Exploratory associations of tacrolimus exposure and clinical outcomes after lung transplantation: A retrospective, single center experience

PURPOSE

This study aimed to investigate the potential impact of tacrolimus (TAC) exposure on clinical outcomes after lung transplantation.

METHODS

This retrospective observational study enrolled a total of 228 lung transplant recipients. TAC trough levels (C0) were collected for 3 intervals: 0-3 months, 3-12 months, and 12-24 months. The intra-patient variability (IPV) was calculated using coefficient of variation. Genotyping of CYP3A5*3 (rs776746) was performed. Patients were further divided into groups based on the C0 cut-off value of 8 ng/mL and IPV cut-off value of 30%. Cox proportional hazards regression models were used to explore the potential impact of C0 and IPV on outcomes of interests, including de-novo donor-specific antibodies (dnDSA), chronic lung allograft dysfunction (CLAD) and mortality.

RESULTS

The influence of CYP3A5*3 polymorphism was only significant for C0 and IPV during the first 3 months. Low C0 (< 8 ng/mL) at 3-12 months increased the risk of dnDSA (hazard ratio [HR] 2.696, 95% confidence interval [CI] 1.046-6.953) and mortality (HR 2.531, 95% CI 1.368-4.685), while High IPV (≥ 30%) during this period was associated with an increased risk of mortality (HR 2.543, 95% CI 1.336-4.839). Patients with Low C0/High IPV combination had significantly higher risks for dnDSA (HR 4.381, 95% CI 1.279-15.008) and survival (HR 6.179, 95% CI 2.598-14.698), surpassing the predictive power provided by C0 or IPV alone.

CONCLUSION

A combination of Low C0/High IPV might be considered in categorizing patients towards risk of adverse clinical outcomes following lung transplantation.

Tocilizumab in chronic active antibody-mediated rejection: rationale and protocol of an in-progress randomized controlled open-label multi-center trial (INTERCEPT study)

BACKGROUND

Chronic active antibody-mediated rejection (caAMR) in kidney transplants is associated with irreversible tissue damage and a leading cause of graft loss in the long-term. However, the treatment for caAMR remains a challenge to date. Recently, tocilizumab, a recombinant humanized monoclonal antibody directed against the human interleukin-6 (IL-6) receptor, has shown promise in the treatment of caAMR. However, it has not been systematically investigated so far underscoring the need for randomized controlled studies in this area.

METHODS

The INTERCEPT study is an investigator-driven randomized controlled open-label multi-center trial in kidney transplant recipients to assess the efficacy of tocilizumab in the treatment of biopsy-proven caAMR. A total of 50 recipients with biopsy-proven caAMR at least 12 months after transplantation will be randomized to receive either tocilizumab (n = 25) added to our standard of care (SOC) maintenance treatment or SOC alone (n = 25) for a period of 24 months. Patients will be followed for an additional 12 months after cessation of study medication. After the inclusion biopsies at baseline, protocol kidney graft biopsies will be performed at 12 and 24 months. The sample size calculation assumed a difference of 5 ml/year in slope of estimated glomerular filtration rate (eGFR) between the two groups for 80% power at an alpha of 0.05. The primary endpoint is the slope of eGFR at 24 months after start of treatment. The secondary endpoints include assessment of the following at 12, 24, and 36 months: composite risk score iBox, safety, evolution and characteristics of donor-specific antibodies (DSA), graft histology, proteinuria, kidney function assessed by measured GFR (mGFR), patient- and death-censored graft survival, and patient-reported outcomes that include transplant-specific well-being, adherence to immunosuppressive medications and perceived threat of the risk of graft rejection.

DISCUSSION

No effective treatment exists for caAMR at present. Based on the hypothesis that inhibition of IL-6 receptor by tocilizumab will reduce antibody production and reduce antibody-mediated damage, our randomized trial has a potential to provide evidence for a novel treatment strategy for caAMR, therewith slowing the decline in graft function in the long-term.

TRIAL REGISTRATION

ClinicalTrials.gov NCT04561986. Registered on September 24, 2020.

Long-term survival from progressive multifocal leukoencephalopathy in living-donor liver transplant recipient with preformed donor-specific antibody

Intensive immunosuppression has enabled liver transplantation even in recipients with preformed donor-specific antibodies (DSA), an independent risk factor for graft rejection. However, these recipients may also be at high risk of progressive multifocal encephalopathy (PML) due to the comorbid immunosuppressed status. A 58-year-old woman presented with self-limited focal-to-bilateral tonic-clonic seizures 9 months after liver transplantation. She was desensitized using rituximab and plasma exchange before transplantation and was subsequently treated with steroids, tacrolimus, and everolimus after transplantation for her preformed DSA. Neurological examination revealed mild acalculia and agraphia. Cranial MRI showed asymmetric, cortex-sparing white matter lesions that increased over a week in the left frontal, left parietal, and right parieto-occipital lobes. Polymerase chain reaction (PCR) of the cerebrospinal fluid for the JC supported the diagnosis of PML. Immune reconstitution by reducing the immunosuppressant dose stopped lesion expansion, and PCR of the cerebrospinal fluid for the JC virus became negative. Graft rejection occurred 2 months after immune reconstitution, requiring readjustment of immunosuppressants. Forty-eight months after PML onset, the patient lived at home without disabling deficits. Intensive immunosuppression may predispose recipients to PML after liver transplantation with preformed DSA. Early immune reconstitution and careful monitoring of graft rejection may help improve outcomes.

Impact of Low-Level Donor-Specific Anti-HLA Antibody on Posttransplant Clinical Outcomes in Kidney Transplant Recipients

Background

The clinical significance of low-level donor-specific anti-HLA antibody (low-DSA) remains controversial. We investigated the impact of low-DSA on posttransplant clinical outcomes in kidney transplant (KT) recipients.

Methods

We retrospectively reviewed 1,027 KT recipients, namely, 629 living donor KT (LDKT) recipients and 398 deceased donor KT (DDKT) recipients, in Seoul St. Mary's Hospital (Seoul, Korea) between 2010 and 2018. Low-DSA was defined as a positive anti-HLA-DSA result in the Luminex single antigen assay (LABScreen single antigen HLA class I - combi and class II - group 1 kits; One Lambda, Canoga Park, CA, USA) but a negative result in a crossmatch test. We compared the incidence of biopsy-proven allograft rejection (BPAR), changes in allograft function, allograft survival, patient survival, and posttransplant infections between subgroups according to pretransplant low-DSA.

Results

The incidence of overall BPAR and T cell-mediated rejection did not differ between the subgroups. However, antibody-mediated rejection (ABMR) developed more frequently in patients with low-DSA than in those without low-DSA in the total cohort and the LDKT and DDKT subgroups. In multivariate analysis, low-DSA was identified as a risk factor for ABMR development. Its impact was more pronounced in DDKT (odds ratio [OR]: 9.60, 95% confidence interval [CI]: 1.79-51.56) than in LDKT (OR: 3.76, 95% CI: 0.99-14.26) recipients. There were no significant differences in other outcomes according to pretransplant low-DSA.

Conclusions

Pretransplant low-DSA has a significant impact on the development of ABMR, and more so in DDKT recipients than in LDKT recipients, but not on long-term outcomes.

Carfilzomib versus rituximab for treatment of de novo donor-specific antibodies in lung transplant recipients

INTRODUCTION

De novo donor-specific antibodies (DSAs) increase the risk of chronic lung allograft dysfunction (CLAD) in lung transplant recipients (LTRs). Both carfilzomib (CFZ) and rituximab (RTX) lower the mean fluorescent intensity (MFI) of DSAs, but comparative data are lacking. We compared CLAD-free survival and the degree and duration of DSA depletion after treatment of LTRs with CFZ or RTX.

METHODS

LTRs that received CFZ or RTX for DSA depletion between 08/01/2015 and 08/31/2020 were included. The primary outcome was CLAD-free survival. Secondary outcomes were change in MFI at corresponding loci within 6 months of treatment (ΔMFI), time to DSA rebound, and change in % predicted FEV₁ 6 months after treatment (ΔFEV₁).

RESULTS

Forty-four LTRs were identified, 7 of whom had ≥2 drug events; therefore, 53 drug events were divided into 2 groups, CFZ (n = 17) and RTX (n = 36). Use of plasmapheresis, immunoglobulin, and mycophenolate augmentation was equivalent in both groups. CLAD-free survival with a single RTX event was superior to that after ≥2 drug events (p = 0.001) but comparable to that with a single CFZ event (p = 0.399). Both drugs significantly lowered the MFI at DQ locus, and the median ΔMFI was comparable. Compared to the RTX group, the CFZ group had a shorter median interval to DSA rebound (p = 0.015) and a lower ΔFEV₁ at 6 months (p = 0.014).

CONCLUSION

Although both CFZ and RTX reduced the MFI of circulating DSAs, RTX prolonged the time to DSA rebound. Despite more pronounced improvement in FEV₁ with RTX, comparable CLAD-free survival between the 2 groups suggests that both drugs offer a reasonable treatment strategy for DSAs in LTRs.

Misidentification of preformed anti-HLA-DP antibodies leads to antibody-mediated kidney transplant rejection: a case report

Background

Patients who are HLA-sensitized are at high risk for early antibody-mediated rejection (AMR) and worse outcomes. Therefore, it is crucial to detect the presence of donor-specific antibodies (DSAs) using pretransplant antibody identification and crossmatch assays. An error in antibody identification can lead to disastrous clinical outcomes. We present a case of acute AMR associated with preformed HLA-DPα and HLA-DPβ DSAs that were not identified before transplantation.

Case presentation

A 27-year-old woman received a second kidney transplant from a deceased donor. Her pretransplant panel-reactive antibody level was 94%. The complement-dependent cytotoxicity crossmatch was negative for T and B cells at the time of transplantation. She experienced early acute AMR proven by a kidney biopsy. Single antigen bead testing of the patient’s serum at the time of rejection as well as the pre-second transplant serum revealed strong antibodies against the DPA1*01:03 and DPB1*02:01 alleles in the second donor. These antibodies were not identified by phenotypic bead assay during the patient’s time on the waiting list. The patient was treated with plasmapheresis and anti-thymocyte globulin. However, she experienced abdominal pain on day 37 post-transplantation. Surgical exploration revealed a laceration on the transplanted kidney, which was then repaired. Subsequently, infected hematoma was suspected and the transplanted kidney was removed.

Conclusion

The present case highlights the clinical significance of preformed HLA-DPα and HLA-DPβ DSAs. Accuracy in determination of HLA antibodies before transplantattion is critical for transplant outcome. HLA-DP typing and single antigen bead testing are recommended for a precise antibody interpretation, especially in highly sensitized patients. Careful interpretation of antibody testing results is essential for the success of organ transplantation.

Romidepsin (FK228) improves the survival of allogeneic skin grafts through downregulating the production of donor-specific antibody via suppressing the IRE1α-XBP1 pathway

Antibody-mediated rejection (AMR) is one of the major causes of graft loss after transplantation. Recently, the regulation of B cell differentiation and the prevention of donor-specific antibody (DSA) production have gained increased attention in transplant research. Herein, we established a secondary allogeneic in vivo skin transplant model to study the effects of romidepsin (FK228) on DSA. The survival of grafted skins was monitored daily. The serum levels of DSA and the number of relevant immunocytes in the recipient spleens were evaluated by flow cytometry. Then, we isolated and purified B cells from B6 mouse spleens in vitro by magnetic bead sorting. The B cells were cultured with interleukin-4 (IL-4) and anti-clusters of differentiation 40 (CD40) antibody with or without FK228 treatment. The immunoglobulin G1 (IgG1) and IgM levels in the supernatant were evaluated by enzyme-linked immunosorbent assay (ELISA). Quantitative reverse transcription-polymerase chain reaction (RT-qPCR) and western blotting were conducted to determine the corresponding levels of messenger RNA (mRNA) and protein expression in cultured cells and the recipient spleens. The results showed that FK228 significantly improved the survival of allogeneic skin grafts. Moreover, FK228 inhibited DSA production in the serum along with the suppression of histone deacetylase 1 (HADC1) and HDAC2 and the upregulation of the acetylation of histones H2A and H3. It also inhibited the differentiation of B cells to plasma cells, decreased the transcription of positive regulatory domain-containing 1 (Prdm1) and X-box-binding protein 1 (Xbp1), and decreased the expression of phosphorylated inositol-requiring enzyme 1 α (p-IRE1α), XBP1, and B lymphocyte-induced maturation protein-1 (Blimp-1). In conclusion, FK228 could decrease the production of antibodies by B cells via inhibition of the IRE1α-XBP1 signaling pathway. Thus, FK228 is considered as a promising therapeutic agent for the clinical treatment of AMR.

Safety, tolerability, and efficacy of monoclonal CD38 antibody felzartamab in late antibody-mediated renal allograft rejection: study protocol for a phase 2 trial

BACKGROUND

Antibody-mediated rejection (ABMR) is a cardinal cause of renal allograft loss. This rejection type, which may occur at any time after transplantation, commonly presents as a continuum of microvascular inflammation (MVI) culminating in chronic tissue injury. While the clinical relevance of ABMR is well recognized, its treatment, particularly a long time after transplantation, has remained a big challenge. A promising strategy to counteract ABMR may be the use of CD38-directed treatment to deplete alloantibody-producing plasma cells (PC) and natural killer (NK) cells.

METHODS

This investigator-initiated trial is planned as a randomized, placebo-controlled, double-blind, parallel-group, multi-center phase 2 trial designed to assess the safety and tolerability (primary endpoint), pharmacokinetics, immunogenicity, and efficacy of the fully human CD38 monoclonal antibody felzartamab (MOR202) in late ABMR. The trial will include 20 anti-HLA donor-specific antibody (DSA)-positive renal allograft recipients diagnosed with active or chronic active ABMR ≥ 180 days post-transplantation. Subjects will be randomized 1:1 to receive felzartamab (16 mg/kg per infusion) or placebo for a period of 6 months (intravenous administration on day 0, and after 1, 2, 3, 4, 8, 12, 16, and 20 weeks). Two follow-up allograft biopsies will be performed at weeks 24 and 52. Secondary endpoints (preliminary assessment) will include morphologic and molecular rejection activity in renal biopsies, immunologic biomarkers in the blood and urine, and surrogate parameters predicting the progression to allograft failure (slope of renal function; iBOX prediction score).

DISCUSSION

Based on the hypothesis that felzartamab is able to halt the progression of ABMR via targeting antibody-producing PC and NK cells, we believe that our trial could potentially provide the first proof of concept of a new treatment in ABMR based on a prospective randomized clinical trial.

TRIAL REGISTRATION

EU Clinical Trials Register (EudraCT) 2021-000545-40 . Registered on 23 June 2021.

CLINICALTRIALS

gov NCT05021484 . Registered on 25 August 2021.

The Biology and Molecular Basis of Organ Transplant Rejection

Allograft rejection is defined as tissue injury in a transplanted allogeneic organ produced by the effector mechanisms of the adaptive alloimmune response. Effector T lymphocytes and IgG alloantibodies cause two different types of rejection that can occur either individually or simultaneously: T cell-mediated rejection (TCMR) and antibody-mediated rejection (ABMR). In TCMR, cognate effector T cells infiltrate the graft and orchestrate an interstitial inflammatory response in the kidney interstitium in which effector T cells engage antigen-presenting myeloid cells, activating the T cells, antigen-presenting cells, and macrophages. The result is intense expression of IFNG and IFNG-induced molecules, expression of effector T cell molecules and macrophage molecules and checkpoints, and deterioration of parenchymal function. The diagnostic lesions of TCMR follow, i.e. interstitial inflammation, parenchymal deterioration, and intimal arteritis. In ABMR, HLA IgG alloantibodies produced by plasma cells bind to the donor antigens on graft microcirculation, leading to complement activation, margination, and activation of NK cells and neutrophils and monocytes, and endothelial injury, sometimes with intimal arteritis. TCMR becomes infrequent after 5-10 years post-transplant, probably reflecting adaptive mechanisms such as checkpoints, but ABMR can present even decades post-transplant. Some rejection is triggered by inadequate immunosuppression and non-adherence, challenging the clinician to target effective immunosuppression even decades post-transplant.

Chronic rejection after liver transplantation: Opening the Pandora’s box

Chronic rejection (CR) of liver allografts causes damage to intrahepatic vessels and bile ducts and may lead to graft failure after liver transplantation. Although its prevalence has declined steadily with the introduction of potent immunosuppressive therapy, CR still represents an important cause of graft injury, which might be irreversible, leading to graft loss requiring re-transplantation. To date, we still do not fully appreciate the mechanisms underlying this process. In addition to T cell-mediated CR, which was initially the only recognized type of CR, recently a new form of liver allograft CR, antibody-mediated CR, has been identified. This has indeed opened an era of thriving research and renewed interest in the field. Liver biopsy is needed for a definitive diagnosis of CR, but current research is aiming to identify new non-invasive tools for predicting patients at risk for CR after liver transplantation. Moreover, the minimization or withdrawal of immunosuppressive therapy might influence the establishment of subclinical CR-related injury, which should not be disregarded. Therapies for CR may only be effective in the “early” phases, and a tailored management of the immunosuppression regimen is essential for preventing irreversible liver damage. Herein, we provide an overview of the current knowledge and research on CR, focusing on early detection, identification of non-invasive biomarkers, immunosuppressive management, re-transplantation and future perspectives of CR.

Approach to Highly Sensitized Kidney Transplant Candidates and a Positive Crossmatch

Human leukocyte antigen (HLA)-incompatible kidney transplantation offers survival benefit compared with ongoing dialysis. There have been considerable advances in the last decade to allow for increased access to transplant for the HLA-sensitized kidney transplant candidates. These include increased priority in the kidney allocation system, kidney paired donation, and novel desensitization strategies. A better understanding of the role of B cells, plasma cells, and complement and inflammatory cytokines in the pathophysiology of HLA antibody-mediated allograft injury has led to the use of novel therapeutics for desensitization and treatment of antibody-mediated rejection. Here we discuss current approaches to kidney transplantation in HLA-sensitized kidney transplant candidates.

Prediction of HLA-DQ in Deceased Donors and its Clinical Significance in Kidney Transplantation

Background

HLA-DQ typing in deceased donors is not mandatory in Korea. Therefore, when patients develop DQ antibodies after kidney transplantation (KT) from deceased donor, it is impossible to determine whether they are donor-specific antibodies (DSA). We developed DQ prediction programs for the HLA gene and evaluated their clinical utility.

Methods

Two HLA-DQ prediction programs were developed: one based on Lewontin's linkage disequilibrium (LD) and haplotype frequency and the other on an artificial neural network (ANN). Low-resolution HLA-A, -B, -DR, and -DQ typing data of 5,603 Korean patients were analyzed in terms of haplotype frequency and used to develop an ANN DQ prediction program. Predicted DQ (pDQ) genotype accuracy was analyzed using the typed DQ data of 403 patients. pDQ DSA agreement, sensitivity, specificity, and false-negative rate was evaluated using 1,970 single-antigen bead assays performed on 885 KT recipients. The clinical significance of DQ and pDQ DSA was evaluated in 411 KT recipients.

Results

pDQ genotype accuracies were 75.4% (LD algorithm) and 75.7% (ANN). When the second most likely pDQ (LD algorithm) was also considered, the genotype accuracy increased to 92.6%. pDQ DSA (LD algorithm) agreement, sensitivity, specificity, and false-negative rate were 97.5%, 97.3%, 98.6%, and 2.4%, respectively. The antibody-mediated rejection treatment frequency was significantly higher in DQ or pDQ DSA-positive patients than in DQ or pDQ DSA-negative patients (P<0.001).

Conclusions

Our DQ prediction programs showed good accuracy and could aid DQ DSA detection in patients who had undergone deceased donor KT without donor HLA-DQ typing.

De novo donor-specific HLA antibodies reduce graft survival rates and increase the risk of kidney transplant rejection: A single-center retrospective study

BACKGROUND

We investigated the impact of de novo donor-specific anti-human leukocyte antigen antibodies (dnDSAs) on long-term death-censored graft survival and renal allograft rejection in kidney transplant recipients.

METHODS

The sample for this retrospective cohort study comprised 121 recipients of kidney transplants with negative complement-dependent cytotoxicity crossmatches to their deceased donors. Recipients were divided into two groups: dnDSAs+ (n = 31) and dnDSAs- (n = 90). We evaluated rejection and long-term graft survival rates in the recipients along with pathologic changes in the transplanted kidneys.

RESULTS

DnDSAs were identified in 31/121 patients (25.6%). The graft survival rate in the dnDSAs+ group was 87.1% (27/31) and that of the dnDSAs- group was 97.8% (88/90). The dnDSAs+ group had lower graft survival rates than patients without dnDSAs (p = 0.007). There was no difference in the graft survival rates between patients with high DSA mean fluorescence intensity (≥4000) and those with low intensity (<4000) (p = 0.669). There was also no difference in the graft survival rates of patients with HLA class I, II, and I + II dnDSAs (p = 0.571). The presence of dnDSA in serum was associated with a higher incidence of antibody- and T-cell-mediated rejection (p < 0.0001). Banff scores for arterial fibrointimal and arteriolar hyalin, thickening as well as C4d deposition differed for the dnDSAs+ and dnDSAs- groups (p < 0.05).

CONCLUSION

DnDSAs were found to be associated with decreased long-term graft survival rates and increased rejection rates, often accompanied by C4d deposition.

Donor-Specific Antibodies and Primary Graft Failure in Allogeneic Hematopoietic Stem Cell Transplantation: A Systematic Review and Meta-Analysis

With the increasing number of non-matched donor hematopoietic stem cell transplantations (HSCTs) has come increasing evidence regarding factors affecting graft outcomes. One factor affecting graft outcomes currently being evaluated is anti-HLA donor-specific antibodies (DSAs). In this, we analyzed the clinical relevance of anti-HLA DSAs in patients who have undergone HSCT at a population level by conducting a systematic review of existing literature. A comprehensive search was conducted through PubMed, Embase, the Cochrane library, and Web of Science from inception to January 1, 2021. A meta-analysis was performed of the association between anti-HLA DSAs and primary graft failure (PGF) with further subgroup analyses. The search was conducted following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. A total of 920 eligible citations were identified, out of which 15 studies were included in the final meta-analyses after application of rigorous selection criteria and independent review. A total of 2436 patients were included in these 15 studies. Patients with anti-HLA DSAs prior to undergoing HSCT had a 7.47-fold increased risk of PGF failure compared with patients without anti-HLA DSAs (odds ratio, 7.47; 95% confidence interval, 4.54 to 12.28, P < .001; I²= 28.91%, P = .1315). In subgroup and meta-regression analyses, area, Newcastle Ottawa Scale score, mean fluorescence intensity cutoff, primary disease, HSCT type, graft source, and pretransplantation desensitization did not affect the impact of anti-HLA DSAs on PGF. There also was no significant difference in impact between HLA class I and II on PGF. We conclude that the prior presence of anti-HLA DSAs has a negative impact on graft outcomes in recipients of haploidentical and umbilical cord blood HSCT.

Effects of re-augmenting maintenance immunosuppression on post-transplant donor-specific HLA antibodies in liver transplantation

BACKGROUND

Donor-specific antibodies (DSAs) have various negative short- and long-term effects after organ transplantation. DSAs are prevalent in patients with insufficient immunosuppression; thus, even patients with stable conditions after liver transplantation should be under optimized immunosuppression. However, the effect of re-augmenting immunosuppression therapy for patients with insufficient immunosuppression remains unclear. In this study, we investigated the long-term changes and the effects of immunosuppression (IS) re-augmentation on the DSA status.

METHODS

Two DSA screenings were performed in 67 patients during long-term follow-up after liver transplantation. After the first screening, IS re-augmentation was performed in patients with consent. The effects of IS re-augmentation on the DSA status were analyzed using data of the serial DSA screenings. Negative conversion was defined as DSA positivity with MFI > 1000 converted to MFI < 1000. Improvement of DSA status was defined as either a 50% reduction of MFI or negative conversion.

RESULTS

The median interval between the first and second DSA screening was 50 months. Among 67 patients, 43 were positive for DSAs on the first screening. Among these 43 patients, 30 had minimal to no IS therapy at the time of the first screening. Among the 30 patients, IS re-augmentation was conducted in 19. A comparison between the patients with a re-augmented IS and those with a sustained minimized IS showed that the DSA levels significantly decreased in the former (63% (12/19) vs. 18% (2/11), p = 0.02).

CONCLUSIONS

The results of this study indicate that post-liver transplant IS re-augmentation had suppressive effects on the DSA status. However, the clinical significance of DSA-negative conversion and/or mean fluorescence intensity reduction needs to be further investigated through histological evaluation and/or graft survival during longer follow-up periods.

Critical evaluation of a possible role of HLA epitope matching in kidney transplantation

Human leukocyte antigen (HLA) matching is one of the cornerstones of organ allocation in deceased-donor kidney transplantation. Increased numbers of HLA allele mismatches are associated with a higher risk of immunological rejection, de novo donor-specific HLA antibody development and graft failure. HLA epitopes are defined as the specific portions of HLA molecules to which antibodies and T-cell receptors bind with their paratopes. The same epitope can be present on different HLA alleles. Therefore, HLA matching at the epitope instead of allele level theoretically offers a more precise assessment of donor-recipient HLA compatibility and may more effectively prevent sensitization against foreign tissue. In this review, we describe the different options proposed to define clinically relevant HLA epitopes and critically discuss the potential role of HLA epitope matching in kidney transplantation.

Transplant outcomes in positive complement-dependent cytotoxicity- versus flow cytometry-crossmatch kidney transplant recipients after successful desensitization: a retrospective study

BACKGROUND

Despite the obvious survival benefit compared to that among waitlist patients, outcomes of positive crossmatch kidney transplantation (KT) are generally inferior to those of human leukocyte antigen (HLA)-compatible KT. This study aimed to compare the outcomes of positive complement-dependent cytotoxicity (CDC) crossmatch (CDC + FC+) and positive flow cytometric crossmatch (CDC-FC+) with those of HLA-compatible KT (CDC-FC-) after successful desensitization.

METHODS

We retrospectively analyzed 330 eligible patients who underwent KTs between June 2011 and August 2017: CDC-FC- (n = 274), CDC-FC+ (n = 39), and CDC + FC+ (n = 17). Desensitization protocol targeting donor-specific antibody (DSA) involved plasmapheresis, intravenous immunoglobulin (IVIG), and rituximab with/without bortezomib for positive-crossmatch KT.

RESULTS

Death-censored graft survival and patient survival were not different among the three groups. The median estimated glomerular filtration rate was significantly lower in the CDC + FC+ group than in the compatible group at 6 months (P < 0.001) and 2 years (P = 0.020). Biopsy-proven rejection within 1 year of CDC-FC-, CDC-FC+, and CDC + FC+ were 15.3, 28.2, and 47.0%, respectively. Urinary tract infections (P < 0.001), Pneumocystis jirovecii pneumonia (P < 0.001), and cytomegalovirus viremia (P < 0.001) were more frequent in CDC-FC+ and CDC + FC+ than in CDC-FC-.

CONCLUSIONS

This study showed that similar graft and patient survival was achieved in CDC-FC+ and CDC + FC+ KT compared with CDC-FC- through DSA-targeted desensitization despite the higher incidence of rejection and infection than that in compatible KT.

Prognostic value of C3d-fixing, preformed donor-specific antibodies in crossmatch-positive living kidney transplantation

The occurrence of acute antibody-mediated rejection (ABMR) is higher in flow cytometric crossmatch (FCXM)-positive patients despite desensitization. Accumulating evidence suggests a correlation between the complement-binding ability of donor-specific antibodies (DSAs) and the risk of ABMR. Here, we investigated the correlation between complement C3d-fixing ability of preformed DSA and ABMR risk, the efficacy of a desensitization protocol for patients with C3d-fixing DSA, and the risk of ABMR in 21 DSA- and FCXM-positive patients. We retrospectively analyzed the C3d-fixing ability and mean fluorescence intensity (MFI) of preformed DSA before and after desensitization. Six patients had non-C3d-fixing DSA and 15 had C3d-fixing DSA. The presence of C3d-fixing DSA before desensitization was correlated with the incidence of acute ABMR within 1 year after transplantation (p = .04) and chronic ABMR (p = .03). Moreover, the MFI of preformed DSA differed between responder and non-responder C3d-fixing DSA after desensitization (p < .0001). The C3d-fixing ability of preformed DSA with low MFI disappeared after desensitization. These results indicate that measuring DSA C3d-fixing ability may identify patients with a high risk of ABMR, especially before desensitization. CLINICAL TRIAL NOTATION: UMIN Clinical Trials Registry (UMIN-CTR) number: UMIN000033449.

The PI3Kδ selective inhibitor AS2541019 suppresses donor-specific antibody production in rat cardiac and non-human primate renal allotransplant models

Long-term graft survival after organ transplantation is difficult to achieve because of the development of chronic rejection. One cause of chronic rejection arises from antibody-mediated rejection (AMR), which is dependent on the production of donor-specific antibodies (DSA). Current immunosuppression in organ transplantation is effective in preventing acute T cell-mediated rejection, but the risk of DSA production and graft loss due to AMR remains unchanged. Phosphatidylinositol-3-kinase p110δ (PI3Kδ), a member of the family of PI3K lipid kinases, is a key mediator of B cell activation, proliferation and antibody production. AS2541019 is a novel PI3Kδ selective inhibitor that prevents antibody production by inhibiting B cell immunity. The purpose of this study was to evaluate the inhibitory effect of AS2541019 on DSA production in preclinical rodent and non-human primate allotransplant models. Concomitant administration of AS2541019 with tacrolimus and mycophenolate mofetil (MMF) inhibited de novo DSA production in an ACI-to-Lewis rat cardiac allotransplant model. To predict the efficacy of AS2541019 in clinical practice, we evaluated its effects in cynomolgus monkeys. AS2541019 inhibited B cell proliferation and major histocompatibility complex (MHC) class II expression on B cells in cynomolgus monkeys. Oral administration of AS2541019 inhibited MHC class II expression on peripheral B cells and anti-tetanus toxoid antibody production. In cynomolgus monkey renal allotransplant model, concomitant administration of AS2541019 with tacrolimus and MMF significantly inhibited de novo DSA production. Together, our findings indicate that the PI3Kδ selective inhibitor AS2541019 is a potential candidate for preventing AMR development by inhibiting DSA production.

Clazakizumab in late antibody-mediated rejection: study protocol of a randomized controlled pilot trial

Background

Late antibody-mediated rejection (ABMR) triggered by donor-specific antibodies (DSA) is a cardinal cause of kidney allograft dysfunction and loss. Diagnostic criteria for this rejection type are well established, but effective treatment remains a major challenge. Recent randomized controlled trials (RCT) have failed to demonstrate the efficacy of widely used therapies, such as rituximab plus intravenous immunoglobulin or proteasome inhibition (bortezomib), reinforcing a great need for new therapeutic concepts. One promising target in this context may be interleukin-6 (IL-6), a pleiotropic cytokine known to play an important role in inflammation and adaptive immunity.

Methods

This investigator-driven RCT was designed to assess the safety and efficacy of clazakizumab, a genetically engineered humanized monoclonal antibody directed against IL-6. The study will include 20 DSA-positive kidney allograft recipients diagnosed with ABMR ≥ 365 days after transplantation. Participants will be recruited at two study sites in Austria and Germany (Medical University of Vienna; Charité University Medicine Berlin). First, patients will enter a three-month double-blind RCT (1,1 randomization, stratification according to ABMR phenotype and study site) and will receive either clazakizumab (subcutaneous administration of 25 mg in monthly intervals) or placebo. In a second open-label part of the trial (months 4–12), all patients will receive clazakizumab at 25 mg every month. The primary endpoint is safety and tolerability. Secondary endpoints are the pharmacokinetics and pharmacodynamics of clazakizumab, its effect on drug metabolism in the liver, DSA characteristics, morphological ABMR lesions and molecular gene expression patterns in three- and 12-month protocol biopsies, serum/urinary biomarkers of inflammation and endothelial activation/injury, Torque Teno viral load as a measure of overall immunosuppression, kidney function, urinary protein excretion, as well as transplant and patient survival.

Discussion

Currently, there is no treatment proven to be effective in halting the progression of late ABMR. Based on the hypothesis that antagonizing the effects of IL-6 improves the outcome of DSA-positive late ABMR by counteracting DSA-triggered inflammation and B cell/plasma cell-driven alloimmunity, we suggest that our trial has the potential to provide proof of concept of a novel treatment of this type of rejection.

Trial registration

ClinicalTrials.gov, NCT03444103. Registered on 23 February 2018 (retrospective registration).

Electronic supplementary material

The online version of this article (10.1186/s13063-018-3158-6) contains supplementary material, which is available to authorized users.

Treatment with plasmapheresis, immunoglobulins and rituximab for chronic-active antibody-mediated rejection in kidney transplantation: Clinical, immunological and pathological results

AIM

To evaluate the role of a therapeutic regimen with plasma exchange, intravenous immunoglobulins and rituximab in chronic-active antibody-mediated rejection (cAMR) settings.

METHODS

We compared 21 kidney transplant recipients (KTRs) with a diagnosis of cAMR in a retrospective case-control analysis: nine KTRs treated with plasmapheresis, intravenous immunoglobulins and rituximab (PE-IVIG-RTX group) vs 12 patients (control group) not treated with antibody-targeted therapies. We examined kidney survival and functional outcomes 24 mo after diagnosis. Histological features and donor-specific antibody (DSA) characteristics (MFI and C1q-fixing ability) were also investigated.

RESULTS

No difference in graft survival between the two groups was noted: three out of nine patients in the PE-IVIG-RTX group (33.3%) and 4/12 in the control group (33.3%) experienced loss of allograft function at a median time after diagnosis of 14 mo (min 12-max 18) and 15 mo (min 7-max 22), respectively. Kidney functional tests and proteinuria 24 mo after cAMR diagnosis were also similar in both groups. Only microvascular inflammation (glomerulitis + peritubular capillaritis score) was significantly reduced after PE-IVIG-RTX in seven out of eight patients (87.5%) in the PE-IVIG-RTX group (median score 3 in pre-treatment biopsy vs 1.5 in post-treatment biopsy; P = 0.047), without any impact on kidney survival and/or DSA characteristics. No functional or histological parameter at diagnosis was predictive of clinical outcome.

CONCLUSION

Our data showed no difference in the two year post-treatment outcome of kidney grafts treated with PE-IVIG-RTX for cAMR diagnosis, however there were notable improvements in microvascular inflammation in post-therapy protocol biopsies. Further studies, especially involving innovative therapeutic approaches, are required to improve the management and long-term results of this severe condition.

HLA epitope matching in pediatric renal transplantation

Chronic graft loss due to antibody-mediated rejection (AMR) and the difficulty of re-transplanting highly sensitized patients are two of the major long-term challenges in pediatric renal transplantation. Treatments for AMR are often ineffective and desensitization protocols can be a high risk, making prevention a highly appealing strategy. Insights into the structural determinants of humoral alloantigenicity present an exciting opportunity to reassess our current paradigm of tissue matching and potentially preventing these complications. We review the theory behind human leukocyte antigen (HLA) B cell epitopes and the various systems that have been proposed to define them, including eplets. There is a growing body of clinical evidence suggesting that epitope-based tissue matching may be superior to traditional HLA antigen matching at predicting a range of clinical outcomes. However, additional studies are required to better understand the biological relevance of these systems of defining epitopes and their role in pediatric transplantation.

Acute antibody-mediated rejection after intestinal transplantation

AIM

To investigate the incidence, risk factors and clinical outcomes of acute antibody-mediated rejection (ABMR) after intestinal transplantation (ITx).

METHODS

A retrospective single-center analysis was performed to identify cases of acute ABMR after ITx, based on the presence of donor-specific antibody (DSA), acute tissue damage, C4d deposition, and allograft dysfunction.

RESULTS

Acute ABMR was identified in 18 (10.3%) out of 175 intestinal allografts with an average occurrence of 10 d (range, 4-162) after ITx. All acute ABMR cases were presensitized to donor human leukocyte antigens class I and/or II antigens with a detectable DSA. A positive cross-match was seen in 14 (77.8%) cases and twelve of 18 patients (66.7%) produced newly-formed DSA following ITx. Histological characteristics of acute ABMR include endothelial C4d deposits, interstitial hemorrhage, and severe congestion with focal fibrin thrombin in the lamina propria capillaries. Multivariate analysis identified a liver-free graft and high level of panel reactive antibody as a significant independent risk factor. Despite initial improvement after therapy, eleven recipients (61.1%) lost transplant secondary to rejection. Of those, 9 (50%) underwent graft removal and 4 (22.2%) received second transplantation following acute ABMR. At an average follow-up of 32.3 mo (range, 13.3-76.4), 8 (44.4%) recipients died.

CONCLUSION

Our results indicate that acute ABMR is an important cause of intestine graft dysfunction, particularly in a liver-exclusive graft and survivors are at an increased risk of developing refractory acute rejection and chronic rejection. More effective strategies to prevent and manage acute ABMR are needed to improve outcomes.

Transplant immuno-diagnostics: crossmatch and antigen detection

Identifying and monitoring donor-directed anti-human leukocyte antigen antibodies are a rapidly evolving area of solid organ transplantation. Donor-specific antibodies dictate pre-transplant donor choice and donor-recipient matching and underlie much acute and chronic allograft rejection and loss. The evolution of available technology has driven this progress. Early, labor-intensive, whole-cell assays based on complement-dependent cytotoxicity suffered from poor sensitivity and specificity, technical challenges and lack of precision. Sequential improvement in assay performance included anti-human immunoglobulin-enhanced, complement-dependent cytotoxicity techniques followed by cell-based flow cytometry. However, variable specificity and sensitivity inherent in cell-based testing continued to limit flow cytometry. The introduction of solid-phase assays led to a second revolution in histocompatibility testing with the use of purified antigens bound to artificial surfaces rather than whole cells. These techniques augmented sensitivity and specificity to detect even low-titer antibodies to previously undetected antigens. Identification of complement-activating antibodies is being introduced, but current technology is in the developmental stage. While the detection of alloantibodies has improved dramatically, our comprehension of their importance remains imperfect. Variability in methodology and a lack of standardization limits the clinical application of these tests. In spite of the hurdles that remain, antibody-mediated rejection has become a key target to improve graft survival.

Rituximab in the treatment of refractory late acute antibody-mediated rejection: Our initial experience

Antibody-mediated rejection (AMR) is not uncommon after renal transplantation and is harder to handle compared to cell-mediated rejection. When refractory to conventional therapies, rituximab is an attractive option. This study aims to examine the effectiveness of rituximab in refractory late acute AMR. This is a retrospective study involving nine renal transplant recipients. Four doses of rituximab were administered at weekly interval for 4 weeks, at a dose of 375 mg/m². The mean age of patients was 35.3 ± 7.38 years. The median period between transplantation and graft dysfunction was 30 ± 20 months. Mean serum creatinine at the time of discharge after transplantation and at the time of acute AMR diagnosis was 1.14 ± 0.19 mg/dl and 2.26 ± 0.57 mg/dl, respectively. After standard therapy, it was 2.68 ± 0.62 mg/dl. One patient died of Pseudomonas sepsis and three patients progressed to end-stage renal disease (ESRD). Four biopsies showed significant plasma cell infiltrations. Mean serum creatinine among non-ESRD patients at the end of 1 year progressed from 2.3 ± 0.4 to 3.8 ± 1.2 mg/dl (P value 0.04). eGFR prior to therapy and at the end of 1 year were 34.4 ± 6.18 and 20.8 ± 7.69 ml/min (P value 0.04), respectively. Only one patient showed improvement in graft function in whom donor-specific antibody (DSA) titers showed significant improvement. Rituximab may not be effective in late acute AMR unlike in early acute AMR. Monitoring of DSA has a prognostic role in these patients and plasma cell rich rejection is associated with poor prognosis.

Correlation of Circulating Complement-Fixing Donor-Specific Antibodies Identified by the C1q Assay and Presence of C4d in Endomyocardial Biopsy Specimens

OBJECTIVES

Donor-specific antibodies (DSAs) are associated with increased cardiac graft loss. We applied a C1q solid-phase assay in parallel with the standard immunoglobulin G (IgG) single antigen bead (SAB) assay to examine the correlation of circulating complement-fixing donor-specific antibodies and the presence of C4d in endomyocardial biopsy (EMB) specimens.

METHODS

We retrospectively studied the relationship of C1q+ DSAs and C4d immunofluorescence (IF) in 49 EMB specimens from 44 heart transplant recipients who had concurrent EMB, C4d IF, and DSA measurements. We applied a C1q SAB in parallel with the standard IgG SAB assay to examine the DSA profiles in heart transplant patients posttransplant.

RESULTS

A better concordance is observed between C1q+ DSAs with C4d IF+ compared with IgG DSAs with C4d IF + (40% vs 24%, P = .02). However, the correlation of C1q DSAs with C4d IF is not statistically significant (P = .24). Importantly, C1q+ DSAs were observed in 16 of 17 cases with C4d IF+; 24 cases had circulating C1q+ DSAs without detectable C4d staining, suggesting that that the presence of C1q+ DSAs may precede the detection of C4d deposition in EMB specimens and/or the development of antibody-mediated rejection.

CONCLUSIONS

In this cohort of 44 patients, no significant correlation was observed between circulating C1q DSAs and C4d IF in EMB specimens. Additional studies are needed to further evaluate the association of C1q DSAs with EMB specimens and C4d staining.

Pathologic sequelae of allosensitization in liver transplantation

The long-term impact of allosensitization between ABO compatible donor/recipient pairs in liver transplantation is unclear. Accumulating clinical evidence suggests that donor-specific antibody formation may lead to antibody-mediated rejection and is causally linked to pathologic injury, graft loss, and death. Although this immune-mediated graft dysfunction is increasingly being associated with poor outcomes, the specific pathologic sequelae are not defined. Herein, we examine the relationship between allosensitization, antibody-mediated rejection, and subsequent graft pathology.

Analysis of preformed donor-specific anti-HLA antibodies characteristics for prediction of antibody-mediated rejection in kidney transplantation

BACKGROUND

The relevance of preformed donor specific antibodies (DSA) detected by Luminex assays, with a negative complement-dependent cytotoxicity (CDC) crossmatch, remains unsettled in kidney transplantation (KT). We aimed to analyze the impact of preformed DSA characteristics on kidney graft outcomes.

METHODS

In 462 patients that received a kidney graft in our unit, between 2007 and 2012, pre-transplant sera were analyzed by Luminex screening assay to determine the presence of anti-human leukocyte antigen (HLA) antibodies and single-antigen bead assay [positive if mean fluorescence intensity (MFI) ≥ 1000] to assign anti-HLA specificities.

RESULTS

Anti-HLA antibodies were present in 95 patients (20.6%), but only 40 (8.7%) had DSA. Antibody-mediated rejection (AMR) at 1-year was higher in patients with DSA (35.0%) than in those without them (0.9%) (P < 0.001). Only DSA with a MFI of >3000 were significantly associated with AMR occurrence. Receiver operator curves revealed that a MFI of >4900 in the highest DSA bead had a high sensitivity (85.7%) and that the sum of all DSA beads MFI > 11,000 had a high specificity (92.3%) for AMR prediction. Anti-thymocyte globulin versus basiliximab induction was more frequent in DSA+ AMR- (65.4%) versus DSA+ AMR+ (34.6%) patients (P = 0.072). Five-year censored graft survival was lower in DSA+ than in DSA- patients (respectively, 84.8% versus 94.9%, P = 0.006), although survival was only reduced in DSA+ AMR+ (68.8%) versus DSA+ AMR- (96.0%) patients (P = 0.038).

CONCLUSIONS

Preformed DSA is associated with kidney graft loss, in relation with AMR occurrence. DSA strength may be used to improve immunological risk stratification of sensitized patients and their clinical management.

Pre-transplant low level HLA antibody shows a composite poor outcome in long-term outcome of renal transplant recipients

To determine the significance of low-level DSA (donor specific antibody) in patients transplanted with negative cytotoxicity AHG (antihuman immunoglobulin) crossmatch, data from 279 patients who received a kidney transplant between July 1999 and March 2006 were collected. All kidney recipients received ABO-compatible donors. A poor outcome was defined as any one of the following: death, Cr>2.0 mmol/L, occurrence of a rejection episode. Luminex Screening and Single Antigen assays from Tepnel Life Codes were used to detect human leukocyte antigen antibodies on pre-transplant sera retrospectively. Twenty-four out of 279 recipients demonstrated the presence of solid-phase DSA (MFI>1000) present pre-transplant. In DSA+ group, the accumulated good versus poor outcome rate was 0.30 versus 0.70, respectively. These rates were 0.49 and 0.51, respectively, in the DSA- group. The difference in composite poor outcome between DSA+ versus DSA- group was significant (p=0.030). The DSA- group had no difference in patient survival as compared to the DSA+ group (p=0.061). There is no statistically significant difference for either mortality or outcome results between high MFI (>2000) and low MFI (≤2000) groups. Our data suggest that solid-phase antibodies which are not strong enough to elicit a positive T-AHG crossmatch may influence long-term graft outcome.

Correlations of lymphocyte subset infiltrates with donor-specific antibodies and acute antibody-mediated rejection in endomyocardial biopsies

BACKGROUND

Acute antibody-mediated rejection (AMR) is a major complication after heart transplantation, posing a significant risk for allograft failure, cardiac allograft vasculopathy, and poor survival. While the inflammatory milieu of cellular rejection and Quilty lesions is well known, the immunologic components of AMR are not well understood. Our aim was to better define the immunophenotype of infiltrating lymphocytes in biopsies with AMR, specifically in relation to donor-specific antibodies to human leukocyte antigen (HLA) class I, II, or both.

METHOD

We performed a retrospective analysis of cardiac transplant patients with concurrent endomyocardial biopsies (EMB), donor-specific antibody (DSA) measurements, and immunofluorescence for C4d at our institution (2005-2011). DSA was evaluated against HLA class I and class II specificities pre- and posttransplant using flow cytometry and/or Luminex bead assays. Acute cellular rejection (ACR) and pathologic AMR (pAMR) were based on the International Society for Heart and Lung Transplantation 2005/2013 reports. Immunohistochemical analysis for CD3, CD4, CD8, and CD79a was performed using standard immunohistochemical protocols on one formalin-fixed, paraffin-embedded EMB from each patient. The number of lymphocytes expressing each protein was enumerated microscopically at 400×. Ratios of T:B cells and CD4:CD8 T cells were then calculated for each EMB.

RESULTS

Seventy-nine cardiac transplant patients who had pre- and posttransplant DSA measurements were analyzed. Of these 79 patients, 37 had DSA against HLA class I, HLA class II, or both. Of patients with DSA, the average CD4:CD8 ratio in the EMB was 0.80, while those with only ACR had a CD4:CD8 ratio of 1.49. Interestingly, the T:B cell ratio in patients with and without DSA was 5.7 and 5.5, respectively.

CONCLUSION

Cardiac transplant patients with DSA against HLA have more CD8 cytotoxic T cells than CD4 helper T cells in the EMB lymphocytic infiltrate compared with patients without DSA against HLA. The inflammatory infiltrate T:B cell ratio was similar in patients both with and without DSA. The relative increase of cytotoxic T cells in EMB while the patient has DSA suggests a possible pathogenic role of these cells and may aid in the diagnosis and treatment of AMR.

Interleukin 5 immunotherapy depletes alloreactive plasma cells

BACKGROUND

Long-lived plasma cells (PCs) that form after alloantigen sensitization produce donor-specific alloantibodies that generate a positive serum crossmatch and preclude transplantation. New approaches for desensitization, including PC depletion with proteasome inhibition, show promise but carry considerable toxicity. Recently, eosinophils have been shown to govern PC persistence. Interleukin 5 (IL-5) depletion is known to reduce eosinophils in human asthmatics. We hypothesized that treatment with an anti-IL-5 antibody can deplete alloreactive PCs, reduce donor-specific alloantibodies, and serve as a less toxic alternative to proteasome inhibition.

METHODS

BALB/c mice were sensitized with B6 skin allografts. Starting at 8 wk after sensitization, control mice received injections of phosphate-buffered saline, whereas experimental mice received weekly injections of an anti-IL-5 antibody. PCs were enumerated by enzyme-linked immunosorbent spot after 8 wk.

RESULTS

All control and experimental recipients of skin allografts developed positive crossmatches when screened at 8 wk after sensitization. All experimental mice treated with anti-IL-5 showed a reduction in their total PC numbers. Also, in contrast to the known adverse effects of proteasome inhibition, experimental mice treated with anti-IL-5 exhibited negligible weight loss or lymphopenia.

CONCLUSIONS

Treatment with anti-IL-5 is sufficient to reduce, but not eliminate, alloreactive PCs in the bone marrow. This is because of the targeted reduction of eosinophils leading to a reduction in the PC survival factors a proliferation-inducing ligand and IL-6. Generalized toxicity was not observed in experimental mice. Overall, IL-5 directed immunotherapy can eliminate PC's but is unlikely to be a clinically significant desensitization strategy given the persistence of DSA.