Donor-specific anti-HLA Antibodies Research Articles

Successful Salvage Therapy by Second Haploidentical Allogeneic Hematopoietic Stem Cell Transplantation in a Severe Aplastic Anemia Patient Presenting Donor-Specific Anti-HLA Antibodies After Graft Failure From Matched Sibling Donor HSCT: A Case Report and Review

Hematopoietic stem cell transplantation (HSCT) is potentially curative for severe aplastic anemia (SAA). Graft failure (GF) remains a life-threatening complication after HSCT. Preexisting anti-HLA antibodies, especially HLA-specific antibodies (DSA), have been demonstrated as a risk of GF. This report describes a woman with acquired SAA who presented with anti-HLA antibodies and GF. After the treatment of anti-HLA antibodies, engraftment was achieved through a second alternative donor HSCT. This work complied with the Declaration of Helsinki and the Declaration of Istanbul. Based on our experience in treating this case, we hold that the presence of preoperative anti-HLA antibodies could discount the efficacy of HSCT and anti-HLA antibody screening should be performed before HSCT. Additionally, a second HSCT is feasible to prolong survival.

Non-adherence assessment to immunosuppressant therapy with a self-report questionnaire and intra-patient variability in renal transplantation: risk factors and clinical correlations.

Non-adherence (NA) to immunosuppressive drugs is to date considered a crucial issue in kidney transplanted patients (KTRs), leading to de-novo donor-specific anti-HLA antibodies (dnDSA) development, acute and chronic rejection, and at least graft loss. However, NA assessment is challenging, often leading to underestimation in real-life settings. NA evaluation in all KTRs referred to our post-transplantation clinic in the period between 01/01-15/07/2018 with self-report questionnaire combined to intra-patient variability (IPV) of the pivotal immunosuppressive drug (based on trough levels of tacrolimus/mTOR inhibitor). Based on both questionnaire and IPV, 86 out of the 504 tested KTRs (17%) were classified as NA. Male gender (OR, 2.0; 95% confidence interval [CI], 1.2 to 3.4), high educational level (OR for KTRs with a degree, 1.8 [95% CI, 1.0 to 3.1]), employment (OR, 2.0 [95% CI, 1.2 to 3.3]), young age at transplantation (P=0.017), longer time on the waiting list and after transplantation (P=0.027 and 0.049 respectively) were all associated with NA. High IPV was mostly documented in KTRs treated with the twice-daily formulation of the immunosuppressive drug (OR, 1.5 [95% CI, 1.0 to 2.1]) and better associated with dnDSA appearance (OR, 2.1 [95% CI, 1.1 to 3.9]). NA is a significant problem, difficult to assess, and can lead to dnDSA development also in our population. Identifying risk factors for NA might be an underestimated tool to improve graft and patient outcome in KTRs.

Development of a humanized mouse model to analyze antibodies specific for human leukocyte antigen (HLA).

In organ transplantation, human leukocyte antigen (HLA)-mismatch grafts not only induce the activation of cellular mediated immune response but also the development of chronic antibody-mediated rejection due to the donor-specific anti-HLA antibody (DSA) produced by B cells and plasma cells interacting with the graft endothelium. Significant improvement in long-term survival after transplantation can be expected if antibody-mediated rejection due to the DSA can be overcome. However, the mechanism of producing or controlling the DSA remains to be elucidated. In recent decades, “humanized” mouse models have been widely used for the basic research of human immune systems, but a humanized mouse model to analyze the mechanism of DSA production has not been established yet. Thus, we aimed to create a humanized mouse using a severe immunodeficiency mouse (NSG mouse) administered with human peripheral blood mononuclear cells (PBMCs). Initially, we detected a very low level of human total-IgG and no anti-HLA antibodies (Abs) in these mice. In our next attempt, we mixed PBMCs of various HLA antigenic combinations with or without regulatory T cells and preconditioned them by culturing on feeder cells stably transfected with human CD40 ligand (h-CD40L) alone or with h-CD40L and human B cell activating factor (h-BAFF). They were subsequently co-cultured with the corresponding irradiated stimulator PBMCs, and all cells were administered into naïve NSG mice. Although all three humanized models had sufficient human total-IgG and anti-HLA antibody production, allospecific anti-HLA Ab production was prominently suppressed whereas non-specific anti-HLA Abs were sufficiently detected. Therefore, this novel humanized mouse model might be useful for analyzing the mechanism of anti-allogeneic human B cell tolerance induction.

Donor – recipient selection using epitope mismatches in kidney transplantation

Purpose . To evaluate the potential option of selecting donor–recipient pairs by using the number of epitope mismatches. Materials and methods . An observational cohort study was carried out, which included 824 adult recipients of ABO compatible deceased donor kidneys. The end point was a transplant loss. If a recipient with a functioning graft died, the observation was censored. The number of epitope mismatches (EpMM) was calculated using open source information on the population frequency of haplotypes and the repertoire of epitopes with confirmed immunogenicity. All possible combinations of the donor and recipient genotypes were compiled, and the probability of each combination was calculated. After that, the number of donor epitopes absent in the recipient was calculated for each combination with a non-zero probability, whereupon the weighted mean EpMM was calculated, where the weight coefficient was the normalized probability of occurrence of each combination. Results . All of the donor – recipient pairs had HLA-mismatches (HLA MM): 1.9% of recipients had 1 HLA MM, 6.7% had 2 HLA MM, 29.9% had 3 HLA MM, 38.5% had 4 HLA MM, 18.1% had 5 HLA MM, and 4.9% had 6 HLA MM. The HLA MM impacted graft survival was determined: log-rank test p < 0.0001, Breslow test p < 0.0001. The median values and the interquartile ranges of EpMM were 6 [4; 7], 12 [7.74; 17.25], 18 [14; 22], 24 [20; 30], 30.5 [25; 37] and 36 [26.5; 44.5] for the cases of 1, 2, 3, 4, 5 and 6 HLA MMs, respectively. An increase in HLA MM resulted in a higher risk of developing donor-specific anti-HLA antibodies (DSA). Hazard ratio (HR) = 1.21 [95% confidence interval (CI): 0.7; 1.9], 1.71 [95% CI: 1.22; 2.36], 2.04 [95% CI: 1.42; 2.73], 2.25 [95% CI: 1.63; 2.96], 2.59 [95% CI: 2.03; 3.29] for 2, 3, 4, 5, and 6 HLA MM, respectively, versus HLA MM = 1. An increase in EpMM also resulted in a higher risk of developing DSA. HR = 1.66 [95% CI: 1.09; 2.47], 2.1 [95% CI: 1.46; 2.91], 2.41 [95% CI: 1.86; 3.03], 2.61 [95% CI: 2.12; 3.12], 2.77 [95% CI: 2.26; 3.33] for 10–19, 20–29, 30–39, 40–49 and > 50 EpMM, respectively, versus EpMM < 10. An increase in HLA MM was associated with an increased risk of transplant loss. HR = 1.24 [95% CI 0.7; 2.15], 1.48 [95% CI 0.86; 2.33], 1.88 [95% CI 1.32; 2.52], 2.41 [95% CI 2; 2.93], 2, 98 [95% CI 2.59; 3.46] at 2, 3, 4, 5, and 6 HLA MM, respectively, versus HLA MM = 1. An increase in EpMM also was associated with an increased risk of transplant loss. HR = 1.71 [95% CI 1.1; 2.49], 2.11 [95% CI 1.59; 2.68], 2.4 [95% CI 1.96; 2.86], 2.59 [95% CI 2.17; 3.04], 2.71 [95% CI 2.31; 3.15] at 10–19, 20–29, 30–39, 40–49 and > 50 EpMM, respectively, versus EpMM < 10. In order to demonstrate the effectiveness of EpMM accounting, we analyzed graft survival among the patients with 4 HLA MM. With the number of EpMM in the range from 10 to 24 and from 25 to 43 the difference in survival rates was statistically significant, but only at the late stages of the post-transplant period: log-rank test p = 0.0067, Breslow test p = 0.0982. The median survival for EpMM 10–24 was 10.33 [95% CI 9.05; 11.61] years, for EpMM 22–43 – 8.67 [95% CI 7.68; 9.66] years, HR 1537 [95% CI 1.114; 2.12]. At the same time, it was not the median of survival that increased, but the proportion of patients with a functioning graft: at 10-24 EpMM after 15 years, 18.28% [95% CI 8.2; 31.67] grafts functioned, while at 25–43 EpMM only 4.75% [95% CI 0.94; 13.64] functioned. Conclusion . In the routine practice of a transplantation center with a short waiting list of its own, it might be possible to improve the kidney transplant survival as a result of considering epitope mismatches, thus reducing the risk of developing donor-specific anti-HLA antibodies and ensuring a higher graft survival rate. This method can be used for additional ranking of transplantation candidates depending on the number of epitope mismatches within the fixed number of HLA-mismatches and thus select the optimal one. Besides, it is theoretically possible to use this method as an alternative to the traditional donor/recipient histocompatibility evaluation. Additional research is required.

Complement non-binding donor-specific anti-HLA antibodies in long-term engraftment cases of transplanted kidney

Complement non-binding donor-specific anti-HLA antibodies in long-term engraftment cases of transplanted kidney

Safety and Cross-Variant Immunogenicity of a Three-Dose COVID-19 mRNA Vaccine Regimen in Kidney Transplant Recipients

Background: The immunogenicity of a two-dose mRNA COVID-19 vaccine regimen is low in kidney transplant (KT) recipients. We report the first complete assessment of safety and cross-variant immunogenicity of a three-dose vaccine regimen in KT recipients.Methods: We performed a prospective longitudinal study in sixty-one KT recipients given three doses of the BNT162b2 COVID-19 vaccine. We performed semi-structured pharmacovigilance interviews and monitored donor-specific antibodies and kidney function. We compared geometric mean titers (GMT) of anti-spike IgG, pseudo-neutralization activity against vaccine homologous and heterologous variants, frequency of spike-specific interferon (IFN)-γ-secreting cells, and antigen-induced cytokine production 28 days after the second and third doses. The immunoassays were also performed in non-transplanted individuals 28 days after the second dose to obtain reference values.Findings: Reactions to vaccine were mild. One patient developed donor-specific anti-HLA antibodies after the second dose which could be explained by non-adherence to immunosuppressive therapy. Spike-specific IgG seroconversion raised from 44·3% (n=27) after the second dose to 62·3% (n=38) after the third dose (pInterpretation: A third dose of the BNT162b2 vaccine increases both SARS-CoV-2-specific humoral and cellular responses in KT recipients with an acceptable tolerability profile. However, neutralizing antibody titres remain low after three doses, especially against variants of concern, and barrier measures and vaccination of the relatives remain essential.Funding Information: This work was supported by grants from the Nice University Hospital (AOI) and the University of Cote d’Azur (IDEX).Declaration of Interests: The authors declare no competing interests. Ethics Approval Statement: The study protocol complies with the principles of the Declaration of Helsinki and was approved by our institutional committee. Written informed consent was obtained from all participants and all collected data and samples were anonymized and securely stored.

Выявление донор-специфических анти-HLA-антител методом индивидуальной перекрестной пробы де-факто у педиатрических реципиентов перед трансплантацией гемопоэтических стволовых клеток от гаплосовместимого донора

Выявление донор-специфических анти-HLA-антител методом индивидуальной перекрестной пробы де-факто у педиатрических реципиентов перед трансплантацией гемопоэтических стволовых клеток от гаплосовместимого донора

Treatment of Anti-HLA Donor-Specific Antibodies Results in Increased Infectious Complications and Impairs Survival after Liver Transplantation.

Donor-specific anti-human leukocyte antigen antibodies (DSA) are controversially discussed in the context of liver transplantation (LT). We investigated the relationship between the presence of DSA and the outcome after LT. All the LTs performed at our center between 1 January 2008 and 31 December 2015 were examined. Recipients < 18 years, living donor-, combined, high-urgency-, and re-transplantations were excluded. Out of 510 LTs, 113 DSA-positive cases were propensity score-matched with DSA-negative cases based on the components of the Balance of Risk score. One-, three-, and five-year survival after LT were 74.3% in DSA-positive vs. 84.8% (p = 0.053) in DSA-negative recipients, 71.8% vs. 71.5% (p = 0.821), and 69.3% vs. 64.9% (p = 0.818), respectively. Rejection therapy was more often applied to DSA-positive recipients (n = 77 (68.1%) vs. 37 (32.7%) in the control group, p < 0.001). At one year after LT, 9.7% of DSA-positive patients died due to sepsis compared to 1.8% in the DSA-negative group (p = 0.046). The remaining causes of death were comparable in both groups (cardiovascular 6.2% vs. 8.0%; p = 0.692; hepatic 3.5% vs. 2.7%, p = 0.788; malignancy 3.5% vs. 2.7%, p = 0.788). DSA seem to have an indirect effect on the outcome of adult LTs, impacting decision-making in post-transplant immunosuppression and rejection therapies and ultimately increasing mortality due to infectious complications.

The clinical utility of preformed C1q-binding donor-specific anti-HLA antibodies in kidney transplantation

The clinical utility of preformed C1q-binding donor-specific anti-HLA antibodies in kidney transplantation

Tailored immunosuppression after kidney transplantation - a single center real-life experience

BackgroundKidney allograft survival continuously improved with introduction of novel immunosuppressants. However, also immunologically challenging transplants (blood group incompatibility and sensitized recipients) increase. Between 2006 and 2008, a new tailored immunosuppression scheme for kidney transplantation was implemented at the University Hospital in Zurich, together with an ABO-incompatible transplant program and systematic pre- and posttransplant anti-human leukocyte antigen (HLA) antibody screening by Luminex technology. This study retrospectively evaluated the results of this tailored immunosuppression approach with a particular focus on immunologically higher risk transplants.MethodsA total of 204 consecutive kidney transplantations were analyzed, of whom 14 were ABO-incompatible and 35 recipients were donor-specific anti-HLA antibodies (DSA) positive, but complement-dependent cytotoxicity crossmatch (CDC-XM) negative. We analyzed patient and graft survival, acute rejection rates and infectious complications in ABO-compatible versus -incompatible and in DSA positive versus negative patients and compared those with a historical control group.ResultsOverall patient, death-censored allograft survival and non-death-censored allograft survival at 4 years were 92, 91 and 87%, respectively. We found that (1) there were no differences between ABO-compatible and -incompatible and between DSA positive and DSA negative patients concerning acute rejection rate and graft survival; (2) compared with the historical control group there was a significant decrease of acute rejection rates in sensitized patients who received an induction with thymoglobulin; (3) there was no increased rate of infection among the patients who received induction with thymoglobulin compared to no induction therapy.ConclusionsWe observed excellent overall mid-term patient and graft survival rates with our tailored immunosuppression approach. Induction with thymoglobulin was efficient and safe in keeping rejection rates low in DSA positive patients with a negative CDC-XM.

Treatment of Antibody-Mediated Rejection After Kidney Transplantation: Immunological Effects, Clinical Response, and Histological Findings.

BackgroundAntibody-mediated rejection (AMR) presents with diverse clinical manifestations and can have a potential negative impact on graft function and survival. If not treated successfully, AMR can lead to 20–30% graft loss after 1 year. Little is known about the efficacy of AMR treatment, and the most appropriate therapeutic strategy has not yet been determined. This study evaluated the effects of AMR treatment with plasmapheresis (PP) and intravenous immunoglobulin (IVIG) on renal function, intensity of anti-HLA antibodies, and graft biopsy morphology.Material/MethodsThis single-center retrospective cohort study included renal transplant recipients with biopsy-proven AMR who were treated with PP and/or IVIG. Clinical findings, mean fluorescence intensity of donor-specific anti-HLA antibodies (DSA), and graft histology findings, classified according to Banff score at the time of AMR and 6 and 12 months later, were evaluated.ResultsOf the 42 patients who met the inclusion criteria, 38 (90.5%) received IVIG and 26 (61.9%) underwent PP. At AMR diagnosis, 36 (85.7%) patients had proteinuria, with their estimated glomerular filtration rate remaining stable during follow-up. During the first year, 8 (19.0%) patients experienced graft failure, but none died with a functioning graft. Reductions in the class I panel of reactive antibodies were observed 6 and 12 months after AMR treatment, with significant reductions in DSA-A and -B fluorescence intensity, but no changes in DSA-DQ. Graft biopsy showed reductions in inflammation and C4d scores, without improvements in microvascular inflammation.ConclusionsAMR treatment reduced biopsy-associated and serological markers of AMR, but did not affect DSA-DQ.

Successful Clearance of Donor Specific Anti-HLA Antibodies after Desensitization with Rituximab, Velcade and Plasma-Exchange Followed By a Haploidentical Stem Cell Transplantion with Post-Transplantation Cyclophosphamide

Background: T cell - replete haploidentical stem cell transplantation (haploSCT) is increasingly performed and has expanded donor pool and transplant option for many patients (pt). However, the presence of recipient antibodies against donor HLA antigens (DSA) have been reported to be associated with engraftment failure and may limit the access to transplantation as the only lifesafing treatment modality. Guidelines for detection and treatment of DSA have been recently published but no standardized desensitization schedule exists so far. We report here the results of our institutional desensitization procedure initially developed for highly immunized patients with severe sickle cell disease undergoing haploSCT and then further adapted to all pt with DSA undergoing a mismatched allogeneic SCT. Methods: From March 2014 to July 2019, 20 pt had detectable DSA and did perform desensitization before undergoing a haploSCT. The DSA level was determined by using the LUMINEX technique (One Lamda, Inc). In case of positivity, the single antigen test was done to identify each class I and II HLA antibody-specificity. The values were expressed in mean fluorescence intensity (MFI). DSA were considered positive if the MFI value was ≥ 1000. The desensitization treatment included Rituximab 375 mg/m2, Velcade 1.3 mg/m2 and Plasma-Exchange followed by intravenous polyvalent immunoglobulins (Figure). DSA level controls were done routinely during desensitization, before starting the conditioning regimen and the day before graft injection. Pt who did not decrease DSA levels were not considered for haploSCT. Results: Median age was 61 years (range, 22-73). Diagnosis was acute myeloid leukemia in 6 pt, myelodysplastic / myeloproliferative syndrome in 10 pt, chronic lymphocytic leukemia in 1 pt and severe sickle cell disease in 3 pt. All donors were first-degree family members. Half of the pt were women [donor-recipient sex match: F/F=4; M/F=6; F/M=5; M/M=5pt]. The median MFI value before desensitization was 4700 (range, 1000-16000). Most pt (17) had DSAs against HLA class I antigens. Seventeen pt successfully decreased DSA levels to a median MFI value of 500 (range, 500-1200) and could proceed to haploSCT. They all engrafted and no DSA rebound was observed. One pt relapsed during the desensitization procedure and 2 pt with high DSAs above 10000 did not respond with remaining MFI of 16000 and 9500, respectively, and did not undergo haploSCT. One pt with CMML experienced primary graft failure for relapse and one pt with CLL did not engraft for unknown cause. Conclusions: The presence of DSA under 10000 should not be a barrier to transplantation. Our report shows that the hereby described desensitization schedule effectively cleared DSA allowing engraftment after haploSCT. Further studies are needed to determine the role of specificity and strength of DSA in order to better predict the likelihood of successful desensitization. Disclosures Harbi: Sanofi: Honoraria. Blaise:Jazz Pharmaceuticals: Honoraria.

Determinants of trajectories of cardiac allograft vasculopathy after heart transplantation: a population based study

Abstract Background Cardiac allograft vasculopathy (CAV) is a major contributor of heart transplant recipient's mortality. Little is known about determinants of CAV trajectories at a population level. Purpose We aimed to identify the respective contribution of immune and non-immune factors in the different evolutive profiles of CAV. Methods Heart transplant recipients receiving care at 2 academic centers (2004 to 2016) were included. Patients underwent prospective, protocol-based monitoring consisting of repeated coronary angiographies together with systematic assessment of clinical, functional, histological and immunological parameters. The outcome was CAV trajectories, identified with unsupervised latent class mixed models. The independent, predictive factors of CAV trajectories were investigated with multinomial regressions (NCT04117152). Results Overall, 815 patients were included. The median follow-up post-transplant was 7.7 years (IQR=5.14) with 2,742 coronary angiographies analyzed. We identified 4 distinct profiles of CAV trajectories over 10 years that were characterized by i) Patients without CAV at baseline and non-progression (n=459, 56.3%), ii) patients without CAV at baseline and late onset CAV progression (n=62, 7.6%), iii) patients with mild baseline CAV and mild progression (n=188 23.1%), iv) patients with mild baseline CAV and accelerated CAV progression (n=106, 13.0%, discrimination 0.92). Six early independent predictors of CAV trajectories were identified: donor age (p&amp;lt;0.001), donor male gender (p&amp;lt;0.001), donor tobacco consumption (p=0.001), recipient post-transplant dyslipidemia (p=0.009), preexisting or de novo class II anti-HLA donor-specific antibodies (p=0.004) and episode of acute cellular rejection ≥2R during the first year post transplantation (p=0.028). Conclusion In a large multicentric and highly phenotyped prospective cohort of heart transplant recipients, we identified 4 robust CAV trajectories and their respective immune and non-immune determinants. Our results provide the basis for a trajectory-based assessment of heart transplant patients for early patient risk stratification and patient monitoring. Factors associated CAV trajectories in multivariate analyses in the derivation cohort. This table shows the association of clinical, immunological, functional and structural parameters associated with CAV trajectories in multivariate multinomial regression analysis. The trajectory of reference was trajectory #1, including patients with no CAV at baseline and stable CAV grade over time. Funding Acknowledgement Type of funding source: None

Donor specific anti-HLA antibodies and cardiac allograft vasculopathy: A prospective study using highly automated 3-D optical coherence tomography analysis

IntroductionRecent studies suggested potential positive correlations between HLA-specific antibodies and development of cardiac allograft vasculopathy (CAV). MethodsThis prospective two-center study investigated early progression of CAV by coronary optical coherence tomography in 1 month and 12 months after heart transplantation (HTx) in 104 patients. Detection and characterization of donor specific (DSA) and MHC class-I polypeptide-related sequence A (MICA) antibodies were performed before, 1, 6 and 12 months after transplantation. ResultsDuring the first post-HTx year, we observed a significant reduction in the mean coronary luminal area (P < .001), and progression in mean intimal thickness (IT) (P < .001). DSA and anti-MICA occurred in 17% of all patients, but no significant relationship was observed between presence of DSA/anti-MICA and IT progression within 12 months after HTx. In contrast, we observed significant association between presence of DSA (p=0.031), de-novo DSA (p=0.031), HLA Class II DSA (p=0.017) and media thickness (MT) progression. ConclusionResults of our study did not identify a direct association between presence of DSA/anti-MICA and intimal thickness progression in an early period after HTx. However, we found significant relationships between DSA and media thickness progression that may identify a newly recognized immune-pathological aspect of CAV.

Class II Donor-Specific Anti-HLA Antibody Level Is the Major Determinant of Elevated Donor-Derived Cell-Free DNA in Renal Allograft Recipients

Class II Donor-Specific Anti-HLA Antibody Level Is the Major Determinant of Elevated Donor-Derived Cell-Free DNA in Renal Allograft Recipients

Double-Filtration Plasmapheresis Plus Low-Dose Anti-thymocyte Globulin and Tacrolimus in Asian Living-Donor Kidney Transplantation With Donor-Specific Anti-HLA Antibody

BackgroundPretransplant desensitization protocols, including plasmapheresis, intravenous immunoglobulin, induction antibody therapy, and intensive maintenance immunosuppression, are generally employed in kidney transplant recipients who have positive status for donor-specific anti-HLA antibody (DSA). To avoid serious infectious complications, the authors designed a novel low-dose protocol in Thai patients undergoing DSA+ living-related kidney transplantation (LRKT). MethodsA retrospective cohort study of the patients who underwent DSA+ LRKT was conducted. The novel protocol consisted of 3 to 5 sessions of pretransplant double-filtration plasmapheresis (DFPP) with or without low-dose intravenous immunoglobulin together with low-dose anti-thymocyte globulin (ATG) induction (1-1.5 mg/kg/d for 3-4 days) and low-dose tacrolimus (Tac) (trough level 5-10 ng/mL), mycophenolate, and prednisolone. ResultsThe study included 17 patients. The lymphocyte crossmatch via complement-dependent cytotoxicity was negative in 12 patients and positive for B cell immunoglobulin M in 5 patients. The novel desensitization protocol resulted in a decrease of at least 50% of DSA mean fluorescence intensity from baseline (from 4320 ± 549 before DFPP to 1601 ± 350 before transplantation, P < .005) and successful kidney transplantation with good allograft function in all cases. Early DSA rebound was observed in 3 patients after transplantation, and kidney biopsy revealed subclinical antibody-mediated rejection in 1 patient and diffuse C4d staining without cell infiltration in 2 patients. There were good long-term outcomes in patient and graft survival (100% and 94.1%, respectively). Only 1 allograft loss occurred because of nonadherence. The majority of patients have stable allograft function with serum creatinine less than 1.5 mg/dL. However, infections, including CMV and other organisms, were commonly observed. ConclusionsDesensitization protocol with DFPP, low-dose ATG, and Tac provides excellent outcomes in living donor kidney transplantation in highly sensitized Asian populations.

Human Leukocyte Antigen Examination Using Luminex®-Based Assays for Donor-Recipient Compatibility Assessment in Kidney Transplantation: Our Preliminary Experience

Background: Detection of anti-HLA antibodies (HLAabs) in organ transplantation recipients is vital to determine whether the recipient has specific HLAabs against the donor’s HLA molecules (donor-specific anti-HLA antibodies [DSA]). Methods: This preliminary study involved seven subjects: five without prior HLA sensitization and two with a history of possible HLA sensitization (kidney transplantation and pregnancy). Two of the subjects were siblings, two of the subjects were mother and son, and two of them were first cousins once removed. All the subjects underwent HLA typing, and four of the subjects underwent HLAabs assays using the sequence-specific oligonucleotide probes (SSOP) method. Results: There were 10/16 HLA matches between subjects who were siblings and between subjects who were mother and son, and 6/16 HLA matches were found between subjects who were first cousins once removed. Subjects with previous kidney transplantation developed 59 HLA-Abs toward class I and class II HLA (the mean fluorescence intensity (MFI) value range: 1,003.36 to 12,404.77). HLAabs were also found among subjects without prior HLA sensitization, albeit with relatively lower MFI values. Conclusions: HLA typing and HLAabs detection for donor-recipient compatibility assessment using the SSOP method offers more detailed, semi-quantitative results. Further research involving larger subjects in cohort settings will be useful for profiling MFI cut-off values for HLAabs.

Impact of Immunoglobulin M-Type Donor-Specific Human Leukocyte Antigen-Antibody Levels in Supernatants from Cultured Peripheral Blood Mononuclear Cells as Predictors of Antibody-Mediated Rejection.

Background: Antibody-mediated rejection (AMR) is a crucial barrier in the long-term prognosis of transplant recipients. Methods: Peripheral blood mononuclear cells (PBMCs) were collected from kidney allograft recipients (N = 41) and cultured in vitro for 1 week. Furthermore, the supernatants of the cultured PBMCs were analyzed by Luminex single-antigen beads. Results: Analyses using Luminex single-antigen beads revealed the presence of immunoglobulin (Ig) G donor-specific anti-HLA antibodies (DSAs) was detected in the supernatants of cultured PBMCs collected more frequently than IgM in de novo DSA-sensitized patients with AMR, and IgM were detectable in patients with stable graft function mainly and several IgM DSAs were detectable in the supernatants of the cultured PBMCs before detecting the IgG levels in sera. We also found that the DSA-specific IgM-secreting memory B cells (mBCs) were more sensitive to the chronic use of immunosuppressive agents than to the IgG-secreting mBCs. Conclusions: In the transplant recipients, the assessment of supernatants of cultured PBMCs provide more details of immune reactions than the commonly used method that directly measures IgG DSA levels in patient sera and some IgM DSA detection may be a better predictor of IgG DSAs production, which may cause AMR and enable early intervention, in initial stages of AMR development.

CT-371: Impact of Donor-Specific Anti-HLA Antibody on Platelet Transfusion Refractoriness in Haplo-Identical Hematopoietic Stem Cell Transplant Patients: A Single-Center Experience

Context Outcomes of haplo-identical hematopoietic stem cell transplantation (haploSCT) have recently improved due to better control of allo-reactive reactions related to the major HLA mismatch between the recipient and the donor. Presence of pretransplant donor-specific anti-HLA antibodies (DSA) is associated with higher risk of graft failure. However, little is known regarding the association between the presence of these antibodies and platelet transfusion refractoriness (PTR) post-haploSCT that could predict poor transplant outcomes. Objective The aim of this study is to evaluate the association between DSA status of the recipient and the corrected platelet count increment (CCI) from day 0-100 post-haploSCT as an objective measure of PTR. Design This is a retrospective study that comprises chart review of patients who underwent haplo-SCT between June 2015 and January 2020 at the American University of Beirut medical center in Lebanon. Main outcome measures Pretransplant panel reactive antibodies (PRA) and DSA status at the time of transplant were collected, and the 24-hour CCI was calculated for every platelet donor transfusion. Results We identified 69 patients with a median age of 36 years (range: 16-77). 44 patients (64%) were males and 52 patients (75%) had myelodysplastic syndrome or acute leukemia. Median time from diagnosis to transplant was 13.8 months (range: 2.5-91.7), and 43 patients (62%) were in complete remission at transplant. Of all patients, only 6 patients (8.7%) were DSA+ at time of transplant, 14 (20.3%) were PRA+/DSA-, and the remaining 49 (71%) were PRA-. All 6 patients with DSAs underwent desensitization with a median MFI decrease of 375 (range: -541-1603). One of these 6 did not reach platelet nor leukocyte engraftment. Patients with persistent DSAs had lower mean CCI (9.27, range: 4.58-12.37) compared to those without DSAs (mean CCI: 11.93, range: 1.34-29.71; p=0.017). Statistical significance was maintained upon comparing PRA+DSA+ patients to PRA+DSA- and to PRA- patients with mean CCI of 14.04 (range: 1.39-29.71; p=0.005) and 11.38 (range: 1.34-28.00, p=0.024), respectively. Conclusions Presence of anti-HLA DSAs in haploSCT recipients, even at MFI lower than 1500, was associated with increased PTR. Larger number of patients is needed to evaluate its impact on survival outcomes.

CLINICAL SIGNIFICANCE OF LATE ANTIBODY-MEDIATED REJECTION WITHOUT DONOR-SPECIFIC ANTI-HLA ANTIBODIES

Background: Late onset antibody-mediated rejection (AMR) is a leading cause of kidney allograft failure. Its diagnosis has been based on a combination of morphologic, immunohistologic findings, and presence of donor-specific anti-HLA antibodies (DSA). Although the presence of DSA is no longer required for AMR diagnosis according to Banff 2017 classification, the clinical significance of late onset AMR without DSA remains unclear. Here we compared clinical outcomes of late onset AMR with and without DSA. Methods: We analyzed 126 cases of late AMR (> 6 months after transplant) that meet the Banff 2017 histologic criteria for AMR. All cases were diagnosed by for cause biopsy and grouped into DSA-positive (n=103) and DSA-negative (n=23) AMR groups. The estimated glomerular filtration rate (eGFR) was calculated using the Chronic Kidney Disease Epidemiology Collaboration equation. Results: The histological picture did not differ between DSA-negative and DSA-positive AMR, with the exception of increased level of peritubular capillaritis in DSA-positive AMR. Median time from transplant to AMR diagnosis was 80 months (IQR, 39-118). At the time of AMR diagnosis, both groups had similar graft function (36.3 ± 16.0 for DSA-negative and 39.7 ± 20.2mL/min/1.73 m2 for DSA-positive AMR, P=0.408). Mean eGFR after AMR were similar irrespective of the presence of DSA. There were 28 (26.2%) graft failures in the DSA-negative and 8 (27.6%) graft failures in the DSA-positive AMR groups, which was not statistically different (P=0.950). Conclusion: In late onset AMR, there was no significant difference between AMR with and without DSA in clinical outcomes.