The mannose receptor

Engineering Glucose Responsiveness Into Insulin

Insulin has a narrow therapeutic index, reflected in a small margin between a dose that achieves good glycemic control and one that causes hypoglycemia. Once injected, the clearance of exogenous insulin is invariant regardless of blood glucose, aggravating the potential to cause hypoglycemia. We sought to create a "smart" insulin, one that can alter insulin clearance and hence insulin action in response to blood glucose, mitigating risk for hypoglycemia. The approach added saccharide units to insulin to create insulin analogs with affinity for both the insulin receptor (IR) and mannose receptor C-type 1 (MR), which functions to clear endogenous mannosylated proteins, a principle used to endow insulin analogs with glucose responsivity. Iteration of these efforts culminated in the discovery of MK-2640, and its in vitro and in vivo preclinical properties are detailed in this report. In glucose clamp experiments conducted in healthy dogs, as plasma glucose was lowered stepwise from 280 mg/dL to 80 mg/dL, progressively more MK-2640 was cleared via MR, reducing by ∼30% its availability for binding to the IR. In dose escalations studies in diabetic minipigs, a higher therapeutic index for MK-2640 (threefold) was observed versus regular insulin (1.3-fold).

Soluble CD163 and mannose receptor associate with chronic hepatitis B activity and fibrosis and decline with treatment

BACKGROUND AND AIM

Liver macrophages are activated in chronic hepatitis B virus (CHB) infection and play a pivotal role in hepatic inflammation and fibrosis. However, their role during antiviral treatment is unclear. The soluble (s) macrophage activation markers, sCD163 and mannose receptor (sMR), are released during liver damage, and their serum levels reflect liver disease severity and portal hypertension. We aimed to investigate associations between sCD163 and sMR and histopathological activity and fibrosis and changes in sCD163, sMR, and hepatic CD163-expression following antiviral treatment in CHB patients.

METHODS

We assessed Ishak histological necroinflammatory activity and fibrosis scores in liver biopsies from 254 CHB patients and serially in 71 patients before and after nucleoside-analogue treatment. Liver CD163-expression was semi-quantitatively determined by immunohistochemistry and serum sCD163 and sMR measured by enzyme-linked immunosorbent assays.

RESULTS

Before treatment, the mean levels of sCD163 and sMR were 3.57 (SD 1.72) mg/L and 0.35 (0.12) mg/L. sCD163 and sMR increased with histological inflammatory activity (sCD163: r = 0.46, P < 0.00001; sMR: r = 0.48, P < 0.00001) and correlated positively with fibrosis (sCD163: OR 1.16, 95% CI:1.03-1.31; sMR: OR 1.34, 95% CI:1.13-1.59); both were markers of fibrosis independent of other biochemical parameters and risk factors. Antiviral treatment significantly reduced sCD163 (3.76 [1.46] vs 2.31 [0.95], P < 0.00001), sMR (0.37 [0.1] vs 0.29 [0.07], P < 0.00001) and hepatic CD163-expression (P = 0.0002).

CONCLUSION

The macrophage activation markers sCD163 and sMR were associated with activity and fibrosis in liver biopsies from CHB patients. Both serum markers decreased with antiviral treatment, along with decreased hepatic CD163 expression.

The macrophage activation marker sMR as a diagnostic and prognostic marker in patients with acute infectious disease with or without sepsis

Sepsis is a leading cause of mortality. This study aims to assess the utility of the soluble mannose receptor (sMR) as a biomarker of sepsis and mortality in patients hospitalized with suspected infection. Using an in-house ELISA assay the concentration of sMR was analyzed in the serum of patients from three prospective studies. Using Sepsis-3 guidelines, patients were stratified as no infection (NI, n = 68), verified infection without sepsis (NSEP, n = 133) and verified infection with sepsis (SEP, n = 190). Adverse outcome was assessed as death before 28 days. We show that the sensitivity of sMR to predict mortality [area under curve (AUC) = 0.77] exceeded the sensitivity of procalcitonin (PCT, AUC = 0.63), C-reactive protein (CRP, AUC = 0.61) and the macrophage soluble receptor, CD163 (sCD163, AUC = 0.74), while it was less accurate to predict diagnosis of sepsis [AUC(sMR) = 0.69 vs. AUC(PCT) = 0.79, AUC(CRP) = 0.71 and AUC(sCD163) = 0.66]. Median sMR was significantly higher in the group with SEP (0.55 mg/L), compared with the groups without sepsis (NI and NSEP) (0.39 mg/L, p < .0001), and among those who died compared to those who survived (0.89 mg/L vs. 0.44 mg/L, p < .0001). Our results, and the current literature, support further evaluation of sMR as a biomarker of sepsis and mortality among patients hospitalized with suspected infection.

A glucose-responsive insulin therapy protects animals against hypoglycemia

Hypoglycemia is commonly associated with insulin therapy, limiting both its safety and efficacy. The concept of modifying insulin to render its glucose-responsive release from an injection depot (of an insulin complexed exogenously with a recombinant lectin) was proposed approximately 4 decades ago but has been challenging to achieve. Data presented here demonstrate that mannosylated insulin analogs can undergo an additional route of clearance as result of their interaction with endogenous mannose receptor (MR), and this can occur in a glucose-dependent fashion, with increased binding to MR at low glucose. Yet, these analogs retain capacity for binding to the insulin receptor (IR). When the blood glucose level is elevated, as in individuals with diabetes mellitus, MR binding diminishes due to glucose competition, leading to reduced MR-mediated clearance and increased partitioning for IR binding and consequent glucose lowering. These studies demonstrate that a glucose-dependent locus of insulin clearance and, hence, insulin action can be achieved by targeting MR and IR concurrently.

O-Mannosylation of Proteins Enables Histoplasma Yeast Survival at Mammalian Body Temperatures

The ability to grow at mammalian body temperatures is critical for pathogen infection of humans. For the thermally dimorphic fungal pathogen Histoplasma capsulatum, elevated temperature is required for differentiation of mycelia or conidia into yeast cells, a step critical for invasion and replication within phagocytic immune cells. Posttranslational glycosylation of extracellular proteins characterizes factors produced by the pathogenic yeast cells but not those of avirulent mycelia, correlating glycosylation with infection. Histoplasma yeast cells lacking the Pmt1 and Pmt2 protein mannosyltransferases, which catalyze O-linked mannosylation of proteins, are severely attenuated during infection of mammalian hosts. Cells lacking Pmt2 have altered surface characteristics that increase recognition of yeast cells by the macrophage mannose receptor and reduce recognition by the β-glucan receptor Dectin-1. Despite these changes, yeast cells lacking these factors still associate with and survive within phagocytes. Depletion of macrophages or neutrophils in vivo does not recover the virulence of the mutant yeast cells. We show that yeast cells lacking Pmt functions are more sensitive to thermal stress in vitro and consequently are unable to productively infect mice, even in the absence of fever. Treatment of mice with cyclophosphamide reduces the normal core body temperature of mice, and this decrease is sufficient to restore the infectivity of O-mannosylation-deficient yeast cells. These findings demonstrate that O-mannosylation of proteins increases the thermotolerance of Histoplasma yeast cells, which facilitates infection of mammalian hosts.IMPORTANCE For dimorphic fungal pathogens, mammalian body temperature can have contrasting roles. Mammalian body temperature induces differentiation of the fungal pathogen Histoplasma capsulatum into a pathogenic state characterized by infection of host phagocytes. On the other hand, elevated temperatures represent a significant barrier to infection by many microbes. By functionally characterizing cells lacking O-linked mannosylation enzymes, we show that protein mannosylation confers thermotolerance on H. capsulatum, enabling infection of mammalian hosts.

Positional isomers of mannose–quinoline conjugates and their copper complexes: exploring the biological activity

Mannoconjugates show significant antibacterial activity. A regioisomer shows antiproliferative activity with copper(ii) ions.

Saccharomyces cerevisiae-Derived Mannan Does Not Alter Immune Responses to Aspergillus Allergens

Severe asthma with fungal sensitization predominates in the population suffering from allergic asthma, to which there is no cure. While corticosteroids are the mainstay in current treatment, other means of controlling inflammation may be beneficial. Herein, we hypothesized that mannan from Saccharomyces cerevisiae would dampen the characteristics of fungal allergic asthma by altering the pulmonary immune responses. Using wild-type and transgenic mice expressing the human mannose receptor on smooth muscle cells, we explored the outcome of mannan administration during allergen exposure on the pathogenesis of fungal asthma through measurement of cardinal features of disease such as inflammation, goblet cell number, and airway hyperresponsiveness. Mannan treatment did not alter most hallmarks of allergic airways disease in wild-type mice. Transgenic mice treated with mannan during allergen exposure had an equivalent response to non-mannan-treated allergic mice except for a prominent granulocytic influx into airways and cytokine availability. Our studies suggest no role for mannan as an inflammatory regulator during fungal allergy.

Mannose receptor modulates macrophage polarization and allergic inflammation through miR-511-3p

BACKGROUND

Mannose receptor (MRC1/CD206) has been suggested to mediate allergic sensitization and asthma to multiple glycoallergens, including cockroach allergens.

OBJECTIVE

We sought to determine the existence of a protective mechanism through which MRC1 limits allergic inflammation through its intronic miR-511-3p.

METHODS

We examined MRC1-mediated cockroach allergen uptake by lung macrophages and lung inflammation using C57BL/6 wild-type (WT) and Mrc1-/- mice. The role of miR-511-3p in macrophage polarization and cockroach allergen-induced lung inflammation in mice transfected with adeno-associated virus (AAV)-miR-511-3p (AAV-cytomegalovirus-miR-511-3p-enhanced green fluorescent protein) was analyzed. Gene profiling of macrophages with or without miR-511-3p overexpression was also performed.

RESULTS

Mrc1-/- lung macrophages showed a significant reduction in cockroach allergen uptake compared with WT mice, and Mrc1-/- mice had an exacerbated lung inflammation with increased levels of cockroach allergen-specific IgE and TH2/TH17 cytokines in a cockroach allergen-induced mouse model compared with WT mice. Macrophages from Mrc1-/- mice showed significantly reduced levels of miR-511-3 and an M1 phenotype, whereas overexpression of miR-511-3p rendered macrophages to exhibit a M2 phenotype. Furthermore, mice transfected with AAV-miR-511-3p showed a significant reduction in cockroach allergen-induced inflammation. Profiling of macrophages with or without miR-511-3p overexpression identified 729 differentially expressed genes, wherein expression of prostaglandin D2 synthase (Ptgds) and its product PGD2 were significantly downregulated by miR-511-3p. Ptgds showed a robust binding to miR-511-3p, which might contribute to the protective effect of miR-511-3p. Plasma levels of miR-511-3p were significantly lower in human asthmatic patients compared with nonasthmatic subjects.

CONCLUSION

These studies support a critical but previously unrecognized role of MRC1 and miR-511-3p in protection against allergen-induced lung inflammation.

Candida albicans-derived mannoproteins activate NF-κB in reporter cells expressing TLR4, MD2 and CD14

The ability of soluble C. albicans 20A (serotype A) mannoprotein (CMP) to serve as a ligand for toll-like receptor 4 (TLR4) and its co-receptors was examined using commercially available and stably-transfected HEK293 cells that express human TLR4, MD2 and CD14, but not MR. These TLR4 reporter cells also express an NF-κB-dependent, secreted embryonic alkaline phosphatase (SEAP) reporter gene. TLR4-reporter cells exhibited a dose-dependent SEAP response to both LPS and CMP, wherein peak activation was achieved after stimulation with 40–50 μg/mL of CMP. Incubation on polymyxin B resin had no effect on CMP’s ligand activity, but neutralized LPS-spiked controls. HEK293 Null cells lacking TLR4 and possessing the same SEAP reporter failed to respond to LPS or CMP, but produced SEAP when activated with TNFα. Reporter cell NF-κB responses were accompanied by transcription of IL-8, TNFα, and COX-2 genes. Celecoxib inhibited LPS-, CMP-, and TNFα-dependent NF-κB responses; whereas, indomethacin had limited effect on LPS and CMP responses. SEAP production in response to C. albicans A9 mnn4Δ mutant CMP, lacking phosphomannosylations on N-linked glycans, was significantly greater (p ≤ 0.005) than SEAP responses to CMP derived from parental A9 (both serotype B). These data confirm that engineered human cells expressing TLR4, MD2 and CD14 can respond to CMP with NF-κB activation and the response can be influenced by variations in CMP-mannosylation. Future characterizations of CMPs from other sources and their application in this model may provide further insight into variations observed with TLR4 dependent innate immune responses targeting different C. albicans strains.

The soluble mannose receptor (sMR) is elevated in alcoholic liver disease and associated with disease severity, portal hypertension, and mortality in cirrhosis patients

Background and aims

Hepatic macrophages (Kupffer cells) are involved in the immunopathology of alcoholic liver disease (ALD). The mannose receptor (MR, CD206), expressed primarily by macrophages, mediates endocytosis, antigen presentation and T-cell activation. A soluble form, sMR, has recently been identified in humans.

We aimed to study plasma sMR levels and its correlation with disease severity and survival in ALD patients.

Methods

We included 50 patients with alcoholic hepatitis (AH), 68 alcoholic cirrhosis (AC) patients (Child-Pugh A (23), B (24), C (21)), and 21 healthy controls (HC). Liver status was described by the Glasgow Alcoholic Hepatitis Score (GAHS), Child-Pugh (CP) and MELD-scores, and in AC patients the hepatic venous pressure gradient (HVPG) was measured by liver vein catheterisation. We used Kaplan-Meier statistics for short-term survival (84-days) in AH patients and long-term (4 years) in AC patients. We measured plasma sMR by ELISA.

Results

Median sMR concentrations were significantly elevated in AH 1.32(IQR:0.69) and AC 0.46(0.5) compared to HC 0.2(0.06) mg/L; p<0.001 and increased in a stepwise manner with the CP-score (p<0.001). In AC sMR predicted portal hypertension (HVPG ≥10 mmHg) with an area under the Receiver Operator Characteristics curve of 0.86 and a high sMR cut-off (>0.43 mg/l) was associated with increased mortality (p = 0.005).

Conclusion

The soluble mannose receptor is elevated in alcoholic liver disease, especially in patients with AH. Its blood level predicts portal hypertension and long-term mortality in AC patients.

Structural Insights into the pH-Dependent Conformational Change and Collagen Recognition of the Human Mannose Receptor

Mannose receptor (MR, CD206) is an endocytic receptor on microphages and dendritic cells. It recognizes multiple ligands and plays important roles in regulating immune responses and maintaining glycoprotein homeostasis. However, the structure and functional mechanism of MR remain unclear. Here we determine the crystal structures of the N-terminal fragments of MR and reveal the potential binding mode of collagen on the fibronectin II domain. The SAXS and other biophysical data suggest that MR adopts an extended conformation at physiological pH and undergoes conformational changes as pH decreases, resulting in a compact conformation in an acidic environment. Moreover, biochemical data show that MR binds to collagen in a Ca²⁺-enhanced manner at physiological pH, whereas Ca²⁺ has no effect on the binding at acidic pH. These results provide a model for the dynamic mechanism of MR regarding its ligand binding and release during the recycling between cell surface and endosomes.

Discovery of a Potential Plasma Protein Biomarker Panel for Acute-on-Chronic Liver Failure Induced by Hepatitis B Virus

Hepatitis B virus (HBV)-associated acute-on-chronic liver failure (HBV-ACLF), characterized by an acute deterioration of liver function in the patients with chronic hepatitis B (CHB), is lack of predicting biomarkers for prognosis. Plasma is an ideal sample for biomarker discovery due to inexpensive and minimally invasive sampling and good reproducibility. In this study, immuno-depletion of high-abundance plasma proteins followed by iTRAQ-based quantitative proteomic approach was employed to analyze plasma samples from 20 healthy control people, 20 CHB patients and 20 HBV-ACLF patients, respectively. As a result, a total of 427 proteins were identified from these samples, and 42 proteins were differentially expressed in HBV-ACLF patients as compared to both CHB patients and healthy controls. According to bioinformatics analysis results, 6 proteins related to immune response (MMR), inflammatory response (OPN, HPX), blood coagulation (ATIII) and lipid metabolism (APO-CII, GP73) were selected as biomarker candidates. Further ELISA analysis confirmed the significant up-regulation of GP73, MMR, OPN and down-regulation of ATIII, HPX, APO-CII in HBV-ACLF plasma samples (p < 0.01). Moreover, receiver operating characteristic (ROC) curve analysis revealed high diagnostic value of these candidates in assessing HBV-ACLF. In conclusion, present quantitative proteomic study identified 6 novel HBV-ACLF biomarker candidates and might provide fundamental information for development of HBV-ACLF biomarker.

Development and plasticity of meningeal lymphatic vessels

The recent discovery of meningeal lymphatic vessels (LVs) has raised interest in their possible involvement in neuropathological processes, yet little is known about their development or maintenance. We show here that meningeal LVs develop postnatally, appearing first around the foramina in the basal parts of the skull and spinal canal, sprouting along the blood vessels and cranial and spinal nerves to various parts of the meninges surrounding the central nervous system (CNS). VEGF-C, expressed mainly in vascular smooth muscle cells, and VEGFR3 in lymphatic endothelial cells were essential for their development, whereas VEGF-D deletion had no effect. Surprisingly, in adult mice, the LVs showed regression after VEGF-C or VEGFR3 deletion, administration of the tyrosine kinase inhibitor sunitinib, or expression of VEGF-C/D trap, which also compromised the lymphatic drainage function. Conversely, an excess of VEGF-C induced meningeal lymphangiogenesis. The plasticity and regenerative potential of meningeal LVs should allow manipulation of cerebrospinal fluid drainage and neuropathological processes in the CNS.

Antifungal Activity of Plasmacytoid Dendritic Cells and the Impact of Chronic HIV Infection

Due to the effectiveness of combined antiretroviral therapy, people living with HIV can control viral replication and live longer lifespans than ever. However, HIV-positive individuals still face challenges to their health and well-being, including dysregulation of the immune system resulting from years of chronic immune activation, as well as opportunistic infections from pathogenic fungi. This review focuses on one of the key players in HIV immunology, the plasmacytoid dendritic cell (pDC), which links the innate and adaptive immune response and is notable for being the body’s most potent producer of type-I interferons (IFNs). During chronic HIV infection, the pDC compartment is greatly dysregulated, experiencing a substantial depletion in number and compromise in function. This immune dysregulation may leave patients further susceptible to opportunistic infections. This is especially important when considering a new role for pDCs currently emerging in the literature: in addition to their role in antiviral immunity, recent studies suggest that pDCs also play an important role in antifungal immunity. Supporting this new role, pDCs express C-type lectin receptors including dectin-1, dectin-2, dectin-3, and mannose receptor, and toll-like receptors-4 and -9 that are involved in recognition, signaling, and response to a wide variety of fungal pathogens, including Aspergillus fumigatus, Cryptococcus neoformans, Candida albicans, and Pneumocystis jirovecii. Accordingly, pDCs have been demonstrated to recognize and respond to certain pathogenic fungi, measured via activation, cytokine production, and fungistatic activity in vitro, while in vivo mouse models indicated a strikingly vital role for pDCs in survival against pulmonary Aspergillus challenge. Here, we discuss the role of the pDC compartment and the dysregulation it undergoes during chronic HIV infection, as well as what is known so far about the role and mechanisms of pDC antifungal activity.

The Mannose Receptor in Regulation of Helminth-Mediated Host Immunity

Infection with parasitic helminths affects humanity and animal welfare. Parasitic helminths have the capacity to modulate host immune responses to promote their survival in infected hosts, often for a long time leading to chronic infections. In contrast to many infectious microbes, however, the helminths are able to induce immune responses that show positive bystander effects such as the protection to several immune disorders, including multiple sclerosis, inflammatory bowel disease, and allergies. They generally promote the generation of a tolerogenic immune microenvironment including the induction of type 2 (Th2) responses and a sub-population of alternatively activated macrophages. It is proposed that this anti-inflammatory response enables helminths to survive in their hosts and protects the host from excessive pathology arising from infection with these large pathogens. In any case, there is an urgent need to enhance understanding of how helminths beneficially modulate inflammatory reactions, to identify the molecules involved and to promote approaches to exploit this knowledge for future therapeutic interventions. Evidence is increasing that C-type lectins play an important role in driving helminth-mediated immune responses. C-type lectins belong to a large family of calcium-dependent receptors with broad glycan specificity. They are abundantly present on immune cells, such as dendritic cells and macrophages, which are essential in shaping host immune responses. Here, we will focus on the role of the C-type lectin macrophage mannose receptor (MR) in helminth-host interactions, which is a critically understudied area in the field of helminth immunobiology. We give an overview of the structural aspects of the MR including its glycan specificity, and the functional implications of the MR in helminth-host interactions focusing on a few selected helminth species.

Precision Targeting of Tumor Macrophages with a CD206 Binding Peptide

Tumor-associated macrophages (TAMs) expressing the multi-ligand endocytic receptor mannose receptor (CD206/MRC1) contribute to tumor immunosuppression, angiogenesis, metastasis, and relapse. Here, we describe a peptide that selectively targets MRC1-expressing TAMs (MEMs). We performed in vivo peptide phage display screens in mice bearing 4T1 metastatic breast tumors to identify peptides that target peritoneal macrophages. Deep sequencing of the peptide-encoding inserts in the selected phage pool revealed enrichment of the peptide CSPGAKVRC (codenamed “UNO”). Intravenously injected FAM-labeled UNO (FAM-UNO) homed to tumor and sentinel lymph node MEMs in different cancer models: 4T1 and MCF-7 breast carcinoma, B16F10 melanoma, WT-GBM glioma and MKN45-P gastric carcinoma. Fluorescence anisotropy assay showed that FAM-UNO interacts with recombinant CD206 when subjected to reducing conditions. Interestingly, the GSPGAK motif is present in all CD206-binding collagens. FAM-UNO was able to transport drug-loaded nanoparticles into MEMs, whereas particles without the peptide were not taken up by MEMs. In ex vivo organ imaging, FAM-UNO showed significantly higher accumulation in sentinel lymph nodes than a control peptide. This study suggests applications for UNO peptide in diagnostic imaging and therapeutic targeting of MEMs in solid tumors.

Targeting C-type lectin receptors: a high-carbohydrate diet for dendritic cells to improve cancer vaccines

There is a growing understanding of why certain patients do or do not respond to checkpoint inhibition therapy. This opens new opportunities to reconsider and redevelop vaccine strategies to prime an anticancer immune response. Combination of such vaccines with checkpoint inhibitors will both provide the fuel and release the brake for an efficient anticancer response. Here, we discuss vaccine strategies that use C-type lectin receptor (CLR) targeting of APCs, such as dendritic cells and macrophages. APCs are a necessity for the priming of antigen-specific cytotoxic and helper T cells. Because CLRs are natural carbohydrate-recognition receptors highly expressed by multiple subsets of APCs and involved in uptake and processing of Ags for presentation, these receptors seem particularly interesting for targeting purposes.

Mannose Surfaces Exhibit Self-Latching, Water Structuring, and Resilience to Chaotropes: Implications for Pathogen Virulence

Several viral and fungal pathogens, including HIV, SARS, Dengue, Ebola, and Cryptococcus neoformans, display a preponderance of mannose residues on their surface, particularly during the infection cycle or in harsh environments. The innate immune system, on the other hand, abounds in mannose receptors which recognize mannose residues on pathogens and trigger their phagocytosis. We pose the question if there is an advantage for pathogens to display mannose on their surface, despite these residues being recognized by the immune system. The surface properties and interactions of opposing monolayers of mannobiose (disaccharide of mannose) were probed using atomic force spectroscopy. Unlike its diastereoisomer lactose, mannobiose molecules exhibited lateral packing interactions that manifest on the surface scale as a self-recognizing latch. A break-in force is required for opposing surfaces to penetrate and a breakout (or self-adhesion force) of similar magnitude is required for penetrated surfaces to separate. A hierarchy of self-adhesion forces was distinguished as occurring at the single residue (∼25 pN), cluster (∼250 pN), monolayer (∼1.1 nN), and supramonolayer level. The break-in force and break-out force appear resilient to the presence of simple chaotropes that attenuate a layer of structured water around the mannose surface. The layer of structured water otherwise extends to distances several times longer than a mannobiose residue, indicating a long-range propagation of the hydrogen bonding imposed by the residues. The span of the structured water increases with the velocity of an approaching surface, similar to shear thickening, but fissures at higher approach velocities. Our studies suggest that mannose residues could guide interpathogen interactions, such as in biofilms, and serve as a moated fortress for pathogens to hide behind to resist detection and harsh environments.

Therapeutic potential of carbohydrates as regulators of macrophage activation

It is well established for a broad range of disease states, including cancer and Mycobacterium tuberculosis infection, that pathogenesis is bolstered by polarisation of macrophages towards an anti-inflammatory phenotype, known as M2. As these innate immune cells are relatively long-lived, their re-polarisation to pro-inflammatory, phagocytic and bactericidal "classically activated" M1 macrophages is an attractive therapeutic approach. On the other hand, there are scenarios where the resolving inflammation, wound healing and tissue remodelling properties of M2 macrophages are beneficial - for example the successful introduction of biomedical implants. Although there are numerous endogenous and exogenous factors that have an impact on the macrophage polarisation spectrum, this review will focus specifically on prominent macrophage-modulating carbohydrate motifs with a view towards highlighting structure-function relationships and therapeutic potential.

Peptide dendrimers: drug/gene delivery and other approaches

Dendrimers are versatile hyperbranched molecules, which have deserved attention especially for their potential in many applications, including biological. Peptide dendrimers comprise interesting classes of dendrimers, and their use has been emphasized as a drug/bioactive compound delivery system, mostly in the antineoplastic area. The bioactive molecules can be covalently linked or entrapped inside the peptide derivative. Self-assembled nanocarriers are a recent trend in the design of potential delivery systems, and pH-sensitive carriers, one of their methods, have been designed to control their systems. In addition, the use of targeting peptides or other specific groups that direct the drug/bioactive compounds to specific organs is an important trend in the search for better drug delivery systems. Recent examples have been given in the literature, showing that gene delivery as another important peptide dendrimer application. It is worth emphasizing that some peptide dendrimers show activity per se, without bioactive compounds. Immune compounds and vaccines are presented herein, as well as uses of other peptide dendrimers are briefly discussed in this review, which encompasses around 10 years of work.

Lectin Receptors Expressed on Myeloid Cells

Lectins recognize a diverse array of carbohydrate structures and perform numerous essential biological functions. Here we focus on only two families of lectins, the Siglecs and C-type lectins. Triggering of intracellular signaling cascades following ligand recognition by these receptors can have profound effects on the induction and modulation of immunity. In this chapter, we provide a brief overview of each family and then focus on selected examples that highlight how these lectins can influence myeloid cell functioning in health and disease. Receptors that are discussed include Sn (Siglec-1), CD33 (Siglec-3), and Siglec-5, -7, -8, -9, -10, -11, -14, -15, -E, -F, and -G as well as Dectin-1, MICL, Dectin-2, Mincle/MCL, and the macrophage mannose receptor.

Mannosylated liposomes improve therapeutic effects of paclitaxel in colon cancer models

Mannose receptor (MR) is a highly effective endocytic receptor. It is closely related to tumour immune escape and metastasis. We found that MR was highly expressed in some colon cancer cell lines such as CT26 and HCT116 cells. Therefore, MR might be a potential target in colon cancer therapy. In this study, we aimed to develop mannosylated liposomes containing anticancer drug paclitaxel and investigate the potential effects on targeted therapy for colon cancer. Mannosylated liposomes were prepared by film dispersion method. Characterisation, drug release behaviour, cytotoxicity, cellular uptake, anti-tumour efficacy and safety profiles of liposomes were investigated. The results showed that mannosylated liposomes had a higher CT26 cells uptake efficiency and tumour inhibition rate, which might be due to the target effect to MR. And no notable toxicity was observed. Taken together, these data demonstrated that mannosylated liposomes could target colon cancer and improve the efficacy of chemotherapy.

Preoperative serum macrophage activated biomarkers soluble mannose receptor (sMR) and soluble haemoglobin scavenger receptor (sCD163), as novel markers for the diagnosis and prognosis of gastric cancer

Soluble mannose receptor (sMR) and soluble haemoglobin scavenger receptor (sCD163) are macrophage activation markers which have previously been demonstrated to be increased in patients with inflammation, auto-immunity and malignancies. To investigate the clinical diagnostic and prognostic significance of preoperative serum sMR and sCD163, the present study investigated 143 gastric cancer (GC) patients, 66 subjects with benign gastric disease and 59 healthy controls, using an ELISA assay. Preoperative serum levels of sMR and sCD163 ranged from 0.165 to 0.885 µg/ml (median=0.374 µg/ml) and from 0.291 to 1.760 µg/ml (median=0.628 µg/ml) in GC patients, respectively. The expression levels of sMR and sCD163 were elevated compared with all controls (P<0.0001). Receiver operating characteristic analyses suggested that the optimum diagnostic cut-offs for sMR and sCD163 were 0.3405 µg/ml [area under curve (AUC) 0.7284, sensitivity 61.54%, and specificity 73.60%] and 0.6645 µg/ml (AUC 0.7766, sensitivity 53.85%, and specificity 86.40%), respectively. Notably, the measurement of serum sMR and sCD163 levels in conjugation, markedly enhanced the diagnostic accuracy (AUC 0.8490, sensitivity 70.63% and specificity 84.00%). Preoperative serum sMR and sCD163 levels correlated significantly with serum carcinoembryonic antigen, CA199, CA724 and CA125 concentrations in GC patients (P<0.05), however this association was not observed with sMR and CA724. High preoperative serum sMR and sCD163 levels correlated significantly with shorter overall survival (P=0.0041; P<0.0001, respectively) and were demonstrated to act as adverse prognostic factors (P=0.006; P<0.001, respectively). Furthermore, preoperative serum sMR and sCD163 levels correlated positively with the degree of lymphatic and distant metastasis of GC. In conclusion, preoperative serum sMR and sCD163 may be novel diagnostic and prognostic markers for GC and further studies are required in order to elucidate the underlying molecular mechanisms of sMR and CD163 in the development and progression of GC.

Carbon monoxide-releasing molecule, CORM-3, modulates alveolar macrophage M1/M2 phenotype in vitro

Alveolar macrophages are key contributors to both the promotion and resolution of inflammation in the lung and are categorized into pro-inflammatory (M1) and anti-inflammatory (M2) phenotypes. The change in M1/M2 balance has been reported in various pulmonary diseases and is a target for therapeutic intervention. The aim of this study was to assess the modulation of M1/M2 phenotype in alveolar macrophages by water-soluble carbon monoxide-releasing molecule-3 (CORM-3). Rat alveolar macrophages (AM) (NR8383) in culture were stimulated with LPS (5 ng/ml)/IFN-γ (10 U/ml) or IL-4 (10 ng/ml)/IL-13 (10 ng/ml) to induce M1 and M2 phenotypes, respectively. Expression of M1 phenotype markers, iNOS and TNF-α, and M2 phenotype markers, CD206 and Ym-1, was assessed by western blotting after 1, 3, 6, or 24 h in the absence or presence of CORM-3 (0.15 mM) treatment. Inactive CORM-3 (iCORM-3) was used as a control. Treatment of naïve (unstimulated) AM with CORM-3 promoted progression of the M2 phenotype as evidenced by the increased expression of CD206 (at 1 h; 1.8-fold) and Ym-1 (at 3 h; 1.9-fold), respectively. Surprisingly, CORM-3 treatment also upregulated the expression of iNOS protein as assessed 6 h following stimulation of AM with CORM-3 (2.6-fold). On the contrary, CORM-3 effectively reduced LPS/IFN-γ-induced expression of iNOS protein (0.6-fold); however, it had no effect on TNF-α expression. Finally, CORM-3 acutely (1-3 h) upregulated CD206 (1.4-fold) and Ym-1 (1.6-fold) levels in IL-4-/IL-13-treated (M2-stimulus) macrophages. These findings indicate that CORM-3 modulates macrophage M1 and M2 phenotypes in vitro with respect to continuous suppression of iNOS expression in M1-polarized macrophages and transient (early-phase) upregulation of CD206 and Ym-1 proteins in M2-polarized macrophages.

Diversity of Human and Macaque Airway Immune Cells at Baseline and during Tuberculosis Infection

Immune cells of the distal airways serve as "first responders" of host immunity to the airborne pathogen Mycobacterium tuberculosis (Mtb). Mtb infection of cynomolgus macaques recapitulates the range of human outcomes from clinically silent latent tuberculosis infection (LTBI) to active tuberculosis of various degrees of severity. To further advance the application of this model to human studies, we compared profiles of bronchoalveolar lavage (BAL) cells of humans and cynomolgus macaques before and after Mtb infection. A simple gating strategy effectively defined BAL T-cell and phagocyte populations in both species. BAL from Mtb-naive humans and macaques showed similar differential cell counts. BAL T cells of macaques were composed of fewer CD4⁺cells but more CD8⁺ and CD4⁺CD8⁺ double-positive cells than were BAL T cells of humans. The most common mononuclear phagocyte population in BAL of both species displayed coexpression of HLA-DR, CD206, CD11b, and CD11c; however, multiple phagocyte subsets displaying only some of these markers were observed as well. Macaques with LTBI displayed a marked BAL lymphocytosis that was not observed in humans with LTBI. In macaques, the prevalence of specific mononuclear phagocyte subsets in baseline BAL correlated with ultimate outcomes of Mtb infection (i.e., LTBI versus active disease). Overall, these findings demonstrate the comparability of studies of pulmonary immunity to Mtb in humans and macaques. They also indicate a previously undescribed complexity of airway mononuclear phagocyte populations that suggests further lines of investigation relevant to understanding the mechanisms of both protection from and susceptibility to the development of active tuberculosis within the lung.

Tissue macrophages: heterogeneity and functions

Macrophages are present in all vertebrate tissues, from mid-gestation throughout life, constituting a widely dispersed organ system. They promote homeostasis by responding to internal and external changes within the body, not only as phagocytes in defence against microbes and in clearance of dead and senescent cells, but also through trophic, regulatory and repair functions. In this review, we describe macrophage phenotypic heterogeneity in different tissue environments, drawing particular attention to organ-specific functions.

Soluble CD206 plasma levels in rheumatoid arthritis reflect decrease in disease activity

Rheumatoid arthritis (RA) is characterized by chronic joint inflammation and infiltration by activated macrophages. TNFα is a central mediator in this process. The mannose receptor, CD206, is a scavenger receptor expressed by M2_A-macrophages and dendritic cells. It is involved in collagen internalization and degradation. The soluble form has been suggested as a biomarker of M2_A-macrophage activation. The aim of this study was to investigate sCD206 plasma levels in early RA patients initiating anti-TNFα treatment. Plasma levels of sCD206 were measured by ELISA in samples from 155 early RA patients with an average symptom duration of 3 months. Patients were randomized to 12 months' methotrexate and placebo (PLA) or methotrexate and adalimumab (ADA) treatment, followed by open-label treatment with disease-modifying anti-rheumatic drugs (DMARD) and if needed, ADA. Disease activity was assessed at baseline and after 3, 6, 12 and 24 months. Baseline plasma level of sCD206 in treatment naïve RA patients was 0.33 mg/L (CI: 0.33-0.38 mg/L) corresponding to the upper part of the reference interval for healthy controls (0.10-0.43 mg/L). In the PLA group, sCD206 levels decreased after 3 months, but did not differ from baseline after 6 months. In the ADA group, however, levels remained lower than baseline throughout the treatment period. In conclusion, initially, plasma sCD206 in early RA patients decreased in accordance with disease activity and initiation of DMARD treatment. Treatment with anti-TNFα preserved this decrease throughout the study period.

Whole Blood Profiling of Bacillus Calmette-Guérin-Induced Trained Innate Immunity in Infants Identifies Epidermal Growth Factor, IL-6, Platelet-Derived Growth Factor-AB/BB, and Natural Killer Cell Activation

Vaccination of infants with bacillus Calmette-Guérin (BCG) activates both the innate and adaptive arms of the immune response. The antimycobacterial effects of these responses most likely account for the ability of BCG to protect against childhood forms of tuberculosis (TB). There is also evidence for a heterologous protective effect of BCG vaccination against TB-unrelated mortality in low birth weight infants. A possible mechanism of action of this effect, the induction of trained innate immunity, has been demonstrated when cells from BCG-vaccinated adults are restimulated in vitro with non-related microbial stimuli. Our aim was to examine an extensive panel of secreted immune biomarkers to characterize the profile of trained innate immunity in infants. Stimulation of whole blood for 48 h was performed 4 months after BCG vaccination, or in control unvaccinated infants. Stimulants were lipopolysaccharide; Pam3Cys (P3C); heat-killed Candida albicans, Staphylococcus aureus, Escherichia coli, and a lysate of Mycobacterium tuberculosis. Culture supernatants were tested for secreted cytokines and chemokines by 42-plex bead array and monocytes and natural killer (NK) cells assessed for expression of activation markers by flow cytometry. BCG-vaccinated infants displayed increases in 11 cytokines and chemokines in response to different non-specific innate immunity stimuli: epidermal growth factor (EGF); eotaxin; IL-6; IL-7; IL-8; IL-10; IL-12p40; monocyte chemotactic protein-3; macrophage inflammatory protein-1α; soluble CD40 ligand and platelet-derived growth factor (PDGF)-AB/BB. Although each stimulant induced a distinct response profile, three analytes, EGF, IL-6, and PDGF-AB/BB, were commonly higher after stimulation with Pam3Cys, C. albicans, and S. aureus. Conversely, certain cytokines such as interferon gamma-inducible protein-10, IL-2, IL-13, IL-17, GM-CSF, and GRO were suppressed in BCG-vaccinated infants, while no increases in TNFα or IL-1β production were detected. We did not observe a concomitant, BCG-associated change in monocyte surface activation markers in response to non-specific stimuli, but we detected a significant increase in CD69 expression on NK cells in response to Pam3Cys. Pam3Cys-induced NK cell activation correlated with the magnitude of IL-12p40 and IL-10 responses to the same stimulant. This study reveals a novel cytokine/chemokine biomarker signature of BCG-induced trained innate immunity in infants and the involvement of NK cells in these responses.

Macrophage-specific nanotechnology-driven CD163 overexpression in human macrophages results in an M2 phenotype under inflammatory conditions

M1 macrophages release proinflammatory factors during inflammation. They transit to an M2 phenotype and release anti-inflammatory factors to resolve inflammation. An imbalance in the transition from M1 to M2 phenotype in macrophages contributes to the development of persistent inflammation. CD163, a member of the scavenger receptor cysteine-rich family, is an M2 macrophage marker. The functional role of CD163 during the resolution of inflammation is not completely known. We postulate that CD163 contributes to the transition from M1 to M2 phenotype in macrophages. We induced CD163 gene in THP-1 and primary human macrophages using polyethylenimine nanoparticles grafted with a mannose ligand (Man-PEI). This nanoparticle specifically targets cells of monocytic origin via mannose receptors. Cells were challenged with a single or a double stimulation of lipopolysaccharide (LPS). A CD163 or empty plasmid was complexed with Man-PEI nanoparticles for cell transfections. Quantitative RT-PCR, immunocytochemistry, and ELISAs were used for molecular assessments. CD163-overexpressing macrophages displayed reduced levels of tumor necrosis factor-alpha (TNF)-α and monocytes chemoattractant protein (MCP)-1 after a single stimulation with LPS. Following a double stimulation paradigm, CD163-overexpressing macrophages showed an increase of interleukin (IL)-10 and IL-1ra and a reduction of MCP-1. This anti-inflammatory phenotype was partially blocked by an anti-CD163 antibody (effects on IL-10 and IL-1ra). A decrease in the release of TNF-α, IL-1β, and IL-6 was observed in CD163-overexpressing human primary macrophages. The release of IL-6 was blocked by an anti-CD163 antibody in the CD163-overexpressing group. Our data show that the induction of the CD163 gene in human macrophages under inflammatory conditions produces changes in cytokine secretion in favor of an anti-inflammatory phenotype. Targeting macrophages to induce CD163 using cell-directed nanotechnology is an attractive and practical approach for inflammatory conditions that could lead to persistent pain, i.e. major surgeries, burns, rheumatoid arthritis, etc.

Intracellular uptake of macromolecules by brain lymphatic endothelial cells during zebrafish embryonic development

The lymphatic system controls fluid homeostasis and the clearance of macromolecules from interstitial compartments. In mammals brain lymphatics were only recently discovered, with significant implications for physiology and disease. We examined zebrafish for the presence of brain lymphatics and found loosely connected endothelial cells with lymphatic molecular signature covering parts of the brain without forming endothelial tubular structures. These brain lymphatic endothelial cells (BLECs) derive from venous endothelium, are distinct from macrophages, and are sensitive to loss of Vegfc. BLECs endocytose macromolecules in a selective manner, which can be blocked by injection of mannose receptor ligands. This first report on brain lymphatic endothelial cells in a vertebrate embryo identifies cells with unique features, including the uptake of macromolecules at a single cell level. Future studies will address whether this represents an uptake mechanism that is conserved in mammals and how these cells affect functions of the embryonic and adult brain.

DOI:http://dx.doi.org/10.7554/eLife.25932.001

Glycans and glycan-specific IgE in clinical and molecular allergology: Sensitization, diagnostics, and clinical symptoms

Glycan-specific IgE antibodies cross-react with highly similar or even identical carbohydrate structures on a variety of different natural allergens, the so-called cross-reactive carbohydrate determinants (CCDs). In clinical practice CCDs often interfere with the specificity of in vitro allergy diagnostics, thus impairing allergy therapy decisions for individual patients. Strikingly, these IgE antibodies directed against CCDs often do not cause clinically relevant allergy symptoms. On the other hand, the IgE-binding glycan allergen galactose-α-(1,3)-galactose (α-Gal) is associated with IgE-mediated delayed anaphylaxis in meat allergy. The reason for this discrepancy is not known. The discovery of α-Gal stimulated new discussions and investigations regarding the relevance of anti-glycan IgE for allergic diseases. In this review the effect of glycans and glycan-specific IgE on sensitization to allergens and allergy diagnosis is described. Because parasite infections elicit a similar immunologic environment as allergic diseases, the association of glycan-specific antibodies against parasite glycoproteins with glycan structures on allergens is discussed.

Regulatory monocytes in helminth infections: insights from the modulation during human hookworm infection

Background

While the macrophage polarization is well characterized in helminth infections, the natural heterogeneity of monocytes with multiple cell phenotypes might influence the outcome of neglected diseases, such hookworm infection. Here, we report the profile of monocytes in human hookworm infections as a model to study the regulatory subpopulation of monocytes in helminth infections.

Methods

Blood samples were collected from 19 Necator americanus-infected individuals and 13 healthy individuals. Peripheral blood mononuclear cells (PBMCs) were isolated, and immunophenotyping was conducted by flow cytometry. The expressions of genes encoding human nitric oxide synthase (iNOS), interleukin 4 (IL-4), arginase-1 (Arg-1) and glyceraldehyde 3-phosphate dehydrogenase were quantified by qPCR. Plasma levels of IL-4 were determined by sandwich ELISA. Unpaired t-tests or Mann-Whitney tests were used depending on the data distribution.

Results

Hookworm infected individuals (HWI) showed a significant increase in the number of monocytes/mm³ (555.2 ± 191.0) compared to that of the non-infected (NI) individuals (120.4 ± 44.7) (p < 0.0001). While the frequencies of CD14⁺IL-10⁺ and CD14⁺IL-12⁺ cells were significantly reduced in the HWI compared to NI group (p = 0.0289 and p < 0.0001, respectively), the ratio between IL-10/IL-12 producing monocytes was significantly elevated in HWI (p = 0.0004), indicating the potential regulatory activity of these cells. Measurement of IL-4 levels and gene expression of IL-4 and Arg-1 (highly expressed in alternatively activated macrophages) revealed no significant differences between the NI and HWI groups. Interestingly, individuals from the HWI group had higher expression of the iNOS gene (associated with a regulatory profile) (20.27 ± 2.97) compared to the NI group (11.28 ± 1.18, p = 0.0409). Finally, individuals from the HWI group had a significantly higher frequency of CD206⁺CD23⁺IL-10⁺ (7.57 ± 1.96) cells compared to individuals from the NI group (0.35 ± 0.09) (p < 0.001), suggesting that activated monocytes are a potential source of regulatory cytokines during hookworm infection.

Conclusions

Natural hookworm infection induces a high frequency of circulating monocytes that present a regulatory profile and promote the downmodulation of the proinflammatory response, which may contribute to prolonged survival of the parasite in the host.

The soluble mannose receptor is released from the liver in cirrhotic patients, but is not associated with bacterial translocation

BACKGROUND & AIMS

Intestinal bacterial translocation is involved in activation of liver macrophages in cirrhotic patients. Macrophages play a key role in liver inflammation and are involved in the pathogenesis of cirrhosis and complications. Bacterial translocation may be determined by presence of bacterial DNA and macrophage activation, by the soluble mannose receptor. We hypothesize that the soluble mannose receptor is released from hepatic macrophages in cirrhosis and associated with bacterial DNA, portal pressure and complications.

METHODS

We investigated 28 cirrhotic patients set for transjugular intrahepatic portosystemic shunt insertion as a result of refractory ascites (n=17), acute (n=3), or recurrent variceal bleeding (n=8). We analysed plasma from the portal and hepatic veins for bacterial DNA and soluble mannose receptor with qPCR and ELISA.

RESULTS

The median soluble mannose receptor level was elevated in the hepatic vein compared with the portal vein (0.57(interquartile range 0.31) vs 0.55(0.40) mg/L, P=.005). The soluble mannose receptor levels were similar in bacterial DNA-positive and -negative patients. The soluble mannose receptor level in the portal and hepatic veins correlated with the portal pressure prior to transjugular intrahepatic portosystemic shunt insertion (r=.52, P<.008, both) and the levels correlated with Child-Pugh score (r=.63 and r=.56, P<.004, both). We observed higher soluble mannose receptor levels in patients with acute variceal bleeding compared to other indications (P<.05).

CONCLUSION

This study showed hepatic soluble mannose receptor excretion with a higher level in the hepatic than the portal vein, though with no associations to bacterial DNA. We observed associations between soluble mannose receptor levels and portal pressure and higher levels in patients with acute variceal bleeding indicating the soluble mannose receptor as a marker of complications of cirrhosis, but not bacterial translocation.

Myeloid C-Type Lectin Receptors in Viral Recognition and Antiviral Immunity

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

Lipid Nanoparticle Assisted mRNA Delivery for Potent Cancer Immunotherapy

The induction of a strong cytotoxic T cell response is an important prerequisite for successful immunotherapy against many viral diseases and tumors. Nucleotide vaccines, including mRNA vaccines with their intracellular antigen synthesis, have been shown to be potent activators of a cytotoxic immune response. The intracellular delivery of mRNA vaccines to the cytosol of antigen presenting immune cells is still not sufficiently well understood. Here, we report on the development of a lipid nanoparticle formulation for the delivery of mRNA vaccines to induce a cytotoxic CD 8 T cell response. We show transfection of dendritic cells, macrophages, and neutrophils. The efficacy of the vaccine was tested in an aggressive B16F10 melanoma model. We found a strong CD 8 T cell activation after a single immunization. Treatment of B16F10 melanoma tumors with lipid nanoparticles containing mRNA coding for the tumor-associated antigens gp100 and TRP2 resulted in tumor shrinkage and extended the overall survival of the treated mice. The immune response can be further increased by the incorporation of the adjuvant LPS. In conclusion, the lipid nanoparticle formulation presented here is a promising vector for mRNA vaccine delivery, one that is capable of inducing a strong cytotoxic T cell response. Further optimization, including the incorporation of different adjuvants, will likely enhance the potency of the vaccine.

Innate immune receptors drive dengue virus immune activation and disease

Dengue is a worldwide disease with 400 million annual infections that can lead to septic shock and viral hemorrhagic fever with internal bleeding. These symptoms are the result of uncontrolled immune activation. Macrophages and dendritic cells are the main target of dengue virus (DENV) and the cellular source of cytokines associated with this immune activation. Macrophages and dendritic cells express several innate immune receptors that have been implicated in DENV immune activation, of which, CLEC5A, RIG-I and MDA5 are most important. Notably, activation of these receptors have profound effects on adaptive immune responses against DENV. This review will focus on how innate immune receptors drive DENV immune activation by inducing inflammatory cytokines and by activating adaptive immune responses.

Investigations on therapeutic glucocerebrosidases through paired detection with fluorescent activity-based probes

Deficiency of glucocerebrosidase (GBA) causes Gaucher disease (GD). In the common non-neuronopathic GD type I variant, glucosylceramide accumulates primarily in the lysosomes of visceral macrophages. Supplementing storage cells with lacking enzyme is accomplished via chronic intravenous administration of recombinant GBA containing mannose-terminated N-linked glycans, mediating the selective uptake by macrophages expressing mannose-binding lectin(s). Two recombinant GBA preparations with distinct N-linked glycans are registered in Europe for treatment of type I GD: imiglucerase (Genzyme), contains predominantly Man(3) glycans, and velaglucerase (Shire PLC) Man(9) glycans. Activity-based probes (ABPs) enable fluorescent labeling of recombinant GBA preparations through their covalent attachment to the catalytic nucleophile E340 of GBA. We comparatively studied binding and uptake of ABP-labeled imiglucerase and velaglucerase in isolated dendritic cells, cultured human macrophages and living mice, through simultaneous detection of different GBAs by paired measurements. Uptake of ABP-labeled rGBAs by dendritic cells was comparable, as well as the bio-distribution following equimolar intravenous administration to mice. ABP-labeled rGBAs were recovered largely in liver, white-blood cells, bone marrow and spleen. Lungs, brain and skin, affected tissues in severe GD types II and III, were only poorly supplemented. Small, but significant differences were noted in binding and uptake of rGBAs in cultured human macrophages, in the absence and presence of mannan. Mannan-competed binding and uptake were largest for velaglucerase, when determined with single enzymes or as equimolar mixtures of both enzymes. Vice versa, imiglucerase showed more prominent binding and uptake not competed by mannan. Uptake of recombinant GBAs by cultured macrophages seems to involve multiple receptors, including several mannose-binding lectins. Differences among cells from different donors (n = 12) were noted, but the same trends were always observed. Our study suggests that further insight in targeting and efficacy of enzyme therapy of individual Gaucher patients could be obtained by the use of recombinant GBA, trace-labeled with an ABP, preferably equipped with an infrared fluorophore or other reporter tag suitable for in vivo imaging.

The class I scavenger receptor CD163 promotes internalization of ADAMTS13 by macrophages

Internalization of ADAMTS13 by macrophages may contribute to its clearance from the circulation. Here we investigated endocytic mechanisms that contribute to the uptake of ADAMTS13 by macrophages. Human monocyte-derived macrophages were used to monitor the uptake of fluorescently labeled recombinant ADAMTS13 by flow cytometry. Internalization of ADAMTS13 was blocked upon addition of the cell-permeable dynamin inhibitor dynasore. Partial blocking of ADAMTS13 uptake was observed by using mannan; however, uptake was not affected by an antibody that blocked binding to the macrophage mannose receptor CD206, which suggests that other endocytic receptors contribute to the internalization of ADAMTS13 by macrophages. A pull-down with ADAMTS13 and subsequent mass spectrometric analysis identified the class I scavenger receptor CD163 as a candidate receptor for ADAMTS13. Blocking experiments with monoclonal anti-CD163 antibody EDHu-1 resulted in decreased ADAMTS13 internalization by macrophages. Pronounced inhibition of ADAMTS13 uptake by EDHu-1 was observed in CD163 high-expressing macrophages. In agreement with these findings, CD163-expressing Chinese hamster ovary cells were capable of rapidly internalizing ADAMTS13. Surface plasmon resonance revealed binding of ADAMTS13 to scavenger receptor cysteine-rich domains 1-9 and 1-5 of CD163. Taken together, our data identify CD163 as a major endocytic receptor for ADAMTS13 on macrophages.

mRNA vaccine delivery using lipid nanoparticles

mRNA vaccines elicit a potent immune response including antibodies and cytotoxic T cells. mRNA vaccines are currently evaluated in clinical trials for cancer immunotherapy applications, but also have great potential as prophylactic vaccines. Efficient delivery of mRNA vaccines will be key for their success and translation to the clinic. Among potential nonviral vectors, lipid nanoparticles are particularly promising. Indeed, lipid nanoparticles can be synthesized with relative ease in a scalable manner, protect the mRNA against degradation, facilitate endosomal escape, can be targeted to the desired cell type by surface decoration with ligands, and as needed, can be codelivered with adjuvants.

Differences in the frequency of macrophage and T cell markers between focal and crescentic classes of anti-neutrophil cytoplasmic antibody (ANCA)-associated glomerulonephritis

Background

Anti-neutrophil cytoplasmic antibody (ANCA)-associated glomerulonephritis (AAGN) can be classified into; focal, crescentic, mixed and sclerotic classes. Macrophages and T lymphocytes are key players in mediating renal injury. The frequency of macrophage and T lymphocytes in different histological classes is unclear.

Objectives

We examined the frequency of macrophage and T lymphocyte markers in AAGN and assessed their correlation with renal function at presentation.

Patients and Methods

Renal biopsies from 38 patients were included in immunohistochemistry analysis of macrophages (CD68, sialoadhesin [Sn] and mannose receptor [MR]) and T cells (CD4 and CD8) markers. The frequency of these markers in glomerular, periglomerular and interstitial compartments were measured in a blinded fashion. Biopsies were allocated a histological class of focal, crescentic, mixed or sclerotic. Scores were then matched to histological class and assessed for correlation with renal function.

Results

The biopsies were crescentic 19 (50%), focal 10 (26.3%), mixed 6 (15.7%) and sclerotic 3 (8%). Interstitial CD68+ macrophages and CD8+ T lymphocytes showed best correlation with renal function at the time of presentation. CD68+ macrophages were significantly increased in crescentic compared to focal AAGN. MR+ macrophages, CD4 and CD8 T cells were also elevated in the interstitium of crescentic compared to focal group.

Conclusions

In this study interstitial CD68 and CD8 showed the highest association with the renal function at presentation. Differences in the cellular infiltrate between focal and crescentic AAGN were related to CD68+ macrophages and to interstitial MR+ macrophages and T lymphocytes. Further studies are needed to assess these differences across all four histological categories.

Pathogen-dependent role of turbot (Scophthalmus maximus) interferon-gamma

Interferon-gamma has been typically described as a pro-inflammatory cytokine playing an important role in the resolution of both viral and bacterial diseases. Nevertheless, some anti-inflammatory functions are also attributed to this molecule. In this work we have characterized for the first time the turbot (Scophthalmus maximus) interferon-gamma gene (ifng) and its expression pattern under basal conditions, after type I IFNs administration, and viral and bacterial infection. The intramuscular injection of an expression plasmid encoding turbot Ifng (pMCV1.4-ifng) was not able to affect the transcription of numerous immune genes directly related to the activity of IFN-gamma, with the exception of macrophage-colony stimulating factor (csf1). It was also unable to reduce the mortality caused by a Viral Hemorrhagic Septicemia Virus (VHSV) or Aeromonas salmonicida challenge. Interestingly, at 24 h post-infection, turbot previously inoculated with pMCV1.4-ifng and infected with VHSV showed an increase in the expression of pro-inflammatory cytokines and type I IFNs compared to those fish not receiving expression plasmid, indicating a synergic effect of Ifng and VHSV. On the other hand, some macrophage markers, such as the macrophage receptor with collagenous structure (marco), were down-regulated by Ifng during the viral infection. Ifng had the opposite effect in those turbot infected with the bacteria, showing a reduction in the transcription of pro-inflammatory and type I IFNs genes, and an increase in the expression of genes related to the activity of macrophages.

C-type lectins facilitate tumor metastasis

Metastasis, a life-threatening complication of cancer, leads to the majority of cases of cancer-associated mortality. Unfortunately, the underlying molecular and cellular mechanisms of cancer metastasis remain to be fully elucidated. C-type lectins are a large group of proteins, which share structurally homologous carbohydrate-recognition domains (CRDs) and possess diverse physiological functions, including inflammation and antimicrobial immunity. Accumulating evidence has demonstrated the contribution of C-type lectins in different steps of the metastatic spread of cancer. Notably, a substantial proportion of C-type lectins, including selectins, mannose receptor (MR) and liver and lymph node sinusoidal endothelial cell C-type lectin, are important molecular targets for the formation of metastases in vitro and in vivo. The present review summarizes what has been found regarding C-type lectins in the lymphatic and hematogenous metastasis of cancer. An improved understanding the role of C-type lectins in cancer metastasis provides a comprehensive perspective for further clarifying the molecular mechanisms of cancer metastasis and supports the development of novel C-type lectins-based therapies the for prevention of metastasis in certain types of cancer.

Targeting cells of the immune system: mannosylated HPMA–LMA block-copolymer micelles for targeting of dendritic cells

Background: Successful tumor immunotherapy depends on the induction of strong and sustained tumor antigen-specific immune responses by activated antigen-presenting cells (APCs) such as dendritic cells (DCs). Since nanoparticles have the potential to codeliver tumor-specific antigen and DC-stimulating adjuvant in a DC-targeting manner, we wanted to assess the suitability of mannosylated HPMA-LMA block polymers for immunotherapy. Materials & methods: Fluorescence-labeled block copolymer micelles derived from P(HPMA)-block-P(LMA) copolymers and according statistical copolymers were synthesized via RAFT polymerization, and loaded with the APC activator L18-MDP. Both types of copolymers were conjugated with D-mannose to target the mannose receptor as expressed by DCs and macrophages. The extent and specificity of micelle binding and activation of APCs was monitored using mouse spleen cells and bone marrow-derived DC (BMDC). Results: Nontargeting HPMA-LMA statistical copolymers showed strong unspecific cell binding. HPMA-LMA block copolymers bound DC only when conjugated with mannose, and in a mannose receptor-specific manner. Mannosylated HPMA-LMA block copolymers were internalized by DC. DC-targeting HPMA-LMA block copolymers mediated DC activation when loaded with L18-MDP. Conclusion: Mannosylated HPMA-LMA block copolymers are a promising candidate for the delvopment of DC-targeting nanovaccines.