Summary of 2017 FDA Public Workshop: Antibody-mediated Rejection in Kidney Transplantation

Chronic Active Antibody-mediated Rejection: Opportunity to Determine the Role of Interleukin-6 Blockade

Chronic active antibody-mediated rejection (caAMR) is arguably the most important cause of late kidney allograft failure. However, there are no US Food and Drug Administration (FDA)-approved treatments for acute or chronic AMR and there is no consensus on effective treatment. Many trials in transplantation have failed because of slow and/or inadequate enrollment, and no new agent has been approved by the FDA for transplantation in over a decade. Several lines of evidence suggest that interleukin-6 is an important driver of AMR, and clazakizumab, a humanized monoclonal antibody that neutralizes interleukin-6, has shown promising results in phase 2 studies. The IMAGINE trial (Interleukin-6 Blockade Modifying Antibody-mediated Graft Injury and Estimated Glomerular Filtration Rate Decline) (NCT03744910) is the first to be considered by the FDA using a reasonably likely surrogate endpoint (slope of estimated glomerular filtration rate decline >1 y) for accelerated approval and is the only ongoing clinical trial for the treatment of chronic rejection. This trial offers us the opportunity to advance the care for our patients in need, and this article is a call to action for all transplant providers caring for patients with caAMR.

Higher Donor Age and Severe Microvascular Inflammation Are Risk Factors for Chronic Rejection After Treatment of Active Antibody-Mediated Rejection

Recent developments in intensive desensitization protocols have enabled kidney transplantation in human leukocyte antigen (HLA)-sensitized recipients. However, cases of active antibody-mediated rejection (AABMR), when they occur, are difficult to manage, graft failure being the worst-case scenario. We aimed to assess the impact of our desensitization and AABMR treatment regimen and identify risk factors for disease progression. Among 849 patients who underwent living-donor kidney transplantation between 2014 and 2021 at our institution, 59 were diagnosed with AABMR within 1 year after transplantation. All patients received combination therapy consisting of steroid pulse therapy, intravenous immunoglobulin, rituximab, and plasmapheresis. Multivariable analysis revealed unrelated donors and preformed donor-specific antibodies as independent risk factors for AABMR. Five-year death-censored graft survival rate was not significantly different between patients with and without AABMR although 27 of 59 patients with AABMR developed chronic AABMR (CABMR) during the study period. Multivariate Cox proportional hazard regression analysis revealed that a donor age greater than 59 years and microvascular inflammation (MVI) score (g + ptc) ≥4 at AABMR diagnosis were independent risk factors for CABMR. Our combination therapy ameliorated AABMR; however, further treatment options should be considered to prevent CABMR, especially in patients with old donors and severe MVI.

Interferon-γ and its response are determinants of antibody-mediated rejection and clinical outcomes in patients after renal transplantation

Interferon-γ (IFN-γ) is an important cytokine in tissue homeostasis and immune response, while studies about it in antibody-mediated rejection (ABMR) are very limited. This study aims to comprehensively elucidate the role of IFN-γ in ABMR after renal transplantation. In six renal transplantation cohorts, the IFN-γ responses (IFNGR) biological process was consistently top up-regulated in ABMR compared to stable renal function or even T cell-mediated rejection in both allografts and peripheral blood. According to single-cell analysis, IFNGR levels were found to be broadly elevated in most cell types in allografts and peripheral blood with ABMR. In allografts with ABMR, M1 macrophages had the highest IFNGR levels and were heavily infiltrated, while kidney resident M2 macrophages were nearly absent. In peripheral blood, CD14+ monocytes had the top IFNGR level and were significantly increased in ABMR. Immunofluorescence assay showed that levels of IFN-γ and M1 macrophages were sharply elevated in allografts with ABMR than non-rejection. Importantly, the IFNGR level in allografts was identified as a strong risk factor for long-term renal graft survival. Together, this study systematically analyzed multi-omics from thirteen independent cohorts and identified IFN-γ and IFNGR as determinants of ABMR and clinical outcomes in patients after renal transplantation.

Microvascular activation and exocytosis after exposure to the serum from mismatched recipients by using donor microvascular cultures

BACKGROUND

Microvascular injury resulting from activation and exocytosis are early signs of tissue damage caused by allografting. However, humoral anti-graft reactions are not easily detectable in transplant biopsies. The aim of this study was to establish a bioassay to recapitulate this process in a prospective approach.

METHODS

The study was executed by using our previously established protocol to isolate and freeze the donors' microvascular endothelial cells (MVEC) at the transplantation (34 living-related donors and 26 cadaver donors); and to collect sera from the recipients before the transplantation, one-, three- and six-months after transplantation. The activation and exocytosis of the MVEC were determined by incubating the donors' cultures with the recipients' sera. We determined if there was any endothelial activation by quantifying the releases of monocyte chemotactic protein-1 (MCP-1) and interleukin 8 (IL-8) in supernatants and the expressions of membrane intercellular adhesion molecule-1 (CD54) and intercellular adhesion molecule-1 (CD106) by flow cytometry. Endothelial exocytosis was determined by quantifying soluble E-selectin (CD62E) and cytoplasmic von Willebrand Factor (vWF) in supernatants. Endothelial activation or exocytosis was considered positive when the fold change (≧1.5) of post-transplantation to pre-transplantation was reached. We also monitored serum PRA and cytokines using Luminex multiple-plex and cytometric bead-based assay respectively.

RESULTS

We found 41.2% recipients (14 out of 34, ranging from 1.5 to 5.2 folds, p < 0.05) exhibited positive MVEC activation in the first month after transplantation as determined by IL-8 levels; 26.5% recipients (9 out of 34, ranging from 1.5 to 11.8 folds, p < 0.05) by MCP-1 levels. In the group of three months post-transplantation, 70.6% patients were positive (12 out of 17, ranging from 1.8 to 87.1 folds, p < 0.05) by IL-8 increased levels; 24% recipients (4 out of 17, ranging from 1.8 to 50.5 folds, p < 0.05) measured by MCP-1 levels. However, these changes disappeared six months after transplantation. Flow cytometric data showed that a time-dependent of CD54+ and CD106+ expressions existed over the course of six months. Most CD54+ and CD106+ cells were CD31- (platelet-endothelial cell adhesion molecule-1), though CD31+/CD106+ (37.5%, 3 out of 8) and CD31+/CD106+ (25%. 2 out of 8) were seen. When comparing donor MVEC activation to their recipient's proinflammatory cytokine levels or PRA status, we could not draw a conclusion regarding the connections between them. The sera collected from recipients at either one- or three-months after allografting did not significantly induce the release of either soluble CD62E or vWF (p > 0.05), indicating exocytosis was not significantly involved in the acute phase of allografting.

CONCLUSIONS

This bioassay enables us to detect the activation and exocytosis of donor MVEC elicited by respective sera from mismatched kidney recipients.

Intravenous immunoglobulin in kidney transplantation: Mechanisms of action, clinical applications, adverse effects, and hyperimmune globulin

Intravenous immunoglobulin (IVIG) has been developed for over 40 years. The mechanisms of action of IVIG are complex and diverse, and there may be multiple mechanisms that combine to influence it. IVIG has been used in kidney transplantation for desensitization, treatment of antibody-mediated rejection, and ABO-incompatible transplantation. and treatment or prevention of some infectious diseases. Hyperimmune globulins such as cytomegalovirus hyperimmune globulin (CMV-IG) and hepatitis B hyperimmune globulin (HBIG) have also been used to protect against cytomegalovirus and hepatitis B virus, respectively. However, IVIG is also associated with some rare but serious adverse effects and some application risks, and clinicians need to weigh the pros and cons and develop individualized treatment programs to benefit more patients. This review will provide an overview of the multiple mechanisms of action, clinical applications, adverse effects, and prophylactic measures of IVIG, and hyperimmune globulin will also be introduced in it.

Belatacept and carfilzomib-based treatment for antibody-mediated rejection in a sensitized nonhuman primate kidney transplantation model

Introduction

One-third of HLA-incompatible kidney transplant recipients experience antibody mediated rejection (AMR) with limited treatment options. This study describes a novel treatment strategy for AMR consisting of proteasome inhibition and costimulation blockade with or without complement inhibition in a nonhuman primate model of kidney transplantation.

Methods

All rhesus macaques in the present study were sensitized to maximally MHC-mismatched donors by two sequential skin transplants prior to kidney transplant from the same donor. All primates received induction therapy with rhesus-specific ATG (rhATG) and were maintained on various immunosuppressive regimens. Primates were monitored postoperatively for signs of acute AMR, which was defined as worsening kidney function resistant to high dose steroid rescue therapy, and a rise in serum donor-specific antibody (DSA) levels. Kidney biopsies were performed to confirm AMR using Banff criteria. AMR treatment consisted of carfilzomib and belatacept for a maximum of four weeks with or without complement inhibitor.

Results

Treatment with carfilzomib and belatacept was well tolerated and no treatment-specific side effects were observed. After initiation of treatment, we observed a reduction of class I and class II DSA in all primates. Most importantly, primates had improved kidney function evident by reduced serum creatinine and BUN as well as increased urine output. A four-week treatment was able to extend graft survival by up to two months.

Discussion

In summary, combined carfilzomib and belatacept effectively treated AMR in our highly sensitized nonhuman primate model, resulting in normalization of renal function and prolonged allograft survival. This regimen may translate into clinical practice to improve outcomes of patients experiencing AMR.

The effect of late-onset CMV infection on the outcome of renal allograft considering initial graft function

BACKGROUND

Delayed graft function (DGF) increases the renal allograft failure risk. Late-onset Cytomegalovirus (CMV) infection's effect on the association between DGF and allograft failure has not been determined.

METHODS

In this retrospective cohort, we included all renal allograft recipients at London Health Sciences Centre from January 1, 2014 to December 30, 2017, and continued clinical follow-up until February 28, 2020. We determined whether late-onset CMV infection affects the association between DGF and allograft failure in stratified and Cox proportional hazard analyses.

RESULTS

Of 384 patients (median age [interquartile range]: 55 [43.3-63]; 38.7% female), 57 recipients (14.8%) were diagnosed with DGF. Patients with DGF were at a greater risk of CMV infection than patients without DGF (22.8% vs. 11.3%, p = .017). Late-onset CMV infection (odds ratio [OR]: 4.7, 95% CI: 2.07-10.68) and rejection (OR: 9.59, 95% CI: 4.15-22.16) significantly increased the risk of allograft failure in recipients with DGF. Patients with DGF had a significantly greater risk of graft failure than those without DGF (17.5% vs. 6.1%, p = .007). In the adjusted Cox hazard model, CMV infection significantly increased the risk of allograft failure (aHR: 3.19, 95% CI: 1.49-6.84).

CONCLUSION

Late-onset CMV infection considerably increased the risk of graft failure in patients with DGF. A hybrid preventive model including prophylaxis followed by CMV-specific cell-mediated immunity monitoring may decrease the risk of allograft failure in recipients with DGF.

Therapy in the Course of Kidney Graft Rejection-Implications for the Cardiovascular System-A Systematic Review

Kidney graft failure is not a homogenous disease and the Banff classification distinguishes several types of graft rejection. The maintenance of a transplant and the treatment of its failure require specific medications and differ due to the underlying molecular mechanism. As a consequence, patients suffering from different rejection types will experience distinct side-effects upon therapy. The review is focused on comparing treatment regimens as well as presenting the latest insights into innovative therapeutic approaches in patients with an ongoing active ABMR, chronic active ABMR, chronic ABMR, acute TCMR, chronic active TCMR, borderline and mixed rejection. Furthermore, the profile of cardiovascular adverse effects in relation to the applied therapy was subjected to scrutiny. Lastly, a detailed assessment and comparison of different approaches were conducted in order to identify those that are the most and least detrimental for patients suffering from kidney graft failure.

The Trend of Serum Creatinine Does Not Predict Follow-Up Biopsy Findings Among Kidney Transplant Recipients With Antibody-Mediated Rejection

Traditionally, antibody-mediated rejection (AMR) has been suspected mainly by a rise in serum creatinine (Scr) and confirmed by allograft biopsy. There is limited literature describing the trend of Scr after treatment, and how that trend might differ between patients with histological response and with no response to treatment.

Methods

We included all cases of AMR at our program between March 2016 and July 2020 who had a follow-up biopsy after the index biopsy, with initial diagnosis of AMR. We trended the Scr and change in Scr (delta Scr) and its association with being a responder (microvascular inflammation, MVI ≤1) or nonresponder (MVI >1), as well as graft failure.

Results

A total of 183 kidney transplant recipients were included, 66 in the responder group and 177 in the nonresponder group. The MVI scores and sum chronicity scores, along with transplant glomerulopathy scores, were higher in the nonresponder group. However, Scr at index biopsy was similar in responders (1.74 ± 0.70) versus nonresponders (1.83 ± 0.65; P = 0.39), as were the delta Scr at various time points. After adjustment for multiple variables, delta Scr was not associated with being a nonresponder. Also, delta Scr value at follow-up biopsy compared with index biopsy among responders was 0 ± 0.67 (P = 0.99) and among nonresponders was -0.01 ± 0.61 (P = 0.89). Being a nonresponder was significantly associated with an increased risk of graft failure at the last follow-up in univariate analysis but was not in multivariate analysis (hazard ratio 1.35; 95% confidence interval, 0.58-3.17; P = 0.49).

Conclusions

We found that Scr is not a good predictor of the resolution of MVI, supporting the utility of follow-up biopsies after treatment of AMR.

Comparison of high-dose IVIG and rituximab versus rituximab as a preemptive therapy for de novo donor-specific antibodies in kidney transplant patients

De novo donor-specific antibody (dnDSA) is associated with a higher risk of kidney graft failure. However, it is unknown whether preemptive treatment of subclinical dnDSA is beneficial. Here, we assessed the efficacy of high-dose intravenous immunoglobulin (IVIG) and rituximab combination therapy for subclinical dnDSA. An open-label randomized controlled clinical trial was conducted at two Korean institutions. Adult (aged ≥ 19 years) kidney transplant patients with subclinical class II dnDSA (mean fluorescence intensity ≥ 1000) were enrolled. Eligible participants were randomly assigned to receive rituximab or rituximab with IVIG at a 1:1 ratio. The primary endpoint was the change in dnDSA titer at 3 and 12 months after treatment. A total of 46 patients (24 for rituximab and 22 for rituximab with IVIG) were included in the analysis. The mean baseline estimated glomerular filtration rate was 66.7 ± 16.3 mL/min/1.73 m². The titer decline of immune-dominant dnDSA at 12 months in both the preemptive groups was significant. However, there was no difference between the two groups at 12 months. Either kidney allograft function or proteinuria did not differ between the two groups. No antibody-mediated rejection occurred in either group. Preemptive treatment with high-dose IVIG combined with rituximab did not show a better dnDSA reduction compared with rituximab alone.Trial registration: IVIG/Rituximab versus Rituximab in Kidney Transplant With de Novo Donor-specific Antibodies (ClinicalTrials.gov Identifier: NCT04033276, first trial registration (26/07/2019).

Extracorporeal Photopheresis Improves Graft Survival in a Full-Mismatch Rat Model of Kidney Transplantation

Extracorporeal photopheresis (ECP) is an immunomodulatory therapy based on the infusion of autologous cellular products exposed to ultraviolet light (UV) in the presence of a photosensitizer. The study evaluates the ECP efficacy as induction therapy in a full-mismatch kidney transplant rat model. Dark Agouti to Lewis (DA-L) kidney transplant model has been established. ECP product was obtained from Lewis rat recipients after DA kidney graft transplantation (Lew^DA). Leukocytes of those Lew^DA rats were exposed to 8-methoxy psoralen, and illuminated with UV-A. The ECP doses assessed were 10 × 10⁶ and 100 × 10⁶ cells/time point. Lewis recipients received seven ECP infusions. DA-L model was characterized by the appearance of donor-specific antibodies (DSA) and kidney function deterioration from day three after kidney transplant. The dysfunction progressed rapidly until graft loss (6.1 ± 0.5 days). Tacrolimus at 0.25 mg/kg prolonged rat survival until 11.4 ± 0.7 days (p = 0.0004). In this context, the application of leukocytes from LewDA sensitized rats accelerated the rejection (8.7 ± 0.45, p = 0.0012), whereas ECP product at high dose extended kidney graft survival until 26.3 ± 7.3 days, reducing class I and II DSA in surviving rats. ECP treatment increases kidney graft survival in full-mismatch rat model of acute rejection and is a suitable immunomodulatory therapy to be explored in kidney transplantation.

Toward generalizing the use of artificial intelligence in nephrology and kidney transplantation

With its robust ability to integrate and learn from large sets of clinical data, artificial intelligence (AI) can now play a role in diagnosis, clinical decision making, and personalized medicine. It is probably the natural progression of traditional statistical techniques. Currently, there are many unmet needs in nephrology and, more particularly, in the kidney transplantation (KT) field. The complexity and increase in the amount of data, and the multitude of nephrology registries worldwide have enabled the explosive use of AI within the field. Nephrologists in many countries are already at the center of experiments and advances in this cutting-edge technology and our aim is to generalize the use of AI among nephrologists worldwide. In this paper, we provide an overview of AI from a medical perspective. We cover the core concepts of AI relevant to the practicing nephrologist in a consistent and simple way to help them get started, and we discuss the technical challenges. Finally, we focus on the KT field: the unmet needs and the potential role that AI can play to fill these gaps, then we summarize the published KT-related studies, including predictive factors used in each study, which will allow researchers to quickly focus on the most relevant issues.

Rationale for the IMAGINE study for chronic active antibody-mediated rejection (caAMR) in kidney transplantation

Chronic active antibody-mediated rejection (caAMR) in kidney transplantation is a major cause of late graft loss and despite all efforts to date, there is no proven effective therapy. Indeed, the Transplant Society (TTS) consensus opinion called for a conservative approach optimizing baseline immunosuppression and supportive care focused on blood pressure, blood glucose, and lipid control. This review provides the rationale and early evidence in kidney transplant recipients with caAMR that supported the design of the IMAGINE study whose goal is to evaluate the potential impact of targeting the IL6/IL6R pathway.

Antibody-mediated rejection: prevention, monitoring and treatment dilemmas

PURPOSE OF REVIEW

Antibody-mediated rejection (AMR) has emerged as the leading cause of late graft loss in kidney transplant recipients. Donor-specific antibodies are an independent risk factor for AMR and graft loss. However, not all donor-specific antibodies are pathogenic. AMR treatment is heterogeneous due to the lack of robust trials to support clinical decisions. This review provides an overview and comments on practical but relevant dilemmas physicians experience in managing kidney transplant recipients with AMR.

RECENT FINDINGS

Active AMR with donor-specific antibodies may be treated with plasmapheresis, intravenous immunoglobulin and corticosteroids with additional therapies considered on a case-by-case basis. On the contrary, no treatment has been shown to be effective against chronic active AMR. Various biomarkers and prediction models to assess the individual risk of graft failure and response to rejection treatment show promise.

SUMMARY

The ability to personalize management for a given kidney transplant recipient and identify treatments that will improve their long-term outcome remains a critical unmet need. Earlier identification of AMR with noninvasive biomarkers and prediction models to assess the individual risk of graft failure should be considered. Enrolling patients with AMR in clinical trials to assess novel therapeutic agents is highly encouraged.

Chronic Active Antibody-mediated Rejection in Kidney Transplant Recipients: Treatment Response Rates and Value of Early Surveillance Biopsies

There is limited information on the value of short-term invasive and noninvasive monitoring in kidney transplant recipients (KTR) undergoing therapy for chronic active antibody-mediated rejection (cAMR).

Methods

We describe response rates in patients with cAMR receiving pulse steroids/IVIG ± rituximab 3-mo after index biopsy.

Results

The study included 82 consecutive KTR. Mean time from transplant to cAMR was 10 y. Mean peritubular capillaritis (ptc), glomerulitis (g), microvascular inflammation (MVI), C4d, and cg Banff scores were 1.1, 2.1, 3.2, 0.2, and 2, respectively. Mean estimated glomerular filtration rate (eGFR) and urine protein creatinine (UPC) ratio were 38 mL/min and 1.6 g/g, respectively. Thirty (37%) patients lost their allograft during the mean follow-up of 2.4 y. In patients treated with pulse steroids/IVIG (n = 41), response rates for eGFR, UPC, donor-specific antibodies (DSAs), and MVI were 27%, 49%, 7%, and 19%, respectively. In the pulse steroids/IVIG/rituximab group, response rates were 66%, 61%, 20%, and 69%, respectively. Univariate analysis identified response in eGFR (HR = 0.03; P = 0.001; 95% CI, 0.004-0.26), UPC (HR = 0.38; P = 0.01; 95% CI, 0.18-0.82), and DSA (HR = 0.11; P = 0.004; 95% CI, 0.02-0.49) as predictors of graft survival. Multivariate analysis only retained eGFR response (HR = 0.12; P = 0.01; 95% CI, 0.02-0.64).

Conclusions

In cAMR, short-term response to treatment for kidney function and DSA was associated with graft survival, but the role of early surveillance biopsies needs further evaluation.

Shifting Clinical Trial Endpoints in Kidney Transplantation: The Rise of Composite Endpoints and Machine Learning to Refine Prognostication

The measurement of outcomes in kidney transplantation has been more accurately documented than almost any other surgical procedure result in recent decades. With significant improvements in short- and long-term outcomes related to optimized immunosuppression, outcomes have gradually shifted away from conventional clinical endpoints (ie, patient and graft survival) to surrogate and composite endpoints. This article reviews how outcomes measurements have evolved in the past 2 decades in the setting of increased data collection and summarizes recent advances in outcomes measurements pertaining to clinical, histopathological, and immune outcomes. Finally, we discuss the use of composite endpoints and Bayesian concepts, specifically focusing on the integrative box risk prediction score, in conjunction with machine learning to refine prognostication.

Patient-Reported Outcomes as Endpoints in Clinical Trials of Kidney Transplantation Interventions

Patient-reported outcomes (PROs) that assess individuals' perceptions of life participation, medication adherence, disease symptoms, and therapy side effects are extremely relevant in the context of kidney transplantation. All PROs are potentially suitable as primary or secondary endpoints in interventional trials that aim to improve outcomes for transplant recipients. Using PRO measures (PROMs) in clinical trials facilitates assessment of the patient's perspective of their health, but few measures have been developed and evaluated in kidney transplant recipients; robust methodologies, which use validated instruments and established frameworks for reporting, are essential. Establishing a core PROM for life participation in kidney transplant recipients is a critically important need, which is being developed and validated by the Standardized Outcomes in Nephrology (SONG)-Tx Initiative. Measures involving electronic medication packaging and smart technologies are gaining traction for monitoring adherence, and could provide more robust information than questionnaires, interviews, and scales. This article summarizes information on PROs and PROMs that was included in a Broad Scientific Advice request on clinical trial design and endpoints in kidney transplantation. This request was submitted to the European Medicines Agency (EMA) by the European Society for Organ Transplantation in 2016. Following modifications, the EMA provided its recommendations in late 2020.

Poor Outcomes in Patients With Transplant Glomerulopathy Independent of Banff Categorization or Therapeutic Interventions

Background

Transplant glomerulopathy (TG) may indicate different disease entities including chronic AMR (antibody-mediated rejection). However, AMR criteria have been frequently changed, and long-term outcomes of allografts with AMR and TG according to Banff 2017 have rarely been investigated.

Methods

282 kidney allograft recipients with biopsy-proven TG were retrospectively investigated and diagnosed according to Banff'17 criteria: chronic AMR (cAMR, n = 72), chronic active AMR (cAAMR, n = 76) and isolated TG (iTG, n = 134). Of which 25/72 (34.7%) patients of cAMR group and 46/76 (60.5%) of cAAMR group were treated with antihumoral therapy (AHT).

Results

Up to 5 years after indication biopsy, no statistically significant differences were detected among iTG, cAMR and cAAMR groups in annual eGFR decline (−3.0 vs. −2.0 vs. −2.8 ml/min/1.73 m2 per year), 5-year median eGFR (21.5 vs. 16.0 vs. 20.0 ml/min/1.73 m2), 5-year graft survival rates (34.1 vs. 40.6 vs. 31.8%) as well as urinary protein excretion during follow-up. In addition, cAMR and cAAMR patients treated with AHT had similar graft and patient survival rates in comparison with those free of AHT, and similar comparing with iTG group. The TG scores were not associated with 5-year postbiopsy graft failure; whereas the patients with higher scores of chronic allograft scarring (by mm-, ci- and ct-lesions) had significantly lower graft survival rates than those with mild scores. The logistic-regression analysis demonstrated that Banff mm-, ah-, t-, ci-, ct-lesions and the eGFR level at biopsy were associated with 5-year graft failure.

Conclusions

The occurrence of TG is closely associated with graft failure independent of disease categories and TG score, and the long-term clinical outcomes were not influenced by AHT. The Banff lesions indicating progressive scarring might be better suited to predict an unfavorable outcome.

Clinical characteristics of renal transplant recipients who developed de novo donor-specific antigen in Kyoto University Hospital: a case series

Background

The clinical significance of de novo donor-specific antigen (DSA) in renal transplant recipients is not yet fully understood. This study aimed to report the prevalence of de novo DSA detected in antihuman leukocyte antigen (HLA) antibody testing and to evaluate the association between de novo DSA and renal transplant prognosis in living-donor renal transplant recipients at our hospital.

Methods

Of the 110 patients who underwent living-donor renal transplantation from 1980 to 2019, 80 patients who underwent anti-HLA antibody screening tests were retrospectively reviewed for the development of de novo DSA and outcomes regarding graft function.

Results

The mean age at transplantation was 43.2 ± 14.6 years. Of the 80 patients, 43 (53.8%) were men and 68 (85.0%) underwent ABO-compatible transplantation. Anti-HLA antibody was detected in 14 patients (17.5%), including eight (10.0%) with de novo DSA. Graft loss occurred in two (25%) of the eight patients with de novo DSA, none of the six patients with non-DSA anti-HLA antibody and no anti-HLA antibody (P = 0.0419, log-rank test). The mean estimated glomerular filtration rate at the time of the anti-HLA antibody test was 45.1 ± 14.4 mL/min/1.73m2 in the 66 patients with no anti-HLA antibody, while it was 35.0 ± 11.5 mL/min/1.73m2 in the eight patients with de novo DSA (P = 0.0702) and 39.3 ± 15.3 mL/min/1.73m2 in the six patients with non-DSA anti-HLA antibody (P = 0.3921). The mean monthly cyclosporin A trough concentration for the past year from the anti-HLA antibody test was 59.2 ± 24.8 ng/ml in the seven patients with no anti-HLA antibody, while it was 61.9 ± 12.5 ng/ml in the five patients with de novo DSA (P = 0.5670) and 36.3 ± 9.0 ng/ml in a patient with non-DSA anti-HLA antibody (P = 0.3921). The mean monthly tacrolimus trough concentration for the past year from the anti-HLA antibody test was 4.62 ± 1.20 ng/ml in the 55 patients with no anti-HLA antibody, while it was 4.09 ± 1.10 ng/ml in the three patients with de novo DSA (P = 0.0027) and 4.21 ± 1.14 ng/ml in the four patients with non-DSA anti-HLA antibody (P = 0.0722).

Conclusions

The optimal treatment for patients with de novo DSA has not been established, and immunosuppressive management that suppresses the development of de novo DSA is essential.

Complement-Binding Donor-Specific Anti-HLA Antibodies: Biomarker for Immunologic Risk Stratification in Pediatric Kidney Transplantation Recipients

Antibody-mediated rejection is a common cause of early kidney allograft loss but the specifics of antibody measurement, therapies and endpoints have not been universally defined. In this retrospective study, we assessed the performance of risk stratification using systematic donor-specific antibody (DSA) monitoring. Included in the study were children who underwent kidney transplantation between January 1, 2010 and March 1, 2018 at Stanford, with at least 12-months follow-up. A total of 233 patients were included with a mean follow-up time of 45 (range, 9–108) months. Median age at transplant was 12.3 years, 46.8% were female, and 76% had a deceased donor transplant. Fifty-two (22%) formed C1q-binding de novo donor-specific antibodies (C1q-dnDSA). After a standardized augmented immunosuppressive protocol was implemented, C1q-dnDSA disappeared in 31 (58.5%). Graft failure occurred in 16 patients at a median of 54 (range, 5–83) months, of whom 14 formed dnDSA. The 14 patients who lost their graft due to rejection, all had persistent C1q-dnDSA. C1q-binding status improved the individual risk assessment, with persistent; C1q binding yielding the strongest independent association of graft failure (hazard ratio, 45.5; 95% confidence interval, 11.7–177.4). C1q-dnDSA is more useful than standard dnDSA as a noninvasive biomarker for identifying patients at the highest risk of graft failure.

Influence of Persistent Inflammation in Follow-Up Biopsies After Antibody-Mediated Rejection in Kidney Transplantation

Background: Despite recent advances in immunosuppression treatment, antibody-mediated rejection (ABMR) remains the leading cause of kidney graft loss. Information about prognostic markers and the efficacy of treatment is scarce.

Methods: Retrospective study with kidney recipients diagnosed an active ABMR from January 1, 2004 to December 31, 2019 to explore the influence of persistent inflammation in follow-up biopsies on graft survival after ABMR treatment.

Results: About 116 patients were included. Active ABMR were treated with a combination of plasma exchange (PE), intravenous immunoglobulin (IVIg), rituximab, and steroids. At 6 months of treatment, 63 (54.3%) patients presented a stabilization or improvement in kidney-graft function. The effectiveness varied depending on the timepoint of the presentation between transplantation and rejection, which is lower for those with late ABMR (63 vs. 21% for early vs. late ABMR, respectively). Ninety patients (77%) underwent a control biopsy after ABMR treatment, from which 46 (51%) responded to the treatment. Microvascular inflammation (MVI) persisted in 64 (71%) biopsies, whereas tubulitis persisted in 17 (19%) biopsies. Death-censored graft survival at 1 year was significantly lower in patients with persistent MVI (86% vs. 95% without persistent MVI, P = 0.002), or with persistent tubulitis (44% vs. 66% without tubulitis, P = 0.02). In the Cox Regression analysis, the persistence of MVI [hazard ratio (HR), 4.50 (95%CI, 1.35–14.96), P = 0.01] and tubulitis [HR 2.88 95%CI (1.24–6.69), P = 0.01) in follow-up biopsies significantly increased the risk of graft failure.

Conclusion: Persistent inflammation in follow-up biopsies after ABMR treatment was associated with an increased risk of graft loss, even without meeting Banff rejection criteria.

Study Registration: Agencia Española de Medicamentos y Productos Sanitarios (AEMPS): 14566/RG 24161. Study code: UTRINM-2017-01.

The Problem of Subclinical Antibody-mediated Rejection in Kidney Transplantation

Defined as histologic evidence of rejection on a protocol biopsy in the absence of kidney dysfunction, subclinical rejection has garnered attention since the 1990s. The major focus of much of this research, however, has been subclinical T cell-mediated rejection (TCMR). Herein, we review the literature on subclinical antibody-mediated rejection (AMR), which may occur with either preexisting donor-specific antibodies (DSA) or upon the development of de novo DSA (dnDSA). In both situations, subsequent kidney function and graft survival are compromised. Thus, we recommend protocol biopsy routinely within the first year with preexisting DSA and at the initial detection of dnDSA. In those with positive biopsies, baseline immunosuppression should be maximized, any associated TCMR treated, and adherence stressed, but it remains uncertain if antibody-reduction treatment should be initiated. Less invasive testing of blood for donor DNA or gene profiling may have a role in follow-up of those with negative initial biopsies. If a protocol biopsy is positive in the absence of detectable HLA-DSA, it also remains to be determined whether non-HLA-DSA should be screened for either in particular or on a genome-wide basis and how these patients should be treated. Randomized controlled trials are clearly needed.

Approaches for Controlling Antibody-Mediated Allograft Rejection Through Targeting B Cells

Both acute and chronic antibody-mediated allograft rejection (AMR), which are directly mediated by B cells, remain difficult to treat. Long-lived plasma cells (LLPCs) in bone marrow (BM) play a crucial role in the production of the antibodies that induce AMR. However, LLPCs survive through a T cell-independent mechanism and resist conventional immunosuppressive therapy. Desensitization therapy is therefore performed, although it is accompanied by severe side effects and the pathological condition may be at an irreversible stage when these antibodies, which induce AMR development, are detected in the serum. In other words, AMR control requires the development of a diagnostic method that predicts its onset before LLPC differentiation and enables therapeutic intervention and the establishment of humoral immune monitoring methods providing more detailed information, including individual differences in the susceptibility to immunosuppressive agents and the pathological conditions. In this study, we reviewed recent studies related to the direct or indirect involvement of immunocompetent cells in the differentiation of naïve-B cells into LLPCs, the limitations of conventional methods, and the possible development of novel control methods in the context of AMR. This information will significantly contribute to the development of clinical applications for AMR and improve the prognosis of patients who undergo organ transplantation.

A noninvasive diagnostic approach to retrospective donor HLA typing in kidney transplant patients using urine

Antibody-mediated rejection (AMR) is a major obstacle to long-term kidney transplantation. AMR is mostly caused by donor specific HLA antibodies, which can arise before or any time after transplantation. Incomplete donor HLA typing and unavailability of donor DNA regularly preclude the assessment of donor-specificity of circulating anti-HLA antibodies. In our centre, this problem arises in approximately 20% of all post-transplant HLA-antibody assessments. We demonstrate that this diagnostic challenge can be resolved by establishing donor renal tubular cell cultures from recipient´s urine as a source of high-quality donor DNA. DNA was then verified for genetic origin and purity by fluorescence in situ hybridization and short tandem repeat analysis. Two representative cases highlight the diagnostic value of this approach which is corroborated by analysis of ten additional patients. The latter were randomly sampled from routine clinical care patients with available donor DNA as controls. In all 12 cases, we were able to perform full HLA typing of the respective donors confirmed by cross-comparison to results from the stored 10 donor DNAs. We propose that this noninvasive diagnostic approach for HLA typing in kidney transplant patients is valuable to determine donor specificity of HLA antibodies, which is important in clinical assessment of suspected AMR.

Incidence, risk factors, and long-term outcomes associated with antibody-mediated rejection - The long-term Deterioration of Kidney Allograft Function (DeKAF) prospective cohort study

Major gaps remain in our understanding of antibody-mediated rejection (AMR) after kidney transplant. We examined the incidence, risk factors, response to treatment, and effects on outcomes of AMR at seven transplant programs in the long-term Deterioration of Kidney Allograft Function prospective study cohort. Among 3131 kidney recipients, there were 194 observed AMR cases (6.2%) during (mean ± SD) 4.85 ± 1.86 years of follow-up. Time to AMR was 0.97 ± 1.17 (median, 0.48) years. Risk factors for AMR included younger recipient age, human leukocyte antigen DR mismatches, panel-reactive antibody >0%, positive T- or B-cell cross-match, and delayed graft function. Compared with no AMR, the adjusted time-dependent hazard ratio for death-censored graft failure is 10.1 (95% confidence interval, 6.5-15.7) for all AMR patients, 4.0 (2.5, 9.1) for early AMR (<90 days after transplant), and 24.0 (14.0-41.1) for late AMR (≥90 days after transplant). Patients were treated with different therapeutic combinations. Of 194 kidney transplant recipients with AMR, 50 (25.8%) did not respond to treatment, defined as second AMR within 100 days or no improvement in estimated glomerular filtration rate by 42 days. Long-term outcomes after AMR are poor, regardless of the initial response to treatment. Better prevention and new therapeutic strategies are needed to improve long-term allograft survival.

Therapies for Chronic Allograft Rejection

Remarkable advances have been made in the pathophysiology, diagnosis, and treatment of antibody-mediated rejection (ABMR) over the past decades, leading to improved graft outcomes. However, long-term failure is still high and effective treatment for chronic ABMR, an important cause of graft failure, has not yet been identified. Chronic ABMR has a relatively different phenotype from active ABMR and is a slowly progressive disease in which graft injury is mainly caused by de novo donor specific antibodies (DSA). Since most trials of current immunosuppressive therapies for rejection have focused on active ABMR, treatment strategies based on those data might be less effective in chronic ABMR. A better understanding of chronic ABMR may serve as a bridge in establishing treatment strategies to improve graft outcomes. In this in-depth review, we focus on the pathophysiology and characteristics of chronic ABMR along with the newly revised Banff criteria in 2017. In addition, in terms of chronic ABMR, we identify the reasons for the resistance of current immunosuppressive therapies and look at ongoing research that could play a role in setting better treatment strategies in the future. Finally, we review non-invasive biomarkers as tools to monitor for rejection.

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.

Therapeutic plasma exchange: single-center experience in children with kidney disorders

BACKGROUND

Therapeutic plasma exchange (TPE) is used in kidney diseases as an adjunct treatment. Little has been described as to its effectiveness in kidney disorders in children. This study aimed to assess the safety, efficacy, and outcomes of patients who underwent TPE for kidney indications.

METHODS

Retrospective chart review of patients receiving TPE from 2010 to 2018 for kidney indications, such as antibody-mediated rejection, bone marrow transplant-associated thrombotic microangiopathy (TA-TMA), atypical hemolytic uremic syndrome, transplant recurrence of focal segmental glomerulosclerosis, and glomerulonephritis. Outcomes assessed were trends in kidney function, mortality, and progression to stage 5 chronic kidney disease (CKD 5). Significant hypocalcemia was defined as ionized calcium < 1 mmol/L.

RESULTS

A total of 641 TPE procedures were performed on 47 patients (25 male). Average age was 12.8 ± 5.9 years. Median glomerular filtration rate (GFR) improved from baseline to end of TPE treatments (pre 44.9 (19.8, 79), end 56.1 (23, 98) [p = 0.02]). Ten out of 47 children developed CKD 5. Seven out of 47 patients died; 5 had TA-TMA. Initial 7 consecutive sessions were reviewed for complications. Among 335 procedures, 41 episodes of significant hypocalcemia were noted (12.2%); only 1 was symptomatic. Of the 26 episodes (7.7%) of allergic reactions, all were associated with the use of FFP; 5 were anaphylactic. No TPE-associated mortality was noted.

CONCLUSIONS

TPE is a relatively well-tolerated useful adjunct therapy in children with kidney indications. The benefit of TPE has to be balanced with risks such as hypocalcemia and allergic reactions which can occur more frequently with FFP. Graphical abstract.

Estimating alloantibody levels in highly sensitized renal allograft candidates: Using serial dilutions to demonstrate a treatment effect in clinical trials

Small reductions in calculated panel-reactive antibody (cPRA) are associated with increased kidney transplantation in 100% cPRA patients. However, the high level of antibody in these patients is such that desensitization may reduce antibody but not cPRA, thus the cPRA change on undiluted serum with desensitization is an insensitive measure of effectiveness. We evaluated cPRA reduction, calculated per antibody titer, as a desensitization trial endpoint. To accomplish this, two serum samples from 20 kidney transplant candidates with cPRA ≥99.9% (100%) were obtained and serially diluted in triplicate to determine the titer of individual human leukocyte antigen (HLA) antibody specificities. CPRA was computed per dilution to identify the titer at which cPRA drops below 98%. Inter- and intra-assay variability and changes overtime were determined. The dilution needed to reach a cPRA <98% was within 1 titer for replicates from the same sample, with 90% (36/40) concordance. This indicates that only changes >2 titers can be deemed clinically meaningful. The median (IQR) titer difference was 0 (0-1) from baseline to follow-up within 12 months. The cPRA per titer also risk-stratified candidates for trial inclusion. In conclusion, determining the cPRA per titer is a reliable approach to simplify complex antibody data and an ideal endpoint for desensitization trials.

Presence of a survival benefit of HLA-incompatible living donor kidney transplantation compared to waiting or HLA-compatible deceased donor kidney transplantation with a long waiting time

HLA-incompatible living donor kidney transplantation (LDKT) is one of efforts to increase kidney transplantation opportunity for sensitized patients with kidney failure. However, there are conflicting reports for outcomes of HLA-incompatible kidney transplantation compared to patients who wait for HLA-compatible deceased donor kidney transplantation (DDKT) in the United States and United Kingdom. Waiting for an HLA-compatible DDKT is relatively disadvantageous in Korea, because the average waiting time is more than five years. To study this further, we compared outcomes of HLA-incompatible LDKT with those who wait for HLA-compatible DDKT in Korea. One hundred eighty nine patients underwent HLA-incompatible LDKT after desensitization between 2006 and 2018 in two Korean hospitals (42 with a positive complement-dependent cytotoxicity cross-match, 89 with a positive flow cytometric cross-match, and 58 with a positive donor-specific antibody with negative cross-match). The distribution of matched variables was comparable between the HLA-incompatible LDKT group and the matched control groups (waiting-list-only group; and the waiting-list-or-HLA-compatible-DDKT groups; 930 patients each). The HLA-incompatible LDKT group showed a significantly better patient survival rate compared to the waiting-list-only group and the waiting-list-or-HLA-compatible-DDKT groups. Furthermore, the HLA-incompatible LDKT group showed a significant survival benefit as compared with the matched groups at all strength of donor-specific antibodies. Thus, HLA-incompatible LDKT could have a survival benefit as compared with patients who were waitlisted for HLA-compatible DDKT or received HLA-compatible DDKT in Korea. This suggests that HLA-incompatible LDKT as a good option for sensitized patients with kidney failure in countries with prolonged waiting times for DDKT.

Considerations and controversies of pharmacologic management of the pediatric kidney transplant recipient

Pediatric kidney transplantation has experienced considerable growth and improvement in patient and allograft outcomes over the past 20 years, in part due to advancements in immunosuppressive regimens and management. Despite this progress, care for this unique population can be challenging due to limited pediatric transplant data and trials, intricacies related to differences in children and adolescents compared with their adult counterparts, and limitations to long-term survival facing all solid organ transplant populations. Immunosuppression and infection prevention practices vary from one pediatric transplant center to another and clinical controversies exist surrounding treatment and dosing. This review aims to summarize key aspects of pharmacologic management in this population and present pertinent data that describe the influence of practice to serve as a resource for practitioners caring for this unique specialty patient population. Additionally, this review highlights select controversies that exist within pediatric kidney transplantation.

Validation of the International Classification of Disease 10th Revision Codes for Kidney Transplant Rejection and Failure

BACKGROUND

Clinical research requires that diagnostic codes captured from routinely collected health administrative data accurately identify individuals with a disease.

OBJECTIVE

In this study, we validated the International Classification of Disease 10th Revision (ICD-10) definition for kidney transplant rejection (T86.100) and for kidney transplant failure (T86.101).

DESIGN

Retrospective cohort study.

SETTING

A large, regional transplantation center in Ontario, Canada.

PATIENTS

All adult kidney transplant recipients from 2002 to 2018.

MEASUREMENTS

Chart review was undertaken to identify the first occurrence of biopsy-confirmed rejection and graft loss for all participants. For each observation, we determined the first date a single ICD-10 code T86.100 or T86.101 was recorded as a hospital encounter discharge diagnosis.

METHODS

Using chart review as the gold standard, we determined the sensitivity, specificity, and positive predictive value (PPV) for the ICD-10 codes T86.100 and T86.101.

RESULTS

Our study population comprised of 1,258 kidney transplant recipients. The prevalence of rejection and death-censored graft loss were 15.6 and 9.1%, respectively. For the ICD-10 rejection code (T86.100), sensitivity was 72.9% (95% confidence interval [CI], 66.6-79.2), specificity 97.5% (96.5-98.4), and PPV 83.8% (78.3-89.4). For the ICD-10 graft loss code (T86.101), sensitivity was 21.2% (95% CI, 13.2-29.3), specificity 86.3% (84.3-88.3), and PPV 11.7% (7.0-16.4).

LIMITATIONS

Single-center study which may limit generalizability of our findings.

CONCLUSIONS

A single ICD-10 code for kidney transplant rejection (T86.100) was present in 84% of true kidney transplant rejections and is an accurate way of identifying kidney transplant recipients with rejection using administrative health data. The ICD-10 code for graft failure (T86.101) performed poorly and should not be used for administrative health research.

Treatment of Chronic Active Antibody-mediated Rejection With Pulse Steroids, IVIG, With or Without Rituximab is Associated With Increased Risk of Pneumonia

Background.

The risk of infection associated with specific treatments of chronic active antibody-mediated rejection (cAMR) after kidney transplantation remains unknown.

Methods.

This was a single-center study of kidney transplant recipients treated with pulse steroids, intravenous immunoglobulin (IVIG) ± rituximab for biopsy-confirmed cAMR. The control group consisted of age- and race-matched patients who underwent donor-specific antibody-based protocol biopsies but had no rejection. We collected data on BK virus (BKV), cytomegalovirus (CMV), urinary tract infection (UTI), and pneumonia postbiopsy.

Results.

There were 49 patients in each group. In those with cAMR, 21 (43%) were treated with steroids, IVIG, and rituximab; the remaining received steroids and IVIG only. The risk of graft failure was greater in the cAMR group [22 (45%) vs. 3 (6%), P < 0.001]. Kaplan-Meier analyses demonstrated a significantly greater risk of pneumonia in the cAMR group (P = 0.02). This was confirmed by multivariable Cox regression analyses [Hazard ratio (HR) = 6.04, P = 0.027, 95% CI, 1.22-29.75]. None of the patients with pneumonia were affected by opportunistic pathogens. Additionally, the risk of CMV, UTI, and BKV was not increased. Rituximab was not independently associated with any of the infections studied.

Conclusions.

Treatment of cAMR, but not rituximab, was associated with a 6-fold increased risk of pneumonia. Additional studies are needed to determine the safety and efficacy of prolonged antimicrobial prophylaxis and monitoring strategies, including for hypogammaglobulinemia, to reduce the risk of pneumonia following the treatment of cAMR.

Efficacy of plasmapheresis and semi-selective immunoadsorption for removal of anti-HLA antibodies

BACKGROUND

In organ transplantation, apheresis is frequently used for removal of anti-HLA antibodies. However, it is unclear whether plasmapheresis (PP) or semi-selective immunoadsorption (IA) should be employed, and the optimal number of apheresis sessions required to reach post-treatment objectives is also unknown.

METHODS

We enrolled 43 patients from Bordeaux University Hospital who were treated with PP (n = 29) or IA (n = 14) for antibody-mediated rejection or pre-transplant desensitization. Using Luminex single-antigen flow beads, we assessed the initial mean fluorescence intensity (MFI) of 1416 positive beads with MFIs obtained after 7 to 8 apheresis sessions (extended protocol) and, if a serum was available, after the first four sessions (short protocol).

RESULTS

MFI reduction after extended apheresis protocol was stronger with IA [87% (61%-100%)] than with PP [73% (22%-100%)] (P < .001). Indeed, 59% of the beads had a final MFI < 2000 with IA, whereas only 38% with PP (P < .001). The efficacy of removal depended on initial MFI but not on HLA specificity. A short protocol of apheresis showed excellent results without superiority of IA over PP for antibodies with an initial MFI < 3000. For antibodies showing MFI ≥2000 after four sessions, the residual MFI predicted the effectiveness of four additional sessions.

CONCLUSION

Monitoring the MFI of anti-HLA antibodies before and during apheresis protocol can guide physicians in the selection of apheresis technique and the number of sessions to be performed.

Donor-specific antibodies in kidney transplantation: the University of Wisconsin experience

PURPOSE OF REVIEW

Antibody-mediated rejection (ABMR) is the leading cause of allograft failure in kidney transplant recipients. This article provides a summary of the clinical research relating to donor-specific antibodies (DSA) and ABMR in kidney transplant recipients at the University of Wisconsin-Madison Transplant Center.

RECENT FINDINGS

Over 40% of the kidney transplant candidates on the UNOS waitlist are sensitized, and both preformed and de novo DSA are associated with increased risk of rejection and graft loss. We have developed graded induction-desensitization treatment and monitoring protocols based on the degree of immunologic risk. We have also implemented standard treatment and surveillance strategies for patients with ABMR. Additional important observations from our studies include high rates of ABMR in patients with positive C4d staining in postreperfusion biopsies and rise in DSA at 1 week after transplant, and increased risk of kidney allograft failure in patients with de novo DSA and ABMR, as well as in patients with HLA-DSA undetectable ABMR. We also found worse outcomes with de novo DSA following simultaneous pancreas--kidney and liver--kidney transplantation. Notably, favorable long-term graft outcomes were observed in patients with DSA who do not present the classic histopathological findings of ABMR.

SUMMARY

In order to improve long-term outcomes for kidney transplant recipients, further research focusing on the pathogenic mechanisms elicited by HLA and non-HLA DSA, and novel therapies targeting these pathways is needed.

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

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

What have we learned about how to prevent and treat antibody-mediated rejection in kidney transplantation?

Antibody-mediated rejection (ABMR) in kidney transplantation is a major cause of late graft loss, and despite all efforts to date the "standard of care" remains plasmapheresis, IVIg, and steroids, which itself is based on low quality evidence. This review focuses on the risk factors leading to memory and de novo donor-specific antibody (DSA)-associated ABMR, the optimal prevention strategies for ABMR, and advances in  adjunctive and emerging therapies for ABMR. Because new agents require regulatory approval via a Phase 3 randomized control trial (RCT), an overview of progress in innovative trial design for ABMR is provided. Finally, based on the insights gained in the biology of ABMR, current knowledge gaps are identified for future research that could significantly affect our understanding of how to optimally treat ABMR.

Short-term Immunopathological Changes Associated with Pulse Steroids/IVIG/Rituximab Therapy in Late Kidney Allograft Antibody Mediated Rejection

Background

B-cell depletion is a common treatment of antibody-mediated rejection (ABMR). We sought to determine the specific immunopathologic effects of this therapeutic approach in kidney transplantation.

Methods

This was a prospective observational study of kidney transplant recipients diagnosed with late ABMR (>3 months after transplant). Patients received treatment with pulse steroids, IVIG, and rituximab. Donor specific HLA antibodies (DSA), kidney allograft pathology, renal function, immune cell phenotypes, and 47 circulating cytokines were assessed at baseline and at three months.

Results

We enrolled 23 patients in this study between April 2015 and March 2019. The majority of patients were male (74%) and Caucasian (78%) with an average age of 45.6±13.8 years. ABMR was diagnosed at 6.8±5.9 years (4 months-25 years) post-transplant. Treatment was associated with a significant decline in circulating HLA class I DSA (P=0.003) and class II DSA (P=0.002) and peritubular capillaritis (ptc, P=0.04) compared to baseline. Serum creatinine, BUN, eGFR, and proteinuria (UPC) remained stable. Circulating B-cells were depleted to barely detectable levels (P≤0.001), whereas BAFF (P=0.001), APRIL (P<0.001), and IL-10 (P=0.02), levels increased significantly post-treatment. Notably, there was a significant rise in circulating CD4+ (P=0.02) and CD8+ T-cells (P=0.003). We also noted a significant correlation between circulating cytotoxic CD8+ T-cells and BAFF (P=0.05), regulatory T-cells and IL10 (P=0.002), and HLA class I DSA (P=0.005).

Conclusions

Short-term pulse steroids/IVIG/rituximab therapy was associated with inhibition of ABMR (DSA and ptc), stabilization of kidney function, and increased regulatory B-cell and T-cell survival cytokines. Additional studies are needed to understand the implications of B cell-depletion on the crosstalk between T-cells, B-cells, and humoral components that regulate ABMR.

Impact of active antibody-mediated rejection treatment on donor-specific antibodies in pediatric kidney transplant recipients

AMR is a major cause of graft loss after kidney transplantation. We evaluated a retrospective cohort of 13 pediatric kidney transplant patients diagnosed with active AMR. All 13 patients were treated with plasmapheresis (PP), IVIg, and rituximab. Anti-HLA DSAs were measured at the time of transplantation, AMR diagnosis, 30 days post-rejection treatment, 90 days post-rejection treatment, and 24 ± 12 months post-AMR. A total of 68 DSAs were identified from 13 patients at the time of active AMR diagnosis. The primary objective of this study was to differentiate treatment response rates between class I and class II anti-HLA DSA post-AMR treatment. Overall, DSAs were significantly reduced at 30 days, and the reduction was sustained at 90 days post-treatment, even for class II anti-HLA and strongly positive DSAs. A significant difference between class I and class II anti-HLA DSA was observed at 30 days; however, between class significance was lost at 90-day follow-up due to continued class II anti-HLA DSA treatment response. Low DSA strength was predictive of treatment response. eGFR demonstrated significant improvement 90 days after AMR diagnosis compared to the initial value at the time of AMR, and the effect was sustained for 12 months. These results suggest that the AMR treatment is effective in pediatric kidney transplant recipients with an early diagnosis of active AMR across both class I and class II anti-HLA DSAs.

Therapeutic apheresis in kidney transplantation: An updated review

Therapeutic apheresis is a cornerstone of therapy for several conditions in transplantation medicine and is available in different technical variants. In the setting of kidney transplantation, immunological barriers such as ABO blood group incompatibility and preformed donor-specific antibodies can complicate the outcome of deceased- or living- donor transplantation. Postoperatively, additional problems such as antibody-mediated rejection and a recurrence of primary focal segmental glomerulosclerosis can limit therapeutic success and decrease graft survival. Therapeutic apheresis techniques find application in these issues by separating and selectively removing exchanging or modifying pathogenic material from the patient by an extracorporeal aphaeresis system. The purpose of this review is to describe the available techniques of therapeutic aphaeresis with their specific advantages and disadvantages and examine the evidence supporting the application of therapeutic aphaeresis as an adjunctive therapeutic option to immunosuppressive agents in protocols before and after kidney transplantation.

Predicting kidney transplant outcomes with partial knowledge of HLA mismatch

We consider prediction of graft survival when a kidney from a deceased donor is transplanted into a recipient, with a focus on the variation of survival with degree of human leukocyte antigen (HLA) mismatch. Previous studies have used data from the Scientific Registry of Transplant Recipients (SRTR) to predict survival conditional on partial characterization of HLA mismatch. Whereas earlier studies assumed proportional hazards models, we used nonparametric regression methods. These do not make the unrealistic assumption that relative risks are invariant as a function of time since transplant, and hence should be more accurate. To refine the predictions possible with partial knowledge of HLA mismatch, it has been suggested that HaploStats statistics on the frequencies of haplotypes within specified ethnic/national populations be used to impute complete HLA types. We counsel against this, showing that it cannot improve predictions on average and sometimes yields suboptimal transplant decisions. We show that the HaploStats frequency statistics are nevertheless useful when combined appropriately with the SRTR data. Analysis of the ecological inference problem shows that informative bounds on graft survival probabilities conditional on refined HLA typing are achievable by combining SRTR and HaploStats data with immunological knowledge of the relative effects of mismatch at different HLA loci.

Association of immunosuppressive agents and cytomegalovirus infection with de novo donor-specific antibody development within 1 year after renal transplantation

The association between immunosuppressive therapy or cytomegalovirus (CMV) infection and detection of de novo donor-specific antibody (dnDSA) at 1 year after transplantation was evaluated. The impact of dnDSA positivity at 1 year after transplantation on long-term death-censored renal graft survival was also evaluated. One hundred and sixty adults receiving living renal allografts were studied. Inclusion criteria were renal graft survival for at least 1 year and a standard regimen of immunosuppressive therapy with tacrolimus, mycophenolate mofetil (MMF), steroids, and basiliximab. DSA were measured retrospectively by the Luminex assay. The coefficient of variation (CV) was calculated and receiver operating characteristic (ROC) analysis was employed to clarify the association of tacrolimus with development of dnDSA. Seven of the 160 patients (4.4%) were positive for dnDSA. The intra-patient minimum trough level of tacrolimus (cutoff value: 3.2 ng/mL) was associated with development of dnDSA. Discontinuation of MMF and treatment of CMV infection were more frequent in patients with dnDSA than in those without dnDSA. In multivariate analysis, a low trough level of tacrolimus, discontinuation of MMF, and treatment of CMV infection within 1 year after transplantation were independently associated with detection of dnDSA at 1 year. In patients with or without dnDSA at 1 year, the 10-year allograft survival rate was 51.4 versus 87.9%, respectively (P = 0.002). A lower tacrolimus trough level, discontinuation of MMF, and treatment of CMV infection were associated with dnDSA positivity. Further investigation is needed to determine whether a new immunosuppressive regimen that avoids these factors can reduce dnDSA positivity.

Prognostic tools to assess candidacy for and efficacy of antibody-removal therapy

Currently, the ability to predict or monitor the efficacy of HLA antibody-removal therapies is deficient. We previously reported that titration studies are a consistent and accurate means of assessing antibody strength. To test whether titration studies can also predict which patients are better candidates for desensitization, we studied 38 patients from 3 centers (29 receiving plasmapheresis/low-dose intravenous immunoglobulin [IVIg]; 9 patients receiving high-dose IVIg). For patients undergoing plasmapheresis/low-dose IVIg, antibody titer reduction correlated with number of treatment cycles for both class I and II antibodies but only up to approximately 4 cycles. Reduction in titer slowed with additional cycles, suggesting a limit to the efficacy of this approach. Furthermore, initial titer (predesensitization) can guide the selection of candidates for successful antibody-removal treatment. In our experience, patients with antibodies at an initial titer >1:512 could not be reduced to the goal of a negative lymphocyte crossmatch, corresponding to a 1:16 titer, despite a significant increase in the number of treatment cycles. Change in mean fluorescence intensity (MFI) value did not correlate with success of treatment if initial MFI values were >10 000, likely due to single antigen bead saturation. Overall, we present a potential prognostic tool to predict candidacy and a monitoring tool to assess efficacy of desensitization treatment.

Application of TruGraf v1: A Novel Molecular Biomarker for Managing Kidney Transplant Recipients With Stable Renal Function

TruGraf v1 is a laboratory-developed DNA microarray-based gene expression blood test to enable proactive noninvasive serial assessment of kidney transplant recipients with stable renal function. It has been previously validated in patients identified as Transplant eXcellence (TX: stable serum creatinine, normal biopsy results, indicative of immune quiescence), and not-TX (renal dysfunction and/or rejection on biopsy results). TruGraf v1 is intended for use in subjects with stable renal function to measure the immune status as an alternative to invasive, expensive, and risky surveillance biopsies.

MATERIALS AND METHODS

In this study, simultaneous blood tests and clinical assessments were performed in 192 patients from 7 transplant centers to evaluate TruGraf v1. The molecular testing laboratory was blinded to renal function and biopsy results.

RESULTS

Overall, TruGraf v1 accuracy (concordance between TruGraf v1 result and clinical and/or histologic assessment) was 74% (142/192), and a result of TX was accurate in 116 of 125 (93%). The negative predictive value for TruGraf v1 was 90%, with a sensitivity 74% and specificity of 73%. Results did not significantly differ in patients with a biopsy-confirmed diagnosis vs those without a biopsy.

CONCLUSIONS

TruGraf v1 can potentially support a clinical decision enabling unnecessary surveillance biopsies with high confidence, making it an invaluable addition to the transplant physician's tool kit for managing patients. TruGraf v1 testing can potentially avoid painful and risky invasive biopsies, reduce health care costs, and enable frequent assessment of patients with stable renal function to confirm the presence of immune quiescence in the peripheral blood.