Abstract
Sensitized kidney transplant recipients experience high rates of antibody-mediated rejection due to the presence of donor-specific antibodies and immunologic memory. Here we show that ...transient peri-transplant treatment with the central complement component C3 inhibitor Cp40 significantly prolongs median allograft survival in a sensitized nonhuman primate model. Despite donor-specific antibody levels remaining high, fifty percent of Cp40-treated primates maintain normal kidney function beyond the last day of treatment. Interestingly, presence of antibodies of the IgM class associates with reduced median graft survival (8 vs. 40 days;
p
= 0.02). Cp40 does not alter lymphocyte depletion by rhesus-specific anti-thymocyte globulin, but inhibits lymphocyte activation and proliferation, resulting in reduced antibody-mediated injury and complement deposition. In summary, Cp40 prevents acute antibody-mediated rejection and prolongs graft survival in primates, and inhibits T and B cell activation and proliferation, suggesting an immunomodulatory effect beyond its direct impact on antibody-mediated injury.
Summary Background More than 40% of patients awaiting a kidney transplant in the UK are sensitised with human leucocyte antigen (HLA) antibodies. Median time to transplantation for such patients is ...double that of unsensitised patients at about 74 months. Removing antibody to perform an HLA-incompatible (HLAi) living donor transplantation is perceived to be high risk, although patient survival data are limited. We compared survival of patients opting for an HLAi kidney transplant with that of similarly sensitised patients awaiting a compatible organ. Methods From the UK adult kidney transplant waiting list, we selected crossmatch positive living donor HLAi kidney transplant recipients who received their transplant between Jan 1, 2007, and Dec 31, 2013, and were followed up to Dec 31, 2014 (end of study). These patients were matched in a 1:4 ratio with similarly sensitised patients cases listed for a deceased-donor transplant during that period. Data were censored both at the time of transplantation (listed only), and at the end of the study period (listed or transplant). We used Kaplan-Meier curves to compare patient survival between HLAi and the matched cohort. Findings Of 25 518 patient listings, 213 (1%) underwent HLAi transplantation during the study period. 852 matched controls were identified, of whom 41% (95% CI 32–50) remained without a transplant at 58 months after matching. We noted no difference in survival between patients who were in the HLAi group compared with the listed only group (log rank p=0·446), or listed or transplant group (log rank p=0·984). Interpretation Survival of sensitised patients undergoing HLAi in the UK is comparable with those on dialysis awaiting a compatible organ, many of whom are unlikely to be have a transplant. Choosing a direct HLAi transplant has no detrimental effect on survival, but offers no survival benefit, by contrast with similar patients studied in a North American multicentre cohort. Funding UK National Health Service Blood & Transplant and Guy's & St Thomas' National Institute for Health Research Biomedical Research Centre.
Donor-specific antibodies are associated with increased risk of antibody-mediated rejection and decreased allograft survival. Therefore, reducing the risk of these antibodies remains a clinical need ...in transplantation. Plasma cells are a logical target of therapy given their critical role in antibody production.
To target plasma cells, we treated sensitized rhesus macaques with daratumumab (anti-CD38 mAb). Before transplant, we sensitized eight macaques with two sequential skin grafts from MHC-mismatched donors; four of them were also desensitized with daratumumab and plerixafor (anti-CXCR4). We also treated two patients with daratumumab in the context of transplant.
The animals treated with daratumumab had significantly reduced donor-specific antibody levels compared with untreated controls (57.9% versus 13% reduction;
<0.05) and prolonged renal graft survival (28.0 days versus 5.2 days;
<0.01). However, the reduction in donor-specific antibodies was not maintained because all recipients demonstrated rapid rebound of antibodies, with profound T cell-mediated rejection. In the two clinical patients, a combined heart and kidney transplant recipient with refractory antibody-mediated rejection and a highly sensitized heart transplant candidate, we also observed a significant decrease in class 1 and 2 donor-specific antibodies that led to clinical improvement of antibody-mediated rejection and to heart graft access.
Targeting CD38 with daratumumab significantly reduced anti-HLA antibodies and anti-HLA donor-specific antibodies in a nonhuman primate model and in two transplant clinical cases before and after transplant. This supports investigation of daratumumab as a potential therapeutic strategy; however, further research is needed regarding its use for both antibody-mediated rejection and desensitization.
Previous evidence suggests that a homeostatic germinal center (GC) response may limit bortezomib desensitization therapy. We evaluated the combination of costimulation blockade with bortezomib in a ...sensitized non‐human primate kidney transplant model. Sensitized animals were treated with bortezomib, belatacept, and anti‐CD40 mAb twice weekly for a month (n = 6) and compared to control animals (n = 7). Desensitization therapy–mediated DSA reductions approached statistical significance (P = .07) and significantly diminished bone marrow PCs, lymph node follicular helper T cells, and memory B cell proliferation. Graft survival was prolonged in the desensitization group (P = .073). All control animals (n = 6) experienced graft loss due to antibody‐mediated rejection (AMR) after kidney transplantation, compared to one desensitized animal (1/5). Overall, histological AMR scores were significantly lower in the treatment group (n = 5) compared to control (P = .020). However, CMV disease was common in the desensitized group (3/5). Desensitized animals were sacrificed after long‐term follow‐up with functioning grafts. Dual targeting of both plasma cells and upstream GC responses successfully prolongs graft survival in a sensitized NHP model despite significant infectious complications and drug toxicity. Further work is planned to dissect underlying mechanisms, and explore safety concerns.
Targeting both plasma cells and the germinal center response with proteasome inhibition and costimulation blockade successfully desensitizes and prolongs renal allograft survival in a highly sensitized nonhuman primate model despite significant infectious complications and drug toxicity.
There is an urgent need for therapeutic interventions for desensitization and antibody-mediated rejection (AMR) in sensitized patients with preformed or
donor-specific HLA antibodies (DSA). The risk ...of AMR and allograft loss in sensitized patients is increased due to preformed DSA detected at time of transplant or the reactivation of HLA memory after transplantation, causing acute and chronic AMR. Alternatively,
DSA that develops post-transplant due to inadequate immunosuppression and again may lead to acute and chronic AMR or even allograft loss. Circulating antibody, the final product of the humoral immune response, has been the primary target of desensitization and AMR treatment. However, in many cases these protocols fail to achieve efficient removal of all DSA and long-term outcomes of patients with persistent DSA are far worse when compared to non-sensitized patients. We believe that targeting multiple components of humoral immunity will lead to improved outcomes for such patients. In this review, we will briefly discuss conventional desensitization methods targeting antibody or B cell removal and then present a mechanistically designed desensitization regimen targeting plasma cells and the humoral response.
Background
“Textbook outcome” (TO) is a novel composite quality measure that encompasses multiple postoperative endpoints, representing the ideal “textbook” hospitalization for complex surgical ...procedures. We defined TO for kidney transplantation using a cohort from a high-volume institution.
Methods
Adult patients who underwent isolated kidney transplantation at our institution between 2016 and 2019 were included. TO was defined by clinician consensus at our institution to include freedom from intraoperative complication, postoperative reintervention, 30-day intensive care unit or hospital readmission, length of stay > 75th percentile of kidney transplant patients, 90-day mortality, 30-day acute rejection, delayed graft function, and discharge with a Foley catheter. Recipient, operative, financial characteristics, and post-transplant patient, graft, and rejection-free survival were compared between patients who achieved and failed to achieve TO.
Results
A total of 557 kidney transplant patients were included. Of those, 245 (44%) achieved TO. The most common reasons for TO failure were delayed graft function (
N
= 157, 50%) and hospital readmission within 30 days (
N
= 155, 50%); the least common was mortality within 90 days (
N
= 6, 2%). Patient, graft, and rejection-free survival were significantly improved among patients who achieved TO. On average, patients who achieved TO incurred approximately $50,000 less in total inpatient charges compared to those who failed TO.
Conclusions
TO in kidney transplantation was associated with favorable post-transplant outcomes and significant cost-savings. TO may offer transplant centers a detailed performance breakdown to identify aspects of perioperative care in need of process improvement.
Multiplex immunoassays with acellular antigens are well-established based on solid-phase platforms such as the Luminex
technology. Cell barcoding by amine-reactive fluorescent dyes enables analogous ...cell-based multiplex assays, but requires multiple labeling reactions and quality checks prior to every assay. Here we describe generation of stable, fluorescent protein-barcoded reporter cell lines suitable for multiplex screening of antibody to membrane proteins. The utility of this cell-based system, with the potential of a 256-plex cell panel, is demonstrated by flow cytometry deconvolution of barcoded cell panels expressing influenza A hemagglutinin trimers, or native human CCR2 or CCR5 multi-span proteins and their epitope-defining mutants. This platform will prove useful for characterizing immunity and discovering antibodies to membrane-associated proteins.
Antibody-mediated allograft rejection (AMR) causes more kidney transplant failure than any other single cause. AMR is mediated by antibodies recognizing antigens expressed by the graft, and ...antibodies generated against major histocompatibility complex (MHC) mismatches are especially problematic. Most research directed towards the management of clinical AMR has focused on identifying and characterizing circulating donor-specific HLA antibody (DSA) and optimizing therapies that reduce B-cell activation and/or block antibody secretion by inhibiting plasmacyte survival. Here we describe a novel set of reagents and techniques to allow more specific measurements of MHC sensitization across different animal transplant models. Additionally, we have used these approaches to isolate and clone individual HLA-specific B cells from patients sensitized by pregnancy or transplantation. We have identified and characterized the phenotypes of individual HLA-specific B cells, determined the V(D)J rearrangements of their paired H and L chains, and generated recombinant antibodies to determine affinity and specificity. Knowledge of the BCR genes of individual HLA-specific B cells will allow identification of clonally related B cells by high-throughput sequence analysis of peripheral blood mononuclear cells and permit us to re-construct the origins of HLA-specific B cells and follow their somatic evolution by mutation and selection.
Patients with previous sensitization events against anti-human leukocyte antigens (HLA) often have circulating anti-HLA antibodies. Following organ transplantation, sensitized patients have higher ...rates of antibody-mediated rejection (AMR) compared to those who are non-sensitized. More stringent donor matching is required for these patients, which results in a reduced donor pool and increased time on the waitlist. Current approaches for sensitized patients focus on reducing preformed antibodies that preclude transplantation; however, this type of desensitization does not modulate the primed immune response in sensitized patients. Thus, an optimized maintenance immunosuppressive regimen is necessary for highly sensitized patients, which may be distinct from non-sensitized patients. In this review, we will discuss the currently available therapeutic options for induction, maintenance, and adjuvant immunosuppression for sensitized patients.
Summary
ABO blood group incompatible renal transplantation, using desensitization procedures, is an effective strategy. Efforts have been made to reduce desensitization: these are usually applied to ...all patients indiscriminately. The Guy's Hospital ABO blood group incompatible desensitization regimen uses a tiered approach, tailoring strategy according to initial antibody titres. Sixty‐two ABO blood group incompatible living donor transplant recipients were compared with 167 recipients of blood group compatible living donor renal transplants. There were no statistically significant differences in allograft survival rates at 1 or 3 years post‐transplant, rejection in the first year post‐transplant or renal function in the first 3 years post‐transplant. There was a higher rate of death in ABO blood group incompatible transplant recipients – this could be associated with differences in age and HLA mismatch between the two groups. Four ABO blood group incompatible patients experienced antibody‐mediated rejection (no episode was associated with a rise in ABO blood group antibodies). Of the patients who received no desensitization, or rituximab alone, none has experienced antibody mediated rejection or experienced allograft loss. Tailoring the use of desensitization in ABO blood group incompatible renal transplantation according to initial ABO blood group antibody titres led to comparable results to blood group compatible transplantation.
PDF
