| 1. |
- Frick, Inga-Maria, et al.
(författare)
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Constitutive and Inflammation-Dependent Antimicrobial Peptides Produced by Epithelium Are Differentially Processed and Inactivated by the Commensal Finegoldia magna and the Pathogen Streptococcus pyogenes.
- 2011
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Ingår i: Journal of immunology. - : The American Association of Immunologists. - 1550-6606 .- 0022-1767. ; 187, s. 4300-4309
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Tidskriftsartikel (refereegranskat)abstract
- Epithelial linings serve as physical barriers and produce antimicrobial peptides (AMPs) to maintain host integrity. Examples are the bactericidal proteins midkine (MK) and BRAK/CXCL14 that are constitutively produced in the skin epidermal layer, where the anaerobic Gram-positive coccoid commensal Finegoldia magna resides. Consequently, this bacterium is likely to encounter both MK and BRAK/CXCL14, making these molecules possible threats to its habitat. In this study, we show that MK expression is upregulated during inflammation, concomitant with a strong downregulation of BRAK/CXCL14, resulting in changed antibacterial conditions. MK, BRAK/CXCL14, and the inflammation-dependent antimicrobial β-defensins human β-defensin (hBD)-2 and hBD-3 all showed bactericidal activity against both F. magna and the virulent pathogen Streptococcus pyogenes at similar concentrations. SufA, a released protease of F. magna, degraded MK and BRAK/CXCL14 but not hBD-2 nor hBD-3. Cleavage was seen at lysine and arginine residues, amino acids characteristic of AMPs. Intermediate SufA-degraded fragments of MK and BRAK/CXCL14 showed stronger bactericidal activity against S. pyogenes than F. magna, thus promoting survival of the latter. In contrast, the cysteine-protease SpeB of S. pyogenes rapidly degraded all AMPs investigated. The proteins FAF and SIC, released by F. magna and S. pyogenes, respectively, neutralized the antibacterial activity of MK and BRAK/CXCL14, protein FAF being the most efficient. Quantitation and colocalization by immunoelectron microscopy demonstrated significant levels and interactions of the molecules in in vivo and ex vivo samples. The findings reflect strategies used by a permanently residing commensal and a virulent pathogen, the latter operating during the limited time course of invasive disease.
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| 2. |
- Johansson, Maria U, et al.
(författare)
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Structure, specificity, and mode of interaction for bacterial albumin-binding modules.
- 2002
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Ingår i: Journal of Biological Chemistry. - 1083-351X .- 0021-9258. ; 277:10, s. 8114-8120
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Tidskriftsartikel (refereegranskat)abstract
- We have determined the solution structure of an albumin binding domain of protein G, a surface protein of group C and G streptococci. We find that it folds into a left handed three-helix bundle similar to the albumin binding domain of protein PAB from Peptostreptococcus magnus. The two domains share 59% sequence identity, are thermally very stable, and bind to the same site on human serum albumin. The albumin binding site, the first determined for this structural motif known as the GA module, comprises residues spanning the first loop to the beginning of the third helix and includes the most conserved region of GA modules. The two GA modules have different affinities for albumin from different species, and their albumin binding patterns correspond directly to the host specificity of C/G streptococci and P. magnus, respectively. These studies of the evolution, structure, and binding properties of the GA module emphasize the power of bacterial adaptation and underline ecological and medical problems connected with the use of antibiotics.
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| 3. |
- Bläckberg, Anna, et al.
(författare)
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Lack of Opsonic Antibody Responses to Invasive Infections With Streptococcus dysgalactiae
- 2021
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Ingår i: Frontiers in Microbiology. - : Frontiers Media SA. - 1664-302X. ; 12
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Tidskriftsartikel (refereegranskat)abstract
- Introduction: Streptococcus dysgalactiae can cause severe recurrent infections. This study aimed to investigate antibody responses following S. dysgalactiae bacteraemia and possible development of protective immunity. Materials and Methods: Patients with S. dysgalactiae bacteraemia in the county of Skåne between 2017 and 2018 were prospectively included. Acute and convalescent sera were obtained. All isolates were emm typed and enzyme-linked immunosorbent assay (ELISA) was utilised to analyse specific antibody responses to bacteria and antigens. Bactericidal- and phagocytosis assays were applied to further establish antibody function. Results: Sixteen patients with S. dysgalactiae bacteraemia were included of whom one had recurrent episodes of bacteraemia. Using ELISA with S. dysgalactiae isolates and mutants, development of IgG antibodies was demonstrated in few patients. Type-specific antibodies were demonstrated in one patient when recombinant M proteins as antigens, were applied. The type-specific serum mediated a small increase in phagocytosis but did not facilitate increased killing of the S. dysgalactiae isolate, carrying that M protein, in blood or by phagocytic cells. Conclusion: S. dysgalactiae bacteraemia sometimes results in increased levels of antibodies to the infecting pathogen. We did not find evidence that these antibodies are effectively opsonising. Apparent failure to produce opsonising antibodies might partially explain why S. dysgalactiae can cause recurrent invasive infections in the same host.
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| 4. |
- Burchacka, Ewa, et al.
(författare)
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Substrate profiling of Finegoldia magna SufA protease, inhibitor screening and application to prevent human fibrinogen degradation and bacteria growth in vitro.
- 2014
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Ingår i: Biochimie. - : Elsevier BV. - 1638-6183 .- 0300-9084. ; 103C:May 22, s. 137-143
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Tidskriftsartikel (refereegranskat)abstract
- SufA, which belongs to the subtilisin-like serine protease family, contains a non-canonical Asp-His-Ser catalytic triad. Under in vitro conditions, SufA is capable of human fibrinogen hydrolysis leading to inhibition of fibrin network formation, thus suggesting its important role in the development and progression of Finegoldia magna infections. In addition, it has been demonstrated that SufA can hydrolyze antibacterial peptides such as LL-37 and the chemokine MIG/CXCL 9, hence evading host defence mechanisms. Although the SufA protease from F. magna was discovered several years ago, its optimal substrate preference has not yet been identified. Considering the role of SufA, we have focused on the profiling of its substrate sequence preference spanning S1-S3 binding pockets using the FRET (fluorescence resonance energy transfer) approach. Next, based on the structure of the P1 residue of the developed substrate, we narrowed the inhibitor screening to the phosphonic analogues of amino acids containing an arginine-like side chain. Among all the compounds tested, only Cbz-6-AmNphth(P)(OPh)2 showed any inhibitory activity against SufA displaying k2/Ki value of 10 800 M(-1) s(-1). In addition, it prevented SufA-mediated human fibrinogen hydrolysis in vitro and exhibited potent antibacterial activity against F. magna, Staphylococcus aureus and Escherichia coli. Herein, we report on the substrate specificity, synthesis and kinetic evaluation of phosphonic inhibitors of SufA protease from F. magna which could help to establish its function in pathogenesis development and may lead to the elaboration of new antibacterial drugs.
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| 5. |
- Diehl, Carl, et al.
(författare)
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Structure and Interactions of a Dimeric Variant of sHIP, a Novel Virulence Determinant of Streptococcus pyogenes.
- 2016
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Ingår i: Frontiers in Microbiology. - : Frontiers Media SA. - 1664-302X. ; 7
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Tidskriftsartikel (refereegranskat)abstract
- Streptococcus pyogenes is one of the most significant bacterial pathogens in the human population mostly causing superficial and uncomplicated infections (pharyngitis and impetigo) but also invasive and life-threatening disease. We have previously identified a virulence determinant, protein sHIP, which is secreted at higher levels by an invasive compared to a non-invasive strain of S. pyogenes. The present work presents a further characterization of the structural and functional properties of this bacterial protein. Biophysical and structural studies have shown that protein sHIP forms stable tetramers both in the crystal and in solution. The tetramers are composed of four helix-loop-helix motifs with the loop regions connecting the helices displaying a high degree of flexibility. Owing to interactions at the tetramer interface, the observed tetramer can be described as a dimer of dimers. We identified three residues at the tetramer interface (Leu84, Leu88, Tyr95), which due to largely non-polar side-chains, could be important determinants for protein oligomerization. Based on these observations, we produced a sHIP variant in which these residues were mutated to alanines. Biophysical experiments clearly indicated that the sHIP mutant appear only as dimers in solution confirming the importance of the interfacial residues for protein oligomerisation. Furthermore, we could show that the sHIP mutant interacts with intact histidine-rich glycoprotein (HRG) and the histidine-rich repeats in HRG, and inhibits their antibacterial activity to the same or even higher extent as compared to the wild type protein sHIP. We determined the crystal structure of the sHIP mutant, which, as a result of the high quality of the data, allowed us to improve the existing structural model of the protein. Finally, by employing NMR spectroscopy in solution, we generated a model for the complex between the sHIP mutant and an HRG-derived heparin-binding peptide, providing further molecular details into the interactions involving protein sHIP.
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| 6. |
- Dinkla, Katrin, et al.
(författare)
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Identification of a streptococcal octapeptide motif involved in acute rheumatic fever
- 2007
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Ingår i: Journal of Biological Chemistry. - 1083-351X. ; 282:26, s. 18686-18693
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Tidskriftsartikel (refereegranskat)abstract
- Acute rheumatic fever is a serious autoimmune sequela of pharyngitis caused by certain group A streptococci. One mechanism applied by streptococcal strains capable of causing acute rheumatic fever is formation of an autoantigenic complex with human collagen IV. In some geographic regions with a high incidence of acute rheumatic fever pharyngeal carriage of group C and group G streptococci prevails. Examination of such strains revealed the presence of M-like surface proteins that bind human collagen. Using a peptide array and recombinant proteins with targeted amino acid substitutions, we could demonstrate that formation of collagen complexes during streptococcal infections depends on an octapeptide motif, which is present in collagen binding M and M-like proteins of different beta-hemolytic streptococcal species. Mice immunized with streptococcal proteins that contain the collagen binding octapeptide motif developed high serum titers of anti-collagen antibodies. In sera of rheumatic fever patients such a collagen autoimmune response was accompanied by specific reactivity against the collagen-binding proteins, linking the observed effect to clinical cases. Taken together, the data demonstrate that the identified octapeptide motif through its action on collagen plays a crucial role in the pathogenesis of rheumatic fever. Eradication of streptococci that express proteins with the collagen binding motif appears advisable for controlling rheumatic fever.
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| 7. |
- Egesten, Arne, et al.
(författare)
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Binding of albumin promotes bacterial survival at the epithelial surface.
- 2011
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Ingår i: Journal of Biological Chemistry. - 1083-351X. ; Dec, s. 2469-2476
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Tidskriftsartikel (refereegranskat)abstract
- Albumin (HSA) is the dominating protein in human plasma. Many bacterial species, especially streptococci, express surface proteins that bind HSA with high specificity and affinity, but the biological consequences of these protein-protein interactions are poorly understood. Group G streptococci (GGS), carrying the HSA-binding protein G, colonize the skin and the mucosa of the upper respiratory tract, mostly without causing disease. In case of bacterial invasion, pro-inflammatory cytokines are released that activate the epithelium to produce antibacterial peptides, in particular the chemokine MIG/CXCL9. In addition, the inflammation causes capillary leakage and extravasation of HSA and other plasma proteins; environmental changes at the epithelial surface to which the bacteria need to respond. In this study, we find that GGS adsorb HSA from both saliva and plasma via binding to protein G, and that HSA bound to protein G binds and inactivates the antibacterial MIG/CXCL9 peptide. Another surface protein of GGS, FOG, was found to mediate adherence of the bacteria to pharyngeal epithelial cells through interaction with glycosaminoglycans. This adherence was not affected by the activation of the epithelium with a combination of IFN-γ and TNF-α, leading to the production of MIG/CXCL9. However, at the activated epithelial surface, adherent GGS were protected against killing by MIG/CXCL9 through protein G dependent HSA-coating. The findings identify a previously unknown bacterial survival strategy that help to explain the evolution of HSA-binding proteins among bacterial species of the normal human microbiota.
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| 8. |
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| 9. |
- Eliasson, Mette, et al.
(författare)
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M1 protein of Streptococcus pyogenes increases production of the antibacterial CXC chemokine MIG/CXCL9 in pharyngeal epithelial cells
- 2007
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Ingår i: Microbial Pathogenesis. - : Elsevier BV. - 1096-1208 .- 0882-4010. ; 43:5-6, s. 224-233
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Tidskriftsartikel (refereegranskat)abstract
- Streptococcus pyogenes adheres to epithelial cells of the human pharynx where it can cause pharyngitis. To counteract infection. inflamed epithelium produces peptide antibiotics, among them the CXC chemokine MIG/CXCL9. M protein is both a surface-associated and released virulence factor of S. pyogenes. Here we show that soluble M1 protein enhances MIG gene expression and synthesis in IFN-gamma stimulated epithelial cells. M1 protein was recognized both by resting and IFN-gamma activated pharyngeal epithelial cells as detected by activation of the transcription factor NF-kappa B. Furthermore, pharmacological inhibition of NF-kappa B. decreased MIG synthesis in IFN-gamma activated cells, demonstrating a key role for NF-kappa B in mediating the enhanced response. Microarrays were used to investigate expression of recognized antimicrobial peptides in pharyngeal epithelial cells after stimulation with a combination of IFN-gamma and M1 protein. Amongst the most up-regulated and expressed genes, were several antibacterial CC and CXC chemokines. To investigate all in vivo context, pharyngeal mucosa was stimulated in vitro and MIG could be detected by immunohistochemistry in epithelial cells. The results show that epithelial cells can recognize solubilized M I protein and intact S. pyogenes, thereby modulating an antibacterial innate host response that may have bearing oil the outcome of streptococcal pharyngitis.
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| 10. |
- Ermert, David, et al.
(författare)
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Binding of complement inhibitor C4b-binding protein to a highly virulent S. pyogenes M1 strain is mediated by protein H and enhances adhesion to and invasion of endothelial cells.
- 2013
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Ingår i: Journal of Biological Chemistry. - 1083-351X. ; 288:45, s. 32172-32183
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Tidskriftsartikel (refereegranskat)abstract
- Streptococcus pyogenes AP1, a strain of the highly virulent M1 serotype, uses exclusively protein H to bind the complement inhibitor C4b-binding protein (C4BP). We found a strong correlation between the ability of AP1 and its isogenic mutants lacking protein H to inhibit opsonisation with complement C3b and binding of C4BP. C4BP bound to immobilized protein H or AP1 bacteria retained its cofactor activity for degradation of 125I-C4b. Further, C4b deposited from serum onto AP1 bacterial surfaces was processed into C4c/C4d fragments, which did not occur on strains unable to bind C4BP. Recombinant C4BP mutants, which (i) lack certain CCP domains, or (ii) have mutations in single aa as well as (iii) mutants with additional aa between different CCP domains were used to determine that the binding is mainly mediated by a patch of positively charged amino acid residues at the interface of domains CCP1 and CCP2. Using recombinant protein H fragments, we narrowed down the binding site to the N-terminal domain A. With a peptide microarray, we identified one single 18 amino acid long peptide comprising residues 92-109, which specifically bound C4BP. Biacore was used to determine KD = 6x10-7 M between protein H and a single subunit of C4BP. C4BP binding also correlated with elevated levels of adhesion and invasion to endothelial cells. Taken together, we identified the molecular basis of C4BP-protein H interaction and found that it is not only important for decreased opsonisation but also for invasion of endothelial cells by Streptococcus pyogenes.
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