Proteomic Analysis Of Three Strains Of Listeria Spp. With Pathogenicity

Listeria monocytogenes is an important food-borne pathogen that can cause septicaemia, encephalitis, meningitis and gastroenteritis in humans and animals. The mortality of Listeriosis can reach 30%. The elderly, children and immunocompromised people are most susceptible. Listeria genus has six species, of which only Listeria monocytogenes (referred to as LM) and Listeria ivanovii (referred to as LI) are pathogenic. LM is the cause of human listeriosis, with 13 serotypes, 90% of the human listeriosis were caused by the 1/2a, 1/2b and 4b serotypes of LM. LI rarely cause human disease, there are few reported cases of animal infection. In this study, comparative proteomic analyses were conducted using the extracted proteins of bacterial cells and the culture supernatants from three strains of pathogenic Listeria spp., including LM type1/2a strain LM4, LM type 4b strain F4636 and one strain of L. ivanovii. And then the immunoproteomics technology which combined two-dimensional electrophoresis with Western blotting assay was utilized to explode the immunoproperties of pathogenic Listeria spp. proteins.To compare the whole cell proteins, the immobilized pH gradient two-dimensional gel electrophoresis was engaged in and got a set of reproducible 2-DE gel maps, and then differentiated proteins were filtered out using PDQuest software, harvested from the 2-DE gels for MALDI -TOF/TOF-MS ananlysis. The biological information of predicted proteins was identified based on peptide mass fingerprinting searched in MASCOT database. The 20 differentiated proteins were successfully obtained. These proteins involve the functions related to sugar metabolism, energy metabolism, cell cycle control and host invasion, molecular chaperones and many other events. All these results supplied the further understanding of pathogenic Listeria spp. and lay the foundation for the demonstration of genetic evolution.The immunoproteomics was further analyzed to define immunogenic proteins of these three Listeria spp. and identified 12 proteins with immunogenicity. Among them, the acetolactate synthase and FeS assembly protein SufD were first found to be immunogenic, the other proteins was also detected in a variety of pathogenic microorganisms. These results provided a theoretical basis for understanding of the pathogenic mechanism of Listeria spp., discovering of new virulence factors and developing of effective Listeria vaccines.Secreted proteins of the three strains of Listeria spp. were extracted using TCA precipitation method for comparative proteomic analysis. It was preliminary identified the differences between LM and LI at protein level. Among the 18 differentiated proteins, there were mainly related to Listeria virulence, cytolysin, material metabolism, energy metabolism, molecular chaperones and others. The results also revealed that a set of proteins in supernatants of these Listeria spp. having no any predicted signal sequence, suggesting that a new type of secretion pathway that might exist. This study found a set of potential Listeria virulence factors, pointed out a new direction for research on the pathogenic difference between LM and LI.