Risk assessment in haematopoietic stem cell transplantation: minor histocompatibility antigens

Allogeneic hematopoietic cell transplantation for patients with AML aged 70 years or older in first remission. A study from the Acute Leukemia Working Party of the European Society for Blood and Marrow Transplantation (EBMT)

Accessibility to allogeneic hematopoietic cell transplantation (HCT) programs for older patients is growing constantly. We report on the clinical outcomes of a group of 701 adults aged ≥70 years, with acute myeloid leukemia (AML) in first complete remission (CR1), who received a first HCT, from HLA-matched sibling donors (MSD), 10/10 HLA-matched unrelated donors (UD), 9/10 HLA-mismatched unrelated donors (mUD) or haploidentical (Haplo) donors. The 2-year overall survival (OS) was 48.1%, leukemia-free survival (LFS) 45.3%, relapse incidence (RI) 25.2%, non-relapse mortality (NRM) 29.5% and GVHD-free, relapse-free survival (GRFS), 33.4%. Compared to MSD, patients transplanted from Haplo and UD presented lower RI (HR 0.46, 95% CI 0.25-0.8, p = 0.02 and HR 0.44, 95% CI: 0.28-0.69, p = 0.001, respectively); this translated into prolonged LFS for Haplo (HR 0.62, 95% CI: 0.39-0.99, p = 0.04). Patients transplanted from mUD exhibited the highest NRM incidence (HR 2.33, 95% CI: 1.26-4.31, p = 0.007). HCT in selected adult CR1 AML patients >70 years is feasible and could be associated with good clinical outcomes. Prospective clinical trials are warranted.

Incidence, risk factors and outcome of extramedullary relapse after allogeneic hematopoietic stem cell transplantation in patients with adult acute lymphoblastic leukemia

Extramedullary relapse (EMR) after allogeneic hematopoietic stem cell transplantation (allo-HSCT) continues to remain a clinical challenge. The data on EMR in acute lymphoblastic leukemia (ALL) are currently limited. Herein, a retrospective analysis of 268 adult ALL patients who underwent allo-HSCT in our center between March 2008 and December 2017 was performed to analyze post-HSCT EMR. Ninety patients (33.58%) experienced relapse; 51(19.03%) experienced bone marrow relapse (BMR), whereas 39 (14.55%) experienced EMR. The 5-year cumulative EMR incidence (CEMRI) revealed that matched sibling donor (MSD)-HSCTs were more likely to develop EMR than unrelated donor (URD)- and haploidentical-related donor (HRD)-HSCTs (CEMRI: 24.02%, 7.69%, and 14.69% for MSD, URD, and HRD, respectively). Notably, MSD-HSCTs (URD vs MSD hazard ratio (HR) = 0.26, p = 0.015; HRD vs MSD HR = 0.46, p = 0.032), history of extramedullary disease (EMD) (HR = 2.45, p = 0.041), and T cell ALL (HR = 2.80, p = 0.012) were independent risk factors for EMR in the multivariate analysis. The median overall survival (OS) for all patients was 15.23 months. However, the OS of EMR patients was significantly longer (19.50 months) than that of BMR patients (12.90 months) (p = 0.003). Multivariate analyses revealed that the leading risk factors for post-relapse deaths were shorter intervals between HSCT and relapse (> 12 months vs ≤ 12 months, HR = 0.30, p < 0.001) and BMR (HR = 0.41, p = 0.002). In conclusion, EMR patients have better survival than BMR patients. ALL patients with allo-HSCT from MSDs, a history of EMD, and the T cell type were significantly associated with EMR.

Refined graft-versus-host disease/relapse-free survival in transplant from HLA-identical related or unrelated donors in acute myeloid leukemia

Refined graft-versus-host disease (GVHD)/relapse-free survival (GRFS) considers main outcomes of allogeneic stem cell transplant (HSCT), estimating long-term survival without significant morbidity as a surrogate of HSCT success. We compared GRFS in 5059 adults with acute myeloid leukemia (AML), undergoing HSCT in first complete remission from 2000 to 2015 either from a matched sibling (MSD, n = 3731) or unrelated donor (MUD, n = 1328). Median age was 49 (range: 18-76) years. Median follow-up was 32 and 60 months in MSD and MUD, respectively (p < 0.01). Compared to MSD, at 4 years, MUD recipients had lower GRFS, with higher NRM, grade III-IV acute GVHD, and extensive chronic GVHD (HR: 1.42, p < 0.01). We also performed a risk factor analyses, showing unfavorable cytogenetics (HR: 1.42, p < 0.01) and peripheral blood as stem cell source (HR: 1.22, p < 0.01) associated to lower GRFS, while this was higher with in vivo T-cell depletion (TCD, HR: 0.73, p < 0.01) and shorter time from diagnosis to HSCT (HR 0.96, p < 0.01). Different factors, modifiable or not, such as donor type, stem cell source, disease biology, and in vivo TCD, impact on GRFS and this may guide in the future transplant choices to improve morbidity and long-term quality of life.

Donor Cell Composition and Reactivity Predict Risk of Acute Graft-versus-Host Disease after Allogeneic Hematopoietic Stem Cell Transplantation

Background. Graft-versus-host disease (GVHD) is a serious complication after allogeneic hematopoietic stem cell transplantation (HSCT). We designed a functional assay for assessment of individual risk for acute GVHD. Study Design and Methods. Blood samples were collected from patients and donors before HSCT. Two groups of seven patients each were selected, one in which individuals developed acute GVHD grades II-IV and one in which none showed any clinical signs of GVHD. Peripheral blood mononuclear cells (PBMCs) isolated from donors were incubated in mixed lymphocyte cultures (MLCs) with recipient PBMCs. The cells were characterized by flow cytometry before and after MLC. Results. Samples from donors in the GVHD group contained significantly lower frequencies of naïve γδ T-cells and T-cells expressing NK-cell markers CD56 and CD94. Donor samples in this group also exhibited lower frequencies of naïve CD95⁺ T-cells compared to controls. After MLC, there were dissimilarities in the CD4/CD8 T-cell ratio and frequency of CD69⁺ T-cells between the two patient groups, with the non-GVHD group showing higher frequencies of CD8⁺ and CD69⁺ T-cells. Conclusion. We conclude that a thorough flow cytometric analysis of donor cells for phenotype and allogeneic reactivity may be of value when assessing pretransplant risk for severe acute GVHD.

[Effects of IL10-592 locus of AA genotype on the incidence of aGVHD and survival after HLA-matched unrelated allogeneic hematopoietic stem cell transplantation]

OBJECTIVE

To explore the impact of IL10-592 (rs1800872) single nucleic acid polymorphism (SNP) on the prognosis of HLA matched unrelated hematopoietic stem cell transplantation (HSCT).

METHODS

The polymorphism of IL10-592 in 104 recipient-donor pairs and 100 healthy volunteers was analyzed with sequence based typing (SBT).

RESULTS

When the genotype of IL10-592 in donors and recipients matched, AA/AA genotype had higher incidence of Ⅲ-Ⅳ aGVHD than AC/AC or CC/CC genotype (47.1%, 3.7%, 0, P=0.002). When the genotype of IL10-592 in donors and recipients mismatched, recipients with AC genotype or donors with AA genotype, there was significant different incidence of Ⅲ-ⅣaGVHD among donors or recipients with different genotype (P=0.046, P=0.041). The recipients with AA genotype had higher incidence of Ⅲ-Ⅳ aGVHD than AC or CC genotype (27.8% vs 10.2%, 11.1%; P=0.072), and higher incidence of intestinal aGVHD (22.2% vs 5.1%,11.1%; P=0.040) , lower incidence of 2-year overall survival (OS: 48.2% vs 75.1%, 85.7%; P=0.002), lower incidence of 2 year disease free survival (DFS: 48.5% vs 66.3%, 76.2%; P=0.045). Patients had higher incidence of Ⅲ-Ⅳ aGVHD with donors of AA genotype than with donors of AC or CC genotype (26.5% vs 8.9%, 0; P= 0.024), and higher incidence of intestinal aGVHD (20.4% vs 4.4%, 0; P=0.026). In multivariate analysis, the genotype of IL10-592AA in recipients and donors had increased risk of Ⅲ-Ⅳ aGVHD (OR=3.3, P= 0.049; OR=3.9, P=0.043). There were no statistical differences on the incidence of cGVHD and relapse.

CONCLUSION

In HLA-10/10 matched unrelated HSCT, the presence of IL10-592 AA genotype in recipients and/or donors is an adverse factor for Ⅲ-ⅣaGVHD, worse OS and 2-year DFS.

HLA mismatching as a strategy to reduce relapse after alternative donor transplantation

Human leukocyte antigen (HLA) mismatches are targets of alloreactive T cells, mediators of graft-versus-leukemia (GvL) and graft-versus-host disease (GvHD) after alternative donor transplantation. Exploitation of HLA mismatching in order to reduce relapse is hampered by necessary interventions aimed at controlling GvHD on the one hand, and by the possibility of immune escape through selective loss of mismatched HLA in relapsing leukemia on the other. Retrospective studies reporting the impact of HLA mismatches on post-transplant relapse need to be interpreted with caution, due to many confounding factors, including disease and use of T-cell depletion, and to be constantly updated to the rapidly changing clinical protocols. Current evidence suggests similar relapse rates for 8/8, 7/8 HLA-matched unrelated, T-cell-replete haploidentical and umbilical cord blood transplantation; however, investigations of locus-specific effects are still scarce in the latter two settings. In unrelated transplantation, a specific role for mismatches at HLA-C and HLA-DPB1, and therein of permissive mismatches defined on the basis of T-cell alloreactivity and/or expression levels, in reducing relapse has been demonstrated in independent studies. This observation suggests new approaches to utilize HLA matching in unrelated donor searches, and the need for further research in the field.

Is there a stronger graft-versus-leukemia effect using HLA-haploidentical donors compared with HLA-identical siblings?

Haploidentical hematopoietic stem cell transplants (HSCTs) are increasingly used, but it is unknown whether they have a stronger graft-versus-leukemia (GVL) effect. We analyzed 10 679 acute leukemia patients who underwent HSCT from an HLA-matched sibling donor (MSD, n=9815) or a haploidentical donor (⩾2 HLA-antigen disparity, n=864) between 2007 and 2012, reported to the European Group for Blood and Marrow Transplantation. In a Cox regression model, acute and chronic graft-versus-host disease (GVHD) was added as time-dependent variables. There was no difference in probability of relapse between recipients of haploidentical and MSD grafts. Factors of importance for relapse after T-cell-replete grafts included remission status at HSCT, Karnofsky score ⩽80, acute GVHD of grade II or higher and chronic GVHD (P<10(-5)). Patients with post-transplant cyclophosphamide (n=194) had similar outcome as other T-cell-replete haploidentical transplants (n=369). Non-relapse mortality was significantly higher in the haploidentical group compared with that in MSD patients (P<10(-5)). Leukemia-free survival was superior in the MSD patients receiving T-cell-replete (P<10(-5)) or T-cell-depleted grafts (P=0.0006). The risk of relapse was the same in acute leukemia patients who received haploidentical donor grafts as in those given MSD transplants, suggesting a similar GVL effect.

High-resolution HLA matching in unrelated donor transplantation in Switzerland: differential impact of class I and class II mismatches may reflect selection of nonimmunogenic or weakly immunogenic DRB1/DQB1 disparities

Unrelated donor searches in Switzerland require high-resolution HLA typing for HLA-A/B/C/DRB1/DRB3,4/DQB1 loci. We evaluated this strategy accepting donors with ⩾9/10 match. Of 802 unrelated donor transplants in 2000-2013, 570 were 10/10 matched, 31 were DRB3/4 mismatched, 261 were single-allele mismatched and 13 had 2 allele mismatches. Of the 261 single-allele disparities, 60 concerned HLA-A/-B, 55 HLA-C and 73 HLA-DRB1/-DQB1 loci. Transplants were reduced intensity conditioning (289, 36%), marrow (187, 23%), EBMT risk score was low in 39, intermediate I in 331, intermediate II in 333 and high in 99 patients. Five-year survival was 48±4%. HLA affected survival in the multivariate model adjusted for risk score. HLA-A/-B and HLA-C mismatches had twice the mortality risks, whereas HLA-DRB1/-DQB1 mismatches were similar to matched transplants. HLA-DRB3/4 mismatches were associated with a nonsignificant increased mortality risk. HLA-DRB3/4 mismatches had higher graft-versus-host disease and transplant-related mortality risks and lower relapse rates compared with matched transplants. We show significant effects of HLA class I, but not HLA class II, mismatches. The lack of impact of DRB1 disparities may be related to the lower immunogenicity of the DRB1*11:01/11:04 and DRB1*14:01/14:54 mismatches, representing 46% of DRB1 incompatibilities. These results support a matching algorithm that prioritizes mismatches considered as more permissive.

Multicenter analyses demonstrate significant clinical effects of minor histocompatibility antigens on GvHD and GvL after HLA-matched related and unrelated hematopoietic stem cell transplantation

The effect of minor H antigen mismatching on the occurrence of graft-versus-host disease (GvHD) and graft-versus-leukemia (GvL) after HLA-matched hematopoietic stem cell transplantation (HSCT) has mainly been demonstrated in single-center studies. Yet, the International Histocompatibility and Immunogenetics Workshops (IHIW) provide a collaborative platform to execute crucial large studies. In collaboration with 20 laboratories of the IHIW, the roles of 10 autosomal and 10 Y chromosome-encoded minor H antigens were investigated on GvHD and relapse incidence in 639 HLA-identical related donor (IRD) and 210 HLA-matched unrelated donor (MUD) HSCT recipients. Donor and recipient DNA samples were genotyped for the minor H antigens HA-1, HA-2, HA-3, HA-8, HB-1, ACC-1, ACC-2, SP110, PANE1, UGT2B17, and HY. The correlations with the primary outcomes GvHD (acute or chronic GvHD), survival, and relapse were statistically analyzed. The results of these multicenter analyses show that none of the HLA class I-restricted HY antigens were found to be associated with any of the primary outcomes. Interestingly, of the HLA class II-restricted HY antigens analyzed, HLA-DQ5 positive recipients showed a significantly increased GvHD-free survival in female-to-male HSCT compared with male-to-female HSCT (P = .013). Yet, analysis of the overall gender effect, thus independent of the known HY antigens, between the gender groups demonstrated an increased GvHD incidence in the female-to-male transplantations (P < .005) and a decreased GvHD-free survival in the female-to-male transplantations (P < .001). Of all autosomally encoded minor H antigens, only mismatching for the broadly expressed minor H antigen HA-8 increased the GvHD incidence in IRD HSCT (Hazard ratio [HR] = 5.28, P < .005), but not in MUD HSCT. Most striking was the influence of hematopoietic restricted minor H antigens on GvL as mismatching for hematopoietic minor H antigens correlated with lower relapse rates (P = .078), higher relapse-free survival (P = .029), and higher overall survival (P = .032) in recipients with GvHD, but not in those without GvHD. In conclusion, the significant GvHD effect of the broadly expressed minor H antigen HA-8 favors matching for HA-8 in IRD, but not in MUD, patient/donor pairs. The GvHD-GvL association demonstrating a significant lower relapse in hematopoietic minor H antigen mismatched patient/donor pairs underlines their clinical applicability for adoptive immunotherapy, enhancing the GvL effect in a GvHD controllable manner.

The potential use of mesenchymal stem cells in hematopoietic stem cell transplantation

In the last 10 years, mesenchymal stem cells (MSCs) have emerged as a therapeutic approach to regenerative medicine, cancer, autoimmune diseases, and many more due to their potential to differentiate into various tissues, to repair damaged tissues and organs, and also for their immunomodulatory properties. Findings in vitro and in vivo have demonstrated immune regulatory function of MSCs and have facilitated their application in clinical trials, such as those of autoimmune diseases and chronic inflammatory diseases. There has been an increasing interest in the role of MSCs in allogeneic hematopoietic stem cell transplantation (HSCT), including hematopoietic stem cell engraftment and the prevention and treatment of graft-versus-host disease (GVHD), and their therapeutic potential has been reported in numerous clinical trials. Although the safety of clinical application of MSCs is established, further modifications to improve their efficacy are required. In this review, we summarize advances in the potential use of MSCs in HSCT. In addition, we discuss their use in clinical trials of the treatment of GVHD following HSCT, the immunomodulatory capacity of MSCs, and their regenerative and therapeutic potential in the field of HSCT.

Impact of HLA-DPB1 haplotypes on outcome of 10/10 matched unrelated hematopoietic stem cell donor transplants depends on MHC-linked microsatellite polymorphisms

Hematopoietic stem cell transplantation (HSCT) with HLA-A, -B, -C, -DRB1, -DQB1 allele matched (10 of 10) unrelated donors is still associated with a significant rate of posttransplantation complications. In order to disclose additional immunogenetic factors, we analyzed the impact of HLA-DPB1 disparities and major histocompatibility complex (MHC)-resident microsatellite polymorphisms in 246 HLA 10 of 10 matched HSCT patients. First we showed that patients with more frequent/conserved HLA haplotypes had a higher 5-year survival (55% ± 18% versus 39% ± 18%, P = .021). In addition, DPB1 incompatibilities and 3 microsatellite alleles were associated with outcome. In a Cox regression model adjusting for European Blood and Marrow Transplant (EBMT) risk score, T cell depletion, and year of treatment, HSCT with a tumor necrosis factor d (TNFd) 4/d5-positive donor was associated with increased mortality (hazard ratio [HR] = 2.03; confidence interval [CI] 1.25-3.31; P = .004), whereas the D6S510-184 allele was protective (HR = 0.44; CI 0.22-0.87; P = .018). The 2 MHC-linked genetic donor factors, DPB1 mismatch (MM), and TNFd4/d5-positivity, acted in synergy with the EBMT risk score with an always lower survival (HR = 2.97; CI 1.27-6.92; P = .012). These data show that multiple MHC-linked genetic donor factors impact on outcome after unrelated donor HSCT. Their additive and potentially divergent effects could explain previous discrepant results, particularly with respect to the role of HLA-DPB1 disparities. We conclude that HLA-DPB1 typing combined with a simple TNFd microsatellite genotyping assay may significantly help in pretransplantation risk assessment for graft-versus-host disease and mortality, particularly for patients with several potential 10 of 10 matched donors.

Immunogenetics of hematopoietic stem cell transplantation: the contribution of microsatellite polymorphism studies

Polymorphisms of short tandem repeats of <10 nucleotides, or microsatellites (Msat), are largely used for post-transplant chimerism analyses in clinical hematopoietic stem cell transplantation (HSCT). Compared to single nucleotide polymorphisms (SNP), they have the advantage of a higher degree of allelic polymorphism and thus a potentially larger degree of informativity. Msat markers contribute to approximately 3% of the human genome and have been highly informative in disease association studies, population genetics, forensic medicine and organ and HSC transplantation. They allowed to expand our knowledge of the haplotypic structure of the HLA complex, including the noncoding sequences in the MHC, and to reach a better characterization of immunological phenotypes. Among the different immunogenetic studies in HSCT patients reviewed here, four Msat loci linked to cytokine genes have been analysed by a number of laboratories as potential candidates markers for HSCT outcome: IFNG, TNFd, IL-10(-1064) and IL-1RN. The low patient numbers and high diversity of clinical parameters account for some heterogeneity of the results. Among the trends starting to emerge from these studies, specific TNFd Msat alleles seem to be associated with acute graft-versus-host disease and mortality. Patient/donor Msat incompatibilities have also been used as surrogate markers to map biologically relevant polymorphisms, with a main focus on MHC-resident genetic variation. High throughput SNP typing and next-generation sequencing technologies will allow acquisition of large-scale genomic data and should allow refined analyses of clinically relevant genotypes in the transplantation settting, although the heterogeneity of the study cohorts will remain an issue. The analysis of Msat polymorphisms may still have a place in functional studies on the impact of Msat diversity in the control of immune response gene expression.

Do FY antigens act as minor histocompatibility antigens in the graft-versus-host disease paradigm after human leukocyte antigen-identical sibling hematopoietic stem cell transplantation?

FY antigens are candidate minor histocompatibility antigens relevant to renal allograft rejection, but no data have been reported about their role in graft-versus-host disease (GVHD) incidence after human leukocyte antigen (HLA)-identical siblings hematopoietic stem cell transplantation (HSCT). The aim of this study was to examine the effect of donor/recipient disparity at FY antigens on the incidence of GVHD in Tunisian patients receiving an HLA-identical HSCT. This work enrolled 105 Tunisian pairs of recipients and their HLA-identical sibling donors of HSCs. FY genotyping was performed with the polymerase chain reaction-sequence-specific primer method and donor/recipient disparity for these antigens was analyzed at two levels: incompatibility and nonidentity. The case-control analyses showed no significant correlation between FY disparity and the incidence of either acute or chronic GVHD. Sample size calculation showed that 572 cases and 1716 controls would be necessary to be able to detect a significant association with 80% power and two-sided type I error level of 5% (α=0.05). The lack of association in the studied cohort may be explained by the low immunogenicity of FY antigens in HSCT context, compared with other antigens such as HA-1 and CD31.

Minor histocompatibility antigens in Tunisians: could platelet endothelial cell adhesion molecule 1 marker be one of them?

Platelet endothelial cell adhesion molecule 1 (PECAM-1/CD31) is one of the human minor histocompatibility antigens that are the main targets of alloreactive T-cells after hematopoietic stem cells or solid organs transplantation. In order to investigate its polymorphism in Tunisians, three single nucleotide polymorphisms (SNPs) (rs668, rs12953 and rs1131012) were selected to perform an allele and haplotype analysis. Hundred-and-forty-two healthy and unrelated subjects were enrolled in this survey. Genomic DNAs were extracted using salting out method. SNP genotyping assays were performed with home-designed sequence-specific primers polymerase chain reaction (SSP-PCR). As a result, molecular analysis showed that PECAM-1 is one of the most polymorphic markers in the Tunisian population because minor allele frequency was 0.3, and minimum haplotype frequency was 0.03. A low linkage disequilibrium (D' = 0.45) between rs12953 and rs1131012 was noticed, although all other loci were in the Hardy-Weinberg equilibrium (minimum P value = 0.07). The frequencies were close to those reported in African-American and Caucasian groups.

Secondary recurrent miscarriage and H-Y immunity

BACKGROUND

Approximately half recurrent miscarriage (RM) cases remain unexplained after standard investigations. Secondary RM (SRM) is, in contrast to primary RM, preceded by a birth, which increases the transfer of fetal cells into the maternal circulation. Mothers of boys are often immunized against male-specific minor histocompatibility (H-Y) antigens, and H-Y immunity can cause graft-versus-host disease after stem-cell transplantation. We proposed the H-Y hypothesis that aberrant H-Y immunity is a causal factor for SRM.

METHODS

This is a critical review of the H-Y hypothesis based on own publications and papers identified by systematic PubMed and EMBASE searches.

RESULTS

SRM is more common after the birth of a boy and the subsequent live birth rate is reduced for SRM patients with a firstborn boy. The male:female ratio of children born prior and subsequent to SRM is 1.49 and 0.76 respectively. Maternal carriage of HLA-class II alleles presenting H-Y antigens to immune cells is associated with a reduced live birth rate and increased risk of obstetric complications in surviving pregnancies in SRM patients with a firstborn boy. In early pregnancy, both antibodies against HLA and H-Y antigens are increased in SRM patients compared with controls. Presence of these antibodies in early pregnancy is associated with a lower live birth rate and a low male:female ratio in subsequent live births, respectively. Births of boys are also associated with subsequent obstetric complications in the background population.

CONCLUSIONS

Epidemiological, immunogenetic and immunological studies support the hypothesis that aberrant maternal H-Y immune responses have a pathogenic role in SRM.

Investigation of the effect of donor platelet endothelial cell adhesion molecule 1 polymorphism on the graft-vs.-host disease occurrence in Tunisian recipients of hematopoietic stem cells

OBJECTIVE

The aim of this study is to examine the effect of donor PECAM-1 alleles and haplotypes for the SNPs L98V, S536N, and R643G on the occurrence of GVHD in Tunisian recipients of HSCs.

DESIGN AND METHODS

This study enrolled 102 patients and their 102 respective HLA-identical sibling donors of HSCs. The PECAM-1 SNPs genotyping assay was performed using sets of sequence specific primers (SSP-PCR).

RESULTS

The single marker association analysis showed that the L98 allele, in a recessive genetic model, may be a potential risk factor only for acute GVHD (p=0.036, OR=2.580, 95% C.I. = 1.053-6.326). However, the haplotype analysis showed a lack of association between donor's PECAM-1 SNPs and GVHD incidence in recipient.

CONCLUSION

The homozygosity state for donor PECAM-1L98 allele may be a significant risk factor for acute GVHD. This is probably due to its action on the function of donor leukocytes especially during the extravasation process.

Concurrent allorecognition has a limited impact on posttransplant vaccination

Transplantation of allogeneic hematopoietic stem cells with or without immunocompetent lymphocytes has proved a successful strategy in the treatment of hematological malignancies. We have recently shown that this approach can also cure mouse prostate cancer, provided that it is combined with tumor-specific vaccination. Whether the response to alloantigens acts by providing helper function to enhance vaccine-specific responses or in other ways impinges on vaccine immunogenicity remains to be clarified, and this question is of clinical relevance. In this study, we have addressed this issue by comparing the immunogenicity of dendritic cells pulsed with a peptide derived from a tumor/viral model Ag in recipients of donor cells either syngeneic to the host or differing for either Y-encoded or multiple minor H antigens. We report that vaccination elicits comparable proliferation and differentiation of peptide-specific CD8(+) T cells despite concurrent expansion and differentiation of minor H antigen-specific IFN-γ effector T cells. Depletion of alloreactive CD4(+) T cells reduced alloreactivity but not vaccine-induced CD8(+) T cell priming, suggesting that alloresponses do not provide helper functions in peripheral lymphoid tissues. Vaccine-mediated T cell priming was also preserved in the case of multiple minor H antigen disparities, prone to graft-versus-host disease. Thus, in the context of nonmyeloablative allotransplantation aimed at restoring an effective tumor-specific T cell repertoire, minor H antigen-specific T cells do not interfere with vaccine-induced T cell priming, supporting the notion that posttransplant vaccination is a valuable strategy to boost tumor and pathogen-specific protective immunity.

Allogeneic transplantation in multiple myeloma

Allogeneic hematopoietic stem cell transplantation in multiple myeloma has been performed since the 1980th, but is still a controversial treatment modality. The aim is to cure the disease and the rational is to eradicate myeloma cells by the dual effect of high dose myeloablative treatment, and the immune reaction against the myeloma cells by the graft (graft versus myeloma =GVM). At the same time the patient is saved from myeloablation by the normal allogeneic donor stem cells. Although outcome has improved with time the transplant related mortality using myeloablation is still high. Therefore reduced intensity non-myelablative conditioning (RIC) has increasingly substituted myeloablation and results have improved. Out of five published or ongoing prospective clinical trials using tandem autologous (ASCT) - RIC-allogeneic transplantation (RIC-allo) compared to tandem or single ASCT the tandem ASCT-RIC-Allo approach was superior. Attempts to improve outcome by adding new drugs ( thalidomide, bortezomib or lenalidomide ) or alternative cell therapies like donor T-cell infusions or NK cell treatment may improve results.

Identification of MHC II-restricted minor histocompatibility antigens after HLA-identical stem-cell transplantation

BACKGROUND

After allogeneic hematopoietic stem-cell transplantation (HSCT), donor-derived T cells may elicit graft-versus-host disease (GVHD) and graft-versus-tumor (GVT) responses. The main targets of GVHD and GVT responses after human leukocyte antigen (HLA)-identical HSCT are minor histocompatibility antigens (mHAgs), that is, polymorphic gene products in which recipient and donor differ. Thus, for increasing beneficial GVT and decreasing life-threatening GVHD responses, knowledge of the relevant mHags is required. Here, we sought to identify mHags recognized by CD4 T cells using a novel serologic approach.

METHODS

To identify candidate mHAgs recognized by CD4 T cells, a cDNA expression library from peripheral blood mononuclear cells of a patient with β-thalassemia major was screened with serum taken at different time points after HLA-identical HSCT.

RESULTS

Immune responses against 18 antigens were identified with serum taken 100 days posttransplantation, when the patients had recovered from acute GVHD II. Except for one, no humoral responses against these antigens were detected 25 days or 1 year after transplantation. Sequence comparison of these antigens between recipient and donor revealed three polymorphisms of which two were contained within epitopes predicted to bind to HLA-DR molecules of the patient. Using cytokine secretion and capture assays, T cells specific for the polymorphic antigens of the recipient, but not the donor, were isolated from peripheral blood monocyte cells after HSCT.

CONCLUSIONS

The serologic approach described here facilitates the rapid identification of mHAgs recognized by CD4 T cells. Furthermore, the correlation of humoral and cellular immune responses with acute GVHD implies a role of these antigens in GVHD pathology.

Acute graft-vs.-host disease correlates with the disparity for the PECAM-1 S536N polymorphism only in the HLA-B44-like positive Tunisian recipients of HSCs

GVHD is the major cause of mortality after HLA-identical HSCT. Such complication has been widely linked to donor/recipient disparity for minor histocompatibility antigens (MiHAgs). PECAM-1 is one of potential human MiHAgs but its effect on the GVHD occurrence remains not clear. In order to examine such association in the Tunisian cohort of HSCs recipients, we performed a retrospective study on patients who undergone HLA-identical HSCT between 2000 and 2009. Genotyping of the three selected PECAM-1 polymorphisms (rs668, rs12953 and rs1131012) was performed with SSP-PCR method. Univariate analyses showed that grades II-IV acute GVHD were considerably linked to the non-identity for rs12953 only in HLA-B44-like positive patients (p=0.010, OR=10.000). Multivariate analysis for chronic GVHD showed that this outcome may be affected only by the adulthood and the conditioning regimen. Our findings support the previously reported data suggesting a significant association between the PECAM-1 disparity and the risk of acute GVHD.

Indoleamine 2,3-dioxygenase in human hematopoietic stem cell transplantation

In recent years tryptophan metabolism and its rate limiting enzyme indoleamine 2,3-dioxygenase (IDO) have attracted increasing attention for their potential to modulate immune responses including the regulation of transplantation tolerance. The focus of this review is to discuss some features of IDO activity which particularly relate to hematopoietic stem cell transplantation (HSCT). HSCT invariably involves the establishment of some degree of a donor-derived immune system in the recipient. Thus, the outstanding feature of tolerance in HSCT is that in this type of transplantation it is not rejection, which causes the most severe problems to HSCT recipients, but the reverse, graft-versus-host (GvH) directed immune responses. We will discuss the peculiar role of IDO activity and accelerated tryptophan metabolism at the interface between immune activation and immune suppression and delineate from theoretical and experimental evidence the potential significance of IDO in mediating tolerance in HSCT. Finally, we will examine therapeutic options for exploitation of IDO activity in the generation of allo-antigen-specific tolerance, i.e. avoiding allo-reactivity while maintaining immunocompetence, in HSCT.

Immunosuppressive cytokine gene polymorphisms and outcome after related and unrelated hematopoietic cell transplantation in a chinese population

Cytokine gene polymorphisms can affect the outcome of allogeneic hematopoietic stem cell transplantation. We analyzed 6 single nucleotide polymorphisms in 3 immunosuppressive cytokine genes, TGFβ1-509(C>T), +869(T>C), TGFβ1 receptor II (TGFβ1RII) +1167(C>T, codon389 AAC/AAT), and IL-10-1082(A>G), -819(T>C), -592(A>C), in a cohort of 138 pairs of recipients and their unrelated donors and a second cohort of 102 pairs of recipients and their HLA-identical sibling donors. TGFβ1-509 T/T genotype in the donors or T allele-positivity in the recipients was associated with a significant protective effect against acute graft-versus-host disease (aGVHD) and grades II-IV aGVHD in the unrelated transplantation cohort. In the combined cohort, multivariate analysis confirmed that donors with the TGFβ1-509 T/T genotype also conferred protection against the risk of aGVHD and grades II-IV aGVHD. In both the unrelated transplantation cohort and the sibling transplantation cohort, the IL-10-819 C/C and -592 C/C genotypes in either recipients or donors were significantly associated with a higher incidence of aGVHD. In the combined cohort, the IL-10 promoter haplotype polymorphisms at positions -1082, -819, and -592 influenced the occurrence of aGVHD and death in remission. Recipients without the A-T-A haplotype or those transplanted from donors without the A-T-A haplotype had a higher incidence of aGVHD than those who were A-T-A homozygotes or heterozygotes. Estimates for death in remission showed a clear advantage for recipients transplanted from donors with the A-T-A haplotype. In multivariate analysis, recipients without the A-T-A IL-10 haplotype had a higher risk of aGVHD (relative risk [RR] = 0.764; 95% confidence interval [CI]: 0.460-1.269; P = .096) and grades II-IV aGVHD (RR = 0.413; 95% CI: 0.245-0.697; P = .001). These results provide the first report of an association between TGFβ1, TGFβ1RII, and IL-10 polymorphic features and outcome of allo-HSCT in a Chinese population, and suggest an interaction between TGFβ1-509 genotypes and IL-10 promoter haplotype polymorphisms at positions -1082, -819, and -592 and the risk of aGVHD.

The impact of anti-HY responses on outcome in current and subsequent pregnancies of patients with recurrent pregnancy losses

Women pregnant with a male fetus often generate cellular and humoral immune responses against male-specific minor histocompatibility (HY) antigens-however, the importance of these responses for pregnancy outcome is unclear. Epidemiologic studies have shown that the birth of a boy compared with a girl prior to a series of miscarriages significantly reduces the chance of a subsequent live birth and pregnancies with boys have an increased risk of placental abruption. This paper aims to review the current knowledge about the impact of anti-HY immunity on pregnancy outcome in terms of miscarriage and placental abruption. Our knowledge primarily comes from studies of the impact on pregnancy outcome of HLA class II alleles known to restrict CD4 T cell mediated anti-HY responses among 358 secondary recurrent miscarriage (SRM) patients and 203 of their children born prior to the miscarriages and investigation of these HLA alleles in 8 patients with recurrent severe placental abruptions. The chance of a subsequent live birth in SRM patients with firstborn boys compared to firstborn girls was significantly lower in women with HY-restricting HLA class II alleles [OR: 0.17 (0.1-0.4), p=0.0001]. Most patients with recurrent placental abruptions had firstborn boys and significantly more of these patients carried HLA haplotypes with HY-restricting class II alleles compared with controls (p=0.009). These findings are strongly indicative of aberrant maternal immune reactions against fetal HY antigens playing a role in recurrent miscarriage and placental abruption. We propose pathogenetic pathways for these conditions that in our view best explain the findings.

Natural-killer cell amplification for adoptive leukemia relapse immunotherapy: comparison of three cytokines, IL-2, IL-15, or IL-7 and impact on NKG2D, KIR2DL1, and KIR2DL2 expression

OBJECTIVE

Natural killer (NK) cells are a lymphocyte subset that, in a hematopoietic stem cell transplantation setting, mediates a graft-vs-leukemia effect without any graft-vs-host disease. We aimed to evaluate an isolation method that can be used with Good Manufacturing Practices-grade reagents and to compare three cytokines for expansion in order to design future clinical protocols based on donor NK-cell infusions to cure relapse after allograft.

MATERIALS AND METHODS

NK cells were enriched using a CD3/CD19 depletion method and expanded for 13 days in the presence of 2, 10, and 50 ng/mL interleukin (IL)-2, IL-15, or IL-7. NK-cell cytotoxicity was evaluated after isolation and culture. Expression of NKG2D, KIR2DL2, and KIR2DL1 was monitored during expansion.

RESULTS

Highly T- and B-cell-depleted NK cells were obtained and enriched 2.6-fold. The optimal cytokine concentration for expansion was 10 ng/mL for IL-2 or 50 ng/mL for IL-15. NK-cell cytotoxicity was significantly improved after an overnight incubation with 10 or 50 ng/mL IL-2 or with 2, 10, or 50 ng/mL IL-15, and after 13 days with 50 ng/mL IL-15. The use of a combination of IL-2 and IL-15 showed no additional benefit and negative results were obtained with IL-7. The three NK cell receptors were significantly upregulated after culture, mainly with IL-2 or IL-15.

CONCLUSION

In our study, 10 ng/mL IL-2 or 50 ng/mL IL-15 were the optimal concentrations for expansion and were equivalent in significantly enhancing cytotoxicity and modifying NK-cell receptor expression patterns.

Does minor histocompatibility antigen HA-1 disparity affect the occurrence of graft-versus-host disease in tunisian recipients of hematopoietic stem cells?

INTRODUCTION

Minor histocompatibility antigen HA-1 (MiHAg-HA-1) disparity between a patient and his or her human leukocyte antigen (HLA) genoidentical donor has been widely associated with an increased risk of graft-versus-host disease following allogeneic hematopoietic stem cell transplantation.

OBJECTIVE

To examine the effect of HA-1 disparity on the incidence of both acute and chronic graft-versus-host disease in Tunisian recipients of hematopoietic stem cells.

METHODS

A total of 60 patients and their 60 respective sibling hematopoietic stem cell donors were enrolled in this study. All patients prophylactically received cyclosporine A and/or methotrexate for graft-versus-host disease. An HA-1 genotyping assay was performed with the SSP-PCR method, and HLA-A*0201- and/or HLA-A*0206-positive samples were identified using the Luminex HLA typing method.

RESULTS

The Luminex HLA typing assay showed that 54 patients were positive for either the HLA-A*0201 or HLA-A*0206 alleles. Among these cases, six pairs were mismatched for MiHAg-HA-1. Both acute and chronic graft-versus-host disease occurred in four mismatched patients (Fisher's p-values were 0.044 and 0.170, respectively). A univariate logistic regression model analysis showed that only acute graft-versus-host disease may be affected by recipient MiHAg-HA-1 disparity (p: 0.041, OR: 6.727), while chronic graft-versus-host disease correlates with both age and recipient/donor sex mismatch (p: 0.014, OR: 8.556 and p: 0.033, OR: 8.664, respectively).

CONCLUSION

Our findings support previously reported data suggesting a significant association between HA-1 disparity and the risk of acute graft-versus-host disease following hematopoietic stem cell transplantation.

Naturally acquired tolerance and sensitization to minor histocompatibility antigens in healthy family members

Bidirectional cell transfer during pregnancy frequently leads to postpartum persistence of allogeneic cells and alloimmune responses in both the mother and in her offspring. The life-long consequences of naturally acquired alloimmune reactivity are probably of importance for the outcome of allogeneic stem cell transplantation. We investigated the presence of CD8(pos) minor histocompatibility (H) antigen-specific cytotoxic T lymphocytes (T(CTL)) and CD8(pos) minor H antigen-specific T regulator cells (T(REG)) in peripheral blood cells obtained from 17 minor H antigen-disparate mother-offspring pairs. Absence of minor H antigen-specific T(REG), as marked by the feasibility to expand T(CTL) from isolated tetramer(pos) populations, was observed in 6 mothers and 1 son. The presence of minor H alloantigen-specific T(REG) was observed in 4 mothers and 5 sons. These T(REG) were detected within isolated tetramer(dim) staining fractions and functioned in a CTLA-4-dependent fashion. Our study indicates that both T(CTL) and T(REG) mediated alloimmunity against minor H antigens may be present in healthy female and male hematopoietic stem cell donors, potentially influencing graft-versus-host reactivity in different ways.

Genetic similarity of chromosome 6 between patients receiving hematopoietic stem cell transplantation and HLA matched sibling donors

BACKGROUND

Matching for HLA genes located on chromosome 6 is required in hematopoietic stem cell transplantation to reduce the incidence of graft-versus-host disease. However, a considerable proportion of patients still suffer from it, obviously due to genetic differences outside the HLA gene region.

DESIGN AND METHODS

We studied the similarity of almost 4,000 single nucleotide polymorphisms on chromosome 6 between patients receiving hematopoietic stem cell transplantation and their HLA-matched sibling donors.

RESULTS

We observed that as a result of routine HLA matching the siblings in fact shared surprisingly long chromosomal fragments with similar single nucleotide polymorphism genotypes--from 11.65 Mb to 134.66 Mb. The number of genes mapped on these shared fragments varied from 402 to 1,302. Considering the whole chromosome 6, the HLA-matched siblings were apparently identical for 65.2-97.8% of the single nucleotide polymorphisms.

CONCLUSIONS

Potentially, genes similar in some transplantation pairs while different in others might have a significant role in determining the outcome after hematopoietic stem cell transplantation.

The graft-versus-leukemia effect using matched unrelated donors is not superior to HLA-identical siblings for hematopoietic stem cell transplantation

Do some patients benefit from an unrelated donor (URD) transplant because of a stronger graft-versus-leukemia (GVL) effect? We analyzed 4099 patients with acute myeloid leukemia (AML), acute lymphoblastic leukemia (ALL), and chronic myeloid leukemia (CML) undergoing a myeloablative allogeneic hematopoietic cell transplantation (HCT) from an URD (8/8 human leukocyte antigen [HLA]-matched, n=941) or HLA-identical sibling donor (n=3158) between 1995 and 2004 reported to the CIBMTR. In the Cox regression model, acute and chronic GVHD were added as time-dependent variables. In multivariate analysis, URD transplant recipients had a higher risk for transplantation-related mortality (TRM; relative risk [RR], 2.76; P< .001) and relapse (RR, 1.50; P< .002) in patients with AML, but not ALL or CML. Chronic GVHD was associated with a lower relapse risk in all diagnoses. Leukemia-free survival (LFS) was decreased in patients with AML without acute GVHD receiving a URD transplant (RR, 2.02; P< .001) but was comparable to those receiving HLA-identical sibling transplants in patients with ALL and CML. In patients without GVHD, multivariate analysis showed similar risk of relapse but decreased LFS for URD transplants for all 3 diagnoses. In conclusion, risk of relapse was the same (ALL, CML) or worse (AML) in URD transplant recipients compared with HLA-identical sibling transplant recipients, suggesting a similar GVL effect.

Separation of graft-vs.-tumor effects from graft-vs.-host disease in allogeneic hematopoietic cell transplantation

Allogeneic hematopoietic cell transplantation (HCT) is an increasingly widely used treatment modality in hematological malignancies. Alloreactivity mediated by donor T cells (and, in some settings, by donor natural killer cells) can produce durable immunologic control or eradication of residual malignancy after allogeneic HCT. However, graft-vs.-tumor (GVT) effects are variably effective and are often accompanied by deleterious alloreactivity against normal host tissue, manifesting as graft-vs.-host disease (GVHD). A major focus of current research in HCT is the separation of beneficial GVT effects from GVHD. Here we review a number of approaches currently under investigation to specifically augment GVT effects, including the identification of minor histocompatibility antigens (mHA), adoptive immunotherapy with tumor-specific or mHA-specific cytotoxic T lymphocytes, vaccination of the donor or recipient to stimulate tumor-specific immunity, and adoptive transfer of natural killer cells. In addition, we review strategies being investigated to specifically suppress GVHD while sparing GVT, including the manipulation and infusion of regulatory T cells, the use of novel pharmacologic and biologic agents, and the use of mesenchymal stem cells. Ultimately, advances in separation of GVT from GVHD will further enhance the potential of allogeneic HCT as a curative treatment for hematological malignancies.

Indications and donor selections for allogeneic stem cell transplantation in children with hematologic malignancies

Allogeneic stem cell transplantation (SCT) is the only curative approach for many patients with advanced or high-risk leukemia. Advances in supportive care and management of graft-versus-host disease have resulted in improvements in outcomes of related and unrelated donor SCT, creating controversies as to which strategy might be the optimal therapy for individual patients. This article discusses the indications and donor selection strategies for SCT in patients with malignant hematologic disease.