Histopathology of experimental invasive pulmonary aspergillosis in rats: Pathological comparison of pulmonary lesions induced by specific virulent factor deficient mutants

Shibuya, Kazutoshi; Takaoka, Masayoshi; Uchida, Katsuhisa; Wakayama, Megumi; Yamaguchi, Hideyo; Takahashi, Kei; Paris, Sophie; Latgé, Jean‐Paul; Naoe, Shiro

doi:10.1006/mpat.1999.0288

Cited by 41 publications

(29 citation statements)

References 15 publications

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“…However, a direct trapping of the deleterious host molecules by RodAp might also occur in a manner similar to that suggested for melanin (18). These data are in agreement with the results of Shibuya et al (34), who showed that pulmonary lesions induced by the rodletless mutant ⌬rodA-47 were limited compared to those induced by the G10 strain. In contrast, RodBp is not directly involved in the resistance of conidia to killing.…”

Section: Discussionsupporting

confidence: 93%

Conidial Hydrophobins ofAspergillus fumigatus

Paris¹,

Debeaupuis²,

Crameri³

et al. 2003

Appl Environ Microbiol

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The surface of Aspergillus fumigatus conidia, the first structure recognized by the host immune system, is covered by rodlets. We report that this outer cell wall layer contains two hydrophobins, RodAp and RodBp, which are found as highly insoluble complexes. The RODA gene was previously characterized, and ⌬rodA conidia do not display a rodlet layer (N. Thau, M. Monod, B. Crestani, C. Rolland, G. Tronchin, J. P. Latgé, and S. Paris, Infect. Immun. 62:4380-4388, 1994). The RODB gene was cloned and disrupted. RodBp was highly homologous to RodAp and different from DewAp of A. nidulans. ⌬rodB conidia had a rodlet layer similar to that of the wild-type conidia. Therefore, unlike RodAp, RodBp is not required for rodlet formation. The surface of ⌬rodA conidia is granular; in contrast, an amorphous layer is present at the surface of the conidia of the ⌬rodA ⌬rodB double mutant. These data show that RodBp plays a role in the structure of the conidial cell wall. Moreover, rodletless mutants are more sensitive to killing by alveolar macrophages, suggesting that RodAp or the rodlet structure is involved in the resistance to host cells.The surface of many fungal conidia is covered by a thin layer of regularly arranged rodlets. This structure, which favors air buoyancy and dispersion of the conidia by air currents (2), is mainly proteinaceous (3,(8)(9)(10)16). The proteins present in the cell wall of aerial structures of fungi responsible for this rodlet configuration are the hydrophobins, a family of small, moderately hydrophobic proteins characterized by the conserved spacing of eight cysteine residues (42, 44). For the human opportunistic pathogen Aspergillus fumigatus, the presence of a rodlet layer has been visualized and the RODA gene has been previously shown to be involved in the formation of the rodlets of its conidia (41). In plants, hydrophobins have been associated with the virulence of phytopathogenic fungi (38). Although it has been repeatedly shown that cell wall and associated structures help human fungal pathogens to resist host defense reactions (22), to date no studies have analyzed the role of the rodlet layer in the resistance of the conidia to phagocytosis. Even though the rodlet layer of the conidia of Neurospora crassa, Beauveria bassiana, and Magnaporthe grisea contained a single hydrophobin (5, 39, 40), A. nidulans, a species phylogenetically close to A. fumigatus, has two conidial hydrophobins, RodAp and DewAp (35,36). These data have prompted us to reexamine the surface layer of the conidia of A. fumigatus with a view to (i) analyzing exhaustively hydrophobins present on the surface of the conidia and (ii) studying their role in resistance to phagocytosis. A. fumigatus is a good model for the later study, since conidia, which are a main component of the airborne thermophilic fungal florae (1), are all engulfed and killed by lung alveolar macrophages (AM) following their inhalation (11; B. Philippe, O. Ibrahim-Granet, M. C. Prévost, M. A. Gougerot-Pocidalo, J. Roes, M. SanchezPerez, A. Van der Meer...

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Section: Discussionsupporting

confidence: 93%

Conidial Hydrophobins ofAspergillus fumigatus

Paris¹,

Debeaupuis²,

Crameri³

et al. 2003

Appl Environ Microbiol

Self Cite

209

178

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“…Sprague-Dawley rats were immunosuppressed and infected by the method of Shibuya et al (43). Briefly, 5-week-old Sprague-Dawley rats (SD-1Crj) were subcutaneously injected with 20 mg of ampicillin per kg, 25 mg of cyclophosphamide per kg, and 25 mg of predonisolone per kg on days Ϫ7, Ϫ5, Ϫ3, Ϫ1, 3, 5, and 10.…”

Section: Methodsmentioning

confidence: 99%

“…In addition, the infectivities of the conidial and mycelial mutants in a rat model were assessed. This model of experimental infection was selected because the histological features observed in rats treated with low doses of immunosuppressive drugs resemble those observed in patients with invasive aspergillosis (43).…”

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confidence: 99%

Catalases of Aspergillus fumigatus

et al. 2003

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Upon infection of a host, the pathogenic fungus Aspergillus fumigatus is attacked by the reactive oxygen species produced by phagocytic cells. Detoxification of hydrogen peroxide by catalases was proposed as a way to overcome this host response. A. fumigatus produces three active catalases; one is produced by conidia, and two are produced by mycelia. The mycelial catalase Cat1p was studied previously. Here we characterized the two other catalases, their genes, and the phenotypes of gene-disrupted mutants. CatAp, a spore-specific monofunctional catalase, is resistant to heat, metal ions, and detergent. This enzyme is a dimeric protein with 84.5-kDa subunits. The 749-amino-acid polypeptide exhibits high levels of similarity to the Aspergillus nidulans CatA catalase and to bacterial catalase HPII of Escherichia coli. In spite of increased sensitivity to H 2 O 2 , killing of ⌬catA conidia by alveolar macrophages and virulence in animals were similar to the killing of conidia by alveolar macrophages and virulence in animals observed for the wild type. In contrast to the Cat1p and CatAp catalases, the mycelial Cat2p enzyme is a bifunctional catalase-peroxidase and is sensitive to heat, metal ions, and detergent. This enzyme, an 82-kDa monomer, is homologous to catalase-peroxidases of several fungi and bacteria. Surprisingly, mycelium of the double ⌬cat1⌬cat2 mutant with no catalase activity exhibited only slightly increased sensitivity to H 2 O 2 and was as sensitive to killing by polymorphonuclear neutrophils as mycelium of the wild-type strain. However, this mutant exhibited delayed infection in the rat model of aspergillosis compared to infection by the wild-type strain. These results indicate that conidial catalase is not a virulence factor and that mycelial catalases transiently protect the fungus from the host.The opportunistic fungal pathogen Aspergillus fumigatus is responsible for a variety of respiratory diseases in humans, such as allergic bronchopulmonary aspergillosis, aspergilloma, and invasive aspergillosis (10). This fungus is an airborne saprophyte that is inhaled by every human. Alveolar macrophages and polymorphonuclear cells, cellular components of the innate defense of the lung, cooperate to control and eliminate the fungus in the airways. Macrophages eliminate conidia, and protection against the hyphal form is mediated by polymorphonuclear cells (41). Reactive oxygen species (ROS) produced by alveolar macrophages play an essential role in the killing of A. fumigatus conidia (38a). Moreover, in vitro studies of neutrophil function have shown that hydrogen peroxide effectively kills fungal hyphae (12) and that neutrophil-mediated damage is blocked by addition of a commercial catalase (13). Accordingly, catalase, which is a good scavenger of H 2 O 2 , was considered to be a putative virulence factor of A. fumigatus that could counteract the oxidative defense reactions of the host phagocytes (20). No conidial catalase has been identified previously in A. fumigatus. In Aspergillus nidulans, however, a...

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“…Aliquots (300 l) of organ homogenates prepared for the chitin assay were centrifuged at 1,500 ϫ g for 10 min at 4°C. Galactomannan antigen (35,38) was detected in supernatants by means of a commercially available kit as recommended by the manufacturer. We calculated the ratio of the absorbance in a sample to the absorbance in threshold serum to determine whether the results should be classified as negative (ratio of Ͻ1) or positive (ratio of Ն1).…”

Section: Reagentsmentioning

confidence: 99%

Differences in Patterns of Infection and Inflammation for Corticosteroid Treatment and Chemotherapy in Experimental Invasive Pulmonary Aspergillosis

Huerre²,

et al. 2005

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Aspergillus fumigatus causes invasive pulmonary aspergillosis (IPA). This disease is one of the most lifethreatening opportunistic infections in immunocompromised patients. The type of immunosuppressive regimen under which IPA occurs has rarely been investigated. In this study, we evaluated various parameters of the innate immune response during the progression of murine IPA induced by the intratracheal administration of A. fumigatus conidia as a function of two immunosuppressive treatments: a corticosteroid and a chemotherapeutic agent. We compared host responses various times after infection in terms of survival, pulmonary production of pro-and anti-inflammatory cytokines, cellular trafficking in the airways, lung injury, respiratory distress, and fungal development. We found that IPA pathogenesis involved predominantly fungal development in mice treated by chemotherapy and an adverse host response in mice treated with a corticosteroid. These previously unrecognized differences should be taken into account in evaluations of the pathogenesis of IPA in animal models.Aspergillus fumigatus belongs to a family of saprophytic filamentous fungi found in most environments. It sporulates abundantly, leading to the release into the atmosphere of large quantities of conidia. A. fumigatus spreads within the environment by means of airborne conidia, and the small diameter of these spores (2 to 3 m) enables them to reach the lung alveoli (19). Pulmonary host defenses against A. fumigatus are mediated by phagocytic cells of the innate immune system. Resident alveolar macrophages are thought to eliminate conidia by phagocytosis, whereas recruited polymorphonuclear neutrophils (PMN) destroy hyphae by producing reactive oxygen species (30,34).If the immune defense system of the lung is weakened, then conidia germinate and produce hyphae that invade the surrounding lung tissues (39), leading to the development of invasive pulmonary aspergillosis (IPA). This disease is one of the most life-threatening opportunistic infections in immunocompromised patients (19), and its incidence has increased in recent decades (14, 18). This increase in incidence has been associated with an increase in the number of people at risk due to solid organ transplantation, hematopoeitic stem cell transplantation, and intensive chemotherapeutic or immunosuppressive regimens (24). Furthermore, the difficulty of diagnosing IPA early and the low efficacy of treatments result in a high rate of mortality due to this disease in immunocompromised patients (10,23).Despite the increase in the number of IPA patients, the pathogenesis of this mycosis remains poorly understood. Experimental animal models of IPA have been developed for investigation of the role of innate immunity in the progression of the disease. Various infection protocols have been used and have generated conflicting data. More importantly, the type of immunosuppressive regimen in which IPA develops has received very little attention. In this study, we investigated various parameters of the innate...

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Histopathology of experimental invasive pulmonary aspergillosis in rats: Pathological comparison of pulmonary lesions induced by specific virulent factor deficient mutants

Cited by 41 publications

References 15 publications

Conidial Hydrophobins ofAspergillus fumigatus

Conidial Hydrophobins ofAspergillus fumigatus

Catalases of Aspergillus fumigatus

Differences in Patterns of Infection and Inflammation for Corticosteroid Treatment and Chemotherapy in Experimental Invasive Pulmonary Aspergillosis

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