Antibody-mediated Rejection Research Articles

#2390 Does incompatible kidney transplantation provide a reliable alternative? An updated meta-analysis

Abstract Background and Aims The ABO system often poses one of the challenges to kidney transplantation, but due to the scarcity of organs, ABO incompatible kidney transplantation (ABOi-kTx) has gained the clinical attention. So, we aim in this study to evaluate the impact of ABO incompatible kidney transplantation on patients' clinical outcomes in comparison with ABO compatible kidney transplantation (ABOc-kTx). Method We searched six electronic databases: PubMed, Scopus, WOS, Cochrane, Embase, and Medline to identify relevant studies published until October 8th 2023, with no filters applied during the research process. After screening of 8562 studies, we included observational studies that compared any clinical outcomes of ABO incompatible kidney transplantation with ABO compatible kidney transplantation across various age groups. Synthesized odds ratios (ORs) with 95% confidence intervals (CIs) are used to present the differences between the two groups based on random-effects models. Results Our comprehensive search according to the eligible criteria of this study resulted in 102 studies including 254 496 patients in both groups. Due to the clinical heterogeneity, we used random effects models for quantitative synthesis of the eligible studies. Our meta-analysis showed that there was a statistically significant higher mortality ratio after one year, 3 years and 5 years (odds ratio [OR] 2.21 [95% CI 1.56–3.14], P < .00001; I² = 53%), (OR 1.86 [1.35–2.75], P = .0001; I² = 61%), (OR 1.69 [1.20–2.40], P = .003; I² = 75%), respectively. While there was no statistically significant difference at 8-years after transplantation (OR 1.05 [0.76–1.46], P = .77; I² = 58%). Pooled data of graft failure from our studies revealed higher incidence in ABOi-kTx group after one year (OR 2.44 [1.81–3.28], P < .00001; I² = 64%), 3 years (OR 1.57 [1.24–1.98], P < .00001; I² = 54%) and after 5 years (OR 1.57 [1.23–2.01], P = .0003; I² = 76%), There was not any statistically significant difference between both groups after 8 years. Acute anti-body mediated rejections were noticed to be statistically higher in ABOi-kTx group (OR 2.51 [2.12–2.97], (P < .00001); I² = 20%). Also, there was a significantly higher incidence of CMV infection in ABOi-kTx group (OR 1.27 [1.08–1.48], (P = .003); I² = 58%). Conclusion Although that ABOi-kTx is inferior to ABOc-kTx in the first 5 years after the transplantation in patient and graft mortality. Both groups are similar in both outcomes after 8 years post transplantation. Considering the higher incidence of acute rejection in the ABOi-kTx group and increased infection rate, desensitization techniques should be furtherly developed for better survival and complication outcomes.

#1492 Metabolic switch in CD8+ T cells may influence immune response in chronic antibody-mediated rejection (CAMR)

Abstract Background and Aims CAMR is the main cause of chronic graft injury and subsequent graft loss, but its pathogenesis is still largely unclear. Our group demonstrated an increase in CD8+ T cells infiltrating biopsies from CAMR patients (PMID: 20595199), but their role remains to be defined. Recently, immunometabolism has emerged as a field connecting cell energy metabolism with the immune cell differentiation and functions. Particularly, the permanent aerobic glycolysis of CD8+ lymphocytes induces their transition from naïve to activated state and effector T cells (PMID: 37315709). Thus, the aim of the study was to investigate the molecular mechanisms underlying the development of CAMR by the analysis of gene expression profiles of CD8+ T lymphocytes in conjunction with their metabolic state. Method We enrolled 14 patients with biopsy-proven CAMR and 12 stable transplant recipients with normal graft histology and function (control group). CD8+ T cells were purified by CD8 MicroBeads (Miltenyi Biotec) then counted (TC20™ Automated Cell Counter). Gene expression profiles of CD8+ T lymphocytes isolated from both groups were assessed using Agilent microarrays. Data obtained were statistically and functionally evaluated (IPA software) and validated by qPCR. Oxygen consumption rate (OCR) in CD8+ and CD8- cells was measured by a Resipher oxygen sensing lid (Lucid Scientific Inc., USA). The contribution of mitochondrial respiration to OCR was investigated in isolated CD8+ T cells from CAMR and controls treated with rotenone/antimycin A (Rot/AA), oligomycin (Olygo) or carbonyl cyanide-p-trifluoromethoxyphenylhydrazone (FCCP) to evaluate spare respiratory capacity (SRC), ATP-linked respiration, proton leak and maximal respiration. Results Gene expression profiles of CD8+ T cells showed a characteristic alteration of lipid metabolism in CAMR patients with the triglyceride biosynthesis pathway (p = 2.69E-3) as the most altered pathway and several genes de-regulated all potentially involved in the altered metabolic state of CD8+ T cells. Among others, we validated the increased expression of Nicotinamide Phosphoribosyltransferase (NAMPT) (FC = +2.39), the rate-limiting enzyme of nicotinamide adenine dinucleotide (NAD+) salvage pathway involved in the glycolysis progression, mostly activated in effector T cells. We then decided to evaluate the OCR and the metabolic state of CD8+T cells. Basal OCR was higher in CD8+ rather than CD8- cells, but with different trends among cells isolated from control and CAMR patients. Indeed, CD8+ cells from CAMR patients showed higher OCR compared to control, while OCR was lower in CD8- from CAMR rather than control patients. CD8+ OCR from both CAMR and control patients was mostly dependent on mitochondrial respiration, since it was deeply reduced by Rot/AA treatment. Interestingly, inhibitory response to Oligo treatment by CD8+ cells from CAMR patients was modest, while OCR was noticeably stimulated by FCCP in these cells, suggesting that mitochondrial oxygen uptake was not ATP linked but rather associated with increased uncoupling. These data suggest that CD8+ T cells from CAMR patients are activated effector T cells primarily utilizing aerobic glycolysis. To confirm this hypothesis, we evaluated the gene expression levels of: i) HIF1a, which involves permanent dependence on glycolysis even in the presence of oxygen (Warburg effect); ii) fatty acid transporter CD36, whose levels mimic an energy dependence on the beta oxidation of fatty acids, a process activated in memory T cells. We confirmed an increased expression of HIF1a and a reduced expression of CD36 in CD8+T cells from CAMR patients compared to controls (p<0.05), that confirm the T effector phenotype. Conclusion Our data suggest that CD8+ T cell from CAMR patients showed permanent dependency on glycolysis leading to altered immune phenotype and response, thus indicating novel opportunities to modulate the immune system for therapeutic purposes in kidney transplanted patients and reduce graft rejection.

#681 Bw4/6 mismatch or missing donor Bw6 allele is a risk of early acute rejection in panel reactive antibodies negative kidney transplant recipients

Abstract Background and Aims Epitope and antibody diversity allows Bw4+ or Bw6+ patients to produce antibodies to Bw4 or Bw6 epitopes without breaking self-tolerance. This study assessed the prevalence of mismatched Bw4/6 or missing donor Bw6 allele in kidney transplant (KT) recipients with early acute rejection and its relation to patients and graft outcomes. Method A retrospective study included 40 live-related KT recipients divided into 2 equal groups. Group A: 20 KT recipients with early acute rejection in 1st 3 months post-KT and group B: 20 KT recipients with no rejection. Bw4/6 mismatches or missing donor Bw6 were examined in all patients with an assessment of the type of rejection, patients, and graft outcomes. Results The prevalence of Bw4/6 mismatch or missing donor Bw6 allele in patients with early acute rejection was 70% (14 patients). Bw4/6 mismatch represented 25% (5 patients) while missing donor Bw6 allele was 45% (9 patients) while the prevalence of Bw4/6 mismatch or missing donor in patients with no rejection was 10% (2 patients) with significant p-value (0.0001). The analysis of demographic data of Bw4/6 mismatch or missing donor Bw6 allele in patients with rejection (N=14) (Fig. 1); mean age was 27.92 years, 71.4% were males (10 patients), panel reactive antibodies (PRA) was positive in 7.1% (1 patient), Donor specific antibodies (DSA) and complement-dependent cytotoxicity (CDC) cross-match were negative in all patients. The most common type of rejection in these patients was acute antibody-mediated rejection (ABMR) 71.4% (10 patients). Patients and graft outcomes; mean serum creatinine after treatment of rejection was 2.16 mg/dl, mortality was 14.3% (2 patients) with graft loss, and survival with functioning graft was 85.7% (12 patients). Conclusion Bw4/6 mismatch or missing donor Bw6 allele is a risk of early acute rejection in PRA-negative kidney transplant recipients and is linked to negative patients and graft outcomes.

#1985 Tocilizumab in chronic active antibody-mediated rejection: a randomized controlled open-label multi-center trial (INTERCEPT study)

Abstract Background and Aims Chronic active antibody mediated graft rejection (caAMR) caused by immune-mediated injury is the leading cause of long-term graft loss in kidney transplant recipients. Nevertheless, no effective treatment exists for caAMR to date, highlighting a great unmet need for evaluation of novel treatment options. Recently, tocilizumab (TCZ), a monoclonal antibody directed against the human interleukin-6 (IL-6) receptor, by antagonizing IL-6-triggered inflammation and B cell/plasma cell-driven immune activation, has shown promise in the treatment of caAMR. However, TCZ has not been assessed systematically in a randomized study. The INTERCEPT study aims to evaluate the efficacy of addition of TCZ to standard of treatment (SOC) as compared to SOC alone in reducing the decline of graft function from baseline at 24 months after start of treatment as assessed by estimated glomerular filtration rate (eGFR) in kidney transplant recipients with caAMR. Method This ongoing randomized controlled open-label multi-center investigator-initiated trial plans to include a total of 50 adult kidney transplant recipients with biopsy-proven caAMR using Banff 2019 criteria at least 12 months after transplantation and eGFR ≥20 ml/min/1.73 m2. Any subject who underwent kidney transplantation in Sweden or is currently living in Sweden and being followed up at any of the Swedish transplant centers or their affiliated regional centers can be considered for participation. Participants are randomized to receive either TCZ (n=25) added to our standard of care (SOC) maintenance treatment or SOC alone (n=25) for a period of 24 months and followed for additional 12 months after cessation of the study medication. After the inclusion transplant biopsy at baseline, protocol biopsies are performed at 12 and 24 months. The study design flow-chart is shown in the Figure. The primary endpoint is the slope of eGFR at 24 months after start of treatment. The eGFR is assessed using Modification of Diet in Renal Disease (MDRD) formula. 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, patient-reported outcomes that include transplant-specific well-being, adherence to immunosuppressive medications and perceived threat of the risk of graft rejection. Results We expect that addition of TCZ to SOC will slow down the decline of graft function in kidney transplant recipients with caAMR. Conclusion Currently there is no effective treatment for caAMR. Based on the hypothesis that inhibition of IL-6 by TCZ 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. If TCZ is found to be effective, our study has the potential to improve long-term graft survival and quality of life, reduce morbidity and mortality in kidney transplant patients as well as lower the health care costs.

#2581 Cryptococcosis in kidney transplant recipients: a nationwide multicenter retrospective cohort study—CRITERE study

Abstract Background and Aims Cryptococcosis stands as the third most common invasive fungal infection in solid organ transplant recipients. Clinical management and prognosis of the disease remains largely unexplored in the context of kidney transplant recipients. Our main objective was to describe the natural history of cryptococcosis after kidney transplantation from the graft patterns of kidney injury to the long term outcomes. Method We established a nationwide cohort of adult kidney transplant recipients diagnosed with cryptococcosis between 2002 and 2019 in France. All data were gathered starting from the transplantation date and encompassed up to the latest follow-up consultation. All putative causes of AKI as claimed by the attending clinicians were recorded. Cases were matched (ratio 1:6) with kidney transplant recipients from the French prospective multicenter cohort DIVAT with parameters at time of transplant including immunosuppression and known risk factors of cryptococcosis such as age, history of smoke, history of cancer and HIV status. Transplant outcomes (graft failure and patient death) were then compared between matched patients. Results 88 patients were included. Patients were predominantly male (n = 61, 69.3%), with a mean age of 57.0 years [SD ±13.3]. The majority of patients were primary kidney transplants (n = 71, 80.7%) with a median time from ESRD to transplantation of 2.8 years [IQ 1.25-5]. The majority of patients received ATG as induction therapy for their transplant (n = 50, 69.4%)Acute kidney injury (AKI) at diagnosis involved 37.3% of the patients with 13.3% requiring renal replacement therapy. AKI staging was distributed as follows, AKI grade 1 in 12.5% of patients, grade 2 in 13.3% of patients, and grade 3 in 11.5% of patients. During the induction stage, 39% of patients developed amphotericin B-related AKI. AKI resulting from tacrolimus overdose subsequent to tacrolimus/fluconazole interaction occurred in 25.7% of patients during the consolidation stage. Among the patients alive at 3 months following the diagnosis of cryptococcosis, 33.7% of patients exhibited graft dysfunction. Following cryptococcosis, 5 patients displayed T cell rejection and 4 patients developed antibody-mediated rejection. A total of 41 patients with cryptococcosis were matched to 246 controls (ratio 1:6), after a median follow-up of 52.3 [28.1-90.2] months, patients with cryptococcosis exhibited a higher risk of mortality with 35.9% compared with 9.8% (p < 0.001) and graft failure with 33.3% compared with 15.0% (p = 0.0005). Conclusion This study has shown that kidney injury manifests itself through a sequential, multi-step process that initially includes pre-renal impairment, ATN and iatrogenic mechanisms. Amphotericin B-related AKI, followed by tacrolimus overdose represent common causes of AKI.

Outcome-based Risk Assessment of Non-HLA Antibodies in Heart Transplantation: A Systematic Review

Current monitoring after heart transplantation (HT) employs repeated invasive endomyocardial biopsies (EMB). Although positive EMB confirms rejection, EMB fails to predict impending, subclinical, or EMB-negative rejection events. While non-human leukocyte antigen (non-HLA) antibodies have emerged as important risk factors for antibody-mediated rejection after HT, their use in clinical risk stratification has been limited. A systematic review of the role of non-HLA antibodies in rejection pathologies has the potential to guide efforts to overcome deficiencies of EMB in rejection monitoring. Databases were searched to include studies on non-HLA antibodies in HT recipients. Data collected included the number of patients, type of rejection, non-HLA antigen studied, association of non-HLA antibodies with rejection, and evidence for synergistic interaction between non-HLA antibodies and donor-specific anti-human leukocyte antigen antibody (HLA-DSA) responses. A total of 56 studies met the inclusion criteria. Strength of evidence for each non-HLA antibody was evaluated based on the number of articles and patients in support versus against their role in mediating rejection. Importantly, despite previous intense focus on the role of anti-major histocompatibility complex class I chain-related gene A (MICA) and anti-angiotensin II type I receptor antibodies (AT1R) in HT rejection, evidence for their involvement was equivocal. Conversely, the strength of evidence for other non-HLA antibodies supports that differing rejection pathologies are driven by differing non-HLA antibodies. This systematic review underscores the importance of identifying peri-HT non-HLA antibodies. Current evidence supports the role of non-HLA antibodies in all forms of HT rejection. Further investigations are required to define the mechanisms of action of non-HLA antibodies in HT rejection.

NAVIGATING THE UNCHARTED WATERS: MANAGING CONCURRENT CYTOMEGALOVIRUS MYOCARDITIS AND ALLOGRAFT REJECTION IN A PATIENT WITH HEART TRANSPLANTATION

Abstract A 49–year–old female with hypertrophic cardiomyopathy underwent orthotopic heart transplantation. She was cytomegalovirus(CMV)–positive and received a heart from a CMV–negative donor, so prophylaptic therapy was not administered. Initial immunosuppression included cyclosporine and induction with Basiliximab in a steroid–free regimen. The first routine biopsy (EMB) showed mild focal cellular rejection (grade 1A) and C4d positivity with granular aspect. Mycophenolate mofetil (MMF) was added. The second EMB, 7 days later, showed mild diffuse cellular rejection (grade 1B) and diffuse C4d positivity. Anti–HLA donor–specific antibodies (DSA) had increased anti–B13 levels (MFI=21298) compared to pre–transplantation tests. Echocardiography showed a normal ejection fraction (LVEF) and mild concentric hypertrophy (LVH). Treatment included pulse methylprednisolone therapy (1 g/day for three days) followed by oral prednisone with a slow tapering regimen, and increased MMF. CMV count weekly monitored was negative. The next two EMBs performed one week apart from each other described a grade 1A mild focal pattern while the 5th EMB (1 month and 2 weeks post–transplant) showed a grade 1A rejection together with focal mild fibrosis and eosinophils, so we replaced cyclosporine with tacrolimus, increased MMF and prednisone. At this time, the patient had no overt clinical signs of CMV infection but a CMV–PCR of 100847 IU/mL so ganciclovir 5 mg/Kg bid was started and CMV–PCR decreased to 42308 IU/mL after 1 week. Subsequently, she developed sinus tachycardia, mildly reduced LVEF, moderate LVH and diastolic dysfunction. Troponin was elevated. A new EMB revealed interstitial edema, diffuse ischemic injury, and eosinophilic inclusions suggesting CMV myocarditis. Treatment involved down–titrating MMF and Prednisone, administering standard intravenous immunoglobulin (IVIG), and high–dose Ganciclovir (7.5 mg/Kg bid). Leukopenia subsequently led to Ganciclovir down–titration. In the next days, the patient improved, CMV cleared, and leukocyte count normalized. She was discharged on Tacrolimus, MMF, Prednisone and Valganciclovir. Subsequent tests showed no cellular or antibody–mediated rejection (AMR), no CMV inclusions, recovered cardiac function, and markedly reduced anti–B13 DSA (MFI 3000). This case raises some concerns: in this context, the use of IVIG in the treatment of CMV infection and AMR appears reasonable, in support of antiviral and immunosuppressive therapy.

Impact of donor-specific antibody with low mean fluorescence intensity on allograft outcomes in kidney transplant

BackgroundImmune-mediated rejection is the most common cause of allograft failure in kidney transplant (KT) patients. Exposure to alloantigen, including human leukocyte antigen (HLA), results in the production of donor-specific antibodies (DSA). There are limited data about low levels of mean fluorescence intensity (MFI) DSA, especially post-transplantation. This study evaluated allograft outcomes in KT patients with low MFI DSA. MethodsFrom January 2007 to December 2021, KT patients who were tested for post-transplant DSA at Ramathibodi Hospital, Bangkok, Thailand, with the DSA MFI ≤ 1000 were evaluated. These KT patients were categorized into two groups: very low DSA (VLL; MFI = 1–500) and low DSA (LL; MFI = 501–1000). All KT patients were evaluated for the primary outcomes, such as the incidence of acute rejection, serum creatinine levels at one and five years after transplantation as well as allograft and patient survivals. ResultsAmong 36 KT patients 25 were included as those with VLL and 11 as those with LL. The LL group had significantly higher T-cell mediated allograft rejection (TCMR) than the VLL group (45% vs. 12%, P = 0.04). In addition, 10 patients, 5 in the VLL group and 5 in the LL group developed antibody-mediated allograft rejection (ABMR). Both TCMR and ABMR were confirmed by biopsy results. There was a trend toward higher MFI in KT patients with ABMR than without ABMR (P = 0.22). At 5 post-transplant years, serum creatinine, allograft and patient survivals were comparable between these two groups. Furthermore, the univariate and multivariate analyzes revealed that the LL group was a high risk for rejection. ConclusionLow MFI DSA values after transplantation may be associated with a higher incidence of rejection, but this finding did not show differences in allograft and patient survival in this study's analysis.

Sequential administration of anti-complement component C5 eculizumab and type-2 anti-CD20 obinutuzumab for the treatment of early antibody-mediated rejection after kidney transplantation: A proof of concept

Kidney transplant (KT) candidates with donor-specific antibodies (DSA) exhibit exceedingly high antibody-mediated rejection (ABMR) and allograft loss rates. Currently, treatment of ABMR remains an unmet clinical need. We report the use of the anti-C5 eculizumab and the type-2 anti-CD20 obinutuzumab in two patients with early ABMR. Eculizumab (900 mg IV) led to complete inhibition of the terminal complement cascade (unremarkable AP50 and CH50 activity) and prompt stoppage of complement-dependent antibody-mediated allograft injury (clearance of intra-graft C4d and C5b-9 deposition). Despite complement inhibition, obinutuzumab (1000 mg IV) determined full and long-lasting peripheral B-cell depletion, with significant reduction in all DSA. Graft function improved, remaining stable up to three years of follow-up. No signs of active ABMR and rebound DSA were detected. Obinutuzumab B-cell depletion and inhibition of DSA production were not affected by complement blockage. Further studies are needed to confirm the potential benefit of obinutuzumab in association with complement inhibitors.

Impact of Transient and Persistent Donor-Specific Antibodies in Lung Transplantation.

Lung transplantation (LuTx) is an established treatment for patients with end-stage lung diseases, however, outcomes are limited by acute and chronic rejection. One aspect that has received increasing attention is the role of the host's humoral alloresponse, particularly the formation of de novo donor-specific antibodies (dnDSAs). The aim of this study was to investigate the clinical significance of transient and persistent dnDSAs and to understand their impact on outcomes after LuTx. A retrospective analysis was conducted using DSA screening data from LuTx recipients obtained at the Medical University of Vienna between February 2016 and March 2021. Of the 405 LuTx recipients analyzed, 205 patients developed dnDSA during the follow-up period. Among these, 167 (81%) had transient dnDSA and 38 (19%) persistent dnDSA. Persistent but not transient dnDSAs were associated with chronic lung allograft dysfunction (CLAD) and antibody-mediated rejection (AMR) (p < 0.001 and p = 0.006, respectively). CLAD-free survival rates for persistent dnDSAs at 1-, 3-, and 5-year post-transplantation were significantly lower than for transient dnDSAs (89%, 59%, 56% vs. 91%, 79%, 77%; p = 0.004). Temporal dynamics of dnDSAs after LuTx have a substantial effect on patient outcomes. This study underlines that the persistence of dnDSAs poses a significant risk to graft and patient survival.

LAG3 regulates antibody responses following kidney transplantation

Abstract Lymphocyte activation gene-3 (LAG3) is a coinhibitory receptor expressed by a range of immune cells. The immunomodulatory potential of LAG3 is being explored in cancer and autoimmunity fields but not in transplantation. Using our mouse kidney transplant models we sought to address the role of LAG3 in graft rejection. Untransplanted LAG3-/- mice have elevated heterologous immunity against a panel of alloantigens. Recipient LAG3 deficiency results in rapid rejection of MHC-mismatched renal allografts that are spontaneously accepted by WT recipients, with graft histology characteristic of antibody mediated rejection (ABMR). Antagonistic LAG3 antibody treatment of WT recipients enhanced anti-donor immune responses and induced kidney damage typical of chronic rejection, indicating that LAG3 regulates de novo alloresponses. Recipient B cell depletion, but not CD8+ T cells, prevented kidney allograft rejection in LAG3-/- recipients further supporting ABMR as the mechanism of graft loss. Posttransplant, follicular T cells and plasma cells are among LAG3 expressing immune cells. To identify the mechanism we used T or B cell conditional LAG3 knockout recipients, neither reject the allograft but both had elevated levels of donor specific antibodies (DSA), indicating LAG3 expression on either T or B cells is sufficient to regulate anti-donor humoral immunity. Our results identify LAG3 as a regulator of DSA following kidney transplantation and a potential therapeutic target for ABMR.

Association of BKV viremia and nephropathy with adverse alloimmune outcomes in kidney transplant recipients.

Immunosuppression reduction for BK polyoma virus (BKV) must be balanced against risk of adverse alloimmune outcomes. We sought to characterize risk of alloimmune events after BKV within context of HLA-DR/DQ molecular mismatch (mMM) risk score. This single-center study evaluated 460 kidney transplant patients on tacrolimus-mycophenolate-prednisone from 2010-2021. BKV status was classified at 6-months post-transplant as "BKV" or "no BKV" in landmark analysis. Primary outcome was T-cell mediated rejection (TCMR). Secondary outcomes included all-cause graft failure (ACGF), death-censored graft failure (DCGF), de novo donor specific antibody (dnDSA), and antibody-mediated rejection (ABMR). Predictors of outcomes were assessed in Cox proportional hazards models including BKV status and alloimmune risk defined by recipient age and molecular mismatch (RAMM) groups. At 6-months post-transplant, 72 patients had BKV and 388 had no BKV. TCMR occurred in 86 recipients, including 27.8% with BKV and 17% with no BKV (p=.05). TCMR risk was increased in recipients with BKV (HR 1.90, (95% CI 1.14, 3.17); p=.01) and high vs. low-risk RAMM group risk (HR 2.26 (95% CI 1.02, 4.98); p=.02) in multivariable analyses; but not HLA serological MM in sensitivity analysis. Recipients with BKV experienced increased dnDSA in univariable analysis, and there was no association with ABMR, DCGF, or ACGF. Recipients with BKV had increased risk of TCMR independent of induction immunosuppression and conventional alloimmune risk measures. Recipients with high-risk RAMM experienced increased TCMR risk. Future studies on optimizing immunosuppression for BKV should explore nuanced risk stratification and may consider novel measures of alloimmune risk.

Anti‐pig antibodies in swine veterinarian serum: Implications for clinical xenotransplantation

AbstractRecent clinical xenotransplantation and human decedent studies demonstrate that clinical hyperacute rejection of genetically engineered porcine organs can be reliably avoided but that antibody mediated rejection (AMR) continues to limit graft survival. We previously identified porcine glycans and proteins which are immunogenic after cardiac xenotransplantation in non‐human primates, but the clinical immune response to antigens present in glycan depleted triple knockout (TKO) donor pigs is poorly understood. In this study we use fluorescence barcoded human embryonic kidney cells (HEK) and HEK cell lines expressing porcine glycans (Gal and SDa) or proteins (tetraspanin‐29 [CD9], membrane cofactor protein [CD46], protectin, membrane attack complex inhibition factor [CD59], endothelial cell protein C receptor, and Annexin A2) to screen antibody reactivity in human serum from 160 swine veterinarians, a serum source with potential occupational immune challenge from porcine tissues and pathogens. High levels of anti‐Gal IgM were present in all samples and lower levels of anti‐SDa IgM were present in 41% of samples. IgM binding to porcine proteins, primarily CD9 and CD46, previously identified as immunogenic in pig to non‐human primate cardiac xenograft recipients, was detected in 28 of the 160 swine veterinarian samples. These results suggest that barcoded HEK cell lines expressing porcine protein antigens can be useful for screening human patient serum. A comprehensive analysis of sera from clinical xenotransplant recipients to define a panel of commonly immunogenic porcine antigens will likely be necessary to establish an array of porcine non‐Gal antigens for effective monitoring of patient immune responses and allow earlier therapies to reverse AMR.

Late graft failure of pig-to-rhesus renal xenografts has features of glomerulopathy and recipients have anti-swine leukocyte antigen class I and class II antibodies.

Prolonged survival in preclinical renal xenotransplantation demonstrates that early antibody mediated rejection (AMR) can be overcome. It is now critical to evaluate and understand the pathobiology of late graft failure and devise new means to improve post xenograft outcomes. In renal allotransplantation the most common cause of late renal graft failure is transplant glomerulopathy-largely due to anti-donor MHC antibodies, particularly anti-HLA DQ antibodies. We evaluated the pig renal xenograft pathology of four long-surviving (>300 days) rhesus monkeys. We also evaluated the terminal serum for the presence of anti-SLA class I and specifically anti-SLA DQ antibodies. All four recipients had transplant glomerulopathy and expressed anti-SLA DQ antibodies. In one recipient tested for anti-SLA I antibodies, the recipient had antibodies specifically reacting with two of three SLA I alleles tested. These results suggest that similar to allotransplantation, anti-MHC antibodies, particularly anti-SLA DQ, may be a barrier to improved long-term xenograft outcomes.

Hepatitis C viremic lung transplantation to aviremic recipients: Comprehensive outcomes and post-transplant viremia.

Direct-acting antiviral (DAA) therapy has revolutionized solid organ transplantation by providing an opportunity to utilize organs from HCV-viremic donors. Though transplantation of HCV-viremic donor organs into aviremic recipients is safe in the short term, midterm data on survival and post-transplant complications is lacking. We provide a midterm assessment of complications of lung transplantation (LT) up to 2 years post-transplant, including patient and graft survival between HCV-viremic transplantation (D+) and HCV-aviremic transplantation (D-). This is a retrospective cohort study including 500 patients from 2018 to 2022 who underwent LT at our quaternary care institution. Outcomes of patients receiving D+ grafts were compared to those receiving D- grafts. Recipients of HCV antibody+ but PCR- grafts were treated as D- recipients. We identified 470 D- and 30 D+ patients meeting inclusion criteria. Crude mortality did not differ between groups (p=.43). Patient survival at years 1 and 2 did not differ between D+ and D- patients (p=.89, p=.87, respectively), and graft survival at years 1 and 2 did not differ between the two groups (p=.90, p=.88, respectively). No extrahepatic manifestations or fibrosing cholestatic hepatitis (FCH) occurred among D+ recipients. D+ and D- patients had similar rates of post-transplant chronic lung allograft rejection (CLAD) (p=6.7%vs. 12.8%, p=.3), acute cellular rejection (60.0%vs. 58.0%, p=.8) and antibody-mediated rejection (16.7%vs. 14.2%, p=.7). There is no difference in midterm patient or graft survival between D+ and D-LT. No extrahepatic manifestations of HCV occurred. No differences in any type of rejection including CLAD were observed, though follow-up for CLAD was limited. These results provide additional support for the use of HCV-viremic organs in selected recipients in LT.

The role of interleukin 27 in donor specific alloantibody responses

Abstract There is a great clinical need for new approaches inhibiting pathogenic donor specific alloantibodies (DSA) and antibody-mediated rejection (AMR) in transplantation. Targeting interleukin-6 (IL-6) showed modest promise for AMR treatment. Interleukin-27 (IL-27) also belongs to IL-6 cytokine family, utilizes the same receptor signaling chain, gp130, and has many overlapping functions with IL-6. The current study tested the role of IL-27 in humoral immune responses using mouse transplant models. First, B6.WT and B6.IL-27R-/- recipients (H-2b) were transplanted with BALB/c heart allografts (H-2d). By d. 21 posttransplant, B6.WT recipients developed serum DSA against donor class I and class II MHC. In contrast, DSA responses were markedly reduced in B6.IL-27R-/- recipients. We next tested how IL-27 neutralization affects DSA using mAbs against p28 IL-27 subunit. B6.WT recipients transplanted with BALB/c skin allografts and treated with mAb against either p28, IL-6, or IL-6R or control IgG for the first two weeks posttransplant. While control recipients developed anti-H-Dd DSA, none of anti-p28 mAb treated recipients generated DSA, comparable to the effects of anti-IL-6 or anti-IL-6R therapies. Anti-IL-27 mAb resulted in a more profound decrease in the numbers of antibody secreting spleen plasma cells compared to anti-IL6 and anti-IL-6R treatments. Our data identify IL-27 as a novel therapeutic target to inhibit pathogenic DSA responses in transplant recipients.

Integrative multi-omics profiling in human decedents receiving pig heart xenografts.

In a previous study, heart xenografts from 10-gene-edited pigs transplanted into two human decedents did not show evidence of acute-onset cellular- or antibody-mediated rejection. Here, to better understand the detailed molecular landscape following xenotransplantation, we carried out bulk and single-cell transcriptomics, lipidomics, proteomics and metabolomics on blood samples obtained from the transplanted decedents every 6 h, as well as histological and transcriptomic tissue profiling. We observed substantial early immune responses in peripheral blood mononuclear cells and xenograft tissue obtained from decedent 1 (male), associated with downstream T cell and natural killer cell activity. Longitudinal analyses indicated the presence of ischemia reperfusion injury, exacerbated by inadequate immunosuppression of T cells, consistent with previous findings of perioperative cardiac xenograft dysfunction in pig-to-nonhuman primate studies. Moreover, at 42 h after transplantation, substantial alterations in cellular metabolism and liver-damage pathways occurred, correlating with profound organ-wide physiological dysfunction. By contrast, relatively minor changes in RNA, protein, lipid and metabolism profiles were observed in decedent 2 (female) as compared to decedent 1. Overall, these multi-omics analyses delineate distinct responses to cardiac xenotransplantation in the two human decedents and reveal new insights into early molecular and immune responses after xenotransplantation. These findings may aid in the development of targeted therapeutic approaches to limit ischemia reperfusion injury-related phenotypes and improve outcomes.

Cellular dynamics in pig-to-human kidney xenotransplantation

Xenotransplantation of genetically engineered porcine organs has the potential to address the challenge of organ donor shortage. Two cases of porcine-to-human kidney xenotransplantation were performed, yet the physiological effects on the xenografts and the recipients' immune responses remain largely uncharacterized. We performed single-cell RNA sequencing (scRNA-seq) and longitudinal RNA-seq analyses of the porcine kidneys to dissect xenotransplantation-associated cellular dynamics and xenograft-recipient interactions. We additionally performed longitudinal scRNA-seq of the peripheral blood mononuclear cells (PBMCs) to detect recipient immune responses across time. Although no hyperacute rejection signals were detected, scRNA-seq analyses of the xenografts found evidence of endothelial cell and immune response activation, indicating early signs of antibody-mediated rejection. Tracing the cells' species origin, we found human immune cell infiltration in both xenografts. Human transcripts in the longitudinal bulk RNA-seq revealed that human immune cell infiltration and the activation of interferon-gamma-induced chemokine expression occurred by 12 and 48h post-xenotransplantation, respectively. Concordantly, longitudinal scRNA-seq of PBMCs also revealed two phases of the recipients' immune responses at 12 and 48-53 h. Lastly, we observed global expression signatures of xenotransplantation-associated kidney tissue damage in the xenografts. Surprisingly, we detected a rapid increase of proliferative cells in both xenografts, indicating the activation of the porcine tissue repair program. Longitudinal and single-cell transcriptomic analyses of porcine kidneys and the recipient's PBMCs revealed time-resolved cellular dynamics of xenograft-recipient interactions during xenotransplantation. These cues can be leveraged for designing gene edits and immunosuppression regimens to optimize xenotransplantation outcomes. This work was supported by NIH RM1HG009491 and DP5OD033430.

Antibody-Mediated Rejection: Mechanisms, Pathology, and Therapeutics

Antibody-Mediated Rejection: Mechanisms, Pathology, and Therapeutics

Mesenchymal Stem Cells and Extracellular Vesicles: Therapeutic Potential in Organ Transplantation.

At present, organ transplantation remains the most appropriate therapy for patients with end-stage organ failure. However, the field of organ transplantation is still facing many challenges, including the shortage of organ donors, graft function damage caused by organ metastasis, and antibody-mediated immune rejection. It is therefore urgently necessary to find new and effective treatment. Stem cell therapy has been regarded as a "regenerative medicine technology." Mesenchymal stem cells (MSCs), as the most common source of cells for stem cell therapy, play an important role in regulating innate and adaptive immune responses and have been widely used in clinical trials for the treatment of autoimmune and inflammatory diseases. Increasing evidence has shown that MSCs mainly rely on paracrine pathways to exert immunomodulatory functions. In addition, mesenchymal stem cell-derived extracellular vesicles (MSC-EVs) are the main components of paracrine substances of MSCs. Herein, an overview of the application of the function of MSCs and MSC-EVs in organ transplantation will focus on the progress reported in recent experimental and clinical findings and explore their uses for graft preconditioning and recipient immune tolerance regulation. Additionally, the limitations on the use of MSC and MSC-EVs are also discussed, covering the isolation of exosomes and preservation techniques. Finally, the opportunities and challenges for translating MSCs and MSC-EVs into clinical practice of organ transplantation are also evaluated.