Pseudoalteromonas sp. SRSBD1_22: A potent prophylactic candidate mediating lipopolysaccharide (LPS) based humoral immune response in Penaeus monodon against WSSV infection

White Spot Disease (WSD), caused by White Spot Syndrome Virus (WSSV), a devastative killer in shrimp farms, causing a severe economic loss to the farmers. This study investigated the immune boosting activity of lipopolysaccharides (LPS) against WSSV infection, extracted from a newly isolated bacterial strain under the genus Pseudoalteromonas, Pseudoalteromonas sp. SRSBD1_22, from the hepatopancreas of a tiger shrimp. LPS was administered orally to the experimental shrimp (Penaeus monodon) for 5 days in three groups at 3 (T1), 5 (T2) and 7 (T3) μg LSP/g feed, and a control group (C) without LPS treatment. T3 outperformed T1 and T2 in terms of cellular (THC; 52-folds than C, ~ 2-folds than T1 and T2) and humoral (SOD; 3-folds than C, ~ 2-folds than T1 and T2) defense properties. Similarly, gene expression of Toll Like Receptors (TLR) in T3 was significantly higher (P < 0.05), 19, 6 and 12.5-folds than C, T1 and T2, respectively. In contrast, 7 μg LSP/g might cause a little cytotoxicity for the expression of Prophenoloxidase (ProPO) and Photorhabdus-like Insect A (PIR A) genes, which was higher in T2 compared to other groups. Challenge test bioassay reported that survival and probability of cumulative survival was significantly higher in the group fed the diet with 7 µg LPS/g feed compared to non-treated group. Similarly, TLR, ProPO, and PIR A gene expression was around 20,11 and 13 folds, and SOD was 1.5-fold in the LPS treated group than the control group. Thus, this study suggested that Pseudoalteromonas sp. SRSBD1_22 might be a novel strain with highly potential LPS mediated immune modulation to protect P. monodon juveniles against WSSV infection.