Fungal beta-glucan interacts with vitronectin and stimulates tumor necrosis factor alpha release from macrophages

Impact of diet and host genetics on the murine intestinal mycobiome

The mammalian gut is home to a diverse microbial ecosystem, whose composition affects various physiological traits of the host. Next-generation sequencing-based metagenomic approaches demonstrated how the interplay of host genetics, bacteria, and environmental factors shape complex traits and clinical outcomes. However, the role of fungi in these complex interactions remains understudied. Here, using 228 males and 363 females from an advanced-intercross mouse line, we provide evidence that fungi are regulated by host genetics. In addition, we map quantitative trait loci associated with various fungal species to single genes in mice using whole genome sequencing and genotyping. Moreover, we show that diet and its' interaction with host genetics alter the composition of fungi in outbred mice, and identify fungal indicator species associated with different dietary regimes. Collectively, in this work, we uncover an association of the intestinal fungal community with host genetics and a regulatory role of diet in this ecological niche.

Oral SARS-CoV-2 Spike Protein Recombinant Yeast Candidate Prompts Specific Antibody and Gut Microbiota Reconstruction in Mice

A recent study showed that patients with coronavirus disease 2019 (COVID-19) have gastrointestinal symptoms and intestinal flora dysbiosis. Yeast probiotics shape the gut microbiome and improve immune homeostasis. In this study, an oral candidate of yeast-derived spike protein receptor-binding domain (RBD) and fusion peptide displayed on the surface of the yeast cell wall was generated. The toxicity and immune efficacy of oral administration were further performed in Institute of Cancer Research (ICR) mice. No significant difference in body weights, viscera index, and other side effects were detected in the oral-treated group. The detectable RBD-specific immunoglobulin G (IgG) and immunoglobulin A (IgA) of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and more complex microbiota were detected from oral administration mice compared with those of the control group. Interestingly, the recombinant yeast was identified in female fetal of the high-dose group. These results revealed that the displaying yeast could fulfill the agent-driven immunoregulation and gut microbiome reconstitution. The findings will shed light on new dimensions against SARS-CoV-2 infection with the synergistic oral agents as promising non-invasive immunization and restoring gut flora.

Dichotomous Role of Tumor Necrosis Factor in Pulmonary Barrier Function and Alveolar Fluid Clearance

Alveolar-capillary leak is a hallmark of the acute respiratory distress syndrome (ARDS), a potentially lethal complication of severe sepsis, trauma and pneumonia, including COVID-19. Apart from barrier dysfunction, ARDS is characterized by hyper-inflammation and impaired alveolar fluid clearance (AFC), which foster the development of pulmonary permeability edema and hamper gas exchange. Tumor Necrosis Factor (TNF) is an evolutionarily conserved pleiotropic cytokine, involved in host immune defense against pathogens and cancer. TNF exists in both membrane-bound and soluble form and its mainly -but not exclusively- pro-inflammatory and cytolytic actions are mediated by partially overlapping TNFR1 and TNFR2 binding sites situated at the interface between neighboring subunits in the homo-trimer. Whereas TNFR1 signaling can mediate hyper-inflammation and impaired barrier function and AFC in the lungs, ligand stimulation of TNFR2 can protect from ventilation-induced lung injury. Spatially distinct from the TNFR binding sites, TNF harbors within its structure a lectin-like domain that rather protects lung function in ARDS. The lectin-like domain of TNF -mimicked by the 17 residue TIP peptide- represents a physiological mediator of alveolar-capillary barrier protection. and increases AFC in both hydrostatic and permeability pulmonary edema animal models. The TIP peptide directly activates the epithelial sodium channel (ENaC) -a key mediator of fluid and blood pressure control- upon binding to its α subunit, which is also a part of the non-selective cation channel (NSC). Activity of the lectin-like domain of TNF is preserved in complexes between TNF and its soluble TNFRs and can be physiologically relevant in pneumonia. Antibody- and soluble TNFR-based therapeutic strategies show considerable success in diseases such as rheumatoid arthritis, psoriasis and inflammatory bowel disease, but their chronic use can increase susceptibility to infection. Since the lectin-like domain of TNF does not interfere with TNF's anti-bacterial actions, while exerting protective actions in the alveolar-capillary compartments, it is currently evaluated in clinical trials in ARDS and COVID-19. A more comprehensive knowledge of the precise role of the TNFR binding sites versus the lectin-like domain of TNF in lung injury, tissue hypoxia, repair and remodeling may foster the development of novel therapeutics for ARDS.

Beta-glucans is a potential inhibitor of ovarian cancer: based on molecular and biological aspects

Ovarian cancer is a lethal type of cancer which is initiated in the ovaries and affects 1 out of every 75 women. Due to the high number of deaths (almost 152,000) related to this cancer, it seems that novel effiecient therapeutic methods are required in this field. Beta-glucans are a type of glucose linear polymers which have proven to have a lot of advantageous activities. Recently, investigations have declared that these polysaccharides have the potential to be used as anti-cancer drugs. These agents are able to affect several mechanisms such as inflammation and apoptosis and that is how cancers are prone to be affected by them. In this review, we attempt to investigate the role of beta-glucans on ovarian cancer. We hope that this paper might give novel insights in the field of ovarian cancer treatment.

Porcine Immunoglobulin Fc Fused P30/P54 Protein of African Swine Fever Virus Displaying on Surface of S. cerevisiae Elicit Strong Antibody Production in Swine

African swine fever virus (ASFV) infects domestic pigs and European wild boars with strong, hemorrhagic and high mortality. The primary cellular targets of ASFV is the porcine macrophages. Up to now, no commercial vaccine or effective treatment available to control the disease. In this study, three recombinant Saccharomyces cerevisiae (S. cerevisiae) strains expressing fused ASFV proteins-porcine Ig heavy chains were constructed and the immunogenicity of the S. cerevisiae-vectored cocktail ASFV feeding vaccine was further evaluated. To be specific, the P30-Fcγ and P54-Fcα fusion proteins displaying on surface of S. cerevisiae cells were produced by fusing the Fc fragment of porcine immunoglobulin IgG1 or IgA1 with p30 or p54 gene of ASFV respectively. The recombinant P30-Fcγ and P54-Fcα fusion proteins expressed by S. cerevisiae were verified by Western blotting, flow cytometry and immunofluorescence assay. Porcine immunoglobulin Fc fragment fused P30/P54 proteins elicited P30/P54-specific antibody production and induced higher mucosal immunity in swine. The absorption and phagocytosis of recombinant S. cerevisiae strains in IPEC-J2 cells or porcine alveolar macrophage (PAM) cells were significantly enhanced, too. Here, we introduce a kind of cheap and safe oral S. cerevisiae-vectored vaccine, which could activate the specific mucosal immunity for controlling ASFV infection.

Functional activities of beta-glucans in the prevention or treatment of cervical cancer

Cervical cancer is the fourth-ranked cancer in the world and is associated with a large number of deaths annually. Chemotherapy and radiotherapy are known as the common therapeutic approaches in the treatment of cervical cancer, but because of their side effects and toxicity, researchers are trying to discovery alternative therapies. Beta-glucans, a group of glucose polymers that are derived from the cell wall of fungi, bacteria, and etc. it has been showed that beta-glucans have some anti-cancer properties which due to their impacts on adaptive and innate immunity. Along to these impacts, these molecules could be used as drug carriers. In this regard, the application of beta-glucans is a promising therapeutic option for the cancer prevention and treatment especially for cervical cancer. Herein, we have summarized the therapeutic potential of beta-glucans alone or as adjuvant therapy in the treatment of cervical cancer. Moreover, we highlighted beta-glucans as drug carriers for preventive and therapeutic purposes.

Functional activities of beta-glucans in the prevention or treatment of cervical cancer

Cervical cancer is the fourth-ranked cancer in the world and is associated with a large number of deaths annually. Chemotherapy and radiotherapy are known as the common therapeutic approaches in the treatment of cervical cancer, but because of their side effects and toxicity, researchers are trying to discovery alternative therapies. Beta-glucans, a group of glucose polymers that are derived from the cell wall of fungi, bacteria, and etc. it has been showed that beta-glucans have some anti-cancer properties which due to their impacts on adaptive and innate immunity. Along to these impacts, these molecules could be used as drug carriers. In this regard, the application of beta-glucans is a promising therapeutic option for the cancer prevention and treatment especially for cervical cancer. Herein, we have summarized the therapeutic potential of beta-glucans alone or as adjuvant therapy in the treatment of cervical cancer. Moreover, we highlighted beta-glucans as drug carriers for preventive and therapeutic purposes.

Unraveling the subtleties of β-(1→3)-glucan phosphorylase specificity in the GH94, GH149, and GH161 glycoside hydrolase families

Glycoside phosphorylases (GPs) catalyze the phosphorolysis of glycans into the corresponding sugar 1-phosphates and shortened glycan chains. Given the diversity of natural β-(1→3)-glucans and their wide range of biotechnological applications, the identification of enzymatic tools that can act on β-(1→3)-glucooligosaccharides is an attractive area of research. GP activities acting on β-(1→3)-glucooligosaccharides have been described in bacteria, the photosynthetic excavate Euglena gracilis, and the heterokont Ochromonas spp. Previously, we characterized β-(1→3)-glucan GPs from bacteria and E. gracilis, leading to their classification in glycoside hydrolase family GH149. Here, we characterized GPs from Gram-positive bacteria and heterokont algae acting on β-(1→3)-glucooligosaccharides. We identified a phosphorylase sequence from Ochromonas spp. (OcP1) together with its orthologs from other species, leading us to propose the establishment of a new GH family, designated GH161. To establish the activity of GH161 members, we recombinantly expressed a bacterial GH161 gene sequence (PapP) from the Gram-positive bacterium Paenibacillus polymyxa ATCC 842 in Escherichia coli. We found that PapP acts on β-(1→3)-glucooligosaccharide acceptors with a degree of polymerization (DP) ≥ 2. This activity was distinct from that of characterized GH149 β-(1→3)-glucan phosphorylases, which operate on acceptors with DP ≥ 1. We also found that bacterial GH161 genes co-localize with genes encoding β-glucosidases and ATP-binding cassette transporters, highlighting a probable involvement of GH161 enzymes in carbohydrate degradation. Importantly, in some species, GH161 and GH94 genes were present in tandem, providing evidence that GPs from different CAZy families may work sequentially to degrade oligosaccharides.

Effects of Yeast (1,3)-(1,6)-Beta-Glucan on Severity of Upper Respiratory Tract Infections: A Double-Blind, Randomized, Placebo-Controlled Study in Healthy Subjects

OBJECTIVES

Each year, adults suffer about two to four upper respiratory tract infections (URTIs), mostly in winter. The aim of the study was to evaluate the effects of brewers' yeast (1,3)-(1,6)-beta-glucan on incidence and severity of upper respiratory tract infections (URTIs).

METHODS

Generally healthy men and women (n = 299) reporting at least three URTIs during the previous year were randomized to receive either a placebo or 900 mg of yeast beta-glucan daily for 16 weeks during winter. In cases of acute URTI, the severity of URTI symptoms was assessed via the WURSS-21 questionnaire and the Jackson scale, and a clinical confirmation was implemented by the investigator.

RESULTS

Overall, 70 subjects under placebo and 71 subjects under yeast beta-glucan experienced at least one clinically confirmed URTI episode. The global severity using WURSS-21 had been quite similar between the study groups (p = 0.5267), whereas during the first days of URTIs the severity was less pronounced in the yeast beta-glucan group. On the episode level, the severity of physical symptoms was significantly lower for all investigated time intervals up to 7 days under yeast beta-glucan (WURSS (Q2-11) (days 1-2: p = 0.0465, days 1-3: p = 0.0323, days 1-4: p = 0.0248, days 1-7: p = 0.0278), also confirmed for the Jackson scale). The reduction of severity was accompanied by a significant increase in the joy subscore of the Perceived Stress Questionnaire (PSQ20) (p = 0.0148). In addition, there was a reduction of systolic (p = 0.0458) and diastolic (p = 0.1439) blood pressure.

CONCLUSION

Subjects supplementing with yeast beta-glucan benefit by a reduced severity of physical URTI symptoms during the first week of an episode, even though the incidence and global severity of common colds could not be altered in comparison to placebo. Furthermore, accompanying benefits in terms of blood pressure and mood were identified. Altogether, yeast beta-glucan supports the immune function.

In vitro bioassessment of the immunomodulatory activity of Saccharomyces cerevisiae components using bovine macrophages and Mycobacterium avium ssp. paratuberculosis

The yeast Saccharomyces cerevisiae and its components are used for the prevention and treatment of enteric disease in different species; therefore, they may also be useful for preventing Johne's disease, a chronic inflammatory bowel disease of ruminants caused by Mycobacterium avium ssp. paratuberculosis (MAP). The objective of this study was to identify potential immunomodulatory S. cerevisiae components using a bovine macrophage cell line (BOMAC). The BOMAC phagocytic activity, reactive oxygen species production, and immune-related gene (IL6, IL10, IL12p40, IL13, IL23), transforming growth factor β, ARG1, CASP1, and inducible nitric oxide synthase expression were investigated when BOMAC were cocultured with cell wall components from 4 different strains (A, B, C, and D) and 2 forms of dead yeast from strain A. The BOMAC phagocytosis of mCherry-labeled MAP was concentration-dependently attenuated when BOMAC were cocultured with yeast components for 6 h. Each yeast derivative also induced a concentration-dependent increase in BOMAC reactive oxygen species production after a 6-h exposure. In addition, BOMAC mRNA expression of the immune-related genes was investigated after 6 and 24 h of exposure to yeast components. All yeast components were found to regulate the immunomodulatory genes of BOMAC; however, the response varied among components and over time. The in vitro bioassessment studies reported here suggest that dead yeast and its cell wall components may be useful for modulating macrophage function before or during MAP infection.

Effective inhibition of Cbf-14 against Cryptococcus neoformans infection in mice and its related anti-inflammatory activity

Cbf-14 (RLLRKFFRKLKKSV), a designed peptide derived from cathelicidin family AMP, has proven to be potent against drug-resistant bacteria. In the present study, we investigated the anti-cryptococcal activity of Cbf-14 in vitro and in a pulmonary infection mouse model. Sensitivity test indicated that Cbf-14 possessed effective antifungal activity against Cryptococcus neoformans with an MIC of 4-16 µg/ml, and killing experiments showed that fungicidal activity was achieved after only 4 h treatment with Cbf-14 at 4× MIC concentrations in vitro. Meanwhile, Cbf-14 was effective at prolonging the survival of infected mice when compared with controls, and significantly inhibited the secretion of pro-inflammatory cytokines TNF-α, IL-1β and IL-6, suggesting its anti-inflammatory activity against fungal infections. As a positively charged peptide, Cbf-14 was proven to neutralize the negative zeta potential of the fungal cell surface, disrupt the capsule polysaccharide of fungi, and further damage cell membrane integrity. These results were confirmed by flow cytometry analysis of the fluorescence intensity after PI staining, while cell membrane damage could be clearly observed by transmission electron microscopy after Cbf-14 (4× MIC) treatment for 1 h. In addition, Cbf-14 increased the IL-10 levels in cultured RAW 264.7 cells, which were stimulated by C. neoformans infection. The obtained data demonstrated that Cbf-14 could rapidly kill C. neoformans cells in vitro, effectively inhibit C. neoformans induced-infection in mice, and inhibit inflammation in vitro / vivo. Therefore, Cbf-14 could potentially be used for the treatment of fungal infections clinically.

TNF Lectin-Like Domain Restores Epithelial Sodium Channel Function in Frameshift Mutants Associated with Pseudohypoaldosteronism Type 1B

Previous in vitro studies have indicated that tumor necrosis factor (TNF) activates amiloride-sensitive epithelial sodium channel (ENaC) current through its lectin-like (TIP) domain, since cyclic peptides mimicking the TIP domain (e.g., solnatide), showed ENaC-activating properties. In the current study, the effects of TNF and solnatide on individual ENaC subunits or ENaC carrying mutated glycosylation sites in the α-ENaC subunit were compared, revealing a similar mode of action for TNF and solnatide and corroborating the previous assumption that the lectin-like domain of TNF is the relevant molecular structure for ENaC activation. Accordingly, TNF enhanced ENaC current by increasing open probability of the glycosylated channel, position N511 in the α-ENaC subunit being identified as the most important glycosylation site. TNF significantly increased Na⁺ current through ENaC comprising only the pore forming subunits α or δ, was less active in ENaC comprising only β-subunits, and showed no effect on ENaC comprising γ-subunits. TNF did not increase the membrane abundance of ENaC subunits to the extent observed with solnatide. Since the α-subunit is believed to play a prominent role in the ENaC current activating effect of TNF and TIP, we investigated whether TNF and solnatide can enhance αβγ-ENaC current in α-ENaC loss-of-function frameshift mutants. The efficacy of solnatide has been already proven in pathological conditions involving ENaC in phase II clinical trials. The frameshift mutations αI68fs, αT169fs, αP197fs, αE272fs, αF435fs, αR438fs, αY447fs, αR448fs, αS452fs, and αT482fs have been reported to cause pseudohypoaldosteronism type 1B (PHA1B), a rare, life-threatening, salt-wasting disease, which hitherto has been treated only symptomatically. In a heterologous expression system, all frameshift mutants showed significantly reduced amiloride-sensitive whole-cell current compared to wild type αβγ-ENaC, whereas membrane abundance varied between mutants. Solnatide restored function in α-ENaC frameshift mutants to current density levels of wild type ENaC or higher despite their lacking a binding site for solnatide, previously located to the region between TM2 and the C-terminus of the α-subunit. TNF similarly restored current density to wild type levels in the mutant αR448fs. Activation of βγ-ENaC may contribute to this moderate current enhancement, but whatever the mechanism, experimental data indicate that solnatide could be a new strategy to treat PHA1B.

Tumor necrosis factor prevents Candida albicans biofilm formation

Candida species are commensals but some develop biofilms in prosthetic materials and host surfaces that may represent up to 30% of deaths related to infections, particularly in immunosuppressed patients. Tumor necrosis factor (TNF) exhibits a plethora of functions in host defense mechanisms whereas excessive release of TNF in inflammation promotes tissue damage. Cytokines released in an inflammatory milieu may influence the development of microorganisms either by promoting their growth or displaying antimicrobial activity. In protozoa, TNF may affect growth by coupling through a lectin-like domain, distinct from TNF receptors. TNF was also shown to interact with bacteria via a mechanism that does not involve classical TNF receptors. Using an in vitro C. albicans biofilm model, we show that TNF dose-dependently prevents biofilm development that is blocked by incubating TNF with N,N’-diacetylchitobiose, a major carbohydrate component of C. albicans cell wall. This finding represents a relevant and hitherto unknown mechanism that adds to the understanding of why TNF blockade is associated with opportunistic C. albicans infections.

Barley β-glucan in poultry diets

There has been an increased interest in the use of immunomodulators as substitutes for antibiotics in food animal production. Beta-glucans from yeast and fungi may be ideal substitutes because of their positive effects on the avian immune system without adversely affecting poultry performance. Barley β-glucans, however, have not shown this potential due to the adverse effects dietary inclusion of barley has on poultry performance.

Recent advances in oral vaccine development: yeast-derived β-glucan particles

Oral vaccination is the most challenging vaccination method due to the administration route. However, oral vaccination has socio-economic benefits and provides the possibility of stimulating both humoral and cellular immune responses at systemic and mucosal sites. Despite the advantages of oral vaccination, only a limited number of oral vaccines are currently approved for human use. During the last decade, extensive research regarding antigen-based oral vaccination methods have improved immunogenicity and induced desired immunological outcomes. Nevertheless, several factors such as the harsh gastro-intestinal environment and oral tolerance impede the clinical application of oral delivery systems. To date, human clinical trials investigating the efficacy of these systems are still lacking. This review addresses the rationale and key biological and physicochemical aspects of oral vaccine design and highlights the use of yeast-derived β-glucan microparticles as an oral vaccine delivery platform.

In vivo effects of dietary (1→3), (1→4)-β-D-glucans from oat on mucosal immune responses in man and mice

OBJECTIVE

Antimicrobial peptides and tight junction proteins are crucial to maintain mucosal immunity. It is known that oat β-glucan may affect intestinal immunity. Therefore, the aim of the present study was to evaluate the effect of oat β-glucan on the presence of antimicrobial peptides and tight junction protein.

MATERIAL AND METHODS

We analyzed antimicrobial peptide levels in fecal water prepared from 24 h ileostomic bag contents obtained from ileostomic patients consuming oat β-glucan enriched or control diets in a cross-over design. In addition, intestinal sections of mice, which received oat β-glucan via oral gavages for 3.5 days, were analyzed for lysozyme and zonula occludens-1 expression.

RESULTS

We observed a trend toward lower lysozyme (-23%; p = 0.076) and bactericidal/permeability-increasing protein (-17%; p = 0.098) levels in oat β-glucan enriched fecal water as compared with placebo. Additionally, mice receiving oat β-glucan showed a lower lysozyme expression in stained distal small intestinal sections (p = 0.011). Staining of zonula occludens-1 was decreased in β-glucan treated mice indicating disruption of the tight junction integrity.

CONCLUSIONS

In conclusion, the consumption of oat β-glucan seems to decrease the levels of antimicrobial peptides in fecal water from human ileostomy patients and its expression in distal small intestine sections in mice. The decreased intestinal integrity in mice could be explained by the drop in antimicrobial peptides.

Earthworm immunity

Earthworms belonging to oligochaete annelids became a model for comparative immunologists in the early sixties with the publication of results from transplantation experiments that proved the existence of self/nonself recognition in earthworms. This initiated extensive studies on the earthworm immune mechanisms that evolved to prevent the invasion of pathogens. In the last four decades important cellular and humoral pathways were described and numerous biologically active compounds were characterized and often cloned.

Dietary modulation of immune function by beta-glucans

The immune response can be modulated by nutrients like beta-glucans, which are glucose polymers that are major structural components of the cell wall of yeast, fungi, and bacteria, but also of cereals like oat and barley. There is a lot of structural variation in the beta-glucans from these different sources, which may influence their physiological functions. In this review the current status concerning possibilities to modulate immune function by beta-glucans is discussed. In vitro as well as in vivo studies in animals and humans show that especially beta-glucans derived from fungi and yeast have immune modulating properties. Most frequently evaluated are effects on leukocyte activity, which has been suggested to contribute to the increased resistance against infections observed after beta-glucan interventions. Although most studies supply the beta-glucans parenteral (e.g. intravenous or subcutaneous), also enteral administrated (dietary) beta-glucan influence the immune response. Although more human studies are needed, it is tempting to suggest that dietary beta-glucans may be a useful tool to prime the host immune system and increase resistance against invading pathogens.

Insight into the host-parasite interplay by proteomic study of host proteins copurified with the human parasite, Schistosoma japonicum

The tegument proteins of schistosome have attracted the most attention in studies of host-parasite interplay, while the host proteins acting at the host-parasite interface remained largely elusive. Here, we undertook a high-throughput proteomic approach to characterize the schistosome-adsorbed host proteins. Fifty five distinct host proteins were confidently identified in S. japonicum samples, including cercaria, schistosomula, adults, eggs, and miracidia, together with tegument and eggshell preparations, of which 23 and 38 host proteins were identified in adult worms and eggs, respectively. Among the schistosome-adsorbed host proteins, host neutrophil elastases were found in the granuloma initiated by schistosome egg deposition, implying that the host innate immune molecules could participate in the granuloma formation for fighting against schistosome invasion, except for the adaptive immune system. In addition, some host proteins, such as proteinase inhibitor and superoxide dismutase, might be utilized by schistosome to counteract or attenuate the host attacks. These parasite-adsorbed host proteins will provide new insights into the host immune responses against schistosome infection, the evasive behavior of the adult worms, and the granuloma formation, which could render an in-depth understanding for the host-parasite interplay.

Characterization of the lipopolysaccharide and beta-glucan of the fish pathogen Francisella victoria

Lipopolysaccharide (LPS) and beta-glucan from Francisella victoria, a fish pathogen and close relative of highly virulent mammal pathogen Francisella tularensis, have been analyzed using chemical and spectroscopy methods. The polysaccharide part of the LPS was found to contain a nonrepetitive sequence of 20 monosaccharides as well as alanine, 3-aminobutyric acid, and a novel branched amino acid, thus confirming F. victoria as a unique species. The structure identified composes the largest oligosaccharide elucidated by NMR so far, and was possible to solve using high field NMR with cold probe technology combined with the latest pulse sequences, including the first application of H2BC sequence to oligosaccharides. The non-phosphorylated lipid A region of the LPS was identical to that of other Francisellae, although one of the lipid A components has not been found in Francisella novicida. The heptoseless core-lipid A region of the LPS contained a linear pentasaccharide fragment identical to the corresponding part of F. tularensis and F. novicida LPSs, differing in side-chain substituents. The linkage region of the O-chain also closely resembled that of other Francisella. LPS preparation contained two characteristic glucans, previously observed as components of LPS preparations from other strains of Francisella: amylose and the unusual beta-(1-6)-glucan with (glycerol)2phosphate at the reducing end.

Determination of the inflammatory potential of bioaerosols from a duck-fattening unit by using a limulus amebocyte lysate assay and human whole blood cytokine response

Inhalation of bioaerosols from animal houses can induce acute inflammatory reactions in the respiratory tract. Determination of the concentration of airborne endotoxins is widely used to characterize this risk. In this study, the activity of bioaerosol samples from a duck-fattening unit to induce interleukin-1beta (IL-1beta) in human blood and to react with Limulus Amebocyte Lysate (LAL) was investigated. The activity detected in the whole blood assay correlated well with the endotoxic activity found in the LAL assay (Spearmen's rho = 0.902). However in all samples, the inflammation-inducing potential was overestimated by the LAL assay. It is assumed that this overestimation could be, in part, a result of an overestimation of the inflammatory potential of endotoxins originating from Pseudomonadaceae by the LAL assay. Pseudomonadaceae were regularly isolated from the air of the duck-fattening unit. The results presented here indicate that the whole blood assay can be used besides the LAL assay as an additional method to characterize the inflammation-inducing potential of bioaerosols.

Comparative study of the CCF-like pattern recognition protein in different Lumbricid species

Coelomic fluid of the Lumbricid Eisenia fetida contains a 42-kDa pattern recognition protein named coelomic cytolytic factor (CCF) that binds microbial cell wall components and triggers the activation of the prophenoloxidase cascade, an important invertebrate defense pathway. Here we report on the sequence characterization of CCF-like molecules of other Lumbricids: Aporrectodea caliginosa, Aporrectodea icterica, Aporrectodea longa, Aporrectodea rosea, Dendrobaena veneta, Lumbricus rubellus and Lumbricus terrestris, and show that CCF from E. fetida has a broader saccharide-binding specificity, being the only one recognizing N,N'-diacetylchitobiose. We suggest that the broad recognition repertoire of E. fetida CCF reflects a particular microbial environment this species lives in.

IFN-γ primes macrophages for enhanced TNF-α expression in response to stimulatory and non-stimulatory amounts of microparticulate β-glucan

beta-(1-->3)-D-Glucan is an integral cell wall component of a variety of fungi, plants, and bacteria. Like the prototypic inflammatory mediator lipopolysaccharide (LPS), some beta-(1--> 3)-D-glucan-containing preparations have been shown to induce the production of proinflammatory cytokines by macrophages. In the present study, we have tested a new microparticulate form of beta-(1--> 3)-D-glucan (MG) from Saccharomyces cerevisiae for its ability to induce proinflammatory cytokine secretion in mouse peritoneal macrophages in vitro, and we have examined the effect of IFN-gamma. MG was rapidly phagocytized by peritoneal macrophages, and these MG-treated macrophages upregulated TNF-alpha, IL-6, and IL-1beta mRNAs and secreted these proinflammatory cytokines. IFN-gamma treatment alone did not induce unstimulated macrophages to produce TNF-alpha. However, a 4 h IFN-gamma pretreatment augmented TNF-alpha secretion by peritoneal macrophages subsequently treated with an optimally stimulatory dose of MG. IFN-gamma pretreatment for 2 h followed by thorough washing and a further 2 h incubation without IFN-gamma still resulted in enhanced TNF-alpha production in response to MG, suggesting that IFN-gamma can prime macrophages for a subsequent proinflammatory response. Most interestingly, we found that IFN-gamma pretreatment of peritoneal macrophages enhanced the TNF-alpha response to amounts of MG that were poorly stimulatory or non-stimulatory in the absence of IFN-gamma priming. These data suggest that a synergy between IFN-gamma and beta-glucan may have evolved to lower the threshold of sensitivity of the innate immune response to fungal pathogens.

Down-modulation of lymphoproliferation and interferon-gamma production by beta-glucan derived from Saccharomyces cerevisiae

beta-glucan, one of the major cell wall components of Saccharomyces cerevisiae, has been found to enhance immune functions. This study investigated in vivo and in vitro effects of beta-glucan on lymphoproliferation and interferon-gamma (IFN-gamma) production by splenic cells from C57BL/6 female mice. All experiments were performed with particulate beta-glucan derived from S. cerevisiae. Data demonstrated that both, i.p. administration of particulate beta-glucan (20 or 100 micrograms/animal) and in vitro stimulation of splenic cells (20 or 100 micrograms/ml of culture) decreased lymphoproliferation and IFN-gamma production induced by concanavalin A. These results suggest that beta-glucan can trigger a down-modulatory effect regulating a deleterious immune system hyperactivity in the presence of a strong stimulus.

Surface glycans of Candida albicans and other pathogenic fungi: physiological roles, clinical uses, and experimental challenges

Although fungi have always been with us as commensals and pathogens, fungal infections have been increasing in frequency over the past few decades. There is a growing body of literature describing the involvement of carbohydrate groups in various aspects of fungal disease. Carbohydrates comprising the cell wall or capsule, or as a component of glycoproteins, are the fungal cell surface entities most likely to be exposed to the surrounding environment. Thus, the fungus-host interaction is likely to involve carbohydrates before DNA, RNA, or even protein. The interaction between fungal and host cells is also complex, and early studies using whole cells or crude cell fractions often produced seemingly conflicting results. What was needed, and what has been developing, is the ability to identify specific glycan structures and determine how they interact with immune system components. Carbohydrate analysis is complicated by the complexity of glycan structures and by the challenges of separating and detecting carbohydrates experimentally. Advances in carbohydrate chemistry have enabled us to move from the foundation of composition analysis to more rapid characterization of specific structures. This, in turn, will lead to a greater understanding of how fungi coexist with their hosts as commensals or exist in conflict as pathogens.

Modulation of immune response through nutraceutical interventions: implications for canine and feline health

Mounting research demonstrates that certain nutraceutical compounds interact with the immune system. These interactions may be positive or negative depending on the compound or dose administered to the individual. Understanding the mechanisms by which these compounds work should provide opportunities to design nutritional interventions to bolster the health of dogs and cats.

Lung epithelial cells and extracellular matrix components induce expression of Pneumocystis carinii STE20, a gene complementing the mating and pseudohyphal growth defects of STE20 mutant yeast

Pneumocystis carinii causes severe pneumonia in immunocompromised hosts. The binding of P. carinii to alveolar epithelial cells and extracellular matrix constituents such as fibronectin and vitronectin is a central feature of infection, which initiates proliferation of the organism. Herein, we demonstrate that P. carinii binding to lung cells specifically alters the gene expression of the organism, regulating fungal growth. Subtractive hybridization was performed to isolate P. carinii genes expressed following binding to mammalian extracellular matrix constituents. P. carinii STE20 (PCSTE20), a gene participating in mating and pseudohyphal growth of other fungi, was identified following adherence to the extracellular matrix constituents fibronectin, vitronectin, collagen, and lung epithelial cells. The expression of PCSTE20 and a related P. carinii mitogen-activated protein kinase (MAPK) kinase gene, also implicated in signaling of mating, were both specifically upregulated by binding to matrix protein. The expression of general cyclin-dependent kinases and other MAPKs not involved in mating pathways were not altered by organism binding. PCSTE20 expression was also strongly enhanced following organism attachment to A549 lung epithelial cells. When expressed in a Saccharomyces cerevisiae ste20Delta mutant, PCSTE20 suppressed defects in both mating and pseudohyphal growth. These findings are consistent with the observed proliferation and filopodial extension of Pneumocystis organisms adherent to the epithelium in the lungs of immunocompromised hosts. PCSTE20 expression appears to represent a significant component in the regulation of the life cycle of this intractable opportunistic pathogen.

A mannose-receptor is possibly involved in the phagocytosis of Saccharomyces cerevisiae by seabream (Sparus aurata L.) leucocytes

In this paper the possible involvement of the mannose-receptor on the non-specific recognition and phagocytosis of heat killed yeast cells (Saccharomyces cerevisiae) by gilthead seabream (Sparus aurata L.) head-kidney leucocytes was established by studying the ability of different sugars to inhibit the uptake of the yeast cells by leucocytes. Leucocytes were preincubated for 30min with different concentrations of sugar (alpha-mannan, d-mannose, d-fucose, l-fucose, d-glucose, d-glucosamine and n-acetyl-glucosamine, all of them described as specific ligands of the vertebrate mannose-receptor) and afterwards incubated with FITC-labelled yeast cells for phagocytosis assays. The phagocytic ability (percentage of cells with one or more ingested yeast cells within the total cell population) and capacity (number of ingested yeast cells per cell) of leucocytes was analysed by flow cytometry. The results demonstrate the potential existence of a specific receptor-sugar or receptor-yeast cell binding process, which was saturable, specific and dose-dependent. More specifically, when leucocytes were preincubated with appropriate doses of d-mannose, d- or l-fucose, d-glucose or n-acetyl-glucosamine the phagocytosis of yeast cells by head-kidney leucocytes was partially blocked. Seabream leucocytes were also preincubated with chloroquine, a lysosomotropic drug which downregulates (in a nonspecific manner) the expression of mannose-receptors in mammals, before phagocytosis assays were performed. The results demonstrated that the phagocytosis of yeast was completely blocked by this substance. The overall results seem to corroborate the presence of the mannose-receptor in seabream phagocytes, which is involved in the non-specific binding and phagocytosis of yeast cells by head-kidney leucocytes.

Pneumocystis carinii cell wall beta-glucan induces release of macrophage inflammatory protein-2 from alveolar epithelial cells via a lactosylceramide-mediated mechanism

Infiltration of the lungs with neutrophils promotes respiratory failure during severe Pneumocystis carinii (PC) pneumonia. Recent studies have shown that alveolar epithelial cells (AECs), in addition to promoting PC attachment, also participate in lung inflammation by the release of cytokines and chemokines. Herein, we demonstrate that a PC beta-glucan rich cell wall isolate (PCBG) stimulates the release of macrophage inflammatory protein-2 (MIP-2) from isolated AECs through a lactosylceramide-dependent mechanism. The results demonstrate that MIP-2 mRNA and protein production is significantly increased at both early and late time points after PCBG challenge. Although CD11b/CD18 (Mac-1, CR3) is the most widely studied beta-glucan receptor, we demonstrate that CD11b/CD18 is not present on AECs. This study instead demonstrates that preincubation of AECs with an antibody directed against the membrane glycosphingolipid lactosylceramide (CDw17) results in a significant decrease in MIP-2 secretion. Preincubation of the anti-CDw17 antibody with solubilized lactosylceramide reverses this effect. Furthermore, incubation of AECs with inhibitors of glycosphingolipid biosynthesis, including N-butyldeoxyno jirimycin and d-threo-1-phenyl-2-decanoylamino-3-morpholino-1-propanol-HCl, also results in a significant decrease in AEC MIP-2 production following challenge with PCBG. These data demonstrate that PC beta-glucan induces significant production of MIP-2 from AECs and that CDw17 participates in the glucan-induced inflammatory signaling in lung epithelial cells during PC infection.

Functional convergence of invertebrate and vertebrate cytokine-like molecules based on a similar lectin-like activity

It is generally accepted that the action of cytokines results from their binding to specific receptors. However, many cytokines possess lectin-like activity that may be essential for the expression of their full biological activities. This review focuses on the physiological relevance of the lectin-like activity of cytokines during the innate immune response in mammals, using TNF as an illustrative example. Moreover, we will show that TNF displays functional analogies with a defense molecule from the earthworm Eisenia foetida termed CCF. These analogies are not reflected by primary sequence homology between CCF and TNF but are particularly based on a similar lectin-like activity/domain. Hence, from a phylogenetic point of view, the lectin-like activity/domain of CCF and TNF may represent an essential recognition mechanism that has been functionally conserved during the innate immune response of invertebrates and vertebrates as a result of convergent evolution.

Invasive pulmonary aspergillosis resulting in respiratory failure during neutrophil recovery from postchemotherapy neutropenia in three patients with acute leukaemia

Respiratory failure is a severe complication of invasive pulmonary aspergillosis (IPA). Its pathogenesis is not well understood. We herein describe three cases of subacute respiratory failure that occurred during the recovery phase of neutropenia following induction chemotherapy for acute leukaemia with IPA. In each case, severe neutropenia (19-85 days), high-grade fever, severe anaemia, the use of granulocyte-colony-stimulating factor and increasing infusion volume were noted. As the neutrophil count was recovering, the shadows on the chest X-ray expanded with progressing hypoxia. We should pay attention to the respiratory failure during the recovery phase of neutropenia in patients with IPA.

Trypanosoma cruzi is lysed by coelomic cytolytic factor-1, an invertebrate analogue of tumor necrosis factor, and induces phenoloxidase activity in the coelomic fluid of Eisenia foetida foetida

A cytolytic protein named Coelomic Cytolytic Factor-1 (CCF-1) was isolated from the coelomic fluid of the earthworm Eisenia foetida foetida. Despite the absence of any gene homology, CCF-1 showed functional analogy with the mammalian cytokine tumour necrosis factor (TNF), particularly based on similar lectin-like activity. Indeed, both CCF-1 and TNF recognise N,N'-diacetylchitobiose and exert lytic activity on African Trypanosoma brucei brucei. In this report, we show that South-American Trypanosoma cruzi trypomastigotes, but not epimastigotes, were lysed by earthworm coelomic fluid or purified CCF-1. However, T. cruzi was less susceptible to lysis than T. brucei brucei. This lytic effect of coelomic fluid and CCF-1 on T. cruzi trypomastigotes was partially inhibited in the presence of anti-CCF-1 monoclonal antibody, antibody neutralising the lectin-like activity of TNF or N,N'-diacetylchitobiose. In contrast, this lytic effect was completely inhibited when using T. b. brucei. In addition, T. cruzi components, upon recognition by CCF-1 in E. f. foetida coelomic fluid, triggered the prophenoloxidase cascade, an invertebrate defence mechanism. These results further extend the functional analogies of CCF-1 and TNF, suggesting that both molecules share a similar lectin-like activity that has been conserved as an innate recognition mechanism in invertebrates and vertebrates. They also establish a link between stercorarian (T. cruzi) and salivarian (T. brucei) trypanosomatids having divergent phylogenetic origins and patterns of evolution, but possessing closely related cell surface sugar moieties.

An invertebrate defense molecule activates membrane conductance in mammalian cells by means of its lectin-like domain

The invertebrate defense molecule Coelomic Cytolytic Factor-1 (CCF-1) and the mammalian cytokine Tumor Necrosis Factor (TNF) share a similar lectin-like domain that, upon interaction with specific sugars, causes lysis of African trypanosomes. In contrast to TNF, CCF-1 does not require an acidification of a lysosomal compartment for this activity. Moreover, we could demonstrate using the whole cell patch clamp technique that both TNF and CCF-1 activate amiloride-sensitive channels in mammalian cells, in a TNF receptor-independent way, but, unlike TNF, CCF-1 does not require acidic conditions for this activity. These data confirm the functional analogies of an invertebrate defense molecule and a mammalian cytokine, based on a similar lectin-like interaction.

Vibrational spectroscopic characterization of wild growing mushrooms and toadstools

Recently, there has been increase of general interest in fungi because of the possible medical applications of their polysaccharide constituents called glucans, some of which are reported to have immunomodulatory properties. Since an extraction method can change the chemical composition of a substance, especially a delicate one such as fungal thallus, it is necessary and useful to know more about the studied matter in advance in order to choose the chemical procedure properly. We demonstrated the usefulness of vibrational spectroscopy in identifying different glucan types in various parts of intact fruiting bodies of Asco- and Basidiomycetes. Fourier transform-infrared (FT-IR) spectroscopy was used for obtaining vibrational spectra of spores and fruiting bodies of more than 70 species belonging to 37 different genera of wild growing mushrooms. The list of the bands in 750-950 cm(-1) interval, assigned to alpha- and beta-glucans, is provided for all species studied. Vibrational spectra in the interval 1000-1200 cm(-1) could serve as an indicator of mushroom genus, although particular species cannot be identified spectroscopically. Great similarities in spectra of spores of the same genus, but different species, e.g. Tricholoma album and Trichloma sulphureum, were observed. On the other hand, spectra of cap, stalk and spores of the same mushroom show great differences, indicating variety in the chemical composition of different parts of the same fruiting body.

Early events in macrophage killing of Aspergillus fumigatus conidia: new flow cytometric viability assay

Detailed investigations of macrophage phagocytosis and killing of Aspergillus fumigatus conidia have been limited by technical difficulties in quantifying fungal uptake and viability. In order to study early events in cell pathogen ingestion and killing, we developed a new flow cytometry assay that utilizes the fungus-specific viability dye FUN-1. Metabolically active A. fumigatus conidia accumulate orange fluorescence in vacuoles, while dormant or dead conidia stain green. After incubation within THP-1 cells, recovered conidia are costained with propidium iodide (PI) to discriminate between dormant and dead cells. Flow cytometric measurements of FUN-1 metabolism and PI uptake provide indicators of conidial viability, dormancy, and death. Conidial phagocytosis and killing are also assessed by measurement of green and orange FUN-1 fluorescence within the THP-1 cell population. Compared to previously described methods, this assay has less error introduced by membrane permeability changes and serial dilution of filamentous fungal forms. Results suggest that the THP-1 cells kill conidia rapidly (within 6 h) after exposure. Conidia that are preexposed to human serum are ingested and killed more quickly than are nonopsonized conidia.

Vitronectin and fibronectin function as glucan binding proteins augmenting macrophage responses to Pneumocystis carinii

beta-glucans represent major structural components of fungal cell walls. We recently reported that Pneumocystis carinii beta-glucans stimulate alveolar macrophages to release proinflammatory cytokines. Macrophage activation by beta-glucan is augmented by serum, implying the presence of circulating factors that interact with beta-glucans and enhance their ability to stimulate macrophages. Using beta-glucan-enriched cell wall fractions from P. carinii and Saccharomyces cerevisiae, two prominent proteins were precipitated from serum and demonstrated to be vitronectin (VN) and fibronectin (FN) by immune analysis. Preincubation of beta-glucan with VN or FN enhanced macrophage activation in response to this cell wall component. Because VN and FN accumulate in the lungs during P. carinii pneumonia, we further investigated hepatic and pulmonary expression of VN and FN messenger RNA during infection. P. carinii pneumonia in rodents is associated with increased hepatic expression of VN and FN as well as increased local expression of FN in the lung. Because interleukin (IL)-6 represents the major regulator of VN and FN expression during inflammatory conditions, we measured macrophage IL-6 release in response to stimulation with P. carinii beta-glucan. Stimulation of macrophages with P. carinii beta-glucan induced significant release of IL-6. Elevated concentrations of IL-6 were noted in the blood of infected animals compared with uninfected control animals. These studies indicate that VN and FN bind to beta-glucan components of P. carinii and augment macrophage inflammatory responses. P. carinii cell wall beta-glucan stimulates secretion of IL-6 by macrophages, thereby enhancing hepatic synthesis of both VN and FN, and lung synthesis of FN during pneumonia.

Cell wall assembly by Pneumocystis carinii. Evidence for a unique gsc-1 subunit mediating beta -1,3-glucan deposition

Pneumocystis carinii remains a persistent cause of severe pneumonia in immune compromised patients. Recent studies indicate that P. carinii is a fungal species possessing a glucan-rich cyst wall. Pneumocandin antagonists of beta-1,3-glucan synthesis rapidly suppress infection in animal models of P. carinii pneumonia. We, therefore, sought to define the molecular mechanisms of beta-glucan cell wall assembly by P. carinii. Membrane extracts derived from freshly purified P. carinii incorporate uridine 5'-diphosphoglucose into insoluble carbohydrate, in a manner that was completely inhibited by the pneumocandin L733-560, an antagonist of Gsc-1-type beta-glucan synthetases. Using degenerative polymerase chain reaction and library screening, the P. carinii Gsc-1 catalytic subunit of beta-1,3-glucan synthetase was cloned and characterized. P. carinii gsc1 exhibited homology to phylogenetically related fungal beta-1,3-glucan synthetases, encoding a predicted 214-kDa integral membrane protein with 12 transmembrane domain structure. Immunoprecipitation of P. carinii extracts, with a synthetic peptide anti-Gsc-1 antibody, specifically yielded a protein of 219.4 kDa, which was also capable of incorporating 5'-diphosphoglucose into insoluble glucan carbohydrate. As opposed to other fungi, the expression of gsc-1 mRNA is uniquely regulated over P. carinii's life cycle, having minimal expression in trophic forms, but substantial expression in the thick-walled cystic form of the organism. These results indicate that P. carinii contains a unique catalytic subunit of beta-1,3-glucan synthetase utilized in cyst wall formation. Because synthesis of beta-1,3-glucan is absent in mammalian cells, inhibition of the P. carinii Gsc-1 represents an attractive molecular target for therapeutic exploitation.

Oral colonization by Candida albicans

Candida albicans is a commensal yeast normally present in small numbers in the oral flora of a large proportion of humans. Colonization of the oral cavity by C. albicans involves the acquisition and maintenance of a stable yeast population. Micro-organisms are continually being removed from the oral cavity by host clearance mechanisms, and so, in order to survive and inhabit this eco-system, C. albicans cells have to adhere and replicate. The oral cavity presents many niches for C. albicans colonization, and the yeast is able to adhere to a plethora of ligands. These include epithelial and bacterial cell-surface molecules, extracellular matrix proteins, and dental acrylic. In addition, saliva molecules, including basic proline-rich proteins, adsorbed to many oral surfaces promote C. albicans adherence. Several adhesins present in the C. albicans cell wall have now been partially characterized. Adherence involves lectin, protein-protein, and hydrophobic interactions. As C. albicans cells evade host defenses and colonize new environments by penetrating tissues, they are exposed to new adherence receptors and respond by expressing alternative adhesins. The relatively small number of commensal Candida cells in the oral flora raises the possibility that strategies can be devised to prevent oral colonization and infection. However, the variety of oral niches and the complex adherence mechanisms of the yeast mean that such a goal will remain elusive until more is known about the contribution of each mechanism to colonization.

Isolated Pneumocystis carinii cell wall glucan provokes lower respiratory tract inflammatory responses

Macrophage-induced lung inflammation contributes substantially to respiratory failure during Pneumocystis carinii pneumonia. We isolated a P. carinii cell wall fraction rich in glucan carbohydrate, which potently induces TNF-alpha and macrophage-inflammatory protein-2 generation from alveolar macrophages. Instillation of this purified P. carinii carbohydrate cell wall fraction into healthy rodents is accompanied by substantial increases in whole lung TNF-alpha generation and is associated with neutrophilic infiltration of the lungs. Digestion of the P. carinii cell wall isolate with zymolyase, a preparation containing predominantly beta-1,3 glucanase, substantially reduces the ability of this P. carinii cell wall fraction to activate alveolar macrophages, thus suggesting that beta-glucan components of the P. carinii cell wall largely mediate TNF-alpha release. Furthermore, the soluble carbohydrate beta-glucan receptor antagonists laminariheptaose and laminarin also substantially reduce the ability of the P. carinii cell wall isolate to stimulate macrophage-inflammatory activation. In contrast, soluble alpha-mannan, a preparation that antagonizes macrophage mannose receptors, had minimal effect on TNF-alpha release induced by the P. carinii cell wall fraction. P. carinii beta-glucan-induced TNF-alpha release from alveolar macrophages was also inhibited by both dexamethasone and pentoxifylline, two pharmacological agents with potential activity in controlling P. carinii-induced lung inflammation. These data demonstrate that P. carinii beta-glucan cell wall components can directly stimulate alveolar macrophages to release proinflammatory cytokines mainly through interaction with cognate beta-glucan receptors on the phagocyte.

Antimicrobial defense of the earthworm

Discrimination of self and nonself is one of the features of all animal species but the ways of elimination of nonself are different. Defense strategies of invertebrates, which lack antibodies and lymphocytes, are based on innate defense mechanisms. The study of such, undoubtedly less complex, defense mechanisms in invertebrates may shed a new light on the more sophisticated immunity of vertebrates. The main aim of this review is to show on one experimental model--an oligochaete annelid--cellular and humoral defense pathways protecting against microbial infection.