Resistance to Paracoccidioides brasiliensis infection is linked to a preferential Th1 immune response, whereas susceptibility is associated with absence of IFN-gamma production.

The secretion of interferon-gamma (IFN-gamma), interleukin-2 (IL-2), IL-4, IL-5, and IL-10 by antigen-stimulated lymph node cells, eosinophil maturation, and the antibody isotypes produced were examined during intraperitoneal infection of susceptible (B10.A) and resistant (A/Sn) mice with Paracoccidioides brasiliensis. Lymph node cells from resistant mice produced early and sustained levels of IFN-gamma and IL-2, whereas susceptible animals secreted low to undetectable amounts of these type 1 cytokines. Both mouse strains presented late and transient production of IL-4, whereas IL-10 was produced constantly throughout the course of disease. Resistant animals produced increasing levels of IL-5 in the chronic phase of the infection (from the eighth week on), whereas susceptible mice showed two peaks of IL-5 production, at the first and twelfth weeks after infection. Only the susceptible strain presented medullary and splenic eosinophilia concomitant with the raised IL-5 production. In resistant mice, the levels of IgG2a antibodies were significantly higher than those observed in susceptible mice, which preferentially secreted IgG2b and IgA isotypes. Taken together, these results demonstrate that a sustained production of IFN-gamma and IL-2 and a predominant secretion of IgG2a antibodies are associated with resistance to P. brasiliensis. In contrast, the production of low levels of IFN-gamma, early secretion of high levels of IL-5 and IL-10, eosinophilia, and a preferential secretion of IgG2b and IgA isotypes characterize the progressive disease in susceptible animals.

Paracoccidioides brasiliensis-stimulated human gamma/delta T cells support antibody production by B cells.

Paracoccidioidomycosis patients show hyperactive humoral immune responses. Consequently, we investigated whether cytokines in supernatants from Paracoccidioides brasiliensis-stimulated gamma/delta T cells support B-cell activation. We detected proliferation of B cells and increased immunoglobulin M (IgM) and IgG production. Thus, gamma/delta T cells may participate in polyclonal B-cell activation during paracoccidioidomycosis.

Human alpha beta and gamma delta T cells from unexposed individuals respond to protein antigens of the yeast form of Paracoccidioides brasiliensis.

Paracoccidioides brasiliensis, a dimorphic fungus, causes chronic granulomatous mycosis in susceptible individuals. Different reports have shown that cell-mediated immunity is essential for protection against systemic mycosis, including paracoccidioidomycosis. We analyzed the reactivity of alpha beta and gamma delta T cells from unexposed Caucasian donors to P. brasiliensis yeast form components. Our results indicate: (i) alpha beta and gamma delta T cells proliferate after in vitro stimulation with lysates of P. brasiliensis; (ii) similar numbers of alpha beta T cells (f = 1/21,000) and of gamma delta T cells (f = 1/8000) respond to P. brasiliensis; (iii) P. brasiliensis-reactive gamma delta T cells express the V gamma 9V delta 2 TCR; (iv) the stimulatory activity of P. brasiliensis for both alpha beta and gamma delta T cells primarily resides in a high molecular weight (100 kDa) and in a low molecular weight (< 1 kDa) fraction; (v) the ligands responsible for stimulation of both alpha beta and gamma delta T cells are sensitive to proteinase treatment. We conclude that both alpha beta and gamma delta T cells from healthy individuals respond to ubiquitous protein antigens of P. brasiliensis.

Resistance to Paracoccidioides brasiliensis in mice is controlled by a single dominant autosomal gene.

In a previous report it was shown that there are resistant, susceptible, and intermediate strains of mice to intraperitoneal Paracoccidioides brasiliensis infection. In the present work, we investigated the type of inheritance and the number of genes that determine resistance to paracoccidioidomycosis. Parental and hybrid mice were inoculated intraperitoneally with 5 X 10(6) P. brasiliensis yeast cells, and mortality was scored daily. Analysis of susceptible and resistant parental strains and of F1, F2, and backcross mice showed that the resistance to P. brasiliensis seems to be controlled genetically by a single dominant gene, which we designated the Pbr locus. The mean survival times of susceptible F2 and backcross hybrids were very similar to that of the susceptible parent. Examination of the pathological changes observed in parental and F1 mice, 6 months after infection, showed that F1 offspring presented a similar number and distribution of lesions to those of the resistant strains. The Pbr gene is not linked to H-2, Hc, and albino genes. Furthermore, resistance to paracoccidioidomycosis is controlled by an autosomal gene.

Role of the fungal cell wall in the granulomatous response of mice to the agents of chromomycosis.

Mice were given, intraperitoneally, inocula of a cell-wall preparation and fractions thereof from Fonsecaea pedrosoi, F. compactum, Cladosporium carrioni and Phialophora verrucosum. Large doses of cell-wall preparation, with or without trypsin treatment, produced a pronounced loss of body weight, a granulomatous reaction and, sometimes, death. After extraction of the cell wall preparation with 1N NaOH, three fractions were obtained: an alkali-insoluble fraction 1; an alkali-soluble acid-insoluble fraction 2; and an alkali- and acid-soluble fraction 3. Intravenous administration showed that only fraction 1 induced a granulomatous reaction and death in mice.

A Paracoccidioides brasiliensis polysaccharide having granuloma-inducing, toxic and macrophage-stimulating activity.

The occurrence of a polysaccharide fraction of Paracoccidioides brasiliensis cell wall with toxic, granuloma-inducing and macrophage-stimulating activities was demonstrated. After fractionation of the lipid-extracted wall with 1 M-NaOH, three fractions were obtained: (1) an alkali-insoluble fraction; (2) an alkali-soluble, acid-insoluble fraction and (3) an alkali-soluble, acid-soluble fraction. When the three fractions were injected into mice only fraction (1) was able to induce chronic lung inflammation, causing a marked loss in body weight and death at a dose of 6 mg per animal. Analysis of the stimulation of peritoneal macrophages of mice (measured by cell spreading on glass) after intraperitoneal injection of fraction 1 showed that 75% of the cells were able to spread even 20 d after inoculation.

Role of cord factor in the modulation of infection caused by mycobacteria.

The subcutaneous, intradermal, and pulmonary inflammatory lesions induced in mice by viable Mycobacterium bovis (BCG) with no glycolipid cord factor (CF) on the outer cell wall (delipidated BCG, dBCG) was drastically different from that induced by inoculation with intact bacteria. The reaction caused by dBCG was of an acute nature: the cells making up the inflammatory infiltrate exhibited polymorphonuclear-like (PMNs) morphologic characteristics, there was a decrease on delayed hypersensitivity response, and the lesion was resolved around the 16th day after inoculation. Complete disappearance of viable organisms from the lungs, liver, and spleen of these animals occurred in parallel with the dissipation of the dBCG-induced inflammatory infiltrate, showing that CF plays an important role in the host-parasite relationship that takes place in infections caused by mycobacteria. In addition, when deprived of this glycolipid component, bacilli lose their immunostimulant ability.