Reduced intensity conditioning and allogeneic stem cell transplantation in childhood malignant and nonmalignant diseases

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.

Pediatric Bone Marrow Failure: A Broad Landscape in Need of Personalized Management

Irreversible severe bone marrow failure (BMF) is a life-threatening condition in pediatric patients. Most important causes are inherited bone marrow failure syndromes (IBMFSs) and (pre)malignant diseases, such as myelodysplastic syndrome (MDS) and (idiopathic) aplastic anemia (AA). Timely treatment is essential to prevent infections and bleeding complications and increase overall survival (OS). Allogeneic hematopoietic stem cell transplantation (HSCT) provides a cure for most types of BMF but cannot restore non-hematological defects. When using a matched sibling donor (MSD) or a matched unrelated donor (MUD), the OS after HSCT ranges between 60 and 90%. Due to the introduction of post-transplantation cyclophosphamide (PT-Cy) to prevent graft versus host disease (GVHD), alternative donor HSCT can reach similar survival rates. Although HSCT can restore ineffective hematopoiesis, it is not always used as a first-line therapy due to the severe risks associated with HSCT. Therefore, depending on the underlying cause, other treatment options might be preferred. Finally, for IBMFSs with an identified genetic etiology, gene therapy might provide a novel treatment strategy as it could bypass certain limitations of HSCT. However, gene therapy for most IBMFSs is still in its infancy. This review summarizes current clinical practices for pediatric BMF, including HSCT as well as other disease-specific treatment options.

Clinical Outcomes after One-day or Two-day Intervals in Conditioning Regimens for allo-HCT

One-day or two-day intervals are generally inserted into scheduled conditioning regimens for allogeneic hematopoietic cell transplantation, primarily due to various social circumstances, such as unexpected natural adversities, abrupt deterioration of patient health, and delays in graft source arrival. We compared the clinical outcomes of patients with interrupted conditioning with those with ordinarily scheduled conditioning. We analyzed 83 patients (children and adolescents) with oncologic disease who underwent myeloablative conditioning with total body irradiation. Overall and event-free survival were similar between the groups ( P =0.955, P =0.908, respectively). Non-relapse mortality and relapse rates were similar between the groups ( P =0.923, P =0.946, respectively). The engraftment rate was not affected by interruption ( P =1.000). In contrast, the incidence of chronic graft-versus-host disease (GVHD) was higher in the interrupted group compared with the scheduled group, although there was no statistical significance (42% vs. 19%, P =0.063). Conditioning interruption was identified to be an independent risk factor for chronic GVHD by multivariate analysis (odds ratio: 3.72; 95% CI: 1.04 to 13.3; P =0.043). In conclusion, apart from the incidence of chronic GVHD, clinical outcomes were not affected by one-day or two-day intervals during conditioning.

Reduced-Intensity Conditioning Mitigates Risk for Primary Ovarian Insufficiency but Does Not Decrease Risk for Infertility in Pediatric and Young Adult Survivors of Hematopoietic Stem Cell Transplantation

Hematopoietic stem cell transplantation (HSCT) is a curative therapy for many pediatric malignant and nonmalignant conditions. Gonadal insufficiency or infertility is present in almost all HSCT survivors who received a myeloablative conditioning (MAC) regimen. Reduced-intensity conditioning (RIC) regimens are being increasingly used in medically fragile patients or in patients with nonmalignant diagnoses to limit the toxicities associated with HSCT; however, the short-term and long-term gonadal toxicity of RIC regimens in pediatric and young adult survivors remains unknown. In this study, we compared the prevalence of gonadal insufficiency and infertility among pubertal and postpubertal pediatric and young adult survivors of HSCT who received a RIC regimen versus those who received a MAC regimen. Twenty-three females (RIC, n = 8; MAC, n = 15) and 35 males (RIC, n = 19; MAC, n = 16) were included in this single-center, retrospective cross-sectional study. Eligible patients were those with available laboratory results who were ≥1 year post-HSCT, age <40 years, and pubertal or postpubertal as assessed by an endocrinologist. Follicle-stimulating hormone (FSH), luteinizing hormone (LH), estradiol, and anti-Müllerian hormone (AMH) levels were measured in females, and FSH, LH, total testosterone, and inhibin B (InhB) levels were measured in males. Twenty-one males (RIC, n = 11; MAC, n = 10) underwent semen analysis through a separate consent. Parametric and nonparametric analyses were undertaken to compare the RIC and MAC groups. Female patients who received RIC were less likely than those who received MAC to develop primary ovarian insufficiency, as demonstrated by elevated FSH (P = .02) and low estradiol (P = .01) or elevated LH (P = .09). Most females in the RIC (75%) and MAC (93%) groups had low AMH levels, indicating low or absent ovarian reserve, with no significant difference between the groups (P = .53). In males, there were no significant differences between the 2 groups in the prevalence of abnormal FSH, LH, testosterone, or InhB levels. Ten of 11 RIC males (91%) and 10 of 10 MAC males (100%) had azoospermia or oligospermia, at a median time to semen analysis from HSCT of 3.7 years (range, 1.3 to 12.2 years). RIC may pose less risk than MAC for primary ovarian insufficiency among female survivors of HSCT; however, both female and male recipients of either RIC or MAC regimens are at high risk for infertility. In the largest reported series of semen analyses of pediatric and young adult male recipients of RIC, azoospermia or oligospermia was found in nearly all (91%) RIC survivors. All patients undergoing HSCT should receive counseling about the high risk of gonadal toxicity, and efforts should be made to preserve fertility in patients undergoing either RIC or MAC.

Reduced-toxicity myeloablative conditioning regimen using fludarabine and full doses of intravenous busulfan in pediatric patients not eligible for standard myeloablative conditioning regimens: Results of a multicenter prospective phase 2 trial

Data regarding the safety and efficacy of reduced-toxicity conditioning regimen (RTC) prior to allogeneic stem cell transplantation (allo-SCT) to treat hematological malignancies in pediatric patients are limited. This prospective multicenter, phase 2 trial investigated a RTC regimen based on the combination of intravenous busulfan (3.2 mg/kg/d x 4 days), fludarabine (30 mg/m²/d x 5 days) and antithymocyte globulin (Thymoglobulin®, Genzyme; 5 mg/kg total dose) with the aim of delivering high dose myeloablation that would allow optimal disease control while minimizing toxicity, in a subgroup of children at very high risk of non-relapse mortality (NRM). The primary endpoint was NRM at 1 year after allo-SCT. A total of 48 high risk patients were included (median age, 13 years; range, 3-24). At 1 year, the cumulative incidence of recurrence/disease progression and NRM were 33% and 8%, respectively. With a median follow-up of 23 months, the Kaplan-Meier estimates of overall survival (OS) and disease-free survival (DFS) at 1 year were 69% and 58%, respectively. We conclude that the RTC regimen used in this prospective trial is safe, with a < 10% NRM rate noted among high-risk children and adolescents, paving the way for larger phase 3 trials incorporating novel agents pre- and post-allo-SCT.(ClinicalTrials.gov Identifier: NCT01572181).

Dynamics of recent thymic emigrants in pediatric recipients of allogeneic hematopoetic stem cell transplantation

After allogeneic hematopoietic stem cell transplantation (allo-HSCT), the recurrence of recent thymic emigrants (RTE) and self-tolerant T cells indicate normalized thymic function. From 2008 to 2019, we retrospectively analyzed the RTE-reconstitution rate and the minimal time to reach normal age-specific first percentiles for CD31⁺CD45RA⁺CD4⁺T cells in 199 pediatric patients after allo-HSCT for various malignant and non-malignant diseases. The impact of clinically significant graft-versus-host disease (GvHD), age at transplantation, underlying disease and cumulative area under the curve of busulfan on RTE-reemergence was assessed in multivariable longitudinal analysis. RTE-reconstitution (coefficient -0.24, 95% CI -0.33 to -0.14, p < 0.001) was slowed down by GvHD and the time to reach P1 was significantly longer (Event Time Ratio 1.49, 95% CI 1.25 to 1.78, p < 0.001). Older age at transplantation was also associated with a slower RTE-reconstitution (coefficient -0.028, 95% CI -0.04 to -0.02, p < 0.001) and time to reach P1 was significantly longer (Event Time Ratio 1.03, 95% CI 1.02 to 1.05, p < 0.001). RTE-reconstitution velocity was not influenced by underlying disease or cumulative busulfan exposure. In summary, duration until thymic reactivation was independent of both conditioning intensity and underlying disease and was negatively influenced by older age and GvHD.

Mixed chimerism after allogeneic hematopoietic stem cell transplantation for severe aplastic anemia

A retrospective study on 287 patients with SAA who underwent allo-HSCT between October 2012 and January 2020 was conducted to explore the outcomes, risk factors and treatment options for MC. Among 287 AA patients who excluded Fanconi anemia (FA), Congenital dyskeratosis (DKC), Paroxysmal nocturnal hemoglobinuria (PNH), etc.112 underwent matched sibling donor (MSD)-HSCT, 91 matched unrelated donor-HSCT and 84 haploidentical-HSCT. Patients were divided into the following 4 groups: group 1: Donor chimerism (DC); group 2: MC without cytopenia; group 3: MC with cytopenia; group 4: secondary graft failure (SGF).

Compared with the other three groups, SGF predicted a poor prognosis of SAA (P< 0.001). In addition, SGF was associated with the early (within 3 months after transplantation) presence of MC and the high levels of MC. Uni- and multivariate logistic regression analysis showed that donor/recipient sex-mismatching and CTX + ATG regimen were high-risk factors for MC. Of note, in MC patients with cytopenia (group 3), the effective response rate reached 55% (6/11) following enhanced immunosuppression combined with cellular therapy, while only one of the four was effective who received enhanced immunosuppression alone.

SGF was associated with poor prognosis, early presence of MC and increased levels of recipient chimerism. The donor/recipient sex-mismatching and CTX + ATG regimen based MSD-HSCT were risk factors for MC. Cellular therapy could improve the effective response rate of patients with progressive MC.

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.

Reduced-intensity single-unit unrelated cord blood transplant with optional immune boost for nonmalignant disorders

Children with many inherited nonmalignant disorders can be cured or their condition alleviated by hematopoietic stem cell transplantation (HSCT). Umbilical cord blood (UCB) units are a rapidly available stem cell source and offer great flexibility in HLA matching, allowing nearly uniform access to HSCT. Although reduced-intensity conditioning (RIC) regimens promise decreased treatment-related morbidity and mortality, graft failure and infections have limited their use in chemotherapy-naive patients. We prospectively evaluated a novel RIC regimen of alemtuzumab, hydroxyurea, fludarabine, melphalan, and thiotepa with a single-unit UCB graft in 44 consecutive patients with inborn errors of metabolism, immunity, or hematopoiesis. In addition, 5% of the UCB graft was re-cryopreserved and reserved for cord donor leukocyte infusion (cDLI) posttransplant. All patients engrafted at a median of 15 days posttransplant, and chimerism was >90% donor in the majority of patients at 1-year posttransplant with only 1 secondary graft failure. The incidence of grade II to IV graft-versus-host disease (GVHD) was 27% (95% confidence interval [CI], 17-43) with no extensive chronic GVHD. Overall survival was 95% (95% CI, 83-99) and 85% (95% CI, 64-93) at 1 and 5 years posttransplant, respectively. No significant end-organ toxicities were observed. The use of cDLI did not affect GVHD and showed signals of efficacy for infection control or donor chimerism. This RIC transplant regimen using single-unit UCB graft resulted in outstanding survival and remarkably low rates of graft failure. Implementation of the protocol not requiring pharmacokinetic monitoring would be feasible and applicable worldwide for children with inherited disorders of metabolism, immunity, or hematopoiesis. This trial was registered at www.clinicaltrials.gov as #NCT01962415.

Fludarabine-based reduced-intensity conditioning regimen for hematopoietic stem cell transplantation in pediatric patient with IL10 receptor deficiency

IL-10R deficiency results in severe immune dysregulation. Herein, we describe the successful treatment of a girl aged 6.8 years with IL10R deficiency by using RIC prior to HSCT from a matched unrelated donor. The regimen was well tolerated, the engraftment was completely attained. On a follow-up of 7 months, the patient remained in good medical conditions with full donor chimerism. All complications before HSCT were completely resolved and her growth was accelerated. RIC regimen might be adequate to induce permanent engraftment and avoid severe organ toxicity in IL-10R deficiency patients.

Acute toxicity and outcome among pediatric allogeneic hematopoietic transplant patients conditioned with treosulfan-based regimens

Treosulfan-based regimens constitute a feasible and increasingly used, but still myeloablative, conditioning in pediatric allogeneic hematopoietic stem cell transplantation (HSCT). We retrospectively analyzed the acute toxicity and outcome of all consecutive (2004-2015) pediatric HSCT patients prepared for HSCT with treosulfan in a single-center setting. We included HSCTs performed for both nonmalignant (n = 23) and malignant diseases (n = 11). The controls were patients with nonmalignant diseases or hematological malignancies conditioned with cyclophosphamide (Cy)-total body irradiation (TBI)-based (39 patients) or busulfan-based regimens (11 patients). The major toxicities of the treosulfan-based regimens were limited to oral mucosa and skin. 50% of the patients needed IV morphine for severe mucositis compared to 31% in patients conditioned with Cy-TBI (P = 0.02). Other toxicities were rare. The disease-free survival (DFS) of patients transplanted for nonmalignant disorders was 88.9 ± 7.5% at 2 years. The event-free survival (EFS) at 2 years in this small cohort for those with a malignant disease and a treosulfan-based conditioning was 54.5 ± 1.5%. We conclude that a treosulfan-based conditioning regimen gives excellent DFS in pediatric HSCT performed for a nonmalignant disorder but with substantial mucosal toxicity. In a malignant disorder a treosulfan-based regimen looks promising but larger, preferably randomized, studies are needed to prove efficacy.

Pediatric acute graft-versus-host disease prophylaxis and treatment: surveyed real-life approach reveals dissimilarities compared to published recommendations

Pediatric allogeneic hematopoietic cell transplantation (HCT) practices differ from those of adults, particularly the heterogeneity of transplantable nonmalignant diseases and the lower incidence of graft‐versus‐host disease (GVHD). Several guidelines regarding the management of acute (a) GVHD in adult HCT have been published. We aimed to capture the real‐life approaches for pediatric aGVHD prophylaxis/treatment, and data from 75/193 (response rate 39%) EBMT centers (26 countries) were included, representing half (48%) of the pediatric EBMT‐HCT activity. Results with ≥75% approval from respondents (74/75) for GVHD prophylaxis after myeloablative HCT for malignancies partially contradict published guidelines: Single‐agent cyclosporine A (CsA) was used for matched sibling donor HCT in 47%; blood CsA levels were reported lower; the relapse risk in malignant diseases influenced GVHD prophylaxis with early withdrawal of CsA; distinct longer duration of CsA was employed in nonmalignant diseases. Most centers used additional anti‐thymocyte globulin for matched unrelated and mismatched donor HCT, but not for matched siblings. Regarding prophylaxis in nonmyeloablative conditioning (mainly for nonmalignant diseases), responses showed broad heterogeneity. High conformity was found for first‐line treatment; however, results regarding steroid‐refractory aGVHD indicate an earlier diagnosis in children. Our findings highlight the need for standardized pediatric approaches toward aGVHD prophylaxis/treatment differentiated for malignant and nonmalignant underlying diseases.

Impact of low-dose irradiation and in vivo T-cell depletion on hematopoietic stem cell transplantation for non-malignant diseases using fludarabine-based reduced-intensity conditioning

Reduced-intensity conditioning is widely used with hematopoietic stem cell transplantation for non-malignant diseases: however, the optimal conditioning to ensure stable engraftment has not been established. In this study, we retrospectively compared the impact of low-dose (1-6 Gy) irradiation and in vivo T-cell depletion on the clinical outcome of 523 patients with non-malignant disease who underwent a first allogeneic hematopoietic stem cell transplantation using fludarabine-based reduced-intensity conditioning. Use of low-dose irradiation, but not of anti-thymocyte globulin/anti-lymphocyte globulin, showed a beneficial effect on overall survival (adjusted hazard ratio: 0.56; 95% confidence interval: 0.35-0.91, P = 0.018). Furthermore, use of low-dose irradiation was strongly associated with lower transplant-related mortality (adjusted hazard ratio: 0.55; 95% confidence interval: 0.32-0.96, P = 0.034). The addition of low-dose irradiation to the conditioning regimen was beneficial, at least to the short-term clinical outcome. A large prospective study with long-term follow-up is now required to extend these findings and establish the optimal hematopoietic stem cell transplant conditioning for patients with at least some subgroups of non-malignant diseases.

Umbilical Cord Blood Transplantation Corrects Very Early-Onset Inflammatory Bowel Disease in Chinese Patients With IL10RA-Associated Immune Deficiency

BACKGROUND

Hematopoietic stem cell transplantation is considered the only curative therapy for very early-onset inflammatory bowel disease with specific immune defects, such as interleukin-10 receptor deficiency. We performed reduced-intensity conditioning before umbilical cord blood transplantation in patients with interleukin-10 receptor-A deficiency.

METHODS

We enrolled 9 very early-onset inflammatory bowel disease patients with typical manifestations. We diagnosed the patients with interleukin-10 receptor-A deficiency by whole-exome sequencing. Umbilical cord blood transplantation was performed in all 9 patients. Eight patients received the reduced-intensity conditioning regimen, and 1 patient received the myeloablative conditioning regimen.

RESULTS

All 9 patients received transplantation between the ages of 6 months to 43 months (average, 16.8 months) with body weights ranging from 3 to 10.4 kg (average, 6.6 kg). The patients displayed complete chimerism at 2-8 weeks after transplantation; 6 patients achieved complete remission without evidence of graft-vs-host disease or infections; 1 patient died of chronic lung graft-vs-host disease at 6 months post-transplantation; and the other 2 patients died of sepsis post-transplantation because of unsuccessful engraftments. Severe malnutrition and growth retardation associated with interleukin-10 receptor-A deficiency were significantly improved post-transplantation.

CONCLUSIONS

We recommend umbilical cord blood transplantation as a potential treatment for very early-onset inflammatory bowel disease with a defined monogenic immunodeficiency, and we suggest that reduced-intensity conditioning chemotherapy is more suitable than myeloablative conditioning for patients with severe malnutrition and bowel disease. We have demonstrated success with reduced-intensity conditioning for interleukin-10 receptor-A deficiency in pediatric patients with severe clinical conditions. 10.1093/ibd/izy028_video1izy028.video15786489183001.

Recipient and donor cells in the graft-versus-solid tumor effect: It takes two to tango

Allogeneic hematopoietic stem cell transplantation (alloHSCT) produces -similar to the long-established graft-versus-leukemia effect- graft-versus-solid-tumor effects. Clinical trials reported response rates of up to 53%, occurring mostly but not invariably in association with full donor chimerism and/or graft-versus-host disease. Although donor-derived T cells are considered the principal effectors of anti-tumor immunity after alloHSCT or donor leukocyte infusion (DLI), growing evidence indicate that recipient-derived immune cells may also contribute. Whereas the role of recipient-derived antigen-presenting cells in eliciting graft-versus-host reactions and priming donor T cells following DLI is well known, resulting inflammatory responses may also break tolerance of recipient effector cells towards the tumor. Additionally, mouse studies indicated that post-transplant recipient leukocyte infusion produces anti-leukemia and anti-solid-tumor effects that were exclusively mediated by recipient-type effector cells, without graft-versus-host disease. Here, we review current preclinical and clinical evidence on graft-versus-solid-tumor effects and growing evidence on the effector role of recipient-derived immune cells in the anti-tumor effect of alloHSCT.

Successful outcome following allogeneic hematopoietic stem cell transplantation in adults with primary immunodeficiency

The primary immunodeficiencies (PIDs), rare inherited diseases characterized by severe dysfunction of immunity, have been successfully treated by allogeneic hematopoietic stem cell transplantation (Allo-HSCT) in childhood. Controversy exists regarding optimal timing and use of Allo-HSCT in adults, due to lack of experience and previous poor outcomes. Twenty-nine consecutive adult patients, with a mean age at transplant of 24 years (range, 17-50 years), underwent Allo-HSCT. Reduced-intensity conditioning (RIC) included fludarabine (Flu)/melphalan/alemtuzumab (n = 20), Flu/busulfan (Bu)/alemtuzumab (n = 8), and Flu/Bu/antithymocyte globulin (n = 1). Stem cell donors were matched unrelated donors or mismatched unrelated donors (n = 18) and matched related donors (n = 11). Overall survival (OS), event-free survival, transplant-related mortality (TRM), acute and chronic graft-versus-host disease incidence and severity, time to engraftment, lineage-specific chimerism, immune reconstitution, and discontinuation of immunoglobulin replacement therapy were recorded. OS at 3 years for the whole cohort was 85.2%. The rarer PID patients without chronic granulomatous disease (CGD) achieved an OS at 3 years of 88.9% (n = 18), compared with 81.8% for CGD patients (n = 11). TRM was low with only 4 deaths observed at a median follow-up of 3.5 years. There were no cases of early or late rejection. In all surviving patients, either stable mixed chimerism or full donor chimerism were observed. At last follow-up, 87% of the surviving patients had no evidence of persistent or recurrent infections. Allo-HSCT is safe and effective in young adult patients with severe PID and should be considered the treatment of choice where an appropriate donor is available.

Reduced-toxicity alternate-donor stem cell transplantation with posttransplant cyclophosphamide for primary immunodeficiency disorders

We describe here the outcomes of reduced-toxicity alternate-donor stem cell transplant (SCT) with posttransplant cyclophosphamide (PTCy) for primary immunodeficiency disorders (PIDs) in eight children (haploidentical-seven and matched unrelated donor-one). The conditioning was with serotherapy (alemtuzumab-3/rabbit-anti-thymoglobulin-5); fludarabine, cyclophosphamide, and total body irradiation-5 (additional thiotepa-3); fludarabine and treosulfan-2; and fludarabine and busulfan-1. All received PTCy 50 mg/kg on days 3 and 4 as graft versus host disease prophylaxis along with tacrolimus and mycophenolate. Mean CD34 dose was 13.8 × 10⁶ /kg. Two children died because of PIDs. Acute graft versus host disease up to grades I and II was seen in three children. All six survivors are fully donor and disease free at median follow-up of 753 days. Alternate donor SCT with PTCy is feasible in PID and has good outcomes.

Bacterial bloodstream infections in pediatric allogeneic hematopoietic stem cell recipients before and after implementation of a central line-associated bloodstream infection protocol: A single-center experience

INTRODUCTION

There are only few reports describing the influence of central line-associated bloodstream infection (CLABSI) prevention strategies on the incidence of bacterial bloodstream infections (BBSIs).

METHODS

We performed a retrospective cohort study among pediatric recipients of allogeneic hematopoietic stem cell transplantation (allo-HCT) to assess potential changes in BBSI rates during 3 time periods: pre-CLABSI prevention era (era 1, 2004-2005), CLABSI prevention implementation era (era 2, 2006-2009), and maintenance of CLABSI prevention era (era 3, 2010-2012). BBSI from day 0-365 following allo-HCT were studied. The comparison of person-years incidence rates among different periods was carried out by Poisson regression analysis.

RESULTS

The mean age of patients was 10.0 years. During the study period, 126 (65%) of 190 patients had at least a single BBSI. From day 0-30, day 31-100, day 101-180, and day 181-365, 20%, 28%, 30%, and 17% of patients, respectively, experienced BBSIs. The rate of Staphylococcus epidermidis and gram-negative pathogens significantly declined from 3.16-0.93 and 6.32-2.21 per 100 person-months during era 1 and era 3, respectively (P = .001).

CONCLUSIONS

Patients undergoing allo-HCT during era 3 were associated with decreased risk of BBSI (P = .012). Maintenance of CLABSI protocols by nursing staff and appropriate education of other care providers is essential to lower incidence of BBSI in this high-risk population, and further strategies to decrease infection burden should be studied.

Survival Impact of Early Post-Transplant Toxicities in Pediatric and Adolescent Patients Undergoing Allogeneic Hematopoietic Cell Transplantation for Malignant and Nonmalignant Diseases: Recognizing Risks and Optimizing Outcomes

In pediatric and adolescent patients undergoing allogeneic hematopoietic cell transplantation, treatment-related toxicities remain a clinical challenge. A paucity of data investigates the risks for and survival impact of treatment-related toxicities in this population. Here the authors assess the relative toxicity of myeloablative, reduced-toxicity, and reduced-intensity conditioning regimens; identify patient-related predictors of post-transplant toxicities; and investigate the impact of early post-transplant toxicities on transplant-related mortality (TRM). In this retrospective study, 164 patients (aged 1 to 22 years) underwent allogeneic stem cell transplantation after busulfan-based conditioning for malignant and nonmalignant diseases between 2000 and 2014. The number of grades III to IV toxicities between days 0 and +30 was calculated for each patient. TRM was calculated to 2 years. Median patient age was 9 years, and median number of toxicities was 3 (range, 0 to 17). The 100-person day incidence of post-transplant toxicities in myeloablative conditioning was not different from the incidence in reduced-toxicity conditioning (13.88 versus 13.59, P = .812). Reduced intensity was less toxic than both myeloablative and reduced toxicity (13.75 versus 8.41, P < .001). Age ≥ 12 years (.276 with SE = .138, P = .045) and unrelated donor transplant (.318 with SE = 0.113, P = .005) were risk factors for ≥3 toxicities. Having ≥3 toxicities or a performance score < 90 conferred higher risk of TRM (P = .021). In pediatric and adolescent patients undergoing hematopoietic cell transplantation, reduced-toxicity conditioning was not significantly less toxic than myeloablative conditioning. Additionally, the number of post-transplant toxicities correlated with the risk of mortality. Further investigations to confirm our findings are warranted.

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.

Stem cell transplantation for the treatment of immunodeficiency in children: current status and hopes for the future

Primary immunodeficiencies (PID) are rare inherited disorders affecting immune function and can be life-threatening if not treated. Haematopoietic stem cell transplantation (HSCT) offers a curative approach for many of these disorders and gene therapy is increasingly used as an alternative therapeutic strategy for patients lacking a suitable donor. Early diagnosis, improved supportive care and advances in gene and cell therapies have resulted in increased survival rates and improved quality of life. This review describes current strategies employed to improve outcomes in PID, focusing on new developments in HSCT, gene and cell therapy. We also address the challenges associated with newborn screening (NBS) programmes and novel mutations identified through improved diagnostic technology.

Case Reports of Severe Congenital Neutropenia Treated With Unrelated Cord Blood Transplantation With Reduced-intensity Conditioning

Allogeneic stem cell transplantation is a curative treatment for severe congenital neutropenia (SCN). However, a standard conditioning regimen and donor source have not been established. We report 3 consecutive cases of SCN who were successfully treated by cord blood transplantation (CBT) with reduced-intensity conditioning consisting of fludarabine, melphalan, and low-dose total body irradiation. All cases achieved complete donor chimerism without severe infectious complications and have maintained normal neutrophil counts for between 3 and 9 years after CBT. These results suggest that CBT with reduced-intensity conditioning can be an alternative therapy for SCN when human leukocyte antigen-matched bone marrow donor is unavailable.

Salvage treatment for relapsed/refractory Hodgkin lymphoma: role of allografting, brentuximab vedotin and newer agents

INTRODUCTION

Second-line, salvage chemotherapy followed by high-dose chemotherapy and autologous stem cell transplantation (AUTO-SCT) is the standard of care for patients with relapsed/refractory (R/R) Hodgkin lymphoma (HL). Approximately 50% of patients relapse after AUTO-SCT and their prognosis is generally poor. Brentuximab Vedotin (BV) has demonstrated efficacy in this setting and allogeneic (ALLO)-SCT represents an option with curative potential in this subgroup of patients.

AREAS COVERED

A systematic review has been conducted to explore the actual knowledge on ALLO-SCT, BV and newer agents in R/R HL.

EXPERT OPINION

The introduction of BV in clinical practice has significantly improved the management of post-AUTO-SCT relapses and the drug can induce durable remissions in a subset of R/R HL. Allografting select patients has been used to improve clinical outcomes and recent case series have begun to explore BV as a potential 'bridge' to allo-SCT, even though the optimal timing of ALLO-SCT after BV response remains undetermined. However, reduced tumor burden at the time of ALLO-SCT is a key factor to decrease relapse risk. Based on the unique composition of the tumor, more recently new agents such as PD-1 inhibitors have been developed. The potential role of PD-1 inhibitors with ALLO-SCT remains to be explored.

Long-term outcomes of fludarabine, melphalan and antithymocyte globulin as reduced-intensity conditioning regimen for allogeneic hematopoietic stem cell transplantation in children with primary immunodeficiency disorders: a prospective single center study

Reduced-intensity conditioning (RIC) has offered many primary immunodeficiency disorder (PID) patients who are ineligible for myeloablative regimens a chance of cure. However, the beneficial role of RIC was questioned following reports suggesting higher chance of rejection and lower symptom resolution rate in mixed chimerism settings. Forty-five children affected by PIDs with a median age of 21 months underwent allogeneic hematopoietic stem cell transplantation in our institute from 2007 to 2013. All patients received an identical RIC regimen. Forty-one patients had successful primary engraftment (91%). Of the successful engraftments, 80% (n=33) had stable full donor chimerism at last contact. Overall, eleven transplant-related mortalities were reported including five patients due to sepsis, three children due to grade IV acute GvHD, two due to chronic GvHD and one patient due to sepsis after primary graft failure. The median post-transplantation follow-up of deceased patients was 55 days. Five-year overall survival and disease-free survival was 75.6% and 68.89%, respectively. All surviving patients with successful engraftment became disease free, regardless of having full or mixed chimerism. Our study suggests that RIC regimen provides satisfactory rates of successful engraftment and full chimerism. Furthermore, patients with mixed chimerism were stable in long-term follow-up and this chimerism status offered the potential to resolve symptoms of immunodeficiency.

Hematopoietic cell transplantation for hemophagocytic lymphohistiocytosis: recent advances and controversies

Hemophagocytic lymphohistiocytosis (HLH) is a life-threatening hyperinflammatory clinical syndrome of uncontrolled immune response which results in hypercytokinemia due to underlying primary or secondary immune defect. A number of genetic defects in transport, processing and function of cytotoxic granules which result in defective granule exocytosis and cytotoxicity of cytotoxic T lymphocytes (CTL) and natural killer (NK) cells have been well identified at the cellular and molecular level. Important advances have been made during the last 20 years in the diagnosis and treatment of HLH. The Histiocyte Society has proposed diagnostic guideline using both clinical and laboratory findings in HLH-2004 protocol, and this has been modified partly in 2009. HLH used to be a fatal disease, but the survival of HLH patients has improved to more than 60% with the use of chemoimmunotherapy combined with hematopoietic cell transplantation (HCT) over the past 2 decades. However, HCT is still the only curative option of treatment for primary HLH and refractory/relapsed HLH after proper chemoimmunotherapy. The outcome of HCT for HLH patients was also improved steadily during last decades, but HCT for HLH still carries significant mortality and morbidity. Moreover, there remain ongoing controversies in various aspects of HCT including indication of HCT, donor selection, timing of HCT, conditioning regimen, and mixed chimerism after HCT. This review summarized the important practical issues which were proven by previous studies on HCT for HLH, and tried to delineate the controversies among them.

Experience with Alemtuzumab, Fludarabine, and Melphalan Reduced-Intensity Conditioning Hematopoietic Cell Transplantation in Patients with Nonmalignant Diseases Reveals Good Outcomes and That the Risk of Mixed Chimerism Depends on Underlying Disease, Stem Cell Source, and Alemtuzumab Regimen

Alemtuzumab, fludarabine, and melphalan reduced-intensity conditioning (RIC) regimens are increasingly used for the hematopoietic cell transplantation (HCT) of pediatric and young adult patients with nonmalignant diseases. Early experience suggests that these regimens are associated with good survival but a high incidence of mixed chimerism, which we have previously shown to be influenced by the alemtuzumab schedule. We hypothesized that the underlying diagnosis and donor graft source would also affect the development of mixed chimerism and that the majority of patients would survive RIC HCT without graft loss. To examine this, we conducted a retrospective study of 206 patients with metabolic diseases, non-Fanconi anemia marrow failure disorders, and primary immune deficiencies who underwent 210 consecutive RIC HCT procedures at Cincinnati Children's Hospital. Ninety-seven percent of the patients engrafted. Mixed donor and recipient chimerism developed in 46% of patients. Patients with marrow failure had a low risk of mixed chimerism (hazard ratio [HR], .208; 95% confidence interval [CI], .061 to .709; P = .012). The risk of mixed chimerism was high in patients who received a cord blood graft (HR, 3.122; 95% CI, 1.236 to 7.888; P = .016). As expected, patients who received a proximal or higher dose per kilogram of alemtuzumab schedule also experienced higher rates of mixed chimerism (all HR > 2, all P < .05). At the time of last follow-up (median, 654 days; range, 13 to 3337), over 75% of patients had greater than 90% whole blood donor chimerism. A second transplantation was performed in 5% of patients. Three-year survival without retransplantation was 84% (95% CI, 71% to 98%) for patients who underwent transplantation with an HLA-matched sibling donor. Survival without retransplantation was negatively affected by lack of a matched related donor, increasing age, and development of grades III and IV acute graft-versus-host disease. We conclude that alemtuzumab, fludarabine, and melphalan RIC HCT offers good results for many patients and that the risk of developing mixed chimerism is influenced by underlying diagnosis, graft source, and alemtuzumab dosing.

Cardiac QTc interval characteristics before and after hematopoietic stem cell transplantation: an analysis of 995 consecutive patients at a single center

Hematopoietic stem cell transplantation (HSCT) treats disorders affecting patients of all ages. We studied the rate-corrected cardiac QT interval (QTc) in 995 consecutive children and adults undergoing HSCT at the University of Minnesota. We sought to (1) describe QTc before and after HSCT; (2) describe the change in QTc after HSCT; (3) identify factors affecting QTc and its change; and (4) scrutinize an 'at risk' sub-cohort with a long QTc before HSCT. Pre HSCT: 952 (96%) patients had an evaluable electrocardiography (ECG); median QTc was 426 ms and depended upon disease necessitating transplant. Post HSCT: 506 (51%) patients had an evaluable ECG; median QTc was 441 ms. Intrapatient QTc change: 490 (49%) evaluable patients showed median QTc change (pre to post HSCT) of +16 ms (P<0.0001). At risk group: 68 patients were 'at risk' (long pre-HSCT QTc). In some, 'at-risk' status trended toward predictive of post-transplant nonrelapse mortality. QTc interval prolongation is evident in a large, diverse cohort undergoing HSCT at our institution. Prospective studies of this patient population may be warranted, particularly for 'at-risk' patients who demonstrate significant QTc prolongation both pre and post HSCT.

Chronic granulomatous disease-haematopoietic stem cell transplantation versus conventional treatment

AIM

Chronic granulomatous disease (CGD) is a rare X-linked or autosomal recessive primary immune deficiency characterized by recurrent, life-threatening bacterial and fungal infections. Mortality rates are high with conventional treatment. However, haematopoietic stem cell transplantation (HSCT) offers cure. Here, we compare the outcome of HSCT in 14 Swedish patients with CGD to that in 27 patients with CGD who were given conventional treatment.

METHODS

Forty-one patients in Sweden were diagnosed with CGD between 1990 and 2012. From 1997 to 2012, 14 patients with CGD, aged 1-35 years, underwent HSCT and received grafts either from an HLA-matched sibling donor or a matched unrelated donor.

RESULTS

Thirteen of the 14 transplanted patients are alive and well. Mean age at transplantation was 10.4 years, and the mean survival time was 7.7 years. In contrast, seven of 13 Swedish men or boys with X-linked CGD who were treated conventionally died from complications of CGD at a mean age of 19 years, while the remaining patients suffered life-threatening infections.

CONCLUSION

The outcome of the patients who underwent HSCT supports HSCT as being the preferable treatment for severe CGD. Our results advocate early HSCT for all patients with X-linked CGD, using grafts from either a matched sibling donor or a matched unrelated donor.

An intermediate alemtuzumab schedule reduces the incidence of mixed chimerism following reduced-intensity conditioning hematopoietic cell transplantation for hemophagocytic lymphohistiocytosis

Reduced-intensity conditioning (RIC) improves the outcomes of hematopoietic cell transplantation (HCT) in patients with hemophagocytic lymphohistiocytosis (HLH). Proximal (ie, close to graft infusion) dosing of alemtuzumab is associated with a high incidence of mixed chimerism, whereas distal (ie, distant from graft infusion) dosing is associated with less mixed chimerism but more acute graft-versus-host disease (GVHD). The alemtuzumab dose per kilogram of body weight also influences these outcomes. We hypothesized that an intermediate alemtuzumab dosing schedule would reduce mixed chimerism and maintain a low incidence of acute GVHD. In this study, 24 consecutive HCTs were performed in patients with HLH or a related disorder using a novel intermediate alemtuzumab schedule of 1 mg/kg starting on day -14. The cumulative incidences (CIs) of mixed chimerism, upfront acute GVHD grades II-IV, and receipt of additional hematopoietic cell products after HCT were compared in patients treated with a distal alemtuzumab schedule (n = 15) and those treated with a proximal alemtuzumab schedule (n = 33). All patients received fludarabine and melphalan. The CI of mixed chimerism was 31% in the intermediate group, 72% in the proximal group (P < .01), and 75% in the distal group patients who received ≥2 mg/kg alemtuzumab (P = .03). The CI of acute GVHD grades II-IV before the development of mixed chimerism was 4% in the intermediate group, 0% in the proximal group, and 13% in the distal group (P = .04, proximal versus distal). The 1-year CI of administration of additional hematopoietic cell products for mixed chimerism (donor lymphocyte infusion ± hematopoietic stem cell boost ± repeat HCT) was 14% in the intermediate group, 53% in the proximal group (P = .01), and 38% in the distal ≥2 mg/kg alemtuzumab group (P = .02). Our findings indicate that intermediate RIC reduces the incidence of mixed chimerism, is associated with a low incidence of upfront acute GVHD, and decreases the need for additional hematopoietic cell products after HCT.

Bone marrow transplantation in Schimke immuno-osseous dysplasia

Schimke immuno-osseous dysplasia (SIOD, OMIM 242900) is a rare autosomal recessive multisystem childhood disorder characterized by short stature, renal failure, T-cell immunodeficiency, and hypersensitivity to genotoxic agents. SIOD is associated with biallelic mutations in SMARCAL1 (SWI/SNF-related matrix-associated actin-dependent regulator of chromatin, subfamily a-like 1), which encodes a DNA stress response enzyme with annealing helicase activity. Two features of SIOD causing much morbidity and mortality are bone marrow failure and T-cell deficiency with the consequent opportunistic infections. To address the safety and efficacy of bone marrow transplantation (BMT) in SIOD, we reviewed the outcomes of the only five SIOD patients known to us in whom bone marrow or hematopoietic stem cell transplantation has been attempted. We find that only one patient survived the transplantation procedure and that the existing indicators of a good prognosis for bone marrow transplantation were not predictive in this small cohort. Given these observations, we also discuss some considerations for the poor outcomes.

Reduced-intensity conditioning followed by allogeneic transplantation in pediatric malignancies: a report from the Société Française des Cancers de l'Enfant and the Société Française de Greffe de Moelle et de Thérapie Cellulaire

We report French prospective experience with reduced-intensity conditioning-allo-SCT in 46 patients (median age: 15.5 years, 4.8-20.2) presenting high-risk AL (n=11), Hodgkin's lymphoma (n=15) or solid tumors (n=20). Graft sources were BM (n=21), PBSC (n=20) and cord blood (CB; n=5) from related (n=20) or unrelated (n=26) donors. For CB grafts, only one patient out of five achieved sustained engraftment. For PBSC/BM grafts, engraftment rate was 95%, hematopoietic recovery times were not significantly different between BM, PBSC, sibling or unrelated grafts, day+100. Full donor chimerism was achieved in 94% of patients, and incidences of primary acute GVHD and chronic GVHD were 49% and 14%, respectively. Underlying disease was fatal in 39% of patients. TRM was 6.9%. Three-year OS was 49.15%. OS and EFS were not significantly different between patients transplanted with different grafts and with or without primary GVHD. Patients with solid tumor or measurable disease at transplant had poorer outcomes. Three-year EFS: 33.3% for ALL, 75.0% for AML, 51.8% for Hodgkin's lymphoma, 28.6% for neuroblastoma and 22.2% for sarcoma patients. This multicentre study concluded that Bu/fludarabine/anti-thymocyte globulin conditioning with PB or BM, related or unrelated grafts in patients with various malignancies at high-risk for transplantation toxicity results in high engraftment rates, low TRM and acceptable survival.

Reduced-intensity conditioning for allogeneic stem cell transplant in primary immune deficiencies

Conventional myeloablative conditioning regimens prior to hematopoietic cell transplantation (HCT) are associated with significant transplant-related morbidity and mortality in children affected by primary immunodeficiency disorders. Reduced-intensity conditioning regimens have been extensively used without severe acute toxicity in patients with pre-HCT comorbidities, with the additional advantage of reducing or avoiding long-term sequelae such as infertility and growth retardation. Compared with myeloablative HCT, reduced-intensity conditioning regimens are associated with an increased incidence of mixed donor chimerism and graft rejection. While mixed donor engraftment is likely to correct the phenotypic expression of most children with primary immunodeficiency disorders, the use of donor lymphocyte infusion to increase donor chimerism or second HCT procedures may be required in some cases. Here we discuss the most recent data on the use of different reduced-intensity conditioning protocols in children with primary immunodeficiency disorders, highlighting significant clinical lessons and areas that need additional study.

Allogeneic hematopoietic stem cell transplantation following reduced-intensity conditioning regimen in children: a single-center experience

This single-center retrospective study reported the outcome of 19 children treated with a reduced-intensity conditioning (RIC) regimen prior to allogeneic stem cell transplantation (allo-SCT), for hematologic malignancies (n = 17), bone marrow failure (n = 1), and neuroblastoma (n = 1). Children were ineligible for standard myeloablative conditioning because of severe comorbidities (n = 9), a previous auto or allo-SCT (n = 7) or a prior history of extensive chemotherapy (n = 3). All patients underwent a fludarabine-based RIC regimen, and received grafts from matched-related donors (n = 5), match-unrelated donors (n = 6), or unrelated cord blood (UCB, n = 8). In this series, two patients treated with UCB failed to engraft and 63% achieved full donor chimerism at day 100 after allo-SCT. With a median follow-up of 537 d (range, 115-4136), treatment-related mortality was 16% and overall survival was 47%. The principal cause of death was disease relapse (n = 7). Acute graft versus host disease (GVHD) occurred in 53% of patients, while only 10% developed extensive chronic GVHD. Overall, results from this series suggest that RIC allo-SCT can be a valid alternative treatment option in unfit children with malignant hematological diseases. Prospective studies are needed to enlarge pediatric experience in this domain and better identify those children more suitable for a RIC allo-SCT approach.

Early recipient chimerism testing in the T- and NK-cell lineages for risk assessment of graft rejection in pediatric patients undergoing allogeneic stem cell transplantation

Timely diagnosis of impending graft rejection is crucial for effective therapeutic intervention after allogeneic hematopoietic stem cell transplantation (SCT). We have investigated the predictive potential of early leukocyte subset-specific chimerism for graft loss in children undergoing SCT. In total, 192 pediatric patients transplanted for the treatment of malignant and non-malignant diseases after reduced-intensity or myeloablative conditioning were investigated. Surveillance of lineage-specific chimerism was initiated upon first appearance of leukocyte counts amenable to cell sorting. Graft rejection occurred in 23 patients between 24 and 492 days post-transplant (median 63 days). The first chimerism analysis of T and NK cells performed at a median of 20 days after SCT identified three different risk groups that were independent from the conditioning regimen: recipient chimerism (RC) levels in T cells below 50% indicated a very low risk of rejection (1.4%), whereas high levels of RC (>90%) both in T and NK cells heralded graft loss in the majority of patients (90%) despite therapeutic interventions. RC >50% in T cells and ≤90% in NK cells defined an intermediate-risk group in which timely immunotherapy frequently prevented rejection. Early assessment of T- and NK-cell chimerism can therefore be instrumental in the risk assessment and therapeutic management of imminent graft rejection.

Reduced intensity transplantation for primary immunodeficiency disorders

Studies so far indicate that reduced intensity transplantation (RIT) may have an important role in treating patients with primary immunodeficiency disease (PID). Unlike more standard approaches, such regimens can be used without severe toxicity in patients with severe pulmonary or hepatic disease. RIT also offers the advantage that long-term sequelae such as infertility or growth retardation may be avoided or reduced. RIT appears to be most appropriate for those patients with significant co-morbidities (eg T cell deficiencies) and those undergoing unrelated donor haematopoietic cell transplantation. More studies are required using pharmacokinetic monitoring (eg busulphan, treosulfan and alemtuzumab) and varying stem cell sources to optimise graft vs marrow reactions and minimise graft vs host disease. In certain PID patients RIT will be the "first step" towards establishing donor cell engraftment; second infusions of donor stem cells, donor lymphocyte infusions, or a second myeloablative HCT, which appears to be well tolerated, may be required in some patients with low level donor chimerism or graft rejection.

Molecular diagnosis of severe combined immunodeficiency--identification of IL2RG, JAK3, IL7R, DCLRE1C, RAG1, and RAG2 mutations in a cohort of Chinese and Southeast Asian children

Severe combined immunodeficiencies (SCID) are a group of rare inherited disorders with profound defects in T cell and B cell immunity. From 2005 to 2010, our unit performed testing for IL2RG, JAK3, IL7R, RAG1, RAG2, DCLRE1C, LIG4, AK2, and ZAP70 mutations in 42 Chinese and Southeast Asian infants with SCID adopting a candidate gene approach, based on patient's gender, immune phenotype, and inheritance pattern. Mutations were identified in 26 patients, including IL2RG (n = 19), IL7R (n = 2), JAK3 (n = 2), RAG1 (n = 1), RAG2 (n = 1), and DCLRE1C (n = 1). Among 12 patients who underwent hematopoietic stem cell transplantation, eight patients survived. Complications and morbidities during transplant period were significant, especially disseminated bacillus Calmette-Guérin disease which was often difficult to control. This is the first cohort study on SCID in the Chinese and Southeast Asian population, based on a multi-centered collaborative research network. The foremost issue is service provision for early detection, diagnosis, management, and definitive treatment for patients with SCID. National management guidelines for SCID should be established, and research into an efficient platform for genetic diagnosis is needed.

Hematopoietic stem cell transplantation and other management strategies for MHC class II deficiency

Major histocompatibility complex (MHC) class II expression deficiency is a rare condition with autosomal recessive transmission. The defect of MHC class II leads to combined immunodeficiency with defective CD4(+) T-cell development and a lack of T helper cell-dependent antibody production by B cells. The clinical course of disease is characterized by the recurrence of bacterial, viral, fungal, and protozoan infections. The optimal symptomatic care that is available involves the prophylactic use of antibiotics and the administration of immunoglobulin with adequate nutritional support. Hematopoietic stem cell transplantation is the only known treatment available to cure MHC class II expression deficiency.

Reduced intensity transplantation for primary immunodeficiency disorders

Many advances have been made since the first successful hematopoietic cell transplants (HCT) in children with primary immunodeficiency disorders (PID) were reported 40 years ago, and many children with PID can now be cured from their otherwise lethal disorders through well-matched HCT procedures. Preexisting morbidity and infection remain the principal adverse factors for poor outcomes with HCT. To improve current results, earlier diagnosis, well-tolerated pretransplant conditioning regimens, and promotion of immune reconstitution need to be considered. This article addresses modifications in the conditioning regimen that might lead to further improvement in HCT outcomes.