DPB1 Mismatches Research Articles

Non-coding mismatches in HLA Class I genes in the presence of DPB1 mismatches predict worse outcomes in hematopoietic cell transplantation

Non-coding mismatches in HLA Class I genes in the presence of DPB1 mismatches predict worse outcomes in hematopoietic cell transplantation

Donor selection in allogeneic stem cell transplantation.

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. 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. 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.

HLA-DPB1 and DPA1 ~ DPB1 linkage mismatch affects the survival of recipients receiving HLA-14/14 matched unrelated donor HSCT.

To analyse the effect of HLA-DPA1 and HLA-DPB1 allelic mismatches on the outcomes of unrelated donor haematopoietic stem cell transplantation (URD-HSCT), we collected 258 recipients with haematological disease who underwent HLA-10/10 matched URD-HSCT. HLA-A, -B, -C, -DRB1, -DQB1, -DRB3/4/5, -DQA1, -DPA1 and -DPB1 typing was performed for the donors and recipients using next-generation sequencing (NGS) technology. After excluding 8 cases with DQA1 or DRB3/4/5 mismatches, we included 250 cases with HLA-14/14 matching for further analysis. Our results showed that the proportion of matched DPA1 and DPB1 alleles was only 10.4% (26/250). The remaining 89.6% of donors and recipients demonstrated DPA1 or DPB1 mismatch. In the DPA1 matched and DPB1 mismatched group, accounting for 18.8% (47/250) of the cohort, DPB1*02:01/DPB1*03:01 allelic mismatches were associated with decreased 2-year OS and increased NRM. DPB1*02:02/DPB1*05:01 and DPB1*02:01/DPB1*05:01 mismatches showed no impact on outcomes. Moreover, the specific allelic mismatches observed were consistent with the DPB1 T-cell epitope (TCE) classification as permissive and non-permissive. We innovatively established an analysis method for DPA1 ~ DPB1 linkage mismatch for cases with both DPA1 and DPB1 mismatched, accounting for 70% (175/250) of the total. DPA1*02:02 ~ DPB1*05:01/DPA1*02:01 ~ DPB1*17:01 linkage mismatches were associated with lower 2-year OS, especially among AML/MDS recipients. DPA1*02:02 ~ DPB1*05:01/DPA1*01:03 ~ DPB1*02:01 linkage mismatches showed no impact on outcomes. In conclusion, applying the DPA1 ~ DPB1 linkage mismatch analysis approach can identify different types of mismatches affecting transplant outcomes and provide valuable insight for selecting optimal donors for AML/MDS and ALL recipients.

Experimental Data on PIRCHE and T-Cell Reactivity: HLA-DPB1-Derived Peptides Identified by PIRCHE-I Show Binding to HLA-A*02:01 in vitro and T-Cell Activation in vivo

Introduction: Human leukocyte antigen (HLA)-DPB1 mismatches during hematopoietic stem cell transplantation (HSCT) with an unrelated donor result in an increased risk for the development of graft-versus-host disease (GvHD). The number of CD8+ T-cell epitopes available for indirect allorecognition as predicted by the PIRCHE algorithm has been shown to be associated with GvHD development. As a proof of principle, PIRCHE-I predictions for HLA-DPB1 mismatches were validated in vitro and in vivo. Methods: PIRCHE-I analysis was performed to identify HLA-DPB1-derived peptides that could theoretically bind to HLA-A*02:01. PIRCHE-I predictions for HLA-DPB1 mismatches were validated in vitro by investigating binding affinities of HLA-DPB1-derived peptides to the HLA-A*02:01 in a competition-based binding assay. To investigate the capacity of HLA-DPB1-derived peptides to elicit a T-cell response in vivo, mice were immunized with these peptides. T-cell alloreactivity was subsequently evaluated using an interferon-gamma ELISpot assay. Results: The PIRCHE-I algorithm identified five HLA-DPB1-derived peptides (RMCRHNYEL, YIYNREEFV, YIYNREELV, YIYNREEYA, and YIYNRQEYA) to be presented by HLA-A*02:01. Binding of these peptides to HLA-A*02:01 was confirmed in a competition-based peptide binding assay, all showing an IC50 value of 21 μm or lower. The peptides elicited an interferon-gamma response in vivo. Conclusion: Our results indicate that the PIRCHE-I algorithm can identify potential immunogenic HLA-DPB1-derived peptides present in recipients of an HLA-DPB1-mismatched donor. These combined in vitro and in vivo observations strengthen the validity of the PIRCHE-I algorithm to identify HLA-DPB1 mismatch-related GvHD development upon HSCT.

Development of TCR-T cell therapy targeting mismatched HLA-DPB1 for relapsed leukemia after allogeneic transplantation.

Relapsed leukemia after allogeneic hematopoietic stem cell transplantation (allo-HSCT) remains a significant challenge, with the re-emergence of the primary disease being the most frequent cause of death. Human leukocyte antigen (HLA)-DPB1 mismatch occurs in approximately 70% of unrelated allo-HSCT cases, and targeting mismatched HLA-DPB1 is considered reasonable for treating relapsed leukemia following allo-HSCT if performed under proper conditions. In this study, we established several clones restricted to HLA-DPB1*02:01, -DPB1*04:02, and -DPB1*09:01 from three patients who underwent HLA-DPB1 mismatched allo-HSCT using donor-derived alloreactive T cells primed to mismatched HLA-DPB1 in the recipient's body after transplantation. A detailed analysis of the DPB1*09:01-restricted clone 2A9 showed reactivity against various leukemia cell lines and primary myeloid leukemia blasts, even with low HLA-DP expression. T cell receptor (TCR)-T cells derived from clone 2A9 retained the ability to trigger HLA-DPB1*09:01-restricted recognition and lysis of various leukemia cell lines in vitro. Our study demonstrated that the induction of mismatched HLA-DPB1 specific T cell clones from physiologically primed post-allo-HSCT alloreactive CD4+ T cells and the redirection of T cells with cloned TCR cDNA by gene transfer are feasible as techniques for future adoptive immunotherapy.

Prediction of Graft-Versus-Host Disease in Recipients of Single Mismatched Unrelated Hematopoietic Cell Transplantation Donor Using a Highly Multiplexed Proteomic Assay, MHC-Pepseq

Graft-versus-host disease (GVHD) remains a major cause of treatment failure after allogeneic hematopoietic cell transplantation (alloHCT). In HLA-mismatched donor setting, indirect presentation of allogeneic peptides from recipient's mismatched HLA class I or II proteins by donor or recipient antigen presenting cells can be an immunogenic driver of GVHD. However, the potential diversity of such antigens is large, and predicting them in a systematic manner has proven challenging. Using a novel, highly-multiplexed peptide-MHC binding assay (MHC-PepSeq) we sought to 1) identify allogeneic peptides derived from mismatched HLA protein that can be efficiently presented by HLA-DR, and 2) explore the possibility that the frequency of these HLA-DRB1 binding allopeptides may be predictive of clinical GVHD in HLA-DPB1 mismatched donor/recipient pairs.Using publicly-available population allele frequency data (allelefrequencies.net), we identified a set of class I and II sequences that cover >95% of alleles at each of 9 human HLA-loci (-A, -B, -C, -DRA1,-DRB1, -DQA1, -DQB1, -DPA1, -DPB1) in 3 major US populations (European Caucasian, African American, Mexican Chicano). When represented in the form of densely overlapping tiled 15-mer peptides, 7,744 unique 15mers were identified. We encoded these peptides into DNA oligonucleotides and used the PepSeq parallel synthesis protocol to generate a library of the corresponding DNA-barcoded peptides. The library was incubated with recombinantly-expressed full-length HLA proteins, washed, eluted, amplified, and sequenced to identify the various HLA-derived peptides that bind to the assayed HLA proteins (Figure 1). In the current study, DPB1-derived allopeptides in the setting of HLA-A, B, C, DRB1, and DQB1 (10/10) matched unrelated (MUD) HCT donors with a mismatch in DPB1 were investigated. The peptide library was assayed for binding to the DRB1*07:01 protein, selected since it was the common allele in this cohort.We identified 327 patients who were transplanted at our center and met these criteria. For each case, we used comprehensive in silico tiling to identify HLA-DPA and DPB-derived peptides present in the recipient but absent in the donor. This set was intersected with the peptides identified as binders to HLA-DRB1*07:01 in the 7,744-plex MHC-PepSeq assay, to arrive at a donor-recipient pair-specific set of ‘allopeptides’ Overall, we identified such allopeptide at the median of 0 (range: 0-8) across the 327 cases.Next, we examined an association between the number of allopeptides and acute GVHD in the cohort of 94 patients with positive HLA-DRB1*07:01. Median age at alloHCT was 60 years (range: 19-78), 53% males, 1.% bone marrow graft and only 7% female to male donors. Ablative (TBI) conditioning was delivered to 34%) pts. 83% received Tacrolimus/Sirolimus-based, and 9% received post-transplant cyclophosphamide-based GVHD prophylaxis. Patient/HCT characteristics are summarized in Table 1.In this cohort, 18% had no DPB1 mismatch, 54% had a single and 28% had double mismatches, with 21% pts carrying non-permissive DPB1 mismatches. Allopeptide score was 0 in 75% of pts. Non-permissive mismatch 9 (39%) vs. 11 (16%) were more likely to have allopeptide score ≥1 and similarly double mismatches 11 (48%) vs. 15 (21%) were more likely to have allopeptide score of ≥1. Among pts with ≥1 allopeptide score 14 (61%) had DPB1 matched or permissive mismatch.The cumulative incidence of grade 2-4 acute GVHD was 40.8% (range: 29-52) in pts with no allopeptides from DPB1 compared with 56% (range: 34-74) in those with ≥1 allopeptides (p=0.259) (Figure 2). The cumulative incidence of grade 3-4 acute GVHD and chronic GVHD were similar between allopeptide 0 vs. ≥1.Together, we show that the “MHC-PepSeq” assay can identify novel candidate HLA-derived allopeptides in 10/10 MUD HCTs. The number of such peptides are relatively low - with a majority having no allopeptide. In an exploratory analysis in a selected cohort of patients with HLA-DRB1*0701 in the setting of 10/10 MUD HCT, the number of allopeptides in our assay may be predictive of GVHD. The expanded analyses on other HLA-DRB1 restriction elements are underway. [Display omitted] DisclosuresAl Malki: CareDx: Consultancy; Hansa Biopharma: Consultancy; Neximmune: Consultancy; Jazz Pharmaceuticals, Inc.: Consultancy; Rigel Pharma: Consultancy. Ali: BMS: Speakers Bureau; Incyte: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; CTI BioPharma: Membership on an entity's Board of Directors or advisory committees. Forman: Mustang Bio: Consultancy, Current holder of individual stocks in a privately-held company; Lixte Biotechnology: Consultancy, Current holder of individual stocks in a privately-held company; Allogene: Consultancy.

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

AbstractHematopoietic 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.

Analysis of biological models to predict clinical outcomes based on HLA-DPB1 disparities in unrelated transplantation

AbstractHLA compatibility is a key factor for survival after unrelated hematopoietic stem cell transplantation (HSCT). HLA-A, -B, -C, -DRB1, and -DQB1 are usually matched between donor and recipient. By contrast, HLA-DPB1 mismatches are frequent, although it is feasible to optimize donor selection and DPB1 matching with prospective typing. Because classical DPB1 allele mismatches are often unavoidable, however, several biological models have been developed to predict the optimal DPB1 mismatch combination for less graft-versus-host disease (GVHD) and better overall survival. In 909 recipient/donor pairs, we analyzed the role of 3 biological models: T-cell epitopes (TCEs) based on the immunogenicity of DPB1, cell surface expression of DPB1 molecules based on a single-nucleotide polymorphism located in the 3′ untranslated region, and the Predicted Indirectly ReCognizable HLA Epitopes (PIRCHE) model based on the presentation of allogeneic peptides derived from mismatched HLA, compared with the classical allele mismatch. Matching for both DPB1 alleles remains the best option to prevent acute GVHD. In the situation of one DPB1 allele mismatch, the donor associated with the lowest acute GVHD risks is mismatched for an allele with a low expression profile in the recipient, followed by a permissive TCE3/4 mismatch and/or the absence of PIRCHE II potential against the recipient. In the context of 2 DPB1 mismatches, the same considerations apply for a permissive TCE3/4 mismatch and no PIRCHE II. By combining the biological models, the most favorable DPB1 constellation can be defined. This approach will help optimize donor selection and improve post-HSCT complications and patient prognosis.

Clinical Impact of Cytokine Release Syndrome on Outcomes of Peripheral Blood Stem Cell Haploidentical Hematopoietic Cell Transplantation with Post-Transplant Cyclophosphamide

Peripheral blood stem cell (PBSC) as a graft source compared to bone marrow has been reported to result in lower risk of relapse after haploidentical hematopoietic cell transplantation (haplo-HCT) with use of post-transplant cyclophosphamide (PTCy) as a graft-versus-host-disease (GvHD) prophylaxis. However, cytokine release syndrome (CRS) is a common complication of this platform that can affect the outcomes of patients after PBSC haplo-HCT. CRS occurs due to rapid activation and proliferation of alloreactive donor T cells resulting in the elevated secretion of inflammatory cytokines. In this study, we sought to examine the risk factors for CRS and the effect of CRS severity on outcomes of PBSC haplo-HCT. We identified total of 271 consecutive patients with hematological malignancies who received their first PBSC haplo-HCT with PTCy-based GVHD prophylaxis at City of Hope (n=157) or Moffitt (n=114) Cancer Centers between 2014 and 2019. The median patient age at HCT was 54 years (INQ range, 37-64) for the entire cohort and 48% of the patients had HCT-CI ³3. Close to 70% of the study cohort had acute leukemia and 33% of all patients had high/very high-risk disease risk index. Myeloablative conditioning was used in 52% of the cases and 81% of all HCT recipients were CMV seropositive. The median donor age at HCT was 33 years (INQ range, 26-43). The HLA -A, -B, -C, -DRB1, -DQB1, or -DPB1 mismatch between the recipient and the donor in the GVH direction was 5/10 in 51%, 4/10 in 29% and £3/10 in 20% of cases. Offspring donors were used in 54% of the patients, sibling donors in 35%, and parent/other relative donors in 11%. Female donors to male recipients were used in only 22% of patients. The median infused CD34 dose was 5.25 x106 cells/kg (range, 2.3-22.4x106) and the CD3 dose was 2.48x108 cells/kg (range, 0.002-8.88 x108). CRS of any grade by ASTCT criteria was observed in 92% of study patients within first 7 days of HCT: 54% had grade 1, 39% grade 2, and 5.2% grade 3-4. Infused cell doses of CD34 >5x106 cells/kg and of CD3 >2.5x108 cells/kg had no significant effect on grade 3-4 CRS. On multivariable analysis, the use of reduced-intensity conditioning (RIC) was associated with increased grade 2-4 CRS (HR = 1.6, 95% CI: 1.11.-2.33, p=0.01) and grade 3-4 CRS (HR = 14.7, 95% CI: 1.97-109.5, p=0.009) compared with the myeloablative conditioning. Donor 5/10 HLA-mismatch was also associated with increased grade 2-4 CRS (HR = 1.5, 95% CI: 1.05-2.18; p=0.03) and grade 3-4 CRS (HR = 3.50, 95% CI: 1.00-12.32; p=0.05) compared with £4/10 HLA-mismatch. Non-relapse mortality (NRM) at day 100, and 1-year overall survival (OS) by CRS severity is shown in Figure. Comparing with the grade 0-1 CRS in multivariable analysis (Table), increase in CRS severity was associated with lower probability of neutrophil engraftment (HR = 0.9 for grade 2 and HR = 0.4 for grade 3-4; p=0.03). Increased CRS severity as compared to the grade 0-1 was also predictive of higher risks of NRM (HR = 1.6, 95% CI: 0.95-2.79 for grade 2 and HR = 6.6, 95% CI: 3.12-13.78 for grade 3-4; p<0.001), lower disease-free survival (DFS; HR = 1.3 for grade 2 and HR = 4.5 for grade 3-4; p<0.001) and lower OS (HR = 1.2 for grade 2 and HR = 4.1 for grade 3-4; p<0.001) after HCT. We observed no association between CRS severity and risk of relapse or the incidence and severity of acute GvHD after transplant. We conclude that CRS is a common complication after PB haplo-HCT/PTCy. CRS severity is associated with post-HCT outcomes with grade 3-4 CRS associated with the highest risk of NRM and overall mortality after HCT. Infused CD34 or CD3 cell doses effect on CRS is unclear. RIC and higher degree of HLA-mismatch are predictive of higher-grade CRS. Identification of modifiable risk factors can help to mitigate the risk for serious CRS and subsequent mortality after PB haplo-HCT/PTCy. Figure 1 Disclosures Nishihori: Karyopharm: Other: Research support to institution; Novartis: Other: Research support to institution. Pidala:CTI Biopharma: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Amgen: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Novartis: Research Funding; Takeda: Research Funding; Janssen: Research Funding; Johnson and Johnson: Research Funding; Pharmacyclics: Research Funding; Abbvie: Research Funding; BMS: Research Funding; Syndax: Consultancy, Membership on an entity's Board of Directors or advisory committees. Nakamura:Merck: Other: advisory board meeting; Alexion: Other: Support on a meeting presentation; Kyowa-Kirin: Other: Support on a meeting presentation; Celgene: Other: Support on seminar; Magenta Therapeutics: Other: Advisory board meeting; Viracor: Consultancy; Kadmon Corporation: Other: Advisory board meeting; NapaJen Pharma: Consultancy. Al Malki:Rigel Pharma: Consultancy; Jazz Pharmacuticals, Inc: Consultancy; Neximmune: Consultancy. Bejanyan:Kiadis Pharma: Membership on an entity's Board of Directors or advisory committees.

Assessment by Extended-Coverage Next-Generation Sequencing Typing of DPA1 and DPB1 Mismatches in Siblings Matching at HLA-A, -B, -C, -DRB1, and -DQ Loci.

Allogeneic hematopoietic stem cell transplant from an HLA matched sibling donor is usually the preferable choice. The use of next-generation sequencing (NGS) for HLA typing in clinical practice provides broader coverage and higher resolution of HLA genes. We evaluated the frequency of DPB1 crossing-over events among patients and potential related donors typed with NGS. From July 2016 to January 2018, 593 patients and 2385 siblings were typed. We evaluated sibling matching status in 546 patients, and 44.8% of these patients had siblings that matched at HLA-A, -B, -C, -DRB1, and -DQB1 loci. In 306 patient-HLA matched sibling pairs, we found 6 pairs (1.96%) with 1 DPB1 mismatch, and 5 of these pairs included an additional mismatch in DPA1. No additional mismatches were observed at the low expression loci. Using the T cell epitope algorithm, 4 of these DP mismatches were classified as permissive, 1 as nonpermissive in the host-versus-graft direction, and 1 as nonpermissive in the graft-versus-host direction. The frequency of DPB1 and DPA1 mismatches is low, and their impact in related donor transplants is not well established. Although DP typing in related transplants goes beyond guidelines, it is especially relevant for sensitized patients. NGS-based HLA typing provides full gene coverage, and its use in clinical practice can enable better donor selection.

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.

Impact of HLA-DPB1 Matching on Outcome of Unrelated Transplant for Hematologic Malignant Diseases: A Systematic Review and Meta-analysis

ObjectiveHuman leukocyte antigen match is the most important donor factor affecting transplant outcome. The HLA-DPB1 mismatch on the clinical outcome of hematopoietic stem cell transplant (HSCT) is less clear. This study is the first meta-analysis to investigate the impact of HLA-DPB1 loci mismatch on clinical outcome after unrelated donor HSCT for hematologic malignant disease. MethodsWe electronically searched the PubMed, EMBASE, Cochrane Central Register of Controlled Trials, and a related database (January 1995-December 2018) for all relevant articles. Comparative studies were carried out to investigate the impact of HLA-DPB1 loci mismatch on clinical outcome after unrelated donor HSCT, that is, the disease-free survival, engraftment, graft-vs-host disease, relapse, and transplant-related mortality (TRM). We performed a meta-analysis using Review Manager 5.3.5 software and adopted funnel plot regression to assess the publication bias. ResultsA total of 1570 articles were retrieved; 21 studies including 27,852 patients were assessed. Pooled comparisons of studies found that the HLA-DPB1–mismatched group had a lower rate of disease-free survival than the DPB1-matched group and lower overall survival in non–T cell–depleted transplant than the DPB1-matched group. The DPB1-mismatched group has higher incidence of acute graft-vs-host disease (aGVHD) and severe (≥ III degree) aGVHD, lower relapse rate, and higher TRM. Moreover, compared with 1-antigen mismatch, 2-antigen mismatch in DPB1 had a higher risk of TRM and a lower relapse rate, and the nonpermissive DPB1 mismatch had significantly higher rate of severe aGvHD and lower rate of disease relapse. ConclusionsThis analysis confirmed that HLA-DPB1 has important influence on survival and transplant-related complications during unrelated donor HSCT, and HLA-DPB1 donor selection strategies have been proposed based on personalized algorithm.

Outcomes of Unrelated Bone Marrow Transplantation in Patients with Thalassemia

Introduction. Bone marrow transplantation from an HLA-matched related or unrelated donor remains the only curative treatment for patients with thalassemia. Although one third of patients with thalassemia can find a matched unrelated donor (MUD) few patients were treated by MUD transplantation. Early experience with the use of MUD transplant in class 3 patients with thalassemia resulted in high rates of graft rejection and transplant-related mortality with thalassemia-free (TFS) survival of 53% (La Nasa G et al. Blood 2002). Significant improvements in MUD transplantation in recent years have prompted us to consider it also for high risk patients with thalassemia.Methods. All patient-donor pairs were typed at high resolution for HLA-A, -B, -C, -DRB1, -DQA1, -DQB1, and DPB1. Fourteen consecutive patients with a median age of 5 years (range, 2-17.2) received unrelated bone marrow transplantation for thalassemia. Four patients were in class 1, 2 were in class 2 and 8 were in class 3 of risk. All patients were treated with the conditioning regimen consisting of weight-based IV Bu, thiotepa (10 mg/kg/d), CY (200 mg/kg) and thymoglobulin (10 mg/kg) preceded by preconditioning with hydroxyurea (30 mg/kg/d), azathioprine (3 mg/kg/d) from D −45, and fludarabine (30 mg/m2/d) from D −16 through D −12. Patients received CSA, methylprednisolone and a short course of MTX as GVHD prophylaxis.Results. Between May 2009 and December 2017 un unrelated donor search was performed for 47 patients at our Institute. Forty one patients were Caucasian and 6 patients black African origin. Among Caucasians 16/41 (39%) found a 10/10 and 5/41 (12%) a 9/10 HLA allele-matched unrelated donor, while 1 of 6 black African patients (16.6%) found a 10/10 HLA-matched donor. Among 22 patients with a suitable donor (10/10 or 9/10 HLA allele-matched) 14 received transplantation, 2 patients withdrew consent, 1 patient's donor refused donation, and the remaining 5 patients are awaiting transplant.Twelve patients received 10/10 and 2 patients 9/10 HLA allele-matched grafts. Eight patients had permissive DPB1 mismatches while 2 patients had non-permissive mismatches in the HvG direction and 4 patients in the GvH direction. Median TNC/kg and CD34+/kg infused were 7.2x108 (range, 3.95-12.5) and 7.75x106 (range, 3.47-16.4), respectively. Sustained engraftment occurred in all patients. The median time to neutrophil and platelet recovery was 20 days (range, 15-27) and 19 days (range, 15-28), respectively. All but one patient showed 100% donor chimerism. The patient with stable mixed chimerism (48% donor DNA) has remained transfusion independent for over 3 years with hemoglobin levels >13.5-14 g/dL. Grade 2 and 3-4 acute GVHD occurred in 3 (21%) and 2 (14%) patients, respectively. Two patients developed mild (skin) or severe (skin, gut and liver) chronic GVHD. There was no association between non permissive DPB1 mismatches in the GvH direction and GVHD. All but one patient are alive and are off immunosuppressive therapy. One patient died due to chronic GVHD-related complications. The median follow-up among surviving patients was 2.8 years (range, 0.8-8.6). The 5-year OS and TFS probabilities were 90% (95% CI 47 to 99%) (Figure 1). Patients showed suboptimal CD4+ recovery within the first year: absolute (mean±SEM) cells/ul of CD4+ at 6 months was 223±48. At 12 and 24 months recovery of CD4+, CD8+, CD19+ and CD56+ were 597±122, 1077±228, 331±75, 229±64 and 812±284, 1067±405, 218±82, 112±22, respectively.One patient developed mild to moderate hepatic sinusoidal obstruction syndrome which resolved with supportive care. CMV reactivation occurred in 9 patients and none developed CMV disease. One patient developed adenovirus gastroenteritis. EBV reactivation occurred in 4 patients; one developed posttransplant lymphoproliferative disorder that was successfully treated with Rituximab. Bacterial infections were common: 5 (38%) patients developed gram negative or gram positive sepsis and 4 (29%) patients pneumonia. Probable invasive fungal infections occurred in 2 (14%) patients.Conclusions. This study showed that unrelated donor BMT can successfully cure a proportion of patients with thalassemia. Remarkably, despite 57% of patients were in class 3 of risk the 5-year OS and TFS rates were 90%. We conclude that class 3 patients with thalassemia who have a suitably matched unrelated donor should not be denied the option of transplantation. DisclosuresNo relevant conflicts of interest to declare.

P067A simple sequencing based method for identification of DPB1 resident SNP rs9277534 defining TH level of DPB1 expression

Aim Hematopoietic cell transplantation from unrelated donors carries the risk of acute graft-versus-host disease (GvHD). HLA-DPB1 matching has recently emerged as an important part of donor selection. HLA-DPB1 classification by T-cell epitope is currently used to identify permissive and non-permissive donor-recipient combinations. In addition, DPB1-linked SNP rs9277534 has been recently implicated in the severity of GvHD following transplantation with non-permissive DPB1 mismatching. Variant rs9277534A was associated in low expression, whereas rs9277534G was associated with high expression of DPB1. Recipients with the high expression variant who received transplant from DPB1-mismatched donors with low expression variant had high risk of GvHD. A simple and low-cost SNP rs9277534A/G test can assist optimal donor selection when multiple HLA suitable donors are available. Methods A simple Sanger sequencing-based method for identification of rs9277534 variants was developed. M13-tagged PCR primers were designed by applying NCBI Primer-BLAST tool to the fragment of DPB1 3’UTR containing the targeted SNP. Amplified fragments were sequenced with M13 sequencing primers. The targeted nucleotide position, n150 from the sequence start, can be visualized using any available sequencing analysis software and clearly shows the variant of SNP (“A”, “G” or “A/G”). Results Using the published list of A/G variants and a large set of samples with different combinations of DPB1 alleles, we defined a number of additional low- and high-expression DPB1 alleles. The published association of individual DPB1 alleles and rs9277534 variants was confirmed. Conclusions The extended list of low- and high-expression DPB1 alleles will provide a basis for assessing the suitability of DPB1-mismatched donors in the situation when a DPB1-matched donor is not available. The developed Sanger sequencing-based method for identification of rs9277534 variants can be used to identify the level of expression of DPB1 alleles previously not assessed.

In silico prediction of nonpermissive HLA-DPB1 mismatches in unrelated HCT by functional distance

AbstractIn silico prediction of high-risk donor–recipient HLA mismatches after unrelated donor (UD) hematopoietic cell transplantation (HCT) is an attractive, yet elusive, objective. Nonpermissive T-cell epitope (TCE) group mismatches were defined by alloreactive T-cell cross-reactivity for 52/80 HLA-DPB1 alleles (TCE-X). More recently, a numerical functional distance (FD) scoring system for in silico prediction of TCE groups based on the median impact of exon 2–encoded amino acid polymorphism on T-cell alloreactivity was developed for all DPB1 alleles (TCE-FD), including the 28/80 common alleles not assigned by TCE-X. We compared clinical outcome associations of nonpermissive DPB1 mismatches defined by TCE-X or TCE-FD in 8/8 HLA-matched UD-HCT for acute leukemia, myelodysplastic syndrome, and chronic myelogenous leukemia between 1999 and 2011 (N = 2730). Concordance between the 2 models was 92.3%, with most differences arising from DPB1*06:01 and DPB1*19:01 being differently assigned by TCE-X and TCE-FD. In both models, nonpermissive mismatches were associated with reduced overall survival (hazard ratio [HR], 1.15, P < .006 and HR, 1.12, P < .03), increased transplant-related mortality (HR, 1.31, P < .001 and HR, 1.26, P < .001) as well as acute (HR, 1.16, P < .02 and HR, 1.22, P < .001) and chronic (HR, 1.20, P < .003 and HR, 1.22, P < .001) graft-versus-host disease (GVHD). We show that in silico prediction of nonpermissive DPB1 mismatches significantly associated with major transplant outcomes is feasible for any DPB1 allele with known exon 2 sequence based on experimentally elaborated FD scores. This proof-of-principle observation opens new avenues for developing HLA risk-prediction models in HCT and has practical implications for UD searches.

Early Fever after Haploidentical Bone Marrow Transplantation Correlates with Class II HLA-Mismatching and Myeloablation but Not Outcomes

Noninfectious fevers are common early after T cell–replete HLA haploidentical (haplo) peripheral blood transplants and have been associated with cytokine release syndrome and overall mortality. However, less is known regarding the incidence and associations of early fever after bone marrow transplantation (BMT) with post-transplant cyclophosphamide (PTCy). We hypothesized that early fever would be associated with myeloablative conditioning (MAC), because of its relative increase in tissue damage augmenting antigen presentation and class II HLA-mismatching because of recognition of antigen-presenting cells by CD4+ T cells. In 672 recipients of MAC HLA-matched related donor (MRD) (n = 183), MAC HLA-matched unrelated donor (MUD) (n = 115), MAC haplo (n = 79), or nonmyeloablative (NMA) haplo (n = 295) T cell–replete BMT with PTCy, we retrospectively analyzed early noninfectious fever defined as temperature of ≥38.3°C once or ≥38.0°C twice or more on days 1 to 6. Fever occurred in 13% after MAC MRD, 23% after MAC MUD, 44% after NMA haplo, and 84% after MAC haplo BMT (P < .0001). Survival outcomes did not differ between patients with and without early fever. In NMA haplo BMT, mismatch in the graft-versus-host direction at HLA-DRB1 or -DPB1 (but not HLA-A, -B, -Cw, or -DQB1) was associated with early fever compared with no mismatches at these loci (P < .0001 and P = .02, respectively). In multivariable modeling, -DRB1 or -DPB1 mismatch and higher CD3+ graft cell dose were significantly associated with early fever. Early fever is more common after haplo compared with HLA-matched BMT. Fever is associated with myeloablation, -DRB1 or -DPB1 mismatching, and higher CD3+ graft cell dose but not survival.

Clinical outcomes of HLA-DPB1 mismatches in 10/10 HLA-matched unrelated donor-recipient pairs undergoing allogeneic stem cell transplant.

HLA-DPB1 matching may impact allogeneic hematopoietic stem cell transplantation (ASCT) outcomes; however, this locus is not in linkage disequilibrium with the remainder of the HLA genes. After classifying HLA-DPB1 mismatches based on T-cell epitope, avoiding non-permissive mismatches may impact survival. We tested this hypothesis at a single academic institution. Retrospective HLA-DPB1 genotyping was performed on 153 adult patients who underwent ASCT and unrelated donors matched for HLA-A, B, C, DRB1, and DQB1 loci (10/10). Using the ImMunoGeneTics/HLA T-cell epitope matching algorithm, mismatch status was classified as permissive or non-permissive. Of 153 donor-recipient pairs, 22 (14.4%) were HLA-DPB1 matches, 64 (42.8%) permissive mismatches, and 67 (43.8%) non-permissive mismatches. DPB1 mismatch increased risk of chronic graft-versus-host disease (cGVHD; RR 2.89 [1.19-9.53], P=.016) compared with DPB1-matched transplants, but there were no differences in overall mortality, risk of relapse, or acute GVHD (aGVHD). Combining matches and permissive mismatches and comparing to non-permissive mismatches, there was no significant difference in overall survival or relapse; however, patients receiving non-permissive mismatched transplants experienced greater risk of aGVHD overall and severe aGVHD (RR 1.66 [1.13-2.44], P=.010 and RR 1.97 [1.10-3.59], P=.024, respectively). In this single-center study, HLA-DPB1 matching influenced outcomes of patients undergoing ASCT for hematologic malignancy.

The Case for High Resolution Extended 6-Loci HLA Typing for Identifying Related Donors in the Indian Subcontinent

Three-loci low-resolution (LR) or intermediate-resolution HLA typing is generally considered adequate in the related blood and marrow transplantation (BMT) context. However, a single high-resolution (HR) mismatch may have a similar adverse impact on BMT outcome as an LR one. We sought to determine the frequency of mismatches that may go undetected when standard typing (LR or 3-loci HR) is used compared with 6-loci HR typing for related donor compatibility testing, and to assess its impact on relevant BMT outcomes. We analyzed data from a total of 2554 6-loci (HLA-A, -B, -C, -DRB1, -DQB1, and -DPB1) HR sequence-based typing (full typing [FT]) from 754 patients, 1011 siblings, and 789 parents done at DKMS Germany (www.DKMS.de) between January 1, 2014, and June 21, 2016. We also studied 38 cases in which the family had undergone 3-loci HLA typing (standard typing [ST]). Patients were from India (70%), Pakistan (22%), and Sri Lanka (8%). The IMGT/HLA database (www.ebi.ac.uk/ipd/imgt/hla) was used to tease out nonpermissive DPB1 mismatches. HLA disparity–related outcomes, such as rejection and graft-versus-host disease (GVHD) were assessed in a retrospective matched-pair cohort of 50 patients (25 with ST and 25 with FT) who underwent BMT for severe thalassemia from compatible related donors. We found fully matched (either 12/12 HR matches or with a single permissive DPB1 mismatch) related donors for 285 patients (38%). Of these donors, 89% were siblings and 11% were parents. The likelihood of matching on an individual locus on LR but not on HR was found to be 5%. A total of 9 donors (3%; 7 siblings and 2 parents) who would have been considered a full match by HR typing on A, B, and DRB1 alone were not a match by extended 6-loci HR typing. Five of these 9 donors had a mismatch on C or DQB1, and 4 had a nonpermissive DPB1 mismatch. In this group, 5 donors (56%) belonged to a consanguineous family, in 2 donors (22%) there was no reported consanguinity, and in 2 donors (22%) consanguinity was unknown. We identified 18 donors (6%; 13 siblings and 5 parents) who would have been considered a 12/12 match by LR HLA typing alone but were found not to match on extended HR typing. In this group, 11 donors (61%) were from consanguineous families, 3 donors (17%) had no reported consanguinity, and in 4 donors (22%) consanguinity was unknown. Outcome analysis showed that the actuarial proportion of patients with GVHD was 4% in the FT group compared with 16% in the ST group, with log-rank P = .1952. The ST group included 2 patients with grade III-IV acute GVHD and 1 patient each with moderate and severe chronic GVHD, whereas the FT group only 1 patient with grade III acute GVHD. We conclude that even in the context of related donors, the use of LR and/or 3-loci (A, B, and DRB1) HR HLA typing might result in a sizable risk of missing a clinically relevant mismatch, which may have an adverse impact on transplantation outcomes. In the Indian subcontinent, this observation is not limited to putatively compatible parents or consanguineous families; we recommend full 6-loci HR HLA typing even for matched related BMTs.

Association Between Multiple Mismatches at the HLA-DPB1 and DRB3/4/5 Genes and Adverse Outcomes in HLA-a, -B, -C, -DRB1 and -DQB1 Identical Hematopoietic Stem Cell Transplantation: A Study on Behalf of the Francophone Society of Stem Cell Transplantation and Cellular Therapy (SFGM-TC) and the Francophone Society for Histocompatibility and Immunogenetics (SFHI)

Background: Matching for all alleles of the HLA-A, -B, -C, and -DRB1 loci (8/8 match) is associated with the highest overall survival (OS) rates after unrelated donor (URD) hematopoietic stem cell transplantation (HSCT). In Europe, patients (pts) are also matched at the HLA-DQB1 loci (10/10 match) with no overall evidence of improved OS. HLA-DPB1 mismatching has been associated with a higher risk of acute graft-versus-host disease (aGvHD) and a decreased risk of relapse. A detrimental role of additional HLA-DQB1, HLA-DPB1 and HLA-DRB3/4/5 mismatches (MM) has been recently identified on OS but only in 7/8 HLA-A, -B, -C, and -DRB1 loci URDs HSCT. We investigated the impact of HLA-DPB1 and HLA-DRB3/4/5 MM on outcomes in a large cohort of 10/10 matched URD HSCTs.Patients and methods: 2,393 pts who received an initial HSCT from a 10/10 matched URD in 35 French centers were included between January 2000 and October 2012. Informed consent was obtained in accordance with the Declaration of Helsinki. High-resolution typing was performed for HLA-A, -B, -C, -DRB1, -DQB1, -DPB1 and -DRB3/4/5 loci for all donor/recipient pairs. Clinical data were obtained through ProMISe (Project Manager Internet Server), an internet-based system shared by all French transplantation centers. Impact of HLA-DRB3/4/5 and -DPB1 MM was quantitatively and qualitatively evaluated. For quantitative evaluation, patients were classified into 5 different groups according to their global matching level for the 7 considered loci (14/14, 13/14, 12/14, 11/14, 10/14). For qualitative evaluation, MM type and directionality (GvH and host versus graft (HvG) directions) were evaluated. HLA-DPB1 MM were classified as permissive or non-permissive (K Fleischhauer, Lancet Oncol. 2012). The primary composite endpoint for the analysis was GvHD-free and relapse-free survival (GRFS). We defined early GRFS as being alive at 3 months after HSCT with no previous grade III-IV aGvHD and no relapse and late GRFS as being alive >3 months with no previous grade III-IV aGvH, no relapse and no moderate or severe chronic GvHD (cGvHD). Late GRFS was evaluated at months 6, 12, 24 and 36 after HSCT. Acute GvHD, cGvHD, relapse and OS were also studied. Models were adjusted for HSCT period, disease risk, age, sex matching, stem cell source, and conditioning regimen.Results: Table 1showspopulation characteristics and distribution of cumulative MM. The median follow-up was 59 months. Compared to 14/14 pairs, quantitative evaluation showed a significantly lower early GRFS for pts who received a 10-11/14 (Hazard Ratio HR 2.0, 95% CI 1.4 to 2.9, p=0.0003) or a 12/14 URD HSCT (HR 1.4, 95% CI 1.1 to 1.8, p=0.01). This was related to a significantly increased risk of grade III-IV aGVHD associated with 10-11/14 (HR 2.3, 95% CI 1.5 to 3.7, p=0.0004) and 12/14 pairs (HR 1.7, 95% CI 1.2 to 2.4, p=0.003). 10-11/14 pairs were also associated with a higher risk of death at 3 months (HR 2, 95% CI 1.1 to 3.6, p=0.024). Qualitatively, in pts matched for HLA-DRB3/4/5 but MM for HLA-DPB1 (n=1846, 77.1%), 2 HLA-DPB1 MM and non-permissive HLA-DPB1 MM were associated with a lower early GRFS (HR 1.4, 95% CI 1.1 to 1.9, p=0.01 and HR 1.3, 95% CI 1.0 to 1.7, p=0.02 respectively) due to an increased risk of aGvHD (HR 1.7, 95% CI 1.2 to 2.5, p=0.002 and HR 1.50, 95% CI 1.08 to 2.08, p= 0.017 respectively). Outcomes were not influenced by either GvHD or HvG mismatch directions. Late GRFS analyses once adjusted were not significantly different according to MM numbers, type and directions. Only 19 pairs (0.8%) were DPB1 matched and DRB3/4/5 mismatched (high linkage disequilibrium between DRB3/4/5 and DRB1); HLA-DRB3/4/5 MM could thus not be qualitatively analyzed.Conclusion: MultipleHLA-DPB1 and HLA-DRB3/4/5 MM have an early impact after 10/10 matched URDs HSCT. The best outcomes are seen in 13 and 14/14 pairs. Early GRFS is significantly impacted by 10-11/14, 12/14, 2 DPB1 MM as well as non-permissive HLA-DPB1 MM URD HSCT which is related to an increased risk of grade III-IV aGvHD. There is a significantly increased risk of mortality for 10-11/14 pairs at 3 months. Prospective evaluation of matching for HLA-DPB1 and HLA-DRB3/4/5 is warranted to reduce early post-HSCT toxicity in donor-recipient 10/10 matched pairs. [Display omitted] DisclosuresMichallet:Bristol-Myers Squibb: Consultancy, Honoraria, Research Funding; Pfizer: Consultancy, Honoraria; Novartis: Consultancy, Honoraria; Pfizer: Consultancy, Honoraria; Astellas Pharma: Consultancy, Honoraria; MSD: Consultancy, Honoraria; Genzyme: Consultancy, Honoraria. Peffault De Latour:Pfizer: Consultancy, Honoraria, Research Funding; Alexion: Consultancy, Honoraria, Research Funding; Novartis: Consultancy, Honoraria, Research Funding; Amgen: Research Funding.

OR43 Frequency of HLA DPA1 and DPB1 mismatching in a population of 1199 pairs of presumed HLA identical sibling transplant pairs

Aim The ideal graft source for allogeneic hematopoietic stem cell transplantation (HCT) is an HLA-identical matched sibling (MSD). The Blood and Marrow Transplant Clinical Trials Network recommends that family donors be HLA-A and -B typed at intermediate or higher resolution and HLA-DRB1 typed at high resolution by DNA-based methods as a minimum requirement. Where possible, familial haplotypes should be assigned to establish presumptive high-resolution match identity between the donor and recipient (additionally HLA-C and DQB1 may be considered). Extended typing at additional HLA loci including DPB1 is not commonly performed. Results from unrelated donor HCT studies suggest that mismatches at HLA-DPB1 increase the risk of acute graft versus host disease. Due to the genetic distance from the other classical loci crossover events may lead to mismatching at DPB1 in the MSD setting and therefore may ultimately play a role in transplant outcomes. Methods A cohort of 1199 presumed MSD pairs, from 55 centers, collected by the CIBMTR Research Repository from 2007 to 2015 were analyzed. All pairs were reported to the CIBMTR as HLA identical siblings and received a transplant for either AML (44%), ALL (24%), MDS (26%) and 6% other diseases. The median patient age was 52, 59% were male, 86% received PBSC and 14% BM. To determine the crossover frequency the subjects were typed by targeted exon NGS of exons 2 and 3 for both Class I and Class II yielding G group or better results, at HLA-A, B, C, DRB1, DRB3/4/5, DQA1, DQB1, DPA1 and DPB1. Results The majority (97.25%) of MSD pairs were identical at all loci tested. A small subset (2.75%) of the pairs contained a mismatch impacting either DPA1, DPB1 or both. The majority of the 33 mismatches, 26 (78.79%) were DPB1, 6 (18.18%) included both DPA1 and DPB1 and 1 (3.03%) only DPA1. Analysis of the T-cell-epitope groups found that 28% of the DPB1 mismatches were not permissive. All were presumed crossover events, but family typing was not available to confirm. Six (18%) of the DPB1 mismatches included a homozygous recipient with a heterozygous donor suggesting a potential loss of heterozygosity. Conclusion The mismatch frequency at the DP loci in MSD pairs was relatively low at 2.75% and 28% were not TCE permissive. The impact of DP mismatching on MSD HCT outcomes are unclear and warrant further study.