Human Leukocyte Antigen Matching Research Articles

O236: The Impact of HLA Matching on Pancreas and Simultaneous Pancreas-Kidney (SPK) Transplantation Outcomes

Abstract Background This study evaluates the controversial impact of human leukocyte antigen (HLA) matching on pancreas graft survival and acute rejection. Methods Utilizing a large-scale multi-center database (UNOS/OPTN), we identified 8,005 pancreas and 7,850 simultaneous pancreas-kidney (SPK) transplant patients. Patients were classified into HLA matched (0-3 mismatches) and mismatched (4-6 mismatches) groups. Subsequently, utilizing multivariate Cox analysis, we evaluated risk-adjusted outcomes, represented through Kaplan-Meier survival curves. We also examined differences in graft survival and acute rejection based on transplant type (SPK or pancreas alone) within the same HLA mismatch group. Findings There were no significant differences in pancreas graft survival or acute rejection observed between HLA matched and mismatched groups for both pancreas and SPK transplant recipients (P > 0.05). However, among HLA mismatched patients, pancreas patients exhibited a 629-day lower pancreas graft survival than SPK patients (3774 vs. 4403 days, P < 0.001) and had a higher likelihood of experiencing acute rejection post-transplant (P < 0.001). Similarly, within the HLA matched groups, pancreas patients showed lower graft survival compared to SPK patients (3774 vs. 4403 days, P < 0.001); however, their acute rejection rates did not significantly differ (P > 0.05). Interpretation Although HLA matching was not associated with improved pancreas graft survival or a reduction in acute rejection, the results suggest a potential protective effect of the kidney in SPK transplants against the consequences of HLA mismatching. This underscores the clinical significance of considering the kidney component in donor-recipient matching for pancreas transplantation.

O204: The influence of HLA matching on graft survival in lung transplant recipients is indication specific: An UNOS database analysis

Abstract Background and aims The importance of human leukocyte antigen (HLA) matching in lung transplantation remains unclear, and the influence of indication in HLA compatibility is unknown. This study aimed to determine the relationship between HLA matching and lung graft survival using a large-scale multi-center database (UNOS/OPTN) and multivariate logistic analysis. The secondary aim was to determine whether this relationship was influenced by transplant indication. Methods This retrospective observational analysis was performed using 26,312 lung transplant recipients from the UNOS/OPTN database. Patients were divided into two groups based on number of HLA mismatches (0-3 mismatches vs 4-6 mismatches) and then subcategorized by indication. Risk-adjusted outcomes were assessed by multivariate Cox analysis adjusting for donor and recipient characteristics and visualized using Kaplan-Meier survival curves. Results Increased HLA mismatch was associated with reduced allograft survival. Adjusted models found that the total HLA mismatch >3 increased the mortality hazard at 15 years (HR 1·05, p <0·05) and 20 years (HR 1·05, p<0·01). Pulmonary hypertension was the only indication with a statistically significant association between HLA mismatch and graft survival. Allografts in patients with 0-3 mismatches survived for 401 days longer than those with 4-6 mismatches (p=0·02). Conclusion Increased HLA mismatch reduced graft survival. When stratified by indication, this association was preserved exclusively in pulmonary hypertension. This finding is of potential clinical relevance to the management of this subsection of lung transplant recipients, impacting organ allocation, transplant surveillance and use of desensitisation and immunosuppression protocols.

O203: HLA Matching Between Donors and Recipients Improves Clinical Liver Transplant Graft Survival

Abstract Background and Aims The importance of human leukocyte antigen (HLA) matching between liver transplant donors and recipients on graft survival remains unclear and is not a clinical consideration in liver transplantation. This study aimed to determine the relationship between HLA matching and liver graft survival using a large-scale multi-center database (UNOS/OPTN) and multivariate logistic analysis. The secondary aim was to determine whether this relationship was influenced by transplant indication and donor status. Methods This retrospective observational analysis was performed using 22,702 liver transplant recipients from the UNOS/OPTN database. Patients were divided into two groups based on number of HLA mismatches (0-3 mismatches vs 4-6 mismatches), and then subcategorized by indication and donor status. Risk-adjusted outcomes were assessed by multivariate Cox analysis adjusting for donor and recipient characteristics and visualized using Kaplan-Meier survival curves. Results Allograft survival and risk of acute rejection were associated with degree of HLA mismatch. This association between HLA mismatch and graft survival persisted in individuals who underwent transplant for hepatitis, metabolic, drug toxicity and congenital indications. Donor status influenced the relationship between HLA mismatch and graft survival. Graft survival in DBD recipients was longer than in DCD in the 4-6 HLA mismatch group, whereas no significant difference was found in the 0-3 HLA mismatch group. Conclusion HLA mismatch significantly reduced graft survival and increased risk of acute rejection. This association was noted only in specific indications. These findings are of potential clinical relevance to organ allocation, allograft matching algorithms, immunosuppression protocols and transplant surveillance.

Expression of Rejection-Associated Transcripts in Early Protocol Renal Transplant Biopsies Is Associated with Tacrolimus Exposure and Graft Outcome.

Subclinical inflammation in protocol biopsies relates to tacrolimus exposure and human leukocyte antigen (HLA) matching. We aimed to characterize transcripts associated with rejection and tacrolimus exposure and the latter's association with transplant outcomes. We tested whether gene expression is associated with rejection using strictly normal protocol biopsies (n = 17) and biopsies with T cell-mediated rejection (TCMR) or antibody-mediated rejection (ABMR) according to Banff criteria (n = 12). Subsequently, we analyzed these transcripts in a set of 4-month protocol biopsies (n = 137) to assess their association with donor and recipient characteristics, the intensity of immunosuppression, and the graft outcome. Differential expression (false discovery rate (FDR) < 0.01, fold (change (FC) > 3) between normal and rejection biopsies yielded a set of 111 genes. In the protocol biopsy cohort (n = 137), 19 out of these 111 genes correlated with tacrolimus trough levels at the time of biopsy (TAC-C0), and unsupervised analysis split this cohort into two clusters. The two clusters differed in donor age and tacrolimus trough levels. Subclinical rejection, including borderline lesions, tended to occur in the same cluster. Logistic regression analysis indicated that TAC-C0 at the time of biopsy (OR: 0.83, 95%CI:0.72-0.06, p = 0.0117) was associated with cluster 2. In a follow-up averaging 70 ± 30 months, this patient group displayed a significant decline in renal function (p = 0.0135). The expression of rejection-associated transcripts in early protocol biopsies is associated with tacrolimus exposure and a faster decline in renal function.

DQB1 antigen matching improves rejection-free survival in pediatric heart transplant recipients

IntroductionPresence of donor-specific antibodies (DSAs), particularly to class II antigens, remains a major challenge in pediatric heart transplantation. Donor-recipient human leukocyte antigen (HLA) matching is a potential strategy to mitigate poor outcomes associated with DSAs. We evaluated the hypothesis that antigen mismatching at the DQB1 locus is associated with worse rejection-free survival. MethodsData was collected from Scientific Registry of Transplant Recipients for all pediatric heart transplant recipients 2010-2021. Only transplants with complete HLA typing at the DQB1 locus for recipient and donor were included. Primary outcome was rejection-free graft survival through 5 years. ResultsOf 5,115 children, 4,135 had complete DQB1 typing and were included. Of those, 503 (12%) had 0 DQB1 donor-recipient mismatches, 2,203 (53%) had 1, and 1,429 (35%) had 2. Rejection-free survival through 5 years trended higher for children with 0 DQB1 mismatches (68%), compared to those with 1 (62%) or 2 (63%) mismatches (pairwise p=0.08 for both). In multivariable analysis, 0 DQB1 mismatches remained significantly associated with improved rejection-free graft survival compared to 2 mismatches, while 1 DQB1 mismatch was not. Subgroup analysis showed the strongest effect in non-Hispanic Black children and those undergoing retransplant. ConclusionMatching at the DQB1 locus is associated with improved rejection-free survival after pediatric heart transplant, particularly in Black children, and those undergoing retransplant. Assessing high-resolution donor typing at the time of allocation may further corroborate and refine this association. DQB1 matching may improve long-term outcomes in children stabilized either with optimal pharmacotherapy or supported with durable devices able to await ideal donors.

Reduced human leukocyte antigen mismatching is associated with more favourable outcomes after unrelated donor haematopoietic stem cell transplantation.

The patient-donor human leukocyte antigen (HLA) match remains the most important prognostic factor for successful unrelated donor haematopoietic stem cell transplantation (UD-HSCT). This single-centre study comprised 125 adult patients with malignant haematological diseases undergoing their first UD-HSCT. The primary goal of this study was to validate the impact of HLA matching on HSCT outcomes, specifically at the HLA-DPB1 and HLA-DRB3/4/5 loci. A multivariable Cox regression analysis with a backward selection algorithm was employed to assess the associations of selected prognostic factors with outcomes after UD-HSCT. Any HLA locus mismatch was found to be associated with an increased incidence of grade II-IV acute graft versus host disease (aGvHD) at 100 days (p=.031; hazard ratio [HR] 1.935) and 6 months (p=.004; HR 2.284) after HSCT. The results of the following analyses also confirmed the strong impact of HLA-DPB1-only mismatch on the incidence of grade II-IV aGvHD at 100-day (p=.006; HR 2.642) as well as at 6-month (p=.007; HR 2.401) time periods. The HLA-DPB1-only mismatch was also shown to be statistically significantly associated with lower relapse incidence (p=.034; HR 0.333). The impact of the HLA-DRB3/4/5 mismatch on outcomes was inconclusive, though the two and more HLA-DPB1+DRB3/4/5-only mismatches showed a trend towards worse outcomes than a single mismatch. Based on our findings and those of more comprehensive studies, the extended HLA loci typing of patients and donors is suggested to avoid unexpected HLA mismatches during the UD selection.

Abstract A081: Patient-derived xenograft models from hematological malignancies for preclinical drug development and biomarker research

Abstract Background: Acute leukemias and lymphomas encompass a diverse group of hematologic malignancies, posing significant challenges in clinical practice. They often exhibit resistance to standard-of-care (SoC) treatments and have a high recurrence rate. Recent advancements in molecular profiling have identified potential drivers for various leukemia and lymphoma subtypes, offering new therapeutic targets. However, the validation of these targets and the development of drugs rely heavily on preclinical models that faithfully represent the different clinical subtypes. These models play a crucial role in refining target selection and facilitating drug development projects. Methods: AML- and ALL-PDX were derived from bone marrow aspirates or peripheral blood samples, from primary or relapsed acute leukemia patients. Purified cells were transplanted either intravenously (i.v.) and/or subcutaneously (s.c.) into immunodeficient mice. Some mice developed a systemic AML, which was monitored by flow cytometric analysis of blood samples. Non-Hodgkin (NHL) - or Hodgkin lymphoma (HL)-PDX were derived from peripheral blood, lymph node extirpations or core needle biopsies, and were usually transplanted subcutaneously into immunodeficient mice. Results: More than 45 PDX models from AML, ALL, NHL and HL have been successfully established and characterized. Highly individual response rates to SoC and investigational drugs were observed and correlated with mutation and gene expression data. An individual Human Leucocyte Antigen (HLA) profile of each PDX was determined by RNA-seq and a comprehensive HLA matching analysis of the models and peripheral blood mononuclear cell (PBMC) donors was performed to enable personalized, preclinical immuno-oncology studies. Conclusions: Our extensively characterized PDX models derived from hematologic malignancies serve as valuable tools for evaluating novel targeted and immunological therapies. These models provide an exceptional platform for identifying and validating new targets, as well as preclinical screening of compounds and combinations for translational research projects in this field. Citation Format: Antje Siegert, Bernadette Brzezicha, Stephan Fuhrmann, Martin Janz, Clemens Schmitt, Ulrich Keller, Christian Rupp, Wolfgang Walther, Jens Hoffmann. Patient-derived xenograft models from hematological malignancies for preclinical drug development and biomarker research [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2023 Oct 11-15; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2023;22(12 Suppl):Abstract nr A081.

Chimeric antigen receptor natural killer cells: a promising antitumor immunotherapy.

Chimeric antigen receptor (CAR) T cells have been successfully used in adoptive cell therapy for malignancies. However, some obstacles, including side effects such as graft-versus-host disease and cytokine release syndrome, therapy resistance, limited sources, as well as high cost, limited the application of CAR T cells. Recently, CAR natural killer (NK) cells have been pursued as the effector cells for adoptive immunotherapy for their attractive merits of strong intrinsic antitumor activity and relatively mild side effects. Additionally, CAR NK cells can be available from various sources and do not require strict human leukocyte antigen matching, which suggests them as promising "off-the-shelf" products for clinical application. Although the use of CAR NK cells is restrained by the limited proliferation and impaired efficiency within the immunosuppressive tumor microenvironment, further investigation in optimizing CAR structure and combination therapies will overcome these challenges. This review will summarize the advancement of CAR NK cells, CAR NK cell manufacture, the clinical outcomes of CAR NK therapy, the challenges in the field, and prospective solutions. Besides, we will discuss the emerging application of other immune cells for CAR engineering. Collectively, this comprehensive review will provide a valuable and informative summary of current progress and evaluate challenges and future opportunities of CAR NK cells in tumor treatment.

Unsupervised Clustering Analysis of Regimen and HLA Characteristics Identifies Subgroups with Improved Relapse-Free Survival in Children with ALL and AML Undergoing Umbilical Cord Blood Transplantation

Introduction. Umbilical cord blood transplantation (UCBT) is an efficacious therapeutic intervention for pediatric acute lymphoblastic leukemia (ALL) and acute myeloid leukemia (AML). However, contention persists regarding how best to achieve long-term relapse-free survival (RFS). Differences in clinical practice can be attributed to an incompletely understood interplay between graft-versus-leukemia (GvL) effect and graft-versus-host disease (GvHD), as well as an incomplete understanding of how UCBTs differ from those of other stem cell sources. Human leukocyte antigen (HLA) matching is a critical determinant of post-transplant outcome, but factors such as GvHD prophylaxis and total body irradiation (TBI) usage also play a key role. Objective. To use unsupervised clustering algorithms to examine the interplay between HLA matching, immunosuppressive regimens, and conditioning factors with greater power than that conferred by conventional multivariate regression analyses. Methodology. Data pertaining to UCBTs performed for pediatric ALL (n = 908) and AML (n = 417) between 2004 and 2022 was obtained from the Eurocord/EBMT registry. ALL and AML UCBTs were separately subjected to a partitioning around medoids clustering algorithm, which identified k = 15 ALL clusters and k = 11 AML clusters. These clusters were used to form hypotheses for post-hoc testing, which were tested using Kaplan-Meier and competing risks analyses. Results. Clusters of both diseases were frequently divided by usage of ATG, which was administered in 77% of 8/8 ABCDR matched UCBTs. ALL and AML patients who did not receive ATG experienced greater RFS than recipients of ATG, and this appeared to be driven by elimination of relapse mortality in the late (≥5 year) post-transplant setting (Figs 1-2). ALL clusters were frequently divided by use of total body irradiation (TBI), and those featuring TBI regimens conferred RFS comparable or superior to non-TBI regimens; this appeared to be driven by a reduction in relapse mortality within the first three years post-UCBT (P = 0.007). In AML but not ALL, both HLA-C and KIR match levels appeared to be relevant (P = 0.04), despite typing only having been performed for 70% and 24% of AML UCBTs, respectively. Patients receiving a 7/8 ABCDR-matched graft with a single HLA-C mismatch experienced significantly poorer RFS than 8/8 matched UCBTs (P = 0.04), but a concomitant single co-mismatch at HLA-A or HLA-B appeared to restore RFS to levels comparable to 8/8 matched grafts. Conclusions. ATG is over-used in ALL and AML patient-graft pairings where risk of non-relapse mortality (NRM) is low, and this may be creating an avoidable risk of relapse. The conflicting results in published literature may be explained by follow-up time, as the effect does not become apparent until 5 years post-UCBT and many studies do not follow patients beyond this. Incorporation of TBI into ALL myeloablative regimens prevents relapse mortality in the early to mid-post UCBT setting, and this effect was independent of HLA matching. These findings align with the known genetic and biological determinants of these diseases and redouble the importance of typing at HLA-C in AML; administration of TBI in ALL; and a measured approach to the usage of ATG.

Racial Disparity in Hematopoietic Stem Cell Transplant Clinical Trial Recruitment

Introduction: Race significantly influences phenotypic and genetic diversity in hematological diseases, consequently affecting disease prognosis, Human Leukocyte Antigen-matching and Hematopoietic Stem Cell Transplant (HSCT) outcomes. To ensure the development of novel transplant strategies effective for patients from diverse backgrounds, all racial groups must have equal opportunities to take part in HSCT clinical trials. Methods: Using ClinicalTrials.gov, a web-based resource that registers all studies meeting the definition of a clinical trial according to the International Committee on Medical Journal Editors, we identified all phase 1 to phase 4 HSCT clinical trials registered from 2006 to 2022. We manually abstracted data on the racial distribution of enrolled participants, sex distribution, transplant type, trial phase, location, and year of trial reporting. We calculated observed ratios of racial participation and compared them with the estimated probability of finding adequate donors from different racial subgroups reported by the National Marrow Donor Program to define the disproportionate enrolment factor. We then conducted subgroup racial distribution based on the trial phase, location, and type of transplant. We further evaluated trends in racial disparity within clinical trial enrolment over the years. Results: We identified 398 clinical trials related to HSCT between 2006 and 2022, of which 72% were allogenic and 28% were autologous HSCT trials. Most of these were phase 2 clinical trials (64.3%) and the majority (78.1%) were conducted in the United States. The racial distribution of enrolled participants was publicly available in 235 (59%) of these clinical trials, including 57.7% allogeneic and 62.5% autologous HSCT. The race distribution of enrolled subjects was reported in 80% of Phase 1 and 79% of Phase 3, whereas only 48% of Phase 1/2 and 44% of Phase 2/3 clinical trials reported racial distribution. The race distribution among 25,075 study participants in 235 clinical trials was: 80.4% Whites (20,175), 7.4% Blacks (1858), 5.3% Asians (1336), 1.6% other races (396), and 5.3% (1310) subjects with unreported race. The same race distribution trend was observed across all subgroups of clinical trials based on phase, location, and transplant type (Table 1). The disproportionate enrolment factor was 0.27 for Black participants, and 0.11 for Asian participants, compared to 1.02 for Whites. From 2006 to 2022, yearly trends for the absolute number of clinical trial enrollees showed a 2.5% and 1.5% increase in Black and Asian subject representation; however, minorities still accounted for only 20.3% of total representation in 2022 (Figure 1). Conclusions: Our results emphasize the significant racial underrepresentation of minority populations with a very low disproportionate enrolment factor in HSCT clinical trials despite the increased probability of finding a suitable donor resulting from novel HSCT technologies in recent years. Addressing these disparities requires urgent action and a multi-faceted approach. Efforts such as targeted outreach, cultural competence training and community engagement to focus on eliminating barriers are urgently needed to increase the enrolment of the minority population to achieve racial equity in HSCT.

Post-Transplant Cyclophosphamide Eliminates Disparity in GvHD-Free, Relapse-Free Survival and Overall Survival between 8/8 Matched and 7/8 Mismatched Unrelated Donor Hematopoietic Cell Transplantation in Adults with Hematologic Malignancies

Background: Post-transplant cyclophosphamide (PTCy) has become a standard of care for graft-versus-host disease (GvHD) prophylaxis in recipients of human leukocyte antigen (HLA)-matched and mismatched unrelated donor (MMUD) allografts, generating new opportunities for successful hematopoietic cell transplantation (HCT) regardless of patient ancestry. The National Marrow Donor Program (NMDP)-sponsored 15-MMUD study, which used PTCy-based GvHD prophylaxis (PMID 3390526), demonstrated encouraging overall survival (OS) in adult patients receiving MMUD bone marrow grafts matched at ≤7/8 HLA alleles. Currently, the follow-up ACCESS study (NCT04904588) will determine if similar outcomes can be achieved using MMUD peripheral blood stem cell allografts. As part of its 5-year strategic plan, the NMDP aims to determine the extent of differences in GvHD-free, relapse-free survival (GRFS) between 8/8 and 7/8 URD allografts using PTCy and seeks to develop approaches over time to close the presumed gap in URD outcomes. Methods: The primary objective was to compare GRFS between 8/8 and 7/8 URD HCT using the Center for International Blood &amp; Marrow Transplant Research (CIBMTR) database. After analyzing primary results, secondary objectives were added to compare GRFS, OS, and other clinical outcomes among 8/8 URD, 7/8 URD, and haploidentical-related donor (Haplo) HCT. The study included adult patients (age≥18y) with hematologic malignancies (ALL, AML, MDS) undergoing first URD or Haplo HCT between 2017-2020 using PTCy-based GvHD prophylaxis. Kaplan-Meier curves were used to estimate probability of GRFS and OS. Cox regression examined the independent effect of HLA match controlling for other clinical factors on outcomes referenced to 8/8 URD HCT. A priori clinically selected factors considered as possible confounders in the regression model included disease risk index, comorbidity risk, pre-HCT Karnofsky score, conditioning regimen intensity, graft source, donor/recipient CMV serostatus, year of HCT, donor/recipient age and race/ethnicity. Final models were stratified by factors violating the proportional hazards assumption. Factors were eliminated in a backwards fashion if p-values were &amp;gt;0.10 unless inclusion affected the hazard ratio (HR) of HLA match by more than 10%. Interactions were tested against a p-value of &amp;lt;0.01. Results: Table 1 shows demographics for the three patient cohorts: Haplo (n=2772), 8/8 URD (N=1517), and 7/8 MMUD (N=540). Notable differences among the cohorts included: 8/8 URD recipients had younger, predominantly Caucasian donors and were more likely to receive myeloablative conditioning. Haplo recipients had more donor/recipient CMV seropositivity and received more reduced intensity conditioning. Otherwise patient characteristics were similar. Contrary to our expectations, multivariable regression analysis (MVA) showed no significant differences in either GRFS or OS between recipients of 8/8 and 7/8 URD HCT at 1, 2 and 3-years post-HCT ( Figure 1). Outcomes, including relapse and NRM, between 8/8 and 7/8 URD HCT were similar irrespective of conditioning intensity. However, 8/8 URD HCT associated with lower two-year moderate/severe chronic GvHD than 7/8 URD [1.30 (1.00-1.68), p=0.049]. We next compared GRFS and OS among 8/8 and 7/8 URD and Haplo at 3y after HCT. On MVA, GRFS [HR 1.15 (1.04-1.26), p=0.005] and OS [HR 1.15 (1.03-1.29), p=0.013] were significantly better in 8/8 URD compared to Haplo HCT. Differences between 8/8 URD and Haplo appeared to be driven by significantly higher NRM [HR 1.46 (1.22-1.74), p&amp;lt;0.001)] and two-year moderate/severe chronic GvHD [HR 1.28 (1.07-1.54), p=0.007] in Haplo. No significant differences were seen in GRFS or OS at 3 years when comparing 7/8 URD to Haplo. Causes of death among donor types were similar with primary disease relapse/progression, infection and organ failure being the most frequent. Conclusions: Use of PTCy-based GvHD prophylaxis seems to have resolved previously observed differences in GRFS and OS between 8/8 and 7/8 URD HCT. HCT using an 8/8 URD HCT, if available, continues to be the best option for patients lacking a matched sibling donor. Further studies comparing Haplo to 7/8 URD HCT are warranted, but will require larger numbers of 7/8 URD HCT. Both mismatched donor sources substantially increase access to HCT for patients regardless of their ancestry.

An Integrated Approach Using HLAMatchmaker and Pirche II for Epitopic Matching in Pediatric Kidney Transplant-A Romanian Single-Center Study.

(1) Background: Renal transplantation (KT) is the most efficient treatment for chronic kidney disease among pediatric patients. Antigenic matching and epitopic load should be the main criteria for choosing a renal graft in pediatric transplantation. Our study aims to compare the integration of new histocompatibility predictive algorithms with classical human leukocyte antigen (HLA) matching regarding different types of pediatric renal transplants. (2) Methods: We categorized our cohort of pediatric patients depending on their risk level, type of donor and type of transplantation, delving into discussions surrounding their mismatching values in relation to both the human leukocyte antigen Matchmaker software (versions 4.0. and 3.1.) and the most recent version of the predicted indirectly identifiable HLA epitopes (PIRCHE) II score. (3) Results: We determined that the higher the antigen mismatch, the higher the epitopic load for both algorithms. The HLAMatchmaker algorithm reveals a noticeable difference in eplet load between living and deceased donors, whereas PIRCHE II does not show the same distinction. Dialysis recipients have a higher count of eplet mismatches, which demonstrates a significant difference according to the transplantation type. Our results are similar to those of four similar studies available in the current literature. (4) Conclusions: We suggest that an integrated data approach employing PIRCHE II and HLAMatchmaker algorithms better predicts histocompatibility in KT than classical HLA matching.

Generation of Human Regulatory Dendritic Cells from Cryopreserved Healthy Donor Cells and Hematopoietic Stem Cell Transplant Recipients.

Acute graft versus host disease (GVHD) remains a significant complication following hematopoietic stem cell transplant (HSCT), despite improved human leukocyte antigen (HLA) matching and advances in prophylactic treatment regimens. Previous studies have shown promising results for future regulatory dendritic cell (DCreg) therapies in the amelioration of GVHD. This study evaluates the effects of cryopreservation on the generation of DCreg, the generation of young and older DCreg in serum-free media, and the feasibility of generating DCreg from young and older HSCT patient monocytes. DCregs were generated in X-vivo 15 serum-free media from donor or patient monocytes. This study includes the use of monocytes from young and older healthy, donor, and HSCT patients with varying hematological diseases. Phenotypic differences in cell populations were assessed via flow cytometry while pro-inflammatory and anti-inflammatory cytokine production was evaluated in culture medium. The number of DCreg generated from cryopreserved monocytes of healthy donors was not significantly different from freshly isolated monocytes. DCreg generated from cryopreserved monocytes had comparable levels of co-stimulatory molecule expression, inhibitory molecule expression, and cytokine production as freshly isolated monocytes. Young and older healthy donor monocytes generated similar numbers of DCreg with similar cytokine production and phenotype. Although monocytes from older HSCT patients generated significantly fewer DCreg, DCreg from young and older HSCT patients had comparable phenotypes and cytokine production. Monocytes from young and older myelodysplastic syndrome (MDS) patients generated reduced numbers of DCreg compared to non-MDS-derived DCreg. We demonstrate that the cryopreservation of monocytes from HSCT patients of varying hematological diseases allows for the cost-effective generation of DCreg on an as-needed basis. Although the generation of DCreg from MDS patients requires further assessment, these data support the possibility of in vitro-generated DCreg as a therapy to reduce GVHD-associated morbidity and mortality in young and older HSCT recipients.

Physician Preferences when Selecting Candidates for Lower-Quality Kidney Offers.

In the United States, more than 50% of kidneys in the lowest 15% quality range (those with Kidney Donor Profile Index >85) are discarded. Studies suggest that using more of these kidneys could benefit patients waiting for a transplant. This study assesses the trade-offs physicians make when selecting recipients for lower-quality kidneys. A discrete choice experiment (DCE) was administered to surgeons and nephrologists in the United States who are involved in kidney acceptance decisions. The DCE presented kidneys that varied in terms of Kidney Donor Profile Index, expected cold ischemia time, donor age, pump parameters, serum creatinine levels, glomerulosclerosis, donor diabetes status, and whether donation was made after circulatory death. Candidate characteristics included recipients' age, diabetes history, time on dialysis, ejection fraction, HLA mismatch, calculated panel reactive antibody, and Karnofsky performance score. Regression analysis was used to estimate acceptability weights associated with kidney and recipient characteristics. A total of 108 physicians completed the DCE. The likelihood of acceptance was significantly lower with deterioration of kidney quality, expected cold ischemia time at transplantation, and missing biopsy and pump information. Acceptance was prioritized for patients who were higher on the waiting list, younger recipients, those who have spent less time on dialysis, and those without a history of diabetes. Performance status (Karnofsky score) and calculated panel reactive antibody also had a statistically significant but smaller association. Finally, ejection fraction had a marginally significant association, and HLA match had no significant association with the acceptance of marginal kidneys. A group of respondents were found to be primarily concerned about cold ischemia time. In this DCE, physicians considered the recipient characteristics that inform expected post-transplant survival score when they decided whether to accept a marginal kidney for a given recipient.

Abstract PO-070: New patient-derived head and neck cancer xenograft (PDX) panel for drug development, immuno-oncology and translational research

Abstract Head and neck squamous cell carcinomas (HNSCC) represent a heterogeneous group of epithelial cell malignancies arising from the upper aerodigestive tract. Despite of improved therapies, HNSCC remain a devastating disease. Oropharynx cancers are mainly attributed to infection with human papillomavirus (HPV). Since 2017, HNSCC are classified into HPV-negative and HPV-positive HNSCC. Therapies in the clinic are surgery and/or radiotherapy (RT)/radiochemotherapy (RCT) with a recurrence of about 50%. Therefore, new approaches are needed to improve long-term remission and patient survival. Recent advances in high-throughput molecular profiling have helped to identify genetic dispositions (TP53, FAT1, CDKNA2, NOTCH1 etc.) for HNSCC. We have generated and characterized a diverse panel (n = 85) of patient-derived xenografts (PDX) of HNSCC for preclinical research and immuno-oncological approaches. We successfully established 85 HNSCC PDX from fresh surgery tissue of primary and recurrent carcinomas by direct subcutaneous transplantation into immune-deficient mice. 14 HNSCC PDX were derived from HPV-positive tumors. We treated 28 HNSCC PDX with radiotherapy alone or radiochemotherapy. Heterogeneous individual responses to treatments resemble the clinical situation. For characterization, the established HNSCC PDX were treated with standard of cares (SoC) such as docetaxel, platinum compounds, cetuximab, 5-fluorouracil and investigational drugs. No correlation was observed to mutations and drug response. Molecular subtypes were determined based on gene expression data. Cetuximab response was associated with basal subtype and inflamed/mesenchymal subtype was negative predictive for cetuximab response. Further, 30 HNSCC PDX were analyzed for PD-L1 expression as suitable candidates for the evaluation of checkpoints inhibitors such as nivolumab and pembrolizumab and other novel immunotherapy approaches on humanized mice. To gain a deeper insight into the molecular biology, RNA sequencing was performed for 46 HNSCC models. Based on RNASeq data, an individual Human Leucocyte Antigen (HLA) profile of each PDX was determined and a comprehensive HLA matching analysis of the HNSCC models and 9 peripheral blood mononuclear cell (PBMC) donors was performed to enable personalized, preclinical immuno-oncology studies. Our newly and comprehensively characterized HNSCC PDX panel enables the evaluation of new targeted and immunological therapies in preclinical phase II studies. It provides an exceptional platform for the identification and validation of new targets and enables the preclinical screening of new combinations in translational research. Citation Format: Bernadette Brzezicha, Theresia Conrad, Maria Stecklum, Michael Becker, Konrad Klinghammer, Jens Hoffmann. New patient-derived head and neck cancer xenograft (PDX) panel for drug development, immuno-oncology and translational research [abstract]. In: Proceedings of the AACR-AHNS Head and Neck Cancer Conference: Innovating through Basic, Clinical, and Translational Research; 2023 Jul 7-8; Montreal, QC, Canada. Philadelphia (PA): AACR; Clin Cancer Res 2023;29(18_Suppl):Abstract nr PO-070.

The Effect of Genetic HLA Matching on Liver Transplantation Outcome: A Systematic Review and Meta-Analysis.

We aim to investigate the effects of genetically based HLA matching on patient and graft survival, and acute and chronic rejection after liver transplantation. Liver transplantation is a common treatment for patients with end-stage liver disease. In contrast to most other solid organ transplantations, there is no conclusive evidence supporting human leukocyte antigen (HLA) matching for liver transplantations. With emerging alternatives such as transplantation of bankable (stem) cells, HLA matching becomes feasible, which may decrease the need for immunosuppressive therapy and improve transplantation outcomes. We systematically searched the PubMed, Embase, and Cochrane databases and performed a meta-analysis investigating the effect of genetic HLA matching on liver transplantation outcomes (acute/chronic rejection, graft failure, and mortality). We included 14 studies with 2682 patients. HLA-C mismatching significantly increased the risk of acute rejection (full mismatching: risk ratio = 1.90, 95% confidence interval = 1.08 to 3.33, P = 0.03; partial mismatching: risk ratio = 1.33, 95% confidence interval = 1.07 to 1.66, P = 0.01). We did not discern any significant effect of HLA mismatching per locus on acute rejection for HLA-A, -B, -DR, and -DQ, nor on chronic rejection, graft failure, or mortality for HLA-DR, and -DQ. We found evidence that genetic HLA-C matching reduces the risk of acute rejection after liver transplantation while matching for other loci does not reduce the risk of acute rejection, chronic rejection, graft failure, or mortality.

Transfusion-Associated Graft-Versus-Host Disease in Adults.

Transfusion-associated graft-versus-host disease (TA-GVHD) is a rare but fatal complication of blood transfusion that usually develops two to 30 days following a blood transfusion giving rise to graft versus host disease (GVHD) clinical features that are consisting of fever, skin rash, jaundice, diarrhea, and pancytopenia. The disease is fulminant in most patients with a mortality rate of >90% of cases. The main aim of this review is to enhance awareness among medical practitioners about this fatal disease. Data were extracted manually from the main medical databases (Medline, Scopus, and Google Scholar) after the revision of selected articles and assessed for their contribution to the knowledge of TA-GVHD. TA-GVHD occurs when the viable donor T-cells in the blood or blood products attack the recipient's tissues which his/her immune system is incapable to destroy due to several reasons. The recipient's tissues that are usually involved in TA-GVHD include the liver, intestine, skin, lungs, and bone marrow. Any blood component either whole blood, packed red blood cells (RBCs), platelets, or fresh non-frozen plasma that contains viable T lymphocytes can cause TA-GVHD. Host immunodeficiency, transfusion of fresh blood, and partial human leukocyte antigen (HLA) matching between the donors and the recipients represent the major risk factors of TA-GVHD. Partial HLA matching includes immunocompetent recipients who receive blood from a first-degree relative also, seen in genetically homogenous populations because of high rates of consanguineous marriage. The diagnosis of TA-GVHD is mainly suspected based on clinical manifestations. However, a histopathological study of either skin or rectal biopsy is diagnostic. The treatment of TA-GVHD is generally not effective, unless the patient received emergency stem cell transplantation, while prevention via irradiation of blood or blood products represents the standard of care for this disease. In conclusion, medical practitioners should have a high index of suspicion for this disease. Moreover, future clinical trials targeting and comparing the outcomes of the different therapeutic options for TA-GVHD are required.

Thalassemia, biobanking infrastructures, and personalized stem cell therapies in Chennai.

Thalassemia and leukemia and related blood disorders are approved for blood stem cell transplants in India, for a stem cell transplant to be successful, the human leukocyte antigen (HLA) complex located on the arm of chromosome six must be a match between the cord blood donor and the recipient. In the quest to find an exact blood stem cell match for an individual, the HLA becomes the node at the center of community genetics where the HLA match is sought (not necessarily successful) in the extended family, the same caste, language, and ethnic (both national and the diaspora) groups. By considering thalassemia as a case study, how do we understand personalized stem cell therapies within biobanking infrastructures in Chennai? How do social categories get entwined with biological materials like cord blood?

Heart Transplant Human Leukocyte Antigen Matching in the Modern Era

Although numerous reports have studied the consequences of human leukocyte antigen (HLA) mismatching in renal transplantation, there are limited and outdated data analyzing this association in thoracic organ transplantation. Therefore, our study reviewed the impact of HLA mismatching at both the total and the loci levels in the modern-era heart-transplant procedure on survival and chronic rejection outcomes. We performed a retrospective analysis of adult patients after heart transplant by using the United Network for Organ Sharing database from January 2005-July 2021. Total HLA and HLA-A, HLA-B and HLA-DR mismatches were analyzed. Survival and cardiac allograft vasculopathy were the outcomes of interest during a 10-year follow-up period using Kaplan-Meier curves, log-rank tests and multivariable regression models. A total of 33,060 patients were included in this study. Recipients with a high degree of HLA mismatching had increased incidences of acute organ rejection. There were no significant differences in mortality rates among any of the total or loci level groups. Similarly, there were no significant differences between total HLA mismatch groups in time to first cardiac allograft vasculopathy, though mismatching at the HLA-DR locus was associated with an increased risk of cardiac allograft vasculopathy. Our analysis suggests that HLA mismatch is not a significant predictor of survival in the modern era. Overall, the clinical implications of this study provide reassuring data for the continued use of non-HLA-matched donors in an effort to increase the donor pool. If HLA matching is to be considered for heart transplant donor-recipient selection, matching at the HLA-DR locus should take priority due to its association with cardiac allograft vasculopathy.

Generation of the NeoThy mouse model for human immune system studies.

Humanized mouse models, created via transplantation of human hematopoietic tissues into immune-deficient mice, support a number of research applications, including transplantation immunology, virology and oncology studies. As an alternative to the bone marrow, liver, thymus humanized mouse, which uses fetal tissues for generating a chimeric human immune system, the NeoThy humanized mouse uses nonfetal tissue sources. Specifically, the NeoThy model incorporates hematopoietic stem and progenitor cells from umbilical cord blood (UCB) as well as thymus tissue that is typically discarded as medical waste during neonatal cardiac surgeries. Compared with fetal thymus tissue, the abundant quantity of neonatal thymus tissue offers the opportunity to prepare over 1,000 NeoThy mice from an individual thymus donor. Here we describe a protocol for processing of the neonatal tissues (thymus and UCB) and hematopoietic stem and progenitor cell separation, human leukocyte antigen typing and matching of allogenic thymus and UCB tissues, creation of NeoThy mice, assessment of human immune cell reconstitution and all experimental steps from planning and design to data analysis. This entire protocol takes a total of ~19 h to complete, with steps broken up into multiple sessions of 4 h or less that can be paused and completed over multiple days. The protocol can be completed, after practice, by individuals with intermediate laboratory and animal handling skills, enabling researchers to make effective use of this promising in vivo model of human immune function.