Donor-specific anti-HLA Antibodies Research Articles

Absence of IL-6 Receptor Blockade Effect on the Outcomes of Transplant Glomerulopathy in the Absence of Anti-HLA Donor-specific Antibodies

Absence of IL-6 Receptor Blockade Effect on the Outcomes of Transplant Glomerulopathy in the Absence of Anti-HLA Donor-specific Antibodies

(778) - Correlation Between the Subtype of Anti-HLA Donor Specific Antibodies and Rejection Assessed by Molecular Microscope

(778) - Correlation Between the Subtype of Anti-HLA Donor Specific Antibodies and Rejection Assessed by Molecular Microscope

(699) - Ten-Year Results of an IgA- and IgM-Enriched Human Immunoglobulin-Based Therapy for Early Detectable Anti-HLA Donor Specific Antibodies After Lung Transplantation

(699) - Ten-Year Results of an IgA- and IgM-Enriched Human Immunoglobulin-Based Therapy for Early Detectable Anti-HLA Donor Specific Antibodies After Lung Transplantation

Lymphocyte Crossmatch Testing or Donor HLA-DP and -DQ Allele Typing Effectiveness in Single Cord Blood Transplantation for Patients With Anti-HLA Antibodies Other Than Against HLA-A, -B, -C, and -DRB1

Anti-human leukocyte antigen (HLA) antibodies other than those against HLA-A, -B, -C, and DRB1 are a risk factor for engraftment delay and failure, especially in cord blood transplantation (CBT). The primary objective of this study was to assess the impact of the presence of anti-HLA antibodies on CBT and to evaluate the utility of lymphocyte crossmatch testing or additional HLA-DP and -DQ typing of CB units in improving transplant outcomes. We retrospectively assessed the engraftment rates and transplant outcomes of 772 patients who underwent their first CBT at our hospital between 2012 and 2021. Donors were routinely typed for HLA-A, -B, -C, and-DRB1 alleles, and the anti-HLA antibodies of recipients were screened before donor selection in all cases. Among patients who had antibodies against other than HLA-A, -B, -C, and DRB1 (n = 58), lymphocyte crossmatch testing (n = 32) or additional HLA-DP/-DQ alleles typing of CB (n = 15) was performed to avoid the use of units with corresponding alleles. The median patient age was 57 years (16 to 77). Overall, 75.7% had a high-risk disease status at transplantation, 83.5% received myeloablative conditioning regimens, and >80% were heavily transfused. Two hundred twenty-nine of the 772 recipients (29.6%) were positive for anti-HLA antibodies. There were no statistical differences in the number of infused CD34-positive cells between the anti-HLA antibody-positive and the anti-HLA antibody-negative patients. Of the 229 patients with anti-HLA antibodies, 168 (73.3%) had antibodies against HLA-A, -B, -C, and-DRB1 (Group A), whereas 58 (25.3%) had antibodies against HLA-DP, HLA-DQ, or -DRB3/4/5 with or without antibodies against HLA-A, -B, -C, and -DRB1 (Group B). No patients in both Groups A and B exhibited donor-specific anti-HLA antibodies against HLA-A, -B, -C, and -DRB1. The neutrophil engraftment rate was lower in patients with anti-HLA antibodies than in those without antibodies (89.9% versus 94.1%), whereas nonrelapse mortality (NRM) before engraftment was higher in antibody-positive patients (9.6% versus 4.9%). In patients who received 2 or more HLA allele-mismatched CB in the host-versus-graft (HVG) direction (n = 685), the neutrophil engraftment rate was lower in the anti-HLA antibody-positive recipients than in the antibody-negative recipients with significant differences (88.8% versus 93.8%) (P = .049). Similarly, transplant outcomes were worse in the antibody-positive patients with respect to 2-year overall survival (OS) (43.1% versus 52.3%) and NRM (44.0% versus 30.7%) than in the antibody-negative patients. In contrast, the results of Group B were comparable to those of the antibodies-negative patients, while the results of Group A were statistically worse than the antibody-negative patients in terms of all engraftment rate (88.6%), OS (34.2%), and NRM (49.0%). The presence of anti-HLA antibodies negatively impacts engraftment, NRM, and OS in CBT. However, HLA-DP/-DQ allele typing of CB units or lymphocyte crossmatch testing could be useful strategies to overcome poor engraftment rates and transplant outcomes, especially in patients with anti-HLA antibodies against HLA-DP, HLA-DQ, or -DRB3/4/5.

Including the liver in the visceral allograft: Impact on donor-specific anti-HLA antibodies and long-term outcomes

Humoral immunity emerges as a risk factor for graft failure after visceral transplantation (VTx) and development of donor-specific anti-HLA antibodies (DSAs) has been linked with poor outcomes. In most cases, a simultaneous liver transplant can be safely performed in sensitized patients with DSA and appears protective against lymphocytotoxic antibodies. We investigated the incidence of acute (AR) and chronic rejection (CR) in 32 VTx without any B cell-depleting pre-treatment (6 isolated intestinal transplants (IT) and 26 liver-containing, multivisceral transplants (MVT) and assessed the presence of donor-specific antibodies (DSA) pre- and post-transplantation. Twenty-one patients (65 %) developed AR, 15 (57 %) of the MVT and 6 (100 %) of the IT (p = 0.05). CR occurred in 4 IT (60 %, p < 0.001). At one month, de novo DSA were present in 71 % of VTx (66 % MVT vs 100 % IT, p = 0.09). At the last available follow-up, 69 % of the MVT and 50 % of the IT patients were DSA-free. De novo DSA seemed more persistent (7/19, 37 %) than pre-Tx DSA (1/6, 17 %; p = n.s.), de novo DSA were more frequently specific for HLA class II than class I, 16/19 (84 %) vs. 7/19 (37 %; p = 0.003), and HLA-DQ was their most frequent target HLA. DQ mismatches appeared to be a risk factor for developing de novo DSA. In conclusion, liver-containing visceral allografts have superior short- and long-term outcomes compared with liver-free allografts. De novo DSA develop early and frequently after VTx performed without B cell-depleting induction therapy, but the exact role of DSA in the pathogenesis of rejection remains unclear.

Donor specific anti-HLA antibodies in hematopoietic stem cell transplantation. Single Center prospective evaluation and desensitization strategies employed.

In the setting of mismatched-hematopoietic stem cells transplantation, the detection of antibodies directed against donor-specific HLA allele(s) or antigen(s) (DSA) represents a barrier for engraftment. It is thus necessary to plan an immunosuppressive strategy, or to select an alternative donor. This prospective study aimed at evaluating the efficacy of our strategy for testing DSAs and the efficacy of the desensitization strategy (DS) employed between November 2017 and November 2020. The anti-HLA antibody search was performed using the Luminex bead assays (Lifecode ID and LSA I/II-Immucor) and expressed as mean fluorescence intensity (MFI >1,000 positive). If the patient had DSAs and no alternative donors, a DS was employed with rituximab (day -15), 2 single volume plasmaphereses (PP; days -9 and -8), intravenous immunoglobulins (day -7) and infusion of HLA selected platelets, if persistent DSAs were directed against class I HLA. DS was scheduled with or without PP, according to the DSA MFI (>1,000 or <5,000) and FCXM (flow cytometry crossmatch). Twenty-two out of 126 patients (17.46%) showed anti-HLA antibodies, 5 of them DSAs (3.97% of total); 3 patients underwent DS obtaining engraftment. Female gender (p=0.033) and a history of previous pregnancies or miscarriages (p=0.009) showed a statistically significant impact on alloimmunization. Factors associated with a delayed neutrophil engraftment were patient's female gender (p=0.039), stem cell source (p=0.025), and a high HSCT-specific comorbidity index (p=0.028). None of the analyzed variables, including the DSA detection, influenced engraftment. Our study confirms the importance to test DSAs in mismatched-hematopoietic stem cells transplantation The DS used proved successful in removing DSAs. Prospective multicenter studies are needed to better define and validate consensus strategies on DSA management in HSCT.

Enhanced Donor Antigen Presentation by B Cells Predicts Acute Cellular Rejection and Late Outcomes After Transplantation.

Enhanced B-cell presentation of donor alloantigen relative to presentation of HLA-mismatched reference alloantigen is associated with acute cellular rejection (ACR), when expressed as a ratio called the antigen presenting index (API) in an exploratory cohort of liver and intestine transplant (LT and IT) recipients. To test clinical performance, we measured the API using the previously described 6-h assay in 84 LT and 54 IT recipients with median age 3.3 y (0.05-23.96). Recipients experiencing ACR within 60 d after testing were termed rejectors. We first confirmed that B-cell uptake and presentation of alloantigen induced and thus reflected the alloresponse of T-helper cells, which were incubated without and with cytochalasin and primaquine to inhibit antigen uptake and presentation, respectively. Transplant recipients included 76 males and 62 females. Rejectors were tested at median 3.6 d before diagnosis. The API was higher among rejectors compared with nonrejectors (2.2 ± 0.2 versus 0.6 ± 0.04, P value = 1.7E-09). In logistic regression and receiver-operating-characteristic analysis, API ≥1.1 achieved sensitivity, specificity, and positive and negative predictive values for predicting ACR in 99 training set samples. Corresponding metrics ranged from 80% to 88% in 32 independent posttransplant samples, and 73% to 100% in 20 independent pretransplant samples. In time-to-event analysis, API ≥1.1 predicted higher incidence of late donor-specific anti-HLA antibodies after API measurements in LT recipients (P = 0.011) and graft loss in IT recipients (P = 0.008), compared with recipients with API <1.1, respectively. Enhanced donor antigen presentation by circulating B cells predicts rejection after liver or intestine transplantation as well as higher incidence of DSA and graft loss late after transplantation.

An Optimal Multi-Locus HLA-Typing in Potential Donors of Allogeneic Hematopoietic Stem Cells

Background. HLA-typing and matched donor selection as well as the detection of donor-specific anti-HLA antibodies are essential for allogeneic hematopoietic cell transplantation (allo-HSCT). In accordance with the guidelines of the Center for International Blood and Marrow Transplant Research (CIBMTR) optimal HLA-typing is performed on 11 HLA genes (-A, ‐B, ‐C, ‐DRB1, ‐DRB3/4/5, ‐DQA1, ‐DQB1, ‐DPA1, and ‐DPB1) with an adequate coverage aiming to obtain the values at the two-field level.&#x0D; Aim. To assess the results of multi-locus HLA-typing in bone marrow/hematopoietic cell donors from the database at the National Research Center for Hematology in terms of their conformance with the CIBMTR guidelines for allo-HSCT and to analyze the frequency and distribution of HLA alleles and multi-locus HLA haplotypes.&#x0D; Materials &amp; Methods. The study enrolled 3485 donors who were HLA-typed by next-generation sequencing.&#x0D; Results. In all donors, the alleles of HLA class I genes were identified at the fourth-field level (nucleotide sequence). When the results were reduced to the second-field level (amino acid sequence), 61 HLA-A, 92 HLA-B, and 49 HLA-C alleles were detected. The alleles of class II genes were discovered either at the two-field or high-resolution levels. Among the HLA-DRB locus genes, 57 DRB1, 11 DRB3, 6 DRB4, and 5 DRB5 alleles were identified. Also, 23 HLA-DQA1, 30 HLA-DQB1, 14 HLA-DPA1, and 33 HLA-DPB1 alleles were detected. There were reported 3289 different HLA haplotypes of A-B-C-DRB1-DQA1-DQB1-DPA1-DPB1 genes.&#x0D; Conclusion. The database created at the National Research Center for Hematology includes potential bone marrow/hematopoietic stem cell donors typed for 11 classical polymorphic genes HLA-A, ‐B, ‐C, ‐DRB1, ‐DRB3/4/5, ‐DQA1, ‐DQB1, ‐DPA1, and -DPB1, which is in line with the guidelines of CIBMTR. The frequency and distribution of HLA alleles and multi-locus HLA haplotypes in our donors correspond to those in populations of European origin. HLA-typing and donor selection with regard to 11 HLA genes will contribute to improving the outcomes of both unrelated and haploidentical HSCTs.

Assessment of IgM DSAs in Transplant Recipients: Relationship to De Novo IgG DSAs and Risk for Antibody Rejection.

The presence of anti-HLA donor-specific antibodies (DSAs) is associated with antibody-mediated rejection (AMR) and inferior graft survival. However, recent data suggest that ~50% of AMR episodes are IgG DSA negative and possibly related to non-HLA DSAs. After the initial activation of B cells to alloantigen, IgM is the first immunoglobulin produced. In addition, both IgM and IgG isotopes can activate the classic complement pathway and induce complement-dependent cytotoxicity to allograft targets. Current practices focus on the assessment of IgG DSAs with little concern for the assessment of IgM DSAs. Here, we examined anti-HLA IgM in a cohort of 22 patients who developed de novo IgG DSAs by a modified single-antigen bead-based test. We found IgM HLA DSAs developed before IgG DSAs. The median time from the detection of IgM DSAs to the appearance of de novo IgG DSAs was 461 d. Most patients had IgM DSAs against the same HLA-DQ antigens, for which IgG de novo DSAs were also later detected. IgM DSAs were detected in patients with biopsies suspected of AMR. The detection of IgM DSAs could be an early indicator of alloimmune responses to allografts before IgG de novo DSAs appear.

Evaluation of rapid optimized flow cytometry crossmatch (Halifaster) in living donor kidney transplantation.

Kidney transplantation is often the preferred treatment for end-stage renal disease. However, the presence of preformed donor-specific antibodies (DSA), including those against HLA, can lead to antibody-mediated rejection and significantly impact transplant outcomes. The Flow Cytometry Crossmatch (FCXM) is a crucial tool in kidney transplantation, as it also enables the measurement of low levels of anti-HLA DSA antibodies. However, current methodologies for detecting these antibodies, however, are time-consuming and require extensive reagents. In this study, we analyzed the performance of the Halifaster FCXM protocol in 133 consecutive living kidney donor pairs, correlating these results with single antigen-based anti-HLA DSA results. Anti-HLA DSA was identified in 31 patients (23.3%). Both T and B lymphocyte FCXM assays demonstrated high sensitivity and specificity in detecting anti-HLA DSA. Furthermore, a Tree model to determine the levels of anti-HLA DSA to produce a flow crossmatch positivity, was developed offering an accuracy of 93% and 90% for T and B lymphocytes, respectively. Both approaches point to a thresh old of 1000-2000 MFI for T lymphocytes and 3000 MFI for B lymphocytes. Our findings indicate that the Halifaster protocol facilitates fast and efficient FCXM testing without compromising accuracy, marking a significant advancement in the field of kidney transplantation. The inclusion of HLA-specific antibody analysis underscores the protocol's comprehensive approach to improving transplant outcomes.

Impact of Immunosuppression Intensified Conditioning Regimen for Patients with Strong Positive Pre-Transplantation Donor Specific Anti-HLA Antibodies (DSAs) Undergoing Haploidentical Hematopoietic Stem Cell Transplantation

Objective: Immunosuppression intensified conditioning regimen has been applied for 10 patients with strong positive pre-transplantation Donor specific Anti-HLA Antibodies (DSAs) undergoing Haploidentical Hematopoietic Stem Cell Transplantation (HSCT), its effects on engraftment of hematopoietic stem cell were examined. Methods: Characteristics of 10 consecutive patients with strong positive pre-transplantation DSAs were retrospectively analyzed, including gender, age, diagnosis, disease status pre-transplantation, presence of DSA, conditioning regimens, engraftment, graft versus host disease (GVHD) incidence and survival. Results: Ten patients [3 males vs 7 females, median age 53.5(36-64)] received immunosuppression intensified conditioning regimen: Fludarabine plus busulfan (FluBu) combining total body irradiation and cyclophosphamide (TBI-Cy). DSA levels gradually decreased in all patients after preparative conditioning, and the mean fluorescence intensity (MFI) values dropped significantly (P＜0.003). The average MFI values dropped 40% at day 7 post-HSCT, 8 cases acquired hematopoietic reconstitution, the median time of neutrophil engraftment was 15.6(10-16) days, and 19(13-22) days for platelet engraftment. One case had primary graft failure and another one had poor graft function. After a median follow-up of 12.5(1.5-27) months, 7 cases remained in disease remission state with negative DSA assay, including 2 cases with MFI values higher than 20000 pre-transplantation. Conclusions：Immunosuppression intensified conditioning regimen can efficiently decrease the Donor specific Anti-HLA Antibodies (DSA) level, which leads to lowered chances of primary graft failure.

CTLA-4 Blockade Results in the Enrichment of Proliferative CD56 dimCD16 + NK Cells Following Infusion of Haploidentical Donor Memory-like Natural Killer Cells Plus IL-15 Superagonist in a Phase 1 Trial

Introduction Regulatory T cells (Tregs) blunt anti-tumor responses of major immune effector cells including CD8 T cells and natural killer (NK) cells. Tregs constitutively express CTLA-4 and thus the use of ipilimumab, a CTLA-4 blocker can potentially overcome the Treg-mediated immune suppression. We (and others) have shown that a brief activation of conventional NK cells with the cytokine combination IL-12, IL-15, and IL-18 generates cytokine-induced memory-like (CIML) NK cells which exhibit enhanced anti-tumor responses, have a longer half-life (up to 90 vs ~12 days of conventional NK cells), and show promising activity in several early phase clinical trials. N-803 is an IL-15 super-agonist with a long half-life that preferentially activates and expands NK and CD8+ T cells without affecting Tregs, making it an ideal cytokine for combining with adoptive immunotherapy. In the current study, we hypothesized the use of ipilimumab (IPI) will abrogate Treg-mediated inhibition and thus allow enhanced proliferation, activation, and anti-tumor responses of the adoptively transferred CIML NK cells.To address this, we conducted a phase 1 trial of HLA-haploidentical CIML NK cells in combination with IPI and N-803 in patients with advanced head and neck cancer (HNC). Using flow cytometry and CITE-Seq on the banked peripheral blood samples, we performed an in-depth characterization of NK cells expanded following IPI pre-exposure and compared it to those who did not receive IPI. Methods We enrolled 10 patients with refractory HNC regardless of human papillomavirus (HPV) status who had prior platinum and immunotherapy (NCT04290546). All patients received lymphodepletion with fludarabine (25 mg/m 2 x 5 days) and cyclophosphamide (60 mg/kg x 2 days) during days -6 to -2 prior to haploidentical CIML NK cell infusion on day 0 (5-10 x 10 6 cells/kg=dose level 0) followed by N-803 (15 mcg/kg subcutaneously) starting on day +1 every 21-days for 4-doses. In cohort 2, patients received IPI (3 mg/kg) on day -7, no ipilimumab was given to the first 6 patients treated on the lead-in safety cohort 1. Flow cytometry using a custom NK cell panel was performed on samples collected on days +7, +14, +21, +28, +42, and +60 after CIML NK cell infusion. FlowSOM clustering was performed on NK cell markers. UMAP clustering was applied to CITE sequencing data acquired from samples collected on day +7 and day +28, and well-defined markers genes for each cluster were used to identify cell populations. NK cell function (cytotoxicity, IFNg, and CD107a) was assessed using flow-cytometry based assays. Results The median age of the patients was 58, 90% were men and 80% had oropharyngeal primaries. Mild CRS (grade 2 or lower) was observed in 60% of patients. No neurotoxicity or graft-versus-host disease was observed. Maximal expansion of NK cells occurred on day +7 following CIML NK cell infusion in 9/10 of patients. The single patient without NK cell expansion was found to have a donor-specific anti-HLA antibody. Day +7 NK cells exhibited upregulation of IFNg expression following cytokine restimulation as compared to resting NK cells. Tumor regression was observed in 50% of treated patients at day +30 based on RECIST v1.1 criteria. Patients who had tumor regression had an expansion of CD56 dimCD16 + NK cell clusters by day +14. IPI treated patients were noted to have a relative enrichment of CD16 + NK cell metaclusters at day +14 compared to no IPI patients (Figure 1A). At the time of maximal NK cell expansion, CITEseq defined NK cell clusters were dominant in both IPI and no IPI patients, but the proliferative gene sets were enriched in the IPI treated patient (Figure 1B). IPI exposure had no effect on the distribution of regulatory T cells or CD8 + T cell populations at day +28 compared to the no IPI patients. Conclusions The use of donor-derived CIML NK cells is safe and associated with tumor regression in patients with advanced HNC. The use of IPI was associated with the preferential expansion of CD16 + NK cell clusters that had enrichment of proliferative gene sets. Tumor regression was associated with CD56 dimCD16 + NK cell expansion. Further work is required to elucidate the mechanism by which IPI exposure is associated with the expansion of specific subsets of CIML NK cells.

Comparison of Non-Relapse Mortality after Haploidentical Hematopoietic Stem Cell Transplantation with Post-Transplant Cyclophosphamide Versus Single Umbilical Cord Blood Transplantation for Hematologic Disease

Introduction: Unrelated cord blood transplantation (UCBT) and haploidentical stem cell transplantation with post-transplant cyclophosphamide as graft-versus-host disease (GVHD) prophylaxis (PTCy-haplo) are alternative options for patients with hematologic disease lacking a human leukocyte antigen (HLA)-matched donor. Non-relapse mortality (NRM) after UCBT may vary depending on the cord blood CD34+ cell count, but no study has accounted for CD34+ cell count when comparing the outcomes after UCBT and PTCy-haplo. Therefore, we analyzed transplant outcomes after UCBT and PTCy-haplo in patients with hematologic disease from data of a nationwide registry that included cord blood CD34+ cell count. Methods: Patients with hematologic disease receiving first UCBT or PTCy-haplo between 2014 and 2020 were identified from the nationwide registration data of the Japanese Data for Hematopoietic Cell Transplantation. Acute GVHD-related mortality was defined as death caused primarily by GVHD or occurred secondary to GVHD, and infection-related mortality as death due to graft failure or infection but not acute GVHD. Patients treated by UCBT were stratified by the median CD34+ cell count for comparison (0.84 × 10 5/kg). Results: A total of 7,499 patients were enrolled and classified into 3 groups: PTCy-haplo (n = 1,142), UCBT with high CD34+ cell count (UCB-H; ≥ 0.84 × 10 5/kg, n = 3,185), and UCBT with low CD34+ cell count (UCB-L; &amp;lt; 0.84 × 10 5/kg, n = 3,172). Patients in the PTCy-haplo group were slightly younger than UCB-H and UCB-L patients (median age: 54 vs. 56 and 55 years). The PTCy-haplo group also included a greater proportion of males than the UCB-H group (62.4% vs. 50.0%) but not the UCB-L group (64.2%). A greater proportion of PTCy-haplo patients had a PS score of 0 (53.2% vs. 46.2% and 45.6%), a hematopoietic cell transplantation-specific comorbidity index of 0 (57.6% vs. 52.7% and 54.4%) and donor-specific anti-HLA antibody (2.7% vs. 1.0% and 1.6%), received reduced-intensity conditioning (58.0% vs. 40.5% and 41.6%), calcineurin inhibitor with mycophenolate mofetil (88.5% vs. 38.6% and 38.4%), and underwent transplantation in the later period (82.0% vs. 54.6% and 50.7%). There were no significant differences in disease-risk index between groups. At 2 years post-transplantation, NRM and overall survival (OS) were significantly better in the PTCy-haplo group than the UCB-H and UCB-L groups (NRM: 18.8% vs. 21.6% and 25.3%, P &amp;lt; 0.001; OS: 56.2% vs. 53.3% vs. 49.6%, P &amp;lt; 0.001). Neutrophil engraftment rate at 42 days was also significantly higher in the PTCy-haplo group than the UCB-H and UCB-L groups (93.7% vs. 87.5% and 82.9%, P &amp;lt; 0.001). The PTCy-haplo group less frequently developed grade II-IV (26.4% vs. 37.3% and 34.4%, P &amp;lt; 0.001) and III-IV acute GVHD (7.0% vs. 12.2% and 10.5%, P &amp;lt; 0.001). While neither the differences in NRM nor that in OS remained significant between PTCy-haplo and UCB-H groups in multivariable analysis (NRM: hazard ratio [HR], 1.18, 95% confidence interval [CI], 0.99-1.41, P = 0.073; OS: HR, 1.05, 95% CI, 0.94-1.17, P = 0.42), significant differences were maintained between PTCy-haplo and UCB-L groups (NRM: HR, 1.35, 95% CI, 1.13-1.61, P = 0.001; OS: HR, 1.12, 95% CI, 1.00-1.26, P = 0.042). Regarding the cause-specific mortality, infection-related mortality was also significantly lower in the PTCy-haplo group compared to UCB-H and UCB-L groups (8.1% vs. 11.1% and 13.6%, P &amp;lt; 0.001) while GVHD-related mortality did not differ among groups (5.0% vs. 5.2% and 4.9%, P = 0.69). Conclusion: UCBT-H resulted in similar NRM and OS as patients receiving PTCy-haplo, whereas outcomes were worse in UCBT-L. These findings indicate that high CD34+ cell count in cord blood is a critical criterion for alternative donor selection.

Comparison of human leukocyte antigen immunologic risk stratification methods in lung transplantation

Outcomes after lung transplantation (LTx) remain poor, despite advances in sequencing technology and development of algorithms defining immunologic compatibility. Presently, there is no consensus regarding the best approach to define human leukocyte antigen (HLA) compatibility in LTx. In this study, we compared 5 different HLA compatibility tools in a high-resolution HLA-typed, clinically characterized cohort, to determine which approach predicts outcomes after LTx. In this retrospective single-center study, 277 donor-recipient transplant pairs were HLA-typed using next generation sequencing. HLA compatibility was defined using HLAMatchmaker, HLA epitope mismatch algorithm (HLA-EMMA), predicted indirectly recognizable HLA epitopes (PIRCHE), electrostatic mismatch score (EMS), and amino acid mismatches (AAMMs). Associations with HLA mismatching and survival, chronic lung allograft dysfunction (CLAD), and anti-HLA donor-specific antibody (DSA) were calculated using adjusted Cox proportional modeling. Lower HLA class II mismatching was associated with improved survival as defined by HLAMatchmaker (P < .01), HLA-EMMA (P < .05), PIRCHE (P < .05), EMS (P < .001), and AAMM (P < .01). All approaches demonstrated that HLA-DRB1345 matching was associated with freedom from restrictive allograft syndrome and HLA-DQ matching with reduced DSA development. Reducing the level of HLA mismatching, in T cell or B cell epitopes, electrostatic differences, or amino acid, can improve outcomes after LTx and potentially guide immunosuppression strategies.

Anti-Hla Donor-Specific Antibodies Are Associated to Infection and Not to the Engraftment Rate in Outpatient Haploidentical Hematopoietic Cell Transplantation.

Recipients of a related haploidentical stem cell transplant (haplo-SCT) can have preformed antibodies to HLA donor’s antigens. The aim of the study was to evaluate the engraftment rate and major clinical associations of anti-HLA donor-specific antibodies (DSA) at two mean fluorescence intensity (MFI) thresholds in recipients of an outpatient haplo-SCT. Seventy haplo-HCT recipients were analyzed. A virtual crossmatch was performed using the donor HLA typing and the recipient’s anti-HLA DSA test results. Data for anti-HLA-A, -B, -C, and -DR were analyzed. Recipients with DSA ≥ 500 MFI were considered positive, and those with < 500 were considered negative; the same was adopted for MFI ≥ 1000. Post-transplant infection was higher in recipients with DSA ≥ 500 MFI (84.6%, p = 0.041). First-year mortality was higher in DSA-positive patients ≥ 500 MFI, p = 0.004, and DSA ≥ 1000 MFI, p = 0.022, than in DSA-negative recipients. Graft failure in the first 100 days was not associated with DSA ≥ 500 or ≥ 1000 MFI. There was no difference in acute (a-GVHD) or chronic (c-GVHD) graft versus host disease between DSA-positive and negative patients. There was no association of anti-HLA DSA at MFI ≥ 500 and ≥ 1000 with graft failure, however, increased infection and 1st-year mortality were documented in related haplo-HCT at the MFI cutoffs studied.

Complement-activating donor-specific anti-HLA antibodies in solid organ transplantation: systematic review, meta-analysis, and critical appraisal.

Several studies have investigated the impact of circulating complement-activating anti-human leukocyte antigen donor-specific antibodies (anti-HLA DSAs) on organ transplant outcomes. However, a critical appraisal of these studies and a demonstration of the prognostic value of complement-activating status over anti-HLA DSA mean fluorescence intensity (MFI) level are lacking. We conducted a systematic review, meta-analysis and critical appraisal evaluating the role of complement-activating anti-HLA DSAs on allograft outcomes in different solid organ transplants. We included studies through Medline, Cochrane, Scopus, and Embase since inception of databases till May 05, 2023. We evaluated allograft loss as the primary outcome, and allograft rejection as the secondary outcome. We used the Newcastle-Ottawa Scale and funnel plots to assess risk of bias and used bias adjustment methods when appropriate. We performed multiple subgroup analyses to account for sources of heterogeneity and studied the added value of complement assays over anti-HLA DSA MFI level. In total, 52 studies were included in the final meta-analysis (11,035 patients). Complement-activating anti-HLA DSAs were associated with an increased risk of allograft loss (HR 2.77; 95% CI 2.33-3.29, p<0.001; I²=46.2%), and allograft rejection (HR 4.98; 95% CI 2.96-8.36, p<0.01; I²=70.9%). These results remained significant after adjustment for potential sources of bias and across multiple subgroup analyses. After adjusting on pan-IgG anti-HLA DSA defined by the MFI levels, complement-activating anti-HLA DSAs were significantly and independently associated with an increased risk of allograft loss. We demonstrated in this systematic review, meta-analysis and critical appraisal the significant deleterious impact and the independent prognostic value of circulating complement-activating anti-HLA DSAs on solid organ transplant risk of allograft loss and rejection.

P204 Use of cell-free DNA analysis to determine need for renal transplant biopsy after detection of circulating donor-specific anti-HLA antibodies in renal transplant recipients

P204 Use of cell-free DNA analysis to determine need for renal transplant biopsy after detection of circulating donor-specific anti-HLA antibodies in renal transplant recipients

P228 De novo anti-HLA donor-specific antibodies not diagnostic for ABMR are associated with a higher risk of persistent/recurrent TCMR and graft dysfunction in kidney transplant patients

P228 De novo anti-HLA donor-specific antibodies not diagnostic for ABMR are associated with a higher risk of persistent/recurrent TCMR and graft dysfunction in kidney transplant patients

Prospective assessment of pre-existing and de novo anti-HLA IgE in kidney, liver, lung and heart transplantation.

Antibody mediated rejection (ABMR) is a major factor limiting outcome after organ transplantation. Anti-HLA donor-specific antibodies (DSA) of the IgG isotype are mainly responsible for ABMR. Recently DSA of the IgE isotype were demonstrated in murine models as well as in a small cohort of sensitized transplant recipients. In the present study, we aimed to determine the frequency of pre-existing and de novo anti-HLA IgE antibodies in a cohort of 105 solid organ transplant recipients. We prospectively measured anti-HLA IgE antibodies in a cohort of kidney (n=60), liver, heart and lung (n=15 each) transplant recipients before and within one-year after transplantation, employing a single-antigen bead assay for HLA class I and class II antigens. Functional activity of anti-HLA IgE antibodies was assessed by an in vitro mediator release assay. Antibodies of the IgG1-4 subclasses and Th1 and Th2 cytokines were measured in anti-HLA IgE positive patients. Pre-existing anti-HLA IgE antibodies were detected in 10% of renal recipients (including 3.3% IgE-DSA) and in 4.4% of non-renal solid organ transplant recipients (heart, liver and lung cohort). Anti-HLA IgE occurred only in patients that were positive for anti-HLA IgG, and most IgE positive patients had had a previous transplant. Only a small fraction of patients developed de novo anti-HLA IgE antibodies (1.7% of kidney recipients and 4.4% of non-renal recipients), whereas no de novo IgE-DSA was detected. IgG subclass antibodies showed a distinct pattern in patients who were positive for anti-HLA IgE. Moreover, patients with anti-HLA IgE showed elevated Th2 and also Th1 cytokine levels. Serum from IgE positive recipients led to degranulation of basophils in vitro, demonstrating functionality of anti-HLA IgE. These data demonstrate that anti-HLA IgE antibodies occur at low frequency in kidney, liver, heart and lung transplant recipients. Anti-HLA IgE development is associated with sensitization at the IgG level, in particular through previous transplants and distinct IgG subclasses. Taken together, HLA specific IgE sensitization is a new phenomenon in solid organ transplant recipients whose potential relevance for allograft injury requires further investigation.

Double filtration plasmapheresis combined with rituximab for donor-specific antibody desensitization in haploidentical haematopoietic stem cell transplantation.

Donor-specific anti-HLA antibodies (DSA) are a major cause of engraftment failure in patients receiving haploidentical haematopoietic stem cell transplantation (Haplo-HSCT). Double filtration plasmapheresis (DFPP) avoids the unnecessary loss of plasma proteins and increases the efficiency of purification. To investigate the effectiveness of the desensitization protocol including DFPP and rituximab, we conducted a nested case-control study. Thirty-three patients who had positive DSA were desensitized by the protocol and 99 patients with negative DSA were randomly matched as control. The median DSA mean fluorescence intensity values before and after DFPP treatment were 7505.88 ± 4424.38 versus 2013.29 ± 4067.22 (p < 0.001). All patients in DSA group achieved haematopoietic reconstitution and the median neutrophils and platelets engraftment times were 13 (10-21) and 13 (10-29) days respectively. Although the cumulative incidence of II-IV aGVHD (41.4% vs. 28.1%) and 3-year moderate to severe cGVHD (16.8% vs. 7.2%) were higher in DSA cohort than in the control, no statistical significance was observed. The 3-year non-relapse mortality and the overall survival were 6.39% and 72.0%, respectively, in the DSA cohort, which were comparable to the negative control. In conclusion, DFPP and rituximab could be effectively used for desensitization and overcome the negative effects of DSA in Haplo-HSCT.