Tissue typing in support of unrelated hematopoietic cell transplantation

Discovery of the novel HLA-A*11:452N allele by next-generation sequencing in a Chinese individual

HLA-A*11:452N differs from A*11:01:01:01 by a single nucleotide exchange in exon 1.

Factors with an impact on chimerism development and long-term survival after umbilical cord blood transplantation

BACKGROUND

Umbilical cord blood transplantation (UCBT) is increasingly used and produces similar results to matched unrelated donor transplantation.

METHODS

We performed a retrospective single-center analysis of 50 umbilical cord blood transplantations UCBTs performed from 2001 to 2010, including 37 single and 13 double umbilical cord blood transplantations UCBTs.

RESULTS

The rate of engraftment of neutrophils was 88% at a median time of 29 days (range, 3-79). Complete donor chimerism (DC) within the CD19, CD3, and CD33 cell lineages was seen in 74%, 72%, and 76% of the patients, respectively. DC was associated with acute graft-versus-host disease (GVHD) grades II to IV for the CD3 cell lineage (P=0.01) and, in multivariate analysis, with total body irradiation for all lineages (P<0.01). Overall survival (OS) at 1 and 5 years was 55% and 43%. Nonmalignant diseases were associated with better 5-year OS (72%) than malignancies (28%; P=0.026). In multivariate analysis, a negative correlation was seen between OS and age (hazard ratio [HR], 1.04; 95% confidence interval [95% CI], 1.02-1.06; P<0.001), acute GVHD grades III and IV (HR, 3.43; 95% CI, 1.95-6.02; P<0.001), and mesenchymal stem cell treatment (HR, 2.66; 95% CI, 1.11-6.35; P=0.027). Transplant-related mortality at 100 days and 1 year was 16% and 30%. The incidence of acute GVHD grades II to IV was 34%. Acute GVHD grades III and IV was associated with ABO incompatibility (HR, 2.61; P=0.05) and myeloablative conditioning (HR, 4.17; P=0.047).

CONCLUSIONS

The outcome in patients with nonmalignant diseases was acceptable, but transplant-related mortality in the whole group remains high. A significantly higher rate of DC was associated with total body irradiation-based conditioning and with acute GVHD grades II and IV.

Tracking human migrations by the analysis of the distribution of HLA alleles, lineages and haplotypes in closed and open populations

The human leucocyte antigen (HLA) system shows extensive variation in the number and function of loci and the number of alleles present at any one locus. Allele distribution has been analysed in many populations through the course of several decades, and the implementation of molecular typing has significantly increased the level of diversity revealing that many serotypes have multiple functional variants. While the degree of diversity in many populations is equivalent and may result from functional polymorphism(s) in peptide presentation, homogeneous and heterogeneous populations present contrasting numbers of alleles and lineages at the loci with high-density expression products. In spite of these differences, the homozygosity levels are comparable in almost all of them. The balanced distribution of HLA alleles is consistent with overdominant selection. The genetic distances between outbred populations correlate with their geographical locations; the formal genetic distance measurements are larger than expected between inbred populations in the same region. The latter present many unique alleles grouped in a few lineages consistent with limited founder polymorphism in which any novel allele may have been positively selected to enlarge the communal peptide-binding repertoire of a given population. On the other hand, it has been observed that some alleles are found in multiple populations with distinctive haplotypic associations suggesting that convergent evolution events may have taken place as well. It appears that the HLA system has been under strong selection, probably owing to its fundamental role in varying immune responses. Therefore, allelic diversity in HLA should be analysed in conjunction with other genetic markers to accurately track the migrations of modern humans.

Strategies to work with HLA data in human populations for histocompatibility, clinical transplantation, epidemiology and population genetics: HLA-NET methodological recommendations

HLA-NET (a European COST Action) aims at networking researchers working in bone marrow transplantation, epidemiology and population genetics to improve the molecular characterization of the HLA genetic diversity of human populations, with an expected strong impact on both public health and fundamental research. Such improvements involve finding consensual strategies to characterize human populations and samples and report HLA molecular typings and ambiguities; proposing user-friendly access to databases and computer tools and defining minimal requirements related to ethical aspects. The overall outcome is the provision of population genetic characterizations and comparisons in a standard way by all interested laboratories. This article reports the recommendations of four working groups (WG1-4) of the HLA-NET network at the mid-term of its activities. WG1 (Population definitions and sampling strategies for population genetics’ analyses) recommends avoiding outdated racial classifications and population names (e.g. ‘Caucasian’) and using instead geographic and/or cultural (e.g. linguistic) criteria to describe human populations (e.g. ‘pan-European’). A standard ‘HLA-NET POPULATION DATA QUESTIONNAIRE’ has been finalized and is available for the whole HLA community. WG2 (HLA typing standards for population genetics analyses) recommends retaining maximal information when reporting HLA typing results. Rather than using the National Marrow Donor Program coding system, all ambiguities should be provided by listing all allele pairs required to explain each genotype, according to the formats proposed in ‘HLA-NET GUIDELINES FOR REPORTING HLA TYPINGS’. The group also suggests taking into account a preliminary list of alleles defined by polymorphisms outside the peptide-binding sites that may affect population genetic statistics because of significant frequencies. WG3 (Bioinformatic strategies for HLA population data storage and analysis) recommends the use of programs capable of dealing with ambiguous data, such as the ‘gene[rate]’ computer tools to estimate frequencies, test for Hardy–Weinberg equilibrium and selective neutrality on data containing any number and kind of ambiguities. WG4 (Ethical issues) proposes to adopt thorough general principles for any HLA population study to ensure that it conforms to (inter)national legislation or recommendations/guidelines. All HLA-NET guidelines and tools are available through its website http://hla-net.eu.

Mesenchymal stem cells inhibit thymic reconstitution after allogeneic cord blood transplantation

Cord blood (CB) as a source of stem cells has been a successful addition to the field of allogeneic stem cell transplantation (ASCT). The increased human leukocyte antigen (HLA) permissiveness of CB grafts has made it possible for more patients to undergo treatment. The drawback is that patients suffer from a longer period of compromised immunity. We analyzed T-cell receptor excision circles (TRECs), immunoglobulin G (IgG), and immunoglobulin M (IgM) levels after cord blood transplantation (CBT) in 50 patients transplanted at our center. These immunological parameters were compared retrospectively with clinical factors and complications. We found that TREC levels after CBT were lower in adults, patients with myeloablative conditioning, and in patients with a lower nucleated cell dose in the graft. In addition mesenchymal stem cells (MSC) as co-infusion at the time of CBT had a negative effect on TREC reconstitution. This was found to be associated with decreased overall survival for this patient category. Reduced IgM and IgG levels post-CBT were associated with a major AB0 mismatch, and infusion of MSCs. Our results highlight the importance of close monitoring of the immune reconstitution after CBT. In addition it shows a potentially new suppressive effect of MSCs on the immune system.

Does high-resolution donor typing of HLA-C or other loci upon registration confer advantages to patients?

Our study compared all requests for confirmatory typing (CT requests) received in our center between May 2007 and December 2009 (n = 134) for donors issued from 3 groups defined by different human leukocyte antigen (HLA) loci typed at different levels of resolution. We observed a significant advantage for volunteers when HLA-C 2-digit typing was available or with HLA-A, -B, -C, -DRB1 4-digit typing compared with generic HLA-A, -B, -DRB1, -DQB1 DNA typing: increased percentage of CT requests (p < 0.001), increased rate of donor selection for donation (p < 0.001), and decreased time frame for donor search (p = 0.025). The time frame for a successful search (donation) is similar among the 3 groups, indicating that the search might be concluded more rapidly when the pathology is clinically active or when the patient is at a high risk of relapse (76% of our cases) or for pediatric patients (24% of our cases), regardless of HLA typing resolution. Improvement of HLA typing for volunteers could be a great advantage for first selection in the absence of emergency or high-risk disease. Knowledge of HLA-C should be used to prioritize the selection of donors for further testing and could allow a better donor selection process, reducing search duration and increasing efficiency. In most cases, 2-digit typing for HLA-C associated with specific tools to estimate the probability of finding a matched donor could be sufficient.

Improved survival after allogeneic hematopoietic stem cell transplantation in recent years. A single-center study

We analyzed the outcome of allogeneic hematopoietic stem cell transplantation (HSCT) over the past 2 decades. Between 1992 and 2009, 953 patients were treated with HSCT, mainly for a hematologic malignancy. They were divided according to 4 different time periods of treatment: 1992 to 1995, 1996 to 2000, 2001 to 2005, and 2006 to 2009. Over the years, many factors have changed considerably regarding patient age, diagnosis, disease stage, type of donor, stem cell source, genomic HLA typing, cell dose, type of conditioning, treatment of infections, use of granulocyte-colony stimulating factor (G-CSF), use of mesenchymal stem cells, use of cytotoxic T cells, and home care. When we compared the last period (2006-2009) with earlier periods, we found slower neutrophil engraftment, a higher incidence of acute graft-versus-host disease (aGVHD) of grades II-IV, and less chronic GVHD (cGHVD). The incidence of relapse was unchanged over the 4 periods (22%-25%). Overall survival (OS) and transplant-related mortality (TRM) improved significantly in the more recent periods, with the best results during the last period (2006-2009) and a 100-day TRM of 5.5%. This improvement was also apparent in a multivariate analysis. When correcting for differences between the 4 groups, the hazard ratio for mortality in the last period was 0.59 (95% confidence interval [CI]: 0.44-0.79; P < .001) and for TRM it was 0.63 (CI: 0.43-0.92; P = .02). This study shows that the combined efforts to improve outcome after HSCT have been very effective. Even though we now treat older patients with more advanced disease and use more alternative HLA nonidentical donors, OS and TRM have improved. The problem of relapse still has to be remedied. Thus, several different developments together have resulted in significantly lower TRM and improved survival after HSCT over the last few years.

Evaluation of DRB1 high resolution typing by a new SSO-based Luminex method

HLA testing is an essential part of the process to identify a donor who may be a good match for the patients who need haematopoietic stem cells from bone marrow, peripheral blood or cord blood and the DNA typing in high resolution is now recommended as the Scientific Societies also describe in their standards. Recently the new PCR-Luminex HLA typing method, based on the reverse sequence specific oligonucleotide probes coupled with a microsphere beads in an array platform, has been well established. We report the data from 146 samples previously typed to a four digits level and used to evaluate the accuracy, sensitivity and performance of the new high definition DRB1 by PCR-Luminex kit. One hundred and forty-six samples from unrelated healthy donors, haematological patients or external proficiency tests were used in this study. The Luminex high definition DRB1 typing represents a versatile method and may be easily introduced in the routine, particularly when the technical team has already acquired experience on the technique. Only few HLA allelic combinations need an additional typing by PCR-SSP or SBT to solve the ambiguous results thus reducing the time necessary to produce a final report.

Association of functional polymorphisms of the transforming growth factor B1 gene with survival and graft-versus-host disease after unrelated donor hematopoietic stem cell transplantation

BACKGROUND

Many genetic factors play major roles in the outcome of hematopoietic stem cell transplants from unrelated donors. Transforming growth factor beta1 is a member of a highly pleiotrophic family of growth factors involved in the regulation of numerous immunomodulatory processes.

DESIGN AND METHODS

We investigated the impact of single nucleotide polymorphisms at codons 10 and 25 of TGFB1, the gene encoding for transforming growth factor beta1, on outcomes in 427 mye-loablative-conditioned transplanted patients. In addition, transforming growth factor beta1 plasma levels were measured in 263 patients and 327 donors.

RESULTS

Patients homozygous for the single nucleotide polymorphism at codon 10 had increased non-relapse mortality (at 3 years: 46.8% versus 29.4%, P=0.014) and reduced overall survival (at 5 years 29.3% versus 42.2%, P=0.013); the differences remained statistically significant in multivariate analysis. Donor genotype alone had no impact, although multiple single nucleotide polymorphisms within the pair were significantly associated with higher non-relapse mortality (at 3 years: 44% versus 29%, P=0.021) and decreased overall survival (at 5 years: 33.8% versus 41.9%, P=0.033). In the 10/10 HLA matched transplants (n=280), recipients of non-wild type grafts tended to have a higher incidence of acute graft-versus-host disease grades II-IV (P=0.052). In multivariate analysis, when analyzed with patients' genotype, the incidences of both overall and grades II-IV acute graft-versus-host disease were increased (P=0.025 and P=0.009, respectively) in non-wild-type pairs.

CONCLUSIONS

We conclude that increasing numbers of single nucleotide polymorphisms in codon 10 of TGFB1 in patients and donors are associated with a worse outcome following hematopoietic stem cell transplantation from unrelated donors.

Reduced intensity conditioning compared with myeloablative conditioning using unrelated donor transplants in patients with acute myeloid leukemia

PURPOSE

Reduced intensity conditioning regimen (RIC) is increasingly used in hematopoietic stem cell transplantation (HSCT). Unrelated donor (UD) transplants have more complications. We wanted to examine if RIC is a valid treatment option using UD in acute myeloblastic leukemia (AML).

PATIENTS AND METHODS

Between 1999 and 2005, 401 patients with AML were treated with RIC and 1,154 received myeloablative conditioning (MAC), using UD and reported to the European Group for Blood and Marrow Transplantation Registry. Patients < and > or = 50 years of age were analyzed separately.

RESULTS

Patients receiving RIC were older, received transplants more recently, received peripheral blood stem cells more frequently, and were treated with total-body irradiation less often. In multivariable analysis, in patients younger than 50 years of age, nonrelapse mortality (NRM) was similar using RIC (hazard ratio [HR], 0.85; P = .41), relapse was increased (HR, 1.46; P = .02) and leukemia-free survival (LFS) was the same (HR, 0.88; P = .28), as compared with MAC. In patients > or = 50 years of age, NRM was decreased in the RIC group (HR, 0.64; P = .04), relapse probability was not significantly different (HR, 1.34; P = .16) and LFS was similar (HR, 1.04; P = .79) compared with MAC. CONCLUSION RIC-UD transplants are associated with higher relapse in AML patients younger than 50 years of age and decreased NRM in those > or = 50 years compared with MAC-UD. LFS was similar after both conditioning regimens, regardless of age. Therefore, RIC-UD extend the use of allotransplants for elderly patients and strategies that decrease relapse should be considered mainly in younger patients with AML.

Immunogenetic factors in donors and patients that affect the outcome of hematopoietic stem cell transplantation

We have correlated the clinical outcome with the level of HLA matching in 423 patients who received a transplant from a volunteer unrelated donor in the United Kingdom. HLA matching was performed at the allelic level (i.e. high-resolution) using reference strand mediated conformation analysis (RSCA) at HLA-A, -B, -C, -DRB1, -DQB1 and -DPB1. The three-year probability of overall survival (OS) was 45% (median survival of 593 days; six-year overall survival probability was 40%). The mean follow-up was 1013 days (range 89-2697). Those matched for their HLA loci had a significantly better overall survival than the mismatched pairs (47% versus 40%, p=0.040). This result could be refined based on the number of alleles that were mismatched. In patients with a single HLA mismatch, the overall survival was 43%, compared to 30% in those with multiple mismatches; however, there was no statistically significant difference between matched pairs or those with one mismatch. Although there was no significant difference in the overall survival dependent on DPB1 matching in the group overall, in acute lymphocytic leukemia, DPB1-matched pairs had a significantly worse overall survival (log rank; p=0.025). Thus, a match for DPB1 is associated with a significantly increased risk of disease relapse, irrespective of the matching status for the other HLA molecules. In a multivariate analysis, a high pre-transplant levels of Tregs resulted in worse overall survival (relative risk (RR), 2.74; p=0.01), a trend to reduce disease-free survival (RR, 2.05; p=0.060) and to increase disease relapse (RR, 3.36; p=0.006). Residual patient CD4(+)CD25(hi) regulatory T cells may suppress graft-versus-tumour responses, decreasing the overall survival by increasing the rates of relapse. In acute leukemia, the presence of NOD2/CARD15 SNPs in the genotype of unrelated donor hematopoietic stem cell transplant pairs results in significant increases in disease relapse and consequently in death. These data show an important role for NOD2/CARD15 genotyping in transplantation and suggest a possible effect of the NOD2 protein in alloreactivity and tumour surveillance. Genotyping recipients and donors prior to transplant may present valuable information for planning and management of pre-transplant conditioning regimens, and for prognosis of the outcome.

Description of HLA-A*0127N, a novel nonexpressed allele identified by SBT

We describe the isolation and characterization of a novel HLA-A null allele, officially named A*0127N. The A*0127N exon 2, 3, and 4 nucleotide sequence is identical to that of A*010101 except at position 553, where a G is substituted by a T, resulting in a coding change in exon 3 (GAG>TAG) from Glu to the stop codon AMB. The mutation described is responsible for the premature ending of the translation.

The importance of HLA-DPB1 in unrelated donor hematopoietic cell transplantation

Hematopoietic cell transplantation (HCT) from an HLA-A, HLA-B, HLA-C, HLA-DRB1, and HLA-DQB1 allele-matched unrelated donor is a well-recognized life-saving treatment modality for patients with hematologic disorders. The morbidity and mortality from clinically significant acute graft-versus-host disease (aGVHD) remains a limitation. The extent to which transplantation outcome may be improved with donor matching for HLA-DP is not well defined. The risks of aGVHD, relapse, and mortality associated with HLA-DPB1 allele mismatching were determined in 5929 patients who received a myeloablative HCT from an HLA-A-, HLA-B-, HLA-C-, HLA-DRB1-, and HLA-DQB1-matched or -mismatched donor. There was a statistically significantly higher risk of both grades 2 to 4 aGVHD (odds ratio [OR] = 1.33; P < .001) and grades 3 to 4 aGVHD (OR = 1.26; P < .001) after HCT from an HLA-DPB1-mismatched donor compared with a matched donor. The increased risk of aGVHD was accompanied by a statistically significantly decrease in disease relapse (hazard ratio [HR] = 0.82; P = .01). HLA-DPB1 functions as a classical transplantation antigen. The increased risk of GVHD associated with HLA-DPB1 mismatching is accompanied by a lower risk of relapse. Knowledge of the DPB1 matching status prior to transplantation will aid in more precise risk stratification for the individual patient.

Allorecognition of human neural stem cells by peripheral blood lymphocytes despite low expression of MHC molecules: role of TGF-beta in modulating proliferation

Neural stem cells (NSCs) transplantation has been proposed as a means of restoring damaged brain tissue, a possibility rendered more likely by reports of low NSCs immunogenicity in various experimental models because of low expression of MHC class I and II as well as co-stimulatory molecules. We investigated the immunogenicity of a human NSC line grown in normal culture conditions and in the presence of pro-inflammatory cytokines IFN-gamma and tumor necrosis factor alpha by one-way mixed lymphocyte reaction (MLR) experiments with peripheral blood lymphocytes from eight HLA-incompatible donors. NSCs stimulated lymphocyte proliferation in almost all donors tested, with stimulation indices in the range of the low-end distribution curve of MLR between donors. The healthy subject that gave negative MLR results was the best compatible donor with respect to NSC haplotype. Since we observed low MLR responses overall, we studied if NSCs might exert any immunomodulatory activity. We detected transcription and release of the immunomodulatory molecule transforming growth factor beta (TGF-beta)-1; moreover, the addition of TGF-beta1 in MLR experiments down-regulated proliferative responses. To further confirm the immunological potential of human NSCs, we studied xenogeneic recognition of NSCs by immunocompetent cells derived from C57BL/6 mice, showing that NSCs can elicit an allo(xeno) response ex vivo. Our data indicate that NSCs have low but not negligible immunogenic potential that is sufficient to activate peripheral lymphocytes. Secretion of TGF-beta1 might balance the immunogenicity of NSCs. Nevertheless, the possibility that allo-NSCs grafting might induce in the long term an immune activation, thus vanishing their therapeutical effect, should not be overlooked and deserves further investigation.

Long-term outcome of unrelated donor transplantation for AML using myeloablative conditioning incorporating pretransplant Alemtuzumab

The outcome of 55 patients who underwent matched unrelated donor (MUD) transplantation for acute myelogenous leukemia (AML) following a conditioning regimen of cyclophosphamide and total-body irradiation (TBI) with the addition of Alemtuzumab 10 mg/kg/day on days -5 to -1 is described. All patients received graft-versus-host disease (GVHD) prophylaxis with cyclosporine as well as 3 doses of posttransplant methotrexate. Forty-one patients were transplanted in complete remission (CR) (20 in CR1, 20 in CR2, and 1 in CR3), and 14 were not in remission at the time of transplantation as they were refractory to chemotherapy either at induction or at relapse. The group consisted of adult patients with a median age of 37 years. Thirty-five patients were fully matched at HLA-A, -B, -C, and -DRB1. All patients engrafted and there were no cases of graft rejection. Grade II-IV acute GVHD occurred in only 2 patients. Chronic GVHD developed in 30% of patients but was extensive in only 3 cases. The predicted TRM was 11% at day 100 and 26% at 1 year. In multivariate analysis the receipt of an HLA mismatched transplant was associated with a higher transplant-related mortality (TRM) (55% versus 15%). Twelve of the 14 transplant-related deaths were due to infection. The 5-year cumulative incidence of relapse was 36% for the whole group and 28% for patients in CR at transplantation. The 5-year cumulative survival for the whole group was 38% and was 49% for those in remission at transplantation. Seven of the 12 patients transplanted in CR1 with adverse risk cytogenetics remain alive and in remission, and the predicted 5-year overall survival (OS) for this group is 50%. These results support the use of Alemtuzumab for unrelated donor hematopoietic stem cell transplant (HSCT) for poor risk AML in CR1 and for relapsed AML in CR2. The addition of Alemtuzumab is highly effective in preventing both rejection and severe acute and extensive chronic GVHD without an increased relapse risk.

Sequencing-based analysis of the HLA-DPB1 polymorphism in Nu ethnic group of south-west China

In the present study, DNA typing for HLA-DPB1 was performed using polymerase chain reaction-sequencing-based typing method in 72 randomly selected Nu ethnic individuals inhabiting the Yunnan province of south-west China. Among the 12 detected DPB1 alleles, the most frequent was DPB1*1301, with the percentage of 20.83%, followed by DPB1*0501 (19.44%), DPB1*040101 (16.67%) and DPB1*2801 (9.72%). The allele DPB1*1501 was found for the first time in the Chinese population. Neighbour-joining showed that the Nu ethnic minority belonged to East Asian cluster and was most closely related to Lisu, being consistent with the historical records. In addition, the results obtained in this study will also provide useful information on organ transplantation, forensic investigations and disease association studies.

Polymorphism of the DPB1 locus in Hani ethnic group of south-western China

Polymorphism of HLA-DPB1 was revealed with a sequencing-based typing (SBT) method in 47 unrelated healthy individuals from Yunnan Hani ethnic minority. The alleles DPB1*5901 and DPB1*7001 were detected for the first time in Chinese populations. A dendrogram showed that the Hani ethnic group belongs to the southern group of Chinese.

HLA-DPB1 matching status has significant implications for recipients of unrelated donor stem cell transplants

Studies in unrelated donor (UD) hematopoietic stem cell transplantations (HSCT) show an effect of the matching status of HLA-DPB1 on complications. We analyzed 423 UD-HSCT pairs. Most protocols included T-cell depletion (TCD). All pairs had high-resolution tissue typing performed for 6 HLA loci. Two hundred eighty-two pairs were matched at 10 of 10 alleles (29% were DPB1 matched). In 141 HLA-mismatched pairs, 28% were matched for DPB1. In the 10 of 10 matched pairs (n = 282), the 3-year probability of relapse was 61%. This was significantly higher in DPB1-matched pairs (74%) as compared with DPB1-mismatched pairs (56%) (log rank, P = .001). This finding persisted in multivariate analysis. In the group overall (n = 423), relapse was also significantly increased if DPB1 was matched (log rank; P < .001). These results were similar in chronic myeloid leukemia (CML; P < .001) and acute lymphoblastic leukemia (ALL; P = .013). In ALL, DPB1-matched pairs had a significantly worse overall survival (log rank; P = .025). Thus, in recipients of TCD UD-HSCT, a match for DPB1 is associated with a significantly increased risk of disease relapse, irrespective of the matching status for the other HLA molecules. It is possible that this effect is especially apparent following TCD transplantations and invites speculation about the function of DPB1 within the immune system.

Is it appropriate to offer allogeneic hematopoietic stem cell transplantation to patients with primary refractory acute myeloid leukemia?

Although continued advances have been made in the treatment of acute myeloid leukemia (AML), approximately 20-30% of patients will never achieve a remission. For these patients with primary refractory AML, the only curative option remains an allogeneic stem cell transplant. Allogeneic transplantation provides the ability to administer myeloablative doses of chemotherapy or chemoradiotherapy, as well as the advantage of a possible graft-versus-leukemia effect. Difficulty in interpreting the literature is due to selection bias, in particular, the varying definitions of primary refractory disease with respect to the morphological criteria and the number of induction regimen required before being defined as being refractory. Regardless, it is a procedure with high treatment-related mortality and risk of relapse. Most studies demonstrate an event-free survival of 10-20% at 5 years. Predictive factors of outcome include blast cell count in the marrow, karyotype, the number of prior regimen, age, performance status and availability of a related donor. These prognostic factors should be considered prior to offering allogeneic transplantation for primary refractory AML. Those patients with many favorable prognostic factors and an HLA-matched related donor available would be the best candidate for the procedure. Those with many poor prognostic factors and only an unrelated donor available may be better served by being offered palliation or being enrolled in investigational studies.

Identification of HLA-A*0111N: a synonymous substitution, introducing an alternative splice site in exon 3, silenced the expression of an HLA-A allele

A new variant of the HLA-A*010101 allele designated as HLA-A*0111N, previously known as HLA-A*010101var, was identified in a patient requiring a stem-cell transplantation. The patient was typed by serologic methods as HLA-A2 homozygous and by sequence-based typing (SBT) as A*010101,020601. Flow-cytometric (FCM) analysis with 11 human monoclonal antibodies (mAbs) for the A1 molecule confirmed lack of any cell membrane expression of the A*0111N allele. One-dimensional isoelectric focusing (1D-IEF) of total cell lysate from the patient's cells revealed no cell surface and cytoplasmic A1 protein expression, whereas the HLA-A2 molecule was identified by both FCM analysis and 1D-IEF. DNA sequence analysis showed the presence of a synonymous substitution from G to T at position 597 in codon 175. RNA SBT revealed a deletion of 24 bp in exon 3, position 596 through 619, encoding codons 175 through 182 of the HLA-A*0111N allele. The synonymous substitution introduced a new splice site, resulting in an efficient splicing, because no classical A1 protein could be detected in the patient. This alternative splicing prevented the translation into a correct and stable class I molecule expression on the cell surface.

Inferred HLA Haplotype Information for Donors From Hematopoietic Stem Cells Donor Registries

Human leukocyte antigen (HLA) matching remains a key issue in the outcome of transplantation. In hematopoietic stem cell transplantation with unrelated donors, the matching for compatible donors is based on the HLA phenotype information. In familial transplantation, the matching is achieved at the haplotype level because donor and recipient share the block-transmitted major histocompatibility complex region. We present a statistical method based on the HLA haplotype inference to refine the HLA information available in an unrelated situation. We implement a systematic statistical inference of the haplotype combinations at the individual level. It computes the most likely haplotype pair given the phenotype and its probability. The method is validated on 301 phase-known phenotypes from CEPH families (Centre d'Etude du Polymorphisme Humain). The method is further applied to 85,933 HLA-A B DR typed unrelated donors from the French Registry of hematopoietic stem cells donors (France Greffe de Moelle). The average value of prediction probability is 0.761 (SD 0.199) ranging from 0.26 to 1. Correlations between phenotype characteristics and predictions are also given. Homozygosity (OR = 2.08; [2.02-2.14] p <10(-3)) and linkage disequilibrium (p <10(-3)) are the major factors influencing the quality of prediction. Limits and relevance of the method are related to limits of haplotype estimation. Relevance of the method is discussed in the context of HLA matching refinement.

Allogeneic haematopoietic stem cell transplantation in children with acute lymphoblastic leukaemia: the BFM/IBFM/EBMT concepts

Children with high risk or relapsed acute lymphoblastic leukaemia (ALL) can benefit from allogeneic haematopoietic stem cell transplantation (SCT). To reduce transplantation-associated complications, the BFM study group, the IBFM study group and the PD-WP-EBMT initiated a prospective cooperative multicentre trail for paediatric ALL patients with an indication for allogeneic stem cell transplantation. Four-digit high-resolution HLA typing for all nonsibling donors, standardised GvHD prophylaxis and therapy, uniform conditioning regimen and minimum standards for supportive care should reduce not only treatment-related mortality but also ameliorate late effects for young patients. Furthermore, the prospective evaluation aims to assess the role of haematopoietic SCT in comparison to chemotherapy to enable valuable treatment recommendations for further decisions.

HLA-DPB1 allelic frequency of the Lisu ethnic group in the Southwest China and evolutionary relationship of Lisu with other populations

A sequencing-based typing of human leukocyte antigen-DPB1 (HLA-DPB1) gene was carried out in 37 unrelated healthy individuals from the Yunnan Lisu ethnic minority. A total of 12 DPB1 alleles, in which DPB1*1301 (33.3%), DPB1*0402 (16.6%), DPB1*040101 (13.8%), and DPB1*0501 (11.1%) were highly predominant, were found, and allele DPB1*200102 was found for the first time in a Chinese population. A dendrogram constructed by neighbor-joining method showed that the Lisu ethnic group belongs to East Asian cluster.

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

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.

World Marrow Donor Association: international standards for unrelated hematopoietic stem cell donor registries

World Marrow Donor Association standards are aimed at enhancing the quality of unrelated volunteer donor hematopoietic stem cell registries assisting transplant physicians in the international search for unrelated donors for their patients. The standards cover: (1) general organization of registries; (2) donor recruitment; (3) donor characterization; (4) information technology; (5) facilitation of search requests; (6) second/subsequent donations; (7) collection/processing/transport of stem cells; (8) follow-up of patient/donor; and (9) financial/legal responsibilities.

Genotypic inhibitory killer immunoglobulin-like receptor ligand incompatibility enhances the long-term antileukemic effect of unmodified allogeneic hematopoietic stem cell transplantation in patients with myeloid leukemias

It remains controversial whether alloreactive donor-derived natural killer (NK) cells display graft-versus-leukemia reactions after unmodified allogeneic hematopoietic stem cell transplantation (HSCT). The present study evaluated the role of inhibitory killer immunoglobulin-like receptor (KIR) ligand incompatibility using a well-defined and uniform setting of unmodified allogeneic HSCT in 374 patients with myeloid leukemias. The most striking finding was a significant heterogeneity in the 5-year estimates of hematologic leukemic relapse after human leukocyte antigen (HLA)-identical (n = 237; 22%), HLA class I-disparate (n = 89; 18%), and KIR ligand-incompatible transplantations (n = 48; 5%) (P < .04). Multivariate analysis confirmed that the relative relapse risk (RR) was influenced by HLA class I disparity alone (RR 0.49), but was lowest after HLA class I-disparate, KIR ligand-incompatible transplantations (RR 0.24) (P < .008). The primary graft failure rates, however, increased from 0.4% after HLA class I-identical to 2.3% after HLA class I-disparate, and to 6.3% after KIR ligand-incompatible transplantations, respectively (P < .02). Unlike some other reports, no beneficial effect of KIR ligand incompatibility on other major endpoints of allogeneic HSCT (transplantation-related mortality, and overall and event-free survival) was detectable in the present study. In conclusion, unmodified allogeneic HSCT from KIR ligand-incompatible donors provides a superior long-term antileukemic efficacy in patients with myeloid malignancies.

Impact of HLA matching on outcome of hematopoietic stem cell transplantation in children with inherited diseases: a single-center comparative analysis of genoidentical, haploidentical or unrelated donors

SUMMARY

Hematological inherited diseases can be cured by hematopoietic stem cell transplantation (HSCT) from an human leukocyte antigen (HLA)-identical sibling donor (MSD), but the outcome of unrelated donors (URD) or haploidentical donors (HMD) has been a cause of concern. In all, 94 children affected with inherited diseases underwent HSCT at a single center using MSD (group A, n=31), URD (group B, n=23) or HMD (group C, n=40). There was no difference in the rate of engraftment or in the incidence of grades III-IV acute graft-versus-host disease (GVHD) between the groups. Survival rate was 80.6% in group A, 62.5% in group B and 47.5% in group C (P=0.023). In group B, survival rate was 73.7% in the subgroup with zero or one class I mismatch, and 25% in the subgroup with two or more class I mismatches (P=0.04). In group C, survival rate was 83.3% in the 9/10-identical subgroup, 64.3% in the seven or 8/10 subgroup, and 25% in the five or 6/10 subgroup (P=0.0007). Thus, engraftment, incidence of GVHD and survival are similar in recipients of grafts from MSD, URD with 0-1 class I-mismatch, or HMD with at least 7/10 HLA matches. The low success of HSCT using more disparate donors suggests reserving them for patients with very poor prognosis.

Differentiation between African populations is evidenced by the diversity of alleles and haplotypes of HLA class I loci

The allelic and haplotypic diversity of the HLA-A, HLA-B, and HLA-C loci was investigated in 852 subjects from five sub-Saharan populations from Kenya (Nandi and Luo), Mali (Dogon), Uganda, and Zambia. Distributions of genotypes at all loci and in all populations fit Hardy-Weinberg equilibrium expectations. There was not a single allele predominant at any of the loci in these populations, with the exception of A*3002 [allele frequency (AF) = 0.233] in Zambians and Cw*1601 (AF = 0.283) in Malians. This distribution was consistent with balancing selection for all class I loci in all populations, which was evidenced by the homozygosity F statistic that was less than that expected under neutrality. Only in the A locus in Zambians and the C locus in Malians, the AF distribution was very close to neutrality expectations. There were six instances in which there were significant deviations of allele distributions from neutrality in the direction of balancing selection. All allelic lineages from each of the class I loci were found in all the African populations. Several alleles of these loci have intermediate frequencies (AF = 0.020-0.150) and seem to appear only in the African populations. Most of these alleles are widely distributed in the African continent and their origin may predate the separation of linguistic groups. In contrast to native American and other populations, the African populations do not seem to show extensive allelic diversification within lineages, with the exception of the groups of alleles A*02, A*30, B*57, and B*58. The alleles of human leukocyte antigen (HLA)-B are in strong linkage disequilibrium (LD) with alleles of the C locus, and the sets of B/C haplotypes are found in several populations. The associations between A alleles with C-blocks are weaker, and only a few A/B/C haplotypes (A*0201-B*4501-Cw*1601; A*2301-B*1503-Cw*0202; A*7401-B* 1503-Cw*0202; A*2902-B*4201-Cw*1701; A*3001-B*4201-Cw*1701; and A*3601-B*5301-Cw*0401) are found in multiple populations with intermediate frequencies [haplotype frequency (HF) = 0.010-0.100]. The strength of the LD associations between alleles of HLA-A and HLA-B loci and those of HLA-B and HLA-C loci was on average of the same or higher magnitude as those observed in other non-African populations for the same pairs of loci. Comparison of the genetic distances measured by the distribution of alleles at the HLA class I loci in the sub-Saharan populations included in this and other studies indicate that the Luo population from western Kenya has the closest distance with virtually all sub-Saharan population so far studied for HLA-A, a finding consistent with the putative origin of modern humans in East Africa. In all African populations, the genetic distances between each other are greater than those observed between European populations. The remarkable current allelic and haplotypic diversity in the HLA system as well as their variable distribution in different sub-Saharan populations is probably the result of evolutionary forces and environments that have acted on each individual population or in their ancestors. In this regard, the genetic diversity of the HLA system in African populations poses practical challenges for the design of T-cell vaccines and for the transplantation medical community to find HLA-matched unrelated donors for patients in need of an allogeneic transplant.

Which donor should be chosen for hematopoietic stem cell transplantation among unrelated HLA-A, -B, and -DRB1 genomically identical volunteers?

The aim of this study was to identify significant prognostic factors by using unrelated genomically HLA-A, -B and -DRB1-identical donors. Such data could help to choose the best donor. We studied 136 consecutive patients with hematologic malignancies and a median age of 32 years (range, 0-55 years) who received hematopoietic stem cell transplantation. Bone marrow grafts were given to 83 and peripheral blood stem cells to 53 patients. The cumulative incidence of grade II to IV acute graft-versus-host disease (GVHD) was 30% and of chronic GVHD was 54%. At 5 years, the overall transplant-related mortality (TRM) was 34%, and patient survival was 50%. In Cox multivariate analysis, 32 potential risk factors were analyzed. Monoclonal antibody OKT-3 during conditioning was correlated with grade II to IV acute GVHD, chronic GVHD, and TRM. HLA-DP mismatch was associated with poor TRM and poor survival. Cytomegalovirus-seropositive patients with a seronegative donor had a decreased leukemia-free survival. Five-year TRM was 14% with no risk factor, 38% with 1 risk factor, and 87% with 2 risk factors. The 5-year survival was 72%, 48%, and 30% with 0, 1, and 2 risk factors, respectively. We concluded that unrelated hematopoietic stem cell transplantation may be improved if an optimal donor and immunosuppression are chosen.

Allogeneic hematopoietic stem cell transplantation for myelofibrosis

Fifty-six patients, 10 to 66 years of age, with idiopathic myelofibrosis (IMF) or end-stage polycythemia vera or essential thrombocythemia received allogeneic hematopoietic cell transplants from related (n = 36) or unrelated (n = 20) donors. Forty-four patients were prepared with busulfan plus cyclophosphamide and 12 with total body irradiation plus chemotherapy. The source of stem cells was marrow in 33 and peripheral blood in 23 patients. All but 3 patients achieved engraftment. While 50 patients showed complete donor chimerism, 3 patients were found to be mixed chimeras at 26, 48, and 86 months after transplantation, respectively. Two patients died from relapse/progressive disease, and 18 died from other causes. There are 36 patients surviving at 0.5 to 11.6 (median, 2.8) years, for a 3-year Kaplan-Meier estimate of 58% (CI, 43%-73%). Dupriez score, cytogenetic abnormalities, and degree of marrow fibrosis were the most significant risk factors for posttransplantation mortality. Patients conditioned with a regimen of busulfan targeted to plasma levels of 800 to 900 ng/mL plus cyclophosphamide had a higher probability of survival (76% [CI, 62%-91%]) than other patients. Results with unrelated donors were comparable with those with HLA-identical sibling transplants. Thus, allogeneic hematopoietic cell transplantation offers long-term relapse-free survival for patients with myelofibrosis.

HLA-C sequence based typing: nucleotide analysis from exon 1 through exon 8. Identification of a new allele: Cw*0718

At present, 128 HLA-Cw alleles have been described. Twenty-four of 128 display critical polymorphisms in contributing to allele identification outside exons 2 and 3. As a matter of fact, complete resolution of Cw*030201, Cw*030202, Cw*0409N, Cw*0501, Cw*0503, Cw*070101, Cw*070102, Cw*070401, Cw*0706, Cw*0711, Cw*0718, Cw*120201, Cw*120202, Cw*150501, Cw*150502, Cw*1701, Cw*1702, Cw*1703, Cw*1801 and Cw*1802 alleles requires nucleotide analysis of exons 1, 4, 5, 6 and 7. Moreover, some alleles (Cw*04010101, Cw*04010102, Cw*07020101 and Cw*07020102) showing nucleotide differences outside the coding regions of HLA-C gene (intron 2) have been reported. High resolution sequence based typing (SBT) developed in this study involves two DNA amplifications and 12 direct sequencing reactions and allows the analysis of HLA-C polymorphisms from exon 1 through exon 8, including intron 2. This typing procedure identifies all 128 Cw alleles described so far. Nevertheless, a number of ambiguous heterozygous typing results may be expected, this being the major drawback of SBT methods. A total of 201 samples were HLA-C typed using SBT strategy here described. The sequence of exons 6, 7 and 8 of HLA-Cw*070102 allele was elucidated. A novel HLA-Cw*07 allele, Cw*0718, was identified in two samples. Cw*0718 differs from the Cw*070101 allele by a unique nucleotide position within exon 6, resulting in an amino acid substitution at codon 324 (Ala-->Val) in the cytoplasmic region of the molecule.

Maximizing optimal hematopoietic stem cell donor selection from registries of unrelated adult volunteers

Today, more than 50 registries of HLA-typed potential adult hematopoietic stem cell donors have been established in 40 countries and include more than 7.5 million volunteers. HLA testing of new volunteers includes HLA-A, -B and often -DR typing at low to intermediate resolution. Searching patients are tested for these same loci, preferably at a higher level of resolution. Over 95,000 patient searches are received by registries annually resulting in approximately 4660 unrelated transplants. In 2001, nearly one-third of transplants involved a patient in one country receiving stem cells from a donor in another. The diversity of the HLA system complicates the search process, requiring sophisticated registry algorithms for matching, and expertise in allele and haplotype frequencies and associations to design search strategies. Within registries, HLA frequency data have been used to evaluate optimal registry size and composition.