Signaling through Toll-like receptor 3 and Dectin-1 potentiates the capability of human monocyte-derived dendritic cells to promote T-helper 1 and T-helper 17 immune responses

Gene Expression Pattern of Peyer's Patch Lymphocytes Exposed to Kagocel Suggests Pattern-Recognition Receptors Mediate Its Action

Kagocel is a synthetic carboxymethylcellulose derivative copolymerized with gossypol. Clinical data evidence its safety and efficiency for the treatment of flu and other viral infections via enhancement of interferon production. The gut-associated lymphoid tissue seems a likely site of kagocel action. The study was aimed to investigate the molecular mechanisms of its action using murine Peyer’s patches lymphocytes as a test system and the cytokines production and gene expression patterns as the primary outcomes. The Peyer’s patches lymphocytes isolated from BALB/c mice were stimulated with concanavalin A, or, to mimic viral infection, with a combination of concanavalin A and TLR3 ligand poly I:C. After 24 h of stimulation the cells were treated with saline, 30, 100, or 300 μg/ml of kagocel, or, as positive controls, 300 μg/ml oats b-D-glucan or 300 μg/ml lentinan. After 24 and 72 h of incubation with these drugs cytokines production was analyzed with ELISA and gene expression pattern was investigated using nCounter Inflammation panel chips followed by bioinformatics analysis. Expression of genes involved in the inflammatory response, antiviral defense, lymphocytes survival and proliferation (C1qa, C2, C3, Ccl21a, Il11, Il1b, Il23a, Il5, Ltb4r2, Alox15, Pla2g4a, Ptger1, Mapkapk5, Hras, Ifna1, Tlr2, Mrc1, Mx2) was upregulated in kagocel-treated Peyer’s patches lymphocytes. A list of plausible transcription factors (CEBPs, IRF, NFκB, RXR, Stat, Tead4, and ZSCAN) and master-regulators has been identified (cIAP, CIKS, dock9, MEKK1, FXR, IKK, IRAK, TRAF, dsRNA:TLR3:TRIF). The changes in gene expression pattern and the outcomes of bioinformatics analysis suggest that pattern recognition receptors, TLRs and dectin-1, are the key mediators of kagocel immunomodulatory action, with the possible involvement of interferon autocrine loop. The genes upregulated with kagocel include diverse components of the innate immune defense system.

Insights Into Dendritic Cells in Cancer Immunotherapy: From Bench to Clinical Applications

Dendritic cells (DCs) are efficient antigen-presenting cells (APCs) and potent activators of naïve T cells. Therefore, they act as a connective ring between innate and adaptive immunity. DC subsets are heterogeneous in their ontogeny and functions. They have proven to potentially take up and process tumor-associated antigens (TAAs). In this regard, researchers have developed strategies such as genetically engineered or TAA-pulsed DC vaccines; these manipulated DCs have shown significant outcomes in clinical and preclinical models. Here, we review DC classification and address how DCs are skewed into an immunosuppressive phenotype in cancer patients. Additionally, we present the advancements in DCs as a platform for cancer immunotherapy, emphasizing the technologies used for in vivo targeting of endogenous DCs, ex vivo generated vaccines from peripheral blood monocytes, and induced pluripotent stem cell-derived DCs (iPSC-DCs) to boost antitumoral immunity.

Evaluation of immunogenicity and protection mediated by Lawsonia intracellularis subunit vaccines

Lawsonia intracellularis is an economically important bacterium that causes ileitis in pigs. Current vaccines for L. intracellularis do not allow for differentiation between infected and vaccinated animals (DIVA), which is beneficial for disease tracking and surveillance. Previously, we identified five putative surface L. intracellularis proteins that were targeted by antibodies from pigs infected with L. intracellularis which could serve as antigens in a subunit vaccine. We conducted two trials to determine whether these antigens were immunogenic and provided protection against infectious challenge and whether truncated glycoprotein D could be used as a DIVA antigen. For Trial 1, 5 week-old piglets were administered intramuscular monovalent vaccines comprised of a recombinant (r) flagella subunit protein (rFliC,) and DIVA antigen (truncated glycoprotein D (TgD), a herpes virus antigen) both formulated with a combination adjuvant consisting of polyinosinic:polycytidylic acid(poly I:C), host defense peptide 1002 and polyphosphazene, referred to as Triple Adjuvant (TriAdj). Relative to control animals, animals vaccinated with rFliC and rTgD had significantly elevated antigen-specific humoral immunity in sera suggesting that rFliC and TgD are immunogenic. Control animals had negligible anti-TgD titres suggesting that TgD may be a suitable DIVA antigen for pigs. For Trial 2, piglets were immunized with a trivalent vaccine (FOG vaccine consisting of rFLiC, rOppA protein (a ABC Type dipeptide transport system) and rGroEL (a stress response protein)) and a divalent vaccine (CM vaccine consisting of rClpP (an ATP-dependent Clp protease proteolytic subunit) and rMetK (a S-adenosyl methionine synthase)) formulated with Emulsigen®. Relative to the control pigs, pigs immunized with the FOG vaccine produced robust and significantly higher serum IgG antibodies against rFliC and rGroEL, and significantly higher anti-FliC and anti-GroEL IgA antibodies in jejunal (GroEL only) and ileal intestinal mucosa. Pigs immunized with CM vaccine produced significantly higher serum antibodies against rClpP and rMetK and significantly higher anti-rClpP IgA antibodies in the ileum relative to the control pigs. Quantitative polymerase chain reaction (qPCR) analysis showed that 18 days after challenge with infectious L. intracellularis, challenged/control pigs and pigs that received the CM vaccine, but not the pigs vaccinated with the FOG vaccine, shed significantly more bacteria in feces than the unchallenged controls pigs. These data suggest that the FOG vaccinated pigs showed limited protection. While promising, more work is needed to enhance the efficiency of the intramuscular vaccine to show significant disease protection.

Oxidized curdlan activates dendritic cells and enhances antitumor immunity

Curdlan activates dendritic cells (DCs) and enhances DC-based antitumor immunity. However, hydrophobicity and heterogeneity of curdlan particulates hinder perfect binding of curdlan to dectin-1 receptor, resulting in the reduced activation of antigen presenting cells and limited antitumor effects. Herein, we synthesized partially oxidized curdlan derivative (β-1,3-polyglucuronic acid, denote PGA). PGA-45 polymer, the reaction product prepared from curdlan by oxidation with 4-acetamido-TEMPO/NaClO/NaClO₂ systems under acid conditions for 45 min, activated DCs, induced the expression of co-stimulatory molecules and cytokines, and promoted allogenic T cell proliferation as well as the expression of IL-2. Mechanistically, PGA-45 polymer strongly enhanced phosphorylation of IKK-β and reduced the expression of phosphorylated Akt, suggesting that PGA-45 may activate multiple cell surface receptors such as TLR4 and dectin-1. Administration of tumor lysate pulsed DCs pre-treated with PGA-45 particles induced strong antitumor activity in B16F10 melanoma model. Our data suggest that PGA-45 have strong adjuvant effects for anti-cancer immunity and the design of PGA polymers may provide insights in the development of novel adjuvants for cancer immunotherapy.

Tethering Innate Surface Receptors on Dendritic Cells: A New Avenue for Immune Tolerance Induction?

Dendritic cells (DCs) play a key role in immunity and are highly potent at presenting antigens and orienting the immune response. Depending on the environmental signals, DCs could turn the immune response toward immunity or immune tolerance. Several subsets of DCs have been described, with each expressing various surface receptors and all participating in DC-associated immune functions according to their specific skills. DC subsets could also contribute to the vicious circle of inflammation in immune diseases and establishment of immune tolerance in cancer. They appear to be appropriate targets in the control of inflammatory diseases or regulation of autoimmune responses. For all these reasons, in situ DC targeting with therapeutic antibodies seems to be a suitable way of modulating the entire immune system. At present, the field of antibody-based therapies has mainly been developed in oncology, but it is undergoing remarkable expansion thanks to a wide variety of antibody formats and their related functions. Moreover, current knowledge of DC biology may open new avenues for targeting and modulating the different DC subsets. Based on an update of pathogen recognition receptor expression profiles in human DC subsets, this review evaluates the possibility of inducing tolerant DCs using antibody-based therapeutic agents.

Fungal polysaccharides

Fungal bioactive polysaccharides are well known and have been widely used in Asia as a part of the traditional diet and medicine. In fact, some biopolymers (mainly β-glucans or glycoconjugate) have already made their way to the market as antitumor or immunostimulating drugs. In the last decades, the relationship between structure and activity of polysaccharides and their detailed mode of action have been the core of intense research to understand and utilize their medicinal properties. Most of the antitumor polysaccharides belong to conserved β-glucans, with a linear β-(1→3)-glucan backbone and attached β-(1→6) branch. Structurally different β-glucans appear to have different affinities toward their receptors and thus generate markedly different host responses. However, their antitumor activities are mainly influenced by molecular mass, degree of branching, conformation, and structure modification of the polysaccharides. β-Glucans act on several immune receptors including Dectin-1, complement receptor (CR3) and TLR-2/6, then trigger both innate and adaptive response and enhance opsonic and nonopsonic phagocytosis. Various receptor interactions explain the possible mode of actions of polysaccharides.

Human thioredoxin, a damage-associated molecular pattern and Malassezia-crossreactive autoallergen, modulates immune responses via the C-type lectin receptors Dectin-1 and Dectin-2

Human thioredoxin (hTrx), which can be secreted from cells upon stress, functions in allergic skin inflammation as a T cell antigen due to homology and cross-reactivity with the fungal allergen Mala s13 of the skin-colonizing yeast Malassezia sympodialis. Recent studies have shown that cell wall polysaccharides of Malassezia are detected by the immune system via the C-type lectin receptors Dectin-1 and Dectin-2, which are expressed on myeloid cells. Therefore, this study aimed to investigate a putative interaction between Dectin-1, Dectin-2 and the allergens Mala s13 and hTrx. Stimulation of human monocyte-derived dendritic cells or macrophages with Mala s13 or hTrx resulted in remarkable secretion of IL-1β and IL-23. Blocking experiments suggest that hTrx induces IL-23 by Dectin-1 binding and IL-1β by binding to either Dectin-1 or Dectin-2. Regarding Mala s13, Dectin-1 appears to be involved in IL-1β signaling. Interference of Syk kinase function was performed to investigate downstream signaling, which led to diminished hTrx responses. In our experiments, we observed rapid internalization of Mala s13 and hTrx upon cell contact and we were able to confirm direct interaction with Dectin-1 as well as Dectin-2 applying a fusion protein screening platform. We hypothesize that this cytokine response may result in a Th2/Th17-polarizing milieu, which may play a key role during the allergic sensitization in the skin, where allergen presentation to T cells is accompanied by microbial colonization and skin inflammation.

Contact, Collaboration, and Conflict: Signal Integration of Syk-Coupled C-Type Lectin Receptors

Several spleen tyrosine kinase-coupled C-type lectin receptors (CLRs) have emerged as important pattern recognition receptors for infectious danger. Because encounter with microbial pathogens leads to the simultaneous ligation of several CLRs and TLRs, the signals emanating from different pattern recognition receptors have to be integrated to achieve appropriate biological responses. In this review, we briefly summarize current knowledge about ligand recognition and core signaling by Syk-coupled CLRs. We then address mechanisms of synergistic and antagonistic crosstalk between different CLRs and with TLRs. Emerging evidence suggests that signal integration occurs through 1) direct interaction between receptors, 2) regulation of expression levels and localization, and 3) collaborative or conflicting signaling interference. Accordingly, we aim to provide a conceptual framework for the complex and sometimes unexpected outcome of CLR ligation in bacterial and fungal infection.

The Correlation of CD206, CD209, and Disease Severity in Behçet's Disease with Arthritis

The purpose of this study was to clarify the role of pattern recognition receptors in Behçet's disease (BD). The frequencies of several pattern recognition receptors (CD11b, CD11c, CD32, CD206, CD209, and dectin-1) were analyzed in patients with BD by flow cytometry, and cytokine levels, interleukin- (IL-) 18, IL-23, and IL-17A, were compared in plasma. The analysis was performed in active (n = 13) and inactive (n = 13) stages of BD patients. Rheumatoid arthritis patients (n = 19), as a disease control, and healthy control (HC) (n = 19) were enrolled. The frequencies of CD11b+ and CD32+ cells were significantly increased in active BD patients compared to HC. Disease severity score was correlated to CD11c+, CD206+, and CD209+ in whole leukocytes and CD11b+, CD11c+, CD206+, CD209+, and Dectin-1+ in granulocytes. The plasma levels of IL-17A were significantly different between HC and active BD. IL-18 showed significant difference between active and inactive BD patients. From this study, we concluded the expressions of several pattern recognition receptors were correlated to the joint symptoms of BD.

Do We Need Worms to Promote Immune Health?

Many immune-mediated diseases like inflammatory bowel disease, multiple sclerosis, type 1 diabetes, asthma, and food allergy appeared to have increased in frequency in developed countries in the latter part of the twentieth century. Reports from less developed countries suggest that the "epidemic" of immune-mediated diseases now is spreading into these regions as well. The "hygiene hypothesis" was developed to partly explain this phenomenon. It has been proposed that modern-day sanitary living has altered our exposure to organisms that provided protection from these diseases in the past. Alternations in the composition of our intestinal flora and fauna could play a role. Helminths are a group of worm-like parasitic organisms that have adapted to live in various regions of their hosts. Epidemiological and some clinical data suggest that these organisms can protect people from developing immune-mediated diseases. Animal experimentation has shown that helminths stimulate the production of regulatory cytokines, activate regulatory T cells, and induce regulatory dendritic cells and macrophages. This could be the mechanism by which they protect the host from these diseases. Early clinical studies also suggest that helminths may prove useful for treating immunological diseases. More sophisticated clinical studies are underway, testing live helminth agents as therapeutic agents. Also, a strong effort is ongoing to discover the agents produced by helminths that modulate host immune responses with an eye on developing new, highly effective immune modulatory therapeutic agent.

Addition of CpG ODN and Poly (I:C) to a standard maturation cocktail generates monocyte-derived dendritic cells and induces a potent Th1 polarization with migratory capacity

Monocyte-derived dendritic cells (DCs) are used as immunoadjuvant cells in cancer vaccines and have made great progress. However, an optimal DCs subset is vital for this treatment effect, the current 'gold standard' cytokine cocktail DCs have a shortcoming in their cytokines secretion, especially IL-12p70, mainly because of the existence of PGE2. Therefore, it is necessary to find an appropriate DCs-based immunotherapeutic protocol. In this study, we compared a novel 'improved' maturation cytokine cocktail with the current 'gold standard' maturation cytokine cocktail used for generating standard DCs. The 'improved' maturation cytokine cocktail DCs showed a higher levels surface markers expression (CD80, CD83, CD86 and HLA-DR), the chemokine receptors CXCR4 and CCR7 and chemokine CCL19, CCL21 and CXCL21, whereas CCR5 expression was reduced. Most importantly, in contrast to 'gold standard' DCs, which secrete little IL-12p70 and as a result induce mainly Th2 immunity, 'improved' cytokine cocktail DCs secreted higher levels IL-12p70 and also secreted similar concentration IL-10. To removal of PGE2 from the 'improved' DCs did increase the IL-12p70 production. In conclusion, we here present the 'improved' DCs, as an optimal maturation cocktail protocol, can induce high migratory potential, generate immunostimulatory DCs, produce higher levels IL-12p70 with superior capacity to induce Th1 immunity, when compared with the 'gold standard' DCs.

Fast dendritic cells matured with Poly (I:C) may acquire tolerogenic properties

BACKGROUND AIMS

Because of the labor-intensive and time-consuming conventional protocols for the generation of dendritic cells (DCs) as the most promising tools for anti-cancer therapy that enable the induction of a T-helper (Th)1-mediated anti-tumor immune response, the use of short-term protocols has been proposed. However, data on the applicability of such protocols in cancer immunotherapy are quite limited.

METHODS

We compared the phenotypic and functional capability of fast DCs (fDCs) differentiated for 24 h and then matured for 48 h with Poly (I:C), a strong Th1-promoting agent, with donor-matched conventional DCs (cDCs) differentiated for 5 days and matured likewise.

RESULTS

Of 12 donors tested, we identified seven whose monocytes failed to develop into immunogenic DCs through the use of fDC protocol, on the basis of incomplete downregulation of CD14, low expression of CD1a and macrophage-like morphology. Such fDCs have significantly lower expression of CD83, CD86, CCR7 and CD40, weaker allo-stimulatory Th1- and Th17-polarizing capacity caused by poor production of interleukin (IL)-12p70 and IL-23 and high production of IL-10, and prominent Th2-polarizing capacity, compared with donor-matched cDCs. Furthermore, such fDCs had tolerogenic properties as judged by higher expression of indolamine dioxigenase-3, IDO-1 and IL-1β and induction of a higher percentage of CD4(+)CD25(+)FoxP3(+) T cells. These findings correlated with increased transforming growth factor (TGF)-β production by fDC-primed CD3(+)T cells and their stronger anti-proliferative capacity.

CONCLUSIONS

We emphasize that although fDCs could probably be applied as an alternative to cDCs for cancer therapy, the fDC protocol should not be applied to donors whose DCs acquire tolerogenic capabilities.

Tumor necrosis factor-α promotes survival and phenotypic maturation of poly(I:C)-treated dendritic cells but impairs their Th1 and Th17 polarizing capability

BACKGROUND AIMS

Toll-like receptor (TLR)-3 synthetic agonist polyinosinic-polycytidylic acid (poly(I:C)) is a promising agent for dendritic cell (DC)-based anti-tumor vaccines because of its ability to induce a strong maturation of DCs, but such an effect is followed by stimulation of DC apoptosis. Tumor necrosis factor (TNF)-α may promote the survival of poly(I:C)-stimulated DCs, but it is not known in detail how this combination affects the maturation and polarization capacity of monocyte-derived (Mo)DCs.

METHODS

Immature MoDCs, generated from human monocytes, were treated with different concentrations of poly(I:C) combined with TNF-α, and the effect on survival, phenotype, production of cytokines, allostimulatory and Th polarization capacity was assessed after 24 and 48 h.

RESULTS

We showed that TNF-α inhibited the dose-dependent pro-apoptotic effect of poly(I:C). However, TNF-α also decreased poly(I:C)-induced production of interleukin (IL)-12 and IL-23 by MoDCs, which correlated with their diminished capacity to stimulate cellular proliferation, interferon-γ and IL-17 production by allogeneic CD4(+)T cells in co-culture. Such an effect was more pronounced after 24 h and could not be restored by CD40 ligation. In the presence of CD40L, TNF-α even stimulated IL-10 production and immunoglobulin-like transcript 3 expression by poly(I:C)-matured DCs, which correlated with their increased capacity to induce IL-10 production by CD4(+)T cells.

CONCLUSION

Even though TNF-α could promote the survival of poly(I:C)-matured MoDCs, it also suppresses key anti-tumor functions of these cells, which could have important implications when considering this, already suggested, protocol for the DC-based anti-tumor therapy.

Helminth infections decrease host susceptibility to immune-mediated diseases

Helminthic infection has become rare in highly industrialized nations. Concurrent with the decline in helminthic infection has been an increase in the prevalence of inflammatory disease. Removal of helminths from our environment and their powerful effects on host immunity may have contributed to this increase. Several helminth species can abrogate disease in murine models of inflammatory bowel disease, type 1 diabetes, multiple sclerosis, and other conditions. Helminths evoke immune regulatory pathways often involving dendritic cells, regulatory T cells, and macrophages that help to control disease. Cytokines, such as IL-4, IL-10, and TGF-β, have a role. Notable is the helminthic modulatory effect on innate immunity, which impedes development of aberrant adaptive immunity. Investigators are identifying key helminth-derived immune modulatory molecules that may have therapeutic usefulness in the control of inflammatory disease.

Reprogramming tumor-infiltrating dendritic cells for CD103+ CD8+ mucosal T-cell differentiation and breast cancer rejection

Our studies showed that tumor-infiltrating dendritic cells (DC) in breast cancer drive inflammatory Th2 (iTh2) cells and protumor inflammation. Here, we show that intratumoral delivery of the β-glucan curdlan, a ligand of dectin-1, blocks the generation of iTh2 cells and prevents breast cancer progression in vivo. Curdlan reprograms tumor-infiltrating DCs via the ligation of dectin-1, enabling the DCs to become resistant to cancer-derived thymic stromal lymphopoietin (TSLP), to produce IL-12p70, and to favor the generation of Th1 cells. DCs activated via dectin-1, but not those activated with TLR-7/8 ligand or poly I:C, induce CD8+ T cells to express CD103 (αE integrin), a ligand for cancer cells, E-cadherin. Generation of these mucosal CD8+ T cells is regulated by DC-derived integrin αvβ8 and TGF-β activation in a dectin-1-dependent fashion. These CD103+ CD8+ mucosal T cells accumulate in the tumors, thereby increasing cancer necrosis and inhibiting cancer progression in vivo in a humanized mouse model of breast cancer. Importantly, CD103+ CD8+ mucosal T cells elicited by reprogrammed DCs can reject established cancer. Thus, reprogramming tumor-infiltrating DCs represents a new strategy for cancer rejection.

Immunostimulatory properties and antitumor activities of glucans (Review)

New foods and natural biological modulators have recently become of scientific interest in the investigation of the value of traditional medical therapeutics. Glucans have an important part in this renewed interest. These fungal wall components are claimed to be useful for various medical purposes and they are obtained from medicinal mushrooms commonly used in traditional Oriental medicine. The immunotherapeutic properties of fungi extracts have been reported, including the enhancement of anticancer immunity responses. These properties are principally related to the stimulation of cells of the innate immune system. The discovery of specific receptors for glucans on dendritic cells (dectin-1), as well as interactions with other receptors, mainly expressed by innate immune cells (e.g., Toll-like receptors, complement receptor-3), have raised new attention toward these products as suitable therapeutic agents. We briefly review the characteristics of the glucans from mycelial walls as modulators of the immunity and their possible use as antitumor treatments.