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Archives of Biochemistry and Biophysics Dec 2020Histoplasma capsulatum is an ascomyceteous fungus and a human lung pathogen, which is present in river valleys of the Americas and other continents. H. capsulatum and...
Histoplasma capsulatum is an ascomyceteous fungus and a human lung pathogen, which is present in river valleys of the Americas and other continents. H. capsulatum and two related human pathogens, Blasmomyces dermatitidis and Paracoccidioides brasiliensis, belongs to the Ajellomycetaceae family. The genomes of all three species code for three homologous and tentative enzymes of the linoleate diol synthase (LDS) family of fusion enzymes with dioxygenase (DOX) and cytochrome P450 domains. One group aligned closely with 8R-DOX-5,8-LDS of Aspergilli, which oxidizes linoleic acid to 5S,8R-dihydroxylinoleic acid; this group was not further investigated. The second group aligned with 10R-DOX-epoxy alcohol synthase (EAS) of plant pathogens. Expression of this enzyme from B. dermatitidis revealed only 10R-DOX activities, i.e., oxidation of linoleic acid to 10R-hydroperoxy-8E,12Z-octadecadienoic acid. The third group aligned in a separate entity. Expression of these enzymes of H. capsulatum and B. dermatitidis revealed no DOX activities, but both enzymes transformed 13S-hydroperoxy-9Z,11E-octadecadienoic acid efficiently to 12(13S)epoxy-11-hydroperoxy-9Z-octadecenoic acid. Other 13-hydroperoxides of linoleic and α-linolenic acids were transformed with less efficiency and the 9-hydroperoxides of linoleic acid were not transformed. In conclusion, a novel EAS has been found in H. capsulatum and B. dermititidis with 13S-hydroperoxy-9Z,11E-octadecadienoic acid as the likely physiological substrate.
Topics: Amino Acid Sequence; Blastomyces; Catalysis; Dioxygenases; Fatty Acids, Unsaturated; Fungal Proteins; Histoplasma; Intramolecular Oxidoreductases; Oxygenases; Phylogeny; Recombinant Proteins
PubMed: 33189651
DOI: 10.1016/j.abb.2020.108669 -
MSphere Jun 2024Histoplasmosis is an endemic mycosis that often presents as a respiratory infection in immunocompromised patients. Hundreds of thousands of new infections are reported...
Histoplasmosis is an endemic mycosis that often presents as a respiratory infection in immunocompromised patients. Hundreds of thousands of new infections are reported annually around the world. The etiological agent of the disease, is a dimorphic fungus commonly found in the soil where it grows as mycelia. Humans can become infected by through inhalation of its spores (conidia) or mycelial particles. The fungi transition into the yeast phase in the lungs at 37°C. Once in the lungs, yeast cells reside and proliferate inside alveolar macrophages. Genomic work has revealed that is composed of at least five cryptic phylogenetic species that differ genetically. Three of those lineages have received new names. Here, we evaluated multiple phenotypic characteristics (colony morphology, secreted proteolytic activity, yeast size, and growth rate) of strains from five of the phylogenetic species of to identify phenotypic traits that differentiate between these species: , , , , and an African lineage. We report diagnostic traits for three species. The other two species can be identified by a combination of traits. Our results suggest that (i) there are significant phenotypic differences among the cryptic species of and (ii) those differences can be used to positively distinguish those species in a clinical setting and for further study of the evolution of this fungal pathogen.IMPORTANCEIdentifying species boundaries is a critical component of evolutionary biology. Genome sequencing and the use of molecular markers have advanced our understanding of the evolutionary history of fungal pathogens, including , and have allowed for the identification of new species. This is especially important in organisms where morphological characteristics have not been detected. In this study, we revised the taxonomic status of the four named species of the genus (), , , and and propose the use of species-specific phenotypic traits to aid their identification when genome sequencing is not available. These results have implications not only for evolutionary study of but also for clinicians, as the species could determine the outcome of disease and treatment needed.
Topics: Histoplasma; Phenotype; Phylogeny; Histoplasmosis; Humans; Genome, Fungal
PubMed: 38771035
DOI: 10.1128/msphere.00009-24 -
MBio Apr 2020Microbial pathogens exploit host nutrients to proliferate and cause disease. Intracellular pathogens, particularly those exclusively living in the phagosome such as ,...
Microbial pathogens exploit host nutrients to proliferate and cause disease. Intracellular pathogens, particularly those exclusively living in the phagosome such as , must adapt and acquire nutrients within the nutrient-limited phagosomal environment. In this study, we investigated which host nutrients could be utilized by as carbon sources to proliferate within macrophages. yeasts can grow on hexoses and amino acids but not fatty acids as the carbon source Transcriptional analysis and metabolism profiling showed that yeasts downregulate glycolysis and fatty acid utilization but upregulate gluconeogenesis within macrophages. Depletion of glycolysis or fatty acid utilization pathways does not prevent growth within macrophages or impair virulence However, loss of function in Pck1, the enzyme catalyzing the first committed step of gluconeogenesis, impairs growth within macrophages and severely attenuates virulence , indicating that yeasts rely on catabolism of gluconeogenic substrates (e.g., amino acids) to proliferate within macrophages. is a primary human fungal pathogen that survives and proliferates within host immune cells, particularly within the macrophage phagosome compartment. The phagosome compartment is a nutrient-limited environment, requiring yeasts to be able to assimilate available carbon sources within the phagosome to meet their nutritional needs. In this study, we showed that yeasts do not utilize fatty acids or hexoses for growth within macrophages. Instead, yeasts consume gluconeogenic substrates to proliferate in macrophages. These findings reveal the phagosome composition from a nutrient standpoint and highlight essential metabolic pathways that are required for a phagosomal pathogen to proliferate in this intracellular environment.
Topics: Animals; Cell Line; Fungal Proteins; Gene Expression Profiling; Gluconeogenesis; Glycolysis; Histoplasma; Histoplasmosis; Lung; Macrophages; Metabolic Networks and Pathways; Metabolomics; Mice; Mice, Inbred C57BL; Phagosomes; Virulence
PubMed: 32265333
DOI: 10.1128/mBio.02712-19 -
MBio Dec 2017is a pathogenic fungus that causes life-threatening lung infections. About 500,000 people are exposed to each year in the United States, and over 60% of the U.S....
is a pathogenic fungus that causes life-threatening lung infections. About 500,000 people are exposed to each year in the United States, and over 60% of the U.S. population has been exposed to the fungus at some point in their life. We performed genome-wide population genetics and phylogenetic analyses with 30 isolates representing four recognized areas where histoplasmosis is endemic and show that the genus is composed of at least four species that are genetically isolated and rarely interbreed. Therefore, we propose a taxonomic rearrangement of the genus. The evolutionary processes that give rise to new pathogen lineages are critical to our understanding of how they adapt to new environments and how frequently they exchange genes with each other. The fungal pathogen provides opportunities to precisely test hypotheses about the origin of new genetic variation. We find that is composed of at least four different cryptic species that differ genetically and also in virulence. These results have implications for the epidemiology of histoplasmosis because not all species are equivalent in their geographic range and ability to cause disease.
Topics: Genetic Speciation; Genetic Variation; Genome, Fungal; Histoplasma; Histoplasmosis; Humans; Phylogeny
PubMed: 29208741
DOI: 10.1128/mBio.01339-17 -
Memorias Do Instituto Oswaldo Cruz May 2009Histoplasma capsulatum is an intracellular fungal pathogen that causes respiratory and systemic disease by proliferating within phagocytic cells. The binding of H.... (Review)
Review
Histoplasma capsulatum is an intracellular fungal pathogen that causes respiratory and systemic disease by proliferating within phagocytic cells. The binding of H. capsulatum to phagocytes may be mediated by the pathogen's cell wall carbohydrates, glucans, which consist of glucose homo and hetero-polymers and whose glycosydic linkage types differ between the yeast and mycelial phases. The alpha-1,3-glucan is considered relevant for H. capsulatum virulence, whereas the beta-1,3-glucan is antigenic and participates in the modulation of the host immune response. H. capsulatum cell wall components with lectin-like activity seem to interact with the host cell surface, while host membrane lectin-like receptors can recognize a particular fungal carbohydrate ligand. This review emphasizes the relevance of the main H. capsulatum and host carbohydrate-driven interactions that allow for binding and internalization of the fungal cell into phagocytes and its subsequent avoidance of intracellular elimination.
Topics: Animals; Carbohydrates; Cell Wall; Histoplasma; Histoplasmosis; Host-Parasite Interactions; Humans; Immunologic Factors
PubMed: 19547878
DOI: 10.1590/s0074-02762009000300016 -
Infection and Immunity Dec 2002
Review
Topics: Animals; Bacteria; Bacterial Infections; Bacterial Proteins; Fungal Proteins; Gene Expression; Genetic Techniques; Histoplasma; Histoplasmosis; Mice; Rabbits; Rats; Virulence
PubMed: 12438320
DOI: 10.1128/IAI.70.12.6518-6523.2002 -
Asian Pacific Journal of Tropical... May 2013To facilitate the recognition of intracellular yeasts of Histoplasma capsulatum and differentiate it from Leishmania amastigotes and other parasites, using the...
OBJECTIVE
To facilitate the recognition of intracellular yeasts of Histoplasma capsulatum and differentiate it from Leishmania amastigotes and other parasites, using the combination of Giemsa and a rapid modification of Grocott stains to peripheral blood smears in a hematological study.
METHODS
The combination of both stains was applied consecutively (first Grocott and then Giemsa) to previously fixed peripheral blood smears. Microscopy was performed with 400× and 1 000×, the latter using immersion oil.
RESULTS
The yeasts of Histoplasma capsulatum were observed into the cytoplasm of leukocytes as brownish oval elements, with 3-4 µm in diameter.
CONCLUSIONS
The combination of both techniques is a simple and fast method to facilitate recognition of intracellular yeasts and it is different from intracellular parasitic elements. Moreover, it allows distinguishing the cell elements that are in the microscopic preparations. It may be very helpful in those cases in which the presumptive diagnosis of histoplasmosis has not been established yet and where other more sophisticated methods are not available.
Topics: Azure Stains; Fungemia; Histoplasma; Histoplasmosis; Humans
PubMed: 23646309
DOI: 10.1016/S2221-1691(13)60088-X -
MBio Apr 2016Dectin-1 is an essential innate immune receptor that recognizes β-glucans in fungal cell walls. Its importance is underscored by the mechanisms that fungal pathogens...
Dectin-1 is an essential innate immune receptor that recognizes β-glucans in fungal cell walls. Its importance is underscored by the mechanisms that fungal pathogens have evolved to avoid detection by this receptor. One such pathogen is Histoplasma capsulatum, and in a recent article in mBio, Rappleye's group presented data showing that yeasts of this organism secrete a β-glucanase, Eng1, which acts to prune β-glucans that are exposed on the fungal cell surface [A. L. Garfoot et al., mBio 7(2):e01388-15, 2016, http://dx.doi.org/10.1128/mBio.01388-15]. The trimming of these sugars reduces immune recognition through Dectin-1 and subsequent inflammatory responses, enhancing the pathogenesis of H. capsulatum.
Topics: Carrier Proteins; Histoplasma; Receptors, Immunologic; beta-Glucans
PubMed: 27118584
DOI: 10.1128/mBio.00553-16 -
In vitro activity of isavuconazole against fluconazole-resistant isolates of Histoplasma capsulatum.Medical Mycology Oct 2018No clinical trials for histoplasmosis have been performed with the newer azoles, leaving itraconazole as the azole of choice. In vitro studies suggest that Histoplasma...
No clinical trials for histoplasmosis have been performed with the newer azoles, leaving itraconazole as the azole of choice. In vitro studies suggest that Histoplasma capsulatum from patients that relapse on fluconazole has higher minimum inhibitory concentrations (MICs) to fluconazole and voriconazole but not itraconazole and posaconazole. The newest azole, isavuconazole, shares structural similarity to voriconazole, but to date nobody has explored emergence of resistance. In vitro susceptibilities to isavucoanzole and fluconazole were performed on previously obtained isolates from the patients who relapsed on fluconazole therapy. Susceptibilities were determined by NCCLS method M27A developed for yeasts, as modified for H. capsulatum. The change in the MIC from the primary to the relapse isolate was tested using Wilcoxon Rank-Sum for paired data. Among the primary isolates, the median MICs were 1.0 (range 0.25 to 4.0) μg/ml for fluconazole and ≤0.007 (range ≤0.007 to 0.015) μg/ml for isavuconazole. In the group of relapsed isolates, the median MICs rose to 8.0 (range 0.25 to 64.0) μg/ml for fluconazole and remained unchanged at ≤0.007 (range ≤0.007 to 0.015) μg/ml for isavuconazole (P < .001). Only one isolate exhibited a nonsignificant increase in MIC to isavuconazole. Histoplasma isolates from patients who relapsed on fluconazole did not have an elevation in MICs to isavuconazole. This differs from the results previously seen with voriconazole and suggests that despite a closer structural similarity to voriconazole than itraconazole and posaconazole, isavuconazole has a higher barrier to resistance and may be effective as therapy for histoplasmosis.
Topics: Antifungal Agents; Drug Resistance, Fungal; Fluconazole; Histoplasma; Histoplasmosis; Humans; Microbial Sensitivity Tests; Nitriles; Pyridines; Recurrence; Triazoles
PubMed: 29253204
DOI: 10.1093/mmy/myx130 -
Mediators of Inflammation 2013Prostaglandins act as mediators of inflammation and, similar to cytokines, function as immune modulators during innate and adaptive immune responses. Therefore, using a...
Prostaglandins act as mediators of inflammation and, similar to cytokines, function as immune modulators during innate and adaptive immune responses. Therefore, using a pharmacological inhibitor, celecoxib, we investigated the role of prostaglandins in host defense against Histoplasma capsulatum infection in C57BL/6 mice. Our results showed that treatment with celecoxib inhibited cyclooxygenase 2, reduced the total fungal burden, and reduced the concentration of PGE2, cytokines, lymphocytes, neutrophils, and mononuclear cells in the bronchoalveolar space and lung parenchyma. In addition, celecoxib treatment increased the synthesis of nitric oxide, IFN- γ, LTB4, and the phagocytic capacity of alveolar macrophages. Moreover, celecoxib treatment increased the survival of mice after infection with a lethal inoculum of H. capsulatum. These results suggest that prostaglandins alter the host immune response and play an important role in the pathogenesis of histoplasmosis. Thus, the inhibition of prostaglandins could be a valuable immunomodulatory strategy and antifungal therapy for histoplasmosis treatment.
Topics: Animals; Celecoxib; Cyclooxygenase 2 Inhibitors; Histoplasma; Histoplasmosis; Interferon-gamma; Leukotriene B4; Macrophages, Alveolar; Mice; Mice, Inbred C57BL; Nitric Oxide; Pyrazoles; Sulfonamides
PubMed: 23818746
DOI: 10.1155/2013/950981