Immunoproteomic Identification of OmpC of Edwardsiella ictaluri as an Immune Target Protein to Elicit Antibody Response in Nile tilapia

The Gram-negative bacteria name Edwardsiella ictaluri was reported to be the cause of Edwardsiellosis diseases infecting several economic fish including Nile tilapia. The result of the immunoproteomic identification found that Outer membrane protein C (OmpC) could react with the serum from the Nile Tilapia that was naturally infected with E. ictaluri. In this study, we successfully produce the OmpC protein in the Escherichia coli strain BL21(DE3) system with a molecular mass of 25 kDa in an insoluble form. The protein was solubilized and refolded before the immunization. When Nile tilapia were immunized with OmpC protein, it showed a significant increase of specific serum antibodies (P<0.05) after 1week post-immunization (7 dpi) and reached the highest titer at 3 weeks post-immunization (21 dpi). Additionally, the serum-specific antibody from Nile Tilapia immunized with OmpC protein displayed a bacterial agglutination property. In summary, the OmpC protein of E. ictaluri might be considered a candidate protein for developing Edwardsiellosis protective vaccine in Nile tilapia.