Resumo

Aspergillus is a ubiquitous fungus which can cause a variety of clinical syndromes, especially in immunosuppressed patients. This fungus has emerged as an agent of fatal systemic infections and has therefore gained considerable public health importance. Several works have reported that the interaction between a fungus and host occurs first at the level of the cell wall surface glycoconjugates. Thus, characterization of these exterior carbohydrate residues can lead to a better understanding of fungal adhesion and the mechanisms by which fungi avoid the host’s immune system, helping to develop diagnostic tests based on identification of carbohydrate components.The aim of this study was to evaluate, through lectin histochemistry, the expression of N-acetyl-D-glucosamine, L-fucose, D-galactose and glucose/mannose on the cell wall surface of Aspergillus species in histopathological specimens of brain (n=1) and lung (n=6) tissues obtained during autopsy of patients diagnosed postmortem as having suffered from invasive aspergillosis. Concanavalin A (Con A), wheat germ agglutinin (WGA), Ulex europeus agglutinin I (UEA-I) and peanut agglutinin (PNA), all conjugated with horseradish peroxidase, were used. Lectin-binding was visualized using 3,3-diaminobendizine (DAB) and hydrogen peroxide in PBS. We observed expression of N-acetyl-D-glucosamine and methyl-α-D-mannoside on the cell wall surface of all Aspergillus species evaluated, while the expression of L-fucose and D-galactose demonstrated inter and intra-specific variations. Numerous reports on the carbohydrate profiling through lectin-binding assays of fungal cell wall surface glycoconjugates of medical importance, such as Aspergillus fumigatus, Cryptococcus neoformans, Paracoccidioides brasiliensis and others, have shown that most of theses fungi exhibit N-acetyl-D-glucosamine and methyl-α-D-mannoside on the cell surface, as inferred by WGA and Con A binding, respectively. The results obtained from this study indicate that the use of WGA and Con A lectins permits visualization of Aspergillus structures such as hyphae, conidial heads and conidia in histopathological specimens of brain and lung tissues.