A Tool for the Assessment of HLA-DQ Heterodimer Variation in Hematopoietic Cell Transplantation: HLA-DQ Heterodimers Tool.

BACKGROUND: When optimizing transplants, clinical decision-makers consider HLA-A, -B, -C, -DRB1 (8 matched alleles out of 8), and sometimes HLA-DQB1 (10 out of 10) matching between the patient and donor. HLA-DQ is a heterodimer formed by the ß chain product of HLA-DQB1 and an α chain product of HLA-DQA1. In addition to molecules defined by the parentally-inherited cis haplotypes, α-ß trans-dimerization is possible between certain alleles, leading to unique molecules and a potential source of mismatched molecules. Recently, researchers uncovered that clinical outcome after HLA-DQB1-mismatched unrelated donor HCT depends on the total number of HLA-DQ molecule mismatches and the specific α-ß heterodimer mismatch. OBJECTIVE: Our objective in this study is to develop an automated tool for analyzing HLA-DQ heterodimer data and validating it through numerous datasets and analyses. By doing so, we provide an HLA-DQ heterodimer tool for DQα-DQß trans-heterodimer evaluation, HLA-DQ imputation, and HLA-DQ-featured source selection to the transplant field. STUDY DESIGN: In our study, we leverage 352,148 high-confidence, statistically-phased (via a modified expectation-maximization algorithm) HLA-DRB1∼DQA1∼DQB1 haplotypes, 1,052 pedigree-phased HLA-DQA1∼DQB1 haplotypes, and 13,663 historical transplants to characterize HLA-DQ heterodimers data. RESULTS: Using our developed QLASSy (HLA-DQA1 and HLA-DQB1 Heterodimers Assessment) tool, we first assessed the data quality of HLA-DQ heterodimers in our data for trans-dimers, missing HLA-DQA1 typing, and unexpected HLA-DQA1 and HLA-DQB1 combinations. Since trans-dimers enable up to four unique HLA-DQ molecules in individuals, we provide in-silico validations for 99.7% of 275 unique trans-dimers generated by 176,074 U.S. donors with HLA-DQA1 and HLA-DQB1 data. Many individuals lack HLA-DQA1 typing, so we developed and validated high-confidence HLA-DQ annotation imputation via HLA-DRB1 with >99% correct predictions in 23,698 individuals. A select few individuals displayed unexpected HLA-DQ combinations. We revisited the typing of 61 donors with unexpected HLA-DQ combinations based on their HLA-DQA1 and HLA-DQB1 typing and corrected 22 out of 61 (36%) cases of donors through data review or retyping and used imputation to resolve unexpected combinations. After verifying the data quality of our datasets, we analyzed our datasets further: we explored the frequencies of observed HLA-DQ combinations to compare HLA-DQ across populations (for instance, we found more high-risk molecules in Asian/Pacific Islander and Black/African American populations), demonstrated the effect of HLA-DQA1 and HLA-DQB1 mismatching on HLA-DQ molecular mismatches, and highlighted where donor selections could be improved at the time of search for historical transplants with this new HLA-DQ information (where 51.9% of G2-mismatched transplants had lower-risk, G2-matched alternatives). CONCLUSION: We encapsulated our findings into a tool that imputes missing HLA-DQA1 as needed, annotates HLA-DQ (mis)matches, and highlights other important HLA-DQ data to consider for the present and future. Altogether, these valuable datasets, analyses, and a culminating tool serve as actionable resources to enhance donor selection and improve patient outcomes.

Decreasing Chronic Graft-Versus-Host Disease rates in all populations.

Since 2005 there has been steady decline in chronic graft-versus-host disease (cGVHD) at Fred Hutchinson Cancer Center (FHCC). To better understand this phenomenon, we studied the risk of cGVHD requiring systemic immunosuppression (cGVHD-IS) as a function of hematopoietic cell transplantation (HCT)-date in 3066 survivors from 2005 through 2019. Cox regression models were fit to assess associations of HCT-date (as a continuous linear variable) with cause-specific hazards of cGVHD, using unadjusted and adjusted models. Median follow-up for study subjects was 7.0 years (range, 1.0-17.2). Two-year probabilities of cGVHD-IS declined among all survivors from 45-52% (2005-2007) to approximately 40% (2008-2012) and then further to ~26% by 2017. A decline was also observed when the analysis was restricted to 502 pediatric survivors, with cGVHD-IS probabilities being <10% since 2013. Among 305 adult and pediatric survivors who were transplanted for nonmalignant diseases, cGVHD rates showed greater fluctuation but remained <20% after 2016. Each 5-year increase in HCT-date was associated with a 27% decrease in the cause-specific hazard of cGVHD (unadjusted hazard ratio [HR] 0.73; 95% confidence interval [CI] 0.68-0.78, p<.0001); the HR was 0.81 (95% CI 0.75-0.87, p<.0001) even after adjusting for various factors (age, donor/stem-cell source, race, sex, conditioning intensity, GVHD prophylaxis, among others) that could lead to cGVHD reduction. The decline in cGVHD was not fully explained by demographic shifts and greater use of HCT approaches generally associated with lower cGVHD rates. This observation underscores that single-cohort cGVHD-prevention studies should use contemporaneous and not historical controls for comparisons.

Interplay between donor age and HLA-DP matching in 10/10 HLA-matched unrelated donor HCT.

In 10/10 HLA-matched unrelated donor (MUD) hematopoietic cell transplantation (HCT) with calcineurin-inhibitor (CNI)-based prophylaxis, T-cell epitope DP-matched and permissive mismatched donors are associated with similar overall survival (OS) while donors with non-permissive mismatches should be avoided. Younger unrelated donors are also favored over older donors. We explored outcomes associated with different combinations of DP-matching and donor age (dichotomized at 35 years) to further guide donor selection. Using a Center for International Blood and Marrow Transplant Research dataset, we categorized 10,783 patients into six groups: DP-matched/younger donor (n=1591), DP-matched/older donor (n=526), permissive-mismatched/younger donor (n=3845), permissive-mismatched/older donor (n=1184), non-permissive mismatched/younger donor (n=2659), non-permissive mismatched/older donor (n=978). We noted that younger donor age, rather than DP-matching, was associated with better OS. Younger donors with permissive mismatches were associated with improved OS compared to older matched donors. Furthermore, younger donors with non-permissive mismatches were associated with improved OS compared to older donors with permissive mismatches. Our study adds further information about the association of DP-matching and donor age with HCT outcomes. Donor age should be prioritized over DP-matching in patients undergoing 10/10 HLA-MUD with CNI prophylaxis. Among those with younger donors, permissive-mismatched or DP-matched donors are preferred over non-permissive mismatched donors.

Haploidentical Versus Mismatched Unrelated Donor Hematopoietic Cell Transplantation: HLA Factors and Donor Age Considerations.

HLA-mismatched unrelated donors and haploidentical related donors are suitable stem cell sources for hematopoietic cell transplantation (HCT) when patients lack HLA-matched donors. Clinical outcome after mismatched HCT is influenced by HLA factors including the similarity of peptide-binding motifs (PBMs) between the patient and unrelated donor, and of the HLA-B leader in unrelated and haploidentical donors. Whether these factors can aid in the selection between mismatched unrelated and haploidentical donors is not known. To address this question, we investigated outcomes between the two donor types defined by matching for the PBM and leader peptide. We compared PBM-matched (n = 614) and mismatched (n = 958) MMUDs with calcineurin-inhibitor-based prophylaxis to four haploidentical groups that received post-transplant cyclophosphamide (PTCy)-based prophylaxis. The haploidentical groups were B-leader matched/DRB1-mismatched (n = 722), B-leader matched/DRB1-matched (n = 154), B-leader mismatched/DRB1-mismatched (n = 493), and B-leader mismatched/DRB1-matched (n = 63). Multivariate analysis showed that the B-leader matched/DRB1-mismatched haploidentical group had the best overall survival (OS) compared to the PBM-matched MMUD, while other haploidentical groups had comparable OS. The PBM-mismatched MMUD showed the poorest outcomes, similar to the B-leader mismatched/DRB1-matched haploidentical group. Among non-HLA factors, donor age was the most significant predictor of OS. These results suggest that a B-leader matched/DRB1 mismatched haploidentical donor might be the preferred choice among donors of similar age. If such a donor is not available, the youngest donor from either PBM-matched unrelated or other haploidentical groups could be a beneficial choice. These findings need validation with both donor groups receiving PTCy-based graft-versus-host disease prophylaxis.

Combined effect of unrelated donor age and HLA peptide-binding motif match status on HCT outcomes.

ABSTRACT: An HLA-mismatched unrelated donor who is class I peptide-binding motif (PBM)-matched is preferred over a PBM-mismatched donor. We hypothesized that using a younger donor (aged ≤35 years vs >35 years) could compensate for the inferior overall survival (OS) associated with PBM mismatches. We compared 6 groups: HLA-matched/younger donor (n = 10 531), HLA-matched/older donor (n = 3572), PBM-matched/younger donor (n = 357), PBM-matched/older donor (n = 257), PBM-mismatched/younger donor (n = 616), and PBM-mismatched/older donor (n = 339) in patients undergoing transplantation with conventional graft-versus-host disease prophylaxis. In multivariate analysis, HLA-matched/younger donors were associated with superior OS relative to any other group. Pairwise comparisons showed that donor age significantly impacted OS in both HLA-matched and HLA-mismatched groups. Moreover, younger donors appeared to negate the detrimental effect of PBM mismatching: the PBM-matched/younger donor group had similar OS as the HLA-matched/older donor group and the PBM-mismatched/younger donor group had similar OS as the PBM-matched/older donor group. Our study suggests that older unrelated donor age and PBM mismatching confer similarly adverse effects on OS and the impacts are additive, a finding which may widen the "acceptable" donor pool. The best OS is observed with HLA-matched/younger donors and the worst with PBM-mismatched/older donors. These findings should be validated with other data sets and with posttransplantation cyclophosphamide-based prophylaxis.

HLA Haplotypes and Relapse After Hematopoietic Cell Transplantation.

PURPOSE: Recurrence of blood malignancy is the major cause of hematopoietic cell transplant failure. HLA class II molecules play a fundamental role in antitumor responses but the role of class II haplotypes is not known. METHODS: HLA-DR, -DQ, -DM, and -DO allele variation was determined in 1,629 related haploidentical transplants to study the clinical significance of individual molecules and haplotypes. RESULTS: Outcome correlated with patient and donor variation for HLA-DRß residue 86 (Gly/Val), HLA-DQ (G1/G2) heterodimers, and donor HLA-DM (DM11,11/nonDM11,11) molecules, and depended on patient-donor mismatching. Risks of relapse were lower for DRß-86 GlyGly patients when the donor was GlyVal (hazard ratio [HR], 0.46 [95% CI, 0.30 to 0.68]; P < .001); GlyVal patients benefited from HLA-DRB1-matched donors, whereas no donor was superior to another for ValVal patients. G1G2 patients with G1G2-mismatched donors had lower relapse. Transplantation from donors with DMα residue 184 ArgHis was associated with higher risk of relapse (HR, 1.60 [95% CI, 1.09 to 2.36]; P = .02) relative to ArgArg. Relapse and mortality risks differed across HLA-DR-DQ-DM haplotypes. CONCLUSION: HLA class II haplotypes may be functional constituents of the transplantation barrier, and their consideration in patients and donors may improve the success of transplantation.

Cryopreservation of Growth Factor-Mobilized Peripheral Blood Stem Cells Does Not Compromise Major Outcomes after Allogeneic Hematopoietic Cell Transplantation: A Single-Center Experience.

During the Coronavirus disease 2019 pandemic, cryopreservation of allogeneic donor stem cell products ensured the availability of products at the start of conditioning for hematopoietic cell transplantation (HCT). Following recommendations from unrelated donor registries, including the National Marrow Donor Program, many centers began to cryopreserve related donor peripheral blood stem cell (PBSC) products. Throughout this process, several centers have published outcomes with cryopreserved versus fresh products, some with conflicting results. Even though cryopreservation was initially considered only a temporary measure driven by the pandemic, potential advantages include greater flexibility of transplantation timing. However, concerns about detrimental effects of cryopreservation, including increased risk of graft rejection, relapse, and consequent mortality, remained. The primary objective of the present study was to describe our center's experience comparing outcomes following PBSC transplantation with cryopreserved versus fresh grafts. This was an observational case study with a retrospective review comparing cryopreserved grafts (n = 213) to a recent historical cohort (controls) using fresh grafts (n = 167). In multivariable analyses, the adjusted hazard ratio (HR) for fresh versus cryopreserved grafts was 1.20 (95% confidence interval [CI], .79 to 1.82; P = .40) for overall mortality, .99 (95% CI, .55 to 1.77; P = .98) for nonrelapse mortality, and .94 (95% CI, .60 to 1.48; P = .80) for relapse. The adjusted HR for platelet engraftment was 1.31 (95% CI, 1.05 to 1.63; P = .02) and the odds ratio of grade III-IV acute GVHD was 1.75 (95% CI, 1.01 to 3.04; P = .05) with fresh grafts compared to cryopreserved grafts. There was no demonstrable difference in the risk of chronic GHVD. Although longer-term follow-up is needed, these data provide preliminary reassurance that in the event of another pandemic or should the logistical need arise in individual patients, cryopreservation of PBSC products is a reasonably safe alternative.

Report from the extended HLA-DPA1 ~ promoter ~ HLA-DPB1 haplotype of the 18th international HLA and immunogenetics workshop.

The primary goal of the HLA-DPA1 ~ promoter ~ HLA-DPB1 haplotype component of the 18th IHIWS was to characterise the extended haplotypes within the HLA-DP region and survey the extent of genetic diversity in this region across human populations. In this report, we analysed single-nucleotide polymorphisms (SNPs) in 255 subjects from 6 different cohorts. The results from the HLA-DP haplotype component have validated findings from the initial pilot study. SNPs in this region were inherited in strong linkage, particularly HLA-DPA1, SNP-linked promoter haplotypes and motifs in exon 2 of HLA-DPB1. We reported 17 SNP-linked haplotypes in the promoter region. Together with HLA-DPA1 and HLA-DPB1 alleles, they formed 74 distinct extended HLA-DP haplotypes in 438 sequences. We also observed the presence of region-specific alleles and promoter haplotypes. Our approach involved phasing extended SNPs including promoter SNPs, HLA-DPA1 and HLA-DPB1 alleles, in a 22 kb region, GRCh38/hg38 (chr6:33,064,111-33,086,679), followed by clustering of these SNPs as one extended haplotype. This hierarchical clustering revealed four major clades, suggesting that haplotypes within each clade may have diverged from a common ancestral haplotype and undergone similar evolutionary processes. The correlation between HLA-DPA1 and the promoter region raises questions about the role of HLA-DPA1 antigen in the heterodimer. This finding requires validation on a larger sample size specifically designed for anthropological analysis. Nevertheless, the results from this study highlight the clinical potential of selecting better-matched donors for patients awaiting haematopoietic stem cell transplants from genetically overlapping groups that share common ancestral haplotypes.

Assessment of HLA-DPB1 genetic variation using an HLA-DP tool and its implications in clinical transplantation.

HLA-DP is a classic transplantation antigen that mediates alloreactivity through T-cell epitope (TCE) diversity and expression levels. A current challenge is to integrate these functional features into the prospective selection of unrelated donor candidates for transplantation. Genetically, HLA-DPB1 exon 2 defines the permissive and nonpermissive TCE groups, and exons 2 and 3 (in linkage with rs9277534) indicate low- and high-expression allotypes. In this study, we analyzed 356 272 exon 2-exon 3-phased sequences from individuals across 5 self-identified race and ethnicity categories: White, Hispanic, Asian or Pacific Islander, Black or African American, and American Indian or Alaskan Native. This sequence data set revealed the complex relationship between TCE and expression models and the importance of exon 3 sequence data. We also studied archived donor search lists for 2545 patients who underwent transplantation from an HLA-11/12 unrelated donor mismatched for a single HLA-DPB1 allele. Depending on the order in which the TCE and expression criteria were considered, some patients had different TCE- and expression-favorable donors. In addition, this data set revealed that many expression-favorable alternatives existed in the search lists. To improve the selection of candidate donors, we provide, disseminate, and automate our findings through our multifaceted tool called Expression of HLA-DP Assessment Tool, consisting of a public web application, Python package, and analysis pipeline.

HLA-B leader genotypes in a clinical population.

The -21 dimorphism in the leader sequences of HLA-B exon 1 is associated with risk of graft-versus-host disease (GVHD), relapse and overall survival after unrelated donor hematopoietic cell transplantation (HCT), haploidentical HCT and cord blood transplantation. Consideration of the leader dimorphism in the prospective selection of allogeneic donors for HCT may help to lower risks for patients, but requires understanding of the frequencies of the leader in patients and candidate transplant donors. We defined the frequencies of the HLA-B leader, and its association to HLA-B Bw4/Bw6 and C1/C2 KIR epitopes. Sequence variants of rs1050458 of exon 1 position -21 for 11,126 haplotypes were analyzed from high resolution HLA typing of over 5500 study subjects. HLA typing was performed by TruSight/AlloSeq NGS and analyzed using TruSight/AlloSeq Assign software. HLA-B Bw4/Bw6 and C1/C2 KIR epitopes were defined based on established sequence alignments and nomenclature. Alleles at rs1050458 of HLA-B exon 1 were validated as dimorphic: rs1050458-C or -T variants encoding threonine (T) or methionine (M) at anchor position 2 (P2) of nonameric HLA-B leader peptides, respectfully. No additional variants were observed. Among study subjects, 70% of HLA-B haplotypes encoded T-leader and 30% encoded M-leader sequences. The genotype frequencies of TT, MT, and MM were consistent among patient, related, and unrelated donor groups. The associations of M/T leader, Bw4/Bw6, and C1/C2 enhanced understanding of the Class I features involved in the innate immune response. A population of patients and transplant donors confirms the rs1050458 leader dimorphism and its association with HLA-B Bw4/Bw6 and C1/C2 KIR features.

What do patients think about palliative care? A national survey of hematopoietic stem cell transplant recipients.

Palliative care (PC) benefits patients undergoing hematopoietic stem cell transplantation (HSCT), but it remains underutilized. Although transplant physicians report concerns regarding how patients perceive PC, HSCT recipients' perceptions about PC remain unaddressed. We conducted a multisite, cross-sectional survey of autologous and allogeneic HSCT recipients 3 to 12 months after transplant to assess their familiarity, knowledge, and perception of PC, as well as their unmet PC needs. We computed a composite score of patients' perceptions of PC and used a generalized linear regression model to examine factors associated with these perceptions. We enrolled 69.6% (250/359) of potential participants (median age = 58.1; 63.1% autologous HSCT). Overall, 44.3.8% (109/249) reported limited knowledge about PC and 52% (127/245) endorsed familiarity with PC. Most patients felt hopeful (54%) and reassured (50%) when they heard the term PC; 83% saw referral as a sign their doctor cared about what was happening to them. In multivariate analyses, patients who were more knowledgeable about PC were more likely to have positive perceptions of PC (B = 7.54, standard error = 1.61, P < .001). Patients' demographics, HSCT features, quality of life, and symptom burden were not significantly associated with perceptions of PC. HSCT recipients have positive perceptions of PC, though many have limited knowledge about its role. Patients who were more knowledgeable about PC were more likely to have positive perceptions of PC. These data do not support transplant physicians' negative concerns about how patients perceive PC and underscore the need to further educate patients and transplant physicians about PC.

Role of NKG2D ligands and receptor in haploidentical related donor hematopoietic cell transplantation.

The recurrence of malignancy after hematopoietic cell transplantation (HCT) is the primary cause of transplantation failure. The NKG2D axis is a powerful pathway for antitumor responses, but its role in the control of malignancy after HCT is not well-defined. We tested the hypothesis that gene variation of the NKG2D receptor and its ligands MICA and MICB affect relapse and survival in 1629 patients who received a haploidentical HCT for the treatment of a malignant blood disorder. Patients and donors were characterized for MICA residue 129, the exon 5 short tandem repeat (STR), and MICB residues 52, 57, 98, and 189. Donors were additionally defined for the presence of NKG2D residue 72. Mortality was higher in patients with MICB-52Asn relative to those with 52Asp (hazard ratio [HR], 1.83; 95% confidence interval [CI], 1.24-2.71; P = .002) and lower in those with MICA-STR mismatch than in those with STR match (HR, 0.66; 95% CI, 0.54-0.79; P = .00002). Relapse was lower with NKG2D-72Thr donors than with 72Ala donors (relapse HR, 0.57; 95% CI, 0.35-0.91; P = .02). The protective effects of patient MICB-52Asp with donor MICA-STR mismatch and NKG2D-72Thr were enhanced when all 3 features were present. The NKG2D ligand/receptor pathway is a transplantation determinant. The immunobiology of relapse is defined by the concerted effects of MICA, MICB, and NKG2D germ line variation. Consideration of NKG2D ligand/receptor pairings may improve survival for future patients.

Race and Survival in Unrelated Hematopoietic Cell Transplantation.

Survival after hematopoietic cell transplantation depends on race/ethnicity and histocompatibility (HLA) between the patient and transplant donor. HLA sequence variation is a genetic construct of continental populations, but its role in accounting for racial disparities of transplant outcome is unknown. To determine disparities in transplant survivorship among patients of diverse race while accounting for patient and donor HLA variation. A total of 26,945 self-described Japanese, U.S. Asian, White, Hispanic, and Black patients received an unrelated donor transplant for the treatment of a life-threatening blood disorder. The risk of mortality with and without adjustment for known HLA risk factors (number and location of donor mismatches; patient HLA-B leader genotype and HLA-DRß peptide-binding motif) was studied using multivariable models. Survival after HLA-matched transplantation for patients with optimal leader and peptide-binding features was estimated for each race, as was the improvement in survival over calendar-year time by considering year of transplantation as a continuous linear variable. The number, location, and nature of donor HLA mismatches and the frequency of patient HLA-B and HLA-DRB1 sequence motifs differed by race. Japanese patients had superior survival compared to other races without consideration of HLA. After HLA adjustment, three mortality risk strata were identified: Japanese and U.S. Asian (low-risk); White and Hispanic (intermediate-risk), and Black patients (high-risk). Survival for patients with optimal donor and HLA characteristics was superior for Japanese, intermediate for U.S. Asian, White, and Hispanic, and lowest for Black patients. Five-year increments of transplant year were associated with greater decreases in mortality hazards for Black and Hispanic patients than for Japanese, U.S. Asian and White patients. Transplant survivorship disparities are influenced by HLA as a genetic construct of race. A more complete understanding of the factors that influence transplant outcomes provides opportunities to narrow disparities for future patients.

HLA-DQ heterodimers in hematopoietic cell transplantation.

HLA-DQ heterodimers increase the susceptibility to autoimmune diseases, but their role in hematopoietic cell transplantation is unknown. We tested the hypothesis that outcome after HLA-matched and HLA-DQ-mismatched hematopoietic cell transplantation is influenced by HLA-DQ heterodimers. Heterodimers were defined in 5164 HLA-matched and 520 HLA-DQ-mismatched patients and their transplant donors according to well-established crystallographic criteria. Group 1 (G1) heterodimers are any DQA1*02/03/04/05/06α paired with any DQB1*02/03/04ß. Group 2 (G2) heterodimers are DQA1*01α paired with any DQB1*05/06ß. Multivariable models identified significantly higher relapse risk in G1G2 and G2G2 compared with G1G1 HLA-matched patients with malignant disease; risk increased with an increasing number of G2 molecules. In HLA-DQ-mismatched transplantation for malignant diseases, matching or mismatching for G2 increased relapse risk. G2 lowered disease-free survival after both HLA-matched and HLA-DQ-mismatched transplantation. A paradigm based on HLA-DQ heterodimers provides a functional definition of the hematopoietic cell transplantation barrier and a means to lower risks for future patients.

Assessment of HLA-B genetic variation with an HLA-B leader tool and implications in clinical transplantation.

Sequence variation in the HLA-B gene is critically linked to differential immune responses. A dimorphism at -21 of HLA-B exon 1 gives rise to leader peptides that are markers for risk of acute graft-versus-host disease, relapse, and mortality after unrelated donor and cord blood transplantation. To optimize the selection of stem cell transplant sources based on the HLA-B leader, an HLA-BLeader Assessment Tool (BLEAT) was developed to automate the assignment of leader genotypes, define HLA-B leader match statuses, and rank order candidate stem cell sources according to clinical risk. The base cohort consisted of 9 417 614 registered donors from the Be The Match Registry with HLA-B typing. Among these donors, the performance of BLEAT was assessed in 1 098 358 donors with sequence data for HLA-B exon 1 (2 196 716 haplotypes). The accuracy of leader assignment was then assessed in a second cohort of 1259 patients and their unrelated transplant donors. We furthermore established the frequencies of HLA-B leader genotype (MM, MT, TT) representations in broad racial categories in the 9.42 million donors. BLEAT has direct applications for the selection of optimal stem cell sources for transplantation and broad utility in basic and clinical research in pharmacogenomics, vaccine development, and cancer and infectious disease studies of human populations.

HLA informs risk predictions after haploidentical stem cell transplantation with posttransplantation cyclophosphamide.

Hematopoietic cell transplantation from HLA-haploidentical related donors is increasingly used to treat hematologic cancers; however, characteristics of the optimal haploidentical donor have not been established. We studied the role of donor HLA mismatching in graft-versus-host disease (GVHD), disease recurrence, and survival after haploidentical donor transplantation with posttransplantation cyclophosphamide (PTCy) for 1434 acute leukemia or myelodysplastic syndrome patients reported to the Center for International Blood and Marrow Transplant Research. The impact of mismatching in the graft-versus-host vector for HLA-A, -B, -C, -DRB1, and -DQB1 alleles, the HLA-B leader, and HLA-DPB1 T-cell epitope (TCE) were studied using multivariable regression methods. Outcome was associated with HLA (mis)matches at individual loci rather than the total number of HLA mismatches. HLA-DRB1 mismatches were associated with lower risk of disease recurrence. HLA-DRB1 mismatching with HLA-DQB1 matching correlated with improved disease-free survival. HLA-B leader matching and HLA-DPB1 TCE-nonpermissive mismatching were each associated with improved overall survival. HLA-C matching lowered chronic GVHD risk, and the level of HLA-C expression correlated with transplant-related mortality. Matching status at the HLA-B leader and HLA-DRB1, -DQB1, and -DPB1 predicted disease-free survival, as did patient and donor cytomegalovirus serostatus, patient age, and comorbidity index. A web-based tool was developed to facilitate selection of the best haploidentical-related donor by calculating disease-free survival based on these characteristics. In conclusion, HLA factors influence the success of haploidentical transplantation with PTCy. HLA-DRB1 and -DPB1 mismatching and HLA-C, -B leader, and -DQB1 matching are favorable. Consideration of HLA factors may help to optimize the selection of haploidentical related donors.

Biobehavioral Research and Hematopoietic Stem Cell Transplantation: Expert Review from the Biobehavioral Research Special Interest Group of the American Society for Transplantation and Cellular Therapy.

Hematopoietic stem cell transplantation (HCT) is a potentially curative treatment for many hematologic conditions. Despite advances in conditioning and supportive measures, however, there remain significant comorbidities that threaten survivorship. Adverse effects of stress-related biobehavioral processes-defined here as the interactions of behavioral, psychological, and socioenvironmental factors with biology-impact immune recovery and function and are particularly salient in the HCT context, given the importance of immune reconstitution for improved survivorship. However, biobehavioral processes have been underinvestigated in this vulnerable group compared with other cancer populations. Here the Biobehavioral Research Special Interest Group (SIG) of the American Society for Transplantation and Cellular Therapy provides an expert review to inform research directions explicating the biological correlates of behavioral symptoms and evaluate the impact of these on HCT outcomes. The goal of this expert review is to provide a foundation for advancing science that effectively integrates behavioral and biological processes to optimize quality of life and improve clinical outcomes for HCT recipients.

Blood and marrow transplantation during the emerging COVID-19 pandemic: the Seattle approach.

On January 20, 2020, the first patient with coronavirus disease 2019 (COVID-19) in the United States of America was diagnosed in Washington state, which subsequently experienced rapidly increasing numbers of COVID-19 cases, hospitalizations, and deaths. This placed the Seattle Blood and Marrow Transplant Program at Fred Hutchinson Cancer Research Center (Fred Hutch) in the national epicenter of this pandemic. Here, we summarize the experience gained during our rapid response to the COVID-19 pandemic. Our efforts were aimed at safely performing urgent and potentially life-saving stem cell transplants in the setting of pandemic-related stresses on healthcare resources and shelter-in-place public health measures. We describe the unique circumstances and challenges encountered, the current state of the program amidst evolving COVID-19 cases in our community, and the guiding principles for recovery. We also estimate the collateral impact of directing clinical resources toward COVID-19-related care on cancer patients in need of stem cell transplantation. Although our experience was influenced by specific regional and institutional factors, it may help inform how transplant programs respond to COVID-19 and future pandemics.

Use of the HLA-B leader to optimize cord blood transplantation

Cord-blood transplantation (CBT) can cure life-threatening blood disorders. The HLA-B leader affects the success of unrelated donor transplantation but its role in CBT is unknown. We tested the hypothesis that the HLA-B leader influences CBT outcomes in unrelated single-unit cord-blood transplants performed by Eurocord/European Blood and Marrow Transplant (EBMT) centers between 1990 and 2018 with data reported to Eurocord. Among 4822 transplants, 2178 had one HLA-B mismatch of which 1013 were HLA-A and HLA-DRB1-matched. The leader (M or T) was determined for each HLA-B allele in patients and units to define the genotype. Among single HLA-B-mismatched transplants, the patient/unit mismatched alleles were defined as leader-matched if they encoded the same leader, or leader-mismatched if they encoded different leaders; the leader encoded by the matched (shared) allele was determined. The risks of GVHD, relapse, non-relapse mortality and overall mortality were estimated for various leaderdefined groups using multivariable regression models. Among the 1013 HLA-A, -DRB1- matched transplants with one HLA-B mismatch, increasing numbers of cord-blood unit M-leader alleles was associated with increased risk of relapse (hazard ratio [HR] for each increase in one M-leader allele 1.30, 95% confidence interval [CI] 1.05 to 1.60, P 0.02). Furthermore, leader mismatching together with an M-leader of the shared HLA-B allele lowered non-relapse mortality (HR 0.44, 95% CI 0.23 to 0.81; P 0.009) relative to leader-matching and a shared T-leader allele. The HLA-B leader may inform relapse and non-relapse mortality risk after CBT. Future patients might benefit from the appropriate selection of units that consider the leader.