Juan Antonio Leal

Dendritic Cell-Specific Intercellular Adhesion Molecule 3-Grabbing Nonintegrin Mediates Binding and Internalization of Aspergillus fumigatus Conidia by Dendritic Cells and Macrophages

Aspergillus fumigatus is responsible for a large percentage of nosocomial opportunistic fungal infections in immunocompromised hosts, especially during cytotoxic chemotherapy and after bone marrow transplantation, and is currently a major direct cause of death in leukemia patients. Dendritic cell-specific ICAM-3-grabbing nonintegrin (DC-SIGN) is a type II C-type lectin that functions as an adhesion receptor and is used by viral and bacterial pathogens to gain access to human DC. We report that DC-SIGN specifically interacts with clinical isolates of A. fumigatus. DC-SIGN-dependent binding of A. fumigatus conidia can be demonstrated with stable transfectants and monocyte-derived DC and is inhibited by anti-DC-SIGN Abs. Binding and internalization of A. fumigatus conidia correlates with DC-SIGN cell surface expression levels and is abolished in the presence of A. funigatus-derived cell wall galactomannans. The clinical relevance of this interaction is emphasized by the presence of DC-SIGN in lung DC and alveolar macrophages, and further illustrated by the DC-SIGN-dependent attachment of A. fumigatus conidia to the cell membrane of IL-4-treated monocyte-derived macrophages. Our results suggest the involvement of DC-SIGN in the initial stages of pulmonary infection as well as in fungal spreading during invasive aspergillosis.

Differences in the cell wall composition in the type species ofEupenicillium andTalaromyces

Abstract The polysaccharide fractions extracted with 1 M NaOH from cell walls of Eupenicillum crustaceum (13–18%) and Talaromyces flavus (4–12%), type species of the teleomorphic states of Penicillium , show differences in composition and structure. The material extracted from three isolates of E. crustaceum was characterized as an α-glucan with absorption bands at 850 and 820 cm −1 in the infrared spectrum. Glucose (87–99%) and mannose (1–11%) were detected in 4 N H 2 SO 4 hydrolysates by gas-liquid chromatography. This polysaccharide was resistant to periodate oxidation and after complete Smith degradation, the recovery of glucose indicated that the linkage type was predominantly 1–3. The spectrum of the alkali-soluble fraction from three isolates of T. flavus showed an absorption band at 890 cm −1 characteristic of β-linked polysaccharides. The monosaccharides released by 4 N H 2 SO 4 hydrolysis were galactose (25–60%), glucose (31–69%), and mannose (6–9%). All the galactose was released by hydrolysis with 0.1 N H 2 SO 4 , characteristic of a furanose configuration. This polysaccharide consumes 0.73 mol of periodate per hexose residue. The products detected after complete Smith degradation were identified as glycerol, erythritol, threitol, arabinitol, mannitol, galactitol, and glucitol.

Chemical and structural similarities in wall polysaccharides of some Penicillium, Eupenicillium and Aspergillus species

Various fractions were extracted from cell-wall material of Eupenicillium crustaceum, Penicillium brevi-compactum, P. decumbens, Aspergillus flavipes and A. ochraceus. The most characteristic fractions, which may have chemotaxonomic relevance, were F1I, an alpha-(1-3) glucan (alkalisoluble, water-insoluble), which amounted to 16.2-32.5% of the cell-wall material, and F1S (alkali and water-soluble) which represented 2.5-6.2% of the cell-wall material and was identified as a beta-(1-5) galactan. 13C-NMR spectra of the F1S fractions showed the same pattern for all the fungal species, characteristic of beta-(1-5) linked galactofuranose.

STRUCTURE OF COMPLEX CELL WALL POLYSACCHARIDES ISOLATED FROM TRICHODERMA AND HYPOCREA SPECIES

The structure of fungal polysaccharides isolated from the cell wall of Trichoderma reesei, T. koningii, and Hypocrea psychrophila, have been investigated by means of chemical analyses and 1D and 2D NMR spectroscopy. The polysaccharides have an irregular structure, idealized as follows: [formula: see text] The proportions of the different side chains vary from a species to another, being n above some three times larger in H. psychrophila than in T. reesei or T. koningii.

Differences among the cell wall galactomannans from Aspergillus wentii and Chaetosartorya chrysella and that of Aspergillus fumigatus.

The alkali extractable and water-soluble cell wall polysaccharides F1SS from Aspergillus wentii and Chaetosartorya chrysella have been studied by methylation analysis, 1D- and 2D-NMR, and MALDI-TOF analysis. Their structures are almost identical, corresponding to the following repeating unit:[→ 3)-β-D-Galf-(1 → 5)-β-D-Galf-(1 →]n → mannan core.The structure of this galactofuranose side chain differs from that found in the pathogenic fungus Aspergillus fumigatus, in other Aspergillii and members of Trichocomaceae:[→ 5)-β-D-Galf-(1 →]n → mannan core.The mannan cores have also been investigated, and are constituted by a (1 → 6)-α-mannan backbone, substituted at positions 2 by chains from 1 to 7 residues of (1 → 2) linked α-mannopyranoses. Published in 2004.

Changes in chemical composition during germination ofbotrytis cinerea sclerotia

Carbohydrates (71%), protein (10%), and lipids (8.8%) were the major chemical components of germinated sclerotia ofBotrytis cinerea Pers. ex Fr. Glucosamine and phosphate ion comprised less than 5%. The alcohol-soluble fraction (21%) contained trehalose, mannitol, arabitol, and glucose. The materials extracted from the germinated sclerotia by different treatments and precipitated with an equal volume of ethanol gave the following yields as a percentage of the initial sclerotium dry-weight: water at 18°C (30.5%), water at 100°C (10.6%), and 1 M alkali at 60°C (13%). The insoluble material amounted to 7.2%. All these fractions gave the characteristic infrared spectrum of β-glucans. The main type of linkage between the monomers was 1→3, as determined by periodate consumption.

Structural studies of fungal cell-wall polysaccharides from two strains of Talaromyces flavus

The water-soluble cell-wall polysaccharides isolated from strains CBS 352.72 and 310.38 of Talaromyces flavus have been investigated by chemical analyses and NMR studies. Two different skeletons coexist, having the structures: [formula:see text]. The small differences between the polysaccharides isolated from both strains are probably due to slight diminution of branching in strain 352.72, as compared with strain 310.38.

An acidic water-soluble cell wall polysaccharide: a chemotaxonomic marker for Fusarium and Gibberella

Alkali-extractable and water-soluble cell-wall polysaccharides were purified from cell walls of some species of Fusarium and Gibberella. Their structures were determined by chemical analysis and NMR. The polysaccharides consisted of a main chain of β-(1 → 6)-linked galactofuranose units almost fully branched at positions O-2 by single residues of glucopyranose or acidic chains containing glucuronic acid and mannose. Individual differences were found, concerning the proportion of neutral and acidic side chains. These polysaccharides showed major differences from those of Microdochium nivale, Plectosphaerella cucumerina, Fusarium ciliatum, F. aquaeductuum and F. cavispermum. Highly specific polyclonal antibodies were raised against this structure, which were used in immunocompetence and immunofluorescence experiments.

Possible chemotypes from cell wall polysaccharides, as an aid in the systematics of Penicillium and its teleomorphic states Eupenicillium and Talaromyces

From the alkali-extractable material obtained from cell walls of 44 species (49 strains) of Penicillium a water-soluble fraction (F1S) was isolated. The main component (F1S-S) of fraction F1S was purified by gel permeation chromatography through Sepharose CL6B, analysed chemically and its structure determined by 1 H- and 13 C-NMR. Galactose was the predominant neutral sugar in this fraction. Six different polysaccharidic structures were found and the species investigated were arranged into six groups according to these structures. These results illustrate the complexity of the cell wall components of Penicillium and add to existing information on the relatedness of species of the genus with Eupenicillium and Talaromyces . The results show that there are several types of cell wall in Penicillium .

Structural investigation of two cell-wall polysaccharides of Penicillium expansum strains

The structure of two cell-wall polysaccharides isolated from three different strains of Penicillium expansum, the type species of the genus, have been established by 1D and 2D NMR spectroscopy, and also by methylation analyses. The water-soluble polysaccharide F1S-B consisted of a linear tetrasaccharide repeating unit with the following structure: [-->6)-beta-D-Galf-(1-->5)-beta-D-Galf-(1-->5)-beta-D-Gal f-(1-->5)-beta-D- Galf-(1-->]n The alkali-soluble polysaccharide F1I is a (1-->3)-alpha-D-glucan.