Machteld Oudshoorn

Effect of T-cell-epitope matching at HLA-DPB1 in recipients of unrelated-donor haemopoietic-cell transplantation: a retrospective study

BACKGROUND The risks after unrelated-donor haemopoietic-cell transplantation with matched HLA-A, HLA-B, HLA-C, HLA-DRB1, HLA-DQB1 alleles between donor and recipient (10/10 matched) can be decreased by selection of unrelated donors who also match for HLA-DPB1; however, such donors are difficult to find. Classification of HLA-DPB1 mismatches based on T-cell-epitope groups could identify mismatches that might be tolerated (permissive) and those that would increase risks (non-permissive) after transplantation. We did a retrospective study to compare outcomes between permissive and non-permissive HLA-DPB1 mismatches in unrelated-donor haemopoietic-cell transplantation. METHODS HLA and clinical data for unrelated-donor [corrected] transplantations submitted to the International Histocompatibility Working Group in haemopoietic-cell transplantation were analysed retrospectively. HLA-DPB1 T-cell-epitope groups were assigned according to a functional algorithm based on alloreactive T-cell crossreactivity patterns. Recipients and unrelated donors matching status were classified as HLA-DPB1 match, non-permissive HLA-DPB1 mismatch (those with mismatched T-cell-epitope groups), or permissive HLA-DPB1 mismatch (those with matched T-cell-epitope groups). The clinical outcomes assessed were overall mortality, non-relapse mortality, relapse, and severe (grade 3-4) acute graft-versus-host disease (aGvHD). FINDINGS Of 8539 transplantations, 5428 (64%) were matched for ten of ten HLA alleles (HLA 10/10 matched) and 3111 (36%) for nine of ten alleles (HLA 9/10 matched). Of the group overall, 1719 (20%) were HLA-DPB1 matches, 2670 (31%) non-permissive HLA-DPB1 mismatches, and 4150 (49%) permissive HLA-DPB1 mismatches. In HLA 10/10-matched transplantations, non-permissive mismatches were associated with a significantly increased risk of overall mortality (hazard ratio [HR] 1·15, 95% CI 1·05-1·25; p=0·002), non-relapse mortality (1·28, 1·14-1·42; p<0·0001), and severe aGvHD (odds ratio [OR] 1·31, 95% CI 1·11-1·54; p=0·001), but not relapse (HR 0·89, 95% CI 0·77-1·02; p=0·10), compared with permissive mismatches. There were significant differences between permissive HLA-DPB1 mismatches and HLA-DPB1 matches in terms of non-relapse mortality (0·86, 0·75-0·98; p=0·03) and relapse (1·34, 1·17-1·54; p<0·0001), but not for overall mortality (0·96, 0·87-1·06; p=0·40) or aGvHD (OR 0·84, 95% CI 0·69-1·03; p=0·09). In the HLA 9/10 matched population, non-permissive HLA-DPB1 mismatches also increased the risk of overall mortality (HR 1·10, 95% CI 1·00-1·22; p=0·06), non-relapse mortality (1·19, 1·05-1·36; p=0·007), and severe aGvHD (OR 1·37, 95% CI 1·13-1·66; p=0·002) compared with permissive mismatches, but the risk of relapse was the same in both groups (HR 0·93, 95% CI 0·78-1·11; p=0·44). Outcomes for HLA 10/10-matched transplantations with non-permissive HLA-DPB1 mismatches did not differ substantially from those for HLA 9/10-matched transplantations with permissive HLA-DPB1 mismatches or HLA-DPB1 matches. INTERPRETATION T-cell-epitope matching defines permissive and non-permissive HLA-DPB1 mismatches. Avoidance of an unrelated donor with a non-permissive T-cell-epitope mismatch at HLA-DPB1 might provide a practical clinical strategy for lowering the risks of mortality after unrelated-donor haemopoietic-cell transplantation. FUNDING National Institutes of Health; Associazione Italiana per la Ricerca sul Cancro; Telethon Foundation; Italian Ministry of Health; Cariplo Foundation; National Cancer Institute; National Heart, Lung and Blood Institute; National Institute of Allergy and Infectious Diseases; Office of Naval Research; IRGHET Paris; Swedish Cancer Society; Childrens Cancer Foundation; Swedish Research Council; Cancer Society in Stockholm; Karolinska Institutet; and Leukemia and Lymphoma Society.

One million haemopoietic stem-cell transplants: a retrospective observational study

BACKGROUND The transplantation of cells, tissues, and organs has been recognised by WHO as an important medical task for its member states; however, information about how to best organise transplantation is scarce. We aimed to document the activity worldwide from the beginning of transplantation and search for region adapted indications and associations between transplant rates and macroeconomics. METHODS Between Jan 1, 2006, and Dec 31, 2014, the Worldwide Network for Blood and Marrow Transplantation collected data for the evolution of haemopoietic stem-cell transplantation (HSCT) activity and volunteer donors in the 194 WHO member states. FINDINGS 953,651 HSCTs (553,350 [58%] autologous and 400,301 [42%] allogeneic) were reported by 1516 transplant centres from 75 countries. No transplants were done in countries with fewer than 300,000 inhabitants, a surface area less than 700 km(2), and a gross national income per person of US

Nonpermissive HLA-DPB1 mismatch increases mortality after myeloablative unrelated allogeneic hematopoietic cell transplantation

1260 or lower. Use of HSCT increased from the first transplant in 1957 to almost 10,000 by 1985. We recorded a cumulative total of about 100,000 transplants by 1995, and an estimated 1 million by December, 2012. Unrelated donor registries contributed 22·3 million typed volunteer donors and 645,646 cord blood products by 2012. Numbers of allogeneic HSCTs increased in the past 35 years with no signs of saturation (R(2)=0·989). Transplant rates were higher in countries with more resources, more transplant teams, and an unrelated donor infrastructure. INTERPRETATION Our findings show achievements and high unmet needs and give guidance for decisions; to grant access for patients, to provide a donor infrastructure, and to limit overuse by defining risk and region adapted indications for HSCT as an efficient and cost-effective approach for life-threatening, potentially curable diseases. FUNDING Funding for this study was indirectly provided by support of the WBMT.

HLA GENE AND HAPLOTYPE FREQUENCIES IN BONE MARROW DONORS WORLDWIDE REGISTRIES

We examined current outcomes of unrelated donor allogeneic hematopoietic cell transplantation (HCT) to determine the clinical implications of donor-recipient HLA matching. Adult and pediatric patients who had first undergone myeloablative-unrelated bone marrow or peripheral blood HCT for acute myelogenous leukemia, acute lymphoblastic leukemia, chronic myelogenous leukemia, and myelodysplastic syndrome between 1999 and 2011 were included. All had high-resolution typing for HLA-A, -B, -C, and -DRB1. Of the total (n = 8003), cases were 8/8 (n = 5449), 7/8 (n = 2071), or 6/8 (n = 483) matched. HLA mismatch (6-7/8) conferred significantly increased risk for grades II to IV and III to IV acute graft vs host disease (GVHD), chronic GVHD, transplant-related mortality (TRM), and overall mortality compared with HLA-matched cases (8/8). Type (allele/antigen) and locus (HLA-A, -B, -C, and -DRB1) of mismatch were not associated with overall mortality. Among 8/8 matched cases, HLA-DPB1 and -DQB1 mismatch resulted in increased acute GVHD, and HLA-DPB1 mismatch had decreased relapse. Nonpermissive HLA-DPB1 allele mismatch was associated with higher TRM compared with permissive HLA-DPB1 mismatch or HLA-DPB1 match and increased overall mortality compared with permissive HLA-DPB1 mismatch in 8/8 (and 10/10) matched cases. Full matching at HLA-A, -B, -C, and -DRB1 is required for optimal unrelated donor HCT survival, and avoidance of nonpermissive HLA-DPB1 mismatches in otherwise HLA-matched pairs is indicated.

Multiple mismatches at the low expression HLA loci DP, DQ, and DRB3/4/5 associate with adverse outcomes in hematopoietic stem cell transplantation.

To calculate reliable HLA gene and haplotype frequencies of bone marrow donors in various regions in the world, we have analyzed the HLA-A, -B, and -DR phenotype frequencies of 18 bone marrow donor registries with a total of more than 300,000 HLA-A, -B-typed donors. These registries were included in the 22nd edition of Bone Marrow Donors Worldwide. Maximum likelihood gene frequencies, Hardy-Weinberg equilibrium fit, and 2- and 3-locus haplotype frequencies were calculated as well as deltas, relative deltas, and their significance. Remarkable gene and haplotype frequency differences exist between the registries. The genetic distances between the different registries were used to draw phylogenetic trees that clearly show that the degree of similarity between registries is related to their geographic locations. The resulting frequencies can be used for the estimation of the probability of finding a hyplotypically identical related or unrelated bone marrow donor for an individual patient. Phylogenetic trees are useful representations of the similarity between donor pools and can also aid in the selection of donors.

Outcomes of pediatric bone marrow transplantation for leukemia and myelodysplasia using matched sibling, mismatched related, or matched unrelated donors

A single mismatch in highly expressed HLA-A, -B, -C, and -DRB1 loci (HEL) is associated with worse outcomes in hematopoietic stem cell transplantation, while less is known about the cumulative impact of mismatches in the lesser expressed HLA loci DRB3/4/5, DQ, and DP (LEL). We studied whether accumulation of LEL mismatches is associated with deleterious effects in 3853 unrelated donor transplants stratified according to number of matches in the HEL. In the 8/8 matched HEL group, LEL mismatches were not associated with any adverse outcome. Mismatches at HLA-DRB1 were associated with occurrence of multiple LEL mismatches. In the 7/8 HEL group, patients with 3 or more LEL mismatches scored in the graft-versus-host vector had a significantly higher risk of mortality (1.45 and 1.43) and transplant-related mortality (1.68 and 1.54) than the subgroups with 0 or 1 LEL mismatches. No single LEL locus had a more pronounced effect on clinical outcome. Three or more LEL mismatches are associated with lower survival after 7/8 HEL matched transplantation. Prospective evaluation of matching for HLA-DRB3/4/5, -DQ, and -DP loci is warranted to reduce posttransplant risks in donor-recipient pairs matched for 7/8 HEL.

How to improve the search for an unrelated haematopoietic stem cell donor. Faster is better than more

Although some trials have allowed matched or single human leukocyte antigen (HLA)-mismatched related donors (mmRDs) along with HLA-matched sibling donors (MSDs) for pediatric bone marrow transplantation in early-stage hematologic malignancies, whether mmRD grafts lead to similar outcomes is not known. We compared patients < 18 years old reported to the Center for International Blood and Marrow Transplant Research with acute myeloid leukemia, acute lymphoblastic leukemia, chronic myeloid leukemia, and myelodysplastic syndrome undergoing allogeneic T-replete, myeloablative bone marrow transplantation between 1993 and 2006. In total, patients receiving bone marrow from 1208 MSDs, 266 8/8 allelic-matched unrelated donors (URDs), and 151 0-1 HLA-antigen mmRDs were studied. Multivariate analysis showed that recipients of MSD transplants had less transplantation-related mortality, acute graft-versus-host disease (GVHD), and chronic GVHD, along with better disease-free and overall survival than the URD and mmRD groups. No differences were observed in transplant-related mortality, acute and chronic GVHD, relapse, disease-free survival, or overall survival between the mmRD and URD groups. These data show that mmRD and 8/8 URD outcomes are similar, whereas MSD outcomes are superior to the other 2 sources. Whether allele level typing could identify mmRD recipients with better outcomes will not be known unless centers alter practice and type mmRD at the allele level.

Phenotype Frequencies of Autosomal Minor Histocompatibility Antigens Display Significant Differences among Populations

Summary:Many patients do not reach haematopoietic stem cell transplantation. Shortage of unrelated donors (UDs) is still seen as the main cause. However, with a worldwide UD pool containing more than 8 million donors, it is possible that other impediments are becoming more important. We analysed 549 UD searches for Dutch patients, performed between 1987 and 2000, in order to find the reasons for failure or success to reach transplantation. Between 1996 and 2000, 59% of the patients of Northwest European origin received a graft from an UD with a median time span of 4.4 months from the start of the search. In all, 11% of the patients lacked a compatible donor, while 30% became medically unfit for transplantation. This is in contrast to the patients of non-Northwest European origin for whom UD shortage is still the most important impediment; only 32% were transplanted while 50% lacked a compatible donor. We conclude that the shortage of donors is no longer the biggest constraint in unrelated stem cell transplantation for patients of Northwest European origin. It may be more effective to optimize the chance on transplantation by making the search process more efficient.

Problems and possible solutions in finding an unrelated bone marrow donor. Results of consecutive searches for 240 Dutch patients.

Minor histocompatibility (H) antigens are allogeneic target molecules having significant roles in alloimmune responses after human leukocyte antigen–matched solid organ and stem cell transplantation (SCT). Minor H antigens are instrumental in the processes of transplant rejection, graft-versus-host disease, and in the curative graft-versus-tumor effect of SCT. The latter characteristic enabled the current application of selected minor H antigens in clinical immunotherapeutic SCT protocols. No information exists on the global phenotypic distribution of the currently identified minor H antigens. Therefore, an estimation of their overall impact in human leukocyte antigen–matched solid organ and SCT in the major ethnic populations is still lacking. For the first time, a worldwide phenotype frequency analysis of ten autosomal minor H antigens was executed by 31 laboratories and comprised 2,685 randomly selected individuals from six major ethnic populations. Significant differences in minor H antigen frequencies were observed between the ethnic populations, some of which appeared to be geographically correlated.

Evaluation of HLA matching in unrelated hematopoietic stem cell transplantation for nonmalignant disorders

To evaluate the efficiency of our protocol for finding an HLA matched unrelated bone marrow donor, search results obtained between 1990 and 1995 for 240 Dutch patients were analyzed. The percentage of patients for whom, according to information given by the registries, a fully split-HLA antigen matched donor is available, increased from 24% in 1990 to over 70% in 1995. As a result the percentage of patients transplanted rose from about 24% in 1990–1991 to 44% in 1994–1995. The median time between the start of the search and transplantation was about 6 months. The systematic use of Bone Marrow Donors Worldwide (BMDW) which comprises the HLA groups of all volunteer bone marrow donors in Europe, Israel, South Africa, North America, Canada, India, Australia and New Zealand has been essential in this context. While searching for a suitable donor several problems were encountered such as unavailability of donors (12%) and discordant typing results (8%; range <1% to >25%). Thus it is advisable to select several donors for a patient. For 86% of patients with at least one HLA identical donor on the serological level for HLA-A,-B,-DR,-DQ, an HLA-DRB1/3/4/5, and -DQB1 identical donor could be identified. As expected, patients with two frequent haplotypes in strong linkage disequilibrium had the best chance of obtaining an HLA matched donor. Unexpectedly, patients with only one such haplotype had an almost similar chance. It could be calculated that HLA-DR typing of HLA-A,-B identical donors was rarely cost-effective after 1992. Only 12 of the 75 transplanted patients (16%) typeable at DNA level for class II, turned out to be completely matched for HLA-A,-B,-C,-DRB1/3/4/5,-DQB1,-DPB1 and had a negative MLC test. In the group of patients transplanted with a fully matched donor and for whom a CTLp test was performed, only 7% (4/54) of the tests were negative. Search results for patients of non-European origin were dismal, with only four of 26 patients referred being transplanted. In summary, of the 240 patients for whom the Europdonor office searched for a donor, about one-third were transplanted, one-third had a potential donor but did not reach transplantation, while for the remaining one-third of patients no suitable donor could be found.