Effects of Dietary Poly I:C on Growth, Disease Resistance, Immunity, and Transcriptomic Responses in Litopenaeus vannamei

Polyinosinic–polycytidylic acid (poly I:C), a synthetic double-stranded RNA analogue, is recognized as a potential immunostimulant; however, its dietary effects and regulatory mechanisms in Litopenaeus vannamei remain unclear. This study investigated the effects of dietary poly I:C supplementation on growth performance, immune responses, disease resistance, and transcriptomic profiles of juvenile L. vannamei. Six isonitrogenous and isolipidic diets supplemented with 0, 1, 5, 25, 125, and 625 mg/kg poly I:C were fed to shrimp for 8 weeks. Dietary poly I:C had no significant effect on survival rate, weight gain rate, specific growth rate, or feed conversion ratio. However, the PIC25 group showed significantly enhanced survival after white spot syndrome virus challenge, whereas the PIC125 and PIC625 groups exhibited significantly higher survival after Vibrio parahaemolyticus challenge. Poly I:C supplementation also increased several serum and hepatopancreatic immune-related enzyme activities and reduced hepatopancreatic malondialdehyde content at lower supplementation levels. Transcriptome analysis identified 6979 and 4808 differentially expressed genes in the PIC25-versus-PIC0 and PIC625-versus-PIC0 comparisons, respectively. Functional enrichment analysis revealed that dietary poly I:C modulated pathways related to endocytosis, SNARE interactions in vesicular transport, autophagy, phosphatidylinositol signaling, inositol phosphate metabolism, FoxO signaling, and PI3K-Akt signaling. These findings suggest that dietary poly I:C may enhance immune competence and disease resistance in L. vannamei, with effects varying depending on supplementation level and pathogen type, potentially through the regulation of phagocytosis-related processes, vesicular trafficking, apoptosis, and immune-associated metabolic pathways.