Specific immunotherapy in asthma: a comprehensive review

Methods for Experimental Allergen Immunotherapy: Subcutaneous and Sublingual Desensitization in Mouse Models of Allergic Asthma

Allergic asthma is characterized by airway hyperresponsiveness, remodeling, and reversible airway obstruction. This is associated with an eosinophilic inflammation of the airways, caused by inhaled allergens such as house dust mite or grass pollen. The inhaled allergens trigger a type-2 inflammatory response with the involvement of innate lymphoid cells (ILC2) and Th2 cells, resulting in high immunoglobulin E (IgE) antibody production by B cells and mucus production by airway epithelial cells. As a consequence of the IgE production, subsequent allergen reexposure results in a classic allergic response with distinct early and late phases, both resulting in bronchoconstriction and shortness of breath. Allergen-specific immunotherapy (AIT) is the only treatment that is capable of modifying the immunological process underlying allergic responses including allergic asthma. Both subcutaneous AIT (SCIT) as well as sublingual AIT (SLIT) have shown clinical efficacy in long-term suppression of the allergic response. Although AIT treatments are very successful for rhinitis, application in asthma is hampered by variable efficacy, long duration of treatment, and risk of severe side effects. A more profound understanding of the mechanisms by which AIT induces tolerance to allergens in sensitized individuals is needed to be able to improve its efficacy. Mouse models have been very valuable in preclinical research for characterizing the mechanisms of desensitization in AIT and evaluating novel approaches to improve its efficacy. Here, we present a rapid and reproducible mouse model for allergen-specific immunotherapy. In this model, mice are sensitized with two injections of allergen adsorbed to aluminum hydroxide, followed by subcutaneous injections (SCIT) or sublingual administrations (SLIT) of allergen extracts as an immunotherapy treatment. Finally, mice are challenged by intranasal allergen administrations. We will also describe the protocols as well as the most important readout parameters for the measurements of invasive lung function, serum immunoglobulin levels, isolation of bronchoalveolar lavage fluid (BALF), and preparation of cytospin slides. Moreover, we describe how to perform ex vivo restimulation of lung single-cell suspensions with allergens, flow cytometry for identification of relevant immune cell populations, and ELISAs and Luminex assays for assessment of the cytokine concentrations in BALF and lung tissue.

Current insights in allergen immunotherapy

OBJECTIVE

Allergen-specific immunotherapy (AIT) in its subcutaneous and sublingual forms is currently a well-established and experimentally supported treatment for respiratory allergy and hymenoptera venom allergy. There have been advances in its use linked strictly to the advancement in the knowledge of the molecular mechanisms of allergy, the production of well-characterized extracts, and diagnostic techniques. The use of AIT in asthma and the application of new approaches are expanding. We briefly review the advances and concerns in the use of AIT.

DATA SOURCES

PubMed and Scopus.

STUDY SELECTIONS

The most recent and clinically relevant literature was selected and reviewed.

RESULTS

The introduction of high-quality products supported by large dose-finding trials has yielded better defined indications, contraindications, and modalities of use. Some specific products in tablet form have recently been approved in the United States. Sublingual immunotherapy has been found to be effective in asthma, which until recently had been a matter of debate. Another promising therapy is oral and sublingual desensitization for food allergy, for which encouraging results have recently been reported. In the near future, other options will be available, including new routes of administration (intralymphatic and epicutaneous), allergoids, engineered allergens, and peptides. The use of component-resolved diagnosis techniques will further refine and target AIT prescriptions.

CONCLUSION

This condensed and updated review shows that AIT remains a viable treatment option, especially after the introduction of standardized tablets for some allergens. Food allergy and new administration routes represent a promising expansion.

Nasal allergen-neutralizing IgG4 antibodies block IgE-mediated responses: Novel biomarker of subcutaneous grass pollen immunotherapy

BACKGROUND

Grass pollen subcutaneous immunotherapy (SCIT) is associated with induction of serum IgG₄-associated inhibitory antibodies that prevent IgE-facilitated allergen binding to B cells.

OBJECTIVE

We sought to determine whether SCIT induces nasal allergen-specific IgG₄ antibodies with inhibitory activity that correlates closely with clinical response.

METHODS

In a cross-sectional controlled study, nasal fluid and sera were collected during the grass pollen season from 10 SCIT-treated patients, 13 untreated allergic patients (with seasonal allergic rhinitis [SAR]), and 12 nonatopic control subjects. Nasal and serum IgE and IgG₄ levels to Phleum pratense components were measured by using the Immuno Solid Allergen Chip microarray. Inhibitory activity was measured by IgE-facilitated allergen binding assay. IL-10⁺ regulatory B cells were quantified in peripheral blood by using flow cytometry.

RESULTS

Nasal and serum Phl p 1- and Phl p 5-specific IgE levels were increased in patients with SAR compared to nonatopic control subjects (all, P < .001) and SCIT-treated patients (nasal, P < .001; serum Phl p 5, P = .073). Nasal IgG₄ levels were increased in the SCIT group compared to those in the SAR group (P < .001) during the pollen season compared to out of season. IgG-associated inhibitory activity in nasal fluid and serum was significantly increased in the SCIT group compared to that in the SAR (both, P < .01). The magnitude of the inhibitory activity was 93% (P < .001) in nasal fluid compared to 66% (P < .001) in serum and was reversed after depletion of IgG. Both nasal fluid (r = -0.69, P = .0005) and serum (r = -0.552, P = .0095) blocking activity correlated with global symptom improvement. IL-10⁺ regulatory B cells were increased in season compared to out of season in the SCIT group (P < .01).

CONCLUSION

For the first time, we show that nasal IgG₄-associated inhibitory activity correlates closely with the clinical response to allergen immunotherapy in patients with allergic rhinitis with or without asthma.

Molecular diagnosis and precision medicine in allergy management

Precision medicine (PM) can be defined as a structural model aimed at customizing healthcare, with medical decisions/products tailored on an individual patient at a highly detailed level. In this sense, allergy diagnostics based on molecular allergen components allows to accurately define the patient's IgE repertoire. The availability of highly specialized singleplexed and multiplexed platforms support allergists with an advanced diagnostic armamentarium. The therapeutic intervention, driven by the standard diagnostic approach, but further supported by these innovative tools may result, for instance, in a more appropriate prescription of allergen immunotherapy (AIT). Also, the phenotyping of patients, which may have relevant effects on the treatment strategy, could be take advantage by the molecular allergy diagnosis.

Subcutaneous and Sublingual Immunotherapy in Allergic Asthma in Children

This review presents up-to-date understanding of immunotherapy in the treatment of children with allergic asthma. The principal types of allergen immunotherapy (AIT) are subcutaneous immunotherapy (SCIT) and sublingual immunotherapy (SLIT). Both of them are indicated for patients with allergic rhinitis and/or asthma, who have evidence of clinically relevant allergen-specific IgE, and significant symptoms despite reasonable avoidance measures and/or maximal medical therapy. Studies have shown a significant decrease in asthma symptom scores and in the use of rescue medication, and a preventive effect on asthma onset. Although the safety profile of SLIT appears to be better than SCIT, the results of some studies and meta-analyses suggest that the efficacy of SCIT is better and that SCIT has an earlier onset than SLIT in children with allergic asthma. Severe, not controlled asthma, and medical error were the most frequent causes of SCIT-induced adverse events.

Subcutaneous and Sublingual Immunotherapy in a Mouse Model of Allergic Asthma

Allergic asthma, caused by inhaled allergens such as house dust mite or grass pollen, is characterized by reversible airway obstruction, associated with an eosinophilic inflammation of the airways, as well as airway hyper responsiveness and remodeling. The inhaled allergens trigger a type-2 inflammatory response with involvement of innate lymphoid cells (ILC2) and Th2 cells, resulting in high production of immunoglobulin E (IgE) antibodies. Consequently, renewed allergen exposure results in a classic allergic response with a distinct early and late phase, both resulting in bronchoconstriction and shortness of breath. Allergen specific immunotherapy (AIT) is the only treatment that is capable of modifying the immunological process underlying allergic responses including allergic asthma and both subcutaneous AIT (SCIT) as well as sublingual AIT (SLIT) have proven clinical efficacy in long term suppression of the allergic response. Although these treatments are very successful for rhinitis, application of AIT in asthma is hampered by variable efficacy, long duration of treatment, and the risk of severe side-effects. A more profound understanding of the mechanisms by which AIT achieves tolerance to allergens in sensitized individuals is needed to improve its efficacy. Mouse models have been very valuable as a preclinical model to characterize the mechanisms of desensitization in AIT and to evaluate novel approaches for improved efficacy. Here, we present a rapid and reproducible mouse model for allergen-specific immunotherapy. In this model, mice are sensitized with two injections of allergen absorbed to aluminum hydroxide to induce allergic sensitization, followed by subcutaneous injections (SCIT) or sublingual administrations (SLIT) of the allergen as immunotherapy treatment. Finally, mice are challenged by three intranasal allergen administrations. We will describe the protocols as well as the most important read-out parameters including measurement of invasive lung function measurements, serum immunoglobulin levels, isolation of broncho-alveolar lavage fluid (BALF), and preparation of cytospins. Moreover, we describe how to restimulate lung single cell suspensions, perform flow cytometry measurements to identify populations of relevant immune cells, and perform ELISAs and Luminex assays to measure the cytokine concentrations in BALF and lung tissue.

Allergen-Specific Immunotherapy

Allergen-specific immunotherapy remains the only causal treatment of allergic disease to date. Its efficacy in symptom reduction was demonstrated in double blind, placebo-controlled studies of allergic rhinoconjunctivitis, allergic asthma, and Hymenoptera venom hypersensitivity, including long-term effects after discontinuation of treatment. In addition, immunotherapy decreases the risk of developing new sensitisations to aeroallergens in monosensitised patients and allergic asthma in patients with mere allergic rhinitis. The mechanism of immunotherapy entails redirection of the T lymphocyte response from a T helper cell Type 2 phenotype in favour of induction of regulatory T cells and/or immune deviation toward a T helper cell Type 1 phenotype, with resulting inhibition of downstream effector pathways and induction of immunoglobulin G-associated blocking antibodies. Two main application forms are used in clinical practice: subcutaneous immunotherapy and sublingual immunotherapy. The advantage of subcutaneous immunotherapy is its proven efficacy over a broad range of indications. Disadvantages are systemic allergic reactions and inconvenience for the patient due to frequent doctor visits. Sublingual immunotherapy has been shown to result in less systemic allergic reactions and may be more convenient due to home application; however, efficacy has only been proven for allergic rhinitis. For clinicians, the adherence to practice guidelines and thorough knowledge of allergen products, application routes, indications, immunomodulatory mechanisms, efficacy, safety, and cost-effectiveness is important for successful treatment and will be addressed in this review article.

Therapeutic interventions in severe asthma

The present paper addresses severe asthma which is limited to 5-10% of the overall population of asthmatics. However, it accounts for 50% or more of socials costs of the disease, as it is responsible for hospitalizations and Emergency Department accesses as well as expensive treatments. The recent identification of different endotypes of asthma, based on the inflammatory pattern, has led to the development of tailored treatments that target different inflammatory mediators. These are major achievements in the perspective of Precision Medicine: a leading approach to the modern treatment strategy. Omalizumab, an anti-IgE antibody, has been the only biologic treatment available on the market for severe asthma during the last decade. It prevents the linkage of the IgE and the receptors, thereby inhibiting mast cell degranulation. In clinical practice omalizumab significantly reduced the asthma exacerbations as well as the concomitant use of oral glucocorticoids. In the "Th2-high asthma" phenotype, the hallmarks are increased levels of eosinophils and other markers (such as periostin). Because anti-IL-5 in this condition plays a crucial role in driving eosinophil inflammation, this cytokine or its receptors on the eosinophil surface has been studied as a potential target for therapy. Two different anti-IL-5 humanized monoclonal antibodies, mepolizumab and reslizumab, have been proven effective in this phenotype of asthma (recently they both came on the market in the United States), as well as an anti-IL-5 receptor alpha (IL5Rα), benralizumab. Other monoclonal antibodies, targeting different cytokines (IL-13, IL-4, IL-17 and TSLP) are still under evaluation, though the preliminary results are encouraging. Finally, AIT, Allergen Immunotherapy, a prototype of Precision Medicine, is considered, also in light of the recent evidences of Sublingual Immunotherapy (SLIT) tablet efficacy and safety in mite allergic asthma patients. Given the high costs of these therapies, however, there is an urgent need to identify biomarkers that can predict the clinical responders.

Update on immunotherapy for the treatment of asthma

PURPOSE OF REVIEW

Despite that specific immunotherapy can boast being more than a century old, there is still skepticism about its real effectiveness, and therefore it is still used too little in clinical practice. The purpose of this review was to analyze the most recent articles in the literature to highlight scientific evidence for the proper use of allergen immunotherapy (AIT).

RECENT FINDINGS

In the near future, the concept of medicine for trials will have to be revised and in certain cases abandoned in favor of a personalized medicine, able to use a drug more targeted for the individual patient and not for the disease.

SUMMARY

For AIT, it will become increasingly important to use products designed properly, standardized and with a well documented effectiveness in clinical studies. We must overcome the disputes of subcutaneous immunotherapy versus sublingual immunotherapy, arrive at the concept of personalized medicine regarding AIT, framing in different phenotypes of asthma patients to use the optimal preparation for each particular patient.

Allergen immunotherapy in asthma; what is new?

The use and role of allergen immunotherapy (AIT) in asthma is still a matter of debate, and no definite recommendation about this is made in guidelines, both for the subcutaneous and sublingual routes. This is essentially due to the fact that most controlled randomised trials were not specifically designed for asthma, and that objective measures of pulmonary function were only occasionally considered. Nonetheless, in many trials, favourable results in asthma (symptoms, medication usage, bronchial reactivity) were consistently reported. There are also several meta analyses in favour of AIT, although their validity is limited by a relevant methodological heterogeneity. In addition to the crude clinical effect, a disease modifying action of AIT (prevention of asthma onset and long-lasting effects) have been reported. The safety is an important aspect to consider in asthma. Fatalities were rare: in Europe no fatality was reported in the last three decades, as in the United States in the last 4 years. Based on previous surveys, and common sense, uncontrolled asthma is still recognized as the most important risk factor for severe adverse events. On the contrary, there is no evidence that AIT can worsen or induce asthma. According to the available evidence, AIT can be safely used as add-on treatment when asthma is associated with rhinitis (a frequent condition), provided that asthma is adequately controlled by pharmacotherapy. AIT cannot be recommended or suggested as single therapy. When asthma is the unique manifestation of respiratory allergy, its use should be evaluated case by case.

Focusing the mechanism of action to dissect the different treatments of respiratory allergy

The treatment of respiratory allergy is based on several drugs with different mechanisms of action, which encompass an effect only on symptoms, limited factors of inflammation or the whole process of inflammation. Dissecting the different treatments by their mechanism of action is relevant for the management of allergic patients. Corticosteroids, administered as nasal sprays in rhinitis or by inhalation devices in asthma, and allergen immunotherapy (AIT) are the most effective treatments for respiratory allergy, achieving the control on inflammation by a number of cellular and molecular mechanisms. What distinguishes corticosteroids from AIT is the duration of clinical outcomes that ends with treatment withdrawal for the former but persists after stopping for AIT, due to its disease-modifying effect.

Specific immunotherapy and biological treatments for occupational allergy

PURPOSE OF REVIEW

Occupational allergy represents a substantial health, social, and financial burden for the society. Its management is a complex task that, in selected cases, may also include allergen-specific immunotherapy. The purpose of this article is to review clinical data on allergen immunotherapy and biological treatments applied to occupational allergy in 2013.

RECENT FINDINGS

Immunotherapy in occupational allergic diseases has been scarcely used, and only for a few sensitizers, such as latex, flour, and Hymenoptera venom, partly due to the lack of standardized extracts. The recent use of the molecular diagnosis can improve the indication and selection of suitable allergens for preparing new standardized and powerful extracts for immunotherapy. Some recent reports suggest a beneficial role of treatment with omalizumab in workers with occupational asthma who continue to be exposed to the causal agent.

SUMMARY

Although scarce, available data suggest that immunotherapy and biological treatments may allow allergic workers to continue their work activity, but further studies are needed to standardize extracts and to evaluate the cost-effectiveness of these treatments, when exposure at the workplace cannot be avoided.

Sublingual Immunotherapy for Asthmatic Children Sensitized to House Dust Mite: A Meta-Analysis

The house dust mite is one of the most common allergens worldwide. There is good evidence that house dust mite subcutaneous immunotherapy is efficacious and has long-term benefit in children. However, the evidence of the benefit of house dust mite sublingual immunotherapy (SLIT) is less convincing. The purpose of this meta-analysis was to evaluate that efficacy and safety of dust mite SLIT in children with asthma. Medical Literature Analysis and Retrieval System Online, ISI Web of Knowledge, and Cochrane Central Register of Controlled Trials databases until February 2014 were searched. The primary outcome was mean change in asthma symptom score. Secondary outcomes included mean change in serum immunoglobulin G4 (sIgG4), specific Dermatophagoides pteronyssinus, immunoglobulin E (IgE) levels, and medication score. Safety was also assessed. We found that SLIT significantly decreased asthma symptom score (P = 0.007) and increased sIgG4 levels (P = 0.011) greater than control in children (<18 years of age) with asthma. There was no difference between SLIT and control groups in specific D pteronyssinus IgE levels (P = 0.076) and medication score (P = 0.408). The safety profile was similar between groups. Our study indicates that dust mite SLIT therapy was effective in reducing asthma symptoms and in increasing sIgG4 but did not significantly reduce medication scores or specific D pteronyssinus IgE levels. Our findings are not enough to support the use of dust mite SLIT in children with asthma.

Predictors of quality of life improvement in allergic rhinitis patients after sublingual immunotherapy

OBJECTIVES

Sublingual immunotherapy (SLIT) has been described as a significant intervention in the treatment of allergic rhinitis (AR). However, factors that may predict treatment outcomes with respect to quality of life (QoL) results and mainly the role of olfactory function are still being underestimated. In this study, we investigated determinants that best predict treatment outcomes for QoL, exploring mainly the role of olfaction.

METHODS

One hundred forty-five patients following SLIT, 45 placebo-controls, and 48 healthy subjects were studied. Olfactory function was objectively evaluated using "Sniffin' Sticks" test pre- and post-cessation of SLIT. Three categories of validated QoL questionnaires were filled out by all subjects: questionnaire specific for olfaction (Questionnaire of Olfactory Deficits), questionnaires for assessing psychology (Beck Depression Inventory, Zung Depression Scale, State & Trait Anxiety Inventory), general Short Form-36 health survey.

RESULTS

Statistically significant improvement of olfactory function by 11.1% and of all QoL questionnaires results (all P<.001) was observed on final evaluation. Anosmia, asthma history, and the severity of symptoms-expressed by the Total Symptoms Score-were proven independent determinants of clinically significant improvement in patients' QoL.

CONCLUSIONS

Several factors were found that may predict QoL outcomes in AR patients following SLIT.

The evolution of allergen and non-specific immunotherapy: past achievements, current applications and future outlook

Recent epidemiological studies estimated that more than 30% of European suffer from allergic rhinitis or conjunctivitis, while up to 20% suffer from asthma and 15% from allergic skin conditions, while for many other regions the prevalence is increasing. Allergen immunotherapy represents the only available treatment that can modify the allergic disease process, and thus is worth considering as a treatment in affected individuals. A beneficial effect of allergen immunotherapy has been shown in both adults and children affected by allergic rhinitis, allergic conjunctivitis, allergic asthma and hymenoptera venom allergy. The present study represents an overview on allergen immunotherapy, focusing on the principal aspects of the use of immunotherapy in the past, its recent clinical applications and future outlook.

Immunotherapy in allergy and cellular tests: state of art

The basophil activation test (BAT) is an in vitro assay where the activation of basophils upon exposure to various IgE-challenging molecules is measured by flow cytometry. It is a cellular test able to investigate basophil behavior during allergy and allergy immunotherapy. A panoply of critical issues and suggestive advances have rendered this assay a promising yet puzzling tool to endeavor a full comprehension of innate immunity of allergy desensitization and manage allergen or monoclonal anti-IgE therapy. In this review a brief state of art of BAT in immunotherapy is described focusing onto the analytical issue pertaining BAT performance in allergy specific therapy.