Clinical-grade purification of natural killer cells in haploidentical hematopoietic stem cell transplantation

BACKGROUND

Because of a high risk of graft-versus-host disease (GVHD), donor lymphocyte infusions with unmodified lymphapheresis products are not used after haploidentical hematopoietic stem cell transplantation. Natural killer (NK) cells have antitumor activity and may consolidate engraftment without inducing GVHD. Production of NK cells under good manufacturing practice (GMP) conditions in a sufficient number is difficult.

STUDY DESIGN AND METHODS

Twenty-four apheresis procedures and subsequent NK-cell enrichment from 14 haploidentical donors were performed. NK-cell enrichment was performed using a GMP suitable immunomagnetic procedure. Factors influencing the NK-cell recovery, purity, and NK-cell dose were analyzed.

RESULTS

A median number of 4.9 x 10(8) NK cells were obtained and median NK-cell recovery was 58 percent. Median T-cell depletion was 4.32 log. The absolute NK-cell number in the final product after processing significantly correlated with the preharvest NK-cell content of the peripheral blood (p = 0.002, r = 0.867). The NK-cell recovery was inversely correlated to the absolute NK-cell number in the apheresis product (p = 0.01, r = -0.51). The NK-cell dose per kg of body weight of the patient was inversely correlated to the weight of the patient (p = 0.007, r = -0.533).

CONCLUSION

Donors with a high NK-cell count in peripheral blood are likely to provide NK-cell products with the highest cell number. However, maximal NK-cell dose is limited and high NK-cell doses may only be obtained for patients with a low body weight, making children and young adults the best candidates for NK-cell therapy.

New insights to the MLL recombinome of acute leukemias

Chromosomal rearrangements of the human MLL gene are associated with high-risk pediatric, adult and therapy-associated acute leukemias. These patients need to be identified, treated appropriately and minimal residual disease was monitored by quantitative PCR techniques. Genomic DNA was isolated from individual acute leukemia patients to identify and characterize chromosomal rearrangements involving the human MLL gene. A total of 760 MLL-rearranged biopsy samples obtained from 384 pediatric and 376 adult leukemia patients were characterized at the molecular level. The distribution of MLL breakpoints for clinical subtypes (acute lymphoblastic leukemia, acute myeloid leukemia, pediatric and adult) and fused translocation partner genes (TPGs) will be presented, including novel MLL fusion genes. Combined data of our study and recently published data revealed 104 different MLL rearrangements of which 64 TPGs are now characterized on the molecular level. Nine TPGs seem to be predominantly involved in genetic recombinations of MLL: AFF1/AF4, MLLT3/AF9, MLLT1/ENL, MLLT10/AF10, MLLT4/AF6, ELL, EPS15/AF1P, MLLT6/AF17 and SEPT6, respectively. Moreover, we describe for the first time the genetic network of reciprocal MLL gene fusions deriving from complex rearrangements.

Reconstitution of cytomegalovirus specific T cells after pediatric allogeneic stem cell transplantation: results from a pilot study using a multi-allele CMV tetramer group

BACKGROUND

Recovery of cytomegalovirus (CMV)-specific T cell mediated immunity after allogeneic hematopoietic stem cell transplantation (SCT) is critical for protection against CMV disease. Tetramer-based technologies have been shown to be a sensitive tool in the enumeration of specific T cells, but have the disadvantage of HLA-restriction of the peptides.

PATIENTS AND METHODS

In this pilot study, we tested the feasibility of a panel of 6 CMV-specific tetrameric HLA/CMV-peptide complexes to enumerate CMV-specific CD8 +T cells (CTLs). The reconstitution of CMV-specific CTLs was assessed in 16 children in the first year after allogeneic SCT (median age, 8 years).

RESULTS

The presented assay covered more than 85% of our patients transplanted in the last 3 years. During CMV-reactivation, all 4 of the 16 analyzed patients with a high virus-load showed less than 10 CMV-specific CTLs/microl; out of these, three had not any detectable CMV-CTLs. On the other hand, five of the children with less than 10 CMV-specific CTLs/microl did not develop CMV reactivation. When enumeration of T cells was performed by means of different tetrameric HLA/CMV-peptide complexes simultaneously, the numbers of CMV-specific CTLs cells widely differed according to the HLA-type.

CONCLUSIONS

Our pilot study suggests that enumeration of CMV-specific T cells by means of a panel of 6 tetramers might be a useful tool in the risk assessment for CMV reactivation in the majority of patients undergoing allogeneic SCT, but future trials have to evaluate whether this method is appropriate in tailoring antiviral therapy in the individual patient.

Targeted cell entry of lentiviral vectors

Retargeting of lentiviral vector entry to cell types of interest is a key factor in improving the safety and efficacy of gene transfer. In this study we show that the retargetable envelope glycoproteins of measles virus (MV), namely, the hemagglutinin (H) responsible for receptor recognition and the fusion protein (F), can pseudotype human immunodeficiency virus 1 (HIV-1) vectors when their cytoplasmic tails are truncated. We then pseudotyped HIV-1 vectors with MV glycoproteins displaying on H either the epidermal growth factor or a single-chain antibody directed against CD20, but without the ability to recognize their native receptors. Gene transfer into cells that expressed the targeted receptor was several orders of magnitude more efficient than into cells that did not. High-target versus nontarget cell discrimination was demonstrated in mixed cell populations, where the targeting vector selectively eliminated CD20-positive cells after suicide gene transfer. Remarkably, primary human CD20-positive B lymphocytes were transduced more efficiently by the CD20-targeted vector than by a vector pseudotyped with the vesicular stomatitis virus G (VSV-G) protein. In addition, the CD20-targeted vector was able to transduce even unstimulated primary B cells, whereas VSV-G pseudotyped vectors were unable to do so. Because MV enters cells through direct fusion at the cell membrane, this novel targeting system should be widely applicable.

Cultivated anti-Aspergillus T(H)1 cells

Invasive aspergillosis remains a serious complication in patients undergoing allogeneic stem cell transplantation. Since it became clear that lymphocytes provide a critical secondary defense against fungi, adoptive transfer of functionally active anti-Aspergillus T cells might be an option to restore adaptive immune effector mechanisms. Using the interferon (IFN)-gamma secretion assay, we isolated human activated T cells upon stimulation with a cellular extract of Aspergillus fumigatus. After a culturing period for 14 days, we could characterize these cells as T(H)1 cells, which also proliferated upon restimulation. The generated cells responded upon stimulation with antigens of A. flavus, A. niger and Penicillium chrysogenum, but not upon activation with Alternaria alternata and Candida albicans. In addition, the cultivated T cells were able to induce damage to A. fumigatus hyphae and showed a reduced alloreactivity compared to unselected CD4+ T cells. We further established a clinical-scale generation of anti-Aspergillus T cells. However, before performing clinical trials, open questions such as which patient population will benefit from adoptive immunotherapy with anti-Aspergillus T cells have to be addressed.

Enumeration of functionally active anti-Aspergillus T-cells in human peripheral blood

Invasive aspergillosis remains a life-threatening complication in patients undergoing allogeneic stem cell transplantation (SCT). Since CD4(+) T-cells provide a critical secondary defense against Aspergillus spp., the quantification of "functional" anti-Aspergillus T-cells might be important in the clinical care of allogeneic transplant patients. We present a rapid, simple and reproducible method to enumerate functionally active, cytokine-producing anti-Aspergillus T-cells in peripheral blood by means of flow cytometry, by which these cells were also phenotypically characterized as memory CD4(+) T-cells. When using 100,000 PBMCs and requiring a minimum of 50 events, at least one anti-Aspergillus T-cell among 1000 CD4(+) T-cells can be detected. Compared to healthy individuals, the number of anti-Aspergillus T-cells in patients up to one year after SCT was significantly lower. The presented method might help to define hematopoietic transplant recipients who will benefit from adoptive transfer of anti-Aspergillus T cells.

Age-matched lymphocyte subpopulation reference values in childhood and adolescence: application of exponential regression analysis

BACKGROUND

Normal values of lymphocyte subpopulations for healthy children and adults have been published in defined age groups exclusively, which results in difficult data interpretation for patients close to the limit of contiguous age group ranges. In addition, normal values for a number of lymphocyte subpopulations have not been established to date.

OBJECTIVE

The aim of this study was to develop a model which provides continuous age-dependent reference values. This model was applied for lymphocyte subpopulations such as naïve and memory T cells as well as their activation profile with diagnostic relevance in children and adults.

STUDY DESIGN

A total of 100 blood samples, obtained from 80 healthy children and 20 adults were analysed by means of four colour-flow cytometry. Continuous age-dependent reference values were computed based on the residual values in an exponential regression model.

RESULTS

We calculated a continuous age-related regression model for both, absolute cell counts and percentages of CD3(+)CD4(+) T helper (T(H)) cells, CD3(+)CD8(+) cytotoxic T cells, CD56(+)CD3(-) natural killer (NK) cells, CD56(+)CD3(+) T cells, CD3(+)CD4(+)CD45RA(+) naïve T(H) cells, CD3(+)CD4(+)CD45RO(+) memory T(H) cells, CD3(+)CD8(+)CD45RA(+)CD28(+) naïve cytotoxic T cells, CD3(+)CD8(+)CD45RO(+) memory cytotoxic T cells, CD3(+)CD8(+)CD69(+) early activated cytotoxic T cells and CD3(+)CD8(+)HLA-DR(+) late activated cytotoxic T cells, respectively, to obtain reference values.

CONCLUSION

Based on an exponential regression model, the obtained reference values reflect the continuous maturation of lymphocyte subsets during childhood.

T cells for suicide gene therapy: activation, functionality and clinical relevance

In order to control graft-versus-host disease after donor lymphocyte infusion, T cells can be retrovirally transduced with a suicide gene. However, the immune competence of activated T cells appears compromised, responsible for reduced alloreactivity. The present study compared different activation protocols using soluble or bead-coupled antibodies regarding T-cell subtype expansion capacity and functionality. T cells were purified on a laboratory and clinical scale using both CD3 and CD4/CD8 antibodies for selection, leading to a mean purity of 96%. Transductions were performed with a GMP-grade CD34/HSV-TK vector. Activation with soluble CD3/CD28-antibodies +1000 U/ml IL-2 induced a 50-fold expansion of T cells over 14 days, whereas T cells activated with bead-coupled antibodies only expanded 2-4-fold restricted to the first week. Apart from using soluble antibodies, proliferation was highly IL-2 dependent. Expansion of CMV-specific T cells coincided with the expansion of whole CD3(+) cells. Soluble antibodies and higher IL-2 concentrations preferentially stimulated CD8(+) T cells, while bead-coupled antibodies +20 U/ml IL-2 preserved the CD4/CD8 ratio. Irrespective of the activation protocol, there was a shift from a naive to memory phenotype. When activated with soluble antibodies, mainly CD8(+) T cells were transduced. Furthermore, Th1/Th2 cytokine secretion was reduced. In contrast, CD4(+)/CD8(+) T cells activated with bead-coupled antibodies were rather homogenously transduced and cytokine secretion did not appear to be affected.

Imbalance in distribution of functional autologous regulatory T cells in rheumatoid arthritis

OBJECTIVES

Regulatory T cells (Tregs) exert their anti-inflammatory activity predominantly by cell contact-dependent mechanisms. A study was undertaken to investigate the regulatory capacity of autologous peripheral blood Tregs in contact with synovial tissue cell cultures, and to evaluate their presence in peripheral blood, synovial tissue and synovial fluid of patients with rheumatoid arthritis (RA).

METHODS

44 patients with RA and 5 with osteoarthritis were included in the study. The frequency of interferon (IFN)gamma-secreting cells was quantified in synovial tissue cell cultures, CD3-depleted synovial tissue cell cultures, synovial tissue cultures co-cultured with autologous CD4+ and with CD4+CD25+ peripheral blood T cells by ELISPOT. Total CD3+, Th1 polarised and Tregs were quantified by real-time PCR for CD3epsilon, T-bet and FoxP3 mRNA, and by immunohistochemistry for FoxP3 protein.

RESULTS

RA synovial tissue cell cultures exhibited spontaneous expression of IFNgamma which was abrogated by depletion of CD3+ T cells and specifically reduced by co-culture with autologous peripheral blood Treg. The presence of Treg in RA synovitis was indicated by FoxP3 mRNA expression and confirmed by immunohistochemistry. The amount of FoxP3 transcripts, however, was lower in the synovial membrane than in peripheral blood or synovial fluid. The T-bet/FoxP3 ratio correlated with both a higher grade of synovial tissue lymphocyte infiltration and higher disease activity.

CONCLUSION

This study has shown, for the first time in human RA, the efficacy of autologous Tregs in reducing the inflammatory activity of synovial tissue cell cultures ex vivo, while in the synovium FoxP3+ Tregs of patients with RA are reduced compared with peripheral blood and synovial fluid. This local imbalance of Th1 and Treg may be responsible for repeated rheumatic flares and thus will be of interest as a target for future treatments.

Effective treatment of leukemic cell lines with wt1 siRNA

The expression of wt1 and bcl-2 is considered to have a proliferating and survival supporting effect in leukemia blast cells. Here we describe the use of siRNA against wt1 and bcl-2 in leukemic cell lines for successful growth inhibition. We have used two different sequences designated as siRNA-A and siRNA-B corresponding to positions within the wt1 coding sequence to downregulate wt1 and a commercially available siRNA kit to downregulate bcl-2. WT1 and bcl-2 gene expression in transfected leukemic cell lines were evaluated with RT-PCR and western blot analyses. MTT assay was used to measure the cell viability and flow cytometry using annexin V/PI-staining for apoptosis. K562 and HL-60 cell lines transfected with siRNA-A targeted to wt1 had greatly decreased levels of both wt1 mRNA and protein expression. In contrast, siRNA-B and control siRNA led almost to no effect on wt1 mRNA and protein expression. siRNA-A-reduced wt1 mRNA expression was associated with a decreased cell proliferation and increased number of apoptotic cells in K562 and HL-60 cells by 24 and 48 h after transfection. Combined treatment with wt1 siRNA and bcl-2 siRNA simultaneously was not able to override the cell growth and apoptosis effects compared to single treatment with wt1 siRNA. siRNAs targeted against human wt1 might be a valuable tool as antiproliferative agent against wt1 expressing leukemic cells.

A novel five-colour flow cytometric assay to determine NK cell cytotoxicity against neuroblastoma and other adherent tumour cells

For the evaluation of novel therapies, and for initial in vitro testing of potential in vivo graft-versus-tumour-effects (GvT), cytotoxicity of effector cells against target tumour cells needs to be determined in a reliable fashion. Recently Zimmermann et al. [Zimmermann, S.Y., Esser, R., Rohrbach, E., Klingebiel, T., Koehl, U., 2005. A novel four-colour flow cytometric assay to determine natural killer cell or T-cell-mediated cellular cytotoxicity against leukaemia cells in peripheral or bone marrow specimens containing greater than 20% of normal cells. J. Immunol. Methods. 296(1-2), 63-76] introduced a single platform, no-wash flow cytometric assay to quantify natural killer (NK) cell cytotoxicity against leukaemia cells. Here we have optimised this method introducing a novel five-colour flow cytometric assay for the evaluation of NK cell activity against adherent tumour cells, in particular neuroblastoma cells (NB cells). Beside an enhanced cytotoxic activity corresponding to increasing effector/target (E:T) ratios, we could demonstrate an increasing cytotoxicity in a time-dependent manner over a time period of 8 h. The usefulness of this novel method was also confirmed with human tumour cells lines of various other origin including breast and ovarian carcinoma and Wilms tumour cells freshly isolated from a patient after surgery. In addition to flow cytometric analysis, we monitored NK-cell-mediated induction of target cell apoptosis via the caspase cascade in attacked NB cells by fluorescence microscopy after immunofluorescence staining of activated Caspase-3 (Casp-3) in combination with detection of CD45(+) and CD9(+) for discrimination between NK and NB cells. In summary, this novel flow cytometric cytotoxicity assay enables efficient quantification of the phenotype of both, effector and adherent target tumour cells, and therefore represents a useful tool for research on immunotherapies that rely on cytotoxic effector cells.

Generation and characterization of anti-Candida T cells as potential immunotherapy in patients with Candida infection after allogeneic hematopoietic stem-cell transplant

Because lymphocytes play a major role in the host response to Candida infection, adoptive transfer of anti-Candida T cells might be a therapeutic option in patients undergoing allogeneic hematopoietic stem-cell transplant (alloHSCT) who have invasive Candida infection. Using the interferon (IFN)- gamma secretion assay, we isolated human anti-Candida T cells after stimulation with a cellular extract of C. albicans. These cells were expanded within 4 weeks to an average number of 2.6x107 T helper 1 type lymphocytes and significantly lost their alloreactive potential, compared with the original cell population. The generated cells were also stimulated by antigens of C. tropicalis but not by antigens of C. glabrata or various molds. In addition, generated anti-Candida T cells were able to induce damage to C. albicans hyphae and significantly increased hyphal damage induced by human neutrophils. Our data suggest that the generation of functionally active anti-Candida T cells is feasible and may be a promising treatment option for patients undergoing alloHSCT.

Immune recovery in children undergoing allogeneic stem cell transplantation: absolute CD8+CD3+ count reconstitution is associated with survival

To evaluate the correlation between kinetics of immune reconstitution and survival, we prospectively evaluated lymphocyte subsets in 32 paediatric patients undergoing allogeneic stem cell transplantation (SCT) for haematological malignancies. Four-colour flow cytometric analysis was performed at short intervals with a median follow-up of 4 years post SCT. A total of 50% of patients reached age-matched 5th percentile of natural killer, cytotoxic T, B and helper T cells 4, 9, 20 and 28 weeks after SCT, respectively, which increased to more than 80% within 1 year after SCT. Transplantation of peripheral blood stem cells (PBSC) seemed to elicit the fastest reconstitution of CD3+, CD4+ CD3+, CD8+ CD3+ and naïve T cells compared to bone marrow (BM) or CD34-selected PBSC, which did not differ. Most importantly, we observed a significantly higher number of survivors among patients whose CD8+ CD3+ absolute counts rose above the 5th percentile of age-matched normal levels during the first year post SCT compared to patients who never reached these levels (19/25 vs 0/7, P<0.001). This was still present in both subgroups, BM- and CD34-selected grafts (P=0.03, 0.02). These results from a small patient sample underline the importance of particular lymphocyte subsets for the outcome of children undergoing SCT. A larger study with detailed subset analysis is underway.

Natural-killer-cell-based treatment in haematopoietic stem-cell transplantation

Adoptive immunotherapy using natural killer (NK) cells is currently under investigation, especially in situations where anti-neoplastic effect is needed but infusion of T cells is considered hazardous, such as in recipients of haematopoietic stem-cell transplantation (HSCT) from haploidentical donors. NK-cell therapy is mainly but not exclusively investigated in the setting of allogeneic stem-cell transplantation. NK cells may induce potent anti-leukaemic and possibly anti-rejection activity, and may even mitigate graft-versus-host disease (GvHD). It remains to be determined whether such effects are clinically important and whether or not they are mediated mainly or exclusively by KIR-HLA class I interactions. Recent advances in graft engineering has provided methods for isolating large numbers of purified NK cells. Several groups have shown that clinical-grade NK cells at doses up to 10(7)/kg may be collected and purified for the purpose of infusion to patients. Early results in a limited number of patients show that these cell doses may be administered without adverse events and possibly without inducing GvHD. Further study is required to determine whether such infusions will be useful in preventing graft rejection, exerting graft-versus-leukaemia effects, and/or hastening immune recovery.

Pharmacology of intracellular cytosine-arabinoside-5'-triphosphate in malignant cells of pediatric patients with initial or relapsed leukemia and in normal lymphocytes

PURPOSE

The prodrug cytosinearabinoside (ara-C) is widely used in the treatment of acute leukemias. The active drug is the intracellular metabolite cytosine-arabinoside-5'-triphosphate (ara-CTP). The purpose of the present study was to investigate the relation between sensitivity and pharmacokinetic parameters Cmax, t1/2 and AUC of ara-CTP. The obtained results were compared to previous studies.

EXPERIMENTAL DESIGN

Cmax, t1/2 and AUC of ara-CTP were assessed in leukemic cells of 17 pediatric patients with acute lymphoblastic leukemia (ALL) and in 6 lymphoblastic cell lines and compared with normal lymphocytes of 9 healthy donors by high pressure liquid chromatography (HPLC). The sensitivity of the cells against ara-C was determined by the MTT assay.

RESULTS

The intracellular accumulation of ara-CTP was significantly lower in normal lymphocytes (Cmax 47.7-60.9 pmol/10(6) cells) compared to leukemic cell lines (Cmax 11-1128 pmol/10(6) cells) and leukemic cells of our patients (Cmax 85.9-631 pmol/10(6) cells). Similar results were found for the AUC. There was no significant difference between initial and relapsed leukemias in our small cohort. A correlation between sensitivity in terms of IC50 values and the intracellular ara-CTP accumulation was observed in cell lines, but not in leukemic cells and normal lymphocytes from healthy donors.

CONCLUSIONS

Pharmacokinetic parameters varied tremendously in leukemic cells in contrast to normal lymphocytes without a difference in sensitivity. It is worthwhile to compare literature data to assess an optimal dosage of ara-C in pediatric patients.

Immunotherapy in children: report from the Reisensburg-Symposium October 20-22, 2004 and recent advances

Immunotherapy of childhood malignancies has a magic aura of promising an easy way to cure. It is not only the public, but also the medical community, which has caused this hope. Therefore, it was worthwhile to bring together a panel of experts working in the field of immunotherapy in order to discuss ongoing projects, and to show hopes and disappointments. The result was a fascinating symposium sponsored by The Kind Philipp Leukemia Foundation (Mönchengladbach, Germany). The symposium took place in the Reissensburg near Ulm (Germany) which gives the ideal location for such an event.

Ex vivo pretreatment of bone marrow mononuclear cells with endothelial NO synthase enhancer AVE9488 enhances their functional activity for cell therapy

Bone marrow mononuclear cells (BMC) from patients with ischemic cardiomyopathy (ICMP) show a reduced neovascularization capacity in vivo. NO plays an important role in neovascularization, and NO bioavailability is typically reduced in patients with ICMP. We investigated whether the impaired neovascularization capacity of ICMP patient-derived progenitor cells can be restored by pretreatment with the novel endothelial NO synthase (eNOS) transcription enhancer AVE9488 (AVE). Ex vivo pretreatment of BMC from patients with ICMP with AVE significantly increased eNOS mRNA expression by 2.1-fold (P < 0.05) and eNOS activity as assessed by ESR by >3-fold (P < 0.05). The increased eNOS expression was associated with an enhanced migratory capacity in vitro (P < 0.01) and improved neovascularization capacity of the infused BMC in an ischemic hind limb model in vivo (P < 0.001). The improvement in ischemic limb perfusion after infusion of AVE-pretreated BMC resulted in an increase in swimming time (P < 0.05). The enhancement of limb perfusion by AVE-treated BMC was abrogated by ex vivo pretreatment with the eNOS inhibitor N(G)-nitro-l-arginine methyl ester. Consistently, AVE showed no effect on the impaired migratory capacity of BMC derived from eNOS-deficient mice, documenting the specific involvement of NO. The reduced neovascularization capacity of BMC from patients with ICMP may limit their therapeutic potential in cell therapy studies. Here, we show that pharmacological enhancement of eNOS expression with AVE at least partially reverses the impaired functional activity of BMC from ICMP patients, highlighting the critical role of NO for progenitor cell function.

The MLL recombinome of acute leukemias

Chromosomal rearrangements of the human MLL gene are a hallmark for aggressive (high-risk) pediatric, adult and therapy-associated acute leukemias. These patients need to be identified in order to subject these patients to appropriate therapy regimen. A recently developed long-distance inverse PCR method was applied to genomic DNA isolated from individual acute leukemia patients in order to identify chromosomal rearrangements of the human MLL gene. We present data of the molecular characterization of 414 samples obtained from 272 pediatric and 142 adult leukemia patients. The precise localization of genomic breakpoints within the MLL gene and the involved translocation partner genes (TPGs) was determined and several new TPGs were identified. The combined data of our study and published data revealed a total of 87 different MLL rearrangements of which 51 TPGs are now characterized at the molecular level. Interestingly, the four most frequently found TPGs (AF4, AF9, ENL and AF10) encode nuclear proteins that are part of a protein network involved in histone H3K79 methylation. Thus, translocations of the MLL gene, by itself coding for a histone H3K4 methyltransferase, are presumably not randomly chosen, rather functionally selected.

Fatal neonatal-onset mitochondrial respiratory chain disease with T cell immunodeficiency

We present the clinical and laboratory features of a boy with a new syndrome of mitochondrial depletion syndrome and T cell immunodeficiency. The child suffered from severe recurrent infectious diseases, anemia, and thrombocytopenia. Clinically, he presented with severe psychomotor retardation, axial hypotonia, and a disturbed pain perception leading to debilitating biting of the thumb, lower lip, and tongue. Brain imaging showed hypoplasia of corpus callosum and an impaired myelinization of the temporo-occipital region with consecutive supratentorial hydrocephalus. Histologic examination of a skeletal muscle biopsy was normal. Biochemical investigation showed combined deficiency of respiratory chain complexes II+III and IV. MtDNA depletion was found by real-time PCR. No pathogenic mutations were identified in the TK2, SUCLA2, DGUOK, and ECGF1 genes. A heterozygous missense mutation was found in POLG1. The pathogenic relevance of this mutation is unclear. Interestingly, a lack of CD8(+) T lymphocytes as well as NK cells was also observed. The percentage of CD45RO-expressing cells was decreased in activated CD8(+) T lymphocytes. Activation of T lymphocytes via IL-2 was diminished. The occurrence of the immunologic deficiency in our patient with mtDNA depletion is a rare finding, implying that cells of the immune system might also be affected by mitochondrial disease.

Quantification of chimerism within peripheral blood, bone marrow and purified leukocyte subsets: comparison of singleplex and multiplex PCR amplification of short tandem repeat (STR) loci

OBJECTIVE AND METHODS

Chimerism analysis has become a routine diagnostic procedure after haematopoietic allogeneic stem cell transplantation for early detection of relapse of disease or graft failure. Whereas some centres developed individual in-house short tandem repeat (STR) systems, others prefer commercial multiplex PCR systems. However, little is known about inter-assay variation, which could have a significant impact on treatment decision. We therefore compared two commercial multiplex PCR kits with our in-house STR system using different sample sources, such as peripheral blood (PB), bone marrow (BM) and specific leukocyte subsets.

RESULTS

Fifty samples of eighteen paediatric patients were analysed. For neither material, PB, BM and leukocyte subtypes, a significant difference between the STR systems tested was observed. Chimerism analyses of each single STR primer, which is component of both the in-house and the commercial STR system, did not reveal significant differences.

CONCLUSION

Our analysis demonstrates that similar results can be obtained with both assays, even when using various sample sources. Further evaluation of different test systems will help to increase interlaboratory standardisation of chimerism analyses for early clinical intervention.

Correction of X-linked chronic granulomatous disease by gene therapy, augmented by insertional activation of MDS1-EVI1, PRDM16 or SETBP1

Gene transfer into hematopoietic stem cells has been used successfully for correcting lymphoid but not myeloid immunodeficiencies. Here we report on two adults who received gene therapy after nonmyeloablative bone marrow conditioning for the treatment of X-linked chronic granulomatous disease (X-CGD), a primary immunodeficiency caused by a defect in the oxidative antimicrobial activity of phagocytes resulting from mutations in gp91(phox). We detected substantial gene transfer in both individuals' neutrophils that lead to a large number of functionally corrected phagocytes and notable clinical improvement. Large-scale retroviral integration site-distribution analysis showed activating insertions in MDS1-EVI1, PRDM16 or SETBP1 that had influenced regulation of long-term hematopoiesis by expanding gene-corrected myelopoiesis three- to four-fold in both individuals. Although insertional influences have probably reinforced the therapeutic efficacy in this trial, our results suggest that gene therapy in combination with bone marrow conditioning can be successfully used to treat inherited diseases affecting the myeloid compartment such as CGD.

Ex vivo expansion of highly purified NK cells for immunotherapy after haploidentical stem cell transplantation in children

BACKGROUND

Allogeneic natural killer (NK) cells are known to show medium to high cytotoxic activity against HLA-nonidentical leukemia or tumor cells. For a possible benefit of post transplant treatment with NK cells after haploidentical stem cell transplantation (haplo-SCT) we developed a clinical scale procedure for NK cell processing observing Good Manufacturing Practice (GMP).

METHODS

Allogeneic donor NK cells were selected from 15 unstimulated leukaphereses using two rounds of immunomagnetic T cell depletion, followed by an NK cell enrichment step. CD56 (+)CD3 (-) NK cells were stimulated and expanded in vitro according to GMP. Quality control of NK cell purity, residual T cells and cytotoxic activity was done by multi-coloured flow cytometric analyses.

RESULTS

Purification led to an absolute number of 234-1 237 x 10 (6) CD56 (+)CD3 (-) NK cells from leukapheresis harvests with a median purity of 95 % and a 4 to 6(1/2) log depletion of T cells. After two weeks stimulation with IL-2 a five-fold expansion of NK cells with a T cell contamination below 0.1 % was reached. Median cell viability was 95 % after purification and 99 % after expansion. The IL-2 stimulated NK cells showed a highly increased lytic activity against the MHC-I deficient K562 cells compared to freshly isolated NK cells and a medium cytotoxicity against patients' leukemic cells.

CONCLUSIONS

Clinical scale enrichment and activation of allogeneic donor NK cells is feasible. High dose NK cell application may be a new treatment option for pediatric patients with leukemia or solid tumors in case of minimal residual disease or unbalanced chimerism post haplo-SCT as we could show for the first three patients .

Generation of highly purified and functionally active human TH1 cells against Aspergillus fumigatus

Invasive aspergillosis remains a serious complication in patients undergoing allogeneic stem cell transplantation (SCT). Since it became clear that lymphocytes provide a critical secondary defense against fungi, adoptive transfer of functionally active anti-Aspergillus T cells might be an option to restore adaptive immune effector mechanisms. Using the interferon (IFN)-γ secretion assay, we isolated human activated T cells upon stimulation with a cellular extract of Aspergillus fumigatus. Culturing this cell population for 14 days, we obtained an average of 1.1 × 107 cells from a single 100-mL blood draw in 7 of 7 healthy individuals. Within another 14 days, these cells were expanded to an average number of 2.0 × 108 T-helper 1 (TH1) cells secreting IFN-γ on stimulation with Aspergillus antigens. Testing various fungal antigen extracts, similar proportions of IFN-γ-producing CD3+/CD4+ cells were obtained upon activation with antigen extracts of A fumigatus, A flavus, A niger, and Penicillium chrysogenum, whereas no significant IFN-γ production was observed upon activation with antigen extracts of Alternaria alternata and Candida albicans. In addition, generated T cells were able to induce damage to A fumigatus hyphae, and significantly increased hyphal damage induced by human neutrophils. CD4+ T-cell-mediated alloreactivity of generated anti-Aspergillus T cells was clearly reduced compared with that of the original cell population. In conclusion, we present a simple and feasible strategy for rapid generation of a high number of functional active T cells against Aspergillus from a single blood draw. Our data suggest that functionally active T cells against Aspergillus could be a promising treatment option for patients undergoing allogeneic SCT. (Blood. 2006;107: 2562-2569)

CD34+-selected stem cell boost for delayed or insufficient engraftment after allogeneic stem cell transplantation

BACKGROUND

Poor graft function without rejection may occur after stem cell transplantation (SCT). CD34(+) stem cell boost (SCB) can restore marrow function but may induce or exacerbate GvHD. We therefore investigated the feasibility and efficacy of CD34(+)-selected SCB in some patients with poor graft function. We present the results for eight patients (median age 46 years) transplanted initially for myelofibrosis, acute leukemia, myeloma and NHL. Six patients had received HLA-matched and two mismatched grafts (PB, BM; n=5, 3). After a median of 128 days post-transplant, the median leukocyte and platelet counts were, respectively, 2.05/nL and 18/nL. None had achieved platelet counts >50/nL even though donor chimerism was >95% in seven recipients.

METHODS

Positive selection of CD34(+) stem cells was performed on a CliniMACS device, observing GMP and achieving a median of 98.5% purity. The patients received a median of 1.7 x 10(6)/kg CD34(+) cells and 2.5 x 10(3)/kg CD3(+) T lymphocytes.

RESULTS

Hemograms at days +30, +60 and +90, respectively, showed steadily increasing median leukocyte (2.55, 3.15 and 4.20/nL) and platelet (29, 39 and 95/nL) counts. After a median follow-up of 144 days, five patients remained alive. No patient had developed acute or chronic GvHD. One patient died of leukemic relapse and two others of systemic mycosis.

DISCUSSION

These preliminary results point to the possibility of safely improving graft function using CD34(+) positively selected stem cells without necessarily increasing the incidence of GvHD in patients with poor graft function post-SCT. Experience with more patients and longer follow-up should clarify the optimal role for this procedure.

Common genetic variants in the interleukin-6 and chitotriosidase genes are associated with the risk for serious infection in children undergoing therapy for acute myeloid leukemia

Infectious complications represent a substantial cause of morbidity and mortality in children undergoing therapy for acute myeloid leukemia (AML). Since it has been shown that alterations in innate immune pathways contribute to the risk for serious infections, we analyzed well-characterized variants in innate immune genes (TNF, IL6, IL8, MPO, CHIT, FCGR2A, TLR2, and TLR4) to determine their possible contribution to infectious complications during therapy for pediatric AML. The study population consisted of 168 North European Caucasian children enrolled on the clinical trial AML-BFM 93. We found an association between Gram-negative bacterial infection and common, functional variants in two genes, IL6 and CHIT. The risk for infection was significantly higher in children with the G allele in the IL6 promoter at -174 bp (P=0.026) and in patients with the H allele of CHIT (P=0.033). The promoter variant in IL6 has been shown to increase expression while the H allele disrupts both function and circulating levels. Our data suggest that variant alleles of both IL6 and CHIT could influence susceptibility to infection with Gram-negative bacteria in children undergoing therapy for AML. Follow-up studies, namely replication association studies and in vitro investigation of these common polymorphisms, are warranted to confirm these observations.

Hourly monitoring of circulating CD34+ cells to optimize timing of autologous apheresis in pediatric patients

In order to increase the CD34+ cell yield in children undergoing autologous stem cell transplantation, the optimum time of apheresis after G-CSF administration has still to be found. We prospectively studied the mobilization of CD34+ cells and white blood cells in the peripheral blood (PB) of 20 pediatric patients before leukapheresis. The monitoring schedule covered 12 h, with blood samples taken before and at 2, 4, 5, 6, 7, 8, 10 and 12 h after G-CSF administration when 10 CD34+ cells/mul were reached. CD34+ cells were measured by flow cytometric analysis both in the single- and dual-platform setting. Two different patterns of mobilization (POM) emerged: 12 patients showed an increase in CD34+ cells in PB during the first 4 h after G-CSF (POM I), while eight patients had an initial decrease of CD34+ cells. However, all patients together showed a significant increase of CD34+ cells about 10 h after G-CSF administration. Further studies with more patients, using an enhanced monitoring schedule will be required to refine the results.

IL-2 activated NK cell immunotherapy of three children after haploidentical stem cell transplantation

Natural killer (NK) cells are thought to be of benefit in HLA-mismatched hematopoietic transplantation (H-SCT). Therefore, we developed a protocol for clinical-use expansion of highly enriched and IL-2-stimulated NK cells. Purification of unstimulated leukaphereses by a two-step T cell depletion with a final CD56 enrichment procedure leads to a mean purity of 95% CD56(+)CD3- NK cells with a four- to five-log depletion of T cells. So far, three pediatric patients with multiply relapsed acute lymphoblastic leukemia (ALL) or acute myelogenous leukemia (AML) were treated with repeated transfusions post-H-SCT. Directed killer immunoglobulin-like receptor (KIR) mismatches were demonstrated in all three cases. Although all patients showed blast persistence at the time of transplant, they reached complete remission and complete donor chimerism within 1 month post-H-SCT. NK cell therapy was tolerated well without graft-versus-host disease (GvHD) induction or other adverse events. The AML patient died of early relapse on day +80, while the ALL patients died of thrombotic-thrombocytopenic purpura and atypical viral pneumonia on days +45 and +152, respectively. This initial trial showed the feasibility of good manufacturing practice (GMP)-compliant NK cell isolation and expansion for clinical applications. We now launch a clinical phase I trial with activated NK cells post-H-SCT.

Use of natural killer cells in hematopoetic stem cell transplantation

Adoptive immunotherapy using natural killer (NK) cells may prove useful, especially in situations where infusion of T cells is impractical such as in recipients of haploidentical stem cell transplantation (HSCT) from haploidentical donors. NK cells may induce potent antileukemic and possibly antirejection activity and may even mitigate graft versus host disease (GvHD). Whether such effects are clinically important and whether they are mediated mainly or exclusively by KIR-HLA class I interactions remains to be determined. Recent advances in graft engineering provide for methods to isolate large numbers of purified NK cells. Several groups have shown that clinical grade NK cells up to a dose of 10(7)/kg may be collected and purified for the purpose of infusion to patients. Early results, in a limited number of patients, show that these cell doses may be administered without adverse events and without inducing GvHD. Whether such infusions will be useful in preventing graft rejection, or exerting graft versus leukemia effects and hastening immune recovery requires further study.

A novel four-colour flow cytometric assay to determine natural killer cell or T-cell-mediated cellular cytotoxicity against leukaemic cells in peripheral or bone marrow specimens containing greater than 20% of normal cells

To be able to determine the cytotoxic activity of NK cells or T cells against leukaemic cells in patient samples containing >20% of normal peripheral blood cells, we have developed a four-colour flow cytometric cytotoxicity assay. The assay is based on differential immunostaining of both leukaemic cells and effector cells in combination with propidium iodide (PI). The cytometer is set for measuring the fluorescence of the monoclonal antibody (mAb) bound fluorochromes, with moderate overcompensation of the third and fourth fluorescence signals. PI-positive events were excluded from analysis by their characteristic uncompensated signal on these two detectors. Thus, all four fluorescence ranges can be used for detection of mAb-derived signals and this allows discrimination between various populations contained in effector and target cell samples. The cytotoxic activity in our assay is calculated by the absolute loss of vital leukaemic cells. For this purpose, fluorescent beads are included as an internal standard. When calculating the effector concentrations after coculture, characteristic changes can be seen which yield additional information about the presence of cytotoxic activity and the active effector cell subset. With this assay, we present a versatile tool that combines minimum cell manipulation before coculture with maximum information from a sample. The assay is suitable for the analysis of complex samples with regard to different cell subsets, their decrease or increase, and conjugate formation.

111In-labeled CD34+ hematopoietic progenitor cells in a rat myocardial infarction model

Transplantation of progenitor cells (PCs) has been shown to improve neovascularization and left ventricular function after myocardial ischemia. The fate of transplanted PCs has been monitored by fluorescence labeling or by genetic modifications introducing reporter genes. However, these techniques are limited by the need to kill the experimental animal. The aim of this study was to radiolabel CD34(+) hematopoietic PCs (HPCs) with (111)In-oxine and to evaluate the feasibility of this in vivo method for monitoring myocardial homing of transplanted cells in a rat myocardial infarction model.

METHODS

Human HPCs were isolated from mobilized peripheral blood and labeled with (111)In-oxine. Labeled HPCs were injected into the cavity of the left ventricle in nude rats 24 h after induction of myocardial infarction (n = 4) or sham operation (n = 4). Scintigraphic images were acquired up to 96 h after HPC injection. After animals were killed, tissue samples of various organs were harvested to calculate tissue-specific activity and for immunostaining.

RESULTS

Labeling efficiency of HPCs was 32% +/- 11%. According to trypan-blue staining, viability of radiolabeled HPCs was impaired by 30% after 48 and 96 h in comparison with unlabeled cells, whereas proliferation and differentiation of HPCs was nullified after 7 d, as assessed by colony-forming assays. After injection of HPCs, the specific activity ratio of heart to peripheral muscle tissue increased from 1.10 +/- 0.32 in sham-operated rats to 2.47 +/- 0.92 (P = 0.020) in infarcted rats. However, the overall radioactivity detected in the heart was only about 1%. A transient high lung uptake of 17% +/- 6% was observed within the first hour after infusion of HPCs. At 24 h after injection, the initial lung activity had shifted toward liver, kidneys, and spleen, resulting in an increase of radioactivity in these organs from 37% +/- 6% to 57% +/- 5%.

CONCLUSION

Radiolabeling with (111)In-oxine is a feasible in vivo method for monitoring transplanted HPCs in a rat myocardial infarction model. The potential to detect differences in myocardial homing between infarcted and normal hearts suggests that this method may provide a noninvasive imaging approach for clinical trials using transplanted HPCs in patients. Our findings, however, also demonstrated a negative effect of (111)In-oxine on cellular function, which resulted in complete impairment of HPC proliferation and differentiation. For future trials in stem cell imaging with (111)In-oxine, therefore, it will be mandatory to carefully check for radiation-induced cell damage.

Meningitis Due to Multiple-Resistant Penicillin- and Cefotaxime-Intermediate Streptococcus pneumoniae in a German Child after Bone Marrow Transplantation

The incidence of infection with penicillin-non-susceptible Streptococcus pneumoniae is increasing rapidly worldwide. Spain and France are highly affected, whereas the level of penicillin resistance in Germany, Italy, The Netherlands and Scandinavia is low. We report a lethal episode of meningitis due to penicillin- and cefotaxime-intermediate S. pneumoniae in a 7-year-old, allogene bone marrow transplanted German boy, 5 weeks after a holiday in Spain. Three days prior to the infection the patient showed good performance status. He was in complete remission without signs of graft-versus-host disease (GVHD). He died on day 341 post bone marrow transplant (BMT), 2 days after the onset of meningitis. Penicillin-non-susceptible S. pneumoniae should be regarded as a potential infectious agent even in countries with a low prevalence of resistance.

Kinetics of cell death in T lymphocytes genetically modified with two novel suicide fusion genes

Donor lymphocyte infusions (DLI) following allogeneic stem cell transplantation are known to mediate graft-versus-leukemia effect (GVL). A major side effect of these immunotherapies is the development of graft-versus-host diseases (GVHD). One promising approach to prevent GVHD is to genetically modify donor T cells with a suicide mechanism that can be induced in the case of GVHD. Here we report on a retroviral vector containing the death effector domain (DED) of the human Fas-associated protein with death domain (FADD). The DED was fused to two copies of an FKBP506-binding protein and a truncated version of the human low-affinity receptor for nerve growth factor (LNGFR). Activation of the death signal pathway can be triggered upon the addition of chemical inducers of dimerization. This construct was functionally compared to an optimized HSV-TK vector in which a hypersensitive mutant of the herpes simplex virus thymidine kinase gene (TK39) was fused to a cytoplasmic truncated version of the cell surface antigen CD34. A direct comparison between both vectors in primary T lymphocytes showed that the number of T cells transduced with vectors containing the DED was significantly reduced within 24 h of drug administration whereas ganciclovir treatment of TK39-transduced T cells showed a delay in cell death of approximately 3-4 days. Our results indicate that constructs containing the DED may prove to be the most efficient mechanism to quickly eliminate alloreactive T cells.

Autologous transplantation of CD133 selected hematopoietic progenitor cells in a pediatric patient with relapsed leukemia

A pediatric patient with very early meningeal relapse of his CD34(+) CD133(-) pre-B-ALL was transplanted with 2.5 x 10(6)/kg CD133 selected autologous progenitor cells. Enrichment of CD133(+) cells resulted in a purity of 92.3 +/- 3.5% CD133(+). Hematopoietic engraftment with >1.0 x 10(9)/l neutrophils and >50 x 10(9)/l platelets was reached within 13 and 24 days, respectively. At a follow-up of 11(1/2) months after autologous transplantation, the patient is in complete remission. To our knowledge, the successful transplantation with a CD133 selected graft is the first one to be reported worldwide. CD133 selected cells may serve as an alternative in the case of CD34(+) malignancy.

Tecelac as antithymocyte globulin in conditioning for childhood allogeneic stem cell transplantation

Antithymocyte globulin (ATG) preparations in allogeneic stem cell transplantation are used in various conditioning regimens both to prevent graft rejection and reduce the incidence and severity of graft-versus-host disease. Tecelac (RATG) is a highly purified ATG preparation with high specific activity. The high specific antibody content implies the need for lower doses, with reduced side-effects in comparison to other ATGs. Here, we report on the first 10 patients worldwide who received RATG as part of conditioning. Patients were heterogeneous with regard to diagnoses and graft characteristics. RATG was given in cases of matched unrelated donors, mismatched family donors, reduced conditioning, or high risk for graft failure. Mostly mild allergic reactions toward RATG were seen. All of the patients engrafted in due time. Two died within 2 months of transplant of pulmonary complications not related to RATG. Two developed GVHD grade I, no chronic GVHD was seen to date. Viremia occurred in two, with no viral disease developed. Of the eight patients surviving, one suffered relapse of acute leukemia, one shows impending graft failure. The others are well. Using RATG in conditioning is feasible.

Bovine seminal ribonuclease exerts selective cytotoxicity toward neuroblastoma cells both sensitive and resistant to chemotherapeutic drugs

BACKGROUND

Bovine seminal ribonuclease (BS-RNase) exerts selective cytotoxicity toward different types of tumor cells. In the present study, we tested the effects of BS-RNase on cultured neuroblastoma (NB) cells resistant to chemotherapeutic agents. The selectivity of the antitumoral activity of BS-RNase was evaluated using cultures of CD34+ hematopoietic stem cells.

MATERIALS AND METHODS

Human NB cell lines including IMR-32, UKF-NB-2 and UKF-NB-3 were selected for resistance against vincristine, doxorubicin or cisplatin by exposure to increasing concentrations of the respective drug. The cytotoxicity of the drugs to NB cells was evaluated using a clonogenic assay in a methylcellulose medium. Peripheral blood progenitor cells were obtained from adult healthy donors by positive selection using specific anti-CD34+ antibodies. The toxicity of BS-RNase to CD34+ cells was assessed in the direct clonogenic assay using methylcellulose medium or in ex vivo expansion culture supplemented with hematopoietic growth factors.

RESULTS

In the clonogenic assay it was shown that BS-RNase completely inhibits growth of both parental NB cells and their sublines resistant to chemotherapeutic drugs at concentrations (up to 50 micrograms/ml) which have no significant influence on the growth of colony-forming units, granulocyte macrophage and erythroid burst-forming units. Moreover, BS-RNase had no effect on the ex vivo expansion of total hematopoietic cells or of colony-forming cells from CD34+ progenitors.

CONCLUSIONS

BS-RNase is a highly efficient agent against NB cells resistant to chemotherapeutic drugs. The lack of toxicity to hematopoietic progenitor cells suggests that BS-RNase is also likely to have tolerable hematopoietic toxicity.