Vitamin D regulation of OX40 ligand in immune responses to Aspergillus fumigatus

Aspergillus in Children and Young People with Cystic Fibrosis: A Narrative Review

Cystic fibrosis is a severe, inherited, life-limiting disorder, and over half of those living with CF are children. Persistent airway infection and inflammation, resulting in progressive lung function decline, is the hallmark of this disorder. Aspergillus colonization and infection is a well-known complication in people with CF and can evolve in a range of Aspergillus disease phenotypes, including Aspergillus bronchitis, fungal sensitization, and allergic bronchopulmonary aspergillosis (ABPA). Management strategies for children with CF are primarily aimed at preventing lung damage and lung function decline caused by bacterial infections. The role of Aspergillus infections is less understood, especially during childhood, and therefore evidence-based diagnostic and treatment guidelines are lacking. This narrative review summarizes our current understanding of the impact of Aspergillus on the airways of children and young people with CF.

Impact of Vitamin D on Skin Aging, and Age-Related Dermatological Conditions

Human skin is a physical and biochemical barrier that protects the internal body from the external environment. Throughout a person's life, the skin undergoes both intrinsic and extrinsic aging, leading to microscopic and macroscopic changes in its morphology. In addition, the repair processes slow with aging, making the older population more susceptible to skin diseases. Intrinsic factors associated with advanced age gradually degrade the dermal collagen matrix, resulting in fine wrinkles and reduced elasticity; this is accelerated in post-menopausal women due to estrogen deficiency. In contrast, extrinsic factors associated with advanced age, primarily caused by exposure to ultraviolet (UV) radiation, lead to coarse wrinkles, solar elastosis, hyperkeratosis, irregular pigmentation, and skin cancers. UVB radiation, while contributing to skin photo-aging, also induces the cutaneous synthesis of vitamin D. Vitamin D, in turn, protects the skin from oxidative stress, inflammation, and DNA damage, thereby delaying both chronological and photo-aging. Moreover, research has demonstrated an association between lower vitamin D levels and a higher prevalence of certain cutaneous diseases. This review explores and summarizes the critical role of vitamin D in skin aging and age-related skin diseases. The data presented highlight the importance of maintaining vitamin D adequacy throughout life.

Treatment of allergic bronchopulmonary aspergillosis: from evidence to practice

Allergic bronchopulmonary aspergillosis (ABPA) is a complex pulmonary disorder caused by dysregulated immune responses against Aspergillus fumigatus. The disorder usually complicates the course of patients with asthma and cystic fibrosis. Patients with ABPA most often present with asthma that is poorly controlled despite inhaled corticosteroids and long-acting β2 agonists. The treatment of ABPA is complicated due to the occurrence of recurrent exacerbations and spontaneous remissions. The drugs used for treating ABPA include systemic glucocorticoids, antifungal agents and biologics, each with its own benefits and drawbacks. In this review, we illustrate the treatment pathway for ABPA in different situations, using a case-based approach. In each case, we present the options for treatment based on the available evidence from recent clinical trials.

Polymorphisms within the TNFSF4 and MAPKAPK2 Loci Influence the Risk of Developing Invasive Aspergillosis: A Two-Stage Case Control Study in the Context of the aspBIOmics Consortium

Here, we assessed whether 36 single nucleotide polymorphisms (SNPs) within the TNFSF4 and MAPKAPK2 loci influence the risk of developing invasive aspergillosis (IA). We conducted a two-stage case control study including 911 high-risk patients diagnosed with hematological malignancies that were ascertained through the aspBIOmics consortium. The meta-analysis of the discovery and replication populations revealed that carriers of the TNFSF4 _rs7526628T/T genotype had a significantly increased risk of developing IA (p = 0.00022). We also found that carriers of the TNFSF4 _rs7526628T allele showed decreased serum levels of TNFSF14 protein (p = 0.0027), and that their macrophages had a decreased fungicidal activity (p = 0.048). In addition, we observed that each copy of the MAPKAPK2 _rs12137965G allele increased the risk of IA by 60% (p = 0.0017), whereas each copy of the MAPKAPK2 _rs17013271T allele was estimated to decrease the risk of developing the disease (p = 0.0029). Mechanistically, we found that carriers of the risk MAPKAPK2 _rs12137965G allele showed increased numbers of CD38+IgM-IgD- plasmablasts in blood (p = 0.00086), whereas those harboring two copies of the allele had decreased serum concentrations of thymic stromal lymphopoietin (p = 0.00097). Finally, we also found that carriers of the protective MAPKAPK2 _rs17013271T allele had decreased numbers of CD27-IgM-IgD- B cells (p = 0.00087) and significantly lower numbers of CD14+ and CD14+CD16- cells (p = 0.00018 and 0.00023). Altogether, these results suggest a role of the TNFSF4 and MAPKAPK2 genes in determining IA risk.

Modulating local airway immune responses to treat allergic asthma: lessons from experimental models and human studies

With asthma affecting over 300 million individuals world-wide and estimated to affect 400 million by 2025, developing effective, long-lasting therapeutics is essential. Allergic asthma, where Th2-type immunity plays a central role, represents 90% of child and 50% of adult asthma cases. Research based largely on animal models of allergic disease have led to the generation of a novel class of drugs, so-called biologicals, that target essential components of Th2-type inflammation. Although highly efficient in subclasses of patients, these biologicals and other existing medication only target the symptomatic stage of asthma and when therapy is ceased, a flare-up of the disease is often observed. Therefore, it is suggested to target earlier stages in the inflammatory cascade underlying allergic airway inflammation and to focus on changing and redirecting the initiation of type 2 inflammatory responses against allergens and certain viral agents. This focus on upstream aspects of innate immunity that drive development of Th2-type immunity is expected to have longer-lasting and disease-modifying effects, and may potentially lead to a cure for asthma. This review highlights the current understanding of the contribution of local innate immune elements in the development and maintenance of inflammatory airway responses and discusses available leads for successful targeting of those pathways for future therapeutics.

Vitamin D levels in asthmatic patients with and without allergic bronchopulmonary aspergillosis

Vitamin D deficiency is believed to be a pathogenetic factor in patients with allergic bronchopulmonary aspergillosis (ABPA) and cystic fibrosis. Whether vitamin D deficiency is also prevalent in ABPA complicating asthma, remains unknown. Herein, we evaluated vitamin D levels in asthmatic patients with and without ABPA. In a prospective study, plasma vitamin D (25[OH]D) levels were measured in consecutive subjects with asthma (n = 75), ABPA (n = 158) and healthy volunteers (n = 50). Vitamin D levels <20 ng/mL were considered as vitamin D deficiency. There was no difference in mean (95% CI) vitamin D levels between healthy controls (15.3 [12.7-17.9]), asthmatics (19.2 [16.3-22.1]) and subjects with ABPA (18.9 [16.9-20.8]) (P = .22). Vitamin D deficiency was encountered in 70%, 64% and 65% of the healthy controls, asthmatics and ABPA subjects, respectively, and was not different between the groups (P = .79). There was no difference in the asthma control, pulmonary function, immunological findings and the severity of bronchiectasis, in patients with ABPA, with and without vitamin D deficiency. Vitamin D deficiency is equally prevalent in asthmatic patients with or without ABPA in the Indian subcontinent, and does not appear to play a major role in the pathogenesis of ABPA complicating asthma.

Dietary vitamin D3 deficiency exacerbates sinonasal inflammation and alters local 25(OH)D3 metabolism

RATIONALE

Patients with chronic rhinosinusitis with nasal polyps (CRSwNP) have been shown to be vitamin D3 (VD3) deficient, which is associated with more severe disease and increased polyp size. To gain mechanistic insights into these observational studies, we examined the impact of VD3 deficiency on inflammation and VD3 metabolism in an Aspergillus fumigatus (Af) mouse model of chronic rhinosinusitis (Af-CRS).

METHODS

Balb/c mice were fed control or VD3 deficient diet for 4 weeks. Mice were then sensitized with intraperitoneal Af, and one week later given Af intranasally every three days for four weeks while being maintained on control or VD3 deficient diet. Airway function, sinonasal immune cell infiltrate and sinonasal VD3 metabolism profiles were then examined.

RESULTS

Mice with VD3 deficiency had increased Penh and sRaw values as compared to controls as well as exacerbated changes in sRaw when coupled with Af-CRS. As compared to controls, VD3 deficient and Af-CRS mice had reduced sinonasal 1α-hydroxylase and the active VD3 metabolite, 1,25(OH)2D3. Differential analysis of nasal lavage samples showed that VD3 deficiency alone and in combination with Af-CRS profoundly upregulated eosinophil, neutrophil and lymphocyte numbers. VD3 deficiency exacerbated increases in monocyte-derived dendritic cell (DC) associated with Af-CRS. Conversely, T-regulatory cells were decreased in both Af-CRS mice and VD3 deficient mice, though coupling VD3 deficiency with Af-CRS did not exacerbate CD4 or T-regulatory cells numbers. Lastly, VD3 deficiency had a modifying or exacerbating impact on nasal lavage levels of IFN-γ, IL-6, IL-10 and TNF-α, but had no impact on IL-17A.

CONCLUSIONS

VD3 deficiency causes changes in sinonasal immunity, which in many ways mirrors the changes observed in Af-CRS mice, while selectively exacerbating inflammation. Furthermore, both VD3 deficiency and Af-CRS were associated with altered sinonasal VD3 metabolism causing reductions in local levels of the active VD3 metabolite, 1,25(OH)2D3, even with adequate circulating levels.

Immunotherapeutic approaches to treatment of fungal diseases

Fungal infections cause morbidity worldwide and are associated with an unacceptably high mortality despite the availability of antifungal drugs. The incidence of mycoses is rising because of the HIV pandemic and because immunomodulatory drugs are increasingly used to treat autoimmune diseases and cancer. New classes of antifungal drugs have only been partly successful in improving the prognosis for patients with fungal infection. Adjunctive host-directed therapy is therefore believed to be the only option to further improve patient outcomes. Recent advances in the understanding of complex interactions between fungi and host have led to the design and exploration of novel therapeutic strategies in cytokine therapy, vaccines, and cellular immunotherapy, each of which might become viable adjuncts to existing antifungal regimens. In this report, we discuss immunotherapeutic approaches-the rationale behind their design, the challenges in their use, and the progress that is so urgently needed to overcome the devastating effect of fungal diseases.

Critical Role of Transcription Factor PU.1 in the Function of the OX40L/TNFSF4 Promoter in Dendritic Cells

PU.1 is a hematopoietic lineage-specific transcription factor belonging to the Ets family. We investigated the role of PU.1 in the expression of OX40L in dendritic cells (DCs), because the regulatory mechanism of cell type-specific expression of OX40L, which is mainly restricted to antigen-presenting cells, is largely unknown despite the critical involvement in Th2 and Tfh development. PU.1 knockdown decreased the expression of OX40L in mouse DCs. Chromatin immunoprecipitation (ChIP) assays demonstrated that PU.1 constitutively bound to the proximal region of the OX40L promoter. Reporter assays and electrophoretic mobility shift assays revealed that PU.1 transactivated the OX40L promoter through direct binding to the most-proximal Ets motif. We found that this Ets motif is conserved between mouse and human, and that PU.1 bound to the human OX40L promoter in ChIP assay using human monocyte-derived DCs. ChIP assays based on ChIP-seq datasets revealed that PU.1 binds to several sites distant from the transcription start site on the OX40L gene in addition to the most-proximal site in mouse DCs. In the present study, the structure of the OX40L promoter regulated by PU.1 is determined. It is also suggested that PU.1 is involved in mouse OX40L expression via multiple binding sites on the gene.

Pattern recognition pathways leading to a Th2 cytokine bias in allergic bronchopulmonary aspergillosis patients

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 IFNγ (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, β-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 IFNγ production compared with healthy controls. All biological agents tested showed the capability to inhibit Th2 responses, but also decreased Aspergillus-induced IFNγ.

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 IFNγ therapy in ABPA as a corticosteroid-sparing treatment option, by dampening Th2 responses and supplementing the IFNγ deficiency at the same time.

Regulation of Dendritic Cell Function by Vitamin D

Studies over the last two decades have revealed profound immunomodulatory aspects of vitamin D on various aspects of the immune system. This review will provide an overview of Vitamin D metabolism, a description of dendritic cell subsets, and highlight recent advances on the effects of vitamin D on dendritic cell function, maturation, cytokine production and antigen presentation. The active form of vitamin D, 1,25(OH)₂D₃, has important immunoregulatory and anti-inflammatory effects. Specifically, the 1,25(OH)₂D₃-Vitamin D₃ complex can affect the maturation and migration of many dendritic cell subsets, conferring a special immunoregulatory role as well as tolerogenic properties affecting cytokine and chemokine production. Furthermore, there have been many recent studies demonstrating the effects of Vitamin D on allergic disease and autoimmunity. A clear understanding of the effects of the various forms of Vitamin D will provide new opportunities to improve human health.

Vitamin D every day to keep the infection away?

Within the last decade, vitamin D has emerged as a central regulator of host defense against infections. In this regard, vitamin D triggers effective antimicrobial pathways against bacterial, fungal and viral pathogens in cells of the human innate immune system. However, vitamin D also mediates potent tolerogenic effects: it is generally believed that vitamin D attenuates inflammation and acquired immunity, and thus potentially limits collateral tissue damage. Nevertheless, several studies indicate that vitamin D promotes aspects of acquired host defense. Clinically, vitamin D deficiency has been associated with an increased risk for various infectious diseases in epidemiological studies; yet, robust data from controlled trials investigating the use of vitamin D as a preventive or therapeutic agent are missing. In this review, we summarize the current knowledge regarding the effect of vitamin D on innate and acquired host defense, and speculate on the difficulties to translate the available molecular medicine data into practical therapeutic or preventive recommendations.

Inflammation and Nutritional Science for Programs/Policies and Interpretation of Research Evidence (INSPIRE)

An increasing recognition has emerged of the complexities of the global health agenda—specifically, the collision of infections and noncommunicable diseases and the dual burden of over- and undernutrition. Of particular practical concern are both 1) the need for a better understanding of the bidirectional relations between nutritional status and the development and function of the immune and inflammatory response and 2) the specific impact of the inflammatory response on the selection, use, and interpretation of nutrient biomarkers. The goal of the Inflammation and Nutritional Science for Programs/Policies and Interpretation of Research Evidence (INSPIRE) is to provide guidance for those users represented by the global food and nutrition enterprise. These include researchers (bench and clinical), clinicians providing care/treatment, those developing and evaluating programs/interventions at scale, and those responsible for generating evidence-based policy. The INSPIRE process included convening 5 thematic working groups (WGs) charged with developing summary reports around the following issues: 1) basic overview of the interactions between nutrition, immune function, and the inflammatory response; 2) examination of the evidence regarding the impact of nutrition on immune function and inflammation; 3) evaluation of the impact of inflammation and clinical conditions (acute and chronic) on nutrition; 4) examination of existing and potential new approaches to account for the impact of inflammation on biomarker interpretation and use; and 5) the presentation of new approaches to the study of these relations. Each WG was tasked with synthesizing a summary of the evidence for each of these topics and delineating the remaining gaps in our knowledge. This review consists of a summary of the INSPIRE workshop and the WG deliberations.

Human CD141+ dendritic cells induce CD4+ T cells to produce type 2 cytokines

Dendritic cells (DCs) play the central role in the priming of naive T cells and the differentiation of unique effector T cells. In this study, using lung tissues and blood from both humans and humanized mice, we analyzed the response of human CD1c(+) and CD141(+) DC subsets to live-attenuated influenza virus. Specifically, we analyzed the type of CD4(+) T cell immunity elicited by live-attenuated influenza virus-exposed DCs. Both DC subsets induce proliferation of allogeneic naive CD4(+) T cells with the capacity to secrete IFN-γ. However, CD141(+) DCs are uniquely able to induce the differentiation of IL-4- and IL-13-producing CD4(+) T cells. CD141(+) DCs induce IL-4- and IL-13-secreting CD4(+) T cells through OX40 ligand. Thus, CD141(+) DCs demonstrate remarkable plasticity in guiding adaptive immune responses.

Vitamin D and experimental invasive aspergillosis

Immune cells express the vitamin D receptor and vitamin D metabolizing enzymes. Favorable vitamin D effects have been indicated in tuberculosis. Vitamin D deficiency increases T helper (Th) 2 responses to Aspergillus, and it suppresses Th2 responses in cystic fibrosis-allergic bronchopulmonary aspergillosis. Can vitamin D modulate the proinflammatory effects of amphotericin B (AmB) therapy in aspergillosis? Groups of mice were infected intravenously (IV) with 3-8 × 10(6) Aspergillus fumigatus conidia. In six experiments, doses of 0.08, 2, or 4 μg/kg calcitriol (active form of vitamin D) were given intraperitoneally +/- AmB-deoxycholate (AmBd) at 0.4, 0.8, 1.2, 1.8, 3.3, or 4.5 mg/kg or 0.8 or 1.2 mg/kg IV. Calcitriol doses were selected to range from doses used in humans to those just below doses shown to decalcify murine bones. In most experiments, doses of calcitriol and AmBd (or control diluents) were given five times, on alternate days, to minimize drug-drug interactions. Calcitriol treatment began on the day of challenge, and survival assessed for 10 days. In no experiments did calcitriol alone significantly worsen or enhance survival or affect residual infection in survivors. Calcitriol also did not affect the efficacy of AmBd. In a representative experiment, AmBd at 0.8 or 1.2 mg/kg IV alone +/- calcitriol at 2 μg/kg enhanced survival (P ≤ 0.01). However, the AmBd regimens with calcitriol were not different than those without, and calcitriol alone was identical to controls. In disseminated invasive aspergillosis, calcitriol did not affect outcome nor influence antifungal efficacy.

Directing traffic: IL-17 and IL-22 coordinate pulmonary immune defense

Respiratory infections and diseases are among the leading causes of death worldwide, and effective treatments probably require manipulating the inflammatory response to pathogenic microbes or allergens. Here, we review mechanisms controlling the production and functions of interleukin-17 (IL-17) and IL-22, cytokines that direct several aspects of lung immunity. Innate lymphocytes (γδ T cells, natural killer cells, innate lymphoid cells) are the major source of IL-17 and IL-22 during acute infections, while CD4(+) T-helper 17 (Th17) cells contribute to vaccine-induced immunity. The characterization of dendritic cell (DC) subsets has revealed their central roles in T-cell activation. CD11b(+) DCs stimulated with bacteria or fungi secrete IL-1β and IL-23, potent inducers of IL-17 and IL-22. On the other hand, recognition of viruses by plasmacytoid DCs inhibits IL-1β and IL-23 release, increasing susceptibility to bacterial superinfections. IL-17 and IL-22 primarily act on the lung epithelium, inducing antimicrobial proteins and neutrophil chemoattractants. Recent studies found that stimulation of macrophages and DCs with IL-17 also contributes to antibacterial immunity, while IL-22 promotes epithelial proliferation and repair following injury. Chronic diseases such as asthma and chronic obstructive pulmonary disease have been associated with IL-17 and IL-22 responses directed against innocuous antigens. Future studies will evaluate the therapeutic efficacy of targeting the IL-17/IL-22 pathway in pulmonary inflammation.

Immunoevasive Aspergillus virulence factors

Individuals with structural lung disease or defective immunity are predisposed to Aspergillus-associated disease. Manifestations range from allergic to cavitary or angio-invasive syndromes. Despite daily spore inhalation, immunocompetence facilitates clearance through initiation of innate and adaptive host responses. These include mechanical barriers, phagocyte activation, antimicrobial peptide release and pattern recognition receptor activation. Adaptive responses include Th1 and Th2 approaches. Understanding Aspergillus virulence mechanisms remains critical to the development of effective research and treatment strategies to counteract the fungi. Major virulence factors relate to fungal structure, protease release and allergens; however, mechanisms utilized to evade immune recognition continue to be important in establishing infection. These include the fungal rodlet layer, dihydroxynaphthalene-melanin, detoxifying systems for reactive oxygen species and toxin release. One major immunoevasive toxin, gliotoxin, plays a key role in mediating Aspergillus-associated colonization in the context of cystic fibrosis. Here, it down-regulates vitamin D receptor expression which following itraconazole therapy is rescued concurrent with decreased Th2 cytokine (IL-5 and IL-13) concentrations in the CF airway. This review focuses on the interaction between Aspergillus pathogenic mechanisms, host immune responses and the immunoevasive strategies employed by the organism during disease states such as that observed in cystic fibrosis.

Fungi in the cystic fibrosis lung: bystanders or pathogens?

Improvement to the life expectancy of people with cystic fibrosis (PWCF) brings about novel challenges including the need for evaluation of the role of fungi in the cystic fibrosis (CF) lung. To determine if such organisms represent bystanders or pathogens affecting clinical outcomes we review the existing knowledge from a clinical, biochemical, inflammatory and immunological perspective. The prevalence and importance of fungi in the CF airway has likely been underestimated with the most frequently isolated filamentous fungi being Aspergillus fumigatus and Scedosporium apiospermum and the major yeast Candida albicans. Developing non-culture based microbiological methods for fungal detection has improved both our classification and understanding of their clinical consequences including localized, allergic and systemic infections. Cross-kingdom interaction between bacteria and fungi are discussed as is the role of biofilms further affecting clinical outcome. A combination of host and pathogen-derived factors determines if a particular fungus represents a commensal, colonizer or pathogen in the setting of CF. The underlying immune state, disease severity and treatment burden represent key host variables whilst fungal type, form, chronicity and virulence including the ability to evade immune recognition determines the pathogenic potential of a specific fungus at a particular point in time. Further research in this emerging field is warranted to fully elucidate the spectrum of disease conferred by the presence of fungi in the CF airway and the indications for therapeutic interventions.