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Contains fulltext : 171637.pdf (Publisher’s version ) (Closed access) BACKGROUND: STAT1 mutations cause chronic mucocutaneous candidiasis (CMC), while STAT3 mutations cause hyper-IgE syndrome (HIES). CMC and HIES patients have T helper (Th) 17 defects suffering from mucosal Candida infections, but only patients with HIES show an allergic phenotype with eczema, eosinophilia and high IgE levels. OBJECTIVE: We investigated whether differential Th2 and Th9 responses may explain the clinical differences. METHODS: Peripheral blood mononuclear cells of patients with CMC (n = 4), patients with HIES (n = 4), patients with atopic dermatitis (n = 4) and healthy volunteers (n = 13) were stimulated with Candida and Staphylococcus aureus, with and without IL-4. The cytokines IL-5, IL-13, IL-9, IL-17 and TGFbeta and regulatory T cells were measured in cell culture supernatants by ELISA or flow cytometry, respectively. RESULTS: Peripheral blood mononuclear cells of patients with CMC showed a significantly impaired production of the Th2 cytokines IL-5 and IL-13, especially in the presence of IL-4. Moreover, IL-9 production was significantly lower in patients with CMC compared to healthy controls. In contrast, patients with HIES and patients with AD showed normal IL-5 and IL-13 production, while IL-9 production was significantly lower in patients with HIES compared to healthy controls. Although TGFbeta was involved in the IL-4-induced IL-9 production, TGFbeta levels and the frequency of regulatory T cells did not differ between patients with HIES and controls. Flow cytometry analysis demonstrated an IL-9+ IL-17+ CD4+ subset in healthy controls after stimulation with Candida which was less present in patients with HIES. CONCLUSION: Patients with CMC have a general Th defect including Th2 and Th9, while patients with HIES have normal Th2 cytokines. These differences are in line with their clinical presentation. Surprisingly, the allergic cytokine IL-9 was deficient in both HIES and CMC, suggesting a Th-17-derived origin.

Invasive pulmonary aspergillosis is increasingly described in non-neutropenic patients, such as patients with COPD receiving corticosteroids and the critically ill. Here, we present a case of a lethal pulmonary Aspergillus niger infection in a COPD patient. Immunological tests showed an impaired innate and adaptive immune response to Aspergillus. A history of COPD, unresponsiveness to antibiotics and especially a suggestive CT-scan should trigger the clinician to consider diseases caused by Aspergillus. Keywords: Invasive pulmonary aspergillosis, Aspergillus niger, Immune system, Intensive care unit, Oxalate crystal

Contains fulltext : 153612.pdf (Publisher’s version ) (Closed access) BACKGROUND: Allergic bronchopulmonary aspergillosis (ABPA) is characterised by an exaggerated Th2 response to Aspergillus fumigatus, but the immunological pathways responsible for this effect are unknown. OBJECTIVE: The aim of this study was to decipher the pattern recognition receptors (PRRs) and cytokines involved in the Aspergillus-specific Th2 response and to study Aspergillus-induced responses in healthy controls and ABPA patients. METHODS: Peripheral blood mononuclear cells (PBMCs) were stimulated with heat-killed Aspergillus conidia, various other pathogens, or PRR ligands. PRRs and cytokine pathways were blocked with PRR-blocking reagents, anti-TNF (Etanercept or Adalimumab), IL-1Ra (Anakinra) or IFNgamma (IFN-gamma). ELISA and FACS were used to analyse cytokine responses. RESULTS: Aspergillus was the only pathogen that stimulated the Th2 cytokines IL-5 and IL-13, while Gram-negative bacteria, Gram-positive bacteria, Candida albicans, chitin, beta-glucan or Toll-like receptor (TLR) ligands did not. Depletion of CD4(+) cells abolished IL-13 production. Blocking complement receptor 3 (CR3) significantly reduced IL-5 and IL-13, while blocking TLR2, TLR4 or dectin-1 had no effect. ABPA patients displayed increased Aspergillus-induced IL-5 and IL-13 and decreased IFNgamma production compared with healthy controls. All biological agents tested showed the capability to inhibit Th2 responses, but also decreased Aspergillus-induced IFNgamma. CONCLUSIONS AND CLINICAL RELEVANCE: Aspergillus conidia are unique in triggering Th2 responses in human PBMCs, through a CR3-dependent pathway. ABPA patients display a significantly increased Aspergillus-induced Th2/Th1 ratio that can be modulated by biologicals. These data provide a rationale to explore IFNgamma therapy in ABPA as a corticosteroid-sparing treatment option, by dampening Th2 responses and supplementing the IFNgamma deficiency at the same time.

The prevalence of pulmonary nontuberculous mycobacterial (pNTM) disease is increasing [1]. The most commonly isolated disease-causing NTMs belong to the Mycobacterium avium complex [1]. Susceptibility to and clinical manifestation of NTM disease are largely governed by the immune status of a person. Disseminated or extrapulmonary NTM infections are strongly associated with severe immunosuppression, such as those with frank defects in the interferon (IFN)-γ–interleukin (IL)-12 axis [2]. Isolated pNTM is strongly associated with certain underlying conditions, such as cystic fibrosis, chronic obstructive pulmonary disease and primary ciliary dyskinesia [3, 4]. However, substantial numbers of pNTM patients have no apparent risk factors, and a significant proportion of them exhibit a body morphotype characterised by lifelong slender body habitus, pectus excavatum, scoliosis and mitral valve prolapse [5, 6], also called the Lady Windermere syndrome. A modest reduction in IFN-γ production and an increase in transforming growth factor (TGF)-β levels have been described [7–10]. Fowler et al. [11] quantified ciliary beat frequency of 58 pNTM patients and 40 controls and found reduced ciliary beat frequency in the pNTM patients. Szymanski et al. [12] performed whole-exome sequencing on patients with pNTM, their unaffected family members and a control group and concluded that pNTM is a multigenic disease, encompassing potential defects in proteins encoded by cilia genes, the cystic fibrosis transmembrane conductance regulator gene, connective tissue genes and certain immune-related genes.

IL-1 drives Th responses, particularly Th17, in host defense. Sharing the same co-receptor, the IL-1 family member IL-36 exhibits properties similar to those of IL-1. In the present study, we investigated the role of IL-36 in Aspergillus fumigatus-induced human Th responses. We observed that different morphological forms of A. fumigatus variably increase steady-state mRNA of IL-36 subfamily members. IL-36α is not significantly induced by any morphological form of Aspergillus. Most strikingly, IL-36γ is significantly induced by live A. fumigatus conidia and heat-killed hyphae, whereas IL-36Ra (IL-36 receptor antagonist) is significantly induced by heat-killed conidia, hyphae, and live conidia. We also observed that IL-36γ expression is dependent on the dectin-1/Syk and TLR4 signaling pathway. In contrast, TLR2 and CR3 inhibit IL-36γ expression. The biological relevance of IL-36 induction by Aspergillus is demonstrated by experiments showing that inhibition of the IL-36 receptor by IL-36Ra reduces Aspergillus-induced IL-17 and IFN-γ. These data describe that IL-36-dependent signals are a novel cytokine pathway that regulates Th responses induced by A. fumigatus, and demonstrate a role for TLR4 and dectin-1 in the induction of IL-36γ.

Chitin is an important cell wall component of Aspergillus fumigatus conidia, of which hundreds are inhaled on a daily basis. Previous studies have shown that chitin has both anti- and proinflammatory properties; however the exact mechanisms determining the inflammatory signature of chitin are poorly understood, especially in human immune cells. Human peripheral blood mononuclear cells were isolated from healthy volunteers and stimulated with chitin from Aspergillus fumigatus. Transcription and production of the proinflammatory cytokine interleukin-1β (IL-1β) and the anti-inflammatory cytokine IL-1 receptor antagonist (IL-1Ra) were measured from the cell culture supernatant by quantitative PCR (qPCR) or enzyme-linked immunosorbent assay (ELISA), respectively. Chitin induced an anti-inflammatory signature characterized by the production of IL-1Ra in the presence of human serum, which was abrogated in immunoglobulin-depleted serum. Fc-γ-receptor-dependent recognition and phagocytosis of IgG-opsonized chitin was identified as a novel IL-1Ra-inducing mechanism by chitin. IL-1Ra production induced by chitin was dependent on Syk kinase and phosphatidylinositol 3-kinase (PI3K) activation. In contrast, costimulation of chitin with the pattern recognition receptor (PRR) ligands lipopolysaccharide, Pam3Cys, or muramyl dipeptide, but not β-glucan, had synergistic effects on the induction of proinflammatory cytokines by human peripheral blood mononuclear cells (PBMCs). In conclusion, chitin can have both pro- and anti-inflammatory properties, depending on the presence of pathogen-associated molecular patterns and immunoglobulins, thus explaining the various inflammatory signatures reported for chitin., IMPORTANCE Invasive aspergillosis and allergic aspergillosis are increasing health care problems. Patients get infected by inhalation of the airborne spores of Aspergillus fumigatus. A profound knowledge of how Aspergillus and its cell wall components are recognized by the host cell and which type of immune response it induces is necessary to develop target-specific treatment options with less severe side effects than the treatment options to date. There is controversy in the literature about the receptor for chitin in human cells. We identified the Fc-γ receptor and Syk/PI3K pathway via which chitin can induce anti-inflammatory immune responses by inducing IL-1 receptor antagonist in the presence of human immunoglobulins but also proinflammatory responses in the presence of bacterial components. This explains why Aspergillus does not induce strong inflammation just by inhalation and rather fulfills an immune-dampening function. While in a lung coinfected with bacteria, Aspergillus augments immune responses by shifting toward a proinflammatory reaction.

Invasive aspergillosis mainly occurs in immunocompromised patients and is commonly caused by Aspergillus fumigatus, while A.nidulans is rarely the causative agent. However, in chronic granulomatous disease (CGD) patients, A. nidulans is a frequent cause of invasive aspergillosis and is associated with higher mortality. Immune recognition of A. nidulans was compared to A. fumigatus to offer an insight into why A. nidulans infections are prevalent in CGD. Live cell imaging with J774A.1 macrophage-like cells and LC3-GFP-mCherry bone marrow-derived macrophages (BMDMs) revealed that phagocytosis of A. nidulans was slower compared to A. fumigatus. This difference could be attributed to slower migration of J774A.1 cells and a lower percentage of migrating BMDMs. In addition, delayed phagosome acidification and LC3-associated phagocytosis was observed with A. nidulans. Cytokine and oxidative burst measurements in human peripheral blood mononuclear cells revealed a lower oxidative burst upon challenge with A. nidulans. In contrast, A. nidulans induced significantly higher concentrations of cytokines. Collectively, our data demonstrate that A. nidulans is phagocytosed and processed at a slower rate compared to A. fumigatus, resulting in reduced fungal killing and increased germination of conidia. This slower rate of A. nidulans clearance may be permissive for overgrowth within certain immune settings.

Contains fulltext : 154096.pdf (Publisher’s version ) (Open Access) BACKGROUND: Fungal skull base osteomyelitis (SBO) is a severe complication of otitis externa or sinonasal infection, and is mainly caused by Aspergillus species. Here we investigate innate and adaptive immune responses in patients with Aspergillus SBO to identify defects in the immune response that could explain the susceptibility to this devastating disease. METHODS: Peripheral blood mononuclear cells isolated from six patients with Aspergillus SBO and healthy volunteers were stimulated with various microbial stimuli, among which also the fungal pathogens Candida albicans and Aspergillus fumigatus. The proinflammatory cytokines IL-6, TNFalpha and IL-1beta, and the T-helper cell-derived cytokines IFNgamma, IL-17 and IL-22 were measured in cell culture supernatants by ELISA. RESULTS: Proinflammatory cytokine responses did not differ between SBO patients and healthy volunteers. The Candida- and Aspergillus-specific Th17 response (production of IL-17 and IL-22) was significantly decreased in the SBO patients compared to healthy individuals, while Th1 cytokine response (IFNgamma production) did not differ between the two groups. CONCLUSIONS: We show that patients with Aspergillus skull base osteomyelitis infection have specific defects in Th17 responses. Since IL-17 and IL-22 are important for stimulating antifungal host defense, we hypothesize that strategies that have the ability to improve IL-17 and IL-22 production may be useful as adjuvant immunotherapy in patients with Aspergillus SBO.

Contains fulltext : 154433.pdf (Publisher’s version ) (Closed access) A large variety of fungi are present in the environment, among which a proportion colonizes the human body, usually without causing any harm. However, depending on the host immune status, commensals can become opportunistic pathogens that induce diseases ranging from superficial non-harmful infection to life-threatening systemic disease. The interplay between the host and the fungal commensal flora is being orchestrated by an efficient recognition of the microorganisms, which in turn ensures a proper balance between tolerance of the normal fungal flora and induction of immune defense mechanisms when invasion occurs. Pattern recognition receptors (PRRs) play a significant role in maintaining this balance due to their capacity to sense fungi and induce host responses such as the induction of proinflammatory cytokines involved in the activation of innate and adaptive immune responses. In the present review, we will discuss the most recent findings regarding the recognition of Candida albicans and Aspergillus fumigatus and the different types of immune cells that play a role in antifungal host defense.

The galactosaminogalactan (GAG) is a cell wall component of Aspergillus fumigatus that has potent anti-inflammatory effects in mice. However, the mechanisms responsible for the anti-inflammatory property of GAG remain to be elucidated. In the present study we used in vitro PBMC stimulation assays to demonstrate, that GAG inhibits proinflammatory T-helper (Th)1 and Th17 cytokine production in human PBMCs by inducing Interleukin-1 receptor antagonist (IL-1Ra), a potent anti-inflammatory cytokine that blocks IL-1 signalling. GAG cannot suppress human T-helper cytokine production in the presence of neutralizing antibodies against IL-1Ra. In a mouse model of invasive aspergillosis, GAG induces IL-1Ra in vivo, and the increased susceptibility to invasive aspergillosis in the presence of GAG in wild type mice is not observed in mice deficient for IL-1Ra. Additionally, we demonstrate that the capacity of GAG to induce IL-1Ra could also be used for treatment of inflammatory diseases, as GAG was able to reduce severity of an experimental model of allergic aspergillosis, and in a murine DSS-induced colitis model. In the setting of invasive aspergillosis, GAG has a significant immunomodulatory function by inducing IL-1Ra and notably IL-1Ra knockout mice are completely protected to invasive pulmonary aspergillosis. This opens new treatment strategies that target IL-1Ra in the setting of acute invasive fungal infection. However, the observation that GAG can also protect mice from allergy and colitis makes GAG or a derivative structure of GAG a potential treatment compound for IL-1 driven inflammatory diseases., Author Summary Aspergillus fumigatus is an opportunistic pathogenic fungus that primarily causes infections in the immunocompromised host. It is known that Aspergillus employs various strategies to evade immune recognition by the host's immune system. Recently, galactosaminogalactan (GAG), a new component of the Aspergillus cell wall, was discovered to have potent anti-inflammatory effects in mice making them more susceptible to Aspergillosis. In the current study we found that this anti-inflammatory property of GAG was due to its capacity to induce the potent anti-inflammatory cytokine interleukin-1 Receptor antagonist. This cytokine interferes with IL-1 signalling and thereby can reduce IL-1–induced immune responses such as T-cell responses. We also found that the induction of this anti-inflammatory cytokine by GAG correlates with increased fungal burden, and mice deficient for this cytokine were protected against aspergillosis. Additionally, we show that the capacity of GAG to induce the natural regulator of IL-1 signalling could be used in the treatment of IL-1–mediated disease such as allergy and colitis. Our study provides new insights on the immunoregulatory activity of GAG and opens up possibilities to exploit the anti-inflammatory potential of GAG as a therapy for inflammatory diseases.

Contains fulltext : 153966.pdf (Publisher’s version ) (Closed access) BACKGROUND: Candida albicans is an opportunistic fungal pathogen that induces strong proinflammatory responses, such as IL-1beta production. Much less is known about the induction of immune modulatory cytokines, such as the IL-1 receptor antagonist (IL-1Ra) that is the main natural antagonist of IL-1, by C. albicans. METHODS: Peripheral blood mononuclear cells (PBMC) of healthy individuals were stimulated with C. albicans and different components of the fungal cell wall. The role of pathogen recognition receptors (PRRs) for the induction of IL-1beta and IL-1Ra was investigated by using specific blockers or in PBMC from Dectin-1 deficient patients. RESULTS: C. albicans induced a strong IL-1Ra response, and this induction was primarily induced by the cell-wall component beta-glucan. Blocking IL-1Ra significantly increased C. albicans beta-glucan hyphae induced IL-1beta and IL-6 production. Surprisingly, blocking the beta-glucan receptor Dectin-1 or the downstream Syk or Raf-1 pathways only marginally reduced C. albicans-induced IL-1Ra production, while blocking of the complement receptor 3 (CR3), TLR2 or TLR4 had no effect. In line with this, blocking MAP kinases had little effect on Candida-induced IL-1Ra production. PBMC isolated from Dectin-1 deficient patients produced normal IL-1Ra amounts in response to C. albicans stimulation. Interestingly, the IL-1Ra synthesis induced by beta-glucan was blocked by inhibitors of the Akt/PI3K pathway. CONCLUSIONS: beta-glucan of C. albicans induces a strong IL-1Ra response, which is independent of the beta-glucan receptors dectin-1 and CR3. These data strongly argue for the existence of an unknown beta-glucan receptor that specifically induces an Akt/PI3K-dependent anti-inflammatory IL-1Ra response upon recognition of C. albicans.

Th cell responses induced by Aspergillus fumigatus have been extensively investigated in mouse models. However, the requirements for differentiation and the characteristics of A. fumigatus–induced human Th cell subsets remain poorly defined. We demonstrate that A. fumigatus induces Th1 and Th17 subsets in human PBMCs. Moreover, we show that the cytokine IL-22 is not restricted to a specific Th subset, in contrast to IL-17A. The pattern recognition and cytokine pathways that skew these Aspergillus-induced Th cell responses are TLR4- and IL-1–, IL-23–, and TNF-α–dependent. These pathways are of specific importance for production of the cytokines IL-17A and IL-22. Additionally, our data reveal that the dectin-1/Syk pathway is redundant and that TLR2 has an inhibitory effect on Aspergillus-induced IL-17A and IL-22 production. Notably, blocking complement receptor (CR)3 significantly reduced Aspergillus-induced Th1 and Th17 responses, and this was independent on the activation of the complement system. CR3 is a known receptor for β-1,3-glucan; however, blocking CR3 had significant effects on Th cell responses induced by heat-killed Aspergillus conidia, which have minimal β-glucan expression on their cell surface. Collectively, these data characterize the human Th cell subsets induced by Aspergillus, demonstrate that the capability to produce IL-22 is not restricted to a specific T cell subset, and provide evidence that CR3 might play a significant role in the adaptive host defense against Aspergillus, although the ligand and its action remain to be elucidated.

IL-1 drives Th responses, particularly Th17, in host defense. Sharing the same co-receptor, the IL-1 family member IL-36 exhibits properties similar to those of IL-1. In the present study, we investigated the role of IL-36 in Aspergillus fumigatus-induced human Th responses. We observed that different morphological forms of A. fumigatus variably increase steady-state mRNA of IL-36 subfamily members. IL-36α is not significantly induced by any morphological form of Aspergillus. Most strikingly, IL-36γ is significantly induced by live A. fumigatus conidia and heat-killed hyphae, whereas IL-36Ra (IL-36 receptor antagonist) is significantly induced by heat-killed conidia, hyphae, and live conidia. We also observed that IL-36γ expression is dependent on the dectin-1/Syk and TLR4 signaling pathway. In contrast, TLR2 and CR3 inhibit IL-36γ expression. The biological relevance of IL-36 induction by Aspergillus is demonstrated by experiments showing that inhibition of the IL-36 receptor by IL-36Ra reduces Aspergillus-induced IL-17 and IFN-γ. These data describe that IL-36-dependent signals are a novel cytokine pathway that regulates Th responses induced by A. fumigatus, and demonstrate a role for TLR4 and dectin-1 in the induction of IL-36γ.