Candida albicans increases the aerobic glycolysis and activates MAPK-dependent inflammatory response of liver sinusoidal endothelial cells.

The liver, and more specifically, the liver sinusoidal endothelial cells, constitute the beginning of one of the most important responses for the elimination of hematogenously disseminated Candida albicans. Therefore, we aimed to study the mechanisms involved in the interaction between these cells and C. albicans. Transcriptomics-based analysis showed an increase in the expression of genes related to the immune response (including receptors, cytokines, and adhesion molecules), as well as to aerobic glycolysis. Further in vitro analyses showed that IL-6 production in response to C. albicans is controlled by MyD88- and SYK-pathways, suggesting an involvement of Toll-like and C-type lectin receptors and the subsequent activation of the MAP-kinases and c-Fos/AP-1 transcription factor. In addition, liver sinusoidal endothelial cells undergo metabolic reprogramming towards aerobic glycolysis induced by C. albicans, as confirmed by the increased Extracellular Acidification Rate and the overexpression of enolase (Eno2), hexonikase (Hk2) and glucose transporter 1 (Slc2a1). In conclusion, these results indicate that the hepatic endothelium responds to C. albicans by increasing aerobic glycolysis and promoting an inflammatory environment.

Microbiota and fungal-bacterial interactions in the cystic fibrosis lung.

The most common genetic hereditary disease affecting Caucasians is cystic fibrosis (CF), which is caused by autosomal recessive mutations in the CFTR gene. The most serious consequence is the production of a thick and sticky mucus in the respiratory tract, which entraps airborne microorganisms and facilitates colonization, inflammation and infection. Therefore, the present article compiles the information about the microbiota and, particularly, the inter-kingdom fungal-bacterial interactions in the CF lung, the molecules involved and the potential effects that these interactions may have on the course of the disease. Among the bacterial compounds, quorum sensing-regulated molecules such as homoserine lactones, phenazines, rhamnolipids, quinolones and siderophores (pyoverdine and pyochelin) stand out, but volatile organic compounds, maltophilin and CF-related bacteriophages are also explained. These molecules exhibit diverse antifungal mechanisms, including iron starvation and induction of reactive oxygen and nitrogen species production. The fungal compounds are less studied, but they include cell wall components, siderophores, patulin and farnesol. Despite the apparent competition between microorganisms, the persistence of significant rates of bacterial-fungal co-colonization in CF suggests that numerous variables influence it. In conclusion, it is crucial to increase scientific and economic efforts to intensify studies on the bacterial-fungal inter-kingdom interactions in the CF lung.

Dot Immunobinding Assay for the Rapid Serodetection of Scedosporium/Lomentospora in Cystic Fibrosis Patients.

The detection of Scedosporium/Lomentospora is still based on non-standardized low-sensitivity culture procedures. This fact is particularly worrying in patients with cystic fibrosis (CF), where these fungi are the second most common filamentous fungi isolated, because a poor and delayed diagnosis can worsen the prognosis of the disease. To contribute to the discovery of new diagnostic strategies, a rapid serological dot immunobinding assay (DIA) that allows the detection of serum IgG against Scedosporium/Lomentospora in less than 15 min was developed. A crude protein extract from the conidia and hyphae of Scedosporium boydii was employed as a fungal antigen. The DIA was evaluated using 303 CF serum samples (162 patients) grouped according to the detection of Scedosporium/Lomentospora in the respiratory sample by culture, obtaining a sensitivity and specificity of 90.48% and 79.30%, respectively; positive and negative predictive values of 54.81% and 96.77%, and an efficiency of 81.72%. The clinical factors associated with the results were also studied using a univariate and a multivariate analysis, which showed that Scedosporium/Lomentospora positive sputum, elevated anti-Aspergillus serum IgG and chronic Pseudomonas aeruginosa infection were significantly associated with a positive result in DIA, while Staphylococcus aureus positive sputum showed a negative association. In conclusion, the test developed can offer a complementary, rapid, simple and sensitive method to contribute to the diagnosis of Scedosporium/Lomentospora in patients with CF.

Nitrogen, Iron and Zinc Acquisition: Key Nutrients to Aspergillus fumigatus Virulence.

Aspergillus fumigatus is a ubiquitous soil decomposer and an opportunistic pathogen that is characterized by its large metabolic machinery for acquiring nutrients from media. Lately, an ever-increasing number of genes involved in fungal nutrition has been associated with its virulence. Of these, nitrogen, iron, and zinc metabolism-related genes are particularly noteworthy, since 78% of them have a direct implication in virulence. In this review, we describe the sensing, uptake and regulation process of the acquisition of these nutrients, the connections between pathways and the virulence-implicated genes. Nevertheless, only 40% of the genes mentioned in this review have been assayed for roles in virulence, leaving a wide field of knowledge that remains uncertain and might offer new therapeutic and diagnostic targets.

ELISA Test for the Serological Detection of Scedosporium/Lomentospora in Cystic Fibrosis Patients.

The detection and diagnosis of the opportunistic fungi Scedosporium spp. and Lomentospora prolificans still relies mainly on low-sensitive culture-based methods. This fact is especially worrying in Cystic Fibrosis (CF) patients in whom these fungal species are frequently isolated and may increase the risk of suffering from an infection or other health problems. Therefore, with the purpose of developing a serologic detection method for Scedosporium/Lomentospora, four different Scedosporium boydii protein extracts (whole cell protein extract, secretome, total cell surface and conidial surface associated proteins) were studied by ELISA to select the most useful for IgG detection in sera from CF patients. The four extracts were able to discriminate the Scedosporium/Lomentospora-infected from Aspergillus-infected and non-infected patients. However, the whole cell protein extract was the one selected, as it was the one with the highest output in terms of protein concentration per ml of fungal culture used, and its discriminatory capacity was the best. The ELISA test developed was then assayed with 212 sera from CF patients and it showed to be able to detect Scedosporium spp. and Lomentospora prolificans with very high sensitivity and specificity, 86%-100% and 93%-99%, respectively, depending on the cut-off value chosen (four values were proposed A450nm= 0.5837, A450nm= 0.6042, A450nm= 0.6404, and A450nm= 0.7099). Thus, although more research is needed to reach a standardized method, this ELISA platform offers a rapid, low-cost and easy solution to detect these elusive fungi through minimally invasive sampling, allowing the monitoring of the humoral response to fungal presence.

Fumagillin, a Mycotoxin of Aspergillus fumigatus: Biosynthesis, Biological Activities, Detection, and Applications.

Fumagillin is a mycotoxin produced, above all, by the saprophytic filamentous fungus Aspergillus fumigatus. This mold is an opportunistic pathogen that can cause invasive aspergillosis, a disease that has high mortality rates linked to it. Its ability to adapt to environmental stresses through the production of secondary metabolites, including several mycotoxins (gliotoxin, fumagillin, pseurotin A, etc.) also seem to play an important role in causing these infections. Since the discovery of the A. fumigatus fumagillin in 1949, many studies have focused on this toxin and in this review we gather all the information currently available. First of all, the structural characteristics of this mycotoxin and the different methods developed for its determination are given in detail. Then, the biosynthetic gene cluster and the metabolic pathway involved in its production and regulation are explained. The activity of fumagillin on its target, the methionine aminopeptidase type 2 (MetAP2) enzyme, and the effects of blocking this enzyme in the host are also described. Finally, the applications that this toxin and its derivatives have in different fields, such as the treatment of cancer and its microsporicidal activity in the treatment of honeybee hive infections with Nosema spp., are reviewed. Therefore, this work offers a complete review of all the information currently related to the fumagillin mycotoxin secreted by A. fumigatus, important because of its role in the fungal infection process but also because it has many other applications, notably in beekeeping, the treatment of infectious diseases, and in oncology.

Scedosporium and Lomentospora: an updated overview of underrated opportunists.

Species of Scedosporium and Lomentospora are considered as emerging opportunists, affecting immunosuppressed and otherwise debilitated patients, although classically they are known from causing trauma-associated infections in healthy individuals. Clinical manifestations range from local infection to pulmonary colonization and severe invasive disease, in which mortality rates may be over 80%. These unacceptably high rates are due to the clinical status of patients, diagnostic difficulties, and to intrinsic antifungal resistance of these fungi. In consequence, several consortia have been founded to increase research efforts on these orphan fungi. The current review presents recent findings and summarizes the most relevant points, including the Scedosporium/Lomentospora taxonomy, environmental distribution, epidemiology, pathology, virulence factors, immunology, diagnostic methods, and therapeutic strategies.

Microglial immune response is impaired against the neurotropic fungus Lomentospora prolificans.

Lomentospora (Scedosporium) prolificans is an opportunistic pathogen capable of causing invasive infections in immunocompromised patients. The fungus is able to disseminate via the bloodstream finally arriving at the central nervous system producing neurological symptoms and, in many cases, patient death. In this context, microglial cells, which are the resident immune cells in the central nervous system, may play an important role in these infections. However, this aspect of anti-L. prolificans immunity has been poorly researched to date. Thus, the interactions and activity of microglial cells against L. prolificans were analysed, and the results show that there was a remarkable impairment in their performance regarding phagocytosis, the development of oxidative burst, and in the production of pro-inflammatory cytokines, compared with macrophages. Interestingly, L. prolificans displays great growth also when challenged with immune cells, even when inside them. We also proved that microglial phagocytosis of the fungus is highly dependent on mannose receptor and especially on dectin-1. Taken together, these data provide evidence for an impaired microglial response against L. prolificans and contribute to understanding the pathobiology of its neurotropism.

Proteomics as a Tool to Identify New Targets Against Aspergillus and Scedosporium in the Context of Cystic Fibrosis.

Cystic fibrosis (CF) is a genetic disorder that increases the risk of suffering microbial, including fungal, infections. In this paper, proteomics-based information was collated relating to secreted and cell wall proteins with potential medical applications from the most common filamentous fungi in CF, i.e., Aspergillus and Scedosporium/Lomentospora species. Among the Aspergillus fumigatus secreted allergens, ß-1,3-endoglucanase, the alkaline protease 1 (Alp1/oryzin), Asp f 2, Asp f 13/15, chitinase, chitosanase, dipeptidyl-peptidase V (DppV), the metalloprotease Asp f 5, mitogillin/Asp f 1, and thioredoxin reductase receive a special mention. In addition, the antigens ß-glucosidase 1, catalase, glucan endo-1,3-ß-glucosidase EglC, ß-1,3-glucanosyltransferases Gel1 and Gel2, and glutaminase A were also identified in secretomes of other Aspergillus species associated with CF: Aspergillus flavus, Aspergillus niger, Aspergillus nidulans, and Aspergillus terreus. Regarding cell wall proteins, cytochrome P450 and eEF-3 were proposed as diagnostic targets, and alkaline protease 2 (Alp2), Asp f 3 (putative peroxiredoxin pmp20), probable glycosidases Asp f 9/Crf1 and Crf2, GPI-anchored protein Ecm33, ß-1,3-glucanosyltransferase Gel4, conidial hydrophobin Hyp1/RodA, and secreted aspartyl protease Pep2 as protective vaccines in A. fumigatus. On the other hand, for Scedosporium/Lomentospora species, the heat shock protein Hsp70 stands out as a relevant secreted and cell wall antigen. Additionally, the secreted aspartyl proteinase and an ortholog of Asp f 13, as well as the cell wall endo-1,3-ß-D-glucosidase and 1,3-ß-glucanosyl transferase, were also found to be significant proteins. In conclusion, proteins mentioned in this review may be promising candidates for developing innovative diagnostic and therapeutic tools for fungal infections in CF patients.

Candida albicans and cancer: Can this yeast induce cancer development or progression?

There is currently increasing concern about the relation between microbial infections and cancer. More and more studies support the view that there is an association, above all, when the causal agents are bacteria or viruses. This review adds to this, summarizing evidence that the opportunistic fungus Candida albicans increases the risk of carcinogenesis and metastasis. Until recent years, Candida spp. had fundamentally been linked to cancerous processes as it is an opportunist pathogen that takes advantage of the immunosuppressed state of patients particularly due to chemotherapy. In contrast, the most recent findings demonstrate that C. albicans is capable of promoting cancer by several mechanisms, as described in the review: production of carcinogenic byproducts, triggering of inflammation, induction of Th17 response and molecular mimicry. We underline the need not only to control this type of infection during cancer treatment, especially given the major role of this yeast species in nosocomial infections, but also to find new therapeutic approaches to avoid the pro-tumor effect of this fungal species.

Candida albicans increases tumor cell adhesion to endothelial cells in vitro: intraspecific differences and importance of the mannose receptor.

The dimorphic fungus Candida albicans is able to trigger a cytokine-mediated pro-inflammatory response that increases tumor cell adhesion to hepatic endothelium and metastasis. To check the intraspecific differences in this effect, we used an in vitro murine model of hepatic response against C. albicans, which made clear that tumor cells adhered more to endothelium incubated with blastoconidia, both live and killed, than germ tubes. This finding was related to the higher carbohydrate/protein ratio found in blastoconidia. In fact, destruction of mannose ligand residues on the cell surface by metaperiodate treatment significantly reduced tumor cell adhesion induced. Moreover, we also noticed that the effect of clinical strains was greater than that of the reference one. This finding could not be explained by the carbohydrate/protein data, but to explain these differences between strains, we analyzed the expression level of ten genes (ADH1, APE3, IDH2, ENO1, FBA1, ILV5, PDI1, PGK1, QCR2 and TUF1) that code for the proteins identified previously in a mannoprotein-enriched pro-metastatic fraction of C. albicans. The results corroborated that their expression was higher in clinical strains than the reference one. To confirm the importance of the mannoprotein fraction, we also demonstrate that blocking the mannose receptor decreases the effect of C. albicans and its mannoproteins, inhibiting IL-18 synthesis and tumor cell adhesion increase by around 60%. These findings could be the first step towards a new treatment for solid organ cancers based on the role of the mannose receptor in C. albicans-induced tumor progression and metastasis.

Molecular fractionation and characterization of a Candida albicans fraction that increases tumor cell adhesion to hepatic endothelium.

Systemic candidiasis remains a major complication among patients suffering from hematological malignancies and favors the development of hepatic metastasis. To contribute to the understanding of the underlying mechanisms, the aim of this study was to identify molecules that may increase tumor cell adhesion to hepatic endothelial cells. To this end, a well-established in vitro model was used to determine the enhancement of tumor cell adhesion induced by Candida albicans and its fractions. Different fractions were obtained according to their molecular weight (M(r)) (five) or to their isoelectric point (pI) (four), using preparative electrophoresis and preparative isoelectric focusing, respectively, followed by affinity chromatography. The fraction that most enhanced melanoma cell adhesion to endothelium had an M(r) range from 45 to 66 kDa. It was characterized using two-dimensional electrophoresis, and 14 proteins were identified by peptide mass fingerprinting: Dor14p, Fba1p, Pdi1p, Pgk1p, Idh2p, Mpg1p, Sfa1p, Ape3p, Ilv5p, Tuf1p, Act1p, Eno1p, Qcr2p, and Adh1p. Of these, several are related to the immunogenic response, and the latter seven belonged to the most reactive fraction according to their pI range, from 5 to 5.6. These findings could represent a step forward in the search for new targets, to suppress the pro-metastatic effect of C. albicans.