Experimental paracoccidioidomycosis in immunosuppressed mice

Thermally Dimorphic Human Fungal Pathogens--Polyphyletic Pathogens with a Convergent Pathogenicity Trait

Fungi are adept at changing their cell shape and developmental program in response to signals in their surroundings. Here we focus on a group of evolutionarily related fungal pathogens of humans known as the thermally dimorphic fungi. These organisms grow in a hyphal form in the environment but shift their morphology drastically within a mammalian host. Temperature is one of the main host signals that initiates their conversion to the "host" form and is sufficient in the laboratory to trigger establishment of this host-adapted developmental program. Here we discuss the major human pathogens in this group, which are Blastomyces dermatiditis, Coccidioides immitis/posadasii, Histoplasma capsulatum, Paracoccidioides brasiliensis/lutzii, Sporothrix schenckii, and Talaromyces marneffei (formerly known as Penicillium marneffei). The majority of these organisms are primary pathogens, with the ability to cause disease in healthy humans who encounter them in endemic areas.

Vaccination of mice against Leishmania mexicana amazonensis with microsomal fraction associated with BCG

Attempts to develop a satisfactory vaccine against New World cutaneous leishmaniasis have been made with varying success. We found that in mice, pretreated subcutaneously with 2 X 10(6) BCG organisms 2 weeks prior to immunization at the same site with as low as 10 micrograms of a microsomal preparation (Pol-F) of Leishmania mexicana amazonensis, a profound alteration was observed in the course of infection produced by inoculation of virulent amastigotes of the same strain. The BCG-Pol-F vaccine preparation was consistently shown to have a protective capacity associated with larger classical cellular immune response (skin test) and higher specific antibody titres in response to leishmanial challenge dose (1 X 10(6) amastigotes/mouse).

Paracoccidioidomycosis in silica-treated rats

An attempt is made to evaluate the importance of macrophages in the early local reaction to infection caused by the fungus Paracoccidioides brasiliensis. With this purpose, an attempt was made to impair macrophagic activity in the site of the fungal inoculum, by means of previous injections of silica. Twenty male rats were intraperitoneally infected with yeast cells of the fungus. Ten of the rats were injected intraperitoneally with silica particles twice, namely 24 and 4 h before the infection. All the animals were killed 4 wk after fungal inoculum. The results showed that the disease was aggravated in rats pre-treated with silica, clearly demonstrated by the 100% metastatic pulmonary involvement, in contrast with only 40% observed in the non-treated controls.