Dendritic cells: functional aspects of glycosylation and lectins

Novel genetically glycoengineered human dendritic cell model reveals regulatory roles of α2,6-linked sialic acids in DC activation of CD4+ T cells and response to TNFα

Dendritic cells (DCs) are central for the initiation and regulation of appropriate immune responses. While several studies suggest important regulatory roles of sialoglycans in DC biology, our understanding is still inadequate primarily due to a lack of appropriate models. Previous approaches based on enzymatic- or metabolic-glycoengineering and primary cell isolation from genetically modified mice have limitations related to specificity, stability, and species differences. This study addresses these challenges by introducing a workflow to genetically glycoengineer the human DC precursor cell line MUTZ-3, described to differentiate and maturate into fully functional dendritic cells, using CRISPR-Cas9, thereby providing and validating the first isogenic cell model for investigating glycan alteration on human DC differentiation, maturation, and activity. By knocking out (KO) the ST6GAL1 gene, we generated isogenic cells devoid of ST6GAL1-mediated α(2,6)-linked sialylation, allowing for a comprehensive investigation into its impact on DC function. Glycan profiling using lectin binding assay and functional studies revealed that ST6GAL1 KO increased the expression of important antigen presenting and co-stimulatory surface receptors and a specifically increased activation of allogenic human CD4 + T cells. Additionally, ST6GAL1 KO induces significant changes in surface marker expression and cytokine response to TNFα-induced maturation, and it affects migration and the endocytic capacity. These results indicate that genetic glycoengineering of the isogenic MUTZ-3 cellular model offers a valuable tool to study how specific glycan structures influence human DC biology, contributing to our understanding of glycoimmunology.

Protein glycosylation: bridging maternal-fetal crosstalk during embryo implantation†

Infertility is a challenging health problem that affects 8-15% of couples worldwide. Establishing pregnancy requires successful embryo implantation, but about 85% of unsuccessful pregnancies are due to embryo implantation failure or loss soon after. Factors crucial for successful implantation include invasive blastocysts, receptive endometrium, invasion of trophoblast cells, and regulation of immune tolerance at the maternal-fetal interface. Maternal-fetal crosstalk, which relies heavily on protein-protein interactions, is a critical factor in implantation that involves multiple cellular communication and molecular pathways. Glycosylation, a protein modification process, is closely related to cell growth, adhesion, transport, signal transduction, and recognition. Protein glycosylation plays a crucial role in maternal-fetal crosstalk and can be divided into N-glycosylation and O-glycosylation, which are often terminated by sialylation or fucosylation. This review article examines the role of protein glycosylation in maternal-fetal crosstalk based on two transcriptome datasets from the GEO database (GSE139087 and GSE113790) and existing research, particularly in the context of the mechanism of protein glycosylation and embryo implantation. Dysregulation of protein glycosylation can lead to adverse pregnancy outcomes, such as missed abortion and recurrent spontaneous abortion, underscoring the importance of a thorough understanding of protein glycosylation in the diagnosis and treatment of female reproductive disorders. This knowledge could have significant clinical implications, leading to the development of more effective diagnostic and therapeutic approaches for these conditions.

Entry receptors - the gateway to alphavirus infection

Alphaviruses are enveloped, insect-transmitted, positive-sense RNA viruses that infect humans and other animals and cause a range of clinical manifestations, including arthritis, musculoskeletal disease, meningitis, encephalitis, and death. Over the past four years, aided by CRISPR/Cas9-based genetic screening approaches, intensive research efforts have focused on identifying entry receptors for alphaviruses to better understand the basis for cellular and species tropism. Herein, we review approaches to alphavirus receptor identification and how these were used for discovery. The identification of new receptors advances our understanding of viral pathogenesis, tropism, and evolution and is expected to contribute to the development of novel strategies for prevention and treatment of alphavirus infection.

Seminal Plasma Glycoproteins as Potential Ligands of Lectins Engaged in Immunity Regulation

Environmental pollution, chronic stress, and unhealthy lifestyle are factors that negatively affect reproductive potential. Currently, 15-20% of couples in industrialized countries face the problem of infertility. This growing health and social problem prompts researchers to explore the regulatory mechanisms that may be important for successful fertilization. In recent years, more attention has been paid to male infertility factors, including the impact of seminal plasma components on regulation of the female immune response to allogenic sperm, embryo and fetal antigens. Directing this response to the tolerogenic pathway is crucial to achieve a healthy pregnancy. According to the fetoembryonic defense hypothesis, the regulatory mechanism may be associated with the interaction of lectins and immunomodulatory glycoepitopes. Such interactions may involve lectins of dendritic cells and macrophages, recruited to the cervical region immediately after intercourse. Carbohydrate binding receptors include C type lectins, such as DC-SIGN and MGL, as well as galectins and siglecs among others. In this article we discuss the expression of the possible lectin ligands, highly fucosylated and high mannose structures, which may be recognized by DC-SIGN, glycans of varying degrees of sialylation, which may differ in their interaction with siglecs, as well as T and Tn antigens in O-glycans.

The fungal Clitocybe nebularis lectin binds distinct cell surface glycoprotein receptors to induce cell death selectively in Jurkat cells

Clitocybe nebularis lectin (CNL) is a GalNAcβ1-4GlcNAc-binding lectin that exhibits an antiproliferative effect exclusively on the Jurkat leukemic T cell line by provoking homotypic aggregation and dose-dependent cell death. Cell death of Jurkat cells exhibited typical features of early apoptosis, but lacked the activation of initiating and executing caspases. None of the features of CNL-induced cell death were effectively blocked with the pan-caspase inhibitor or different cysteine peptidase inhibitors. Furthermore, CNL binding induced Jurkat cells to release the endogenous damage-associated molecular pattern molecule high-mobility group box 1 (HMGB1). A plant lectin with similar glycan-binding specificity, Wisteria floribunda agglutinin (WFA) showed less selective toxicity and induced cell death in Jurkat, Tall-104, and Hut-87 cell lines. HMGB1 release was also detected when Jurkat cells were treated with WFA. We identified the CD45 and CD43 cell surface glycoproteins on Jurkat cells as the main targets for CNL binding. However, the blockade of CD45 phosphatase activity failed to block either CNL-induced homotypic agglutination or cell death. Overall, our results indicate that CNL triggers atypical cell death selectively on Jurkat cells, suggesting the potential applicability of CNL in novel strategies for treating and/or detecting acute T cell leukemia.

96-well plate format in conjunction with ultra-high-performance liquid chromatography coupled to orbitrap mass spectrometry for high-throughput screening protein binders from ginseng

Conventional strategies for screening of protein binders cannot be used for complicated samples such as ligand libraries created by combinatorial chemistry or from natural product extracts. In the current study, we developed a novel method in a competitive binding configuration for screening protein binders from complicated samples by a combination of streptavidin-coated 96-well plate format in conjunction with ultra-high-performance liquid chromatography coupled with Orbitrap mass spectrometry (UHPLC-Orbitrap-MS). The concanavalin A (Con A) modified 96-well plate and lysozyme modified 96-well plate (as control) were incubated with oligosaccharide standards respectively, and the compounds with the decreased peak areas in experimental group compared to those in the control group were detected as binders by UHPLC-ESI-MS. The factors such as incubation time, incubation temperature, and buffer, which might affect the binding affinity and reproducibility were optimized. The potential of the approach is examined using the extracts of Radix ginseng cruda and American ginseng. The relative binding degrees (RBDs) of the detected disaccharides were relatively high in the extracts of Radix ginseng cruda, and those of the trisaccharides were similar in the extracts of the two kinds of ginseng. To our knowledge, it's the first time to reveal the differences and analogies in lectin peanut agglutinin (PNA)-binding capabilities of oligosaccharides between the extracts of radix ginseng cruda and American ginseng, indicating the efficiency of the method for analysis of complicated samples.

Synthesis of bodipy-labeled bacterial polysaccharides and their interaction with human dendritic cells

In this report, we describe the fluorescent labeling of bacterial polysaccharides (Escherichia coli O86:B7, Escherichia coli O19ab, Pseudomonas aeruginosa O10a10b, and Shigella flexneri 2b) at the "natural" amino group of their phosphoethanolamine moiety. Two protocols for labeling are compared: 1) on a scale of a few mg of the polysaccharide, with a dialysis procedure for purification from excessive reagents; and 2) on a scale of 0.1 mg of the polysaccharide, with a simple precipitation procedure instead of dialysis. The microscale version is sufficient for comfortable cytofluorometric analysis. The resulting probes were found to specifically bind to human dendritic cells in a dose-dependent manner. The used limited set of polysaccharides did not allow us even to get close to understanding which dendritic cell-associated lectins and which cognate polysaccharide epitopes are involved in recognition, but the proposed microscale protocol allows to generate a library of fluorescent probes for further mapping of the polysaccharide specificity of the dendritic cells.

A molecular understanding of alphavirus entry

Alphaviruses cause severe human illnesses including persistent arthritis and fatal encephalitis. As alphavirus entry into target cells is the first step in infection, intensive research efforts have focused on elucidating aspects of this pathway, including attachment, internalization, and fusion. Herein, we review recent developments in the molecular understanding of alphavirus entry both in vitro and in vivo and how these advances might enable the design of therapeutics targeting this critical step in the alphavirus life cycle.

Increased CD83 expression of CD34-positive monocytes in donors during peripheral blood stem cell mobilization in humans

CD34-positive monocytes (CD34+mono) have recently been identified in grafts mobilized by granulocyte-colony stimulating factor. We analyzed transplant outcomes of 73 patients whose donor's peripheral blood cells were cryopreserved during mobilization. CD34+mono was detected more frequently in male donors (67% vs. 40%, P = 0.03), while the detection of CD34+mono in donors was not associated with the patient background. Although there was no significant difference in overall survival in the whole cohort, the detection of CD34+mono in donors were significantly associated with a decreased risk of non-relapse mortality (HR 0.23, P = 0.035). Fatal infectious events tended to be less frequent in donors with CD34+mono. Gene expression profile analyses of CD34+mono in humans revealed that the expressions of pro-inflammatory cytokines like IL6, CCL3, IL8, VEGFA, and IL1A were elevated in CD34+mono, and those cytokines were enriched in the immune response, especially against infectious pathogens in the gene ontology analyses. In addition, the expression of CD83 was specifically increased in CD34+mono. It might play a role of antigen presentation in the immune network, leading in a clinical benefit against infections. Further investigations will be required to confirm the biological functions and clinical roles of CD34+mono in transplantation.

Regulation of peripheral and central immunity: Understanding the role of Src homology 2 domain-containing tyrosine phosphatases, SHP-1 & SHP-2

Protein tyrosine phosphorylation is a potent post-translational regulatory mechanism necessary for maintaining normal physiological functioning of immune cells and it is under the stringent control of antagonizing actions of Protein tyrosine phosphatases and kinases. Two such important Non-Receptor protein tyrosine phosphatases, SHP-1 and SHP-2, have been found to be expressed in immune cells and reported to be key regulators of immune cell development, functions, and differentiation by modulating the duration and amplitude of the downstream cascade transduced via receptors. They also have been conceded as the immune checkpoints & therapeutic targets and hence, it is important to understand their significance intricately. This review compares the roles of these two important cytoplasmic PTPs, SHP1 & SHP-2 in the regulation of peripheral as well as central immunity.

Dendritic cells and the extracellular matrix: A challenge for maintaining tolerance/homeostasis

The importance of the extracellular matrix (ECM) in contributing to structural, mechanical, functional and tissue-specific features in the body is well appreciated. While the ECM was previously considered to be a passive bystander, it is now evident that it plays active, dynamic and flexible roles in shaping cell survival, differentiation, migration and death to varying extents depending on the specific site in the body. Dendritic cells (DCs) are recognized as potent antigen presenting cells present in many tissues and in blood, continuously scrutinizing the microenvironment for antigens and mounting local and systemic host responses against harmful agents. DCs also play pivotal roles in maintaining homeostasis to harmless self-antigens, critical for preventing autoimmunity. What is less understood are the complex interactions between DCs and the ECM in maintaining this balance between steady-state tissue residence and DC activation during inflammation. DCs are finely tuned to inflammation-induced variations in fragment length, accessible epitopes and post-translational modifications of individual ECM components and correspondingly interpret these changes appropriately by adjusting their profiles of cognate binding receptors and downstream immune activation. The successful design and composition of novel ECM-based mimetics in regenerative medicine and other applications rely on our improved understanding of DC-ECM interplay in homeostasis and the challenges involved in maintaining it.

Galectin-1 regulates tissue exit of specific dendritic cell populations

During inflammation, dendritic cells emigrate from inflamed tissue across the lymphatic endothelium into the lymphatic vasculature and travel to regional lymph nodes to initiate immune responses. However, the processes that regulate dendritic cell tissue egress and migration across the lymphatic endothelium are not well defined. The mammalian lectin galectin-1 is highly expressed by vascular endothelial cells in inflamed tissue and has been shown to regulate immune cell tissue entry into inflamed tissue. Here, we show that galectin-1 is also highly expressed by human lymphatic endothelial cells, and deposition of galectin-1 in extracellular matrix selectively regulates migration of specific human dendritic cell subsets. The presence of galectin-1 inhibits migration of immunogenic dendritic cells through the extracellular matrix and across lymphatic endothelial cells, but it has no effect on migration of tolerogenic dendritic cells. The major galectin-1 counter-receptor on both dendritic cell populations is the cell surface mucin CD43; differential core 2 O-glycosylation of CD43 between immunogenic dendritic cells and tolerogenic dendritic cells appears to contribute to the differential effect of galectin-1 on migration. Binding of galectin-1 to immunogenic dendritic cells reduces phosphorylation and activity of the protein-tyrosine kinase Pyk2, an effect that may also contribute to reduced migration of this subset. In a murine lymphedema model, galectin-1(-/-) animals had increased numbers of migratory dendritic cells in draining lymph nodes, specifically dendritic cells with an immunogenic phenotype. These findings define a novel role for galectin-1 in inhibiting tissue emigration of immunogenic, but not tolerogenic, dendritic cells, providing an additional mechanism by which galectin-1 can dampen immune responses.

A universal chemical enrichment method for mapping the yeast N-glycoproteome by mass spectrometry (MS)

Glycosylation is one of the most common and important protein modifications in biological systems. Many glycoproteins naturally occur at low abundances, which makes comprehensive analysis extremely difficult. Additionally, glycans are highly heterogeneous, which further complicates analysis in complex samples. Lectin enrichment has been commonly used, but each lectin is inherently specific to one or several carbohydrates, and thus no single or collection of lectin(s) can bind to all glycans. Here we have employed a boronic acid-based chemical method to universally enrich glycopeptides. The reaction between boronic acids and sugars has been extensively investigated, and it is well known that the interaction between boronic acid and diols is one of the strongest reversible covalent bond interactions in an aqueous environment. This strong covalent interaction provides a great opportunity to catch glycopeptides and glycoproteins by boronic acid, whereas the reversible property allows their release without side effects. More importantly, the boronic acid-diol recognition is universal, which provides great capability and potential for comprehensively mapping glycosylation sites in complex biological samples. By combining boronic acid enrichment with PNGase F treatment in heavy-oxygen water and MS, we have identified 816 N-glycosylation sites in 332 yeast proteins, among which 675 sites were well-localized with greater than 99% confidence. The results demonstrated that the boronic acid-based chemical method can effectively enrich glycopeptides for comprehensive analysis of protein glycosylation. A general trend seen within the large data set was that there were fewer glycosylation sites toward the C termini of proteins. Of the 332 glycoproteins identified in yeast, 194 were membrane proteins. Many proteins get glycosylated in the high-mannose N-glycan biosynthetic and GPI anchor biosynthetic pathways. Compared with lectin enrichment, the current method is more cost-efficient, generic, and effective. This method can be extensively applied to different complex samples for the comprehensive analysis of protein glycosylation.

Dendritic cells: a spot on sialic Acid

Glycans decorating cell surface and secreted proteins and lipids occupy the juncture where critical host–host and host-pathogen interactions occur. The role of glycan epitopes in cell–cell and cell-pathogen adhesive events is already well-established, and cell surface glycan structures change rapidly in response to stimulus and inflammatory cues. Despite the wide acceptance that glycans are centrally implicated in immunity, exactly how glycans and their changes contribute to the overall immune response remains poorly defined. Sialic acids are unique sugars that usually occupy the terminal position of the glycan chains and may be modified by external factors, such as pathogens, or upon specific physiological cellular events. At cell surface, sialic acid-modified structures form the key fundamental determinants for a number of receptors with known involvement in cellular adhesiveness and cell trafficking, such as the Selectins and the Siglec families of carbohydrate recognizing receptors. Dendritic cells (DCs) preside over the transition from innate to the adaptive immune repertoires, and no other cell has such relevant role in antigen screening, uptake, and its presentation to lymphocytes, ultimately triggering the adaptive immune response. Interestingly, sialic acid-modified structures are involved in all DC functions, such as antigen uptake, DC migration, and capacity to prime T cell responses. Sialic acid content changes along DC differentiation and activation and, while, not yet fully understood, these changes have important implications in DC functions. This review focuses on the developmental regulation of DC surface sialic acids and how manipulation of DC surface sialic acids can affect immune-critical DC functions by altering antigen endocytosis, pathogen and tumor cell recognition, cell recruitment, and capacity for T cell priming. The existing evidence points to a potential of DC surface sialylation as a therapeutic target to improve and diversify DC-based therapies.

Weighted set enrichment of gene expression data

Background

Sets of genes that are known to be associated with each other can be used to interpret microarray data. This gene set approach to microarray data analysis can illustrate patterns of gene expression which may be more informative than analyzing the expression of individual genes. Various statistical approaches exist for the analysis of gene sets. There are three main classes of these methods: over-representation analysis, functional class scoring, and pathway topology based methods.

Methods

We propose weighted hypergeometric and weighted chi-squared methods in order to assign a rank to the degree to which each gene participates in the enrichment. Each gene is assigned a weight determined by the absolute value of its log fold change, which is then raised to a certain power. The power value can be adjusted as needed. Datasets from the Gene Expression Omnibus are used to test the method. The significantly enriched pathways are validated through searching the literature in order to determine their relevance to the dataset.

Results

Although these methods detect fewer significantly enriched pathways, they can potentially produce more relevant results. Furthermore, we compare the results of different enrichment methods on a set of microarray studies all containing data from various rodent neuropathic pain models.

Discussion

Our method is able to produce more consistent results than other methods when evaluated on similar datasets. It can also potentially detect relevant pathways that are not identified by the standard methods. However, the lack of biological ground truth makes validating the method difficult.

Gene expression signatures defining fundamental biological processes in pluripotent, early, and late differentiated embryonic stem cells

Investigating the molecular mechanisms controlling the in vivo developmental program postembryogenesis is challenging and time consuming. However, the developmental program can be partly recapitulated in vitro by the use of cultured embryonic stem cells (ESCs). Similar to the totipotent cells of the inner cell mass, gene expression and morphological changes in cultured ESCs occur hierarchically during their differentiation, with epiblast cells developing first, followed by germ layers and finally somatic cells. Combination of high throughput -omics technologies with murine ESCs offers an alternative approach for studying developmental processes toward organ-specific cell phenotypes. We have made an attempt to understand differentiation networks controlling embryogenesis in vivo using a time kinetic, by identifying molecules defining fundamental biological processes in the pluripotent state as well as in early and the late differentiation stages of ESCs. Our microarray data of the differentiation of the ESCs clearly demonstrate that the most critical early differentiation processes occur at days 2 and 3 of differentiation. Besides monitoring well-annotated markers pertinent to both self-renewal and potency (capacity to differentiate to different cell lineage), we have identified candidate molecules for relevant signaling pathways. These molecules can be further investigated in gain and loss-of-function studies to elucidate their role for pluripotency and differentiation. As an example, siRNA knockdown of MageB16, a gene highly expressed in the pluripotent state, has proven its influence in inducing differentiation when its function is repressed.

Microbiota and dietary interactions: an update to the hygiene hypothesis?

The dramatic increase in the incidence and severity of allergy and asthma has been proposed to be linked with an altered exposure to, and colonization by, micro-organisms, particularly early in life. However, other lifestyle factors such as diet and physical activity are also thought to be important, and it is likely that multiple environmental factors with currently unrecognized interactions contribute to the atopic state. This review will focus on the potential role of microbial metabolites in immunoregulatory functions and highlights the known molecular mechanisms, which may mediate the interactions between diet, microbiota, and protection from allergy and asthma.

The glycosylation pattern of common allergens: the recognition and uptake of Der p 1 by epithelial and dendritic cells is carbohydrate dependent

Allergens are initiators of both innate and adaptive immune responses. They are recognised at the site of entry by epithelial and dendritic cells (DCs), both of which activate innate inflammatory circuits that can collectively induce Th2 immune responses. In an attempt to have a better understanding of the role of carbohydrates in the recognition and uptake of allergens by the innate immune system, we defined common glycosylation patterns in major allergens. This was done using labelled lectins and showed that allergens like Der p 1 (Dermatophagoides pteronyssinus group 1), Fel d 1 (Felis domisticus), Ara h 1 (Arachis hypogaea), Der p 2 (Dermatophagoides pteronyssinus group 2), Bla g 2 (Blattella germanica) and Can f 1 (Canis familiaris) are glycosylated and that the main dominant sugars on these allergens are 1-2, 1-3 and 1-6 mannose. These observations are in line with recent reports implicating the mannose receptor (MR) in allergen recognition and uptake by DCs and suggesting a major link between glycosylation and allergen recognition. We then looked at TSLP (Thymic Stromal Lymphopoietin) cytokine secretion by lung epithelia upon encountering natural Der p 1 allergen. TSLP is suggested to drive DC maturation in support of allergic hypersensitivity reactions. Our data showed an increase in TSLP secretion by lung epithelia upon stimulation with natural Der p 1 which was carbohydrate dependent. The deglycosylated preparation of Der p 1 exhibited minimal uptake by DCs compared to the natural and hyperglycosylated recombinant counterparts, with the latter being taken up more readily than the other preparations. Collectively, our data indicate that carbohydrate moieties on allergens play a vital role in their recognition by innate immune cells, implicating them in downstream deleterious Th2 cell activation and IgE production.

CNL, a ricin B-like lectin from mushroom Clitocybe nebularis, induces maturation and activation of dendritic cells via the toll-like receptor 4 pathway

A novel lectin, isolated from the basidiomycete mushroom Clitocybe nebularis and termed C. nebularis lectin (CNL), exhibits an immunostimulatory effect on the most potent antigen-presenting cells, the dendritic cells (DCs). Treatment of human monocyte-derived DCs with CNL in doses from 1 to 10 μg/ml resulted in a dose-dependent induction of overall DC maturation characteristics. Exposure of DCs to CNL for 48 hr resulted in extensive up-regulation of co-stimulatory molecules CD80 and CD86, as well as of the maturation marker CD83 and HLA-DR molecules. Such CNL-matured DCs (CNL-DCs) were capable of inducing a T helper type 1-polarized response in naive CD4+  CD45RA+ T cells in 5-day allogeneic co-cultures. The allostimulatory potential of CNL-DCs was significantly increased relative to untreated controls, as was their capacity to produce several pro-inflammatory cytokines such as interleukin-6, interleukin-8 and tumour necrosis factor-α. By using a specific Toll-like receptor 4 (TLR4) signalling inhibitor, CLI-095, as well as Myd88 inhibitory peptide, we have shown that DC activation by CNL is completely dependent on the TLR4 activation pathway. Furthermore, activation of TLR4 by CNL was confirmed via TLR4 reporter assay. Measurement of p65 nuclear factor-κB and p38 mitogen-activated protein kinase (MAPK) phosphorylation levels following CNL stimulation of DCs revealed primarily an increase in nuclear factor-κB activity, with less effect on the induction of p38 MAPK signalling than of lipopolysaccharide-matured DCs. The CNL had the ability to activate human DCs in such a way as to subsequently direct T helper type 1 T-cell responses. Our results encourage the use of mushroom-derived lectins for use in therapeutic strategies with aims such as to strengthen anti-tumour immune responses.

Potential application of tregitopes as immunomodulating agents in multiple sclerosis

The induction of immunologic tolerance is an important clinical goal in autoimmunity. CD4(+) regulatory T (Treg) cells, defined by the expression of the transcription factor forkhead box P3 (FoxP3), play a central role in the control of autoimmune responses. Quantitative and qualitative defects of Tregs have been postulated to contribute to failed immune regulation in multiple sclerosis (MS) and other autoimmune diseases. This paper highlights the potential uses of T regulatory cell epitopes (Tregitopes), natural Treg epitopes found to be contained in human immunoglobulins, as immunomodulating agents in MS. Tregitopes expand Treg cells and induce "adaptive Tregs" resulting in immunosuppression and, therefore, are being considered as a potential therapy for autoimmune diseases. We will compare Tregitopes versus intravenous immunoglobulin (IVIg) in the treatment of EAE with emphasis on the potential applications of Tregitope for the treatment of MS.

The phosphatase SRC homology region 2 domain-containing phosphatase-1 is an intrinsic central regulator of dendritic cell function

Dendritic cells (DCs) initiate proinflammatory or regulatory T cell responses, depending on their activation state. Despite extensive knowledge of DC-activating signals, the understanding of DC inhibitory signals is relatively limited. We show that Src homology region 2 domain-containing phosphatase-1 (SHP-1) is an important inhibitor of DC signaling, targeting multiple activation pathways. Downstream of TLR4, SHP-1 showed increased interaction with several proteins including IL-1R-associated kinase-4, and modulated LPS signaling by inhibiting NF-κB, AP-1, ERK, and JNK activity, while enhancing p38 activity. In addition, SHP-1 inhibited prosurvival signaling through AKT activation. Furthermore, SHP-1 inhibited CCR7 protein expression. Inhibiting SHP-1 in DCs enhanced proinflammatory cytokines, IL-6, IL-12, and IL-1β production, promoted survival, and increased DC migration to draining lymph nodes. Administration of SHP-1-inhibited DCs in vivo induced expansion of Ag-specific cytotoxic T cells and inhibited Foxp3(+) regulatory T cell induction, resulting in an enhanced immune response against pre-established mouse melanoma and prostate tumors. Taken together, these data demonstrate that SHP-1 is an intrinsic global regulator of DC function, controlling many facets of T cell-mediated immune responses.

Genome-wide identification of susceptibility alleles for viral infections through a population genetics approach

Viruses have exerted a constant and potent selective pressure on human genes throughout evolution. We utilized the marks left by selection on allele frequency to identify viral infection-associated allelic variants. Virus diversity (the number of different viruses in a geographic region) was used to measure virus-driven selective pressure. Results showed an excess of variants correlated with virus diversity in genes involved in immune response and in the biosynthesis of glycan structures functioning as viral receptors; a significantly higher than expected number of variants was also seen in genes encoding proteins that directly interact with viral components. Genome-wide analyses identified 441 variants significantly associated with virus-diversity; these are more frequently located within gene regions than expected, and they map to 139 human genes. Analysis of functional relationships among genes subjected to virus-driven selective pressure identified a complex network enriched in viral products-interacting proteins. The novel approach to the study of infectious disease epidemiology presented herein may represent an alternative to classic genome-wide association studies and provides a large set of candidate susceptibility variants for viral infections.

Viruses have represented a constant threat to human communities throughout their history, therefore, human genes involved in anti-viral response can be thought of as targets of virus-driven selective pressure. Here we utilized the marks left by selection to identify viral infection-associated allelic variants. We analyzed more than 660,000 single nucleotide polymorphisms (SNPs) genotyped in 52 human populations, and we used virus diversity (the number of different viruses in a geographic region) to measure virus-driven selective pressure. Results showed that genes involved in immune response and in the biosynthesis of glycan structures functioning as viral receptors display more variants associated with virus diversity than expected by chance. The same holds true for genes encoding proteins that directly interact with viral components. Genome-wide analysis identified 441 variants, mapping to 139 human genes, significantly associated with virus-diversity. We analyzed the functional relationships among genes subjected to virus-driven selective pressure and identified a complex interaction network enriched in viral products-interacting proteins. Therefore, we describe a novel approach for the identification of gene variants that may be involved in the susceptibility to viral infections.

Bioaccumulation of amylose-like glycans by Helicobacter pylori

BACKGROUND

Helicobacter pylori cell surface is composed of lipopolysaccharides (LPSs) yielding structures homologous to mammalian Lewis O-chains blood group antigens. These structures are key mediators in the definition of host-microbial interactions and known to change their expression pattern in response to environmental pressure.

AIMS

The present work is focused on the identification of new H. pylori cell-surface glycosides. Special attention is further devoted to provide insights on the impact of in vitro subcultivation on H. pylori cell-surface phenotypes.

METHODS

Cell-surface glycans from H. pylori NCTC 11637 and two clinical isolates were recovered from the aqueous phase resulting from phenol:water extraction of intact bacteria. They were evaluated in relation to their sugars and glycosidic-linkages composition by CG-MS, size-exclusion chromatography, NMR, and Mass Spectrometry. H. pylori glycan profile was also monitored during subcultivation in vitro in agar and F12 liquid medium.

RESULTS

All three studied strains produce LPS expressing Lewis epitopes and express bioaccumulate amylose-like glycans. Bioaccumulation of amylose was found to be enhanced with the subcultivation of the bacterium on agar medium and accompanied by a decrease in the expression of LPS O-chains. In contrast, during exponential growth in F12 liquid medium, an opposite behavior is observed, that is, there is an increase in the overall amount of LPS and decrease in amylose content.

CONCLUSIONS

This work shows that under specific environmental conditions, H. pylori expresses a phase-variable cell-surface alpha-(1-->4)-glucose moiety.