HLA Mismatch Is Associated with Worse Outcomes after Unrelated Donor Reduced-Intensity Conditioning Hematopoietic Cell Transplantation: An Analysis from the Center for International Blood and Marrow Transplant Research

Donor selection in allogeneic stem cell transplantation

PURPOSE OF REVIEW

Recent progress in human leukocyte antigen (HLA) characterization, increased accrual of unrelated donors and cord blood units, and a new platform for haploidentical transplantation have resulted in the widespread availability of donors for allogeneic hematopoietic stem cell transplantation.

RECENT FINDINGS

Advances in HLA typing have identified an increasing number of loci and alleles that are crucial for successful transplantation. Newer HLA A, B, C, DRB1, and DQB1 alleles, DPB1 mismatches, and HLA B leader sequence matching are incorporated into donor selection algorithms. Donor selection is highly relevant because of recently published conflicting studies using different donor types. These studies are largely retrospective and compare patients with different diseases and stages, conditioning regimens, graft versus host disease (GVHD) prophylaxis, and time periods. A broad consensus indicates that the best donor is an available matched sibling, followed by a matched unrelated donor, and then alternative donors such as haploidentical, mismatched unrelated, and cord blood units. This consensus is being challenged by other factors, such as donor age, patient condition, urgency of transplantation, and costs involved.

SUMMARY

In this review, we will analyze the unique characteristics of each donor type, the HLA and non HLA factors that affect donor choices, and the outstanding comparative outcome studies of different donor usage in hematologic malignancies.

Post-Transplant Cyclophosphamide-Based Graft-Versus-Host Disease Prophylaxis Attenuates Disparity in Outcomes Between Use of Matched or Mismatched Unrelated Donors

PURPOSEAccess to allogeneic hematopoietic cell transplantation (HCT) remains limited among persons of non-European ancestry if human leukocyte antigen (HLA) matching is required. We evaluated whether post-transplant cyclophosphamide (PTCy)-based graft-versus-host disease (GVHD) prophylaxis improved HCT outcomes with HLA-matched unrelated donor (MUD) and mismatched unrelated donor (MMUD) HCT when compared with calcineurin inhibitor (CNI)-based prophylaxis.METHODSThree-year overall survival (OS) and GVHD-free, relapse-free survival (GRFS) were compared between adult recipients undergoing initial MUD or single HLA locus MMUD HCT with either PTCy- or CNI-based prophylaxis who were reported to the Center for International Blood and Marrow Transplant Research between 2017 and 2021.RESULTSIncluded were 10,025 HCT recipients (7,272 recipients of MUD with CNI, 1,681 MUD with PTCy, 613 MMUD with CNI, and 459 MMUD with PTCy) who underwent HCT for acute leukemia (70.9%) or myelodysplastic syndromes (29.2%). Median patient age was 60.7 years (range, 18.0-82.7) and median follow-up was 36.6 (range, 3.0-77.8) months. When compared with MUD HCT with PTCy, MMUD HCT with PTCy had similar OS (hazard ratio [HR], 0.96 [95% CI, 0.823 to 1.11]; P = .60) and GRFS (HR, 0.90 [0.79 to 1.02]; P = .1). When compared with MUD HCT with CNI, OS was improved after MUD HCT with PTCy (HR, 0.88 [0.80 to 0.96]; P = .004) and GRFS was improved with PTCy after either MUD (HR, 0.61 [0.57 to 0.66]; P < .0001) or MMUD (HR, 0.68 [0.60 to 0.76]; P < .0001) HCT. Benefit from PTCy was independent of patient ancestry. Global registry level analysis demonstrated that inclusion of MMUD increased donor availability regardless of recipient ancestry.CONCLUSIONUse of PTCy results in comparable OS and GRFS using either MUD or MMUD HCT, expanding access to HCT for patients from all racial and ethnic ancestry groups.

Younger unrelated donors may be preferable over HLA match in the PTCy era: a study from the ALWP of the EBMT

ABSTRACT

There is a paucity of information on how to select the most appropriate unrelated donor (UD) in hematopoietic stem cell transplantation (HSCT) using posttransplant cyclophosphamide (PTCy). We retrospectively analyzed the characteristics of 10/10 matched UDs (MUDs) and 9/10 mismatched UDs (MMUDs) that may affect transplant outcomes in patients with acute myeloid leukemia (AML) in first or second complete remission (CR1 or CR2). The primary end point was leukemia-free survival (LFS). Overall, 1011 patients were included with a median age of 54 years (range, 18-77). Donors had a median age of 29 years (range, 18-64); 304 (30%) were females, of which 150 (15% of the whole group) were donors to male recipients, and 621 (61%) were MUDs; 522 (52%) had negative cytomegalovirus (CMV-neg) serostatus, of which 189 (19%) were used for CMV-neg recipients. Donor age older than 30 years had a negative impact on relapse (hazard ratio [HR], 1.38; 95% confidence interval [CI], 1.06-1.8), LFS (HR, 1.4; 95% CI, 1.12-1.74), overall survival (HR 1.45; 95% CI, 1.14-1.85) and graft-versus-host disease (GVHD) free, relapse-free survival (HR, 1.29; 95% CI, 1.07-1.56). In addition, CMV-neg donors for CMV-neg recipients were associated with improved LFS (HR, 0.74; 95% CI, 0.55-0.99). The use of MMUD and female donors for male recipients did not significantly impact any transplant outcomes. For patients undergoing HSCT from a UD with PTCy for AML, donor age <30 years significantly improves survival. In this context, donor age might be prioritized over HLA match considerations. In addition, CMV-neg donors are preferable for CMV-neg recipients. However, further research is needed to validate and refine these recommendations.

Engineering the best transplant outcome for high-risk acute myeloid leukemia: the donor, the graft and beyond

Allogeneic hemopoietic cell transplantation remains the goal of therapy for high-risk acute myeloid leukemia (AML). However, treatment failure in the form of leukemia relapse or severe graft-versus-host disease remains a critical area of unmet need. Recently, significant progress has been made in the cell therapy-based interventions both before and after transplant. In this review, the Stem Cell Engineering Committee of the International Society for Cell and Gene Therapy summarizes the literature regarding the identification of high risk in AML, treatment approaches before transplant, optimal transplant platforms and measures that may be taken after transplant to ideally prevent, or, if need be, treat AML relapse. Although some strategies remain in the early phases of clinical investigation, they are built on progress in pre-clinical research and cellular engineering techniques that are already improving outcomes for children and adults with high-risk malignancies.

Optimizing Access to Unrelated Donors in Canada: Re-Examining the Importance of Donor Factors on Outcomes Following Hematopoietic Cell Transplantation

HLA-matched allogeneic hematopoietic cell transplantation (HCT) is a curative therapy for many patients. Unrelated HLA-matched donors are the most frequently used donor for HCT. When more than one donor transplant option is available, transplant centers can select donors based on non-HLA factors. With improved ability to prevent and treat immune complications, such as graft-versus-host disease and infections, it may be possible to proceed more often using HLA-mismatched donors, allowing greater consideration of non-HLA factors, such as donor age, CMV serostatus, and ABO blood group matching, which have demonstrated important impacts on transplant outcomes. Additional factors to consider are donor availability rates and the usage of domestic donors to optimize outcomes. A review of non-HLA factors and considerations on the selection of optimal unrelated donors for HCT are provided within this updated current context.

Characterization of the novel HLA-B*35:08:17 allele

HLA-B*35:08:17 differs from B*35:08:01:01 by a single nucleotide change in codon 105 (CCC > CCG).

[Unrelated donor selection for allogeneic hematopoietic stem cell transplantation: Guidelines from the Francophone Society of Bone Marrow Transplantation and Cellular Therapy (SFGM-TC)]

The selection of a donor is an essential element in allogeneic hematopoietic stem cell transplantation. In the absence of an HLA-matched related donor, the selection of an unrelated donor is considered, and is currently the most common type of allogenic donor used in practice. Many criteria are considered for the selection when multiple donors are available, particularly in case of partial match. The aim of this workshop is to assist in the selection of an unrelated donor, in keeping with recent data from the literature.

Alternative donor strategy in unrelated hematopoietic stem cell transplantation - outcome with mismatched donors

PURPOSE

This study retrospectively investigated the association between the level of human leukocyte antigen (HLA) mismatches (MMs), direction of disparities and differences at particular HLA locus on clinical outcomes of hematopoietic stem cell transplantation (HSCT). Investigated outcomes were overall survival (OS) and disease-free survival (DFS), graft-versus-host disease (GvHD), relapse and non-relapse mortality (NRM).

PATIENTS AND METHODS

Study cohort included 108 adult patients transplanted between 2011 and 2021 and their 9/10 mismatched unrelated donors (MMUD). All individuals were typed for HLA-A, -B, -C, -DRB1, -DQB1 and -DPB1 loci using Polymerase Chain Reaction-Sequence Specific Primers, PCR-Sequence Based Typing and Next-Generation Sequencing. All statistical analyses were done in the MedCalc software, version 19.2.6.

RESULTS

Patients with MMs at HLA-B locus demonstrated worse OS (P ​= ​0.0440, HR ​= ​2.00, n ​= ​20). Absence of HLA-DRB5 was associated with a higher incidence of GvHD (P ​= ​0.0112, HR ​= ​1.93, n ​= ​67). A lower incidence of GvHD was observed in patients with HLA class II MMs compared to patients with HLA class I MMs (P ​= ​0.0166, HR ​= ​1.94, n ​= ​29). Finally, analysis of PIRCHE score (PS) impact revealed that patients with HLA class II PS ​> ​10 in GvH direction showed higher incidence of GvHD compared to patients with HLA class II PS ​< ​10 (P ​= ​0.0073, HR ​= ​2.01, n ​= ​55).

CONCLUSION

Obtained results undisputedly indicate the necessity to further investigate this matter on a larger patient group, with focus on specific HLA alleles to define precisely priority criteria for selecting the best donor for all patients, thus improving the outcome of HSCT with an MMUD.

Impact of HLA-mismatched unrelated transplantation in patients with adult T-cell leukemia/lymphoma

This Japanese nationwide retrospective study investigated the impact of HLA-mismatched unrelated transplantation for adult T-cell leukemia-lymphoma (ATL) patients who received transplantation between 2000 and 2018. We compared 6/6 antigen-matched related donor (MRD), 8/8 allele-matched unrelated donor (8/8MUD), and 1 allele-mismatched unrelated donor (7/8MMUD) in the graft-versus-host direction. We included 1191 patients; 449 (37.7%) were in the MRD group, 466 (39.1%) in the 8/8MUD group, and 276 (23.7%) in the 7/8MMUD group. In the 7/8MMUD group, 97.5% of patients received bone marrow transplantation, and no patients received post-transplant cyclophosphamide. The cumulative incidences of non-relapse mortality (NRM) and relapse at 4 years, and the probabilities of overall survival at 4 years in the MRD group were 24.7%, 44.4%, 37.5%, in the 8/8MUD group were 27.2%, 38.2%, and 37.9%, and in the 7/8MMUD group were 34.0%, 34.4%, and 35.3%, respectively. The 7/8MMUD group had a higher risk of NRM (hazard ratio (HR) 1.50 [95% CI, 1.13-1.98; P = 0.005]) and a lower risk of relapse (HR 0.68 [95% CI, 0.53-0.87; P = 0.003]) than the MRD group. The donor type was not a significant risk factor for overall mortality. These data suggest that 7/8MMUD is an acceptable alternative donor when an HLA-matched donor is unavailable.

Distributions of the HLA-A, HLA-B, HLA-C, HLA-DRB1, and HLA-DQB1 alleles and haplotype frequencies of 1763 stem cell donors in the Colombian Bone Marrow Registry typed by next-generation sequencing

The HLA compatibility continues to be the main limitation when finding compatible donors, especially if an identical match is not found within the patient's family group. The creation of bone marrow registries allowed a therapeutic option by identifying 10/10 compatible unrelated donors (URD). However, the availability and frequency of haplotypes and HLA alleles are different among ethnic groups and geographical areas, increasing the difficulty of finding identical matches in international registries. In this study, the HLA-A, -B, -C, -DRB1, and -DQB1 loci of 1763 donors registered in the Colombian Bone Marrow Registry were typed by next-generation sequencing. A total of 52 HLA-A, 111 HLA-B, 41 HLA-C, 47 HLA-DRB1, and 20 HLA-DQB1 alleles were identified. The 3 most frequent alleles for each loci were A*24:02g (20,8%), A*02:01g (16,1%), A*01:01g (7.06%); B*35:43g (7.69%), B*40:02g (7.18%), B*44:03g (6.07%); C*04:01g (15.40%), C*01:02g (10.49%), C*07:02g (10.44%); DRB1*04:07g (11.03%), DRB1*07:01g (9.78%), DRB1*08:02g (6.72%); DQB1*03:02g (20.96%), DQB1*03:01g (17.78%) and DQB1*02:01g (16.05%). A total of 497 HLA-A-C-B-DRB1-DQB1 haplotypes were observed with a frequency greater than or equal to 0.05% (> 0.05%); the haplotypes with the highest frequency were A*24:02g~B*35:43g~C*01:02g~DQB1*03:02g~DRB1*04:07g (3.34%), A*29:02g~B*44:03g~C*16:01g~DQB1*02:01g~DRB1*07:01g (2.04%), and A*01:01g~B*08:01g~C*07:01g~DQB1*02:01g~DRB1*03:01g (1.83%). This data will allow the new Colombian Bone Marrow Donor Registry to assess the genetic heterogeneity of the Colombian population and serve as a tool of interest for future searches of unrelated donors in the country.

Outcomes with mismatched unrelated donor allogeneic hematopoietic stem cell transplantation in adults: A systematic review and meta-analysis

Background

Allogeneic hematopoietic stem cell transplantation (HSCT) is a potentially curative therapy for various hematologic disorders. Alternative donor strategies such as mismatched unrelated donors (MMUD) offer the option of HSCT to patients lacking a human leukocyte antigen (HLA)-matched donor. We conducted a systematic review and meta-analysis to evaluate outcomes after MMUD-HSCT.

Methods

A literature search was performed on PubMed, Cochrane Library, and ClinicalTrials.gov from the inception date through April 6, 2022. After screening 2477 manuscripts, 19 studies were included. Data was extracted following the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines. Pooled analysis was done using the meta-package by Schwarzer et al. Proportions with 95% confidence intervals (CI) were computed.

Results

A total of 3336 patients from 19 studies were included. The median age was 52.1 years, and 53% of recipients were males. The graft source was bone marrow in 19% and peripheral blood stem cells in 81% of recipients. The median time to transplant from hematologic diagnosis was 10 (1-247) months. Hematologic diagnoses included myeloid (82.9%), lymphoid (41.1%), and other disorders (3%). The reduced intensity and myeloablative conditioning were used in 65.6% and 32% of recipients, respectively. In-vivo T-cell depletion was performed in 56.7% of the patients. Most patients had one (87.9%) or two (11.4%) antigen HLA-mismatch. The pooled 1-year overall survival (OS) was 63.9% (95% CI 0.57-0.71, n=1426/2706), and the pooled 3-year OS was 42.1% (95% CI 0.34.2-0.50, n=907/2355). The pooled progression-free survival was 46.6% (95% CI 0.39-0.55, n=1295/3253) after a median follow-up of 1.8 (range 1-6) years. The pooled relapse rate was 26.8% (95% CI 0.22-0.32, n=972/3253) after a median follow-up of 2.25 (1-3) years. The pooled incidence of acute (grade II-IV) graft-versus-host disease (GVHD) and chronic GVHD was 36.4% (95% CI 0.31-0.42, n=1131/3030) and 41.2% (95% CI 0.35-0.48, n=1337/3228), respectively. The pooled non-relapse mortality was 22.6% (95% CI 0.17-0.29, n=888/3196) after a median follow-up of 2.6 (1-5) years.

Conclusion

MMUD-HSCT has demonstrated favorable outcomes with an acceptable toxicity profile. It represents a promising option in patients lacking an HLA-matched or haploidentical donor and may expand HSCT access to underrepresented racial and ethnic populations.

UM171 Expansion of Cord Blood Improves Donor Availability and HLA Matching For All Patients, Including Minorities

Cord blood (CB) stem cell transplantation offers a greater tolerance to HLA mismatches compared to adult-derived stem cell transplants (i.e., bone marrow or peripheral blood stem cells). Indeed, 4/6 or 5/8 HLA-matched CB transplantations are regularly performed for patients lacking a matched unrelated donor. Unfortunately, most banked CB units contain a stem cell dose that is too small to treat adult patients, resulting in only 4% to 5% of available CB units offering an adequate cell dose for prompt engraftment for adult patients. Ex vivo stem cell expansion appears to be an attractive strategy to circumvent this cell dose issue, while also enabling the selection of better HLA-matched CB units. In this study, we retrospectively performed HLA matching simulations to assess how the minimal cell content requirements associated with UM171 CB expansion may improve usability of existing CB unit inventories and donor availability for patients of different races and ethnicities. We analyzed a dataset of 58,971 adults for whom a donor search was initiated through the National Marrow Donor Program Be The Match registry against 142,942 CB units from major U.S. public CB banks listed on the Be The Match registry. Our results show that by enabling selection of smaller CB units, UM171-expanded CB transplantation increases donor availability from 72% to 84% for all patients compared to single unmanipulated CB transplantation. Furthermore, the low cell dose criteria for UM171-expanded CB also increases donor availability compared to double CB transplantation, while enabling better HLA matching between donor and recipient. UM171 expanded CB appears particularly beneficial for racial and ethnic minority patients as CB availability increases from 53% to 78% for African Americans, from 66% to 85% for Hispanics, and from 68% to 84% for Asians and Pacific Islanders, compared to single unmanipulated CB transplantation. In addition, UM171 expansion dramatically improves usability of CB units currently in inventories, as only 4.3% and 0.6% of banked CBs have sufficient cell doses for a 70 kg and 100 kg patient, respectively. UM171 raises this proportion to 53.8% and 20.2%, respectively, making CB banks potentially more cost effective. In conclusion, UM171 expansion allows the use of smaller CB units while also improving access to transplantation for racial and ethnic minorities.

Improved GRFS after posttransplant cyclophosphamide-based vs ATG-based HLA-mismatched unrelated donor transplant

A common method to prevent graft-versus-host disease after allogeneic hematopoietic cell transplantation (HCT) from an HLA-mismatched unrelated donor (MMUD) is tacrolimus, methotrexate, and antithymocyte globulin (ATG). The use of posttransplant cyclophosphamide (PTCy) showed promise in a prospective trial for MMUD HCT. We compared 1-year graft-versus-host disease–free, relapse-free survival (GRFS) in 128 recipients of prophylaxis based on tacrolimus/methotrexate/ATG (ATG group, n = 46) vs PTCy, mycophenolate mofetil, and tacrolimus or sirolimus (PTCy group, n = 82) after MMUD HCT. Patients receiving HCT from a MMUD mismatched at ≥1 locus among HLA-A, HLA-B, HLA-C, and HLA-DRB1 were included. The 2 groups were well matched for HCT indication, high-risk disease, and HCT comorbidity index, whereas more patients on PTCy received bone marrow (50% vs 26%; P = .01) and >1 locus HLA-mismatched (30.5% vs 2.2%; P = .001) grafts. The 1-year GRFS was 16% (95% confidence interval (CI): 8%-31%) vs 54% (95% CI: 44%-66%; P < .001) in the ATG and PTCy groups, respectively. The multivariable adjusted hazard ratio for GRFS was 0.34 (95% CI: 0.21-0.55; P < .001) with the use of PTCy. The 1-year overall survival in the ATG group was 45% (95% CI: 32%-62%) vs 75% (95% CI: 66%-85%) in the PTCy group (P < .001). Relapse incidence was similar. One-year nonrelapse mortality was greater after ATG-based prophylaxis: 38% (95% CI: 23%-52%) vs 16% (95 CI: 9%-25%), P < .001. In summary, PTCy-based prophylaxis resulted in superior GRFS and overall survival in recipients of MMUD.

HSCT with mismatched unrelated donors: Bone marrow versus peripheral blood stem cells sources in pediatric patients

BACKGROUND

Allogeneic hematopoietic stem cell transplantation (HSCT) from an unrelated HLA-mismatched donor (MMUD) is one of the alternatives where an HLA-matched donor is not found. The aim of this study was to compare bone marrow (BM) versus peripheral blood stem cells (PBSC) as hematopoietic rescue following allogeneic unrelated mismatched stem cell transplantation (MMUD).

METHODS

The patients were divided into two groups: 43 pediatric patients were treated with BM and 17 pediatric patients with PBSC. The study was registered at ClinicalTrials.gov NCT04598789.

RESULTS

The 3-year Overall Survival (OS) was 74% versus 31% (p = .0011). Transplant related mortality (TRM) was 16% versus 33% (p = .025), and relapse incidence (RI) was 16% versus 35% (p = .005). The day-100 acute Graft-versus-host disease (GvHD) incidence grade II-IV and III-IV was 30% versus 28% (p = NS) and 17% versus 17% (p = NS). The 3-year chronic GvHD incidence was 22% versus 33% (p = NS).

CONCLUSION

Despite all the limits of this retrospective study we were able to show how the combination of BM and ATG is able to prevent GvHDs and guarantee a high OS. Future studies addressing the issue of a post-transplant cellular therapy approach may potentially reduce relapses when GvHD is absent.

A calibrated Bayesian method for the stratified proportional hazards model with missing covariates

Missing covariates are commonly encountered when evaluating covariate effects on survival outcomes. Excluding missing data from the analysis may lead to biased parameter estimation and a misleading conclusion. The inverse probability weighting method is widely used to handle missing covariates. However, obtaining asymptotic variance in frequentist inference is complicated because it involves estimating parameters for propensity scores. In this paper, we propose a new approach based on an approximate Bayesian method without using Taylor expansion to handle missing covariates for survival data. We consider a stratified proportional hazards model so that it can be used for the non-proportional hazards structure. Two cases for missing pattern are studied: a single missing pattern and multiple missing patterns. The proposed estimators are shown to be consistent and asymptotically normal, which matches the frequentist asymptotic properties. Simulation studies show that our proposed estimators are asymptotically unbiased and the credible region obtained from posterior distribution is close to the frequentist confidence interval. The algorithm is straightforward and computationally efficient. We apply the proposed method to a stem cell transplantation data set.

Biomarkers of immune tolerance in kidney transplantation: an overview

Kidney failure, one of the most prevalent diseases in the world and with increasing incidence, is associated with substantial morbidity and mortality. Currently available modes of kidney replacement therapy include dialysis and kidney transplantation. Though kidney transplantation is the preferred and ideal mode of kidney replacement therapy, this modality, however, is not without its risks. Kidney transplant recipients are constantly at risk of complications associated with immunosuppression, namely, opportunistic infections (e.g., Epstein-Barr virus and cytomegalovirus infections), post-transplant lymphoproliferative disorder^, and complications associated with immunosuppressants (e.g., calcineurin inhibitor- and corticosteroid-associated new onset diabetes after transplantation and calcineurin inhibitor-associated nephrotoxicity). Transplantation tolerance, an acquired state in which immunocompetent recipients have developed donor-specific unresponsiveness, may be the Holy Grail in enabling optimal allograft survival and obviating the risks associated with immunosuppression in kidney transplant recipients. This review aims to discuss the biomarkers available to predict, identify, and define the transplant immune tolerant state and various tolerance induction strategies. Regrettably, pediatric patients have not been included in any tolerance studies and this should be the focus of future studies.

HSCT with Mismatched Unrelated Donors (MMUD): A Comparison of Different Platforms for GvHD Prophylaxis

HSCT from an unrelated HLA-mismatched donor (MMUD) is one of the alternatives where an HLA-matched donor is not found. The aim of this study was to compare GvHD prophylaxis with anti-thymocyte globulin (ATG) vs. post-transplant cyclophosphamide (PT-Cy). Thirty-nine adult patients were uniformly treated with rabbit ATG-Cy-A-MTX and peripheral blood stem cell (PBSC) and 40 adult patients with PT-Cy-MMF-tacrolimus and PBSC. This retrospective study was registered at ClinicalTrials.gov NCT04598789. Three-year overall survival was 42% vs. 64% for ATG and PT-Cy (p < 0.0005), three-year treatment-related mortality (TRM) was 36% vs. 8% (p = 0.0033) and the three-year relapse incidence (RI) was 15% vs. 28% (p = NS), respectively. The incidences of day-100 GvHD graded II–IV and III–IV were 39% vs. 7% (p = 0.0006) and 11% vs. 0% (p = 0.04), respectively, whereas the three-year cGvHD incidences were 48% vs. 13% (p = 0.0005), respectively. We were able to show how PT-Cy can reduce the incidence of GvHDs and TRM in adults, but relapse remains an issue.

HLA-DRB3/4/5 Matching Improves Outcome of Unrelated Hematopoietic Stem Cell Transplantation

The HLA-DRB3/4/5 loci are closely linked to the HLA-DRB1 gene. Mismatches in these loci occur with a frequency of about 8%–12% in otherwise 10/10 HLA-matched transplant pairs. There is preliminary evidence that these disparities may associate with increased acute graft-versus-host disease (GvHD) rates. The aim of this study was to analyze a large cohort of German patients and their donors for HLA-DRB3/4/5 compatibility and to correlate the HLA-DRB3/4/5 matching status with the outcome of unrelated hematopoietic stem cell transplantation (uHSCT). To this end, 3,410 patients and their respective donors were HLA-DRB3/4/5 and HLA-DPB1 typed by amplicon-based next-generation sequencing (NGS). All patients included received their first allogeneic transplant for malignant hematologic diseases between 2000 and 2014. Mismatches in the antigen recognition domain (ARD) of HLA-DRB3/4/5 genes were correlated with clinical outcome. HLA-DRB3/4/5 incompatibility was seen in 12.5% (n = 296) and 17.8% (n = 185) of the 10/10 and 9/10 HLA-matched cases, respectively. HLA-DRB3/4/5 mismatches in the ARD associated with a worse overall survival (OS), as shown in univariate (5-year OS: 46.1% vs. 39.8%, log-rank p = 0.038) and multivariate analyses [hazard ratio (HR) 1.25, 95% CI 1.02–1.54, p = 0.034] in the otherwise 10/10 HLA-matched subgroup. The worse outcome was mainly driven by a significantly higher non-relapse mortality (HR 1.35, 95% CI 1.05–1.73, p = 0.017). In the 9/10 HLA-matched cases, the effect was not statistically significant. Our study results suggest that mismatches within the ARD of HLA-DRB3/4/5 genes significantly impact the outcome of otherwise fully matched uHSCT and support their consideration upon donor selection in the future.

Characterization of the novel HLA-DPA1 allele, HLA-DPA1*01:86

HLA-DPA1*01:86 differs from DPA1*01:03:01:05 by a single nucleotide change in codon 94 (AAG>GAG).

Posttransplant cyclophosphamide as GVHD prophylaxis for peripheral blood stem cell HLA-mismatched unrelated donor transplant

Efficacy of PTCy after mismatched unrelated donor (MMUD) HCT is unknown. In this pilot clinical trial, we enrolled 38 patients with hematologic malignancies scheduled to undergo MMUD-HCT (≥6/8 HLA-matched donors) onto 1 of 2 conditioning strata: myeloablative using fludarabine and fractionated total body irradiation (n = 19) or reduced intensity with fludarabine/melphalan (n = 19). Graft source was peripheral blood stem cells (PBSCs), and GVHD prophylaxis was PTCy, tacrolimus, and mycophenolate mofetil. Patients' median age was 53 years (range, 21-72 years). Median number of HLA mismatches was 2 (range, 1-4) of 12 loci. Twenty-three patients (61%) were considered racial (n = 12) or ethnic (n = 11) minorities. Median time to neutrophil engraftment was 16 days (range, 13-35 days). With a median follow-up of 18.3 months (range, 4.3-25.0 months) for surviving patients, 1-year overall survival (OS) and GVHD-free/relapse-free survival (GRFS) were 87% (95% confidence interval [CI]: 71-94) and 68% (95% CI: 51-81), respectively. Cumulative incidence of nonrelapse mortality at 100 days and 1 year were 0% and 11% (95% CI: 4-27), respectively, whereas relapse/progression was 11% (95% CI: 4-27). Cumulative incidence of 100-day acute GVHD grades 2-4 and 3-4 and 1-year chronic GVHD were 50% (95% CI: 36-69), 18% (95% CI: 9-36), and 48% (95% CI: 34-68), respectively. The rate of moderate/severe chronic GVHD was 3% in the entire cohort. We showed highly promising OS/GRFS rates with an acceptable risk profile after PBSC-MMUD-HCT with PTCy. This trial was registered at www.clinicaltrials.gov as #NCT03128359.

Optimizing Transplant Approaches and Post-Transplant Strategies for Patients With Acute Myeloid Leukemia

Acute Myeloid Leukemia (AML) is the commonest indication for allogeneic stem cell transplantation (allo-SCT) worldwide. The increasingly important role of allo-SCT in the management of AML has been underpinned by two important advances. Firstly, improvements in disease risk stratification utilizing genetic and Measurable Residual Disease (MRD) technologies permit ever more accurate identification of allo-mandatory patients who are at high risk of relapse if treated by chemotherapy alone. Secondly, increased donor availability coupled with the advent of reduced intensity conditioning (RIC) regimens has substantially expanded transplant access for patients with high risk AML In patients allografted for AML disease relapse continues to represent the commonest cause of transplant failure and the development of novel strategies with the potential to reduce disease recurrence represents a major unmet need.

Sirolimus with CSP and MMF as GVHD prophylaxis for allogeneic transplantation with HLA antigen-mismatched donors

This trial aimed to evaluate the efficacy of sirolimus in addition to cyclosporine (CSP) and mycophenolate mofetil (MMF) for graft-versus-host disease (GVHD) prophylaxis after nonmyeloablative conditioning for HLA class I or II mismatched hematopoietic cell transplantation (HCT). Eligible patients had hematologic malignancies treatable by allogeneic HCT. Conditioning consisted of fludarabine (90 mg/m2) and 2 to 3 Gy total body irradiation. GVHD prophylaxis comprised cyclosporine, mycophenolate mofetil, and sirolimus. The primary objective was to determine whether the cumulative incidence of grade 2 to 4 acute GVHD could be reduced to <70% in HLA class I or II mismatched HCT. The study was closed on December 20, 2018. Seventy-seven participants were recruited between April 14, 2011, and December 12, 2018, of whom 76 completed the study intervention. Median follow-up was 47 months (range, 4-94 months). The cumulative incidence of grade 2 to 4 acute GVHD at day 100 was 36% (95% confidence interval [CI], 25-46), meeting the primary end point. The cumulative incidence of nonrelapse morality, relapse/progression, and overall survival was 18% (95% CI, 9-27), 30% (interquartile range, 19-40), and 62% (95% CI, 50-73) after 4 years. In conclusion, the addition of sirolimus to cyclosporine and mycophenolate mofetil resulted in a lower incidence of acute GVHD, thus translating into superior overall survival compared with historical results. This trial was registered at www.clinicaltrials.gov as #NCT01251575.

Identification of a new HLA-A allele: A*31:187

HLA-A*31:187 differs from A*31:01:02:04 by a single nucleotide change in codon 80 (ACC > AAC).

Translational and clinical advances in acute graft-versus-host disease

Acute graft-versus-host disease (aGvHD) is induced by immunocompetent alloreactive T lymphocytes in the donor graft responding to polymorphic and non-polymorphic host antigens and causing inflammation in primarily the skin, gastrointestinal tract and liver. aGvHD remains an important toxicity of allogeneic transplantation, and the search for better prophylactic and therapeutic strategies is critical to improve transplant outcomes. In this review, we discuss the significant translational and clinical advances in the field which have evolved based on a better understanding of transplant immunology. Prophylactic advances have been primarily focused on the depletion of T lymphocytes and modulation of T-cell activation, proliferation, effector and regulatory functions. Therapeutic strategies beyond corticosteroids have focused on inhibiting key cytokine pathways, lymphocyte trafficking, and immunologic tolerance. We also briefly discuss important future trends in the field, the role of the intestinal microbiome and dysbiosis, as well as prognostic biomarkers for aGvHD which may improve stratification-based application of preventive and therapeutic strategies.

Identification of a single nucleotide deletion in the novel HLA-DQB1*06:379N allele, detected by Polymerase Chain Reaction-Sequence Based Typing but not by Next Generation Sequencing

In this report we describe the characterization of a novel null HLA-DQB1 allele, detected by polymerase chain reaction-sequence-based typing but not by next-generation sequencing (NGS). The new allele, HLA-DQB1*06:379N, was discovered in an Italian patient with acute myeloid leukemia and also in one of her healthy siblings. The new allele is largely homologous to DQB1*06:02:01:01 with a T deletion in exon 2, in codon 11, which causes a frameshift and the formation of an unusual and premature TGA STOP in codon 27. This case report underlines the importance of not removing Sanger method sequencing from routine use for high-resolution HLA typing, but to maintain it together with NGS technology.

Impact of patient: donor HLA disparity on reduced-intensity-conditioned allogeneic stem cell transplants from HLA mismatched unrelated donors for AML: from the ALWP of the EBMT

Patients with acute myeloid leukaemia (AML) who lack a matched sibling or unrelated donor commonly undergo transplantation from a donor matched at 9/10 HLA-A, -B, -C, -DRB1, -DQB1 alleles, and it is unclear if a specific locus mismatch is preferable to any other. We therefore studied 937 patients with AML in complete remission transplanted using a reduced intensity conditioning regimen from an unrelated donor mismatched at a single allele. In a multivariate analysis, patient age, adverse karyotype and patient cytomegalovirus (CMV) seropositivity were correlated with decreased leukaemia free survival (LFS) and overall survival (OS). There was no significant difference in LFS or OS between patients transplanted from donors mismatched at HLA-A, -B, -C or -DRB1 in comparison to a HLA-DQB1 mismatched transplant. In a multivariate analysis, patients transplanted with a HLA-A mismatched donor had higher rates of acute graft-versus-host disease (GVHD) and non-relapse mortality (NRM) than patients transplanted with a HLA-DQB1 mismatched donor. Patient CMV seropositivity was associated with an increase in NRM and acute GVHD and reduced LFS and OS, regardless of donor CMV status. For CMV seropositive patients lacking a fully matched donor, alternative GVHD and CMV prophylaxis strategies should be considered.

Racial disparities in access to HLA-matched unrelated donor transplants: a prospective 1312-patient analysis

Availability of 8/8 HLA-allele matched unrelated donors (URDs) is a barrier for ethnic and racial minorities. We prospectively evaluated receipt of 8/8 HLA-allele matched URD or either 7/8 URD or cord blood (CB) transplants by patient ancestry from 2005 to 2017. Matched URDs were given priority if they were available. Of 1312 patients, 723 (55%) received 8/8 URD, 219 (17%) 7/8 URD, 319 (24%) CB, and 51 (4%) had no 7/8 or 8/8 URD or CB graft. Europeans were more likely to receive an 8/8 URD transplant than non-Europeans (67% vs 33%) and less likely to have no URD or CB graft (1% vs 9%). Southern Europeans received 8/8 URD transplants (41%) at rates similar to those of Asians (34%) and white Hispanics (35%); Africans were the least likely (18%) to undergo 8/8 URD transplantation. CB and 7/8 URDs extended transplant access to all groups. In 742 recent patients, marked racial disparity in 8/8 URD access between groups observed in earlier years persisted with only a modest increase in the percentage of 8/8 URD transplants. Of 78 recent African patients, 46% received a CB transplant and 14% had no 7/8 or 8/8 URD or CB graft. Increasing registry size has not resolved the racial disparity in URD access, which emphasizes the importance of alternative graft sources.

Long-term Outcome of Allogeneic Hematopoietic Stem Cell Transplantation From Unrelated Donor Using Tacrolimus/Sirolimus-based GvHD Prophylaxis: Impact of HLA Mismatch

BACKGROUND

While tacrolimus and sirolimus (T/S)-based graft-versus-host disease (GvHD) prophylaxis has been effective in preventing acute GvHD post hematopoietic cell transplantation (HCT), its efficacy and long-term outcome in matched (MUD) and mismatched unrelated donor (mMUD) setting is not well defined.

METHODS

Herein, we evaluated a consecutive case-series of 482 patients who underwent unrelated donor HCT (2005-2013) with T/S-based GvHD prophylaxis.

RESULTS

With a median follow-up of 6.2 years (range = 2.4-11.3), the 5-year overall survival (OS) and relapse/progression-free survival were 47.5% (95% confidence interval [CI]: 43.0-52.0) and 43.6% (95% CI: 39.1-48.1), respectively; and the 5-year cumulative incidence of nonrelapse mortality (NRM) and relapse were 24.9%, and 31.5%, respectively. In this cohort, mMUD was associated with worse OS (39.0% versus 50.7% at 5 y; P = 0.034), primarily due to greater risk of NRM (33.5% versus 21.7%; P = 0.038). While rates of relapse, acute (II-IV or III-IV) or chronic GvHD (limited or extensive) were not different, death caused by chronic GvHD (20.8% versus 12.8%; P = 0.022) and infection (33.0% versus 18.1%; P < 0.01) were significantly greater in mMUD. In multivariable analysis, high-risk disease (hazard ratio [HR] = 2.21, 95% CI: 1.16-4.23; P < 0.01) and mMUD (HR = 1.55, 95% CI: 1.15-2.08; P = 0.004) were independent predictive factors for OS.

CONCLUSIONS

T/S-based GvHD prophylaxis is an effective and acceptable GvHD prophylactic regimen. However, survival after mMUD remained poor, possibly related to the severity of chronic GvHD.

The role of allogeneic stem cell transplantation in the management of acute myeloid leukaemia: a triumph of hope and experience

Acute myeloid leukaemia (AML) is the commonest indication for allogeneic stem cell transplantation (allo-SCT) worldwide. The accumulated experience of allografting in AML over the last four decades has provided critical insights into both the contribution of the conditioning regimen and the graft-versus-leukaemia effect to the curative potential of the most common form of immunotherapy utilised in standard clinical practice. Coupled with advances in donor availability and transplant technologies, this has resulted in allo-SCT becoming an important treatment modality for the majority of adults with high-risk AML. At the same time, advances in genomic classification, coupled with progress in the accurate quantification of measurable residual disease, have increased the precision with which allo-mandatory patients can be identified, whilst simultaneously permitting accurate identification of those patients who can be spared the toxicity of an allograft. Despite this progress, disease recurrence still remains a major cause of transplant failure and AML has served as a paradigm for the development of strategies to reduce the risk of relapse - notably the novel concept of post-transplant maintenance, utilising pharmacological or cellular therapies.

Evaluation of Cord Blood Total Nucleated and CD34+ Cell Content, Cell Dose, and 8-Allele HLA Match by Patient Ancestry

How cord blood (CB) CD34⁺ cell content and dose and 8-allele HLA match vary by patient ancestry is unknown. We analyzed cell content, dose, and high-resolution HLA-match of units selected for CB transplantation (CBT) by recipient ancestry. Of 544 units (286 infused, 258 next-best backups) chosen for 144 racially diverse adult patients (median weight, 81 kg), the median total nucleated cell (TNC) and CD34⁺cell ⁺contents were higher for Europeans than for non-Europeans: 216 × 10⁷versus 197 × 10⁷ (P = .002) and 160 × 10⁵ versus 132 × 10⁵ (P = .007), respectively. There were marked cell content disparities among ancestry groups, with units selected for Africans having the lowest TNC (189 × 10⁷) and CD34⁺ cell (122 × 10⁵) contents. Units for non-Europeans were also more HLA-mismatched (P = .017). When only the 286 transplanted units were analyzed, the adverse effect of reduced cell content was exacerbated by the higher weights in some groups. For example, northwestern Europeans (high patient weight, high unit cell content) had the best-dosed units, and Africans (high weight, low unit cell content) had the lowest. In Asians, low cell content was partially compensated for by lower weight. Marked differences in 8-allele HLA-match distribution were also observed by ancestry group; for example, 23% of units for northwestern Europeans were 3/8 to 4/8 HLA-matched, compared with 40% for southern Europeans, 46% for white Hispanics, and 51% for Africans. During the study period, 20 additional patients (17 non-Europeans; median weight, 98 kg) did not undergo CBT owing to the lack of a suitable graft. CB extends transplantation access to most patients, but racial disparities exist in cell content, dose, and HLA match.

ASSESSMENT OF HLA-COMPATIBILITY AND REQUIREMENTS FOR HLA-TYPING OF PATIENT AND DONOR IN ALLOGENEIC HEMATOPOIETIC STEM CELL TRANSPLANTATION

Introduction.Unification of guidelines and standards concerning requirements for HLA typing and assessment of the degree of HLA match between the recipient and the donor for different types of allogeneic hematopoietic stem cell transplantation (allo-HSCT) is of a great importance.

Aim.To present contemporary requirements for the HLA typing of a recipient and a donor for allo-HSCT, to generalize recom mendations for assessing a required match degree of a recipient and a donor and to provide data on additional immunogenetic factors capable of improving the results of allogeneic hematopoietic stem cell transplantation.

General findings.Allo-HSCT appears to be an effective, and, in some cases, non-alternative treatment for many diseases of the blood system. The number of allo-HSCT types is constantly growing globally. Currently, an allogeneic hematopoietic stem cell donor can be selected for almost every recipient having indication for this type of therapy. Such a transplantation can be performed from an HLA-identical sibling, an HLA-match unrelated donor, a partially HLA-match unrelated donor, a relative haploidentical donor or cord blood. HLA match between the recipient and the donor present itself as an important factor affecting the results of allo-HSCT. The choice of a donor should involve a correct assessment the HLA match degree between the recipient and the donor, as well as consideration of additional factors that may affect the results of allo-HSCT.

HLA-A, -B, -C, -DRB1, and -DQB1 allele and haplotype frequencies: An analysis of umbilical cord blood units at the Barcelona Cord Blood Bank

Allele-level HLA compatibility in cord blood transplantation has been associated with better transplant outcomes and is recommended as a selection criterion. It is also a crucial aspect for other therapeutic applications involving cord blood-derived cells. Determination of high-resolution HLA frequencies is an important step towards improving the quality of cord blood banks. We analyzed HLA-A, -B, -C, -DRB1, and -DQB1 allele frequencies in 5458 high-quality cord blood units from the Barcelona Cord Blood Bank and identified 275 class I and 121 class II HLA alleles. A*02:01, B*44:03, C*07:01, DRB1*07:01 and DQB1*03:01 were the most frequent alleles at each locus. We detected 26 novel alleles and were able to determine the presence or absence of some null alleles, including C*04:09N, in a large number of units. We also analyzed maternal HLA typing information for 1877 units to determine real haplotype frequencies and linkage disequilibrium. A*29:02-B*44:03-C*16:01-DRB1*07:01-DQB1*02:02 was the most frequent HLA haplotype and the DRB1-DQB1 gene pair contained the two-locus haplotypes with the strongest linkage disequilibrium values. Four of the 11 unique haplotypes identified in the HLA-homozygous cord blood units were the top-ranking haplotypes identified and were present in 18% of the cohort. This is the first study to report on HLA allele and haplotype frequencies for umbilical cord blood units from the Barcelona Cord Blood Bank and the largest study to date involving two fields of HLA resolution typing of Spanish registry data.

Phase I study of graft-versus-host disease prophylaxis including bortezomib for allogeneic hematopoietic cell transplantation from unrelated donors with one or two HLA loci mismatches in Japanese patients

This phase I study was designed for graft-versus-host disease (GVHD) prophylaxis including bortezomib in allogeneic hematopoietic cell transplantation (allo-HCT) from human leukocyte antigen (HLA)-mismatched unrelated donors in Japanese patients. Patients were administered bortezomib on days 1, 4, and 7, with short-term methotrexate and tacrolimus. Three bortezomib dose levels were prepared (1.0, 1.3, and 1.5 mg/m²). A dose of 1.3 mg/m² was planned for administration to the initial six patients, and was adjusted if dose-limiting toxicity developed. Five of six patients enrolled for the initial dose had bone marrow donors. Two cases had single-antigen and single-allele mismatches; four had single-antigen mismatch at the A, B, C, and/or DRB1 loci in the GVH direction. All patients achieved neutrophil engraftment and complete donor chimerism. Three patients developed grade II acute GVHD, and none developed grade III-IV GVHD or any dose-limiting toxicity attributable to bortezomib by day 100. Two patients developed late-onset acute GVHD, and two developed chronic GVHD, but all cases were manageable. All patients were alive without relapse after a median follow-up period of 52 months. The optimal dose of bortezomib was determined to be 1.3 mg/m². Prophylaxis against GVHD using a regimen including bortezomib thus seems feasible for HLA-mismatched unrelated allo-HCT.

HLA Matching in Unrelated Stem Cell Transplantation up to Date

Unrelated hematopoietic stem cell transplantation (HSCT) has evolved from an experimental protocol to a potentially curative first-line treatment in certain disease instances. Factors enabling this transformation were the optimization of treatment protocols and supportive care as well as the availability of a large number of donors worldwide along with the higher quality and reliability of HLA typing. The main criterion for donor selection is HLA compatibility. In this review we discuss the current clinical evidence of HLA matching in unrelated HSCT. In this context, we address methodical aspects of transplantation immunobiology research and discuss the impact of locus and resolution of HLA differences. Furthermore, we address special constellations such as unidirectional mismatches or the presence of nonexpressed alleles as well as HLA alloimmunization and describe the perspective for HLA typing and matching strategies in the future, given the implementation of novel complete or near-complete gene typing approaches using next-generation sequencing short read technology, which are now entering the standard of clinical care.

Extended HLA Haplotypes and Their Impact on DPB1 Matching of Unrelated Hematologic Stem Cell Transplant Donors

Although HLA-DPB1 has long been considered of lesser importance in the selection of an unrelated donor (URD) hematologic stem cell transplantation, currently in many instances the DPB1 type of the donor is relevant or even critical. At present, however, only a minority of registry donors are DPB1 typed. It is also unclear to what extent the DPB1 alleles are linked to the 5-locus HLA-A-, B-, C-, DRB1, -DQB1 haplotypes. We sought to study whether there is such a linkage by using donors in the Finnish Stem Cell Registry as the study population. The 6-locus HLA-A, -B, -C, -DRB1, -DQB1, -DPB1 haplotype frequencies were estimated from a group of 43,365 Finnish registry donors using the German National Bone Marrow Registry algorithm. Five-locus haplotype (HLA-A, -B, -C, -DRB1, -DQB1) and HLA-DPB1 allele frequencies were calculated as marginal frequencies of the estimated 6-locus haplotype frequencies. The Finnish average frequency of individual DPB1 alleles was compared with their respective frequencies in association with individual 5-locus HLA haplotypes (haplotype-specific frequencies). Finally, the probability of DPB1 matching in 10/10 matched URD transplants was assessed. Haplotype-specific DPB1 frequencies differed significantly from the average DPB1 frequencies in 81 of 100 most frequent Finnish 5-locus HLA haplotypes, including some infrequent DPB1 alleles that were associated almost exclusively with certain individual 5-locus haplotypes. Five-locus haplotypes that are enriched in Finland but rare among other Europeans carried stronger DPB1 associations than haplotypes that are frequent European-wide. Finally, 10/10 matched transplants from domestic registry donors were significantly more likely to also be DPB1 matched than those from foreign donors. The results indicate an extension of linkage disequilibrium in the MHC complex in the Finnish population. With continuing upfront DPB1 typing of registry donors, it will be possible to perform similar extended 6-locus haplotype frequency estimations also in other registries. The associations are likely to be population specific but may be weaker in more heterogeneous populations. In the future the results might be used to predict the probability of DPB1 match or permissive/nonpermissive DPB1 mismatch for non-DPB1 typed donors in registry donor searches.

Selection of unrelated donors and cord blood units for hematopoietic cell transplantation: guidelines from the NMDP/CIBMTR

Allogeneic hematopoietic cell transplantation involves consideration of both donor and recipient characteristics to guide the selection of a suitable graft. Sufficient high-resolution donor-recipient HLA match is of primary importance in transplantation with adult unrelated donors, using conventional graft-versus-host disease prophylaxis. In cord blood transplantation, optimal unit selection requires consideration of unit quality, cell dose and HLA-match. In this summary, the National Marrow Donor Program (NMDP) and the Center for International Blood and Marrow Transplant Research, jointly with the NMDP Histocompatibility Advisory Group, provide evidence-based guidelines for optimal selection of unrelated donors and cord blood units.

High-resolution analysis of the HLA-A, -B, -C and -DRB1 alleles and national and regional haplotype frequencies based on 120 926 volunteers from the Italian Bone Marrow Donor Registry

HLA genes are highly polymorphic and structurally complex. They are located in the major histocompatibility complex (MHC) on chromosome 6, and the frequency of alleles and haplotypes varies widely among human populations. In this paper, we calculated the allele and haplotype frequencies using the HLA data of more than 120 000 Italian unrelated bone marrow donors enrolled in the national registry (IBMDR) and typed them with a high-resolution (HR) method for the HLA-A, -B, -C and -DRB1 alleles. The allele frequency data were obtained by manual counting; haplotype frequencies were calculated using the expectation maximisation (EM) algorithm. The total numbers of observed alleles were 226 for HLA-A, 343 for HLA-B, 201 for HLA-C and 210 for HLA-DRB1, which account for 5.4%, 6.7%, 5.2% and 8.5%, respectively, of each locus allele (IPD-IMGT/HLA Database Release 3.32, April 2018). The three most frequent Italian haplotypes were HLA-A*01:01~B*08:01~C*07:01~DRB1*03:01 (2.5%), A*02:01~B*18:01~C*07:01~DRB1*11:04 (1.1%) and A*30:01~B*13:02~C*06:02~DRB1*07:01 (1.1%). Moreover, for a relevant subset of the examined population (>100 000 individuals), the birthplace was available, and thus, we grouped the frequency data based on the corresponding Italian geographic areas, describing the HLA specificity of the Italian regional populations. The haplotype frequencies were also compared between national and regional data, and we observed remarkable differences in the regional haplotype frequencies, particularly in Sardinia. This study represents a valid tool to identify a more efficient haematopoietic stem cell unrelated donor recruitment and selection strategy, as well as for population genetic and HLA-disease association fields.

Allogeneic transplantation outcomes amongst a contemporary cohort of high-risk myelodysplastic syndrome and acute myeloid leukemia patients aged ≥70 years

Allogeneic hematopoietic stem cell transplantation (HSCT) is an integral therapy for patients with hematological malignancies, myelodysplasia, and bone marrow failure. Its use has been increasing over the past decade, as understanding of the treatment and its related toxicities has led to changes in patient selection, conditioning regimens, and post-transplant care. Older (age ≥65 years) patients are often considered unfit for transplantation; however, more recent data suggest that older patients, when selected appropriately, tolerate transplantation well. We report our institutional experience with HSCT in patients aged ≥70 years. A cohort of 22 patients underwent HSCT. Median overall survival was 5.16 years [95% confidence interval (CI): 1.5-8.7 years], and median post-transplant survival was 2.2 years (myelodysplastic syndrome: median 1.3 years, 95% CI: 4.7 months-2.2 years; acute myeloid leukemia: median not reached). Thirty-day mortality following HSCT was 9.5% (n = 2). These data provide further support for the use of HSCT in selected older patients, and highlight the impact of HSCT on overall survival among a patient cohort primarily of acute myeloid leukemia and myelodysplasia.

Survival signal REG3α prevents crypt apoptosis to control acute gastrointestinal graft-versus-host disease

Graft-versus-host disease (GVHD) in the gastrointestinal (GI) tract remains the major cause of morbidity and nonrelapse mortality after BM transplantation (BMT). The Paneth cell protein regenerating islet-derived 3α (REG3α) is a biomarker specific for GI GVHD. REG3α serum levels rose in the systematic circulation as GVHD progressively destroyed Paneth cells and reduced GI epithelial barrier function. Paradoxically, GVHD suppressed intestinal REG3γ (the mouse homolog of human REG3α), and the absence of REG3γ in BMT recipients intensified GVHD but did not change the composition of the microbiome. IL-22 administration restored REG3γ production and prevented apoptosis of both intestinal stem cells (ISCs) and Paneth cells, but this protection was completely abrogated in Reg3g-/- mice. In vitro, addition of REG3α reduced the apoptosis of colonic cell lines. Strategies that increase intestinal REG3α/γ to promote crypt regeneration may offer a novel, nonimmunosuppressive approach for GVHD and perhaps for other diseases involving the ISC niche, such as inflammatory bowel disease.

Relative Impact of HLA Matching and Non-HLA Donor Characteristics on Outcomes of Allogeneic Stem Cell Transplantation for Acute Myeloid Leukemia and Myelodysplastic Syndrome

Increasing donor-recipient HLA disparity is associated with negative outcomes of allogeneic hematopoietic stem cell transplantation (HSCT), but its comparative relevance amid non-HLA donor characteristics is not well established. We addressed this question in 3215 HSCTs performed between 2005 and 2013 in Germany for acute myeloid leukemia (AML) or myelodysplastic syndrome (MDS). Donors were HLA-matched related (MRD; n = 872) or unrelated (10/10 MUD, n = 1553) or HLA-mismatched unrelated (<10/10 MMUD, n = 790). Overall survival (OS) was similar after MRD compared with 10/10 MUD HSCT, reflecting opposing hazards of relapse (hazard ratio [HR], 1.32; P < .002) and nonrelapse mortality (HR, .63; P < .001). After UD HSCT, increasing HLA disparity was associated with inferior OS (HR, 1.21 [P < .02] and HR, 1.57 [P < .001] for 9/10 and ≤8/10 MMUD, respectively, compared with 10/10 MUD). Among non-HLA donor characteristics, age, sex mismatching (male recipient-female donor), and cytomegalovirus (CMV) mismatching (positive recipient-negative donor) impacted OS. Multivariate subgroup analysis showed that OS was similar after HSCT from the youngest 9/10 MMUD (<30 years) compared with the oldest 10/10 MUD (>40 years) (HR, 1.18; P = .25) and also in male patients transplanted from female 10/10 MUD compared with male 9/10 MMUD (HR, .89; P = .46). In contrast, OS of CMV-positive patients tended to be better with CMV-negative 10/10 MUDs compared with CMV-positive 9/10 MMUDs (HR, 1.31; P = .04). Because of low patient numbers in subgroups, definite conclusions and establishment of a hierarchy among HLA matching and non-HLA donor characteristics could not be made. Our data suggest that the impact of donor age and sex mismatch but not CMV mismatch on outcome of allogeneic HSCT may be comparable with that of single HLA disparity.

Recipient single nucleotide polymorphisms in Paneth cell antimicrobial peptide genes and acute graft-versus-host disease: analysis of BMT CTN-0201 and -0901 samples

Host genetics shape the gut microbiota, and gut dysbiosis increases the risk of acute graft-versus-host disease (aGVHD). Paneth cells and microbiota have interactions that contribute to immune regulation. α-defensin-5 (HD5) and regenerating islet-derived protein 3 alpha (Reg3A) are the most abundant Paneth cell antimicrobial peptides (AMPs). We hypothesized that single nucleotide polymorphisms (SNPs) in the genes for HD5 (DEFA5) and Reg3A (REG3A) predict aGVHD risk. We analysed pre-transplant recipient peripheral blood mononuclear cell samples from randomized Blood and Marrow Transplant Clinical Trials Network (BMT CTN) studies 0201 (94 patients with bone marrow and 93 with peripheral blood grafts) and 0901 (86 patients with myeloablative and 77 with reduced-intensity conditioning; all using peripheral blood grafts). In multivariable analysis (with a SNP × graft source interaction term in CTN-0201 and a SNP × conditioning intensity term in CTN-0901), DEFA5 rs4415345 and rs4610776 were associated with altered incidence of aGVHD grade II-IV [rs4415345 G vs. C: hazard ratio (HR) 0·58, 95% confidence interval (95% CI) 0·37-0·92, P = 0·02; rs4610776 T vs. A: HR 1·53, 95% CI 1·01-2·32, P = 0·05] in CTN-0201, but not CTN-0901, suggesting a stronger effect in bone marrow allografts. REG3A SNP was not associated with aGVHD. Host genetics may influence aGVHD risk by modulating Paneth cell function.

Variable selection with group structure in competing risks quantile regression

We study the group bridge and the adaptive group bridge penalties for competing risks quantile regression with group variables. While the group bridge consistently identifies nonzero group variables, the adaptive group bridge consistently selects variables not only at group level but also at within-group level. We allow the number of covariates to diverge as the sample size increases. The oracle property for both methods is also studied. The performance of the group bridge and the adaptive group bridge is compared in simulation and in a real data analysis. The simulation study shows that the adaptive group bridge selects nonzero within-group variables more consistently than the group bridge. A bone marrow transplant study is provided as an example.