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TolC plays a crucial role in immune protection conferred by Edwardsiella tarda whole-cell vaccines.

ABSTRACT: Although vaccines developed from live organisms have better efficacy than those developed from dead organisms, the mechanisms underlying this differential efficacy remain unexplored. In this study, we combined sub-immunoproteomics with immune challenge to investigate the action of the outer membrane proteome in the immune protection conferred by four Edwardsiella tarda whole-cell vaccines prepared via different treatments and to identify protective immunogens that play a key role in this immune protection. Thirteen spots representing five outer membrane proteins and one cytoplasmic protein were identified, and it was found that their abundance was altered in relation with the immune protective abilities of the four vaccines. Among these proteins, TolC and OmpA were found to be the key immunogens conferring the first and second highest degrees of protection, respectively. TolC was detected in the two effective vaccines (live and inactivated-30-F). The total antiserum and anti-OmpA titers were higher for the two effective vaccines than for the two ineffective vaccines (inactivated-80-F and inactivated-100). Further evidence demonstrated that the live and inactivated-30-F vaccines demonstrated stronger abilities to induce CD8+ and CD4+ T cell differentiation than the other two evaluated vaccines. Our results indicate that the outer membrane proteome changes dramatically following different treatments, which contributes to the effectiveness of whole-cell vaccines.

SUBMITTER: Wang C

PROVIDER: S-EPMC4942608 | biostudies-literature | 2016 Jul

REPOSITORIES: biostudies-literature

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TolC plays a crucial role in immune protection conferred by Edwardsiella tarda whole-cell vaccines.

Wang Chao C Peng Bo B Li Hui H Peng Xuan-Xian XX

Scientific reports 20160712

Although vaccines developed from live organisms have better efficacy than those developed from dead organisms, the mechanisms underlying this differential efficacy remain unexplored. In this study, we combined sub-immunoproteomics with immune challenge to investigate the action of the outer membrane proteome in the immune protection conferred by four Edwardsiella tarda whole-cell vaccines prepared via different treatments and to identify protective immunogens that play a key role in this immune ...[more]

PMID: 27406266

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Project description:Edwardsiella tarda is a severe fish pathogen, featured by its capacity to live inside host phagocytes. For intracellular survival, it is crucial for E. tarda to neutralize the deleterious effect of host reactive oxygen species (ROS). Accumulating evidence suggests that bacterial metabolism is closely connected to oxidative resistance. However, the roles of E. tarda metabolic proteins in antioxidative adaptation and intracellular proliferation remain elusive. In this study, we performed a proteomic analysis on E. tarda and identified 111 proteins responsive to H2O2-mediated oxidative stress. Based on this data, we further obtained eight crucial proteins, including seven metabolic proteins, for E. tarda antioxidation and intracellular infection. Among them, two C4-dicarboxylate transporters were found necessary for E. tarda to disseminate in fish tissues. Furthermore, the substrate of the two transporters was identified as L-aspartate, which was proven to be essential for the full antioxidative capacity of E. tarda. Our results indicate that reprogramming the metabolic flux to the production of pyruvate, a ketoacid capable of neutralizing ROS, was likely a pivotal strategy of E. tarda to survive the oxidative environments inside host cells. Together, the findings of this study highlight the significance of metabolic reprogramming for bacterial redox homeostasis and intracellular infection. IMPORTANCE Edwardsiella tarda is a significant fish pathogen that can live in challenging environments of reactive oxygen species (ROS), such as inside the phagocytes. Metabolic reconfiguration has been increasingly associated with bacterial oxidative tolerance and virulence. However, the metabolic proteins of E. tarda involved in such processes remain elusive. By proteomic analysis and functional characterization of protein null mutants, the present study identified eight crucial proteins for bacterial oxidative resistance and intracellular infection. Seven of them are metabolic proteins dictating the metabolic flux toward the generation of pyruvate, a key metabolite capable of scavenging ROS molecules. Furthermore, L-aspartate uptake, which can fuel the pyruvate generation, was found essential for the full antioxidative capacity of E. tarda. These findings identified seven metabolic proteins involved in bacterial oxidative adaptation and indicate that metabolic reprogramming toward pyruvate was likely a pivotal strategy of bacteria for antioxidative adaptation and intracellular survival.

Project description:UnlabelledEdwardsiella tarda is an important pathogenic bacterium that can replicate in macrophages. However, how the intramacrophage infection process affects the virulence of this bacterium is essentially unknown. Here, we show that E. tarda replicates and induces a caspase-1-dependent cell pyroptosis in a murine macrophage model. Via pyroptosis, intracellular E. tarda escapes to the extracellular milieu, forming a unique bacterial population. Being different from the bacteria cultured alone, this unique population possesses a reprogrammed transcriptional profile, particularly with upregulated type III secretion system (T3SS)/T6SS cluster genes. Subsequent studies revealed that the macrophage-released population gains enhanced infectivity for host epithelial cells and increases resistance to multiple host defenses and hence displays significantly promoted virulence in vivo Further studies indicated that T3SS is essentially required for the macrophage infection process, while T6SS contributes to infection-induced bacterial virulence. Altogether, this work demonstrates that E. tarda can utilize macrophages as a niche for virulence priming and for spreading infection, suggesting a positive role for intramacrophage infection in bacterial pathogenesis.ImportanceMany pathogens can replicate in macrophages, which is crucial for their pathogenesis. To survive in the macrophage cell, pathogens are likely to require fitness genes to counteract multiple host-killing mechanisms. Here, Edwardsiella tarda is proved to exit from macrophages during infection. This macrophage-released population displays a reprogrammed transcriptional profile with significantly upregulated type III secretion system (T3SS)/T6SS-related genes. Furthermore, both enhanced infectivity in epithelial cells and activated resistance to complex host defenses were conferred on this macrophage-primed population, which consequently promoted the full virulence of E. tarda in vivo Our work provides evidence that E. tarda can utilize macrophages as a niche for virulence priming and for spreading infection, highlighting the importance of the intramacrophage infection cycle for the pathogenesis of E. tarda.

Dataset Information

TolC plays a crucial role in immune protection conferred by Edwardsiella tarda whole-cell vaccines.

Publications

TolC plays a crucial role in immune protection conferred by Edwardsiella tarda whole-cell vaccines.

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