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 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 Bacterial T6SS Effector EvpP Inhibits Neutrophil Recruitment via Jnk-Caspy Inflammasome Signaling In vivo

2018 ◽  
Author(s):  
Jinchao Tan ◽  
Dahai Yang ◽  
Zhuang Wang ◽  
Xin Zheng ◽  
Yuanxing Zhang ◽  
...  
Keyword(s):  
Bacterial Colonization ◽  
Critical Role ◽  
Neutrophil Recruitment ◽  
Host Cells ◽  
Infection Model ◽  
Inflammasome Activation ◽  
Type Vi Secretion System ◽  
Zebrafish Larvae

ABSTRACTThe type VI secretion system (T6SS) comprises dynamic complex bacterial contractile nanomachines and is used by many bacteria to inhibit or kill other prokaryotic or eukaryotic cells. Previous studies have revealed that T6SS is constitutively active in response to various stimuli, or fires effectors into host cells during infection. It has been proposed that the T6SS effector EvpP in Edwardsiella piscicida can inhibit NLRP3 inflammasome activation via the Ca2+-dependent JNK pathways. Here, we developed an in vivo infection model by microinjecting bacteria into the tail vein muscle of 3-day-post-fertilized zebrafish larvae, and found that both macrophages and neutrophils are essential for bacterial clearance. Further study revealed that EvpP plays a critical role in promoting the pathogenesis of E. piscicida via inhibiting the phosphorylation of Jnk signaling to reduce the expression of cxcl8a, mmp13 and IL-1β in vivo. Subsequently, by utilizing Tg (mpo:eGFP+/+) zebrafish larvae for E. piscicida infection, we found that the EvpP-inhibited Jnk-caspy inflammasome signaling axis significantly suppressed the recruitment of neutrophils to infection sites, and the caspy‐ or IL-1β-MO knockdown larvae were more susceptible to infection and failed to restrict bacterial colonization in vivo.IMPORTANCEInnate immunity is regulated by phagocytic cells and is critical for host control of bacterial infection. In many bacteria, T6SSs can affect bacterial virulence in certain environments, but little is known about the mechanisms underlying T6SS regulation of innate immune responses during infection in vivo. Here, we investigated the role of an E. piscicida T6SS effector EvpP in manipulating the reaction of neutrophils in vivo. We show that EvpP inhibits the activation of Jnk-caspy inflammasome pathway in zebrafish larvae, and reveal that macrophages are essential for neutrophil recruitment in vivo. This interaction improves our understanding about the complex and contextual role of a bacterial T6SS effector in modulating the action of myeloid cells during infection, and offers new insights into the warfare between bacterial weapons and host immunological surveillance.

scholarly journals Epitope specificity plays a critical role in regulating antibody-dependent cell-mediated cytotoxicity against influenza A virus

2016 ◽  
Vol 113 (42) ◽  
pp. 11931-11936 ◽  
Author(s):  
Wenqian He ◽  
Gene S. Tan ◽  
Caitlin E. Mullarkey ◽  
Amanda J. Lee ◽  
Mannie Man Wai Lam ◽  
...  
Keyword(s):  
Influenza Virus ◽  
Influenza A Virus ◽  
Neutralizing Antibodies ◽  
Influenza A ◽  
Critical Role ◽  
Host Cells ◽  
Viral Glycoprotein ◽  
Effector Functions ◽  
Dependent Cell

The generation of strain-specific neutralizing antibodies against influenza A virus is known to confer potent protection against homologous infections. The majority of these antibodies bind to the hemagglutinin (HA) head domain and function by blocking the receptor binding site, preventing infection of host cells. Recently, elicitation of broadly neutralizing antibodies which target the conserved HA stalk domain has become a promising “universal” influenza virus vaccine strategy. The ability of these antibodies to elicit Fc-dependent effector functions has emerged as an important mechanism through which protection is achieved in vivo. However, the way in which Fc-dependent effector functions are regulated by polyclonal influenza virus-binding antibody mixtures in vivo has never been defined. Here, we demonstrate that interactions among viral glycoprotein-binding antibodies of varying specificities regulate the magnitude of antibody-dependent cell-mediated cytotoxicity induction. We show that the mechanism responsible for this phenotype relies upon competition for binding to HA on the surface of infected cells and virus particles. Nonneutralizing antibodies were poor inducers and did not inhibit antibody-dependent cell-mediated cytotoxicity. Interestingly, anti-neuraminidase antibodies weakly induced antibody-dependent cell-mediated cytotoxicity and enhanced induction in the presence of HA stalk-binding antibodies in an additive manner. Our data demonstrate that antibody specificity plays an important role in the regulation of ADCC, and that cross-talk among antibodies of varying specificities determines the magnitude of Fc receptor-mediated effector functions.

The Legionella pneumophila effector RavY contributes to a replication-permissive vacuolar environment during infection

2021 ◽  
Author(s):  
Luying Liu ◽  
Craig R. Roy
Keyword(s):  
Legionella Pneumophila ◽  
Effector Proteins ◽  
Type Iv Secretion ◽  
Host Cells ◽  
Effector Protein ◽  
Intracellular Replication ◽  
Phagocytic Cells ◽  
Host Molecules ◽  
Type Iv ◽  
Legionnaires Disease

Legionella pneumophila is the causative agent of Legionnaires’ Disease and is capable replicating inside phagocytic cells such as mammalian macrophages. The Dot/Icm type IV secretion system is a L. pneumophila virulence factor that is essential for successful intracellular replication. During infection, L. pneumophila builds a replication permissive vacuole by recruiting multiple host molecules and hijacking host cellular signaling pathways, a process mediated by the coordinated functions of multiple Dot/Icm effector proteins. RavY is a predicted Dot/Icm effector protein found to be important for optimal L. pneumophila replication inside host cells. Here, we demonstrate that RavY is a Dot/Icm-translocated effector protein that is dispensable for axenic replication of L. pneumophila , but critical for optimal intracellular replication of the bacteria. RavY is not required for avoidance of endosomal maturation, nor does RavY contribute to the recruitment of host molecules found on replication-permissive vacuoles, such as ubiquitin, RAB1a, and RTN4. Vacuoles containing L. pneumophila ravY mutants promote intracellular survival but limit replication. The replication defect of the L. pneumophila ravY mutant was complemented when the mutant was in the same vacuole as wild type L. pneumophila . Thus, RavY is an effector that is essential for promoting intracellular replication of L. pneumophila once the specialized vacuole has been established.

scholarly journals Novel Salmonella enterica Serovar Typhimurium Protein That Is Indispensable for Virulence and Intracellular Replication

2001 ◽  
Vol 69 (12) ◽  
pp. 7413-7418 ◽  
Author(s):  
Tahar van der Straaten ◽  
Angela van Diepen ◽  
Kitty Kwappenberg ◽  
Sjaak van Voorden ◽  
Kees Franken ◽  
...  
Keyword(s):  
Amino Acid ◽  
Protein Function ◽  
Salmonella Enterica ◽  
Host Cells ◽  
Wild Type ◽  
Intracellular Replication ◽  
Oxygen Intermediates ◽  
Serovar Typhimurium

ABSTRACT Upon contact with host cells, the intracellular pathogenSalmonella enterica serovar Typhimurium promotes its uptake, targeting, and survival in intracellular niches. In this process, the bacterium evades the microbicidal effector mechanisms of the macrophage, including oxygen intermediates. This study reports the phenotypic and genotypic characterization of an S. enterica serovar Typhimurium mutant that is hypersusceptible to superoxide. The susceptible phenotype is due to a MudJ insertion-inactivation of a previously undescribedSalmonella gene designated sspJ that is located between 54.4 and 64 min of the Salmonellachromosome and encodes a 392-amino-acid protein. In vivo, upon intraperitoneal injection of 104 to 107bacteria in C3H/HeN and 101 to 104 bacteria in BALB/c mice, the mutant strain was less virulent than the wild type. Consistent with this finding, during the first hour after ingestion by macrophage-like J774 and RAW264.7 cells in vitro, the intracellular killing of the strain carrying sspJ::MudJ is enhanced fivefold over that of wild-type microorganisms. Wild-type salmonellae displayed significant intracellular replication during the first 24 h after uptake, but sspJ::MudJ mutants failed to do so. This phenotype could be restored to that of the wild type by sspJ complementation. The SspJ protein is found in the cytoplasmic membrane and periplasmic space. Amino acid sequence homology analysis did reveal a leader sequence and putative pyrroloquinoline quinone-binding domains, but no putative protein function. We excluded the possibility that SspJ is a scavenger of superoxide or has superoxide dismutase activity.

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 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 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.

scholarly journals Siderophore-Mediated Iron Acquisition Plays a Critical Role in Biofilm Formation and Survival of Staphylococcus epidermidis Within the Host

2021 ◽  
Vol 8 ◽  
Author(s):  
Fernando Oliveira ◽  
Tânia Lima ◽  
Alexandra Correia ◽  
Ana Margarida Silva ◽  
Cristina Soares ◽  
...  
Keyword(s):  
Staphylococcus Epidermidis ◽  
Iron Acquisition ◽  
Critical Role ◽  
Siderophore Production ◽  
Restricted Environment ◽  
Underlying Mechanisms ◽  
First Time ◽  
Comprehensive Study

Iron acquisition through siderophores, a class of small, potent iron-chelating organic molecules, is a widely spread strategy among pathogens to survive in the iron-restricted environment found in the host. Although these molecules have been implicated in the pathogenesis of several species, there is currently no comprehensive study addressing siderophore production in Staphylococcus epidermidis. Staphylococcus epidermidis is an innocuous skin commensal bacterium. The species, though, has emerged as a leading cause of implant-associated infections, significantly supported by an inherent ability to form biofilms. The process of adaptation from skin niche environments to the hostile conditions during invasion is yet not fully understood. Herein, we addressed the possible role of siderophore production in S. epidermidis virulence. We first identified and deleted a siderophore homolog locus, sfaABCD, and provided evidence for its involvement in iron acquisition. Our findings further suggested the involvement of siderophores in the protection against oxidative stress-induced damage and demonstrated the in vivo relevance of a siderophore-mediated iron acquisition during S. epidermidis infections. Conclusively, this study addressed, for the first time in this species, the underlying mechanisms of siderophore production, highlighting the importance of a siderophore-mediated iron acquisition under host relevant conditions and, most importantly, its contribution to survival within the host.

scholarly journals The antioxidant (−)-epigallocatechin-3-gallate inhibits activated hepatic stellate cell growth and suppresses acetaldehyde-induced gene expression

2002 ◽  
Vol 368 (3) ◽  
pp. 695-704 ◽  
Author(s):  
Anping CHEN ◽  
Li ZHANG ◽  
Jianye XU ◽  
Jun TANG
Keyword(s):  
Transforming Growth Factor ◽  
Stellate Cell ◽  
Present Report ◽  
Smooth Muscle Actin ◽  
Critical Role ◽  
Dependent Manner ◽  
Liver Fibrogenesis ◽  
Underlying Mechanisms

Activated hepatic stellate cells (HSC) are the primary source of excessive production of extracellular matrix during liver fibrogenesis. Although the underlying mechanisms remain incompletely understood, it is widely accepted that oxidative stress plays a critical role in liver fibrogenesis. Suppression of HSC growth and activation, as well as induction of apoptosis, have been proposed as therapeutic strategies for treatment and prevention of this disease. In the present report, we elucidated, for the first time, effects of the antioxidant (—)-epigallocatechin-3-gallate (EGCG), a major (and the most active) component of green tea extracts, on cultured HSC growth and activation. Our results revealed that EGCG significantly inhibited cultured HSC growth by inducing cell cycle arrest and apoptosis in a dose- and time-dependent manner. In addition, EGCG markedly suppressed the activation of cultured HSC as demonstrated by blocking transforming growth factor-β signal transduction and by inhibiting the expression of α1(I) collagen, fibronectin and α-smooth muscle actin genes induced by acetaldehyde, the most active metabolite of ethanol. Furthermore, EGCG reacted differently in the inhibition of nuclear factor-κB activity between cultured HSC with or without acetaldehyde stimulation. Taken together, our results indicated that EGCG was a novel and effective inhibitor for activated HSC growth and activation in vitro. Further studies are necessary to evaluate the effect of this polyphenol in prevention of quiescent HSC activation in vivo, and to further elucidate the underlying mechanisms.

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