Comparison of incremental and bolus dose inhaled allergen challenge in asthmatic patients

EAACI position paper on the clinical use of the bronchial allergen challenge: Unmet needs and research priorities

Allergic asthma (AA) is a common asthma phenotype, and its diagnosis requires both the demonstration of IgE-sensitization to aeroallergens and the causative role of this sensitization as a major driver of asthma symptoms. Therefore, a bronchial allergen challenge (BAC) would be occasionally required to identify AA patients among atopic asthmatics. Nevertheless, BAC is usually considered a research tool only, with existing protocols being tailored to mild asthmatics and research needs (eg long washout period for inhaled corticosteroids). Consequently, existing BAC protocols are not designed to be performed in moderate-to-severe asthmatics or in clinical practice. The correct diagnosis of AA might help select patients for immunomodulatory therapies. Allergen sublingual immunotherapy is now registered and recommended for controlled or partially controlled patients with house dust mite-driven AA and with FEV1 ≥ 70%. Allergen avoidance is costly and difficult to implement for the management of AA, so the proper selection of patients is also beneficial. In this position paper, the EAACI Task Force proposes a methodology for clinical BAC that would need to be validated in future studies. The clinical implementation of BAC could ultimately translate into a better phenotyping of asthmatics in real life, and into a more accurate selection of patients for long-term and costly management pathways.

Allergen Provocation Tests in Respiratory Research: Building on 50 Years of Experience

Allergen provocation test is an established model of allergic airway diseases, including asthma and allergic rhinitis, allowing the study of allergen-induced changes in respiratory physiology and inflammatory mechanisms in sensitised individuals as well as their associations. In the upper airways, allergen challenge is focused on the clinical and pathophysiological sequelae of the early allergic response and applied both as a diagnostic tool and in research settings. In contrast, the bronchial allergen challenge has almost exclusively served as a research tool in specialised research settings with a focus on the late asthmatic response and the underlying type 2 inflammation. The allergen-induced late asthmatic response is also characterised by prolonged airway narrowing, increased non-specific airway hyperresponsiveness and features of airway remodelling including the small airways, and hence, allows the study of several key mechanisms and features of asthma. In line with these characteristics, the allergen challenge has served as a valued tool to study the crosstalk of the upper and lower airways and in proof of mechanism studies of drug development. In recent years, several new insights into respiratory phenotypes and endotypes including the involvement of the upper and small airways, innovative biomarker sampling methods and detection techniques, refined lung function testing as well as targeted treatment options, further shaped the applicability of the allergen provocation test in precision medicine. These topics, along with descriptions of subject populations and safety, in line with the updated GINA2021, will be addressed in this paper.

Risk and safety requirements for diagnostic and therapeutic procedures in allergology: World Allergy Organization Statement

One of the major concerns in the practice of allergy is related to the safety of procedures for the diagnosis and treatment of allergic disease. Management (diagnosis and treatment) of hypersensitivity disorders involves often intentional exposure to potentially allergenic substances (during skin testing), deliberate induction in the office of allergic symptoms to offending compounds (provocation tests) or intentional application of potentially dangerous substances (allergy vaccine) to sensitized patients. These situations may be associated with a significant risk of unwanted, excessive or even dangerous reactions, which in many instances cannot be completely avoided. However, adverse reactions can be minimized or even avoided if a physician is fully aware of potential risk and is prepared to appropriately handle the situation. Information on the risk of diagnostic and therapeutic procedures in allergic diseases has been accumulated in the medical literature for decades; however, except for allergen specific immunotherapy, it has never been presented in a systematic fashion. Up to now no single document addressed the risk of the most commonly used medical procedures in the allergy office nor attempted to present general requirements necessary to assure the safety of these procedures. Following review of available literature a group of allergy experts within the World Allergy Organization (WAO), representing various continents and areas of allergy expertise, presents this report on risk associated with diagnostic and therapeutic procedures in allergology and proposes a consensus on safety requirements for performing procedures in allergy offices. Optimal safety measures including appropriate location, type and required time of supervision, availability of safety equipment, access to specialized emergency services, etc. for various procedures have been recommended. This document should be useful for allergists with already established practices and experience as well as to other specialists taking care of patients with allergies.

In vivo diagnosis of allergic diseases--allergen provocation tests

The allergen challenge test has been the mainstay of diagnosis of allergic diseases for a long time since it offers a direct proof of the clinical relevance of a particular allergen for the allergic disease symptoms and severity. Standardisation and availability for daily practice (including safety issues) are still to be refined but most of the challenge tests have safely crossed the border from research tools to diagnostic tests available for daily practice for a well trained clinical staff.

Disease models of chronic inflammatory airway disease: applications and requirements for clinical trials

PURPOSE OF REVIEW

This review will discuss methodologies and applicability of key inflammatory models of respiratory disease in proof of concept or proof of efficacy clinical studies. In close relationship with these models, induced sputum and inflammatory cell counts will be addressed for phenotype-directed drug development. Additionally, important regulatory aspects regarding noninvestigational medicinal products used in bronchial challenges or clinical inflammatory models of respiratory disease will be highlighted.

RECENT FINDINGS

The recognition of an ever increasing number of phenotypes and endotypes within conditions such as asthma and chronic obstructive pulmonary disease urges phenotyping of study populations already in early clinical phases of drug development. Apart from the choice of a relevant disease model, recent studies show that especially targeted therapies need to be tested in well defined disease subsets for adequate efficacy assessment. Noninvasive biomarkers, especially sputum inflammatory cell counts, aid phenotyping and are useful outcome measures for novel, targeted therapies.

SUMMARY

Disease phenotyping becomes increasingly important for efficient and cost-effective drug development and subsequent disease management. Inflammatory models of respiratory disease combined with sputum biomarkers are important tools in this approach.

Inhaled allergen bronchoprovocation tests

The allergen bronchoprovocation test is a long-standing exacerbation model of allergic asthma that can induce several clinical and pathophysiologic features of asthma in sensitized subjects. Standardized allergen challenge is primarily a research tool, and when properly conducted by qualified and experienced investigators, it is safe and highly reproducible. In combination with validated airway sampling and sensitive detection techniques, allergen challenge allows the study of several features of the physiology of mainly TH2 cell-driven asthma in relation to the kinetics of the underlying airway pathology occurring during the allergen-induced late response. Furthermore, given the small within-subject variability in allergen-induced airway responses, allergen challenge offers an adequate disease model for the evaluation of new (targeted) controller therapies for asthma in a limited number of subjects. In proof-of-efficacy studies thus far, allergen challenge showed a fair positive predicted value and an excellent negative predictive value for the actual clinical efficacy of new antiasthma therapies, underscoring its important role in early drug development. In this review we provide recommendations on challenge methods, response measurements, sample size, safety, and harmonization for future applications.

Evidence for primary laryngeal inhalant allergy: a randomized, double-blinded crossover study

BACKGROUND

Despite anecdotal reports, no controlled studies to date link allergen exposure with a change in vocal function or dysphonia. The aim of this study was to determine whether allergen exposure in susceptible individuals impairs vocal function.

METHODS

The study was a prospective, double-blind, placebo-controlled study in which subjects serve as their own controls. The participants were 5 inhalant allergic adults with suspected dysphonia from allergies, without evidence of reactive lower airways based on methacholine challenge. All subjects were exposed to 2 experimental conditions in which they were challenged with (1) orally inhaled diluent placebo on 1 day, and (2) orally inhaled allergen on another day. Conditions were randomly ordered across subjects and separated by at least 48 hours. Phonatory threshold pressure (PTP) at the 80th percentile pitch was measured prior to diluent and allergen challenge, and 15 and 60 minutes postchallenge to assess potential change in vocal function after challenge testing.

RESULTS

A repeated measures ANOVA revealed a significant main effect for treatment (allergen vs placebo, p = 0.013) with greater PTP required post-allergen challenge compared to placebo and an effect size of 0.821.

CONCLUSION

A primary causal relationship between allergen exposure and impaired vocal function, as assessed by PTP, was observed in adults with documented allergy independent of asthma or nasal exposure. The current design establishes a safe model for laryngeal inhalant allergen challenge.

Airway responses and inflammation in subjects with asthma after four days of repeated high-single-dose allergen challenge

BACKGROUND

Both standard and low-dose allergen provocations are an established tool in asthma research to improve our understanding of the pathophysiological mechanism of allergic asthma. However, clinical symptoms are less likely to be induced. Therefore, we designed a protocol for repetitive high-dose bronchial allergen challenges to generate clinical symptoms and airway inflammation.

METHODS

A total of 27 patients aged 18 to 40 years with positive skin-prick tests and mild asthma underwent repetitive high-dose allergen challenges with household dust mites for four consecutive days. Pulmonary function and exhaled NO were measured at every visit. Induced sputum was analysed before and after the allergen challenges for cell counts, ECP, IL-5, INF-γ, IL-8, and the transcription factor Foxp3.

RESULTS

We found a significant decrease in pulmonary function, an increased use of salbutamol and the development of a late asthmatic response and bronchial hyperresponsiveness, as well as a significant induction of eNO, eosinophils, and Th-2 cytokines. Repeated provocation was feasible in the majority of patients. Two subjects had severe adverse events requiring prednisolone to cope with nocturnal asthma symptoms.

CONCLUSIONS

Repeated high-dose bronchial allergen challenges resulted in severe asthma symptoms and marked Th-2-mediated allergic airway inflammation. The high-dose challenge model is suitable only in an attenuated form in diseased volunteers for proof-of-concept studies and in clinical settings to reduce the risk of severe asthma exacerbations.

TRIAL REGISTRATION

ClinicalTrials.govNCT00677209.

Increase in allergen-specific IgE and ex vivo Th2 responses after a single bronchial challenge with house dust mite in allergic asthmatics

BACKGROUND

  Airway responsiveness to allergen in patients with allergic asthma is studied by bronchial allergen challenge. Although the typical features of the early and late responses on lung function and bronchial inflammation after allergen challenge are well known, little has been reported as yet on any changes in systemic allergic and immunologic parameters after 4-6 weeks.

METHODS

  In a clinical study, 27 subjects with allergic asthma and house dust mite (HDM) allergy underwent a bronchial allergen challenge with HDM. Blood samples were collected before and 5 weeks after allergen challenge. Serum levels of total IgE and allergen-specific IgE were measured, and peripheral blood mononuclear cells were isolated and stimulated ex vivo with HDM to determine the allergen-specific T-cell cytokine response.

RESULTS

  Five weeks after bronchial allergen challenge with HDM, the amount of circulating IgE against HDM and the major allergenic components Der p1 and Der p2 was significantly increased (10.8% and 8.8%, respectively). IgE antibodies against other environmental allergens decreased (grass pollen) or remained unchanged (cat dander). Allergen-induced Th2-cytokine production was also significantly increased (P< 0.001, P=0.014, and P=0.006 for IL-4, IL-5, and IL-13, respectively). The increase in Der p1- and Der p2-specific IgE in serum correlated with increased numbers of Th2-cytokine-producing cells (Rs=0.56, P=0.002 and Rs=0.54, P=0.004 for IL-4 and IL-13, respectively).

CONCLUSIONS

  A single bronchial allergen challenge with HDM is accompanied by increased levels of allergen-specific IgE for HDM in serum and an enhanced Th2 response to HDM still detectable 5 weeks after challenge.

Bronchial allergen challenge using the Medicaid dosimeter

BACKGROUND

Bronchial allergen provocations are well established in asthma research. We evaluated the reproducibility of single-concentration, single-step allergen challenges in volunteers with grass pollen allergy.

METHODS

Forty-seven subjects underwent bronchial challenges using the aerosol provocation system nebulizer (Medicaid Sidestream) with incremental doses of grass pollen to define the individual allergen dose that causes a 20% drop in FEV(1) (PD(20)FEV(1)). In 39 subjects this procedure was followed by single-step challenges. Early and late asthmatic responses were monitored, and increases in exhaled nitric oxide were measured before and 24 h after single-step challenges.

RESULTS

After the first single-step challenge, the maximum drop in FEV(1) was 21.3% ± 8.0. A comparison of the drop in FEV(1) to the initial incremental challenge (29.7% ± 7.5) revealed an intraclass correlation of -0.30 (p < 0.05). In the second single-step challenge, the mean drop in FEV(1) was 20.9% ± 7.2. Compared with the first single-step challenge, the intraclass correlation was 0.37 (p < 0.05) and the 95% limits of agreement according to Bland and Altman were -17.5 to 18.1%. The increases in exhaled nitric oxide revealed substantial agreement in repeated single-step challenges (26.8 ppb ± 27.8 and 21.8 ppb ± 21.9, ICC 0.62, p < 0.001).

CONCLUSIONS

The use of aerosol provocation system to calculate the PD(20)FEV(1) allergen is a timesaving procedure and is less prone to errors because only one dilution of the allergen is used. The repeatability in well-defined subjects is excellent to study the mechanisms of allergen-induced airway inflammation and the development of new treatments for allergic diseases.

Repeated high-dose inhalation allergen challenge in asthma

INTRODUCTION

Inhalation allergen challenge in humans is used to investigate lung pathophysiology and responses to novel therapies. However, the single high-dose allergen challenges that are commonly performed do not mimic repeated symptomatic environmental allergen exposure.

OBJECTIVES

To develop and evaluate the safety of a repeated high-dose symptomatic inhalation allergen challenge model.

METHODS

Sixteen subjects with atopic asthma were recruited. Each underwent three inhalation allergen challenges using house dust mite (Dermatophagoides pteronyssinus) antigen at 48-h intervals with a target of symptom induction and an early asthmatic reaction fall in forced expiratory volume in 1 s (FEV(1) ) of 15% from baseline.

RESULTS

All of the subjects completed the three-challenge protocol and the target immediate airway bronchoconstrictor response was achieved in all the subjects at all challenges. There were no adverse events recorded. The early asthmatic reaction was similar for the three challenges whether measured as mean maximal fall in FEV(1) or mean area under the curve. The late asthmatic reaction was also similar over the three challenges with no evidence of priming or desensitisation. Symptom scores and reliever medication use significantly increased over the time of the challenges. Baseline lung function and reversibility was unchanged 4 days after the last challenge.

CONCLUSION

We demonstrate that repeated high-dose inhaled house dust mite allergen challenge in human volunteers with mild asthma is safe, repeatable and acceptable. This allows the use of this model in further studies focused on understanding the pathophysiology of allergen induced asthma and the impact of therapeutic interventions.

Remodeling and airway hyperresponsiveness but not cellular inflammation persist after allergen challenge in asthma

RATIONALE

Airway hyperresponsiveness (AHR) increases up to 2 weeks after allergen inhalational challenge of subjects with asthma who show a late-phase asthmatic reaction (dual responders). Cellular inflammation and airway remodeling are increased 24 hours after allergen challenge.

OBJECTIVES

To determine whether persistence of increased AHR is associated with persistent activation of remodeling and enhanced inflammation.

METHODS

Fiberoptic bronchoscopy was performed at baseline and at 24 hours and 7 days after allergen inhalational challenge of dual responders with mild-moderate asthma. At each time point, AHR, spirometry, and expression of tenascin (extracellular matrix protein), procollagen I, procollagen III, and heat shock protein (HSP)-47 (markers of collagen synthesis), and alpha-smooth muscle actin (myofibroblasts) were evaluated as markers of activation of airway remodeling, together with numbers of mucosal major basic protein-positive eosinophils, CD68(+) macrophages, CD3(+), CD4(+), CD8(+) T cells, elastase-positive neutrophils, and tryptase-positive mast cells.

MEASUREMENTS AND MAIN RESULTS

AHR was increased from baseline at 24 hours and 7 days after allergen challenge. Reticular basement membrane tenascin expression was elevated at 24 hours and returned to baseline levels at 7 days. Reticular basement membrane procollagen III expression was significantly elevated at 7 days. Expression of procollagen I, HSP-47, and alpha-smooth muscle actin were all higher at 7 days compared with 24 hours. At 24 hours, eosinophil, macrophage, neutrophil, and CD3(+) T cells were increased but had returned to baseline by 7 days.

CONCLUSIONS

In dual responders with asthma, the 24-hour increase in airway wall cellular inflammation after allergen challenge resolves by 7 days, whereas the increases in AHR and markers of remodeling persist.

Bimosiamose, an inhaled small-molecule pan-selectin antagonist, attenuates late asthmatic reactions following allergen challenge in mild asthmatics: a randomized, double-blind, placebo-controlled clinical cross-over-trial

BACKGROUND

Asthma is characterized by increased recruitment of inflammatory cells from the circulation into the airways. As selectins mediate tethering and rolling of leukocytes on the vascular endothelium, they constitute a promising target for the therapeutic modulation of inflammation. We evaluated the effect of inhaled bimosiamose (TBC1269), a synthetic pan-selectin antagonist, on allergen-induced late asthmatic reactions (LAR) in mild asthmatics.

METHODS

Twelve male subjects with mild allergic asthma (only beta-agonists prn) with demonstrable LAR (fall of FEV1 3-8h after allergen inhalation >15% of baseline) at screening completed a randomized, double-blind, placebo-controlled clinical cross-over-trial. Subjects were treated with inhaled bimosiamose 70 mg bid or matching placebo on days 1-3 and 70 mg once on the morning of day 4. On day 4 following the last inhalation of study drug, an allergen challenge was performed. The primary endpoint was the maximum fall in FEV1 between 3 and 8h after allergen inhalation on active treatment vs. placebo. Secondary endpoints included early asthmatic response, exhaled nitric oxide, and airway hyperresponsiveness to methacholine 24h post allergen.

RESULTS

Bimosiamose significantly attenuated the maximum LAR compared to placebo by 50.2% (placebo mean+/-SEM fall -13.10+/-2.30%, bimosiamose -6.52+/-3.86%, treatment effect p=0.045; linear mixed-effects model). There was no effect of active treatment on early asthmatic response, post allergen airway hyperresponsiveness or exhaled nitric oxide, and peripheral blood cells.

CONCLUSIONS

Administration of the pan-selectin antagonist bimosiamose is effective in a human allergen challenge model of asthma. The result of this proof-of-concept exploratory trial is the first study that demonstrates clinical efficacy of selectin-antagonists as novel therapeutic strategy in asthma.

Effect of IVL745, a VLA-4 antagonist, on allergen-induced bronchoconstriction in patients with asthma

BACKGROUND

Very late antigen (VLA-4) antagonists have been proposed as potential therapies for diseases in which cell recruitment and accumulation are causative. Asthma, which is characterized by airway inflammation involving the accumulation of eosinophils and mononuclear cells, is one such disease.

OBJECTIVE

We sought to assess the effect of IVL745, a VLA-4 antagonist, on the early and late asthmatic response (LAR) and on markers of airway inflammation after allergen inhalation.

METHODS

The study was of a placebo-controlled, double-blind, randomized, 2-way crossover design. Sixteen subjects with mild-to-moderate asthma controlled with short-acting beta2-agonists only and with a LAR to inhaled allergen participated in the study. At one treatment period they took 20 mg of IVL745 and one treatment period placebo. Both treatments were taken twice daily for 7 days, with a single dose on day 8. Treatments were separated by a washout period of at least 2 weeks. On day 7 of each treatment period, sputum was induced and collected, and exhaled nitric oxide (NO) was measured. On day 8, an inhaled bolus allergen challenge was performed, and blood was taken for pharmacokinetics. On day 9, exhaled NO was measured, and a methacholine challenge was done. On day 10, sputum was induced and collected. Adverse events, peak expiratory flow (PEF), use of short-acting beta2-agonists, and asthma symptoms were recorded daily throughout the study.

RESULTS

There was no statistically significant difference between IVL745 and placebo in the effect on the LAR after allergen challenge, as measured by the area under the curve of the percentage change in FEV1 from the prechallenge baseline (mean [SEM], -81.99 [18.80] after IVL745 and -72.58 [21.29] after placebo; 95% CI of difference, -36 to 16.8; P = .46) or by the maximum percentage change from the prechallenge baseline (mean [SEM], -23.44 [4.73] after IVL745 and -21.30 [5.17] after placebo; 95% CI of difference, -11 to 6.29; P = .60). There was a statistically significant decrease in the percentage of eosinophils in sputum on day 7 of treatment with IVL745 (mean [SEM], 7.32 [1.46]) compared with placebo (mean [SEM], 15.00 [1.92]; 95% CI of difference, -13 to -1.2; P = .02). There was no statistically significant difference between IVL745 and placebo with respect to the early asthmatic response, methacholine hyperresponsiveness, exhaled NO, postallergen sputum, symptoms, inhaled beta2-agonist use, or PEF.

CONCLUSION

In patients with mild-to-moderate atopic asthma, IVL745 did not affect the early and late response to inhaled allergen or markers of airway inflammation, except for a modest reduction in sputum eosinophils.

Discrepant nasal and bronchial nitric oxide kinetics during early and late phase allergic reactions

Late allergic reactions (LAR) following allergen challenge occur in different compartments. We studied the kinetics of nasal and bronchial nitric oxide (NO) in mild asthmatics after allergen challenge. Twelve males with intermittent asthma (28 yr, FEV1 97% of predicted, PC20methacholine <8 mg/ml) and known LAR after bronchial allergen challenge underwent nasal and bronchial allergen provocation using the same allergen separated by a washout of 3 weeks. Nasal and bronchial NO were measured before challenge, during early (EAR) and late phase reactions, and 24 h after allergen. The mean (sem) maximum fall of FEV1 at EAR was 31.9+/-3.2% (P=0.001), and 17.6+/-2.2% (P=0.004) during LAR. All patients developed nasal EAR (max. fall in nasal rhinomanometric flow 64.8+/-7.6% of baseline) after nasal challenge, and 10 patients demonstrated nasal LAR with a fall in nasal flow of 65.9+/-6.6% (both P=0.002, respectively). During EAR, there was stronger reduction of nasal (-19.2+/-6.2%,P=0.039) than bronchial NO (-6.9+/-5.2% of baseline, P=ns). In contrast, bronchial NO also tended to decrease during bronchial LAR (-8.8+/-6.8%,P=ns), while nasal NO slightly increased non-significantly (+17+/-10.8%, P=ns). After 24 h, bronchial NO was significantly elevated (+78.1+/-40.1%, P=0.039), whereas nasal NO was unchanged (+6.1+/-15.1%, P=ns). The intraindividual difference between bronchial and nasal changes of NO during LAR, but not EAR or after 24 h, was significant (lung vs. nose: -35.6+/-14.1% relative difference, P=0.039). Despite similar functional responses in nose and bronchi, nasal NO kinetics following allergen challenge differ from bronchial NO. The concise mechanisms accounting for this discrepancy warrant further investigations.

Effects of an interleukin-5 blocking monoclonal antibody on eosinophils, airway hyper-responsiveness, and the late asthmatic response

BACKGROUND

Interleukin-5 (IL-5) is essential for the formation of eosinophils, which are thought to have a major role in the pathogenesis of asthma and other allergic diseases. We aimed to assess the effects of monoclonal antibody to IL-5 on blood and sputum eosinophils, airway hyper-responsiveness, and the late asthmatic reaction to inhaled allergen in patients with mild asthma.

METHODS

We did a double-blind randomised placebo-controlled trial, in which a single intravenous infusion of humanised (IgG-K) monoclonal antibody to IL-5 (SB-240563) was given at doses of 2.5 mg/kg (n=8) or 10.0 mg/kg (n=8). The effects of treatment on responses to inhaled allergen challenge, sputum eosinophils, and airway hyper-responsiveness to histamine were measured at weeks 1 and 4 with monitoring of blood eosinophil counts for up to 16 weeks.

FINDINGS

Monoclonal antibody against IL-5 lowered the mean blood eosinophil count at day 29 from 0.25x10(9)/L (95% CI 0.16-0.34) in the placebo group to 0.04x10(9)/L (0.00-0.07) in the 10 mg/kg group (p<0.0001), and prevented the blood eosinophilia that follows allergen challenge. After inhaled allergen challenge, 9 days after treatment, the percentage sputum eosinophils were 12.2% in the placebo group and lowered to 0.9% (-1.2 to 3.0; p=0.0076) in the 10 mg/kg group, and this effect persisted at day 30 after the dose. There was no significant effect of monoclonal antibody to IL-5 on the late asthmatic response or on airway hyper-responsiveness to histamine.

INTERPRETATION

A single dose of monoclonal antibody to IL-5 decreased blood eosinophils for up to 16 weeks and sputum eosinophils at 4 weeks, which has considerable therapeutic potential for asthma and allergy. However, our findings question the role of eosinophils in mediating the late asthmatic response and causing airway hyper-responsiveness.