Silkrose: A novel acidic polysaccharide from the silkmoth that can stimulate the innate immune response.

We have identified a novel acidic polysaccharide from silkmoth (Antheraea yamamai) pupae that activates the mammalian innate immune response. This bioactive polysaccharide was isolated using nitric oxide production in mouse RAW264 macrophages as an indicator of immunostimulatory activity. We named this polysaccharide "silkrose". It has a molecular weight of 3.15 × 10(5) and comprises nine monosaccharides. The expression profiles indicated that silkrose induced the expression of proinflammatory cytokines and interferon β that exist downstream of MyD88-dependent and MyD88-indeptendent signaling pathways. Also, the inhibition of Toll-like receptor 4 (TLR4), which exists upstream of the signaling pathways, led to the suppression of NO production by silkrose. Furthermore, this polysaccharide promoted the activation of nuclear factor kappa B in RAW264 cells, indicating that it stimulates the induction of various cytokines in macrophages through the TLR4 signaling pathway. Our results thus suggest that silkrose activates the innate immune response to various pathogenic microorganisms and viral infections.