Identification and immunogenicity of immunodominant mimotopes of outer membrane protein U (OmpU) of Vibrio mimicus from phage display peptide library

Vibrio mimicus (V. mimicus) is the causative agent of ascites disease in aquatic animals. Outer membrane protein U (OmpU) is an important antigen of V mimicus, but its protective epitopes are still unclear. A random 12-mer phage-displayed peptide library was used to screen and identify immunodominant mimotopes of the OmpU protein in V. mimicus by panning against purified OmpU-specific polyclonal antibody. Then the immunogenicity and immunoprotection in fish of these mimotopes was evaluated. Nine positive phage clones presented seven different 12- peptide sequences and more than 50% of them carried a consensus core motif of DSSK-P. These positive clones reacted with the target antibody and this interaction could be blocked, in a dose-dependent manner, by OmpU protein. Intraperitoneal injection of seven positive phage clones into fish induced a specific antibody response to OmpU protein. The fish immunized respectively with the positive phage clones C17, C24, C60 and C66 obtained 100% immunoprotective effect against experimental V mimic-us challenge. Taken together, these mimotopes presented by clone C17, C24, C60 and C66 were immunodominant mimotopes of the OmpU protein and exhibited a more appropriate candidate as epitope-based vaccine against V mimicus infection in aquatic animals. (c) 2012 Elsevier Ltd. All rights reserved.