| 1. |
- Åkesson, Per, et al.
(author)
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Streptococcal inhibitor of complement-mediated lysis (SIC): an anti-inflammatory virulence determinant
- 2010
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In: Microbiology. - : Microbiology Society. - 1465-2080 .- 1350-0872. ; 156, s. 3660-3668
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Journal article (peer-reviewed)abstract
- Since the late 1980s, a worldwide increase of severe Streptococcus pyogenes infections has been associated with strains of the M1 serotype, strains which all secrete the streptococcal inhibitor of complement-mediated lysis (SIC). Previous work has shown that SIC blocks complement-mediated haemolysis, inhibits the activity of antibacterial peptides and has affinity for the human plasma proteins clusterin and histidine-rich glycoprotein; the latter is a member of the cystatin protein family. The present work demonstrates that SIC binds to cystatin C, high-molecular-mass kininogen (HK) and low-molecular-mass kininogen, which are additional members of this protein family. The binding sites in HK are located in the cystatin-like domain D3 and the endothelial cell-binding domain D5. Immobilization of HK to cellular structures plays a central role in activation of the human contact system. SIC was found to inhibit the binding of HK to endothelial cells, and to reduce contact activation as measured by prolonged blood clotting time and impaired release of bradykinin. These results suggest that SIC modifies host defence systems, which may contribute to the virulence of S. pyogenes strains of the M1 serotype.
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| 2. |
- Herwald, Heiko, et al.
(author)
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Activation of the contact-phase system on bacterial surfaces - A clue to serious comlications in infections deseases
- 1998
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In: Nature Medicine. - : Springer Science and Business Media LLC. - 1078-8956 .- 1546-170X. ; 4:3, s. 298-302
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Journal article (peer-reviewed)abstract
- Fever, hypotension and bleeding disorders are common symptoms of sepsis and septic shock. The activation of the contact-phase system is thought to contribute to the development of these severe disease states by triggering proinflammatory and procoagulatory cascades; however, the underlying molecular mechanisms are obscure. Here we report that the components of the contact-phase system are assembled on the surface of Escherichia coil and Salmonella through their specific interactions with fibrous bacterial surface proteins, curli and fimbriae. As a consequence, the proinflammatory pathway is activated through the release of bradykinin, a potent inducer of fever, pain and hypotension. Absorption of contact-phase proteins and fibrinogen by bacterial surface proteins depletes relevant coagulation factors and causes a hypocoagulatory state. Thus, the complex interplay of microbe surface proteins and host contact-phase factors may contribute to the symptoms of sepsis and septic shock.
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| 3. |
- Persson, Kristin, et al.
(author)
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Severe lung lesions caused by Salmonella are prevented by inhibition of the contact system
- 2000
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In: Journal of Experimental Medicine. - : Rockefeller University Press. - 1540-9538 .- 0022-1007. ; 192:10, s. 1415-1424
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Journal article (peer-reviewed)abstract
- Vascular damage induced by trauma, inflammation, or infection results in an alteration of the endothelium from a nonactivated to a procoagulant, vasoconstrictive, and proinflammatory state, and can lead to life-threatening complications. Here we report that activation of the contact system by Salmonella leads to massive infiltration of red blood cells and fibrin deposition in the lungs of infected rats. These pulmonary lesions were prevented when the infected animals were treated with H-D-Pro-Phe-Arg-chloromethylketone, an inhibitor of coagulation factor XII and plasma kallikrein, suggesting that inhibition of contact system activation could be used therapeutically in severe infectious disease.
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| 4. |
- Ben Nasr, Abdelhakim, et al.
(author)
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Absorption of kininogen from human plasma by Streptococcus pyogenes is followed by the release of bradykinin
- 1997
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In: Biochemical Journal. - : Portland Press Ltd.. - 0264-6021 .- 1470-8728. ; 326:3, s. 657-660
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Journal article (peer-reviewed)abstract
- H-kininogen (high-molecular-mass kininogen, HK) is the precursor of the vasoactive peptide hormone bradykinin (BK). Previous work has demonstrated that HK binds to Streptococcus pyogenes through M-proteins, fibrous surface proteins and important virulence factors of these bacteria. Here we find that M-protein-expressing bacteria absorb HK from human plasma. The HK bound to the bacteria was found to be cleaved, and analysis of the degradation pattern suggested that the cleavage of HK at the bacterial surface is associated with the release of BK. Moreover, addition of activated plasma prekallikrein to bacteria preincubated with human plasma, resulted in BK release. This mechanism, by which a potent vasoactive and proinflammatory peptide is generated at the site of infection, should influence the host-parasite relationship during S. pyogenes infections.
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| 5. |
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| 6. |
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| 7. |
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| 8. |
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| 9. |
- Herwald, Heiko, et al.
(author)
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Streptococcal cysteine proteinase releases kinins: a novel virulence mechanism
- 1996
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In: Journal of Experimental Medicine. - 1540-9538. ; 184:2, s. 665-673
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Journal article (peer-reviewed)abstract
- Previous work has indicated a crucial role for the extracellular cysteine proteinase of Streptococcus pyogenes in the pathogenicity and virulence of this important human pathogen. Here we find that the purified streptococcal cysteine proteinase releases biologically active kinins from their purified precursor protein, H-kininogen, in vitro, and from kininogens present in the human plasma, ex vivo. Kinin liberation in the plasma is due to the direct action of the streptococcal proteinase on the kininogens, and does not involve the previous activation of plasma prekallikrein, the physiological plasma kininogenase. Judged from the amount of released plasma kinins the bacterial proteinase is highly efficient in its action. This is also the case in vivo. Injection of the purified cysteine proteinase into the peritoneal cavity of mice resulted in a progressive cleavage of plasma kininogens and the concomitant release of kinins over a period of 5 h. No kininogen degradation was seen in mice when the cysteine proteinase was inactivated by the specific inhibitor, Z-Leu-Val-Gly-CHN2, before administration. Intraperitoneal administration into mice of living S. pyogenes bacteria producing the cysteine proteinase induced a rapid breakdown of endogenous plasma kininogens and release of kinins. Kinins are hypotensive, they increase vascular permeability, contract smooth muscle, and induce fever and pain. The release of kinins by the cysteine proteinase of S. pyogenes could therefore represent an important and previously unknown virulence mechanism in S. pyogenes infections.
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| 10. |
- Kahn, Fredrik, et al.
(author)
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Antibodies against a surface protein of Streptococcus pyogenes promote a pathological inflammatory response.
- 2008
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In: PLoS Pathogens. - : Public Library of Science (PLoS). - 1553-7366 .- 1553-7374. ; 4:9
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Journal article (peer-reviewed)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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