Oligomeric Coiled-Coil Adhesin YadA Is a Double-Edged Sword

Yersinia adhesin A (YadA) is an essential virulence factor for the food-borne pathogens Yersinia enterocolitica and Yersinia pseudotuberculosis. Suprisingly, it is a pseudogene in Yersinia pestis. Even more intriguing, the introduction of a functional yadA gene in Y. pestis EV76 was shown to correlate with a decrease in virulence in a mouse model. Here, we report that wild type (wt) Y. enterocolitica E40, as well as YadA-deprived E40 induced the synthesis of neutrophil extracellular traps (NETs) upon contact with neutrophils, but only YadA-expressing Y. enterocolitica adhered to NETs and were killed. As binding seemed to be a prerequisite for killing, we searched for YadA-binding substrates and detected the presence of collagen within NETs. E40 bacteria expressing V98D,N99A mutant YadA with a severely reduced ability to bind collagen were found to be more resistant to killing, suggesting that collagen binding contributes significantly to sensitivity to NETs. Wt Y. pestis EV76 were resistant to killing by NETs, while recombinant EV76 expressing YadA from either Y. pseudotuberculosis or Y. enterocolitica were sensitive to killing by NETs, outlining the importance of YadA for susceptibility to NET-dependent killing. Recombinant EV76 endowed with YadA from Y. enterocolitica were also less virulent for the mouse than wt EV76, as shown before. In addition, EV76 carrying wt YadA were less virulent for the mouse than EV76 expressing YadAV98D,N99A. The observation that YadA makes Yersinia sensitive to NETs provides an explanation as for why evolution selected for the inactivation of yadA in the flea-borne Y. pestis and clarifies an old enigma. Since YadA imposes the same cost to the food-borne Yersinia but was nevertheless conserved by evolution, this observation also illustrates the duality of some virulence functions

Identification of Chromosomal Genes in Yersinia pestis that Influence Type III Secretion and Delivery of Yops into Target Cells

Pathogenic Yersinia species possess a type III secretion system, which is required for the delivery of effector Yop proteins into target cells during infection. Genes encoding the type III secretion machinery, its substrates, and several regulatory proteins all reside on a 70-Kb virulence plasmid. Genes encoded in the chromosome of yersiniae are thought to play important roles in bacterial perception of host environments and in the coordinated activation of the type III secretion pathway. Here, we investigate the contribution of chromosomal genes to the complex regulatory process controlling type III secretion in Yersinia pestis. Using transposon mutagenesis, we identified five chromosomal genes required for expression or secretion of Yops in laboratory media. Four out of the five chromosomal mutants were defective to various extents at injecting Yops into tissue culture cells. Interestingly, we found one mutant that was not able to secrete in vitro but was fully competent for injecting Yops into host cells, suggesting independent mechanisms for activation of the secretion apparatus. When tested in a mouse model of plague disease, three mutants were avirulent, whereas two strains were severely attenuated. Together these results demonstrate the importance of Y. pestis chromosomal genes in the proper function of type III secretion and in the pathogenesis of plague

Évaluation de la prise en charge de la lombalgie ::développement de vignettes cliniques

Bien que la littérature décrive plusieurs vignettes cliniques (associées à des questions) destinées à évaluer les attitudes/comportements des professionnels de la santé face à un patient souffrant de lombalgie, ces vignettes sont généralement incomplètes et n’abordent que peu, voire pas, les facteurs psychosociaux. De plus, celles-ci n’examinent pas l’adéquation entre la prise en charge préconisée et les recommandations récentes de la HAS et l’itinéraire de soins proposés par le KCE. Dès lors, les objectifs de cette étude étaient : 1) de développer 3 vignettes originales (patient fictif souffrant d’une lombalgie non spécifique aiguë, subaiguë/récurrente ou chronique) et un questionnaire (pouvant être utilisé avec chaque vignette) répondant aux limites des outils existants afin d’apprécier les attitudes de (futurs) professionnels de la santé ; 2) de mesurer les qualités psychométriques de base (effet plancher/plafond, validité et reproductibilité) de ce nouvel outil

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Yersinia enterocolitica can deliver Yop proteins into a wide range of cell types: development of a delivery system for heterologous proteins.

Y. enterocolitica translocates virulence proteins, called Yop effectors, into the cytosol of eukaryotic cells. Here we investigated whether Y. enterocolitica could translocate Yops into a range of eukaryotic cells including neurons and insect cells. Y. enterocolitica translocated the hybrid reporter protein YopE-Cya into each of the eukaryotic cell types tested. In addition, Y. enterocolitica was cytotoxic for each of the adherent cell types. Thus we detected no limit to the range of eukaryotic cells into which Y. enterocolitica can translocate Yops. The Yop effectors YopE, YopH and YopT were each cytotoxic for the adherent cell types tested, showing that not only is Y. enterocolitica not selective in its translocation of particular Yop effectors into each cell type, but also that the action of these Yop effectors is not cell type specific. Invasin and/or YadA, two powerful adhesins were required for translocation of Yop into non-phagocytic cells but not for translocation into macrophages. To use the Yersinia translocation system for broad applications, a Y. enterocolitica translocation strain and vector for the delivery of heterologous proteins into eukaryotic cells was constructed. This strain + vector combination lacks the translocated Yop effectors and allows delivery into eukaryotic cells of heterologous proteins fused to the minimal N-terminal secretion/translocation signal of YopE. Using this strategy translocation of a YopE-Diphtheria toxin subunit A hybrid protein into several cell types has been shown

The Yersinia pestis type III secretion system: expression, assembly and role in the evasion of host defenses

Yersinia pestis, the etiologic agent of plague, utilizes a type III secretion system (T3SS) to subvert the defenses of its mammalian hosts. T3SSs are complex nanomachines that allow bacterial pathogens to directly inject effector proteins into eukaryotic cells. The Y. pestis T3SS is not expressed during transit through the flea vector, but T3SS gene expression is rapidly thermoinduced upon entry into a mammalian host. Assembly of the T3S apparatus is a highly coordinated process that requires the homo- and hetero-oligomerization over 20 Yersinia secretion (Ysc) proteins, several assembly intermediates and the T3S process to complete the assembly of the rod and external needle structures. The activation of effector secretion is controlled by the YopN/TyeA/SycN/YscB complex, YscF and LcrG in response to extracellular calcium and/or contact with a eukaryotic cell. Cell contact triggers the T3S process including the secretion and assembly of a pore-forming translocon complex that facilitates the translocation of effector proteins, termed Yersinia outer proteins (Yops), across the eukaryotic membrane. Within the host cell, the Yop effector proteins function to inhibit bacterial phagocytosis and to suppress the production of pro-inflammatory cytokines