Paracoccidioidomycosis in nude mice: Presence of filamentous forms of the fungus

Abstract

Congenitally athymic nude mice (nu/nu) and their phenotypically normal littermates (nu/+) were intraperitoneally infected with yeast cells of a strain of Paracoccidioides brasiliensis. The nude mice developed a severe and generalized infection with an intense parasitism of several organs, accompanied by a low-grade of tissue reaction. The lesions were characterized by abundant yeast-like cells of the fungus, and in some animals, numerous hyphal forms could be well visualized. In control animals, infection was moderate, almost exclusively restricted to the area of inoculation, and the lesions presented few parasites surrounded by an inflammatory response. Filamentous forms of the fungus were never encountered in these animals.

Cell-mediated immunity in host resistance against infection caused byPenicillium marneffei

“…In this case, nude mice are more severely affected than normal animals by infectious pathogens which are cleared by the cell-mediated immune mechanisms. This group contains C. neoJormans [10], B. dermatitidis [11], C. immitis [12], P. brasiliensis [13] and H. capsulatum [14]. In the present study, nude mice showed a higher susceptibility to infection with P. marneffei compared with euthymic mice.…”

“…To confirm our hypothesis, we used congenitally athymic nude mice, which are known to have deficient cell-mediated immunity and impaired T cell-dependent antibody production [21]. These animals have been used in the past to study the pathological effects of a variety of infectious agents [10][11][12][13][14]22,23]. Previous studies demonstrated that the resistance to fungal infection involves two different mechanisms.…”

“…To define the host defence mechanisms against other fungal micro-organisms such as Cryptococcus neoJormans [10], Blastomyces dermatitidis [11], Coccidioides immitis [12], Paracoccidioides brasiliensis [13] and Histoplasma capsulatum [14], several experimental animal models were developed in the past. With regard to P. marneJfi, i, Deng et al l15] demonstrated that the fungus causes abdominal abscess through the intraperitoneal route.…”

Inoculation experimental animals withParacoccidioides brasiliensis strains: An attempt to reestablish the dimorphic process and variation in pathogenicity as a function of time of preservation under mineral oil

“…A low inoculum in the 5 x 102 range causes a [8] concluded that the virulence of P. brasiliensis may be attenuated or lost in subcultures carried out for long periods of time. Considering the times of isolation and continued preservation under mineral oil of the strains studied here, and the possibility of in vivo filamentation of P. brasiliensis reported by Londero et al [9] for man and by Kerr et al [10] for nude mice, we suggest that some factors regulating the mechanism of dimorphism and virulence still need elucidation.…”