Studies on plating efficiency and estimation of viability of suspensions of Paracoccidioides brasiliensis yeast cells

Purpureocillium lilacinum an emergent pathogen: antifungal susceptibility of environmental and clinical strains

Purpureocillium lilacinum is a filamentous and hyaline fungus cosmopolitan, saprophytic, largely used in the biological control of plant-parasitic nematodes and insects, also considered an emerging and opportunistic human pathogen. The standard treatment for hyalohyphomycosis caused by P. lilacinum is not yet defined, since this fungus is resistant to different antifungals, in vitro and in vivo. The aim of this study was to evaluate and compare in vitro antifungal activity against environmental and clinical P. lilacinum isolates and our results demonstrated that these isolates can be resistant to newer generation triazoles, such as voriconazole, and to caspofungin, a drug of the echinocandin class. In summary, we highlight the importance of knowing the different susceptibility profiles of P. lilacinum isolates, and besides that, the emergence of uncommon human and animal opportunistic fungi, such P. lilacinum, especially during COVID-19, highlight the need for antifungal susceptibility testing of isolates since empirical therapy with different treatment schedules failed in great number of patients.

Clinical and Anatomopathological Evaluation of BALB/c Murine Models Infected with Isolates of Seven Pathogenic Sporothrix Species

Background: Sporotrichosis is a subcutaneous mycosis with worldwide distribution and caused by seven pathogenic species of Sporothrix genus: S. schenckii sensu stricto, S. brasiliensis, S. globosa and S. luriei (clinical clade), and the species S. mexicana, S. pallida and S. chilensis (environmental clade). Isolates of the same species of Sporothrix may have different pathogenicities; however, few isolates of this fungus have been studied. Thus, the aim of this work was to analyze the clinical and anatomopathological changes in immunocompetent and immunosuppressed BALB/c mice infected with clinical and environmental isolates of seven different species of Sporothrix, from both clades. One human clinical isolate of S. schenckii sensu stricto, S. brasiliensis, S. globosa, S. luriei, S. mexicana and S. chilensis species and one environmental isolate of S. pallida were inoculated subcutaneously in immunocompetent mice and the same isolates of S. brasiliensis and S.schenckii sensu stricto were inoculated in immunossupressed mice. Clinical manifestations as external lesions, apathy, and alopecia were observed. At 21, 35, and 49 days after fungal inoculation, four mice from each group were weighed, euthanized and necropsied for evaluation of splenic index, recovery of fungal cells, macroscopic and histopathological analysis of livers, lungs, kidneys, and hearts. The survival assessment was observed for 50 days following inoculation. Our results demonstrated that, clinical S. schenckii isolate, followed by clinical S. mexicana, and environmental S. pallida isolates, the last two, species grouped in the environmental clade, were capable of inducing greater anatomopathological changes in mice, which was reflected in the severity of the clinical signs of these animals. Thus, we reinforce the hypothesis that the pathogenicity of Sporothrix is not only related to the species of this fungus, but also shows variation between different isolates of the same species.

Brazilian Red Propolis shows antifungal and immunomodulatory activities against Paracoccidioides brasiliensis

ETHNOPHARMACOLOGICAL RELEVANCE

Paracoccidioidomycosis (PCM) is a systemic mycosis with high prevalence in South America and especially in Brazil with severe clinical consequences that need broadened therapeutic options. Propolis is a natural resin from bees used in folk medicine for centuries with the first report in the ancient history of Egypt by Eberly papyrus, in Middle-Ages used to wash the newborn's umbilical cord and World War II as antiseptic or antibiotics. Nowadays it is a natural product worldwide consumed as food and traditionally used for oral and systemic diseases as an anti-inflammatory, antimicrobial, antifungal, and other diseases. Brazilian red propolis (BRP) is a new type of propolis with a distinguished chemical profile and biological activities from propolis (green) with pharmacological properties such as antimicrobial, anti-inflammatory, antioxidant, and others.

AIM OF STUDY

Thus, the main purpose of this study was to investigate the direct in vitro and ex vivo effect of BRP on Paracoccidioides brasiliensis.

MATERIAL AND METHODS

Antifungal activity of different concentrations of BRP on a virulent P. brasiliensis isolate (Pb18) was evaluated using the microdilution technique. Also, mice splenic cells co-cultured with Pb18 were treated with BRP at different times and concentrations (only Pb18 = negative control). Mice were inoculated with Pb18 and treated with different concentrations of BRP (50-500 mg/mL) in a subcutaneous air pouch. In this later experimental model, macroscopic characteristics of the air pouch were evaluated, and cellular exudate was collected and analyzed for cellular composition, mitochondrial activity, total protein reactive oxygen specimens (ROS), and nitric oxide production, as well as the number of viable fungal cells.

RESULTS

The in vitro experiments showed remarkable direct antifungal activity of BRP, mainly with the highest concentration employed (500 mg/mL), reducing the number of viable cells to 10% of the original inoculum after 72 h incubation. The splenocytes co-cultivation assays showed that BRP had no cytotoxic effect on these cells, on the contrary, exerted a stimulatory effect. This stimulation was also observed on the PMNs at the air pouch, as verified by production of ROS and total proteins and mitochondrial activity. This activation resulted in enhanced fungicidal activity, mainly with the 500 mg/mL concentration of BRP. An anti-inflammatory effect was also detected, as verified by the smaller volume of the BRP-treated air pouch as well as by an earlier shift from neutrophils to mononuclear cells present in the infection site.

CONCLUSION

Our results strongly suggest, for the first time in the literature, that Brazilian Red propolis has four protective mechanisms in experimental paracoccidioidomycosis: activating neutrophils, exerting a direct antifungal effect, preventing fungal dissemination, and controlling excessive inflammation process.

Skin Immune Response of Immunocompetent and Immunosuppressed C57BL/6 Mice After Experimental Subcutaneous Infection Caused by Purpureocillium lilacinum

Hyalohyphomycosis is a fungal infection characterized by the presence of a hyaline mycelium in the host. It is caused by several agents, such as Purpureocillium lilacinum. Our study aimed to evaluate some cell subsets and inflammatory markers involved in the in situ immune response to subcutaneous hyalohyphomycosis by P. lilacinum in C57BL/6 murine models. The fungal isolate was inoculated in mice randomly distributed in immunocompetent/infected (CI) and immunosuppressed/infected (SI) groups. Mice were evaluated on days 1, 3, 5, and 7 after inoculation. Histopathological studies showed several lesions in the site of infection as well as the formation of multifocal and mixed inflammatory infiltrates, which differed between the CI and SI groups. This analysis also revealed conidia and hypha-like structures in subcutaneous tissues of mice of both groups. The immunohistochemical analysis showed lower percentages of macrophages and neutrophils in the SI group compared to those in the CI group. Moreover, the intensity of interleukin (IL)-1β and nitric oxide synthase 2 production by cells of immunosuppressed mice was discreet, compared to immunocompetent mice that ranged from moderate to intense over time. The quantitative interference of dexamethasone in the response to the fungus was also demonstrated. We concluded that our results can be useful not only to broaden the knowledge on P. lilacinum but also, based on this host-parasite relationship, to contribute to the understanding of the mechanisms of infection.

Ethanol modulates the effector functions of human monocyte-derived macrophages in response to Paracoccidioides brasiliensis yeast cells

We aimed to investigate the effects of ethanol and its metabolites (β-hydroxybutyrate and sodium acetate) in the effector functions of macrophages in response to Paracoccidioides brasiliensis yeast cells and to determine their influence in the development of the adaptive response. Purified peripheral blood monocytes were differentiated into macrophages and were treated with ethanol, β-hydroxybutyrate, and sodium acetate, and stimulated with P. brasiliensis yeast cells and evaluated for their phenotypic characteristics, functional activity, and capability to induce T cells activation/differentiation. We found that the ethanol treatment diminished the expression of HLA-AB, HLA-DR, CD80, and CD86, modulating the expression of dectin-1, as well as Syk phosphorylation. The ethanol treatment increased the phagocytic activity, expression of CD206, and IL-10 production; however, reduced ROS production, fungicidal activity, caspase-1 cleavage, and IL-1β and IL-6 production. Our data also showed that the presence of ethanol reduced the differentiation of Th1 and Th17 cells and increased the frequency of Th2 cells. Our results indicated that ethanol exposure could suppress effector function of macrophages, possibly leading to the polarization of M2 macrophages. The ethanol modulates the expression of costimulatory and antigen-presentation molecules and interferes with the NLRP3 inflammasome. Altogether, these alterations affect the development of the adaptive response, decreasing the frequency of IL-17, IL-22, and IFN- γ producing cells, and increasing the frequency of IL-4 producing cells. Therefore, exposure to ethanol can impair the capability of macrophages to exert their effector functions and activate the acquired response related to resistance to P. brasiliensis infection.

Transcriptional Remodeling Patterns in Murine Dendritic Cells Infected with Paracoccidioides brasiliensis: More Is Not Necessarily Better

Most people infected with the fungus Paracoccidioides spp. do not get sick, but approximately 5% develop paracoccidioidomycosis. Understanding how host immunity determinants influence disease development could lead to novel preventative or therapeutic strategies; hence, we used two mouse strains that are resistant (A/J) or susceptible (B10.A) to P. brasiliensis to study how dendritic cells (DCs) respond to the infection. RNA sequencing analysis showed that the susceptible strain DCs remodeled their transcriptomes much more intensely than those from the resistant strain, agreeing with a previous model of more intense innate immunity response in the susceptible strain. Contrastingly, these cells also repress genes/processes involved in antigen processing and presentation, such as lysosomal activity and autophagy. After the interaction with P. brasiliensis, both DCs and macrophages from the susceptible mouse reduced the autophagy marker LC3-II recruitment to the fungal phagosome compared to the resistant strain cells, confirming this pathway’s repression. These results suggest that impairment in antigen processing and presentation processes might be partially responsible for the inefficient activation of the adaptive immune response in this model.

Tregs in the immune response of BALB/c mice experimentally infected with species of the Sporothrix genus

Background: Sporotrichosis occurs through contact with contaminated soil and plant. However, the incidence of sporotrichosis as a zoonotic epidemic has increased, particularly in Rio de Janeiro. Aim: In this work, we decided to evaluate some T-cell phenotypes involved in the immune response. Materials & methods: We used flow cytometry to quantify TCD4⁺ and TCD8⁺ and Treg from immunocompetent and immunosuppressed mice infected with Sporothrix species with different levels of virulence and pathogenicity. Results: It was demonstrated the predominance of TCD4⁺ over the TCD8⁺ cells in both groups, inoculated with all the species, and percentages of Treg observed in infected immunocompetent mice. Conclusion: This regulatory phenotype can be associated with a protective immunity in the initial periods of infection.

A case of sporotrichosis caused by different Sporothrix brasiliensis strains: mycological, molecular, and virulence analyses

BACKGROUND

Sporotrichosis is a subcutaneous mycosis caused by dimorphic pathogenic fungi belonging to the Sporothrix genus. Pathogenic Sporothrix species typically produce melanin, which is known to be a virulence factor.

OBJECTIVES

The aim of this study was to perform phenotypic, genotypic, and virulence analyses of two distinct Sporothrix brasiliensis strains isolated from the same lesion on a patient from Rio de Janeiro.

METHODS AND FINDINGS

Genotypic analyses by partial sequencing of the calmodulin, β-tubulin, and chitin synthase genes, as well as polymerase chain reaction (PCR)-fingerprinting by T3B, M13, and GACA, showed that the isolates were very similar but not identical. Both isolates had similar phenotypic characteristics and effectively produced melanin in their yeast forms, accounting for their ability of causing disease in a murine sporotrichosis model. Remarkably, isolate B was albino in its environmental form but caused more severe disease than the pigmented A isolate.

CONCLUSIONS

These findings indicate that the patient was infected by two genetically and biologically distinct S. brasiliensis that vary in their production of melanin in their environmental forms. The results underscore the importance of characterizing phenotypically different isolates found in the same clinical specimen or patient.

Broth Microdilution In Vitro Screening: An Easy and Fast Method to Detect New Antifungal Compounds

Fungal infections have become an important medical condition in the last decades, but the number of available antifungal drugs is limited. In this scenario, the search for new antifungal drugs is necessary. The protocol reported here details a method to screen peptides for their antifungal properties. It is based on the broth microdilution susceptibility test from the Clinical and Laboratory Standards Institute (CLSI) M27-A3 guidelines with modifications to suit the research of antimicrobial peptides as potential new antifungals. This protocol describes a functional assay to evaluate the activity of antifungal compounds and may be easily modified to suit any particular class of molecules under investigation. Since the assays are performed in 96-well plates using small volumes, a large-scale screening can be completed in a short amount of time, especially if carried out in an automation setting. This procedure illustrates how a standardized and adjustable clinical protocol can help the bench-work pursuit of new molecules to improve the therapy of fungal diseases.

Experimental Hyalohyphomycosis by Purpureocillium lilacinum: Outcome of the Infection in C57BL/6 Murine Models

Purpureocillium lilacinum is a filamentous, hyaline fungus considered an emerging pathogen in humans. The aim of our study was to evaluate the outcome of hyalohyphomycosis in C57BL/6 murine models inoculated with two clinical P. lilacinum isolates (S1 and S2). Each isolate was inoculated in mice randomly distributed in immunocompetent (CPT) and immunosuppressed (SPS) groups. Mice were evaluated at day 7, 21, and 45 after inoculation for histopathological analysis, recovery of fungal cells, and immunological studies. Histological analysis showed scarce conidia-like structures in lung tissue from CPT mice and a lot of fungal cells in SPS mice inoculated with S2 compared to mice inoculated with S1. The maximum recovery of fungal cells was seen in CPT mice inoculated with both isolates at day 7, but with mean significantly higher in those inoculated with S2 isolate. Phenotypical characterization of T cells showed TCD8⁺ lymphocytes predominance over TCD4⁺ in immunosuppressed mice infected and control groups. We also observed higher percentages of the central and effector memory/effector phenotype in CPT mice infected with S2 strain, especially in TCD8⁺ in the initial period of infection. Regulatory T cells showed higher percentages in immunosuppressed, predominantly after the acute phase. Our results showed that the P. lilacinum is a fungus capable to cause damages in competent and immunosuppressed experimental hosts. Furthermore, S2 isolate seems to cause more damage to the experimental host and it was possible to identify different cellular subsets involved in the mice immune response.

The Effects of Paracoccidioides brasiliensis Infection on GM-CSF- and M-CSF-Induced Mouse Bone Marrow-Derived Macrophage from Resistant and Susceptible Mice Strains

Considering the importance of macrophages as the first line of defense against fungal infection and the different roles played by the two M1- and M2-like polarized macrophages, we decided to evaluate the effects of Paracoccidioides brasiliensis infection on GM-CSF- and M-CSF-induced bone marrow-derived macrophages (BMM) from the A/J and B10.A mouse strains, an established model of resistance/susceptibility to PCM, respectively. Upon differentiation, the generated GM- or M-BMMs were characterized by morphological analyses, gene expression profiles, and cytokines production. Our main results demonstrate that GM-BMMs derived from A/J and B.10 produced high levels of pro- and anti-inflammatory cytokines that may contribute to generate an unbalanced early immune response. In accordance with the literature, the B10.A susceptible mice lineage has an innate tendency to polarize into M1-like phenotype, whereas the opposite phenotype occurs in A/J resistance mice. In this context, our data support that susceptibility and resistance are strongly correlated with M1 and M2 polarization, respectively.

Use of image cytometry for quantification of pathogenic fungi in association with host cells

Studies of the cellular pathogenesis mechanisms of pathogenic yeasts such as Candida albicans, Histoplasma capsulatum, and Cryptococcus neoformans commonly employ infection of mammalian hosts or host cells (i.e. macrophages) followed by yeast quantification using colony forming unit analysis or flow cytometry. While colony forming unit enumeration has been the most commonly used method in the field, this technique has disadvantages and limitations, including slow growth of some fungal species on solid media and low and/or variable plating efficiencies, which is of particular concern when comparing growth of wild-type and mutant strains. Flow cytometry can provide rapid quantitative information regarding yeast viability, however, adoption of flow cytometric detection for pathogenic yeasts has been limited for a number of practical reasons including its high cost and biosafety considerations. Here, we demonstrate an image-based cytometric methodology using the Cellometer Vision (Nexcelom Bioscience, LLC) for the quantification of viable pathogenic yeasts in co-culture with macrophages. Our studies focus on detection of two human fungal pathogens: Histoplasma capsulatum and Candida albicans. H. capsulatum colonizes alveolar macrophages by replicating within the macrophage phagosome, and here, we quantitatively assess the growth of H. capsulatum yeasts in RAW 264.7 macrophages using acridine orange/propidium iodide staining in combination with image cytometry. Our method faithfully recapitulates growth trends as measured by traditional colony forming unit enumeration, but with significantly increased sensitivity. Additionally, we directly assess infection of live macrophages with a GFP-expressing strain of C. albicans. Our methodology offers a rapid, accurate, and economical means for detection and quantification of important human fungal pathogens in association with host cells.

Rapid quantification of pathogenic fungi by Cellometer image-based cytometry

The objective of this study was to develop an image-based cytometric methodology for the quantification of viable pathogenic yeasts, which can offer increased sensitivity and efficiency when compared to the traditional colony forming unit (CFU) assay. Live/dead yeast quantification by flow cytometry has been previously demonstrated, however, adoption of flow cytometric detection of pathogenic yeasts has been limited for a number of practical reasons including its high cost and biosafety considerations. Our studies focus on detection of two human fungal pathogens: Histoplasma capsulatum and Candida albicans. H. capsulatum colonizes alveolar macrophages by replicating within the macrophage phagosome. Here, we quantitatively assess the growth of H. capsulatum yeasts within RAW 264.7 macrophages using acridine orange/propidium iodide staining in combination with Cellometer image-based cytometry; this method faithfully recapitulates growth trends as measured by traditional CFU enumeration, but with significantly increased sensitivity. Additionally, we directly assess infection of bone marrow-derived macrophages with a GFP-expressing strain of C. albicans. To demonstrate that image-based cytometry can be used as a tool to assess the susceptibility of fungi to antifungal drugs, we perform dose response experiments with the antifungal drugs amphotericin B and itraconazole and show that image-based cytometry allows rapid assessment of the kinetics of cytotoxicity induced by these antifungals. Our methodology offers a rapid, accurate, and economical means for detection and quantification of important human fungal pathogens, either alone or in association with host cells.

Characteristics of Paecilomyces lilacinus infection comparing immunocompetent with immunosuppressed murine model

The characteristics of Paecilomyces lilacinus infection were evaluated using two murine experimental models: immunocompetent and immunosuppressed. The evaluation criteria for characteristics of infection were clinical signs, weight loss, survival rates, histopathological alterations and the number of viable fungal cells re-isolated from different organs; and those for immunological status were in vitro lymphoproliferative response, cell surface phenotyping and IFN-γ production. Morphological evaluation showed that P. lilacinus isolates presented morphological characteristics consistent with those described in the literature. The immunocompetent mice could be infected by the fungi, but they did not develop the disease, unlike the immunosuppressed mice, which showed clinical signs of mycosis in an environment of suppressed cellular immune response. The hypothesis of latent infection reactivation in mice was not confirmed. The difference observed in the infection rate of the two fungi isolates points to an intrinsic variation between strains of P. lilacinus and led us to hypothesise that even in the presence of immunosuppressed environment, the fungus virulence can play a role in the pathogenesis of hyalohyphomycosis.

Excretion-secretion products and proteases from live Sporothrix schenckii yeast phase: immunological detection and cleavage of human IgG

Antigenic preparations from Sporothrix schenckii usually involve materials from mixed cultures of yeast and mycelia presenting cross-reactions with other deep mycoses. We have standardized pure yeast phase with high viability of the cells suitable to obtain specific excretion-secretion products without somatic contaminations. These excretion-secretion products were highly immunogenic and did not produce noticeable cross-reactions in either double immunodiffusion or Western blot. The antigenic preparation consists mainly of proteins with molecular weights between 40 and 70 kDa, some of them with proteolytic activity in mild acidic conditions. We also observed cathepsin-like activity at two days of culture and chymotrypsin-like activity at four days of culture consistent with the change in concentration of different secreted proteins. The proteases were able to cleave different subclasses of human IgG suggesting a sequential production of antigens and molecules that could interact and interfere with the immune response of the host.

Antimicrobial effect of farnesol, a Candida albicans quorum sensing molecule, on Paracoccidioides brasiliensis growth and morphogenesis

Background

Farnesol is a sesquiterpene alcohol produced by many organisms, and also found in several essential oils. Its role as a quorum sensing molecule and as a virulence factor of Candida albicans has been well described. Studies revealed that farnesol affect the growth of a number of bacteria and fungi, pointing to a potential role as an antimicrobial agent.

Methods

Growth assays of Paracoccidioides brasiliensis cells incubated in the presence of different concentrations of farnesol were performed by measuring the optical density of the cultures. The viability of fungal cells was determined by MTT assay and by counting the colony forming units, after each farnesol treatment. The effects of farnesol on P. brasiliensis dimorphism were also evaluated by optical microscopy. The ultrastructural morphology of farnesol-treated P. brasiliensis yeast cells was evaluated by transmission and scanning electron microscopy.

Results

In this study, the effects of farnesol on Paracoccidioides brasiliensis growth and dimorphism were described. Concentrations of this isoprenoid ranging from 25 to 300 μM strongly inhibited P. brasiliensis growth. We have estimated that the MIC of farnesol for P. brasiliensis is 25 μM, while the MLC is around 30 μM. When employing levels which don't compromise cell viability (5 to 15 μM), it was shown that farnesol also affected the morphogenesis of this fungus. We observed about 60% of inhibition in hyphal development following P. brasiliensis yeast cells treatment with 15 μM of farnesol for 48 h. At these farnesol concentrations we also observed a significant hyphal shortening. Electron microscopy experiments showed that, despite of a remaining intact cell wall, P. brasiliensis cells treated with farnesol concentrations above 25 μM exhibited a fully cytoplasmic degeneration.

Conclusion

Our data indicate that farnesol acts as a potent antimicrobial agent against P. brasiliensis. The fungicide activity of farnesol against this pathogen is probably associated to cytoplasmic degeneration. In concentrations that do not affect fungal viability, farnesol retards the germ-tube formation of P. brasiliensis, suggesting that the morphogenesis of this fungal is controlled by environmental conditions.

Upregulation of glyoxylate cycle genes upon Paracoccidioides brasiliensis internalization by murine macrophages and in vitro nutritional stress condition

Paracoccidioides brasiliensis, the etiologic agent of paracoccidioidomycosis, is a facultative intracellular human pathogen that can persist within macrophage phagolysosomes, indicating that the fungus has evolved defense mechanisms in order to survive under nutritionally poor environments. The analysis of P. brasiliensis transcriptome revealed several virulence factor orthologs of other microorganisms, including the glyoxylate cycle genes. This cycle allows the utilization of two-carbon (C2) compounds as carbon source in gluconeogenesis. Semiquantitative RT-PCR analyses revealed that these genes were upregulated when P. brasiliensis was recovered from murine macrophages, without any additional in vitro growth. The induction of this cycle, in response to macrophage microenvironments, was shown to be coordinated with the upregulation of the gluconeogenic phosphoenolpyruvate carboxykinase gene. In addition, assays employing RNA extracted from P. brasiliensis grown in a medium with acetate instead of glucose also showed increased levels of glyoxylate cycle transcripts. Our main results suggest that P. brasiliensis uses the glyoxylate cycle as an important adaptive metabolic pathway.

Hygromycin B-resistance phenotype acquired in Paracoccidioides brasiliensis via plasmid DNA integration

Yeast cells of the human pathogenic fungus Paracoccidioides brasiliensis strain Pb01 were transformed to hygromycin B resistance using the plasmid pAN7.1. Transformation was achieved by electroporation, with intact or linearized plasmid DNA. The fungus was transformed using 200 mM manitol, 5 or 7 kV/cm field strength, 25 microF capacitance, 400 omega resistance, 5 microg plasmid DNA and 10(7) yeast cells in 400 microl, and selected in BHI medium overlaid with 30 microg/ml hygromycin B (hygB). Mitotic stability was assessed by growing transformants on non-selective BHI medium, followed by plating on hygromycin B (30 microg/ml). Transformants were analyzed by PCR and Southern blotting, confirming the hph gene integration into the transformants genome. A low level of stability of the integrated hph sequence in the transformant genomes was observed, probably because of the multinuclearity of P. brasiliensis yeast cells.

Viability of yeast form cells of Paracoccidioides brasiliensis after sonication

To perform in-vitro studies with Paracoccidioides brasiliensis yeast cells it is necessary to avoid the presence of clumps of cells while maintaining their integrity. Because of the multiple budding type of growth, the bud cells are always attached to the mother cell and the yeast cells keep growing, resulting in the formation of large clumps. In order to obtain free cells, the cultures are usually sonicated. The present study shows that sonication induces lesions in a significant number of cells, as evaluated by labelling of the cells with acridine orange and Janus green vital dyes. In some cases labelling was initially observed in only one cell of the clump; however, the other cells also became labelled after a few minutes. These observations were confirmed by scanning and transmission electron microscopy of treated cells. Colony forming units (c.f.u.) on BHI plates also confirmed the decrease in cell viability following sonication.

A morphological and cytochemical study of the interaction between Paracoccidiodes brasiliensis and neutrophils

Paracoccidioidomycosis is a systemic granulomatous disease caused by the dimorphic fungus Paracoccidioides brasiliensis. It is the most prevalent systemic mycosis of Latin America and 80% of the reported cases are from Brazil. Because of the great number of neutrophils found in the P. brasiliensis granuloma, studies have been done to evaluate the role of these cells during the development of the infection. Scanning and transmission electron microscopy of thin sections showed that the neutrophils ingest yeast cells through a typical phagocytic process with the formation of pseudopodes. The pseudopodes even disrupt the connection established between the mother and the bud cells. Neutrophils also associate to each other, forming a kind of extracellular vacuole where large yeast cells are encapsulated. Cytochemical studies showed that once P. brasiliensis attaches to the neutrophil surface, it triggers a respiratory burst with release of oxygen-derived products. Attachment also triggers neutrophils degranulation, with release of endogenous peroxidase localized in cytoplasmic granules. Together, these processes lead to killing of both ingested and extracellular P. brasiliensis.

Fungicidal activity of fluconazole against Candida albicans in a synthetic vagina-simulative medium

Fluconazole (FLZ) has emerged as a highly successful agent in the management of systemic infections of Candida. Cure rates for symptomatic candidiasis following single 150-mg FLZ dose therapy exceed 90%. In vitro, however, FLZ is fungistatic only in a narrow pH range and is not effective at vaginal pH, 4.2. This study evaluated the effect of FLZ on Candida albicans under in vitro conditions resembling the vaginal microenvironment, using vagina-simulative medium (VS). We found that FLZ was fungicidal for C. albicans in VS, but not in other media at the same pH, 4.2. In VS, FLZ was fungicidal at concentrations of >/=8 micro g/ml and reduced viability by greater than 99.9%. Analysis of the components of VS indicated that 17 mM acetic acid, a concentration achieved in the vagina, was responsible for the synergistic, fungicidal effect. This effect was not seen at neutral pH. Other substrates were not effective substitutes for acetic acid; however, short-chained carboxylic acids, glyoxylate and malonate, were effective. Most strains of C. albicans that were resistant to FLZ under standard conditions were killed by FLZ plus acetate. Other species of Candida were also killed, except C. krusei and C. glabrata. This study shows that FLZ has fungicidal activity for Candida species under in vitro conditions that mimic the vaginal microenvironment. This raises the possibility that FLZ may also have fungicidal effects during treatment of vaginal candidiasis. Elucidating the mechanism by which FLZ and acetate interact may disclose vulnerable pathways that could be exploited in drug development.

Paracoccidioides brasiliensis: virulence and an attempt to induce the dimorphic process with fetal calf serum

The virulence of Paracoccidioides brasiliensis strains and the induction of the dimorphic process of the fungus were investigated. The strains were kept under mineral oil for different periods of time, except for one that was successively subcultured on agar slants. Four strains with transitional morphology at room temperature were avirulent to experimental animals. Two strains with typical morphology at 36 degrees C, one of them preserved under mineral oil for 16 years and the other maintained by successive subcultures for 10 years, were virulent to mice. These strains caused macro- and microscopic lesions in various organs, with enlargement of the spleen and heart. An attempt to induce the dimorphic process with fetal calf serum (FCS) in P.brasiliensis strains with transitional morphology failed. FCS was probably unable to stimulate the synthesis of Y cell wall alpha-1,3-glucan. The results demonstrate that keeping strains under mineral oil for a long period of time may have altered the enzymatic activities of the proteinases and other virulence factors that participate in the transition process and in pathogenesis.

Regulation of serine-type exoproteinases by endogenous inhibitors present in exoantigens of the mycelial form of Paracoccidioides brasiliensis

We have partially characterized some biochemical properties of exoproteinases secreted into culture medium by the mycelial form of Paracoccidioides brasiliensis, a dimorphic fungus that causes human disease in Latin America. Proteinase activity was analyzed in solid- and liquid-phase systems using zymography and Azocoll, respectively. Minimal or no gelatinase activity was observed by zymography in the crude filtrates among proteins with a relative mobility greater than 200 kDa. When the crude filtrate was fractionated by isoelectric focusing or ion exchange chromatography, we observed striking activation of gelatinases, both those of high apparent molecular mass and alkaline isoelectric points (pI), as well as those of lower molecular mass and acidic pI. The apparent high molecular mass gelatinases, pI 10, showed optimal activity at pH 7.0. They were totally inhibited by phenylmethylsulfonylfluoride and partially inhibited by incubation with previously neutralized fractions of pI 5.4 and 6.1. The latter inhibition could be reversed by exposure to 10% isopropanol. These results provide evidence of regulatory mechanisms controlling proteinase activity in secreted proteins. The principal mechanism appears to be the formation of reversible complexes with endogenous inhibitors.

Alkaline phosphatase at the cell wall of the yeast phase of Paracoccidioides brasiliensis

The activity of alkaline phosphatase demonstrated by histochemical techniques was shown at the cell wall of the yeast form of Paracoccidioides brasiliensis at 3, 6, and 9 days of culture. The results showed a very active deposition at the cell wall as early as 9 days of culture of the fungus which made us think an inactive salt precipitate was also present.

A comparative study of four different staining methods for estimation of live yeast form cells of Paracoccidioides brasiliensis

A comparative study of four different staining methods for estimation of live yeast form cells of Paracoccidioides brasiliensis was carried out. The staining methods used were fluorescent staining, vital dye exclusion tests with erythrosin B and by Janus green and lactophenol cotton blue staining. Colony forming units (cfu) of the yeast form of eight P. brasiliensis isolates on brain heart infusion agar (BHIA) supplemented with 4% horse serum plus 5% P. brasiliensis cell extract (BHIA + HS + EXT) were examined for reliability of staining in determining the number of live fungal units in eight different isolates. Cfu on BHIA + HS + EXT plates showed an excellent plating efficiency over 96% in all isolates tested. The percentage of the live cells indicated by fluorescent staining (FL) or vital dye exclusion test with erythrosin B (EB) or Janus green (JG-1) was lower than that of cfu. By contrast, the percentage due to modified dye exclusion test with Janus green (JG-2) and that due to lactophenol cotton blue staining (LPCB) showed a close correration to that of cfu. Our results indicate that the modified dye exclusion test with Janus green and lactophenol cotton blue staining are useful for estimating cell viability of yeast form cells of P. brasiliensis.

Specific digestive deficiency of phagocytes in paracoccidioidomycosis. Its absence in peripheral blood neutrophils of members of the nuclear family of patients. An initial report

Paracoccidioidomycosis (PARA) affects only a minority of individuals, who have presumably been exposed to the causative fungus (Paracoccidioides brasiliensis). Neutrophils (PMNs) from patients with PARA show a significant and specific digestive deficiency phagocytosed P. brasiliensis in vitro. It is not known whether the defect is acquired after contact with the fungus, or precedes it. We studied the spouses and offspring of three patients with PARA. Individuals studied stayed in the same house as their husband or father. None of the relatives had evidence of PARA, and their PMNs showed no defect in their ability to digest or kill the fungus. Relatives showed no indication of sensitization against P. brasiliensis. These results are compatible with the view that effective contact with P. brasiliensis may occur only under restricted conditions and that the defect in digestive ability is an infrequent and specific occurrence.

Paracoccidioidomycosis: an update

This review summarizes knowledge on various aspects of paracoccidioidomycosis. Mycelial propagules, chlamydospores, and arthroconidia exhibit thermal dimorphism; arthroconidia are infectious in animals and, by electron microscopy, appear well provided for survival. The mycelial-to-yeast-phase transformation requires a strict control of glucan synthesis probably mediated by membrane enzymes. Hormonal influences on the transformation of the fungus (mycelium or conidium to yeast phase) have been demonstrated. Estrogen-binding proteins have been detected in the fungal cytosol, and during the transformation novel proteins are produced as a result of estradiol incorporation. Clinical forms have been better defined on the basis of better experimental models. Emphasis has been placed on the lungs as the portal of entry and on the existence of silent pulmonary infections. A specific Paracoccidioides brasiliensis antigen, the 43-kDa glycoprotein (Gp43), has been identified, characterized, and cloned. This has led to improved reproducibility and specificity of serologic tests. The depression of cell-mediated immune responses has been associated with severe disease in humans and in the experimental host. T-cell subsets in patients' tissues were characterized by means of monoclonal antibodies, and a reduced CD4/CD8 ratio was demonstrated. This has been related to alterations in lymphokine and tumor necrosis factor production, production of antigen-antibody complexes, etc. Amphotericin B has provided effective therapy. Azole derivatives have also improved prognosis and facilitated therapy. Itraconazole is presently the drug of choice, yet incapacitating sequelae (mainly pulmonary fibrosis) still constitute major problems.

An improved culture medium for detecting live yeast phase cells of Paracoccidioides brasiliensis

The plating efficiency of standard mycological media such as brain heart infusion (BHI) agar is poor for Paracoccidioides brasiliensis. We prepared a water-extract of yeast phase cells of P. brasiliensis and examined it for growth-enhancing activity for the fungus. The water-extract, when added to BHI agar to a concentration of 5%, improved the plating efficiency of the medium for the fungus to some extent, but the degree of improvement was considerably varied among P. brasiliensis isolates. By contrast, when the water-extract was added in combination with horse serum (4%), the plating efficiency was highly improved (to 94-99%) for all the P. brasiliensis isolates employed. The growth-enhancing factor(s) in the water-extract was heat-stable and heating at 120 degrees C for 15 min had little, if any, effect on growth-enhancing activity.

Relationship between digestive and killing abilities of neutrophils against Paracoccidioides brasiliensis

Peripheral blood neutrophils (PMN) from patients with paracoccidioidomycosis killed and digested Paracoccidioides brasiliensis much less than did PMN from normal individuals or from patients with other diseases. However, deficiency in killing ability was less specific than digestive deficiency and correlated poorly with it. We conclude that the capacities of PMN to digest and kill P. brasiliensis are not intimately related phenomena, and that in paracoccidioidomycosis the key deficiency of neutrophil function is that of digestion of P. brasiliensis.

The source of the growth-promoting factor(s) affects the plating efficiency of Paracoccidioides brasiliensis

We studied the influence of the growth factor (GF) source, concentration and production time on the plating efficiency of Paracoccidioides brasiliensis yeast cells. The highest plating efficiencies were achieved when the GF was derived from a fast growing P. brasiliensis isolate which was not homologous to the plated samples.

Adenosine triphosphatase in yeast phase Paracoccidioides brasiliensis

We have previously detected various enzymatic activities in P. brasiliensis. In the present study we have examined Adenosine Triphosphatase (ATPase) activity in yeast phase cultures of P. brasiliensis of increasing age. We employed Wachstein and Meisel's method and electron microscopy and found specific electron-dense deposits indicating ATPase activity to be present in the cytoplasm around vacuoles. Their distribution varied according to age. Deposits decreased or became absent in old cultures. We assume that in P. brasiliensis, ATPase is involved (as in other systems) with transport of Na+ and K+.

Influence of serum on in vitro digestion of Paracoccidioides brasiliensis by neutrophils

Serum from patients with paracoccidioidomycosis (PARA) did not block digestive abilities of neutrophils (PMNs) from healthy individuals against Paracoccidioides brasiliensis. Conversely, serum from healthy donors did not enhance digestive capacities of PMNs from patients with PARA vis á vis the causative organism. We conclude that the specific digestive defect present in PMNs from patients with PARA is not mediated by serum factors.

Functions of polymorphonuclear leukocytes and individuality of Jorge Lobo's disease: absence of the specific leukocyte digestive defect against Paracoccidioides brasiliensis

Peripheral blood neutrophils (PMNs) from a patient with Jorge Lobo's disease (JLD) digested well phagocytosed Paracoccidioides brasiliensis. We found no circulating antibodies against P. brasiliensis in the patient's serum. Such neutrophils showed myeloperoxidase activity and also digested normally phagocytosed Candida albicans. We had previously reported the presence of a specific digestive deficiency of PMNs from patients with paracoccidioidomycosis (PARA) vis à vis P. brasiliensis. Current findings provide new information about leukocyte functions in JLD and bolster the view that JLD, PARA and their respective causative microorganisms are distinct.

Digestion of killed Paracoccidioides brasiliensis by neutrophils

We previously described an in vitro assay showing that neutrophils (PMNs) from patients with paracoccidioidomycosis (PARA) have a specific digestive deficiency against suspensions of live Paracoccidioides brasiliensis. We now report that this defect is equally detectable against autoclaved, but not Amphotericin B-killed P. brasiliensis. The use of autoclaved suspensions facilitates the use of our in vitro assay. It might allow the development of an in vitro intradermal test for digestion of fungi. Differential digestive ability of phagocytes against live (or autoclaved) and Amphotericin-B killed fungi is of conceptual interest. It may be relevant in understanding therapeutic effect of Amphotericin B.

Nutritional studies on Paracoccidioides brasiliensis: the role of organic sulfur in dimorphism

The nutritional requirements of the mycelial and yeast-like phases of the dimorphic fungus Paracoccidioides brasiliensis, a human pathogen, were investigated. For all nine isolates tested, mycelial cells were prototrophic, whereas yeast-like cells required a sulfur-containing amino acid for growth. Moreover, changing the source of nitrogen greatly affected the morphology of the yeast-like cells.

T-cell dysfunction and hyperimmunoglobulinemia E in paracoccidioidomycosis

Various aspects of T and B cell mediated immunity were investigated in 20 well documented cases of active (10) or inactive (10) paracoccidioidomycosis (Pcm), as well as in 8 healthy individuals living in the endemic area of the disease. The results confirm previous reports that active Pcm produces diverse grades of depression of T cell mediated immunity. Such T cell dysfunction is not associated with a reduction in the number of peripheral E rosette-forming cells, and the immunodepression is reversed by chemotherapy. Sera from Pcm (active or inactive) patients have significantly increased levels of total IgE, but the actual proportion of IgE antibodies against P. brasiliensis was very low (0.4-0.6%). The highest levels of total IgE were found in active patients with disease-related immune depression, suggesting that T cell dysfunction might contribute to the excessive IgE production.

Comparison of various techniques for determining viability of Paracoccidioides brasiliensis yeast-form cells

The viability of Paracoccidioides brasiliensis yeast-form cells was determined by colony-forming units, direct fluorescent staining, and production of germ tubes in slide culture. The first procedure was unreliable and time consuming; the latter two showed better correlation with hemacytometer total cell counts and required significantly less time.