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

Common virulence factors between Histoplasma and Paracoccidioides: Recognition of Hsp60 and Enolase by CR3 and plasmin receptors in host cells

Over the last two decades, the incidence of Invasive Fungal Infections (IFIs) globally has risen, posing a considerable challenge despite available antifungal therapies. Addressing this, the World Health Organization (WHO) prioritized research on specific fungi, notably Histoplasma spp. and Paracoccidioides spp. These dimorphic fungi have a mycelial life cycle in soil and a yeast phase associated with tissues of mammalian hosts. Inhalation of conidia and mycelial fragments initiates the infection, crucially transforming into the yeast form within the host, influenced by factors like temperature, host immunity, and hormonal status. Survival and multiplication within alveolar macrophages are crucial for disease progression, where innate immune responses play a pivotal role in overcoming physical barriers. The transition to pathogenic yeast, triggered by increased temperature, involves yeast phase-specific gene expression, closely linked to infection establishment and pathogenicity. Cell adhesion mechanisms during host-pathogen interactions are intricately linked to fungal virulence, which is critical for tissue colonization and disease development. Yeast replication within macrophages leads to their rupture, aiding pathogen dissemination. Immune cells, especially macrophages, dendritic cells, and neutrophils, are key players during infection control, with macrophages crucial for defense, tissue integrity, and pathogen elimination. Recognition of common virulence molecules such as heat- shock protein-60 (Hsp60) and enolase by pattern recognition receptors (PRRs), mainly via the complement receptor 3 (CR3) and plasmin receptor pathways, respectively, could be pivotal in host-pathogen interactions for Histoplasma spp. and Paracoccidioides spp., influencing adhesion, phagocytosis, and inflammatory regulation. This review provides a comprehensive overview of the dynamic of these two IFIs between host and pathogen. Further research into these fungi's virulence factors promises insights into pathogenic mechanisms, potentially guiding the development of effective treatment strategies.

Fast and cost-effective protocol to produce Paracoccidioides spp. antigens

INTRODUCTION

The existing methods for Paracoccidioides spp. antigen production are problematic in terms of standardization, specificity, stability, repeatability, and reproducibility.

OBJECTIVE

To optimize the methodology for Paracoccidioides spp. antigen production and evaluate its applicability in paracoccidioidomycosis immunodiagnosis.

MATERIALS AND METHODS

The antigens were obtained from Paracoccidioides lutzii isolates (01, 66, and 8334), Paracoccidioides brasiliensis sensu stricto (113), and Paracoccidioides restripiensis (B-339). These fungi were grown at 36 °C ± 1 °C, on modified Fava-Netto agar, according to Freitas et al. (2018). Paracoccidioides lutzii antigens were obtained after , 10, and 20 days of culture, whereas P. brasiliensis and P. restripiensis antigens were obtained after 10 days. Antigens were evaluated in natura, 10 and 20 times concentrated. Antigenic capacity was evaluated using a double immunodiffusion assay against serum samples from patients with paracoccidioidomycosis, histoplasmosis, and aspergillosis, and random blood donors.

RESULTS

Cross-reactivity between Paracoccidioides spp. antigens was observed when P. brasiliensis, P. restrepiensis antigens, and P. lutzii antigens were evaluated with the polyclonal antibodies against P. lutzii and P. brasiliensis, respectively. No cross-reactivity was obtained for polyclonal antibodies against Histoplasma capsulatum, Aspergillus fumigatus, and random blood donors. The proposed protocol allowed stable, repeatable, and reproducible genus-specific antigen production at a low cost and in a short cultivation time.

CONCLUSION

The proposed protocol allowed us to obtain genus-specific antigens that can be developed and reproduced in all laboratories in Brazil and South America, where paracoccidioidomycosis is a neglected disease, contributing to an early diagnosis, especially in endemic regions, regardless of the species.

Molecular Phylogenetic Analysis of Paracoccidioides Species Complex Present in Paracoccidioidomycosis Patient Tissue Samples

Paracoccidioidomycosis (PCM) is the main and most prevalent systemic mycosis in Latin America, that until recently, it was believed to be caused only by Paracoccidioides brasiliensis (P. brasiliensis). In 2006, researchers described three cryptic species: S1, PS2, PS3, and later, another one, PS4. In 2009, Paracoccidioides lutzii (Pb01-like) was described, and in 2017, a new nomenclature was proposed for the different agents: P. brasiliensis (S1), P. americana (PS2), P. restrepiensis (PS3), and P. venezuelensis (PS4). These species are not uniformly distributed throughout Latin America and, knowing that more than one cryptic species could coexist in some regions, we aimed to identify those species in patients’ biopsy samples for a better understanding of the distribution and occurrence of these recently described species in Botucatu region. The Hospital of Medical School of Botucatu—UNESP, which is a PCM study pole, is located in São Paulo State mid-west region and is classified as a PCM endemic area. Genotyping analyses of clinical specimens from these patients that have been diagnosed and treated in our Hospital could favor a possible correlation between genetic groups and mycological and clinical characteristics. For this, molecular techniques to differentiate Paracoccidioides species in these biopsies, such as DNA extraction, PCR, and sequencing of three target genes (ITS, CHS2, and ARF) were conducted. All the sequences were analyzed at BLAST to testify the presence of P. brasiliensis. The phylogenetic trees were constructed using Mega 7.0 software and showed that 100% of our positive samples were from S1 cryptic species, therefore P. brasiliensis. This is important data, demonstrating the predominance of this species in the São Paulo State region.

Molecular Interactions of the Copper Chaperone Atx1 of Paracoccidioides brasiliensis with Fungal Proteins Suggest a Crosstalk between Iron and Copper Homeostasis

Paracoccidioides spp. are endemic fungi from Latin America that cause Paracoccidioidomycosis, a systemic disease. These fungi present systems for high-affinity metal uptake, storage, and mobilization, which counteract host nutritional immunity and mitigate the toxic effects of metals. Regarding Cu mobilization, the metallochaperone Atx1 is regulated according to Cu bioavailability in Paracoccidioides spp., contributing to metal homeostasis. However, additional information in the literature on PbAtx1 is scarce. Therefore, in the present work, we aimed to study the PbAtx1 protein-protein interaction networks. Heterologous expressed PbAtx1 was used in a pull-down assay with Paracoccidioides brasiliensis cytoplasmic extract. Nineteen proteins that interacted with PbAtx1 were identified by HPLC-MS^E. Among them, a relevant finding was a Cytochrome b₅ (PbCyb5), regulated by Fe bioavailability in Aspergillus fumigatus and highly secreted by P. brasiliensis in Fe deprivation. We validated the interaction between PbAtx1-PbCyb5 through molecular modeling and far-Western analyses. It is known that there is a relationship between Fe homeostasis and Cu homeostasis in organisms. In this sense, would PbAtx1-PbCyb5 interaction be a new metal-sensor system? Would it be supported by the presence/absence of metals? We intend to answer those questions in future works to contribute to the understanding of the strategies employed by Paracoccidioides spp. to overcome host defenses.

Paracoccidioides lutzii Formamidase Contributes to Fungal Survival in Macrophages

Nitrogen is a crucial nutrient for microorganisms that compose essential biomolecules. However, hosts limit this nutrient as a strategy to counter infections, therefore, pathogens use adaptive mechanisms to uptake nitrogen from alternative sources. In fungi, nitrogen catabolite repression (NCR) activates transcription factors to acquire nitrogen from alternative sources when preferential sources are absent. Formamidase has been related to nitrogen depletion in Aspergillus nidulans through formamide degradation to use the released ammonia as a nitrogen source. In Paracoccidioides spp., formamidase is highly expressed in transcriptomic and proteomic analyses. Here, we aim to investigate the importance of formamidase to Paracoccidioides lutzii. Thereby, we developed a P. lutzii silenced strain of fmd gene (AsFmd) by antisense RNA technology using Agrobacterium tumefaciens-mediated transformation (ATMT). The AsFmd strain led to increased urease expression, an enzyme related to nitrogen assimilation in other fungi, suggesting that P. lutzii might explore urease as an alternative route for ammonia metabolism as a nitrogen source. Moreover, formamidase was important for fungal survival inside macrophages, as fungal recovery after macrophage infection was lower in AsFmd compared to wild-type (WT) strain. Our findings suggest potential alternatives of nitrogen acquisition regulation in P. lutzii, evidencing formamidase influence in fungal virulence.

Mesenchymal Stromal Cells: an Antimicrobial and Host-Directed Therapy for Complex Infectious Diseases

There is an urgent need for new antimicrobial strategies for treating complex infections and emerging pathogens. Human mesenchymal stromal cells (MSCs) are adult multipotent cells with antimicrobial properties, mediated through direct bactericidal activity and modulation of host innate and adaptive immune cells. More than 30 in vivo studies have reported on the use of human MSCs for the treatment of infectious diseases, with many more studies of animal MSCs in same-species models of infection. MSCs demonstrate potent antimicrobial effects against the major classes of human pathogens (bacteria, viruses, fungi, and parasites) across a wide range of infection models. Mechanistic studies have yielded important insight into their immunomodulatory and bactericidal activity, which can be enhanced through various forms of preconditioning. MSCs are being investigated in over 80 clinical trials for difficult-to-treat infectious diseases, including sepsis and pulmonary, intra-abdominal, cutaneous, and viral infections. Completed trials consistently report MSCs to be safe and well tolerated, with signals of efficacy against some infectious diseases. Although significant obstacles must be overcome to produce a standardized, affordable, clinical-grade cell therapy, these studies suggest that MSCs may have particular potential as an adjunct therapy in complex or resistant infections.

PbGP43 Genotyping Using Paraffin-Embedded Biopsies of Human Paracoccidioidomycosis Reveals a Genetically Distinct Lineage in the Paracoccidioides brasiliensis Complex

Paracoccidioidomycosis (PCM) is a systemic mycosis caused by a group of cryptic species embedded in the Paracoccidioides brasiliensis complex and Paracoccidioides lutzii. Four species were recently inferred to belong to the P. brasiliensis complex, but the high genetic diversity found in both human and environmental samples have suggested that the number of lineages may be higher. This study aimed to assess the 43-kilodalton glycoprotein genotypes (PbGP43) in paraffin-embedded samples from PCM patients to infer the phylogenetic lineages of the P. brasiliensis complex responsible for causing the infection. Formalin-fixed, paraffin-embedded (FFPE) tissue samples from patients with histopathological diagnosis of PCM were analyzed. DNAs were extracted and amplified for a region of the second exon of the PbGP43 gene. Products were sequenced and aligned with other PbGP43 sequences available. A haplotype network and the phylogenetic relationships among sequences were inferred. Amino acid substitutions were investigated regarding the potential to modify physicochemical properties in the proteins. Six phylogenetic lineages were identified as belonging to the P. brasiliensis complex. Two lineages did not group with any of the four recognized species of the complex, and, interestingly, one of them comprised only FFPE samples. A coinfection involving two lineages was found. Five parsimony-informative sites were identified and three of them showed radical non-synonymous substitutions with the potential to promote changes in the protein. This study expands the knowledge regarding the genetic diversity existing in the P. brasiliensis complex and shows the potential of FFPE samples in species identification and in detecting coinfections.

Epidemiology of paracoccidioidomycosis in Venezuela: a retrospective study from 1954 to 2019

BACKGROUND

Paracoccidioidomycosis (PCM) is a systemic mycosis endemic to Latin America. Etiological agents are Paracoccidioides species that diverge phylogenetically throughout South America.

OBJECTIVES

This study aimed to document the epidemiology of PCM in Venezuela.

METHODS

We have performed a retrospective cross-sectional descriptive study in 31,081 clinical records of patients from two reference centres during 65 years (1954-2019).

FINDINGS

PCM diagnosis was confirmed in 745 patients. Chronic PCM was the most prevalent form (90.06% cases); 80.67% were male and the most affected age range was 41-60. Farming and construction were the most prevalent occupation and Miranda State had a higher prevalence. Lung and skin were the most affected organs, followed by oral manifestations. Direct examination, culture and serology showed a high sensibility, and no statistical difference was observed among the diagnostic tools. Out of 17 Paracoccidioides isolates genotyped from Venezuela, one was typed as Paracoccidioides americana and 16 as Paracoccidioides venezuelensis.

MAIN CONCLUSIONS

Clinical manifestations observed, information about the epidemiology and molecular profile is essential not only for diagnosis but also for understanding therapeutic responses to mycotic drugs and prognosis. Therefore, it is necessary to sequence all positive isolated strains in order to confirm the dominance of P. venezuelensis in Venezuela.

Paracoccidioides brasiliensis activates mesenchymal stem cells through TLR2, TLR4, and Dectin-1

Numerous researchers have described the potential of bone marrow-derived mesenchymal stem cells (BM-MSCs) for the treatment of various infectious and inflammatory diseases. However, contrary to what has been reported, the transplantation of BM-MSCs in a mouse model of Paracoccidioides brasiliensis-induced pulmonary fibrosis exacerbated the inflammatory process and fibrosis, worsening the course of the infection. The aim of this work was to determine whether P. brasiliensis exerts an immunomodulatory effect on BM-MSCs. The results indicate that P. brasiliensis can activate BM-MSCs through a mechanism dependent on TLR2, TLR4 and Dectin-1. In addition, it was found that these fungal cells can adhere and internalize within BM-MSCs. Nonetheless, this process did not affect the survival of the fungus and on the contrary, triggered the expression of inflammatory mediators such as IL-6, IL-17, TNF-α, and TGF-β. The present findings correlate with the loss of a fungicidal effect and poor control of the fungus, evidenced by the count of the colony-forming units. Previously reported in vivo results are thus confirmed, showing that P. brasiliensis induces an inflammatory profile in BM-MSCs when producing pro-inflammatory molecules that amplify such response. Numerous researchers have described the potential of bone marrow-derived mesenchymal stem cells (BM-MSCs) for the treatment of various infectious and inflammatory diseases. However, contrary to what has been reported, the transplantation of BM-MSCs in a mouse model of Paracoccidioides brasiliensis-induced pulmonary fibrosis exacerbated the inflammatory process and fibrosis, worsening the course of the infection. The aim of this work was to determine whether P. brasiliensis exerts an immunomodulatory effect on BM-MSCs. The results indicate that P. brasiliensis can activate BM-MSCs through a mechanism dependent on TLR2, TLR4 and Dectin-1. In addition, it was found that these fungal cells can adhere and internalize within BM-MSCs. Nonetheless, this process did not affect the survival of the fungus and on the contrary, triggered the expression of inflammatory mediators such as IL-6, IL-17, TNF-α, and TGF-β. The present findings correlate with the loss of a fungicidal effect and poor control of the fungus, evidenced by the count of the colony-forming units. Previously reported in vivo results are thus confirmed, showing that P. brasiliensis induces an inflammatory profile in BM-MSCs when producing pro-inflammatory molecules that amplify such response.

Circulating Nestin-GFP+ Cells Participate in the Pathogenesis of Paracoccidioides brasiliensis in the Lungs

Multiple infectious diseases lead to impaired lung function. Revealing the cellular mechanisms involved in this impairment is crucial for the understanding of how the lungs shift from a physiologic to a pathologic state in each specific condition. In this context, we explored the pathogenesis of Paracoccidioidomycosis, which affects pulmonary functioning. The presence of cells expressing Nestin-GFP has been reported in different tissues, and their roles as tissue-specific progenitors have been stablished in particular organs. Here, we explored how Nestin-GFP⁺ cells are affected after lung infection by Paracoccidioides brasiliensis, a model of lung granulomatous inflammation with fibrotic outcome. We used Nestin-GFP transgenic mice, parabiosis surgery, confocal microscopy and flow cytometry to investigate the participation of Nestin-GFP⁺ cells in Paracoccidioides brasiliensis pathogenesis. We revealed that these cells increase in the lungs post-Paracoccidioides brasiliensis infection, accumulating around granulomas. This increase was due mainly to Nestin-GPF⁺ cells derived from the blood circulation, not associated to blood vessels, that co-express markers suggestive of hematopoietic cells (Sca-1, CD45 and CXCR4). Therefore, our findings suggest that circulating Nestin-GFP⁺ cells participate in the Paracoccidioides brasiliensis pathogenesis in the lungs.

An update on the occurrence of Paracoccidioides species in the Midwest region, Brazil: Molecular epidemiology, clinical aspects and serological profile of patients from Mato Grosso do Sul State

BACKGROUND

Paracoccidioidomycosis (PCM) is a systemic and endemic fungal infection in Latin American, mainly in Brazil. The majority of PCM cases occur in large areas in Brazil, comprising the South, Southeast and Midwest regions, with the latter demonstrating a higher incidence of the species Paracoccidioides lutzii.

METHODOLOGY AND MAIN FINDINGS

This study presents clinical, molecular and serological data of thirteen new PCM cases during 2016 to 2019 from the state of Mato Grosso do Sul, located in the Midwest region, Brazil. From these thirteen cases, sixteen clinical isolates were obtained and their genomic DNAs were subjected to genotyping by tub1 -PCR-RFLP. Results showed Paracoccidioides brasiliensis sensu stricto (S1) (11/16; 68.8%), Paracoccidioides restrepiensis (PS3) (4/16; 25.0%) and P. lutzii (1/16; 6.2%) as Paracoccidiodes species. Therefore, in order to understand whether the type of phylogenetic species that are circulating in the state influence the reactivity profile of serological tests, we performed double agar gel immunodiffusion (DID), using exoantigens from genotyped strains found in this series of PCM cases. Overall, our DID tests have been false negative in about 30% of confirmed PCM cases. All patients were male, most with current or previous rural activity, with ages ranging from 17 to 59 years, with 11 patients (84.6%) over 40 years of age. No clinical or epidemiological differences were found between Paracoccidioides species. However, it is important to note that the only case of P. lutzii died as an outcome.

CONCLUSIONS

This study suggests P. brasiliensis sensu stricto (S1) as the predominant species, showing its wide geographic distribution in Brazil. Furthermore, our findings revealed, for the first time, the occurrence of P. restrepiensis (PS3) in the state of Mato Grosso do Sul, Brazil. Despite our setbacks, it would be interesting to provide the complete sequencing of these clinical isolates to complement the molecular information presented.

Gene expression of Paracoccidioides virulence factors after interaction with macrophages and fibroblasts

BACKGROUND

Paracoccidioidomycosis (PCM) is a systemic mycosis with high prevalence in Latin America that is caused by thermodimorphic fungal species of the Paracoccidioides genus.

OBJECTIVES

In this study, we used quantitative polymerase chain reaction (qPCR) to investigate the expression of genes related to the virulence of Paracoccidioides brasiliensis (Pb18) and P. lutzii (Pb01) strains in their mycelial (M) and yeast (Y) forms after contact with alveolar macrophages (AMJ2-C11 cell line) and fibroblasts (MRC-5 cell line).

METHODS

The selected genes were those coding for 43 kDa glycoprotein (gp43), enolase, glyceraldehyde-3-phosphate dehydrogenase (GAPDH), 14-3-3 protein (30 kDa), phospholipase, and aspartyl protease.

FINDINGS

In the Pb18 M form, the aspartyl protease gene showed the highest expression among all genes tested, both before and after infection of host cells. In the Pb18 Y form after macrophage infection, the 14-3-3 gene showed the highest expression among all genes tested, followed by the phospholipase and gp43 genes, and their expression was 50-fold, 10-fold, and 6-fold higher, respectively, than that in the M form. After fibroblast infection with the Pb18 Y form, the 14-3-3 gene showed the highest expression, followed by the phospholipase and aspartyl protease genes, and their expression was 25-fold, 10-fold, and 10-fold higher, respectively, than that in the M form. Enolase and aspartyl protease genes were expressed upon infection of both cell lines. After macrophage infection with the Pb01 Y form, the 14-3-3 gene showed the highest expression, followed by the phospholipase and aspartyl protease genes, and their expression was 18-fold, 12.5-fold, and 6-fold higher, respectively, than that in the M form.

MAIN CONCLUSIONS

In conclusion, the data show that the expression of the genes analysed may be upregulated upon fungus-host interaction. Therefore, these genes may be involved in the pathogenesis of paracoccidioidomycosis.

The Trojan Horse Model in Paracoccidioides: A Fantastic Pathway to Survive Infecting Human Cells

Paracoccidioidomycosis (PCM) is the most relevant systemic endemic mycosis limited to Latin American countries. The etiological agents are thermally dimorphic species of the genus Paracoccidioides. Infection occurs via respiratory tract by inhalation of propagules from the environmental (saprophytic) phase. In the lung alveoli the fungus converts to the characteristic yeast phase (parasitic) where interact with extracellular matrix proteins, epithelial cells, and the host cellular immunity. The response involves phagocytic cells recognition but intracellular Paracoccidioides have demonstrated the ability to survive and also multiply inside the neutrophils, macrophages, giant cells, and dendritic cells. Persistence of Paracoccidioides as facultative intracellular pathogen is important in terms of the fungal load but also regarding to the possibility to disseminate penetrating other tissues even protected by the phagocytes. This strategy to invade other organs via transmigration of infected phagocytes is called Trojan horse mechanism and it was also described for other fungi and considered a factor of pathogenicity. This mini review comprises a literature revision of the spectrum of tools and mechanisms displayed by Paracoccidioides to overcame phagocytosis, discusses the Trojan horse model and the immunological context in proven models or the possibility that Paracoccidioides apply this tool for dissemination to other tissues.

Interacting with Hemoglobin: Paracoccidioides spp. Recruits hsp30 on Its Cell Surface for Enhanced Ability to Use This Iron Source

Paracoccidioides spp. are thermally dimorphic fungi that cause paracoccidioidomycosis and can affect both immunocompetent and immunocompromised individuals. The infection can lead to moderate or severe illness and death. Paracoccidioides spp. undergo micronutrients deprivation within the host, including iron. To overcome such cellular stress, this genus of fungi responds in multiple ways, such as the utilization of hemoglobin. A glycosylphosphatidylinositol (GPI)-anchored fungal receptor, Rbt5, has the primary role of acquiring the essential nutrient iron from hemoglobin. Conversely, it is not clear if additional proteins participate in the process of using hemoglobin by the fungus. Therefore, in order to investigate changes in the proteomic level of P. lutzii cell wall, we deprived the fungus of iron and then treated those cells with hemoglobin. Deprived iron cells were used as control. Next, we performed cell wall fractionation and the obtained proteins were submitted to nanoUPLC-MS^E. Protein expression levels of the cell wall F1 fraction of cells exposed to hemoglobin were compared with the protein expression of the cell wall F1 fraction of iron-deprived cells. Our results showed that P. lutzii exposure to hemoglobin increased the level of adhesins expression by the fungus, according to the proteomic data. We confirmed that the exposure of the fungus to hemoglobin increased its ability to adhere to macrophages by flow cytometry. In addition, we found that HSP30 of P. lutzii is a novel hemoglobin-binding protein and a possible heme oxygenase. In order to investigate the importance of HSP30 in the Paracoccidioides genus, we developed a Paracoccidioides brasiliensis knockdown strain of HSP30 via Agrobacterium tumefaciens-mediated transformation and demonstrated that silencing this gene decreases the ability of P. brasiliensis to use hemoglobin as a nutrient source. Additional studies are needed to establish HSP30 as a virulence factor, which can support the development of new therapeutic and/or diagnostic approaches.

Unraveling the susceptibility of paracoccidioidomycosis: Insights towards the pathogen-immune interplay and immunogenetics

Paracoccidioidomycosis (PCM) is a life-threatening systemic mycosis caused by Paracoccidioides spp. This disease comprises three clinical forms: symptomatic acute and chronic forms (PCM disease) and PCM infection, a latent form without clinical symptoms. PCM disease differs markedly according to severity, clinical manifestations, and host immune response. Fungal virulence factors and adhesion molecules are determinants for entry, latency, immune escape and invasion, and dissemination in the host. Neutrophils and macrophages play a paramount role in first-line defense against the fungus through the recognition of antigens by pattern recognition receptors (PRRs), activating their microbicidal machinery. Furthermore, the clinical outcome of the PCM is strongly associated with the variability of cytokines and immunoglobulins produced by T and B cells. While the mechanisms that mediate susceptibility or resistance to infection are dictated by the immune system, some genetic factors may alter gene expression and its final products and, hence, modulate how the organism responds to infection and injury. This review outlines the main findings relative to this topic, addressing the complexity of the immune response triggered by Paracoccidioides spp. infection from preclinical investigations to studies in humans. Here, we focus on mechanisms of fungal pathogenesis, the patterns of innate and adaptive immunity, and the genetic and molecular basis related to immune response and susceptibility to the development of the PCM and its clinical forms. Immunogenetic features such as HLA system, cytokines/cytokines receptors genes and other immune-related genes, and miRNAs are likewise discussed. Finally, we point out the occurrence of PCM in patients with primary immunodeficiencies and call attention to the research gaps and challenges faced by the PCM field.

Characterization of a Paracoccidioides spp. strain from southeastern Brazil genotyped as Paracoccidioides restrepiensis (PS3) and review of this phylogenetic species

Phylogenetic species of Paracoccidioides brasiliensis complex (S1a and S1b, PS2, PS3, and PS4) and Paracoccidioides lutzii are agents of paracoccidioidomycosis, an endemic fungal disease in Latin America. P. restrepiensis (PS3 genotype) was classified as monophyletic and geographically restricted to Colombia and neighboring territories. BAT (or Pb-327B) was isolated from a patient living in the southeast region of Brazil but with genotype similar to Colombian Paracoccidioides spp. strains. This study aimed to define the phylogenetic species of BAT isolate by using additional genotyping methods, as well as reviewing the epidemiological and clinical studies related to P. restrepiensis isolates. Genomic DNA of BAT isolate and reference strains of P. brasiliensis sensu stricto (S1b), P. americana (PS2), P. restrepiensis (PS3), and P. lutzii were analyzed by conventional polymerase chain reaction (PCR) of partial gp43 exon 2 loci, by PCR-RFLP technique of tub1 gene, and by sequencing of the whole gp43 exon 2 loci. Here, we show that BAT isolate belongs to P. restrepiensis species, which is an unusual identification in southeastern Brazil, where P. brasiliensis sensu stricto is the prevalent genotype. This identification has relevance for geographical distribution and propagation of the genus Paracoccidioides in South America.

Propionate metabolism in a human pathogenic fungus: proteomic and biochemical analyses

Fungi of the complex Paracoccidioides spp. are thermodimorphic organisms that cause Paracoccidioidomycosis, one of the most prevalent mycoses in Latin America. These fungi present metabolic mechanisms that contribute to the fungal survival in host tissues. Paracoccidioides lutzii activates glycolysis and fermentation while inactivates aerobic metabolism in iron deprivation, a condition found during infection. In lungs Paracoccidioides brasiliensis face a glucose poor environment and relies on the beta-oxidation to support energy requirement. During mycelium to yeast transition P. lutzii cells up-regulate transcripts related to lipid metabolism and cell wall remodeling in order to cope with the host body temperature. Paracoccidioides spp. cells also induce transcripts/enzymes of the methylcitrate cycle (MCC), a pathway responsible for propionyl-CoA metabolism. Propionyl-CoA is a toxic compound formed during the degradation of odd-chain fatty acids, branched chain amino acids and cholesterol. Therefore, fungi require a functional MCC for full virulence and the ability to metabolize propionyl-CoA is related to the virulence traits in Paracoccidioides spp. On this way we sought to characterize the propionate metabolism in Paracoccidioides spp. The data collected showed that P. lutzii grows in propionate and activates the MCC by accumulating transcripts and proteins of methylcitrate synthase (MCS), methylcitrate dehydratase (MCD) and methylisocitrate lyase (MCL). Biochemical characterization of MCS showed that the enzyme is regulated by phosphorylation, an event not yet described. Proteomic analyses further indicate that P. lutzii yeast cells degrades lipids and amino acids to support the carbon requirement for propionate metabolism. The induction of a putative propionate kinase suggests that fungal cells use propionyl-phosphate as an intermediate in the production of toxic propionyl-CoA. Concluding, the metabolism of propionate in P. lutzii is under regulation at transcriptional and phosphorylation levels and that survival on this carbon source requires additional mechanisms other than activation of MCC.

[Climate change and systemic fungal infections]

BACKGROUND

Climate change may cause profound and complex changes in the prevalence of infectious diseases. Obligate pathogenic fungi causing endemic mycoses and the agents of cryptococcosis are environmental pathogens adapted to environmental niches. They may be exposed to changing climatic conditions, which may change the epidemiology of human infections.

OBJECTIVES

To review documented changes in the epidemiology of endemic fungal infections and cryptococcosis. To review evidence that changing climate is a potential mechanism for changes in the epidemiology of these infections.

METHODS

A selective literature review focusing on endemic mycoses and cryptococcosis.

RESULTS

Changes in endemic regions of infections caused by C. gattii and selected endemic mycoses have been well documented. Significant increases in the incidence of infections have been demonstrated for some areas. Climatic factors (temperature, precipitation, and extreme weather events), changes in land use, distribution of potential host animals, and global trade routes are discussed as contributory factors.

CONCLUSIONS

Improved surveillance of fungal infections of humans and animals including molecular typing of clinical and environmental isolates is necessary to understand the epidemiology of these infections. The characterization of environmental niches, mechanisms of distribution of fungi, and fungal adaptation mechanisms are needed to guide prevention strategies.

Fungal evolution: major ecological adaptations and evolutionary transitions

Fungi are a highly diverse group of heterotrophic eukaryotes characterized by the absence of phagotrophy and the presence of a chitinous cell wall. While unicellular fungi are far from rare, part of the evolutionary success of the group resides in their ability to grow indefinitely as a cylindrical multinucleated cell (hypha). Armed with these morphological traits and with an extremely high metabolical diversity, fungi have conquered numerous ecological niches and have shaped a whole world of interactions with other living organisms. Herein we survey the main evolutionary and ecological processes that have guided fungal diversity. We will first review the ecology and evolution of the zoosporic lineages and the process of terrestrialization, as one of the major evolutionary transitions in this kingdom. Several plausible scenarios have been proposed for fungal terrestralization and we here propose a new scenario, which considers icy environments as a transitory niche between water and emerged land. We then focus on exploring the main ecological relationships of Fungi with other organisms (other fungi, protozoans, animals and plants), as well as the origin of adaptations to certain specialized ecological niches within the group (lichens, black fungi and yeasts). Throughout this review we use an evolutionary and comparative-genomics perspective to understand fungal ecological diversity. Finally, we highlight the importance of genome-enabled inferences to envision plausible narratives and scenarios for important transitions.

ParaDB: A manually curated database containing genomic annotation for the human pathogenic fungi Paracoccidioides spp

BACKGROUND

The genus Paracoccidioides consists of thermodymorphic fungi responsible for Paracoccidioidomycosis (PCM), a systemic mycosis that has been registered to affect ~10 million people in Latin America. Biogeographical data subdivided the genus Paracoccidioides in five divergent subgroups, which have been recently classified as different species. Genomic sequencing of five Paracoccidioides isolates, representing each of these subgroups/species provided an important framework for the development of post-genomic studies with these fungi. However, functional annotations of these genomes have not been submitted to manual curation and, as a result, ~60-90% of the Paracoccidioides protein-coding genes (depending on isolate/annotation) are currently described as responsible for hypothetical proteins, without any further functional/structural description.

PRINCIPAL FINDINGS

The present work reviews the functional assignment of Paracoccidioides genes, reducing the number of hypothetical proteins to ~25-28%. These results were compiled in a relational database called ParaDB, dedicated to the main representatives of Paracoccidioides spp. ParaDB can be accessed through a friendly graphical interface, which offers search tools based on keywords or protein/DNA sequences. All data contained in ParaDB can be partially or completely downloaded through spreadsheet, multi-fasta and GFF3-formatted files, which can be subsequently used in a variety of downstream functional analyses. Moreover, the entire ParaDB environment has been configured in a Docker service, which has been submitted to the GitHub repository, ensuring long-term data availability to researchers. This service can be downloaded and used to perform fully functional local installations of the database in alternative computing ecosystems, allowing users to conduct their data mining and analyses in a personal and stable working environment.

CONCLUSIONS

These new annotations greatly reduce the number of genes identified solely as hypothetical proteins and are integrated into a dedicated database, providing resources to assist researchers in this field to conduct post-genomic studies with this group of human pathogenic fungi.

Thiosemicarbazone of lapachol acts on cell membrane in Paracoccidioides brasiliensis

Paracoccidioidomycosis (PCM) is the most prevalent systemic mycosis in Latin American countries. Amphotericin B, sulfonamides, and azoles may be used in the treatment of PCM. However, the high toxicity, prolonged course of treatment, and significant frequency of disease relapse compromise their use. Therefore, there is a need to seek new therapeutic options. We conducted tests with thiosemicarbazone of lapachol (TSC-lap) to determine the antifungal activity and phenotypic effects against several isolates of Paracoccidioides spp. In addition, we evaluated the toxicity against murine macrophages and the ability to enhance phagocytosis. Further, we verified that TSC-lap was active against yeasts but did not show any interaction with the drugs tested. The TSC-lap showed no toxicity at the concentration of 40 μg/ml in macrophages, and at 15.6 μg/ml it could increase the phagocytic index. We observed that this compound induced in vitro ultrastructural changes manifested as withered and broken cells beyond a disorganized cytoplasm with accumulation of granules. We did not observe indications of activity in the cell wall, although membrane damages were noted. We observed alterations in the membrane permeability, culminating in a significant increase in K+ efflux and a gradual loss of the cellular content with increase in the concentration of TSC-lap. In addition, we showed a significant reduction of ergosterol amount in the Pb18 membrane. These data reinforce the possible mechanism of action of this compound to be closely associated with ergosterol biosynthesis and reaffirms the antifungal potential of TSC-lap against Paracoccidioides spp.

DC-SIGN and VDR polymorphisms are associated with chronic form of paracoccidioidomycosis with oral manifestations

Paracoccidioidomycosis (PCM) is a granulomatous disease caused by fungi of the species complex of the Paracoccidioides genus. One of the main clinical manifestations of PCM is the presence of oral lesions with the presence of epithelioid granulomas. In this work, we aimed to evaluate the frequency of SNPs in the TNF-α, JAK1, VDR, DC-SIGN and FcγRIIa genes in patients with chronic PCM and verify possible association of these SNPs with the organisation pattern of the granulomas in the oral lesions. A total of 66 samples of DNA were obtained from oral lesions biopsies and 106 DNA samples were obtained from healthy individuals. The individuals were genotyped for SNPs in DC-SIGN (rs4804803), FcγRIIa (rs1801274), JAK1 (rs11208534), TNF-α (rs1800629) and VDR (rs7975232) by real-time PCR and allele discrimination method. Granulomas were classified as loose or dense according to the histological pattern. In the VDR (rs7975232), the CC genotype (P < 0.001, OR = 5.94, 95% CI = 2.07-17.05), and the C allele (P = 0.027, OR = 2.71, 95% CI = 1.07-6.86), as well as the GG genotype in DC-SIGN (rs4804803) (P = 0.032, OR: 3.76, 95%, I = 1.06-13.38) are associated with an increased risk of oral PCM. Our data indicate that VDR and DC-SIGN genetics variations are related to the susceptibility of oral PCM in the group of patients analysed.

Evaluation of Caenorhabditis elegans as a host model for Paracoccidioides brasiliensis and Paracoccidioides lutzii

Paracoccidioidomycosis is a systemic fungal infection affecting mainly Latin American countries that is caused by Paracoccidioides brasiliensis and Paracoccidioides lutzii. During the study of fungal pathogenesis, in vivo studies are crucial to understand the overall mechanisms involving the infection as well as to search for new therapeutic treatments and diagnosis. Caenorhabditis elegans is described as an infection model for different fungi species and a well-characterized organism to study the innate immune response. This study evaluates C. elegans as an infection model for Paracoccidioides spp. It was observed that both species do not cause infection in C. elegans, as occurs with Candida albicans, and one possible explanation is that the irregular size and shape of Paracoccidioides spp. difficult the ingestion of these fungi by the nematode. Besides this difficulty in the infection, we could observe that the simple exposition of C. elegans to Paracoccidioides species was able to trigger a distinct pattern of expression of antimicrobial peptide genes. The expression of cnc-4, nlpl-27 and nlp-31 was superior after the exposure to P. brasiliensis in comparison to P. lutzii (P < 0.05), and these findings demonstrate important differences regarding innate immune response activation caused by the two species of the Paracoccidioides genus.

The Interaction of Human Pathogenic Fungi With C-Type Lectin Receptors

Fungi, usually present as commensals, are a major cause of opportunistic infections in immunocompromised patients. Such infections, if not diagnosed or treated properly, can prove fatal. However, in most cases healthy individuals are able to avert the fungal attacks by mounting proper antifungal immune responses. Among the pattern recognition receptors (PRRs), C-type lectin receptors (CLRs) are the major players in antifungal immunity. CLRs can recognize carbohydrate ligands, such as β-glucans and mannans, which are mainly found on fungal cell surfaces. They induce proinflammatory immune reactions, including phagocytosis, oxidative burst, cytokine, and chemokine production from innate effector cells, as well as activation of adaptive immunity via Th17 responses. CLRs such as Dectin-1, Dectin-2, Mincle, mannose receptor (MR), and DC-SIGN can recognize many disease-causing fungi and also collaborate with each other as well as other PRRs in mounting a fungi-specific immune response. Mutations in these receptors affect the host response and have been linked to a higher risk in contracting fungal infections. This review focuses on how CLRs on various immune cells orchestrate the antifungal response and on the contribution of single nucleotide polymorphisms in these receptors toward the risk of developing such infections.

Overview of &#946;-Glucans from Laminaria spp.: Immunomodulation Properties and Applications on Biologic Models

Glucans are a group of glucose polymers that are found in bacteria, algae, fungi, and plants. While their properties are well known, their biochemical and solubility characteristics vary considerably, and glucans obtained from different sources can have different applications. Research has described the bioactivity of β-glucans extracted from the algae of the Laminaria genus, including in vivo and in vitro studies assessing pro- and anti-inflammatory cytokines, vaccine production, inhibition of cell proliferation, and anti- and pro-oxidant activity. Thus, the objective of this article was to review the potential application of β-glucans from Laminaria spp. in terms of their immunomodulatory properties, microorganism host interaction, anti-cancer activity and vaccine development.

Species boundaries in the human pathogen Paracoccidioides

The use of molecular taxonomy for identifying recently diverged species has transformed the study of speciation in fungi. The pathogenic fungus Paracoccidioides spp has been hypothesized to be composed of five phylogenetic species, four of which compose the brasiliensis species complex. Nuclear gene genealogies support this divergence scenario, but mitochondrial loci do not; while all species from the brasiliensis complex are differentiated at nuclear coding loci, they are not at mitochondrial loci. We addressed the source of this incongruity using 11 previously published gene fragments, 10 newly-sequenced nuclear non-coding loci, and 10 microsatellites. We hypothesized and further demonstrated that the mito-nuclear incongruence in the brasiliensis species complex results from interspecific hybridization and mitochondrial introgression, a common phenomenon in eukaryotes. Additional population genetic analyses revealed possible nuclear introgression but much less than that seen in the mitochondrion. Our results are consistent with a divergence scenario of secondary contact and subsequent mitochondrial introgression despite the continued persistence of species boundaries. We also suggest that yeast morphology slightly-but significantly-differs across all five Paracoccidioides species and propose to elevate four of these phylogenetic species to formally described taxonomic species.

Standardization and validation of Dot-ELISA assay for Paracoccidioides brasiliensis antibody detection

Background

Paracoccidioidomycosis (PCM) is a neglected systemic mycosis caused by a dimorphic fungus of the Paracoccidioides genus. The standard diagnosis is based on isolation of the fungi in culture, and by microscopic visualization of characteristic multiple budding yeast cells in biological samples. However, in some situations, access to the site of injury prevents the collection of biological material. A variety of immuno-serological techniques has proven useful for allowing inferring diagnosis with a certain degree of certainty, thus optimizing time. The aim of this study was to standardize and validate the Dot-ELISA (DE) assay, comparing it with the serological standard, double immunodiffusion (DI).

Methods

In order to standardize the DE assay, 143 serum samples were used. Out of those, 23 were from apparently healthy patients, 77 were from patients with confirmed PCM and 43 were from patients with other lung infections (tuberculosis, aspergillosis and histoplasmosis). To validate the DE technique, 300 serum samples from patients with PCM clinical suspicion (probable and possible cases) were employed, and these results were compared with those of DI.

Results

The DE assay showed sensitivity of 91%, specificity of 95.4%, positive predictive value of 96%, negative predictive value of 98.2%, accuracy of 93%, and great precision (k = 0.93). In addition, the nitrocellulose membranes have proved to be viable for using at least 90 days after P. brasiliensis B-339 antigen sensitization.

Conclusion

Dot-ELISA method was found to be an extremely promising tool as serologic screening technique, because of its high sensitivity. Furthermore, Dot-ELISA shows the prospect of being transferred to laboratories of mycoserology including those with fewer resources or even to be used directly in the field. It has an excellent shelf life – membranes coated with antigen can be used for testing without changes in the pattern of reactivity among laboratories – and presents reliable values of sensitivity, specificity, predictive values, accuracy and a high correlation with the serological standard methodology. Based on the present findings, it possible to state that this technique constitutes a remarkable option to be used in routine diagnosis for public health centers.