Roles of chaperone/usher pathways of Yersinia pestis in a murine model of plague and adhesion to host cells.

Yersinia pestis and many other Gram-negative pathogenic bacteria use the chaperone/usher (CU) pathway to assemble virulence-associated surface fibers termed pili or fimbriae. Y. pestis has two well-characterized CU pathways: the caf genes coding for the F1 capsule and the psa genes coding for the pH 6 antigen. The Y. pestis genome contains additional CU pathways that are capable of assembling pilus fibers, but the roles of these pathways in the pathogenesis of plague are not understood. We constructed deletion mutations in the usher genes for six of the additional Y. pestis CU pathways. The wild-type (WT) and usher deletion strains were compared in the murine bubonic (subcutaneous) and pneumonic (intranasal) plague infection models. Y. pestis strains containing deletions in CU pathways y0348-0352, y1858-1862, and y1869-1873 were attenuated for virulence compared to the WT strain by the intranasal, but not subcutaneous, routes of infection, suggesting specific roles for these pathways during pneumonic plague. We examined binding of the Y. pestis WT and usher deletion strains to A549 human lung epithelial cells, HEp-2 human cervical epithelial cells, and primary human and murine macrophages. Y. pestis CU pathways y0348-0352 and y1858-1862 were found to contribute to adhesion to all host cells tested, whereas pathway y1869-1873 was specific for binding to macrophages. The correlation between the virulence attenuation and host cell binding phenotypes of the usher deletion mutants identifies three of the additional CU pathways of Y. pestis as mediating interactions with host cells that are important for the pathogenesis of plague.

Integrated microRNA and mRNA gene expression in peripheral blood mononuclear cells in response to acute psychosocial stress: a repeated-measures within-subject pilot study.

OBJECTIVE: The impact of psychosocial stress on a variety of negative health outcomes is well documented, with current research efforts directed at possible mechanisms. Here, we focused on a potential mechanism involving differential expression of mRNA and microRNA in response to acute psychosocial stress. We utilized a validated behavioral paradigm, the Trier Social Stress Test (TSST), to induce acute psychosocial stress in a cohort of volunteers. Stress reactivity was assessed repeatedly during the TSST using saliva samples that were analyzed for levels of cortisol. Peripheral blood mononuclear cells were extracted from blood drawn at baseline and at two time points following the stress paradigm. Total RNA was extracted, and mRNA and microRNA microarrays were utilized to assess within-subject changes in gene expression between baseline and the two post-stressor time points. RESULTS: For microarray gene expression analysis, we focused on 12 participants who showed a robust cortisol response to the task, as an indicator of robust HPA-axis activation. We discovered a set of mRNAs and miRNAs that exhibited dynamic expression change in response to the TSST in peripheral blood mononuclear cells, further characterizing the link between psychosocial stress and cellular response mechanisms.