Expression Of Dectin-1 Research Articles

Dectin-1 rs3901533 and rs7309123 Polymorphisms Increase Susceptibility to Pulmonary Invasive Fungal Disease in Patients with Acute Myeloid Leukemia from a Chinese Han Population.

This study aimed to assess whether genetic variants of dendritic cell-associated C-type lectine-1 (Dectin-1), Toll-like receptor 2 (TLR2), Toll-like receptor 4 (TLR4), and myeloid differentiation primary response 88 (MyD88) influence the susceptibility to pulmonary invasive fungal disease (IFD) in patients with acute myeloid leukemia (AML) from a Chinese Han population. Eight single nucleotide polymorphisms (SNPs) of Dectin-1 (rs16910526, rs3901533, and rs7309123), TLR2 (rs5743708), TLR4 (rs4986790 and rs4986791) and MyD88 (rs4988453 and rs4988457) in the genomic DNA of 172 adult AML patients were genotyped. Pulmonary IFD was diagnosed as proven or probable according to the 2008 European Organization for Research and Treatment of Cancer/Invasive Fungal Infections Cooperative Group and the National Institute of Allergy and Infectious Diseases Mycoses Study Group (EORTC/MSG) consensus guidelines. SNPs that were significant in the univariate analysis were further analyzed using the multiple logistic regression analysis to determine their association with the occurrence of pulmonary IFD. The mRNA expression of Dectin-1 was detected according to the genotype by quantitative realtime PCR (qRT-PCR), and the correlation of this expression with the occurrence of pulmonary IFD in AML patients was analyzed. Two Dectin-1 intron SNPs (rs3901533 and rs7309123) were found to be significantly associated with the susceptibility to pulmonary IFD in AML patients in a Chinese Han population. Significant associations were noted between pulmonary IFD and Dectin-1 rs3901533 dominant model (G/T+G/G vs. T/T, OR: 2.158; 95% CI: 1.109-4.2, P=0.02), Dectin-1 rs3901533 G allele (OR: 2.201; 95% CI: 1.206-4.019, P=0.01), or Dectin-1 rs7309123 C allele (OR: 1.919; 95% CI: 1.047-3.518, P=0.03). There were no significant associations between pulmonary IFD and the remaining Dectin-1 SNPs (rs16910526), TLR2 (rs5743708), TLR4 (rs4986790 and rs4986791) or MyD88 (rs4988453 and rs4988457). In conclusion, two Dectin-1 SNPs (rs3901533 and rs7309123) are associated with increased susceptibility to pulmonary IFD in AML patients in a Chinese Han population.

Divergent Roles for Macrophage C-Type Lectin Receptors, Dectin-1 and Mannose Receptors, in Inflammatory Bowel Diseases

Colonic macrophages are considered as major effectors of inflammatory bowel diseases (IBD), and the control of gut inflammation through C-type lectin receptors is an emerging concept. We show that during colitis the loss of Dectin-1 prevents intestinal inflammation, while the lack of MR exacerbates it. A marked increase in Dectin-1 expression in DSS-exposed MR-deficient mice, support the critical contribution of Dectin-1 in the development of colitis. Dectin-1 is crucial for Ly6ChighCCR2high monocyte population enrichment in the blood and their recruitment to inflamed colon as precursors of M1 inflammatory macrophages. Dectin-1 also promotes inflammasome-dependent IL-1β secretion through the leukotriene B4 production. Interestingly, the colonic inflammation is associated with a concomitant overexpression of Dectin-1/CCL2/LTA4H and a down-regulation of MR on macrophages from IBD patients. Thus, MR and Dectin-1 on macrophage are important mucosal inflammatory regulators during IBD. Finally, this study offers breakthroughs on the mechanism may contribute to the pathogenesis of IBD in humans.

Orally administered salecan ameliorates methotrexate-induced intestinal mucositis in mice.

Methotrexate (MTX) is a widely used cancer chemotherapy agent. The efficacy of MTX is often limited by serious side effects, such as intestinal mucositis. The aim of this study was to evaluate the protective effect of water-soluble β-glucan salecan on MTX-induced intestinal toxicity in mice. Intestinal mucositis was induced in C57BL/6 mice by intraperitoneal injection of MTX for two consecutive days. Mice were orally administrated with saline or salecan for 6days before MTX injection and continued to the end of the study. Several histological and biochemical parameters were measured in the jejunum. Orally administration of salecan improved the severity of intestinal mucositis in a dose-dependent manner, as evidenced by the well-maintained mucosal architecture and body weight in salecan-treated groups. Salecan treatment inhibited MTX-induced oxidative stress and effectively scavenged free radicals both in vitro and in vivo. Metabolomics analysis revealed that salecan treatment reversed the intestinal metabolic profiling changes in mice with MTX-induced mucositis. Salecan treatment modulated the innate immunity through the regulation of TLR and Dectin1 expression in the jejunum, thus protecting mice from MTX-induced intestinal damage. Salecan has potential advantages in the treatment of MTX-induced intestinal mucositis, and its protective effect is mainly attributed to its antioxidant and immunomodulatory properties.

β-glucan suppresses cell death of ASC deficient macrophages invaded by periodontopathic bacteria through the caspase-11 pathway.

β-glucan is an abundant cell wall component of fungi and yeast. Dectin-1, a β-glucan receptor, plays an important regulatory role in the natural immunity. In the present study, we investigated the effect of β-glucan on mouse macrophages that had been invaded by the periodontopathic bacterium, Aggregatibacter actinomycetemcomitans. Exposure to curdlan, a type of β-glucan, suppressed cell death and led to the accumulation of a sub-G1-phase population upon A. actinomycetemcomitans invasion under conditions of constitutive expression of dectin-1. Members of the nucleotide-binding domain leucine-rich repeat-containing (NLR) protein family, such as NLR protein 3 (NLRP3), NLR family apoptosis inhibitory protein (NAIP), and NLR family CARD domain-containing protein 4 (NLRC4), as well as an associated protein, caspase-11, were clearly detected in A. actinomycetemcomitans-invaded control RAW cells (c-RAW cells; negative control). Interestingly, NAIP expression was upregulated and caspase-11 expression was downregulated by dectin-1 activity in A. actinomycetemcomitans-invaded dectin-1 overexpressing RAW 264.7 cells (d-RAW cells), suggesting that dectin-1 in macrophages regulates cell death upon A. actinomycetemcomitans invasion. These results support a potential correlation between dectin-1 and regulation of cell death in macrophages.

Circulating (1→3)-β-D-glucan Is Associated With Immune Activation During Human Immunodeficiency Virus Infection.

Microbial translocation from the gut to systemic circulation contributes to immune activation during human immunodeficiency virus (HIV) infection and is usually assessed by measuring plasma levels of bacterial lipopolysaccharide (LPS). Fungal colonization in the gut increases during HIV-infection and people living with HIV (PLWH) have increased plasma levels of fungal polysaccharide (1→3)-β-D-Glucan (βDG). We assessed the contribution of circulating DG to systemic immune activation in PLWH. Cross-sectional and longitudinal assessments of plasma βDG levels were conducted along with markers of HIV disease progression, epithelial gut damage, bacterial translocation, proinflammatory cytokines, and βDG-specific receptor expression on monocytes and natural killer (NK) cells. Plasma βDG levels were elevated during early and chronic HIV infection and persisted despite long-term antiretroviral therapy (ART). βDG increased over 24 months without ART but remained unchanged after 24 months of treatment. βDG correlated negatively with CD4 T-cell count and positively with time to ART initiation, viral load, intestinal fatty acid-binding protein, LPS, and soluble LPS receptor soluble CD14 (sCD14). Elevated βDG correlated positively with indoleamine-2,3-dioxygenase-1 enzyme activity, regulatory T-cell frequency, activated CD38+Human Leukocyte Antigen - DR isotype (HLA-DR)+ CD4 and CD8 T cells and negatively with Dectin-1 and NKp30 expression on monocytes and NK cells, respectively. PLWH have elevated plasma βDG in correlation with markers of disease progression, gut damage, bacterial translocation, and inflammation. Early ART initiation prevents further βDG increase. This fungal antigen contributes to immune activation and represents a potential therapeutic target to prevent non-acquired immunodeficiency syndrome events.

Exopolysaccharides from Cyanobacterium aponinum induce a regulatory dendritic cell phenotype and inhibit SYK and CLEC7A expression in dendritic cells, T cells and keratinocytes

Regular bathing in the Blue Lagoon has beneficial effects on psoriasis. Previously, we showed that exopolysaccharides (EPS-Ca) secreted by Cyanobacterium aponinum, a dominating organism in the Blue Lagoon, increased IL-10 secretion by human dendritic cells (DCs). In addition, co-culturing allogeneic CD4+ T cells with DCs matured in the presence of EPS-Ca increased differentiation of T cells into T regulatory cells at the cost of the disease inducing Th17 cells. In the present study, EPS-Ca increased the proportion of DCs expressing CD141, a surface molecule linked to regulatory DCs, and the CD141+ cells secreted more IL-10 than the CD141− cells. EPS-Ca decreased T cell secretion of IL-17, IL-13 and IL-10 and the proportion of T cells expressing the activation marker CD69 that has also been linked to lymphocyte retention. In addition, EPS-Ca reduced keratinocyte secretion of CCL20 and CXCL10, chemokines implicated in recruitment of inflammatory cells. EPS-Ca decreased DC expression of Dectin-1/CLEC7A and SYK, keratinocyte expression of CLEC7A, SYK and CAMP (the gene for LL37), and T cell expression of phosphorylated Zap70. These results indicate that EPS-Ca may induce a regulatory phenotype of DCs, T cells that are less active/inflammatory and less prone to being retained in the skin, and keratinocytes that induce less recruitment of inflammatory cells to the skin and that these effects may be mediated by the effects of EPS-Ca on CLEC7A and SYK. Overall the results indicate that EPS-Ca may be involved in the beneficial effects psoriasis patients experience when bathing in the Blue Lagoon.

Involvement of the Dectin-1 Receptor upon the Effector Mechanisms of Human Phagocytic Cells against Paracoccidioides brasiliensis.

Paracoccidioidomycosis (PCM), a systemic mycosis endemic in Latin America, occurs after inhalation of mycelial components of Paracoccidioides spp. When the fungus reaches the lungs and interacts with the alveolar macrophages and other cells, phagocytic cells such as neutrophils and monocytes are immediately recruited to the injured site. The interaction between surface molecules of pathogens and homologous receptors, present on the surface membrane of phagocytes, modulates the innate immune cell activation. Studies have shown the importance of fungal recognition by the Dectin-1 receptor, which can induce a series of cellular protective responses against fungi. The objective of the present study was to evaluate Dectin-1 receptor expression and the effector mechanisms of human monocytes and neutrophils activated or not with different cytokines, such as IFN-γ, TNF-α, and GM-CSF, followed by the challenge with Paracoccidioides brasiliensis (P. brasiliensis or Pb265). Therefore, analysis of Dectin-1 receptor expression was done by flow cytometry whereas the effector mechanisms were evaluated by fungal recovery by colony-forming unit (CFU) counting and hydrogen peroxide (H2O2) production. Our results showed that, after treatment with IFN-γ, TNF-α, and GM-CSF and challenge with Pb265, cells, especially monocytes, demonstrated an increase in Dectin-1 expression. Both types of cells treated with the cytokines exhibited a decreased fungal recovery and, conversely, an increased production of H2O2. However, when cultures were treated with an anti-Dectin-1 monoclonal antibody, to block the P. brasiliensis binding, a decrease in H2O2 production and an increase in fungal recovery were detected. This effect was observed in all cultures treated with the specific monoclonal antibody. These results show the involvement of the Dectin-1 receptor in fungal recognition and its consequent participation in the induction of the killing mechanisms against P. brasiliensis.

Dectin-1 Contributes to Myocardial Ischemia/Reperfusion Injury by Regulating Macrophage Polarization and Neutrophil Infiltration.

Macrophage-associated immune response plays an important role in myocardial ischemia/reperfusion (IR) injury. Dectin-1, expressed mainly on activated myeloid cells, is crucial for the regulation of immune homeostasis as a pattern recognition receptor. However, its effects and roles during the myocardial IR injury remain unknown. Genetic ablation, antibody blockade, or Dectin-1 activation, along with the adoptive bone marrow transfer chimeric model, was used to determine the functional significance of Dectin-1 in myocardial IR injury. Immune cell filtration and inflammation were examined by flow cytometry, quantitative real-time polymerase chain reaction, and immunohistochemistry. Moreover, Dectin-1+ cells were analyzed by flow cytometry in the blood of patients with ST-segment-elevation myocardial infarction and stable patients with normal coronary artery (control). We demonstrated that Dectin-1 expression observed on the bone marrow-derived macrophages is increased in the heart during the early phase after IR injury. Dectin-1 deficiency and antibody-mediated Dectin-1 inhibition led to a considerable improvement in cardiac function, accompanied by a reduction in cardiomyocyte apoptosis, which was associated with a decrease in M1 macrophage polarization and Ly-6C+ monocyte and neutrophil infiltration. Activation of Dectin-1 with its agonist had the opposite effects. Furthermore, Dectin-1 contributed to neutrophil recruitment through the regulation of Cxcl1 and granulocyte colony-stimulating factor expression. In addition, Dectin-1-dependent interleukin-23/interleukin-1β production was shown to be essential for interleukin-17A expression by γδT cells, leading to neutrophil recruitment and myocardial IR injury. Furthermore, we demonstrated that circulating Dectin-1+CD14++CD16- and Dectin-1+CD14++CD16+ monocyte levels were significantly higher in patients with ST-segment-elevation myocardial infarction than in controls and positively correlated with the severity of cardiac dysfunction. Our results reveal a crucial role of Dectin-1 in the process of mouse myocardial IR injury and provide a new, clinically significant therapeutic target.

Paracoccidioidomycosis: characterization of subpopulations of macrophages and cytokines in human mucosal lesions.

Mucosal lesions of paracoccidioidomycosis (PCM) are frequently described and clinically important. Macrophages are classified as M1 or M2. M1 are proinflammatory and M2 are related to chronicity. Dectin-1 recognizes β-glucan and plays an important role against fungal cells. The objective was to verify the presence of M1, M2, and dectin-1 and a possible correlation with Th1/Th2 cytokines in mucosal PCM lesions. In sum, 33 biopsies of oral PCM were submitted to histological and immunohistochemistry analysis, and positive cells were quantified. Eleven biopsies were characterized by compact granulomas (G1), 12 with loose granulomas (G2), and 10 with both kind of granulomas (G3). pSTAT-1 was equally increased in the three groups. G1 was characterized by an increased number of CD163+ macrophages. G2 presented similar number of arginase 1, iNOS, and CD163 expressing cells. G3 presented an increased number of cells expressing arginase 1 and CD163 over iNOS. G1 and G3 presented high number of cells expressing interferon (IFN)-γ; interleukin (IL) 5 was increased in G2 and G3; the expression of IL10 was similar among the three groups, and the expression of tumor necrosis factor (TNF)-α was higher in G3. G1 correlates to Th1 cytokines and pSTAT-1 and G2 correlates to Th2 cytokines. G3 presents both kinds of cytokines. We could not associate the expression of arginase-1, CD163, iNOS, and dectin-1 with the pattern of cytokines or kind of granuloma.

Wnt5a contributes to dectin-1 and LOX-1 induced host inflammatory response signature in Aspergillus fumigatus keratitis

Fungal keratitis causes devastating corneal ulcers which can result in significant visual impairment and even blindness. As a ligand that activates the non-canonical Wnt signaling pathways, Wnt5a triggers the production of important inflammatory chemokines and the chemotactic migration of neutrophils. In this study we aimed to characterize the role of Wnt5a production, in situ, in vivo and in vitro in response to fungal keratitis. Wnt5a expression in corneas of Aspergillus fumigatus (A. fumigatus) keratitis patients was determined by quantitative polymerase chain reaction (qRT-PCR) and immunofluorescence. In vivo and in vitro experiments were then performed in mouse models and THP-1 macrophages cell cultures infected with A. fumigatus, respectively. C57BL/6 mice were pretreated with siRNAs or neutralizing antibodies for dectin-1, LOX-1 and Wnt5a, or inhibitors of erk1/2 and JNK. Changes in Wnt5a expression were assessed by clinical evaluation, qRT-PCR, immunofluorescence, western blot and bioluminescence imaging system image acquisition. We confirmed that corneal Wnt5a expression increased with A. fumigatus keratitis in patients and a murine model. Wnt5a production was dependent on dectin-1 and LOX-1 expression with contributions by Erk1/2 and JNK pathways. Additionally, Wnt5a knockdown revealed decreased levels of MPO, lower neutrophil recruitment, and a higher fungal load in mouse models. Compared with controls, Wnt5a knockdown impaired pro-inflammatory cytokine IL-1β production in response to A. fumigatus exposure. Wnt5a also produces dectin-1 and LOX-1 induced inflammatory signature via effective neutrophil recruitment and inflammatory cytokine production in response to A. fumigatus keratitis. These findings demonstrate that Wnt5a is a critical component of the antifungal immune response.

Candida tropicalis induces pro-inflammatory cytokine production, NF-κB and MAPKs pathways regulation, and dectin-1 activation

The prevalence of Candida infection induced by non-albicans Candida (NAC) species is increasing. However, as a common NAC species, C. tropicalis has received much less study in terms of host immunity than C. albicans has. In this study, we evaluated the pro-inflammatory cytokine responses evoked by C. tropicalis and determined whether dectin-1 and downstream NF-κB and mitogen-activated protein kinases (MAPKs) signaling pathways played roles in inflammation in human peripheral blood mononuclear cells (PBMCs) and THP-1 macrophage-like cells. Exposure of PBMCs and THP-1 macrophage-like cells to C. tropicalis led to the enhanced gene expression and secretion of TNF-α and IL-6 in a time- and dose-dependent manner. THP-1 macrophage-like cells being challenged by C. tropicalis resulted in the activation of the NF-κB, p38, and ERK1/2 MAPK signaling pathways. We also found that the expression of dectin-1 was increased with C. tropicalis treatment. These data reveal that dectin-1 may play a role in sensing the inflammation response induced by C. tropicalis and that NF-κB and MAPK are involved in the downstream signaling pathways in macrophages.

3076 - Mir-16 Regulates Crosstalk in NF-KB Inflammatory Signaling between Myeloma Cells and Bone Marrow Macrophages (MQ)

Multiple myeloma plasma cells (MM-PC) home to and dynamically interact with the bone marrow (BM) microenvironment (BM-ME). Of the different factors secreted by the BM-ME, NF-KB-induced cytokines including IL-6 play a central role in MM-PC survival and resistance to treatments. Extracellular vesicles (EV) are membrane-covered cell fragments released by all cell types, and recently they have been shown to play a pivotal role in creating a tumor supportive BM-ME. Here, we investigated whether MM derived EV can play a pivotal role in supporting monocyte to TAM differentiation that can be reversed by miR-16. Our in vitro data show that EV isolated from the supernatant of MM cell lines (MM-EV) can promote monocyte differentiation to CD163+ TAM. MQ differentiation was also observed when peripheral blood monocytes (PB-M) obtained from both MM and healthy donors were treated with EV isolated from the BM acellular fraction of MM patients (n = 4). Limited differentiation was instead observed when the acellular fraction was EV-depleted. Our data show that PB-M differentiation was partially reversed by the addition of an EV-miR-16 mimic. Our Ex vivo data showed that isolation of MQ from the BM of miR-16 knockout mice differentiated towards M2-TAM phenotype as marked by higher surface expression of Dectin-1 and CD206 compared to MQ isolated from the BM of Wild type B6 mice. We also found that miR-16 is dramatically down regulated when PB-M is induced by macrophage colony stimulating factor to differentiate to TAM, and it is also down regulated in primary BM-MQ as compared to PB-M of the same patients and to the BM-MQ of 3 age matched healthy donors. We learned that BM-MQ isolated from MM patients are the main source of NF-KB-induced cytokines including IL-6 and IL-10 under unstimulated conditions as well as IL-6, IL-8, IL-10, TNF-a and VEGF under Toll-like receptor stimulated conditions, as the MQ-depleted BM cellular fraction had significantly low levels. NF-KB decreases MM cells dependency on extrinsic growth factors, at the onset of the disease miR-16 downregulation in MM-PCs can support NF-kB intrinsic inflammatory activation and increase fitness of MM cells.

Complex consisting of antisense DNA and β-glucan promotes internalization into cell through Dectin-1 and hybridizes with target mRNA in cytosol.

Antisense oligonucleotides (AS-ODNs) hybridize with specific mRNAs, resulting in interference with the splicing mechanism or the regulation of protein translation. We previously demonstrated that the β-glucan schizophyllan (SPG) can form a complex with AS-ODNs with attached dA40 (AS-ODNs/SPG), and this complex can be incorporated into cells, such as macrophages and dendritic cells, expressing the β-glucan receptor Dectin-1. We have achieved efficient gene silencing in animal models, but the uptake mechanism and intracellular distribution are unclear. In this study, we prepared the complex consisting of SPG and AS-ODNs (AS014) for Y-box binding protein-1 (YB-1). After treatment with endocytosis inhibitor Pitstop 2 and small interfering RNA targeting Dectin-1, we found that AS014/SPG complexes are incorporated into cells by Dectin-1-mediated endocytosis and inhibit cell growth in a Dectin-1 expression level-dependent manner. After treatment with AS014/SPG complexes, we separated the cell lysate into endosomal and cytoplasmic components by ultracentrifugation and directly determined the distribution of AS014 by reverse transcription PCR using AS014 ODNs as a template or a reverse transcription primer. In the cytoplasm, AS014 clearly hybridized with YB-1 mRNAs. This is the first demonstration of the distinct distribution of the complex in cells. These results could facilitate the clinical application of the complex.

Induction of dectin-1 expression and intracellular signal transduction by β-Glucan of ganoderma lucidum

Induction of dectin-1 expression and intracellular signal transduction by β-Glucan of ganoderma lucidum

Adeno-associated Virus Vector-mediated Interleukin-10 Induction Prevents Vascular Inflammation in a Murine Model of Kawasaki Disease

Kawasaki disease (KD), which is the leading cause of pediatric heart disease, is characterized by coronary vasculitis and subsequent aneurysm formation. Although intravenous immunoglobulin therapy is effective for reducing aneurysm formation, a certain number of patients are resistant to this therapy. Because interleukin-10 (IL-10) was identified as a negative regulator of cardiac inflammation in a murine model of KD induced by Candida albicans water-soluble fraction (CAWS), we investigated the effect of IL-10 supplementation in CAWS-induced vasculitis. Mice were injected intramuscularly with adeno-associated virus (AAV) vector encoding IL-10, then treated with CAWS. The induction of AAV-mediated IL-10 (AAV-IL-10) significantly attenuated the vascular inflammation and fibrosis in the aortic root and coronary artery, resulting in the improvement of cardiac dysfunction and lethality. The predominant infiltrating inflammatory cells in the vascular walls were Dectin-2+CD11b+ macrophages. In vitro experiments revealed that granulocyte/macrophage colony-stimulating factor (GM-CSF) induced Dectin-2 expression in bone marrow-derived macrophages and enhanced the CAWS-induced production of tumor necrosis factor-α (TNF-α) and IL-6. IL-10 had no effect on the Dectin-2 expression but significantly inhibited the production of cytokines. IL-10 also inhibited CAWS-induced phosphorylation of ERK1/2, but not Syk. Furthermore, the induction of AAV-IL-10 prevented the expression of TNF-α and IL-6, but not GM-CSF and Dectin-2 at the early phase of CAWS-induced vasculitis. These findings demonstrate that AAV-IL-10 may have therapeutic application in the prevention of coronary vasculitis and aneurysm formation, and provide new insights into the mechanism underlying the pathogenesis of KD.

An multivalent vaccine elicits protective Th17 response via activation of C-type lectin receptor- and Card9-mediated signal against pulmonary Coccidioides posadasii infection

Abstract Coccidioidomycosis is a potentially life-threatening fungal infection that is responsible for ~150,000 infections annually in the United States. Development of a vaccine against Coccidioides infection is urgent. We have created a multivalent coccidioidal antigen (rCpa1) that contains promiscuous human T cell epitopes. The rCpa1 was formulated with 5 types of experimental adjuvants including yeast cell-wall particles and CpG adjuvant. The rCpa1 formulated with glucan chitin particles (GCPs) derived from a non-pathogenic yeast demonstrated the best protective efficacy for susceptible C57BL/6 and HLA-DR4 transgenic mice against this disease compared to the other 4 tested vaccines. This is the first report of a subunit vaccine that can provide a comparable degree of protection to a live, attenuated vaccine against coccidioidomycosis. The GCP-rCpa1 vaccine elicited a robust and durable Th17 memory response. Depletion of Th17 cells significantly reduced the protective efficacy of this vaccine, indicating that Th17 cells play an indispensable role. Dectin-1 and Dectin-2 molecules can bind to the GCP-rCpa1 vaccine particles. Macrophages derived from mice lacking expression of Dectin-1, Dectin-2 and downstream immune adapter CARD9 secreted reduced amounts of IL-1β and IL-6 upon stimulation with GCP-rCpa1 that are essential for Th17 development. Furthermore, vaccinated Dectin-1−/−, Dectin-2−/− and CARD9 −/− mice recruited significantly reduced amounts of Th17 cells to the lungs compared to C57BL/6 mice and succumbed to coccidioidomycosis. Taken together, protection against Coccidioides provided by GCP-rCpa1 vaccine requires Dectin-1- and Dectin-2-CARD9-mediated signaling to activate Th17 immune response.

A Comprehensive in Silico Analysis of Regulatory SNPs of Human CLEC7A Gene and Its Validation as Genotypic and Phenotypic Disease Marker in Recurrent Vulvovaginal Infections.

Recurrent Vulvovaginal infections (RVVI) are the commonly reported microbiological syndrome affecting millions of women globally. Various molecules of innate immune system are instrumental in clearance of these microbial pathogens, thus suggested as one of the most important contributing factor in determining the disease outcome. Dendritic cell-associated C-type lectin-1 (Dectin-1) is an important molecule of innate immunity that is primarily known for its role in antifungal defenses. However, role of dectin-1 in recognition of other pathogens is also documented. The intracellular expression of dectin-1 was shown to be up-regulated by Mannose Binding Lectin (MBL)-mediated opsonophagocytosis of pathogens. Dectin-1 is encoded by CLEC7A, postulated to be a candidate gene in modulating risk of developing RVVI. In this study, we identified CLEC7A causal variants using in silico analysis. To assess their impact on susceptibility to RVVI, these causal variants along with serum dectin-1 levels (sDectin-1) were investigated using polymerase chain reaction-restriction fragment length polymorphism (PCR–RFLP) and Enzyme Linked Immnosorbent Assay (ELISA) respectively, under a case-control design. Furthermore, effect of these polymorphisms was also assessed on sMBL levels. In silico analysis revealed 9 putative functional conserved SNPs of CLEC7A. Association analysis revealed a significantly lower risk of developing RVVI and its types in carriers of CLEC7A rs3901533 G allele and its homozygous genotypes (p < 0.05). The heterozygous genotype was associated with significant protection against RVVI (p = 0.004). Haplotypes GGG and GTA showed significant protection against RVVI (p < 0.0001; p = 0.0003), Bacterial Vaginosis (p = 0.03; p = 0.002), Vulvovaginal Candidiasis (p = 0.03; p = 0.01) and Mixed Infections (p = 0.007; p = 0.04). Mean sDectin-1 levels were significantly high in RVVI and its types compared to controls (p < 0.05). Further, genotype-phenotype stratification showed significant differences within/between cases groups and controls. The CLEC7A rs3901533 polymorphism was also found to be associated with sMBL levels. The present study contributed novel insights into the role of dectin-1 in RVVI. CLEC7A rs3901533 polymorphism and high sDectin-1 levels along with low sMBL levels were found to be associated with RVVI susceptibility. Thus, screening of women with RVVI for these novel associations may lead to better diagnosis and treatment. Also genotyping method used in this study constitutes a simple and reliable assay, which can be confidently, used as a cheaper alternative for genotyping these variants in clinical settings. Finally, new restorative markers for other infectious diseases might be found by exploring nine functionally identified CLEC7A SNPs.

Dectin-1 limits allergic responses

Allergy Aberrant activation of pattern recognition receptors (PRRs) drives inflammation in autoimmune and allergic diseases. Gour et al. identified invertebrate tropomyosin from house dust mites and shrimp as a ligand for dectin-1. Dectin-1 is a PRR that recognizes fungal β-glucans in antifungal immune responses. Engagement of dectin-1 by invertebrate tropomyosins limited type 2 inflammation, and dectin-1–deficient mice were more prone to allergic airway inflammation. Furthermore, expression of dectin-1 was repressed in allergic individuals. Thus, dectin-1 is important in limiting allergic responses. Sci. Immunol. 3 , eaam9841 (2018).

Dectin-1 Positive Dendritic Cells Expand after Infection with Leishmania major Parasites and Represent Promising Targets for Vaccine Development.

Resistant mouse strains mount a protective T cell-mediated immune response upon infection with Leishmania (L.) parasites. Healing correlates with a T helper (Th) cell-type 1 response characterized by a pronounced IFN-γ production, while susceptibility is associated with an IL-4-dependent Th2-type response. It has been shown that dermal dendritic cells are crucial for inducing protective Th1-mediated immunity. Additionally, there is growing evidence that C-type lectin receptor (CLR)-mediated signaling is involved in directing adaptive immunity against pathogens. However, little is known about the function of the CLR Dectin-1 in modulating Th1- or Th2-type immune responses by DC subsets in leishmaniasis. We characterized the expression of Dectin-1 on CD11c+ DCs in peripheral blood, at the site of infection, and skin-draining lymph nodes of L. major-infected C57BL/6 and BALB/c mice and in peripheral blood of patients suffering from cutaneous leishmaniasis (CL). Both mouse strains responded with an expansion of Dectin-1+ DCs within the analyzed tissues. In accordance with the experimental model, Dectin-1+ DCs expanded as well in the peripheral blood of CL patients. To study the role of Dectin-1+ DCs in adaptive immunity against L. major, we analyzed the T cell stimulating potential of bone marrow-derived dendritic cells (BMDCs) in the presence of the Dectin-1 agonist Curdlan. These experiments revealed that Curdlan induces the maturation of BMDCs and the expansion of Leishmania-specific CD4+ T cells. Based on these findings, we evaluated the impact of Curdlan/Dectin-1 interactions in experimental leishmaniasis and were able to demonstrate that the presence of Curdlan at the site of infection modulates the course of disease in BALB/c mice: wild-type BALB/c mice treated intradermally with Curdlan developed a protective immune response against L. major whereas Dectin-1−/− BALB/c mice still developed the fatal course of disease after Curdlan treatment. Furthermore, the vaccination of BALB/c mice with a combination of soluble L. major antigens and Curdlan was able to provide a partial protection from severe leishmaniasis. These findings indicate that the ligation of Dectin-1 on DCs acts as an important checkpoint in adaptive immunity against L. major and should therefore be considered in future whole-organism vaccination strategies.

Fusarium solani Activates Dectin-1 in Experimentally Induced Keratomycosis.

In this study, the response of Dectin-1 on macrophages to Fusarium solani (F. solani) and the expression patterns of Dectin-1 in experimentally F. solani-induced keratomycosis were investigated. Peritoneal macrophages isolated after intraperitoneal injection of sodium thioglycollate were co-cultured with laminarin and spores of F. solani for 12 h. The expression levels of Dectin-1 and CARD9 were detected by immunofluorescence and real-time quantitative polymerase chain reaction. A mouse model of fungal keratitis was established by substromal inoculation with spores of F. solani. Corneal lesions and inflammatory responses were observed by slit-lamp and histopathology at 1, 2, 3, 5, and 7 day(s) after infection. Dectin-1 expression was significantly upregulated on macrophages stimulated by spores of F. solani. Dectin-1 was not detected in normal corneas of C57BL/6 mice, but detected in infected corneas from the first day after inoculation, with high mRNA levels observed on days 2 and 3. CARD9, a key transducer of Dectin-1 signaling, was also upregulated in infected corneas. In conclusion, Dectin-1 is an important recognition receptor in F. solani-induced keratitis, but the molecular mechanisms warrant further investigation.