Antiherpetic mechanism of a sulfated derivative of Agaricus brasiliensis fruiting bodies polysaccharide.

OBJECTIVE: To study the anti-herpes simplex virus (HSV) activity of a (1→6)-(1→3)-ß-D-glucan isolated from Agaricus brasiliensis fruiting bodies (FR) as well as its chemically sulfated derivative (FR-S). METHODS: The antiherpetic activity and mechanism of action was studied by viral plaque assay applying different methodological strategies. RESULTS: Although FR presented no in vitro antiherpetic action at 1 mg/ml, FR-S displayed promising anti-HSV-1 and anti-HSV-2 activities in both simultaneous and postinfection treatments, resulting in selectivity indices (CC50/EC50) higher than 393. FR-S had no virucidal effect, but significantly suppressed HSV-1 (EC50 = 0.32 µg/ml) and HSV-2 (EC50 = 0.10 µg/ml) adsorption. FR-S was less effective on adsorption inhibition of mutant virus strains devoid of gC (HSV-1 gC⁻39 and HSV-2 gCneg1), indicating a possible interaction with this glycoprotein. The reduction of viral adsorption upon cell pretreatment with FR-S also suggests its interaction with cellular components. FR-S inhibited HSV-1 (EC50 = 8.39 µg/ml) and HSV-2 (EC50 = 2.86 µg/ml) penetration more efficiently than heparin. FR-S reduced HSV-1 and HSV-2 cell-to-cell spread. A synergic effect between FR-S and acyclovir was also detected. CONCLUSIONS: FR-S displays an interesting mechanism of antiviral action and represents a promising candidate for the treatment and/or prevention of herpetic infections, to be used as a single therapeutic agent or in combination with acyclovir.

Antiherpetic activity of a sulfated polysaccharide from Agaricus brasiliensis mycelia.

Sulfated polysaccharides are good candidates for drug discovery in the treatment of herpetic infections. Agaricus brasiliensis (syn A. subrufescens, A. blazei) is a Basidiomycete fungus native to the Atlantic forest region of Southeastern Brazil. Herein we report the chemical modification of a polysaccharide extracted from A. brasiliensis mycelia to obtain its sulfated derivative (MI-S), which presented a promising inhibitory activity against HSV-1 [KOS and 29R (acyclovir-resistant) strains] and HSV-2 strain 333, with selectivity indices (SI = CC50/IC50) higher than 439, 208, and 562, respectively. The mechanisms underlying this inhibitory activity were scrutinized by plaque assay with different methodological strategies. MI-S had no virucidal effects, but inhibited HSV-1 and HSV-2 attachment, penetration, and cell-to-cell spread, as well as reducing the expression of HSV-1 ICP27, UL42, gB, and gD proteins. MI-S also presented synergistic antiviral effect with acyclovir. These results suggest that MI-S presents multiple modes of anti-HSV action.

Structural characterization of beta-glucans of Agaricus brasiliensis in different stages of fruiting body maturity and their use in nutraceutical products.

beta-Glucans of Agaricus brasiliensis fruiting bodies in different stages of maturity were isolated and characterized by FTIR and NMR. These fractions had greater amount of (1-->6)-beta-glucan and the (1-->3)-beta-glucan increased with fruiting bodies maturation. Yields of beta-glucans increased from 42 mg beta-glucans g(-1) fruiting bodies (dry wt) in immature stage to 43 mg g(-1) in mature stage with immature spores, and decreased to 40 mg g(-1) in mature stage with spore maturation. Mature fruiting bodies, which included these glucans, have potential therapeutical benefits for use in nutraceutical products.