Species-Specific Immunological Reactivities Depend on the Cell-Wall Organization of the Two Aspergillus, Aspergillus fumigatus and A. flavus

Although belong to the same genus, Aspergillus fumigatus is primarily involved in invasive pulmonary infection, whereas Aspergillus flavus is a common cause of superficial infection. In this study, we compared conidia (the infective propagules) of these two Aspergillus species. In immunocompetent mice, intranasal inoculation with conidia of A. flavus resulted in significantly higher inflammatory responses in the lungs compared to mice inoculated with A. fumigatus conidia. In vitro assays revealed that the dormant conidia of A. flavus, unlike A. fumigatus dormant conidia, are immunostimulatory. The conidial surface of A. fumigatus was covered by a rodlet-layer, while that of A. flavus were presented with exposed polysaccharides. A. flavus harbored significantly higher number of proteins in its conidial cell wall compared to A. fumigatus conidia. Notably, β-1,3-glucan in the A. flavus conidial cell-wall showed significantly higher percentage of branching compared to that of A. fumigatus. The polysaccharides ensemble of A. flavus conidial cell wall stimulated the secretion of proinflammatory cytokines, and conidial cell wall associated proteins specifically stimulated IL-8 secretion from the host immune cells. Furthermore, the two species exhibited different sensitivities to antifungal drugs targeting cell wall polysaccharides, proposing the efficacy of species-specific treatment strategies. Overall, the species-specific organization of the conidial cell wall could be important in establishing infection by the two Aspergillus species.

Download Full-text

Differential Aspergillus lentulus Echinocandin Susceptibilities Are Fksp Independent

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.00774-10 ◽

2010 ◽

Vol 54 (12) ◽

pp. 4992-4998 ◽

Cited By ~ 23

Author(s):

Janet F. Staab ◽

Jennifer Nielsen Kahn ◽

Kieren A. Marr

Keyword(s):

Cell Wall ◽

Aspergillus Fumigatus ◽

Hot Spot ◽

Cellular Level ◽

Antifungal Drugs ◽

Gene Encoding ◽

Glucan Synthase ◽

Kinetic Inhibition ◽

Aspergillus Lentulus

ABSTRACT The recently described species Aspergillus lentulus exhibits differential and reduced susceptibilities to echinocandins and other antifungal drugs in vitro. A. lentulus isolates overall are less susceptible to caspofungin, although they maintain susceptibility to anidulafungin and micafungin. Mutations or polymorphisms in fks, the gene encoding the catalytic subunit of β-1,3-glucan synthase, are known to confer decreased susceptibility to echinocandins in Candida spp. and Aspergillus fumigatus. The analysis of the A. lentulus fks sequence did not reveal a polymorphism at any of the known hot-spot regions of the gene. Caspofungin and micafungin kinetic inhibition profiles of the A. lentulus glucan synthase were comparable to those from susceptible A. fumigatus enzymes. Although the basal cell wall chitin levels in A. lentulus averaged 60% of those in A. fumigatus, echinocandin treatment promoted the increase of cell wall chitin in both organisms, indicating that A. lentulus displays a compensatory chitin response similar to that of A. fumigatus. The data suggest that differential echinocandin susceptibilities in A. lentulus are independent of the echinocandin target, Fksp, and they emphasize the potential that the drugs' capacity to inhibit the target enzyme is unequal at the cellular level.

Download Full-text

Deficiency of GPI Glycan Modification by Ethanolamine Phosphate Results in Increased Adhesion and Immune Resistance of Aspergillus fumigatus

Frontiers in Cellular and Infection Microbiology ◽

10.3389/fcimb.2021.780959 ◽

2021 ◽

Vol 11 ◽

Author(s):

Haomiao Ouyang ◽

Yi Zhang ◽

Hui Zhou ◽

Yubo Ma ◽

Ruoyu Li ◽

...

Keyword(s):

Immune Response ◽

Cell Wall ◽

Aspergillus Fumigatus ◽

Cell Wall Polysaccharides ◽

Gpi Anchor ◽

Mannose Residue ◽

Immune Resistance ◽

Immunocompromised Mouse ◽

Ethanolamine Phosphate

Glycosylphosphatidylinositol (GPI)-anchored proteins play important roles in maintaining the function of the cell wall and participating in pathogenic processes. The addition and removal of phosphoethanolamine (EtN-P) on the second mannose residue in the GPI anchor are vital for maturation and sorting of GPI-anchored proteins. Previously, we have shown that deletion of the gpi7, the gene that encodes an EtN-P transferase responsible for the addition of EtN-P to the second mannose residue of the GPI anchor, leads to the mislocalization of GPI-anchored proteins, abnormal polarity, reduced conidiation, and fast germination in Aspergillus fumigatus. In this report, the adherence and virulence of the A. fumigatus gpi7 deletion mutant were further investigated. The germinating conidia of the mutant exhibited an increased adhesion and a higher exposure of cell wall polysaccharides. Although the virulence was not affected, an increased adherence and a stronger inflammation response of the mutant were documented in an immunocompromised mouse model. An in vitro assay confirmed that the Δgpi7 mutant induced a stronger immune response and was more resistant to killing. Our findings, for the first time, demonstrate that in A. fumigatus, GPI anchoring is required for proper organization of the conidial cell wall. The lack of Gpi7 leads to fast germination, stronger immune response, and resistance to macrophage killing.

Download Full-text

8 The Cell Wall Polysaccharides of Aspergillus fumigatus

Biochemistry and Molecular Biology ◽

10.1007/978-3-319-27790-5_8 ◽

2016 ◽

pp. 147-165 ◽

Cited By ~ 1

Author(s):

Mark J. Lee ◽

Donald C. Sheppard

Keyword(s):

Cell Wall ◽

Aspergillus Fumigatus ◽

Cell Wall Polysaccharides

Download Full-text

Evaluation of Antifungal Activity and Mode of Action of New Coumarin Derivative, 7-Hydroxy-6-nitro-2H-1-benzopyran-2-one, againstAspergillusspp.

Evidence-based Complementary and Alternative Medicine ◽

10.1155/2015/925096 ◽

2015 ◽

Vol 2015 ◽

pp. 1-8 ◽

Cited By ~ 11

Author(s):

Felipe Queiroga Sarmento Guerra ◽

Rodrigo Santos Aquino de Araújo ◽

Janiere Pereira de Sousa ◽

Fillipe de Oliveira Pereira ◽

Francisco J. B. Mendonça-Junior ◽

...

Keyword(s):

Cell Wall ◽

Mode Of Action ◽

Cell Walls ◽

Coumarin Derivative ◽

Antifungal Drugs ◽

Azole Resistance ◽

Subinhibitory Concentration ◽

Fungal Cell ◽

Mycelia Growth

Aspergillusspp. produce a wide variety of diseases. For the treatment of such infections, the azoles and Amphotericin B are used in various formulations. The treatment of fungal diseases is often ineffective, because of increases in azole resistance and their several associated adverse effects. To overcome these problems, natural products and their derivatives are interesting alternatives. The aim of this study was to examine the effects of coumarin derivative, 7-hydroxy-6-nitro-2H-1-benzopyran-2-one (Cou-NO2), both alone and with antifungal drugs. Its mode of action againstAspergillusspp. Cou-NO2was tested to evaluate its effects on mycelia growth and germination of fungal conidia ofAspergillusspp. We also investigated possible Cou-NO2action on cell walls (0.8 M sorbitol) and on Cou-NO2to ergosterol binding in the cell membrane. The study shows that Cou-NO2is capable of inhibiting both the mycelia growth and germination of conidia for the species tested, and that its action affects the structure of the fungal cell wall. At subinhibitory concentration, Cou-NO2enhanced thein vitroeffects of azoles. Moreover, in combination with azoles (voriconazole and itraconazole) Cou-NO2displays an additive effect. Thus, our study supports the use of coumarin derivative 7-hydroxy-6-nitro-2H-1-benzopyran-2-one as an antifungal agent againstAspergillusspecies.

Download Full-text

Mitogen-Activated Protein Kinase Cross-Talk Interaction Modulates the Production of Melanins in Aspergillus fumigatus

mBio ◽

10.1128/mbio.00215-19 ◽

2019 ◽

Vol 10 (2) ◽

Cited By ~ 17

Author(s):

Adriana Oliveira Manfiolli ◽

Filipe Silva Siqueira ◽

Thaila Fernanda dos Reis ◽

Patrick Van Dijck ◽

Sanne Schrevens ◽

...

Keyword(s):

Cell Wall ◽

Aspergillus Fumigatus ◽

Cross Talk ◽

Pathogenic Fungus ◽

Antifungal Drugs ◽

Mitogen Activated Protein Kinase ◽

Melanin Production ◽

Content Type ◽

Mitogen Activated Protein ◽

Salvage Pathways

ABSTRACT The pathogenic fungus Aspergillus fumigatus is able to adapt to extremely variable environmental conditions. The A. fumigatus genome contains four genes coding for mitogen-activated protein kinases (MAPKs), which are important regulatory knots involved in diverse cellular responses. From a clinical perspective, MAPK activity has been connected to salvage pathways, which can determine the failure of effective treatment of invasive mycoses using antifungal drugs. Here, we report the characterization of the Saccharomyces cerevisiae Fus3 ortholog in A. fumigatus, designated MpkB. We demonstrate that MpkB is important for conidiation and that its deletion induces a copious increase of dihydroxynaphthalene (DHN)-melanin production. Simultaneous deletion of mpkB and mpkA, the latter related to maintenance of the cell wall integrity, normalized DHN-melanin production. Localization studies revealed that MpkB translocates into the nuclei when A. fumigatus germlings are exposed to caspofungin stress, and this is dependent on the cross-talk interaction with MpkA. Additionally, DHN-melanin formation was also increased after deletion of genes coding for the Gα protein GpaA and for the G protein-coupled receptor GprM. Yeast two-hybrid and coimmunoprecipitation assays confirmed that GpaA and GprM interact, suggesting their role in the MpkB signaling cascade. IMPORTANCE Aspergillus fumigatus is the most important airborne human pathogenic fungus, causing thousands of deaths per year. Its lethality is due to late and often inaccurate diagnosis and the lack of efficient therapeutics. The failure of efficient prophylaxis and therapy is based on the ability of this pathogen to activate numerous salvage pathways that are capable of overcoming the different drug-derived stresses. A major role in the protection of A. fumigatus is played by melanins. Melanins are cell wall-associated macromolecules classified as virulence determinants. The understanding of the various signaling pathways acting in this organism can be used to elucidate the mechanism beyond melanin production and help to identify ideal drug targets.

Download Full-text

Limited Evolutionary Conservation of the Phenotypic Effects of Antibiotic Resistance Mutations

Molecular Biology and Evolution ◽

10.1093/molbev/msz109 ◽

2019 ◽

Vol 36 (8) ◽

pp. 1601-1611 ◽

Cited By ~ 8

Author(s):

Gábor Apjok ◽

Gábor Boross ◽

Ákos Nyerges ◽

Gergely Fekete ◽

Viktória Lázár ◽

...

Keyword(s):

Drug Hypersensitivity ◽

Bacterial Species ◽

Treatment Strategies ◽

Specific Treatment ◽

Resistant Bacteria ◽

Resistance Mutations ◽

Aminoglycoside Resistance ◽

Collateral Sensitivity ◽

Depth Analysis ◽

Species Specific

AbstractMultidrug-resistant clinical isolates are common in certain pathogens, but rare in others. This pattern may be due to the fact that mutations shaping resistance have species-specific effects. To investigate this issue, we transferred a range of resistance-conferring mutations and a full resistance gene into Escherichia coli and closely related bacteria. We found that resistance mutations in one bacterial species frequently provide no resistance, in fact even yielding drug hypersensitivity in close relatives. In depth analysis of a key gene involved in aminoglycoside resistance (trkH) indicated that preexisting mutations in other genes—intergenic epistasis—underlie such extreme differences in mutational effects between species. Finally, reconstruction of adaptive landscapes under multiple antibiotic stresses revealed that mutations frequently provide multidrug resistance or elevated drug susceptibility (i.e., collateral sensitivity) only with certain combinations of other resistance mutations. We conclude that resistance and collateral sensitivity are contingent upon the genetic makeup of the bacterial population, and such contingency could shape the long-term fate of resistant bacteria. These results underlie the importance of species-specific treatment strategies.

Download Full-text

Surface Structure Characterization of Aspergillus fumigatus Conidia Mutated in the Melanin Synthesis Pathway and Their Human Cellular Immune Response

Infection and Immunity ◽

10.1128/iai.01726-14 ◽

2014 ◽

Vol 82 (8) ◽

pp. 3141-3153 ◽

Cited By ~ 67

Author(s):

Jagadeesh Bayry ◽

Audrey Beaussart ◽

Yves F. Dufrêne ◽

Meenu Sharma ◽

Kushagra Bansal ◽

...

Keyword(s):

Cell Wall ◽

Cell Surface ◽

Aspergillus Fumigatus ◽

Surface Defects ◽

Structure Characterization ◽

Inert Material ◽

Cell Wall Polysaccharides ◽

Melanin Biosynthesis ◽

Content Type ◽

Conidial Surface

ABSTRACTInAspergillus fumigatus, the conidial surface contains dihydroxynaphthalene (DHN)-melanin. Six-clustered gene products have been identified that mediate sequential catalysis of DHN-melanin biosynthesis. Melanin thus produced is known to be a virulence factor, protecting the fungus from the host defense mechanisms. In the present study, individual deletion of the genes involved in the initial three steps of melanin biosynthesis resulted in an altered conidial surface with masked surface rodlet layer, leaky cell wall allowing the deposition of proteins on the cell surface and exposing the otherwise-masked cell wall polysaccharides at the surface. Melanin as such was immunologically inert; however, deletion mutant conidia with modified surfaces could activate human dendritic cells and the subsequent cytokine production in contrast to the wild-type conidia. Cell surface defects were rectified in the conidia mutated in downstream melanin biosynthetic pathway, and maximum immune inertness was observed upon synthesis of vermelone onward. These observations suggest that although melanin as such is an immunologically inert material, it confers virulence by facilitating proper formation of theA. fumigatusconidial surface.

Download Full-text

Molecular Studies Reveal Frequent Misidentification of Aspergillus fumigatus by Morphotyping

Eukaryotic Cell ◽

10.1128/ec.00162-06 ◽

2006 ◽

Vol 5 (10) ◽

pp. 1705-1712 ◽

Cited By ~ 147

Author(s):

S. Arunmozhi Balajee ◽

David Nickle ◽

Janos Varga ◽

Kieren A. Marr

Keyword(s):

Aspergillus Fumigatus ◽

Amphotericin B ◽

Distinct Species ◽

Enzyme Polymorphism ◽

Antifungal Drugs ◽

Clinical Isolates ◽

Polymorphism Analysis ◽

In Vitro Susceptibility ◽

Epidemiological Surveys

ABSTRACT Aspergillus fumigatus has been understood to be the most common cause of invasive aspergillosis (IA) in all epidemiological surveys. However, recent studies have uncovered a large degree of genetic heterogeneity between isolates morphologically identified as A. fumigatus, leading to the description of a new species, Aspergillus lentulus. Here, we examined the genetic diversity of clinical isolates identified as A. fumigatus using restriction enzyme polymorphism analysis and sequence-based identification. Analysis of 50 clinical isolates from geographically diverse locations recorded the presence of at least three distinct species: A. lentulus, Aspergillus udagawae, and A. fumigatus. In vitro, A. lentulus isolates demonstrated decreased susceptibility to antifungal drugs currently used for IA, including amphotericin B, voriconazole, and caspofungin; A. udagawae isolates demonstrated decreased in vitro susceptibility to amphotericin B. Results of the present study demonstrate that current phenotypic methods to identify fungi do not differentiate between genetically distinct species in the A. fumigatus group. Differential antifungal susceptibilities of these species may account for some of the reported poor outcomes of therapy in clinical studies.

Download Full-text

In VitroInteraction between Alginate Lyase and Amphotericin B against Aspergillus fumigatus Biofilm Determined by Different Methods

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.01875-12 ◽

2012 ◽

Vol 57 (3) ◽

pp. 1275-1282 ◽

Cited By ~ 32

Author(s):

Francesca Bugli ◽

Brunella Posteraro ◽

Massimiliano Papi ◽

Riccardo Torelli ◽

Alessandro Maiorana ◽

...

Keyword(s):

Invasive Aspergillosis ◽

Aspergillus Fumigatus ◽

Amphotericin B ◽

Extracellular Polymeric Substances ◽

Alginate Lyase ◽

Antifungal Drugs ◽

Antibiofilm Activity ◽

Content Type ◽

Time Kill

ABSTRACTAspergillus fumigatusbiofilms represent a problematic clinical entity, especially because of their recalcitrance to antifungal drugs, which poses a number of therapeutic implications for invasive aspergillosis, the most difficult-to-treatAspergillus-related disease. While the antibiofilm activities of amphotericin B (AMB) deoxycholate and its lipid formulations (e.g., liposomal AMB [LAMB]) are well documented, the effectiveness of these drugs in combination with nonantifungal agents is poorly understood. In the present study,in vitrointeractions between polyene antifungals (AMB and LAMB) and alginate lyase (AlgL), an enzyme degrading the polysaccharides produced as extracellular polymeric substances (EPSs) within the biofilm matrix, againstA. fumigatusbiofilms were evaluated by using the checkerboard microdilution and the time-kill assays. Furthermore, atomic force microscopy (AFM) was used to image and quantify the effects of AlgL-antifungal combinations on biofilm-growing hyphal cells. On the basis of fractional inhibitory concentration index values, synergy was found between both AMB formulations and AlgL, and this finding was also confirmed by the time-kill test. Finally, AFM analysis showed that whenA. fumigatusbiofilms were treated with AlgL or polyene alone, as well as with their combination, both a reduction of hyphal thicknesses and an increase of adhesive forces were observed compared to the findings for untreated controls, probably owing to the different action by the enzyme or the antifungal compounds. Interestingly, marked physical changes were noticed inA. fumigatusbiofilms exposed to the AlgL-antifungal combinations compared with the physical characteristics detected after exposure to the antifungals alone, indicating that AlgL may enhance the antibiofilm activity of both AMB and LAMB, perhaps by disrupting the hypha-embedding EPSs and thus facilitating the drugs to reach biofilm cells. Taken together, our results suggest that a combination of AlgL and a polyene antifungal may prove to be a new therapeutic strategy for invasive aspergillosis, while reinforcing the EPS as a valuable antibiofilm drug target.

Download Full-text