title: Inhibitory effect of melanin on the interaction of Fonsecaea pedrosoi with mammalian cells in vitro.
abstract: Conidial forms of Fonsecaea pedrosoi, grown under conditions where melanin was or was not synthesized, were allowed to interact with normal and cytochalasin treated macrophages. Melanin-free conidia were more infective to the macrophages. Treatment of macrophages with either cytochalasin B or D before the interaction decreased, but did not totally prevent their infection by the fungi. This inhibitory effect was higher (approximately 90%) if F. pedrosoi was grown under conditions where melanin was not synthesized. When melanin-containing conidia were used, the inhibitory effect of the cytochalasin on the infection was lower (approximately 50%). At least two mechanisms of infection of the host cell were observed: typical phagocytosis and another process in which the fungi played a more active role. Infection by F.pedrosoi was also observed in the non-professional phagocytic MDCK epithelial cell line. Two types of cytoplasmic vacuoles which contained parasites were seen in thin sections of host cells infected with F.pedrosoi: a 'tight' type and a 'loose' type. At least 200 conidia-containing vacuoles were analysed by transmission electron microscopy. The 'tight' type was observed in 75% of the vacuoles of non-treated macrophages, suggesting an association with classical phagocytosis. On the other hand, the 'loose' type vacuole was seen in 75% of the vacuoles present in cytochalasin treated macrophages and seemed to be related to induced phagocytosis or active penetration by the fungi.
authors.affiliation: Instituto de Biofisica Carlos Chagas Filho, Universidade Federal de Rio de Janeiro, Brazil.
authors.forename: S R
authors.initials: SR
authors.lastname: Farbiarz
authors.forename: T U
authors.initials: TU
authors.lastname: de Carvalho
authors.forename: C
authors.initials: C
authors.lastname: Alviano
authors.forename: W
authors.initials: W
authors.lastname: de Souza
mesh_terms: D000818:Animals; D003572:Cytochalasins / Q000494:pharmacology; D004285:Dogs; D004705:Endocytosis / Q000502:physiology; D066298:In Vitro Techniques; D008264:Macrophages / Q000187:drug effects / Q000382:microbiology* / Q000648:ultrastructure; D008543:Melanins / Q000378:metabolism / Q000502:physiology*; D051379:Mice; D008853:Microscopy; D008854:Microscopy, Electron; D003904:Mitosporic Fungi / Q000378:metabolism / Q000472:pathogenicity*
chemical_list: D003572:Cytochalasins; D008543:Melanins