Comparison of de novo IgM and IgG anti-HLA DSAs between belatacept- and calcineurin-treated patients: An analysis of the BENEFIT and BENEFIT-EXT trial cohorts

Assessment of IgM DSAs in Transplant Recipients: Relationship to De Novo IgG DSAs and Risk for Antibody Rejection

Background

The presence of anti-HLA donor-specific antibodies (DSAs) is associated with antibody-mediated rejection (AMR) and inferior graft survival. However, recent data suggest that ~50% of AMR episodes are IgG DSA negative and possibly related to non-HLA DSAs. After the initial activation of B cells to alloantigen, IgM is the first immunoglobulin produced. In addition, both IgM and IgG isotopes can activate the classic complement pathway and induce complement-dependent cytotoxicity to allograft targets. Current practices focus on the assessment of IgG DSAs with little concern for the assessment of IgM DSAs.

Methods

Here, we examined anti-HLA IgM in a cohort of 22 patients who developed de novo IgG DSAs by a modified single-antigen bead-based test.

Results

We found IgM HLA DSAs developed before IgG DSAs. The median time from the detection of IgM DSAs to the appearance of de novo IgG DSAs was 461 d. Most patients had IgM DSAs against the same HLA-DQ antigens, for which IgG de novo DSAs were also later detected. IgM DSAs were detected in patients with biopsies suspected of AMR.

Conclusions

The detection of IgM DSAs could be an early indicator of alloimmune responses to allografts before IgG de novo DSAs appear.

IgM marks persistent IgG anti-human leukocyte antigen antibodies in highly sensitized heart transplant patients

BACKGROUND

Sensitization to human leukocyte antigens (HLA) is a persistent problem in heart transplant (HT) candidates. We sought to characterize the anti-HLA antibody and circulating B cell repertoire in a cohort of highly sensitized HT candidates.

METHODS

We assessed immunoglobulin G (IgG) and immunoglobulin M (IgM) anti-HLA antibodies using Luminex single antigen bead assays in a cohort of 11 highly sensitized (HS; calculated panel reactive antibody ≥ 90%) and 3 mildly sensitized (MS) candidates. We also performed B cell receptor repertoire sequencing (BCRseq) in HS candidates and 33 non-candidate controls. HLA antibody strength was measured by mean fluorescence intensity (MFI).

RESULTS

We found that IgM anti-HLA antibodies were present in all HS candidates, but with a lower breadth and strength as compared to IgG. When anti-HLA IgG specificities intersected with IgM, binding strength was higher. In contrast, there were IgM but no intersecting IgG specificities for the MS group. In four candidates in the HS group, IgG anti-HLA antibodies decreased in both breadth and strength after HT, but the decrease in strength was smaller if the IgG possessed a specificity that intersected with pre-transplant IgM. BCRseq revealed larger B cell clonotypes in HS candidates but similar diversity as compared to controls.

CONCLUSIONS

IgM marks IgG anti-HLA antibodies with higher strength before HT and persistence after HT. The presence of IgM intersecting IgG for an anti-HLA specificity may be a useful approach to determine which donor HLA should be avoided for a sensitized candidate.

Cellular Immunobiology and Molecular Mechanisms in Alloimmunity-Pathways of Immunosuppression

Current maintenance immunosuppression commonly comprises a synergistic combination of tacrolimus as calcineurin inhibitor (CNI), mycophenolic acid, and glucocorticoids. Therapy is often individualized by steroid withdrawal or addition of belatacept or inhibitors of the mechanistic target of rapamycin. This review provides a comprehensive overview of their mode of action, focusing on the cellular immune system. The main pharmacological action of CNIs is suppression of the interleukin-2 pathway that leads to inhibition of T cell activation. Mycophenolic acid inhibits the purine pathway and subsequently diminishes T and B cell proliferation but also exerts a variety of effects on almost all immune cells, including inhibition of plasma cell activity. Glucocorticoids exert complex regulation via genomic and nongenomic mechanisms, acting mainly by downregulating proinflammatory cytokine signatures and cell signaling. Belatacept is potent in inhibiting B/T cell interaction, preventing formation of antibodies; however, it lacks the potency of CNIs in preventing T cell-mediated rejections. Mechanistic target of rapamycin inhibitors have strong antiproliferative activity on all cell types interfering with multiple metabolic pathways, partly explaining poor tolerability, whereas their superior effector T cell function might explain their benefits in the case of viral infections. Over the past decades, clinical and experimental studies provided a good overview on the underlying mechanisms of immunosuppressants. However, more data are needed to delineate the interaction between innate and adaptive immunity to better achieve tolerance and control of rejection. A better and more comprehensive understanding of the mechanistic reasons for failure of immunosuppressants, including individual risk/benefit assessments, may permit improved patient stratification.

Sensitization in transplantation: Assessment of Risk 2022 Working Group Meeting Report

The Sensitization in Transplantation: Assessment of Risk workgroup is a collaborative effort of the American Society of Transplantation and the American Society of Histocompatibility and Immunogenetics that aims at providing recommendations for clinical testing, highlights gaps in current knowledge, and proposes areas for further research to enhance histocompatibility testing in support of solid organ transplantation. This report provides updates on topics discussed by the previous Sensitization in Transplantation: Assessment of Risk working groups and introduces 2 areas of exploration: non-human leukocyte antigen antibodies and utilization of human leukocyte antigen antibody testing measurement to evaluate the efficacy of antibody-removal therapies.

Assessment and management of allosensitization following heart transplant in adults

Immunological injury to the allograft, specifically by antibodies to de novo donor specific human leukocyte antigen (dnDSA) and antibody mediated injury and rejection are the major limitations to graft survival after heart transplantation (HT). As such, our approach to allosensitization remains limited by the inability of contemporaneous immunoassays to unravel pathogenic potential of dnDSA. Additionally, the role of dnDSA is continuously evaluated with emerging methods to detect rejection. Moreover, the timing and frequency of dnDSA monitoring for early detection and risk mitigation as well as management of dnDSA remain challenging. A strategic approach to dnDSA employs diagnostic assays to determine relevant antibodies in conjunction with clinical presentation and injury/rejection of allograft to tailor therapeutics. In this review, we aim to outline contemporary knowledge involving detection, monitoring and management of dnDSA after HT. Subsequently, we propose a diagnostic and therapeutic approach that may mitigate morbidity and mortality while balancing adverse reactions from pharmacotherapy.

Chronic CD40L blockade is required for long-term cardiac allograft survival with a clinically relevant CTLA4-Ig dosing regimen

Introduction

In de-novo kidney transplantation, the CTLA4-Ig fusion protein belatacept is associated with improved graft function but also an increased risk of acute rejection compared to calcineurin inhibitor therapy. The combination with a second costimulation blocker could potentially improve outcome while avoiding calcineurin inhibitor toxicity. The aim of this study was to define the conditions under which the combination of CTLA4-Ig and CD40L blockade leads to rejection-free permanent graft survival in a stringent murine heart transplantation model.

Methods

Naïve wild-type or CD40L (CD154) knock-out mice received a fully mismatched BALB/c cardiac allograft. Selected induction and maintenance protocols for CTLA4-Ig and blocking αCD40L monoclonal antibodies (mAB) were investigated. Graft survival, rejection severity and donor-specific antibody (DSA) formation were assessed during a 100-day follow-up period.

Results and Discussion

Administering αCD40L mAb as monotherapy at the time of transplantation significantly prolonged heart allograft survival but did not further improve the outcome when given in addition to chronic CTLA4-Ig therapy (which prolongs graft survival to a median of 22 days). Likewise, chronic αCD40L mAb therapy (0.5mg) combined with perioperative CTLA4-Ig led to rejection in a proportion of mice and extensive histological damage, despite abrogating DSA formation. Only the permanent interruption of CD40-CD40L signaling by using CD40L^-/- recipient mice or by chronic αCD40L administration synergized with chronic CTLA4-Ig to achieve long-term allograft survival with preserved histological graft integrity in all recipients without DSA formation. The combination of α-CD40L and CTLA4-Ig works most effectively when both therapeutics are administered chronically.

From bench to bedside: reversing established antibody responses and desensitization

PURPOSE OF REVIEW

Basic transplant immunology has primarily focused on the definition of mechanisms, but an often-stated aspirational goal is to translate basic mechanistic research into future therapy. Pretransplant donor-specific antibodies (DSA) mediate hyperacute as well as early antibody-mediated rejection (AMR), whereas DSA developing late posttransplantation may additionally mediate chronic rejection. Although contemporary immunosuppression effectively prevents early cellular rejection after transplant in nonsensitized patients, it is less effective at controlling preexisting HLA antibody responses or reversing DSA once established, thus underscoring a need for better therapies.

RECENT FINDINGS

We here review the development of a bench-to-bedside approach involving transient proteasome inhibition to deplete plasma cells, combined with maintenance co-stimulation blockade, with CTLA-4Ig or belatacept, to prevent the generation of new antibody-secreting cells (ASCs).

SUMMARY

This review discusses how this treatment regimen, which was rationally designed and validated to reverse established DSA responses in mouse models, translated into reversing active AMR in the clinic, as well as desensitizing highly sensitized patients on the transplant waitlist.

Longitudinal evaluation of the impact of immunosuppressive regimen on immune responses to COVID-19 vaccination in kidney transplant recipients

Immunocompromised patients have a high risk of death from SARS-CoV-2 infection. Vaccination with an mRNA vaccine may protect these patients against severe COVID-19. Several studies have evaluated the impact of immune-suppressive drug regimens on cellular and humoral responses to SARS-CoV-2 variants of concern in this context. We performed a prospective longitudinal study assessing specific humoral (binding and neutralizing antibodies against spike (S) and T-lymphocyte (cytokine secretion and polyfunctionality) immune responses to anti-COVID-19 vaccination with at least two doses of BNT162b2 mRNA vaccine in stable kidney transplant recipients (KTR) on calcineurin inhibitor (CNI)- or belatacept-based treatment regimens. Fifty-two KTR−31 receiving CNI and 21 receiving belatacept—were enrolled in this study. After two doses of vaccine, 46.9% of patients developed anti-S IgG. Anti-spike IgG antibodies were produced in only 21.4% of the patients in the belatacept group, vs. 83.3% of those in the CNI group. The Beta and Delta variants and, more importantly, the Omicron variant, were less well neutralized than the Wuhan strain. T-cell functions were also much weaker in the belatacept group than in the CNI group. Renal transplant patients have an impaired humoral response to BNT162b2 vaccination. Belatacept-based regimens severely weaken both humoral and cellular vaccine responses. Clinically, careful evaluations of at least binding IgG responses, and prophylactic or post-exposure strategies are strongly recommended for transplant recipients on belatacept-based regimens.

Dual Costimulatory and Coinhibitory Targeting with a Hybrid Fusion Protein as an Immunomodulatory Therapy in Lupus Nephritis Mice Models

Systemic lupus erythematosus is a complex autoimmune disorder mostly mediated by B-cells in which costimulatory signals are involved. This immune dysregulation can cause tissue damage and inflammation of the kidney, resulting in lupus nephritis and chronic renal failure. Given the previous experience reported with CTLA4-Ig as well as recent understanding of the PD-1 pathway in this setting, our group was encouraged to evaluate, in the NZBWF1 model, a human fusion recombinant protein (Hybri) with two domains: CTLA4, blocking the CD28—CD80 costimulatory pathway, and PD-L2, exacerbating the PD-1–PD-L2 coinhibitory pathway. After achieving good results in this model, we decided to validate the therapeutic effect of Hybri in the more severe MRL/lpr model of lupus nephritis. The intraperitoneal administration of Hybri prevented the progression of proteinuria and anti-dsDNA antibodies to levels like those of cyclophosphamide and reduced the histological score, infiltration of B-cells, T-cells, and macrophages and immune deposition in both lupus-prone models. Additionally, Hybri treatment produced changes in both inflammatory-related circulating cytokines and kidney gene expression. To summarize, both in vivo studies revealed that the Hybri effect on costimulatory-coinhibitory pathways may effectively mitigate lupus nephritis, with potential for use as a maintenance therapy.

The proliferation of belatacept-resistant T cells requires early IFNα pathway activation

Belatacept was developed to replace calcineurin inhibitors in kidney transplantation. Its use is associated with better kidney transplant function, a lower incidence of anti-donor antibodies and higher graft survival. However, it is also associated with a higher risk of cellular rejection. We studied the activation and proliferation mechanisms of belatacept-resistant T lymphocytes (TLs), to identify new pathways for control. We performed a transcriptomic analysis on CD4⁺ CD57⁺ PD1^- memory TLs, which are responsible for a higher incidence of graft rejection, after allogeneic stimulation with activated dendritic cells (aDCs) in the presence or absence of belatacept. After six hours of contact with aDCs, the (CD4⁺ CD57⁺ PD1^- ) (CD4⁺ CD57⁺ PD1⁺ ) and (CD4⁺ CD57^- ) lymphocytes had different transcriptional profiles with or without belatacept. In the CD4⁺ CD57⁺ PD1^- population, the IFNα-dependent activation pathway was positively overrepresented, and IRF7 transcript levels were high. IRF7 was associated with IFNα/β and IL-6 regulation. The inhibition of both these cytokines in a context of belatacept treatment inhibited the proliferation of CD4⁺ CD57⁺ PD1^- T cells. Our results show that IRF7 is rapidly upregulated in belatacept-resistant CD4⁺ CD57⁺ PD1^- TLs. The inhibition of type I IFN or IL-6 in association with belatacept treatment reduces the proliferation of belatacept-resistant TLs, paving the way for new treatments for use in organ transplantation.

Transcriptomic heterogeneity of antibody mediated rejection after heart transplant with or without donor specific antibodies

BACKGROUND

Antibody mediated rejection (AMR) is an increasingly studied cause of graft failure after heart transplantation. AMR diagnosis previously required the detection of circulating donor specific antibodies (DSA); however, the most recent criteria only require pathological findings. This classification defined a subset of patients with AMR, yet without known antibodies. Here, we sought to evaluate differences in the transcriptome profile associated with different types of AMR.

METHODS

RNA sequencing was used on endomyocardial biopsies to analyze and compare transcriptomic profiles associated with different subtypes of AMR defined by immunopathological and histopathological findings, as well as the presence or absence of DSA. Gene expression profiles were characterized for each diagnostic group.

RESULTS

The most divergent gene expression profiles were observed between patients with or without DSA. AMR subtypes associated with DSA showed expression of signature genes involved in monocyte activation and response to interferon. There was also substantial difference between the transcriptomic profiles of AMR defined by histopathological and immunopathological findings, the latter being associated with expression of mucin genes. In contrast, there was no differential RNA expression between patients with pAMR1i without DSA and those without AMR. Likewise, no differential expression was observed between patients with pAMR1h with DSA and pAMR2.

CONCLUSIONS

Overall, our studies reveal different expression profiles in endomyocardial biopsies in relation to some key criteria used to diagnose AMR. These findings support the view that the diagnosis of AMR encompasses several phenotypes that may rely on distinct mechanisms of injury.

Belatacept rescue therapy of CNI-induced nephrotoxicity, meta-analysis

There is growing evidence about the potential favorable effects that can be obtained from converting the administration of calcineurin inhibitors (CNIs) to Belatacept in kidney transplantation recipients. We conducted a meta-analysis to formulate strong evidence from the current literature about this effect on kidney functions, as measured by the estimated glomerular filtration rate (eGFR). Our search was conducted on the following databases: PubMed, Web of Science, Scopus, Embase, Google Scholar, Cochrane library, the clinical trials, and the International Standard Randomized Controlled Trial Number registries to obtain all studies that investigated the effect of post-transplantation CNIs conversion to Belatacept on kidney functions. Thirteen studies were finally included in the current study. The results showed a significant improvement in the eGFR following the conversion as compared to its value prior to it (MD = 10.41; 95% CI = 6.93, 13.90; P-value < 0.001). Although, there was no risk of bias among the pooled studies (P-value = 0.391), there was a significant heterogenity (I 2 = 80%; P value < 0.001). Serum creatinine levels showed no significant change following the conversion as compared to its value prior to it (MD = -1.22; 95% CI = -2.61, 0.16; P-value = 0.083). Nevertheless, a significant heterogeneity among the included studies was observed (I 2 = 87%; P-value = 0.005). Belatacept can be a good alternative to the CNI-based regimens following the kidney transplantation. The conversion to Belatacept resulted in an improvement in eGFR.

Belatacept Conversion Protocols and Outcomes in Kidney Transplant Recipients

BACKGROUND

Conversion from calcineurin inhibitor (CNI)-based to belatacept-based immunosuppression has become common; however, numerous protocols have emerged in lieu of a standardized protocol. The purpose of this study was to characterize belatacept conversion protocols from multiple centers and observe outcomes.

METHODS

This was a retrospective study that included Kaiser Permanente Southern California members. The primary outcome was rejection 6 months after conversion and secondary outcomes included change in serum creatinine and graft loss.

RESULTS

Seventy-eight patients were included. Thirteen distinct protocols were identified from 8 different transplant centers. Protocols varied by initial dose, induction schedule, and CNI taper. The observed rate of rejection was 6%. There was a trend toward an association of rejection with lower tacrolimus exposure at the time of conversion and lower mycophenolic acid dosing postconversion. Graft survival was 88% and patient survival was 94%. There was a significant improvement in creatinine after conversion. Those with early conversions and creatinine >2.0 mg/dL at the time of conversion had the best response.

CONCLUSIONS

A large variety of belatacept conversion protocols were identified. Protocols were defined by the initial dose, induction regimen, and CNI taper. Rejection rates were low and may be influenced by exposure to maintenance immunosuppression during and after conversion. Most patients showed stabilization and improvement in creatinine postconversion, with the largest effect in those with an early conversion and serum creatinine >2.0 mg/dL.

Reversing donor-specific antibody responses and antibody-mediated rejection with bortezomib and belatacept in mice and kidney transplant recipients

Active antibody-mediated rejection (AMR) is a potentially devastating complication and consistently effective treatment remains elusive. We hypothesized that the reversal of acute AMR requires rapid elimination of antibody-secreting plasma cells (PC) with a proteasome inhibitor, bortezomib, followed by the sustained inhibition of PC generation with CTLA4-Ig or belatacept (B/B). We show in mice that B/B therapy selectively depleted mature PC producing donor-specific antibodies (DSA) and reduced DSA, when administered after primary and secondary DSA responses had been established. A pilot investigation was initiated to treat six consecutive patients with active AMR with B/B. Compassionate use of this regimen was initiated for the first patient who developed early, severe acute AMR that did not respond to steroids, plasmapheresis, and intravenous immunoglobulin after his third kidney transplant. B/B treatment resulted in a rapid reversal of AMR, leading us to treat five additional patients who also resolved their acute AMR episode and had sustained disappearance of circulating DSA for ≤30 months. This study provides a proof-of-principle demonstration that mouse models can identify mechanistically rational therapies for the clinic. Follow-up investigations with a more stringent clinical design are warranted to test whether B/B improves on the standard of care for the treatment of acute AMR.

Costimulation Blockade in Vascularized Composite Allotransplantation

Vascular composite allotransplantation (VCA) is a field under research and has emerged as an alternative option for the repair of severe disfiguring defects that result from infections or traumatic amputation in a selected group of patients. VCA is performed in centers with appropriate expertise, experience and adequate resources to effectively manage the complexity and complications of this treatment. Lifelong immunosuppressive therapy, immunosuppression associated complications, and the effects of the host immune response in the graft are major concerns in VCA. VCA is considered a quality of life transplant and the risk-benefit ratio is dissimilar to life saving transplants. Belatacept seems a promising drug that prolongs patient and graft survival in kidney transplantation and it could also be an alternative approach to VCA immunosuppression. In this review, we are summarizing current literature about the role of costimulation blockade, with a focus on belatacept in VCA.

Conversion to belatacept maintenance immunosuppression in HIV-positive kidney transplant recipients

There are only scattered case reports documenting belatacept use in HIV + kidney transplant recipients. We performed a retrospective review to describe short-term outcomes following conversion to belatacept in a cohort of HIV + patients. Patients were included if they were converted to belatacept between May 2015 and May 2019, had an HIV- donor, and received ≥4 doses of belatacept. All patients were treated with non-depleting induction and triple maintenance immunosuppression. Allograft and HIV-related outcomes were collected from the date of belatacept infusion until May 2020. Ten HIV + kidney transplant recipients were identified, who were converted to belatacept a median of 364 days post-transplant. At last follow-up (median 3.3 years), 8 patients remained on belatacept therapy, and all patients were alive with functioning allografts. Mean estimated glomerular filtration rates (eGFR) improved from 31.6 mL/min at baseline to 42.8 mL/min at 1 year (P = .03). Two patients developed acute rejection, with one necessitating conversion back to tacrolimus. All patients maintained undetectable HIV-1 viral loads at last follow-up. One patient each developed pneumocystis pneumonia and Kaposi sarcoma following conversion, which were responsive to standard medical therapy. In our cohort of stable HIV + kidney transplant recipients, conversion to belatacept was associated with excellent early patient and allograft survival and improved eGFR at 1 year.

Vascularized composite allotransplantation versus solid organ transplantation: innate-adaptive immune interphase

PURPOSE OF REVIEW

Vascularized composite allotransplantation (VCA), a life-enhancing treatment for patients with complex tissue defects, trauma or illness, expounds upon the foundation of solid organ transplantation (SOT), the gold standard in end-stage organ failure. As innate and adaptive immunity remain the fundamental concern, this review highlights divergent immunobiology responses in VCA and SOT recipients.

RECENT FINDINGS

Host innate immune activation drives peritransplant tissue ischemia-reperfusion injury (IRI). Despite the direct relationship between ischemia-reperfusion (IR)-stress and cell-mediated acute rejection, the mechanism of how IRI may affect VCA loss needs investigation. With skin grafts being highly immunogenic, the incidence of cell-mediated rejection is higher in VCA than SOT; whereas ex-vivo perfusion may exert cytoprotection against IRI in VCA and SOT. New treatment concepts, such as topical immunosuppression or cell-based tolerogenic therapies, may avoid systemic immunosuppression in VCA. Although antibody-mediated rejection is relatively rare in VCA and its disease seems to be distinct from that in SOT, little is known as to whether and how IRI may influence humoral immune rejection cascade in VCA or SOT.

SUMMARY

Further understanding of the innate-adaptive immune crosstalk should contribute to much needed development of novel therapies to improve VCA outcomes, based on strategies established in SOT.

The impact of belatacept on third-party HLA alloantibodies in highly sensitized kidney transplant recipients

Recent evidence suggests that belatacept reduces the durability of preexisting antibodies to class I and class II human leukocyte antigens (HLAs). In this case series of 163 highly sensitized kidney transplant candidates whose calculated panel-reactive antibody (cPRA) activity was ≥98% to 100%, the impact of belatacept on preexisting HLA antibodies was assessed. Of the 163 candidates, 72 underwent transplantation between December 4, 2014 and April 15, 2017; 60 of these transplanted patients remained on belatacept consecutively for at least 6 months. We observed a decrease in the breadth and/or strength of HLA class I antibodies as assessed by FlowPRA in belatacept-treated patients compared to controls who did not receive belatacept. Specifically, significant HLA antibody reduction was evident for class I (P < .0009). Posttransplant belatacept-treated patients also had a clinically significant reduction in their cPRA compared to controls (P < .01). Collectively, these findings suggest belatacept can reduce HLA class I antibodies in a significant proportion of highly sensitized recipients and could be an option to improve pretransplant compatibility with organ donors.

Belatacept and CD28 Costimulation Blockade: Preventing and Reducing Alloantibodies over the Long Term

Purpose of Review

Highlight developments in T and B cell biology that are helping elucidate the mechanisms underlying CD28 pathway blockade-mediated inhibition of alloantibodies in transplantation, and discuss recent clinical observations on the impact of belatacept on de novo and established HLA antibodies.

Recent Findings

The identification of T follicular helper cells as the CD4+ T cell subset required for optimal humoral immunity, along with newly identified roles for CD28 and the B7 molecules on B cell lineage cells has begun to pave the way for improved understanding and discovery of the mechanisms of CD28 costimulation blockade-mediated antibody inhibition. There has been resurgent clinical interest in the ability of belatacept to attenuate alloantibody responses. New reports have continued to document its ability to prevent de novo antibody responses, and more recent studies have surfaced exploring its potential to control nascent or pre-existing HLA antibodies.

Summary

A growing understanding of the mechanisms of anti-CD28-mediated alloantibody inhibition and continued clinical successes will guide the clinical optimization of belatacept and next generation CD28 blockers to prevent and reduce alloantibodies over the long-term.

The therapeutic challenge of late antibody-mediated kidney allograft rejection

Late antibody‐mediated rejection (ABMR) is a cardinal cause of kidney allograft failure, manifesting as a continuous and, in contrast with early rejection, often clinically silent alloimmune process. While significant progress has been made towards an improved understanding of its molecular mechanisms and the definition of diagnostic criteria, there is still no approved effective treatment. In recent small randomized controlled trials, therapeutic strategies with promising results in observational studies, such as proteasome inhibitor bortezomib, anti‐C5 antibody eculizumab, or high dose intravenous immunoglobulin plus rituximab, had no significant impact in late and/or chronic ABMR. Such disappointing results reinforce a need of new innovative treatment strategies. Potential candidates may be the interference with interleukin‐6 to modulate B cell alloimmunity, or innovative compounds that specifically target antibody‐producing plasma cells, such as antibodies against CD38. Given the phenotypic heterogeneity of ABMR, the design of adequate systematic trials to assess the safety and efficiency of such therapies, however, is challenging. Several trials are currently being conducted, and new developments will hopefully provide us with effective ways to counteract the deleterious impact of antibody‐mediated graft injury. Meanwhile, the weight of evidence would suggest that, when approaching using existing treatments for established antibody‐mediated rejection, “less may be more”.

Switching renal transplant recipients to belatacept therapy: results of a real-life gradual conversion protocol

Conversion to belatacept immunosuppression is a therapeutic option for renal-transplant recipients with calcineurin inhibitors (CNI) toxicity, but it associates with high risk of acute rejection. Gradual conversion and serial immune monitoring with urinary chemokine CXCL9 may allow increasing safety of this maneuver. We converted kidney transplant recipients with signs of toxicity to CNI or other immunosuppressive drugs to belatacept over a 2-month period. We monitored renal function, metabolic profile, and circulating lymphocyte subsets. We also quantified urinary CXCL9 over a 12-month follow-up period. Between September 2016 and March 2017, 35 patients were successfully switched to belatacept immunosuppression at 3.3 (1.3-7.2) years after transplant. Two patients had a reversible rise in serum creatinine, associated with acute rejection in one case. Urinary CXCL9 increased before serum creatinine. After conversion, blood pressure and HbA1c significantly declined while eGFR and proteinuria remained stable. The percentage of circulating effector T cells and memory B cells significantly declined. Conversion from CNI to belatacept, in this setting, was feasible and safe, provided it was performed over a 2-month time-period. Monitoring urinary CXCL9 may further increase safety through earlier identification of patients at risk for acute rejection. The procedure associates with improved blood pressure, metabolic profile, and reduced circulating effector T and B cells.