Circulating TSLP associates with decreased wheezing in non-atopic preschool children: data from the URECA birth cohort

From preschool wheezing to asthma: Immunological determinants

Asthma represents a chronic respiratory disease affecting millions of children worldwide. The transition from preschool wheezing to school-age asthma involves a multifaceted interplay of various factors, including immunological aspects in early childhood. These factors include complex cellular interactions among different immune cell subsets, induction of pro-inflammatory mediators and the molecular impact of environmental factors like allergens or viral infections on the developing immune system. Furthermore, the activation of specific genes and signalling pathways during this early phase plays a pivotal role in the manifestation of symptoms and subsequent development of asthma. Early identification of the propensity or risk for asthma development, for example by allergen sensitisation and viral infections during this critical period, is crucial for understanding the transition from wheeze to asthma. Favourable immune regulation during a critical 'window of opportunity' in early childhood can induce persistent changes in immune cell behaviour. In this context, trained immunity, including memory function of innate immune cells, has significant implications for understanding immune responses, potentially shaping long-term immunological outcomes based on early-life environmental exposures. Exploration of these underlying immune mechanisms that drive disease progression will provide valuable insights to understand childhood asthma development. This will be instrumental to develop preventive strategies at different stages of disease development for (i) inhibiting progression from wheeze to asthma or (ii) reducing disease severity and (iii) uncovering novel therapeutic strategies and contributing to more tailored and effective treatments for childhood asthma. In the long term, this shall empower healthcare professionals to develop evidence-based interventions that reduce the burden of asthma for children, families and society overall.

Nasal TSLP and periostin in infants with severe bronchiolitis and risk of asthma at 4 years of age

BACKGROUND

Severe bronchiolitis is often associated with subsequent respiratory morbidity, mainly recurrent wheezing and asthma. However, the underlying immune mechanisms remain unclear. The main goal of this study was to investigate the association of nasal detection of periostin and thymic stromal lymphopoietin (TSLP) during severe bronchiolitis with the development of asthma at 4 years of age.

METHODS

Observational, longitudinal, post-bronchiolitis, hospital-based, follow-up study. Children hospitalized for bronchiolitis between October/2013 and July/2017, currently aged 4 years, included in a previous study to investigate the nasal airway secretion of TSLP and periostin during bronchiolitis, were included. Parents were contacted by telephone, and were invited to a clinical interview based on a structured questionnaire to obtain information on the respiratory evolution. The ISAAC questionnaire for asthma symptoms for 6-7-year-old children, was also employed.

RESULTS

A total of 248 children were included (median age 4.4 years). The mean age at admission for bronchiolitis was 3.1 (IQR: 1.5-6.5) months. Overall, 21% had ever been diagnosed with asthma and 37% had wheezed in the last 12 months. Measurable nasal TSLP was detected at admission in 27(11%) cases and periostin in 157(63%). The detection of nasal TSLP was associated with the subsequent prescription of maintenance asthma treatment (p = 0.04), montelukast (p = 0.01), and the combination montelukast/inhaled glucocorticosteroids (p = 0.03). Admissions for asthma tended to be more frequent in children with TSLP detection (p = 0.07). In the multivariate analysis, adjusting for potential confounders, the detection of TSLP remained independently associated with chronic asthma treatment prescription (aOR:2.724; CI 1.051-7.063, p:0.04) and with current asthma (aOR:3.41; CI 1.20-9.66, p:0.02). Nasal detection of periostin was associated with lower frequency of ever use of short-acting beta2-agonists (SABA) (p = 0.04), lower prevalence of current asthma (p = 0.02), less prescription of maintenance asthma treatment in the past 12 months (p = 0.02, respectively). In the multivariate analysis, periostin was associated with lower risk of asthma at 4 years, independently of the atopic status (aOR:0.511 CI 95% 0.284-0.918, p:0.025).

CONCLUSIONS

Our results show a positive correlation between nasal TSLP detection in severe bronchiolitis and the presence of current asthma, prescription of asthma maintenance treatment and respiratory admissions up to the age of 4 years. By contrast, we found a protective association between nasal periostin detection and current asthma at 4 years, ever diagnosis of asthma, maintenance asthma treatment prescription, and respiratory admissions.

TSLP disease-associated genetic variants combined with airway TSLP expression influence asthma risk

BACKGROUND

Thymic stromal lymphopoietin (TSLP) is an epithelial-derived cytokine important in initiation of allergic inflammation. Single nucleotide polymorphisms (SNPs) in TSLP are associated with asthma, yet studies have shown inconsistent associations between circulating TSLP and asthma. Studies that integrate the combined effects of TSLP genotype, TSLP mRNA, circulating TSLP levels, and asthma outcome are lacking.

OBJECTIVES

This study sought to recruit a novel cohort based on asthma-relevant TSLP SNPs and determine their impact on TSLP mRNA expression and TSLP circulating protein levels, and their individual and combined effects on asthma.

METHODS

This study developed an algorithm to prioritize TSLP SNPs and recruited 51 carriers and noncarriers based on TSLP genotypes. TSLP mRNA was quantified in nasal epithelial cells and circulating TSLP levels in plasma. This study determined the associations of defined TSLP risk genotypes and/or TSLP mRNA and protein levels with asthma.

RESULTS

TSLP mRNA expression, but not circulating TSLP, was significantly increased in people who are asthmatic compared with in people who are nonasthmatic (P = .007; odds ratio, 1.44). Notably, 90% of children with the defined TSLP risk genotypes and high nasal TSLP mRNA expression (top tertile) had asthma compared with 40% of subjects without risk genotypes and with low TSLP expression (bottom tertile) (P = .024). No association between circulating TSLP and asthma was observed.

CONCLUSIONS

Collectively, these data suggest childhood asthma is modified by the combined effects of TSLP genotype and TSLP expression in the nasal epithelium. The increased asthma risk likely manifests when genetic variation enables expression quantitative trait loci in the TSLP locus to elevate TSLP. It is important to consider both biomarkers when factoring asthma risk.

Asthma-Associated Long TSLP Inhibits the Production of IgA

Thymic stromal lymphopoietin (TSLP) contributes to asthmatic disease. The concentrations of protective IgA may be reduced in the respiratory tract of asthma patients. We investigated how homeostatic short TSLP (shTSLP) and asthma-associated long TSLP (loTSLP) regulate IgA production. B cells from healthy donors were stimulated in the presence or absence of shTSLP or loTSLP; the concentrations of IgA, IgM, IgE, and IgG antibodies were determined in cell culture supernatants; and B cells were analyzed by flow cytometry. LoTSLP, but not shTSLP, suppressed the secretion of IgA but not of IgE. The type 2 cytokine IL-4, which in addition to loTSLP contributes to asthmatic disease, did not affect the production of IgA or the frequency of IgA+ B cells. Instead, IL-4 increased IgG production, especially of the subclasses IgG2 and IgG4. LoTSLP inhibited IgA secretion by sorted memory B cells but not by naïve B cells. Although loTSLP inhibited IgA production, the vitamin A metabolite retinoic acid promoted the secretion of IgA, also in the presence of loTSLP, suggesting that vitamin A may promote IgA production in asthma. Our data demonstrate that asthma-associated loTSLP negatively regulates the secretion of IgA, which may negatively impact the surveillance of mucosal surfaces in asthma.

Developments in the field of allergy in 2014 through the eyes of Clinical and Experimental Allergy

The pathogenesis of asthma continues to be a major topic of interest to our authors with reviews and original papers on the role of viruses, mechanisms of inflammation, biomarkers, and phenotypes of asthma being major topics. A number of papers described new treatments for asthma focusing on blocking the Th2 response reflecting the fact that two decades of work in this area is finally bearing fruit. The pathogenesis of chronic rhinosinusitis is a growing area of interest, but there has been less on the genetics of airways disease than in previous years possibly reflecting the degree of rigour (and therefore a smaller body of work), with which these sorts of studies are now being undertaken. There continues to be a wide range of papers dealing with mechanisms of allergic disease ranging from clinical-based studies to basic research and the use of in vivo animal models especially mice. As before, mechanisms and new approaches to immunotherapy are common themes. Several were published in the allergens section investigating modification of allergens to increase their effectiveness and reduce the risk of adverse events. Risk factors for allergic disease was a common theme in the epidemiology section and food allergy a common theme in clinical allergy with papers on the development of protocols to induce tolerance and attempts to find biomarkers to distinguish sensitization from allergic disease. This was another exciting year for the editors, and we hope the readers of the journal.

The Notch Intracellular Domain Has an RBPj-Independent Role during Mouse Hair Follicular Development

Ligand-dependent activation, γ-secretase-processed cleavage, and recombining binding protein Jk (RBPj)-mediated downstream transcriptional activities of Notch receptors constitute the "canonical" Notch signaling pathway, which is essential for skin organogenesis. However, in Msx2-Cre mice, keratinocyte-specific deletion of the Rbpj gene in utero produced a significantly milder phenotype than either global Notch or γ-secretase loss. Herein, we investigated the underlying mechanisms for this apparent noncanonical signal using mouse genetics. We found no evidence that ligand back-signaling contributed to skin organogenesis. The perdurance of RBPj protein did not establish an epigenetic memory of a canonical signal in the youngest epidermal stem cells, and Notch targets were not derepressed. We provide evidence that γ-secretase-dependent but RBPj-independent Notch intracellular domain activity operating in the first hair follicles is responsible for a delay in follicular destruction, which results in lower serum thymic stromal lymphopoietin levels, milder B-cell lymphoproliferative disease, and improved survival in Msx2-Cre(+/tg);Rbpj(f/f) mice. Minimal amounts of the Notch intracellular domain were sufficient for rescue, which was not mediated by transcription, suggesting that the Notch intracellular domain is acting through a novel mechanism.

A clinical biomarker assay to quantitate thymic stromal lymphopoietin in human plasma at sub-pg/ml level

BACKGROUND

Thymic stromal lymphopoietin (TSLP) is an attractive therapeutic target for the treatment of allergic diseases, and plasma TSLP is a potential patient selection marker in the development of therapeutic agents.

RESULTS

We developed and validated an ultrasensitive electrochemiluminescence assay for measurement of TSLP in plasma with a lower limit of quantitation of 0.12 pg/ml, which allowed the quantitation of TSLP in approximately 90% of human plasma samples tested. The assay demonstrated excellent performance characteristics, including precision, accuracy, sensitivity and dilution linearity. Stability and biological variability of TSLP in plasma were also assessed for clinical sample analysis and data interpretation.

CONCLUSION

The validated TSLP assay enables assessment of circulating TSLP as a patient selection marker in the development of therapeutics to treat atopic diseases.

Thymic stromal lymphopoietin activation of basophils in patients with allergic asthma is IL-3 dependent

BACKGROUND

Thymic stromal lymphopoietin (TSLP) released after antigenic stimulation of allergic asthmatic airways is a key initiator of type 2 inflammation. Basophils are important effectors of allergic inflammation in the airways. Murine basophils have been shown to respond to TSLP independently of IL-3 by increasing functional thymic stromal lymphopoietin receptor (TSLPR) expression.

OBJECTIVE

The purpose of this study was to investigate the effect of TSLP stimulation on human basophil function.

METHODS

Ten patients with mild allergic asthma underwent diluent and allergen inhalation challenges. Peripheral blood and sputum samples were collected at baseline and 7 and 24 hours after challenge, and bone marrow samples were collected at baseline and 24 hours after challenge to measure basophil TSLPR expression. In vitro experiments were conducted on purified human basophils to measure the effect of TSLP on degranulation, expression of activation markers and TH2 cytokines, and eotaxin-induced shape change.

RESULTS

Allergen inhalation increased basophil numbers in the airways and significantly upregulated the expression of activation markers, TH2 intracellular cytokines, and receptors for TSLP, IL-3, and eotaxin in blood, bone marrow, and sputum basophils. In vitro stimulation with TSLP primed basophil migration to eotaxin and induced rapid and sustained basophil activation mediated directly through TSLPR and indirectly through an IL-3-mediated basophil autocrine loop. Basophils responded to TSLP at a similar magnitude and potency as the well-described basophil-activating stimuli IL-3 and anti-IgE.

CONCLUSION

Our findings indicate that basophil activation during early- and late-phase responses to inhaled allergen might be driven at least in part by TSLP.