Search

Histopathologic lung allograft injuries are putative harbingers for chronic lung allograft dysfunction (CLAD). However, the mechanisms responsible are not well understood. CXCL9 and CXCL10 are potent chemoattractants of mononuclear cells and potential propagators of allograft injury. We hypothesized that these chemokines would be quantifiable in plasma, and would associate with subsequent CLAD development. In this prospective multicenter study, we evaluated 721 plasma samples for CXCL9/CXCL10 levels from 184 participants at the time of transbronchial biopsies during their first-year post-transplantation. We determined the association between plasma chemokines, histopathologic injury, and CLAD risk using Cox proportional hazards models. We also evaluated CXCL9/CXCL10 levels in bronchoalveolar lavage (BAL) fluid and compared plasma to BAL with respect to CLAD risk. Plasma CXCL9/CXCL10 levels were elevated during the injury patterns associated with CLAD, acute rejection, and acute lung injury, with a dose-response relationship between chemokine levels and CLAD risk. Importantly, there were strong interactions between injury and plasma CXCL9/CXCL10, where histopathologic injury associated with CLAD only in the presence of elevated plasma chemokines. We observed similar associations and interactions with BAL CXCL9/CXCL10 levels. Elevated plasma CXCL9/CXCL10 during allograft injury may contribute to CLAD pathogenesis and has potential as a minimally invasive immune monitoring biomarker.

Incompatible living donor kidney transplant recipients (ILDKTr) have pre-existing donor-specific antibody (DSA) that, despite desensitization, may persist or reappear with resulting consequences, including delayed graft function (DGF) and acute rejection (AR). To quantify the risk of DGF and AR in ILDKT and downstream effects, we compared 1406 ILDKTr to 17 542 compatible LDKT recipients (CLDKTr) using a 25-center cohort with novel SRTR linkage. We characterized DSA strength as positive Luminex, negative flow crossmatch (PLNF); positive flow, negative cytotoxic crossmatch (PFNC); or positive cytotoxic crossmatch (PCC). DGF occurred in 3.1% of CLDKT, 3.5% of PLNF, 5.7% of PFNC, and 7.6% of PCC recipients, which translated to higher DGF for PCC recipients (aOR = 1.03 1.682.72 ). However, the impact of DGF on mortality and DCGF risk was no higher for ILDKT than CLDKT (p interaction > .1). AR developed in 8.4% of CLDKT, 18.2% of PLNF, 21.3% of PFNC, and 21.7% of PCC recipients, which translated to higher AR (aOR PLNF = 1.45 2.093.02 ; PFNC = 1.67 2.403.46 ; PCC = 1.48 2.243.37 ). Although the impact of AR on mortality was no higher for ILDKT than CLDKT (p interaction = .1), its impact on DCGF risk was less consequential for ILDKT (aHR = 1.34 1.621.95 ) than CLDKT (aHR = 1.96 2.292.67 ) (p interaction = .004). Providers should consider these risks during preoperative counseling, and strategies to mitigate them should be considered.

Kidney transplant (KT) outcomes for HIV-infected (HIV+) persons are excellent, yet acute rejection (AR) is common and optimal immunosuppressive regimens remain unclear. Early steroid withdrawal (ESW) is associated with AR in other populations, but its utilization and impact are unknown in HIV+ KT. Using SRTR, we identified 1225 HIV+ KT recipients between January 1, 2000, and December 31, 2017, without AR, graft failure, or mortality during KT admission, and compared those with ESW with those with steroid continuation (SC). We quantified associations between ESW and AR using multivariable logistic regression and interval-censored survival analysis, as well as with graft failure and mortality using Cox regression, adjusting for donor, recipient, and immunologic factors. ESW utilization was 20.4%, with more zero HLA mismatch (8% vs 4%), living donors (26% vs 20%), and lymphodepleting induction (64% vs 46%) compared to the SC group. ESW utilization varied widely across 129 centers, with less use at high- versus moderate-volume centers (6% vs 21%, P

Background: The influence of converting to once daily, extended‐release LCP‐Tacrolimus (Tac) for those with high tacrolimus variability in kidney transplant recipients (KTRs) is not well‐studied. Methods: Single‐center, retrospective cohort study of adult KTRs converted from Tac immediate release to LCP‐Tac 1‐2 years post‐transplant. Primary measures were Tac variability, using the coefficient of variation (CV) and time in therapeutic range (TTR), as well as clinical outcomes (rejection, infections, graft loss, death). Results: A total of 193 KTRs included with a follow‐up of 3.2 ±.7 years and 1.3 ±.3 years since LCP‐Tac conversion. Mean age was 52 ± 13 years; 70% were African American, 39% were female, 16% living donor and 12% donor after cardiac death (DCD). In the overall cohort, tac CV was 29.5% before conversion, which increased to 33.4% after LCP‐Tac (p =.008). In those with Tac CV >30% (n = 86), conversion to LCP‐Tac reduced variability (40.6% vs. 35.5%; p =.019) and for those with Tac CV >30% and nonadherence or med errors (n = 16), LCP‐Tac conversion substantially reduced Tac CV (43.4% vs. 29.9%; p =.026). TTR significantly improved for those with Tac CV >30% with (52.4% vs. 82.8%; p =.027) or without nonadherence or med errors (64.8% vs. 73.2%; p =.005). CMV, BK, and overall infections were significantly higher prior to LCP‐Tac conversion. In the overall cohort, 3% had rejection before conversion and 2% after (p = NS). At end of follow‐up, graft and patient survival were 94% and 96%, respectively. Conclusions: In those with high Tac CV, conversion to LCP‐Tac is associated with a significant reduction in variability and improvement in TTR, particularly in those with nonadherence or medication errors. [ABSTRACT FROM AUTHOR]

Lymphocytic bronchitis (LB) precedes chronic lung allograft dysfunction. The relationships of LB (classified here as Endobronchial or E-grade rejection) to small airway (A- and B-grade) pathologies are unclear. We hypothesized that gene signatures common to allograft rejection would be present in LB. We studied LB in two partially overlapping lung transplant recipient cohorts: Cohort 1 included large airway brushes (6 LB cases and 18 post-transplant referents). Differential expression using DESeq2 was used for pathway analysis and to define an LB-associated metagene. In Cohort 2, eight biopsies for each pathology subtype were matched with pathology-free biopsies from the same subject (totaling 48 samples from 24 subjects). These biopsies were analyzed by multiplexed digital counting of immune transcripts. Metagene score differences were compared by paired t tests. Compared to referents in Cohort 1, LB demonstrated upregulation of allograft rejection pathways, and upregulated genes in these cases characterized an LB-associated metagene. We observed statistically increased expression in Cohort 2 for this LB-associated metagene and four other established allograft rejection metagenes in rejection vs paired non-rejection biopsies for both E-grade and A-grade subtypes, but not B-grade pathology. Gene expression-based categorization of allograft rejection may prove useful in monitoring lung allograft health.

The clinical significance and treatment strategies for minimal acute rejection (grade A1), the most common form of acute rejection (AR), remain controversial. In this retrospective single-center cohort study of 441 lung transplant recipients, we formally evaluate the association between minimal AR and chronic lung allograft dysfunction (CLAD) and test a novel hypothesis using bronchoalveolar lavage (BAL) CXCL9 concentration during minimal AR as a biomarker of subsequent CLAD development. In univariable and multivariable models adjusted for all histopathologic injury patterns, minimal AR was not associated with CLAD development. However, minimal AR with elevated BAL CXCL9 concentrations markedly increased CLAD risk in a dose-response manner. Minimal AR with CXCL9 concentrations greater than the 25th, 50th, and 75th percentile had adjusted hazard ratios (HRs) for CLAD of 1.1 (95% confidence interval [CI] 0.8-1.6), 1.6 (95% CI 1.1-2.3), and 2.2 (95% CI 1.4-3.4), respectively. Thus we demonstrate the utility of BAL CXCL9 measurement as a prognostic biomarker that allows discrimination of recipients at increased risk of CLAD development after minimal AR. BAL CXCL9 measurement during transbronchial biopsies may provide clinically useful prognostic data and guide treatment decisions for this common form of AR, as a possible strategy to minimize CLAD development.

Little is known about the effects of hepatitis C viremia on immunologic outcomes in the era of direct‐acting antivirals. We conducted a prospective, single‐arm trial of lung transplantation from hepatitis C‐infected donors into hepatitis C‐naïve recipients (n = 21). Recipients were initiated on glecaprevir‐pibrentasvir immediately post‐transplant and were continued on therapy for a total of 8 weeks. A control group of recipients of hepatitis C‐negative lungs were matched 1:1 on baseline variables (n = 21). The primary outcome was the frequency of acute cellular rejection over 1‐year post‐transplant. Treatment with glecaprevir‐pibrentasvir was well tolerated and resulted in viremia clearance after a median of 16 days of therapy (IQR 10–24 days). At one year, there was no difference in incidence of acute cellular rejection (71.4% vs. 85.7%, P =.17) or rejection requiring treatment (33.3% vs. 57.1%, P =.12). Mean cumulative acute rejection scores were similar between groups (.46 [SD ±.53] vs..52 [SD ±.37], P =.67). Receipt of HCV+ organs was not associated with acute rejection on unadjusted Cox regression analysis (HR.55, 95% CI.28‐1.11, P =.09), or when adjusted for risk factors known to be associated with acute rejection (HR.57, 95% CI.27‐1.21, P =.14). Utilization of hepatitis C infected lungs with immediate treatment leads to equivalent immunologic outcomes at 1 year. [ABSTRACT FROM AUTHOR]

The impact of allograft injury time of onset on the risk of chronic lung allograft dysfunction (CLAD) remains unknown. We hypothesized that episodes of late-onset (≥6 months) allograft injury would produce an augmented CXCR3/ligand immune response, leading to increased CLAD. In a retrospective single-center study, 1894 transbronchial biopsy samples from 441 lung transplant recipients were reviewed for the presence of acute rejection (AR), lymphocytic bronchiolitis (LB), diffuse alveolar damage (DAD), and organizing pneumonia (OP). The association between the time of onset of each injury pattern and CLAD was assessed by using multivariable Cox models with time-dependent covariates. Bronchoalveolar lavage (BAL) CXCR3 ligand concentrations were compared between early- and late-onset injury patterns using linear mixed-effects models. Late-onset DAD and OP were strongly associated with CLAD: adjusted hazard ratio 2.8 (95% confidence interval 1.5-5.3) and 2.0 (1.1-3.4), respectively. The early-onset form of these injury patterns did not increase CLAD risk. Late-onset LB and acute rejection (AR) predicted CLAD in univariable models but lost significance after multivariable adjustment for late DAD and OP. AR was the only early-onset injury pattern associated with CLAD development. Elevated BAL CXCR3 ligand concentrations during late-onset allograft injury parallel the increase in CLAD risk and support our hypothesis that late allograft injuries result in a more profound CXCR3/ligand immune response.

Chronic lung allograft dysfunction (CLAD) remains one of the major limitations to long-term survival after lung transplantation. We modified a murine model of CLAD and transplanted left lungs from BALB/c donors into B6 recipients that were treated with intermittent cyclosporine and methylprednisolone postoperatively. In this model, the lung allograft developed acute cellular rejection on day 15 which, by day 30 after transplantation, progressed to severe pleural and peribronchovascular fibrosis, reminiscent of changes observed in restrictive allograft syndrome. Lung transplantation into splenectomized B6 alymphoplastic (aly/aly) or splenectomized B6 lymphotoxin-β receptor-deficient mice demonstrated that recipient secondary lymphoid organs, such as spleen and lymph nodes, are necessary for progression from acute cellular rejection to allograft fibrosis in this model. Our work uncovered a critical role for recipient secondary lymphoid organs in the development of CLAD after pulmonary transplantation and may provide mechanistic insights into the pathogenesis of this complication., Competing Interests: Declaration of competing interest The authors of this manuscript have no conflicts of interest to disclose as described by the American Journal of Transplantation., (Copyright © 2024 American Society of Transplantation & American Society of Transplant Surgeons. Published by Elsevier Inc. All rights reserved.)

Abstract: Little is known about the impact of CYP3A5 polymorphisms on transplantation outcomes among African American (AA) kidney transplant recipients (KTRs). To assess this issue, clinical outcomes were compared between AA CYP3A5*1 expressers and nonexpressers. This retrospective cohort study analyzed AA KTRs. Biopsy‐proven acute rejection (BPAR), delayed graft function (DGF), glomerular filtration rate (GFR), infections, and tacrolimus dosing requirements were examined in 106 immunologically high‐risk AA kidney transplant patients over a 2‐year follow‐up period. In CYP3A5*1 expressers compared to nonexpressers, the incidence of BPAR was significantly higher in the first 6 months (13% vs 0%; P = .016) compared to 24 months (13% vs 7%; P = .521). Tacrolimus total daily dose at first therapeutic level was significantly higher in CYP3A5*1 expressers (12 mg/day) compared to nonexpressers (8 mg/day; P < .001). Compared to CYP3A5*1 nonexpressers, DGF incidence was significantly higher among CYP3A5*1 expressers (27.6% vs 6.7%; P = .006). By contrast, median GFR was significantly higher in CYP3A5*1 expressers compared to nonexpressers (54.5 mL/min vs 50.0 mL/min; P = .003) at 24 months. The findings from this retrospective study suggest that AAs with CYP3A5*1 expression require 50% more tacrolimus and have an increased incidence of DGF and acute rejection. [ABSTRACT FROM AUTHOR]

Acute rejection (AR) is an important factor that leads to poor prognosis after liver transplantation (LT). Macrophage M1-polarization is an important mechanism in AR development. MicroRNAs play vital roles in disease regulation; however, their effects on macrophages and AR remain unclear. In this study, rat models of AR were established following LT, and macrophages and peripheral blood mononuclear cells were isolated from rats and humans, respectively. We found miR-449a expression to be significantly reduced in macrophages and peripheral blood mononuclear cells. Overexpression of miR-449a not only inhibited the M1-polarization of macrophages in vitro but also improved the AR of transplant in vivo. The mechanism involved inhibiting the noncanonical nuclear factor-kappaB (NF-κB) pathway. We identified procollagen-lysine1,2-oxoglutarate5-dioxygenase 1 (PLOD1) as a target gene of miR-449a, which could reverse miR-449a's inhibition of macrophage M1-polarization, amelioration of AR, and inhibition of the NF-κB pathway. Overall, miR-449a inhibited the NF-κB pathway in macrophages through PLOD1 and also inhibited the M1-polarization of macrophages, thus attenuating AR after LT. In conclusion, miR-449a and PLOD1 may be new targets for the prevention and mitigation of AR., (Copyright © 2022 American Society of Transplantation & American Society of Transplant Surgeons. Published by Elsevier Inc. All rights reserved.)

Outcomes following heart transplantation remain suboptimal with acute and chronic rejection being major contributors to poor long-term survival. IL-6 is increasingly recognized as a critical pro-inflammatory cytokine involved in allograft injury and has been shown to play a key role in regulating the inflammatory and alloimmune responses following heart transplantation. Therapies that inhibit IL-6 signaling have emerged as promising strategies to prevent allograft rejection. Here, we review experimental and pre-clinical evidence that supports the potential use of IL-6 signaling blockade to improve outcomes in heart transplant recipients., (© 2022 The American Society of Transplantation and the American Society of Transplant Surgeons.)

Acute rejection (AR) of corneal transplants (CT) has a profound effect on subsequent graft survival but detailed immunological studies in human CT recipients are lacking. In this multi-site, cross-sectional study, clinical details and blood samples were collected from adults with clinically diagnosed AR of full-thickness (FT)-CT (n = 35) and posterior lamellar (PL)-CT (n = 21) along with Stable CT recipients (n = 177) and adults with non-transplanted corneal disease (n = 40). For those with AR, additional samples were collected 3 months later. Immune cell analysis was performed by whole-genome microarrays (whole blood) and high-dimensional multi-color flow cytometry (peripheral blood mononuclear cells). For both, no activation signature was identified within the B cell and T cell repertoire at the time of AR diagnosis. Nonetheless, in FT- but not PL-CT recipients, AR was associated with differences in B cell maturity and regulatory CD4 + T cell frequency compared to stable allografts. These data suggest that circulating B cell and T cell subpopulations may provide insights into the regulation of anti-donor immune response in human CT recipients with differing AR risk. Our results suggest that, in contrast to solid organ transplants, genetic or cellular assays of peripheral blood are unlikely to be clinically exploitable for prediction or diagnosis of AR., (© 2022 The Authors. American Journal of Transplantation published by Wiley Periodicals LLC on behalf of The American Society of Transplantation and the American Society of Transplant Surgeons.)

Plasma donor-derived cell-free DNA (dd-cfDNA) is a sensitive biomarker for the diagnosis of acute rejection in lung transplant recipients; however, differences in dd-cfDNA levels between single and double lung transplant remains unknown. We performed an observational analysis that included 221 patients from two prospective cohort studies who had serial measurements of plasma dd-cfDNA at the time of bronchoscopy and pulmonary function testing, and compared dd-cfDNA between single and double lung transplant recipients across a range of disease states. Levels of dd-cfDNA were lower for single vs. double lung transplant in stable controls (median [IQR]: 0.15% [0.07, 0.44] vs. 0.46% [0.23, 0.74], p < .01) and acute rejection (1.06% [0.75, 2.32] vs. 1.78% [1.18, 5.73], p = .05). Doubling dd-cfDNA for single lung transplant to account for differences in lung mass eliminated this difference. The area under the receiver operating curve (AUC) for the detection of acute rejection was 0.89 and 0.86 for single and double lung transplant, respectively. The optimal dd-cfDNA threshold for the detection of acute rejection was 0.54% in single lung and 1.1% in double lung transplant. In conclusion, accounting for differences in dd-cfDNA in single versus double lung transplant is key for the interpretation of dd-cfDNA testing in research and clinical settings., (© 2022 The Authors. American Journal of Transplantation published by Wiley Periodicals LLC on behalf of The American Society of Transplantation and the American Society of Transplant Surgeons.)

The importance of PD-1/PD-L1 interaction to alloimmune response is unknown in intestinal transplantation. We tested whether PD-L1 regulates allograft tissue injury in murine intestinal transplantation. PD-L1 expression was observed on the endothelium and immune cells in the intestinal allograft. Monoclonal antibody treatment against PD-L1 led to accelerated allograft tissue damage, characterized by severe cellular infiltrations, massive destruction of villi, and increased crypt apoptosis in the graft. Interestingly, PD-L1 -/- allografts were more severely rejected than wild-type allografts, but the presence or absence of PD-L1 in recipients did not affect the degree of allograft injury. PD-L1 -/- allografts showed increased infiltrating Ly6G + and CD11b + cells in lamina propria on day 4, whereas the degree of CD4 + or CD8 + T cell infiltration was comparable to wild-type allografts. Gene expression analysis revealed that PD-L1 -/- allografts had increased mRNA expressions of Cxcr2, S100a8/9, Nox1, IL1rL1, IL1r2, and Nos2 in the lamina propria cells on day 4. Taken together, study results suggest that PD-L1 expression in the intestinal allograft, but not in the recipient, plays a critical role in mitigating allograft tissue damage in the early phase after transplantation. The PD-1/PD-L1 interaction may contribute to immune regulation of the intestinal allograft via the innate immune system., (© 2021 The American Society of Transplantation and the American Society of Transplant Surgeons.)

Donor-derived cell-free DNA (dd-cfDNA) has been evaluated as a rejection marker in organ transplantation. This study sought to assess the utility of dd-cfDNA to diagnose graft injury in liver transplant recipients (LTR) and as a predictive biomarker prior to different causes of graft dysfunction. Plasma from single and multicenter LTR cohorts was analyzed for dd-cfDNA. Phenotypes of treated biopsy-proven acute rejection (AR, N = 57), normal function (TX, N = 94), and acute dysfunction no rejection (ADNR; N = 68) were divided into training and test sets. In the training set, dd-cfDNA was significantly different between AR versus TX (AUC 0.95, 5.3% cutoff) and AR versus ADNR (AUC 0.71, 20.4% cutoff). Using these cutoffs in the test set, the accuracy and NPV were 87% and 100% (AR vs. TX) and 66.7% and 87.8% (AR vs. ADNR). Blood samples collected serially from LTR demonstrated incremental elevations in dd-cfDNA prior to the onset of graft dysfunction (AR > ADNR), but not in TX. Dd-cfDNA also decreased following treatment of rejection. In conclusion, the serial elevation of dd-cfDNA identifies pre-clinical graft injury in the context of normal liver function tests and is greatest in rejection. This biomarker may help detect early signs of graft injury and rejection to inform LTR management strategies., (© 2021 The American Society of Transplantation and the American Society of Transplant Surgeons.)

Early insults associated with cardiac transplantation increase the immunogenicity of donor microvascular endothelial cells (ECs), which interact with recipient alloreactive memory T cells and promote responses leading to allograft rejection. Thus, modulating EC immunogenicity could potentially alter T cell responses. Recent studies have shown modulating mitochondrial fusion/fission alters immune cell phenotype. Here, we assess whether modulating mitochondrial fusion/fission reduces EC immunogenicity and alters EC-T cell interactions. By knocking down DRP1, a mitochondrial fission protein, or by using the small molecules M1, a fusion promoter, and Mdivi1, a fission inhibitor, we demonstrate that promoting mitochondrial fusion reduced EC immunogenicity to allogeneic CD8 + T cells, shown by decreased T cell cytotoxic proteins, decreased EC VCAM-1, MHC-I expression, and increased PD-L1 expression. Co-cultured T cells also displayed decreased memory frequencies and Ki-67 proliferative index. For in vivo significance, we used a novel murine brain-dead donor transplant model. Balb/c hearts pretreated with M1/Mdivi1 after brain-death induction were heterotopically transplanted into C57BL/6 recipients. We demonstrate that, in line with our in vitro studies, M1/Mdivi1 pretreatment protected cardiac allografts from injury, decreased infiltrating T cell production of cytotoxic proteins, and prolonged allograft survival. Collectively, our data show promoting mitochondrial fusion in donor ECs mitigates recipient T cell responses and leads to significantly improved cardiac transplant survival., (© 2021 The Authors. American Journal of Transplantation published by Wiley Periodicals LLC on behalf of The American Society of Transplantation and the American Society of Transplant Surgeons.)

The histopathologic diagnosis of acute allograft injury is prognostically important in lung transplantation with evidence demonstrating a strong and consistent association between acute rejection (AR), acute lung injury (ALI), and the subsequent development of chronic lung allograft dysfunction (CLAD). The pathogenesis of these allograft injuries, however, remains poorly understood. CXCL9 and CXCL10 are CXC chemokines induced by interferon-γ and act as potent chemoattractants of mononuclear cells. We hypothesized that these chemokines are involved in the mononuclear cell recruitment associated with AR and ALI. We further hypothesized that the increased activity of these chemokines could be quantified as increased levels in the bronchoalveolar lavage fluid. In this prospective multicenter study, we evaluate the incidence of histopathologic allograft injury development during the first-year post-transplant and measure bronchoalveolar CXCL9 and CXCL10 levels at the time of the biopsy. In multivariable models, CXCL9 levels were 1.7-fold and 2.1-fold higher during AR and ALI compared with "normal" biopsies without histopathology. Similarly, CXCL10 levels were 1.6-fold and 2.2-fold higher during these histopathologies, respectively. These findings support the association of CXCL9 and CXCL10 with episodes of AR and ALI and provide potential insight into the pathogenesis of these deleterious events., (© 2021 The American Society of Transplantation and the American Society of Transplant Surgeons.)

Personalizing immunosuppression is a major objective in transplantation. Transplant recipients are heterogeneous regarding their immunological memory and primary alloimmune susceptibility. This biomarker-guided trial investigated whether in low immunological-risk kidney transplants without pretransplant DSA and donor-specific T cells assessed by a standardized IFN-γ ELISPOT, low immunosuppression (LI) with tacrolimus monotherapy would be non-inferior regarding 6-month BPAR than tacrolimus-based standard of care (SOC). Due to low recruitment rates, the trial was terminated when 167 patients were enrolled. ELISPOT negatives (E-) were randomized to LI (n = 48) or SOC (n = 53), E+ received the same SOC. Six- and 12-month BPAR rates were higher among LI than SOC/E- (4/35 [13%] vs. 1/43 [2%], p = .15 and 12/48 [25%] vs. 6/53 [11.3%], p = .073, respectively). E+ patients showed similarly high BPAR rates than LI at 6 and 12 months (12/55 [22%] and 13/66 [20%], respectively). These differences were stronger in per-protocol analyses. Post-hoc analysis revealed that poor class-II eplet matching, especially DQ, discriminated E- patients, notably E-/LI, developing BPAR (4/28 [14%] low risk vs. 8/20 [40%] high risk, p = .043). Eplet mismatch also predicted anti-class-I (p = .05) and anti-DQ (p < .001) de novo DSA. Adverse events were similar, but E-/LI developed fewer viral infections, particularly polyoma-virus-associated nephropathy (p = .021). Preformed T cell alloreactivity and HLA eplet mismatch assessment may refine current baseline immune-risk stratification and guide immunosuppression decision-making in kidney transplantation., (© 2021 The American Society of Transplantation and the American Society of Transplant Surgeons.)

Acute rejection after heart transplantation increases the risk of chronic dysfunction. Disturbances in mitochondrial function may play a contributory role, however, the relationship between histological signs of rejection in the human transplanted heart and expression levels of circulating mitochondrial genes, such as the mitochondrial Ca 2+ uniporter (MCU) complex, remains unexplored. We conducted an RNA-sequencing analysis to identify altered mitochondrial genes in serum and to evaluate their diagnostic accuracy for rejection episodes. We included 40 consecutive samples from transplant recipients undergoing routine endomyocardial biopsies. In total, 112 mitochondrial genes were identified in the serum of posttransplant patients, of which 28 were differentially expressed in patients with acute rejection (p < .05). Considering the receiver operating characteristic analysis with an area under the curve (AUC) >0.900 to discriminate patients with moderate or severe degrees of rejection, we found that the MCU system showed a strong capability for detection: MCU (AUC = 0.944, p < .0001), MCU/MCUR1 ratio (AUC = 0.972, p < .0001), MCU/MCUB ratio (AUC = 0.970, p < .0001), and MCU/MICU1 ratio (AUC = 0.970, p < .0001). Mitochondrial alterations are reflected in peripheral blood and are capable of discriminating between patients with allograft rejection and those not experiencing rejection with excellent accuracy. The dysregulation of the MCU complex was found to be the most relevant finding., (© 2020 The Authors. American Journal of Transplantation published by Wiley Periodicals LLC on behalf of The American Society of Transplantation and the American Society of Transplant Surgeons.)

Background: It has been shown that glomerulonephritis (GN) recurrence affects graft survival more than acute rejection. Thus, we assessed allograft survival after biopsy‐confirmed diagnosis of acute rejection or recurrent GN in current era of immunosuppression. Methods: Allograft survival following a biopsy diagnosis of acute rejection or recurrent GN was determined in adult kidney transplant recipients from 1994 to 2013. A total of 306 patients (35%) with IgA, 298 (35%) with FSGS, 177 (21%) with lupus nephritis, and 81 (9%) with membranous nephropathy were followed for a median of 6.3 years. Results: Among the 862 transplant recipients with primary GN, allograft loss was similar following a biopsy diagnosis of acute rejection or recurrent glomerular disease (11.5 vs 14.2/100 person‐years, P =.15). Differences in allograft survival emerged after 2.5 years following recurrent disease, with significantly higher graft failure in patients with FSGS, MN, or LN compared with IgA after recurrence of disease (16.7 vs 7.5/100 person‐years, P =.05). The advantage in allograft survival for IgA patients did not achieve significance after acute rejection (P =.10 for IgA vs FSGS, MN, and LN). Conclusions: Allograft survival was similar after disease recurrence or acute rejection after kidney transplant in patients with ESRD due to GN. [ABSTRACT FROM AUTHOR]

Kidney transplant recipients administered belatacept-based maintenance immunosuppression present with a more favorable metabolic profile, reduced incidence of de novo donor-specific antibodies (DSAs), and improved renal function and long-term patient/graft survival relative to individuals receiving calcineurin inhibitor (CNI)-based immunosuppression. However, the rates and severity of acute rejection (AR) are greater with the approved belatacept-based regimen than with CNI-based immunosuppression. Although these early co-stimulation blockade-resistant rejections are typically steroid sensitive, the higher rate of cellular AR has led many transplant centers to adopt immunosuppressive regimens that differ from the approved label. This article summarizes the available data on these alternative de novo belatacept-based maintenance regimens. Steroid-sparing, belatacept-based immunosuppression (following T cell-depleting induction therapy) has been shown to yield AR rates comparable to those seen with CNI-based regimens. Concomitant treatment with belatacept plus a mammalian target of rapamycin inhibitor (mTORi; sirolimus or everolimus) has yielded AR rates ranging from 0 to 4%. Because the optimal induction agent and number of induction doses; blood levels of mTORi; and dose, duration, and use of corticosteroids have yet to be determined, larger prospective clinical trials are needed to establish the optimal alternative belatacept-based regimen for minimizing early cellular AR occurrence., (© 2020 The Authors. American Journal of Transplantation published by Wiley Periodicals LLC on behalf of The American Society of Transplantation and the American Society of Transplant Surgeons.)

Improving long-term kidney transplant outcomes requires novel treatment strategies, including delayed calcineurin inhibitor (CNI) substitution, tested using informative trial designs. An alternative approach to the usual superiority-based trial is a noninferiority trial design that tests whether an investigational agent is not unacceptably worse than standard of care. An informative noninferiority design, with biopsy-proven acute rejection (BPAR) as the endpoint, requires determination of a prespecified, evidence-based noninferiority margin for BPAR. No such information is available for delayed CNI substitution in kidney transplantation. Herein we analyzed data from recent kidney transplant trials of CNI withdrawal and "real world" CNI- based standard of care, containing subjects with well-documented evidence of immune quiescence at 6 months posttransplant-ideal candidates for delayed CNI substitution. Our analysis indicates an evidence-based noninferiority margin of 13.8% for the United States Food and Drug Administration's composite definition of BPAR between 6 and 24 months posttransplant. Sample size estimation determined that ~225 randomized subjects would be required to evaluate noninferiority for this primary clinical efficacy endpoint, and superiority for a renal function safety endpoint. Our findings provide the basis for future delayed CNI substitution noninferiority trials, thereby increasing the likelihood they will provide clinically implementable results and achieve regulatory approval., (© 2020 The American Society of Transplantation and the American Society of Transplant Surgeons.)

Individualized posttransplant immunosuppression is hampered by suboptimal monitoring strategies. To validate the utility of urinary CXCL10/Cr immune monitoring in children, we conducted a multicenter prospective observational study in children <21 years with serial and biopsy-associated urine samples (n = 97). Biopsies (n = 240) were categorized as normal (NOR), rejection (>i1t1; REJ), indeterminate (IND), BKV infection, and leukocyturia (LEU). An independent pediatric cohort of 180 urines was used for external validation. Ninety-seven patients aged 11.4 ± 5.5 years showed elevated urinary CXCL10/Cr in REJ (3.1, IQR 1.1, 16.4; P < .001) and BKV nephropathy (median = 5.6, IQR 1.3, 26.9; P < .001) vs. NOR (0.8, IQR 0.4, 1.5). The AUC for REJ vs. NOR was 0.76 (95% CI 0.66-0.86). Low (0.63) and high (4.08) CXCL10/Cr levels defined high sensitivity and specificity thresholds, respectively; validated against an independent sample set (AUC = 0.76, 95% CI 0.66-0.86). Serial urines anticipated REJ up to 4 weeks prior to biopsy and declined within 1 month following treatment. Elevated mean CXCL10/Cr was correlated with first-year eGFR decline (ρ = -0.37, P ≤ .001), particularly when persistently exceeding ≥4.08 (ratio = 0.81; P < .04). Useful thresholds for urinary CXCL10/Cr levels reproducibly define the risk of rejection, immune quiescence, and decline in allograft function for use in real-time clinical monitoring in children., (© 2020 The American Society of Transplantation and the American Society of Transplant Surgeons.)

The optimal duration and frequency of routine surveillance endomyocardial biopsy (EMB) have been questioned in the current era of heart transplantation (HT), where the advances in immunosuppression and donor selection strategies have led to a decline in acute allograft rejection. We investigated the utility of routine EMB beyond 6 months post-HT. A single-center retrospective review was performed on 2963 EMBs from 220 HT recipients over 10 years. Each EMB was categorized into protocol or symptom-triggered biopsy and reviewed for rejection. Heart transplant recipients with ≥2 known risk factors for rejection were designated as an elevated risk group. The majority of rejections occurred within 3 months following HT. The yield of routine protocol EMBs was significantly lower than symptom-triggered EMBs, not only during the first 6 months post-HT (1.6% vs. 33.3%, P < .0001), but more so during the 6-12 months (0.1% vs 83.0%, P < .0001). A similar pattern was observed in heart transplant recipients at both elevated and standard risk for rejection. In conclusion, EMB was found to be a low-yield screening modality for rejection beyond 6 months post-HT., (© 2020 The American Society of Transplantation and the American Society of Transplant Surgeons.)

Recent data suggest that frequent endoscopy and biopsy without evidence of graft dysfunction does not appear to confer survival advantage after intestinal transplantation. After abandoning protocol surveillance, endoscopic examination was decreased significantly at our center. These observations led us to question the need for stoma creation in intestinal transplantation. Herein, we report clinical outcomes of intestinal transplantation without stoma, compared to conventional transplant with stoma. Data analysis was limited to adult intestinal transplantation without liver allograft between 2015 and 2018. We compared patient and graft survival, frequency of endoscopic evaluation, episodes of acute rejection, nutritional therapy, and renal function between "Control group (with stoma)," n = 18 grafts in 16 patients and "Study group (without stoma)," n = 16 grafts in 15 patients. Overall outcome was similar between the 2 groups with respect to graft and patient survival, episodes of acute rejection, and its response to treatment. Nutritional outcomes were similar in both groups. Fewer antidiarrheal medications were required in the study group, but this did not translate into demonstrable gains in preservation of renal function, despite an apparent trend to improvement. Intestinal transplantation without stoma appears to be an acceptable practice model without obvious adverse impact on outcome., (© 2020 The American Society of Transplantation and the American Society of Transplant Surgeons.)

The urinary chemokines CXCL9 and CXCL10 are promising noninvasive diagnostic markers of acute rejection (AR) in kidney recipients, but their levels might be confounded by urinary tract infection (UTI) and BK virus (BKV) reactivation. Multiparametric model development and validation addressed these confounding factors in a training set of 391 samples, optimizing the diagnostic performance of urinary chemokines. CXCL9/creatinine increased in UTI and BKV viremia with or without nephropathy (BKVN) (no UTI/leukocyturia/UTI: -0.10/1.61/2.09, P = .0001 and no BKV/viremia/BKVN: -0.10/1.90/2.29, P < .001) as well as CXCL10/creatinine (1.17/2.09/1.98, P < .0001 and 1.13/2.21/2.51, P < .001, respectively). An optimized 8-parameter model (recipient age, sex, estimated glomerular filtration rate, donor specific antibodies, UTI, BKV blood viral load, CXCL9, and CXCL10) diagnosed AR with high accuracy (area under the curve [AUC]: 0.85, 95% confidence interval [CI]: 0.80-0.89) and remained highly accurate at the time of screening (AUC: 0.81, 95% CI: 0.48-1) or indication biopsies (AUC: 0.85, 95% CI: 0.81-0.90) and within the first year (AUC: 0.86, 95% CI: 0.80-0.91) or later (AUC: 0.90, 95% CI: 0.84-0.96), achieving AR diagnosis with an AUC of 0.85 and 0.92 (P < .0001) in 2 external validation cohorts. Decision curve analyses demonstrated the clinical utility of the model. Considering confounding factors rather than excluding them, we optimized a noninvasive multiparametric diagnostic model for AR of kidney allografts with unprecedented accuracy., (© 2020 The American Society of Transplantation and the American Society of Transplant Surgeons.)

After heart transplant, adding everolimus (EVL) to standard immunosuppressive regimen mostly relies on converting calcineurin inhibitors (CNIs) into EVL. The aim of this study was to describe the effects of combining low-dose EVL and CNIs in maintenance immunosuppression regimen (quadritherapy) and compare it with standard tritherapy associating standard-dose CNIs, mycophenolate mofetil, and corticosteroids. In the 3-year registry cohort of heart transplanted patients, those who received quadritherapy were compared with those who received tritherapy. EVL was added after 3 months posttransplant. Three analyses were performed to control for confounders: propensity score matching, multivariable survival, and inverse probability score weighting analyses. Among 213 patients who were included (75 with quadritherapy), propensity score matching selected 64 unique pairs of patients with similar characteristics. In the matched cohort (n = 128), quadritherapy was associated with fewer deaths (3 [4.7%] vs 17 [21.9%], P = .007) and biopsy-proven acute rejections (15 [23.4%] vs 31 [48.4%], P = .002). These results were confirmed in the overall cohort (n = 213), after multivariable and inverse probability score weighting analyses. Renal function and donor-specific HLA-antibodies remained similar in both groups. Low-dose combination quadritherapy was associated with fewer deaths and rejections, compared with standard immunosuppression tritherapy., (© 2020 The American Society of Transplantation and the American Society of Transplant Surgeons.)

Tumor necrosis factor receptor 2 (TNFR2) is strongly upregulated on renal tubular epithelial cells by acute cell-mediated rejection (ACR. In human kidney organ culture, TNFR2 signaling both upregulates TNFR2 expression and promotes cell cycle entry of tubular epithelial cells. We find significantly more cells express CD133 mRNA and protein, a putative stem cell marker, in allograft biopsy samples with ACR compared to acute tubular injury without rejection or pretransplant "normal kidney" biopsy samples. Of CD133 + cells, ~85% are within injured tubules and ~15% are interstitial. Both populations express stem cell marker TRA-1-60 and TNFR2, but only tubular CD133 + cells express proximal tubular markers megalin and aquaporin-1. TNFR2 + CD133 + cells in tubules express proliferation marker phospho-histone H3 S10 (pH3 S10 ). Tubular epithelial cells in normal kidney organ cultures respond to TNFR2 signaling by expressing CD133 mRNA and protein, stem cell marker TRA-1-60, and pH3 S10 within 3 hours of treatment. This rapid response time suggests that CD133 + cells in regenerating tubules of kidneys undergoing ACR represent proliferating tubular epithelial cells with TNFR2-induced stem cell markers rather than expansion of resident stem cells. Infiltrating host mononuclear cells are a likely source of TNF as these changes are absent in acute tubular injury ., (© 2020 The Authors. American Journal of Transplantation published by Wiley Periodicals LLC on behalf of The American Society of Transplantation and the American Society of Transplant Surgeon.)

Regulatory T (Treg) cells are important in preventing acute rejection (AR) in solid organ transplantation, but the clinical relevance of the different kinetics early after liver transplantation (LT) in acute rejectors and non-rejectors is unclear. We analyzed peripheral blood samples of 128 LT recipients receiving basiliximab induction plus tacrolimus immunosuppression. Samples were obtained at pretransplant, D7, and D30 after LT. Frequency and phenotype of Tregs were analyzed by flow cytometry. The predictive value of Treg frequency at D7 was assessed for suspected acute rejection (SAR) and was validated for biopsy-proven AR (BPAR). We found that the frequencies of total and activated Tregs at D7 were significantly lower in recipients with SAR and BPAR. Treg was more reduced in BPARs by in vitro tacrolimus treatment in the presence of basiliximab. Moreover, an early reduction of Treg frequency in rejectors was associated with a greater increase in Treg apoptosis and further attenuated IL-2 signaling. D7 Treg frequency was an independent risk factor for SAR, which was also validated for BPAR. In conclusion, first-week peripheral blood Treg frequency correlates with AR after LT under tacrolimus-based immunosuppression, which needs to be proven in larger, geographically and clinically diverse populations., (© 2020 The American Society of Transplantation and the American Society of Transplant Surgeons.)

In a phase 2 multicenter open-label randomized trial sponsored by the National Institutes of Health, simultaneous pancreas-kidney (SPK) recipients were randomized to a calcineurin inhibitor (CNI)-based immunosuppressive regimen (tacrolimus) (n = 21), or an investigational arm using low-dose CNI plus costimulation blockade (belatacept) with intended CNI withdrawal (n = 22). Both arms included induction therapy with rabbit ATG, mycophenolate sodium, or mycophenolate mofetil and rapid withdrawal of steroids. Enrollment and CNI withdrawal were stopped after 43/60 planned subjects had been enrolled. At that time, the rate of biopsy-proven acute rejection (BPAR) of the pancreas was low in both groups until CNI was withdrawn, with four of the five pancreas rejections occurring during or after CNI withdrawal. The rate of BPAR of kidney allografts was low in both control (9.5%) and investigational (9.1%) arms. Pancreas graft survival at 52 weeks, defined by insulin independence, was 21 (100%) in the control group and 19 (86%) in the investigational arm. One subject in the investigational arm died with functioning pancreas and kidney grafts. Renal function at week 52 was similar in both arms. Costimulation blockade with belatacept did not provide sufficient immunosuppression to reliably prevent pancreas rejection in SPK transplants undergoing CNI withdrawal., (© 2020 The American Society of Transplantation and the American Society of Transplant Surgeons.)

Long-term survival after lung transplant lags behind that of other commonly transplanted organs, reflecting the current incomplete understanding of the mechanisms involved in the development of posttransplant lung injury, rejection, infection, and chronic allograft dysfunction. To address this unmet need, 2 ongoing National Institute of Allergy and Infectious Disease funded studies through the Clinical Trials in Organ Transplant Consortium (CTOT) CTOT-20 and CTOT-22 were dedicated to understanding the clinical factors and biological mechanisms that drive chronic lung allograft dysfunction and those that maintain cytomegalovirus polyfunctional protective immunity. The CTOT-20 and CTOT-22 studies enrolled 800 lung transplant recipients at 5 North American centers over 3 years. Given the number and complexity of subjects included, CTOT-20 and CTOT-22 utilized innovative data transfers and capitalized on patient-entered data collection to minimize site manual data entry. The data were coupled with an extensive biosample collection strategy that included DNA, RNA, plasma, serum, bronchoalveolar lavage fluid, and bronchoalveolar lavage cell pellet. This Special Article describes the CTOT-20 and CTOT-22 protocols, data and biosample strategy, initial results, and lessons learned through study execution., (© 2020 The American Society of Transplantation and the American Society of Transplant Surgeons.)

Acute cellular rejection (ACR) is a significant risk factor for chronic lung allograft dysfunction (CLAD). Although clinically manifest and higher grade (≥A2) ACR is generally treated with augmented immunosuppression, management of minimal (grade A1) ACR remains controversial. In our program, patients with subclinical and spirometrically stable A1 rejection (StA1R) are routinely not treated with augmented immunosuppression. We hypothesized that an untreated first StA1R does not increase the risk of CLAD or death compared to episodes of spirometrically stable no ACR (StNAR). The cohort was drawn from all consecutive adult, first, bilateral lung transplantations performed between 1999 and 2017. Biopsies obtained in the first-year posttransplant were paired with (forced expiratory volume in 1 second FEV 1 ). The first occurrence of StA1R was compared to a time-matched StNAR. The risk of CLAD or death was assessed using univariable and multivariable Cox proportional hazards models. The analyses demonstrated no significant difference in risk of CLAD or death in patients with a first StA1R compared to StNAR. This largest study to date shows that, in clinically stable patients, an untreated first A1 ACR in the first-year posttransplant is not significantly associated with an increased risk for CLAD or death. Watchful-waiting approach may be an acceptable tactic for stable A1 episodes in lung transplant recipients., (© 2019 The American Society of Transplantation and the American Society of Transplant Surgeons.)