PirAB from Vibrio parahaemolyticus Exhibits a Binary Toxin Action with Bactericidal Activity and Cytotoxicity in Penaeus vannamei

PirAB is a binary protein complex secreted by specific strains of Vibrio parahaemolyticus (Vp) that harbor the pVA1 virulence plasmid and express PirAVp and PirBVp toxins. PirABVp causes acute hepatopancreatic necrosis disease (AHPND), a newly emergent penaeid shrimp disease that can cause 70–100% mortality and has resulted in great economic losses since its appearance. The cy-totoxic effect of PirABVp on the epithelial cell of the shrimp hepatopancreas has been extensively reported. Our studies found that the PirBVp subunit has lectin activity and recognizes mucin-like O-glycosidic structures in the shrimp hepatopancreas. The PirAVp subunit may have a stabiliza-tion function of the binary complex. However, we also found that Vp AHPND changes the water microbiota community structure and causes a significant reduction in several bacteria, especially Neptuniibacter spp. We propose that the PirABvp toxin could exhibit a dual role: damage the shrimp hepatopancreas and kill surrounding bacteria.