Measurement of blood clearance time by Limulus G test of Candida-water soluble polysaccharide fraction, CAWS, in mice

[Fungal Beta-glucans: Structure and Effect on Host Immune Responses]

Fungi are eukaryotic microorganisms that show complex life cycles, including both anamorph and teleomorph stages. Beta-1,3-1,6-glucans (BGs) are major cell wall components in fungi. BGs are also found in a soluble form and are secreted by fungal cells. Studies of fungal BGs extensively expanded from 1960 to 1990 due to their applications in cancer immunotherapy. However, progress in this field slowed down due to the low efficacy of such therapies. In the early 21st century, the discovery of C-type lectin receptors significantly enhanced the molecular understanding of innate immunity. Moreover, pathogen-associated molecular patterns (PAMPs) and pattern recognition receptors (PRRs) were also discovered. Soon, dectin-1 was identified as the PRR of BGs, whereas BGs were established as PAMPs. Then, studies on fungal BGs focused on their participation in the development of deep-seated mycoses and on their role as a source of functional foods. Fungal BGs may have numerous and complex linkages, making it difficult to systematize them even at the primary structure level. Moreover, elucidating the structure of BGs is largely hindered by the multiplicity of genes involved in cell wall biosynthesis, including those for BGs, and by fungal diversity. The present review mainly focused on the characteristics of fungal BGs from the viewpoint of structure and immunological activities.

Coronary Vasculitis Induced in Mice by Cell Wall Mannoprotein Fractions of Clinically Isolated Candida Species

Kawasaki disease (KD) is an inflammatory disease that was identified by Professor Tomisaku Kawasaki in 1961. Candida albicans-derived substances (CADS) such as the hot water extract of C. albicans and Candida water-soluble fractions (CAWS) induce coronary vasculitis similar to KD in mice. An increasing proportion of deep-seated candidiasis cases are caused by non-albicans Candida and are often resistant to antifungal drugs. We herein investigated whether the mannoprotein fractions (MN fractions) of clinically isolated Candida species induce vasculitis in mice. We prepared MN fractions from 26 strains of Candida species by conventional hot water extraction and compared vasculitis in DBA/2 mice. The results obtained revealed that the induction of vasculitis and resulting heart failure were significantly dependent on the species; namely, death rates on day 200 were as follows: Candida krusei (100%), Candida albicans (84%), Candida dubliniensis (47%), Candida parapsilosis (44%), Candida glabrata (32%), Candida guilliermondii (20%), and Candida tropicalis (20%). Even for C. albicans, some strains did not induce vasculitis. The present results suggest that MN-induced vasculitis is strongly dependent on the species and strains of Candida, and also that the MN fractions of some non-albicans Candida induce similar toxicity to those of C. albicans.

Development of a novel β-1,6-glucan-specific detection system using functionally-modified recombinant endo-β-1,6-glucanase

β-1,3-d-Glucan is a ubiquitous glucose polymer produced by plants, bacteria, and most fungi. It has been used as a diagnostic tool in patients with invasive mycoses via a highly-sensitive reagent consisting of the blood coagulation system of horseshoe crab. However, no method is currently available for measuring β-1,6-glucan, another primary β-glucan structure of fungal polysaccharides. Herein, we describe the development of an economical and highly-sensitive and specific assay for β-1,6-glucan using a modified recombinant endo-β-1,6-glucanase having diminished glucan hydrolase activity. The purified β-1,6-glucanase derivative bound to the β-1,6-glucan pustulan with a KD of 16.4 nm We validated the specificity of this β-1,6-glucan probe by demonstrating its ability to detect cell wall β-1,6-glucan from both yeast and hyphal forms of the opportunistic fungal pathogen Candida albicans, without any detectable binding to glucan lacking the long β-1,6-glucan branch. We developed a sandwich ELISA-like assay with a low limit of quantification for pustulan (1.5 pg/ml), and we successfully employed this assay in the quantification of extracellular β-1,6-glucan released by >250 patient-derived strains of different Candida species (including Candida auris) in culture supernatant in vitro We also used this assay to measure β-1,6-glucan in vivo in the serum and in several organs in a mouse model of systemic candidiasis. Our work describes a reliable method for β-1,6-glucan detection, which may prove useful for the diagnosis of invasive fungal infections.

The involvement of the vasa vasorum in the development of vasculitis in animal model of Kawasaki disease

BACKGROUND

Kawasaki Disease (KD) involves a diffuse and systemic vasculitis of unknown etiology that mainly affects infants and children. Although a considerable number of analyses of the clinical, histopathological and molecular biological details underlying the mechanism responsible for the development of coronary arterial lesions, it is still poorly understood.The purpose of this study was to analyze the state of angiogenesis, vasculogenesis and the distribution of blood vessels using an animal model of KD like vasculitis. We investigated the involvement of the vasa vasorum from the adventitia in the vascular involvement and the development of the disease state by performing sequential histopathology, scanning electron microscopy (SEM) and micro computed tomography (CT) studies using a murine model of vasculitis induced by the Candida albicans water-soluble fraction (CAWS).

METHODS

To prepare the animal model of KD like vasculitis, CAWS was intraperitoneally injected into C57BL/6N mice for five consecutive days as reported by Ohno et al. We observed the changes of the vasa vasorum at the aorta and the orifices of the coronary arteries by SEM and micro CT, and also compared the neovascularization at the media and adventitia of the aorta by an immunohistochemical analysis.

RESULTS

As previously reported, obvious inflammation was detected two weeks after the injection of CAWS, and also intimal thickening was observed three weeks after the injection. We found that the vasa vasorum in the adventitia of the aorta was increased in the model mice. The vasa vasorum started increasing one week after the injection of CAWS, before any obvious vasculitis was microscopically detected.

CONCLUSION

The present results indicate that the vasculitis in Kawasaki disease starts as a disorder of the vasa vasorum.

Increased Inhibitory Capacity of an Anti-C5a Complementary Peptide Following Acetylation of N-terminal Alanine

Amino acids 37 to 53 (RAARISLGPRCIKAFTE) of C5a anaphylatoxin form an essential region for C5a function. To target this sequence, we generated a complementary peptide (ASGAPAPGPAGPLRPMF) designated PepA which has a potent inhibitory effect on C5a activity. By introducing an acetyl group at the N-terminal alanine of PepA, an acetylated form was generated which was designated AcPepA. The acetylation resulted in increased inhibition of C5a stimulation of neutrophils as determined by Ca influx. Furthermore, AcPepA partially inhibited the lethal shock induced in mice by intravenous administration of Candida albicans water-soluble mannoprotein-beta-glucan complex. In addition, local skin inflammation in rats caused by an anti-Crry monoclonal antibody was suppressed when AcPepA and the antibody were injected together, while PepA had little inhibitory capacity. The potent inhibitory capacity of AcPepA was also confirmed by a skin reaction of guinea pigs inoculated with recombinant human C5a together with AcPepA.

Trafficking of QD-Conjugated MPO-ANCA in Murine Systemic Vasculitis and Glomerulonephritis Model Mice

In systemic vasculitis, the serum level of myeloperoxidase (MPO)-specific anti-neutrophil cytoplasmic autoantibodies (MPO-ANCA) is significantly elevated with the progression of disease. We have established a model of murine systemic vasculitis by administration of MPO-ANCA and fungal mannoprotein to C57BL/6 mice. We examined the role of MPO and MPO-ANCA in the pathogenesis of glomerulonephritis and systemic vasculitis in this model using quantum dots (QDs). We demonstrated that QD-conjugated MPO-ANCA (ANCA-QD) visualized the translocation of MPO on the neutrophil membrane surface after stimulation with proinflammatory cytokines. We also observed that MPO translocation on neutrophils in both patients with rapid progressive glomerulonephritis and these model mice without any stimulation, suggesting that MPO translocation is certain to contribute to the development of glomerular lesion. In addition, blood flow on the kidney surface vessel was significantly decelerated in both SCG/Kj mice and this model, suggesting that ANCA induces the damage of blood vessel. These results indicate that MPO-ANCA and surface-translocated MPO on the activated neutrophils coordinately plays essential roles in the initial steps of the glomerulonephritis.

[Negative regulatory factor of CAWS (Candida albicans water-soluble fraction) -vasculitis in CBA/J mice as assessed by comparison with Bruton's tyrosine kinase-deficient CBA/N mice]

Candida albicans water-soluble fraction (CAWS) has microbial pathogen-associated molecular patterns (PAMPs). It is a mannoprotein-β glucan complex obtained from the culture supernatant of Candida albicans NBRC1385 and exhibits vasculitis-inducing activity (CAWS vasculitis) in mice. The sensitivity to CAWS vasculitis varies greatly among mouse strains. This study examined the factors contributing to or inhibiting CAWS vasculitis using CAWS-vasculitis-resistant CBA/J mice and Bruton's tyrosine kinase (Btk)-deficient CBA/N mice, which is a CAWS-vasculitis-sensitive strain having the same origin as CBA/J mice. After stimulation with various kinds of pathogen-associated molecular patterns (PAMPs), the production of inflammatory cytokines IL-6 and IFN-γwas induced in CBA/N mice, whereas that of immunosuppressive IL-10 was induced in CAWS-vasculitis-resistant CBA/J mice. The production of TIMP1, an endogenous matrix metalloproteinase (MMP) inhibitor, was observed in CBA/J mice. Furthermore, the induction of CAWS-vasculitis was inhibited by gene therapy using plasmid (pCAGGS-mIL-10). The results strongly suggest that the difference in the production of these cytokines is closely linked to the development of CAWS vasculitis.

Administration of human immunoglobulin suppresses development of murine systemic vasculitis induced with Candida albicans water-soluble fraction: an animal model of Kawasaki disease

We investigated the inhibitory effect of human immunoglobulin (h-Ig) on the development of coronary arteritis in a murine model of vasculitis induced with a Candida albicans water-soluble fraction (CAWS). CAWS was intraperitoneally injected to C57BL/6 mice for 5 days. Then h-Ig was administered according to various schedules. The animals were sacrificed in week 5, and the status of vasculitis in the coronary arteries and the aortic root was investigated histologically. The groups in which h-Ig was administered for 5 days from day 3 and from day 5 of the experiment showed a significant reduction in the incidence of panvasculitis. In addition, the scope and severity of the inflammation of the aortic root and the coronary arteries were reduced in both groups. In the group administered h-Ig for 5 days from day 1 and the group administered a high dose of h-Ig once on day 1 or day 3, no suppression of development of vasculitis was observed. The h-Ig acted by suppressing the generation and progression of vasculitis in this CAWS-induced murine vasculitis model.

Involvement of Platelet Activating Factor, Histamine and Serotonin in Acute Lethal Shock Induced by Candida albicans Water-Soluble Extracellular Polysaccharide Fraction (CAWS) in Mice

CAWS (Candida albicans water-soluble extracellular polysaccharide fraction) is a water-soluble extracellular mannoprotein-beta-glucan complex obtained from the culture supernatant following the culture of pathogenic Candida albicans in a completely synthetic medium. CAWS administered intraperitoneally induces vasculitis in mice, however, administered intravenously, it causes lethal shock. The acute lethal reaction to CAWS occurs within 1 h of intravenous administration, with the mice demonstrating anaphylactic shock-like symptoms including convulsion, diarrhea, and collapse. In this study, we analyzed the factors involved in this lethal effect. We examined physiologically active substances believed to be involved in anaphylactic shock, and found that the lethal effect of CAWS could be inhibited by blocking histamine, serotonin, and platelet activating factor (PAF) simultaneously, but by blocking only one. This finding strongly suggests that the acute lethal reaction to CAWS is a result of the simultaneous production of several physiologically active substances.

Lethal and severe coronary arteritis in DBA/2 mice induced by fungal pathogen, CAWS, Candida albicans water-soluble fraction

CAWS is a microbial pathogen-associated molecular patterns (PAMPs) produced by Candida albicans. CAWS is a mannoprotein-beta-glucan complex and secreted into the culture supernatant. CAWS has various biological effects, causing acute shock and disrupting vascular permeability. Intraperitoneal administration of CAWS induces coronary arteritis in various strains of inbred mice. The CAWS-induced coronary arteritis is strain-dependent and most severe in DBA/2 mice with a significant number of these animals expiring with cardiomegaly during the observation period. In vivo and in vitro, splenocytes of DBA/2 mice produced various cytokines, such as IL-6, TNF-alpha, and IFN-gamma in response to CAWS. GM-CSF was also produced in response to CAWS. The production of cytokines was significantly enhanced in the presence of recombinant GM-CSF. In contrast, anti-GM-CSF significantly reduced the production of TNF-alpha and IFN-gamma. Augmented production of cytokines in response to CAWS would be a key to the severity of coronary arteritis.

Candida albicans derived fungal PAMPS, CAWS, water soluble mannoprotein-beta-glucan complex shows similar immunotoxicological activity with bacterial endotoxin from Escherichia coli O9

Candida albicans water soluble fraction (CAWS), water soluble fraction of Candida albicans mainly composed of mannoprotein-beta-glucan complex, has various biological effects, such as anaphylactoid shock and coronary arteritis. These toxicological effects fit CAWS as one of PAMPs, pathogen-associated molecular patterns. Acute anaphylactoid reaction is known to be induced by lipopolysaccharide from Escherichia coli O9 (O9 LPS), which possesses the mannose homopolysaccharide as the O-antigen region. In the present study, we compared immunotoxicological and immunochemical similarity between CAWS and O9 LPS. CAWS strongly reacted with Candida serum factors, and the reactivity was found to be partially competed with O9 LPS. CAWS induced lethal toxicity was inhibited by pretreatment of mice with i.v. injection of CAWS. The lethality was found to be inhibited by i.v. injection of O9 LPS. Vice versa, O9 LPS induced acute lethal toxicity was also inhibited by pretreatment of mice with CAWS. These results suggested that CAWS, fungal PAMPs, and O9 LPS from Gram-negative bacteria share, at least in part, immunochemical and immunotoxicological activities.

Effect of Candida albicans cell wall glucan as adjuvant for induction of autoimmune arthritis in mice

Collagen-induced arthritis (CIA) is an experimental model of rheumatoid arthritis (RA) and has aided research into the pathogenesis of inflammatory joint disease. Typically, Type II collagen (CII) emulsified with Freund's complete adjuvant (FCA) is injected into DBA/1 mice. After a booster injection, the mice develop inflammation of the paws. But the fact that the immunization of CII alone does not induce arthritis suggests that activation of the immune system by an adjuvant is necessary for induction of the arthritis. In the present study, we investigated the ability of beta-glucans derived from Candida albicans to act as an adjuvant to induce autoimmune arthritis. DBA/1 mice were injected with CII emulsified with FCA or particulate beta-glucan, OX-CA, on day 0 and given a booster at day 21. Mice immunized with CII plus OX-CA developed arthritis at around 7-10 days after the booster injection. Similarly, mice administered CII emulsified with FCA developed arthritis with the same time course. The mice immunized with CII and OX-CA had a more severe arthritis than those immunized with CII and FCA. Histological changes and production of anti-CII antibody were observed regardless of the type of injection. In addition, components of C. albicans were also tested for their ability to induce arthritis as an adjuvant. The results showed that CSBG, which is a soluble beta-glucan, acted as an adjuvant for CIA but CAWS, which is a mannoprotein-beta-glucan complex, did not. In conclusion, beta-glucan derived from C. albicans acted as an adjuvant and the injection with CII resulted in arthritis with the production of anti-CII autoantibody. The results strongly suggested that fungal metabolites such as beta-glucans have the capacity to induce and exacerbate autoimmune diseases such as RA.

Chemistry and biology of angiitis inducer, Candida albicans water-soluble mannoprotein-beta-glucan complex (CAWS)

Deep mycoses have been clearly demonstrated to release beta-glucans into the blood. Structure of the beta-glucan was, at least in part, suggested to be a mannoprotein beta-glucan complex (CAWS) as assessed by biochemical and immunochemical analyses of the extracellular macromolecular fraction of Candida albicans. Half clearance time of i.v. administered CAWS was about 30 min in mice. In addition to the reactivity with limulus G-test, CAWS was found to exhibit various biological activities, such as cytokine synthesis by leukocyte, platelet aggregation, lethal toxicity, enhancement of side effect of indomethacin, induction of coronary arteritis in mice, and so on. In this review, the chemical properties and biological activities of CAWS are discussed.

Comparison of glucan detection and galactomannan enzyme immunoassay in gastrointestinal and systemic murine candidiasis

Mouse models of systemic and gastrointestinal infection with the yeast Candida albicans were used to investigate the ability of a commercial mannan antigen enzyme immunoassay and a commercial (1-->3) beta-D-glucan limulus assay to detect systemic infection and to differentiate between colonization and infection. Both assays were positive in all i.v. infected mice and negative in all uninfected control mice. In gastrointestinal infection both tests were positive whenever organ cultures were positive. In colonized mice with no detectable dissemination, there were mostly negative results with the glucan assay whereas the mannan assay was positive or intermediate in all colonized mice. Therefore, in the mouse model used, glucan detection appeared to be superior for differentiation between colonization and dissemination.

Saccharomyces cerevisiae- and Candida albicans-derived mannan induced production of tumor necrosis factor alpha by human monocytes in a CD14- and Toll-like receptor 4-dependent manner

The cytokine-inducing activities of fungal polysaccharides were examined in human monocytes in culture, with special reference to CD14 and Toll-like receptors (TLRs). Tumor necrosis factor alpha (TNF-alpha) production by monocytes was markedly induced in a dose-dependent manner upon stimulation with cell walls from Candida albicans and mannan from Saccharomyces cerevisiae and C. albicans, although relatively high concentrations (10 to 100 microg/ml) of stimulants were required for activation as compared with the reference lipopolysaccharide (LPS) (1 to 10 ng/ml). The yeast form C. albicans and its mannan and cell wall fractions exhibited higher TNF-alpha production than respective preparations from the hyphal form. Only slight TNF-alpha production was induced by the S. cerevisiae glucan. The TNF-alpha production triggered by reference LPS and purified fungal mannans required the presence of LPS-binding protein (LBP), and these responses were inhibited by anti-CD14 and anti-TLR4 antibodies, but not by anti-TLR2 antibody. In contrast to the activity of LPS, the activity of purified S. cerevisiae mannan was not inhibited by polymyxin B. These findings suggested that the mannan-LBP complex is recognized by CD14 on monocytes and that signaling through TLR4 leads to the production of proinflammatory cytokines in a manner similar to that induced by LPS.

Effect of CAWS, a mannoprotein-beta-glucan complex of Candida albicans, on leukocyte, endothelial cell, and platelet functions in vitro

Candida albicans is a medically important fungus which induces a disseminated candidasis and candidemia in immunocompromised hosts, and releases a polysaccharide fraction into the blood. We recently found that C. albicans released a water-soluble polysaccharide fraction (CAWS) into synthetic medium and demonstrated that CAWS was mainly composed of a complex of mannan and beta-glucan. In the murine system, CAWS showed a lethality resembling anaphylactic shock when administered i.v., and induced coronary arteritis similar to Kawasaki Disease (KD) when given i.p. In the present study, we examined the biological activity of CAWS in the cell culture and found the following: i) CAWS slightly induced production of IFN-gamma and IL-6 by splenocytes at lower dose (ca. 10 micro g/ml), but at a higher dose strongly inhibited the proliferation of splenocytes induced by a B cell mitogen, lipopolysaccharide (LPS) and a T cell mitogen, concanavalin A. ii) The viability of these splenocytes monitored by propidium iodide staining was significantly reduced. iii) The addition of CAWS to a culture of monophage RAW264.7 cells significantly reduced cellular growth rate dose dependently. iv) The LPS-mediated synthesis of cytokines by RAW264.7 cells was significantly inhibited by CAWS. v) CAWS induced an aggregation of platelets in human platelet-rich plasma, and vi) CAWS inhibited the production of thrombomodulin by human umbilical endothelial cells and acted synergistically with TNF-alpha. Thus, CAWS strongly inhibited the cellular functions of leukocytes in vitro, partly through direct cytotoxicity. The enhanced production in injured cells of the vascular endothelium would be related to the local inflammatory response in the coronary artery.