scholarly journals Autophagy and Lc3-Associated Phagocytosis in Zebrafish Models of Bacterial Infections

Cells ◽  
2020 ◽  
Vol 9 (11) ◽  
pp. 2372
Author(s):  
Salomé Muñoz-Sánchez ◽  
Michiel van der Vaart ◽  
Annemarie H. Meijer
Keyword(s):  
Defense Mechanisms ◽  
Bacterial Infections ◽  
Shigella Flexneri ◽  
Host Cells ◽  
Bacterial Degradation ◽  
Phagocytic Cells ◽  
Infection Models ◽  
Novel Therapeutic Strategies ◽  
Ubiquitin Receptors

Modeling human infectious diseases using the early life stages of zebrafish provides unprecedented opportunities for visualizing and studying the interaction between pathogens and phagocytic cells of the innate immune system. Intracellular pathogens use phagocytes or other host cells, like gut epithelial cells, as a replication niche. The intracellular growth of these pathogens can be counteracted by host defense mechanisms that rely on the autophagy machinery. In recent years, zebrafish embryo infection models have provided in vivo evidence for the significance of the autophagic defenses and these models are now being used to explore autophagy as a therapeutic target. In line with studies in mammalian models, research in zebrafish has shown that selective autophagy mediated by ubiquitin receptors, such as p62, is important for host resistance against several bacterial pathogens, including Shigella flexneri, Mycobacterium marinum, and Staphylococcus aureus. Furthermore, an autophagy related process, Lc3-associated phagocytosis (LAP), proved host beneficial in the case of Salmonella Typhimurium infection but host detrimental in the case of S. aureus infection, where LAP delivers the pathogen to a replication niche. These studies provide valuable information for developing novel therapeutic strategies aimed at directing the autophagy machinery towards bacterial degradation.

scholarly journals Small-Molecule Type III Secretion System Inhibitors Block Assembly of the Shigella Type III Secreton

2008 ◽  
Vol 191 (2) ◽  
pp. 563-570 ◽  
Author(s):  
Andreas K. J. Veenendaal ◽  
Charlotta Sundin ◽  
Ariel J. Blocker
Keyword(s):  
Type Iii Secretion ◽  
Bacterial Infections ◽  
Shigella Flexneri ◽  
Effector Proteins ◽  
Host Cells ◽  
Incomplete Penetrance ◽  
Secretion Systems ◽  
Bacterial Surface ◽  
Type Iii ◽  
Type Iii Secretion Systems

ABSTRACT Type III secretion systems (T3SSs) are essential virulence devices for many gram-negative bacteria that are pathogenic for plants, animals, and humans. They serve to translocate virulence effector proteins directly into eukaryotic host cells. T3SSs are composed of a large cytoplasmic bulb and a transmembrane region into which a needle is embedded, protruding above the bacterial surface. The emerging antibiotic resistance of bacterial pathogens urges the development of novel strategies to fight bacterial infections. Therapeutics that rather than kill bacteria only attenuate their virulence may reduce the frequency or progress of resistance emergence. Recently, a group of salicylidene acylhydrazides were identified as inhibitors of T3SSs in Yersinia, Chlamydia, and Salmonella species. Here we show that these are also effective on the T3SS of Shigella flexneri, where they block all related forms of protein secretion so far known, as well as the epithelial cell invasion and induction of macrophage apoptosis usually demonstrated by this bacterium. Furthermore, we show the first evidence for the detrimental effect of these compounds on T3SS needle assembly, as demonstrated by increased numbers of T3S apparatuses without needles or with shorter needles. Therefore, the compounds generate a phenocopy of T3SS export apparatus mutants but with incomplete penetrance. We discuss why this would be sufficient to almost completely block the later secretion of effector proteins and how this begins to narrow the search for the molecular target of these compounds.

scholarly journals Virulent Shigella flexneri subverts the host innate immune response through manipulation of antimicrobial peptide gene expression

2008 ◽  
Vol 205 (5) ◽  
pp. 1121-1132 ◽  
Author(s):  
Brice Sperandio ◽  
Béatrice Regnault ◽  
Jianhua Guo ◽  
Zhi Zhang ◽  
Samuel L. Stanley ◽  
...  
Keyword(s):  
Innate Immunity ◽  
Shigella Flexneri ◽  
Host Cells ◽  
Virulence Plasmid ◽  
Cationic Peptides ◽  
Immunity Genes ◽  
Genes Encoding ◽  
Peptide Gene

Antimicrobial factors are efficient defense components of the innate immunity, playing a crucial role in the intestinal homeostasis and protection against pathogens. In this study, we report that upon infection of polarized human intestinal cells in vitro, virulent Shigella flexneri suppress transcription of several genes encoding antimicrobial cationic peptides, particularly the human β-defensin hBD-3, which we show to be especially active against S. flexneri. This is an example of targeted survival strategy. We also identify the MxiE bacterial regulator, which controls a regulon encompassing a set of virulence plasmid-encoded effectors injected into host cells and regulating innate signaling, as being responsible for this dedicated regulatory process. In vivo, in a model of human intestinal xenotransplant, we confirm at the transcriptional and translational level, the presence of a dedicated MxiE-dependent system allowing S. flexneri to suppress expression of antimicrobial cationic peptides and promoting its deeper progression toward intestinal crypts. We demonstrate that this system is also able to down-regulate additional innate immunity genes, such as the chemokine CCL20 gene, leading to compromised recruitment of dendritic cells to the lamina propria of infected tissues. Thus, S. flexneri has developed a dedicated strategy to weaken the innate immunity to manage its survival and colonization ability in the intestine.

scholarly journals A critical role of the T3SS effector EseJ in intracellular trafficking and replication ofEdwardsiella piscicidain non-phagocytic cells

2018 ◽  
Author(s):  
Lingzhi Zhang ◽  
Jiatiao Jiang ◽  
Tianjian Hu ◽  
Jin Zhang ◽  
Xiaohong Liu ◽  
...  
Keyword(s):  
Bacterial Colonization ◽  
Critical Role ◽  
Host Cells ◽  
Intracellular Replication ◽  
Phagocytic Cells ◽  
T3ss Effector ◽  
Early Endosomes ◽  
Underlying Mechanisms ◽  
Endosome Maturation

AbstractEdwardsiella piscicida(E. piscicida) is an intracellular pathogen within a broad spectrum of hosts. Essential toE. piscicidavirulence is its ability to survive and replicate inside host cells, yet the underlying mechanisms and the nature of the replicative compartment remain unclear. Here, we characterized its intracellular lifestyle in non-phagocytic cells and showed that intracellular replication ofE. piscicidain non-phagocytic cells is dependent on its type III secretion system. Following internalization,E. piscicidais contained in vacuoles that transiently mature into early endosomes, but subsequently bypasses the classical endosome pathway and fusion with lysosomes which depends on its T3SS. Following a rapid escape from the degradative pathway,E. piscicidawas found to create a specialized replication-permissive niche characterized by endoplasmic reticulum (ER) markers. We also found that a T3SS effector EseJ is responsible for intracellular replication ofE. piscicidaby preventing endosome/lysosome fusion. Furthermore,in vivoexperiments confirmed that EseJ is necessary for bacterial colonization ofE. piscicidain both mice and zebrafish. Thus, this work elucidates the strategies used byE. piscicidato survive and proliferate within host non-phagocytic cells.Author summaryE. piscicidais a facultative intracellular bacterium associated with septicemia and fatal infections in many animals, including fish and humans. However, little is known about its intracellular life, which is important for successful invasion of the host. The present study is the first comprehensive characterization ofE. piscicida’s intracellular life-style in host cells. Upon internalization,E. piscicidais transiently contained in Rab5-positive vacuoles, but the pathogen prevents further endosome maturation and fusion with lysosomes by utilizing an T3SS effector EseJ. In addition, the bacterium creates an specialized replication niche for rapid growth via an interaction with the ER. Our study provides new insights into the strategies used byE. piscicidato successfully establishes an intracellular lifestyle that contributes to its survival and dissemination during infection.

scholarly journals STUDIES ON TUBERCULIN FEVER

1970 ◽  
Vol 131 (3) ◽  
pp. 483-498 ◽  
Author(s):  
William J. Hall ◽  
Lorraine Francis ◽  
Elisha Atkins
Keyword(s):  
Mononuclear Cells ◽  
Reticuloendothelial System ◽  
Passive Transfer ◽  
Host Cells ◽  
Endogenous Pyrogen ◽  
Phagocytic Cells ◽  
Lymph Node Cells ◽  
Intermediate Substance

Utilizing techniques of passive transfer, we have investigated the factors responsible for production of fever when tuberculin is given intravenously to specifically sensitized rabbits. The ability to develop a febrile response to tuberculin could be passively transferred to normal recipients with viable mononuclear cells from peritoneal exudates, spleen, or lymph nodes of donor rabbits sensitized with BCG. Sensitivity was usually apparent 48 hr after transfer, maximal at 7 to 14 days, and rapidly declined thereafter. Granulocytes and nonviable, sonicated, mononuclear cells from similarly sensitized donors were unable to transfer this form of reactivity. Passive transfer of reactivity was also effected with plasma and serum, suggesting that the reaction of antibody with antigen contained in tuberculin is one of the initial steps by which the host cells are activated to release the endogenous pyrogen (EP) that mediates this form of hypersensitivity fever. An intravenous infusion of granulocytes, as well as of several types of mononuclear cells from sensitized donors, made most recipients responsive to the pyrogenic effect of old tuberculin (OT) given 2 hr later. Some of these passively transferred cells, such as the granulocyte and alveolar macrophage, may be activated in vivo by OT, as they are in vitro. However, in the case of splenic and lymph node cells that cannot be activated by OT to produce EP in vitro, it seems likely that an intravenous injection of OT causes these transferred, sensitized cells to liberate an intermediate substance that either directly, or in association with antigen, activates the host's normal cells to produce EP. In support of previous suggestions that leukocytes of several types, as well as phagocytic cells of the reticuloendothelial system, serve as potential sources of EP in tuberculin-induced fever, evidence was presented that OT also activates both granulocytes and mononuclear cells from sterile exudates of BCG-sensitized donors to produce EP in vitro.

scholarly journals Surfactant Protein D Increases Phagocytosis of Hypocapsular Cryptococcus neoformans by Murine Macrophages and Enhances Fungal Survival

2009 ◽  
Vol 77 (7) ◽  
pp. 2783-2794 ◽  
Author(s):  
Scarlett Geunes-Boyer ◽  
Timothy N. Oliver ◽  
Guilhem Janbon ◽  
Jennifer K. Lodge ◽  
Joseph Heitman ◽  
...  
Keyword(s):  
Cryptococcus Neoformans ◽  
Defense Mechanisms ◽  
Protein A ◽  
Surfactant Protein ◽  
Immune Defense ◽  
Surfactant Protein D ◽  
Wild Type ◽  
Phagocytic Cells

ABSTRACT Cryptococcus neoformans is a facultative intracellular opportunistic pathogen and the leading cause of fungal meningitis in humans. In the absence of a protective cellular immune response, the inhalation of C. neoformans cells or spores results in pulmonary infection. C. neoformans cells produce a polysaccharide capsule composed predominantly of glucuronoxylomannan, which constitutes approximately 90% of the capsular material. In the lungs, surfactant protein A (SP-A) and SP-D contribute to immune defense by facilitating the aggregation, uptake, and killing of many microorganisms by phagocytic cells. We hypothesized that SP-D plays a role in C. neoformans pathogenesis by binding to and enhancing the phagocytosis of the yeast. Here, the abilities of SP-D to bind to and facilitate the phagocytosis and survival of the wild-type encapsulated strain H99 and the cap59Δ mutant hypocapsular strain are assessed. SP-D binding to cap59Δ mutant cells was approximately sixfold greater than binding to wild-type cells. SP-D enhanced the phagocytosis of cap59Δ cells by approximately fourfold in vitro. To investigate SP-D binding in vivo, SP-D−/− mice were intranasally inoculated with Alexa Fluor 488-labeled cap59Δ or H99 cells. By confocal microscopy, a greater number of phagocytosed C. neoformans cells in wild-type mice than in SP-D−/− mice was observed, consistent with in vitro data. Interestingly, SP-D protected C. neoformans cells against macrophage-mediated defense mechanisms in vitro, as demonstrated by an analysis of fungal viability using a CFU assay. These findings provide evidence that C. neoformans subverts host defense mechanisms involving surfactant, establishing a novel virulence paradigm that may be targeted for therapy.

scholarly journals Pseudomonas aeruginosa Cytotoxin ExoU Is Injected into Phagocytic Cells during Acute Pneumonia

2010 ◽  
Vol 78 (4) ◽  
pp. 1447-1456 ◽  
Author(s):  
Maureen H. Diaz ◽  
Alan R. Hauser
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Immune Cells ◽  
Type Iii Secretion ◽  
Cell Types ◽  
Secretion System ◽  
Host Cells ◽  
Phagocytic Cells ◽  
Acute Pneumonia

ABSTRACT ExoU, a cytotoxin translocated into host cells via the type III secretion system of Pseudomonas aeruginosa, is associated with increased mortality and disease severity. We previously showed that impairment of recruited phagocytic cells allowed survival of ExoU-secreting P. aeruginosa in the lung. Here we analyzed types of cells injected with ExoU in vivo using translational fusions of ExoU with a β-lactamase reporter (ExoU-Bla). Cells injected with ExoU-Bla were detectable in vitro but not in vivo, presumably due to the rapid cytotoxicity induced by the toxin. Therefore, we used a noncytotoxic ExoU variant, designated ExoU(S142A)-Bla, to analyze injection in vivo. We determined that phagocytic cells in the lung were frequently injected with ExoU(S142A). Early during infection, resident macrophages constituted the majority of cells into which ExoU was injected, but neutrophils and monocytes became the predominant types of cells into which ExoU was injected upon recruitment into the lung. We observed a modest preference for injection into neutrophils over injection into other cell types, but in general the repertoire of injected immune cells reflected the relative abundance of these cells in the lung. Our results indicate that phagocytic cells in the lung are injected with ExoU and support the hypothesis that ExoU-mediated impairment of phagocytes has a role in the pathogenesis of pneumonia caused by P. aeruginosa.

scholarly journals Edwardsiella piscicida interferes with classical endocytic trafficking and replicates in a specialized replication-permissive niche in non-phagocytic cells

2021 ◽  
Author(s):  
Lingzhi Zhang ◽  
Jiatiao Jiang ◽  
Jin Zhang ◽  
Xiaohong Liu ◽  
Dahai Yang ◽  
...  
Keyword(s):  
Bacterial Colonization ◽  
Secretion System ◽  
Host Cells ◽  
Intracellular Replication ◽  
Type Vi Secretion System ◽  
Phagocytic Cells ◽  
T3ss Effector ◽  
Early Endosomes ◽  
Edwardsiella Piscicida

Edwardsiella piscicida ( E. piscicida ) is an intracellular pathogen within a broad spectrum of hosts. Essential to E. piscicida virulence is its ability to invade and replicate inside host cells, yet the survival mechanisms and the nature of the replicative compartment remain unknown. Here, we characterized its intracellular lifestyle in non-phagocytic cells and showed that intracellular replication of E. piscicida in non-phagocytic cells is dependent on its type III secretion system but not type VI secretion system. Following internalization, E. piscicida is contained in vacuoles that transiently mature into early endosomes but subsequently bypasses the classical endosome pathway and fusion with lysosomes which depend on its T3SS. Following a rapid escape from the degradative pathway, E. piscicida was found to create a specialized replication-permissive niche characterized by endoplasmic reticulum (ER) markers. Furthermore, we found that a T3SS effector EseJ is responsible for intracellular replication of E. piscicida by preventing endosome/lysosome fusion. In vivo experiments also confirmed that EseJ is necessary for bacterial colonization of E. piscicida in the epithelial layer followed by systemic dissemination both in zebrafish and mice. Thus, this work elucidates the tactics used by E. piscicida to survive and proliferate within host non-phagocytic cells. IMPORTANCE E. piscicida is a facultative intracellular bacterium associated with septicemia and fatal infections in many animals, including fish and humans. However, little is known about its intracellular life, which is important for successful invasion of the host. The present study is the first comprehensive characterization of E. piscicida ’s intracellular life-style in host cells. Upon internalization, E. piscicida is transiently contained in Rab5-positive vacuoles, but the pathogen prevents further endosome maturation and fusion with lysosomes by utilizing a T3SS effector EseJ. In addition, the bacterium creates a specialized replication niche for rapid growth via an interaction with the ER. Our study provides new insights into the strategies used by E. piscicida to successfully establishes an intracellular lifestyle that contributes to its survival and dissemination during infection.

scholarly journals Stabilin-1 plays a protective role against Listeria monocytogenes infection through the regulation of cytokine and chemokine production and immune cell recruitment

2021 ◽  
Author(s):  
Rita Pombinho ◽  
Jorge Pinheiro ◽  
Mariana Resende ◽  
Diana Meireles ◽  
Sirpa Jalkanen ◽  
...  
Keyword(s):  
Listeria Monocytogenes ◽  
Defense Mechanisms ◽  
Bacterial Infections ◽  
Immune Cell ◽  
Scavenger Receptor ◽  
Protective Role ◽  
Host Cells ◽  
Cell Trafficking ◽  
Host Cell Membrane ◽  
Chemokine Production

ABSTRACTScavenger receptors are part of a complex surveillance system expressed by host cells to efficiently orchestrate innate immune response against bacterial infections. Stabilin-1 (STAB-1) is a scavenger receptor involved in cell trafficking, inflammation and cancer, however its role in infection remains to be elucidated. Listeria monocytogenes (Lm) is a major intracellular human food-borne pathogen causing severe infections in susceptible hosts. Using a mouse model of infection, we demonstrate here that STAB-1 controls Lm-induced cytokine and chemokine production and immune cell accumulation in Lm-infected organs. We show that STAB-1 also regulates the recruitment of myeloid cells in response to Lm infection and contributes to clear circulating bacteria. In addition, whereas STAB-1 appears to promote bacterial uptake by macrophages, infection by pathogenic Listeria induces the down regulation of STAB-1 expression and its delocalization from the host cell membrane.We propose STAB-1 as a new SR involved in the control of Lm infection through the regulation of host defense mechanisms, a process that would be targeted by bacterial virulence factors to promote infection.

scholarly journals A large panel of chicken cells are invaded in vivo by Salmonella Typhimurium even when depleted of all known invasion factors

2020 ◽  
Author(s):  
S. M. Roche ◽  
S. Holbert ◽  
Y. Le Vern ◽  
C. Rossignol ◽  
A. Rossignol ◽  
...  
Keyword(s):  
Gall Bladder ◽  
Wild Type Strain ◽  
Host Cells ◽  
Poultry Meat ◽  
Tissue Tropism ◽  
Wild Type ◽  
Phagocytic Cells ◽  
Mutant Strains ◽  
Meat And Eggs

AbstractSalmonella are among the most important foodborne pathogens and contaminated poultry meat and eggs are the main source of human infection. Infected poultry are a major problem as they are asymptomatic, thus rendering the identification of infected poultry farms difficult. In this context, controlling animal infections is of primary importance. It is known that cell and tissue tropism govern disease in many infectious models, our aim was therefore to identify the infected host-cell types in chicks and the role of the three known bacterial invasion factors in this process (T3SS-1, Rck and PagN). Chicks were inoculated with wild-type or isogenic fluorescent Salmonella Typhimurium mutant strains via the intraperitoneal route. Then infected cells in the liver, spleen, gall bladder and aortic vessels were identified using flow-cytometric analyses and invasion confirmed by confocal microscopy. Our results show that all these organs could be foci of infection and that a wide array of phagocytic and non-phagocytic cells is invaded in vivo in each organ. These cells include immune cells and also epithelial and endothelial cells. Moreover, we demonstrated that, despite the invalidation of the three known invasion factors (T3SS-1, Rck and PagN), S. Typhimurium remained able to colonize internal organs and invade non-phagocytic cells in each organ studied. In line with this result, the mutant strains colonized these organs more efficiently than the wild-type strain. S. Typhimurium invasion of gall bladder cells was confirmed by immunohistochemistry and infection was shown to last several weeks after inoculation of chicks and at a level similar to that observed in the spleen. All together, these findings provide new insights into the dynamics of Salmonella spread in vivo in chicks at the organ and cellular levels.Author summaryIn many infectious models, cell and tissue tropism govern disease. Moreover, depending on the entry process, both bacterial behavior and host response are different. It is therefore important to identify the host cells targeted in vivo by a pathogen and the entry routes used by this pathogen to invade the different host cells. This is all the more important with a pathogen that enters cells in several ways like Salmonella, which is responsible for human and animal salmonellosis. As poultry meat and eggs are the main sources of human contamination, controlling animal infections is of primary importance. In this paper, we identified a large array of phagocytic and non-phagocytic cells targeted in vivo using fluorescent Salmonella Typhimurium strains inoculated by the intraperitoneal route. Surprisingly, the same host cells were infected by the wild-type strain or its isogenic mutants deleted of either the T3SS-1 or of the three known invasion factors (T3SS-1, Rck and PagN). These cells were immune cells but also epithelial and endothelial cells. Moreover, we demonstrated for the first time that the gall bladder and the aortic vessels could be foci of infection in chicks in addition to the liver and spleen.

Alcohol-induced downregulation of superoxide anion release by hepatic phagocytes in endotoxemic rats

1991 ◽  
Vol 260 (5) ◽  
pp. R969-R976
Author(s):  
A. P. Bautista ◽  
N. B. D'Souza ◽  
C. H. Lang ◽  
J. Bagwell ◽  
J. J. Spitzer
Keyword(s):  
Kupffer Cells ◽  
Superoxide Anion ◽  
Defense Mechanisms ◽  
Immune Defense ◽  
Polymorphonuclear Neutrophils ◽  
Ethanol Administration ◽  
Ethanol Intoxication ◽  
Phagocytic Cells

Bacterial endotoxins [lipopolysaccharide (LPS)] are potent immunomodulators, and ethanol is known to depress certain immune defense mechanisms. Thus the combined impact of these two agents on the generation of superoxide anion (O2(-).) by isolated hepatic phagocytic cells was investigated. Ethanol was infused intravenously into rats for 7 h, and Escherichia coli LPS was injected intravenously at 4 h after ethanol administration. Control groups received an equal volume of saline or ethanol alone. Nonparenchymal cells that were composed of endothelial and Kupffer cells and few polymorphonuclear neutrophils (PMN; less than 1%) were obtained after collagenase-pronase digestion. In the LPS-treated rats, the total number of PMN per liver increased significantly. Histological sections of the liver showed PMN infiltration and areas of necrosis after LPS treatment with or without ethanol. In the presence of either phorbol 12-myristate 13-acetate or opsonized zymosan in vitro, Kupffer cells and hepatic PMN from LPS-treated rats generated large amounts of O2(-).. Ethanol intoxication in vitro by these cells to 50%. Ethanol alone (without LPS) had no effect on the production of O2(-).. These studies demonstrate that ethanol intoxication was associated with the downregulation of the LPS-enhanced in vivo priming of hepatic phagocytes to generate O2(-). in vitro and may thus contribute to the enhanced susceptibility of alcoholic subjects to develop an infection.

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