Endemic mycoses in patients with STAT3-mutated hyper-IgE (Job) syndrome

Human immunity to fungal infections

Fungi increasingly threaten health globally. Mycoses range from life-threatening, often iatrogenic conditions, to enigmatic syndromes occurring without apparent immunosuppression. Despite some recent advances in antifungal drug development, complementary therapeutic strategies are essential for addressing these opportunistic pathogens. One promising avenue is leveraging host immunity to combat fungal infections; this necessitates deeper understanding of the molecular immunology of human fungal susceptibility to differentiate beneficial versus harmful immunopathological responses. Investigating human models of fungal diseases in natural settings, particularly through genetic immunodeficiencies and ethnographic-specific genetic vulnerabilities, reveals crucial immune pathways essential for fighting various yeasts and molds. This review highlights the diversity in intrinsic fungal susceptibility across individuals and populations, through genetic- and autoantibody-mediated processes, complementing previous principles learned from animal studies and iatrogenic contexts. Improved understanding of human immunity to fungal diseases will facilitate the development of host-directed immunotherapies and targeted public health interventions, paving the way for precision medicine in fungal disease management.

Evaluation of Inborn Errors of Immunity Among Patients with Opportunistic Pulmonary Infection

This review of immunocompromised host pneumonia as the result of inborn errors of immunity (IEI) is organized by opportunistic pulmonary pathogen. The authors identify patients who warrant an evaluation for an IEI based on their clinical presentation. Their recommendations are guided by the immune defect(s) associated with each opportunistic pulmonary infection. Physicians without expertise in immunology may begin an evaluation for IEI using the guidance provided here. Comprehensive evaluation by an immunologist may also be warranted in many instances.

Inborn errors of immunity and invasive fungal infections: presentation and management

PURPOSE OF REVIEW

We review the clinical presentations of invasive fungal infections in a selection of inborn errors of immunity. In addition, we review the particularities of their management, including antifungal therapy, prophylaxis, and immunomodulatory treatments.

RECENT FINDINGS

Patients with chronic granulomatous disease and with signal transducer and activator of transcription 3 (STAT3) deficiency are particularly prone to aspergillosis. Mold-active antifungal prophylaxis should be prescribed to all patients with chronic granulomatous disease, and in patients with STAT3 deficiency and underlying parenchymal lung disease. Invasive fungal infections are rare in patients with STAT1 gain-of-function mutations, while the clinical phenotype of caspase-associated recruitment domain-containing protein 9 deficiency encompasses a wide range of superficial and invasive fungal infections. Most patients with inborn errors of immunity and invasive fungal infections require prolonged durations of antifungals. Hematopoietic stem cell transplantation should be considered early for patients with chronic granulomatous disease, but results have been more mixed for other inborn errors of immunity with active invasive fungal infections.

SUMMARY

Inborn errors of immunity can confer increased susceptibility to a variety of invasive fungal infections, which can present with specific clinical and radiological features. Management of fungal infections in these patients is often challenging, and relies on a combination of antimicrobial prophylaxis, antifungal treatments, and immunomodulation.

Infections in Inborn Errors of STATs

The Janus kinase (JAK)-signal transducer and activator of transcription (STAT) pathway is highly conserved and essential for numerous biological functions triggered by extracellular signals, including cell proliferation, metabolism, immune response, and inflammation. Defects in STATs, either loss-of-function or gain-of-function defects, lead to a broad spectrum of clinical phenotypes in humans, including a wide range of infectious complications. The susceptibility to pathogens can stem from defects in immune cells within the hematopoietic compartment, impaired barrier functions of non-hematopoietic compartment, or a combination of both, depending on the specific STAT defect as well as the pathogen exposure history. Effective management involves antimicrobial prophylaxis tailored to the patient's infection risk and improving disease control with targeted therapies and/or hematopoietic cell transplantation.

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.

A Recombinant Multivalent Vaccine (rCpa1) Induces Protection for C57BL/6 and HLA Transgenic Mice against Pulmonary Infection with Both Species of Coccidioides

Coccidioidomycosis is caused by Coccidioides posadasii (Cp) and Coccidioides immitis (Ci), which have a 4-5% difference in their genomic sequences. There is an urgent need to develop a human vaccine against both species. A previously created recombinant antigen (rCpa1) that contains multiple peptides derived from Cp isolate C735 is protective against the autologous isolate. The focus of this study is to evaluate cross-protective efficacy and immune correlates by the rCpa1-based vaccine against both species of Coccidioides. DNA sequence analyses of the homologous genes for the rCpa1 antigen were conducted for 39 and 17 clinical isolates of Cp and Ci, respectively. Protective efficacy and vaccine-induced immunity were evaluated for both C57BL/6 and human HLA-DR4 transgenic mice against five highly virulent isolates of Cp and Ci. There are total of seven amino acid substitutions in the rCpa1 antigen between Cp and Ci. Both C57BL/6 and HLA-DR4 mice that were vaccinated with an rCpa1 vaccine had a significant reduction of fungal burden and increased numbers of IFN-γ- and IL-17-producing CD4+ T cells in the first 2 weeks post challenge. These data suggest that rCpa1 has cross-protection activity against Cp and Ci pulmonary infection through activation of early Th1 and Th17 responses.

Inborn Errors of Immunity and Cytokine Storm Syndromes

Inborn errors of immunity (IEI) are a diverse and growing category of more than 430 chronic disorders that share susceptibilities to infections. Whether the result of a genetic lesion that causes defective granule-dependent cytotoxicity, excessive lymphoproliferation, or an overwhelming infection represents a unique antigenic challenge, IEIs can display a proclivity for cytokine storm syndrome (CSS) development. This chapter provides an overview of CSS pathophysiology as it relates to IEIs. For each IEI, the immunologic defect and how it promotes or discourages CSS phenomena are reviewed. The IEI-associated molecular defects in pathways that are postulated to be critical to CSS physiology (i.e., toll-like receptors, T regulatory cells, the IL-12/IFNγ axis, IL-6) and, whenever possible, review strategies for treating CSS in IEI patients with molecularly directed therapies are highlighted.

Coccidioidomycosis Granulomas Informed by Other Diseases: Advancements, Gaps, and Challenges

Valley fever is a respiratory disease caused by a soil fungus, Coccidioides, that is inhaled upon soil disruption. One mechanism by which the host immune system attempts to control and eliminate Coccidioides is through granuloma formation. However, very little is known about granulomas during Coccidioides infection. Granulomas were first identified in tuberculosis (TB) lungs as early as 1679, and yet many gaps in our understanding of granuloma formation, maintenance, and regulation remain. Granulomas are best defined in TB, providing clues that may be leveraged to understand Coccidioides infections. Granulomas also form during several other infectious and spontaneous diseases including sarcoidosis, chronic granulomatous disease (CGD), and others. This review explores our current understanding of granulomas, as well as potential mechanisms, and applies this knowledge to unraveling coccidioidomycosis granulomas.

JAKs and STATs from a Clinical Perspective: Loss-of-Function Mutations, Gain-of-Function Mutations, and Their Multidimensional Consequences

The JAK/STAT signaling pathway plays a key role in cytokine signaling and is involved in development, immunity, and tumorigenesis for nearly any cell. At first glance, the JAK/STAT signaling pathway appears to be straightforward. However, on closer examination, the factors influencing the JAK/STAT signaling activity, such as cytokine diversity, receptor profile, overlapping JAK and STAT specificity among non-redundant functions of the JAK/STAT complexes, positive regulators (e.g., cooperating transcription factors), and negative regulators (e.g., SOCS, PIAS, PTP), demonstrate the complexity of the pathway's architecture, which can be quickly disturbed by mutations. The JAK/STAT signaling pathway has been, and still is, subject of basic research and offers an enormous potential for the development of new methods of personalized medicine and thus the translation of basic molecular research into clinical practice beyond the use of JAK inhibitors. Gain-of-function and loss-of-function mutations in the three immunologically particularly relevant signal transducers STAT1, STAT3, and STAT6 as well as JAK1 and JAK3 present themselves through individual phenotypic clinical pictures. The established, traditional paradigm of loss-of-function mutations leading to immunodeficiency and gain-of-function mutation leading to autoimmunity breaks down and a more differentiated picture of disease patterns evolve. This review is intended to provide an overview of these specific syndromes from a clinical perspective and to summarize current findings on pathomechanism, symptoms, immunological features, and therapeutic options of STAT1, STAT3, STAT6, JAK1, and JAK3 loss-of-function and gain-of-function diseases.

Primary Invasive Cutaneous Fusariosis in Patients with STAT3 Hyper-IgE Syndrome

Dominant negative (DN) mutations in signal transducer and activator of transcription 3 (STAT3) are known to cause hyper-IgE syndrome, a rare primary immunodeficiency. STAT3 DN patients are prone to develop fungal infections, including chronic mucocutaneous candidiasis due to impaired IL-17-mediated immunity, and pulmonary aspergillosis. Despite having preserved phagocyte functions, STAT3 DN patients present connective tissue abnormalities and a defect in the immunological skin barrier. Fusarium species are ubiquitous molds, whose potential to infect humans depends on the host's innate and cellular immune status. Our aim was to describe four STAT3 DN patients with fusariosis confined to the skin. Medical records were reviewed and summarized. Four patients, aged 4, 11, 30, and 33 years, presented with chronic skin lesions which started in the extremities. Two patients had remote lesions, and none had systemic involvement. Skin biopsies showed mycelial threads with deep inflammatory-occasionally granulomatous-infiltrates, reaching the dermis; cultures grew Fusarium solani. Response to treatment was heterogeneous, often requiring multimodal therapies, including topical antifungal preparations. In this work, we describe primary invasive cutaneous fusariosis as a syndromic entity in four STAT3 DN patients.

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.

Infections in Inborn Errors of Immunity with Combined Immune Deficiency: A Review

Enhanced susceptibility to microbes, often resulting in severe, intractable and frequent infections due to usually innocuous organisms at uncommon sites, is the most striking feature in individuals with an inborn error of immunity. In this narrative review, based on the International Union of Immunological Societies' 2022 (IUIS 2022) Update on phenotypic classification of human inborn errors of immunity, the focus is on commonly encountered Combined Immunodeficiency Disorders (CIDs) with susceptibility to infections. Combined immune deficiency disorders are usually commensurate with survival beyond infancy unlike Severe Combined Immune Deficiency (SCID) and are often associated with clinical features of a syndromic nature. Defective humoral and cellular immune responses result in susceptibility to a broad range of microbial infections. Although disease onset is usually in early childhood, mild defects may present in late childhood or even in adulthood. A precise diagnosis is imperative not only for determining management strategies, but also for providing accurate genetic counseling, including prenatal diagnosis, and also in deciding empiric treatment of infections upfront before investigation reports are available.

Evaluation of Host Constitutive and Ex Vivo Coccidioidal Antigen-Stimulated Immune Response in Dogs with Naturally Acquired Coccidioidomycosis

The early innate immune response to coccidioidomycosis has proven to be pivotal in directing the adaptive immune response and disease outcome in mice and humans but is unexplored in dogs. The objectives of this study were to evaluate the innate immune profile of dogs with coccidioidomycosis and determine if differences exist based on the extent of infection (i.e., pulmonary or disseminated). A total of 28 dogs with coccidioidomycosis (pulmonary, n = 16; disseminated, n = 12) and 10 seronegative healthy controls were enrolled. Immunologic testing was performed immediately, without ex vivo incubation (i.e., constitutive), and after coccidioidal antigen stimulation of whole blood cultures. Whole blood cultures were incubated with a phosphate-buffered solution (PBS) (negative control) or a coccidioidal antigen (rCTS1 (105-310); 10 µg/mL) for 24 h. A validated canine-specific multiplex bead-based assay was used to measure 12 cytokines in plasma and cell culture supernatant. Serum C-reactive protein (CRP) was measured with an ELISA assay. Leukocyte expression of toll-like receptors (TLRs)2 and TLR4 was measured using flow cytometry. Dogs with coccidioidomycosis had higher constitutive plasma keratinocyte chemotactic (KC)-like concentrations (p = 0.02) and serum CRP concentrations compared to controls (p < 0.001). Moreover, dogs with pulmonary coccidioidomycosis had higher serum CRP concentrations than those with dissemination (p = 0.001). Peripheral blood leukocytes from dogs with coccidioidomycosis produced higher concentrations of tumor necrosis factor (TNF)-α (p = 0.0003), interleukin (IL)-6 (p = 0.04), interferon (IFN)-γ (p = 0.03), monocyte chemoattractant protein (MCP)-1 (p = 0.02), IL-10 (p = 0.02), and lower IL-8 (p = 0.003) in supernatants following coccidioidal antigen stimulation when compared to those from control dogs. There was no detectable difference between dogs with pulmonary and disseminated disease. No differences in constitutive or stimulated leukocyte TLR2 and TLR4 expression were found. These results provide information about the constitutive and coccidioidal antigen-specific stimulated immune profile in dogs with naturally acquired coccidioidomycosis.

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.

Eosinophilia Associated With Immune Deficiency

The differential diagnosis of eosinophilia is broad and includes infections, malignancies, and atopy as well as inborn errors of immunity (IEI). Certain types of IEIs are known to be associated with elevated numbers of eosinophils and frequently elevated serum IgE, whereas for others the degree and frequency of eosinophilia are less established. The molecular defects underlying IEI are heterogeneous and affect different pathways, which highlights the complex regulations of this cell population within the immune system. In this review, we list and discuss clinical manifestations and therapies of immune deficiency or immune dysregulation disorders associated with peripheral blood or tissue eosinophilia with or without raised IgE levels. We present illustrative case vignettes for the most common entities and propose a diagnostic algorithm aiming to help physicians systematically to evaluate patients with eosinophilia and suspicion of an underlying IEI.

Case Report: Invasive Cryptococcosis in French Guiana: Immune and Genetic Investigation in Six Non-HIV Patients

Objectives

We describe the clinical, mycological, immunological, and genetic characteristics of six HIV-negative patients presenting with invasive cryptococcosis.

Methods

Patients with cryptococcosis without any of the classical risk factors, such as HIV infection, followed at Cayenne Hospital, were prospectively included. An immunologic and genetic assessment was performed.

Results

Five male patients and one female patient, 5 adults and one child, were investigated. All presented a neuromeningeal localization. Cryptococcus neoformans var. gattii and C. neoformans var. grubii were isolated in two and three patients, respectively, whereas one patient could not be investigated. Overall, we did not observe any global leukocyte defect. Two patients were found with high levels of circulating autoantibodies against Granulocyte macrophage-colony stimulating factor (GM-CSF), and none had detectable levels of autoantibodies against Interferon gamma (IFN-γ) Sequencing of STAT1 exons and flanking regions performed for four patients was wild type.

Conclusion

To better understand cryptococcosis in patients with cryptococcosis but otherwise healthy, further explorations are needed with repeated immune checkups and strain virulence studies.

Disseminated Coccidioidomycosis as the First Presentation of a C-Terminal NFKB2 Pathogenic Variant: A Case Report and Review of the Literature

INTRODUCTION

Although most cases of coccidioidomycosis are subclinical or self-limited respiratory disease, 1% lead to extrathoracic dissemination and become fatal, especially in patients with an associated immunodeficiency. Up to 30%-50% of patients with defects in cell-mediated immunity, those with AIDS and recipients of solid-organ transplants, may develop disseminated coccidioidomycosis (DC). Within the primary immunodeficiencies, an uncommon group is caused by C-terminal NFKB2 pathogenic variants.

MATERIALS AND METHODS

We performed a literature search of core databases. Written informed consent for the study and for publication was obtained.

CASE PRESENTATION

A 7-year-old Mexican girl, eldest of 3 sisters, no relevant family history, and a history of recurrent upper respiratory infections and alopecia totalis was admitted with DC involving pulmonary, soft tissue, skin, bone and joint compromise. The immunodeficiency assessment showed low IgM and NK cells. We found an NFKB2 de novo heterozygous nonsense mutation of c.2611C>T (p.Gln871*). She was treated with liposomal amphotericin B and itraconazole with surgical debridement. The clinical phenotype of this primary immunodeficiency is characterized by antibody deficiency and associated broncho-pulmonary predisposition to infection, but moreover also opportunistic infections and autoimmunity, most recognizable alopecia and adrenocorticotropic hormone-deficiency. After 1 year of her discharge, she continues under surveillance with antifungal therapy with itraconazole and replacement intravenous immunoglobulin until today.

CONCLUSION

This is the first case report of DC in a patient with an NFKB2 pathogenic variant and it illustrates the importance of screening for primary immunodeficiencies in patients with disseminated fungal infections.

Vaccine Protection of Mice With Primary Immunodeficiencies Against Disseminated Coccidioidomycosis

Disseminated coccidioidomycosis (DCM), often a severe and refractory disease leading to poor outcomes, is a risk for people with certain primary immunodeficiencies (PID). Several DCM-associated PID (STAT4, STAT3, IFNγ, and Dectin-1) are modeled in mice. To determine if vaccination could provide these mice protection, mice with mutations in Stat4, Stat3, Ifngr1, Clec7a (Dectin-1), and Rag-1 (T- and B-cell deficient) knockout (KO) mice were vaccinated with the live, avirulent, Δcps1 vaccine strain and subsequently challenged intranasally with pathogenic Coccidioides posadasii Silveira strain. Two weeks post-infection, vaccinated mice of all strains except Rag-1 KO had significantly reduced lung and spleen fungal burdens (p<0.05) compared to unvaccinated control mice. Splenic dissemination was prevented in most vaccinated immunodeficient mice while all unvaccinated B6 mice and the Rag-1 KO mice displayed disseminated disease. The mitigation of DCM by Δcps1 vaccination in these mice suggests that it could also benefit humans with immunogenetic risks of severe disease.

Meningitis Caused by Cryptococcus neoformans in an Apparently Immunocompetent Patient

Cryptococcal meningitis (CM), as a life-threatening opportunistic infection, often is among cases with cell-mediated immunodeficiencies, such as AIDS, hematologic malignancies, and solid organ transplant recipients. Cryptococcal meningitis in healthy individuals is uncommon, and its detection in immunocompetent cases may be tricky because the presentation is generally more indolent than the traditional meningitis presentation, leading to late diagnosis and potential sequels. We present a CM case in an immunocompetent Iranian male patient who was treated successfully.

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.

Histoplasmosis in Children; HIV/AIDS Not a Major Driver

The classification of histoplasmosis as an AIDS-defining illness has largely attributed its occurrence in people to the presence of HIV/AIDS especially in Africa. Prior to the advent of the HIV/AIDS epidemic, several cases of histoplasmosis were documented both in the pediatric and adult populations. Our review revealed 1461 reported cases of pediatric histoplasmosis globally in the last eight decades (1939-2021). North America (n = 1231) had the highest number of cases, followed by South America (n = 135), Africa (n = 65), Asia (n = 26) and Europe (n = 4). Histoplasmosis was much more common in the non-HIV pediatric population (n = 1418, 97.1%) compared to the HIV population. The non-HIV factors implicated were, childhood malignancies (n = 207), such as leukemias and lymphomas as well as their treatment, lung diseases (n = 7), environmental exposures and toxins (n = 224), autoimmune diseases (n = 12), organ transplants (n = 12), long-term steroid therapy (n = 3), the use of immunosuppressive drugs such as TNF-alpha inhibitors (n = 7) malnutrition (n = 12), histiocytosis (n = 3), Hyper immunoglobulin M and E syndromes (n = 15, 1.2%), pancytopenia (n = 26), diabetes mellitus (n = 1) and T-cell deficiency (n = 21). Paediatricians should always consider or rule out a diagnosis of histoplasmosis in children presenting with symptoms suggestive of the above clinical conditions.

A Chronic Murine Disease Model of Coccidioidomycosis Using Coccidioides posadasii, Strain 1038

Murine infections with most Coccidioides spp. strains are lethal by 3 weeks, limiting the study of immune responses. Coccidioides posadasii, strain 1038 (Cp1038), while slowly lethal, resulted in protracted survival of C57BL/6 (B6) mice. In resistant (B6D2)F1/J mice, lung fungal burdens stabilized by week 4 without progression through week 16, better modeling human coccidioidal infections after their immunologic control. Immunodeficient tumor necrosis factor (Tnf) α knockout (KO) and interferon (Ifn) γ receptor 1 (Ifn-γr1) KO mice survived a median of 22.5 and 34 days, compared with 70 days in B6 mice (P = .001 and P < .01, respectively), though 14-day lung fungal burden studies showed little difference between Ifn-γr1 KO and B6 mice. B6 mice showed peak concentrations of key inflammatory lung cytokines, including interleukin 6, 23, and 17A, Tnf-α, and Ifn-γ, only after 4 weeks of infection. The slower progression in B6 and the acquired fungal burden stability in B6D2 mice after Cp1038 infection greatly increases the array of possible immunologic studies.

Paediatric Histoplasmosis 2000-2019: A Review of 83 Cases

Histoplasmosis is an endemic fungal infection that is confined to specific geographical regions. Histoplasma spp. are primary pathogens that cause disease in both immunocompetent and immunocompromised patients, ranging from a single-organ (mostly affecting the lungs) infection to life-threatening disseminated disease. Knowledge about the clinical epidemiology relies on data from adult populations; little is known about the patient and disease characteristics in the paediatric population. Therefore, a structured review of published cases of paediatric histoplasmosis between 2000 and 2019 was performed. A literature search of PubMed was conducted and the epidemiological and clinical data from 83 cases were analysed. The mean age at presentation was 9.5 ± 5.5 years, and 51% were girls. Two-thirds of the children were immunocompromised. The majority of children presented with disseminated disease. The most frequently observed clinical symptoms were respiratory symptoms, alongside non-specific systemic features, including fever, myalgia, fatigue and weight loss. The mortality rate was 11%. Histoplasmosis affects children of any age. Being immunocompromised is a risk factor for severe and disseminated disease. The lack of specific presenting features leads to underreporting and delay in diagnosis. To improve the recognition and outcome of histoplasmosis in childhood, increased awareness and surveillance systems are warranted.

The Known Unknowns of the Immune Response to Coccidioides

Coccidioidomycosis, otherwise known as Valley Fever, is caused by the dimorphic fungi Coccidioides immitis and C. posadasii. While most clinical cases present with self-limiting pulmonary infection, dissemination of Coccidioides spp. results in prolonged treatment and portends higher mortality rates. While the structure, genome, and niches for Coccidioides have provided some insight into the pathogenesis of disease, the underlying immunological mechanisms of clearance or inability to contain the infection in the lung are poorly understood. This review focuses on the known innate and adaptive immune responses to Coccidioides and highlights three important areas of uncertainty and potential approaches to address them. Closing these gaps in knowledge may enable new preventative and therapeutic strategies to be pursued.

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.

Host Response to Coccidioides Infection: Fungal Immunity

Coccidioidomycosis is a fungal, respiratory disease caused by Coccidioides immitis and Coccidioides posadasii. This emerging infectious disease ranges from asymptomatic to pulmonary disease and disseminated infection. Most infections are cleared with little to no medical intervention whereas chronic disease often requires life-long medication with severe impairment in quality of life. It is unclear what differentiates hosts immunity resulting in disease resolution versus chronic infection. Current understanding in mycology-immunology suggests that chronic infection could be due to maladaptive immune responses. Immunosuppressed patients develop more severe disease and mouse studies show adaptive Th1 and Th17 responses are required for clearance. This is supported by heightened immunosuppressive regulatory responses and lowered anti-fungal T helper responses in chronic Coccidioides patients. Diagnosis and prognosis is difficult as symptoms are broad and overlapping with community acquired pneumonia, often resulting in misdiagnosis and delayed treatment. Furthermore, we lack clear biomarkers of disease severity which could aid prognosis for more effective healthcare. As the endemic region grows and population increases in endemic areas, the need to understand Coccidioides infection is becoming urgent. There is a growing effort to identify fungal virulence factors and host immune components that influence fungal immunity and relate these to patient disease outcome and treatment. This review compiles the known immune responses to Coccidioides spp. infection and various related fungal pathogens to provide speculation on Coccidioides immunity.

Opportunist Coinfections by Nontuberculous Mycobacteria and Fungi in Immunocompromised Patients

Nontuberculous mycobacteria (NTM) and many fungal species (spp.) are commonly associated with opportunistic infections (OPIs) in immunocompromised individuals. Moreover, occurrence of concomitant infection by NTM (mainly spp. of Mycobacterium avium complex and Mycobacterium abscessus complex) and fungal spp. (mainly, Aspergillus fumigatus, Histoplasma capsulatum and Cryptococcus neoformans) is very challenging and is associated with poor patient prognosis. The most frequent clinical symptoms for coinfection and infection by single agents (fungi or NTM) are similar. For this reason, the accurate identification of the aetiological agent(s) is crucial to select the best treatment approach. Despite the significance of this topic it has not been sufficiently addressed in the literature. This review aims at summarizing case reports and studies on NTM and fungi coinfection during the last 20 years. In addition, it briefly characterizes OPIs and coinfection, describes key features of opportunistic pathogens (e.g., NTM and fungi) and human host predisposing conditions to OPIs onset and outcome. The review could interest a wide spectrum of audiences, including medical doctors and scientists, to improve awareness of these infections, leading to early identification in clinical settings and increasing research in the field. Improved diagnosis and availability of therapeutic options might contribute to improve the prognosis of patients' survival.

Impaired B-Cell Differentiation in a Patient With STAT1 Gain-of-Function Mutation

Hypogammaglobulinemia is a rare complication of STAT1 gain-of-function (GOF) mutations. We report an adult patient diagnosed with hypogammaglobulinemia caused by B-cell depletion during the treatment of disseminated cryptococcosis. The patient carried the STAT1 GOF mutation (c.820C>T, p.R274W). The flow cytometric analysis of his bone marrow revealed that B-cell differentiation was blocked in the stages between pre-B1b and pre-B2 cells. On the other hand, his brother who carried the same mutation displayed normal B-cell counts, thereby indicating that the unrecognized variants in same or other gene might be associated with abnormal B-cell differentiation in the patients. In conclusion, impaired B-cell differentiation in the bone marrow can cause hypogammaglobulinemia in patients with STAT1 GOF mutations.

The Child with Elevated IgE and Infection Susceptibility

PURPOSE OF REVIEW

Over the last 13 years, the genetic etiologies have been determined for multiple conditions causing elevated serum IgE, infection susceptibilities, and variable other features. In this review, we discuss the clinical presentation, laboratory features, and genetics of these diseases caused by mutations in STAT3, DOCK8, PGM3, IL6ST, ZNF341, IL6R, IL6ST, CARD11, and CARD14, with particular focus given to STAT3LOF and DOCK8 deficiency.

RECENT FINDINGS

Defining the phenotype of each of these syndromes with high IgE and infection susceptibility shows that some have a pronounced connective tissue phenotype such as STAT3LOF and IL6ST deficiency, some have worse viral susceptibility such as DOCK8 deficiency and heterozygous LOF CARD11, and some have more severe allergy and eczema such as LOF CARD14. Studying these distinct but overlapping monogenic diseases will allow a better understanding of more common disease processes such as allergy, eczema, infection susceptibility, scoliosis, and aneurysm.

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.

Recent progress on pathophysiology, inflammation and defense mechanism of mast cells against invading microbes: inhibitory effect of IL-37

Mast cells (MCs) have historically been considered masters of allergy, but there is substantial evidence supporting their contribution to tissue microorganism clearance. Their activation through the cross-linking of bound IgE provokes mast cell degranulation and activates tyrosine kinase (Syk and Lyn), leading to cytokine/chemokine generation and release. Current consensus holds that mast cells participate in the body’s defense against numerous pathogens, including bacteria, fungi, viruses and parasites, but also contribute to the inflammatory response induced by these biological agents. In the light of the latest findings, we describe the cross-talk between mast cells and pathogenic microorganisms. This review summarizes our current understanding of the host immune response, with emphasis on the roles of MCs and the cytokine/chemokine network in provoking inflammation and generating protective immunity.

This review addresses the ability of microorganisms to activate MCs provoking inflammation. We describe some MC-specific biological activities related to infections and discuss the evidence of MC mechanisms involved in the microbial activation which cause cytokine/chemokine generation-mediated inflammation, and provide a description of novel functions of mast cells during microbial infection.

Interleukin (IL)-37 binds the α chain of the IL-18 receptor and suppresses MyD88-mediated inflammatory responses. IL-37 plays a pathological role in certain infections by inhibiting the production of pro-inflammatory cytokines, such as IL-1 and TNF. Here we report the interrelationship between IL-37, inflammatory cytokines and mast cells.

Our report offers opportunities for the design of new therapeutic interventions in inflamed tissue induced by microorganism infections, acting on manipulation of mast cells and/or inflammatory cytokine blockage.

An Update on Syndromes with a Hyper-IgE Phenotype

Improvement in genetic testing has allowed specific delineation of several distinct clinical causes characterized by the hyperimmunoglobulin E (IgE) phenotype of eczema, recurrent infections, and elevated serum IgE. Mutations in STAT3, DOCK8, PGM3, ERBIN, IL6ST, and CARD11 cause clinical phenotypes that can present in this manner. This article focuses on loss of function STAT3 mutations causing autosomal-dominant hyper-IgE syndrome and dedicator of cytokinesis 8 deficiency, with discussion of other more recently described diseases.

Structural Implications of STAT3 and STAT5 SH2 Domain Mutations

Src Homology 2 (SH2) domains arose within metazoan signaling pathways and are involved in protein regulation of multiple pleiotropic cascades. In signal transducer and activator of transcription (STAT) proteins, SH2 domain interactions are critical for molecular activation and nuclear accumulation of phosphorylated STAT dimers to drive transcription. Sequencing analysis of patient samples has revealed the SH2 domain as a hotspot in the mutational landscape of STAT proteins although the functional impact for the vast majority of these mutations remains poorly characterized. Despite several well resolved structures for SH2 domain-containing proteins, structural data regarding the distinctive STAT-type SH2 domain is limited. Here, we review the unique features of STAT-type SH2 domains in the context of all currently reported STAT3 and STAT5 SH2 domain clinical mutations. The genetic volatility of specific regions in the SH2 domain can result in either activating or deactivating mutations at the same site in the domain, underscoring the delicate evolutionary balance of wild type STAT structural motifs in maintaining precise levels of cellular activity. Understanding the molecular and biophysical impact of these disease-associated mutations can uncover convergent mechanisms of action for mutations localized within the STAT SH2 domain to facilitate the development of targeted therapeutic interventions.

Application of Flow Cytometry in the Diagnostics Pipeline of Primary Immunodeficiencies Underlying Disseminated Talaromyces marneffei Infection in HIV-Negative Children

Talaromyces (Penicillium) marneffei is an AIDS-defining infection in Southeast Asia and is associated with high mortality. It is rare in non-immunosuppressed individuals, especially children. Little is known about host immune response and genetic susceptibility to this endemic fungus. Genetic defects in the interferon-gamma (IFN-γ)/STAT1 signaling pathway, CD40/CD40 ligand- and IL12/IL12-receptor-mediated crosstalk between phagocytes and T-cells, and STAT3-mediated Th17 differentiation have been reported in HIV-negative children with talaromycosis and other endemic mycoses such as histoplasmosis, coccidioidomycosis, and paracoccidioidomycosis. There is a need to design a diagnostic algorithm to evaluate such patients. In this article, we review a cohort of pediatric patients with disseminated talaromycosis referred to the Asian Primary Immunodeficiency Network for genetic diagnosis of PID. Using these illustrative cases, we propose a diagnostics pipeline that begins with immunoglobulin pattern (IgG, IgA, IgM, and IgE) and enumeration of lymphocyte subpopulations (T-, B-, and NK-cells). The former could provide clues for hyper-IgM syndrome and hyper-IgE syndrome. Flow cytometric evaluation of CD40L expression should be performed for patients suspected to have X-linked hyper-IgM syndrome. Defects in interferon-mediated JAK-STAT signaling are evaluated by STAT1 phosphorylation studies by flow cytometry. STAT1 hyperphosphorylation in response to IFN-α or IFN-γ and delayed dephosphorylation is diagnostic for gain-of-function STAT1 disorder, while absent STAT1 phosphorylation in response to IFN-γ but normal response to IFN-α is suggestive of IFN-γ receptor deficiency. This simple and rapid diagnostic algorithm will be useful in guiding genetic studies for patients with disseminated talaromycosis requiring immunological investigations.

Investigation of Genetic Susceptibility to Blastomycosis Reveals Interleukin-6 as a Potential Susceptibility Locus

Genetic differences are hypothesized to underlie ethnic disparities in incidence rates of the endemic systemic mycoses, including blastomycosis. Individuals of Hmong ancestry display elevated risk for this serious fungal infection. Here, we interrogated the genomes of Wisconsin (WI) Hmong blastomycosis patients using homozygosity mapping to uncover regions of the genome that are likely shared among the greater Hmong population and filtered for variants with high potential to affect disease susceptibility. This approach uncovered 113 candidate susceptibility variants, and among the most promising are those in genes involved in the interleukin-17 (IL-17) response. In particular, we identified 25 linked variants near the gene encoding IL-6 (IL6). We validated differences in cytokine production between Hmong and European volunteers and formally demonstrated a critical role for IL-6 in the development of adaptive immunity to Blastomyces dermatitidis Our findings suggest that the dysregulation of IL-17 responses underlies a recently reported and poorly understood ethnic health disparity.IMPORTANCE Blastomycosis is a potentially life-threatening infection caused by the fungus Blastomyces dermatitidis As with related fungal diseases, blastomycosis is noted to affect some populations more than others. These patterns of illness are often not related to predisposing conditions or exposure risks; thus, genetic differences are thought to underlie these health disparities. People of Hmong ancestry in Wisconsin are at elevated risk of blastomycosis compared to the general population. We studied the genetic codes of Hmong blastomycosis patients and identified candidate sites in their genomes that may explain their susceptibility to this infection. We further studied one particular region of the genome that is involved with the immune processes that fight B. dermatitidis Our work revealed population differences in the response to fungi. A better understanding of the genetic underpinnings of susceptibility to infectious diseases has broader implications for community health, especially in the paradigm of personalized medicine.

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.

Definition of Opportunistic Infections in Immunocompromised Children on the Basis of Etiologies and Clinical Features: A Summary for Practical Purposes

Opportunistic Infections (OIs) still remain a major cause of morbidity and death in children with either malignant or nonmalignant disease. OIs are defined as those infections occurring due to bacteria, fungi, viruses or commensal organisms that normally inhabit the human body and do not cause a disease in healthy people, but become pathogenic when the body's defense system is impaired. OIs can also be represented by unusually severe infections caused by common pathogens. An OI could present itself at the onset of a primary immunodeficiency syndrome as a life-threatening event. More often, OI is a therapyassociated complication in patients needing immunosuppressive treatment, among long-term hospitalised patients or in children who undergo bone marrow or solid organ transplantation. The aim of the present review is to provide a comprehensive and 'easy to read' text that briefly summarises the currently available knowledge about OIs in order to define when an infection should be considered as opportunistic in pediatrics as a result of an underlying congenital or acquired immune-deficit.

[What's new in pediatric dermatology?]

The association of a birth defect and a segmental hemangioma is well established, a consensus concerning evaluation and monitoring of infants with PHACE or LUMBAR syndromes has been published. The efficacy of propranolol in infantile hemangioma is proven; however there were still unresolved issues concerning the safety in children; after 8 years of use on thousands of children safety data collection did not show any unexpected side effects. Topical treatment of infantile hemangiomas with beta-blockers, such as timolol, is very popular, but recent publications revealed a significant systemic absorption that could be responsible for severe side effects, such as bradycardia, in low birthweight infants. As a consequence, this therapeutic option should be considered with caution. In the last 2 years mTOR inhibitors have been tested in low-flow vascular malformations with varying success, but progress remains to be done in the treatment of vascular abnormalities. Today, genetics has led to advances in the understanding of the pathophysiology and in the future targeted therapies could probably be feasible. Skin barrier deficiency is responsible for the development of allergic phenomena in atopic patients, since it has been shown that sensibilisation, even to food, could probably be induced by skin contact. Unfortunately, the topical treatment with crisaborole, a phosphodiesterase 4 inhibitor, does not look like a revolution in children atopic dermatitis, its efficacy seems equivalent to emollient application. In the field of infectious diseases, changes in viral outbreaks are the most reported. Furthermore epidemic Zika virus, enteroviruses are responsible for expanded dermatological manifestations and also severe meningoencephalitis. Paraviral character of various eruptions, such as gloves and socks syndrome or eruptive pseudoangiomatosis is challenged.

Coccidioides immitis and posadasii; A review of their biology, genomics, pathogenesis, and host immunity

Coccidioides immitis and C. posadasii are two highly pathogenic dimorphic fungal species that are endemic in the arid areas of the new world, including the region from west Texas to southern and central California in the USA that cause coccidioidomycosis (also known as Valley Fever). In highly endemic regions such as southern Arizona, up to 50% of long term residents have been infected. New information about fungal population genetics, ecology, epidemiology, and host-pathogen interactions is becoming available. However, our understanding of some aspects of coccidioidomycosis is still incomplete, including the extent of genetic variability of the fungus, the genes involved in virulence, and how the changes in gene expression during the organism's dimorphic life cycle are related to the transformation from a free-living mold to a parasitic spherule. Unfortunately, efforts to develop an effective subunit vaccine have not yet been productive, although two potential live fungus vaccines have been developed.

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).

Emerging Infections and Pertinent Infections Related to Travel for Patients with Primary Immunodeficiencies

In today's global economy and affordable vacation travel, it is increasingly important that visitors to another country and their physician be familiar with emerging infections, infections unique to a specific geographic region, and risks related to the process of travel. This is never more important than for patients with primary immunodeficiency disorders (PIDD). A recent review addressing common causes of fever in travelers provides important information for the general population Thwaites and Day (N Engl J Med 376:548-560, 2017). This review covers critical infectious and management concerns specifically related to travel for patients with PIDD. This review will discuss the context of the changing landscape of infections, highlight specific infections of concern, and profile distinct infection phenotypes in patients who are immune compromised. The organization of this review will address the environment driving emerging infections and several concerns unique to patients with PIDD. The first section addresses general considerations, the second section profiles specific infections organized according to mechanism of transmission, and the third section focuses on unique phenotypes and unique susceptibilities in patients with PIDDs. This review does not address most parasitic diseases. Reference tables provide easily accessible information on a broader range of infections than is described in the text.

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.

Immunity against fungi

Pathogenic fungi cause a wide range of syndromes in immune-competent and immune-compromised individuals, with life-threatening disease primarily seen in humans with HIV/AIDS and in patients receiving immunosuppressive therapies for cancer, autoimmunity, and end-organ failure. The discovery that specific primary immune deficiencies manifest with fungal infections and the development of animal models of mucosal and invasive mycoses have facilitated insight into fungus-specific recognition, signaling, effector pathways, and adaptive immune responses. Progress in deciphering the molecular and cellular basis of immunity against fungi is guiding preclinical studies into vaccine and immune reconstitution strategies for vulnerable patient groups. Furthermore, recent work has begun to address the role of endogenous fungal communities in human health and disease. In this review, we summarize a contemporary understanding of protective immunity against fungi.