scholarly journals Role of NADase in Virulence in Experimental Invasive Group A Streptococcal Infection

2005 ◽  
Vol 73 (10) ◽  
pp. 6562-6566 ◽  
Author(s):  
Angela L. Bricker ◽  
Vincent J. Carey ◽  
Michael R. Wessels
Keyword(s):  
Human Infection ◽  
Host Animal ◽  
Cytotoxic Effects ◽  
Invasive Group ◽  
Streptolysin O ◽  
Group A ◽  
Wild Type Parent

ABSTRACT Group A streptococci (GAS) produce several exoproteins that are thought to contribute to the pathogenesis of human infection. Two such proteins, streptolysin O (SLO) and NAD+-glycohydrolase (NADase), have been shown to interact functionally as a compound signaling toxin. When GAS are bound to the surface of epithelial cells in vitro, SLO forms pores in the cell membrane and delivers NADase to the epithelial cell cytoplasm. In vitro, intoxication of keratinocytes with NADase is associated with cytotoxic effects and induction of apoptosis; however, the importance of NADase during infection of an animal host has not been established. We employed isogenic GAS mutants to assess the contribution of NADase activity to GAS virulence in vivo using mouse models of invasive soft-tissue infection and septicemia. In both models, mutant GAS that lacked NADase activity were significantly attenuated for virulence compared with the isogenic wild-type parent, confirming an important role for NADase in the infection of a host animal. A double mutant lacking SLO and NADase activity had an intermediate virulence phenotype, consistent with the hypothesis that SLO evokes a protective innate immune response. We conclude that NADase and SLO together enhance GAS virulence in vivo.

scholarly journals Downregulation of S100A4 Alleviates Cardiac Fibrosis via Wnt/β -Catenin Pathway in Mice

2018 ◽  
Vol 46 (6) ◽  
pp. 2551-2560 ◽  
Author(s):  
LiJun Qian ◽  
Jian Hong ◽  
YanMei Zhang ◽  
MengLin Zhu ◽  
XinChun Wang ◽  
...  
Keyword(s):  
Calcium Binding ◽  
Cardiac Fibrosis ◽  
Cardiac Fibroblasts ◽  
Group A ◽  
Ischemic Diseases ◽  
Fibrotic Diseases ◽  
Signaling Activation

Background/Aims: Cardiac fibrosis is a pathological change leading to cardiac remodeling during the progression of myocardial ischemic diseases, and its therapeutic strategy remains to be explored. S100A4, a calcium-binding protein, participates in fibrotic diseases with an unclear mechanism. This study aimed to investigate the role of S100A4 in cardiac fibrosis. Methods: Cardiac fibroblasts from neonatal C57BL/6 mouse hearts were isolated and cultured. Myocardial infarction was induced by ligating the left anterior descending coronary artery (LAD). The ligation was not performed in the sham group. A volume of 5×105pfu/g adenovirus or 5 µM/g ICG-001 was intramyocardially injected into five parts bordering the infarction zone or normal region. We used Western blotting, quantitative RT-PCR, immunofluorescence, immunohistochemistry and Masson’s trichrome staining to explore the function of S100A4. Results: We found significant increases of S100A4 level and cardiac fibrosis markers, and β-catenin signaling activation in vitro and in vivo. In addition, knockdown of S100A4 significantly reduced cardiac fibrosis and β-catenin levels. Moreover, the expression of S100A4 decreased after ICG-001 inhibited β-catenin signal pathway. Conclusion: Downregulation of S100A4 alleviates cardiac fibrosis via Wnt/β -catenin pathway in mice. S100A4 may be a therapeutic target of cardiac fibrosis.

Role of Streptolysin O in a Mouse Model of Invasive Group A Streptococcal Disease

2000 ◽  
Vol 68 (11) ◽  
pp. 6384-6390 ◽  
Author(s):  
Brandi Limbago ◽  
Vikram Penumalli ◽  
Brian Weinrick ◽  
June R. Scott
Keyword(s):  
Mouse Model ◽  
Invasive Group ◽  
Streptococcal Disease ◽  
Streptolysin O ◽  
Group A

scholarly journals Streptolysin O concentration and activity is central to in vivo phenotype and disease outcome in Group A Streptococcus infection

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Jenny Clarke ◽  
Murielle Baltazar ◽  
Mansoor Alsahag ◽  
Stavros Panagiotou ◽  
Marion Pouget ◽  
...  
Keyword(s):  
Septic Arthritis ◽  
Rapid Development ◽  
Clinical Manifestations ◽  
Disease Outcome ◽  
Haemolytic Activity ◽  
Human Pathogens ◽  
Streptolysin O ◽  
Group A

AbstractGroup A Streptoccocus (GAS) is among the most diverse of all human pathogens, responsible for a range of clinical manifestations, from mild superficial infections such as pharyngitis to serious invasive infections such as necrotising fasciitis and sepsis. The drivers of these different disease phenotypes are not known. The GAS cholesterol-dependent cytolysin, Streptolysin O (SLO), has well established cell and tissue destructive activity. We investigated the role of SLO in determining disease outcome in vivo, by using two different clinical lineages; the recently emerged hypervirulent outbreak emm type 32.2 strains, which result in sepsis, and the emm type 1.0 strains which cause septic arthritis. Using clinically relevant in vivo mouse models of sepsis and a novel septic arthritis model, we found that the amount and activity of SLO was vital in determining the course of infection. The emm type 32.2 strain produced large quantities of highly haemolytic SLO that resulted in rapid development of sepsis. By contrast, the reduced concentration and lower haemolytic activity of emm type 1.0 SLO led to translocation of bacteria from blood to joints. Importantly, sepsis associated strains that were attenuated by deletion or inhibition of SLO, then also translocated to the joint, confirming the key role of SLO in determining infection niche. Our findings demonstrate that SLO is key to in vivo phenotype and disease outcome. Careful consideration should be given to novel therapy or vaccination strategies that target SLO. Whilst neutralising SLO activity may reduce severe invasive disease, it has the potential to promote chronic inflammatory conditions such as septic arthritis.

scholarly journals Streptolysin-induced endoplasmic reticulum stress promotes group A streptococcal in vivo biofilm formation and necrotizing fasciitis

2017 ◽  
Author(s):  
Anuradha Vajjala ◽  
Debabrata Biswas ◽  
Kelvin Kian Long Chong ◽  
Wei Hong Tay ◽  
Emanuel Hanski ◽  
...  
Keyword(s):  
Soft Tissue ◽  
Er Stress ◽  
Necrotizing Fasciitis ◽  
Biofilm Formation ◽  
Mammalian Cells ◽  
Chronic Infections ◽  
Group A

AbstractGroup A Streptococcus (GAS) is a human pathogen that causes infections ranging from mild to fulminant and life-threatening. Biofilms have been implicated in acute GAS soft-tissue infections such as necrotizing fasciitis (NF). However, most in vitro models used to study GAS biofilms have been designed to mimic chronic infections and insufficiently recapitulate in vivo conditions and the host-pathogen interactions that might influence biofilm formation. Here we establish and characterize an in vitro model of GAS biofilm development on mammalian cells that simulates microcolony formation observed in a murine model of human NF. We show that on mammalian cells, GAS forms dense aggregates that display hallmark biofilm characteristics including a three-dimensional architecture and enhanced tolerance to antibiotics. In contrast to abiotic-grown biofilms, host-associated biofilms require the expression of secreted GAS streptolysins O and S (SLO, SLS) resulting in the release of a host-associated biofilm promoting-factor(s). Supernatants from GAS-infected mammalian cells or from cells treated with endoplasmic reticulum (ER) stressors restore biofilm formation to an SLO and SLS null mutant that is otherwise attenuated in biofilm formation on cells, together suggesting a role for streptolysin-induced ER stress in this process. In an in vivo mouse model, the streptolysin-null mutant is attenuated in both microcolony formation and bacterial spread, but pre-treatment of softtissue with an ER-stressor restores the ability of the mutant to form wild type like microcolonies that disseminate throughout the soft tissue. Taken together, we have identified a new role of streptolysin-driven ER stress in GAS biofilm formation and NF disease progression.Significance StatementAlthough it is well-accepted that bacterial biofilms are associated with many chronic infections, little is known about the mechanisms by which group A Streptococcus (GAS) biofilms contribute to acute soft tissue-invasive diseases like necrotizing fasciitis (NF). In this study, we establish a physiologically relevant in vitro model to study GAS biofilm formation on mammalian cells and validate our findings in a mouse model that mimics human NF. This study demonstrates a novel role of GAS streptolysin-mediated ER stress in the development and spread of GAS biofilms in acute softtissue infections. We also show that biofilm formation depends on the release of a host-associated factor that promotes microcolony formation and GAS dissemination in vivo.

scholarly journals Cytotoxic Effects of Streptolysin O and Streptolysin S Enhance the Virulence of Poorly Encapsulated Group A Streptococci

2003 ◽  
Vol 71 (1) ◽  
pp. 446-455 ◽  
Author(s):  
Gabriele Sierig ◽  
Colette Cywes ◽  
Michael R. Wessels ◽  
Cameron D. Ashbaugh
Keyword(s):  
Bacterial Resistance ◽  
Cell Injury ◽  
Natural Infection ◽  
Group A Streptococci ◽  
Cytotoxic Effects ◽  
In Vivo Models ◽  
Streptolysin S ◽  
Streptolysin O ◽  
Group A

ABSTRACT Although the toxicity of streptolysin O (SLO) and streptolysin S (SLS) in purified group A streptococci (GAS) has been established, the effect of these molecules in natural infection is not well understood. To identify whether biologically relevant concentrations of SLO and SLS were cytotoxic to epithelial and phagocytic cells that the bacteria would typically encounter during human infection and to characterize the influence of cell injury on bacterial pathogenesis, we derived GAS strains deficient in SLO or SLS in the background of an invasive GAS M3 isolate and determined their virulence in in vitro and in vivo models of human disease. Whereas bacterial production of SLO resulted in lysis of both human keratinocytes and polymorphonuclear leukocytes, GAS expression of SLS was associated only with keratinocyte injury. Expression of SLO but not SLS impaired polymorphonuclear leukocyte killing of GAS in vitro, but this effect could only be demonstrated in the background of acapsular organisms. In mouse invasive soft-tissue infection, neither SLO or SLS expression significantly influenced mouse survival. By contrast, in a mouse model of bacterial sepsis after intraperitoneal inoculation of GAS, SLO expression enhanced the virulence of both encapsulated and acapsular GAS, whereas SLS expression increased the virulence only of acapsular GAS. We conclude that the cytotoxic effects of SLO protect GAS from phagocytic killing and enhance bacterial virulence, particularly of strains that may be relatively deficient in hyaluronic acid capsule. Compared to SLO, SLS in this strain background has a more modest influence on GAS pathogenicity and the effect does not appear to involve bacterial resistance to phagocytosis.

Targeting Pathological Amyloid Aggregates with Conformation-Sensitive Antibodies

2020 ◽  
Vol 17 (8) ◽  
pp. 722-734
Author(s):  
Alessandra Bigi ◽  
Gilda Loffredo ◽  
Roberta Cascella ◽  
Cristina Cecchi
Keyword(s):  
Senile Plaques ◽  
Neuronal Cells ◽  
Cytotoxic Effects ◽  
Specificity And Sensitivity ◽  
Amyloid Aggregates ◽  
Culture Models ◽  
Therapeutic Tools

Background: The pathogenesis of Alzheimer's disease (AD) is not directly caused by the presence of senile plaques but rather by the detrimental effects exerted on neuronal cells by toxic soluble oligomers. Such species are formed early during the aggregation process of the Aβ1-42 peptide or can be released from mature fibrils. Nowadays, efficient tools for an early diagnosis, as well as pharmaceutical treatments targeting the harmful agents in samples of AD patients, are still missing. Objective: By integrating in vitro immunochemical assay with in vivo neuronal models of toxicity, we aim to understand and target the principles that drive toxicity in AD. Methods: We evaluated the specificity and sensitivity of A11 and OC conformational antibodies to target a range of pathologically relevant amyloid conformers and rescue their cytotoxic effects in neuronal culture models using a number of cellular readouts. Results: We demonstrated the peculiar ability of conformational antibodies to label pathologically relevant Aβ1-42 oligomers and fibrils and to prevent their detrimental effects on neuronal cells. Conclusion: Our results substantially improve our knowledge on the role of toxic assemblies in neurodegenerative diseases, thus suggesting new and more effective diagnostic and therapeutic tools for AD.

Are all granzymes cytotoxic in vivo?

2014 ◽  
Vol 395 (2) ◽  
pp. 181-202 ◽  
Author(s):  
Lars T. Joeckel ◽  
Phillip I. Bird
Keyword(s):  
Serine Proteases ◽  
Ex Vivo ◽  
Cytotoxic Lymphocytes ◽  
Cytotoxic Effects ◽  
Knock Out ◽  
Granzyme A ◽  
Knock Out Mice

Abstract Granzymes are serine proteases mainly found in cytotoxic lymphocytes. The most-studied member of this group is granzyme B, which is a potent cytotoxin that has set the paradigm that all granzymes are cyototoxic. In the last 5 years, this paradigm has become controversial. On one hand, there is a plethora of sometimes contradictory publications showing mainly caspase-independent cytotoxic effects of granzyme A and the so-called orphan granzymes in vitro. On the other hand, there are increasing numbers of reports of granzymes failing to induce cell death in vitro unless very high (potentially supra-physiological) concentrations are used. Furthermore, experiments with granzyme A or granzyme M knock-out mice reveal little or no deficit in their cytotoxic lymphocytes’ killing ability ex vivo, but indicate impairment in the inflammatory response. These findings of non-cytotoxic effects of granzymes challenge dogma, and thus require alternative or additional explanations to be developed of the role of granzymes in defeating pathogens. Here we review evidence for granzyme cytotoxicity, give an overview of their non-cytotoxic functions, and suggest technical improvements for future investigations.

Ganoderma lucidum Polysaccharides: Immunomodulation and Potential Anti-Tumor Activities

2011 ◽  
Vol 39 (01) ◽  
pp. 15-27 ◽  
Author(s):  
Zengtao Xu ◽  
Xiuping Chen ◽  
Zhangfeng Zhong ◽  
Lidian Chen ◽  
Yitao Wang
Keyword(s):  
Ganoderma Lucidum ◽  
Tumor Therapy ◽  
White Rot ◽  
In Vivo Studies ◽  
White Rot Fungus ◽  
Bioactive Substances ◽  
Cytotoxic Effects

Ganoderma lucidum (G. lucidum), a basidiomycete white rot fungus, has long been prescribed to prevent and treat various human diseases, particularly in China, Japan, and Korea. Several classes of bioactive substances have been isolated and identified from G. lucidum, such as triterpenoids, polysaccharides, nucleosides, sterols, and alkaloids, among others. This paper examines the potential role of G. lucidum polysaccharide (GLPS) in tumor therapy and the possible mechanisms involved. Both in vitro and in vivo studies suggested that the anti-tumor activities of GLPS are mediated by its immunomodulatory, anti-angiogenic, and cytotoxic effects. GLPS affects immune cells and immune-related cells including B lymphocytes, T lymphocytes, dendritic cells, macrophages, and natural killer cells. In addition, recent data also suggest that GLPS suppresses tumorigenesis or inhibits tumor growth through direct cytotoxic effect and anti-angiogenic actions. However, many questions still need to be answered before both G. lucidum and GLPS can be widely accepted and used as anti-tumor agents.

scholarly journals Reciprocal, Temporal Expression of SpeA and SpeB by Invasive M1T1 Group A Streptococcal Isolates In Vivo

2001 ◽  
Vol 69 (8) ◽  
pp. 4988-4995 ◽  
Author(s):  
Shahana U. Kazmi ◽  
Rita Kansal ◽  
Ramy K. Aziz ◽  
Massoumeh Hooshdaran ◽  
Anna Norrby-Teglund ◽  
...  
Keyword(s):  
Gene Expression ◽  
Sequential Sampling ◽  
Environmental Signals ◽  
Group A ◽  
Chamber Model ◽  
Kinetics Of ◽  
Chamber Fluid

ABSTRACT The streptococcal pyrogenic exotoxins (Spes) play a central role in the pathogenesis of invasive group A streptococcal (GAS) infections. The majority of recent invasive GAS infections have been caused by an M1T1 strain that harbors the genes for several streptococcal superantigens, including speA, speB,speF, speG, and smeZ. However, considerable variation in the expression of Spe proteins among clonal M1 isolates has been found, and many of thespeA-positive M1 strains do not produce detectable amounts of SpeA in vitro. This study was designed to test the hypothesis that speA gene expression can be induced in vivo. A mouse infection chamber model that allows sequential sampling of GAS isolates at various time points postinfection was developed and used to monitor the kinetics of Spe production in vivo. Micropore Teflon diffusion chambers were implanted subcutaneously in BALB/c mice, and after 3 weeks the pores became sealed with connective tissue and sterile fluid containing a white blood cell infiltrate accumulated inside the infection chambers. Representative clonal M1T1 isolates expressing no detectable SpeA were inoculated into the implanted chambers, and the expression of SpeA in the aspirated aliquots of the chamber fluid was analyzed on successive days postinfection. Expression of SpeA was detected in the chamber fluid as early as days 3 to 5 postinfection in most animals, with a significant increase in expression by day 7 in all infected mice. Isolates recovered from the chamber and grown in vitro continued to produce SpeA even after 21 passages in vitro, suggesting stable switch on of thespeA gene. A temporal relation between the upregulation of SpeA expression and the downregulation of SpeB expression was observed in vivo. These data suggest that in vivo host and/or environmental signals induced speA gene expression and suppressed speB gene expression. This underscores the role of the host-pathogen interaction in regulating the expression of streptococcal virulence factors in vivo. The model described here should facilitate such studies.

scholarly journals STAT2 Limits Host Species Specificity of Human Metapneumovirus

Viruses ◽  
2020 ◽  
Vol 12 (7) ◽  
pp. 724
Author(s):  
Meredith C. Rogers ◽  
Margot Miranda-Katz ◽  
Yu Zhang ◽  
Tim D. Oury ◽  
Melissa B. Uccellini ◽  
...  
Keyword(s):  
Human Infection ◽  
Human Metapneumovirus ◽  
Innate Immune ◽  
Type I ◽  
Immune Recognition ◽  
Surface Receptors ◽  
Hmpv Infection

The host tropism of viral infection is determined by a variety of factors, from cell surface receptors to innate immune signaling. Many viruses encode proteins that interfere with host innate immune recognition in order to promote infection. STAT2 is divergent between species and therefore has a role in species restriction of some viruses. To understand the role of STAT2 in human metapneumovirus (HMPV) infection of human and murine tissues, we first infected STAT2−/− mice and found that HMPV could be serially passaged in STAT2−/−, but not WT, mice. We then used in vitro methods to show that HMPV inhibits expression of both STAT1 and STAT2 in human and primate cells, but not in mouse cells. Transfection of the murine form of STAT2 into STAT2-deficient human cells conferred resistance to STAT2 inhibition. Finally, we sought to understand the in vivo role of STAT2 by infecting hSTAT2 knock-in mice with HMPV, and found that mice had increased weight loss, inhibition of type I interferon signaling, and a Th2-polarized cytokine profile compared to WT mice. These results indicate that STAT2 is a target of HMPV in human infection, while the murine version of STAT2 restricts tropism of HMPV for murine cells and tissue.

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