| 1. |
- Granath, Anna, et al.
(författare)
-
Reduced iNOS expression in adenoids from children with otitis media with effusion.
- 2010
-
Ingår i: Pediatric allergy and immunology : official publication of the European Society of Pediatric Allergy and Immunology. - : Wiley. - 1399-3038. ; 21:8, s. 1151-1156
-
Tidskriftsartikel (refereegranskat)abstract
- Granath A, Norrby-Teglund A, Uddman R, Cardell L-O. Reduced iNOS expression in adenoids from children with otitis media with effusion. Pediatr Allergy Immunol 2010: 21: 1151-1156. © 2010 John Wiley & Sons A/S Nitric oxide (NO) is a key mediator in the local immune response of human airways. Inducible NO-synthases (iNOS), and endothelial NO-synthases (eNOS) are two enzymes known to regulate its production. The role of NO in middle ear disease is not fully known. Previous studies suggest that NO might have a dual role, both promoting and suppressing middle ear inflammation. The aim of the present study was to compare the eNOS and iNOS expression in adenoids obtained from children with otitis media with effusion (OME) with the expression seen in adenoids derived from children without middle ear disease. In addition, the expression of IL-1β and TNF-α were analyzed, because of their role in the iNOS-induction pathway. The iNOS and eNOS expression were analyzed with real-time PCR in 8 OME and 11 control adenoids. The corresponding proteins were demonstrated by immunohistochemical staining of adenoid tissue. A Luminex(®) assay was performed to analyze IL-1β and TNF-α in nasopharyngeal secretion in 10 OME and 8 controls, and immunohistochemistry was performed on adenoid tissue and imprints from the adenoid surface. Children with OME exhibited lower levels of iNOS than controls without middle ear disease. No such difference was seen for eNOS. The corresponding proteins were found mainly in conjunction with surface epithelium. No significant changes were seen among the cytokines tested. The present results indicate that local induction of iNOS in adenoids might be of importance for preventing development of OME.
|
|
| 2. |
- Johansson, Linda, et al.
(författare)
-
HMGB1 in severe soft tissue infections caused by Streptococcus pyogenes.
- 2014
-
Ingår i: Frontiers in cellular and infection microbiology. - : Frontiers Media SA. - 2235-2988. ; 4:Jan 30
-
Tidskriftsartikel (refereegranskat)abstract
- Extracellular High Mobility Group Box 1 (HMGB1) has been associated with acute and chronic inflammatory conditions. However, little is known about HMGB1 in necrotizing bacterial infections. We hypothesized that the local HMGB1 response is excessive in severe soft tissue infections (STIs), which are characterized by necrosis and hyperinflammation. To explore this, tissue biopsies were collected from patients with varying severity of Streptococcus pyogenes skin and STIs, including erysipelas, cellulitis, and necrotizing fasciitis. Tissue sections were immunostained for HMGB1, S. pyogenes, and inflammatory cell infiltrates and results quantified by acquired computerized image analysis (ACIA). HMGB1 expression increased in parallel to disease severity and was significantly higher in necrotizing fasciitis than in erysipelas (p = 0.0023). Confocal microscopy of sections co-stained for HMGB1 and cell markers revealed both extracellular and cytoplasmic HMGB1, the latter of which was found predominantly in macrophages. To further verify macrophages as main source of activation triggered HMGB1 release, human macrophages were infected with clinical S. pyogenes isolates. The results demonstrated infection triggered release of HMGB1. Dual staining's visualized HMGB1 in areas close to, but not overlapping, with neutrophils, indicating a potential chemotactic role. In vitro transmigration experiments showed a chemotactic effect of HMGB1 on neutrophils. The data furthermore provided in vivo support that HGMB1 may form immunostimulatory complexes with IL-1β. Taken together, the findings provide the first in vivo evidence that HMGB1 is abundant at the local site of severe bacterial STIs and its levels correlated to severity of infections; hence, indicating its potential value as a biomarker for tissue pathology.
|
|
| 3. |
- Johansson, Linda, et al.
(författare)
-
Neutrophil-Derived Hyperresistinemia in Severe Acute Streptococcal Infections
- 2009
-
Ingår i: Journal of Immunology. - : The American Association of Immunologists. - 1550-6606 .- 0022-1767. ; 183:6, s. 4047-4054
-
Tidskriftsartikel (refereegranskat)abstract
- The concept of neutrophil activation and degranulation as important contributors to disease pathology in invasive group A streptococcal infections has recently been emphasized. This study focuses on two of the most severe streptococcal manifestations, toxic shock syndrome and necrotizing fasciitis, and the newly described proinflammatory molecule resistin, known to derive from adipocytes and monocytes. We demonstrate for the first time that these conditions are characterized by hyperresistinemia in circulation as well as at the local site of infection. Importantly, analyses of patient tissue biopsies and whole blood revealed that neutrophils represent a novel and dominant source of resistin in bacterial septic shock. This was confirmed by the identification of resistin within neutrophil azurophilic granules. In vitro assays using primary neutrophils showed that resistin release was readily triggered by streptococcal cell wall components and by the streptococcal M1 protein, but not by the potent streptococcal superantigens. This is the first report demonstrating that resistin is released from neutrophils in response to microbial stimuli, which adds resistin to the neutrophil granule proteins that are likely to contribute to the pathologic inflammatory responses associated with severe streptococcal infections. The Journal of Immunology, 2009, 183: 4047-4054.
|
|
| 4. |
- Linner, Anna, et al.
(författare)
-
Clinical Efficacy of Polyspecific Intravenous Immunoglobulin Therapy in Patients With Streptococcal Toxic Shock Syndrome : A Comparative Observational Study
- 2014
-
Ingår i: Clinical Infectious Diseases. - : Oxford University Press (OUP). - 1058-4838 .- 1537-6591. ; 59:6, s. 851-857
-
Tidskriftsartikel (refereegranskat)abstract
- Background. Streptococcal toxic shock syndrome (STSS) and necrotizing fasciitis are the 2 most severe invasive manifestations caused by group A Streptococcus (GAS). Intravenous immunoglobulin (IVIG) therapy has been suggested as adjunctive treatment with a beneficial effect on mortality. However the clinical evidence is limited. Here we aim to further document the clinical efficacy of administered IVIG therapy in a comparative observational study of well-defined patients with STSS. Methods. The effect of IVIG was evaluated in patients with STSS prospectively identified in a nationwide Swedish surveillance study conducted between April 2002 and December 2004. Detailed data on symptoms, severity of disease, treatment, and outcome were obtained from 67 patients. Crude and adjusted analyses with logistic regression were performed. Results. Twenty-three patients received IVIG therapy compared with 44 who did not. No significant difference in comorbidities, severity of disease, organ failures, or sex was seen, but the IVIG group was slightly younger and had a higher degree of necrotizing fasciitis (56% vs 14%). The primary endpoint was 28-day survival. Adjusted analysis revealed that factors influencing survival in STSS were Simplified Acute Physiology Score II (odds ratio [OR], 1.1; P = .007), clindamycin (OR, 8.6; P = .007), and IVIG (OR, 5.6; P = .030). Conclusions. This comparative observational study of prospectively identified STSS patients demonstrates that both IVIG and clindamycin therapy contribute to a significantly improved survival in STSS.
|
|
| 5. |
|
|
| 6. |
- Snäll, Johanna, et al.
(författare)
-
Differential neutrophil responses to bacterial stimuli: Streptococcal strains are potent inducers of heparin-binding protein and resistin-release.
- 2016
-
Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 6
-
Tidskriftsartikel (refereegranskat)abstract
- Neutrophils are critical for the control of bacterial infections, but they may also contribute to disease pathology. Here we explore neutrophil responses, in particular the release of sepsis-associated factors heparin-binding protein (HBP) and resistin in relation to specific bacterial stimuli and sepsis of varying aetiology. Analyses of HBP and resistin in plasma of septic patients revealed elevated levels as compared to non-infected critically ill patients. HBP and resistin correlated significantly in septic patients, with the strongest association seen in group A streptococcal (GAS) cases. In vitro stimulation of human neutrophils revealed that fixed streptococcal strains induced significantly higher release of HBP and resistin, as compared to Staphylococcus aureus or Escherichia coli. Similarly, neutrophils stimulated with the streptococcal M1-protein showed a significant increase in co-localization of HBP and resistin positive granules as well as exocytosis of these factors, as compared to LPS. Using a GAS strain deficient in M1-protein expression had negligible effect on neutrophil activation, while a strain deficient in the stand-alone regulator MsmR was significantly less stimulatory as compared to its wild type strain. Taken together, the findings suggest that the streptococcal activation of neutrophils is multifactorial and involves, but is not limited to, proteins encoded by the FCT-locus.
|
|
| 7. |
- Vikerfors, Anna, et al.
(författare)
-
Severe group A streptococcal infections in Uppsala County, Sweden : clinical and molecular characterization of a case cluster from 2006 to 2007
- 2009
-
Ingår i: Scandinavian Journal of Infectious Diseases. - : Informa UK Limited. - 0036-5548 .- 1651-1980. ; 41:11-12, s. 823-830
-
Tidskriftsartikel (refereegranskat)abstract
- This study describes a recent cluster of 30 patients (median age 52 years) with serious group A streptococcal (GAS) infections in Uppsala County, Sweden, from December 2006 to May 2007. Patients hospitalized with a severe GAS infection, i.e. cases with either invasive GAS (iGAS) disease or patients with a positive non-sterile site culture/rapid antigen test for GAS and clinically considered as having a critical disease, were included in the study. Common clinical presentations were skin and soft tissue infections (53%) and pneumonia (17%). Eight patients (27%) were diagnosed with streptococcal toxic shock syndrome. In 40% of the cases no relevant underlying disease was reported. Among the 16 patients with soft tissue infections, the upper chest, neck or upper arm area was frequently affected and the infection was associated with severe pain. Among the 20 collected isolates, the T1/emm1 type dominated (80%). The majority (86%) of 7 analysed acute sera lacked neutralizing activity against superantigens produced by the patients' own infecting isolate. The study underscores the association between T1/emm1 and outbreaks of serious GAS infections. This highlights the importance of surveillance for prompt identification of more aggressive isolates in the community, thereby increasing awareness among healthcare professionals of these life-threatening infections.
|
|
| 8. |
- Bengtson, Sara H, et al.
(författare)
-
Kinin receptor expression during Staphylococcus aureus infection.
- 2006
-
Ingår i: Blood. - : American Society of Hematology. - 1528-0020 .- 0006-4971. ; 108:6, s. 2055-2063
-
Tidskriftsartikel (refereegranskat)abstract
- An inappropriate host response to invading bacteria is a critical parameter that often aggravates the outcome of an infection. Staphylococcus aureus is a major human Gram-positive pathogen that causes a wide array of community- and hospital-acquired diseases ranging from superficial skin infections to severe conditions such as staphylococcal toxic shock. Here we find that S aureus induces inflammatory reactions by modulating the expression and response of the B1 and B2 receptors, respectively. This process is initiated by a chain of events, involving staphylococcal-induced cytokine release from monocytes, bacteria-triggered contact activation, and conversion of bradykinin to its metabolite desArg9bradykinin. The data of the present study implicate an important and previously unknown role for kinin receptor regulation in S aureus infections.
|
|
| 9. |
- Darenberg, Jessica, et al.
(författare)
-
Molecular and clinical characteristics of invasive group A streptococcal infection in Sweden
- 2007
-
Ingår i: Clinical Infectious Diseases. - : Oxford University Press (OUP). - 1537-6591 .- 1058-4838. ; 45:4, s. 8-450
-
Tidskriftsartikel (refereegranskat)abstract
- Background. The incidence and severity of invasive group A streptococcal infection demonstrate great variability over time, which at least, in part, seems to be related to group A streptococcal type distribution among the human population. Methods. An enhanced surveillance study of invasive group A streptococcal infection (746 isolates) was performed in Sweden from April 2002 through December 2004. Noninvasive isolates from either the throat or skin (773 isolates) were collected in parallel for comparison. Clinical and epidemiological data were obtained from 88% of patients with invasive disease and were related to isolate characteristics, including T type, emm sequence type, and the presence of 9 superantigen genes, as well as pulsed-field gel electrophoresis pattern comparisons of selected isolates. Results. The annual incidence was 3.0 cases per 100,000 population. Among the patients with invasive disease, 11% developed streptococcal toxic shock syndrome, and 9.5% developed necrotizing fasciitis. The overall case-fatality rate was 14.5%, and 39% of the patients with streptococcal toxic shock syndrome died (P < .001). The T3/13/B3264 cluster accounted for 33% of invasive and 25% of noninvasive isolates. Among this most prevalent type cluster, emm types 89 and 81 dominated. Combined results from pulsed-field gel electrophoresis, emm typing, and superantigen gene profiling identified subgroups within specific emm types that are significantly more prone to cause invasive disease than were other isolates of the same type. Conclusions. This study revealed a changing epidemiology of invasive group A streptococcal infection in Sweden, with emergence of new emm types that were previously not described. The results also suggest that some clones may be particularly prone to cause invasive disease.
|
|
| 10. |
- Goscinski, Gunilla, et al.
(författare)
-
Release of SpeA from Streptococcus pyogenes after exposure to penicillin : dependency on dose and inhibition by clindamycin
- 2006
-
Ingår i: Scandinavian Journal of Infectious Diseases. - : Informa UK Limited. - 0036-5548 .- 1651-1980. ; 38:11-12, s. 983-987
-
Tidskriftsartikel (refereegranskat)abstract
- The amount and time course of SpeA release from group A streptococci (GAS) was studied at different starting inoculae after exposure to different doses of penicillin, clindamycin or a combination of the 2. The release was related to the bacterial concentration and killing rate. A clinical GAS strain was exposed to benzylpenicillin, 2 and 1000 × MIC, clindamycin, 2 and 32 × MIC, or combinations of the 2. Samples for viable counts and SpeA analyses were drawn before and after the addition of antibiotics and at 3, 6 and 24 h. The SpeA release was higher at low than at high concentrations of penicillin and the combination (both, p < 0.05). The addition of clindamycin to penicillin reduced SpeA production at both concentrations (p < 0.01). Most SpeA was released before 3 h, and for penicillin and the combination, the amount correlated to the number of killed bacteria during this period (r = 0.50; p < 0.05). A positive correlation was found between the inoculum size and the SpeA concentration at time zero (r = 0.54; p < 0.05). The SpeA concentration was dependent on the initial number of bacteria, the class of antibiotic, the dose of penicillin and the killing rate.
|
|
| 11. |
|
|
| 12. |
- Hertzen, Erika, et al.
(författare)
-
M1 Protein-Dependent Intracellular Trafficking Promotes Persistence and Replication of Streptococcus pyogenes in Macrophages
- 2010
-
Ingår i: Journal of Innate Immunity. - : S. Karger AG. - 1662-811X .- 1662-8128. ; 2:6, s. 534-545
-
Tidskriftsartikel (refereegranskat)abstract
- Streptococcus pyogenes is an important human pathogen that causes a variety of diseases including life-threatening invasive diseases, such as toxic shock and deep tissue infections. Although S. pyogenes are classically considered extracellular pathogens, a clinical significance of an intracellular source has been emphasized. In patients with deep tissue infections, an intracellular reservoir of S. pyogenes within macrophages was shown to contribute to prolonged bacterial persistence. Here we demonstrate that intracellular survival of S. pyogenes in macrophages is associated with an M1 protein-dependent intracellular trafficking in the phagosomal-lysosomal pathway, which results in impaired fusion with lysosomes. The phagocytic vacuoles harbouring M1 protein-expressing bacteria not only served as a safe haven for the bacteria, but also as a replicating niche. An M1 protein-dependent modulation of macrophages was further supported by differences in NF-kappa B signalling between cells infected with either the wild-type or M1 protein-deficient strains, thereby indicating a suppressed inflammatory response when M1 protein was involved. Evidence of egress of bacteria out of their host cell and subsequent re-infection of new cells emphasize the importance of intracellular bacteria as a reservoir for dissemination of infection and continued tissue injury. Copyright (C) 2010 S. Karger AG, Basel
|
|
| 13. |
|
|
| 14. |
- Johansson, Linda, et al.
(författare)
-
Cathelicidin LL-37 in Severe Streptococcus pyogenes Soft Tissue Infections in Humans
- 2008
-
Ingår i: Infection and Immunity. - 1098-5522. ; 76:8, s. 3399-3404
-
Tidskriftsartikel (refereegranskat)abstract
- Severe soft tissue infections, such as necrotizing fasciitis and severe cellulitis, caused by group A streptococcus (GAS) are rapidly progressing life-threatening infections characterized by massive bacterial load in the tissue even late after onset of infection. Antimicrobial peptides are important components of the innate host defence and cathelicidins have been shown to protect against murine necrotic skin infection caused by GAS. However, the streptococcal cysteine protease SpeB has been demonstrated to proteolytically inactivate the human cathelicidin LL-37 in vitro. Here we have investigated the expression of LL-37 and its interaction with GAS and SpeB during acute severe soft tissue infections by analyses of patient tissue biopsies. The results showed high amounts of LL-37, both the proform (hCAP18) and the mature peptide, present in the tissue. Confocal microscopy identified neutrophils as the main source of the peptide. A distinct co-localization between the bacteria and LL-37 could be noted, and bacterial load showed a positive correlation to the LL-37 levels. Areas with high LL-37 levels coincided with areas with high amounts of SpeB. Confocal microscopy confirmed a strong co-localization of GAS, SpeB and LL-37 at the bacterial surface. Taken together the findings of this study provides in vivo support that SpeB-mediated inactivation of LL-37 at the streptococcal surface represent a bacterial resistance mechanism at the infected tissue site in patients with severe GAS tissue infections.
|
|
| 15. |
- Kahn, Fredrik, et al.
(författare)
-
Antibodies against a surface protein of Streptococcus pyogenes promote a pathological inflammatory response.
- 2008
-
Ingår i: PLoS Pathogens. - : Public Library of Science (PLoS). - 1553-7366 .- 1553-7374. ; 4:9
-
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.
|
|
| 16. |
- Lannergård, Jonas, et al.
(författare)
-
Sequence variability is correlated with weak immunogenicity in Streptococcus pyogenes M protein.
- 2015
-
Ingår i: MicrobiologyOpen. - : Wiley. - 2045-8827. ; 4:5, s. 774-789
-
Tidskriftsartikel (refereegranskat)abstract
- The M protein of Streptococcus pyogenes, a major bacterial virulence factor, has an amino-terminal hypervariable region (HVR) that is a target for type-specific protective antibodies. Intriguingly, the HVR elicits a weak antibody response, indicating that it escapes host immunity by two mechanisms, sequence variability and weak immunogenicity. However, the properties influencing the immunogenicity of regions in an M protein remain poorly understood. Here, we studied the antibody response to different regions of the classical M1 and M5 proteins, in which not only the HVR but also the adjacent fibrinogen-binding B repeat region exhibits extensive sequence divergence. Analysis of antisera from S. pyogenes-infected patients, infected mice, and immunized mice showed that both the HVR and the B repeat region elicited weak antibody responses, while the conserved carboxy-terminal part was immunodominant. Thus, we identified a correlation between sequence variability and weak immunogenicity for M protein regions. A potential explanation for the weak immunogenicity was provided by the demonstration that protease digestion selectively eliminated the HVR-B part from whole M protein-expressing bacteria. These data support a coherent model, in which the entire variable HVR-B part evades antibody attack, not only by sequence variability but also by weak immunogenicity resulting from protease attack.
|
|
| 17. |
- Lannergård, Jonas, et al.
(författare)
-
The Hypervariable Region of Streptococcus pyogenes M Protein Escapes Antibody Attack by Antigenic Variation and Weak Immunogenicity.
- 2011
-
Ingår i: Cell Host and Microbe. - : Elsevier BV. - 1934-6069 .- 1931-3128. ; 10:2, s. 147-157
-
Tidskriftsartikel (refereegranskat)abstract
- Sequence variation of antigenic proteins allows pathogens to evade antibody attack. The variable protein commonly includes a hypervariable region (HVR), which represents a key target for antibodies and is therefore predicted to be immunodominant. To understand the mechanism(s) of antibody evasion, we analyzed the clinically important HVR-containing M proteins of the human pathogen Streptococcus pyogenes. Antibodies elicited by M proteins were directed almost exclusively against the C-terminal part and not against the N-terminal HVR. Similar results were obtained for mice and humans with invasive S. pyogenes infection. Nevertheless, only anti-HVR antibodies protected efficiently against infection, as shown by passive immunizations. The HVR fused to an unrelated protein elicited no antibodies, implying that it is inherently weakly immunogenic. These data indicate that the M protein HVR evades antibody attack not only through antigenic variation but also by weak immunogenicity, a paradoxical observation that may apply to other HVR-containing proteins.
|
|
| 18. |
- Linder, Adam, et al.
(författare)
-
Erysipelas Caused by Group A Streptococcus Activates the Contact System and Induces the Release of Heparin-Binding Protein.
- 2010
-
Ingår i: Journal of Investigative Dermatology. - : Elsevier BV. - 1523-1747 .- 0022-202X. ; 130, s. 1365-1372
-
Tidskriftsartikel (refereegranskat)abstract
- Bacterial skin infections, such as erysipelas or cellulitis, are characterized by fever and a painful erythematous rash. Despite the high prevalence of these infections, little is known about the underlying pathogenic mechanisms. This is partly due to the fact that a bacterial diagnosis is often difficult to attain. To gain insight into the pathogenesis of erysipelas, we investigated the samples obtained from infected and noninfected areas of skin from 12 patients with erysipelas. Bacterial cultures, detection of specific streptococcal antibodies in convalescent sera, and immunohistochemical analyses of biopsies indicated group A streptococcal etiology in 11 of the 12 patients. Also, electron micrographs of erythematous skin confirmed the presence of group A streptococcal cells and showed a limited solubilization of the surface-attached M protein. Degradation of high-molecular-weight kininogen and upregulation of the bradykinin-1 receptor in inflamed tissues indicated activation of the contact system in 11 patients. Analyses of release of the vasoactive heparin-binding protein (HBP) showed increased levels in the infected as compared with the noninfected areas. The results suggest that group A streptococci induce contact activation and HBP release during skin infection, which likely contribute to the symptoms seen in erysipelas: fever, pain, erythema, and edema.Journal of Investigative Dermatology advance online publication, 28 January 2010; doi:10.1038/jid.2009.437.
|
|
| 19. |
- Loof, Torsten, et al.
(författare)
-
Coagulation, an ancestral serine protease cascade, exerts a novel function in early immune defense
- 2011
-
Ingår i: Blood. - : American Society of Hematology. - 0006-4971 .- 1528-0020. ; 118:9, s. 2589-2598
-
Tidskriftsartikel (refereegranskat)abstract
- Phylogenetically conserved serine protease cascades play an important role in invertebrate and vertebrate immunity. The mammalian coagulation system can be traced back some 400 million years and shares homology with ancestral serine proteinase cascades that are involved in, for example, Toll receptor signaling in insects and release of antimicrobial peptides during hemolymph clotting. In the present study, we show that the induction of coagulation by bacteria leads to immobilization and killing of Streptococcus pyogenes bacteria inside the clot. The entrapment is mediated via cross-linking of bacteria to fibrin fibers by the action of coagulation factor XIII (fXIII), an evolutionarily conserved transglutaminase. In a streptococcal skin infection model, fXIII(-/-) mice developed severe signs of patho-logic inflammation at the local site of infection, and fXIII treatment of wild-type animals dampened bacterial dissemination during early infection. Bacterial killing and cross-linking to fibrin networks was also detected in tissue biopsies from patients with streptococcal necrotizing fasciitis, supporting the concept that coagulation is part of the early innate immune system.
|
|
| 20. |
- Lövkvist, Lena, et al.
(författare)
-
CD46 contributes to the severity of group A streptococcal infection
- 2008
-
Ingår i: Infection and Immunity. - 0019-9567 .- 1098-5522. ; 76:9, s. 3951-3958
-
Tidskriftsartikel (refereegranskat)abstract
- Streptococcus pyogenes (group A Streptococcus) is a human pathogen that causes a wide variety of diseases ranging from uncomplicated superficial infections to severe infections such as streptococcal toxic shock syndrome and necrotizing fasciitis. These bacteria interact with several host cell receptors, one of which is the cell surface complement regulator CD46. In this study, we demonstrate that infection of epithelial cells with S. pyogenes leads to the shedding of CD46 at the same time as the bacteria induce apoptosis and cell death. Soluble CD46 attached to the streptococcal surface, suggesting that bacteria might bind available extracellular CD46 as a strategy to survive and avoid host defenses. The protective role of human CD46 was demonstrated in ex vivo whole-blood assays showing that the growth of S. pyogenes was enhanced in blood from mice expressing human CD46. Finally, in vivo experimental infection showed that bacteremia levels, arthritis frequency, and mortality were higher in CD46 transgenic mice than in nontransgenic mice. Taken together, these results argue that bacterial exploitation of human CD46 enhances bacterial survival and represents a novel pathogenic mechanism that contributes to the severity of group A streptococcal disease.
|
|
| 21. |
|
|
| 22. |
- Malmström, Erik, et al.
(författare)
-
Protein C inhibitor - a novel antimicrobial agent
- 2009
-
Ingår i: PLoS Pathogens. - : Public Library of Science (PLoS). - 1553-7366 .- 1553-7374. ; 5:12, s. e1000698-
-
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.
|
|
| 23. |
- Movert, Elin, et al.
(författare)
-
Interplay between human STING genotype and bacterial NADase activity regulates inter-individual disease variability
- 2023
-
Ingår i: Nature Communications. - 2041-1723. ; 14:1
-
Tidskriftsartikel (refereegranskat)abstract
- Variability in disease severity caused by a microbial pathogen is impacted by each infection representing a unique combination of host and pathogen genomes. Here, we show that the outcome of invasive Streptococcus pyogenes infection is regulated by an interplay between human STING genotype and bacterial NADase activity. S. pyogenes-derived c-di-AMP diffuses via streptolysin O pores into macrophages where it activates STING and the ensuing type I IFN response. However, the enzymatic activity of the NADase variants expressed by invasive strains suppresses STING-mediated type I IFN production. Analysis of patients with necrotizing S. pyogenes soft tissue infection indicates that a STING genotype associated with reduced c-di-AMP-binding capacity combined with high bacterial NADase activity promotes a ‘perfect storm’ manifested in poor outcome, whereas proficient and uninhibited STING-mediated type I IFN production correlates with protection against host-detrimental inflammation. These results reveal an immune-regulating function for bacterial NADase and provide insight regarding the host-pathogen genotype interplay underlying invasive infection and interindividual disease variability.
|
|
| 24. |
- Neumann, Ariane, et al.
(författare)
-
Immunoregulation of Neutrophil Extracellular Trap Formation by Endothelial-Derived p33 (gC1q Receptor)
- 2018
-
Ingår i: Journal of Innate Immunity. - : S. Karger AG. - 1662-811X .- 1662-8128. ; 10:1, s. 30-43
-
Tidskriftsartikel (refereegranskat)abstract
- The formation of neutrophil extracellular traps (NETs) is a host defence mechanism, known to facilitate the entrapment and growth inhibition of many bacterial pathogens. It has been implicated that the translocation of myeloperoxidase (MPO) from neutrophilic granules to the nucleus is crucial to this process. Under disease conditions, however, excessive NET formation can trigger self-destructive complications by releasing pathologic levels of danger-associated molecular pattern molecules (DAMPs). To counteract such devastating immune reactions, the host has to rely on precautions that help circumvent these deleterious effects. Though the induction of DAMP responses has been intensively studied, the mechanisms that are used by the host to down-regulate them are still not understood. In this study, we show that p33 is an endothelial-derived protein that has the ability to annul NET formation. We found that the expression of human p33 is up-regulated in endothelial cells upon infections with Streptococcus pyogenes bacteria. Using tissue biopsies from a patient with streptococcal necrotising fasciitis, we monitored co-localisation of p33 with MPO. Further in vitro studies revealed that p33 is able to block the formation of DAMP-induced NET formation by inhibiting the enzymatic activity of MPO. Additionally, mice challenged with S. pyogenes bacteria demonstrated diminished MPO activity when treated with p33. Together, our results demonstrate that host-derived p33 has an important immunomodulating function that helps to counterbalance an overwhelming DAMP response.
|
|
| 25. |
- Norrby-Teglund, Anna, et al.
(författare)
-
Correlation between serum TNF alpha and IL6 levels and severity of group A streptococcal infections
- 1995
-
Ingår i: Scandinavian Journal of Infectious Diseases. - 0036-5548 .- 1651-1980. ; 27:2, s. 125-130
-
Tidskriftsartikel (refereegranskat)abstract
- The multiorgan failure syndrome caused by group A streptococci (GAS) designated streptococcal toxic shock syndrome (STSS) is believed to be mediated by cytokines induced by superantigens. In order to study the relationship between superantigen production, cytokine levels in patient sera, and clinical GAS manifestation we examined acute-phase sera and strains from 25 patients with GAS bacteremia. The patients had various disease manifestations, including STSS (44%), erysipelas (28%), septicemia (24%), wound infections (16%), and pneumonia (12%). Serotype T1M1 dominated, representing 56% of the isolates, but also strains of other serotypes were identified. The strains were found to produce the streptococcal pyrogenic exotoxins (Spe) A, B, and F, as determined by immuno-blot analyses. There was no difference in amounts of toxin produced between strains isolated from patients with different manifestations of disease. Levels of TNF alpha, IL1 alpha, IL6, IL8, and IFN gamma in acute-phase sera were determined by use of ELISA and RIA assays. The analyses showed higher levels of IL6 in sera from patients with STSS than in sera from patients with bacteremia without shock. TNF alpha was elevated in sera from patients with STSS, as compared to sera from patients with uncomplicated pharyngotonsillitis. No increase in the levels of IL1 alpha, IL8, and IFN gamma could be found in the patient sera and there was no difference in the level of those cytokines between the various patient categories.
|
|
