Local phagocytic responses after murine infection with different forms of Fonsecaea pedrosoi and sclerotic bodies originating from an inoculum of conidiogenous cells

Abstract

Fonsecaea pedrosoi is an important causative agent of chromoblastomycosis (CBM) especially in humid areas of the world; however, little is known about the infective forms of this agent that cause CBM. The aim of this study was to investigate the murine tissue response to inoculation with different forms of F. pedrosoi and the morphological changes of the fungal cells in vivo. BALB/c mice were inoculated intraperitoneally with hyphae, conidia or conidiogenous cells and conidia (CCC) at a single site. In addition, the abdomen and footpads were infected subcutaneously with CCC. Fungal forms were inoculated at a final concentration of 1 × 10(6) cells. Hyphae and ungerminated conidia inocula could not be transformed into parasitic forms. In tissue, a great number of conidiogenous cells underwent transformation into sclerotic bodies, which were more resistant to phagocytes in vivo than conidia and hyphae. Clinical and mycological cure of animals infected with CCC was observed from the fourth to the sixth week of infection, while conidia and hyphae infections were faster and generally lasted 2 to 3 weeks. A high number of destructed conidia was observed intracellularly in macrophages. The migration of neutrophils to the inflammatory site seems important for microbicidal activity, particularly against hyphae. Our observations suggest that inocula with conidiogenous cells are associated with in vivo transformation into sclerotic bodies and that local immune response involved with host resistance to experimental F. pedrosoi-infection is primarily mediated by neutrophils as observed in histological sections.