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1.
Front Immunol ; 14: 1127485, 2023.
Article in English | MEDLINE | ID: mdl-37251386

ABSTRACT

A single population of interferon-regulatory factor 8 (Irf8)-dependent conventional dendritic cell (cDC type1) is considered to be responsible for both immunogenic and tolerogenic responses depending on the surrounding cytokine milieu. Here, we challenge this concept of an omnipotent single Irf8-dependent cDC1 cluster through analysis of pulmonary cDCs at single cell resolution. We report existence of a pulmonary cDC1 cluster lacking Xcr1 with an immunogenic signature that clearly differs from the Xcr1 positive cDC1 cluster. The Irf8+Batf3+Xcr1- cluster expresses high levels of pro-inflammatory genes associated with antigen presentation, migration and co-stimulation such as Ccr7, Cd74, MHC-II, Ccl5, Il12b and Relb while, the Xcr1+ cDC1 cluster expresses genes corresponding to immune tolerance mechanisms like Clec9a, Pbx1, Cadm1, Btla and Clec12a. In concordance with their pro-inflammatory gene expression profile, the ratio of Xcr1- cDC1s but not Xcr1+cDC1 is increased in the lungs of allergen-treated mice compared to the control group, in which both cDC1 clusters are present in comparable ratios. The existence of two distinct Xcr1+ and Xcr1- cDC1 clusters is furthermore supported by velocity analysis showing markedly different temporal patterns of Xcr1- and Xcr1+cDC1s. In summary, we present evidence for the existence of two different cDC1 clusters with distinct immunogenic profiles in vivo. Our findings have important implications for DC-targeting immunomodulatory therapies.


Subject(s)
Dendritic Cells , Lung , Animals , Mice , Sequence Analysis, RNA
2.
Int J Mol Sci ; 23(6)2022 Mar 17.
Article in English | MEDLINE | ID: mdl-35328665

ABSTRACT

Rift Valley fever virus (RVFV) is a mosquito-borne bunyavirus endemic to Africa and the Arabian Peninsula, which causes diseases in humans and livestock. C-type lectin receptors (CLRs) represent a superfamily of pattern recognition receptors that were reported to interact with diverse viruses and contribute to antiviral immune responses but may also act as attachment factors or entry receptors in diverse species. Human DC-SIGN and L-SIGN are known to interact with RVFV and to facilitate viral host cell entry, but the roles of further host and vector CLRs are still unknown. In this study, we present a CLR-Fc fusion protein library to screen RVFV-CLR interaction in a cross-species approach and identified novel murine, ovine, and Aedes aegypti RVFV candidate receptors. Furthermore, cross-species CLR binding studies enabled observations of the differences and similarities in binding preferences of RVFV between mammalian CLR homologues, as well as more distant vector/host CLRs.


Subject(s)
Aedes , Rift Valley Fever , Rift Valley fever virus , Animals , Humans , Lectins, C-Type/genetics , Mammals , Mice , Mosquito Vectors/genetics , Sheep
3.
J Control Release ; 334: 201-212, 2021 06 10.
Article in English | MEDLINE | ID: mdl-33865899

ABSTRACT

Antibiotic treatment of tuberculosis (TB) is complex, lengthy, and can be associated with various adverse effects. As a result, patient compliance often is poor, thus further enhancing the risk of selecting multi-drug resistant bacteria. Macrophage mannose receptor (MMR)-positive alveolar macrophages (AM) constitute a niche in which Mycobacterium tuberculosis replicates and survives. Therefore, we encapsulated levofloxacin in lipid nanocarriers functionalized with fucosyl residues that interact with the MMR. Indeed, such nanocarriers preferentially targeted MMR-positive myeloid cells, and in particular, AM. Intracellularly, fucosylated lipid nanocarriers favorably delivered their payload into endosomal compartments, where mycobacteria reside. In an in vitro setting using infected human primary macrophages as well as dendritic cells, the encapsulated antibiotic cleared the pathogen more efficiently than free levofloxacin. In conclusion, our results point towards carbohydrate-functionalized nanocarriers as a promising tool for improving TB treatment by targeted delivery of antibiotics.


Subject(s)
Mycobacterium tuberculosis , Tuberculosis , Anti-Bacterial Agents/pharmacology , Humans , Lipids , Macrophages , Tuberculosis/drug therapy
4.
Int J Mol Sci ; 21(15)2020 Jul 25.
Article in English | MEDLINE | ID: mdl-32722514

ABSTRACT

C-type lectin receptor (CLR)/carbohydrate recognition occurs through low affinity interactions. Nature compensates that weakness by multivalent display of the lectin carbohydrate recognition domain (CRD) at the cell surface. Mimicking these low affinity interactions in vitro is essential to better understand CLR/glycan interactions. Here, we present a strategy to create a generic construct with a tetrameric presentation of the CRD for any CLR, termed TETRALEC. We applied our strategy to a naturally occurring tetrameric CRD, DC-SIGNR, and compared the TETRALEC ligand binding capacity by synthetic N- and O-glycans microarray using three different DC-SIGNR constructs i) its natural tetrameric counterpart, ii) the monomeric CRD and iii) a dimeric Fc-CRD fusion. DC-SIGNR TETRALEC construct showed a similar binding profile to that of its natural tetrameric counterpart. However, differences observed in recognition of low affinity ligands underlined the importance of the CRD spatial arrangement. Moreover, we further extended the applications of DC-SIGNR TETRALEC to evaluate CLR/pathogens interactions. This construct was able to recognize heat-killed Candida albicans by flow cytometry and confocal microscopy, a so far unreported specificity of DC-SIGNR. In summary, the newly developed DC-SIGNR TETRALEC tool proved to be useful to unravel novel CLR/glycan interactions, an approach which could be applied to other CLRs.


Subject(s)
Candida albicans/metabolism , Flow Cytometry , Immunoglobulin Fc Fragments/chemistry , Lectins, C-Type/chemistry , Recombinant Fusion Proteins/chemistry , Candida albicans/cytology , Immunoglobulin Fc Fragments/genetics , Lectins, C-Type/genetics , Ligands , Recombinant Fusion Proteins/genetics
5.
Vet Immunol Immunopathol ; 224: 110047, 2020 Apr 18.
Article in English | MEDLINE | ID: mdl-32325253

ABSTRACT

C-type lectin receptors (CTLRs) are pattern recognition receptors which are important constituents of the innate immunity. However, their role has mostly been studied in humans and in mouse models. To bridge the knowledge gap concerning CTLRs of veterinary relevant species, a novel ovine CTLR hFc-fusion protein library which allows in vitro ligand identification and pathogen binding studies has been established. Its utility was tested with known ligands of corresponding murine CTLRs in ELISA- and flow cytometry based binding studies. The ovine CTLR-hFc library was subsequently used in a proof-of-principle pathogen binding study with the ruminant pathogen Mycoplasma mycoides subsp. capri. Some ovine CTLRs, such as Dendritic Cell Immunoreceptor (DCIR, Clec4a), Macrophage C-Type Lectin (MCL, Clec4d) and Myeloid Inhibitory C-Type Lectin-Like Receptor (MICL, Clec12a) were identified as possible candidate receptors whose role in Mycoplasma recognition can now be unraveled in further studies. This study thus shows the utility of this novel ovine CTLR-hFc fusion protein library to screen for CTLR/pathogen interactions.

6.
J Med Microbiol ; 68(11): 1649-1654, 2019 Nov.
Article in English | MEDLINE | ID: mdl-31609198

ABSTRACT

Myeloid C-type lectin receptors (CLRs) are innate immune recognition molecules that bind to microorganisms via their carbohydrate recognition domains. In this study, we utilized a library of CLRs that recognize fungal mannans. We used this library to screen against Pneumocystis carinii (Pc) homogenates or purified Pc major surface glycoprotein (Msg) present on Pneumocystis. The results demonstrated that all of the mammalian CLR hFc-fusions tested displayed significant interaction/binding with Pc organisms, and furthermore to isolated Msg. Highest Pc organism and Msg binding activities were with CLR members Mincle, Dectin-2, DC-SIGN and MCL. An immunofluorescence assay with the respective CLR hFc-fusions against whole Pc life forms corroborated these findings. Although some of these CLRs have been implicated previously as important for Pneumocystis pathogenesis (Dectin-1/Dectin-2/Mincle), this is the first analysis of head-to-head comparison of known fungal mannan binding CLR-hFc fusions with Pc. Lastly, heat treatment resulted in reducted CLR binding.


Subject(s)
Fungal Proteins/metabolism , Lectins, C-Type/metabolism , Mannans/metabolism , Membrane Glycoproteins/metabolism , Pneumocystis Infections/metabolism , Pneumocystis carinii/metabolism , Humans , Lectins, C-Type/genetics , Pneumocystis Infections/genetics , Pneumocystis Infections/microbiology , Pneumocystis carinii/genetics , Protein Binding
7.
Viruses ; 11(3)2019 03 26.
Article in English | MEDLINE | ID: mdl-30917612

ABSTRACT

La Crosse virus (LACV) is a mosquito-transmitted arbovirus and the main cause of virus-mediated neurological diseases in children. To date, little is known about the role of C-type lectin receptors (CLRs)-an important class of pattern recognition receptors-in LACV recognition. DC-SIGN remains the only well-described CLR that recognizes LACV. In this study, we investigated the role of additional CLR/LACV interactions. To this end, we applied a flow-through chromatography method for the purification of LACV to perform an unbiased high-throughput screening of LACV with a CLR-hFc fusion protein library. Interestingly, the CARD9-associated CLRs Mincle, Dectin-1, and Dectin-2 were identified to strongly interact with LACV. Since CARD9 is a common adaptor protein for signaling via Mincle, Dectin-1, and Dectin-2, we performed LACV infection of Mincle-/- and CARD9-/- DCs. Mincle-/- and CARD9-/- DCs produced less amounts of proinflammatory cytokines, namely IL-6 and TNF-α, albeit no reduction of the LACV titer was observed. Together, novel CLR/LACV interactions were identified; however, the Mincle/CARD9 axis plays a limited role in early antiviral responses against LACV.


Subject(s)
CARD Signaling Adaptor Proteins/immunology , Encephalitis, California/immunology , Immunity, Innate , Lectins, C-Type/immunology , Membrane Proteins/immunology , Signal Transduction/immunology , Animals , Antiviral Agents , CARD Signaling Adaptor Proteins/genetics , Cytokines/immunology , Dendritic Cells/immunology , La Crosse virus/immunology , Lectins, C-Type/genetics , Membrane Proteins/genetics , Mice , Mice, Inbred C57BL , Mice, Knockout , Th17 Cells/immunology
8.
Sci Rep ; 8(1): 6603, 2018 04 26.
Article in English | MEDLINE | ID: mdl-29700341

ABSTRACT

Understanding blood group antigen binding preferences for C-type lectin receptors holds promise for modulating immune responses, since several Gram-negative bacteria express blood group antigens as molecular mimicry to evade immune responses. Herein, we report the synthesis of ABO blood group antigen active tri and disaccharides to investigate the binding specificity with various C-type lectin receptors using glycan microarray. The results of binding preferences show that distinct glycosylation on the galactose and fucose motifs are key for C-type lectin receptor binding and that these interactions occur in a Ca2+-dependent fashion.


Subject(s)
ABO Blood-Group System/immunology , ABO Blood-Group System/metabolism , Lectins, C-Type/metabolism , Polysaccharides/immunology , Animals , Disaccharides/chemistry , Disaccharides/immunology , Glycosylation , Humans , Mice , Molecular Structure , Polysaccharides/chemistry , Protein Array Analysis , Protein Binding/immunology
9.
Front Immunol ; 9: 213, 2018.
Article in English | MEDLINE | ID: mdl-29487596

ABSTRACT

C-type lectin receptors (CLRs) are carbohydrate-binding receptors that recognize their ligands often in a Ca2+-dependent manner. Upon ligand binding, myeloid CLRs in innate immunity trigger or inhibit a variety of signaling pathways, thus initiating or modulating effector functions such as cytokine production, phagocytosis, and antigen presentation. CLRs bind to various pathogens, including viruses, fungi, parasites, and bacteria. The bacterium Campylobacter jejuni (C. jejuni) is a very frequent Gram-negative zoonotic pathogen of humans, causing severe intestinal symptoms. Interestingly, C. jejuni expresses several glycosylated surface structures, for example, the capsular polysaccharide (CPS), lipooligosaccharide (LOS), and envelope proteins. This "Methods" paper describes applications of CLR-Fc fusion proteins to screen for yet unknown CLR/bacteria interactions using C. jejuni as an example. ELISA-based detection of CLR/bacteria interactions allows a first prescreening that is further confirmed by flow cytometry-based binding analysis and visualized using confocal microscopy. By applying these methods, we identified Dectin-1 as a novel CLR recognizing two selected C. jejuni isolates with different LOS and CPS genotypes. In conclusion, the here-described applications of CLR-Fc fusion proteins represent useful methods to screen for and identify novel CLR/bacteria interactions.


Subject(s)
Campylobacter jejuni/immunology , Host-Parasite Interactions/immunology , Lectins, C-Type/immunology , Receptors, Fc/immunology , Recombinant Fusion Proteins/immunology , Enzyme-Linked Immunosorbent Assay/methods , Flow Cytometry/methods , Humans , Lectins, C-Type/genetics , Lectins, C-Type/isolation & purification , Microscopy, Confocal , Receptors, Fc/genetics , Receptors, Fc/isolation & purification , Recombinant Fusion Proteins/genetics , Recombinant Fusion Proteins/isolation & purification
10.
Chembiochem ; 2018 Mar 25.
Article in English | MEDLINE | ID: mdl-29575424

ABSTRACT

Carbohydrate-protein interactions (CPIs) are involved in a wide range of biological phenomena. Hence, the characterization and presentation of carbohydrate epitopes that closely mimic the natural environment is one of the long-term goals of glycosciences. Inspired by the multivalency, heterogeneity and nature of carbohydrate ligand-mediated interactions, we constructed a combinatorial library of mannose and galactose homo- and hetero-glycodendrons to study CPIs. Microarray analysis of these glycodendrons with a wide range of biologically important plant and animal lectins revealed that oligosaccharide structures and heterogeneity interact with each other to alter binding preferences.

11.
J Med Chem ; 60(21): 9012-9021, 2017 11 09.
Article in English | MEDLINE | ID: mdl-29045792

ABSTRACT

The macrophage galactose-type lectin (MGL) recognizes glycan moieties exposed by pathogens and malignant cells. Particularly, mucin-1 (MUC1) glycoprotein presents an altered glycosylation in several cancers. To estimate the ability of distinct MGL orthologs to recognize aberrant glycan cores in mucins, we applied evanescent-field detection to a versatile MUC1-like glycopeptide microarray platform. Here, as binding was sequence-dependent, we demonstrated that not only sugars but also peptide region impact the recognition of murine MGL1 (mMGL1). In addition, we observed for all three MGL orthologs that divalent glycan presentation increased the binding. To assess the utility of the glycopeptide binders of the MGL orthologs for MGL targeting, we performed uptake assays with fluorescein-MUC1 using murine dendritic cells. A diglycosylated MUC1 peptide was preferentially internalized in an MGL-dependent fashion, thus showing the utility for divalent MGL targeting. These findings may be relevant to a rational design of antitumor vaccines targeting dendritic cells via MGL.


Subject(s)
Dendritic Cells/immunology , Glycopeptides/immunology , Lectins, C-Type/metabolism , Mucin-1/metabolism , Animals , Glycosylation , Humans , Lectins, C-Type/chemistry , Mice , Protein Binding
12.
Viruses ; 9(3)2017 03 22.
Article in English | MEDLINE | ID: mdl-28327518

ABSTRACT

Recognition of viral glycans by pattern recognition receptors (PRRs) in innate immunity contributes to antiviral immune responses. C-type lectin receptors (CLRs) are PRRs capable of sensing glycans present in viral pathogens to activate antiviral immune responses such as phagocytosis, antigen processing and presentation, and subsequent T cell activation. The ability of CLRs to elicit and shape adaptive immunity plays a critical role in the inhibition of viral spread within the host. However, certain viruses exploit CLRs for viral entry into host cells to avoid immune recognition. To block CLR interactions with viral glycoproteins, antiviral strategies may involve the use of multivalent glycan carrier systems. In this review, we describe the role of CLRs in antiviral immunity and we highlight their dual function in viral clearance and exploitation by viral pathogens.


Subject(s)
Immunity, Innate , Lectins, C-Type/metabolism , Virus Diseases/immunology , Viruses/immunology , Adaptive Immunity , Animals , Host-Pathogen Interactions , Humans , Immune Evasion , Viruses/pathogenicity
13.
Microbiology (Reading) ; 162(3): 503-512, 2016 Mar.
Article in English | MEDLINE | ID: mdl-26764024

ABSTRACT

Helicobacter pullorum is an avian enterohepatic species that, more recently, has also been found as a naturally acquired infection in mice and rats, and isolated from patients with gastrointestinal and hepatobiliary diseases. In this work, the interaction between H. pullorum and murine macrophages was examined. Firstly, the impact of nitric oxide, which is an antimicrobial produced by mammalian macrophages, on H. pullorum 6350-92 viability and morphology was studied by colony-forming assays and light microscopy, respectively. Exposure to nitric oxide lowered H. pullorum viability, in a growth-phase-dependent manner, and decreased the mean cell size. However, the number of coccoid forms remained low, contrasting with what has been observed for other Helicobacter species. Confocal microscopy showed that H. pullorum is internalized by murine macrophages, triggering nitric oxide production that promotes phagocytosis and killing of the pathogen. Interaction between H. pullorum and macrophages stimulated secretion of pro-inflammatory cytokines, such as TNF-α, IL-1ß, IL-6 and MIP-2. These results show that H. pullorum is able to infect mammalian murine cells triggering an inflammatory response.


Subject(s)
Helicobacter/immunology , Macrophages/immunology , Microbial Viability/drug effects , Nitric Oxide/metabolism , Phagocytosis , Animals , Cell Line , Colony Count, Microbial , Cytokines/metabolism , Helicobacter/cytology , Helicobacter/drug effects , Mice , Microscopy
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