Antiviral, antioxidant, and anti-inflammatory activities of rhein against white spot syndrome virus infection in red swamp crayfish ( Procambarus clarkii )

ABSTRACT Infection caused by white spot syndrome virus (WSSV) leads to massive mortality and huge economic losses in the crustacean aquaculture industry; however, to date, no effective control means are available to control the disease. Thus, to better understand the pathological aspects of WSSV and to find effective compounds that have the potential to be developed as anti-WSSV agents are imperative. Herein, based on screening of plants with antiviral activity, we found that rhein, an anthraquinone compound in Rheum palmatum L., exhibited strong activity against WSSV infection in a red swamp crayfish ( Procambarus clarkii ) model. The results showed that rhein could dose dependently inhibit transcription of WSSV ie1, DNApol, and Vp28 genes, reduce viral load in vivo , and significantly improve the survival rate of WSSV-infected crayfish. Through investigation of the mechanisms of action, we found that rhein did not affect the infectivity of viral particles in vitro as well as the entry and release process in vivo . Alternatively, rhein could activate JAK/STAT and NF-κB pathways, significantly decrease the expression of crustin-1 and BAF but increase the expression of C-type lectin and proPO to arrest WSSV replication. Moreover, rhein also attenuated WSSV-induced oxidative and inflammatory stresses by regulating the expression of antioxidant and anti-inflammatory-related genes and enhanced innate immunity by reducing total protein levels while increasing the phosphatase activity. Taken together, our study shows rhein as a potent WSSV inhibitor, which provides great potential for the development of prophylaxis and therapy agents for controlling WSSV infection in crustacean aquaculture. IMPORTANCE Aquaculture is essential for ensuring global food security by providing a significant source of animal protein. However, the spread of the white spot syndrome virus (WSSV) has resulted in considerable economic losses in crustacean industries. In this study, we evaluated the antiviral activity of rhein, the primary bioactive component of Rheum palmatum L., against WSSV infection, and many pathological aspects of WSSV were also described for the first time. Our mechanistic studies indicated that rhein effectively arrested the replication of WSSV in crayfish by modulating innate immunity to inhibit viral gene transcription. Furthermore, we observed that rhein attenuated WSSV-induced oxidative and inflammatory stresses by regulating the expression of antioxidant and anti-inflammatory-related genes while enhancing innate immunity by reducing total protein levels and increasing phosphatase activity. Our findings suggest that rhein holds great promise as a potent antiviral agent for the prevention and treatment of WSSV in aquaculture.