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Eukaryotic Cell Jan 2012Regulation of iron acquisition genes is critical for microbial survival under both iron-limiting conditions (to acquire essential iron) and iron-replete conditions (to...
Regulation of iron acquisition genes is critical for microbial survival under both iron-limiting conditions (to acquire essential iron) and iron-replete conditions (to limit iron toxicity). In fungi, iron acquisition genes are repressed under iron-replete conditions by a conserved GATA transcriptional regulator. Here we investigate the role of this transcription factor, Sre1, in the cellular responses of the fungal pathogen Histoplasma capsulatum to iron. We showed that cells in which SRE1 levels were diminished by RNA interference were unable to repress siderophore biosynthesis and utilization genes in the presence of abundant iron and thus produced siderophores even under iron-replete conditions. Mutation of a GATA-containing consensus site found in the promoters of these genes also resulted in inappropriate gene expression under iron-replete conditions. Microarray analysis comparing control and SRE1-depleted strains under conditions of iron limitation or abundance revealed both iron-responsive genes and Sre1-dependent genes, which comprised distinct but overlapping sets. Iron-responsive genes included those encoding putative oxidoreductases, metabolic and mitochondrial enzymes, superoxide dismutase, and nitrosative-stress-response genes; Sre1-dependent genes were of diverse functions. Genes regulated by iron levels and Sre1 included all of the siderophore biosynthesis genes, a gene involved in reductive iron acquisition, an iron-responsive transcription factor, and two catalases. Based on transcriptional profiling and phenotypic analyses, we conclude that Sre1 plays a critical role in the regulation of both traditional iron-responsive genes and iron-independent pathways such as regulation of cell morphology. These data highlight the evolving realization that the effect of Sre1 orthologs on fungal biology extends beyond the iron regulon.
Topics: Base Sequence; Biosynthetic Pathways; Consensus Sequence; Fungal Proteins; GATA Transcription Factors; Gene Expression; Gene Expression Profiling; Gene Expression Regulation, Fungal; Gene Knockdown Techniques; Genes, Fungal; Histoplasma; Iron; Oligonucleotide Array Sequence Analysis; RNA Interference; Real-Time Polymerase Chain Reaction; Siderophores
PubMed: 22117028
DOI: 10.1128/EC.05274-11 -
Pathogens and Global Health Feb 2020: Histoplasmosis is a fungal infection acquired through inhalation of microconidia, mostly present in the Americas. Both immunocompetent and immunocompromised patients...
: Histoplasmosis is a fungal infection acquired through inhalation of microconidia, mostly present in the Americas. Both immunocompetent and immunocompromised patients can present a wide spectrum of signs/symptoms, ranging from mild disease to a severe, disseminated infection. The aim of this observational study is to describe histoplasmosis cases diagnosed in travelers and their clinical/radiological and therapeutic pattern.: Retrospective study at the Department of Infectious - Tropical Diseases and Microbiology (DITM) of Negrar, Verona, Italy, between January 2005 and December 2015.: Twenty-three cases of acute histoplasmosis were diagnosed, 17 of which belong to the same cluster. Seven of the 23 patients (30.4%) were admitted to hospital, four of whom underwent invasive diagnostic procedures. Thirteen patients (56.5%) received oral itraconazole. All patients recovered, although nine (39.1%) had radiological persisting lung nodules at 12 month follow up.: Clinical, laboratory and radiological features of histoplasmosis can mimic other conditions, resulting in unnecessary invasive diagnostic procedures. However, a history of travel to endemic areas and of exposure to risk factors (such as visits to caves and presence of bats) should trigger the clinical suspicion of histoplasmosis. Treatment may be indicated in severe or prolonged disease.
Topics: Acute Disease; Adult; Aged; Female; Histoplasma; Histoplasmosis; Humans; Italy; Male; Middle Aged; Retrospective Studies; Travel; Young Adult
PubMed: 31959091
DOI: 10.1080/20477724.2020.1716517 -
PLoS Pathogens Nov 2018Copper toxicity and copper limitation can both be effective host defense mechanisms against pathogens. Tolerance of high copper by fungi makes toxicity as a defense...
Copper toxicity and copper limitation can both be effective host defense mechanisms against pathogens. Tolerance of high copper by fungi makes toxicity as a defense mechanism largely ineffective against fungal pathogens. A forward genetic screen for Histoplasma capsulatum mutant yeasts unable to replicate within macrophages showed the Ctr3 copper transporter is required for intramacrophage proliferation. Ctr3 mediates copper uptake and is required for growth in low copper. Transcription of the CTR3 gene is induced by differentiation of H. capsulatum into pathogenic yeasts and by low available copper, but not decreased iron. Low expression of a CTR3 transcriptional reporter by intracellular yeasts implies that phagosomes of non-activated macrophages have moderate copper levels. This is further supported by the replication of Ctr3-deficient yeasts within the phagosome of non-activated macrophages. However, IFN-γ activation of phagocytes causes restriction of phagosomal copper as shown by upregulation of the CTR3 transcriptional reporter and by the failure of Ctr3-deficient yeasts, but not Ctr3 expressing yeasts, to proliferate within these macrophages. Accordingly, in a respiratory model of histoplasmosis, Ctr3-deficient yeasts are fully virulent during phases of the innate immune response but are attenuated after the onset of adaptive immunity. Thus, while technical limitations prevent direct measurement of phagosomal copper concentrations and copper-independent factors can influence gene expression, both the CTR3 promoter induction and the attenuation of Ctr3-deficient yeasts indicate activation of macrophages switches the phagosome from a copper-replete to a copper-depleted environment, forcing H. capsulatum reliance on Ctr3 for copper acquisition.
Topics: Animals; Antiporters; Cation Transport Proteins; Cell Line; Copper; Histoplasma; Histoplasmosis; Interferon-gamma; Iron; Macrophage Activation; Macrophages; Mice; Mice, Inbred C57BL; Phagosomes
PubMed: 30452484
DOI: 10.1371/journal.ppat.1007444 -
The American Journal of Case Reports Jun 2024BACKGROUND Histoplasma capsulatum is prevalent in the mid-eastern United States and is an environmental fungus that causes human infection by the inhalation of its...
BACKGROUND Histoplasma capsulatum is prevalent in the mid-eastern United States and is an environmental fungus that causes human infection by the inhalation of its spores. It is commonly associated with areas containing large amounts of bird excrement and can survive for years in the soil. Only 1% of infected individuals develop disseminated histoplasmosis or Histoplasma endocarditis. CASE REPORT A 61-year-old man with atrial fibrillation had 8 months of fatigue, low-grade fevers, night sweats, and unexplained weight loss presented to the Emergency Department. He worked and lived in Central Florida and although he raised cattle, he denied exposure to birds or bats with regularity. A transesophageal echocardiogram confirmed a sessile echo density on the atrial surface of the mitral valve. His microbial Karius cell-free DNA test from his blood sample was positive for Histoplasma capsulatum, and he was immediately given intravenous liposomal amphotericin for 2 weeks. A tissue valve was used to successfully replace his mitral valve along with a coronary artery bypass and a maze procedure for his persistent atrial fibrillation and atrial flutter. The diagnosis of mitral valve endocarditis from disseminated histoplasmosis was confirmed by pathological analysis, and he was sent home on long-term itraconazole maintenance treatment. CONCLUSIONS Surgical intervention in combination with anti-fungal medication can be a lifesaving intervention for disseminated histoplasmosis. A thorough history is particularly important when evaluating a patient with an unknown infectious source, especially assessing for risk factors, including exposure to environmental factors, workplace, and animals.
Topics: Humans; Histoplasmosis; Male; Middle Aged; Mitral Valve; Endocarditis; Florida; Antifungal Agents; Echocardiography, Transesophageal; Heart Valve Diseases; Histoplasma
PubMed: 38863182
DOI: 10.12659/AJCR.943306 -
Infection and Immunity Oct 2014The yeast phase of Histoplasma capsulatum is the virulent form of this thermally dimorphic fungal pathogen. Among the secreted proteome of Histoplasma, culture filtrate...
The yeast phase of Histoplasma capsulatum is the virulent form of this thermally dimorphic fungal pathogen. Among the secreted proteome of Histoplasma, culture filtrate protein 4 (Cfp4) is a heavily glycosylated factor produced abundantly and specifically by Histoplasma yeast cells, suggesting its role in pathogenesis. We have generated three monoclonal antibodies as tools for characterization and detection of Cfp4 and determined the epitope each recognizes. Through site-directed mutagenesis of Cfp4, we identified three asparagines that function as the principal sites of N-linked glycan modification. To test the function of Cfp4 in Histoplasma pathogenesis, we generated Cfp4-deficient strains by insertional mutagenesis and by RNA interference. Cfp4-deficient strains are not attenuated in virulence in human macrophages or during lung infection in a murine model of histoplasmosis. Coinfection of differentially marked Cfp4-producing and Cfp4-deficient strains demonstrates that production of Cfp4 does not confer a fitness advantage to Histoplasma yeasts during murine lung infection. Despite no apparent role in acute virulence in mice, secretion of the Cfp4 glycoprotein by yeast cells is consistent across clinical and laboratory isolates of the North American type 1 and type 2 phylogenetic groups as well as a strain from Panama. In addition, human immune sera recognize the Histoplasma Cfp4 protein, confirming Cfp4 production during infection of human hosts. These results suggest the potential utility of Cfp4 as a diagnostic exoantigen for histoplasmosis.
Topics: Animals; Antibodies, Fungal; Antibodies, Monoclonal; Cells, Cultured; DNA Mutational Analysis; Disease Models, Animal; Epitope Mapping; Fungal Proteins; Gene Knockdown Techniques; Gene Knockout Techniques; Glycosylation; Histoplasma; Histoplasmosis; Humans; Macrophages; Mice; Mice, Inbred C57BL; Mutagenesis, Insertional; Protein Processing, Post-Translational; RNA Interference
PubMed: 25114108
DOI: 10.1128/IAI.01893-14 -
Cellular Microbiology Sep 2020Histoplasma capsulatum is a dimorphic fungus that most frequently causes pneumonia, but can also disseminate and proliferate in diverse tissues. Histoplasma capsulatum...
Histoplasma capsulatum is a dimorphic fungus that most frequently causes pneumonia, but can also disseminate and proliferate in diverse tissues. Histoplasma capsulatum has a complex secretion system that mediates the release of macromolecule-degrading enzymes and virulence factors. The formation and release of extracellular vesicles (EVs) are an important mechanism for non-conventional secretion in both ascomycetes and basidiomycetes. Histoplasma capsulatum EVs contain diverse proteins associated with virulence and are immunologically active. Despite the growing knowledge of EVs from H. capsulatum and other pathogenic fungi, the extent that changes in the environment impact the sorting of organic molecules in EVs has not been investigated. In this study, we cultivated H. capsulatum with distinct culture media to investigate the potential plasticity in EV loading in response to differences in nutrition. Our findings reveal that nutrition plays an important role in EV loading and formation, which may translate into differences in biological activities of these fungi in various fluids and tissues.
Topics: Culture Media; Extracellular Vesicles; Fungal Proteins; Histoplasma; Nutrients
PubMed: 32406582
DOI: 10.1111/cmi.13217 -
Infection and Immunity Apr 2000The zoopathogenic fungus Histoplasma capsulatum, like other eukaryotic aerobic microorganisms, requires iron for growth. Under conditions of low iron availability, the...
The zoopathogenic fungus Histoplasma capsulatum, like other eukaryotic aerobic microorganisms, requires iron for growth. Under conditions of low iron availability, the fungus secretes hydroxamates that function as siderophores (iron chelators). The experiments to be reported were designed to gather further information on the hydroxamate siderophores of H. capsulatum. The fungus was grown in a synthetic medium deferrated with the cationic exchange resin Chelex 100. Siderophores were detected after 4 days of incubation at 37 degrees C in media containing 0.3 to 1.0 microM iron. The secretion was suppressed by 10 microM iron. The hydroxamates were purified by reverse-phase and size-exclusion chromatography. On the basis of ions observed during electrospray mass spectroscopy, five hydroxamate siderophores were tentatively identified: dimerum acid, acetyl dimerum acid, coprogen B, methyl coprogen B, and fusarinine (monomeric). A polyclonal antibody to dimerum acid was generated. This reagent cross-reacted with coprogen B and fusarinine. Thus, the antibody detects hydroxamates in all three families of siderophores excreted by H. capsulatum.
Topics: Antibodies; Chelating Agents; Chromatography, High Pressure Liquid; Dose-Response Relationship, Drug; Histoplasma; Hydrolysis; Hydroxamic Acids; Immunoblotting; Iron; Mass Spectrometry; Piperazines; Siderophores; Time Factors
PubMed: 10722639
DOI: 10.1128/IAI.68.4.2338-2343.2000 -
BMC Pulmonary Medicine Aug 2019Histoplasmosis is a mycosis caused by soil-based fungus Histoplasma capsulatum endemic in the USA, Latin America, Africa and South-East Asia. The disease is usually...
BACKGROUND
Histoplasmosis is a mycosis caused by soil-based fungus Histoplasma capsulatum endemic in the USA, Latin America, Africa and South-East Asia. The disease is usually self-resolving, but exposure to a large inoculum or accompanying immune deficiencies may result in severe illness. Symptoms are unspecific with fever, cough and malaise as the most common. Thus, this is a case of disease which is difficult to diagnose and very rare in Europe. As a result, it is usually not suspected in elderly patients with cough and dyspnea.
CASE PRESENTATION
This is a case of a 78-year-old patient, admitted to our department due to respiratory failure, cough, shortness of breath, fever and weight loss with no response to antibiotics administered before the admission. Chest CT revealed numerous reticular and nodular infiltrations with distribution in all lobes. The cytopathology of BAL showed small parts of mycelium and numerous oval spores. Considering clinical presentation and history of travel to Mexico before onset of disease, pulmonary histoplasmosis was diagnosed. After introduction of antifungal treatment rapid improvement was achieved in terms of both clinical picture and respiratory function.
CONCLUSIONS
Since the risk of Histoplasma exposure in Europe is minimal, patients, who present with dyspnea, fever and malaise are not primarily considered for diagnosis of histoplasmosis. However, taking into account increasing popularity of travelling, also by elderly or patients with impaired immunity, histoplasmosis should be included into differential diagnosis.
Topics: Aged; Antifungal Agents; Diagnosis, Differential; Histoplasma; Histoplasmosis; Humans; Lung Diseases, Fungal; Male; Mexico; Poland; Tomography, X-Ray Computed; Travel
PubMed: 31412842
DOI: 10.1186/s12890-019-0914-7 -
Microbiology Spectrum Apr 2024var (HCF) is a dimorphic fungus that causes epizootic lymphangitis in equids. Current diagnostic approaches, including culture, microscopy, and clinical presentation,...
UNLABELLED
var (HCF) is a dimorphic fungus that causes epizootic lymphangitis in equids. Current diagnostic approaches, including culture, microscopy, and clinical presentation, lack speed, sensitivity, and specificity when diagnosing clinical cases. In this study, equine blood and pus samples on Whatman FTA cards from Senegal ( = 3), The Gambia ( = 19), Ethiopia ( = 16), and Mali ( = 13) were tested using a real-time PCR (qPCR) protocol. The assay was optimized and tested for its suitability to detect and quantify HCF in blood and pus loaded onto Whatman FTA cards at sampling. Whatman FTA cards were tested for their suitability for use with qPCR and were found to recover DNA more efficiently than from direct extraction. Using TaqMan fluorescent probes and specific primers, the assay demonstrated 100% analytical specificity when detecting multiple strains of and no false positives with off-target organisms. The assay's diagnostic performance was measured against an existing nested internal transcribed spacer PCR protocol using a receiver operating characteristic curve. The test was found to have a diagnostic specificity and sensitivity of 100% and 71.4%, respectively, when analyzing pus samples using a cycle threshold (Ct) cutoff determined by Youden's index (27.75). Blood sample cutoff Ct value was proposed at 34.55. Further optimization is required to improve the performance of the protocol when applied to blood samples. This study has, for the first time, demonstrated the ability to detect and quantify the DNA of spp. in equine blood and pus samples with a high degree of accuracy, providing a platform to further investigate the pathogenesis and epidemiology of this disease.
IMPORTANCE
Histoplasmosis is a neglected yet major cause of morbidity and mortality in both equids and people in resource-scarce settings. One of the major hindrances to the control of histoplasmosis is a lack of readily available diagnostic tests. Tests are needed to support clinical decision-making and to be applied in population-based research to further understand this disease . This paper reports, for the first time, the validation and application of a qPCR to detect directly from equine clinical samples, bypassing the need to culture this notoriously difficult organism. We report and comment on the performance of the qPCR in comparison with our previously developed nested PCR.
Topics: Horses; Animals; Humans; Histoplasma; Histoplasmosis; Real-Time Polymerase Chain Reaction; Nucleic Acids; DNA, Fungal; Suppuration
PubMed: 38411051
DOI: 10.1128/spectrum.03100-23 -
Infection and Immunity Mar 1989Four monoclonal antibodies (MAbs) were produced by immunizing mice with a disrupted yeast cell homogenate of Histoplasma capsulatum. MAbs 1 and 2 reacted only with the...
Four monoclonal antibodies (MAbs) were produced by immunizing mice with a disrupted yeast cell homogenate of Histoplasma capsulatum. MAbs 1 and 2 reacted only with the yeast cell antigens of H. capsulatum and Blastomyces dermatitidis, whereas MAbs 3 and 4 showed broader cross-reactivity. MAb 3 cross-reacted with B. dermatitidis, Paracoccidioides brasiliensis, Sporothrix schenckii, and Candida albicans, and MAb 4 cross-reacted with B. dermatitidis, C. albicans, Coccidioides immitis, Aspergillus fumigatus, and Mycobacterium tuberculosis. All four MAbs exhibited unique specificity when reacted with three different strains of H. capsulatum (G217B, A811, and P-IN). MAb 1 belonged to the IgG2b subclass, MAb 3 belonged to the IgG1 subclass, and MAbs 2 and 4 belonged to the IgG3 subclass. MAbs 1, 2, and 3 formed bands in the Western immunoblot assay; the two dominant distinct bands had apparent molecular masses of 72 and 62 kilodaltons.
Topics: Antibodies, Fungal; Antibodies, Monoclonal; Antibody Specificity; Antigens, Fungal; Blotting, Western; Histoplasma; Immunoglobulin Isotypes; Molecular Weight; Species Specificity
PubMed: 2917790
DOI: 10.1128/iai.57.3.896-901.1989