Publications by authors named "Mohamed I Abdelwahab Hassan"

6 Publications

  • Page 1 of 1

Expression Patterns in Reductive Iron Assimilation and Functional Consequences during Phagocytosis of , an Emerging Cause of Mucormycosis.

J Fungi (Basel) 2021 Apr 3;7(4). Epub 2021 Apr 3.

Jena Microbial Resource Collection, Leibniz Institute for Natural Product Research, and Infection Biology-Hans Knöll Institute (HKI), 07745 Jena, Germany.

Iron is an essential micronutrient for most organisms and fungi are no exception. Iron uptake by fungi is facilitated by receptor-mediated internalization of siderophores, heme and reductive iron assimilation (RIA). The RIA employs three protein groups: (i) the ferric reductases (Fre5 proteins), (ii) the multicopper ferroxidases (Fet3) and (iii) the high-affinity iron permeases (Ftr1). Phenotyping under different iron concentrations revealed detrimental effects on spore swelling and hyphal formation under iron depletion, but yeast-like morphology under iron excess. Since access to iron is limited during pathogenesis, pathogens are placed under stress due to nutrient limitations. To combat this, gene duplication and differential gene expression of key iron uptake genes are utilized to acquire iron against the deleterious effects of iron depletion. In the genome of the human pathogenic fungus , three, four and three copies were identified for , and genes, respectively. As in other fungi, and are syntenic and co-expressed in . Expression of , and genes is highly up-regulated during iron limitation (Fe-), but lower during iron excess (Fe+). Fe- dependent upregulation of gene expression takes place in II and III, I and II, as well as I and II suggesting a functional role in pathogenesis. The syntenic I- I gene pair is co-expressed during germination, whereas II- II is co-expressed during hyphal proliferation. I, II and IV were overexpressed in to represent high and moderate expression of intracellular transport of Fe3+, respectively. Challenge of macrophages with the yeast mutants revealed no obvious role for I, but possible functions of II and IVs in recognition by macrophages. RIA expression pattern was used for a new model of interaction between and macrophages.
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http://dx.doi.org/10.3390/jof7040272DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8065604PMC
April 2021

The impact of episporic modification of on virulence and interaction with phagocytes.

Comput Struct Biotechnol J 2021 20;19:880-896. Epub 2021 Jan 20.

Leibniz Institute for Natural Product Research and Infection Biology - Hans Knöll Institute (HKI), Jena, Germany.

Fungal infections caused by the ancient lineage Mucorales are emerging and increasingly reported in humans. Comprehensive surveys on promising attributes from a multitude of possible virulence factors are limited and so far, focused on and . This study addresses a systematic approach to monitor phagocytosis after physical and enzymatic modification of the outer spore wall of , one of the major causative agents of mucormycosis. Episporic modifications were performed and their consequences on phagocytosis, intracellular survival and virulence by murine alveolar macrophages and in an invertebrate infection model were elucidated. While depletion of lipids did not affect the phagocytosis of both strains, delipidation led to attenuation of LCA strain but appears to be dispensable for infection with LCV strain in the settings used in this study. Combined glucano-proteolytic treatment was necessary to achieve a significant decrease of virulence of the LCV strain in during maintenance of the full potential for spore germination as shown by a novel automated germination assay. Proteolytic and glucanolytic treatments largely increased phagocytosis compared to alive resting and swollen spores. Whilst resting spores barely (1-2%) fuse to lysosomes after invagination in to phagosomes, spore trypsinization led to a 10-fold increase of phagolysosomal fusion as measured by intracellular acidification. This is the first report of a polyphasic measurement of the consequences of episporic modification of a mucormycotic pathogen in spore germination, spore surface ultrastructure, phagocytosis, stimulation of Toll-like receptors (TLRs), phagolysosomal fusion and intracellular acidification, apoptosis, generation of reactive oxygen species (ROS) and virulence.
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http://dx.doi.org/10.1016/j.csbj.2021.01.023DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7851798PMC
January 2021

Functional surface proteomic profiling reveals the host heat-shock protein A8 as a mediator of Lichtheimia corymbifera recognition by murine alveolar macrophages.

Environ Microbiol 2020 09 21;22(9):3722-3740. Epub 2020 Jul 21.

Jena Microbial Resource Collection, Leibniz Institute for Natural Product Research and Infection Biology - Hans Knöll Institute (HKI), Jena, Germany.

Mucormycosis is an emergent, fatal fungal infection of humans and warm-blooded animals caused by species of the order Mucorales. Immune cells of the innate immune system serve as the first line of defence against inhaled spores. Alveolar macrophages were challenged with the mucoralean fungus Lichtheimia corymbifera and subjected to biotinylation and streptavidin enrichment procedures followed by LC-MS/MS analyses. A total of 28 host proteins enriched for binding to macrophage-L. corymbifera interaction. Among those, the HSP70-family protein Hspa8 was found to be predominantly responsive to living and heat-killed spores of a virulent and an attenuated strain of L. corymbifera. Confocal scanning laser microscopy of infected macrophages revealed colocalization of Hspa8 with phagocytosed spores of L. corymbifera. The amount of detectable Hspa8 was dependent on the multiplicity of infection. Incubation of alveolar macrophages with an anti-Hspa8 antibody prior to infection reduced their capability to phagocytose spores of L. corymbifera. In contrast, anti-Hspa8 antibodies did not abrogate the phagocytosis of Aspergillus fumigatus conidia by macrophages. These results suggest an important contribution of the heat-shock family protein Hspa8 in the recognition of spores of the mucoralean fungus L. corymbifera by host alveolar macrophages and define a potential immunomodulatory therapeutic target.
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http://dx.doi.org/10.1111/1462-2920.15140DOI Listing
September 2020

Quantitative Impact of Cell Membrane Fluorescence Labeling on Phagocytosis Measurements in Confrontation Assays.

Front Microbiol 2020 5;11:1193. Epub 2020 Jun 5.

Applied Systems Biology, Leibniz Institute for Natural Product Research and Infection Biology - Hans Knöll Institute, Jena, Germany.

Phagocytosis is series of steps where the pathogens and the immune cells interact during an invasion. This starts with the adhesion process between the host and pathogen cells, and is followed by the engulfment of the pathogens. Many analytical methods that are applied to characterize phagocytosis based on imaging the host-pathogen confrontation assays rely on the fluorescence labeling of cells. However, the potential effect of the membrane labeling on the quantitative results of the confrontation assays has not been studied in detail. In this study, we determine whether the fluorescence labeling processes themselves influence the results of the phagocytosis measurements. Here, alveolar macrophages, which form one of the most important compartments of the innate immune system, were used as an example of host cells, whereas and that cause aspergillosis and mucormycosis, respectively, were studied as examples for pathogens. At first, our study investigated the importance of the sequence of steps of the fixation process when preparing the confrontation assay sample for microscopy studies. Here we showed that applying the fixation agent before the counter-staining causes miscalculations during the determination of the phagocytic measures. Furthermore, we also found that staining the macrophages with various concentrations of DID, as a typical membrane label, in most cases altered the capability of macrophages to phagocytose FITC-stained and spores in comparison with unlabeled macrophages. This effect of the DID staining showed a differential character dependent upon the labeling status and the specific type of pathogen. Moreover, labeling the spores of and with FITC increased the phagocytic measures during confrontation with unlabeled macrophages when compared to label-free spores. Overall, our study confirms that the staining process itself may significantly manipulate the quantitative outcome of the confrontation assay. As a result of our study, we also developed a user-friendly image analysis tool that analyses confrontation assays both with and without fluorescence labeling of the host cells and of the pathogens. Our image analysis algorithm saves experimental work effort and time, provides more precise results when calculating the phagocytic measures, and delivers a convenient analysis tool for the biologists to monitor host-pathogen interactions as they happen without the artifacts that fluorescence labeling imposes on biological interactions.
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http://dx.doi.org/10.3389/fmicb.2020.01193DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7289966PMC
June 2020

The geographical region of origin determines the phagocytic vulnerability of Lichtheimia strains.

Environ Microbiol 2019 12 5;21(12):4563-4581. Epub 2019 Aug 5.

Institute of Microbiology, Faculty of Biological Sciences, Friedrich Schiller University Jena, Jena, Germany.

Mucormycoses are life-threatening infections that affect patients suffering from immune deficiencies. We performed phagocytosis assays confronting various strains of Lichtheimia species with alveolar macrophages, which form the first line of defence of the innate immune system. To investigate 17 strains from four different continents in a comparative fashion, transmitted light and confocal fluorescence microscopy was applied in combination with automated image analysis. This interdisciplinary approach enabled the objective and quantitative processing of the big volume of image data. Applying machine-learning supported methods, a spontaneous clustering of the strains was revealed in the space of phagocytic measures. This clustering was not driven by measures of fungal morphology but rather by the geographical origin of the fungal strains. Our study illustrates the crucial contribution of machine-learning supported automated image analysis to the qualitative discovery and quantitative comparison of major factors affecting host-pathogen interactions. We found that the phagocytic vulnerability of Lichtheimia species depends on their geographical origin, where strains within each geographic region behaved similarly, but strongly differed amongst the regions. Based on this clustering, we were able to also classify clinical isolates with regard to their potential geographical origin.
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http://dx.doi.org/10.1111/1462-2920.14752DOI Listing
December 2019

Pathogenicity patterns of mucormycosis: epidemiology, interaction with immune cells and virulence factors.

Med Mycol 2019 Apr;57(Supplement_2):S245-S256

Jena Microbial Resource Collection, Leibniz Institute for Natural Product Research and Infection Biology - Hans Knoell Institute, Adolf-Reichwein-Strasse 23, 07745 Jena, Germany.

Fungi of the basal lineage order Mucorales are able to cause infections in animals and humans. Mucormycosis is a well-known, life-threatening disease especially in patients with a compromised immune system. The rate of mortality and morbidity caused by mucormycosis has increased rapidly during the last decades, especially in developing countries. The systematic, phylogenetic, and epidemiological distributions of mucoralean fungi are addressed in relation to infection in immunocompromised patients. The review highlights the current achievements in (i) diagnostics and management of mucormycosis, (ii) the study of the interaction of Mucorales with cells of the innate immune system, (iii) the assessment of the virulence of Mucorales in vertebrate and invertebrate infection models, and (iv) the determination of virulence factors that are key players in the infection process, for example, high-affinity iron permease (FTR1), spore coat protein (CotH), alkaline Rhizopus protease enzyme (ARP), ADP-ribosylation factor (ARF), dihydrolipoyl dehydrogenase, calcineurin (CaN), serine and aspartate proteases (SAPs). The present mini-review attempts to increase the awareness of these difficult-to-manage fungal infections and to encourage research in the detection of ligands and receptors as potential diagnostic parameters and drug targets.
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http://dx.doi.org/10.1093/mmy/myz011DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6394756PMC
April 2019
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