Exposure-response analysis of alemtuzumab in pediatric allogeneic HSCT for nonmalignant diseases: the ARTIC study

Alemtuzumab (anti-CD52 antibody) is frequently prescribed to children with nonmalignant diseases undergoing allogeneic hematopoietic stem cell transplantation (HSCT) to prevent graft failure (GF) and acute graft-versus-host disease (aGVHD). The aim of this multicenter study was the characterization of alemtuzumab population pharmacokinetics to perform a novel model-based exposure-response analysis in 53 children with nonmalignant immunological or hematological disease and a median age of 4.4 years (interquartile range [IQR], 0.8-8.7). The median cumulative alemtuzumab dose was 0.6 mg/kg (IQR, 0.6-1) administered over 2 to 7 days. A 2-compartment population pharmacokinetics model with parallel linear and nonlinear elimination including allometrically scaled bodyweight (median, 17.50 kg; IQR, 8.76-33.00) and lymphocyte count at baseline (mean, 2.24 × 109/L; standard deviation ± 1.87) as significant pharmacokinetic predictors was developed using nonlinear mixed effects modeling. Based on the model-estimated median concentration at day of HSCT (0.77 μg/mL; IQR, 0.33-1.82), patients were grouped into a low- (≤0.77 μg/mL) or high- (>0.77 μg/mL) exposure groups. High alemtuzumab exposure at day of HSCT correlated with delayed CD4+ and CD8+ T-cell reconstitution (P value < .0001) and increased risk of GF (P value = .043). In contrast, alemtuzumab exposure did not significantly influence the incidence of aGVHD grade ≥2, mortality, chimerism at 1 year, viral reactivations, and autoimmunity at a median follow-up of 3.3 years (IQR, 2.5-8.0). In conclusion, this novel population pharmacokinetics model is suitable for individualized intravenous precision dosing to predict alemtuzumab exposure in pediatric allogeneic HSCT for nonmalignant diseases, aiming at the achievement of early T-cell reconstitution and prevention of GF in future prospective studies.

A unique immune signature in blood separates therapy-refractory from therapy-responsive acute graft-versus-host disease

Acute graft-versus-host disease (aGVHD) is an immune cell‒driven, potentially lethal complication of allogeneic hematopoietic stem cell transplantation affecting diverse organs, including the skin, liver, and gastrointestinal (GI) tract. We applied mass cytometry (CyTOF) to dissect circulating myeloid and lymphoid cells in children with severe (grade III-IV) aGVHD treated with immune suppressive drugs alone (first-line therapy) or in combination with mesenchymal stromal cells (MSCs; second-line therapy). These results were compared with CyTOF data generated in children who underwent transplantation with no aGVHD or age-matched healthy control participants. Onset of aGVHD was associated with the appearance of CD11b+CD163+ myeloid cells in the blood and accumulation in the skin and GI tract. Distinct T-cell populations, including TCRγδ+ cells, expressing activation markers and chemokine receptors guiding homing to the skin and GI tract were found in the same blood samples. CXCR3+ T cells released inflammation-promoting factors after overnight stimulation. These results indicate that lymphoid and myeloid compartments are triggered at aGVHD onset. Immunoglobulin M (IgM) presumably class switched, plasmablasts, and 2 distinct CD11b- dendritic cell subsets were other prominent immune populations found early during the course of aGVHD in patients refractory to both first- and second-line (MSC-based) therapy. In these nonresponding patients, effector and regulatory T cells with skin- or gut-homing receptors also remained proportionally high over time, whereas their frequencies declined in therapy responders. Our results underscore the additive value of high-dimensional immune cell profiling for clinical response evaluation, which may assist timely decision-making in the management of severe aGVHD.

Enrichment of serum IgG4 in MuSK myasthenia gravis patients

Muscle-specific kinase (MuSK) myasthenia gravis (MG) is a neuromuscular autoimmune disease belonging to a growing group of IgG4 autoimmune diseases (IgG4-AIDs), in which the majority of pathogenic autoantibodies are of the IgG4 subclass. The more prevalent form of MG with acetylcholine receptor (AChR) antibodies is caused by IgG1-3 autoantibodies. A dominant role for IgG4 in autoimmune disease is intriguing due to its anti-inflammatory characteristics. It is unclear why MuSK autoantibodies are predominantly IgG4. We hypothesized that MuSK MG patients have a general predisposition to generate IgG4 responses, therefore resulting in high levels of circulating IgG4. To investigate this, we quantified serum Ig isotypes and IgG subclasses using nephelometric and turbidimetric assays in MuSK MG and AChR MG patients not under influence of immunosuppressive treatment. Absolute serum IgG1 was increased in both MuSK and AChR MG patients compared to healthy donors. In addition, only MuSK MG patients on average had significantly increased and enriched serum IgG4. Although more MuSK MG patients had elevated serum IgG4, for most the IgG4 serum levels fell within the normal range. Correlation analyses suggest MuSK-specific antibodies do not solely explain the variation in IgG4 levels. In conclusion, although serum IgG4 levels are slightly increased, the levels do not support ubiquitous IgG4 responses in MuSK MG patients as the underlying cause of dominant IgG4 MuSK antibodies.

IL-7 and IL-15 Levels Reflect the Degree of T Cell Depletion during Lymphopenia and Are Associated with an Expansion of Effector Memory T Cells after Pediatric Hematopoietic Stem Cell Transplantation

Differentially and functionally distinct T cell subsets are involved in the development of complications after allogeneic hematopoietic stem cell transplantation (HSCT), but little is known about factors regulating their recovery after HSCT. In this study, we investigated associations between immune-regulating cytokines, T cell differentiation, and clinical outcomes. We included 80 children undergoing allogeneic HSCT for acute leukemia using bone marrow or peripheral blood stem cells grafted from a matched sibling or unrelated donor. Cytokines (IL-7, IL-15, IL-18, SCF, IL-6, IL-2, and TNF-α) and active anti-thymocyte globulin (ATG) levels were longitudinally measured along with extended T cell phenotyping. The cytokine profiles showed a temporary rise in IL-7 and IL-15 during lymphopenia, which was strongly dependent on exposure to active ATG. High levels of IL-7 and IL-15 from graft infusion to day +30 were predictive of slower T cell recovery during the first 2 mo post-HSCT; however, because of a major expansion of memory T cell stages, only naive T cells remained decreased after 3 mo (p < 0.05). No differential effect was seen on polarization of CD4⁺ T cells into Th1, Th2, or Th17 cells or regulatory T cells. Low levels of IL-7 and IL-15 at day +14 were associated with acute graft-versus-host disease grades II-IV in ATG-treated patients (p = 0.0004 and p = 0.0002, respectively). Children with IL-7 levels comparable to healthy controls at day +14 post-HSCT were less likely to develop EBV reactivation posttransplant. These findings suggest that quantification of IL-7 and IL-15 may be useful as biomarkers in assessing the overall T cell depletion and suggest a potential for predicting complications after HSCT.

Loss of ZBTB24 impairs nonhomologous end-joining and class-switch recombination in patients with ICF syndrome

The autosomal recessive immunodeficiency, centromeric instability, and facial anomalies (ICF) syndrome is a genetically heterogeneous disorder. Despite the identification of the underlying gene defects, it is unclear how mutations in any of the four known ICF genes cause a primary immunodeficiency. Here we demonstrate that loss of ZBTB24 in B cells from mice and ICF2 patients affects nonhomologous end-joining (NHEJ) during immunoglobulin class-switch recombination and consequently impairs immunoglobulin production and isotype balance. Mechanistically, we found that ZBTB24 associates with poly(ADP-ribose) polymerase 1 (PARP1) and stimulates its auto-poly(ADP-ribosyl)ation. The zinc-finger in ZBTB24 binds PARP1-associated poly(ADP-ribose) chains and mediates the PARP1-dependent recruitment of ZBTB24 to DNA breaks. Moreover, through its association with poly(ADP-ribose) chains, ZBTB24 protects them from degradation by poly(ADP-ribose) glycohydrolase (PARG). This facilitates the poly(ADP-ribose)-dependent assembly of the LIG4/XRCC4 complex at DNA breaks, thereby promoting error-free NHEJ. Thus, we uncover ZBTB24 as a regulator of PARP1-dependent NHEJ and class-switch recombination, providing a molecular basis for the immunodeficiency in ICF2 syndrome.

Proceeding of the European Group for Blood and Marrow Transplantation (EBMT) congress on sickle cell disease, 16-17 may 2019, Regensburg, Germany: What is the impact of antithymocyte globulin pharmacokinetics on haploidentical hematopoietic stem cell transplantation?

Antithymocyte globulin (ATG) is a widely accepted part of the conditioning regimen applied in the setting of hematopoietic stem cell transplantation (HSCT) to prevent graft rejection and graft-versus-host disease. Although weight-based dosing of ATG has been introduced to optimize ATG dosing, substantial variance in clearance of active ATG, the actual lymphocyte binding component, remains a challenge. Therefore, further research regarding ATG pharmacokinetics and pharmacodynamics in different HSCT settings and in patients with different types of underlying diseases is required.

Differential Elimination of Anti-Thymocyte Globulin of Fresenius and Genzyme Impacts T-Cell Reconstitution After Hematopoietic Stem Cell Transplantation

Anti-thymocyte globulin (ATG) is a lymphocyte depleting agent applied in hematopoietic stem cell transplantation (HSCT) to prevent rejection and Graft-vs.-Host Disease (GvHD). In this study, we compared two rabbit ATG products, ATG-Genzyme (ATG-GENZ), and ATG-Fresenius (ATG-FRES), with respect to dosing, clearance of the active lymphocyte binding component, post-HSCT immune reconstitution and clinical outcome. Fifty-eigth pediatric acute leukemia patients (n = 42 ATG-GENZ, n = 16 ATG-FRES), who received a non-depleted bone marrow or peripheral blood stem cell graft from an unrelated donor were included. ATG-GENZ was given at a dosage of 6-10 mg/kg; ATG-FRES at 45-60 mg/kg. The active component of ATG from both products was cleared at different rates. Within the ATG-FRES dose range no differences were found in clearance of active ATG or T-cell re-appearance. However, the high dosage of ATG-GENZ (10 mg/kg), in contrast to the low dosage (6-8 mg/kg), correlated with prolonged persistence of active ATG and delayed T-cell reconstitution. Occurrence of serious acute GvHD (grade III-IV) was highest in the ATG-GENZ-low dosage group. These results imply that dosing of ATG-GENZ is more critical than dosing of ATG-FRES due to the difference in clearance of active ATG. This should be taken into account when designing clinical protocols.

An unusual presentation of a patient with severe hypogammaglobulinemia

We present a patient who was diagnosed with severe hypogammaglobulinemia after her newborn child presented with two episodes of meningitis. The patient had no history or symptoms suggestive of immunodeficiency. Thus far, a cause for the immunodeficiency has not been found, even after extensive immunological evaluation.

Immunoglobulin G Fragment Crystallizable Glycosylation After Hematopoietic Stem Cell Transplantation Is Dissimilar to Donor Profiles

Immunoglobulin G (IgG) fragment crystallizable (Fc) N-glycosylation has a large influence on the affinity of the antibody for binding to Fcγ-receptors (FcγRs) and C1q protein, thereby influencing immune effector functions. IgG Fc glycosylation is known to be partly regulated by genetics and partly by stimuli in the microenvironment of the B cell. Following allogeneic hematopoietic stem cell transplantation (HSCT), and in the presence of (almost) complete donor chimerism, IgG is expected to be produced by, and glycosylated in, B cells of donor origin. We investigated to what extent IgG glycosylation in patients after transplantation is determined by factors of the donor (genetics) or the recipient (environment). Using an IgG subclass-specific liquid chromatography–mass spectrometry method, we analyzed the plasma/serum IgG Fc glycosylation profiles of 34 pediatric patients pre-HSCT and at 6 and 12 months post-HSCT and compared these to the profiles of their donors and age-matched healthy controls. Patients treated for hematological malignancies as well as for non-malignant hematological diseases showed after transplantation a lower Fc galactosylation than their donors. Especially for the patients treated for leukemia, the post-HSCT Fc glycosylation profiles were more similar to the pre-HSCT recipient profiles than to profiles of the donors. Pre-HSCT, the leukemia patient group showed as distinctive feature a decrease in sialylation and in hybrid-type glycans as compared to healthy controls, which both normalized after transplantation. Our data suggest that IgG Fc glycosylation in children after HSCT does not directly mimic the donor profile, but is rather determined by persisting environmental factors of the host.

Human Lymphoid Tissues Harbor a Distinct CD69+CXCR6+ NK Cell Population

Knowledge of human NK cells is based primarily on conventional CD56(bright) and CD56(dim) NK cells from blood. However, most cellular immune interactions occur in lymphoid organs. Based on the coexpression of CD69 and CXCR6, we identified a third major NK cell subset in lymphoid tissues. This population represents 30-60% of NK cells in marrow, spleen, and lymph node but is absent from blood. CD69(+)CXCR6(+) lymphoid tissue NK cells have an intermediate expression of CD56 and high expression of NKp46 and ICAM-1. In contrast to circulating NK cells, they have a bimodal expression of the activating receptor DNAX accessory molecule 1. CD69(+)CXCR6(+) NK cells do not express the early markers c-kit and IL-7Rα, nor killer cell Ig-like receptors or other late-differentiation markers. After cytokine stimulation, CD69(+)CXCR6(+) NK cells produce IFN-γ at levels comparable to CD56(dim) NK cells. They constitutively express perforin but require preactivation to express granzyme B and exert cytotoxicity. After hematopoietic stem cell transplantation, CD69(+)CXCR6(+) lymphoid tissue NK cells do not exhibit the hyperexpansion observed for both conventional NK cell populations. CD69(+)CXCR6(+) NK cells constitute a separate NK cell population with a distinct phenotype and function. The identification of this NK cell population in lymphoid tissues provides tools to further evaluate the cellular interactions and role of NK cells in human immunity.

Mutations in DNMT3B Modify Epigenetic Repression of the D4Z4 Repeat and the Penetrance of Facioscapulohumeral Dystrophy

Facioscapulohumeral dystrophy (FSHD) is associated with somatic chromatin relaxation of the D4Z4 repeat array and derepression of the D4Z4-encoded DUX4 retrogene coding for a germline transcription factor. Somatic DUX4 derepression is caused either by a 1-10 unit repeat-array contraction (FSHD1) or by mutations in SMCHD1, which encodes a chromatin repressor that binds to D4Z4 (FSHD2). Here, we show that heterozygous mutations in DNA methyltransferase 3B (DNMT3B) are a likely cause of D4Z4 derepression associated with low levels of DUX4 expression from the D4Z4 repeat and increased penetrance of FSHD. Recessive mutations in DNMT3B were previously shown to cause immunodeficiency, centromeric instability, and facial anomalies (ICF) syndrome. This study suggests that transcription of DUX4 in somatic cells is modified by variations in its epigenetic state and provides a basis for understanding the reduced penetrance of FSHD within families.

Deletion of the entire interferon-γ receptor 1 gene causing complete deficiency in three related patients

PURPOSE

Complete interferon-γ receptor 1 (IFN-γR1) deficiency is a primary immunodeficiency causing predisposition to severe infection due to intracellular pathogens. Only 36 cases have been reported worldwide. The purpose of this article is to describe a large novel deletion found in 3 related cases, which resulted in the complete removal of the IFNGR1 gene.

METHODS

Whole blood from three patients was stimulated with lipopolysaccharide (LPS) and IFN-γ to determine production of tumor necrosis factor (TNF), interleukin-12 p40 (IL-12p40) and IL-10. Expression of IFN-γR1 on the cell membrane of patients' monocytes was assessed using flow cytometry. IFNGR1 transcript was analyzed in RNA and the gene and adjacent regions were analyzed in DNA. Finally, IL22RA2 transcript levels were analyzed in whole blood cells and dendritic cells.

RESULTS

There was no expression of the IFN-γR1 on the monocytes. Consistent with this finding, there was no IFN-γ response in the whole blood assay as measured by effect on LPS-induced IL-12p40, TNF and IL-10 production. A 119.227 nt homozygous deletion on chromosome 6q23.3 was identified, removing the IFNGR1 gene completely and ending 117 nt upstream of the transcription start of the IL22RA2 gene. Transcript levels of IL22RA2 were similar in patient and control.

CONCLUSIONS

We identified the first large genomic deletion of IFNGR1 causing complete IFN-γR1 deficiency. Despite the deletion ending very close to the IL22RA2 gene, it does not appear to affect IL22RA2 transcription and, therefore, may not have any additional clinical consequence.

Neuronal antibodies in pediatric epilepsy: Clinical features and long-term outcomes of a historical cohort not treated with immunotherapy

OBJECTIVE

In autoimmune encephalitis the etiologic role of neuronal cell-surface antibodies is clear; patients diagnosed and treated early have better outcomes. Neuronal antibodies have also been described in patients with pediatric epilepsy without encephalitis. The aim was to assess whether antibody presence had any effect on long-term outcomes in these patients.

METHODS

Patients (n = 178) were recruited between 1988 and 1992 as part of the prospective Dutch Study of Epilepsy in Childhood; none received immunotherapy. Healthy age-matched bone-marrow donors served as controls (n = 112). All sera were tested for serum N-methyl-d-aspartate receptor (NMDAR), alpha amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor, leucine rich glioma inactivated 1, contactin associated protein like 2 (CASPR2), contactin-2, glutamic acid decarboxylase, and voltage gated potassium channel (VGKC)-complex antibodies by standard techniques. No cerebrospinal fluid (CSF) samples were available. Results were correlated with clinical data collected over 15 years.

RESULTS

Seventeen patients (9.5%) were positive for VGKC complex (n = 3), NMDAR (n = 7), CASPR2 (n = 4), and contactin-2 (n = 3), compared to three (3/112; 2.6%) healthy controls (VGKC complex [n = 1], NMDAR [n = 2]; p = 0.03; Fisher's exact test). Titers were relatively low (≤1:100 for cell-surface antibodies), but 8 (47%) of the 17 positive samples bound to the surface of live hippocampal neurons consistent with a potential pathogenic antibody. Preexisting cognitive impairment was more frequent in antibody-positive patients (9/17 vs. 33/161; p = 0.01). Fourteen antibody-positive patients were treated with standard antiepileptic drugs (AEDs); three (17%) became intractable but this was not different from the 16 (10%) of 161 antibody-negative patients. In 96 patients with available follow-up samples at 6 and/or 12 months, 6 of 7 positive antibodies had disappeared and, conversely, antibodies had appeared for the first time in a further 7 patients.

SIGNIFICANCE

Neuronal antibodies were found at low levels in 9.5% of patients with new-onset pediatric epilepsy but did not necessarily persist over time, and the development of antibodies de novo in later samples suggests they could be due to a secondary response to neuronal damage or inflammation. Moreover, as the response to standard AEDs and the long-term outcome did not differ from those of antibody-negative pediatric patients, these findings suggest that routine neuronal antibody testing is unlikely to be helpful in pediatric epilepsy. However, the higher incidence of preexisting cognitive problems in the antibody-positive group, the CASPR2 and contactin-2 antibodies in 7 of 17 patients, and the binding of 8 of 17 of serum samples to live hippocampal neurons suggest that neuronal antibodies, even if secondary, could contribute to the comorbidities of pediatric epilepsy.

Gene-expression and in vitro function of mesenchymal stromal cells are affected in juvenile myelomonocytic leukemia

An aberrant interaction between hematopoietic stem cells and mesenchymal stromal cells has been linked to disease and shown to contribute to the pathophysiology of hematologic malignancies in murine models. Juvenile myelomonocytic leukemia is an aggressive malignant disease affecting young infants. Here we investigated the impact of juvenile myelomonocytic leukemia on mesenchymal stromal cells. Mesenchymal stromal cells were expanded from bone marrow samples of patients at diagnosis (n=9) and after hematopoietic stem cell transplantation (n=7; from 5 patients) and from healthy children (n=10). Cells were characterized by phenotyping, differentiation, gene expression analysis (of controls and samples obtained at diagnosis) and in vitro functional studies assessing immunomodulation and hematopoietic support. Mesenchymal stromal cells from patients did not differ from controls in differentiation capacity nor did they differ in their capacity to support in vitro hematopoiesis. Deep-SAGE sequencing revealed differential mRNA expression in patient-derived samples, including genes encoding proteins involved in immunomodulation and cell-cell interaction. Selected gene expression normalized during remission after successful hematopoietic stem cell transplantation. Whereas natural killer cell activation and peripheral blood mononuclear cell proliferation were not differentially affected, the suppressive effect on monocyte to dendritic cell differentiation was increased by mesenchymal stromal cells obtained at diagnosis, but not at time of remission. This study shows that active juvenile myelomonocytic leukemia affects the immune response-related gene expression and function of mesenchymal stromal cells. In contrast, the differential gene expression of hematopoiesis-related genes could not be supported by functional data. Decreased immune surveillance might contribute to the therapy resistance and progression in juvenile myelomonocytic leukemia.

Association between anti-thymocyte globulin exposure and CD4+ immune reconstitution in paediatric haemopoietic cell transplantation: a multicentre, retrospective pharmacodynamic cohort analysis

BACKGROUND

Anti-thymocyte globulin (ATG) was introduced into the conditioning regimen in haemopoietic cell transplantation (HCT) to prevent graft-versus-host-disease (GvHD) and graft failure. However, ATG can also cause delayed immune reconstitution of donor T cells. We studied the relation between exposure to active ATG and clinical outcomes in children.

METHODS

In this retrospective analysis, all patients (age 0·2-23 years) receiving their first HCT between April 1, 2004, and April 1, 2012, who received ATG (thymoglobulin) in two Dutch paediatric HCT programmes were included. The cumulative dose of ATG was chosen according to local protocols and was given intravenously over 4 days consecutively. ATG exposure measures (maximum concentration, concentration at time of HCT, clearance, days to reach a concentration below the lympholytic concentration of one arbitrary unit [AU] per mL, total area under the curve [AUC], AUC before HCT, and AUC after HCT) were calculated using a validated population pharmacokinetic model. The main outcome of interest was immune reconstitution (defined as CD4+ T cells >0·05 × 10(9) cells per L in two consecutive measurements within 100 days). Other outcomes of interest were survival, acute and chronic GvHD, and graft failure. We used Cox proportional hazard models, logistic regression models, and Fine-Gray competing risk regressions for analyses.

FINDINGS

251 patients were included. The chance of successful immune reconstitution decreased as the ATG AUC after HCT increased (odds ratio 0·991, 95% CI 0·987-0·996; p<0·0001). Within the cord blood group, we noted decreased immune reconstitution above the lowest AUC quartile (≥ 20 AU × day/mL; p=0·0024), whereas in the bone marrow or peripheral blood stem cell group, decreased immune reconstitution was noted only in the highest quartile (≥ 100 AU × day/mL; p=0·0024). Successful immune reconstitution by day 100 was associated with increased overall survival (hazard ratio [HR] 0·49, 95% CI 0·29-0·81; p=0·0047) caused by reduced non-relapse mortality (0·40, 0·21-0·77; p=0·0062), and relapse-related mortality in myeloid leukaemia (0·25, 0·08-0·76; p=0·015). An AUC before transplantation of at least 40 AU × day/mL resulted in a lower incidence of acute GvHD (grade 2-4 HR 0·979, 95% CI 0·963-0·994; p=0·0081; and grade 3-4 0·975, 0·952-0·998; p=0·033), chronic GvHD (0·983, 0·968-0·998; p=0·029), and graft failure (0·981, 0·965-0·997; p=0·020) compared with an AUC of less than 40 AU × day/mL.

INTERPRETATION

These results stress the importance of improving the efficacy and safety of ATG in HCT by amending dosage and timing. Individualised dosing and timing of ATG to aim for optimum exposure before and after HCT could result in improved outcomes after paediatric HCT.

FUNDING

Dutch Organization for Scientific Research.

Mesenchymal stromal cell therapy is associated with increased adenovirus-associated but not cytomegalovirus-associated mortality in children with severe acute graft-versus-host disease

Beneficial effects of mesenchymal stromal cells (MSCs) in patients with severe steroid-refractory acute graft-versus-host disease (aGvHD) have been reported. However, controversy exists about the effect of MSCs on virus-specific T cells. We evaluated 56 patients with grade II-IV aGvHD who responded to steroids (n = 21) or were steroid refractory receiving either MSCs (n = 22) or other second-line therapy (n = 13). Although the overall incidence of cytomegalovirus (CMV), Epstein-Barr virus, and human adenovirus (HAdV) infections was not significantly increased, HAdV infection was associated with decreased survival in children treated with MSCs. Thus, we investigated in vitro the effects of MSCs on virus-specific T cells. Both CMV-specific and, to a lesser extent, HAdV-specific T-cell activation and proliferation were negatively affected by MSCs either after induction of a response in peripheral blood mononuclear cells (PBMCs) or after restimulation of virus-specific T-cell lines. In patient-derived PBMCs, CMV-specific proliferative responses were greatly decreased on first-line treatment of aGvHD with systemic steroids and slowly recovered after MSC administration and tapering of steroids. HAdV-specific T-cell proliferation could not be detected. In contrast, the proportion of CMV- and HAdV-specific effector T cells, measured as interferon-γ-secreting cells, remained stable or increased after treatment with MSCs. In conclusion, although in vitro experimental conditions indicated a negative impact of MSCs on CMV- and HAdV-specific T-cell responses, no solid evidence was obtained to support such an effect of MSCs on T-cell responses in vivo. Still, the susceptibility of steroid-refractory severe aGvHD patients to viral reactivation warrants critical viral monitoring during randomized controlled trials on second-line treatment including MSCs.

Macrophages inhibit human osteosarcoma cell growth after activation with the bacterial cell wall derivative liposomal muramyl tripeptide in combination with interferon-γ

Background

In osteosarcoma, the presence of tumor-infiltrating macrophages positively correlates with patient survival in contrast to the negative effect of tumor-associated macrophages in patients with other tumors. Liposome-encapsulated muramyl tripeptide (L-MTP-PE) has been introduced in the treatment of osteosarcoma patients, which may enhance the potential anti-tumor activity of macrophages. Direct anti-tumor activity of human macrophages against human osteosarcoma cells has not been described so far. Hence, we assessed osteosarcoma cell growth after co-culture with human macrophages.

Methods

Monocyte-derived M1-like and M2-like macrophages were polarized with LPS + IFN-γ, L-MTP-PE +/− IFN-γ or IL-10 and incubated with osteosarcoma cells. Two days later, viable tumor cell numbers were analyzed. Antibody-dependent effects were investigated using the therapeutic anti-EGFR antibody cetuximab.

Results

M1-like macrophages inhibited osteosarcoma cell growth when activated with LPS + IFN-γ. Likewise, stimulation of M1-like macrophages with liposomal muramyl tripeptide (L-MTP-PE) inhibited tumor growth, but only when combined with IFN-γ. Addition of the tumor-reactive anti-EGFR antibody cetuximab did not further improve the anti-tumor activity of activated M1-like macrophages. The inhibition was mediated by supernatants of activated M1-like macrophages, containing TNF-α and IL-1β. However, specific blockage of these cytokines, nitric oxide or reactive oxygen species did not inhibit the anti-tumor effect, suggesting the involvement of other soluble factors released upon macrophage activation. While LPS + IFN-γ–activated M2-like macrophages had low anti-tumor activity, IL-10–polarized M2-like macrophages were able to reduce osteosarcoma cell growth in the presence of the anti-EGFR cetuximab involving antibody-dependent tumor cell phagocytosis.

Conclusion

This study demonstrates that human macrophages can be induced to exert direct anti-tumor activity against osteosarcoma cells. Our observation that the induction of macrophage anti-tumor activity by L-MTP-PE required IFN-γ may be of relevance for the optimization of L-MTP-PE therapy in osteosarcoma patients.

Multiple infusions of mesenchymal stromal cells induce sustained remission in children with steroid-refractory, grade III-IV acute graft-versus-host disease

Mesenchymal stromal cell (MSC) infusions have been reported to be effective in patients with steroid-refractory, acute graft-versus-host disease (aGvHD) but comprehensive data on paediatric patients are limited. We retrospectively analysed a cohort of 37 children (aged 3 months-17 years) treated with MSCs for steroid-refractory grade III-IV aGvHD. All patients but three received multiple MSC infusions. Complete response (CR) was observed in 24 children (65%), while 13 children had either partial (n = 8) or no response (n = 5). Cumulative incidence of transplantation-related mortality (TRM) in patients who did or did not achieve CR was 17% and 69%, respectively (P = 0.001). After a median follow-up of 2.9 years, overall survival (OS) was 37%; it was 65% vs. 0% in patients who did or did not achieve CR, respectively (P = 0.001). The median time from starting steroids for GvHD treatment to first MSC infusion was 13 d (range 5-85). Children treated between 5 and 12 d after steroid initiation showed a trend for better OS (56%) and lower TRM (17%) as compared with patients receiving MSCs 13-85 d after steroids (25% and 53%, respectively; P = 0.22 and 0.06, respectively). Multiple MSC infusions are safe and effective for children with steroid-refractory aGvHD, especially when employed early in the disease course.

Gastrointestinal acute graft-versus-host disease in children: histology for diagnosis, mesenchymal stromal cells for treatment, and biomarkers for prediction of response

Steroid-nonresponsive acute graft-versus-host disease (aGVHD) after hematopoietic stem cell transplantation carries a poor prognosis. Various groups have reported beneficial effects of mesenchymal stromal cell (MSC) infusion as salvage treatment. Response to treatment is typically evaluated using the diagnostic clinical criteria for aGVHD. In this study, we evaluated the usefulness of additional gastrointestinal biopsy specimens paired with serum biomarkers. In a cohort of 22 pediatric patients, persistent or recurrent diarrhea was seen in 18 children treated with MSC infusion for steroid-refractory aGVHD. To exclude other causes of gastrointestinal pathology, patients were biopsied for histological analysis. Eight of 12 patients exhibited residual tissue damage and villous atrophy, but no active aGVHD. Serum biomarkers have been identified as an alternative tool for monitoring the response to aGVHD treatment. The value of biomarkers for inflammation, tissue, and endothelial cell damage was evaluated in our cohort. Although predictive of response to treatment and survival, these markers lack the necessary specificity and sensitivity to predict response to MSC therapy. Objective endpoints for clinical trials on the treatment of steroid-refractory aGVHD remain to be defined. Thus, we recommend including biopsies and biomarkers to discriminate between ongoing aGVHD and postinflammatory malabsorption.

Antibody-dependent cell lysis by NK cells is preserved after sarcoma-induced inhibition of NK cell cytotoxicity

Osteosarcoma and Ewing's sarcoma tumor cells are susceptible to IL15-induced or antibody-mediated cytolytic activity of NK cells in short-term cytotoxicity assays. When encountering the tumor environment in vivo, NK cells may be in contact with tumor cells for a prolonged time period. We explored whether a prolonged interaction with sarcoma cells can modulate the activation and cytotoxic activity of NK cells. The 40 h coculture of NK cells with sarcoma cells reversibly interfered with the IL15-induced expression of NKG2D, DNAM-1 and NKp30 and inhibited the cytolytic activity of NK cells. The inhibitory effects on receptor expression required physical contact between NK cells and sarcoma cells and were independent of TGF-β. Five days pre-incubation of NK cells with IL15 prevented the down-regulation of NKG2D and cytolytic activity in subsequent cocultures with sarcoma cells. NK cell FcγRIIIa/CD16 receptor expression and antibody-mediated cytotoxicity were not affected after the coculture. Inhibition of NK cell cytotoxicity was directly linked to the down-regulation of the respective NK cell-activating receptors. Our data demonstrate that the inhibitory effects of sarcoma cells on the cytolytic activity of NK cells do not affect the antibody-dependent cytotoxicity and can be prevented by pre-activation of NK cells with IL15. Thus, the combination of cytokine-activated NK cells and monoclonal antibody therapy may be required to improve tumor targeting and NK cell functionality in the tumor environment.

Adenovirus type 35, but not type 5, stimulates NK cell activation via plasmacytoid dendritic cells and TLR9 signaling

In hematopoietic stem cell transplant (HSCT) recipients, disseminated adenoviral infections during the first two months after HSCT can lead to severe complications and fatal outcome. Since NK cells are usually the first lymphocytes to reconstitute after HSCT and have been implicated in the clearance of adenovirus-infected cells, it was investigated whether NK cells are activated by adenovirus in vitro. Exposure of PBMC to human adenovirus type 5 (HAdV5) or HAdV35 resulted in the up-regulation of the activation marker CD69 on NK cells and enhanced the cytolytic activity of NK cells. HAdV5-induced NK cell activation relied on the contribution of T cells as the depletion of T cells from PBMC abolished NK cell activation. In contrast, NK cell activation in response to HAdV35 occurred in the absence of T cells. Plasmacytoid dendritic cells (pDC) were necessary and sufficient to mediate NK cell activation. HAdV35 induced significantly more interferon-α (IFN-α) production by pDC than HAdV5. The increased IFN-α production and NK cell activation correlated with a higher infection efficiency of viruses with the type 35 fiber. The IFN-α response of pDC was enhanced by the presence of NK cells, suggesting a reciprocal interaction between pDC and NK cells. Incubation with a TLR9 antagonist impaired the IFN-α production by pDC as well as NK cell activation, implying that TLR9 signaling is critically involved in the IFN-α response of pDC and NK cell activation after HAdV35 exposure. In conclusion, two human adenovirus serotypes from two different species differ considerably in their capacity to stimulate pDC and NK cells.

Chemokine/chemokine receptor interactions in extramedullary leukaemia of the skin in childhood AML: differential roles for CCR2, CCR5, CXCR4 and CXCR7

Chemokine receptor/ligand interactions orchestrate the migration of cells to peripheral tissues such as the skin. We analysed chemokine receptor expression by acute myeloid leukaemic (AML) cells present in peripheral blood (n = 7), bone marrow (n = 6), or skin (n = 11) obtained from 15 paediatric AML patients with skin involvement and in 10 AML patients without skin involvement. High percentages of circulating CCR2(pos) AML cells were only detected in patients with extramedullary disease. Skin-residing AML cells displayed a different set of receptors in situ, namely: CCR5, CXCR4, CXCR7 and CX3CR1. These results suggest the involvement of different chemokine/chemokine receptor interactions in homing and retention of AML blasts in the skin.

Differential susceptibility of adenovirus clinical isolates to cidofovir and ribavirin is not related to species alone

BACKGROUND

We have previously reported that human adenovirus (HAdV) reference strains clearly show species-dependent resistance to ribavirin, whereas different species of HAdV are equally sensitive to cidofovir. All the serotypes tested were susceptible to cidofovir, whereas only serotypes from species C were sensitive to ribavirin. Here, we aimed to extend these investigations to clinical isolates.

METHODS

In vitro, we tested 126 isolates obtained from 65 patients included in a European survey of HAdV infection.

RESULTS

Among the 126 isolates tested, all presented cidofovir 50% inhibitory concentration (IC50) in the same range as the HAdV 5 reference strain. Regarding ribavirin, all isolates from species C (79 tested) showed an IC50 comparable with previously reported results for reference strains; however, 24/32, 2/6 and 3/3 tested isolates from species A, B and D, respectively, were shown to have a ribavirin IC50 comparable with the HAdV 5 reference strain (species C), contrary to previous observations for reference strains of the same species. Among patients who were treated with cidofovir for disseminated HAdV infection, > or = 4 sequential isolates could be obtained from 9 patients; no variation in cidofovir susceptibility could be detected.

CONCLUSIONS

Cidofovir is active in vitro in all HAdV clinical isolates. Ribavirin was revealed to be active on most HAdV isolates from species A, B and D, and in all isolates from species C. Finally, no resistance to cidofovir became apparent in sequential isolates obtained from treated patients.

NK cells recognize and lyse Ewing sarcoma cells through NKG2D and DNAM-1 receptor dependent pathways

INTRODUCTION

Ewing sarcoma (EWS) is a malignant bone-associated sarcoma, with poor prognosis in case of metastasis or relapse. To explore the feasibility of natural killer (NK) cell mediated immunotherapy and to identify molecular mechanisms involved, the susceptibility of EWS to NK cells was investigated.

METHODS AND RESULTS

All EWS cell lines tested (n=7) were lysed by purified allogeneic NK cells from healthy donors, and the efficacy of lysis was increased by activating NK cells with interleukin-15 (IL-15). FACS analysis and immunohistochemistry revealed that EWS cell lines as well as primary tumor cells expressed ligands for the activating NK cell receptors NKG2D and DNAM-1. NK cell cytotoxicity to EWS cells critically depended on the combination of NKG2D and DNAM-1 signaling, since blocking either of these receptors abrogated lysis by resting NK cells. Cytokine-activated NK cells more efficiently recognized EWS cells, since only combined, but not single blockade of NKG2D and DNAM-1 by antibodies inhibited lysis of EWS cells. Induction or blockade of HLA class I on EWS cells did not significantly influence lysis. This suggests that predominantly activating, rather than inhibitory signals on EWS cells determined susceptibility to NK cell cytotoxicity. NK cell cytotoxicity to EWS cells and K562 was reduced in EWS patients at diagnosis (n=11) compared to age matched controls, despite normal NK cell numbers and increased expression of NKG2D. The impaired function of these NK cells was restored after activation with IL-15 in vitro.

CONCLUSION

These results demonstrate that EWS cells are potentially susceptible to NK cell cytotoxicity due to the expression of activating NK cell receptor ligands. The use of cytokine-activated NK cells rather than resting NK cells in immunotherapy may be instrumental to optimize NK cell reactivity to EWS.

Differential responsiveness to immunoablative therapy in refractory rheumatoid arthritis is associated with level and avidity of anti-cyclic citrullinated protein autoantibodies: a case study

In order to identify pathogenic correlates of refractory rheumatoid arthritis (RA), antibodies against anti-cyclic citrullinated protein (ACPAs) were investigated in RA patients in whom the dysregulated immune system had been ablated by high-dose chemotherapy (HDC) and autologous haematopoietic stem cell transplantation (HSCT). Six patients with refractory RA were extensively characterized in terms of levels of total immunoglobulins, RA-specific autoantibodies (ACPAs and rheumatoid factor) and antibodies against rubella, tetanus toxoid (TT) and phosphorylcholine before and after HDC plus HSCT. Additionally, the avidity of ACPAs was measured before and after treatment and compared with the avidity of TT antibodies following repeated immunizations. Synovial biopsies were obtained by arthroscopy before HDC plus HSCT, and analyzed by immunohistochemistry. In the three patients with clinically long-lasting responses to HDC plus HSCT (median 423 days), significant reductions in ACPA-IgG levels after therapy were observed (median level dropped from 215 to 34 arbitrary units/ml; P = 0.05). In contrast, stable ACPA-IgG levels were observed in three patients who relapsed shortly after HDC plus HSCT (median of 67 days). Clinical responders had ACPA-IgG of lower avidity (r = 0.75; P = 0.08) and higher degree of inflammation histologically (r = 0.73; P = 0.09). Relapse (after 38 to 530 days) in all patients was preceded by rising levels of low avidity ACPA-IgG (after 30 to 388 days), in contrast to the stable titres of high avidity TT antibodies. In conclusion, humoral autoimmune responses were differentially modulated by immunoablative therapy in patients with synovial inflammation and low avidity ACPA-IgG autoantibodies as compared with patients with high levels of high avidity ACPA-IgG. The distinct clinical disease course after immunoablative therapy based on levels and avidity of ACPA-IgG indicates that refractory RA is not a single disease entity.

Assessment of disseminated adenovirus infections using quantitative plasma PCR in adult allogeneic stem cell transplant recipients receiving reduced intensity or myeloablative conditioning

OBJECTIVES

Disseminated adenovirus (AdV) infections following allogeneic stem cell transplantation (allo-SCT) are increasingly recognised, particularly in children. This study evaluated the clinical relevance of disseminated AdV infections in adult allo-SCT recipients, after different conditioning regimens.

METHODS

In a cohort of 107 adult allo-SCT recipients, receiving either reduced intensity conditioning (RIC, n = 48) or myeloablative conditioning (MAC, n = 59), AdV DNA levels in plasma were determined retrospectively at 1, 3 and 6 months following transplantation. Results of this screening regimen were compared with a cohort of 58 paediatric allo-SCT recipients, in whom AdV DNA load was monitored prospectively, as part of a pre-emptive treatment strategy. In positive cases, the course of AdV DNA load and clinical outcome were assessed.

RESULTS

AdV DNA levels > or =1000 copies/mL were detected in five adults (4.7%) and eight children (13.8%). Screening for AdV viraemia at 1, 3 and 6 months would have detected seven of eight paediatric patients. One adult, receiving MAC, died with disseminated AdV disease and in four (three RIC and one MAC) AdV viraemia was transient without clinical symptoms specifically attributable to AdV. Seven paediatric patients with AdV viraemia were pre-emptively treated with ribavirin or cidofovir and in three of them disseminated AdV infection was related to a fatal outcome.

CONCLUSIONS

Disseminated AdV infections following allo-SCT was a rare event in the adults and cause morbidity in a minority of these patients. In four of five adult patients, spontaneous clearance of AdV viraemia occurred. Results did not differ between the conditioning regimens that were applied in the adult cohort.

Adenovirus-specific CD4+ T cell clones recognizing endogenous antigen inhibit viral replication in vitro through cognate interaction

Human adenovirus (HAdV) infection is a frequent and potentially severe complication following allogeneic stem cell transplantation in children. Because treatment with antiviral drugs is often ineffective, adoptive transfer of donor-derived HAdV-specific T cells able to control viral replication of HAdV of multiple serotypes may be an option for therapy. In healthy donors, predominantly HAdV-specific T cells expressing CD4 are detected. In this study, a preclinical in vitro model was used to measure the antiviral effect of HAdV-specific CD4+ T cells. CD4+ HAdV-specific T cell clones restricted by HLA class II molecules were generated and most of these clones recognized conserved peptides derived from the hexon protein. These cross-reactive T cell clones were able to control viral replication of multiple serotypes of HAdV in EBV-transformed B cells (B-LCL), melanoma cells (MJS) and primary bronchial epithelial cells through cognate interaction. The HAdV-specific CD4+ T cell clones were able to specifically lyse infected target cells using a perforin-dependent mechanism. Antigenic peptides were also presented to the CD4+ T cell clones when derived from endogenously produced hexon protein. Together, these results show that cross-reactive HAdV-specific CD4+ T cells can control replication of HAdV in vitro and provide a rationale for the use of HAdV-specific T cells in adoptive immunotherapy protocols for control of life-threatening HAdV-infections in immunocompromised patients.

Expression of Cellular FLICE Inhibitory Protein, Caspase-8, and Protease Inhibitor-9 in Ewing Sarcoma and Implications for Susceptibility to Cytotoxic Pathways

PURPOSE

Ewing sarcoma is a common pediatric bone tumor with an unfavorable prognosis for metastatic or recurrent disease. Cellular immunotherapy may provide new treatment options and depends on the cytolytic death receptor and perforin/granzyme pathways. Expression of death receptor pathway inhibitor cellular FLICE inhibitory protein (cFLIP), initiator caspase-8, and granzyme B inhibitor protease inhibitor-9 (PI-9) have been reported to determine susceptibility to cell- and chemotherapy-mediated killing in several tumor types. Here, we have studied their in vitro and in vivo expression in Ewing sarcoma and the implications for susceptibility to cytotoxicity.

EXPERIMENTAL DESIGN

Ewing sarcoma cell lines (n = 8) were tested for cFLIP, PI-9, and caspase-8 expression. Functional significance was tested by anti-Fas antibody (death receptor pathway) or natural killer cell (perforin/granzyme pathway) treatment. Immunohistochemistry was done on 28 sections from 18 patients. In half of the cases, sequential material, including metastases, was available.

RESULTS

Although all tested Ewing sarcoma cell lines expressed cFLIP, resistance to CD95/Fas-mediated apoptosis was only observed in two cell lines lacking caspase-8 expression. PI-9 was expressed at low levels in four of eight Ewing sarcoma cell lines, but positive cell lines remained susceptible to perforin/granzyme-mediated killing. In primary Ewing sarcoma, including metastases, cFLIP was abundantly expressed in 18 of 18 patients. Caspase-8 was expressed in all patients but showed more intertumoral and intratumoral variation in both intensity and heterogeneity of staining. PI-9, in contrast, was undetectable.

CONCLUSIONS

The expression patterns of cFLIP, caspase-8, and the absence of PI-9 provide a rationale to preferentially exploit the perforin/granzyme pathway in cytotoxic therapies against Ewing sarcoma.

B-cell recovery after stem cell transplantation of Artemis-deficient SCID requires elimination of autologous bone marrow precursor-B-cells

Severe combined immunodeficiencies (SCID) are commonly fatal early in life. Adequate diagnosis and rapid institution of treatment, such as allogeneic stem cell transplantation (SCT), is essential. Several studies demonstrated that reconstitution of B-cell function after SCT is better in B-positive SCID than in B-negative SCID. We demonstrate that B-cell reconstitution in a B-negative SCID patient due to an Artemis mutation required the elimination of the autologous precursor-B-cells in bone marrow, probably to create physical space in the precursor-B-cell niches. Apparently, occupation of the precursor-B-cell niches is a potential dominant factor influencing repopulation of a functional B-cell compartment in B-negative SCID.

Human CD4+ T cells stimulated by conserved adenovirus 5 hexon peptides recognize cells infected with different species of human adenovirus

The immune response against human adenovirus (HAdV) has gained interest because of the application of HAdV-based vectors in gene therapy and the high incidence of infections in pediatric recipients of allogeneic stem cell grafts. Because antiviral medication is frequently ineffective, the option of adoptive transfer of HAdV-specific donor-derived T cells in these immunocompromised patients is investigated. To generate good manufacturing practice-compatible reagents, a panel of 63 long, overlapping, peptides of the hexon protein was screened for recognition by T cells. Five conserved peptides of 30 amino acids were identified that were recognized by the majority of adult donors. CD4+ T cells from long-term cultures of PBMC, stimulated with this set of five peptides, recognized cells infected with HAdV serotypes belonging to different species. These data demonstrate that adult human T cells preferentially recognize conserved sequences of amino acid residues from a structural protein of HAdV. In the context of gene therapy, this observation may limit the beneficial effect of switching to HAdV-based vectors derived from less common serotypes of HAdV in an attempt to circumvent pre-existing immunity. However, this cross-reactivity benefits the application of HAdV-specific T cells for adoptive immunotherapy in immunocompromised transplant recipients.

A possible role for CCL27/CTACK-CCR10 interaction in recruiting CD4 T cells to skin in human graft-versus-host disease

Graft-versus-host disease (GvHD) is a serious complication of allogeneic stem cell transplantation (SCT) affecting the skin, gut and liver. The involvement of distinct organs suggests a role for tissue-specific chemokines and their receptors in directing activated donor T cells to these sites. In this study the potential involvement of the skin-specific CCL27/CTACK-CCR10 interaction was investigated in 15 paediatric SCT patients with skin GvHD. During the course of skin GvHD, peripheral blood T cells from these patients contained a high proportion of CD4+ CCR10+ T cells that disappeared after the GvHD was resolved. These cells were CD45RO+, expressed additional skin homing markers (cutaneous lymphocyte-associated antigen and CCR4), and produced the T-cell helper type 1-cytokines tumour necrosis factor-alpha and interleukin-2. The increase in CD4+ CCR10+ T cells was absent in SCT patients without GvHD. Immunohistochemical investigations showed CD4+ CCR10+ T cells in the GvHD skin biopsies of the same patients, but not in the gut biopsies of patients also suffering from gut GvHD. The infiltration of CD4+ CCR10+ T cells in the GvHD-affected skin correlated with an enhanced epidermal expression of CCL27/CTACK, the ligand for CCR10. These findings support the involvement of CCL27/CTACK-CCR10 interaction in recruiting CD4+ T cells to the skin, thus contributing to the pathogenesis of acute GvHD.

Management of Epstein-Barr Virus (EBV) Reactivation after Allogeneic Stem Cell Transplantation by Simultaneous Analysis of EBV DNA Load and EBV-Specific T Cell Reconstitution

BACKGROUND

Epstein-Barr virus (EBV) reactivation is a frequent event after allogeneic stem cell transplantation and may progress to life-threatening lymphoproliferative disease (EBV-LPD) in the absence of adequate EBV-specific T cell immunity. Quantification of EBV DNA load in asymptomatic individuals who are at risk is a useful (although not entirely predictive) indicator of progression to EBV-LPD and guide for preemptive treatment with CD20 antibodies.

METHODS

With the aim of improving the identification of patients at risk, we retrospectively analyzed, within a cohort of 25 consecutive allogeneic stem cell transplant recipients at risk for EBV-LPD, the pattern of T cell reconstitution during EBV reactivation in all preemptively treated patients (8 patients).

RESULTS

In 6 of 8 cases, a significant T cell reconstitution (i.e., a CD3+ T cell count of >300 cells/microL) was documented during EBV reactivation, which included an expansion of EBV-specific memory T cells, as shown by human leukocyte antigen class I tetramer analysis. Additional evidence for the antiviral potential of this T cell reconstitution was obtained prospectively from a cohort of 14 consecutive allogeneic stem cell transplant recipients at risk for EBV-LPD. EBV reactivation occurred in 3 patients. Preemptive treatment was successfully withheld for 2 of these patients in light of concurrent (EBV-specific) T cell recovery.

CONCLUSION

We conclude that analysis of the level of (EBV-specific) T cell reconstitution during EBV reactivation is an important second parameter, in addition to quantification of EBV DNA load, that will be instrumental in a more accurate definition of patients at risk for EBV-LPD who, given their immunoincompetence, will be most certainly dependent on preemptive interventions.

An antibody-deficiency syndrome due to mutations in the CD19 gene

BACKGROUND

The CD19 protein forms a complex with CD21, CD81, and CD225 in the membrane of mature B cells. Together with the B-cell antigen receptor, this complex signals the B cell to decrease its threshold for activation by the antigen.

METHODS

We evaluated four patients from two unrelated families who had increased susceptibility to infection, hypogammaglobulinemia, and normal numbers of mature B cells in blood. We found a mutation in the CD19 gene in all four patients. The CD19 gene in the patients and their first-degree relatives was sequenced, and flow-cytometric immunophenotyping of B cells, immunohistochemical staining of lymphoid tissues, and DNA and messenger RNA analysis were performed. B-cell responses on the triggering of the B-cell receptor were investigated by in vitro stimulation; the antibody response after vaccination with rabies vaccine was also studied.

RESULTS

All four patients had homozygous mutations in the CD19 gene. Levels of CD19 were undetectable in one patient and substantially decreased in the other three. Levels of CD21 were decreased, whereas levels of CD81 and CD225 were normal, in all four patients. The composition of the precursor B-cell compartment in bone marrow and the total numbers of B cells in blood were normal. However, the numbers of CD27+ memory B cells and CD5+ B cells were decreased. Secondary follicles in lymphoid tissues were small to normal in size and had a normal cellular composition. The few B cells that showed molecular signs of switching from one immunoglobulin class to another contained V(H)-C(alpha) and V(H)-C(gamma) transcripts with somatic mutations. The response of the patients' B cells to in vitro stimulation through the B-cell receptor was impaired, and in all four patients, the antibody response to rabies vaccination was poor.

CONCLUSIONS

Mutation of the CD19 gene causes a type of hypogammaglobulinemia in which the response of mature B cells to antigenic stimulation is defective.

Internally controlled real-time PCR monitoring of adenovirus DNA load in serum or plasma of transplant recipients

Adenoviruses have been recognized as important pathogens in immunocompromised hosts. Particularly in pediatric allogeneic stem cell transplant recipients, the morbidity of the patients and mortality in those patients with disseminated infections have been found to increase over the last few years. Severe infections are predominantly but not exclusively caused by subgroup C adenoviruses. A multiplex real-time PCR assay using molecular beacons as probes was developed to enable monitoring of adenovirus DNA in those patients with simultaneous identification of subgroups. An internal control was coamplified in the multiplex PCR to check for the DNA isolation procedure as well as the presence of inhibitors in the clinical samples. The assay has been applied retrospectively in patient groups with different clinical outcomes of infection. In fatal cases, significantly higher adenovirus loads developed, exceeding even 10(11) copies/ml of serum or plasma. Patients with viral loads over 10(6) copies/ml appear to have an increased risk for fatal complications. This quantitative real-time PCR assay has been prospectively used clinically since 2002 to study the course of adenovirus infection. In addition, the assay provides objective start and end points of therapeutic interventions, including the clinically important evaluation of antiviral drugs.

Immune reconstitution and clearance of human adenovirus viremia in pediatric stem-cell recipients

BACKGROUND

Human adenovirus (HAdV) infections are increasingly frequent complications of allogeneic stem-cell transplantation (SCT), especially in children. Only a few data on the correlation between immune recovery and the course of HAdV infection are available, and data on HAdV-specific responses are lacking.

METHODS

In a prospective study, we determined the correlation between the HAdV DNA load in plasma and lymphocyte reconstitution in 48 children after allogeneic SCT. Additionally, HAdV-specific humoral and cellular immune responses were investigated.

RESULTS

HAdV infection occurred in 21 patients (44%), and, in 6 of these patients, the infection progressed to viremia, as demonstrated by the presence of HAdV DNA in plasma. Low lymphocyte counts at the onset of infection were predictive of HAdV viremia. Survival of patients with HAdV viremia was associated with an increase in lymphocyte counts during the first weeks after infection. In these patients, HAdV-specific CD4+ T cell responses, as well as increases in titers of neutralizing antibody, were detected after clearance of HAdV DNA from plasma.

CONCLUSIONS

Lymphocyte reconstitution appears to play a crucial role in clearance of HAdV viremia and survival of the host, warranting further development of therapeutic interventions aimed at improving immune recovery.

Possible link between unique chemokine and homing receptor expression at diagnosis and relapse location in a patient with childhood T-ALL

Childhood acute lymphoblastic leukemia (ALL) is often associated with extramedullary infiltration by leukemic cells at diagnosis or at relapse. To understand the mechanisms behind the dissemination of T-cell ALL (T-ALL) cells this study investigated the homing receptor expression on the blast cells of 11 pediatric T-ALL patients at diagnosis. One patient revealed a unique profile with high expression of the chemokine receptor CCR9 and the integrin CD103 on the T-ALL cells. Both of these molecules are specifically associated with homing to the gut. This finding was clinically significant as the patient later suffered a relapse that was confined to the gut. Immunohistochemistry revealed that the leukemic cells in the gut still expressed CCR9 and colocalized with a high expression of the CCR9 ligand, CCL25. These findings suggest that the original expression of CCR9 and CD103 on the leukemic cells contributed to the relapse location in the gut of this patient.

Meconium is a source of pro-inflammatory substances and can induce cytokine production in cultured A549 epithelial cells

Inflammation plays an important role in the pathogenesis of meconium aspiration syndrome, and pneumonitis is one of the major characteristics. We have previously shown that meconium has chemotactic properties because of the presence of IL-8. We hypothesize that IL-8 and other proinflammatory substances in meconium may amplify inflammation in meconium aspiration syndrome, inducing endogenous cytokine production by lung epithelial cells. We measured proinflammatory substances in first-pass meconium from healthy newborns and evaluated the effect of sterile meconium on cytokine production in cultured A549 alveolar epithelial cells in vitro. IL-1beta, IL-6, IL-8, and tumor necrosis factor-alpha were measured by ELISA, and heme was measured spectrophotometrically. After incubation of meconium samples with A549 cells, cytokine concentrations in the supernatant were measured. Meconium samples contained variable amounts of IL-1beta, IL-6, IL-8, tumor necrosis factor-alpha, and heme. On stimulation of A549 cells with meconium, the IL-8 concentration in the culture supernatant significantly increased above baseline measurements, whereas tumor necrosis factor-alpha showed a variable pattern and IL-1beta or IL-6 remained unchanged. There was no quantitative relationship between the concentration of the measured cytokines and heme in meconium and cytokine release by the A549 cells after meconium exposure. Meconium contains proinflammatory substances. All samples induced IL-8 release and some induced tumor necrosis factor-alpha release in cultured A549 epithelial cells. We speculate that proinflammatory substances in meconium can induce lung inflammation in meconium aspiration syndrome in two ways: directly via cytokines and heme present in meconium and indirectly by inducing cytokine release by the epithelial lung cells.

Extensive cross-reactivity of CD4+ adenovirus-specific T cells: implications for immunotherapy and gene therapy

Adenovirus (Ad)-specific T-cell responses in healthy adult donors were investigated. Ad5, inactivated by methylene blue plus visible light, induced proliferation and gamma interferon (IFN-gamma) production in peripheral blood mononuclear cells of the majority of donors. Responding T cells were CD4(+) and produced IFN-gamma upon restimulation with infectious Ad5 and Ads of different subgroups. T-cell clones showed distinct cross-reactivity patterns recognizing Ad serotypes from either one subgroup (C), two subgroups (B and C), or three subgroups (A, B, and C). This cross-reactivity of Ad-specific T cells has relevance both for Ad-based gene therapy protocols, as well as for the feasibility of T-cell-mediated adoptive immunotherapy in recipients of an allogeneic stem cell transplantation.

Concentration and avidity of anti-Haemophilus influenzae type b (Hib) antibodies in serum samples obtained from patients for whom Hib vaccination failed

Haemophilus influenzae type b (Hib) conjugate vaccines are extremely effective in protecting infants and children from invasive Hib infections; however, vaccine failures do occur. The anti-Hib antibody production was studied both quantitatively and qualitatively in 12 patients who experienced Hib failure, all of whom had normal serum immunoglobulin concentrations and all of whom were without clinical risk factors for invasive Hib disease. Both anti-Hib antibody concentration and immunoglobulin-G2 anti-Hib antibody avidity were significantly lower in patients who experienced Hib failure, at onset of disease and after reconvalescence, when compared with controls. This finding suggests that the patients who developed invasive Hib disease--despite having received 3-4 Hib conjugate vaccinations--were inadequately primed by these vaccinations.