Donor-specific Antibody Monitoring Research Articles

The Clinical Utility of Post-Transplant Monitoring of Donor-Specific Antibodies in Stable Renal Transplant Recipients: A Consensus Report With Guideline Statements for Clinical Practice.

Solid phase immunoassays improved the detection and determination of the antigen-specificity of donor-specific antibodies (DSA) to human leukocyte antigens (HLA). The widespread use of SPI in kidney transplantation also introduced new clinical dilemmas, such as whether patients should be monitored for DSA pre- or post-transplantation. Pretransplant screening through SPI has become standard practice and DSA are readily determined in case of suspected rejection. However, DSA monitoring in recipients with stable graft function has not been universally established as standard of care. This may be related to uncertainty regarding the clinical utility of DSA monitoring as a screening tool. This consensus report aims to appraise the clinical utility of DSA monitoring in recipients without overt signs of graft dysfunction, using the Wilson & Junger criteria for assessing the validity of a screening practice. To assess the evidence on DSA monitoring, the European Society for Organ Transplantation (ESOT) convened a dedicated workgroup, comprised of experts in transplantation nephrology and immunology, to review relevant literature. Guidelines and statements were developed during a consensus conference by Delphi methodology that took place in person in November 2022 in Prague. The findings and recommendations of the workgroup on subclinical DSA monitoring are presented in this article.

Routine Donor-Specific Antibody Monitoring in Heart Transplant Recipients: Is There a Role?

Routine Donor-Specific Antibody Monitoring in Heart Transplant Recipients: Is There a Role?

(997) Routine Donor Specific Antibody Monitoring in Heart Transplant Recipients - Is There a Role?

(997) Routine Donor Specific Antibody Monitoring in Heart Transplant Recipients - Is There a Role?

Donor specific antibody surveillance among pediatric kidney transplant programs: A report from the improving renal outcome collaborative.

Kidney transplantation (KT) is the preferred treatment for children with end-stage kidney disease. Recent advances in immunosuppression and advances in donor specific antibody (DSA) testing have resulted in prolonged allograft survival; however, standardized approaches for surveillance DSA monitoring and management of de novo (dn) DSA are widely variable among pediatric KT programs. Pediatric transplant nephrologists in the multi-center Improving Renal Outcomes Collaborative (IROC) participated in a voluntary, web-based survey between 2019 and 2020. Centers provided information pertaining to frequency and timing of routine DSA surveillance and theoretical management of dnDSA development in the setting of stable graft function. 29/30 IROC centers responded to the survey. Among the participating centers, screening for DSA occurs, on average, every 3 months for the first 12months post-transplant. Antibody mean fluorescent intensity and trend most frequently directed changes in patient management. Increased creatinine above baseline was reported by all centers as an indication for DSA assessment outside of routine surveillance testing. 24/29 centers would continue to monitor DSA and/or intensify immunosuppression after detection of antibodies in the setting of stable graft function. In addition to enhanced monitoring, 10/29 centers reported performing an allograft biopsy upon detection of dnDSA, even in the setting of stable graft function. This descriptive report is the largest reported survey of pediatric transplant nephrologist practice patterns on this topic and provides a reference for monitoring dnDSA in the pediatric kidney transplant population.

Role of therapeutic plasma exchange as a desensitization therapy in human leukocyte antigen incompatible renal transplant patients: A single-center experience

ObjectiveDespite an increase in the rate of successful live donor renal transplantation done annually, the number of potential recipients with acceptable donors is relegated to the ever-expanding cadaver-donor waiting list due to sensitization to human leukocyte antigen (HLA) antibodies. If not sufficiently suppressed, these preformed HLA antibodies can trigger antimicrobial resistance (AMR) and early graft loss. To ameliorate this situation, various desensitization treatments are administered to provide a survival benefit to highly sensitized patients. MethodOne hundred and six patients in the time frame of January 2017 to March 2019 were included in the study group. The desensitization protocol included therapeutic plasma exchange and administration of low-dose intravenous immunoglobulin (100 mg/kg per therapeutic plasma exchange (TPE) session) to highly sensitized patients (treatment group) who subsequently underwent renal transplantation after negative pre-transplant Centers for Disease Control and Prevention Luminex crossmatch (CDC/LumXM). We compared graft survival rates between the group undergoing desensitization (treatment group) and matched control group of patients that underwent HLA-compatible transplantation. ResultsIn the treatment group, Kaplan-Meier analysis estimates an average rate of patient graft survival of 95.2% at 3 years post-transplant, as compared with the rate of 86.9% in the same time frame for the control-matched group (p < 0.05 for both comparisons). ConclusionDesensitization treatment with TPE before live donor renal transplantation in the case of patients with HLA sensitization provides better survival benefits along with monitoring for donor-specific antibodies (DSAs) and other infections, rather than waiting for a compatible organ donor. The data lays out evidence that desensitization treatments can assist overcome HLA incompatibility barriers in live donor renal transplantation.

Antibody-Mediated Rejection and Recurrent Primary Disease: Two Main Obstacles in Abdominal Kidney, Liver, and Pancreas Transplants.

The advances in acute phase care have firmly established the practice of organ transplantation in the last several decades. Then, the next issues that loom large in the field of transplantation include antibody-mediated rejection (ABMR) and recurrent primary disease. Acute ABMR is a daunting hurdle in the performance of organ transplantation. The recent progress in desensitization and preoperative monitoring of donor-specific antibodies enables us to increase positive outcomes. However, chronic active ABMR is one of the most significant problems we currently face. On the other hand, recurrent primary disease is problematic for many recipients. Notably, some recipients, unfortunately, lost their vital organs due to this recurrence. Although some progress has been achieved in these two areas, many other factors remain largely obscure. In this review, these two topics will be discussed in light of recent discoveries.

Posttransplant de novo donor specific HLA antibody monitoring and clinical outcomes: a single-center experience

Objectives: Despite the improvements in early-term outcomes of kidney transplantation, late-term graft failure still remained as a critical problem. De novo donor specific antibodies (DSA) developing against direct human leukocyte antigens (HLA) are the significant risk factors for shortened graft survival in the previously non-sensitized cases. The purpose of this study is to evaluate the clinical outcomes of de novo DSA development in the kidney transplant cases. Methods: The present study included 121 (alive/cadaver: 106/15) of 148 (alive/cadaver: 125/23) cases who were not previously sensitized (PRA and DSA negative) and undergone kidney transplantation between August 2012-January 2018. DSAs of the cases without expected declines in creatinine levels in the polyclinic follow-ups and postoperative early-term were evaluated. Renal biopsy was performed in the cases encountered with &amp;gt;2000 mean fluorescence intensity (MFI) de novo DSA against HLA-A, HLA-B, HLA-DR. Treatment protocol of plasmapheresis+intravenous immunoglobulin (IVIG)+rituximab (in the cases without clinical response) was administered in the cases with antibody-mediated rejection (AMR) detected by renal biopsy. In addition, the presence of de novo non-DSA was also evaluated in the cases. The presence of de novo was encountered by identifying the specificities of anti-HLA antibody specificities using Luminex single antigen beads in the recipient serum. Results: De novo DSA (antibodies against HLA-A, HLA-B, HLA-DR and HLA-DQ) were monitored in 23 cases. DQ positivity was detected in 10 cases. MFI values were &amp;gt; 4000 and 2000-4000 in 8 and 2 cases, respectively. De novo non-DSA was found in 19 cases. Biopsy was performed in 8 cases due to the development of MFI &amp;gt; 2000 de novo DSA against HLA-A, HLA-B and HLA-DR and the findings of acute humoral rejection (AHR) were encountered in 2 cases. Additionally, acute humoral rejection was diagnosed in 1 case that developed de novo non-DSA. Two cases were diagnosed with AHR by biopsy although no de novo DSA or non-DSA developed and renal graft loss occurred in these two cases. Conclusions: The fact that routine DSA monitoring in all the cases provided no significant contribution to the outcomes of our study may contribute to the debates on the necessity of DSA monitoring in the patients with low immunological risk.

A207 DE NOVO DONOR-SPECIFIC ANTIBODY FORMATION IN LIVER TRANSPLANTS: RISK FACTORS FOR DEVELOPMENT AND IMPACT ON GRAFT SURVIVAL.

Abstract Background Antibody mediated rejection (AMR) is an area of great importance in solid organ transplantation. Donor-specific antibodies (DSA) have emerged as relevant biomarkers in predicting graft function and survival. DSA detected post-transplant may either be preformed or de novo and emerging evidence suggests de novo DSA, in particular, is associated with inferior graft outcomes. In contrast to the clear role that AMR plays in renal and thoracic organ transplantation, its importance in liver transplants remains controversial. Aims The aim of this study was to determine the risk factors associated with de novo DSA formation and to evaluate its role in determining clinical outcomes after liver transplantation. Methods This single-center retrospective study compiled data on liver transplants performed between 2005 and 2019 in Edmonton, Canada. Data collected from medical charts included gender, age at transplant, reason for transplant, and immunosuppressive regimens, among several others. The presence of DSA was determined by single antigen flow beads until 2009 and by Luminex thereafter. Potential predictors of DSA formation were evaluated using Cox proportional hazard models. Graft survival estimates were obtained using the Kaplan-Meier method and comparisons between patient groups were conducted using the log-rank test. Results Between 2005–2019, 131 patients had measurements of DSA both before and after liver transplantation. In this cohort, 17 patients (13%) tested negative on DSA screening before transplant but developed new antibodies against either Class I or Class II molecules post-transplant. Risk factor analysis revealed transplants performed in the setting of autoimmune liver disease (PSC, PBC, and autoimmune hepatitis) had higher risks of developing de novo DSA post-transplant (p=0.002. See Table 1). Graft survival probability at 5- and 10-years was 72% and 61% in those with de novo DSA formation, compared to 93% and 89% in patients without de novo DSA formation (p=0.04. See Figure 1). Overall patient survival was similar between the two groups. Conclusions In this single-center study, a transplant done in the setting of autoimmune liver disease had a higher risk of de novo DSA formation. Furthermore, de novo DSA formation lead to a decreased graft survival time in liver transplant patients but overall patient survival was not significantly decreased. A standard approach to DSA monitoring, especially in high risk populations, is required to better understand its prevalence and impact in liver transplantation. Funding Agencies None

Safety and Efficacy of a Steroid Avoidance Immunosuppression Regimen in Renal Transplant Patients With De Novo or Preformed Donor-Specific Antibodies: A Single-Center Study

Although interest in the role of donor-specific antibodies (DSAs) in kidney transplant rejection, graft survival, and histopathological outcomes is increasing, their impact on steroid avoidance or minimization in renal transplant populations is poorly understood. Primary outcomes of graft survival, rejection, and histopathological findings were assessed in 188 patients who received transplants between 2012 and 2015 at the Scripps Center for Organ Transplantation, which follows a steroid avoidance protocol. Analyses were performed using data from the United Network for Organ Sharing. Cohorts included kidney transplant recipients with de novo DSAs (dnDSAs; n = 27), preformed DSAs (pfDSAs; n = 15), and no DSAs (nDSAs; n = 146). Median time to dnDSA development (classes I and II) was shorter (102 days) than in previous studies. Rejection of any type was associated with DSAs to class I HLA (P < .05) and class II HLA (P < .01) but not with graft loss. Although mean fluorescence intensity (MFI) independently showed no association with rejection, an MFI >5000 showed a trend toward more antibody-mediated rejection (P < .06), though graft loss was not independently associated. Banff chronic allograft nephropathy scores and a modified chronic injury score were increased in the dnDSA cohort at 6 months, but not at 2 years (P < .001 and P < .08, respectively). Our data suggest that dnDSAs and pfDSAs impact short-term rejection rates but do not negatively impact graft survival or histopathological outcomes at 2 years. Periodic protocol post-transplant DSA monitoring may preemptively identify patients who develop dnDSAs who are at a higher risk for rejection.

The Utility of Donor-specific Antibody Monitoring and the Role of Kidney Biopsy in Simultaneous Liver and Kidney Recipients With De Novo Donor-specific Antibodies.

There is limited information about the utility of donor-specific antibody (DSA) against HLA monitoring and the role of protocol kidney biopsy for de novo DSA (dnDSA) in simultaneous liver and kidney (SLK) transplant recipients. We analyzed SLK transplant recipients transplanted between January 2005 and December 2017, who had DSA checked posttransplant. Patients were divided into 2 groups based on whether they developed dnDSA posttransplant (dnDSA+) or not (dnDSA-). Kidney graft rejection ±45 d of dnDSA and a kidney death-censored graft survival were the primary endpoints. A total of 83 SLK transplant recipients fulfilled our selection criteria. Of those, 23 were dnDSA+ and 60 were dnDSA-. Twenty-two of 23 dnDSA+ patients had DSA against class II HLA, predominantly against DQ. Fifteen recipients underwent kidney biopsy ±45 d of dnDSA. Six of these were clinically indicated due to kidney graft dysfunction. The other 9 had a protocol kidney biopsy only due to dnDSA, and 6 of these 9 had a rejection. Also, 3 recipients had sequential biopsies of both the kidney and liver grafts. Among those with sequential biopsies of both grafts, there was a difference between the organs in the rate and types of rejections. At last follow up, dnDSA was not associated with graft failure of either the kidney or liver. Although our study was limited by a small sample size, it suggests the potential utility of DSA monitoring and protocol kidney biopsy for dnDSA.

Precision transplant pathology.

Transplant pathology contributes substantially to personalized treatment of organ allograft recipients. Rapidly advancing next-generation human leukocyte antigen (HLA) sequencing and pathology are enhancing the abilities to improve donor/recipient matching and allograft monitoring. The present review summarizes the workflow of a prototypical patient through a pathology practice, highlighting histocompatibility assessment and pathologic review of tissues as areas that are evolving to incorporate next-generation technologies while emphasizing critical needs of the field. Successful organ transplantation starts with the most precise pratical donor-recipient histocompatibility matching. Next-generation sequencing provides the highest resolution donor-recipient matching and enables eplet mismatch scores and more precise monitoring of donor-specific antibodies (DSAs) that may arise after transplant. Multiplex labeling combined with hand-crafted machine learning is transforming traditional histopathology. The combination of traditional blood/body fluid laboratory tests, eplet and DSA analysis, traditional and next-generation histopathology, and -omics-based platforms enables risk stratification and identification of early subclinical molecular-based changes that precede a decline in allograft function. Needs include software integration of data derived from diverse platforms that can render the most accurate assessment of allograft health and needs for immunosuppression adjustments.

Subclinical Antibody-mediated Rejection After Kidney Transplantation: Treatment Outcomes.

Antibody-mediated rejection (AMR) is a leading cause of morbidity and mortality after kidney transplantation. Early diagnosis and treatment of subclinical AMR based on the donor-specific antibody (DSA) testing may result in better outcomes. We tested this hypothesis in 220 kidney transplant recipients who underwent an indication or DSA-based surveillance protocol biopsies between March 1, 2013 and December 31, 2016. Patients were divided into 3 groups: clinical AMR (n = 118), subclinical AMR (n = 25), or no rejection on protocol biopsy (controls; n = 77). Both clinical and subclinical AMR groups underwent similar treatment including plasmapheresis, pulse steroids, IVIG, and rituximab (P = ns). Mean follow-up after AMR was 29.5 ± 16.8 months. There were 2 (3%), 2 (8%), and 54 (46%) death-censored graft failures in the control, subclinical, and clinical AMR groups, respectively (P < 0.001). Graft outcomes were similar in the subclinical rejection and control groups. In adjusted Cox regression analysis, only clinical rejection (hazards ratio [HR], 4.31; 95% confidence interval [CI], 1.01-18.94; P = 0.05) and sum chronicity scores (HR, 1.16; 95% CI, 1.01-1.35; P = 0.03) were associated with increased risk of graft failure, while estimated glomerular filtration rate at time of biopsy (HR, 0.98; 95% CI, 0.96-0.99; P = 0.01) was associated with decreased risk of graft failure. Our study suggests that early diagnosis and treatment of subclinical AMR using DSA monitoring may improve outcomes after kidney transplantation.

Class and Kinetics of Weakly Reactive Pretransplant Donor-specific HLA Antibodies Predict Rejection in Kidney Transplant Recipients.

The clinical impact of weakly reactive pretransplant donor-specific antibody (DSA) in kidney transplantation is controversial. While some evidence suggests that weakly reactive DSA can lead to rejection, it is unclear which patients are at risk for rejection and whether posttransplant changes in weakly reactive DSA are clinically meaningful. We retrospectively studied 80 kidney transplant recipients with weakly reactive pretransplant DSA between 2007 and 2014. We performed a multivariate Cox regression analysis to identify immunologic factors most associated with risk of biopsy-proven rejection. Biopsy-proven rejection occurred in 13 of 80 (16%) patients. The presence of both class I and II DSA before transplant (hazards ratio 17.4, P < 0.01) and any posttransplant increase in DSA reactivity above a mean fluorescence intensity of 3000 (hazards ratio 7.8, P < 0.01) were each significantly associated with an increased risk of rejection, which primarily occurred within the first 18 months. Pretransplant DSA class and DSA kinetics after transplantation are useful prognostic indicators in patients with weak DSA reactivity. These results identify a small, high-risk patient group that warrants aggressive posttransplant DSA monitoring and may benefit from alternative donor selection.

350.6: The impact of circulating DSA in visceral transplant recipients without histological evidence of rejection: How should we treat or not treat?

Backgrounds: There has been accumulating evidence that donor-specific antibody (DSA) has a negative impact on the outcome of visceral allografts. Prospective DSA monitoring allows detection of circulating DSA without histological evidence of acute rejection. However, its association with acute rejection and natural course without treatment are yet to be determined. Methods: Between 2012 and 2019, 94 visceral transplantation with 25 liver-contained grafts were performed at a single institution. Induction therapy for preformed DSA included rituximab or bortezomib. DSA were monitored at 1 and 2weeks, followed by 1, 3, and 6 months, and yearly after transplant. De-novo DSA was not treated without histologically proved rejection. The characteristics and impact of DSA in terms of predictability of rejection, and its correlation of severity of acute rejection were analyzed. Results: One-year cumulative rejection rate in the entire cohort was 67%. With the protocol of anti-B cell therapy, preformed DSA did not increase the risk of rejection, regardless of the status of liver-free allografts, high titer (>4000 MFI) or persistence of DSA. Moreover, there was no difference in severity of rejection with the presence of preformed DSA (n=12) compared to that without DSA (n=36). However, 3-years graft survival was inferior in patients with preformed DSA to those without (52% vs. 64%, p=0.069), due to increased infectious complications. De-novo DSA was detected in 32 patients (35%) with an HLA-ABDR mismatch as the only predictor (Odds ratio 1.7, p=0.036). De-novo DSAs were more likely to be class II with high inclusion of anti-DQ DSA (69%). Prospective monitoring detected de-novo DSA in 25 occasions without ongoing rejection. Accordingly, it turned negative without rejection episode in 19 (76%) (Silent DSA), while subsequent rejection occurred in 6 occasions (24%) (DSA before rejection). In 10 occasions, de-novo DSA turned positive during the rejection episodes (DSA during rejection). The rejection episodes that induced DSA circulation was with a more severe grade. Conclusions: Increased immunosuppressant induction to treat preformed DSA may compensate the rejection risk, but can negatively impact the overall graft survival. With prospective monitoring and no preemptive treatment, high proportion of de-novo DSA was self-limiting, and rarely precipitated rejection episodes particularly with a severe grade.

Donor-specific antibody management in intestine transplantation: hope for improving the long-term durability of the intestine allograft?

In this review, we appraise the current status of donor-specific antibody (DSA) monitoring and treatment in the literature and highlight the current challenges in DSA management for the intestine transplant community. Sensitizing events are common in patients referred for intestinal transplant, as these patients universally are repeatedly exposed to immune activation and inflammatory events. Both preformed and de novo DSA have been shown to increase rejection and graft loss in intestine recipients. Avoidance of preformed DSA with the use of virtual crossmatch (VXM) and antibody monitoring protocols to detect and treat de novo DSA may improve intestine transplant outcomes. There is no consensus on the clinical and pathologic criteria that are required to diagnose antibody-mediated rejection (AMR) in the intestine recipient. Therefore, many clinicians treat AMR based on the coincidence of DSA and acute biopsy-proven rejection. Inclusion of the liver in the intestine allograft appears to be immunologically protective in the setting of DSA with improved outcomes and a higher rate of preformed DSA clearance. Critically, DSA has been linked to chronic rejection and poor long-term outcomes in the intestine recipient. On the basis of increasing evidence in the intestine transplant literature, it appears that avoidance of preformed DSA and aggressive monitoring and treatment of de novo DSA is a key to long-term survival following intestine transplantation.

OR53 Post transplant monitoring to include donor derived cell free DNA (%ddcfDNA): Steps toward personalized medicine

Aim Elevated %ddcfDNA levels have been shown to correlate with allograft injury and acute rejection in lung transplantation. This case highlights how conventional post-transplant monitoring may underestimate the complex interactions between infection, injury, and de novo donor specific antibody (DSA) development. Methods Quantitation of %ddcfDNA via next generation sequencing was performed as part of the Genomic Research Alliance for Transplantation (GRAfT) consortium. DSA monitoring utilized Luminex phenotype and single bead immunoassays. Spirometry was used to assess pulmonary function and transbronchial biopsies to assess rejection. Bronchoalveolar lavage, blood samples and sputum cultures were used to diagnose infections. Results A 60 year old male with interstitial lung disease received a single lobe lung transplant. This patient was entered into GRAfT, a blinded prospective trial to investigate the use of %ddcfDNA to monitor allograft injury and predict long term outcomes. Immediately after transplant, high %ddcfDNA was detected in the recipient’s plasma which declined over several weeks. A biopsy on post-operative day (POD) 192 indicated mild acute cellular rejection concomitant with an infection and a spike in %ddcfDNA. The elevated %ddcfDNA ( > 1% threshold) suggested substantial injury to the allograft despite stable lung function. The patient experienced several infections prior to the detection of HLA-DQB1 de novo DSA. The second %ddcfDNA spike was concurrent with an increase in DSA and loss in lung function. Therapeutic plasma exchange reduced DSA with corresponding %ddcfDNA regression and improved lung function. An infection on POD 338 correlated with a third %ddcfDNA spike (last available measurement). The patient experienced further infections with a diminishing trend in lung function. Conclusion %ddcfDNA monitoring to detect cumulative clinical and subclinical injury may aid in assessing de novo DSA risk and in the development of interventions to prevent chronic allograft loss. Download : Download high-res image (141KB) Download : Download full-size image A.M. Jackson: 3. Speaker’s Bureau; Company/Organization; Thermo Fisher Scientific. DRB4*01:03:01 DQA1*03:01:01 DQB1*03:02:01 DPA1*01:03:01 DPB1*04:02:01 (HF = 0.03). A new DPA1*02:07:01_5407G > A was found. Conclusions As we published previously, the DRB1*04-DQA1*03-DQB1*03 association is strong but it is shown for the first time, that A*, B*, C* DQA1* and DPB1* alleles of Mexican AMI ancestry are strongly associated. The genetics of VKH is undoubtedly of Oriental origin, and present therefore in AMI, admixed groups such as Hispanics, Mediterranean and Asians. The shared epitope at S57-LLEQRRAA 67-74 in DR β 1 chain and the new class I associations are the basis to look for immunological intervention to block the T-cell response vs. the antigens that trigger the autoimmune response in VKH.

Immunologic and Histologic Monitoring after Renal Transplantation a Single Center Experience.

Introduction Antibody mediated rejection (ABMR) is now recognized as responsible for the loss of most kidney grafts. The presence of donor specific antibodies (DSA) in the recipient’s serum either pre transplant (preDSA) or develop after transplantation (de novo DSA) is the main risk factor for ABMR both clinical and subclinical. On the other hand clinical and sub clinical T cell mediated rejection (TCMR) is associated with the development of de novo DSA. In this context graft histology and immunologic monitoring for the presence of DSA after transplantation are considered valuables tools to guide therapeutic decisions. Objective Our purpose was to describe the findings of the histologic and immunologic monitoring after renal transplantation at CEMIC. Material and Methods This was a Retrospective cohort analysis of all patients who received a renal transplant at CEMIC from 01/01/2012 to 31/12/2016. Patients who presented technical failure were excluded. DSA Monitoring: panel reactive antibodies (PRA) by ELISA were tested pre transplant and then at 6 months, 1, 3, 5 and 10 years post-transplant. In cases where PRA>0, history of previous transplants, transfusions, pregnancy or known DSA, a single antigen bead (SAB) Luminex essay (OneLambda®) was also performed. Histologic monitoring: surveillance percutaneous renal graft biopsy (PRB) was performed at 6 months,1, 3, 5 and 10 years post-transplant. PRB for cause was also indicated whenever there were graft dysfunction or immunosuppression changes. Patients with PreDSA were desensitized and acute rejections were treated accordingly per local practice guidelines. Results During the analyzed period 179 renal transplants were performed at CEMIC. 8 cases of technical failure were excluded, leaving 171 patients for analysis. Median age was 54,5±15 years, 69,6% were males, 73,7% received kidneys from diseased donors. 22(12,8%) patients had a positive PRA pre transplant (ELISA) and 32(18,7%) had anti HLA antibodies by SAB, 14/32 were DSA. Median follow up time was 43, 7±20 months. During this period all patients with preDSA showed a reduction in MFI levels. 7/171 (4%) developed de novo DSA post-transplant. Additionally 13/171 (7,6%) developed anti HLA antibodies without DSA detected. A total of 293 PRB were performed of which 168/293 (57,3%) were surveillance biopsies accomplished during the first year. Acute rejection was diagnosed in 67/293(22, 8%), 14/67 (20,9%) were borderline changes, 45/67 (67,1%) were TCMR and 8/67 (11,9%) were ABMR or mixed rejection. 24/67 (35,8 %) were subclinical rejections diagnosed in surveillance biopsies. 8/21(38%) of patients with DSA developed ABMR or mixed rejection, 3/21(14,2%) lost their graft and 2/21(9,5%) died. Death censored graft survival at 2 years was 82,9% vs 95,2% in DSA vs non DSA patients (NS) Conclusions In our experience, DSA and histologic post-transplant monitoring were useful tools for the detection of aloimmune events in general and those subclinical in particular.

Complement-fixing donor-specific anti-HLA antibodies and kidney allograft failure

Detection of donor-specific antibodies (DSA) has improved the risk classification and post-transplant evaluation of kidney recipients. Moreover, assessment of DSA C1q-binding ability has been shown to improve the individual risk classification of transplant patients for allograft loss, especially when detected after transplantation. The aim of this study was to evaluate the additional clinical impact of C1q-binding DSA detection in a population that was extensively monitored for DSA and MFI alterations. Forty-two kidney allograft recipients were followed-up at multiple time points for up to 5 years after transplantation for the presence of anti-HLA DSA-IgG total. The samples that were positive for these antibodies were retrospectively tested for the presence of complement-binding antibodies. Overall, 24 patients presented DSA, 29% (7) of which also produced complement-binding DSA. Compared to patients with non-C1q-binding DSA and non-sensitized patients, patients with C1q-binding DSA after transplantation had the lowest allograft survival rate at 5 years (p = 0.042) and showed a lower estimated glomerular filtration rate (based on the Modification of Diet in Renal Disease formula) during the post-transplant follow-up period (p = 0.01). Thus, post-transplant monitoring for complement-binding DSA is a useful tool for predicting individuals most at risk for allograft failure, and might also be beneficial for evaluation of immunosuppression regimens.

P180 Moving onto plan C: Finding detours when DSA creates a roadblock to bone marrow transplantation

Aim This case study illustrates potential avenues to consider when identifying hematopoietic stem cell donor options for HLA sensitized patients. Methods HLA typing was performed using reverse sequence specific oligonucleotide probe hybridization assays (One Lambda, Inc.) and Sanger sequence base typing assays (local and commercial kits). HLA-specific antibody was assessed using class I and class II phenotypes (Lifecodes®, Immucor) and single antigen panels (One Lambda Inc.). Results The presence of donor specific antibody (DSA) can adversely impact the likelihood of bone marrow engraftment depending on the specificity and strength of the DSA. DSA assessment and monitoring is becoming crucial as centers are utilizing HLA mismatched donors. In the last 5 years, 60–70% of the overall allogeneic bone marrow transplants at our center utilized HLA mismatched donors. In a majority of our sensitized patients, the availability of multiple eligible donors allowed for either the avoidance of DSA or the minimization of DSA to levels that did not warrant desensitization. But, in 6% of the cases evaluated in 2016, DSA caused roadblocks requiring alternate pathways. The case of a 41 year old female with Acute Lymphocytic Leukemia illustrates the “Moving onto Plan C” mantra. Plan A: A related haploidentical transplant was diverted due to crossmatch positive DSA against the patient’s four eligible donors. Plan B: An unrelated matched transplant was deterred due to DRB3*01 allele specific DSA against several 10/10 HLA loci matched donors with the DRB1*13:01/DRB3*01 association instead of patient’s DRB1*13:01/DRB3*02 association. Plan C: An unrelated mismatched donor search was initiated to identify 9/10 HLA loci matched donors with a DRB1 mismatch likely to avoid the patient’s broad specificity and eliminate the potential of a DRB3*01 typed donor. Conclusion Even though there is a low incidence of patients requiring an alternate route due to DSA, the impact of the DSA is life-threatening to the individuals in this cohort. With the increase of HLA mismatched transplants, there is a greater need for initial HLA antibody assessments, continual HLA antibody monitoring, alternative back-up plans and creative solutions in order to offer all patients the best chance of survival.

OR16 Donor-specific antibodies (DSA) detected by C1Q and C3D assays predict antibody-mediated rejection (AMR) in renal transplant (TX) patients, but specific detection of IGG2, IGG3, IGG4, IGA, and IGM DSA, and ANTI-AT1R and anti-etar antibodies do not

Aim To investigate the specific roles for Class I and Class II DSA, complement binding and activation, and non-HLA antibodies, in renal tx patients with AMR. Methods One Lambda®: LABScreen™ (routine total IgG and modified to detect IgG1, IgG2, IgG3, IgG4, IgA, IgM); C1qScreen™; anti-AT1R; anti-ETAR. Immucor®: LIFECODES C3d. Assays were used to detect the presence of antibodies and DSA. The quantity of each antibody and capacity to bind and activate complement were correlated with the histopathologic features found in biopsy specimens. Among 480 renal transplants performed between 2009 and 2014, we enrolled 17 (∼4%) patients with clinical and histopathologic diagnosis of AMR, and compared with matched-controls who had anti-HLA antibodies and apparent DSA, but had not exhibited AMR. We assessed antibodies and DSA MFI values prior to transplantation and at the time of AMR. Results Detection of anti-AT1R, anti-ETAR, and Class I DSA did not correlate with AMR. Class II IgG2, IgG3, IgG4, IgA, and IgM DSA did not correlate with AMR. Class II DSA >500 MFI detected by LABScreen™ + C1q + IgG1 + C3d identified 82% of patients and only 12% of controls, p = 0.00009 (88% PPV, 17% NPV), whereas, C1q + C3d identified 71% of patients and no controls, p = 0.00002 (100% PPV, 23% NPV). Notable is that anti-HLA Class II DSA detected by C1q and C3d correlates with rejection, and the injury found on biopsies was primarily tubulointerstitial, consistent with the region where constitutive expression of HLA Class II occurs in renal tissue. Conclusions Clinically “reversible” AMR appears to be due to Class II anti-HLA DSA, which can bind and activate complement. Detection of anti-HLA DSA by the C1q and C3d assays correlate with histological characteristics (tubulointerstitial injury) of AMR in renal allografts, and indicates that monitoring for anti-HLA DSA, which can bind and activate complement, may be useful to detect patients at risk for AMR; thus allowing for earlier detection and treatment prior to graft injury or graft loss.