Antibody-mediated rejection in kidney transplantation: a review of pathophysiology, diagnosis, and treatment options

Bortezomib for antibody-mediated rejection of kidney transplant in youth: Associations with donor-specific antibody

BACKGROUND

Antibody-mediated rejection is one of the most significant risk factors for allograft dysfunction and failure in children and adolescents with kidney transplants, yet optimal treatment remains unidentified. To date, there are mixed findings regarding the use of Bortezomib, a plasma cell apoptosis inducer, as an adjunct therapy in the treatment of antibody-mediated rejection.

METHODS

In a retrospective single center study, we reviewed the efficacy and tolerability of bortezomib as adjunct therapy for treatment-refractory antibody-mediated rejection.

RESULTS

Six patients with a median age of 14.6 years (range 6.9-20.1 years) received bortezomib at a mean of 71 months (range 15-83 months) post-kidney transplant. Four patients experienced decline in estimated glomerular filtration rate (eGFR) from 4% to 42%. One patient started bortezomib while on hemodialysis and did not recover graft function, and another patient progressed to hemodialysis 6 months after receiving bortezomib. Although DSA did not completely resolve, there was a statistically significant decline in DSA MFI pre and 12-months post-BZ (p = .012, paired t-test) for the subjects who were not on dialysis at the time of bortezomib. Chronic Allograft Damage Index (CADI) score of ≥3 was seen in all six subjects at their biopsy prior to therapy. No adverse effects were reported.

CONCLUSIONS

Bortezomib was well tolerated and resulted in improvements in MFI of DSA among four pediatric subjects without allograft failure, although no effects were observed on eGFR trajectory. Further studies are needed to clarify whether earlier intervention with bortezomib could prevent renal failure progression.

An autophagy-associated diagnostic signature based on peripheral blood for antibody-mediated rejection in renal transplantation

BACKGROUND

Antibody-mediated rejection (ABMR) emerged as a major cause of graft loss in renal transplantation. Needle biopsy is the gold standard for diagnosis of ABMR in renal allografts. Thus, noninvasive diagnosis methods of ABMR with high accuracy are urgently needed to prevent unnecessary biopsies.

METHODS

We collected peripheral blood transcriptome data from two independent renal transplantation cohorts with patients with ABMR, stable well-functioning transplants (STA), and T-cell mediated rejection (TCMR). Differentially expressed genes (DEGs) were identified by comparing the ABMR group with the STA group. In addition, functional enrichment analysis and gene set enrichment analysis were performed to seek new key underlying mechanisms in ABMR. Subsequently, we utilized a Boruta algorithm and least absolute shrinkage and selection operator logistic algorithm to establish a diagnostic model which was then evaluated and validated in an independent cohort.

RESULTS

According to functional enrichment analysis, autophagy was found to be the primary upregulated biological process in ABMR. Based on algorithms, three autophagy-associated genes, ubiquitin specific peptidase 33 (USP33), Ras homolog mTORC1 binding (RHEB), and ABL proto-oncogene 2 (ABL2), were selected to establish the diagnostic model in the training cohort. This autophagy-related gene model possessed good diagnostic value in distinguishing ABMR from STA blood samples in the training cohort (AUC = 0.907) and in the validation cohort (AUC = 0.972). In addition, this model also showed good discernibility in distinguishing ABMR from TCMR in the training and validation cohorts (AUCs = 0.908 and 0.833).

CONCLUSION

We identified and validated an autophagy-associated diagnostic model with high accuracy for renal transplant patients with ABMR. Our study provided a new potential test for the non-invasive diagnosis of ABMR in clinical practice and highlighted the importance of autophagy in ABMR.

Effect of Plasmapheresis on the Efficacy of Rituximab in Antibody-Mediated Rejection Patients

BACKGROUND

Rituximab and plasmapheresis (PP) suppress and eliminate antibody production in patients experiencing antibody-mediated rejection (AMR). Herein, we discuss a case where rituximab was less effective after PP for treating AMR.

CASE

A 55-year-old male patient underwent kidney transplantation. His renal function remained normal for 1 year. Subsequently, renal function declined, and (donor-specific antibodies showed positive results. A biopsy of the transplanted kidney revealed AMR. On the day of the biopsy, the medical staff administered 200 mg of rituximab, followed by IV immunoglobulin (IVIg) and PP the next day. The time interval between PP + IVIg treatment and rituximab was 12 h. As a result, the B-cell markers CD19 and CD20 did not decrease sufficiently, and the patient's creatinine and glomerular filtration rate muscles did not recover adequately.

CONCLUSION

We report a case in which PP was administered shortly after rituximab injection, resulting in insufficient B-cell inhibition due to the removal of rituximab.

Economic and humanistic burden in kidney transplant rejection: a literature review

INTRODUCTION

Antibody-mediated rejection (ABMR) is a major cause of late kidney allograft failure, but its economic and humanistic impacts have not been well-characterized in the literature.

AREAS COVERED

We reviewed available literature on economic burden (costs and healthcare resource use) and humanistic burden (health-related quality of life impacts [HRQOL] and utility estimates) in patients diagnosed with kidney transplant rejection; ABMR-specific studies were of particular interest. In total, 21 publications reporting economic and humanistic burden were included in the review; 9 of these reported ABMR-specific outcomes. The reviewed studies consistently showed a greater burden associated with ABMR-related transplant rejection than with non-ABMR transplant rejection.

EXPERT OPINION

Evidence suggests greater economic burden and increased HRQOL impairment with ABMR-related kidney transplant rejection relative to non-ABMR, although small sample sizes and missing definitions for ABMR make meaningful comparisons between studies challenging. Because no International Classification of Diseases (ICD)-10 codes currently describe the etiologies of transplant rejection, it is difficult to characterize the burden of distinct types of transplant rejection. The paucity of high-quality data on the burden of ABMR in kidney transplant rejection demonstrates the need for more etiology-centric ICD-10 codes.

Canadian Kidney Transplant Professionals' Perspectives on Precision Medicine and Molecular Matching in Kidney Allocation

Background

Antibody-mediated rejection is an important cause of kidney transplant loss. A new strategy requiring application of precision medicine tools in transplantation considers molecular compatibility between donors and recipients and holds the promise of improved immunologic risk, preventing rejection and premature graft loss. The objective of this study was to gather Canadian transplant professionals' perspectives on molecular compatibility in kidney transplantation.

Methods

Seventeen Canadian transplant professionals (14 nephrologists, 2 nurses, and 1 surgeon) participated in semistructured interviews in 2021. The interviews were digitally recorded, transcribed, and analyzed using the qualitative description approach.

Results

Participants identified fair access to transplantation as the most important principle in kidney allocation. Molecular compatibility was viewed as a promising innovation. However, participants were concerned about increased waiting times, negative impact on some patients, and potential problems related to the adequacy of information explaining this new technology. To mitigate the challenges associated with molecular matching, participants suggested integrating a maximum waiting time for molecular-matched kidneys and expanding the program nationally/internationally.

Conclusions

Molecular matching in kidney transplantation is viewed as a promising technology for decreasing the incidence of antibody-mediated rejection and improving graft survival. Further studies are needed to determine how to ethically integrate this technology into the kidney allocation algorithm.

Complement and Non-Complement Binding Anti-HLA Antibodies Are Differentially Detected with Different Antigen Bead Assays in Renal Transplant Recipients

Two semi-quantitative, Luminex-based, single-antigen bead (SAB) assays are available to detect anti-HLA antibodies and evaluate their reactivity with complement binding. Sera from 97 patients with positive panel reactive antibody tests (>5%) were analyzed with two SAB tests, Immucor (IC) and One-Lambda (OL), for anti-HLA antibody detection and the evaluation of their complement-binding capacity. IC detected 1608/8148 (mean fluorescent intensity (MFI) 4195 (1995-11,272)) and 1136/7275 (MFI 6706 (2647-13,184)) positive anti-HLA class I and II specificities, respectively. Accordingly, OL detected 1942/8148 (MFI 6185 (2855-12,099)) and 1247/7275 (MFI 9498 (3630-17,702)) positive anti-HLA class I and II specificities, respectively. For the IC assay, 428/1608 (MFI 13,900 (9540-17,999)) and 409/1136 (MFI 11,832 (7128-16,531)) positive class I and II specificities bound C3d, respectively. Similarly, OL detected 485/1942 (MFI 15,452 (9369-23,095)) and 298/1247 (MFI18,852 (14,415-24,707)) C1q-binding class I and II specificities. OL was more sensitive in detecting class I and II anti-HLA antibodies than IC was, although there was no significant difference in the number of class II specificities per case. MFI was higher for complement vs. non-complement-binding anti-HLA antibodies in both assays. Both methods were equal in detecting complement-binding anti-HLA class I antibodies, whereas the C3d assay was more sensitive in detecting complement-binding anti-HLA class II antibodies.

TNF-α -308A/G SNP association with kidney allograft rejection in Algerian population: A retrospective case-control study

No consensus has been reached regarding the association beween the -308A/G single nucleotide polymorphism (SNP) in the tumor necrosis factor-α gene (TNFA) and kidney allograft rejection (KAR). Our retrospective case-control study aimed to assess the association of the SNP with KAR in Algerian patients who underwent kidney transplantation. The study enrolled 313 Algerian patients: 58 kidney-transplant recipients without rejection events (PWoR); 58 kidney-transplant recipients with at least one rejection event, with or without graft loss (PWR); and 197 healthy individuals (HI). The TNFA -308A/G SNP was genotyped using a real-time polymerase chain reaction. The results demonstrated that, the frequencies of TNFA -308A allele and AA genotype were higher in the PWR than in the HI groups (p = 0.001, OR = 2.26, CI = 1.33-3.77 and p = 0.0004, OR = 5.53, CI-1.89-16.6, respectively). Furthermore, the frequencies were higher among the PWR than among the PWoR groups (p = 0.001, OR = 3.29, CI = 1.56-7.21 and p = 0.0006, OR = 28.26, CI = 1.62-493.2, respectively), particularly among PWR patients with de novo anti-human leukocyte antigens (HLA) antibodies (PG-a-HLA-Ab). However, the frequency of TNFA -308G allele was lower in the PWR group than in the PWoR group (p = 0.001, OR = 0.3, CI = 0.1-0.64) and the HI group (p = 0.001, OR = 0.44, CI = 0.27-0.44). Our results suggest an association of the TNFA -308A/G alleles with KAR in Algerian patients who underwent kidney transplantation. Carriers of TNFA -308A allele who have PG-a-HLA-Ab might have a higher risk, whereas TNFA -308G allele carriers could have a lower risk of KAR. Thus, therapeutic strategies can be adapted to minimize KAR risk in patients who have a genetic proclivity for increased pro-inflammatory TNF-α activity.

Early Versus Late Acute AMR in Kidney Transplant Recipients-A Comparison of Treatment Approaches and Outcomes From the ANZDATA Registry

BACKGROUND

Antibody-mediated rejection (AMR) is a major cause of kidney allograft failure and demonstrates different properties depending on whether it occurs early (<6 mo) or late (>6 mo) posttransplantation. We aimed to compare graft survival and treatment approaches for early and late AMR in Australia and New Zealand.

METHODS

Transplant characteristics were obtained for patients with an AMR episode reported to the Australia and New Zealand Dialysis and Transplant Registry from January 2003 to December 2019. The primary outcome of time to graft loss from AMR diagnosis, with death considered a competing risk, was compared between early and late AMR using flexible parametric survival models. Secondary outcomes included treatments used, response to treatment, and time from AMR diagnosis to death.

RESULTS

After adjustment for other explanatory factors, late AMR was associated with twice the risk of graft loss relative to early AMR. The risk was nonproportional over time, with early AMR having an increased early risk. Late AMR was also associated with an increased risk of death. Early AMR was treated more aggressively than late with more frequent use of plasma exchange and monoclonal/polyclonal antibodies. There was substantial variation in treatments used by transplant centers. Early AMR was reported to be more responsive to treatment than late.

CONCLUSIONS

Late AMR is associated with an increased risk of graft loss and death compared with early AMR. The marked heterogeneity in the treatment of AMR highlights the need for effective, new therapeutic options for these conditions.

A bibliometric and knowledge-map analysis of antibody-mediated rejection in kidney transplantation

OBJECTIVES

Antibody-mediated rejection (AMR) is a large obstacle to the long-term survival of allograft kidneys. It is urgent to find novel strategies for its prevention and treatment. Bibliometric analysis is helpful in understanding the directions of one field. Hence, this study aims to analyze the state and emerging trends of AMR in kidney transplantation.

METHODS

Literature on AMR in kidney transplantation from 1999 to 2022 was collected from the Web of Science Core Collection. HistCite (version 12.03.17), CiteSpace (version 6.2.R2), Bibliometrix 4.1.0 Package from R language, and Gephi (https://gephi.org) were applied to the bibliometric analysis of the annual publications, leading countries/regions, core journals, references, keywords, and trend topics.

RESULTS

A total of 2522 articles related to AMR in kidney transplantation were included in the analysis and the annual publications increased year by year. There were 10874 authors from 118 institutions located in 70 countries/regions contributing to AMR studies, and the United States took the leading position in both articles and citation scores. Halloran PF from Canada made the most contribution to AMR in kidney transplantation. The top 3 productive journals, American Journal of Transplantation, Transplantation, and Transplantation Proceedings, were associated with transplantation. Moreover, the recent trend topics mainly focused on transplant outcomes, survival, and clinical research.

CONCLUSIONS

North American and European countries/regions played central roles in AMR of kidney transplantation. Importantly, the prognosis of AMR is the hotspot in the future. Noninvasive strategies like plasma and urine dd-cfDNA may be the most potential direction in the AMR field.

Single-Cell Heterogeneity Restorative Chimeric Engineering Nanoparticles for Alleviating Antibody-Mediated Allograft Injury

Disturbance of single-cell transcriptional heterogeneity is an inevitable consequence of persistent donor-specific antibody (DSA) production and allosensitization. However, identifying and efficiently clearing allospecific antibody repertoires to restore single-cell transcriptional profiles remain challenging. Here, inspired by the high affinity of natural bacterial proteins for antibodies, a genetic engineered membrane-coated nanoparticle termed as DSA trapper by the engineering chimeric gene of protein A/G with phosphatidylserine ligands for macrophage phagocytosis was reported. It has been shown that DSA trappers adsorbed alloreactive antibodies with high saturation and activated the heterophagic clearance of antibody complexes, alleviating IgG deposition and complement activation. Remarkably, DSA trappers increased the endothelial protective lineages by 8.39-fold, reversed the highly biased cytotoxicity, and promoted the proliferative profiles of Treg cells, directly providing an obligate immune tolerant niche for single-cell heterogeneity restoration. In the mice of allogeneic transplantation, the DSA trapper spared endothelial from inflammatory degenerative rosette, improved the glomerular filtration rate, and prolonged the survival of allogeneic mice from 23.6 to 78.3 days. In general, by identifying the lineage characteristics of rejection-related antibodies, the chimeric engineered DSA trapper realized immunoadsorption and further phagocytosis of alloantibody complexes to restore the single-cell genetic architecture of the allograft, offering a promising prospect for the treatment of alloantibody-mediated immune injury.

Emerging Therapies for Antibody-Mediated Rejection in Kidney Transplantation

Despite the advances in immunosuppressive medications, antibody-mediated rejection (AMR) continues to be a major cause of kidney allograft failure and remains a barrier to improving long-term allograft survival. Recently, there have been significant advances in the understanding of the pathophysiological process of AMR, along with the development of new therapeutic options. Additionally, surveillance protocols with donor-derived cell-free DNA and gene profile testing have been established, leading to the early detection of AMR. A multitude of clinical trials are ongoing, opening numerous opportunities for improving outcome in kidney transplant recipients. In this brief review, we discuss the emerging therapies for managing both active and chronic active AMR and highlight the ongoing clinical trials.

Pathophysiology of Rejection in Kidney Transplantation

Kidney transplantation has been the optimal treatment for end-stage kidney disease for almost 70 years, with increasing frequency over this period. Despite the prevalence of the procedure, allograft rejection continues to impact transplant recipients, with consequences ranging from hospitalization to allograft failure. Rates of rejection have declined over time, which has been largely attributed to developments in immunosuppressive therapy, understanding of the immune system, and monitoring. Developments in these therapies, as well as an improved understanding of rejection risk and the epidemiology of rejection, are dependent on a foundational understanding of the pathophysiology of rejection. This review explains the interconnected mechanisms behind antibody-mediated and T-cell-mediated rejection and highlights how these processes contribute to outcomes and can inform future progress.

Preventative effect of TSPO ligands on mixed antibody-mediated rejection through a Mitochondria-mediated metabolic disorder

BACKGROUND

Immune-mediated rejection was the major cause of graft dysfunction. Although the advances in immunosuppressive agents have markedly reduced the incidence of T-cell-mediated rejection after transplantation. However, the incidence of antibody-mediated rejection (AMR) remains high. Donor-specific antibodies (DSAs) were considered the major mediators of allograft loss. Previously, we showed that treatment with 18-kDa translocator protein (TSPO) ligands inhibited the differentiation and effector functions of T cells and reduced the rejection observed after allogeneic skin transplantation in mice. This study we further investigate the effect of TSPO ligands on B cells and DSAs production in the recipients of mixed-AMR model.

METHODS

In vitro, we explored the effect of treatment with TSPO ligands on the activation, proliferation, and antibody production of B cells. Further, we established a heart-transplantation mixed-AMR model in rats. This model was treated with the TSPO ligands, FGIN1-27 or Ro5-4864, to investigate the role of ligands in preventing transplant rejection and DSAs production in vivo. As TSPO was the mitochondrial membrane transporters, we then investigated the TSPO ligands effect on mitochondrial-related metabolic ability of B cells as well as expression of downstream proteins.

RESULTS

In vitro studies, treatment with TSPO ligands inhibited the differentiation of B cells into CD138⁺CD27⁺ plasma cells; reduced antibodies, IgG and IgM, secretion of B cells; and suppressed the B cell activation and proliferation. In the mixed-AMR rat model, treatment with FGIN1-27 or Ro5-4864 attenuated DSA-mediated cardiac-allograft injury, prolonged graft survival, and reduced the numbers of B cells, including IgG⁺ secreting B cells, T cells and macrophages infiltrating in grafts. For the further mechanism exploration, treatment with TSPO ligands inhibited the metabolic ability of B cells by downregulating expression of pyruvate dehydrogenase kinase 1 and proteins in complexes I, II, and IV of the electron transport chain.

CONCLUSIONS

We clarified the mechanism of action of TSPO ligands on B-cell functions and provided new ideas and drug targets for the clinical treatment of postoperative AMR.

Donor-Derived Cell-free DNA for Personalized Immunosuppression in Renal Transplantation

BACKGROUND

The long-term outcomes of solid organ transplantation remain suboptimal. Therefore, appropriate biomarkers are needed in addition to immunosuppressive drugs and other traditional approaches for graft monitoring to achieve personalized immunosuppression and reduce premature graft loss.

METHODS

Donor-derived cell-free DNA (dd-cfDNA) is a minimally invasive biomarker of cell death due to graft injury. It can be quantified using droplet digital polymerase chain reaction and next-generation sequencing. Fractional dd-cfDNA determination can be affected by changes in recipient cfDNA, such as those caused by leukopenia or infection, leading to false-positive or false-negative results, respectively. Absolute quantification of dd-cfDNA helps in overcoming this limitation.

RESULTS

Overall, there is sufficient evidence of the clinical validity of dd-cfDNA. It detects rejection episodes early at an actionable stage and reflects the severity of graft injury without being rejection-specific. Owing to its high negative predictive value, dd-cfDNA is very useful for ruling out graft injury. Dd-cfDNA complements histological findings and can help in avoiding unnecessary biopsies. It indicates a response to rejection treatment and detects underimmunosuppression.

CONCLUSIONS

Monitoring changes in dd-cfDNA over time may be helpful in adapting immunosuppression to prevent graft rejection. Moreover, serial dd-cfDNA determination may increase the effectiveness of transplant recipient surveillance and facilitate personalized immunosuppression when combined with other relevant clinical and diagnostic findings.

Integrative metagenomic and metabolomic analyses reveal the role of gut microbiota in antibody-mediated renal allograft rejection

BACKGROUND

Antibody-mediated rejection (AMR) remains one of the major barriers for graft survival after kidney transplantation. Our previous study suggested a gut microbiota dysbiosis in kidney transplantation recipients with AMR. However, alternations in gut microbial function and structure at species level have not been identified. In the present study, we investigated the metagenomic and metabolic patterns of gut microbiota in AMR patients to provide a comprehensive and in-depth understanding of gut microbiota dysbiosis in AMR.

METHODS

We enrolled 60 kidney transplantation recipients, 28 showed AMR and 32 were non-AMR controls with stable post-transplant renal functions. Shotgun sequencing and untargeted LC/MS metabolomic profiling of fecal samples were performed in kidney transplantation recipients with AMR and controls.

RESULTS

Totally, we identified 311 down-regulated and 27 up-regulated gut microbial species associated with AMR after kidney transplantation, resulting in the altered expression levels of 437 genes enriched in 22 pathways, of which 13 were related to metabolism. Moreover, 32 differential fecal metabolites were found in recipients with AMR. Among them, alterations in 3b-hydroxy-5-cholenoic acid, L-pipecolic acid, taurocholate, and 6k-PGF1alpha-d4 directly correlated with changes in gut microbial species and functions. Specific differential fecal species and metabolites were strongly associated with clinical indexes (Cr, BUN, etc.), and could distinguish the recipients with AMR from controls as potential biomarkers.

CONCLUSIONS

Altogether, our findings provided a comprehensive and in-depth understanding of the correlation between AMR and gut microbiota, which is important for the etiological and diagnostic study of AMR after kidney transplantation.

Modelling acute antibody-mediated rejection of human kidney transplants using ex-vivo warm machine perfusion

BACKGROUND

Transplant rejection is a major cause of graft loss and morbidity. Currently, no human models of antibody-mediated rejection (AMR) exist, limiting mechanistic investigation and organ-specific targeted therapy. Here, using 12 human kidneys and ex-vivo normothermic machine perfusion, we demonstrate phenotypes of AMR after addition of antibodies against either human HLA class I or blood group antigens (A, B), thus modelling clinical AMR that can follow HLA incompatible (HLAi) or blood group incompatible (ABOi) transplantation.

METHODS

Discarded human kidneys with wide ranging demographics and cold ischaemia times (11-54 h) were perfused with red blood cells and fresh frozen plasma (FFP) as a source of complement/coagulation factors. For the HLAi model, 600 μg of W6/32 anti-class 1 HLA antibody was added to the circuit (time '0'). For the ABOi model, high titre FFP of the relevant blood group antibody was added. Renal blood flow index (RBFi, mL/min/100 g), C3 desArg, prothrombin fragments 1 + 2 and histology were determined. Our endpoints included haemodynamic changes, thrombosis, and biopsy proven complement deposition.

FINDINGS

Compared to control kidneys perfused without anti-donor antibodies, both models demonstrated haemodynamic collapse after antibody perfusion with only the HLAi model showing glomerular C4d deposition.

INTERPRETATION

We show that a clinically relevant human kidney model of AMR is feasible, and anticipate that these models, with refinements, could provide a basis to test different strategies to prevent AMR.

FUNDING

The Rosetrees and Stonygate Trust, The Royal College of Surgeons of England Fellowship Grant, NIHR Biomedical Research Centre/KCL Early Career Grant, Kidney Research U.K.

Investigation of Circulating MicroRNA Levels in Antibody-Mediated Rejection After Kidney Transplantation

BACKGROUND

One of the most important possible complications determining long-term graft survival after kidney transplant is antibody-mediated rejection (ABMR). The criterion standard approach to recognize ABMR is currently the kidney biopsy with histopathologic analysis. However, this test has limitations because of difficulties in timing of sampling, the evaluability of histology because of the questionable representativeness of specimens, and the limited number of this intervention. Hence, new reliable, noninvasive biomarkers are required to detect the development of ABMR in time.

METHODS

In this study, we analyzed the clinical data of 45 kidney transplant patients (mean age of 44.51 years, 20 male and 25 female subjects). These participants were recruited into 5 subcohorts based on their clinical status, histologic findings, and level of donor-specific anti-HLA antibodies. Circulating microRNAs (miR-21, miR-181b, miR-146a, miR-223, miR-155, miR-150) in plasma samples were quantified by quantitative polymerase chain reaction and their levels were correlated with the clinical characteristics in different subgroups.

RESULTS

The relative expression of plasma miR-155 (P = .0003), miR-223 (P = .0316), and miR-21 (P = .0147) were significantly higher in patients who had subsequent histology-approved ABMR with donor-specific anti-HLA antibody positivity (n = 10) than in the "triple negative" group (n = 21), and miR-155 showed the highest sensitivity (90%) and specificity (81%) to indicate ABMR development based on receiver operating characteristic analysis.

CONCLUSIONS

According to our preliminary data, plasma miR-155, miR-21, and miR-223 can indicate the development of ABMR after kidney transplant in correlation with classic clinical parameters. However, future studies with larger number of participants are necessary to further evaluate the diagnostic properties of blood miRNAs in prediction of this life-threatening condition.

Donor-derived cell-free DNA as a diagnostic tool in transplantation

There is a need to improve personalized immunosuppression in organ transplantation to reduce premature graft loss. Biomarkers are needed to better detect rejection, asymptomatic graft injury, and under-immunosuppression. Assessment of minimal necessary exposure to guide tapering and prevent immune activation is also important. There is robust clinical evidence from a large number of published studies supporting the role of dd-cfDNA for monitoring graft integrity and detection or exclusion of rejection. Dd-cfDNA indicates graft cell death without being rejection specific. It can be determined in plasma through droplet digital PCR using preselected SNPs or next generation sequencing. Changes in recipient cfDNA (e.g., by infection) can affect the results of dd-cfDNA fractional determination. This limitation can be overcome using absolute dd-cfDNA quantification. The combination of fractional and absolute determination including total cfDNA is recommended for meaningful interpretation of the results. The value proposition for the patient includes earlier transplant injury detection and intervention, less full blown rejection risk, an alternative to invasive biopsies, and personalized immunosuppression with potential for improved long-term outcome. Transplant physicians benefit from better immunosuppressive guidance and having an alternative when biopsies are refused or contraindicated. Further advantages are improved biopsy interpretation, less trial and error changes in immunosuppression, and less time dealing with complications. The laboratory medicine specialist can provide more effective services. Hospital management and insurance companies could benefit from more cost-effective surveillance of transplant recipients. Potential cost savings would result from fewer biopsies as a result of the tests’ high negative predictive value, fewer re-transplantations, and less organ failure with return to dialysis. A pathway to implementation and metrics is suggested to measure the effectiveness of dd-cfDNA testing.

Lack of Efficacy and Safety of Eculizumab for Treatment of Antibody-Mediated Rejection Following Renal Transplantation

BACKGROUND

We evaluated the efficacy and safety of eculizumab in comparison with plasmapheresis and intravenous immunoglobulin therapy in renal transplant recipients diagnosed with antibody-mediated rejection (AMR).

METHODS

This was a multicenter, open-label, prospective, randomized analysis. The patients were randomized by therapy type (eg, eculizumab infusions or standard of care [SOC]: plasmapheresis/intravenous immunoglobulin). The patients (ie, eculizumab arm: 7 patients, SOC arm: 4 patients) were evaluated for the continued presence of donor-specific antibodies (DSAs) and C4d (staining on biopsy), as well as histologic evidence, using repeat renal biopsy after treatment.

RESULTS

The allograft biopsies revealed that eculizumab did not prevent the progression to transplant glomerulopathy. Only 2 patients in the SOC arm experienced rejection reversal, and no graft losses occurred in either group. After AMR treatment, the DSA titers generally decreased compared to titers taken at the time of AMR diagnosis. There were no serious adverse effects in the eculizumab arm.

CONCLUSIONS

Eculizumab alone cannot treat AMR effectively and does not prevent acute AMR from progressing to chronic AMR or transplant glomerulopathy. However, it should be considered as a potential alternative therapy because it may be associated with decreased DSA levels.

Antibodies against complement component C5 prevent antibody-mediated rejection after lung transplantation in murine orthotopic models with skin-graft-induced pre-sensitization

OBJECTIVE

Antibody-mediated rejection (AMR) could induce acute or chronic graft failure during organ transplantation. Several reports have shown that anti-C5 antibodies are effective against AMR after kidney transplantation. However, few reports have assessed the efficacy of anti-C5 antibodies against AMR after lung transplantation. Therefore, this study aimed to evaluate the efficacy of this novel therapy against AMR after lung transplantation.

METHODS

BALB/c and C57BL/6 mice were used as donors and recipients. One group was pre-sensitized (PS) by skin transplantation 14 days before lung transplantation. The other group was non-sensitized (NS). Orthotopic left-lung transplantation was performed in both groups. Animals were killed at 2 or 7 days after lung transplantation and evaluated for histopathology, C4d immunostaining, and serum donor-specific antibodies (DSAs) (n = 5 per group). Isograft (IS) models with C57BL/6 mice were used as controls. To evaluate the efficacy of C5 inhibition, other animals, which received similar treatments to those in the PS group, were treated with anti-C5 antibodies, cyclosporine/methylprednisolone, anti-C5 antibodies/cyclosporine/methylprednisolone, or isotype-matched irrelevant control monoclonal antibodies (n = 5 per group).

RESULTS

Two days after lung transplantation, the NS group exhibited mild, localized graft-rejection features (rejection score: 0.45 ± 0.08, p = 0.107). The PS group exhibited AMR features with a significantly higher rejection score (2.29 ± 0.42, p = 0.001), C4d vascular-endothelium deposition, and substantial presence of serum DSA. On day 7 after lung transplantation, both groups showed extensive graft alveolar wall destruction, and high acute-rejection scores. Mice receiving anti-C5 antibodies or anti-C5/antibodies/cyclosporine/methylprednisolone demonstrated significantly lower acute-rejection scores (0.63 ± 0.23, p = 0.002; 0.59 ± 0.22, p = 0.001, respectively) than those receiving isotype control antibodies.

CONCLUSIONS

Murine orthotopic allograft lung transplant models met the clinical diagnosis and pathogenesis classification criteria of AMR. In these models, anti-C5 antibodies suppressed AMR. Therefore, anti-C5 therapy may be effective against AMR after lung transplantation.

Differential Treatment Effects for Renal Transplant Recipients With DSA-Positive or DSA-Negative Antibody-Mediated Rejection

Background

Antibody-mediated rejection (ABMR) is the main cause of renal allograft loss. The most common treatment strategy is based on plasmapheresis plus the subsequent administration of intravenous immunoglobulin (IVIG). Unfortunately, no approved long-term therapy is available for ABMR. The current study was designed to analyze the effect of various ABMR treatment approaches on allograft survival and to compare treatment effects in the presence or absence of donor-specific antibodies (DSAs).

Methods

This single-center study retrospectively analyzed 102 renal allograft recipients who had biopsy-proven ABMR after transplant. DSA was detectable in 61 of the 102 patients. Initial standard treatment of ABMR consisted of plasmapheresis (PS) or immunoadsorption (IA), followed by a single course of IVIG. In case of nonresponse or recurrence, additional immunosuppressive medications, such as rituximab, bortezomib, thymoglobulin, or eculizumab, were administered. In a second step, persistent ABMR was treated with increased maintenance immunosuppression, long-term therapy with IVIG (more than 1 year), or both.

Results

Overall graft survival among transplant patients with ABMR was <50% after 3 years of follow-up. Compared to the use of PS/IA and IVIG alone, the use of additional immunosuppressive medications had no beneficial effect on allograft survival (p = 0.83). Remarkably, allografts survival rates were comparable between patients treated with the combination of PS/IA and IVIG and those treated with a single administration of IVIG (p = 0.18). Renal transplant patients with ABMR but without DSAs benefited more from increased maintenance immunosuppression than did DSA-positive patients with ABMR (p = 0.01). Recipients with DSA-positive ABMR exhibited significantly better allograft survival after long-term application of IVIG for more than 1 year than did recipients with DSA-negative ABMR (p = 0.02).

Conclusions

The results of our single-center cohort study involving kidney transplant recipients with ABMR suggest that long-term application of IVIG is more favorable for DSA-positive recipients, whereas intensification of maintenance immunosuppression is more effective for recipients with DSA-negative ABMR.

Histocompatibility and Reproduction: Lessons from the Anglerfish

Reproduction in certain deep-sea anglerfishes involves the permanent attachment of dwarf males to much larger females and fusion of their tissues leading to the establishment of a shared circulatory system. This unusual phenomenon of sexual parasitism enables anglerfishes to maximize reproductive success in the vast and deep oceans, where females and males otherwise rarely meet. An even more surprising phenomenon relates to the observation that joining of genetically disparate male and female anglerfishes does not evoke a strong anti-graft immune rejection response, which occurs in vertebrates following allogeneic parabiosis. Recent studies demonstrated that the evolutionary processes that led to the unique mating strategy of anglerfishes coevolved with genetic changes that resulted in loss of functional genes encoding critical components of the adaptive immune system. These genetic alterations enabled anglerfishes to tolerate the histoincompatible tissue antigens of their mate and prevent the occurrence of reciprocal graft rejection responses. While the exact mechanisms by which anglerfishes defend themselves against pathogens have not yet been deciphered, it is speculated that during evolution, anglerfishes adopted new immune strategies that compensate for the loss of B and T lymphocyte functions and enable them to resist infection by pathogens.

Iguratimod reduces panel reactive antibody in high mismatched renal transplant recipients: One single-center experience

OBJECTIVE

To evaluate the clinical efficacy and safety of iguratimod (IGU) for reducing panel reactive antibody (PRA) in high-mismatched renal transplant recipients.

METHODS

Eligible recipients positive for PRAs who received or did not receive IGU treatment were enrolled. We retrospectively reviewed, collected, and analyzed statistically the clinical data of the recipients.

RESULTS

A total of 80 recipients were included for further analysis. After IGU was administered for nine months, no significant difference was found in the change rates of donor specific antibodies between two groups. Meanwhile, the reduction in the PRAs in the IGU group was greater than that in the non-IGU group in anti-human leukocyte antigen (HLA) class I and class II, anti-HLA class I, anti-HLA class II, anti-HLA A, and anti-HLA DR antibodies. However, no differences were found in the anti-HLA B, anti-HLA Cw, anti-HLA DP, and anti-HLA DQ antibodies between the two groups. No serious adverse events were reported, and the incidence of adverse events was comparable between the two groups.

CONCLUSION

PRA levels in high-mismatched renal transplant recipients were significantly reduced after the administration of IGU. The high safety of IGU was also determined. This article is protected by copyright. All rights reserved.

The role of endothelin II type A receptor (ETAR) in transplant injury

PURPOSE OF REVIEW

Antibody-mediated rejection is the leading cause of deterioration of graft function and graft loss after kidney transplantation. Recent studies have reported an increasing role of non-HLA antibodies in the humoral injury after kidney transplantation. We decided to present the influence of non-HLA antibodies - anti-endothelin II type A receptor (ETAR) on a transplanted kidney and characterize the significance of their receptor.

RECENT FINDINGS

The role of non-HLA antibodies is still uncertain. Many studies suggest that the presence of non-HLA antibodies, including anti-ETAR antibodies, is among the risk factors for antibody-mediated rejection, graft injury, and graft loss. The discovery of new antigen targets and antibodies, which participate in the humoral response, has provided a significantly better understanding of the mechanism of antibody-mediated rejection after organ transplantation.

SUMMARY

Endothelin and its receptors play an important role in physiology and pathophysiology after solid organ transplantation. ETAR and antibodies against ETAR may participate in humoral rejection and graft damage. The measurement of anti-ETAR antibodies may identify patients with an increased risk of rejection and even loss of a transplanted organ. Expression of ETAR detected in biopsy of transplant could become an additional tool used to better understand humoral activity. More research is needed to address many questions about non-HLA directed rejection and graft damage.

Liquid biopsies: donor-derived cell-free DNA for the detection of kidney allograft injury

In kidney transplantation, the use of minimally invasive damage biomarkers that are more sensitive and specific than plasma creatinine will be crucial to enable early, actionable detection or exclusion of structural kidney damage due to acute or chronic rejection. Donor-derived cell-free DNA (dd-cfDNA), which can be quantified, for example, through next-generation sequencing, droplet digital PCR and quantitative PCR, is a candidate biomarker with great potential for enabling comprehensive monitoring of allograft injury. dd-cfDNA has a favourable overall diagnostic performance for the detection of rejection and its high negative predictive value might be especially useful for avoiding unnecessary biopsies. Elevated dd-cfDNA levels have been shown to be detectable before graft injury can be clinically identified using current diagnostic methods. Moreover, dd-cfDNA falls rapidly to baseline levels after successful treatment for rejection owing to its short half-life. dd-cfDNA can detect graft injury caused by immune activation owing to insufficient immunosuppression and might therefore also help guide immunosuppression dosing. The fractional abundance of dd-cfDNA can be affected by changes in the recipient cfDNA (for example, due to infection or physical exercise) but the use of absolute quantification of dd-cfDNA overcomes this limitation. Serial dd-cfDNA determinations might therefore facilitate cost-effective personalized clinical management of kidney transplant recipients to reduce premature graft loss.

Do anti-IL-6R blockers have a beneficial effect in the treatment of antibody-mediated rejection resistant to standard therapy after kidney transplantation?

Antibody-mediated rejection (AMR) that resists to standard of care (SOC) therapy remains a major challenge after kidney transplantation and leads to graft failure in a majority of cases. The use of anti-IL6 receptor antibodies was suggested to treat chronic antibody-mediated rejection (cAMR) after failure of classical treatments. We treated nine patients with AMR resistant to apheresis, rituximab, and intravenous immunoglobulins, with a monthly infusion of tocilizumab and compared them with a historical cohort of 37 patients with similar clinical, immunological, and histological characteristics. The 1-year graft survival and the decline in renal function did not differ between patients who received tocilizumab and those who did not. Histological follow-up showed that despite a decrease in inflammation and tubulitis scores after tocilizumab, the course of antibody-mediated lesions and chronic glomerulopathy were similar in both groups. In our study, the addition of monthly infusions of tocilizumab did not alter the course of AMR that resist to SOC therapy. Large randomized studies are urgently needed to assess the effect of tocilizumab in this context.

Urinary epidermal growth factor is a novel biomarker for early diagnosis of antibody mediated kidney allograft rejection: A urinary proteomics analysis

Although antibody mediated rejection (AMR) accounts for 20-30% of all acute renal allograft rejections, introducing biomarkers for a timely detection of allograft rejection has been remained challenging. This study investigated novel diagnostic biomarkers of AMR by examining of urine proteome in renal transplant patients. Thirty-six patients with kidney transplantation including 22 AMR patients and 14 patients with stable renal function (control group) were enrolled in this study. Urinary samples were collected and Label free quantification (LFQ) proteomics technique was applied on urine samples and data was subjected to Random Forest (RF) algorithm to predict main candidate proteins contributing in AMR. Finally, applicability of candidate diagnostic biomarkers was evaluated in new sets of AMR subjects, stable patients and healthy volunteers. A total of 1020 proteins were detected in urine proteome. RF algorithm predicted 20 differentially expressed proteins with the highest sensitivity and specificity and combination of EGF, COL6A, and NID-1 was identified as possible panel for early diagnosis of AMR. Applicability of EGF as diagnostic biomarker was validated in urine samples of independent set of AMR subjects. This is the first urinary proteomics study in AMR patients demonstrating that urinary EGF might be used as early diagnostic biomarker for AMR. SIGNIFICANCE: Renal antibody mediated rejection (AMR) accounts for 20-30% of all acute rejections of allografted kidneys. Although several possible biomarkers have been proposed to predict AMR, ineffectiveness of current urinary biomarkers in early diagnosing of AMR patients and in distinguishing AMR subjects from patients with stable kidney function casts doubts on their applicability in clinic. Here for the first time and based on the analysis of urinary proteome we showed that uEGF and uEGF/Cr might be candidate biomarkers to predict AMR with high diagnostic power.

Gut microbiota alterations associated with antibody-mediated rejection after kidney transplantation

Antibody-mediated rejection (AMR) has become the major challenge for kidney transplantation, and the efficacy of existing therapies was limited to prevent AMR. Increasing evidences have demonstrated the link between gut microbiota alterations and allograft outcome. However, there has been no comprehensive analysis to profile the gut microbiota associated with AMR after kidney transplantation. We performed this study to characterize the gut microbiota possibly associated with AMR. Fecal specimens were collected from 24 kidney transplantation recipients with AMR and 29 controls. DNA extracted from the specimens was processed for 16S rRNA gene sequencing using Illumina MiSeq. Gut microbial community of recipients with AMR was significantly different from that of controls based on unweighted (P = 0.001) and weighted (P = 0.02) UniFrac distances, and the bacterial richness (observed species: P = 0.0448; Chao1 index: P = 0.0450; ACE index: P = 0.0331) significantly decreased in the AMR group. LEfSe showed that 1 phylum, 5 classes, 7 families, and 10 genera were increased, whereas 1 class, 2 order, 3 families, and 4 genera were decreased in the AMR group. Specific taxa such as Clostridiales could be potentially used as biomarkers to distinguish the recipients with AMR from the controls (AUC = 0.77). PICRUSt analysis illustrated that 16 functional pathways were with significantly different abundances in the AMR and control groups. Our findings provide a foundation for further investigation on the role of gut microbiota in AMR after kidney transplantation, and potentially support novel diagnostic biomarkers and therapeutic options for AMR. KEY POINTS: • Gut microbial community of kidney recipients with AMR was different from that of controls. • Clostridiales is a potential marker to distinguish recipients with AMR from controls.

Renal Transplant Pathology: Demographic Features and Histopathological Analysis of the Causes of Graft Dysfunction

Background

Renal transplant has emerged as a preferred treatment modality in cases of end-stage renal disease; however, a small percentage of cases suffer from graft dysfunction.

Aim

To evaluate the renal transplant biopsies and analyze the various causes of graft dysfunction.

Materials and Methods

163 renal transplant biopsies, reported between 2014 and 2019 and who fulfilled the inclusion criteria, were evaluated with respect to demographics, clinical, histological, and immunohistochemical features.

Results

Of 163 patients, 26 (16%) were females and 137 (84%) were males with a mean age of 34 ± 7 years. 53 (32.5%) cases were of rejection (ABMR and TCMR), 1 (0.6%) was borderline, 15 were of IFTA, and rest of 94 cases (57.7%) belonged to the others category. SCr (serum creatinine) in cases of rejection was 3.85 ± 0.55 mg/dl. Causes of early graft dysfunction included active ABMR (7.1 ± 4.7 months), acute TCMR (5.5 months), and acute tubular necrosis (after 6 ± 2.2 months of transplant) while the causes of late rejection were CNIT and IFTA (34 ± 4.7 and 35 ± 7.8 months, respectively).

Conclusion

Renal graft dysfunction still remains a concerning area for both clinicians and patients. Biopsy remains the gold standard for diagnosing the exact cause of graft dysfunction and in planning further management.

Treatment of Antibody-Mediated Rejection After Kidney Transplantation: Immunological Effects, Clinical Response, and Histological Findings

Background

Antibody-mediated rejection (AMR) presents with diverse clinical manifestations and can have a potential negative impact on graft function and survival. If not treated successfully, AMR can lead to 20–30% graft loss after 1 year. Little is known about the efficacy of AMR treatment, and the most appropriate therapeutic strategy has not yet been determined. This study evaluated the effects of AMR treatment with plasmapheresis (PP) and intravenous immunoglobulin (IVIG) on renal function, intensity of anti-HLA antibodies, and graft biopsy morphology.

Material/Methods

This single-center retrospective cohort study included renal transplant recipients with biopsy-proven AMR who were treated with PP and/or IVIG. Clinical findings, mean fluorescence intensity of donor-specific anti-HLA antibodies (DSA), and graft histology findings, classified according to Banff score at the time of AMR and 6 and 12 months later, were evaluated.

Results

Of the 42 patients who met the inclusion criteria, 38 (90.5%) received IVIG and 26 (61.9%) underwent PP. At AMR diagnosis, 36 (85.7%) patients had proteinuria, with their estimated glomerular filtration rate remaining stable during follow-up. During the first year, 8 (19.0%) patients experienced graft failure, but none died with a functioning graft. Reductions in the class I panel of reactive antibodies were observed 6 and 12 months after AMR treatment, with significant reductions in DSA-A and -B fluorescence intensity, but no changes in DSA-DQ. Graft biopsy showed reductions in inflammation and C4d scores, without improvements in microvascular inflammation.

Conclusions

AMR treatment reduced biopsy-associated and serological markers of AMR, but did not affect DSA-DQ.

Antigen-Specific Immunoadsorption With the Glycosorb® ABO Immunoadsorption System as a Novel Treatment Modality in Pure Red Cell Aplasia Following Major and Bidirectional ABO-Incompatible Allogeneic Hematopoietic Stem Cell Transplantation

Pure red cell aplasia (PRCA) after ABO-incompatible allogeneic hematopoietic stem cell transplantation (HSCT) is caused by persisting host-derived isohemagglutinins directed against donor red blood cell (RBC) antigens. ABO antigen-specific immunoadsorption (ABO-IA) with Glycosorb®, commonly used for desensitization therapy in ABO-incompatible living donor renal transplantation, specifically eliminates circulating isohemagglutinins and might represent a novel treatment option for post-HSCT PRCA. In this prospective observational (n = 3) and retrospective (n = 3) analysis of six adult HSCT-recipients with PRCA, ABO-IA was initiated at 159 (range: 104–186) days following HSCT. The median treatment frequency was 4.5 (range: 3.9–5.5) sessions/week. ABO-IA-treatment led to a continuous decrease in isohemagglutinin titers. Reticulocytes increased to ≥30 G/L after 17.5 (range: 4–37) immunoadsorption sessions over 28.5 (range: 6–49) days and continued to rise after that. By the end of the 3-month follow-up period after discontinuation of ABO-IA, all patients showed a sustained remission of PRCA and were independent of erythropoietin-stimulating agents and transfusions. No case of infection or graft-versus-host disease was observed. After a median follow-up of 22.03 (range: 6.08–149.00) months after ABO-IA-treatment, all patients were alive and showed a stable RBC engraftment of the donor blood group. Our data provide the first evidence for ABO-IA as an effective treatment for post-HSCT PRCA.

Donor-Derived Cell-Free DNA Testing in Solid Organ Transplantation: A Value Proposition

BACKGROUND

There is a need to improve personalized immunosuppression in organ transplantation to reduce premature graft loss. More efficient biomarkers are needed to better detect rejection, asymptomatic graft injury, and under-immunosuppression. Assessment of minimal necessary exposure to guide tapering and to prevent immune activation is also important. Donor-derived cell-free DNA (dd-cfDNA) has become available for comprehensive monitoring of allograft integrity. A value proposition concept was applied to assess the potential benefits of dd-cfDNA to stakeholders (patient, transplant physician, laboratory medicine specialist, hospital management, insurance companies) involved in solid organ transplantation care.

CONTENT

There is robust clinical evidence from more than 48 published studies supporting the role of dd-cfDNA for monitoring graft integrity and detection or exclusion of rejection. The value proposition framework was used to evaluate published key evidence regarding clinical validity, economic implications, and limitations of this approach. It has been shown that dd-cfDNA testing is essential for guiding earlier transplant injury intervention with potential for improved long-term outcome.

SUMMARY

Monitoring dd-cfDNA offers a rapid and reproducible method to detect graft injuries at an early actionable stage without protocol biopsies and allows for more effective personalized immunosuppression. The appropriate use of dd-cfDNA testing can provide both clinical and economic benefits to all transplantation stakeholders.

Risk Factors of Antibody-Mediated Rejection and Predictors of Outcome in Kidney Transplant Recipients

OBJECTIVES

Kidney transplant is the treatment of choice for patients with end-stage renal disease. Antibody-mediated rejection is associated with higher rates of graft loss in kidney transplant recipients. Determining the risk factors of antibody-mediated rejection is vital for its prevention, early diagnosis, and appropriate treatment, as these factors may be important in maintaining long-term graft survival in transplant recipients. In our study, we analyzed the risk factors of antibody-mediated rejection in kidney transplant recipients and the negative impact of antibody-mediated rejection on graft function.

MATERIALS AND METHODS

We analyzed demographic and clinical data of 124 kidney transplant recipients (37 female [30%] and 87 male [70%] patients) who were diagnosed with antibody-mediated rejection at transplant biopsy. We compared graft outcomes of this patient cohort versus 75 kidney transplant recipients (24 female [32%] and 51 male [68%] patients) who were not diagnosed with antibody-mediated rejection.

RESULTS

Mean ages of patients with and without antibody-mediated rejection were 38.2 ± 13.6 and 34.4 ± 13.0 years, respectively. Mean ages of donors for patients with antibody-mediated rejection was significantly higher (48.0 ± 13.2 y) than for donors of patients without antibody-mediated rejection (47.1 ± 11.4 y; P < .05). Rate of graft loss was 15.3% in patients with antibody-mediated rejection; patients without antibody-mediated rejection had no graft loss (P < .05). Positive panel reactive antibody levels and blood transfusion before transplant were found to be risk factors of antibody-mediated rejection in kidney transplant recipients. However, recipients who received tacrolimus had less antibody-mediated rejection episodes than recipients who received sirolimus or cyclophosphamide.

CONCLUSIONS

Antibody-mediated rejection is associated with high rates of graft loss in kidney transplant recipients. Avoiding blood transfusion, lowering panel reactive antibody levels, choosing younger donors, and using tacrolimus in high-risk kidney transplant recipients may reduce antibody-mediated rejection rates and provide better graft survival.

Guidelines on the Use of Therapeutic Apheresis in Clinical Practice - Evidence-Based Approach from the Writing Committee of the American Society for Apheresis: The Eighth Special Issue

The American Society for Apheresis (ASFA) Journal of Clinical Apheresis (JCA) Special Issue Writing Committee is charged with reviewing, updating and categorizing indications for the evidence-based use of therapeutic apheresis (TA) in human disease. Since the 2007 JCA Special Issue (Fourth Edition), the committee has incorporated systematic review and evidence-based approaches in the grading and categorization of apheresis indications. This Eighth Edition of the JCA Special Issue continues to maintain this methodology and rigor in order to make recommendations on the use of apheresis in a wide variety of diseases/conditions. The JCA Eighth Edition, like its predecessor, continues to apply the category and grading system definitions in fact sheets. The general layout and concept of a fact sheet that was introduced in the Fourth Edition, has largely been maintained in this edition. Each fact sheet succinctly summarizes the evidence for the use of TA in a specific disease entity or medical condition. The Eighth Edition comprises 84 fact sheets for relevant diseases and medical conditions, with 157 graded and categorized indications and/or TA modalities. The Eighth Edition of the JCA Special Issue seeks to continue to serve as a key resource that guides the utilization of TA in the treatment of human disease.

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.

Antithymocyte Globulin Antibody Titer Congruent With Kidney Transplantation: Analysis of Incidence, Outcomes, Cost, and Alternative Targets

Rabbit antithymocyte globulin (rATG) use for immunosuppression induction is widespread but is contraindicated by the presence of anti-rATG antibodies. This study reports the incidence of positive anti-rATG antibody titers in patients before and after renal transplant and evaluates associated outcomes and costs. In addition, it will correlate CD40L and interleukin (IL)-21 with anti-rATG antibody titers.

METHODS

Clinical and billing records from the Indiana University Transplant Laboratory were reviewed for positive versus negative anti-rATG antibody titers, graft survival, and 7-day readmission costs between 2004 and 2018. Serum from patients with positive and negative rATG antibody titers were quantitated for CD40L and IL-21 by enzyme-linked immunosorbent assay.

RESULTS

On average, between 2004 and May 2018, 163 kidney transplants per year were performed. Anti-rATG antibody titers were ordered for 17 patients/year, of which 18.2% were positive at 1:100 titer either pre- or post-transplant. Time to graft loss correlated with a positive rATG titer at time of readmission. Moreover, second kidney transplant increased the anti-rATG positive rate. A weak correlation was observed between anti-rATG titer and recipient age. Seven-day readmission treatment costs were significantly lower in patients with positive anti-rATG titer. IL-21 and CD40L were significantly greater in patients with positive anti-rATG titers after transplant when compared with negative anti rATG patients.

CONCLUSIONS

Positive anti-rATG antibody titer is associated with a significant negative impact on outcomes. Monitoring of anti-rATG antibody titer is recommended to optimize treatment options in patients, especially in the setting of second transplants. Elucidation of the mechanisms associated with positive anti-rATG antibody is required. IL-21 and CD40L are potential targets for future study.

Detecting donor-specific antibodies: the importance of sorting the wheat from the chaff

Human leukocyte antigen (HLA) compatibility is very important for successful transplantation of solid organs. In this paper, we focused on the humoral arm of immunity in the clinical setting of organ transplantation: how HLA antibodies develop, how they can be detected, and what they can do to injure organ transplants. Specifically, we explore the technical perspectives of detecting donor-specific antibodies (DSA) in HLA laboratories, and use real-life clinical cases to explain the principles. Currently there are many tools in our HLA antibody detection toolbox: conventional cytotoxicity cross match, flow cross match, and solid phase assays using beads conjugated with single or multiple HLA antigens. Single antigen bead (SAB) assay is the most sensitive tool available for detecting HLA antibodies and assessing the immunological risk for organ transplant. However, there are intrinsic limitations to solid-phase assays and they are prone to both false negativity and importantly, false positivity. Denatured antigens on single antigen beads might be the most prominent source of false positive reactivity, and may have been underestimated by many HLA experts. No single assay is perfect and therefore multiple methods, including the less sensitive assays, should be employed to determine the clinical relevance of detected HLA antibodies. Thoughtful process, including knowledge of HLA systems, cross reactivity, epitopes, and the patient's clinical history should be employed to correctly interpret data. The clinical team should work closely with HLA laboratories to ensure accurate interpretation of information and optimal management of patients before and after organ transplantation.

Emphysematous pyelonephritis in renal allograft related to antibody-mediated rejection: A case report and literature review

Emphysematous pyelonephritis (EPN) is a rare condition which can rapidly progress to sepsis and multiple organ failure with high mortality. We experienced a rare case of EPN in a renal allograft related to antibody-mediated rejection (AMR). The patient received a deceased donor kidney transplant due to end-stage renal disease secondary to diabetes mellitus. Cross-match test was negative but she had remote history of anti-HLA-A2 antibody corresponding with the donor HLA. Surgery concluded without any major events. Anti-thymoglobulin was given perioperatively for induction. She was compliant with her immunosuppressive medications making urine of 2 L/d with serum creatinine of 1.9 mg/dL at discharge on post-operative day (POD) 6. She did well until POD 14 when she presented to the clinic with features of sepsis, pain over the transplanted kidney area and decline in urine volume with elevated serum creatinine. CT revealed extensive gas throughout the transplanted kidney. Renal scan revealed non-functional transplant kidney with no arterial flow. Based on these findings, a decision to perform transplant nephrectomy was made. At laparotomy, the kidney was completely necrotic. Pathology showed non-viable kidney parenchyma with the tubules lacking neutrophilic casts suggestive of ischemic necrosis. Donor-specific antibody (DSA) returned positive with high intensity anti-HLA-A2 antibody. This is the first case of early EPN in allograft considered to have occurred as a result of thrombotic ischemia secondary to AMR. This case suggests consideration of perioperative anti-B-cell and/or anti-plasma cell therapies for historical DSA and strict post-operative follow-up in immunologically high-risk recipients to detect early signs of rejection and avoid deleterious outcomes.

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.

Incidence of Infectious Disease and Malignancies After Rituximab Therapy in Kidney Transplant Recipients: Results From a Cohort in Germany

BACKGROUND

Rituximab is frequently used in solid organ transplantation off-label, especially in patients with renal allografts. Few data are available on the safety aspects of solid organ transplant recipients receiving rituximab. There is a knowledge gap on long-term follow-up data, in particular on infectious complications.

PATIENTS AND METHODS

A retrospective observational registry study (German Registry on Autoimmune Diseases) comprising a total of 681 patients was conducted. The data of 63 adult kidney transplant recipients who received rituximab between 2006 and 2013 were used in this analysis.

RESULTS

Median follow-up was 42 (1-109) months. At least 1 severe infection occurred in 57% of patients. The median time between the first rituximab infusion and the first infection was 4 (1-48) months. Of the overall 88 infections, 74 were severe bacterial infections, 5 were severe viral infections, 3 were severe fungal infections, 2 were combined severe bacterial and fungal infections, and 4 were combined severe viral, fungal and bacterial infections. Seven patients died during the observational period, 2 of them due to infectious complications. In the observational period, 1 case of squamous cell carcinoma but no other malignancies were observed.

CONCLUSION

Consistent with previous data, a high incidence of infections was observed after rituximab treatment in kidney transplant recipients. Most infections occurred within 6 months after rituximab initiation. With more than 3 years of follow-up, we were able to document a low incidence of secondary malignancies after rituximab with only 1 case in our cohort.

Triptolide inhibits donor-specific antibody production and attenuates mixed antibody-mediated renal allograft injury

Donor-specific antibodies (DSAs) are major mediators of renal allograft injury, and strategies to inhibit DSAs are important in promoting long-term graft survival. Triptolide exhibits a wide spectrum of antiinflammatory and immunosuppressive activities, and in autoimmune diseases it inhibits autoantibody levels. In this study, we investigated the suppressive role of triptolide in the generation of DSAs in transplant recipients. We found that triptolide treatment of skin allograft recipients in mice significantly suppressed the development of circulating anti-donor-specific IgG and effectively alleviated DSA-mediated renal allograft injury, which led to prolonged allograft survival. In vitro studies revealed that triptolide inhibited the differentiation of B cells into CD138⁺ CD27⁺⁺ plasma cells; reduced the levels of IgA, IgG, and IgM secreted by plasma cells; and repressed somatic hypermutation and class switch recombination of B cells. Moreover, triptolide-treated recipients showed reduced numbers of B cells, plasma cells, and memory B cells in spleens and decreased numbers of T, B, natural killer (NK) cells, and macrophages infiltrating grafts. These findings highlight the importance of triptolide in suppressing DSAs and establish triptolide as a novel therapeutic agent for antibody-mediated allograft rejection.

Antibody-mediated rejection: New approaches in prevention and management

Despite the success of desensitization protocols, antibody-mediated rejection (AMR) remains a significant contributor to renal allograft failure in patients with donor-specific antibodies. Plasmapheresis and high-dose intravenous immunoglobulin have proved to be effective treatments to prevent and treat AMR, but irreversible injury in the form of transplant glomerulopathy can commonly manifest months to years later. There is an unmet need to improve the outcomes for patients at risk for AMR. Updated Banff criteria now take into account the increasing understanding of the complex and heterogeneous nature of AMR phenotypes, including the timing of rejection, subclinical and chronic AMR, C4d-negative AMR, and antibody-mediated vascular rejection. Treatment for AMR is not standardized, and there is little in the way of evidence-based treatment guidelines. Refining more precisely the mechanisms of injury responsible for different AMR phenotypes and establishing relevant surrogate endpoints to facilitate more informative studies will likely allow for more accurate determination of prognosis and efficacious intervention using new therapeutic approaches. In addition to plasma exchange and intravenous immunoglobulin, a number of other add-on therapies have been tried in small studies without consistent benefit, including anti-CD20, proteasome inhibitors, complement inhibitors, anti-interleukin-6 receptor blockers, and immunoglobulin G-degrading enzyme of Streptococcus pyogenes (called IdeS).

De novo glomerular diseases after renal transplantation: How is it different from recurrent glomerular diseases?

The glomerular diseases after renal transplantation can occur de novo, i.e., with no relation to the native kidney disease, or more frequently occur as a recurrence of the original disease in the native kidney. There may not be any difference in clinical features and histological pattern between de novo glomerular disease and recurrence of original glomerular disease. However, structural alterations in transplanted kidney add to dilemma in diagnosis. These changes in architecture of histopathology can happen due to: (1) exposure to the immunosuppression specifically the calcineurin inhibitors (CNI); (2) in vascular and tubulointerstitial alterations as a result of antibody mediated or cell-mediated immunological onslaught; (3) post-transplant viral infections; (4) ischemia-reperfusion injury; and (5) hyperfiltration injury. The pathogenesis of the de novo glomerular diseases differs with each type. Stimulation of B-cell clones with subsequent production of the monoclonal IgG, particularly IgG3 subtype that has higher affinity to the negatively charged glomerular tissue, is suggested to be included in PGNMID pathogenesis. De novo membranous nephropathy can be seen after exposure to the cryptogenic podocyte antigens. The role of the toxic effects of CNI including tissue fibrosis and the hemodynamic alterations may be involved in the de novo FSGS pathophysiology. The well-known deleterious effects of HCV infection and its relation to MPGN disease are frequently reported. The new concepts have emerged that demonstrate the role of dysregulation of alternative complement pathway in evolution of MPGN that led to classifying into two subgroups, immune complex mediated MPGN and complement-mediated MPGN. The latter comprises of the dense deposit disease and the C3 GN disease. De novo C3 disease is rather rare. Prognosis of de novo diseases varies with each type and their management continues to be empirical to a large extent.