Novel acute hypersensitivity pneumonitis model induced by airway mycosis and high dose lipopolysaccharide

BACKGROUND

Inhalation of fungal spores is a strong risk factor for severe asthma and experimentally leads to development of airway mycosis and asthma-like disease in mice. However, in addition to fungal spores, humans are simultaneously exposed to other inflammatory agents such as lipopolysaccharide (LPS), with uncertain relevance to disease expression. To determine how high dose inhalation of LPS influences the expression of allergic airway disease induced by the allergenic mold Aspergillus niger (A. niger).

METHODS

C57BL/6J mice were intranasally challenged with the viable spores of A. niger with and without 1 μg of LPS over two weeks. Changes in airway hyperreactivity, airway and lung inflammatory cell recruitment, antigen-specific immunoglobulins, and histopathology were determined.

RESULTS

In comparison to mice challenged only with A. niger, addition of LPS (1 μg) to A. niger abrogated airway hyperresponsiveness and strongly attenuated airway eosinophilia, PAS+ goblet cells and TH2 responses while enhancing TH1 and TH17 cell recruitment to lung. Addition of LPS resulted in more severe, diffuse lung inflammation with scattered, loosely-formed parenchymal granulomas, but failed to alter fungus-induced IgE and IgG antibodies.

CONCLUSIONS

In contrast to the strongly allergic lung phenotype induced by fungal spores alone, addition of a relatively high dose of LPS abrogates asthma-like features, replacing them with a phenotype more consistent with acute hypersensitivity pneumonitis (HP). These findings extend the already established link between airway mycosis and asthma to HP and describe a robust model for further dissecting the pathophysiology of HP.

NLRX1 is a key regulator of immune signaling during invasive pulmonary aspergillosis

Aspergillus fumigatus is an opportunistic fungal pathogen of immunocompromised patient populations. Mortality is thought to be context-specific and occurs via both enhanced fungal growth and immunopathogenesis. NLRX1 is a negative regulator of immune signaling and metabolic pathways implicated in host responses to microbes, cancers, and autoimmune diseases. Our study indicates loss of Nlrx1 results in enhanced fungal burden, pulmonary inflammation, immune cell recruitment, and mortality across immuno-suppressed and immuno-competent models of IPA using two clinically derived isolates (AF293, CEA10). We observed that the heightened mortality is due to enhanced recruitment of CD103+ dendritic cells (DCs) that produce elevated amounts of IL-4 resulting in a detrimental Th2-mediated immune response. Adoptive transfer of Nlrx1-/- CD103+ DCs in neutropenic NRG mice results in enhanced mortality that can be ablated using IL-4 neutralizing antibodies. In vitro analysis of CD103+ DCs indicates loss of Nlrx1 results in enhanced IL-4 production via elevated activation of the JNK/JunB pathways. Interestingly, loss of Nlrx1 also results in enhanced recruitment of monocytes and neutrophils. Chimeras of irradiated Nlrx1-/- mice reconstituted with wild type bone marrow have enhanced neutrophil recruitment and survival during models of IPA. This enhanced immune cell recruitment in the absence of Nlrx1 is mediated by excessive production of CXCL8/IL-8 family of chemokines and IL-6 via early and enhanced activation of P38 in response to A. fumigatus conidia as shown in BEAS-2B airway epithelial cells. In summary, our results point strongly towards the cell-specific and contextual function of Nlrx1 during invasive pulmonary aspergillosis and may lead to novel therapeutics to reduce Th2 responses by CD103+ DCs or heightened recruitment of neutrophils.

Fungal infections are mitigated and controlled in part by a robust immune response and generation of reactive oxygen species. In certain instances, the immune response may become harmful to the host. Nlrx1 is a known negative regulator of inflammatory aspects of the immune system in response to viruses, bacteria, and cancers. In this study we describe the novel importance of Nlrx1 in controlling and fighting fungal infections in two different host cell populations through two distinct mechanisms. Nlrx1 may function as a future target to mitigate inflammation and immunopathogenesis during fungal pulmonary infection as well as enhance beneficial neutrophil recruitment.

Platelets are critical for survival and tissue integrity during murine pulmonary Aspergillus fumigatus infection

Beyond their canonical roles in hemostasis and thrombosis, platelets function in the innate immune response by interacting directly with pathogens and by regulating the recruitment and activation of immune effector cells. Thrombocytopenia often coincides with neutropenia in patients with hematologic malignancies and in allogeneic hematopoietic cell transplant recipients, patient groups at high risk for invasive fungal infections. While neutropenia is well established as a major clinical risk factor for invasive fungal infections, the role of platelets in host defense against human fungal pathogens remains understudied. Here, we examined the role of platelets in murine Aspergillus fumigatus infection using two complementary approaches to induce thrombocytopenia without concurrent neutropenia. Thrombocytopenic mice were highly susceptible to A. fumigatus challenge and rapidly succumbed to infection. Although platelets regulated early conidial phagocytosis by neutrophils in a spleen tyrosine kinase (Syk)-dependent manner, platelet-regulated conidial phagocytosis was dispensable for host survival. Instead, our data indicated that platelets primarily function to maintain hemostasis and lung integrity in response to exposed fungal antigens, since thrombocytopenic mice exhibited severe hemorrhage into the airways in response to fungal challenge in the absence of overt angioinvasion. Challenge with swollen, heat-killed, conidia was lethal in thrombocytopenic hosts and could be reversed by platelet transfusion, consistent with the model that fungus-induced inflammation in platelet-depleted mice was sufficient to induce lethal hemorrhage. These data provide new insights into the role of platelets in the anti-Aspergillus host response and expand their role to host defense against filamentous molds.

Aspergillus fumigatus is a ubiquitous environmental mold that forms airborne spores, termed conidia. When inhaled by immune compromised individuals, A. fumigatus conidia can germinate into tissue-invasive hyphae and cause invasive aspergillosis, a major cause of infectious morbidity and mortality in patients with leukemia and in bone marrow transplant recipients. Although a low platelet count has been identified as a risk factor for clinical outcomes in patients with invasive aspergillosis, the precise role of platelets in the anti-fungal host response remains poorly understood. Here, we report an essential requirement for platelets in anti-Aspergillus host defence in a mouse model of fungal pneumonia. Although platelets play a role in activating the innate immune system after infection, they are critical for preventing lethal hemorrhage after A. fumigatus challenge. Our findings raise the question as to whether platelets can be used as a basis for therapeutic strategies in vulnerable patient populations.

Pulmonary infection due to Acrophialophora fusispora in a patient with underlying mixed connective tissue disease and chronic pulmonary aspergillosis: A case report and review of literature

Acrophialophora fusispora is a soil-borne fungus rarely implicated in human infections. Here, we report a case of pulmonary infection due to A. fusispora in a 59-year-old male who presented with productive cough and gradually progressive dyspnoea for 20 days. He had a past history of pulmonary tuberculosis and was a known case of chronic obstructive pulmonary disease for past five years. He was diagnosed with mixed connective tissue disease and had been receiving oral azathioprine and prednisolone for three months. CECT thorax revealed an aspergilloma and serum Aspergillus fumigatus-specific IgG levels were raised, suggestive of chronic pulmonary aspergillosis. He was also tested positive for influenza A (H1N1) and received treatment with oral oseltamivir without any clinical benefit. Culture of sputum and bronchoalveolar lavage fluid showed growth of a fungus which was identified as Acrophialophora fusispora based on characteristic microscopic morphology and internal transcribed spacer sequencing of the ribosomal DNA. Antifungal susceptibility testing for six antifungal drugs showed itraconazole to have the most potent in vitro activity (MIC=0.25μg/mL) against A. fusispora in comparison to the other drugs tested. Treatment with itraconazole capsule 200mg twice daily was initiated and favourable clinical response was observed after 10 days of therapy. Follow-up visit after three months showed marked clinical and radiological improvement. A. fusispora is an emerging opportunistic fungus capable of causing invasive infections in immunocompromised hosts. Lack of knowledge about this fungus and confusion with morphologically similar opportunistic fungi have led to its misidentification and hence its prevalence remains largely underestimated. Accurate identification is crucial as it can help initiate early effective antifungal therapy and improve patient outcomes. To our knowledge, this is the first case of pulmonary infection due to A. fusispora reported from India.

Aspergillus fumigatus calcium-responsive transcription factors regulate cell wall architecture promoting stress tolerance, virulence and caspofungin resistance

Aspergillus fumigatus causes invasive aspergillosis, the most common life-threatening fungal disease of immuno-compromised humans. The treatment of disseminated infections with antifungal drugs, including echinocandin cell wall biosynthesis inhibitors, is increasingly challenging due to the rise of drug-resistant pathogens. The fungal calcium responsive calcineurin-CrzA pathway influences cell morphology, cell wall composition, virulence, and echinocandin resistance. A screen of 395 A. fumigatus transcription factor mutants identified nine transcription factors important to calcium stress tolerance, including CrzA and ZipD. Here, comparative transcriptomics revealed CrzA and ZipD regulated the expression of shared and unique gene networks, suggesting they participate in both converged and distinct stress response mechanisms. CrzA and ZipD additively promoted calcium stress tolerance. However, ZipD also regulated cell wall organization, osmotic stress tolerance and echinocandin resistance. The absence of ZipD in A. fumigatus caused a significant virulence reduction in immunodeficient and immunocompetent mice. The ΔzipD mutant displayed altered cell wall organization and composition, while being more susceptible to macrophage killing and eliciting an increased pro-inflammatory cytokine response. A higher number of neutrophils, macrophages and activated macrophages were found in ΔzipD infected mice lungs. Collectively, this shows that ZipD-mediated regulation of the fungal cell wall contributes to the evasion of pro-inflammatory responses and tolerance of echinocandin antifungals, and in turn promoting virulence and complicating treatment options.

[Pulmonary Aspergillosis in immunocompetent patient]

Aspergillus is a group of molds which is found everywhere worldwide, exposition of human being is common. Most of immunocompetent people do not develop disease caused by Aspergillus. However, diseases in different forms may occur in certain conditions in immunocompetent patient. These diseases include hypersensitivity reactions, like allergic broncho-pulmonary aspergillosis, or infectious process like chronic pulmonary aspergillosis or invasive pulmonary aspergillosis. This article reviewed the clinical features of these diseases and the current available diagnostic techniques.

Preparations for Invasion: Modulation of Host Lung Immunity During Pulmonary Aspergillosis by Gliotoxin and Other Fungal Secondary Metabolites

Pulmonary aspergillosis is a severe infectious disease caused by some members of the Aspergillus genus, that affects immunocompetent as well as immunocompromised patients. Among the different disease forms, Invasive Aspergillosis is the one causing the highest mortality, mainly, although not exclusively, affecting neutropenic patients. This genus is very well known by humans, since different sectors like pharmaceutical or food industry have taken advantage of the biological activity of some molecules synthetized by the fungus, known as secondary metabolites, including statins, antibiotics, fermentative compounds or colorants among others. However, during infection, in response to a hostile host environment, the fungal secondary metabolism is activated, producing different virulence factors to increase its survival chances. Some of these factors also contribute to fungal dissemination and invasion of adjacent and distant organs. Among the different secondary metabolites produced by Aspergillus spp. Gliotoxin (GT) is the best known and better characterized virulence factor. It is able to generate reactive oxygen species (ROS) due to the disulfide bridge present in its structure. It also presents immunosuppressive activity related with its ability to kill mammalian cells and/or inactivate critical immune signaling pathways like NFkB. In this comprehensive review, we will briefly give an overview of the lung immune response against Aspergillus as a preface to analyse the effect of different secondary metabolites on the host immune response, with a special attention to GT. We will discuss the results reported in the literature on the context of the animal models employed to analyse the role of GT as virulence factor, which is expected to greatly depend on the immune status of the host: why should you hide when nobody is seeking for you? Finally, GT immunosuppressive activity will be related with different human diseases predisposing to invasive aspergillosis in order to have a global view on the potential of GT to be used as a target to treat IA.

The Serum Level of IL-1B Correlates with the Activity of Chronic Pulmonary Aspergillosis

Background

Until now, there have been no objective criteria to determine the activity of chronic pulmonary aspergillosis (CPA). This study aims to analyze the correlation between serum level of IL-1B and the activity of CPA and to determine whether serum IL-1B could be used to assess the activity of CPA.

Methods

A total of 469 newly diagnosed CPA patients were enrolled. Correlation analysis in the whole subjects showed that only IL-1B level was associated with the activity of CPA. Then, 381 cases with factors significantly affecting IL-1B expression was excluded through multiple linear regression; the remaining 88 patients were divided into high IL-1B group and low IL-1B group, according to the median value of serum IL-1B, for subgroup analysis. A retrospective comparative analysis was subsequently performed between the two groups, including the clinical manifestation, microbiology and laboratory tests results, and imaging findings. We further investigated the relationship between IL-1B levels and CT characteristic which acted as the indicator of CPA activity, as well as changes in IL-1B level before and after surgery.

Results

For all patients, correlation analysis revealed that IL-1B level correlated with both cavitary diameter (P=0.035) and aspergilloma size (P<0.047) but not with the thickness of the cavity (P=0.479). In subgroup comparative analysis, CT characteristics suggested that high activity of CPA, such as cavitary (27/44 vs 13/44, P=0.003) and aspergilloma lesions (25/44 vs. 11/44, P<0.002), were more frequently found in high IL-1B group. The cavity diameter (P<0.001), aspergilloma size (P=0.006), and cavity wall thickness (P=0.023) were significantly different between the two groups. When Spearman correlation analysis was performed once again in subgroup, an even stronger relationship of serum IL-1B with the cavity diameter (Rs=0.501, P=0.002) and aspergilloma size (Rs=0.615, P=0.001) was observed. Interestingly, a significant reduction of IL-1B level was observed after successful resection of CPA lesions.

Conclusion

Higher level of serum IL-1B is associated with more severe cavitary and aspergilloma lesions, which are indicative of more active CPA. In addition, IL-1B level reduced accordingly after lesion resection. Measuring IL-1B level therefore could be served as a convenient method to monitor the activity of CPA and be a potential predictive/prognostic marker for treatment response.

Evaluation of a commercial quantitative Aspergillus fumigatus-specific IgM assay for the diagnosis of invasive pulmonary aspergillosis

Invasive pulmonary aspergillosis (IPA) is a common fungal infection with high mortality rates in immunocompromised patients. Early diagnosis of IPA is still challenging because of its nonspecific clinical symptoms and radiological presentations.To evaluate the clinical value of a commercial Aspergillus fumigates-specific IgM antibody assay in diagnosis of IPA, a multicenter prospective study was performed in 12 hospitals in Zhejiang Province, China, from January 1 to December 31, 2016.A total of 59 patients were enrolled in this study, including 30 IPA and 29 non-IPA patients. The sensitivities of IgM assay were 30.0%, 26.7%, 23.3%, and 20.0%, and the specificities were 79.3%, 86.2%, 86.2%, and 96.6% at the cutoff values of 50, 60, 70 and 80 AU/mL, respectively. The area under the curve of the IgM assay revealed by the receiver-operating characteristic analysis was 0.511 in the IPA cases. This study is the first to evaluate the clinical performance of a commercial A. fumigatus-specific IgM antibody assay that uses envelopes galactomannan extracted from A. fumigatus as the sole antigen in diagnosis of IPA.In conclusion, the A. fumigatus-specific IgM antibody assay has limited value and should not be a prior recommendation for IPA diagnosis.

Deciphering the Counterplay of Aspergillus fumigatus Infection and Host Inflammation by Evolutionary Games on Graphs

Microbial invaders are ubiquitously present and pose the constant risk of infections that are opposed by various defence mechanisms of the human immune system. A tight regulation of the immune response ensures clearance of microbial invaders and concomitantly limits host damage that is crucial for host viability. To investigate the counterplay of infection and inflammation, we simulated the invasion of the human-pathogenic fungus Aspergillus fumigatus in lung alveoli by evolutionary games on graphs. The layered structure of the innate immune system is represented by a sequence of games in the virtual model. We show that the inflammatory cascade of the immune response is essential for microbial clearance and that the inflammation level correlates with the infection-dose. At low infection-doses, corresponding to daily inhalation of conidia, the resident alveolar macrophages may be sufficient to clear infections, however, at higher infection-doses their primary task shifts towards recruitment of neutrophils to infection sites.

FleA Expression in Aspergillus fumigatus Is Recognized by Fucosylated Structures on Mucins and Macrophages to Prevent Lung Infection

The immune mechanisms that recognize inhaled Aspergillus fumigatus conidia to promote their elimination from the lungs are incompletely understood. FleA is a lectin expressed by Aspergillus fumigatus that has twelve binding sites for fucosylated structures that are abundant in the glycan coats of multiple plant and animal proteins. The role of FleA is unknown: it could bind fucose in decomposed plant matter to allow Aspergillus fumigatus to thrive in soil, or it may be a virulence factor that binds fucose in lung glycoproteins to cause Aspergillus fumigatus pneumonia. Our studies show that FleA protein and Aspergillus fumigatus conidia bind avidly to purified lung mucin glycoproteins in a fucose-dependent manner. In addition, FleA binds strongly to macrophage cell surface proteins, and macrophages bind and phagocytose fleA-deficient (∆fleA) conidia much less efficiently than wild type (WT) conidia. Furthermore, a potent fucopyranoside glycomimetic inhibitor of FleA inhibits binding and phagocytosis of WT conidia by macrophages, confirming the specific role of fucose binding in macrophage recognition of WT conidia. Finally, mice infected with ΔfleA conidia had more severe pneumonia and invasive aspergillosis than mice infected with WT conidia. These findings demonstrate that FleA is not a virulence factor for Aspergillus fumigatus. Instead, host recognition of FleA is a critical step in mechanisms of mucin binding, mucociliary clearance, and macrophage killing that prevent Aspergillus fumigatus pneumonia.

IL-1α signaling is critical for leukocyte recruitment after pulmonary Aspergillus fumigatus challenge

Aspergillus fumigatus is a mold that causes severe pulmonary infections. Our knowledge of how A. fumigatus growth is controlled in the respiratory tract is developing, but still limited. Alveolar macrophages, lung resident macrophages, and airway epithelial cells constitute the first lines of defense against inhaled A. fumigatus conidia. Subsequently, neutrophils and inflammatory CCR2+ monocytes are recruited to the respiratory tract to prevent fungal growth. However, the mechanism of neutrophil and macrophage recruitment to the respiratory tract after A. fumigatus exposure remains an area of ongoing investigation. Here we show that A. fumigatus pulmonary challenge induces expression of the inflammasome-dependent cytokines IL-1β and IL-18 within the first 12 hours, while IL-1α expression continually increases over at least the first 48 hours. Strikingly, Il1r1-deficient mice are highly susceptible to pulmonary A. fumigatus challenge exemplified by robust fungal proliferation in the lung parenchyma. Enhanced susceptibility of Il1r1-deficient mice correlated with defects in leukocyte recruitment and anti-fungal activity. Importantly, IL-1α rather than IL-1β was crucial for optimal leukocyte recruitment. IL-1α signaling enhanced the production of CXCL1. Moreover, CCR2+ monocytes are required for optimal early IL-1α and CXCL1 expression in the lungs, as selective depletion of these cells resulted in their diminished expression, which in turn regulated the early accumulation of neutrophils in the lung after A. fumigatus challenge. Enhancement of pulmonary neutrophil recruitment and anti-fungal activity by CXCL1 treatment could limit fungal growth in the absence of IL-1α signaling. In contrast to the role of IL-1α in neutrophil recruitment, the inflammasome and IL-1β were only essential for optimal activation of anti-fungal activity of macrophages. As such, Pycard-deficient mice are mildly susceptible to A. fumigatus infection. Taken together, our data reveal central, non-redundant roles for IL-1α and IL-1β in controlling A. fumigatus infection in the murine lung.

Aspergillus spp. are ubiquitous in the environment, and even though individuals are regularly exposed to fungal spores clinical invasive disease is a rare manifestation. In contrast, individuals with weakened immune systems develop severe disease, such as invasive pulmonary aspergillosis (IPA). IPA is associated with extremely poor prognoses and unacceptably high mortality rates. Knowledge gained from understanding how immunocompetent mammals control Aspergillus challenge will help develop new immunomodulatory strategies aimed at improving patient outcomes. It is well known that neutrophils and monocytes are crucial immune cells that act to limit fungal growth. Our work demonstrates a central role for the cytokine IL-1α in orchestrating the optimal recruitment of neutrophils and monocytes, whereas IL-1β and the inflammasome are more important in activation of anti-fungal activity of the monocytes. Moreover, our studies indicate that CCR2⁺ monocytes are required for optimal production of IL-1α in the lungs of A. fumigatus challenged mice. Thus, our data highlight a crucial role of the IL-1 cytokine in mediating anti-fungal immunity which might be harnessed to treat clinical cases of IPA.

Myeloid derived hypoxia inducible factor 1-alpha is required for protection against pulmonary Aspergillus fumigatus infection

Hypoxia inducible factor 1α (HIF1α) is the mammalian transcriptional factor that controls metabolism, survival, and innate immunity in response to inflammation and low oxygen. Previous work established that generation of hypoxic microenvironments occurs within the lung during infection with the human fungal pathogen Aspergillus fumigatus. Here we demonstrate that A. fumigatus stabilizes HIF1α protein early after pulmonary challenge that is inhibited by treatment of mice with the steroid triamcinolone. Utilizing myeloid deficient HIF1α mice, we observed that HIF1α is required for survival and fungal clearance early following pulmonary challenge with A. fumigatus. Unlike previously reported research with bacterial pathogens, HIF1α deficient neutrophils and macrophages were surprisingly not defective in fungal conidial killing. The increase in susceptibility of the myeloid deficient HIF1α mice to A. fumigatus was in part due to decreased early production of the chemokine CXCL1 (KC) and increased neutrophil apoptosis at the site of infection, resulting in decreased neutrophil numbers in the lung. Addition of recombinant CXCL1 restored neutrophil survival and numbers, murine survival, and fungal clearance. These results suggest that there are unique HIF1α mediated mechanisms employed by the host for protection and defense against fungal pathogen growth and invasion in the lung. Additionally, this work supports the strategy of exploring HIF1α as a therapeutic target in specific immunosuppressed populations with fungal infections.

Pulmonary immune responses to Aspergillus fumigatus in rats

OBJECTIVE

To evaluate immunologic mechanisms underlying Aspergillus fumigatus pulmonary infections in immunocompetent Dark Agouti (DA) and Albino Oxford (AO) rats recognized as being susceptible to some inflammatory diseases in different manners.

METHODS

Lung fungal burden (quantitative colony forming units, CFU, assay), leukocyte infiltration (histology, cell composition) and their function (phagocytosis, oxidative activity, CD11b adhesion molecule expression) and cytokine interferon-γ (IFN-γ) and interleukin-17 and -4 (IL-17 and IL-4) lung content were evaluated following infection (intratracheally, 1x10(7) conidia).

RESULTS

Slower reduction of fungal burden was observed in AO rats in comparison with that in DA rats, which was coincided with less intense histologically evident lung cell infiltration and leukocyte recovery as well as lower level of most of the their activities including intracellular myeloperoxidase activity, the capacity of nitroblue tetrazolium salt reduction and CD11b adhesion molecule expression (except for phagocytosis of conidia) in these rats. Differential patterns of changes in proinflammatory cytokine levels (unchanged levels of IFN-γ and transient increase of IL-17 in AO rats vs continuous increase of both cytokines in DA rats) and unchanged levels of IL-4 were observed.

CONCLUSION

Genetically-based differences in the pattern of antifungal lung leukocyte activities and cytokine milieu, associated with differential efficiency of fungal elimination might be useful in the future use of rat models in studies of pulmonary aspergillosis.

Gene expression profiles of human dendritic cells interacting with Aspergillus fumigatus in a bilayer model of the alveolar epithelium/endothelium interface

The initial stages of the interaction between the host and Aspergillus fumigatus at the alveolar surface of the human lung are critical in the establishment of aspergillosis. Using an in vitro bilayer model of the alveolus, including both the epithelium (human lung adenocarcinoma epithelial cell line, A549) and endothelium (human pulmonary artery epithelial cells, HPAEC) on transwell membranes, it was possible to closely replicate the in vivo conditions. Two distinct sub-groups of dendritic cells (DC), monocyte-derived DC (moDC) and myeloid DC (mDC), were included in the model to examine immune responses to fungal infection at the alveolar surface. RNA in high quantity and quality was extracted from the cell layers on the transwell membrane to allow gene expression analysis using tailored custom-made microarrays, containing probes for 117 immune-relevant genes. This microarray data indicated minimal induction of immune gene expression in A549 alveolar epithelial cells in response to germ tubes of A. fumigatus. In contrast, the addition of DC to the system greatly increased the number of differentially expressed immune genes. moDC exhibited increased expression of genes including CLEC7A, CD209 and CCL18 in the absence of A. fumigatus compared to mDC. In the presence of A. fumigatus, both DC subgroups exhibited up-regulation of genes identified in previous studies as being associated with the exposure of DC to A. fumigatus and exhibiting chemotactic properties for neutrophils, including CXCL2, CXCL5, CCL20, and IL1B. This model closely approximated the human alveolus allowing for an analysis of the host pathogen interface that complements existing animal models of IA.

Inflammatory monocytes orchestrate innate antifungal immunity in the lung

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

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

Environmental monitoring for Aspergillus fumigatus in association with an immunosuppressed rabbit model of pulmonary aspergillosis

Aspergillus fumigatus causes life-threatening pneumonia in immunocompromised patients. Conidia, the infectious form of the organism, are handled in a biologic safety cabinet under BSL2 conditions. However because germinated conidia form noninfectious hyphae in tissue, we hypothesized that rabbits inoculated intratracheally would grow A. fumigatus in their lungs but that the environment would remain free of this fungus, potentially permitting maintenance of infected animals under ABSL1 conditions. We performed a surveillance study for the presence of A. fumigatus in the environment before proceeding with antifungal therapy studies of experimental pulmonary aspergillosis. The expected outcome included absence of A. fumigatus in the environment, stool, and blood and presence in rabbit lungs. Female SPF New Zealand white rabbits were immunosuppressed and inoculated intratracheally (n = 4) or intraesophageally (n = 2) with 1.25 × 10(8) conidia of A. fumigatus. Feces, pan liners, and walls were sampled daily during the 11-d experiment, and blood was sampled on days 2, 6, and 8 after inoculation. Samples were cultured on 5% Sabouraud glucose agar plates. Lungs were weighed and scored for hemorrhagic infarcts and homogenized for culture on 5% Sabouraud glucose agar and trypticase soy agar plates. Blood cultures, rabbit stool, and environmental swabs were all negative for A. fumigatus whereas the lungs inoculated intratracheally demonstrated 4.5 × 10(2) ± 0.8 × 10(2) CFU/g of A. fumigatus. Therefore, neutropenic rabbits with experimental invasive pulmonary aspergillosis do not shed conidia of A. fumigatus and can be safely housed under ABSL1 conditions after inoculation.

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

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

Invasive tracheobronchial aspergillosis in a patient with systemic lupus erythematosus-dermatomyositis overlap syndrome

A 45-year-old man was referred to our hospital with a 3-month history of dyspnea, polyarthralgia, myalgia and weight loss. He was diagnosed with systemic lupus erythematosus/dermatomyositis overlap syndrome with lung involvement, which presented as organizing pneumonia. However, a bronchoscopic examination revealed the presence of multiple plaque-like white lesions with ulcers on the bronchial membrane, located mainly in the central airway. The pathological specimens obtained from bronchoscopy showed numerous filamentous fungal hyphae that were aggressively invading the bronchial walls, suggesting a diagnosis of invasive tracheobronchial aspergillosis. The present case, along with a review of the literature, demonstrates that invasive tracheobronchial aspergillosis can occur in patients who do not appear to be immunosuppressed. This case of aspergillosis should thus be recognized as an extremely rare presentation of an Aspergillus infection.

Hypothermic endpoint for an intranasal invasive pulmonary aspergillosis mouse model

Immunocompromised mice were infected intranasally with Aspergillus fumigatus as part of a vaccine efficacy study. Although body temperature was measured throughout the study, a formal evaluation of its usefulness as an endpoint criterion was not performed. We retrospectively evaluated survival data and temperature records to determine whether body temperature can be used as an objective predictor of death and included in the humane endpoint criteria for this mouse model. CF1 mice were immunosuppressed with either cortisone acetate or by treatment with antiGR1 (a neutrophil-depleting antibody) and then intranasally challenged with A. fumigatus. Body temperature was measured by using an infrared noncontact thermometer a maximum of 3 times daily until death or euthanasia. A surface body temperature below 29.0 °C was correlated with a poor chance of survival, and using this cutoff point with signs of morbidity (hunched, ruffled fur, respiratory distress) reliably indicates mice for euthanasia without negatively affecting data collection. Using 2 subsequent readings of less than 31.0 °C as an endpoint would have led to premature euthanasia of only one mouse (2.2%). As a single reading, a body temperature of 28.8 °C had a sensitivity of 92.2% and specificity of 90.9%. Hypothermia proved to be a useful addition to the humane endpoint criteria for this mouse model, and veterinary and research groups should discuss their study needs in relation to animal welfare to best determine the most appropriate means of including this parameter.

Characterisation of innate fungal recognition in the lung

The innate recognition of fungi by leukocytes is mediated by pattern recognition receptors (PRR), such as Dectin-1, and is thought to occur at the cell surface triggering intracellular signalling cascades which lead to the induction of protective host responses. In the lung, this recognition is aided by surfactant which also serves to maintain the balance between inflammation and pulmonary function, although the underlying mechanisms are unknown. Here we have explored pulmonary innate recognition of a variety of fungal particles, including zymosan, Candida albicans and Aspergillus fumigatus, and demonstrate that opsonisation with surfactant components can limit inflammation by reducing host-cell fungal interactions. However, we found that this opsonisation does not contribute directly to innate fungal recognition and that this process is mediated through non-opsonic PRRs, including Dectin-1. Moreover, we found that pulmonary inflammatory responses to resting Aspergillus conidia were initiated by these PRRs in acidified phagolysosomes, following the uptake of fungal particles by leukocytes. Our data therefore provides crucial new insights into the mechanisms by which surfactant can maintain pulmonary function in the face of microbial challenge, and defines the phagolysosome as a novel intracellular compartment involved in the innate sensing of extracellular pathogens in the lung.

Dectin-1-dependent interleukin-22 contributes to early innate lung defense against Aspergillus fumigatus

We have previously reported that mice deficient in the beta-glucan receptor Dectin-1 displayed increased susceptibility to Aspergillus fumigatus lung infection in the presence of lower interleukin 23 (IL-23) and IL-17A production in the lungs and have reported a role for IL-17A in lung defense. As IL-23 is also thought to control the production of IL-22, we examined the role of Dectin-1 in IL-22 production, as well as the role of IL-22 in innate host defense against A. fumigatus. Here, we show that Dectin-1-deficient mice demonstrated significantly reduced levels of IL-22 in the lungs early after A. fumigatus challenge. Culturing cells from enzymatic lung digests ex vivo further demonstrated Dectin-1-dependent IL-22 production. IL-22 production was additionally found to be independent of IL-1β, IL-6, or IL-18 but required IL-23. The addition of recombinant IL-23 augmented IL-22 production in wild-type (WT) lung cells and rescued IL-22 production by lung cells from Dectin-1-deficient mice. In vivo neutralization of IL-22 in the lungs of WT mice resulted in impaired A. fumigatus lung clearance. Moreover, mice deficient in IL-22 also demonstrated a higher lung fungal burden after A. fumigatus challenge in the presence of impaired IL-1α, tumor necrosis factor alpha (TNF-α), CCL3/MIP-1α, and CCL4/MIP-1β production and lower neutrophil recruitment, yet intact IL-17A production. We further show that lung lavage fluid collected from both A. fumigatus-challenged Dectin-1-deficient and IL-22-deficient mice had compromised anti-fungal activity against A. fumigatus in vitro. Although lipocalin 2 production was observed to be Dectin-1 and IL-22 dependent, lipocalin 2-deficient mice did not demonstrate impaired A. fumigatus clearance. Moreover, lung S100a8, S100a9, and Reg3g mRNA expression was not lower in either Dectin-1-deficient or IL-22-deficient mice. Collectively, our results indicate that early innate lung defense against A. fumigatus is mediated by Dectin-1-dependent IL-22 production.

[Investigation of interleukin-10, tumor necrosis factor-alpha and interferon-gamma expression in experimental model of pulmonary aspergillosis]

Pulmonary aspergillosis which is an important opportunistic infection in neutropenic patients, is usually caused by Aspergillus fumigatus. Since the pathogenesis of disease is not well understood, the main proposed mechanism is thought to be cell-mediated immunity and cytokine response. The aim of this study was to investigate the local production of cytokines in the lung tissues of rats with experimentally developed aspergillosis, by reverse transcriptase-polymerase chain reaction (RT-PCR). A total of 33 Wistar albino type rats were included in the study with the consent of Experimental Animal Ethics Committee. Twenty-five of the rats were infected with A.fumigatus by intratracheal way, while 8 animals were used as controls. The presence of A.fumigatus in the lung tissues of infected rats was confirmed with the use of quantitative culture and histologic staining methods. RNA isolation from the lung tissue samples of both groups were performed by a commercial kit (Qiagen, Germany). After obtaining complementary DNAs from the genomic RNAs, in-house qualitative and quantitative (real-time) PCR methods were used to amplify the target regions for interleukin-10 (IL-10), tumor necrosis factor-alpha (TNF-?) and interferon-gamma (IFN-?) by using specific primers (Tıb Molbiol, Germany). Mean mRNA levels achieved by real-time PCR for IL-10, TNF-? and IFN-? in aspergillosis group were 6.5 x 106 copies/ml, 7.9 x 105 copies/ml and 2.2 x 103 copies/ml, respectively, while those values in control group were 4.3 x 102 copies/ml, 5.6 x 103 copies/ml and 1.3 x 102 copies/ml, respectively. Our data indicated that rat model of aspergillosis was associated with significantly increased expression of mRNA encoding IL-10 and TNF-? than controls (p< 0.05), however there was no statistically significant difference between the groups with respect to IFN-? expression (p= 0.53). In conclusion, the production of proinflammatory cytokines which mediate the influx of phagocytic cells might account for the localization of Aspergillus infection to the upper respiratory tract. The up-regulation of the expression of the immunomodulatory cytokine TNF-? and IL-10 in lung tissue from infected rats might be important to limit the extent of local tissue destruction, but might also account for the fact that infected rats are generally unable to clear the infection spontaneously.

Central airways obstruction due to Aspergillus fumigatus after lung transplantation

Aspergillus fumigatus may affect immunocompromised lung transplant patients in many ways. We report a new pulmonary manifestation of A fumigatus in 3 patients who underwent bilateral lung transplantation. All 3 subjects developed rapid decreases in pulmonary function and were found to have large central airways obstruction with thick plugs of mucus, heavily laden with Aspergillus species. All 3 patients presented with atypical features of Aspergillus infection, but all responded to treatments with either steroids, anti-fungals or both.

[Diagnosis and treatment of pulmonary aspergillosis in patients without immunodeficiency: report of 15 cases]

OBJECTIVE

To study the diagnosis and treatment of pulmonary aspergillosis in patients without immunodeficiency.

METHOD

Pulmonary aspergillosis in 15 patients without immunodeficiency was reviewed.

RESULTS

Twelve of the patients had underlying lung diseases (lung cancer), 2 showed masses in the lung by radiography and CT halo, and 1 had aspergilloma within the left main bronchus. The diagnosis of intra-cavitary aspergilloma had been made in all the patients with lung cancer before surgery. Only 3 cases were confirmed by fungal examination before surgery. Thirteen patients received surgical removal of the lesions, and the post-operative recovery was uneventful. Antifungal therapy and open drainage were administered in 1 patient with pleural residual cavity infection, but the treatment failed. Anti-cancer therapy alone was given in 1 patient. Sudden death occurred in another patient.

CONCLUSION

In suspected cases of aspergillosis, CT halo sign, histology examination are helpful for the diagnosis. Aspergilloma complicated with underlying lung diseases and mass lesions can be cured by surgery.