Separation of Paracoccidioides brasiliensis conidia through percoll gradients.

The conidia of Paracoccidioides brasiliensis are the structures most likely to serve as the infectious propagules of this fungus. This study describes our attempts to purify conidia by eliminating mycelial fragments. Purification was attempted using discontinuous 95% and 60% Percoll gradients with densities of 1.167 and 1.107, respectively, prepared either in 0.15 mol/L PBS or 0.25 mol/L sucrose. The best results were observed with the 95% and 90% gradients in sucrose; with the former, conidial purity ranged from 70.6 to 100%, with a mean of 82.3% and a coefficient of variation (VC) of 11.7. With 90% gradients, purity was achieved between 70.4 and 92.5%. The mean in this case was 80.6% and the VC was 9.2%. The use of two consecutive 95% Percoll gradients in sucrose was tested. The recovery efficiency per plate, which averaged 2.5 x 10(6) conidia per plate with one gradient, increased to 5.1 +/- 1.3 x 10(6) conidia with two gradients. The use of Percoll did not affect the viability of the conidia, which was always > or = 90%. This method allows the preparation of a conidial sample almost free from contamination with mycelial fragments, thus facilitating quantitative determination of cause and effect in in-vivo interactions between P brasiliensis and its hosts.

Residual pulmonary abnormalities in adult patients with chronic paracoccidioidomycosis: prolonged follow-up after itraconazole therapy.

Itraconazole effectively controls active paracoccidioidomycosis but appears not to hinder lung fibrosis. Clinical records and chest radiographs from 47 itraconazole-treated patients with prolonged posttherapy follow-up (mean follow-up period, 5.6 years) were analyzed; the radiographs were interpreted following pneumoconiosis standards that consider the lungs as 6 fields and grade damage according to the number of fields involved. Infiltrative lesions were observed at diagnosis in 93.6% of the patients. Fibrosis was observed in 31.8% of the patients at diagnosis and had not cleared at the end of the observation period in any of these patients. Fibrosis also developed de novo in 11 patients (25%), so that by the end of the follow-up period it was seen in 53.2% of patients overall. Fibrosis correlated with severity of infiltrates at diagnosis: fibrosis was present in 83% of patients with very severe infiltration and in 12.5% of patients with minor infiltration. Among patients with severe infiltration, fibrosis was present in 30%; this increased (to 75%) when bullae were concomitantly present at diagnosis. Prompt initiation of treatment is necessary to avoid the development of fibrosis.

Detection of melanin-like pigments in the dimorphic fungal pathogen Paracoccidioides brasiliensis in vitro and during infection.

Melanins are implicated in the pathogenesis of several human diseases, including some microbial infections. In this study, we analyzed whether the conidia and the yeasts of the thermally dimorphic fungal pathogen Paracoccidioides brasiliensis produce melanin or melanin-like compounds in vitro and during infection. Growth of P. brasiliensis mycelia on water agar alone produced pigmented conidia, and growth of yeasts in minimal medium with L-3,4-dihydroxyphenylalanine (L-DOPA) produced pigmented cells. Digestion of the pigmented conidia and yeasts with proteolytic enzymes, denaturant, and hot concentrated acid yielded dark particles that were the same size and shape as their propagules. Immunofluorescence analysis demonstrated reactivity of a melanin-binding monoclonal antibody (MAb) with the pigmented conidia, yeasts, and particles. Electron spin resonance spectroscopy identified the yeast-derived particles produced in vitro when P. brasiliensis was grown in L-DOPA medium as a melanin-like compound. Nonreducing polyacrylamide gel electrophoresis of cytoplasmic yeast extract revealed a protein that catalyzed melanin synthesis from L-DOPA. The melanin binding MAb reacted with yeast cells in tissue from mice infected with P. brasiliensis. Finally digestion of infected tissue liberated particles reactive to the melanin binding MAb that had the typical morphology of P. brasiliensis yeasts. These data strongly suggest that P. brasiliensis propagules, both conidia and yeast cells, can produce melanin or melanin-like compounds in vitro and in vivo. Based on what is known about the function of melanin in the virulence of other fungi, this pigment may play a role in the pathogenesis of paracoccidioidomycosis.

Fibrotic sequelae in pulmonary paracoccidioidomycosis: histopathological aspects in BALB/c mice infected with viable and non-viable paracoccidioides brasiliensis propagules.

Patients with paracoccidioidomycosis often present pulmonary fibrosis and exhibit important respiratory limitations. Based on an already established animal model, the contribution of viable and non-viable P. brasiliensis propagules to the development of fibrosis was investigated. BALB/c male mice, 4-6 weeks old were inoculated intranasally either with 4x10(6) viable conidia (Group I), or 6. 5x10(6) fragmented yeast cells (Group II). Control animals received PBS. Six mice per period were sacrificed at 24, 48, 72h (initial) and 1, 2, 4, 8, 12 and 16 weeks post-challenge (late). Paraffin embedded lungs were sectioned and stained with H&E, trichromic (Masson), reticulin and Grocot&tacute;s. During the initial period PMNs influx was important in both groups and acute inflammation involving 34% to 45% of the lungs was noticed. Later on, mononuclear cells predominated. In group I, the inflammation progressed and granulomas were formed and by the 12th week they fussed and became loose. Thick collagen I fibers were observed in 66.6% and 83.3% of the animals at 8 and 12 weeks, respectively. Collagen III, thick fibers became apparent in some animals at 4 weeks and by 12 weeks, 83% of them exhibited alterations in the organization and thickness of these elements. In group II mice, this pattern was different with stepwise decrease in the number of inflammatory foci and lack of granulomas. Although initially most animals in this group had minor alterations in thin collagen I fibers, they disappeared by the 4th week. Results indicate that tissue response to fragmented yeast cells was transitory while viable conidia evoked a progressive inflammatory reaction leading to granuloma formation and to excess production and/or disarrangement of collagens I and III; the latter led to fibrosis.

Depletion of CD8(+) T cells in vivo impairs host defense of mice resistant and susceptible to pulmonary paracoccidioidomycosis.

Using a pulmonary model of infection, we demonstrated previously that A/Sn and B10.A mice are, respectively, resistant and susceptible to Paracoccidioides brasiliensis infection. Employing the same experimental model, we examined herein the role of CD8(+) T cells in the course of paracoccidioidomycosis. Treatment with anti-CD8 monoclonal antibodies caused a selective depletion of pulmonary and splenic CD8(+) T cells in both mouse strains. The number of pulmonary CD4(+) T cells and immunoglobulin-positive cells was independent of the number of CD8(+) T cells. In susceptible mice, the loss of CD8(+) T cells by in vivo treatment with anti-CD8 monoclonal antibodies impaired the clearance of yeasts from the lungs and increased the fungal dissemination to the liver and spleen. The same treatment in resistant mice increased fungal dissemination to extrapulmonary tissues but did not alter the pulmonary fungal load. Furthermore, CD8(+) T-cell depletion did not modify delayed-type hypersensitivity reactions of A/Sn mice but increased these reactions in B10.A mice. The production of P. brasiliensis-specific antibodies by resistant and susceptible mice depleted of CD8(+) T cells was similar to that of mice given control antibody. Histopathologically, depletion of CD8(+) T cells did not disorganize the focal granulomatous lesions developed by both mouse strains. These results indicate that CD8(+) T cells are necessary for optimal clearance of the fungus from tissues of mice infected with P. brasiliensis and demonstrate more prominent protective activity by those cells in the immune responses mounted by susceptible animals.

Protective role of gamma interferon in experimental pulmonary paracoccidioidomycosis.

We have developed a murine model of pulmonary infection by Paracoccidioides brasiliensis in which resistance was associated with immunological activities governed by gamma interferon (IFN-gamma). To better characterize this model, we measured type 1 and type 2 cytokines in the lungs and investigated the effect of endogenous IFN-gamma depletion by monoclonal antibodies in the course of infection of susceptible (B10.A) and resistant (A/Sn) mice. At weeks 4 and 8 after infection, lungs from susceptible animals presented levels of IFN-gamma, interleukin-4 (IL-4), IL-5, and IL-10 higher than those in resistant mice. In both mouse strains, neutralization of endogenous IFN-gamma induced exacerbation of the pulmonary infection, earlier fungal dissemination to the liver and spleen, impairment of the specific cellular immune response resulting in significantly lower delayed-type hypersensitivity reactions, and increased levels of immunoglobulin G1 (IgG1)- and IgG2b-specific antibodies. Histopathological analysis demonstrated that depletion of IFN-gamma changes the focal granulomatous lesions found in the lungs of B10.A and A/Sn mice into coalescent granulomata which destroy the pulmonary architecture. These results suggest that irrespective of the mouse strain, IFN-gamma plays a protective role and that this cytokine is one major mediator of resistance against P. brasiliensis infection in mice.

Pulmonary paracoccidioidomycosis in resistant and susceptible mice: relationship among progression of infection, bronchoalveolar cell activation, cellular immune response, and specific isotype patterns.

Using the intraperitoneal route of infection, we demonstrated previously that A/Sn mice are resistant and B10.A mice are susceptible to Paracoccidioides brasiliensis infection. Since paracoccidioidomycosis is a deep systemic granulomatous disorder that involves primarily the lungs and then disseminates to other organs and systems, we herein investigated the course of the infection and the resulting immune responses developed by A/Sn and B10.A mice after intratracheal infection with P. brasiliensis yeast cells. It was observed that A/Sn mice develop a chronic benign pulmonary-restricted infection, whereas B10.A mice present a chronic progressive disseminated disease. A/Sn animals were able to restrict fungal infection to the lungs despite the increased fungal load at the beginning of the infection. This behavior was associated with low mortality rates, the presence of adequate and persistent delayed-type hypersensitivity reactions, oxidative burst by bronchoalveolar cells, and production of high levels of specific antibodies in which immunoglobulin G2a (IgG2a) and IgG3 isotype titers were significantly higher than those observed in the susceptible mice. In contrast, B10.A animals showed a constant pulmonary fungal load and dissemination to the liver and spleen. This infection pattern resulted in high mortality rates, discrete delayed-type hypersensitivity reactivity, poorly activated or nonactivated bronchoalveolar cells, and production of specific IgG2b isotype titers significantly higher than those observed in the resistant mice at week 4 of infection. Thus, A/Sn and B10.A mice maintain the same resistance patterns as those observed previously with the intraperitoneal route of infection. Furthermore, the obtained results suggest that resistance to paracoccidioidomycosis is associated with T-cell, macrophage, and B-cell activities that are known to be mediated by gamma interferon.

Inhibitory effect of deferoxamine or macrophage activation on transformation of Paracoccidioides brasiliensis conidia ingested by macrophages: reversal by holotransferrin.

Conidia of P. brasiliensis ingested by murine macrophages at 37 degrees C showed enhanced transformation to yeast cells and further intracellular growth compared with conidia in culture medium alone. Treatment of macrophages with the iron chelator deferoxamine inhibited the intracellular conidium-to-yeast transformation. Cytokine-activated macrophages could also exert this inhibitory effect. Holotransferrin reversed the inhibitory effect of either deferoxamine or activated macrophages on intracellular conidium-to-yeast transformation. These results indicate that iron restriction is one of the mechanisms by which activated macrophages control the intracellular transformation of ingested conidia and growth of yeast cells.

Fate of conidia of Paracoccidioides brasiliensis after ingestion by resident macrophages or cytokine-treated macrophages.

Conidia ingested by resident macrophages had an enhanced percentage of transformation to yeast cells compared with those in culture medium without macrophages. The yeast cells subsequently grew intracellularly by budding. Macrophages treated with cytokines from antigen-stimulated spleen cells from immunized mice significantly inhibited transformation of ingested conidia.

Porencephalic cyst: a complication of fetal intravascular transfusion.

A case of unilateral porencephalic cyst as a result of intravascular intrauterine transfusion is reported. Although other factors may have contributed, fetal bradycardia and relative hyperviscosity as a result of increased fetal hematocrit value were considered to be related to this event. Because some authors recommend direct intravascular transfusion to supraphysiologic hematocrits to prolong the interval between procedures, we would caution the use of this approach on the basis of theoretic considerations and the occurrence of this complication.

Itraconazole in the treatment of paracoccidioidomycosis: a preliminary report.

The preliminary results of itraconazole therapy in 16 patients with active paracoccidioidomycosis were evaluated. The course of therapy--itraconazole administration for six months at a dose of 100 mg per day--was completed in 13 cases. This new triazole appeared as effective as ketoconazole in reducing the symptoms and arresting the progression of the mycosis. The scoring system employed to evaluate the effect of the drug showed that the condition of no patient worsened or remained the same during therapy. On the contrary, 11 (84.6%) of the 13 patients experienced major improvement and the other two (15.4%), minor improvement. No adverse reactions were reported by the patients, and there were no toxic effects on bone marrow or liver. Although experience with itraconazole is still limited, results to date indicate that this new drug is safe and effective for the treatment of paracoccidioidomycosis. Further trials with shorter periods of therapy seem warranted.

An evaluation of the enzyme-linked immunoabsorbent assay (ELISA) for quantitation of antibodies to Paracoccidioides brasiliensis.

The ELISA procedure was adapted for quantitation of antibodies against Paracoccidioides brasiliensis. Using a yeast cytoplasmic antigen and sera from patients with proven paracoccidioidomycosis, we found that 66% of sera reacted at titers greater than or equal to 1:128. Titers of this magnitude were obtained only for 4-5% of sera from healthy blood donors, tuberculosis patients and patients with other systemic mycoses. The exception was sera from patients with histoplasmosis (36% had titers greater than or equal to 1:128). Follow-up of 10 paracoccidioidomycosis patients during the course of therapy indicated a gradual decrease in antibody titers. Because of the technical advantages of the ELISA procedure in comparison with the standard complement fixation test, the ELISA test has potential utility for the quantitative determination of antibodies in patients with paracoccidioidomycosis.

A yeast-derived antigen from Paracoccidioides brasiliensis useful for serologic testing.

Antigens prepared from P. brasiliensis yeast cells subjected to ultrasonic treatment proved reliable in the serological diagnosis of paracoccidioidomycosis. Detection of antibodies was possible in over 90% from paracoccidioidomycosis patients in tests with agar gel immunodiffusion and counterimmunoelectrophoresis. Specificity was high and only histoplasmosis sera produced cross reactions, albeit at a lower frequency (10%). The new antigens compared favorably to the standard yeast culture filtrate antigen used in the past and they have the advantage of being reproducible. Proper control of proteolysis is required if activity is to be preserved.

Estrogens inhibit mycelium-to-yeast transformation in the fungus Paracoccidioides brasiliensis: implications for resistance of females to paracoccidioidomycosis.

Evidence that disease due to the thermally dimorphic fungus Paracoccidioides brasiliensis occurs post-puberty predominantly in males led us to hypothesize that hormonal factors critically affect its pathogenesis. We show here that estrogens inhibit mycelial- to yeast-form transformation of P. brasiliensis in vitro. Transformation of three isolates was inhibited to 71, 33, and 19% of the control values in the presence of 10(-10), 10(-8), and 10(-6) M 17 beta-estradiol, respectively. The synthetic estrogen diethylstilbestrol was active but less potent than estradiol, whereas testosterone, 17 alpha-estradiol, tamoxifen, and corticosterone were inactive. This function was specifically inhibited, since yeast-to-mycelium transformation, yeast growth, and yeast reproduction by budding were unaffected by 17 beta-estradiol. Of note is the fact that mycelium-to-yeast transformation occurs as the first step in vivo in the establishment of infection. The cytosol of the three isolates studied possesses a steroid-binding protein which has high affinity for 17 beta-estradiol. We believe that this binding protein represents a P. brasiliensis hormone receptor which can also recognize mammalian estrogens. We hypothesize that the ability of estrogen to decrease or delay mycelium-to-yeast transformation at the initial site of infection contributes to or is responsible for the marked resistance of females, and that the binder described is the molecular site of action.