Cloning, expression and immunogenicty analysis of five outer membrane proteins of Vibrio parahaemolyticus zj2003

Genes of five outer membrane proteins of Vibrio parahaemolyticus zj2003, including OmpW, OmpV, OmpK, OmpU and TolC, were cloned and expressed as N-terminal His(6)-tagged proteins in Escherichia coli. The recombinant fusion proteins were purified with nickel chelate affinity chromatography. To analyze the immunogenicity of these proteins, large yellow croaker (Pseudosciaena crocea) were immunized by intraperitoneal injection. Antibody response was assessed by method of enzyme-linked immunosorbent assay. Titres to all five recombinant proteins increased during 4 to 8 weeks post immunization, within the range of log 2 values of 5.75 to 10.8. Recorded relative survival percent (RPS) of the vaccinated groups varied from 80% to 90%, while 10 fish in control group all died. Western blot tests were undertaken with the serum of survival fish after experimental infection. Except for recombinant TolC, the other four recombinant proteins were recognized by the serum. It is indicated that four outer membrane proteins of V. parahaemolyticus zj2003, including OmpW, OmpV, OmpU and OmpK, are immunogenic during in vivo infection, which would be of some significance in developing efficient vaccine in aquaculture. This is the first report of successful vaccination against V. parahaemolyticus with purified recombinant outer membrane proteins.