Intercellular Adhesion Molecule 3-grabbing Nonintegrin Research Articles

Polymorphisms in Immune Genes and Their Association with Tuberculosis Susceptibility: An Analysis of the African Population.

Tuberculosis remains a global health concern, with substantial mortality rates worldwide. Genetic factors play a significant role in influencing susceptibility to tuberculosis. This review examines the current progress in studying polymorphisms within immune genes associated with tuberculosis susceptibility, focusing on African populations. The roles of various proteins, including Toll-like receptors, Dendritic Cell-Specific Intercellular Adhesion Molecule-3 Grabbing Non-Integrin, vitamin D nuclear receptor, soluble C-type lectins such as surfactant proteins A and D, C-type Lectin Domain Family 4 Member E, and mannose-binding lectin, phagocyte cytokines such as Interleukin-1, Interleukin-6, Interleukin-10, Interleukin-12, and Interleukin-18, and chemokines such as Interleukin-8, monocyte chemoattractant protein 1, Regulated upon activation, normal T-cell expressed and secreted are explored in the context of tuberculosis susceptibility. We also address the potential impact of genetic variants on protein functions, as well as how these findings align with the genetic polymorphisms not associated with tuberculosis. Functional studies in model systems provide insights into the intricate host-pathogen interactions and susceptibility mechanisms. Despite progress, gaps in knowledge remain, highlighting the need for further investigations. This review emphasizes the association of Single Nucleotide Polymorphisms with diverse aspects of tuberculosis pathogenesis, including disease detection and Mycobacterium tuberculosis infection.

Engineered Nanovesicles Expressing Bispecific Single Chain Variable Fragments to Protect against SARS-CoV-2 Infection.

Coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has resulted in high morbidity and mortality rates worldwide. Although the epidemic has been controlled in many areas and numerous patients have been successfully treated, the risk of reinfection persists due to the low neutralizing antibody titers and weak immune response. To provide long-term immune protection for infected patients, novel bispecific CB6/dendritic cell (DC)-specific intercellular adhesion molecule 3-grabbing nonintegrin (SIGN) nanovesicles (NVs) were constructed to target both the SARS-CoV-2 spike protein (S) and the DC receptors for virus neutralization and immune activation. Herein, we designed NVs expressing both CB6 and DC-SIGN single chain variable fragments (scFvs) on the surface to block SARS-CoV-2 invasion and activate DC function. Monophosphoryl lipid A (MPLA) was loaded into the CB6/DC-SIGN NVs as an adjuvant to promote this process. The CB6/DC-SIGN NVs prevented a pseudovirus expressing the S protein from infecting the target cells expressing high levels of angiotensin-converting enzyme 2 in vitro. Additionally, CB6/DC-SIGN NVs admixed with S-expressing pseudoviruses activated the DCs, which was promoted by the adjuvant MPLA loaded in the NVs. Using a mouse model, we also confirmed that the CB6/DC-SIGN NVs effectively improved the neutralizing antibody titer and inhibited the growth of tumors expressing the S protein after 3 weeks of treatment. This potential NV-based treatment not only exerts a blocking effect by binding the S protein in the short term but may also provide patients with long-term protection against secondary infections.

Nanoscale clustering of mycobacterial ligands and DC-SIGN host receptors are key determinants for pathogen recognition.

The bacterial pathogen Mycobacterium tuberculosis binds to the C-type lectin DC-SIGN (dendritic cell-specific intercellular adhesion molecule 3-grabbing nonintegrin) on dendritic cells to evade the immune system. While DC-SIGN glycoconjugate ligands are ubiquitous among mycobacterial species, the receptor selectively binds pathogenic species from the M. tuberculosis complex (MTBC). Here, we unravel the molecular mechanism behind this intriguing selective recognition by means of a multidisciplinary approach combining single-molecule atomic force microscopy with Förster resonance energy transfer and bioassays. Molecular recognition imaging of mycobacteria demonstrates that the distribution of DC-SIGN ligands markedly differs between Mycobacterium bovis Bacille Calmette-Guérin (BCG) (model MTBC species) and Mycobacterium smegmatis (non-MTBC species), the ligands being concentrated into dense nanodomains on M. bovis BCG. Upon bacteria-host cell adhesion, ligand nanodomains induce the recruitment and clustering of DC-SIGN. Our study highlights the key role of clustering of both ligands on MTBC species and DC-SIGN host receptors in pathogen recognition, a mechanism that might be widespread in host-pathogen interactions.

Interleukin-34 permits Porphyromonas gingivalis survival and NF-κB p65 inhibition in macrophages.

Interleukin-34 (IL-34) is a cytokine that supports the viability and differentiation of macrophages. An important cytokine for the development of epidermal immunity, IL-34, is present and plays a role in the immunity of the oral environment. IL-34 has been linked to inflammatory periodontal diseases, which involve innate phagocytes, including macrophages. Whether IL-34 can alter the ability of macrophages to effectively interact with oral microbes is currently unclear. Using macrophages derived from human blood monocytes with either the canonical cytokine colony-stimulating factor (CSF)1 or IL-34, we compared the ability of the macrophages to phagocytose, kill, and respond through the production of cytokines to the periodontal keystone pathogen Porphyromonas gingivalis. While macrophages derived from both cytokines were able to engulf the bacterium equally, IL-34-derived macrophages were much less capable of killing internalized P.gingivalis. Of the macrophage cell surface receptors known to interact with P.gingivalis, dendritic cell-specific intercellular adhesion molecule-grabbing nonintegrin was found to have the largest variation between IL-34- and CSF1-derived macrophages. We also found that upon interaction with P.gingivalis, IL-34-derived macrophages produced significantly less of the neutrophil chemotactic factor IL-8 than macrophages derived in the presence of CSF1. Mechanistically, we identified that the levels of IL-8 corresponded with P. gingivalis survival and dephosphorylation of the major transcription factor NF-κB p65. Overall, we found that macrophages differentiated in the presence of IL-34, a dominant cytokine in the oral gingiva, have a reduced ability to kill the keystone pathogen P.gingivalis and may be susceptible to specific bacteria-mediated cytokine modification.

Depletion and Dysfunction of Dendritic Cells: Understanding SARS-CoV-2 Infection.

Uncontrolled severe acute respiratory syndrome-coronavirus (SARS-CoV)-2 infection is closely related to disorders of the innate immune and delayed adaptive immune systems. Dendritic cells (DCs) “bridge” innate immunity and adaptive immunity. DCs have important roles in defending against SARS-CoV-2 infection. In this review, we summarize the latest research concerning the role of DCs in SARS-CoV-2 infection. We focus on the complex interplay between DCs and SARS-CoV-2: pyroptosis-induced activation; activation of the renin–angiotensin–aldosterone system; and activation of dendritic cell-specific intercellular adhesion molecule 3-grabbing non-integrin. We also discuss the decline in DC number, the impaired antigen-presentation capability, and the reduced production of type-I interferon of DCs in severe SARS-CoV-2 infection. In addition, we discuss the potential mechanisms for pathological activation of DCs to understand the pattern of SARS-CoV-2 infection. Lastly, we provide a brief overview of novel vaccination and immunotherapy strategies based on DC targeting to overcome SARS-CoV-2 infection.

Fluid resuscitation via colon alleviates systemic inflammation in rats with early-stage severe acute pancreatitis

Fluid resuscitation via colon (FRVC) is a complementary therapeutic procedure for early-stage cases of severe acute pancreatitis (SAP). The expression of intestinal dendritic cell-specific intercellular adhesion molecule 3-grabbing nonintegrin (DC-SIGN) regulates systemic inflammation. This study aimed to investigate the effect of FRVC on the expression of DC-SIGN in the colon tissue of SAP rats and its effect on the early response of systemic inflammatory and multiple organ injury. SAP was induced in rats via retrograde injection of sodium taurocholate into the biliopancreatic duct. DC-SIGN expression of appeared in the proximal and distal colon. Histological characteristics and inflammatory cytokines were examined to compare the effect of FRVC and intravenous fluid resuscitation (IVFR). The results showed that DC-SIGN expression in the proximal colon increased in a time-dependent manner in the early-stage of SAP rats. FRVC inhibited DC-SIGN expression in the proximal colon. Both FRVC and IVFR alleviated histological injuries of the pancreas and colon. However, FRVC had an advantage over IVFR in alleviating lung injury and reducing serum TNF-α, IL-6 and LPS. These results suggest that FRVC treatment might help suppress systemic inflammation and prevent subsequent organ failure in early-stage SAP rats likely through inhibiting DC-SIGN expression in the proximal colon.

A Dendritic Cells-Targeting Nano-Vaccine by Coupling Polylactic-Co-Glycolic Acid-Encapsulated Allergen with Mannan Induces Regulatory T Cells

Background: The efficacy of allergen-specific immunotherapy (AIT) is mainly depended on the tolerogenic immune responses elicited. Properly conjugated nano-vaccine has the advantages of both specific targeting and continuous and on-demand release of allergen. Objectives: The aim of this study is to investigate the effects of a dendritic cells (DCs)-targeting nano-vaccine for AIT. Methods: The nano-vaccine was produced by coupling polylactic-co-glycolic acid (PLGA)-encapsulated ovalbumin (OVA) with mannan. Allergen capture, human monocytes-derived DCs (hMoDCs) activation, and T cells responses were assessed by flow cytometry, confocal microscopy, quantitative real-time PCR, ELISA, and Cytometric Bead Array. Balb/c mice were immunized with the nano-vaccines, and the immune responses were analyzed. Results: OVA-PLGA nanoparticle (NP) displayed favorable safety profile. OVA-mannan-PLGA NP was captured more efficiently by hMoDCs than OVA-PLGA NP, which was mediated mainly through DC-specific intercellular adhesion molecule 3-grabbing nonintegrin. A tolerogenic phenotype of hMoDCs was induced by OVA-mannan-PLGA NP, but not OVA-PLGA NP, and increased number of regulatory T (Treg) cells was generated subsequently in in vitro coculture. Immunization of Balb/c mice with OVA-mannan-PLGA NP resulted in lower serum level of OVA-specific immunoglobulins and less production of pro-inflammatory cytokines in splenocytes culture than the mice immunized with OVA-PLAG NP, PLGA NP, or OVA, while the number of splenic Treg cells was higher in OVA-mannan-PLGA group than in other groups. Moreover, preimmunization with OVA-mannan-PLGA NP significantly inhibited the Th2 immune response induced by OVA sensitization. Conclusions: The biocompatible PLGA-encapsulated OVA coupling with mannan has augmented ability for tolerance induction and could be developed as a novel vaccine for AIT.

Prominent Receptors of Liver Sinusoidal Endothelial Cells in Liver Homeostasis and Disease.

Liver sinusoidal endothelial cells (LSECs) are the most abundant non-parenchymal cells lining the sinusoidal capillaries of the hepatic system. LSECs are characterized with numerous fenestrae and lack basement membrane as well as a diaphragm. These unique morphological characteristics of LSECs makes them the most permeable endothelial cells of the mammalian vasculature and aid in regulating flow of macromolecules and small lipid-based structures between sinusoidal blood and parenchymal cells. LSECs have a very high endocytic capacity aided by scavenger receptors (SR), such as SR-A, SR-B (SR-B1 and CD-36), SR-E (Lox-1 and mannose receptors), and SR-H (Stabilins). Other high-affinity receptors for mediating endocytosis include the FcγRIIb, which assist in the antibody-mediated removal of immune complexes. Complemented with intense lysosomal activity, LSECs play a vital role in the uptake and degradation of many blood borne waste macromolecules and small (<280 nm) colloids. Currently, seven Toll-like receptors have been investigated in LSECs, which are involved in the recognition and clearance of pathogen-associated molecular pattern (PAMPs) as well as damage associated molecular pattern (DAMP). Along with other SRs, LSECs play an essential role in maintaining lipid homeostasis with the low-density lipoprotein receptor-related protein-1 (LRP-1), in juxtaposition with hepatocytes. LSECs co-express two surface lectins called L-Specific Intercellular adhesion molecule-3 Grabbing Non-integrin Receptor (L-SIGN) and liver sinusoidal endothelial cell lectin (LSECtin). LSECs also express several adhesion molecules which are involved in the recruitment of leukocytes at the site of inflammation. Here, we review these cell surface receptors as well as other components expressed by LSECs and their functions in the maintenance of liver homeostasis. We further discuss receptor expression and activity and dysregulation associated with the initiation and progression of many liver diseases, such as hepatocellular carcinoma, liver fibrosis, and cirrhosis, alcoholic and non-alcoholic fatty liver diseases and pseudocapillarization with aging.

Single-nucleotide polymorphisms in dendritic cell (dendritic cell-specific intercellular adhesion molecule 3-grabbing nonintegrin) gene of hepatocellular carcinoma patients from India.

Hepatocellular carcinoma (HCC) is one of the major causes of morbidity and mortality in the world. Numerous genomic and proteomic studies have been carried out across the globe to understand cancer biology related to HCC. Dendritic cell-specific intercellular adhesion molecule 3-grabbing nonintegrin (DC-SIGN) is also known as cluster of differentiation 209. The current study was designed to investigate the association of mutation in DC-SIGN promoter region in HCC patients and healthy controls and to analyze the association of these mutations as a risk factor for HCC development from India. total of 40 cases of HCC and 40 healthy controls without any underlying liver diseases were included in the study. A total of 5 ml of peripheral blood samples were collected, and genomic DNA was isolated using phenol-chloroform method. Polymerase chain reaction amplification was carried out for DC gene, and the amplicons were subjected to direct sequencing (Macrogen, Korea). Mutations were analyzed comparing these sequences with those published sequences from the database using bioinformatics software. A total of eight point mutations were observed in the HCC cases. The natures of mutation observed were deletion, transition, and transversion. All mutations were located in the 19th chromosome at nine different loci (51,079, 51,493, 51,561, 51,124, 51,125, 51,127, 51,169, 51,170, and 51,172). Mutation in the promoter region of the DC-SIGN gene may be a possible risk factor for the development of HCC in India. The findings of the study reveal the possible role of these mutants with HCC, and future large-scale prospective studies will further validate the findings of the current study.

DC-SIGN mediates gastric cancer progression by regulating the JAK2/STAT3 signaling pathway and affecting LncRNA RP11-181G12.2 expression

BackgroundThe molecular mechanisms of gastric cancer (GC) development are very complicated. Recent studies revealed that DC-specific intercellular adhesion molecule 3-grabbing nonintegrin (DC-SIGN)-related protein (DC-SIGNR) is involved in colon cancer and GC biological processes. However, the exact roles of DC-SIGN in GC remain unrevealed. MethodsDC-SIGN overexpression and knockdown experiments were performed by using DC-SIGN shRNA or DC-SIGN plasmid to investigate the biological roles of DC-SIGN in proliferation, cell cycle progression, migration and invasion of GC cells in vitro. Furthermore, the lncRNA profiles of SGC-7901 cells with control shRNA and DC-SIGN shRNA were generated by using microarray analysis. Mechanistically, the relationship between DC-SIGN, RP11-181G12.2 and the JAK2/STAT3 signaling pathway was then investigated using qRT-PCR and western blot assays. Additionally, we analyzed DC-SIGN and RP11-181G12.2 expression levels in GC specimens based on the Cancer Genome Atlas database. ResultsIn this study, the results showed that DC-SIGN was highly expressed in GC cells and significantly correlated with advanced clinical stage and lymphatic metastasis. Downregulation of DC-SIGN significantly inhibited the proliferation, cell cycle progression, migration and invasion of GC cells in vitro. The reverse results could partly be seen with the upregulation of DC-SIGN. Mechanistically, knockdown of DC-SIGN inactivated the JAK2/STAT3 signaling pathway, and overexpression of DC-SIGN activated the JAK2/STAT3 signaling pathway. In addition, through LncPath microarray analysis, we identified a lncRNA, RP11-181G12.2, that was significantly upregulated after knockdown of DC-SIGN; this was also confirmed by qRT-PCR. Furthermore, RP11-181G12.2 knockdown enhanced DC-SIGN expression in GC cells, further activating the JAK2/STAT3 signaling pathway. In contrast, DC-SIGN overexpression suppressed RP11-181G12.2 expression. ConclusionsOur study suggests that DC-SIGN might be involved in the progression of GC by regulating the JAK2/STAT3 signaling pathway and affecting lncRNA RP11-181G12.2 expression.

DC-SIGN Expression in Intestinal Epithelial Cells Regulates Sepsis-Associated Acute Intestinal Injury Via Activating ERK1/2-NF-κB/P65 Signaling.

The aim of the study was to investigate the role of dendritic cell-specific intercellular adhesion molecule 3-grabbing nonintegrin (DC-SIGN) in intestinal epithelial cells (IECs) in regulating sepsis-induced acute intestinal injury and systemic inflammatory response. To induce sepsis condition, Male C57BL/6 mice were exposed to cecal ligation and puncture (CLP) in vivo, whereas a normal human IECs line (FHs74Int) was stimulated with lipopolysaccharide (LPS) in vitro. DC-SIGN siRNA pretreatment was used to knock down DC-SIGN expression both in vivo and in vitro. The expression of DC-SIGN was detected by western blot and immunohistochemistry. The expression of total and phosphorylation of ERK1/2 and NF-κB/p65 was examined by western blot. The levels of cytokines in serum and culture supernatant were measured by ELISA. The survival rate and organ injures of septic mice were also assessed. In vivo, DC-SIGN expression in mouse IECs was time-dependently upregulated by CLP. CLP-induced phosphorylation of ERK1/2 and NF-κB/p65 was effectively inhibited by DC-SIGN siRNA pretreatment, leading to the decrease of systemic inflammatory cytokines (TNF-α, IL-1β, IL-6, IL-10, and IFN-γ), which alleviated multiple organ injuries and increased the survival rate of septic mice. In vitro, DC-SIGN expression in FHs74Int was significantly upregulated by LPS stimulation in a time- and dose-dependent manner. DC-SIGN knockdown abolished LPS-induced ERK1/2 and NF-κB/p65 phosphorylation, resulting in the decrease of cytokines release by FHs74Int. Sepsis-induced DC-SIGN expression in IECs plays a significant role in regulating acute intestinal injury and systemic inflammatory response. The inhibition of DC-SIGN exhibited protective effects on sepsis-associated organ injury and systemic inflammation.

Serum Amyloid P and a Dendritic Cell–Specific Intercellular Adhesion Molecule-3–Grabbing Nonintegrin Ligand Inhibit High-Fat Diet–Induced Adipose Tissue and Liver Inflammation and Steatosis in Mice

High-fat diet (HFD)-induced inflammation is associated with a variety of health risks. The systemic pentraxin serum amyloid P (SAP) inhibits inflammation. SAP activates the high-affinity IgG receptor Fcγ receptor I (FcγRI; CD64) and the lectin receptor dendritic cell-specific intercellular adhesion molecule-3-grabbing nonintegrin (DC-SIGN; CD209). Herein, we show that for mice on an HFD, injections of SAP and a synthetic CD209 ligand (1866) reduced HFD-increased adipose and liver tissue inflammation, adipocyte differentiation, and lipid accumulation in adipose tissue. HFD worsened glucose tolerance test results and caused increased adipocyte size; for mice on an HFD, SAP improved glucose tolerance test results and reduced adipocyte size. Mice on an HFD had elevated serum levels of IL-1β, IL-23, interferon (IFN)-β, IFN-γ, monocyte chemoattractant protein 1 [MCP-1; chemokine (C-C motif) ligand 2 (CCL2)], and tumor necrosis factor-α. SAP reduced serum levels of IL-23, IFN-β, MCP-1, and tumor necrosis factor-α, whereas 1866 reduced IFN-γ. Invitro, SAP, but not 1866, treated cells isolated from white fat tissue (stromal vesicular fraction) produced the anti-inflammatory cytokine IL-10. HFD causes steatosis, and both SAP and 1866 reduced it. Conversely, compared with control mice, SAP knockout mice fed on a normal diet had increased white adipocyte cell sizes, increased numbers of inflammatory cells in adipose and liver tissue, and steatosis; and these effects were exacerbated on an HFD. SAPand1866 may inhibit some, but not all, of the effects of a high-fat diet.

Evaluation of polymorphisms in inflammatory mediator and cellular adhesion genes as risk factors for feline infectious peritonitis.

Feline infectious peritonitis (FIP) is a high mortality infectious disease. Single nucleotide polymorphisms (SNPs) in the genes encoding interferon gamma (IFNG), tumour necrosis factor alpha (TNFA) and dendritic cell-specific intercellular adhesion molecule-grabbing non-integrin (DC-SIGN; CD209) have been associated with increased and decreased risk of developing FIP. This study was designed to determine whether these associations were present in a UK population of pedigree cats using samples from cats euthanased with a confirmed diagnosis (FIP, n = 22; non-FIP, n = 10) or clinically healthy cats over 11 years of age (n = 3). DNA was extracted from tissue (n = 32) or blood (n = 3) and PCR performed for regions of IFNG, TNFA and CD209. PCR amplicons were sequenced, each SNP genotype was determined, and genotype/allele frequency for each SNP and FIP status were compared. No significant association was found between the genotype and FIP status for any SNP analysed. There was a trend for the heterozygous CT genotype at both IFNG g.401 and IFNG g.408 to be associated with FIP (P = 0.13), but this genotype was also found in a substantial proportion of non-FIP cats. There was also a trend for the heterozygous CT genotype at IFNG g.428 to be associated with FIP (P = 0.06), although most cats with FIP had the CC genotype at this locus. No associations were found between any allele at TNFA g.-421, CD209 g.1900, CD209 g.2276, CD209 g.2392 and CD209 g.2713 and FIP. The use of the IFNG, TNFA and CD209 SNPs described to predict the risk of FIP cannot currently be recommended.

Unraveling Sugar Binding Modes to DC-SIGN by Employing Fluorinated Carbohydrates.

A fluorine nuclear magnetic resonance (19F-NMR)-based method is employed to assess the binding preferences and interaction details of a library of synthetic fluorinated monosaccharides towards dendritic cell-specific intercellular adhesion molecule 3-grabbing non-integrin (DC-SIGN), a lectin of biomedical interest, which is involved in different viral infections, including HIV and Ebola, and is able to recognize a variety of self- and non-self-glycans. The strategy employed allows not only screening of a mixture of compounds, but also obtaining valuable information on the specific sugar–protein interactions. The analysis of the data demonstrates that monosaccharides Fuc, Man, Glc, and Gal are able to bind DC-SIGN, although with decreasing affinity. Moreover, a new binding mode between Man moieties and DC-SIGN, which might have biological implications, is also detected for the first time. The combination of the 19F with standard proton saturation transfer difference (1H-STD-NMR) data, assisted by molecular dynamics (MD) simulations, permits us to successfully define this new binding epitope, where Man coordinates a Ca2+ ion of the lectin carbohydrate recognition domain (CRD) through the axial OH-2 and equatorial OH-3 groups, thus mimicking the Fuc/DC-SIGN binding architecture.

Is asthma a protective factor for dengue fever? In vitro experiment and nationwide population-based cohort analysis

BackgroundDengue fever (DF) is the most rapidly spreading mosquito-borne viral disease. Practical vaccines or specific therapeutics are still expected. Environmental factors and genetic factors affect the susceptibility of Dengue virus (DV) infection. Asthma is a common allergic disease, with house dust mites (HDMs) being the most important allergens. Asthmatic patients are susceptible to several microorganism infections. MethodsA nationwide population-based cohort analysis was designed to assess whether to determine whether asthma can be a risk factor for DF. ResultsUnexpectedly, our data from a nationwide population-based cohort revealed asthmatic patients are at a decreased risk of DF. Compared to patients without asthma, the hazard ratio (HR) for DF in patients with asthma was 0.166 (95% CI: 0.118–0.233) after adjustment for possible confounding factors. In the age stratification, the adjusted HR for DF in young adult patients with asthma was 0.063. Dendritic cell-specific intercellular adhesion molecule 3-grabbing non-integrin (DC-SIGN) of dendritic cells (DCs) is an important entry for DV. Through another in vitro experiment, we found that HDM can diminish surface expression of DC-SIGN in monocyte-derived DCs and further decrease the cellular entry of DV. ConclusionsDecreased DC-SIGN expression in DCs of allergic asthmatic patient may be one of many factors for them to be protected against DF. This could implicate the potential for DC-SIGN modulation as a candidate target for designing therapeutic strategies for DF.

Surface (S) Layer Proteins of Lactobacillus acidophilus Block Virus Infection via DC-SIGN Interaction.

Alphaviruses and flaviviruses are important human pathogens that include Chikungunya virus (CHIKV), Dengue virus (DENV), and Zika virus (ZIKV), which can cause diseases in humans ranging from arthralgia to hemorrhagic fevers and microcephaly. It was previously shown that treatment with surface layer (S-layer) protein, present on the bacterial cell-envelope of Lactobacillus acidophilus, is able to inhibit viral and bacterial infections by blocking the pathogen’s interaction with DC-specific intercellular adhesion molecule 3-grabbing non-integrin (DC-SIGN), a trans-membrane protein that is a C-type calcium-dependent lectin. DC-SIGN is known to act as an attachment factor for several viruses including alphaviruses and flaviviruses. In the present study, we used alphaviruses as a model system to dissect the mechanism of S-layer inhibition. We first evaluated the protective effect of S-layer using 3T3 cells, either wild type or stably expressing DC-SIGN, and infecting with the alphaviruses Semliki Forest virus (SFV) and CHIKV and the flaviviruses ZIKV and DENV. DC-SIGN expression significantly enhanced infection by all four viruses. Treatment of the cells with S-layer prior to infection decreased infectivity of all viruses only in cells expressing DC-SIGN. In vitro ELISA experiments showed a direct interaction between S-layer and DC-SIGN; however, confocal microscopy and flow cytometry demonstrated that S-layer binding to the cells was independent of DC-SIGN expression. S-layer protein prevented SFV binding and internalization in DC-SIGN-expressing cells but had no effect on virus binding to DC-SIGN-negative cells. Inhibition of virus binding occurred in a time-dependent manner, with a significant reduction of infection requiring at least a 30-min pre-incubation of S-layer with DC-SIGN-expressing cells. These results suggest that S-layer has a different mechanism of action compared to mannan, a common DC-SIGN-binding compound that has an immediate effect in blocking viral infection. This difference could reflect slower kinetics of S-layer binding to the DC-SIGN present at the plasma membrane (PM). Alternatively, the S-layer/DC-SIGN interaction may trigger the activation of signaling pathways that are required for the inhibition of viral infection. Together our results add important information relevant to the potential use of L. acidophilus S-layer protein as an antiviral therapy.

C-Type Lectin Receptors in Asthma.

Asthma is a heterogeneous disease that affects approximately 300 million people worldwide, largely in developed countries. The etiology of the disease is poorly understood, but is likely to involve specific innate and adaptive responses to inhaled microbial components that are found in allergens. Fungal-derived allergens represent a major contributing factor in the initiation, persistence, exacerbation, and severity of allergic asthma. C-type lectin like receptors, such as dectin-1, dectin-2, DC-specific intercellular adhesion molecule 3-grabbing nonintegrin, and mannose receptor, recognize many fungal-derived allergens and other structurally similar allergens derived from house dust mites (HDM). In some cases, the fungal derived allergens have been structurally and functionally identified alongside their respective receptors in both humans and mice. In this review, we discuss recent understanding on how selected fungal and HDM derived allergens as well as their known or unknown receptors shape allergic airway diseases.

DC-SIGN reacts with TLR-4 and regulates inflammatory cytokine expression via NF-κB activation in renal tubular epithelial cells during acute renal injury.

In the pathological process of acute kidney injury (AKI), innate immune receptors are essential in inflammatory response modulation; however, the precise molecular mechanisms are still unclear. Our study sought to demonstrate the inflammatory response mechanisms in renal tubular epithelial cells via Toll-like receptor-4 (TLR-4) and dendritic cell-specific intercellular adhesion molecule 3-grabbing non-integrin 1 (DC-SIGN) signalling. We found that DC-SIGN exhibited strong expression in renal tubular epithelial cells of human acute renal injury tissues. DC-SIGN protein expression was increased significantly when renal tubular epithelial cells were exposed to lipopolysaccharide (LPS) for a short period. Furthermore, DC-SIGN was involved in the activation of p65 by TLR-4, which excluded p38 and c-Jun N-terminal kinases (JNK). Interleukin (IL)-6 and tumour necrosis factor (TNF)-α expression was decreased after DC-SIGN knock-down, and LPS induced endogenous interactions and plasma membrane co-expression between TLR-4 and DC-SIGN. These results show that DC-SIGN and TLR-4 interactions regulate inflammatory responses in renal tubular epithelial cells and participate in AKI pathogenesis.

Bovine Lactoferrin Inhibits Dengue Virus Infectivity by Interacting with Heparan Sulfate, Low-Density Lipoprotein Receptor, and DC-SIGN.

Bovine lactoferrin (bLF) presents in milk and has been shown to inhibit several viral infections. Effective drugs are unavailable for the treatment of dengue virus (DENV) infection. In this study, we evaluated the antiviral effect of bLF against DENV infection in vivo and in vitro. Bovine LF significantly inhibited the infection of the four serotypes of DENV in Vero cells. In the time-of-drug addition test, DENV-2 infection was remarkably inhibited when bLF was added during or prior to the occurrence of virus attachment. We also revealed that bovine LF blocks binding between DENV-2 and the cellular membrane by interacting with heparan sulfate (HS), dendritic cell-specific intercellular adhesion molecule 3-grabbing non-integrin (DC-SIGN), and low-density lipoprotein receptors (LDLR). In addition, bLF inhibits DENV-2 infection and decreases morbidity in a suckling mouse challenge model. This study supports the finding that bLF may inhibit DENV infection by binding to the potential DENV receptors.

Lactobacillus reuteri Surface Mucus Adhesins Upregulate Inflammatory Responses Through Interactions With Innate C-Type Lectin Receptors.

The vertebrate gut symbiont Lactobacillus reuteri exhibits strain-specific adhesion and health-promoting properties. Here, we investigated the role of the mucus adhesins, CmbA and MUB, upon interaction of L. reuteri ATCC PTA 6475 and ATCC 53608 strains with human monocyte-derived dendritic cells (moDCs). We showed that mucus adhesins increased the capacity of L. reuteri strains to interact with moDCs and promoted phagocytosis. Our data also indicated that mucus adhesins mediate anti- and pro-inflammatory effects by the induction of interleukin-10 (IL-10), tumor necrosis factor alpha (TNF-α), IL-1β, IL-6, and IL-12 cytokines. L. reuteri ATCC PTA 6475 and ATCC 53608 were exclusively able to induce moDC-mediated Th1 and Th17 immune responses. We further showed that purified MUB activates moDCs and induces Th1 polarized immune responses associated with increased IFNγ production. MUB appeared to mediate these effects via binding to C-type lectin receptors (CLRs), as shown using cell reporter assays. Blocking moDCs with antibodies against DC-specific intercellular adhesion molecule 3-grabbing non-integrin (DC-SIGN) or Dectin-2 did not affect the uptake of the MUB-expressing strain, but reduced the production of TNF-α and IL-6 by moDCs significantly, in line with the Th1 polarizing capacity of moDCs. The direct interaction between MUB and CLRs was further confirmed by atomic force spectroscopy. Taken together these data suggest that mucus adhesins expressed at the cell surface of L. reuteri strains may exert immunoregulatory effects in the gut through modulating the Th1-promoting capacity of DCs upon interaction with C-type lectins.