Invasive fungal disease in autosomal-dominant hyper-IgE syndrome

The Known and Unknown "Knowns" of Human Susceptibility to Coccidioidomycosis

Coccidioidomycosis occurs after inhalation of airborne spores of the endemic, dimorphic fungus, Coccidioides. While the majority of individuals resolve the infection without coming to medical attention, the fungus is a major cause of community-acquired pneumonia in the endemic region, and chronic pulmonary and extrapulmonary disease poses significant personal and economic burdens. This review explores the literature surrounding human susceptibility to coccidioidomycosis, including chronic pulmonary and extrapulmonary dissemination. Over the past century of study, themes have emerged surrounding factors impacting human susceptibility to severe disease or dissemination, including immune suppression, genetic susceptibility, sex, pregnancy, and genetic ancestry. Early studies were observational, frequently with small numbers of cases; several of these early studies are highly cited in review papers, becoming part of the coccidioidomycosis "canon". Specific genetic variants, sex, and immune suppression by TNF inhibitors have been validated in later cohort studies, confirming the original hypotheses. By contrast, some risk factors, such as ABO blood group, Filipino ancestry, or lack of erythema nodosum among black individuals, are repeated in the literature despite the lack of supporting studies or biologic plausibility. Using examination of historical reports coupled with recent cohort and epidemiology studies, evidence for commonly reported risk factors is discussed.

From Mendel to mycoses: Immuno-genomic warfare at the human-fungus interface

Fungi are opportunists: They particularly require a defect of immunity to cause severe or disseminated disease. While often secondary to an apparent iatrogenic cause, fungal diseases do occur in the absence of one, albeit infrequently. These rare cases may be due to an underlying genetic immunodeficiency that can present variably in age of onset, severity, or other infections, and in the absence of a family history of disease. They may also be due to anti-cytokine autoantibodies. This review provides a background on how human genetics or autoantibodies underlie cases of susceptibility to severe or disseminated fungal disease. Subsequently, the lessons learned from these inborn errors of immunity marked by fungal disease (IEI-FD) provide a framework to begin to mechanistically decipher fungal syndromes, potentially paving the way for precision therapy of the mycoses.

The mycobiome in atopic diseases: Inducers and triggers

Atopic diseases are characterized by type 2 inflammation, with high levels of allergen-specific TH2 cell immune responses and elevated production of IgE. These common disorders have increased in incidence around the world, which is partly explained by detrimental disturbances to the early-life intestinal microbiome. Although most studies have focused exclusively on bacterial members of the microbiome, intestinal fungi have started to be recognized for their impact on host immune development and atopy pathogenesis. From this perspective, we review recent findings demonstrating the strong interactions between members of the mycobiome and the host immune system early in life, leading to immune tolerance during eubiosis or inducing sensitization and overt TH2 cell responses during dysbiosis. Current evidence places intestinal fungi as central players in the development of allergic diseases and potential targets for atopy prevention and treatments.

Primary immunodeficiency diseases of adults: a review of pulmonary complication imaging findings

Our objective in this review is to familiarize radiologists with the spectrum of initial and progressive CT manifestations of pulmonary complications observed in adult patients with primary immunodeficiency diseases, including primary antibody deficiency (PAD), hyper-IgE syndrome (HIES), and chronic granulomatous disease (CGD). In patients with PAD, recurrent pulmonary infections may lead to airway remodeling with bronchial wall-thickening, bronchiectasis, mucus-plugging, mosaic perfusion, and expiratory air-trapping. Interstitial lung disease associates pulmonary lymphoid hyperplasia, granulomatous inflammation, and organizing pneumonia and is called granulomatous-lymphocytic interstitial lung disease (GLILD). The CT features of GLILD are solid and semi-solid pulmonary nodules and areas of air space consolidation, reticular opacities, and lymphadenopathy. These features may overlap those of mucosa-associated lymphoid tissue (MALT) lymphoma, justifying biopsies. In patients with HIES, particularly the autosomal dominant type (Job syndrome), recurrent pyogenic infections lead to permanent lung damage. Secondary infections with aspergillus species develop in pre-existing pneumatocele and bronchiectasis areas, leading to chronic airway infection. The complete spectrum of CT pulmonary aspergillosis may be seen including aspergillomas, chronic cavitary pulmonary aspergillosis, allergic bronchopulmonary aspergillosis (ABPA)-like pattern, mixed pattern, and invasive. Patients with CGD present with recurrent bacterial and fungal infections leading to parenchymal scarring, traction bronchiectasis, cicatricial emphysema, airway remodeling, and mosaicism. Invasive aspergillosis, the major cause of mortality, manifests as single or multiple nodules, areas of airspace consolidation that may be complicated by abscess, empyema, or contiguous extension to the pleura or chest wall. CLINICAL RELEVANCE STATEMENT: Awareness of the imaging findings spectrum of pulmonary complications that can occur in adult patients with primary immunodeficiency diseases is important to minimize diagnostic delay and improve patient outcomes. KEY POINTS: • Unexplained bronchiectasis, associated or not with CT findings of obliterative bronchiolitis, should evoke a potential diagnosis of primary autoantibody deficiency. • The CT evidence of various patterns of aspergillosis developed in severe bronchiectasis or pneumatocele in a young adult characterizes the pulmonary complications of hyper-IgE syndrome. • In patients with chronic granulomatous disease, invasive aspergillosis is relatively frequent, often asymptomatic, and sometimes mimicking or associated with non-infectious inflammatory pulmonary lesions.

Atypical imaging patterns during lung invasive mould diseases: lessons for clinicians

Imaging of pulmonary invasive mould diseases (IMDs), which represents a cornerstone in their work-up, is mainly based on computed tomography (CT). The purpose of this review is to discuss their CT features, mainly those related to aspergillosis and mucormycosis. We will especially focus on atypical radiological presentations that are increasingly observed among non-neutropenic emerging populations of patients at risk, such as those receiving novel anticancer therapies or those in the intensive care unit. We will also discuss the interest of other available imaging techniques, mainly positron emission tomography/CT, that may play a role in the diagnosis as well as evaluation of disease extent and follow-up. We will show that any new airway-centred abnormality or caveated lesion should evoke IMDs in mildly immunocompromised hosts. Limitations in their recognition may be due to potential underlying abnormalities that increase the complexity of interpretation of lung imaging, as well as the non-specificity of imaging features. In this way, the differentials of all morphological/metabolic aspects must be kept in mind for the optimal management of patients, as well as the benefit of evaluation of the vascular status.

Of Mycelium and Men: Inherent Human Susceptibility to Fungal Diseases

In medical mycology, the main context of disease is iatrogenic-based disease. However, historically, and occasionally, even today, fungal diseases affect humans with no obvious risk factors, sometimes in a spectacular fashion. The field of “inborn errors of immunity” (IEI) has deduced at least some of these previously enigmatic cases; accordingly, the discovery of single-gene disorders with penetrant clinical effects and their immunologic dissection have provided a framework with which to understand some of the key pathways mediating human susceptibility to mycoses. By extension, they have also enabled the identification of naturally occurring auto-antibodies to cytokines that phenocopy such susceptibility. This review provides a comprehensive update of IEI and autoantibodies that inherently predispose humans to various fungal diseases.

A challenging differential diagnosis in a patient with autosomal dominant STAT3 deficiency

Autosomal dominant hyper IgE syndrome (AD-HIES) is a primary immunodeficiency caused by loss-of-function (LOF) mutations in the Signal Transducer and Activator of Transcription 3 (STAT3) gene. In these patients, performing a correct differential diagnosis of pulmonary infections is difficult and challenging, as they usually have atypical presentations. However, establishing a correct diagnostic and therapeutic approach is essential, as pulmonary complications are responsible for high morbidity and mortality rates in these patients. We report the case of a teenage girl with AD-HIES and respiratory symptoms and fever in whom performing a correct differential diagnosis was challenging.

Inborn Errors of Immunity Causing Pediatric Susceptibility to Fungal Diseases

Inborn errors of immunity are a heterogeneous group of genetically determined disorders that compromise the immune system, predisposing patients to infections, autoinflammatory/autoimmunity syndromes, atopy/allergies, lymphoproliferative disorders, and/or malignancies. An emerging manifestation is susceptibility to fungal disease, caused by yeasts or moulds, in a superficial or invasive fashion. In this review, we describe recent advances in the field of inborn errors of immunity associated with increased susceptibility to fungal disease.

A B1a-natural IgG-neutrophil axis is impaired in viral- and steroid-associated aspergillosis

The lung naturally resists Aspergillus fumigatus (Af) in healthy individuals, but multiple conditions can disrupt this resistance, leading to lethal invasive infections. Core processes of natural resistance and its breakdown are undefined. We investigated three distinct conditions predisposing to lethal aspergillosis-severe SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2) infection, influenza A viral pneumonia, and systemic corticosteroid use-in human patients and murine models. We found a conserved and essential coupling of innate B1a lymphocytes, Af-binding natural immunoglobulin G antibodies, and lung neutrophils. Failure of this axis concealed Af from neutrophils, allowing rapid fungal invasion and disease. Reconstituting the axis with immunoglobulin therapy reestablished resistance, thus representing a realistic pathway to repurpose currently available therapies. Together, we report a vital host resistance pathway that is responsible for protecting against life-threatening aspergillosis in the context of distinct susceptibilities.

Main human inborn errors of immunity leading to fungal infections

BACKGROUND

The host molecular and genetic features are essential in providing susceptibility to a broad spectrum of fungal infections; most of these do not cause disease in healthy individuals because of mutual benefits with opportunistic fungi besides the host's capacity to control the infections. In contrast, patients with primary immunodeficiency (PID) can develop mild superficial to life-threatening invasive infections. In the last years, thanks to next-generation sequencing (NGS), several inborn-error variants have been discovered in genes encoding protein acting against fungal infections, contributing to better defining the role of innate and adaptive immunity cooperation during infection resolution. Candida fungal infection, that sometimes-striking healthy subjects, is responsible for the chronic mucocutaneous candidiasis (CMC) that is one of the principal clinical manifestations occurring in several rare PIDs associated with an inborn error of IL17-immunity.

OBJECTIVE

This review aimed to provide an overview of CMC-derived genetic defects, including IL17-deficiencies (IL17A, IL17F, IL17RA, IL17RC), STAT1 gain-of-function (GOF)- deficiency, STAT3-HIES and CARD9-deficiency.

SOURCES

We carried out detailed research work to identify interesting articles, commentaries, and reviews in the PubMed literature to ensure a correct and updated for this narrative review.

CONTENT

We propose an in-depth description and an update of genetic and cellular mechanisms underlying fungal infections, focusing on the IL17-mediated response, a report of clinical manifestations and describe therapeutic options.

IMPLICATION

This narrative review will help clinician to identify the correct management of patients based on molecular and cellular findings underlying pathogenic mechanisms of different IEIs. Moreover achieve the genetic diagnosis will be useful to offer genetic counselling intra- and inter-family and to ensure a personalized treatment of patients.

Aspergillus Endophthalmitis: Epidemiology, Pathobiology, and Current Treatments

Fungal endophthalmitis is one of the leading causes of vision loss worldwide. Post-operative and traumatic injuries are major contributing factors resulting in ocular fungal infections in healthy and, more importantly, immunocompromised individuals. Among the fungal pathogens, the Aspergillus species, Aspergillus fumigatus, continues to be more prevalent in fungal endophthalmitis patients. However, due to overlapping clinical symptoms with other endophthalmitis etiology, fungal endophthalmitis pose a challenge in its diagnosis and treatment. Hence, it is critical to understand its pathobiology to develop and deploy proper therapeutic interventions for combating Aspergillus infections. This review highlights the different modes of Aspergillus transmission and the host immune response during endophthalmitis. Additionally, we discuss recent advancements in the diagnosis of fungal endophthalmitis. Finally, we comprehensively summarize various antifungal regimens and surgical options for the treatment of Aspergillus endophthalmitis.

Respiratory Infections in Patients with Primary Immunodeficiency

Recurrent and life-threatening respiratory infections are nearly universal in patients with primary immunodeficiency diseases (PIDD). Early recognition, aggressive treatment, and prophylaxis with antimicrobials and immunoglobulin replacement have been the mainstays of management and will be reviewed here with an emphasis on respiratory infections. Genetic discoveries have allowed direct translation of research to clinical practice, improving our understanding of clinical patterns of pathogen susceptibilities and guiding prophylaxis. The recent identification of inborn errors in type I interferon signaling as a basis for life-threatening viral infections in otherwise healthy individuals suggests another targetable pathway for treatment and/or prophylaxis. The future of PIDD diagnosis will certainly involve early genetic identification by newborn screening before onset of infections, with early treatment offering the potential of preventing disease complications such as chronic lung changes. Gene editing approaches offer tremendous therapeutic potential, with rapidly emerging delivery systems. Antiviral therapies are desperately needed, and specific cellular therapies show promise in patients requiring hematopoietic stem cell transplantation. The introduction of approved therapies for clinical use in PIDD is limited by the difficulty of studying outcomes in rare patients/conditions with conventional clinical trials.

Rare clinical presentations of hyper-IgE syndrome in a patient with dental abnormalities: A case report

Asthma and anaphylaxis are two atypical presentations of hyper-IgE syndrome (HIES). Early diagnosis and management of HIES can improve quality of life of patients through minimizing orthodontic problems and other complications related to this disorder.

STAT3 Hyper-IgE Syndrome-an Update and Unanswered Questions

The hyper-IgE syndromes (HIES) are a heterogeneous group of inborn errors of immunity sharing manifestations including increased infection susceptibility, eczema, and raised serum IgE. Since the prototypical HIES description 55 years ago, areas of significant progress have included description of key disease-causing genes and differentiation into clinically distinct entities. The first two patients reported had what is now understood to be HIES from dominant-negative mutations in signal transduction and activator of transcription 3 (STAT3-HIES), conferring a broad immune defect across both innate and acquired arms, as well as defects in skeletal, connective tissue, and vascular function, causing a clinical phenotype including eczema, staphylococcal and fungal skin and pulmonary infection, scoliosis and minimal trauma fractures, and vascular tortuosity and aneurysm. Due to the constitutionally expressed nature of STAT3, initial reports at treatment with allogeneic stem cell transplantation were not positive and treatment has hinged on aggressive antimicrobial prophylaxis and treatment to prevent the development of end-organ disease such as pneumatocele. Research into the pathophysiology of STAT3-HIES has driven understanding of the interface of several signaling pathways, including the JAK-STAT pathways, interleukins 6 and 17, and the role of Th17 lymphocytes, and has been expanded by identification of phenocopies such as mutations in IL6ST and ZNF341. In this review we summarize the published literature on STAT3-HIES, present the diverse clinical manifestations of this syndrome with current management strategies, and update on the uncertain role of stem cell transplantation for this disease. We outline key unanswered questions for further study.

Human STAT3 variants underlie autosomal dominant hyper-IgE syndrome by negative dominance

Most patients with autosomal dominant hyper-IgE syndrome (AD-HIES) carry rare heterozygous STAT3 variants. Only six of the 135 in-frame variants reported have been experimentally shown to be dominant negative (DN), and it has been recently suggested that eight out-of-frame variants operate by haploinsufficiency. We experimentally tested these 143 variants, 7 novel out-of-frame variants found in HIES patients, and other STAT3 variants from the general population. Strikingly, all 15 out-of-frame variants were DN via their encoded (1) truncated proteins, (2) neoproteins generated from a translation reinitiation codon, and (3) isoforms from alternative transcripts or a combination thereof. Moreover, 128 of the 135 in-frame variants (95%) were also DN. The patients carrying the seven non-DN STAT3 in-frame variants have not been studied for other genetic etiologies. Finally, none of the variants from the general population tested, including an out-of-frame variant, were DN. Overall, our findings show that heterozygous STAT3 variants, whether in or out of frame, underlie AD-HIES through negative dominance rather than haploinsufficiency.

Evaluating the Role of STAT3 in CD4+ T Cells in Susceptibility to Invasive Aspergillosis

We aimed to determine whether T cell-specific STAT3 deletion influences the immune response to Aspergillus in the immunosuppressed context in CD4^Stat3−/− mice. Immunosuppressed and nonimmunosuppressed CD4^Stat3−/− mice and littermate Stat3^flox/flox (Stat3^fl/fl) mice were infected with Aspergillus fumigatus in an aerosol chamber, and the weight, activity, appearance, and respiratory rate of the mice were monitored daily for 21 days to evaluate their survival. Aspergillus infection was confirmed by lung fungal culture counts, histology, and a galactomannan test.

We aimed to determine whether T cell-specific STAT3 deletion influences the immune response to Aspergillus in the immunosuppressed context in CD4^Stat3−/− mice. Immunosuppressed and nonimmunosuppressed CD4^Stat3−/− mice and littermate Stat3^flox/flox (Stat3^fl/fl) mice were infected with Aspergillus fumigatus in an aerosol chamber, and the weight, activity, appearance, and respiratory rate of the mice were monitored daily for 21 days to evaluate their survival. Aspergillus infection was confirmed by lung fungal culture counts, histology, and a galactomannan test. Cytokines were measured at 3 days postinfection in bronchoalveolar lavage (BAL) fluid and serum. Immunosuppressed CD4^Stat3−/− mice began succumbing to infection by day 4, and by day 7, only 30% of mice survived. Immunosuppressed Stat3^fl/fl mice started to succumb to the disease on day 5, and 40% of mice remained by day 7. The nonimmunosuppressed control Stat3^fl/fl and CD4^Stat3−/− mice maintained their weight over the study period, without any evidence of infection by A. fumigatus by histology. In the BAL fluid, tumor necrosis factor alpha (TNF-α), interleukin-6 (IL-6), interferon gamma (IFN-γ), IL-17A, and IL-22 levels were elevated in Stat3^fl/fl immunosuppressed mice compared to immunosuppressed CD4^Stat3−/− mice at 3 days postinfection. STAT3 in CD4⁺ T cells modulates the production of cytokines in the IL-17 pathway in immunosuppressed mice. However, it has no meaningful effect on the clearance of Aspergillus or the concomitant increase in susceptibility to Aspergillus infection.

Respiratory Mycoses in COPD and Bronchiectasis

Chronic obstructive pulmonary disease (COPD) and bronchiectasis represent chronic airway diseases associated with significant morbidity and mortality. Bacteria and viruses are commonly implicated in acute exacerbations; however the significance of fungi in these airways remains poorly defined. While COPD and bronchiectasis remain recognized risk factors for the occurrence of Aspergillus-associated disease including chronic and invasive aspergillosis, underlying mechanisms that lead to the progression from colonization to invasive disease remain uncertain. Nonetheless, advances in molecular technologies have improved our detection, identification and understanding of resident fungi characterizing these airways. Mycobiome sequencing has revealed the complex varied and myriad profile of airway fungi in COPD and bronchiectasis, including their association with disease presentation, progression, and mortality. In this review, we outline the emerging evidence for the clinical importance of fungi in COPD and bronchiectasis, available diagnostic modalities, mycobiome sequencing approaches and association with clinical outcomes.

Genetic susceptibility to fungal infection in children

PURPOSE OF REVIEW

Fungal infections have steadily increased in incidence, emerging as a significant cause of morbidity and mortality in patients with iatrogenic immunosuppression. Simultaneously, we have witnessed a growing population of newly described inherited immune disorders that have enhanced our understanding of the human immune response against fungi. In the present review, we provide an overview and diagnostic roadmap to inherited disorders which confer susceptibility to superficial and invasive fungal infections.

RECENT FINDINGS

Inborn errors of fungal immunity encompass a heterogeneous group of disorders, some of which confer fungal infection-specific susceptibility, whereas others also feature broader infection vulnerability and/or noninfectious manifestations. Infections by Candida, Aspergillus, endemic dimorphic fungi, Pneumocystis, and dermatophytes along with their organ-specific presentations provide clinicians with important clues in the assessment of patients with suspected immune defects.

SUMMARY

The absence of iatrogenic risk factors should raise suspicion for inborn errors of immunity in children and young adults with recurrent or severe fungal diseases. Expeditious diagnosis and prompt initiation of antifungal therapy and management of complications are paramount to achieve remission of fungal disease in the setting of primary immunodeficiency disorders.

Emergence of azole resistant-Aspergillus fumigatus infections during STAT3-deficiency

Introduction. Signal transducer and activator of transcription 3 (STAT3) deficiency is a rare primary immunodeficiency associated with increased susceptibility to bacterial and fungal infections, notably pulmonary aspergillosis.Aim. We describe the emergence of azole-resistant Aspergillus fumigatus infections in STAT3-deficient patients.Methodology. During a retrospective study of 13 pulmonary aspergillosis cases in STAT3-deficient patients conducted in France, we identified patients infected with azole-resistant A. fumigatus isolates.Results. Two out of the 13 STAT3-deficient patients with aspergillosis had azole-resistant A. fumigatus infection, indicating an unexpectedly high prevalence of resistance. The first patient with STAT3 deficiency presented several flares of allergic bronchopulmonary aspergillosis-like episodes. He was chronically infected with two azole-resistant A. fumigatus isolates (TR₃₄/L98). Despite prolonged antifungal treatment, including caspofungin and amphotericin B, the patient was not able to clear the azole-resistant A. fumigatus. The second patient had chronic cavitary pulmonary aspergillosis (CCPA). The A. fumigatus isolate was initially azole susceptible but harboured three F46Y, M172V and E427K point mutations. Despite prolonged antifungal therapies, lesions worsened and the isolate became resistant to all azoles. Surgery and caspofungin treatments were then required to cure CCPA. Resistance was probably acquired from the environment (TR₃₄/L98) in the first case whereas resistance developed under antifungal treatments in the second case. These infections required long-term antifungal treatments and surgery.Conclusions. The emergence of azole-resistant A. fumigatus infections in STAT3-deficiency dramatically impacts both curative and prophylactic antifungal strategies. Physicians following patients with primary immune-deficiencies should be aware of this emerging problem as it complicates management of the patient.

Advances in Understanding Human Genetic Variations That Influence Innate Immunity to Fungi

Fungi are ubiquitous. Yet, despite our frequent exposure to commensal fungi of the normal mammalian microbiota and environmental fungi, serious, systemic fungal infections are rare in the general population. Few, if any, fungi are obligate pathogens that rely on infection of mammalian hosts to complete their lifecycle; however, many fungal species are able to cause disease under select conditions. The distinction between fungal saprophyte, commensal, and pathogen is artificial and heavily determined by the ability of an individual host's immune system to limit infection. Dramatic examples of commensal fungi acting as opportunistic pathogens are seen in hosts that are immune compromised due to congenital or acquired immune deficiency. Genetic variants that lead to immunological susceptibility to fungi have long been sought and recognized. Decreased myeloperoxidase activity in neutrophils was first reported as a mechanism for susceptibility to Candida infection in 1969. The ability to detect genetic variants and mutations that lead to rare or subtle susceptibilities has improved with techniques such as single nucleotide polymorphism (SNP) microarrays, whole exome sequencing (WES), and whole genome sequencing (WGS). Still, these approaches have been limited by logistical considerations and cost, and they have been applied primarily to Mendelian impairments in anti-fungal responses. For example, loss-of-function mutations in CARD9 were discovered by studying an extended family with a history of fungal infection. While discovery of such mutations furthers the understanding of human antifungal immunity, major Mendelian susceptibility loci are unlikely to explain genetic disparities in the rate or severity of fungal infection on the population level. Recent work using unbiased techniques has revealed, for example, polygenic mechanisms contributing to candidiasis. Understanding the genetic underpinnings of susceptibility to fungal infections will be a powerful tool in the age of personalized medicine. Future application of this knowledge may enable targeted health interventions for susceptible individuals, and guide clinical decision making based on a patient's individual susceptibility profile.

Aspergillus fumigatus Infection in Humans With STAT3-Deficiency Is Associated With Defective Interferon-Gamma and Th17 Responses

In humans, loss-of-function mutation in the Signal Transducer and Activator of Transcription 3 (STAT3) gene is frequently associated with susceptibility to bacterial as well as fungal infections including aspergillosis, although its pathogenesis remains largely unknown. In the present study, we investigated the immune responses obtained after stimulation with Aspergillus fumigatus in STAT3-deficient patients. A. fumigatus conidial killing efficiencies of both monocytes and neutrophils isolated from whole blood samples of STAT3-deficient patients were not different compared to those of healthy controls. After stimulation with A. fumigatus conidia, lower concentrations of adaptive cytokines (IFN-γ, IL-17 and IL-22) were secreted by peripheral blood mononuclear cells from STAT3-deficient patients compared to those from healthy controls. Moreover, the frequency of IFN-γ and IL-17 producing CD4+ T cells was lower in STAT3-deficient patients vs. healthy controls. Among the STAT3-deficient patients, those with aspergillosis showed further lower secretion of IFN-γ upon stimulation of their PBMCs with A. fumigatus conidia compared to the patients without aspergillosis. Together, our study indicated that STAT3-deficiency leads to a defective adaptive immune response against A. fumigatus infection, particularly with a lower IFN-γ and IL-17 responses in those with aspergillosis, suggesting potential therapeutic benefit of recombinant IFN-γ in STAT3-deficient patients with aspergillosis.

Analysis of pathogenetic process of fungal rhinosinusitis: Report of two cases

BACKGROUND

Fungal rhinosinusitis is an infectious and/or allergic disease caused by fungi in the sinus and nasal cavity. Due to the warm and humid climate in Guangxi Zhuang Autonomous Region, the incidence of fungal rhinosinusitis is higher than that in other provinces. However, its physiological mechanism is not yet clear. Not every patient colonized by fungi develops a fungal infection. To a large extent, the immune status of the patient determines the nature of fungal disease in the nasal passages. The pathologic process of progression from harmless fungal colonization to fungal rhinosinusitis is unclear and has not been reported.

CASE SUMMURY

We report two patients, one who developed fungal rhinosinusitis 1.5 years after surgery performed to treat an inverted papilloma, and the other with a history of hypertension and cerebral infarction. Both patients recovered from their surgeries. An average time of 2.5 years elapsed from the development of maxillary sinus cysts to the development of fungal rhinosinusitis.

CONCLUSION

According to these case reports, we speculate that the progression of fungal rhinosinusitis from harmless colonization to disease onset requires approximately one to three years and that the length of the process may be related to underlying diseases, surgical treatment, deficient autoimmune status, and abuse of hormone antibiotics and hormones. Additional data are needed to conduct relevant studies to appropriately prevent and treat fungal rhinosinusitis.

T Cell Antifungal Immunity and the Role of C-Type Lectin Receptors

Fungi can cause disease in humans, from mucocutaneous to life-threatening systemic infections. Initiation of antifungal immunity involves fungal recognition by pattern recognition receptors such as C-type lectin receptors (CLRs). These germline-encoded receptors trigger a multitude of innate responses including phagocytosis, fungal killing, and antigen presentation which can also shape the development of adaptive immunity. Recently, studies have shed light on how CLRs directly or indirectly modulate lymphocyte function. Moreover, CLR-mediated recognition of commensal fungi maintains homeostasis and prevents invasion from opportunistic commensals. We present an overview of current knowledge of antifungal T cell immune responses, with emphasis on the role of C-type lectins, and discuss how these receptors modulate these responses at different levels.

CLRs are essential pattern recognition receptors involved in fungal recognition and initiation of protective antifungal immunity.

CLRs promote the differentiation of mammalian T helper cell subsets essential for the control of systemic (Th1) and mucosal (Th17) fungal infections.

CLRs are involved in antigen presentation, the expression of co-stimulatory molecules, and cytokine secretion; therefore, they can regulate lymphocyte function and adaptive immune responses at different levels.

Fungal morphological changes, such as the transition from yeast to hyphae in Candida albicans during tissue invasion, affects recognition by CLRs and impacts on adaptive immune responses.

CLRs recognize the fungal component of the microbiome that can influence T cell responses during infection at intestinal and peripheral sites.

Genetic variation and fungal infection risk: State of the art

Purpose of review

Fungal infections cause significant mortality in patients with acquired immunodeficiencies including AIDS, hematological malignancies, transplantation, and receipt of corticosteroids, biologics or small-molecule kinase inhibitors that impair key immune pathways. The contribution of several such pathways in antifungal immunity has been uncovered by inherited immunodeficiencies featuring profound fungal susceptibility. Furthermore, the risk of fungal infection in patients with acquired immunodeficiencies may be modulated by single nucleotide polymorphisms (SNPs) in immune-related genes. This review outlines key features underlying human genetic fungal predisposition.

Recent findings

The discovery of monogenic disorders that cause fungal disease and the characterization of immune-related gene SNPs that may regulate fungal susceptibility have provided important insights into how genetic variation affects development and outcome of fungal infections in humans.

Summary

Recognition of individualized genetic fungal susceptibility traits in humans should help devise precision-medicine strategies for risk assessment, prognostication and treatment of patients with opportunistic fungal infections.

Why are so many cases of invasive aspergillosis missed?

Invasive aspergillosis (IA) incidence is increasing in several countries like France, and numerous cases are indeed missed and still only diagnosed at autopsy as evidenced by recently published data. Such missed diagnoses are obviously encountered when appropriate diagnostic tools are not available especially in low resource areas or when biologists have not been trained enough in medical mycology (i.e., microscopic examination and culture in most of those areas). Besides logistical issues, which are indeed critical, IA may not be recognized because clinicians failed to consider that risk factors are evolving with the IA burden now observed among patients with chronic lymphoid malignancies or receiving new biotherapies, with diabetes mellitus or liver cirrhosis and/or acute alcoholic hepatitis, with patients from the intensive care unit (ICU) and among patients with some predisposing primary immune deficiencies now reaching the adult's age. This is also the case for human immunodeficiency virus (HIV)-infected patients who failed to meet the classical definitions of IA. From the radiology perspective, new entities of IA have also emerged which absolutely need to be recognized especially bronchial-based-IA among allogeneic stem cell transplant recipients. Finally, from the laboratory side, contribution and limits of indirect blood biomarkers should be integrated to the clinical life in order not to miss IA cases. To conclude, several diagnostic tools should be combined and a constant dialog between laboratory and clinics is crucial to appropriately diagnose IA.

Spectrum of Pulmonary Aspergillosis in Hyper-IgE Syndrome with Autosomal-Dominant STAT3 Deficiency

BACKGROUND

Autosomal-dominant signal transducer and activator of transcription 3 (STAT3) deficiency predisposes to recurrent bacterial pneumonia, complicated by bronchiectasis and cavitations. Aspergillosis is a major cause of morbidity in these patients. However, its diagnosis, classification, and treatment are challenging.

OBJECTIVE

We aimed to assess the prevalence and describe the clinical, mycological, and radiological presentation and related therapy and outcome of Aspergillus infections of the respiratory tract in the STAT3-deficient patients of the National French cohort.

METHODS

We performed a retrospective study of all pulmonary aspergillosis cases in STAT3-deficient patients (n = 74). Clinical and mycological data were collected up to October 2015 and imaging was centralized.

RESULTS

Twenty-one episodes of pulmonary aspergillosis in 13 (17.5%) STAT3-deficient patients were identified. The median age at first episode was 13 years (interquartile range, 10-26 years). Ninety percent of patients had previous bronchiectasis or cavitations. Infections were classified as follows: 5 single aspergilloma, 9 chronic cavity pulmonary aspergillosis, 5 allergic bronchopulmonary aspergillosis-like disease, and 2 mixed forms of concomitant allergic bronchopulmonary aspergillosis-like disease and chronic cavity pulmonary aspergillosis. No invasive aspergillosis cases were identified. Aspergillus species were isolated in 71% of episodes and anti-Aspergillus antibodies in 93%. Eleven episodes were breakthrough infections. Antifungal treatment was prolonged, with a median of 13 months, and 6 patients (7 episodes) required surgery, with a high rate of postsurgical complications. One patient died and 6 had a relapse.

CONCLUSIONS

Chronic and allergic forms of aspergillosis occurred in 17.5% of STAT3-deficient patients, mostly in lung cavities. Almost half had recurrences, despite prolonged antifungal treatment and/or surgery.

The molecular immunology of human susceptibility to fungal diseases: lessons from single gene defects of immunity

INTRODUCTION

Fungal diseases are a threat to human health. Therapies targeting the fungus continue to lead to disappointing results. Strategies targeting the host response represent unexplored opportunities for innovative treatments. To do so rationally requires the identification and neat delineation of critical mechanistic pathways that underpin human antifungal immunity. The study of humans with single-gene defects of the immune system, i.e. inborn errors of immunity (IEIs), provides a foundation for these paradigms. Areas covered: A systematic literature search in PubMed, Scopus, and abstracts of international congresses was performed to review the history of genetic resistance/susceptibility to fungi and identify IEIs associated with fungal diseases. Immunologic mechanisms from relevant IEIs were integrated with current definitions and understandings of mycoses to establish a framework to map out critical immunobiological pathways of human antifungal immunity. Expert opinion: Specific immune responses non-redundantly govern susceptibility to their corresponding mycoses. Defining these molecular pathways will guide the development of host-directed immunotherapies that precisely target distinct fungal diseases. These findings will pave the way for novel strategies in the treatment of these devastating infections.

Current State of the Diagnosis of Invasive Pulmonary Aspergillosis in Lung Transplantation

As the number of lung transplants performed worldwide each year continues to grow, the success of this procedure is threatened by the incidence of non-CMV infections such as invasive aspergillosis. Despite tremendous efforts and the availability of numerous diagnostic tests (especially in hematological malignancies) the diagnosis of invasive aspergillosis continues to be a challenge. Lung transplantation remains a unique clinical scenario, where additional host defenses are immunocompromized, making many of the available tests unsuitable. In this review we will navigate through the myriad of diagnostic tests currently available and how they apply to this unique patient population, as well as have a look into what the future holds.

Emerging Aspergillus Species Almost Exclusively Associated With Primary Immunodeficiencies

Invasive aspergillosis (IA) is the most serious mold infection encountered in patients with iatrogenic immunosuppression. IA is also a major cause of mortality and morbidity in individuals with primary immunodeficiency (PID). Although Aspergillus fumigatus is the most common etiologic agent of IA reported in PID patients, followed by A. nidulans, multiple poorly recognized Aspergillus species such as A. udagawae, A. quadrilineatus, A. pseudoviridinutans, A. tanneri, A. subramanianii, and A. fumisynnematus have been reported almost exclusively from patients with inborn defects in host antifungal defense pathways. Infection in PID patients exhibits patterns of disease progression distinct from those in iatrogenic immunosuppression. Specifically, the disease can be extrapulmonary and chronic with a tendency to disseminate in a contiguous manner across anatomical planes. It is also more refractory to standard antifungal therapy. This synopsis summarizes our understanding of emerging rare Aspergillus species that primarily affect patients with PIDs but not those with acquired immunodeficiencies.

Intestinal Candida parapsilosis isolates from Rett syndrome subjects bear potential virulent traits and capacity to persist within the host

BACKGROUND

Rett syndrome (RTT) is a neurological disorder mainly caused by mutations in MeCP2 gene. It has been shown that MeCP2 impairments can lead to cytokine dysregulation due to MeCP2 regulatory role in T-helper and T-reg mediated responses, thus contributing to the pro-inflammatory status associated with RTT. Furthermore, RTT subjects suffer from an intestinal dysbiosis characterized by an abnormal expansion of the Candida population, a known factor responsible for the hyper-activation of pro-inflammatory immune responses. Therefore, we asked whether the intestinal fungal population of RTT subjects might contribute the sub-inflammatory status triggered by MeCP2 deficiency.

METHODS

We evaluated the cultivable gut mycobiota from a cohort of 50 RTT patients and 29 healthy controls characterizing the faecal fungal isolates for their virulence-related traits, antifungal resistance and immune reactivity in order to elucidate the role of fungi in RTT's intestinal dysbiosis and gastrointestinal physiology.

RESULTS

Candida parapsilosis, the most abundant yeast species in RTT subjects, showed distinct genotypic profiles if compared to healthy controls' isolates as measured by hierarchical clustering analysis from RAPD genotyping. Their phenotypical analysis revealed that RTT's isolates produced more biofilm and were significantly more resistant to azole antifungals compared to the isolates from the healthy controls. In addition, the high levels of IL-1β and IL-10 produced by peripheral blood mononuclear cells and the mixed Th1/Th17 cells population induced by RTT C. parapsilosis isolates suggest the capacity of these intestinal fungi to persist within the host, being potentially involved in chronic, pro-inflammatory responses.

CONCLUSIONS

Here we demonstrated that intestinal C. parapsilosis isolates from RTT subjects hold phenotypic traits that might favour the previously observed low-grade intestinal inflammatory status associated with RTT. Therefore, the presence of putative virulent, pro-inflammatory C. parapsilosis strains in RTT could represent an additional factor in RTT's gastrointestinal pathophysiology, whose mechanisms are not yet clearly understood.

Immune responses to invasive aspergillosis: new understanding and therapeutic opportunities

PURPOSE OF REVIEW

Invasive aspergillosis is a worldwide disease that primarily affects immune-compromised patients, agricultural workers with corneal abrasions, individuals with structural lung disease, and patients with primary immune deficiency. The critical function of the immune system is to prevent the germination of airborne conidia into tissue-invasive hyphae. This review covers recent advances that shape our understanding of anti-Aspergillus immunity at the molecular and cellular level.

RECENT FINDINGS

Host defense against conidia and hyphae occurs via distinct molecular mechanisms that involve intracellular and extracellular killing pathways, as well as cooperation between different myeloid cell subsets. The strength and efficacy of the host response is shaped by the tissue microenvironment. In preclinical models of disease, host immune augmentation strategies have yielded benefits, yet translating these insights into therapeutic strategies in humans remains challenging.

SUMMARY

Although advances in early diagnostic strategies and in antifungal drugs have ameliorated clinical outcomes of invasive aspergillosis, further improvements depend on gaining deeper insight into and translating advances in anti-Aspergillus immunity.

Epidemiology of Invasive Fungal Disease in Children

Considerable progress has been made in the prevention, diagnosis, and management of pediatric patients with invasive fungal disease (IFD). The reported decreasing trend in the incidence of invasive candidiasis (IC) over the past 15 years in both neonates and children has been encouraging. Nevertheless, due to the growing number of immunocompromised children at risk for IFD, this disease continues to be associated with significant morbidity and death and with increased financial burden to the health care system. Therefore, it is important to understand the contemporary epidemiology of IFD. Incidence rates of IFD in children are affected by geographical, population, and time variability. There is an ongoing effort to constantly document and update the incidence of IFD and species distribution among different pediatric populations as a means to direct preventative, diagnostic, and therapeutic resources to the most appropriate subset of patients. Children with a hematologic malignancy or a primary or secondary immunodeficiency, those undergoing solid organ or hematopoietic stem cell transplantation, and premature neonates are the major subsets of pediatric patients at risk of developing IFD. In this review, we focus on fungal disease epidemiology with a specific emphasis on the 2 most common pediatric IFDs, IC and invasive aspergillosis (IA).

How neutrophils kill fungi

Neutrophils play a critical role in the prevention of invasive fungal infections. Whereas mouse studies have demonstrated the role of various neutrophil pathogen recognition receptors (PRRs), signal transduction pathways, and cytotoxicity in the murine antifungal immune response, much less is known about the killing of fungi by human neutrophils. Recently, novel primary immunodeficiencies have been identified in patients with a susceptibility to fungal infections. These human 'knock-out' neutrophils expand our knowledge to understand the role of PRRs and signaling in human fungal killing. From the studies with these patients it is becoming clear that neutrophils employ fundamentally distinct mechanisms to kill Candida albicans or Aspergillus fumigatus.

Cellular and Molecular Defects Underlying Invasive Fungal Infections-Revelations from Endemic Mycoses

The global burden of fungal diseases has been increasing, as a result of the expanding number of susceptible individuals including people living with human immunodeficiency virus (HIV), hematopoietic stem cell or organ transplant recipients, patients with malignancies or immunological conditions receiving immunosuppressive treatment, premature neonates, and the elderly. Opportunistic fungal pathogens such as Aspergillus, Candida, Cryptococcus, Rhizopus, and Pneumocystis jiroveci are distributed worldwide and constitute the majority of invasive fungal infections (IFIs). Dimorphic fungi such as Histoplasma capsulatum, Coccidioides spp., Paracoccidioides spp., Blastomyces dermatiditis, Sporothrix schenckii, Talaromyces (Penicillium) marneffei, and Emmonsia spp. are geographically restricted to their respective habitats and cause endemic mycoses. Disseminated histoplasmosis, coccidioidomycosis, and T. marneffei infection are recognized as acquired immunodeficiency syndrome (AIDS)-defining conditions, while the rest also cause high rate of morbidities and mortalities in patients with HIV infection and other immunocompromised conditions. In the past decade, a growing number of monogenic immunodeficiency disorders causing increased susceptibility to fungal infections have been discovered. In particular, defects of the IL-12/IFN-γ pathway and T-helper 17-mediated response are associated with increased susceptibility to endemic mycoses. In this review, we put together the various forms of endemic mycoses on the map and take a journey around the world to examine how cellular and molecular defects of the immune system predispose to invasive endemic fungal infections, including primary immunodeficiencies, individuals with autoantibodies against interferon-γ, and those receiving biologic response modifiers. Though rare, these conditions provide importance insights to host defense mechanisms against endemic fungi, which can only be appreciated in unique climatic and geographical regions.

Fungal Contaminants in Drinking Water Regulation? A Tale of Ecology, Exposure, Purification and Clinical Relevance

Microbiological drinking water safety is traditionally monitored mainly by bacterial parameters that indicate faecal contamination. These parameters correlate with gastro-intestinal illness, despite the fact that viral agents, resulting from faecal contamination, are usually the cause. This leaves behind microbes that can cause illness other than gastro-intestinal and several emerging pathogens, disregarding non-endemic microbial contaminants and those with recent pathogenic activity reported. This white paper focuses on one group of contaminants known to cause allergies, opportunistic infections and intoxications: Fungi. It presents a review on their occurrence, ecology and physiology. Additionally, factors contributing to their presence in water distribution systems, as well as their effect on water quality are discussed. Presence of opportunistic and pathogenic fungi in drinking water can pose a health risk to consumers due to daily contact with water, via several exposure points, such as drinking and showering. The clinical relevance and influence on human health of the most common fungal contaminants in drinking water is discussed. Our goal with this paper is to place fungal contaminants on the roadmap of evidence based and emerging threats for drinking water quality safety regulations.

Bronchiectasis and Aspergillus: How are they linked?

Bronchiectasis is a chronic airway infection syndrome, distinct from cystic fibrosis that is rising in prevalence and is associated with significant morbidity and mortality. It can be caused by many etiologies including post-infectious effects or be seen in common lung diseases such as chronic obstructive pulmonary disease (COPD) or severe asthma. Bronchiectasis is associated with many Aspergillus-associated syndromes: allergic bronchopulmonary aspergillosis (ABPA) may complicate asthma, thus leading to bronchiectasis as part of the diagnostic criteria of ABPA or can complicate preexisting bronchiectasis due to another etiology. Aspergilloma can develop in areas of lung damage seen in patients with bronchiectasis, whereas fungal bronchitis may lead to later bronchiectasis. Invasive aspergillosis, perhaps more commonly viewed as a consequence of significant immunosuppression, is also seen in the absence of immunosuppression in those with underlying lung diseases including bronchiectasis. The pathogenesis and treatments of these diverse Aspergillus-associated diseases in bronchiectasis are discussed.

Pediatric Invasive Aspergillosis

Invasive aspergillosis (IA) is a disease of increasing importance in pediatrics due to growth of the immunocompromised populations at risk and improvements in long-term survival for many of these groups. While general principles of diagnosis and therapy apply similarly across the age spectrum, there are unique considerations for clinicians who care for children and adolescents with IA. This review will highlight important differences in the epidemiology, clinical manifestations, diagnosis, and therapy of pediatric IA.

Hyper-IgE Syndromes and the Lung

Elevated serum IgE has many etiologies including parasitic infection, allergy and asthma, malignancy, and immune dysregulation. The hyper-IgE syndromes caused by mutations in STAT3, DOCK8, and PGM3 are monogenic primary immunodeficiencies associated with high IgE, eczema, and recurrent infections. These primary immunodeficiencies are associated with recurrent pneumonias leading to bronchiectasis; however, each has unique features and genetic diagnosis is essential in guiding therapy, discussing family planning, and defining prognosis. This article discusses the clinical features of these primary immunodeficiencies with a particular focus on the pulmonary manifestations and discussion of the genetics, pathogenesis, and approaches to therapy.

New advances in invasive aspergillosis immunobiology leading the way towards personalized therapeutic approaches

Invasive aspergillosis (IA) remains a devastating disease in immune compromised patients despite significant advances in our understanding of fungal virulence and host defense mechanisms. In this review, we summarize important research advances in the fight against IA with particular focus on early events in the interactions between Aspergillus fumigatus and the host that occur in the respiratory tract. Advances in understanding mechanisms of immune effector cell recruitment, antifungal effector mechanisms, and how the dynamic host-fungal interaction alters the local microenvironment to effect outcomes are highlighted. These advances illustrate exciting new therapeutic opportunities, but also emphasize the importance of understanding each unique fungus-host interaction for improving patient outcomes.

New clinical phenotypes of fungal infections in special hosts

Incidence of invasive fungal infections increases over time with the rise in at-risk populations; in particular, patients with acquired immunodeficiencies due to immunosuppressive therapies such as anti-tumour necrosis factor-α (TNF-α) treatment, cirrhosis or burns. Some primary immunodeficiencies (PID) can also predispose selectively to invasive fungal diseases. Conversely, some atypical fungal diseases can reveal new PID. Deep dermatophytosis, Candida central nervous system infections or gastrointestinal disease, or disseminated phaeohyphomycosis-revealed CARD9 deficiency. Most patients with inherited chronic mucocutaneous candidiasis were found to carry STAT1 gain-of-function mutations. The spectrum of fungal susceptibility and clinical presentation varies according to the PID. Among acquired immunodeficiencies, immunosuppressive treatments such as TNF-α blocker therapy, which has revolutionized autoimmune disorder treatment, may be complicated by endemic mycosis, aspergillosis, pneumocystosis or cryptococcosis. Burn patients with damaged skin barrier protection are susceptible to severe Candida infections and filamentous fungal infections (such as Aspergillus spp., Mucorales). Moreover, patients with cirrhosis are at increased risk of fungal infections. Therefore, physicians should think of any potential underlying acquired or inherited immunodeficiency in a patient developing an atypical fungal infection, or of a potential fungal disease in the context of an atypical presentation in specific hosts.

Filamentous Fungi

Filamentous mycoses are often associated with significant morbidity and mortality. Prompt diagnosis and aggressive treatment are essential for good clinical outcomes in immunocompromised patients. The host immune response plays an essential role in determining the course of exposure to potential fungal pathogens. Depending on the effectiveness of immune response and the burden of organism exposure, fungi can either be cleared or infection can occur and progress to a potentially fatal invasive disease. Nonspecific cellular immunity (i.e., neutrophils, natural killer [NK] cells, and macrophages) combined with T-cell responses are the main immunologic mechanisms of protection. The most common potential mold pathogens include certain hyaline hyphomycetes, endemic fungi, the Mucorales , and some dematiaceous fungi. Laboratory diagnostics aimed at detecting and differentiating these organisms are crucial to helping clinicians make informed decisions about treatment. The purpose of this chapter is to provide an overview of the medically important fungal pathogens, as well as to discuss the patient characteristics, antifungal-therapy considerations, and laboratory tests used in current clinical practice for the immunocompromised host.

Genetic Susceptibility to Fungal Infections: What is in the Genes?

The development of severe fungal infections has long been associated with traditional risk factors such as profound immunosuppression, yet it remains challenging to understand why under similar conditions only some patients will develop these infections while others will not. Recent studies have demonstrated the importance of host genetic variation in influencing the severity and susceptibility to invasive fungal infections (IFIs). In this review, we examine selected primary immunodeficiencies characterized by their vulnerability to a narrow range of fungal pathogens, and then focus on recently identified genetic polymorphisms associated with an increased susceptibility to IFIs.

The Fungal Exopolysaccharide Galactosaminogalactan Mediates Virulence by Enhancing Resistance to Neutrophil Extracellular Traps

Of the over 250 Aspergillus species, Aspergillus fumigatus accounts for up to 80% of invasive human infections. A. fumigatus produces galactosaminogalactan (GAG), an exopolysaccharide composed of galactose and N-acetyl-galactosamine (GalNAc) that mediates adherence and is required for full virulence. Less pathogenic Aspergillus species were found to produce GAG with a lower GalNAc content than A. fumigatus and expressed minimal amounts of cell wall-bound GAG. Increasing the GalNAc content of GAG of the minimally pathogenic A. nidulans, either through overexpression of the A. nidulans epimerase UgeB or by heterologous expression of the A. fumigatus epimerase Uge3 increased the amount of cell wall bound GAG, augmented adherence in vitro and enhanced virulence in corticosteroid-treated mice to levels similar to A. fumigatus. The enhanced virulence of the overexpression strain of A. nidulans was associated with increased resistance to NADPH oxidase-dependent neutrophil extracellular traps (NETs) in vitro, and was not observed in neutropenic mice or mice deficient in NADPH-oxidase that are unable to form NETs. Collectively, these data suggest that cell wall-bound GAG enhances virulence through mediating resistance to NETs.

The ubiquitous mold A. fumigatus is isolated in over 80% of all patients with invasive aspergillosis (IA). A. nidulans is a relatively non-pathogenic species that rarely causes IA except in patients with chronic granulomatous disease (CGD), a hereditary disease characterized by impaired neutrophil function due to mutations in the NADPH oxidase complex. Here, we demonstrate that one factor underlying the differences in the intrinsic virulence between A. fumigatus and A. nidulans is the amount of the exopolysaccharide galactosaminogalactan that is associated with the cell wall of these species. A. fumigatus produces higher amounts of cell wall-associated galactosaminogalactan and is more resistant than A. nidulans to neutrophil killing by NADPH-oxidase dependent extracellular traps (NETs). Increasing cell wall-associated galactosaminogalactan in A. nidulans enhanced resistance to NETs and increased the virulence of this species to the same level as A. fumigatus in mice with intact NET formation. Collectively, these data suggest that A. nidulans is more sensitive than A. fumigatus to NADPH-oxidase dependent NETosis due to lower levels of cell wall-associated GAG.