Identification of plasma-responsive outer membrane proteins and their vaccine potential in Edwardsiella tarda using proteomic approach.

We have used differential sub-proteomic methodologies to detect Edwardsiella tarda outer membrane (OM) protein expression regulation during interaction with fish and human plasma, which is the critical step of the bacterial invasion internal organs via blood circulation. Seven and nine OM proteins were differentially expressed in response to fish and human plasma stress, respectively. Six proteins, TolB2, ETAE_2935, ETAE_0245, EvpA, ETAE_2675 and OmpA, were the shared proteins with the similar changes between the two plasma treatments. Except for EvpA, which was a known protein involved in bacterial pathogenesis and stress sensing, the others were first reported here to be related to bacterial invasion and infection. Out of them, four, upregulated ETAE_0245 and OmpA and downregulated ETAE_2675 and ETAE_2935, were selected for investigation of immune protection. The upregulated OmpA and ETAE_0245 were able to induce bactericidal antibodies in mice. These findings demonstrate that differential proteomic methodologies following protein expression regulation to interaction between host and pathogen with bacterial challenge post immunization of these altered proteins is a valid approach for identifying new vaccine candidates and nicely complements other high throughput mining strategies used for vaccine discovery.