Antifungal Response Research Articles

S1.3a Genetics andgenomics of Malassezia species

S1.3 Malassezia: genetics, genomics, and biology, September 21, 2022, 11:00 AM - 12:30 PM Malassezia includes yeasts belonging to the subphylum Ustilaginomycotina within the Basidiomycota. Malassezia yeasts are attracting the interest of both basic and applied scientists for their unique biological features, and for their importance in clinical and cosmetic settings. Although Malassezia yeasts are commonly found as commensal on human and animal skin, they are also associated with several skin disorders, such as dandruff/seborrheic dermatitis, atopic eczema, pityriasis versicolor, and folliculitis. More recently, an association of Malassezia with Crohn's disease, pancreatic ductal adenocarcinoma, and psoriasis exacerbation has been reported. To understand the genetic basis of Malassezia commensalism and pathogenicity, the availability of genomic and molecular tools plays a crucial role. Genomics advances in Malassezia reveal karyotype variations and gene turnover events, including genes horizontally transferred from bacteria. Moreover, the increasing availability of transcriptomic data allows us to prioritize studies on novel key genes that potentially characterize the pathophysiology of Malassezia fungi. For gene function studies, protocols for Agrobacterium tumefaciens-mediated transformation were developed and utilized in strategies of random insertional mutagenesis or targeted gene replacement through CRISPR/Cas9. Developed tools can be combined with the use of host-pathogen interaction models, such as the easy-to-use wax moth larvae of Galleria mellonella or the more complex murine skin model, enabling the characterization of both the fungal components that trigger skin damage and inflammation, and the inflammatory and antifungal response of the host to prevent fungal infection through immunological and molecular analyses of experimentally infected tissue.

S9.5c Malassezia-host interactions and the Il-23/17 axis

S9.5 Malassezia: pathogenesis and disease, September 23, 2022, 4:45 PM - 6:15 PMThe mycobiome of the skin is dominated by a single fungal genus, Malassezia. While Malassezia normally exists as a commensal without inflicting disease, the fungus has also been associated with numerous skin disorders ranging from mild conditions such as dandruff or pityriasis versicolor to severe chronic pathologies such as seborrheic or atopic dermatitis. Maintaining stable colonization and preventing pathogenicity of Malassezia is key for skin homeostasis. Our understanding of the fungal factors and host mechanisms that, through mutual interactions, promote Malassezia commensalism in healthy skin remains incomplete. From studies in humans and mice, we learned that homeostatic immunity against Malassezia is characterized by IL-17-producing T cells, including Th17 and γδT17 cells. Recent endeavors start to unravel the cellular and molecular pathways responsible for driving the protective antifungal response in the skin. While Malassezia-responsive T cells are non-inflammatory and host-beneficial, they can bear pathogenic potential and thereby be involved in the pathogenesis of inflammatory and allergic skin conditions, as preclinical studies suggest. During my lecture, I will report on recent findings from my lab regarding the role and regulation of the IL-23/IL-17 axis in response to Malassezia under normal and diseased skin conditions.

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.

Aedes aegypti CLIPB9 activates prophenoloxidase-3 in the presence of CLIPA14 after fungal infection

Melanization is an integral part of the insect defense system and is often induced by pathogen invasion. Phenoloxidases (POs) are critical enzymes that catalyze melanin formation. PO3 is associated with the antifungal response of the mosquito, Aedes aegypti, but the molecular mechanism of the prophenoloxidase-3 (PPO3) activation is unclear. Here we report that PPO3 cleavage activation is mediated by a clip-domain serine protease, CLIPB9. We purified recombinant CLIPB9 and found that it cleaved PPO3 and increased PO activity in the hemolymph. We then identified CLIPA14 (a serine protease homolog) by co-immunoprecipitation using anti-CLIPB9 antibody. After being cleaved by CLIPB9, Ae. aegypti CLIPA14 acted as a cofactor for PPO3 activation. In addition, dsRNA co-silencing of CLIPB9 and CLIPA14 genes reduced melanization after infection with the entomopathogen, Beauveria bassiana, making the adult mosquitoes more sensitive to fungal infection. These results illustrate the roles of CLIPB9 and CLIPA14 in the PPO activation pathway and revealed the complexity of the upstream serine protease network controlling melanization.

Inhibition of myeloid-derived suppressor cell arginase-1 production enhances T-cell-based immunotherapy against Cryptococcus neoformans infection

Cryptococcosis is a potentially lethal disease that is primarily caused by the fungus Cryptococcus neoformans, treatment options for cryptococcosis are limited. Here, we show glucuronoxylomannan, the major polysaccharide component of C. neoformans, induces the recruitment of neutrophilic myeloid-derived suppressor cells in mice and patients with cryptococcosis. Depletion of neutrophilic myeloid-derived suppressor cells enhances host defense against C. neoformans infection. We identify C-type lectin receptor-2d recognizes glucuronoxylomannan to potentiate the immunosuppressive activity of neutrophilic myeloid-derived suppressor cells by initiating p38-mediated production of the enzyme arginase-1, which inhibits T-cell mediated antifungal responses. Notably, pharmacological inhibition of arginase-1 expression by a specific inhibitor of p38, SB202190, or an orally available receptor tyrosine kinase inhibitor, vandetanib, significantly enhances T-cell mediated antifungal responses against cryptococcosis. These data reveal a crucial suppressive role of neutrophilic myeloid-derived suppressor cells during cryptococcosis and highlight a promising immunotherapeutic application by inhibiting arginase-1 production to combat infectious diseases.

Stimulating the autophagic-lysosomal axis enhances host defense against fungal infection in a zebrafish model of invasive Aspergillosis

ABSTRACT The increasing prevalence of antifungal-resistant human pathogenic fungi, particularly azole-resistant Aspergillus fumigatus, is a life-threatening challenge to the immunocompromised population. Autophagy-related processes such as LC3-associated phagocytosis have been shown to be activated in the host response against fungal infection, but their overall effect on host resistance remains uncertain. To analyze the relevance of these processes in vivo, we used a zebrafish animal model of invasive Aspergillosis. To confirm the validity of this model to test potential treatments for this disease, we confirmed that immunosuppressive treatments or neutropenia rendered zebrafish embryos more susceptible to A. fumigatus. We used GFP-Lc3 transgenic zebrafish to visualize the autophagy-related processes in innate immune phagocytes shortly after phagocytosis of A. fumigatus conidia, and found that both wild-type and melanin-deficient conidia elicited Lc3 recruitment. In macrophages, we observed GFP-Lc3 accumulation in puncta after phagocytosis, as well as short, rapid events of GFP-Lc3 decoration of single and multiple conidia-containing vesicles, while neutrophils covered single conidia-containing vesicles with bright and long-lasting GFP-Lc3 signal. Next, using genetic and pharmacological stimulation of three independent autophagy-inducing pathways, we showed that the antifungal autophagy response improves the host survival against A. fumigatus infection, but only in the presence of phagocytes. Therefore, we provide proof-of-concept that stimulating the (auto)phagolysosomal pathways is a promising approach to develop host-directed therapies against invasive Aspergillosis, and should be explored further either as adjunctive or stand-alone therapy for drug-resistant Aspergillus infections.

P321: PERTURBATIONS IN STIMULUS-INDUCED CYTOKINE RESPONSES IN CHILDREN WITH BCP-ALL

Background: B-cell precursor acute lymphoblastic leukemia (BCP-ALL) is the most common subtype of childhood leukemia with a peak during early childhood when children are exposed to viral infections. About 5% of all newborns carry a preleukemic clone, but only about 0,2% of them develop BCP-ALL later in life. It has been assumed that a dysregulated, altered immune response underlies the outgrowth of a pre-leukemic clone in infection-triggered B-cell precursor acute lymphoblastic leukemia (BCP-ALL). Aims: We investigated whether children with BCP-ALL differ in their cytokine response from healthy, age-matched, non-leukemic children, after immune cells were challenged with viral, fungal or bacterial stimuli. Methods: We set up a functional experimental platform with 73 stimulus-cytokine pairs to comprehensively characterize the immune profile of pediatric patients with BCP-ALL with the two most common genetic subtypes, either carrying the ETV6/RUNX1 (E/R) gene fusion or the high-hyperdiploid (HD) karyotype in comparison with an age-and gender-matched healthy control cohort without BCP-ALL and their healthy parents (in total n = 101 individuals). Children were in stable first remission, at least two years after the end of therapy and had a fully reconstituted immune system. Blood was taken of patients and controls in parallel and peripheral blood mononuclear cells (PBMCs) were isolated using a density gradient centrifugation. Cells had been stimulated with various fungal, bacterial and viral pathogens, such as Candida albicans, Staphylococcus aureus, Influenza virus, Respiratory Syncytial virus and toll-like receptor ligands (TLR), such as lipopolysaccharide (TLR4), R848 (TLR7/8) or CpG (TLR9); subsequently cytokines (IFNa, IL-1b, IL-1Ra, IL-10, IL-12p70, IL-17, IFNg) had been measured in the cell culture supernatant. Results: Cytokine base line level did not differ between the groups, while the challenge with various infectious antigens resulted in an overall elevated cytokine production of the BCP-ALL patients with E/R fusion (n=11) (p < 0.01, Mann-Whitney-Wilcoxon test two-sided with Benjamini-Hochberg correction). By deciphering the characteristics of the immune response, a remarkable difference for the anti-viral immune response (p < 0.01) was identified, while the anti-bacterial and anti-fungal response did not differ: The IFNa-response induced by Influenza virus and R848 and the IL-17-response induced by R848 differed most prominently, although not significantly after correction for multiple testing. Further analysis of the cytokine profile of the E/R parents compared with an age- and gender-matched healthy control group revealed an overall significantly elevated cytokine response (p < 0.05) after stimulation, but the different sub-features, such as the fungal, bacterial and viral immune responses were not different. Most strikingly, we could identify this pattern specifically for the E/R cohort. Comparing the cytokine responses of the HD patients (n=8) with the healthy controls (n=22) did not result in any significant differences. Image:Summary/Conclusion: Our study suggests that an altered pro-inflammatory anti-viral cytokine response pattern in children with E/R-BCP-ALL is specific to those children, who later developed the BCP-ALL. It is still present years after chemotherapy and possibly contributes to the outgrowth of a pre-leukemic clone, consistently generated in utero during fetal hematopoiesis.

Exposure of Keratinocytes to Candida Albicans in the Context of Atopic Milieu Induces Changes in the Surface Glycosylation Pattern of Small Extracellular Vesicles to Enhance Their Propensity to Interact With Inhibitory Siglec Receptors.

Candida albicans (C. albicans) infection is a potential complication in the individuals with atopic dermatitis (AD) and can affect clinical course of the disease. Here, using primary keratinocytes we determined that atopic milieu promotes changes in the interaction of small extracellular vesicles (sEVs) with dendritic cells and that this is further enhanced by the presence of C. albicans. sEV uptake is largely dependent on the expression of glycans on their surface; modelling of the protein interactions indicated that recognition of this pathogen through C. albicans-relevant pattern recognition receptors (PRRs) is linked to several glycosylation enzymes which may in turn affect the expression of sEV glycans. Here, significant changes in the surface glycosylation pattern, as determined by lectin array, could be observed in sEVs upon a combined exposure of keratinocytes to AD cytokines and C. albicans. This included enhanced expression of multiple types of glycans, for which several dendritic cell receptors could be proposed as binding partners. Blocking experiments showed predominant involvement of the inhibitory Siglec-7 and -9 receptors in the sEV-cell interaction and the engagement of sialic acid-containing carbohydrate moieties on the surface of sEVs. This pointed on ST6 β-Galactoside α-2,6-Sialyltransferase 1 (ST6GAL1) and Core 1 β,3-Galactosyltransferase 1 (C1GALT1) as potential enzymes involved in the process of remodelling of the sEV surface glycans upon C. albicans exposure. Our results suggest that, in combination with atopic dermatitis milieu, C. albicans promotes alterations in the glycosylation pattern of keratinocyte-derived sEVs to interact with inhibitory Siglecs on antigen presenting cells. Hence, a strategy aiming at this pathway to enhance antifungal responses and restrict pathogen spread could offer novel therapeutic options for skin candidiasis in AD.

Immunological Effects of Anti‒IL-17/12/23 Therapy in Patients with Psoriasis Complicated by Candida Infections

Biologics that block the T helper (Th) 17 pathway are very effective in the treatment of psoriasis and other inflammatory diseases. However, IL-17 is also crucial for antifungal host defense, and clinical trial data suggest an increase in the incidence of Candida infections during IL-17 inhibitor (IL-17i) therapy. We investigated the innate and adaptive immune responses of patients with psoriasis with a history of skin and/or mucosal candidiasis during IL-17i or IL-12/23 inhibitor therapy, comparing those responses with those of healthy controls. Patients with psoriasis with IL-17i showed significantly lower CD4+Th1-like (CCR6‒CXCR3+CCR4‒) and Th1 Th17-like (CD4+CCR6+CXCR3+CCR4‒) cell percentages. Patient cells stimulated with Candida albicans produced significantly lower IL-6 in the IL-12/23 inhibitor group and IL-1β in the IL-17i group, whereas the release of TNF-α and ROS was similar between patients and controls. IFN-γ and IL-10 production in response to several stimuli after 7 days was particularly decreased in patients receiving IL-17i therapy. Finally, after stimulation with the polarizing cytokines IL-1β and IL-23, the Th17 cytokine response was significantly lower in the IL-17i patient group. These innate and adaptive immune response defects can diminish antifungal host immune response and thereby increase susceptibility to candidiasis in patients treated with IL-17i or IL-12/23 inhibitor.

Recognition of Cell Wall Mannosylated Components as a Conserved Feature for Fungal Entrance, Adaptation and Survival Within Trophozoites of Acanthamoeba castellanii and Murine Macrophages.

Acanthamoeba castellanii (Ac) is a species of free-living amoebae (FLAs) that has been widely applied as a model for the study of host-parasite interactions and characterization of environmental symbionts. The sharing of niches between Ac and potential pathogens, such as fungi, favors associations between these organisms. Through predatory behavior, Ac enhances fungal survival, dissemination, and virulence in their intracellular milieu, training these pathogens and granting subsequent success in events of infections to more evolved hosts. In recent studies, our group characterized the amoeboid mannose binding proteins (MBPs) as one of the main fungal recognition pathways. Similarly, mannose-binding lectins play a key role in activating antifungal responses by immune cells. Even in the face of similarities, the distinct impacts and degrees of affinity of fungal recognition for mannose receptors in amoeboid and animal hosts are poorly understood. In this work, we have identified high-affinity ligands for mannosylated fungal cell wall residues expressed on the surface of amoebas and macrophages and determined the relative importance of these pathways in the antifungal responses comparing both phagocytic models. Mannose-purified surface proteins (MPPs) from both phagocytes showed binding to isolated mannose/mannans and mannosylated fungal cell wall targets. Although macrophage MPPs had more intense binding when compared to the amoeba receptors, the inhibition of this pathway affects fungal internalization and survival in both phagocytes. Mass spectrometry identified several MPPs in both models, and in silico alignment showed highly conserved regions between spotted amoeboid receptors (MBP and MBP1) and immune receptors (Mrc1 and Mrc2) and potential molecular mimicry, pointing to a possible convergent evolution of pathogen recognition mechanisms.

Human Conventional and Plasmacytoid Dendritic Cells Differ in Their Ability to Respond to Saccharomyces cerevisiae.

Saccharomyces cerevisiae is a commensal yeast colonizer of mucosal surfaces and an emerging opportunistic pathogen in the mucosa and bloodstream. The role of S. cerevisiae has been largely characterized in peripheral blood mononuclear cells and monocyte-derived dendritic cells, where yeast cells induce the production of inflammatory cytokines through the interaction with mannose receptors, chitin receptors, DC SIGN, and dectin1. However, the response of blood-circulating dendritic cells (DCs) to S. cerevisiae has never been investigated. Among blood DCs, conventional DCs (cDCs) are producers of inflammatory cytokines, while plasmacytoid DCs (pDCs) are a specialized population producing a large amount of interferon (IFN)-α, which is involved in the antiviral immune response. Here we report that both human DC subsets are able to sense S. cerevisiae. In particular, cDCs produce interleukin (IL)-6, express activation markers, and promotes T helper 17 cell polarization in response to yeasts, behaving similarly to monocyte-derived DCs as previously described. Interestingly, pDCs, not cDCs, sense fungal nucleic acids, leading to the generation of P1-pDCs (PD-L1+CD80–), a pDC subset characterized by the production of IFN-α and the induction of a Th profile producing IL-10. These results highlight a novel role of pDCs in response to S. cerevisiae that could be important for the regulation of the host microbiota–immune system balance and of anti-fungal immune response.

Radiation Exposure Perturbs IL-17RA-Mediated Immunity Leading to Changes in Neutrophil Responses That Increase Susceptibility to Oropharyngeal Candidiasis.

Fungal infections caused by Candida albicans are a serious problem for immunocompromised individuals, including those undergoing radiotherapy for head and neck cancers. Targeted irradiation causes inflammatory dysregulation and damage to the oral mucosa that can be exacerbated by candidiasis. Post-irradiation the cytokine interleukin-17 (IL-17) protects the oral mucosae by promoting oral epithelial regeneration and balancing the oral immune cell populations, which leads to the eventual healing of the tissue. IL-17 signaling is also critical for the antifungal response during oropharyngeal candidiasis (OPC). Yet, the benefit of IL-17 during other forms of candidiasis, such as vulvovaginal candidiasis, is not straightforward. Therefore, it was important to determine the role of IL-17 during OPC associated with radiation-induced inflammatory damage. To answer this question, we exposed Il17ra−/− and wild-type mice to head-neck irradiation (HNI) and OPC to determine if the IL-17 signaling pathway was still protective against C. albicans. HNI increased susceptibility to OPC, and in Il17ra−/− mice, the mucosal damage and fungal burden were elevated compared to control mice. Intriguingly, neutrophil influx was increased in Il17ra−/− mice, yet these cells had reduced capacity to phagocytose C. albicans and failed to clear OPC compared to immunocompetent mice. These findings suggest that radiotherapy not only causes physical damage to the oral cavity but also skews immune mediators, leading to increased susceptibility to oropharyngeal candidiasis.

IL-23 signaling limits ferroptosis-driven immunopathology during systemic fungal infection

Abstract Pattern recognition receptors initiate antifungal immune responses during infection. Recently, we identified that the ephrin type-A receptor 2 (EphA2) is a fungal β-glucan receptor which orchestrates innate immune responses and prevents oral Candida infection. However, the role of EphA2 during invasive candidiasis (IC) remains unknown. Here we found that EphA2 induces renal inflammation and injury; thus, promoting immunopathology during IC. In Epha2−/− mice, dendritic cells migrated more efficient in infected tissues, while secreting more IL-23. Furthermore, Epha2−/− mice had reduced lipid peroxidation in kidneys, a marker of ferroptotic cell death. Pharmacological inhibtion of ferroptosis increased macrophage fungal killing, reduced inflammation, and increased disease outcomes during IC. Previously, IL-23 signaling has been associated with myeloid cell survival during candidiasis. Treatment of macrophages with IL-23 reduced ferroptotic macrophage cell death and excessive inflammation, while increasing killing capacity. Furthermore, IL-23 treatment of infected mice increased survival and reduced ferroptosis during IC. Collectively, our study demonstrates that ferroptotic host cell death is linked to immunopathology and can be targeted by recombinant cytokine therapy during fungal infection. This work was supported in part by NIH grant R00DE026856, an American Association of Immunologists Careers in Immunology Fellowship, and a TLI Seed grant to MS

Batf3-dependent regulation of the antifungal inflammatory response after pulmonary Aspergillus fumigatus challenge

Abstract Aspergillus fumigatus is a ubiquitous fungus that causes invasive aspergillosis in immunocompromised individuals. The innate immune system is critical in the maintenance of host resistance against A. fumigatus. While it is well established that monocyte-derived dendritic cells (moDC) are critical in maintaining host resistance against A. fumigatus, the role of other dendritic cells populations has not been thoroughly explored. Here we demonstrate that Batf3-dependent cells, likely classical type 1 dendritic cells (cDC1s), are critical in preventing invasive aspergillosis. Surprisingly, Batf3(−/−) mice display an elevated inflammatory response against A. fumigatus, particularly IL-17A/F. We show that elevated concentrations of IL-17A/F in the lungs of Batf3(−/−) mice following A. fumigatus infection perpetuates the secretion of various inflammatory lung cytokines in vivo. Neutralization of both IL-17A and IL-17F in Batf3(−/−) mice prevent excessive cytokine secretion and mortality due to A. fumigatus challenge of Batf3(−/−) mice. Following A. fumigatus challenge regulatory T cells are known to limit inflammation. Our preliminary antibody-mediated depletion studies demonstrate that CD4+ CD25+ T cells may be involved in preventing excessive IL-17A/F release in immunocompetent mice. In this study we have identified a critical role for Batf3-dependent cells in limiting A. fumigatus induced inflammatory and mortality due to IL-17 driven lung pathology. Supported by NIH: [R01 AI139133-01A1]

T cell intrinsic Nod2 controls Th17 immunity to Candida albicans infection

Abstract We recently discovered a role for Nod2 within T cells in controlling Th17-immunity, such that deletion of Nod2 exacerbated experimental autoimmune arthritis and uveitis. Protection against opportunistic Candida albicans infection relies on intact Th17-responses. Thus, we considered whether the T cell intrinsic Nod2 might control antifungal Th17 responses at the cost of increasing host susceptibility to autoimmunity. Nod2−/− mice infected with 105 (LD50) Candida albicans had increased survival and reduced fungal burden in the kidney within 24–72 h post-infection, suggesting a critical role for Nod2 in C. albicans immunity. Rag−/− mice reconstituted with Nod2fl/fl/CD4-cre CD4+ T cells and infected with C. albicans had decreased fungal burden compared to control CD4-Cre T cell recipients, and IL-17 depletion reverted the phenotype. After 48h infection, Nod2fl/fl/CD4-cre CD4+ T cells in the kidney had increased activation (CD69), increased proportion of T effector cells, and decreased Tregs compared to controls, suggesting endogenous Nod2 negatively regulates fungal-triggered Teff/Th17 cell responses. We next asked how Nod2 might function in SKG mice that are genetically susceptible to arthritis. Whereas Nod2−/− SKG mice developed an exacerbated form of arthritis compared to Nod2+/+ SKG controls, these same mice cleared C. albicans infection better than Nod2+/+ SKG mice. Cumulatively our data indicate a critical role for T cell intrinsic Nod2 in antifungal Th17 immunity. Given these studies we posit that human NOD2 genetic variants may offer enhanced ability to fight fungal infection via a T cell intrinsic mechanism, at the cost of triggering autoimmunity. Supported by grants from VA (CDA-2 IK2BX004523 and Merit I01BX002180) and NIH (R01 EY025250).

Suppression of Aspergillus fumigatus Germination by Neutrophils Is Enhanced by Endothelial-Derived CSF3 Production.

Infection with Aspergillus fumigatus can cause life-threatening diseases in immunocompromised patients with an unacceptable mortality rate. Angioinvasion is one of the features of severe invasive aspergillosis. Neutrophils are short-lived immune cells regulated by colony-stimulating factor 3 (CSF3) that play a key role in anti-fungal immune responses. To investigate the interactions between A. fumigatus and the host immune cells, such as neutrophils, we stimulated human umbilical vein endothelial cells (HUVECs) with the conidia of A. fumigatus, and co-cultured them with human neutrophils. Apoptosis and functions of neutrophils were analyzed. Our results showed that HUVECs upregulate the expression of CSF3, which could reduce the apoptosis of neutrophils while enhancing their functions. Lack of CSF3 was associated with enhanced apoptosis of neutrophils with impaired function. This work indicated that the CSF3 is required for neutrophil survival and function, at least in the early stages of A. fumigatus infection.

CCPG1 involved in corneal Aspergillus fumigatus infection

To investigate whether non-canonical autophagy transport receptor cell cycle progression 1 (CCPG1) is involved in the corneal antifungal immune response. Human corneal epithelial cells (HCECs) and human myeloid leukemia mononuclear cells (THP-1) macrophages stimulated by Aspergillus fumigatus (A. fumigatus) were used as cell models. The expression of CCPG1 mRNA was detected by qRT-PCR. Western blot was used to determine the protein expression of CCPG1 and interleukin-1β (IL-1β). The dectin-1 neutralizing antibody was used to detect the association between dectin-1 and CCPG1. Immunofluorescence was used to observe the colocalization of CCPG1 and C-type lectin-like receptor-1 (CLEC-1) in THP-1 macrophages. The expression of CCPG1 started to increase at 4h after infection and increased in a time-dependent manner in HCECs and THP-1 macrophages. With dectin-1 neutralizing antibody pretreatment, the expression of IL-1β was down-regulated. CCPG1 up-regulation in response to A. fumigatus infection was independent of dectin-1. Immunofluorescence showed the colocalization of CCPG1 and CLEC-1 in THP-1 macrophages. As a specific autophagy protein of non-canonical autophagy pathway, CCPG1 is involved in corneal infection with A. fumigatus.

Inhibition of Galectin-3 Impairs Antifungal Immune Response in Fungal Keratitis.

Galectin-3 is one of the galectin family members which are master regulators of immune homeostasis, especially in infectious diseases. However, its mechanism of immune regulation in fungal keratitis has not been thoroughly studied. Our study is aimed at clarifying the role of galectin-3 in the fungal keratitis mouse model in vivo, thereby providing a new biomarker of antifungal therapy. In our study, aspergillus, the most common pathogenic fungi of fungal keratitis, was identified and isolated by corneal tissue fungus culture. Then, the RNA expression levels of galectin family members in corneas of the mouse model with aspergillus fumigatus keratitis were screened by transcriptome sequencing (RNA-seq). The expression of the galectin-3 was detected by quantitative real-time Polymerase Chain Reaction (qPCR), enzyme-linked immunosorbent assay (ELISA), and immunofluorescence in the corneal tissue of the fungal keratitis mouse model. Recruitment of neutrophils and the co-immunofluorescence of galectin-3 and related markers in corneal tissue were determined by flow cytometry analysis and immunofluorescence staining. The regulatory role of galectin-3 for proinflammatory cytokines and neutrophils was validated by the knockout mouse model. Galectin-3 knockout deteriorated the condition for the inhibition of galectin-3 was benefecial for fungi to survive and thrive in corneal lesions. These results demonstrated that in the ocular fungal infection, galectin-3 is capable of regulating the pathogenesis of fungal keratitis by modulating neutrophil recruitment. The deterioration of fungal keratitis and increased fungal load in corneal lesions of galectin-3 knockout mice proved the regulatory role of galectin-3 in fungal keratitis. In conclusion, galectin-3 is going to be an essential target to modulate neutrophil recruitment and its related antifungal immune response in fungal keratitis.

Phagosomal signalling of the C-type lectin receptor Dectin-1 is terminated by intramembrane proteolysis

Sensing of pathogens by pattern recognition receptors (PRR) is critical to initiate protective host defence reactions. However, activation of the immune system has to be carefully titrated to avoid tissue damage necessitating mechanisms to control and terminate PRR signalling. Dectin-1 is a PRR for fungal β-glucans on immune cells that is rapidly internalised after ligand-binding. Here, we demonstrate that pathogen recognition by the Dectin-1a isoform results in the formation of a stable receptor fragment devoid of the ligand binding domain. This fragment persists in phagosomal membranes and contributes to signal transduction which is terminated by the intramembrane proteases Signal Peptide Peptidase-like (SPPL) 2a and 2b. Consequently, immune cells lacking SPPL2b demonstrate increased anti-fungal ROS production, killing capacity and cytokine responses. The identified mechanism allows to uncouple the PRR signalling response from delivery of the pathogen to degradative compartments and identifies intramembrane proteases as part of a regulatory circuit to control anti-fungal immune responses.

Immune regulation by fungal strain diversity in inflammatory bowel disease.

The fungal microbiota (mycobiota) is an integral part of the complex multikingdom microbial community colonizing the mammalian gastrointestinal tract and has an important role in immune regulation1-6. Although aberrant changes in the mycobiota have been linked to several diseases, including inflammatory bowel disease3-9, it is currently unknown whether fungal species captured by deep sequencing represent living organisms and whether specific fungi have functional consequences for disease development in affected individuals. Here we developed a translational platform for the functional analysis of the mycobiome at the fungal-strain- and patient-specific level. Combining high-resolution mycobiota sequencing, fungal culturomics and genomics, a CRISPR-Cas9-based fungal strain editing system, in vitro functional immunoreactivity assays and in vivo models, this platform enables the examination of host-fungal crosstalk in the human gut. We discovered a rich genetic diversity of opportunistic Candida albicans strains that dominate the colonic mucosa of patients with inflammatory bowel disease. Among these human-gut-derived isolates, strains with high immune-cell-damaging capacity (HD strains) reflect the disease features of individual patients with ulcerative colitis and aggravated intestinal inflammation in vivo through IL-1β-dependent mechanisms. Niche-specific inflammatory immunity andinterleukin-17A-producing T helper cell (TH17 cell) antifungal responses by HD strains in the gut were dependent on the C. albicans-secreted peptide toxin candidalysin during the transition from a benign commensal to a pathobiont state. These findings reveal the strain-specific nature of host-fungal interactions in the human gut and highlight new diagnostic and therapeutic targets for diseases of inflammatory origin.