Product Information

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

To date,studies on T cells in acute myeloid leukemia (AML) have been limited to flow cytometric analysis of whole peripheral blood mononuclear cell (PBMC) specimens or functional work looking at the impact of AML myeloblasts on normal or remission T cells. This lack of information on T cells at the time of presentation with disease is due in part to the difficulty in isolating sufficiently pure T cells from these specimens for further study. Negative immunomagnetic selection has been the method of choice for isolating immune cells for functional studies due to concerns that binding antibodies to the cell surface may induce cellular activation,block ligand-receptor interactions or result in immune clearance. In order specifically to study T cells in presentation AML specimens,we set out to develop a method of isolating highly pure CD4 and CD8 T cells by negative selection from the peripheral blood (PB) of newly diagnosed AML patients. This technique,unlike T cell selection from PB from normal individuals or from patients with chronic lymphocytic leukaemia,was extremely problematic due to properties of the leukaemic myeloblasts. A successful method was eventually optimized requiring the use of a custom antibody cocktail consisting of CD33,CD34,CD123,CD11c and CD36,to deplete myeloblasts. View Publication

Although natural Abs (NAbs) are present from birth,little is known about what drives their selection and whether they have housekeeping functions. The prototypic T15-NAb,first identified because of its protective role in infection,is representative of a special type of NAb response that specifically recognizes and forms complexes with apoptotic cells and which promotes cell-corpse engulfment by phagocytes. We now show that this T15-NAb IgM-mediated clearance process is dependent on the recruitment of C1q and mannose-binding lectin,which have known immune modulatory activities that also provide eat me" signals for enhancing phagocytosis. Further investigation revealed that the addition of T15-NAb significantly suppressed in vitro LPS-induced TNF-alpha and IL-6 secretion by the macrophage-like cell line� View Publication

Here,we describe a procedure and first-in-man clinical effects of adoptive transfer of ex vivo expanded CD4+CD25+CD127- T regulatory cells (Tregs) in the treatment of graft versus host disease (GvHD). The cells were sorted from buffy coats taken from two family donors,expanded ex vivo and transferred to respective recipients who suffered from either acute or chronic GvHD. The therapy allowed for significant alleviation of the symptoms and reduction of pharmacologic immunosuppression in the case of chronic GvHD,while in the case of grade IV acute GvHD it only transiently improved the condition,for the longest time within all immunosuppressants used nonetheless. View Publication