Immunoproteomics analysis of whole cell bacterial proteins of Riemerella anatipestifer

Riemerella antipestifer is one of the most important duck pathogens. It has worldwide distribution, and the lack of the information on bacteria-host interactions and an effective vaccine are limitations on the control of this infection. In this study, an immunoproteomic assay was used to identify immunogenic proteins among the whole cell bacterial proteins of R. anatipestifer virulent strain Th4. Duck antiserum against R. anatipestifer Th4 recognized 64 protein spots which were transferred from two-dimensional electrophoresis (2-DE) gel of the whole cell bacterial proteins onto polyvinylidene fluoride (PVDF) membrane. Immunogenic proteins on a duplicate gel were excised and identified by matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF-MS) and peptide mass fingerprinting (PMF), a total of 34 immunogenic proteins were found. With the exception of OmpA and GroEL, the other 32 proteins were newly recognized immunogenic antigens of R. anatipestifer. In addition, TonB-dependent outer membrane receptor was found to be a cross immunogenic antigen among serotypes 1, 2 and 10 of R. anatipestifer. Bioinformatics analysis showed that most of the immunogenic proteins were located in the outer membrane and cytoplasm, and were involved in cellular processes and metabolism. The newly identified immunogenic proteins of R. anatipestifer may help us to uncover the pathogenesis of the bacteria, develop novel vaccine candidates and serological diagnosis marker.