Outcomes of donor lymphocyte infusion for treatment of mixed donor chimerism after a reduced-intensity preparative regimen for pediatric patients with nonmalignant diseases

Safety but limited efficacy of donor lymphocyte infusion for post-transplantation cyclophosphamide-treated patients

The therapeutic efficacy of donor lymphocyte infusions (DLIs) given after allogeneic hematopoietic cell transplantation (HCT) is limited by risk of graft-versus-host disease (GVHD). Post-transplantation cyclophosphamide (PTCy) effectively prevents severe GVHD, but there are limited data on outcomes of DLIs given to PTCy-treated patients. We reviewed 162 consecutive PTCy-treated patients transplanted between 2015-2022 within the Center for Immuno-Oncology at the National Cancer Institute. Of 38 DLIs given to 21 patients after 22 HCTs, few DLIs were associated with toxicities of acute GVHD (7.8%), cytokine release syndrome (CRS, 7.8%), or chronic GVHD (2.6%), and all occurred in those receiving serotherapy-containing pre-HCT conditioning (50% of HCTs). Seven DLIs resulted in complete response (18.4%), with 5 of these given after HCTs using serotherapy-containing conditioning. Excluding infectious indications, complete response to DLIs given after transplants with versus without serotherapy-containing pre-HCT conditioning were 30% and 4.3%, respectively. Two patients received DLI for infection and experienced complete resolution without GVHD or CRS, although the efficacy cannot be definitively attributable to the DLI. DLIs given to PTCy-treated patients had low toxicity but limited efficacy, although pre-HCT serotherapy may modulate both toxicity and response. Novel strategies are needed to enhance the therapeutic efficacy of post-transplant cellular therapies without aggravating GVHD.

Modified Prophylactic Donor Lymphocyte Infusion (DLI) in an Adult T Cell Lymphoma/Leukemia (ATLL) Patient-Modality of Relapse Prevention

Adult T-cell Leukemia/Lymphoma (ATLL) is a rare but aggressive malignancy associated with the human T-cell lymphotropic virus type 1 (HTLV-1). ATLL is a challenging malignancy characterized by its aggressive nature and poor prognosis. Despite advancements in treatment, relapse rates remain high. Donor lymphocyte infusion (DLI) is a promising therapeutic option post-hematopoietic stem cell transplantation (HSCT) to prevent relapse. However, the prophylactic use of DLI in ATLL patients remains underexplored. We report the case of a 45-year-old female diagnosed with ATLL. Following induction chemotherapy and successful HSCT, a modified prophylactic DLI regimen was administered, consisting of gradually increasing doses of donor lymphocytes. The patient demonstrated a favorable response with no significant graft-versus-host disease (GVHD) and maintained remission over a 40-month follow-up period, suggesting a potential benefit of this approach. This case highlights the potential efficacy and safety of modified prophylactic DLI in ATLL patients, warranting further investigation. Our findings suggest that modified prophylactic DLI is a viable option for ATLL patients post-HSCT, offering a balance between efficacy and safety. Future research should focus on optimizing DLI protocols and exploring biomarkers for response prediction.

Age Impacts Risk of Mixed Chimerism Following Reduced-Intensity Conditioning Hematopoietic Cell Transplantation for Non-Severe Combined Immune Deficiency Inborn Errors of Immunity

Alemtuzumab, fludarabine, and melphalan containing-reduced intensity conditioning (RIC) is commonly used in patients undergoing allogeneic hematopoietic cell transplantation (HCT) for definitive treatment of high-risk inborn errors of immunity (IEI). Although survival is favorable, there is an increased risk of mixed chimerism leading to secondary graft failure. This study evaluated factors associated with the risk of developing mixed chimerism, particularly the influence of age in patients undergoing allogeneic HCT for non-severe combined immune deficiency (SCID) IEI who received a uniform RIC regimen that included intermediate schedule alemtuzumab, fludarabine, and melphalan. We hypothesized that age would impact the incidence of mixed chimerism. We retrospectively reviewed records of patients who underwent HCT for non-SCID IEI with a uniform RIC regimen that included intermediate schedule alemtuzumab (1 mg/kg divided over days -14 to -10), fludarabine (150 mg/m2 or 5 mg/kg if weight <10 kg divided over days -9 to -4), and melphalan (140 mg/m2 or 4.7 mg/kg if weight <10 kg on day -3) between 2010 and 2020 at our institution. Mixed chimerism was defined as <95% donor chimerism on 2 or more consecutive occasions in whole blood. Ninety-three patients who underwent RIC-HCT for non-SCID IEI using intermediate schedule alemtuzumab, fludarabine, and melphalan were categorized into 3 groups: age <1 year, age 1 to 5 years, and age >5 years. Forty-nine patients (52.7%) developed mixed chimerism, at a median of 34 days post-HCT (range, 10 to 1396 days). Mixed chimerism developed in 88.9% (n = 16/18) of the age <1 year group, in 57.1% (n = 20/35) of the age 1 to 5 years group, and in 35% (n =14/40) of the age >5 years group. Patients age <5 years were significantly more likely to develop mixed chimerism (χ2 (3, N = 93) = 14.8; P = .001). We observed a significantly increased cumulative incidence of developing mixed chimerism associated with age <1 year (P = .0002). Competing risk regression analysis showed a 3-fold higher risk of developing mixed chimerism for age <1 year (subdistribution hazard ratio (HR), 3.05; 95% confidence interval [CI], 1.11 to 8.38; P = .031,) compared to age >5 years and a significantly decreased risk of mixed chimerism in patients who developed acute GVHD prior to any intervention (OR, .24; 95% CI, .09 to .65; P = .005) There were no significant associations between mixed chimerism and graft source, graft type, CD34+ or CD3+ cell dose, HLA match, or underlying disease (hemophagocytic lymphohistiocytosis [HLH] versus non-HLH). Additionally, the need for secondary intervention was evaluated; 27 patients (29.0%) required 1 or more secondary interventions (donor lymphocyte infusion, CD34 boost, or second HCT). Patients age <1 year with mixed chimerism were significantly more likely than patients age >5 years to require secondary intervention for mixed chimerism (P = .004). Our study demonstrates that age <5 years, especially age <1 year, is associated with an increased risk of developing mixed chimerism in patients undergoing RIC-HCT for non-SCID IEI using intermediate-schedule alemtuzumab, fludarabine, and melphalan. Our data suggest tailoring regimen intensity based on age to reduce the incidence of mixed chimerism. Children age <5 years, particularly those age <1 year, require a higher-intensity regimen. Possible strategies include adding thiotepa or using a busulfan-based reduced toxicity regimen.

CD34 Stem Cell Boost in Pediatric Allogeneic Stem Cell Transplant Recipients: A Case Series and Review of Literature

Patients with poor graft function (PGF) or declining donor chimerism (DC) post allogeneic hematopoietic cell transplantation (HCT) may benefit from a CD34-selected stem cell boost (SCB). We retrospectively studied outcomes of fourteen pediatric patients (PGF: 12 and declining DC: 2), with a median age of 12.8 (range 0.08-20.6) years at HCT, who received a SCB. Primary and secondary endpoints included resolution of PGF or improvement in DC (≥ 15% increase), overall survival (OS) and transplant-related mortality (TRM), respectively. The median CD34 dose infused was 7.47 × 10⁶/kg (range 3.51 × 10⁶-3.39 × 10⁷/kg). Among patients with PGF who survived ≥ 3 months post-SCB (n = 8), we observed a non-significant decrease in the cumulative median number of red cell transfusions, platelet transfusions, and GCSF but not intravenous immunoglobulin doses in the 3 months before and after SCB. Overall response rate (ORR) was 50%, with 29% complete and 21% partial responses. ORR was better in recipients who received lymphodepletion (LD) pre-SCB versus none (75% versus 40%; p = 0.56). The incidence of acute and chronic graft-versus-host-disease was 7% and 14%, respectively. The 1-year OS was 50% (95% CI 23-72%) and TRM was 29% (95% CI 8-58%). SCB was effective in half of our cohort with possible benefit of LD pre-SCB.

Case report: HLA-haploidentical HSCT rescued with donor lymphocytes infusions in a patient with X-linked chronic granulomatous disease

Chronic granulomatous disease is an inborn error of immunity due to disrupted function of the nicotinamide adenine dinucleotide phosphate (NADPH) oxidase complex. This results in impaired respiratory burst of phagocytes and insufficient killing of bacteria and fungi. Patients with chronic granulomatous disease are at increased risk for infections, autoinflammation and autoimmunity. Allogeneic hematopoietic stem cell transplantation (HSCT) is the only widely available curative therapy. While HSCT from human leukocyte antigen (HLA) matched siblings or unrelated donors are standard of care, transplantation from HLA-haploidentical donors or gene therapy are considered alternative options. We describe a 14-month-old male with X-linked chronic granulomatous disease who underwent a paternal HLA-haploidentical HSCT using T-cell receptor (TCR) alpha/beta⁺/CD19⁺ depleted peripheral blood stem cells followed by mycophenolate graft versus host disease prophylaxis. Decreasing donor fraction of CD3⁺ T cells was overcome by repeated infusions of donor lymphocytes from the paternal HLA-haploidentical donor. The patient achieved normalized respiratory burst and full donor chimerism. He remained disease-free off any antibiotic prophylaxis for more than three years after HLA-haploidentical HSCT. In patients with x-linked chronic granulomatous disease without a matched donor paternal HLA-haploidentical HSCT is a treatment option worth to consider. Administration of donor lymphocytes can prevent imminent graft failure.

Escalated Dose Donor Lymphocyte Infusion Treatment in Patients with Primary Immune Deficiencies After HSCT with Reduced-Intensity Conditioning Regimen

OBJECTIVE/BACKGROUND

Mixed chimerism is a major concern after allogenic hematopoietic stem cell transplantation (HSCT) using a reduced-intensity conditioning (RIC) regimen in primary immunodeficiencies (PIDs). A donor lymphocyte infusion (DLI) escalating dose regimen has been developed with the aim of reducing toxicity while preserving efficacy. However, the graft-versus-host disease (GvHD) development remains the most common and adverse effect of DLI and continues to be a limiting factor in its application, especially nonmalignant diseases such as PIDs. We prospectively evaluated PID patients after HSCT using RIC in Childrens Medical Center, who were candidates for an escalating dose of DLI for MC from 2016 to 2018.

METHODS

With the median follow-up of 16.4 months, 12 patients (nine males and three females) with a median age of 3.72 years received DLI. The median number of DLI was 3.2 (range, 1-5), the maximum and total dose of DLIs administered per patient were 3.6 × 10⁷ (range, 1-5) cells/kg CD3⁺ and 9.3 × 10⁷ (range, 1-15) cells/kg CD3⁺ cells, respectively.

RESULTS

Median donor chimerism at baseline before the DLIs was 41% (range, 11-73%), patients received DLIs at a median of 105 (range, 37-230) days and 52 (range, 3-168) days after the HSCT and onset of the MC, respectively. At the final assessment, six (54.5%) patients improved after DLIs at a median of 47.3 days.

CONCLUSION

PID patients may benefit from DLI with an escalating dose regimen, but the GvHD development remains a concern during the DLI, and the optimum dose and frequency must be standardized.

Mixed T cell CHIMERISM in bone marrow at day+30 after allogeneic stem cell transplantation: Correlation with acute GVHD grades III-IV and no impact on relapse and overall survival

OBJECTIVES

Early chimerism analysis is important to assess engraftment in allogeneic hematopoietic stem cell transplantations.

METHODS

We retrospectively investigated the impact of T-cell chimerism at day 30 in bone marrow on acute graft-versus-host disease (aGVHD), relapse, and overall survival in 142 adult allo-transplanted patients.

RESULTS

The majority of patients (89%) received myeloablative conditioning and 90% have undergone T-cell replete donor graft. At day 30, 103 patients showed T-complete chimerism with prevalence in haploidentical transplants, whereas 39 cases had CD3+ mixed chimerism, including 30 patients transplanted with HLA identical donors, and 21 with T-cell donors<90%. T-cell chimerism at day 30 was weakly inversely related to aGVHD grades II-IV (p = .078) with no cases of grades III-IV aGVHD in patients with CD3+ <95%. Mixed T-cell chimerism did not impact on relapse (p = .448) and five of the seven patients who relapsed had T-cell chimerism ≤90%. Older age and active disease at transplant had a statistically significant negative effect on overall survival (p = .01 and p = .0001, respectively), whereas mixed CD3+ chimerism did not.

CONCLUSIONS

T lymphocyte chimerism analysis at day +30 in bone marrow could identify allo-transplanted patients at major risk of aGVHD grades III-IV (CD3+ donors >95%) mainly post-myeloablative conditioning regimen.

Allogeneic hematopoietic stem cell transplantation for inherited metabolic disorders

Allogeneic hematopoietic stem cell transplantation (HSCT) has been used to treat patients with inherited metabolic disorders (IMDs) for more than 40 years. In the first two decades, various IMDs were treated by HSCT with a wide variety of donor sources and conditioning regimens selected at the institutional level. However, HSCT was not always successful due to post-transplant complications such as graft failure. In the third decade, myeloablative conditioning with targeted busulfan-based pharmacokinetic monitoring was established as an optimal conditioning regimen, and unrelated cord blood was recognized as an excellent donor source. During the fourth decade, further improvements were made to transplant procedures, including modification of the conditioning regimen, and the survival rate after HSCT markedly improved. Simultaneously, several long-term observational studies for patients after HSCT clarified its therapeutic effects on growth and development of cognitive function, fine motor skills, and activities of daily living when compared with enzyme replacement therapy. Although immune-mediated cytopenia was newly highlighted as a problematic morbidity after HSCT for IMDs, especially in younger patients who received unrelated cord blood, a recent study with rituximab added to the conditioning raised expectations that this issue can be overcome.

Retrospective, Landmark Analysis of Long-term Adult Morbidity Following Allogeneic HSCT for Inborn Errors of Immunity in Infancy and Childhood

Purpose

Allogeneic hematopoietic stem cell transplant (HSCT) remains the treatment of choice for patients with inborn errors of immunity (IEI). There is little published medical outcome data assessing late medical complications following transition to adult care. We sought to document event-free survival (EFS) in transplanted IEI patients reaching adulthood and describe common late-onset medical complications and factors influencing EFS.

Methods

In this landmark analysis, 83 adults surviving 5 years or more following prior HSCT in childhood for IEI were recruited. The primary endpoint was event-free survival, defined as time post-first HSCT to graft failure, graft rejection, chronic infection, life-threatening or recurrent infections, malignancy, significant autoimmune disease, moderate to severe GVHD or major organ dysfunction. All events occurring less than 5 years post-HSCT were excluded.

Results

EFS was 51% for the whole cohort at a median of 20 years post HSCT. Multivariable analysis identified age at transplant and whole blood chimerism as independent predictors of long-term EFS. Year of HSCT, donor, conditioning intensity and underlying diagnosis had no significant impact on EFS. 59 events occurring beyond 5 years post-HSCT were documented in 37 patients (45% cohort). A total of 25 patients (30% cohort) experienced ongoing significant complications requiring active medical intervention at last follow-up.

Conclusion

Although most patients achieved excellent, durable immune reconstitution with infrequent transplant-related complications, very late complications are common and associated with mixed chimerism post-HSCT. Early intervention to correct mixed chimerism may improve long-term outcomes and adult health following HSCT for IEI in childhood.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10875-022-01278-6.

Programmed death 1 monoclonal antibody helped to treat mixed chimeric and reactivation of Epstein-Barr virus in a patient with adult-onset chronic active Epstein-Barr virus infection after allogeneic hematopoietic stem cell transplantation: A case report

RATIONALE

Systemic forms of chronic active Epstein-Barr virus infection (CAEBV) can predispose a patient to a protracted course of fulminant hemophagocytic lymphohistiocytosis, which has a poor prognosis. Epstein-Barr virus (EBV) infection may persist even after theoretically curative hematopoietic stem cell transplantation.

PATIENT CONCERNS

A female patient with CAEBV underwent chemotherapy followed by allogeneic hematopoietic stem cell transplantation from her human leukocyte antigen-matched sister. Neutrophil and platelet engraftment was observed on day +12 and +10. Full donor chimerism (DC) was achieved on Day +21.

DIAGNOSES

From day +38, EBV-DNA in the blood was persistently positive, and DC declined. We attempted empirical interventions such as withdrawal of immune suppression, multiple donor lymphocyte infusion, stem cell boost, and interferon-α treatment. However, EBV-DNA copies continued to increase aggressively, whereas DC decreased rapidly and then reached a nadir of 63.27%.

INTERVENTIONS

Salvage programmed death 1 (PD-1) antibody treatment was administered as salvage therapy at +69 and +84.

OUTCOMES

EBV-DNA was negative on day +97 and was ultimately undetectable. Equivalently, a full and stable DC was obtained at +97.

LESSONS

We summarize a case of PD-1 antibody used as salvage treatment in a post-transplant patient with CAEBV, which was eradicated and full DC was obtained. This case suggests that the PD-1 antibody appears to be a promising option for fighting EBV and mixed DCs.

Use of chimerism analysis after allogeneic stem cell transplantation: Belgian guidelines and review of the current literature

Background: Allogeneic hematopoietic stem cell transplantation (HSCT) is a curative treatment option in both adult and pediatric patients with malignant and non-malignant hematological diseases.  Chimerism analysis, which determines the donor or recipient origin of hematopoietic cells in HSCT recipients, is an essential aspect of post-HSCT follow-up.Objectives: To review the current literature and develop Belgian consensus guidelines for the use of chimerism analysis in the standard of care after allogeneic HSCT.Methods: Non-systematic review of the literature in consultancy with the members of the BHS transplantation committee.Results: Clinical application with regards to prediction of graft failure or relapse as well as cell source are reviewed. A consensus guideline on the use of chimerism analysis after HSCT is presented.Conclusion: Monitoring of the dynamics or kinetics of a patient's chimerism status by serial analysis at fixed time points, as well as on suspicion of relapse or graft failure, is needed to monitor engraftment levels, as well as disease control and possible relapse.

Donor-Host Lineage-Specific Chimerism Monitoring and Analysis in Pediatric Patients Following Allogeneic Stem Cell Transplantation: Influence of Pretransplantation Variables and Correlation with Post-Transplantation Outcomes

The impact of donor-host chimerism in post-hematopoietic stem cell transplantation (HSCT) outcomes is poorly understood. We were interested in studying whether pre-HSCT variables influenced lineage-specific donor-host chimerism and how lineage-specific chimerism impacts post-HSCT outcomes. Our main objective was to study pre-HSCT variables as predictors of lineage-specific donor-host chimerism patterns and to better characterize the relationship between post-HSCT lineage-specific chimerism and adverse outcomes, including graft failure and disease relapse. We conducted a retrospective data analysis of all patients who underwent allogeneic HSCT at the Pediatric Transplantation and Cellular Therapy service at Memorial Sloan Kettering Cancer Center between January 2010 and June 2015 and had at least 2 measurements of split-lineage chimerism. The trend of lineage-specific donor-host chimerism post-HSCT and the impact of age, disease, graft type, and pretransplantation conditioning regimen on chimerism at 3 months and 12 months post-HSCT were studied. The Wilcoxon signed-rank test, Mann-Whitney-Wilcoxon test, and Cox proportional hazard models were used for statistical analyses. A total of 137 patients were included (median age, 11.3 years). Most patients had a hematologic malignancy (n = 95), and fewer had a nonmalignant disorder (n = 27) or primary immune deficiency (n = 15). Myeloablative conditioning regimens (n = 126) followed by T cell-depleted (TCD) peripheral blood stem cell or bone marrow grafts (n = 101) were most commonly used. Mixed chimerism (MC) of total peripheral blood leukocytes (PBLs) did not predict loss of donor chimerism in all lineages and when stable was not associated with graft failure or rejection in this analyses. Split chimerism with complete donor chimerism (CC) of myeloid, B, and natural killer cells, but not T cells, occurred early post-HSCT, but full donor T cell chimerism was achieved at 12 months post-HSCT by most patients. MC within the T cell lineage was the major contributor to PBL MC, with lower median donor T cell chimerism at 3 months than at 12 months (91%) post-HSCT (51% versus 91%; P < .0001). Predictors of MC at 3 and 12 months were (1) age <3 years (P = .01 for PBLs and P = .003 for myeloid lineage); (2) nonmalignant disorder (P = .007 for PBLs); and (3) the use of reduced-intensity conditioning regimens. TCD grafts produced lower donor T cell chimerism at 3 months post-HSCT compared with unmodified grafts (P < .0001), where T cell lineage CC was achieved early post-HSCT. The donor T cell chimerism was similar at 12 months in the 2 types of grafts. Umbilical cord blood grafts had CC in all lineages at all time points post-HSCT. Loss of donor B cell chimerism was associated with increased risk of relapse in hematologic malignancies (hazard ratio, 1.33; P = .05). Age, underlying disease, conditioning regimen, and graft manipulation can impact post-HSCT donor-host chimerism and be predictors for early MC. MC in total PBLs and T cells was not related to graft failure or disease relapse. Whole-blood PBL chimerism analysis is not sufficient to assess the significance of post-HSCT donor-host status; rather, lineage-specific chimerism, particularly for myeloid, T, and B cells, should be analyzed to guide interventions and inform outcomes.

The incidence, clinical outcome, and protective factors of mixed chimerism following hematopoietic stem cell transplantation for severe aplastic anemia

OBJECTIVES

The aim of our study was to determine possible predictors and clinical course of mixed chimerism (MC) in aplastic anemia after transplantation.

METHODS

A total of 207 transplants were obtained from haploidentical donors (HID) using busulfan (Bu), cyclophosphamide (Cy), and anti-thymocyte globulin (ATG) regimens, and 69 transplants from matched related donors (MRD) and 29 transplants from unrelated donors (URD) using Cy/ATG regimens were obtained.

RESULTS

Incidences of MC were 1.93 ± 0.01%, 20.29 ± 0.01%, and 35.71 ± 0.01% in HID, MRD, and URD transplantation (p < .001). In multivariate analysis, incidence of MC was significantly higher in patients without adding Bu in conditioning (p < .001) and receiving a lower number of CD3 + cells in graft (p = .042). MC was associated with significantly lower II-IV aGvHD (3.70% vs. 27.7%, p = .007), but higher secondary graft rejection rates (14.8% vs. 0.4%, p < .001) and poorer overall survival (72.7 ± 8.9% vs. 89.6 ± 2.0%, p = .011) than those of donor chimerism cohort.

CONCLUSIONS

Mixed chimerism was an unsettling status even in non-malignancy. Haploidentical transplantation with more intense regimen by adding Bu to Cy and ATG was associated with reduced MC following HSCT for SAA. An intensified regimen should be explored in matched related or unrelated donors.

Prediction, management, and prognosis of mixed chimerism after hematopoietic stem cell transplantation in transfusion-dependent pediatric thalassemia patients

BACKGROUND

Early-onset mixed chimerism (MC) with a high proportion of residual host cells is considered a signal of graft rejection in patients undergoing allogenic hematopoietic stem cell transplantation for transfusion-dependent thalassemia. In order to prevent graft rejection and minimize the risk of treatment-related graft-versus-host disease (GVHD), we established a hierarchical management system based on chimerism analysis.

METHOD

This retrospective study provides a comprehensive review of the characteristics, interventions, and outcomes of the 38 patients who developed MC after transplantation among the 144 pediatric thalassemia patients between July 2007 and January 2019 at our center.

RESULTS

A sibling donor, a blood type-matched donor, conditioning regimens without fludarabine, and transplants containing <10 × 10⁸ total nucleated cells/kg were identified to be associated with the development of MC. Among the 38 patients developing MC, only four patients rejected the grafts. The response rate to donor lymphocyte infusion (DLI, only for patients receiving sibling donor transplantation) and cytokine immunomodulation without DLI was 70.6% and 42.9%, respectively. Patients that developed GVHD after DLI or cytokine therapy had a more significant increase in donor cell chimerism (16%, range 0%-35%) than those without (8.5%, range -21% to 40%, P = .049). However, even when treatment-related GVHD was included, patients with MC had a lower cumulative incidence of total acute GVHD than patients with complete donor chimerism (29.2% vs 48.0%, P = .030).

CONCLUSIONS

Interventions based on chimerism analysis were effective in preventing graft rejection and did not increase treatment-related GVHD in thalassemia patients with MC.

Innovative Cell-Based Therapies and Conditioning to Cure RAG Deficiency

Genetic defects in recombination activating genes (RAG) 1 and 2 cause a broad spectrum of severe immune defects ranging from early severe and repeated infections to inflammation and autoimmune manifestations. A correlation between in vitro recombination activity and immune phenotype has been described. Hematopoietic cell transplantation is the treatment of care; however, the availability of next generation sequencing and whole genome sequencing has allowed the identification of novel genetic RAG variants in immunodeficient patients at various ages, raising therapeutic questions. This review addresses the recent advances of novel therapeutic approaches for RAG deficiency. As conventional myeloablative conditioning regimens are associated with acute toxicities and transplanted-related mortality, innovative minimal conditioning regimens based on the use of monoclonal antibodies are now emerging and show promising results. To overcome shortage of compatible donors, gene therapy has been developed in various RAG preclinical models. Overall, the transplantation of autologous gene corrected hematopoietic precursors and the use of non-genotoxic conditioning will open a new era, offering a cure to an increasing number of RAG patients regardless of donor availability and severity of clinical conditions.

HLA-mismatched GPBSC infusion therapy in refractory Epstein-Barr virus-associated hemophagocytic lymphohistiocytosis: an observational study from a single center

Background

Hemophagocytic lymphohistiocytosis (HLH) is a severe or even fatal inflammatory state. Epstein–Barr virus (EBV) infection-associated HLH (EBV-HLH) is one of the most common secondary HLH and suffers a very poor prognosis. Allo-HSCT is often required for refractory EBV-HLH, but some patients still cannot proceed to the next allo-HSCT due to various factors. This study aimed to observe the efficacy of HLA-mismatched granulocyte colony-stimulating factor (G-CSF)-mobilized peripheral blood stem cells (GPBSCs) infusion for refractory EBV-HLH.

Methods

A retrospective case-control study of refractory EBV-HLH patients with GPBSC infusion from HLA-mismatched donors after chemotherapy (as GPBSC group) and sole chemotherapy (as control group) was performed. Efficacy was evaluated 2 and 4 weeks and all patients were followed-up until March 1, 2018.

Results

There were 18 cases who accepted infusion between March 2016 and Sep 2017 and 19 were randomly selected from refractory EBV-HLH patients who underwent salvage therapy during the same period for the control group. In GPBSC group, WBC (p = 0.017), Fbg (p = 0.040), and ferritin (p = 0.039) improved significantly after treatment. The overall response rate was 66.7% (CR 22.2%, PR 44.4%). However, there are no significant differences in changes of WBC, HGB, PLT, TG, Fbg, Ferritin, AST, ALT, and T-bil between two groups. Only the Fbg level was recovered better in the GPBSC infusion group (p = 0.003). In the GPBSC group, EBV-DNA decreased significantly after 2 weeks (p = 0.001) and 4 weeks (p = 0.012) after treatment, and the effect of the decrease was significantly better than that of the chemotherapy alone group in 2 weeks but not 4 weeks (p2w = 0.011, p4w = 0.145). The median survival time in the infusion group was 20.4 weeks [95% CI 10.9, 29.9], and the median survival time in the control group was 10.8 weeks [95% CI 0–24.34]. In the short-term, the infusion group’s survival rate was better (2-month 88.89% vs. 52.63%, p = 0.008; 3-month 83.33% vs. 47.09%, p = 0.012), but there was no difference in OS (p = 0.287).

Conclusions

Infusing GPBSCs combined with chemotherapy is effective, especially in decreasing EBV-DNA, performs better than chemotherapy alone, and improves short-term survival rate. GPBSC infusion is suggested as a bridging treatment method to allo-HSCT.

Hematopoietic Stem Cell Transplantation Beyond Severe Combined Immunodeficiency: Seeking a Cure for Primary Immunodeficiency

Hematopoietic stem cell transplantation (HSCT) can provide definitive therapy for patients with primary immunodeficiency disease (PIDD). Modern HSCT techniques and supportive care have significantly improved outcomes for patients with PIDD. This review examines current HSCT practice for PIDD other than severe combined immunodeficiency, and explores indications, risks, and long-term outcomes for this group of challenging diseases.

Influence of Mixed Chimerism on Outcome in Children With Anaemia After Haematopoietic Stem Cell Transplantation

BACKGROUND/AIM

In patients with non-malignant diseases, mixed chimerism is not a rare phenomenon. The clinical impacts of chimerism following allogeneic haematopoietic stem cell transplantation (allo-HSCT) in children with congenital anaemia (CA) and severe aplastic anaemia (SAA) were analysed.

PATIENTS AND METHODS

We studied twenty-seven consecutive children with congenital and acquired anaemia who had undergone allogeneic haematopoietic stem cell transplantations. In the observed group of patients, the median of the follow-up was 6.12 years (2.00-14.8 years).

RESULTS

Overall survival (OS) did not depend on the type of disease p=0.1. OS did not significantly differ in patients who received more than 5x10⁶/kg stem cells (91%) and those who received less than 5x10⁶/kg (85%) (p=0.61). Two patterns of stable mixed chimerism (SMC) were observed: SMC (95-97% cells of the donor), and SMC with a fluctuation between 50-90% of the cells of the donor. None of the surviving patients received immunosuppression treatments of chronic Graft-versus-Host Disease (cGvHD).

CONCLUSION

Our results showed that mixed chimerism did not influence the survival of children with congenital and aplastic anaemia following allo-HSCT.

Clinical applications of donor lymphocyte infusion from an HLA-haploidentical donor: consensus recommendations from the Acute Leukemia Working Party of the EBMT

Donor lymphocyte infusion has been used in the management of relapsed hematologic malignancies after allogeneic hematopoietic cell transplantation. It can eradicate minimal residual disease or be used to rescue a hematologic relapse, being able to induce durable remissions in a subset of patients. With the increased use of haploidentical hematopoietic cell transplantation, there is renewed interest in the use of donor lymphocytes to either treat or prevent disease relapse post transplant. Published retrospective and small prospective studies have shown encouraging results with therapeutic donor lymphocyte infusion in different haploidentical transplantation platforms. In this consensus paper, finalized on behalf of the Acute Leukemia Working Party of the European Society for Blood and Marrow Transplantation, we summarize the available evidence on the use of donor lymphocyte infusion from haploidentical donor, and provide recommendations on its therapeutic, pre-emptive and prophylactic use in clinical practice.

Autoimmune Cytopenias in Pediatric Hematopoietic Cell Transplant Patients

Background: Autoimmune cytopenias (AICs) are potentially life-threatening complications following hematopoietic cell transplantation (HCT), yet little is understood about the mechanism by which they develop. We hypothesized that discordant B cell and T cell recovery is associated with AICs in transplant patients, and that this might differ based on transplant indication. Methods: In this case control study of children who underwent HCT at our institution, we evaluated the clinical and transplant characteristics of subjects who developed AICs compared to a control group matched by transplant indication and donor type. In cases, we analyzed the state of immune reconstitution, including B cell recovery, T cell recovery, and chimerism, immediately prior to AIC onset. Subjects were stratified by primary indication for transplant as malignancy (n = 7), primary immune deficiency (PID, n = 9) or other non-malignant disease (n = 4). We then described the treatment and outcomes for 20 subjects who developed AICs. Results: In our cohort, cases were older than controls, were more likely to receive a myeloablative conditioning regimen and had a significantly lower prevalence of chronic GVHD. There were distinct differences in the state of immune recovery based on transplant indication. None of the patients (0/7) transplanted for primary malignancy had T cell recovery at AIC onset compared to 71% (5/7) of patients with PID and 33% (1/3) of patients with non-malignant disease. The subset of patients with PID and non-malignant disease who achieved T cell reconstitution (6/6) prior to AIC onset, all demonstrated mixed or split chimerism. Subjects with AIHA or multi-lineage cytopenias had particularly refractory courses with poor treatment response to IVIG, steroids, and rituximab. Conclusions: These results highlight the heterogeneity of AICs in this population and suggest that multiple mechanisms may contribute to the development of post-transplant AICs. Patients with full donor chimerism may have early B cell recovery without proper T cell regulation, while patients with mixed or split donor chimerism may have residual host B or plasma cells making antibodies against donor blood cells. A prospective, multi-center trial is needed to develop personalized treatment approaches that target the immune dysregulation present and improve outcomes in patients with post-transplant AICs.

Haploidentical hematopoietic stem cell transplantation using reduced-intensity conditioning for pediatric patients with familial hemophagocytic lymphohistiocytosis

IMPORTANCE

Allogeneic hematopoietic stem cell transplantation (HSCT) is considered to be the only curative treatment for familial hemophagocytic lymphohistiocytosis (FHLH). Treatment of pediatric FHLH with reduced-intensity conditioning (RIC)-based haploidentical donor (HID) HSCT has been rarely reported.

OBJECTIVE

To investigate outcomes and adverse events in patients with FHLH who received HID-HSCT.

METHODS

We conducted a retrospective study of five patients, including three with mutations in PRF1 and two with XIAP deficiency. Four of the five donors were heterozygous for these mutations. The conditioning regimen included fludarabine, cyclophosphamide, and antithymocyte globulin, with or without low-dose irradiation. Unmanipulated mobilized bone marrow and peripheral blood stem cells were used as the grafts.

RESULTS

All five patients were successfully engrafted. Four patients survived, and one patient died. All exhibited complete response (CR) after HSCT. All of the patients who survived exhibited CR to FHLH without severe regimen-related complications at a median of 29.5 months (range: 23-34 months) after HSCT. Four of the five patients had mixed donor chimerism. Three patients had 17% to 87% mixed donor chimerism but remained free of disease. Four patients received donor lymphocyte infusion (DLI), which improved the level of mixed donor chimerism. One patient experienced a decrease in donor chimerism to 1% and relapsed; Four patients developed acute graft-versus-host disease (GvHD) (grade I or II), and one patient developed grade IV GvHD.

INTERPRETATION

HID-HSCT with RIC can be considered for treatment for patients with FHLH, but the conditions and DLI regimens need to be optimized for long-term use, and more prospective studies should be conducted.

Evaluation of Chimerism Dynamics after Allogeneic Hematopoietic Stem Cell Transplantation in Children with Nonmalignant Diseases

It is recognized that chimerism following hematopoietic stem cell transplantation (HSCT) is a dynamic process. The aims of this study were to describe the evolution of chimerism in children with nonmalignant diseases who underwent allogeneic HSCT, and to analyze the risk factors influencing chimerism status. A total of 101 HSCTs were performed in 85 patients with nonmalignant diseases. The donor was unrelated in 62.4% of HSCTs. Reduced-intensity conditioning (RIC) regimen was administered in 48.5% of patients. Acute graft-versus-host disease (aGVHD) occurred in 51.7% and chronic GVHD (cGVHD) in 39.7% of patients. Analysis of chimerism was performed through amplification of 9 specific short tandem repeats by polymerase chain reaction at engraftment and 1, 6, and 12 months after HSCT. Upon first evaluation, complete chimerism (CC) was detected in 34.7% and mixed chimerism (MC) in 55.4%, whereas graft failure occurred in 9.9% of patients. Severe aGVHD was associated with CC (P = .031). The last chimerism evaluation showed CC in 72.1%, stable MC in 12.8%, and progressive MC in 3.5%. CC was associated with a higher incidence of aGVHD (P = .016) and cGVHD (P = .022), whereas the RIC regimen was associated with graft failure (P = .026). One- and 3-year overall survival (OS) was 87.4% and 80.5%, respectively, with a lower OS at 3 years in patients with CC compared with those with MC (P = .008). aGVHD and cGVHD represent factors favoring CC, thus close, careful follow-up of chimerism is recommended in patients affected by nonmalignant disease.

HLA-mismatched unrelated donor transplantation using TLI-ATG conditioning has a low risk of GVHD and potent antitumor activity

Many patients lack a fully HLA-matched donor for hematopoietic cell transplantation (HCT), and HLA mismatch is typically associated with inferior outcomes. Total lymphoid irradiation and antithymocyte globulin (TLI-ATG) is a nonmyeloablative conditioning regimen that is protective against graft-versus-host disease (GVHD), and we hypothesized that the protective effect would extend beyond HLA-matched donors. We report outcomes for all consecutively transplanted patients at Stanford University from December 2001 through May 2015 who received TLI-ATG conditioning and HCTs from 8 to 9 out of 10 HLA-mismatched unrelated donors (MMUDs, N = 72) compared with 10 out of 10 HLA-matched unrelated donors (MUDs, N = 193). The median age of the patients was 60 years with a median follow-up of 2 years, and there was a similar distribution of lymphoid and myeloid malignancies in both cohorts. There were no significant differences between MMUD and MUD cohorts in overall survival (46% vs 46% at 5 years, P = .86), disease-free survival (38% vs 28% at 5 years, P = .25), nonrelapse mortality (17% vs 12% at 2 years, P = .34), acute GVHD grades III-IV (6% vs 3% at day +100, P = .61), or chronic GVHD (39% vs 35% at 5 years, P = .49). There was a trend toward less relapse in the MMUD cohort (45% vs 60% at 5 years, hazard ratio: 0.71, P = .094), which was significant for patients with lymphoid malignancies (29% vs 57% at 5 years, hazard ratio: 0.55, P = .044). Achieving full donor chimerism was strongly associated with lower relapse rates. TLI-ATG conditioning may overcome the traditionally poorer outcome associated with HLA-mismatched donors and may be particularly well suited for patients with lymphoid malignancies who lack HLA-matched donors.

Comparison of second transplantation and donor lymphocyte infusion for donor mixed chimerism after allogeneic stem cell transplantation for nonmalignant diseases

BACKGROUND

Donor mixed chimerism (MC) is an increasing problem after hematopoietic stem cell transplantation (HSCT) for nonmalignant diseases.

PROCEDURE

In this study, a self-administered questionnaire was used to retrospectively compare efficacy and safety in 49 patients undergoing second HSCT (n = 13) or donor lymphocyte infusion (DLI; n = 36) as treatment for MC.

RESULTS

The response rate to DLI of patients with secondary graft failure (GF) (25.0%) was significantly lower than that of patients without secondary GF (81.3%; P = 0.041). Among patients undergoing DLI, the rates of successful response were significantly higher in patients having at least 30% donor chimerism (94.1%) than in patients having less than 30% donor chimerism (61.1%; P = 0.041). Furthermore, the rates of successful response were significantly higher in patients receiving larger first or maximum doses of DLI. Sixteen (50.0%) of 32 patients without secondary GF attained complete chimerism after DLI. The cumulative incidence of grade II-IV acute graft-versus-host disease and cytopenia was 37.6 and 26.1%, respectively.

CONCLUSIONS

DLI yields promising response rates in most patients with higher donor chimerism levels, whereas second HSCT is more likely to benefit patients with lower donor chimerism levels.

Long-Term Stable Mixed Chimerism after Hematopoietic Stem Cell Transplantation in Patients with Non-Malignant Disease, Shall We Be Tolerant?

Long-term stable mixed chimerism is a rare and poorly understood phenomenon post hematopoietic stem cell transplantation. This study aims to shed light on whether the two hematopoietic systems in patients with mixed chimerism remain functional. Additionally, we investigate possible immunologic differences in these individuals compared to patients with only donor derived immune cells. Patients with donor and mixed chimerism, at median 10 (5–16) years post-HSCT for non-malignant diseases, were assessed regarding clinical situation and immune system (phenotypical and functional). No difference in long-term outcome was seen in terms of general wellbeing, central phenotypic immune system features (e.g., differentiation status, CD4/CD8 ratio, B and NK-cell frequency) and antibody responses to immunizations. At a median of 10 years post transplantation, patients with mixed chimerism had significantly higher IgG3 and platelet levels. Additionally, these patients had higher NKT-cell levels (CD94+CD8+ and CD56+CD8+) than patients with donor chimerism. In depth phenotypic analysis of patients with mixed chimerism demonstrated recipient-derived fractions in most immune cell lineages (e.g., T-cell, B-cell and NK-cell subsets). Recipient cells were also capable of responding to mitogenic stimulation with production of several cytokines. In conclusion, long-term mixed chimerism did not negatively affect patient wellbeing and long-term outcome. Moreover, recipient-derived immunity may still be functional in these patients, suggesting an active state of tolerance and immunologic dependence on both hematopoietic systems.

Peripheral blood late mixed chimerism in leucocyte subpopulations following allogeneic stem cell transplantation for childhood malignancies: does it matter?

The impact of persistent mixed chimerism (MC) after haematopoietic stem cell transplantation (HSCT) remains unclarified. We investigated the incidence of MC in peripheral blood beyond day +50 after HSCT and its impact on rejection, chronic graft-versus-host disease (c-GvHD) and relapse in 161 children receiving allogeneic HSCT for haematological malignancies. The 1-year incidence of late MC was 26%. Spontaneous conversion to complete donor chimerism (CC) occurred in 43% of patients as compared to 62% after donor lymphocyte infusions. No graft rejection occurred. The 1-year incidence of c-GvHD was 20 ± 7% for MC, and 18 ± 4% for CC patients (P = 0·734). The 3-year cumulative incidence of relapse (CIR) according to chimerism status at days +50 and +100 was 22 ± 4% for CC patients vs. 22 ± 8% for MC patients (day +50; P = 0·935) and 21 ± 4% vs. 20 ± 7% (day +100; P = 0·907). Three-year CIRs in patients with persistent MC and patients with CC/limited MC were comparable (8 ± 7% vs. 19 ± 4%; P = 0·960). HSCT for acute leukaemia or myelodysplastic syndrome as secondary malignancies (hazard ratio (HR) 4·7; P = 0·008), for AML (HR 3·0; P = 0·02) and from mismatched donors (HR 3·1; P = 0·03) were independent factors associated with relapse. Our data suggest that late MC neither protects from c-GvHD nor does it reliably predict impending disease relapse.

Alemtuzumab levels impact acute GVHD, mixed chimerism, and lymphocyte recovery following alemtuzumab, fludarabine, and melphalan RIC HCT

Reduced intensity conditioning (RIC) allogeneic hematopoietic cell transplantation (HCT) with alemtuzumab, fludarabine, and melphalan is an effective approach for patients with nonmalignant disorders. Mixed chimerism and graft-versus-host-disease (GVHD) remain limitations on success. We hypothesized that higher levels of alemtuzumab at day 0 would result in a low risk of acute GVHD, a higher risk of mixed chimerism, and delayed early lymphocyte recovery and that alemtuzumab level thresholds for increased risks of these outcomes would be definable. We collected data from 105 patients to examine the influence of peritransplant alemtuzumab levels on acute GVHD, mixed chimerism, and lymphocyte recovery. The cumulative incidences of initial grades I-IV, II-IV, and III-IV acute GVHD in patients with alemtuzumab levels ≤0.15 vs ≥0.16 μg/mL were 68% vs 18% (P < .0001), 47% vs 13% (P = .0002), and 32% vs 8%, respectively (P = .005). The cumulative incidence of mixed chimerism in patients with an alemtuzumab level ≤0.15 μg/mL was 21%, vs 42% with levels of 0.16 to 4.35 μg/mL, and 100% with levels >4.35 μg/mL (P = .003). Patients with alemtuzumab levels ≤0.15 or 0.16 to 0.56 μg/mL had higher lymphocyte counts at day +30 and higher T-cell counts at day +100 compared with patients with levels ≥0.57 μg/mL (all P < .05). We conclude that peritransplant alemtuzumab levels impact acute GVHD, mixed chimerism, and lymphocyte recovery following RIC HCT with alemtuzumab, fludarabine, and melphalan. Precision dosing trials are warranted. We recommend a day 0 therapeutic range of 0.2 to 0.4 μg/mL.

New strategies of DLI in the management of relapse of hematological malignancies after allogeneic hematopoietic SCT

DLI is an effective strategy for patients with recurrent hematological malignancies after allogeneic hematopoietic SCT (allo-HSCT). DLI has been widely applied to boost the graft vs tumor (GVT) or GVL effects. However, given the potentially severe complications associated with conventional DLI and transient GVL effect, new strategies for DLI are emerging. In this review, we have discussed the recent important studies on DLI as a prophylactic or therapeutic modality for relapsed hematological disorders after allo-HSCT. The strategies to separate GVL from GVHD have also been discussed. Leukemia-targeting therapy and lymphodepletion combined with DLI, and prophylactic DLI after allo-HSCT are often employed for patients with high risk of relapse, which has been reviewed as well. In addition, we have also discussed the issues on DLI to be further addressed, such as the doses, timing and frequency of DLI in different clinical settings, leukemic antigen-specific DLI as well as how to augment GVL effect while attenuating GVHD.