Protection of Pacific white shrimp (Penaeus vannamei) against white spot syndrome virus infection by nitric oxide-generating compound S-nitrosoglutathione

Abstract

Nitric oxide (NO), a highly reactive free radical generated endogenously by nitric oxide synthase (NOS), plays crucial roles in immune defense against a broad range of pathogens including viruses, bacteria, fungi, and protozoans. However, the regulation and effect of NO during viral infection in invertebrates remain largely unexplored. White spot syndrome virus (WSSV) is one of the most severe pathogens affecting the global shrimp farming industry. Our study shows that NO production in Pacific white shrimp Penaeus vannamei decreases during WSSV infection. Reducing NO production using the NOS inhibitor N-nitro-L-arginine methyl ester (L-NAME) significantly promotes WSSV replication in primary culture of hemocytes isolated from P. vannamei. This effect is partically reversed by L-arginine, a native substrate for NOS, indicating that L-NAME's immunity-reducing action is NO-dependent. In vitro studies also reveal inhibition of WSSV replication in the presence of three NO donors: S-nitrosoglutathione (GSNO), S-nitro-N-acetylpenicillamine (SNAP), and diethylenetriamine nitric oxide adduct (DETA/NO). The involvement of NO in anti-WSSV protection is further demonstrated by an in vivo study where dietary supplementation with GSNO at non-toxic doses increases NO levels and reduces viral load and mortality in WSSV-challenged shrimp. Our results contribute to understanding the antiviral activity of NO in invertebrates and provide a theoretical basis for developing NO-based therapeutic strategies to control WSSV infection.