Donor HLA-specific Abs: to BMT or not to BMT?

A Single Centre Experience of Effective Desensitization Strategy for Children with High Anti-HLA Donor-Specific Antibodies Undergoing Haploidentical Hematopoietic Stem Cell Transplantation

To assess the incidence of anti-HLA donor-specific antibodies and the effectiveness of desensitization strategy in children who underwent haploidentical HSCT at our hospital. A retrospective review, management and outcomes of children with positive anti-HLA DSA who underwent haploidentical HSCT at our hospital from 2020 to 2022. Three patients with Thalassemia major were treated with 2 cycles of pretransplant immune suppression (PTIS) comprising Fludarabine and Dexamethasone in addition to desensitization. Five out of the 26 children who underwent haploidentical HSCT had positive anti-HLA DSA. Post desensitization, three out of the 5 children engrafted with sustained full donor chimerism, 1 patient developed primary graft rejection, while 1 patient died. It is feasible to desensitize children with high anti-HLA donor specific antibodies undergoing haploidentical HSCT to improve outcomes.

The impact of donor-specific anti-HLA antibody levels on primary poor graft function and graft rejection in rituximab desensitized haploidentical stem cell transplantation

This study investigates the influence of donor-specific anti-HLA antibodies (DSA) levels on primary poor graft function (PGF) and graft rejection (GR) after haploidentical stem cell transplantation (haplo-SCT) with rituximab desensitization. A total of 155 DSA-positive haplo-SCT candidates with mean fluorescence intensity (MFI) between 2000 and 10,000 were enrolled in this prospective clinical trial. Receiver operating characteristic (ROC) curves determined the optimal DSA MFI cutoff for identifying high-risk patients. Patients were categorized into two groups: DSA low-level group (2000 ≤ DSA MFI < 5000, Group A) and high-level group (5000 ≤ DSA MFI ≤ 10,000, Group B). The incidence of primary PGF was 6.5% (2.6%-10.3%), while GR incidence was 0.6% (0.0%-1.9%). Group A had significantly lower primary PGF rates than Group B (2.3% [0.0%-5.7%] vs. 12.9% [4.8%-21.0%], p = 0.017). Only one patient in Group B experienced GR. High DSA levels (5000 ≤ MFI ≤ 10,000) were identified as the sole independent risk factor for primary PGF and GR after haplo-SCT with rituximab desensitization (HR = 7.282, 95% CI 1.517-34.953, p = 0.013). The 4-year cumulative incidence of relapse, non-relapse mortality, disease-free survival, and overall survival were 14.7% (11.6%-17.8%), 16.3% (13.1%-19.4%), 69.0% (65.9%-76.2%), and 70.6% (66.4%-74.8%), respectively. DSA levels have an impact on efficiency of rituximab desensitization, and a DSA MFI threshold is provided for predicting primary PGF and GR.

Successful allogeneic hematopoietic stem cell transplantation in a patient with type I CD36 deficiency: a case study and literature review

BACKGROUND

CD36-deficient individuals may produce anti-CD36 antibodies through antigenic exposure to CD36, in situations including blood transfusions. Therefore, allogeneic hematopoietic stem cell transplantation (HSCT) from CD36-positive donors to CD36-negative patients remains a challenge.

CASE REPORT

A 64-year-old man with acute myeloid leukemia became refractory to platelet transfusions during chemotherapy. Anti-CD36 antibodies without anti-HLA antibodies were detected in serum, and the absence of CD36 expression on platelets and monocytes confirmed type I CD36 deficiency. The patient achieved complete remission, and received maintenance therapy with CD36-negative platelet transfusions. However, he relapsed soon afterward, and thus underwent peripheral blood stem cell transplantation (PBSCT) from a CD36-positive unrelated donor. The anti-CD36 antibody titer had decreased before the transplant, and the PBSCT-course was uneventful. The patient has been well without any complications associated with CD36 status mismatch.

DISCUSSION

The few reports of allogeneic HSCT in patients with CD36 deficiency have suggested that anti-CD36 antibodies could be involved in several post-transplant complications, such as delayed platelet recovery, transfusion refractoriness, and transfusion-related acute lung injury. Our present case confirmed that stem cell transplantation from CD36-positive donors to negative patients is feasible, when it includes careful prior assessment of anti-CD36 antibody titers and interventions to attenuate them.

Results of haploidentical transplant in patients with donor-specific antibodies: a survey on behalf of the Spanish Group of Hematopoietic Transplant and Cell Therapy

Background

Donor-specific antibodies (DSAs) are IgG allo-antibodies against mismatched donor HLA molecules and can cause graft failure (GF) in the setting of haploidentical hematopoietic stem cell transplantation (haplo-HSCT). Our aim was to report the experience of the Spanish Group of Hematopoietic Transplant (GETH-TC) in DSA-positive patients who had undergone haplo-HSCT.

Methods

We conducted a survey of patients who underwent haplo-HSCT in GETH-TC centers between 2012 and 2021. Data were collected on the DSA assay used, monitoring strategy, complement fixation, criteria for desensitization, desensitization strategies and transplant outcomes.

Results

Fifteen centers from the GETH-TC responded to the survey. During the study period, 1,454 patients underwent haplo-HSCT. Seventy of the transplants were performed in 69 DSA-positive patients, all of whom lacked a suitable alternative donor; 61 (88%) patients were female (90% with prior pregnancies). All patients received post-transplant cyclophosphamide-based graft-versus-host disease prophylaxis. Regarding baseline DSA intensity, 46 (67%) patients presented mean fluorescence intensity (MFI) >5,000, including 21 (30%) with MFI >10,000 and three (4%) with MFI >20,000. Six patients did not receive desensitization treatment, four of them with MFI <5,000. Of 63 patients receiving desensitization treatment, 48 (76%) were tested after desensitization therapy, and a reduction in intensity was confirmed in 45 (71%). Three patients (5%) experienced an increase in MFI after desensitization, two of whom experienced primary GF. Cumulative incidence of neutrophil engraftment at day 28 was 74% in a median of 18 days (IQR, 15─20); six patients died before engraftment due to toxicity or infection and eight patients had primary GF despite desensitization in seven of them. After a median follow-up of 30 months, two-year overall and event-free survival were 46.5% and 39%, respectively. The two-year cumulative incidence of relapse was 16% and non-relapse mortality (NRM) was 43%. Infection was the most frequent cause of NRM, followed by endothelial toxicity. Multivariate analysis identified baseline MFI >20,000 as an independent risk factor for survival and an increase in titers after infusion as an independent risk factor for GF.

Conclusions

Haplo-HSCT is feasible in DSA-positive patients, with high rates of engraftment after desensitization guided by DSA intensity. Baseline MFI >20,000 and increased intensity after infusion are risk factors for survival and GF.

Donor-specific HLA antibodies are associated with graft failure and delayed hematologic recovery after unrelated donor hematopoietic cell transplantation

BACKGROUND

Graft failure (GF) is one of the major concerns after allogeneic hematopoietic cell transplantation (allo-HCT) and remains a significant cause of morbidity and mortality. Although earlier reports have associated the presence of donor-specific HLA antibodies (DSAs) with increased risk of GF after unrelated donor allo-HCT, recent studies have failed to confirm this association.

OBJECTIVE

We sought to validate the presence of DSAs as a risk factor for GF and hematologic recovery in the unrelated donor allo-HCT setting.

STUDY DESIGN

We retrospectively evaluated 303 consecutive patients who underwent their first unrelated donor allo-HCT at our institution from January 2008 to December 2017. DSA evaluation was performed using 2 Single Antigen Beads (SAB) assays, DSA titration with 1:2, 1:8, and 1:32 dilutions, C1q-binding assay, and absorption/elution protocol to assess possible false-positive DSA reactivity. The primary endpoints were neutrophil and platelet recovery and GF, whereas the secondary endpoint was overall survival. Multivariable analyses were performed using Fine-Gray competing risks regression or Cox proportional hazards regression models.

RESULTS

The median patient age was 14 years (range, 0-61 years), 56.1% were male, and 52.5% were transplanted for nonmalignant diseases. Eleven patients (3.63%) were DSA-positive. Of them, 10 had preexisting DSAs, and one showed post-transplant de novo DSA. Nine patients had 1 DSA, 1 had 2 DSAs, and 1 had 3 DSAs, with a median MFI of 4334 (range, 588-20,456) and 3581 (range, 227-12,266) in LABScreen and LIFECODES SAB assays, respectively. Overall, 21 patients experienced GF. Of them, 12 had primary graft rejection, 8 had secondary graft rejection, and 1 had primary poor graft function. The cumulative incidences of GF at 28, 100, and 365 days were 4.0% (95% CI, 2.2%-6.6%), 6.6% (95% CI, 4.2%-9.8%), and 6.9% (95% CI, 4.4%-10.2%), respectively. In the multivariable analyses, DSA-positive patients had significantly delayed neutrophil (subdistribution hazard ratio [SHR] = 0.48; 95% CI, 0.29-0.81; P = .006) and platelet recovery (SHR = 0.51; 95% CI, 0.35-0.74; P = .0003) than patients without DSAs. In addition, only DSAs were significant predictors of primary GF at 28 days (SHR = 2.78; 95% CI, 1.65-4.68; P = .0001). The Fine-Gray regression also demonstrated that the presence of DSAs was strongly associated with a higher incidence of overall GF (SHR = 7.60; 95%CI, 2.61-22.14; P = .0002). DSA-positive patients with GF had significantly higher median MFI values than DSA-positive patients who achieved engraftment in LIFECODES SAB assay using neat serum (10,334 vs. 1250; P = .006) and in LABScreen SAB at 1:32 dilution (1627 vs. 61; P = .006). All 3 patients with C1q-positive DSAs failed to engraft. DSAs were not predictive of inferior survival (hazard ratio = 0.50; 95% CI, 0.20-1.26, P = .14).

CONCLUSIONS

Our results validate the presence of DSAs as a significant risk factor for GF and poor hematologic recovery after unrelated donor allo-HCT. Thus, careful pre-transplant DSA evaluation may optimize unrelated donor selection and improve allo-HCT outcomes.

Case report: Daratumumab treatment in pre-transplant alloimmunization and severe hemolytic anemia

Daratumumab, a CD38 monoclonal antibody that has been FDA-approved to treat multiple myeloma, has acquired popularity and is used off-label for both auto- and alloantibody mediated disorders, particularly in refractory/resistant circumstances. Much of the published data for its use in pediatric blood disorders has been in post-transplant autoimmune cytopenias. Here we describe three patients in whom daratumumab was used outside of post-transplant autoimmune cytopenias, highlighting further potential uses of this medication.

Antigen-guided depletion of anti-HLA antibody-producing cells by HLA-Fc fusion proteins

Platelet transfusion and transplantation of allogeneic stem cells and solid organs are life-saving therapies. Unwanted alloantibodies to nonself human leukocyte antigens (HLAs) on donor cells increase the immunological barrier to these therapies and are important causes of platelet transfusion refractoriness and graft rejection. Although the specificities of anti-HLA antibodies can be determined at the allelic level, traditional treatments for antibody-mediated rejection nonselectively suppress humoral immunity and are not universally successful. We designed HLA-Fc fusion proteins with a bivalent targeting module derived from extracellular domains of HLA and an Fc effector module from mouse IgG2a. We found that HLA-Fc with A2 (A2Fc) and B7 (B7Fc) antigens lowered HLA-A2- and HLA-B7-specific reactivities, respectively, in sera from HLA-sensitized patients. A2Fc and B7Fc bound to B-cell hybridomas bearing surface immunoglobulins with cognate specificities and triggered antigen-specific and Fc-dependent cytotoxicity in vitro. In immunodeficient mice carrying HLA-A2-specific hybridoma cells, A2Fc treatment lowered circulating anti-HLA-A2 levels, abolished the outgrowth of hybridoma cells, and prolonged survival compared with control groups. In an in vivo anti-HLA-A2-mediated platelet transfusion refractoriness model, A2Fc treatment mitigated refractoriness. These results support HLA-Fc being a novel strategy for antigen-specific humoral suppression to improve transfusion and transplantation outcomes. With the long-term goal of targeting HLA-specific memory B cells for desensitization, further studies of HLA-Fc's efficacy in immune-competent animal models are warranted.

Current donor selection strategies for allogeneic hematopoietic cell transplantation

Since the first allogeneic hematopoietic stem cell transplantation (HCT) was performed by Dr. E. Donnall Thomas in 1957, the field has advanced with new stem cell sources, immune suppressive regimens, and transplant protocols. Stem cells may be collected from bone marrow, peripheral or cord blood from an identical twin, a sibling, or a related or unrelated donor, which can be human leukocyte antigen (HLA) matched, mismatched, or haploidentical. Although HLA matching is one of the most important criteria for successful allogeneic HCT (allo-HCT) to minimize graft vs host disease (GVHD), prevent relapse, and improve overall survival, the novel immunosuppressive protocols for GVHD prophylaxis offered improved outcomes in haploidentical HCT (haplo-HCT), expanding donor availability for the majority of HCT candidates. These immunosuppressive protocols are currently being tested with the HLA-matched and mismatched donors to improve HCT outcomes further. In addition, fine-tuning the DPB1 mismatching and discovering the B leader genotype and mismatching may offer further optimization of donor selection and transplant outcomes. While the decision about a donor type largely depends on the patient's characteristics, disease status, and the transplant protocols utilized by an individual transplant center, there are general approaches to donor selection dictated by donor-recipient histocompatibility and the urgency for HCT. This review highlights recent advances in understanding critical factors in donor selection strategies for allo-HCT. It uses clinical vignettes to demonstrate the importance of making timely decisions for HCT candidates.

Donor specific HLA antibody in hematopoietic stem cell transplantation: Implications for donor selection

Advances in hematopoietic stem cell transplant (HSCT) have led to changes in the approach to donor selection. Many of these new approaches result in greater HLA loci mismatching, either through the selection of haploidentical donors or permissive HLA mismatches. Although these approaches increase the potential of transplant for many patients by expanding the number of acceptable donor HLA genotypes, they add the potential barrier of donor-specific HLA antibodies (DSA). DSA presents a unique challenge in HSCT, as it can limit engraftment and lead to graft failure. However, transient reduction of HLA antibodies through desensitization treatments can limit the risk of graft failure and facilitate engraftment. Thus, the consideration of DSA in donor selection and the management of DSA prior to transplant are playing an increasingly important role in HSCT. In this review, we will discuss studies addressing the role of HLA antibodies in HSCT, the reported impact of desensitization on DSA levels, and the implications for selecting donors for patients with DSA. We found that there is a clear consensus that moderate strength DSA should be avoided, while desensitization strategies are reported to be effective in most cases at reducing DSA to amenable levels. There is limited information regarding the impact of specific characteristics of DSA, such as HLA loci or overall level of sensitization, which could further aid in donor selection for sensitized HSCT candidates.

Successful desensitization of high level donor-specific anti-HLA antibody in patients with hematological diseases receiving haploidentical allografts

Donor-specific anti-human leukocyte antigen (HLA) antibody (DSA) is associated with a higher incidence of graft failure and mortality in HLA-mismatched allograft settings. However, the optimal protocol of desensitization for patients with positive DSA remains uncertain. We investigated the effectiveness of a desensitization protocol, including rituximab, high-dose intravenous immunoglobulin (IVIG), and a single session of plasma exchange (PE), for haploidentical allograft recipients with a high mean fluorescence intensity (MFI) level of DSA (≥ 5,000). Eleven patients with hematological disease who had positive DSA (median, 11,676, range 5387-20,435) were desensitized by the protocol. All of the patients achieved hematopoietic recovery. The median times for neutrophil and platelet engraftment were 13 (range, 11-26) days and 19 (range, 11-90) days, respectively. Grade II-IV acute graft-versus-host disease (GVHD) was seen in one patient and was controlled completely. Chronic cutaneous GVHD was seen in eight patients. Nine patients are alive with good performance so far. One patient suffered extramedullary relapse, and one patient died of transplantation-associated thrombotic microangiopathy. The 1-year probability of overall survival was 81.8%. These results suggest that successful desensitization could be obtained by a combination of rituximab, high-dose IVIG, and PE for haploidentical allograft recipients with high MFI levels of DSA.

The impact of HLA donor-specific antibodies on engraftment and the evolving desensitization strategies

The majority of contemporary allogeneic hematopoietic stem cell transplantation (HCT) procedures utilize partially HLA-mismatched stem cell grafts. Donor-specific anti-HLA antibodies (DSA) are associated with primary graft failure independent of the graft source, conditioning intensity and other patient and donor factors. Here we provide an update on testing and monitoring of DSA, review the impact of DSA on stem cell engraftment, and present promising desensitization modalities. Ultimately, we attempt to provide practical recommendations for DSA screening and mitigation strategies.

Treatment of allosensitized patients receiving allogeneic transplantation

Treatment with PE, rituximab, IVIg, and donor buffy coat is effective in promoting engraftment in patients with DSA <20 000 MFI.

Patients with persistent positive C1q at transplant have a higher risk of engraftment failure and poor survival.

Donor-specific anti-HLA antibodies (DSAs) are a major cause of engraftment failure in patients receiving haploidentical stem cell transplantation (HaploSCT). Effective treatments are needed for these patients, who often have no other donor options and/or are in need to proceed urgently to transplantation. We studied a multimodality treatment with alternate-day plasma exchange (PE), rituximab, intravenous γ globulin (IVIg) and an irradiated donor buffy coat for patients with DSAs at 2 institutions. Thirty-seven patients with a median age of 51 years were treated with this desensitization protocol. Treatment outcomes were compared with a control group of HaploSCT patients without DSAs (n = 345). The majority of patients in the DSA group were female (83.8% vs 37.1% in controls, P < .001) and received stem cells from a child as the donor (67.6% vs 44.1%, P = .002). Mean DSA level before and after desensitization was 10 198 and 5937 mean fluorescence intensity (MFI), respectively, with mean differences of 4030 MFI. Fourteen of 30 tested patients (46.7%) had C1q positivity, while 8 of 29 tested patients (27.6%) remained positive after desensitization. In multivariable analysis, patients with initial DSA > 20 000 MFI and persistent positive C1q after desensitization had a significantly lower engraftment rate, which resulted in significantly higher non-relapse mortality and worse overall survival (OS) than controls, whereas graft outcome and survival of patients with initial DSA < 20 000 MFI and those with negative C1q after treatment were comparable with controls. In conclusion, treatment with PE, rituximab, IVIg, and donor buffy coat is effective in promoting engraftment in patients with DSAs ≤20 000 MFI.

Management of Donor-Specific Antibodies in Haploidentical Transplant: Multicenter Experience From the Madrid Group of Hematopoietic Transplant

Background

Donor specific antibodies (DSAs) can be responsible for graft failure (GF) in the setting of mismatched hematopoietic stem cell transplantation (HSCT). The aim of our study is to report the experience of the Madrid Group of Hematopoietic Transplant (GMTH) in patients with DSAs undergoing haplo-HSCT.

Methods

Patients undergoing haplo-HSCT in centers from the GMTH from 2012 to 2020 were included in the study. DSAs were analyzed with a solid-phase single-antigen immunoassay; monitoring was performed during desensitization on days -14, -7, 0 and in a weekly basis until neutrophil engraftment. Desensitization strategies varied depending on center experience, immunofluorescence intensity, complement fixation and type of antibodies.

Results

We identified a total of 20 haplo-HSCT in 19 patients performed with DSAs in 5 centers. 10 (53%) patients presented anti-HLA class I DSAs (6 of them with > 5000 mean fluorescence intensity (MFI)), 4 (21%) presented anti-HLA class II (1 with > 5000 MFI) and 5 (26%) presented both anti-HLA class I and II (5 with > 5000 MFI). 90% of patients received at least two treatments as desensitization strategy and all experienced a decrease of MFI after desensitization (mean reduction 74%). Only one patient who developed progressive increase of MFI after infusion developed GF. Desensitization treatments used included rituximab, immunoglobulins, therapeutic plasma exchange, incompatible platelets, buffy coat and immunosuppressors. Seventeen (90%) patients achieved neutrophil engraftment; one patient died before engraftment because of infection and one patient with class I DSAs developed primary GF despite an intensive desensitization. After a median follow-up of 10 months, OS and EFS were 60% and 58%, respectively, cumulative incidence of relapse was 5% and NRM was 32%.

Conclusions

Despite the optimal strategy of DSAs desensitization remains unclear, the use of desensitization treatment guided by DSAs intensity kinetics constitute an effective approach with high rates of engraftment for patients with DSAs in need for an haplo-HSCT lacking an alternative suitable donor.

The impact of donor-specific anti-human leukocyte antigen antibodies in salvage haploidentical hematopoietic cell transplantation with posttransplant cyclophosphamide in patients with nonmalignant disorders

The presence of donor-specific anti-human leukocyte antigen (HLA) antibodies (DSAs) has been recognized as a major risk factor for graft failure (GF) after haploidentical hematopoietic cell transplantation with posttransplant cyclophosphamide (haplo-PTCy). However, the role of DSAs in salvage haplo-PTCy for rescuing patients with nonmalignant disorders (NMDs) has not yet been reported. The present study retrospectively analyzed 22 patients with NMDs who underwent salvage haplo-PTCy from January 2008 to December 2017. The median age at the time of the rescue haplo-PTCy was 9 years (range, 1-26 years). Median time from the first transplant to second haplo-PTCy was 56 days (range, 37-591 days). Among all patients, six (27.3%) had DSAs, with a median DSA strength (mean fluorescence intensity [MFI]) of 5201 (range, 1412-11,543) in the first DSA testing. In addition, the median DSA MFI was 2672 (range, 832-10,498) before the bone marrow infusion. Overall, GF occurred in 5 (25%) of the 20 assessable patients. Three of four (75%) patients with DSAs experienced GF versus 2 of 16 (12.5%) DSA-negative patients (P = 0.032). The median DSA MFI for patients with GF was 6437 (range, 1412-10,498) versus 1845 (range, 832-2672) for those who engrafted or had early death (P = 0.030). One-year event-free survival was significantly lower in DSA-positive patients than in those without DSAs (16.7% vs. 62.5%, P = 0.002). DSA-negative patients had an acceptable 1-year survival of 62.5%. In conclusion, this study suggests that DSAs may be associated with deleterious outcomes after salvage haplo-PTCy in patients with NMDs.

Rebound and overshoot of donor-specific antibodies to human leukocyte antigens (HLA) during desensitization with plasma exchanges in hematopoietic progenitor cell transplantation: A case report

BACKGROUND

Donor-specific antibodies (DSA) to HLA have been associated with graft loss in hematopoietic progenitor cell (HPC) transplantation. Limited data associate therapeutic plasma exchange (TPE) with desensitization and successful engraftment. We report an attempt of desensitization and observed overshooting of DSA during transplantation.

CASE REPORT AND RESULTS

A 27-year-old female with cutaneous T cell lymphoma was scheduled for HPC transplantation from her HLA-haploidentical half-sister, who carried the HLA-DRB1*13:03:01 allele. The patient had the corresponding DSA. Lacking an alternative donor option at the time, we attempted a desensitization approach by immunosuppression with tacrolimus and mycophenolate mofetil (MMF). Unexpectedly, DSA increased from a mean fluorescence intensity (MFI) of 1835 on day -63 to 9008 on day -7. The MFI increased further during 3 TPE procedures and intravenous immunoglobulin (IVIG) until day -1. After transplantation, the DSA remained elevated despite 2 more TPE/IVIG procedures and graft-versus-host disease prophylaxis with high-dose cyclophosphamide, sirolimus, and MMF. Flow cytometric crossmatch, initially negative, turned positive after transplantation. Primary graft failure occurred and was attributed to antibody-mediated rejection. A second transplantation from a 7/8 HLA-matched unrelated donor, not carrying DRB1*13:03 allele, resulted in successful engraftment.

CONCLUSION

Unexpected and rapid increases of a DSA can occur despite the use of current desensitization approaches. This is problematic when conditioning has already started, as such increases are unlikely to be overcome by TPE or other interventions for desensitization. Overshoot of DSA in HPC transplantation has rarely been reported. Its cause remains unclear and can include underlying disease, immunotherapy, chemotherapy, or TPE.

Correlation analysis between virtual and Complement-Dependent-Cytotoxicity crossmatch in a monocenter retrospective series of 118 allografted patients

PURPOSE OF THE STUDY

The detection of patients' anti-HLA antibodies before allogeneic hematopoietic stem cell transplantation (HSCT) may affect post-transplant outcome, due to a potential detrimental impact on engraftment or toxicity-related issues. Crossmatch (XM) techniques provide support to physicians during the pre-transplant phase but the role of Complement-Dependent Cytotoxicity XM (CDC-XM) is not well-defined when performed routinely and in parallel with the virtual XM.

PATIENTS AND METHODS

We report here our experience with both virtual and CDC-XM tests on n = 118 patients undergoing search for a donor other than HLA-identical sibling from July 2013 to June 2018 at our Institution. When anti-HLA antibodies (Abs) were present, they were classified as donor-specific Abs (DSA) or non-DSA.

RESULTS

On the n = 118 patients, n = 35 (29.7 %) had a positive virtual XM test (of which one of more DSA were found in n = 8; 6.8 %) and n = 5 had a positive CDC-XM test. These latter, positive for HLA class II only, were interpreted as false-positive results due to prior administration of anti-CD20 to the patients, all affected by lymphoma; none of them had a positive virtual XM for anti-HLA Abs of class II. Importantly, all these patients successfully engrafted, further supporting the lack of significant impact of CDC-XM positive results in this series.

CONCLUSIONS

According to our data on more than a hundred patients, routinely performed CDC-XM does not seem to add significant information with respect to virtual XM. We cannot exclude the usefulness of CDC-XM in specific situations, although a positive CDC-XM result was an unfrequent event.

Successful Salvage Therapy by Second Haploidentical Allogeneic Hematopoietic Stem Cell Transplantation in a Severe Aplastic Anemia Patient Presenting Donor-Specific Anti-HLA Antibodies After Graft Failure From Matched Sibling Donor HSCT: A Case Report and Review

BACKGROUND

Hematopoietic stem cell transplantation (HSCT) is potentially curative for severe aplastic anemia (SAA). Graft failure (GF) remains a life-threatening complication after HSCT. Preexisting anti-HLA antibodies, especially HLA-specific antibodies (DSA), have been demonstrated as a risk of GF.

CASE PRESENTATION

This report describes a woman with acquired SAA who presented with anti-HLA antibodies and GF. After the treatment of anti-HLA antibodies, engraftment was achieved through a second alternative donor HSCT. This work complied with the Declaration of Helsinki and the Declaration of Istanbul.

CONCLUSIONS

Based on our experience in treating this case, we hold that the presence of preoperative anti-HLA antibodies could discount the efficacy of HSCT and anti-HLA antibody screening should be performed before HSCT. Additionally, a second HSCT is feasible to prolong survival.

Impaired Hematopoiesis after Allogeneic Hematopoietic Stem Cell Transplantation: Its Pathogenesis and Potential Treatments

Impaired hematopoiesis is a serious complication after allogeneic hematopoietic stem cell transplantation (allo-HSCT). Bone marrow aplasia and peripheral cytopenias arise from primary and secondary graft failure or primary and secondary poor graft function. Chimerism analysis is useful to discriminate these conditions. By determining the pathogenesis of impaired hematopoiesis, a timely and appropriate treatment can be performed. Hematopoietic system principally consists of hematopoietic stem cells and bone marrow microenvironment termed niches. Abnormality in hematopoietic stem and progenitor cells and/or abnormality in the relevant niches give rise to hematological diseases. Allo-HSCT is intended to cure each hematological disease, replacing abnormal hematopoietic stem cells and bone marrow niches with hematopoietic stem cells and bone marrow niches derived from normal donors. Therefore, treatment for graft failure and poor graft function after allo-HSCT is required to proceed based on determining the pathogenesis of impaired hematopoiesis. Recent progress in this area suggests promising treatment manipulations for graft failure and poor graft function.

Advances in the understanding of poor graft function following allogeneic hematopoietic stem-cell transplantation

Poor graft function (PGF) following allogeneic hematopoietic stem-cell transplantation (allo-HSCT) is a life-threatening complication and is characterized by bilineage or trilineage blood cell deficiency and hypoplastic marrow with full chimerism. With the rapid development of allo-HSCT, especially haploidentical-HSCT, PGF has become a growing concern. The most common risk factors illustrated by recent studies include low dose of infused CD34+ cells, donor-specific antibody, cytomegalovirus infection, graft versus host disease (GVHD), iron overload and splenomegaly, among others. Because of the poor prognosis of PGF, it is crucial to uncover the underlying mechanism, which remains elusive. Recent studies have suggested that the bone marrow microenvironment may play an important role in the pathogenesis of PGF. Deficiency and dysfunction of endothelial cells and mesenchymal stem cells, elevated reactive oxygen species (ROS) levels, and immune abnormalities are believed to contribute to PGF. In this review, we also discuss recent clinical trials that evaluate the safety and efficacy of new strategies in patients with PGF. CD34+-selected stem-cell boost (SCB) is effective with an acceptable incidence of GVHD, despite the need for a second donation. Alternative strategies including the applications of mesenchymal stem cells, N-acetyl-l-cysteine (NAC), and eltrombopag have shown favorable outcomes, but further large-scale studies are needed due to the small sample sizes of the recent clinical trials.

Evolution of the role of haploidentical stem cell transplantation: past, present, and future

INTRODUCTION

The accessibility to haplo-donors has led to an increase in the number of haplo-HSCT worldwide. A systematic search of the PubMed database between 2000 to present was performed.

AREAS COVERED

In this review, the authors discussed the most used approaches to perform haplo-HSCT and its results: T-cell depletion (TCD, including Perugia platform and its modifications) and T-cell repleted haplo (TCR, including the high-dose post-transplant cyclophosphamide strategy (Baltimore protocol) and the Beijing protocol). The improvements and modifications made to the different strategies have increased the indications of haplo-HSCT, including both malignant and nonmalignant disorders. Focusing on the Baltimore protocol, the authors review the results of the retrospective studies that have compared it to other donor transplants. The limitations of this strategy in terms of toxicity, graft complications, and GVHD are also discussed in detail. Finally, possible approaches to improve the outcomes of TCR haplo-HSCT are presented.

EXPERT OPINION

The recent advances in the field of haplo-HSCT have allowed a large number of patients with incurable diseases to benefit from this procedure despite not having a matched donor. With all available strategies, virtually no patient who needs an allogeneic transplant should be excluded by the absence of a donor.

Combination treatment of rituximab and donor platelets infusion to reduce donor-specific anti-HLA antibodies for stem cells engraftment in haploidentical transplantation

BACKGROUND

Donor-specific anti-human leukocyte antigen (HLA) antibodies (DSAs) in recipients is a risk factor for donor stem cell graft failure in haploidentical hematopoietic stem cell transplantation (haplo-HSCT), and the treatment to reduce the levels of DSAs is not unanimous. This study was to analysis the role of DSAs for stem cell engraftment and to discuss the effective treatment to reduce DSAs in haplo-HSCT.

METHODS

We retrospectively evaluated the levels of DSAs and the effect of the combination treatment of rituximab and donor platelets (PLTs) for donor stem cell engraftment in haplo-HSCT patients from June 2016 to March 2018 at our center.

RESULTS

Nine patients (11.5%) out of the total 78 patients were DSAs-positive and multivariate analysis revealed DSAs was the only factor that affected engraftment. Seven out of the 9 DSAs (+) patients received therapy: Four had antibodies against donor HLA class I (HLA-I) antigens and were administered two therapeutic amounts of donor apheresis platelets (platelet count approximately 3-5 × 10¹¹ ) before donor stem cell infusion and the other three patients received a combination therapy of donor apheresis platelets and rituximab due to the antibodies against both donor HLA-I antigens and HLA class II (HLA-II) antigens. All the seven patients achieved donor stem cell engraftment successfully, and the DSAs levels decreased rapidly after transplantation.

CONCLUSIONS

DSAs is an important factor affecting engraftment in haplo-HSCT. Donor platelet transfusion is one simple and effective treatment for HLA-I DSAs, and a combination therapy should be administered if patients have both HLA-I and HLA-II antibodies.

How we perform haploidentical stem cell transplantation with posttransplant cyclophosphamide

HLA-haploidentical hematopoietic stem cell transplantation is now one of the most commonly employed alternative donor techniques, with most centers applying T-cell-replete strategies such as that developed by the Baltimore group using high-dose posttransplant cyclophosphamide. HLA-haploidentical hematopoietic stem cell transplantation using posttransplant cyclophosphamide is associated with low rates of severe graft-versus-host disease and nonrelapse mortality and does not require graft manipulation or storage, which results in a low graft acquisition cost. Its remarkable safety when used with reduced-intensity conditioning has been demonstrated in patients up to 75 years old with outcomes similar to those of patients in their 50s. Several large, registry-based retrospective studies have confirmed the efficacy of HLA-haploidentical hematopoietic stem cell transplantation with posttransplant cyclophosphamide, achieving results comparable to those of HLA-matched hematopoietic stem cell transplantation. In this article, we describe our approach to this rapidly available and clinically simple platform and address some of the key clinical questions associated with its use.

How we perform haploidentical stem cell transplantation with posttransplant cyclophosphamide

HLA-haploidentical hematopoietic stem cell transplantation is now one of the most commonly employed alternative donor techniques, with most centers applying T-cell-replete strategies such as that developed by the Baltimore group using high-dose posttransplant cyclophosphamide. HLA-haploidentical hematopoietic stem cell transplantation using posttransplant cyclophosphamide is associated with low rates of severe graft-versus-host disease and nonrelapse mortality and does not require graft manipulation or storage, which results in a low graft acquisition cost. Its remarkable safety when used with reduced-intensity conditioning has been demonstrated in patients up to 75 years old with outcomes similar to those of patients in their 50s. Several large, registry-based retrospective studies have confirmed the efficacy of HLA-haploidentical hematopoietic stem cell transplantation with posttransplant cyclophosphamide, achieving results comparable to those of HLA-matched hematopoietic stem cell transplantation. In this article, we describe our approach to this rapidly available and clinically simple platform and address some of the key clinical questions associated with its use.

Guidelines on the Use of Therapeutic Apheresis in Clinical Practice - Evidence-Based Approach from the Writing Committee of the American Society for Apheresis: The Eighth Special Issue

The American Society for Apheresis (ASFA) Journal of Clinical Apheresis (JCA) Special Issue Writing Committee is charged with reviewing, updating and categorizing indications for the evidence-based use of therapeutic apheresis (TA) in human disease. Since the 2007 JCA Special Issue (Fourth Edition), the committee has incorporated systematic review and evidence-based approaches in the grading and categorization of apheresis indications. This Eighth Edition of the JCA Special Issue continues to maintain this methodology and rigor in order to make recommendations on the use of apheresis in a wide variety of diseases/conditions. The JCA Eighth Edition, like its predecessor, continues to apply the category and grading system definitions in fact sheets. The general layout and concept of a fact sheet that was introduced in the Fourth Edition, has largely been maintained in this edition. Each fact sheet succinctly summarizes the evidence for the use of TA in a specific disease entity or medical condition. The Eighth Edition comprises 84 fact sheets for relevant diseases and medical conditions, with 157 graded and categorized indications and/or TA modalities. The Eighth Edition of the JCA Special Issue seeks to continue to serve as a key resource that guides the utilization of TA in the treatment of human disease.

Effective desensitization for a strong donor-specific HLA antibody in a case of HLA-mismatched allogeneic hematopoietic cell transplantation

We describe a unique ABO compatible and 9/10 HLA-matched case of successful allogeneic hematopoietic cell transplantation (HCT) after effective desensitization of a strong anti-HLA-A24 donor-specific antibody (DSA) with mean fluorescence intensity of approximately 18 000. Due to absence of a suitable matched unrelated donor the patient sibling was considered the best available donor, and it was decided to desensitize patient prior to transplant. The strength of HLA-A24 DSA slowly decreased over the course of treatment, necessitating a total of 23 sessions of therapeutic plasma exchange in order to bring the DSA strength to undetectable levels, followed by a successful transplant. In summary, the outcome of this case shows effective application of desensitization treatment to remove strong DSA in HCT patients.

Factors affecting HLA expression: A review

The detection and semiquantitative measurement of circulating human leucocyte antigen (HLA)-specific antibodies is essential for the management of patients before and after transplantation. In addition, the pretransplant cross-match to assess the reactivity of recipient HLA antibody against donor lymphocytes has long been the gold standard to prevent hyperacute rejection. Whilst both of these tests assume that recipient HLA-specific antibody is the only variable in the assessment of transplant risk, this is not the case. Transplant immunologists recognize that some HLA antigens are expressed at levels a magnitude lower than others (e.g., HLA-C, HLA-DQ), but within loci, and between different cell types there are many factors that influence HLA expression in both resting and activated cells. HLA is not usually expressed without the specific promoter proteins NLRC5, for HLA class I, and CIITA, for class II. The quantity of HLA protein production is then affected by factors including promoter region polymorphisms, alternative exon splice sites, methylation and microRNA-directed degradation. Different loci are influenced by multiple combinations of these control mechanisms making prediction of HLA regulation difficult, but an ability to measure the cellular expression of each HLA antigen, in conjunction with knowledge of circulating HLA-specific antibody, would lead to a more informed algorithm to assess transplant risk.

Hematopoietic stem cell transplant with HLA-mismatched grafts: impact of donor, source, conditioning, and graft versus host disease prophylaxis

INTRODUCTION

Allogeneic hematopoietic cell transplantation is frequently used to treat malignant and non-malignant conditions, and many patients lack a human leukocyte antigen (HLA) matched related or unrelated donor. For those patients, available alternative graft sources include HLA mismatched unrelated donors, cord blood, or haplo-identical donors. These graft sources have unique characteristics and associated outcomes requiring graft-specific variations to conditioning regimens, graft-versus-host disease prophylaxis, and post-transplant care. Areas covered: This manuscript will cover approaches in selecting donors, conditioning regimens, graft versus host disease prophylaxis, post-transplant care, and ongoing clinical trials related to mismatched grafts. Expert commentary: In the setting, haplo-identical grafts are increasingly popular due to low graft versus host disease (GVHD) risk and control of cellular dose. We recommend young male donors, utilizing bone marrow with post-transplant cyclophosphamide for GVHD prophylaxis. Cord blood transplant is appropriate for young healthy patients, and we recommend 6/8 HLA matched grafts with at least 2.0 × 10⁷/kg total nucleated cell dose. For mismatched unrelated donors we recommend young male donors, utilizing bone marrow with in vivo T-cell conditioning with post-transplant cyclophosphamide, alemtuzumab, or ATG. With these transplants, significant post-transplant surveillance and infectious prophylaxis is key to reducing treatment-related mortality.

Haploidentical Donor Bone Marrow Transplantation for Severe Aplastic Anemia

Hematopoietic stem cell transplantation (bone marrow transplantation [BMT]) is the only curative treatment of severe aplastic anemia. BMT from an human leukocyte antigen (HLA)-matched sibling donor is the standard of care for young patients; immunosuppressive therapy is used for older patients or those lacking matched sibling donors. Patients with refractory or relapsed disease are increasingly treated with HLA haploidentical BMT. Historically, haploidentical BMT led to high rates of graft rejection and graft-versus-host disease. High-dose post transplant cyclophosphamide, which mitigates the risk of graft-versus-host disease, is a major advance. This article provides an overview of the haploidentical BMT approach in severe aplastic anemia.

The European Society for Blood and Marrow Transplantation (EBMT) Consensus Guidelines for the Detection and Treatment of Donor-specific Anti-HLA Antibodies (DSA) in Haploidentical Hematopoietic Cell Transplantation

Haploidentical donors are now increasingly considered for transplantation in the absence of HLA-matched donors or when an urgent transplant is needed. Donor-specific anti-HLA antibodies (DSA) have been recently recognized as an important barrier against successful engraftment of donor cells, which can affect transplant survival. DSA appear more prevalent in this type of transplant due to higher likelihood of alloimmunization of multiparous females against offspring's HLA antigens, and the degree of mismatch. Here we summarize the evidence for the role of DSA in the development of primary graft failure in haploidentical transplantation and provide consensus recommendations from the European Society for Blood and Marrow Transplant Group on testing, monitoring, and treatment of patients with DSA receiving haploidentical hematopoietic progenitor cell transplantation.

HLA donor-specific antibodies in allogeneic hematopoietic stem cell transplantation: challenges and opportunities

Allogenic hematopoietic stem cell recipients may have preformed antibodies directed against foreign HLA antigens. The use of partially HLA-mismatched allogeneic hematopoietic stem cell donors allows for the possibility of the presence of circulating HLA donor-specific antibodies (DSAs) in the recipient. The presence of DSAs at the time of stem cell infusion increases the risk of primary graft failure. More recently developed technology using solid phase immunoassays (SPIs) with fluorochrome-conjugated beads has greatly improved the ability to detect and classify DSAs. When used in combination with the classic lymphocytotoxic complement-dependent and flow cytometric crossmatch tests, SPIs help provide DSA strength assessment. Parous females frequently harbor DSAs. DSAs tend to be of higher intensity when directed against haploidentical first-degree relatives. DSA assessment requires frequent monitoring as their relative strength can change over time. Although the criteria that constitutes a prohibitive DSA is unknown, desensitization techniques can result in engraftment rates as experienced in fully HLA-matched allogeneic blood or marrow transplantation recipients.

Related haploidentical donors are a better choice than matched unrelated donors: Point

Publisher's Note: This article has a companion Counterpoint by Shaw. Publisher's Note: Join in the discussion of these articles at Blood Advances Community Conversations.

Complex Transfusion Issues in Pediatric Hematopoietic Stem Cell Transplantation

Advances in the fields of pediatric transfusion medicine and hematopoietic stem cell transplant have resulted in improved outcomes but also present new questions for research. The diagnostic capabilities involved in transfusion medicine have improved in recent times, now including methods for determination of red blood cell minor antigens, detection of anti-human leukocyte antigen antibodies, and noninvasive iron quantification. At the same time, transplants are being performed for more indications including nonmalignant disease and with less intense conditioning regimens that allow some recipient blood cells to persist after transplant. We are therefore faced with new opportunities to understand the implications of transfusion medicine testing and to develop data-driven guidelines relevant to the current-day approach to transfusion and transplantation.

Advances in haploidentical stem cell transplantation for hematologic malignancies

One of the most important advances in allogeneic hematopoietic stem cell transplantation (allo-HSCT) is the use of alternative donors and cell sources, such as haploidentical transplants (haplo-HSCT) from family donors. Several approaches have been developed to overcome the challenging bidirectional alloreactivity. We discuss these approaches, including ex vivo T-cell-depleted grafts with megadose of CD34(+) cells, not requiring immunosuppression after allogeneic transplantation for graft-versus-host disease (GVHD) prophylaxis, and other strategies using unmanipulated T-cell-replete grafts with intensive immunosuppression or post-transplantation cyclophosphamide to minimize the GVHD. We also address the role of other strategies developed in the context of the haplo-HSCT platforms, such as ex vivo selective depletion of alloreactive donor T-cell subpopulations, infusion of antigen-specific T-cells against several pathogens, and infusion of regulatory T-cells, among other experimental approaches. Finally, some considerations about the selection of the most suitable donor, when more than one family member is available, are also addressed.

Supportive care in alternative donor transplantation

Alternative donor hematopoietic cell transplantation (HCT) using umbilical cord blood, haploidentical or mismatched unrelated donors is a viable option for patients without human leukocyte antigen (HLA)-identical sibling or matched unrelated donors. The same principles of supportive care as conventional graft sources apply to alternative donor HCT recipients. However, there are some unique supportive care issues related to post-transplant complications, engraftment, graft-versus-host disease, immune reconstitution, and infections that are unique to each of the three alternative graft sources, both in the early and late post-transplant periods. This review discusses the supportive care issues relevant to this population and their management.

Donor Specific Anti-HLA Antibody and Risk of Graft Failure in Haploidentical Stem Cell Transplantation

Outcomes of allogeneic hematopoietic stem cell transplantation (AHSCT) using HLA-half matched related donors (haploidentical) have recently improved due to better control of alloreactive reactions in both graft-versus-host and host-versus-graft directions. The recognition of the role of humoral rejection in the development of primary graft failure in this setting has broadened our understanding about causes of engraftment failure in these patients, helped us better select donors for patients in need of AHSCT, and developed rational therapeutic measures for HLA sensitized patients to prevent this unfortunate event, which is usually associated with a very high mortality rate. With these recent advances the rate of graft failure in haploidentical transplantation has decreased to less than 5%.

Cord blood transplant for acute myeloid leukaemia

Umbilical cord blood is a haematopoietic progenitor cell source for patients with acute myeloid leukaemia (AML), other haematological malignancies and metabolic diseases who can be cured by allogeneic haematopoietic cell transplantation, but who do not have a human leucocyte antigen compatible related or unrelated donor. Although the first cord blood transplants were done in children, there are currently more cord blood transplants performed in adults. In this review, we explore the history of umbilical cord blood transplantation, paediatric and adult outcome results, and novel trends to improve engraftment and reduce infection. Umbilical cord blood transplantation cures approximately 30-40% of adults and 60-70% of children with AML. Controversial issues, including the use of double versus single cord blood units for transplantation, optimal cord blood unit selection, infection prophylaxis, conditioning regimens and graft versus host disease prophylaxis, will be reviewed. Finally, comparison to other graft sources, cost, access to care, and the ideal graft source are discussed.

Modern approaches to HLA-haploidentical blood or marrow transplantation

Allogeneic blood or bone-marrow transplantation (alloBMT) is a potentially curative treatment for a variety of haematological malignancies and nonmalignant diseases. Historically, human leukocyte antigen (HLA)-matched siblings have been the preferred source of donor cells owing to superior outcomes compared with alloBMT using other donors. Although only approximately one-third of patients have an HLA-matched sibling, nearly all patients have HLA-haploidentical related donors. Early studies using HLA-haploidentical alloBMT resulted in unacceptably high rates of graft rejection and graft-versus-host disease (GVHD), leading to high nonrelapse mortality and consequently poor survival. Several novel approaches to HLA-haploidentical alloBMT have yielded encouraging results with high rates of successful engraftment, effective GVHD control and favourable outcomes. In fact, outcomes of several retrospective comparative studies seem similar to those seen using other allograft sources, including those of HLA-matched-sibling alloBMT. In this Review, we provide an overview of the three most-developed approaches to HLA-haploidentical alloBMT: T-cell depletion with 'megadose' CD34(+) cells; granulocyte colony-stimulating factor-primed allografts combined with intensive pharmacological immunosuppression, including antithymocyte globulin; and high-dose, post-transplantation cyclophosphamide. We review the preclinical and biological data supporting each approach, results from major clinical studies, and completed or ongoing clinical studies comparing these approaches with other alloBMT platforms.