Alleviating effects of Gracilaria verrucosa supplement on non-specific immunity, antioxidant capacity and immune-related genes of pacific white shrimp (Litopenaeus vannamei) provoked with white spot syndrome virus

Our work evaluated the possible underlying roles of dietary dried seaweed (Gracilaria verrucosa; GV) on the inherent immune response, antioxidant capacity, immune-related gene expression, and protection of whiteleg shrimp (Litopenaeus vannamei) contra white spot syndrome virus (WSSV). Three hundred and sixty healthy L. vannamei (15.26 g ± 1.29 g) were graded into four supplemental groups ( Triplicate/group) and fed with diets including 0 (control), 2, 4, and 8 g GV (kg diet) ^-1 for 21 days. Following the feeding period, each group of shrimp received an intramuscular WSSV injection (1.4 × 10⁶ copies/ml). Hemolymph and gills samples were collected before and after the challenge with WSSV. Notably, the administration of dietary GV significantly enhanced the innate immune parameters of pacific white shrimp including total hemocyte count (THC), phagocytosis, phenoloxidase activity, reactive oxygen species (ROS) production, and lysozyme activity before and after challenge with WSSV. Additionally, dietary supplementation of 4, and 8 g of GV (kg diet)^-1 remarkably elevated ACP, AKP, SOD, GPx, and catalase activities along with a decrease in the MDA level in gills of shrimp before and post-WSSV challenge. In response to the GV supplement, significant upregulation of expression of ALF1, CRU1, PEN4, and CTL with downregulation of TRAF6, STAT, TLR1, and NOS genes was recorded in the gills tissue before and post-challenge with WSSV, especially at a dose of 8.0 GV g kg ^{- 1}. Dietary inoculated shrimp with GV revealed notably higher survival percentages after being challenged with WSSV. Conclusively, these data indicate that Gracilaria verrucosa can be recommended as a valuable supplemented seaweed to stimulate the innate immunity and enhance the health of Litopenaeus vannamei against viral infection.