Survival in primary hemophagocytic lymphohistiocytosis, 2016 to 2021: etoposide is better than its reputation.

ABSTRACT: Primary hemophagocytic lymphohistiocytosis (pHLH) is a life-threatening hyperinflammatory syndrome that develops mainly in patients with genetic disorders of lymphocyte cytotoxicity and X-linked lymphoproliferative syndromes. Previous studies with etoposide-based treatment followed by hematopoetic stem cell transplantation (HSCT) resulted in 5-year survival of 50% to 59%. Contemporary data are lacking. We evaluated 88 patients with pHLH documented in the international HLH registry from 2016-2021. In 12 of 88 patients, diagnosis was made without HLH activity, based on siblings or albinism. Major HLH-directed drugs (etoposide, antithymocyte globulin, alemtuzumab, emapalumab, ruxolitinib) were administered to 66 of 76 patients who were symptomatic (86% first-line etoposide); 16 of 57 patients treated with etoposide and 3 of 9 with other first-line treatment received salvage therapy. HSCT was performed in 75 patients; 7 patients died before HSCT. Three-year probability of survival (pSU) was 82% (confidence interval [CI], 72%-88%) for the entire cohort and 77% (CI, 64%-86%) for patients receiving first-line etoposide. Compared with the HLH-2004 study, both pre-HSCT and post-HSCT survival of patients receiving first-line etoposide improved, 83% to 91% and 70% to 88%. Differences to HLH-2004 included preferential use of reduced-toxicity conditioning and reduced time from diagnosis to HSCT (from 148 to 88 days). Three-year pSU was lower with haploidentical (4 of 9 patients [44%]) than with other donors (62 of 66 [94%]; P < .001). Importantly, early HSCT for patients who were asymptomatic resulted in 100% survival, emphasizing the potential benefit of newborn screening. This contemporary standard-of-care study of patients with pHLH reveals that first-line etoposide-based therapy is better than previously reported, providing a benchmark for novel treatment regimes.

[Updated AWMF Guideline on the Diagnosis and Treatment of Langerhans cell Histiocytosis in Children and Adolescents]. / Aktualisierte AWMF Leitlinie zur Diagnostik und Therapie der Langerhanszell Histiozytose (LCH) im Kindes- und Jugendalter.

Langerhans cell Histiocytosis is a rare neoplastic disease, which occurs mainly in children and adolescents. The disease may affect any organ, and therefore, the clinical symptoms vary widely. Some patients have a spontaneous remission of the disease, whereas others experience a rapid and potentially lethal clinical course. The therapeutic approach depends on the extent of the disease, and reaches from a watch-and-wait strategy to chemotherapy with the standard drugs vinblastine and prednisone. The identification of mutations in the MAPK-pathway resulted in growing interest in targeted therapy using compounds such as the BRAF inhibitors. Chronic relapses and permanent sequelae are important problems of LCH and are the focus of current research.

Letermovir for Prophylaxis and Pre-emptive Therapy of Cytomegalovirus Infection in Paediatric Allogeneic Haematopoietic Cell Transplant Patients.

BACKGROUND: Cytomegalovirus (CMV) infection is a frequent event in patients undergoing allogeneic haematopoietic cell transplantation (HCT) and is associated with increased morbidity and mortality due to eventual progress to end-organ disease. Letermovir prophylaxis for CMV infections has become a standard of care in adult HCT recipients due to its efficacy and high tolerability. However, it is not yet approved for paediatric patients. OBJECTIVE: In a retrospective single-centre observational study we evaluated the use of letermovir for prophylaxis or pre-emptive treatment of cytomegalovirus (CMV) infection in seropositive paediatric HCT recipients receiving the compound outside of clinical trials. The primary endpoint was CMV reactivation requiring a change of medication. METHODS: A total of 17 patients (seven female/ten male; median age 12.2 [range 3.5-19] years, median body weight 39.5 [range 15-63] kg; median follow-up time 463.7 [range 41-1022] days) were identified who were started on oral (14) or intravenous (3) followed by oral (2) letermovir shortly after neutrophil engraftment at doses determined on the basis of age, weight, and concomitant cyclosporine use. RESULTS: Five patients had no evidence of viral replication (prophylactic use), while 12 patients had varying extents of viral replication (pre-emptive therapy). A change of therapy was required in one patient due to a sustained increase in CMV viral load, and in two patients, letermovir was stopped without later reactivation after initiation of palliative care for recurrent leukaemia. Of the 14 patients who completed treatment, 3 had evidence of transient viral replication after end of treatment that required no further antiviral treatment. No patients (of 17) discontinued letermovir due to an adverse event. CONCLUSION: Letermovir was effective in controlling CMV infection in seropositive paediatric allogeneic HCT recipients and was overall well tolerated. Pending completion of the still ongoing paediatric investigation plans, letermovir will be an important adjunct to our options for control of infectious complications in this special population.

Extracorporeal Membrane Oxygenation in Children With Cancer or Hematopoietic Cell Transplantation: Single-Center Experience in 20 Consecutive Patients.

Extracorporeal membrane oxygenation (ECMO) is a rescue therapy for severe respiratory and/or circulatory failure. Few data exist on the potential benefit of ECMO in immunocompromised pediatric patients with cancer and/or hematopoietic cell transplantation (HCT). Over a period of 12 years, eleven (1.9%) of 572 patients with new diagnosis of leukemia/lymphoma and nine (3.5%) of 257 patients post allogeneic HCT underwent ECMO at our center. Five (45%) and two (22%) patients, respectively, survived to hospital discharge with a median event-free survival of 4.2 years. Experiences and outcomes in this cohort may aid clinicians and families when considering ECMO for individual patients.

Cord Blood Low-Density Granulocytes Correspond to an Immature Granulocytic Subset with Low Expression of S100A12.

Although substantial progress has been achieved concerning neonatal sepsis, its lethality remains considerably high, and further insights into peculiarities and malfunctions of neonatal immunity are needed. This study aims to contribute to a better understanding of the role of human neonatal granulocyte subpopulations and calgranulin C (S100A12). For this purpose, we gathered 136 human cord blood (CB) samples. CD66b+ CB low-density granulocytes (LDG) and CB normal-density granulocytes were isolated and functionally and phenotypically compared with healthy adult control granulocytes. We could identify CB-LDG as CD66bbright CD64high CD16low CD35low CD10low S100A12med-low and, based on these markers, recovered in whole CB stainings. Consistent with flow cytometric findings, microscopic imaging supported an immature phenotype of CB-LDG with decreased S100A12 expression. In CB serum of healthy neonates, S100A12 was found to be higher in female newborns when compared with males. Additionally, S100A12 levels correlated positively with gestational age independently from sex. We could solidify functional deficits of CB-LDG concerning phagocytosis and generation of neutrophil extracellular traps. Our study reveals that previously described suppressive effects of CB-LDG on CD4+ T cell proliferation are exclusively due to phagocytosis of stimulation beads used in cocultures and absent when using soluble or coated Abs. In conclusion, we characterize CB-LDG as immature neutrophils with functional deficits and decreased expression and storage of S100A12. Concerning their cross-talk with the adaptive immunity, we found no direct inhibitory effect of LDG. Neonatal LDG may thus represent a distinct population that differs from LDG populations found in adults.

Emapalumab in Children with Primary Hemophagocytic Lymphohistiocytosis.

BACKGROUND: Primary hemophagocytic lymphohistiocytosis is a rare syndrome characterized by immune dysregulation and hyperinflammation. It typically manifests in infancy and is associated with high mortality. METHODS: We investigated the efficacy and safety of emapalumab (a human anti-interferon-γ antibody), administered with dexamethasone, in an open-label, single-group, phase 2-3 study involving patients who had received conventional therapy before enrollment (previously treated patients) and previously untreated patients who were 18 years of age or younger and had primary hemophagocytic lymphohistiocytosis. The patients could enter a long-term follow-up study until 1 year after allogeneic hematopoietic stem-cell transplantation or until 1 year after the last dose of emapalumab, if transplantation was not performed. The planned 8-week treatment period could be shortened or extended if needed according to the timing of transplantation. The primary efficacy end point was the overall response, which was assessed in the previously treated patients according to objective clinical and laboratory criteria. RESULTS: At the cutoff date of July 20, 2017, a total of 34 patients (27 previously treated patients and 7 previously untreated patients) had received emapalumab; 26 patients completed the study. A total of 63% of the previously treated patients and 65% of the patients who received an emapalumab infusion had a response; these percentages were significantly higher than the prespecified null hypothesis of 40% (P = 0.02 and P = 0.005, respectively). In the previously treated group, 70% of the patients were able to proceed to transplantation, as were 65% of the patients who received emapalumab. At the last observation, 74% of the previously treated patients and 71% of the patients who received emapalumab were alive. Emapalumab was not associated with any organ toxicity. Severe infections developed in 10 patients during emapalumab treatment. Emapalumab was discontinued in 1 patient because of disseminated histoplasmosis. CONCLUSIONS: Emapalumab was an efficacious targeted therapy for patients with primary hemophagocytic lymphohistiocytosis. (Funded by NovImmune and the European Commission; NI-0501-04 and NI-0501-05 ClinicalTrials.gov numbers, NCT01818492 and NCT02069899.).

Epidemiology, utilisation of healthcare resources and outcome of invasive fungal diseases following paediatric allogeneic haematopoietic stem cell transplantation.

BACKGROUND: Epidemiology and management practices of invasive fungal diseases (IFD) after allogeneic haematopoietic stem cell transplantation (HSCT) are a subject of constant change. We investigated the contemporary incidence, diagnostics, antifungal management and outcome at a major paediatric transplant centre in Germany. METHODS: The single-centre retrospective observational study included all paediatric allogeneic HSCT patients (pts) transplanted between 2005 and 2015. Patient-related data were assessed up to 365 days post-transplant. The primary endpoint was the incidence of possible, probable and proven IFDs. Secondary endpoints included diagnostics and antifungal treatment; analysis of risk factors; and overall survival with the last follow-up in January 2017. RESULTS: A total of 221 first (196), second (21) or third (4) procedures were performed in 200 pts (median age: 9 years, range, 0.5-22) for leukaemia/lymphoma (149) and non-malignant disorders (72). Prophylaxis was administered in 208 HSCT procedures (94%; fluconazole, 116, mould-active agents, 92). At least one computed tomography scan of the chest was performed in 146, and at least one galactomannan antigen assay in 60 procedures. There were 15 cases of proven (candidemia, 4; aspergillosis, 4) or probable (aspergillosis, 7) IFDs, accounting for an incidence rate of 6.8%. Overall mortality at last follow-up was 30%; the occurrence of proven/probable IFDs was associated with a reduced survival probability (P < .001). CONCLUSION: Morbidity and mortality from IFDs at our institution were consistent with data reported from other centres. Utilisation of healthcare resources for prevention, diagnosis and management of IFDs was considerable.

Vemurafenib for Refractory Multisystem Langerhans Cell Histiocytosis in Children: An International Observational Study.

PURPOSE: Off-label use of vemurafenib (VMF) to treat BRAFV600E mutation-positive, refractory, childhood Langerhans cell histiocytosis (LCH) was evaluated. PATIENTS AND METHODS: Fifty-four patients from 12 countries took VMF 20 mg/kg/d. They were classified according to risk organ involvement: liver, spleen, and/or blood cytopenia. The main evaluation criteria were adverse events (Common Terminology Criteria for Adverse Events [version 4.3]) and therapeutic responses according to Disease Activity Score. RESULTS: LCH extent was distributed as follows: 44 with positive and 10 with negative risk organ involvement. Median age at diagnosis was 0.9 years (range, 0.1 to 6.5 years). Median age at VMF initiation was 1.8 years (range, 0.18 to 14 years), with a median follow-up of 22 months (range, 4.3 to 57 months), whereas median treatment duration was 13.9 months (for 855 patient-months). At 8 weeks, 38 complete responses and 16 partial responses had been achieved, with the median Disease Activity Score decreasing from 7 at diagnosis to 0 (P < .001). Skin rash, the most frequent adverse event, affected 74% of patients. No secondary skin cancer was observed. Therapeutic plasma VMF concentrations (range, 10 to 20 mg/L) seemed to be safe and effective. VMF discontinuation for 30 patients led to 24 LCH reactivations. The blood BRAFV600E allele load, assessed as circulating cell-free DNA, decreased after starting VMF but remained positive (median, 3.6% at diagnosis, and 1.6% during VMF treatment; P < .001) and was associated with a higher risk of reactivation at VMF discontinuation. None of the various empirical therapies (hematopoietic stem-cell transplantation, cladribine and cytarabine, anti-MEK agent, vinblastine, etc) used for maintenance could eradicate the BRAFV600E clone. CONCLUSION: VMF seemed safe and effective in children with refractory BRAFV600E-positive LCH. Additional studies are needed to find effective maintenance therapy approaches.

Plasma exposures following posaconazole delayed-release tablets in immunocompromised children and adolescents.

BACKGROUND: Posaconazole is a recommended option for antifungal prophylaxis in paediatric patients >12 years of age. However, little is known about plasma exposures and safety following administration of the delayed-release tablets (DRTs) in children and adolescents. METHODS: In a retrospective observational study, we analysed steady-state trough concentrations of posaconazole in all paediatric patients who had received the DRT formulation between May 2015 and December 2018 for antifungal prophylaxis. Dosing was guided by a published population pharmacokinetic model with weight-based dosing. Drug concentrations in plasma were measured by a validated tandem MS method. Liver function and drug discontinuations due to adverse effects were also assessed. RESULTS: A total of 34 patients (21 male, 13 female; median age 12 years, range 5-17 years; median body weight 43.5 kg, range 16-84 kg) undergoing treatment for haemato-oncological disorders (n=23) or immunosuppression for polyarthritis (n=1) or post-allogeneic HSCT (n=11) received posaconazole DRTs for a median of 70 days (range 9-391 days). The median first steady-state trough plasma concentration following model-derived dosing was 1607 ng/mL (range 501-8485 ng/mL) with trough concentrations being above the dosing target of ≥700 ng/mL in 32/34 patients (94%). Considering all (first and subsequent) trough concentrations, target attainment was 90% (63/70 samples). Posaconazole was well tolerated without adverse event-related discontinuations or breakthrough infections. CONCLUSIONS: Administration of posaconazole DRTs to paediatric patients guided by a population pharmacokinetic-derived dosing algorithm resulted in predictable and potentially effective exposures and was well tolerated over prolonged time periods.

Epidemiology and management burden of invasive fungal infections after autologous hematopoietic stem cell transplantation: 10-year experience at a European Pediatric Cancer Center.

BACKGROUND: Autologous hematopoietic stem cell transplantation (HSCT) carries risks of infectious morbidity. We analysed epidemiology and management burden associated with invasive fungal diseases (IFDs) in children and adolescents undergoing autologous HSCT. METHODS: In a retrospective, single-centre observational study, epidemiology and management burden associated with IFDs were analysed in all paediatric cancer patients who underwent autologous HSCT between 2005 and 2014. Clinical, radiographic and microbiological data were assessed up to 100 days post-transplant. The primary endpoint was the incidence of proven, probable and possible IFDs. Further endpoints included the use of systemic antifungal agents for prevention and management of IFDs; infectious and non-infectious comorbidities; and survival until day + 100. RESULTS: Of 95 patients (median age: 8 years; r, 0.75-20) underwent 103 HSCT procedures for solid tumours (92) or lymphoma (11). Primary antifungal prophylaxis was administered in 49 procedures (47.5%). No single case of proven/probable IFD was diagnosed. Nine cases (8.7%) fulfilled criteria of possible pulmonary mould infection and received treatment for a median of 14 days (r, 7-35). In an additional 12 procedures, empiric antifungal therapy with mould active agents was given for a median of 8 days (r, 3-105). Microbiologically documented non-fungal infections were observed in 17 procedures, and five patients were transferred to the ICU. There was one death from biopsy documented toxic endothelial damage at day 83 post-transplant. CONCLUSIONS: Autologous HSCT for solid tumours or lymphoma was associated with low morbidity from IFDs. However, utilisation of systemic antifungal agents for prevention and management of suspected IFDs was considerable.

Presence of centromeric but absence of telomeric group B KIR haplotypes in stem cell donors improve leukaemia control after HSCT for childhood ALL.

Although allogeneic hematopoietic stem-cell transplantation (HSCT) provides high cure rates for children with high-risk acute lymphoblastic leukaemia (ALL), relapses remain the main cause of treatment failure. Whereas donor killer cell immunoglobulin-like receptor (KIR) genotype was shown to impact on relapse incidence in adult myeloid leukaemia similar studies in paediatric ALL are largely missing. Effect of donor KIR genotype on transplant outcome was evaluated in 317 children receiving a first myeloablative HSCT from an HLA-matched unrelated donor or sibling within the prospective ALL-SCT-BFM-2003 trial. Analysis of donor KIR gene polymorphism revealed that centromeric presence and telomeric absence of KIR B haplotypes was associated with reduced relapse risk. A centromeric/telomeric KIR score (ct-KIR score) integrating these observations correlated with relapse risk (hazard ratio (HR) 0.58; P = 0.002) while it had no impact on graft-versus-host disease or non-relapse mortality. In multivariable analyses ct-KIR score was associated with reduced relapse risk (HR 0.58; P = 0.003) and a trend towards improved event-free survival (HR 0.76; P = 0.059). This effect proved independent of MRD level prior to HSCT. Our data suggest that in children with ALL undergoing HSCT after myeloablative conditioning, donor selection based on KIR genotyping holds promise to improve clinical outcome by decreasing relapse risk and prolonged event-free survival.

Longitudinal assessment of peripheral blood BRAFV600E levels in patients with Langerhans cell histiocytosis.

BACKGROUND: Langerhans cell histiocytosis (LCH) is a histiocytic disorder driven by a constitutive activation of the MAPK signaling pathway in myeloid cells. In 50-60% of cases, it is caused by the BRAFV600E mutation. There is evidence that levels of BRAFV600E in the peripheral blood of patients with LCH correlate with disease burden and could be used as marker for disease extent and response to therapy. However, there is currently no consensus on how testing for minimal disseminated disease should be performed. METHODS: Different approaches to determine the mutation load in patients with LCH were assessed and longitudinal evaluation of patient DNA during treatment with chemotherapy and/or the RAF inhibitor vemurafenib was performed. DNA was isolated from whole blood, different leukocyte subsets, and circulating cell-free DNA (ccf-DNA). RESULTS: We show that determining BRAF levels from whole blood is superior to using ccfDNA. Furthermore, it is important to identify the clinically relevant BRAF-mutated cellular subpopulations such as CD14+ monocytes or CD1c+ DCs, since other blood cells can also harbor the mutation and therefore confound whole blood or ccfDNA measurements. CONCLUSION: Our data support the view that single-agent treatment with an RAF inhibitor reduces disease activity but does not cure LCH.

Disseminated Bartonella henselae disease mimicking Langerhans' cell histiocytosis.

Bartonella henselae, the causative agent of cat-scratch disease, has been recognized to be responsible for a broad range of clinical syndromes. We report the case of a patient with disseminated B. henselae infection mimicking Langerhans cell histiocytosis at presentation and its successful management with neurosurgery, prolonged antibacterial therapy, and observation.

Successful Extracorporeal Life Support in a Pediatric Hematopoietic Stem Cell Transplant Recipient With Periengraftment Respiratory Failure.

The use of extracorporeal life support (ECLS) as ultimate salvage therapy for hematopoietic stem cell transplant recipients remains controversial among oncologists and critical care specialists. Prognosis is poor, particularly after allogeneic transplantation, and literature to guide clinical decision-making is scarce. Our report describes successful ECLS in a pediatric patient undergoing allogeneic hematopoietic stem cell transplantation, who developed acute respiratory failure during severe neutropenia, followed by immediate neutrophil engraftment. This unique case highlights periengraftment respiratory failure as a possible patient subgroup that could benefit from ECLS; and illustrates that the distinct etiologies of respiratory failure and the patients' immune status deserve closer consideration in future studies evaluating ECLS in this high-risk population.

Vaccination against influenza at a European pediatric cancer center: immunization rates and attitudes among staff, patients, and their families.

BACKGROUND: Influenza is an important cause of infectious morbidity in pediatric cancer patients. We conducted a single-center survey to explore adherence and attitudes towards the recommended annual influenza vaccination. METHODS: Self-administered, standardized questionnaires were distributed to 143 staff members and 264 families. Items analyzed included demographic data, knowledge about influenza, history of prior influenza infections and vaccinations, routes of information and education, and attitudes towards the recommended influenza. Variables associated with vaccination were explored by univariate and multivariate analyses. RESULTS: One hundred six staff members with patient contact and 139 primary caretakers completed the questionnaire. Fifty-nine percent of staff members and 60% of the caretakers provided correct answers to all four knowledge questions; 32 and 54% reported a history of prior influenza, and 61 and 47% had received at least one influenza vaccination in the past. Vaccination rates for the previous season were 47, 34, 30, 25, and 29% in staff members, primary caretakers, their partners, diseased children, and their siblings, respectively. Main motivations (>75% in ≥ 1 cohort) for vaccination were prevention of influenza disease and concerns to transmit it to others (77-100%) and reasons for not being immunized concerns of adverse effects and use of alternative protection (33-83%). Variables significantly associated with vaccination by multivariate analysis included receipt of influenza vaccinations in the past (OR 2.2-20.5), recommendations by health care providers (OR 4.8-45.5), a lower level of education (caretakers; OR 2.2), and younger age (children; OR 0.9). CONCLUSIONS: The results of this survey indicate insufficient vaccination rates and provide potential approaches for improved vaccination strategies in the setting of pediatric cancer care.

The effect of cyclophosphamide on the immune system: implications for clinical cancer therapy.

Cyclophosphamide is an alkylating agent belonging to the group of oxazaphosporines. As cyclophosphamide is in clinical use for more than 40 years, there is a lot of experience using this drug for the treatment of cancer and as an immunosuppressive agent for the treatment of autoimmune and immune-mediated diseases. Besides antimitotic and antireplicative effects, cyclophosphamide has immunosuppressive as well as immunomodulatory properties. Cyclophosphamide shows selectivity for T cells and is therefore now frequently used in tumour vaccination protocols and to control post-transplant allo-reactivity in haplo-identical unmanipulated bone marrow after transplantation. The schedule of administration is of special importance for the immunological effect: while cyclophosphamide can be used in high-dose therapy for the complete eradication of haematopoietic cells, lower doses of cyclophosphamide are relatively selective for T cells. Of special interest is the fact that a single administration of low-dose cyclophosphamide is able to selectively suppress regulatory T cells (Tregs). This effect can be used to counteract immunosuppression in cancer. However, cyclophosphamide can also increase the number of myeloid-derived suppressor cells. Combination of cyclophosphamide with other immunomodulatory agents could be a promising approach to treat different forms of advanced cancer.

A novel mutation in PIGW causes glycosylphosphatidylinositol deficiency without hyperphosphatasia.

In recent years, many mutations have been identified that affect the biosynthesis of the glycosylphosphatidylinositol anchor, a biomolecule that attaches surface molecules to cell membranes. Here, we present two second-degree cousins with unexplained patterns of seizures. Next-generation sequencing identified the homozygous c.460A>G; p.(R154G) PIGW mutation in both patients. Transfection of the mutated allele into Pigw-defective CHO cells indicated impaired enzymatic activity of the mutated PIGW product. Alkaline phosphatase did not exceed the upper normal range and flow cytometry of CD16, CD24, and CD66c on granulocytes showed subtle changes of the cellular expression of the glycosylphosphatidylinositol-anchored proteins. The patients' phenotype is therefore remarkably different from the phenotype of the only other described individual with PIGW mutations. Patients might therefore be missed when relying on traditional flow cytometry of glycosylphosphatidylinositol-anchored proteins only and we suggest that glycosylphosphatidylinositol-deficiency should be considered even with patients not showing the typical clinical phenotypes. © 2016 Wiley Periodicals, Inc.

Common Ewing sarcoma-associated antigens fail to induce natural T cell responses in both patients and healthy individuals.

Disseminated or relapsed Ewing sarcoma (EwS) has remained fatal in the majority of patients. A promising approach to preventing relapse after conventional therapy is to establish tumor antigen-specific immune control. Efficient and specific T cell memory against the tumor depends on the expansion of rare T cells with native specificity against target antigens overexpressed by the tumor. Candidate antigens in EwS include six-transmembrane epithelial antigen of the prostate-1 (STEAP1), and the human cancer/testis antigens X-antigen family member 1 (XAGE1) and preferentially expressed antigen in melanoma (PRAME). Here, we screened normal donors and EwS patients for the presence of circulating T cells reactive with overlapping peptide libraries of these antigens by IFN-γ Elispot analysis. The majority of 22 healthy donors lacked detectable memory T cell responses against STEAP1, XAGE1 and PRAME. Moreover, ex vivo detection of T cells specific for these antigens in both blood and bone marrow were limited to a minority of EwS patients and required nonspecific T cell prestimulation. Cytotoxic T cells specific for the tumor-associated antigens were efficiently and reliably generated by in vitro priming using professional antigen-presenting cells and optimized cytokine stimulation; however, these T cells failed to interact with native antigen processed by target cells and with EwS cells expressing the antigen. We conclude that EwS-associated antigens fail to induce efficient T cell receptor (TCR)-mediated antitumor immune responses even under optimized conditions. Strategies based on TCR engineering could provide a more effective means to manipulating T cell immunity toward targeted elimination of tumor cells.

Complex MLL rearrangement in non-infiltrated bone marrow in an infant with stage II precursor B-lymphoblastic lymphoma.

PURPOSE: Precursor B-lymphoblastic lymphoma cells are indistinguishable by morphology, and immune phenotype from lymphoblasts in acute leukemia which in infancy is associated with MLL rearrangements and a poor prognosis. The role of MLL gene deregulation in rare cases of isolated lymphoblastic lymphoma in infants is obscure. We report the case of a 10-month-old child who presented with a cutaneous nodule on the left foot. Histological diagnosis was precursor B-lymphoblastic lymphoma. The young age of the patient motivated us to investigate the presence of an MLL rearrangement. METHODS: Cytogenetic analysis was performed by fluorescence in situ hybridization (FISH), and the genomic fusion partner of MLL was identified by long-distance inverse (LDI-)PCR and confirmed by direct PCR. RESULTS: Fluorescence in situ hybridization screening of paraffin-embedded formalin-fixed tissue indeed revealed the presence of an MLL rearrangement. The genomic fusion partner was identified as AF10 by DNA sequencing of the MLL breakpoint region. The MLL-AF10 fusion gene was further detected in cytologically normal pretreated bone marrow. Treatment was started with standard four-drug induction chemotherapy. Because of the unfavorable outcome associated with MLL rearrangements in infant leukemia, we intensified postremission treatment according to the Interfant-06 study protocol. The child is in continuous first remission 36 months after diagnosis. CONCLUSION: This is the first report of submicroscopic bone marrow involvement in MLL-rearranged isolated cutaneous B-cell precursor lymphoma in an infant. To prospectively address the role of MLL rearrangements in extramedullary B-lymphoblastic malignancies in infants, we suggest to assess both tumors and non-infiltrated bone marrow for the presence of this genetic abnormality.

High proportions of CD4⁺ T cells among residual bone marrow T cells in childhood acute lymphoblastic leukemia are associated with favorable early responses.

Residual nonmalignant T cells in the bone marrow of patients with acute leukemias may be involved in active immune responses to leukemic cells. Here, we investigated the phenotypic signature of T cells present at diagnosis in 39 pediatric patients with acute lymphoblastic leukemia (ALL) treated within standardized ALL-BFM study protocols. Previously described age associations of lymphocyte subpopulations in the peripheral blood of healthy children were reproduced in leukemic bone marrow. Analysis of individual lymphocyte parameters and risk-associated variables using univariate linear regression models revealed a correlation of higher CD4/CD8 ratios at diagnosis with a favorable bone marrow response on day 15. Separate analysis of CD4⁺ cells with the CD4⁺CD25(hi)FoxP3⁺ T(reg) cell phenotype showed that the association was caused by non-T(reg) CD4⁺ cells. The association of higher CD4/CD8 ratios with a favorable bone marrow response on day 15 of treatment persisted in a cohort extended to 69 patients. We conclude that CD4⁺ non-T(reg) cells in leukemic bone marrow at diagnosis may have a role in early response to treatment. Prospective analysis of the CD4/CD8 ratio in a large cohort of pediatric patients is now needed. Moreover, future experiments will establish the functional role of the individual T cell subsets in immune control in pediatric ALL.