Superoxide dismutase B (sodB), an important virulence factor of Vibrio alginolyticus, contributes to antioxidative stress and its potential application for live attenuated vaccine

Vibrio alginolyticus is an opportunistic and halophilic Gram-negative pathogen in limiting the development of aquatic industry and affecting human health. SODs are oxidative enzymes that play a critical role in oxidative defense. In this study, an in-frame deleted mutant strain (Delta sodB) was constructed by allelic exchange mutagenesis to investigate physiological role of sodB in pathogenicity of V. alginolyticus. The results exhibited that Delta sodB showed no differences in growth compared with wild-type strain HY9901 (WT), but led to increasing in biofilm formation, ECPase activity and sensitivity to hydrogen peroxide, decreasing in swarming motility, adherence to CIK cells, SOD activity and virulence. In addition, Delta sodB induced a high antibody titer and provided a valid protection with a relative percent survival value of 86.5% without inducing clinical symptoms after challenging with WT. These results suggest that sodB is important for normal physiological function, oxidation resistance and virulence in V. alginolyticus, and Delta sodB may be considered as an effective live attenuated vaccine against V. alginolyticus.