Donor-specific Antibodies Research Articles

Induction immunosuppression strategies and outcomes post-lung transplant: A single center experience

PurposeCurrently 80% of lung transplant centers use induction immunosuppression. However, there is a lack of standardization of induction protocols within and across lung transplant centers. This study explores the association of two different induction immunosuppression strategies used at our center [single dose rabbit antithymocyte globulin (rATG) vs. alemtuzumab] compared to no induction with immunologic and clinical outcomes after lung transplantation. MethodsA total of 174 consecutive lung transplant recipients (LTR) between 2016 and 2019 were included in the analysis. Twenty nine LTR (16.7%) received no induction, 22 LTR (12.6%) received alemtuzumab, 123 LTR (70.6%) received a single dose of rATG; 1.5 mg/kg within 24 h of transplant for induction. All LTR had a negative flow cytometry crossmatch on the day of the transplant. All LTR were assessed for de novo HLA donor-specific antibodies (DSA) development and clinical outcomes, including the risk of acute cellular rejection (ACR), antibody-mediated rejection (AMR), chronic lung allograft dysfunction (CLAD), and overall survival post-transplant. ResultsThe median lung allocation score (LAS) was significantly higher in LTR that did not receive Induction immunosuppression (76; range = 35.3–94.3) compared to induction with rATG (41.6; range = 31.6–91) and alemtuzumab (51; range = 33.1–88.2) (p < 0.001). De novo HLA DSA were detected in 50/174 (28.7%) LTR within 12 months post-transplant. They were detected in 13/29 (44.8%) LTR without induction immunosuppression compared to 28/123 (22.8%) and 9/22 (40.9%) LTR with rATG and alemtuzumab induction, respectively (p = 0.02). The percent freedom from ACR rates between LTR who received alemtuzumab induction was significantly higher compared to LTR who received rATG or no induction at 1 (p = 0.02), 2 (p = 0.01) and 3 (p = 0.05) years post-transplant. In addition, the overall 1-year survival rates were significantly higher in LTR who received rATG or alemtuzumab induction compared to LTR without induction immunosuppression (p = 0.02). ConclusionInduction immunosuppression strategies utilizing rATG or Alemtuzumab have unique and contrasting benefits in LTR. Combination of alemtuzumab induction and a lower dose of maintenance immunosuppression may reduce the incidence of ACR in LTR. Single-dose rATG or alemtuzumab induction immunosuppression may also improve the 1 year overall LTR survival compared to no induction.

Daratumumab for De-sensitization of Donor Specific Antibodies: Is it a Quicker and Easier way?

Antibodies directed against donor-specific HLA loci (DSA) has been proved as a main culprit for graft rejection, more specifically in HLA mismatched and haplo-identical transplant settings. There is no standardized regimen to manage the presence of DSAs in allogeneic stem cell transplantations (allo-SCTs). Most widely regimen includes combination of rituximab (anti CD20 antibody), Immunoglobulin (IVIG), plasma exchange, and buffy coat infusion, which is costly and time-consuming. Daratumumab (anti CD38 monoclonal antibody) is an effective therapeutic agent to deplete plasma cells and hence, it has a potential to reduce DSA. It has been utilized widely in solid organ transplantation for this purpose. We used this agent in two haplo-identical transplant patients to eliminate or reduce DSA. We observed definite either reduction or elimination in DSA levels in these cases and we could perform haplo-identical transplantation without much delay and with successful primary engraftment in both scenarios. We emphasize that literature on real-world utilization of daratumumab in allo-SCTs is limited. However, it has been utilized widely in solid organ transplantation for this purpose. Our experience with daratumumab regarding effective reduction of DSA followed by successful engraftment might encourage its use in de-sensitization protocols without much delay in transplantation.

Pseudomonas aeruginosa infection correlates with high MFI donor-specific antibody development following lung transplantation with consequential graft loss and shortened CLAD-free survival

BackgroundDonor-specific antibodies (DSAs) are common following lung transplantation (LuTx), yet their role in graft damage is inconclusive. Mean fluorescent intensity (MFI) is the main read-out of DSA diagnostics; however its value is often disregarded when analyzing unwanted post-transplant outcomes such as graft loss or chronic lung allograft dysfunction (CLAD). Here we aim to evaluate an MFI stratification method in these outcomes.MethodsA cohort of 87 LuTx recipients has been analyzed, in which a cutoff of 8000 MFI has been determined for high MFI based on clinically relevant data. Accordingly, recipients were divided into DSA-negative, DSA-low and DSA-high subgroups. Both graft survival and CLAD-free survival were evaluated. Among factors that may contribute to DSA development we analyzed Pseudomonas aeruginosa (P. aeruginosa) infection in bronchoalveolar lavage (BAL) specimens.ResultsHigh MFI DSAs contributed to clinical antibody-mediated rejection (AMR) and were associated with significantly worse graft (HR: 5.77, p < 0.0001) and CLAD-free survival (HR: 6.47, p = 0.019) compared to low or negative MFI DSA levels. Analysis of BAL specimens revealed a strong correlation between DSA status, P. aeruginosa infection and BAL neutrophilia. DSA-high status and clinical AMR were both independent prognosticators for decreased graft and CLAD-free survival in our multivariate Cox-regression models, whereas BAL neutrophilia was associated with worse graft survival.ConclusionsP. aeruginosa infection rates are elevated in recipients with a strong DSA response. Our results indicate that the simultaneous interpretation of MFI values and BAL neutrophilia is a feasible approach for risk evaluation and may help clinicians when to initiate DSA desensitization therapy, as early intervention could improve prognosis.

Comparative Analysis of Ischemia-Reperfusion Injury in Heart Transplantation: A Single-Center Study Evaluating Conventional Ice-Cold Storage versus the Paragonix SherpaPak Cardiac Transport System.

Since the 2018 allocation system change in heart transplantation (HT), ischemic times have increased, which may be associated with peri-operative and post-operative complications. This study aimed to compare ischemia reperfusion injury (IRI) in hearts preserved using ice-cold storage (ICS) and the Paragonix SherpaPak TM Cardiac Transport System (CTS). From January 2021 to June 2022, consecutive endomyocardial biopsies from 90 HT recipients were analyzed by a cardiac pathologist in a single-blinded manner: 33 ICS and 57 CTS. Endomyocardial biopsies were performed at three-time intervals post-HT, and the severity of IRI manifesting histologically as coagulative myocyte necrosis (CMN) was evaluated, along with graft rejection and graft function. The incidence of IRI at weeks 1, 4, and 8 post-HT were similar between the ICS and CTS groups. There was a 59.3% statistically significant reduction in CMN from week 1 to 4 with CTS, but not with ICS. By week 8, there were significant reductions in CMN in both groups. Only 1 out of 33 (3%) patients in the ICS group had an ischemic time >240mins, compared to 10 out of 52 (19%) patients in the CTS group. During the follow-up period of 8 weeks to 12 months, there were no significant differences in rejection rates, formation of de novo donor-specific antibodies and overall survival between the groups. The CTS preservation system had similar rates of IRI and clinical outcomes compared to ICS despite longer overall ischemic times. There is significantly more recovery of IRI in the early post operative period with CTS. This study supports CTS as a viable option for preservation from remote locations, expanding the donor pool.

Clinical Utility of the Molecular Microscope Diagnostic System in a Real-World Transplant Cohort: Moving Towards a New Paradigm.

To evaluate the clinical implications of adjunctive molecular gene expression analysis (MMDx ) of biopsy specimens in heart transplant (HT ) recipients with suspected rejection. Histopathological evaluation remains the standard method for rejection diagnosis in HT. However, the wide interobserver variability combined with a relatively common incidence of "biopsy-negative" rejection has raised concerns about the likelihood of false-negative results. MMDx, which uses gene expression to detect early signs of rejection, is a promising test to further refine the assessment of HT rejection. Single-center prospective study of 418 consecutive for-cause endomyocardial biopsies performed between November 2022 and May 2024. Each biopsy was graded based on histology and assessed for rejection patterns using MMDx. MMDx results were deemed positive if borderline or definitive rejection was present. The impact of MMDx results on clinical management was evaluated. Primary outcomes were 1-year survival and graft dysfunction following MMDx-guided clinical management. Secondary outcomes included changes in donor-specific antibodies, MMDx gene transcripts, and donor-derived cell-free DNA (dd-cfDNA) levels. We analyzed 418 molecular samples from 237 unique patients. Histology identified rejection in 32 cases (7.7%), while MMDx identified rejection in 95 cases (22.7%). Notably, in 79 of the 95 cases where MMDx identified rejection, histology results were negative, with the majority of these cases being antibody-mediated rejection (62.1%). Samples with rejection on MMDx were more likely to show a combined elevation of dd-cfDNA and peripheral blood gene expression profiling than those with borderline or negative MMDx results (36.7% vs 28.0% vs 10.3%; p<0.001). MMDx results led to the implementation of specific antirejection protocols or changes in immunosuppression in 20.4% of cases, and in 73.4% of cases where histology was negative and MMDx showed rejection. 1-year survival was better in the positive MMDx group where clinical management was guided by MMDx results (87.0% vs 78.6%; log rank p=0.0017). In our cohort, MMDx results more frequently indicated rejection than histology, often leading to the initiation of antirejection treatment. Intervention guided by positive MMDx results was associated with improved outcomes.

Graft protective effects and donor-specific antibody suppression by CD4+CD25+Foxp3+ regulatory T cell induced by HMG-CoA reductase inhibitor rosuvastatin in a murine heart transplant model

BackgroundWe previously demonstrated that the hydroxymethylglutaryl-CoA (HMG-CoA) reductase inhibitor (statins) play an important role in the regulation of alloimmune responses. However, little is known regarding the effects of statin on allograft protection or donor-specific antibodies (DSA). In this study, we investigated the graft-protective and immunomodulatory effects of rosuvastatin in a model of fully major histocompatibility complex-mismatched murine cardiac allograft transplantation.MethodsCBA mice underwent transplantation of C57BL/6 (B6) hearts and received 50 and 500 μg/kg/day of rosuvastatin from the day of transplantation until seven days after the completion of transplantation. To confirm the requirement for regulatory T cells (Tregs), we administered an anti-interleukin-2 receptor alpha antibody (PC-61) to rosuvastatin-treated CBA recipients. Additionally, histological and fluorescent staining, cell proliferation analysis, flow cytometry, and DSA measurements were performed.ResultsCBA recipients with no treatment rejected B6 cardiac graft acutely (median survival time [MST], 7 days). CBA mice treated with 500 μg/kg/day of rosuvastatin prolonged allograft survival (MSTs, 77 days). Fluorescent staining studies showed that rosuvastatin-treated recipients had strong aggregation of CD4+Foxp3+ cells in the myocardium and around the coronary arteries of cardiac allografts two weeks after grafting. Flow cytometry studies performed two weeks after transplantation showed an increased number of splenic CD4+CD25+Foxp3+ T cells in rosuvastatin-treated recipients. The addition of rosuvastatin to mixed leukocyte cultures suppressed cell proliferation by increasing the number of CD4+CD25+Foxp3+ Tregs. Additionally, Tregs suppressed DSA production in rosuvastatin-treated recipients.ConclusionRosuvastatin treatment may be a complementary graft-protective strategy for suppressing DSA production in the acute phase, driven by the promotion of splenic and graft-infiltrating CD4+CD25+Foxp3+ Tregs.

Natural Killer Cell Presence in Antibody-Mediated Rejection.

Transcript analyses highlight an important contribution of natural killer (NK) cells to microvascular inflammation (MVI) in antibody-mediated rejection (ABMR), but only few immunohistologic studies have quantified their spatial distribution within graft tissue. This study included 86 kidney transplant recipients who underwent allograft biopsies for a positive donor-specific antibody (DSA) result. NK cells were visualized and quantified within glomeruli and peritubular capillaries (PTC), using immunohistochemistry for CD34 alongside CD16/T-bet double-staining. Staining results were analyzed in relation to histomorphology, microarray analysis utilizing the Molecular Microscope Diagnostic System, functional NK cell genetics, and clinical outcomes. The number of NK cells in glomeruli per mm2 glomerular area (NKglom) and PTC per mm2 cortical area (NKPTC) was substantially higher in biopsies with ABMR compared to those without rejection, and correlated with MVI scores (NKglom Spearman's correlation coefficient [SCC] = 0.55, p < 0.001, NKPTC 0.69, p < 0.001). In parallel, NK cell counts correlated with molecular classifiers reflecting ABMR activity (ABMRprob: NKglom 0.59, NKPTC 0.75) and showed a trend towards higher levels in association with high functional FCGR3A and KLRC2 gene variants. Only NKPTC showed a marginally significant association with allograft function and survival. Our immunohistochemical results support the abundance of NK cells in DSA-positive ABMR.

Development of donor specific antibodies after SARS-CoV-2 vaccination: What do we know so far?

Development of donor specific antibodies after SARS-CoV-2 vaccination: What do we know so far?

Optimum tacrolimus trough levels for enhanced graft survival and safety in kidney transplantation: a retrospective multicenter real-world evidence study.

The current study aimed to determine the optimal tacrolimus trough levels for balancing graft survival and patient safety following kidney transplantation. We conducted a retrospective cohort study involving 11,868 kidney transplant recipients from five medical centers. The association between tacrolimus exposures (periodic mean trough level, coefficient of variability, time in therapeutic range) and composite allograft outcome (de novo donor specific antibody, biopsy-proven rejection, kidney dysfunction, and graft failure), as well as safety outcomes (severe infection, cardiovascular events, malignancy, and mortality) were assessed. Data were sourced from Clinical Data Warehouses and analyzed using advanced statistical methods, including Cox marginal structural models with inverse probability treatment weighting. Tacrolimus levels of 5.0-7.9ng/mL and 5.0-6.9ng/mL during the 2-12 month and 12-72 month post-transplantation periods, respectively, were associated with reduced risks of composite allograft outcomes. During the first post-transplant year, the adjusted hazard ratios (aHR) for composite allograft outcomes were: 0.69 (95% CI 0.55-0.85, P<0.001) for 5.0-5.9ng/mL; 0.81 (95% CI 0.67-0.98, P=0.033) for 6.0-6.9ng/mL; and 0.73 (95% CI 0.60-0.89, P=0.002) for 7.0-7.9ng/mL (compared to levels ≥8.0ng/mL). For the 6-year composite outcomes, aHRs were 0.68 (95% CI 0.53-0.87, P=0.002) for 5.0-5.9ng/mL and 0.65 (95% CI 0.50-0.85, P=0.001) for 6.0-6.9ng/mL. These optimal ranges showed reduced rates of severe infection (6y), malignancy (6y), and mortality (1y). This multicenter study provides robust evidence for optimal tacrolimus trough levels during the periods 2-12 and 12-72 months following kidney transplantation.

The fate of anti-HLA antibodies following liver transplantation.

Liver transplant recipients may have pre-formed anti-HLA antibodies directed to mismatched HLA of the liver donor (donor specific antibodies, DSA) or not directed to the liver donor (non-donor specific, non-DSA). We observed the fate of these antibodies (DSA and non-DSA) at 12 months after transplant. Patients transplanted between 4/2015 and 12/2018 (N = 216) who had anti-HLA antibody measurements at both transplant and 12 months posttransplant (N = 124) and with DSAs at transplant (N = 31) were considered informative for a paired analysis of the natural history of DSA and non-DSA following liver transplantation. Class I DSAs and non-DSAs decreased between transplant and 12 months; however, Class I DSAs essentially disappeared by 12 months while Class I non-DSAs did not. Anti-HLA Class II DSAs performed differently. While there was a significant drop in values between transplant and 12 months, these antibodies mostly persisted at a low level. Our study demonstrated a significant difference in the kinetics of DSA compared to non-DSA following liver transplantation, most profoundly for anti-HLA Class I antibodies. Class I DSAs were mostly absent at 12 months while Class II DSAs persisted, although at lower levels. The mechanisms of reduction in anti-HLA antibodies following liver transplantation are not completely understood and were not pursued as a part of this study. This detailed analysis of Class I and Class II DSAs and non-DSAs represents and important study to explore the change in antibodies at one year from liver transplantation.

Long-Term Outcome Following Treatment With Allogeneic Mesenchymal Stem/Stromal Cells for Radiation-Induced Hyposalivation and Xerostomia.

Adipose-derived mesenchymal stem/stromal cells (ASCs) are proposed as a new xerostomia treatment. The study evaluated the long-term safety and effectiveness of allogeneic ASCs in radiation-induced xerostomia among patients with previous oropharyngeal cancer. This study constitutes 3-year follow-up on the original 10 patients who received allogeneic ASCs injections to the submandibular and parotid glands as part of the MESRIX-II trial. The MESRIX-II trial included the preliminary 4-month follow-up. The primary endpoint was long-term safety. Secondary endpoints were effectiveness evaluated by changes in salivary flow rate and patient-reported outcomes (PROs). Immune response was evaluated by assessing the development of donor-specific antibodies (DSA). All 10 MESRIX-II patients completed the long-term follow-up (ie, no missing data). During the long-term follow-up, 2 patients encountered a significant adverse event, which was determined to be unrelated to the treatment. No DSAs were detectable at 3 years. The stimulated salivary flow rate increased significantly from an average of 0.66 mL/minute at baseline to 0.86 mL/minute at follow-up, corresponding to an increase of 0.20 [95% CI 0.08 to 0.30] mL/minute, or approximately 30%. Among the PROs, sticky saliva symptoms were reduced, with a -20.0 [95% CI -37.3 to -2.7] units. In conclusion, this study is the first to present long-term follow-up outcomes of allogeneic ASC treatment as a therapeutic option for radiation-induced xerostomia. The study found that ASC treatment appears safe, and there were no indications of adverse immune responses at the 3-year follow-up. Further studies are warranted to evaluate the findings in larger settings.

Evaluating the Clinical Relevance of Antibodies against Non-Human Leukocyte Antigen in Kidney Transplantation.

Introduction: Kidney transplantation is the preferred modality of kidney replacement therapy for eligible patients with end-stage kidney disease (ESKD), given that it has been found to reduce mortality rates, improve quality of life, and is cost-effective compared to dialysis. Recent advancements in human leukocyte antigen (HLA) typing and donor-specific antibody (DSA) detection have helped to reduce the risk of rejection, but antibody-mediated rejection (AMR) can still occur without DSA. Previous studies suggest that rejection can be attributed to antibodies against Non-Human Leucocyte Antigens (non-HLAs). We aimed to acquire further understanding of the prevalence and distribution of non-HLA antibodies in our local population and attempt to correlate these findings with graft outcomes, as well as assess whether non-HLA antibodies can be utilized to determine graft impairment and dysfunction. Methods: We conducted a retrospective study involving kidney transplant recipients between January 2010 and December 2020. All included individuals were aged over 18 and underwent kidney-alone transplants; were ABO- and HLA-compatible; and were matched at A, B, and DR loci (mismatch 0:0:0). HLA testing was negative at the time of transplantation. The samples from both cases of early graft rejection and the control group were tested for non-HLA antibodies using One Lambda LABScreenTM, Autoantibody kit groups 1, 2, and 3, as well as the Immucor LIFECODES non-HLA autoantibody assay. Results: A total of 850 kidney transplant recipients were included, in which 12 patients experienced early graft rejection within the first month post transplant and 18 patients who did not experience graft rejection were selected as study controls. Our study reported no correlation between the total burden of non-HLA antibodies and early rejection, most likely as the result of a small sample size. Nevertheless, a sub-analysis revealed that specific high-frequency pre-transplant non-HLA antibodies such as GSTT, CXCL11, CXCL10, and HNR, detected by LIFECODES, were associated with rejection (Fisher's exact test with Bonferroni correction, p < 0.001). Most pre-transplant non-HLA antibody levels were reduced after transplantation, which was attributed to immunosuppression. Conclusion: The 'high frequency' non-HLA antibodies displayed an association with graft rejection, though the overall associations between the burden of non-HLA antibodies and rejection episodes remain inconclusive. Further work is needed to establish the rebound phenomenon of non-HLA antibodies, the development of de novo non-HLA antibodies in the long run, and their implications on graft survival.

Successful A2 to O Simultaneous Liver and Kidney Transplantation in the Setting of Pre-operative Positive HLA Crossmatch: A Case Report

Simultaneous liver and kidney transplantation (SLKT) is possible for patients with high donor-specific HLA antibodies or with A2 donors to O recipients with high A2 titers. We report the first case of SLKT in a highly sensitized O recipient with organs from an A2 donor. The recipient is a 59-year-old woman with chronic kidney disease and liver failure due to autoimmune hepatitis and drug-induced liver injury. Immune work-up 8 days pre-transplant demonstrated a negative crossmatch and no HLA antibody (calculated panel reactive antibodies = 0%). Anti-A2 IgG levels were 512. The donor was a deceased 24-year-old man. One day before transplantation, serum from the recipient showed a significant increase in antibody reactivity (calculated panel reactive antibodies = 100%) attributable to blood product transfusion and memory response from previous pregnancies. Consequently, a crossmatch was positive for T and B cells with two newly detected HLA antibodies against the donor's antigens. On the day of surgery, the liver was transplanted first. Six hours and 37 minutes later, a repeat flow crossmatch was negative; donor-specific antibodies (DSAs) fell below the positive threshold, and anti-A2 IgG titer fell to 256. Thus, the kidney was transplanted after basiliximab induction therapy. Seven days post-transplant, non-donor-specific HLA antibodies were present but DSAs remain negative. The patient was discharged on postoperative day 57 with no signs of rejection at 4 months. This case illustrates a rapid and prolonged reduction in antibody titers (HLA and ABO) after SLKT. SLKT is feasible in patients with both DSA and high anti-A2 titer.

A personalised delisting strategy enables successful kidney transplantation in highly sensitised patients with preformed donor-specific anti HLA antibodies.

This study investigates kidney transplant outcomes in highly sensitised patients after implementing a delisting strategy aimed at enabling transplantation despite preformed donor-specific antibodies (preDSA), with the goal of reducing acute antibody-mediated rejection (aAMR) risk. Fifty-three sensitised recipients underwent kidney transplant after delisting prohibited HLA antigens, focusing initially in low MFI antibodies (<5000), except for anti-HLA-DQ. If insufficient, higher MFI antibodies were permitted, especially for those without an immunogenic eplet pattern assigned. Delisting of Complement-fixing antibodies (C1q+) was consistently avoided. Comparison cohorts included 53 sensitised recipients without DSA (SwoDSA) and 53 non-sensitised (NS). The average waiting time prior to delisting was 4.4 ± 1.8 years, with a reduction in cPRA from 99.7 ± 0.5 to 98.1 ± 0.7, followed by transplantation within 7.2 ± 8.0 months (analysed in 34 patients). Rejection rates were similar among preDSA, SwoDSA, and NS groups (16%, 8%, and 11%, respectively; p = 0.46). However, aAMR was higher in the preDSA group (12%, 4%, and 2%, respectively; p = 0.073), only presented in recipients with DSA of MFI >5000. The highest MFI DSA were against HLA-DP (Median: 10796 MFI), with 50% of preDSA aAMR cases due to anti-DP antibodies (n = 3). Graft survival rates at 1 and 5 years in preDSA group were 94%, and 67%, comparable to SwoDSA (94%, and 70%; p = 0.69), being significantly higher in the NS group (p = 0.002). The five-year recipient survival rate was 89%, comparable to SwoDSA and NS groups (p = 0.79). A delisting strategy enables safe kidney transplant in highly sensitised patients with preDSA, with a slight increase in aAMR and comparable graft and patient survivals to non-DSA cohorts.

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

Antibody-mediated rejection is one of the most significant risk factors for allograft dysfunction and failure in children and adolescents with kidney transplants, yet optimal treatment remains unidentified. To date, there are mixed findings regarding the use of Bortezomib, a plasma cell apoptosis inducer, as an adjunct therapy in the treatment of antibody-mediated rejection. In a retrospective single center study, we reviewed the efficacy and tolerability of bortezomib as adjunct therapy for treatment-refractory antibody-mediated rejection. Six patients with a median age of 14.6 years (range 6.9-20.1 years) received bortezomib at a mean of 71 months (range 15-83 months) post-kidney transplant. Four patients experienced decline in estimated glomerular filtration rate (eGFR) from 4% to 42%. One patient started bortezomib while on hemodialysis and did not recover graft function, and another patient progressed to hemodialysis 6 months after receiving bortezomib. Although DSA did not completely resolve, there was a statistically significant decline in DSA MFI pre and 12-months post-BZ (p = .012, paired t-test) for the subjects who were not on dialysis at the time of bortezomib. Chronic Allograft Damage Index (CADI) score of ≥3 was seen in all six subjects at their biopsy prior to therapy. No adverse effects were reported. Bortezomib was well tolerated and resulted in improvements in MFI of DSA among four pediatric subjects without allograft failure, although no effects were observed on eGFR trajectory. Further studies are needed to clarify whether earlier intervention with bortezomib could prevent renal failure progression.

BK polyomavirus DNAemia, allograft rejection, and de novo donor-specific antibodies after lowering target tacrolimus levels in pediatric kidney transplant recipients.

BK polyomavirus (BKV) DNAemia is a challenging infectious complication after kidney transplant (KT). Reduction of immunosuppression is the mainstay of management, and tacrolimus is often the first immunosuppressive medication adjusted upon the diagnosis of BKV DNAemia. This study aimed to evaluate the impact of a new institutional protocol with lower target tacrolimus levels on BKV DNAemia, allograft rejection, and de novo donor-specific antibodies (dnDSA) among pediatric KT recipients. We conducted a retrospective chart review of all KT episodes between January 2013 and December 2018. The new protocol with lower target tacrolimus levels was implemented in March 2015. One hundred twenty-seven patients were included in primary analysis. All patients received induction with basiliximab and methylprednisolone and were maintained on a steroid-based immunosuppressive regimen. In the post-intervention cohort, cumulative incidence of BKV DNAemia at 100 days (13.4% vs. 17.8%, p = .605) and 18 months post-KT (34.1% vs. 26.7%, p = .504) was not significantly different from the pre-intervention cohort. Biopsy-proven rejection rate did not change. However, we observed a trend toward earlier development of dnDSA in the post-intervention cohort using the Kaplan-Meier survival analysis (log-rank p = .06). Younger recipient age at the time of transplant was found to slightly increase the risk of BKV DNAemia (OR: 1.09, 95% CI [1.01, 1.16], p = .024). There was an association between BKV DNAemia and biopsy-proven rejection of any type (adjustedOR: 2.77, 95% CI [1.26, 6.23], p = .012), especially acute T-cell-mediated rejection grade 1A and above (adjustedOR: 2.95, 95% CI [1.06, 8.30], p = .037), after adjusted for recipient age at the time of transplant. Targeting lower tacrolimus levels did not decrease the incidence of BKV DNAemia within 100 days or 18 months post-KT, nor did it increase the risk of biopsy-proven rejection among pediatric KT recipients in our center. However, there was a trend toward earlier development of dnDSA, which may portend worse long-term graft outcome post-KT. Our findings highlight the need for individualized immunosuppressive regimens based on immunologic and infectious risk factors and the importance of implementing innovative biomarkers to guide therapy and improve outcomes.

Association of HLA B- and T-cell molecular mismatches with HLA antibodies, rejection, and graft survival in pediatric kidney transplantation.

Optimizing graft survival and diminishing human leukocyte antigen (HLA) sensitization are essential for pediatric kidney transplant recipients. More precise HLA matching predicting epitope mismatches could reduce alloreactivity. We investigated the association of predicted HLA B- and T-cell molecular mismatches with the formation of de novo donor-specific antibodies, HLA antibodies, rejection, and graft survival. Forty-nine pediatric kidney transplant recipients transplanted from 2009 to 2020 were retrospectively studied. Donors and recipients were high-resolution HLA typed, and recipients were screened for HLA antibodies posttransplant. HLA-EMMA (HLA Epitope MisMatch Algorithm) and PIRCHE-II (Predicted Indirectly ReCognizable HLA Epitopes) predicted the molecular mismatches. The association of molecular mismatches and the end-points was explored with logistic regression. Five recipients (11%) developed de novo donor-specific antibodies. All five had de novo donor-specific antibodies against HLA class II, with four having HLA-DQ antibodies. We found no associations between PIRCHE-II or HLA-EMMA with de novo donor-specific antibodies, HLA sensitization, graft loss, or rejection. However, we did see a tendency towards an increased odds ratio in PIRCHE-II predicting de novo donor-specific antibodies formation, with an odds ratio of 1.12 (95% CI: 0.99; 1.28) on HLA class II. While the study revealed no significant associations between the number of molecular mismatches and outcomes, a notable trend was observed - indicating a reduced risk of dnDSA formation with improved molecular match. It is important to acknowledge, however, that the modest population size and limited observed outcomes preclude us from making definitive conclusions.

Belatacept based immunosuppression: What and when to combine?

IntroductionThis study examines the effect of belatacept based salvage regimens on kidney transplant outcomes. MethodsThis single-center retrospective study included all adult kidney transplant recipients between 2011 and 2022 who were converted to belatacept salvage therapy during their follow up. eGFR, graft survival, incidence of infections and neoplasia, histology and DSA data were collected through systematic review of the medical record. ResultsPatients were divided into 3 groups based on salvage regimen: Mycophenolate mofetil/belatacept (MMF/Bela) (n = 28), low-dose Calcineurin inhibitors/belatacept (CNI/Bela) (n = 22), and low-dose Calcineurin inhibitors/ Mycophenolate mofetil /belatacept (CNI/MMF/Bela) (n = 13). Patients with antibody-mediated rejection were more likely to receive CNIs in addition to belatacept (low-dose CNI/MMF/Bela 54%, low-dose CNI/Bela 45%, MMF/Bela 3.6%, p < 0.001). DSA decreased in all groups after transition to belatacept by 15.67% (p = 0.15). No difference in Glomerular filtration rate (eGFR) over time was observed between the groups, and eGFR remained stable over the first year after transition to belatacept. The incidence of death and allograft failure was similar between the groups (low- dose CNI/MMF/Bela n = 3, low-dose CNI/Bela n = 7, MMF/Bela n = 4; p = 0.41). Patients in the low-dose CNI/Bela cohort who were transitioned to belatacept within 6 months from transplant showed a decline in eGFR over the first year after transition, while the other treatment cohorts demonstrated stable or slight increase in eGFR. ConclusionsThe present study demonstrates comparable transplant outcomes in terms of eGFR, graft survival, incidence of infections and neoplasia, rejection rate and donor specific antibody (DSA) in three belatacept-based maintenance immunosuppression regimens supporting the safety and efficacy of these therapeutic options.

A Randomized Phase 2 Trial of Felzartamab in Antibody-Mediated Rejection

BackgroundAntibody-mediated rejection is a leading cause of kidney-transplant failure. The targeting of CD38 to inhibit graft injury caused by alloantibodies and natural killer (NK) cells may be a therapeutic option.MethodsIn this phase 2, double-blind, randomized, placebo-controlled trial, we assigned patients with antibody-mediated rejection that had occurred at least 180 days after transplantation to receive nine infusions of the CD38 monoclonal antibody felzartamab (at a dose of 16 mg per kilogram of body weight) or placebo for 6 months, followed by a 6-month observation period. The primary outcome was the safety and side-effect profile of felzartamab. Key secondary outcomes were renal-biopsy results at 24 and 52 weeks, donor-specific antibody levels, peripheral NK-cell counts, and donor-derived cell-free DNA levels.ResultsA total of 22 patients underwent randomization (11 to receive felzartamab and 11 to receive placebo). The median time from transplantation until trial inclusion was 9 years. Mild or moderate infusion reactions occurred in 8 patients in the felzartamab group. Serious adverse events occurred in 1 patient in the felzartamab group and in 4 patients in the placebo group; graft loss occurred in 1 patient in the placebo group. At week 24, resolution of morphologic antibody-mediated rejection was more frequent with felzartamab (in 9 of 11 patients [82%]) than with placebo (in 2 of 10 patients [20%]), for a difference of 62 percentage points (95% confidence interval [CI], 19 to 100) and a risk ratio of 0.23 (95% confidence interval [CI], 0.06 to 0.83). The median microvascular inflammation score was lower in the felzartamab group than in the placebo group (0 vs. 2.5), for a mean difference of −1.95 (95% CI, −2.97 to −0.92). Also lower was a molecular score reflecting the probability of antibody-mediated rejection (0.17 vs. 0.77) and the level of donor-derived cell-free DNA (0.31% vs. 0.82%). At week 52, the recurrence of antibody-mediated rejection was reported in 3 of 9 patients who had a response to felzartamab, with an increase in molecular activity and biomarker levels toward baseline levels.ConclusionsFelzartamab had acceptable safety and side-effect profiles in patients with antibody-mediated rejection. (Funded by MorphoSys and Human Immunology Biosciences; ClinicalTrials.gov number, NCT05021484; and EUDRACT number, 2021-000545-40.)

#3036 The influence of first renal graft on second graft rejection and survival: the importance of revisiting histocompatibility and clinical outcomes

Abstract Background and Aims Kidney retransplantation confers a robust survival benefit over dialysis and recent data has shown similar outcomes to first kidney transplant. The number of HLA mismatches is an important predictor of graft loss and sensitization and the presence of donor specific antibodies (DSA) -pre and -post transplant is a major risk factor for rejection and worst outcomes. However, the importance of HLA matching of first graft and the relevance of first donor DSAs on second graft outcomes is less known. Our aim was to identify risk factors to second graft acute rejection and graft loss, related to second and first graft features. Method We performed a retrospective, longitudinal study including all patients submitted to a 2nd kidney transplant between January 2008 and December 2021, excluding patients with more than 2 grafts or multi-organ transplant. Clinical and histocompatibility data from the first and second donor and recipient were collected. HLA antibodies were detected by solid phase assays and considered if MFI &amp;gt;2500. For subsequent kidney transplants, repeated mismatches are not allowed and unacceptable antigens are those for which the patient has pre-formed -A, -B and -DR antibodies, with MFI&amp;gt;1000. Biopsy proven acute rejection was defined according to Banff 2017 criteria. Follow-up was 31st December 2023 for functioning grafts or time to graft failure, with a mean time of 92 ± 53 months. Results We included 114 patients, 73 (64%) males, mostly Caucasians (96%), with a mean age of 43.9 ± 13 years at 2nd transplant. First kidney transplant was performed before 2010 for 99 patients (87%), with a median first graft survival of 82.5 [12.5-144] months and 19 patients (16.7%) presented primary disfunction due to surgical/vascular complications. After graft loss, 43 patients (37.7%) had their graft removed. For second transplant, 11 (9.6%) patients had a living donor. Induction therapy with thymoglobulin occurred in 94 patients (83%) and maintenance therapy with mycophenolic acid, calcineurin inhibitors and steroids was prescribed in 83 patients (73%). During follow-up, 20 patients (17.5%) presented biopsy proven acute rejection, 13 (65%) T cell mediated and 7 (35%) antibody-mediated, the majority during the first-year post-transplant (N = 17, 85%). The risk factors for second graft rejection are summarized in Table 1. Patients with a first graft nephrectomy had a higher risk of acute rejection (OR 3.9, 95% CI [1.4-10.9], p &amp;lt; 0.006) and were more susceptible to the development of second donor post-transplant DSA (58% vs 35%, p = 0.02). Death censored second allograft loss occurred in 24 patients (21%) at follow up and acute rejection was an important risk factors (OR 4.3, 95% CI [1.5-12.1], p = 0.004). First-year graft survival was 93% and a survival at follow up was 79%. On survival analysis the presence of second graft DSA was a major risk factor for graft loss, especially class 2 -DQ and -DR. First transplant total mismatch load, especially on class 1 contributed to worst graft survival. Conclusion Worst outcomes in first kidney transplant were related with an increased risk of acute rejection in second graft and 1st graft nephrectomy increases the risk of the development of 2nd graft DSA and acute rejection. First transplant mismatch load decreased second graft survival.