| 1. |
- Bahnan, Wael, et al.
(author)
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A human monoclonal antibody bivalently binding two different epitopes in streptococcal M protein mediates immune function
- 2023
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In: EMBO Molecular Medicine. - : EMBO. - 1757-4684 .- 1757-4676. ; 15:2, s. 1-21
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Journal article (peer-reviewed)abstract
- Group A streptococci have evolved multiple strategies to evade human antibodies, making it challenging to create effective vaccines or antibody treatments. Here, we have generated antibodies derived from the memory B cells of an individual who had successfully cleared a group A streptococcal infection. The antibodies bind with high affinity in the central region of the surface-bound M protein. Such antibodies are typically non-opsonic. However, one antibody could effectively promote vital immune functions, including phagocytosis and in vivo protection. Remarkably, this antibody primarily interacts through a bivalent dual-Fab cis mode, where the Fabs bind to two distinct epitopes in the M protein. The dual-Fab cis-binding phenomenon is conserved across different groups of M types. In contrast, other antibodies binding with normal single-Fab mode to the same region cannot bypass the M protein's virulent effects. A broadly binding, protective monoclonal antibody could be a candidate for anti-streptococcal therapy. Our findings highlight the concept of dual-Fab cis binding as a means to access conserved, and normally non-opsonic regions, regions for protective antibody targeting.
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| 2. |
- Happonen, Lotta, et al.
(author)
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A quantitative Streptococcus pyogenes-human protein-protein interaction map reveals localization of opsonizing antibodies
- 2019
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In: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 10:1, s. 2727-2727
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Journal article (peer-reviewed)abstract
- A fundamental challenge in medical microbiology is to characterize the dynamic protein-protein interaction networks formed at the host-pathogen interface. Here, we generate a quantitative interaction map between the significant human pathogen, Streptococcus pyogenes, and proteins from human saliva and plasma obtained via complementary affinity-purification and bacterial-surface centered enrichment strategies and quantitative mass spectrometry. Perturbation of the network using immunoglobulin protease cleavage, mixtures of different concentrations of saliva and plasma, and different S. pyogenes serotypes and their isogenic mutants, reveals how changing microenvironments alter the interconnectivity of the interaction map. The importance of host immunoglobulins for the interaction with human complement proteins is demonstrated and potential protective epitopes of importance for phagocytosis of S. pyogenes cells are localized. The interaction map confirms several previously described protein-protein interactions; however, it also reveals a multitude of additional interactions, with possible implications for host-pathogen interactions involving other bacterial species.
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| 3. |
- Malmström, Johan, et al.
(author)
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Streptococcus pyogenes in human plasma: adaptive mechanisms analyzed by mass spectrometry based proteomics.
- 2012
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In: Journal of Biological Chemistry. - 1083-351X. ; 287:2, s. 1415-1425
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Journal article (peer-reviewed)abstract
- Streptococcus pyogenes is a major bacterial pathogen and a potent inducer of inflammation causing plasma leakage at the site of infection. A combination of label free quantitative mass spectrometry-based proteomics strategies were used to measure how the intracellular proteome homeostasis of S. pyogenes is influenced by the presence of human plasma, identifying and quantifying 842 proteins. In plasma the bacterium modifies its production of 213 proteins, and the most pronounced change was the complete down-regulation of proteins required for fatty acid biosynthesis (FAB). Fatty acids are transported by albumin (HSA) in plasma. S. pyogenes expresses HSA-binding surface proteins, and HSA carrying fatty acids reduced the amount of FAB proteins to the same extent as plasma. The results clarify the function of HSA-binding proteins in S. pyogenes and underline the power of the quantitative mass spectrometry strategy used here to investigate bacterial adaptation to a given environment.
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| 4. |
- Wisniewska, Magdalena, et al.
(author)
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Functional and Structural Properties of a Novel Protein and Virulence Factor (sHIP) in Streptococcus pyogenes.
- 2014
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In: Journal of Biological Chemistry. - 1083-351X. ; 289:26, s. 18175-18188
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Journal article (peer-reviewed)abstract
- Streptococcus pyogenes is a significant bacterial pathogen in the human population. The importance of virulence factors for the survival and colonization of S. pyogenes is well established, and many of these factors are exposed to the extracellular environment enabling bacterial interactions with the host. In the present study we quantitatively analyzed and compared S. pyogenes proteins in the growth medium of a strain that is virulent to mice, with a non-virulent strain. Particularly one of these proteins was present at significantly higher levels in stationary growth medium from the virulent strain. We determined the three-dimensional structure of the protein that showed a unique tetrameric organization composed of four helix-loop-helix motifs. Affinity pull-down mass spectrometry analysis in human plasma demonstrated that the protein interacts with histidine-rich glycoprotein (HRG), and the name sHIP (streptococcal Histidine-rich glycoprotein Interacting Protein) is therefore proposed. HRG has antibacterial activity, and when challenged by HRG, sHIP was found to rescue S. pyogenes bacteria. This and the finding that patients with invasive S. pyogenes infection respond with antibody production against sHIP, suggest a role for the protein in S. pyogenes pathogenesis.
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| 5. |
- Diehl, Carl, et al.
(author)
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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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In: Frontiers in Microbiology. - : Frontiers Media SA. - 1664-302X. ; 7
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Journal article (peer-reviewed)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. |
- Karlsson, Christofer A.Q., et al.
(author)
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Streptococcus pyogenes Infection and the Human Proteome with a Special Focus on the Immunoglobulin G-cleaving Enzyme IdeS
- 2018
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In: Molecular and Cellular Proteomics. - 1535-9476. ; 17:6, s. 1097-1111
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Journal article (peer-reviewed)abstract
- Infectious diseases are characterized by a complex interplay between host and pathogen, but how these interactions impact the host proteome is unclear. Here we applied a combined mass spectrometry-based proteomics strategy to investigate how the human proteome is transiently modified by the pathogen Streptococcus pyogenes, with a particular focus on bacterial cleavage of IgG in vivo. In invasive diseases, S. pyogenes evokes a massive host response in blood, whereas superficial diseases are characterized by a local leakage of several blood plasma proteins at the site of infection including IgG. S. pyogenes produces IdeS, a protease cleaving IgG in the lower hinge region and we find highly effective IdeS-cleavage of IgG in samples from local IgG poor microenvironments. The results show that IdeS contributes to the adaptation of S. pyogenes to its normal ecological niches. Additionally, the work identifies novel clinical opportunities for in vivo pathogen detection.
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| 7. |
- Nordenfelt, Pontus, et al.
(author)
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Antibody orientation at bacterial surfaces is related to invasive infection.
- 2012
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In: Journal of Experimental Medicine. - : Rockefeller University Press. - 1540-9538 .- 0022-1007. ; 209:13, s. 2367-2381
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Journal article (peer-reviewed)abstract
- Several of the most significant bacterial pathogens in humans, including Streptococcus pyogenes, express surface proteins that bind IgG antibodies via their fragment crystallizable (Fc) region, and the dogma is that this protects the bacteria against phagocytic killing in blood. However, analysis of samples from a patient with invasive S. pyogenes infection revealed dramatic differences in the presence and orientation of IgG antibodies at the surface of bacteria from different sites. In the throat, IgG was mostly bound to the bacterial surface via Fc, whereas in the blood IgG was mostly bound via fragment antigen-binding (Fab). In infected and necrotic tissue, the Fc-binding proteins were removed from the bacterial surface. Further investigation showed that efficient bacterial IgGFc-binding occurs only in IgG-poor environments, such as saliva. As a consequence, the bacteria are protected against phagocytic killing, whereas in blood plasma where the concentration of IgG is high, the antibodies preferentially bind via Fab, facilitating opsonization and bacterial killing. IgG-poor environments represent the natural habitat for IgGFc-binding bacteria, and IgGFc-binding proteins may have evolved to execute their function in such environments. The lack of protection in plasma also helps to explain why cases of severe invasive infections with IgGFc-binding bacteria are so rare compared with superficial and uncomplicated infections.
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| 8. |
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| 9. |
- Wollein Waldetoft, Kristofer, et al.
(author)
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Saliva-Induced Clotting Captures Streptococci : Novel Roles for Coagulation and Fibrinolysis in Host Defense and Immune Evasion
- 2016
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In: Infection and Immunity. - 1098-5522. ; 84:10, s. 23-2813
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Journal article (peer-reviewed)abstract
- Streptococcal pharyngitis is among the most common bacterial infections, but the molecular mechanisms involved remain poorly understood. Here we investigate the interactions among three major players in streptococcal pharyngitis: streptococci, plasma, and saliva. We find that saliva activates the plasma coagulation system through both the extrinsic and the intrinsic pathways, entrapping the bacteria in fibrin clots. The bacteria escape the clots by activating host plasminogen. Our results identify a potential function for the intrinsic pathway of coagulation in host defense and a corresponding role for fibrinolysis in streptococcal immune evasion.
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| 10. |
- Wollein Waldetoft, Kristofer, et al.
(author)
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Surface proteins of the Group G Streptococcus in different phases of growth: patterns of production and implications for the host-bacteria relationship.
- 2014
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In: Microbiology. - : Microbiology Society. - 1465-2080 .- 1350-0872. ; 160:Nov 12, s. 279-286
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Journal article (peer-reviewed)abstract
- Group G streptococcus (GGS) is a human bacterial pathogen expressing surface proteins FOG and protein G (PG) which interact with several host defense systems, including the complement and contact systems. Selected reaction monitoring mass spectrometry, electron microscopy, and protein binding assays were used to follow the amounts of FOG and PG intracellularly and on the bacterial surface during different phases of growth. Large and increasing amounts of PG were present on the surface in the stationary growth phase, and this was due to de novo production. In contrast, the amount of FOG did not change substantially during this phase. Apart from PG, a number of housekeeping proteins also increased in abundance in the stationary phase. These results show that GGS protein production is active during the stationary phase and that the bacteria actively remodel their surface and enter a less pro-inflammatory state in this phase.
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