We obtained data on priming of an immune response through a series of critical interactions between the cholera toxin (CT) adjuvant and the dendritic cells (DC) of the splenic marginal zone (MZ). The in vivo mechanisms of action of most vaccine adjuvants are poorly understood. Splenic marginal zone dendritic cells mediate the cholera toxin adjuvant effect. We demonstrated in mice that a series of critical interactions between the cholera toxin adjuvant and the dendritic cells of the splenic marginal zone lead to effective priming of an immune response. Thus, for ...

Our group has MRI data available on the migration of DCs in vivo in melanoma patients. From isolated lymphnodes obtained after surgery we could identify single DC after staining with Prussian blue for iron. We are in the process of analysing the T cell rosettes (activation stage) that surround these DC to get insight in the functional activity. It was also demonstrated that DCs transfected with RNA produce derived proteins in vivo in the lymph nodes. Also efforts were spent to get further information on the dynamics of immature and mature DCs. We discovered (van...

We have data available on the inadequate nature of the antitumor CTL response, generated in a syngeneic mouse tumor model expressing an Ag derived from the early region 1A of human adenovirus type 5. We demonstrated using this syngeneic mouse tumor model that the inadequate nature of the antitumor CTL response is not due to direct Ag presentation by the tumor cells, but results from presentation of tumor-derived Ag by nonactivated CD11c(+) APC. Although this event results in division of naive CTL in tumor draining lymph nodes, it does not establish a productive i...

Our lab has obtained data on indirect activation of DC by immunomodulatory mediators. TLRs signal directly for DC activation but also promote production of immunomodulatory mediators by many other cell types. These mediators could be sufficient to activate DC indirectly, thereby potentially allowing responses to organisms with which DC do not come into direct contact. We tested this hypothesis and, surprisingly, found that indirect signals alone led only to partial DC activation and resulted in clonal expansion of T cells lacking typical Th1 or Th2 function. Th...

Our lab obtained data on the induction of antigen-specific CD8+ cytotoxic T cells by dendritic cells co-electroporated with a dsRNA analogue and tumor antigen mRNA. The maturation state of dendritic cells (DCs) is an important determinant for the initiation and regulation of adaptive immune responses. In this study, we wanted to assess whether functional activation of human monocyte-derived DCs can be achieved by electroporation of an activation signal in the form of double-stranded (ds) RNA and whether simultaneous electroporation of the dsRNA with tumor antigen...

We have data available on the induction of effective therapeutic antitumor immunity by direct in vivo administration of ovalbumin (OVA) encoding lentiviral vectors. Ex vivo lentivirally transduced dendritic cells (DC) have been described to induce CD8+ and CD4+ T-cell responses against various tumor-associated antigens (TAAs) in vitro and in vivo. We report here that direct administration of ovalbumin (OVA) encoding lentiviral vectors caused in vivo transduction of cells that were found in draining lymph nodes (LNs) and induced potent anti-OVA cytotoxic T cells ...

We have obtained data from an analysis of the uptake, conservation and cross-presentation of the model antigen OVA after Fc receptor-mediated uptake by DC and from an analysis of the immunological consequences of the antigen depot. We found that MHC class I presentation is relatively short-lived in contrast to MHC class II. However, CD8 cross-priming capacity of OVA-loaded DC was functionally retained for many days, while peptide-pulsed DC had lost their priming capacity after 24 hours. Strikingly, OVA protein antigen was conserved intracellularly in DC for many ...

Our laboratory obtained data on the induction of immune responses after targeting antigens to DC via TLR agonists.

Our lab has immunological data available on human Hemato-Lymphoid System Rag2-/-gc-/- mice infected with EBV. Both Epstein Bar Virus (EBV) and Human Immunodeficiency Virus (HIV) are human specific lymphotropic viruses. Human Hemato-Lymphoid System Rag2-/-gc-/- mice were infected with EBV and mount an immune response (i.e. cytotoxic T cell proliferation, some control of EBV driven B cell proliferation, perforine and granzyme expressing T cell infiltration in B cell infected areas in lymphoid organs in situ), however, specific T cells could not be detected directl...

Data is available on human Hemato-Lymphoid System Rag2gc-/- mice infected with both CXCR4 as well as CCR5 tropic HIV-1 strains. HIV causes a disseminated infection and spreads in all newly generated lymphoid tissues, thus closely resembling HIV infection in humans. However, as in EBV infected animals, adaptive T and B cell responses were not consistently detected. Thus, although these “humanized” mice represent a major step forward in generating an in vivo preclinical testing system, they still harbor limitations as inconsistent/weak adaptive immune respons...

Our lab generated integrated microarray data on cellular pathways and gene ontology annotation. This has been done in the context of the program DC_Eu.Gene freely available for the DC-THERA users, using ENSEMBL as a conversion table.

Central to all T cell responses is the interaction between the T cell receptor and peptide antigen presented by the MHC molecules. This interaction selects the dominant T cell clones with the most favourable (not necessarily highest) affinity and determines the extent of cross-reaction with epitope variants. I am currently collaborating with the structural biology group of Professor Yvonne Jones in the Nuffield Department of Medicine (NDM) at the Wellcome Trust Centre for Human Genetics. This collaboration has led to structural data on the CD1b in complex with s...

Data is available on the interaction between microorganism-associated molecular patterns and individual toll-like receptors on dendritic cells that turn on signal transduction pathways leading to the activation of different transcription factors. Microbial invasions are perceived by pattern recognition receptor (PRR)-expressing cells of the innate immune system. PRRs bind a number of microbial products collectively referred to as microorganism-associated molecular patterns (MAMPs). Toll-like receptors (TLRs) are the best-characterized PRRs. The interaction of MAM...

We further our understanding of different DC populations and their soluble products in adults but in particular in neonatal mice. We have concentrated on the evaluation of the interplay between the hematopoetic factor Flt3L and IFNalpha,beta and have data available from our studies. We found that the cooperation between IFNalpha,beta and Flt3L (FL) plays an important role in the defense against Herpes simplex virus type 1 (HSV-1) in neonates. Treatment of neonatal mice with recombinant IFNalpha has a short-term, FL-independent and a long-term, FL-dependent protect...

Data was obtained on Fabs that bind strongly to L-SIGN, but to a lesser degree or not at all to dendritic cell-specific ICAM-grabbing nonintegrin (DC-SIGN). The C-type lectin L-SIGN is expressed on liver and lymph node endothelial cells,where it serves as a receptor for a variety of carbohydrate ligands, including ICAM-3, Ebola, and HIV. To consider targeting liver/lymph node-specific ICAM-3-grabbing nonintegrin (L-SIGN) for therapeutic purposes in autoimmunity and infectious disease, we isolated and characterized Fabs that bind strongly to L-SIGN, but to a lesse...

Our lab obtained data on maturation of DC by TLR agonists.

We have obtained data on the ability of mMature DCs to efficiently present antigens associated with MHC molecules to T lymphocytes. Dendritic cells (DCs) are major actors of innate and adaptive immune responses. Immature DCs express a great diversity of receptors at their cell surface, which provide them the ability to uptake antigen and induce an intracellular signal. DCs become mature after encountering soluble mediators or conserved pathogen associated molecular patterns (PAMPs) or after interacting with other cells. Mature DCs acquire the ability to efficient...

Based on the data we recently reported concerning the role of GM-CSF in regulating human DC differentiation (Conti et al., EJI 2008), we will perform a detailed analysis of mRNA and microRNA expression in immature and TLR ligand-stimulated GM-DCs in order to identify specific mechanisms that control the generation/activation of these cells. Data obtained in this study will become available. Moreover, the role of microRNAs in controlling the switch of GM-CSF-exposed monocyte precursors toward DCs or macrophages will also be investigated.

Our lab generated data on the mechanisms for DC-induced Th1 development and the molecular pathways for inducing Th1 cells producing IFN-gamma solely, or Th1 cells producing IFN-gamma and IL-10. We have reported that plasmacytoid precursor dendritic cells (pDC) activated with the TLR-9 ligand CpG induce strong development of Th1 responses (Boonstra et al, 2003). In contrast, bone marrow-derived myeloid DC (BM-myeloid DC) and splenic CD8alpha+ and CD8alpha- DC, despite expression of TLR9 mRNA, were poor at directing Th1 responses when activated with CpG. We have ...

To understand whether these regulators of gene expression could somehow contribute to the fine tuning of CCL2 expression in MD-DCs, a quantitative microarray approach that detects 723 human mature miR (miRBase 10.1, Dec 2007), was used to measure miR expression profile in these cells, either untreated or stimulated with LPS, R848, or their combination for 8 h. The analysis of the microarray data generated from 4 independent experiments is in progress.