The role of cytokines and chemokines in Histoplasma capsulatum infection

Common virulence factors between Histoplasma and Paracoccidioides: Recognition of Hsp60 and Enolase by CR3 and plasmin receptors in host cells

Over the last two decades, the incidence of Invasive Fungal Infections (IFIs) globally has risen, posing a considerable challenge despite available antifungal therapies. Addressing this, the World Health Organization (WHO) prioritized research on specific fungi, notably Histoplasma spp. and Paracoccidioides spp. These dimorphic fungi have a mycelial life cycle in soil and a yeast phase associated with tissues of mammalian hosts. Inhalation of conidia and mycelial fragments initiates the infection, crucially transforming into the yeast form within the host, influenced by factors like temperature, host immunity, and hormonal status. Survival and multiplication within alveolar macrophages are crucial for disease progression, where innate immune responses play a pivotal role in overcoming physical barriers. The transition to pathogenic yeast, triggered by increased temperature, involves yeast phase-specific gene expression, closely linked to infection establishment and pathogenicity. Cell adhesion mechanisms during host-pathogen interactions are intricately linked to fungal virulence, which is critical for tissue colonization and disease development. Yeast replication within macrophages leads to their rupture, aiding pathogen dissemination. Immune cells, especially macrophages, dendritic cells, and neutrophils, are key players during infection control, with macrophages crucial for defense, tissue integrity, and pathogen elimination. Recognition of common virulence molecules such as heat- shock protein-60 (Hsp60) and enolase by pattern recognition receptors (PRRs), mainly via the complement receptor 3 (CR3) and plasmin receptor pathways, respectively, could be pivotal in host-pathogen interactions for Histoplasma spp. and Paracoccidioides spp., influencing adhesion, phagocytosis, and inflammatory regulation. This review provides a comprehensive overview of the dynamic of these two IFIs between host and pathogen. Further research into these fungi's virulence factors promises insights into pathogenic mechanisms, potentially guiding the development of effective treatment strategies.

Utilization of a Histoplasma capsulatum zinc reporter reveals the complexities of fungal sensing of metal deprivation

Histoplasma capsulatum is a dimorphic fungal pathogen acquired via inhalation of soil-resident spores. Upon exposure to mammalian body temperatures, these fungal elements transform into yeasts that reside primarily within phagocytes. Macrophages (MΦ) provide a permissive environment for fungal replication until T cell-dependent immunity is engaged. MΦ activated by granulocyte macrophage colony stimulating factor (GM-CSF) induces metallothioneins (MTs) that bind zinc (Zn) and deprive yeast cells of labile Zn, thereby disabling fungal growth. Prior work demonstrated that the zinc transporter, ZRT2, was important for fungal survival in vivo. Hence, we constructed a yeast cell reporter strain that expresses green fluorescent protein (GFP) under control of the ZRT2 zinc-regulated promoter. This reporter accurately responds to a medium devoid of Zn. ZRT2 expression increased in GM-CSF, but not interferon-γ, stimulated MΦ. To examine the in vivo response, we infected mice with a reporter yeast strain and assessed ZRT2 expression at 0, 3, 7, and 14 days post-infection (dpi). ZRT2 expression minimally increased at 3 dpi and peaked at 7 dpi, corresponding with the onset of adaptive immunity. We discovered that the major MΦ populations that restrict Zn from the fungus are interstitial MΦ and exudate MΦ. Neutralizing GM-CSF blunted the control of infection but unexpectedly increased ZRT2 expression. This increase was dependent on another cytokine that activates MΦ to control H. capsulatum replication, M-CSF. These findings illustrate the reporter's ability to sense Zn in vitro and in vivo and correlate ZRT2 expression with GM-CSF and M-CSF activation of MΦ.IMPORTANCEPhagocytes use an arsenal of defenses to control the replication of Histoplasma yeasts, one of which is the limitation of trace metals. On the other hand, H. capsulatum combats metal restriction by upregulating metal importers such as the Zn importer ZRT2. This transporter contributes to H. capsulatum pathogenesis upon activation of adaptive immunity. We constructed a fluorescent ZRT2 transcriptional reporter to probe H. capsulatum Zn sensing during infection and exposed the role for M-CSF activation of macrophages when GM-CSF is absent. These data highlight the ways in which fungal pathogens sense metal deprivation in vivo and reveal the potential of metal-sensing reporters. The work adds a new dimension to study how intracellular pathogens sense and respond to the changing environments of the host.

Screening with urine Histoplasma antigen test in asymptomatic patients starting TNF-alpha inhibitor therapy: a cohort study

Background

Histoplasmosis is the second most frequent granulomatous disease in patients treated with tumor necrosis factor (TNF)-α inhibitors, second only to tuberculosis. However, there is limited information about pre-therapy screening procedures and the need for preventive treatments for patients who will start immunobiologicals.

Methods

This is a cohort study that evaluated the prevalence of histoplasmosis in asymptomatic HIV-negative patients before initiation of TNF-α inhibitors by testing for Histoplasma antigen in urine samples. The patients included completed a 180-day follow-up after the initiation of the biologics to assess the onset of symptoms suggestive of histoplasmosis.

Results

From January 2021 to December 2022, 54 patients who were prescribed a TNF-α inhibitor agent for treating autoimmune diseases in centers in southern Brazil were included. In the screening before therapy, the prevalence of a positive urinary Histoplasma antigen test was 14.8%. None of the 54 patients developed histoplasmosis after 6 months of immunobiological therapy, including the eight patients who tested positive.

Conclusion

The prevalence of Histoplasma capsulatum infection in chronic patients may be higher than expected, but the impact of latent infection in asymptomatic patients is still uncertain, including those starting treatment with immunobiological drugs such as TNF-α inhibitors. Our study did not identify risk factors for the diagnosis of disseminated histoplasmosis in this group, including a positive result in an antigen test performed before immunobiological therapy. To date, there is no evidence to recommend routine antigen-based screening or preventive therapy for histoplasmosis before initiating a TNF-α inhibitor.

Modulatory immune responses in fungal infection associated with organ transplant - advancements, management, and challenges

Organ transplantation stands as a pivotal achievement in modern medicine, offering hope to individuals with end-stage organ diseases. Advancements in immunology led to improved organ transplant survival through the development of immunosuppressants, but this heightened susceptibility to fungal infections with nonspecific symptoms in recipients. This review aims to establish an intricate balance between immune responses and fungal infections in organ transplant recipients. It explores the fundamental immune mechanisms, recent advances in immune response dynamics, and strategies for immune modulation, encompassing responses to fungal infections, immunomodulatory approaches, diagnostics, treatment challenges, and management. Early diagnosis of fungal infections in transplant patients is emphasized with the understanding that innate immune responses could potentially reduce immunosuppression and promise efficient and safe immuno-modulating treatments. Advances in fungal research and genetic influences on immune-fungal interactions are underscored, as well as the potential of single-cell technologies integrated with machine learning for biomarker discovery. This review provides a snapshot of the complex interplay between immune responses and fungal infections in organ transplantation and underscores key research directions.

Utilization of a Histoplasma capsulatum zinc reporter reveals the complexities of fungal sensing of metal deprivation

Histoplasma capsulatum is a dimorphic fungal pathogen acquired via inhalation of soil-resident spores. Upon exposure to mammalian body temperatures, these fungal elements transform into yeasts that reside primarily within phagocytes. Macrophages (MΦ) provide a permissive environment for fungal replication until T cell-dependent immunity is engaged. MΦ activated by granulocyte-MΦ colony stimulating factor (GM-CSF) induce metallothioneins (MTs) that bind zinc (Zn) and deprive yeast cells of labile Zn, thereby disabling fungal growth. Prior work demonstrated that the high affinity zinc importer, ZRT2, was important for fungal survival in vivo. Hence, we constructed a yeast cell reporter strain that expresses green fluorescent protein (GFP) under the control of this importer. This reporter accurately responds to medium devoid of Zn. ZRT2 expression increased (∼5-fold) in GM-CSF, but not interferon-γ, stimulated MΦ. To examine the in vivo response, we infected mice with reporter yeasts and assessed ZRT2 expression at 0-, 3-, 7-, and 14-days post-infection (dpi). ZRT2 expression minimally increased at 3-dpi and peaked on 7-dpi, corresponding with onset of adaptive immunity. We discovered that the major phagocyte populations that restrict Zn to the fungus are interstitial MΦ and exudate MΦ. Neutralizing GM-CSF blunted control of infection but unexpectedly increased ZRT2 expression. This increase was dependent on another cytokine that activates MΦ to control H. capsulatum replication, M-CSF. These findings illustrate the reporter's ability to sense Zn in vitro and in vivo and correlate ZRT2 activity with GM-CSF and M-CSF activation of MΦ.

Importance

Phagocytes use an arsenal of defenses to control replication of Histoplasma yeasts, one of which is limitation of trace metals. On the other hand, H. capsulatum combats metal restriction by upregulating metal importers such as the Zn importer ZRT2. This transporter contributes to H. capsulatum pathogenesis upon activation of adaptive immunity. We constructed a fluorescent ZRT2 reporter to probe H. capsulatum Zn sensing during infection and exposed a role for M-CSF activation of macrophages when GM-CSF is absent. These data highlight the ways in which fungal pathogens sense metal deprivation in vivo and reveal the potential of metal-sensing reporters. The work adds a new dimension to studying how intracellular pathogens sense and respond to the changing environments of the host.

Fungal infections: Immune defense, immunotherapies and vaccines

Invasive fungal infection is an under recognized and emerging global health threat. Recently, the World Health Organization (WHO) released the first ever list of health-threatening fungi to guide research and public health interventions to strengthen global response to fungi infections and antifungal resistance. Currently, antifungal drugs only demonstrate partial success in improving prognosis of infected patients, and this is compounded by the rapid evolution of drug resistance among fungi species. The increased prevalence of fungal infections in individuals with underlying immunological deficiencies reflects the importance of an intact host immune system in controlling mycoses, and further highlights immunomodulation as a potential new avenue for the treatment of disseminated fungal diseases. In this review, we will summarize how host innate immune cells sense invading fungi through their pattern recognition receptors, and subsequently initiate a series of effector mechanisms and adaptive immune responses to mediate fungal clearance. In addition, we will discuss emerging preclinical and clinical data on antifungal immunotherapies and fungal vaccines which can potentially expand our antifungal armamentarium in future.

Polyfunctional Antigen Specific CD4+ T cell Responses in Patients With Human Immunodeficiency Virus/AIDS and Histoplasmosis Immune Reconstitution Inflammatory Syndrome

In the combination antiretroviral era, there are limited data regarding the pathogenesis of histoplasmosis immune reconstitution inflammatory syndrome (IRIS) in people with human immunodeficiency virus (HIV). We immunologically characterized 10 cases of histoplasmosis, 4 of whom developed histoplasmosis IRIS. CD4+ T cells in histoplasmosis IRIS demonstrated a significant polyfunctional cytokine response to histoplasma antigen.

The roles of fungus in CNS autoimmune and neurodegeneration disorders

Fungal infection or proliferation in our body is capable of initiation of strong inflammation and immune responses that result in different consequences, including infection-trigged organ injury and inflammation-related remote organ dysfunction. Fungi associated infectious diseases have been well recognized in the clinic. However, whether fungi play an important role in non-infectious central nervous system disease is still to be elucidated. Recently, a growing amount of evidence point to a non-negligible role of peripheral fungus in triggering unique inflammation, immune response, and exacerbation of a range of non-infectious CNS disorders, including Multiple sclerosis, Neuromyelitis optica, Parkinson's disease, Alzheimer's disease, and Amyotrophic lateral sclerosis et al. In this review, we summarized the recent advances in recognizing patterns and inflammatory signaling of fungi in different subsets of immune cells, with a specific focus on its function in CNS autoimmune and neurodegeneration diseases. In conclusion, the fungus is capable of triggering unique inflammation by multiple mechanisms in the progression of a body of CNS non-infectious diseases, suggesting it serves as a key factor and critical novel target for the development of potential therapeutic strategies.

Antifungal Encapsulated into Ligand-Functionalized Nanoparticles with High Specificity for Macrophages

Infectious diseases caused by intracellular microorganisms such as Histoplasma capsulatum represent a significant challenge worldwide. Drug encapsulation into functionalized nanoparticles (NPs) is a valuable alternative to improving drug solubility and bioavailability, preventing undesirable interactions and drug degradation, and reaching the specific therapeutic target with lower doses. This work reports on Itraconazole (ITZ) encapsulated into core-shell-like polymeric NPs and functionalized with anti-F4/80 antibodies for their targeted and controlled release into macrophages. Uptake assay on co-culture showed significant differences between the uptake of functionalized and bare NPs, higher with functionalized NPs. In vitro assays showed that F4/80-NPs with 0.007 µg/mL of encapsulated ITZ eliminated the H. capsulatum fungus in co-culture with macrophages effectively compared to the bare NPs, without any cytotoxic effect on macrophages after 24 h interaction. Furthermore, encapsulated ITZ modulated the gene expression of anti and pro-inflammatory cytokines (IL-1, INF-Y, IL-6 and IL-10) on macrophages. Additionally, the anti-F4/80 antibody-coating enhanced natural and adequate antifungal response in the cells, exerting a synergistic effect that prevented the growth of the fungus at the intracellular level. Functionalized NPs can potentially improve macrophage-targeted therapy, increasing NPs endocytosis and intracellular drug concentration.

T cell responses to control fungal infection in an immunological memory lens

In recent years, fungal vaccine research emanated significant findings in the field of antifungal T-cell immunity. The generation of effector T cells is essential to combat many mucosal and systemic fungal infections. The development of antifungal memory T cells is integral for controlling or preventing fungal infections, and understanding the factors, regulators, and modifiers that dictate the generation of such T cells is necessary. Despite the deficiency in the clear understanding of antifungal memory T-cell longevity and attributes, in this review, we will compile some of the existing literature on antifungal T-cell immunity in the context of memory T-cell development against fungal infections.

Progressive disseminated histoplasmosis in HIV-positive patients

BACKGROUND

Histoplasmosis is the most common endemic mycosis among people living with advanced HIV infection.

PURPOSE

Describe general aspects and challenges of this disease and its association with HIV.

RESEARCH DESIGN

Review of literature.

STUDY SAMPLE

Articles found using different combinations of terms including "disseminated histoplasmosis" and AIDS/HIV or immunosuppression in PubMed, Scopus, WHO Global health library, and Scielo database.

ANALYSIS

We look for information on epidemiology, pathogenesis, diagnosis, and treatment of histoplasmosis in AIDS patients.

RESULTS

Histoplasmosis is caused by Histoplasma capsulatum, a dimorphic fungus encountered throughout the world, mainly in soil enriched with bat and bird excreta. Progressive disseminated histoplasmosis is the main presentation of this mycosis in people living with advanced HIV and is fatal if left untreated. Symptoms include a systemic disease characterized by fever, weight loss, night sweats, skin manifestations, hepatomegaly, splenomegaly, and septic shock. Diagnostic tests include culture, visualization of H. capsulatum by direct and histopathological examination, serology, antigen, molecular, and skin testing. Patients with disseminated disease require aggressive and prolonged treatment to eradicate the pathogen and include amphotericin B and itraconazole. In many low income countries of endemic regions, histoplasmosis in HIV-positive patients is often undiagnosed or misdiagnosed as another opportunistic infection, due to the similarity in clinical manifestations and to the paucity of better diagnostic tests.

CONCLUSION

Histoplasmosis remains a neglected disease. Few studies about the disease and expensive treatments make it difficult to reduce the morbidity and mortality of this condition. Public health services and physicians must be aware of histoplasmosis' burden among the HIV-positive population.

Disseminated histoplasmosis and hemophagocytic lymphohistiocytosis in a patient receiving TNF-alpha inhibitor therapy

Histoplasmosis commonly presents as an asymptomatic or self-limited infection in immunocompetent patients, but immunocompromised hosts may present with severe and disseminated disease. Herein, we present a 26-year-old male with history of ulcerative colitis receiving long-term TNF-alpha inhibitor therapy who presented with six months of diarrhea and recently fever and hematochezia. On admission, he was febrile and hypotensive, with initial workup revealing pancytopenia and imaging reporting pulmonary infiltrates, pancolitis, and enlarged mesenteric lymph nodes. Disseminated histoplasmosis was ultimately diagnosed after examination of the colonic biopsy. Bone marrow biopsy was also consistent with the diagnosis of histoplasmosis but also demonstrated hemophagocytic lymphohistiocytosis. The patient was ultimately treated with amphotericin B, intravenous immunoglobulin, etoposide, and corticosteroids.

Detection of Cytokines and Collectins in Bronchoalveolar Fluid Samples of Patients Infected with Histoplasma capsulatum and Pneumocystis jirovecii

Histoplasmosis and pneumocystosis co-infections have been reported mainly in immunocompromised humans and in wild animals. The immunological response to each fungal infection has been described primarily using animal models; however, the host response to concomitant infection is unknown. The present work aimed to evaluate the pulmonary immunological response of patients with pneumonia caused either by Histoplasma capsulatum, Pneumocystis jirovecii, or their co-infection. We analyzed the pulmonary collectin and cytokine patterns of 131 bronchoalveolar lavage samples, which included HIV and non-HIV patients infected with H. capsulatum, P. jirovecii, or both fungi, as well as healthy volunteers and HIV patients without the studied fungal infections. Our results showed an increased production of the surfactant protein-A (SP-A) in non-HIV patients with H. capsulatum infection, contrasting with HIV patients (p < 0.05). Significant differences in median values of SP-A, IL-1β, TNF-α, IFN-γ, IL-18, IL-17A, IL-33, IL-13, and CXCL8 were found among all the groups studied, suggesting that these cytokines play a role in the local inflammatory processes of histoplasmosis and pneumocystosis. Interestingly, non-HIV patients with co-infection and pneumocystosis alone showed lower levels of SP-A, IL-1β, TNF-α, IFN-γ, IL-18, IL-17A, and IL-23 than histoplasmosis patients, suggesting an immunomodulatory ability of P. jirovecii over H. capsulatum response.

Histoplasmosis in an off-trail Hiker receiving ustekinumab: Implications for Preventive and diagnostic strategies for patients receiving anti-IL-12/23 therapy

Ustekinumab, an IL-12/23 inhibitor, is an important agent in treatment of inflammatory bowel disease and psoriasis. Clinical trials have not demonstrated significantly increased infection risk with ustekinumab. We report a case of disseminated histoplasmosis in the setting of ustekinumab and methotrexate following a hike in the Catskill Mountains, a region not commonly associated with Histoplasma encapsulatum. To our knowledge, this is the first reported case of newly acquired histoplasmosis complicating treatment with ustekinumab.

Peptidogalactomannan from Histoplasma capsulatum yeast cell wall: role of the chemical structure in recognition and activation by peritoneal macrophages

Histoplasma capsulatum is the causative agent of histoplasmosis, a systemic disease responsible for most reported causes of morbidity and mortality among immunosuppressed individuals. Peptidogalactomannan (pGM) was purified from the yeast cell wall of H. capsulatum isolated from bats, and its structure and involvement in modulating the host immune response were evaluated. Gas chromatography, methylation analysis, and two-dimensional nuclear magnetic resonance (2D-NMR) were used for the structural characterization of pGM. Methylation and 2D-NMR data revealed that pGM comprises a main chain containing α-D-Manp (1 → 6) residues substituted at O-2 by α-D-Manp (1 → 2)-linked side chains, non-reducing end units of α-D-Galf, or β-D-Galp linked (1→ 6) to α-D-Manp side chains. The involvement of H. capsulatum pGM in antigenic reactivity and in interactions with macrophages was demonstrated by ELISA and phagocytosis assay, respectively. The importance of the carbohydrate and protein moieties of pGM in sera reactivity was evaluated. Periodate oxidation abolished much pGM antigenic reactivity, suggesting that the sugar moiety is the most immunogenic part of pGM. Reactivity slightly decreased in pGM treated with proteinase K, suggesting that the peptide moiety plays a minor role in pGM antigenicity. In vitro experiments suggested that pGM is involved in the phagocytosis of H. capsulatum yeast and induction of IL-10 and IFN-γ secretion by peritoneal macrophages from C57BL/6 mice. These findings demonstrated the role of pGM in the H. capsulatum-host interaction.

Central Nervous System Histoplasma-Associated Post-infectious Inflammatory Response Syndrome (Histo-PIIRS)

We present a case of central nervous system (CNS) histoplasmosis in a previously healthy adult with hepatitis C (HCV) presenting with neurological symptoms refractory to antifungal therapy and ventriculoperitoneal (VP) shunting 4 months after initial diagnosis. Persistent symptoms were thought to be inflammatory rather than infectious given negative cerebrospinal fluid (CSF) and serum fungal antigens. The patient promptly improved after initiation of corticosteroid therapy. Elevated CSF cytokines and regional enhancement on brain MRI resolved with corticosteroid treatment. This is the first case of Histoplasma-associated post-infectious inflammatory response syndrome (Histo-PIIRS) documented by CSF cytokine reduction in response to corticosteroid therapy.

Pulmonary Mycosis Drives Forkhead Box Protein A2 Degradation and Mucus Hypersecretion through Activation of the Spleen Tyrosine Kinase-Epidermal Growth Factor Receptor-AKT/Extracellular Signal-Regulated Kinase 1/2 Signaling

Pulmonary mycoses are difficult to treat and detrimental to patients. Fungal infections modulate the lung immune response, induce goblet cell hyperplasia and metaplasia, and mucus hypersecretion in the airways. Excessive mucus clogs small airways and reduces pulmonary function by decreasing oxygen exchange, leading to respiratory distress. The forkhead box protein A2 (FOXA2) is a transcription factor that regulates mucus homeostasis in the airways. However, little is known whether pulmonary mycosis modulates FOXA2 function. Herein, we investigated whether Blastomyces dermatitidis and Histoplasma capsulatum-infected canine and feline lungs and airway epithelial cells could serve as higher animal models to examine the relationships between fungal pneumonia and FOXA2-regulated airway mucus homeostasis. The results indicate that fungal infection down-regulated FOXA2 expression in airway epithelial cells, with concomitant overexpression of mucin 5AC (MUC5AC) and mucin 5B (MUC5B) mucins. Mechanistic studies reveal that B. dermatitidis infection, as well as β-glucan exposure, activated the Dectin-1-SYK-epidermal growth factor receptor-AKT/extracellular signal-regulated kinase 1/2 signaling pathway that inhibits the expression of FOXA2, resulting in overexpression of MUC5AC and MUC5B in canine airway cells. Further understanding of the role of FOXA2 in mucus hypersecretion may lead to novel therapeutics against excessive mucus in both human and veterinary patients with pulmonary mycosis.

The Role of the Interleukin-17 Axis and Neutrophils in the Pathogenesis of Endemic and Systemic Mycoses

Systemic and endemic mycoses are considered life-threatening respiratory diseases which are caused by a group of dimorphic fungal pathogens belonging to the genera Histoplasma, Coccidioides, Blastomyces, Paracoccidioides, Talaromyces, and the newly described pathogen Emergomyces. T-cell mediated immunity, mainly T helper (Th)1 and Th17 responses, are essential for protection against these dimorphic fungi; thus, IL-17 production is associated with neutrophil and macrophage recruitment at the site of infection accompanied by chemokines and proinflammatory cytokines production, a mechanism that is mediated by some pattern recognition receptors (PRRs), including Dectin-1, Dectine-2, TLRs, Mannose receptor (MR), Galectin-3 and NLPR3, and the adaptor molecules caspase adaptor recruitment domain family member 9 (Card9), and myeloid differentiation factor 88 (MyD88). However, these PRRs play distinctly different roles for each pathogen. Furthermore, neutrophils have been confirmed as a source of IL-17, and different neutrophil subsets and neutrophil extracellular traps (NETs) have also been described as participating in the inflammatory process in these fungal infections. However, both the Th17/IL-17 axis and neutrophils appear to play different roles, being beneficial mediating fungal controls or detrimental promoting disease pathologies depending on the fungal agent. This review will focus on highlighting the role of the IL-17 axis and neutrophils in the main endemic and systemic mycoses: histoplasmosis, coccidioidomycosis, blastomycosis, and paracoccidioidomycosis.

Utilization of Galectins by Pathogens for Infection

Galectins are glycan-binding proteins which are expressed by many different cell types and secreted extracellularly. These molecules are well-known regulators of immune responses and involved in a broad range of cellular and pathophysiological functions. During infections, host galectins can either avoid or facilitate infections by interacting with host cells- and/or pathogen-derived glycoconjugates and less commonly, with proteins. Some pathogens also express self-produced galectins to interfere with host immune responses. This review summarizes pathogens which take advantage of host- or pathogen-produced galectins to establish the infection.

CARD9-Associated Dectin-1 and Dectin-2 Are Required for Protective Immunity of a Multivalent Vaccine against Coccidioides posadasii Infection

Coccidioides species are fungal pathogens that can cause a widely varied clinical manifestation from mild pulmonary symptom to disseminated, life-threatening disease. We have previously created a subunit vaccine by encapsulating a recombinant coccidioidal Ag (rCpa1) in glucan-chitin particles (GCPs) as an adjuvant-delivery system. The GCP-rCpa1 vaccine has shown to elicit a mixed Th1 and Th17 response and confers protection against pulmonary coccidioidomycosis in mice. In this study, we further delineated the vaccine-induced protective mechanisms. Depletion of IL-17A in vaccinated C57BL/6 mice prior to challenge abrogated the protective efficacy of GCP-rCpa1 vaccine. Global transcriptome and Ingenuity Pathway Analysis of murine bone marrow-derived macrophages after exposure to this vaccine revealed the upregulation of proinflammatory cytokines (TNF-α, IL-6, and IL-1β) that are associated with activation of C-type lectin receptors (CLR) Dectin-1- and Dectin-2-mediated CARD9 signaling pathway. The GCP formulation of rCpa1 bound soluble Dectin-1 and Dectin-2 and triggered ITAM signaling of corresponding CLR reporter cells. Furthermore, macrophages that were isolated from Dectin-1 -/-, Dectin-2 -/-, and CARD9 -/- mice significantly reduced production of inflammatory cytokines in response to the GCP-rCpa1 vaccine compared with those of wild-type mice. The GCP-rCpa1 vaccine had significantly reduced protective efficacy in Dectin-1 -/-, Dectin-2 -/-, and CARD9 -/- mice that showed decreased acquisition of Th cells in Coccidioides-infected lungs compared with vaccinated wild-type mice, especially Th17 cells. Collectively, we conclude that the GCP-rCpa1 vaccine stimulates a robust Th17 immunity against Coccidioides infection through activation of the CARD9-associated Dectin-1 and Dectin-2 signal pathways.

IL-22 Promotes IFN-γ-Mediated Immunity against Histoplasma capsulatum Infection

Histoplasma capsulatum is the agent of histoplasmosis, one of the most frequent mycoses in the world. The infection initiates with fungal spore inhalation, transformation into yeasts in the lungs and establishment of a granulomatous disease, which is characterized by a Th1 response. The production of Th1 signature cytokines, such as IFN-γ, is crucial for yeast clearance from the lungs, and to prevent dissemination. Recently, it was demonstrated that IL-17, a Th17 signature cytokine, is also important for fungal control, particularly in the absence of Th1 response. IL-22 is another cytokine with multiple functions on host response and disease progression. However, little is known about the role of IL-22 during histoplasmosis. In this study, we demonstrated that absence of IL-22 affected the clearance of yeasts from the lungs and increased the spreading to the spleen. In addition, IL-22 deficient mice (Il22-/-) succumbed to infection, which correlated with reductions in the numbers of CD4+ IFN-γ+ T cells, reduced IFN-γ levels, and diminished nitric oxide synthase type 2 (NOS2) expression in the lungs. Importantly, treatment with rIFN-γ mitigated the susceptibility of Il22-/- mice to H. capsulatum infection. These data indicate that IL-22 is crucial for IFN-γ/NO production and resistance to experimental histoplasmosis.

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.

Fungal Extracellular Vesicles as Potential Targets for Immune Interventions

The release of extracellular vesicles (EVs) by fungi is a fundamental cellular process. EVs carry several biomolecules, including pigments, proteins, enzymes, lipids, nucleic acids, and carbohydrates, and are involved in physiological and pathological processes. EVs may play a pivotal role in the establishment of fungal infections, as they can interact with the host immune system to elicit multiple outcomes.

The release of extracellular vesicles (EVs) by fungi is a fundamental cellular process. EVs carry several biomolecules, including pigments, proteins, enzymes, lipids, nucleic acids, and carbohydrates, and are involved in physiological and pathological processes. EVs may play a pivotal role in the establishment of fungal infections, as they can interact with the host immune system to elicit multiple outcomes. It has been observed that, depending on the fungal pathogen, EVs can exacerbate or attenuate fungal infections. The study of the interaction between fungal EVs and the host immune system and understanding of the mechanisms that regulate those interactions might be useful for the development of new adjuvants as well as the improvement of protective immune responses against infectious or noninfectious diseases. In this review, we describe the immunomodulatory properties of EVs produced by pathogenic fungi and discuss their potential as adjuvants for prophylactic or therapeutic strategies.

Disseminated histoplasmosis: case report and review of the literature

Case report We report the case of a young Cameroonian woman who presented with cough, hyperthermia, weight loss, pancytopenia, and hepatosplenomegaly. A positive HIV serology was discovered and a chest radiography revealed a 'miliary pattern'. Bone marrow aspiration pointed out yeast inclusions within macrophages. Given the morphological aspect, the clinical presentation and immunosuppression, histoplasmosis was retained as a working hypothesis. Antiretroviral and amphotericin B treatments were promptly initiated. Review Given the immigration wave that Europe is currently experiencing, we think it is important to share experience and knowledge, especially in non-endemic areas such as Europe, where clinicians are not used to face this disease. Histoplasmosis is due to Histoplasma capsulatum var. capsulatum, a dimorphic fungus. Infection occurs by inhaling spores contained in soils contaminated by bat or bird droppings. The clinical presentation depends on the immune status of the host and the importance of inoculum, varying from asymptomatic to disseminated forms. AIDS patients are particularly susceptible to develop a severe disease. Antigen detection, molecular biology techniques, and microscopic examination are used to make a rapid diagnosis. However, antigen detection is not available in Europe and diagnosis needs a strong clinical suspicion in non-endemic areas. Because of suggestive imagery, clinicians might focus on tuberculosis. Our case illustrates the need for clinicians to take histoplasmosis in the differential diagnosis, depending on the context and the patient's past history.

Helper T-cell responses and pulmonary fungal infections

The mucosal surface of the respiratory tract encounters microbes, such as fungal particles, with every inhaled breath. When pathogenic fungi breach the physical barrier and innate immune system within the lung to establish an infection, adaptive immunity is engaged, often in the form of helper CD4 T-cell responses. Type 1 responses, characterized by interferon-γ production from CD4 cells, promote clearance of Histoplasma capsulatum and Cryptococcus neoformans infection. Likewise, interleukin-17A (IL-17A) production from Th17 cells promotes immunity to Blastomyces dermatitidis and Coccidioides species infection by recruiting neutrophils. In contrast the development of T helper type 2 responses, characterized by IL-5 production from T cells and eosinophil influx into the lungs, drives allergic bronchopulmonary aspergillosis and poor outcomes during C. neoformans infection. Experimental vaccines against several endemic mycoses, including Histoplasma capsulatum, Coccidioides, Cryptococcus and Blastomyces dermatitidis, induce protective T-cell responses and foreshadow the development of vaccines against pulmonary fungal infections for use in humans. Additionally, recent work using antifungal T cells as immunotherapy to protect immune-compromised patients from opportunist fungal infections also shows great promise. This review covers the role of T-cell responses in driving protection and pathology in response to pulmonary fungal infections, and highlights promising therapeutic applications of antifungal T cells.

Diagnosis and Assessment of Microbial Infections with Host and Microbial MicroRNA Profiles

MicroRNAs (miRNAs) encoded by viral genome or host have been found participating in host-microbe interactions. Differential expression profiles of miRNAs were shown linking to specific disease pathologies which indicated its potency as diagnostic/prognostic biomarkers of infectious disease. This was emphasized by the discovery of circulating miRNAs which were found to be remarkably stable in mammalian biofluids. Standardized methods of miRNA quantification including RNA isolation should be established before they will be ready for use in clinical practice.

Fungal infections in HIV/AIDS

Fungi are major contributors to the opportunistic infections that affect patients with HIV/AIDS. Systemic infections are mainly with Pneumocystis jirovecii (pneumocystosis), Cryptococcus neoformans (cryptococcosis), Histoplasma capsulatum (histoplasmosis), and Talaromyces (Penicillium) marneffei (talaromycosis). The incidence of systemic fungal infections has decreased in people with HIV in high-income countries because of the widespread availability of antiretroviral drugs and early testing for HIV. However, in many areas with high HIV prevalence, patients present to care with advanced HIV infection and with a low CD4 cell count or re-present with persistent low CD4 cell counts because of poor adherence, resistance to antiretroviral drugs, or both. Affordable, rapid point-of-care diagnostic tests (as have been developed for cryptococcosis) are urgently needed for pneumocystosis, talaromycosis, and histoplasmosis. Additionally, antifungal drugs, including amphotericin B, liposomal amphotericin B, and flucytosine, need to be much more widely available. Such measures, together with continued international efforts in education and training in the management of fungal disease, have the potential to improve patient outcomes substantially.

Presentation and Treatment of Histoplasmosis in Pediatric Oncology Patients: Case Series and Review of the Literature

Histoplasmosis is an endemic fungus in several regions of the United States. The diagnosis and treatment of this infection can be challenging in pediatric oncology patients. We present 5 patients diagnosed with histoplasmosis while receiving treatment at a midsize pediatric oncology center in Iowa. Two cases occurred in patients with acute lymphoblastic leukemia and 3 cases in patients with solid tumors. All patients were treated with antifungal therapy and demonstrated excellent clinical response. Histoplasmosis should be considered as a potential cause of nonspecific febrile illness, pulmonary masses, and bone marrow suppression in immunocompromised patients in endemic regions. Prompt and accurate diagnosis can facilitate timely antifungal therapy and avoidance of prolonged hospital stays, invasive testing, unnecessary antibiotics, and unwarranted anticancer therapies.

Eosinophils subvert host resistance to an intracellular pathogen by instigating non-protective IL-4 in CCR2-/- mice

Eosinophils contribute to type II immune responses in helminth infections and allergic diseases; however, their influence on intracellular pathogens is less clear. We previously reported that CCR2-/- mice exposed to the intracellular fungal pathogen Histoplasma capsulatum exhibit dampened immunity caused by an early exaggerated interleukin (IL)-4 response. We sought to identify the cellular source promulgating IL-4 in infected mutant animals. Eosinophils were the principal instigators of non-protective IL-4 and depleting this granulocyte population improved fungal clearance in CCR2-/- animals. The deleterious impact of eosinophilia on mycosis was also recapitulated in transgenic animals overexpressing eosinophils. Mechanistic examination of IL-4 induction revealed that phagocytosis of H. capsulatum via the pattern recognition receptor complement receptor (CR) 3 triggered the heightened IL-4 response in murine eosinophils. This phenomenon was conserved in human eosinophils; exposure of cells to the fungal pathogen elicited a robust IL-4 response. Thus, our findings elucidate a detrimental attribute of eosinophil biology in fungal infections that could potentially trigger a collapse in host defenses by instigating type II immunity.

Immunoregulation in larval Echinococcus multilocularis infection

Alveolar echinococcosis (AE) is a clinically very severe zoonotic helminthic disease, characterized by a chronic progressive hepatic damage caused by the continuous proliferation of the larval stage (metacestode) of Echinococcus multilocularis. The proliferative potential of the parasite metacestode tissue is dependent on the nature/function of the periparasitic immune-mediated processes of the host. Immune tolerance and/or down-regulation of immunity are a marked characteristic increasingly observed when disease develops towards its chronic (late) stage of infection. In this context, explorative studies have clearly shown that T regulatory (Treg) cells play an important role in modulating and orchestrating inflammatory/immune reactions in AE, yielding a largely Th2-biased response, and finally allowing thus long-term parasite survival, proliferation and maturation. AE is fatal if not treated appropriately, but the current benzimidazole chemotherapy is far from optimal, and novel options for control are needed. Future research should focus on the elucidation of the crucial immunological events that lead to anergy in AE, and focus on providing a scientific basis for the development of novel and more effective immunotherapeutical options to support cure AE by abrogating anergy, anticipating also that a combination of immuno- and chemotherapy could provide a synergistic therapeutical effect.

Protective Effect of Galectin-1 during Histoplasma capsulatum Infection Is Associated with Prostaglandin E2 and Nitric Oxide Modulation

Histoplasma capsulatum is a dimorphic fungus that develops a yeast-like morphology in host's tissue, responsible for the pulmonary disease histoplasmosis. The recent increase in the incidence of histoplasmosis in immunocompromised patients highlights the need of understanding immunological controls of fungal infections. Here, we describe our discovery of the role of endogenous galectin-1 (Gal-1) in the immune pathophysiology of experimental histoplasmosis. All infected wild-type (WT) mice survived while only 1/3 of Lgals1^−/− mice genetically deficient in Gal-1 survived 30 days after infection. Although infected Lgals1^−/− mice had increased proinflammatory cytokines, nitric oxide (NO), and elevations in neutrophil pulmonary infiltration, they presented higher fungal load in lungs and spleen. Infected lung and infected macrophages from Lgals1^−/− mice exhibited elevated levels of prostaglandin E₂ (PGE₂, a prostanoid regulator of macrophage activation) and prostaglandin E synthase 2 (Ptgs2) mRNA. Gal-1 did not bind to cell surface of yeast phase of H. capsulatum, in vitro, suggesting that Gal-1 contributed to phagocytes response to infection rather than directly killing the yeast. The data provides the first demonstration of endogenous Gal-1 in the protective immune response against H. capsulatum associated with NO and PGE₂ as an important lipid mediator in the pathogenesis of histoplasmosis.

HcZrt2, a zinc responsive gene, is indispensable for the survival of Histoplasma capsulatum in vivo

Histoplasma capsulatum (Hc) exists in the soil and is capable of adapting to the shift in environment during infection to ensure survival. Yeast encounter a restrictive host environment low in nutrients such as zinc. In this study we functionally analyzed a putative zinc regulated transporter, HcZrt2, in zinc limiting conditions by complementation of HcZrt2 and gene knockdown through RNA interference (RNAi). Complementation analysis demonstrated HcZrt2's ability to functionally replace the characterized Saccharomyces cerevisiae zinc plasma membrane transporters Zrt1 and Zrt2 in zinc deficient medium. Gene silencing revealed that HcZrt2 is essential for growth in zinc deficient medium and plays a role in zinc accumulation. Fungal burden was reduced in mice infected with HcZrt2 silenced strains compared to a control strain. Sixty-seven percent of mice infected with a lethal dose of HcZrt2-RNAi#1 survived, and 100% of mice infected with HcZrt2-RNAi#2 withstood lethal infection. Our data suggest that HcZrt2 is a vital part of zinc homeostasis and essential for the pathogenesis of histoplasmosis.

Transcription Factor KLF2 in Dendritic Cells Downregulates Th2 Programming via the HIF-1α/Jagged2/Notch Axis

The adaptive immune response is tightly regulated by complex signals in dendritic cells (DCs). Although Th2 polarization is dictated by defined functional DC subsets, the molecular factors that govern the amplitude of these responses are not well understood. Krüppel-like factor 2 (KLF2) is a transcription factor that negatively regulates the activation of numerous immune cells in response to stimuli. Here, we demonstrate that suppression of KLF2 in conditioned DCs preferentially amplifies Th2 responses in two model systems, one of which is a prototypical intracellular pathogen and the other an allergen. This elevation in Th2 responses was dependent on contact-mediated Notch signaling in vitro and in vivo. A deficiency of KLF2 increased the expression of Notch ligand Jagged2 via hypoxia-inducible factor 1α (HIF-1α), which led to Th2 amplification. Our results revealed a novel circuit in DCs for Th2 polarization that is governed by KLF2.

Dendritic cells are the key element that bridges innate and adaptive immunity. A complex and not-well-understood area in dendritic cell biology is the regulatory network that predetermines or moderates their function to shape the adaptive immune response. Our study for the first time demonstrates that KLF2, a transcription factor, conditions dendritic cells to regulate Th2 responses via a Jagged2/Notch axis. Downregulation of KLF2 expression in dendritic cells may provide a beneficial effect for treatment of diseases such as obesity or parasitic infections but may be deleterious in the case of invasion by intracellular pathogens. Strategies to tune KLF2 may be useful for future therapeutic approaches to particular diseases of mankind.

Transcriptomic Crosstalk between Fungal Invasive Pathogens and Their Host Cells: Opportunities and Challenges for Next-Generation Sequencing Methods

Fungal invasive infections are an increasing health problem. The intrinsic complexity of pathogenic fungi and the unmet clinical need for new and more effective treatments requires a detailed knowledge of the infection process. During infection, fungal pathogens are able to trigger a specific transcriptional program in their host cells. The detailed knowledge of this transcriptional program will allow for a better understanding of the infection process and consequently will help in the future design of more efficient therapeutic strategies. Simultaneous transcriptomic studies of pathogen and host by high-throughput sequencing (dual RNA-seq) is an unbiased protocol to understand the intricate regulatory networks underlying the infectious process. This protocol is starting to be applied to the study of the interactions between fungal pathogens and their hosts. To date, our knowledge of the molecular basis of infection for fungal pathogens is still very limited, and the putative role of regulatory players such as non-coding RNAs or epigenetic factors remains elusive. The wider application of high-throughput transcriptomics in the near future will help to understand the fungal mechanisms for colonization and survival, as well as to characterize the molecular responses of the host cell against a fungal infection.

Erythropoietin Exacerbates Inflammation and Increases the Mortality of Histoplasma capsulatum-Infected Mice

Erythropoietin (EPO) is a key hormone involved in red blood cell formation, but its effects on nonerythroid cells, such as macrophages, have not been described. Macrophages are key cells in controlling histoplasmosis, a fungal infection caused by Histoplasma capsulatum (Hc). Considering that little is known about EPO's role during fungal infections and its capacity to activate macrophages, in this study we investigated the impact of EPO pretreatment on the alveolar immune response during Hc infection. The consequence of EPO pretreatment on fungal infection was determined by evaluating animal survival, fungal burden, activation of bronchoalveolar macrophages, inflammatory mediator release, and lung inflammation. Pretreatment with EPO diminished mononuclear cell numbers, increased the recruitment of F4/80⁺/CD80⁺ and F4/80⁺/CD86⁺ cells to the bronchoalveolar space, induced higher production of IFN-γ, IL-6, MIP-1α, MCP-1, and LTB₄, reduced PGE₂ concentration, and did not affect fungal burden. As a consequence, we observed an increase in lung inflammation with extensive tissue damage that might account for augmented mouse mortality after infection. Our results demonstrate for the first time that EPO treatment has a deleterious impact on lung immune responses during fungal infection.

Profile of cytokines in the lungs of BALB/c mice after intra-nasal infection with Histoplasma capsulatum mycelial propagules

The host pulmonary response to the fungus Histoplasma capsulatum was evaluated, through the profile of cytokines detected by the MagPix magnetic beads platform in lung homogenates and by lung-granulomas formation, from mice intra-nasally infected with mycelial propagules (M-phase) of two virulent H. capsulatum strains, EH-46 and G-217B. Results highlight that mice lung inflammatory response depends on the H. capsulatum strain used, during the first step of the fungal infection. IL-1β and TNF-α increased their concentrations in mice infected with both strains. The highest levels of IL-6, IL-17, and IL-23 were found in EH-46-infected mice, whereas levels of IL-22 were variable at all post-infection times for both strains. Significant increases of IL-12, IFN-γ, IL-4, and IL-10 were associated to EH-46-infected mice. Histological lung findings from EH-46-infected mice revealed incipient and numerous well-developed granulomas, distributed in lung-lobes at the 14th and the 21st days after infection, according to cytokine profiles.

Type II cytokines impair host defense against an intracellular fungal pathogen by amplifying macrophage generation of IL-33

Interleukin (IL)-4 subverts protective immunity to multiple intracellular pathogens, including the fungus Histoplasma capsulatum. Previously, we reported that H. capsulatum-challenged CCR2(-/-) mice manifest elevated pulmonary fungal burden owing to exaggerated IL-4. Paradoxical to our anticipation in IL-33 driving IL-4, we discovered that the latter prompted IL-33 in mutant mice. In infected CCR2(-/-) animals, amplified IL-33 succeeded the heightened IL-4 response and inhibition of IL-4 signaling decreased IL-33. Moreover, macrophages, but not epithelial cells or dendritic cells, from these mice expressed higher IL-33 in comparison with controls. Dissection of mechanisms that promulgated IL-33 revealed type-II cytokines and H. capsulatum synergistically elicited an IL-33 response in macrophages via signal transducer and activator of transcription factor 6/interferon-regulatory factor-4 and Dectin-1 pathways, respectively. Neutralizing IL-33 in CCR2(-/-) animals, but not controls, enhanced their resistance to histoplasmosis. Thus we describe a previously unrecognized role for IL-4 in instigating IL-33 in macrophages. Furthermore, in the presence of intracellular fungal pathogens, the type-II cytokine-driven IL-33 response impairs immunity.

Mononuclear phagocyte-mediated antifungal immunity: the role of chemotactic receptors and ligands

Over the past two decades, fungal infections have emerged as significant causes of morbidity and mortality in patients with hematological malignancies, hematopoietic stem cell or solid organ transplantation and acquired immunodeficiency syndrome. Besides neutrophils and CD4(+) T lymphocytes, which have long been known to play an indispensable role in promoting protective antifungal immunity, mononuclear phagocytes are now being increasingly recognized as critical mediators of host defense against fungi. Thus, a recent surge of research studies has focused on understanding the mechanisms by which resident and recruited monocytes, macrophages and dendritic cells accumulate and become activated at the sites of fungal infection. Herein, we critically review how a variety of G-protein coupled chemoattractant receptors and their ligands mediate mononuclear phagocyte recruitment and effector function during infection by the most common human fungal pathogens.

Cutaneous, Subcutaneous and Systemic Mycology

The first description of dermatophytosis was recorded by Celsus, a Roman encyclopaedist who described a suppurative infection of scalp (‘porrigo’ or ‘kerion of Celsus’) in De Re Medicina (30 A.D.). Throughout the middle ages, several descriptions of dermatophytosis were produced where it is described as ‘tinea’. The keratin-destroying moths which made circular holes in the woollen garments are known as Tinea. Due to similarity in the structure of circular lesion of dermatophytosis on the smooth skin with the circular hole made by moth, Cassius Felix introduced the term ‘tinea’ to describe the lesions. In 1806, Alibert used the term ‘favus’ to describe the honey-like exudate in some scalp infections. However, the fungal aetiology of tinea was first detected by Robert Remak, a Polish physician who first observed the presence of hyphae in the crusts of favus. This detection is also a landmark in medical history because this is the first description of a microbe causing a human disease. He himself did not publish his work, but he permitted the reference of his observations in a dissertation by Xavier Hube in 1837. Remak gave all the credits of his discovery to his mentor Schoenlein who first published the fungal etiological report of favus in 1839. He observed the infectious nature of the favus by autoinoculation into his own hands and also successfully isolated the fungus later (1945) and named Achorion schoenleinii (Trichophyton schoenleinii) in honour of his mentor. In 1844, Gruby described the etiologic agent of tinea endothrix, later became known as Trichophyton tonsurans. The genus Trichophyton was created and described by Malmsten (1845) with its representative species T. tonsurans. Charles Robin identified T. mentagrophytes in 1847 and T. equinum was identified by Matruchot and Dassonville in 1898. Raymond Jacques Adrien Sabouraud (France) first compiled the description of Trichophyton in his book (Les Teignes) in 1910 which was based on his observation in artificial culture. The sexual state of dermatophyte was described by Nannizzi (1927). Emmons (1934) first reported the classification of dermatophytes based on vegetative structures and conidia. Gentles (1958) established the successful treatment of tinea capitis with griseofulvin.

Fungal Pathogens: Survival and Replication within Macrophages

The innate immune system is a critical line of defense against pathogenic fungi. Macrophages act at an early stage of infection, detecting and phagocytizing infectious propagules. To avoid killing at this stage, fungal pathogens use diverse strategies ranging from evasion of uptake to intracellular parasitism. This article will discuss five of the most important human fungal pathogens (Candida albicans, Aspergillus fumigatus, Cryptococcus neoformans, Coccidiodes immitis, and Histoplasma capsulatum) and consider the strategies and virulence factors adopted by each to survive and replicate within macrophages.

Histoplasmosis in HIV-Infected Patients: A Review of New Developments and Remaining Gaps

Histoplasma capsulatum is responsible for histoplasmosis, a fungal disease with worldwide distribution that can affect both immunocompromised and imunocompetent individuals. During the highly active antiretroviral therapy (HAART) era, morbidity and mortality due to histoplasmosis remained a public heatlh problem in low-income and high-income countries. The true burden of HIV-associated histoplasmosis is either not fully known or neglected since it is not a notifiable disease. Progress has been made in DNA patterns of strains and understanding of pathogenesis, and hopefully these will help identify new therapeutic targets. Unfortunately, histoplasmosis is still widely mistaken for multidrug-resistant tuberculosis, leading to numerous avoidable deaths, even if they are easily distinguishable. The new diagnostic tools and therapeutics developments have still not been made available in most endemic regions. Still, recent developments are promising because of their good clinical characteristics and also because they will be commercially available and affordable. This review of published data and gaps may help define and guide future research.

Disseminated histoplasmosis in two juvenile raccoons (Procyon lotor) from a nonendemic region of the United States

Two 6-month-old raccoon kits, which had been rescued and fostered in preparation for return to the wild, became acutely ill and died 3 weeks before scheduled release. At necropsy, the kits had grossly enlarged livers and spleens, diffusely consolidated lungs, and generalized lymphadenopathy. Histologically, extensive infiltrates of macrophages containing yeast organisms were identified in lung, liver, kidney, spleen, lymph nodes, intestinal tissues, brain, adrenal gland, bone marrow, and thymus of both animals. Histiocytic inflammation with accompanying fibrosis was widespread, with necrotic foci evident in lungs, spleen, and intestinal sections. Fungal organisms were observed on sheep blood agar plates; however, repeated subcultures to fungal media designed to induce conidial structures for fungal identification were unsuccessful. Partial DNA sequencing of the 28S ribosomal RNA gene of the blood agar isolate identified 100% homology with Ajellomyces capsulatus (anamorphic name Histoplasma capsulatum). The kits were rescued and fostered in the San Francisco Bay area and it is likely that the exposure to H. capsulatum occurred in this area. Histoplasma sp. infection in wild mammal species is often used as an indication of spore contamination of a geographic region. Northern California is not known to be an endemic region for H. capsulatum, which is not a reportable disease in this state. The presence of severe, disseminated disease and the need for molecular identification associated with the isolate from a nonendemic region identified in the present report may indicate genetic adaptation and altered characteristics of this agent and may warrant further investigation.

The predominance of alternatively activated macrophages following challenge with cell wall peptide-polysaccharide after prior infection with Sporothrix schenckii

Sporotrichosis is a subcutaneous mycosis that is caused by the dimorphic fungus Sporothrix schenckii. This disease generally occurs within the skin and subcutaneous tissues, causing lesions that can spread through adjacent lymphatic vessels and sometimes leading to systemic diseases in immunocompromised patients. Macrophages are crucial for proper immune responses against a variety of pathogens. Furthermore, macrophages can play different roles in response to different microorganisms and forms of activation, and they can be divided into "classic" or "alternatively" activated populations, as also known as M1 and M2 macrophages. M1 cells can lead to tissue injury and contribute to pathogenesis, whereas M2 cells promote angiogenesis, tissue remodeling, and repair. The aim of this study was to investigate the roles of M1 and M2 macrophages in a sporotrichosis model. Toward this end, we performed phenotyping of peritoneal exudate cells and evaluated the concomitant production of several immunomediators, including IL-12, IL-10, TGF-β, nitric oxide, and arginase-I activity, which were stimulated ex vivo with cell wall peptide-polysaccharide. Our results showed the predominance of the M2 macrophage population, indicated by peaks of arginase-I activity as well as IL-10 and TGF-β production during the 6th and 8th weeks after infection. These results were consistent with cellular phenotyping that revealed increases in CD206-positive cells over this period. This is the first report of the participation of M2 macrophages in sporotrichosis infections.

Redundant catalases detoxify phagocyte reactive oxygen and facilitate Histoplasma capsulatum pathogenesis

Histoplasma capsulatum is a respiratory pathogen that infects phagocytic cells. The mechanisms allowing Histoplasma to overcome toxic reactive oxygen molecules produced by the innate immune system are an integral part of Histoplasma's ability to survive during infection. To probe the contribution of Histoplasma catalases in oxidative stress defense, we created and analyzed the virulence defects of mutants lacking CatB and CatP, which are responsible for extracellular and intracellular catalase activities, respectively. Both CatB and CatP protected Histoplasma from peroxide challenge in vitro and from antimicrobial reactive oxygen produced by human neutrophils and activated macrophages. Optimal protection required both catalases, as the survival of a double mutant lacking both CatB and CatP was lower than that of single-catalase-deficient cells. Although CatB contributed to reactive oxygen species defenses in vitro, CatB was dispensable for lung infection and extrapulmonary dissemination in vivo. Loss of CatB from a strain also lacking superoxide dismutase (Sod3) did not further reduce the survival of Histoplasma yeasts. Nevertheless, some catalase function was required for pathogenesis since simultaneous loss of both CatB and CatP attenuated Histoplasma virulence in vivo. These results demonstrate that Histoplasma's dual catalases comprise a system that enables Histoplasma to efficiently overcome the reactive oxygen produced by the innate immune system.