My laboratory obtained data from a continued analysis of the ability of invariant NKT (iNKT) cells to assist priming of antigen specific T and B cell responses. We have carried out three complementary lines of research: 1) We have demonstrated that activation of human DC by Toll like receptor ligands (TLR-L) modulates the lipid biosynthetic pathway, resulting in enhanced recognition of CD1d-associated lipids by iNKT cells. 2) We have clarified the mechanisms by which CD1d-restricted lymphocytes translate T cell receptor (TCR) recognition of lipids with similar g...

Data have been obtained on the use of nano-particles for intestinal vaccine delivery from our continued investigation of the use of nano-particles as oral vaccine vehicles (Cerovic). We have identified an important role for complement C1q in the uptake of scrapie agent by dendritic cells (Flores-Langarica).We have shown that a protein from Schistosomes has dramatic effects on intestinal physiology, including dendritic cells (Nassar). We have shown that steady-state intestinal denritic cells are not constitutively biased towards stimluating Th2 responses (Milling). ...

Data have been obtained defining the differential roles of intestinal lymph DC subsets in activation of naïve and memory T cells in rats. We have shown that two of the three DC subsets are highly potent activators of naïve CD4+ T cells, and do not appear to be constitutively suppressed in any way. We are currently examining the phenotype of the activated cells and determining if Tregs are induced. We have initiated (in collaboration with Pfizer) a study of nano-particles as potential deliverers of intestinal vaccines.

We have obtained data on the immuno-physiology of rat and mouse intestinal dendritic cells. We have used a known adjuvant, E. coli heat-labile toxin (Etx) and a potential adjuvant R-848, a small TLR7/8 ligand. We have shown that R-848 causes massive changes in DC migration and leads to their activation in lymph nodes but not lymph. These changes are due to TNF-alpha (migration) and Type 1 interferons (activation), but are not accompanied by obvious oral adjuvant effects. In contrast Etx causes only minor changes in migration and activation but is a potent oral adju...

Our lab has obtained data on the role of p50 NF-kB in differentiation, survival and APC function in mice. Tumor growth is supported by tumor stroma, which is made by matrix and infiltrating cells, such as tumor associated macrophages (TAM) and tumor associated dendritic cells (TADC). We have recently reported that TAM display massive nuclear localization of the p50 NF-kB inhibitory homodimer, which correlates with impaired inflammatory functions (Saccani et al., 2006).The functional significance of this observation was demonstrated in p50 NF-kB deficient mice, whi...

We have obtained data from our work on biodegradable poly (D, L-lactide-co-glycolide) (PLGS) micropsheres (MS) coencapsulating ligands for endosomally expressed TLRs plus exogeneous Antigen (Ag) to deliver its cargo to endosomes of murine Dendritic cells (DCs), thus initiating TLR mediated DC maturation as well as processing of MHC class I and class II restricted epitopes. In these studies we used as Ag either Ovalbumin, or rec. Prion-protein. In the latter system, a CD4 T cell response could be initiated. We also found that the DNA sugar backbone determines TLR9...

Our lab obtained data on the activation of immature monocyte-derived dendritic cells after transduction with high doses of lentiviral vectors. Dendritic cells (DCs) are an attractive tool for immunomodulation, targeting mature DCs (mDCs) for immunization or immature/semimature DCs (iDCs) for tolerization. Therefore, introducing antigens into DCs has become a prime topic in various immunological disciplines. Numerous studies have shown that lentiviruses are an efficient vehicle for this purpose. This study evaluates the effects of lentiviral transduction on iDC ...

Data were obtained on the effect of enhanced CD83 expression on dendritic cells and T cells and its correlation with effective immune responses. Human CD83 is a marker molecule for mature dendritic cells (DC) and is also expressed on activated B and T cells. Although CD83 has been implicated in immune responses, its function on DC and T cells remains unclear. In this study, we wanted to assess the role of CD83 expressed on DC and T cells in the immune response. Down-regulation of CD83 expression on human DC through RNA interference (RNAi) results in a less potent...

Understanding the distribution, function, and lineage relationship of CD8+ T-cell subpopulations is of fundamental value for the monitoring of the immune system in several experimental and clinical situations. However, the available data concerning the description of effector and memory CD8+ subsets in humans remain rather fragmentary because different studies favored the usage of distinct and restricted sets of cell surface markers and functional parameters. We obtained coexpression data of 18 genes simultaneously in individual cells from CD8+ T cell subsets (as...

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 obtained data on the effect of pro-inflammatory stroma-derived cytokines on DC in vivo. Our investigation has shown that, in the absence of additional stimuli, such inflammatory signals are ineffectual in promoting DC activation and cannot substitute for engagement of innate receptors directly on DC.

We have obtained data from in vitro studies to demonstrate that DC can be activated via the dectin-1/Syk pathway to become APC capable of priming CD8+ T cells. In addition, we have shown that the same DC can interact with Tregs and convert them into cells that co-express ROR?t and Foxp3 and produce IL-17. We have shown that this pathway can serve as an alternative to TLR signalling for allowing DC to become effector cells capable of priming CD4+ T cells. We have used agonists of the dectin-1/Syk pathway as adjuvants in vivo to induce DC activation and CD4+ T cell ...

We have generated data on the developmental control of translation during DC activation. Our work (Lelouard et al., JCB) demonstrates that DCs down-regulate and change the quality of translation in order to increase their survival, however during this process MHC I antigen processing is affected. This has important consequences for the way antigens should be introduced in DCs and how long after stimulation they should be used during vaccination application. We have also initiated studies on the impact of dsRNA on the regulation of translation and the functional re...

Data were produced in our lab on a broad spectrum of priming events and their impact on the effector and memory phases of the CTL response. Activation of a cytotoxic T lymphocyte (CTL) response in an antigen-exposed lymph node involves a great diversity of encounters between naive CTLs and APCs that differ in both duration and quality. This broad spectrum of priming events instigates a complex blend of CTL developmental pathways. Using an experimental system that allows tight control over CTL priming, we have singled out defined priming events and analyzed the ...

Data has been obtained on the effect of exposure of DCs or gamma-delta T lymphocytes to HIV-1 and on the miR profile expressed in HIV-exposed DCs. Based on our previous findings demonstrating a bidirectional activating interaction between immature MDDCs and gamma-delta T lymphocytes (Conti et al., JI. 2005), as well as on the demonstration that HIV-1 exposed MDDCs exhibit an impaired functional maturation (Fantuzzi et al., J Virol 2004), we are currently investigating whether exposure of DCs or gamma-delta T lymphocytes to HIV-1 can directly modulate their functi...

Our lab gathered data on DC activation by pathogen-derived stimuli. We focused on the study of the response of MDDCs to the combined stimulation with TLR ligands and we observed that simultaneous activation of TLR4 and TLR8 signaling cascades results in a marked inhibition of the secretion of the proinflammatory chemokine CCL2 with respect to stimulation through a single TLR. This inhibition is specific for both CCL2 and TLR agonist combination and could represent a novel regulatory mechanism evolved to maintain immunological balance (Del Cornò et al.). Future st...

We obtained data on the influence of bLf, whose immunomodulant properties are now recognized, on MDDC differentiation/activation. We found that bLF interferes with the activation of MD-DC induced by different TLR agonists, but not by T cell mediated signals. Although bLF did not significantly influence monocyte differentiation in DCs, we found that it markedly reduced the up-modulation of CD83, co-stimulatory and MHC molecules (i.e. CD80, CD86, MHC class I and II), and cytokine secretion (IL-12, TNF-? and IL-23) induced by LPS or polyI-C. Consistently with an impa...

Our lab has obtained data on maturation stimuli for GMP-grade DC.

We have obtained data from a study where we addressed a model antigen to exosomes secreted by tumor cells in vivo, to allow capture of antigen-bearing exosomes by DCs and cross-presentation of the antigen. For this purpose, the model antigen OVA was fused to the C1C2 exosome-binding domain of MFG-E8/lactadherin. Tumors secreting the exosome-bound antigen grow slower than tumors secreting soluble OVA, because they induce activation of OVA-specific CD8+ T cells into killer cells. In addition, inducing in vivo secretion of the C1C2-coupled antigen by DNA vaccination i...

Our lab has generated data on receptors on dendritic cells necessary for capture of exosomes. In 2007, we have finalized analysis of the receptors on DCs responsible for capture of exosomes secreted by mature DCs. We have shown that expression of LFA-1, but not of Mac-1, integrin, on DCs is required for capture of ICAM-1-bearing exosomes. Furthermore, the CD8+ subpopulation of DCs in lymph nodes expresses LFA-1 at higher levels than the CD8- subpopulation, and is responsible for in vivo capture of injected exosomes. We have thus proposed a new role for LFA-1 on DCs...