Plasma thymic stromal lymphopoietin (TSLP) in adults with non-severe asthma: the EGEA study.

Thymic stromal lymphopoietin (TSLP), a cytokine involved in severe asthma treatment, was never studied in non-severe asthma.Among 969 adults from a large epidemiological study, cross-sectional analyses showed that plasma TSLP levels were associated with increased age and BMI, male sex, smoking and high TSLP levels (one IQR increase) with current asthma and poor lung function. High TSLP levels were also associated with persistence of asthma attacks (aOR=2.14 (95% CI 1.23 to 3.72)) and dyspnoea (aOR=2.71 (95% CI 1.39 to 5.28)) 10 years later.Our results suggest that TSLP could be a cytokine of interest in non-severe asthma, and its determinants of circulating levels could be considered in asthma management.

Blood eosinophil cationic protein and eosinophil-derived neurotoxin are associated with different asthma expression and evolution in adults.

BACKGROUND: Eosinophil-derived neurotoxin (EDN) and eosinophil cationic protein (ECP) are proteins released by activated eosinophils whose role in adult asthma remains unclear. OBJECTIVE: To study associations between ECP, EDN and various asthma characteristics in adults from the Epidemiological Study on the Genetics and Environment of Asthma (EGEA). METHODS: Plasma ECP and EDN levels were measured by ELISA. Cross-sectional analyses were performed in 941 adults (43±16 years old, 39% with asthma) at EGEA2 (2003-2007). Longitudinal analyses investigated the associations between EDN level at EGEA2 and changes in asthma characteristics between EGEA2 and EGEA3 (2011-2013, n=817). We used generalised estimated equations adjusted for age, sex, smoking status and body mass index to take into account familial dependence. RESULTS: At EGEA2, both high ECP and EDN levels were associated with current asthma (adjusted OR (aOR) (95% CI): 1.69 (1.35-2.12) and 2.12 (1.76-2.57)). Among asthmatics, high EDN level was associated with asthma attacks (aOR: 1.50 (1.13-1.99)), wheezing and breathlessness (aOR: 1.38 (1.05-1.80)), use of asthma treatments (aOR: 1.91 (1.37-2.68)) and bronchial hyper-responsiveness (aOR: 2.03 (1.38-2.97)), even after further adjustment on ECP. High ECP level was associated with high neutrophil count and tended to be associated with chronic bronchitis. High EDN level at EGEA2 was associated with persistent asthma (aOR: 1.62 (1.04-2.52)), nocturnal symptoms (aOR from 2.19 to 3.57), worsening wheezing and breathlessness (aOR: 1.97 (1.36-2.85)) and nocturnal shortness of breath (aOR: 1.44 (1.04-1.98)) between EGEA2 and EGEA3. CONCLUSIONS: EDN and ECP were associated with different asthma expression in adults. EDN could be a potential biomarker to monitor asthma evolution in adults.

Is CCL18 a potential biomarker of type-2 asthma endotypes?

Objective: This exploratory cross-sectional study aimed to evaluate the associations between the chemokine ligand 18 (CCL18) blood level and phenotypic characteristics of asthma.Methods: We evaluated in a sample of 173 asthmatic adult patients from the Cohort of Bronchial obstruction and Asthma (63.4% women; median age 50 ± interquartile range 27.5 years; median level of CCL18 was 44.1 ± interquartile range 27.5 ng/mL) the association between CCL18 blood level and allergic features of asthma using a multivariate analysis.Results: We found an association between the log-transformed value of blood CCL18 and age (+0.7% [0.1; 1.3] per 1-year increase, p = 0.033), gender (-25.1% [-42; -3.2] in women, p = 0.029), and nasal polyposis (+38.1% [11.6; 70.9], p = 0.004). No association was observed between CCL18 level and the other main phenotypic characteristics of asthma.Conclusions: Our exploratory study suggests that CCL18 is not an effective biomarker of allergic asthma endotype but may rather be a biomarker of tissue eosinophilia as supported by its association with nasal polyposis.

NOD1 sensing of house dust mite-derived microbiota promotes allergic experimental asthma.

BACKGROUND: Asthma severity has been linked to exposure to gram-negative bacteria from the environment that are recognized by NOD1 receptor and are present in house dust mite (HDM) extracts. NOD1 polymorphism has been associated with asthma. OBJECTIVE: We sought to evaluate whether either host or HDM-derived microbiota may contribute to NOD1-dependent disease severity. METHODS: A model of HDM-induced experimental asthma was used and the effect of NOD1 deficiency was evaluated. Contribution of host microbiota was evaluated by fecal transplantation. Contribution of HDM-derived microbiota was assessed by 16S ribosomal RNA sequencing, mass spectrometry analysis, and peptidoglycan depletion of the extracts. RESULTS: In this model, loss of the bacterial sensor NOD1 and its adaptor RIPK2 improved asthma features. Such inhibitory effect was not related to dysbiosis caused by NOD1 deficiency, as shown by fecal transplantation of Nod1-deficient microbiota to wild-type germ-free mice. The 16S ribosomal RNA gene sequencing and mass spectrometry analysis of HDM allergen, revealed the presence of some muropeptides from gram-negative bacteria that belong to the Bartonellaceae family. While such HDM-associated muropeptides were found to activate NOD1 signaling in epithelial cells, peptidoglycan-depleted HDM had a decreased ability to instigate asthma in vivo. CONCLUSIONS: These data show that NOD1-dependent sensing of HDM-associated gram-negative bacteria aggravates the severity of experimental asthma, suggesting that inhibiting the NOD1 signaling pathway may be a therapeutic approach to treating asthma.

NOD2 Signaling Circuitry during Allergen Sensitization Does Not Worsen Experimental Neutrophilic Asthma but Promotes a Th2/Th17 Profile in Asthma Patients but Not Healthy Subjects.

Nucleotide-binding oligomerization domain 2 (NOD2) recognizes pathogens associated with the development of asthma. Moreover, NOD2 adjuvants are used in vaccine design to boost immune responses. Muramyl di-peptide (MDP) is a NOD2 ligand, which is able to promote Th2/Th17 responses. Furthermore, polymorphisms of the NOD2 receptor are associated with allergy and asthma development. This study aimed to evaluate if MDP given as an adjuvant during allergen sensitization may worsen the development of Th2/Th17 responses. We used a mouse model of Th2/Th17-type allergic neutrophil airway inflammation (AAI) to dog allergen, with in vitro polarization of human naive T cells by dendritic cells (DC) from healthy and dog-allergic asthma subjects. In the mouse model, intranasal co-administration of MDP did not modify the AAI parameters, including Th2/Th17-type lung inflammation. In humans, MDP co-stimulation of allergen-primed DC did not change the polarization profile of T cells in healthy subjects but elicited a Th2/Th17 profile in asthma subjects, as compared with MDP alone. These results support the idea that NOD2 may not be involved in the infection-related development of asthma and that, while care has to be taken in asthma patients, NOD2 adjuvants might be used in non-sensitized individuals.

Natural Killer Cells from Allergic Donors Are Defective in Their Response to CCL18 Chemokine.

Natural killer (NK) cells were originally described as cytolytic effector cells, but since then have been recognized to possess regulatory functions on immune responses. Chemokines locate NK cells throughout the body in homeostatic and pathological conditions. They may also directly stimulate immune cells. CCL18 is a constitutive and inducible chemokine involved in allergic diseases. The aim of this study was to evaluate CCL18's effect on NK cells from allergic and nonallergic donors in terms of both chemotactic and immune effects. Results showed that CCL18 was able to induce migration of NK cells from nonallergic donors in a G-protein-dependent manner, suggesting the involvement of a classical chemokine receptor from the family of seven-transmembrane domain G-protein-coupled receptors. In contrast, NK cells from allergic patients were unresponsive. Similarly, CCL18 was able to induce NK cell cytotoxicity only in nonallergic subjects. Purified NK cells did not express CCR8, one of the receptors described to be involved in CCL18 functions. Finally, the defect in CCL18 response by NK cells from allergic patients was unrelated to a defect in CCL18 binding to NK cells. Overall, our results suggest that some NK cell functions may be defective in allergic diseases.

Aberrant anti-viral response of natural killer cells in severe asthma.

Rhinovirus infections are the main cause of asthma exacerbations. As natural killer (NK) cells are important actors of the antiviral innate response, we aimed at evaluating the functions of NK cells from severe asthma patients in response to rhinovirus-like molecules or rhinoviruses.Peripheral blood mononuclear cells from patients with severe asthma and healthy donors were stimulated with pathogen-like molecules or with the rhinoviruses (RV)-A9 and RV-2. NK cell activation, degranulation and interferon (IFN)-γ expression were analysed.NK cells from severe asthma patients were less cytotoxic than those from healthy donors in response to toll-like receptor (TLR)3, TLR7/8 or RV-A9 but not in response to RV-2 stimulation. Furthermore, when cultured with interleukin (IL)-12+IL-15, cytokines which are produced during viral infections, NK cells from patients with severe asthma were less cytotoxic and expressed less IFN-γ than NK cells from healthy donors. NK cells from severe asthmatics exhibited an exhausted phenotype, with an increased expression of the checkpoint molecule Tim-3.Together, our findings indicate that the activation of NK cells from patients with severe asthma may be insufficient during some but not all respiratory infections. The exhausted phenotype may participate in NK cell impairment and aggravation of viral-induced asthma exacerbation in these patients.

The Aryl Hydrocarbon Receptor in Asthma: Friend or Foe?

The aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor that has emerged as an important player in asthma control. AhR is responsive to environmental molecules and endogenous or dietary metabolites and regulates innate and adaptive immune responses. Binding of this receptor by different ligands has led to seemingly opposite responses in different asthma models. In this review, we present two sides of the same coin, with the beneficial and deleterious roles of AhR evaluated using known endogenous or exogenous ligands, deficient mice or antagonists. On one hand, AhR has an anti-inflammatory role since its activation in dendritic cells blocks the generation of pro-inflammatory T cells or shifts macrophages toward an anti-inflammatory M2 phenotype. On the other hand, AhR activation by particle-associated polycyclic aromatic hydrocarbons from the environment is pro-inflammatory, inducing mucus hypersecretion, airway remodelling, dysregulation of antigen presenting cells and exacerbates asthma features. Data concerning the role of AhR in cells from asthmatic patients are also reviewed, since AhR could represent a potential target for therapeutic immunomodulation.

Innate lymphoid cells at the interface between obesity and asthma.

Obesity and asthma prevalence has dramatically and concomitantly increased over the last 25 years, and many epidemiological studies have highlighted obesity as an important risk factor for asthma. Although many studies have been performed, the underlying mechanisms remain poorly understood. Innate mechanisms have been involved in both diseases, in particular through the recently described innate lymphoid cells (ILCs). ILCs are subdivided into three groups that are defined by their cytokine production and by their master transcription factor expression, in sharp correlation with their T helper counterparts. However, unlike T helper cells, ILCs do not express antigen-specific receptors, but respond to damage-induced signals. ILCs have been found in target tissues of both diseases, and data have implicated these cells in the pathogenesis of both diseases. In particular group 2 ILCs (ILC2) are activated in both the adipose and lung tissues under the effect of interleukin-33 and interleukin-25 expression. However, counter-intuitively to the well-known association between obesity and asthma, ILC2 are beneficial for obesity but deleterious for asthma. This review will examine the roles of ILCs in each disease and recent data highlighting ILCs as a putative link between obesity and asthma.

CCL18 - Beyond chemotaxis.

The chemokine CCL18 is constitutively expressed in human lung and serum, and is further elevated during pathologic conditions such as allergy, fibrosis and cancer, suggesting that it may participate in both homeostatic and inflammatory processes. Under steady state conditions, CCL18 has chemotactic activity, albeit modest, toward naïve T cells and as such, may be involved in the initiation of the adaptive response. Its chemotactic effect on inflammatory cells is ambiguous as it attracts both regulatory and inflammatory immune cells. CCL18 can also modulate tissue inflammation by inhibiting cell recruitment through binding to glycosaminoglycans with high affinity, thereby displacing other chemokines bound to the endothelial surface. CCL18 induces regulatory phenotype and function of immune cells through direct activation and plays a major role in fibrotic processes, particularly in the lung. Finally, CCL18 is involved in cancer cell activation and migration and also participates in immune tolerance toward cancer. Its high constitutive expression levels and its further up-regulation in many diseases, together with its moderate chemoattractant properties support the fact that this chemokine has activities beyond cell recruitment.

Endocan, sepsis, pneumonia, and acute respiratory distress syndrome.

Acute respiratory distress syndrome (ARDS) and hospital-acquired pneumonia (HAP) are major problems of public health in intensive care units (ICUs), occurring in 15% of critically ill patients. Among the factors explaining ARDS development, sepsis is known as a frequent cause. Sepsis, ARDS, and HAP increase morbidity, mortality, length of stay in the ICU, and the overall costs of healthcare. The major challenge remains to identify accurately among critically ill patients those at risk of poor outcomes who could benefit from novel therapies. Endocan is released by the pulmonary endothelium in response to local or systemic injury. It inhibits mainly leukocyte diapedesis rather than leukocyte rolling or adhesion to the endothelial cells both in vitro and in vivo. Endocan was evaluated in 25 clinical reports, including 2454 critically ill patients and 452 healthy controls. The diagnostic value of endocan for sepsis or sepsis severity was equal to procalcitonin but its prognostic value was better. A predictive value for postoperative pneumonia was evidenced in two studies, and a predictive value for ARDS in four studies from three independent centers. This review presents an overview of the structure, expression, and functions of endocan. We also hereby summarize the potential applications of endocan in the prediction and prognosis of ARDS and HAP, as well as in the prognosis of sepsis.

Innate lymphoid cells contribute to allergic airway disease exacerbation by obesity.

BACKGROUND: Epidemiologic and clinical observations identify obesity as an important risk factor for asthma exacerbation, but the underlying mechanisms remain poorly understood. Type 2 innate lymphoid cells (ILC2s) and type 3 innate lymphoid cells (ILC3s) have been implicated, respectively, in asthma and adipose tissue homeostasis and in obesity-associated airway hyperresponsiveness (AHR). OBJECTIVE: We sought to determine the potential involvement of innate lymphoid cells (ILCs) in allergic airway disease exacerbation caused by high-fat diet (HFD)-induced obesity. METHODS: Obesity was induced by means of HFD feeding, and allergic airway inflammation was subsequently induced by means of intranasal administration of house dust mite (HDM) extract. AHR, lung and visceral adipose tissue inflammation, humoral response, cytokines, and innate and adaptive lymphoid populations were analyzed in the presence or absence of ILCs. RESULTS: HFD feeding exacerbated allergic airway disease features, including humoral response, airway and tissue eosinophilia, AHR, and TH2 and TH17 pulmonary profiles. Notably, nonsensitized obese mice already exhibited increased lung ILC counts and tissue eosinophil infiltration compared with values in lean mice in the absence of AHR. The numbers of total and cytokine-expressing lung ILC2s and ILC3s further increased in HDM-challenged obese mice compared with those in HDM-challenged lean mice, and this was accompanied by high IL-33 and IL-1ß levels and decreased ILC markers in visceral adipose tissue. Furthermore, depletion of ILCs with an anti-CD90 antibody, followed by T-cell reconstitution, led to a profound decrease in allergic airway inflammatory features in obese mice, including TH2 and TH17 infiltration. CONCLUSION: These results indicate that HFD-induced obesity might exacerbate allergic airway inflammation through mechanisms involving ILC2s and ILC3s.

Apical Organelle Secretion by Toxoplasma Controls Innate and Adaptive Immunity and Mediates Long-Term Protection.

Apicomplexan parasites have unique apical rhoptry and microneme secretory organelles that are crucial for host infection, although their role in protection against Toxoplasma gondii infection is not thoroughly understood. Here, we report a novel function of the endolysosomal T. gondii sortilin-like receptor (TgSORTLR), which mediates trafficking to functional apical organelles and their subsequent secretion of virulence factors that are critical to the induction of sterile immunity against parasite reinfection. We further demonstrate that the T. gondii armadillo repeats-only protein (TgARO) mutant, which is deficient only in apical secretion of rhoptries, is also critical in mounting protective immunity. The lack of TgSORTLR and TgARO proteins completely inhibited T-helper 1-dependent adaptive immunity and compromised the function of natural killer T-cell-mediated innate immunity. Our findings reveal an essential role for apical secretion in promoting sterile protection against T. gondii and provide strong evidence for rhoptry-regulated discharge of antigens as a key effector for inducing protective immunity.

CCL17 production by dendritic cells is required for NOD1-mediated exacerbation of allergic asthma.

RATIONALE: Pattern recognition receptors are attractive targets for vaccine adjuvants, and polymorphisms of the innate receptor NOD1 have been associated with allergic asthma. OBJECTIVES: To elucidate whether NOD1 agonist may favor allergic asthma in humans through activation of dendritic cells, and to evaluate the mechanisms involved using an in vivo model. METHODS: NOD1-primed dendritic cells from allergic and nonallergic donors were characterized in vitro on their phenotype, cytokine secretion, and Th2 polarizing ability. The in vivo relevance was examined in experimental allergic asthma, and the mechanisms were assessed using transfer of NOD1-conditioned dendritic cells from wild-type or CCL17-deficient mice. MEASUREMENTS AND MAIN RESULTS: NOD1 priming of human dendritic cells promoted a Th2 polarization profile that involved the production of CCL17 and CCL22 in nonallergic subjects but only CCL17 in allergic patients, without requiring allergen costimulation. Moreover, NOD1-primed dendritic cells from allergic donors exhibited enhanced maturation that led to abnormal CCL22 and IL-10 secretion compared with nonallergic donors. In mice, systemic NOD1 ligation exacerbated allergen-induced experimental asthma by amplifying CCL17-mediated Th2 responses in the lung. NOD1-mediated sensitization of purified murine dendritic cells enhanced production of CCL17 and CCL22, but not of thymic stromal lymphopoietin and IL-33, in vitro. Consistently, adoptive transfer of NOD1-conditioned dendritic cells exacerbated the Th2 pulmonary response in a CCL17-dependent manner in vivo. CONCLUSIONS: Data from this study unveil a deleterious role of NOD1 in allergic asthma through direct induction of CCL17 by dendritic cells, arguing for a need to address vaccine formulation safety issues related to allergy.

Pulmonary CCL18 recruits human regulatory T cells.

CCL18 is both a constitutively expressed and an inducible chemokine, whose role in the inflammatory reaction is poorly known. The aim of this study was to evaluate whether CCL18 has the capacity to attract human T cells with a regulatory function (regulatory T cells [Treg]). Results from chemotaxis assays performed on different types of Treg showed that CD4(+)CD25(+)CD127(low) cells, but neither T regulatory type 1 clones nor Treg differentiated in vitro with anti-CD3/CD46 mAbs, were recruited by CCL18 in a dose-dependent manner. CCL18-recruited memory CD4(+) T cells were enriched in CD25(high), CD25(+)CD127(low), latency-associated peptide/TGF-ß1, and CCR4-expressing T cells, whereas there was no enrichment in Foxp3(+) cells as compared with controls. Stimulated CCL18-recruited memory T cells produced significantly increased amounts of the regulatory cytokines IL-10 and TGF-ß1, as well as IL-4, but not IFN-γ and IL-17. Cell surface CCL18 binding was found predominantly on IL-10(+) (26.3 ± 5.8%) and on a few latency-associated peptide/TGF-ß1(+) (18.1 ± 1.9%) and IL-4(+) (14.5 ± 2.9%) memory T cells. In an in vivo model of SCID mice grafted with human skin and reconstituted with autologous PBMCs, the intradermal injection of CCL18 led to the cutaneous recruitment of CD4(+), CD25(+), and IL-10(+) cells, but not Foxp3(+) cells. Furthermore, CCL18-recruited memory T cells inhibited the proliferation of CD4(+)CD25(-) effector T cells through an IL-10-dependent mechanism. These data suggest that CCL18 may contribute to maintaining tolerance and/or suppressing deleterious inflammation by attracting memory Tregs into tissues, particularly in the lung, where it is highly and constitutively expressed.

CCL18 differentiates dendritic cells in tolerogenic cells able to prime regulatory T cells in healthy subjects.

The aim of this study was to evaluate the nonchemotactic function of CCL18 on human dendritic cells (DCs). In different protocols of DC differentiation, CCL18 was highly produced, suggesting that it may constitute a mandatory mediator of the differentiation process. Differentiation of monocytes from healthy subjects in the presence of granulocyte-macrophage colony-stimulating factor and CCL18 led to the development of DCs with a semimature phenotype, with intermediate levels of costimulatory and MHC class II molecules, increased CCR7 expression, which induced, in coculture with allogenic naive T cells, an increase in IL-10 production. The generated T cells were able to suppress the proliferation of effector CD4(+)CD25(-) cells, through a cytokine-dependent mechanism, and exhibited characteristics of type 1 T regulatory cells. The generation of tolerogenic DCs by CCL18 was dependent on the production of indoleamine 2,3-dioxigenase through an interleukin-10-mediated mechanism. Surprisingly, when DCs originated from allergic patients, the tolerogenic effect of CCL18 was lost in relation with a decreased binding of CCL18 to its putative receptor. This study is the first to define a chemokine able to generate tolerogenic DCs. However, this function was absent in allergic donors and may participate to the decreased tolerance observed in allergic diseases.

The disulfide bond between cysteine 10 and cysteine 34 is required for CCL18 activity.

Asthma is a Th2-mediated disease that involves Th2 cell and eosinophil migration into the bronchial mucosa which is dependent upon the expression of a specific set of chemokines within the lung. Among them, CCL18 seems to play a key role because of its preferential expression in the lung, and its up-regulation by Th2 cytokines. Here, we show that the optimal naïve T cell and basophil chemotaxis, and basophil histamine release induced by rhCCL18 occurred at a 100 time lower concentration with CHO-derived rhCCL18 than with E. coli-derived rhCCL18. FT-ICR mass spectrometry of the intact chemokines showed that the rhCCL18 produced by CHO cells contained the 2 disulfide bonds Cys10-Cys34 and Cys11-Cys50, in clear contrast to the rhCCL18 derived from E. coli where the Cys10-Cys34 bond was absent. We found that reduction of the Cys10-Cys34 of the CHO-derived rhCCL18 resulted in a shift of its activity, reaching the same level as the E. coli-derived rhCCL18. These results demonstrate that the Cys10-Cys34 disulfide bond is involved in the function of CCL18.