Human Leukocyte Antigen Matching Research Articles

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 & 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 >0.10 unless inclusion affected the hazard ratio (HR) of HLA match by more than 10%. Interactions were tested against a p-value of <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<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.

Multilineage Differentiating Stress Enduring (Muse) Cells: A New Era of Stem Cell-Based Therapy.

Stem cell transplantation has recently demonstrated a significant therapeutic efficacy in various diseases. Multilineage-differentiating stress-enduring (Muse) cells are stress-tolerant endogenous pluripotent stem cells that were first reported in 2010. Muse cells can be found in the peripheral blood, bone marrow and connective tissue of nearly all body organs. Under basal conditions, they constantly move from the bone marrow to peripheral blood to supply various body organs. However, this rate greatly changes even within the same individual based on physical status and the presence of injury or illness. Muse cells can differentiate into all three-germ-layers, producing tissue-compatible cells with few errors, minimal immune rejection and without forming teratomas. They can also endure hostile environments, supporting their survival in damaged/injured tissues. Additionally, Muse cells express receptors for sphingosine-1-phosphate (S1P), which is a protein produced by damaged/injured tissues. Through the S1P-S1PR2 axis, circulating Muse cells can preferentially migrate to damaged sites following transplantation. In addition, Muse cells possess a unique immune privilege system, facilitating their use without the need for long-term immunosuppressant treatment or human leucocyte antigen matching. Moreover, they exhibit anti-inflammatory, anti-apoptotic and tissue-protective effects. These characteristics circumvent all challenges experienced with mesenchymal stem cells and induced pluripotent stem cells and encourage the wide application of Muse cells in clinical practice. Indeed, Muse cells have the potential to break through the limitations of current cell-based therapies, and many clinical trials have been conducted, applying intravenously administered Muse cells in stroke, myocardial infarction, neurological disorders and acute respiratory distress syndrome (ARDS) related to novel coronavirus (SARS-CoV-2) infection. Herein, we aim to highlight the unique biological properties of Muse cells and to elucidate the advantageous difference between Muse cells and other types of stem cells. Finally, we shed light on their current therapeutic applications and the major obstacles to their clinical implementation from laboratory to clinic.

#5950 MAJOR HLA ALLELE AND HAPLOTYPE FREQUENCIES IN THE MALTESE KIDNEY TRANSPLANT REGISTRY

Abstract Background and Aims The human leukocyte antigens (HLA) are the most diverse and polymorphic genes in the human genome and matching them is of vital importance for maximising the survival of kidney transplants. The Maltese archipelago consists of three inhabited islands in the Mediterranean Sea, with a total population of just over half a million people. HLA polymorphisms in Malta have never been described. The aim of this study was to investigate allelic frequencies and determine the most common haplotypes for major HLA Class I and Class II groups in the Maltese kidney transplant registry. This will hopefully facilitate organ sharing with other European countries and improve the HLA matching for kidney transplant recipients. Method All patients of Maltese ethnicity on the national kidney transplant list between 2018 and 2022 were analysed retrospectively. HLA typing is routinely performed at medium to high resolution using polymerase chain reaction sequence specific oligonucleotide probes and Luminex technology at the HLA-A, HLA-B, HLA-C, HLA-DR, HLA-DQ and HLA-DP loci. Allele and haplotype frequencies were calculated by direct counting and simple percentages. Results A total of 191 patient samples were analysed yielding the following allele types: 16 HLA-A, 31 HLA-B, 17 HLA-C, 15 HLA-DRB1, 6 HLA-DP, 7 HLA-DQ, 5 HLA-DRB3, one HLA-DRB4 and one HLA DRB5. The most frequent allele groups for the HLA-A locus were HLA-A*02 (30.9%), HLA-A*24 (12.0%) and HLA-A*01 (11.8%) whilst for the HLA-B locus these were HLA-B*35 (16.2%), HLA-B*18 (11.5%) and HLA-B*51 (7.1%). The most prevalent allele groups for the HLA-DRB1 locus were HLA-DRB1*11 (24.1%), HLA-DRB1*04 (13.1%) and HLA-DRB1*07 (11.3%). The commonest allele group for each of HLA-C, HLA-DP and HLA-DR loci were HLA-C*07 (23.6%), HLA-DP4 (5.8%), HLA-DQ7 (31.2%) respectively. The five most frequently encountered haplotypes were HLA-A*02-B*13-DRB1*07 (2.1%), HLA-A*02-B*35-DRB1*04 (1.6%), HLA-A*02-B*18-DRB1*10 (1.3%), HLA-A*02-B*35-DRB1*11 (1.3%), HLA-A*24-B*35-DRB1*11 (1.3%). Conclusion This study provides the first data on the Major HLA allele and haplotype frequencies in Maltese kidney transplant candidates. Such data may be crucial in setting up international kidney exchange programmes.

A Retrospective Analysis of Autologous Stem Cell Transplantation Outcomes in Adult Philadelphia Chromosome Positive-Acute Lymphoblastic Leukemia

Abstract Introduction Philadelphia chromosome positivity (Ph + ) is a poor prognostic feature in adult acute lymphoblastic leukemia (ALL). Allogenic hematopoietic stem cell transplantation in first complete remission (CR1) is recommended. There is limited literature on the role of consolidation autologous stem cell transplantation (ASCT). This study was undertaken to assess the potential of consolidation ASCT in CR1 in adults with Ph + ALL. Objectives The aim of this study was to analyze the safety and efficacy of ASCT in CR1 in adults with Ph + ALL. Materials and Methods Adult patients diagnosed with Ph + ALL who underwent ASCT in CR1 after modified ALL-BFM95 protocol from 2015 to 2017 were included. Patients who achieved major molecular response or better were considered for ASCT with cyclophosphamide-total body irradiation regimen and peripheral blood stem cells infused on day 0. Toxicities as per Common Terminology Criteria for Adverse Event v4.0, disease-free survival (DFS), and overall survival (OS) were assessed. Inclusion criteria: Following patients were included—patients aged 18 years and above diagnosed with Ph + ALL; patients receiving BFM-95 induction chemotherapy protocol; patients who achieved CR after induction therapy; nonavailability of human leukocyte antigen match from a matched sibling donor or matched unrelated donor. Exclusion criteria: Patients not willing or unfit for ASCT and patients planned for allogenic hematopoietic stem cell transplantation were excluded. Results Six adult patients with Ph + ALL underwent ASCT in CR1 (median age: 23 [range: 19–36] years, five patients were males [83%]). Imatinib was started at a median of 11 days from the start of induction IA (range: 10–21). Five patients achieved morphological CR after induction 1A and, one patient at the end of induction 1B. The median time to ASCT (from diagnosis) was 8 months (range: 6.4–13). All the six patients had disease relapse and died due to progressive ALL. The median DFS and OS were 19.2 months and 23.3 months, respectively. Conclusion Consolidation ASCT yielded poor outcomes in this study. There was a significant delay from diagnosis to ASCT, which might have impacted the results.

Clinical characteristics and correlative factors of dry eye disease associated with graft-versus-host disease

Objective: To investigate the clinical features of dry eye disease in patients with graft-versus-host disease (GVHD) and to identify the correlative factors that contribute to its severity. Methods: It was a retrospective case series study. A total of 62 patients with dry eye disease caused by GVHD after allogeneic hematopoietic stem cell transplantation (HSCT) were recruited from the First Affiliated Hospital of Soochow University between 2012 and 2020. The study population comprised 38 males (61%) and 24 females (39%), with an average age of (35.29±11.75) years. Only the right eye of each patient was evaluated. The patients were divided into two groups based on the severity of corneal epitheliopathy: a mild group (15 eyes) and a severe group (47 eyes). Demographic information, including gender, age, primary disease, type of allogeneic HSCT, donor-to-recipient information, source of hematopoietic stem cells, systemic GVHD, and the time from HSCT to the first visit, was collected. Ophthalmologic assessments, including the Schirmer Ⅰ test, tear breakup time, corneal epithelial staining, and eye margin assessment, were performed during the first visit to the ophthalmology department and compared between the two groups. Results: The average time from HSCT to the first visit to the ophthalmology department among the 62 patients was (20.26±13.09) months. The median corneal fluorescein staining score was 4.5 points. In the mild group, the main characteristic of corneal staining was scattered punctate staining in the peripheral region in 80% of cases, while in the severe group, corneal staining fused into clumps in both the peripheral region (64%) and the pupillary zone (28%). Results of the Schirmer Ⅰ test were significantly lower in the severe group compared to the mild group (P<0.05). The median total eyelid margin score in the severe group was higher than that in the mild group [9 (7, 12) points vs. 6 (5, 8) points] (P<0.05). The median eyelid congestion score in the severe group was, also higher than that in the mild group [2 (1, 3) points vs. 1 (0, 2) points] (P<0.05). The compatibility between the blood types of the donor and recipient was found to be statistically significant (P<0.05). There was no significant difference in gender, age, family relationship, human leukocyte antigen matching, gender consistency, source of hematopoietic stem cells, or the occurrence of systemic GVHD between the two groups (P>0.05). Conclusions: Patients in the mild group had scattered punctate corneal staining in the peripheral region, while those in the severe group showed fusion of corneal staining into clumps in both the peripheral and pupillary zones. The severity of dry eye disease caused by GVHD was strongly correlated with eyelid margin lesions. A higher degree of eyelid margin lesions indicated more severe dry eye disease caused by GVHD. Additionally, compatibility between the blood types of the donor and recipient may play a role in the development of GVHD-associated dry eye.

Transplanting highly sensitized patients

Immunological barrier posed by preformed antibodies against donor's human leukocyte antigen (HLA) antigens compounds the situation of global shortage of kidney donors. Pretransplantation sensitization carries a high risk of acute rejection and allograft loss. Therefore, there is a need for careful evaluation of potential recipients, based on HLA typing, HLA match, and comprehensive screening of antibodies (is conceptual). Sensitization events include previous transplantations, blood transfusions, or pregnancies. Despite advances in molecular techniques and solid-phase assays used to identify at-risk patients, kidney transplantation continues to be challenging in patients with calculated panel reactive antibodies greater than 85%. The development of desensitization protocols has been used to overcome acute rejection risk; however, the associated further increase in the risk of infection and malignancy is of significant concern owing to enhanced immunosuppression. The introduction of rituximab, bortezomib, plasmapheresis, and intravenous immunoglobulins has improved the success rate of desensitization protocols. On the contrary, paired (pooled) exchange kidney program has been instrumental in widening access to allografts to highly sensitized patients by offering lesser HLA mismatches. Moreover, desensitization protocols are rather expensive, leading to a high economic burden in the pretransplantation and posttransplantation period. This review aims to discuss the scientific basis and practical issues of managing highly sensitized patients.

Modeling unrelated blood stem cell donor recruitment using simulated registrant cohorts: Assessment of human leukocyte antigen matching across ethnicity groups.

Human leukocyte antigen (HLA)-matched unrelated donors are not available for some patients considered for allogeneic hematopoietic cell transplantation, particularly among certain ethnic groups. Simulated recruitment modeling can inform efforts to find new matches for more patients. Simulated recruits were generated by assigning a pair of donor HLA haplotypes from historical data files and matched against HLA data of patient searches in the Canadian Blood Services Stem Cell Registry. Recruitment cohorts reflected the proportion of five specific ethnic groups in the 2016 Canadian census data. Novel 8/8 HLA matches between simulated recruits and patients increased linearly with larger recruitment cohorts. The proportion of novel 8/8 HLA matches from Caucasian, Hispanic, and Native American/First Nations recruits was equal to or greater than their relative proportion in the recruited cohort (match to: recruit ratio (MRR) ≥ 1). In contrast, African American and Asian & Pacific Islander recruits represented a smaller proportion of novel matches relative to their percentage of the recruited cohort (MRR <1). The proportion of novel 7/8 HLA-matches from each ethnic group was approximately the same as their proportion in the recruited cohort (MRR ~ 1) and high rates of 7/8 HLA-matching already exist within the Canadian Blood Services registry for all ethnic groups. Continued large recruitment cohorts are needed to add new 8/8 HLA matches to registry inventories. Likelihoods of novel HLA matches varied across ethnic groups, reflecting varied HLA haplotype frequencies across groups. Simulated cohort modeling can inform recruitment strategies that will generate new donor options for patients.

Matching for HLA-DR excluding diabetogenic HLA-DR3 and HLA-DR4 predicts insulin independence after pancreatic islet transplantation.

In pancreatic islet transplantation, the exact contribution of human leukocyte antigen (HLA) matching to graft survival remains unclear. Islets may be exposed to allogenic rejection but also the recurrence of type 1 diabetes (T1D). We evaluated the HLA-DR matching, including the impact of diabetogenic HLA-DR3 or HLA-DR4 matches. We retrospectively examined the HLA profile in 965 transplant recipients and 2327 islet donors. The study population was obtained from patients enrolled in the Collaborative Islet Transplant Registry. We then identified 87 recipients who received a single-islet infusion. Islet-kidney recipients, 2nd islet infusion, and patients with missing data were excluded from the analysis (n=878). HLA-DR3 and HLA-DR4 were present in 29.7% and 32.6% of T1D recipients and 11.6% and 15.8% of the donors, respectively. We identified 52 T1D islet recipients mismatched for HLA-DR (group A), 11 with 1 or 2 HLA-DR-matches but excluding HLA-DR3 and HLA- DR4 (group B), and 24 matched for HLA-DR3 or HLA-DR4 (group C). Insulin-independence was maintained in a significantly higher percentage of group B recipients from year one through five post-transplantation (p<0.01). At five-year post-transplantation, 78% of group B was insulin-independent compared to 24% (group A) and 35% (group C). Insulin-independence correlated with significantly better glycemic control (HbA1c <7%), fasting blood glucose, and reduced severe hypoglycemic events. Matching HLA-A-B-DR (≥3) independently of HLA- DR3 or HLA-DR4 matching did not improve graft survival. This study suggests that matching HLA-DR but excluding the diabetogenic HLA-DR3 and/or 4 is a significant predictor for long-term islet survival.