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IL-33,a new member of the IL-1 family,has been described as an important inducer of Th2 cytokines and mediator of inflammatory responses. In this study,we demonstrate that murine basophils sorted directly from the bone marrow,without prior exposure to IL-3 or Fc(epsilon)R cross-linking,respond to IL-33 alone by producing substantial amounts of histamine,IL-4,and IL-6. These cells express ST2 constitutively and generate a cytokine profile that differs from their IL-3-induced counterpart by a preferential production of IL-6. In vivo,IL-33 promotes basophil expansion in the bone marrow (BM) through an indirect mechanism of action depending on signaling through the beta(c) chain shared by receptors for IL-3,GM-CSF,and IL-5. IL-3 can still signal through its specific beta(IL-3) chain in these mutant mice,which implies that it is not the unique growth-promoting mediator in this setup,but requires IL-5 and/or GMCSF. Our results support a major role of the latter growth factor,which is readily generated by total BM cells as well as sorted basophils in response to IL-33 along with low amounts of IL-3. Furthermore,GM-CSF amplifies IL-3-induced differentiation of basophils from BM cells,whereas IL-5 that is also generated in vivo,affects neither their functions nor their growth in vitro or in vivo. In conclusion,our data provide the first evidence that IL-33 not only activates unprimed basophils directly,but also promotes their expansion in vivo through induction of GM-CSF and IL-3. View Publication

RATIONALE: Tolerogenic dendritic cells and natural regulatory T cells have been implicated in the process of infectious tolerance in human allergic asthma. However,the significance of the influence of natural regulatory T cells on tolerogenic dendritic cells in the disease has not been investigated. OBJECTIVES: We aimed to characterize the mechanism of induction of the tolerogenic phenotype in circulating blood dendritic cells by allergic asthmatic natural regulatory T cells. METHODS: The study was performed in a cohort of 21 subjects with allergic asthma,21 healthy control subjects,and 21 subjects with nonallergic asthma. We cultured blood dendritic cells with natural regulatory T cells to study the induction of tolerogenic dendritic cells. Flow cytometry and proliferation assays were employed to analyze phenotype and function of dendritic cells as well as IL-10 production from natural regulatory T cells. MEASUREMENTS AND MAIN RESULTS: Dendritic cells cultured with natural regulatory T cells up-regulated IL-10,down-regulated costimulatory molecules,and stimulated the proliferation of CD4(+)CD25(-) effector T cells less potently. Allergic asthmatic natural regulatory T cells were significantly less efficient in inducing this tolerogenic phenotype of dendritic cells compared with healthy control and nonallergic asthmatic counterparts. Furthermore,this defective function of natural regulatory T cells was associated with their decreased IL-10 expression,disease severity,and could be reversed by oral corticosteroid therapy. CONCLUSIONS: These results provided the first evidences of impaired induction of tolerogenic dendritic cells mediated by natural regulatory T cells in human allergic asthma. View Publication

A variety of nonmalignant cells present in the tumor microenvironment promotes tumorigenesis by stimulating tumor cell growth and metastasis or suppressing host immunity. The role of such stromal cells in T-cell lymphoproliferative disorders is incompletely understood. Monocyte-derived cells (MDCs),including professional antigen-presenting cells such as dendritic cells (DCs),play a central role in T-cell biology. Here,we provide evidence that monocytes promote the survival of malignant T cells and demonstrate that MDCs are abundant within the tumor microenvironment of T cell-derived lymphomas. Malignant T cells were observed to remain viable during in vitro culture with autologous monocytes,but cell death was significantly increased after monocyte depletion. Furthermore,monocytes prevent the induction of cell death in T-cell lymphoma lines in response to either serum starvation or doxorubicin,and promote the engraftment of these cells in nonobese diabetic/severe combined immunodeficient mice. Monocytes are actively recruited to the tumor microenvironment by CCL5 (RANTES),where their differentiation into mature DCs is impaired by tumor-derived interleukin-10. Collectively,the data presented demonstrate a previously undescribed role for monocytes in T-cell lymphoproliferative disorders. View Publication

Up to now,no lentiviral vector (LV) tool existed to govern efficient and stable gene delivery into quiescent B lymphocytes,which hampers its application in gene therapy and immunotherapy areas. Here,we report that LVs incorporating measles virus (MV) glycoproteins,H and F,on their surface allowed transduction of 50% of quiescent B cells,which are not permissive to VSVG-LV transduction. This high transduction level correlated with B-cell SLAM expression and was not at cost of cell-cycle entry or B-cell activation. Moreover,the naive and memory phenotypes of transduced resting B cells were maintained. Importantly,H/F-LVs represent the first tool permitting stable transduction of leukemic cancer cells,B-cell chronic lymphocytic leukemia cells,blocked in G(0)/G(1) early phase of the cell cycle. Thus,H/F-LV transduction overcomes the limitations of current LVs by making B cell-based gene therapy and immunotherapy applications feasible. These new LVs will facilitate antibody production and the study of gene functions in these healthy and cancer immune cells. View Publication

Genital herpes,caused by herpes simplex virus type 2 (HSV-2),is one of the most prevalent sexually transmitted diseases worldwide and a risk factor for acquiring human immunodeficiency virus. Although many vaccine candidates have shown promising results in animal models,they have failed to be effective in human trials. In this study,a humanized mouse strain was evaluated as a potential preclinical model for studying human immune responses to HSV-2 infection and vaccination. Immunodeficient mouse strains were examined for their abilities to develop human innate and adaptive immune cells after transplantation of human umbilical cord stem cells. A RAG2(-/-) gammac(-/-) mouse strain with a BALB/c background was chosen as the most appropriate model and was then examined for its ability to mount innate and adaptive immune responses to intravaginal HSV-2 infection and immunization. After primary infection,human cells in the lymph nodes were able to generate a protective innate immune response and produce gamma interferon (IFN-gamma). After intravaginal immunization and infection,human T cells and NK cells were found in the genital tract and iliac lymph nodes. In addition,human T cells in the spleen,lymph nodes,and vaginal tract were able to respond to stimulation with HSV-2 antigens by replicating and producing IFN-gamma. Human B cells were also able to produce HSV-2-specific immunoglobulin G. These adaptive responses were also shown to be protective and reduce local viral replication in the genital tract. This approach provides a means for studying human immune responses in vivo using a small-animal model and may become an important preclinical tool. View Publication

Recent studies involving bone marrow mesenchymal stromal cells (MSCs) demonstrated that interferon (IFN)-gamma stimulation induces major histocompatibility complex (MHC) class II-mediated antigen presentation in MSCs both in vitro and in vivo. Concordantly,we investigated the ability of MSCs to present extracellular antigen through their MHC class I molecules,a process known as cross-presentation. Using an in vitro antigen presentation assay,we demonstrated that murine MSCs can cross-present soluble ovalbumin (OVA) to naive CD8(+) T cells from OT-I mice. Cross-presentation by MSC was proteasome dependent and partly dependent on transporter associated with antigen-processing molecules. Pretreatment of MSC with IFN-gamma increased cross-presentation by up-regulating antigen processing and presentation. However,although the transcription of the transporter associated with antigen processing-1 molecules and the immunoproteasome subunit LMP2 induced by IFN-gamma was inhibited by transforming growth factor-beta,the overall cross-presentation capacity of MSCs remained unchanged after transforming growth factor-beta treatment. These observations were validated in vivo by performing an immune reconstitution assay in beta(2)-microglobulin(-/-) mice and show that OVA cross-presentation by MSCs induces the proliferation of naive OVA-specific CD8(+) T cells. In conclusion,we demonstrate that MSCs can cross-present exogenous antigen and induce an effective CD8(+) T-cell immune response,a property that could be exploited as a therapeutic cell-based immune biopharmaceutic for the treatment of cancer or infectious diseases. View Publication

Acute lymphoblastic leukemia (ALL) is the most common childhood cancer and remains a major cause of mortality in children with recurrent disease and in adults. Despite observed graft-versus-leukemia effects after stem cell transplantation,successful immune therapies for ALL have proven elusive. We previously reported immunostimulatory oligodeoxynucleotides containing CpG motifs (CpG ODN) enhance allogeneic T(h)1 responses and reduce leukemic burden of primary human ALL xenografts. To further the development of CpG ODN as a novel ALL therapy,we investigated the antileukemia activity induced by CpG ODN in a transplantable syngeneic pre-B ALL model. CpG ODN induced early killing of leukemia by innate immune effectors both in vitro and in vivo. Mice were treated with CpG ODN starting 7 days after injection with leukemia to mimic a minimal residual disease state and achieved T cell-dependent remissions of more than 6 months. In addition,mice in remission after CpG ODN treatment were protected from leukemia rechallenge,and adoptive transfer of T cells from mice in remission conferred protection against leukemia growth. To our knowledge,this is the first demonstration that CpG ODN induce a durable remission and ongoing immune-mediated protection in ALL,suggesting this treatment may have clinical utility in patients with minimal residual disease. View Publication

Human immunodeficiency virus type 1 (HIV-1) vectors transduce rhesus blood cells poorly due to a species-specific block by TRIM5alpha and APOBEC3G,which target HIV-1 capsid and viral infectivity factor (Vif),respectively. We sought to develop a lentiviral vector capable of transducing both human and rhesus blood cells by combining components of both HIV-1 and simian immunodeficiency virus (SIV),including SIV capsid (sCA) and SIV Vif. A chimeric HIV-1 vector including sCA (chiHIV) was superior to the conventional SIV in transducing a human blood cell line and superior to the conventional HIV-1 vector in transducing a rhesus blood cell line. Among human CD34(+) hematopoietic stem cells (HSCs),the chiHIV and HIV-1 vectors showed similar transduction efficiencies; in rhesus CD34(+) HSCs,the chiHIV vector yielded superior transduction rates. In in vivo competitive repopulation experiments with two rhesus macaques,the chiHIV vector demonstrated superior marking levels over the conventional HIV-1 vector in all blood lineages (first rhesus,15 to 30% versus 1 to 5%; second rhesus,7 to 15% versus 0.5 to 2%,respectively) 3 to 7 months postinfusion. In summary,we have developed an HIV-1-based lentiviral vector system that should allow comprehensive preclinical testing of HIV-1-based therapeutic vectors in the rhesus macaque model with eventual clinical application. View Publication

BACKGROUND: Despite the promising therapeutic potential of regulatory T cells (Treg) in animal studies of graft-versus-host disease (GVHD),little is known about their effect on human GVHD. Whether Treg are capable of ameliorating GVHD tissue damage has never been demonstrated in humans. It is also unknown whether Treg modulation of GVH histopathologic damage relies on their presence during effector T-cell priming,or whether allogeneic Treg are safe to use clinically. METHODS: To address these questions,we used an in vitro human skin explant GVHD model,which mimics the physiopathology of GVHD. First,donor"-derived CD8 T cells were stimulated with human leukocyte antigen-unmatched "recipient" dendritic cells (priming phase)� View Publication

Natural killer T (NKT) cells are innate-like lymphocytes that recognize lipid antigens and have been shown to enhance B-cell activation and antibody production. B cells typically recruit T-cell help by presenting internalized antigens recognized by their surface antigen receptor. Here,we demonstrate a highly efficient means whereby human B cells present lipid antigens to NKT cells,capturing the antigen using apolipoprotein E (apoE) and the low-density lipoprotein receptor (LDL-R). ApoE dramatically enhances B-cell presentation of alpha-galactosylceramide (alphaGalCer),an exogenous CD1d presented antigen,inducing activation of NKT cells and the subsequent activation of B cells. B cells express the LDL-R on activation,and the activation of NKT cells by B cells is completely LDL-R dependent,as shown by blocking experiments and the complete lack of presentation when using apoE2,an isoform of apoE incapable of LDL-R binding. The dependence on apoE and the LDL-R is much more pronounced in B cells than we had previously seen in dendritic cells,which can apparently use alternate pathways of lipid antigen uptake. Thus,B cells use an apolipoprotein-mediated pathway of lipid antigen presentation,which constitutes a form of innate help for B cells by NKT cells. View Publication

Off-patent drugs with previously unrecognized anticancer activity could be rapidly repurposed for this new indication. To identify such compounds,we conducted 2 independent cell-based chemical screens and identified the antimicrobial ciclopirox olamine (CPX) in both screens. CPX decreased cell growth and viability of malignant leukemia,myeloma,and solid tumor cell lines as well as primary AML patient samples at low-micromolar concentrations that appear pharmacologically achievable. Furthermore,oral CPX decreased tumor weight and volume in 3 mouse models of leukemia by up to 65% compared with control without evidence of weight loss or gross organ toxicity. In addition,oral CPX prevented the engraftment of primary AML cells in nonobese diabetic/severe combined immunodeficiency mouse models,thereby establishing its ability to target leukemia stem cells. Mechanistically,CPX bound intracellular iron,and this intracellular iron chelation was functionally important for its cytotoxicity. By electron paramagnetic resonance,CPX inhibited the iron-dependent enzyme ribonucleotide reductase at concentrations associated with cell death. Thus,in summary,CPX has previously unrecognized anticancer activity at concentrations that are pharmacologically achievable. Therefore,CPX could be rapidly repurposed for the treatment of malignancies,including leukemia and myeloma. View Publication

The ability of NK cells to directly recognize pathogens and be activated via Toll-like receptors (TLR) is increasingly recognized. Nevertheless,controversial results on the NK cell ability to be directly activated by lipopolysaccharide (LPS),the ligand of TLR4,have been recently reported. To start elucidating the reasons explaining the contrasting observations of the literature,we focused on the potential role of currently used NK cell purification procedures to condition putative NK cell responsiveness to LPS. To do so,human NK cells were isolated by negative selection,using three different commercial kits,to be comparatively evaluated for the production of IFNgamma in response to ultra-pure LPS and/or IL-2. Despite the lack of surface TLR4,we found that two out of the three NK cell-enriched populations released IFNgamma (and one of the two,IL-12p70 as well) in response to the LPS plus IL-2 combination,whereas the last one did not. However,the two LPS plus IL-2-responsive NK cell populations were found variably contaminated with 6-sulfo LacNAc(+) dendritic cells (slanDC),demonstrated responsible for triggering,via the production of IL-12p70 in response to LPS,the release of IFNgamma by IL-2-stimulated NK cells. Accordingly,slanDC depletion completely abrogated the capacity to produce both IL-12p70 and IFNgamma in response to LPS plus IL-2 by slanDC-containing NK cells. Taken together,our data uncover that two commercially available kits,specifically designed to isolate NK cells by negative selection,also co-purify variable amounts of slanDC. The latter cells may dramatically affect the outcome of experiments carried on to evaluate NK cell responsiveness to TLR agonists such as LPS. View Publication