4 results on '"Innate immunity"'
Search Results
2. A Virtual Infection Model Quantifies Innate Effector Mechanisms and Candida albicans Immune Escape in Human Blood.
- Author
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Hünniger, Kerstin, Lehnert, Teresa, Bieber, Kristin, Martin, Ronny, Figge, Marc Thilo, and Kurzai, Oliver
- Subjects
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NATURAL immunity , *BLOOD , *CANDIDA albicans , *FUNGAL cell walls , *NEUTROPHILS - Abstract
Candida albicans bloodstream infection is increasingly frequent and can result in disseminated candidiasis associated with high mortality rates. To analyze the innate immune response against C. albicans, fungal cells were added to human whole-blood samples. After inoculation, C. albicans started to filament and predominantly associate with neutrophils, whereas only a minority of fungal cells became attached to monocytes. While many parameters of host-pathogen interaction were accessible to direct experimental quantification in the whole-blood infection assay, others were not. To overcome these limitations, we generated a virtual infection model that allowed detailed and quantitative predictions on the dynamics of host-pathogen interaction. Experimental time-resolved data were simulated using a state-based modeling approach combined with the Monte Carlo method of simulated annealing to obtain quantitative predictions on a priori unknown transition rates and to identify the main axis of antifungal immunity. Results clearly demonstrated a predominant role of neutrophils, mediated by phagocytosis and intracellular killing as well as the release of antifungal effector molecules upon activation, resulting in extracellular fungicidal activity. Both mechanisms together account for almost of C. albicans killing, clearly proving that beside being present in larger numbers than other leukocytes, neutrophils functionally dominate the immune response against C. albicans in human blood. A fraction of C. albicans cells escaped phagocytosis and remained extracellular and viable for up to four hours. This immune escape was independent of filamentation and fungal activity and not linked to exhaustion or inactivation of innate immune cells. The occurrence of C. albicans cells being resistant against phagocytosis may account for the high proportion of dissemination in C. albicans bloodstream infection. Taken together, iterative experiment–model–experiment cycles allowed quantitative analyses of the interplay between host and pathogen in a complex environment like human blood. [ABSTRACT FROM AUTHOR]
- Published
- 2014
- Full Text
- View/download PDF
3. A Mathematical Model of CR3/TLR2 Crosstalk in the Context of Francisella tularensis Infection
- Author
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Rachel Leander, Larry S. Schlesinger, Avner Friedman, and Shipan Dai
- Subjects
MAPK/ERK pathway ,Bacterial Diseases ,Biology (General) ,Francisella tularensis ,Immune Response ,Tularemia ,0303 health sciences ,Ecology ,biology ,030302 biochemistry & molecular biology ,Pattern recognition receptor ,Innate Immunity ,Bacterial Pathogens ,Host-Pathogen Interaction ,Crosstalk (biology) ,Infectious Diseases ,Computational Theory and Mathematics ,Modeling and Simulation ,Host-Pathogen Interactions ,Medicine ,Research Article ,Signal Transduction ,QH301-705.5 ,Immunology ,Macrophage-1 Antigen ,Microbiology ,Models, Biological ,Immunomodulation ,03 medical and health sciences ,Cellular and Molecular Neuroscience ,Phagocytosis ,Genetics ,Humans ,Computer Simulation ,Molecular Biology ,Protein kinase B ,Biology ,Ecology, Evolution, Behavior and Systematics ,PI3K/AKT/mTOR pathway ,030304 developmental biology ,Innate immune system ,Macrophages ,Immunity ,biology.organism_classification ,Toll-Like Receptor 2 ,TLR2 ,Computer Science ,Infectious Disease Modeling - Abstract
Complement Receptor 3 (CR3) and Toll-like Receptor 2 (TLR2) are pattern recognition receptors expressed on the surface of human macrophages. Although these receptors are essential components for recognition by the innate immune system, pathogen coordinated crosstalk between them can suppress the production of protective cytokines and promote infection. Recognition of the virulent Schu S4 strain of the intracellular pathogen Francisella tularensis by host macrophages involves CR3/TLR2 crosstalk. Although experimental data provide evidence that Lyn kinase and PI3K are essential components of the CR3 pathway that influences TLR2 activity, additional responsible upstream signaling components remain unknown. In this paper we construct a mathematical model of CR3 and TLR2 signaling in response to F. tularensis. After demonstrating that the model is consistent with experimental results we perform numerical simulations to evaluate the contributions that Akt and Ras-GAP make to ERK inhibition. The model confirms that phagocytosis-associated changes in the composition of the cell membrane can inhibit ERK activity and predicts that Akt and Ras-GAP synergize to inhibit ERK., Author Summary In the current work we construct a highly contextual model of membrane-proximal crosstalk between the ERK and PI3K cascades that is initiated through contact with F. tularensis. The model is used to test the hypothesis that phagocytic signaling downstream from CR3 is responsible for an early inhibition of ERK activity, which is seen subsequent to contact with the complement C3-opsonized Schu S4 strain of F. tularensis. In addition, the model predicts that Akt and Ras-GAP synergize to inhibit ERK. To the best of our knowledge this is the first mathematical model to investigate crosstalk between these pathways within the context of infection. By providing a comprehensive picture of the initial host-pathogen interaction, and pathogen-induced crosstalk between cell surface receptors in particular, this model is important in the context of microbial immunopathogenesis.
- Published
- 2012
4. A Kinetic Platform to Determine the Fate of Nitric Oxide in Escherichia coli
- Author
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Robinson, Jonathan L. and Brynildsen, Mark P.
- Subjects
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NITRIC oxide , *IMMUNE response , *PATHOGENIC microorganisms , *OXIDATION , *CHEMICAL kinetics , *ESCHERICHIA coli , *DIOXYGENASES - Abstract
Nitric oxide (NO•) is generated by the innate immune response to neutralize pathogens. NO• and its autoxidation products have an extensive biochemical reaction network that includes reactions with iron-sulfur clusters, DNA, and thiols. The fate of NO• inside a pathogen depends on a kinetic competition among its many targets, and is of critical importance to infection outcomes. Due to the complexity of the NO• biochemical network, where many intermediates are short-lived and at extremely low concentrations, several species can be measured, but stable products are non-unique, and damaged biomolecules are continually repaired or regenerated, kinetic models are required to understand and predict the outcome of NO• treatment. Here, we have constructed a comprehensive kinetic model that encompasses the broad reactivity of NO• in Escherichia coli. The incorporation of spontaneous and enzymatic reactions, as well as damage and repair of biomolecules, allowed for a detailed analysis of how NO• distributes in E. coli cultures. The model was informed with experimental measurements of NO• dynamics, and used to identify control parameters of the NO• distribution. Simulations predicted that NO• dioxygenase (Hmp) functions as a dominant NO• consumption pathway at O2 concentrations as low as 35 µM (microaerobic), and interestingly, loses utility as the NO• delivery rate increases. We confirmed these predictions experimentally by measuring NO• dynamics in wild-type and mutant cultures at different NO• delivery rates and O2 concentrations. These data suggest that the kinetics of NO• metabolism must be considered when assessing the importance of cellular components to NO• tolerance, and that models such as the one described here are necessary to rigorously investigate NO• stress in microbes. This model provides a platform to identify novel strategies to potentiate the effects of NO•, and will serve as a template from which analogous models can be generated for other organisms. [ABSTRACT FROM AUTHOR]
- Published
- 2013
- Full Text
- View/download PDF
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