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

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

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

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

HLA-B leader genotypes in a clinical population

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

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

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

Identification of the rs9277534 HLA-DP expression marker by next generation sequencing for the selection of unrelated donors for hematopoietic cell transplantation

Mismatching of an unrelated donor against a high-expression HLA-DPB1 recipient allele is associated with a high risk of graft-versus-host disease and mortality. The Seattle Cancer Care Alliance (SCCA) and Fred Hutchinson Cancer Research Center transplant program employs an algorithm to match for HLA-A, B, C, DRB1, DQB1 and DPB1 alleles (12/12) and to avoid, whenever possible, donor mismatching against a recipient high-expression HLA-DPB1 allele. HLA-DPB1 expression is associated with the rs9277534 A/G polymorphism located in the 3'UTR of the HLA-DPB1 gene. Next generation sequencing of HLA-DPB1 using the Illumina TruSight HLA V2 Sequencing Panel and Conexio Assign software analyses provides information on rs9277534 variants without the need for any additional SNP testing. Here we present the molecular location of rs9277534 in NGS data and discuss the challenges to resolve HLA-DPB1 ambiguities.

What do transplant physicians think about palliative care? A national survey study

BACKGROUND

Despite its established benefits, palliative care (PC) is rarely utilized for hematopoietic stem cell transplant (HSCT) patients. We sought to examine transplant physicians' perceptions of PC.

METHODS

We conducted a cross-sectional survey of transplant physicians recruited from the American-Society-for-Blood-and-Marrow-Transplantation. Using a 28-item questionnaire adapted from prior studies, we examined physicians' access to PC services, and perceptions of PC. We computed a composite score of physicians' attitudes about PC (mean = 16.9, SD = 3.37) and explored predictors of attitudes using a linear mixed model.

RESULTS

277/1005 (28%) of eligible physicians completed the questionnaire. The majority (76%) stated that they trust PC clinicians to care for their patients, but 40% felt that PC clinicians do not have enough understanding to counsel HSCT patients about their treatments. Most endorsed that when patients hear the term PC, they feel scared (82%) and anxious (76%). Nearly half (46%) reported that the service name 'palliative care' is a barrier to utilization. Female sex (β = 0.85, P = .024), having <10 years of clinical practice (β = 1.39, P = .004), and perceived quality of PC services (β = 0.60, P < .001) were all associated with a more positive attitude towards PC. Physicians with a higher sense of ownership over their patients' PC issues (β = -0.36, P < .001) were more likely to have a negative attitude towards PC.

CONCLUSIONS

The majority of transplant physicians trust PC, but have substantial concerns about PC clinicians' knowledge about HSCT and patients' perception of the term 'palliative care'. Interventions are needed to promote collaboration, improve perceptions, and enhance integration of PC for HSCT recipients.

Cord-Blood Transplantation in Patients with Minimal Residual Disease

BACKGROUND

The majority of patients in need of a hematopoietic-cell transplant do not have a matched related donor. Data are needed to inform the choice among various alternative donor-cell sources.

METHODS

In this retrospective analysis, we compared outcomes in 582 consecutive patients with acute leukemia or the myelodysplastic syndrome who received a first myeloablative hematopoietic-cell transplant from an unrelated cord-blood donor (140 patients), an HLA-matched unrelated donor (344), or an HLA-mismatched unrelated donor (98).

RESULTS

The relative risks of death and relapse between the cord-blood group and the two other unrelated-donor groups appeared to vary according to the presence of minimal residual disease status before transplantation. Among patients with minimal residual disease, the risk of death was higher in the HLA-mismatched group than in the cord-blood group (hazard ratio, 2.92; 95% confidence interval [CI], 1.52 to 5.63; P=0.001); the risk was also higher in the HLA-matched group than in the cord-blood group but not significantly so (hazard ratio, 1.69; 95% CI, 0.94 to 3.02; P=0.08). Among patients without minimal residual disease, the hazard ratios were lower (hazard ratio in the HLA-mismatched group, 1.36; 95% CI, 0.76 to 2.46; P=0.30; hazard ratio in the HLA-matched group, 0.78; 95% CI, 0.48 to 1.28; P=0.33). The risk of relapse among patients with minimal residual disease was significantly higher in the two unrelated-donor groups than in the cord-blood group (hazard ratio in the HLA-mismatched group, 3.01; 95% CI, 1.22 to 7.38; P=0.02; hazard ratio in the HLA-matched group, 2.92; 95% CI, 1.34 to 6.35; P=0.007). Among patients without minimal residual disease, the magnitude of these associations was lower (hazard ratio in the HLA-mismatched group, 1.28; 95% CI, 0.51 to 3.25; P=0.60; hazard ratio in the HLA-matched group, 1.30; 95% CI, 0.65 to 2.58; P=0.46).

CONCLUSIONS

Our data suggest that among patients with pretransplantation minimal residual disease, the probability of overall survival after receipt of a transplant from a cord-blood donor was at least as favorable as that after receipt of a transplant from an HLA-matched unrelated donor and was significantly higher than the probability after receipt of a transplant from an HLA-mismatched unrelated donor. Furthermore, the probability of relapse was lower in the cord-blood group than in either of the other groups.

Allogeneic Hematopoietic Cell Transplantation as Curative Therapy for Patients with Non-Hodgkin Lymphoma: Increasingly Successful Application to Older Patients

Non-Hodgkin lymphoma (NHL) constitutes a collection of lymphoproliferative disorders with widely varying biological, histological, and clinical features. For the B cell NHLs, great progress has been made due to the addition of monoclonal antibodies and, more recently, other novel agents including B cell receptor signaling inhibitors, immunomodulatory agents, and proteasome inhibitors. Autologous hematopoietic cell transplantation (auto-HCT) offers the promise of cure or prolonged remission in some NHL patients. For some patients, however, auto-HCT may never be a viable option, whereas in others, the disease may progress despite auto-HCT. In those settings, allogeneic HCT (allo-HCT) offers the potential for cure. Over the past 10 to 15 years, considerable progress has been made in the implementation of allo-HCT, such that this approach now is a highly effective therapy for patients up to (and even beyond) age 75 years. Recent advances in conventional lymphoma therapy, peritransplantation supportive care, patient selection, and donor selection (including the use of alternative hematopoietic cell donors), has allowed broader application of allo-HCT to patients with NHL. As a result, an ever-increasing number of NHL patients over age 60 to 65 years stand to benefit from allo-HCT. In this review, we present data in support of the use of allo-HCT for patients with diffuse large B cell lymphoma, follicular lymphoma, and mantle cell lymphoma. These histologies account for a large majority of allo-HCTs performed for patients over age 60 in the United States. Where possible, we highlight available data in older patients. This body of literature strongly supports the concept that allo-HCT should be offered to fit patients well beyond age 65 and, accordingly, that this treatment should be covered by their insurance carriers.

Indications and Results of HLA-Identical Sibling Hematopoietic Cell Transplantation for Sickle Cell Disease

Although a number of published trials exist of HLA-identical sibling hematopoietic cell transplantation (HCT) for sickle cell disease (SCD) that span 2 decades, when and for whom this therapy should be pursued is a subject of debate. Assessments of the risks of transplant-related complications that include infertility and debilitating graft-versus-host disease and long-term quality of life after successful HCT are difficult to perform without prospective trials in transplant and nontransplant cohorts. However, it is possible to assess the risk of mortality and to compare published rates of survival in individuals with SCD treated and not treated by HCT. In this brief review, projections about mortality risk based on recent published reports are reviewed and summarized. The published data show overall survival and event-free survival rates of 95% and 92%, respectively, in children treated by HLA-identical sibling HCT. The overall survival rates in the Center for International Blood and Marrow Transplant Research (N = 412) and European Blood and Marrow Transplant (N = 487) registries were 91% and 95%, respectively. These results provide broad support for the therapeutic value of HLA-identical sibling HCT for children with SCD and serve as the basis for a strong recommendation in favor of the option of HCT when a suitable donor is available. The experience of HLA-identical sibling HCT in adults with SCD is limited but appears to be similar to results in children. These preliminary observations, however, warrant further investigation.

MICA, a gene contributing strong susceptibility to ankylosing spondylitis

OBJECTIVE

The human major histocompatibility complex class I chain-related gene A (MICA) controls the immune process by balancing activities of  natural killer cells, γδ T cells and αβ CD8 T cells, and immunosuppressive CD4 T cells. MICA is located near HLA-B on chromosome 6. Recent genomewide association studies indicate that genes most strongly linked to ankylosing spondylitis (AS) susceptibility come from the region containing HLA-B and MICA. While HLA-B27 is a well-known risk genetic marker for AS, the potential effect of linkage disequilibrium (LD) shields any associations of genes around HLA-B with AS. The aim of this study was to investigate a novel independent genetic association of MICA to AS.

METHODS

We examined 1543 AS patients and 1539 controls from two ethnic populations by sequencing MICA and genotyping HLA-B alleles. Initially, 1070 AS patients and 1003 controls of European ancestry were used as a discovery cohort, followed by a confirmation cohort of 473 Han Chinese AS patients and 536 controls. We performed a stratified analysis based on HLA-B27 carrier status. We also conducted logistic regression with a formal interaction term.

RESULTS

Sequencing of MICA identified that MICA*007:01 is a significant risk allele for AS in both Caucasian and Han Chinese populations, and that MICA*019 is a major risk allele in Chinese AS patients. Conditional analysis of MICA alleles on HLA-B27 that unshielded LD effect confirmed associations of the MICA alleles with AS.

CONCLUSIONS

Parallel with HLA-B27, MICA confers strong susceptibility to AS in US white and Han Chinese populations.

HLA-C-dependent prevention of leukemia relapse by donor activating KIR2DS1

BACKGROUND

Of the cancers treated with allogeneic hematopoietic stem-cell transplantation (HSCT), acute myeloid leukemia (AML) is most sensitive to natural killer (NK)-cell reactivity. The activating killer-cell immunoglobulin-like receptor (KIR) 2DS1 has ligand specificity for HLA-C2 antigens and activates NK cells in an HLA-dependent manner. Donor-derived NK reactivity controlled by KIR2DS1 and HLA could have beneficial effects in patients with AML who undergo allogeneic HSCT.

METHODS

We assessed clinical data, HLA genotyping results, and donor cell lines or genomic DNA for 1277 patients with AML who had received hematopoietic stem-cell transplants from unrelated donors matched for HLA-A, B, C, DR, and DQ or with a single mismatch. We performed donor KIR genotyping and evaluated the clinical effect of donor KIR genotype and donor and recipient HLA genotypes.

RESULTS

Patients with AML who received allografts from donors who were positive for KIR2DS1 had a lower rate of relapse than those with allografts from donors who were negative for KIR2DS1 (26.5% vs. 32.5%; hazard ratio, 0.76; 95% confidence interval [CI], 0.61 to 0.96; P=0.02). Of allografts from donors with KIR2DS1, those from donors who were homozygous or heterozygous for HLA-C1 antigens could mediate this antileukemic effect, whereas those from donors who were homozygous for HLA-C2 did not provide any advantage (24.9% with homozygosity or heterozygosity for HLA-C1 vs. 37.3% with homozygosity for HLA-C2; hazard ratio, 0.46; 95% CI, 0.28 to 0.75; P=0.002). Recipients of KIR2DS1-positive allografts mismatched for a single HLA-C locus had a lower relapse rate than recipients of KIR2DS1-negative allografts with a mismatch at the same locus (17.1% vs. 35.6%; hazard ratio, 0.40; 95% CI, 0.20 to 0.78; P=0.007). KIR3DS1, in positive genetic linkage disequilibrium with KIR2DS1, had no effect on leukemia relapse but was associated with decreased mortality (60.1%, vs. 66.9% without KIR3DS1; hazard ratio, 0.83; 95% CI, 0.71 to 0.96; P=0.01).

CONCLUSIONS

Activating KIR genes from donors were associated with distinct outcomes of allogeneic HSCT for AML. Donor KIR2DS1 appeared to provide protection against relapse in an HLA-C-dependent manner, and donor KIR3DS1 was associated with reduced mortality. (Funded by the National Institutes of Health and others.).

From trees to the forest: genes to genomics

Crick, Watson, and colleagues revealed the genetic code in 1953, and since that time, remarkable progress has been made in understanding what makes each of us who we are. Identification of single genes important in disease, and the development of a mechanistic understanding of genetic elements that regulate gene function, have cast light on the pathophysiology of many heritable and acquired disorders. In 1990, the human genome project commenced, with the goal of sequencing the entire human genome, and a "first draft" was published with astonishing speed in 2001. The first draft, although an extraordinary achievement, reported essentially an imaginary haploid mix of alleles rather than a true diploid genome. In the years since 2001, technology has further improved, and efforts have been focused on filling in the gaps in the initial genome and starting the huge task of looking at normal variation in the human genome. This work is the beginning of understanding human genetics in the context of the structure of the genome as a complete entity, and as more than simply the sum of a series of genes. We present 3 studies in this review that apply genomic approaches to leukemia and to transplantation to improve and extend therapies.

The outcomes of family haploidentical hematopoietic stem cell transplantation in hematologic malignancies are not associated with patient age

Haploidentical hematopoietic cell transplantation (HCT) has been used to treat hematologic malignancies, but it is unknown whether the procedure is more effective in adults or children. To address this question, we analyzed patients aged 1 to 65 years old receiving myeloablative conditioning regimens followed by family 2 to 3 antigen HLA-mismatched HCT and reported to the Center for International Blood and Marrow Transplant Research (CIBMTR; n = 137) or performed in Dao-Pei Hospital in China, China (n = 181). The Dao-Pei cohort had more acute and chronic graft-versus-host disease (GVHD), less relapse, lower transplant-related mortality (TRM), and better leukemia-free survival (LFS) than the CIBMTR cohort. Overall survival (OS) and outcomes were similar between adults and children. In the CIBMTR cohort receiving ex vivo T cell depletion (TCD), adults had higher TRM (relative risk [RR] 2.71, 95% confidence interval [CI] 1.29-5.69, P = .008) and lower OS (RR 1.75, 95% CI 1.08-2.84, P = .023) than children. In the CIBMTR subset that did not receive ex vivo TCD, relapse was lower in adults compared to children (RR 0.24, 95% CI 0.07-0.80, P = .020), but TRM, LFS, and OS were similar. We conclude that outcomes in adults and children are similar overall, although children have better survival than adults if ex vivo TCD is used.

HLA-C antigen mismatch is associated with worse outcome in unrelated donor peripheral blood stem cell transplantation

The association between HLA matching and outcome in unrelated-donor peripheral blood stem cell (PBSC) transplantation has not yet been established. In the present study, a total of 1933 unrelated donor-recipient pairs who underwent PBSC transplantation between 1999 and 2006 for acute myelogenous leukemia, acute lymphoblastic leukemia, myelodysplastic syndrome, or chronic myelogenous leukemia and received high-resolution HLA typing for HLA-A, -B, -C, -DRB1, -DQA1, and -DQB1 were included in the analysis. Outcomes were compared between HLA-matched and HLA-mismatched pairs, adjusting for patient and transplant characteristics. Matching for HLA-A, -B, -C, and -DRB1 alleles (8/8 match) was associated with better survival at 1 year compared with 7/8 HLA-matched pairs (56% vs 47%). Using 8/8 HLA-matched patients as the baseline (n = 1243), HLA-C antigen mismatches (n = 189) were statistically significantly associated with lower leukemia-free survival (relative risk [RR], 1.36; 95% confidence interval [CI], 1.13-1.64; P = .0010), and increased risk for mortality (RR, 1.41; 95% CI, 1.16-1.70; P = .0005), treatment-related mortality (RR, 1.61; 95% CI, 1.25-2.08; P = .0002), and grade III-IV graft-versus-host disease (RR, 1.98; 95% CI, 1.50-2.62; P < .0001). HLA-B antigen or allele mismatching was associated with an increased risk for acute GVHD grade III-IV. No statistically significant differences in outcome were observed for HLA-C allele (n = 61), HLA-A antigen/allele (n = 136), HLA-DRB1 allele (n = 39), or HLA-DQ antigen/allele (n = 114) mismatches compared with 8/8 HLA-matched pairs. HLA mismatch was not associated with relapse or chronic GVHD. HLA-C antigen-mismatched unrelated PBSC donors were associated with worse outcomes compared with 8/8 HLA-matched donors. The study's limited power due to small sample size precludes conclusions about other mismatches.

HLA-allele matched unrelated donors compared to HLA-matched sibling donors: role of cell source and disease risk category

To determine whether the risks of allogeneic transplantation are different when the donor is a fully matched unrelated donor (MUD; based on 10/10 HLA alleles) compared to an HLA-identical sibling, we performed a retrospective analysis of 1448 patients with high-risk or advanced hematologic malignancies given T-replete grafts after myeloablative conditioning. No statistically significant differences were found between recipients of a matched sibling donor (MSD) and 10/10 MUD in survival, disease-free survival (DFS), and nonrelapse mortality (NRM) for patients with high-risk disease or those given bone marrow as a graft source. However, for patients with intermediate-risk disease receiving peripheral blood grafts, we observed higher NRM and lower overall survival (OS) in the 10/10 MUD group compared to the MSD cohort. Graft-versus-host disease (GVHD) was higher in the MUD group compared to the MSD group. These results suggest that if a patient has high-risk disease and an MSD is not available, selection of an HLA-allele-matched MUD may provide similar OS and DFS, and therefore lack of an MSD in and of itself should not preclude such a patient from undergoing transplantation. However, for patients with intermediate-risk disease, transplantation with peripheral blood from a 10/10 MUD is associated with lower survival than an MSD.

Novel sequence feature variant type analysis of the HLA genetic association in systemic sclerosis

We describe a novel approach to genetic association analyses with proteins sub-divided into biologically relevant smaller sequence features (SFs), and their variant types (VTs). SFVT analyses are particularly informative for study of highly polymorphic proteins such as the human leukocyte antigen (HLA), given the nature of its genetic variation: the high level of polymorphism, the pattern of amino acid variability, and that most HLA variation occurs at functionally important sites, as well as its known role in organ transplant rejection, autoimmune disease development and response to infection. Further, combinations of variable amino acid sites shared by several HLA alleles (shared epitopes) are most likely better descriptors of the actual causative genetic variants. In a cohort of systemic sclerosis patients/controls, SFVT analysis shows that a combination of SFs implicating specific amino acid residues in peptide binding pockets 4 and 7 of HLA-DRB1 explains much of the molecular determinant of risk.

Low-dose total body irradiation and fludarabine conditioning for HLA class I-mismatched donor stem cell transplantation and immunologic recovery in patients with hematologic malignancies: a multicenter trial

HLA-mismatched grafts are a viable alternative source for patients without HLA-matched donors receiving ablative hematopoietic cell transplantation (HCT), although their use in reduced intensity conditioning (RIC) or nonmyeloablative (NMA) conditioning HCT has been not well established. Here, we extended HCT to recipients of HLA class I-mismatched grafts to investigate whether NMA conditioning can establish stable donor engraftment. Fifty-nine patients were conditioned with fludarabine (Flu) 90 mg/m(2) and 2 Gy total body irradiation (TBI), followed by immunosuppression with cyclosporine (CsA) 5.0 mg/kg twice a day and mycophenolate mofetil (MMF) 15 mg/kg 3 times a day for transplantation of granulocyte colony-stimulating factor (G-CSF)-mobilized peripheral blood stem cells (PBSCs) from related (n = 5) or unrelated donors (n = 54) with 1 antigen +/- 1 allele HLA class I mismatch or 2 HLA class I allele mismatches. Sustained donor engraftment was observed in 95% of the evaluable patients. The incidence of grade II-IV acute and extensive chronic graft-versus-host disease (aGVHD, cGVHD) was 69% and 41%, respectively. The cumulative probability of nonrelapse mortality (NRM) was 47% at 2 years. Two-year overall and progression-free survival (OS, PFS) was 29% and 28%, respectively. NMA conditioning with Flu and low-dose TBI, followed by HCT using HLA class I-mismatched donors leads to successful engraftment and long-term survival; however, the high incidence of aGVHD and NRM needs to be addressed by alternate GVHD prophylaxis regimens.

High-resolution donor-recipient HLA matching contributes to the success of unrelated donor marrow transplantation

The relative importance of various human leukocyte antigen (HLA) loci and the resolution level at which they are matched has not been fully defined for unrelated donor transplantation. To address this question, National Marrow Donor Program data from 3857 transplantations performed from 1988 to 2003 in the United States were analyzed. Patient-donor pairs were fully typed for HLA-A, -B, -C, -DRB1, -DQB1, -DQA1, -DPB1, and -DPA1 alleles. High-resolution DNA matching for HLA-A, -B, -C, and -DRB1 (8/8 match) was the minimum level of matching associated with the highest survival. A single mismatch detected by low- or high-resolution DNA testing at HLA-A, -B, -C or -DRB1 (7/8 match) was associated with higher mortality (relative risk, 1.25; 95% CI, 1.13-1.38; P < .001) and 1-year survival of 43% compared with 52% for 8/8 matched pairs. Single mismatches at HLA-B or HLA-C appear better tolerated than mismatches at HLA-A or HLA-DRB1. Mismatching at 2 or more loci compounded the risk. Mismatching at HLA-DP or -DQ loci and donor factors other than HLA type were not associated with survival. In multivariate modeling, patient age, race, disease stage, and cytomegalovirus status were as predictive of survival as donor HLA matching. High-resolution DNA matching for HLA-A, -B, -C, and -DRB1 alleles is associated with higher rates of survival.

Extended mycophenolate mofetil and shortened cyclosporine failed to reduce graft-versus-host disease after unrelated hematopoietic cell transplantation with nonmyeloablative conditioning

We previously reported data from 103 patients with hematologic malignancies (median age 54 years) who received peripheral blood stem cell (PBSC) grafts from HLA-matched unrelated donors after nonmyeloablative conditioning and were given postgrafting immunosuppression consisting of mycophenolate mofetil (MMF; administered from day 0 until day +40 with taper through day +96) and cyclosporine (CSP; given from day -3 to day +100, with taper through day 180) (historical patients). The incidences of grade II-IV acute and extensive chronic graft-versus-host disease (aGVHD, cGVHD) were 52% and 49%, respectively, and the 1-year probabilities of relapse, nonrelapse mortality (NRM), and progression-free survival (PFS) were 26%, 18%, and 56%, respectively. Here, we treated 71 patients with hematologic malignancies (median age 56 years) with unrelated PBSC grafts and investigated whether postgrafting immunosuppression with an extended course of MMF, given at full dosing until day +150 and then tapered through day +180, and a shortened course of CSP, through day +80, would promote tolerance induction and reduce the incidence of GVHD (current patients). We observed 77% grade II-IV aGVHD and 45% extensive cGVHD (P=.03, and P=.43, respectively, in current compared to historical patients). The 1-year probabilities of relapse, NRM, and PFS were 23%, 29%, and 47%, respectively (P=.89, P=.02, and P=.08 compared to the historical patients). We conclude that postgrafting immunosuppression with extended MMF and shortened CSP failed to decrease the incidence of GVHD among unrelated PBSC recipients given nonmyeloablative conditioning.

14thInternational HLA and Immunogenetics Workshop: report on hematopoietic cell transplantation

Deciphering the role of human leukocyte antigen (HLA), killer immunoglobulin like receptor, and immune response genes in a model as complex as unrelated donor hematopoietic cell transplantation is a challenge. The allelic diversity of these genes is shaped by the race and ethnicity of transplant donors and recipients. Coupled with the genetic polymorphism is the complexity of clinical phenotypes of transplant populations: donor and recipient demographic characteristics and the regimens used by transplant physicians to prepare patients for transplantation and to prevent and treat graft-vs-host disease (GVHD). Furthermore, GVHD is itself a complex disease shaped by both genes and 'environment'. How does one begin to deconstruct the genetic barrier to understand risk factors important to transplant outcome? To begin with, population-based studies, particularly retrospective ones, benefit from adequate sample sizes to measure genetic effects. The more homogeneous the population for variables that influence clinical endpoints, the higher the likelihood that a real genetic effect can be uncovered. Even so, the feasibility of studies can be hampered if genotype and clinical data are not both complete and precise. For studies of HLA, diversity of alleles and antigens contributed by ethnically different transplant populations is an asset, because not only can a broader range of HLA mismatches be studied but they provide the opportunity for side-by-side analyses that may yield clues as to why transplant outcomes differ between populations.

Hematopoietic cell transplantation as curative therapy for idiopathic myelofibrosis, advanced polycythemia vera, and essential thrombocythemia

A total of 104 patients, aged 18 to 70 years, with a diagnosis of chronic idiopathic myelofibrosis (CIMF), polycythemia vera (PV), or essential thrombocythemia (ET) with marrow fibrosis were transplanted from allogeneic (56 related and 45 unrelated) or syngeneic (n = 3) donors. Busulfan (BU) or total body irradiation (TBI)-based myeloablative conditioning regimens were used in 95 patients, and a nonmyeloablative regimen of fludarabine plus TBI was used in 9 patients. The source of stem cells was bone marrow in 43 patients and peripheral blood in 61 patients. A total of 63 patients were alive at a follow-up of 1.3-15.2 years (median, 5.3 years), for an estimated 7-year actuarial survival rate of 61%. Eleven patients had recurrent/persistent disease, of whom 8 died. Nonrelapse mortality was 34% at 5 years. Patients conditioned with targeted BU (plasma levels 800-900 ng/mL) plus cyclophosphamide (tBUCY) had a higher probability of survival (68%) than other patients. Dupriez score, platelet count, patient age, and comorbidity score were statistically significantly associated with mortality in univariate models. In a multivariable regression model, use of tBUCY (P = .03), high platelet count at transplantation (P = .01 for PV/ET; P = .39 for other diagnoses), younger patient age (P = .04), and decreased comorbidity score (P = .03) remained statistically significant for improved survival. Our findings show that hematopoietic cell transplantation offers potentially curative treatment for patients with ICMF, PV, or ET.

Interleukin-1 alpha genotype and outcome of unrelated donor haematopoietic stem cell transplantation for chronic myeloid leukaemia

Interleukin-1 alpha (IL-1alpha) is a pro-inflammatory cytokine that is implicated in the initiation/maintenance of graft-versus-host disease (GVHD) and the immune response to infection. A cytosine (C) to thymine (T) transition at position -889 is believed to influence gene transcription. A previous single institution study showed that the presence of at least one IL1A T allele in the donor was associated with improved survival after unrelated donor haematopoietic stem cell transplant and lower transplant-related mortality if the donor and recipient each possessed the IL1A T allele. The present study sought to confirm these results in a larger homogeneous population. Thus the study population included 426 patients older than 18 years with chronic myeloid leukaemia (CML), transplanted in first chronic phase and receiving a total body irradiation and cyclophosphamide preparative regimen. Donor recipient pairs were categorised into four groups according to the presence or absence of an IL1A T allele in the donor and recipient. There were no significant differences in patient, donor and transplant characteristics between the groups. We did not observe an association with IL-1alpha genotype in donor and/or recipient and transplant-outcome. These data suggest that the outcome of unrelated donor transplant for CML is not influenced by IL-1alpha genotype.

A High Degree of HLA Disparity Arises From Limited Allelic Diversity: Analysis of 1775 Unrelated Bone Marrow Transplant Donor-Recipient Pairs

The allelic diversity and associated human leukocyte antigen (HLA) disparity of 1775 bone marrow recipients and their unrelated donors, matched for six of six (1361/1775,77%), five of six (397/1775, 22%), or four of six (17/1775, 1%) HLA-A, -B, -DR antigens, were retrospectively evaluated. The comprehensive HLA analysis included the class I (A, B, C) and II (DRB1, DQA1, DQB1, DPA1, DPB1) loci. Most (>66%) of the predominantly Caucasian study population carried one or two of five to seven common alleles at each HLA locus. In spite of this limited diversity, 29% of the six of six antigen-matched transplants carried allele mismatches at HLA-A, -B, and/or -DRB1, and 92% carried at least one allele mismatch at one of the eight HLA loci tested. Of the 968 HLA-A,-B,-DRB1 allele-matched pairs, 89% carried mismatches at other HLA loci, predominantly at DP loci. The substantially greater than expected HLA allelic disparity between donor and recipient suggests extensive haplotypic diversity and underscores the importance of enhancing approaches to mitigate the deleterious effect of HLA mismatches.

KIR ligands and prediction of relapse after unrelated donor hematopoietic cell transplantation for hematologic malignancy

Recurrent malignancy remains a significant complication after allogeneic hematopoietic cell transplantation (HCT). Efforts to decrease relapse have included donor lymphocyte infusion to stimulate donor anti-recipient T-cell allorecognition of major and minor histocompatibility differences. Recently, alloreactive effects of donor natural killer cell-mediated inhibitory killer immunoglobulin-like receptor (KIR) recognition of recipient HLA-C and -B ligands have been described. We examined KIR ligand effects on risk of relapse in 1770 patients undergoing myeloablative T-replete HCT from HLA-matched or -mismatched unrelated donors for the treatment of myeloid and lymphoid leukemias. KIR ligands defined by HLA-B and -C genotypes were used to determine donor-recipient ligand incompatibility or recipient lack of KIR ligand. Among HLA-mismatched transplantations, recipient homozygosity for HLA-B or -C KIR epitopes predicted lack of KIR ligand and was associated with a decreased hazard of relapse (hazard ratio, 0.61; 95% confidence interval, .043-0.85; P = .004). Absence of HLA-C group 2 or HLA-Bw4 KIR ligands was associated with lower hazards of relapse (hazard ratio, 0.47; 95% confidence interval, 0.28-0.79, P = .004; hazard ratio, 0.56; 95% confidence interval, 0.33-0.97; P = .04, respectively). The decrease in hazard of relapse in patients with acute myelogenous leukemia was similar to that in patients with chronic myelogenous leukemia and acute lymphoblastic leukemia (P = .95). Recipient homozygosity for HLA-B or -C epitopes that define KIR ligands is likely to be a predictive factor for leukemia relapse after myeloablative HCT from HLA-mismatched unrelated donors. This effect was not observed in HLA-identical unrelated transplants.

MHC microsatellite diversity and linkage disequilibrium among common HLA-A, HLA-B, DRB1 haplotypes: implications for unrelated donor hematopoietic transplantation and disease association studies

Twenty-two human major histocompatibility complex (MHC) region microsatellite (Msat) markers were studied for diversity and linkage disequilibrium (LD) with HLA loci in hematopoietic cell transplant recipients and their HLA-A, HLA-B, HLA-C, HLA-DRB1, and HLA-DQB1 allele-matched unrelated donors. These Msats showed highly significant LD over much of the MHC region. The Msat diversity of five common Caucasian haplotypes (HLA-A1-B8-DR3, A3-B7-DR15, A2-B44-DR4, A29-B44-DR7, and A2-B7-DR15) was examined using a new measure called 'haplotype specific heterozygosity' (HSH). Each of the five haplotypes had at least one Msat marker with an HSH value of zero indicating that only one Msat allele was observed for the particular HLA haplotype. In addition, the ability of Msats to predict HLA-A-B-DRB1 haplotypes was studied. Over 90% prediction probability of two common haplotypes (HLA-A1-B8-DR3 and HLA-A3-B7-DR15) was achieved with information from three Msats (D6S265/D6S2787/D6S2894 and D6S510/D6S2810/D6S2876, respectively). We demonstrate how the HSH index can be used in the selection of informative Msats for transplantation and disease association studies. Markers with low HSH values can be used to predict specific HLA haplotypes or multilocus genotypes to supplement the screening of HLA-matched donors for transplantation. Markers with high HSH values will be most informative in studies investigating MHC region disease-susceptibility genes where HLA haplotypic effects are known to exist.

BCR-ABL transcripts are early predictors for hematological relapse in chronic myeloid leukemia after hematopoietic cell transplantation with reduced intensity conditioning

Kinetics of BCR-ABL transcript elimination and its prognostic implications on relapse were analyzed in patients with chronic myeloid leukemia (CML) after reduced intensity hematopoietic cell transplantation (HCT). In all, 19 CML patients were conditioned with 2 Gy total-body irradiation in combination with (n=14) or without (n=3) fludarabine 3 x 30 mg/m(2) (Flu) or 4.5 Gy total lymphoid irradiation (TLI) with Flu and OKT3 3 x 5 mg (n=2) and were treated with cyclosporine (CSP) and mycophenolate mofetil after allogeneic HCT. BCR-ABL transcripts were analyzed by nested RT-PCR and Taqman((R)) RT-PCR on days +28, +56 and +84 after HCT and were evaluated for their association with relapse. Of the 19 patients, 14 achieved sustained remissions of which six had a negative RT-PCR 28 days after HCT. Five patients relapsed +41, +54, +57, +136 and +234 days after HCT. Predictors for relapse were advanced disease stage (P=0.02) and slow reduction of BCR-ABL transcripts at day 28 (P=0.006) and day 56 (P=0.047) post-transplant. We conclude that a complete clearance of BCR-ABL transcripts is achievable within 4 weeks from HCT even after minimal conditioning and that early kinetics of BCR-ABL transcripts significantly correlate with the probability of hematological relapse.

Impact of HLA class I and class II high-resolution matching on outcomes of unrelated donor bone marrow transplantation: HLA-C mismatching is associated with a strong adverse effect on transplantation outcome

Outcome of unrelated donor marrow transplantation is influenced by donor-recipient matching for HLA. Prior studies assessing the effects of mismatches at specific HLA loci have yielded conflicting results. The importance of high-resolution matching for all HLA loci has also not been established. We therefore examined the effects of HLA matching (low or high resolution or both) on engraftment, graft-versus-host disease (GVHD), and mortality in 1874 donor-recipient pairs retrospectively typed at high resolution for HLA-A, -B, -C, -DRB1, -DQ, and -DP. Mismatches at HLA-A, -B, -C, and -DRB1 each had similar adverse effects on mortality. Only HLA-A mismatches demonstrated significant adverse effects on GVHD. These adverse effects on outcome were more evident in transplants with low-resolution versus only high-resolution mismatches. Mismatches for HLA-DQ or -DP did not significantly affect outcome. When high-resolution mismatches at HLA-A, -B, -C, and -DRB1 were considered together, adverse effects on survival and GVHD were observed. We therefore conclude that matching for HLA-C should be incorporated into algorithms for unrelated donor selection. High-resolution mismatches at HLA-A, -B, -C, and -DRB1 adversely affect outcome, but less so than low-resolution mismatches. When clinical circumstances allow, high-resolution class I typing may help optimize donor selection and improve outcome.

HLA-matched unrelated donor hematopoietic cell transplantation after nonmyeloablative conditioning for patients with hematologic malignancies

A hematopoietic cell transplantation (HCT) approach was developed for elderly or ill patients with hematologic malignancies that employed nonmyeloablative conditioning to avoid common regimen-related toxicities and relied on graft-versus-tumor effects for control of malignancy. Eighty-nine patients, median age 53 years, were given fludarabine (90 mg/m2) and 2 Gy total body irradiation. Marrow (n = 18) or granulocyte colony-stimulating factor (G-CSF)-stimulated peripheral blood mononuclear cells (G-PBMCs; n = 71) were transplanted from unrelated donors matched for human leukocyte antigen A (HLA-A), -B, -C antigens and -DRB1 and -DQB1 alleles. Postgrafting immunosuppression included mycophenolate mofetil and cyclosporine. Donor T-cell chimerism was higher for G-PBMCs compared with marrow recipients. Durable engraftment was observed in 85% of G-PBMCs and 56% of marrow recipients. Cumulative probabilities of grade II, III, and IV acute graft-versus-host disease (GVHD) were 42%, 8%, and 2%, respectively. Nonrelapse mortality at day 100 and at 1 year was 11% and 16%, respectively. One-year overall survivals and progression-free survivals were 52% and 38%, respectively. G-PBMC recipients had improved survival (57% vs 33%) and progression-free survival (44% vs 17%) compared with marrow recipients. HLA-matched unrelated donor HCT after nonmyeloablative conditioning is feasible in patients ineligible for conventional HCT. G-PBMCs conferred higher donor T-cell chimerism, greater durable engraftment, and better progression-free and overall survivals compared with marrow.

Hematopoietic stem cell transplantation for advanced myelodysplastic syndrome after conditioning with busulfan and fractionated total body irradiation is associated with low relapse rate but considerable nonrelapse mortality

The objectives of this study were to develop transplantation regimens for patients with advanced myelodysplastic syndrome (MDS) that would be associated with low transplantation-related mortality and improved relapse-free survival. Sixty patients with advanced MDS or acute myeloid leukemia evolving from MDS (sAML), 12 to 62 years old (median, 40 years), were conditioned with busulfan (7 mg/kg) and TBI (6 x 200 cGy) (BU/TBI) and received transplants from related (n = 20) or unrelated donors (n = 40). By French-American-British (FAB) criteria, 21 patients had refractory anemia with excess blasts (RAEB), 16 had RAEB in transformation (RAEB-T), 15 had sAML, and 8 had chronic myelomonocytic leukemia (CMML). By International Prognostic Scoring System (IPSS) criteria, 1 patient had low, 10 had intermediate-1, 13 had intermediate-2, and 31 had high-risk MDS (5 patients had proliferative CMML). All evaluable patients achieved sustained engraftment. The cumulative incidence (CI) of acute GVHD grades II to IV was 83% with unrelated donors and 85% with related donors. The CI of relapse was 25% at 3 years. The incidence of nonrelapse mortality (NRM) at 100 days was 38%. The Kaplan-Meier estimate of survival was 26% at 3 years. Major causes of death were relapse, organ failure, GVHD, and infection. In multivariate analysis, improved relapse-free survival was associated with good cytogenetic risk (P = .002) and shorter disease duration (P = .004). NRM was increased with longer disease duration (P = .0002), positive cytomegalovirus serology (P = .02), and male sex (P = .02). Relapse was associated with poor cytogenetic risk (P = .0004). Thus, BU/TBI conditioning as used in this trial was associated with relapse rates comparable to those observed with a previously used more intensive regimen combining BU/TBI with cyclophosphamide. However, despite the omission of cyclophosphamide, transplantation-related morbidity and mortality were considerable, particularly with transplants from unrelated donors. Future trials should explore the efficacy and tolerability of reduced-intensity conditioning regimens.

Low-dose total body irradiation (TBI) and fludarabine followed by hematopoietic cell transplantation (HCT) from HLA-matched or mismatched unrelated donors and postgrafting immunosuppression with cyclosporine and mycophenolate mofetil (MMF) can induce durable complete chimerism and sustained remissions in patients with hematological diseases

Toxicities of high-dose conditioning regimens have limited the use of conventional unrelated donor hematopoietic cell transplantation (HCT) to younger, medically fit patients. Based on preclinical studies, an HCT approach has been developed for elderly or medically infirm patients with HLA-matched or mismatched unrelated donors. In this study, 52 patients with hematological diseases were included. Most (88%) had preceding unsuccessful conventional HCT or refractory/advanced disease. Patients were treated with fludarabine 30 mg/m(2)/d from days -4 to -2, 2 Gy total body irradiation on day 0, cyclosporine at 6.25 mg/kg twice daily from day -3, and mycophenolate mofetil at 15 mg/kg twice daily from day 0. Durable donor chimerism was attained in 88% of the patients. By day 28, a median of 100% of CD56(+) cells were of donor origin. Granulocyte and T-cell donor chimerism increased to medians of 100% on day 56 and day 180 (range, 55%-100%), respectively. Acute GVHD, grade II, was seen in 42% (CI, 29%-56%); grade III in 8% (CI, 0%-15%); and grade IV in 13% (CI, 4%-23%) of patients; it was fatal in 9%. The 100-day transplantation-related mortality was 11%. Complete remissions, including molecular remissions, were seen in 45% of patients with measurable disease before transplantation. Mortality from disease progression was 27% at one year. With a median follow-up of 19 months, 18 of the 52 patients (35%) were alive and 25% were in remission. HCT from HLA-matched or mismatched unrelated donors can be performed with a reduced intensity conditioning regimen in patients ineligible for conventional HCT.

Conditioning with targeted busulfan and cyclophosphamide for hemopoietic stem cell transplantation from related and unrelated donors in patients with myelodysplastic syndrome

A total of 109 patients (aged 6-66 years; median, 46 years) with myelodysplastic syndrome (MDS) were treated with busulfan (BU) targeted to plasma concentrations of 800 to 900 ng/mL plus cyclophosphamide (CY), 2 x 60 mg/kg, and hemopoietic stem cell (HSC) transplantation from related (n = 45) or unrelated donors (n = 64). At the time of transplantation, 69 patients had less than 5% myeloblasts in the marrow, and 40 patients had more advanced disease. All but 2 evaluable patients had engraftment. The Kaplan-Meier estimates of 3-year relapse-free survival (RFS) were 56% for related and 59% for unrelated recipients. The cumulative incidences of relapse were 16% for related and 11% for unrelated recipients. Nonrelapse mortality (NRM) at 100 days (3 years) was 12% (28%) for related and 13% (30%) for unrelated recipients. The only factor significant for RFS was the etiology of MDS (de novo better than treatment related; P =.03). Factors significantly correlated with relapse were advanced French-American-British classification (P =.002) and International Prognostic Scoring System score (P =.009), poor-risk cytogenetics (P =.03), and treatment-related etiology (P =.03). None of the factors examined was statistically significant for NRM. Patient age and donor type had no significant impact on outcome. RFS tended to be superior in patients receiving transplants with peripheral blood rather than marrow stem cells. Thus, a targeted BUCY regimen provided effective transplant conditioning for patients with MDS receiving transplants from HLA-identical siblings or alternative donors. Although there was still considerable nonrelapse morbidity and mortality, the present regimen was used successfully even in patients older than 60 years of age.

Factors associated with outcome after unrelated marrow transplantation for treatment of acute lymphoblastic leukemia in children

Acute lymphoblastic leukemia (ALL) is the most common indication for transplantation of marrow from unrelated donors in children. We analyzed results of this procedure in children with ALL treated according to a standard protocol to determine risk factors for outcome. From January 1987 to 1999, 88 consecutively seen patients with ALL who were younger than 18 years received a marrow transplant from an HLA-matched (n = 56) or partly matched (n = 32) unrelated donor during first complete remission (CR1; n = 10), second remission (CR2; n = 34), third remission (CR3; n = 10), or relapse (n = 34). Patients received cyclophosphamide and fractionated total-body irradiation as conditioning treatment and were given methotrexate and cyclosporine for graft-versus-host disease (GVHD) prophylaxis. Three-year rates of leukemia-free survival (LFS) according to phase of disease were 70% for CR1, 46% for CR2, 20% for CR3, and 9% for relapse (P <.0001). Three-year cumulative relapse rates were 10%, 33%, 20%, and 50%, respectively, and 3-year cumulative rates of death not due to relapse were 20%, 22%, 60%, and 41%, respectively, for patients with CR1, CR2, CR3, and relapse. Grades III to IV acute GVHD occurred in 43% of patients given HLA-matched transplants and in 59% given partly matched transplants (P =.10); clinical extensive chronic GVHD occurred in 32% and 38%, respectively (P =.23). LFS rates were lower in patients with advanced disease (P <.0001), age 10 years or older (P =.002), or short duration of CR1 (P =.007). Thus, in addition to phase of disease, age and duration of CR1 were predictors of outcome after unrelated-donor transplantation for treatment of ALL in children. Outcome was particularly favorable in younger patients with early phases of the disease.

Allogeneic bone marrow transplantation for chronic myelogenous leukemia: comparative analysis of unrelated versus matched sibling donor transplantation

Allogeneic bone marrow transplantation (BMT) offers the only curative therapy for chronic myelogenous leukemia. We compared prospectively collected results of 2464 unrelated donor (URD) transplantations with 450 HLA-identical, matched sibling donor (MSD) transplantations performed at collaborating National Marrow Donor Program institutions. A total of 63% of URDs were matched at HLA-A, -B, and at -DRB1 alleles; all MSDs were genotypically identical at major histocompatibility loci. URD recipients were younger (median 36 vs 39, P =.001) than MSDs and underwent BMT later after diagnosis (median 17 [0-325 months] vs 7 [1-118 months], P =.001) and less often in chronic phase (CP) (67% vs 82%, P =.001). Multivariate analysis demonstrated a significantly increased risk of graft failure and acute graft versus host disease after URD BMT. The risk of hematologic relapse was low after either matched URD or MSD transplantations. We observed significantly though modestly poorer survival and disease-free survival (DFS) after URD transplantations. However, for those undergoing transplantation during CP within 1 year from diagnosis, 5-year DFS was similar or only slightly inferior after matched URD versus MSD transplantation (age < 30: URD 61% +/- 8% vs MSD 68% +/- 15%, P =.18; 30-40: URD 57% +/- 9% vs MSD 67% +/- 10%, P =.05; > 40: URD 46% +/- 9% vs MSD 57% +/- 9%, P =.02). Delay from diagnosis to BMT in CP patients led to substantially poorer 5-year DFS after matched URD than MSD BMT (CP 1-2 years: URD 39% +/- 6% vs MSD 63% +/- 12%; beyond 2 years: URD 33% +/- 7% vs MSD 50% +/- 20%). Outcome of matched URD BMT for early CP chronic myelogenous leukemia yields survival and DFS approaching that of MSD transplantation. However, delay may compromise URD outcomes to a greater extent. Improvements in URD and MSD transplantation are still needed, and results of newer, nontransplantation therapies should be evaluated against the established curative potential of URD and MSD marrow transplantation.

Genomics of unrelated-donor hematopoietic cell transplantation

Unrelated-donor hematopoietic cell transplantation is a proven curative modality for hematologic malignancies. The success of unrelated-donor transplantation has been achieved through a better understanding of the immunobiology of the HLA system and through more precise and comprehensive matching of donors and recipients. The extensive polymorphism of HLA genes confers important biological implications affecting engraftment, graft-versus-host disease and overall survival. Although more-complete HLA identity of the donor and recipient is associated with optimal transplant outcome, new information suggests that not every HLA disparity is functionally relevant. Future advances in unrelated-donor transplantation must include the identification of tolerable HLA mismatches, so that more patients may benefit from this therapeutic modality. Furthermore, the role of cytokine-gene polymorphisms and minor histocompatibility genes in transplant outcome requires investigation. Delineation of the function of these markers as transplantation determinants may provide alternative means for optimizing the results of hematopoietic cell transplantation.

The role of HLA matching in hematopoietic cell transplantation

Hematopoietic cell transplantation (HCT) can be a life-saving therapy for patients with genetic and acquired hematologic diseases. Despite major advances in supportive care during HCT, immunological complications of the alloimmune response, including graft rejection and graft-versus-host disease (GVHD), remain major impediments to successful clinical outcomes. Although graft rejection mediated by host immune cells and GVHD mediated by donor immune cells can be prevented or mediated by immune suppression therapy, genetic HLA matching remains essential for successful strategies designed to minimize the risks of transplantation. The most favorable HCT results are seen in patients with a genotypically HLA-identical sibling donor, but the limited availability of matched related donors has severely restricted the clinical application of this therapy. Fortunately, the establishment of large unrelated volunteer donor registries now provides the opportunity to identify HLA matches for many patients who lack a family donor. The criteria for unrelated donor matching, however, are poorly defined. Until recently, an analysis of matching beyond HLA-identical siblings has been limited by typing technology. The introduction within the past few years of new methods for high resolution typing and definition of HLA alleles has had a profound impact on our ability to identify and interpret the multiple nucleotide sequence polymorphisms that encode HLA antigens. Preliminary studies clearly demonstrate the importance of precise matching at the allele level for successful transplantation. There remain, however, important unanswered questions about the relative importance of different HLA loci in matching strategies, as well as incomplete information about permissible limits of mismatching in different patient populations.

HLA matching in hematopoietic cell transplantation

Progress in hematopoietic cell transplantation has been greatly facilitated by our increasing knowledge of the HLA system, as well as by improved therapies for achieving sustained engraftment, preventing graft-versus-host disease, and protecting the patient from infection. Disparity for HLA genes can cause graft rejection and graft-versus-host disease and decrease survival in patients receiving grafts from both related and unrelated donors. The presence of patient alloantibodies against donor antigens demonstrated by a positive crossmatch is a strong risk factor for graft rejection. The availability of matched donors for patients lacking a genotypically HLA-matched sibling has been greatly improved by the establishment of international registries of HLA-typed volunteer donors. The development of accurate and reproducible high-resolution DNA-based typing methods has significantly improved the prospects for identifying unrelated donors who are well matched with the patient for HLA. The use of these methods to optimize donor selection will improve both donor identification and the success of unrelated donor transplants.

Identification of a novel HLA-C allele, Cw*0406, in a Singapore Malay

A novel allele, C*0406, has been identified and is characterised by a single nucleotide substitution at position 196 of exon 3 when compared with its closest related allele, C*0403. The latter is found in 4/69 Chinese and 7/80 Malays while Cw*0406 was found in only one Malay individual within the study populations. The data suggest that Cw*0406 may have arisen as a relatively recent genetic event either by gene conversion or as a simple point mutation variant of Cw*0403.

Effect of HLA matching on outcome of related and unrelated donor transplantation therapy for chronic myelogenous leukemia

This article examines the diversity and biologic role of human lymphocyte antigen (HLA) genes as related to marrow transplantation for chronic myelogenous leukemia (CML). A better understanding of the nature and function of HLA variation is necessary as unrelated marrow transplantation evolves into a safe and effective treatment for CML. HLA matching is an important aspect of donor selection criteria and has a role in engraftment as well as the development of graft-versus-host disease and tolerance after transplant.