Marcia R. Pinto

Structure and biological functions of fungal cerebrosides

Ceramide monohexosides (CMHs, cerebrosides) are glycosphingolipids composed of a hydrophobic ceramide linked to one sugar unit. In fungal cells, CMHs are very conserved molecules consisting of a ceramide moiety containing 9-methyl-4,8-sphingadienine in amidic linkage to 2-hydroxyoctadecanoic or 2-hydroxyhexadecanoic acids, and a carbohydrate portion consisting of one residue of glucose or galactose. 9-Methyl 4,8-sphingadienine-containing ceramides are usually glycosylated to form fungal cerebrosides, but the recent description of a ceramide dihexoside (CDH) presenting phytosphingosine in Magnaporthe grisea suggests the existence of alternative pathways of ceramide glycosylation in fungal cells. Along with their unique structural characteristics, fungal CMHs have a peculiar subcellular distribution and striking biological properties. In Pseudallescheria boydii, Candida albicans, Cryptococcus neoformans, Aspergillus nidulans, A. fumigatus, and Schizophyllum commune, CMHs are apparently involved in morphological transitions and fungal growth. The elucidation of structural and functional aspects of fungal cerebrosides may therefore contribute to the design of new antifungal agents inhibiting growth and differentiation of pathogenic species.

A peptidorhamnomannan from the mycelium of Pseudallescheria boydii is a potential diagnostic antigen of this emerging human pathogen

The ascomycete Pseudallescheria boydii is an emerging human pathogen frequently found in soil and polluted water. A peptidopolysaccharide antigen has been isolated from mycelial forms of P. boydii, and characterized using chemical and immunological methods. Monosaccharide composition, methylation analysis, and (1)H- and (13)C-NMR spectra indicated the presence of a rhamnomannan with a structure distinct from those of similar components isolated from other fungi, containing Rhap(1-->3)Rhap epitopes on side chains which may be linked (1-->3) to (1-->6)-linked mannose. The peptidorhamnomannan from P. boydii reacted poorly with an antiserum raised against whole cells of Sporothrix schenckii and strongly with one against P. boydii hyphae. These characteristics and immunological differences suggest that this major rhamnose-containing antigen of P. boydii may be useful for the specific diagnosis of infections attributable to this fungus.

Glucosylceramides in Colletotrichum gloeosporioides are involved in the differentiation of conidia into mycelial cells

Glucosylceramides (GlcCer) were extracted from the plant pathogen Colletotrichum gloeosporioides and purified by several chromatographic steps. By using electrospray ionization mass spectrometry and nuclear magnetic resonance, GlcCer from C. gloeosporioides were identified as N‐2′‐hydroxyoctadecanoyl‐1‐β‐D‐glucopyranosyl‐9‐methyl‐4,8‐sphingadienine and N‐2′‐hydroxyoctadecenoyl‐1‐β‐D‐glucopyranosyl‐9‐methyl‐4,8‐sphingadienine. Monoclonal antibodies against these structures were produced and used as tools for the evaluation of the role of GlcCer in the morphological transition of C. gloeosporioides. In the presence of antibodies to GlcCer, the differentiation of conidia into mycelia was blocked. Since GlcCer is present in several plant pathogens, the inhibitory activity of external ligands recognizing these structures may be applicable in other models of fungal infections.

Structural and Functional Aspects of Fungal Glycosphingolipids

ABSTRACT: During the last decade, significant progress has been made on the field of biosynthesis and structural elucidation of fungal glycosphingolipids (GSLs), molecules composed of a hydrophobic ceramide moiety linked to one or more sugars. Ceramide monohexosides (CMHs) from several fungal species were characterized in detail, all of them presenting a ceramide moiety containing 9-methyl-4,8-sphingadienine in amidic linkage to 2-hydroxyoctadecanoic or 2-hydroxyhexadecanoic acids, and a carbohydrate portion consisting of one residue of glucose or galactose. CMHs seem to be associated with growth or differentiation of fungal species such as Pseudallescheria boydii, Candida albicans. Cryptococcus neoformans, Aspergillus nidulans, A. fumigatus , and Schizophyllum commune . A ceramide dihexoside (CDH) was recently described in Magnaporthe grisea . This glycolipid presented phytosphingosine as the long chain base, and this observation revealed the existence of alternative pathways of ceramide glycosylation in fungal cells. Glycoinositolphosphoryl ceramides (GIPCs), a class of acidic glycosphingolipids expressed by plants and certain parasitic organisms, but not in higher animals, were also identified in fungi, representing potential targets for the development of antifungal agents. The structural characterization of GIPCs, CMHs and, more recently, CDHs from fungal cells allows therefore the design of experimental models for studies involving biosynthesis and function of these molecules.

Pesquisa de fungos em 20 pacientes com polipose nasossinusal

Introducao: Polipose nasossinusal e uma doenca frequente na pratica clinica otorrinolaringologica. Sua associacao com fungos, porem, tem recebido mais atencao apenas nos ultimos 20 anos, principalmente apos o reconhecimento da sinusite fungica alergica. Objetivo: Identificar a presenca de fungos nos seios paranasais de pacientes portadores de polipose nasossinusal e analisar a reatividade destes pacientes para aeroalergenos. Forma de Estudo: Clinico prospectivo. Material e Metodo: Avaliamos de forma prospectiva 20 pacientes com diagnostico de polipose nasossinusal, que se apresentaram ao ambulatorio de Otorrinolaringologia do Hospital Universitario Clementino Fraga Filho. Durante o tratamento cirurgico, a secrecao removida dos seios paranasais foi colocada em Sabouraud com cloranfenicol e submetida a analise histopatologica. Foram dosados niveis sericos de IgE total, IgE especifica para Aspergillus fumigatus e contagem de eosinofilos do sangue periferico. Testes cutâneos com antigenos de Dermatophagoides pteronyssinus, Dermatophagoides farinae, Blomia tropicalis, Blattella germânica, Blattella americana e Aspergillus fumigatus foram realizados .Resultados: Seis pacientes (30%) apresentaram crescimento fungico, sendo quatro Aspergillus sp, um Candida tropicalis e outro Cladophialophora carrionii. Treze (68,42%) apresentaram teste de puntura positivo para os aeroalergenos acima citados. Em dez pacientes (50%) foi encontrada eosinofilia. Niveis sericos elevados de IgE total foram encontrados em oito (44,4%). Nivel serico elevado de IgE especifica para Aspergillus fumigatus foi encontrado em apenas um. Conclusao: Salientamos a importância da pesquisa de fungos e de uma investigacao do sistema imune nos pacientes com polipose nasossinusal para ser feito um diagnostico preciso e tratamento adequado.