The pathobiology of Paracoccidioides brasiliensis

Recombinant 60-kDa heat shock protein from Paracoccidioides brasiliensis induces the death of mouse lymphocytes in a mechanism dependent on Toll-like receptor 4 and tumor necrosis factor

Paracoccidioides fungi are thermodimorphic microorganisms that cause paracoccidioidomycosis (PCM), an autochthonous disease from Latin America, with most cases in Brazil. Humans become infected by inhaling conidia or mycelial fragments that transform into yeast at body temperature. These fungi cause chronic-granulomatous inflammation, which may promote fibrosis and parenchyma destruction in the lungs. In response to stress imposed by the host, fungi Paracoccidioides spp. increase the expression of heat shock proteins (HSP), which protect them by sustaining cellular proteostasis. Our group has studied the role of HSP60 in PCM, and previous data show that the recombinant HSP60 (rHSP60) has a deleterious effect when used in a single dose as therapy for experimental PCM. Here, we investigated the mechanism by which rHSP60 could worsen the disease. We found that rHSP60 caused the viability loss of splenic or lymph node cells from both immunized and non-immunized mice, including in splenic T lymphocytes under polyclonal stimulation with concanavalin A, probably by undergoing apoptosis. Among analyzed splenic cells, lymphocytes were indeed the main cells to die. When we investigated the death mechanisms, remarkably, we found that there was no viability loss in rHSP60-stimulated splenic cells from mice deficient in Toll-like receptor 4, TRIF adapter protein, and TNF receptor 1(TNFR1), as well as rHSP60-stimulated WT cells incubated with anti-TNF antibody. Besides, caspase-8 inhibitor IETD-CHO blocked the rHSP60 effect on splenic cells, suggesting that rHSP60 induces the extrinsic apoptosis pathway dependent on signaling via TLR4/TRIF and TNFR1.

The Mechanism of Transcription Factor Swi6 in Regulating Growth and Pathogenicity of Ceratocystis fimbriata: Insights from Non-Targeted Metabolomics

Ceratocystis fimbriata (C. fimbriata) is a notorious pathogenic fungus that causes sweet potato black rot disease. The APSES transcription factor Swi6 in fungi is located downstream of the cell wall integrity (CWI)-mitogen-activated protein kinase (MAPK) signaling pathway and has been identified to be involved in cell wall integrity and virulence in several filamentous pathogenic fungi. However, the specific mechanisms by which Swi6 regulates the growth and pathogenicity of plant pathogenic fungi remain elusive. In this study, the SWI6 deletion mutants and complemented strains of C. fimbriata were generated. Deletion of Swi6 in C. fimbriata resulted in aberrant growth patterns. Pathogenicity assays on sweet potato storage roots revealed a significant decrease in virulence in the mutant. Non-targeted metabolomic analysis using LC-MS identified a total of 692 potential differentially accumulated metabolites (PDAMs) in the ∆Cfswi6 mutant compared to the wild type, and the results of KEGG enrichment analysis demonstrated significant enrichment of PDAMs within various metabolic pathways, including amino acid metabolism, lipid metabolism, nucleotide metabolism, GPI-anchored protein synthesis, and ABC transporter metabolism. These metabolic pathways were believed to play a crucial role in mediating the growth and pathogenicity of C. fimbriata through the regulation of CWI. Firstly, the deletion of the SWI6 gene led to abnormal amino acid and lipid metabolism, potentially exacerbating energy storage imbalance. Secondly, significant enrichment of metabolites related to GPI-anchored protein biosynthesis implied compromised cell wall integrity. Lastly, disruption of ABC transport protein metabolism may hinder intracellular transmembrane transport. Importantly, this study represents the first investigation into the potential regulatory mechanisms of SWI6 in plant filamentous pathogenic fungi from a metabolic perspective. The findings provide novel insights into the role of SWI6 in the growth and virulence of C. fimbriata, highlighting its potential as a target for controlling this pathogen.

Polypeptides Targeting Paracoccidioides brasiliensis Drk1

Considering the toxicity of conventional therapeutic approaches and the importance of precise mechanistic targets, it is important to explore signaling pathways implicated in fungal pathobiology. Moreover, treatment of paracoccidioidomycosis, a systemic mycosis caused by a dimorphic fungus, requires prolonged therapeutic regimens. Among the numerous factors underpinning the establishment of Paracoccidioides spp. infection, the capacity to transition from the mycelial to the yeast form is of pivotal importance. The Drk1 protein of Paracoccidioides brasiliensis likely plays a decisive role in this morphological shift and subsequent virulence. We identified peptides with affinity for the PbDrk1 protein using the phage-display method and assessed the effects of these peptides on P. brasiliensis. The peptides were found to inhibit the phase transition of P. brasiliensis. Furthermore, a substantial proportion of these peptides prevented adhesion to pneumocytes. Although these peptides may not possess inherent antifungal properties, they can augment the effects of certain antifungal agents. Notably, the cell wall architecture of P. brasiliensis appears to be modulated by peptide intervention, resulting in a reduced abundance of glycosylated proteins and lipids. These peptides were also evaluated for their efficacy in a Galleria mellonella model and shown to contribute to enhanced larval survival rates. The role of PbDrk1, which is notably absent in mammals, should be further investigated to improve the understanding of its functional role in P. brasiliensis, which may be helpful for designing novel therapeutic modalities.

Fungal mechanisms of intracellular survival: what can we learn from bacterial pathogens?

Fungal infections represent a major, albeit neglected, public health threat with serious medical and economic burdens globally. With unacceptably high mortality rates, invasive fungal pathogens are responsible for millions of deaths each year, with a steadily increasing incidence primarily in immunocompromised individuals. The poor therapeutic options and rise of antifungal drug resistance pose further challenges in controlling these infections. These fungal pathogens have adapted to survive within mammalian hosts and can establish intracellular niches to promote survival within host immune cells. To do that, they have developed diverse methods to circumvent the innate immune system attack. This includes strategies such as altering their morphology, counteracting macrophage antimicrobial action, and metabolic adaptation. This is reminiscent of how bacterial pathogens have adapted to survive within host cells and cause disease. However, relative to the great deal of information available concerning intracellular bacterial pathogenesis, less is known about the mechanisms fungal pathogens employ. Therefore, here we review our current knowledge and recent advances in our understanding of how fungi can evade and persist within host immune cells. This review will focus on the major fungal pathogens, including Cryptococcus neoformans, Candida albicans, and Aspergillus fumigatus, among others. As we discover and understand the strategies used by these fungi, similarities with their bacterial counterparts are becoming apparent, hence we can use the abundant information from bacteria to guide our studies in fungi. By understanding these strategies, new lines of research will open that can improve the treatments of these devastating fungal diseases.

"Star of Bethlehem sign" in the analysis of the evolution of brain lesions during and after treatment for neuroparacoccidioidomycosis

Objective

To describe the clinical and radiological evolution of lesions during and after treatment in patients diagnosed with neuroparacoccidioidomycosis (NPCM).

Materials and Methods

This was a retrospective study of the medical records, computed tomography scans, and magnetic resonance imaging (MRI) scans of patients with NPCM treated between September 2013 and January 2022.

Results

Of 36 cases of NPCM, eight were included in the study. One patient presented only with pachymeningeal and skull involvement, and seven presented with pseudotumors in the brain. Collectively, the eight patients presented with 52 lesions, of which 46 (88.5%) were supratentorial. There were 32 lesions with a diameter ≤ 1.2 cm, of which 27 (84.4%) disappeared during the treatment. In three cases, there were lesions > 1.2 cm that showed a characteristic pattern of evolution on MRI: an eccentric gadolinium contrast-enhanced nodule, with a subsequent decreased in the size and degree of contrast enhancement of the lesions.

Conclusion

In NPCM, supratentorial lesions seem to predominate. Lesions ≤ 1.2 cm tend to disappear completely during treatment. Lesions > 1.2 cm tend to present with a similar pattern, designated the "Star of Bethlehem sign", throughout treatment.

Biochemical characterization and analysis of gene expression of an α-mannosidase secreted by Paracoccidioides brasiliensis

Paracoccidioidomycosis (PCM) is a systemic mycosis caused by fungi of the Paracoccidioides genus, being endemic in Latin America and with the highest number of cases in Brazil. Paracoccidioides spp. release a wide range of molecules, such as enzymes, which may be important for PCM establishment. Here, we identified the 85- and 90-kDa proteins from the supernatants of P. brasiliensis cultures as being an α-mannosidase. Because the expected mass of this α-mannosidase is 124.2-kDa, we suggest that the proteins were cleavage products. Indeed, we found an α-mannosidase activity in the culture supernatants among the excreted/secreted antigens (ESAg). Moreover, we determined that the enzyme activity was optimal in buffer at pH 5.6, at the temperature of 45ºC, and with a concentration of 3 mM of the substrate p-NP-α-D-Man. Remarkably, we showed that the gene expression of this α-mannosidase was higher in yeasts than hyphae in three P. brasiliensis isolates with different virulence degrees that were grown in Ham's F12 synthetic medium for 15 days. But in complex media YPD and Fava Netto, the significantly higher gene expression in yeasts than in hyphae was seen only for the virulent isolate Pb18, but not for intermediate virulence Pb339 and low virulence Pb265 isolates. These results about the high expression of the α-mannosidase gene in the pathogenic yeast form of P. brasiliensis open perspectives for studying this α-mannosidase concerning the virulence of P. brasiliensis isolates.

In vitro and in silico analysis reveals antifungal activity and potential targets of curcumin on Paracoccidioides spp

The search for new compounds with activity against Paracoccidioides, etiologic agents of Paracoccidioidomycosis (PCM), is extremely necessary due to the current scenario of the available therapeutic arsenal. Treatment is restricted to three classes of antifungals with side effects. Curcumin is a polyphenol with antifungal effects that is extracted from Curcuma longa. The present work aimed to evaluate the activity of curcumin in different species of Paracoccidioides and to evaluate the potential molecular targets of curcumin using computational strategies. In addition, interactions with classic antifungals used in the treatment of PCM were evaluated. Curcumin inhibits the growth of Paracoccidioides spp. exerting a fungicidal effect. The combination of curcumin with amphotericin B, co-trimoxazole, and itraconazole showed a synergistic or additive interaction. Molecular targets as superoxide dismutase, catalase, and isocitrate lyase were proposed based on in silico approaches. Curcumin affects the fungal plasma membrane and increases the production of reactive oxygen species. Therefore, curcumin is a good alternative for the treatment of PCM.

Curcumin, the active substance of turmeric: its effects on health and ways to improve its bioavailability

Turmeric (Curcuma longa L.) is a spice utilized widely in India, China, and Southeast Asia as an aromatic stimulant, a food preservative, and coloring material. The commonly used names of turmeric are castor saffron, turmeric, and saffron root. Turmeric is a yellow-orange polyphenolic natural substance derived from C. longa rhizomes. It has been used to treat common inflammatory diseases, tumors, biliary diseases, anorexia, cough, topical wounds, diabetic injuries, liver disorders, rheumatism, and sinusitis. Extensive studies on the biological properties and pharmacological consequences of turmeric extracts have been conducted in recent years. Curcumin, the primary yellow biocomponent of turmeric, has anti-inflammatory, antioxidant, anticarcinogenic, antidiabetic, antibacterial, antiprotozoal, antiviral, antifibrotic, immunomodulatory, and antifungal properties. Defense assessment tests showed that curcumin is tolerated well at high doses, without adverse effects. Thus, curcumin is a highly active biological material with the potential to treat different diseases in modern medicine. This review article focuses on curcumin's biological characteristics. The most popular methods for curcumin encapsulation are also discussed. Several effective techniques and approaches have been proposed for curcuminoid capsulation, including nanocomplexing, gelation, complex coacervation, electrospraying, and solvent-free pH-driven encapsulation. This review also highlights curcumin's chemical properties, allowing the readers to expand their perspectives on its use in the development of functional products with health-promoting properties. © 2021 Society of Chemical Industry.

Type 3 Innate Lymphoid Cells as Regulators of the Host-Pathogen Interaction

Type 3 Innate lymphoid cells (ILC3s) have been described as tissue-resident cells and characterized throughout the body, especially in mucosal sites and classical first barrier organs such as skin, gut and lungs, among others. A significant part of the research has focused on their role in combating pathogens, mainly extracellular pathogens, with the gut as the principal organ. However, some recent discoveries in the field have unveiled their activity in other organs, combating intracellular pathogens and as part of the response to viruses. In this review we have compiled the latest studies on the role of ILC3s and the molecular mechanisms involved in defending against different microbes at the mucosal surface, most of these studies have made use of conditional transgenic mice. The present review therefore attempts to provide an overview of the function of ILC3s in infections throughout the body, focusing on their specific activity in different organs.

Insights on the Functional Role of Beta-Glucans in Fungal Immunity Using Receptor-Deficient Mouse Models

Understanding the host anti-fungal immunity induced by beta-glucan has been one of the most challenging conundrums in the field of biomedical research. During the last couple of decades, insights on the role of beta-glucan in fungal disease progression, susceptibility, and resistance have been greatly augmented through the utility of various beta-glucan cognate receptor-deficient mouse models. Analysis of dectin-1 knockout mice has clarified the downstream signaling pathways and adaptive effector responses triggered by beta-glucan in anti-fungal immunity. On the other hand, assessment of CR3-deficient mice has elucidated the compelling action of beta-glucans in neutrophil-mediated fungal clearance, and the investigation of EphA2-deficient mice has highlighted its novel involvement in host sensing and defense to oral mucosal fungal infection. Based on these accounts, this review focuses on the recent discoveries made by these gene-targeted mice in beta-glucan research with particular emphasis on the multifaceted aspects of fungal immunity.

Updates in Paracoccidioides Biology and Genetic Advances in Fungus Manipulation

The dimorphic fungi of the Paracoccidioides genus are the causative agents of paracoccidioidomycosis (PCM). This disease is endemic in Latin America and primarily affects workers in rural areas. PCM is considered a neglected disease, despite being a disabling disease that has a notable impact on the public health system. Paracoccidioides spp. are thermally dimorphic fungi that present infective mycelia at 25 °C and differentiate into pathogenic yeast forms at 37 °C. This transition involves a series of morphological, structural, and metabolic changes which are essential for their survival inside hosts. As a pathogen, the fungus is subjected to several varieties of stress conditions, including the host immune response, which involves the production of reactive nitrogen and oxygen species, thermal stress due to temperature changes during the transition, pH alterations within phagolysosomes, and hypoxia inside granulomas. Over the years, studies focusing on understanding the establishment and development of PCM have been conducted with several limitations due to the low effectiveness of strategies for the genetic manipulation of Paracoccidioides spp. This review describes the most relevant biological features of Paracoccidioides spp., including aspects of the phylogeny, ecology, stress response, infection, and evasion mechanisms of the fungus. We also discuss the genetic aspects and difficulties of fungal manipulation, and, finally, describe the advances in molecular biology that may be employed in molecular research on this fungus in the future.

Paracoccin Overexpression in Paracoccidioides brasiliensis Enhances Fungal Virulence by Remodeling Chitin Properties of the Cell Wall

BACKGROUND

The thermodimorphic fungi Paracoccidioides spp. are the etiological agents of paracoccidioidomycosis. Although poorly studied, paracoccin (PCN) from Paracoccidioides brasiliensis has been shown to harbor lectinic, enzymatic, and immunomodulatory properties that affect disease development.

METHODS

Mutants of P. brasiliensis overexpressing PCN (ov-PCN) were constructed by Agrobacterium tumefaciens-mediated transformation. ov-PCN strains were analyzed and inoculated intranasally or intravenously to mice. Fungal burden, lung pathology, and survival were monitored to evaluate virulence. Electron microscopy was used to evaluate the size of chito-oligomer particles released by ov-PCN or wild-type strains to growth media.

RESULTS

ov-PCN strains revealed no differences in cell growth and viability, although PCN overexpression favored cell separation, chitin processing that results in the release of smaller chito-oligomer particles, and enhanced virulence. Our data show that PCN triggers a critical effect in the cell wall biogenesis through the chitinase activity resulting from overexpression of PCN. As such, PCN overexpression aggravates the disease caused by P. brasiliensis.

CONCLUSIONS

Our data are consistent with a model in which PCN modulates the cell wall architecture via its chitinase activity. These findings highlight the potential for exploiting PCN function in future therapeutic approaches.

Living Within the Macrophage: Dimorphic Fungal Pathogen Intracellular Metabolism

Histoplasma and Paracoccidioides are related thermally dimorphic fungal pathogens that cause deadly mycoses (i.e., histoplasmosis and paracoccidioidomycosis, respectively) primarily in North, Central, and South America. Mammalian infection results from inhalation of conidia and their subsequent conversion into pathogenic yeasts. Macrophages in the lung are the first line of defense, but are generally unable to clear these fungi. Instead, Histoplasma and Paracoccidioides yeasts survive and proliferate within the phagosomal compartment of host macrophages. Growth within macrophages requires strategies for acquisition of sufficient nutrients (e.g., carbon, nitrogen, and essential trace elements and co-factors) from the nutrient-depleted phagosomal environment. We review the transcriptomic and recent functional genetic studies that are defining how these intracellular fungal pathogens tune their metabolism to the resources available in the macrophage phagosome. In addition, recent studies have shown that the nutritional state of the macrophage phagosome is not static, but changes upon activation of adaptive immune responses. Understanding the metabolic requirements of these dimorphic pathogens as they thrive within host cells can provide novel targets for therapeutic intervention.

Metabolomics and Machine Learning Approaches Combined in Pursuit for More Accurate Paracoccidioidomycosis Diagnoses

Brazil and many other Latin American countries are areas of endemicity for different neglected diseases, and the fungal infection paracoccidioidomycosis (PCM) is one of them. Among the clinical manifestations, pneumopathy associated with skin and mucosal lesions is the most frequent. PCM definitive diagnosis depends on yeast microscopic visualization and immunological tests, but both present ambiguous results and difficulty in differentiating PCM from other fungal infections. This research has employed metabolomics analysis through high-resolution mass spectrometry to identify PCM biomarkers in serum samples in order to improve diagnosis for this debilitating disease. To upgrade the biomarker selection, machine learning approaches, using Random Forest classifiers, were combined with metabolomics data analysis. The proposed combination of these two analytical methods resulted in the identification of a set of 19 PCM biomarkers that show accuracy of 97.1%, specificity of 100%, and sensitivity of 94.1%. The obtained results are promising and present great potential to improve PCM definitive diagnosis and adequate pharmacological treatment, reducing the incidence of PCM sequelae and resulting in a better quality of life.IMPORTANCE Paracoccidioidomycosis (PCM) is a fungal infection typically found in Latin American countries, especially in Brazil. The identification of this disease is based on techniques that may fail sometimes. Intending to improve PCM detection in patient samples, this study used the combination of two of the newest technologies, artificial intelligence and metabolomics. This combination allowed PCM detection, independently of disease form, through identification of a set of molecules present in patients' blood. The great difference in this research was the ability to detect disease with better confidence than the routine methods employed today. Another important point is that among the molecules, it was possible to identify some indicators of contamination and other infection that might worsen patients' condition. Thus, the present work shows a great potential to improve PCM diagnosis and even disease management, considering the possibility to identify concomitant harmful factors.

Proteome characterization of Paracoccidioides lutzii conidia by using nanoUPLC-MSE

Fungi of the genus Paracoccidioides are the etiological agents of Paracoccidioidomycosis (PCM), the most prevalent mycosis in Latin America. Paracoccidioidomycosis infection is acquired by inhalation of Paracoccidioides conidia, which have first contact with the lungs and can subsequently spread to other organs/tissues. Until now, there have been no proteomic studies focusing on this infectious particle of Paracoccidioides. In order to identify the Paracoccidioides lutzii conidia proteome, conidia were produced and purified. Proteins were characterized by use of the nanoUPLC-MS^E approach. The strategy allowed us to identify a total of 242 proteins in P. lutzii conidia. In the conidia proteome, proteins were classified in functional categories such as protein synthesis, energy production, metabolism, cellular defense/virulence processes, as well as other processes that can be important for conidia survival. Through this analysis, a pool of ribosomal proteins was identified, which may be important for the initial processes of dimorphic transition. In addition, molecules related to energetic and metabolic processes were identified, suggesting a possible basal metabolism during this form of resistance of the fungus. In addition, adhesins and virulence factors were identified in the P. lutzii conidia proteome. Our results demonstrate the potential role that these molecules can play during early cell-host interaction processes, as well as the way in which these molecules are involved in environmental survival during this form of propagation.

New Role of P. brasiliensis α-Glucan: Differentiation of Non-conventional Dendritic Cells

The cell wall has a critical role in the host immune response to fungal pathogens. In this study, we investigated the influence of two cell wall fractions of the dimorphic fungi Paracoccidioides brasiliensis (Pb) in the in vitro generation of monocyte-derived dendritic cells (MoDCs). Monocytes were purified from the peripheral blood of healthy donors and cultivated for 7 days in medium supplemented with IL-4 and GM-CSF in the presence of Pb cell wall fractions: the alkali-insoluble F1, constituted by β-1,3-glucans, chitin and proteins, and the alkali-soluble F2, mainly constituted by α-glucan. MoDCs phenotypes were evaluated regarding cell surface expression of CD1a, DC-SIGN, HLA-DR, CD80, and CD83 and production of cytokines. The α-glucan-rich cell wall fraction downregulated the differentiation of CD1a⁺ MoDCs, a dendritic cell subset that stimulate Th1 responses. The presence of both cell fractions inhibited DC-SIGN and HLA-DR expression, while the expression of maturation markers was differentially induced in CD1a^– MoDCs. Differentiation upon F1 and F2 stimulation induced mixed profile of inflammatory cytokines. Altogether, these data demonstrate that Pb cell wall fractions differentially induce a dysregulation in DCs differentiation. Moreover, our results suggest that cell wall α-glucan promote the differentiation of CD1a^– DCs, potentially favoring Th2 polarization and contributing to pathogen persistence.

Galectin-3 Inhibits Paracoccidioides brasiliensis Growth and Impacts Paracoccidioidomycosis through Multiple Mechanisms

The thermodimorphic pathogenic fungi Paracoccidioides brasiliensis and Paracoccidioides lutzii are the etiologic causes of paracoccidioidomycosis (PCM), the most prevalent systemic mycosis in Latin America. Galectin-3 (Gal-3), an animal β-galactoside-binding protein, modulates important roles during microbial infections, such as triggering a Th2-polarized immune response in PCM. Herein, we demonstrate that Gal-3 also plays other important roles in P. brasiliensis infection. We verified that Gal-3 levels are upregulated in human and mice infections and established that Gal-3 inhibited P. brasiliensis growth by inhibiting budding. Furthermore, Gal-3 affected disruption and internalization of extracellular vesicles (EVs) from P. brasiliensis by macrophages. Our results suggest important protective roles for Gal-3 in P. brasiliensis infection, indicating that increased Gal-3 production during P. brasiliensis infection may affect fungal growth and EV stability, thus promoting beneficial effects that could influence the course of PCM. The finding that Gal-3 has effects against P. brasiliensis together with previously reported effects against Cryptococcus neoformans suggests that molecule has a general antifungal role in innate defenses against fungal pathogens.IMPORTANCE Paracoccidioidomycosis (PCM) is the most prevalent systemic mycosis in Latin America. Although the immune mechanisms to control PCM are still not fully understood, several events of the host innate and adaptive immunity are crucial to determine the progress of the infection. Mammalian β-galactoside-binding protein galectin-3 (Gal-3) plays significant roles during microbial infections and has been studied for its immunomodulatory roles, but it can also have direct antimicrobial effects. We asked whether this protein plays a role in Paracoccidioides brasiliensis We report herein that Gal-3 indeed has direct effects on the fungal pathogen, inhibiting fungal growth and reducing extracellular vesicle stability. Our results suggest a direct role for Gal-3 in P. brasiliensis infection, with beneficial effects for the mammalian host.

ADRENAL INSUFFICIENCY CAUSED BY PARACOCCIDIOIDOMYCOSIS: THREE CASE REPORTS AND REVIEW

Objective

Fungal infections can affect the adrenal glands, causing primary adrenal insufficiency (PAI). Although endemic to South America, paracoccidioidomycosis (PCM), which can lead to PAI, has gained global relevance with the increase in international travel and migration.

Methods

The present report describes 3 patients with PAI caused by PCM.

Results

Patients in cases 1 and 2 both reported indisposition, asthenia, nausea, hyperpigmentation of the skin, hypotension, and weight loss. Complementary exams confirmed PAI due to PCM. Case 1 was serologically diagnosed. In contrast, the definitive diagnosis of case 2 was only reached by computed tomography (CT)-guided adrenal biopsy after negative serologies for PCM. Case 3, with diabetes mellitus, had a history of asthenia, nausea and weight loss after persistent sinusitis. Initially, serologic results were negative for PCM and the patient's CT-guided biopsy resulted in insufficient tissue to obtain a definitive diagnosis. Contrary to the initial hypothesis of invasive aspergillosis, since the only etiological evidence for the patient's clinical condition were positive serologies for Aspergillus fumigatus, histopathologic examination of the specimen provided by a left adrenalectomy finally confirmed PCM as the etiology for PAI in this case as well.

Conclusion

The 3 cases illustrate the necessity to investigate PAI whenever there are suspicious clinical findings. They also show that fungal infections should be considered among the diagnostic hypotheses during the etiological investigation of PAI. Finally, they teach us that definitive diagnosis of PCM may require direct visualization of the pathogen.

Study of differential expression of miRNAs in lung tissue of mice submitted to experimental infection by Paracoccidioides brasiliensis

MicroRNAs (miRNAs) are small single stranded RNA sequences involved in post-transcriptional regulation of different biological and physiological processes. Paracoccidioidomycosis (PCM) is an infection caused by Paracoccidioides brasiliensis, and it is a major cause of mortality due to systemic mycoses in Brazil. To date, there have been few reports on the role of miRNAs in the immune response against fungi, especially PCM. The objective of this study was to evaluate the differential expression of miRNAs related to the inflammatory response associated with pulmonary infection by P. brasiliensis. For this purpose, lungs from BALB/c mice, intravenously infected with P. brasiliensis (2.7×107 yeast cells/ml, n = 12) and noninfected BALB/c mice (n = 8), were collected at the 28 and 56 day after infection. The lung parenchyma presented a great number of yeast cells, granulomas, and edema at 28 days and a framework of resolution of the inflammatory process after 56 days. The mRNAs gata-3, ror-γt, foxp3, and IL-6 were positively regulated at the moment at the 56 day, while the TGF-β1 mRNA was positively regulated at both moments. The miRNAs 126a-5p, 340-5p, 30b-5p, 19b-3p, 221-3p, 20a-5p, 130a-3p, and 301a-3p, 466k presented the greatest increase in expression levels 28 days after infection, and the miRNAs let-7f-5p, let-7a-5p, 5p-26b, let-7e-5p and 369-3p, 466k presented a greater increase in levels of expression 56 days after infection. This study shows a set of differentially expressed miRNAs possibly involved in the immune response in mice during pulmonary infection by P. brasiliensis.

Effect of ArtinM on Human Blood Cells During Infection With Paracoccidioides brasiliensis

Infections caused by fungi are prominent in our environment and can be potentially fatal. paracoccidioidomycosis (PCM), caused by fungi of the Paracoccidioides genus, is the most frequent systemic mycosis in Brazil and the main cause of death among immunocompetent individuals. The antifungal therapy for PCM is usually effective but side effects and relapses are often reported. The latter could be avoided with alternative or complementary therapies aimed at boosting the immune response to combat this pathogen. Recent reports have pointed at the importance of an effective cellular immune response, with the participation of Th1 cells, in the resistance to and control of Paracoccidioides infection. The ArtinM lectin, extracted from jackfruit (Artocarpus heterophyllus) seeds, exhibits immunomodulatory activity against several intracellular pathogens, including Paracoccidioides brasiliensis, by promoting the development of a Th1 immune response. The aim of this work was to characterize the effect of ArtinM on peripheral blood cells of patients with PCM and on those of control individuals infected with fungal yeasts cells in vitro. Our results demonstrate that ArtinM activates human neutrophils in vitro, leading to an increase in cytokine production and CD54 expression. ArtinM activated P. brasiliensis-infected neutrophils from both healthy individuals and patients with PCM. This activation was not dependent on the dectin-1 receptor, because pre-incubation with laminarin, a dectin-1 receptor blocker, did not reverse the activated state of the cells. ArtinM also stimulated human peripheral blood mononuclear cells to secrete pro-inflammatory Th1-related cytokines, which are protective against Paracoccidioides infection. These data support the immunostimulatory action of ArtinM and encourage new studies using the lectin for the immunotherapy of PCM.

Characterization of extracellular proteins in members of the Paracoccidioides complex

Paracoccidioides is a thermodimorphic fungus that causes Paracoccidioidomycosis (PCM) - an endemic systemic mycosis in Latin America. The genus comprises several phylogenetic species which present some genetic and serological differences. The diversity presented among isolates of the same genus has been explored in several microorganisms. There have also been attempts to clarify differences that might be related to virulence existing in isolates that cause the same disease. In this work, we analyzed the secretome of two isolates in the Paracoccidioides genus, isolates Pb01 and PbEpm83, and performed infection assays in macrophages to evaluate the influence of the secretomes of those isolates upon an in vitro model of infection. The use of a label-free proteomics approach (LC-MS^E) allowed us to identify 92 proteins that are secreted by those strains. Of those proteins, 35 were differentially secreted in Pb01, and 36 in PbEpm83. According to the functional annotation, most of the identified proteins are related to adhesion and virulence processes. These results provide evidence that different members of the Paracoccidioides complex can quantitatively secrete different proteins, which may influence the characteristics of virulence, as well as host-related processes.

Dynamic Fungal Cell Wall Architecture in Stress Adaptation and Immune Evasion

Deadly infections from opportunistic fungi have risen in frequency, largely because of the at-risk immunocompromised population created by advances in modern medicine and the HIV/AIDS pandemic. This review focuses on dynamics of the fungal polysaccharide cell wall, which plays an outsized role in fungal pathogenesis and therapy because it acts as both an environmental barrier and as the major interface with the host immune system. Human fungal pathogens use architectural strategies to mask epitopes from the host and prevent immune surveillance, and recent work elucidates how biotic and abiotic stresses present during infection can either block or enhance masking. The signaling components implicated in regulating fungal immune recognition can teach us how cell wall dynamics are controlled, and represent potential targets for interventions designed to boost or dampen immunity.

Targeting the Homoserine Dehydrogenase of Paracoccidioides Species for Treatment of Systemic Fungal Infections

This work evaluated new potential inhibitors of the enzyme homoserine dehydrogenase (HSD) of Paracoccidioides brasiliensis, one of the etiological agents of paracoccidioidomycosis. The tertiary structure of the protein bonded to the analogue NAD, and l-homoserine was modeled by homology. The model with the best output was subjected to gradient minimization, redocking, and molecular dynamics simulation. Virtual screening simulations with 187,841 molecules purchasable from the Zinc database were performed. After the screenings, 14 molecules were selected and analyzed by the use of absorption, distribution, metabolism, excretion, and toxicity criteria, resulting in four compounds for in vitro assays. The molecules HS1 and HS2 were promising, exhibiting MICs of 64 and 32 μg · ml^-1, respectively, for the Pb18 isolate of P. brasilensis, 64 μg · ml^-1 for two isolates of P. lutzii, and also synergy with itraconazole. The application of these molecules to human-pathogenic fungi confirmed that the HSD enzyme may be used as a target for the development of drugs with specific action against paracoccidioidomycosis; moreover, these compounds may serve as leads in the design of new antifungals.

Impact of Paracoccin Gene Silencing on Paracoccidioides brasiliensis Virulence

Among the endemic deep mycoses in Latin America, paracoccidioidomycosis (PCM), caused by thermodimorphic fungi of the Paracoccidioides genus, is a major cause of morbidity. Disease development and its manifestations are associated with both host and fungal factors. Concerning the latter, several recent studies have employed the methodology of gene modulation in P. brasiliensis using antisense RNA (AsRNA) and Agrobacterium tumefaciens-mediated transformation (ATMT) to identify proteins that influence fungus virulence. Our previous observations suggested that paracoccin (PCN), a multidomain fungal protein with both lectin and enzymatic activities, may be a potential P. brasiliensis virulence factor. To explore this, we used AsRNA and ATMT methodology to obtain three independent PCN-silenced P. brasiliensis yeast strains (AsPCN1, AsPCN2, and AsPCN3) and characterized them with regard to P. brasiliensis biology and pathogenicity. AsPCN1, AsPCN2, and AsPCN3 showed relative PCN expression levels that were 60%, 40%, and 60% of that of the wild-type (WT) strain, respectively. PCN silencing led to the aggregation of fungal cells, blocked the morphological yeast-to-mycelium transition, and rendered the yeast less resistant to macrophage fungicidal activity. In addition, mice infected with AsPCN1, AsPCN2, and AsPCN3 showed a reduction in fungal burden of approximately 96% compared with those inoculated with the WT strain, which displayed a more extensive destruction of lung tissue. Finally, mice infected with the PCN-silenced yeast strains had lower mortality than those infected with the WT strain. These data demonstrate that PCN acts as a P. brasiliensis contributory virulence factor directly affecting fungal pathogenesis.

The nonexistence of efficient genetic transformation systems has hampered studies in the dimorphic fungus Paracoccidioides brasiliensis, the etiological agent of the most frequent systemic mycosis in Latin America. The recent development of a method for gene expression knockdown by antisense RNA technology, associated with an Agrobacterium tumefaciens-mediated transformation system, provides new strategies for studying P. brasiliensis. Through this technology, we generated yeasts that were silenced for paracoccin (PCN), a P. brasiliensis component that has lectin and enzymatic properties. By comparing the phenotypes of PCN-silenced and wild-type strains of P. brasiliensis, we identified PCN as a virulence factor whose absence renders the yeasts unable to undergo the transition to mycelium and causes a milder pulmonary disease in mice, with a lower mortality rate. Our report highlights the importance of the technology used for P. brasiliensis transformation and demonstrates that paracoccin is a virulence factor acting on fungal biology and pathogenesis.

Shrinking Daughters: Rlm1-Dependent G1/S Checkpoint Maintains Saccharomyces cerevisiae Daughter Cell Size and Viability

The Rlm1 transcription factor is a target of the cell wall integrity pathway. We report that an rlm1Δ mutant grown on a nonfermentable carbon source at low osmolarity forms cell groups in which a mother cell is surrounded by smaller "satellite-daughter" cells. Mother cells in these groups progressed through repeated rounds of cell division with normal rates of bud growth and genetic stability; however, these cells underwent precocious START relative to wild-type mothers. Thus, once activated, Rlm1 delays the transition from G₁ to S, a mechanism we term the cell wall/START (CW/START) checkpoint. The rlm1Δ satellite-cell phenotype is suppressed by deletion of either SLT2, which encodes the kinase that activates Rlm1, or SWI4, which is also activated by Slt2; suggesting that Slt2 can have opposing roles in regulating the START transition. Consistent with an Rlm1-dependent CW/START checkpoint, rlm1Δ satellite daughters were unable to grow or divide further even after transfer to rich medium, but UV irradiation in G₁ could partially rescue rlm1Δ satellite daughters in the next division. Indeed, after cytokinesis, these satellite daughters shrank rapidly, displayed amorphous actin staining, and became more permeable. As a working hypothesis, we propose that duplication of an "actin-organizing center" in late G₁ may be required both to progress through START and to reestablish the actin cytoskeleton in daughter cells.

Anti-Immune Strategies of Pathogenic Fungi

Pathogenic fungi have developed many strategies to evade the host immune system. Multiple escape mechanisms appear to function together to inhibit attack by the various stages of both the adaptive and the innate immune response. Thus, after entering the host, such pathogens fight to overcome the immune system to allow their survival, colonization and spread to different sites of infection. Consequently, the establishment of a successful infectious process is closely related to the ability of the pathogen to modulate attack by the immune system. Most strategies employed to subvert or exploit the immune system are shared among different species of fungi. In this review, we summarize the main strategies employed for immune evasion by some of the major pathogenic fungi.

Severe Changes in Thymic Microenvironment in a Chronic Experimental Model of Paracoccidioidomycosis

T cell maturation takes place within the thymus, a primary lymphoid organ that is commonly targeted during infections. Previous studies showed that acute infection with Paracoccidioides brasiliensis (Pb), the causative agent of paracoccidioidomycosis (PCM), promotes thymic atrophy that is associated with the presence of yeast cells in the organ. However, as human PCM is a chronic infection, it is imperative to investigate the consequences of Pb infection over the thymic structure and function in chronic infection. In this sense, we developed a new experimental model where Pb yeast cells are injected through the intraperitoneal route and mice are evaluated over 120 days of infection. Thymuses were analyzed in chronically infected mice and we found that the thymus underwent extensive morphological alterations and severe infiltration of P. brasiliensis yeast cells. Further analyses showed an altered phenotype and function of thymocytes that are commonly found in peripheral mature T lymphocytes. We also observed activation of the NLRP3 inflammasome in the thymus. Our data provide new information on the severe changes observed in the thymic microenvironment in a model of PCM that more closely mimics the human infection.

Antifungal activity of extracts from Atacama Desert fungi against Paracoccidioides brasiliensis and identification of Aspergillus felis as a promising source of natural bioactive compounds

Fungi of the genus Paracoccidioides are responsible for paracoccidioidomycosis. The occurrence of drug toxicity and relapse in this disease justify the development of new antifungal agents. Compounds extracted from fungal extract have showing antifungal activity. Extracts of 78 fungi isolated from rocks of the Atacama Desert were tested in a microdilution assay against Paracoccidioides brasiliensis Pb18. Approximately 18% (5) of the extracts showed minimum inhibitory concentration (MIC) values≤ 125.0 µg/mL. Among these, extract from the fungus UFMGCB 8030 demonstrated the best results, with an MIC of 15.6 µg/mL. This isolate was identified as Aspergillus felis (by macro and micromorphologies, and internal transcribed spacer, β-tubulin, and ribosomal polymerase II gene analyses) and was grown in five different culture media and extracted with various solvents to optimise its antifungal activity. Potato dextrose agar culture and dichloromethane extraction resulted in an MIC of 1.9 µg/mL against P. brasiliensis and did not show cytotoxicity at the concentrations tested in normal mammalian cell (Vero). This extract was subjected to bioassay-guided fractionation using analytical C18RP-high-performance liquid chromatography (HPLC) and an antifungal assay using P. brasiliensis. Analysis of the active fractions by HPLC-high resolution mass spectrometry allowed us to identify the antifungal agents present in the A. felis extracts cytochalasins. These results reveal the potential of A. felis as a producer of bioactive compounds with antifungal activity.

Immunomodulation over the course of experimental Arthrographis kalrae infection in mice

Arthrographis kalrae is occasionally described as an opportunistic human pathogen. This study investigated the immune response to A. kalrae during murine experimental infection (7, 14, 28 and 56 days post infection). The fungal load was higher in the early phase and mice presented with neurological syndrome over the course of the infection. There was a gradual increase in the level of anti-A. kalrae IgG and increased levels of DTH at 14 days. There was decreased IFN-γ (14-56 days) and an increase in IL-4 (7 and 56 days). Decreased levels of cytokines (IFN-γ, IL-4, IL-10 and IL-17) were observed in the brain at 56 days p.i. The results suggest that the immune response during murine A. kalrae infection modulates to the pattern of Th2 response. This study shows for the first time the cytokines and cellular immunomodulation that occur in response to an experimental infection with A. kalrae in mice.

A conserved dimorphism-regulating histidine kinase controls the dimorphic switching in Paracoccidioides brasiliensis

Paracoccidioides brasiliensis and P. lutzii, thermally dimorphic fungi, are the causative agents of paracoccidioidomycosis (PCM). Paracoccidioides infection occurs when conidia or mycelium fragments are inhaled by the host, which causes the Paracoccidioides cells to transition to the yeast form. The development of disease requires conidia inside the host alveoli to differentiate into yeast cells in a temperature-dependent manner. We describe the presence of a two-component signal transduction system in P. brasiliensis, which we investigated by expression analysis of a hypothetical protein gene (PADG_07579) that showed high similarity with the dimorphism-regulating histidine kinase (DRK1) gene of Blastomyces dermatitidis and Histoplasma capsulatum This gene was sensitive to environmental redox changes, which was demonstrated by a dose-dependent decrease in transcript levels after peroxide stimulation and a subtler decrease in transcript levels after NO stimulation. Furthermore, the higher PbDRK1 levels after treatment with increasing NaCl concentrations suggest that this histidine kinase can play a role as osmosensing. In the mycelium-yeast (M→Y) transition, PbDRK1 mRNA expression increased 14-fold after 24 h incubation at 37°C, consistent with similar observations in other virulent fungi. These results demonstrate that the PbDRK1 gene is differentially expressed during the dimorphic M→Y transition. Finally, when P. brasiliensis mycelium cells were exposed to a histidine kinase inhibitor and incubated at 37°C, there was a delay in the dimorphic M→Y transition, suggesting that histidine kinases could be targets of interest for PCM therapy.

Oral Paracoccidioidomycosis Granulomas are Predominantly Populated by CD163+ Multinucleated Giant Cells

Multinucleated giant cells (MGC) are considered to be a hallmark of granulomatous inflammation; thus, they may play an essential role in the host response against pathogens, particularly Paracoccidioides brasiliensis. This study characterizes the MGC found in oral paracoccidioidomycosis and assesses the correlation of MGC with the amount of fungi within oral tissues. Twenty-six cases were included. They were classified as loose or dense granulomas, and the total MGC, including foreign-body and Langhans giant cells, besides the total and intracellular fungi, were taken into consideration. CD163 immunoexpression was performed, and CD163+ multinucleated giant cells were also quantified. Dense granulomas revealed more foreign-body type and total giant cells than loose granulomas (P < 0.05). Total giant cells showed a positive linear correlation with the CD163+ cells (P = 0.003; r = 0.56) and intracellular fungi quantification (P = 0.045; r = 0.40). Oral paracoccidioidomycosis lesions contain MGC that mainly belong to a CD163+ phenotype, also showing both Langhans and foreign-body arrangements. Additionally, the higher the presence of MGC, the higher the amount of phagocytized fungi.

Decreased expression of 14-3-3 in Paracoccidioides brasiliensis confirms its involvement in fungal pathogenesis

The interaction between the fungal pathogen Paracoccidioides brasiliensis and host cells is usually mediated by specific binding events between adhesins on the fungal surface and receptors on the host extracellular matrix or cell surface. One molecule implicated in the P. brasiliensis-host interaction is the 14-3-3 protein. The 14-3-3 protein belongs to a family of conserved regulatory molecules that are expressed in all eukaryotic cells and are involved in diverse cellular functions. Here, we investigated the relevance of the 14-3-3 protein to the virulence of P. brasiliensis. Using antisense RNA technology and Agrobacterium tumefaciens-mediated transformation, we generated a 14-3-3-silenced strain (expression reduced by ˜55%). This strain allowed us to investigate the interaction between 14-3-3 and the host and to correlate the functions of P. brasiliensis 14-3-3 with cellular features, such as morphological characteristics and virulence, that are important for pathogenesis.

Protection against Paracoccidioides brasiliensis infection in mice treated with modulated dendritic cells relies on inhibition of interleukin-10 production by CD8+ T cells

Paracoccidioidomycosis is a systemic infection prevalent in Latin American countries. Disease develops after inhalation of Paracoccidioides brasiliensis conidia followed by an improper immune activation by the host leucocytes. Dendritic cells (DCs) are antigen-presenting cells with the unique ability to direct the adaptive immune response by the time of activation of naive T cells. This study was conducted to test whether extracts of P. brasiliensis would induce maturation of DCs. We found that DCs treated with extracts acquired an inflammatory phenotype and upon adoptive transfer conferred protection to infection. Interestingly, interleukin-10 production by CD8(+) T cells was ablated following DC transfer. Further analyses showed that lymphocytes from infected mice were high producers of interleukin-10, with CD8(+) T cells being the main source. Blockage of cross-presentation to CD8(+) T cells by modulated DCs abolished the protective effect of adoptive transfer. Collectively, our data show that adoptive transfer of P. brasiliensis-modulated DCs is an interesting approach for the control of infection in paracoccidioidomycosis.

A Gβ protein and the TupA Co-Regulator Bind to Protein Kinase A Tpk2 to Act as Antagonistic Molecular Switches of Fungal Morphological Changes

The human pathogenic fungus Paracoccidioides brasiliensis (Pb) undergoes a morphological transition from a saprobic mycelium to pathogenic yeast that is controlled by the cAMP-signaling pathway. There is a change in the expression of the Gβ-protein PbGpb1, which interacts with adenylate cyclase, during this morphological transition. We exploited the fact that the cAMP-signaling pathway of Saccharomyces cerevisiae does not include a Gβ-protein to probe the functional role of PbGpb1. We present data that indicates that PbGpb1 and the transcriptional regulator PbTupA both bind to the PKA protein PbTpk2. PbTPK2 was able to complement a TPK2Δ strain of S. cerevisiae, XPY5a/α, which was defective in pseudohyphal growth. Whilst PbGPB1 had no effect on the parent S. cerevisiae strain, MLY61a/α, it repressed the filamentous growth of XPY5a/α transformed with PbTPK2, behaviour that correlated with a reduced expression of the floculin FLO11. In vitro, PbGpb1 reduced the kinase activity of PbTpk2, suggesting that inhibition of PbTpk2 by PbGpb1 reduces the level of expression of Flo11, antagonizing the filamentous growth of the cells. In contrast, expressing the co-regulator PbTUPA in XPY5a/α cells transformed with PbTPK2, but not untransformed cells, induced hyperfilamentous growth, which could be antagonized by co-transforming the cells with PbGPB1. PbTUPA was unable to induce the hyperfilamentous growth of a FLO8Δ strain, suggesting that PbTupA functions in conjunction with the transcription factor Flo8 to control Flo11 expression. Our data indicates that P. brasiliensis PbGpb1 and PbTupA, both of which have WD/β-propeller structures, bind to PbTpk2 to act as antagonistic molecular switches of cell morphology, with PbTupA and PbGpb1 inducing and repressing filamentous growth, respectively. Our findings define a potential mechanism for controlling the morphological switch that underpins the virulence of dimorphic fungi.

M2 macrophages and inflammatory cells in oral lesions of chronic paracoccidioidomycosis

BACKGROUND

Paracoccidioidomycosis (PCM) is a systemic fungal infection caused by Paracoccidioides brasiliensis (Pb) and associated with deficient cellular immune response, which is modulated by inflammatory cells, mainly macrophages, and cytokines. Recently, the comprehension of the macrophage polarization mediated by Th1 and Th2 cytokines has contributed to elucidate the immune response that takes part in some diseases. Thus, the aim of this study was to assess the presence of Th1- and Th2-immune response and also Pb counting in oral lesions of chronic PCM.

METHODS

Forty-eight cases of chronic PCM oral lesions were included. All cases were classified as loose or dense granulomas. S100 protein, IL-1β, IL-6, TNF-α, CD163 and CD68 immunoexpressions, and Pb localization were evaluated. The fungi present in the tissue were quantified by anti-Pb antibody.

RESULTS

Most patients were white men with mean age of 47 years old and showed higher incidence of multiple lesions. Loose granulomas were predominant and exhibited a great amount of M2 macrophages, which were visualized with anti-CD163 antibody. The expression for CD163 and CD68 was similar (P = 0.05), highlighting the predominance of M2 macrophages in PCM. IL-1β, IL-6, and TNF-α immunoexpression did not significantly change with CD163, CD68, and S100 protein. The number of fungi was significantly higher in cases with intense IL-1β immunoexpression (P = 0.003).

CONCLUSIONS

M2-activated macrophages were the majority among inflammatory cells in chronic PCM, characterizing the action of a Th2-immune response. Nevertheless, Th1 cytokines were also found; mainly IL-1β, which was associated with fungi counting in oral lesions.

Saccharomyces cerevisiae expressing Gp43 protects mice against Paracoccidioides brasiliensis infection

The dimorphic fungus Paracoccidioides brasiliensis is the etiological agent of paracoccidioidomycosis (PCM). It is believed that approximately 10 million people are infected with the fungus and approximately 2% will eventually develop the disease. Unlike viral and bacterial diseases, fungal diseases are the ones against which there is no commercially available vaccine. Saccharomyces cerevisiae may be a suitable vehicle for immunization against fungal infections, as they require the stimulation of different arms of the immune response. Here we evaluated the efficacy of immunizing mice against PCM by using S. cerevisiae yeast expressing gp43. When challenged by inoculation of P. brasiliensis yeasts, immunized animals showed a protective profile in three different assays. Their lung parenchyma was significantly preserved, exhibiting fewer granulomas with fewer fungal cells than found in non-immunized mice. Fungal burden was reduced in the lung and spleen of immunized mice, and both organs contained higher levels of IL-12 and IFN-γ compared to those of non-vaccinated mice, a finding that suggests the occurrence of Th1 immunity. Taken together, our results indicate that the recombinant yeast vaccine represents a new strategy to confer protection against PCM.

Therapeutic administration of recombinant Paracoccin confers protection against paracoccidioides brasiliensis infection: involvement of TLRs

BACKGROUND

Paracoccin (PCN) is an N-acetylglucosamine-binding lectin from the human pathogenic fungus Paracoccidioides brasiliensis. Recombinant PCN (rPCN) induces a T helper (Th) 1 immune response when prophylactically administered to BALB/c mice, protecting them against subsequent challenge with P. brasiliensis. In this study, we investigated the therapeutic effect of rPCN in experimental paracoccidioidomycosis (PCM) and the mechanism accounting for its beneficial action.

METHODOLOGY/PRINCIPAL FINDINGS

Four distinct regimens of rPCN administration were assayed to identify which was the most protective, relative to vehicle administration. In all rPCN-treated mice, pulmonary granulomas were less numerous and more compact. Moreover, fewer colony-forming units were recovered from the lungs of rPCN-treated mice. Although all therapeutic regimens of rPCN were protective, maximal efficacy was obtained with two subcutaneous injections of 0.5 µg rPCN at 3 and 10 days after infection. The rPCN treatment was also associated with higher pulmonary levels of IL-12, IFN-γ, TNF-α, nitric oxide (NO), and IL-10, without IL-4 augmentation. Encouraged by the pulmonary cytokine profile of treated mice and by the fact that in vitro rPCN-stimulated macrophages released high levels of IL-12, we investigated the interaction of rPCN with Toll-like receptors (TLRs). Using a reporter assay in transfected HEK293T cells, we verified that rPCN activated TLR2 and TLR4. The activation occurred independently of TLR2 heterodimerization with TLR1 or TLR6 and did not require the presence of the CD14 or CD36 co-receptors. The interaction between rPCN and TLR2 depended on carbohydrate recognition because it was affected by mutation of the receptor's N-glycosylation sites. The fourth TLR2 N-glycan was especially critical for the rPCN-TLR2 interaction.

CONCLUSIONS/SIGNIFICANCE

Based on our results, we propose that PCN acts as a TLR agonist. PCN binds to N-glycans on TLRs, triggers regulated Th1 immunity, and exerts a therapeutic effect against P. brasiliensis infection.

New developments of RNAi in Paracoccidioides brasiliensis: prospects for high-throughput, genome-wide, functional genomics

Background

The Fungal Genome Initiative of the Broad Institute, in partnership with the Paracoccidioides research community, has recently sequenced the genome of representative isolates of this human-pathogen dimorphic fungus: Pb18 (S1), Pb03 (PS2) and Pb01. The accomplishment of future high-throughput, genome-wide, functional genomics will rely upon appropriate molecular tools and straightforward techniques to streamline the generation of stable loss-of-function phenotypes. In the past decades, RNAi has emerged as the most robust genetic technique to modulate or to suppress gene expression in diverse eukaryotes, including fungi. These molecular tools and techniques, adapted for RNAi, were up until now unavailable for P. brasiliensis.

Methodology/Principal Findings

In this paper, we report Agrobacterium tumefaciens mediated transformation of yeast cells for high-throughput applications with which higher transformation frequencies of 150±24 yeast cell transformants per 1×10⁶ viable yeast cells were obtained. Our approach is based on a bifunctional selective marker fusion protein consisted of the Streptoalloteichus hindustanus bleomycin-resistance gene (Shble) and the intrinsically fluorescent monomeric protein mCherry which was codon-optimized for heterologous expression in P. brasiliensis. We also report successful GP43 gene knock-down through the expression of intron-containing hairpin RNA (ihpRNA) from a Gateway-adapted cassette (cALf) which was purpose-built for gene silencing in a high-throughput manner. Gp43 transcript levels were reduced by 73.1±22.9% with this approach.

Conclusions/Significance

We have a firm conviction that the genetic transformation technique and the molecular tools herein described will have a relevant contribution in future Paracoccidioides spp. functional genomics research.

Diverse eukaryotes, including various fungi, utilize RNA interference (RNAi) pathways to regulate genome-wide gene expression. Since the initial characterization of these pathways and the demonstration of its artificial induction in the filamentous ascomycete Neurospora crassa, RNAi has emerged as the most robust reverse-genetic technique to scrutinize the function of genes and has been increasingly adopted in high-throughput functional genomics in search of new insights into fungal pathobiology. Herein, we have developed appropriate molecular tools and straightforward techniques to streamline the generation of stable loss-of-function phenotypes for the human-pathogen Paracoccidioides brasiliensis, which is phylogenetically related to Blastomyces dermatitidis, Coccidioides immitis and Histoplasma capsulatum. Likewise these thermo-dimorphic fungi, P. brasiliensis infection in immunocompetent or immunocompromised individuals ensue in a life-threatening systemic mycosis known as Paracoccidioidomycosis.

Correlation between histopathological and FT-Raman spectroscopy analysis of the liver of Swiss mice infected with Paracoccidioides brasiliensis

Paracoccidioidomycosis is the most important systemic mycosis in Latin America. The main entrance of the fungus is the airway. It primarily occurs in the lung, but in its disseminated form may affect any organ. The liver is one of the organs afflicted by this disease and its homeostasis may be impaired. The aim of the present study was to evaluate the evolution of paracoccidioidomycosis in the liver of Swiss mice and correlate morphological factors with the expression of gp43 and with physicochemical analysis via FT-Raman of the infected organ. According to colony forming unit (CFU) and granuloma counting, the first and second weeks were the periods when infection was most severe. Tissue response was characterized by the development of organized granulomas and widespread infection, with yeasts located within the macrophages and isolated hepatocytes. The gp43 molecule was distributed throughout the hepatic parenchyma, and immunostaining was constant in all observed periods. The main physicochemical changes of the infected liver were observed in the spectral ranges between 1700-1530 cm(-1) and 1370-1290 cm(-1), a peak shifting center attributed to phenylalanine and area variation of -CH2 and -CH3 compounds associated to collagen, respectively. Over time, there was a direct proportional relationship between the number of CFUs, the number of granulomas and the physicochemical changes in the liver of mice infected with Paracoccidioides brasiliensis. The expression of gp43 was similar in all observed periods.

Paracoccidioidomycosis in southern Rio Grande do Sul: a retrospective study of histopathologically diagnosed cases

Paracoccidioidomycosis (PCM) is a systemic mycosis caused by the fungus Paracoccidioides brasiliensis and is endemic to Brazil. The aim of this study was to perform a retrospective analysis of the PCM cases in the countryside south of Rio Grande do Sul, Brazil. The files from four histopathology laboratories located in the city of Pelotas were obtained, and all of the epidemiological and clinical data from the PCM diagnosed cases were collected for analysis. A total of 123 PCM cases diagnosed between 1966 and 2009 were selected. Of these patients, 104 (84.5%) were male, and 17 were female. The patients ranged from 02 to 92 years of age. Fifty-two cases (41.9%) were obtained from the oral pathology laboratory, and the remaining 71 cases (58.1%) were obtained from the three general pathology laboratories. Of all of the patients studied, 65.2% lived in rural zones and worked in agriculture or other related fields. Data on the evolution of this disease was available for 43 cases, and the time frame ranged from 20 to 2920 days (mean = 572.3 days). An accurate diagnosis performed in less than 30 days only occurred in 21% of the cases. PCM is endemic to the countryside of Rio Grande do Sul. Therefore, it is recommended that PCM be included as a differential diagnosis, mainly for individuals between 30 and 60 years of age, living in rural zones and who have respiratory signs and associated-oropharyngeal lesions.

Hemoglobin uptake by Paracoccidioides spp. is receptor-mediated

Iron is essential for the proliferation of fungal pathogens during infection. The availability of iron is limited due to its association with host proteins. Fungal pathogens have evolved different mechanisms to acquire iron from host; however, little is known regarding how Paracoccidioides species incorporate and metabolize this ion. In this work, host iron sources that are used by Paracoccidioides spp. were investigated. Robust fungal growth in the presence of the iron-containing molecules hemin and hemoglobin was observed. Paracoccidioides spp. present hemolytic activity and have the ability to internalize a protoporphyrin ring. Using real-time PCR and nanoUPLC-MS^E proteomic approaches, fungal growth in the presence of hemoglobin was shown to result in the positive regulation of transcripts that encode putative hemoglobin receptors, in addition to the induction of proteins that are required for amino acid metabolism and vacuolar protein degradation. In fact, one hemoglobin receptor ortholog, Rbt5, was identified as a surface GPI-anchored protein that recognized hemin, protoporphyrin and hemoglobin in vitro. Antisense RNA technology and Agrobacterium tumefaciens-mediated transformation were used to generate mitotically stable Pbrbt5 mutants. The knockdown strain had a lower survival inside macrophages and in mouse spleen when compared with the parental strain, which suggested that Rbt5 could act as a virulence factor. In summary, our data indicate that Paracoccidioides spp. can use hemoglobin as an iron source most likely through receptor-mediated pathways that might be relevant for pathogenic mechanisms.

Fungal infections contribute substantially to human morbidity and mortality. During infectious processes, fungi have evolved mechanisms to obtain iron from high-affinity iron-binding proteins. In the current study, we demonstrated that hemoglobin is the preferential host iron source for the thermodimorphic fungus Paracoccidioides spp. To acquire hemoglobin, the fungus presents hemolytic activity and the ability to internalize protoporphyrin rings. A putative hemoglobin receptor, Rbt5, was demonstrated to be GPI-anchored at the yeast cell surface. Rbt5 was able to bind to hemin, protoporphyrin and hemoglobin in vitro. When rbt5 expression was inhibited, the survival of Paracoccidioides sp. inside macrophages and the fungal burden in mouse spleen diminished, which indicated that Rbt5 could participate in the establishment of the fungus inside the host. Drugs or vaccines could be developed against Paracoccidioides spp. Rbt5 to disturb iron uptake of this micronutrient and, thus, the proliferation of the fungus. Moreover, this protein could be used in routes to introduce antifungal agents into fungal cells.

Ribosomal DNA nanoprobes studied by Fourier transform infrared spectroscopy

Paracoccidioides brasiliensis (P. brasiliensis) is a thermo-dimorphic fungus that causes paracoccidioidomycosis. Brazil epidemiological data shows that endemic areas are the subtropical regions, especially where agricultural activities predominate such as the Southeast, South, and Midwest. There are several tests to diagnose paracoccidioidomycosis, but they have many limitations such as low sensitivity, high cost, and a cross-reacting problem. In this work, gold nanoprobes were used to identify P. brasiliensis as an alternative diagnostic technique, which is easier to apply, costs less, and has great potential for application. The specific Ribosomal sequence of P. brasiliensis DNA was amplified and used to design the nanoprobes using a thiol-modified oligonucleotide. The results of positive and negative tests were done by UV-visible and Fourier Transform Infrared (FT-IR) measurements. The deconvolution of FT-IR sample spectra showed differences in the vibrational modes from the hydrogen bridge NHN and NHO bands that form the double helix DNA for samples matching the DNA sequence of nanoprobes that could be used to classify the samples.

Pro- and Anti-Inflammatory Cytokines Produced by Human Monocytes ChallengedIn VitrowithParacoccidioides brasiliensis

Monocytes and macrophages play a central role in innate and adaptive immune response against systemic fungal infections. Imbalances in suppressor or stimulatory cytokine secretion caused by these cells may influence disease development, microorganism death, and the nature of the adaptive immune response. This study analyzed the monocyte cytokine profiles of healthy individuals challenged with high and low virulent strains of P. brasiliensis and mRNA cytokine expression kinetics by reverse transcription polymerase chain reaction (RT-PCR). Peripheral blood monocytes from healthy volunteers were cultured in vitro with and without virulent (Pb18) or low virulence (Pb265) strains from P. brasiliensis viable yeast cells. Interleukin-1 beta (IL-1beta), IL-6, IL-8, IL-10, tumor necrosis factor-alpha (TNF-alpha), and transforming growth factor-beta (TGF-beta1) were measured in culture supernatants by enzyme immunoassay (ELISA), and mRNA cytokine expression was determined by RT-PCR at 0, 4, 8, 12, 18 and 48 hr. Both P. brasiliensis strains induced monocyte production of IL-1beta, IL-6, IL-10 and TNF-alpha. Pb18 induced higher levels of IL-1beta, IL-6, and IL-10 than Pb265. IL-8 and TGF-beta1 levels were not significantly different from those cultured without stimulus. The mRNA cytokine expression was similar to supernatant cytokines measured by ELISA. In vitro monocyte challenge with virulent P. brasiliensis strain induces earlier and higher levels of pro- and anti-inflammatory cytokines than low virulence strain.

B cell-deficient mice display enhanced susceptibility to Paracoccidioides brasiliensis Infection

Paracoccidioidomycosis (PCM) is a chronic granulomatous disease caused by the thermally dimorphic fungus Paracoccidioides brasiliensis. T helper 1 (Th1)-mediated immunity is primarily responsible for acquired resistance during P. brasiliensis infection. On the contrary, the susceptibility is associated with occurrence of type-2 immunity (Th2), which is characterized by IL-4 release, B cell activation, and production of antibodies. Although antibodies are frequently associated with severe PCM, it is not clear whether they contribute to susceptibility or merely constitute a marker of infection stage. Here, we assessed the function of B cells during experimental P. brasiliensis infection in mice, and our results showed that B cell-knockout (B(KO)) mice are more susceptible than their wild-type littermate controls (C57BL/6, WT). The B(KO) mice showed higher mortality rate, increased number of colony-forming units in the lungs, and larger granulomas than WT mice. In the absence of B cells, we observed high levels of IL-10, whereas IFN-γ, TNF-α, and IL-4 levels were similar between both groups. Finally, we showed that transference of WT immune serum to B(KO) mice resulted in diminished infiltration of inflammatory cells and better organization of the pulmonary granulomas. Taken together, these data suggest that B cells are effectively involved in the control of P. brasiliensis growth and organization of the granulomatous lesions observed during the experimental PCM.