| 1. |
- Kahn, Fredrik, et al.
(författare)
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Antibodies against a surface protein of Streptococcus pyogenes promote a pathological inflammatory response.
- 2008
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Ingår i: PLoS Pathogens. - : Public Library of Science (PLoS). - 1553-7366 .- 1553-7374. ; 4:9
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Tidskriftsartikel (refereegranskat)abstract
- Streptococcal toxic shock syndrome (STSS) caused by Streptococcus pyogenes is a clinical condition with a high mortality rate despite modern intensive care. A key feature of STSS is excessive plasma leakage leading to hypovolemic hypotension, disturbed microcirculation and multiorgan failure. Previous work has identified a virulence mechanism in STSS where M1 protein of S. pyogenes forms complexes with fibrinogen that activate neutrophils to release heparin-binding protein (HBP), an inducer of vascular leakage. Here, we report a marked inter-individual difference in the response to M1 protein-induced HBP release, a difference found to be related to IgG antibodies directed against the central region of the M1 protein. To elicit massive HBP release, such antibodies need to be part of the M1 protein-fibrinogen complexes. The data add a novel aspect to bacterial pathogenesis where antibodies contribute to the severity of disease by promoting a pathologic inflammatory response.
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| 2. |
- Malmström, Erik, et al.
(författare)
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Protein C inhibitor - a novel antimicrobial agent
- 2009
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Ingår i: PLoS Pathogens. - : Public Library of Science (PLoS). - 1553-7366 .- 1553-7374. ; 5:12, s. e1000698-
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Tidskriftsartikel (refereegranskat)abstract
- Protein C inhibitor (PCI) is a heparin-binding serine proteinase inhibitor belonging to the family of serpin proteins. Here we describe that PCI exerts broad antimicrobial activity against bacterial pathogens. This ability is mediated by the interaction of PCI with lipid membranes, which subsequently leads to their permeabilization. As shown by negative staining electron microscopy, treatment of Escherichia coli or Streptococcus pyogenes bacteria with PCI triggers membrane disruption followed by the efflux of bacterial cytosolic contents and bacterial killing. The antimicrobial activity of PCI is located to the heparin-binding site of the protein and a peptide spanning this region was found to mimic the antimicrobial activity of PCI, without causing lysis or membrane destruction of eukaryotic cells. Finally, we show that platelets can assemble PCI on their surface upon activation. As platelets are recruited to the site of a bacterial infection, these results may explain our finding that PCI levels are increased in tissue biopsies from patients suffering from necrotizing fasciitis caused by S. pyogenes. Taken together, our data describe a new function for PCI in innate immunity.
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| 3. |
- Malmström, Erik, et al.
(författare)
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Targeted mass spectrometry analysis of neutrophil-derived proteins released during sepsis progression.
- 2014
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Ingår i: Thrombosis and Haemostasis. - 0340-6245. ; 112:6, s. 1230-1243
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Tidskriftsartikel (refereegranskat)abstract
- Early diagnosis of severe infectious diseases is essential for timely implementation of lifesaving therapies. In a search for novel biomarkers in sepsis diagnosis we focused on polymorphonuclear neutrophils (PMNs). Notably, PMNs have their protein cargo readily stored in granules and following systemic stimulation an immediate increase of neutrophil-borne proteins can be observed into the circulation of sepsis patients. We applied a combination of mass spectrometry (MS) based approaches, LC-MS/MS and selected reaction monitoring (SRM), to characterise and quantify the neutrophil proteome in healthy or disease conditions. With this approach we identified a neutrophil-derived protein abundance pattern in blood plasma consisting of 20 proteins that can be used as a protein signature for severe infectious diseases. Our results also show that SRM is highly sensitive, specific, and reproducible and, thus, a promising technology to study a complex, dynamic and multifactorial disease such as sepsis.
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| 4. |
- Naudin, Clément, et al.
(författare)
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Active but inoperable thrombin is accumulated in a plasma protein layer surrounding Streptococcus pyogenes.
- 2015
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Ingår i: Thrombosis and Haemostasis. - 0340-6245. ; 114:4, s. 717-726
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Tidskriftsartikel (refereegranskat)abstract
- Activation of thrombin is a critical determinant in many physiological and pathological processes including haemostasis and inflammation. Under physiological conditions many of these functions are involved in wound healing or eradication of an invading pathogen. However, when activated systemically, thrombin can contribute to severe and life-threatening conditions by causing complications such as multiple multi-organ failure and disseminated intravascular coagulation. In the present study we investigated how the activity of thrombin is modulated when it is bound to the surface of Streptococcus pyogenes. Our data show that S. pyogenes bacteria become covered with a proteinaceous layer when incubated with human plasma, and that thrombin is a constituent of this layer. Though the coagulation factor is found attached to the bacteria with a functional active site, thrombin has lost its capacity to interact with its natural substrates and inhibitors. Thus, the interaction of bacteria with human plasma renders thrombin completely inoperable at the streptococcal surface. This could represent a host defense mechanism to avoid systemic activation of coagulation which could be otherwise induced when bacteria enter the circulation and cause systemic infection.
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| 5. |
- Oehmcke, Sonja, et al.
(författare)
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Streptococcal M proteins and their role as virulence determinants.
- 2010
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Ingår i: Clinica Chimica Acta. - : Elsevier BV. - 0009-8981. ; 411, s. 1172-1180
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Tidskriftsartikel (refereegranskat)abstract
- Group A streptococci (GAS, Streptococcus pyogenes) are exclusive human pathogens that have been extensively studied for many decades. The spectrum of diseases caused by these bacteria ranges from uncomplicated and superficial to severe and invasive infections. In order to give rise to these complications, GAS have evolved a number of surface-bound and secreted virulence factors, of which the M proteins are probably the best characterized. Evidence has emerged that M proteins are multifunctional pathogenic determinants, and over the years many interactions between M proteins and the human host have been reported. The present review article aims to present a state-of-the-art overview of the most important virulence mechanisms employed by M proteins to trigger disease.
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| 6. |
- Oehmcke, Sonja, et al.
(författare)
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Treatment of invasive streptococcal infection with a peptide derived from human high molecular weight kininogen.
- 2009
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Ingår i: Blood. - : American Society of Hematology. - 1528-0020 .- 0006-4971. ; 114:2, s. 444-451
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Tidskriftsartikel (refereegranskat)abstract
- Sepsis and septic shock remain an important medical problem, emphasizing the need to identify novel therapeutic opportunities. Hypovolemic hypotension, coagulation dysfunction, disturbed microcirculation, and multiorgan failure due to vascular leakage are often observed in these severe conditions. In the present study, we find that HKH20, a peptide derived from human high molecular weight kininogen (HK), down-regulates inflammatory reactions caused by Streptococcus pyogenes in a mouse model of sepsis. HK is a component of the pro-inflammatory and pro-coagulant contact system. Activation of the contact system in the bloodstream by S. pyogenes leads to massive tissue damage in the lungs of the infected mice, which eventually results in the death of the animals. HKH20 inhibits activation of the contact system and protects mice with invasive S. pyogenes infection from lung damage. In combination with clindamycin treatment, the peptide also significantly prolongs the survival of infected mice.
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| 7. |
- Shannon, Oonagh, et al.
(författare)
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Modulation of the Coagulation System During Severe Streptococcal Disease.
- 2012
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Ingår i: Current Topics in Microbiology and Immunology. - Berlin, Heidelberg : Springer Berlin Heidelberg. - 0070-217X.
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Tidskriftsartikel (refereegranskat)abstract
- Haemostasis is maintained by a tightly regulated coagulation system that comprises platelets, procoagulant proteins, and anticoagulant proteins. During the local and systemic response to bacterial infection, the coagulation system becomes activated, and contributes to the pathophysiological response to infection. The significant human pathogen, Streptococcus pyogenes has multiple strategies to modulate coagulation. This can range from systemic activation of the intrinsic and extrinsic pathway of coagulation to local stimulation of fibrinolysis. Such diverse effects on this host system imply a finely tuned host-bacteria interaction. The molecular mechanisms that underlie this modulation of the coagulation system are discussed in this review.
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