LpxD gene knockout elicits protection to Litopenaeus vannamei, white shrimp, against Vibrio parahaemolyticus infection

Vibrio parahaemolyticus is a Gram-negative bacterium causing acute hepatopancreatic necrosis disease (AHPND) in white shrimp, Litopenaeus vannamei. LpxD gene, a principal component of lipid A, which plays a vital role in the biosynthesis of lipopolysaccharides (LPSs) responsible for the pathogenesis of Gram-negative bacteria However, the function of lpxD in V. parahaemolyticus' virulence has not been studied. In this study, lpxD gene knockout and its role in V. parahaemolyticus' virulence in white shrimp were determined. The lpxD gene was knocked out by homologous recombination. Virulence and immunogenicity of the lpxD gene was disrupted and the pirA, the major virulence factor of AHPND, and AP1 gene were intact in white shrimp. White shrimp fed with normal diet with VPolpxD displayed protection (reduced mortality rate from 66 to 27%) after challenge with V. parahaemolyticus. Our results indicated that knockout of the lpxD gene can cause attenuation of V. parahaemolyticus in white shrimp, and VPolpxD could be used as a live attenuated oral vaccine against V. parahaemolyticus in white shrimp.