Apresentação pseudotumoral de paracoccidioidomicose em sistema nervoso central: relato de caso / Pseudotumoral presentation of paracoccidioidomycosis in the central nervous system: case report / Informe pseudotumoral de paracoccidioidomicosis en el sistema nervioso central: reporte de caso

Introdução: A Paracoccidioidomicose causada pelo fungo dimórfico Paracoccidioides brasiliensis, é uma doença exclusiva de países latinos, com maior prevalência na América do Sul. A doença é adquirida por via respiratória, pela inalação de conídios fúngicos em suspenção no ar. O grande fator de risco para a aquisição do fungo está relacionado com o manejo do solo contaminado por profissionais agrícolas. Dentre as formas de acometimento sistêmico, pode ocorrer a infecção do SNC pelo P. brasiliensis, sendo a lesão parenquimatosa com apresentação pseudotumoral a de maior incidência, cursando mais comumente com sinais e sintomas motores e sugestivos de hipertensão intracraniana. O tratamento deve incluir medidas de suporte e terapia antifúngica (anfotericina B, sulfamidicos e azólicos), a qual deve ser iniciada precocemente. Objetivo: O objetivo deste trabalho foi relatar um caso clínico de paracoccidioidomicose em sistema nervoso central, que se apresentou com lesões pseudotumorais em lobo temporal esquerdo e hemisfério cerebelar direito, e discutir os métodos diagnósticos e terapêuticos empregados. Método: Trata-se de um estudo observacional descritivo, que se configura como um relato de caso de um paciente masculino, de 58 anos, internado em um hospital terciário de uma cidade do noroeste paulista, por quadro de paracoccidioidomicose de SNC. Conclusão: A apresentação pseudotumoral da paracoccidioidomicose em SNC é uma forma grave de apresentação da doença. Nesse sentido, é necessário que, em regiões endêmicas como o Brasil, seja sempre elencada a neuroparacoccidioidomicose como hipótese diagnóstica em pacientes com condições neurológicas, principalmente quando há, na história clínica do paciente, associação com atividades rurais. (AU)

Introduction: Paracoccidioidomycosis caused by the dimorphic fungus Paracoccidioides brasiliensis is a disease exclusive to Latin countries, with higher prevalence in South America. The disease is acquired by breathing, by inhaling fungal conidia in air. The great risk factor for fungus acquisition is related to soil management contaminated by agricultural professionals. Among the forms of systemic involvement, P. brasiliensis infection of the CNS may occur, with parenchymal lesion with pseudotumoral presentation being the most frequent, with motor signs and symptoms and suggestive of intracranial hypertension. Treatment should include supportive measures and antifungal therapy (amphotericin B, sulfamidic and azolic), which should be initiated early. Objective: The objective of this study was to report a clinical case of paracoccidioidomycosis in the central nervous system, which presented with pseudotumor lesions in the left temporal lobe and right cerebellar hemisphere, and to discuss the diagnostic and therapeutic methods used. Method: This is a descriptive observational study, which is configured as a case report of a 58-year-old male patient admitted to a tertiary hospital in a city of northwestern São Paulo, by CNS paracoccidioidomycosis. Conclusion: The pseudotumoral presentation of paracoccidioidomycosis in CNS is a severe form of disease presentation. In this sense, it is necessary that, in endemic regions such as Brazil, neuroparacoccidioidomycosis is always listed as a diagnostic hypothesis in patients with neurological conditions, especially when there is, in the patient's clinical history, an association with rural activities.(AU)

Introducción: La paracoccidioidomicosis causada por el hongo dimórfico Paracoccidioides brasiliensis es una enfermedad exclusiva de los países latinos, con mayor prevalencia en América del Sur, la enfermedad se adquiere por vía respiratoria, por inhalación de conidios fúngicos suspendidos en el aire. El principal factor de riesgo para la adquisición del hongo está relacionado con el manejo del suelo contaminado por parte de los profesionales agrícolas. Entre las formas de afectación sistémica, puede ocurrir infección del SNC por P. brasiliensis, siendo las lesiones parenquimatosas con presentación pseudotumoral las de mayor incidencia, más comúnmente con signos motores y síntomas sugestivos de hipertensión intracraneal. El tratamiento debe incluir medidas de soporte y terapia antifúngica (anfotericina B, sulfamidas y azoles), que...(AU)

Identification of Potentially Therapeutic Immunogenic Peptides From Paracoccidioides lutzii Species.

Paracoccidioidomycosis (PCM) is an endemic mycosis in Latin America caused by the thermodimorphic fungi of the genus Paracoccidioides spp. Paracoccidioides lutzii (PL) is one of the 5 species that constitute the Paracoccidioides genus. PL expresses low amounts of glycoprotein (Gp) 43 (PLGp43) and PLGp43 displays few epitopes in common with the P. brasiliensis (PB) immunodominant antigen PBGp43, which is commonly used for serological diagnosis of PCM. This difference in structure between the glycoproteins markedly reduces the efficiency of serological diagnosis in patients infected with PL. We previously demonstrated that peptide 10 (P10) from the PBGp43 induces protective immune responses in in vitro and in vivo models of PB PCM. Since, P10 has proven to be a promising therapeutic to combat PB, we sought to identify peptides in PL that could similarly be applied for the treatment of PCM. PL yeast cell proteins were isolated from PL: dendritic cell co-cultures and subjected to immunoproteomics. This approach identified 18 PL peptides that demonstrated in silico predictions for immunogenicity. Eight of the most promising peptides were synthesized and applied to lymphocytes obtained from peptide-immunized or PL-infected mice as well as to in vitro cultures with peptides or dendritic cells pulsed the peptides. The peptides LBR5, LBR6 and LBR8 efficiently promoted CD4+ and CD8+ T cell proliferation and dendritic cells pulsed with LBR1, LBR3, LBR7 or LBR8 stimulated CD4+ T cell proliferation. We observed increases of IFN-γ in the supernatants from primed T cells for the conditions with peptides without or with dendritic cells, although IL-2 levels only increased in response to LBR8. These novel immunogenic peptides derived from PL will be employed to develop new peptide vaccine approaches and the proteins from which they are derived can be used to develop new diagnostic assays for PL and possibly other Paracoccidioides spp. These findings identify and characterize new peptides with a promising therapeutic profile for future against this important neglected systemic mycosis.

Puzzling paracoccidioidomycosis: Factors associated with the severity of Paracoccidioides lutzii infections.

OBJECTIVES: Historically, the Brazilian Central-West region has had high numbers of paracoccidioidomycosis (PCM) cases caused by the dimorphic fungus Paracoccidioides lutzii. METHODS: This epidemiological, observational, analytical, cross-sectional study was performed to investigate the clinical and laboratory data of 44 PCM patients with a culture-proven P. lutzii infection. All patients were referred to the Systemic Mycosis Center, Júlio Muller University Hospital, Cuiabá, Brazil, during January 2017 to March 2020. The neutrophil to lymphocyte ratio (NLR) was calculated and dichotomized by its median value to include in the identification of factors associated with severity. RESULTS: At admission, 13 (31.7%) patients showed the disseminated multifocal chronic form of PCM and 16 (36.4%) patients met the clinical severity criteria. Treatment prescribed on admission did not follow the recommendations of the Brazilian Guideline for the Clinical Management of Paracoccidioidomycosis in 26% of the severe PCM cases (prevalence ratio 0.26, 95% confidence interval 0.14-0.49; P < 0.0001). Patients with severe PCM had a higher NLR that was greater than the median (≥4.11). CONCLUSIONS: The NLR biomarker complements the criteria for PCM severity. Applying the low-cost NLR test can greatly increase the diagnostic sensitivity when screening patients for PCM and contribute to better control of the disease, management of complications, and therapeutic strategies.

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 (ß-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, ß-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-1ß 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.

Paracoccidioides brasiliensis downmodulates α3 integrin levels in human lung epithelial cells in a TLR2-dependent manner.

Paracoccidioidomycosis (PCM) is the most prevalent systemic mycosis in Latin America and may be caused by the species Paracoccidioides brasiliensis. In the lungs, this fungus interacts with epithelial cells, activating host cell signalling pathways, resulting in the production of inflammatory mediators. This event may be initiated through the activation of Pattern-Recognition Receptors such as Toll-like Receptors (TLRs). By interacting with cell wall components, TLR2 is frequently related to fungal infections. In this work, we show that, after 24 h post-infection with P. brasiliensis, A549 lung epithelial cells presented higher TLR2 levels, which is important for IL-8 secretion. Besides, integrins may also participate in pathogen recognition by host cells. We verified that P. brasiliensis increased α3 integrin levels in A549 cells after 5 h of infection and promoted interaction between this receptor and TLR2. However, after 24 h, surprisingly, we verified a decrease of α3 integrin levels, which was dependent on direct contact between fungi and epithelial cells. Likewise, we observed that TLR2 is important to downmodulate α3 integrin levels after 24 h of infection. Thus, P. brasiliensis can modulate the host inflammatory response by exploiting host cell receptors and cell signalling pathways.

Paracoccidioides species present distinct fungal adherence to epithelial lung cells and promote different IL-8 secretion levels.

Fungi that belong to the genus Paracoccidioides are the etiologic agents of paracoccidioidomycosis, a human systemic mycosis, which occurs in Latin America. Epithelial cell is one of the first cells that interact with these fungi and responds by secreting inflammatory mediators such as cytokines. In the present study, we demonstrate that yeasts of different isolates of Paracoccidioides brasiliensis (Pb18 and Pb03) and Paracoccidioides lutzii (Pb01) distinctly promoted interleukin (IL)-8 secretion by the lung epithelial cell line A549. Depending on the isolate, this cytokine release may rely on the epithelial cell interaction with fungal secreted components or direct contact with the pathogen. In addition, adhesion of yeasts to the pulmonary epithelial cells was also different among Paracoccidioides isolates, and the highest percentage of A549 cells with adhered fungi was observed with P. lutzii. All Paracoccidioides isolates induced an expression increase of α3 and α5 integrins in A549 cells and, using small interfering RNA, we observed that the integrin silencing promoted a reduction of P. lutzii adhesion, which suggests the involvement of integrins in this event. Together, these results indicate that host epithelial cell response may depend on the isolate of Paracoccidioides.

A hidden battle in the dirt: Soil amoebae interactions with Paracoccidioides spp.

Paracoccidioides spp. are thermodimorphic fungi that cause a neglected tropical disease (paracoccidioidomycosis) that is endemic to Latin America. These fungi inhabit the soil, where they live as saprophytes with no need for a mammalian host to complete their life cycle. Despite this, they developed sophisticated virulence attributes allowing them not only to survive in host tissues but also to cause disease. A hypothesis for selective pressures driving the emergence or maintenance of virulence of soil fungi is their interaction with soil predators such as amoebae and helminths. We evaluated the presence of environmental amoeboid predators in soil from armadillo burrows where Paracoccidioides had been previously detected and tested if the interaction of Paracoccidioides with amoebae selects for fungi with increased virulence. Nematodes, ciliates, and amoebae-all potential predators of fungi-grew in cultures from soil samples. Microscopical observation and ITS sequencing identified the amoebae as Acanthamoeba spp, Allovahlkampfia spelaea, and Vermamoeba vermiformis. These three amoebae efficiently ingested, killed and digested Paracoccidioides spp. yeast cells, as did laboratory adapted axenic Acanthamoeba castellanii. Sequential co-cultivation of Paracoccidioides with A. castellanii selected for phenotypical traits related to the survival of the fungus within a natural predator as well as in murine macrophages and in vivo (Galleria mellonella and mice). These changes in virulence were linked to the accumulation of cell wall alpha-glucans, polysaccharides that mask recognition of fungal molecular patterns by host pattern recognition receptors. Altogether, our results indicate that Paracoccidioides inhabits a complex environment with multiple amoeboid predators that can exert selective pressure to guide the evolution of virulence traits.

Identification and characterization of Paracoccidioides lutzii proteins interacting with macrophages.

Paracoccidioidomycosis (PCM), caused by thermodimorphic fungi of the Paracoccidioides genus, is a systemic disorder that involves the lungs and other organs. The adherence of pathogenic microorganisms to host tissues is an essential event in the onset of colonization and spread. The host-pathogen interaction is a complex interplay between the defense mechanisms of the host and the efforts of pathogenic microorganisms to colonize it. Therefore, the identification of fungi proteins interacting with host proteins is an important step understanding the survival strategies of the fungus within the host. In this paper, we used affinity chromatography based on surface proteomics (ACSP) to investigate the interactions of pathogen proteins with host surface molecules. Paracoccidioides lutzii extracts enriched of surface proteins were captured by chromatographic resin, which was immobilized with macrophage cell surface proteins, and identified by mass spectrometry. A total of 215 proteins of P. lutzii were identified interacting with macrophage proteins. In silico analysis classified those proteins according to the presence of sites for N- and O-glycosylation and secretion by classical and non-classical pathways. Serine proteinase (SP) and fructose-1,6-bisphosphate aldolase (FBA) were identified in our proteomics analysis. Immunolocalization assay and flow cytometry both showed an increase in the expression of these two proteins during host-pathogen interaction.

Cross-talk between the Ras GTPase and the Hog1 survival pathways in response to nitrosative stress in Paracoccidioides brasiliensis.

Paracoccidioides brasiliensis is a temperature-dependent dimorphic fungus that cause paracoccidioidomycosis (PCM), the major systemic mycosis in Latin America. The capacity to evade the innate immune response of the host is due to P. brasiliensis ability to respond and to survive the nitrosative stress caused by phagocytic cells. However, the regulation of signal transduction pathways associated to nitrosative stress response are poorly understood. Ras GTPase play an important role in the various cellular events in many fungi. Ras, in its activated form (Ras-GTP), interacts with effector proteins and can initiate a kinase cascade. In this report, we investigated the role of Ras GTPase in P. brasiliensis after in vitro stimulus with nitric oxide (NO). We observed that low concentrations of NO induced cell proliferation in P. brasiliensis, while high concentrations promoted decrease in fungal viability, and both events were reversed in the presence of a NO scavenger. We observed that high levels of NO induced Ras activation and its S-nitrosylation. Additionally, we showed that Ras modulated the expression of antioxidant genes in response to nitrosative stress. We find that the Hog1 MAP kinase contributed to nitrosative stress response in P. brasiliensis in a Ras-dependent manner. Taken together, our data demonstrate the relationship between Ras-GTPase and Hog1 MAPK pathway allowing for the P. brasiliensis adaptation to nitrosative stress.

Autophagy in Paracoccidioides brasiliensis under normal mycelia to yeast transition and under selective nutrient deprivation.

Paracoccidioides spp. is a thermally dimorphic fungus endemic to Latin America and the etiological agent of paracoccidioidomycosis (PCM), a granulomatous disease acquired through fungal propagule inhalation by its mammalian host. The infection is established after successful mycelia to yeast transition in the host pulmonary alveoli. The challenging environment inside the host exposes the fungus to the need of adaptation in order to circumvent nutritional, thermal, oxidative, immunological and other stresses that can directly affect their survival. Considering that autophagy is a response to abrupt environmental changes and is induced by stress conditions, this study hypothesizes that this process might be crucially involved in the adaptation of Paracoccidioides spp. to the host and, therefore, it is essential for the proper establishment of the disease. By labelling autophagous vesicles with monodansylcadaverine, autophagy was observed as an early event in cells during the normal mycelium to yeast transition, as well as in yeast cells of P. brasiliensis under glucose deprivation, and under either rapamycin or 3-methyladenine (3-MA). Findings in this study demonstrated that autophagy is triggered in P. brasiliensis during the thermal-induced mycelium to yeast transition and by glucose-limited conditions in yeasts, both of which modulated by rapamycin or 3-MA. Certainly, further genetic and in vivo analyses are needed in order to finally address the contribution of autophagy for adaptation. Yet, our data propose that autophagy possibly plays an important role in Paracoccidioides brasiliensis virulence and pathogenicity.

Recovery of the Paracoccidioides brasiliensis virulence after animal passage promotes changes in the antioxidant repertoire of the fungus.

Paracoccidioides brasiliensis is the agent of paracoccidioidomycosis (PCM), a cause of disease in healthy and immunocompromised persons in Latin America. The infection begins after inhalation of the fungal propagules and their thermo-dimorphic shift to yeast form. The development of the disease depends on factors associated with the host immune response and the infectious agent's characteristics, especially virulence. The oxidative stress response is an important virulence attribute in several fungi. In this study, we assessed the enzymatic repertoire of responses to oxidative stress in the Pb18 isolate with different degrees of virulence. The virulence of attenuated Pb18 (aPb18) strain was recovered after several animal passages. Virulent strain (vPb18) showed an effective fungal oxidative stress response and several genes involved in response to oxidative stress were up-regulated in this isolate. These genes expressed the same profile when we recovered the phenotypic virulence in attenuated strain aPb18. Our study demonstrated that attenuated P. brasiliensis recovered their virulence after serial animal passages (vPb18), and this process positively modulated the fungus's antioxidant repertoire.

Ecology of Paracoccidioides brasiliensis, P. lutzii and related species: infection in armadillos, soil occurrence and mycological aspects.

Paracoccidioides brasiliensis and the related species P. americana, P. restrepiensis, P. venezuelensis, and P. lutzii (Ascomycota, Ajellomycetaceae) are the etiological agents of paracoccidoidoimycosis (PCM), one of the most important systemic mycoses in Latin America. They are dimorphic fungi, with a mycelial life cycle in soil and a yeast phase associated with tissues of mammalian hosts. This study aimed to detect Paracoccidioides spp. in armadillo tissues and associated soil samples in three well-defined geographic areas, including the Alta Floresta, an area not only endemic for PCM in the central region of Brazil but also of probable P. lutzii occurrence, whose ecology and geographic distribution are poorly elucidated. The isolates were genotyped by sequencing ITS-rDNA and the gp43-exon-2 region, and by PCR-RFLP of alpha tubulin (tub1) gene; mycological aspects such as yeast-to-mycelial transition, growth and conidial production in soil extract agar were also evaluated. We confirmed that while armadillos are highly infected by P. brasiliensis, including multiple infections by distinct genotypes or species (P. brasiliensis and P. americana) in the same animal, the same does not hold true for P. lutzii, which in turn seems to present less capacity for mycelial growth and conidial production, when developing in a soil-related condition.

Paracoccidioides brasiliensis presents metabolic reprogramming and secretes a serine proteinase during murine infection.

Paracoccidoides brasiliensis and Paracoccidioides lutzii, the etiologic agents of paracoccidioidomycosis, cause disease in healthy and immunocompromised persons in Latin America. We developed a method for harvesting P. brasiliensis yeast cells from infected murine lung to facilitate in vivo transcriptional and proteomic profiling. P. brasiliensis harvested at 6 h post-infection were analyzed using RNAseq and LC-MSE. In vivo yeast cells had 594 differentially expressed transcripts and 350 differentially expressed proteins. Integration of transcriptional and proteomic data indicated that early in infection (6 h), P. brasiliensis yeast cells underwent a shift in metabolism from glycolysis to ß-oxidation, upregulated detoxifying enzymes to defend against oxidative stress, and repressed cell wall biosynthesis. Bioinformatics and functional analyses also demonstrated that a serine proteinase was upregulated and secreted in vivo. To our knowledge this is the first study depicting transcriptional and proteomic data of P. brasiliensis yeast cells upon 6 h post-infection of mouse lung.

In Vivo Paracoccidioides sp. Biofilm on Vascular Prosthesis.

Paracoccidioidomycosis is an endemic mycosis caused by Paracoccidioides species limited to Latin America arising with the chronic form in 90% of cases. The capacity of microorganisms to form biofilms is considered of great importance medical since can contribute to the persistence and to the chronic state of the diseases. The ability of Paracoccidioides to form biofilm has been demonstrated in vitro. In our study, for the first time we have observed this capability in vivo on a vascular prosthesis using scanning electron microscope showing a dense network of Paracoccidioides yeasts covered by an extracellular matrix.

Anti-apoptotic effects of decyl gallate on the induction of apoptosis in A549 pneumocytes by Paracoccidioides brasiliensis gp43.

Apoptosis is considered an escape mechanism from the host immune system for the fungus Paracoccidioides spp, and it serves as a vehicle for entry into macrophages without stimulating microbicidal activities. Recently, gp43 of P. brasiliensis was demonstrated to be involved in this process. Therefore, as a new therapeutic alternative, it is very important to study compounds that could reduce the modulation of the induction of apoptosis caused by this fungus. Decyl gallate (G14) is a known antifungal compound, and we decided to investigate its anti-apoptotic properties. Our results demonstrate that G14 was effective against apoptosis induced by gp43, as observed in epithelial cells, and led to a reduction in DNA damage, Bak down-regulation and Bcl-2 up-regulation. Together, these data show that G14 presents promising anti-apoptotic activity.

Identification and characterisation of elongation factor Tu, a novel protein involved in Paracoccidioides brasiliensis-host interaction.

Paracoccidioides spp., which are temperature-dependent dimorphic fungi, are responsible for the most prevalent human systemic mycosis in Latin America, the paracoccidioidomycosis. The aim of this study was to characterise the involvement of elongation factor Tu (EF-Tu) in Paracoccidioides brasiliensis-host interaction. Adhesive properties were examined using recombinant PbEF-Tu proteins and the respective polyclonal anti-rPbEF-Tu antibody. Immunogold analysis demonstrated the surface location of EF-Tu in P. brasiliensis. Moreover, PbEF-Tu was found to bind to fibronectin and plasminogen by enzyme-linked immunosorbent assay, and it was determined that the binding to plasminogen is at least partly dependent on lysine residues and ionic interactions. To verify the participation of EF-Tu in the interaction of P. brasiliensis with pneumocytes, we blocked the respective protein with an anti-rPbEF-Tu antibody and evaluated the consequences on the interaction index by flow cytometry. During the interaction, we observed a decrease of 2- and 3-fold at 8 and 24 h, respectively, suggesting the contribution of EF-Tu in fungal adhesion/invasion.

Osmotic stress adaptation of Paracoccidioides lutzii, Pb01, monitored by proteomics.

The ability to respond to stressful conditions is essential for most living organisms. In pathogenic organisms, this response is required for effective transition from a saprophytic lifestyle to the establishment of pathogenic interactions within a susceptible host. Hyperosmotic stress has been used as a model to study signal transduction and seems to cause many cellular adaptations, including the alteration of protein expression and cellular volume as well as size regulation. In this work, we evaluated the proteomic profile of Paracoccidioides lutzii Pb01 yeast cells during osmotic stress induced by potassium chloride. We performed a high accuracy proteomic technique (NanoUPLC-MS(E)) to identify differentially expressed proteins during osmotic shock. The data describe an osmoadaptative response of this fungus when subjected to this treatment. Proteins involved in the synthesis of cell wall components were modulated, which suggested cell wall remodeling. In addition, alterations in the energy metabolism were observed. Furthermore, proteins involved in amino acid metabolism and hydrogen peroxide detoxification were modulated during osmotic stress. Our study suggests that P. lutzii Pb01. presents a vast osmoadaptative response that is composed of different proteins that act together to minimize the effects caused by osmotic stress.

Paracoccidioides brasiliensis infection promotes thymic disarrangement and premature egress of mature lymphocytes expressing prohibitive TCRs.

BACKGROUND: Paracoccidioidomycosis, a chronic granulomatous fungal disease caused by Paracoccidioides brasiliensis yeast cells affects mainly rural workers, albeit recently cases in immunosuppressed individuals has been reported. Protective immune response against P. brasiliensis is dependent on the activity of helper T cells especially IFN-γ-producing Th1 cells. It has been proposed that Paracoccidioides brasiliensis is able to modulate the immune response towards a permissive state and that the thymus plays a major role in it. METHODS: In this paper, we show that acute infection of BALB/c mice with P. brasiliensis virulent isolate (Pb18) might cause alterations in the thymic environment as well as the prohibitive TCR-expressing T cells in the spleens. RESULTS: After seven days of infection, we found yeast cells on the thymic stroma, the thymic epithelial cells (TEC) were altered regarding their spatial-orientation and inflammatory mediators gene expression was increased. Likewise, thymocytes (differentiating T cells) presented higher migratory ability in ex vivo experiments. Notwithstanding, P. brasiliensis-infected mice showed an increased frequency of prohibitive TCR-expressing T cells in the spleens, suggesting that the selection processes that occur in the thymus may be compromised during the acute infection. CONCLUSION: In this paper, for the first time, we show that acute infection with Paracoccidioides brasiliensis yeast cells promotes thymic alterations leading to a defective repertoire of peripheral T cells. The data presented here may represent new mechanisms by which P. brasiliensis subverts the immune response towards the chronic infection observed in humans.

New insights into a complex fungal pathogen: the case of Paracoccidioides spp.

Paracoccidioidomycosis is a systemic mycosis endemic to Latin America, with Paracoccidioides brasiliensis and P. lutzii being the causal agents of this disorder. Several issues have been raised in the 100 years since its discovery and in this article we discuss features of this fascinating fungal pathogen, including its biology, eco-epidemiology and aspects of its pathogenicity. We also consider some of its virulence determinants, the most recent advances in the study of its metabolic pathways and the molecular and genetic research tools developed for this research. We also review the animal models used to study host-fungal interactions and how the host defence mechanisms against this pathogen work.