DC-SIGN; a related gene, DC-SIGNR; and CD23 form a cluster on 19p13

Receptors and host factors: key players in human metapneumovirus infection

Human metapneumovirus (hMPV) is a significant global pathogen that causes acute respiratory tract infections, especially in infants, young children, the elderly, and immunocompromised individuals. Despite its increasing prevalence, there are currently no vaccines or effective treatments available for hMPV. The pathogenesis of hMPV infection is a complex process involving a multitude of host factors and viral receptors. These interactions determine the virus ability to enter host cells, replicate, and evade the immune response. This review is the first to provide a comprehensive overview of the current understanding of host-virus interactions in hMPV pathogenesis. By elucidating these mechanisms, we can identify potential targets for antiviral drugs and improve the management of hMPV infections.

Simultaneous Blockade of CD209 and CD209L by Monoclonal Antibody Does Not Provide Sufficient Protection Against Multiple Viral Infections In Vivo

Many virus species, including Ebola virus, Marburg virus, SARS-CoV-2, dengue virus (DENV) and Zika virus (ZIKV), exploit CD209 and CD209L as alternative or attachment receptors for viral cis- or trans-infection. Thus, CD209 and CD209L may be critical targets for the development of therapeutic monoclonal blocking antibody drugs to disrupt the infection process caused by multiple viruses. Here, we produced a human chimeric monoclonal blocking antibody that simultaneously blocks CD209 and CD209L, namely 7-H7-B1. We show that 7-H7-B1 effectively blocks multiple pseudotyped or live viral infections in vitro, including SARS-CoV, SARS-CoV-2, Ebola virus, Marburg virus, ZIKV and DENV infections. However, the 7-H7-B1 mAb does not provide favourable protection against Zaire Ebola virus or ZIKV infection in hCD209 knock-in mice in vivo. Thus, our findings indicate that although CD209 and CD209L are critical for multiple viral infections in vitro, they may play only a partial role in viral infections in vivo.

Glycan-Silica Nanoparticles as Effective Inhibitors for Blocking Virus Infection

Small solid silica nanoparticles (SiNPs) have been used for multivalent carbohydrate presentation in DC-/L-SIGN-mediated viral infection models. Glycosylated SiNPs (glycoSiNPs) were fully characterized by different experimental techniques, including NMR, DLS, TGA, FTIR, and XPS, which confirmed their chemical structures. As a proof-of-concept, the capacity of glycoSiNPs to interact with Concanavalin A (ConA), a model lectin, using DLS binding experiments and UV-vis turbidimetry assays was analyzed. Their antiviral activity was assessed in a cellular assay using an artificial Ebola virus, demonstrating the potent inhibition of DC-SIGN-mediated infection. Notably, glycoSiNPs functionalized with a trivalent Manα1,2Man glycodendron exhibited the strongest inhibitory activity, with an IC50 of 135 ng/mL and a 170-fold lower efficiency in blocking L-SIGN-mediated viral infection. These findings suggest that glycoSiNPs present a promising approach for developing antiviral agents that selectively target the DC-SIGN pathway over the L-SIGN one.

Unprecedented selectivity for homologous lectin targets: differential targeting of the viral receptors L-SIGN and DC-SIGN

DC-SIGN (CD209) and L-SIGN (CD209L) are two C-type lectin receptors (CLRs) that facilitate SARS-CoV-2 infections as viral co-receptors. SARS-CoV-2 manipulates both DC-SIGN and L-SIGN for enhanced infection, leading to interest in developing receptor antagonists. Despite their structural similarity (82% sequence identity), they function differently. DC-SIGN, found in dendritic cells, shapes the immune response by recognizing pathogen-associated carbohydrate patterns. In contrast, L-SIGN, expressed in airway epithelial endothelial cells, is not directly involved in immunity. COVID-19's primary threat is the hyperactivation of the immune system, potentially reinforced if DC-SIGN engages with exogenous ligands. Therefore, L-SIGN, co-localized with ACE2-expressing cells in the respiratory tract, is a more suitable target for anti-adhesion therapy. However, designing a selective ligand for L-SIGN is challenging due to the high sequence identity of the Carbohydrate Recognition Domains (CRDs) of the two lectins. We here present Man84, a mannose ring modified with a methylene guanidine triazole at position 2. It binds L-SIGN with a K D of 12.7μM ± 1 μM (ITC) and is the first known L-SIGN selective ligand, showing 50-fold selectivity over DC-SIGN (SPR). The X-ray structure of the L-SIGN CRD/Man84 complex reveals the guanidinium group's role in achieving steric and electrostatic complementarity with L-SIGN. This allows us to trace the source of selectivity to a single amino acid difference between the two CRDs. NMR analysis confirms the binding mode in solution, highlighting Man84's conformational selection upon complex formation. Dimeric versions of Man84 achieve additional selectivity and avidity in the low nanomolar range. These compounds selectively inhibit L-SIGN dependent trans-infection by SARS-CoV-2 and Ebola virus. Man84 and its dimeric constructs display the best affinity and avidity reported to date for low-valency glycomimetics targeting CLRs. They are promising tools for competing with SARS-CoV-2 anchoring in the respiratory tract and have potential for other medical applications.

Identification and Analysis of Gene Biomarkers for Ovarian Cancer

Objective: To identify potential diagnostic markers for ovarian cancer (OC) and explore the contribution of immune cells infiltration to the pathogenesis of OC. Methods: As the study cohort, two gene expression datasets of human OC (GSE27651 and GSE26712, taken as the metadata) taken from the Gene Expression Omnibus (GEO) database were combined, comprising 228 OC and 16 control samples. Analysis was performed to identify the differentially expressed genes between the OC and control samples, while support vector machine analysis using the recursive feature elimination algorithm and least absolute shrinkage and selection operator regression were performed to identify candidate biomarkers that could discriminate OC. In addition, immunohistochemistry staining was performed to verify the diagnostic value and protein expression levels of the candidate biomarkers. The GSE146553 dataset (OC n = 40, control n = 3) was used to further validate the diagnostic values of those biomarkers. Further, the proportions of various immune cells infiltration in the OC and control samples were evaluated using the CIBERSORT algorithm. Results: CLEC4M, PFKP, and SCRIB were identified as potential diagnostic markers for OC in both the metadata (area under the receiver operating characteristic curve [AUC] = 0.996, AUC = 1.000, AUC = 1.000) and GSE146553 dataset (AUC = 0.983, AUC = 0.975, AUC = 0.892). Regarding immune cell infiltration, there was an increase in the infiltration of follicular helper dendritic cells, and a decrease in the infiltration of M2 macrophages and neutrophils, as well as activated natural killer (NK) cells and T cells in OC. CLEC4M showed a significantly positive correlation with neutrophils (r = 0.57, p < 0.001) and resting NK cells (r = 0.42, p = 0.0047), but a negative correlation with activated dendritic cells (r = -0.33, p = 0.032). PFKP displayed a significantly positive correlation with activated NK cells (r = 0.36, p = 0.016) and follicular helper T cells (r = 0.32, p = 0.035), but a negative correlation with the naive B cells (r = -0.3, p = 0.049) and resting NK cells (r = -0.41, p = 0.007). SCRIB demonstrated a significantly positive correlation with plasma cells (r = 0.39, p = 0.01), memory B cells (r = 0.34, p = 0.025), and follicular helper T cells (r = 0.31, p = 0.04), but a negative correlation with neutrophils (r = -0.46, p = 0.002) and naive B cells (r = -0.48, p = 0.0012). Conclusion: CLEC4M, PFKP, and SCRIB were identified and verified as potential diagnostic biomarkers for OC. This work and identification of the three biomarkers may provide guidance for future studies into the mechanism and treatment of OC.

An Aptamer-Based Proteomic Analysis of Plasma from Cats (Felis catus) with Clinical Feline Infectious Peritonitis

Feline infectious peritonitis (FIP) is a systemic disease manifestation of feline coronavirus (FCoV) and is the most important cause of infectious disease-related deaths in domestic cats. FIP has a variable clinical manifestation but is most often characterized by widespread vasculitis with visceral involvement and/or neurological disease that is typically fatal in the absence of antiviral therapy. Using an aptamer-based proteomics assay, we analyzed the plasma protein profiles of cats who were naturally infected with FIP (n = 19) in comparison to the plasma protein profiles of cats who were clinically healthy and negative for FCoV (n = 17) and cats who were positive for the enteric form of FCoV (n = 9). We identified 442 proteins that were significantly differentiable; in total, 219 increased and 223 decreased in FIP plasma versus clinically healthy cat plasma. Pathway enrichment and associated analyses showed that differentiable proteins were related to immune system processes, including the innate immune response, cytokine signaling, and antigen presentation, as well as apoptosis and vascular integrity. The relevance of these findings is discussed in the context of previous studies. While these results have the potential to inform diagnostic, therapeutic, and preventative investigations, they represent only a first step, and will require further validation.

Dengue Vaccination: Towards a New Dawn of Curbing Dengue Infection

Dengue is an infectious disease caused by dengue virus (DENV) and is a serious global burden. Antibody-dependent enhancement and the ability of DENV to infect immune cells, along with other factors, lead to fatal Dengue Haemorrhagic Fever and Dengue Shock Syndrome. This necessitates the development of a robust and efficient vaccine but vaccine development faces a number of hurdles. In this review, we look at the epidemiology, genome structure and cellular targets of DENV and elaborate upon the immune responses generated by human immune system against DENV infection. The review further sheds light on various challenges in development of a potent vaccine against DENV which is followed by presenting a current account of different vaccines which are being developed or have been licensed.

PU.1-CD23 signaling mediates pulmonary innate immunity against Aspergillus fumigatus infection by driving inflammatory response

BACKGROUND

Aspergillosis is a common cause of morbidity and mortality in immunocompromised populations. PU.1 is critical for innate immunity against Aspergillus fumigatus (AF) in macrophages. However, the molecular mechanism underlying PU.1 mediating immunity against AF infection in human alveolar macrophages (AMs) is still unclear.

METHODS

In this study, we detected the expressions of PU.1, CD23, p-ERK, CCL20 and IL-8 and key inflammatory markers IL-1β, IL-6, TNF-α and IL-12 in human THP-1-derived macrophages (HTMs) or PU.1/CD23-overexpressed immunodeficient mice with AF infection. Moreover, we examined these expressions in PU.1-overexpressed/interfered HTMs. Additionally, we detected the phagocytosis of macrophages against AF infection with altered PU.1 expression. Dual luciferase, ChIP and EMSAs were performed to detect the interaction of PU.1 and CD23. And we invested the histological changes in mouse lung tissues transfected with PU.1/CD23-expressing adenoviruses in AF infection.

RESULTS

The results showed that the expressions of PU.1, CD23, p-ERK, CCL20, IL-8, IL-1β, IL-6, TNF-α and IL-12 increased significantly with AF infection, and PU.1 regulated the later 8 gene expressions in HTMs. Moreover, CD23 was directly activated by PU.1, and overexpression of CD23 in PU.1-interfered HTMs upregulated IL-1β, IL-6, TNF-α and IL-12 levels which were downregulated by PU.1 interference. PU.1 overexpression strengthened the phagocytosis of the HTMs against AF. And injection of PU.1/CD23-expressing adenoviruses attenuated pathological defects in immunodeficient mouse lung tissues with AF infection. Adenovirus (Ad)-PU.1 increased the CD23, p-ERK, CCL20, IL-8 levels.

CONCLUSIONS

Our study concluded that PU.1-CD23 signaling mediates innate immunity against AF in lungs through regulating inflammatory response. Therefore, PU.1-CD23 may be a new anti-aspergillosis therapeutic for the treatment of invasive aspergillosis with the deepening of gene therapy and its wide application in the clinic.

Tinker, tailor, soldier, cell: the role of C-type lectins in the defense and promotion of disease

C-type lectins (CTLs) represent a large family of soluble and membrane-bound proteins which bind calcium dependently via carbohydrate recognition domains (CRDs) to glycan residues presented on the surface of a variety of pathogens. The deconvolution of a cell's glycan code by CTLs underpins several important physiological processes in mammals such as pathogen neutralization and opsonization, leukocyte trafficking, and the inflammatory response. However, as our knowledge of CTLs has developed it has become apparent that the role of this innate immune family of proteins can be double-edged, where some pathogens have developed approaches to subvert and exploit CTL interactions to promote infection and sustain the pathological state. Equally, CTL interactions with host glycoproteins can contribute to inflammatory diseases such as arthritis and cancer whereby, in certain contexts, they exacerbate inflammation and drive malignant progression. This review discusses the 'dual agent' roles of some of the major mammalian CTLs in both resolving and promoting infection, inflammation and inflammatory disease and highlights opportunities and emerging approaches for their therapeutic modulation.

Sweet Immune Checkpoint Targets to Enhance T Cell Therapy

Despite tremendous success against hematological malignancies, the performance of chimeric Ag receptor T cells against solid tumors remains poor. In such settings, the lack of success of this groundbreaking immunotherapy is in part mediated by ligand engagement of immune checkpoint molecules on the surface of T cells in the tumor microenvironment. Although CTLA-4 and programmed death-1 (PD-1) are well-established checkpoints that inhibit T cell activity, the engagement of glycans and glycan-binding proteins are a growing area of interest due to their immunomodulatory effects. This review discusses exemplary strategies to neutralize checkpoint molecules through an in-depth overview of genetic engineering approaches aimed at overcoming the inhibitory programmed death ligand-1 (PD-L1)/PD-1 axis in T cell therapies and summarizes current knowledge on glycoimmune interactions that mediate T cell immunosuppression.

Cholesterol-Rich Lipid Rafts as Platforms for SARS-CoV-2 Entry

Since its appearance, the Severe Acute Respiratory Syndrome Coronavirus (SARS-CoV-2), the causal agent of Coronavirus Disease 2019 (COVID-19), represents a global problem for human health that involves the host lipid homeostasis. Regarding, lipid rafts are functional membrane microdomains with highly and tightly packed lipid molecules. These regions enriched in sphingolipids and cholesterol recruit and concentrate several receptors and molecules involved in pathogen recognition and cellular signaling. Cholesterol-rich lipid rafts have multiple functions for viral replication; however, their role in SARS-CoV-2 infection remains unclear. In this review, we discussed the novel evidence on the cholesterol-rich lipid rafts as a platform for SARS-CoV-2 entry, where receptors such as the angiotensin-converting enzyme-2 (ACE-2), heparan sulfate proteoglycans (HSPGs), human Toll-like receptors (TLRs), transmembrane serine proteases (TMPRSS), CD-147 and HDL-scavenger receptor B type 1 (SR-B1) are recruited for their interaction with the viral spike protein. FDA-approved drugs such as statins, metformin, hydroxychloroquine, and cyclodextrins (methyl-β-cyclodextrin) can disrupt cholesterol-rich lipid rafts to regulate key molecules in the immune signaling pathways triggered by SARS-CoV-2 infection. Taken together, better knowledge on cholesterol-rich lipid rafts in the SARS-CoV-2-host interactions will provide valuable insights into pathogenesis and the identification of novel therapeutic targets.

Controlled density glycodendron microarrays for studying carbohydrate-lectin interactions

Glycodendron microarrays with defined valency have been constructed by on-chip synthesis on hydrophobic indium tin oxide (ITO) coated glass slides and employed in lectin-carbohydrate binding studies with several plant and human lectins. Glycodendrons presenting sugar epitopes at different valencies were prepared by spotwise strain-promoted azide-alkyne cycloaddition (SPAAC) between immobilised cyclooctyne dendrons and azide functionalised glycans. The non-covalent immobilisation of dendrons on the ITO surface by hydrophobic interaction allowed us to study dendron surface density and SPAAC conversion rate by in situ MALDI-TOF MS analysis. By diluting the dendron surface density we could study how the carbohydrate-lectin interactions became exclusively dependant on the valency of the immobilised glycodendron.

In silico screening and identification of deleterious missense SNPs along with their effects on CD-209 gene: An insight to CD-209 related-diseases

DC-SIGN receptor articulated by macrophages and dendritic cells is encoded by CD209 gene and plays a role to activate and proliferate the T-lymphocytes in response of virus attack. The dysfunctional activity of DC-SIGN receptor because of missense SNPs can lead to cause dengue haemorrhage fever, HIV-1 infection etc. Out of 11 transcripts of CD209, all missense SNPs of canonical transcript were retrieved from Ensembl database and evaluated by their deleteriousness by using Polyphen-2, PMut, SIFT, MutPred, PROVEAN and PhD-SNP together with stimulation of its complete 3D structure. 10 nsSNPs were chosen depending on both the significance value of nsSNP and their prediction among SNPs evaluating servers which are based on different algorithms. Moreover, the position and native role of 10 nsSNPs in wild 3D model has been described which assist to acknowledge their importance. This study urges the researcher’s community to experimentally validate these SNPs and their association in causing the diseases like dengue fever, Tuberculosis etc.

C-type Lectin CD209L/L-SIGN and CD209/DC-SIGN: Cell Adhesion Molecules Turned to Pathogen Recognition Receptors

C-type lectin CD209/DC-SIGN and CD209L/L-SIGN proteins are distinct cell adhesion and pathogen recognition receptors that mediate cellular interactions and recognize a wide range of pathogens, including viruses such as SARS, SARS-CoV-2, bacteria, fungi and parasites. Pathogens exploit CD209 family proteins to promote infection and evade the immune recognition system. CD209L and CD209 are widely expressed in SARS-CoV-2 target organs and can contribute to infection and pathogenesis. CD209 family receptors are highly susceptible to alternative splicing and genomic polymorphism, which may influence virus tropism and transmission in vivo. The carbohydrate recognition domain (CRD) and the neck/repeat region represent the key features of CD209 family proteins that are also central to facilitating cellular ligand interactions and pathogen recognition. While the neck/repeat region is involved in oligomeric dimerization, the CRD recognizes the mannose-containing structures present on specific glycoproteins such as those found on the SARS-CoV-2 spike protein. Considering the role of CD209L and related proteins in diverse pathogen recognition, this review article discusses the recent advances in the cellular and biochemical characterization of CD209 and CD209L and their roles in viral uptake, which has important implications in understanding the host-pathogen interaction, the viral pathobiology and driving vaccine development of SARS-CoV-2.

mTOR-Myc axis drives acinar-to-dendritic cell transition and the CD4+ T cell immune response in acute pancreatitis

The inflammatory response in acute pancreatitis (AP) is associated with acinar-to-dendritic cell transition. The CD4+ T-cell-mediated adaptive immune response is necessary for pancreatic inflammatory damage. However, the effect of acinar-to-dendritic cell transition on the CD4+ T-cell response and the regulatory mechanism remain undefined. A mouse animal model of AP was established by repeated intraperitoneal injection of CAE. The mTOR inhibitor rapamycin was administered before AP induction. Primary acinar cells were isolated and co-incubated with subsets of differentiated CD4+ T cells. The expression of DC-SIGN was also assessed in pancreatic tissues from human AP patients. We found acinar cells expressed DC-SIGN and displayed the phenotype of dendritic cells (DCs), which promoted the differentiation of naive CD4+ T cells into CD4+/IFN-γ+ Th1 and CD4+/IL-17A+ Th17 cells in pancreatic tissues during AP. DC-SIGN was the target gene of Myc. The mTOR inhibitor rapamycin inhibited AP-induced DC-SIGN expression, CD4+ Th1/Th17 cell differentiation and the pro-inflammatory response via Myc. Acinar cells expressed DC-SIGN in pancreatic tissues of human patients with AP. In conclusion, acinar-to-dendritic cell transition is implicated in the CD4+ T-cell immune response via mTOR-Myc-DC-SIGN axis, which might be an effective target for the prevention of local pancreatic inflammation in AP.

C-Type Lectin Receptors in Antifungal Immunity

Most fungal species are harmless to humans and some exist as commensals on mucocutaneous surfaces. Yet many fungi are opportunistic pathogens, causing life-threatening invasive infections when the immune system becomes compromised. The fungal cell wall contains conserved pathogen-associated molecular patterns (PAMPs), which allow the immune system to distinguish between self (endogenous molecular patterns) and foreign material. Sensing of invasive microbial pathogens is achieved through recognition of PAMPs by pattern recognition receptors (PRRs). One of the predominant fungal-sensing PRRs is the C-type lectin receptor (CLR) family. These receptors bind to structures present on the fungal cell wall, eliciting various innate immune responses as well as shaping adaptive immunity. In this chapter, we specifically focus on the four major human fungal pathogens, Candida albicans, Aspergillus fumigatus, Cryptococcus neoformans and Pneumocystis jirovecii, reviewing our current understanding of the CLRs that are involved in their recognition and protection of the host.

Signaling C-Type Lectin Receptors in Antifungal Immunity

We are all exposed to fungal organisms daily, and although many of these organisms are not harmful, billions of people a year contract a fungal infection. Most of these infections are not fatal and can be cleared by the host immune response. However, due to an increase in high-risk populations, the global fungal burden has increased, with more than 1.5 million deaths per year caused by invasive fungal infections. The fungal cell wall is an important surface for interacting with the host immune system as it contains pathogen-associated molecular patterns (PAMPs) which are detected as being foreign by the host pattern recognition receptors (PRRs). C-type lectin receptors are a group of PRRs that play a central role in the protection against invasive fungal infections. Following the recognition of fungal PAMPs, CLRs trigger various innate and adaptive immune responses. In this chapter, we specifically focus on C-type lectin receptors capable of activating downstream signaling pathways, resulting in protective antifungal immune responses. The current roles that these signaling CLRs play in protection against four of the most prevalent fungal infections affecting humans are reviewed. These include Candida albicans, Aspergillus fumigatus, Cryptococcus neoformans and Pneumocystis jirovecii.

Human DC-SIGN and CD23 do not interact with human IgG

The precise mechanisms underlying anti-inflammatory effects of intravenous immunoglobulin (IVIg) therapies remain elusive. The sialylated IgG fraction within IVIg has been shown to be therapeutically more active in mouse models. Functionally, it has been suggested that IgG undergoes conformational changes upon Fc-sialylation which sterically impede binding to conventional FcγRs, but simultaneously allow binding to human DC-SIGN (SIGN-R1 in mice) and also CD23. These latter C-type lectins have been proposed responsible for the immunomodulatory effects in mouse models. However, there is conflicting evidence supporting direct interactions between sialylated human IgG and CD23/DC-SIGN. While cells expressing human CD23 and DC-SIGN in their native configuration bound their natural ligands IgE and ICAM-3, respectively, no IgG binding was observed, regardless of Fc-glycan sialylation in any context (with or without bisection and/or fucosylation) or presence of sialylated Fab-glycans. This was tested by both by FACS and a novel cellular Surface Plasmon Resonance imaging (cSPRi) approach allowing for monitoring low-affinity but high-avidity interactions. In summary, we find no evidence for human CD23 or DC-SIGN being bona fide receptors to human IgG, regardless of IgG Fc- or Fab-glycosylation status. However, these results do not exclude the possibility that either IgG glycosylation or C-type lectins affect IVIg therapies.

DC-SIGN-LEF1/TCF1-miR-185 feedback loop promotes colorectal cancer invasion and metastasis

DC-SIGN is previously focused on its physiologic and pathophysiologic roles in immune cells. Little is known about whether DC-SIGN is expressed in malignant epithelial cells and how DC-SIGN participates in tumor progression. Here we showed that DC-SIGN expression was increased in metastatic colorectal cancer (CRC) cell lines and patient tissues. The overall survival in CRC patients with positive DC-SIGN was remarkably reduced. Gain of DC-SIGN function facilitated the CRC metastases both in vitro and in vivo, and this effect was reversed by miR-185. DC-SIGN and Lyn interacted physically, and Lyn maintained the stability of DC-SIGN in cells. DC-SIGN activation recruited Lyn and p85 to form the DC-SIGN-Lyn-p85 complex, which promoted CRC metastasis by increasing PI3K/Akt/β-catenin signaling in tyrosine kinase Lyn-dependent manner. Furthermore, activation of DC-SIGN promoted the transcription of MMP-9 and VEGF by increasing PI3K/Akt/β-catenin signaling, and induced TCF1/LEF1-mediated suppression of miR-185. Our findings reveal the presence of the DC-SIGN–TCF1/LEF1–miR-185 loop in cancer cells with metastatic traits, implying that it may represent a new pathogenic mechanism of CRC metastasis. This character of the loop promises to provide new targets for blocking CRC invasive and metastatic activity.

On-Chip Screening of a Glycomimetic Library with C-Type Lectins Reveals Structural Features Responsible for Preferential Binding of Dectin-2 over DC-SIGN/R and Langerin

A library of mannose‐ and fucose‐based glycomimetics was synthesized and screened in a microarray format against a set of C‐type lectin receptors (CLRs) that included DC‐SIGN, DC‐SIGNR, langerin, and dectin‐2. Glycomimetic ligands able to interact with dectin‐2 were identified for the first time. Comparative analysis of binding profiles allowed their selectivity against other CLRs to be probed.

Current immunogenetic predisposition to tuberculosis in the Moroccan population

Tuberculosis (TB) is a serious infectious disease that kills approximately two million people per year, particularly in low- and middle-income countries. Numerous genetic epidemiology studies have been conducted of many ethnic groups worldwide and have highlighted the critical impact of the genetic environment on TB distribution. Many candidate genes associated with resistance or susceptibility to TB have been identified. In Morocco, where TB is still a major public health problem, various observations of clinical, microbiological and incidence distribution are heavily affected by genetic background and external environment. Morocco has almost the same clinical profile as do other North African countries, mainly the increase in more extrapulmonary than pulmonary forms of the diseases, when compared to European, Asian or American populations. In addition, a linkage analysis study that examined Moroccan TB patients identified a unique chromosome region that had a strong association with the risk of contracting TB. Other genes in the Moroccan population that were found to be associated seem to be involved predominantly in modulating the innate immunity. In this review, we appraise the major candidate genes that have been reported in Moroccan immunogenetic studies and discuss their updated role in TB, particularly during the first phase of the immune response to Mycobacterium tuberculosis (Mtb) infection.

Overexpression of dendritic cell-specific intercellular adhesion molecule-3-grabbing nonintegrin-related protein in cervical cancer and correlation with squamous cell carcinoma antigen

Dendritic cell-specific intercellular adhesion molecule-3-grabbing nonintegrin-related protein (DC-SIGNR) is a type II transmembrane protein that has been reported to bind to various pathogens and participate in immunoregulation and tumorigenesis. However, further research is required to investigate whether the level of DC-SIGNR and cervical cancer are associated. The present study aimed to explore the clinical diagnostic significance of DC-SIGNR in cervical cancer. Immunohistochemical staining of DC-SIGNR was performed in samples from 25 patients with early stage cervical cancer, 14 patients with cervical intraepithelial neoplasia (CIN) and cervical polyp samples from 15 individuals. DC-SIGNR expression in cervical cancer tissue was significantly higher compared with that in CIN and cervical polyp tissue (P=0.0184 and P=0.0236, respectively). However, there was no significant difference in DC-SIGNR expression between CIN and cervical polyp tissue (P=0.8103). Additionally, the serum DC-SIGNR levels in 84 cervical cancer patients and 69 healthy female individuals were measured using an ELISA. Serum (s)DC-SIGNR levels were significantly higher in cervical cancer patients compared with healthy female individuals (P<0.0001). A sDC-SIGNR level of 93.7 ng/ml was revealed by receiver operating characteristic curve analysis to predict the presence of cervical cancer with 69.57% sensitivity and 66.67% specificity (area under the curve, 0.6989; P<0.0001). Levels of sDC-SIGNR in cervical cancer patients were also correlated with serum levels of squamous cell carcinoma antigen (r=0.2583; P=0.0348). The results of the present study demonstrate that DC-SIGNR is overexpressed in cervical cancer tissue, and suggest that DC-SIGNR could serve as a biomarker for the early diagnosis of cervical cancer. Nevertheless, further studies are required to demonstrate what role DC-SIGNR serves in cervical cancer.

Diversification of IgG effector functions

IgG is the major immunoglobulin class produced during an immune response against foreign antigens and efficiently provides protection through its bifunctional nature. While the Fab domains confer highly specific recognition of the antigen, the Fc domain mediates a wide range of effector functions that modulate several aspects of innate and adaptive immunity. Engagement of the various types of Fcγ receptors (FcγRs) by an IgG Fc domain can activate distinct immunomodulatory pathways with pleiotropic functional consequences for several leukocyte types. Fc effector functions are not limited to phagocytosis and cytotoxicity of IgG-opsonized targets but exhibit remarkable diversity and include modulation of leukocyte activity and survival, cytokine and chemokine expression, maturation of antigen-presenting cells, antigen processing and presentation, B-cell selection and IgG affinity maturation, as well as regulation of IgG production. These functions are initiated upon specific interactions of the Fc domain with the various types of FcγRs-a process that is largely determined by the structural heterogeneity of the IgG Fc domain. Modulation of the Fc-associated glycan structure and composition along with differences in the primary amino acid sequence among the IgG subclasses represent the two main diversification mechanisms of the Fc domain that generate a spectrum of Fc domain phenotypes with distinct affinity for the various FcγR types and differential capacity to activate immunomodulatory pathways.

JNK1 negatively controls antifungal innate immunity by suppressing CD23 expression

Opportunistic fungal infections are a leading cause of death among immune-compromised patients, and there is a pressing need to develop new antifungal therapeutic agents because of toxicity and resistance to the antifungal drugs currently in use. Although C-type lectin receptor- and Toll-like receptor-induced signaling pathways are key activators of host antifungal immunity, little is known about the mechanisms that negatively regulate host immune responses to a fungal infection. Here we found that JNK1 activation suppresses antifungal immunity in mice. We showed that JNK1-deficient mice had a significantly higher survival rate than wild-type control mice in response to Candida albicans infection, and the expression of JNK1 in hematopoietic innate immune cells was critical for this effect. JNK1 deficiency leads to significantly higher induction of CD23, a novel C-type lectin receptor, through NFATc1-mediated regulation of the CD23 gene promoter. Blocking either CD23 upregulation or CD23-dependent nitric oxide production eliminated the enhanced antifungal response found in JNK1-deficient mice. Notably, JNK inhibitors exerted potent antifungal therapeutic effects in both mouse and human cells infected with C. albicans, indicating that JNK1 may be a therapeutic target for treating fungal infection.

N-Glycans on the Rift Valley Fever Virus Envelope Glycoproteins Gn and Gc Redundantly Support Viral Infection via DC-SIGN

Rift Valley fever is a mosquito-transmitted, zoonotic disease that infects humans and ruminants. Dendritic cell specific intercellular adhesion molecule 3 (ICAM-3) grabbing non-integrin (DC-SIGN) acts as a receptor for members of the phlebovirus genus. The Rift Valley fever virus (RVFV) glycoproteins (Gn/Gc) encode five putative N-glycan sequons (asparagine (N)–any amino acid (X)–serine (S)/threonine (T)) at positions: N438 (Gn), and N794, N829, N1035, and N1077 (Gc). The N-glycosylation profile and significance in viral infection via DC-SIGN have not been elucidated. Gc N-glycosylation was first evaluated by using Gc asparagine (N) to glutamine (Q) mutants. Subsequently, we generated a series of recombinant RVFV MP-12 strain mutants, which encode N-to-Q mutations, and the infectivity of each mutant in Jurkat cells stably expressing DC-SIGN was evaluated. Results showed that Gc N794, N1035, and N1077 were N-glycosylated but N829 was not. Gc N1077 was heterogeneously N-glycosylated. RVFV Gc made two distinct N-glycoforms: “Gc-large” and “Gc-small”, and N1077 was responsible for “Gc-large” band. RVFV showed increased infection of cells expressing DC-SIGN compared to cells lacking DC-SIGN. Infection via DC-SIGN was increased in the presence of either Gn N438 or Gc N1077. Our study showed that N-glycans on the Gc and Gn surface glycoproteins redundantly support RVFV infection via DC-SIGN.

Sweet complementarity: the functional pairing of glycans with lectins

Carbohydrates establish the third alphabet of life. As part of cellular glycoconjugates, the glycans generate a multitude of signals in a minimum of space. The presence of distinct glycotopes and the glycome diversity are mapped by sugar receptors (antibodies and lectins). Endogenous (tissue) lectins can read the sugar-encoded information and translate it into functional aspects of cell sociology. Illustrated by instructive examples, each glycan has its own ligand properties. Lectins with different folds can converge to target the same epitope, while intrafamily diversification enables functional cooperation and antagonism. The emerging evidence for the concept of a network calls for a detailed fingerprinting. Due to the high degree of plasticity and dynamics of the display of genes for lectins the validity of extrapolations between different organisms of the phylogenetic tree yet is inevitably limited.

C-Type Lectin Receptors

C-type lectins, originally defined as proteins binding carbohydrates in a Ca²⁺-dependent manner, form a large family containing soluble and membrane-bound proteins. Among them, those expressed on phagocytes and working as pathogen pattern-recognition receptors were designated as C-type lectin receptors (CLRs), in accordance with Toll-like receptors (TLRs), NOD-like receptors (NLRs), and RIG-I–like receptors (RLRs). Most of the genes for CLRs are clustered in human chromosome 12 close to the natural killer gene complex. Similar to the killer lectin-like receptors whose genes are clustered in this complex, most of the CLRs induce activating or regulatory signal cascades in response to distinct pathogen- or self-derived components, through the immunoreceptor tyrosine-based activating or inhibitory motif, respectively. In this chapter, some representative CLRs are picked up and their structural features leading to the functional consequences are discussed, especially on the signaling cascades and pathogen interactions, including some impacts on cutaneous pathophysiology. These CLRs should provide targets to develop effective vaccination and therapeutics for distinct infectious and autoimmune/inflammatory diseases.

Association of DC-SIGNR Expression in Peripheral Blood Mononuclear Cells with DC-SIGNR Genotypes in HIV-1 Infection

Dendritic cell-specific intracellular adhesion molecule 3 grabbing nonintegrin related molecule (DC-SIGNR) is a C-type lectin, calcium-dependent carbohydrate-binding protein, which can act as a cell-adhesion and pathogen recognition receptor. DC-SIGNR is known to be highly expressed on liver sinusoidal cells and in the lymph nodes. However, its expression in peripheral blood mononuclear cells (PBMCs) in HIV-1 infection has not been addressed. Therefore, this study determined the expression of DC-SIGNR in PBMCs of HIV-1-infected patients and healthy seronegative individuals by real-time polymerase chain reaction and assessed its correlation with CD4+ T cell counts and DC-SIGNR genotypes. A significantly higher expression of DC-SIGNR was observed in the PBMCs of HIV-1-infected patients compared with healthy seronegative individuals. Further, there was a negative correlation between DC-SIGNR expression and CD4+ T cell counts and positive with viral load, with higher DC-SIGNR expression in the PBMCs of HIV-1-infected patients with a CD4+ T cell count <200 cells/μL than those with >200 cells/μL. This is the first study to report the expression of DC-SIGNR in PBMCs of HIV-1-infected patients. A salient finding of this study is that the DC-SIGNR expression was higher in HIV-1-infected patients, and its positive correlation with viral load and negative with CD4+ T cells counts suggesting a potential role of DC-SIGNR in HIV-1 infection.

Perinatal transmission of hepatitis C antigens: envelope 1, envelope 2 and non-structural 4

BACKGROUND

Perinatal exposure to hepatitis C virus (HCV) antigens during pregnancy may affect the developing immune system in the fetus. We aimed to study the perinatal transmission of HCV structural and non-structural antigens.

METHODS

Sera from 402 pregnant mothers were tested for anti-HCV antibody and HCV RNA. HCV antigens were determined in sera from 101 HCV-infected mothers and their cord blood.

RESULTS

In both serum and cord blood samples, HCV NS4 (non-structural 4) at 27 kDa, E1 (envelope 1) at 38 kDa and E2 (envelope 2) at 40 kDa were identified, purified and quantified using western blotting, electroelution and ELISA. Maternal sera and neonate cord blood samples had similar detection rates for NS4 (94.1%), E1 (90.1%) and E2 (90.1%). The mean maternal serum levels (optical density, OD) of HCV NS4 (0.87 ± 0.01), E1 (0.86 ± 0.01) and E2 (0.85 ± 0.01) did not differ significantly (p > 0.05) from those of neonatal cord blood (0.83 ± 0.01, 0.87 ± 0.01 and 0.85 ± 0.01, respectively). Also, strong correlations (p < 0.0001) were shown between sera and cord blood sample levels of HCV NS4, r = 0.77; E1, r = 0.76 and E2, r = 0.80. The vertical transmission of these antigens in vaginal delivery did not differ significantly (p > 0.05) from those in caesarean section.

CONCLUSIONS

These findings indicate that vertical transmission of HCV NS4, E1 and E2 antigens was very high. Thus, exposure to these antigens may influence the developing immune responses to natural infection or future vaccination.

Human lectins and their roles in viral infections

Innate recognition of virus proteins is an important component of the immune response to viral pathogens. A component of this immune recognition is the family of lectins; pattern recognition receptors (PRRs) that recognise viral pathogen-associated molecular patterns (PAMPs) including viral glycoproteins. In this review we discuss the contribution of soluble and membrane-associated PRRs to immunity against virus pathogens, and the potential role of these molecules in facilitating virus replication. These processes are illustrated with examples of viruses including human immunodeficiency virus (HIV), hepatitis C virus (HCV) and Ebola virus (EBOV). We focus on the structure, function and genetics of the well-characterised C-type lectin mannose-binding lectin, the ficolins, and the membrane-bound CD209 proteins expressed on dendritic cells. The potential for lectin-based antiviral therapies is also discussed.

The clinical significance of DC-SIGN and DC-SIGNR, which are novel markers expressed in human colon cancer

Background

Colon cancer has always been diagnosed at a late stage, which is associated with poor prognosis. The currently used serum tumor markers CEA and CA19-9 display low sensitivity and specificity and may not have diagnostic value in early stage colon cancer. Thus, there is an urgent need to identify novel serum biomarkers for use in the early detection of colon cancer.

Methods

In this study, the expression of DC-SIGN and DC-SIGNR in serum was detected by enzyme-linked immunosorbent assay (ELISA). DC-SIGN and DC-SIGNR expression was detected in cancer tissues by immunohistochemistry (IHC).

Results

The level of sDC-SIGN was lower in patients than in the healthy controls, while the level of sDC-SIGNR in patients was higher than in the healthy controls. Both sDC-SIGN and sDC-SIGNR had diagnostic significances for cancer patients, and the combined diagnosis of these two markers was higher than both of them alone. Furthermore, there were significant differences between both sDC-SIGN and sDC-SIGNR in stage I/II patients and the healthy controls. Moreover, high sDC-SIGN level was accompanied with the long survival time. Additionally, DC-SIGNR was negative in the cancer foci and matched normal colon tissues but was weakly positive between the cancer foci. DC-SIGN staining was faint in matched normal colon tissues, strong in the tumor stroma and the invasive margin of colon cancer tissues, and negatively correlated with the sDC-SIGN level in serum from the same patient. Interestingly, the percent survival of patients with a DC-SIGN mean density of>0.001219 (the upper 95% confidence interval of matched normal colon tissues) was higher than for all other patients.

Conclusion

DC-SIGN and DC-SIGNR are blood-based molecular markers that can potentially be used for the diagnosis of early stage patients. Moreover, expression of DC-SIGN in serum and cancer tissues may affect the survival time for colon cancer patients.

The evolution of HIV-1 interactions with coreceptors and mannose C-type lectin receptors

The phenotype of human immunodeficiency virus type 1 (HIV-1) commonly evolves between and within infected individuals, at virus transmission, and during disease progression. This evolution includes altered interactions between the virus and its coreceptors, i.e., chemokine receptors, as well as mannose C-type lectin receptors (CLRs). Transmitted/founder viruses are predominantly restricted to CCR5, whereas the subsequent intrapatient evolution of HIV-1 coreceptor use during progressive disease can be subdivided into two distinct pathways. Accordingly, the CCR5-restricted virus population is either gradually replaced by virus variants able to use CXCR4 or evolves toward an altered, more flexible use of CCR5. Despite a strong dependency on these coreceptors for host cell entry, HIV-1 also interacts with other cell surface molecules during target cell attachment, including the CLRs. The virus interaction with the CLRs may result either in the efficient transfer of virus to CD4(+) T cells or in the degradation of the virus in endosomal compartments. The determinants of the diverse outcomes depend on which CLR is engaged and also on the glycan makeup of the envelope glycoproteins, which may evolve with the strength of the immune pressure during the disease course. With the current clinical introduction of CCR5 antagonists and the development of additional entry inhibitors, knowledge on the evolution and baseline characteristics of HIV-1 interactions with coreceptor and CLR interactions may play important roles for individualized and optimized treatment strategies. This review summarizes our current understanding of the evolution of HIV-1 interactions with these receptors.

The allele 4 of neck region liver-lymph node-specific ICAM-3-grabbing integrin variant is associated with spontaneous clearance of hepatitis C virus and decrease of viral loads

L‐SIGN is a C‐type lectin expressed on liver sinusoidal endothelial cells involved in the capture of hepatitis C virus and trans‐infection of adjacent hepatocyte cells. The neck region of L‐SIGN is highly polymorphic, with three to nine tandem repeats of 23 residues. This polymorphism is associated with a number of infectious diseases, but has not been explored in HCV. We therefore investigated the impact of L‐SIGN neck region length variation on the outcome of HCV infection. We studied 322 subjects, 150 patients with persistent HCV infection, 63 individuals with spontaneous clearance and 109 healthy controls. In healthy subjects, we found a total of nine genotypes, with the 7/7 genotype being the most frequent (33%) followed by the 7/6 (22.9%) and the 7/5 (18.3%). The frequencies of the alleles were as follows: 7‐LSIGN (56.4%), 6‐LSIGN (20.2%), 5‐L‐SIGN (18.3%) and 4‐L‐SIGN (5%). The frequency of the 7/4 genotype was higher in spontaneous resolvers (14.3%) as compared with the persistent group (4%) (OR = 0.25, 95% CI = 0.07–0.82, p 0.022). In addition, we found that 4‐L‐SIGN was associated with spontaneous resolution of HCV infection (OR = 0.30, 95%CI, 0.12–0.74, p 0.005). Interestingly, patients with 4‐L‐SIGN had lower viral loads when compared with carriers of the 5 (p 0.001), 6 (p 0.021) and 7‐alleles (p 0.048). The results indicate that neck region polymorphism of L‐SIGN can influence the outcome of HCV infection and the four‐tandem repeat is associated with clearance of HCV infection.

DC-SIGN, DC-SIGNR and LSECtin: C-type lectins for infection

The C-type lectins DC-SIGN, DC-SIGNR and LSECtin are encoded by the lectin gene cluster on chromosome 19p13.3 and perform cell-adhesion and pathogen recognition functions on dendritic cells, liver cells and lymph node sinusoidal endothelial cells. DC-SIGN and DC-SIGNR share similar overall gene and protein molecule structures, and they exhibit high affinity for high-mannose carbohydrates. LSECtin, a Ca2+-dependent C-type lectin, interacts with mannose, NAcGlc and fucose. These lectins allow pathogen recognition (e.g., viruses, bacteria and allergens) and cell adhesion for dendritic and endothelial cells in different tissues, which may enhance the infection and facilitate the spread of those pathogens. A better understanding of these lectins may yield information about how pathogens are captured by particular cells and how they spread in different tissues. These studies would provide more detail about the physiopathological mechanisms of viral and bacterial infections and may also lead to new strategies to treat or prevent infections.

Solution NMR analyses of the C-type carbohydrate recognition domain of DC-SIGNR protein reveal different binding modes for HIV-derived oligosaccharides and smaller glycan fragments

The C-type lectin DC-SIGNR (dendritic cell-specific ICAM-3-grabbing non-integrin-related; also known as L-SIGN or CD299) is a promising drug target due to its ability to promote infection and/or within-host survival of several dangerous pathogens (e.g. HIV and severe acute respiratory syndrome coronavirus (SARS)) via interactions with their surface glycans. Crystallography has provided excellent insight into the mechanism by which DC-SIGNR interacts with small glycans, such as (GlcNAc)2Man3; however, direct observation of complexes with larger, physiological oligosaccharides, such as Man9GlcNAc2, remains elusive. We have utilized solution-state nuclear magnetic resonance spectroscopy to investigate DC-SIGNR binding and herein report the first backbone assignment of its active, calcium-bound carbohydrate recognition domain. Direct interactions with the small sugar fragments Man3, Man5, and (GlcNAc)2Man3 were investigated alongside Man9GlcNAc derived from recombinant gp120 (present on the HIV viral envelope), providing the first structural data for DC-SIGNR in complex with a virus-associated ligand, and unique binding modes were observed for each glycan. In particular, our data show that DC-SIGNR has a different binding mode for glycans on the HIV viral envelope compared with the smaller glycans previously observed in the crystalline state. This suggests that using the binding mode of Man9GlcNAc, instead of those of small glycans, may provide a platform for the design of DC-SIGNR inhibitors selective for high mannose glycans (like those on HIV). (15)N relaxation measurements provided the first information on the dynamics of the carbohydrate recognition domain, demonstrating that it is a highly flexible domain that undergoes ligand-induced conformational and dynamic changes that may explain the ability of DC-SIGNR to accommodate a range of glycans on viral surfaces.

Filovirus entry

A number of advances in recent years have significantly furthered our understanding of filovirus attachment and cellular tropism. For example, several cell-surface molecules have been identified as attachment factors with the potential to facilitate the in vivo targeting of particular cell types such as macrophages and hepatic cells. Furthermore, our knowledge of internalization and subsequent events during filovirus entry has also been widened, adding new variations to the paradigms for viral entry established for HIV and influenza. In particular, host cell factors such as endosomal proteases and the intracellular receptor Niemann-Pick C1 are now known to play a vital role in activating the membrane fusion potential of filovirus glycoproteins.

General mechanism for modulating immunoglobulin effector function

Immunoglobulins recognize and clear microbial pathogens and toxins through the coupling of variable region specificity to Fc-triggered cellular activation. These proinflammatory activities are regulated, thus avoiding the pathogenic sequelae of uncontrolled inflammation by modulating the composition of the Fc-linked glycan. Upon sialylation, the affinities for Fcγ receptors are reduced, whereas those for alternative cellular receptors, such as dendritic cell-specific intercellular adhesion molecule-3-grabbing nonintegrin (DC-SIGN)/CD23, are increased. We demonstrate that sialylation induces significant structural alterations in the Cγ2 domain and propose a model that explains the observed changes in ligand specificity and biological activity. By analogy to related complexes formed by IgE and its evolutionarily related Fc receptors, we conclude that this mechanism is general for the modulation of antibody-triggered immune responses, characterized by a shift between an "open" activating conformation and a "closed" anti-inflammatory state of antibody Fc fragments. This common mechanism has been targeted by pathogens to avoid host defense and offers targets for therapeutic intervention in allergic and autoimmune disorders.

Recent advances in DENV receptors

Dengue is an old disease caused by the mosquito-borne dengue viruses (DENVs), which have four antigenically distinct serotypes (DENV1-4). Infection by any of them can cause dengue fever (DF) and/or a more serious disease, that is, dengue hemorrhagic fever (DHF) or dengue shock syndrome (DSS). In recent decades, incidence of dengue disease has increased 30-fold, putting a third to half of the world's population living in dengue-endemic areas at high infection risk. However, the pathogenesis of the disease is still poorly understood. The virus binding with its host cell is not only a first and critical step in their replication cycle but also a key factor for the pathogenicity. In recent years, there have been significant advances in understanding interactions of DENVs with their target cells such as dendritic cells (DC), macrophages, endothelial cells, and hepatocytes. Although DENVs reportedly attach to a variety of receptors on these cells, consensus DENV receptors have not been defined. In this review, we summarize receptors for DENVs on different cells identified in recent years.

The physiological role of DC-SIGN: a tale of mice and men

The innate immune receptor DC-SIGN (dendritic cell-specific intercellular adhesion molecule-3 grabbing non-integrin) was discovered over a decade ago and was initially identified as a pattern recognition receptor. In addition to its ability to recognize a broad range of pathogen-derived ligands and self-glycoproteins, DC-SIGN also mediates intercellular adhesion, as well as antigen uptake and signaling, which is a functional hallmark of dendritic cells (DCs). Most research on DC-SIGN has relied on in vitro studies. The in vivo function of DC-SIGN is difficult to address, in part because there are eight genetic homologs in mice with no clear DC-SIGN ortholog. Here, we summarize the functions attributed to DC-SIGN based on in vitro data and discuss the limitations of available mouse models to uncover the physiological role of this receptor in vivo.

The C-type lectin receptor CLEC4M binds, internalizes, and clears von Willebrand factor and contributes to the variation in plasma von Willebrand factor levels

Genetic variation in or near the C-type lectin domain family 4 member M (CLEC4M) has been associated with plasma levels of von Willebrand factor (VWF) in healthy individuals. CLEC4M is a lectin receptor with a polymorphic extracellular neck region possessing a variable number of tandem repeats (VNTR). A total of 491 participants (318 patients with type 1 von Willebrand disease [VWD] and 173 unaffected family members) were genotyped for the CLEC4M VNTR polymorphism. Family-based association analysis on kindreds with type 1 VWD demonstrated an excess transmission of VNTR 6 to unaffected individuals (P = .0096) and an association of this allele with increased VWF:RCo (P = .029). CLEC4M-Fc bound to VWF. Immunofluorescence and enzyme-linked immunosorbent assay demonstrated that HEK 293 cells transfected with CLEC4M bound and internalized VWF. Cells expressing 4 or 9 copies of the CLEC4M neck region VNTR showed reduced interaction with VWF relative to CLEC4M with 7 VNTR (CLEC4M 4%-60% reduction, P < .001; CLEC4M 9%-45% reduction, P = .006). Mice expressing CLEC4M after hydrodynamic liver transfer have a 46% decrease in plasma levels of VWF (P = .0094). CLEC4M binds to and internalizes VWF, and polymorphisms in the CLEC4M gene contribute to variable plasma levels of VWF.

Kaposi's sarcoma-associated herpesvirus K3 and K5 proteins down regulate both DC-SIGN and DC-SIGNR

Kaposi’s sarcoma-associated herpesvirus (KSHV) is the etiological agent of multicentric Castleman’s disease, primary effusion lymphoma and Kaposi’s sarcoma. In this study, we show that like the C-type lectin DC-SIGN, the closely related DC-SIGNR can also enhance KSHV infection. Following infection, they are both targeted for down modulation and our data indicate that the KSHV MARCH-family ubiquitin ligase K5 is mediating this regulation and subsequent targeting for degradation of DC-SIGN and DC-SIGNR in the context of the virus. The closely related viral K3 protein, is also able to target these lectins in exogenous expressions studies, but only weakly during viral infection. In addition to requiring a functional RING-CH domain, several protein trafficking motifs in the C-terminal region of both K3 and K5 are important in regulation of DC-SIGN and DC-SIGNR. Further exploration of this modulation revealed that DC-SIGN is endocytosed from the cell surface in THP-1 monocytes, but degraded from an internal location with minimal endocytosis in HEK-293 cells. Pull-down data indicate that both K3 and K5 preferentially associate with immature forms of the lectins, mediating their ubiquitylation and degradation. Together, these data emphasize the molecular complexities of K3 and K5, while expanding the repertoire of targets of these two viral proteins.

Low expression of dendritic cell-specific intercellular adhesion molecule-grabbing nonintegrin-related protein in non-Hodgkin lymphoma and significant correlations with lactic acid dehydrogenase and β2-microglobulin

Dendritic cell-specific intercellular adhesion molecule-grabbing nonintegrin-related protein (DC-SIGNR), a type II integral membrane protein and a member of the C-type lectins, has been reported to bind various strains of HIV-1, HIV-2, and simian immunodeficiency virus. Serum DC-SIGNR is not currently available for the detection of non-Hodgkin lymphoma (NHL). Using an enzyme-linked immunosorbent assay (ELISA), we assessed the serum levels of DC-SIGNR in 70 cancer patients and 100 healthy controls. Additionally, using immunohistochemistry, we determined the expression of DC-SIGNR in the lymph nodes. Using the ELISA, low serum levels of DC-SIGNR were detected in the patients (median, 4.513 ng·L(-1); range, 1.066-9.232 ng·L(-1); p = 0.0003). Serum concentrations of DC-SIGNR correlated significantly with age (p = 0.0077) and lactic acid dehydrogenase (p = 0.0046) and β2-microglobulin (p = 0.0491) levels. However, we found no statistically significant correlation between serum DC-SIGNR levels and clinical data such as sex, Ann Arbor stage, B symptoms, and histologic subtypes. Moreover, NHL patients with a lower level of serum DC-SIGNR expression in lymphatic endothelial cells also showed negative immunostaining levels. These results suggest that DC-SIGNR is a biological molecule that may be potentially useful in NHL clinical settings.

Pathogenesis of hepatitis C during pregnancy and childhood

The worldwide prevalence of HCV infection is between 1% and 8% in pregnant women and between 0.05% and 5% in children. Yet the pathogenesis of hepatitis C during pregnancy and in the neonatal period remains poorly understood. Mother-to-child transmission (MTCT), a leading cause of pediatric HCV infection, takes place at a rate of <10%. Factors that increase the risk of MTCT include high maternal HCV viral load and coinfection with HIV-1 but, intriguingly, not breastfeeding and mode of delivery. Pharmacological prevention of MTCT is not possible at the present time because both pegylated interferon alfa and ribavirin are contraindicated for use in pregnancy and during the neonatal period. However, this may change with the recent introduction of direct acting antiviral agents. This review summarizes what is currently known about HCV infection during pregnancy and childhood. Particular emphasis is placed on how pregnancy-associated immune modulation may influence the progression of HCV disease and impact MTCT, and on the differential evolution of perinatally acquired HCV infection in children. Taken together, these developments provide insights into the pathogenesis of hepatitis C and may inform strategies to prevent the transmission of HCV from mother to child.

Antibodies and carbohydrate ligands binding to DC-SIGN differentially modulate receptor trafficking

DCs are regarded as key APCs that initiate humoral and cellular immune responses. Consequently, targeted delivery of Ag toward DC-specific receptors enhances vaccine efficacy. DC-SIGN is a C-type lectin receptor that facilitates DC-specific delivery of Ag. This is accomplished by conjugating Ag to receptor-specific Ab or carbohydrate ligands that bind to its carbohydrate recognition domain. Here, we investigated the fate of DC-SIGN following receptor triggering with Ab. Both whole and single-chain Ab induced rapid internalization of about half of the surface receptor molecules. Biochemical studies showed that about half of the receptor molecules were still intracellular after 3 h, while minimal or no resurfacing of internalized or newly synthesized unbound DC-SIGN molecules was observed. Prolonged exposure of DCs to DC-SIGN Ab, but not carbohydrate ligands, resulted in reduced receptor expression levels, which lasted up to 2 days following removal of the Ab. In addition, exposure to DC-SIGN Ab reduced the ability of the receptor to internalize. Consequently, DC-SIGN showed a poor ability to accumulate targeting Abs within DCs. Vaccine efficacy may therefore be enhanced by strategies increasing the amount of Ag entering via a single receptor molecule, such as the use of targeting moieties allowing DC-SIGN recycling or Ab-coated vaccine carriers.

The VNTR polymorphism of the DC-SIGNR gene and susceptibility to HIV-1 infection: a meta-analysis

Background

Dendritic cell-specific intercellular adhesion molecule-3-grabbing nonintegrin related (DC-SIGNR) can bind to the human immunodeficiency virus-1 (HIV-1) gp120 envelope glycoprotein and is thus important for the host-pathogen interaction in HIV-1 infection. Studies of the association between the variable number tandem repeat (VNTR) polymorphism of the DC-SIGNR gene and HIV-1 susceptibility have produced controversial results.

Methods and Findings

We conducted a meta-analysis of the data contained in the literature to clarify these findings. In total, 10 studies consisting of 2683 HIV-1 patients and 3263 controls (2130 healthy controls and 1133 HIV-1 exposed but seronegative (HESN) controls) were included. Odds ratios (ORs) with 95% confidence intervals (95% CIs) were assessed in the main analyses. Further stratified analyses by ethnicity and sample size were performed. By dividing the controls into two groups, healthy controls and HIV-1 exposed but seronegative (HESN) controls, we explored different genetic models to detect any association between the VNTR polymorphism and predisposition to HIV-1 infection. The results showed that the 5-repeat allele carriers (OR = 0.84, 95% CI = 0.73–0.96) and the 5/5 homozygous (OR = 0.68, 95% CI = 0.50–0.93) had significantly reduced risk when using the HIV-1 exposed but seronegative (HESN) as controls. The stratified analyses by ethnicity and sample size confirmed these findings. However, a low to moderate degree of heterogeneity was also found across studies.

Conclusions

Our findings demonstrate that the VNTR polymorphism of the DC-SIGNR gene is associated with a moderate effect on host susceptibility to HIV-1 infection. Similar to the 32-bp deletion in the chemokine receptor-5 gene (CCR5Δ32), the DC-SIGNR VNTR 5-repeat allele might have a role in resistance to HIV infection, particularly in Asian populations.

Association between CD209 -336A/G and -871A/G polymorphisms and susceptibility of tuberculosis: a meta-analysis

Background

The association between CD209 promoter polymorphisms (-336A/G, -871A/G) and tuberculosis (TB) risk has been widely reported, but results of previous studies remain controversial and ambiguous. To assess the association between CD209 polymorphisms and TB risk, a meta-analysis was performed.

Methods

Based on comprehensive searches of the PubMed, Embase, Web of Science, Weipu, and CBM databases, we identified outcome data from all articles estimating the association between CD209 polymorphisms and TB risk. The pooled odds ratio (OR) with 95% confidence intervals (CIs) were calculated.

Results

A total of 14 studies with 3,610 cases and 3,539 controls were identified. There was no significant association between CD209 -336A/G polymorphism and TB risk (OR = 1.04, 95% CI = 0.91–1.19 for G vs. A; OR = 1.13, 95% CI = 0.84–1.53 for GG vs. AA; OR = 1.04, 95% CI = 0.87–1.24 for GG+AG vs. AA; OR = 1.11, 95% CI = 0.88–1.39 for GG vs. AG+AA). However, the significant association was revealed for Asians in GG vs. AA (OR = 2.48, 95% CI = 1.46–4.22, P = 0.0008) and GG vs. AG+AA (OR = 2.10, 95% CI = 1.33–3.32, P = 0.001). For the CD209 -871A/G polymorphism, lack of an association was also found (OR = 0.81, 95% CI = 0.70–0.95 for G vs. A; OR = 1.00, 95% CI = 0.52–1.93 for GG vs. AA; OR = 0.73, 95% CI = 0.60–0.89 for GG+AG vs. AA; OR = 1.09, 95% CI = 0.57–2.10 for GG vs. AG+AA).

Conclusion

The present meta-analysis suggested that CD209 promoter polymorphisms (-336A/G, -871A/G) were unlikely to substantially contribute to TB susceptibility. However, the GG genotype of CD209 -336A/G polymorphism might be a genetic risk factor that increases TB susceptibility for Asians in GG vs. AA and GG vs. AG+AA.