Expression and immune characteristics of FlaA-OmpK protein in Vibrio parahaemolyticus

Marine vibrio is a causative agent of vibriosis,a disease that results in severe losses to the aquaculture industry.The development of Vibrio vaccines would likely lower the abuse of antibiotics that are currently used to ensure the safety of aquatic products.We prepared and characterized a FlaA-OmpK enteric microsphere vaccine and evaluated the effectiveness of oral vaccination.We cloned the ompK and flaA genes from the total DNA of V.parahaemolyticus.FlaA was fused with ompK into flaA-ompK by overlap extension PCR.The expression systems OmpK,FlaA,and FlaA-OmpK were then constructed.The recombinant proteins were expressed in large scale in E.coli BL21 and purified.OmpK,FlaA-OmpK,and mixed OmpK and FlaA were administered as antigens to immu-nize Centropristis striata.Vaccination with FlaA-OmpK protected against the infection by V.parahaemolyticus.The titers of the anti-serum from immunized C.striata against FlaA-OmpK were highest 40 d after immunization,and were two times that of the OmpK group and four times that of the OmpK group.The serum titers of the FlaA-Ompk were significantly lower in fish that were treated orally relative to those that were injected.The fish immunized with r-FlaA-OmpK had high survival(80%) compared with the control group.Similarly,the oral FlaA-OmpK protection rate(50%) was lower than that in the injection group.Our results suggest that V.para-haemolyticus FlaA-Ompk is an ideal candidate for development of a Vibriosis vaccine.