creatinine showed a low correlation (r = 0.37) with dd‐cfDNA(cp/mL). In a patient subset (N = 24) there was a significantly higher rate of patients with elevated dd‐cfDNA(cp/mL) with lower tacrolimus levels (<8 μg/L) compared to the group with higher tacrolimus concentrations (P = .0036) suggesting that dd‐cfDNA may detect inadequate immunosuppression resulting in subclinical graft damage. Absolute dd‐cfDNA(cp/mL) allowed for better discrimination than dd‐cfDNA(%) of KTx patients with BPR and is useful to avoid unnecessary biopsies.     

Development and outcomes of de novo donor‐specific antibodies in low,moderate, and high immunological risk kidney transplant recipients

De novo donor‐specific antibodies (dnDSA) play an important role in antibody‐mediated rejection (ABMR) and graft failure, yet their development in kidney transplant recipients (KTx) of higher immunological risk has not been characterized. We prospectively determined the incidence of dnDSA at 3 and 12 months posttransplant and assessed their associations with outcomes in recipients stratified by low, moderate, and high immunological risk. Adult KTx were screened for DSA pretransplant, months 3 and 12 posttransplant, and when clinically indicated. Outcomes included incidence of dnDSA, death‐censored graft survival (DCGS), and ABMR. Of 371 recipients, 154 (42%) were transplanted across a pretransplant DSA that became undetectable by 12 months posttransplant in 78% of cases. dnDSA were detected in 16% (95% confidence interval [CI]: 12‐20%) by 3 months and 23% (95% CI: 18‐29%) by 12 months posttransplant. Incidence at 12 months was higher in the moderate (30%) and high‐risk groups (29%) compared to the low‐risk group (16%). dnDSA were associated with an increased risk of ABMR (hazard ratio [HR] 2.2; 95% CI: 1.1‐4.4; P = .04) but were not an independent risk factor for DCGS. In conclusion, dnDSA were more frequent in transplant recipients of higher immune risk and associated with an increased risk of ABMR.     

Diagnostic value of donor-derived cell-free DNA to predict antibody-mediated rejection in donor-specific antibody-positive renal allograft recipients

Circulating donor-specific antibodies (DSA) do not necessarily indicate antibody-mediated rejection (ABMR). Here, we evaluated the diagnostic value of donor-derived cell-free DNA (dd-cfDNA) as an add-on to DSA detection. The study included two independent cohorts of DSA⁺ kidney allograft recipients, 45 subclinical cases identified by cross-sectional antibody screening (cohort 1), and 30 recipients subjected to indication biopsies (cohort 2). About 50% of the DSA⁺ recipients had ABMR and displayed higher dd-cfDNA levels than DSA⁺ABMR⁻ recipients (cohort 1: 1.90% [median; IQR: 0.78–3.90%] vs. 0.52% [0.35–0.72%]; P < 0.001); (cohort 2: 1.20% [0.82–2.50%] vs. 0.59% [0.28–2.05%]; P = 0.086). Receiver operating characteristic (ROC) analysis revealed an area under the curve (AUC) of 0.89 and 0.69 for dd-cfDNA, and 0.88 and 0.77 for DSA mean fluorescence intensity (MFI), respectively. In combined models, adding dd-cfDNA to DSA-MFI or vice versa significantly improved the diagnostic accuracy. Limited diagnostic performance of dd-cfDNA in cohort 2 was related to the frequent finding of other types of graft injury among ABMR⁻ recipients, like T cell-mediated rejection or glomerulonephritis. For dd-cfDNA in relation to injury of any cause an AUC of 0.97 was calculated. Monitoring of dd-cfDNA in DSA⁺ patients may be a useful tool to detect ABMR and other types of injury.     

Higher rates of rejection in HIV‐infected kidney transplant recipients on ritonavir‐boosted protease inhibitors: 3‐year follow‐up study

Rejection rates in HIV‐infected kidney transplant (KTx) recipients are higher than HIV‐negative recipients. Immunosuppression and highly active antiretroviral therapy (HAART) protocols vary with potentially significant drug‐drug interactions, likely influencing outcomes. This is an IRB‐approved, single‐center, retrospective study of adult HIV‐infected KTx patients between 5/2009 and 12/2014 with 3‐year follow‐up, excluding antibody‐depleting induction. A total of 42 patients were included; median age was 52 years, 81% male, 50% African American, 29% Hispanic, 17% Caucasian. The most common renal failure etiology was hypertensive nephrosclerosis (50%) with 5.8 median years of pre‐transplant dialysis. All patients received IL‐2 receptor antagonist, were maintained on tacrolimus (76%) or cyclosporine (17%), and 40% received ritonavir‐boosted PI‐based HAART (rtv+) regimen. Patient and graft survival at 3 years were 93% and 90%. At 1‐, 2‐, and 3‐year time points, median serum creatinine was 1.49, 1.35, and 1.67; treated biopsy‐proven rejection was 38%, 38%, and 40.5%; and 92% of episodes were acute rejection. At these time points, rejection rates were significantly higher with boosted PI HAART regimens compared to other HAART regimens, 59% vs 24% (P = 0.029), 59% vs 24% (P = 0.029), and 68% vs 24% (P = 0.01). Despite higher rejection rates, HIV‐infected KTx recipients have reasonable outcomes. Given significantly higher rejection rates using rtv+ regimens, alternative HAART regimens should be considered prior to transplantation.     

Donor-derived cell-free DNA: An independent biomarker in kidney transplant patients with antibody-mediated rejection

IntroductionAntibody-mediated rejection (ABMR) is a major cause of kidney transplant failure which requires donor-specific antibodies (DSA) for a definitive diagnosis. Donor-derived cell-free DNA (ddcfDNA) is an emerging biomarker used to assess kidney allograft injury. However, current data is limited to predict the accuracy of ddcfDNA in ABMR diagnosis. This study was conducted to compare the performance of DSA with plasma ddcfDNA for the diagnosis of ABMR.MethodsIn this retrospective single-center observational study, we enrolled 50 kidney transplant recipients who were diagnosed with the suspicion of rejection between June 2018 and May 2019 at the Jinling Hospital. Plasma ddcfDNA was measured by using a novel target region capture sequencing methodology. A total of 37 patients who were tested with DSA and biopsy were divided into four subgroups (ABMR+/DSA+, ABMR+/DSA-, ABMR-/DSA+, ABMR-/DSA-) for the distribution of ddcfDNA (%) by ABMR and DSA.ResultsThe median level of ddcfDNA in biopsy showed that the ABMR group (1.66%, IQR 1.34–3.76%) was significantly higher than the median level (0.63%, IQR 0.43–0.74%) in non-ABMR (p < 0.001). With a ddcfDNA cutoff of 0.96%, the AUC was 0.90 (95%CI, 0.86–0.95), which was associated with a sensitivity of 90.5% (95%CI, 69.6–98.8%) and specificity of 96.6% (95%CI, 82.2–100%), a PPV of 95% (95%CI, 73.4–99.2%) and NPV of 93.3% (95%CI, 78.9–98.1%) were also observed. Among the four subgroups, ddcfDNA had no significant difference in both DSA+ group and DSA-group (p > 0.05). In the diagnosis of ABMR, the specificity, sensitivity, PPV and NPV of DSA were 50%, 74.1%, 41.7%, 80%, respectively.ConclusionsddcfDNA levels in the blood could highly distinguish (biopsy-supported) ABMR occurrence, irrespective of whether this method is accompanied by DSA or not.     

Anti‐C1s monoclonal antibody BIVV009 in late antibody‐mediated kidney allograft rejection—results from a first‐in‐patient phase 1 trial

The classical pathway (CP) of complement may contribute to the pathogenesis of antibody‐mediated rejection (ABMR). Selective CP blockade may be a promising strategy to counteract rejection. The objective of this first‐in‐patient phase 1b trial was to evaluate the safety/tolerability and CP‐blocking potential of 4 weekly doses (60 mg/kg) of the anti‐C1s antibody BIVV009 in complement‐mediated disorders. Here we describe the results in a cohort of 10 stable kidney transplant recipients (median of 4.3 years posttransplantation) with late active ABMR and features of CP activation, such as capillary C4d or complement‐fixing donor‐specific antibodies (DSA). During 7 weeks follow‐up, no severe adverse events were reported, and BIVV009 profoundly inhibited overall and DSA‐triggered CP activation in serum. Five of 8 C4d‐positive recipients turned C4d‐negative in 5‐week follow‐up biopsies, while another 2 recipients showed a substantial decrease in C4d scores. There was, however, no change in microcirculation inflammation, gene expression patterns, DSA levels, or kidney function. In conclusion, we demonstrate that BIVV009 effectively blocks alloantibody‐triggered CP activation, even though short‐course treatment had no effect on indices of activity in late ABMR. This initial trial provides a valuable basis for future studies designed to clarify the therapeutic value of CP blockade in transplantation. ClinicalTrials.gov NCT#02502903.     

Graft and patient outcomes of zero‐human leucocyte‐antigen‐mismatched deceased and live donor kidney transplant recipients

Greater compatibility of human leucocyte antigen (HLA) alleles between kidney donors and recipients may lead to improved graft outcomes. This study aimed to compare the incidence of acute rejection and graft failure in zero‐HLA‐mismatched recipients of living‐related (LD) and deceased donor (DD) kidney transplants. Using data from the Australia and New Zealand Dialysis and Transplant Registry, we compared the risk of any acute rejection and biopsy‐proven acute rejection (BPAR) and graft failure in recipients of zero‐HLA‐mismatched kidneys between LD and DD using logistic and Cox regression models. Of the 931 zero‐HLA‐mismatched recipients transplanted between 1990 and 2012, 19 (2.0%) received kidneys from monozygotic/dizygotic twins (twin), 500 (53.7%) from nontwin LD and 412 (44.3%) from DD. Twin kidney transplant recipients did not experience rejection. Compared to DD transplant recipients, the risk of any acute rejection (adjusted odds ratio 0.52, 95%CI 0.34–0.79, P = 0.002) and overall graft failure (adjusted hazard ratio 0.55, 95%CI 0.41–0.73, P < 0.001) was significantly lower in LD recipients independent of initial immunosuppression, but not for BPAR (adjusted odds ratio 0.52, 95%CI 0.16–1.64, P = 0.263). Zero‐HLA‐mismatched DD kidney transplant recipients have a significantly higher risk of any acute rejection episodes and graft loss compared to zero‐HLA‐mismatched LD kidney transplant recipients. A cautious and careful approach in reducing immunosuppression appears to be warranted in this group of transplant recipients.     

Belatacept in renal transplant recipient with mild immunologic risk factor: A pilot prospective study (BELACOR)

The benefit of belatacept on antibody‐mediated rejection (ABMR) incidence after kidney transplant with preformed donor‐specific antibodies (DSAs) has never been assessed. Between 2014 and 2016, we conducted a multicenter prospective clinical trial with 49 patients to determine kidney allograft outcome in recipients with preformed DSAs (maximal mean fluorescence intensity 500 to 3000) treated with belatacept (BELACOR trial). Immunosuppressive strategy included antithymocyte globulin, belatacept, mycophenolate mofetil, and steroids. An ancillary control group was designed retrospectively, including patients fulfilling the same inclusion criteria treated with calcineurin inhibitors. In BELACOR group, no patient exhibited acute ABMR, patient and allograft survival at 1 year was 100% and 95.4%, respectively, and the estimated glomerular filtration rate was 53.2 mL/min/1.73 m². However, the 12‐month incidence of acute T cell–mediated rejection was 25.4% (14.5% to 42.4%). Comparison with the control group showed significantly higher T cell–mediated rejection incidence only in the BELACOR group (P = .003). Considering the DSAs, the outcome was similar in the 2 groups except a significantly higher number of patients displayed a complete disappearance of class II DSAs in the BELACOR group (P = .001). Belatacept was not associated with an acute ABMR increased risk and may be considered as immunosuppressive strategy in transplant recipients with preformed DSAs (maximal mean fluorescence intensity 500 to 3000). Prospective randomized trials are needed to confirm these results.     

Diagnostic yield of 18F‐FDG PET/CT imaging and urinary CXCL9/creatinine levels in kidney allograft subclinical rejection

Subclinical kidney allograft acute rejection (SCR) corresponds to “the unexpected histological evidence of acute rejection in a stable patient.” SCR detection relies on surveillance biopsy. Noninvasive approaches may help avoid biopsy‐associated complications. From November 2015 to January 2018, we prospectively performed positron emission tomography/computed tomography (PET/CT) after injection of F¹⁸‐fluorodeoxyglucose (¹⁸F‐FDG) in adult kidney transplant recipients with surveillance biopsy at ~3 months posttransplantation. The Banff‐2017 classification was used. The ratio of the mean standard uptake value (mSUVR) between kidney cortex and psoas muscle was measured. Urinary levels of CXCL‐9 were concomitantly quantified. Our 92‐patient cohort was categorized upon histology: normal (n = 70), borderline (n = 16), and SCR (n = 6). No clinical or biological difference was observed between groups. The mSUVR reached 1.87 ± 0.55, 1.94 ± 0.35, and 2.41 ± 0.54 in normal, borderline, and SCR groups, respectively. A significant difference in mSUVR was found among groups. Furthermore, mSUVR was significantly higher in the SCR vs normal group. The area under the receiver operating characteristic curve (AUC) was 0.79, with 83% sensitivity using an mSUVR threshold of 2.4. The AUC of urinary CXCL‐9/creatinine ratios comparatively reached 0.79. The mSUVR positively correlated with ti and acute composite Banff scores. ¹⁸F‐FDG‐PET/CT helps noninvasively exclude SCR, with a negative predictive value of 98%. External validations are required.     

Value of monitoring circulating donor‐reactive memory B cells to characterize antibody‐mediated rejection after kidney transplantation

Antibody‐mediated rejection (ABMR) is defined by specific histopathological lesions and evidence of circulating donor‐specific antibodies (DSA). Although DSA are not always detectable, monitoring donor‐reactive memory B cells (mBC) could identify patients at risk of developing ABMR. Peripheral donor‐reactive mBC using a novel HLA B cell ELISpot assay, serum DSA, and numbers of different B cell subsets were assessed in 175 consecutive kidney transplants undergoing either for‐cause or 6‐ and 24‐month surveillance biopsies for their association with main histological lesions of ABMR and impact on allograft outcome. In 85 incident for‐cause biopsies, high frequencies of donor‐reactive mBC were detected in all 16 (100%) acute ABMR/DSA+ and most chronic ABMR, with or without DSA (24/30[80%] and 21/29[72.4%], respectively). In a longitudinal cohort of 90 nonsensitized patients, a progressively higher expansion of donor‐reactive mBC than de novo DSA was observed at 6 and 24 months (8.8% vs 7.7% and 15.5% vs 11.1%, respectively) and accurately identified patients with ongoing subclinical ABMR (area under the curve = 0.917 and area under the curve = 0.809, respectively). An unsupervised hierarchical cluster analysis revealed a strong association between donor‐reactive mBC with main fundamental allograft lesions associated with ABMR and conferred a significant deleterious impact on graft outcome. Monitoring donor‐reactive mBC may be useful to further characterize humoral rejection after kidney transplantation.     

Banff survey on antibody‐mediated rejection clinical practices in kidney transplantation: Diagnostic misinterpretation has potential therapeutic implications

The aim of this study was to determine how the Banff antibody‐mediated rejection (ABMR) classification for kidney transplantation is interpreted in practice and affects therapy. The Banff Antibody‐Mediated Injury Workgroup electronically surveyed clinicians and pathologists worldwide regarding diagnosis and treatment for 6 case‐based scenarios. The participants' (95 clinicians and 72 renal pathologists) assigned diagnoses were compared to the Banff intended diagnoses (reference standard). The assigned diagnoses and reference standard differed by 26.1% (SD 28.1%) for pathologists and 34.5% (SD 23.3%) for clinicians. The greatest discordance between the reference standard and clinicians' diagnosis was when histologic features of ABMR were present but donor‐specific antibody was undetected (49.4% [43/87]). For pathologists, the greatest discordance was in the case of acute/active ABMR C4d staining negative in a positive crossmatch transplant recipient (33.8% [23/68]). Treatment approaches were heterogeneous but linked to the assigned diagnosis. When acute/active ABMR was diagnosed by the clinician, treatment was recommended 95.3% (SD 18.4%) of the time vs only 77.7% (SD 39.2%) of the time when chronic active ABMR was diagnosed (P < .0001). In conclusion, the Banff ABMR classification is vulnerable to misinterpretation, which potentially has patient management implications. Continued efforts are needed to improve the understanding and standardized application of ABMR classification in the transplant community.     

Efficacy and safety of prolonged‐release tacrolimus in stable pediatric allograft recipients converted from immediate‐release tacrolimus – a Phase 2, open‐label,single‐arm,one‐way crossover study

There are limited clinical data regarding prolonged‐release tacrolimus (PR‐T) use in pediatric transplant recipients. This Phase 2 study assessed the efficacy and safety of PR‐T in stable pediatric kidney, liver, and heart transplant recipients (aged ≥5 to ≤16 years) over 1 year following conversion from immediate‐release tacrolimus (IR‐T), on a 1:1 mg total‐daily‐dose basis. Endpoints included the incidence of acute rejection (AR), a composite endpoint of efficacy failure (death, graft loss, biopsy‐confirmed AR, and unknown outcome), and safety. Tacrolimus dose and whole‐blood trough levels (target 3.5–15 ng/ml) were also evaluated. Overall, 79 patients (kidney, n = 48; liver, n = 29; heart, n = 2) were assessed. Following conversion, tacrolimus dose and trough levels remained stable; however, 7.6–17.7% of patients across follow‐up visits had trough levels below the target range. Two (2.5%) patients had AR, and 3 (3.8%) had efficacy failure. No graft loss or deaths were reported. No new safety signals were identified. Drug‐related treatment‐emergent adverse events occurred in 28 patients (35.4%); most were mild, and all resolved. This study suggests that IR‐T to PR‐T conversion is effective and well tolerated over 1 year in pediatric transplant recipients and highlights the importance of therapeutic drug monitoring to maintain target tacrolimus trough levels.     

Utility of protocol kidney biopsies for de novo donor‐specific antibodies

There is limited information about the role of protocol kidney biopsies for de novo donor‐specific antibodies (dnDSA) in kidney transplant recipients, especially in those with stable graft function. We initiated a routine posttransplant DSA monitoring and surveillance biopsy program for dnDSA since 2014. We identified 45 kidney transplant recipients with dnDSA detected between January 2014 and February 2017 who underwent kidney biopsy within 60 days of detection of dnDSA. Twenty‐nine (64%) had stable graft function and 16 (36%) had impaired graft function at the time of dnDSA detection. Even in the group with stable graft function, we found a high rate of rejection (53%) on biopsy. Eighty‐eight percent of patients with impaired graft function had rejection. Those patients with impaired graft function had significantly lower estimated glomerular filtration rate at 12 months postbiopsy and at last follow‐up. Those with impaired graft function had more graft failures; however, this result was not statistically significant. The high rate of asymptomatic rejection, and the fact that outcomes in asymptomatic patients are poor, is in support of the utility of surveillance biopsies in patients with dnDSA.     

Torque teno virus for risk stratification of graft rejection and infection in kidney transplant recipients—A prospective observational trial

The nonpathogenic and ubiquitous torque teno virus (TTV) is associated with immunosuppression in solid organ transplant recipients. Studies in kidney transplant patients proposed TTV quantification for risk stratification of graft rejection and infection. In this prospective trial (DRKS00012335) 386 consecutive kidney transplant recipients were subjected to longitudinal per‐protocol monitoring of plasma TTV load by polymerase chain reaction for 12 months posttransplant. TTV load peaked at the end of month 3 posttransplant and reached steady state thereafter. TTV load after the end of month 3 was analyzed in the context of subsequent rejection diagnosed by indication biopsy and infection within the first year posttransplant, respectively. Each log increase in TTV load decreased the odds for rejection by 22% (odds ratio [OR] 0.78, 95% confidence interval [CI] 0.62‐0.97; P = .027) and increased the odds for infection by 11% (OR 1.11, 95% CI 1.06‐1.15; P < .001). TTV was quantified at a median of 14 days before rejection was diagnosed and 27 days before onset of infection, respectively. We defined a TTV load between 1 × 10⁶ and 1 × 10⁸ copies/mL as optimal range to minimize the risk for rejection and infection. These data support the initiation of an interventional trial assessing the efficacy of TTV‐guided immunosuppression to reduce infection and graft rejection in kidney transplant recipients.     

Discovery of non‐HLA antibodies associated with cardiac allograft rejection and development and validation of a non‐HLA antigen multiplex panel: From bench to bedside

We analyzed humoral immune responses to nonhuman leukocyte antigen (HLA) after cardiac transplantation to identify antibodies associated with allograft rejection. Protein microarray identified 366 non‐HLA antibodies (>1.5 fold, P < .5) from a discovery cohort of HLA antibody–negative, endothelial cell crossmatch–positive sera obtained from 12 cardiac allograft recipients at the time of biopsy‐proven rejection. From these, 19 plasma membrane proteins and 10 autoantigens identified from gene ontology analysis were combined with 48 proteins identified through literature search to generate a multiplex bead array. Longitudinal sera from a multicenter cohort of adult cardiac allograft recipients (samples: n = 477 no rejection; n = 69 rejection) identified 18 non‐HLA antibodies associated with rejection (P < .1) including 4 newly identified non‐HLA antigenic targets (DEXI, EMCN, LPHN1, and SSB). CART analysis showed 5/18 non‐HLA antibodies distinguished rejection vs nonrejection. Antibodies to 4/18 non‐HLA antigens synergize with HLA donor‐specific antibodies and significantly increase the odds of rejection (P < .1). The non‐HLA panel was validated using an independent adult cardiac transplant cohort (n = 21 no rejection; n = 42 rejection, >1R) with an area under the curve of 0.87 (P < .05) with 92.86% sensitivity and 66.67% specificity. We conclude that multiplex bead array assessment of non‐HLA antibodies identifies cardiac transplant recipients at risk of rejection.     

Safety and efficacy of eculizumab for the prevention of antibody‐mediated rejection after deceased‐donor kidney transplantation in patients with preformed donor‐specific antibodies

The presence of preformed donor‐specific antibodies in transplant recipients increases the risk of acute antibody‐mediated rejection (AMR). Results of an open‐label single‐arm trial to evaluate the safety and efficacy of eculizumab in preventing acute AMR in recipients of deceased‐donor kidney transplants with preformed donor‐specific antibodies are reported. Participants received eculizumab as follows: 1200 mg immediately before reperfusion; 900 mg on posttransplant days 1, 7, 14, 21, and 28; and 1200 mg at weeks 5, 7, and 9. All patients received thymoglobulin induction therapy and standard maintenance immunosuppression including steroids. The primary end point was treatment failure rate, a composite of biopsy‐proved grade II/III AMR (Banff 2007 criteria), graft loss, death, or loss to follow‐up, within 9 weeks posttransplant. Eighty patients received transplants (48 women); the median age was 52 years (range 24‐70 years). Observed treatment failure rate (8.8%) was significantly lower than expected for standard care (40%; P < .001). By 9 weeks, 3 of 80 patients had experienced AMR, and 4 of 80 had experienced graft loss. At 36 months, graft and patient survival rates were 83.4% and 91.5%, respectively. Eculizumab was well tolerated and no new safety concerns were identified. Eculizumab has the potential to provide prophylaxis against injury caused by acute AMR in such patients (EudraCT 2010‐019631‐35).     

Identifying Subphenotypes of Antibody‐Mediated Rejection in Kidney Transplants

The key lesions in antibody‐mediated kidney transplant rejection (ABMR) are microcirculation inflammation (peritubular capillaritis and/or glomerulitis lesions, abbreviated “pg”) and glomerular double contours (cg lesions). We used these features to explore subphenotypes in 164 indication biopsies with ABMR‐related diagnoses: 137 ABMR (109 pure and 28 mixed with T cell–mediated rejection [TCMR]) and 27 transplant glomerulopathy (TG), identified from prospective multicenter studies. The lesions indicated three ABMR subphenotypes: pgABMR, cgABMR, and pgcgABMR. Principal component analysis confirmed these subphenotypes and showed that TG can be reclassified as pgcgABMR (n = 17) or cgABMR (n = 10). ABMR‐related biopsies included 45 pgABMR, 90 pgcgABMR, and 25 cgABMR, with four unclassifiable. Dominating all time intervals was the subphenotype pgcgABMR. The pgABMR subphenotype presented earliest (median <2 years), frequently mixed with TCMR, and was most associated with nonadherence. The cgABMR subphenotype presented late (median 9 years). Subphenotypes differed in their molecular changes, with pgABMR having the most histologic–molecular discrepancies (i.e. potential errors). Donor‐specific antibody (DSA) was not identified in 29% of pgcgABMR and 46% of cgABMR, but failure rates and molecular findings were similar to cases where DSA was known to be positive. Thus, ABMR presents distinct subphenotypes, early pg‐dominant, late cg‐dominant, and combined pgcg phenotype, differing in time, molecular features, accompanying TCMR, HLA antibody, and probability of nonadherence.