The immunomodulation of outer membrane vesicles from Vibrio parahaemolyticus causing acute hepatopancreatic necrosis disease in Pacific white shrimp Litopenaeus vannamei

Vibrio parahaemolyticus causing acute hepatopancreatic necrosis disease (VpAHPND) is a significant bacterial pathogen to Litopenaeus vannamei aquaculture with a substantial economic burden. Outer membrane vesicles (OMVs) released by Gram-negative pathogenic bacteria play complex roles in the modulation on host's immune response. To elucidate the potential roles of VpAHPND-OMVs on L. vannamei innate immune responses, this study investigated the immune responses and molecular mechanisms induced by VpAHPND-OMVs in hepatopancreas using transcriptomic and proteomic analysis. Shrimps were fed diets supplemented with 30 μg kg^-1 (T1 group) or 60 μg kg^-1VpAHPND-OMVs (T2 group), and the control group was fed a normal diet (CK group). Neither growth rate and hepatopancreas histological structure were affected by VpAHPND-OMVs. The most pronounced changes in the activities of immune-related enzymes, including lysozyme, superoxide dismutase, alkaline phosphatase and glutathione S-transferase, were observed at 7 and 14 days of the experiment, which suggested that VpAHPND-OMVs can rapidly and significantly enhance the activity of immune enzymes within a short period. The transcription levels of genes associated with immune and pathogen defense were significantly downregulated in the T1 and T2 groups including heat shock 70 kDa protein cognate 4-like (HSP70), beta-1,3-glucan-binding protein-like (GNBP1), C-type mannose receptor 2-like (MRC2), penaeidin-3a-like (PEN-3), and chitinase 10 (Cht10). Several key proteins were also significantly downregulated in the proteomics analysis, including alkaline phosphatase, integrin, cathepsin, C-type lectin 2, ras-related protein Rab-11A, and ferritin. Furthermore, the KEGG enrichment analysis revealed that the differentially expressed genes and differentially expressed proteins were associated with innate immune signaling pathways like apoptosis (ko04210), phagosome (ko04145) and lysosome (ko04142). All these results suggest that VpAHPND-OMVs may have a dual regulatory effect on shrimp, initially activating the immune system but potentially leading to an immunosuppressive with prolonged exposure. This study enhanced our understanding on shrimp immune regulation.