Water-Soluble Polysaccharides From Pleurotus Eryngii Fruiting Bodies, Their Activity And Affinity For Toll-Like Receptor 2 And Dectin-1

The mushroom cell wall contains polysaccharides that can activate cells of the innate immune system through receptors such as Toll-like receptors (TLR) and dectin-1. In the present study, Pleurotus eryngii polysaccharide fractions containing a 3-O methylated mannogalactan and (1 -> 3)/(1 -> 6)-beta-D-glucans were isolated and extensively characterized by 2D NMR and methylation analysis. Traces of a (1 -> 3)-alpha-D-glucan and a (1 -> 2)-alpha-Dmannan were also observed. Affinity for TLR2, TLR2-TLR6 and dectin-1 using HEK-cells expressing the relevant receptor genes was tested. PeWN, containing the 3-O methylated mannogalactan, was inactive towards TLR2, whereas fraction PeWB, containing more beta-glucan, activated the TLR2-TLR6 heterodimer. Activation of the human ss-glucan receptor dectin-1 correlated with the amount of beta-glucan in each fraction. Nitric oxide and cytokine supernatant levels of D2SC/1 dendritic cells stimulated with the P. eryngii fractions and interferon-gamma were low to moderate. The results indicate that the immunomodulatory activity of water-soluble P. eryngii polysaccharide fractions is modest.