[Effect of oral administration of ß-D-glucan from Aureobasidium pullulans ADK-34 on Candida and MRSA infections in immunosuppressed mice].

UNLABELLED: We examined the effect of the oral administration of ß-D-glucan derived from Aureobasidium pullulans ADK-34 (AP-FBG) on Candida albicans or methicillin-resistant Staphylococcus aureus (MRSA) infection in immunosuppressed mice. Mice pretreated with cyclophosphamide (CY) were intraperitoneally administered AP-FBG for 4 days and then infected with 6×10(4) C. albicans cells. In a preliminary experiment, the survival time of the Candida-infected mice treated with AP-FBG was clearly prolonged. Similarly, the effect of the oral administration of AP-FBG was examined. Mice were orally given 2.5% AP-FBG in feed for 42 days from 14 days prior to 2×10(4) C. albicans cells infection. The survival time of mice treated with AP-FBG was significantly prolonged and the viable cell count in the kidneys of the survivors was significantly decreased at 30 days after infection. The effects of the oral administration of AP-FBG on intestinal MRSA infection were also examined. Mice were given 2.5% AP-FBG orally in feed for 30 days before and after oral MRSA infection and treated with CY 12 days after the infection. The number of viable MRSA cells or the IgA production in feces did not significantly change, while AP-FBG administration seemed to relieve temporally the loss of body weight of mice. CONCLUSIONS: These results suggest that oral pre-administration of AP-FBG promoted resistance of CY-treated mice to C. albicans and lessened the weight reduction of CY-mice infected by MRSA.

Barley low molecular weight ß-glucan potently induces maturation of mouse dendritic cells.

BACKGROUND: Accumulating evidence indicates that non-toxic immunostimulants with strong differentiation/maturation-inducing activity for dendritic cells (DCs) might be useful for preventing or even curing cancer. MATERIALS AND METHODS: Mouse bone marrow (BM) cells were cultured in the presence of various glucans and their differentiation/maturation-inducing activities were compared by measuring cytokines secreted in the culture medium. RESULTS: Barley-derived ß-glucan with an average molecular weight of 2 kDa (BBG-Low) remarkably stimulated the formation of mature DCs from immature mouse DCs. The amount of interleukin-6 produced by sequential treatment of BM cells with granulocyte-macrophage colony-stimulating factor and 10 µg/mL of BBG-Low was approximately 30 times higher than that obtained by a similar sequential treatment using barley ß-glucan of 40-70 kDa instead of BBG-Low. CONCLUSION: BBG-Low induces the formation of mature DCs from immature DCs and suggests that BBG-Low will be useful as a potent nontoxic immunostimulator.

Induction of IFN-γ by a highly branched 1,3-ß-d-glucan from Aureobasidium pullulans in mouse-derived splenocytes via dectin-1-independent pathways.

We have previously elucidated the precise structure of a unique type of 1,3-ß-D-glucan, AP-FBG (Aureobasidium pullulans-fermented ß-D-glucan), from the fungus A. pullulans and found that AP-FBG strongly induced the production of various cytokines in DBA/2 mouse-derived splenocytes in vitro. However, the mechanism(s) of action of AP-FBG on in vitro mouse primary cells have not been characterized in detail. Herein, we report that the production of IFN-γ in DBA/2 mouse-derived splenocytes by AP-FBG was not inhibited following treatment with an anti-dectin-1 neutralizing antibody. In addition, AP-FBG not only failed to activate dectin-1-mediated signaling pathways, examined by a reporter gene assay but also failed to bind to dectin-1, a pivotal receptor for 1,3-ß-D-glucan. Taken together, AP-FBG induced cell activation via dectin-1-independent pathways.

Granulocyte macrophage colony-stimulating factor is required for cytokine induction by a highly 6-branched 1,3-ß-D-glucan from Aureobasidium pullulans in mouse-derived splenocytes.

We have previously obtained and elucidated the precise structure of a highly branched 1,3-ß-D-glucan (with 6-monoglucopyranosyl side chains), Aureobasidium pullulans-fermented ß-D-glucan (AP-FBG), from the fungus A. pullulans. However, the mechanism(s) of the effects of AP-FBG on in vitro mouse primary cells have not been analyzed in detail. Herein, we report that the induction of cytokines by AP-FBG was dependent on the existence of a granulocyte macrophage colony-stimulating factor (GM-CSF); this is similar way to be a typical 1,3-ß-D-glucan from Sparassis crispa (SCG), which is a 1,3-ß-D-glucopyranosyl backbone with single 1,6-ß-D-glucopyranosyl side branching units every three residues. In other words, the production of cytokines in DBA/2-mouse-derived splenocytes by AP-FBG was completely hampered by an anti-GM-CSF neutralizing monoclonal antibody. Furthermore, the addition of exogenous GM-CSF to C57BL/6-derived splenocytes, which are less sensitive to AP-FBG, induced the production of cytokines by AP-FBG. Therefore, GM-CSF is indispensable for the induction of cytokines by AP-FBG in mouse-derived splenocytes. This finding has provided a new insight into our understanding of the actions of ß-D-glucan but will also aid in the design and development of more effective ß-D-glucan agents.

A highly branched 1,3-beta-D-glucan extracted from Aureobasidium pullulans induces cytokine production in DBA/2 mouse-derived splenocytes.

We recently elucidated the structure of a highly branched 1,3-beta-D-glucan with 6-monoglucopyranosyl side chains, extracted from Aureobasidium pullulans (AP-FBG). Although the biological effects of beta-D-glucans are known to depend on their structures, the effects of a highly branched 1,3-beta-D-glucan on the production of cytokines by leukocytes in mice have not yet been elucidated. In this study, we found that AP-FBG strongly induced the production of various cytokines, especially Th1 cytokines (e.g., IFN-gamma and IL-12p70) and Th17 cytokines (e.g., IL-17A), but did not induce the production of IL-4, IL-10, and TNF-alpha in DBA/2 mouse-derived splenocytes in vitro.

Barley-derived beta-D-glucan induces immunostimulation via a dectin-1-mediated pathway.

Barley-derived beta-glucan, a linear mixed-linkage beta-glucan composed of 1,3- and 1,4-beta-D-glucopyranose polymers, binds to dectin-1. However, whether it can trigger signal transduction via dectin-1 remains unclear. In this study, we used a reporter gene assay to determine whether barley-derived beta-d-glucan can activate NF-kappaB via dectin-1-mediated signaling when dectin-1 is cotransfected with Syk, CARD9, and Bcl10 in 293T cells. We found that barley-derived beta-D-glucan can activate NF-kappaB leading to cytokine production when dectin-1, Syk, CARD9, and Bcl10 are coexpressed in the cells. We also found that barley-derived beta-D-glucan can induce the phosphorylation of Syk and production of IL-6 in thioglycolate-elicited peritoneal macrophages. These results indicated that the immunostimulatory effects of barley-derived beta-d-glucan might be exerted, at least in part, via dectin-1.

Involvement of branched units at position 6 in the reactivity of a unique variety of beta-D-glucan from Aureobasidium pullulans to antibodies in human sera.

We recently determined the structure of a unique type of 1,3-beta-D-glucan obtained from Aureobasidium pullulans (AP-FBG) and found that it reacted with the antibodies in human sera. The reactivity of AP-FBG to the antibodies was stronger than that of 1,3-beta-D-glucan obtained Grifola frondosa (GRN) but weaker than that of 1,3-beta-D-glucan from Candida albicans (CSBG). Here, we demonstrated that AP-FBG reacted to IgG antibodies, especially those of the subclasses IgG2, IgG1, and IgG3, in human sera. Moreover, the results of competitive enzyme-linked immunosorbent assays (ELISAs) using various glucan competitors showed that these IgGs recognized branched chains at position 6. This is the first study to report that the branched chains at position 6 of beta-D-glucan strongly contribute to its recognition by antibodies in human sera. This high reactivity of AP-FBG to human IgG could be advantageous for the use of this glucan in medicine, e.g., as an immunostimulatory agent.

Structural characterisation and biological activities of a unique type beta-D-glucan obtained from Aureobasidium pullulans.

A beta-D-glucan obtained from Aureobasidium pullulans (AP-FBG) exhibits various biological activities: it exhibits antitumour and antiosteoporotic effects and prevents food allergies. An unambiguous structural characterisation of AP-FBG is still awaited. The biological effects of beta-D-glucan are known to depend on its primary structures, conformation, and molecular weight. Here, we elucidate the primary structure of AP-FBG by NMR spectroscopy, and evaluate its biological activities. Its structure was shown to comprise a mixture of a 1-3-beta-D-glucan backbone with single 1-6-beta-D-glucopyranosyl side-branching units every two residues (major structure) and a 1-3-beta-D-glucan backbone with single 1-6-beta-D-glucopyranosyl side-branching units every three residues (minor structure). Furthermore, this beta-D-glucan exhibited immunostimulatory effects such as the accumulation of immune cells and priming effects against enterobacterium. To our knowledge, 1-3-beta-glucans like AP-FBG with such a high number of 1-6-beta-glucopyranosyl side branching have a unique structure; nevertheless, many 1-3-beta-glucans were isolated from various sources, e.g. fungi, bacteria, and plants.