Enemy of the (immunosuppressed) state: an update on the pathogenesis of Aspergillus fumigatus infection

Use of Limestone Sludge in the Preparation of ɩ-Carrageenan/Alginate-Based Films

The use of processed limestone sludge as a crosslinking agent for films based on Na-alginate and ɩ-carrageenan/Na-alginate blends was studied. Sorbitol was tested as a plasticizer. The produced gel formulations included alginate/sorbitol and carrageenan/alginate/sorbitol mixtures, with tested sorbitol concentrations of 0.0, 0.5 and 1.0 wt%. The limestone sludge waste obtained from the processing of quarried limestone was converted into an aqueous solution of Ca2+ by dissolution with mineral acid. This solution was then diluted in water and used to induce gel crosslinking. The necessity of using sorbitol as a component of the crosslinking solution was also assessed. The resulting films were characterized regarding their dimensional stability, microstructure, chemical structure, mechanical performance and antifungal properties. Alginate/sorbitol films displayed poor dimensional stability and were deemed not viable. Carrageenan/alginate/sorbitol films exhibited higher dimensional stability and smooth and flat surfaces, especially in compositions with 0.5 wt% sorbitol. However, an increasing amount of plasticizer appears to result in severe surface cracking, the development of a segregation phenomenon affecting carrageenan and an overall decrease in films' mechanical resistance. Although further studies regarding film composition-including plasticizer fraction, film optimal thickness and film/mold material interaction-are mandatory, the attained results show the potential of the reported ɩ-carrageenan/alginate/sorbitol films to be used towards the development of viable films derived from algal polysaccharides.

Aspergillus granulosus femoral osteomyelitis in a cardiac transplant patient: first reported case and literature review

Aspergillus osteomyelitis is a rare complication of extrapulmonary invasive aspergillosis, which usually presents as spondylodiscitis. The clinical picture is usually paucisymptomatic and of long evolution, which leads to diagnostic difficulties, especially in immunosuppressed patients presenting a delayed systemic host response. We report a case of femoral osteomyelitis caused by Aspergillus granulosus in a heart transplant recipient successfully treated with a combined surgical and antifungal approach. A 65-year-old heart transplant male presented with left knee pain lasting 3 months. X-ray and magnetic resonance imaging identified a lesion with aggressive characteristics at the distal third of the left femur, due to which the patient underwent excisional surgery. Aspergillus granulosus was cultured from the removed material and antifungal treatment with oral isavuconazole was started. Chest imaging excluded pulmonary aspergillosis, while the positron emission tomography/computed tomography (PET/CT) identified a remnant of a prosthetic vascular graft sewn to the proximal third of the right axillary artery, through which a catheter-based micro-axial left ventricular assist device was implanted previously as bridge to transplant therapy. The patient presented a rapid clinical improvement with complete functional recovery following the surgical treatment and the antifungal therapy and finally underwent surgical removal of the residual vascular graft. This is the first reported episode of long bone osteomyelitis due to A. granulosus that occurred in a heart transplant recipient without pulmonary infection and was successfully treated with isavuconazole. The PET/CT was useful in supporting the diagnostic process and follow-up. Cryptic fungal species can cause invasive infections, particularly in immunocompromised patients. Molecular methods are crucial in fungal identification.

Towards a High-Affinity Peptidomimetic Targeting Proliferating Cell Nuclear Antigen from Aspergillus fumigatus

Invasive fungal infections (IFIs) are prevalent in immunocompromised patients. Due to alarming levels of increasing resistance in clinical settings, new drugs targeting the major fungal pathogen Aspergillus fumigatus are required. Attractive drug targets are those involved in essential processes like DNA replication, such as proliferating cell nuclear antigens (PCNAs). PCNA has been previously studied in cancer research and presents a viable target for antifungals. Human PCNA interacts with the p21 protein, outcompeting binding proteins to halt DNA replication. The affinity of p21 for hPCNA has been shown to outcompete other associating proteins, presenting an attractive scaffold for peptidomimetic design. p21 has no A. fumigatus homolog to our knowledge, yet our group has previously demonstrated that human p21 can interact with A. fumigatus PCNA (afumPCNA). This suggests that a p21-based inhibitor could be designed to outcompete the native binding partners of afumPCNA to inhibit fungal growth. Here, we present an investigation of extensive structure-activity relationships between designed p21-based peptides and afumPCNA and the first crystal structure of a p21 peptide bound to afumPCNA, demonstrating that the A. fumigatus replication model uses a PIP-box sequence as the method for binding to afumPCNA. These results inform the new optimized secondary structure design of a potential peptidomimetic inhibitor of afumPCNA.

Associations between invasive aspergillosis and cytomegalovirus in lung transplant recipients: a nationwide cohort study

Cytomegalovirus (CMV) and invasive aspergillosis (IA) cause morbidity among lung transplant recipients (LTXr). Early diagnosis and treatment could improve outcomes. We examined rates of CMV after IA and vice versa to assess whether screening for one infection is warranted after detecting the other. All Danish LTXr, 2010-2019, were followed for IA and CMV for 2 years after transplantation. IA was defined using ISHLT criteria. Adjusted incidence rate ratios (aIRR) were estimated by Poisson regression adjusted for time after transplantation. We included 295 LTXr, among whom CMV and IA were diagnosed in 128 (43%) and 48 (16%). The risk of CMV was high the first 3 months after IA, IR 98/100 person-years of follow-up (95% CI 47-206). The risk of IA was significantly increased in the first 3 months after CMV, aIRR 2.91 (95% CI 1.32-6.44). Numbers needed to screen to diagnose one case of CMV after IA, and one case of IA after CMV was approximately seven and eight, respectively. Systematic screening for CMV following diagnosis of IA, and vice versa, may improve timeliness of diagnosis and outcomes for LTXr.

Protective role of CFTR during fungal infection of cystic fibrosis bronchial epithelial cells with Aspergillus fumigatus

Lung infection with the fungus Aspergillus fumigatus (Af) is a common complication in cystic fibrosis (CF) and is associated with loss of pulmonary function. We established a fungal epithelial co-culture model to examine the impact of Af infection on CF bronchial epithelial barrier function using Af strains 10AF and AF293-GFP, and the CFBE41o- cell line homozygous for the F508del mutation with (CF+CFTR) and without (CF) normal CFTR expression. Following exposure of the epithelial surface to Af conidia, formation of germlings (early stages of fungal growth) was detected after 9-12 hours and hyphae (mature fungal growth) after 12-24 hours. During fungal morphogenesis, bronchial epithelial cells showed signs of damage including rounding, and partial detachment after 24 hours. Fluorescently labeled conidia were internalized after 6 hours and more internalized conidia were observed in CF compared to CF+CFTR cells. Infection of the apical surface with 10AF conidia, germlings, or hyphae was performed to determine growth stage-specific effects on tight junction protein zona occludens protein 1 (ZO-1) expression and transepithelial electrical resistance (TER). In response to infection with conidia or germlings, epithelial barrier function degraded time-dependently (based on ZO-1 immunofluorescence and TER) with a delayed onset in CF+CFTR cell monolayers and required viable fungi and apical application. Infection with hyphae caused an earlier onset and faster rate of decline in TER compared to conidia and germlings. Gliotoxin, a major Af virulence factor, caused a rapid decline in TER and induced a transient chloride secretory response in CF+CFTR but not CF cells. Our findings suggest growth and internalization of Af result in deleterious effects on bronchial epithelial barrier function that occurred more rapidly in the absence of CFTR. Bronchial epithelial barrier breakdown was time-dependent and morphotype-specific and mimicked by acute administration of gliotoxin. Our study also suggests a protective role for CFTR by turning on CFTR-dependent chloride transport in response to gliotoxin, a mechanism that will support mucociliary clearance, and could delay the loss of epithelial integrity during fungal development in vivo.

Host Factors Associated with Gut Mycobiome Structure

Recent studies revealed a significant role of the gut fungal community in human health. Here, we investigated the content and variation of gut mycobiota among subjects from the European population. We explored the interplay between gut fungi and various host-related sociodemographic, lifestyle, health, and dietary factors. The study included 923 participants. Fecal DNA samples were analyzed by whole-metagenome high-throughput sequencing. Subsequently, fungi taxonomic profiles were determined and accompanied by computational and statistical analyses of the association with 53 host-related factors. Fungal communities were characterized by a high prevalence of Saccharomyces, Candida, and Sporisorium. Ten factors were found to correlate significantly with the overall mycobiota variation. Most were diet related, including the consumption of chips, meat, sodas, sweetening, processed food, and alcohol, followed by age and marital status. Differences in α- and/or β-diversity were also reported for other factors such as body mass index (BMI), job type, autoimmunological diseases, and probiotics. Differential abundance analysis revealed fungal species that exhibited different patterns of changes under specific conditions. The human gut mycobiota is dominated by yeast, including Saccharomyces, Malassezia, and Candida. Although intervolunteer variability was high, several fungal species persisted across most samples, which may be evidence that a core gut mycobiota exists. Moreover, we showed that host-related factors such as diet, age, and marital status influence the variability of gut mycobiota. To our knowledge, this is the first large and comprehensive study of the European cohort in terms of gut mycobiota associations with such an extensive and differentiated host-related set of factors. IMPORTANCE The human gut is inhabited by many organisms, including bacteria and fungi, that may affect human health. However, research on human gut mycobiome is still rare. Moreover, the large European-based cohort study is missing. Here, we analyzed the first large European cohort in terms of gut mycobiota associations with a differentiated host-related set of factors. Our results showed that chips, meat, sodas, sweetening, processed food, beer, alcohol consumption, age, and marital status were associated with the variability of gut mycobiota. Moreover, our analysis revealed changes in abundances at the fungal species level for many investigated factors. Our results can suggest potentially valuable paths for further, narrowly focused research on gut mycobiome and its impact on human health. In the coming era of gut microbiome-based precision medicine, further research into the relationship between different mycobial structures and host-related factors may result in new preventive approaches or therapeutic procedures.

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.

Surgical resection for patients with pulmonary aspergillosis in the national inpatient sample

Background

The role of lung resection in patients with pulmonary aspergillosis is generally reserved for those with localized disease who fail medical management. We used a national database to investigate the influence of preoperative patient comorbidities on inpatient mortality and need for surgery.

Methods

Patients admitted with pulmonary aspergillosis between 2007 to 2015 were identified in the National Inpatient Sample dataset. Inpatient mortality rates were compared between patients treated medically and surgically. Predictors of mortality, surgical intervention, and non-elective admission were evaluated using multivariable logistic regression.

Results

Among a population estimate of 112,998 patients with pulmonary aspergillosis, 107,606 (95.2%) underwent medical management alone and 5,392 (4.8%) underwent surgical resection. Positive predictors for surgery included hemoptysis, and history of lung cancer or chronic pulmonary diseases. Surgically treated patients had a lower inpatient mortality when compared to those treated medically (11.5% vs. 15.1%, P<0.001) in univariate analysis, but this finding did not persist in multivariable analysis (AOR 0.97, P=0.509). The odds of mortality were lower in patients undergoing video assisted thoracoscopic surgery compared to an open approach (AOR 0.77, P=0.001). Among patients treated surgically, mortality was higher in those with a history of lung cancer, solid organ transplantation, liver disease, human immunodeficiency virus infection, hematologic diseases, chronic pulmonary diseases, and those admitted non-electively requiring surgery.

Conclusions

In this generalizable study, medical and surgical management of pulmonary aspergillosis were comparable in terms of inpatient mortality. However, non-elective admission and patients with select comorbidities have significantly worse outcomes after surgical intervention.

Predictors of Early and Late Mortality for Patients with Hematologic Malignancy and Invasive Mold Disease

Background: Invasive mold infections (IMI) are leading infectious causes of mortality among patients with hematological malignancies. Objectives: To determine the relative contribution of host, disease, and treatment-related factors to patient survival. Methods: An observational, retrospective cohort study reviewing the medical records of patients with hematological malignancy and IMI (2006–2016). Causes of death were classified up to 90 days after diagnosis. Kaplan–Meier and Cox regression analyses were used to determine risk factors for early, late, and overall mortality. Results: Eighty-six patients with IMI were included; 29 (34%) and 41 (47%) died within 6 and 12 weeks of diagnosis, respectively. Death was attributed to IMI in 22 (53.6%) patients, all of whom died within 45 days of diagnosis. Risk factors for early mortality were elevated serum galactomannan, treatment with amphotericin B, IMI progression 3 weeks after diagnosis, and lymphoma undergoing HCT. Late mortality was associated with relapsed/refractory malignancy and elevated serum galactomannan. Conclusions: In this single-center study of patients with IMI, infections were the most frequent causes of death, and time-dependent risk factors for death were identified. These results may help direct risk-assessment and monitoring of patients undergoing treatment of IMI.

Aspergillus fumigatus AR04 obeys Arrhenius' rule in cultivation temperature shifts from 30 to 40°C

To set a benchmark in fungal growth rate, a differential analysis of prototrophic Aspergillus fumigatus AR04 with three ascomycetes applied in > 103 t year-1 scale was performed, i.e. Ashbya gosspyii (riboflavin), Aspergillus niger (citric acid) and Aspergillus oryzae (food-processing). While radial colony growth decreased 0.5-fold when A. gossypii was cultivated at 40°C instead of 28°C, A. fumigatus AR04 responded with 1.7-fold faster hyphal growth. A. niger and A. oryzae formed colonies at 40°C, but not at 43°C. Moreover, all A. fumigatus strains tested grew even at 49°C. In chemostat experiments, A. fumigatus AR04 reached steady state at a dilution rate of 0.7 h-1 at 40°C, 120% more than reported for A. gossypii at 28°C. To study mycelial growth rates under unlimited conditions, carbon dioxide increase rates were calculated from concentrations detected online in the exhaust of batch fermentations for 3 h only. All rates calculated suggest that A. fumigatus AR04 approximates Arrhenius' rule when comparing short cultivations at 30°C with those at 40°C. Linearization of the exponential phase and comparison of the slopes revealed an increase to 192% by the 10°C up-shift.

How Long Do We Need to Treat an Invasive Mold Disease in Hematology Patients? Factors Influencing Duration of Therapy and Future Questions

Treatment duration for invasive mold disease (IMD) in patients with hematological malignancy is not standardized and is a challenging subject in antifungal stewardship. Concerns for IMD relapse during subsequent reinduction or consolidation chemotherapy or graft versus host disease treatment in hematopoietic stem cell transplant recipients often results in prolonged or indefinite antifungal treatment. There are no validated criteria that predict when it is safe to stop antifungals. Decisions are individualized and depend on the offending fungus, site and extent of IMD, comorbidities, hematologic disease prognosis, and future plans for chemotherapy or transplantation. Recent studies suggest that FDG-PET/CT could help discriminate between active and residual fungal lesions to support decisions for safely stopping antifungals. Validation of noninvasive biomarkers for monitoring treatment response, tests for quantifying the "net state of immunosuppression," and genetic polymorphisms associated with poor fungal immunity could lead to a personalized assessment for the continued need for antifungal therapy.

Dysregulation of Key Proteinases in Aspergillus fumigatus Induced by Blood Platelets

Background

Aspergillus fumigatus is the most common species causing invasive aspergillosis (IA), a life-threatening infection with more than 80% mortality. Interactions between A. fumigatus and human blood platelets lead to intravascular thrombosis and localized infarcts. To better understand A. fumigatus pathogenesis, we aimed to analyze the genetic basis of interactions between the pathogen and blood platelets.

Methods

A bioinformatic pipeline on microarray gene expression dataset, including analysis of differentially expressed genes (DEGs) using Limma R package and their molecular function, as well as biological pathways identification, was conducted to find the effective genes involved in IA. In the wet phase, the gene expression patterns following fungal exposure to blood platelets at 15, 30, 60, and 180 min were evaluated by quantitative reverse transcriptase-PCR analysis.

Results

Three genes encoding aspartic endopeptidases including (Pep1), (Asp f 13), and (β-glucanase) were the standing candidates. The invasion-promoting fungal proteinase-encoding genes were down-regulated after 30 min of hyphal incubation with blood platelets, and then up-regulated at 60 and 180 min, although only Pep1 was greater than the control at the 60and 180 min time points. Also, the same genes were downregulated in more the clinical isolates relative to the standard strain CBS 144.89.

Conclusion

Our findings delineate the possible induction of fungal-encoded proteinases by blood platelets. This provides a new research line into A. fumigatus' molecular pathogenesis. Such insight into IA pathogenesis might also guide researchers toward novel platelet-based therapies that involve molecular interventions, especially in IA patients.

Cerebral Invasive Aspergillosis in a Case of Chronic Lymphocytic Leukemia with Bruton Tyrosine Kinase Inhibitor

Bruton tyrosine kinase (BTK) inhibitors have become an important therapy for untreated and previously treated patients with chronic lymphocytic leukemia (CLL). Despite improved outcomes, rare adverse events, such as invasive fungal infections, have been reported with the use of first-generation BTK inhibitors. Invasive fungal infections carry a high morbidity and mortality risk. There have been several case reports describing the association between aspergillosis and ibrutinib treatment, but none with acalabrutinib, to our knowledge. In this case report, we describe a patient with CLL who developed an intracranial Aspergillus fumigatus infection while receiving acalabrutinib.

Aspergillosis infection over 20 years: a case report of probable vascular invasion in central nervous system

Background

Aspergillosis infection of central nervous system (CNS) is rare and fatal. Diagnosis of invasive aspergillosis remains difficult. Aspergillosis of CNS can be an acute, subacute, or chronic onset, and the longest course of the disease was currently reported to be 4 years. Here, we report a case with recurrent headache over 20 years.

Case presentation

A 54-year-old man was admitted to our neurological disease ward due to intermittent throbbing headache lasting for more than 20 years that had grown notably worse over the past week. The headache was localized to the side of his head blown by a cold wind. He also experienced nausea and vomiting when the headache became severe. The headache usually lasted for 3–4 h after he was blown by the cold wind, though he had no fever. The neurological examination was normal. Magnetic resonance imaging (MRI) of the brain was negative for parenchymal and meningeal lesions. However, the case had increased intracranial pressure (ICP), and elevated protein level in the cerebrospinal fluid (CSF). Aspergillus fumigatus was found in CSF by nanopore targeted sequencing (NTS) and in blood by enzyme-linked immunosorbent assay (ELISA). Aspergillus fumigatus-specific antibody IgG was 104.62 AU/mL, aspergillus galactomannan (GM) antigen was 3.27 μg/L, D-dimer was 3.25 mg/L and fibrinogen degradation product was 11.50 mg/L, which were markedly higher than the normal levels. The patient was prescribed by voriconazole. After the treatment of 14 days, the ICP, CSF protein level, Aspergillus fumigatus-specific antibody IgG, GM antigen, D-dimer and fibrinogen degradation product returned normal. Aspergillus was disappeared by NTS test of CSF. His headache has never occurred again after blowing by a cold wind.

Conclusions

This report reveals that aspergillosis infection of CNS can last for more than 20 years and the major symptom is only intermittent throbbing headache in an immunocompetent patient. Vascular invasion is probably the mechanism of headache in our case with CNS aspergillosis infection. Performing high-throughput gene sequencing technology in CSF is important when the pathogen is not determined for the patients with suspected CNS infection.

A transcriptional signature accurately identifies Aspergillus Infection across healthy and immunosuppressed states

Invasive aspergillosis (IA) is a major cause of critical illness in immunocompromised (IC) patients. However, current fungal tests are limited. Disease-specific gene expression patterns in circulating host cells show promise as novel diagnostics, however it is unknown whether such a 'signature' exists for IA and the effect of iatrogenic immunosuppression on any such biomarkers. Male BALB/c mice were separated into 6 experimental groups based on Aspergillus fumigatus inhalational exposure and IC status (no immunosuppression, cyclophosphamide, and corticosteroids). Mice were sacrificed 4 days postinfection. Whole blood was assayed for transcriptomic responses in peripheral white blood cells via microarray. An elastic net regularized logistic regression was employed to develop classifiers of IA based on gene expression. Aspergillus infection triggers a powerful response in non-IC hosts with 2718 genes differentially expressed between IA and controls. We generated a 146-gene classifier able to discriminate between non-IC infected and uninfected mice with an AUC of 1. However, immunosuppressive medications exhibited a confounding effect on this transcriptomic classifier. After controlling for the genomic effects of immunosuppression, we were able to generate a 187-gene classifier with an AUC of 0.92 in the absence of immunosuppression, 1 with cyclophosphamide, and 0.9 with steroids. The host transcriptomic response to IA is robust and conserved. Pharmacologic perturbation of the host immune response has powerful effects on classifier performance and must be considered when developing such novel diagnostics. When appropriately designed, host-derived peripheral blood transcriptomic responses demonstrate the ability to accurately diagnose Aspergillus infection, even in the presence of immunosuppression.

A Higher Rate of Pulmonary Fungal Infection in Chronic Obstructive Pulmonary Disease Patients with Influenza in a Large Tertiary Hospital

BACKGROUND

Influenza is considered a self-limiting disease. However, in patients with chronic obstructive pulmonary disease (COPD), it may result in serious outcomes during the flu season.

OBJECTIVES

The aims of this retrospective study were to explore the characteristics of hospitalized patients with COPD complicated by influenza and determine the factors affecting the prognosis of these patients.

METHOD

Demographic and clinical data were collected for 278 patients totally from the West China Hospital between January 1, 2016 and February 28, 2018.

RESULTS

Among the patients with influenza, the positive fungal culture rate, and the rates of antifungal drug and systemic corticosteroids use were higher for those with COPD than for those without COPD. Respiratory failure was more common in patients with influenza and COPD than in patients with influenza only, while the proportion of severe cases was higher among the former than among the latter. Among the patients with COPD, the positive fungal culture rate, particularly for Aspergillus, and the rate of systemic corticosteroids use were higher for those with influenza than for those without influenza. Multivariate analysis revealed that a COPD history of >20 years and smoking for >20 pack-years were independent factors for susceptibility of COPD patients to influenza.

CONCLUSIONS

Aspergillus infection seems to be more common in patients with influenza and COPD. In addition, COPD complicated by influenza during the seasonal outbreak can easily progress to a severe disease state. Heavy smokers and patients with a prolonged COPD history are more likely to be infected by influenza.

Characterizing the Pathogenic, Genomic, and Chemical Traits of Aspergillus fischeri, a Close Relative of the Major Human Fungal Pathogen Aspergillus fumigatus

Aspergillus fischeri is closely related to Aspergillus fumigatus, the major cause of invasive mold infections. Even though A. fischeri is commonly found in diverse environments, including hospitals, it rarely causes invasive disease. Why A. fischeri causes less human disease than A. fumigatus is unclear. A comparison of A. fischeri and A. fumigatus for pathogenic, genomic, and secondary metabolic traits revealed multiple differences in pathogenesis-related phenotypes. We observed that A. fischeri NRRL 181 is less virulent than A. fumigatus strain CEA10 in multiple animal models of disease, grows slower in low-oxygen environments, and is more sensitive to oxidative stress. Strikingly, the observed differences for some traits are of the same order of magnitude as those previously reported between A. fumigatus strains. In contrast, similar to what has previously been reported, the two species exhibit high genomic similarity; ∼90% of the A. fumigatus proteome is conserved in A. fischeri, including 48/49 genes known to be involved in A. fumigatus virulence. However, only 10/33 A. fumigatus biosynthetic gene clusters (BGCs) likely involved in secondary metabolite production are conserved in A. fischeri and only 13/48 A. fischeri BGCs are conserved in A. fumigatus Detailed chemical characterization of A. fischeri cultures grown on multiple substrates identified multiple secondary metabolites, including two new compounds and one never before isolated as a natural product. Additionally, an A. fischeri deletion mutant of laeA, a master regulator of secondary metabolism, produced fewer secondary metabolites and in lower quantities, suggesting that regulation of secondary metabolism is at least partially conserved. These results suggest that the nonpathogenic A. fischeri possesses many of the genes important for A. fumigatus pathogenicity but is divergent with respect to its ability to thrive under host-relevant conditions and its secondary metabolism.IMPORTANCEAspergillus fumigatus is the primary cause of aspergillosis, a devastating ensemble of diseases associated with severe morbidity and mortality worldwide. A. fischeri is a close relative of A. fumigatus but is not generally observed to cause human disease. To gain insights into the underlying causes of this remarkable difference in pathogenicity, we compared two representative strains (one from each species) for a range of pathogenesis-relevant biological and chemical characteristics. We found that disease progression in multiple A. fischeri mouse models was slower and caused less mortality than A. fumigatus Remarkably, the observed differences between A. fischeri and A. fumigatus strains examined here closely resembled those previously described for two commonly studied A. fumigatus strains, AF293 and CEA10. A. fischeri and A. fumigatus exhibited different growth profiles when placed in a range of stress-inducing conditions encountered during infection, such as low levels of oxygen and the presence of chemicals that induce the production of reactive oxygen species. We also found that the vast majority of A. fumigatus genes known to be involved in virulence are conserved in A. fischeri, whereas the two species differ significantly in their secondary metabolic pathways. These similarities and differences that we report here are the first step toward understanding the evolutionary origin of a major fungal pathogen.

Transcriptomic and proteomic host response to Aspergillus fumigatus conidia in an air-liquid interface model of human bronchial epithelium

Aspergillus fumigatus (A. fumigatus) is a wide-spread fungus that is a potent allergen in hypersensitive individuals but also an opportunistic pathogen in immunocompromised patients. It reproduces asexually by releasing airborne conidiospores (conidia). Upon inhalation, fungal conidia are capable of reaching the airway epithelial cells (AECs) in bronchial and alveolar tissues. Previous studies have predominantly used submerged monolayer cultures for studying this host-pathogen interaction; however, these cultures do not recapitulate the mucocililary differentiation phenotype of the in vivo epithelium in the respiratory tract. Thus, the aim of this study was to use well-differentiated primary human bronchial epithelial cells (HBECs) grown at the air-liquid interface (ALI) to determine their transcriptomic and proteomic responses following interaction with A. fumigatus conidia. We visualized conidial interaction with HBECs using confocal laser scanning microscopy (CLSM), and applied NanoString nCounter and shotgun proteomics to assess gene expression changes in the human cells upon interaction with A. fumigatus conidia. Western blot analysis was used to assess the expression of top three differentially expressed proteins, CALR, SET and NUCB2. CLSM showed that, unlike submerged monolayer cultures, well-differentiated ALI cultures of primary HBECs were estimated to internalize less than 1% of bound conidia. Nevertheless, transcriptomic and proteomic analyses revealed numerous differentially expressed host genes; these were enriched for pathways including apoptosis/autophagy, translation, unfolded protein response and cell cycle (up-regulated); complement and coagulation pathways, iron homeostasis, nonsense mediated decay and rRNA binding (down-regulated). CALR and SET were confirmed to be up-regulated in ALI cultures of primary HBECs upon exposure to A. fumigatus via western blot analysis. Therefore, using transcriptomics and proteomics approaches, ALI models recapitulating the bronchial epithelial barrier in the conductive zone of the respiratory tract can provide novel insights to the molecular response of bronchial epithelial cells upon exposure to A. fumigatus conidia.

Comparative genotyping and phenotyping of Aspergillus fumigatus isolates from humans, dogs and the environment

Background

Aspergillus fumigatus is a ubiquitous saprotrophic fungus and an opportunistic pathogen of humans and animals. Humans and animals can inhale hundreds of A. fumigatus spores daily. Normally this is harmless for humans, but in case of immunodeficiency, invasive pulmonary aspergillosis (IPA) can develop with a high mortality rate. A. fumigatus also causes non-invasive mycoses like sino-nasal aspergillosis (SNA) in dogs.

Results

In this study we compared A. fumigatus isolates from humans with suspected IPA, dogs with SNA, and a set of environmental isolates. Phylogenetic inference based on calmodulin (CaM) and beta-tubulin (benA) sequences did not reveal A. fumigatus sub-groups linked to the origin of the isolates. Genotyping and microsatellite analysis showed that each dog was infected by one A. fumigatus genotype, whereas human patients had mixed infections. Azole resistance was determined by antifungal susceptibility testing and sequencing of the cyp51A gene. A total of 12 out of 29 human isolates and 1 out of 27 environmental isolates were azole resistant. Of the azole resistant strains, 11 human isolates showed TR₃₄/L98H (n = 6) or TR46/Y121F/T289A (n = 5). Phenotypically, isolates from dogs were more variable in growth speed and morphology when compared to those isolated from human and the environment.

Conclusions

A. fumigatus from dogs with SNA are phenotypically very diverse in contrast to their environmental and human counterparts.

Phenotypic variability can be induced during the chronic infection process in the sinus of the dogs. The basis of this heterogeneity might be due to genomic differences and/or epigenetic variations.

Differences in dogs is a could be a result of within-host adaption and might be triggered by environmental factors in the sinus, however this hypothesis still needs to be tested.

Electronic supplementary material

The online version of this article (10.1186/s12866-018-1244-2) contains supplementary material, which is available to authorized users.

Identification of a novel anoikis signalling pathway using the fungal virulence factor gliotoxin

Anoikis is a form of apoptosis induced by cell detachment. Integrin inactivation plays a major role in the process but the exact signalling pathway is ill-defined. Here we identify an anoikis pathway using gliotoxin (GT), a virulence factor of the fungus Aspergillus fumigatus, which causes invasive aspergillosis in humans. GT prevents integrin binding to RGD-containing extracellular matrix components by covalently modifying cysteines in the binding pocket. As a consequence, focal adhesion kinase (FAK) is inhibited resulting in dephosphorylation of p190RhoGAP, allowing activation of RhoA. Sequential activation of ROCK, MKK4/MKK7 and JNK then triggers pro-apoptotic phosphorylation of Bim. Cells in suspension or lacking integrin surface expression are insensitive to GT but are sensitised to ROCK-MKK4/MKK7-JNK-dependent anoikis upon attachment to fibronectin or integrin upregulation. The same signalling pathway is triggered by FAK inhibition or inhibiting integrin αV/β3 with Cilengitide. Thus, GT can target integrins to induce anoikis on lung epithelial cells.

A Rare and Potentially Catastrophic Infection: Primary Intestinal Aspergillosis-Case Report in an HIV Patient

Aspergillus species are ubiquitous in nature; however, infection is uncommon, except in immunocompromised or immunosuppressed hosts. We present the case of a 71-year-old woman with a history of human immunodeficiency virus infection who presented with fever, weight loss, and diarrhea, posteriorly diagnosed with intestinal aspergillosis after examination of a segmental enterectomy piece. The diagnosis was made postmortem once the patient died after fast and progressive deterioration in the postoperative period.

Genetic deficiency of NOD2 confers resistance to invasive aspergillosis

Invasive aspergillosis (IA) is a severe infection that can occur in severely immunocompromised patients. Efficient immune recognition of Aspergillus is crucial to protect against infection, and previous studies suggested a role for NOD2 in this process. However, thorough investigation of the impact of NOD2 on susceptibility to aspergillosis is lacking. Common genetic variations in NOD2 has been associated with Crohn's disease and here we investigated the influence of these  genetic variations on the anti-Aspergillus host response. A NOD2 polymorphism reduced the risk of IA after hematopoietic stem-cell transplantation. Mechanistically, absence of NOD2 in monocytes and macrophages increases phagocytosis leading to enhanced fungal killing, conversely, NOD2 activation reduces the antifungal potential of these cells. Crucially, Nod2 deficiency results in resistance to Aspergillus infection in an in vivo model of pulmonary aspergillosis. Collectively, our data demonstrate that genetic deficiency of NOD2 plays a protective role during Aspergillus infection.

The utility of contrast-enhanced hypodense sign for the diagnosis of pulmonary invasive mould disease in patients with haematological malignancies

OBJECTIVE

The hypodense sign (HyS) on CT imaging is highly suggestive of pulmonary invasive mould disease (IMD) in patients with haematological malignancies, but its diagnostic utility has not been systematically evaluated on contrast-enhanced CT. The objective of this study was to compare the diagnostic performance of the HyS to other common CT findings in a cohort of haematology patients with proven, probable or possible IMD based on European Organization for Research and Treatment of Cancer/Mycoses Study Group criteria.

METHODS

We analysed the diagnostic performance of the HyS to other common CT signs among 127 neutropenic patients with haematological malignancies submitted to both non-contrast-enhanced and contrast-enhanced CT scans of the lungs, including CT pulmonary angiography.

RESULTS

The HyS was detected in 15.7% of patients imaged without contrast, and 44.1% after contrast administration. A contrast-aided HyS was detected in 86.6, 78.0 and 15.5% of patients with European Organization for Research and Treatment of Cancer/Mycoses Study Group proven, probable and possible IMD, respectively. When analysed per clinical diagnosis (proven, probable and highly possible IMD-i.e. no alternative diagnosis to mould disease reached), the contrast-enhanced HyS was as sensitive as the halo sign but significantly more specific [halo sign 0.56, 95% CI (0.39-0.71) vs HyS 0.98, 95% CI (0.87-1.00)]. Only the vessel occlusion sign was more sensitive [0.97, 95% CI (0.91-0.99)] and specific [0.97, 95% CI (0.86-0.99)] than the HyS for IMD diagnosis.

CONCLUSION

The high specificity of the HyS strongly supports the diagnosis of pulmonary IMD in neutropenic patients, and is highly suggestive breakthrough fungal disease in patients on mould-active antifungal prophylaxis. Advances in knowledge: This is the first systematic analysis of the hypodense sign on contrast-enhanced CT; the sign can support the diagnosis of IMD when other CT signs are uncertain.

The Absence of NOD1 Enhances Killing of Aspergillus fumigatus Through Modulation of Dectin-1 Expression

One of the major life-threatening infections for which severely immunocompromised patients are at risk is invasive aspergillosis (IA). Despite the current treatment options, the increasing antifungal resistance and poor outcome highlight the need for novel therapeutic strategies to improve outcome of patients with IA. In the current study, we investigated whether and how the intracellular pattern recognition receptor NOD1 is involved in host defense against Aspergillus fumigatus. When exploring the role of NOD1 in an experimental mouse model, we found that Nod1^−/− mice were protected against IA and demonstrated reduced fungal outgrowth in the lungs. We found that macrophages derived from bone marrow of Nod1^−/− mice were more efficiently inducing reactive oxygen species and cytokines in response to Aspergillus. Most strikingly, these cells were highly potent in killing A. fumigatus compared with wild-type cells. In line, human macrophages in which NOD1 was silenced demonstrated augmented Aspergillus killing and NOD1 stimulation decreased fungal killing. The differentially altered killing capacity of NOD1 silencing versus NOD1 activation was associated with alterations in dectin-1 expression, with activation of NOD1 reducing dectin-1 expression. Furthermore, we were able to demonstrate that Nod1^−/− mice have elevated dectin-1 expression in the lung and bone marrow, and silencing of NOD1 gene expression in human macrophages increases dectin-1 expression. The enhanced dectin-1 expression may be the mechanism of enhanced fungal killing of Nod1^−/− cells and human cells in which NOD1 was silenced, since blockade of dectin-1 reversed the augmented killing in these cells. Collectively, our data demonstrate that NOD1 receptor plays an inhibitory role in the host defense against Aspergillus. This provides a rationale to develop novel immunotherapeutic strategies for treatment of aspergillosis that target the NOD1 receptor, to enhance the efficiency of host immune cells to clear the infection by increasing fungal killing and cytokine responses.

Ketoacidosis alone does not predispose to mucormycosis by Lichtheimia in a murine pulmonary infection model

Mucormycosis is a rare fungal infection; however, the number of cases increased during the last decades. The main risk factors are immunosuppression and uncontrolled diabetes mellitus. Although Lichtheimia species represent a common cause of mucormycosis in Europe, virulence and pathogenesis of this genus has not been investigated in detail yet. Using murine pulmonary infection models, we found that immunosuppression is essential for establishment of infection. The disease was characterized by necrosis, angioinvasion, thrombosis, and the lethal course of infection was associated with systemic activation of platelets. Furthermore, dissemination to internal organs was frequently observed. While the virulence potential of individual L. corymbifera and L. ramosa isolates differed, pathogenicity of both species was comparable. Although ketoacidosis promoted Rhizopus infection in mice, it did not predispose mice to infection with Lichtheimia in the absence of additional immunosuppression. This might partially explain the dominance of Rhizopus as cause of mucormycosis in countries with high prevalence of ketoacidotic patients.

Fungal Pneumonia in Patients with Hematologic Malignancy and Hematopoietic Stem Cell Transplantation

Fungal pneumonias cause unacceptable morbidity among patients with hematologic malignancies (HM) and recipients of hematopoietic stem cell transplantation (HSCT). The high incidence of fungal pneumonias in HM/HSCT populations arises from their frequently severe, complex, and persistent immune dysfunction caused by the underlying disease and its treatment. The cytopenias, treatment toxicities, and other immune derangements that make patients susceptible to fungal pneumonia frequently complicate its diagnosis and increase the intensity and duration of antifungal therapy. This article addresses the host factors that contribute to susceptibility, summarizes diagnostic recommendations, and reviews current guidelines for management of fungal pneumonia in patients with HM/HSCT.

Neutrophil Interactions Stimulate Evasive Hyphal Branching by Aspergillus fumigatus

Invasive aspergillosis (IA), primarily caused by Aspergillus fumigatus, is an opportunistic fungal infection predominantly affecting immunocompromised and neutropenic patients that is difficult to treat and results in high mortality. Investigations of neutrophil-hypha interaction in vitro and in animal models of IA are limited by lack of temporal and spatial control over interactions. This study presents a new approach for studying neutrophil-hypha interaction at single cell resolution over time, which revealed an evasive fungal behavior triggered by interaction with neutrophils: Interacting hyphae performed de novo tip formation to generate new hyphal branches, allowing the fungi to avoid the interaction point and continue invasive growth. Induction of this mechanism was independent of neutrophil NADPH oxidase activity and neutrophil extracellular trap (NET) formation, but could be phenocopied by iron chelation and mechanical or physiological stalling of hyphal tip extension. The consequence of branch induction upon interaction outcome depends on the number and activity of neutrophils available: In the presence of sufficient neutrophils branching makes hyphae more vulnerable to destruction, while in the presence of limited neutrophils the interaction increases the number of hyphal tips, potentially making the infection more aggressive. This has direct implications for infections in neutrophil-deficient patients and opens new avenues for treatments targeting fungal branching.

First Line of Defense: Innate Cell-Mediated Control of Pulmonary Aspergillosis

Mycotic infections and their effect on the human condition have been widely overlooked and poorly surveilled by many health organizations even though mortality rates have increased in recent years. The increased usage of immunosuppressive and myeloablative therapies for the treatment of malignant as well as non-malignant diseases has contributed significantly to the increased incidence of fungal infections. Invasive fungal infections have been found to be responsible for at least 1.5 million deaths worldwide. About 90% of these deaths can be attributed to Cryptococcus, Candida, Aspergillus, and Pneumocystis. A better understanding of how the host immune system contains fungal infection is likely to facilitate the development of much needed novel antifungal therapies. Innate cells are responsible for the rapid recognition and containment of fungal infections and have been found to play essential roles in defense against multiple fungal pathogens. In this review we summarize our current understanding of host-fungi interactions with a focus on mechanisms of innate cell-mediated recognition and control of pulmonary aspergillosis.

Regulatory roles of phosphorylation in model and pathogenic fungi

Over the past 20 years, considerable advances have been made toward our understanding of how post-translational modifications affect a wide variety of biological processes, including morphology and virulence, in medically important fungi. Phosphorylation stands out as a key molecular switch and regulatory modification that plays a critical role in controlling these processes. In this article, we first provide a comprehensive and up-to-date overview of the regulatory roles that both Ser/Thr and non-Ser/Thr kinases and phosphatases play in model and pathogenic fungi. Next, we discuss the impact of current global approaches that are being used to define the complete set of phosphorylation targets (phosphoproteome) in medically important fungi. Finally, we provide new insights and perspectives into the potential use of key regulatory kinases and phosphatases as targets for the development of novel and more effective antifungal strategies.

Characteristic clinical features of Aspergillus appendicitis: Case report and literature review

This work aims to facilitate diagnosing Aspergillus appendicitis, which can be missed clinically due to its rarity, by proposing a clinical pentad for Aspergillus appendicitis based on literature review and one new case. The currently reported case of pathologically-proven Aspergillus appendicitis was identified by computerized search of pathology database at William Beaumont Hospital, 1999-2014. Prior cases were identified by computerized literature search. Among 10980 pathology reports of pathologically-proven appendicitis, one case of Aspergillus appendicitis was identified (rate = 0.01%). A young boy with profound neutropenia, recent chemotherapy, and acute myelogenous leukemia presented with right lower quadrant pain, pyrexia, and generalized malaise. Abdominal computed tomography scan showed a thickened appendiceal wall and periappendiceal inflammation, suggesting appendicitis. Emergent laparotomy showed an inflamed, thickened appendix, which was resected. The patient did poorly postoperatively with low-grade-fevers while receiving antibacterial therapy, but rapidly improved after initiating amphotericin therapy. Microscopic examination of a silver stain of the appendectomy specimen revealed fungi with characteristic Aspergillus morphology, findings confirmed by immunohistochemistry. Primary Aspergillus appendicitis is exceptionally rare, with only 3 previously reported cases. All three cases presented with (1)-neutropenia, (2)-recent chemotherapy, (3)-acute leukemia, and (4)-suspected appendicitis; (5)-the two prior cases initially treated with antibacterial therapy, fared poorly before instituting anti-Aspergillus therapy. The current patient satisfied all these five criteria. Based on these four cases, a clinical pentad is proposed for Aspergillus appendicitis: clinically-suspected appendicitis, neutropenia, recent chemotherapy, acute leukemia, and poor clinical response if treated solely by antibacterial/anti-candidial therapy. Patients presenting with this proposed pentad may benefit from testing for Aspergillus infection by silver-stains/immunohistochemistry and considering empirical anti-Aspergillus therapy pending a tissue diagnosis.

Pseudallescheria boydii with Aspergillus fumigatus and Aspergillus terreus in a Critically Ill Hematopoietic Stem Cell Recipient with ARDS

Pseudallescheria boydii is a fungal organism known to affect immunocompromised patients. This organism is known to cause, in severe cases, invasive infection of various organs such as the central nervous, cardiovascular, and respiratory systems. We report an unusual case of pulmonary P. boydii pneumonia in an immunocompromised critically ill patient with a co-infection of Aspergillus fumigatus and Aspergillus terreus with ARDS. This case highlights the importance of a high index of suspicion for superimposed fungal infections in patients who are critically ill and immunocompromised. Uncommon fungal pathogens should be considered in the differential diagnosis of respiratory failure, especially if diagnostic markers such as galactomannan (from BAL and serum) or 1,3-beta-d-glucan are elevated. Further diagnostic interventions are warranted when insufficient clinical improvement is observed to prevent treatment failure and adverse outcomes.

Survival following lung resection in immunocompromised patients with pulmonary invasive fungal infection

OBJECTIVES

Pulmonary invasive fungal infections (IFIs) are associated with high mortality in patients being treated for haematological malignancy. There is limited understanding of the role for surgical lung resection and outcomes in this patient population.

METHODS

This is a retrospective cohort of 50 immunocompromised patients who underwent lung resection for IFI. Patient charts were reviewed for details on primary malignancy and treatment course, presentation and work-up of IFI, reasons for surgery, type of resection and outcomes including postoperative complications, mortality, disease relapse and survival. Analysis was also performed on two subgroups based on year of surgery from 1990-2000 and 2001-2014.

RESULTS

The median age was 39 years (range: 5-64 years). Forty-seven patients (94%) had haematological malignancies and 38 (76%) underwent haematopoietic stem cell transplantation (HSCT). Surgical indications included haemoptysis, antifungal therapy failure and need for eradication before HSCT. The most common pathogen was Aspergillus in 34 patients (74%). Wedge resections were performed in 32 patients (64%), lobectomy in 9 (18%), segmentectomy in 2 (4%) and some combination of the 3 in 7 (14%) for locally extensive, multifocal disease. There were 9 (18%) minor and 14 (28%) major postoperative complications. Postoperative mortality at 30 days was 12% (n = 6). Acute respiratory distress syndrome was the most common cause of postoperative death. Overall 5-year survival was 19%. Patients who had surgery in the early period had a median survival of 24 months compared with 5 months for those who had surgery before 2001 (P = 0.046). At the time of death, 15 patients (30%) had probable or proven recurrent IFI. Causes of death were predominantly related to refractory malignancy, fungal lung disease or complications of graft versus host disease (GVHD). Patients who had positive preoperative bronchoscopy cultures had a trend towards worse survival compared with those with negative cultures (hazard ratio: 1.80, P = 0.087).

CONCLUSIONS

Surgical resection of IFI in immunocompromised patients is associated with high perioperative mortality. Long-term survival is limited by recurrent malignancy, persistent fungal infection and GVHD but has improved in recent years. Selection for surgical resection is difficult in this patient population, but should be carefully considered in those who are symptomatic, or have failed antifungal treatment.

ChIP-seq and in vivo transcriptome analyses of the Aspergillus fumigatus SREBP SrbA reveals a new regulator of the fungal hypoxia response and virulence

The Aspergillus fumigatus sterol regulatory element binding protein (SREBP) SrbA belongs to the basic Helix-Loop-Helix (bHLH) family of transcription factors and is crucial for antifungal drug resistance and virulence. The latter phenotype is especially striking, as loss of SrbA results in complete loss of virulence in murine models of invasive pulmonary aspergillosis (IPA). How fungal SREBPs mediate fungal virulence is unknown, though it has been suggested that lack of growth in hypoxic conditions accounts for the attenuated virulence. To further understand the role of SrbA in fungal infection site pathobiology, chromatin immunoprecipitation followed by massively parallel DNA sequencing (ChIP-seq) was used to identify genes under direct SrbA transcriptional regulation in hypoxia. These results confirmed the direct regulation of ergosterol biosynthesis and iron uptake by SrbA in hypoxia and revealed new roles for SrbA in nitrate assimilation and heme biosynthesis. Moreover, functional characterization of an SrbA target gene with sequence similarity to SrbA identified a new transcriptional regulator of the fungal hypoxia response and virulence, SrbB. SrbB co-regulates genes involved in heme biosynthesis and demethylation of C4-sterols with SrbA in hypoxic conditions. However, SrbB also has regulatory functions independent of SrbA including regulation of carbohydrate metabolism. Loss of SrbB markedly attenuates A. fumigatus virulence, and loss of both SREBPs further reduces in vivo fungal growth. These data suggest that both A. fumigatus SREBPs are critical for hypoxia adaptation and virulence and reveal new insights into SREBPs' complex role in infection site adaptation and fungal virulence.

Despite improvements in diagnostics and antifungal drug treatments, mortality rates from invasive mold infections remain high. Defining the fungal adaptation and growth mechanisms at the infection site microenvironment is one research focus that is expected to improve treatment of established invasive fungal infections. The Aspergillus fumigatus transcription factor SrbA is a major regulator of the fungal response to hypoxia found at sites of invasive fungal growth in vivo. In this study, new insights into how SrbA mediates hypoxia adaptation and virulence were revealed through identification of direct transcriptional targets of SrbA under hypoxic conditions. A major novel finding from these studies is the identification of a critical role in fungal hypoxia adaptation and virulence of an SrbA target gene, srbB, which is also in the SREBP family. SrbB plays a major role in regulation of heme biosynthesis and carbohydrate metabolism early in the response to hypoxia. The discovery of SrbA-dependent regulation of srbB gene expression, and the target genes they regulate opens new avenues to understand how SREBPs and their target genes mediate adaptation to the in vivo infection site microenvironment and responses to current antifungal therapies.

Immunoevasive Aspergillus virulence factors

Individuals with structural lung disease or defective immunity are predisposed to Aspergillus-associated disease. Manifestations range from allergic to cavitary or angio-invasive syndromes. Despite daily spore inhalation, immunocompetence facilitates clearance through initiation of innate and adaptive host responses. These include mechanical barriers, phagocyte activation, antimicrobial peptide release and pattern recognition receptor activation. Adaptive responses include Th1 and Th2 approaches. Understanding Aspergillus virulence mechanisms remains critical to the development of effective research and treatment strategies to counteract the fungi. Major virulence factors relate to fungal structure, protease release and allergens; however, mechanisms utilized to evade immune recognition continue to be important in establishing infection. These include the fungal rodlet layer, dihydroxynaphthalene-melanin, detoxifying systems for reactive oxygen species and toxin release. One major immunoevasive toxin, gliotoxin, plays a key role in mediating Aspergillus-associated colonization in the context of cystic fibrosis. Here, it down-regulates vitamin D receptor expression which following itraconazole therapy is rescued concurrent with decreased Th2 cytokine (IL-5 and IL-13) concentrations in the CF airway. This review focuses on the interaction between Aspergillus pathogenic mechanisms, host immune responses and the immunoevasive strategies employed by the organism during disease states such as that observed in cystic fibrosis.

Induction of gliotoxin secretion in Aspergillus fumigatus by bacteria-associated molecules

Aspergillus fumigatus is the most common causative agent of mold diseases in humans, giving rise to life-threatening infections in immunocompromised individuals. One of its secreted metabolites is gliotoxin, a toxic antimicrobial agent. The aim of this study was to determine whether the presence of pathogen-associated molecular patterns in broth cultures of A. fumigatus could induce gliotoxin production. Gliotoxin levels were analyzed by ultra-performance liquid chromatography and mass spectrometry. The presence of a bacteria-derived lipopolysaccharide, peptidoglycan, or lipoteichoic acid in the growth media at a concentration of 5 μg/ml increased the gliotoxin concentration in the media by 37%, 65%, and 35%, respectively. The findings reveal a correlation between the concentrations of pathogen-associated molecular patterns and gliotoxin secretion. This shows that there is a yet uncharacterized detection system for such compounds within fungi. Inducing secondary metabolite production by such means in fungi is potentially relevant for drug discovery research. Our results also give a possible explanation for the increased virulence of A. fumigatus during bacterial co-infection, one that is important for the transition from colonization to invasiveness in this pulmonary disease.

Inflammatory monocytes orchestrate innate antifungal immunity in the lung

Aspergillus fumigatus is an environmental fungus that causes invasive aspergillosis (IA) in immunocompromised patients. Although -CC-chemokine receptor-2 (CCR2) and Ly6C-expressing inflammatory monocytes (CCR2⁺Mo) and their derivatives initiate adaptive pulmonary immune responses, their role in coordinating innate immune responses in the lung remain poorly defined. Using conditional and antibody-mediated cell ablation strategies, we found that CCR2⁺Mo and monocyte-derived dendritic cells (Mo-DCs) are essential for innate defense against inhaled conidia. By harnessing fluorescent Aspergillus reporter (FLARE) conidia that report fungal cell association and viability in vivo, we identify two mechanisms by which CCR2⁺Mo and Mo-DCs exert innate antifungal activity. First, CCR2⁺Mo and Mo-DCs condition the lung inflammatory milieu to augment neutrophil conidiacidal activity. Second, conidial uptake by CCR2⁺Mo temporally coincided with their differentiation into Mo-DCs, a process that resulted in direct conidial killing. Our findings illustrate both indirect and direct functions for CCR2⁺Mo and their derivatives in innate antifungal immunity in the lung.

Despite the significant impact of fungal infections to human health our understanding of immunity to these pathogens remains incomplete. Human mycoses are associated with high morbidity and mortality, even with modern antifungal therapies. Aspergillus fumigatus is the most common etiologic agent of invasive aspergillosis (IA), a serious infection that develops in immunodeficient patients. In this study we employ a combination of cell ablation strategies to examine the role of CCR2⁺Ly6C⁺ inflammatory monocytes (CCR2⁺Mo) in innate responses against a pulmonary infection with A.fumigatus conidia. We find that CCR2⁺Mo and their derivative dendritic cells (Mo-DCs) are required for defense against IA and that mice lacking these cells succumb to infection with A.fumigatus. Our studies indicate that CCR2⁺Mo and Mo-DCs exert crucial innate antifungal defense by two main mechanisms: 1) CCR2⁺Mo and Mo-DCs are a significant source of inflammatory mediators that augment the killing capacity of neutrophils and 2) conidial uptake by CCR2⁺Mo is coincident with their differentiation into Mo-DCs that directly kill fungal conidia via partially NADPH oxidase-dependent mechanisms. In aggregate, our studies find a novel essential function for CCR2⁺Mo in innate defense against a pulmonary fungal pathogen by mediating indirect and direct containment of fungal cells at the portal of infection.

Human pathogenic bacteria, fungi, and viruses in Drosophila: disease modeling, lessons, and shortcomings

Drosophila has been the invertebrate model organism of choice for the study of innate immune responses during the past few decades. Many Drosophila-microbe interaction studies have helped to define innate immunity pathways, and significant effort has been made lately to decipher mechanisms of microbial pathogenesis. Here we catalog 68 bacterial, fungal, and viral species studied in flies, 43 of which are relevant to human health. We discuss studies of human pathogens in flies revealing not only the elicitation and avoidance of immune response but also mechanisms of tolerance, host tissue homeostasis, regeneration, and predisposition to cancer. Prominent among those is the emerging pattern of intestinal regeneration as a defense response induced by pathogenic and innocuous bacteria. Immunopathology mechanisms and many microbial virulence factors have been elucidated, but their relevance to human health conventionally necessitates validation in mammalian models of infection.

The invasive chytrid fungus of amphibians paralyzes lymphocyte responses

The chytrid fungus, Batrachochytrium dendrobatidis, causes chytridiomycosis and is a major contributor to global amphibian declines. Although amphibians have robust immune defenses, clearance of this pathogen is impaired. Because inhibition of host immunity is a common survival strategy of pathogenic fungi, we hypothesized that B. dendrobatidis evades clearance by inhibiting immune functions. We found that B. dendrobatidis cells and supernatants impaired lymphocyte proliferation and induced apoptosis; however, fungal recognition and phagocytosis by macrophages and neutrophils was not impaired. Fungal inhibitory factors were resistant to heat, acid, and protease. Their production was absent in zoospores and reduced by nikkomycin Z, suggesting that they may be components of the cell wall. Evasion of host immunity may explain why this pathogen has devastated amphibian populations worldwide.

Aspergillus-associated airway disease, inflammation, and the innate immune response

Aspergillus moulds exist ubiquitously as spores that are inhaled in large numbers daily. Whilst most are removed by anatomical barriers, disease may occur in certain circumstances. Depending on the underlying state of the human immune system, clinical consequences can ensue ranging from an excessive immune response during allergic bronchopulmonary aspergillosis to the formation of an aspergilloma in the immunocompetent state. The severest infections occur in those who are immunocompromised where invasive pulmonary aspergillosis results in high mortality rates. The diagnosis of Aspergillus-associated pulmonary disease is based on clinical, radiological, and immunological testing. An understanding of the innate and inflammatory consequences of exposure to Aspergillus species is critical in accounting for disease manifestations and preventing sequelae. The major components of the innate immune system involved in recognition and removal of the fungus include phagocytosis, antimicrobial peptide production, and recognition by pattern recognition receptors. The cytokine response is also critical facilitating cell-to-cell communication and promoting the initiation, maintenance, and resolution of the host response. In the following review, we discuss the above areas with a focus on the innate and inflammatory response to airway Aspergillus exposure and how these responses may be modulated for therapeutic benefit.

Exserohilum infections associated with contaminated steroid injections: a clinicopathologic review of 40 cases

September 2012 marked the beginning of the largest reported outbreak of infections associated with epidural and intra-articular injections. Contamination of methylprednisolone acetate with the black mold, Exserohilum rostratum, was the primary cause of the outbreak, with >13,000 persons exposed to the potentially contaminated drug, 741 confirmed drug-related infections, and 55 deaths. Fatal meningitis and localized epidural, paraspinal, and peripheral joint infections occurred. Tissues from 40 laboratory-confirmed cases representing these various clinical entities were evaluated by histopathological analysis, special stains, and IHC to characterize the pathological features and investigate the pathogenesis of infection, and to evaluate methods for detection of Exserohilum in formalin-fixed, paraffin-embedded (FFPE) tissues. Fatal cases had necrosuppurative to granulomatous meningitis and vasculitis, with thrombi and abundant angioinvasive fungi, with extensive involvement of the basilar arterial circulation of the brain. IHC was a highly sensitive method for detection of fungus in FFPE tissues, demonstrating both hyphal forms and granular fungal antigens, and PCR identified Exserohilum in FFPE and fresh tissues. Our findings suggest a pathogenesis for meningitis involving fungal penetration into the cerebrospinal fluid at the injection site, with transport through cerebrospinal fluid to the basal cisterns and subsequent invasion of the basilar arteries. Further studies are needed to characterize Exserohilum and investigate the potential effects of underlying host factors and steroid administration on the pathogenesis of infection.

Special issue Oceans and Humans Health: the ecology of marine opportunists

Opportunistic marine pathogens, like opportunistic terrestrial pathogens, are ubiquitous in the environment (waters, sediments, and organisms) and only cause disease in immune-compromised or stressed hosts. In this review, we discuss four host-pathogen interactions within the marine environment that are typically considered opportunistic: sea fan coral-fungus, eelgrass-Labyrinthula zosterae, sea fan-Labyrinthulomycetes, and hard clam-Quahog Parasite Unknown with particular focus on disease ecology, parasite pathology, host response, and known associated environmental conditions. Disease is a natural part of all ecosystems; however, in some cases, a shift in the balance between the host, pathogen, and the environment may lead to epizootics in natural or cultured populations. In marine systems, host-microbe interactions are less understood than their terrestrial counterparts. The biological and physical changes to the world's oceans, coupled with other anthropogenic influences, will likely lead to more opportunistic diseases in the marine environment.

Low-volume toolbox for the discovery of immunosuppressive fungal secondary metabolites

The secondary metabolome provides pathogenic fungi with a plethoric and versatile panel of molecules that can be deployed during host ingress. While powerful genetic and analytical chemistry methods have been developed to identify fungal secondary metabolites (SMs), discovering the biological activity of SMs remains an elusive yet critical task. Here, we describe a process for identifying the immunosuppressive properties of Aspergillus SMs developed by coupling a cost-effective microfluidic neutrophil chemotaxis assay with an in vivo zebrafish assay. The microfluidic platform allows the identification of metabolites inhibiting neutrophil recruitment with as little as several nano-grams of compound in microliters of fluid. The zebrafish assay demonstrates a simple and accessible approach for performing in vivo studies without requiring any manipulation of the fish. Using this methodology we identify the immunosuppressive properties of a fungal SM, endocrocin. We find that endocrocin is localized in Aspergillus fumigatus spores and its biosynthesis is temperature-dependent. Finally, using the Drosophila toll deficient model, we find that deletion of encA, encoding the polyketide synthase required for endocrocin production, yields a less pathogenic strain of A. fumigatus when spores are harvested from endocrocin permissive but not when harvested from endocrocin restrictive conditions. The tools developed here will open new "function-omic" avenues downstream of the metabolomics, identification, and purification phases.

Colonization with small conidia Aspergillus species is associated with bronchiolitis obliterans syndrome: a two-center validation study

Aspergillus colonization after lung transplantation may increase the risk for bronchiolitis obliterans syndrome (BOS), a disease of small airways. We hypothesized that colonization with small conidia Aspergillus species would be associated with a greater risk of BOS, based upon an increased likelihood of deposition in small airways. We studied adult primary lung recipients from two large centers; 298 recipients at University of California, Los Angeles and 482 recipients at Duke University Medical Center. We grouped Aspergillus species by conidia diameter≤3.5 μm. We assessed the relationship of colonization with outcomes in Cox models. Pre-BOS colonization with small conidia Aspergillus species, but not large, was a risk factor for BOS (p=0.002, HR 1.44, 95% CI 1.14-1.82), along with acute rejection, single lung and Pseudomonas. Colonization with small conidia species also associated with risk of death (p=0.03, HR 1.30, 95% CI 1.03-1.64). Although other virulence traits besides conidia size may be important, we have demonstrated in two large independent cohorts that colonization with small conidia Aspergillus species increases the risk of BOS and death. Prospective evaluation of strategies to prevent Aspergillus colonization of small airways is warranted, with the goal of preserving lung allograft function as long as possible.