| 1. |
- Areschoug, Thomas, et al.
(författare)
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Host-pathogen interactions in Streptococcus pyogenes infections, with special reference to puerperal fever and a comment on vaccine development.
- 2004
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Ingår i: Vaccine. - : Elsevier BV. - 1873-2518 .- 0264-410X. ; 22 Suppl 1:Suppl 1, s. 9-14
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Tidskriftsartikel (refereegranskat)abstract
- Streptococcus pyogenes (group A streptococcus) causes a variety of diseases, including acute pharyngitis, impetigo, rheumatic fever and the streptococcal toxic shock syndrome. Moreover, S. pyogenes was responsible for the classical example of a nosocomial infection, the epidemics of puerperal fever (childbed fever) that caused the death of numerous women in earlier centuries. The most extensively studied virulence factor of S. pyogenes is the surface M protein, which inhibits phagocytosis and shows antigenic variation. Recent data indicate that many M proteins confer phagocytosis resistance because the variable N-terminal region has non-overlapping sites that specifically bind two components of the human immune system, the complement inhibitor C4b-binding protein (C4BP) and IgA-Fc. Concerning puerperal fever, molecular and epidemiological analysis suggests that the S. pyogenes surface protein R28 may have played a pathogenetic role in these epidemics. This article summarizes the properties of M protein and the R28 protein and considers a potential problem encountered in connection with the use of animal models for vaccine development.
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| 2. |
- Carlsson, Fredric, et al.
(författare)
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Evasion of phagocytosis through cooperation between two ligand-binding regions in Streptococcus pyogenes M protein.
- 2003
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Ingår i: Journal of Experimental Medicine. - : Rockefeller University Press. - 1540-9538 .- 0022-1007. ; 198:7, s. 1057-1068
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Tidskriftsartikel (refereegranskat)abstract
- The M protein of Streptococcus pyogenes is a major bacterial virulence factor that confers resistance to phagocytosis. To analyze how M protein allows evasion of phagocytosis, we used the M22 protein, which has features typical of many M proteins and has two well-characterized regions binding human plasma proteins: the hypervariable NH2-terminal region binds C4b-binding protein (C4BP), which inhibits the classical pathway of complement activation; and an adjacent semivariable region binds IgA-Fc. Characterization of chromosomal S. pyogenes mutants demonstrated that each of the ligand-binding regions contributed to phagocytosis resistance, which could be fully explained as cooperation between the two regions. Deposition of complement on S. pyogenes occurred almost exclusively via the classical pathway, even under nonimmune conditions, but was down-regulated by bacteria-bound C4BP, providing an explanation for the ability of bound C4BP to inhibit phagocytosis. Different opsonizing antisera shared the ability to block binding of both C4BP and IgA, suggesting that the two regions in M22 play important roles also under immune conditions, as targets for protective antibodies. These data indicate that M22 and similar M proteins confer resistance to phagocytosis through ability to bind two components of the human immune system.
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| 3. |
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| 4. |
- Carlsson, Fredric
(författare)
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Resistance to phagocytosis in Streptococcus pyogenes
- 2005
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Phagocytosis of Streptococcus pyogenes is complement dependent. However, the cell wall-associated M protein, which exists in >100 different serotypes (M types), enables the bacteria to evade phagocytosis. To analyze the mechanisms by which M protein confers this ability we used, as model systems, two representative M proteins, the M22 and M5 proteins, which have properties typical for many M proteins of different M type.
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| 5. |
- Carlsson, Fredric, et al.
(författare)
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Signal sequence directs localized secretion of bacterial surface proteins.
- 2006
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 442:7105, s. 943-946
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Tidskriftsartikel (refereegranskat)abstract
- All living cells require specific mechanisms that target proteins to the cell surface. In eukaryotes, the first part of this process involves recognition in the endoplasmic reticulum of amino-terminal signal sequences and translocation through Sec translocons, whereas subsequent targeting to different surface locations is promoted by internal sorting signals(1). In bacteria, N-terminal signal sequences promote translocation across the cytoplasmic membrane, which surrounds the entire cell, but some proteins are nevertheless secreted in one part of the cell by poorly understood mechanisms(2,3). Here we analyse localized secretion in the Gram-positive pathogen Streptococcus pyogenes, and show that the signal sequences of two surface proteins, M protein and protein F ( PrtF), direct secretion to different subcellular regions. The signal sequence of M protein promotes secretion at the division septum, whereas that of PrtF preferentially promotes secretion at the old pole. Our work therefore shows that a signal sequence may contain information that directs the secretion of a protein to one subcellular region, in addition to its classical role in promoting secretion. This finding identifies a new level of complexity in protein translocation and emphasizes the potential of bacterial systems for the analysis of fundamental cell-biological problems(4).
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| 6. |
- Gårdhagen, Roland, et al.
(författare)
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Large Eddy Simulation of Stenotic Flow for Wall Shear Stress Estimation - Validation and Application
- 2011
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Ingår i: WSEAS Transactions on Biology and Biomedicine. - 1109-9518. ; 8:3, s. 86-101
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Tidskriftsartikel (refereegranskat)abstract
- Turbulent flow in the cardiovascular system may increase the risk for severe arterial disease. This workaddresses the feasibility of Large Eddy Simulation (LES) using a general purpose code as a tool for assessmentof cardiovascular flow and investigates Wall Shear Stress (WSS) in steady as well as pulsating turbulent pipeflow. Poiseuille flow was specified at the inlet, and with a suitable ammount of perturbations at the inlet it waspossible to predict experimental data. The extent of the recirculation zone was affected by the inlet disturbances,and magnitude as well as direction of the WSS vector varied significantly at the reattachment point. For thepulsating flow, WSS shows a complex pattern with different spatial and temporal variation along the pipe. Thewall shear stress gradient was calculated on the entire post-stenotic surface and each component in the gradientwas investigated. The off-diagonal components in the gradient are usually assumed to be small, but here they werefound to be on the same order of magnitude as the diagonal terms. This work demonstrates the need for a scaleresolving simulation technique to accurately model cardiovascular flows.
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| 7. |
- Lienard, Julia, et al.
(författare)
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A Murine Mycobacterium marinum Infection Model for Longitudinal Analyses of Disease Development and the Inflammatory Response
- 2023. - 2
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Ingår i: Bacterial Pathogenesis : Methods and Protocols - Methods and Protocols. - 1064-3745 .- 1940-6029. - 9781071632451 - 9781071632437 ; 2674, s. 313-326
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Bokkapitel (refereegranskat)abstract
- Mycobacterial infections, including tuberculosis, are a major health problem globally. Prevention and treatments of tuberculosis are challenging due to the poor efficacy of the current vaccine and the emergence of drug-resistant strains. Therefore, it is critical to increase our basic understanding of mycobacterial virulence strategies as well as the host immune response during infection in the complex in vivo setting. While existing infection models provide valuable tools for investigating mycobacterial pathogenesis, they also exhibit limitations that can be addressed by the development of complementary models. Here we describe recent advances to the murine Mycobacterium marinum infection model, in which the bacteria produce a local infection restricted to the tail tissue. The M. marinum model has the advantage of mimicking some of the key hallmarks of human tuberculosis not replicated in the conventional murine Mycobacterium tuberculosis model, such as the formation of granulomas with central caseating necrosis and the spontaneous development of a latency-like stage. Moreover, the model is non-lethal and enables longitudinal analysis of disease development in live animals. In this chapter, we report protocols to prepare infected tissue samples for detailed and quantitative analysis of the immune response by flow cytometry, immunofluorescence microscopy, RT-qPCR, ELISA, and Western blot, as well as for the analysis of bacterial load and localization.
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| 8. |
- Lienard, Julia, et al.
(författare)
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ESX-1 exploits type I IFN-signalling to promote a regulatory macrophage phenotype refractory to IFNγ-mediated autophagy and growth restriction of intracellular mycobacteria
- 2016
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Ingår i: Cellular Microbiology. - : Hindawi Limited. - 1462-5814. ; 18:10, s. 1471-1485
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Tidskriftsartikel (refereegranskat)abstract
- Summary: The ability of macrophages to eradicate intracellular pathogens is normally greatly enhanced by IFNγ, a cytokine produced mainly after onset of adaptive immunity. However, adaptive immunity is unable to provide sterilizing immunity against mycobacteria, suggesting that mycobacteria have evolved virulence strategies to inhibit the bactericidal effect of IFNγ-signalling in macrophages. Still, the host-pathogen interactions and cellular mechanisms responsible for this feature have remained elusive. We demonstrate that the ESX-1 type VII secretion systems of Mycobacterium tuberculosis and Mycobacteriummarinum exploit type I IFN-signalling to promote an IL-12low/IL-10high regulatory macrophage phenotype characterized by secretion of IL-10, IL-27 and IL-6. This mechanism had no impact on intracellular growth in the absence of IFNγ but suppressed IFNγ-mediated autophagy and growth restriction, indicating that the regulatory phenotype extends to function. The IFNγ-refractory phenotype was partly mediated by IL-27-signalling, establishing functional relevance for this downstream cytokine. These findings identify a novel macrophage-modulating function for the ESX-1 secretion system that may contribute to suppress the efficacy of adaptive immunity and provide mechanistic insight into the antagonistic cross talk between type I IFNs and IFNγ in mycobacterial infection.
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| 9. |
- Lienard, Julia, et al.
(författare)
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Intragranuloma Accumulation and Inflammatory Differentiation of Neutrophils Underlie Mycobacterial ESX-1-Dependent Immunopathology
- 2023
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Ingår i: mBio. - 2161-2129. ; 14:2
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Tidskriftsartikel (refereegranskat)abstract
- The conserved ESX-1 type VII secretion system is a major virulence determinant of pathogenic mycobacteria, including Mycobacterium tuberculosis and Mycobacterium marinum. ESX-1 is known to interact with infected macrophages, but its potential roles in regulating other host cells and immunopathology have remained largely unexplored. Using a murine M. marinum infection model, we identify neutrophils and Ly6C +MHCII + monocytes as the main cellular reservoirs for the bacteria. We show that ESX-1 promotes intragranuloma accumulation of neutrophils and that neutrophils have a previously unrecognized required role in executing ESX-1-mediated pathology. To explore if ESX-1 also regulates the function of recruited neutrophils, we performed a single-cell RNA-sequencing analysis that indicated that ESX-1 drives newly recruited uninfected neutrophils into an inflammatory phenotype via an extrinsic mechanism. In contrast, monocytes restricted the accumulation of neutrophils and immunopathology, demonstrating a major host-protective function for monocytes specifically by suppressing ESX-1-dependent neutrophilic inflammation. Inducible nitric oxide synthase (iNOS) activity was required for the suppressive mechanism, and we identified Ly6C +MHCII + monocytes as the main iNOS-expressing cell type in the infected tissue. These results suggest that ESX-1 mediates immunopathology by promoting neutrophil accumulation and phenotypic differentiation in the infected tissue, and they demonstrate an antagonistic interplay between monocytes and neutrophils by which monocytes suppress host-detrimental neutrophilic inflammation. IMPORTANCE The ESX-1 type VII secretion system is required for virulence of pathogenic mycobacteria, including Mycobacterium tuberculosis. ESX-1 interacts with infected macrophages, but its potential roles in regulating other host cells and immunopathology have remained largely unexplored. We demonstrate that ESX-1 promotes immunopathology by driving intragranuloma accumulation of neutrophils, which upon arrival adopt an inflammatory phenotype in an ESX-1-dependent manner. In contrast, monocytes limited the accumulation of neutrophils and neutrophil-mediated pathology via an iNOS-dependent mechanism, suggesting a major host-protective function for monocytes specifically by restricting ESX-1-dependent neutrophilic inflammation. These findings provide insight into how ESX-1 promotes disease, and they reveal an antagonistic functional relationship between monocytes and neutrophils that might regulate immunopathology not only in mycobacterial infection but also in other infections as well as in inflammatory conditions and cancer.
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| 10. |
- Lienard, Julia, et al.
(författare)
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Murine Mycobacterium marinum infection as a model for tuberculosis
- 2017
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Ingår i: Methods in Molecular Biology. - New York, NY : Springer New York. - 1064-3745. ; 1535, s. 301-315
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Bokkapitel (refereegranskat)abstract
- Mycobacteria are a major human health problem globally. Regarding tuberculosis the situation is worsened by the poor efficacy of current vaccine regimens and by emergence of drug-resistant strains (Manjelievskaia J et al, Trans R Soc Trop Med Hyg 110: 110, 2016; Pereira et al., Lancet Infect Dis 12:300–306, 2012; http://www.who.int/tb/publications/global_report/en/) undermining both disease-prevention and available treatments. Thus, increased basic understanding of mycobacterial—and particularly Mycobacterium tuberculosis —virulence strategies and pathogenesis is of great importance. To this end several in vivo infection models are available (Guirado and Schlesinger, Front Immunol 4:98, 2013; Leung et al., Eur J Immunol 43:2246–2254, 2013; Patel et al., J Lab Physicians 3:75–79, 2011; van Leeuwen et al., Cold Spring Harb Perspect Med 5:a018580, 2015). While these models all have their merits they also exhibit limitations, and none perfectly mimics all aspects of human tuberculosis. Thus, there is a need for multiple models that may complement each other, ultimately allowing us to gain true insight into the pathogenesis of mycobacterial infections. Here, we describe a recently developed mouse model of Mycobacterium marinum infection that allows kinetic and quantitative studies of disease progression in live animals [8]. Notably, this model exhibits features of human tuberculosis not replicated in M. tuberculosis infected mice, and may provide an important complement to the field. For example, granulomas in the M. marinum model develop central caseating necrosis (Carlsson et al., PLoS Pathog 6:e1000895, 2010), a hallmark of granulomas in human tuberculosis normally not replicated in murine M. tuberculosis infection. Moreover, while tuberculosis is heterogeneous and presents with a continuum of active and latent disease, M. tuberculosis infected mice essentially lack this dynamic range and do not replicate latency (Guirado and Schlesinger, Front Immunol 4:98, 2013; Patel et al., J Lab Physicians 3(2):75–79, 2011). In contrast, M. marinum infected mice may naturally develop latency, as suggested by reduced inflammation and healing of the diseased tissue while low numbers of bacteria persist in granulomatous lesions (Carlsson et al., PLoS Pathog 6:e1000895, 2010). Thus, infection with M. marinum may offer a unique murine model for studying granuloma formation as well as latency— and possibly also for studies of disease-reactivation. In addition to the in vivo model, we describe infection of bone marrow-derived murine macrophages, an in vitro platform enabling detailed mechanistic studies of host-pathogen interactions occurring in the principal host target cell for pathogenic mycobacteria.
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