Discovery of a substance that enhances the immune response in Litopenaeus vannamei against WSSV: Baicalein, a major component of Scutellaria baicalensis

Abstract

White spot syndrome virus (WSSV) is a pathogen that can infect many crustaceans, and that has caused huge economic losses in the shrimp industry. No effective prevention and control measures are currently available. In the present study, the ethanolic extract of Scutellaria baicalensis (SBEE) at 200 mg/L provided >50% protection for WSSV-infected shrimp larvae, and baicalein at 100 μM, one of the main anti-WSSV active substances in S. baicalensis, was 66.7% effective. When shrimp larvae were infected with WSSV after 8 h of SBEE and baicalein preincubation, the respective copy numbers of the viral genome were decreased by 31% and 46% versus the control group. Similarly, WSSV genome copy number reductions of 49% and 55% were observed in WSSV-infected shrimp larvae after 72 h of SBEE and baicalein immersion, respectively. In addition, SBEE or baicalein continuous treatment significantly reduced the viral loads in vivo, effectively blocking the horizontal transmission of WSSV between hosts. SBEE or baicalein also enhanced the expression of Toll4, Dorsal and antimicrobial peptides (AMPs) to restrict WSSV infection. In conclusion, S. baicalensis and baicalein are promising feed additives and immune enhancers for the control of WSSV infection.