IFN-gamma-inducing factor (IL-18) increases allergic sensitization, serum IgE, Th2 cytokines, and airway eosinophilia in a mouse model of allergic asthma

Progressive accumulation of hyperinflammatory NKG2Dlow NK cells in early childhood severe atopic dermatitis

Atopic dermatitis (AD) is a chronic inflammatory skin disease that often precedes the development of food allergy, asthma, and allergic rhinitis. The prevailing paradigm holds that a reduced frequency and function of natural killer (NK) cell contributes to AD pathogenesis, yet the underlying mechanisms and contributions of NK cells to allergic comorbidities remain ill-defined. Here, analysis of circulating NK cells in a longitudinal early life cohort of children with AD revealed a progressive accumulation of NK cells with low expression of the activating receptor NKG2D, which was linked to more severe AD and sensitivity to allergens. This was most notable in children co-sensitized to food and aeroallergens, a risk factor for development of asthma. Individual-level longitudinal analysis in a subset of children revealed coincident reduction of NKG2D on NK cells with acquired or persistent sensitization, and this was associated with impaired skin barrier function assessed by transepidermal water loss. Low expression of NKG2D on NK cells was paradoxically associated with depressed cytolytic function but exaggerated release of the proinflammatory cytokine tumor necrosis factor-α. These observations provide important insights into a potential mechanism underlying the development of allergic comorbidity in early life in children with AD, which involves altered NK cell functional responses, and define an endotype of severe AD.

Allergen-induced CD11c + dendritic cell pyroptosis aggravates allergic rhinitis

BACKGROUND

Pyroptosis is crucial for controlling various immune cells. However, the role of allergen-induced CD11c + dendritic cell (DC) pyroptosis in allergic rhinitis (AR) remains unclear.

METHODS

Mice were grouped into the control group, AR group and necrosulfonamide-treated AR group (AR + NSA group). The allergic symptom scores, OVA-sIgE titres, serum IL-1β/IL-18 levels, histopathological characteristics and T-helper cell-related cytokines were evaluated. CD11c/GSDMD-N-positive cells were examined by immunofluorescence analysis. Murine CD11c + bone marrow-derived DCs (BMDCs) were induced in vitro, stimulated with OVA/HDM, treated with necrosulfonamide (NSA), and further cocultured with lymphocytes to assess BMDC function. An adoptive transfer murine model was used to study the role of BMDC pyroptosis in allergic rhinitis.

RESULTS

Inhibiting GSDMD-N-mediated pyroptosis markedly protected against Th1/Th2/Th17 imbalance and alleviated inflammatory responses in the AR model. GSDMD-N was mainly coexpressed with CD11c (a DC marker) in AR mice. In vitro, OVA/HDM stimulation increased pyroptotic morphological abnormalities and increased the expression of pyroptosis-related proteins in a dose-dependent manner; moreover, inhibiting pyroptosis significantly decreased pyroptotic morphology and NLRP3, C-Caspase1 and GSDMD-N expression. In addition, OVA-induced BMDC pyroptosis affected CD4 + T-cell differentiation and related cytokine levels, leading to Th1/Th2/Th17 cell imbalance. However, the Th1/Th2/Th17 cell immune imbalance was significantly reversed by NSA. Adoptive transfer of OVA-loaded BMDCs promoted allergic inflammation, while the administration of NSA to OVA-loaded BMDCs significantly reduced AR inflammation.

CONCLUSION

Allergen-induced dendritic cell pyroptosis promotes the development of allergic rhinitis through GSDMD-N-mediated pyroptosis, which provides a clue to allergic disease interventions. Video Abstract.

Progressive accumulation of hyperinflammatory NKG2D low NK cells in early childhood severe atopic dermatitis

Atopic dermatitis (AD) is a chronic inflammatory skin disease that often precedes the development of food allergy, asthma, and allergic rhinitis. The prevailing paradigm holds that a reduced frequency and function of natural killer (NK) cell contributes to AD pathogenesis, yet the underlying mechanisms and contributions of NK cells to allergic co-morbidities remain ill-defined. Herein, analysis of circulating NK cells in a longitudinal early life cohort of children with AD revealed a progressive accumulation of NK cells with low expression of the activating receptor NKG2D, which was linked to more severe AD and sensitivity to allergens. This was most notable in children co-sensitized to food and aero allergens, a risk factor for development of asthma. Individual-level longitudinal analysis in a subset of children revealed co-incident reduction of NKG2D on NK cells with acquired or persistent sensitization, and this was associated with impaired skin barrier function assessed by transepidermal water loss. Low expression of NKG2D on NK cells was paradoxically associated with depressed cytolytic function but exaggerated release of the proinflammatory cytokine TNF-α. These observations provide important insights into a potential mechanism underlying the development of allergic co-morbidity in early life in children with AD which involves altered NK-cell functional responses, and define an endotype of severe AD.

Recombinant BCG to Enhance Its Immunomodulatory Activities

The bacillus Calmette-Guérin (BCG) is an attenuated Mycobacterium bovis derivative that has been widely used as a live vaccine against tuberculosis for a century. In addition to its use as a tuberculosis vaccine, BCG has also been found to have utility in the prevention or treatment of unrelated diseases, including cancer. However, the protective and therapeutic efficacy of BCG against tuberculosis and other diseases is not perfect. For three decades, it has been possible to genetically modify BCG in an attempt to improve its efficacy. Various immune-modulatory molecules have been produced in recombinant BCG strains and tested for protection against tuberculosis or treatment of several cancers or inflammatory diseases. These molecules include cytokines, bacterial toxins or toxin fragments, as well as other protein and non-protein immune-modulatory molecules. The deletion of genes responsible for the immune-suppressive properties of BCG has also been explored for their effect on BCG-induced innate and adaptive immune responses. Most studies limited their investigations to the description of T cell immune responses that were modified by the genetic modifications of BCG. Some studies also reported improved protection by recombinant BCG against tuberculosis or enhanced therapeutic efficacy against various cancer forms or allergies. However, so far, these investigations have been limited to mouse models, and the prophylactic or therapeutic potential of recombinant BCG strains has not yet been illustrated in other species, including humans, with the exception of a genetically modified BCG strain that is now in late-stage clinical development as a vaccine against tuberculosis. In this review, we provide an overview of the different molecular engineering strategies adopted over the last three decades in order to enhance the immune-modulatory potential of BCG.

Intrapulmonary administration of purified NEIL2 abrogates NF-κB-mediated inflammation

Aberrant or constitutive activation of nuclear factor kappa B (NF-κB) contributes to various human inflammatory diseases and malignancies via the upregulation of genes involved in cell proliferation, survival, angiogenesis, inflammation, and metastasis. Thus, inhibition of NF-κB signaling has potential for therapeutic applications in cancer and inflammatory diseases. We reported previously that Nei-like DNA glycosylase 2 (NEIL2), a mammalian DNA glycosylase, is involved in the preferential repair of oxidized DNA bases from the transcriptionally active sequences via the transcription-coupled base excision repair pathway. We have further shown that Neil2-null mice are highly sensitive to tumor necrosis factor α (TNFα)- and lipopolysaccharide-induced inflammation. Both TNFα and lipopolysaccharide are potent activators of NF-κB. However, the underlying mechanism of NEIL2's role in the NF-κB-mediated inflammation remains elusive. Here, we have documented a noncanonical function of NEIL2 and demonstrated that the expression of genes, such as Cxcl1, Cxcl2, Cxcl10, Il6, and Tnfα, involved in inflammation and immune cell migration was significantly higher in both mock- and TNFα-treated Neil2-null mice compared with that in the WT mice. NEIL2 blocks NF-κB's binding to target gene promoters by directly interacting with the Rel homology region of RelA and represses proinflammatory gene expression as determined by co-immunoprecipitation, chromatin immunoprecipitation, and electrophoretic mobility-shift assays. Remarkably, intrapulmonary administration of purified NEIL2 via a noninvasive nasal route significantly abrogated binding of NF-κB to cognate DNA, leading to decreased expression of proinflammatory genes and neutrophil recruitment in Neil2-null as well as WT mouse lungs. Our findings thus highlight the potential of NEIL2 as a biologic for inflammation-associated human diseases.

Decrease of IL-5 Production by Naive T Cells Cocultured with IL-18-Producing BCG-Pulsed Dendritic Cells from Patients Allergic to House Dust Mite

The only currently available anti-tuberculosis vaccine, Bacillus Calmette–Guérin (BCG), has been reported to also protect against unrelated diseases, including inflammatory diseases such as allergic asthma. Recombinant BCG strains that produce IL-18 have been shown to enhance Th1 responses over non-recombinant BCG and to reduce IL-5 production and bronchoalveolar eosinophilia in mice. However, their ability to decrease the immune polarization of human Th2 cells is not known. Here, we show that BCG and recombinant BCG producing human IL-18 (rBCG-hIL-18) induced the maturation of Der p 1-stimulated monocyte-derived dendritic cells (MD-DCs) from healthy controls and from patients allergic to house dust mites. After incubation with mycobacteria and Der p 1, MD-DCs produced significantly more IL-23 and IP-10 but had no effect on IL-12p70 or IL-10 production compared to Der p 1-pulsed MD-DCs in the absence of mycobacteria. In the presence of Der p 1, BCG- and rBCG-hIL-18-pulsed MD-DCs cocultured with naive, but not with memory T cells from allergic patients, resulted in a decrease in IL-5 production compared to non-pulsed MD-DCs cultured in the presence of Der p 1. BCG, and especially rBCG-hIL-18, may thus be potential therapeutic tools to reduce exacerbated Th2 responses in patients with allergic asthma.

Airway hyperresponsiveness development and the toxicity of PM2.5

Airway hyperresponsiveness (AHR) is characterized by excessive bronchoconstriction in response to nonspecific stimuli, thereby leading to airway stenosis and increased airway resistance. AHR is recognized as a key characteristic of asthma and is associated with significant morbidity. At present, many studies on the molecular mechanisms of AHR have mainly focused on the imbalance in Th1/Th2 cell function and the abnormal contraction of airway smooth muscle cells. However, the specific mechanisms of AHR remain unclear and need to be systematically elaborated. In addition, the effect of air pollution on the respiratory system has become a worldwide concern. To date, numerous studies have indicated that certain concentrations of fine particulate matter (PM2.5) can increase airway responsiveness and induce acute exacerbation of asthma. Of note, the concentration of PM2.5 does correlate with the degree of AHR. Numerous studies exploring the toxicity of PM2.5 have mainly focused on the inflammatory response, oxidative stress, genotoxicity, apoptosis, autophagy, and so on. However, there have been few reviews systematically elaborating the molecular mechanisms by which PM2.5 induces AHR. The present review separately sheds light on the underlying molecular mechanisms of AHR and PM2.5-induced AHR.

High serum free IL-18 is associated with decreased omalizumab efficacy: findings from a 2-year omalizumab treatment study

OBJECTIVE

Omalizumab is more effective in severe allergic patients with eosinophilic asthma than those with non-eosinophilic asthma. IL-18, a unique cytokine involved in allergic but non-eosinophilic inflammation, might be associated with the latter condition. We aimed to clarify the roles of IL-18 related pathways in insufficient response to omalizumab treatment.

METHODS

Patients with severe allergic asthma who completed 2-year omalizumab treatments at Kyoto University Hospital were included in this study (UMIN000002389). Associations between pretreatment levels of serum free IL-18 in addition to other mediators and asthma phenotypes including responses to omalizumab treatment were analyzed. Changes in serum free IL-18, periostin and total IgE levels during the treatment were also examined.

RESULTS

Twenty-seven patients (19 females, average age of 55.7 years) were examined. Fifteen incomplete responders who experienced exacerbations in the second year, were significantly and more frequently obese and showed significantly earlier asthma onset, lower blood eosinophils and more exacerbations before omalizumab treatment than complete responders. Significantly more patients showed high baseline serum free IL-18 levels (≥141 pg/mL, a threshold for the highest tertile) among the incomplete responders than complete responders. Patients with high serum free IL-18 levels shared similar characteristics with incomplete responders, showing significant reductions in serum total IgE levels during omalizumab treatment. Finally, serum free IL-18 levels negatively correlated with serum periostin levels at baseline and in change ratios.

CONCLUSIONS

High baseline serum free IL-18 levels may predict reduced omalizumab efficacy in severe allergic patients with type-2 low asthma, regarding reduction of exacerbations.

The Transcription Factor PLZF Is Necessary for the Development and Function of Mouse Basophils

Basophils are innate immune cells associated with type 2 immunity, allergic reactions, and host defense against parasite infections. In this study, we show that the transcription factor PLZF, which is known for its essential role in the function and development of several innate lymphocyte subsets, is also important for the myeloid-derived basophil lineage. PLZF-deficient mice had decreased numbers of basophil progenitors in the bone marrow and mature basophils in multiple peripheral tissues. Functionally, PLZF-deficient basophils were less responsive to IgE activation and produced reduced amounts of IL-4. The altered function of basophils resulted in a blunted Th2 T cell response to a protein allergen. Additionally, PLZF-deficient basophils had reduced expression of the IL-18 receptor, which impacted migration to lungs. PLZF, therefore, is a major player in controlling type 2 immune responses mediated not only by innate lymphocytes but also by myeloid-derived cells.

Proteomic and transcriptomic analysis of lung tissue in OVA-challenged mice

Asthma is a long term inflammatory disease of the airway of lungs characterized by variable airflow obstruction and bronchospasm. Asthma is caused by a complex combination of environmental and genetic interactions. In this study, we conducted proteomic analysis of samples derived from control and OVA challenged mice for environmental respiratory disease by using 2-D gel electrophoresis. In addition, we explored the genes associated with the environmental substances that cause respiratory disease and conducted RNA-seq by next-generation sequencing. Proteomic analysis revealed 7 up-regulated (keratin KB40, CRP, HSP27, chaperonin containing TCP-1, TCP-10, keratin, and albumin) and 3 down-regulated proteins (PLC-α, PLA2, and precursor ApoA-1). The expression diversity of many genes was found in the lung tissue of OVA challenged moue by RNA-seq. 146 genes were identified as significantly differentially expressed by OVA treatment, and 118 genes of the 146 differentially expressed genes were up-regulated and 28 genes were downregulated. These genes were related to inflammation, mucin production, and airway remodeling. The results presented herein enable diagnosis and the identification of quantitative markers to monitor the progression of environmental respiratory disease using proteomics and genomic approaches.

Functional polymorphisms affecting Th1 differentiation are associated with the severity of autoimmune thyroid diseases

The prognosis for autoimmune thyroid diseases (AITDs), such as Hashimoto's disease (HD) and Graves' disease (GD), varies among patients. Interleukin (IL)-12 and IL-18 also induce Th1 differentiation, and SOCS1 (Suppressor of cytokine signaling 1) and TIM-3 (T cell immunoglobulin and mucin domain-3) are known to be negative regulators of Th1 cells. To clarify the association of functional polymorphisms in the IL12, IL12Rβ1, IL18, SOCS1 and TIM3 genes with the intractability and severity of autoimmune thyroid disease (AITD), we genotyped these polymorphisms in 151 GD patients, including 61 patients with intractable GD and 51 patients with GD in remission, in 140 HD patients, including 59 patients with severe HD and 55 patients with mild HD, and in 74 healthy controls. The frequency of the IL18 -607CC genotype which correlates with a high production of IL-18, was significantly higher in patients with GD in remission than in those with intractable GD (p=0.0178). The -607C allele was significantly higher in patients with severe HD than in those with mild HD (p=0.0050). The -607CC genotype in IL18 gene may be protective against the intractability of GD, and the -607C allele may enhance the severity of HD.

Association of interleukin-18 and asthma

Cytokine-mediated immunity plays a dominant role in the pathogenesis of various immune diseases, including asthma. The recent identification of the family interleukin (IL)-1-related cytokine IL-18 now contributes to our understanding of the fine-tuning of cellular immunity. IL-18 can act as a cofactor for Th2 cell development and IgE production and also plays an important role in the differentiation of Th1 cells. Recent work identified an IL-18 association with the pathogenesis of asthma, wherein increased IL-18 expression was found in the serum of patients. Furthermore, IL-18 polymorphisms with susceptibility to asthma were reported, suggesting that IL-18 may be therapeutically relevant to asthma. In this review, we discuss the role of IL-18 in the pathogenesis of asthma and its therapeutic potential based on current research.

Clinical Signs, Staphylococcus and Atopic Eczema-Related Seromarkers

Childhood eczema or atopic dermatitis (AD) is a distressing disease associated with pruritus, sleep disturbance, impaired quality of life and Staphylococcus aureus isolation. The pathophysiology of AD is complex and various seromarkers of immunity are involved. We investigated if anti-staphylococcal enterotoxin IgE (anti-SE), selected seromarkers of T regulatory (Treg), T helper (Th) and antigen-presenting cells (APC) are associated with clinical signs of disease severity and quality of life. Disease severity was assessed with the Scoring Atopic Dermatitis (SCORAD) index, and quality of life with the Children's Dermatology Life Quality Index (CDLQI) in AD patients ≤18 years old. Concentrations of anti-staphylococcus enterotoxin A and B immunoglobulin E (anti-SEA and anti-SEB), selected Treg/Th/APC chemokines, skin hydration and transepidermal water loss (TEWL) were measured in these patients. Forty patients with AD [median (interquartile range) age of 13.1 (7.9) years) were recruited. Backward stepwise linear regression (controlling for age, personal allergic rhinitis and asthma, and other blood markers) showed the serum anti-SEB level was positively associated with S. aureus and S. epidermidis isolations, objective SCORAD, clinical signs and CDLQI. TNF-α (a Th1 cytokine) was positively associated with objective SCORAD (B = 4.935, p = 0.010), TGF-β (a Treg cytokine) negatively with disease extent (B = -0.015, p = 0.001), IL-18 (an APC cytokine) positively with disease extent (B = 0.438, p = 0.001) and with TEWL (B = 0.040, p = 0.010), and IL-23 (an APC cytokine) negatively with disease extent (B = -2.812, p = 0.006) and positively with pruritus (B = 0.387, p = 0.007).

CONCLUSIONS

Blood levels of anti-SEB, Th1, Treg and APC cytokines are correlated with various clinical signs of AD. AD is a systemic immunologic disease involving Staphylococcus aureus, cellular, humoral, cytokine and chemokine pathophysiology.

Biomarkers for Atopic Dermatitis in Children

Numerous studies investigating the correlations between the severity of atopic dermatitis (AD) and various biomarkers have been reported over the past few decades. Recent studies have indicated that certain soluble mediators, including chemokines (such as thymus and activation-regulated chemokine/C-C motif chemokine ligand [CCL]17 and macrophage-derived chemokine/CCL22) and cytokines (such as thymic stromal lymphopoietin), could be good markers of inflammation in AD. This review focuses on circulating biomarkers of AD, including pediatric AD.

Role of interleukin-18 in the pathophysiology of allergic diseases

Interleukin (IL)-18 is an IL-1 family cytokine expressed by macrophages, dendritic cells, epithelial cells, and keratinocytes and is implicated in various aspects of both the innate and adaptive immune systems. IL-18 signals similar to IL-1β intracellularly to activate gene transcription. Since its discovery, IL-18 has been demonstrated to play a key role in pathogen defense from helminths and some bacteria. Recently however, evidence has accumulated that IL-18 expression is increased in many presentations of allergic disease. A pathologic role for IL-18 includes stimulating mast cell and basophil degranulation, recruiting granulocytes to sites of inflammation, increasing cytotoxic activity of natural killer (NK) and NK-T cells, inducing Immunoglobulin (Ig)E production and isotype switching, and affecting a broad range of T cells to promote a type II helper T cell (Th2) response. Evidence and importance of these effects are presented, including novel results from our lab implicating IL-18 in the direct expansion of mast cells, basophils, and other myeloid-lineage cells from bone-marrow precursors. The development of urticaria, asthma, dermatitis, rhinitis, and eosinophilic disorders all have demonstrated correlations to increased IL-18 levels either in the tissue or systemically. IL-18 represents a novel site of immune regulation in not only allergic conditions, but also autoimmune diseases and other instances of aberrant immune functioning. Diagrammatic summarized abstract for readers convinance is presented in Fig. 1.

Abietic acid attenuates allergic airway inflammation in a mouse allergic asthma model

Abietic acid (AA), one of the terpenoids isolated from Pimenta racemosa var. grissea, has been reported to have anti-inflammatory and immunomodulatory effects. However, the anti-allergic effects of AA remain unclear. The aim of this study was to investigate the anti-allergic effects of AA in an ovalbumin (OVA)-induced asthma murine model. The model of mouse asthma was established by induction of OVA. AA (10, 20, 40mg/kg) was administered by oral gavage 1h after the OVA treatment on days 21 to 23. At 24h after the last challenge, bronchoalveolar lavage fluid (BALF) and lung tissues were collected to assess pathological changes, cytokines production, and NF-κB expression. The results showed that AA attenuated lung histopathologic changes, inflammatory cells infiltration, and bronchial hyper-responsiveness. AA also inhibited OVA-induced the nitric oxide (NO), IL-4, IL-5, IL-13, and OVA-specific IgE production, as well as NF-κB activation. In conclusion, the current study demonstrated that AA exhibited protective effects against OVA-induced allergic asthma in mice and the possible mechanism was involved in inhibiting NF-κB activation.

Facilitation of Allergic Sensitization and Allergic Airway Inflammation by Pollen-Induced Innate Neutrophil Recruitment

Neutrophil recruitment is a hallmark of rapid innate immune responses. Exposure of airways of naive mice to pollens rapidly induces neutrophil recruitment. The innate mechanisms that regulate pollen-induced neutrophil recruitment and the contribution of this neutrophilic response to subsequent induction of allergic sensitization and inflammation need to be elucidated. Here we show that ragweed pollen extract (RWPE) challenge in naive mice induces C-X-C motif ligand (CXCL) chemokine synthesis, which stimulates chemokine (C-X-C motif) receptor 2 (CXCR2)-dependent recruitment of neutrophils into the airways. Deletion of Toll-like receptor 4 (TLR4) abolishes CXCL chemokine secretion and neutrophil recruitment induced by a single RWPE challenge and inhibits induction of allergic sensitization and airway inflammation after repeated exposures to RWPE. Forced induction of CXCL chemokine secretion and neutrophil recruitment in mice lacking TLR4 also reconstitutes the ability of multiple challenges of RWPE to induce allergic airway inflammation. Blocking RWPE-induced neutrophil recruitment in wild-type mice by administration of a CXCR2 inhibitor inhibits the ability of repeated exposures to RWPE to stimulate allergic sensitization and airway inflammation. Administration of neutrophils derived from naive donor mice into the airways of Tlr4 knockout recipient mice after each repeated RWPE challenge reconstitutes allergic sensitization and inflammation in these mice. Together these observations indicate that pollen-induced recruitment of neutrophils is TLR4 and CXCR2 dependent and that recruitment of neutrophils is a critical rate-limiting event that stimulates induction of allergic sensitization and airway inflammation. Inhibiting pollen-induced recruitment of neutrophils, such as by administration of CXCR2 antagonists, may be a novel strategy to prevent initiation of pollen-induced allergic airway inflammation.

Low-Dose Intestinal Trichuris muris Infection Alters the Lung Immune Microenvironment and Can Suppress Allergic Airway Inflammation

Immunological cross talk between mucosal tissues such as the intestine and the lung is poorly defined during homeostasis and disease. Here, we show that a low-dose infection with the intestinally restricted helminth parasite Trichuris muris results in the production of Th1 cell-dependent gamma interferon (IFN-γ) and myeloid cell-derived interleukin-10 (IL-10) in the lung without causing overt airway pathology. This cross-mucosal immune response in the lung inhibits the development of papain-induced allergic airway inflammation, an innate cell-mediated type 2 airway inflammatory disease. Thus, we identify convergent and nonredundant roles of adaptive and innate immunity in mediating cross-mucosal suppression of type 2 airway inflammation during low-dose helminth-induced intestinal inflammation. These results provide further insight in identifying novel intersecting immune pathways elicited by gut-to-lung mucosal cross talk.

Targeted deep sequencing identifies rare loss-of-function variants in IFNGR1 for risk of atopic dermatitis complicated by eczema herpeticum

BACKGROUND

A subset of atopic dermatitis is associated with increased susceptibility to eczema herpeticum (ADEH+). We previously reported that common single nucleotide polymorphisms (SNPs) in the IFN-γ (IFNG) and IFN-γ receptor 1 (IFNGR1) genes were associated with the ADEH+ phenotype.

OBJECTIVE

We sought to interrogate the role of rare variants in interferon pathway genes for the risk of ADEH+.

METHODS

We performed targeted sequencing of interferon pathway genes (IFNG, IFNGR1, IFNAR1, and IL12RB1) in 228 European American patients with AD selected according to their eczema herpeticum status, and severity was measured by using the Eczema Area and Severity Index. Replication genotyping was performed in independent samples of 219 European American and 333 African American subjects. Functional investigation of loss-of-function variants was conducted by using site-directed mutagenesis.

RESULTS

We identified 494 single nucleotide variants encompassing 105 kb of sequence, including 145 common, 349 (70.6%) rare (minor allele frequency <5%), and 86 (17.4%) novel variants, of which 2.8% were coding synonymous, 93.3% were noncoding (64.6% intronic), and 3.8% were missense. We identified 6 rare IFNGR1 missense variants, including 3 damaging variants (Val14Met [V14M], Val61Ile, and Tyr397Cys [Y397C]) conferring a higher risk for ADEH+ (P = .031). Variants V14M and Y397C were confirmed to be deleterious, leading to partial IFNGR1 deficiency. Seven common IFNGR1 SNPs, along with common protective haplotypes (2-7 SNPs), conferred a reduced risk of ADEH+ (P = .015-.002 and P = .0015-.0004, respectively), and both SNP and haplotype associations were replicated in an independent African American sample (P = .004-.0001 and P = .001-.0001, respectively).

CONCLUSION

Our results provide evidence that both genetic variants in the gene encoding IFNGR1 are implicated in susceptibility to the ADEH+ phenotype.

Myeloid differentiation protein 2 facilitates pollen- and cat dander-induced innate and allergic airway inflammation

BACKGROUND

The National Health and Nutrition Examination Survey identified several pollens and cat dander as among the most common allergens that induce allergic sensitization and allergic diseases. We recently reported that ragweed pollen extract (RWPE) requires Toll-like receptor 4 (TLR4) to stimulate CXCL-mediated innate neutrophilic inflammation, which in turn facilitates allergic sensitization and airway inflammation. Myeloid differentiation protein 2 (MD2) is a TLR4 coreceptor, but its role in pollen- and cat dander-induced innate and allergic inflammation has not been critically evaluated.

OBJECTIVE

We sought to elucidate the role of MD2 in inducing pollen- and cat dander-induced innate and allergic airway inflammation.

METHODS

TCM(Null) (TLR4(Null), CD14(Null), MD2(Null)), TLR4(Hi), and TCM(Hi) cells and human bronchial epithelial cells with small interfering RNA-induced downregulation of MD2 were stimulated with RWPE, other pollen allergic extracts, or cat dander extract (CDE), and activation of nuclear factor κB (NF-κB), secretion of the NF-κB-dependent CXCL8, or both were quantified. Wild-type mice or mice with small interfering RNA knockdown of lung MD2 were challenged intranasally with RWPE or CDE, and innate and allergic inflammation was quantified.

RESULTS

RWPE stimulated MD2-dependent NF-κB activation and CXCL secretion. Likewise, Bermuda, rye, timothy, pigweed, Russian thistle, cottonwood, walnut, and CDE stimulated MD2-dependent CXCL secretion. RWPE and CDE challenge induced MD2-dependent and CD14-independent innate neutrophil recruitment. RWPE induced MD2-dependent allergic sensitization and airway inflammation.

CONCLUSIONS

MD2 plays an important role in induction of allergic sensitization to cat dander and common pollens relevant to human allergic diseases.

Animal models of allergic airways disease: where are we and where to next?

In a complex inflammatory airways disease such as asthma, abnormalities in a plethora of molecular and cellular pathways ultimately culminate in characteristic impairments in respiratory function. The ability to study disease pathophysiology in the setting of a functioning immune and respiratory system therefore makes mouse models an invaluable tool in translational research. Despite the vast understanding of inflammatory airways diseases gained from mouse models to date, concern over the validity of mouse models continues to grow. Therefore the aim of this review is twofold; firstly, to evaluate mouse models of asthma in light of current clinical definitions, and secondly, to provide a framework by which mouse models can be continually refined so that they continue to stand at the forefront of translational science. Indeed, it is in viewing mouse models as a continual work in progress that we will be able to target our research to those patient populations in whom current therapies are insufficient.

IL-37 requires IL-18Rα and SIGIRR/IL-1R8 to diminish allergic airway inflammation in mice

BACKGROUND

Interleukin (IL) 37 has been described as a negative regulator of innate immunity, as it reduces the activation and cytokine production of different innate immune cells. Recently, results from the CLARA childhood asthma cohort suggested an implication of IL-37 for human asthma pathogenesis. This study aimed to investigate the effects of IL-37 on allergic airway inflammation in a mouse model of experimental asthma.

METHODS

Peripheral blood mononuclear cells (PBMCs) of children were cultured for 48 h (anti-CD3/anti-CD28 stimulation or unstimulated), and IL-37 concentrations in supernatants were determined. Wild-type, IL-18Rα-deficient ((-/-) ), and SIGIRR(-/-) C57BL/6 mice were sensitized to ovalbumin (OVA) and challenged with OVA aerosol to induce acute experimental asthma, and IL-37 was applied intranasally prior to each OVA challenge. Airway hyper-responsiveness (AHR), airway inflammation, cytokine levels in broncho-alveolar lavage fluid, and mucus production were determined.

RESULTS

IL-37 production of human PBMCs was significantly lower in allergic asthmatics vs healthy children. In wild-type mice, intranasal administration of IL-37 ablated allergic airway inflammation as well as cytokine production and subsequently diminished the hallmarks of experimental asthma including mucus hyperproduction and AHR. In contrast, local application of IL-37 produced none of these effects in mice lacking either IL18Rα or SIGIRR/IL-1R8.

CONCLUSIONS

This study demonstrates that IL-37 is able to ablate a TH2 cell-directed allergic inflammatory response and the hallmarks of experimental asthma in mice, suggesting that IL-37 may be critical for asthma pathogenesis. Furthermore, these data suggest a mode of action of IL-37 that involves IL18Rα as well as the orphan receptor SIGIRR/IL-1R8.

AcCystatin, an immunoregulatory molecule from Angiostrongylus cantonensis, ameliorates the asthmatic response in an aluminium hydroxide/ovalbumin-induced rat model of asthma

Epidemiological surveys have demonstrated that helminth infections are negatively related to atopic diseases, including asthma. Defining and characterising specific helminth molecules that have excellent immunomodulatory capacities as potential therapeutics for the treatment or prophylaxis of allergic manifestations are of great interest. AcCystatin, a cystatin protease inhibitor of Angiostrongylus cantonensis, is a homologue of other nematode cystatins with immunoregulatory properties. Here, we aim to determine the effects of AcCystatin on an ovalbumin/aluminium hydroxide (OVA/Al[OH]3)-induced rat model of asthma. Wistar rats were randomly divided into four groups, including a control group, an OVA/Al[OH]3-induced asthma group, a group receiving AcCystatin immunisation prior to OVA/Al[OH]3-induced asthma and a group receiving AcCystatin treatment after OVA/Al[OH]3-induced asthma. The numbers of eosinophils, basophils, neutrophils, lymphocytes and monocytes in the peripheral blood and of eosinophils in the bronchoalveolar lavage fluid (BALF) were counted for each animal. The expression levels of the cytokines interferon-γ, interleukin (IL) 4, IL-5, IL-6, IL-10, IL17A and tumour necrosis factor receptor-α in BALF, of OVA-specific immunoglobulin E in BALF and serum and of the chemokines eotaxin-1, eotaxin-2, eotaxin-3, MCP-1 and MCP-3 in lung tissue were measured. In addition, the degree of peribronchial and perivascular inflammation and the intensity of goblet cell metaplasia were qualitatively evaluated. The sensitised/challenged rats developed an extensive cell inflammatory response of the airways. AcCystatin administration significantly reduced the cellular infiltrate in the perivascular and peribronchial lung tissues and reduced both goblet mucous production and eosinophil infiltration. The rats that were treated with AcCystatin before or after sensitisation with OVA showed significant decreases in eotaxin-1, eotaxin-3 and MCP-1 expression in the lung tissue. The production of IL-4, IL-5, IL-6 and IL-17A and of OVA-specific IgE antibodies was also significantly reduced in AcCystatin-treated rats compared with untreated asthmatic rats. The AcCystatin treatment was associated with a significant increase in IL-10 levels. Our present findings provide the first demonstration that AcCystatin is an effective agent in the prevention and treatment of the airway inflammation associated with asthma.

B cell-intrinsic MyD88 signaling is essential for IgE responses in lungs exposed to pollen allergens

Allergen-specific IgE is linked to asthma pathogenesis, but the underlying mechanisms of IgE production in response to allergen exposure are poorly understood. In this article, we show that B cell-intrinsic MyD88 is essential for IgE/IgG1 production evoked by ragweed pollen instilled into lungs. MyD88-deficient mice showed defective IgE/IgG1 production and germinal center responses to lung instillation of ragweed pollen. However, MyD88 was dispensable for dendritic cell activation and Th2 cell development. B cell-specific deletion of MyD88 replicated the defective Ab production observed in MyD88-deficient mice. Although ragweed pollen contains TLR ligands, TLR2/4/9-deficient mice developed normal allergic responses to ragweed pollen. However, anti-IL-1R1 Ab-treated mice and IL-18-deficient mice showed decreased IgE/IgG1 production with normal Th2 development. Furthermore, B cell-specific MyD88-deficient mice showed reduced IgE/IgG1 production in response to lung instillation of OVA together with IL-1α, IL-1β, or IL-18. Thus, pollen instillation into lungs induces IL-1α/β and IL-18 production, which activates B cell-intrinsic MyD88 signaling to promote germinal center responses and IgE/IgG1 production.

Eosinophils are recruited in response to chitin exposure and enhance Th2-mediated immune pathology in Aspergillus fumigatus infection

In patients infected with the fungus Aspergillus fumigatus, Th1 responses are considered protective, while Th2 responses are associated with increased morbidity and mortality. How host-pathogen interactions influence the development of these protective or detrimental immune responses is not clear. We compared lung immune responses to conidia from two fungal isolates that expressed different levels of the fungal cell wall component chitin. We observed that repeated aspirations of the high-chitin-expressing isolate Af5517 induced increased airway eosinophilia in the lungs of recipient mice compared to the level of eosinophilia induced by isolate Af293. CD4(+) T cells in the bronchoalveolar lavage fluid (BALF) of Af5517-aspirated mice displayed decreased gamma interferon secretion and increased interleukin-4 transcription. In addition, repeated aspirations of Af5517 induced lung transcription of the Th2-associated chemokines CCL11 (eotaxin-1) and CCL22 (macrophage-derived chemokine). Eosinophil recruitment in response to conidial aspiration was correlated with the level of chitin exposure during germination and was decreased by constitutive lung chitinase expression. Moreover, eosinophil-deficient mice subjected to multiple aspirations of Af5517 prior to neutrophil depletion and infection exhibited decreased morbidity and fungal burden compared to the levels of morbidity and fungal burden found in wild-type mice. These results suggest that exposure of chitin in germinating conidia promotes eosinophil recruitment and ultimately induces Th2-skewed immune responses after repeated aspiration. Furthermore, our results suggest that eosinophils should be examined as a potential therapeutic target in patients that mount poorly protective Th2 responses to A. fumigatus infection.

Interleukin 1-β, interleukin-1 receptor antagonist, and interleukin 18 in children with acute spontaneous urticaria

Very little is known about the role of interleukin-1β (IL-1β) and interleukin-18 (IL-18) in urticaria. Material and Methods. Serum levels of IL-1β, IL-1 receptor antagonist (IL-1RA), and IL-18 were measured in 56 children with urticaria and in 41 healthy subjects. Results. Serum IL-1β did not differ between children with acute urticaria and controls. Children with single episode of urticaria had higher levels of IL-1RA and IL-18 than healthy subjects. In children with single episode of urticaria, level of IL-1RA correlated with C-reactive protein (CRP), D-dimer, and IL-1β levels. In subjects with recurrence of urticaria IL-1RA was positively correlated with WBC and D-dimer levels. No correlation of cytokine levels and urticaria severity scores (UAS) in all children with urticaria was observed. In children with single episode of urticaria UAS correlated with CRP level. In the group with single episode of urticaria and in children with symptoms of upper respiratory infection, IL-1RA and IL-18 levels were higher than in controls. The former was higher than in noninfected children with urticaria. In conclusion, this preliminary study documents that serum IL-1RA and IL-18 levels are increased in some children with acute urticaria. However further studies are necessary to define a pathogenic role of IL-1β, IL-1RA, and IL-18 in urticaria.

Cytokines in chronic respiratory diseases

Cytokines are small, secreted proteins that control immune responses. Within the lung, they can control host responses to injuries or infection, resulting in clearance of the insult, repair of lung tissue, and return to homeostasis. Problems can arise when this response is over exuberant and/or cytokine production becomes dysregulated. In such cases, chronic and repeated inflammatory reactions and cytokine production can be established, leading to airway remodeling and fibrosis with unintended, maladaptive consequences. In this report, we describe the cytokines and molecular mechanisms behind the pathology observed in three major chronic diseases of the lung: asthma, chronic obstructive pulmonary disease (COPD), and pulmonary fibrosis. Overlapping mechanisms are presented as potential sites for therapeutic intervention.

Protective role of IL-18 -137G/C polymorphism in a North Indian population with asthma: a pilot study

BACKGROUND

IL-18, a pleiotropic, pro-inflammatory cytokine that plays a major role in innate as well as acquired immunity, has been implicated in asthma etiology and this is the first study investigating the role of IL-18 -137G/C (rs 187238) promoter polymorphism in asthma pathogenesis in a North Indian population.

METHODS

A pilot study was conducted with a total of 824 subjects, out of which 410 were asthma patients including 323 patients suffering from allergic rhinitis and 414 healthy controls from regions of North India. Tetra-Primer Amplification Refractory Mutation System Polymerase Chain Reaction (Tetra-Primer ARMS PCR) was used for genotyping the IL-18 -137G/C polymorphism.

RESULTS

While the homozygous wild (GG) genotype was equally prevalent in asthma patients as well as control subjects (70.0%), the homozygous mutant (CC) genotype was more prevalent among the controls (8.0%) than in asthma patients (3.4%), which yielded a significant protection or decreased risk towards asthma. Statistical analysis revealed Odds Ratio (OR)=0.43 (95% CI=0.21-0.85), Chi2 (χ2)=6.93 and p-value=0.008 (p<0.005). Moreover, a few asthma phenotypic traits also revealed significant protective associations with the polymorphism.

CONCLUSIONS

The IL-18 -137G/C polymorphism confers a significant protection from asthma in the studied North Indian population. This is the first study to report the protective association of the polymorphism with the disease.

Characterization of IL-18 expression and release in the pathogenesis of chronic rhinosinusitis

BACKGROUND

Interleukin-18 (IL-18) is a member of the IL-1 cytokine family that affects chronic inflammation. We sought to characterize IL-18 expression and investigate its release during chronic rhinosinusitis (CRS).

METHODS

The expression of IL-18 in nasal polyps (NPs) and uncinate tissues (UTs) from both CRS and non-CRS patients was examined via immunohistochemistry. After culturing dispersed NP cells (DNPCs) with or without various stimulations, IL-18 levels were measured in the culture supernatants. Furthermore, the effect of IL-18 neutralization on staphylococcus enterotoxin B (SEB)-induced cytokine production was also examined.

RESULTS

Similar expression of IL-18 in the epithelial layers was observed between the NPs and UTs. However, there was a significantly higher number of IL-18(+) cells in the lamina propria from NPs compared to UTs without CRS. This increased number was significantly correlated with the radiological severity of sinusitis and local eosinophilia. After the dispersion, IL-18 was spontaneously released by NP cells in a phase-dependent manner. While SEB, fungal antigens, and TLR agonists did not enhance the release, exposure to protease or one cycle of a freeze-and-thaw treatment did induce release of IL-18 from rested DNPCs. In addition, neutralization of IL-18 significantly suppressed SEB-induced IL-5, IL-13, and IFN-γ, but not IL-17A production.

CONCLUSIONS

These results suggest that the pro-inflammatory effect of IL-18 released by danger signals may be involved in the pathogenesis of CRS, which includes eosinophilic inflammation and NP formation, via the augmentation of both Th2- and Th1-associated cytokine production.

Polymorphisms of the IL-18 promoter and bronchial asthma

To study the association of polymorphisms of the IL-18 promoter (-607C/A and -137G/C) with bronchial asthma, 120 subjects with bronchial asthma were selected as the experimental group (49 cases with bronchial asthma and allergic rhinitis as experimental group 1 and 71 cases with bronchial asthma without allergic rhinitis as experimental group 2) and 120 healthy individuals were selected as the control group. A polymerase chain reaction sequence-specific primer (PCR-SSP) was used to identify the genotypic polymorphisms between the experimental and control groups. The results revealed that the frequencies of the CC, CA and AA genotypes at -607C/A in experimental group 1 were 18.37, 40.82 and 40.82%, respectively; these frequencies were 32.39, 54.92 and 12.68%, respectively, in experimental group 2. There was a statistically significant difference in the genotype distribution between experimental groups 1 and 2 (χ²=12.81; P<0.05). The allele frequencies of genotypes C and A were 38.78 and 61.22%, respectively, in experimental group 1 and 59.86 and 40.14%, respectively, in experimental group 2. The allele frequencies at -607C/A were significantly different between experimental groups 1 and 2 (χ²=10.32; P<0.05). Frequencies of genotypes GG, GC and CC at -137C/A in experimental group 1 were 48.98, 46.94 and 4.08%, respectively, and 80.28, 14.08 and 4.08% in experimental group 2 with significant difference (χ²=15.73, P<0.05). Allele frequencies of G and C in experimental group 1 were 72.45 and 27.55%, and 87.32 and 12.68% in experimental group 2 with statistically significant difference (χ²=8.42, P<0.05). In conclusion, polymorphisms of the IL-18 gene promoter at -607C/A and -137G/C were associated with allergic rhinitis in bronchial asthma, indicating that polymorphisms of the IL-18 gene promoter at -607C/A and -137G/C differentially affect the pathogenesis of asthma and allergic rhinitis.

Low doses of exogenous interferon-γ attenuated airway inflammation through enhancing Fas/FasL-induced CD4+ T cell apoptosis in a mouse asthma model

To investigate whether low doses of exogenous interferon (IFN)-γ attenuate airway inflammation, and the underlying mechanisms, in asthma. C57BL/6 mice (n=42), after intraperitoneal ovalbumin (OVA) sensitization on day 0 and day 12, were challenged with OVA aerosol for 6 consecutive days. Different doses of IFN-γ were then administered intraperitoneally 5 min before each inhalation during OVA challenge. Airway hyperresponsiveness, airway inflammatory cells, cytokine profiles, and Fas/FasL expression on CD4(+) T cells were evaluated in an asthma model. The effect of various IFN-γ doses on Fas/FasL expression and CD4(+) T cell apoptosis were assessed in vitro. We demonstrated that low doses of IFN-γ reduced pulmonary infiltration of inflammatory cells, Th2 cytokine production, and goblet cells hyperplasia (P<0.05), while high doses of endogenous IFN-γ had almost no effect. We also found that low doses of IFN-γ relocated Fas/FasL to the CD4(+) T cell surface in the asthma model (P<0.05) and increased FasL-induced apoptosis in vitro (P<0.05). Furthermore, treatment with MFL-3, an anti-FasL antibody, partially abolished the anti- inflammatory properties of IFN-γ in the airway rather than affecting the Th1/Th2 balance. This research has revealed an alternative mechanism in asthma that involves low doses of IFN-γ, which attenuate airway inflammation through enhancing Fas/FasL-induced CD4(+) T cell apoptosis.

Bronchial hyperresponsiveness in seasonal allergic rhinitis patients is associated with increased IL-18 during natural pollen exposure

BACKGROUND

The mechanism of bronchial hyperresponsiveness (BHR) is not certain in seasonal allergic rhinitis (SAR) patients.

OBJECTIVE

We aimed to investigate the effects of natural pollen exposure on IL-18 and its relationship with BHR.

METHODS

Thirty-two SAR patients with grass pollen sensitivity, 14 nonallergic rhinitis (NAR) patients and 17 normal-controls were included. Sixteen SAR patients had BHR during pollen season and off-season. Serum IL-18 levels were measured in SAR patients during pollen season between May-August and off-season between November-February. IL-18 levels were measured in NAR patients and normal controls once.

RESULTS

During pollen season, SAR patients with BHR had significantly increased levels of IL-18 than those without BHR (279.2 ± 161.1 versus 145.3 ± 101.0 pg/ml, p=0.012). Serum IL-18 levels were not different between SAR patients with and without BHR during off-season (233.8 ± 139.7 versus 183.2 ± 162.9 pg/ml, p=0.16). Serum IL-18 levels in SAR patients during pollen season (212.3 ± 148.8 pg/ml) and off-season (208.5 ± 151.5 pg/ml) were not different than those NAR patients (224.8 ± 180.1 pg/ml, p=0.98 and p=1.0, respectively) and normal controls (174.8 ± 76.0 pg/ml, p=0.60 and p=0.76, respectively).

CONCLUSION

The results suggested us that BHR in SAR patients is associated with increased IL-18 during natural pollen exposure.

Genetic variants in interferon regulatory factor 2 (IRF2) are associated with atopic dermatitis and eczema herpeticum

Interferon regulatory factor 2 (IRF2) is a member of a family of transcriptional factors involved in the modulation of IFN-induced immune responses to viral infection. To test whether genetic variants in IRF2 predict risk of atopic dermatitis (AD) and ADEH (atopic dermatitis complicated by eczema herpeticum), we genotyped 78 IRF2 tagging single-nucleotide polymorphisms (SNPs) in both European-American (n = 435) and African-American (n = 339) populations. Significant associations were observed between AD and two SNPs (rs793814, P = 0.007, odds ratio (OR) = 0.52; rs3756094, P = 0.037, OR = 0.66) among European Americans and one SNP (rs3775572, P = 0.016, OR = 0.46) among African Americans. Significant associations were also observed between ADEH and five SNPs (P = 0.049-0.022) among European Americans. The association with ADEH was further strengthened by haplotype analyses, wherein a five-SNP (CAGGA) haplotype showed the strongest association with ADEH (P = 0.0008). Eight IRF2 SNPs were significantly associated with IFN-γ production after herpes simplex virus (HSV) stimulation (P = 0.048-0.0008), including an AD-associated SNP (rs13139310, P = 0.008). Our findings suggest that distinct markers in IRF2 may be associated with AD and ADEH, which may depend upon ethnic ancestry, and genetic variants in IRF2 may contribute to an abnormal immune response to HSV.

Alternaria-induced release of IL-18 from damaged airway epithelial cells: an NF-κB dependent mechanism of Th2 differentiation?

Background

A series of epidemiologic studies have identified the fungus Alternaria as a major risk factor for asthma. The airway epithelium plays a critical role in the pathogenesis of allergic asthma. These reports suggest that activated airway epithelial cells can produce cytokines such as IL-25, TSLP and IL-33 that induce Th2 phenotype. However the epithelium-derived products that mediate the pro-asthma effects of Alternaria are not well characterized. We hypothesized that exposure of the airway epithelium to Alternaria releasing cytokines that can induce Th2 differentiation.

Methodology/Principal Finding

We used ELISA to measure human and mouse cytokines. Alternaria extract (ALT-E) induced rapid release of IL-18, but not IL-4, IL-9, IL-13, IL-25, IL-33, or TSLP from cultured normal human bronchial epithelial cells; and in the BAL fluids of naïve mice after challenge with ALT-E. Both microscopic and FACS indicated that this release was associated with necrosis of epithelial cells. ALT-E induced much greater IL-18 release compared to 19 major outdoor allergens. Culture of naïve CD4 cells with rmIL-18 induced Th2 differentiation in the absence of IL-4 and STAT6, and this effect was abrogated by disrupting NF- κB p50 or with a NEMO binding peptide inhibitor.

Conclusion/Significance

Rapid and specific release of IL-18 from Alternaria-exposed damaged airway epithelial cells can directly initiate Th2 differentiation of naïve CD4⁺ T-cells via a unique NF-κB dependent pathway.

Association of serum interleukin-18 and other biomarkers with disease severity in adults with atopic dermatitis

Atopic dermatitis (AD) is a chronic inflammatory disease of the skin for which there are no reliable biomarkers to assess clinical severity. Serum interleukin-18 (IL-18) levels may be associated with AD severity. To identify putative biomarkers associated with clinical severity in adult AD patients, we enrolled 121 adult AD patients (mean age 35.7 years) and 50 healthy controls (mean age 31.7 years). We compared these groups for blood eosinophils and serum levels of IL-18, thymus and activation-regulated chemokine (TARC), total IgE, and lactate dehydrogenase (LDH). We also determined S. aureus enterotoxin B (SEB) specific IgE levels and the SCORingAD (SCORAD) scores for AD patients. For AD patients, stepwise logistic regression was used to estimate odds ratios (OR) for each biomarker for the likelihood of having AD, and multiple linear regression was used to identify biomarkers associated with SCORAD scores. Compared with healthy controls, adult AD patients had higher levels of IL-18, TARC, total IgE, eosinophils, and LDH. TARC levels had the highest OR for AD occurrence, while the OR for IL-18 was insignificant. Also, IL-18 was not related to the presence of SEB-IgE. Notably, IL-18 levels were significantly associated with SCORAD scores, as were TARC, total IgE, and LDH levels. A panel of biomarkers (IL-18, TARC, total IgE, and LDH) may be more useful to accurately assess clinical severity in adult AD patients.

Young patients with both type 1 diabetes mellitus and asthma have a unique IL-12 and IL-18 secretory pattern

BACKGROUND

The expression of the regulatory cytokines interleukin (IL)-12 and IL-18 in patients with both Th1- and Th2-mediated diseases, type 1 diabetes mellitus (T1DM) and asthma, is unknown.

OBJECTIVE

To investigate the in vivo and in vitro IL-12 and IL-18 secretion patterns in patients with both T1DM and asthma.

METHODS

Peripheral blood mononuclear cells (PBMC) were collected from 44 patients. Mean age 19.4 ± 4.7 yr (10.5-28 yr), divided into four paired groups: T1DM and asthma, asthma only, T1DM only, and healthy controls. T-cell proliferative response was assessed. IL-12 and IL-18 serum levels and expression by PBMC following in vitro stimulation by lipopolysaccharide (LPS) were determined by enzyme-linked immunosorbent assay (ELISA).

RESULTS

Patients with T1DM and asthma had higher serum levels of both IL-12 and IL-18 compared to controls: 146.2 ± 69.2 and 109.7 ± 34.6 pg/mL, p = 0.038 and 436.1 ± 117.9, 320.2 ± 99.1 pg/mL, p = 0.028, respectively. Stimulated IL-12 secretion was significantly lower in these patients compared to those with one disease only: 809 ± 426.4, 2111.6 ± 2214.3, 3188.1 ± 2692.9 pg/mL and after 48 h: 956.3 ± 489.3, 2429.8 ± 2394.6, 3874.5 ± 2820.3 pg/mL, respectively, p < 0.03 for all. The IL-18/IL-12 serum ratio was also significantly higher in patients with both diseases compared to those with asthma only, p = 0.017.

CONCLUSION

Patients with both T1DM and asthma display a different pattern of IL-12 and IL-18 expression compared to patients with one disease only and controls.

Hardy-Weinberg disequilibrium of the IL-18 C-607A SNP suggesting selective advantage of heterozygotes

Interleukin-18 (IL-18) plays a key role in autoimmune, inflammatory, and infectious diseases. The IL-18 gene contains a C to A single nucleotide polymorphism (SNP) at position -607 (C-607A) within the promoter region, which was found to affect the promoter activity and subsequently the protein level of IL-18. We investigated this SNP in a group of healthy Singaporeans and found that CA was the most common genotype and the C allele was more prevalent than the A allele, which was not always the case in other ethnic groups. In addition, Singaporean Chinese were significantly different from Singaporean Indians in both allelic and genotypic distributions. Furthermore, significant deviations from Hardy-Weinberg equilibrium of this SNP were found in all three ethnic groups studied (Chinese, Indians, and Malays) and also in other published literature, suggesting that heterozygotes of this IL-18 C-607A SNP may have certain selective advantages.

The interaction between IL-18 and IL-18 receptor limits the magnitude of protective immunity and enhances pathogenic responses following infection with intracellular bacteria

The binding of IL-18 to IL-18Rα induces both proinflammatory and protective functions during infection, depending on the context in which it occurs. IL-18 is highly expressed in the liver of wild-type (WT) C57BL/6 mice following lethal infection with highly virulent Ixodes ovatus ehrlichia (IOE), an obligate intracellular bacterium that causes acute fatal toxic shock-like syndrome. In this study, we found that IOE infection of IL-18Rα(-/-) mice resulted in significantly less host cell apoptosis, decreased hepatic leukocyte recruitment, enhanced bacterial clearance, and prolonged survival compared with infected WT mice, suggesting a pathogenic role for IL-18/IL-18Rα in Ehrlichia-induced toxic shock. Although lack of IL-18R decreased the magnitude of IFN-γ producing type-1 immune response, enhanced resistance of IL-18Rα(-/-) mice against Ehrlichia correlated with increased proinflammatory cytokines at sites of infection, decreased systemic IL-10 production, increased frequency of protective NKT cells producing TNF-α and IFN-γ, and decreased frequency of pathogenic TNF-α-producing CD8(+) T cells. Adoptive transfer of immune WT CD8(+) T cells increased bacterial burden in IL-18Rα(-/-) mice following IOE infection. Furthermore, rIL-18 treatment of WT mice infected with mildly virulent Ehrlichia muris impaired bacterial clearance and enhanced liver injury. Finally, lack of IL-18R signal reduced dendritic cell maturation and their TNF-α production, suggesting that IL-18 might promote the adaptive pathogenic immune responses against Ehrlichia by influencing T cell priming functions of dendritic cells. Together, these results suggested that the presence or absence of IL-18R signals governs the pathogenic versus protective immunity in a model of Ehrlichia-induced immunopathology.

Interleukin-18 promoter polymorphism and asthma risk: a meta-analysis

Some studies have shown that IL-18 was associated with aetiology and progression of asthma. However, the association between single-nucleotide polymorphisms -607C/A (rs1946518) and -137G/C (rs187238) located in the IL-18 gene promoter and asthma risk was still controversial and ambiguous. To derive a more precise effect on the association between these polymorphisms and asthma risk, we performed a meta-analysis based on the currently available evidence of the literature. A total of 5 studies with 1411 cases and 1525 controls for -607C/A polymorphism and 5 studies with 1883 cases and 6645 controls for -137G/C polymorphism were identified to perform a meta-analysis, up to October 2010. Summary ORs and corresponding 95% CIs for IL-18 polymorphisms and asthma were estimated using fixed- and random-effects models when appropriate. Heterogeneity and publication bias were evaluated. We found that individuals carrying AC/CC genotype of -607C/A polymorphism were associated with an increased asthma risk in recessive model (OR = 1.278; 95% CI, 1.073-1.522). However, no significant association was observed between -137G/C polymorphism and asthma risk under different contrast models. There was no evidence of publication bias. The present meta-analysis suggested that IL-18 -607C/A polymorphism in promoter region was associated with asthma risk.

Co-immunization with interlukin-18 enhances the protective efficacy of liposomes encapsulated recombinant Cu-Zn superoxide dismutase protein against Brucella abortus

Brucellosis is a worldwide zoonotic disease caused by Brucella abortus and a number of closely related species. Brucellosis has severe impact on the health and economic prosperity of the developing countries due to the persistent nature of infection and unavailability of effective control measures. The Cu-Zn superoxide dismuatse (SOD) protein of Brucella have been extensively studied as a major antigen involved in bacterial evading mechanism of host defence. Being a critical pro-inflammatory cytokine interleukin-18 (IL-18) plays key role in induction of immune mediated protection against intracellular pathogens. In the present study, we aimed to investigate the immunogenic potential of fusogenic liposomes (escheriosomes) encapsulated recombinant Cu-Zn SOD (rSOD) protein alone or in combination with recombinant IL-18 (rIL-18). Escheriosomes encapsulated rSOD mediated immune responses were further increased upon co-immunization with rIL-18. Furthermore, immunization with escheriosomes encapsulated rSOD alone or in combination with rIL-18, increased resistance in mice against challenge with B. abortus 544.

Contribution of the proinflammatory cytokine IL-18 in the formation of human nasal polyps

Nasal polyposis is a chronic inflammatory disease of the nasal mucosa. The etiology and the mechanisms of formation of nasal polyps are still not clear. Interleukin (IL)-18 is a novel proinflammatory cytokine that plays important roles in regulating immune inflammatory responses. However, the presence of IL-18 in human nasal mucosa and its roles in the inflammatory process of nasal polyps has not been studied yet. In this study, it was the first time to investigate the expression of IL-18 in human nasal mucosa and nasal polyps, and its potential function in the formation of nasal polyps. Surgical samples were analyzed by Western blot and immunohistochemistry to evaluate the expression and location of IL-18, and its correlated cytokines, IL-4, and IFN-γ. Furthermore, the airway epithelial cell line, A549, was used to investigate the mutual regulation of IFN-γ, IL-4, and IL-18. IFN-γ, IL-4, and IL-18 were all highly expressed in the epithelial cells, submucosal glands, and infiltrating inflammatory cells in the nasal polyp tissues, comparing with the control samples. Especially, the expression of IL-18 was upregulated significantly in nasal polyp tissues compared with control tissues. In addition, IL-18 was expressed in A549 cells in response to lipopolysaccharide and IL-4. Our data suggest that nasal epithelial cells are involved in the pathogenesis of nasal polyps formation and potentially via the secretion of IL-18, which is likely to play important roles in the formation of nasal polyps.

Clonorchis sinensis-derived total protein attenuates airway inflammation in murine asthma model by inducing regulatory T cells and modulating dendritic cell functions

Asthma is characterized by Th2-mediated inflammation, resulting in airway hyperresponsiveness (AHR) through airway remodeling. Recent epidemiological and experimental reports have suggested an inverse relationship between the development of allergy and helminth infections. Infection by Clonorchis sinensis, a liver fluke that resides in the bile duct of humans, is endemic predominantly in Asia including Korea and China. Using a murine model for asthma, we investigated the effects of C. sinensis-derived total protein (Cs-TP) on allergen-induced airway inflammation and the mechanism underlying the protective effects of Cs-TP administration on asthma. Treatment with Cs-TP attenuated OVA-induced airway inflammation and methacholine-induced AHR, as well as eosinophilia development, lymphocyte infiltration into the lung, and goblet cell metaplasia. This protective effect of Cs-TP is associated with markedly reduced OVA-specific IgE and Th1/Th2 cytokine production. Moreover, Cs-TP increased the number of CD4(+)CD25(+)Foxp3(+) regulatory T (Treg) cells as well as their suppressive activity. In fact, proliferation of OVA-restimulated splenocytes was suppressed significantly. Cs-TP also inhibited the expression of such co-stimulatory molecules as CD80, CD86, and CD40 in LPS- or OVA-stimulated dendritic cells (DCs), suggesting that Cs-TP could interfere with the capacity of airway DCs to prime naïve T cells. These data demonstrate the capacity of C. sinensis to ameliorate allergic asthma and broaden our understanding of the paradoxical relationship between the allergic immune response and helminth infection.

Autologous serum skin test response in chronic spontaneous urticaria and respiratory diseases and its relationship with serum interleukin-18 level

Autologous serum skin test (ASST) is mostly used in chronic spontaneous urticaria (CSU) to show autoreactivity. Interleukin-18 (IL-18) has also been shown to be involved in autoimmune conditions. To investigate the role of autoreactivity assessed by ASST in CSU and respiratory diseases and to investigate whether this autoreactive state is related to IL-18 level or other clinical covariates. Fifty-five patients with CSU (mean age: 40.3 ± 12.3 years), 70 patients with persistent asthma (mean age: 43.7 ± 9.6 years), 21 patients with seasonal allergic rhinitis (SAR) (mean age: 35.5 ± 11.8 years) and 20 normal controls (mean age: 37.7 ± 9.8) were included. All subjects underwent a laboratory examination and skin prick test. ASST was performed and serum IL-18 levels were measured in all subjects. Positive response to ASST and serum IL-18 levels were higher in CSU patients than those with respiratory diseases (asthma and SAR) (P = 0.034 and 0.002, respectively) and normal controls (P = 0.004 and 0.031, respectively). Considering all patients, IL-18 levels were higher in patients with positive ASST (301.8 ± 194.4 vs. 241.8 ± 206.3 pg/ml, P = 0.036) than ASST negative patients. ASST response was associated with disease severity in CSU (P = 0.037) and asthma patients (P = 0.001). Multivariate analysis showed that positive response to ASST was significantly associated with diagnosis of CSU (OR: 3.13, 95% CI: 1.25-7.87) and female gender (OR: 3.98, 95% CI: 1.19-13.38). ASST response could be related with activity of the disease. A positive ASST response found in respiratory diseases patients suggests that it may occur as a result of some inflammatory events during the diseases' process.

The role of the NLRP3 inflammasome in the pathogenesis of airway disease

The incidences of respiratory diseases like asthma and Chronic Obstructive Pulmonary Disease (COPD) are increasing dramatically. Significantly, there are currently no treatments that can slow or prevent the relentless progression of COPD; and a sub-population of asthmatics are resistant to available therapies. What is more, currently prescribed medication has only minimal effect on the symptoms suffered in these patient groups. There is therefore an urgent need to develop effective drugs to treat these diseases. Whilst asthma and COPD are thought to be distinct diseases, it is currently believed that the pathogenesis of both is driven by the chronic inflammation present in the airways of these patients. It is thus hypothesised that if the inflammation could be attenuated, disease development would be slowed and symptoms reduced. It is therefore paramount to determine the pathways driving/propagating the inflammation. Recently there has been a growing body of evidence to suggest that the multimeric protein complex known as the Inflammasome may play key roles in the inflammation observed in respiratory diseases. The aim of this review is to discuss the role of the NLRP3 Inflammasome, and its associated inflammatory mediators (IL-1β and IL-18), in the pathogenesis of asthma and COPD.