The effects of Anoectochilus roxburghii polysaccharides on the innate immunity and disease resistance of Procambarus clarkii

Anoectochilus roxburghii polysaccharides (ARPs) are composed of glucose (75.71%) and galactose (14.53%) with α-type glycosidic chains, and the sugar chains contained the functional groups of S=O, C=O, and -COO-. A white spot syndrome virus (WSSV) infection experiment was performed to determine the effect of ARPs on the innate immunity of crayfish. Dietary ARPs were proven to increase the survival of WSSV-infected crayfish up to 40%. It was also found that ARPs could up-regulate the expression level of multiple immune genes, including crustin 1 , proPO , Toll-like receptors , c-type-lectin , and decrease the expression of NF-κB . Additionally, ARPs promoted phenoloxidase (PO), superoxide dismutase (SOD), catalase (CAT), and lysozyme (LZM) activity in crayfish. The apoptosis of hemocytes in crayfish was promoted by ARPs, whether challenged or not. This study showed that ARPs could be used as a potential source of therapeutic or preventive drugs to regulate crayfish immunity and increase the survival rate of crayfish infected with WSSV. • ARPs are composed of glucose (75.71%) and galactose (14.53%) with α-type glycosidic chains. • ARPs could enhance the survival rate of WSSV-infected crayfish. • ARPs promoted the activities of PO, SOD, and CAT in crayfish. • ARPs promoted the apoptosis of hemocytes in crayfish.