Dendritic cells (DCs) are antigen-presenting cells efficient in capturing pathogens, and processing their antigenic determinants for presentation to antigen-specific T cells to induce robust immune ...responses. Their location at peripheral tissues and the expression of pattern-recognition receptors, among them DC-specific intercellular adhesion molecule-3-grabbing non-integrin (DC-SIGN), facilitates the capture of pathogens before spreading. However, some pathogens have developed strategies to escape the immune system. One of the most successful is HIV-1, which targets DC-SIGN for transport to the lymph node where the virus infects CD4(+) T cells. Contact of HIV-1 with DC-SIGN is thus the first event in the pathogenic cascade and, therefore, it is the primary target point for therapies aimed at HIV infection prevention. DC-SIGN recognizes specific glycans on HIV-1 and this interaction can be blocked by competitive inhibition through glycans. Although the affinity of glycans is relatively low, multivalency may increase avidity and the strength to compete with HIV-1 virions. We have designed multivalent dendrimeric compounds based on Lewis-type antigens that bind DC-SIGN with high selectivity and avidity and that effectively block gp120 binding to DC-SIGN and, consequently, HIV transmission to CD4(+) T cells. Binding to DC-SIGN and gp120 inhibition was higher on glycodendrimers with larger molecular diameter, indicating that the geometry of the compounds is an important factor determining their functionality. Our compounds elicited DC-SIGN internalization, a property of the receptor upon triggering, but did not affect the maturation status of DCs. Thus, Le(X) glycodendrimers could be incorporated into topic prophylactic approaches for the prevention of HIV-1 transmission.
Abstract
Recent clinical trials in glioblastoma have yet to show any benefit of immune checkpoint inhibitors and are mostly driven by the fact that these inhibitors have efficacy in other cancer ...types. For immunotherapy to succeed in glioblastoma patients, we need to understand the immunological subsets and phenotypes involved to target and manipulate them. To this end, we set up different glioblastoma mouse models and used multiparameter flow cytometry and t-SNE unsupervised clustering of immune subsets including co-expression of immune checkpoints and their ligands. When comparing the brain tumor microenvironment with immune cells present in the contralateral hemisphere and the systemic compartment, we identified unique immune subsets. Different populations of infiltrating CD4 T cells were characterized by expression of TIGIT, PD-1 and HVEM. PD-1 expression was also significantly increased on infiltrating CD8 T cells. Furthermore, analysis of myeloid subsets showed massive infiltration of macrophages in the brain tumor microenvironment, which is also apparent in clinical glioblastoma samples. Co-expression of PD-L1, CD155 and BTLA was observed on both infiltrating macrophages and brain-resident microglia. Together, these results suggest a glioblastoma-induced ‘tolerogenic’ microenvironment and, while T cells are present, myeloid cells might prove to be a better target for combination immunotherapy.
Veillonella parvula, prototypical member of the oral and gut microbiota, is at times commensal yet also potentially pathogenic. The definition of the molecular basis tailoring this contrasting ...behavior is key for broadening our understanding of the microbiota‐driven pathogenic and/or tolerogenic mechanisms that take place within our body. In this study, we focused on the chemistry of the main constituent of the outer membrane of V. parvula, the lipopolysaccharide (LPS). LPS molecules indeed elicit pro‐inflammatory and immunomodulatory responses depending on their chemical structures. Herein we report the structural elucidation of the LPS from two strains of V. parvula and show important and unprecedented differences in both the lipid and carbohydrate moieties, including the identification of a novel galactofuranose and mannitol‐containing O‐antigen repeating unit for one of the two strains. Furthermore, by harnessing computational studies, in vitro human cell models, as well as lectin binding solid‐phase assays, we discovered that the two chemically diverse LPS immunologically behave differently and have attempted to identify the molecular determinant(s) governing this phenomenon. Whereas pro‐inflammatory potential has been evidenced for the lipid A moiety, by contrast a plausible “immune modulating” action has been proposed for the peculiar O‐antigen portion.
The chemistry of lipopolysaccharides (LPS) from gut microbes might tip the delicate balance towards tolerance or inflammation. By analyzing the chemistry of LPS from two strains of the pathobiont Veillonella parvula, key and unprecedented structural differences were uncovered, which were reflected in diverse immunoactivities. Attempts were made to identify the molecular determinants governing this phenomenon.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Successful anti-cancer vaccines aim to prime and reinvigorate cytotoxic T cells and should therefore comprise a potent antigen and adjuvant. Antigen targeting to splenic CD169
macrophages was shown ...to induce robust CD8
T cell responses via antigen transfer to cDC1. Interestingly, CD169
macrophages can also activate type I natural killer T-cells (NKT). NKT activation via ligands such as α-galactosylceramide (αGC) serve as natural adjuvants through dendritic cell activation. Here, we incorporated ganglioside GM3 and αGC in ovalbumin (OVA) protein-containing liposomes to achieve both CD169
targeting and superior DC activation. The systemic delivery of GM3-αGC-OVA liposomes resulted in specific uptake by splenic CD169
macrophages, stimulated strong IFNγ production by NKT and NK cells and coincided with the maturation of cDC1 and significant IL-12 production. Strikingly, superior induction of OVA-specific CD8
T cells was detected after immunization with GM3-αGC-OVA liposomes. CD8
T cell activation, but not B cell activation, was dependent on CD169
macrophages and cDC1, while activation of NKT and NK cells were partially mediated by cDC1. In summary, GM3-αGC antigen-containing liposomes are a potent vaccination platform that promotes the interaction between different immune cell populations, resulting in strong adaptive immunity and therefore emerge as a promising anti-cancer vaccination strategy.
Dendritic cells (DCs) are antigen-presenting cells that play an essential role in mucosal tolerance. They regularly encounter beneficial intestinal bacteria, but the nature of these cellular contacts ...and the immune responses elicited by the bacteria are not entirely elucidated. Here, we examined the interactions of Lactobacillus acidophilus NCFM and its cell surface compounds with DCs. L. acidophilus NCFM attached to DCs and induced a concentration-dependent production of IL-10, and low IL-12p70. We further demonstrated that the bacterium binds to DC-specific ICAM-3-grabbing nonintegrin (DC-SIGN), a DC- specific receptor. To identify the DC-SIGN ligand present on the bacterium, we took advantage of a generated array of L. acidophilus NCFM mutants. A knockout mutant of L. acidophilus NCFM lacking the surface (S) layer A protein (SlpA) was significantly reduced in binding to DC-SIGN. This mutant incurred a chromosomal inversion leading to dominant expression of a second S layer protein, SlpB. In the SlpB-dominant strain, the nature of the interaction of this bacterium with DCs changed dramatically. Higher concentrations of proinflammatory cytokines such as IL-12p70, TNFα, and IL-1β were produced by DCs interacting with the SlpB-dominant strain compared with the parent NCFM strain. Unlike the SlpA-knockout mutant, T cells primed with L. acidophilus NCFM stimulated DCs produced more IL-4. The SlpA-DC-SIGN interaction was further confirmed as purified SlpA protein ligated directly to the DC-SIGN. In conclusion, the major S layer protein, SlpA, of L. acidophilus NCFM is the first probiotic bacterial DC-SIGN ligand identified that is functionally involved in the modulation of DCs and T cells functions.
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BFBNIB, NMLJ, NUK, PNG, SAZU, UL, UM, UPUK
CD14+ dendritic cells (DCs) present in the dermis of human skin represent a large subset of dermal DCs (dDCs) that are considered macrophage-like cells with poor antigen (cross)-presenting capacity ...and limited migratory potential to the lymph nodes. CD14+ dDC highly express DC-specific ICAM-3-grabbing non-integrin (DC-SIGN), a receptor containing potent endocytic capacity, facilitating intracellular routing of antigens to major histocompatibility complex I and II (MHC-I andII) loading compartments for the presentation to antigen-specific CD8+ and CD4+ T cells. Here we show using a human skin explant model that the in situ targeting of antigens to DC-SIGN using glycan-modified liposomes enhances the antigen-presenting capacity of CD14+ dDCs. Intradermal vaccination of liposomes modified with the DC-SIGN-targeting glycan LewisX, containing melanoma antigens (MART-1 or Gp100), accumulated in CD14+ dDCs and resulted in enhanced Gp100- or MART-1-specific CD8+ T-cell responses. Simultaneous intradermal injection of the cytokines GM-CSF and IL-4 as adjuvant enhanced the migration of the skin DCs and increased the expression of DC-SIGN on the CD14+ and CD1a+ dDCs. These data demonstrate that human CD14+ dDCs exhibit potent cross-presenting capacity when targeted in situ through DC-SIGN.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Dendritic cells (DCs) are key to the maintenance of peripheral tolerance to self-antigens and the orchestration of an immune reaction to foreign antigens. C-type lectins, expressed by DCs, recognize ...carbohydrate moieties on antigens that can be internalized for processing and presentation. Little is known about the exact glycan structures on self-antigens and pathogens that are specifically recognized by the different C-type lectins and how this interaction influences DC function. We have analyzed the carbohydrate specificity of the human C-type lectin macrophage galactose-type lectin (MGL) using glycan microarray profiling and identified an exclusive specificity for terminal α- and β-linked GalNAc residues that naturally occur as parts of glycoproteins or glycosphingolipids. Specific glycan structures containing terminal GalNAc moieties, expressed by the human helminth parasite Schistosoma mansoni as well as tumor antigens and a subset of gangliosides, were identified as ligands for MGL. Our results indicate an endogenous function for DC-expressed MGL in the clearance and tolerance to self-gangliosides, and in the pattern recognition of tumor antigens and foreign glycoproteins derived from helminth parasites.
Trafficking of myelin-reactive CD4(+) T-cells across the brain endothelium, an essential step in the pathogenesis of multiple sclerosis (MS), is suggested to be an antigen-specific process, yet which ...cells provide this signal is unknown. Here we provide direct evidence that under inflammatory conditions, brain endothelial cells (BECs) stimulate the migration of myelin-reactive CD4(+) T-cells by acting as non-professional antigen presenting cells through the processing and presentation of myelin-derived antigens in MHC-II. Inflamed BECs internalized myelin, which was routed to endo-lysosomal compartment for processing in a time-dependent manner. Moreover, myelin/MHC-II complexes on inflamed BECs stimulated the trans-endothelial migration of myelin-reactive Th1 and Th17 2D2 cells, while control antigen loaded BECs did not stimulate T-cell migration. Furthermore, blocking the interaction between myelin/MHC-II complexes and myelin-reactive T-cells prevented T-cell transmigration. These results demonstrate that endothelial cells derived from the brain are capable of enhancing antigen-specific T cell recruitment.
DC-SIGN: escape mechanism for pathogens Geijtenbeek, Teunis B. H; van Kooyk, Yvette
Nature reviews. Immunology,
200309, 2003-Sep, 2003-9-00, 20030901, Volume:
3, Issue:
9
Journal Article
Peer reviewed
Dendritic cells (DCs) are crucial in the defence against pathogens. Invading pathogens are recognized by Toll-like receptors (TLRs) and receptors such as C-type lectins expressed on the surface of ...DCs. However, it is becoming evident that some pathogens, including viruses, such as HIV-1, and non-viral pathogens, such as Mycobacterium tuberculosis, subvert DC functions to escape immune surveillance by targeting the C-type lectin DC-SIGN (DC-specific intercellular adhesion molecule-grabbing nonintegrin). Notably, these pathogens misuse DC-SIGN by distinct mechanisms that either circumvent antigen processing or alter TLR-mediated signalling, skewing T-cell responses. This implies that adaptation of pathogens to target DC-SIGN might support pathogen survival.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
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