Effectsof Aspergillus fumigatusgliotoxin and methylprednisolone on human neutrophils: implications for the pathogenesis of invasive aspergillosis

Gliotoxin elicits immunotoxicity in the early innate immune system of ducks

Gliotoxin (GT) belongs to the epipolythiodioxopiperazine (ETP) family, which is considered a crucial virulence determinant among the secondary metabolites produced by Aspergillus fumigatus. The metabolites are commonly found in food and feed, contributing to the invasion and immune escape of Aspergillus fumigatus, thereby posing a significant threat to the health of livestock, poultry, and humans. Heterophil extracellular traps (HETs), a novel form of innate immune defense, have been documented in the chicken's innate immune systems for capturing and eliminating invading microbes. However, the effects and mechanisms of GT on the production of duck HETs in vitro remain unknown. In this study, we first confirmed the presence of HETs in duck innate immune systems and further investigated the molecular mechanism underlying GT-induced HETs release. Our results demonstrate that GT can trigger typical release of HETs in duck. The structures of GT-induced HETs structures were characterized by DNA decoration, citrullinated histones 3, and elastase. Furthermore, NADPH oxidase, glycolysis, ERK1/2 and p38 signaling pathway were found to regulate GT-induced HETs. In summary, our findings reveal that gliotoxin activates HETs release in the early innate immune system of duck while providing new insights into the immunotoxicity of GT towards ducks.

Aspergillus Species and Human Papillomavirus Infections in Epithelial Tumors of Nasal and Paranasal Cavities

Background: There are diverse lesions originating from the paranasal sinuses and nasal cavity. Tobacco use, alcohol consumption, and malnutrition have been identified to play a role in the development of head and neck carcinomas. Recently, fungi and viruses have been recognized as potential causes of nasal cavity and paranasal tumors. Objectives: This study aimed at specifying the prevalence of Aspergillus and human papillomavirus (HPV) infections in the epithelial tumors of nasal cavity and paranasal sinuses. Methods: In this cross-sectional study, 57 paraffin-embedded tissue samples of malignant and benign lesions of the paranasal sinuses and nasal cavity were evaluated for the presence of Aspergillus and HPV DNA by nested polymerase chain reaction (nPCR) technique with specific primers. Results: Despite the absence of angular hyphae (acute angle) of the fungus on histopathological slides, overall, 10 (17.54%) out of 57 paraffin-embedded samples were found to be positive for Aspergillus species. However, HPV-DNA was not found in any of the samples. Conclusions: Our data suggest that fungal infections (especially aspergillosis) as an etiological factor can be contributed to the development of sinonasal cancer and, therefore, they should be considered in the management of patients with sinonasal cancer. In addition, PCR can provide an alternative to culture-dependent identification methods.

COVID-19 associated mold infections: Review of COVID-19 associated pulmonary aspergillosis and mucormycosis

COVID-19-associated mold infection (CAMI) is defined as development of mold infections in COVID-19 patients. Co-pathogenesis of viral and fungal infections include the disruption of tissue barrier following SARS CoV-2 infection with the damage in the alveolar space, respiratory epithelium and endothelium injury and overwhelming inflammation and immune dysregulation during severe COVID-19. Other predisposing risk factors permissive to fungal infections during COVID-19 include the administration of immune modulators such as corticosteroids and IL-6 antagonist. COVID-19-associated pulmonary aspergillosis (CAPA) and COVID-19-associated mucormycosis (CAM) is increasingly reported during the COVID-19 pandemic. CAPA usually developed within the first month of COVID infection, and CAM frequently arose 10-15 days post diagnosis of COVID-19. Diagnosis is challenging and often indistinguishable during the cytokine storm in COVID-19, and several diagnostic criteria have been proposed. Development of CAPA and CAM is associated with a high mortality despiteappropriate anti-mold therapy. Both isavuconazole and amphotericin B can be used for treatment of CAPA and CAM; voriconazole is the primary agent for CAPA and posaconazole is an alternative for CAM. Aggressive surgery is recommended for CAM to improve patient survival. A high index of suspicion and timely and appropriate treatment is crucial to improve patient outcome.

Exposure to the Pseudomonas aeruginosa secretome alters the proteome and secondary metabolite production of Aspergillus fumigatus

The fungal pathogen Aspergillus fumigatus is frequently cultured from the sputum of cystic fibrosis (CF) patients along with the bacterium Pseudomonas aeruginosa. A. fumigatus secretes a range of secondary metabolites, and one of these, gliotoxin, has inhibitory effects on the host immune response. The effect of P. aeruginosa culture filtrate (CuF) on fungal growth and gliotoxin production was investigated. Exposure of A. fumigatus hyphae to P. aeruginosa cells induced increased production of gliotoxin and a decrease in fungal growth. In contrast, exposure of A. fumigatus hyphae to P. aeruginosa CuF led to increased growth and decreased gliotoxin production. Quantitative proteomic analysis was used to characterize the proteomic response of A. fumigatus upon exposure to P. aeruginosa CuF. Changes in the profile of proteins involved in secondary metabolite biosynthesis (e.g. gliotoxin, fumagillin, pseurotin A), and changes to the abundance of proteins involved in oxidative stress (e.g. formate dehydrogenase) and detoxification (e.g. thioredoxin reductase) were observed, indicating that the bacterial secretome had a profound effect on the fungal proteome. Alterations in the abundance of proteins involved in detoxification and oxidative stress highlight the ability of A. fumigatus to differentially regulate protein synthesis in response to environmental stresses imposed by competitors such as P. aeruginosa. Such responses may ultimately have serious detrimental effects on the host.

Cytoskeletal Alteration Is an Early Cellular Response in Pulmonary Epithelium Infected with Aspergillus fumigatus Rather than Scedosporium apiospermum

Invasive aspergillosis and scedosporiosis are life-threatening fungal infections with similar clinical manifestations in immunocompromised patients. Contrarily, Scedosporium apiospermum is susceptible to some azole derivative but often resistant to amphotericin B. Histopathological examination alone cannot diagnose these two fungal species. Pathogenesis studies could contribute to explore candidate protein markers for new diagnosis and treatment methods leading to a decrease in mortality. In the present study, proteomics was conducted to identify significantly altered proteins in A549 cells infected with or without Aspergillus fumigatus and S. apiospermum as measured at initial invasion. Protein validation was performed with immunogold labelling alongside immunohistochemical techniques in infected A549 cells and lungs from murine models. Further, cytokine production was measured, using the Bio-Plex-Multiplex immunoassay. The cytoskeletal proteins HSPA9, PA2G4, VAT1, PSMA2, PEX1, PTGES3, KRT1, KRT9, CLIP1 and CLEC20A were mainly changed during A. fumigatus infection, while the immunologically activated proteins WNT7A, GAPDH and ANXA2 were principally altered during S. apiospermum infection. These proteins are involved in fungal internalisation and structural destruction leading to pulmonary disorders. Interleukin (IL)-21, IL-1α, IL-22, IL-2, IL-8, IL-12, IL-17A, interferon-γ and tumour necrosis factor-α were upregulated in both aspergillosis and scedosporiosis, although more predominately in the latter, in accordance with chitin synthase-1 and matrix metalloproteinase levels. Our results demonstrated that during invasion, A. fumigatus primarily altered host cellular integrity, whereas S. apiospermum chiefly induced and extensively modulated host immune responses.

Antifungal and Anti-inflammatory Effect of Punicalagin on Murine Aspergillus fumigatus Keratitis

PURPOSE

This study aimed to investigate the anti-inflammatory effect and antifungal effect of punicalagin in murine fungal keratitis.

METHODS

We used in vitro and in vivo protocols to assess the anti-inflammatory effect and antifungal effect of punicalagin. In vitro, time kill and mycelial stain were done. In vivo, murine fungal keratitis was established and treated with PBS or PUN. Clinical scores were taken on days 1, 3, and 5 post infection. The mRNA and protein levels of inflammatory factors were detected by RT-PCR and Western blot, and the number and location of macrophages were analyzed by flow cytometry and immunofluorescence. Also, fungal plate counting was used to assess the antifungal effect. The DCFH-DA fluorescence probe detected the ROS level.

RESULTS

In vitro, PUN showed activity against A.fumigatus. (A.F.), with MIC90 values of 250 μg/ml, and significantly reduced A.F. biofilm formation (p < .001). In vivo, the mouse fungal keratitis model after punicalagin treatment exhibited less disease, lower clinical scores (p < .05), lower reduced macrophage infiltrate (p < .001), and fungal load (p < .001) than those treated with PBS. Treatment with punicalagin also reduced the mRNA expression and protein level of pro-inflammatory factors. At the cellular level, PUN significantly reduced the mRNA expression of inflammatory factors and ROS production caused by the stimulation of mycelia in RAW264.7 (p < .001).

CONCLUSIONS

The results show that punicalagin is beneficial in the treatment of murine fungal keratitis. The mechanism of its anti-inflammatory effect was synthetical, including antifungal activity, an inhibitory effect of proinflammatory factor and macrophages, and anti-oxidation.

The Toxic Mechanism of Gliotoxins and Biosynthetic Strategies for Toxicity Prevention

Gliotoxin is a kind of epipolythiodioxopiperazine derived from different fungi that is characterized by a disulfide bridge. Gliotoxins can be biosynthesized by a gli gene cluster and regulated by a positive GliZ regulator. Gliotoxins show cytotoxic effects via the suppression the function of macrophage immune function, inflammation, antiangiogenesis, DNA damage by ROS production, peroxide damage by the inhibition of various enzymes, and apoptosis through different signal pathways. In the other hand, gliotoxins can also be beneficial with different doses. Low doses of gliotoxin can be used as an antioxidant, in the diagnosis and treatment of HIV, and as an anti-tumor agent in the future. Gliotoxins have also been used in the control of plant pathogens, including Pythium ultimum and Sclerotinia sclerotiorum. Thus, it is important to elucidate the toxic mechanism of gliotoxins. The toxic mechanism of gliotoxins and biosynthetic strategies to reduce the toxicity of gliotoxins and their producing strains are summarized in this review.

Aspergillus fumigatus Fumagillin Contributes to Host Cell Damage

The activity of fumagillin, a mycotoxin produced by Aspergillus fumigatus, has not been studied in depth. In this study, we used a commercial fumagillin on cultures of two cell types (A549 pneumocytes and RAW 264.7 macrophages). This toxin joins its target, MetAP2 protein, inside cells and, as a result, significantly reduces the electron chain activity, the migration, and the proliferation ability on the A549 cells, or affects the viability and proliferation ability of the RAW 264.7 macrophages. However, the toxin stimulates the germination and double branch hypha production of fungal cultures, pointing out an intrinsic resistant mechanism to fumagillin of fungal strains. In this study, we also used a fumagillin non-producer A. fumigatus strain (∆fmaA) as well as its complemented strain (∆fmaA::fmaA) and we tested the fumagillin secretion of the fungal strains using an Ultra High-Performance Liquid Chromatography (UHPLC) method. Furthermore, fumagillin seems to protect the fungus against phagocytosis in vitro, and during in vivo studies using infection of immunosuppressed mice, a lower fungal burden in the lungs of mice infected with the ∆fmaA mutant was demonstrated.

Fungal Toxins and Host Immune Responses

Fungi are ubiquitous organisms that thrive in diverse natural environments including soils, plants, animals, and the human body. In response to warmth, humidity, and moisture, certain fungi which grow on crops and harvested foodstuffs can produce mycotoxins; secondary metabolites which when ingested have a deleterious impact on health. Ongoing research indicates that some mycotoxins and, more recently, peptide toxins are also produced during active fungal infection in humans and experimental models. A combination of innate and adaptive immune recognition allows the host to eliminate invading pathogens from the body. However, imbalances in immune homeostasis often facilitate microbial infection. Despite the wide-ranging effects of fungal toxins on health, our understanding of toxin-mediated modulation of immune responses is incomplete. This review will explore the current understanding of fungal toxins and how they contribute to the modulation of host immunity.

Fungal-Induced Programmed Cell Death

Fungal infections are a cause of morbidity in humans, and despite the availability of a range of antifungal treatments, the mortality rate remains unacceptably high. Although our knowledge of the interactions between pathogenic fungi and the host continues to grow, further research is still required to fully understand the mechanism underpinning fungal pathogenicity, which may provide new insights for the treatment of fungal disease. There is great interest regarding how microbes induce programmed cell death and what this means in terms of the immune response and resolution of infection as well as microbe-specific mechanisms that influence cell death pathways to aid in their survival and continued infection. Here, we discuss how programmed cell death is induced by fungi that commonly cause opportunistic infections, including Candida albicans, Aspergillus fumigatus, and Cryptococcus neoformans, the role of programmed cell death in fungal immunity, and how fungi manipulate these pathways.

Fungal immunity and pathogenesis in mammals versus the invertebrate model organism Galleria mellonella

In recent decades, Galleria mellonella (Lepidoptera: Pyralidae) have emerged as a model system to explore experimental aspects of fungal pathogenesis. The benefits of the G. mellonella model include being faster, cheaper, higher throughput and easier compared with vertebrate models. Additionally, as invertebrates, their use is subject to fewer ethical and regulatory issues. However, for G. mellonella models to provide meaningful insight into fungal pathogenesis, the G. mellonella-fungal interactions must be comparable to mammalian-fungal interactions. Indeed, as discussed in the review, studies suggest that G. mellonella and mammalian immune systems share many similarities, and fungal virulence factors show conserved functions in both hosts. While the moth model has opened novel research areas, many comparisons are superficial and leave large gaps of knowledge that need to be addressed concerning specific mechanisms underlying G. mellonella-fungal interactions. Closing these gaps in understanding will strengthen G. mellonella as a model for fungal virulence in the upcoming years. In this review, we provide comprehensive comparisons between fungal pathogenesis in mammals and G. mellonella from immunological and virulence perspectives. When information on an antifungal immune component is unknown in G. mellonella, we include findings from other well-studied Lepidoptera. We hope that by outlining this information available in related species, we highlight areas of needed research and provide a framework for understanding G. mellonella immunity and fungal interactions.

The Pathogenesis of Aspergillus fumigatus, Host Defense Mechanisms, and the Development of AFMP4 Antigen as a Vaccine

Aspergillus fumigatus is one of the ubiquitous fungi with airborne conidia, which accounts for most aspergillosis cases. In immunocompetent hosts, the inhaled conidia are rapidly eliminated. However, immunocompromised or immunodeficient hosts are particularly vulnerable to most Aspergillus infections and invasive aspergillosis (IA), with mortality from 50% to 95%. Despite the improvement of antifungal drugs over the last few decades, the therapeutic effect for IA patients is still limited and does not provide significant survival benefits. The drawbacks of antifungal drugs such as side effects, antifungal drug resistance, and the high cost of antifungal drugs highlight the importance of finding novel therapeutic and preventive approaches to fight against IA. In this article, we systemically addressed the pathogenic mechanisms, defense mechanisms against A. fumigatus, the immune response, molecular aspects of host evasion, and vaccines' current development against aspergillosis, particularly those based on AFMP4 protein, which might be a promising antigen for the development of anti-A. fumigatus vaccines.

Phenotypic and Molecular Biological Analysis of Polymycovirus AfuPmV-1M From Aspergillus fumigatus: Reduced Fungal Virulence in a Mouse Infection Model

The filamentous fungal pathogen Aspergillus fumigatus is one of the most common causal agents of invasive fungal infection in humans; the infection is associated with an alarmingly high mortality rate. In this study, we investigated whether a mycovirus, named AfuPmV-1M, can reduce the virulence of A. fumigatus in a mouse infection model. AfuPmV-1M has high sequence similarity to AfuPmV-1, one of the polymycovirus that is a capsidless four-segment double-stranded RNA (dsRNA) virus, previously isolated from the genome reference strain of A. fumigatus, Af293. However, we found the isolate had an additional fifth dsRNA segment, referred to as open reading frame 5 (ORF5), which has not been reported in AfuPmV-1. We then established isogenic lines of virus-infected and virus-free A. fumigatus strains. Mycovirus infection had apparent influences on fungal phenotypes, with the virus-infected strain producing a reduced mycelial mass and reduced conidial number in comparison with these features of the virus-free strain. Also, resting conidia of the infected strain showed reduced adherence to pulmonary epithelial cells and reduced tolerance to macrophage phagocytosis. In an immunosuppressed mouse infection model, the virus-infected strain showed reduced mortality in comparison with mortality due to the virus-free strain. RNA sequencing and high-performance liquid chromatography (HPLC) analysis showed that the virus suppressed the expression of genes for gliotoxin synthesis and its production at the mycelial stage. Conversely, the virus enhanced gene expression and biosynthesis of fumagillin. Viral RNA expression was enhanced during conidial maturation, conidial germination, and the mycelial stage. We presume that the RNA or translation products of the virus affected fungal phenotypes, including spore formation and toxin synthesis. To identify the mycovirus genes responsible for attenuation of fungal virulence, each viral ORF was ectopically expressed in the virus-free KU strain. We found that the expression of ORF2 and ORF5 reduced fungal virulence in the mouse model. In addition, ORF3 affected the stress tolerance of host A. fumigatus in culture. We hypothesize that the respective viral genes work cooperatively to suppress the pathogenicity of the fungal host.

Proinflammatory effects of environmental cadmium boost resistance to opportunistic pathogen Aspergillus fumigatus: Implications for sustained low-level pulmonary inflammation?

Cadmium (Cd) is one of the most toxic environmental heavy metals to which the general population is exposed mainly via the oral route. Owing to its immunomodulatory potential, orally acquired Cd affects antimicrobial immune defense in several organs, including the lungs. While there are data concerning Cd and viral and bacterial pulmonary infections, effects on fungal infections are not studied yet. In the present study, the effect of the Cd (5 mg/L for 30 days, in drinking water, the average daily Cd intake 0.641 ± 0.089 mg/kg) on the immune response of rats to pulmonary A. fumigatus infection was examined. Data obtained showed that orally acquired cadmium does not affect the elimination of the fungus in immunocompetent rats owing to the preservation of some aspects of innate immune responses (lung leukocyte infiltration and NBT reduction) and an increase in other (increased numbers of mucus-producing goblet cells, MPO release). Cd does not affect an IFN-γ response in lung leukocytes during the infection (despite suppression of cytokine production in cells of lung-draining lymph nodes), while it stimulates IL-17 and suppresses IL-10 response to the fungus. As a result, the elimination of the fungus occurs in a milieu with the prevailing proinflammatory response in Cd-exposed animals that preserved fungal elimination from the lungs, though with more intense injury to the lung tissue. Therefore, the proinflammatory microenvironment in the lungs created by Cd that sustains inflammatory/immune response to the fungus to which humans are exposed for a lifetime, raises a concern of orally acquired Cd as a risk factor for the development of chronic low-grade pulmonary inflammation.

Gliotoxin Aggravates Experimental Autoimmune Encephalomyelitis by Triggering Neuroinflammation

Gliotoxin (GTX) is the major and the most potent mycotoxin that is secreted by Aspergillus fumigatus, which is capable of injuring and killing microglial cells, astrocytes, and oligodendrocytes. During the last years, studies with patients and experimental models of multiple sclerosis (MS), which is an autoimmune disease of the central nervous system (CNS), suggested that fungal infections are among the possible initiators or aggravators of this pathology. The deleterious effect can occur through a direct interaction of the fungus with the CNS or by the toxin release from a non-neurological site. In the present work, we investigated the effect of GTX on experimental autoimmune encephalomyelitis (EAE) development. Female C57BL/6 mice were immunized with myelin oligodendrocyte glycoprotein and then intraperitoneally injected with three doses of GTX (1 mg/kg b.w., each) on days 4, 7, and 10. GTX aggravated clinical symptoms of the disease in a dose-dependent way and this outcome was concomitant with an increased neuroinflammation. CNS analyses revealed that GTX locally increased the relative expression of inflammatory genes and the cytokine production. Our results indicate that GTX administered in a non-neuronal site was able to increase neuroinflammation in EAE. Other mycotoxins could also be deleterious to many neurological diseases by similar mechanisms.

Preparations for Invasion: Modulation of Host Lung Immunity During Pulmonary Aspergillosis by Gliotoxin and Other Fungal Secondary Metabolites

Pulmonary aspergillosis is a severe infectious disease caused by some members of the Aspergillus genus, that affects immunocompetent as well as immunocompromised patients. Among the different disease forms, Invasive Aspergillosis is the one causing the highest mortality, mainly, although not exclusively, affecting neutropenic patients. This genus is very well known by humans, since different sectors like pharmaceutical or food industry have taken advantage of the biological activity of some molecules synthetized by the fungus, known as secondary metabolites, including statins, antibiotics, fermentative compounds or colorants among others. However, during infection, in response to a hostile host environment, the fungal secondary metabolism is activated, producing different virulence factors to increase its survival chances. Some of these factors also contribute to fungal dissemination and invasion of adjacent and distant organs. Among the different secondary metabolites produced by Aspergillus spp. Gliotoxin (GT) is the best known and better characterized virulence factor. It is able to generate reactive oxygen species (ROS) due to the disulfide bridge present in its structure. It also presents immunosuppressive activity related with its ability to kill mammalian cells and/or inactivate critical immune signaling pathways like NFkB. In this comprehensive review, we will briefly give an overview of the lung immune response against Aspergillus as a preface to analyse the effect of different secondary metabolites on the host immune response, with a special attention to GT. We will discuss the results reported in the literature on the context of the animal models employed to analyse the role of GT as virulence factor, which is expected to greatly depend on the immune status of the host: why should you hide when nobody is seeking for you? Finally, GT immunosuppressive activity will be related with different human diseases predisposing to invasive aspergillosis in order to have a global view on the potential of GT to be used as a target to treat IA.

Fungal burden exposure assessment in podiatry clinics from Ireland

Fungi are amongst the bioaerosols of most importance, as indicated by the growing interest in this field of research. The aim was to characterize the exposure to fungal burden in podiatry clinics using culture-based and molecular methods.

METHODS

Airborne fungi were collected using an impaction air sampler and surface samples were also performed. Fourteen air samples were collected for direct detection of fungal DNA from filamentous fungi and dermatophytes. Overall, 63.6 % of the evening samples and 46 % of the morning samples surpassed the threshold values (150 CFU/m³). Molecular detection, by real time PCR, of the target fungal species/strains (Aspergillus and Stachybotrys species) was negative for all samples collected. Trichophyton rubrum was detected by PCR analysis in one DNA sample collected on day six. Results suggest the use of both culture-based and molecular methodologies are desirable for a complete evaluation of fungal burden in this particular health care setting.

Functional convergence of gliP and aspf1 in Aspergillus fumigatus pathogenicity

Gliotoxin contributes to the virulence of the fungus Aspergillus fumigatus in non-neutropenic mice that are immunosuppressed with corticosteroids. To investigate how the absence of gliotoxin affects both the fungus and the host, we used a nanoString nCounter to analyze their transcriptional responses during pulmonary infection of a non-neutropenic host with a gliotoxin-deficient ΔgliP mutant. We found that the ΔgliP mutation led to increased expression of aspf1, which specifies a secreted ribotoxin. Prior studies have shown that aspf1, like gliP, is not required for virulence in a neutropenic infection model, but its role in a non-neutropenic infection model has not been fully investigated. To investigate the functional significance of this up-regulation of aspf1, a Δaspf1 single mutant and a Δaspf1 ΔgliP double mutant were constructed. Both Δaspf1 and ΔgliP single mutants had reduced lethality in non-neutropenic mice, and a Δaspf1 ΔgliP double mutant had a greater reduction in lethality than either single mutant. Analysis of mice infected with these mutants indicated that the presence of gliP is associated with massive apoptosis of leukocytes at the foci of infection and inhibition of chemokine production. Also, the combination of gliP and aspf1 is associated with suppression of CXCL1 chemokine expression. Thus, aspf1 contributes to A. fumigatus pathogenicity in non-neutropenic mice and its up-regulation in the ΔgliP mutant may partially compensate for the absence of gliotoxin.

ABBREVIATIONS

PAS: periodic acid-Schiff; PBS: phosphate buffered saline; ROS: reactive oxygen species; TUNEL: terminal deoxynucleotidyl transferase dUTP nick-end labeling.

A Nonredundant Phosphopantetheinyl Transferase, PptA, Is a Novel Antifungal Target That Directs Secondary Metabolite, Siderophore, and Lysine Biosynthesis in Aspergillus fumigatus and Is Critical for Pathogenicity

Secondary metabolites are key mediators of virulence for many pathogens. Aspergillus fumigatus produces a vast array of these bioactive molecules, the biosynthesis of which is catalyzed by nonribosomal peptide synthetases (NRPSs) or polyketide synthases (PKSs). Both NRPSs and PKSs harbor carrier domains that are primed for acceptance of secondary metabolic building blocks by a phosphopantetheinyl transferase (P-pant). The A. fumigatus P-pant PptA has been shown to prime the putative NRPS Pes1 in vitro and has an independent role in lysine biosynthesis; however, its role in global secondary metabolism and its impact on virulence has not been described. Here, we demonstrate that PptA has a nonredundant role in the generation of the vast majority of detectable secondary metabolites in A. fumigatus, including the immunomodulator gliotoxin, the siderophores triacetylfusarinine C (TAFC) and ferricrocin (FC), and dihydroxy naphthalene (DHN)-melanin. We show that both the lysine and iron requirements of a pptA null strain exceed those freely available in mammalian tissues and that loss of PptA renders A. fumigatus avirulent in both insect and murine infection models. Since PptA lacks similarity to its mammalian orthologue, we assert that the combined role of this enzyme in both primary and secondary metabolism, encompassing multiple virulence determinants makes it a very promising antifungal drug target candidate. We further exemplify this point with a high-throughput fluorescence polarization assay that we developed to identify chemical inhibitors of PptA function that have antifungal activity.IMPORTANCE Fungal diseases are estimated to kill between 1.5 and 2 million people each year, which exceeds the global mortality estimates for either tuberculosis or malaria. Only four classes of antifungal agents are available to treat invasive fungal infections, and all suffer pharmacological shortcomings, including toxicity, drug-drug interactions, and poor bioavailability. There is an urgent need to develop a new class of drugs that operate via a novel mechanism of action. We have identified a potential drug target, PptA, in the fungal pathogen Aspergillus fumigatus PptA is required to synthesize the immunotoxic compound gliotoxin, DHN-melanin, which A. fumigatus employs to evade detection by host cells, the amino acid lysine, and the siderophores TAFC and FC, which A. fumigatus uses to scavenge iron. We show that strains lacking the PptA enzyme are unable to establish an infection, and we present a method which we use to identify novel antifungal drugs that inactivate PptA.

Transcriptional Control of Drug Resistance, Virulence and Immune System Evasion in Pathogenic Fungi: A Cross-Species Comparison

Transcription factors are key players in the control of the activation or repression of gene expression programs in response to environmental stimuli. The study of regulatory networks taking place in fungal pathogens is a promising research topic that can help in the fight against these pathogens by targeting specific fungal pathways as a whole, instead of targeting more specific effectors of virulence or drug resistance. This review is focused on the analysis of regulatory networks playing a central role in the referred mechanisms in the human fungal pathogens Aspergillus fumigatus, Cryptococcus neoformans, Candida albicans, Candida glabrata, Candida parapsilosis, and Candida tropicalis. Current knowledge on the activity of the transcription factors characterized in each of these pathogenic fungal species will be addressed. Particular focus is given to their mechanisms of activation, regulatory targets and phenotypic outcome. The review further provides an evaluation on the conservation of transcriptional circuits among different fungal pathogens, highlighting the pathways that translate common or divergent traits among these species in what concerns their drug resistance, virulence and host immune evasion features. It becomes evident that the regulation of transcriptional networks is complex and presents significant variations among different fungal pathogens. Only the oxidative stress regulators Yap1 and Skn7 are conserved among all studied species; while some transcription factors, involved in nutrient homeostasis, pH adaptation, drug resistance and morphological switching are present in several, though not all species. Interestingly, in some cases not very homologous transcription factors display orthologous functions, whereas some homologous proteins have diverged in terms of their function in different species. A few cases of species specific transcription factors are also observed.

Aspergillosis and stem cell transplantation: An overview of experimental pathogenesis studies

Invasive aspergillosis is a life-threatening infection caused by the opportunistic filamentous fungus Aspergillus fumigatus. Patients undergoing haematopoietic stem cell transplant (HSCT) for the treatment of hematological malignancy are at particularly high risk of developing this fatal infection. The susceptibility of HSCT patients to infection with A. fumigatus is a consequence of a complex interplay of both fungal and host factors. Here we review our understanding of the host-pathogen interactions underlying the susceptibility of the immunocompromised host to infection with A. fumigatus with a focus on the experimental validation of fungal and host factors relevant to HSCT patients. These include fungal factors such as secondary metabolites, cell wall constituents, and metabolic adaptations that facilitate immune evasion and survival within the host microenvironment, as well as the innate and adaptive immune responses involved in host defense against A. fumigatus.

Ecophysiology of environmental Aspergillus fumigatus and comparison with clinical strains on gliotoxin production and elastase activity

The aim of this manuscript was to study the influence of water activity (aW ) and pH in the ecophysiological behaviour of Aspergillus fumigatus strains at human body temperature. In addition, gliotoxin production and enzymatic ability among environmental (n = 2) and clinical (n = 5) strains were compared. Ecophysiological study of environmental strains was performed on agar silage incubated at 37°C, studying the interaction at eight aW levels (0·8, 0·85, 0·9, 0·92, 0·94, 0·96, 0·98 and 0·99) and eight pH levels (3·5, 4, 4·5, 5, 6, 7, 7·5 and 8). Considering the influence of the assumed lung conditions on growth of A. fumigatus (aW 0·98/0·99 and pH of 7/7·5), the optimal condition for the development of A. fumigatus RC031 was at aW 0·99 at pH 7. At aW 0·98/0·99 and pH of 7/7·5, the highest growth rate and the lowest lag phase was reported, whereas there were no significant differences at aW 0·98/0·99 and pH 7/7·5 interactions on growth of A. fumigatus RC032. Gliotoxin production of A. fumigatus strains was evaluated. The gliotoxin production was similar in clinical and environmental strains. Elastin activity was studied in solid medium, highest elastase activity index was found for clinical strain A. fumigatus RC0676, followed by the environmental strain A. fumigatus RC031. Opportunistic environmental strains can be considered as pathogenic in some cases when rural workers are exposed constantly to handling silage.

SIGNIFICANCE AND IMPACT OF THE STUDY

Aspergillus fumigatus is one of the main opportunist pathogen agents causing invasive aspergillosis. Rural workers present a constant exposition to A. fumigatus spores caused by feed-borne manipulation. In this study, environmental A. fumigatus strains were able to grow and produce gliotoxin onto the studied conditions including the lung ones. Environmental and clinical strains were physiologically similar and could be an important putative infection source in rural workers.

Gliotoxin--bane or boon?

Gliotoxin (GT) is the most important epidithiodioxopiperazine (ETP)-type fungal toxin. GT was originally isolated from Trichoderma species as an antibiotic substance involved in biological control of plant pathogenic fungi. A few isolates of GT-producing Trichoderma virens are commercially marketed for biological control and widely used in agriculture. Furthermore, GT is long known as an immunosuppressive agent and also reported to have anti-tumour properties. However, recent publications suggest that GT is a virulence determinant of the human pathogen Aspergillus fumigatus. This compound is thus important on several counts - it has medicinal properties, is a pathogenicity determinant, is a potential diagnostic marker and is important in biological crop protection. The present article addresses this paradox and the ecological role of GT. We discuss the function of GT as defence molecule, the role in aspergillosis and suggest solutions for safe application of Trichoderma-based biofungicides.

Methylprednisolone impairs conidial phagocytosis but does not attenuate hyphal damage by neutrophils against Exserohilum rostratum

Exserohilum rostratum caused a multistate fungal meningitis outbreak following iatrogenic inoculation of contaminated methylprednisolone in the United States. To gain insight into the immunopathogenesis of this infection, we studied the innate host responses of human neutrophils against E. rostratum conidia and hyphae with or without methylprednisolone. The neutrophil-induced percentage fungal damage against conidia and hyphae was effector-to-target ratio dependent (≤55%). While methylprednisolone did not affect neutrophil-induced fungal damage by treatment of Exserohilum or neutrophils, it compromised phagocytosis of conidia (P < 0.05). These findings suggest that methylprednisolone-treated neutrophils may have altered phagocytic clearance of Exserohilum conidia, reducing host capacity to contain the invasive process.

Antifungal and antihepatotoxic effects of sepia ink extract against oxidative stress as a risk factor of invasive pulmonary aspergillosis in neutropenic mice

BACKGROUND

There is a great need for novel strategies to overcome the high mortality associated with invasive pulmonary aspergillosis (IPA) in immunocompromised patients. To evaluate the antifungal and antihepatotoxic potentials of Sepia ink extract, its effect on liver oxidative stress levels was analyzed against IPA in neutropenic mice using amphotercin B as a reference drug.

MATERIALS AND METHODS

Eighty neutropenic infected mice were randomly assigned into four main groups. The 1(st) group was treated with saline, neutropenic infected (NI), the 2(nd) group was treated with ink extract (200 mg/kg) (IE) and the 3(rd) group was treated with amphotericin B (150 mg/kg) (AMB) and 4(th) group was treated with IE plus AMB. Treatment was started at 24 h after fungal inoculation (1×10(9) conidia/ml).

RESULTS

The present study revealed good in vitro and in vivo antifungal activity of IE against A. fumigatus. IE significantly reduced hepatic fungal burden and returns liver function and histology to normal levels. Compared with the untreated infected group, mice in the IE, AMB, and IE+ AMB groups had increased glutathione reduced (GSH) and superoxide dismutase (SOD) and significantly reduced malondialdehyde (MDA) levels at 24 and 72 h after inoculation with A. fumigatus conidia.

CONCLUSION

It is then concluded that in combination with antifungal therapy (AMB), IE treatment can reduce hepatic fungal burden, alleviate hepatic granulomatous lesions and oxidative stress associated with IPA in neutropenic mice.

Accessing indoor fungal contamination using conventional and molecular methods in Portuguese poultries

Epidemiological studies showed increased prevalence of respiratory symptoms and adverse changes in pulmonary function parameters in poultry workers, corroborating the increased exposure to risk factors, such as fungal load and their metabolites. This study aimed to determine the occupational exposure threat due to fungal contamination caused by the toxigenic isolates belonging to the complex of the species of Aspergillus flavus and also isolates from Aspergillus fumigatus species complex. The study was carried out in seven Portuguese poultries, using cultural and molecular methodologies. For conventional/cultural methods, air, surfaces, and litter samples were collected by impaction method using the Millipore Air Sampler. For the molecular analysis, air samples were collected by impinger method using the Coriolis μ air sampler. After DNA extraction, samples were analyzed by real-time PCR using specific primers and probes for toxigenic strains of the Aspergillus flavus complex and for detection of isolates from Aspergillus fumigatus complex. Through conventional methods, and among the Aspergillus genus, different prevalences were detected regarding the presence of Aspergillus flavus and Aspergillus fumigatus species complexes, namely: 74.5 versus 1.0 % in the air samples, 24.0 versus 16.0 % in the surfaces, 0 versus 32.6 % in new litter, and 9.9 versus 15.9 % in used litter. Through molecular biology, we were able to detect the presence of aflatoxigenic strains in pavilions in which Aspergillus flavus did not grow in culture. Aspergillus fumigatus was only found in one indoor air sample by conventional methods. Using molecular methodologies, however, Aspergillus fumigatus complex was detected in seven indoor samples from three different poultry units. The characterization of fungal contamination caused by Aspergillus flavus and Aspergillus fumigatus raises the concern of occupational threat not only due to the detected fungal load but also because of the toxigenic potential of these species.

What can we learn and what do we need to know amidst the iatrogenic outbreak of Exserohilum rostratum meningitis?

The tragedy of the ongoing epidemic of meningitis caused by Exserohilum rostratum brings into focus the epidemiology, risk factors, pathogenesis, diagnosis, and treatment of a multitude of opportunistic mold infections of the central nervous system. Herein we provide our perspective regarding the translational research objectives of this infection that are needed to make an impact on this important healthcare crisis.

Biosynthesis and function of gliotoxin in Aspergillus fumigatus

Gliotoxin (GT) is the prototype of the epidithiodioxopiperazine (ETP)-type fungal toxins. GT plays a critical role in the pathobiology of Aspergillus fumigatus. It modulates the immune response and induces apoptosis in different cell types. The toxicity has been attributed to the unusual intramolecular disulfide bridge, which is the functional motif of all ETPs. Because of the extraordinary structure and activity of GT, this fungal metabolite has been the subject of many investigations. The biosynthesis of GT involves unprecedented reactions catalysed by recently discovered enzymes. Here, we summarize the recent progress in elucidating the GT biosynthetic pathway and its role in virulence.

The role of reactive-oxygen-species in microbial persistence and inflammation

The mechanisms of chronic infections caused by opportunistic pathogens are of keen interest to both researchers and health professionals globally. Typically, chronic infectious disease can be characterized by an elevation in immune response, a process that can often lead to further destruction. Reactive-Oxygen-Species (ROS) have been strongly implicated in the aforementioned detrimental response by host that results in self-damage. Unlike excessive ROS production resulting in robust cellular death typically induced by acute infection or inflammation, lower levels of ROS produced by host cells are increasingly recognized to play a critical physiological role for regulating a variety of homeostatic cellular functions including growth, apoptosis, immune response, and microbial colonization. Sources of cellular ROS stimulation can include “danger-signal-molecules” such as extracellular ATP (eATP) released by stressed, infected, or dying cells. Particularly, eATP-P2X₇ receptor mediated ROS production has been lately found to be a key modulator for controlling chronic infection and inflammation. There is growing evidence that persistent microbes can alter host cell ROS production and modulate eATP-induced ROS for maintaining long-term carriage. Though these processes have yet to be fully understood, exploring potential positive traits of these “injurious” molecules could illuminate how opportunistic pathogens maintain persistence through physiological regulation of ROS signaling.

What makes Aspergillus fumigatus a successful pathogen? Genes and molecules involved in invasive aspergillosis

Aspergillus fumigatus is an opportunistic pathogen that causes 90% of invasive aspergillosis (IA) due to Aspergillus genus, with a 50-95% mortality rate. It has been postulated that certain virulence factors are characteristic of A. fumigatus, but the "non-classical" virulence factors seem to be highly variable. Overall, published studies have demonstrated that the virulence of this fungus is multifactorial, associated with its structure, its capacity for growth and adaptation to stress conditions, its mechanisms for evading the immune system and its ability to cause damage to the host. In this review we intend to give a general overview of the genes and molecules involved in the development of IA. The thermotolerance section focuses on five genes related with the capacity of the fungus to grow at temperatures above 30°C (thtA, cgrA, afpmt1, kre2/afmnt1, and hsp1/asp f 12). The following sections discuss molecules and genes related to interaction with the host and with the immune responses. These sections include β-glucan, α-glucan, chitin, galactomannan, galactomannoproteins (afmp1/asp f 17 and afmp2), hydrophobins (rodA/hyp1 and rodB), DHN-melanin, their respective synthases (fks1, rho1-4, ags1-3, chsA-G, och1-4, mnn9, van1, anp1, glfA, pksP/alb1, arp1, arp2, abr1, abr2, and ayg1), and modifying enzymes (gel1-7, bgt1, eng1, ecm33, afpigA, afpmt1-2, afpmt4, kre2/afmnt1, afmnt2-3, afcwh41 and pmi); several enzymes related to oxidative stress protection such as catalases (catA, cat1/catB, cat2/katG, catC, and catE), superoxide dismutases (sod1, sod2, sod3/asp f 6, and sod4), fatty acid oxygenases (ppoA-C), glutathione tranferases (gstA-E), and others (afyap1, skn7, and pes1); and efflux transporters (mdr1-4, atrF, abcA-E, and msfA-E). In addition, this review considers toxins and related genes, such as a diffusible toxic substance from conidia, gliotoxin (gliP and gliZ), mitogillin (res/mitF/asp f 1), hemolysin (aspHS), festuclavine and fumigaclavine A-C, fumitremorgin A-C, verruculogen, fumagillin, helvolic acid, aflatoxin B1 and G1, and laeA. Two sections cover genes and molecules related with nutrient uptake, signaling and metabolic regulations involved in virulence, including enzymes, such as serine proteases (alp/asp f 13, alp2, and asp f 18), metalloproteases (mep/asp f 5, mepB, and mep20), aspartic proteases (pep/asp f 10, pep2, and ctsD), dipeptidylpeptidases (dppIV and dppV), and phospholipases (plb1-3 and phospholipase C); siderophores and iron acquisition (sidA-G, sreA, ftrA, fetC, mirB-C, and amcA); zinc acquisition (zrfA-H, zafA, and pacC); amino acid biosynthesis, nitrogen uptake, and cross-pathways control (areA, rhbA, mcsA, lysF, cpcA/gcn4p, and cpcC/gcn2p); general biosynthetic pathway (pyrG, hcsA, and pabaA), trehalose biosynthesis (tpsA and tpsB), and other regulation pathways such as those of the MAP kinases (sakA/hogA, mpkA-C, ste7, pbs2, mkk2, steC/ste11, bck1, ssk2, and sho1), G-proteins (gpaA, sfaD, and cpgA), cAMP-PKA signaling (acyA, gpaB, pkaC1, and pkaR), His kinases (fos1 and tcsB), Ca(2+) signaling (calA/cnaA, crzA, gprC and gprD), and Ras family (rasA, rasB, and rhbA), and others (ace2, medA, and srbA). Finally, we also comment on the effect of A. fumigatus allergens (Asp f 1-Asp f 34) on IA. The data gathered generate a complex puzzle, the pieces representing virulence factors or the different activities of the fungus, and these need to be arranged to obtain a comprehensive vision of the virulence of A. fumigatus. The most recent gene expression studies using DNA-microarrays may be help us to understand this complex virulence, and to detect targets to develop rapid diagnostic methods and new antifungal agents.

Gender differences in pulmonary inflammation following systemic cadmium administration in rats

OBJECTIVE

To examine the presence of gender differences in pulmonary inflammation evoked by acute systemic cadmium administration in rats.

METHODS

Presence of basic indicators of lung inflammation (inflammatory cytokine lung content, leukocyte infiltration and activity of cells recovered from lungs by enzyme digestion) was analyzed and compared in animals of the two sexes.

RESULTS

Intraperitoneal administration of cadmium (1.0 mg/kg) resulted in higher cadmium content in lungs of female rats. Higher tumor necrosis factor (TNF) content was noted in lung homogenates of male rats, while interleukin-6 (IL-6) content was slightly, but significantly greater in lungs of female rats. Increased leukocyte infiltration was observed in lungs of male rats, mainly due to neutrophils. Increased responsiveness to phorbol myristate acetate (PMA) stimulation was noted in cells recovered from lungs of male rats. Rise in intracellular content of myeloperoxidase (MPO) was noted in lung cells from cadmium-treated rats of both sexes, but higher in cells from male rats.

CONCLUSIONS

Presented data documented a more intense pulmonary inflammatory response to systemic cadmium administration in males, with higher IL-6 levels in lungs of female individuals. These sex differences in proinflamatory activity of cadmium in lungs should be taken into consideration in studying the remote toxicity of this heavy metal.

Role of Aspergillus fumigatus DvrA in host cell interactions and virulence

The transcription factors that regulate Aspergillus fumigatus interactions with host cells and virulence are incompletely defined. We investigated the role of the putative C2H2 transcription factor DvrA in governing these processes. Although DvrA was identified by its limited homology to Candida albicans Bcr1, a ΔdvrA mutant strain of A. fumigatus had wild-type adherence to host constituents in vitro. However, it had increased capacity to damage both endothelial cells and a pulmonary epithelial cell line compared to the ability of the wild-type strain and a ΔdvrA::dvrA-complemented strain. This increase in damage required direct contact between the mutant and host cells. The ΔdvrA mutant also stimulated greater CCL20, interleukin-8, and tumor necrosis factor mRNA expression in a pulmonary epithelial cell line compared to levels induced by the control strains. Also, it was resistant to nikkomycin Z, suggesting an altered cell wall composition. As predicted by these in vitro results, the ΔdvrA mutant had increased virulence and stimulated a greater pulmonary inflammatory response than the wild-type strain and ΔdvrA::dvrA-complemented strains in the nonneutropenic mouse model of invasive pulmonary aspergillosis. These results indicate that DvrA influences A. fumigatus virulence as well as its capacity to damage host cells and stimulate a proinflammatory response.

Inhibition of neutrophil function following exposure to the Aspergillus fumigatus toxin fumagillin

The filamentous fungus Aspergillus fumigatus produces a variety of enzymes and toxins that may facilitate fungal colonization of tissue and evasion of the host immune response. One such toxin, fumagillin, was investigated for its ability to inhibit the action of neutrophils, which are a central component of the innate immune response to microbial infection. Neutrophils exposed to 2 microg fumagillin ml(-1) for 25 min showed a significantly reduced ability to kill yeast cells (P<0.02), to phagocytose conidia of A. fumigatus (P<0.023) and to consume oxygen (P<0.032). The ability of neutrophils to generate superoxide is dependent upon the action of a functional NADPH oxidase complex which is composed of cytosolic (p40phox, p47phox, p67phox, Rac2) and membrane (gp91phox) proteins. Exposure of neutrophils to fumagillin inhibited the formation of the NADPH oxidase complex by blocking the translocation of p47phox from the cytosolic to the membrane fraction (P=0.02). In addition to the production of superoxide, neutrophils also undergo degranulation, which leads to the release of proteolytic enzymes that contribute to the microbicidal activity of the cell. Fumagillin-treated neutrophils showed reduced degranulation as evidenced by lower myeloperoxidase activity (P<0.019). Fumagillin-treated cells demonstrated reduced levels of F-actin, thus indicating that retarding the formation of F-actin may contribute to the inhibition of the structural rearrangements required in the activated neutrophil. This work indicates that fumagillin may contribute to reducing the local immune response by altering the activity of neutrophils and thus facilitate the continued persistence and growth of A. fumigatus in the host.

Healthy human T-Cell Responses to Aspergillus fumigatus antigens

Background

Aspergillus fumigatus is associated with both invasive and allergic pulmonary diseases, in different hosts. The organism is inhaled as a spore, which, if not cleared from the airway, germinates into hyphal morphotypes that are responsible for tissue invasion and resultant inflammation. Hyphae secrete multiple products that function as antigens, evoking both a protective (T_H1–T_H17) and destructive allergic (T_H2) immunity. How Aspergillus allergens (Asp f proteins) participate in the development of allergic sensitization is unknown.

Methodology/Principal Findings

To determine whether Asp f proteins are strictly associated with T_H2 responses, or represent soluble hyphal products recognized by healthy hosts, human T cell responses to crude and recombinant products were characterized by ELISPOT. While responses (number of spots producing IFN-γ, IL-4 or IL-17) to crude hyphal antigen preparations were weak, responses to recombinant Asp f proteins were higher. Recombinant allergens stimulated cells to produce IFN-γ more so than IL-4 or IL-17. Volunteers exhibited a diverse CD4+ and CD8+ T cell antigen recognition profile, with prominent CD4 T_H1-responses to Asp f3 (a putative peroxismal membrane protein), Asp f9/16 (cell wall glucanase), Asp f11 (cyclophilin type peptidyl-prolyl isomerase) and Asp f22 (enolase). Strong IFN-γ responses were reproduced in most subjects tested over 6 month intervals.

Conclusions

Products secreted after conidial germination into hyphae are differentially recognized by protective T cells in healthy, non-atopic individuals. Defining the specificity of the human T cell repertoire, and identifying factors that govern early responses may allow for development of novel diagnostics and therapeutics for both invasive and allergic Aspergillus diseases.

Chronic fungal sinusitis leading to disastrous cerebral aspergillosis: a case report

Cerebral angioinvasion is a fatal complication of disseminated aspergillosis and has been rarely described in diabetic population in the absence of ketoacidosis. We present a case of invasive fungal sinusitis in a 79 year old diabetic man who presented with chronic frontal headaches. Despite appropriate medical and surgical treatment, the disease progressed and the patient eventually succumbed to a fatal ruptured mycotic aneurysm. We emphasize that clinicians should consider this in the differential diagnoses of all diabetics who present with chronic sinusitis, as early diagnosis could be the key in the successful treatment.

Aspergillus fumigatus inhibits angiogenesis through the production of gliotoxin and other secondary metabolites

In susceptible hosts, angioinvasion by Aspergillus fumigatus triggers thrombosis, hypoxia, and proinflammatory cytokine release, all of which are stimuli for angiogenesis. We sought to determine whether A fumigatus directly modulates angiogenesis. A fumigatus culture filtrates profoundly inhibited the differentiation, migration, and capillary tube formation of human umbilical vein endothelial cells in vitro. To measure angiogenesis at the site of infection, we devised an in vivo Matrigel assay in cyclophosphamide-treated BALB/c mice with cutaneous invasive aspergillosis. Angiogenesis was significantly suppressed in Matrigel plugs implanted in A fumigatus-infected mice compared with plugs from uninfected control mice. The antiangiogenic effect of A fumigatus was completely abolished by deletion of the global regulator of secondary metabolism, laeA, and to a lesser extent by deletion of gliP, which controls gliotoxin production. Moreover, pure gliotoxin potently inhibited angiogenesis in vitro in a dose-dependent manner. Finally, overexpression of multiple angiogenesis mediator-encoding genes was observed in the lungs of cortisone-treated mice during early invasive aspergillosis, whereas gene expression returned rapidly to baseline levels in cyclophosphamide/cortisone-treated mice. Taken together, these results indicate that suppression of angiogenesis by A fumigatus both in vitro and in a neutropenic mouse model is mediated through secondary metabolite production.

Lungs: remote inflammatory target of systemic cadmium administration in rats

Pulmonary inflammation is a biological response to cadmium entering the body via the respiratory route. Systemic administration of this metal revealed the lungs as a significant site of its disposition. In this study, the presence of basic indicators of lung inflammation (leukocyte infiltration and activity of cells recovered from lungs by enzyme digestion) was analyzed in the rat model of acute systemic cadmium intoxication. Intraperitoneal administration of both cadmium doses (0.5mg/kg and 1.0mg/kg) resulted in increased numbers of neutrophils. Signs of spontaneous activation of lung cells including the capacity of reduction of nitroblue tetrazolium (NBT), increase in myeloperoxidase (MPO) intracellular content and increase in interleukin-6 (IL-6) production were noted at both cadmium doses. Increased lung cell responsiveness to stimulation in vitro was noted at the higher cadmium dose. The presence of pulmonary inflammatory parameters in rats administered intraperitoneally with cadmium revealed the lungs as remote inflammatory targets of this metal.

What do we know about the role of gliotoxin in the pathobiology of Aspergillus fumigatus?

Gliotoxin is a member of the epipolythiodioxopiperazine class of toxins and is both the major and the most potent toxin produced by Aspergillus fumigatus. Since the discovery of the putative gliotoxin biosynthetic 12-gene cluster in the genome of A. fumigatus, five different laboratories have attempted to determine the role of this toxin in the virulence of A. fumigatus. The genes in the cluster that have been disrupted to study the pathobiological importance of gliotoxin include gliZ that encodes a transcription factor and gliP that encodes a nonribosomal peptide synthase. Two of the five laboratories have reported gliotoxin to be an important virulence determinant of A. fumigatus, while the other three laboratories have shown it to be unimportant. Comparisons of the data generated among the five laboratories revealed that the immunosuppressive regimen used for mice was the key factor that contributed to the observed disparity. Regardless of either the mouse strains used or the route of infection, immunosuppression with a combination of cyclophosphamide and corticosteroids (neutropenic mice) showed gliotoxin to be unimportant. The mice immunosuppressed with corticosteroids alone, however, revealed that gliotoxin is an important virulence determinant of A. fumigatus. These studies indicate that the neutropenic mice model is inadequate to reveal the pathobiological importance of fungal secondary metabolites in invasive pulmonary aspergillosis.