Induction of innate immunity by Aspergillus fumigatus cell wall polysaccharides is enhanced by the composite presentation of chitin and beta-glucan

Proteomics of Paracoccidioides lutzii: Overview of Changes Triggered by Nitrogen Catabolite Repression

Members of the Paracoccidioides complex are the causative agents of Paracoccidioidomycosis (PCM), a human systemic mycosis endemic in Latin America. Upon initial contact with the host, the pathogen needs to uptake micronutrients. Nitrogen is an essential source for biosynthetic pathways. Adaptation to nutritional stress is a key feature of fungi in host tissues. Fungi utilize nitrogen sources through Nitrogen Catabolite Repression (NCR). NCR ensures the scavenging, uptake and catabolism of alternative nitrogen sources, when preferential ones, such as glutamine or ammonium, are unavailable. The NanoUPLC-MSE proteomic approach was used to investigate the NCR response of Paracoccidioides lutzii after growth on proline or glutamine as a nitrogen source. A total of 338 differentially expressed proteins were identified. P. lutzii demonstrated that gluconeogenesis, β-oxidation, glyoxylate cycle, adhesin-like proteins, stress response and cell wall remodeling were triggered in NCR-proline conditions. In addition, within macrophages, yeast cells trained under NCR-proline conditions showed an increased ability to survive. In general, this study allows a comprehensive understanding of the NCR response employed by the fungus to overcome nutritional starvation, which in the human host is represented by nutritional immunity. In turn, the pathogen requires rapid adaptation to the changing microenvironment induced by macrophages to achieve successful infection.

Allergy to fungi: Advances in the understanding of fungal allergens

Allergic diseases are a major health problem due to their increasing incidence and high prevalence worldwide. Asthma has several aetiologies, and allergy plays an important role in its development in approximately 60% of adults and 80% of children and adolescents. Although the link between aeroallergen sensitization and asthma exacerbations has been long recognized, the investigations of the triggering allergens may be superficial in many asthma cases. The main allergenic sources related to asthma, and other allergic diseases, are pollens, mites, fungi, and animal epithelia. Fungi are considered the third most frequent cause of respiratory pathologies. Asthma caused by several fungi species may have a bad prognosis in some cases due to its severity and difficulty in avoidance methods. Despite the recognised relevance of fungi in respiratory allergies, the knowledge about fungal allergens seems to be scarce, with few descriptions of new allergens, compared to other allergenic sources. The study of major, minor, and cross-reactive fungal allergens, and their relevance in the allergic disease, might be crucial, not only to accurately diagnose these allergies, but also to predict exacerbations and responses to therapies, as well as for the development of personalized treatment plans in a fast-changing climate scenario.

Functional immune boosters; the herb or its dead microbiome? Antigenic TLR4 agonist MAMPs found in 65 medicinal roots and algae's

Background

Humans have been consuming medicinal plants (as herbs/ spices) to combat illness for centuries while ascribing beneficial effects predominantly to the plant/phytochemical constituents, without recognizing the power of obligatory resident microorganism' communities (MOCs) (live/dead bacteria, fungus, yeast, molds etc.) which remain after industrial microbial reduction methods. Very little is known about the taxonomic identity of residual antigenic microbial associated molecular patterns (MAMPs) debris in our botanical over the counter (OTC) products, which if present would be recognized as foreign (non-self) antigenic matter by host pattern recognition receptors (PRRs) provoking a host immune response; this the basis of vaccine adjuvants. As of today, only few research groups have removed the herbal MAMP biomass from herbs, all suggesting that immune activation may not be from the plant but rather its microbial biomass; a hypothesis we corroborate.

Purpose

The purpose of this work was to conduct a high through put screening (HTPS) of over 2500 natural plants, OTC botanical supplements and phytochemicals to elucidate those with pro-inflammatory; toll like receptor 4 (TLR4) activating properties in macrophages.

Study Design

The HTPS was conducted on RAW 264.7 cells vs. lipopolysaccharide (LPS) E. coli 0111:B4, testing iNOS / nitric oxide production ( NO 2 - ) as a perimeter endpoint. The data show not a single drug/chemical/ phytochemical and approximately 98 % of botanicals to be immune idle (not effective) with only 65 pro-inflammatory (hits) in a potency range of LPS. Method validation studies eliminated the possibility of false artifact or contamination, and results were cross verified through multiple vendors/ manufacturers/lot numbers by botanical species. Lead botanicals were evaluated for plant concentration of LPS, 1,3:1,6-β-glucan, 1,3:1,4-β-D-glucan and α-glucans; where the former paralleled strength in vitro. LPS was then removed from plants using high-capacity endotoxin poly lysine columns, where bioactivity of LPS null "plant" extracts were lost. The stability of E.Coli 0111:B4 in an acid stomach mimetic model was confirmed. Last, we conducted a reverse culture on aerobic plate counts (APCs) from select hits, with subsequent isolation of gram-negative bacteria (MacConkey agar). Cultures were 1) heat destroyed (retested/ confirming bioactivity) and 2) subject to taxonomical identification by genetic sequencing 18S, ITS1, 5.8 s, ITS2 28S, and 16S.

Conclusion

The data show significant gram negative MAMP biomass dominance in A) roots (e.g. echinacea, yucca, burdock, stinging nettle, sarsaparilla, hydrangea, poke, madder, calamus, rhaponticum, pleurisy, aconite etc.) and B) oceanic plants / algae's (e.g. bladderwrack, chlorella, spirulina, kelp, and "OTC Seamoss-blends" (irish moss, bladderwrack, burdock root etc), as well as other random herbs (eg. corn silk, cleavers, watercress, cardamom seed, tribulus, duckweed, puffball, hordeum and pollen). The results show a dominance of gram negative microbes (e.g. Klebsilla aerogenes, Pantoae agglomerans, Cronobacter sakazakii), fungus (Glomeracaea, Ascomycota, Irpex lacteus, Aureobasidium pullulans, Fibroporia albicans, Chlorociboria clavula, Aspergillus_sp JUC-2), with black walnut hull, echinacea and burdock root also containing gram positive microbial strains (Fontibacillus, Paenibacillus, Enterococcus gallinarum, Bromate-reducing bacterium B6 and various strains of Clostridium).

Conclusion

This work brings attention to the existence of a functional immune bioactive herbal microbiome, independent from the plant. There is need to further this avenue of research, which should be carried out with consideration as to both positive or negative consequences arising from daily consumption of botanicals highly laden with bioactive MAMPS.

Pseudolaric Acid B Ameliorates Fungal Keratitis Progression by Suppressing Inflammation and Reducing Fungal Load

This study aimed to determine the mechanisms of antifungal and anti-inflammation effects of pseudolaric acid B (PAB) on Aspergillus fumigatus (A. fumigatus) keratitis. In vitro MIC assay and crystal violet staining were conducted to evaluate the efficacy of PAB against A. fumigatus. PAB inhibited A. fumigatus growth and inhibited the formation of fungal biofilms in a dose-dependent manner. Molecular docking analysis revealed that PAB possesses strong binding properties with Rho1 of A. fumigatus, which is devoted to encoding (1,3)-β-d-glucan of A. fumigatus. RT-PCR results also showed that Rho1 was inhibited by PAB. In vivo, PAB treatment reduced clinical scores, fungal load, and macrophage infiltration, which were increased by A. fumigatus in mice corneas. In addition, PAB treatment suppressed the expression of Mincle, p-Syk, and cytokines (TNF-α, MIP2, iNOS, and CCL2) in infected corneas and in RAW264.7 cells, which were tested by RT-PCR, Western blot, and enzyme-linked Immunosorbent Assay. Notably, trehalose-6,6-dibehenate, an agonist of Mincle, pretreatment reversed the regulatory function of PAB in RAW 264.7 cells. Moreover, flow cytometry showed that PAB upregulated the ratio of M2/M1 macrophages in A. fumigatus-infected corneas and RAW264.7 cells. In conclusion, PAB produced antifungal activities against A. fumigatus and decreased the inflammatory response in mouse A. fumigatus keratitis.

Chitin Biosynthesis in Aspergillus Species

The fungal cell wall (FCW) is a dynamic structure responsible for the maintenance of cellular homeostasis, and is essential for modulating the interaction of the fungus with its environment. It is composed of proteins, lipids, pigments and polysaccharides, including chitin. Chitin synthesis is catalyzed by chitin synthases (CS), and up to eight CS-encoding genes can be found in Aspergillus species. This review discusses in detail the chitin synthesis and regulation in Aspergillus species, and how manipulation of chitin synthesis pathways can modulate fungal growth, enzyme production, virulence and susceptibility to antifungal agents. More specifically, the metabolic steps involved in chitin biosynthesis are described with an emphasis on how the initiation of chitin biosynthesis remains unknown. A description of the classification, localization and transport of CS was also made. Chitin biosynthesis is shown to underlie a complex regulatory network, with extensive cross-talks existing between the different signaling pathways. Furthermore, pathways and recently identified regulators of chitin biosynthesis during the caspofungin paradoxical effect (CPE) are described. The effect of a chitin on the mammalian immune system is also discussed. Lastly, interference with chitin biosynthesis may also be beneficial for biotechnological applications. Even after more than 30 years of research, chitin biosynthesis remains a topic of current interest in mycology.

BTK Inhibitors Impair Platelet-Mediated Antifungal Activity

In recent years, the introduction of new drugs targeting Bruton’s tyrosine kinase (BTK) has allowed dramatic improvement in the prognosis of patients with chronic lymphocytic leukemia (CLL) and other B-cell neoplasms. Although these small molecules were initially considered less immunosuppressive than chemoimmunotherapy, an increasing number of reports have described the occurrence of unexpected opportunistic fungal infections, in particular invasive aspergillosis (IA). BTK represents a crucial molecule in several signaling pathways depending on different immune receptors. Based on a variety of specific off-target effects on innate immunity, namely on neutrophils, monocytes, pulmonary macrophages, and nurse-like cells, ibrutinib has been proposed as a new host factor for the definition of probable invasive pulmonary mold disease. The role of platelets in the control of fungal growth, through granule-dependent mechanisms, was described in vitro almost two decades ago and is, so far, neglected by experts in the field of clinical management of IA. In the present study, we confirm the antifungal role of platelets, and we show, for the first time, that the exposure to BTK inhibitors impairs several immune functions of platelets in response to Aspergillus fumigatus, i.e., the ability to adhere to conidia, activation (as indicated by reduced expression of P-selectin), and direct killing activity. In conclusion, our experimental data suggest that antiplatelet effects of BTK inhibitors may contribute to an increased risk for IA in CLL patients.

The LAMMER Kinase, LkhA, Affects Aspergillus fumigatus Pathogenicity by Modulating Reproduction and Biosynthesis of Cell Wall PAMPs

The LAMMER kinase in eukaryotes is a well-conserved dual-specificity kinase. Aspergillus species cause a wide spectrum of diseases called aspergillosis in humans, depending on the underlying immune status of the host, such as allergy, aspergilloma, and invasive aspergillosis. Aspergillus fumigatus is the most common opportunistic fungal pathogen that causes invasive aspergillosis. Although LAMMER kinase has various functions in morphology, development, and cell cycle regulation in yeast and filamentous fungi, its function in A. fumigatus is not known. We performed molecular studies on the function of the A. fumigatus LAMMER kinase, AfLkhA, and reported its involvement in multiple cellular processes, including development and virulence. Deletion of AflkhA resulted in defects in colonial growth, production of conidia, and sexual development. Transcription and genetic analyses indicated that AfLkhA modulates the expression of key developmental regulatory genes. The AflkhA-deletion strain showed increased production of gliotoxins and protease activity. When conidia were challenged with alveolar macrophages, enodocytosis of conidia by macrophages was increased in the AflkhA-deletion strain, resulting from changes in expression of the cell wall genes and thus content of cell wall pathogen-associated molecular patterns, including β-1,3-glucan and GM. While T cell-deficient zebrafish larvae were significantly susceptible to wild-type A. fumigatus infection, AflkhA-deletion conidia infection reduced host mortality. A. fumigatus AfLkhA is required for the establishment of virulence factors, including conidial production, mycotoxin synthesis, protease activity, and interaction with macrophages, which ultimately affect pathogenicity at the organismal level.

LYSMD3: A mammalian pattern recognition receptor for chitin

Chitin, a major component of fungal cell walls, has been associated with allergic disorders such as asthma. However, it is unclear how mammals recognize chitin and the principal receptor(s) on epithelial cells that sense chitin remain to be determined. In this study, we show that LYSMD3 is expressed on the surface of human airway epithelial cells and demonstrate that LYSMD3 is able to bind chitin, as well as β-glucan, on the cell walls of fungi. Knockdown or knockout of LYSMD3 also sharply blunts the production of inflammatory cytokines by epithelial cells in response to chitin and fungal spores. Competitive inhibition of the LYSMD3 ectodomain by soluble LYSMD3 protein, multiple ligands, or antibody against LYSMD3 also blocks chitin signaling. Our study reveals LYSMD3 as a mammalian pattern recognition receptor (PRR) for chitin and establishes its role in epithelial cell inflammatory responses to chitin and fungi.

Immunologic mechanism of fungal keratitis

Fungal keratitis (FK) is a refractory disease that poses a serious threat to vision, with common risk factors like eye trauma, contact lens wearing, topical corticosteroids and antibiotic abuse. Nowadays, topical and systemic anti-fungal drugs and ocular surgeries are still the main therapeutic modalities. However, the pathogenesis of FK, especially the immunologic mechanism within it, has not yet been deeply clarified. A better understanding of the pathogenesis of FK is imperative for more effective therapies and prognosis. Meanwhile, the immune protection strategies are also urgently required to manage FK. This review highlights recent advances in the immunologic mechanism in the pathogenesis of FK, in hope of providing valuable reference information for more effective anti-fungal treatment.

Chitin-rich heteroglycan from Sporothrix schenckii sensu stricto potentiates fungal clearance in a mouse model of sporotrichosis and promotes macrophages phagocytosis

Background

Fungal cell wall polysaccharides maintain the integrity of fungi and interact with host immune cells. The immunomodulation of fungal polysaccharides has been demonstrated in previous studies. However, the effect of chitin-rich heteroglycan extracted from Sporothrix schenckiisensu stricto on the immune response has not been investigated.

Results

In this study, chitin-rich heteroglycan was extracted from S. schenckiisensu stricto, and immunomodulation was investigated via histopathological analysis of skin lesions in a mouse model of sporotrichosis and evaluation of the phagocytic function and cytokine secretion of macrophages in vitro. The results showed that the skin lesions regressed and granulomatous inflammation was reduced in infected mice within 5 weeks. Moreover, heteroglycan promoted the fungal phagocytosis by macrophages and modulated the cytokine secretion. Heteroglycan upregulated TNF-α expression early at 24 h and IL-12 expression late at 72 h after incubation, which might result from moderate activation of macrophages and contribute to the subsequent adaptive immune response.

Conclusions

Chitin-rich heteroglycan extracted from S. schenckiisensu stricto potentiated fungal clearance in a mouse model of sporotrichosis. Moreover, chitin-rich heteroglycan promoted fungus phagocytosis by macrophages and modulated cytokines secretion. These results might indicate that chitin-rich heteroglycan could be considered as an immunomodulator used in the treatment of sporotrichosis.

The Clinical Relevance of Pollen Versus Fungal Spores in Allergic Diseases

Pollen and fungal spores are associated with seasonal and perennial allergies. However, most scientific literature thus far suggests that pollen allergy is more clinically relevant than fungal allergy. Several environmental and biological factors and the difficulty in producing reliable fungal extracts account for this. Biodiversity, taxonomy, and meteorology are responsible for the types and levels of pollen and fungal spores, their fragments, and the presence of free airborne allergens. Therefore, it is difficult to accurately measure both pollen and fungal allergen exposure. In addition, understanding the enzymatic nature of fungal and some pollen allergens, the presence of allergenic and nonallergenic substances that may modulate the allergic immune response, and allergen cross-reactivity are all necessary to appropriately evaluate both sensitivity and exposure. The raw materials and manufacturing processes used to prepare pollen versus fungal extracts differ, further increasing the complexity to properly determine allergic sensitivity and degrees of exposure. The pollen extracts used for diagnosis and treatment are relatively consistent, and some have been standardized. However, obtaining clinically relevant fungal extracts is more difficult. Doing so will allow for the proper selection of such extracts to more appropriately diagnose and treat both pollen- and fungal-induced allergic diseases.

Paracoccin Overexpression in Paracoccidioides brasiliensis Enhances Fungal Virulence by Remodeling Chitin Properties of the Cell Wall

BACKGROUND

The thermodimorphic fungi Paracoccidioides spp. are the etiological agents of paracoccidioidomycosis. Although poorly studied, paracoccin (PCN) from Paracoccidioides brasiliensis has been shown to harbor lectinic, enzymatic, and immunomodulatory properties that affect disease development.

METHODS

Mutants of P. brasiliensis overexpressing PCN (ov-PCN) were constructed by Agrobacterium tumefaciens-mediated transformation. ov-PCN strains were analyzed and inoculated intranasally or intravenously to mice. Fungal burden, lung pathology, and survival were monitored to evaluate virulence. Electron microscopy was used to evaluate the size of chito-oligomer particles released by ov-PCN or wild-type strains to growth media.

RESULTS

ov-PCN strains revealed no differences in cell growth and viability, although PCN overexpression favored cell separation, chitin processing that results in the release of smaller chito-oligomer particles, and enhanced virulence. Our data show that PCN triggers a critical effect in the cell wall biogenesis through the chitinase activity resulting from overexpression of PCN. As such, PCN overexpression aggravates the disease caused by P. brasiliensis.

CONCLUSIONS

Our data are consistent with a model in which PCN modulates the cell wall architecture via its chitinase activity. These findings highlight the potential for exploiting PCN function in future therapeutic approaches.

Host Response to Coccidioides Infection: Fungal Immunity

Coccidioidomycosis is a fungal, respiratory disease caused by Coccidioides immitis and Coccidioides posadasii. This emerging infectious disease ranges from asymptomatic to pulmonary disease and disseminated infection. Most infections are cleared with little to no medical intervention whereas chronic disease often requires life-long medication with severe impairment in quality of life. It is unclear what differentiates hosts immunity resulting in disease resolution versus chronic infection. Current understanding in mycology-immunology suggests that chronic infection could be due to maladaptive immune responses. Immunosuppressed patients develop more severe disease and mouse studies show adaptive Th1 and Th17 responses are required for clearance. This is supported by heightened immunosuppressive regulatory responses and lowered anti-fungal T helper responses in chronic Coccidioides patients. Diagnosis and prognosis is difficult as symptoms are broad and overlapping with community acquired pneumonia, often resulting in misdiagnosis and delayed treatment. Furthermore, we lack clear biomarkers of disease severity which could aid prognosis for more effective healthcare. As the endemic region grows and population increases in endemic areas, the need to understand Coccidioides infection is becoming urgent. There is a growing effort to identify fungal virulence factors and host immune components that influence fungal immunity and relate these to patient disease outcome and treatment. This review compiles the known immune responses to Coccidioides spp. infection and various related fungal pathogens to provide speculation on Coccidioides immunity.

Caspofungin Induced Cell Wall Changes of Candida Species Influences Macrophage Interactions

Candida species are known to differ in their ability to cause infection and have been shown to display varied susceptibilities to antifungal drugs. Treatment with the echinocandin, caspofungin, leads to compensatory alterations in the fungal cell wall. This study was performed to compare the structure and composition of the cell walls of different Candida species alone and in response to caspofungin treatment, and to evaluate how changes at the fungal cell surface affects interactions with macrophages. We demonstrated that the length of the outer fibrillar layer varied between Candida species and that, in most cases, reduced fibril length correlated with increased exposure of β-1,3-glucan on the cell surface. Candida glabrata and Candida guilliermondii, which had naturally more β-1,3-glucan exposed on the cell surface, were phagocytosed significantly more efficiently by J774 macrophages. Treatment with caspofungin resulted in increased exposure of chitin and β-1,3-glucan on the surface of the majority of Candida species isolates that were tested, with the exception of C. glabrata and Candida parapsilosis isolates. This increase in exposure of the inner cell wall polysaccharides, in most cases, correlated with reduced uptake by macrophages and in turn, a decrease in production of TNFα. Here we show that differences in the exposure of cell wall carbohydrates and variations in the repertoire of covalently attached surface proteins of different Candida species contributes to their recognition by immune cells.

Acidic Mammalian Chitinase Negatively Affects Immune Responses during Acute and Chronic Aspergillus fumigatus Exposure

Chitin is a polysaccharide that provides structure and rigidity to the cell walls of fungi and insects. Mammals possess multiple chitinases, which function to degrade chitin, thereby supporting a role for chitinases in immune defense. However, chitin degradation has been implicated in the pathogenesis of asthma. Here, we determined the impact of acidic mammalian chitinase (AMCase) (Chia) deficiency on host defense during acute exposure to the fungal pathogen Aspergillus fumigatus as well as its contribution to A. fumigatus-associated allergic asthma. We demonstrate that chitin in the fungal cell wall was detected at low levels in A. fumigatus conidia, which emerged at the highest level during hyphal transition. In response to acute A. fumigatus challenge, Chia^-/- mice unexpectedly demonstrated lower A. fumigatus lung burdens at 2 days postchallenge. The lower fungal burden correlated with decreased lung interleukin-33 (IL-33) levels yet increased IL-1β and prostaglandin E₂ (PGE₂) production, a phenotype that we reported previously to promote the induction of IL-17A and IL-22. During chronic A. fumigatus exposure, AMCase deficiency resulted in lower dynamic and airway lung resistance than in wild-type mice. Improved lung physiology correlated with attenuated levels of the proallergic chemokines CCL17 and CCL22. Surprisingly, examination of inflammatory responses during chronic exposure revealed attenuated IL-17A and IL-22 responses, but not type 2 responses, in the absence of AMCase. Collectively, these data suggest that AMCase functions as a negative regulator of immune responses during acute fungal exposure and is a contributor to fungal asthma severity, putatively via the induction of proinflammatory responses.

Dynamic Fungal Cell Wall Architecture in Stress Adaptation and Immune Evasion

Deadly infections from opportunistic fungi have risen in frequency, largely because of the at-risk immunocompromised population created by advances in modern medicine and the HIV/AIDS pandemic. This review focuses on dynamics of the fungal polysaccharide cell wall, which plays an outsized role in fungal pathogenesis and therapy because it acts as both an environmental barrier and as the major interface with the host immune system. Human fungal pathogens use architectural strategies to mask epitopes from the host and prevent immune surveillance, and recent work elucidates how biotic and abiotic stresses present during infection can either block or enhance masking. The signaling components implicated in regulating fungal immune recognition can teach us how cell wall dynamics are controlled, and represent potential targets for interventions designed to boost or dampen immunity.

Fusarium solani Activates Dectin-1 in Experimentally Induced Keratomycosis

In this study, the response of Dectin-1 on macrophages to Fusarium solani (F. solani) and the expression patterns of Dectin-1 in experimentally F. solani-induced keratomycosis were investigated. Peritoneal macrophages isolated after intraperitoneal injection of sodium thioglycollate were co-cultured with laminarin and spores of F. solani for 12 h. The expression levels of Dectin-1 and CARD9 were detected by immunofluorescence and real-time quantitative polymerase chain reaction. A mouse model of fungal keratitis was established by substromal inoculation with spores of F. solani. Corneal lesions and inflammatory responses were observed by slit-lamp and histopathology at 1, 2, 3, 5, and 7 day(s) after infection. Dectin-1 expression was significantly upregulated on macrophages stimulated by spores of F. solani. Dectin-1 was not detected in normal corneas of C57BL/6 mice, but detected in infected corneas from the first day after inoculation, with high mRNA levels observed on days 2 and 3. CARD9, a key transducer of Dectin-1 signaling, was also upregulated in infected corneas. In conclusion, Dectin-1 is an important recognition receptor in F. solani-induced keratitis, but the molecular mechanisms warrant further investigation.

Evaluation of murine lung epithelial cells (TC-1 JHU-1) line to develop Th2-promoting cytokines IL-25/IL-33/TSLP and genes Tlr2/Tlr4 in response to Aspergillus fumigatus

OBJECTIVE

The aims of this study were to determine the role of live and heat-killed Aspergillus fumigatus conidia in releasing interleukin (IL)-25, IL-33 and thymic stromal lymphopoietin (TSLP) and to express Toll-like receptor (Tlr)2 and Tlr4 genes.

MATERIALS AND METHODS

Murine lung epithelial cells were incubated with live and heat-killed A. fumigatus conidia at 37°C for 6, 24 and 48h. After treatments, ELISA was performed to measure the concentrations of IL-25, IL-33 and TSLP in the supernatants. Quantitative real-time PCR (qPCR) was performed to assess the expression levels of Tlr2 and Tlr4 genes.

RESULTS

The concentrations of IL-25 and IL-33 significantly increased after exposure to live and heat-killed conidia for various times when compared with untreated control (P<0.05). The secretion of TSLP at different concentrations of heat-killed conidia was significantly higher than both live conidia and untreated control (P<0.05). qRT-PCR results indicated a up-regulation from 1.08 to 3.60-fold for Tlr2 gene expression and 1.20 to 1.80-fold for Tlr4 gene expression exposed to heat-killed conidia.

CONCLUSION

A. fumigatus has a potential ability to stimulate murine lung epithelial cells to produce IL-25/IL-33/TSLP, as well as to express Tlr2/Tlr4 genes, indicating an important role of lung epithelial cells in innate immune responses to A. fumigatus interaction.

In vitro immunostimulatory potential of fungal β-glucans in pacific red snapper (Lutjanus peru) cells

This study attempts to describe the immunostimulatory effects of three fungal glucans on innate immunity responses in an in vitro assays using Pacific red snapper leukocytes. First, the yield glucans obtained was higher in Aspergillus niger, follow by Aspergillus ochraceus and Alternaria botrytis (40, 20 and 10%, respectively). Structural characterization of these fungal glucans by proton nuclear magnetic resonance (NMR) indicated structures containing (1-6)-branched (1-3)-β-D-glucan. The immunostimulatory activity of fungal glucans were assessed in head-kidney leukocytes at 24 h using colorimetric assays and molecular gene expression. In addition, the response against bacterial infection using Aeromonas hydrophila was evaluated by flow cytometry with annexin V/propidium iodide. Leukocytes responded positively to fungal glucans where the viability was higher than 80%. Interestingly, A. niger β-glucans enhanced the phagocytic ability and capacity in head-kidney leukocytes. Immunological assays reveled an increased in nitric oxide production, myeloperoxidase, superoxide dismutase and catalase activities, in fish stimulated with A. niger β-glucans. Induction of cytokines (IL-1β, TNF-α, IL-6, IL-8 and IL-12) were more pronounced in A. niger β-glucans leukocytes stimulated compared to other group. Finally, flow cytometry assay showed that A. botrytis and A. niger β-glucans were able to inhibit apoptosis caused by Aeromonas hydrophila in the Pacific red snapper leukocytes indicating an immunostimulant potent response by fungi derived-glucans. These results strongly support the idea that fungal β-glucans can stimulate the immune mechanism in head-kidney leukocytes and that Aspergillus niger β-glucan possess immunostimulatory properties cell increasing viability, and reducing necrotic cell death caused by Aeromonas hydrophila.

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.

Immunotherapeutic approaches to treatment of fungal diseases

Fungal infections cause morbidity worldwide and are associated with an unacceptably high mortality despite the availability of antifungal drugs. The incidence of mycoses is rising because of the HIV pandemic and because immunomodulatory drugs are increasingly used to treat autoimmune diseases and cancer. New classes of antifungal drugs have only been partly successful in improving the prognosis for patients with fungal infection. Adjunctive host-directed therapy is therefore believed to be the only option to further improve patient outcomes. Recent advances in the understanding of complex interactions between fungi and host have led to the design and exploration of novel therapeutic strategies in cytokine therapy, vaccines, and cellular immunotherapy, each of which might become viable adjuncts to existing antifungal regimens. In this report, we discuss immunotherapeutic approaches-the rationale behind their design, the challenges in their use, and the progress that is so urgently needed to overcome the devastating effect of fungal diseases.

The Carbohydrate Lectin Receptor Dectin-1 Mediates the Immune Response to Exserohilum rostratum

Dematiaceous molds are found ubiquitously in the environment and cause a wide spectrum of human disease, including infections associated with high rates of mortality. Despite this, the mechanism of the innate immune response has been less well studied, although it is key in the clearance of fungal pathogens. Here, we focus on Exserohilum rostratum, a dematiaceous mold that caused 753 infections during a multistate outbreak due to injection of contaminated methylprednisolone. We show that macrophages are incapable of phagocytosing Exserohilum Despite a lack of phagocytosis, macrophage production of tumor necrosis factor alpha is triggered by hyphae but not spores and depends upon Dectin-1, a C-type lectin receptor. Dectin-1 is specifically recruited to the macrophage-hyphal interface but not the macrophage-spore interface due to differences in carbohydrate antigen expression between these two fungal forms. Corticosteroid and antifungal therapy perturb this response, resulting in decreased cytokine production. In vivo soft tissue infection in wild-type mice demonstrated that Exserohilum provokes robust neutrophilic and granulomatous inflammation capable of thwarting fungal growth. However, coadministration of methylprednisolone acetate results in robust hyphal tissue invasion and a significant reduction in immune cell recruitment. Our results suggest that Dectin-1 is crucial for macrophage recognition and the macrophage response to Exserohilum and that corticosteroids potently attenuate the immune response to this pathogen.

A potential link between TSLP/TSLPR/STAT5 and TLR2/MyD88/NFκB-p65 in human corneal epithelial cells for Aspergillus fumigatus tolerance

Our previous studies reported that pattern recognition receptors (PRRs), including the cell surface Toll-like receptors (TLRs) and cytoplasmic NOD-like receptors (NLRs), recognize pathogen-associated molecular patterns (PAMPS) to initiate downstream signal cascades to active immunity responses. Thymic stromal lymphopoietin (TSLP) has recently emerged as a key cytokine in the development of type 2 adaptive immune responses. However, the crosstalk between PRRs and TSLP has not been well elucidated in Aspergillus fumigates keratitis. Our studies demonstrated that HCECs not only respond to TSLP, but also initiate immunological regulation through TSLP/TSLPR/STAT5 signaling pathway. In addition, we revealed that zymosan TLR2 agonist enhanced the expression of TSLP and TSLPR and phosphorylation of STAT5. Furthermore, neutralization of TLR2 with monoclonal Ab prevented the production of TSLP and TSLPR and phosphorylation of STAT5 from increasing which induced by A. fumigatus hyphae. Interestingly, we also found that human recombinant TSLP induced the increase of TLR2 downstream signal molecules, and TSLP knockdown could reduce the increase of TLR2 downstream signaling molecules(MyD88 and NF-κB-p65) induced by A. fumigatus hyphae. These studies indicated that HCECs represent a novel target of TSLP, TSLP/TSLPR/STAT5 signaling plays an important role in response to A. fumigatus infection in HCECs, and TLR2 downstream signaling molecules up regulate TSLP/TSLPR/STAT5 signaling as well as TSLP downstream signaling molecules up regulate TLR2/MyD88/NFκB-p65 signaling in this phenomenon.

Protective effects of surfactant protein D treatment in 1,3-β-glucan-modulated allergic inflammation

Surfactant protein D (SP-D) is a pulmonary collectin important in lung immunity. SP-D-deficient mice (Sftpd(-/-)) are reported to be susceptible to ovalbumin (OVA)- and fungal allergen-induced pulmonary inflammation, while treatment with exogenous SP-D has therapeutic effects in such disease models. β-Glucans are a diverse group of polysaccharides previously suggested to serve as fungal ligands for SP-D. We set out to investigate if SP-D could interact with 1,3-β-glucan and attenuate allergic pulmonary inflammation in the presence of 1,3-β-glucan. Allergic airway disease was induced in Sftpd(-/-) and Sftpd(+/+) mice by OVA sensitization and subsequent challenge with OVA, 1,3-β-glucan, or OVA/1,3-β-glucan together. Mice in the combined treatment group were further treated with a high dose of recombinant fragment of human SP-D (rfhSP-D). We demonstrated direct interaction between SP-D and 1,3-β-glucan. OVA-induced mucous cell metaplasia was increased in Sftpd(-/-) mice, supporting previously reported protective effects of endogenous SP-D in allergy. OVA-induced parenchymal CCL11 levels and eosinophilic infiltration in bronchoalveolar lavage were unaffected by 1,3-β-glucan, but were reversed with rfhSP-D treatment. 1,3-β-Glucan treatment did, however, induce pulmonary neutrophilic infiltration and increased TNF-α levels in bronchoalveolar lavage, independently of OVA-induced allergy. This infiltration was also reversed by treatment with rfhSP-D. 1,3-β-Glucan reduced OVA-induced mucous cell metaplasia, T helper 2 cytokines, and IFN-γ production. rfhSP-D treatment further reduced mucous metaplasia and T helper 2 cytokine secretion to background levels. In summary, rfhSP-D treatment resulted in attenuation of both allergic inflammation and 1,3-β-glucan-mediated neutrophilic inflammation. Our data suggest that treatment with high-dose SP-D protects from mold-induced exacerbations of allergic asthma.

Velvet-mediated repression of β-glucan synthesis in Aspergillus nidulans spores

Beta-glucans are a heterologous group of fibrous glucose polymers that are a major constituent of cell walls in Ascomycetes and Basidiomycetes fungi. Synthesis of β (1,3)- and (1,6)-glucans is coordinated with fungal cell growth and development, thus, is under tight genetic regulation. Here, we report that β-glucan synthesis in both asexual and sexual spores is turned off by the NF-kB like fungal regulators VosA and VelB in Aspergillus nidulans. Our genetic and genomic analyses have revealed that both VosA and VelB are necessary for proper down-regulation of cell wall biosynthetic genes including those associated with β-glucan synthesis in both types of spores. The deletion of vosA or velB results in elevated accumulation of β-glucan in asexual spores. Double mutant analyses indicate that VosA and VelB play an inter-dependent role in repressing β-glucan synthesis in asexual spores. In vivo chromatin immuno-precipitation analysis shows that both VelB and VosA bind to the promoter region of the β-glucan synthase gene fksA in asexual spores. Similarly, VosA is required for proper repression of β-glucan synthesis in sexual spores. In summary, the VosA-VelB hetero-complex is a key regulatory unit tightly controlling proper levels of β-glucan synthesis in asexual and sexual spores.

Co-recognition of β-glucan and chitin and programming of adaptive immunity to Aspergillus fumigatus

The prevalence of fungal infections has increased concurrently with increases in immune suppressive therapies and susceptible individuals. Opportunistic fungal pathogens such as Aspergillus fumigatus may exhibit invasive growth and dissemination resulting in a high mortality rate. Herein, we discuss how immune sensing of germination directs innate immune responses and programs adaptive responses that could promote or impair immune protection during periods of heightened susceptibility. In infected individuals, Th1 responses are the most protective, while Th2 responses lead to poor disease outcomes. In particular, the roles of β-glucan and chitin co-recognition in shaping Th1- and Th2-type immunity to fungal infection are explored. We discuss how fungal responses to environmental stresses could result in decreased immune protection from infection, particularly in response to anti-fungal drugs that target β-glucan synthesis. Furthermore, we consider how experimental modulation of host-pathogen interactions might elucidate the mechanisms of protective and detrimental immunity and the potential of current and future studies to promote the development of improved treatments for patients that respond poorly to existing therapies.

Keeping track of the growing number of biological functions of chitin and its interaction partners in biomedical research

Chitin is a vital polysaccharide component of protective structures in many eukaryotic organisms but seems absent in vertebrates. Chitin or chitin oligomers are therefore prime candidates for non-self-molecules, which are recognized and degraded by the vertebrate immune system. Despite the absence of polymeric chitin in vertebrates, chitinases and chitinase-like proteins (CLPs) are well conserved in vertebrate species. In many studies, these proteins have been found to be involved in immune regulation and in mediating the degradation of chitinous external protective structures of invading pathogens. Several important aspects of chitin immunostimulation have recently been uncovered, advancing our understanding of the complex regulatory mechanisms that chitin mediates. Likewise, the last few years have seen large advances in our understanding of the mechanisms and molecular interactions of chitinases and CLPs in relation to immune response regulation. It is becoming increasingly clear that their function in this context is not exclusive to chitin producing pathogens, but includes bacterial infections and cancer signaling as well. Here we provide an overview of the immune signaling properties of chitin and other closely related biomolecules. We also review the latest literature on chitinases and CLPs of the GH18 family. Finally, we examine the existing literature on zebrafish chitinases, and propose the use of zebrafish as a versatile model to complement the existing murine models. This could especially be of benefit to the exploration of the function of chitinases in infectious diseases using high-throughput approaches and pharmaceutical interventions.

Chitin enhances serum IgE in Aspergillus fumigatus induced allergy in mice

Aspergillus fumigatus (A. fumigatus) is a ubiquitous fungus that activates, suppresses or modulates the immune response by changing its cell wall structure and by secreting proteases. In this study, we show that chitin acts as an adjuvant in a murine model of A. fumigatus protease induced allergy. The mice were immunised intraperitoneally with A. fumigatus culture filtrate antigen either with or without chitin and were subsequently challenged with the culture filtrate antigen intranasally. Alum was used as an adjuvant control. Compared to alum, chitin induced a weaker inflammatory response in the lungs, measured as the total cell efflux in BAL, EPO and chitinase production. However, chitin enhanced the total IgE, specific IgE and specific IgG1 production as efficiently as alum. Pre-treatment with chitin but not with alum depressed the concentration of the Th2 cytokines IL-4 and IL-13 in BAL fluid. These results shows that chitin, in spite of a reduction of the Th2 cytokine levels in the lungs, enhanced the total and specific IgE production in A. fumigatus culture filtrate induced allergy.

Resveratrol plus carboxymethyl-β-glucan reduces nasal symptoms in children with pollen-induced allergic rhinitis

OBJECTIVE

Allergic rhinitis (AR) is caused by an IgE-mediated inflammatory reaction consequent to the exposure to causal allergen. Resveratrol is a natural non-flavonoid polyphenol, exerting anti-inflammatory activity; β-glucan is a polysaccharide with immuno-modulatory properties. Thus, this study aimed to investigate whether these combined compounds are able of relieving nasal symptoms in children with AR due to pollen allergy.

RESEARCH DESIGN AND METHODS

The present study was conducted as placebo-controlled, double-blinded, and randomized. Globally, 68 children (36 males; mean age 7.9 years) were treated with resveratrol plus β-glucan or placebo (the diluent of active drug) two sprays (100 µL/spray) in each nostril three times/day for 2 months. Nasal symptoms, including itching, sneezing, rhinorrhea, and obstruction, were assessed at baseline and after treatment. Use of rescue medication, such as cetirizine syrup, was also evaluated.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov ID NCT02130440.

RESULTS

Children treated with active drug achieved a significant reduction in all nasal symptoms: itching (p = 0.0001), sneezing (p = 0.0009), rhinorrhea (p = 0.009), and obstruction (0.002) as well as antihistamine use (p = 0.003). Placebo did not affect nasal complaints and cetirizine use. The intergroup analysis showed that active treatment was significantly superior to placebo about reduction of AR symptoms and rescue medication use.

CONCLUSIONS

The present preliminary study firstly showed that intranasal resveratrol plus carboxymethyl-β-glucan is capable of significantly improving nasal symptoms in children with pollen-induced AR.

Biological activities of derivatized D-glucans: a review

D-Glucans have triggered increasing interest in commercial applications in the chemical and pharmaceutical sectors because of their technological properties and biological activities. The glucans are foremost among the polysaccharide groups produced by microorganisms with demonstrated activity in stimulating the immune system, and have potential in treating human disease conditions. Chemical alterations in the structure of D-glucans through derivatization (sulfonylation, carboxymethylation, phosphorylation, acetylation) contributes to their increased solubility that, in turn, can alter their biological activities such as antioxidation and anticoagulation. This review surveys and cites the latest advances on the biological and technological potential of D-glucans following chemical modifications through sulfonylation, carboxymethylation, phosphorylation or acetylation, and discusses the findings of their activities. Several studies suggest that chemically modified d-glucans have potentiated biological activity as anticoagulants, antitumors, antioxidants, and antivirals. This review shows that in-depth future studies on chemically modified glucans with amplified biological effects will be relevant in the biotechnological field because of their potential to prevent and treat numerous human disease conditions and their clinical complications.

The effect of chitin size, shape, source and purification method on immune recognition

The animal immune response to chitin is not well understood and needs to be investigated further. However, this is a challenging topic to study because of the technical difficulties in purifying chitin, and because this material usually comes associated with contaminating components that can activate the immune system. In this study, improvements to previously described purification protocols were investigated for chitin obtained from different sources, including commercial shellfish, Candida albicans yeast and hyphal cell walls, as well as cell walls of the filamentous fungi Aspergillus fumigatus and Mucor circinelloides. The immune response to these different chitin preparations was tested using human peripheral blood mononuclear cells. In agreement with previous literature, small chitin particles of an average size of 0.2 µm were not immunogenic. On the other hand, bigger chitin particles induced in some cases a pro-inflammatory response. The results of this work suggest that not only the purity and size of the chitin particles, but also their shape can influence immune recognition.