Vibrio alginolyticus is one of the Vibrio pathogens common to humans and marine animals.During infection and induction of the host immune response,outer membrane proteins of bacteria play an important role.In this study,an outer membrane protein gene (ompW) was cloned from V. alginolyticus and expressed in Escherichia coli.The 645 bp open reading frame (ORF) encodes a protein of 214 amino acid residues with a predicted molecular weight of 23.3 kDa.The amino acid sequence showed a high identity with that of Photobacterium damselae(96.2%) and Vibrio parahaemolyticus(94.4%).The alignment analysis indicated that OmpW was highly conserved.Sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed that the gene was over-expressed in E.coli BL21(DE3).Weste blot analysis revealed that the expressed protein had immunoreactivity.The recombinant protein was purified by affinity chromatography on Ni-NTA Superflow resin.Large yellow croaker vaccinated with the purified OmpW showed significantly increased antibody to OmpW,which could resist the infection by V.alginolyticus.A specific antibody was detected by enzyme-linked immunosorbent assay.This study suggested that the conserved OmpW could be an effective vaccine candidate against infection by V.alginolyticus.