Interleukin-5 and its receptor system: implications in the immune system and inflammation

Post-marketing safety of anti-IL-5 monoclonal antibodies (mAbs): an analysis of the FDA Adverse Event Reporting System (FAERS)

BACKGROUND

Anti-IL-5 monoclonal antibodies (mAbs) targeting IL-5 or IL-5 R α (including mepolizumab, benralizumab, and reslizumab) are widely used for inflammatory diseases such as asthma, eosinophilia, and polyangiitis. However, real-world data regarding its safety in a large sample population are incomplete. So, we evaluated the safety of anti-IL-5 mAbs by pharmacovigilance analyzes based on related adverse events (AEs) from the FDA Adverse Event Reporting System (FAERS).

METHODS

In disproportionality analysis, four algorithms were employed to detect the signals of anti-IL-5 mAbs from the FAERS between 2016 and 2022. In addition, we also used MYSQL 8.0, Navicat Premium 15, and Microsoft EXCEL 2019 to analyze the signals of anti-IL-5 mAbs systematically.

RESULTS

There are 9,476,351 reports collected from the FAERS database, of which 22,174 reports listed anti-IL-5 mAbs as the 'primary suspected (PS)' drug. A total of 59 (20 new signals, mepolizumab) and 62 (19 new signals, benralizumab) significant disproportionality preferred terms (PTs) conforming to the four algorithms were retained synchronously. Finally, we detected that the anti-IL-5 mAbs-induced AEs occurred in 31 organ systems (mepolizumab) and 30 organ systems (benralizumab). For mepolizumab and reslizumab, unexpected and new significant PTs of AEs were found, such as asthmatic crisis, chronic obstructive pulmonary disease (COPD), pneumonia, COVID-19, pneumothorax, adrenal insufficiency and so on. Notably, the risk signal of asthmatic crisis for mepolizumab was stronger than benralizumab (ROR 108.04 [95%CI, 96.09-121.47] vs 26.83 [95%CI, 18.91-38.06]). Comparing with mepolizumab and benralizumab, we found the proportion of serious adverse events in mepolizumab was both greater than benralizumab in each age group (≤20, 20-65, and ≥ 65). The median onset time of mepolizumab was 280 days (interquartile range [IQR] 1-367 days).

CONCLUSION

Analysis of FAERS data identified anti-IL-5 mAbs-associated AEs, and our findings supported continuous clinical monitoring, pharmacovigilance, and further studies of anti-IL-5 mAbs. In addition, clinicians may be more aware of the limitations of use in package inserts of anti-IL-5 mAbs: Not for relief of acute bronchospasm or status asthmaticus. Because of some limitations in the FAERS such as self-reports from patients and other confounding factors, the safety of anti-IL-5 mAbs needed more studies in different dimensions, especially the risk of cancer.

Blood transcriptomic signature in type-2 biomarker-low severe asthma and asthma control

BACKGROUND

Patients with type-2 (T2) cytokine-low severe asthma often have persistent symptoms despite suppression of T2 inflammation with corticosteroids.

OBJECTIVES

We sought to analyze whole blood transcriptome from 738 samples in T2-biomarker-high/-low patients with severe asthma to relate transcriptomic signatures to T2 biomarkers and asthma symptom scores.

METHODS

Bulk RNA-seq data were generated for blood samples (baseline, week 24, week 48) from 301 participants recruited to a randomized clinical trial of corticosteroid optimization in severe asthma. Unsupervised clustering, differential gene expression analysis, and pathway analysis were performed. Patients were grouped by T2-biomarker status and symptoms. Associations between clinical characteristics and differentially expressed genes (DEGs) associated with biomarker and symptom levels were investigated.

RESULTS

Unsupervised clustering identified 2 clusters; cluster 2 patients were blood eosinophil-low/symptom-high and more likely to be receiving oral corticosteroids (OCSs). Differential gene expression analysis of these clusters, with and without stratification for OCSs, identified 2960 and 4162 DEGs, respectively. Six hundred twenty-seven of 2960 genes remained after adjusting for OCSs by subtracting OCS signature genes. Pathway analysis identified dolichyl-diphosphooligosaccharide biosynthesis and assembly of RNA polymerase I complex as significantly enriched pathways. No stable DEGs were associated with high symptoms in T2-biomarker-low patients, but numerous associated with elevated T2 biomarkers, including 15 that were upregulated at all time points irrespective of symptom level.

CONCLUSIONS

OCSs have a considerable effect on whole blood transcriptome. Differential gene expression analysis demonstrates a clear T2-biomarker transcriptomic signature, but no signature was found in association with T2-biomarker-low patients, including those with a high symptom burden.

Treatment of allergic eosinophilic asthma through engineered IL-5-anchored chimeric antigen receptor T cells

Severe eosinophilic asthma (SEA) is a therapy-resistant respiratory condition with poor clinical control. Treatment efficacy and patient compliance of current therapies remain unsatisfactory. Here, inspired by the remarkable success of chimeric antigen receptor-based cellular adoptive immunotherapies demonstrated for the treatment of a variety of malignant tumors, we engineered a cytokine-anchored chimeric antigen receptor T (CCAR-T) cell system using a chimeric IL-5-CD28-CD3ζ receptor to trigger T-cell-mediated killing of eosinophils that are elevated during severe asthma attacks. IL-5-anchored CCAR-T cells exhibited selective and effective killing capacity in vitro and restricted eosinophil differentiation with apparent protection against allergic airway inflammation in two mouse models of asthma. Notably, a single dose of IL-5-anchored CCAR-T cells resulted in persistent protection against asthma-related conditions over three months, significantly exceeding the typical therapeutic window of current mAb-based treatments in the clinics. This study presents a cell-based treatment strategy for SEA and could set the stage for a new era of precision therapies against a variety of intractable allergic diseases in the future.

Interleukin-5 (IL-5) Therapy Prevents Allograft Rejection by Promoting CD4+CD25+ Ts2 Regulatory Cells That Are Antigen-Specific and Express IL-5 Receptor

CD4⁺CD25⁺Foxp3⁺T cell population is heterogenous and contains three major sub-groups. First, thymus derived T regulatory cells (tTreg) that are naïve/resting. Second, activated/memory Treg that are produced by activation of tTreg by antigen and cytokines. Third, effector lineage CD4⁺CD25⁺T cells generated from CD4⁺CD25^- T cells' activation by antigen to transiently express CD25 and Foxp3. We have shown that freshly isolated CD4⁺CD25⁺T cells are activated by specific alloantigen and IL-4, not IL-2, to Ts2 cells that express the IL-5 receptor alpha. Ts2 cells are more potent than naïve/resting tTreg in suppressing specific alloimmunity. Here, we showed rIL-5 promoted further activation of Ts2 cells to Th2-like Treg, that expressed foxp3, irf4, gata3 and il5. In vivo, we studied the effects of rIL-5 treatment on Lewis heart allograft survival in F344 rats. Host CD4⁺CD25⁺T cells were assessed by FACS, in mixed lymphocyte culture and by RT-PCR to examine mRNA of Ts2 or Th2-like Treg markers. rIL-5 treatment given 7 days after transplantation reduced the severity of rejection and all grafts survived ≥60d whereas sham treated rats fully rejected by day 31 (p<0.01). Treatment with anti-CD25 or anti-IL-4 monoclonal antibody abolished the benefits of treatment with rIL-5 and accelerated rejection. After 10d treatment with rIL-5, hosts' CD4⁺CD25⁺ cells expressed more Il5ra and responded to specific donor Lewis but not self. Enriched CD4⁺CD25⁺ cells from rIL-5 treated rats with allografts surviving >60 days proliferated to specific donor only when rIL-5 was present and did not proliferate to self or third party. These cells had more mRNA for molecules expressed by Th2-like Treg including Irf4, gata3 and Il5. These findings were consistent with IL-5 treatment preventing rejection by activation of Ts2 cells and Th2-like Treg.

Monoclonal Antibodies Targeting IL-5 or IL-5Rα in Eosinophilic Chronic Obstructive Pulmonary Disease: A Systematic Review and Meta-Analysis

Background: Although the predominant airway inflammation in chronic obstructive pulmonary disease (COPD) is neutrophilic, approximately 20-40% of COPD patients present with eosinophilic airway inflammation. Compared with non-eosinophilic COPD patients, eosinophilic COPD patients are characterized by a greater number of total exacerbations and higher hospitalization rates. Furthermore, anti-interleukin-5 (IL-5) therapy, consisting of monoclonal antibodies (mAbs) targeting IL-5 or IL-5 receptor α (IL-5Rα), has been proven to be effective in severe eosinophilic asthma. This meta-analysis aimed to determine the efficacy and safety of anti-IL-5 therapy in eosinophilic COPD. Methods: We searched the PubMed, Web of Science, Embase, and Cochrane Library databases from inception to August 2020 (updated in June 2021) to identify studies comparing anti-IL-5 therapy (including mepolizumab, benralizumab, and reslizumab) with placebo in eosinophilic COPD patients. Results: Anti-IL-5 therapy was associated with a decrease in acute exacerbation rate (RR 0.89; 95% CI 0.84 to 0.95, I ² = 0%) and the severe adverse events (RR 0.90; 95% CI 0.84 to 0.97, I ² = 0%). However, no significant improvement was observed in pre-bronchodilator forced expiratory volume in 1 s (FEV₁) (WMD 0.01; 95% CI -0.01 to 0.03, I ² = 25.9%), SGRQ score (WMD -1.17; 95% CI -2.05 to -0.29, I ² = 0%), and hospital admission rate (RR 0.91; 95% CI 0.78 to 1.07, I ² = 20.8%). Conclusion: Anti-IL-5 therapy significantly reduced the annual acute exacerbation rate and severe adverse events in eosinophilic COPD patients. However, it did not improve lung function, quality of life, and hospitalization rate.

A Phase II, Multicenter, Randomized, Placebo-Controlled Study of Benralizumab, a Humanized Anti-IL-5R Alpha Monoclonal Antibody, in Patients With Eosinophilic Chronic Rhinosinusitis

BACKGROUND

Strong eosinophil infiltration in chronic rhinosinusitis with nasal polyp (CRSwNP) is highly associated with recalcitrance and higher nasal polyp recurrence rate after surgery. The prevalence of eosinophilic CRSwNP (ECRS) is increasing in Asian countries including Japan. Benralizumab is a humanized anti-IL-5R alpha monoclonal antibody that depletes eosinophils by antibody-dependent cell-mediated cytotoxicity.

OBJECTIVE

To assess the efficacy and safety of benralizumab in patients with ECRS.

METHODS

This phase II, randomized, double-blind, placebo-controlled study was conducted in Japan. Patients were randomized 1:2:2 to placebo, a single administration of benralizumab 30 mg, or benralizumab 30 mg every 4 weeks (q4w) for a total of three doses. The primary endpoint was the change in nasal polyp score from baseline at Week 12.

RESULTS

Overall, 56 patients were enrolled (placebo, n = 11; benralizumab single dose, n = 22; benralizumab q4w, n = 23). Although the mean total nasal polyp score began to decrease after the initiation of benralizumab treatment, there were no statistically significant differences in change in nasal polyp score from baseline at Week 12 between benralizumab and placebo (placebo, -0.5 ± 0.8; benralizumab single, -0.3 ± 0.8; benralizumab q4w, -0.5 ± 1.5). Post-hoc analysis showed that the administration of benralizumab decreased nasal polyp scores ≥2 points in 42.2% of ECRS patients and that patients with high blood eosinophil levels had a greater tendency to respond to benralizumab treatment. The safety profile was similar to that in previous studies and no unexpected adverse events were noted.

CONCLUSION

Although benralizumab did not meet the primary efficacy endpoint, reductions of nasal polyp scores were seen in the benralizumab group compared with the placebo group over the whole study period, especially in patients with high levels of blood eosinophils.

Elevated Eosinophils as a Feature of Inflammation Associated With Hypertension in Virally Suppressed People Living With HIV

Background

People living with HIV (PLWH) are at increased risk of cardiovascular disease, including hypertension, which persists despite effective plasma viral suppression on antiretroviral therapy. HIV infection is characterized by long‐term alterations in immune function, but the contribution of immune factors to hypertension in PLWH is not fully understood. Prior studies have found that both innate and adaptive immune cell activation contributes to hypertension.

Methods and Results

We hypothesized that chronic inflammation may contribute to hypertension in PLWH. To test this hypothesis, we enrolled a cohort of 70 PLWH (44% hypertensive) on a long‐term single antiretroviral therapy regimen for broad phenotyping of inflammation biomarkers. We found that hypertensive PLWH had higher levels of inflammatory cytokines, including tumor necrosis factor‐α receptor 1, interleukin‐6, interleukin‐17, interleukin‐5, intercellular adhesion molecule 1 and macrophage inflammatory protein‐1α. After adjustment for age, sex, and fat mass index, the circulating eosinophils remained significantly associated with hypertension. On the basis of these results, we assessed the relationship of eosinophils and hypertension in 2 cohorts of 50 and 81 039 similar HIV‐negative people; although eosinophil count was associated with prevalent hypertension, this relationship was abrogated by body mass index.

Conclusions

These findings may represent a unique linkage between immune status and cardiovascular physiological characteristics in HIV infection, which should be evaluated further.

IL-10-producing B cells are enriched in murine pericardial adipose tissues and ameliorate the outcome of acute myocardial infarction

Acute myocardial infarction (MI) provokes an inflammatory response in the heart that removes damaged tissues to facilitate tissue repair/regeneration. However, overactive and prolonged inflammation compromises healing, which may be counteracted by antiinflammatory mechanisms. A key regulatory factor in an inflammatory response is the antiinflammatory cytokine IL-10, which can be produced by a number of immune cells, including subsets of B lymphocytes. Here, we investigated IL-10-producing B cells in pericardial adipose tissues (PATs) and their role in the healing process following acute MI in mice. We found that IL-10-producing B cells were enriched in PATs compared to other adipose depots throughout the body, with the majority of them bearing a surface phenotype consistent with CD5⁺ B-1a cells (CD5⁺ B cells). These cells were detected early in life, maintained a steady presence during adulthood, and resided in fat-associated lymphoid clusters. The cytokine IL-33 and the chemokine CXCL13 were preferentially expressed in PATs and contributed to the enrichment of IL-10-producing CD5⁺ B cells. Following acute MI, the pool of CD5⁺ B cells was expanded in PATs. These cells accumulated in the infarcted heart during the resolution of MI-induced inflammation. B cell-specific deletion of IL-10 worsened cardiac function, exacerbated myocardial injury, and delayed resolution of inflammation following acute MI. These results revealed enrichment of IL-10-producing B cells in PATs and a significant contribution of these cells to the antiinflammatory processes that terminate MI-induced inflammation. Together, these findings have identified IL-10-producing B cells as therapeutic targets to improve the outcome of MI.

Evaluation of Different Stabilizers and Inactivating Compounds for the Enhancement of Vero Cell Rabies Vaccine Stability and Immunogenicity: In Vitro Study

Inactivation of rabies virus is essential for rabies vaccine preparation where the inactivating compound that is currently recommended for rabies vaccine preparation is β-propiolactone (β-PL). This compound is considered better than phenol and formalin but it is expensive and potentially carcinogenic. Data revealed that Ascorbic acid (AA) with cupric ions could yield complete and irreversible inactivation of rabies virus without adversely affecting its antigenicity. Additionally, the results of testing the vaccine potency with the selected inactivating compounds were comparable (P<0.05), and ED50 was higher than the recommended World Health Organization (WHO) limits. The use of HemaGel (plasma substitute) for testing vaccine stabilization was compared with the currently used vaccine stabilizers (human albumin and lactose). HemaGel yielded better stability than the other tested stabilizers. Monitoring of cellular and humoral immune responses indicated that both the total IgG level against rabies vaccine and the IFN and IL5 levels obtained with the HemaGel-stabilized vaccines were higher than those obtained with human albumin- and lactose-stabilized vaccine candidates.

Modulation of blood inflammatory markers by benralizumab in patients with eosinophilic airway diseases

Background

Benralizumab, a humanized, afucosylated, monoclonal antibody that targets interleukin-5 receptor α, depletes eosinophils and basophils by enhanced antibody-dependent cell-mediated cytotoxicity. It demonstrated efficacy for patients with moderate to severe asthma and, in a Phase IIa trial, for chronic obstructive pulmonary disease (COPD) with eosinophilic inflammation. We investigated effects of benralizumab 100 mg every 8 weeks (first three doses every 4 weeks) subcutaneous on blood inflammatory markers through proteomic and gene-expression analyses collected during two Phase II studies of patients with eosinophilic asthma and eosinophilic COPD.

Methods

Serum samples for proteomic analysis and whole blood for gene expression analysis were collected at baseline and 52 weeks (asthma study) or 32 weeks (COPD study) post-treatment. Proteomic analyses were conducted on a custom set of 90 and 147 Rules-Based Medicine analytes for asthma and COPD, respectively. Gene expression was profiled by Affymetrix Human Genome U133 plus 2 arrays (~ 54 K probes). Gene set variation analysis (GSVA) was used to determine transcriptomic activity of immune signatures. Treatment-related differences between analytes, genes, and gene signatures were analyzed for the overall population and for patient subgroups stratified by baseline blood eosinophil count (eosinophil-high [≥300 cells/μL] and eosinophil-low [< 300 cells/μL]) via t-test and repeated measures analysis of variance.

Results

Eosinophil chemokines eotaxin-1 and eotaxin-2 were significantly upregulated (false discovery rate [FDR] < 0.05) by approximately 2.1- and 1.4-fold in the asthma study and by 2.3- and 1.7-fold in the COPD study following benralizumab treatment. Magnitude of upregulation of these two chemokines was greater for eosinophil-high patients than eosinophil-low patients in both studies. Benralizumab was associated with significant reductions (FDR < 0.05) in expression of genes associated with eosinophils and basophils, such as CLC, IL-5Rα, and PRSS33; immune-signaling complex genes (FCER1A); G-protein–coupled receptor genes (HRH4, ADORA3, P2RY14); and further immune-related genes (ALOX15 and OLIG2). The magnitude of downregulation of gene expression was greater for eosinophil-high than eosinophil-low patients. GSVA on immune signatures indicated significant treatment reductions (FDR < 0.05) in eosinophil-associated signatures.

Conclusions

Benralizumab is highly selective, modulating blood proteins or genes associated with eosinophils or basophils. Modulated protein and gene expression patterns are most prominently altered in eosinophil-high vs. eosinophil-low patients.

Trial registration

NCT01227278 and NCT01238861.

Electronic supplementary material

The online version of this article (10.1186/s12931-018-0968-8) contains supplementary material, which is available to authorized users.

Benralizumab: From the Basic Mechanism of Action to the Potential Use in the Biological Therapy of Severe Eosinophilic Asthma

Asthma is a very frequent chronic airway disease that includes many different clinical phenotypes and inflammatory patterns. In particular, eosinophilic bronchial inflammation is often associated with allergic as well as nonallergic asthma. The most important cytokine involved in the induction, maintenance, and amplification of airway eosinophilia in asthma is interleukin-5 (IL-5), released by both T helper 2 (Th2) lymphocytes and group 2 innate lymphoid cells (ILC2). Hence, IL-5 and its receptor are suitable targets for selective biologic drugs which can play a key role in add-on treatment of severe eosinophilic asthma refractory to corticosteroids. Within such a context, the anti-IL-5 monoclonal antibodies mepolizumab and reslizumab have been developed and approved for biological therapy of uncontrolled eosinophilic asthma. In this regard, on the basis of several successful randomized controlled trials, the anti-IL-5 receptor benralizumab has also recently obtained the approval from US Food and Drug Administration (FDA).

Allergic diseases: From bench to clinic - Contribution of the discovery of interleukin-5

T helper 2 cells produce a number of cytokines including inteleukin (IL)-5, IL-4 and IL-13. Group 2 innate lymphoid cells (ILC2s) also produce IL-5 under sterile conditions. IL-5 is interdigitating homodimeric glycoprotein and a member of the four α helical bundle motifs conserved among hematopoietic cytokines. IL-5 exerts its effects on target cells via IL-5 receptor (IL-5R), composed of an IL-5R α and βc subunit. The membrane proximal proline-rich motif of the cytoplasmic domain of both IL-5R α and βc subunits is essential for IL-5 signal transduction. Although IL-5 was initially identified by its ability to support the growth and terminal differentiation of mouse B cells into antibody-secreting cells, recombinant IL-5 exerts pleiotropic activities on various target cells. For example, IL-5 is now recognized as the major maturation and differentiation factor for eosinophils in mice and humans. Overexpression of IL-5 in mouse significantly increases eosinophil numbers and antibody levels in vivo, while mice lacking a functional gene for IL-5 or IL-5R display developmental and functional impairments in B cell and eosinophil lineages. In mice, the role of the IL-5/IL-5R system in the production and secretion of Immunoglobulin (Ig) M and IgA in mucosal tissues has been reported. Although eosinophils protect against invading pathogens including virus, bacteria and helminthes, they are also involved in the pathogenesis of various diseases, such as food allergy, asthma, and inflammatory bowel diseases. The recent expansion in our understanding in the context of IL-5 and IL-5-producing ILC2s in eosinophil activation and the pathogenesis of eosinophil-dependent inflammatory diseases has led to advances in therapeutic options. A new therapy currently under invetigarion in clinical trials uses humanized monoclonal antibodies against IL-5 or the IL-5R. In this review, we summarize our current understanding of the functions of IL-5 and its receptor, the innate regulation of IL-5-producing cells, and therapeutic potential of anti-IL-5 and anti-eosinophil (IL-5R) antibodies.

Benralizumab in the treatment of severe asthma: design, development and potential place in therapy

Asthma is a widespread and heterogeneous inflammatory disease of the airways, which is characterized by several different phenotypes and endotypes. In particular, eosinophilic airway inflammation is a common pathologic trait of both allergic and nonallergic asthma. The key cytokine responsible for maturation, activation, recruitment, and survival of eosinophils is interleukin (IL)-5, which is mainly produced by T helper 2 (Th2) lymphocytes and group 2 innate lymphoid cells. Therefore, for uncontrolled patients with severe eosinophilic asthma, who are not fully responsive to corticosteroids, IL-5 represents a very important molecular target for add-on biological therapies. Among these new treatments, anti-IL-5 monoclonal antibodies such as mepolizumab and reslizumab have been developed and clinically evaluated. Furthermore, benralizumab is currently the only available biologic drug that specifically binds to the IL-5 receptor, thus preventing the interaction with its ligand and the consequent pro-inflammatory effects. The effectiveness of benralizumab in improving severe eosinophilic asthma has been well-documented by many randomized controlled trials.

Efficacy and safety of benralizumab for eosinophilic asthma: A systematic review and meta-analysis of randomized controlled trials

CONTEXT

Benralizumab is a humanized monoclonal antibody that targets the α chain of the IL-5 receptor (IL-5Rα) and is currently being assessed in clinical trials for asthma control.

OBJECTIVE

Our systematic review and meta-analysis intends to evaluate the therapeutic efficacy and safety of benralizumab in patients with eosinophilic asthma.

DATA SOURCES AND EXTRACTION

Literature searches of PubMed, Embase, and the Cochrane Library were performed to identify randomized controlled trials of benralizumab and clinic outcomes in asthmatics.

RESULTS

In total, 7 articles with 2,321 subjects met our inclusion criteria. From this pooled analysis, we found that benralizumab significantly reduces exacerbations (RR: 0.63, 95% CI: 0.52-0.76, p < 0.00001; I² = 52%, p = 0.06) compared to placebo in eosinophilic asthma. There was no statistical trend for improvement in forced expiratory volume in 1 second or asthma control indices such as Quality of Life Assessment (AQLQ) and Asthma Control Questionnaire score in benralizumab-treated patients. In addition, safety data indicated that benralizumab administration resulted no increasing incidence of adverse events and was well tolerated (RR: 1.00, 95% CI: 0.95-1.05, p = 0.96; I² = 40%, p = 0.13).

CONCLUSION

These results demonstrate the efficacy and safety of benralizumab for asthma patients with severe or uncontrolled symptoms and elevated eosinophils and provide support for benralizumab as an ideal option to treat asthma in this patient population.

Discovery of novel 3-(hydroxyalkoxy)-2-alkylchromen-4-one analogs as interleukin-5 inhibitors

A series of novel chromen-4-one analogs 9a-d and 10a-u was designed, synthesized and evaluated for their IL-5 inhibitory activity. Most of the chromen-4-one analogs showed strong inhibitory activity in low micro molar potency. Among them, 5-(cyclohexylmethoxy)-3-(3-hydroxypropoxy)-2-isopropyl-4H-chromen-4-one (10t, 90.0% inhibition at 30 μM, IC₅₀ = 5.5 μM, CLogP = 4.76887) and 2-cyclohexyl-5-(cyclohexylmethoxy)-3-(3-hydroxypropoxy)-4H-chromen-4-one (10u, 95.5% inhibition at 30 μM, IC₅₀ = 3.0 μM, CLogP = 5.96187) showed the best inhibition. The structure activity relationship reveals that the hydrophobic cyclohexylmethoxy group at the position 5 of the chromen-4-one ring A is preferable than at position 6 and the dual hydrogen bonding acceptor property on the chromen-4-one ring should be important for the inhibitory activity. In addition, the optimum length of the side chain at position 3 of chromen-4-one ring is critical for the donation of hydrogen to the binding site and the 3-hydroxypropoxy group showed the best activity. Moreover, the conformational restrictor (isopropyl, cyclohexyl group) at position 2 is much more favorable for the formation of effective conformer of side chain with hydrogen bonding donor property of these chromen-4-one analogs.

Bringing Stability to the Chronic Obstructive Pulmonary Disease Patient: Clinical and Pharmacological Considerations for Frequent Exacerbators

Acute exacerbations of chronic obstructive pulmonary disease (AECOPD) are critical events associated with an accelerated loss of lung function, increased morbidity, and excess mortality. AECOPD are heterogeneous in nature and this may directly impact clinical decision making, specifically in patients with frequent exacerbations. A 'frequent exacerbator' is a sub-phenotype of chronic obstructive pulmonary disease (COPD) and is defined as an individual who experiences two or more moderate-to-severe exacerbations per year. This distinct subgroup has higher mortality and accounts for more than half of COPD-related hospitalizations annually. Thus, it is imperative to identify individuals at risk for frequent exacerbations and choose optimal strategies to minimize risk for these events. New paradigms for using combination inhalers and the introduction of novel oral compounds provide expanded treatment options to reduce the risk and frequency of exacerbations. The goals of managing frequent exacerbators or patients at risk for AECOPD are: (1) maximizing bronchodilation; (2) reducing inflammation; and (3) targeting specific molecular pathways implicated in COPD and AECOPD pathogenesis. Novel inhaler therapies including combination long-acting muscarinic agents plus long-acting beta agonists show promising results compared with monotherapy or a long-acting beta agonist inhaled corticosteroid combination in reducing exacerbation risk among individuals at risk for exacerbations and among frequent exacerbators. Likewise, oral medications including macrolides and phosphodiesterase-4 inhibitors reduce the risk for AECOPD in select groups of individuals at high risk for exacerbation. Future direction in COPD management is based on the identification of various subtypes or 'endotypes' and targeting therapies based on their pathophysiology. This review describes the impact of AECOPD and the challenges posed by frequent exacerbators, and explores the rationale for different pharmacologic approaches to preventing AECOPD in these individuals.

Population Pharmacokinetics and Pharmacodynamics of Benralizumab in Healthy Volunteers and Patients With Asthma

Benralizumab is a humanized, afucosylated, anti‐interleukin‐5 receptor α, immunoglobulin G (IgG) ₁ κ monoclonal antibody. We developed a population pharmacokinetic (PK)/pharmacodynamic (PD) model for benralizumab by analyzing PK and blood eosinophil count data from two healthy volunteer studies (N = 48) and four studies in patients with asthma (N = 152). Benralizumab PK was dose‐proportional and adequately described by a two‐compartment model with first‐order elimination from the central compartment and first‐order absorption from the subcutaneous dosing site. The estimated systemic clearance and volume of distribution were typical for human IgG. Body weight and high‐titer antidrug antibodies were identified as relevant covariates influencing the PK of benralizumab. Depletion of blood eosinophil counts was depicted by a modified transit model in which benralizumab induced depletion of eosinophils in each age compartment. Stochastic simulations supported an every‐8‐week dosing schedule of benralizumab for a phase IIb study in patients with uncontrolled asthma.

Inundation of asthma target research: Untangling asthma riddles

Asthma is an inveterate inflammatory disorder, delineated by the airway inflammation, bronchial hyperresponsiveness (BHR) and airway wall remodeling. Although, asthma is a vague term, and is recognized as heterogenous entity encompassing different phenotypes. Targeting single mediator or receptor did not prove much clinical significant, as asthma is complex disease involving myriad inflammatory mediators. Asthma may probably involve a large number of different types of molecular and cellular components interacting through complex pathophysiological pathways. This review covers the past, present, and future therapeutic approaches and pathophysiological mechanisms of asthma. Furthermore, review describe importance of targeting several mediators/modulators and receptor antagonists involved in the physiopathology of asthma. Novel targets for asthma research include Galectins, Immunological targets, K ⁺ Channels, Kinases and Transcription Factors, Toll-like receptors, Selectins and Transient receptor potential channels. But recent developments in asthma research are very promising, these include Bitter taste receptors (TAS2R) abated airway obstruction in mouse model of asthma and Calcium-sensing receptor obliterate inflammation and in bronchial hyperresponsiveness allergic asthma. All these progresses in asthma targets, and asthma phenotypes exploration are auspicious in untangling of asthma riddles.

Efficacy and Safety of Benralizumab, a Monoclonal Antibody against IL-5Rα, in Uncontrolled Eosinophilic Asthma

Nonresponders to maximal guideline-based therapies of asthma account for most of the morbidity, mortality, and economic burden of the disease. Because eosinophils are key effector cells in asthmatic airway inflammation, blocking IL-5, the main cytokine responsible for its survival and activation, seems to be a rational strategy. While previous monoclonal antibodies against the IL-5 ligand resulted in inconsistent improvements in asthma outcomes, benralizumab has shown promise. Benralizumab is a monoclonal antibody against IL-5 receptor, and has an enhanced antibody dependent cell-mediated cytotoxicity function. In this article, we review the theoretical advantages of benralizumab compared to previous compounds, as well as current status of the clinical development of benralizumab in asthma. Lastly, we briefly discuss the potential role of benralizumab in chronic obstructive pulmonary disease.

Benralizumab: a unique IL-5 inhibitor for severe asthma

The presence of eosinophilic inflammation is a characteristic feature of chronic and acute inflammation in asthma. An estimated 5%–10% of the 300 million people worldwide who suffer from asthma have a severe form. Patients with eosinophilic airway inflammation represent approximately 40%–60% of this severe asthmatic population. This form of asthma is often uncontrolled, marked by refractoriness to standard therapy, and shows persistent airway eosinophilia despite glucocorticoid therapy. This paper reviews personalized novel therapies, more specifically benralizumab, a humanized anti-IL-5Rα antibody, while also being the first to provide an algorithm for potential candidates who may benefit from anti-IL-5Rα therapy.

Splicing Regulation of Pro-Inflammatory Cytokines and Chemokines: At the Interface of the Neuroendocrine and Immune Systems

Alternative splicing plays a key role in posttranscriptional regulation of gene expression, allowing a single gene to encode multiple protein isoforms. As such, alternative splicing amplifies the coding capacity of the genome enormously, generates protein diversity, and alters protein function. More than 90% of human genes undergo alternative splicing, and alternative splicing is especially prevalent in the nervous and immune systems, tissues where cells need to react swiftly and adapt to changes in the environment through carefully regulated mechanisms of cell differentiation, migration, targeting, and activation. Given its prevalence and complexity, this highly regulated mode of gene expression is prone to be affected by disease. In the following review, we look at how alternative splicing of signaling molecules—cytokines and their receptors—changes in different pathological conditions, from chronic inflammation to neurologic disorders, providing means of functional interaction between the immune and neuroendocrine systems. Switches in alternative splicing patterns can be very dynamic and can produce signaling molecules with distinct or antagonistic functions and localization to different subcellular compartments. This newly discovered link expands our understanding of the biology of immune and neuroendocrine cells, and has the potential to open new windows of opportunity for treatment of neurodegenerative disorders.

Benralizumab for chronic obstructive pulmonary disease and sputum eosinophilia: a randomised, double-blind, placebo-controlled, phase 2a study

BACKGROUND

Chronic obstructive pulmonary disease (COPD) is associated with eosinophilic airway inflammation in 10-20% of patients. Benralizumab, an anti-interleukin-5 receptor α monoclonal antibody, depletes blood and sputum eosinophils. We aimed to establish whether benralizumab reduces acute exacerbations of COPD in patients with eosinophilia and COPD.

METHODS

We did this randomised, double-blind, placebo-controlled, phase 2a study between Nov 18, 2010, and July 13, 2013, at 26 sites in the UK, Poland, Germany, Canada, the USA, Denmark, and Spain. Adults aged 40-85 years, with moderate-to-severe COPD, at least one acute exacerbation of COPD, and a sputum eosinophil count of 3·0% or more within the previous year, were randomly assigned (1:1) via computer-generated permuted block randomisation (block size of four), with an interactive voice or web-response system, to receive placebo or 100 mg benralizumab subcutaneously, every 4 weeks (three doses), then every 8 weeks (five doses) over 48 weeks. Study site personnel included in study assessments, participants, and data analysts, were masked to treatment allocation. The primary endpoint was the annualised rate of acute exacerbations of COPD at week 56, defined as the number of acute exacerbations divided by total duration of person-year follow-up. Secondary and exploratory endpoints included COPD-specific Saint George's Respiratory Questionnaire (SGRQ-C), Chronic Respiratory Questionnaire self-administered standardised format (CRQ-SAS), pre-bronchodilator forced expiratory volume in 1 second (FEV1), and safety. We did a prespecified subgroup analysis by baseline blood eosinophil count. Analyses were by intention to treat and per-protocol. This trial is registered with ClinicalTrials.gov, number NCT01227278.

FINDINGS

We randomly assigned 101 patients to receive placebo (n=50) or benralizumab (n=51), of whom 88 (87%) patients completed the study. Six patients who completed the study were excluded from the per-protocol population because of major protocol violations; the per-protocol population thus included 82 patients. Benralizumab did not reduce the annualised rate of acute exacerbations of COPD compared with placebo in the per-protocol population, with rates of 0·95 (0·68-1·29; n=40) versus 0·92 (0·67-1·25; n=42). Mean pre-bronchodilator FEV1 change from baseline to week 56 was -0·06 L (SD 0·24) with placebo, and 0·13 L (0·41) with benralizumab (p=0·014). Numerical, albeit non-significant, improvement in acute exacerbations of COPD, SGRQ-C, CRQ-SAS, and FEV1 were greater in benralizumab-treated patients with baseline blood eosinophil concentrations of 200 cells per μL or more or 300 cells per μL or more. Incidence of treatment-emergent adverse events was similar between the two groups, with the most common events being respiratory disorders (31 [62%] of 50 patients given placebo vs 32 [63%] of 51 given benralizumab) and infections (28 [56%] vs 27 [53%]). A higher incidence of serious treatment-emergent adverse events were recorded in patients in the benralizumab group than in those in the placebo group (14 vs nine patients), although none of these events were considered by the investigator to be benralizumab related.

INTERPRETATION

Compared with placebo, benralizumab did not reduce the rate of acute exacerbations of COPD. However, the results of prespecified subgroup analysis support further investigation of benralizumab in patients with COPD and eosinophilia.

FUNDING

MedImmune.

TRIF Deficiency does not Affect Severity of Ovalbumin-induced Airway Inflammation in Mice

Allergic asthma is a chronic pulmonary inflammatory disease characterized by reversible airway obstruction, hyperresponsiveness and eosinophils infiltration. Toll-like receptors (TLRs) signaling are closely associated with asthma and have emerged as a novel therapeutic target in allergic disease. The functions of TLR3 and TLR4 in allergic airway inflammation have been studied; however, the precise role of TIR-domain-containing adapter-inducing interferon-β (TRIF), the adaptor molecule for both TLR3 and TLR4, is not yet fully understood. To investigate this, we developed a mouse model of OVA-induced allergic airway inflammation and compared the severity of allergic airway inflammation in WT and TRIF^-/- mice. Histopathological assessment revealed that the severity of inflammation in airway inflammation in TRIF-deficient mice was comparable to that in WT mice. The total number of cells recovered from bronchoalveolar lavage fluid did not differ between WT and TRIF-deficient mice. Moreover, TRIF deficiency did not affect Th1 and Th2 cytokine production in lung tissue nor the level of serum OVA-specific IgE, IgG₁ and IgG_2c. These findings suggest that TRIF-mediated signaling may not be critical for the development of allergic airway inflammation.

Anti-Interleukin-5 Monoclonal Antibodies

Descriptive studies have shown an association between eosinophils, interleukin (IL)-5 and pathophysiological processes in patients with atopic asthma. These observations have led to an interest in the eosinophil as the pathogenic cell responsible for many of the clinical features of asthma including symptoms of wheeze, shortness of breath and cough, along with the physiological events such as airway hyperresponsiveness (AHR) and changes in lung function. IL-5 is one of the key cytokines responsible for eosinopoiesis in the bone marrow, along with recruitment and survival of eosinophils in the tissues. In view of this, IL-5 has been an attractive target for the development of anti-IL-5 monoclonal antibodies, inhibiting its action. The results of preclinical studies are viewed as encouraging. Preclinical development involved studies in mice, guinea-pigs and cynomolgus monkeys, with conflicting results in terms of changes in blood and bronchoalveolar lavage eosinophils, AHR and pulmonary resistance. These may be attributed to interspecies differences and to the different models used. Monoclonal antibodies directed against IL-5 have been used in at least four studies involving patients with asthma. Those preliminary studies have shown clear reductions in both blood and sputum eosinophils but no significant changes in physiological parameters of AHR, the late asthmatic reaction or in lung function or symptoms. As in the animal studies, these results suggest a dissociation between eosinophils, AHR, lung function and symptoms of asthma, which may be explained by the multitude of cells involved in the pathogenesis of asthma.

Evolutionary divergence and functions of the human interleukin (IL) gene family

Cytokines play a very important role in nearly all aspects of inflammation and immunity. The term 'interleukin' (IL) has been used to describe a group of cytokines with complex immunomodulatory functions -- including cell proliferation, maturation, migration and adhesion. These cytokines also play an important role in immune cell differentiation and activation. Determining the exact function of a particular cytokine is complicated by the influence of the producing cell type, the responding cell type and the phase of the immune response. ILs can also have pro- and anti-inflammatory effects, further complicating their characterisation. These molecules are under constant pressure to evolve due to continual competition between the host's immune system and infecting organisms; as such, ILs have undergone significant evolution. This has resulted in little amino acid conservation between orthologous proteins, which further complicates the gene family organisation. Within the literature there are a number of overlapping nomenclature and classification systems derived from biological function, receptor-binding properties and originating cell type. Determining evolutionary relationships between ILs therefore can be confusing. More recently, crystallographic data and the identification of common structural motifs have led to a more accurate classification system. To date, the known ILs can be divided into four major groups based on distinguishing structural features. These groups include the genes encoding the IL1-like cytokines, the class I helical cytokines (IL4-like, γ-chain and IL6/12-like), the class II helical cytokines (IL10-like and IL28-like) and the IL17-like cytokines. In addition, there are a number of ILs that do not fit into any of the above groups, due either to their unique structural features or lack of structural information. This suggests that the gene family organisation may be subject to further change in the near future.

Interleukin-5 and IL-5 receptor in health and diseases

While interleukin-5 (IL-5) is initially identified by its ability to support the growth and terminal differentiation of mouse B cells in vitro into antibody-secreting cells, recombinant IL-5 exerts pleiotropic activities on various target cells including B cells, eosinophils, and basophils. IL-5 is produced by both hematopoietic and non-hematopoietic cells including T cells, granulocytes, and natural helper cells. IL-5 exerts its effects for proliferation and differentiation via receptors that comprise an IL-5-specific α and common β-subunit. IL-5Rα expression in activated B cells is regulated by a complex of transcription factors including E12, E47, Sp1, c/EBPβ, and Oct2. IL-5 signals are transduced through JAK-STAT, Btk, and Ras/Raf-ERK signaling pathways and lead to maintenance of survival and functions of B cells and eosinophils. Overexpression of IL-5 in vivo significantly increases eosinophils and B cells in number, while mice lacking a functional gene for IL-5 or IL-5 receptor display a number of developmental and functional impairments in B cells and eosinophil lineages. In humans, the biologic effects of IL-5 are best characterized for eosinophils. The recent expansion in our understanding of eosinophil development and activation and pathogenesis of eosinophil-dependent inflammatory diseases has led to advance in therapeutic options. Intravenous administration of humanized anti-IL-5 monoclonal antibody reduces baseline bronchial mucosal eosinophils in mild asthma; providing important implications for strategies that inhibit the actions of IL-5 to treat asthma and other allergic diseases.

Eosinophils in innate immunity: an evolving story

Eosinophils are innate immune leukocytes found in relatively low numbers within the blood. Terminal effector functions of eosinophils, deriving from their capacity to release their content of tissue-destructive cationic proteins, have historically been considered primary effector mechanisms against specific parasites, and are likewise implicated in tissue damage accompanying allergic responses such as asthma. However, the past decade has seen dramatic advancements in the field of eosinophil immunobiology, revealing eosinophils to also be key participants in many other facets of innate immunity, from bridging innate and adaptive immune responses to orchestrating tissue remodeling events. Here, we review the multifaceted functions of eosinophils in innate immunity that are currently known, and discuss new avenues in this evolving story.

Effects of Salmonella on spatial-temporal processes of jejunal development in chickens

To study effects of Salmonella enteritidis on morphological and functional changes in chicken jejunal development, we analysed gene expression profiles at seven points post-infection in 1-21 day-old broiler chickens. Nine clusters with different gene expression patterns were identified, and the genes in each cluster were further analyzed by a functional annotation clustering method (DAVID). Functional and morphological developmental processes dominated in all the nine clusters. Salmonella infection caused delays in several intestinal-morphological processes, whereas functional metabolic processes occurred in a similar spatial-temporal frame compared to normal jejunum development. A clear difference between normal developing- and Salmonella disturbed jejunum was the higher expression of genes involved in cell turn-over at early stages in the infected jejunum. Surprisingly, we found no clustered immune related processes in the infected birds. To compare the immunological processes between control and Salmonella infected chickens, the gene expression data was superimposed on known immunological KEGG pathways. Furthermore an in-depth analysis on the immune gene level was performed. As expected, we did find immunological processes in the Salmonella infected jejunum. Several of these processes could be verified by immunohistochemistry measurements of different immunological cell types. However, the well-ordered spatial-temporal development of the immune system, as observed in control non-infected animals, was completely abolished in the infected animals. Several immunological processes started much earlier in time, whereas other processes are disorganised. These data indicate that normal morphological and immunological development of jejunum is changed dramatically by a disturbance due to Salmonella infection. Due to the disturbance, the well-organized spatial-temporal development of morphological processes are delayed, those of the immunological development are scattered, whereas metabolic functional processes are almost not affected. This demonstrates the flexibility of developmental processes in the broiler chicken intestine.

The activity of medicinal plants and secondary metabolites on eosinophilic inflammation

Eosinophils are leukocytes that are present in several body compartments and in the blood at relatively low numbers under normal conditions. However, an increase in the number of eosinophils, in the blood or in the tissues, is observed in allergic or parasitic disorders. Although some progress has been made in understanding the development of eosinophil-mediated inflammation in allergic and parasitic diseases, the discovery of new compounds to control eosinophilia has lagged behind other advances. Plant-derived secondary metabolites are the basis for many drugs currently used to treat pathologic conditions, including eosinophilic diseases. Several studies, including our own, have demonstrated that plant extracts and secondary metabolites can reduce eosinophilia and eosinophil recruitment in different experimental animal models. In this review, we summarize these studies and describe the anti-eosinophilic activity of various plant extracts, such as Ginkgo biloba, Allium cepa, and Lafoensia pacari, as well as those of secondary metabolites (compounds isolated from plant extracts), such as quercetin and ellagic acid. In addition, we highlight the medical potential of these plant-derived compounds for treating eosinophil-mediated inflammation, such as asthma and allergy.

The clinical significance of eosinophils in the amniotic fluid in preterm labor

OBJECTIVE

White blood cells are not traditionally considered to be normally present in amniotic fluid. This study was conducted after the observation that a patient with preterm labor and intact membranes had eosinophils as a predominant cell in the amniotic fluid, and had an episode of asthma during the index pregnancy. The goal of this study was to determine whether women presenting with preterm labor with eosinophils in the amniotic fluid had a different outcome than those without eosinophils as the predominant white blood cell in the amniotic cavity.

METHODS

This retrospective case-control study included women who presented with preterm labor and intact membranes between 24 and 34 weeks of gestation. Patients underwent an amniocentesis shortly after admission for the assessment of the microbiologic status of the amniotic cavity and/or fetal lung maturity. Amniotic fluid was cultured for aerobic and anaerobic bacteria as well as genital mycoplasmas. Cytologic studies included amniotic fluid white blood cell count and differential, which was performed on cytocentrifuged specimens. Patients with microbial invasion of the amniotic cavity and/or an amniotic fluid white blood cell count >20 cells/mm(3) were excluded from the study. Cases were defined as women in whom the differential contained >20% of eosinophils. Controls were selected among women with an amniotic fluid eosinophil count

RESULTS

The study population consisted of 10 cases and 50 controls. Gestational age and cervical dilatation at admission were similar in both groups. Cases had a lower gestational age at delivery than controls [34.6 weeks, inter-quartile range (IQR) 32-37.3 weeks vs. 38.0 weeks, IQR 35-40 weeks, respectively; p = 0.018]. The prevalence of preterm delivery 20% eosinophils than in the control group [50% (5/10) vs. 18% (9/50), respectively; p = 0.029]. Similar results were observed for delivery at <37 weeks [cases: 70% (7/10) vs. controls: 36% (18/50); p = 0.046].

CONCLUSIONS

Women with preterm labor and intact membranes who have a large proportion of eosinophils in the amniotic fluid are at an increased risk for spontaneous preterm delivery. These patients may have had an episode of preterm labor related to a type I hypersensitivity reaction.

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Key Words

• premature birth
• preterm birth
• prematurity
• premature labor
• mast cells
• amniotic fluid cells
• amniotic fluid white blood cells
• allergy
• allergy-induced preterm labor
• atopy
• pregnancy
• type i hypersensitivity reaction
• parturition
• labor
• eosinophil granule proteins

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MESH Headings

• Amniocentesis
• Amniotic Fluid/cytology
• Asthma/pathology
• Case-Control Studies
• Eosinophils/pathology
• Female
• Gestational Age
• Humans
• Obstetric Labor, Premature/pathology
• Pregnancy
• Pregnancy Complications/pathology
• Retrospective Studies

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Grants

• ZIA HD002400 Intramural NIH HHS
• ZIA HD002400-18 Intramural NIH HHS

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Affiliation(s)

Roberto Romero Perinatology Research Branch, NICHD/NIH/DHHS, Bethesda, Maryland, USA.
Juan Pedro Kusanovic
Ricardo Gomez
Ronald Lamont
Egle Bytautiene
Robert E Garfield
Pooja Mittal
Sonia S Hassan
Lami Yeo

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IL-5- and eosinophil-mediated inflammation: from discovery to therapy

IL-5 was originally defined as a T-cell-derived cytokine that triggers activated B cells for terminal differentiation into antibody-secreting plasma cells, at least in mice. Concurrently, IL-5 was recognized as the major maturation and differentiation factor for eosinophils in mice and humans. Over-expression of IL-5 significantly increases eosinophil numbers and antibody levels in vivo. Conversely, mice lacking a functional gene for IL-5 or the IL-5 receptor alpha chain (IL-5Ralpha) display a number of developmental and functional impairments in B-cell and eosinophil lineages. In addition to the Janus kinase-signal transducer and activator of transcription pathway, the tyrosine kinases Lyn and Btk (Bruton agammaglobulinemia tyrosine kinase) are involved, and Ras GTPase-extracellular signal-regulated kinase (Ras-ERK) signals are important for IL-5-dependent cell proliferation and survival. IL-5 critically regulates expression of genes involved in proliferation, cell survival and maturation and effector functions of B cells and eosinophils. Thus, IL-5 plays a pivotal role in innate and acquired immune responses and eosinophilia. In humans, the biologic effects of IL-5 are best characterized for eosinophils. The recent expansion in our understanding of the mechanisms of eosinophil development and activation in the context of IL-5 has led to advances in therapeutic options. A new therapy currently in clinical trials uses humanized mAbs against IL-5 or the IL-5R.

Interleukin 5 in the link between the innate and acquired immune response

Interleukin-5 (IL-5) is an interdigitating homodimeric glycoprotein that is initially identified by its ability to support the in vitro growth and differentiation of mouse B cells and eosinophils. IL-5 transgenic mouse shows two predominant features, remarkable increase in B-1 cells resulting in enhanced serum antibody levels, predominantly IgM, IgA, and IgE classes and in expansion of eosinophil numbers in the blood and eosinophil infiltration into various tissues. Conversely, mice lacking a functional gene for IL-5 or IL-5 receptor alpha chain (IL-5Ralpha) display a number of developmental and functional impairments in B cells and eosinophils. IL-5 receptor (IL-5R) comprises alpha and betac chains. IL-5 specifically binds to IL-5Ralpha and induces the recruitment of betac to IL-5R. Although precise mechanisms on cell-lineage-specific IL-5Ralpha expression remain elusive, several transcription factors including Sp1, E12/E47, Oct-2, and c/EBPbeta have been shown to regulate its expression in B cells and eosinophils. JAK2 and JAK1 tyrosine kinase are constitutively associated with IL-5Ralpha and betac, respectively, and are activated by IL-5 stimulation. IL-5 activates at least three different signaling pathways including JAK2/STAT5 pathway, Btk pathway, and Ras/ERK pathway. IL-5 is one of key cytokines for mouse B cell differentiation in general, particularly for fate-determination of terminal B cell differentiation to antibody-secreting plasma cells. IL-5 critically regulates homeostatic proliferation and survival of and natural antibody production by B-1 cells, and enhances the AID and Blimp-1 expression in activated B-2 cells leading to induce mu to gamma1 class switch recombination and terminal differentiation to IgM- and IgG1-secreting plasma cells, respectively. In humans, major target cells of IL-5 are eosinophils. IL-5 appears to play important roles in pathogenesis of asthma, hypereosinophilic syndromes, and eosinophil-dependent inflammatory diseases. Clinical studies will provide a strong impetus for investigating the means of modulating IL-5 effects. We will discuss the role of IL-5 in the link between innate and acquired immune response, particularly emphasis of the molecular basis of IL-5-dependent B cell activation, allergen-induced chronic inflammation and hypereosinophilic syndromes on a novel target for therapy.

Eosinophilic gastroenteritis: a review

Eosinophilic gastroenteritis is a clinicopathological disease affecting both children and adults that is characterized by patchy or diffuse eosinophilic infiltration of the gastrointestinal tract with variable resultant clinical gastrointestinal manifestations. The eosinophil, eotaxin, and Th-2 cytokines are important in pathogenesis of this disease entity. It may be confused with parasitic and bacterial infections (including Helicobacter pylori), inflammatory bowel disease, hypereosinophilic syndrome, myeloproliferative disorders, periarteritis, allergic vasculitis, scleroderma, drug injury, and drug hypersensivity. Obtaining the correct diagnosis is important, and a pathologist usually makes this distinction. Effective treatments include systemic/topical corticosteroids, specific food elimination or an elemental diet, certain drugs, and even surgery. A variety of new therapeutic approaches are now under trial.

IL-5 and eosinophilia

While Interleukin-5 (IL-5) is initially identified by its ability to support the growth and differentiation of activated B cells, overexpression of IL-5 significantly increases eosinophil numbers and antibody levels predominantly from an expanded population of B-1 cells in vivo. Conversely, mice lacking a functional gene for IL-5 or IL-5 receptor alpha chain (IL-5Ralpha) display a number of developmental and functional impairments in B cell and eosinophil lineages. In addition to the JAK-STAT and Btk pathway, the Ras-extracellular signal-regulated kinase (ERK) signals are important for IL-5-dependent cell survival. IL-5 critically regulates expression of genes involved in cell survival, IgH switch recombination, maturation in B cells and genes required for growth, survival, and effector function of eosinophils. IL-5Ralpha expression in B cells, but not in eosinophils is regulated by Oct-2. Eosinophilia is associated with a wide variety of conditions, including asthma and atopic diseases, helminth infections, drug hypersensitivity, and neoplastic disorders. In humans, the biologic effects of IL-5 are best characterized for eosinophils. The Sprouty-related Ena/VASP homology 1-domain containing protein (Spred)-1 negatively controls eosinophil numbers and functions by modulating IL-5 signaling in allergic asthma. We will emphasize that IL-5 plays a pivotal role in the innate and acquired immune response and eosinophilia.

Alteration of enzymatic properties of cell-surface antigen CD38 by agonistic anti-CD38 antibodies that prolong B cell survival and induce activation

Leukocyte cell-surface antigen CD38 is a single-transmembrane protein. CD38 ligation by anti-CD38 antibodies triggers the growth or apoptosis of immune cells. Although the extracellular domain of CD38 has multifunctional catalytic activities including NAD(+) glycohydrolase and cyclase, the CD38-mediated cell survival or death appears to be independent of its catalytic activity. It is proposed that a conformational change of CD38 triggers the signalling. The conformational change of CD38 could influence its catalytic activity. However, the agonistic anti-CD38 antibody that alters the catalytic activity of CD38 has not been reported so far. In the present study, we demonstrated that two agonistic anti-mouse CD38 mAbs (CS/2 and clone 90) change the catalytic activities of CD38. CS/2 was clearly more potent than clone 90 in prolonging B cell survival and activation. CS/2 inhibited the NAD(+) glycohydrolase activity of both the isolated extracellular domain of CD38 (FLAG-CD38) and cell-surface CD38. Kinetic analysis suggested a non-competitive inhibition. On the other hand, clone 90 stimulated the NAD(+) glycohydrolase activity of FLAG-CD38 and had little effect on the NAD(+) glycohydrolase activity of cell-surface CD38. CS/2 and clone 90 had no effect on the cyclase activity of FLAG-CD38 and inhibited the cyclase activity of cell-surface CD38. Accordingly, these agonistic antibodies probably induce the conformational changes of CD38 that are evident in the distinct alterations of the catalytic site. The antibodies will be useful tools to analyze the conformational change of CD38 in the process of triggering B cell survival and the activation signal.

Cerebrospinal fluid cytokine responses in human eosinophilic meningitis associated with angiostrongyliasis

The levels of interleukin 5 (IL5), IL10, and IL13 in the cerebrospinal fluid (CSF) were markedly higher in 30 patients with eosinophilic meningitis associated with angiostrongyliasis (EOMA) than in the controls (P<0.001). IL2, IL4, interferon gamma (IFNgamma), and tumor necrosis factor alpha (TNFalpha) levels were not significantly different (P>0.05). IL5, IL10, and TNFalpha levels correlated with eosinophil levels (P=0.023, P=0.018, and P=0.005, respectively) while IL2, IL4, IL13, and IFNgamma did not (P>0.05). Our data suggest that local T-helper-2 (TH2) cytokine responses are predominant in the CSF of patients with EOMA. Data on T lymphocyte-parasite interactions are important for the design of effective vaccines and immunotherapies. The measurement of T-helper-1 (TH1)/TH2 cytokines in the CSF may also have some potential for the diagnosis of parasite associated meningitis.

Role of cytokines in allergic airway inflammation

Asthma is characterized by intense infiltration of eosinophils and CD4+ T cells into the submucosal tissue of airways. Accumulating evidence indicates that T helper type 2 cell-derived cytokines such as interleukin (IL)-4, IL-5 and IL-13 play critical roles in orchestrating and amplifying allergic inflammation in asthma. In addition, it has been suggested that newly identified cytokines including thymic stromal lymphopoietin, IL-25 and IL-33 are involved in the induction of allergic inflammation in asthma. In this review, we discuss the role of individual cytokines in the pathogenesis of asthma.

Experimental immunization with Thalassophryne nattereri fish venom: Striking IL-5 production and impaired of B220+ cells

Murine experimental model have been useful to understanding the toxic as well as the pharmacological properties of the Thalassophryne nattereri venom. However, the specific immune response to T. nattereri venom in mice is yet unclear. Our results showed that the venom elicited in BALB/c mice high levels of specific IgG1 and total IgE isotype with high affinity, accompanied by a striking IL-5 production, what point out to a Th2-like response. Meanwhile, the production of IFN-gamma by lymphocytes pool expanded upon mitogen stimulus, suggests that the venom was also able to activate Th1 clones. Elevated number of antigen-presenting cells expressing CD11c or CD11b from day 4 to 6 supported ongoing antigen presentation process in the primary response and efficient T-cell expansion (increase of CD4(+) cells). In contrast, decreased B220 expression was observed, suggesting that the formation of memory long lived cell compartment. In conclusion, T. natterri venom stimulates an association of cytokine of both Th1 and Th2 profile, with a notable IL-5 production and specific IgG1 and total IgE isotypes secretion. Furthermore, our finding showed that T. natterri venom can affect the B cell fate and induce a memory antibody response through the secretion of protective IgG subclasses. Further studies with the venom protein toxins may provide clues to molecular mechanism regulating proliferation and differentiation of antibody-secreting cells in our model. A better understating of how T. natterri venom can modulate immune response could be useful in therapeutic strategies.

Requirement of 8-mercaptoguanosine as a costimulus for IL-4-dependent mu to gamma1 class switch recombination in CD38-activated B cells

Mature B-2 cells expressing surface IgM and IgD proliferate upon stimulation by CD38, CD40 or lipopolysaccharide (LPS) and differentiate into IgG1-producing plasma cells in the presence of cytokines. The process of class switch recombination (CSR) from IgM to other isotypes is highly regulated by cytokines and activation-induced cytidine deaminase (AID). Blimp-1 and XBP-1 play an essential role in the terminal differentiation of switched B-2 cells to Ig-producing plasma cells. IL-5 induces AID and Blimp-1 expression in CD38- and CD40-activated B-2 cells, leading to mu to gamma1 CSR at DNA level and IgG1 production. IL-4, a well-known IgG1-inducing factor, does not induce mu to gamma1 CSR in CD38-activated B-2 cells or Blimp-1, while IL-4 induces mu to gamma1 CSR, XBP-1 expression, and IgG1 production expression in CD40-activated B-2 cells. Interestingly, the addition of 8-mercaptoguanosine (8-SGuo) with IL-4 to the culture of CD38-activated B cells can induce mu to gamma1 CSR, Blimp-1 expression, and IgG1 production. Intriguingly, 8-SGuo by itself induces AID expression in CD38-activated B cells. However, it does not induce mu to gamma1 CSR. These results imply that the mode of B-cell activation for extracellular stimulation affects the outcome of cytokine stimulation with respect to the efficiency and direction of CSR, and the requirements of the transcriptional regulator and the generation of antibody-secreting cells. Furthermore, our data suggest the requirement of additional molecules in addition to AID for CSR.

The role of IL-5 for mature B-1 cells in homeostatic proliferation, cell survival, and Ig production

B-1 cells, distinguishable from conventional B-2 cells by their cell surface marker, anatomical location, and self-replenishing activity, play an important role in innate immune responses. B-1 cells constitutively express the IL-5R alpha-chain (IL-5Ralpha) and give rise to Ab-producing cells in response to various stimuli, including IL-5 and LPS. Here we report that the IL-5/IL-5R system plays an important role in maintaining the number and the cell size as well as the functions of mature B-1 cells. The administration of anti-IL-5 mAb into wild-type mice, T cell-depleted mice, or mast cell-depleted mice resulted in reduction in the total number and cell size of B-1 cells to an extent similar to that of IL-5Ralpha-deficient (IL-5Ralpha(-/-)) mice. Cell transfer experiments have demonstrated that B-1 cell survival in wild-type mice and homeostatic proliferation in recombination-activating gene 2-deficient mice are impaired in the absence of IL-5Ralpha. IL-5 stimulation of wild-type B-1 cells, but not IL-5Ralpha(-/-) B-1 cells, enhances CD40 expression and augments IgM and IgG production after stimulation with anti-CD40 mAb. Enhanced IgA production in feces induced by the oral administration of LPS was not observed in IL-5Ralpha(-/-) mice. Our results illuminate the role of IL-5 in the homeostatic proliferation and survival of mature B-1 cells and in IgA production in the mucosal tissues.

Abrogation of autoimmune disease in Lyn-deficient mice by the deletion of IL-5 receptor alpha chain gene

Lyn, the src-family protein tyrosine kinase, plays a crucial role in the regulation of B cell antigen receptor (BCR)- and IL-5-receptor (IL-5R)-mediated signaling. Lyn-deficient mice have been reported to exhibit an increase in B-1 cell numbers, splenomegaly and accumulation of lymphoblast-like cells in the spleen with age, resulting in hyperimmunoglobulinemia and glomerulonephritis caused by the deposition of autoantibody complexes. To elucidate the role of IL-5 in B-1 cell activation, autoantibody production and autoimmune diseases, Lyn-deficient mice were crossed with IL-5Ralpha chain (IL-5Ralpha)-deficient mice and generated Lyn- and IL-5Ralpha-deficient (DKO) mice. In contrast to Lyn-deficient mice, DKO mice showed significantly reduced splenomegaly and lymphoadenopathy and reduced B-1 cell number in the peritoneal cavity. DKO mice also secreted low levels of IgM and IgG autoantibodies. Biochemical and histological analyses revealed that DKO mice showed milder pathogenesis of autoimmune-like disorders than Lyn-deficient mice. These results suggest involvement of IL-5 in enhanced B-1 cell activation, autoantibody production, and development of autoimmune disease in Lyn-deficient mice.

Intraepithelial infiltration of eosinophils and their contribution to the elimination of adult intestinal nematode, Strongyloides venezuelensis in mice

Eosinophils were examined for the capacity of attacking Strongyloides venezuelensis adult worms in the intestinal mucosa by using interleukin (IL)-5 transgenic mice. In IL-5 transgenic mice, most of the subcutaneously inoculated infective larvae were killed during migration, and only a few worms could reach the small intestine. When the same number of adult worms were surgically implanted in the small intestine of IL-5 transgenic and control mice, fecal egg output as well as the number of adult worms recovered from the intestine was significantly lower in IL-5 transgenic mice. In the intestinal mucosa of IL-5 transgenic mice, large number of eosinophils was present in the lamina propria even before adult worm implantation. The number of eosinophils increased significantly as early as 24 h after implantation and tripled by day 3, whereas mucosal eosinophilia remained low in wild-type mice. Most notably, eosinophils infiltrated into the intestinal epithelium and surrounded adult worms in IL-5 transgenic mice, which was never seen in wild-type control mice. However, IL-5 transgenic mice required the same period as normal mice to completely expel implanted adult worms. The amount of specific IgA as well as total IgA in the stool was high in IL-5 transgenic mice before adult worm implantation, and dropped rapidly after adult worm implantation. The present study suggests that eosinophils are capable of attacking adult nematodes in the intestinal epithelia, probably in conjunction with secretory IgA, although they are not enough for the complete worm expulsion.

Elevated levels of thymus and activation-regulated chemokine (TARC) in pleural effusion samples from patients infested with Paragonimus westermani

To investigate the pathogenic mechanisms of eosinophilic pleural effusion in patients with paragonimiasis, we measured the levels of various chemokines including thymus and activation-regulated chemokine (TARC), eotaxin, RANTES and IL-8 in pleural effusion samples. Samples were obtained from 11 patients with Paragonimus westermani infection, six patients with pleural transudate, eight with tuberculous pleurisy and five with empyema. High percentages of eosinophils were detected in pleural fluid (range 9-100%, median 81%) of patients with paragonimiasis. TARC concentrations in pleural effusions of paragonimiasis were markedly higher than those of other groups. Eotaxin levels were also higher in pleural effusions of paragonimiasis patients, although significant difference was noted only against transudate samples. There was a significant correlation between TARC concentrations and percentages of eosinophils, and between TARC and eotaxin concentrations in pleural effusion. There were also significant correlations between TARC concentration and the titre of anti-P. westermani IgG and between eotaxin concentration and the titre of anti-P. westermani IgG. Our findings suggest that TARC contributes to the pathogenesis of eosinophilic pleural effusion in paragonimiasis.

Retinoic acid modulates IL-5 receptor expression and selectively inhibits eosinophil-basophil differentiation of hemopoietic progenitor cells

BACKGROUND

IL-5 plays a central role in eosinophil and basophil differentiation, exerting its effects through the IL-5 receptor (IL-5Ralpha). Currently, little is known concerning regulation of IL-5Ralpha expression in the context of commitment of hemopoietic progenitor cells to the eosinophil and basophil lineages.

OBJECTIVE

Because all-trans retinoic acid (ATRA) is known to modulate some aspects of hemopoietic differentiation, we examined the effects of ATRA on eosinophil-basophil differentiation and IL-5Ralpha expression.

METHODS

Progenitor cells were obtained from bone marrow aspirates and cord blood samples. Enriched populations of CD34(+) cells were isolated by means of positive immunomagnetic selection with MACS beads.

RESULTS

In semisolid methylcellulose cultures of normal human bone marrow, ATRA (10(-6) mol/L) selectively suppressed eosinophil-basophil colony-forming units but had no effect on granulocyte-macrophage colony-forming units. Similarly, ATRA (10(-6) mol/L) inhibited eosinophil-basophil differentiation of cord blood CD34(+) cells in liquid culture, whereas neutrophil differentiation proceeded without impediment. Most importantly, these effects of ATRA (10(-8) to 10(-6) mol/L) on CD34(+) cells were associated with a dose-dependent inhibition of IL-5Ralpha but no change in GM-CSF receptor expression, as detected with flow cytometry.

CONCLUSIONS

These findings indicate that retinoids can differentially regulate expression of IL-5Ralpha, but not GM-CSF receptor, and that these effects have functional consequences in vitro on eosinophil and basophil differentiation.

Essential role of Stat5 for IL-5-dependent IgH switch recombination in mouse B cells

IL-5 stimulation of CD38-activated murine splenic B cells induces mu-gamma1 CSR at the DNA level leading to a high level of IgG1 production. Further addition of IL-4 in the system enhances IL-5-dependent mu-gamma1 CSR. Although some of the postreceptor signaling events initiated by IL-5 in activated B cells have been characterized, the involvement of Stat in IL-5 signaling has not been thoroughly evaluated. In this study, we examined the activation of Stat5 and activation-induced cytidine deaminase (AID) in CD38-activated murine splenic B cells by IL-5. The role of Stat5a and Stat5b in IL-5-induced mu-gamma1 CSR and also IgG1 and IgM production was documented, as IL-5 does not act on CD38-stimulated splenic B cells from Stat5a(-/-) and Stat5b(-/-) mice. Expression levels of CD38-induced germline gamma1 transcripts and AID in Stat5a(-/-) and Stat5b(-/-) B cells upon IL-5 stimulation were comparable to those of wild-type B cells. The impaired mu-gamma1 CSR by Stat5b(-/-) B cells, but not by Stat5a(-/-) B cells, was rescued in part by IL-4, as the addition of IL-4 to the culture of CD38- and IL-5-stimulated B cells induced mu-gamma1 CSR leading to IgG1 production. Analysis of cell division cycle number of wild-type B cells revealed that mu-gamma1 CSR was observed after five or six cell divisions. Stat5a(-/-) and Stat5b(-/-) B cells showed similar cell division cycles, but they did not undergo mu-gamma1 CSR. Our data support the notion that both Stat5a and Stat5b are essential for IL-5-dependent mu;-gamma1 CSR and Ig secretion; however, their major target may not be AID. Stat5a and Stat5b are not redundant, but rather are at least partially distinctive in their function.