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D Chabasse

Publications and source records attributed to D Chabasse.

At least 19 recordsLinked to original sources
PubMed1999

Association of a myosin immunoanalogue with cell envelopes of Aspergillus fumigatus conidia and its participation in swelling and germination.

A myosin immunoanalogue was identified in conidia of Aspergillus fumigatus by Western blotting, indirect immunofluorescence assay, and gold immunoelectron microscopy with two different antimyosin antibodies. The distribution pattern of this protein was followed during the early stages of germination. A single 180-kDa polypeptide, detected predominantly in a cell envelope extract, was found to cross-react with monoclonal and polyclonal antibodies raised against vertebrate muscle myosin. Immunoelectron microscopy permitted precise localization of this polypeptide, indicating that myosin analogue was mainly distributed along the plasma membrane of resting and swollen conidia. In germinating conidia, indirect immunofluorescence microscopy revealed myosin analogue at the periphery of germ tubes, whereas actin appeared as dispersed punctate structures in the cytoplasm that were more concentrated at the site of germ tube emergence. A myosin ATPase inhibitor, butanedione monoxime, greatly reduced swelling and blocked germination. In contrast, when conidia were treated with cytochalasin B, an inhibitor of actin polymerization, swelling was not affected and germination was only partially reduced. Butanedione monoxime-treated conidia showed accumulation of cytoplasmic vesicles and did not achieve cell wall reorganization, unlike swollen conidia. Collectively, these results suggest an essential role for this myosin analogue in the deposition of cell wall components during germination of A. fumigatus conidia and therefore in host tissue colonization.

Actins↗
PubMed1998

[Cutaneous Scedosporium infection revealed by bullous-necrotic purpura].

BACKGROUND: Non-mycetomatous cutaneous scedosprium is an uncommon mycosis observed in immunodepressed subjects. We report a case with an inaugural presentation of bullous and necrotic purpura. CASE REPORT: A 79-year-old man on intermittent corticosteroid therapy for bronchospasm was admitted for bullous and necrotic purpura and fever. Subcutaneous nodules with a sporotrichoid aspect developed despite wide-spectrum antibiotics. Microbiology samples cultured on Sabouraud medium evidenced Scedosporium apiospermum. The pathogenic nature of the infection was proven on a skin biopsy showing numerous myceleal filaments with Gomori-Grocott staining despite negative PAS. No pulmonary involvement was evidenced. The patient was treated unsuccessfully with itraconazole. A Pseudomonas lung infection was fatal. DISCUSSION: Scedosporium apiospermum, an ubiquitous ascomycetes anamorphous to Pseudallescheria boydii, is the cause of a growing number of human infections due to widespread use of immunosuppressors. Skin and lung localizations predominate. The inaugural bullous and necrotic purpural skin manifestations in this case are unusual. In addition, the patient was only minimally immunodepressed and despite demonstrated in vitro sensitivity, itraconazole was ineffective clinically. Treatment is not well defined, but surgery is essential in combination with empirically chosen antifungals.

Aged↗
PubMed1997

Expression and identification of a laminin-binding protein in Aspergillus fumigatus conidia.

Adhesion of Aspergillus fumigatus, the causative agent of human aspergillosis, to the extracellular matrix protein laminin has been previously demonstrated. This study investigated the expression of laminin receptors during swelling of conidia, a step leading to germination and subsequent colonization of tissues. Scanning electron microscopy showed that the laminin binding sites were distributed over the external rodlet layer of resting conidia. During swelling, the characteristic rodlet layer progressively disintegrated and conidia surrounded by a smooth cell wall layer appeared. Flow cytometry using fluorescein isothiocyanate-conjugated laminin demonstrated that expression of laminin receptors at the surface of conidia was swelling dependent. Resting conidia expressed high levels of laminin receptors on their surface. A gradual decrease of laminin binding was then observed as swelling occurred, reaching a minimum for 4-h-swollen conidia. This correlated with a loss of adherence of swollen conidia to laminin immobilized on microtiter plates. Trypsin pretreatment of conidia reduced laminin binding. Analysis by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and ligand blotting with laminin identified in a cell wall extract a major 72-kDa cell wall glycoprotein which binds laminin. Thus, one of the initial events in the host colonization may be the recognition of basement membrane laminin by this 72-kDa cell wall surface component.

Aspergillus fumigatus↗
PubMed1997

Sialic acid-dependent recognition of laminin and fibrinogen by Aspergillus fumigatus conidia.

In an attempt to define the molecular basis of the adherence of Aspergillus fumigatus conidia to the host tissues, a step which might be mediated by the recognition of basement membrane laminin or fibrinogen, we analyzed the binding of these glycoproteins by flow cytometry and a microtiter plate adherence assay. Flow cytometry revealed that the binding of fluorescein isothiocyanate-labeled laminin to conidia was saturable and specific. Moreover, the ability of conidia to bind laminin increased with their maturation. Competition experiments showed a cross-reactivity between laminin and fibrinogen binding and a lack of interactions with glycosaminoglycans. In addition, the binding of laminin was not inhibited by the different adhesive synthetic peptides tested. Furthermore, the microtiter plate assay of adherence to chymotrypsin degradation products of laminin or fibrinogen purified by gel filtration suggested a unique binding site common to sequential degradation fragments or the presence of multiple binding sites on the two ligands. Therefore, the role of carbohydrates in the recognition process was investigated. Among the carbohydrates tested, constitutive of the conidial wall or of the oligosaccharide side chains of laminin and fibrinogen, only N-acetylneuraminic acid and sialyllactose inhibited the binding of these glycoproteins to conidia. In conclusion, these results strengthen the idea that the laminin and fibrinogen receptors in A. fumigatus are identical and suggest an interaction mediated by a sialic acid-specific lectin of the conidial wall.

Aspergillus fumigatus↗
PubMed1996

A 33 kDa serine proteinase from Scedosporium apiospermum.

An extracellular proteinase produced by the filamentous fungus Scedosporium apiospermum has been purified and characterized. Initially, in vitro conditions for enzyme synthesis were investigated. The highest yield of enzyme production was obtained when the fungus was cultivated in modified Czapek-Dox liquid medium supplemented with 0.1% bacteriological peptone and 1% (w/v) glucose as the nitrogen and carbon sources respectively. Purification to homogeneity of the proteinase was accomplished by (NH4)2SO4 precipitation, followed by gel filtration through Sephadex G-75 and finally affinity chromatography through immobilized phenylalanine. Analysis of the purified enzyme by SDS/PAGE revealed a single polypeptide chain with an apparent molecular mass of 33 kDa. Further investigation of its physical and biochemical properties disclosed numerous similarities with those of the previously described serine proteinase of Aspergillus fumigatus. The enzyme was not glycosylated and its pI was 9.3. Proteinase activity was optimum between 37 and 50 degrees C and at pH 9.0, but remained high within a large range of pH values between 7 and 11. The inhibition profile and N-terminal amino acid sequencing confirmed that this enzyme belongs to the subtilisin family of serine proteinases. In agreement with this, the specific synthetic substrate N-succinyl-Ala-Ala-Pro-Phe-p-nitroanilide proved to be an excellent substrate for the proteinase with an estimated Km of 0.35 mM. Like the alkaline proteinase of A. fumigatus, this enzyme was able to degrade human fibrinogen, and thus may act as a mediator of the severe chronic bronchopulmonary inflammation from which cystic fibrosis patients suffer.

Amino Acid Sequence↗
PubMed1996

Pleural effusion and toxocariasis.

The case history is described of a woman who presented with bilateral pleural effusions caused by Toxocara canis infestation. The condition responded rapidly to treatment.

Eosinophilia↗
PubMed1996

[Cercarial dermatitis in Europe: a new public health problem?].

Cercarial dermatitis is a parasitic impasse that has worldwide distribution. The condition manifests itself as a highly pruriginous skin rash and is due to penetration of the dermis by larval stages (furcocercariae) of avian trematodes. Many species may be responsible for this disease. In Europe the genus Trichobilharzia is widely represented, in particular by the species T. ocellata; the definitive host is the duck (Anas platyrhinchos); the intermediate hosts are snails of the genus Lymnea (L. ovata or L. stagnalis). In France, cases of cercarial dermatitis were reported in June and July 1994 to the health authorities of three départements in the Pays de la Loire Region (western France). The epidemiological situation, common to the three maintained ponds that were concerned, is as follows: high level of eutrophication of the sites, colonization of the ponds by L. ovata, and settlement by many duck colonies. The simultaneous occurrence of these three phenomena, combined with long hours of sunshine in the summer, is responsible for most of the foci of cercarial dermatitis recently described in Europe. Control of this condition is difficult, requiring strict maintenance of bodies of water and if necessary the use of molluscicides such as niclosamide. The use of praziquantel in baits for treating the definitive hosts appears to interrupt the natural cycle of the avian Schistosomatidae. In the light of the observations reported here and the analysis of recent publications, cercarial dermatitis may be regarded as an emerging disease. Its public health impact needs to be evaluated at the global level.

Animals↗
PubMed1996

Attachment of spores of the human pathogenic fungus Rhizopus oryzae to extracellular matrix components.

Fungi of the order Mucorales determine various infections involving principally the respiratory tract. In spite of their medical importance, little is known about their mechanisms of adherence to the host tissues. Thus we have attempted to define the morphological stages involved in the adherence process of Rhizopus oryzae which is the main causative agent of mucormycoses. The study of the kinetics of germination and adherence to plastic revealed that attachment occurred prior to germination and decreased dramatically with germ tube formation. This correlates with important modifications of the cell wall of the fungus with respect to both carbohydrate composition and distribution of anionic sites. Moreover, the attachment of spores to extracellular matrix components immobilized onto wells of polystyrene microtiter plates has been investigated. Spores adhered readily to immobilized laminin or type IV collagen, but not to fibronectin or the glycosaminoglycans. Attachment to laminin and collagen was dose-dependent and specific. Adhesion was not inhibited by the different carbohydrates tested, suggesting that a lectin was not involved in these interactions. Finally, immunofluorescence revealed that laminin and type IV collagen interacted exclusively with spores and mother cells of germ tubes. Thus, the recognition of laminin or collagen by spores may participate in their adherence to epithelial basement membranes exposed after epithelial tissue damage which frequently accompanies the predisposing factors for mucormycoses.

Antibodies↗
PubMed1995

Prevalence of Candida ciferrii in elderly patients with trophic disorders of the legs.

In order to define the prevalence of Candida ciferrii in onychomycosis, the fungal biota associated with toe nail onyxis was examined in 50 elderly patients with trophic disorders of the legs and in 220 patients without clinical evidence of trophic disorders. Candida ciferrii was more frequent in the first group of patients since it was recovered from 24% of these patients, whereas its prevalence was only 1.4% in the control group. Moreover, the positivity of the direct examination of toe nail scrapings, the absence of any other associated pathogens, and the repeated isolation of this yeast species for some of the patients confirmed its pathogenicity.

Adult↗
PubMed1995

The search for virulence determinants in Aspergillus fumigatus.

The development of aspergillosis in an immunodeficient host depends on interactions between fungal and host components. The recognition by Aspergillus fumigatus of fibrinogen and laminin, and the secretion of extracellular proteinases and ribonucleotoxin have been suggested to mediate adherence to mucosal surfaces and subsequently to bring about host-tissue invasion.

Aspergillus fumigatus↗
PubMed1995

Cell surface properties of Aspergillus fumigatus conidia: correlation between adherence, agglutination, and rearrangements of the cell wall.

Culture conditions that lead to swelling and germination dramatically influence cell surface characteristics and properties of Aspergillus fumigatus conidia. Conidial adherence to polystyrene and agglutination markedly increased during swelling, in a time-dependent manner. Agglutination appeared to be sensitive to cycloheximide and calcium. Removal of cell wall polysaccharides by lyticase or sodium metaperiodate suppressed agglutination of conidia. Proteinase K weakly decreased it whereas dithiothreitol strongly dispersed the cells. These observations suggest that both cell surface carbohydrates and proteins are involved in the agglutination process. Electron microscopic observations demonstrated that the cell wall of conidia was subject to some rearrangements during swelling, involving degradation and loss of the external convoluted layer, and subsequent exposure of underlying ligands. This was confirmed using lectins labelled with gold or fluorescein isothiocyanate, which showed that some carbohydrates, particularly those acting as ligands for peanut agglutinin, are largely exposed during the process. Finally, SDS-PAGE revealed major protein changes between resting and swollen conidia. We conclude that the ability of A. fumigatus conidia to aggregate correlates with an increase in adherence and biochemical reorganization of the cell wall.

Aspergillus fumigatus↗
PubMed1994

Epidemiologic approach to human toxocariasis in western France.

Toxocara canis is a common parasite in puppies. The danger to human health has not been properly established. We estimated the current incidence of this pathogen in two western districts of France, Loire-Atlantique and Maine et Loire. Blood samples from 1836 eosino-philic patients were collected and tested by an enzyme-linked immunosorbent assay (ELISA) excretory-secretory Toxocara antigen test. We obtained positive results in 22% of the cases and highly positive results in 7%. The ELISA data seemed to be age-dependent, with older patients having more positive results (P < 0.0001). The interlaboratory distribution of positive test results was statistically significantly different (P < 0.0001), suggesting regional sources. The main clinical expressions of toxocariasis were: asthenia, gastric pain, and pulmonary disease. Individual and collective surveys of this zoonotic disease need to be carried out.

Animals↗
PubMed1994

Specific interaction of Aspergillus fumigatus with fibrinogen and its role in cell adhesion.

Interaction between Aspergillus fumigatus conidia and different proteins known to mediate the attachment of malignant tumor cells or microorganisms to the host tissues was studied in vitro. Flow cytometry using fluorescein isothiocyanate-conjugated fibrinogen confirmed that binding of human fibrinogen to the conidia was dose dependent and specific. Binding was inhibited by unlabeled fibrinogen and by basement membrane laminin. Moreover, the expression of fibrinogen receptors at the surfaces of conidia seemed to be related to the maturation of the conidia. Binding sites appeared to be located in the D domains of the fibrinogen molecule. However, the peptide sequence recognized by the fungus could not be identified but was different from the classical adhesive recognition sequences, RGDS and fibrinogen gamma-chain dodecapeptide. In addition, an assay of adherence to proteins immobilized onto microtiter plates allowed us to establish the role of these interactions in fungal adhesion. Conidia strongly adhered to human fibrinogen and to laminin but not to fibronectin. Adhesion to fibrinogen substrates was specific, since it was inhibited by soluble fibrinogen and by specific antibodies, and seemed to be mediated by the D domains of the molecule. Study of the adhesion of numerous strains or clinical isolates to various mammalian fibrinogens did not reveal any particular affinity of strains for some animal species. Finally, by cultivation of the fungus in the presence of 125I-human fibrinogen and analysis of the radiolabeled material bound to the surface of the fungus, we were able to specify the sequence of events allowing its installation within the host. The interactions identified here may play an important role in governing fungal adherence and host tissue invasion.

Aspergillus fumigatus↗
PubMed1994

[Mechanisms and implications of the adhesion phenomenon in Aspergillus fumigatus].

During the last few years, several works have demonstrated the fixation of different host proteins on Aspergillus fumigatus conidia. Thus, after incubation in the presence of normal human plasma, the C3 component of complement is detected at the surface of conidia. In fact, most of the C3 deposited on conidia is converted in C3b or iC3b which would facilitate their phagocytosis by the macrophages. In the non immune host, the activation of the alternative pathway seems to be the main mechanism of the activation of the complement system by the conidia, but the participation of the classical pathway initiated by the fixation of the C-reactive protein has also been suggested. Aspergillus fumigatus conidia interact also with fibrinogen and laminin. These interactions which are mediated by the D domains of fibrinogen and by the fragment P1 of laminin, are specific. The number of fibrinogen binding sites at the surface of conidia has been calculated to be 1200 by cell, and the dissociation constant 2.2 x 10(-7) M. These interactions could determine the adhesion of conidia to the host tissues as suggested by adherence assays of conidia to proteins immobilized onto wells of microtiter plates. Conidia would bind to the fibrin deposits formed on damaged epithelia in response to the inflammatory reaction, or directly to laminin of the subepithelial basement membrane. Finally, different experiments suggested the identity of the binding sites for C3, fibrinogen and laminin at the surface of A. fumigatus conidia.

Aspergillus fumigatus↗
PubMed1993

Interaction between Aspergillus fumigatus and basement membrane laminin: binding and substrate degradation.

Aspergillus fumigatus, the causative agent of human aspergillosis, binds to and degrades basement membrane laminin. Using immunoelectron microscopy, laminin binding appeared to be associated with the cell wall expansions of resting conidia, and progressively extended to the outer electron dense layer of the conidial wall during the germination process. Labeling of thin sections revealed numerous binding sites in the cytoplasm, whereas the inner cell wall and the plasma membrane were not labeled. Attachment of A fumigatus conidia on microtiter plates coated with laminin and its fragments P1 and E8 was also investigated. Conidia cells showed good adhesion to wells coated with laminin. As indicated by inhibition experiments, the interaction was specific and fragment P1 represented the major binding site on the laminin molecule. In addition, since A fumigatus produced an extracellular serine protease, we determined the susceptibility of laminin to this enzyme. We demonstrated that protease extract was capable to degrade laminin in solution as well as in tissue sections. The laminin cleavage products were detected by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. All the three chains were extensively degraded within 1 h. Treatment of the crude protease extract with the enzyme inhibitors, phenylmethylsulfonyl-fluoride and chymostatin, blocked the degradation of laminin, indicating a chymotrypsin-like serine protease activity. Immunofluorescence microscopy of cryostat sections of mouse and rat kidneys treated with the protease extract showed widespread loss of laminin epitopes from basement membranes. Enzyme treatment also removed immunoreactivity from lungs as observed after immunoperoxidase performed on paraffin sections. Binding and proteolytic degradation of laminin may together facilitate initial interaction of A fumigatus with the host tissues.

Aspergillus fumigatus↗
PubMed1993

Extracellular fibrinogenolytic enzyme of Aspergillus fumigatus: substrate-dependent variations in the proteinase synthesis and characterization of the enzyme.

To get a better understanding of the role of the previously reported fibrinogenolytic enzyme of Aspergillus fumigatus, we investigated the in vitro conditions of enzyme synthesis and attempted to characterize it. Modification of the nitrogen source did not influence the extracellular serine-proteinase profile, but resulted in important quantitative differences in the yields in batch cultures. The enzyme synthesis appeared to be an inducible phenomenon in A. fumigatus since it was initiated exclusively in the presence of proteins or protein hydrolysate. Free amino acids or inorganic nitrogen compounds could not promote significant enzyme production. Moreover, peptone at a concentration of 0.1% appeared to be the best inducer of enzyme synthesis. Conversely, modification of the carbon source did not affect fungal growth or enzyme synthesis. However, the production of chymotrypsin was highly sensitive to the carbohydrate level in the culture medium and, with peptone as nitrogen source, highest yields were obtained in the presence of 0.3 or 0.5% glucose. Culture filtrates of A. fumigatus CBS 113.26 grown with peptone or nitrate as nitrogen source were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Comparison of the protein patterns suggested for the proteinase a molecular mass of 33 kDa which was confirmed by chromatographic purification of the enzyme through (N alpha-CBZ)-D-phenylalanine agarose.

Amino Acid Sequence↗
PubMed1992

Purification and characterization of a fibrinogenolytic serine proteinase from Aspergillus fumigatus culture filtrate.

A fibrinogenolytic proteinase has been isolated from Aspergillus fumigatus culture filtrate by ammonium sulfate precipitation followed by successive chromatographies on Sephadex G-75 and immobilized phenylalanine. The purified proteinase exhibited a molecular weight of about 33 kDa. When analysed by SDS-polyacrylamide gels containing co-polymerized fibrinogen, the proteinase appeared as a broad band at the top of the gels, which could correspond to polymerization of the enzyme, as suggested by SDS-PAGE analysis of the unboiled eluate. The isoelectric point was 8.75 and the enzyme was not glycosylated. Proteinase activity was optimum at pH 9 and between 37 and 42 degrees C, although a decrease in activity was observed above 37 degrees C. PMSF and chymostatin markedly inhibited the proteinase activity, and good kinetic constants were obtained for the synthetic substrate, N-Suc-Ala-Ala-Pro-Phe-pNA. These results provide direct evidence that this enzyme belongs to the chymotrypsin-like serine proteinase group.

Amino Acid Sequence↗