Composition and Methods for Treating \u3cem\u3eYersinia Pestis\u3c/em\u3e Infection

Compositions and methods for treating a Yersinia pestis (Y. pestis) infection are provided. Compositions and methods of for inducing an immune response in a subject are provided. Composition can include a YadC polypeptide

Toward a molecular pathogenic pathway for Yersinia pestis YopM

YopM is one of the six “effector Yops” of the human-pathogenic Yersinia, but its mechanism has not been defined. After delivery to J774A.1 monocyte-like cells, YopM can rapidly bind and activate the serine/threonine kinases RSK1 and PRK2. However, in infected mice, effects of Y. pestis YopM have been seen only after 24–48 h post-infection (p.i.). To identify potential direct effects of YopM in-vivo we tested for effects of YopM at 1 h and 16–18 h p.i. in mice infected systemically with 106 bacteria. At 16 h p.i., there was a robust host response to both parent and ΔyopM-1 Y. pestis KIM5. Compared to cells from non-infected mice, CD11b+ cells from spleens of infected mice produced more than 100-fold greater IFNγ. In the corresponding sera there were more than 100-fold greater amounts of IFNγ, G-CSF, and CXCL9, as well as more than 10-fold greater amounts of IL-6, CXCL10, and CXCL1. The only YopM-related differences were slightly lower CXCL10 and IL-6 in sera from mice infected 16 h with parent compared to ΔyopM-1 Y. pestis. Microarray analysis of the CD11b+ cells did not identify consistent transcriptional differences of ≥4-fold at 18 h p.i. However, at 1 h p.i. mRNA for early growth response transcription factor 1 (Egr1) was decreased when YopM was present. Bone marrow-derived macrophages infected for 1 h also expressed lower Egr1 message when YopM was present. Infected J774A.1 cells showed greater expression of Egr1 at 1 h p.i. when YopM was present, but this pattern reversed at 3 h. At 6 h p.i., Cxcl10 mRNA was lower in parent-strain infected cells. We conclude that decreased Egr1 expression is a very early transcriptional effect of YopM and speculate that a pathway may exist from RSK1 through Egr1. These studies revealed novel early transcriptional effects of YopM but point to a time after 18 h of infection when critical transitional events lead to later major effects on cytokine gene transcription

Caspase-3 Mediates the Pathogenic Effect of \u3cem\u3e Yersinia pestis \u3c/em\u3e YopM in Liver of C57BL/6 Mice and Contributes to YopM\u27s Function in Spleen

The virulence protein YopM of the plague bacterium Yersinia pestis has different dominant effects in liver and spleen. Previous studies focused on spleen, where YopM inhibits accumulation of inflammatory dendritic cells. In the present study we focused on liver, where PMN function may be directly undermined by YopM without changes in inflammatory cell numbers in the initial days of infection, and foci of inflammation are easily identified. Mice were infected with parent and ΔyopM-1 Y. pestis KIM5, and effects of YopM were assessed by immunohistochemistry and determinations of bacterial viable numbers in organs. The bacteria were found associated with myeloid cells in foci of inflammation and in liver sinusoids. A new in-vivo phenotype of YopM was revealed: death of inflammatory cells, evidenced by TUNEL staining beginning at d 1 of infection. Based on distributions of Ly6G+, F4/80+, and iNOS+ cells within foci, the cells that were killed could have included both PMNs and macrophages. By 2 d post-infection, YopM had no effect on distribution of these cells, but by 3 d cellular decomposition had outstripped acute inflammation in foci due to parent Y. pestis, while foci due to the Δ-1yopM strain still contained many inflammatory cells. The destruction depended on the presence of both PMNs in the mice and YopM in the bacteria. In mice that lacked the apoptosis mediator caspase-3 the infection dynamics were novel: the parent Y. pestis was limited in growth comparably to the ΔyopM-1 strain in liver, and in spleen a partial growth limitation for parent Y. pestis was seen. This result identified caspase-3 as a co-factor or effector in YopM\u27s action and supports the hypothesis that in liver YopM\u27s main pathogenic effect is mediated by caspase-3 to cause apoptosis of PMNs