Yersinia pestis Two-Component Gene Regulatory Systems Promote Survival in Human Neutrophils

ABSTRACT Human polymorphonuclear leukocytes (PMNs, or neutrophils) are the most abundant innate immune cell and kill most invading bacteria through combined activities of reactive oxygen species (ROS) and antimicrobial granule constituents. Pathogens such as Yersinia pestis resist destruction by the innate immune system and are able to survive in macrophages and neutrophils. The specific molecular mechanisms used by Y. pestis to survive following phagocytosis by human PMNs are incompletely defined. To gain insight into factors that govern Y. pestis intracellular survival in neutrophils, we inactivated 25 two-component gene regulatory systems (TCSs) with known or inferred function and assessed susceptibility of these mutant strains to human PMN granule extracts. Y. pestis strains deficient for PhoPQ, KdpED, CheY, CvgSY, and CpxRA TCSs were selected for further analysis, and all five strains were altered for survival following interaction with PMNs. Of these five strains, only Y. pestis ΔphoPQ demonstrated global sensitivity to a panel of seven individual neutrophil antimicrobial peptides and serine proteases. Notably, Y. pestis ΔphoPQ was deficient for intracellular survival in PMNs. Iterative analysis with Y. pestis strains lacking the PhoP-regulated genes ugd and pmrK indicated that the mechanism most likely responsible for increased resistance to killing is 4-amino-4-deoxy-l-arabinose modification of lipid A. Together, the data provide new information about Y. pestis evasion of the innate immune system.

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Expression Microarray and Mouse Virulence Analysis of Four Conserved Two-Component Gene Regulatory Systems in Group A Streptococcus

Infection and Immunity ◽

10.1128/iai.74.2.1339-1351.2006 ◽

2006 ◽

Vol 74 (2) ◽

pp. 1339-1351 ◽

Cited By ~ 39

Author(s):

Izabela Sitkiewicz ◽

James M. Musser

Keyword(s):

Mutant Strain ◽

Group A Streptococcus ◽

Expression Microarray ◽

Regulatory Systems ◽

Significant Difference ◽

Two Component ◽

Mutant Strains ◽

Group A ◽

Gene Regulatory ◽

Component Gene

ABSTRACT Group A streptococcus (GAS) is a gram-positive human bacterial pathogen that causes diseases ranging from relatively mild epithelial cell surface infections to life-threatening invasive episodes. Much is known about the extracellular molecules that contribute to host-pathogen interactions, but in contrast, far less information is available about regulatory genes that control the expression of individual or multiple GAS virulence factors. The eight GAS genomes that have been sequenced have 12 conserved two-component gene regulatory systems (TCSs), but only 3 of these 12 have been studied in detail. Using an allelic replacement strategy with a nonpolar cassette, we inactivated the response regulator of four TCSs that have only weak homology with TCS genes of known or inferred function in other bacteria. The mutant strains were analyzed by expression microarray analysis at four time points and tested in two mouse infection models. Each TCS influenced expression (directly or indirectly) of 12 to 41% of all chromosomal genes, as assessed by growth in Todd-Hewitt broth and a custom Affymetrix GeneChip. None of the isogenic mutant strains was significantly altered for mouse virulence based on intraperitoneal inoculation. Similarly, compared to the wild-type strain, there was no significant difference in skin lesion size for three of the four mutants. In contrast, the ΔM5005_Spy_0680 mutant strain produced significantly larger abscesses after subcutaneous inoculation into mice, consistent with a hypervirulence phenotype. The mutant strain had significantly higher in vitro expression of several proven and putative virulence genes, including scpA, encoding a peptidase that inactivates complement protein C5a. Together, the data provide new information about previously uncharacterized GAS TCSs.

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Redundant Catalases Detoxify Phagocyte Reactive Oxygen and Facilitate Histoplasma capsulatum Pathogenesis

Infection and Immunity ◽

10.1128/iai.00173-13 ◽

2013 ◽

Vol 81 (7) ◽

pp. 2334-2346 ◽

Cited By ~ 35

Author(s):

Eric D. Holbrook ◽

Katherine A. Smolnycki ◽

Brian H. Youseff ◽

Chad A. Rappleye

Keyword(s):

Immune System ◽

Innate Immune System ◽

Histoplasma Capsulatum ◽

Reactive Oxygen ◽

Innate Immune ◽

Respiratory Pathogen ◽

Human Neutrophils ◽

Content Type

ABSTRACTHistoplasma capsulatumis a respiratory pathogen that infects phagocytic cells. The mechanisms allowingHistoplasmato overcome toxic reactive oxygen molecules produced by the innate immune system are an integral part ofHistoplasma's ability to survive during infection. To probe the contribution ofHistoplasmacatalases in oxidative stress defense, we created and analyzed the virulence defects of mutants lacking CatB and CatP, which are responsible for extracellular and intracellular catalase activities, respectively. Both CatB and CatP protectedHistoplasmafrom peroxide challengein vitroand from antimicrobial reactive oxygen produced by human neutrophils and activated macrophages. Optimal protection required both catalases, as the survival of a double mutant lacking both CatB and CatP was lower than that of single-catalase-deficient cells. Although CatB contributed to reactive oxygen species defensesin vitro, CatB was dispensable for lung infection and extrapulmonary disseminationin vivo. Loss of CatB from a strain also lacking superoxide dismutase (Sod3) did not further reduce the survival ofHistoplasmayeasts. Nevertheless, some catalase function was required for pathogenesis since simultaneous loss of both CatB and CatP attenuatedHistoplasmavirulencein vivo. These results demonstrate thatHistoplasma's dual catalases comprise a system that enablesHistoplasmato efficiently overcome the reactive oxygen produced by the innate immune system.

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Comparative analysis of neutrophil and monocyte epigenomes

10.1101/237784 ◽

2017 ◽

Cited By ~ 1

Author(s):

Daniel Rico ◽

Joost HA Martens ◽

Kate Downes ◽

Enrique Carrillo-de-Santa-Pau ◽

Vera Pancaldi ◽

...

Keyword(s):

Dna Methylation ◽

Immune System ◽

Innate Immune System ◽

Regulatory Elements ◽

Innate Immune ◽

Human Neutrophils ◽

Integrated Analysis ◽

Differentiation Potential ◽

Differentiated Cells ◽

Health And Disease

ABSTRACTNeutrophils and monocytes provide a first line of defense against infections as part of the innate immune system. Here we report the integrated analysis of transcriptomic and epigenetic landscapes for circulating monocytes and neutrophils with the aim to enable downstream interpretation and functional validation of key regulatory elements in health and disease. We collected RNA-seq data, ChIP-seq of six histone modifications and of DNA methylation by bisulfite sequencing at base pair resolution from up to 6 individuals per cell type. Chromatin segmentation analyses suggested that monocytes have a higher number of cell-specific enhancer regions (4-fold) compared to neutrophils. This highly plastic epigenome is likely indicative of the greater differentiation potential of monocytes into macrophages, dendritic cells and osteoclasts. In contrast, most of the neutrophil-specific features tend to be characterized by repressed chromatin, reflective of their status as terminally differentiated cells. Enhancers were the regions where most of differences in DNA methylation between cells were observed, with monocyte-specific enhancers being generally hypomethylated. Monocytes show a substantially higher gene expression levels than neutrophils, in line with epigenomic analysis revealing that gene more active elements in monocytes. Our analyses suggest that the overexpression of c-Myc in monocytes and its binding to monocyte-specific enhancers could be an important contributor to these differences. Altogether, our study provides a comprehensive epigenetic chart of chromatin states in primary human neutrophils and monocytes, thus providing a valuable resource for studying the regulation of the human innate immune system.

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Regulation of plant antiviral defense genes via host RNA-silencing mechanisms

Virology Journal ◽

10.1186/s12985-021-01664-3 ◽

2021 ◽

Vol 18 (1) ◽

Author(s):

Paola Leonetti ◽

Johannes Stuttmann ◽

Vitantonio Pantaleo

Keyword(s):

Immune System ◽

Innate Immune System ◽

Rna Silencing ◽

Molecular Mechanisms ◽

Limited Range ◽

Innate Immune ◽

Transcriptional Level ◽

Regulatory Systems ◽

Viral Components ◽

Resistance To Viruses

Abstract Background Plants in nature or crops in the field interact with a multitude of beneficial or parasitic organisms, including bacteria, fungi and viruses. Viruses are highly specialized to infect a limited range of host plants, leading in extreme cases to the full invasion of the host and a diseased phenotype. Resistance to viruses can be mediated by various passive or active mechanisms, including the RNA-silencing machinery and the innate immune system. Main text RNA-silencing mechanisms may inhibit viral replication, while viral components can elicit the innate immune system. Viruses that successfully enter the plant cell can elicit pattern-triggered immunity (PTI), albeit by yet unknown mechanisms. As a counter defense, viruses suppress PTI. Furthermore, viral Avirulence proteins (Avr) may be detected by intracellular immune receptors (Resistance proteins) to elicit effector-triggered immunity (ETI). ETI often culminates in a localized programmed cell death reaction, the hypersensitive response (HR), and is accompanied by a potent systemic defense response. In a dichotomous view, RNA silencing and innate immunity are seen as two separate mechanisms of resistance. Here, we review the intricate connections and similarities between these two regulatory systems, which are collectively required to ensure plant fitness and resilience. Conclusions The detailed understanding of immune regulation at the transcriptional level provides novel opportunities for enhancing plant resistance to viruses by RNA-based technologies. However, extensive use of RNA technologies requires a thorough understanding of the molecular mechanisms of RNA gene regulation. We describe the main examples of host RNA-mediated regulation of virus resistance.

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