Purification and characterization of an immuno-stimulatory compound from the water extract of royoporus badius (Pers.) A.B. De

A novel immuno-stimulatory polysaccharide-protein complex (ISPP-Rb) was isolated from Royoporus badius sporocarps, collected in northern BC forests. ISPP-Rb was purified from the water extract of R. badius using anion-exchange and size-exclusion chromatography and could significantly activate murine macrophage (RAW 264.7) cells. ISPP-Rb is highly branched and has an average molecular weight of 400 kDa. GC-MS data suggest the polysaccharide component of ISPP-Rb has a backbone of (1 → 6)-Gal/Man and (1 → 2,6)-Glc, with the latter being attached to either glucose, galactose or fucose at its terminal end. The protein component, found to be indispensable for its immuno-stimulatory activity, is proposed to link to a mannose residue via O-linked glycosylation. ISPP-Rb was able to induce various proinflammatory cytokines including TNF-α, IP-10, MIP-2, G-CSF, GM-CSF, MIP-1α, and MIP-1β. This is the first immuno-stimulatory compound to be reported from R. badius, and hence making ISPP-Rb novel.