Immuno-regulatory cytokines in asthma: IL-15 and IL-13 in induced sputum

Recombinant T-cell epitope conjugation: A new approach for Dermatophagoides hypoallergen design

BACKGROUND

Allergen-specific immunotherapy (AIT) is the only clinical approach that can potentially cure some allergic diseases by inducing immunological tolerance. Dermatophagoides pteronyssinus is considered as the most important source of mite allergens worldwide, with high sensitization rates for the major allergens Der p 1, Der p 2 and Der p 23. The aim of this work is to generate a hypoallergenic hybrid molecule containing T-cell epitopes from these three major allergens.

METHODS

The hybrid protein termed Der p 2231 containing T-cell epitopes was purified by affinity chromatography. The human IgE reactivity was verified by comparing those with the parental allergens. The hybrid was also characterized immunologically through an in vivo mice model.

RESULTS

The hybrid rDer p 2231 stimulated in peripheral blood mononuclear cells (PBMCs) isolated from allergic patients with higher levels of IL- 2, IL-10, IL-15 and IFN-γ, as well as lower levels of IL-4, IL-5, IL-13, TNF-α and GM-CSF. The use of hybrid molecules as a therapeutic model in D. pteronyssinus allergic mice led to the reduction of IgE production and lower eosinophilic peroxidase activity in the airways. We found increased levels of IgG antibodies that blocked the IgE binding to the parental allergens in the serum of allergic patients. Furthermore, the stimulation of splenocytes from mice treated with rDer p 2231 induced higher levels of IL-10 and IFN-γ and decreased the secretion of IL-4 and IL-5, when compared with parental allergens and D. pteronyssinus extract.

CONCLUSIONS

rDer p 2231 has the potential to be used in AIT in patients co-sensitized with D. pteronyssinus major allergens, once it was able to reduce IgE production, inducing allergen-specific blocking antibodies, restoring and balancing Th1/Th2 immune responses, and inducing regulatory T-cells.

Attenuation of Allergen-, IL-13-, and TGF-α-induced Lung Fibrosis after the Treatment of rIL-15 in Mice

Endogenous IL-15 deficiency promotes lung fibrosis; therefore, we examined the effect of induced IL-15 in restricting the progression of lung fibrosis. Our objective in this work was to establish a novel therapeutic molecule for pulmonary fibrosis. Western blot, qPCR, and ELISA were performed on the lung tissues of IL-15-deficient mice, and recombinant IL-15 (rIL-15)-treated CC10-IL-13 and CC10-TGF-α mice, and allergen-challenged CC10-IL-15 mice were examined to establish the antifibrotic effect of IL-15 in lung fibrosis. We show that endogenous IL-15 deficiency induces baseline profibrotic cytokine and collagen accumulation in the lung, and pharmacological delivery of rIL-15 downregulates Aspergillus antigen-induced lung collagen, the profibrotic cytokines IL-13 and TGF-β1, and α-SMA⁺ and FSP1⁺ cells in mice. To confirm that overexpression of IL-15 diminishes pulmonary fibrosis, we generated CC10-rtTA-tetO7-IL-15 transgenic mice and challenged them with Aspergillus antigen. Aspergillus antigen-challenged, doxycycline (DOX)-treated CC10-IL-15 transgenic mice exhibited decreased collagen accumulation, profibrotic cytokine (IL-13 and TGF-β1) expression, and α-SMA⁺ and FSP1⁺ cells compared with IL-15-overexpressing mice not treated with DOX. Additionally, to establish that the antifibrotic effect of IL-15 is not limited to allergen-induced fibrosis, we showed that rIL-15 or IL-15 agonist treatment restricted pulmonary fibrosis even in CC10-IL-13 and CC10-TGF-α mice. Mechanistically, we show that T-helper cell type 17 suppressor IL-15-responsive RORγ⁺ T regulatory cells are induced in DOX-treated, allergen-challenged IL-15-overexpressing mice, which may be a novel pathway for restricting progression of pulmonary fibrosis. Taken together, our data establishes antifibrotic activity of IL-15 that might be a novel therapeutic molecule to combat the development of pulmonary fibrosis.

The Safety and Efficacy of Anti-IL-13 Treatment with Tralokinumab (CAT-354) in Moderate to Severe Asthma: A Systematic Review and Meta-Analysis

BACKGROUND

Several clinical studies have evaluated the use of tralokinumab (CAT-354) administration in patients with moderate to severe asthma; no consensus on tralokinumab efficacy and safety was reached. Thus, further analysis is required on the efficacy and safety of tralokinumab as an asthma biologic.

OBJECTIVE

To assess the efficacy and safety of subcutaneous injection of tralokinumab in patients with moderate to severe asthma.

METHODS

Clinical trials were identified from MEDLINE, EMBASE, Cochrane Central Register of Controlled Trials, and ClinicalTrials.gov from their inception to November 4, 2018. Only randomized clinical trials (RCTs) with tralokinumab versus placebo treatment in patients with moderate to severe asthma were evaluated. Efficacy and safety outcomes were extracted, and a meta-analysis was performed using a random-effects model. The Cochrane Collaboration's risk-of-bias assessment tool was used to assess the risk of bias.

RESULTS

Five studies describing 6 RCTs (including 2928 adults with moderate to severe asthma) were pooled and analyzed in this study. Absolute FEV₁ was statistically improved in patients receiving tralokinumab at 300 mg every 2 weeks (mean difference [MD], 0.14 L; 95% CI, 0.08-0.21) and 600 mg every 2 weeks (MD, 0.20 L; 95% CI, 0.01-0.39), as well as FEV₁% changes (MD, 5.82%, 95% CI, 3.58-8.06, and MD, 11.8%, 95% CI, 0.79-22.81, respectively). Also, absolute forced vital capacity volume changes (MD, 0.11 L; 95% CI, 0.01-0.21) and percentage changes (MD, 4.44%; 95% CI, 0.84-8.04) improved in tralokinumab at 300 mg every 2 weeks. Asthma Quality of Life Questionnaire scores were not significantly different, and absolute Asthma Control Questionnaire 6 scores were statistically improved but did not reach the clinically meaningful difference. Tralokinumab treatment did not decrease annualized asthma exacerbation rate in unselected patients with moderate to severe asthma, but it was associated with improved annualized asthma exacerbation rate in patients with severe asthma with high fractional exhaled nitric oxide levels (rate ratio, 0.72; 95% CI, 0.53-0.97). Tralokinumab was not associated with an increased incidence of serious adverse events, but it did show an increase in mild injection-site reactions (odds ratio, 5.92; 95% CI, 1.61-21.76).

CONCLUSION

This pooled analysis of 6 RCTs suggested that tralokinumab was well tolerated and it modestly improved FEV₁ and forced vital capacity in patients with moderate to severe asthma. It did not render clinically important improvements in asthma-related quality of life, and nor did it reduce asthma exacerbations.

Targeting the interleukin-4 and interleukin-13 pathways in severe asthma: current knowledge and future needs

PURPOSE OF REVIEW

Severe asthma is a heterogeneous disease that can be classified into phenotypes and endotypes based upon clinical or biological characteristics. Interleukin (IL)-4 and IL-13 play a key role in type 2 (T2) asthma. This article reviews the signaling pathway of IL-4 and IL-13 and highlights its targeted therapy in severe asthma.

RECENT FINDINGS

Several clinical trials of biologics targeting the IL-4/IL-13 pathway have recently been completed. In patients with severe, uncontrolled asthma, targeting IL-13 alone with biologics including lebrikizumab and tralokinumab has not shown consistent reduction in asthma exacerbations. Simultaneous targeting of both IL-4 and IL-13 by blocking IL-4 receptor α using dupilumab has yielded more consistent results in reducing asthma exacerbations and improving lung function, especially in patients with increased blood eosinophils. Other biomarkers of T2 inflammation such as exhaled nitric oxide and serum periostin may also predict response to biologics targeting the IL-4/IL-13 pathway.

SUMMARY

No biologic targeting the IL-4/IL-13 pathway is currently available for treatment of asthma, but emerging data suggest that biologics targeting IL-4 and IL-13 together may benefit patients with T2 high asthma. Additional data are needed about long-term efficacy and safety prior to incorporating these drugs into routine clinical practice.

Tralokinumab for the treatment of severe, uncontrolled asthma: the ATMOSPHERE clinical development program

Tralokinumab, a fully human IgG₄ monoclonal antibody, specifically neutralizes IL-13. The ATMOSPHERE clinical development program comprised four randomized, placebo-controlled clinical trials and an open-label study that aimed to assess the efficacy and safety of tralokinumab for the treatment of severe, uncontrolled asthma. The two pivotal trials (STRATOS 1 and STRATOS 2; NCT02161757 and NCT02194699) evaluated the efficacy and safety of tralokinumab, with STRATOS 1 identifying a subgroup most likely to demonstrate enhanced response to treatment. Further trials have assessed the ability of tralokinumab to reduce oral corticosteroid use (TROPOS; NCT02281357) and determined its mechanistic effects (MESOS; NCT02449473). An open-label study in Japanese individuals (NCT02902809) assessed the long-term safety and tolerability of tralokinumab in this population.

Regulatory effects of IL-15 on allergen-induced airway obstruction

BACKGROUND

Airway obstruction is a physiologic feature of asthma, and IL-15 might have an important role in asthma pathogenesis.

OBJECTIVE

We tested the hypothesis that regulation of IL-15 is critical for preservation of allergen-induced airway hyperresponsiveness (AHR), airway resistance, and compliance in response to methacholine.

METHODS

Airway inflammation, AHR, resistance, and compliance were assessed in Il15 gene-deficient mice and IL-15-overexpressing mice in an allergen-induced murine model of asthma. We assessed eosinophil numbers by using anti-major basic protein immunostaining, goblet cell hyperplasia by using periodic acid-Schiff staining, and cytokine and chemokine levels by performing quantitative PCR and ELISA.

RESULTS

We made a novel observation that IL-15 deficiency promotes baseline airway resistance in naive mice. Moreover, rIL-15 delivery to the lung downregulates expression of proinflammatory cytokines and improves allergen-induced AHR, airway resistance, and compliance. These observations were further validated in doxycycline-inducible CC10-IL-15 bitransgenic mice. Doxycycline-exposed, Aspergillus species extract-challenged CC10-IL-15 bitransgenic mice exhibited significantly reduced levels of proinflammatory cytokines (IL-4, IL-5, and IL-13) and decreased goblet cell hyperplasia. Airway obstruction, including AHR and airway resistance, was diminished in allergen-challenged doxycycline-exposed compared with non-doxycycline-exposed CC10-IL-15 bitransgenic mice. Mechanistically, we observed that IL-15-mediated protection of airway obstruction is associated with induced IFN-γ- and IL-10-producing regulatory CD4+CD25+ forkhead box p3 (Foxp3)+ T cells. Additionally, we found that a human IL-15 agonist (ALT-803) improved airway resistance and compliance in an experimental asthma model.

CONCLUSION

We report our novel finding that IL-15 has a potent inhibitory effect on the airway obstruction that occurs in response to environmental allergens.

Development and analytical performance of a new ARCHITECT automated dipeptidyl peptidase-4 immunoassay

Background

Dipeptidyl peptidase-4 (DPP-4) may be a suitable biomarker to identify people with severe asthma who have greater activation of the interleukin-13 (IL-13) pathway and may therefore benefit from IL-13-targeted treatments. We report the analytical performance of an Investigational Use Only immunoassay and provide data on the biological range of DPP-4 concentrations.

Methods

We assessed assay performance, utilising analyses of precision, linearity and sensitivity; interference from common endogenous assay interferents, and from asthma and anti-diabetic medications, were also assessed. The assay was used to measure the range of serum DPP-4 concentrations in healthy volunteers and subjects with diabetes and severe, uncontrolled asthma.

Results

The total precision of DPP-4 concentration measurement (determined using percentage coefficient of variation) was ≤5% over 20 days. Dilution analysis yielded linear results from 30 to 1305 ng/mL; the limit of quantitation was 19.2 ng/mL. No notable endogenous or drug interferences were observed at the expected therapeutic concentration. Median DPP-4 concentrations in healthy volunteers and subjects with asthma or Type 1 diabetes were assessed, with concentrations remaining similar in subjects with diabetes and asthma across different demographics.

Conclusion

These analyses indicate that the ARCHITECT DPP-4 Immunoassay is a reliable and robust method for measuring serum DPP-4 concentration.

Role of IL-15 in the modulation of TGF-β1-mediated inflammation in asthma

Transforming growth factor (TGF)-β1 has an essential role in bronchitis and the induction of bronchial remodelling, which are critical processes in the pathogenesis of asthma. However, the role of interleukin (IL)-15 in asthma inflammation remains unclear. The aim of the present study was to evaluate the effect of TGF-β1 mRNA expression on IL-15 mRNA expression in asthmatic patients and to assess the role of IL-15 in the clinical course of asthma. The study included 221 participants, comprising 130 patients with asthma and 91 healthy volunteers. The participants were subjected to testing using spirometry, as well as the Asthma Control Test™ and Borg Scale. The expression of TGF-β1 and IL-15 mRNA was analyzed in blood samples using reverse transcription-quantitative polymerase chain reaction. Statistical analysis indicated that IL-15 and TGF-β1 mRNA expression each differed significantly between the patient and control groups (P=0.0016 and P=0.033, respectively). A significant correlation was identified between IL-15 expression and TGF-β1 expression (R=0.41, P=0.0005). No correlation was observed between IL-15 expression and the degree of asthma severity, the results of spirometric examination or the frequency of asthma exacerbations. Further analysis revealed that IL-15 expression was elevated following the administration of inhaled glucocorticosteroids (iGCs; P=0.024), and reduced following methylxanthine treatment (P<0.001). The occurrence of dyspnoea differed between the study and control groups, and this was not found to be associated with IL-15 expression. Since IL-15 expression was correlated with TGF-β1 expression among asthmatic patients, and IL-15 expression was elevated following iGC administration, the results of the study suggest that IL-15 activity might be associated with the pathogenesis of asthma.

IL-15-deficient mice develop enhanced allergic responses to airway allergen exposure

BACKGROUND

Interleukin-15 is a pleiotropic cytokine that is critical for the development and survival of multiple haematopoietic lineages. Mice lacking IL-15 have selective defects in populations of several pro-allergic immune cells including natural killer (NK) cells, NKT cells, and memory CD8+ T cells. We therefore hypothesized that IL-15-/- mice will have reduced inflammatory responses during the development of allergic airway disease (AAD).

OBJECTIVE

To determine whether IL-15-/- mice have attenuated allergic responses in a mouse model of AAD.

METHODS

C57BL/6 wild-type (WT) and IL-15-/- mice were sensitized and challenged with ovalbumin (OVA), and the development of AAD was ascertained by examining changes in airway inflammatory responses, Th2 responses, and lung histopathology.

RESULTS

Here, we report that IL-15-/- mice developed enhanced allergic responses in an OVA-induced model of AAD. In the absence of IL-15, OVA-challenged mice exhibited enhanced bronchial eosinophilic inflammation, elevated IL-13 production, and severe lung histopathology in comparison with WT mice. In addition, increased numbers of CD4+ T and B cells in the spleens and bronchoalveolar lavage (BAL) were also observed. Examination of OVA-challenged IL-15Rα-/- animals revealed a similar phenotype resulting in enhanced airway eosinophilia compared to WT mice. Adoptive transfer of splenic CD8+ T cells from OVA-sensitized WT mice suppressed the enhancement of eosinophilia in IL-15-/- animals to levels observed in WT mice, but had no further effects.

CONCLUSION AND CLINICAL RELEVANCE

These data demonstrate that mice with an endogenous IL-15 deficiency are susceptible to the development of severe, enhanced Th2-mediated AAD, which can be regulated by CD8+ T cells. Furthermore, the development of disease as well as allergen-specific Th2 responses occurs despite deficiencies in several IL-15-dependent cell types including NK, NKT, and γδ T cells, suggesting that these cells or their subsets are dispensable for the induction of AAD in IL-15-deficient mice.

Strategies targeting the IL-4/IL-13 axes in disease

IL-4 and IL-13 are pleiotropic Th2 cytokines produced by a wide variety of different cell types and responsible for a broad range of biology and functions. Physiologically, Th2 cytokines are known to mediate host defense against parasites but they can also trigger disease if their activities are dysregulated. In this review we discuss the rationale for targeting the IL-4/IL-13 axes in asthma, atopic dermatitis, allergic rhinitis, COPD, cancer, inflammatory bowel disease, autoimmune disease and fibrotic disease as well as evaluating the associated clinical data derived from blocking IL-4, IL-13 or IL-4 and IL-13 together.

A novel approach to understanding the role of polymorphic forms of the NR3C1 and TGF-β1 genes in the modulation of the expression of IL-5 and IL-15 mRNA in asthmatic inflammation

The aim of the present study was to identify polymorphic forms of the nuclear receptor subfamily 3, group C, member 1 (NR3C1) and transforming growth factor β1 (TGF-β1) genes and evaluate their impact on the expression levels of interleukin (IL)-5 and IL‑15 in asthma. The study was conducted on a control group consisting of 91 people (54 women and 37 men). The patient group consisted of 130 participants (86 women and 44 men). Genotyping was performed by polymerase chain reaction‑restriction fragment length polymorphism (PCR‑RFLP) and PCR‑high resolution melting (HRM) methods. Interleukin expression was measured by reverse transcription‑quantitative polymerase chain reaction. The frequency of the polymorphic forms in the analyzed group were observed to be: Tth111I (rs10052957) controls AA 0.0440, AG 0.5714, GG 0.3846, patients AA 0.1538/AG 0.4692, GG 0.3769; ER22/23EK (rs6189 /rs6190) controls AG 0.0556, GG 0.9444, patients AG 0.0385, GG 0.9615; N363S (rs6195) controls AA 0.6444, AG 0.2667, GG 0.0889, patients AA 0.7846, AG 0.1385, GG 0.0769; BclI (rs41423247) controls CC 0.0879, CG 0.5604, GG 0.3516, patients CC 0.1008, CG 0.5736, GG 0.3256; C‑509T (rs1800469) controls TT 0.0805, CT 0.6322, CC 0.2874, patients TT 0.1102, CT 0.5669, CC 0.3228. The results indicated that the C‑509T single nucleotide polymorphism (SNP) of the TGF-β1 gene contributed to an increase in the IL‑5 mRNA expression levels. The GG genotype of the N363S SNP of the NR3C1 gene was observed to result in an increase in the expression levels of IL‑15. The present study indicated that the selected SNPs of the NR3C1 and TGF‑β1 genes demonstrate a regulatory effect on the expression of IL‑5 and IL‑15. Therefore, genetic variation affects inflammation in asthma and the clinical course of the disease.

Current and future biomarkers in allergic asthma

Diagnosis early in life, sensitization, asthma endotypes, monitoring of disease and treatment progression are key motivations for the exploration of biomarkers for allergic rhinitis and allergic asthma. The number of genes related to allergic rhinitis and allergic asthma increases steadily; however, prognostic genes have not yet entered clinical application. We hypothesize that the combination of multiple genes may generate biomarkers with prognostic potential. The current review attempts to group more than 161 different potential biomarkers involved in respiratory inflammation to pave the way for future classifiers. The potential biomarkers are categorized into either epithelial or infiltrate-derived or mixed origin, epithelial biomarkers. Furthermore, surface markers were grouped into cell-type-specific categories. The current literature provides multiple biomarkers for potential asthma endotypes that are related to T-cell phenotypes such as Th1, Th2, Th9, Th17, Th22 and Tregs and their lead cytokines. Eosinophilic and neutrophilic asthma endotypes are also classified by epithelium-derived CCL-26 and osteopontin, respectively. There are currently about 20 epithelium-derived biomarkers exclusively derived from epithelium, which are likely to innovate biomarker panels as they are easy to sample. This article systematically reviews and categorizes genes and collects current evidence that may promote these biomarkers to become part of allergic rhinitis or allergic asthma classifiers with high prognostic value.

PPAR-γ inhibits IL-13-induced collagen production in mouse airway fibroblasts

Interleukin-13 (IL-13) plays an important role in extracellular matrix production of airway remodeling in asthma. Activation of PPAR-γ has been shown to inhibit the occurrence of airway fibrosis in asthma, yet it remains unknown whether the effect of PPAR-γ on suppression of airway fibrosis is associated with the inhibition of IL-13 signaling. In the present study, primary cultured airway fibroblasts were stimulated with IL-13, and JAK inhibitor, PDGF receptor blocker and MEK inhibitor were applied to investigate the involvement of these pathways in IL-13-induced collagen production. Our results demonstrate that IL-13 dose- and time-dependently induced collagen production in primary cultured mouse airway fibroblasts; this effect was blocked by inhibition of JAK/STAT6 signal pathway. IL-13 also stimulated JAK/STAT6-dependent PDGF production, elevation of PDGF in turn activated ERK1/2 MAPK and caused collagen production. Activation of PPAR-γ by rosiglitazone reduced IL-13-induced collagen expression by suppression of STAT6-driven PDGF production. Our results indicate that activation of JAK/STAT6 signal and subsequent PDGF generation and ERK1/2 MAPK activation mediate IL-13-induced collagen production in airway fibroblasts. This study suggests that activation of PPAR-γ might be a novel strategy for the treatment of asthma partially by inhibition of airway fibrosis.

Which biomarkers are effective for identifying Th2-driven inflammation in asthma?

Recognition of asthma as a heterogeneous disease revealed different potential molecular targets and urged the development of targeted, customized treatment modalities. Evidence was provided for different inflammatory subsets of asthma and more recently, further refined to T helper (Th)2-high and Th2-low subphenotypes with different responsiveness to standard and targeted pharmacotherapy. Given these differences in immunology and pathophysiology, proof of concept studies of novel treatment modalities for asthma should be performed in adequate, well-defined phenotypes. In this review, we describe both existing and novel biomarkers of Th2-inflammation in asthma that can be applied to classify asthma subphenotypes in clinical studies and for treatment monitoring.

Interleukin-13 signaling and its role in asthma

Asthma affects nearly 300 million people worldwide. The majority respond to inhaled corticosteroid treatment with or without beta-adrenergic agonists. However, a subset of 5 to 10% with severe asthma do not respond optimally to these medications. Different phenotypes of asthma may explain why current therapies show limited benefits in subgroups of patients. Interleukin-13 is implicated as a central regulator in IgE synthesis, mucus hypersecretion, airway hyperresponsiveness, and fibrosis. Promising research suggests that the interleukin-13 pathway may be an important target in the treatment of the different asthma phenotypes.

Preclinical development of CAT-354, an IL-13 neutralizing antibody, for the treatment of severe uncontrolled asthma

BACKGROUND AND PURPOSE

IL-13 is a pleiotropic Th2 cytokine considered likely to play a pivotal role in asthma. Here we describe the preclinical in vitro and in vivo characterization of CAT-354, an IL-13-neutralizing IgG4 monoclonal antibody (mAb), currently in clinical development.

EXPERIMENTAL APPROACH

In vitro the potency, specificity and species selectivity of CAT-354 was assayed in TF-1 cells, human umbilical vein endothelial cells and HDLM-2 cells. The ability of CAT-354 to modulate disease-relevant mechanisms was tested in human cells measuring bronchial smooth muscle calcium flux induced by histamine, eotaxin generation by normal lung fibroblasts, CD23 upregulation in peripheral blood mononuclear cells and IgE production by B cells. In vivo CAT-354 was tested on human IL-13-induced air pouch inflammation in mice, ovalbumin-sensitization and challenge in IL-13 humanized mice and antigen challenge in cynomolgus monkeys.

KEY RESULTS

CAT-354 has a 165 pM affinity for human IL-13 and functionally neutralized human, human variant associated with asthma and atopy (R130Q) and cynomolgus monkey, but not mouse, IL-13. CAT-354 did not neutralize human IL-4. In vitro CAT-354 functionally inhibited IL-13-induced eotaxin production, an analogue of smooth muscle airways hyperresponsiveness, CD23 upregulation and IgE production. In vivo in humanized mouse and cynomolgus monkey antigen challenge models CAT-354 inhibited airways hyperresponsiveness and bronchoalveolar lavage eosinophilia.

CONCLUSIONS AND IMPLICATIONS

CAT-354 is a potent and selective IL-13-neutralizing IgG4 mAb. The preclinical data presented here support the trialling of this mAb in patients with moderate to severe uncontrolled asthma.

The role of IL-15 deficiency in the pathogenesis of virus-induced asthma exacerbations

Rhinovirus infections are the major cause of asthma exacerbations. We hypothesised that IL-15, a cytokine implicated in innate and acquired antiviral immunity, may be deficient in asthma and important in the pathogenesis of asthma exacerbations. We investigated regulation of IL-15 induction by rhinovirus in human macrophages in vitro, IL-15 levels in bronchoalveolar lavage (BAL) fluid and IL-15 induction by rhinovirus in BAL macrophages from asthmatic and control subjects, and related these to outcomes of infection in vivo. Rhinovirus induced IL-15 in macrophages was replication-, NF-κB- and α/β interferon-dependent. BAL macrophage IL-15 induction by rhinovirus was impaired in asthmatics and inversely related to lower respiratory symptom severity during experimental rhinovirus infection. IL-15 levels in BAL fluid were also decreased in asthmatics and inversely related with airway hyperresponsiveness and with virus load during in vivo rhinovirus infection. Deficient IL-15 production in asthma may be important in the pathogenesis of asthma exacerbations.

We previously reported deficiency in interferon production in asthma, which correlated with disease severity and viral load during experimental rhinovirus infection. Here we show that macrophages produce IL-15 upon rhinovirus infection and that IFN-β plays an important role in IL-15 production. In asthmatic subjects, there is a deficiency in rhinovirus-induced production of IL-15 by macrophages, which indicates immunodeficiency in asthma is surprisingly broad, also involving IL-15, an important cytokine that bridges innate and acquired immunity. These results show that IFN-β therapy in asthma exacerbations could be effective not only due to direct anti-viral effects of IFN-β, but also by inducing IL-15 production. We also show induction of IFN-β and IL-15 to be NF-kB dependent, an important finding which has implications for NF-kB inhibitor drug development programmes as these drugs have potential to worsen rather than improve asthma exacerbation severity, by further enhancing deficiencies of IL-15 and IFN-β. This study investigating the role of IL-15 in rhinovirus infection and asthma has also major implications in other diseases, for example pandemic influenza, where asthma is a major risk factor for severe disease and death, and COPD and cystic fibrosis where IFN-β deficiency is also present.

IL-13 expression by blood T cells and not eosinophils is increased in asthma compared to non-asthmatic eosinophilic bronchitis

BACKGROUND

In asthma interleukin (IL)-13 is increased in the airway compared with non-asthmatic eosinophilic bronchitis. Whether this differential expression is specific to the airway or is more generalised is uncertain.

METHODS

We sought to examine IL-13 expression in peripheral blood T-cells and eosinophils in asthma and non-asthmatic eosinophilic bronchitis. Peripheral blood CD3+ cell and eosinophil intracellular IL-13 expression from subjects with asthma, non-asthmatic eosinophilic bronchitis and healthy controls was assessed. The effect of priming by asthmatic serum on the release of IL-13 by peripheral blood mononuclear cells from healthy subjects was examined and the serum from these subjects was analysed for a range of chemokines and cytokines.

RESULTS

The median (IQR)% intracellular IL-13 expression by CD3+ cells was increased in asthma [5.3 (2.7-9.8)%; n = 12] compared to non-asthmatic eosinophilic bronchitis [1.1 (0.5-3)%; n = 7] and healthy controls [1.7 (0.2-3%); n = 9] (p = 0.02), but was not significantly different in eosinophils across the groups. IL-13 released from healthy peripheral blood mononuclear cells (n = 10) was increased by asthmatic serum [117 (47.8-198)pg/ml] compared to control [78.5 (42.6-128)pg/ml; p = 0.02), but was not affected by non-asthmatic serum.

CONCLUSION

Our findings support the view that IL-13 expression is increased in peripheral blood-derived T cells in asthma and that asthmatic serum up-regulates IL-13 release from healthy peripheral blood mononuclear cells.

Th2 cells as targets for therapeutic intervention in allergic bronchial asthma

Th2 cells play a central role in the pathogenesis of allergic bronchial asthma, since each of their characteristic cytokines such as IL-4, IL-5, IL-9 and IL-13 contributes to hallmarks of this disease, including airway eosinophilia, increased mucus production, production of allergen-specific IgE and development of airway hyper-responsiveness. Therefore, these cells are predisposed as target cells for therapeutic intervention. Experimental approaches targeted Th2-type effector cytokines, Th2-cell recruitment and Th2-cell development. Another strategy uses the immunomodulatory potential of tolerance-inducing cytokines such as IL-10 or of cytokines such as IL-12, IL-18 and IFN-gamma that are able to induce a counterbalancing Th1 immune response.

Inflammatory and functional effects of increasing asthma treatment with formoterol or double dose budesonide

Adding a long-acting beta(2)-agonist to inhaled corticosteroids (ICS) for asthma treatment is better than increasing ICS dose in improving clinical status, although there is no consensus about the impact of this regimen on inflammation. In this double-blind, randomized, parallel group study, asthmatics with moderate to severe disease used budesonide (400 mcg/day) for 5 weeks (run-in period); then they were randomized to use budesonide (800 mcg/day--BUD group) or budesonide plus formoterol (400 mcg and 24 mcg/day, respectively--FORMO group) for 9 weeks (treatment period). Home PEF measurements, symptom daily reporting, spirometry, sputum induction (for differential cell counts and sputum cell cultures), and hypertonic saline bronchial challenge test were performed before and after treatments. TNF-alpha, IL-4 and eotaxin-2 levels in the sputum and cell culture supernatants were determined. Morning and night PEF values increased in the FORMO group during the treatment period (p<0.01), from 435+/-162 to 489+/-169 and 428+/-160 to 496+/-173 L/min, respectively. The rate of exacerbations in the FORMO group was lower than in the BUD group (p<0.05). Neutrophil counts in sputum increased in both groups (p<0.05) and leukocyte viability after 48 h-culture increased in the FORMO group (p<0.05). No other parameter changed significantly in either group. This study showed that adding formoterol to budesonide improved home PEF and provided protection from exacerbations, although increase of leukocyte viability in cell culture may be a matter of concern and needs further investigation.

Increased sputum and bronchial biopsy IL-13 expression in severe asthma

BACKGROUND

The importance of IL-13 in the asthma paradigm is supported by increased expression in human subjects, particularly in patients with mild-to-moderate asthma. However, the role of IL-13 in severe asthma needs to be further defined.

OBJECTIVE

We sought to assess IL-13 expression in sputum and bronchial biopsy specimens from subjects with mild-to-severe asthma.

METHODS

Sputum IL-13 concentrations were measured in 32 control subjects, 34 subjects with mild asthma, 21 subjects with moderate asthma, and 26 subjects with severe asthma. Enumeration of mast cells, eosinophils, and IL-13+ cells in the bronchial submucosa and airway smooth muscle (ASM) bundle was performed in 7 control subjects, 14 subjects with mild asthma, 7 subjects with moderate asthma, and 7 subjects with severe asthma.

RESULTS

The proportion of subjects with measurable IL-13 in the sputum was increased in the mild asthma group (15/34) and severe asthma group (10/26) compared with that seen in the control group (4/32; P = .004). IL-13+ cells were increased within the submucosa in all asthma severity groups compared with control subjects (P = .006). The number of IL-13+ cells were increased within the ASM bundle in the severe asthma group compared with that seen in the other groups (P < .05). Asthma control questionnaire scores positively correlated with sputum IL-13 concentrations (R(s) = 0.35, P = .04) and mast cells in the ASM bundle (R(s) = 0.7, P = .007). IL-13+ cells within the submucosa and ASM correlated with sputum eosinophilia (R(s) = 0.4, P < or = .05).

CONCLUSIONS

IL-13 overexpression in sputum and bronchial biopsy specimens is a feature of severe asthma.

NKT cells in the induced sputum of severe asthmatics

To determine whether there was a specific inflammatory process in severe asthmatics, the phenotypic characteristics of induced sputum immune cells were analysed among patients with severe asthma. Twenty-two induced sputa (10 severe asthmatics) were studied. Flow cytometric analysis was performed using immune cells of the sputum and monoclonal antibodies to CD3, CD4, CD8, CD56, CD25, and TCRγδ. The number of NKT (CD3⁺CD56⁺) cells was significantly higher in the sputum of severe asthmatics compared with mild asthmatic and healthy control groups (P < .05). CD8⁺CD56⁺ cells were the predominant subtype of the increased NKT cells in severe asthmatics. CD3⁺CD56⁺Vα24⁺, TCRγδ⁺ CD56⁺, and CD4⁺CD25⁺ T cells were significantly increased in severe asthmatic patients. These results suggest that the immunopathogenesis of severe asthmatics vary between severe and mild asthmatics, and that CD8⁺CD56⁺ NKT cells may play an important role in the immunopathogenesis of severe asthma.

Evaluation of airway inflammation by quantitative Th1/Th2 cytokine mRNA measurement in sputum of asthma patients

BACKGROUND

Asthma is a chronic inflammatory disorder of the airways driven by T cell activation. Th2 cells and their cytokines are thought to play a role in the pathophysiology of allergic as well as non-allergic asthma.

METHODS

Airway cells were obtained by sputum induction from 15 healthy and 39 asthmatic individuals and the airway T cell cytokine profiles (interleukin (IL)-4, IL-5, IL-13, IL-10 and interferon (IFN)-gamma) at the mRNA level were studied by real time RT-PCR.

RESULTS

Asthma patients had increased expression of IL-5 (p = 0.001) and IL-13 (p = 0.03) mRNA in sputum compared with non-asthmatic controls. IL-4 mRNA and IFN-gamma mRNA were detectable in the sputum of 44% and 21% of patients, respectively, but not in controls. Sputum IL-10 mRNA levels did not differ significantly between patients and controls. Sputum mRNA expression levels of IL-4, IL-5, and IL-13 were significantly correlated with the percentage of eosinophils and were higher in subjects with allergic asthma than in those with non-allergic asthma (p = 0.03, p = 0.02 and p = 0.0002, respectively); they did not differ between mild asthmatic subjects and those with moderate to severe asthma. In contrast, IFN-gamma mRNA expression was higher in non-allergic than in allergic patients (p = 0.04) and higher in patients with moderate to severe asthma than in those with mild asthma (p<0.01). Sputum IL-5 mRNA levels (but not the other cytokine mRNA levels) were also correlated with exhaled nitric oxide (eNO) and with bronchial hyperreactivity expressed as the histamine concentration resulting in a 20% decrease in forced expiratory volume in 1 second.

CONCLUSION

Real time RT-PCR analysis of mRNA in induced sputum confirms a predominance of Th2 cytokines in both allergic and non-allergic asthma. IL-5 levels reflect eosinophil infiltration as well as eNO levels and hyperreactivity, and levels of the Th1 cytokine IFN-gamma indicate asthma severity. The technique is a promising tool for use in further studies of asthma severity and disease activity.

Interleukin-18 levels in induced sputum are reduced in asthmatic and normal smokers

BACKGROUND

IL-18 is a cytokine which is known to have an important role in the development of a Th1 lymphocyte response. As such, it may have a regulatory role in asthma by modifying Th2 lymphocyte responses. Cigarette smoking may amplify the airway inflammation associated with asthma.

OBJECTIVE

This study investigated if IL-18 could be detected in induced sputum from asthmatics and normal subjects and if smoking altered IL-18 levels.

METHODS

Induced sputum was obtained from asthmatic (31 smokers, 35 non-smokers) and normal (20 smokers, 20 non-smokers) subjects. All smokers had a smoking history of > or =15 pack years. IL-18 levels in sputum supernatant were measured by ELISA. IL-18 mRNA expression and cellular localization were assessed by quantitative PCR and immunocytochemistry, respectively.

RESULTS

Smoking was associated with a significant reduction in IL-18 levels (median (interquartile range) - smokers 20 (0-102) pg/mL vs. non-smokers 358 (50-876) pg/mL, P<0.001). This was more pronounced in asthmatics (smokers, 47 (40-64) pg/mL vs. non-smokers, 530 (30-1484) pg/mL; P<0.001) than in normal subjects (smokers, 25 (0-78) pg/mL vs. non-smokers, 247 (50-656) pg/mL; P<0.01). Within each of the smoking and non-smoking groups there was no significant difference in IL-18 levels between asthmatic and normal subjects. There was no correlation between sputum IL-18 levels and any specific cell type in the sputum samples nor serum IgE levels. IL-18 mRNA expression was reduced in asthmatic smokers compared with non-smokers. IL-18 production was localized to sputum macrophages by immunocytochemistry.

CONCLUSIONS

IL-18 is detectable in induced sputum samples from both asthmatic and normal subjects. Cigarette smoking significantly reduces sputum IL-18 levels. This effect is more pronounced in asthmatics than in normal subjects.